POSSIBLE DIFFERENTIATION OF OSTEOGENIC ELEMENTS INVITRO FROM CHICK LIMB MESODERMAL CELLS .1. MORPHOLOGICAL EVIDENCE

In the developing chick limb bud, myogenic, fibrogenic, chondrogenic and osteogenic tissues are derived from embryonic mesenchyme. Previous reports show that when stage 24 limb mesenchymal cells are cultured in vitro, chondrocytes, fibrocytes and myocytes can be identified on the basis of morphological and biochemical parameters. In similar cultures, crystalline calcium phosphate material is deposited in the chondrocytic and fibrocytic matrices. Such crystalline material is not observed before Day 10 of culture life. Subsequent to Day 10 of culture, first amorphous, then crystalline calcium phosphate is observed. On the basis of light microscopy and EM, it appears that the in vitro calcification phenomenon closely resembles the morphological and temporal sequence of osteogenesis observed in vivo.