Figure 1.

  rhMK stimulates proliferation of rat articular chondrocytes in vitro. (a) rhMK promotes proliferation of rat primary articular chondrocytes in vitro in a dose‐dependent manner. Freshly isolated chondrocytes cultured in the presence of 10% FBS were treated with rhMK at indicated concentrations for 48 h. Cells were labelled with anti‐BrdU for an additional 4 h followed by quantification of BrdU incorporating cells at OD450 nm after immunochemical staining. (b) Proliferative role of rhMK was detected by MTT assay. After initial culture of rat primary articular chondrocytes in high serum concentration (10%) for 48 h, medium was changed to low serum (0.5%) supplemented with or without rhMK (3 μg/ml). The effect of rhMK on chondrocyte proliferation exposed for various time intervals was determined. (c, d) Cumulative cell expansion of rat primary articular chondrocytes cultured in 10% FBS (c), or in serum‐free medium (d) supplemented without (control) or with rhMK (3 μg/ml) was determined by direct cell counting. Cell number expansion in fold was based on direct cell counts and calculated as described in the Materials and methods section. All data are expressed as mean ± SD from triplicate cultures. Similar results were obtained in three independent experiments. *Value compared to controls without rhMK, using Student’s t‐test. *P < 0.05, **P < 0.01.