Expression of transforming growth factor β and its correlation with lipodystrophy in oral submucous fibrosis: an immunohistochemical study

Interplay of Transforming Growth Factor-Beta 1 and 3 in the Pathogenesis of Oral Submucous Fibrosis and Its Malignant Transformation: An Immunohistochemical Study

Introduction Oral submucous fibrosis (OSF) is a chronic and potentially malignant oral condition that poses a significant public health issue due to its insidious nature. Transforming growth factor-beta (TGF-β) is a key player in the pathogenesis of OSF and is responsible for fibrosis. This study aims to investigate the relationship between the expression of TGF-β1 and TGF-β3 in OSF and its malignant transformation by using immunohistochemistry. Materials and method The present study comprised of 120 formalin-fixed paraffin-embedded tissue samples, which included 20 normal oral mucosa (NOM), 80 OSF (20 each of stage 1- 4), and 20 oral squamous cell carcinoma (OSCC) (10 each of OSCC with and without OSF), and were stained for TGF-β1 and TGF-β3 by immunohistochemistry. Data were analyzed using R software version 4.1.2, GraphPad Prism 9.3.1 (GraphPad Software, San Diego, CA, USA) and Excel (Microsoft Corp., Redmond, WA). Results TGF-β1 immunoexpression was negative in NOM with no significant difference among OSF and OSCC (with or without OSF). TGF-β3 was significantly higher in OSCC (with or without OSF) than in OSF, and no significant difference was noted between OSF and NOM and between OSCC and NOM. A significant increase was seen in TGF-β3 compared to TGF-β1 in NOM, OSF (stage 1- 4), and OSCC with and without OSF. Conclusion TGF-β3 has higher immunoexpression levels than TGF-β1 in NOM, OSF, and OSCC. We speculate that quantitative or qualitative TGF- β3 may be inadequate to prevent or attenuate fibrosis in OSF patients. There is also a modicum of probability that TGF-β3 has a preventive rather than causative role in OSF pathogenesis. The role of TGF-β3 in OSF needs further clarification.

Expression of transforming growth factor-β in oral submucous fibrosis: A systematic review

Oral submucous fibrosis (OSF) is a potentially malignant disorder characterised by inflammation and progressive fibrosis. Transforming growth factor-β (TGF-β) has been established as a master regulator of fibrosis in various organs; however, lack of systematic review on expression of TGF-β and its isoforms in OSF restrict the understanding of their behaviour in its pathogenesis. Online electronic databases, such as PubMed Medline, Cochrane Library, Embase, and Scopus, were searched from their respective dates of inception till 31st March 2022. Human studies related to TGF-β expression in histopathologically diagnosed OSF cases, with or without malignant transformation, were included and assessed using a Cochrane risk of bias assessment tool: For non randomised studies of interventions (ACROBAT NRSI). The electronic literature search yielded 394 articles. Of those, ten articles met the inclusion criteria and involved total of 579 OSF patients. The risk of bias (RoB) was low to moderate. These studies demonstrated a significant positive expression of TGF-β and its isoforms in OSF compared to that in normal tissue samples. An increased pan TGF-β expression was observed in the early stages of OSF, and an increased expression of TGF-β1 and TGF-β2 were seen in advanced stages of OSF. Stage wise expression of TGF-β3 has not been discussed in the included studies. No significant relationship was observed between epithelial dysplasia and TGF-β expression in OSF. The distinct pattern in the expression of pan TGF-β, TGF-β1 and TGF-β2 in various stages of OSF indicates their different roles in OSF progression. We believe isoform targeted studies exploring stage wise expression of the marker will open new treatment avenues for OSF.

Leaving no stone unturned: Role of profibrotic genes in oral submucous fibrosis - A systematic review

Introduction

Understanding the molecular pathogenesis of an entity helps in devising the mode of progression as well as mode of therapy. Even with years of research to claim the understanding of the molecular pathogenesis of oral submucous fibrosis (OSMF) is limited. More deeper knowledge of the genes responsible for this will help in understanding and managing this disease better.

Materials and Methods

The articles published during a time period of 1990-2020 were chosen in accordance with the inclusion and exclusion criteria according to the PRISMA guidelines.

Results

From a total of 80 articles obtained from both electronic search of PUBMED, EMBASE, MEDLINE and Cochrane registry as well as the manual search only 21 articles were selected and analyzed.

Conclusion

Careful analysis of the samples revealed that transforming growth factor-beta may be a potential biomarker or a candidate for targeted therapy in OSMF.

Potentiated action on the progression of OSMF by hypoxia mediated signaling pathway by the epithelial mesenchymal transition and angiogenic apparatus

Background

Epithelial-mesenchymal transition (EMT) is a complex process, in which epithelial cells acquire the characteristics of invasive mesenchymal cells. EMT has been implicated in cancer progression and metastasis as well as the formation of many tissues and organs during development.

Aim

The aim of the study was to ascertain the role of hypoxia-mediated signaling pathways influencing EMT and angiogenesis in progression of oral submucous fibrosis (OSMF).

Materials and Methods

Evaluation of the immunoexpression of alpha-smooth muscle actin (α-SMA), E-cadherin, vimentin, and factor VIII receptor antigen in OSMF and oral squamous cell carcinoma (OSCC) arising from OSMF was done. Differences between the different variables were analyzed using ANOVA test and Pearson's Chi-square test, and Mann-Whitney test was also calculated.

Results

The mean α-SMA positive myofibroblasts increased from Group 1 (OSMF) to Group 2 (OSCC), especially those in the deeper connective tissue stroma. The mean labeling index of vimentin and mean vessel density immunoexpression was more in Group 2 (OSCC) as compared to Group 1 (OSMF). Mean α-SMA correlated negatively with E-cadherin expression and positively with vimentin and factor VIII immunoexpression. E-cadherin expression correlated negatively with factor VIII and positively with Vimentin expression.

Conclusions

The molecular mechanisms responsible for the development of OSCC in patients with OSMF require unification of multiple progressive pathogenetic mechanisms involved in the progression of the disease.

Adipose-derived mesenchymal stem cell exosomes inhibit transforming growth factor-β1-induced collagen synthesis in oral mucosal fibroblasts

Oral submucosal fibrosis (OSF) is a potentially malignant oral disorder that requires the further development of advanced treatment strategies. TGF-β1 has been reported to be the main trigger for the increased collagen production and reduced activity of matrix degradation pathways in OSF. Exosomes are key mediators of paracrine signaling that have been proposed for direct use as therapeutic agents for tissue repair and regeneration. The present study aimed to investigate the effects of human adipose-derived mesenchymal stem cell (ADSC) exosomes (ADSC-Exos) on TGF-β1-treated oral fibroblasts in vitro and to unravel the potential underlying mechanism of action. Oral mucosal fibroblasts were obtained from the buccal tissues of patients without OSF during extraction of the third molar. ADSCs were obtained from three healthy female individuals during liposuction procedures. ADSC-Exos were isolated by ultracentrifugation and identified by electron microscopy, nanoparticle tracking and western blotting. Immunofluorescence and immunocytochemistry staining were performed to measure the expression levels of vimentin and α-smooth muscle actin in the fibroblasts. Reverse transcription-quantitative PCR and western blotting were used to determine the expression levels of mRNAs and proteins associated with collagen production. The p38 MAPK activator anisomycin was used to identify the underlying mechanisms of the effects of ADSC-Exos on TGF-β1-induced collagen synthesis in oral mucosal fibroblasts. The results of the present study revealed that ADSC-Exos exhibited a cup- or sphere-shaped morphology, with a mean diameter of 58.01±16.17 nm. ADSC-Exos were also found to be positive for CD63 and tumor susceptibility 101 expression. ADSC-Exos treatment reversed the TGF-β1-induced upregulation of collagen I and III protein expression. In addition, in the presence of TGF-β1, the expression levels of collagen type I α 1 chain and collagen type III α 1 chain mRNA were downregulated, whilst the expression levels of matrix metalloproteinase (MMP)1 and MMP3 were upregulated following ADSC-Exos treatment. The TGF-β1-induced upregulation in the phosphorylation of p38 in addition to the increased protein expression of collagens I and III were also reversed in fibroblasts following ADSC-Exos treatment. However, anisomycin treatment alleviated these ADSC-Exos-induced changes. In conclusion, findings from the present study suggest that ADSC-Exos may represent a promising strategy for OSF treatment by targeting the p38 MAPK signaling pathway.

A contemporary narrative review to guide molecular epidemiology of oral submucous fibrosis

Oral submucous Fibrosis (OSMF) is a chronic disease that mainly affects the upper part of the aerodigestive tract. Areca nut and betel quid chewing has been established as the most significant causative factor for this condition. While OSMF is a predominantly Asian disease, the migrant populations from the region have taken the disease across the globe. Additionally, areca nut is now easily accessible in flavors and aggressively marketed. Many research activities have been undertaken for decades to understand the etiopathogenesis and risk factors of OSMF. Although OSMF is a slowly progressing disease, it has the potential to transform to an oral malignancy. This article is an attempt to review the literature and provide an update on its prevalence, etiopthogenesis and its diagnosis. We also highlight certain clinical, histopathological and molecular features that aid in the diagnosis and prognostication of OSMF, highlighting the importance of identifying the possibly high risk OSMF that is prone to malignant transformation. Using this information, future directions can be developed to include treatmentof OSMF through a dynamic gene-specific approach.

The Role of Increased Connective Tissue Growth Factor in the Pathogenesis of Oral Submucous Fibrosis and its Malignant Transformation-An Immunohistochemical Study

Connective tissue growth factor (CTGF), a matricellular protein of the CCN family of extracellular matrix-associated heparin-binding proteins, is highly expressed in various organ fibrosis and several malignant tumors. Although a few studies have been conducted using CTGF in oral submucous fibrosis (OSF) and oral squamous cell carcinoma, no study has demonstrated its relation with various stages of OSF and its malignant transformation. The present study investigated the possible role of CTGF in the pathogenesis of OSF and its malignant transformation by using immunohistochemistry. Ten formalin-fixed paraffin-embedded tissue blocks, each of Stage 1 OSF, Stage 2 OSF, Stage 3 OSF, Stage 4 OSF, well- differentiated squamous cell carcinoma (WDSCC) with OSF and WDSCC without OSF were stained for CTGF by immunohistochemistry. Ten cases of healthy buccal mucosa (NOM) were included as controls. The present study demonstrated a statistically significant expression of CTGF in the epithelium and connective tissue of OSF and WDSCC with and without OSF cases against its complete absence in NOM. We observed an upregulation of CTGF expression from NOM to various stages of OSF to WDSCC with or without OSF. A gradual upregulation of the CTGF expression in various stages of OSF to WDSCC (with and without OSF) against its complete absence in NOM suggests that CTGF plays an important role in the pathogenesis of OSF and its malignant transformation.

Genetic Susceptibility and Protein Expression of Extracellular Matrix Turnover-Related Genes in Oral Submucous Fibrosis

Betel quid (BQ) chewing increased the risk of oral cancer and oral submucous fibrosis (OSMF), an oral premalignant disorder (OPMD) with malignant transformation potential. BQ components such as areca nut (AN), trauma by coarse AN fiber, catechin, copper, alkaloids, stimulated reactive oxygen species (ROS), inflammation and cytotoxicity are suggested to be the contributing factors. They may induce tissue inflammation, proliferation of fibroblasts and collagen deposition, myofibroblast differentiation and contraction, collagen cross-links and inhibit collagen phagocytosis, finally leading to the development of OSMF and oral cancer. These events are mediated by BQ components-induced changes of extracellular matrix (ECM) turnover via regulation of TGF-β1, plasminogen activator inhibitor-1 (PAI-1), cystatin, lysyl oxidase (LOX) and tissue inhibitors of metalloproteinases (TIMPs) and metalloproteinases (MMPs). Genetic susceptibility is also involved in these disease processes. Further understanding the molecular mechanisms of BQ-induced OSMF and oral cancer can be helpful for future disease prevention and treatment.

Expression of transforming growth factor beta in oral submucous fibrosis

Background

Oral submucous fibrosis (OSMF) is a premalignant condition mainly caused by areca nut chewing and is characterized by progressive fibrosis of submucosal tissues and epithelial atrophy. Activation of transforming growth factor beta (TGF-β) signaling is considered main causative event for increased collagen production and fibrosis. In this study, molecular pathogenesis of OSMF was investigated based on the expression of the TGF-β genes in OSMF tissues compared to normal controls.

Methods

A total of 33 OSMF and 10 normal tissues were collected from patients and their clinic-epidemiological data was recorded. The expression of TGF-β isoform genes- TGF β1, TGF β2, TGF β3 and its receptor TGF βR1, TGF βR2 was studied by real time polymerase chain reaction (PCR). Comparison of the expression of these genes among normal controls and OSMF patients was done. The PCR results were confirmed by histopathological and immunohistochemical staining.

Results

The histological changes included atrophic epithelium, loss of rete ridges, presence of inflammatory cells and dense collagen bundles in connective tissue. PCR showed statistically significant upregulation of TGF-β isoforms in OSMF as compared to normal tissues. Of the three isoforms, maximum fold change was observed in TGF-β1. Similarly, both TGF-βR1 and TGF-βR2 were found to be elevated in OSMF tissues compared to normal. The semi-quantitative analysis by immunohistochemical staining revealed statistically significant difference between normal and OSMF tissues.

Conclusion

TGF-β signaling plays a major role in the molecular pathogenesis of OSMF as shown by increased mRNA expression of all the three TGF-β isotypes and their receptors.

The common pathophysiologic threads between Asian Indian diabetic's 'Thin Fat Phenotype' and partial lipodystrophy: the peripheral adipose tissue transcriptomic evidences

T2D is a complex disease with poorly understood mechanisms. In Asian Indians, it is associated with “thin fat” phenotype which resembles with partial lipodystrophy. We hypothesized that disturbed expression of lipodystrophy genes might play a role in T2D pathogenesis. Therefore, we attempted to establish a link between these two diseases by studying the overlap between the network of lipodystrophy genes and the differentially expressed genes (DEGs) in the peripheral subcutaneous adipose tissue of Asian Indians diabetics. We found that 16, out of 138 lipodystrophy genes were differentially regulated in diabetics and around 18% overlap between their network and the DEGs; the expression level of lipodystrophy genes showed an association with disease-related intermediate phenotypic traits among diabetics but not in the control group. We also attempted to individualize the diabetic patients based on ±2 fold altered expression of lipodystrophy genes as compared to their average expression in the control group. In conclusion, significant overlap exists between some of the lipodystrophy genes and their network with DEGs in the peripheral adipose tissue in diabetics. They possibly play a role in the pathogenesis of diabetes and individualization of diabetics is possible based on their altered expression in their peripheral adipose tissue.

Immunoexpression of alpha smooth muscle actin correlates with serum transforming growth factor-β1 levels in oral submucous fibrosis

AIM

The aim of the present study was to correlate the immunoexpression of alpha-smooth muscle actin (α-SMA) for myofibroblasts with the serum levels of transforming growth factor-β1 (TGF-β1) in oral submucous fibrosis (OSMF).

METHODS

A total of 100 cases of histopathologically confirmed OSMF were assessed for α-SMA expression. Clinical data, such as age, sex, mouth opening, and habit history, were obtained for each case. Serum TGF-β1 levels were recorded in 73 patients with the help of enzymelinked immunosorbent assay technique.

RESULTS

The staining index of α-SMA increased concomitantly with higher myofibroblast count in the increasing histopathological grades of OSMF (P ≤ .05). Serum TGF-β1 levels were highest in the intermediate grades of OSMF. Clinical parameters, such as mouth opening, cheek flexibility, and tongue protrusion, showed a direct correlation with increasing clinical grades of OSMF.

CONCLUSIONS

The progressive increase in myofibroblasts from early to advanced stages suggests their potential use as markers for evaluating the severity of OSMF. Additionally, as myofibroblasts are responsible for producing a variety of factors that are involved in the fibrotic processes; they could be the key link in the pathogenesis of OSMF. Interruption of their development, recruitment, or activation could provide a unique therapeutic target for future treatment options in patients with OSMF.

Curcumin Can Improve Spinal Cord Injury by Inhibiting TGF-β-SOX9 Signaling Pathway

Spinal cord injury (SCI) is a severe nervous system disease with high morbidity and disability rate. Signaling pathways play a key role in the neuronal restorative mechanism following SCI. SRY-related high mobility group (HMG)-box gene 9 (SOX9) affects glial scar formation via Transforming growth factor beta (TGF-β) signaling pathway. Activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) is transferred into nucleus to upregulate TGF-β-SOX9. Curcumin exhibits potent anti-inflammatory and anti-oxidant properties. Curcumin can play an important role in SCI recovery by inhibiting the expression of NF-κB and TGF-β-SOX9. Herein, we review the potential mechanism of curcumin-inhibiting SOX9 signaling pathway in SCI treatment. The inhibition of NF-κB and SOX9 signaling pathway by curcumin has the potentiality of serving as neuronal regenerative mechanism following SCI.

Expression of atresia biomarkers in granulosa cells after ovarian stimulation in heifers

The use of younger gamete donors in dairy cattle genetic selection programs significantly accelerates genetic gains by decreasing the interval between generations. Ovarian stimulation (OS) and the practice of follicle-stimulating hormone (FSH) withdrawal, also known as coasting, are intensively used in pre-pubertal heifers without detrimental effects on subsequent reproductive performance but generally with lower embryo yields. However, recent data from embryo transfer programs showed similar embryo yields in younger and sexually mature animals but with a significant difference in the coasting period. The aim of the present study was to identify a set of granulosa cell biomarkers capable of distinguishing optimal follicle differentiation from late differentiation and atresia in order to assess the differences in coasting dynamics between pre- and post-pubertal donors. We integrated transcriptomic data sets from a public depository and used vote counting meta-analysis in order to elucidate the molecular changes occurring in granulosa cells during late follicle differentiation and atresia. The meta-analysis revealed the gene expression associated with follicle demise, and most importantly, identified potential biomarkers of that status in bovine granulosa cells. The comparison of the expression of six biomarkers between pre- and post-pubertal donors revealed that younger donors had more signs of atresia after the same period of coasting. We found different follicular dynamics following coasting in younger donors. It is possible that younger donors are less capable to sustain follicular survival most likely due to insufficient luteinizing hormone signaling. In summary, the pre-pubertal status influences follicular dynamics and reduces the oocyte developmental competence curve following OS and FSH withdrawal in heifers.

Effect of curcumin on the expression of p53, transforming growth factor-β, and inducible nitric oxide synthase in oral submucous fibrosis: A pilot study

AIM

The purpose of the present study was to find out the expression of p53, transforming growth factor-β TGF-β), and inducible nitric oxide synthase (iNOS) in oral submucous fibrosis (OSMF), proteins implicated in its pathophysiology, as well as malignant transformation. We also sought to determine the effect of curcumin on the expression of these markers through immunohistochemistry.

METHODS

The expression of p53, TGF-β, and iNOS was evaluated through immunohistochemistry in 28 patients with OSMF before and after treatment with curcumin. Expression was evaluated semiquantitatively using a four-point scale based on the percentage of cells showing positive staining.

RESULTS

The expression of p53, TGF-β, and iNOS in OSMF was found to be statistically significant (P<.05). After therapy with curcumin, a decrease in the expression of p53, TGF-β, and iNOS was seen in 25%, 32.1%, and 32.1% of the samples, respectively; however, the difference in pretreatment and post-treatment expressions was not found to be statistically significant.

CONCLUSION

The present finding suggest that curcumin could have an effect on the expression of p53, iNOS, and TGF-β in OSMF, and thus, could prove to be an effective chemopreventive agent for its management. The increased expression of p53, TGF-β, and iNOS in OSMF is suggestive of the role of these markers in its pathophysiology.

Transforming growth factor-β1 and TGF-β2 act synergistically in the fibrotic pathway in oral submucous fibrosis: An immunohistochemical observation

Background and objectives:

Oral Submucous Fibrosis (OSF) is a potentially malignant oral disorder which leads to fibrosis of the oral mucosa and has a high rate of malignant transformation. The consumption of various forms of areca nut is causatively linked to the condition. The constituents of areca nut activate several pro-fibrotic cytokines, chiefly transforming growth factor-β1, β2, which leads to an increased deposition and decreased degradation of extracellular matrix and collagen. TGF-β1, β2 probably represent the major pathway in the deposition of collagen fibres in this condition. The present study aims to identify and correlate the expressions of TGF-β1 and TGF-β2 immunohistochemically on paraffin sections of various stages of OSF. A comparison was also made between normal oral mucosa and scar tissue and OSF to judge the mode, extent and type of expression of TGF β1, β2.

Methods:

The expression of TGF-β1 antibody (8A11, NovusBio, USA) and TGF-β2 antibody (TB21, NovusBio, USA) was detected immunohistochemically on paraffin sections of 58 and 70 cases of OSF respectively, 10 cases of normal oral mucosal tissue and 4 cases of scar tissue. A mapping of the positivity of the two cytokines was done using JenOptik camera and ProReg image analysis software. The results were statistically analysed using one way ANOVA and students “t” test.

Results:

Expression of TGF-β1 and TGF-β2 was more in OSF as compared with normal oral mucosa, scar/keloid tissue showing highest values. Positivity for both the markers was seen in epithelium, around the blood vessels, in areas of inflammatory infiltrate, fibroblasts and in muscles. TGF-β1 expression was higher and more intense than that of TGF-β2 in all the cases. TGF-β2 was restricted in its expression to submucosal area with minimal involvement of the epithelium and the deeper muscle tissue.

Conclusion:

TGF-β1 is the most prominent cytokine in the fibrotic pathway and TGF-β2 plays a contributory role.

Comparative study of the efficacy of herbal antioxdants oxitard and aloe vera in the treatment of oral submucous fibrosis

Objectives: Oral submucous fibrosis (OSMF) is a potentially malignant disorder predominantly seen in the Indian subcontinent due to areca nut, tobacco and their products. The aim of the present study was to compare the efficacy of oxitard and aloe vera in the management of OSMF. Material and Methods: 120 subjects with OSMF were included in the study. The patients were clinico-pathologically diagnosed and divided equally in 2 groups, Group A (oxitard group) and Group B (aloe vera group). Group A was administered 2 oxitard capsules twice daily and Group B was given 5 mg aloe vera gel to be applied topically thrice daily for 3 months. Different clinical parameters were evaluated at regular intervals. Data was analyzed using the Student’s paired t test and Chi-square test. P-value <0.001 was considered to be statistically significant. Results: Clinical improvements in mouth opening and tongue protrusion was significant in the oxitard group (p=0.0005). Subjective symptoms of pain associated with the lesion (p=0.0003), difficulty in swallowing (p=0.0000) and speech (p=0.0001) also significantly improved in the Group A. The improvement in burning sensation was not statistically significant between the 2 groups (p=0.002). There was a mild to moderate decrease in the size of the lesion. Conclusions: Though there is no definitive treatment for the condition however, overall assessment of symptoms like mouth opening, tongue protrusion, difficulty in swallowing and speech and pain associated with the lesion showed that oxitard capsules can bring about significant clinical improvements than aloe vera gel in the treatment of OSMF.

Key words:Oral submucous fibrosis, oxitard capsules, aloe vera, burning sensation, mouth opening.

Altered immunohistochemical expression of mast cell tryptase and chymase in the pathogenesis of oral submucous fibrosis and malignant transformation of the overlying epithelium

Mast cells (MCs) expressing serine proteases; tryptase and chymase, are associated with fibrosis in various diseases. However, little is known about their involvement in oral submucous fibrosis (OSF). Our goal was to evaluate the role of MC tryptase and chymase in the pathogenesis of OSF and its malignant transformation. Immunohistochemical expression of MC tryptase and chymase was evaluated in 20 cases of OSF, 10 cases of oral squamous cell carcinoma (OSCC) and 10 cases of healthy controls. Subepithelial zone of Stage 1 and 2 while deep zone of Stage 3 and 4 OSF demonstrated increased tryptase positive MCs. OSCC revealed a proportionate increase in tryptase and chymase positive MCs irrespective of areas of distribution. An altered balance in the subepithelial and deep distribution of tryptase and chymase positive MCs play an important role in the pathogenesis of OSF and its malignant transformation.

Arecoline inhibits epithelial cell viability by upregulating the apoptosis pathway: implication for oral submucous fibrosis

Oral submucous fibrosis (OSF) is a chronic inflammatory disease characterized by the accumulation of excess collagen, and areca nut chewing has been proposed as a significant etiological factor for disease manifestation. However, the underlying molecular mechanisms regarding areca nut chewing-induced OSF are only partially understood. Herein, we reported that arecoline markedly induced morphologic change in HaCaT epithelial cells, but had no obvious effect on Hel fibroblast cells. MTS assay revealed that arecoline significantly suppressed HaCaT cell viability. Moreover, flow cytometric analysis indicated that arecoline substantially promoted HaCaT cell, but not Hel cell apoptosis in a dose-dependent manner. Furthermore, arecoline-induced HaCaT cell apoptosis was found to be associated with increased expression and activation of cleaved-Bid, cleaved-PARA and cleaved-caspase-3. Collectively, our results suggest that HaCaT epithelial cells are more sensitive than Hel fibroblast cells to arecoline-induced cytotoxicity, which may be involved in the pathogenesis of OSF.