Cellular and molecular mechanisms of the epithelial repair in IBD.

Inflammatory bowel diseases such as ulcerative colitis or Crohn's disease frequently cause epithelial damage in the intestine. In general, the intestinal epithelium is able to rapidly repair itself by the restitution, proliferation, and differentiation of epithelial cells when such tissue damage occurs. However, severe and continuous inflammation could disturb the intrinsic repair system, resulting in refractory ulcers in the intestine. In this review, we will describe the recent findings of the cellular and molecular mechanisms regulating the regeneration process of the intestinal epithelium. Furthermore, we will propose bone marrow cells as a novel source of cells to regenerate the damaged intestinal epithelium. Bone marrow cells are the only cells of extra-gastrointestinal origin that are shown to contribute to the regeneration of the intestinal epithelium. Further studies of these cells and molecules may lead to a novel therapy for the repair of damaged intestinal epithelium.