Retinal blood vessel-origin yes-associated protein (YAP) governs astrocytic maturation via leukaemia inhibitory factor (LIF).

OBJECTIVES:To testify that endothelial cells (ECs) induce astrocyte maturation by leukaemia inhibitory factor (LIF) secretion. MATERIALS AND METHODS:In vivo experiments, mice bearing floxed alleles of YAP were crossed with mice expressing a Cre recombinase driven by the endothelial Tek promoter (Tek-Cre) to finally obtain the following three genotypes: YAP^f/f , Tek-Cre; YAP^f/w , Tek-Cre; and YAP^f/f . Retinal vascularization and astrocyte network were evaluated by whole-mount fluorescence and Western blotting. In vitro, experiments were performed in an astrocyte and human microvascular endothelial cell (HMEC-1) coculture model to analyse the mechanisms underlying the effect of endothelial YAP on astrocytes. RESULTS:In vivo, YAP^f/f ;Tek-Cre mice showed delayed angiogenesis, sparse vessels and decreased glial fibrillary acidic protein (GFAP)+ astrocytes but aberrant growth of endothelial networks and immature astrocytes (platelet-derived growth factor A, PDGFRA+ astrocytes) overgrowth. In vitro, Yap deletion attenuated the LIF release that delayed the maturation of retinal astrocyte which was consistent with the results of HMEC-1-astrocyte coculture. The effect of YAP overexpression on LIF-LIFR axis in HMEC-1 interferes the GFAP expression of astrocyte. In contrast, LIF protein rescues the astrocytic GFAP expression when EC YAP was inhibited by siRNAs. CONCLUSIONS:We show that EC yes-associated protein (YAP) is not only a critical coactivator of Hippo signalling in retinal vessel development but also plays an essential role in retinal astrocyte maturation by regulating LIF production. © 2020 The Authors. published by John Wiley & Sons Ltd.

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