ABSTRACT
ObjectiveTo investigate the effects of long-term oxygen exposure on the pulmonary microvascular development and the expression of Ephrin-B2 of lungt issue in neonatal mice.MethodsForty-eight 2-day-old Kunming mice were randomly divided into hyperoxia group and air group, with 24 mice in each group. Mice in hyperoxia group were exposed to 70% oxygen to establish a model of bronchopulmonary dysplasia (BPD). Six mice from each group were sacrificed at 3, 7, 14 and 21 days of age, and lung tissue was collected for further test. The lung sections were stained with hematoxylin and eosin for histological evaluation, radial alveolar counts (RAC) and microvessel density (MVD) measurement by CD34 immunohistochemistry. Location and expression of Ephrin-B2 in lung tissue were measured by immunohistochemistry. Ephrin-B2 mRNA and protein levels were detected by fluorescent quantitative reverse transcriptase-polymerase chain reaction and Western blot, respectively. Two independent samplest-test was used for statistical analysis. Results(1) Pathological changes: The pathology of lung tissue in hyperoxia group showed typical BPD-like changes with advancing postnatal age, presenting mainly with simplified alveolar development and decreased microvessel number. Compared with the air group, RAC and MVD were significantly decreased in 14-day-old mice (6.067±0.432 vs 6.950±0.243,t=4.365,P<0.05; 4.133±0.476 vs 4.867±0.472,t=2.680,P<0.01) and 21-day-old mice in the hyperoxia group (8.050±0.362 vs 9.817±0.487,t=7.127,P<0.05; 4.333±0.532 vs 6.017±0.937,t=3.828,P<0.01). (2) Location and expression of Ephrin-B2: Ephrin-B2 was mainly expressed in alveolar epithelial cells, and weakly expressed in alveolar septum. Compared with the air group, the average optical density of Ephrin-B2 was significantly decreased in 7-day-old (0.146±0.013 vs 0.153±0.009), 14-day-old (0.140±0.007 vs 0.161±0.006) and 21-day-old mice in the hyperoxia group (0.138±0.008 vs 0.166±0.009)(t=-2.049,-9.442 and-10.087, allP<0.05). (3) Ephrin-B2 mRNA and protein levels: The Ephrin-B2 mRNA levels in 14-day-old (0.65±0.14 vs 1.05±0.16,t=4.609,P<0.01) and 21-day-old mice (0.57±0.09 vs 1.13±0.18,t=6.816,P<0.01) were significantly lower in hyperoxia group than in the air group. The Ephrin-B2 protein levels were also significantly lower in hyperoxia group than in the air group in 21-day-old mice (0.13±0.03 vs 0.29±0.08,t=4.587,P=0.000).ConclusionsOxygen-induced BPD model mice have simplified alveolar development, reduced MVD and decreased expression of Ephrin-B2 in lung tissue, which may play an important role in the pathogenesis of BPD.