Local angiogenic interplay of Vegfc/d and Vegfa drives brain region-specific development of fenestrated capillaries

Abstract

ABSTRACTFenestrated and blood-brain barrier (BBB)-forming endothelial cells constitute major brain capillaries, and this vascular heterogeneity is crucial for region-specific neural function and brain homeostasis. How these capillary types emerge in a brain region-specific manner and subsequently establish intrabrain vascular heterogeneity remains unclear. Here, we show a core angiogenic mechanism critical for fenestrated brain capillary development via a comparative analysis of the zebrafish choroid plexuses (CPs) and circumventricular organs (CVOs), demonstrating capillary-type-selective vascularization mechanisms. We found that zebrafish deficient for Gpr124, Reck, or Wnt7aa exhibit severely-impaired BBB angiogenesis without any apparent defect in fenestrated capillary formation in the CPs and CVOs. Conversely, simultaneous genetic loss of various Vegf combinations revealed remarkable heterogeneity of endothelial requirements for Vegfs-dependent angiogenesis within and across these organs, identifying unexpected interplay of Vegfc/d and Vegfa in fenestrated brain capillary formation. Expression analysis and paracrine activity-deficientvegfcmutant characterization suggest that endothelial cells and non-neuronal specialized cell types present in the CPs and CVOs are major sources of Vegfs responsible for regionally-restricted angiogenic interplay. Thus, local presentations and interplay of Vegfc/d and Vegfa control brain region-specific emergence of fenestrated capillaries, providing insight into fenestrated capillary formation in other organs and also how intra-organ vascular heterogeneity arises.