High inoculation cell density could accelerate the differentiation of human bone marrow mesenchymal stem cells to chondrocyte cells

The effects of the density of human mesenchymal stem cells (MSCs) on their differentioation to chondrocytes in a differentiation medium supplemented with dexamethasone, TGF beta 3, and IGF-1 were investigated for the regenerative therapy of cartilage. The increase in the initial density of MSCs from 0.05x10(4) to 0.9x10(4) cells/cm(2) accelerated the increase in the expression level of aggrecan mRNA during the differentiation culture for 7 d. The conditioned medium harvested at 7 d from the differentiation culture with an initial MSC density of 0.3 x 10(4) cells/cm(2) accelerated the initial increase in the expression level for 3 d in the differentiation culture with an initial MSC density of 0.3 x 10(4) cells/cm(2), whereas the conditioned medium harvested at 7 d in the differentiation culture with an initial MSC density of 0.05x10(4) cells/cm(2) did not. The differentiation culture after 14 d with an initial MSC concentration of 0.3 x 10(4) cells/cm(2) showed an expression level 1.7-fold that in the case of the culture with an initial MSC concentration of 0.05x10(4) cells/cm(2). Thus, a high MSC inoculum density might be appropriate for the rapid differentiation of MSCs to chondrocytes.