Ultrastructural and Immunohistochemical Study on the Lamina Propria Cells Beneath Paneth Cells in the Rat Ileum

Abstract

Paneth cells secrete bactericidal substances in response to bacterial proliferation on the mucosal surface without directly contacting bacteria. However, the induction mechanism of this transient secretion has not been clarified, although nervous system and/or immunocompetent cells in the lamina propria (LP) might be involved. In this study, we ultrastructurally and immunohistochemically investigated which LP cells are localized beneath Paneth cells and examined the relationship between the Paneth cell-derived cellular processes which extended into the LP and the LP cells. The results showed that various cells-including blood capillary, subepithelial stromal cell, and nerve fiber-were present in the LP beneath Paneth cells. Endothelial cells of blood capillary were the cells most frequently found in this location; they were situated within 1 μm of the Paneth cells and possessed fenestration on the surfaces adjacent to Paneth cells. The Paneth cells rarely extended the cellular processes toward the LP across the basal lamina. Most of the cellular processes of Paneth cells contacted the subepithelial stromal cells. Immunohistochemistry revealed that the CD34 CD31 αSMA stromal cells preferentially localized in the LP beneath the intestinal crypt base, while PDGFRα αSMA stromal cells mainly localized around the lateral portions of the intestinal crypt and PDGFRα αSMA stromal cells localized in the intestinal villus. From these findings, the existence of blood capillaries beneath Paneth cells might reflect the active exocrine function of Paneth cells. Furthermore, subepithelial stromal cells, probably with a CD34 CD31 αSMA PDGFRα phenotype, beneath the crypt base might affect Paneth cell activity by interacting with their cellular processes. Anat Rec, 301:1074-1085, 2018. © 2018 Wiley Periodicals, Inc.

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

“…On the other hand, although the connect between the epithelial cells and nerve fibers were highly scarce in the present study, the extensions of the cellular process from epithelial cells into the lamina propria found in the present study might be noteworthy. This phenomenon has been reported in Paneth cells [ 26 ] and intestinal enteroendocrine cells [ 3 ]. The extension of the cellular processes penetrating the basal lamina might be important for intercellular communication between the epithelial cells and the cells in the lamina propria.…”

“…Our earlier investigation revealed that type II FBLCs form a basket-like reticular structure surrounding the crypt epithelium by being in contact with each other around the intestinal crypts [ 25 ]. Such FBLCs around the crypts were immunopositive for CD34 and in direct contact with Paneth cells [ 26 ]. Therefore, considering that the secretion of antibacterial substances from Paneth cells is promoted by ACh [ 35 ] despite scarce direct contacts as shown in the present study, we speculate that type II FBLCs might regulate the secretion of antibacterial substances, and possibly intestinal juice, by mediating neurotransmission to crypt epithelial cells.…”

Three-dimensional analysis of fibroblast-like cells in the lamina propria of the rat ileum using serial block-face scanning electron microscopy

“…The subepithelial FBLCs localizing just beneath the epithelial cells, which correspond to FBLC type III in the present study, show PDGFRα hi αSMA + CD34 − around the intestinal crypt, but PDGFRα hi αSMA − CD34 − in the intestinal villus [28], suggesting that FBLC type III in the present study could be subdivided into two phenotypes by the cellular markers. On the other hand, candidates for the cellular markers of FBLC type I and II are CD34 + CD31 − , because subepithelial FBLCs showing this phenotype localize around the intestinal crypt of the rat and mouse small intestine [28, 40], although a cellular marker for discrimination between FBLC type I and II has not been established. The distinctive, spherically shaped endoplasmic reticulum in FBLC type I was also found in the endothelial cells of the central lymph vessels, but not of the blood capillaries.…”

“…Among FBLCs, subepithelial FBLCs have been perhaps best investigated in the rat intestinal LP, where they have been shown to form a reticular structure beneath the epithelium and to communicate with each other via gap junctions [9, 12, 14, 25]. Moreover, subepithelial FBLCs have been reported to directly contact several epithelial cells, such as goblet cells [13] and Paneth cells [28] in the rat small intestine, suggesting that they also communicate with various epithelial cells. Subepithelial FBLCs might contribute to the antigen presentation, because they express major histocompatibility complex molecule class II and costimulatory molecules in the human colon [38].…”

“…Subepithelial FBLCs are themselves a heterogenous cellular population. For example, in case classified by cellular markers, subepithelial FBLCs contain α smooth muscle actin (SMA) + cells (human [37], mouse [40], rat [28]), platelet-derived growth factor receptor (PDGFR) α + cells (mouse [18, 19], rat [28]) and CD34 + αSMA − cells (mouse [40], rat [28]). In addition, a distinctive type of FBLCs called telocytes have also been reported in the subepithelial region of the duodenal and jejunal crypt by ultrastructural observation [6, 7].…”