Traumatic brain injury (TBI) is a major cause of long-term neurological impairment, with aging amplifying vulnerability and worsening recovery. Older individuals face greater cognitive and motor deficits post-TBI and respond less effectively to treatments, as both aging and TBI independently elevate neuroinflammation and cognitive decline. This study evaluated the therapeutic effects of human adipose-derived stem cell small extracellular vesicles (hASC-sEVs) on neurological recovery and neuroinflammation in a mouse model of TBI. Male C57BL/6 mice (3, 15, and 20 months old) underwent controlled cortical impact (CCI) and received intranasal hASC-sEVs 48 h post-injury; control groups received PBS. A dose–response study at 7 days post injury (dpi) identified 20 µg as the optimal therapeutic dose, improving motor function, reducing neuroinflammation, and enhancing neurogenesis. This was followed by a 30-dpi study assessing cognitive function, neuroinflammation, neurogenesis, and proteomic changes in microglia and astrocytes via mass spectrometry. hASC-sEV treatment significantly improved behavioral outcomes and reduced neuroinflammatory markers (GFAP, IBA-1, and MHC-II), with reduced efficacy observed in older mice. Proteomics revealed that hASC-sEVs reduce inflammatory proteins (TNF-α, IL-1β, IFNG, CCL2) and modulated mitochondrial dysfunction and reactive oxygen species. These results highlight hASC-sEVs as a promising cell-free therapy for improving TBI outcomes, especially in aging populations.

Microglial activity in the aging neuroimmune system is a central player in aging-related dysfunction. Aging alters microglial function via shifts in protein signaling cascades. These shifts can propagate neurodegenerative pathology. Therapeutics require a multifaceted approach to understand and address the stochastic nature of this process. Polyphenols offer one such means of rectifying age-related decline. Our group used mass spectrometry (MS) analysis to explicate the complex nature of these aging microglial pathways. In our first experiment, we compared primary microglia isolated from young and aged rats and identified 197 significantly differentially expressed proteins between these groups. Then, we performed bioinformatic analysis to explore differences in canonical signaling cascades related to microglial homeostasis and function with age. In a second experiment, we investigated changes to these pathways in aged animals after 30-day dietary supplementation with NT-020, which is a blend of polyphenols. We identified 144 differentially expressed proteins between the NT-020 group and the control diet group via MS analysis. Bioinformatic analysis predicted an NT-020 driven reversal in the upregulation of age-related canonical pathways that control inflammation, cellular metabolism, and proteostasis. Our results highlight salient aspects of microglial aging at the level of protein interactions and demonstrate a potential role of polyphenols as therapeutics for age-associated dysfunction.