Mucopolysaccharide localization in gingival epithelium

Short incubations, at 37°C, of small freshly excised pieces of healthy human gingivae iancorporated [³⁵S]-sulphate and [³H]-acetate into macromolecular material which could be precipitated intercellularly in the epithelium. Following radioactively pulse-chased incubations, such localization was observed by autoradiography on cryostat histological sections fixed in cetylpyridinium chloride. Critical electrolyte salt concentration elution indicated that most of the intercellular material was soluble in 0.63M-MgCl₂, and any material which remained was intracellular. In vitro and in vivo incorporation studies were compared. These data corroborate biochemical studies (Wiebkin, Bartold & Thonard 1979) together with other histochemical observations that proteoglycans (mucopolysaccharides) are a major intercellular component of human gingival epithelium. Molecular conformation and the relatively rapid synthesis and secretion rate for this class of epithelial macromolecule may explain the lack of susceptibility of this material in the intercellular site, both to degradation by some specific enzymes previously reported and to elution with critical salt concentrations from cationic detergent precipitates.
The method described, together with in vivo incorporation studies, provides a useful technique for studying direct effects of some microenvironmental influences on gingival epithelium.     

Mucopolysaccharide localization in gingival epithelium Factors affecting biosynthesis of sulphated proteoglycans in organ cultures of gingival epithelium

The effect of extraneous hyaluronidase, trypsin, hyaluronic acid, chrondroitin sulphate, and commercial heparin on the synthesis and secretion of proteoglycans (mucopolysaccharides) by gingival epithelium in short term incubations was investigated by autoradiography. Small pieces of human gingivae were incubated at 37°C in tissue culture medium (T.C. 199) for 75 min. The first 15 min incubation included a “pulse” of (³⁵S)-sulphate, after which the radioactive incorporation was “chased” in radioactive free medium. Cryostat sections of these pieces were cut, air dried, slide fixed with cetylpyridinium chloride, and prepared for autoradiography. The effect of the various additives in the “pulse” or the “chase” incubations on the autoradiographic localization of incorporated (³⁵S)-sulphate in the epithelium was noted. The responses by the epithelium to the enzymes hyaluronidase and trypsin were different. The former caused marked tissue disruption, probably due in part to degradation of the ground substance. Synthesis and secretion of sulphated macromolecules were evident when the lower concentrations of hyaluronidase were used. Tissue disruption appeared to be less severe. Trypsin in the medium of the gingival incubations appeared to cause both metabolic and secretory disruption. Both the sulphated polyanions, chrondroitin sulphate and heparin, when added to gingival incubations, showed inhibition of localization of (³⁵S)-sulphate label inlercellularly. Chrondroitin sulphate included in the “chase” incubations alone resulted in the inhibition, while only low concentrations of heparin caused any inhibition. These latter data were curious. The interpretations of a comparison of the data from “pulse” and “chase” additions of the non-sulphated hyaluronic acid imply that there was an initial inhibitory effect on secretion which in turn resulted in a subsequent regulation of synthesis of the intercellular sulphated macromolecules. These data and those derived from other tissues such as endothelium, cartilage, and chondrocyte cultures are briefly contrasted.     

Expression of fibronectin-binding integrins in gingival epithelium in drug-induced gingival overgrowth

BACKGROUND AND OBJECTIVE: Gingival overgrowth is a side-effect of nifedipine and cyclosporin medications. Integrins are transmembrane glycoproteins that mediate cell adhesion, regulate cell proliferation and participate in the regulation of tissue fibrosis. The aim of this study was to investigate whether expression of epithelial cell integrins is linked to the development of drug-induced gingival overgrowth. MATERIAL AND METHODS: Human gingival biopsies of patients taking nifedipine, cyclosporin, or a combination of both medications, were used. Expression of the alpha5beta1, alphavbeta1 and alphavbeta6 integrins, and of cellular extra domain A of fibronectin, was localized in frozen sections using immunohistochemistry. RESULTS: The activated conformation of the beta1, alpha5beta1 and alphavbeta6 integrins were more frequently expressed in distinct locations in the oral epithelium in the combined drug group. Cellular extra domain A of fibronectin, a ligand for both alpha5beta1 and alphavbeta6 integrins, was expressed within the connective tissue of all groups. It was also expressed around the basal keratinocytes of the control, nifedipine and cyclosporin-induced gingival overgrowth groups, but not in the combined medication group. No relationship between the presence of inflammation and integrin expression was found. CONCLUSION: The results indicate that expression of certain integrins is up-regulated in the epithelium of drug-induced gingival overgrowth where they could participate in controlling the formation of elongated rete ridges and tissue fibrosis.     

Langerhans cells in the gingival epithelium

Langerhans cells (LCs) were specifically demonstrated by monoclonal antibody OKT 6. In healthy gingival tissue LCs were mainly seen in stratum spinosum of the surface epithelium. They had small nuclei and with long cell processes. The LCs of oral epithelium in marginal gingivitis and adult periodontitis tissue were more in numbers than in healthy tissue. In juvenile periodontitis tissue LCs numbers seemed to be increased obviously in comparison to the healthy tissue. The LCs were round and often located in both deep spinous and basal layers. These results demonstrate that LCs play an important role in the local immune response of the periodontal tissues.     

Analysis of in situ proliferative activity in oral gingival epithelium in patients with xerostomia

BACKGROUND: Sj?gren's syndrome is an autoimmune disease characterized by xerostomia and keratoconjunctivitis sicca. The relationship between xero-stomia and proliferative activity in human gingival epithelium is not known. Proliferating cell nuclear antigen (PCNA) is a nuclear protein associated with the cell cycle. Nuclear PCNA immunoreactivity is found in the proliferative compartment of normal tissues. The aims of this study were to evaluate PCNA expression in oral gingival epithelium of healthy and inflamed gingiva obtained from patients with Sj?gren's syndrome, and to compare the results to age- and gender-matched subjects with normal salivary function. METHODS: Eighteen Sj?gren's syndrome patients and 28 controls (14 with chronic periodontitis and 14 with no clinical evidence of periodontal disease) were included in the study. Biopsies were obtained from both inflamed and healthy gingiva. The expression of PCNA was evaluated in formalin-fixed, paraffin-embedded gingival samples using an immunoperoxidase technique and PC10 monoclonal antibody to PCNA. RESULTS: PCNA expression was observed both in the basal and suprabasal layers, and was found to be more prominent in the suprabasal layers. Proliferative index (PI) in inflamed gingiva was significantly lower in the Sj?gren's syndrome group. However, no significant difference was observed between the study and control groups with respect to PI in healthy gingiva. In both groups, PI was found to be increased due to inflammation. CONCLUSIONS: Our data indicate that proliferative activity is observed in the suprabasal layers and, less frequently, in the basal layer. Inflammation caused increased proliferative activity. However, this positive effect of inflammation on epithelial cell proliferation decreased significantly with a lack of saliva. Therefore, it appears that saliva-derived biological mediators may also contribute to increased proliferative activity observed during inflammation.     

Electron microscopy of normal auman gingival epithelium

Biopsies of the labial part of normal gingival epithelium were obtained from 18 females (average age of 25 years) who had performed strict oral hygiene for two weeks or more. Standardized areas of the specimens were investigated electron microscopically. All specimens exhibited parakeratosis and were free from inflammatory cells. The optical basement membrane corresponded. to the basement lamina and an intermediate layer about 0.5 to 1 micron wide, containin various fibrils at random orientation. Cell junctions in each of the epithelial layers were typical desmosomes and maculae or zonulae occludentes. The intercellular space was interpreted to be closed from outside at the epithelial surface, subdivided into numerous compartments within all epithelial strata and open against the basement lamina. Glycogen was occasionally found in cells of the upper stratum spinosum and stratum granulosum only. The transition of cells into the stratum corneum was either abrupt or more gradual. Superficial to the stratum corneum, single or several cells of considerably less density were frequently observed. Melanocytes and Langerhans cells occurred interspersed between basal and spinous cells. The ultrastructural details are discussed with reference to the existing knowledge of other squamous epithelia.     

牙龈上皮中的中性白细胞和单核细胞

本研究对健康龈（Ｈ）、边缘性龈炎（Ｇ）、青少年牙周炎（ＪＰ）和成人牙周炎（ＡＰ）牙龈上皮内的中性白细胞（ＰＭＮ）和单核细胞及龈下菌进行了定量观察，并分析了它们之间的关系。结果表明，ＪＰ组袋上皮和表面上皮内的ＰＭＮ显著低于Ｇ组和ＡＰ组。ＡＰ组的ＰＭＮ数均明显高于其它三个组。直线相关分析表明，沟（袋）上皮ＰＭＮ数与龈下能动菌％呈正相关（ｒ＝０．５３６．Ｐ＜０．０１）。单核／吞噬细胞用ＮＡＥ方法显示主要位于结合上皮和袋上皮深处，三个炎症组的数目均高于健康组，而这些部位未见郎格罕氏细胞，可能此处的单核细胞替代了郎格罕氏细胞的功能。     

Gap junctions in human gingival keratinized epithelium

Gap junctions were found in all layers of human gingival keratinizing epithelium, except the stratum corneum. En bloc staining revealed the seven-layered structure of these junctions, with a gap of approximately 20Å between the outer leaflets of adjacent unit membranes. Treatment of specimens with lanthanum strikingly demonstrated the gap junctions, since the lanthanum completely fills the central gap. Oblique and tangential sections of gap junctions in lanthanum-treated specimens produced characteristic striated and honey-comb appearances, respectively. It appears as though many junctions in gingival epithelium formerly thought to be variants of tight junctions (and thus regions of membrane fusion) are, in reality, gap junctions. In view of findings regarding the function of gap junctions in other tissues, it is suggested that gap junctions have a significant role in the synchronous differentiation of normal human gingival keratinizing epithelium.     

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目的    探讨吸烟对牙龈上皮棘层细胞凋亡的影响及可能的机制。方法    本研究于2004年12月至2010年12月在济南市口腔医院和山东大学口腔医院进行。选取52例具有不同吸烟史、无严重系统疾病且行牙冠延长术或智齿拔除术的患者,根据吸烟史、日平均吸烟支数和总吸烟支数将患者分为轻度吸烟组（吸烟史＜5年或日平均吸烟≥2～10支,且总吸烟支数约1.5万支以下）21例、重度吸烟组（吸烟史≥5年或日平均吸烟≥10支,且总吸烟支数约1.5万支以上）31例。另取无吸烟史的10例患者作为对照组。采用原位末端标记（ TdT-mediated- dUTP nick end labeling, TUNEL） 法检测各组患者牙龈上皮棘层细胞的凋亡情况;Student-Newman-Keuls（SNK）法计算各吸烟组与对照组及各吸烟组之间的差异,取α=0.05水准;PV免疫组化法对凋亡抑制基因Bcl-2的表达进行组织定位。结果    各吸烟组患者牙龈上皮棘层细胞凋亡阳性的表达与对照组患者间差异均有统计学意义（P＜0.01）;轻度吸烟组和重度吸烟组患者间差异也有统计学意义（P＜0. 01）。Bcl-2在吸烟者牙龈上皮的基底层和棘层表达较对照组减弱。结论    吸烟可能通过降低促Bcl-2的表达,促进牙龈上皮棘层细胞凋亡的发生,干扰牙龈上皮的正常代谢。