The effect of varying oxygen tensions on hydroxyproline synthesis in mouse calvaria in vitro

Six-day-old mouse calvaria were grown in vitro on a grid culture system in Medium 199 containing titriated proline. Gas atmospheres containing various oxygen concentrations up to 25% were introduced to influence the rate of collagen formation as determined by the synthesis of labelled hydroxyproline in the explants. There was an increase in synthesis in response to 15% oxygen with a possible further small increase in 25% oxygen. Measurement of the release of unlabelled hydroxyproline into the medium as an estimate of collagen breakdown indicates an increase in resorption with increasing oxygen concentrations up to 20%. In this model, therefore, there is increased collagen turnover with increasing oxygen tension in the physiologic range. Although the observations reflect collagen formation and do not necessarily measure bone formation, the results are consistent with data derived from other sources suggesting that bone formation is increased by improved oxygenation.