Matrix-derived soluble components influence type II pneumocytes in primary culture

Abstract

Type II pulmonary epithelial cells cultured on a plastic surface fail to retain differentiated form and function. During the first 3 days in primary culture, the cells flatten and lose characteristic lamellar inclusions; they increase in size and exhibit accelerated rates of protein synthesis and thymidine incorporation. These transitions are inhibited markedly if the cells are plated on matrigel (MG), a laminin-rich surface derived from the Englebreth-Holm-Swarm (EHS) sarcoma. Soluble components released from matrigel (MGS) mimic some of the effects of the solid gel. As on a plastic surface, the cells flatten when exposed to MGS during culture. In contrast, MGS inhibits thymidine incorporation and protein synthesis; it is most effective when added early in the culture interval. Direct contact of the cells with the matrigel surface itself is always more effective than maximal MGS activity. The effects of MGS are not reproduced by purified laminin or by transforming growth factor-beta, both of which are present in matrigel. These results indicate that the effects of the solid matrigel surface on cell morphology are caused in part by direct cell-matrix contact but that additional effects, such as decreased DNA synthesis, can be mediated by activity of solubilized gel components. They further provide a model wherein changes in type II cell morphology and function, which typically occur in parallel during primary culture, can be separated experimentally.