Pulmonary hypoplasia in mice homozygous for the cartilage matrix deficiency (cmd) gene: a model for human congenital disorder.

As a potential model for the study of pulmonary hypoplasia in the lethal chondrodystrophies in man, lungs of day 18 mouse fetuses homozygous for cartilage matrix deficiency (cmd) were studied by biochemical, histological, and morphometric techniques. Wet and dry mutant lung weights were 30% less than corresponding normal lung weights. Total DNA and protein contents per whole mutant lung were decreased by 23% and 29%, respectively. An increased number of smaller-than-normal primary saccules were observed in histological sections of mutant lungs, which correspond to the difference in lung wet weight. The thoracic volume of mutants was decreased by an average of 38%. Amniotic fluid volume measurements indicated polyhydramnios in the mutant. The smaller-than-normal thoracic cavity observed in the cmd mutant, imposing a significant restriction on the developing lungs, is the most likely mechanism of pulmonary hypoplasia in this form of chondrodystrophy-confirming that reported for the cho mouse mutant.