The effect of smoking on epithelial proliferation in healthy and periodontally diseased marginal gingival epithelium

Type 17 immune response promotes oral epithelial cell proliferation in periodontitis

OBJECTIVES

This study aims to investigate the effects of type 17 immune response on the proliferation of oral epithelial cells in periodontitis.

DESIGN

A time-dependent ligature induced periodontitis mouse model was utilized to explore gingival hyperplasia and the infiltration of interleukin 17A (IL-17A) positive cells. Immunohistochemistry and flow cytometry were employed to determine the localization and expression of IL-17A in the ligature induced periodontitis model. A pre-existing single-cell RNA sequencing dataset, comparing individuals affected by periodontitis with healthy counterparts, was reanalyzed to evaluate IL-17A expression levels. We examined proliferation markers, including proliferating cell nuclear antigen (PCNA), signal transducer and activator of transcription (STAT3), Yes-associated protein (YAP), and c-JUN, in the gingival and tongue epithelium of the periodontitis model. An anti-IL-17A agent was administered daily to observe proliferative changes in the oral mucosa within the periodontitis model. Cell number quantification, immunofluorescence, and western blot analyses were performed to assess the proliferative responses of human normal oral keratinocytes to IL-17A treatment in vitro.

RESULTS

The ligature induced periodontitis model exhibited a marked infiltration of IL-17A-positive cells, alongside significant increase in thickness of the gingival and tongue epithelium. IL-17A triggers the proliferation of human normal oral keratinocytes, accompanied by upregulation of PCNA, STAT3, YAP, and c-JUN. The administration of an anti-IL-17A agent attenuated the proliferation in oral mucosa.

CONCLUSIONS

These findings indicate that type 17 immune response, in response to periodontitis, facilitates the proliferation of oral epithelial cells, thus highlighting its crucial role in maintaining the oral epithelial barrier.

Long-term exposure to cigarette smoke influences characteristics in human gingival fibroblasts

BACKGROUND

Periodontal disease is a chronic inflammatory disease caused by periodontopathic bacteria accumulated in the gingival sulcus and periodontal pocket. Cigarette smoking is a well-established risk factor for periodontal disease, and periodontal tissues in smokers are chronically exposed to cigarette smoke on a long-term basis.

OBJECTIVE

In this study, we investigated the effects of long-term exposure to nicotine or cigarette smoke condensate (CSC) on cellular functions of human gingival fibroblasts (HGFs).

METHODS

In vitro-maintained HGFs were divided into two groups. The HGFs of the short-term and the long-term culture groups were cultured for 4 and 25 days, respectively, in the presence or absence of nicotine, which is one of the main components of cigarette smoke, or CSC. The cellular proliferation and migration capacities of HGFs exposed to nicotine or CSC were evaluated by WST-1 and wound healing assays. The effects of exposure to nicotine or CSC on the expression of various extracellular matrix (ECM) components, inflammatory cytokines, and senescence-related genes were examined by real-time polymerase chain reaction and enzyme-linked immunosorbent assay. The cellular senescence of HGFs exposed to nicotine or CSC was detected by the senescence-associated β-galactosidase (SA-β-gal) assay. To explore the senescence-associated microRNA (miRNA), we extracted miRNA from the HGFs and the expression profiles were examined by miRNA array.

RESULTS

In short-term culture, no significant changes were observed. Long-term exposure of HGFs to nicotine or CSC significantly suppressed their cellular proliferation and migration and upregulated type Ⅰ collagen, type Ⅲ collagen, interleukin (IL)-6, IL-8, p16, p21, and p53 mRNA expression, and IL-6 and IL-8 protein expression. Furthermore, long-term nicotine or CSC exposure significantly increased the percentage of SA-β-gal-positive HGFs. In addition, long-term nicotine or CSC exposure reduced miR-29b and miR-199a expression to less than 50% of that in the unstimulated HGFs.

CONCLUSION

These data suggest that long-term smoking habits may reduce wound healing ability, modulate ECM protein homeostasis, stimulate the inflammatory response, and accelerate cellular senescence in HGFs, and consequently accelerate the progression of periodontal diseases.

Tobacco smoking decreases clinical symptoms of gingivitis in patients with type 1 diabetes-a cross-sectional study

OBJECTIVE

Periodontal disease may develop on the background of microvascular complications of diabetes. However, some modifying factors, such as tobacco smoking, should be taken into consideration when assessing risk of development of chronic complications. The aim of the study was the clinical assessment of the periodontal status in patients with type 1 diabetes according to tobacco smoking.

SUBJECTS AND METHODS

A total of 362 subjects aged 29 (IQR 22-35) years, type 1 diabetes duration 12 (8-18) years, hemoglobin A1c, HbA1c 8.0 (7.2-9.1)% were included. We used Gingival Index, Approximal Plaque Index, and Sulcus Bleeding Index to assess periodontal health. Patients were divided into two subgroups according to current cigarette smoking.

RESULTS

No differences in age, diabetes duration, and chronic complications were found between subgroups. A better metabolic control of diabetes expressed by lower HbA1c (p = 0.00001) and triglyceride levels (p = 0.004) was shown in nonsmokers. Smokers presented significantly lower gingival bleeding, p = 0.009. HbA1c correlated with API in study group (Rs = 0.16; p = 0.002) and in nonsmokers subgroup (Rs = 0.2;p = 0.004), however, not in smoker's subgroup. In multivariable regression analysis, smoking cigarettes (β = -0.26; p = 0.0002), hs-CRP (β = 0.15; p = 0.03) and age (β = -0.19; p = 0.007) occurred to be independent predictors of SBI after adjustment for confounding variables (R²  = 0.13; p = 0.001).

CONCLUSIONS

Patients with type 1 diabetes smoking cigarettes presented lower gingival sulcus bleeding and worse metabolic control of diabetes than nonsmoking patients.

Repeated exposure to whole cigarette smoke promotes primary human gingival epithelial cell growth and modulates keratin expression

BACKGROUND AND OBJECTIVE

The gingiva is the first oral tissue directly exposed to cigarette smoke (CS). Exposure to CS compromises the structure and function of gingival tissue. Damaging or altering the gingival epithelium leads to a compromised protective barrier of the periodontium, resulting in several diseases. The aim of this study was to assess the effect of repeated exposure to CS on gingival epithelial cell growth and on expression of apoptotic protein and keratin.

MATERIAL AND METHODS

Primary human gingival epithelial cells were seeded on a collagen scaffold for 5 d to allow growth and stratification. The cells were then exposed for 5 min to whole CS for 3, 6 and 9 d. At the end of each exposure period, cell proliferation [using (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) (MTT) and 5-bromo-2'-deoxyuridine (BrdU) assays], gene expression [by quantitative reverse transcription polymerase chain reaction (qRT-PCR)] and protein production (by western blot analysis) were investigated.

RESULTS

Higher metabolic activity was found in the CS-exposed cells than in the nonexposed cells, specifically after 3 and 6 d of exposure to CS. At 9 d there was no significant difference between CS-exposed and nonexposed cells. Metabolic activity was supported by the BrdU cell-proliferation analyses, which showed increased cell growth at 3 d compared with the control. However, at 6 and 9 d, cell proliferation in the CS-exposed culture was comparable to that in the nonexposed culture. Interestingly, the Bax/Bcl-2 protein ratios decreased with increased CS exposure, suggesting cell resistance. Moreover, protein analyses showed that CS decreased expression of keratin(K) 5 at 3, 6 and 9 d, and increased expression of K14 at 6 and 9 d. Finally, mRNA analyses showed significant decreases of K1, K6, K10 and K16 in CS-exposed cultures, correlating, at times, with a decrease of protein production.

CONCLUSION

CS was shown to increase epithelial cell proliferation, which may involve cell resistance to apoptosis. This is supported by the modulation of expression of different keratin genes and proteins. Altogether, these data may explain the hyperplasia reported in gingival tissue, as well as periodontal disease, in smokers.

Correlations between supra- and subgingival clinical parameters in smokers and individuals who have never smoked

Introduction Smoking is a risk factor for prevalence, severity and progression of periodontal disease and appears to suppress marginal periodontium inflammatory response. Purpose To correlate Visible Plaque Index (VPI) and Gingival Bleeding Index (GBI) in smokers and never-smokers, as well as GBI and bleeding on probing (BOP ) in these groups. Material and method We used baseline data of one quasi-experimental study in which 11 smokers and 14 subjects who never smoked were submitted to clinical periodontal examinations between September 2010 and October 2011. Result The correlation between VPI and GBI was positive for both groups, it was strong and statistically significant in subjects who had never smoked and moderate in smokers. Regarding GBI and BOP correlations were moderate for smokers and weaker for individuals who had never smoked. Conclusion Smokers have lower strength correlation between VPI and GBI compared to individuals who had never smoked resulting in a less pronounced marginal gingival bleeding.

Matrix remodeling response of human periodontal tissue cells toward fibrosis upon nicotine exposure

It is widely accepted that fibrosis is frequently observed in the gingiva of smokers. However, the mechanisms by which smoking results in pathological changes in periodontal tissue that lead to fibrosis are not entirely clear. Our former report showed that type I collagen synthesis was promoted by nicotine via CCN family protein 2 in human periodontal tissue cells. Here, we evaluated other aspects of nicotine function from a viewpoint of extracellular matrix (ECM) remodeling. Human gingival fibroblasts (n = 4) and periodontal ligament cells (n = 3) were isolated. The cells were treated with nicotine at a variety of concentrations for 12-48 h. Modulators of matrix remodeling were measured using enzyme-linked immunosorbent assays. Cell migration and morphology were also evaluated. As a result, following treatment with 1 μg/ml nicotine, tissue inhibitor of metalloproteinase-1 and transforming growth factor-β1 production in both cell lysates and supernatants, and matrix metalloproteinases-1 production in cell lysates, were significantly increased (p < 0.05). Compared to controls, cell migration was significantly inhibited (p < 0.005) by nicotine in a time-dependent manner. Electron microscopic analysis revealed the presence of a number of vacuoles in nicotine-treated cells. These results indicate that nicotine not only impairs fibroblast motility, and induces cellular degenerative changes, but also alters ECM-remodeling systems of periodontal cells. Induction of matrix remodeling molecules, combined with type I collagen accumulation, may account for the molecular mechanism of nicotine-induced periodontal fibrosis.

Evaluation of HPV infection and smoking status impacts on cell proliferation in epithelial layers of cervical neoplasia

Accurate cervical intra-epithelial neoplasia (CIN) lesion grading is needed for effective patient management. We applied computer-assisted scanning and analytic approaches to immuno-stained CIN lesion sections to more accurately delineate disease states and decipher cell proliferation impacts from HPV and smoking within individual epithelial layers. A patient cohort undergoing cervical screening was identified (n = 196) and biopsies of varying disease grades and with intact basement membranes and epithelial layers were obtained (n = 261). Specimens were sectioned, stained (Mib1), and scanned using a high-resolution imaging system. We achieved semi-automated delineation of proliferation status and epithelial cell layers using Otsu segmentation, manual image review, Voronoi tessellation, and immuno-staining. Data were interrogated against known status for HPV infection, smoking, and disease grade. We observed increased cell proliferation and decreased epithelial thickness with increased disease grade (when analyzing the epithelium at full thickness). Analysis within individual cell layers showed a ≥50% increase in cell proliferation for CIN2 vs. CIN1 lesions in higher epithelial layers (with minimal differences seen in basal/parabasal layers). Higher rates of proliferation for HPV-positive vs. -negative cases were seen in epithelial layers beyond the basal/parabasal layers in normal and CIN1 tissues. Comparing smokers vs. non-smokers, we observed increased cell proliferation in parabasal (low and high grade lesions) and basal layers (high grade only). In sum, we report CIN grade-specific differences in cell proliferation within individual epithelial layers. We also show HPV and smoking impacts on cell layer-specific proliferation. Our findings yield insight into CIN progression biology and demonstrate that rigorous, semi-automated imaging of histopathological specimens may be applied to improve disease grading accuracy.

Effect of smoking on gingival microvasculature: A histological study

BACKGROUND

Smoking has been reported as a major risk factor for periodontal disease. Studies have demonstrated decreased bleeding on probing and reduced inflammatory response among smokers, which has been attributed to the alterations in gingival microvasculature, gingival epithelium. In previous investigations, vascular and epithelial changes have been studied in the gingival tissues of smokers suffering from periodontitis and compared with healthy periodontium of non smokers. Inflammation is known to cause vascular and epithelial changes in the gingiva on its own in the absence of smoking. Hence, in the present investigation, an attempt is made to study and to compare the vascular and epithelial changes in the gingiva of smokers and non smokers suffering from chronic periodontitis.

AIM OF STUDY

The purpose of this study was to evaluate the vascular and epithelial changes in gingiva of smokers and non smokers with chronic periodontitis.

STUDY DESIGN

Cross sectional study

MATERIALS AND METHODS

Gingival biopsies were obtained from 33 male patients (18 smokers and 15 non smokers) who were undergoing periodontal therapy or extraction. The sections were stained with eosin and hematoxylin. Vascular density, area of the lumen, and epithelial thickness were assessed using histomorphometric image analysis.

STATISTICAL METHOD

Data was analyzed using student unpaired 't' test, Karl Pearsons correlation, and Chi-square test.

RESULTS

The mean blood vessel density for smokers was 12.388±6.472 and for non smokers was 14.800±4.91. The mean lumen area of the vessels among smokers and non smokers was 19.290±8.775 μm(2) and 20.044±7.896 μm(2), respectively. The mean epithelial thickness among smokers was 150.551±32.994 μ and 134.941±30.63 μ for non smokers.

CONCLUSION

Based on the present histomorphometric study, it could be concluded that smokers have less vascular density and reduced lumen area and increased epithelial thickness than non smokers. However, these changes were not statistically significant.

Neurofibromatosis type 1 associated with bilateral central giant cell granuloma of the mandible

Neurofibromatosis type 1, or von Recklinghausen disease, is one of the most common hereditary neurocutaneous disorders in humans. Clinically, Neurofibromatosis type 1 is characterized by café-au-lait spots, freckling, skin neurofibroma, plexiform neurofibroma, bony defects, Lisch nodules and tumors of the central nervous system. Central giant cell granuloma is a benign central lesion of bone, primarily involving the jaws, of variably aggressive nature characterized by aggregates of multinucleated giant cells in a background of cellular vascular fibrous connective tissue and spindle-shaped mononuclear stromal cells. The association between neurofibromatosis and central giant cell granuloma has been reported in the literature. A case of mandibular bilateral central giant cell granuloma in a patient with Neurofibromatosis type 1 was conservatively but successfully treated by adequate surgical curettage of mandibular bone lesions.

The effect of cigarette smoking on cell proliferation in normal uterine cervix epithelium

BACKGROUND

The aim of this study was to evaluate the effect of smoking on cell proliferation in normal cervical epithelium.

METHODS

A total of 45 women undergoing hysterectomies due to uterine leiomyomata were investigated. Thirty were nonsmokers and 15 were current smokers. A segment of tissue was taken from cervix after removal of the uterus, and the identification of cell proliferation was performed by immunohistochemical analysis employing Ki-67 staining. The number of positive cells colored by Ki-67 staining was finally expressed as number of cells per square millimeter (mm²) of epithelium.

RESULTS

The comparison of the number of proliferating cells measured by ki-67 staining among smoking and nonsmoking women did not show significant difference. Among smoking women, there was no significant difference related to the number of cigarettes smoked per day or time of consumption and epithelial cell proliferation. However, the total amount of cigarettes smoked throughout presented significant association with Ki-67 staining (p < 0.001); the number of proliferating cells per mm² increased proportionally to the increase in consumption of cigarettes.

CONCLUSIONS

The results indicated that there was no significant difference between cell proliferation in smokers and nonsmokers; however, it was shown that in the smokers' group, amount of cigarettes smoked during throughout lifetime can increase cell proliferation in normal cervical epithelium.