Maldevelopment of intrapulmonary bronchial cartilage in congenital diaphragmatic hernia.

Background: Pulmonary hypoplasia is an important cause of morbidity and mortality in infants with congenital diaphragmatic hernia (CDH). This study aimed to verify our hypothesis that the abnormal development of bronchial cartilage as well as alveolar immaturity, might play a central role in hypoplasia of the lung in human CDH.

Method: We retrospectively analyzed autopsied lungs from 10 CDH cases and compared with nine age-matched controls to assess the bronchial cartilage and alveolar maturity using morphological techniques.

Result: Ki-67 and thyroid transcription factor-1 (TTF-1) expression in the alveoli significantly increased in bilateral lungs with CDH. The shortest distance from the bronchial cartilage to the pleura was significantly shorter in ipsilateral (left) lungs with CDH, showing a positive correlation with the radial alveolar count (RAC). Regarding the small bronchial cartilages less than 20 000 μm , the average cartilage area significantly decreased in left lungs with CDH, and tended to decrease in right lungs with CDH. In addition, cartilage around the bronchi less than 200 μm in diameter tended to be smaller in left lungs with CDH. In contrast, regarding the cartilage around the bronchi 200 to 400 μm in diameter, the ratio of the total cartilage area relative to the bronchial diameter tended to be higher in left lungs with CDH, although there was a large variation.

Conclusions: These opposite directional cartilage abnormalities around the distal and more proximal bronchi support our hypothesis that abnormal development of bronchial cartilage might play an important role in the hypoplastic lung in CDH.