Immunocytochemical study of nerve fibers containing substance P in the junctional epithelium of rats

Abstract

Nerve fibers with substance P-like immunoreactivity (SP-IR) in the junctional epithelium (JE) of 32-42-d-old rats were examined by both light and electron microscopy using the avidin-biotin-peroxidase complex method. The density of nerve fibers with SP-IR was highest in the middle portion of the JE; however, a few fibers were localized in the coronal portion of the JE and close to the enamel surface. Also, rich innervation was found especially in the basal cell layer of the JE. Unmyelinated axons with SP-IR in the connective tissue underlying the JE were enveloped by Schwann cells but lost their Schwann cell sheath almost completely in the JE. The axons often formed varicosities with SP-IR as terminals in various areas of the JE. The terminals contained numerous large granular vesicles, small clear vesicles and a few mitochondria, and were surrounded by the cytoplasmic processes of the junctional epithelial cells. These terminals were sometimes located close to neutrophils in the JE; the minimum gap distance between the terminals and the processes of junctional epithelial cells or neutrophils was about 20 nm. A few terminals with SP-IR came close to the enamel surface, and the minimal distance between the terminals and the enamel surface was about 5 microns. SP-IR in the nerve terminals in the JE fixed with 0.1% or 0.25% glutaraldehyde was distributed diffusely in the axoplasm or was confined to the granular vesicles. These findings show that substance P is contained in the large granular vesicles in the nerve terminals, and suggest that these terminals may function as modulators of junctional epithelial cells and neutrophils.

Characterization of the peri-implant epithelium in hamster palatine mucosa: Behavior of Merkel cells and nerve endings

“…A number of regenerative nerve fibers were also evident. These had invaded the superficial layer of the peri-implant epithelium in a manner similar to the invasion into the junctional epithelium as described by Tanaka et al All of these regenerative nerve fibers possess free endings, and their functions might be a sensory system for pain, touch and pressure (27). We suggest that these free nerve endings play a role not only in the sensory system but also as part of the defense system, even though Merkel cells do not regenerate after implantation.…”

“…However, Buser et al showed that there are wide intercellular spaces and transmigrating polymorpho-nuclear leukocytes and lymphocytes in the junctional epithelium around the implant surface (2). Concerning nerve fibers, Tanaka et al reported that many nerve fibers containing substance P are present in the middle portion of the junctional epithelium, whereas they are sparse in the oral sulcular epithelium and in the oral epithelium (27). They suggested that substance P, which is released from the nerve fibers into the junctional epithelium, might regulate the endocytotic activity of neutrophils and junctional epithelial cells to form a part of the defense network against noxious stimuli.…”

Biological Sealing and Defense Mechanisms in Peri-Implant Mucosa of Dental Implants

“…These receptors are also localized in neutrophils invading into the intercellular spaces between PIE cells (Figure 8c). Overall, the PIE shows a similar distribution of substance P-containing sensory nerve fibers and their neurokinin-1 receptors, compared to junctional epithelium Tanaka et al, 1996;Kido et al, 1999). …”

“…The sensory nerve fibers contain the neuropeptides, calcitonin gene-related peptide (Byers et al, 1987;Nagata et al, 1992Nagata et al, , 1994 and substance P (Nagata et al, , 1994Tanaka et al, 1996;Kido et al, 1999), and terminate close to endothelial cells, neutrophils, and junctional epithelial cells Tanaka et al, 1996). The peri-implant mucosa is also supplied with sensory nerves containing calcitonin generelated peptide (Fujii et al, 2003) and substance P (Yamaza et al, 2009) (Figure 7a).…”

“…Various mechanisms of peripheral host defense have been demonstrated in this epithelium (Schroeder & Listgarten, 1997) (Figure 9): (1) phagocytosis and anti-bacterial activity of neutrophils infiltrating into the junctional epithelium (Yamasaki et al, 1979, Tanaka et al, 1988, (2) outward flow of gingival sulcular fluid through the junctional epithelium (McDougall, 1970;Tanaka, 1984;Tanaka and Sakano, 1987), (3) fast turnover or apoptosis of junctional epithelial cells (Schroeder, 1986, Ekuni et al, 2005, (4) continuous epithelial attachment via the IBL throughout the enamel surface (Squier, 1991;Bartold, et al, 2000), (5) endocytotic capacity of junctional epithelial cells for external pathogens (Yamasaki et al, 1979;Tanaka 1984;Tanaka & Sakano, 1987;Ayasaka et al, 1989, Yamaza et al, 1997, and (6) neurotrophic modulation in the junctional epithelium (Kondo et al, 1995;Tanaka et al, 1996;Kido et al, 1999). Fig.…”