Chemoanatomische Charakterisierung der Innervation der Gingiva unter dem Einfluss experimenteller Gingivitis in verschiedenen Altersgruppen

Periodontal inflammation the leading reason followed by caries for tooth loss in adults is a multifactorial disease being predominantly triggered by dental microbial plaque. Besides, structural and functional vascular changes are considered to hallmark the progression of inflammatory diseases, including periodontal inflammation and post-inflammatory regeneration processes. Regulating the blood flow and vascular function, innervation of blood vessels has been in the centre of scientific interest in other tissues, e.g., the skin. However, the authentic vascular innervation within human gingiva has not been characterized yet. Likewise, there is no detailed information whether or not innervation patterns vary within the course of inflammation or aging. The aim of this study was to analyse the local monoaminergic, cholinergic and sensory innervation in periodontally healthy adults (n=14; 18-77 years) in controlled conditions of an experimental, plaque-induced gingivitis study by immunohistochemistry. Gingival biopsies were taken from each patient twice; one specimen was obtained from healthy gingiva, the other after the induction of experimental gingivitis and clinical examination. Transmitter- and target-related gingival innervation patterns in non-inflamed gingival biopsies were differentiated by using single and double staining immunohistochemistry with specific antibodies against unequivocal markers of peripheral transmitter systems. i) Noradrenergic sympathetic nerves were marked by antibodies against the vesicular monoamine transporter 2 (VMAT2), the catecholamine synthesizing enzymes tyrosine hydroxylase (TH), L-Dopa decarboxylase (DDC), Dopamine-ß-hydroxylase (DBH) and the peptide co-transmitter neuropeptide Y (NPY), ii) cholinergic parasympathetic nerves by antibodies against the vesicular acetylcholine transporter (VAChT), choline acetyl-transferase (ChAT) and the concomitant cholinergic neuropeptides vasoactive intestinal polypeptide (VIP) and peptide histidine-methionine (PHM) and iii) sensory innervation by antibodies against the representative sensory neuropeptides calcitonin gene-related peptide (CGRP) and substance P (SP) were assessed in both series. For the first time we could prove that within the human gingiva the same blood vessels are innervated by sympathetic VMAT2+/TH+/DDC+ and parasympathetic ChAT+/VAChT+/VIP+, as well as sensory CGRP+/SP+ nerves. All three qualities were also observed independently in nonvascular nerves. Double immunofluorescence staining revealed the combinatorial presence of proteins distinctive for either the catecholaminergic or cholinergic trait, i.e., fibres copositive for VMAT2, TH, DDC and NPY, as well as fibres copositive for VAChT and VIP but strict segregation of cholinergic traits from catecholaminergic traits and segregation of sensory (CGRP+, SP+) traits from both cholinergic and noradrenergic traits. These findings were persistent in all groups. Concerning age-dependent modifications in healthy gingiva, only TH+, deep and NPY+ papillary perivascular nerves as well as NPY+ nonvascular fibres were observed to be significantly diminished with advancing age. Except for those findings no significant differences within the innervation patterns were ascertained. Inflammation-induced changes in both age-groups showed not only to be reciprocal in the plasticity of sympathetic and parasympathetic nerves after the induction of experimental gingivitis in young patients, but also the alterations of innervation patterns in the gingiva of elderly patients showed inverse action compared to those in young gingiva. While sympathetic nerves significantly declined in young but increased in elderly gingiva with advanced state of inflammation, the cholinergic nerve patterns showed the opposite, enhancing in young and reducing in old, inflamed gingiva. Regarding sensory innervation the signalling for CGRP-positive fibres increased in both age groups with worsening gingival condition, while the density of SP-ir staining rose only in deep blood vessel walls within elderly patients’ gingival specimens. These observations indicate a simultaneous triple neurovascular regulation in the human gingiva by mutually segregated noradrenergic, cholinergic and peptidergic sensory nerves. Furthermore, there is evidence for converted anti-inflammatory pathways between young and old patients, implying a modified neuronal distribution and altered host response. Given the pleiotropic vasoregulatory and immunomodulatory properties of noradrenaline, acetylcholine and neuropeptides it is likely that this triple innervation and the nonvascular innervation play a role in gingivitis and periodontitis.