Preliminary study of in vitro chondrogenesis by co-culture of bone marrow stromal cells and chondrocytes

Objective This study explored the feasibility of in vitro bone marrow stromal cell (BMSC) chondro-genesis induced by the chondrogenic microenvironment that was provided by chondrocytes at various concentrations. Methods Porcine BMSCs and auricular chondrocytes were isolated and in vitro expanded respectively and then were mixed at the ratio of 9: 1 , 8:2 (BMSCs:chondrocytes). The mixed cells were seeded onto polyglycolic acid/polylac-tic acid( PGA/PLA) scaffold at the ultimate concentration of 5. 0×107/mL as co-culture group. Chondrocytes and BMSCs of the same ultimate concentration were seeded respectively onto the scaffold as positive control group ( chon-drocyte group) and negative control group (BMSC group). 20% of above concentration chondrocytes (1.0 ×107 / mL) were seeded as low chondrocyte group. The specimens were collected after in vitro culture for 4 weeks. Gross observation, histology and immunohistochemistry were used to evaluate the results. Results Cells in all groups had fine adhesion to the scaffold and could secrete extracellular matrix. In 8 : 2 co-culture group and positive control group, the cell-scaffold constructs could maintain the original size and shape during in vitro culture. At 4 weeks, cartilage-like tissue had formed and type Ⅱ collagen could be detected for strong expression by immunohistochemistry. In 9: 1 co-culture group, the constructs shrunk slightly and histology showed cartilage-like tissue formed only at the edges of constructs. In negative control, the constructs deformed and shrunk gradually without mature cartilagelacuna in histology. The constructs in low chondrocyte group also shrunk obviously in thickness with small amount of cartilage formation. Conclusion Chondrocytes can provide chondrogenic microenvironment to promote in vitro BMSC chondrogenesis. 20% chondrocytes have fine capacity of inducing BMSC chondrogenic differentiation.