Kartogenin Enhanced Chondrogenesis in Cocultures of Chondrocytes and Bone Mesenchymal Stem Cells

Articular cartilage has poor capability of regeneration due to the avascular surrounding and low metabolic activity. Kartogenin (KGN), an emerging nonprotein heterocyclic compound, was screened to stimulate chondrogenic differentiation of bone mesenchymal stem cells (BMSCs). Coculturing BMSCs and chondrocytes was reported to overcome the shortcomings of forming fibroblastic and hypertrophic cartilages. In this study, KGN was incorporated into the Col-Tgel hydrogel to form a Gel/Cell/KGN complex, which fabricated an appropriate microenvironment for effective cartilage regeneration of BMSCs and/or chondrocytes. The complexes that incorporated KGN, BMSCs, and chondrocytes achieved higher lubricin expression and extracellular matrix production, such as characteristic glycosaminoglycans (GAGs) and collagen type II (COL II), compared to the monocultures of BMSCs or chondrocytes in vitro. The complexes compounding KGN, BMSCs, and chondrocytes (at an optimal ratio in the in vitro experiment) were transplanted into rat models to evaluate the repair effects. Our results suggested that the interaction between BMSCs and chondrocytes can substitute the use of growth factors to some degree and indicated the role of KGN in chondrogenesis induction. Besides, it is the first time (to our knowledge) that the expression of lubricin was found to be delayed in the coculture of mixed cells comparing with GAGs and COL II, which could be significant in cartilage tissue engineering.