Background: In vitro studies have suggested that transforming growth factor β1 (TGF-β1) plays an important role in the regulation of proliferation of intestinal epithelial cells, effecting strong inhibition of proliferation in intestinal epithelial cell lines. Studies were undertaken to assess its role in repair after injury using an in vitro wounding model. Methods: Wounds were created in confluent monolayers of the intestinal epithelial cell line of IEC-6. Exogenous TGF-β1, conditioned media from wounded IEC-6 cultures, or control media were added. Restitution was quantified as the number of cells migrating across the wound edge. Proliferation was assessed by uptake of bromodeoxyuridine and thymidine incorporation. Results: Although TGF-β was a potent inhibitor of proliferation, it promoted rapid "healing" of the monolayers through stimulation of migration of cells across the wound margin. The physiological importance of this activity was supported by the demonstration that conditioned medium from IEC-6 cells stimulated repair of the wounded monolayers. Effects of the conditioned medium could be entirely blocked by immunoneutralizing anti-TGF-β antisera. Further, addition of protease inhibitors (aprotinin, ε-aminocaproic acid) that prevented the bioactivation of latent TGF-β secreted by the IEC-6 cells also ablated the effect of the conditioned medium. In addition, expression of TGF-β1 messenger RNA was significantly enhanced in the wounded monolayers. Conclusions: These findings suggest that TGF-β may play an important role in reconstitution of epithelial integrity after mucosal injury.
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