Nerve growth factor receptor and neurochemical markers in human oral mucosa: an immunohistochemical study

Expression of p75(NGFR), a Proliferative and Basal Cell Marker, in the Buccal Mucosa Epithelium during Re-epithelialization

We investigated the expression of p75^NGFR, a proliferative and basal cell marker, in the mouse buccal mucosa epithelium during wound healing in order to elucidate the role of epithelial stem cells. Epithelial defects were generated in the epithelium of the buccal mucosa of 6-week-old mice using CO₂ laser irradiation. BrdU was immediately administered to mice following laser irradiation. They were then sacrificed after 1, 3, 7, and 14 days. Paraffin sections were prepared and the irradiated areas were analyzed using immunohistochemistry with anti-p75^NGFR, BrdU, PCNA, and CK14 antibodies. During re-epithelialization, PCNA (–)/p75^NGFR (+) cells extended to the wound, which then closed, whereas PCNA (+)/p75^NGFR (+) cells were not observed at the edge of the wound. In addition, p75^NGFR (–)/CK14 (+), which reflected the presence of post-mitotic differentiating cells, was observed in the supra-basal layers of the extended epithelium. BrdU (+)/p75^NGFR (+), which reflected the presence of epithelial stem cells, was detected sparsely in buccal basal epithelial cells after healing, and disappeared after 7 days. These results suggest that p75^NGFR (+) keratinocytes are localized in the basal layer, which contains oral epithelial stem cells, and retain the ability to proliferate in order to regenerate the buccal mucosal epithelium.

Assessment of the innervation pattern of oral squamous cell carcinoma using neural protein gene product (9.5)-An immunocytochemical study

BACKGROUND

This study was carried out to assess the innervation patterns in oral cancer using the general neuronal marker protein gene product 9.5 (PGP 9.5) and to find an explanation for why oral cancer tends to be painless in the early stages.

MATERIALS AND METHODS

Tumor tissue from 30 unselected patients with oral squamous cell carcinoma was evaluated for this study. PGP 9.5 was used to localize nerve fibers in oral squamous cell carcinoma. An indirect immunofluorescence technique using biotin/FITC streptavidin detection system was used on paraffin wax sections of tumor tissue fixed in neutral buffered formalin.

RESULTS

There was no PGP9.5 immunoreactivity in the normal tissue adjacent to the tumor in 18 cases out of 30 (60%). In 12/30 of oral squamous cell carcinoma, preexisting nerve fibers were detected in tissue stroma adjacent to the cancer tissue. Labeled nerve fibers between tumor cells were detected only in 2 out of the 30 cases.

CONCLUSION

There are no apparent patterns of innervations in the cancer tissues themselves, but there are innervations patterns in the surrounding tissue, which presumably represents preexisting nerves. These results may partly explain why oral cancer tends to be painless in the early stages.

Unilateral Severe Chronic Periodontitis Associated With Ipsilateral Surgical Resection of Cranial Nerves V, VI, and VII

BACKGROUND

The central and peripheral nervous systems participate in several local physiological and pathological processes. There is experimental evidence that the inflammatory, local immune, and wound healing responses of a tissue can be modulated by its innervation. The aim of this clinical report is to present a case of unilateral severe periodontitis associated with ipsilateral surgical resection of the fifth, sixth, and seventh cranial nerves and to discuss the possible contribution of the nervous system to periodontal pathogenesis.

METHODS

A 39-year-old female patient with a history of a cerebrovascular accident caused by a right pontine arteriovenous malformation and destruction of the right fifth, sixth, and seventh cranial nerves was diagnosed with severe chronic periodontitis affecting only the right maxillary and mandibular quadrants. The patient's oral hygiene was similar for right and left sides of the mouth. Percentages of tooth surfaces carrying dental plaque were 41% and 36% for right and left sides, respectively. Non-surgical and surgical periodontal therapy was performed, and the patient was placed on a regular periodontal maintenance schedule.

RESULTS

Healing following initial periodontal therapy and osseous periodontal surgery occurred without complications. Follow-up clinical findings at 1 year revealed stable periodontal health.

CONCLUSIONS

This case report suggests that periodontal innervation may contribute to the regulation of local processes involved in periodontitis pathogenesis. It also suggests that periodontal therapy can be performed successfully at sites and in patients affected by paralysis.

Support of trigeminal sensory neurons by nonneuronal p75 neurotrophin receptors

The p75 neurotrophin receptor (p75NTR) binds all four mammalian neurotrophins, including neurotrophin-3 (NT-3) required for the development of select sensory neurons. This study demonstrated that many gustatory and somatosensory neurons of the tongue depend upon p75NTR. Each of thousands of filiform papillae at the front of the tongue as well as each somatosensory prominence at the back of the tongue has a small cluster of p75NTR-positive epithelial cells that is targeted by somatosensory innervation. This expression of p75NTR by epithelial target cells required NT-3 but not adult innervation. NT-3-secreting cells were adjacent to the p75NTR-positive target cells of each somatosensory organ, as demonstrated in NT-3(lacZneo) transgenic mice. In NT-3 null mutant mice, there were few lingual somatosensory neurons. In p75NTR null mutant mice, the lingual somatosensory axons were likewise absent or had deficient terminal arborizations. Cell culture indicated that substrate p75NTR can influence neuronal outgrowth. Specifically, dissociated trigeminal sensory neurons more than doubled their neurite lengths when grown on a lawn of p75NTR-overexpressing fibroblasts. This enhancement of neurite outgrowth by fibroblast p75NTR raises the possibility that epithelial target cell p75NTR may help to promote axonal arborization in vivo. The co-occurrence in p75NTR null mice of a 35% reduction in geniculate ganglion taste neurons and a shortfall of taste buds is consistent with the established role of gustatory innervation in prompting mammalian taste receptor cell differentiation.

Capsaicin-evoked CGRP release from rat buccal mucosa: development of a model system for studying trigeminal mechanisms of neurogenic inflammation

Many of the physiological hallmarks associated with neurogenic inflammatory processes in cutaneous tissues are similarly present within orofacial structures. Such attributes include the dependence upon capsaicin-sensitive sensory neurons and the involvement of certain inflammatory mediators derived therein, including calcitonin gene-related peptide (CGRP). However, there are also important differences between the trigeminal and spinal nervous systems, and the potential contributions of neurogenic processes to inflammatory disease within the trigeminal system have yet to be fully elucidated. We present here a model system that affords the ability to study mechanisms regulating the efferent functions of peptidergic terminals that may subserve neurogenic inflammation within the oral cavity. Freshly dissected buccal mucosa tissue from adult, male, Sprague-Dawley rats was placed into chambers and superfused with oxygenated, Krebs buffer. Serial aliquots of the egressing superfusate were acquired and analysed by radioimmunoassay for immunoreactive CGRP (iCGRP). Addition of the selective excitotoxin, capsaicin (10-300 microm), to the superfusion buffer resulted in a significant, concentration-dependent increase in superfusate levels of iCGRP. Similarly, release of iCGRP from the buccal mucosa could also be evoked by a depolarizing concentration of potassium chloride (50 mm) or by the calcium ionophore A23187 (1 microm). The specific, capsaicin receptor antagonist, capsazepine (300 microm), completely abolished the capsaicin-evoked release of iCGRP while having no effect whatsoever on the potassium-evoked release. Moreover, capsaicin-evoked release was dependent upon the presence of extracellular calcium ions and was significantly, though incompletely, attenuated by neonatal capsaicin denervation. Collectively, these data indicate that the evoked neurosecretion of iCGRP in response to capsaicin occurs via a vanilloid receptor-mediated, exocytotic mechanism. The model system described here should greatly facilitate future investigations designed to identify and characterize the stimuli that regulate the release of CGRP or other neurosecretory substances in isolated tissues. This system may also be used to elucidate the role of these mediators in the aetiology of inflammatory processes within the trigeminal field of innervation.

Immunohistochemical demonstration of nerve terminals in the whole hard palate of rats by use of an antiserum against protein gene product 9.5 (PGP 9.5)

Sensory innervation of the entire hard palate was investigated in the rat using serial sections immunostained for protein gene product 9.5 (PGP 9.5), a neuronal marker. PGP 9.5-immunoreactive nerve endings were widely distributed in the hard palate, but the innervation pattern and density differed among portions. They were numerous at papillary protrusions including the incisal papilla, antemolar/intermolar rugae, and postrugal filiform papillae. Immunoreactive free nerve endings gathered at the summits of the connective tissue papillae, some of them entering deeply into the epithelium. Electron microscopy demonstrated that nerves in the postrugal filiform papillae reached the stratum corneum. The atrial region, possibly the most sensitive in the hard palate, showed unique innervation: its anterior part, adjacent to incisors, developed intraepithelial networks of fine and beaded nerves, whereas its posterior part revealed cone-shaped nerve terminals formed on the connective tissue papillae of the atrial folds which comprised two lines of longitudinal flaps. Taste bud-like corpuscles gathered in the medial walls of the incisal canals and in the "Geschmacksstreifen" (taste stripes) present at the most anterior part of the soft palate. The hard palate of the rat is thus richly innervated, and is characterized by region-specific nerve endings which may be involved in mechano- and chemoreception in the oral cavity.

Mast cells and their mediators in cutaneous wound healing--active participants or innocent bystanders?

Mast cells are traditionally viewed as effector cells of immediate type hypersensitivity reactions. There is, however, a growing body of evidence that the cells might play an important role in the maintenance of tissue homeostasis and repair. We here present our own data and those from the literature elucidating the possible role of mast cells during wound healing. Studies on the fate of mast cells in scars of varying ages suggest that these cells degranulate during wounding, with a marked decrease of chymase-positive cells, although the total number of cells does not decrease, based on SCF-receptor staining. Mast cells contain a plethora of preformed mediators like heparin, histamine, tryptase, chymase, VEGF and TNF-alpha which, on release during the initial stages of wound healing, affect bleeding and subsequent coagulation and acute inflammation. Various additional vasoactive and chemotactic, rapidly generated mediators (C3a, C5a, LTB4, LTC4, PAF) will contribute to these processes, whereas mast cell-derived proinflammatory and growth promoting peptide mediators (VEGF, FGF-2, PDGF, TGF-beta, NGF, IL-4, IL-8) contribute to neoangiogenesis, fibrinogenesis or re-epithelization during the repair process. The increasing number of tryptase-positive mast cells in older scars suggest that these cells continue to be exposed to specific chemotactic, growth- and differentiation-promoting factors throughout the process of tissue remodelling. All these data indicate that mast cells contribute in a major way to wound healing. their role as potential initiators of or as contributors to this process, compared to other cell types, will however have to be further elucidated.