Preliminary study of mesenchymal stem cells-seeded type I collagen-glycosaminoglycan matrices for cartilage repair.

OBJECTIVE: To investigate the possibility of repairing articular cartilage defects with the mesenchymal stem cells (MSCs)- seeded type I collagen-glycosaminoglycan(CG) matrices after being cultured with the chondrogenic differentiation medium.

METHODS: The adherent population of MSCs from bone marrow of 10 adult dogs were expanded in number to the 3rd passage. MSCs were seeded into the dehydrothermal treatment (DHT) cross-linked CG matrices; 2 x 10(6) cells per 9-mm diameter samples were taken. Chondrogenic differentiation was achieved by the induction media for 3 weeks. Cell contractility was evaluated by the measurement of the cell-mediated contraction of the CG matrices with time in culture. The in vitro formation of the cartilage was assessed by an assay employing immunohistochemical identification of type II collagen and by immunohistochemistry to demonstrate smooth muscle actin (SMA). The cells seedling CGs were implanted into cartilage defects of canine knee joints. Twelve weeks after surgery, the dogs were sacrificed and results were observed.

RESULTS: There was significant contraction of the MSCs-seeded DHT cross-linked CG scaffolds cultured in the cartilage induction medium. After 21 days, the MSC-seeded DHT cross-linked matrices were contracted to 64.4% +/- 0.3%; histologically, the pores were found to be compressed and the contraction coupled with the newly synthesized matrix, transforming the MSCs-seeded CG matrix into a solid tissue in most areas. The type II collagen staining was positive. The SMA staining was positive when these MSCs were seeded and the contracted CGs were implanted into the cartilage defects of the canine knee joints to repair the cartilage defects. The function of the knee joints recovered and the solid cartilaginous tissue filled the cartilage defects. Conclusion The results demonstrates that MSCs grown in the CG matrices can produce a solid cartilaginous tissue containing type II collagen after being cultured with the chondrogenic differentiation medium and implanted into cartilage defects. We hypothesize that the following steps can be performed in the chondrogenic process: (1)MSCs express SMA, resulting in matrix contraction, thus achieving a required cell density (allowing the cells to operate in a necessary society); (2)Cells interact to form a type II collagen-containing extracellular matrix (and cartilaginous tissue); (3)Other factors, such as an applied mechanical stress, may be required to form a mature cartilage with the normal architecture.