Abstract WP217: Increase Of Exosome Uptake By Activated Neurons In The Peri-infarct Region Improves Neurological Outcomes After Stroke

Abstract

Background: We hypothesized that an increase of exosome uptake by activated neurons in the peri-infarct region enhances functional outcome. We tested this hypothesis by administering exosomes derived from cerebral endothelial cells (CEC-exos) to ischemic rats in conjunction with whisker stimulation. Methods and Results: Male adult rats were subjected to a transient right middle cerebral artery occlusion (tMCAO). Neuronal activation in the barrel cortex of the peri-infarct region after left whisker stimulation was confirmed by c-fos positive neurons. CEC-exos at a dose of 1x10^11 particles/injection were administered (i.v.) to tMCAO rats 15 min after whisker stimulation at every other day for 2 consecutive weeks, starting 1 day after tMCAO. Ischemic rats treated with CEC-exos alone or whisker stimulation alone significantly (p<0.05) improved sensorimotor functions (modified neurological severity scores, mNSS, 6±1 in CEC-exos or stimulation; foot-fault, FF, 11±1% in CEC-exos, 14±1% in stimulation) compared to ischemic rats treated with PBS (mNSS, 10±1; FF, 25±2%, n=7/group). However, combination of whisker stimulation with CEC-exos resulted in a super-additive (p<0.05) effect to improve sensorimotor functions (mNSS, 3±1, FF, 6±1%, p<0.05, n=7) compared to the monotherapies. Confocal microscopic analysis showed that stimulation significantly (p<0.05) increased neuronal uptake of CEC-exos (21±3 vs 3±1 exosomes/cell in CEC-exos alone, n=200 neurons/group), which was associated with significant (p<0.05) reduction of axonal inhibitory protein Sema6a in axons of activated neurons (relative levels 0.11±0.02 vs 0.31±0.07 in CEC-exos alone, n=3) . Increased neuronal uptake of CEC-exos was further confirmed at the ultra-structural level. Conclusion: Activated neurons in the peri-infarct areas preferentially increase uptake of CEC-exos, which contributes to significantly enhanced and robust improvement of neurological outcome during stroke recovery.