Developmental stage is a major determinant of lung injury in a murine model of bronchopulmonary dysplasia.

Bronchopulmonary dysplasia (BPD) is a common inflammatory lung disease in premature infants. To study the hypothesis that the sensitivity of the lung to inflammatory injury depends on the developmental stage, we studied postnatal lung development in transgenic mice expressing human IL-1β (hIL-1β) in the lungs during the late canalicular-early saccular, saccular, or late saccular-alveolar stage. Overexpression of hIL-1β in the saccular stage caused arrest in alveolar development, airway remodeling, and goblet cell hyperplasia in the lungs as well as poor growth and survival of infant mice. Overexpression of hIL-1β during the late canalicular-early saccular stage did not adversely affect lung development, growth, or survival of the pups. Mice expressing hIL-1β from the late saccular to alveolar stage had smaller alveolar chord length, thinner septal walls, less airway remodeling and mucus metaplasia, and better survival than mice expressing hIL-1β during the saccular stage. Human IL-1β overexpression in the saccular stage was sufficient to cause a BPD-like illness in infant mice, whereas the lung was more resistant to hIL-1β-induced injury at earlier and later developmental stages.