Suppression of chondrogenic expression in mixtures of normal chondrocytes and BUDR-altered chondrocytes grown in vitro

When normal chondrocytes are mixed with suspended liver, or kidney, or muscle cells and reared in monolayers $\text{in}$$\text{vitro}$, the heteretypic cells suppress the synthesis of chendroitin sulfate by adjacent chondrecytes. Chondrecytes grown in BudR, though replicating normally, do not synthesize chondroitin sulfate. BudR-altered chondrocytes exhibit cell surface properties very different from those exhibited by functional chondrecytes. BudR-altered cells do not adhere to one another and they are amoeboid. In mixtures of BudR-altered chondrocytes and normal chondrecytes, the former cells function as heterotypic cells: BudR-altered cells suppress chondreitin sulfate synthesis by contiguous normal chondrecytes.