Protein-engineered microenvironments can promote endothelial differentiation of human mesenchymal stem cells in the absence of exogenous growth factors.

Peripheral artery disease often requires treatments with vascular grafts for vessel reconstruction. Endothelialization of the vascular grafts is important to achieve long-term patency because endothelial cells regulate thrombosis, inflammation, and growth of smooth muscle cells. One potential source of endothelial cells is human mesenchymal stem cells (hMSCs), which can be routinely differentiated towards the endothelial lineage using exogenous growth factors such as vascular endothelial growth factor (VEGF). However, there are few studies that investigate the effect of materials on endothelial differentiation in the absence of growth factors. This study demonstrates that exogenous growth factors are not needed to achieve endothelial differentiation of hMSCs and that protein-based microenvironments promote endothelial differentiation. Specifically, we genetically engineered proteins containing a VEGF-mimicking peptide and resilin repeats and demonstrated that cells grown on the protein-engineered microenvironments were viable, had normal metabolic activity, and displayed increased endothelial-specific markers and endothelial function compared to negative control cells. In particular, cells cultured on our proteins formed networks that were statistically equivalent to positive control cells. We confirmed that the mere presence of protein on surfaces was insufficient to promote endothelial differentiation of hMSCs, and the specific composition of the RZ-QK protein appeared to be necessary for promoting differentiation. Thus, our protein-based materials are promising tools for obtaining endothelial cells for use in vascular grafts.