Adipose-derived stem cells (ASCs) as a source of endothelial cells in the reconstruction of endothelialized skin equivalents

Tissue-engineered autologous skin is a potential alternative to autograft for burn coverage, but produces poor clinical responses such as unsatisfactory graft intake due to insufficient vascularization. Endothelialized skin equivalents comprising human umbilical vein endothelial cells (HUVECs) survive significantly longer due to inosculation with the capillaries of the host, but these cells are allogeneic by definition. The aim of this study was to reconstruct an autologous endothelialized skin equivalent by incorporating progenitor or pre-differentiated endothelial cells derived from adipose tissue, easily accessible source for autologous transplantation. Human adipose tissue-derived stem cells were isolated from lipoaspirates and amplified to obtain endothelial progenitor cells, which were subsequently differentiated into endothelial cells. These cells were then seeded along with human fibroblasts into a porous collagen-glycosaminoglycan-chitosan scaffold to obtain an endothelialized dermal equivalent. Then, human keratinocytes give rise to a endothelialized skin equivalent. Immunohistochemistry and transmission electron microscopy results demonstrate the presence of capillary-like tubular structures in skin equivalents comprising pre-differentiated endothelial cells, but not endothelial progenitor cells. The former expressed both EN4 and von Willebrand factor, and Weibel-Palade bodies were detected in their cytoplasm. This study demonstrates that adipose tissue is an excellent source of autologous endothelial cells to reconstruct endothelialized tissue equivalents, and that pre-differentiation of stem cells is necessary to obtain vasculature in such models.