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Background: The enteric nervous system (ENS) contains chemically coded populations of neurons that serve specific functions for the control of the gastrointestinal tract. The ability of neurons to modify their chemical code in response to luminal changes has recently been discovered. It is possible that enteric neuronal plasticity may sustain the adaptability of the gut to changes in intestinal activity or injury, and that gut neurons may respond to an altered intestinal environment by changing their neuropeptide expression., Methods: We used immunohistochemical methods to investigate the presence and localization of several neuronal populations and enteric glia in both the small (ileum) and large (cecum) intestine of piglets. We assessed their abundance in submucosal and myenteric plexus from animals treated with the probiotic Pediococcus acidilactici compared with untreated controls., Key Results: The treated piglets had a larger number of galanin- and calcitonin gene-related peptide (CGRP)-immunoreactive neurons than controls, but this was limited to the submucosal plexus ganglia of the ileum. Moreover, immunohistochemistry revealed that glial fibrillary acidic protein-positive enteric glial cells were significantly higher in the inner and outer submucosal plexuses of treated animals., Conclusions & Inferences: The neuronal and glial changes described here illustrate plasticity of the ENS in response to an altered luminal environment in the gastrointestinal tract.

Subepithelial tissues have an important role in the structure and function of the intestinal epithelium. Basement membrane components (BMC) stimulate epithelial cell migration and differentiation in vitro. The aim of this study was to determine the effect of BMC and/or interstitial tissue collagen (type I) on the in vivo intestinal regenerative response to intestinal patching. Twenty rabbits had two 2 x 5 cm ileal defects patched with the serosal surface of adjacent caecum. Group 1 (n = 5) were controls; group 2 (n = 5), group 3 (n = 5) and group 4 (n = 5) had collagen, collagen plus BMC, and BMC respectively applied to the distal patched defect. Animals were killed at 7 d and evaluated grossly for epithelialization and contraction of the defects. Epithelial coverage was greatest in the distal patch of group 4 animals (62 +/- 9%) and was significantly greater than the group 4 proximal patch and control values (43 +/- 7 and 40 +/- 14%, P less than 0.05). Contraction was similar in all groups (38 +/- 5 to 45 +/- 5%). Crypt cell production rate, villus height, and disaccharidase activities were similar in all groups. BMC stimulated epithelialization via a local mechanism since only the distal patch was affected. Type I collagen did not stimulate epithelialization and inhibited the effect of BMC. Since crypt cell production rate was similar in all groups, the enhanced epithelialization seen with BMC is primarily due to increased cell migration.

Variations in percentage labelling (LI) and mitotic activity (mitoses per crypt) have been studied over a 24-hr period in the epithelial cells and pericryptal fibroblast sheath (PCFS) of the small intestine, caecum, and colon of the mouse. All three tissues displayed clear, synchronized circadian rhythms in DNA-synthetic activity in both the epithelial cells and PCFS. Peak values were coincident within a tissue, but staggered between tissues. In the epithelial cells, peak mitotic values were found between 3 and 6 hr after the peak LI values. The low level of mitotic activity in the PCFS appeared to be synchronized with the rhythms in the adjacent epithelia. The epithelial cells of the lowest crypt third displayed the clearest circadian rhythms. However, the PCFS cells at all levels produced similar curves. A craniocaudal wave of proliferative activity is proposed.