Development of a mouse model of arecoline-induced oral mucosal fibrosis

Hypoxia amplifies arecoline-induced invasion and metastasis in oral squamous cell carcinoma - Insights into TGF-β1 signaling and collagen production

Background/Purpose

Betel quid chewing is a major risk factor for oral squamous cell carcinoma (OSCC), largely due to arecoline, a key alkaloid. Hypoxia, common in the tumor microenvironment, also influences cancer progression. This study investigated the combined effects of arecoline and hypoxia on proliferation, migration, and protein expression in tongue squamous cell carcinoma (SCC-25) cells, focusing on the TGF-β1 signaling pathway and type I collagen production.

Materials and methods

SCC-25 cells were treated with arecoline and incubated for 24 h under normoxia or hypoxia. Cytotoxicity assays and Western blotting were performed to assess cell viability and protein expression.

Results

At 2.5 μg/mL, arecoline enhanced SCC-25 cell proliferation under normoxia, while hypoxia suppressed this effect. Arecoline significantly promoted cell migration that was further amplified by hypoxia. Western blotting revealed that arecoline upregulated TGF-β1, Smad2/3, phosphorylated Smad2/3, and type I collagen. Under hypoxia, HIF1-α expression increased along with TGF-β1 and type I collagen, indicating that hypoxia enhances arecoline-induced collagen production through TGF-β1 signaling.

Conclusion

Arecoline stimulates SCC-25 cell proliferation and migration, with hypoxia amplifying these effects by promoting TGF-β1 signaling and type I collagen production. These findings suggest that betel quid consumption, in combination with hypoxia, may exacerbate the invasion and metastasis of OSCC.

Choosing the proper animal model for oral submucous fibrosis research: considerations and challenges

Objectives

Animal models of oral submucous fibrosis (OSF) are essential for the studying on the pathogenesis of this disease. Current research on animal models of OSF requires further investigation. In this review, we aim to summarize the strengths and weaknesses of existing OSF animal models, as well as the recent progress in this field.

Subject and methods

OSF is an oral potentially malignant disorder (OPMD) characterized by fibrotic bands, burning sensations, and limited mouth opening. Numerous experimental animal models have been developed to replicate the pathological processes in patients with OSF. Therefore, we systematically evaluated existing animal models of OSF classifying them according to the elements of building an animal model.

Results

In this study, we propose that the elements of animal models for OSF include inducers, animal species, and methods of intervention. Additionally, we highlighted the advantages and limitations of these models and provided directions for future research.

Conclusion

Using human-like animals as experimental subjects, combining both physical and chemical stimulation, and adjusting the dosage and type of inducer may represent the direction of future studies in this field.

Epithelium-derived exosomal dipeptidyl peptidase-4 involved in arecoline-induced oral submucous fibrosis

INTRODUCTION

Dipeptidyl peptidase-4 is known to be involved in the progression of several fibrogenic diseases, but its association with oral submucous fibrosis remains unclear. This study aims to ascertain whether dipeptidyl peptidase-4 plays a role in the pathogenesis of arecoline-induced oral submucous fibrosis.

METHODS

We assessed the expression of dipeptidyl peptidase-4 in arecoline-treated epithelial cells and the exosomes derived from cells. We cocultured the fibroblast and exosomes derived from epithelium cells and assessed fibrogenic activity by measuring collagen secretion, α-SMA expression, and gel contraction capability. An animal study was conducted to confirm the fibrogenic activity of exosomes derived from arecoline-treated epithelial cells. Additionally, we employed a dipeptidyl peptidase-4 inhibitor to assess its efficacy in mitigating fibrogenesis.

RESULTS

Following arecoline treatment, an increase dipeptidyl peptidase-4 expression was observed in exosomes from the treated epithelium cells. When these exosomes cocultured with fibroblast, fibrogenic gene α-SMA was upregulated, increased collagen secretion, and enhanced gel contraction capability. In a mouse model, the administration of arecoline-treated epithelium-derived exosomes induced oral submucous fibrosis phenotype, characterized by a reduction in incisal distance and epithelial atrophy.

CONCLUSIONS

These findings offer valuable insights into clinical strategies for combating oral fibrotic disease and contribute to the foundation of future research in this field.

Oral submucous fibrosis: pathogenesis and therapeutic approaches

Oral submucous fibrosis (OSF), characterized by excessive deposition of extracellular matrix (ECM) that causes oral mucosal tissue sclerosis, and even cancer transformation, is a chronic, progressive fibrosis disease. However, despite some advancements in recent years, no targeted antifibrotic strategies for OSF have been approved; likely because the complicated mechanisms that initiate and drive fibrosis remain to be determined. In this review, we briefly introduce the epidemiology and etiology of OSF. Then, we highlight how cell-intrinsic changes in significant structural cells can drive fibrotic response by regulating biological behaviors, secretion function, and activation of ECM-producing myofibroblasts. In addition, we also discuss the role of innate and adaptive immune cells and how they contribute to the pathogenesis of OSF. Finally, we summarize strategies to interrupt key mechanisms that cause OSF, including modulation of the ECM, inhibition of inflammation, improvement of vascular disturbance. This review will provide potential routes for developing novel anti-OSF therapeutics.

Comparative analysis of two arecoline-induced oral submucous fibrosis models

OBJECTIVE

The limited understanding of the molecular mechanism for oral submucosal fibrosis (OSF) poses challenges to the development of effective prevention and treatment strategies. The lack of suitable animal models is a major hindrance. Therefore, this study aimed to address this issue by comparing commonly used arecoline-induced water drinking and injection mouse models.

MATERIALS AND METHODS

The mice were subjected to two protocols: receiving 2 mg/mL arecoline in drinking water and 4 mg/mL arecoline saline solution injections every other day. Tissues were collected at regular 4-week intervals, with a final time point of 20 weeks. Stereo microscopy and histomorphological analysis were performed on live and harvested tissues, respectively.

RESULTS

During arecoline treatment, collagen deposition and myofibroblast proliferation progressively increased in both models. Changes in the collagen I/III ratio indicated that both models exhibited characteristics of the early and intermediate stages of OSF after 20 weeks of arecoline induction. The water-drinking model also demonstrated multi-organ fibrosis involving the tongue, lungs, and small intestine.

CONCLUSION

Both the water drinking and injection mouse models effectively induced OSF, but the water-drinking model better mirrored the observed pathogenesis in patients with OSF. These models provide valuable tools for investigating the mechanisms underlying OSF.

Up regulation of serum L fucose glycoprotein as a diagnostic biomarker for dysplasia in oral sub mucous fibrosis patients

Glycoproteins, essential for cellular functions, contain monosaccharides like Levo-fucose, crucial for cell communication. Recent research highlights serum L-fucose as a potential biomarker for early detection of malignancies. Typically, serum L-fucose levels are low but rise with malignancy. This study evaluates serum L-fucose as an early biomarker in oral submucous fibrosis (OSMF) patients.

Aim

Assess serum L-fucose's diagnostic potential for dysplasia in OSMF patients.

Objectives

Determine the Association between Serum L Fucose Glycoprotein Levels and Dysplasia in OSF Patients.Evaluate the Diagnostic Accuracy of Serum L Fucose Glycoprotein as a Biomarker for OSF-Related Dysplasia.

Methodology

Over a span of two years, this study encompassed 80 subjects, aged between 18 and 60 years, who were clinically and histopathologically identified as OSMF patients, with or without dysplastic alterations. From each participant, 5 ml of blood was collected. Following centrifugation to separate the serum, the samples were analyzed to determine the levels of Levo-fucose.

Statistical analysis

Using SPSS (version 17.0), serum L-Fucose levels of the case group were compared to the control group using ANOVA. Frequencies were analyzed with the chi-square test, and Tukey's Test was used for multiple comparisons. Significance was set at p < 0.01.

Results

The analysis revealed a statistically significant disparity in the mean serum L-Fucose levels between the two groups (p < 0.01). Notably, Group II patients (those with OSMF and dysplasia) exhibited markedly elevated mean serum L-fucose levels.

Conclusion

Elevated serum L-Fucose levels were observed in OSMF patients with dysplasia. Harmful habits, especially gutkha chewing, were linked to Oral Squamous Cell Carcinoma onset. Serum L-fucose can be a reliable marker for evaluating precancerous conditions.

Targeting histone deacetylase 9 represses fibrogenic phenotypes in buccal mucosal fibroblasts with arecoline stimulation

Background/purpose

Oral submucosal fibrosis (OSF) is a premalignant disorder positively associated with betel nut chewing. Recent studies supported the promising benefits of histone deacetylase (HDAC) inhibitors for fibrosis treatment. Here we aim to clarify the pro-fibrogenic role of HDAC9 in regulating OSF.

Materials and methods

Healthy and OSF specimens were collected to investigate the clinical significance of HDAC9. Chronic arecoline treatment process was used to induce arecoline-mediated myofibroblasts-related activation of primary buccal mucosa fibroblasts (BMFs). Functional analysis of collagen gel contraction, transwell migration, and wound-healing assays were performed to assess the change in pro-fibrogenic properties of BMFs and fibrotic BMFs (fBMFs). Lentiviral-mediated HDAC9 knockdown was used to verify the role of HDAC9 in the pro-fibrogenic process.

Results

We found that arecoline significantly increased the mRNA and protein expression of HDAC9 of BMFs in a dose-dependent manner. Knockdown of HDAC9 in BMFs reversed the strengthened effects of arecoline on collagen gel contraction, cell migration, and wound-healing ability. We further demonstrated that knockdown of HDAC9 in fBMFs significantly attenuated its inherent pro-fibrogenic properties. Furthermore, we confirmed a significantly increased expression of HDAC9 mRNA in OSF compared to normal tissues, which suggested a positive correlation between the up-regulation of HDAC9 and OSF.

Conclusion

We demonstrated that silencing of HDAC9 inhibited arecoline-induced activation and inherent pro-fibrogenic properties, suggesting potential therapeutics by targeting HDAC9 in the OSF treatment.

Systematic Review of Roles of Arecoline and Arecoline N-Oxide in Oral Cancer and Strategies to Block Carcinogenesis

Betel quid and areca nut are complex mixture carcinogens, but little is known about whether their derived single-agent arecoline or arecoline N-oxide (ANO) is carcinogenic, and the underlying mechanisms remain unclear. In this systematic review, we analyzed recent studies on the roles of arecoline and ANO in cancer and strategies to block carcinogenesis. In the oral cavity, flavin-containing monooxygenase 3 oxidizes arecoline to ANO, and both alkaloids conjugate with N-acetylcysteine to form mercapturic acid compounds, which are excreted in urine, reducing arecoline and ANO toxicity. However, detoxification may not be complete. Arecoline and ANO upregulated protein expression in oral cancer tissue from areca nut users compared to expression levels in adjacent normal tissue, suggesting a causal relationship between these compounds and oral cancer. Sublingual fibrosis, hyperplasia, and oral leukoplakia were diagnosed in mice subjected to oral mucosal smearing of ANO. ANO is more cytotoxic and genotoxic than arecoline. During carcinogenesis and metastasis, these compounds increase the expression of epithelial-mesenchymal transition (EMT) inducers such as reactive oxygen species, transforming growth factor-β1, Notch receptor-1, and inflammatory cytokines, and they activate EMT-related proteins. Arecoline-induced epigenetic markers such as sirtuin-1 hypermethylation, low protein expression of miR-22, and miR-886-3-p accelerate oral cancer progression. Antioxidants and targeted inhibitors of the EMT inducers used reduce the risk of oral cancer development and progression. Our review findings substantiate the association of arecoline and ANO with oral cancer. Both of these single compounds are likely carcinogenic to humans, and their mechanisms and pathways of carcinogenesis are useful indicators for cancer therapy and prognosis.

RNA N6-Methyladenosine (m6A) Methyltransferase-like 3 Facilitates Tumorigenesis and Cisplatin Resistance of Arecoline-Exposed Oral Carcinoma

BACKGROUND

Arecoline is known as the main active carcinogen found in areca nut extract that drives the pathological progression of oral squamous cell carcinoma (OSCC). Studies have revealed that dysregulation of RNA N6-methyladenosine (m6A) methyltransferase components is intimately linked to cancer initiation and progression, including oral cancer.

METHODS

The arecoline-induced dysregulated methyltransferase-like 3 (METTL3) gene was identified using RNA-seq transcriptome assay. Using in vitro and in vivo models, the biological roles of METTL3 in arecoline-transformed oral cancer were examined.

RESULTS

We found that METTL3 was markedly elevated in arecoline-exposed OSCC cell lines and OSCC tissues of areca nut chewers. We identified that hypoxia-inducible factor 1-alpha (HIF-1α) stimulated METTL3 expression at the transcriptional level and further proved that METTL3-MYC-HIF-1α formed a positive autoregulation loop in arecoline-transformed OSCC cells. Subsequently, we manifested that METTL3 depletion profoundly reduced cell proliferation, cell migration, oncogenicity, and cisplatin resistance of arecoline-exposed OSCC cells.

CONCLUSIONS

Developing novel strategies to target METTL3 may be a potential way to treat OSCC patients, particularly those with areca nut chewing history and receiving cisplatin treatment.

A novel approach to develop an animal model for oral submucous fibrosis

Epidemiological data have proved the association of consumption of areca nut with the causation of oral submucous fibrosis (OSF). OSF is a chronic inflammatory disease with the potential for malignant transformation from 7 to 13%. The establishment of animal models makes it easier for researchers to focus on the therapeutic options to combat this disease further. We developed and compared two areca nut extract (ANE) administration methods in Swiss albino mice to establish OSF. This study compared an invasive intrabuccal injection technique with a non-invasive intraoral droplet administration. The duration of induction was around 12 weeks. Histopathology (H&E, Masson's trichrome staining) and gene expression analysis (COL-I, COL-II, and α-SMA) were performed using RT-PCR to confirm the OSF in animals. Our study showed that ANE administration through the intraoral droplet method exhibited significantly higher fibrosis than the intrabuccal injections, as evidenced by the H&E and Masson's trichrome staining. Furthermore, intraoral administration of ANE significantly upregulated the mRNA expression of COL-I, COL-II, and α-SMA, as revealed by the RT-PCR analysis. The non-invasive droplet method could simulate the absorption of areca nut seen in humans through daily dosing. This study establishes the intraoral droplet method as an efficient and non-invasive method to administer the ANE to develop OSF. These findings will aid in the efficient development of OSF animal models for interventional studies, including screening novel drugs in the reversal of the OSF.

Fucoidan-Mediated Inhibition of Fibrotic Properties in Oral Submucous Fibrosis via the MEG3/miR-181a/Egr1 Axis

Oral submucous fibrosis (OSF) is a chronic fibrotic remodeling disease that can progress to oral cancer. However, efficient clinical diagnosis and treatment methods for OSF are still lacking. This study investigated the anti-fibrotic effect of fucoidan on oral fibrosis. To evaluate the fibrotic ability (myofibroblast activities), we performed wound-healing, Transwell migration, and collagen contraction assays by using patient-derived normal and fibrotic buccal submucous fibroblasts (BMFs and fBMFs, respectively). RNA-sequencing and dual-luciferase reporter and RNA immunoprecipitation chip assays were performed to identify the clinical significance and molecular mechanism of non-coding RNAs. Fucoidan suppressed the myofibroblast activities and inhibited the MEG3 in fBMFs. MEG3 was overexpressed in the OSF tissue and was positively associated with myofibroblast markers. Knockdown of MEG3 markedly inhibited myofibroblast activities, which were restored by inhibiting miR-181a and overexpressing Egr1. The results from luciferase reporter and RIP assays confirmed that MEG3 functioned as a competing endogenous RNA (ceRNA) and could directly target miR-181a, thereby preventing the miR-181a-mediated translational repression of Egr1. This study demonstrated that MEG3 exerts a profibrotic effect on OSF by targeting miR-181a/Egr1. Therefore, the administration of fucoidan may serve as a potential therapeutic strategy for OSF by targeting the overexpression of MEG3.

VEGF gene transfection restores the angiogenesis of oral submucous fibrosis in mice

BACKGROUND

To explore the effectiveness of adenovirus-enhanced green fluorescent protein-vascular endothelial growth factor165 (AD-EGFP-VEGF165) transfection on fibroblasts from mice, and we assessed whether VEGF165 restores the angiogenesis of oral submucous fibrosis (OSF) in mice.

METHODS

AD-EGFP-VEGF165 and AD-EGFP were transfected into fibroblasts from mouse buccal tissues in vitro. The expression of VEGF before and after transfection was detected by RT-qPCR and ELISA in each group of fibroblasts. Fifteen OSF mice (pre-experimental construction) were randomly divided into 3 groups, and equal amounts of AD-EGFP-VEGF165 virus, AD-EGFP virus, and saline were injected into the buccal submucosal tissue of OSF mice. The expression of VEGF and local tissue angiogenesis were observed and measured in each group of animals.

RESULTS

The Ad-EGFP-VEGF165-transfected fibroblasts increased human and mouse VEGF expression compared to the Ad-EGFP group and control group (P<0.05). The buccal submucosal tissue of mice was injected with Ad-EGFP-VEGF165 after the 6th day, and the expression of VEGF was effectively expressed in AD-EGFP-VEGF165 group (P<0.05), while no positive expression observed in other groups. and the number of microvessels in the AD-EGFP-VEGF165 group increased significantly compared to the other groups (P<0.05).

CONCLUSIONS

Ad-EGFP-VEGF165 can be successfully transfected into fibroblasts from mice, and restored the angiogenesis of OSF in mice.

Oral Submucous Fibrosis: A Review on Biomarkers, Pathogenic Mechanisms, and Treatments

Oral submucous fibrosis (OSF) is a collagen deposition disorder that affects a patient’s oral function and quality of life. It may also potentially transform into malignancy. This review summarizes the risk factors, pathogenic mechanisms, and treatments of OSF based on clinical and bio-molecular evidence. Betel nut chewing is a major risk factor that causes OSF in Asia. However, no direct evidence of arecoline-induced carcinogenesis has been found in animal models. Despite identification of numerous biomarkers of OSF lesions and conducting trials with different drug combinations, clinicians still adopt conservative treatments that primarily focus on relieving the symptoms of OSF. Treatments focus on reducing inflammation and improving mouth opening to improve a patient’s quality of life. In conclusion, high-quality clinical studies are needed to aid clinicians in developing and applying molecular biomarkers as well as standard treatment guidelines.

Photobiomodulation therapy inhibits oral submucous fibrosis in mice

Objectives

Oral submucous fibrosis (OSMF) is a chronic inflammatory disease and a potentially malignant oral disorder. However, the best therapeutic treatment for OSMF remains uncertain. Our previous study showed that photobiomodulation (PBM) therapy and forskolin could reduce arecoline‐induced fibrosis reactions via the cAMP pathway. The present study aimed to establish an animal model of areca nut extract (ANE)‐induced OSMF and to evaluate the therapeutic potential of PBM and forskolin for ANE‐induced OSMF.

Subjects and methods

The mice were divided into five groups. The buccal tissues were harvested for histomorphological analysis and immunoblotting.

Results

Our results showed that PBM significantly reduced the development of ANE‐induced OSMF, quantified by changes in submucosal layer thickness and collagen deposition. Additionally, PBM could extensively reduce the protein expression of the fibrotic marker genes alpha‐smooth muscle actin (α‐SMA) and connective tissue growth factor (CTGF) in buccal submucous lesions. However, forskolin treatment significantly decreased the protein expression of fibrotic marker genes but slightly decreased the observed histomorphological changes.

Conclusions

We established an ANE‐induced OSMF mouse model, which also provided a model for the development of a therapeutic treatment for OSMF. The anti‐fibrotic effects of PBM and forskolin may be useful for clinical interventions.

[Rat model with oral submucous fibrosis induced by arecoline and mechanical stimulation]

OBJECTIVE

The aim of this study was to induce oral submucous fibrosis (OSF) in Sprague-Dawley(SD) rat models by arecoline and mechanical stimulation.

METHODS

Two factors factorial design was used to divide 48 rats into 8 groups (n=6). Different concentrations of arecoline (0, 0.5, 2, and 8 mg·mL⁻¹) and mechanical stimulation (with or without brush) were treated. After 16 weeks of treatment, the mouth opening was measured, the pathological changes of the buccal mucosa were observed, and the expressions of type Ⅲ collagen, transforming growth factor β1 (TGF-β1), and interferon-γ (IFN-γ) were detected.

RESULTS

In rats with moderate and high concentrations of arecoline, typical OSF pathological features were observed in the buccal mucosa, the mouth openings were significantly reduced, and the expression levels of type Ⅲ colla-gen and TGF-β1 were significantly increased (P<0.05). Although mechanical stimulation can increase the three indexes of mucosa (P<0.05), no pathological change and difference in the mouth opening was observed (P>0.05).

CONCLUSIONS

Moderate and high concentrations of arecoline can induce OSF in SD rats, but mechanical stimulation cannot induce OSF.