[Protective effect of vitamin D against hyperoxia-induced bronchopulmonary dysplasia in newborn mice].

OBJECTIVE: To investigate the protective effect of vitamin D (VD) against hyperoxia-induced bronchopulmonary dysplasia (BPD) in newborn mice and explore the mechanism. METHODS: Thirty-six newborn mice were randomly divided into air + VD group, air + saline group, hyperoxia + VD group, and hyperoxia + saline group. In all the groups, saline or VD was administered on a daily basis via intramuscular injection. After 3 weeks of treatment, the mice were weighed and cardiac blood was collected for measurement of serum VD level using ELISA, and histological examination of the lungs was performed. Radial alveolar counting (RAC) and alveolar secondary interval volume density were measured using image analysis software. The expression levels of vascular endothelial cell growth factor (VEGF) and VEGF receptor 2 (VEGFR2) in the lung tissues were detected using Western blotting. RESULTS: The weight gain rate of the mice and the weight of the lungs were significantly higher in air + saline group and air + VD group than in the hyperoxia + saline group. The RAC was significantly lower in hyperoxic+saline group than that in hyperoxia+VD group (P < 0.001), and was significantly higher in hyperoxic+VD (125 times) than in hyperoxia + VD (1250 times) group (P < 0.01). The alveolar secondary protrusion count was significantly higher in hyperoxic+VD (1250 times) group than in hyperoxic+saline group (P < 0.001), and was significantly higher in hyperoxia+VD (125 times) group than in hyperoxia + VD (1250 times) group (P < 0.01). Compared with that in air + saline group, VEGFR2 expression was significantly lowered in hyperoxia+saline group (P < 0.05) and in air+VD group (P < 0.05); VEGFR2 expression was significantly higher in hyperoxia+VD (1250 times) group than in hyperoxia+saline group (P < 0.001) and hyperoxia+VD (125 times) group (P < 0.001); VEGFR2 expression was significantly higher in hyperoxia+VD (125 times) group than in hyperoxia+ saline group (P < 0.05). CONCLUSIONS: In newborn mice with BPD, VD supplement can increase the weight of the lungs and promote lung maturation, and a higher concentration of VD can better protect the lungs and promote the growth of pulmonary blood vessels.