Regulation of endothelial cell and endothelial progenitor cell survival and vasculogenesis by integrin-linked kinase

Objective - New vessel formation is a dynamic process of attachment, detachment, and reattachment of endothelial cells (ECs) and endothelial progenitor cells (EPCs) with each other and with the extracellular matrix (ECM). Integrin-linked kinase (ILK) plays a pivotal role in ECM-mediated signaling. Therefore, we investigated the role of ILK in ECs and EPCs during neovascularization. Methods and Results - In human umbilical cord vein ECs and EPCs, endogenous ILK expression, along with subsequent cell survival signals phospho-Akt and phospho-glycogen synthase kinase 3β, was reduced after anchorage or nutrient deprivation. Even brief anchorage deprivation resulted in retarded capillary tube formation by ECs. Adenoviral ILK gene transfer in ECs and EPCs reversed the decrease in cell survival signals after anchorage or nutrient deprivation, leading to enhanced survival, reduced apoptosis, and significantly accelerated the functional recovery after reattachment. And ILK overexpressing EPCs significantly improved blood flow recovery and prevented limb loss in nude mice hindlimb ischemia model. Furthermore, the efficacy of systemic delivery was equivalent to local injection of ILK-EPCs. Conclusions - ILK overexpression protects ECs and EPCs from anchorage- or nutrient-deprived stress and enhances neovascularization, suggesting that ILK is an optimal target gene for genetically modified cell-based therapy. Neovascularization is a dynamic process of detachment and reattachment of ECs and EPCs. Endogenous ILK expression was decreased in various stress conditions, and the gene transfer of ILK protected ECs and EPCs from temporary anchorage or nutrient deprivation. Furthermore, ILK gene transfer in EPCs significantly enhanced neovascularization in vivo.