ANGPTL2 overexpression promotes angiogenic responses in human retinal microvascular endothelial cells with accompanying integrin α5β1 molecular changes.

BACKGROUND: Diabetic retinopathy (DR) is a leading cause of preventable vision loss worldwide, characterized by retinal microvascular dysfunction and progressive angiogenic dysregulation. Angiopoietin-like protein 2 (ANGPTL2) promotes endothelial activation and pathological angiogenesis in multiple vascular disease contexts, yet its effects on retinal endothelial angiogenic behavior have not been directly characterized. Whether integrin α5β1 and PI3K/AKT phosphorylation changes in the diabetic retina are associated with alterations in ANGPTL2 expression levels also remains unexamined. METHODS: ANGPTL2 was overexpressed in human retinal microvascular endothelial cells (HRMECs), and effects on cell viability, wound closure, invasion, and tube formation were assessed by CCK-8, wound healing, Transwell invasion, and tube formation assays. Integrin α5β1, VEGF, and PI3K/AKT phosphorylation were characterized by western blot. Retinal tissues from streptozotocin (STZ)-induced diabetic rats across groups with varying ANGPTL2 expression levels were analyzed by RT-qPCR, western blot, and immunofluorescence to characterize accompanying molecular changes. The protein-level association between ANGPTL2 and integrin α5β1 was examined by co-immunoprecipitation and co-localization immunofluorescence under overexpression conditions. RESULTS: ANGPTL2 overexpression significantly enhanced cell viability, wound closure, invasion, and tube formation in HRMECs, accompanied by upregulation of VEGF, p-VEGFR2, integrin α5β1, and PI3K/AKT phosphorylation. Retinal tissues from STZ-diabetic rats showed elevated integrin α5β1 expression, increased CD31 levels, and increased PI3K/AKT phosphorylation relative to non-diabetic controls; these molecular changes were directionally lower in the ANGPTL2 knockdown comparison group (i.e., the STZ + sh-ANGPTL2 group), providing supportive retinal molecular context. Co-immunoprecipitation and co-localization analyses indicated a protein-level association between ANGPTL2 and integrin α5β1 under overexpression conditions. CONCLUSION: ANGPTL2 overexpression promotes angiogenic responses in retinal endothelial cells in vitro, with accompanying integrin α5β1 upregulation and broader signaling-associated phosphorylation changes. Retinal tissue molecular findings and the ANGPTL2-integrin α5β1 protein-level association provide supportive molecular context. The functional roles of specific molecular partners in mediating these responses remain to be determined through targeted validation studies.