Outgrowth endothelial cells isolated and expanded from human peripheral blood progenitor cells as a potential source of autologous cells for endothelialization of silk fibroin biomaterials

One challenge of particular importance in tissue engineering is to improve vascularization of larger size defects, which would then facilitate a sufficient supply with oxygen and nutrients to the central regions of a larger tissue-engineered construct or in highly vascularized tissues. In this study, we show that outgrowth endothelial cells (OECs) derived from human peripheral blood can serve as a source of human autologous endothelial cells and can be used in combination with fibroin silk fiber meshes for applications in tissue engineering. OEC reveal a highly differentiated endothelial phenotype as well as a high phenotypic stability during their expansion. Furthermore, OEC showed very promising results in the endothelialization of fibroin silk fiber meshes, maintaining their endothelial characteristics and functions. On the fibroin fiber meshes OECs formed differentiated endothelial cell layers covering the single fibers as shown by data from scanning electron microscopy, immunofluorescence, and gene expression analysis. After embedding in a wound-healing matrix, mimicked by fibrin gels, OEC migrated from the fibroin scaffolds into the fibrin and formed a microvessel-like network. Thus, we conclude that OEC could serve as a valuable source of autologous endothelial cells, supporting pro-angiogenic therapies in combination with silk fibroin-based scaffolding materials in the field of tissue engineering and regenerative medicine.