Characterization of Sox9‐overexpressing human umbilical cord blood‐derived mesenchymal stem cells‐based engineered cartilage both in vitro and in vivo

The source of seed cells is a critical factor for tissue engineering. The goal of this study was to evaluate the chondrogenesis of Sox9‐overexpressing human umbilical cord mesenchymal stem cells (hUCMSCs) seeded onto bone matrix gelatin (BMG)/fibrin hybrid scaffolds both in vitro and in vivo. hUCMSCs were stably transfected with Sox9‐expressing plasmid and grown on the three‐dimensional BMG/fibrin hybrid scaffold for 8 weeks. Scanning electron microscopy and histochemistry were performed. The hUCMSC‐loaded scaffolds were implanted into the subcutaneous layer of immunocompetent rats and chondrogenesis and host immune responses were monitored for 8 weeks. We found that hUCMSCs spread well and proliferated from 2 weeks after culturing. They produced abundant glycosaminoglycans and collagen II. At 8 weeks after implanting into rats, the hUCMSCs on the scaffolds formed cartilage‐like tissue and displayed positive staining for toluidine blue, safranin O, Masson's trichrome, and collagen II. No significant changes in serum levels of lgG, lgA, lgM, C3, and C4 were observed after implantation of the hUCMSC‐loaded scaffolds. Xenogeneic implantation of Sox9‐overexpressing hUCMSCs embedded in the BMG/fibrin scaffolds promotes the formation of cartilage‐like tissue without inducing evident host immune response. Therefore, Sox9‐overexpressing hUCMSCs represent a promising cell candidate for cartilage tissue engineering. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 1150–1155, 2017.