AKAP12 Regulates Perivascular OPC Accumulation in the Corpus Callosum During Cerebral Hypoperfusion

Oligodendrocyte precursor cells (OPCs) have been reported to interact with cerebral microvessels, but the extent and spatiotemporal regulation of this relationship across maturation and hypoperfusion-induced stress remain incompletely defined. Here, we quantified OPC-vessel relationships in the mouse corpus callosum using PDGFR-α/OLIG2/CD31 immunohistochemistry and distance-based spatial analysis, classifying OPCs within 10 μm of CD31+ vessels as perivascular OPCs. We show that while total OPC density decreases from development to adulthood, the proportion of perivascular OPCs increases in the mature brain. Under cerebral hypoperfusion induced by bilateral common carotid artery stenosis (BCAS), OPC density and the enrichment of perivascular OPCs were increased by Day 7 and remained elevated through Days 14-28. Proliferative OPCs (Ki67-positive OPCs) were preferentially observed within the vessel-proximal domain, indicating that the perivascular compartment functions as a stress-responsive proliferative niche. To identify regulators of this response, we focused on A-kinase anchoring protein 12 (AKAP12), a scaffolding protein expressed in vascular cells. In middle-aged Akap12 global knockout mice subjected to BCAS, hypoperfusion-induced OPC increase was preserved, but perivascular accumulation was reduced. This defect was accompanied by increased IgG leakage without a corresponding reduction in vascular area density, suggesting that AKAP12 supports the integrity of the perivascular microenvironment required for OPC niche remodeling. Together, these findings reveal the perivascular niche as a hypoperfusion-responsive compartment for OPC activation and suggest that AKAP12-dependent vascular barrier integrity contributes to the maintenance of this oligovascular niche.