Independent modulation of enterocyte migration and proliferation by growth factors, matrix proteins, and pharmacologic agents in an in vitro model of mucosal healing

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, laminm, fibronectin) with growth factors (epidermal growth factor [EGF] and transforming growth factor-β₁ [TGF-β₁]) 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 < 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 < 0.05). TGF-β¹, (200 pg/ml) stimulated migration over laminin (187% ± 18%, p < 0.005) but inhibited migration over collagen (89% ± 3%, p < 0.01) and did not affect ³H-thymidine uptake. When cultured on laminin, EGF but not TGF-β₁ altered organization of the α₂ integrin subunit. Genistein (100 μmol/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 < 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 < 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.