Stromal myofibroblasts in focal reactive overgrowths of the gingiva

The yes-associated protein-1 (YAP1) inhibitor celastrol suppresses the ability of transforming growth factor β to activate human gingival fibroblasts

OBJECTIVE

To determine whether celastrol, an inhibitor of the mechanosensitive transcriptional cofactor yes-associated protein-1 (YAP1), impairs the ability of TGFβ1 to stimulate fibrogenic activity in human gingival fibroblast cell line.

DESIGN

Human gingival fibroblasts were pre-treated with celastrol or DMSO followed by stimulation with or without TGFβ1 (4 ng/ml). We then utilized bulk RNA sequencing (RNAseq), real-time polymerase chain reaction (RT-PCR), Western blot, immunofluorescence, cell proliferation assays to determine if celastrol impaired TGFβ1-induced responses in a human gingival fibroblast cell line.

RESULTS

Celastrol impaired the ability of TGFβ1 to induce expression of the profibrotic marker and mediator CCN2. Bulk RNAseq analysis of gingival fibroblasts treated with TGFβ1, in the presence or absence of celastrol, revealed that celastrol impaired the ability of TGFβ1 to induce mRNA expression of genes within extracellular matrix, wound healing, focal adhesion and cytokine/Wnt signaling clusters. RT-PCR analysis of extracted RNAs confirmed that celastrol antagonized the ability of TGFβ1 to induce expression of genes anticipated to contribute to fibrotic responses. Celastrol also reduced gingival fibroblast proliferation, and YAP1 nuclear localization in response to TGFβ1.

CONCLUSION

YAP1 inhibitors such as celastrol could be used to impair pro-fibrotic responses to TGFβ1 in human gingival fibroblasts.

Immunohistochemical Characterization of Gingival Fibromas

PURPOSE

Gingival fibromas (GFs) are fibrous lesions of the gingiva that are not well defined in the literature. They are histologically similar to peripheral ossifying fibromas (POFs), both being characterized as cellular proliferations of dense fibrous tissue, with POFs differing in that they demonstrate foci of calcification. This study aims to expand upon the immunohistochemical characterization of GFs, and to confirm their osteoblastic phenotype.

METHODS

Formalin fixed, paraffin embedded GFs, POFs and fibroepithelial polyps (FEPs) of the gingiva were examined. Immunohistochemical staining was performed for special AT-rich sequence binding protein 2 (SATB2), runt-related transcription factor 2 (RUNX2), osteocalcin and alpha-smooth muscle actin (αSMA). Sections were evaluated by light microscopy and the immunohistochemical staining patterns were assigned immunoreactive scores (IRS) based on percentage of stained cells and intensity of staining.

RESULTS

GFs, POFs, and FEPs of the gingiva expressed osteoblastic markers SATB2, RUNX2 and osteocalcin. GFs and POFs expressed αSMA while FEPs of the gingiva did not. GFs and POFs had similar staining patterns of SATB2, RUNX2 and αSMA.

DISCUSSION

These findings demonstrate that GFs and POFs exhibit a similar immunohistochemical profile, and supports a theory that GFs are osteoblastic lesions possibly related to POFs.

SATB2 is frequently expressed in ossifying and non-ossifying peripheral oral fibroma of the gingival region but not in reactive fibromatous lesions from other intraoral sites

Ossifying and non-ossifying peripheral oral fibromas (POF) of the gingival and alveolar mucosa are localized, cellular, small fibrous nodular lesions likely resulting from diverse external/ internal physical and chemical irritation or injuries. A central nidus of metaplastic woven bone characterizes and defines the ossifying variant. The inherent tendency of these lesions to ossify remains elusive. We herein analyze SATB2 expression as osteoblastic transcription and differentiation factor in 28 gingival POFs (10 of them ossifying) and compare them to 28 fibrous lesions from different non-gingival intraoral sites. Strong to moderate diffuse nuclear SATB2 immunoreactivity was detected in all ossifying (10/10; 100%) and in 8/18 (44%) non-ossifying gingival POFs, but in only 1/28 (3%) non-gingival oral reactive nodular fibrous lesions. This study illustrates for the first-time consistent expression of the osteoblastic marker SATB2 in ossifying and most of non-ossifying POFs of the gingival area but lack of this marker in reactive fibrous lesions from other oral cavity sites. This finding is in line with the proposed origin of gingival POFs from periodontal ligaments and may explain the frequent ossification observed in them. It is mandatory to consider this finding when assessing biopsies from SATB2-positive oral cavity neoplasms to avoid misinterpretation.

Antioxidants and NOX1/NOX4 inhibition blocks TGFβ1-induced CCN2 and α-SMA expression in dermal and gingival fibroblasts

TGFbeta induces fibrogenic responses in fibroblasts. Reactive oxygen species (ROS)/nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) may contribute to fibrogenic responses. Here, we examine if the antioxidant N-acetylcysteine (NAC), the NOX inhibitor diphenyleneiodonium (DPI) and the selective NOX1/NOX4 inhibitor GKT-137831 impairs the ability of TGFbeta to induce profibrotic gene expression in human gingival (HGF) and dermal (HDF) fibroblasts. We also assess if GKT-137831 can block the persistent fibrotic phenotype of lesional scleroderma (SSc) fibroblasts. We use real-time polymerase chain reaction and Western blot analysis to evaluate whether NAC and DPI impair the ability of TGFbeta1 to induce expression of fibrogenic genes in fibroblasts. The effects of GKT-137831 on TGFbeta-induced protein expression and the persistent fibrotic phenotype of lesional scleroderma (SSc) fibroblasts were tested using Western blot and collagen gel contraction analyses. In HDF and HGF, TGFbeta1 induces CCN2, CCN1, endothelin-1 and alpha-smooth muscle actin (SMA) in a fashion sensitive to NAC. Induction of COL1A1 mRNA was unaffected. Similar results were seen with DPI. NAC and DPI impaired the ability of TGFbeta1 to induce protein expression of CCN2 and alpha-SMA in HDF and HGF. GKT-137831 impaired TGFbeta-induced CCN2 and alpha-SMA protein expression in HGF and HDF. In lesional SSc dermal fibroblasts, GKT-137831 reduced alpha-SMA and CCN2 protein overexpression and collagen gel contraction. These results are consistent with the hypothesis that antioxidants or NOX1/4 inhibition may be useful in blocking profibrotic effects of TGFbeta on dermal and gingival fibroblasts and warrant consideration for further development as potential antifibrotic agents.

5Z-7-Oxozeanol Inhibits the Effects of TGFβ1 on Human Gingival Fibroblasts

Transforming growth factor (TGF)β acts on fibroblasts to promote the production and remodeling of extracellular matrix (ECM). In adult humans, excessive action of TGFβ is associated with fibrotic disease and fibroproliferative conditions, including gingival hyperplasia. Understanding how the TGFβ1 signals in fibroblasts is therefore likely to result in valuable insights into the fundamental mechanisms underlying fibroproliferative disorders. Previously, we used the TAK1 inhibitor (5Z)-7-Oxozeaenol to show that, in dermal fibroblasts, the non-canonical TAK1 pathway mediates the ability of TGFβ1 to induce genes promoting tissue remodeling and repair. However, the extent to which TAK1 mediates fibroproliferative responses in fibroblasts in response to TGFβ1 remains unclear. Herein, we show that, in gingival fibroblasts, (5Z)-7-Oxozeaenol blocks the ability of TGFβ1 to induce expression of the pro-fibrotic mediator CCN2 (connective tissue growth factor, CTGF) and type I collagen protein. Moreover, genome-wide expression profiling revealed that, in gingival fibroblasts, (5Z)-7-Oxozeaenol reduces the ability of TGFβ1 to induce mRNA expression of essentially all TGFβ1-responsive genes (139/147), including those involved with a hyperproliferative response. Results from microarray analysis were confirmed using real time polymerase chain reaction analysis and a functional cell proliferation assay. Our results are consistent with the hypothesis that TAK1 inhibitors might be useful in treating fibroproliferative disorders, including that in the oral cavity.

Phenytoin-induced gingival overgrowth management with periodontal treatment

Phenytoin-induced gingival overgrowth (PIGO) is a common complication of the continuous use of medications. This paper presents a case of PIGO hindering oral function and compromising oral hygiene and aesthetics, which was treated with a combination of nonsurgical and surgical periodontal therapies. A 39-year-old male patient was referred for dental treatment with several complaints, especially upper and lower gingival overgrowth that hindered speech and swallowing. Generalized deep probing pockets and bone loss were detected. Diagnosis of gingival overgrowth associated with phenytoin and chronic periodontitis was established. The treatment plan consisted of conservative therapy with education on oral health, motivation and meticulous oral hygiene instruction in combination with scaling and root planing. During the revaluation period, a marked reduction in the clinical parameters was noted, particularly probing pocket depth reduction. Surgical therapy for removal of gingival overgrowth was also performed to achieve pocket reduction. Supportive periodontal therapy was proposed and the patient is currently under follow-up for 4 years. Management of PIGO may be obtained by the use of periodontal procedures combined with good oral hygiene and periodontal supportive care.

miR-218 regulates focal adhesion kinase-dependent TGFβ signaling in fibroblasts

Unlike other tissues in the body, the oral cavity does not scar. Myofibroblasts are the essential cell type in scar tissue formation; gingival fibroblasts are relatively unable to differentiate into myofibroblasts in response to TGFβ. This differential response is attributed to the relative lack of miR-218 in gingival fibroblasts.

Scarring, which occurs in essentially all adult tissue, is characterized by the excessive production and remodeling of extracellular matrix by α-smooth muscle actin (SMA)–expressing myofibroblasts located within connective tissue. Excessive scarring can cause organ failure and death. Oral gingivae do not scar. Compared to dermal fibroblasts, gingival fibroblasts are less responsive to transforming growth factor β (TGFβ) due to the reduced expression, due to the reduced expression and activity of focal adhesion kinase (FAK) by this cell type. Here we show that, compared with dermal fibroblasts, gingival fibroblasts show reduced expression of miR-218. Introduction of pre–miR-218 into gingival fibroblasts elevates FAK expression and, via a FAK/src-dependent mechanism, results in the ability of TGFβ to induce α-SMA. The deubiquitinase cezanne is a direct target of miR-218 and has increased expression in gingival fibroblasts compared with dermal fibroblasts. Knockdown of cezanne in gingival fibroblasts increases FAK expression and causes TGFβ to induce α-smooth muscle actin (α-SMA). These results suggest that miR-218 regulates the ability of TGFβ to induce myofibroblast differentiation in fibroblasts via cezanne/FAK.

Cellular proliferation markers in peripheral and central fibromas: a comparative study

OBJECTIVE

To perform a comparative study of the cellular proliferation in the peripheral and central fibromas.

MATERIAL AND METHODS

Immunohistochemistry for PCNA and the AgNOR technique were performed in 9 cases of peripheral odontogenic fibroma (POF), in 4 cases of odontogenic fibroma (OdF), in 8 cases of peripheral ossifying fibroma (PEOF) and 7 cases of ossifying fibroma (OsF). The Kruskal-Wallis and Mann-Whitney tests were used for the statistical analyses.

RESULTS

Mesenchymal component of the central lesions presented a higher mean number of AgNOR per nucleus and PCNA index than did the peripheral lesions (P≤0.05). The mean number of AgNOR per nucleus in the epithelial component proved to be higher in the OdF than in the POF (P≤0.05). The mesenchymal and epithelial components presented similar mean numbers of AgNOR per nucleus and PCNA index in the OdF, as well as a similar mean number of AgNOR per nucleus in the POF.

CONCLUSIONS

The mesenchymal component may well play a role in the differences between the biological behaviour of the central lesions as compared to the peripheral lesions. Moreover, considering that the epithelial and mesenchymal components in odontogenic fibromas presented a similar proliferation index, more research is warranted to understand the true role of the epithelial components, which are believed to be inactive in nature, as well as in the development and biological behaviour of these lesions.

Myofibroblasts and transforming growth factor-beta1 in reactive gingival overgrowths

Objectives

The purpose of this study was to evaluate the oral health-related quality of life of patients treated with implant-supported mandibular overdentures and to compare the attachment systems used.

Material and Methods

The presence of myofibroblasts as well as transforming growth factor-beta1 was examined in twenty cases of fibrous epulis and 22 ossifying fibrous epulis, using immunohistochemistry.

Results

Myofibroblasts positive for alpha smooth muscle actin and vimentin but negative to desmin were found in 20% and 45% in fibrous epulis and ossifying fibrous epulis, respectively. Myofibroblasts were distributed in areas with and without inflammatory infiltration and their presence in inflammatory areas was not related with the degree of inflammatory infiltration. A percentage of 21 - 60% of fibroblasts and chronic inflammatory cells expressed transforming growth factor-beta1 in all cases.

Conclusions

These data suggest that transforming growth factor-beta1 and myofibroblasts contribute to the formation of collagenous connective tissue in fibrous epulis and ossifying fibrous epulis. Myofibroblasts are mainly presented in ossifying fibrous epulis than in fibrous epulis. It seems to be no relationship between the presence of myofibroblasts and the degree of inflammatory infiltration of the lesions.