Distribution of integrins during human fetal lung development.

Interactions between epithelial cells and the extracellular matrix through integrins play a key role in the development of the lung by modulating branching morphogenesis, epithelial cell polarization, and differentiation. To determine the role of integrins during the different stages of lung development, we investigated the distribution of eight integrin subunits in the trachea and lung from human fetuses. In distal airways, during the early pseudoglandular stage of development, the alpha2-, alpha5-, alpha6-, alphav-, and beta1-subunits were detected in all epithelial cell plasma membranes, and polarized but undifferentiated tracheal epithelial cells expressed alpha3-, alpha6-, and beta1-subunits in the plasma membrane of the cells facing the basement membrane. The alpha6- and beta4-chains were detected along the basal plasma membrane of the basal cells in differentiated tracheal epithelia. The alpha4-subunit was detected in all respiratory cells throughout fetal development. In the submucosal glands, myoepithelial cells expressed the integrin subunits found in the undifferentiated cells of the developing airways, whereas the secretory cells expressed only alpha2-, alpha3-, alpha4-, alpha6-, and beta1-subunits. These results demonstrate differential expression of integrins during lung development and suggest that integrins may play multiple roles in organogenesis and maturation of respiratory surface epithelium and glands.