Rab27a-mediated extracellular vesicle release drives astrocytic CSPG secretion and glial scarring in spinal cord injury.

Traumatic spinal cord injury (SCI) prevents axonal regeneration by impairing neuronal function and causing glial scarring. Chondroitin sulfate proteoglycans (CSPGs) from astrocytes drive this process, yet the release mechanism, potentially involving extracellular vesicles (EVs), remains unclear. Rab27a releases EVs from multivesicular bodies (MVBs) by enabling their docking and fusion with the plasma membrane. We confirmed Rab27a expression, and its localization, subsequently, EV release was validated with CD9, Alix, and TSG101 markers. Rab27a-mediated EV release was confirmed in both Rab27a-induced and Rab27a-siRNA-treated cells. Rab27a-derived EVs inhibited neuronal cell growth, while Rab27a-siRNA EVs promoted neuronal growth. Our study also observed upregulated Rab27a expression in the rat contusion model of SCI. Further analysis showed increased CSPG expression in Rab27a-induced conditions via the Rho/ROCK pathway, with altered pAkt, and β-tubulin III, levels. Immunohistochemistry confirmed CSPG/Rab27a/GFAP and CSPG/CD9 co-localization in tissue sections, verifying that Rab27a mediates EV release containing CSPG from astrocytes. These findings suggest that Rab27a plays a crucial role in CSPG release via EVs and scar formation. Functional recovery was significantly improved with Rab27a-siRNA treatment, suggesting Rab27a as a potential target for astrocytic scar modulation in SCI. The study reveals the detailed mechanistic insight of Rab27a-dependent CSPG release via EVs for sub-acute scar formation in contusion SCI.