Based On Ectomesenchymal Stem Cell Co-culture System Inspection Regulation Research Of Articular Cartilage Phenotype

Currently, injuries to articular cartilage are one of the most challenging issues due to the poor intrinsic tissue repair. The lack of efficient modalities of treatment prompts the development of tissue engineering by combining chondrogenic cells, biomaterials and soluble factors. Mesenchymal stem cells (MSCs) are one of promising cells for cartilage tissue engineering. During developmental process, cell-cell interactions are important in tissue morphogenesis. However, in cartilage tissue engineering, the interplay of MSCs and ACs is not clearly understood. Though researchers believe that ACs may induce chondrogenic differentiation of MSCs. the effect of MSCs on ACs has not been reported. Coculture in vitro makes the investigation on the interaction between two kinds of cells possible. Therefore, in this work, we cocultured MSCs and ACs to study the effect of MSCs on ACs’ phenotype.This study includes two aspects. First, the knee joints of New Zealand white rabbits were digested by type Ⅱ collagenase to isolate the chondrocytes, followed by subculture of rACs in vitro to examine the growth characteristics. Second, a Transwell system was used to study the effect of MSCs on rACs. Concerning the latter one, several factors were investiaged in our study, including different coculture modes, i.e. two or three dimensional culture, different pre-culture time periods of rACs, coculture time periods, and the sources of MSCs. Additionly. we adopted the MSCs’conditioned medium to cultivate rACs. Cocultured rACs were analyzed regarding cell morphology, GAG secretion and gene expression.Based on above studies, following results were obtained:when rACs subcultured in vitro, apparent dedifferentation was observed. Specifically, the morphology of rACs changed from small round, polygonal to a spindle-like shape; secretion of extracelluar matrix (GAG and collagen) declined. After coculture with MSCs, monolayer rACs turned from round to spindle-like shape, and the aggregation of rACs in alginate hydrogel beads was inhibited, the secretion of ECM also decreased, while the expression of dedifferentiation-related genes increased. Both hMSCs and rMSCs showed similar effects despite with different extents. In addition. MSCs-conditioned medium had the similar effects as co-culture.Collectively. rACs gradually dedifferentiate during subculture, losing cartilaginous phenotype. Presence of MSCs accelerated dedifferentiation. probably due to paracrine effects of MSCs. However, the molecular mechanisms remain to be unraveled further. Nevertheless, this study demonstrated that MSCs could regulate the ACs phenotype notablely. thus providing new insights to cartilage tissue engineering.