Self-endothelialization of vascular prostheses by immobilized capture molecules for circulating endothelial progenitor cells

Objective: Due to their insufficient biocompatibility and high thrombogenicity, small diameter artificial vascular prostheses still do not show a satisfactory patency rate. In vitro endothelialization of artificial grafts before implantation has been established experimentally years ago, but, has never been used for routine clinical applications. This study deals with the coating of graft surfaces with capture molecules for circulating endothelial progenitor cells (EPCs), mimicking a pro-homing substrate to fish out EPCs from the bloodstream after implantation. Methods: Aptamers against EPCs were generated by systematic evolution of ligands by exponential enrichment (SELEX), a technique from combinatorial chemistry. They can be selected from a library of 10 15 starting nucleotides. We have spotted a defined aptamer onto a hydrogel coated surface, installed in a flow chamber, to detect the attachment of EPCs from fresh human whole blood. Finally these cells were cultivated in growth factor enriched medium and fluorescence marked antibodies against CD34, CD 31, von Willebrand factor and VEGFR-2 were used to characterize the cell attachment. Results: After eight SELEX rounds 36 aptamers in total were cloned, sequenced, synthesized and evaluated by flow cytometry. The best binding aptamers were immobilized in a flow chamber. The captured cells were positive for CD34, CD 31, von Willebrand factor and VEGFR-2 and able to differentiate into a confluent endothelial layer. Conclusion: We hypothesize that in vivo self-endothelialization of blood contacting implants by homing factor mimetic capture molecules for EPCs may bring new perspectives towards future clinical applications of stem cell and tissue engineering strategies.