Role of organic phosphate in mineralization of bone in vitro

Calvarial periostea were dissected from 17-day-old embryonic chicks and folded with the osteogenic cells in apposition. The folded explants were cultured for up to six d on serum and plasma clots or in serum-free hormone-supplemented completely-defined medium. Osteoid consistently formed in such cultures in both types of media, and this osteoid mineralized when appropriate levels of beta-glycerophosphate were added to each type of medium. The data presented suggest that the levels of organic phosphates as a limiting factor in the initiation of mineralization of bone in vitro.