Dependence of the differentiated state on the cellular environment: modulation of collagen synthesis in tendon cells.

Abstract

In an adequate environment, primary avian tendon cells are capable of retaining the full expression of differentiated function and a correct morphological orientation for 1 wk in culture. At high density and in the presence of ascorbate, they are fully stabilized in that they devote 25-30% of their total protein synthesis to collagen, a level comparable to that in tendon cells in ovo. Either at low density or in medium without ascorbate, they synthesize collagen at only 1/3 of this level. If plated on a collagen matrix, these cells will orient themselves in a manner similar to that of tendon cells in vivo. They are capable of fully modulating the percentage of collagen synthesis upon addition or removal of ascorbate and serum [fetal calf]. The variation in percentage of collagen produced is a result of alterations in collagen synthesis rather than of changes in total protein synthesis or hydroxylation of proline in collagen. Primary avian tendon cells, therefore, provide a suitable model for understanding the stability of the differentiated state, mechanism of action of ascorbate and regulation of collagen biosynthesis.