Limb bud chondrogenesis in cell culture, with particular reference to serum concentration in the culture medium.

When limb bud mesodermal cells of stages 23-24 chick embryos were plated at low cell density (2 X 10(5) cells/cm2) and cultured in medium containing 10% fetal calf serum (FCS) (serum-rich medium), all cells became fibroblastic and no chondrocyte differentiation occurred in the culture. However, when cells of the same origin were cultured in a medium containing only 0.1% FCS (serum-poor medium), almost all the cells formed aggregates which developed further to form cartilage nodules. The loss of chondrogenic activity in serum-rich medium culture was irreversible: cultivation of the limb bud cells in serum-rich medium for 12 h abolished chondrogenic activity completely and these cells could not resume activity on re-cultivation in serum-poor medium. Calf, horse and chick serum at a concentration of 10% also induced the loss of chondrogenic activity in low cell density culture. Failure of chondrogenesis in serum-rich medium culture seemed to be due to the commitment of bipotential limb bud mesodermal cells to fibroblastic cells rather than to selective detachment of pre-committed chondroblasts.