Brain Endothelial Microvesicles Regulate Astrocyte Trans-Differentiation in Stroke

摘要

Astrocytes, the most abundant glial cell type in the brain, undergo dramatic phenotypic changes in response to ischemic stroke. While traditionally viewed as passive responders, accumulating evidence suggests that reactive astrocytes can acquire neurogenic potential after injury. However, the mechanisms regulating this phenotypic transition remain poorly understood. In this study, we identify a novel non-cell-autonomous pathway in which ischemia-activated brain endothelial cells(BECs) reprogram astrocytes into neural progenitor-like cells through the release of extracellular microvesicles(MVs) carrying the proneural transcription factor Ascl1. Using an in vitro oxygen-glucose deprivation(OGD) model to simulate stroke conditions, we found that astrocytes alone failed to exhibit neuronal reprogramming. In contrast, co-culture with OGD-stimulated BECs—but not neurons or pericytes—induced morphological and molecular features characteristic of neural progenitors, including the expression of DCX and Nestin. We further demonstrated that BEC-derived MVs were significantly increased after OGD and were sufficient to induce glial-toneural morphological changes, expression of Tuj1 and MAP2, and neuronal-like calcium signaling in recipient astrocytes. Mechanistically, we identified Ascl1 as a key MV cargo selectively upregulated in BECs after ischemia. Overexpression of Ascl1 in BECs enhanced reprogramming capacity of their MVs, as validated by luciferase reporter assays and gene expression profiling in astrocytes. In vivo studies using a distal middle cerebral artery occlusion(MCAO) model showed increased Ascl1 expression in BECs post-stroke, and FACS analyses confirmed that BECs were the primary source of Ascl1 among brain cell types. Endothelial-specific overexpression of Ascl1 led to enhanced neurogenesis and improved functional recovery. Moreover, injection of Ascl1-enriched BEC-MVs into the lateral ventricle of Aldh1l1-CreERT2;YFP reporter mice induced YFP-positive astrocytes to express neural progenitor markers and reduced infarct size. These findings position BECs as active participants in post-stroke neural reprogramming and suggest microvesicle-mediated Ascl1 delivery as a promising therapeutic strategy for brain repair.

关键词

astrocyte reprogramming / brain endothelial cells / stroke / microvesicles