Routine colonic biopsies as a new tool to study the enteric nervous system in living patients

Abstract  Better characterization of enteric neuropathies during the course of gastrointestinal diseases could be of great diagnostic and/or therapeutic interest. However, studies using whole mounts of the enteric nervous system (ENS) are restricted to specific diseases requiring surgery and are also limited by the small number of specimens available. Therefore, we here describe a novel method to obtain whole mounts of submucosal plexus in routine colonic biopsies. We show that a single biopsy displays a substantial number of submucosal ganglia and neurons and that it can be reliably used to perform morphometric and neurochemical analysis and Western Blots quantification of neuronal or glial markers. This method of analysis of the human ENS will enable us to gain better insight into the characterization of enteric neuropathies in living patients.     

ATP-dependent paracrine communication between enteric neurons and glia in a primary cell culture derived from embryonic mice

Abstract  The importance of dynamic interactions between glia and neurons is increasingly recognized, both in the central and enteric nervous system. However, apart from their protective role, little is known about enteric neuro–glia interaction. The aim was to investigate neuro–glia intercellular communication in a mouse culture model using optical techniques. Complete embryonic (E13) guts were enzymatically dissociated, seeded on coverslips and studied with immunohistochemistry and Ca²⁺-imaging. Putative progenitor-like cells (expressing both PGP9.5 and S-100) differentiated over approximately 5 days into glia or neurons expressing typical cell-specific markers. The glia–neuron ratio could be manipulated by specific supplements (N2, G5). Neurons and glia were functionally identified both by their Ca²⁺-response to either depolarization (high K⁺) or lysophosphatidic acid and by the expression of typical markers. Neurons responded to ACh, DMPP, 5-HT, ATP and electrical stimulation, while glia responded to ATP and ADPβs. Inhibition of glial responses by MRS2179 suggests involvement of P2Y1 receptors. Neuronal stimulation also caused delayed glial responses, which were reduced by suramin and by exogenous apyrases that catalyse nucleotide breakdown. Conversely, glial responses were enhanced by ARL-67156, an ecto-ATPase inhibitor. In this mouse enteric co-culture, functional glia and neurons can be easily monitored using optical techniques. Glial cells can be activated directly by ATP or ADPβs. Activation of neuronal cells (DMPP, K⁺) causes secondary responses in glial cells, which can be modulated by tuning ATP and ADP breakdown. This strongly supports the involvement of paracrine purinergic communication between enteric neurons and glia.     

Neurochemical plasticity in the enteric nervous system of a primate animal model of experimental Parkinsonism

Abstract  Emerging evidences suggest that the enteric nervous system (ENS) is affected by the degenerative process in Parkinson's disease (PD). In addition lesions in the ENS could be associated with gastrointestinal (GI) dysfunctions, in particular constipation, observed in PD. However, the precise alterations of the ENS and especially the changes in the neurochemical phenotype remain largely unknown both in PD and experimental Parkinsonism. The aim of our study was thus to characterize the neurochemical coding of the ENS in the colon of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated monkeys, a well-characterized model of PD. In the myenteric plexus, there was a significant increase in the number of neurons per ganglia (identified with Hu), especially nitric oxide synthase immunoreactives (IR) neurons in MPTP-treated monkeys compared to controls. A concomitant 72% decrease in the number of tyrosine hydroxylase-IR neurons was observed in MPTP-treated monkeys compared to controls. In contrast no change in the cholinergic or vasoactive intestinal peptide-IR population was observed. In addition, the density of enteric glial cells was not modified in MPTP-treated monkeys. Our results demonstrate that MPTP induces major changes in the myenteric plexus and to a lesser extent in the submucosal plexus of monkeys. They further reinforce the observation that lesions of the ENS occur in the course of PD that might be related to the GI dysfunction observed in this pathology.