Abstract Su104: Neuronal Damage in Elderly Cerebral Ischemia/Reperfusion Injury: Role of Small Extracellular Vesicles from Senescent Microvascular Endothelial Cells

Background: The incidence of cardiac arrest (CA) increases with age, leading to poorer neurological outcomes after the return of spontaneous circulation (ROSC) in the elderly. The neurovascular unit, particularly the interaction between brain microvascular endothelial cells (BMECs) and neurons, is crucial in cerebral ischemia/reperfusion (I/R) injury. Senescent BMEC-derived small extracellular vesicles (sEVs), as part of the senescence-associated secretory phenotype (SASP), play a role in signaling between these cells. These sEVs can exacerbate damage by changing their cargo, but the mechanisms are not fully understood. Methods: Young(8-10weeks) and aged(20-24months) C57BL/6J mice were utilized to establish the CA-CPR-ROSC model via electrical stimulation through the esophagus. Primary BMECs and neurons were used in vitro experiments. Senescence in BMECs was induced in vitro using D-(+)-Galactose. sEVs were isolated by ultracentrifugation thereafter. Aging-related proteins, BMEC-sEVs secretome and neuronal damage were evaluated by western blot analysis and immunofluorescence staining. High-throughput sequencing is employed to identify disparities in miRNAs within plasma sEVs obtained from both young and aged mice. Results: Aged mice exhibited a significantly higher rate of neuronal apoptosis after ROSC, with decreased levels of neuronal synaptic proteins. More pronounced senescence in BMECs and increased secretion of plasma sEVs were observed in age mice. In vitro, senescent BMECs secreted more sEVs compared to young BMECs. Furthermore, early intravenous administration of senescent BMEC-sEVs exacerbated neuronal apoptosis and the reduction in synaptic protein levels in young mice after ROSC, whereas young BMEC- sEVs mitigated these effects. And the sequencing results of plasma sEVs from young and aged mice have revealed a total of 17 significantly differentially expressed miRNAs. Conclusion: As components of the SASP, sEVs secreted by senescent BMEC-sEVs may partially explain the enhanced neuronal damage observed in aged mice following the ROSC. The modulatory impact of senescent BMEC-sEVs on neuronal apoptosis and synaptic protein expression alterations is mediated by variations in the sEVs cargos, which correlate with the miRNAs they carry. This provides evidence for cell communication within neurovascular units after I/R injury in the elderly, however, the specific regulatory mechanism requires further investigation.