Transforming Growth Factor-β-Neutralizing Antibodies Improve Alveolarization in the Oxygen-Exposed Newborn Mouse Lung

Abnormal alveolar formation and excessive disordered elastin accumulation are key pathological features in bronchopulmonary dysplasia. Transforming growth factor (TGF)-β is an important regulator of the extracellular matrix in the developing lung. To determine if increased TGF-β would injure alveolar development by activating TGF-β signaling and by influencing the expression of elastogenesis-related protein, we performed intraperitoneal injection of newborn mice with the TGF-β-neutralizing antibody 1D11 and observed whether 1D11 had a protective role in the oxygen (O₂)-exposed newborn mouse lung. The newborn mice were exposed to 85% O₂ for 14 and 21 days. 1D11 was administered by intraperitoneal injection every day from postnatal days 3 to 20. Alveolar morphology was assessed by hematoxylin and eosin staining. The expression and distribution of elastin were evaluated by immunohistochemistry. The level of TGF-β signaling-related proteins were measured by immunohistochemistry, enzyme-linked immunosorbent assay, and Western blot. The expression levels of elastogenesis-related proteins, including tropoelastin, fibulin-5, and neutrophil elastase (NE), which participate in the synthesis, assembly, and degradation of elastin, were detected by real-time PCR and Western blot. In this research, impaired alveolar development and elastin deposition as well as the excessive activation of TGF-β signaling were observed in the newborn mouse lung exposed to hyperoxia. 1D11 improved alveolarization as well as the distribution of elastin in the newborn lung with hyperoxia exposure. The expression levels of tropoelastin, fibulin-5, and NE, which are important components of elastogenesis, were decreased by treatment with 1D11 in the injured newborn lung. These data demonstrate that 1D11 improved alveolarization by blocking the TGF-β signaling pathway and by reducing the abnormal expression of elastogenesis-related proteins in the O₂-exposed newborn mouse lung. 1D11 may become a new therapeutic method to prevent the development of bronchopulmonary dysplasia.