Chondroitin sulfate inhibits calcification of bone formed in vitro

Chondroitin sulfate is known to inhibit formation of hydroxyapatite in solution. It is not known whether chondroitin sulfate will prevent mineralization in a cellularly controlled environment. In order to evaluate this possibility, chondroitin sulfate was added to the medium of periosteal bone-forming cultures. These cultures normally form mineralized bone in the presence of 10 mM beta-glycerophosphate. Chondroitin sulfate prevented calcium accumulation and thus mineralization in these cultures. However, chondroitin sulfate did not prevent phosphate accumulation in cultures, thus suggesting that calcium and phosphate accumulation in bone may be dependent on two different mechanisms.