Effect of oxygen tension on chondrocyte extracellular matrix accumulation

Since cartilage is mainly an avascular tissue, chondrocytes exist in a low- level oxygen environment in vivo. In the present study, we investigated the effect of oxygen tension (20%, 5% and 1% gas phase oxygen concentrations) over a 20-day period on the extracellular matrix accumulation of bovine art icular chondrocytes in confluent surface cultures. Matrix accumulation was assessed by the amount of glycosaminoglycan and collagen deposited in the m atrix. From initially confluent monolayers, the chondrocytes became distrib uted throughout a thick layer of extracellular matrix, thus forming a multi cell-layer of tissue. Cells maintained their normal rounded shape, indicati ve of the differentiated phenotype, throughout the 20-day culture period. O n a per culture and a per cell basis, the amount of collagen and glycosamin oglycan accumulation in the matrix was lower at the reduced oxygen tensions . Specifically, in 1% oxygen, matrix GAG content reached a steady-state lev el, with no net increase in GAG levels after two weeks, whereas in 20% oxyg en, matrix GAG increased with time. It is concluded that oxygen has a signi ficant effect on the amount of macromolecules accumulated in the extracellu lar matrix. The implications of these findings in growing cartilage constru cts in vitro are discussed.