Stem Cell-Derived Vesicles Improve Cognition in Aged Monkeys

The treated macaques had better memory.

by Arkadi Mazin

Published on December 9, 2025

Study Overview

Aged rhesus macaques were given extracellular vesicles derived from mesenchymal stem cells (MSCs), which resulted in significantly better performance on spatial memory tests. This study suggests the potential reversal of age-related cognitive decline and was published in the journal GeroScience [1].

The “Normal” Decline

Even “healthy” aging, which is devoid of obvious age-related diseases such as dementia, leads to notable cognitive impairments. These impairments particularly affect working memory, executive function, and recognition memory [2]. This incessant cognitive decline begins at midlife and is associated with myelin pathology in the brain, rather than extensive neuronal loss [3].

Methodology

In this innovative study, researchers from the Boston University Chobanian & Avedisian School of Medicine evaluated the hypothesis that MSC-derived extracellular vesicles could mitigate age-related cognitive decline in rhesus monkeys.

Extracellular vesicles (EVs) are tiny lipid bubbles secreted by cells, utilized for intercellular communication, and contain various molecules including proteins and RNA. The use of EVs derived from MSCs is believed to replicate some benefits of stem cell therapies while minimizing immunogenic risks [4].

Thirteen late middle-aged rhesus monkeys, aged between 17 to 24 years (equivalent to approximately 51-72 human years), were selected for this study. Following baseline cognitive testing and MRI scans, these animals were randomly assigned to receive either MSC-EV treatment or a control group receiving sham injections. The MSC-EV treatment was administered bi-weekly for 18 months, using bone-marrow MSCs from a young 6-year-old monkey.

Cognitive Assessment Methods

The cognitive assessments consisted of two primary tests:

  • Delayed Non-Matching to Sample (DNMS) Task: Designed to evaluate recognition memory.
  • Delayed Recognition Span Task – Spatial (DRSTsp): Assesses spatial working memory.

Results

The MSC-EV treatment group demonstrated dramatic improvements in spatial working memory, effectively reversing age-related cognitive decline. The performance levels of the treated monkeys were comparable to those of younger monkeys in prior studies.

Though differences in recognition memory between the two groups were not statistically significant at the study’s end, adjustments for baseline scores revealed that one part of the DNMS test (the two-minute delay) reached significance.

MRI Findings

The MRI scans illustrated enhancements in white matter integrity in critical areas such as the right middle temporal region and the fornix, alongside preserved functional connectivity in the MSC-EV group compared to controls. Correlation analyses identified specific connectivity patterns associated with cognitive performance, indicating a relationship between brain structure/function and cognitive outcomes.

Limitations and Future Directions

The study did present limitations, including the lack of a sex-balanced MSC-EV group (four females, two males), which could have influenced outcomes. To strengthen findings, future research should aim for larger sample sizes and extended treatment periods.

As we look ahead, the research team emphasizes the need for comprehensive molecular changes analyses and histological studies to further elucidate mechanisms behind cognitive improvements.

Conclusions

This groundbreaking study suggests that the aging brain maintains a remarkable capacity for resilience, challenging the notion that aging is irreversible. The implications extend beyond healthy aging and may offer therapeutic avenues for conditions like Alzheimer's disease, multiple sclerosis, stroke, and brain injury.

Evan Mackie, a Ph.D. student and corresponding author, stated, “Our findings suggest that brain health can be supported and maintained even in older age.”

Literature Cited

No. Reference
1 Mackie, E. C., et al. (2025). Mesenchymal cell-derived extracellular vesicles ameliorate age-related deficits in working memory and in vivo MRI measures of white matter structure and function in rhesus monkeys. GeroScience, 1-25.
2 Buckner, R. L. (2004). Memory and executive function in aging and AD: multiple factors that cause decline and reserve factors that compensate. Neuron, 44(1), 195-208.
3 Gong, Z., et al. (2023). Lower myelin content is associated with more rapid cognitive decline among cognitively unimpaired individuals. Alzheimer’s & Dementia, 19(7), 3098-3107.
4 Tan, F., et al. (2024). Clinical applications of stem cell-derived exosomes. Signal Transduction and Targeted Therapy, 9(1), 17.

We invite your support in sustaining our non-profit efforts. Your contributions help maintain independent journalism and allow us to provide accessible, quality information to the public.