Dynamic changes of collagen III and IV in lungs of neonatal rats with chronic lung disease induced by prolonged hyperoxia

Objective: To determine the dynamic changes of collagen Ⅲ and Ⅳ in lungs of neonatal rats with chronic lung disease induced by prolonged hyperoxia.Methods: Full-term newborn rats were continuously exposed to 90%~95% oxygen(hyperoxia group) or room air(air control group) after birth.On days 1,3,7,14,and 21,hematoxylin-eosin staining,Masson and Gomori staining and imaging analysis,and enzyme-linked immunosorbent assay were performed for lung histological study,measuring the area percentages of collagen fibers and reticular fibers,and detecting the protein content of collagen Ⅲ and Ⅳ,respectively.Results: In hyperoxia group,inflammation response occurred on day 3 of oxygen exposure;the arrest of lung development was evident on day 7 of oxygen exposure and developed into interstitial fibrosis at last;collagen fibers and reticular fibers were strongly stained in alveolar septum and interstitium,and the area percentage of collagen fibers and reticular fibers were significantly larger than that in air control group 7 days after oxygen exposure.The difference in the area percentage increased with the prolongation of oxygen exposure(P 0.01).There were significant differences in the protein content of collagen Ⅲ and Ⅳ between hyperoxia group and air control group on days 14 and 21 of oxygen exposure,respectively(on day 14,protein content of collagen Ⅲ 52.52±5.73 vs.29.71±2.62 ng/mg,P 0.01,protein content of collagen Ⅳ 24.78±5.42 vs.14.90±2.44 ng/mg,P 0.05;on day 21,protein content of collagen Ⅲ 81.90±6.33 vs.53.31±1.34 ng/mg,P 0.01,protein content of collagen Ⅳ 40.27±1.94 vs.26.13±1.94,P 0.01).Conclusion: Lung fibrosis associated with the increase of collagen Ⅲ and Ⅳ may be the result of prolonged hyperoxia.