Neurotrophic factors and gastrointestinal mucosa

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To further clarify the regulatory mechanisms of barrier homeostasis in the gastrointestinal mucosa, we determined whether the neurotrophic factors could have a role in regulating mucus metabolism.1. Neurotrophic factors and their receptors in the gastrointestinal mucosa.In this study, the mRNA expression of NGF, BDNF, and NT-3 was seen in the stomachs, small intestines, and colons in rats and mice. In contrast, the receptors for the neurotrophic factors were not immunohistochemically detected in the rat gastrointestinal mucosa.2. Nerve fibers in the gastrointestinal mucosa.The density of the CGRP nerve fibers was reduced in both the lamina propria and submucosa of the middle-aged rats compared to the young rats. CGRP stimulated the mucin biosynthesis in the cultured corpus mucosa from 7-week-old rats, but not from the 52-week-old rats.3. Investigation of recovery processes in the mucosal injury.We prepared aspirin-or acetic acid-induced mucosal lesions in the rat gastric mucosae and microscopically observed the alterations of the epithelial cells of the corpus mucosae stained with the anti-mucin monoclonal antibodies^RGM21, PGM34, and RGM26, developed in our laboratory. The appearance of specific mucin species was observed in the regenerating epithelia of the rat during the healing processes from acute and chronic gastric mucosal damage.4. Effect of the neurotrophic factors on mucin metabolism.The mucin biosynthesis in the cultured rat gastric mucosa was stimulated by EGF and HGF, but not by the major neurotrophic factors such as NGF, BDNF, and NT-3.In summary, these findings suggest that certain nerve fiber has an important role in regulating mucus metabolism, but the major neurotrophic factors such as NGF, BDNF, and NT-3, have no effect on mucin biosynthesis in rat gastric mucus cells directly.