Growth of oral and skin fibroblasts from patients with oral submucous fibrosis

Exploring the varied expressions of basic fibroblast growth factor in different histopathological grades of oral submucous fibrosis

Context

Oral submucous fibrosis (OSMF) is a chronic disorder with multi-factorial aetiology. The OSMF pathophysiology includes the homeostatic equilibrium disruption between synthesis and degradation of extracellular matrix. Thus, various growth factors produced by activated inflammatory cells may promote fibrosis by inducing fibroblast proliferation, collagen synthesis upregulation, and reduced collagenase production.

Aims

To correlate the role of basic fibroblast growth factor (bFGF) in the endothelial cells, fibroblasts, and connective tissue stroma in varying grades of OSMF. The bFGF expression was also correlated with the amount of inflammation.

Settings and Design

This retrospective study was designed to evaluate bFGF expression in 30 histopathologically diagnosed cases of OSMF from the Department of Oral and Maxillofacial Pathology, I.T.S CDSR, Muradnagar.

Materials and Methods

We included 30 cases, ten each of early, intermediate, and advanced stages of OSMF. Immunohistochemical staining using bFGF antibody was performed, and bFGF expression was noted in the blood vessels, fibroblasts, and connective tissue stroma in all the study cases.

Statistical Analysis Used

Different variables were analysed using the ANOVA test, post hoc test, and Bonferroni test.

Results

The bFGF-labelled blood vessels and fibroblasts were significantly higher in early OSMF cases than in the intermediate and advanced groups. bFGF expression was significantly observed in the connective tissue stroma in most of the cases.

Conclusions

The bFGF intensity was mild, moderate, and severe in early, intermediate, and advanced OSMF cases, respectively. Moreover, bFGF expression was noted in the blood vessels, fibroblasts, and connective tissue stroma in the majority of the cases.

The Bigger Picture: Why Oral Mucosa Heals Better Than Skin

Wound healing is an essential process to restore tissue integrity after trauma. Large skin wounds such as burns often heal with hypertrophic scarring and contractures, resulting in disfigurements and reduced joint mobility. Such adverse healing outcomes are less common in the oral mucosa, which generally heals faster compared to skin. Several studies have identified differences between oral and skin wound healing. Most of these studies however focus only on a single stage of wound healing or a single cell type. The aim of this review is to provide an extensive overview of wound healing in skin versus oral mucosa during all stages of wound healing and including all cell types and molecules involved in the process and also taking into account environmental specific factors such as exposure to saliva and the microbiome. Next to intrinsic properties of resident cells and differential expression of cytokines and growth factors, multiple external factors have been identified that contribute to oral wound healing. It can be concluded that faster wound closure, the presence of saliva, a more rapid immune response, and increased extracellular matrix remodeling all contribute to the superior wound healing and reduced scar formation in oral mucosa, compared to skin.

New Gene Markers Involved in Molecular Processes of Tissue Repair, Response to Wounding and Regeneration Are Differently Expressed in Fibroblasts from Porcine Oral Mucosa during Long-Term Primary Culture

Simple Summary

Wound healing and vascularization mechanisms are key steps in the complex morphological process of tissue reconstruction. Additionally, these processes in the oral cavity are more rapid than in the skin and result in less scar formation. Epithelial cells and fibroblasts play an important role in the process of wound healing. In our study, we focused on fibroblasts and monitored changes in gene expression during their in vitro culture. Based on the analysis, we distinguished three groups of processes that play important roles in tissue regeneration: response to wounding, wound healing and vascularization. We identified genes that were involved in all three processes. These genes could be selected as tissue specific repair markers for oral fibroblasts.

Abstract

The mechanisms of wound healing and vascularization are crucial steps of the complex morphological process of tissue reconstruction. In addition to epithelial cells, fibroblasts play an important role in this process. They are characterized by dynamic proliferation and they form the stroma for epithelial cells. In this study, we have used primary cultures of oral fibroblasts, obtained from porcine buccal mucosa. Cells were maintained long-term in in vitro conditions, in order to investigate the expression profile of the molecular markers involved in wound healing and vascularization. Based on the Affymetrix assays, we have observed three ontological groups of markers as wound healing group, response to wounding group and vascularization group, represented by different genes characterized by their expression profile during long-term primary in vitro culture (IVC) of porcine oral fibroblasts. Following the analysis of gene expression in three previously identified groups of genes, we have identified that transforming growth factor beta 1 (TGFB1), ITGB3, PDPN, and ETS1 are involved in all three processes, suggesting that these genes could be recognized as markers of repair specific for oral fibroblasts within the porcine mucosal tissue.

Extracellular matrix remodeling in oral submucous fibrosis: its stage-specific modes revealed by immunohistochemistry and in situ hybridization

BACKGROUND

Oral submucous fibrosis (OSF) is a chewing habit-related pre-cancerous condition of the oral mucosa affecting predominantly south Asians. It is histopathologically characterized by epithelial atrophy and fibrosis of the subepithelial connective tissue. Fibrosis extends all the way into the muscle layer, leading to difficulty in mouth opening. However, the dynamics of extracellular matrix (ECM) remodeling with OSF progression is largely unknown.

METHODS

Forty biopsy specimens of OSF and 10 of normal buccal mucosa were examined for expression/deposition modes of eight ECM molecules by histochemistry, immunohistochemistry, and in situ hybridization.

RESULTS

In the early stage of OSF, tenascin, perlecan, fibronectin, collagen type III were characteristically enhanced in the lamina propria and the submucosal layer. In the intermediate stage, the ECM molecules mentioned above and elastin were extensively and irregularly deposited around muscle fibers. In the advanced stage, such ECM depositions decreased and were entirely replaced with collagen type I only. Their gene expression levels varied with progression of fibrosis, but the mRNA signals were confirmed in fibroblasts in the submucosal fibrotic areas.

CONCLUSIONS

The results indicate that the ECM remodeling steps in OSF are similar to each phase of usual granulation tissue formation. Restricted mouth opening may be a result of loss of variety of ECM molecules including elastin into the homogeneity of collagen type I replacing muscle fibers.

Augmented mRNA expression of tissue inhibitor of metalloproteinase-1 in buccal mucosal fibroblasts by arecoline and safrole as a possible pathogenesis for oral submucous fibrosis

Oral submucous fibrosis (OSF) is an oral precancerous condition, and is associated with betel quid (BQ) chewing habits. It is a disorder of excessive deposition of collagen in the connective tissues that results from disruption in the regulation of the equilibrium between matrix metalloproteinases (MMPs) and tissue inhibitor of metalloproteinases (TIMPs). Elevated TIMP-1 protein has been thought to be associated with oral fibrosis, however whether TIMP-1 expression in OSF is modulated at the transcriptional level is still unknown. The present study used arecoline, arecaidine and safrole, which are thought to be major toxic ingredients in BQ, as candidates to explore the role of TIMP-1 expression in OSF pathogenesis. Fresh tissue biopsies of oral mucosa from 20 OSF males were included in this study, and fibroblasts were cultured from one OSF buccal mucosa and one normal buccal mucosa of the same OSF patient. To quantify the TIMP-1 expression, enzyme-linked immunosorbent assay (ELISA) was used in the present study. The results indicated that OSF fibroblasts produced more TIMP-1 protein (569.2+/-79.5 ng/ml) than normal fibroblasts (303.0+/-59.3 ng/ml) from the same patients, and the mRNA expression of TIMP-1 in OSF fibroblasts was higher (1.76 fold) than normal fibroblasts of the same patients. Arecoline and safrole significantly elevated TIMP-1 protein and mRNA expression. We concluded that increased mRNA expression of TIMP-1 in buccal mucosal fibroblasts by arecoline and safrole is a possible pathogenesis for oral submucous fibrosis.

Elevated expression of hepatocyte and keratinocyte growth factor in cultured buccal-mucosa-derived fibroblasts compared with normal-skin-derived fibroblasts

Oral mucosa heals faster with less scar formation than skin and a hypertrophic scar is very rare in the oral cavity, but its mechanism has not been elucidated enough. To elucidate whether or not there are differences in growth factor expression between fibroblasts derived from buccal mucosal and normal skin, we investigated the expression of hepatocyte growth factor (HGF), keratinocyte growth factor (KGF) and stem cell factor (SCF) by cultured fibroblasts. The semiquantitative RT-PCR revealed that the expression of HGF and KGF transcripts by buccal mucosal fibroblasts was significantly elevated compared with that by dermal fibroblasts. In parallel, ELISA revealed the significant increase of HGF production by buccal mucosal fibroblasts. The level of production of SCF protein did not differ significantly. Our study suggests that increased expression of HGF and KGF by buccal mucosal fibroblasts may partly be responsible for the faster wound healing with less scar formation in the oral cavity compared with normal skin.

Elevated vimentin expression in buccal mucosal fibroblasts by arecoline in vitro as a possible pathogenesis for oral submucous fibrosis

Areca quid chewing is strongly correlated with oral submucous fibrosis (OSF) in Taiwan. The cytotoxicity of arecoline, a major areca nut alkaloid, on human oral fibroblasts has been extensively studied. To date, however, there has been little research exploring the possible effects of arecoline on cytoskeleton components. In this study, in addition to conducting a cytotoxicity assay, we examine the effect of arecoline on vimentin, an intermediate filament, and its expression in human buccal mucosal fibroblasts on exposure to various levels of arecoline (0-200 microg/ml) for 48 h. At a concentration above 50 microg/ml, arecoline demonstrated dose-dependent cytotoxicity (P<0.05) for cultured fibroblasts. Using sodium dodecyl sulphate-polyacrylamide gel electrophoresis, we demonstrated dose-dependent elevation of 57 kDa cytoskeletal-protein levels for arecoline. Evidence from immunoblotting assay indicated this 57 kDa cytoskeletal protein was vimentin. The increase in vimentin with arecoline exposure corresponded to that noted for fibroblasts cultured from OSF patients. Immunohistochemical assay also revealed that vimentin expression was much higher for OSF specimens than for normal buccal mucosa. We suggest these results may advance understanding of the possible pathogenesis for submucous fibrosis through the transformation of normal buccal mucosa as a result of areca quid chewing.

The oral health consequences of chewing areca nut

Deleterious effects of areca nut on oral soft tissues are published extensively in the dental literature. Its effects on dental caries and periodontal tissues, two major oral diseases, are less well researched. Areca-induced lichenoid lesions mainly on buccal mucosa or tongue are reported at quid retained sites. In chronic chewers a condition known as betel chewer's mucosa, a discoloured areca nut-encrusted change, is often found where the quid particles are retained. Areca nut chewing is implicated in oral leukoplakia and submucous fibrosis, both of which are potentially malignant in the oral cavity. Oral cancer often arises from such precancerous changes in Asian populations. In 1985 the International Agency for Research on Cancer concluded that there is limited evidence to conclude that areca chewing may directly lead to oral cancer. There is, however, new information linking oral cancer to pan chewing without tobacco, suggesting a strong cancer risk associated with this habit. Public health measures to quit areca use are recommended to control disabling conditions such as submucous fibrosis and oral cancer among Asian populations.

Role of areca nut in betel quid-associated chemical carcinogenesis: current awareness and future perspectives

Betel quid (BQ)-chewing is a popular oral habit with potential links to the occurrence of oral cancer. Many of the literature-based studies reveal that areca nut (AN) extract may demonstrate mutagenic and genotoxic effects, in addition to inducing preneoplastic as well as neoplastic lesions in experimental animals. Areca nut should, thus, be highly suspected as a human carcinogen. Toxicity studies relating to AN-contained polyphenols and tannins are not conclusive, with both carcinogenic and anti-carcinogenic effects being reported. The mutagenicity and genotoxicity of areca alkaloids has been detected by many short-term assays. However, their genotoxicity to oral fibroblasts and keratinocytes, the target cells of BQ, has not been identified. It would thus appear that AN toxicity is not completely due to its polyphenol, tannin and alkaloid content. The single agent which is responsible for AN carcinogenicity awaits further clarification. Reactive oxygen species produced during auto-oxidation of AN polyphenols in the BQ-chewer's saliva, are crucial in the initiation and promotion of oral cancer. Nitrosation of areca alkaloids also produces AN-specific nitrosamines, that have been demonstrated to be mutagenic, genotoxic and are capable of inducing tumors in experimental animals. Arecaidine and AN extract are further suggested to be tumor promoters. Antioxidants such as glutathione and N-acetyl-L-cysteine can potentially prevent such AN-elicited cytotoxicity. Further studies are needed to delineate the metabolism of AN ingredient and their roles in the multi-step chemical carcinogenesis, in order to enhance the success of the future chemoprevention of oral cancer and oral submucous fibrosis.

Synergistic effects of peroxynitrite on arecoline-induced cytotoxicity in human buccal mucosal fibroblasts

Epidemiological studies have demonstrated a clear association between betel nut chewing and an increased risk for oral mucosal lesions. Arecoline, the most abundant betel alkaloid, is considered the most important etiologic factor in betel nuts. In addition, most betel nut chewers are also smokers. In order to elucidate the potential toxicological implications of interactions of arecoline and peroxynitrite (a reaction product of cigarette smoking), cell viability, and cellular levels of glutathione (GSH) were investigated, using cultured human buccal mucosal fibroblasts. At a concentration higher than 0.8 mM, arecoline was cytotoxic to buccal mucosal fibroblasts in a concentration- and time-dependent manner. Arecoline also depleted intracellular GSH in a dose-dependent manner (P<0.05). The addition of extracellular peroxynitrite acted as a synergistic effect on the arecoline-induced cytotoxicity (P<0.05). Furthermore, at a concentration of 0.8 mM, arecoline depleted intracellular GSH by about 42%, while 2 mM peroxynitrite enhanced the arecoline-depleted GSH level further to 86% as compared with the control. During GSH depletion, arecoline may render the human buccal mucosal fibroblasts more vulnerable to other reactive agents within cigarette smoking. Taken together, we suggest that people who combine the habits of betel nut chewing with cigarette smoking could be more susceptible to oral mucosal damage than betel quid chewing alone.

Differences between fibroblasts cultured from oral mucosa and normal skin: implication to wound healing

It is generally agreed that oral mucosa heals faster with less scar than skin does, and hypertrophic scar or keloid is very rare in the oral cavity. Fibroblasts are thought to play an important role in wound healing and scar formation, whose control is mediated by growth factors. We have studied whether there are any differences in the cellular behavior of fibroblasts between oral mucosa and skin, and in their response to growth factors. Oral mucosal fibroblasts proliferated slightly more than dermal fibroblasts on average. Dermal fibroblasts in collagen gel possessed greater contraction potency than oral mucosa fibroblasts, irrespective of the presence of growth factors; however, oral mucosa fibroblasts showed an earlier collagen gel contraction with or without TGF-beta1. There were no differences in basal collagen synthetic rate between dermal and oral mucosal fibroblasts, while the latter synthesized more collagen than dermal fibroblasts when they were stimulated with TGF-beta1. Our study showed that oral mucosal fibroblasts and dermal fibroblasts had selective differences in cellular behavior and in their responses to growth factors, which seems to contribute to the differences in wound healing.

Cytotoxic and non-genotoxic effects of arecoline on human buccal fibroblasts in vitro

Betel quid chewing has been linked to oral submucous fibrosis and oral cancer. Cytotoxicity and genotoxicity assays were used to investigate the pathobiological effects of arecoline on cultured human buccal fibroblasts. Arecoline increased double-stranded polynucleic acid at the concentration of 0.1 to 10 micrograms/ml in a concentration-dependent manner. At a concentration higher than 50 micrograms/ml, arecoline was cytotoxic to cultured fibroblasts and the cytotoxicity was dose-dependent. No genotoxicity for arecoline was found even at a concentration of 400 micrograms/ml. On the other hand, 600 micrograms/ml glutathione (GSH) and 200 micrograms/ml glycyrrhizin could prevent the arecoline-induced cytotoxicity. These results indicate that arecoline is a cytotoxic agent and no genotoxicity was found to human buccal fibroblasts. Furthermore, increasing consumption of GSH- and glycyrrhizin-rich foods may reduce the oral diseases associated with betel quid chewing.