Alzheimer’s disease is characterized by the progressive accumulation of amyloid-β, synaptic dysfunction, and inexorable cognitive decline, yet approved therapies remain largely symptomatic and incapable of halting neurodegeneration. Mounting evidence points to oxidative stress, mitochondrial dysfunction, and chronic inflammatory signaling as interconnected drivers of the disease process, creating a pressing need for interventions that target these pathways early. MicroRNAs—short, non-coding RNA molecules that fine-tune gene expression after transcription—have emerged as attractive candidates precisely because single microRNAs can modulate entire networks of stress-responsive genes. The obstacle has always been delivery: free microRNAs are rapidly degraded in biological fluids, are poor at crossing cell membranes, and lose their function before reaching intracellular targets.

Extracellular vesicles offer a natural solution to this delivery problem. These nano-sized, lipid-bilayer-bound packets are secreted by nearly all cell types and circulate in blood, cerebrospinal fluid, and milk, where they shield RNA cargo from enzymatic attack while ferrying it efficiently into recipient cells. The research team, led by neurologist Sinan Gönüllü of Bursa City Hospital and geneticist Selçuk Özdemir of Atatürk University, chose milk as the vesicle source for pragmatic reasons: milk-derived vesicles are biocompatible, exhibit low immunogenicity, carry intrinsic antioxidant and anti-inflammatory properties, and can be isolated at industrial scale—a combination of traits that synthetic nanoparticles have struggled to match.

The isolation protocol was rigorous. Sterile bovine milk was subjected to sequential centrifugation steps to strip away cells, fat globules, and protein aggregates, followed by ultracentrifugation at 100,000 × g to pellet the vesicles. The preparation was then polished through size-exclusion chromatography using qEV columns, and the final suspension was filtered through 0.22-micrometer membranes. Characterization followed the MISEV2018 guidelines: transmission electron microscopy revealed the classic round, cup-shaped vesicle morphology; dynamic light scattering placed the intensity-weighted size distribution around 190–200 nanometers; and nanoparticle tracking analysis showed peak diameters predominantly between 80 and 250 nanometers, with stock preparations containing roughly 10⁸ particles per milliliter.

Loading the vesicles with cargo required a chemical trick. The researchers incubated 1,000 micrograms of a synthetic miR-126-3p mimic with 200 micrograms of vesicle protein in the presence of 0.2 percent saponin, a mild detergent that transiently permeabilizes the vesicle membrane and allows the microRNA to enter. Unencapsulated RNA and residual saponin were then removed using PD-10 size-exclusion columns. Reverse transcription quantitative PCR confirmed that the microRNA was genuinely inside the vesicles rather than stuck to their surfaces: the signal survived treatment with RNase alone, which degrades only external RNA, but collapsed when RNase was combined with a membrane disruptor. Importantly, loading left vesicle morphology, size distribution, and colloidal properties essentially unchanged.

Why miR-126-3p? The choice rests on an accumulating body of mechanistic evidence. This microRNA is known to regulate vascular integrity and inflammatory signaling, dampening expression of adhesion molecules such as VCAM-1 and ICAM1, and it activates the SIRT1/Nrf2 antioxidant axis. Bioinformatic targetome analyses implicate it in neurotrophin and PI3K/AKT survival pathways, and experimental work has identified Alzheimer’s-relevant proteins—including BACE1 and EFHD2—as direct targets. In APP/PS1 mice, miR-126 overexpression reduces amyloid plaque burden and neuroinflammation, and circulating miR-126-3p has been reported as elevated in Alzheimer’s patients, marking it as an inflammation-associated biomarker of disease progression.

The disease model itself was deliberately conservative. Human SH-SY5Y neuroblastoma cells were exposed to oligomeric amyloid-β₁₋₄₂ at a sublethal dose of 0.5 micromolar for 24 hours—conditions chosen to elicit measurable redox and inflammatory alterations without outright cytotoxicity. Before therapeutic testing, an MTT viability assay established that the loaded vesicles were well tolerated at concentrations up to 5 micrograms per milliliter, corresponding to roughly 2.5 × 10⁶ particles per milliliter, while the highest tested dose of 10 micrograms per milliliter proved toxic. Four experimental groups were then compared: untreated controls, amyloid-β-exposed cells, amyloid-β-exposed cells given blank vesicles, and amyloid-β-exposed cells given miR-126-3p-loaded vesicles.

The results were striking in their breadth. Amyloid-β exposure drove intracellular reactive oxygen species, lactate dehydrogenase, glutathione peroxidase 1, and malondialdehyde sharply upward while suppressing superoxide dismutase activity—a signature of lipid peroxidation, membrane damage, and failing antioxidant defense. Blank vesicles produced only partial relief, but the miR-126-3p-loaded vesicles normalized essentially every oxidative parameter, returning values to statistically indistinguishable levels from healthy controls. The same pattern held at the transcriptional level: amyloid-β had upregulated the inflammatory genes ICAM1 and TNF-α and suppressed brain-derived neurotrophic factor, and only the loaded vesicles fully reversed this imbalance.

Mitochondrial and cytoskeletal readouts told an equally compelling story. Amyloid-β exposure elevated cytochrome c, 8-hydroxy-2′-deoxyguanosine (a marker of oxidative DNA damage), PINK1, and DNM1L, while reducing mitochondrial transcription factor A, indicating impaired mitochondrial DNA maintenance and dysregulated dynamics. Intracellular neurofilament light chain—an indicator of cytoskeletal stress in this cellular context rather than clinical axonal degeneration—soared with amyloid-β treatment and fell back to baseline only in the loaded-vesicle group. Synaptic and extracellular matrix-associated proteins followed suit: complexin 2 and SMOC1, which amyloid-β had depressed, and ROR1, which it had elevated, all normalized with miR-126-3p delivery. Finally, the hallmark molecular markers of Alzheimer’s pathology—total tau, phosphorylated tau at residues 181 and 217, and intracellular amyloid-β₁₋₄₀ itself—all rose sharply with amyloid-β exposure and returned to control-equivalent levels with treatment.

The authors are careful to frame these findings appropriately. SH-SY5Y cells are not fully differentiated, synaptically mature neurons, and the observed changes reflect modulation of stress-responsive gene programs rather than repair of brain tissue or reversal of established neurodegeneration. Several methodological gaps remain: the study lacked direct visualization of vesicle uptake, a scramble-miRNA control vesicle, free-miRNA comparison groups, and assessment of the broader mitochondrial biogenesis network involving PGC-1α, NRFs, and PARKIN. Downstream target validation of miR-126-3p within the cells also awaits future work. Validation in primary neuronal cultures, co-culture systems, brain organoids, and animal models will be essential before any translational claims can be made.

Even with those caveats, the study lands at a moment of intense interest in milk-derived vesicles as therapeutic carriers. Their lipid bilayers protect RNA payloads from ribonucleases in the bloodstream, their natural origin may allow them to navigate biological barriers with less immune pushback than synthetic vectors, and the raw material is abundant, inexpensive, and ethically uncontroversial. If miR-126-3p-loaded milk vesicles can retain their cytoprotective effects in living brain tissue—and, crucially, if they can cross the blood-brain barrier at therapeutically meaningful concentrations—the platform could open a non-invasive route for RNA-based modulation of the oxidative, inflammatory, and mitochondrial cascades that drive Alzheimer’s disease. For now, the image of a common dairy product yielding nanoscale couriers capable of quieting amyloid-β’s assault on human neurons is a vivid illustration of how therapeutic innovation increasingly borrows from biology’s own logistics network.

Detailed investigations utilizing two distinct transgenic mouse models of AD demonstrated that the intracerebral administration of these double-stranded RNA-containing circular RNAs (ds-cRNAs) can substantially decrease aberrant PKR activation localized in neurons and microglia. The researchers employed adeno-associated virus (AAV) vectors to deliver the ds-cRNAs directly into the hippocampus, a region pivotal for learning and memory and severely affected during AD progression. This targeted suppression of PKR resulted in pronounced reductions of neuroinflammatory markers and amyloid-β plaque burden, pathological hallmarks notoriously linked to cognitive decline. Crucially, the treatment’s safety profile was favorable, showing minimal signs of neural toxicity or adverse immune responses, underscoring the therapeutic specificity and biocompatibility of engineered circular RNA elements.

One of the most compelling aspects of this work is the demonstration of effective systemic delivery of ds-cRNAs to the entire brain. Utilizing the AAV-PHP.eB serotype, capable of crossing the blood–brain barrier (BBB) upon intravenous injection, the team achieved widespread central nervous system transduction. This non-invasive delivery method resulted in broad attenuation of PKR-driven neuroinflammation and was accompanied by measurable improvements in spatial learning and memory across mouse cohorts at various stages of AD pathology. The capacity to circumvent the BBB—a formidable obstacle in neurotherapeutics—positions ds-cRNA-based treatment as a highly translational candidate with the potential to impact multiple brain regions implicated in AD.

The structural design of ds-cRNAs is a critical element underpinning their efficacy. Circular RNAs are inherently more stable than their linear counterparts, lacking free ends that are substrates for exonucleases. Incorporating short double-stranded motifs enables these circular RNAs to engage PKR directly, acting as aptamers that competitively inhibit the kinase’s proinflammatory activation without eliciting unintended immune activation. This specific structural mimicry offers potent suppression of PKR signaling pathways while minimizing collateral damage often observed with broad-spectrum small-molecule inhibitors. Such molecular finesse is particularly important for chronic diseases like AD where long-term safety and efficacy are paramount.

Further genetic and biochemical analyses revealed that PKR hyperactivity promotes an exacerbated neuroinflammatory milieu by amplifying microglial reactivity and downstream cytokine release, exacerbating amyloidogenic processes and synaptic dysfunction. By intercepting PKR activation, ds-cRNAs reduce these inflammatory circuits, fostering a neuroprotective environment that preserves neuronal integrity and connectivity. Importantly, this modulation does not completely abolish PKR’s physiologic roles but selectively intervenes in its pathologic overactivation, maintaining necessary cellular functions while curbing disease-driving inflammation.

The therapeutic impact of ds-cRNA administration was sustained impressively over extended periods. Mice receiving a one-time dose of AAV-delivered ds-cRNAs exhibited reduced neuroinflammation and plaque pathology for at least six months, corresponding with durable improvements in behavioral assays assessing hippocampus-dependent memory. This long-lasting effect raises the prospect that a single treatment could confer prolonged disease modification, a much-desired goal in AD therapeutics that currently relies on repeated dosing regimens with variable outcomes.

Notably, the intervention demonstrated efficacy at multiple stages of disease progression. Early, mid, and late-stage treated mice all exhibited amelioration of key pathological and cognitive symptoms, suggesting that ds-cRNAs could be applied flexibly in clinical scenarios ranging from early diagnosis to symptomatic management. This versatility contrasts with many contemporary AD treatments whose effectiveness diminishes once pathology is relatively advanced, underscoring the strategic advantage of directly targeting maladaptive neuroinflammatory signaling pathways.

Beyond the immediate implications for AD, the study’s successful repurposing of ds-cRNAs previously deployed in psoriasis models highlights a broader paradigm for targeting innate immune regulators via RNA aptamer technology. This modular platform enables rapid adaptation to diverse neuroinflammatory or autoimmune diseases, guided by precise molecular recognition principles. The convergence of RNA biology, viral vector engineering, and immunomodulation exemplified here signals an emerging frontier in precision neurotherapeutics.

While translation from murine models to human patients will necessitate comprehensive validation of safety, pharmacodynamics, and dosing regimens, the data provide a compelling rationale for clinical exploration. The use of adeno-associated viruses, already employed in several FDA-approved gene therapies, and the mechanistic specificity of ds-cRNAs collectively enhance the likelihood of regulatory and clinical success. Furthermore, improvements in vector design and delivery routes may optimize brain-wide distribution and target engagement in humans.

Mechanistic insights derived from this research also invite investigation into combinatorial strategies incorporating ds-cRNA aptamers alongside existing treatments such as anti-amyloid antibodies, tau-directed therapies, or symptom-targeting drugs. Synergistic modulation of multiple pathological axes may ultimately be required to arrest or reverse the complex cascade underlying Alzheimer’s disease. The precision inhibition of neuroinflammatory kinases like PKR sets a foundational milestone toward such multi-modal intervention.

In sum, the development of circular RNA aptamers capable of selectively targeting and inhibiting PKR within the Alzheimer’s brain represents a paradigm shift. By harnessing the intrinsic stability and binding specificity of engineered circular RNAs packaged within clinically relevant viral vectors, this approach offers a potent, durable, and minimally toxic means of curbing neuroinflammation and its downstream pathological consequences. As the global burden of AD continues to escalate, this innovative RNA-based platform may usher in a new wave of disease-modifying therapies addressing an urgent unmet medical need.

This landmark study not only advances our understanding of RNA therapeutic design but also illuminates novel molecular strategies to rein in the chronic neuroinflammatory state that drives neurodegeneration. The result is a hopeful horizon for patients, clinicians, and researchers alike, where targeted molecular therapies informed by cutting-edge bioengineering have the potential to reclaim cognitive function and quality of life from the grip of Alzheimer’s disease.

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Subject of Research: Circular RNA aptamers targeting PKR to reduce neuroinflammation and ameliorate Alzheimer’s disease phenotypes in mouse models.

Article Title: Circular RNA aptamers targeting neuroinflammation ameliorate Alzheimer disease phenotypes in mouse models.

Article References:
Feng, X., Jiang, BW., Zhai, SN. et al. Circular RNA aptamers targeting neuroinflammation ameliorate Alzheimer disease phenotypes in mouse models.
Nat Biotechnol (2025). https://doi.org/10.1038/s41587-025-02624-w

Image Credits: AI Generated

Li-Huei Tsai, a prominent Picower Professor at MIT and the director of MIT’s Aging Brain Initiative, has been at the forefront of this work. In collaboration with postdoctoral researcher Jung Park, Tsai emphasizes the consistency of results emerging from their lab alongside numerous contributions from other academic groups worldwide. The findings corroborate the notion that delivering stimulation at the precise frequency of 40 Hz results in beneficial neurobiological changes. Many methodologies, ranging from sensory-induced stimuli to advanced techniques like transcranial magnetic stimulation, have demonstrated similar beneficial outcomes in reducing Alzheimer’s disease pathology.

The journey into gamma stimulation began in earnest with a groundbreaking publication in Nature in 2016 that highlighted various methods of inducing 40Hz stimulation, such as through specific light and sound modalities. Subsequent studies have built upon these foundations, showcasing how such stimulation significantly reduces amyloid plaques and tau protein tangles—two primary hallmarks of Alzheimer’s pathology. Rigorous investigations reveal that these interventions do more than decrease harmful proteins; they also foster healthier synaptic function, mitigate neuron death, and enhance cognitive performance across diverse mouse models of Alzheimer’s.

A particularly revealing study conducted by Tsai’s collaboration demonstrated that auditory and visual stimuli operating at 40 Hz induce the release of vasoactive intestinal peptide (VIP), which aids in the clearance of amyloid from brain tissues via the glymphatic system. This discovery not only underscores the intricate molecular pathways activated by gamma stimulation but also paints a hopeful picture for its potential clinical applications.

At the heart of ongoing clinical endeavors is Cognito Therapeutics, a spinoff from MIT that aims to harness the gamma stimulation approach for therapeutic use. Phase II clinical trials conducted by Cognito have yielded promising outcomes, demonstrating that participants with Alzheimer’s disease exhibited notable improvements in cognitive measures and reduced brain atrophy after being exposed to auditory and visual stimuli at 40 Hz. The ongoing Phase III trial aims to affirm these findings on a larger scale.

As research expands, the burgeoning evidence base continues to draw attention. A range of studies from international collaborators has reinforced the hypothesis that 40 Hz stimulation can induce favorable cognitive outcomes and mitigate Alzheimer’s-related symptoms. For instance, a notable study carried out in China corroborated that such sensory intervention increases glymphatic fluid flow, an essential process for waste clearance in the brain. Another investigation originating from Harvard Medical School reported significant reductions in tau protein burden in human participants subjected to Transcranial Alternating Current Stimulation at 40 Hz.

While the excitement surrounding these findings is palpable, the researchers recognize that significant questions remain. Understanding the exact cellular and molecular mechanisms underpinning the therapeutic effects of gamma stimulation is crucial for translating these discoveries into clinical practices effectively. Tsai’s lab is currently investigating various neuropeptides and regulatory systems to dissect the cascade of physiological changes that follow sensory stimulation. The complexity of cellular responses, particularly among immune-related microglial cells, remains a high-priority research focus.

The ongoing endeavors at the Picower Institute aim not merely to understand Alzheimer’s disease but also to explore the broader implications of gamma stimulation therapy. Preliminary investigations suggest that GENUS (Gamma Entrainment Using Sensory Stimulation) could have potential applications beyond Alzheimer’s, especially in treating conditions such as Parkinson’s disease, stroke, and even certain psychiatric disorders like anxiety and depression. Understanding how GENUS can be used to enhance cognitive capabilities or mitigate the impacts of various neurological conditions represents a critical frontier in neuroscience.

As interest in this area continues to surge, the research community remains committed to unveiling the depths of GENUS therapy. Ongoing collaborations across the globe promise to shed light on the mechanisms and efficacy of gamma stimulation, ensuring that both fundamental research and clinical applications evolve in tandem. Insights gleaned over the next decade may not only optimize treatment paradigms for existing neurodegenerative diseases but also open new avenues for addressing a host of cognitive disorders.

Through an innovative landscape of research and exploration, scientists are on a promising trajectory toward developing impactful interventions against some of humanity’s most challenging neurological diseases. The intersection of technology, cognitive neuroscience, and therapeutic discovery hints at a future where non-invasive approaches could significantly alleviate the burden of neurodegenerative conditions.

In conclusion, the endeavor to utilize gamma wave stimulation as an accessible and non-invasive therapy highlights both the potential risks and rewards of tackling complex neurological issues. As investigations continue, the possibility of offering hope through scientifically anchored methods becomes increasingly attainable, an aspiration that could one day shape the future of neurotherapeutics.

Subject of Research: People
Article Title: Innovations in noninvasive sensory stimulation treatments to combat Alzheimer’s disease
News Publication Date: 28-Feb-2025
Web References: PLOS Biology
References: Not available
Image Credits: MIT Picower Institute

Keywords: Alzheimer disease, Human brain, Memory disorders, Brain stimulation, Neurology, Cellular neuroscience, Glia, Clinical neuroscience.