Organization of the Lamina propria mucosae of Rat Intestinal Mucosa, with Special Reference to the Subepithelial Connective Tissue

Abstract

Light microscopy, scanning electron microscopy and transmission electron microscopy have been used to delineate the structure and function of the lamina propria mucosae in the rat jejunum. In silver-impregnated sections, the adepithelial surface of the lamina propria mucosae was framed by a sheet of reticular fibers (reticular sheet). Short-term (3-hour) immersion of jejunal tissues in 2 N NaOH solution enabled us to simultaneously view networks of reticular fibrils and fibroblasts residing in the subepithelial connective tissue under a scanning electron microscope. The reticular fibrils, which measured about 40 nm in diameter and were interwoven in dense networks, formed a sheet 2–3 µm thick. In the villi, this sheet contained numerous foramina ranging from 3 to 7 µm in diameter, through which lymphocytes, macrophages, basal extensions of epithelial cells and fat particles traversed. The reticular sheet in the domes of isolated lymphoid nodules was markedly porous, and many lymphocytes migrated into or out of the epithelium through the foramina. The foramina of the reticular sheet may participate in the communication between the intestinal epithelium and the lamina propria mucosae. It was noted that the foramina of the reticular sheet in the villi were surrounded by end feet of the cytoplasmic processes of fibroblasts. In addition, these fibroblasts were combined with lymphocytes or dendritic cells in the lamina propria mucosae.

Extracellular Matrix Conditions T Cells for Adhesion to Tissue Interstitium

“…However, the T cell area of lymph nodes is a cellular environment with minimal accessible collagen due to stromal cell processes that sheath the abundant collagen fibers forming the reticular fiber network (27,28,42). In contrast, once an activated T cell enters tissue, it is exposed to Ag again and to interstitial ECM (43,44). We demonstrate that tissue T cells, due to residency in an ECM microenvironment, possess differences in their ability to adhere to various ECMs and in their integrin expression profile compared with their circulating counterparts.…”

Characteristics of subepithelial fibroblasts as a mechano-sensor in the intestine: cell-shape-dependent ATP release and P2Y1 signaling

“…(1) Subepithelial fibroblasts secrete extracellular matrices and form basal lamina, which are perforated by numerous fenestrations (Komuro, 1985;Komuro and Hashimoto, 1990;Toyoda et al, 1997). Under basal lamella, dense collagenous fibrils and subepithelial fibroblasts form subepithelial reticular sheets.…”

“…Ca 2+ waves evoked by mechanical stimulation may propagate to capillaries, and regulate absorption of nutrients or regulate blood flow by cell contraction. Moreover, subepithelial fibroblasts represent cellular communication with α-SMA-negative fibroblast-like cells, which enclose smooth muscles in the lamina propria (Güldner et al, 1972;Toyoda et al, 1997;Adegboyega et al, 2002). Although these fibroblast-like cells do not synthesize collagen fibrils, they are rich in ET receptors as subepithelial fibroblasts (Furuya et al, 1990).…”

Localization of NK1 receptors and roles of substance-P in subepithelial fibroblasts of rat intestinal villi

“…Both ICC-DMP and villous subepithelial fibroblasts are NK1R-positive and form synapse-like structures with substance-P and non-substance-P nerve varicosities and are also in close contact with immune cells such as lymphocytes, mast cells, and macrophages (Deane 1964;Komuro 1990;Hashimoto and Komuro 1988;Toyoda et al 1997;Popescu et al 2005). Although the NK1R expression is constitutive in ICC-DMP and age-dependent in villous subepithelial fibroblasts, these fibroblast-like cells may play key roles in the reflex, motility, and immune response in the muscular layer and villi, respectively.…”

“…In the villi, subepithelial fibroblasts are stellate-shaped with many cell processes and communicate with each other via gap junctions. Moreover, they are in close contact with nerve varicosities, capillaries, smooth muscles, immune cells, and epithelial cells (Deane 1964;Güldner et al 1972;Desaki et al 1984;Hashimoto and Komuro 1988;Komuro and Hashimoto 1990;Berthoud et al 1995;Toyoda et al 1997;Hosoyamada and Sakai 2007). Subepithelial fibroblasts not only work as the contractile mechanical frame of the lamina propria, they have many other functions including the regulation of epithelial proliferation and differentiation, water and electrocyte transports, and the secretion of extracellular matrix molecules, growth factors, cytokines, chemokines, and inflammatory mediators, etc.…”