Abstract TMP35: Perivascular Astrocytes Alter the Basement Membrane Through TGF-Beta in an Aged Brain Post-Stroke

Abstract

Individuals over 65 make up the majority of stroke patients in the United States. Post-stroke recovery within the elderly population maybe impeded through enhanced glial scarring and reduced glymphatic flow. Following stroke, reactive astrocytes remodel the basement membrane through transforming growth factor-beta (B) signaling (TGF-B), altering glymphatic flow. Impaired glymphatic flow leads to a buildup of waste products, such as amyloid-beta, further inhibiting post-stroke recovery. We hypothesize that post-stroke astrogliosis and basement membrane fibrosis are induced through TGF-B signaling, resulting in chronic glymphatic impairment in aged mice. To test this hypothesis, we used an in vivo model of ischemia to measure TGF-B signaling and reactive astrogliosis. In vivo studies used young (3 month, n=5-8) and aged (20-month, n=5-8) male C57/Bl6 mice that underwent distal middle cerebral artery occlusion (DMCAO). Outcome measurements included TGF-B signaling, reactive astrogliosis within the glymphatic system, and impaired glymphatic flow. As a potential therapy, an implantable subcutaneous osmotic pump was inserted post-stroke with a TGF-B antagonist (GW788388 Hydrate-10mg/kg/day) to determine the impact on astrogliosis, glymphatic flow, and functional outcome. Results for in vivo studies using immunohistochemistry demonstrated a significant increase (p<0.05) in TGF-B expression in aged sham/DMCAO compared to young sham/DMCAO. There was a significant (p<0.01) increase in astrogliosis in aged sham/DMCAO compared to young sham/DMCAO. Glymphatic flow was assessed using an injected dextran dye, results demonstrated a significant (p<0.05) reduction in glymphatic flow for aged DMCAO compared to naïve mice. Functional measurements demonstrated that aged DMCAO had a significant reduction (p<0.05) in Paw Area/Time (Digigait) compared to naïve. Following TGF-B antagonist treatment, there was no difference between aged DMCAO and naïve mice in astrogliosis, glymphatic flow, or Paw Area/Time. This demonstrates that TGF-B impairs post-stroke recovery through astrogliosis, and impaired glymphatic flow. While this study demonstrated positive effects post-stroke, future studies should target downstream pathways of TGF-B.