Proteoglycan synthesis by sternal chondrocytes perturbed with vitamin A

Proteoglycan synthesis by sternal chondrocytes was studied in the presence of excess vitamin A (10 i.u./ml). Proteoglycans synthesized by the treated cells were smaller, and had larger amounts of chondroitinase ABC-resistant materials than control cells. Vitamin A-pretreated cells, when provided with normal feeding medium, failed to revert back to normal morphology and synthetic processes. Chondrocyte cultures prelabelled with [35S]-sulphate, when maintained in the presence of excess of vitamin A, showed: (1) increased release of labelled proteoglycans into the medium, and (2) increased (19%) degradation of the proteoglycans. The proteoglycans synthesized by the vitamin A-treated chondrocytes are also incapable of binding with exogenous large molecular weight hyaluronic acid. Thus, high levels of vitamin A modulate the differentiation of chondrocytes by altering cellular synthetic processes.