Apelin-13 promotes late endothelial progenitor cells differentiation by regulating Krüppel-like factor 4.

Abstract

The endothelial progenitor cells (EPCs) differentiation plays an essential role in angiogenesis. The purpose of this study is to determine the potential mechanisms of apelin-13 in EPCs differentiation. The rats EPCs were isolated from the bone marrow and identified by DIL-acLDL and FITC-UEA-1 staining. EPCs were divided into four groups: the negative control group, the Krüppel-like factor 4 (KLF4) upregulation group, the KLF4 downregulation group, and the apelin-13 group. The EPCs differentiation was evaluated by cell migration, proliferation, and the expressions of surface markers CD31, CD34, CD133, and VEGFR-2 on mRNA and the protein levels, as well as immunofluorescence. In the KLF4 up-regulation and apelin-13 groups, the EPCs number of G1, S, and G2/M phases decreased and suggested that KLF4 and apelin-13 were closely related to the EPCs proliferation. EPCs showed stronger migration ability with the elevation of KLF4 and apelin-13 while declined migration was detected in KLF4 siRNA transfected EPCs. The surface markers expressions on mRNA and the protein levels increased in the KLF4 upregulation group, and in the apelin-13 group there were similar results, as well as increased KLF4 expression. The upregulation of apelin-13 significantly increased the expressions of EPCs surface markers, which were involved in early EPCs differentiated into late EPCs and influenced the cells migration and proliferation. Taking the elevation of KLF4 which performed similar effects of apelin-13, we believe that apelin-13 activates or synergizes with KLF4 to promote this process.