EFFECTS OF THYROXINE AND LOW OXYGEN TENSION ON CHONDROGENIC EXPRESSION IN CELL CULTURE

The effects of thyroxine and low oxygen tension on embryonic chick chondrocytes in cell culture were investigated. The assays for chondrogenic expression involved (1) morphological and histological observations for a resemblance between the cultured cells and hyaline cartilage in vivo, (2) measurements of the rates of polysaccharide synthesis by monolayers, and (3) analysis of the polysaccharides for the presence of chondroitin sulfate. Thyroxine (10-6 M) was markedly stimulatory to both monolayers and clones; a delayed addition of the hormone to clones caused the conversions of some non-CMC's into CMC's. Low oxygen tension stimulated the rate of chondroitin sulfate synthesis by monolayers but had no apparent effect on clones. The effects of low oxygen tension, which were reversible, were apparent only in the presence of added thyroxine. Relatively short-term exposures to BUdR (10 μg/ml) strongly inhibited chondrogenic expression, even in the presence of thyroxine and low oxygen tension. The results support previous reports that thyroxine and low oxygen tension may play a physiological role in chondrogenesis in vivo. © 1969.