Three-dimensional analysis of neural connectivity with cells in rat ileal mucosa by serial block-face scanning electron microscopy

Abstract

The comprehensive targets of innervation in the intestinal mucosa are unknown, partly because of the diversity of cell types and the complexity of the neural circuits. Herein, we investigated the comprehensive targets of neural connectivity and analyzed the precise characteristics of their contact structures in the mucosa of rat ileum. We examined target cells of neural connections and the characteristics of their contact structures by serial block-face scanning electron microscopy at four portions of the rat ileal mucosa: the apical and basal portions in the villi, and the lateral and basal portions around/in the crypts. Nerve fibers were in contact with several types of fibroblast-like cells (FBLCs), macrophage-like cells, eosinophils, lymphocyte-like cells, and other types of cells. The nerve fibers almost always ran more inside of lamina propria than subepithelial FBLC, and thus contacts with epithelial cells were very scarce. The contact structures of the nerve fibers were usually contained synaptic vesicle-like structures, and we classified them into patterns based on the number of nerve fiber contacting the target cells at one site, the maximum diameter of the contact structures, and the relationship between nerve fibers and nerve bundles. The contact structures for each type of cells occasionally dug into the cellular bodies of the target cells. We revealed the comprehensive targets of neural connectivity based on the characteristics of contact structures, and identified FBLCs, immunocompetent cells, and eosinophils as the candidate targets for innervation in the rat ileal mucosa.

Histological study on the reginal difference in the localization of mucosal enteric glial cells and their sheath structure in the rat intestine

“…A recently developed imaging technology called three-dimensional analysis with electron microscopy enables us to easily understand the ultrastructures of animal tissues well. Indeed, using a method for this technology called serial block-face scanning electron microscopy (SBF-SEM), has thus far enabled us to clarify that the micromilieu in the intestinal mucosa differs among regions throughout the intestine [ 2 , 16 , 17 , 18 , 19 , 24 ]. For example, we have clarified that the histological characteristics of fibroblast-like cells, one of the main cell types in the lamina propria, differ among the ileum [ 17 ], the cecum, and the descending colon [ 24 ].…”

“…For example, we have clarified that the histological characteristics of fibroblast-like cells, one of the main cell types in the lamina propria, differ among the ileum [ 17 ], the cecum, and the descending colon [ 24 ]. Moreover, the characteristics of contact between the nerve fibers and various kinds of cells in the intestinal mucosa also are different among the ileum [ 18 ], the cecum, and the descending colon [ 19 ]. However, the regional differences in mEGCs throughout the intestine have not been clarified.…”

“…All procedures performed in studies involving animals were in accordance with the ethical standards of the institution (the Kobe University Animal Experimentation Regulations). We focused on the three different regions, the ileum, the cecum, and the descending colon, in this study because the other types of cells in the mucosa, such as fibroblast-like cells [ 17 , 24 ] and the nerve network [ 18 , 19 ], exhibited the regional differences among these three regions. The data stacks obtained from SBF-SEM in our previous studies [ 17 , 18 , 19 , 24 ] were reused in the present study ( Supplementary Fig.…”

“…Therefore, a sheath structure left incomplete by mEGCs might lead to effective neurotransmission through diffusion. Moreover, in our previous studies, we clarified that the nerve fibers are in contact with more abundant cells in the apical portions of intestinal villi than around the crypt using same data stacks of SBF-SEM [ 18 ], and that the nerve fibers are widely in contact with fibroblast-like cells and macrophages in the luminal side of the cecum [ 19 ]. Thus, the coverage level by mEGCs seems to inversely correlate with the abundance of contact between nerve fibers and various types of cells ( e.g.…”

Avaliação de marcadores de neurônios entéricos Dogiel tipo II: caracterização neuroquímica dos neurônios aferentes primários intrínsecos (IPANs) no SNE do cólon humano

“…O plexo submucoso é contínuo ao redor da circunferência e ao longo do comprimento dos intestinos delgado e grosso e em geral, os filamentos de interconexão do plexo submucoso são mais finos e os gânglios são menores do que os do plexo mioentérico (Henle, 1871;Goniaew, 1875;Timmermans et al, 2001). Os arranjos dos gânglios no plexo submucoso e os tipos funcionais de neurônios nesses gânglios diferem entre as espécies (Scheuermann et al, 1987;Schemann et al, 2004;Timmermans et al, 1990;Nakanishi et al, 2020). Em animais de grande porte, sendo bons exemplos o porco e o ser humano, os gânglios submucosos formam plexos distintos, mas interconectados, em níveis diferentes, conforme descrito claramente por Schabadasch (Schabadasch, 1930).…”