Role of urokinase and its receptor in basal and stimulated colonic epithelial cell migration in vitro

Background - Migration of colonic epithelial cells is important for mucosal repair following injury. The urokinase (u-PA) system regulates migration in other cell types. Aim - To examine the role of u-PA and its receptor (u-PAR) in colonic epithelial cell migration. Methods - Migration was assessed over 24 hours in circular wounds made in confluent monolayers of LIM1215 and Caco-2 human colon cancer cells. The function of u-PA and u-PAR was ablated with antisense oligonucleotides to block expression, with synthetic u-PA peptides to block interaction, and with aprotinin to block u- PA mediated proteolysis. Results - Migration was stimulated two to threefold by exogenous u-PA, an effect dependent on u-PAR binding but independent of u- PA mediated mitogenesis and proteolysis. Expression of u-PA and u-PAR was inhibited by 80% by the appropriate antisense oligonucleotide. Basal migration and the motogenic effects of butyrate, epidermal growth factor, and phorbol-12-myristate-13-acetate were suppressed by the u-PAR antisense oligonucleotide (40-60%) but were at best minimally affected following inhibition of u-PA expression and binding. Conclusions - In an in vitro model of wounded colonic epithelium, u-PAR promotes cell migration through mechanisms that are not exclusively dependent on u-PA binding. Therefore, u- PA and u-PAR may contribute to colonic mucosal repair in vivo.