Abstract 3668: Endothelial Progenitor Cells Express Connexins which may be Important for the Functional Integration of Circulating Progenitor Cells into the Endothelium
Bone marrow (BM)-derived endothelial progenitor cells (EPC) enhance endothelial cell (EC) repair after focal EC damage, improve endothelial dysfunction, and are an important cellular risk predictor for cardiovascular mortality. For an effective EC repair, functional integration of circulating EPC into the damaged endothelium is a pre-requisite. Here, we determine the importance of connexins (Cx) for the interaction with mature ECs. Expression of Cx was evaluated on magnetic-bead selected CD133+ cells using immunocytochemistry and flow cytometry. CD133+ cells expressed Cx 40 and Cx 43 but not Cx 37. Mononuclear cells were cultivated to obtain early outgrowth EPC or colony forming units-endothelial cells (CFU-EC). Cx 37, 40, and 43 were expressed on cultured EPC. Co-culture experiments with mature human coronary artery endothelial cells (HCAEC) and EPC demonstrated the development of Cx 40, and 43 positive gap-junctions between both cells types. In order to investigate whether the interaction between HCAEC and EPC results in a functional communication between cells, dye transfer experiments were performed. Di-Ac-LDL labelled EPC transformed into Di-Ac-LDL and Calcein AM double positive cells when co-cultured with Calcein AM positive HCAEC and vice versa. In order to study the role of connexins in reendothelialization, C57bl6 (wild-type, WT) mice were subjected to a focal endothelial cell denudation and repetitively treated with WT and Cx37−/− deficient mononuclear cells. In contrast to the treatment with WT mononuclear cells, treatment with Cx37−/− cells was not associated with enhanced reendothelialization. Furthermore, endothelial function of isolated aortic rings derived from Cx37−/− mice showed an impaired endothelial-dependent vasorelaxation compared to WT mice. We provide evidence that connexins are differentially expressed on immature naíve EPC and cultured early-outgrowth EPC. The expression of connexin 37, 40, and 43 may be required for the functional integration of endothelial progenitor cells into the damaged endothelium.