Change in the expression of collagen genes in dividing and nondividing chondrocytes

Chondrocytes were isolated from the sterna of 17-day-old chick embryos by enzyme digestion. Rapid proliferation of chondrocytes was achieved in the presence of chick serum (10%, v/v). Addition of either hydroxyurea (10(-3) M) or cytosine arabinoside (10 microgram/ml) to the culture medium was used to arrest growth of cells. Under both conditions, however, a rather fast switch of synthesis from type II to type I collagen was observed. This suggests that the loss of the differentiated state of chondrocytes in culture is not necessarily bound to mitosis.