Antibodies against hepatoma-derived growth factor and mucosal repair in ulcerative colitis

Ulcerative colitis is a chronic inflammatory disease of colonic mucosa in which the pathogenesis of any immunological disorders would likely be related. Various circulating autoantibodies have been reported in patients with ulcerative colitis, although their possible roles in this disease process have not yet been clarified. Autoantibody against hepatoma-derived growth factor (HDGF) was detected at high frequency in the serum of patients with ulcerative colitis, especially in patients with total colitis and left-sided colitis. In pursuit of the possible role of anti-HDGF autoantibody in the pathogenesis, we investigated HDGF expression in the intestinal mucosa by Western blotting and immunohistochemistry and the effects of recombinant proteins and antirecombinant HDGF antibody on the proliferation of the colonic epithelial cell-derived cell line, HT-29. HDGF was expressed in the nucleus of the colonic epithelial cells dominantly in the bottom of the crypts. Recombinant HDGF stimulated the proliferation of HT-29 cells significantly, although its effects were small, about 20% greater than the control at 100 ng/ml. On the other hand, the polyclonal IgG antibody against recombinant HDGF generated by rabbits suppressed their proliferation almost completely at 250 microg/ml. These findings suggest that HDGF plays an important role in epithelial cell renewal of intestinal crypts as a growth and survival factor, and that autoantibody against HDGF may delay mucosal healing and repair by inhibiting the stimulatory effects of HDGF on epithelial cell proliferation, resulting in a chronic process of colonic mucosal injury.