Expression of type X collagen is transiently stimulated in redifferentiating chondrocytes pretreated with retinoic acid.

Growth of quail chondrocytes in the presence of retinoic acid (RA) results in the suppression of the differentiated phenotype. RA-treated chondrocytes recover their differentiated phenotype if they are cultured for an additional 15 days in the absence of RA. A few days after removal from RA, treated chondrocytes acquire the polygonal morphology characteristic of chondrocytes growing as attached cells; they also gradually resume collagen II expression and synthesize cultures. The levels of collagen X mRNA decrease during the second week of culture in the absence of RA. Finally, at the end of 15 days, the absolute levels of collagen II and collagen X mRNAs are very similar in control and recovering chondrocytes.