The function of epithelial-stromal interactions in the intestine

摘要

The intestinal epithelium has a complex organization but is capable of dynamic change and adaptation following changes to the diet, after exposure to infectious agents, or following physical injury. Adaptation is possible because this is a renewing epithelium in which most cells are replaced every 5-7 days in humans. The old cells are shed into the bowel lumen and replaced by migration of new cells that ultimately derive from a few stem cells that reside near the base of the epithelial crypts. These pluripotent stem cells give rise to, e.g., enterocytes, mucin-secreting goblet cells, entero-endocrine cells, and Paneth cells, but even among these types there are further specialized subsets. The complex patterns of epithelial differentiation along the proximal-distal and crypt to villus axes and the kinetic organization of cell renewal in this organ have been extensively reviewed elsewhere. Tissue grafting studies have shown that connective tissue cells generally provide permissive signals for the development of the intestinal epithelium3'4. Suggesting a plasticity in the potential of this mesenchyme to support a programmed pattern of epithelial differentiation. However, instructive effects of mesenchyme have been reported where, for example, ileal mesoderm induced small intestinal differentiation when grafted with colonic endoderm.