EFFECTS OF VARYING OXYGEN CONCENTRATIONS ON OSTEOGENESIS AND EMBRYONIC CARTILAGE IN VITRO

An improved method of organ culture, employing embryonic chick tibiae, demonstrated consistent patterns of osteogenesis. With all other factors constant, the amount of bone and collagen formed or destroyed could be controlled solely by altering the amount of O2 available to the explants from the gaseous phase of the culture. Maximum osteogenesis was observed, with an O2 concentration of 35%. Collagen-fiber formation and osteogenesis were suppressed by lowering the O2 concentration to 5% and, to a lesser degree, by raising it to 95%. High O2 concentrations also appeared to cause osteoclasia. Cartilage matrix and cells near the cut ends of explants also demonstrated significant alterations under various O2 concentrations. High O2 concentrations (95%) caused extensive chondroclasia. Intermediate O2 concentrations (20 to 65%) produced numerous large collagen fibers in and about the lacunae of degenerating chondrocytes, while other chondrocytes, undergoing alterations of morphology, came to resemble osteoblasts. Metachromasia of cartilage matrix was lost. Low (5%) and high (95%) O2 concentrations did not produce similar collagen fiber production, alterations of chondrocyte morphology, or loss of matrix metachromasia.