In contrast, the alveolar septa in the hyperoxia group were significantly thickened with decreased secondary septa formation as shown in enlarged squares in Fig. 2B. To explore whether the TN-C protein level changes during the pathogenesis of alveolar epithelial cell injury in BPD, we measured the expression of the TN-C protein in pulmonary tissues using Western blotting and ELISA. The gene discussed is TNC; the disease is bronchopulmonary dysplasia.