TREFOIL PEPTIDES PROMOTE EPITHELIAL MIGRATION THROUGH A TRANSFORMING GROWTH-FACTOR BETA-INDEPENDENT PATHWAY

The trefoil peptides, a recently recognized family of protease-resista nt peptides, expressed in a regional specific pattern throughout the n ormal gastrointestinal tract. Although these peptides have been hypoth esized to act as growth factors, their functional properties are large ly unknown. Addition of recombinant trefoil peptides human spasmolytic polypeptide (HSP), rat and human intestinal trefoil factor (RITF and HITF) to subconfluent nontransformed rat intestinal epithelial cell Li nes (IEC-6 and IEC-17), human colon cancer-derived cell lines (HT-29 a nd CaCO2) or nontransformed fibroblasts (NRK and BHK) had no significa nt effect on proliferation. However addition of the trefoil peptides t o wounded monolayers of confluent IEC-6 cells in an in vitro model of epithelial restitution resulted in a 3-6-fold increase in the rate of epithelial migration into the wound. Stimulation of restitution by the trefoil peptide HSP was enhanced in a cooperative fashion by the addi tion of mucin glycoproteins purified from the colon or small intestine of either rat or man, achieving up to a 15-fold enhancement in restit ution. No synergistic effect was observed by the addition of nonmucin glycoproteins. In contrast to cytokine stimulation of intestinal epith elial cell restitution which is mediated through enhanced TGF beta bio activity, trefoil peptide, and trefoil peptide-mucin glycoprotein stim ulation of restitution was not associated with alteration in concentra tions of bioactive TGF-beta and was not affected by the presence of im munoneutralizing anti-TGF beta antiserum. Collectively, these findings suggest that the trefoil peptides which are secreted onto the lumenal surface of the gastrointestinal tract may act in conjunction with the mucin glycoprotein products of goblet cells to promote reestablishmen t of mucosal integrity after injury through mechanisms distinct from t hose which may act at the basolateral pole of the epithelium.