Endothelial colony forming cell rolling and adhesion supported by peptide-grafted hydrogels

The aim of this study was to investigate the ability of peptides and peptide combinations to support circulating endothelial colony forming cell (ECFC) rolling and adhesion under shear flow, informing biomaterial design in moving toward rapid cardiovascular device endothelialization. ECFCs have high proliferative capability and can differentiate into endothelial cells, making them a promising cell source for endothelialization. Both single peptides and peptide combinations designed to target integrins α₄β₁ and α₅β₁ were coupled to poly(ethylene glycol) hydrogels, and their performance was evaluated by monitoring velocity patterns during the ECFC rolling process, in addition to firm adhesion (capture). Tether percentage and velocity fluctuation, a parameter newly defined here, were found to be valuable in assessing cell rolling velocity patterns and when used in combination were able to predict cell capture. REDV-containing peptides binding integrin α₄β₁ have been previously shown to reduce ECFC rolling velocity but not to support firm adhesion. This study finds that the performance of REDV-containing peptides in facilitating ECFC dynamic adhesion and capture can be improved by combination with α₅β₁ integrin-binding peptides, which support ECFC static adhesion. Moreover, when similar in length, the peptide combinations may have synergistic effects in capturing ECFCs. With matching lengths, the peptide combinations including CRRETAWAC(cyclic)+REDV, P_RGDS+KSSP_REDV, and P_RGDS+P_REDV showed high values in both tether percentage and velocity fluctuation and improvement in ECFC capture compared to the single peptides at the shear rate of 20 s^-1. These newly identified peptide combinations have the potential to be used as vascular device coatings to recruit ECFCs. STATEMENT OF SIGNIFICANCE: Restoration of functional endothelium following placement of stents and vascular grafts is critical for maintaining long-term patency. Endothelial colony forming cells (ECFCs) circulating in blood flow are a valuable cell source for rapid endothelialization. Here we identify and test novel peptides and peptide combinations that can potentially be used as coatings for vascular devices to support rolling and capture of ECFCs from flow. In addition to the widely used assessment of final ECFC adhesion, we also recorded the rolling process to quantitatively evaluate the interaction between ECFCs and the peptides, obtaining detailed performance of the peptides and gaining insight into effective capture molecule design. Peptide combinations targeting both integrin α₄β₁ and integrin α₅β₁ showed the highest percentages of ECFC capture.