BACKGROUND: Bronchopulmonary dysplasia (BPD) is a major complication of extreme prematurity, characterized by alveolar simplification and pulmonary malfunction. Hyperoxia-induced lung injury in neonatal rats has been used as a model of BPD, as indicated by lung architectural change and alveolar simplification that resembles clinical feature of BPD. β-defensin-2 (BD2) plays an important role in lung diseases by inhibiting inflammation response. However, little is known about its role in BPD. The aim of this study was to determine the effect of human BD2 (hBD2) gene on hyperoxia-induced animal model of BPD.

MATERIAL AND METHODS: The neonatal rats were exposed to 90% oxygen (O₂) continuously for 14 days to mimic the BPD-like lung injury. These rats were then randomly assigned to the following four groups: in room air (air), in 90% O₂, in 90% O₂ with null adenovirus vector infection (O₂+Ad), and in 90% O₂ with gene therapy through adenovirus transfected hBD2 (O₂+Ad-hBD2). Morphology of lungs, pulmonary function and expression of inflammatory cytokines on P7, P10, P14, and P21 were documented and compared across the 4 groups.

RESULTS: The overexpression of hBD2 mediated by the adenovirus vector was successfully constructed. hBD2 gene therapy increased hBD2 mRNA expression, increased radial alveolar count (RAC), lung volume and compliance, decreased mean linear intercept (MLI), tissue damping, and elastance. Furthermore, pro-inflammatory cytokines IL-1β, IL-6, and TNF-α were inhibited and anti-inflammatory cytokines IL-10 was increased in the lungs of rats in O₂+Ad-hBD2 group.

CONCLUSIONS: In hyperoxia-induced rat models of BPD, hBD2 promotes alveolarization and improves pulmonary function. The mechanism may contribute in alleviating inflammation response and inhibiting pro-inflammatory factors including IL-1β, IL-6, and TNF-α.

Keywords: Alveolar Process, beta-Defensins, Bronchopulmonary Dysplasia, Hyperoxia, Respiratory Function Tests, Animals, Newborn, Interleukin-6, Lung, Lung Injury, Oxygen, Pregnancy