Composition of extracellular matrix of type II pulmonary epithelial cells in primary culture.

Type II pulmonary epithelial cells in primary culture synthesize and deposit an extracellular matrix which has reciprocal biological effects on cellular differentiation. The present work establishes conditions for metabolic labeling of matrix constituents and for separation of cells from the associated matrix; it also defines matrix composition, which does not appear to change qualitatively between days 2 and 6 of primary culture. Type II cells synthesize and deposit a spectrum of radiolabeled components on the culture surface. These include fibronectin, laminin, type IV collagen, and plasminogen activator inhibitor-1, along with additional unidentified proteins. Few radiolabeled proteins in medium conditioned by type II cells bind nonspecifically to the culture surface in the absence of cells. Fibroblasts and macrophages, which may contaminate the primary cultures, do not appear to contribute substantially to the type II cell matrix. These results demonstrate that type II cells synthesize and deposit a complex multicomponent extracellular matrix. The work provides a basis for further investigations of bidirectional interactions between type II cells and the extracellular matrix.