The association between CKAP2 and HIF-1α in retinal neovascularization under hypoxic conditions

This study aimed to explore the expression patterns and pathological roles between cytoskeleton-associated protein 2 (CKAP2) and hypoxia-inducible factor 1-alpha (HIF-1α) under hypoxic conditions, both in vitro and in vivo. Single-cell RNA sequencing (scRNA-seq) data from an oxygen-induced retinopathy (OIR) model were analyzed to evaluate cell-type-specific expression of CKAP2 and HIF-1α. Protein expression, localization, and potential interaction of CKAP2 and HIF-1α were assessed in hypoxia-stimulated human retinal microvascular endothelial cells (HRMECs). Knockdown of Ckap2 was further employed to examine its effect on HIF-1α signaling. scRNA-seq analysis showed that Ckap2 was notably upregulated in endothelial and stalk cells, whereas Hif-1α was predominantly elevated in retinal neurons. In OIR mice, CKAP2 expression increased progressively at later time points (P17 and P22), contrasting with the early hypoxia-responsive upregulation of HIF-1α (P12). Under hypoxia in HRMECs, HIF-1α level increased rapidly, while CKAP2 expression remained stable. Immunoprecipitation confirmed an interaction between CKAP2 and HIF-1α. Ckap2 knockdown reduced HIF-1α expression under normoxia and limited its induction under hypoxia, implying CKAP2 may contribute to HIF-1α stability and the adaptive cellular response to hypoxia. These findings highlight a functionally significant correlation between CKAP2 and HIF-1α under hypoxic conditions, providing new insights into their cooperative role in ischemic retinopathy.