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.