Hyperoxia inhibits fetal rat lung fibroblast proliferation and expression of procollagens

The direct effects of hyperoxia on collagen production by fetal lung fibroblasts are unknown and would be important to the understanding of the molecular mechanisms involved in bronchopulmonary dysplasia in premature infants. We studied the effect of hyperoxia on 1) proliferation, 2) mRNA levels for type I and III procollagens, and 3) net collagen production in primary cultures of fetal rat lung fibroblasts. Fibroblasts from 19-day-old rat fetuses (term is 22 days) were obtained. Test plates were incubated in hyperoxia and controls in room air for varying time periods. Cell viability in both conditions was >97% as determined by trypan blue exclusion. Fibroblast proliferation in nonconfluent cultures was found to be significantly reduced with exposure to hyperoxia (P < 0.001). Steady-state levels of type I and III precollagen mRNAs, analyzed on Northern blots hybridized to [³²p]cDNA probes, were significantly decreased in hyperoxia (P < 0.01). This effect was noted as early as 4 h of exposure to hyperoxia and persisted for 5 days. There was a significant inverse correlation between duration of exposure to O₂ and steady-state levels of mRNA for α₁(I)- procollagen (r = -0.904) and α₁(III)-precollagen (r = -0.971). There were no significant changes in steady-state levels of β-actin mRNA. We also found a significant decrease in collagen synthesis in hyperoxia-exposed fibroblasts (P < 0.05). We conclude that hyperoxia directly effects a reduction in fetal lung fibroblast proliferation and net collagen production at a pretranslational level.