Slowing down aging of cultured embryonal chick chondrocytes by maintenance under lowered oxygen tension

Cultured epiphyseal-chondrocytes from embryonic chick may serve as a useful in vitro model to study aging processes in cartilage. The accelerated aging process in cultured chondrocytes is completed within a month and is manifested by typical changes in both cellular and extracellular compartments. Under common maintenance conditions, cells show a gradual loss of replicative capacity, increase in the rate of proteoglycan synthesis and age-dependent changes in the structure and composition of proteoglycan. An environmental factor - reduced oxygen tension - was found to slow down aging processes and preserve the young features of chondrocytes for a longer duration in culture. Cultures maintained under lower oxygen tension had higher proliferation rate, smaller cell size, lower rate of proteoglycan synthesis, and lower content of keratan sulfate side chains in the proteoglycan. In addition higher concentrations of free cytosolic calcium [Ca²⁺]_in as compared to control cultures, was found. It is suggested that the increased proliferation rate and the decrease in proteoglycan synthesis caused by low oxygen tension may be signalled by the higher [Ca²⁺]_in in these cells.