Fibroblast-endothelial partners for vascularization strategies in tissue engineering

Cell-based approaches have emerged as a promising therapy to achieve successful vascularization in tissue engineering. Since fibroblasts activation and migration is required for physiological events relying on angiogenesis, we hypothesize herein that different fibroblasts exhibit distinct capacity to promote capillary-like structures assembly, by mature and progenitor endothelial cells (ECs). Outgrowth endothelial cells (OECs) were isolated from human umbilical cord blood samples and characterized by immunofluorescence and imaging flow cytometry for endothelial markers. Co-culture systems were established using either human umbilical vein ECs (HUVECs) or OECs with fibroblasts, being evaluated at 7, 14 and 21 days of culture. Two types of human dermal fibroblasts were used, namely neonatal human foreskin fibroblasts (HFF-1) and juvenile human dermal fibroblasts (HDF). OECs expressed EC markers and formed capillary-like structures. HFF-1 exhibited higher expression of transglutaminase-2, while HDF exhibited a higher expression of α-smooth muscle actin and podoplanin, which were not observed for HFF-1. Formation of capillary-like structures was only observed in co-cultures with HDF and not with HFF-1. No significant differences were found between HDF and OECs or HUVECs co-cultures. These findings suggest that HDF is a preferential cell source for promoting vascularization, either using mature or progenitor ECs, probably due to their higher expression of α-smooth muscle actin and podoplanin, and increased synthesis of extracellular matrix. This work opens new research possibilities regarding the use of specific fibroblast populations co-cultured with ECs, as efficient partners for vascular development in regenerative medicine strategies.