A research team led by Ke Li and colleagues at institutions in China has now deciphered a self-reinforcing molecular circuit that drives this decline, and has built a tiny biomimetic machine to break it. Writing in the journal Materials Today Bio, the researchers describe a nanoreactor called CLPM that simultaneously delivers nitric oxide and magnesium ions into senescent LepR-positive cells while scavenging the reactive oxygen species that accumulate inside them. In aged mice, a single course of local treatment restored youthful gene expression patterns, reversed measurable bone loss, and even stimulated the regeneration of vascular, lymphatic, and neural components of the marrow niche. The work offers a striking example of how precision nanomedicine might one day rejuvenate not just individual cells but entire aging tissues.

The team began by mining gene expression data from young and aged mouse bone marrow. Principal component analysis and gene set enrichment analysis revealed that aged LepR-positive cells were strongly enriched for senescence programs, and that three interconnected pathways had shifted in a coordinated fashion: nitric oxide biosynthesis was downregulated, magnesium ion homeostasis was impaired, and reactive oxygen species metabolism was upregulated. Immunofluorescence staining of aged marrow sections confirmed the shift at the cellular level, showing a marked increase in the proportion of LepR-positive cells expressing P21, a canonical senescence marker, and IL-6, a pro-inflammatory cytokine released by senescent cells.

The connection between these three pathways forms the core of the team’s mechanistic insight. Nitric oxide is a gaseous signaling molecule that regulates vasodilation, neurotransmission, and stem cell fate, and its production declines progressively with age. Nitric oxide signaling is closely linked to intracellular magnesium concentration, because the gas modulates the activity of magnesium transporters through cGMP-dependent and calcium-mediated mechanisms. When nitric oxide production falls, magnesium influx into the cell falls with it. Magnesium deficiency, in turn, promotes electron leakage from the mitochondrial respiratory chain, which drives excessive production of reactive oxygen species. The accumulated ROS then push the cell further into senescence, and senescent cells produce even less nitric oxide and take up even less magnesium. The researchers describe this as a vicious cycle of aging, decreased nitric oxide and magnesium, accumulated ROS, and further aging, and their data suggest it operates in aged LepR-positive cells in the bone marrow.

To disrupt the cycle, the team constructed a nanoparticle system with three complementary functions packed into a single platform roughly 115 nanometers in diameter. The core is made of a block copolymer called mPEG-b-PPS, loaded with L-arginine that has been converted into a hydrophobic ion pair with oleate. L-arginine serves as a substrate for endogenous nitric oxide synthase enzymes, allowing the cell to generate its own nitric oxide once the cargo is released. Magnesium ions were then introduced to coordinate with the carboxylate groups of the L-arginine-oleate complex, forming multivalent crosslinks that stabilize the nanoparticle core. Finally, the researchers isolated cell membrane vesicles from senescent LepR-positive cells and coated them onto the core by extrusion, creating a biomimetic shell that exploits homologous targeting: the membrane carries the same surface markers as the target cells, encouraging uptake while helping the particles evade immune surveillance.

The design has a built-in trigger that makes the particles respond specifically to the aged intracellular environment. The PPS block contains oxidation-sensitive thioether groups. When senescent cells take up the particles, the elevated reactive oxygen species inside them oxidize the hydrophobic sulfide groups into more hydrophilic sulfoxide and sulfone groups. This hydrophobic-to-hydrophilic transition destabilizes the nanoparticle core and promotes its disassembly, and because ROS are consumed during the oxidation, the process simultaneously neutralizes the very molecules that triggered it. Disassembly of the core weakens the magnesium-carboxylate coordination network, facilitating intracellular magnesium release, while the freed L-arginine becomes available for conversion into nitric oxide. In effect, the aged cell’s own oxidative stress acts as the switch that activates the therapy.

Physicochemical characterization confirmed the construction. Transmission electron microscopy showed well-dispersed spherical particles with mean diameters of 98.2 nanometers for the uncoated core and 114.7 nanometers for the membrane-coated version. Zeta potential measurements shifted from 4.3 millivolts for the core to -12.6 millivolts after coating, consistent with the addition of the cell membrane, and immunofluorescence staining showed substantial colocalization of LepR and membrane markers on the final particles. Fourier-transform infrared spectroscopy revealed shifts in the carboxylate stretching peaks upon magnesium coordination, and X-ray photoelectron spectroscopy detected a characteristic magnesium signal at approximately 1303 electron volts, verifying successful incorporation of the metal ions. Elemental mapping demonstrated homogeneous magnesium distribution throughout the core.

Functional assays in cultured cells demonstrated that the nanoreactor works as intended. Senescent LepR-positive cells treated with the membrane-coated particles showed a time-dependent increase in uptake compared with uncoated particles, confirming the targeting advantage. Intracellular nitric oxide levels rose, magnesium concentrations increased, and accumulated reactive oxygen species were effectively eliminated. Senescence-associated beta-galactosidase staining, a standard measure of cellular aging, showed a marked reduction in senescent cells after treatment. The cells also shifted their differentiation commitment: alkaline phosphatase and alizarin red staining indicated a pronounced bias toward osteogenic, or bone-forming, differentiation, while Oil Red O staining showed reduced lipid droplet formation. Gene expression analysis confirmed the shift, with downregulation of the senescence marker P21 and the adipogenic genes PPARγ and FABP4, alongside restoration of the osteogenic genes OSX and OCN.

In aged mice, local administration of the nanoreactor produced measurable remodeling of the bone marrow. Micro-computed tomography of the femurs revealed significantly increased bone volume fraction, trabecular number, and trabecular thickness, along with decreased trabecular separation, indicating new bone formation. Histological examination showed reduced proportions of P21-positive cells and fewer marrow adipocytes. Markers of vascular, lymphatic, and neural regeneration, including CD31, VEGF-C, LYVE1, NGF, and TUBB3, were all elevated in the treated marrow, suggesting that rejuvenating the LepR-positive population had ripple effects throughout the niche. H&E staining of major organs revealed no apparent histopathological abnormalities, though the authors note that systemic pharmacokinetics, biodistribution, immunogenicity, and long-term safety remain to be investigated.

To confirm that the therapy works by breaking the vicious cycle rather than through some unrelated mechanism, the team performed RNA sequencing on treated cells and found that cellular senescence, cell cycle, and p53 signaling pathways were significantly altered. In vivo nitric oxide probes injected into the marrow cavity confirmed elevated nitric oxide production in treated animals, and inductively coupled plasma analysis of cell lysates showed substantially higher magnesium levels. Critically, when the researchers added a nitric oxide inhibitor, a magnesium-depleting agent, or a ROS activator to cells isolated from treated mice, the senescent phenotype returned, with increased proportions of senescence-associated beta-galactosidase and P21-positive cells. This loss-of-function experiment provides direct evidence that the anti-aging effect depends on the nitric oxide, magnesium, and ROS axis. The authors acknowledge that the optimal therapeutic dosage may vary with the severity of senescence, and they suggest that integrating imaging modalities such as MRI, PET, and fluorescence imaging to enable spatiotemporally controlled release will be important for next-generation anti-aging nanomedicines. Validation in broader aging models and large-animal studies will be required before clinical translation, but the work establishes a compelling proof of concept that breaking a single molecular circuit in a key stem cell population can remodel an entire aging tissue.

Subject of Research: Aging and Regenerative Medicine

Article Title: Aged microenvironment-triggered nanoreactors rejuvenate senescent LepR + cells to remodel aged bone marrow

Article References: Li, K., Li, Z., Xue, Y., Liu, H., Guo, J., Zhang, X., Li, B., & Rui, Y. (2026). Aged microenvironment-triggered nanoreactors rejuvenate senescent LepR+ cells to remodel aged bone marrow. Materials Today Bio, 41, Article 103751. https://doi.org/10.1016/j.mtbio.2026.103751

Image Credits: AI Generated

DOI: 10.1016/j.mtbio.2026.103751

Keywords: aging, nanomedicine, bone marrow, stem cells, senescence, nanotechnology, Aged, microenvironment-triggered, nanoreactors, rejuvenate, senescent, LepR

The numbers tell a striking story. Among 63 evaluable patients, 81 percent achieved pain control without needing any additional radiation. Three in five patients reported relief within the first month of treatment, and by six months that figure had grown to four in five. Patient-reported pain reduction measured 66 percent four weeks after treatment, 64 percent at eight weeks, and an impressive 86 percent at six months. The median time to pain relief was 36 days, and the median duration of relief stretched to 148 days. Notably, outcomes were essentially identical whether patients received the dose in a single session or spread across two, offering flexibility in how clinics schedule care.

Multiple myeloma is a cancer of plasma cells, a type of white blood cell that resides in the bone marrow. As malignant plasma cells accumulate, they disrupt normal bone remodeling, carving out destructive lesions that cause deep, persistent pain, fractures, and a steep decline in quality of life. Bone disease is one of the defining complications of the illness, and painful lesions are among the most common reasons patients with myeloma are referred for radiation therapy. For many patients, these lesions multiply over time, meaning palliative radiation may be needed on several separate occasions throughout the course of the disease.

Despite how effective radiation can be for these lesions, patients are often referred late in their care, after symptoms have already worsened. The hesitation stems partly from concerns about damaging healthy bone marrow, which is already compromised in myeloma and is critical for producing blood cells. There are also practical hurdles: coordinating radiation sessions around systemic therapies such as chemotherapy, immunotherapy, and targeted agents can be logistically complicated, and clinicians worry that a course of radiation might force interruptions in drug treatment. The new trial directly addresses both concerns by demonstrating that far less radiation than conventionally used can still do the job.

Multiple myeloma is exceptionally sensitive to radiation, a property that allows lower doses to effectively treat painful lesions while limiting exposure to healthy marrow. The trial’s design drew on longstanding experience using ultra-low-dose radiation therapy for similarly radiosensitive lymphomas. Principal investigator Leslie Ballas, MD, FASTRO, a professor of radiation oncology at Cedars Sinai in Los Angeles, explained the underlying strategy: start with a dose sufficient to relieve pain but low enough to preserve bone marrow and leave room to add more radiation if needed. That flexibility, she noted, may help patients access radiation earlier in their disease course while keeping future treatment options open.

The prospective, single-arm phase 2 trial enrolled patients at seven institutions. Eligible participants had bone lesions that were painful but not causing spinal cord compression, pathologic fracture of a long bone, or other urgent complications requiring more aggressive intervention. Each patient received 4 Gy of radiation, either as one 4 Gy treatment or two treatments of 2 Gy each. For context, conventional palliative radiation courses for bone metastases often deliver considerably higher total doses across multiple fractions, making 4 Gy a genuinely ultra-low prescription by standard practice.

Researchers assessed pain response at four weeks, eight weeks, and six months using patient-reported Brief Pain Inventory scores alongside oral morphine equivalent dosing, applying international consensus criteria for palliative radiation therapy. The primary endpoint was patient-reported pain response at four weeks. Importantly, patients who did not achieve adequate pain control could receive additional radiation beginning four weeks after their first treatment, creating a response-adapted framework in which escalation was available but frequently unnecessary.

The escalation data proved particularly telling. Overall, only 19 percent of patients required a second course of radiation to the same site, delivered at a median of 71 days after the initial treatment. After reirradiation, the pain response rate reached 63 percent at four weeks, showing that the low-dose starting point did not compromise the effectiveness of follow-up treatment. Side effects across the trial were rare and mild: four patients experienced grade 1 or 2 fatigue, and one patient reported mild radiation-related skin changes. No serious toxicity attributable to the low dose was reported, reinforcing the safety profile that makes the approach attractive for earlier use.

For most patients, the initial low-dose treatment alone was sufficient to control symptoms. Ballas emphasized that four out of five patients did not need more radiation after the first course, a result she said demonstrates that the strategy can provide effective pain control without interrupting other treatments and with almost no side effects. The brevity of the regimen, one or two visits rather than a protracted series, also makes radiation easier to integrate with systemic therapy and may help preserve healthy bone marrow function over time. Because patients with myeloma often live for years while cycling through multiple lines of therapy, minimizing treatment burden and protecting marrow reserves carry growing clinical weight.

Expert response to the findings has been enthusiastic. Chelsea Pinnix, MD, PhD, FASTRO, ASTRO Education Council Chair and a radiation oncologist at the University of Texas MD Anderson Cancer Center, described the study as combining patient-reported outcomes with a practical, response-adapted treatment strategy, noting that many patients can experience meaningful pain relief with a very low initial dose of 4 Gy in one or two fractions. She said the results may help clinicians consider radiotherapy earlier in the course of care for patients with myeloma experiencing painful bone disease. Ballas echoed that hope, adding that even though the study was relatively small, the prospective data from multiple institutions show the approach is a practical and flexible strategy for routine clinical care. Next steps include testing whether some patients might benefit from low-dose radiation even earlier, before pain becomes severe, and identifying which lesions are most likely to respond, work that could eventually turn this gentle therapy from a late-stage rescue into a first-line comfort measure.

Subject of Research: Ultra-low-dose palliative radiation therapy for painful bone lesions in multiple myeloma

Article Title: Ultra-low-dose radiation therapy relieves bone pain from multiple myeloma

Article References: Ultra-low-dose radiation therapy relieves bone pain from multiple myeloma. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: multiple myeloma, radiation therapy, palliative care, bone lesions, clinical trial, phase 2, ASTRO, pain management, bone marrow, low-dose radiation, oncology, patient-reported outcomes

The researchers focused on RNA rather than DNA for several reasons. RNA is generally more indicative of recent microbial activity, since it is transcribed from active genes and degrades more quickly than DNA. In addition, a much larger portion of microbial genomes is transcribed into RNA, making it a richer analyte for detecting microbial presence. The team reasoned that these properties could make RNA a more sensitive and informative marker of circulating microbes than DNA, which had been the focus of earlier studies.

To conduct the analysis, the researchers used a large whole-transcriptome dataset from hundreds of patients with acute myeloid leukemia. The samples included blood and bone marrow specimens collected at diagnosis. The team applied stringent quality control measures to distinguish true microbial signals from artifacts, filtering out low-confidence classifications and removing taxa that were unlikely to be members of the human microbiome. They also compared their findings against healthy controls to ensure that the microbial signals were specific to leukemia patients.

The analysis revealed that bacterial RNA far outnumbered viral RNA in the samples, with bacterial reads dominating the circulating metatranscriptome. The researchers found that the overall microbial load varied considerably from patient to patient, and that this variation was not explained by differences in sample collection or processing. When they compared patients with high versus low microbial loads, they observed differences in the composition of the immune cell populations in the samples, suggesting a link between circulating microbes and the immune environment of the disease.

One of the most striking findings involved the relationship between microbial load and treatment response. The researchers found that patients with higher microbial loads tended to show differences in the expression of genes involved in immune pathways, including the complement cascade and the antibacterial response. They also observed that the abundance of specific microbial taxa correlated with the expression of genes involved in butyrate metabolism, a pathway that has been implicated in immune regulation and cancer progression.

The team also explored whether the microbial signals could predict response to specific therapies. They found that the abundance of certain taxa was associated with differences in the sensitivity of leukemia cells to a range of drugs, including agents that target the BCL-2 protein and other survival pathways. While the study did not establish a causal relationship between circulating microbes and drug response, the findings suggest that the circulating metatranscriptome may carry information relevant to therapeutic decision-making.

The researchers applied several statistical models to account for potential confounders, including differences in sequencing batch, age, and sample type. They also used permutation testing to assess the significance of their findings, ensuring that the observed associations were unlikely to arise by chance. The team emphasized that the study was exploratory in nature and that further work would be needed to validate the findings in independent cohorts.

The study has important implications for the field of cancer microbiome research. Earlier studies have reported microbial DNA in tumors and blood samples from cancer patients, but the field has been plagued by concerns about contamination and artifacts. The new study addresses these concerns by applying rigorous quality control measures and by focusing on RNA, which is less susceptible to contamination from environmental sources. The findings suggest that the circulating metatranscriptome may be a valuable and underexplored source of clinical information in leukemia.

The researchers also noted that their findings may have relevance beyond acute myeloid leukemia. The pathways implicated in the study, including immune regulation and butyrate metabolism, are involved in a range of cancers and inflammatory diseases. The team suggested that the circulating metatranscriptome may be a useful analyte in other cancers as well, and that further work should explore its potential in these settings.

The study represents an important step forward in the effort to understand the role of microbes in cancer. By focusing on RNA and by applying rigorous quality control measures, the researchers have provided a valuable resource for the field and have opened a new avenue for clinical investigation. The findings suggest that the circulating metatranscriptome may carry information relevant to treatment response and immune regulation, and that further work should explore its potential as a clinical tool in leukemia and beyond.

Subject of Research: Circulating microbial RNA in acute myeloid leukemia patients

Article Title: The circulating metatranscriptome in acute myeloid leukemia patients: an RNA-seq reanalysis

Article References: Nguyen, A. D. D., Kern, R., Dombrovski, T., & LaFramboise, T. (2026). The circulating metatranscriptome in acute myeloid leukemia patients: an RNA-seq reanalysis. Frontiers in Microbiomes, 5, Article 1903806. https://doi.org/10.3389/frmbi.2026.1903806

Image Credits: AI Generated

DOI: 10.3389/frmbi.2026.1903806

Keywords: acute myeloid leukemia, microbiome, metatranscriptome, RNA, treatment response, immune regulation, butyrate metabolism, cancer, blood, bone marrow, circulating, acute

MicroRNAs are short, evolutionarily conserved strands of non-coding RNA that do not make proteins themselves. Instead, they fine-tune gene expression by binding to messenger RNAs and blocking their translation or marking them for destruction. Because a single miRNA can regulate dozens of genes at once, these molecules serve as powerful master regulators of cellular behavior. In allergic diseases such as asthma, allergic rhinitis, and atopic dermatitis, patterns of miRNA expression are known to shift dramatically, reflecting both the changing cellular composition of inflamed tissues and the pathological state of individual cell types.

The research team, led by investigators at the Krefting Research Centre at the University of Gothenburg in Sweden, focused on interleukin-33 (IL-33), a so-called alarmin cytokine released by damaged airway epithelial cells. IL-33 is a central driver of type 2 immunity, the branch of the immune system that evolved to combat parasites but which, in modern environments, fuels allergic disease. Genome-wide association studies have repeatedly linked IL-33 signaling to allergic conditions, and the cytokine is known to activate type 2 innate lymphoid cells (ILC2s), enhance T helper 2 cell responses, and promote the development of eosinophils in the bone marrow by upregulating the IL-5 receptor alpha chain on committed progenitors.

To model this process, the researchers exposed C57BL/6 mice to recombinant murine IL-33 intranasally every other day for five days. The treatment triggered a dramatic influx of eosinophils into the bronchoalveolar lavage fluid, confirming that airway IL-33 alone is sufficient to drive systemic eosinophilic inflammation. Crucially, the bone marrow of these mice showed a corresponding increase in both immature and mature eosinophils, demonstrating that the airway signal had reached the primary site of eosinophil production and activated local maturation programs.

Using a combination of miRNA microarray, NanoString nCounter profiling, quantitative PCR, and a technique called PrimeFlow—which merges flow cytometry with single-cell miRNA detection—the team mapped miRNA expression in both the lungs and the bone marrow. The results revealed striking compartmentalization. In the lungs, IL-33 upregulated miRNAs previously implicated in type 2 immunity, including miR-155-5p, miR-223-3p, miR-21, and miR-210. In the bone marrow, by contrast, a larger subset of miRNAs was downregulated, including regulators of lymphoid effector cell differentiation such as miR-29a/c-3p, the miR-23∼27∼24 cluster, and miR-15a/b-5p.

Only two miRNAs, miR-378a-3p and miR-501-3p, were significantly altered in both compartments, and they moved in opposite directions: upregulated in the lungs but downregulated in the bone marrow. miR-378a-3p, which has been linked to IL-33 regulation, eosinophil differentiation, and poor bronchodilator responses in pediatric asthma, displayed a significant negative correlation between lung and bone marrow expression, hinting at a coordinated but tissue-specific regulatory role.

The most consistent hit across all profiling platforms was miR-150-5p, which was significantly downregulated in the bone marrow of IL-33-challenged mice. PrimeFlow analysis revealed that miR-150-5p is highly enriched in ILC2s and CD4-positive T cells but expressed at low levels in eosinophils and eosinophil progenitors. Although total bone marrow miR-150-5p decreased after IL-33 challenge, cell-specific levels within ILC2s and CD4-positive T cells remained unchanged, suggesting that the drop reflects the expanding population of eosinophils, which naturally carry little of this miRNA, rather than a direct suppression within lymphoid subsets.

Functional experiments showed that bone marrow ILC2s from IL-33-challenged mice produced significantly more IL-5 upon ex vivo restimulation than those from control animals, and expressed higher levels of the IL-33 receptor ST2. When the researchers used a synthetic miR-150-5p inhibitor in bone marrow cultures, they successfully knocked down the miRNA but did not observe changes in IL-5 or IL-10 production, indicating that miR-150-5p may not directly control cytokine output in this setting. However, RNA sequencing analysis of isolated ILC2s revealed that 44 conserved miR-150-5p target genes were actively modulated during both inflammatory and regulatory ILC2 activation states, suggesting a broader role in shaping ILC2 functionality.

Targeted mRNA profiling of the bone marrow further revealed that IL-33 modulated genes associated with eosinophil maturation and migration, including Csf2rb, a shared receptor subunit for IL-5 and GM-CSF, as well as Il13ra1 and Il4ra, which encode receptors for type 2 cytokines. Computational analysis using TargetScan Mouse 8.0 showed that predicted miR-223-3p target genes were downregulated in the bone marrow, and that expression of miR-19b-3p and miR-760-3p correlated significantly with their predicted targets, including Csf2rb, Ets1, and Casp3, providing mechanistic links between miRNA regulation and eosinophil biology.

The findings carry significant clinical implications. Severe eosinophilic asthma is characterized by persistent airway eosinophilia that correlates with disease severity and exacerbations, and while biologics targeting IL-5 or IL-4/IL-13 pathways are available, some patients exhibit residual tissue eosinophilia or paradoxical hypereosinophilia. The authors suggest that identifying miRNAs that control specific cellular trajectories during type 2 inflammation could lead to novel therapeutic strategies that selectively restrict bone marrow eosinophil egress or reprogram mature cells into a less inflammatory state, rather than systemically depleting the entire eosinophil pool. Although miRNA-directed therapeutics face delivery and safety challenges, the study provides a detailed molecular map that may guide future efforts to dampen excessive bone marrow eosinophilopoiesis in allergic disease.

Subject of Research: Exploration of miRNAs promoting eosinophilia and type 2 immunity

Article Title: Exploration of miRNAs promoting eosinophilia and type 2 immunity

Article References: Sayedali, H., Calvén, J., Boberg, E., Lässer, C., Dahlberg, F., Weidner, J., Malmhäll, C., Rådinger, M., & Johansson, K. (2026). Exploration of miRNAs promoting eosinophilia and type 2 immunity. Frontiers in Allergy, 7, Article 1968077. https://doi.org/10.3389/falgy.2026.1968077

Image Credits: AI Generated

DOI: 10.3389/falgy.2026.1968077

Keywords: microRNA, eosinophils, interleukin-33, type 2 immunity, asthma, bone marrow, ILC2, allergic inflammation, Exploration, miRNAs, promoting, eosinophilia

The study, led by Ananya Datta Mitra and colleagues in the Department of Pathology and Laboratory Medicine, assembles a collection of bone marrow specimens in which non-neoplastic histiocytic proliferations created genuine diagnostic dilemmas. These reactive expansions of macrophages can be driven by an extraordinarily diverse set of triggers, including mycobacterial, fungal, and viral infections, autoimmune and inflammatory disorders, lysosomal storage diseases such as Gaucher disease, hemophagocytic syndromes, drug effects, and cytokine activation associated with underlying malignancies. The morphologic consequences are equally varied: increased histiocytes with or without hemophagocytosis, granuloma formation, or accumulations of pigmented macrophages known as sea-blue histiocytes, often set against a backdrop of altered marrow cellularity. The danger, the authors emphasize, is that any of these patterns can be mistaken for histiocytic sarcoma, Langerhans cell histiocytosis, or marrow involvement by lymphoma or leukemia, with potentially serious consequences for the patient.

The first case in the series is perhaps the most technically striking. An elderly man in his seventies with metastatic non-small cell lung cancer, previously treated with multiple lines of chemotherapy, immune checkpoint inhibitors, and surgery, developed pancytopenia, a dangerous drop in all three blood cell lineages. His marrow showed features consistent with a myelodysplastic neoplasm with low blasts arising after cytotoxic therapy. But the core biopsy also revealed a focal aggregate of epithelioid cells with enlarged, pleomorphic nuclei and abundant cytoplasm. Given his history of metastatic carcinoma, the immediate concern was tumor spread to the marrow. Immunohistochemistry complicated matters further: the cells stained strongly for pan-cytokeratin with a characteristic dot-like, paranuclear pattern, a staining signature usually associated with epithelial cells. Yet the same cells expressed CD163, a robust histiocytic marker, and were negative for TTF-1, CAM5.2, Napsin A, and other carcinoma markers, as well as for myeloid and stem cell markers.

The conclusion was remarkable: aberrant cytokeratin expression in bone marrow macrophages. Cytokeratin positivity with a dot-like pattern has been described before in hematopoietic neoplasms, including myelodysplastic syndrome, acute myeloid leukemia, and myeloid sarcoma, where it is a recognized pitfall. Similar aberrant expression has been documented in tissue macrophages in prior studies, but never before in bone marrow macrophages. The practical lesson is stark. In a patient with a known carcinoma undergoing marrow evaluation for cytopenias, reliance on a single cytokeratin stain could easily lead to a false diagnosis of metastatic disease, triggering inappropriate oncologic treatment. The authors argue that a comprehensive immunohistochemical panel, including histiocytic markers such as CD163 and CD68 alongside lineage-specific epithelial and hematopoietic markers, is essential before any such conclusion is drawn.

The second case shifts the focus to metabolic disease. A teenage boy with a congenital neurodevelopmental disorder presented with acute hypoxemic respiratory failure from a viral infection complicated by bacterial pneumonia, and was found to have profound pancytopenia. CT imaging revealed massive splenomegaly measuring over thirty centimeters with hypoenhancing lesions, raising fears of lymphoma. The bone marrow, however, was nearly one hundred percent cellular and packed with large histiocytes whose cytoplasm had a distinctive crinkled tissue-paper appearance, the morphologic hallmark of Gaucher cells. Rapid trio whole genome sequencing identified biallelic pathogenic variants in the GBA1 gene, one inherited from each parent, and biochemical testing showed deficient beta-glucocerebrosidase activity alongside markedly elevated glucosylsphingosine. The diagnosis was type 1 Gaucher disease, and the ominous splenic lesions were in fact Gaucheromas, collections of storage-laden macrophages characteristic of the disease rather than malignancy.

This case carries an important subtlety: the pitfall of pseudo-Gaucher cells. In hematologic malignancies such as chronic myeloid leukemia, myelodysplastic syndromes, Hodgkin lymphoma, and multiple myeloma, macrophages overwhelmed by debris from rapid cell turnover can acquire a nearly identical tissue-paper morphology at light microscopy. Distinguishing true from pseudo-Gaucher cells cannot rest on enzyme assays alone, since demonstrating deficient beta-glucocerebrosidase activity confirms Gaucher disease, but iron staining offers a useful clue, often positive in true Gaucher cells and typically absent or faint in their mimics. The clinical background, a known storage disorder versus a state of high cell turnover, remains decisive. The authors also caution against diagnostic anchoring: the patient’s neurological findings, including congenital hypotonia and developmental delay, could not be explained by type 1 Gaucher disease and reflect a separate, still-unresolved genetic condition, a reminder that not every finding in a complex patient belongs to a single diagnosis.

The third case introduces crystal-storing histiocytosis, a rare phenomenon in which histiocytes accumulate crystallized immunoglobulin within their lysosomes. A man in his sixties with progressive fatigue and a femoral neck stress fracture was found to have monoclonal gammopathy of undetermined significance, with a small IgG lambda protein in his serum. His hypocellular marrow contained numerous histiocytes filled with irregular, non-polarizing crystalline inclusions, and remarkably, similar crystals were visible within the plasma cells themselves. Immunohistochemistry confirmed that the crystals stained for IgG and lambda, matching the monoclonal protein, while IgD and kappa stains were negative and Congo red excluded amyloid. The pathogenesis is thought to involve overproduction or structural alteration of immunoglobulins that impairs lysosomal degradation, leading to intracellular crystallization. Prior mass spectrometric analysis of stored proteins in one reported case revealed amino acid substitutions hypothesized to disrupt hydrophobic packing of the light chain, suggesting that conformational changes derail normal protein degradation. Because the crystal-laden histiocytes can dominate the marrow and conceal the underlying plasma cell or lymphoplasmacytic disorder, recognition of this entity is critical for directing the appropriate workup.

The fourth case tackles one of hematology’s most contested morphologic signs: hemophagocytosis, the engulfment of blood cells by macrophages. A man in his fifties with severe aplastic anemia and tiny paroxysmal nocturnal hemoglobinuria clones, awaiting an allogeneic stem cell transplant after failing immunosuppressive therapy, was hospitalized for gangrenous cholecystitis, during which a markedly elevated CMV viral load was detected and later resolved spontaneously. His pre-transplant marrow biopsy unexpectedly showed prominent hemophagocytic histiocytes ingesting granulocytes and nucleated erythroid precursors. Expert review excluded Langerhans cell histiocytosis, Rosai-Dorfman disease, and Erdheim-Chester disease through a negative immunophenotypic profile, including absent CD1a, S100, langerin, Factor XIIIa, and BRAF V600E expression. Laboratory results, including a ferritin of 7,757 ng/mL and elevated soluble CD25, raised concern for hemophagocytic lymphohistiocytosis under the HLH-2004 and 2024 revised criteria, yet the patient had no fever or organomegaly, and a repeat marrow two months later showed no hemophagocytosis at all.

The ambiguity is the point. As the authors note, hemophagocytosis is a hallmark of HLH but a nonspecific finding that appears in infectious, inflammatory, autoimmune, and neoplastic conditions. Isolated marrow hemophagocytosis has limited sensitivity and specificity for HLH in adult studies, and the North American Consortium for Histiocytosis guidelines explicitly state that it is not specific to, or essential for, the diagnosis, though certain subtypes, particularly phagocytosis of multiple nucleated cells including granulocytes, are more strongly associated with true HLH than simple erythrophagocytosis. The overlap between aplastic anemia and HLH compounds the difficulty, since both can produce profound cytopenias and hypocellular marrows through immune-mediated mechanisms, and reactive hemophagocytosis can appear in marrow failure syndromes without fulfilling formal diagnostic criteria.

The final two cases round out the spectrum. A man in his forties with advanced HIV and a CD4 count below twenty cells per cubic millimeter underwent marrow biopsy for unexplained anemia and imaging findings suggestive of disseminated disease. The marrow was nearly acellular, containing poorly formed granulomas without necrosis, and special stains revealed histiocytes stuffed with rod-shaped organisms that stained with both PAS and acid-fast stains, confirming disseminated Mycobacterium avium complex infection. In severely immunocompromised patients lacking robust CD4 T-cell responses, well-formed granulomas are uncommon; instead, macrophages distended with organisms and minimal inflammation are typical, and the mild reticulin fibrosis seen here is a recognized reactive finding rather than primary myelofibrosis. In the sixth case, a sixteen-year-old boy with a white blood cell count exceeding 425 billion per liter and the t(9;22) translocation diagnostic of chronic myeloid leukemia also harbored scattered sea-blue histiocytes and a pseudo-Gaucher cell, secondary manifestations of massive myeloid turnover rather than a storage disorder. Together, the series argues that morphology alone is rarely sufficient: only the systematic integration of clinical history, laboratory data, immunohistochemistry, microbiology, and molecular testing, often within a multidisciplinary team, allows pathologists to separate these reactive mimics from true histiocytic neoplasia and spare patients the consequences of overdiagnosis.

Subject of Research: Reactive non-neoplastic histiocytic proliferations in bone marrow and their distinction from histiocytic neoplasms

Article Title: Non-neoplastic histiocytic proliferations in bone marrow: a case series of uncommon morphologic findings

Article References: Ha, M., Parsazad, S., Dang, L. T., Vali Betts, E., Dwyre, D. M., & Datta Mitra, A. (2026). Non-neoplastic histiocytic proliferations in bone marrow: a case series of uncommon morphologic findings. Frontiers in Hematology, 5, Article 1939019. https://doi.org/10.3389/frhem.2026.1939019

Image Credits: AI Generated

DOI: 10.3389/frhem.2026.1939019

Keywords: bone marrow, histiocytes, macrophages, Gaucher disease, hemophagocytic lymphohistiocytosis, crystal-storing histiocytosis, cytokeratin, Mycobacterium avium complex, chronic myeloid leukemia, sea-blue histiocytes, pathology, differential diagnosis

The team, led by immunologist Susanna Mandruzzato of the Veneto Institute of Oncology and the University of Padua, focused on a family of cells known as myeloid-derived suppressor cells, or MDSCs. These immature cells of the myeloid lineage, which includes precursors of granulocytes and monocytes, are best known from cancer research, where they accumulate in tumors and suppress the T cell responses that would otherwise attack malignant tissue. But MDSCs are not exclusive to cancer. They expand during infection, sepsis, and chronic inflammatory diseases, and recent work has implicated them in bone pathologies ranging from osteoporosis to inflammatory arthritis, where they can even act as dysfunctional osteoclast progenitors that contribute directly to bone destruction.

What made the question urgent for osteoarthritis is the disease’s peculiar inflammatory profile. Hip osteoarthritis is not an autoimmune condition like rheumatoid arthritis, yet it features a persistent, smoldering inflammation marked by elevated levels of cytokines such as IL-1β, TNF-α, and IL-6 in the joint environment. This inflammatory milieu promotes synovial activation, disrupts subchondral bone remodeling, enhances osteoclast formation, and accelerates cartilage breakdown through catabolic enzymes like metalloproteinases. In parallel, aging itself drives a phenomenon called inflammaging, a chronic low-grade inflammatory state that biases hematopoietic stem cells in the bone marrow toward producing myeloid cells at the expense of lymphoid lineages. The Padua team asked whether these two forces, aging and disease-associated inflammation, converge in the bone marrow of osteoarthritis patients.

To find out, the researchers collected fresh bone marrow aspirates from 13 patients undergoing total hip arthroplasty for osteoarthritis and 13 patients undergoing surgery for proximal femoral fracture, all recruited at the University-Hospital of Padova. The samples were drawn from the medullary canal of the femur during the earliest stage of surgical preparation, before any broaching of the canal, ensuring that the cellular composition reflected the living marrow environment. Patients with active malignancies, autoimmune diseases, infections, or hematological disorders were excluded. The two cohorts were not identical: the fracture patients were, on average, older than the osteoarthritis group, a difference the authors acknowledge as a potential confounder, but it makes the direction of their key finding all the more remarkable.

Using multiparametric flow cytometry, the team quantified the myeloid and lymphoid compartments in each sample. Despite being younger on average, the osteoarthritis patients showed a significantly higher proportion of myeloid cells in their bone marrow than the fracture patients, a difference that reached statistical significance at p = 0.0036. Lymphoid cell frequencies, by contrast, did not differ between the groups. This selective myeloid enrichment could not be explained by advanced age alone, suggesting that the chronic inflammation associated with hip osteoarthritis actively amplifies the age-related skewing of hematopoiesis toward the myeloid lineage. In other words, the disease may be superimposing its own inflammatory signature on top of the normal immunological remodeling of aging.

The researchers then drilled down into the maturation stages of these myeloid cells, using the surface markers CD11b and CD16 to distinguish granulocytic precursors at different points along their developmental path. Here a specific subset stood out. Cells with a CD11b-positive, CD16-low phenotype, which correspond to metamyelocytes, an intermediate stage of granulocyte maturation, were significantly enriched in the osteoarthritis samples, both when analyzed directly ex vivo and after the cells were cultured for four days with the growth factors G-CSF and GM-CSF to drive myeloid expansion. After cytokine stimulation, this metamyelocyte-like fraction reached a median of 31.5 percent in the osteoarthritis cultures versus 20.3 percent in the fracture cultures, a persistent difference indicating that the osteoarthritic marrow environment favors the production of these intermediate myeloid cells even under standardized laboratory conditions.

The functional heart of the study, however, lay in the suppressive capacity of these cells. In earlier work, the same group had established that the immunosuppressive power of bone marrow-derived MDSCs resides almost entirely in the most immature fraction, a CD11b-negative or low, CD16-negative population with promyelocyte-like features. In the new experiments, the researchers co-cultured these myeloid fractions with T cells from healthy donors that had been labeled with a fluorescent proliferation dye and activated with anti-CD3 and anti-CD28 antibodies. The result was unambiguous: only the immature fraction significantly inhibited T cell proliferation, in both osteoarthritis and fracture samples, while the more differentiated CD11b-positive fractions and unsorted bulk cultures had little or no effect. Suppression was accompanied by a marked downregulation of CD3 expression on the T cell surface, a well-established indicator of impaired T cell receptor signaling.

Crucially, the degree of suppression did not differ between the two patient groups. Even though the osteoarthritic marrow was more myeloid-skewed and richer in intermediate metamyelocyte-like cells, the core immunoregulatory machinery of the immature MDSC fraction remained intact and functionally equivalent to that of the fracture donors. This extends the team’s earlier observation that MDSC suppressive function is preserved during aging, from comparisons between pediatric and elderly donors, into the specific context of chronic osteoarthritis-associated inflammation. Morphological analysis by May-Grünwald-Giemsa staining of sorted populations confirmed the phenotypic story: the suppressive CD11b-low fraction showed uniform promyelocyte-like morphology with prominent nucleoli, while the more mature fractions contained myelocytes, metamyelocytes, band cells, and even macrophage-like cells with cytoplasmic vacuolation.

The authors are careful to frame these findings as an association rather than proof of a disease-specific mechanism. The fracture cohort, they note, is not a healthy control group; femoral fracture triggers its own acute, time-limited inflammatory response, and no ethically defensible route exists for harvesting bone marrow from truly healthy elderly volunteers. Differences in age and sex distribution between the cohorts, along with the modest sample size, particularly for the correlation analyses, further limit statistical power. The study also did not assess whether the osteoarthritic MDSCs can differentiate into osteoclasts, a question of obvious importance given evidence from breast cancer and inflammatory arthritis models that MDSCs can drive pathological bone resorption while simultaneously suppressing T cells. Whether the same dual function operates in hip osteoarthritis remains an open question for future work.

Even with those caveats, the study reframes osteoarthritis as a systemic immunological condition rather than a purely local joint disease. If the bone marrow of osteoarthritis patients is chronically pumping out expanded myeloid populations, those cells could feed the synovial inflammation, cartilage degradation, and aberrant subchondral bone remodeling that characterize disease progression, while their preserved suppressive activity simultaneously holds immune activation in check. The authors suggest this balance between heightened myelopoiesis and conserved immunoregulation may define the distinctive low-grade, persistent inflammatory state of osteoarthritis, setting it apart from overt autoimmune arthritis. It also raises a therapeutic possibility worth taking seriously: modulating myeloid responses, rather than broadly suppressing the immune system, might one day offer a way to slow joint degeneration in the elderly without compromising host defense. For a disease affecting hundreds of millions of people worldwide and currently treatable only with pain management and, ultimately, joint replacement, that would be a genuinely transformative shift in perspective.

Subject of Research: Bone marrow myeloid cell remodeling and myeloid-derived suppressor cell function in elderly patients with hip osteoarthritis

Article Title: Bone marrow myeloid skewing and preserved immunoregulation in hip osteoarthritis of elderly patients

Article References: Tushe, A., Binatti, E., Belluzzi, E., Pozzuoli, A., Francescato, S., Buldini, B., Biz, C., Ruggieri, P., & Mandruzzato, S. (2026). Bone marrow myeloid skewing and preserved immunoregulation in hip osteoarthritis of elderly patients. GeroScience. https://doi.org/10.1007/s11357-026-02578-0

Image Credits: AI Generated

DOI: 10.1007/s11357-026-02578-0

Keywords: hip osteoarthritis, bone marrow, myeloid-derived suppressor cells, inflammaging, myelopoiesis, immunosenescence, T cell suppression, osteoimmunology, flow cytometry, granulopoiesis, chronic inflammation, GeroScience

The stakes are considerable. Hematopoietic stem and progenitor cells, collectively known as HSPCs, sit at the top of the blood cell hierarchy, and their sustained function underpins everything from oxygen transport to immune defense. As organisms age, HSPCs lose their regenerative power and their output skews toward the myeloid lineage, the branch that produces granulocytes and monocytes, at the expense of lymphoid cells. This myeloid skewing is accompanied by immunosenescence, the progressive deterioration of immune function that raises the incidence of cancer, cardiovascular disease, neurodegenerative disorders, and autoimmune conditions in the elderly. Previous work has shown that replacing aged HSCs with young-donor cells extends median lifespan and lowers mortality hazard in aged mice, underscoring how central the aging of this compartment is to the healthspan and lifespan of the whole organism.

ANGPTL8, also called betatrophin, RIFL, or TD26, is a secreted glycoprotein produced mainly by the liver and adipose tissue. Its expression rises after caloric intake and falls during fasting, tying it closely to feeding rhythms and to glucose and lipid metabolism. The protein is a physiological inhibitor of lipoprotein lipase, and its overexpression markedly elevates plasma triglyceride levels. Prior studies from the same group had already connected ANGPTL8 to degenerative processes: serum levels were elevated in patients with aortic dissection, the protein correlated with the grade of intervertebral disc degeneration, and in mice it promoted liver fibrosis and hepatocarcinogenesis. A clue to the new direction came from RNA sequencing of liver tissue, which unexpectedly revealed altered expression of numerous genes involved in hematopoietic differentiation when ANGPTL8 was knocked out.

To test whether ANGPTL8 influences systemic aging, the team generated ANGPTL8 knockout mice and compared them with wild-type littermates under both normal chow and high-fat diets over periods of 10 and 20 months. Quantitative PCR, Western blotting, and immunohistochemistry showed that the expression of the senescence markers P53, P21, and P16, along with components of the senescence-associated secretory phenotype, was significantly lower in the liver, lung, and spleen of knockout animals. Functional tests reinforced the molecular picture: knockout mice performed better in the Morris water maze, crossing the former platform location more often and locating it faster, and micro-CT scans of the femur revealed higher bone mineral density and bone volume fraction, suggesting protection against osteoporosis. Notably, under a high-fat diet, which stimulates ANGPTL8 secretion, knockout mice survived significantly longer than wild-type controls.

The heart of the study, however, lay in the bone marrow. Flow cytometry showed that the proportion of long-term hematopoietic stem cells, defined by the surface phenotype Lin-negative c-Kit-positive Sca-1-positive CD48-negative CD150-positive, was significantly greater in knockout mice across diet and age conditions. Cell cycle analysis revealed an increased fraction of G1-phase cells among c-Kit-positive HSPCs, indicating enhanced quiescence, a state considered essential for preserving stemness and lifelong self-renewal. In knockout HSPCs, the researchers also observed reduced levels of the cell polarity protein Cdc42 and the DNA damage marker phosphorylated gamma-H2AX, both closely associated with HSPC aging. Mitochondrial measurements added a metabolic dimension: reactive oxygen species content was markedly lower, and JC-1 probing of mitochondrial membrane potential showed less depolarization, consistent with healthier mitochondria in the absence of ANGPTL8.

Because HSPCs themselves do not express ANGPTL8, the protein must reach them through the circulation, secreted from liver and fat tissue and entering the bone marrow cavity from the blood. To model this, the team cultured sorted c-Kit-positive HSPCs with recombinant ANGPTL8 at 600 nanograms per milliliter for four days. The treated cells showed a dose-dependent rise in aging-related proteins, an increased proportion of beta-galactosidase-positive cells, a hallmark of senescence, downregulation of the proliferation marker Ki67, and elevated expression of P53, P21, P16, and SASP genes. The total number of HSPCs declined after treatment, and the cells shifted toward myeloid differentiation, producing more CD11b-positive and CD14-positive cells. Complementary assays of colony formation showed that HSPCs from knockout mice generated fewer myeloid clones, while their bone marrow contained fewer common myeloid progenitors and more common lymphoid progenitors than wild-type controls, together indicating that ANGPTL8 aggravates the myeloid bias characteristic of hematopoietic aging.

Functional consequences were tested through transplantation. Bone marrow cells from knockout or wild-type donors were injected into lethally irradiated BALB/c recipients, and early hematopoietic regeneration was assessed 15 days later. Recipients of knockout marrow showed significantly higher proportions of donor-derived hematopoietic cells, LSK HSPCs, lymphoid cells, myeloid cells, and granulocytes in both bone marrow and spleen. Conversely, when wild-type HSPCs were pre-treated with recombinant ANGPTL8 before transplantation into irradiated C57BL/6 recipients, the proportions of total hematopoietic cells, LSK cells, myeloid cells, and granulocytes were significantly reduced in recipient marrow, and lymphoid, myeloid, and granulocytic populations were diminished in the spleen. In short, exposure to ANGPTL8 impaired the regenerative and engraftment capacity of HSPCs, while its absence enhanced it.

The mechanistic thread runs through the PI3K/AKT signaling pathway, a canonical regulator of cell survival, growth, and aging. RNA sequencing of knockout and wild-type HSPCs identified the PI3K/AKT pathway as the most enriched set of differentially expressed genes, with knockout mice showing significantly upregulated pathway activity. Western blotting confirmed that the ratios of phosphorylated to total PI3K, AKT, and the downstream kinase mTOR were all elevated in knockout HSPCs and bone marrow cells, and reduced in cells treated with recombinant ANGPTL8 in vitro. Crucially, a PI3K activator, YS-49, reversed the senescence effects of recombinant ANGPTL8, lowering the percentage of beta-galactosidase-positive cells, dampening the expression of age-related molecules, and correcting the myeloid differentiation bias. This rescue experiment establishes the pathway as the functional mediator of ANGPTL8’s pro-aging action in HSPCs.

The final piece identified the receptor. Paired immunoglobulin-like receptor B, or PirB, the mouse ortholog of human LILRB2, is known to bind several angiopoietin-like proteins and is highly expressed on the HSPC membrane. Co-immunoprecipitation demonstrated that recombinant ANGPTL8 directly interacts with PirB on HSPCs, and treatment with the recombinant protein increased PirB expression. Recombinant PirB alone reduced phosphorylation of PI3K and AKT, while knocking down PirB with two distinct siRNAs not only raised PI3K/AKT phosphorylation on its own but also blocked the inhibitory effect of recombinant ANGPTL8. The authors note that PirB has independently been implicated in aging of the nervous system, where it is upregulated in the aged hippocampus and represses the PI3K/AKT/mTOR axis, suggesting a conserved role for this receptor in tissue aging that now extends to the blood-forming system.

The work carries clear translational implications, though the authors are careful about its limits. Because ANGPTL8 secretion rises after eating and caloric restriction is among the most effective anti-aging interventions in animal models, reducing ANGPTL8 through dietary approaches or direct pharmacological targeting may represent promising strategies to alleviate hematopoietic aging. The protein’s dual role in lipid metabolism adds another layer, since triglyceride accumulation is a prominent lipidomic signature of human aging and impaired lipoprotein lipase function has been shown to damage the HSPC compartment. The team acknowledges that HSPC subpopulation heterogeneity remains incompletely characterized and that the PirB mechanism, while supported by in vitro rescue and knockdown experiments, will require conditional knockout models and competitive transplantation assays for full in vivo validation. Even so, the identification of a circulating, diet-responsive metabolic protein that ages blood stem cells through a defined receptor-pathway axis offers a concrete new target in the effort to keep the aging immune system younger for longer.

Subject of Research: The role of ANGPTL8 in inducing senescence of hematopoietic stem and progenitor cells via PirB-mediated inhibition of PI3K/AKT signaling

Article Title: ANGPTL8 induces the aging of hematopoietic stem/progenitor cells

Article References: Chen, M., Zhang, M., Mei, H., Bai, X., Wang, X., Tang, Y., Jiang, H., Zhang, L., Zhou, C., & Yuan, Y. (2026). ANGPTL8 induces the aging of hematopoietic stem/progenitor cells. Biogerontology, 27(5), Article 174. https://doi.org/10.1007/s10522-026-10517-x

Image Credits: AI Generated

DOI: 10.1007/s10522-026-10517-x

Keywords: ANGPTL8, hematopoietic stem cells, aging, cellular senescence, PI3K/AKT pathway, PirB, myeloid skewing, immunosenescence, SASP, bone marrow, mitochondrial ROS, caloric restriction

The research, conducted by a team at Mashhad University of Medical Sciences in Iran and published in the journal Molecular Biology Reports, examined bone marrow samples from 40 children who had been newly diagnosed with acute myeloid leukemia, one of the most aggressive cancers of the blood and bone marrow. The investigators compared the expression levels of two genes, BMAL1 and WEE1, against samples from 20 non-malignant control subjects. BMAL1, also known by its alternate name ARNTL, is widely regarded as the engine of the molecular circadian clock, forming a transcriptional complex that drives rhythmic gene expression throughout the body. WEE1, by contrast, is a kinase that acts as a gatekeeper at the G2/M checkpoint of the cell cycle, holding cells back from entering mitosis when their DNA is damaged or replication is incomplete.

The results were unambiguous. Using real-time quantitative PCR to measure messenger RNA levels, the team found that both genes were expressed at significantly lower levels in the leukemic samples than in the healthy controls, with statistical significance reaching a P value of less than 0.001. The magnitude of the difference was substantial: relative expression of BMAL1 in the patients’ bone marrow was just 0.18-fold that of the control group, while WEE1 expression stood at 0.31-fold. In other words, the core clock gene had been reduced to less than a fifth of its normal activity, and the cell cycle checkpoint kinase to less than a third.

Perhaps the most intriguing finding emerged when the researchers looked at how gene expression related to clinical measurements. BMAL1 expression showed a significant negative correlation with both white blood cell count and blast percentage, the proportion of immature, leukemic cells in the bone marrow. The correlation coefficients were -0.440 for white blood cell count, with a P value of 0.004, and -0.418 for blast percentage, with a P value of 0.007. This means that the more aggressive the disease appeared by standard hematological measures, the more profoundly the circadian clock gene was suppressed. WEE1 expression, in contrast, showed no significant correlation with any of the hematological parameters evaluated, including white blood cell count, hemoglobin, platelet count, and blast percentage.

To understand why these findings matter, it helps to appreciate how deeply the circadian clock and the cell cycle are intertwined. The clock operates through a transcription-translation feedback loop: BMAL1 pairs with CLOCK to activate expression of Period and Cryptochrome genes, whose protein products later feed back to inhibit BMAL1-CLOCK activity, creating an oscillation with a period of roughly 24 hours. Crucially, many of the genes controlled by this loop are involved in cell division. Landmark work published in Science in 2003 showed that the clock directly times cell division in vivo, and subsequent studies demonstrated that BMAL1 regulates the expression of p21, a key inhibitor of cell proliferation. When BMAL1 activity collapses, this timing coordination is lost, and cells may divide without the temporal safeguards that normally restrain them.

WEE1 sits at the intersection of this crosstalk. The kinase phosphorylates and inhibits CDK1, the master driver of mitotic entry, thereby enforcing the G2/M checkpoint that gives cells time to repair DNA damage before dividing. Loss of WEE1 function is known to produce genomic instability, and experiments in mice have shown that WEE1 deficiency leads to hyperactivation of the APC/C complex, chromosomal abnormalities, and ultimately carcinogenesis. At the same time, WEE1 has become a major target in cancer drug development, because many tumors become dependent on WEE1-mediated checkpoint control to survive the DNA damage inflicted by chemotherapy. WEE1 inhibitors are currently being explored in clinical trials across a range of malignancies, and prior work has suggested that WEE1 and PARP-1 play critical roles in the treatment of myelodysplastic syndrome and acute myeloid leukemia.

The downregulation of both genes in pediatric AML therefore paints a coherent, if preliminary, mechanistic picture. A silenced BMAL1 could mean that the leukemic cells have lost clock-driven control of proliferation and DNA damage responses, while reduced WEE1 might reflect a breakdown of checkpoint integrity that allows genetically damaged cells to progress through the cycle. It is worth noting, however, that the relationship between BMAL1 and cancer is not simple. Some studies have found that BMAL1 can actually accelerate certain tumors; one 2023 investigation reported that the clock protein promotes acute myeloid leukemia progression by inhibiting ferroptosis, a form of regulated cell death, through the EBF3/ALOX15 axis. In other cancers, including pancreatic, colorectal, and tongue squamous cell carcinoma, BMAL1 appears to act as a tumor suppressor, and its loss promotes growth and drug resistance. The new pediatric AML data, showing that lower BMAL1 tracks with higher tumor burden, leans toward the tumor-suppressive interpretation in this context, but the authors are careful to frame the finding as suggestive of a role rather than proof of one.

The study also fits into a broader literature on clock gene disruption in blood cancers. Researchers have previously documented downregulation of circadian genes in chronic myeloid leukemia, where altered methylation patterns of the PER3 gene have been observed, and in chronic lymphocytic leukemia, where both clock genes and clock-controlled cell cycle genes show deregulated expression. More recently, the circadian clock circuitry has been shown to modulate the activity of leukemia-initiating cells in T-cell acute lymphoblastic leukemia, and BMAL1 and CLOCK expression patterns have been examined as potential diagnostic markers in multiple myeloma. Animal work adds further weight to the connection: disrupting the light-dark cycle in mice has been shown to impair the hematopoietic function of the bone marrow, the very tissue from which leukemia arises.

For clinicians and researchers, the immediate value of the study lies in its potential biomarker implications. Because BMAL1 expression correlated inversely with white blood cell count and blast percentage, it is conceivable that measuring clock gene activity could eventually help gauge disease burden or track response to therapy in pediatric AML, a disease in which risk stratification remains a major clinical challenge. The authors also point toward therapeutic possibilities, noting that the significant downregulation of BMAL1 and WEE1 suggests that disrupted circadian and cell cycle regulatory pathways may contribute to the pathogenesis of the disease. The emerging field of chronotherapy, which seeks to time drug administration to the patient’s internal rhythms to maximize efficacy and minimize toxicity, could also be informed by a better understanding of how the clock is rewired in leukemic cells.

Significant caveats remain. The study involved a relatively modest sample of 40 patients from a single center, and it measured messenger RNA rather than protein levels, leaving open the question of whether the observed transcriptional changes translate into altered protein function. Correlation does not establish causation, and it is not yet clear whether BMAL1 suppression drives leukemic progression or is merely a consequence of it. The authors note that the data supporting the findings are available from the corresponding author upon reasonable request, and the work was carried out under the ethical oversight of Mashhad University of Medical Sciences with written informed consent from the parents or legal guardians of all pediatric participants. Follow-up studies with larger cohorts, longitudinal sampling, and functional experiments in leukemic cell models will be needed to determine whether restoring clock gene activity could one day form part of a therapeutic strategy. For now, the message is clear and quietly profound: the machinery that tells our cells what time it is may also help decide whether they stay healthy, and in the bone marrow of children with acute myeloid leukemia, that machinery appears to have fallen silent.

Subject of Research: Dysregulation of the circadian clock gene BMAL1 and the cell cycle regulator WEE1 in pediatric acute myeloid leukemia

Article Title: Dysregulation of circadian clock gene BMAL1 and cell cycle regulator WEE1 in pediatric AML

Article References: Oraei Sajjadi, K., Ayatollahi, H., Sheikhi, M., & Ahmadi, M. H. (2026). Dysregulation of circadian clock gene BMAL1 and cell cycle regulator WEE1 in pediatric AML. Molecular Biology Reports, 53(1), Article 1624. https://doi.org/10.1007/s11033-026-12812-9

Image Credits: AI Generated

DOI: 10.1007/s11033-026-12812-9

Keywords: acute myeloid leukemia, BMAL1, WEE1, circadian clock, cell cycle, pediatric cancer, gene expression, bone marrow, G2/M checkpoint, hematologic malignancy, chronotherapy, biomarker

The team, led by Yuman Wang and Teding Chang, assembled publicly available and newly generated datasets spanning the lung, heart, brain, vasculature, peripheral blood, intestine, kidney, and liver. After quality control and integration using reciprocal principal component analysis, the atlas comprised 66 samples and 256,949 cells. The compositional analysis revealed a striking pattern: neutrophil abundance rose markedly in several aged tissues. In the liver, the proportion of neutrophils among captured cells climbed from 0.75 percent in young mice to 5.26 percent in old ones; in the lung it rose from 0.88 to 4.14 percent; in vascular tissue from 1.05 to 3.68 percent; and in the intestine from 1.22 to 3.57 percent. The brain, shielded by the blood–brain barrier, showed no comparable increase.

These numbers were not artifacts of sequencing. Immunofluorescence staining for CD11b and myeloperoxidase confirmed dense neutrophil infiltration in aged lung, intestine, vasculature, and liver, while flow cytometry of bone marrow revealed a higher proportion of neutrophils in aged animals. A Bayesian compositional method called scCODA, which treats each biological sample as the unit of inference, independently supported a credible age-associated increase in neutrophil abundance in the liver, with a log2 fold change of 2.61 and an inclusion probability of 0.968.

Functionally, the aged neutrophils looked different at the molecular level. Pseudobulk differential expression analysis, which aggregates cells by sample to avoid inflating statistical significance, identified 26 genes upregulated in neutrophils from aged mice and 985 enriched in young ones. Gene set enrichment showed that glycolysis and reactive oxygen species pathways were activated in the aged cells, while TNF-α and interferon-λ signaling dominated in young ones. When the researchers isolated bone marrow neutrophils and cultured them for four hours, cells from aged mice died more readily and formed more neutrophil extracellular traps—web-like structures of DNA and antimicrobial proteins that, when deployed excessively, can damage surrounding tissue.

The most provocative experiments involved conditioned medium. When culture fluid from aged neutrophils was applied to mouse vascular smooth muscle cells and hepatocytes, both cell types showed increased beta-galactosidase activity, a classic marker of cellular senescence, along with elevated expression of matrix metalloproteinases and senescence-associated proteins such as P16 and P21. Quantitative PCR further revealed increased expression of senescance-associated secretory phenotype genes, including Il6, Tnf, and Ifn, in the exposed cells. In other words, factors released by aged neutrophils appeared to nudge tissue cells toward a stress-associated, inflammatory state.

To dissect neutrophil heterogeneity, the team re-clustered 5,210 neutrophils into 16 transcriptionally distinct subtypes, ranging from TNF-α-producing inflammatory cells to complement-associated, IL-6-expressing, E2F-driven, and unfolded-protein-response states. Several subtypes were preferentially enriched in aged mice, including Neu05-Complement, Neu06-IL6, and Neu08-E2F, while Neu01-TNFA and Neu04-Myc characterized young animals. Maturation scoring suggested that Neu05 and Neu08 resembled early marrow-emigrant neutrophils, mapping closest to the preNeu developmental stage, hinting that aged tissues may be receiving a wave of immature, hyper-responsive cells.

Cross-tissue co-occurrence analysis added a systems-level dimension. The researchers identified seven cellular modules whose member cell types varied in concert across samples. One module, CM3, was the most neutrophil-enriched and contained endothelial cells and fibroblasts alongside aged-enriched neutrophil states, suggesting that neutrophil accumulation covaries with stromal remodeling. CellChat-based ligand–receptor modeling predicted that aged endothelial cells, fibroblasts, and hepatocytes shift from CXCL12-dominant signaling toward CXCL1, CCL7, CCL6, and CCL4 signals. The young-enriched Neu01-TNFα subset preferentially engaged the CXCL12–CXCR4 axis, whereas the age-expanded Neu05 and Neu06 subsets were associated with CXCL1–CXCR2, providing a plausible chemotactic mechanism for the tissue-specific infiltration patterns.

The Neu06-IL6 state emerged as a central character. Pseudotime analysis placed these cells at the distal end of an inferred trajectory, with aged mice showing extended trajectory length and enrichment of Neu06 cells along the late path. The transcription factor CEBPB, which drives emergency granulopoiesis, and STAT3, the canonical IL-6 downstream effector, both increased along the aged ordering. In vitro, recombinant IL-6 activated STAT3 and raised reactive oxygen species production in HL-60 neutrophil-like cells, and conditioned medium from IL-6-stimulated cells induced senescence and matrix-remodeling markers in vascular smooth muscle and liver cell lines—an effect that persisted even after IL-6 washout, implying that IL-6-primed neutrophils release additional factors that propagate the signal.

The study also looked upstream, to the bone marrow. Single-cell analysis of hematopoietic progenitors revealed an aged-enriched state, HPC11, characterized by myeloid-biased genes such as Gata2, Car2, and Prtn3, in contrast to the lymphoid-primed HPC5 state enriched in young mice. Computational perturbation analysis predicted that FGF2 and angiopoietin-like 4 signaling shape the HPC11 program, consistent with the well-known myeloid skewing of aging hematopoiesis and providing a potential source for the flood of atypical neutrophils observed in peripheral tissues.

The authors are careful about causality. Their in vivo findings remain primarily associative, and the term aging-associated neutrophils refers to states enriched in aged organisms rather than neutrophils undergoing canonical senescence. Computational ligand–receptor and regulatory-network inferences are explicitly hypothesis-generating. Still, the partial conservation of these transcriptional programs in human multi-organ data from the Tabula Sapiens atlas, where older donors showed higher proportions of inflammatory and stress-responsive neutrophil states, lends weight to the framework. If future depletion, adoptive-transfer, or IL-6 blockade experiments confirm that these cells actively drive tissue decline, neutrophils may graduate from immune foot soldiers to prime suspects in the biology of aging—and targets for interventions aimed at slowing it.

Subject of Research: Aging-associated neutrophil remodeling across multiple mouse organs identified by single-cell transcriptomics

Article Title: Single‐Cell Mapping Identifies Aging‐Associated Neutrophil Remodeling Across Multiple Organs

Article References: Wang, Y., Chang, T., Fu, Y., Liang, G., Liu, H., Zhang, L., Yan, J., Liu, M., Liu, A., & Zhang, C. (2026). Single‐Cell Mapping Identifies Aging‐Associated Neutrophil Remodeling Across Multiple Organs. Aging Cell, 25(10), Article e70735. https://doi.org/10.1111/acel.70735

Image Credits: AI Generated

DOI: 10.1111/acel.70735

Keywords: neutrophils, aging, single-cell RNA sequencing, IL-6, senescence, bone marrow, granulopoiesis, inflammation, NETs, chemokines, STAT3, geromedicine

The rationale behind the study rests on a strategy that has gained considerable traction in oncology: drug repurposing. Bringing a brand-new molecule from discovery to the clinic can take well over a decade and cost more than a billion dollars, whereas established drugs come with known safety profiles, manufacturing routes, and, in some cases, prior human exposure data. Clofoctol, an antibiotic with a long clinical history in parts of Europe, had already attracted attention for direct antitumor activity in preclinical studies. What remained poorly understood—and what motivated the Beijing team led by Yue Wang, Wei Han, and Xiaozhong Peng—was whether the drug could also act on the immune landscape of glioblastoma, a tumor whose microenvironment is famously hostile to infiltrating lymphocytes.

To probe that question, the researchers turned to an orthotopic GL261 model, in which glioblastoma cells are implanted directly into the brains of immunocompetent mice. This model is widely regarded as one of the most faithful experimental systems for glioblastoma immunology because it preserves an intact blood-brain barrier and an intact immune system, both of which are essential when the question at hand concerns systemic immune trafficking. Using flow cytometry, the team compared the immune composition of tumors from clofoctol-treated animals against controls, and the differences were striking. Tumors from treated mice contained a substantially higher proportion of CD8-positive cytotoxic T cells—the immune system’s primary tumor-killing operatives—and those cells expressed elevated levels of cytotoxic effector molecules, hallmarks of a tumor microenvironment shifting from immunologically cold to immunologically active.

Perhaps the most intriguing finding, however, lay outside the tumor itself. When the researchers analyzed the composition of cells in the bone marrow, they observed that glioblastoma was associated with an accumulation of T cells sequestered in that compartment, a phenomenon consistent with the systemic T-cell dysfunction that increasingly is recognized as a barrier to immunotherapy in brain tumors. Clofoctol treatment partially relieved this sequestration, promoting a redistribution of T cells back into systemic circulation and, ultimately, into the tumor. In other words, the drug appears to work not only within the tumor microenvironment but at the level of whole-body immune architecture, releasing a reservoir of cytotoxic lymphocytes that the tumor had effectively locked away.

The causal importance of CD8-positive T cells to the therapeutic effect was confirmed in a depletion experiment. When the researchers eliminated CD8-positive T cells from the animals, the antitumor efficacy of clofoctol was markedly attenuated. That result matters because it elevates the drug from a possible bystander to a demonstrably T-cell-dependent intervention: whatever else clofoctol may be doing to tumor cells directly, its benefit in this model hinges on the presence of a functional cytotoxic T-cell population. For a field in which many repurposed drugs show antitumor effects that turn out to be independent of immunity—and therefore unlikely to synergize with checkpoint blockade—this distinction is critical.

In vitro co-culture experiments added a second layer of mechanistic support. When CD8-positive T cells were pretreated with clofoctol and then exposed to target cells, their cytotoxic activity increased, accompanied by upregulated expression of granzyme B, perforin, and interferon-gamma—the molecular arsenal that cytotoxic lymphocytes use to punch holes in target-cell membranes and trigger programmed cell death, along with the inflammatory cytokine that amplifies antitumor immune signaling. The drug, in short, did not merely deliver more T cells to the tumor; it made the T cells that arrived more lethal.

To trace the signaling pathway behind this activation, the team employed an affinity-based chemoproteomic approach known as ITSA-MS, which screens for proteins that bind a drug of interest in cellular lysates. That screen identified BCL9, a scaffolding protein best known for its role in Wnt signaling and previously implicated in various cancers, as a candidate clofoctol-responsive protein. Subsequent western blot analyses revealed that clofoctol treatment was associated with increased phosphorylation of VAV1, AKT, and ERK—a cascade of signaling events well established in T-cell activation, in which VAV1 relays receptor proximal signals downstream to AKT and ERK pathways that drive proliferation, survival, and effector differentiation. The authors are careful to note that the precise regulatory relationship between BCL9 and this phosphorylation cascade remains to be worked out, but the convergence of chemoproteomic and biochemical evidence points to a coherent mechanism by which the antibiotic potentiates T-cell function.

The translational payoff came in the combination experiments. Glioblastoma’s failure to respond to PD-1 blockade is thought to stem from multiple converging deficits: a physically and immunologically protected location behind the blood-brain barrier, a profoundly immunosuppressive microenvironment, and a systemic T-cell compartment that is itself dysfunctional. Checkpoint inhibitors address only one link in that chain—releasing the molecular brakes on T cells—but they cannot help if there are too few functional T cells reaching the tumor in the first place. Clofoctol, according to the new data, addresses complementary links in the chain by mobilizing T cells from the bone marrow and sharpening their cytotoxic program. When the researchers combined clofoctol with an anti-PD-1 antibody, the treated animals showed greater intratumoral CD8-positive T cell abundance and effector activity, tighter tumor control, and significantly prolonged survival compared with either monotherapy.

The implications extend beyond glioblastoma itself. The finding that a systemically administered, clinically familiar small molecule can redistribute T cells from a bone marrow reservoir and enhance their killing capacity suggests a generalizable strategy for tumors characterized by T-cell sequestration and exhaustion. It also adds to a growing appreciation that the bone marrow acts as a dynamic immunological compartment in cancer, one that can be therapeutically targeted rather than simply observed. If the mechanisms hold up in further studies, clofoctol-like approaches could complement checkpoint blockade in other poorly immunotherapy-responsive cancers, where the limiting factor is not T-cell priming but T-cell delivery and function.

Considerable caution is nonetheless warranted before extrapolating to patients. The findings derive from a single murine model, and glioblastoma models have a well-documented history of promising immunotherapy results that failed to translate into human benefit. The authors themselves emphasize that the link between BCL9 and the observed signaling changes requires further investigation, and the dosing, safety, and pharmacokinetic questions specific to combining an antibiotic with checkpoint inhibitors in the setting of brain tumors remain open. Still, the study exemplifies the promise of drug repurposing viewed through an immunological lens: an old molecule, examined with modern flow cytometry, chemoproteomics, and combination-design thinking, reveals an unexpected capacity to reorganize the immune system in ways that make immunotherapy work better. For a disease whose median survival has barely moved in decades, that is a direction worth pursuing with urgency.

Subject of Research: Repurposing the antibiotic clofoctol to enhance T-cell-mediated immunotherapy response in glioblastoma

Article Title: Clofoctol promotes systemic T-cell redistribution and intratumoral cytotoxicity to improve the response to PD-1 blockade in glioblastoma

Article References: Wang, Y., Li, E., Ai, C., Zhang, Y., Yin, B., Hou, L., Han, W., & Peng, X. (2026). Clofoctol promotes systemic T-cell redistribution and intratumoral cytotoxicity to improve the response to PD-1 blockade in glioblastoma. Cancer Immunology, Immunotherapy. https://doi.org/10.1007/s00262-026-04544-3

Image Credits: AI Generated

DOI: 10.1007/s00262-026-04544-3

Keywords: glioblastoma, clofoctol, drug repurposing, immunotherapy, PD-1 blockade, CD8-positive T cells, bone marrow, tumor microenvironment, BCL9, granzyme B, immune checkpoint blockade, Cancer Immunology Immunotherapy