Establishment and evaluation of hypoxia-induced mouse model of bronchopulmonary dysplasia associated with pulmonary hypertension

Objective To establish an animal model of hypoxia-induced bronchopulmonary dysplasia asso-ciated with pulmonary hypertension (BPD-PH). Methods C57BL/6 male and female specific pathogen free mice mated and female mice with their offspring mice were randomly divided into normoxic group and hypoxia group by way of numerical method.Normoxic group was placed in the indoor environment directly.Hypoxia group was placed in 120 mL/L oxygen concentration environment within 12 hours after birth.Body weight gain and mortality of the neonatal mice were recorded.The mice lungs and hearts were harvested on day 14 for immunofluorescence staining and HE staining, and Western blot was used to observe the morphological changes and vascular endothelial growth factor (VEGF) protein level. Results The mortality rates of normoxic group and hypoxic group were 11.8% and 47.3%, respectively.Compared with the normoxic group, body weight of hypoxia group increased slowly, as the final body weight of 2 groups were (12.40±2.33) g and (5.50±0.32) g, respectively, and the difference was significant (χ2=13.38, t=20.50, all P<0.01). Hypoxia group showed higher right ventricular hypertrophy index [(96.00±0.15)% vs.(40.40±4.00)%, t=41.67, P<0.01], fusion of alveolar, diminished microvasculature, thickening alveolar septal, decreased alveolar radiation coefficient (RAC)(19.73±2.33 vs.10.90±1.85) and increased mean linear intercept(MLI) (33.2±4.33 vs.58.70±7.27) with statistical significance, respectively (t=16.27, 9.53, all P<0.01). In the lung HE staining, pulmonary arterial thickening, pulmonary smooth muscle cell proliferation and intimal roughness in immunofluorescence, significantly decreased expression of VEGF protein level by Western blot were observed in hypoxic group (0.41±0.04 vs.1.19±0.08, t=15.10, P<0.01). Conclusions Hypoxia-induced mouse BPD-PH model was consistent with the pathophysiological process of pulmonary vascular remodeling of pulmonary hypertension, which increase pulmonary vascular resistance eventually leading to right ventricular hypertrophy. Key words: Bronchopulmonary dysplasia; Hypoxia; Pulmonary hypertension; Mice