Targeted exosome-delivered CD151 siRNA maintains brain endothelial cell immune homeostasis to alleviate blood–brain barrier disruption after ischemic stroke

Imbalance of immune homeostasis in vascular endothelial cells (VECs) plays a crucial role in blood–brain barrier (BBB) disruption and secondary brain injury following ischemic stroke (IS). Downregulation of CD151 in VECs has demonstrated significant therapeutic effects in IS. However, the role of CD151 in endothelial immune homeostasis remains unclear, and no noninvasive delivery system currently targets CD151 within the ischemic region. Therefore, we aimed to establish an exosome (Exo)-based delivery system capable of targeting and suppressing CD151 in ischemia-injured VECs and to explore the effects and molecular mechanisms of CD151 in regulating VEC immune homeostasis and BBB repair after IS. Exosomes were isolated from oxygen–glucose deprivation (OGD)-preconditioned primary brain microvascular endothelial cells (BMVECs). The Exo-siCD151 system was established by loading siCD151 via electroporation. In vitro, Exo-siCD151 was applied to BMVECs to evaluate cellular targeting and its role in regulating endothelial immune homeostasis. In vivo, Exo-siCD151 was administered via tail vein injection in a rat model of transient middle cerebral artery occlusion (tMCAO) to assess targeting efficiency and therapeutic effects. RNA sequencing (RNA-seq) and western blotting were performed to identify signaling pathways involved in the protective effects of Exo-siCD151. RNA-seq identified CD151 as a key regulator of immune homeostasis in VECs. Following systemic administration, Exo-siCD151 selectively accumulated in ischemic brain regions, demonstrated specific targeting to VECs, and effectively downregulated CD151 expression. In tMCAO rats, Exo-siCD151 significantly reduced infarct volume, Evans blue extravasation, and brain edema, while improving neurological function. Both in vitro and in vivo, Exo-siCD151 partially restored immune homeostasis in VECs, as evidenced by reduced endothelial apoptosis, decreased inflammatory cytokine release and adhesion molecule expression, and increased tight junction protein levels. Mechanistically, inhibition of the MAPK/ERK signaling pathway and activation of the PI3K/AKT signaling pathway were involved in the neuroprotective effects of Exo-siCD151. As a targeted delivery platform, Exo-siCD151 downregulated CD151 expression, modulated the MAPK/ERK and PI3K/AKT signaling pathways, and restored immune homeostasis in ischemia-injured VECs, thereby alleviating BBB disruption after IS. These findings suggest that Exo-siCD151 represents a promising therapeutic strategy targeting endothelial immune homeostasis for stroke recovery.