Background: Gastrointestinal mucosa heals by restitution and proliferation. These are difficult to distinguish in vivo.
Methods: Human Caco-2 enterocytes were cultured on matrix proteins (collagen I, laminin, fibronectin) with growth factors (epidermal growth factor [EGF] and transforming growth factor-beta 1 [TGF-beta 1]) and the tyrosine kinase and prostaglandin inhibitors genistein and indomethacin. Healing was modeled by means of monolayer expansion, proliferation by means of 3H-thymidine uptake, and restitution by means of mitomycin-blocked migration.
Results: Changing matrix composition failed to alter proliferation, but collagen I stimulated migration more than laminin or fibronectin (laminin/collagen, 68% +/- 2%; p less than 0.05). EGF (30 ng/ml) increased proliferation on both collagen (225% +/- 11% of basal) and laminin (206% +/- 26%) but increased migration only over laminin (210% +/- 17%) (all, p less than 0.05). TGF-beta 1 (200 pg/ml) stimulated migration over laminin (187% +/- 18%, p less than 0.005) but inhibited migration over collagen (89% +/- 3%, p less than 0.01) and did not affect 3H-thymidine uptake. When cultured on laminin, EGF but not TGF-beta 1 altered organization of the alpha 2 integrin subunit. Genistein (100 mumol/L) inhibited basal and EGF-stimulated 3H-thymidine uptake. In addition, it prevented EGF stimulation of replication-blocked migration (81% +/- 10% vs 190% +/- 20% of basal, p less than 0.0001) without altering basal replication-blocked migration. Indomethacin (10(-5) mol/L) did not alter migration but inhibited basal and EGF-stimulated proliferation by 7% +/- 1% (each, p less than 0.005).
Conclusions: Restitution and proliferation appear independently regulated by matrix and growth factors. It may be possible to individually target specific phases of mucosal healing by means of pharmacologic agents.