Since we aimed to investigate the GH–IGF1 axis in impaired alveolarization and matrix remodeling of the newborn as a model for the changes seen in infants with severe BPD [18], we used 85% O2 for a prolonged period in neonatal mice, inducing characteristic features of BPD [14,15]. This evidence concerns the gene IGF1 and bronchopulmonary dysplasia.