Introduction The aim of this study effects of BCG vaccine on the histopathologic and gene expression changes seen in hyperoxia induced neonatal rat lung injury.

Method Twenty-three rat pubs were divided into four groups: air-exposed control group (n = 5), hyperoxia-exposed placebo group (n = 7), hyperoxia-exposed BCG-vaccinated group (n = 7), and air-exposed BCG-vaccinated group (n = 4). neonatal hyperoxic lung injury model was established according to the previous studies. Measurement of alveolar surface area, quantification of secondary crest formation, microvessel count, evaluation of alveolar septal fibrosis, and smooth muscle actin immunostaining were performed to assess hyperoxia-induced changes in lung morphology. The gene expression level was evaluated by RT-PCR.

Results The alveolar surface areas were significant different between the oxygen exposed placebo group and oxygen exposed BCG vaccinated group (alveolar surface area; 0.29 ± 0.02 µm² and 0.52 ± 0.04 µm² p < 0.05 respectively). Number of crests and microvessel count was found to be significantly increased in the oxygen exposed BCG vaccinated group compared with the animals in the oxygen exposed placebo group (p < 0.05). Exposure to hyperoxia resulted in a significant decrease in mean alveolar surface area and number of crests formed compared with air-exposed animals (p < 0.05). The degree of fibrosis was found to be significantly increased in the oxygen exposed placebo group compared with the animals in the oxygen exposed BCG vaccinated group (degree of fibrosis: 1.88 ± 0.33 and 0.91 ± 0.66 p < 0.05 respectively). Immunostaining for SMA demonstrated hyperoxia-exposed animals with BCG vaccine in a significantly decrese in smooth muscle content compared with hyperoxia-exposed placebo animals (p < 0.05). The expression of VEGF, FGF1, IL13, NFκB1 and TNFα in the lungs of vaccinated animals was significantly higher than that of non-vaccinated animals (p < 0.05).

Conclusion Our results suggest that BCG vaccination can be a new protective strategy against neonatal hyperoxic lung injury. These benefical effects may be interpreted with its immunomodulatory effects on proinflammatory-antiinflammatory cytocin balance and expression of growth factors.