The research, led by Professor Won-Jae Kim of the Stem Cell Secretome Research Center in the Department of Oral Physiology at Chonnam National University School of Dentistry, investigated whether the secretome of human dental pulp stem cells, or hDPSCs, could improve functional recovery after ischemic stroke. The work, published online on July 23, 2026, in the journal Advanced Science, combined proteomic profiling, cell-based assays, and a photothrombotic mouse model of ischemic stroke to map both the molecular contents of the secretome and its downstream effects on the injured brain. The central idea is elegant in its simplicity: rather than transplanting living stem cells, clinicians could one day deliver the cocktail of bioactive molecules those cells naturally release.

That distinction matters more than it might first appear. Cell transplantation therapies have long been haunted by practical obstacles, including poor survival of grafted cells, immune rejection, and the theoretical risk of tumorigenesis. Secretome-based approaches sidestep these problems entirely, because the therapeutic agents are cell-free. As Professor Kim explained, utilizing the bioactive factors secreted by stem cells rather than the cells themselves overcomes the classic hurdles of cell transplantation. His team wanted to determine whether the hDPSC secretome could serve as a safe, supportive treatment to mitigate secondary brain injury, modulate neuroinflammation, and accelerate neural repair after a stroke.

To understand what makes the dental pulp secretome special, the researchers first catalogued its contents. Proteomic analysis identified 299 proteins uniquely present in the hDPSC secretome, and their functions clustered around themes that read like a wish list for neuroprotection: extracellular vesicles, immunomodulation, neuroprotection, angiogenesis, apoptosis regulation, and resistance to oxidative stress. Several proteins stood out for their roles in antioxidant defense, including SOD2, GSR, and GSTP1, which are tied directly to the brain’s antioxidant network. Others, notably GRN, CSF1, and LRP1, emerged as key regulators of microglial phenotype, positioning the secretome to influence the brain’s resident immune cells at a critical moment.

In laboratory dishes, those molecular assets translated into measurable protection. When microglial cells, the brain’s primary immune sentinels, were treated with the hDPSC secretome, their viability improved, oxidative stress declined, and mitochondrial function was restored. The treatment reinstated expression of Mfn2, a protein essential for mitochondrial fusion, and SOD1, a key antioxidant enzyme, while reducing levels of HIF-1α, a transcription factor associated with hypoxic stress. Just as importantly, the secretome suppressed microglial migration and inflammation, nudging these cells away from the pro-inflammatory M1 phenotype and toward the pro-healing, repair-associated M2 state. In the aftermath of a stroke, that shift in microglial polarity can mean the difference between a brain that continues to destroy its own tissue and one that begins to rebuild.

The animal experiments brought these cellular effects into a living, injured brain. Using a photothrombotic model of ischemic stroke, in which a targeted clot-like lesion is induced in a defined cortical region, the researchers administered the hDPSC secretome and tracked both structural and molecular outcomes. Treated mice showed significantly reduced infarct volume and markedly less neuronal apoptosis in both the cortex and the hippocampus, two regions central to motor and cognitive function. At the molecular level, the secretome activated the Nrf2/HO-1 pathway, a master regulator of cellular antioxidant responses, while suppressing TLR4, the NOX1–NOX4 NADPH oxidase system, and NF-κB signaling, three interconnected drivers of oxidative damage and inflammation.

The regenerative effects extended well beyond damage control. In the treated animals, the secretome promoted the proliferation of neural stem cells and their differentiation into new neurons, hinting at genuine neurogenesis in the injured brain. It also restored vascular density, a process consistent with angiogenesis and vascular remodeling that can improve blood supply to recovering tissue. Perhaps most strikingly, the treatment helped rebuild synaptic architecture: levels of synaptophysin and PSD95, two cornerstone proteins of functional synapses, were upregulated in the treated brains, suggesting that the secretome was not merely preserving surviving neurons but actively supporting the reconnection of neural circuits.

Those structural and molecular changes were mirrored in behavior. Stroke-injured mice that received the secretome showed dramatic improvements in physical balance, motor coordination, and sensory-motor responses compared with untreated animals. The cognitive benefits were equally broad. Across Barnes maze, cross-maze, and fear-conditioning paradigms, treated mice demonstrated significant improvements in spatial learning, working memory, and associative memory. The treatment even reduced post-stroke anxiety-like behaviors, a common and often overlooked consequence of stroke that can profoundly affect quality of life. Taken together, the behavioral data indicate that the secretome’s effects penetrate multiple functional domains rather than narrowly rescuing a single task.

The broader implications reach past stroke. Because the secretome targets fundamental mechanisms shared by many neurological conditions, including oxidative stress, mitochondrial dysfunction, and maladaptive inflammation, the same platform could eventually be applied to other devastating brain disorders. Professor Kim noted that over the next decade, secretome-based therapies could transform stroke care by limiting brain damage and actively repairing neural networks, and that because the approach targets fundamental mechanisms like inflammation and cellular stress, it could eventually be extended to disorders such as Alzheimer’s and Parkinson’s disease. That vision depends on a critical next step: standardizing the active therapeutic components of the hDPSC secretome so that treatments become safer, more reliable, and widely accessible, rather than varying from batch to batch.

For now, the findings remain anchored in cell culture and mouse models, and the path from a photothrombotic lesion in a laboratory animal to a therapy for human stroke survivors will require careful dose optimization, delivery studies, and clinical trials. Yet the study offers a compelling proof of concept that the bioactive cargo of dental pulp stem cells, tissue that is routinely discarded after tooth extractions, can reprogram redox and inflammatory signaling in the injured brain and translate that molecular rescue into restored movement, learning, and memory. If subsequent work confirms and standardizes these effects, the humble tooth could become an unlikely source of one of neurology’s most versatile regenerative medicines, offering stroke survivors not just survival, but recovery.

Subject of Research: Therapeutic potential of human dental pulp stem cell secretome for functional recovery after ischemic stroke

Article Title: Chonnam National University study explores therapeutic potential of human dental pulp stem cell secretome in post-stroke functional recovery

Article References: Chonnam National University study explores therapeutic potential of human dental pulp stem cell secretome in post-stroke functional recovery. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: ischemic stroke, dental pulp stem cells, secretome, neuroinflammation, oxidative stress, neurogenesis, microglia, Nrf2 pathway, neuroprotection, angiogenesis, synaptic recovery, cell-free therapy

The research team, led by Wen Zhang and Xintong Wang, focused on a stage of brain development called neuronal differentiation, the process by which precursor cells stop dividing, extend slender projections called neurites, and mature into functional neurons. This process is central to neurogenesis, which underpins neural plasticity, brain homeostasis, and cognitive function throughout life. Adult neurogenesis is notoriously vulnerable to disruption by poor diet, alcohol, aging, oxidative stress, and neuroinflammation, and its decline has been implicated in Alzheimer’s, Huntington’s, and Parkinson’s diseases. Because recent studies suggest that enhancing adult neurogenesis may improve cognition, identifying dietary factors that promote neuronal differentiation has become an attractive strategy for delaying or preventing neurodegeneration. Edible bird’s nest, derived from the salivary secretions of swiftlets in Thailand, Indonesia, and Malaysia, was a natural candidate: it is rich in sialic acid, a nutrient linked to neuroprotection, brain development, and enhanced memory, and it also contains lactoferrin, transferrin, N-acetylgalactosamine, and epidermal growth factor, all of which have been associated with healthy brain development.

Previous work by the same group had shown that feeding edible bird’s nest to pregnant and lactating rats improved spatial learning and memory in their offspring by promoting neurogenesis in the hippocampus, the brain’s memory hub. What remained unclear was the molecular mechanism. To probe it, the researchers turned to PC12 cells, a pheochromocytoma line derived from an adrenal tumor that behaves much like a sympathetic neuron. When exposed to nerve growth factor, or NGF, PC12 cells cease proliferating, extend neurites, and acquire the characteristic appearance of neurons, which makes them a standard laboratory model for studying neuronal differentiation. The team first simulated human digestion: they soaked dried Malaysian bird’s nest, heated it, exposed it to pepsin at stomach-like acidity, then to trypsin at intestinal pH, and finally lyophilized the resulting digest, which they abbreviated EBND. This digestive preprocessing was crucial, because it converted the nest’s complex proteins into a form resembling what the gut would actually deliver to the body.

Safety came first. Using a cell viability assay, the researchers confirmed that EBND showed no toxicity toward PC12 cells across a broad concentration range from 1 to 1000 micrograms per milliliter, with a gradual rise in viability observed between 1 and 100 micrograms per milliliter. They then selected 10, 50, and 100 micrograms per milliliter for the differentiation experiments. The first result was intriguing but incomplete. When PC12 cells were treated with EBND alone for seven days, the cells did not visibly extend neurites, the classic morphological hallmark of differentiation. Yet at the biochemical level something significant was happening: all three neurofilament proteins, the structural backbone of the neuronal cytoskeleton, were upregulated. NF68 expression more than tripled, while NF160 and NF200 at least doubled at the highest dose, changes that were highly statistically significant. Because NF68 and NF160 typically appear early in neuronal differentiation and NF200 marks more mature neurons, the finding suggested that EBND was switching on the molecular program of differentiation even without producing visible neurites.

The decisive experiment came when the researchers added a whisper of NGF. At a concentration of 1.5 nanograms per milliliter, far below the 50 nanograms per milliliter used as a positive control, NGF alone failed to induce any differentiation. But when that subthreshold dose of NGF was combined with EBND, the cells responded robustly. Differentiation rates climbed in a dose-dependent fashion, reaching 22.8 percent at 10 micrograms per milliliter, 31.2 percent at 50, and 42.7 percent at 100, compared with cells given the low NGF dose alone. Mean neurite length rose in parallel, and the expression of all three neurofilament subunits increased two- to threefold at the higher EBND doses. In other words, EBND alone primed the cells for differentiation, while NGF provided the essential trophic signal that translated that priming into visible structural growth. The authors describe this as a state of differentiation priming, in which EBND raises the cell’s responsiveness to coexisting neurotrophic cues.

To uncover the pathway responsible, the team examined the TrkA receptor, the high-affinity docking site through which NGF commands neurons to differentiate. In cells receiving only the trace dose of NGF, TrkA phosphorylation was minimal. Co-treatment with EBND more than doubled TrkA phosphorylation, and purified sialic acid produced a smaller but significant 1.5-fold increase. Downstream, the effects amplified: phosphorylation of ERK1/2, a kinase that relays signals from the receptor toward the nucleus, tripled, and phosphorylation of CREB, a transcription factor that activates neurotrophic genes, doubled. Consistent with this, brain-derived neurotrophic factor, or BDNF, a protein critical for neurogenesis and neuronal survival that CREB helps regulate, rose by nearly 45 percent in the co-treated cells. The cascade traced a coherent line from receptor to nucleus: NGF signal potentiated at TrkA, relayed through ERK1/2, consolidated by CREB, and ultimately expressed as more BDNF.

The most convincing piece of evidence came from a pharmacological blockade. When the researchers pre-treated cells with GW441756, a selective inhibitor of the TrkA receptor, the neurofilament increases driven by EBND and NGF collapsed, with significant reductions in NF68, NF160, and NF200. That loss-of-function experiment confirmed that EBND does not act through some unrelated route but specifically by amplifying signaling at TrkA, thereby making cells far more sensitive to otherwise insufficient amounts of NGF. The finding echoes earlier reports that natural products such as lignans, pterostilbene, and luteolin can bind NGF or potentiate its receptor signaling, suggesting that edible bird’s nest joins a growing family of dietary compounds capable of enhancing neurotrophic pathways.

Notably, the study also revealed that sialic acid alone cannot explain the effect. Although purified sialic acid activated the same TrkA-ERK1/2-CREB-BDNF cascade, it was markedly less potent than the full enzymatic digest at equivalent amounts. This points to a synergistic contribution from other bioactive constituents, possibly epidermal growth factor-like molecules or specific peptides released during enzymatic digestion. The authors are candid about the limitations of their work. The conclusions rest entirely on a single cell line and will need validation in other neuronal models. The boiling step used to terminate enzymatic hydrolysis may have degraded heat-sensitive components, potentially understating the digest’s true activity. And the dissociation between molecular priming and morphological outgrowth under EBND alone remains incompletely understood, leaving open questions about the temporal dynamics of the priming effect and the identity of the key active factors.

Even with those caveats, the study carries real weight. It provides a plausible molecular mechanism for cognitive benefits previously observed in animal studies, and it reframes a centuries-old delicacy as a candidate functional food for brain health. Because deficiencies in NGF and BDNF have been closely linked to depression and Alzheimer’s disease, a safe dietary substance that potentiates NGF signaling could, in principle, support the development of supplements aimed at neurodegenerative conditions related to neurotrophic factor deficiency. The researchers emphasize that much remains to be done: identifying the specific bioactive components within the digest, clarifying exactly how they enhance NGF signaling, and testing whether the priming effect translates from cell culture to living brain. For now, the Caviar of the East has earned something rarer than its culinary price: a testable, receptor-level explanation for its legendary reputation, written in the language of phosphorylated kinases and growing neurites.

Subject of Research: Effects of enzyme-digested edible bird's nest on neuronal differentiation via the TrkA-ERK1/2-CREB-BDNF signaling pathway in PC12 cells

Article Title: Enzyme‐Digested Edible Bird's Nest Promotes NGF‐Induced Differentiation of PC12 Cells by Activating the TrkA‐ERK1/2‐CREB‐BDNF Signaling Pathway

Article References: Zhang, W., Wang, X., Zhu, H., Lin, X., Li, R., Yuan, M., Xu, B., Wang, D., Xiong, W., & Li, Y. (2026). Enzyme‐Digested Edible Bird's Nest Promotes NGF‐Induced Differentiation of PC12 Cells by Activating the TrkA‐ERK1/2‐CREB‐BDNF Signaling Pathway. Food Science & Nutrition, 14(10), Article e72419. https://doi.org/10.1002/fsn3.72419

Image Credits: AI Generated

DOI: 10.1002/fsn3.72419

Keywords: edible bird's nest, neuronal differentiation, PC12 cells, nerve growth factor, TrkA, ERK1/2, CREB, BDNF, sialic acid, neurogenesis, neurofilaments, neurodegenerative disease

The core of CLOK is a clever pairing of two well-established technologies. The first is HaloTag, a self-labeling protein that covalently binds specific synthetic ligands; the second is the family of Janelia Fluor dyes, exceptionally bright and photostable fluorescent molecules that cross cell membranes readily. In CLOK, developing neurons are genetically engineered to express HaloTag as they differentiate. Researchers then bathe the animal in a chosen JF dye at a defined moment. Every neuron that switches on HaloTag around that time becomes permanently fluorescent in that dye’s color. Because the HaloTag-dye complex is stable, a second dye applied later cannot relabel the earlier cohort. By applying different dyes sequentially, the team can paint successive generations of neurons in distinct hues, effectively producing a time-lapse record of neurogenesis written directly into the brain of a living vertebrate.

The validation experiments were rigorous. In larval zebrafish expressing HaloTag under the elavl3 promoter, a well-known marker of early neuronal differentiation, incubation with the dye JF525 labeled 97.4 percent of HaloTag-expressing neurons, confirming near-complete labeling efficiency. Control experiments showed that the dye-HaloTag complex remains stable over days, so neurons born after a dye pulse stay dark until the next dye is applied. Unbound dye washes out almost completely within four hours, keeping background fluorescence low, and loading single or multiple dyes early in development had no measurable effect on survival, swim bladder development, or body length. When the team compared CLOK against the classic thymidine-analog birthdating method EdU, which labels cells undergoing DNA replication but requires tissue fixation, both approaches revealed similar brain-wide topographic organization. However, quantitative analysis using Gaussian mixture modeling of dye signal ratios showed that CLOK labeled significantly more specific neuronal populations across all age groups, with far less overlap between cohorts. EdU, by contrast, also stained non-neuronal progenitors in the ventricular zone and produced broader, blurrier spatial distributions.

The temporal precision of CLOK proved remarkable. Short-pulse experiments demonstrated that neurons born within a six-hour window could be clearly distinguished, suggesting a resolution of six hours or better for the elavl3 promoter. This is a dramatic improvement over methods that typically resolve cohorts only at the scale of days. The system also scales in color: by applying five different JF dyes at 24-hour intervals, the researchers simultaneously visualized five distinct neuronal age cohorts within a single living fish, reconstructing the chronological architecture of the entire larval brain in one animal rather than averaging across many specimens.

One of CLOK’s most striking capabilities is subcellular resolution. By fusing HaloTag to localization sequences, the team targeted the protein either to axon terminals, using a synaptophysin tag, or to somatodendritic compartments, using the Kv2.1 localization sequence from the Voltron1 construct. This revealed an unexpected level of chronological organization across the brain. In regions including the optic tectum, cerebellum, and hindbrain, axon terminals from progressively later-born populations occupied successively more peripheral layers of the neuropil, while most dendritic domains were dominated by the earliest-born neurons. In other words, the brain not only organizes neuronal cell bodies by age but also arranges their processes according to birthdate, a layer of developmental order that had never been visualized at this scale before.

The labeling also proved remarkably durable. Neurons tagged at larval stages remained clearly fluorescent for up to eight weeks, well into juvenile stages, and dyes could still be successfully incorporated at 14 days post fertilization. Triple-labeling experiments confirmed that distinct birthdate cohorts remained separable weeks after the original dye pulses. This persistence opens the door to longitudinal studies that follow the same neurons from their birth through their integration into circuits and beyond, something previously impossible with fixation-based methods.

Crucially, CLOK is not just an anatomical tool; it is compatible with functional imaging. The team combined birthdate labeling with the calcium indicator GCaMP6s and presented head-fixed larvae with a battery of visual stimuli, including flashes, moving gratings, and looming shadows that mimic approaching predators, while performing two-photon calcium imaging in the optic tectum. Early-born tectal neurons, which occupy central regions, generally responded more strongly than late-born peripheral neurons, particularly to moving gratings and looming stimuli. Bright flashes, by contrast, evoked similar responses in both populations, suggesting comparable baseline visual sensitivity. Single-cell analysis using the ratio of the two dyes as a continuous birthdate proxy confirmed that older neurons were more likely to be activated across all stimulus types. The team also found that direction selectivity, the ability of neurons to respond preferentially to motion in a specific direction, was stronger and more consistent in early-born neurons, consistent with the idea that this property emerges progressively during development.

The approach worked even in brain regions where position does not predict age. Tectal neuropil interneurons, whose somata are spatially intermingled regardless of when they were born, could be sorted by birthdate using the dual-dye ratio, demonstrating that CLOK can establish birthdate-function relationships even where anatomy alone is uninformative. In the hindbrain, the team birthdated neurons born before and after 24 hours post fertilization and tracked their activity during fictive locomotion at two and four days post fertilization. At the earlier stage, fish could escape in response to electrical shocks but rarely swam spontaneously, and only a small proportion of late-born neurons were active during these behaviors. By four days, fish had acquired spontaneous swimming with a much broader repertoire of muscle activity patterns, and the late-born population showed a dramatic increase in both the proportion of active neurons and the diversity of their functional clusters, eventually exceeding the diversity of the early-born group. Notably, early-born neurons were also recruited into behaviors that did not exist at the earlier stage, hinting at functional coordination between age groups during behavioral maturation.

Perhaps most ambitiously, the researchers coupled CLOK to chemigenetic optical actuators and sensors, creating a complete birthdate-resolved toolkit for manipulating and measuring neural activity. They validated the approach with WHaloCaMP, a calcium indicator built on a HaloTag scaffold, showing that spontaneous activity could be recorded separately from early- and late-born neurons, with the early-born population displaying higher event frequencies. They applied the same logic to Voltron2, a rhodopsin-based voltage indicator, recording fast fluorescent transients corresponding to individual action potentials in the olfactory epithelium of birthdate-defined populations. Finally, they fused HaloTag to the CoChR opsin and performed all-optical experiments in which specific neurons were identified by their birthdate colors, selectively stimulated with two-photon holographic illumination, and monitored via GCaMP calcium imaging. Photostimulation-evoked responses were similar whether early- or late-born neurons were targeted, demonstrating that either cohort can be activated at will with equal efficiency. Notably, the JF dyes’ two-photon absorption profile, with minimal absorption near 920 nanometers, makes them ideal partners for GFP-based indicators, and GFP-tagged opsins produced substantially larger imaging-induced photocurrents than the dye-tagged versions, highlighting a real technical advantage of the chemigenetic design.

The authors emphasize that CLOK’s power comes from its flexibility. Because HaloTag itself is not fluorescent, transgenic lines are spectrally neutral, letting experimenters choose dyes that best complement whatever fluorescent proteins or indicators their experiment requires. The method is primarily demonstrated in zebrafish, where dye penetration through the skin is excellent, but the authors note that the underlying mechanism could extend to other models including worms, flies, mice, and even brain organoids, as well as to studies of glial development and hematopoietic lineages. Some caveats remain: promoter choice affects temporal sharpness, dye bioavailability varies with lactone-zwitterion equilibrium, and interpreting dye ratios as continuous age measures requires careful validation. Still, by uniting single-cell birthdating, functional imaging, and all-optical circuit manipulation within one framework, CLOK gives developmental neuroscientists something they have long lacked: the ability to ask not just where a neuron is and what it does, but exactly when it was born, and to watch how that birthdate shapes its journey into a working circuit.

Subject of Research: A chemigenetic multicolor labeling system for visualizing neuronal birthdate and circuit integration in developing zebrafish

Article Title: CLOK: a chemigenetic multicolor labeling system to visualize neuronal birthdate and circuit integration

Article References: Faini, G., Tuffery, M., Saleem, A., Zhang, L., Du, F., Le Bourdelles, G., Duroure, K., Schreiter, E. R., Tanese, D., Emiliani, V., Del Bene, F., & Koyama, M. (2026). CLOK: a chemigenetic multicolor labeling system to visualize neuronal birthdate and circuit integration. Nature Neuroscience. https://doi.org/10.1038/s41593-026-02423-9

Image Credits: AI Generated

DOI: 10.1038/s41593-026-02423-9

Keywords: CLOK, HaloTag, Janelia Fluor dyes, neuronal birthdating, zebrafish, neurogenesis, circuit development, calcium imaging, voltage imaging, optogenetics, optic tectum, chemigenetic indicators

The technical foundation of this story lies in how the brain handles carbon and energy. Neurons are voracious consumers of glucose, and under aerobic conditions glycolysis converts glucose to pyruvate, which is then imported into mitochondria and oxidized by the tricarboxylic acid cycle. When oxygen is scarce or demand outpaces oxidative capacity, lactate dehydrogenase converts pyruvate to lactate, regenerating NAD+ so glycolysis can continue. In the brain, this is not merely an emergency fallback. The astrocyte-neuron lactate shuttle describes a division of labor in which astrocytes, which take up glucose and glutamate from the synaptic environment, export lactate through monocarboxylate transporters for neurons to oxidize as fuel. A complementary intracellular lactate shuttle moves lactate into mitochondria via mitochondrial monocarboxylate transporters, where it can be reconverted to pyruvate and fed into oxidative phosphorylation. The result is a metabolically flexible network in which lactate flows between cell types and compartments as both fuel and signal.

What transformed lactate from fuel to regulator was the discovery in 2019 that lactate can covalently modify lysine residues on histones—the proteins around which DNA is wound—in a reaction termed lactylation. Histone lactylation requires lactyl-coenzyme A as the acyl-donor, and the addition of a lactyl group to lysine residues alters chromatin accessibility, generally opening DNA and promoting gene transcription. This places lactylation alongside acetylation and methylation as an epigenetic mark, but with a crucial difference: its abundance tracks directly with metabolic state. When glycolysis is high and lactate accumulates, lactylation rises; when lactate falls, the mark recedes. Metabolism is thereby coupled to gene expression through a single chemical handle, and the review emphasizes that this coupling is now being mapped in detail across the nervous system.

In neural stem cells and neural progenitor cells, histone lactylation appears to be a molecular throttle on the decision to proliferate and differentiate. The review describes evidence that elevated lactate promotes the expression of genes associated with neural stem cell proliferation and neuronal maturation, including activity-regulated cytoskeletal-associated protein and brain-derived neurotrophic factor, through lactylation-driven epigenetic activation. In the adult brain, neurogenesis persists in two niches: the subgranular zone of the dentate gyrus in the hippocampus and the subventricular zone lining the lateral ventricles. Adult hippocampal neurogenesis, in particular, underpins learning, memory, and mood regulation, and markers such as doublecortin flag the newborn neurons it produces. By linking glycolytic flux to the chromatin state of neural stem cells, lactylation provides a mechanism by which the metabolic environment of the niche—oxygen tension, vascular supply, inflammatory tone—can be translated into instructions about whether progenitors stay quiescent, divide, or commit to a neuronal fate.

Lactylation is not confined to histones. Non-histone proteins, including enzymes, structural proteins, and signaling molecules, carry lysine lactylation marks that can alter their activity, stability, localization, or interaction partners. The review highlights that non-histone lactylation regulates specific protein functions in ways that extend the modification’s influence well beyond gene regulation, though the precise functional consequences at individual sites remain an active area of investigation. Because lactylation, like acetylation, adds a bulky, negatively charged group to lysine, it can compete with or mimic other modifications, creating a dense regulatory cross-talk in which metabolic state reshapes the entire post-translational modification landscape of a cell.

The protective face of lactate in the nervous system rests on three pillars described in the review. First, lactate is an efficient energy substrate for neurons, and supporting neuronal metabolism can buffer cells against the energetic stress that accompanies aging and disease. Second, lactate signaling promotes neurotrophic effects: lactate can stimulate vascular endothelial growth factor A production, supporting the vascular niche that nourishes neural progenitors, and it engages hydroxycarboxylic acid receptor 1, a G-protein-coupled receptor that mediates anti-inflammatory signaling. Third, lactate can dampen neuroinflammation. In models of activated immune cells, elevated lactate has been shown to shift macrophage and microglial behavior toward less inflammatory phenotypes, in part through lactylation-dependent and HCAR1-dependent pathways. In the context of neurodegeneration, where chronic inflammation and mitochondrial dysfunction are hallmarks, these mechanisms suggest that boosting lactate availability or lactylation could, in principle, slow neuronal loss.

The toxic face emerges when the same chemistry is applied in the wrong context. The review is explicit that the switch between protection and harm depends on concentration, cell type, pathological setting, and the specific lactylation site involved. Excessive lactate accumulation accompanies the acidic, hypoxic conditions of injury and chronic disease, where it can exacerbate oxidative damage and support inflammatory programs. In neurodegenerative diseases characterized by protein aggregation—amyloid-beta and tau in Alzheimer’s disease, alpha-synuclein in Parkinson’s disease, huntingtin in Huntington’s disease—altered post-translational modification landscapes may influence how proteins misfold, aggregate, and evade clearance. Lactylation of proteins involved in aggregation or in the machinery that clears misfolded proteins could tip the balance toward pathology. Similarly, in amyotrophic lateral sclerosis, where motor neuron degeneration is coupled to defects in the motor neuron lactate shuttle and disrupted energy metabolism, the direction of lactate flux may determine whether supporting cells nourish or starve the vulnerable neurons they surround.

The disease-specific evidence reviewed by the authors paints a picture of context-dependence rather than simple causation. In Alzheimer’s disease, impaired glucose metabolism and reduced lactate handling are observed alongside amyloid precursor protein pathology, and altered lactate dynamics in the cerebrospinal fluid reflect broader metabolic decline; yet lactate’s neurotrophic and anti-inflammatory actions suggest potential benefit if delivered appropriately. In Parkinson’s disease, dopaminergic neurons in the substantia nigra are energetically fragile, with high mitochondrial demand and susceptibility to reactive oxygen species, making metabolic support attractive but also raising the stakes of any intervention that perturbs redox balance. In Huntington’s disease, mutant huntingtin disrupts transcription and metabolism broadly, and lactylation-dependent gene regulation could either compensate for or compound these defects. The unifying insight is that lactate is not simply good or bad; it is a dose-, timing-, and site-dependent variable that must be read in the context of each disease stage and cellular environment.

Therapeutic implications follow directly from this framing, and the review evaluates several strategies for manipulating lactate metabolism and lactylation. Approaches include modulating lactate dehydrogenase activity, targeting monocarboxylate transporters to redirect lactate flux between cells, pharmacologically shifting metabolism with agents such as dichloroacetate that favor mitochondrial oxidation over glycolysis, and exploiting exercise—high-intensity interval training elevates circulating lactate and has been associated with enhanced neurotrophic signaling and adult hippocampal neurogenesis. Enzymes that write and erase lysine lactylation marks are also candidate drug targets, analogous to the histone acetyltransferases and deacetylases that have yielded epigenetic therapies in oncology. The challenge, as the authors stress, is achieving the right modification at the right site in the right cells: systemic manipulation of lactate would simultaneously affect neurons, astrocytes, microglia, endothelial cells, and peripheral immune cells, each of which may respond differently.

The review’s conclusion is a call for precision rather than enthusiasm. Lactate and protein lactylation exhibit a genuine regulatory duality in neurogenesis and neurodegenerative disease, and the factors that determine which face prevails—concentration, cell type, pathological context, and lactylation site—are only beginning to be mapped. Site-specific mapping of the lactylome in human disease tissue, tools for cell-type-selective manipulation of lactylation, and biomarkers that report on lactylation state in living patients are among the needs the authors identify for clinical translation. If those gaps close, the molecule once dismissed as metabolic exhaust may become a lever for regenerating the aging and diseased brain—one lysine residue at a time.

Subject of Research: Roles of lactate metabolism and lysine lactylation in adult neurogenesis and neurodegenerative disease

Article Title: Roles of lactate and protein lactylation in neurogenesis and neurodegenerative disease

Article References: Zhou, X., Han, J., Cui, X., Wu, S., Lu, Z., & Zong, S. (2026). Roles of lactate and protein lactylation in neurogenesis and neurodegenerative disease. Journal of Translational Medicine, 24(1), Article 1210. https://doi.org/10.1186/s12967-026-08940-2

Image Credits: AI Generated

DOI: 10.1186/s12967-026-08940-2

Keywords: lactate, protein lactylation, neurogenesis, neural stem cells, epigenetics, Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, astrocyte-neuron lactate shuttle, histone modification, neuroinflammation

Transglutaminases catalyze transamidation reactions, a calcium-dependent chemistry that forms new bonds between proteins and can attach small amines to protein targets. In mammals, the family includes several members, and in higher mammals transglutaminase 2, commonly abbreviated TG2, is the most abundantly expressed form in the brain. Yet when scientists knocked out TG2 in mice, the animals showed no major neurodevelopmental abnormalities. That puzzling result has long suggested that other transglutaminase family members expressed in the mammalian central nervous system may compensate for the loss, masking the true importance of these enzymes during brain formation. Compensation of this kind makes mammalian genetics a blunt instrument for probing what transglutaminases actually do as the brain takes shape.

This is precisely where the fruit fly offers an advantage. Drosophila melanogaster carries only a single transglutaminase gene, known as dTg, which means that removing it eliminates the entire enzymatic family in one genetic stroke. There is no redundancy to hide behind. Despite this experimental appeal, the contribution of dTg to brain development and function had remained poorly understood, and the new study set out to fill that gap by asking what happens to the fly nervous system, and to fly behavior, when dTG is absent.

The answer, at the structural level, was unambiguous. Animals lacking functional dTG displayed defects in the mushroom body, the fly brain structure that serves as a crucial associative learning center and is often compared, in function, to parts of the mammalian cortex and hippocampus. The mutants also showed abnormalities in brain dopaminergic neurons, the cells that produce and release dopamine, both when examined in living animals and when the neurons were grown in vitro. Because dopaminergic systems in flies, as in humans, govern movement, motivation, and social behavior, these anatomical findings pointed toward functional consequences that the team then went on to test directly.

Those consequences were readily apparent in the behavior of the mutant animals. Flies deficient in dTG showed altered locomotion, a hallmark of dopaminergic dysfunction, and, more strikingly, a strong asocial-like phenotype. Social behavior in Drosophila is a well-established experimental readout, and disruptions of dopamine signaling are known to alter how flies aggregate, interact, and respond to one another. The concordance between the structural defects in dopaminergic neurons and the behavioral abnormalities in movement and social interaction strengthened the case that transglutaminase activity is genuinely required for the proper maturation of these neuronal populations and the circuits they build, rather than producing incidental or downstream effects.

To understand the molecular basis of these defects, the researchers turned to transcriptomics, profiling gene expression across the fly brain. In dTG-deficient animals, the expression of numerous genes associated with neurogenesis and neurodevelopment was altered. This pattern suggests that transglutaminase activity influences the transcriptional programs that guide neural progenitors and young neurons as they differentiate and wire into circuits. In other words, the enzyme appears to act upstream of gene regulation during brain maturation, not merely as a structural accessory protein, and its absence ripples outward through the developmental transcriptome.

The most provocative experiment, however, was the one that crossed the species boundary. When the researchers expressed human transglutaminase 6, hTG6, in the fly under the control of the endogenous dTg promoter, meaning the human enzyme was produced exactly where and when the fly enzyme would normally be, the results were remarkable. The human enzyme rescued the social phenotype of the mutants and prevented the loss of dopaminergic neurons. It also partially reverted the changes in gene expression observed in the mutants and partially corrected the motor defects. A human protein, operating in an insect brain, could substantially stand in for the fly’s own enzyme, a demonstration of functional conservation spanning roughly 600 million years of independent evolution.

Why only partial rescue? The authors point to epigenetics, specifically a chemical mark known as histone dopaminylation. This modification, in which dopamine itself is attached to histone proteins around which DNA is wrapped, links neuronal activity and dopamine signaling to the regulation of gene expression, and transglutaminase enzymes have been implicated in catalyzing it. In the dTG mutants, this epigenetic mark is disrupted, and the expression of hTG6 only partially restores it. That incomplete restoration of histone dopaminylation provides a coherent mechanistic explanation for the incomplete rescue of the transcriptomic, motor, and behavioral phenotypes, and it ties the developmental role of transglutaminases to the emerging field of dopamine-driven epigenetic regulation in the brain.

Taken together, the findings carry two significant implications. First, they support the idea that the functions of transglutaminases in the nervous system are evolutionarily conserved across species, from insects to humans, and that these enzymes contribute to the maturation of brain neurons and circuits in a fundamentally similar way. Second, they validate the fly as a streamlined model for studying transglutaminase biology in the brain. Because Drosophila has only one transglutaminase gene, researchers can dissect the enzyme’s roles without the confounding compensation that complicates mammalian studies, and the partial interchangeability with human TG6 means that discoveries made in the fly are likely to be relevant to human neurobiology.

The study also resonates beyond basic developmental neuroscience. Transglutaminases have been linked to human neurological conditions, and the related subjects highlighted alongside the article include Huntington’s disease and amyotrophic lateral sclerosis, disorders in which protein chemistry, neuronal vulnerability, and brain circuit dysfunction intersect. While the current work does not establish a direct therapeutic pathway, it clarifies the normal developmental functions of these enzymes and demonstrates that their activity shapes dopaminergic neurons and social behavior through conserved molecular mechanisms. As research into histone dopaminylation and transglutaminase biology advances, the humble fruit fly, equipped with a single enzyme that a human protein can partially replace, is likely to remain at the center of efforts to understand how brains are built, one calcium-dependent chemical bond at a time.

Subject of Research: Evolutionarily conserved roles of transglutaminase enzymes in Drosophila brain development and dopaminergic neuron maturation

Article Title: Drosophila and human transglutaminases are partially interchangeable, revealing evolutionary conserved roles in brain development

Article References: Almonacid-Torres, I., Almonacid-Torres, J., Gómez-Fett, P., González-Ramírez, M. C., Chamorro-González, A., Zárate, R. V., Maze, I., Oliva, C., Andrés, M. E., & Campusano, J. M. (2026). Drosophila and human transglutaminases are partially interchangeable, revealing evolutionary conserved roles in brain development. Cellular and Molecular Life Sciences. https://doi.org/10.1007/s00018-026-06413-9

Image Credits: AI Generated

DOI: 10.1007/s00018-026-06413-9

Keywords: transglutaminase, Drosophila, human TG6, dopaminergic neurons, brain development, mushroom body, histone dopaminylation, neurogenesis, epigenetics, locomotion, social behavior, evolutionary conservation

The research team, led by Qing Liu and Fei Huang, began with a deceptively simple question: how do you make a therapeutic vesicle find the right cells? Conventional exosome therapies rely on passive accumulation at injury sites, where inflamed tissue happens to attract circulating nanoparticles. That passive approach rarely delivers enough cargo to the endogenous neural stem cells scattered around a lesion to change their behavior. To solve this, the researchers turned to phage display, a combinatorial screening technique that pits billions of random peptides against a target cell and lets binding affinity do the selecting. They immobilized neural stem cells harvested from embryonic rat spinal cords and ran three successive rounds of biopanning against a random 12-mer peptide library, washing away weak binders and amplifying the survivors in bacterial hosts.

The screen delivered a clear winner. Of 45 sequenced phage clones showing strong binding, 41 carried the same peptide sequence: WTLPPQLMFANI, which the team designated TGP1. When synthesized with a fluorescent tag, TGP1 bound neural stem cell neurospheres with the strongest and most localized signal among all candidates. More importantly, after intravenous injection into rats with spinal cord injuries, the peptide accumulated in the injured spinal cord region, demonstrating that a systemically administered molecule could reach the very tissue where repair is needed. The researchers caution that phage display identifies ligands by binding behavior rather than by receptor identity, so the specific surface molecule that TGP1 recognizes remains unknown—a question they acknowledge will require future affinity-capture studies.

With the targeting peptide in hand, the team built a dual-function delivery vehicle. They used lentiviral vectors to engineer human induced pluripotent stem cells with two genetic payloads: one encoding a fusion protein that displays TGP1 on the exosomal membrane via the abundant membrane protein Lamp2b, and another that boosts production of Apelin, a signaling peptide with known pro-regenerative effects in the nervous system. These engineered cells were then differentiated into neural stem cells, and the exosomes they secreted were harvested by differential ultracentrifugation. Quality control followed the MISEV2018 guidelines of the International Society for Extracellular Vesicles: dynamic light scattering confirmed a hydrodynamic diameter of roughly 100 nanometers, transmission electron microscopy revealed the characteristic cup-shaped morphology, western blots detected the canonical markers Alix, TSG101, and CD81 while excluding endoplasmic reticulum contamination, and endotoxin levels stayed below 1 EU/mL across all preparations.

The engineering worked as designed. ELISA measurements showed that Apelin content in the engineered exosomes was approximately 2.8-fold higher than in unmodified controls. A competitive binding assay provided mechanistic proof that surface TGP1 drives targeting: when free fluorescent TGP1 peptide was mixed with TGP1-displaying exosomes, the two competed for the same binding sites on neural stem cell neurospheres in a ratio-dependent manner. In injured rats, TGP1-modified exosomes accumulated more prominently in damaged spinal cord segments than unmodified vesicles, and confocal microscopy of tissue sections revealed a 4.6-fold increase in co-localization with Nestin- and SOX2-positive endogenous neural stem cells. Co-localization with mature neurons and microglia remained limited, indicating genuine preferential engagement rather than nonspecific tissue penetration.

The functional payload proved equally consequential. In culture, exosome treatment shifted neural stem cell differentiation toward the neuronal lineage, increasing the βIII-tubulin-positive neuronal area and reducing the GFAP-positive astrocytic area. The Apelin-enriched, TGP1-targeted formulation showed the strongest effect on both counts, and also drove the highest levels of Ki67 expression and BrdU incorporation, markers of active proliferation. The real test came under inflammatory stress. The researchers co-cultured neural stem cells with mixed glial cells activated by lipopolysaccharide and interferon-gamma, a Transwell system that recapitulates the cytokine-rich, pro-gliogenic environment of an injured cord. Under these conditions, neuronal differentiation was nearly abolished, with some microscopic fields showing barely detectable βIII-tubulin. TGP1-modified exosomes partially rescued neuronal commitment, and the Apelin-enriched version restored it most effectively, producing the largest βIII-tubulin areas and the smallest GFAP areas at both three and seven days.

In vivo results followed the same pattern. Rats received a standardized compression injury at the T9-T10 vertebral level, followed by weekly tail vein injections of exosomes at 0.5 mg/kg. Eight weeks of repeated dosing produced no detectable toxicity: histology of major organs was unremarkable, and serum markers of liver and kidney function showed no treatment-related deterioration. At the lesion site, BrdU labeling revealed that TGP1-targeted exosomes increased the proliferating neural stem cell population by roughly 1.8-fold compared with untreated injured animals, and Apelin enrichment added a further 1.6-fold increase on top of that. Newly generated immature neurons, marked by DCX, rose approximately 1.5-fold with targeted exosomes and a further 2.3-fold with Apelin enrichment, while later-stage NF200-positive neuronal lineage cells increased 3.3-fold and then 1.5-fold respectively. Three-dimensional reconstruction showed BrdU-labeled cells acquiring NeuN and βIII-tubulin signals, with synaptophysin-positive and VGLUT2-positive puncta in close spatial association—early evidence of synapse-associated neuronal maturation.

The treatment also remodeled the lesion environment itself. Immunofluorescence analysis showed that Apln-TGP1 exosomes most strongly suppressed the accumulation of C3-positive neurotoxic astrocytes and iNOS-positive pro-inflammatory microglia, the two cellular hallmarks of the inhibitory glial response. Anterograde tracing with an AAV-delivered fluorescent reporter revealed greater extension of corticospinal tract fibers in treated animals, and markers of axonal integrity, serotonergic and catecholaminergic innervation, and myelin reconstruction all pointed toward improved structural preservation. MRI confirmed smaller lesions and better tissue continuity. Functionally, the benefits were sustained: BBB locomotor scores improved progressively through 56 days post-injury, motor-evoked potential amplitudes increased, footprint patterns and toe-spreading normalized, thermal withdrawal latency recovered, and hindlimb muscle preserved more of its oxidative slow-twitch fiber character.

Transcriptomic profiling of treated spinal cords tied these effects to molecular programs. RNA sequencing showed differential expression of inflammation-related genes such as Cxcl1 and Ccl19, enrichment of ion transport and synaptic signaling processes, and activation of Apelin and calcium signaling pathways. Gene set enrichment analysis highlighted the PPAR signaling pathway, serotonergic synapse signaling, and ion channel activity. Western blotting confirmed increased expression of APJ, the Apelin receptor, and of PPAR-gamma specifically, with no change in other PPAR subtypes. When the researchers blocked PPAR-gamma with the antagonist GW9662 in cultured neural stem cells, neuronal markers fell and astrocytic markers rose; co-treatment with Apln-TGP1 exosomes reversed these trends and restored proliferative activity. The authors are careful to frame these findings appropriately: the newly generated cells show structural features consistent with neuronal maturation, but functional integration into circuits will require further electrophysiological validation, and longer-term safety studies remain to be done. Still, by separating the problem of targeted delivery from the problem of fate regulation—and solving both within a single nanoscale vesicle—the platform offers a coherent blueprint for coaxing the spinal cord’s own stem cells into doing what they have always been capable of, but rarely choose, to do.

Subject of Research: Engineered exosome-based targeted delivery to endogenous neural stem cells for spinal cord injury repair

Article Title: An engineered exosome-based platform for targeted delivery to endogenous neural stem cells and fate modulation after spinal cord injury

Article References: An engineered exosome-based platform for targeted delivery to endogenous neural stem cells and fate modulation after spinal cord injury. (n.d.). https://doi.org/10.1016/j.mtbio.2026.103718

Image Credits: AI Generated

DOI: 10.1016/j.mtbio.2026.103718

Keywords: spinal cord injury, exosomes, neural stem cells, phage display, Apelin, Lamp2b, neurogenesis, PPAR-gamma, targeted drug delivery, glial scar, neuroinflammation, regenerative medicine

The central insight behind the work is that bone repair is not simply a materials problem but an ecological one. When a scaffold is implanted, the first cells to arrive are macrophages, the immune system’s resident first responders. Depending on the chemical signals they encounter, these macrophages polarize into two broad phenotypes: the M1 state, which drives inflammation and can stall healing, and the M2 state, which releases growth factors that recruit stem cells, build blood vessels, and lay down new matrix. Conventional implants often leave this immune decision to chance. The new scaffold is designed to tip the balance deliberately, converting the inevitable inflammatory response into a constructive one without any drugs, external stimulation, or electronic control.

To achieve this, the researchers drew directly on the composition and microstructure of natural bone. Using a hydrothermal process—essentially growing crystals in a hot, pressurized aqueous solution—they formed a coating of calcium titanate on the struts of three-dimensional printed porous titanium alloy scaffolds. Calcium titanate is chemically akin to the mineral phase of bone and is known to bond readily with living tissue. Crucially, the coating was doped with trace amounts of bioactive metal ions and engineered with a micro- and nano-scale gradient morphology, meaning its texture transitions across length scales the way natural bone surfaces do, from rough micro-features down to nanocrystalline detail. This hierarchical topography matters because cells on surfaces sense features at exactly these dimensions, and their behavior—adhesion, spreading, migration, differentiation—shifts in response.

The functional surface works through two coupled mechanisms. First, the micro/nano topography itself provides physical cues that guide cell behavior, a phenomenon well established in biomaterials science but here integrated into a load-bearing printed implant. Second, the trace ions incorporated into the calcium titanate coating are released slowly and sustainably into the local microenvironment. Rather than flooding the tissue with a burst of soluble factors that fades within days, the scaffold acts like a reservoir, dosing the surrounding cells continuously as the coating gradually exchanges ions with body fluid. The result, according to the authors, is a surface that modulates its own microenvironment—hence the term self-regulated in the study’s title.

What makes the study particularly striking is the breadth of the biological response it documents. Most bone implant research focuses narrowly on osteogenesis, the formation of new bone. This team evaluated the scaffolds both in vitro, with cells cultured on their surfaces, and in vivo, in animal defect models, and assessed not only bone formation but also angiogenesis—the sprouting of new blood vessels—and neurogenesis, the ingrowth of nerve fibers. The vascular component is well appreciated: without blood supply, newly formed bone cannot survive, and the deep pores of a large scaffold are notorious dead zones for vessel penetration. The neural component is newer territory. Nerve fibers are increasingly recognized as active participants in bone remodeling, releasing neuropeptides that regulate both osteoblasts, the bone-forming cells, and osteoclasts, the bone-resorbing cells. A scaffold that simultaneously supports vessels and nerves is, in effect, rebuilding the entire neurovascular infrastructure that living bone depends on.

Beneath these observable outcomes, the researchers mapped the molecular machinery driving the effect. Their analysis points to the simultaneous activation of two signaling axes: PPAR, the peroxisome proliferator-activated receptor pathway, and the PI3K-Akt-mTOR cascade, a central growth-and-metabolism pathway shared across many cell types. Together, these pathways pushed infiltrating macrophages toward the M2 phenotype—the pro-healing, anti-inflammatory state. In practical terms, the scaffold’s surface chemistry and topography appear to reprogram the immune response at its source, so that the cells arriving first at the implant set a regenerative tone for everything that follows. This immunomodulatory framing reflects a broader shift in the biomaterials field, where the goal is no longer to make surfaces that the immune system tolerates, but surfaces that recruit the immune system as an ally.

The technical achievement of growing such a coating in situ on a printed titanium lattice should not be understated. Three-dimensional printed porous titanium alloys are already used clinically in spinal fusion, hip revision surgery, and maxillofacial reconstruction, prized for their stiffness matching and the interconnected porosity that lets tissue grow in. But post-printing surface functionalization is delicate: any treatment must not clog the pores, weaken the struts, or introduce brittleness. Hydrothermal growth is attractive precisely because it is a low-temperature, solution-based method that conformally coats complex geometries, following every curve and corner of the printed architecture. The gradient morphology of the resulting layer suggests the crystal growth was tuned across scales, producing a surface that is rough at the micron level and textured at the nanoscale—conditions that favor protein adsorption and cell attachment.

The implications for patients are considerable. Implant failure due to poor osseointegration—the direct structural bond between bone and implant surface—remains a costly and painful problem, particularly in patients with diabetes, osteoporosis, or compromised vasculature, where healing is slow and inflammation is chronic. A scaffold that actively accelerates vascularization and calibrates the immune response could expand the pool of patients for whom large bone reconstructions succeed. Because the functionalization is a surface treatment rather than a change to the bulk metal, it could in principle be retrofitted onto existing printing workflows without redesigning the implants themselves. The authors position the work as a foundation for intelligent implants—devices that manage their own healing process rather than depending on the body to overcome their presence.

Caveats remain, as they always do at this stage of translation. The study’s biological evaluation, while spanning cell culture and animal models, precedes the clinical trials that any new implant surface must eventually face. Long-term durability of the ion-releasing coating under years of mechanical loading, the behavior of the surface in infected or osteoporotic bone beds, and the scalability of hydrothermal processing for commercial manufacturing are all questions that future work must answer. The research was conducted by a large multidisciplinary team led by corresponding authors Hai Huang, Hao Wu, and Zheng Guo, with support from China’s National Key Research and Development Program and the National Natural Science Foundation of China, and the article is open access, allowing clinicians and materials scientists worldwide to examine the data in full.

Still, the conceptual leap is hard to miss. For half a century, biomaterials have been judged by how quietly they disappear into the body’s background. This work argues for a different standard: that an implant’s surface can be an active participant in healing, sensing nothing yet regulating everything through nothing more than geometry and chemistry. A printed titanium lattice, dressed in a bone-like mineral skin that speaks the language of macrophages, endothelial cells, neurons, and osteoblasts, may represent the clearest demonstration yet that the smartest implant is not the one packed with electronics, but the one designed to let biology do what it already knows how to do—provided the surface gives it the right instructions.

Subject of Research: Bioactive surface-functionalized 3D-printed titanium scaffolds that self-regulate immune, neurovascular, and osteogenic bone repair

Article Title: Self-regulated immune-neurovascular bone repair scaffold via functional surface features

Article References: Yu, D., Tang, Z., Yang, T., Guo, S., Bao, S., Li, C., Wu, Q., Chen, C., Liu, Y., Li, X., Huang, H., Wu, H., & Guo, Z. (2026). Self-regulated immune-neurovascular bone repair scaffold via functional surface features. Advanced Composites and Hybrid Materials. https://doi.org/10.1007/s42114-026-02095-w

Image Credits: AI Generated

DOI: 10.1007/s42114-026-02095-w

Keywords: bone regeneration, 3D-printed titanium scaffold, calcium titanate coating, macrophage polarization, M2 phenotype, angiogenesis, neurogenesis, osseointegration, PPAR signaling, PI3K-Akt-mTOR pathway, bioinspired materials, immunomodulation

The research team, led by Lei Shi of the Kunming Institute of Zoology at the Chinese Academy of Sciences, exploited an unusual comparative tool: the tree shrew. This small, squirrel-like mammal is not a primate, but it sits close enough to the primate branch on the evolutionary tree to serve as an outgroup, a reference point that allows scientists to distinguish what is genuinely primate-specific from what is shared more broadly among mammals. By comparing the developing brains of humans, macaques, tree shrews and mice, the researchers could trace which genetic changes coincided with the expansion of cortical territory that defines our order.

Their first discovery was that CCNB1IP1, a gene that had little or no activity in the developing brains of other mammals, acquired expression in the primate brain. More strikingly, the level of that expression climbed progressively across the evolutionary ladder, from lower primates through monkeys to apes and finally humans. That gradient mirrored the gradient in cortical size and gyrification, the technical term for the degree of cortical folding, suggesting a quantitative relationship rather than a simple on-off switch. Statistical analysis confirmed that both the gyrification index and brain weight correlate with evolutionary divergence time across species, consistent with a gradual, cumulative process rather than a sudden leap.

Where did the increased expression come from? The answer, according to the study, lies not in the protein-coding sequence of the gene itself but in its regulatory DNA. Comparative analysis of cis-regulatory elements, the short stretches of DNA near a gene that control when and how strongly it is transcribed, revealed evolutionary changes that ratcheted up CCNB1IP1 activity. The researchers focused on two candidate regulatory regions, CRE1 and CRE2, and examined histone modifications such as H3K4me3 and H3K27ac, chemical tags on chromatin that mark active regulatory elements in human neural progenitor cells. Sequence alignments across twenty mammalian species highlighted sites that changed specifically in the human lineage, and one region, CRE1, contained sub-elements associated with the gradual expression increase during primate evolution.

To test whether the gene could actually reshape a brain, the team turned to experiment. When they overexpressed CCNB1IP1 in the embryonic mouse cortex using in utero electroporation, they saw a cascade of cellular effects: more cells entering DNA synthesis, an expanded pool of basal progenitors, and increased neuronal output. Basal progenitors are the self-amplifying stem cells of the subventricular zone, a germinal layer that is disproportionately well developed in primates and is widely regarded as the engine of cortical expansion. In the human fetal cortex, single-cell analysis showed that CCNB1IP1 is expressed most strongly in neural progenitor cells, and higher in basal progenitors than in apical progenitors at the peak of neurogenesis, precisely where extra rounds of cell division would matter most.

The mechanistic heart of the paper concerns what CCNB1IP1 actually does inside those cells. The researchers demonstrated that it represses E2F1, a transcription factor that drives the cell cycle, by targeting it for ubiquitin-mediated degradation, the cellular waste-disposal pathway that tags proteins for destruction by the proteasome. By damping E2F1, CCNB1IP1 alters the tempo of the cell cycle in neural progenitors. Slower, differently timed cycles are a long-standing theme in cortical evolution: since the classic work of Pasko Rakic and others, developmental biologists have argued that small changes in the duration and timing of progenitor cell divisions, repeated over thousands of rounds, can yield enormous differences in final neuron number. CCNB1IP1 offers a concrete molecular handle on that process.

The most dramatic experiment came next. Using CRISPR-Cas9, the team created conditional knock-in mice carrying the human CCNB1IP1 gene at the Rosa26 locus, activated in the excitatory neuronal lineage via Emx1-Cre. Ordinary mice have smooth, lissencephalic brains; their cortices lack the folds seen in humans and other gyrencephalic species. Remarkably, the knock-in mice developed recognizable cortical folding, along with an expanded cortical area, an increased proportion of upper-layer neurons, and measurable gains in cognitive performance on behavioral tests such as novel object recognition and the Morris water maze. In effect, a single regulatory change was sufficient to push a rodent brain partway toward a primate-like architecture.

The findings fit into a broader and increasingly rich picture of human brain evolution. Previous work has identified other human-specific genetic innovations that expand cortical progenitors, including the NOTCH2NL gene family, which enhances Notch signaling, and ARHGAP11B, a human-specific gene that promotes basal progenitor amplification and can even induce folding in mouse embryos. What distinguishes the new study is its emphasis on gradualism. Rather than a single human-specific invention, CCNB1IP1 shows a stepped increase in expression across the primate tree, implying that the enlargement and folding of the cortex were built incrementally, species by species, through cumulative regulatory tweaks rather than one dramatic mutation.

It is also a study in methodological craft. The authors combined laser microdissection of individual cortical layers in tree shrew embryos, bulk and single-cell transcriptomics across species, comparative genomics of regulatory elements, protein interaction assays, and transgenic mouse modeling into a single coherent argument. Data from brain organoids derived from humans, chimpanzees, bonobos and gorillas reinforced the expression gradient, and postnatal expression data from public brain atlases showed that the gene’s activity persists across multiple brain regions during development. All sequencing data have been deposited in public repositories, allowing other groups to scrutinize and extend the results.

Caveats remain, as they always do. Correlation between gene expression and cortical complexity across species does not by itself prove causation for every step of primate evolution, and the knock-in mouse, while striking, models only one component of a process that surely involved many genes. CCNB1IP1 has also been implicated in other contexts, including cancer biology, where it modulates ubiquitination of proteins such as MYCN, so its functions are likely broader than neurodevelopment alone. Still, the study delivers something rare: a gene whose evolutionary upregulation tracks the growth of the primate cortex, a plausible molecular mechanism linking it to progenitor behavior, and proof that boosting it can fold a smooth brain. In the long story of how our ancestors’ minds swelled and wrinkled into their modern form, CCNB1IP1 now stands as one of the clearest characters yet identified.

Subject of Research: Evolutionary changes in CCNB1IP1 gene regulation and their role in primate cortical expansion and folding

Article Title: CCNB1IP1 regulatory evolution underlies gradual increases in cortical size and folding in primates

Article References: Hu, T., Ma, P., Kong, Y., Tan, Y., Sun, X., Wang, J., Xiang, K., Mao, B., Wu, Q., Yi, S. V., & Shi, L. (2026). CCNB1IP1 regulatory evolution underlies gradual increases in cortical size and folding in primates. Nature Genetics. https://doi.org/10.1038/s41588-026-02773-x

Image Credits: AI Generated

DOI: 10.1038/s41588-026-02773-x

Keywords: CCNB1IP1, primate evolution, cortex, cortical folding, neurogenesis, basal progenitors, cis-regulatory elements, E2F1, ubiquitin degradation, tree shrew, knock-in mice, brain evolution

One of the most striking exceptions is the common marmoset (Callithrix jacchus), a small South American monkey that has become an increasingly important model organism in biomedical research. Despite being a genuine primate, the marmoset carries a brain that is smooth and virtually unfolded, a feature that sets it apart from the majority of its relatives. For developmental neuroscientists, this raises an obvious and compelling question: if marmosets and humans descend from a shared primate lineage, what cellular changes during embryonic development cause the marmoset brain to grow less, remain smaller, and never acquire the pronounced folds seen in other species?

A team at the German Primate Center (DPZ) — the Leibniz Institute for Primate Research in Göttingen — set out to answer exactly that question. In a study published in Science Advances, the researchers traced the developmental divergence between smooth and folded primate brains back to specific differences in neural progenitor cells, the self-renewing precursors from which all neurons arise. Their central finding is that the marmoset brain does not start out different. In early embryogenesis it displays the typical structure and composition of a large, folded primate brain, and only later do particular processes intervene to slow the production of nerve cells.

“We wanted to understand which changes at the cellular level cause the marmoset brain to grow less and form fewer folds,” explains Lidiia Tynianskaia, one of the study’s two first authors and a PhD student in the Junior Research Group Brain Development and Evolution at the DPZ. “At the beginning of development, the common marmoset brain exhibits the typical structure and composition of a large, folded primate brain. As development progresses, processes must therefore occur that effectively slow down the production of nerve cells.” That framing matters, because it reframes the smooth marmoset brain not as a primitive starting point but as the outcome of active developmental regulation imposed partway through embryogenesis.

To investigate those processes, the researchers turned to brain organoids — small, three-dimensional cell cultures grown from stem cells that recapitulate key aspects of early brain development. Comparative organoid experiments using marmoset and human cells allowed the team to focus on the brain’s progenitor cells, the population whose behavior largely determines how many neurons the cortex will ultimately contain. Since neuron number is one of the decisive factors governing both the size of a brain and the degree to which its surface folds, differences in progenitor behavior are a natural place to look for the roots of anatomical divergence.

The comparisons revealed that several distinct mechanisms, operating at different levels and in different progenitor cell types, converge to reduce the size and folding of the marmoset cerebral cortex. “Our investigations have shown that certain progenitor cells in the common marmoset divide significantly more slowly than in humans,” says César Mateo Bastidas Betancourt, the study’s other first author and also a PhD student in the Junior Research Group. “Other progenitor cells have a simpler structure than their human counterparts, with fewer processes, and are therefore less proliferative. Both of these factors ultimately result in fewer nerve cells, which contributes to a smaller size and less folding of the cerebral cortex in marmosets.”

These two mechanisms are complementary rather than redundant. Slower cell division directly limits how quickly the progenitor pool expands, while a simpler morphology — fewer of the cellular processes that in more proliferative progenitors help sustain repeated rounds of division — appears to constrain the cells’ proliferative capacity itself. In folded primate brains, progenitor cells in the developing neocortex typically undergo many rounds of division, amplifying the pool of neurons that will populate the expanding cortical sheet. When that amplification is dialed down, as it is in marmosets, the downstream consequence is a thinner, smaller cortex with less surface area to fold.

Timing emerged as a third, crucial dimension of the story. The scientists showed that certain characteristics and behaviors of marmoset progenitor cells appear at altered time points compared with their human counterparts, with the net effect that marmoset progenitors have a shorter overall window during which they can proliferate rapidly. In developmental biology, such shifts in timing are a well-known engine of evolutionary change: modest adjustments to when developmental programs switch on or off can produce large differences in final organ size without requiring wholesale redesign of the underlying machinery. The marmoset data suggest that a compressed proliferative window is one such adjustment, quietly capping the neuron output of the developing cortex.

Because most of the experiments relied on organoids, establishing that the cultures faithfully mirrored real development was essential. “The study combines the advantages of in vivo and in vitro methods,” says Michael Heide, head of the Junior Research Group Brain Development and Evolution. “Organoids are well-suited for obtaining statistically robust results because such sample sizes are not feasible in primates. We subsequently repeated some key experiments in fetal brain tissue to confirm the results from the organoids.” The team found that 50-day-old marmoset organoids closely resemble natural brain development at day 90, a correspondence that allowed them to align the developmental clock of the organoids with that of the actual marmoset embryo and interpret their results with confidence. That validation step is what elevates the findings from an interesting culture phenomenon to a credible account of what happens inside a developing primate.

The broader significance of the work runs in two directions. Evolutionarily, it offers a concrete, mechanistic scenario for how the striking diversity of primate brain sizes and shapes could have arisen: not through the appearance of entirely new cell types, but through coordinated changes in how existing progenitor cells divide, mature, and keep to their developmental schedule. Medically, the same cellular programs that scale a brain up or down are the ones that can go awry in developmental disorders, and the study provides an important framework for understanding both the processes themselves and the consequences of their disruption in the human brain. For a small monkey with a smooth brain, the common marmoset is now teaching scientists a great deal about what it took to build a folded one.

Subject of Research: Cellular mechanisms of neural progenitor development underlying smooth versus folded primate brains

Article Title: Smooth instead of folded—brain development in primates

Article References: Smooth instead of folded—brain development in primates. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: marmoset, brain development, neural progenitor cells, brain organoids, cortical folding, primate evolution, cerebral cortex, neurogenesis, German Primate Center, Science Advances, developmental neuroscience, brain size

Depression remains one of the most prevalent psychiatric conditions worldwide, and epidemiological evidence has long shown that early-life adversity is a powerful risk factor for psychopathology in adulthood. Women are diagnosed with stress-related mood disorders roughly twice as often as men, yet the biological mechanisms underlying this sex bias remain only partially understood. Animal models have repeatedly implicated the hippocampus—a brain region essential for memory, emotion regulation, and one of the few adult brain regions where new neurons continue to be born—as a key site where stress leaves lasting traces. But most previous studies examined single outcomes in isolation or focused on one sex. The Málaga team instead adopted a two-hit experimental framework: a first hit of stress during the juvenile, peripubertal period, and a second hit of acute stress in adulthood, testing whether the early experience changes the way the adult brain responds.

The researchers exposed juvenile mice to stress and then, later in life, subjected the same animals to an acute adult stressor, creating four comparison groups for each sex: no stress, juvenile stress only, adult stress only, and combined juvenile-plus-adult stress. They then measured an unusually broad battery of endpoints. Behaviorally, they assessed saccharin preference, a classic measure of anhedonia, or loss of interest in rewards, together with social exploratory behavior toward an unfamiliar mouse. At the cellular level, they analyzed microglial morphology—the shape and branching complexity of the brain’s resident immune cells—along with cell proliferation and the abundance of immature neurons in the dentate gyrus, the hippocampal subregion where adult neurogenesis occurs. They also quantified inflammatory cytokines and performed an unbiased proteomic analysis of hippocampal tissue to capture the full molecular fingerprint of each stress condition.

The results that emerged were strikingly selective, the authors report. Effects depended on sex, on the timing and combination of stress, on the endpoint measured, and even on the hippocampal subregion examined. In males, stress did not clearly alter saccharin preference or the social behaviors assessed, suggesting that the behavioral readouts of depression-like states were largely spared. At the molecular level, however, adult acute stress increased hippocampal interferon-gamma, a signaling molecule of the immune system, and was associated with selective changes in microglial morphology. Proliferation and neurogenic effects in males were limited and confined to specific cell populations and subregions. When juvenile and adult stress were combined, males showed proteomic differences concentrated in proteins related to synaptic signaling and metabolic processes—changes that, notably, were not accompanied by overt behavioral alterations.

In females, the picture was different in almost every respect. Juvenile stress was associated with sex-dependent alterations in saccharin preference, although the authors emphasize that it did not produce a consistent, wholesale loss of sweet-reward interest. Juvenile stress and the combined stress condition both affected specific components of social exploratory behavior, pointing to subtle but measurable disruptions in how females approach and investigate novel conspecifics. The cellular consequences in females were subtle and region-specific, yet the proteomic changes were broader and more densely interconnected than in males, particularly after combined stress, which produced the widest hippocampal protein response observed in the study.

Perhaps the most important takeaway is a methodological one: the different biological levels did not move in lockstep. Most cytokines were unchanged across conditions, microglial morphology was shaped mainly by sex itself rather than by stress exposure, and neurogenic effects were restricted to particular cell populations and hippocampal subregions. Behavioral changes, when they appeared, were not always mirrored by corresponding cellular or molecular alterations, and molecular signatures did not always predict behavioral outcomes. This decoupling across levels of analysis challenges the widespread assumption that depression-like behavior in animal models must be accompanied by uniform, measurable changes in neurogenesis, neuroinflammation, or brain immune cells, and it cautions researchers against relying on any single biomarker as a proxy for stress vulnerability.

From a technical standpoint, the study’s strength lies in its breadth and its factorial design. By crossing stress timing with sex and measuring everything from cytokine concentrations to protein interaction networks, the authors could show that the female hippocampus responds to combined stress with a broad, coordinated proteomic reorganization, whereas the male hippocampus responds with narrower, more compartmentalized changes in immune signaling and synaptic-metabolic proteins. The selective increase of interferon-gamma in stressed males hints at a neuroimmune contribution to the stress response that is not shared, or at least not expressed the same way, in females. Meanwhile, the finding that microglial morphology differed primarily between the sexes rather than between stress conditions suggests that baseline sexual differentiation of the brain’s immune landscape may set the stage on which stress later acts, rather than being a direct consequence of it.

The authors are careful about interpretation. The study was conducted in mice, and depression-like behaviors in rodents—anhedonia measured by sweet preference, social withdrawal measured by exploration—are imperfect proxies for the human syndrome. Many of the cellular effects were subtle, and the absence of overt behavioral change in males despite clear molecular signatures underscores that biological perturbation can occur silently, without manifesting as measurable behavior. Still, the two-hit model captures a clinical reality: early adversity rarely acts alone, but instead appears to calibrate the brain’s later responses to stress. Identifying precisely which molecular pathways are reprogrammed in each sex during that calibration could ultimately guide sex-specific preventive strategies or treatments for people with histories of childhood adversity.

The work also adds to a growing recognition in neuroscience that sex must be treated as a biological variable rather than a nuisance factor. Funding bodies and journals increasingly mandate the inclusion of both sexes, and this study demonstrates why: pooling males and females, or studying only one, would have obscured entirely distinct patterns of hippocampal response. The Málaga group’s finding that combined stress produces the broadest proteomic response in females aligns with the epidemiological observation of greater female vulnerability to stress-related disorders, and it provides concrete molecular targets—synaptic and metabolic proteins, immune signaling components, neurogenic populations—that future research can interrogate. As the authors conclude, males and females respond differently depending on when stress occurs and which outcome is examined, and understanding those distinct trajectories may help explain why the same stressful world leaves such different imprints on different brains.

Subject of Research: Sex-specific hippocampal responses to peripubertal and adult acute stress involving microglia, neurogenesis, proteomics, and depression-like behavior in mice.

Article Title: Sex-specific hippocampal trajectories induced by peripubertal and adult acute stress: proteomic profile, microglial alterations, neurogenic dysregulation, and depression-like behaviors

Article References: Sex-specific hippocampal trajectories induced by peripubertal and adult acute stress: proteomic profile, microglial alterations, neurogenic dysregulation, and depression-like behaviors. (n.d.). https://doi.org/10.1186/s13293-026-00979-6

Image Credits: AI Generated

DOI: 10.1186/s13293-026-00979-6

Keywords: stress, hippocampus, sex differences, depression, microglia, neurogenesis, proteomics, juvenile stress, cytokines, anhedonia, neuroinflammation, two-hit model