Effects of inflammation on cell proliferation in the myenteric plexus of the guinea-pig ileum

Abstract.

This study was undertaken to investigate the occurrence and identity of dividing cells within the myenteric plexus of the guinea-pig ileum and to analyze the effects of inflammation induced by trinitrobenzene sulfonic acid. The incorporation of 5-bromo-2-deoxyuridine, or BrdU, into replicating DNA was used to label proliferative cells, and immunohistochemistry was used to assess the occurrence of BrdU in specific cells of the myenteric plexus. Compared to normal tissue, inflammation is associated with increased BrdU labelling in the crypts and in the substantially thickened muscle layers. In longitudinal muscle/myenteric plexus whole-mounts, there was a significant increase in BrdU labelling of the myenteric plexus after induced inflammation. No BrdU-labelled neurons were detected in tissue double labelled with neuron-specific antibodies. Fluorescein isothiocyanate/dextran-labelled macrophages were rare or absent from the ganglia, and none were double labelled with BrdU in the muscle layers. CD3-immunoreactive T cells were substantially increased in the inflamed longitudinal muscle, but still rare or absent within the enteric ganglia. Some BrdU-labelled T cells were observed in the longitudinal muscle but not in the myenteric ganglia. Lastly, in tissues double labelled with anti-BrdU and anti-S-100, many BrdU-containing cells within the myenteric ganglia were found to be S-100-immunoreactive glial cells. We conclude that inflammation does not stimulate the appearance of new myenteric neurons but does stimulate mitosis in myenteric glia.