Prevascularized mesenchymal stem cell-sheets increase survival of random skin flaps in a nude mouse model

A random skin flap is commonly applied in plastic and reconstructive surgery. The distal part of the random skin flap often risks necrosis because the blood flow may be compromised. Prevascularization is a widely used technology to intensify the vascularization function of biomaterials. In fact, human mesenchymal stem cell (hMSC) sheets promote neoangiogenesis. We speculated that prevascularized hMSC cell sheets (PHCS) would further improve neovascularization by producing more angiogenic growth factors in a random skin flap animal model. In this study, PHCS were set up by co-culturing human umbilical vein endothelial cells (HUVECs) with hMSC cell sheets (HCS). In vitro, we observed microvessel formation and significantly increased production of angiogenesis-related factors. Thus, we analyzed the microvessel networks, vascular maturation, and angiogenic growth factors of the cell sheet. In vivo, PHCS and HCS were implanted in a murine ischemic random skin flap model. Implanted PHCS significantly increased blood perfusion and improved skin flap survival when compared to untreated control skin flaps. The survival rate of the prevascularized and control skin flaps was assessed after 3, 5, and 7 days via analysis of macroscopic images and Laser Doppler Perfusion Imaging (LDPI). Additionally, the numbers of skin appendages, collagen fibers deposition, and epidermal thickness were evaluated. Moreover, the PHCS group also induced the most intense neovascularization, the upshot of which was a robust blood microcirculation supporting skin flap survival. Therefore, PHCS implantation can effectively enhance local neoangiogenesis and hence increase the survival of otherwise ischemic skin flaps. Hence, local administration of PHCS may serve as an alternative approach in improving random skin flap survival.