Alveolar epithelial type II cells and their microenvironment in the caveolin-1-deficient mouse.

Caveolin-1 (Cav-1) is highly expressed in alveolar epithelial type I (AE1) and endothelial cells of the alveolar region of the lung. Interestingly, alveolar epithelial type II (AE2) cells that are progenitors of the AE1 cells do not express Cav-1. We investigated whether genetic Cav-1 deficiency alters the phenotype of AE2 cells and their microenvironment using stereology. Total number, mean volume, and subcellular composition of the AE2 cells were not altered in Cav-1(-/-) when compared with wild-type mice. The alveolar septa were thickened and contained a significantly greater volume of extracellular matrix. Thus, AE2 cells as progenitors of AE1 cells are not critically involved in the severe pulmonary phenotype in Cav-1-deficient mice.