Mechanism of retinal angiogenesis induced by HIF-1α and HIF-2α under hyperoxic conditions

In retinopathy of prematurity (ROP), preventing avascular dysplasia may be more critical than inhibiting abnormal neovascularization. While hypoxia-inducible factors (HIFs) are implicated in angiogenesis, their role in preventing ROP remains unclear. Oxygen-induced retinopathy (OIR) model and hyperoxic cell model were used in this study. Immunofluorescence, western blot, ELISA, cell counting kit-8 (CCK-8), and flow cytometry were applied to assess the effects of hyperoxia on the astrocytes. Co-culture of astrocytes with retinal microvascular endothelial cells (RMECs) was used to observe the effects of astrocyte inactivation on the RMECs. Overexpression of HIFs in astrocytes was used to investigate the mechanism. The OIR model revealed a decreased number of retinal astrocytes and the expression of dystrophin and R-cadherin in hyperoxic environments (P12), which was reversed after room air rearing (P17-P21), with an upward trend in RMECs (P21). In vitro hyperoxia induced significant apoptosis in astrocytes at 24 h. Moreover, the expression of angiogenesis-related factors (VEGF and ANGPTL4), vascular stabilization, and development-related factors (Laminin-β2, Dystrophin, R-cadherin) was decreased. Co-culture of astrocytes and RMECs yielded similar conclusions, with astrocyte inactivation decreasing the tube-forming capacity of RMECs. Overexpression of HIFs in astrocytes promoted the expression of VEGF, ANGPTL4, and Laminin-β2 under hyperoxic conditions. Emphatically, HIF-1α was more effective than HIF-2α in promoting the expression of integrin β1, dystrophin, and R-cadherin. Overexpression of HIFs in astrocytes reverses hyperoxia-induced retinal astrocyte inactivation and retinal vascular structural disruption and dysplasia. Strikingly, HIF-1α is a more suitable therapeutic target for ROP prevention than HIF-2α.