Soluble and insoluble fibronectin increases alveolar epithelial wound healing in vitro

Adhesive interactions between cells and extracellular matrix proteins are important in cell attachment, migration, and proliferation. The present work defines the role of fibronectin (soluble and insoluble) compared with type I and type IV collagen on in vitro alveolar epithelial wound healing. Repeated video microscopy experiments demonstrated that the half-time of wound closure was decreased in the presence of soluble fibronectin (6.6 +/- 2.1 vs. 17.4 +/- 0.8 h in serum-free medium, P < 0.05). Video microscopy, electron microscopy, and vinculin distribution demonstrated the contribution of two main events during the repair process: the migration of epithelial cell sheets and the spreading of the cells. During the wound healing, the internuclear distance between two adjacent cells at the migrating edge of the wound was significantly increased 10 h after wounding in the presence of soluble fibronectin (67 +/- 3.0 vs. 45 +/- 1.5 microns in serum-free medium, P < 0.05), indicating that cell spreading is involved as part of the mechanism for wound closure. Compared with type I and type IV collagen, insoluble fibronectin was the most potent stimulus for alveolar type II cell motility and wound healing in the absence of other serum factors. These results demonstrate that alveolar epithelial wound healing can be modulated in vitro by the composition of the extracellular matrix, an effect that may be mediated by changes in cell shape.