OBJECTIVETo investigate the feasibility of chondrogenesis in vitro with bone marrow stromal cells (BMSCs) induced by the co-cultured chondrocytes.

METHODSThe BMSCs and chondrocytes were separated from pig and cultured. The supernatant of chondrocytes was used as the inducing solution for BMSCs from the 2nd generation. 7 days later, samples were taken and underwent immunohistochemistry and RT-PCR for detection of the expression of specific type II cartilage collagen, type II collagen and aggrecan mRNA. The cultured BMSCs and chondrocytes were mixed at a ratio of 8:2 (BMSC: cartilage cell) and were inoculated into a polyglycolic acid/polylactic acid (PGA/PLA) scaffold at the final concentration of 5.0 x 10(7)/ml. The cartilage cells and BMSCs were also inoculated separately at the same concentration as the positive and negative control. Pure cartilage cells at 20% of the above mentioned concentration (1.0 x 10(7)/ml) were used as the low concentration cartilage cell control group. Samples were collected 8 weeks later. General observations, wet weight, glycosaminoglycans (GAGs) determination and histological and immunohistochemistry examinations were performed.

RESULTSThe expression of type II collagen, type II collagen and aggrecan mRNA were positive in induced BMSCs. In the co-cultured group and the positive control group, pure mature cartilage was formed after 8 weeks of culture in vitro, and the size and shape of the scaffold were maintained. The newly formed cartilage in the two groups were almost the same in appearance and histological properties. The immunohistochemistry results indicated that the cartilage cells of the two groups all expressed ample cartilage-specific type II collagen. The average wet weight and GAG content in the co-cultured group reached more than 70% of those in positive control group. Only an extremely small amount of immature cartilage tissues was formed in local regions in pure BMSC group, and the scaffold was obviously shrunk and deformed. Although the wet weight of newly generated cartilage tissue in the low concentration cartilage cell group reached 30% of that in positive control group, the scaffold was obviously shrunken and deformed. Only regional and discontinuous cartilage tissues were formed, and the amount of newly formed cartilage was obviously less than that in the co-culture group and the positive control group.

CONCLUSIONSChondrocytes can provide a micro-environment for the formation of cartilage, and also effectively induce BMSC to differentiate into chondrocytes and form tissue-engineered cartilage in vitro.