Figure 1.

Morphological transition to a cortical actin pattern is required for chondrogenic differentiation of limb mesenchymal cells. (A) Differentiation-competent mesenchymal cells were prepared as described in the Methods section. Cells were grown on coverslips, treated with cytochalasin D (CD), stained with PNA on day 3 of culture, immunostained for F-actin with Alexa488-phalloidin on day 4 of culture, or stained with Alcian blue on day 5 of culture. Dedifferentiated chondrocytes were cultured on a chitosan membrane. (B) Cells were stained with Alexa-488-conjugated phalloidin. (C) Changes in the protein levels of type I and type II collagen were examined by Western blotting. The data shown are representative of at least four independent experiments. ^*, statistically different from control cells (P < 0.001).