Abstract
Temporomandibular joint discs (TMJ discs) are unable to repair themselves in disease states, while induced stem cell differentiation is a common method to repair tissue defects. Nowadays, kinds of stem cells are attempted for tissue regeneration of TMJ disc, but these methods have several downsides, which limit their wide application. The proliferation and differentiation ability of human induced pluripotent stem cells (hiPSC) provides a new research direction for TMJ disc tissue regeneration. In this study, we investigated the feasibility of induced differentiation of hiPSC into TMJ disc cells in vitro and the differentiation efficiency of different methods to clarify the possibility and conditions of hiPSC application in TMJ disc tissue engineering. We collected sheep TMJ disc cells cultures for adding in hiPSC culture environment and treated hiPSC by both direct induction and Transwell co-culture for 7 days, 14 days and 21 days. The secretion of extracellular matrix in TMJ disc cells was detected by Sirius Red and Safranin O staining. Collagen Ⅰ and Collagen Ⅱ were qualitatively detected by immunohistochemical staining. The expression of extracellular matrix genes (type I collagen (COL1A1), type II collagen(COL2), glycosaminoglycan (GAG)), chondrogenic differentiation gene SOX9 and pluripotency gene OCT4 were detected by RT-qPCR. Our results showed that hiPSC had the ability to differentiate to TMJ disc cells by direct induction in TMJ disc cell culture medium and by Transwell co-culture method. The highest degree of differentiation was observed after 14 days of direct induction, while Transwell co-culture showed significant differentiation at different times and with different major directions. Meanwhile, Transwell co-culture not only differentiates hiPSC but also promotes the growth and proliferation of TMJ disc cells. Our study is valuable to investigate the possibility of differentiation of hiPSC toward TMJ disc cells and to determine the time of differentiation. It provides new ideas for the selection of seed cells for TMJ disc tissue engineering.