Role of organized intestinal lymphoid aggregates in intestinal regeneration

Intestinal lymphoid tissue has a complex interrelationship with the epithelium. The epithelia of intestinal crypts associated with lymphoid aggregates have an increased proliferation rate. In the present study, the authors tested the hypothesis that organized intestinal lymphoid tissue (Peyer's patches) enhances intestinal regeneration by studying this process with and without an adjacent Peyer's patch. Forty adult male Sprague-Dawley rats had full-thickness ileal defects patched with cecal serosa to allow regeneration of ileal mucosa. Control animals (group I) had the patch constructed adjacent to a Peyer's patch, whereas this Peyer's patch was excised in group II. Intestinal regeneration in both groups was evaluated on the third, fifth, seventh, and ninth days after operation. During the early phase of regeneration, both epithelial cell proliferation and migration were decreased in the patched defect after excision of the Peyer's patch. Crypt cell production rate in the adjacent normal mucosa also was decreased after excision of the Peyer's patch. Excision of the Peyer's patch resulted in less well-developed crypts and villi. Wound contraction, however, was greater in the intestinal defect adjacent to the Peyer's patch until day 7. In conclusion, Peyer's patches have a facilitative effect on the healing of intestinal wounds by promoting both epithelial cell migration on the defect and epithelial cell proliferation in the crypts adjacent to the wound and by decreasing the rate of wound contraction. These findings support a role for intestinal lymphoid tissue in the regulation of epithelial cell maintenance.