The geographic pathology of pulmonary emphysema and chronic bronchitis. I. Review

Conditional overexpression of bioactive transforming growth factor-beta1 in neonatal mouse lung: a new model for bronchopulmonary dysplasia?

Research interest in bronchopulmonary dysplasia (BPD) has steadily increased, and numerous potential mediators have been implicated in the development of the disease. Among such mediators is transforming growth factor (TGF)-beta. Unfortunately, commonly utilized murine transgenic models are not optimal to investigate the effects of TGF-beta specifically during the 2-3 wk period of alveolar formation, the developmental stage that corresponds histologically to early alveolar development in humans, and the time frame during which BPD develops. In the current study, we utilized a triple-transgenic construct to overexpress bioactive TGF-beta1 in the neonatal mouse lung during the period of alveolar formation. Lungs were then examined by histologic, Western blot, and immunofluorescent methods. We found that overexpression of bioactive TGF-beta1 in neonatal mouse lungs resulted in structural changes that have been described in BPD. Included in those characteristics are abnormal alveolar structure, cellular composition, and vascular development. Our study indicates that TGF-beta1 overexpression in the neonatal mouse lung results in histologic alterations that have striking similarities to pathologic descriptions of BPD. We encourage the use of conditional transgenic models for the study of BPD, and hypothesize that the TGF-beta system is a central mediator for the histologic alterations described in association with the disease.

Morphological and biochemical features of elastase-induced emphysema in strain A/J mice

Elastase-induced animal models of pulmonary emphysema are potentially useful to study the physiological, anatomical, and biochemical injuries associated with emphysema. After the endotracheal instillation of porcine pancreatic elastase (0.15 or 0.30 mg elastase per 100 g body weight) into strain A/J mice, selected biochemical and morphometric indices od lung damage were examined. Elastase produced extensive air space enlargement without appreciable mortality. Lesions involving the lung parenchyma distal to the terminal bronchioles were observed within 2 weeks and possessed features resembling panlobular and centrilobular emphysema. Morphometric analyses of emphysema indicated that after the acute phase of tissue damage and repair, the lesions stabilize without further deterioration of alveolar structure. Increased lung elastin synthesis was noted following endotracheal elastase, resulting in lung elastin levels 30% higher than controls 8 weeks after treatment. Minimal alterations to lung DNA and protein levels indicated that elastase produced specific lung lesions exclusive of inflammation and edema.