A mammalian periosteal cell culture system was developed to investigate the metabolic response of fresh calf bone periosteal cells to various oxygen tensions in vitro. Two predominant cell phenotypes were seen in the culture system. A rapidly proliferating mat of alkaline phosphatase-negative cells supported the growth of overlying clusters of alkaline phosphatase-positive cells. The appearance and subsequent population growth of the alkaline phosphatase-positive cells correlated directly with increases in enzyme activity on biochemical assay. Alkaline phosphatase production was optimal at lower oxygen tensions (5%, 9%), which approximated capillary pO2. In addition, the preconfluence oxygen environment was more critical to the final expression of the enzyme activity than the postconfluence environment. The mechanism of the environmental regulation of alkaline phosphatase gene expression at various oxygen tensions is not known. Periosteal cells were highly sensitive to oxygen tension and expressed alkaline phosphatase enzyme activity at oxygen levels approximating capillary rather than atmospheric pO2.
From the McKay Laboratory of Orthopaedic Surgery Research, University of Pennsylvania School of Medicine, Philadelphia. Pennsylvania.
Reprint requests to Frederick S. Kaplan, M.D., McKay Laboratory of Orthopaedic Surgery Research, University of Pennsylvania School of Medicine, Philadelphia, PA 19104.
This work was supported in part by an American Heart Association Medical Student Research Fellowship grant, grants AM-18033 and SCOR 1-P50-AR39226–01 from the National Institutes of Health and by a Hartford Foundation Fellowship for Research on Aging.
Received: October 18, 1988.