Connective tissue growth factor in drug-induced gingival overgrowth

Molecular and clinical aspects of drug-induced gingival overgrowth

Drug-induced gingival overgrowth is a tissue-specific condition and is estimated to affect approximately one million North Americans. Lesions occur principally as side-effects from phenytoin, nifedipine, or ciclosporin therapy in approximately half of the people who take these agents. Due to new indications for these drugs, their use continues to grow. Here, we review the molecular and cellular characteristics of human gingival overgrowth lesions and highlight how they differ considerably as a function of the causative drug. Analyses of molecular signaling pathways in cultured human gingival fibroblasts have provided evidence for their unique aspects compared with fibroblasts from the lung and kidney. These findings provide insights into both the basis for tissue specificity and into possible therapeutic opportunities which are reviewed here. Although ciclosporin-induced gingival overgrowth lesions exhibit principally the presence of inflammation and little fibrosis, nifedipine- and especially phenytoin-induced lesions are highly fibrotic. The increased expression of markers of gingival fibrosis, particularly CCN2 [also known as connective tissue growth factor (CTGF)], markers of epithelial to mesenchymal transition, and more recently periostin and members of the lysyl oxidase family of enzymes have been documented in phenytoin or nifedipine lesions. Some oral fibrotic conditions such as leukoplakia and oral submucous fibrosis, after subsequent additional genetic damage, can develop into oral cancer. Since many pathways are shared, the study of gingival fibrosis and comparisons with characteristics and molecular drivers of oral cancer would likely enhance understandings and functional roles of molecular drivers of these oral pathologies.

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.

Increased and correlated expression of connective tissue growth factor and transforming growth factor beta 1 in surgically removed periodontal tissues with chronic periodontitis

BACKGROUND AND OBJECTIVE

Both gingival tissue destruction and regeneration are associated with chronic periodontitis, although the former overwhelms the latter. Studies have shown that transforming growth factor beta 1 (TGF-β1), a growth factor largely involved in tissue regeneration and remodeling, is upregulated in chronic periodontitis. However, the gingival expression of connective tissue growth factor (CTGF or CCN2), a TGF-β1-upregulated gene, in patients with periodontitis remains undetermined. Although both CTGF/CCN2 and TGF-b1 increase the production of extracellular matrix, they have many different biological functions. Therefore, it is important to delineate the impact of periodontitis on gingival CTGF/CCN2 expression.

MATERIAL AND METHODS

Periodontal tissue specimens were collected from seven individuals without periodontitis (group 1) and from 14 with periodontitis (group 2). The expression of CTGF and TGFβ1 mRNAs were quantified using real-time PCR.

RESULTS

Analysis using the nonparametric Mann-Whitney U-test showed that the levels of expression of both CTGF/CCN2 and TGFβ1 mRNAs were significantly increased in individuals with periodontitis compared with individuals without periodontitis. Furthermore, analysis using a nonparametric correlation (Spearman r) test showed a positive correlation between TGFβ1 and CTGF/CCN2 mRNAs.

CONCLUSION

The gingival expression levels of CTGF/CCN2 and TGFβ1 mRNAs in individuals with periodontitis are upregulated and correlated.

Effects of topical phenytoin on nasal wound healing after mechanical trauma: An experimental study

OBJECTIVES/HYPOTHESIS

Impaired postoperative wound healing is the second most common morbidity after synechia formation in endoscopic sinus surgery. The aim of this experimental study was to investigate the potential effects of topical phenytoin on wound healing after nasal mucosal trauma in rats.

STUDY DESIGN

An experimental study at the Inonu University Faculty of Medicine.

METHODS

Twenty-four rats were randomized into three groups: 1) phenytoin group (n = 8), 2) control group (n = 8), and 3) vehicle group (n = 8). After damaging the right nasal cavity, in the phenytoin group, 1% topical phenytoin cream was applied for 7 days. The rats in the control group did not receive any treatment. The vehicle group was treated with daily topical cold cream for 1 week. The rats were sacrificed at the end, and the nasal cavities were excised. Tissue edema and inflammatory cell infiltration were compared among the groups. Additionally, proliferating cell nuclear antigen (PCNA) and cluster of differentiation 31 (CD31) immunoexpression levels were evaluated. Furthermore, in biochemical analysis, the tissue levels of vascular endothelial growth factor and (EGF) of the groups were investigated.

RESULTS

In the phenytoin group, tissue edema and inflammatory cell infiltration were significantly decreased, and PCNA and CD31 immunoexpression levels were more prominent (P < .001) and the tissue EGF levels were significantly higher (P < .01).

CONCLUSIONS

Topical phenytoin treatment may alter the nasal wound healing after mechanical trauma. The potential beneficial effects of topical phenytoin on nasal mucosa should be investigated by further experimental and human trials.

LEVEL OF EVIDENCE

NA.

Nifedipine induces periostin expression in gingival fibroblasts through TGF-beta

Gingival enlargement is a fibrotic condition that can arise from systemic administration of the dihydropyridine calcium channel blocker nifedipine. Periostin, a transforming growth factor-beta (TGF-β)-inducible matricellular protein, has been associated with fibrosis in numerous tissues, but its expression has never been examined in nifedipine-influenced gingival enlargement (NIGE). The objective of this study was to assess if periostin up-regulation is associated with NIGE and whether nifedipine induces periostin expression in gingival fibroblasts. In NIGE tissue (n = 6), periostin is overexpressed in the gingival connective tissue compared with healthy control tissue (n = 6). The transcription factor p-SMAD2/3, which is associated with canonical TGF-β signaling, localizes to the nuclei in both HGFs and oral epithelial cells in NIGE tissues, but not in control healthy tissue. In vitro culture of HGFs with 30 and 100 ng/mL of nifedipine significantly increased periostin mRNA and protein levels, which correlated with increased levels of active TGF-β and increased phosphorylation and nuclear localization of SMAD3. Blocking of canonical TGF-β signaling through inhibition of the TGF-β receptor I with SB431542 significantly reduced nifedipine-induced SMAD3 phosphorylation and periostin expression. Our results demonstrate that nifedipine up-regulates periostin in HGFs in a TGF-β-dependent manner.

Requirement for active glycogen synthase kinase-3β in TGF-β1 upregulation of connective tissue growth factor (CCN2/CTGF) levels in human gingival fibroblasts

Connective tissue growth factor (CCN2/CTGF) mediates transforming growth factor-β (TGF-β)-induced fibrosis. Drug-induced gingival overgrowth is tissue specific. Here the role of the phosphoinositol 3-kinase (PI3K) pathway in mediating TGF-β1-stimulated CCN2/CTGF expression in primary human adult gingival fibroblasts and human adult lung fibroblasts was compared. Data indicate that PI3K inhibitors attenuate upregulation of TGF-β1-induced CCN2/CTGF expression in human gingival fibroblasts independent of reducing JNK MAP kinase activation. Pharmacologic inhibitors and small interfering (si)RNA-mediated knockdown studies indicate that calcium-dependent isoforms and an atypical isoform of protein kinase C (PKC-δ) do not mediate TGF-β1-stimulated CCN2/CTGF expression in gingival fibroblasts. As glycogen synthase kinase-3β (GSK-3β) can undergo phosphorylation by the PI3K/pathway, the effects of GSK-3β inhibitor kenpaullone and siRNA knockdown were investigated. Data in gingival fibroblasts indicate that kenpaullone attenuates TGF-β1-mediated CCN2/CTGF expression. Activation of the Wnt canonical pathways with Wnt3a, which inhibits GSK-3β, similarly inhibits TGF-β1-stimulated CCN2/CTGF expression. In contrast, inhibition of GSK-3β by Wnt3a does not inhibit, but modestly stimulates, CCN2/CTGF levels in primary human adult lung fibroblasts and is β-catenin dependent, consistent with previous studies performed in other cell models. These data identify a novel pathway in gingival fibroblasts in which inhibition of GSK-3β attenuates CCN2/CTGF expression. In adult lung fibroblasts inhibition of GSK-3β modestly stimulates TGF-β1-regulated CCN2/CTGF expression. These studies have potential clinical relevance to the tissue specificity of drug-induced gingival overgrowth.

The possible potential therapeutic targets for drug induced gingival overgrowth

Gingival overgrowth is a side effect of certain medications. The most fibrotic drug-induced lesions develop in response to therapy with phenytoin, the least fibrotic lesions are caused by cyclosporin A, and the intermediate fibrosis occurs in nifedipine-induced gingival overgrowth. Fibrosis is one of the largest groups of diseases for which there is no therapy but is believed to occur because of a persistent tissue repair program. During connective tissue repair, activated gingival fibroblasts synthesize and remodel newly created extracellular matrix. Proteins such as transforming growth factor (TGF), endothelin-1 (ET-1), angiotensin II (Ang II), connective tissue growth factor (CCN2/CTGF), insulin-like growth factor (IGF), and platelet-derived growth factor (PDGF) appear to act in a network that contributes to the development of gingival fibrosis. Since inflammation is the prerequisite for gingival overgrowth, mast cells and its protease enzymes also play a vital role in the pathogenesis of gingival fibrosis. Drugs targeting these proteins are currently under consideration as antifibrotic treatments. This review summarizes recent observations concerning the contribution of TGF-β, CTGF, IGF, PDGF, ET-1, Ang II, and mast cell chymase and tryptase enzymes to fibroblast activation in gingival fibrosis and the potential utility of agents blocking these proteins in affecting the outcome of drug-induced gingival overgrowth.

Influence of mast cells in drug-induced gingival overgrowth

Mast cells (MCs) are multifunctional effector cells that were originally thought to be involved in allergic disorders. Now it is known that they contain an array of mediators with a multitude of effects on many other cells. MCs have become a recent concern in drug-induced gingival overgrowth (DIGO), an unwanted outcome of systemic medication. Most of the studies have confirmed the significant presence of inflammation as a prerequisite for the overgrowth to occur. The inflammatory changes within the gingival tissue appear to influence the interaction between the inducing drug and the fibroblast activity. The development of antibodies to MC-specific enzymes, tryptase and chymase, has facilitated the study of mast cells in DIGO. Many immunohistochemical studies involving MCs have been conducted; as a result, DIGO tissues are found to have increased the number of MCs in the gingiva, especially in the area of fibrosis. At the cellular level, gingival fibrogenesis is initiated by several mediators which induce the recruitment of a large number of inflammatory cells, including MCs. The purpose of this paper is to access the roles played by MCs in gingival overgrowth to hypothesize a relationship between these highly specialized cells in the pathogenesis of DIGO.

Phenytoin-induced gingival overgrowth

Gingival overgrowth is a common adverse effect of therapy with Phenytoin, having important medical and cosmetic implications. Poor periodontal hygiene is an important risk factor for severity of Phenytoin-induced gingival overgrowth (PIGO), which is a time-dependent process. There is complex interplay of altered fibroblast biology, connective tissue turnover, inflammatory processes, and growth factors on a background of genetic susceptibility to produce increase in various components of interstitial matrix in PIGO tissue. Treatment options have included change of PHT to another anti-seizure drug, measures to improve periodontal hygiene and gingivectomy. There is conclusive evidence that folic acid supplementation significantly decreases the incidence of PIGO.

Recombinant lysyl oxidase propeptide protein inhibits growth and promotes apoptosis of pre-existing murine breast cancer xenografts

Lysyl oxidase propeptide (LOX-PP) ectopic overexpression inhibits the growth of cancer xenografts. Here the ability and mode of action of purified recombinant LOX-PP (rLOX-PP) protein to inhibit the growth of pre-existing xenografts was determined. Experimental approaches employed were direct intratumoral injection (i.t.) of rLOX-PP protein into murine breast cancer NF639 xenografts, and application of a slow release formulation of rLOX-PP implanted adjacent to tumors in NCR nu/nu mice (n = 10). Tumors were monitored for growth, and after sacrifice were subjected to immunohistochemical and Western blot analyses for several markers of proliferation, apoptosis, and for rLOX-PP itself. Direct i.t. injection of rLOX-PP significantly reduced tumor volume on days 20, 22 and 25 and tumor weight at harvest on day 25 by 30% compared to control. Implantation of beads preloaded with 35 micrograms rLOX-PP (n = 10) in vivo reduced tumor volume and weight at sacrifice when compared to empty beads (p<0.05). A 30% reduction of tumor volume on days 22 and 25 (p<0.05) and final tumor weight on day 25 (p<0.05) were observed with a reduced tumor growth rate of 60% after implantation. rLOX-PP significantly reduced the expression of proliferation markers and Erk1/2 MAP kinase activation, while prominent increases in apoptosis markers were observed. rLOX-PP was detected by immunohistochemistry in harvested rLOX-PP tumors, but not in controls. Data provide pre-clinical findings that support proof of principle for the therapeutic anti-cancer potential of rLOX-PP protein formulations.

Effect of cannabidiol on human gingival fibroblast extracellular matrix metabolism: MMP production and activity, and production of fibronectin and transforming growth factor β

BACKGROUND AND OBJECTIVE

Marijuana (Cannabis sativa) use may be associated with gingival enlargement, resembling that caused by phenytoin. Cannabidiol (CBD), a nonpsychotropic Cannabis derivative, is structurally similar to phenytoin. While there are many reports on effects of phenytoin on human gingival fibroblasts, there is no information on effects of Cannabis components on these cells. The objective of this study was to determine effects of CBD on human gingival fibroblast fibrogenic and matrix-degrading activities.

MATERIAL AND METHODS

Fibroblasts were incubated with CBD in serum-free medium for 1-6 d. The effect of CBD on cell viability was determined by measuring activity of a mitochondrial enzyme. The fibrogenic molecule transforming growth factor β and the extracellular matrix molecule fibronectin were measured by ELISA. Pro-MMP-1 and total MMP-2 were measured by ELISA. Activity of MMP-2 was determined via a colorimetric assay in which a detection enzyme is activated by active MMP-2. Data were analysed using ANOVA and Scheffe's F procedure for post hoc comparisons.

RESULTS

Cannabidiol had little or no significant effect on cell viability. Low CBD concentrations increased transforming growth factor β production by as much as 40% (p < 0.001), while higher concentrations decreased it by as much as 40% (p < 0.0001). Cannabidiol increased fibronectin production by as much as approximately 100% (p < 0.001). Lower CBD concentrations increased MMP production, but the highest concentrations decreased production of both MMPs (p < 0.05) and decreased MMP-2 activity (p < 0.02).

CONCLUSION

The data suggest that the CBD may promote fibrotic gingival enlargement by increasing gingival fibroblast production of transforming growth factor β and fibronectin, while decreasing MMP production and activity.

Phenytoin-induced gingival overgrowth: a review of the molecular, immune, and inflammatory features

Gingival overgrowth (GO) is a side effect associated with some distinct classes of drugs, such as anticonvulsants, immunosuppressant, and calcium channel blockers. GO is characterized by the accumulation of extracellular matrix in gingival connective tissues, particularly collagenous components, with varying degrees of inflammation. One of the main drugs associated with GO is the antiepileptic phenytoin, which affects gingival tissues by altering extracellular matrix metabolism. Nevertheless, the pathogenesis of such drug-induced GO remains fulfilled by some contradictory findings. This paper aims to present the most relevant studies regarding the molecular, immune, and inflammatory aspects of phenytoin-induced gingival overgrowth.

Loss of basement membrane integrity in human gingival overgrowth

Gingival overgrowth tissues have thickened connective tissue stroma, sometimes accompanied by the increased presence of collagen fibers, thickened epithelia, and elongated rete pegs. We have previously shown that expression of CCN2, also known as connective tissue growth factor (CTGF), correlates positively with the degree of gingival fibrosis, and that markers of epithelial to mesenchymal transition (EMT) are characteristic of all drug-induced forms of gingival overgrowth. Here we experimentally evaluate whether increased degradation of the basement membrane and apparent invasion of the underlying stroma by epithelial cells could be observed in human gingival overgrowth tissues. Tissues from 20 different individuals with human gingival overgrowth and 15 non-overgrowth samples were evaluated by histological analyses and by immunohistochemistry assays of basement membrane proteins. The results demonstrate that there are significantly higher numbers of basement membrane discontinuities in overgrowth tissues, sometimes containing epithelial-like cells. Disrupted basal membrane structure in gingival overgrowth tissues is accompanied by a discontinuous collagen type IV expression pattern and decreased laminin 5. These findings provide new additional support for the hypothesis that epithelial plasticity and EMT promote gingival overgrowth, resulting in compromised basal membrane structure and increased interactions between epithelial and connective tissue layers that contribute to fibrotic pathology.

Mechanical tension increases CCN2/CTGF expression and proliferation in gingival fibroblasts via a TGFβ-dependent mechanism

Unlike skin, oral gingival do not scar in response to tissue injury. Fibroblasts, the cell type responsible for connective tissue repair and scarring, are exposed to mechanical tension during normal and pathological conditions including wound healing and fibrogenesis. Understanding how human gingival fibroblasts respond to mechanical tension is likely to yield valuable insights not only into gingival function but also into the molecular basis of scarless repair. CCN2/connective tissue growth factor is potently induced in fibroblasts during tissue repair and fibrogenesis. We subjected gingival fibroblasts to cyclical strain (up to 72 hours) using the Flexercell system and showed that CCN2 mRNA and protein was induced by strain. Strain caused the rapid activation of latent TGFβ, in a fashion that was reduced by blebbistatin and FAK/src inhibition, and the induction of endothelin (ET-1) mRNA and protein expression. Strain did not cause induction of α-smooth muscle actin or collagen type I mRNAs (proteins promoting scarring); but induced a cohort of pro-proliferative mRNAs and cell proliferation. Compared to dermal fibroblasts, gingival fibroblasts showed reduced ability to respond to TGFβ by inducing fibrogenic mRNAs; addition of ET-1 rescued this phenotype. Pharmacological inhibition of the TGFβ type I (ALK5) receptor, the endothelin A/B receptors and FAK/src significantly reduced the induction of CCN2 and pro-proliferative mRNAs and cell proliferation. Controlling TGFβ, ET-1 and FAK/src activity may be useful in controlling responses to mechanical strain in the gingiva and may be of value in controlling fibroproliferative conditions such as gingival hyperplasia; controlling ET-1 may be of benefit in controlling scarring in response to injury in the skin.

Cyclosporin A-induced gingival overgrowth is not associated with myofibroblast transdifferentiation

Cyclosporin A (CyA) induces gingival overgrowth via its stimulatory effects on expression of transforming growth factor-beta1 (TGF-beta1) and collagen. It is not known whether CyA has a direct effect on gingival fibroblasts or induces its effect indirectly via stimulation of myofibroblast transdifferentiation. The present study was undertaken to examine the in vivo and in vitro effect of CyA on myofibroblast transdifferentiation. Rats were treated for 60 days with a daily subcutaneous injection of CyA, and the gingival overgrowth tissue was analyzed by immunohistochemistry. In vitro, fibroblasts from normal gingiva (NG) were cultured in the presence of different concentrations of CyA, and subjected to semi-quantitative reverse transcriptase-polymerase chain reaction and western blot. Although CyA treatment stimulated TGF-beta1 expression by NG fibroblasts, it lacked to induce expression and production of isoform alpha of smooth muscle actin (alpha-SMA), the specific myofibroblast marker. The expression levels of connective tissue growth factor (CTGF), which has been considered a key molecule to promote the transdifferentiation of myofibroblasts via TGF-beta1 activation, were unaffected by CyA. Our results demonstrate that CyA-induced gingival overgrowth is not associated with activation of myofibroblast transdifferentiation, since CyA is not capable to increase CTGF expression.

Lysyl oxidase-like-2 (LOXL2) is a major isoform in chondrocytes and is critically required for differentiation

The lysyl oxidase family is made up of five members: lysyl oxidase (LOX) and lysyl oxidase-like 1-4 (LOXL1-LOXL4). All members share conserved C-terminal catalytic domains that provide for lysyl oxidase or lysyl oxidase-like enzyme activity; and more divergent propeptide regions. LOX family enzyme activities catalyze the final enzymatic conversion required for the formation of normal biosynthetic collagen and elastin cross-links. The importance of lysyl oxidase enzyme activity to normal bone development has long been appreciated, but regulation and roles for specific LOX isoforms in bone formation in vivo is largely unexplored. Fracture healing recapitulates aspects of endochondral bone development. The present study first investigated the expression of all LOX isoforms in fracture healing. A remarkable coincidence of LOXL2 expression with the chondrogenic phase of fracture healing was found, prompting more detailed analyses of LOXL2 expression in normal growth plates, and LOXL2 expression and function in developing ATDC5 chondrogenic cells. Data show that LOXL2 is expressed by pre-hypertrophic and hypertrophic chondrocytes in vivo, and that LOXL2 expression is regulated in vitro as a function of chondrocyte differentiation. Moreover, LOXL2 knockdown studies in vitro show that LOXL2 expression is required for ATDC5 chondrocyte cell line differentiation through regulation of SNAIL and SOX9, important transcription factors that control chondrocyte differentiation. Taken together, data provide evidence that LOXL2, like LOX, is a multifunctional protein. LOXL2 promotes chondrocyte differentiation by mechanisms that are likely to include roles as both a regulator and an effector of chondrocyte differentiation.

ALK5 inhibition blocks TGFß-induced CCN2 expression in gingival fibroblasts

Connective tissue growth factor (CCN2/CTGF) is not normally expressed in gingival fibroblasts, but is induced by the potent profibrotic cytokine TGFβ and is overexpressed in gingival fibrosis. Since CCN2 is a marker and mediator of fibrosis, targeting CCN2 expression in gingival fibroblasts may provide new insights into the future development of novel therapeutic opportunities to treat oral fibrosis. Herein we used real-time polymerase chain-reaction, Western blot, and indirect immunofluorescence analysis to evaluate whether SB-431542, a specific pharmacological inhibitor of TGFβ type I receptor (ALK5), blocks the ability of TGFβ to induce CCN2 mRNA and protein expression in human gingival fibroblasts. Our results indicate that CCN2 mRNA and protein are induced by TGFβ in gingival fibroblasts in a SB-431542-sensitive fashion. These results suggest that blocking ALK5 may be useful in blocking the profibrotic effects of TGFβ in gingival fibroblasts.

Epithelial to mesenchymal transition in gingival overgrowth

Epithelial to mesenchymal transition (EMT) occurs normally in development. In pathology, EMT drives cancer and fibrosis. Medication with phenytoin, nifedipine, and cyclosporine-A often causes gingival overgrowth. Based partly on the histopathology of gingival overgrowth, the present study investigates the hypothesis that EMT could contribute to its development. We found that phenytoin-induced human gingival overgrowth tissues, the most fibrotic drug-induced variety, contain diminished epithelial E-cadherin expression, whereas fibroblast-specific protein-1 (FSP-1) and alphavbeta6 integrin levels are up-regulated. In connective tissue stroma, fibronectin and alternatively spliced fibronectin extra type III domain A (FN-ED-A) levels are increased in overgrowth lesions. Transforming growth factor (TGF)-beta1 treatment of primary human gingival epithelial cells cultured in transwell plates resulted in inhibited barrier function as determined by reduced electrical resistance, paracellular permeability assays, and cell surface E-cadherin expression. Moreover, TGF-beta1 altered the expression of other markers of EMT determined at the mRNA and protein levels: E-cadherin decreased, whereas SLUG, fibronectin, matrix metalloproteinase (MMP)2, MMP9, and MMP13 increased. Nifedipine- and cyclosporine A-induced gingival overgrowth tissues similarly contain diminished E-cadherin and elevated levels of FSP-1 and fibronectin, but normal levels of alphavbeta6 integrin. In summary, data in vitro support that human gingival epithelial cells undergo functional and gene expression changes consistent with EMT in response to TGF-beta1, and in vivo studies show that important EMT markers occur in clinical gingival overgrowth tissues. These findings support the hypothesis that EMT likely occurs in drug-induced gingival overgrowth.

Flutamide inhibits nifedipine- and interleukin-1 beta-induced collagen overproduction in gingival fibroblasts

BACKGROUND AND OBJECTIVE

To understand the role of the androgen receptor in gingival overgrowth, the effects of flutamide on interleukin-1 beta- and nifedipine-induced gene expression of connective tissue growth factor (CTGF/CCN2) and collagen production in gingival fibroblasts were examined.

MATERIAL AND METHODS

Gingival fibroblasts from healthy subjects and patients with dihydropyridine-induced gingival overgrowth (DIGO) were used. Confluent cells were treated with nifedipine, interleukin-1 beta or both. The mRNA expression was examined using real-time polymerase chain reaction, and the concentration of total soluble collagen in conditioned media was analysed by Sircol Collagen Assay. In addition, the protein expressions of androgen receptor, CTGF/CCN2 and type I collagen in gingival tissue were determined by western blot.

RESULTS

Interleukin-1 beta was more potent than nifedipine in stimulating CTGF/CCN2 and procollagen alpha1(I) mRNA expression, and there was an additive effect of the two drugs. Healthy cells exhibited an equal or stronger response of procollagen alpha1(I) than those with DIGO, but DIGO cells displayed a stronger response in the secretion of soluble collagen in the same conditions. Flutamide, an androgen receptor antagonist, inhibited stimulation by nifedipine or interleukin-1 beta. Additionally, the protein expressions of androgen receptor and type I collagen were higher in DIGO gingival tissue than those in healthy gingival tissue.

CONCLUSION

The data suggest that both nifedipine and interleukin-1 beta play an important role in DIGO via androgen receptor upregulation and that gingival overgrowth is mainly due to collagen accumulation. Flutamide decreases the gene expression and protein production of collagen from dihydropyridine-induced overgrowth cells.

Cyclosporin A and phenytoin modulate inflammatory responses

Gingival overgrowth is a common side-effect of administration of the immunosuppressant cyclosporin A and the anti-epileptic drug phenytoin. While cyclosporin-induced gingival overgrowth is often accompanied by gingival inflammation, phenytoin-induced gingival overgrowth usually forms fibrotic lesions. To determine whether these drugs alter the inflammatory responses of gingival fibroblasts, we investigated the effects of cyclosporin and phenytoin on Toll-like receptor (TLR)-mediated responses to microbial components. In Chinese hamster ovary reporter cell lines, cyclosporin alone triggered signaling, whereas phenytoin down-regulated signaling induced by the TLR2 or TLR4 ligand. In human gingival fibroblasts, cyclosporin alone did not induce evident inflammatory responses, but augmented the expression of CD54 and the production of interleukin (IL)-6 and IL-8 induced by TLR ligands, whereas phenytoin attenuated those responses. Cyclosporin also augmented CD54 expression in gingiva of mice injected with lipopolysaccharide. These results indicated that cyclosporin positively and phenytoin negatively modulated inflammatory responses of human gingival fibroblasts.

Differential gene and protein expression of tissue inhibitors of metalloproteinases (TIMP)-3 and TIMP-4 in gingival tissues from drug induced gingival overgrowth

OBJECTIVES

The purpose of this study was to analyse mRNA expression and protein localization of tissue inhibitors of metalloproteinases (TIMP)-3 and TIMP-4 in gingival tissues removed from drug (calcium-channel blocker) induced gingival overgrowth and periodontitis patients.

DESIGN

Employing RT-PCR, we evaluated TIMP-3 and TIMP-4 mRNA levels of 20 human gingival tissue samples taken from patients suffering gingival overgrowth (GO) and periodontitis (P). Then, using immunohistochemistry we investigated the TIMP-3 and TIMP-4 protein localization of five sample tissues from each group.

RESULTS

TIMP-4 mRNA levels in GO-gingiva tended to be lower than in P-gingiva but the results differed little (p = 0.22). Varying degrees of inflammation in the protein localization of TIMP-3 and TIMP-4 were found. TIMP-4 immunoreactivity (IR) was weak in the endothelial cells, fibroblasts, epithelial basal and parabasal cells while the degree of inflammation differed as well. TIMP-3 and TIMP-4 IR in inflammatory cells, including lymphocytes, plasma cells, and macrophages, were faint and intense respectively. For P-gingiva, both TIMP-3 and TIMP-4 IR expression was weak in the endothelial cells, fibroblasts, basal and parabasal epithelial layers. Expression of TIMP-3 was faint in the inflammatory cells, whereas TIMP-4 IR was strong.

CONCLUSION

Our findings suggest that TIMP-3 and TIMP-4 expression differs in GO and P-gingival tissues, both of which are potentially involved in pathogenesis.

Effects of cyclosporin, phenytoin, and nifedipine on the synthesis and degradation of gingival collagen in tufted capuchin monkeys (Cebus apella): histochemical and MMP-1 and -2 and collagen I gene expression analyses

BACKGROUND

The purpose of this experimental study was to evaluate the collagen fiber distribution histologically after phenytoin, cyclosporin, or nifedipine therapy and to correlate it with collagen I and matrix metalloproteinase (MMP)-1 and -2 gene expression levels.

METHODS

Gingival samples from the canine area were obtained from 12 male monkeys (Cebus apella). The mesial part of each sample was assessed by reverse transcription-polymerase chain reaction, whereas the distal part was processed histologically for picrosirius red and hematoxylin and eosin stainings, as well as for collagen IV immunostaining. One week after the first biopsy, the animals were assigned to three groups that received daily oral dosages of cyclosporin, phenytoin, or nifedipine for 120 days. Additional gingival samples were obtained on days 52 and 120 of treatment from two animals from each group on the opposite sides from the first biopsies.

RESULTS

Picrosirius red staining showed a predominance of mature collagen fibers in the control group. Conversely, there was an enlargement of areas occupied by immature collagen fibers in all groups at days 52 and 120, which was not uniform over each section. There was a general trend to lower levels of MMP-1 gene expression on day 52 and increased levels on day 120. Phenytoin led to increased levels of MMP-2 and collagen I gene expression on day 120, whereas the opposite was observed in the nifedipine group.

CONCLUSION

Cyclosporin, phenytoin, and nifedipine led to phased and drug-related gene expression patterns, resulting in impaired collagen metabolism, despite the lack of prominent clinical signs.

Transforming growth factor-beta1 (TGFbeta1) stimulates connective tissue growth factor (CCN2/CTGF) expression in human gingival fibroblasts through a RhoA-independent, Rac1/Cdc42-dependent mechanism: statins with forskolin block TGFbeta1-induced CCN2/CTGF expression

Regulation of connective tissue growth factor (CCN2/CTGF) in gingival fibroblasts is unique and may provide therapeutic opportunities to treat oral fibrotic diseases. RhoA was previously implicated in mediating the expression of CCN2/CTGF. We now present evidence that Rho family GTPases Rac1 and Cdc42 are the principal mediators of the transforming growth factor-beta1 (TGFbeta1)-stimulated expression of CCN2/CTGF in primary human gingival fibroblasts. TGFbeta1 does not stimulate RhoA activation in gingival fibroblasts, and the overexpression of dominant-negative RhoA does not reduce CCN2/CTGF expression in response to TGFbeta1. In contrast, the overexpression of dominant-negative forms of Cdc42 or Rac1 results in a dramatic reduction of CCN2/CTGF protein levels. Lovastatin and a geranylgeranyltransferase inhibitor reduce the TGFbeta1-stimulated levels of CCN2/CTGF protein by approximately 75 and 100%, respectively. We previously demonstrated that JNK1 phosphorylation by TGFbeta1 is also critical for TGFbeta1-induced CCN2/CTGF expression, and forskolin partially reduces levels of phosphorylated JNK1. Inhibition of geranylgeranyltransferase has no effect on levels of JNK phosphorylation in response to TGFbeta1 suggesting Rho-GTPases act independently of JNK1. The combination of lovastatin and forskolin results in a greater inhibitory effect than each agent alone and reduces CCN2/CTGF mRNA and protein expression by greater than 90%. This novel combination has additive inhibitory effects on the TGFbeta1-stimulated expression of CCN2/CTGF in human gingival fibroblasts through the simultaneous disruption of Rho- and JNK1-mediated pathways, respectively. This combination of available therapeutic compounds may therefore be useful in designing treatment strategies for oral fibrotic conditions in which gingival CCN2/CTGF is elevated.

Enamel matrix derivative induces connective tissue growth factor expression in human osteoblastic cells

BACKGROUND

Enamel matrix derivative (EMD) stimulates the production of transforming growth factor-beta (TGF-beta), which has been suggested to play a role in mediating the effects of EMD in periodontal tissue regeneration. Connective tissue growth factor (CTGF) is a mediator of TGF-beta and promotes cell development. The interaction between EMD and CTGF is unknown. This study explored the effects of EMD on CTGF expression in human osteoblastic cells and whether the interaction is modulated by the TGF-beta signaling pathway. Also, the roles of CTGF in cell proliferation, cell cycle progression, and mineralized nodule formation of EMD-induced osteoblastic cultures were examined.

METHODS

Human osteoblastic cells (Saos-2) were treated with 25 to 100 microg/ml EMD with or without the addition of TGF-beta inhibitor. CTGF mRNA expression was detected by reverse transcription-polymerase chain reaction (RT-PCR), and CTGF protein levels were assayed by Western blot analysis. In addition, cell cycle progression and DNA synthesis were determined by flow cytometry and 5-bromo-2'-deoxyuridine (BrdU) incorporation following EMD treatment with or without CTGF antibody. Mineralization was examined by alizarin red staining and quantified by elution with cetylpyridinium chloride.

RESULTS

Western blot and RT-PCR analysis demonstrated a dose-dependent increase of CTGF expression by EMD. EMD-induced CTGF expression was reduced significantly in the presence of TGF-beta inhibitor. Cell cycle and BrdU analysis revealed an increase in cell proliferation following EMD treatment, which was due to an increase in the percentage of cells in the G2/M phase of the cell cycle. No significant effect was found when anti-CTGF antibody was added. Conversely, mineralization was inhibited significantly in EMD-treated cultures in the presence of anti-CTGF antibody.

CONCLUSIONS

EMD stimulates CTGF expression, and the interaction is modulated via TGF-beta in osteoblastic cells. Also, CTGF affects EMD-induced osteoblastic mineralization but not cell proliferation. To our knowledge, these results provide novel insight into EMD-CTGF interaction, two biomodifiers that have therapeutic relevance to tissue engineering and regeneration.

Non-surgical periodontal treatment of cyclosporin A-induced gingival overgrowth: immunohistochemical results

AIM

The present study was planned to analyze the effects of a 12-month non-surgical periodontal treatment on histologic and immunohistochemical features of cyclosporin A (CsA)-induced gingival overgrowth (GO).

MATERIALS AND METHODS

Gingival samples were collected from 21 liver transplant subjects exhibiting CsA-induced GO prior to, and 12 months after non-surgical periodontal therapy including oral hygiene instructions, scaling and 2-month recall appointments, and also from 18 healthy control subjects. Gingival biopsy specimens were stained with hematoxylin-eosin and monoclonal antibodies for vimentin, CD3 (T-lymphocytes), CD20 (B-lymphocytes), CD34 (endothelium) and Ki-67 (fibroblasts proliferation rate), using a streptavidin-biotin-peroxidase complex method.

RESULTS

Total inflammatory cells, gingival vessels and fibroblast proliferation rate demonstrated significant reduction after non-surgical periodontal treatment (P < 0.0001) in overgrown gingiva, while B- and T-lymphocytes remained nearly unchanged (P = 0.61 and 0.33, respectively). At the 12-month evaluation no significant differences were found when comparing the gingival biopsies from CsA-treated patients and those from healthy controls (P > 0.05).

CONCLUSIONS

Control of clinical inflammation by means of non-surgical periodontal treatment results both in lowering of inflammatory infiltrate and in changes in connective tissue composition. Thus, plaque-induced inflammation would seem to modulate the drug-gingival tissue interaction.

CLINICAL RELEVANCE

A strict plaque control program play a pivotal role in the management of transplant patients exhibiting cyclosporin A-GO.

Lysyl oxidase propeptide inhibits smooth muscle cell signaling and proliferation

Lysyl oxidase is required for the normal biosynthesis and maturation of collagen and elastin. It is expressed by vascular smooth muscle cells, and its increased expression has been previously found in atherosclerosis and in models of balloon angioplasty. The lysyl oxidase propeptide (LOX-PP) has more recently been found to have biological activity as a tumor suppressor, and it inhibits Erk1/2 Map kinase activation. We reasoned that LOX-PP may have functions in normal non-transformed cells. We, therefore, investigated its effects on smooth muscle cells, focusing on important biological processes mediated by Erk1/2-dependent signaling pathways including proliferation and matrix metalloproteinase-9 (MMP-9) expression. In addition, we investigated whether evidence for accumulation of LOX-PP could be found in vivo in a femoral artery injury model. Recombinant LOX-PP was expressed and purified, and was found to inhibit primary rat aorta smooth muscle cell proliferation and DNA synthesis by more than 50%. TNF-alpha-stimulated MMP-9 expression and Erk1/2 activation were both significantly inhibited by LOX-PP. Immunohistochemistry studies carried out with affinity purified anti-LOX-PP antibody showed that LOX-PP epitopes were expressed at elevated levels in vascular lesions of injured arteries. These novel data suggest that LOX-PP may provide a feedback control mechanism that serves to inhibit properties associated with the development of vascular pathology.

Stimulation of cells derived from nifedipine-induced gingival overgrowth with Porphyromonas gingivalis, lipopolysaccharide, and interleukin-1beta

The purpose of this study was to clarify the main contributory factor of nifedipine-induced gingival overgrowth either by Porphyromonas gingivalis lipopolysaccharide (Pg-LPS) or interleukin-1beta (IL-1beta). Human gingival fibroblasts from healthy tissues and nifedipine-induced gingival overgrowth tissues were stimulated with nifedipine, IL-1beta, Escherichia coli lipopolysaccharide (Ec-LPS), and Pg-LPS, and the gene expressions were analyzed by RT-PCR. Analysis of the data showed no strong evidence of a synergistic effect of nifedipine and Pg-LPS on IL-6, connective tissue growth factor (CTGF), and type 1 collagen gene expression of either healthy cells or nifedipine-induced gingival overgrowth cells. Among the three stimulants--IL-1beta, Pg-LPS, and Ec-LPS--androgen receptor and IL-6 gene expressions in both the healthy and nifedipine-induced gingival overgrowth groups were strongly up-regulated by the presence of IL-1beta only. Furthermore, the responses to IL-1beta in the nifedipine-induced gingival overgrowth group were stronger than those of the healthy group. It can be concluded that IL-1beta is an important mediator responsible for the higher IL-6 and androgen receptor expression of nifedipine-induced gingival overgrowth cells.

Apoptosis in gingival overgrowth tissues

Variations in the balance between cell proliferation and apoptosis could contribute to the etiology of gingival overgrowth. The aim of this study was to test the hypothesis that, in fibrotic gingival lesions, fibroblast proliferation is stimulated and apoptosis is decreased. Apoptotic index, caspase 3 expression, the proliferative index, FOXO1 expression, and histological inflammation were measured in situ. Analysis of data showed that apoptosis decreased in all forms of gingival overgrowth examined (p < 0.05), and inflammation caused a small but significant increase compared with non-inflamed tissues (p < 0.05). The greatest decrease of apoptosis occurred in the most fibrotic tissues. Cell proliferation was elevated in all forms of gingival overgrowth tested, independent of inflammation (p < 0.05). To identify potential mechanisms of transcriptional regulation of apoptosis, we assessed FOXO1 and caspase 3 expression levels and found them to correlate well with diminished apoptosis. Analysis of data suggests that increased fibroblast proliferation and a simultaneous decrease in apoptosis contribute to gingival overgrowth.

Oral manifestations of Wegener's granulomatosis: a report of three cases and a literature review

BACKGROUND

Hyperplastic granular gingivitis or "strawberry gingivitis" is a rare manifestation of Wegener's granulomatosis (WG), but it is nearly pathognomonic for this multisystem autoimmune vasculitis. The dentist may be the first health care professional to see patients with symptoms and findings of this condition. Early diagnosis and treatment is the most important factor in the management of this potentially fatal disease.

METHODS

The authors present three case reports that demonstrate the disease spectrum and conducted a literature review focused on current understanding of this disease.

RESULTS

The first patient had only the classic gingival manifestations of the disease. The second patient had simultaneous typical gingival lesions, as well as dermatologic findings. The third patient had an atypical oral presentation of aphthous ulcers and erythematous gingiva, as well as respiratory and genital involvement. Reaching a definitive diagnosis sometimes is challenging owing to the subtle onset of the disease and variable clinical and laboratory findings.

CONCLUSION AND CLINICAL IMPLICATIONS

Clinicians should be familiar with the broad variety of oral and systemic components of WG, as well as strategies to facilitate prompt disease recognition and to provide continued oral health care to these medically complex patients.

Expression of fibronectin-binding integrins in gingival epithelium in drug-induced gingival overgrowth

BACKGROUND AND OBJECTIVE

Gingival overgrowth is a side-effect of nifedipine and cyclosporin medications. Integrins are transmembrane glycoproteins that mediate cell adhesion, regulate cell proliferation and participate in the regulation of tissue fibrosis. The aim of this study was to investigate whether expression of epithelial cell integrins is linked to the development of drug-induced gingival overgrowth.

MATERIAL AND METHODS

Human gingival biopsies of patients taking nifedipine, cyclosporin, or a combination of both medications, were used. Expression of the alpha5beta1, alphavbeta1 and alphavbeta6 integrins, and of cellular extra domain A of fibronectin, was localized in frozen sections using immunohistochemistry.

RESULTS

The activated conformation of the beta1, alpha5beta1 and alphavbeta6 integrins were more frequently expressed in distinct locations in the oral epithelium in the combined drug group. Cellular extra domain A of fibronectin, a ligand for both alpha5beta1 and alphavbeta6 integrins, was expressed within the connective tissue of all groups. It was also expressed around the basal keratinocytes of the control, nifedipine and cyclosporin-induced gingival overgrowth groups, but not in the combined medication group. No relationship between the presence of inflammation and integrin expression was found.

CONCLUSION

The results indicate that expression of certain integrins is up-regulated in the epithelium of drug-induced gingival overgrowth where they could participate in controlling the formation of elongated rete ridges and tissue fibrosis.

Tissue-specific mechanisms for CCN2/CTGF persistence in fibrotic gingiva: interactions between cAMP and MAPK signaling pathways, and prostaglandin E2-EP3 receptor mediated activation of the c-JUN N-terminal kinase

Prostaglandin E(2) blocks transforming growth factor TGF beta1-induced CCN2/CTGF expression in lung and kidney fibroblasts. PGE(2) levels are high in gingival tissues yet CCN2/CTGF expression is elevated in fibrotic gingival overgrowth. Gingival fibroblast expression of CCN2/CTGF in the presence of PGE(2) led us to compare the regulation of CCN2/CTGF expression in fibroblasts cultured from different tissues. Data demonstrate that the TGFbeta1-induced expression of CCN2/CTGF in human lung and renal mesangial cells is inhibited by 10 nm PGE(2), whereas human gingival fibroblasts are resistant. Ten nm PGE(2) increases cAMP accumulation in lung but not gingival fibroblasts, which require 1 mum PGE(2) to elevate cAMP. Micromolar PGE(2) only slightly reduces the TGFbeta1-stimulated CCN2/CTGF levels in gingival cells. EP2 prostaglandin receptor activation with butaprost blocks the TGFbeta1-stimulated expression of CCN2/CTGF expression in lung, but not gingival, fibroblasts. In lung fibroblasts, inhibition of the TGFbeta1-stimulated CCN2/CTGF by PGE(2), butaprost, or forskolin is due to p38, ERK, and JNK MAP kinase inhibition that is cAMP-dependent. Inhibition of any two MAPKs completely blocks CCN2/CTGF expression stimulated by TGFbeta1. These data mimic the inhibitory effects of 10 nm PGE(2) and forskolin that were dependent on PKA activity. In gingival fibroblasts, the sole MAPK mediating the TGFbeta1-stimulated CCN2/CTGF expression is JNK. Whereas forskolin reduces TGFbeta1-stimulated expression of CCN2/CTGF by 35% and JNK activation in gingival fibroblasts, micromolar PGE(2)-stimulated JNK in gingival fibroblasts and opposes the inhibitory effects of cAMP on CCN2/CTGF expression. Stimulation of the EP3 receptor with sulprostone results in a robust increase in JNK activation in these cells. Taken together, data identify two mechanisms by which TGFbeta1-stimulated CCN2/CTGF levels in human gingival fibroblasts resist down-regulation by PGE(2): (i) cAMP cross-talk with MAPK pathways is limited in gingival fibroblasts; (ii) PGE(2) activation of the EP3 prostanoid receptor stimulates the activation of JNK.

Plasma and gingival crevicular fluid phenytoin concentrations as risk factors for gingival overgrowth

BACKGROUND

Gingival enlargement is one of the side effects associated with the administration of phenytoin. The mechanism by which phenytoin induces gingival enlargement is not well understood. This study was conducted to investigate the relationship between plasma and gingival crevicular fluid (GCF) phenytoin concentrations and the degree of gingival overgrowth in patients with similar gingival and plaque indices and also to determine the risk factors for gingival enlargement.

METHODS

Eighteen patients taking phenytoin in regular doses > or =6 months prior to the investigation participated in the study. Gingival enlargement was evaluated with two indices to score vertical and horizontal overgrowth. The gingival index (GI), plaque index (PI), gingival bleeding time index (GBTI), probing depth (PD), and clinical attachment level (CAL) were also evaluated. GCF and plasma phenytoin concentrations were determined by using high-performance liquid chromatography (HPLC).

RESULTS

There was no significant difference between responders and non-responders for PD, CAL, PI, GI, and GBTI. Phenytoin was detected in all of the GCF and plasma samples using the HPLC analysis method. The mean concentration of phenytoin in GCF was significantly greater than the concentration of phenytoin in plasma. No significant difference was observed for the concentration of GCF phenytoin between responders and non-responders. However, the concentration of plasma phenytoin was significantly higher in responders than non-responders.

CONCLUSION

This study showed that plasma phenytoin level appeared to be a risk factor for phenytoin-induced gingival overgrowth.

Relationship between IL-1A polymorphisms and gingival overgrowth in renal transplant recipients receiving Cyclosporin A

AIM

Levels of interleukin-1alpha (IL-1alpha) are elevated in periodontal inflammation. IL-1A gene polymorphisms are associated with inflammatory diseases. This study aimed to investigate IL-1A gene polymorphism in Cyclosporin A (CsA)-treated renal transplant patients and investigate the association between this polymorphism and gingival crevicular fluid (GCF) levels of several cytokines.

MATERIALS AND METHODS

Fifty-one renal transplant patients on CsA treatment (25 with and 26 without gingival overgrowth) and 29 healthy controls were recruited for the study. Demographic, pharmacological and periodontal parameters were recorded and gingival overgrowth was assessed.

RESULTS

Multiple regression analysis showed that genotype was significantly associated with gingival overgrowth (p=0.02). Carriage of the IL-1A (-889) T allele was strongly protective [95% confidence interval (CI): 0.046-0.77], although not significantly associated with IL-1alpha protein levels in GCF. IL-1alpha, IL-1beta and IL-8, but not IL-6, were detected in GCF of CsA-treated patients, but none of them was significantly associated with gingival overgrowth.

CONCLUSIONS

This study is the first to associate a gene polymorphism as a risk factor for CsA-induced gingival overgrowth in renal transplant patients, demonstrating that IL-1A polymorphism might alter individual susceptibility to CsA. However, there was no association between GCF cytokine levels and the presence of gingival overgrowth or patient IL-1A genotype.

Epithelial and connective tissue cell CTGF/CCN2 expression in gingival fibrosis

Gingival overgrowth is a side effect of certain medications and occurs in non-drug-induced forms either as inherited (human gingival fibromatosis) or idiopathic gingival overgrowth. The most fibrotic drug-induced lesions develop in response to therapy with phenytoin; the least fibrotic lesions are caused by cyclosporin A; and intermediate fibrosis occurs in nifedipine-induced gingival overgrowth. Connective tissue growth factor (CTGF/CCN2) expression is positively related to the degree of fibrosis in these tissues. The present study has investigated the hypothesis that CTGF/CCN2 is expressed in human gingival fibromatosis tissues and contributes to this form of non-drug-induced gingival overgrowth. Histopathology/immunohistochemistry studies showed that human gingival fibromatosis lesions are highly fibrotic, similar to phenytoin-induced lesions. Connective tissue CTGF/CCN2 levels were equivalent to the expression in phenytoin-induced gingival overgrowth. The additional novel observation was made that CTGF/CCN2 is highly expressed in the epithelium of fibrotic gingival tissues. This finding was confirmed by in situ hybridization. Real-time polymerase chain reaction (PCR) analyses of RNA extracted from drug-induced gingival overgrowth tissues for CTGF/CCN2 were fully consistent with these findings. Finally, normal primary gingival epithelial cell cultures were analysed for basal and transforming growth factor beta1 (TGF-beta1) or lysophosphatidic acid-stimulated CTGF/CCN2 expression at protein and RNA levels. These data indicate that fibrotic human gingival tissues express CTGF/CCN2 in both the epithelium and connective tissues; that cultured gingival epithelial cells express CTGF/CCN2; and that lysophosphatidic acid further stimulates CTGF/CCN2 expression. These findings suggest that interactions between epithelial and connective tissues could contribute to gingival fibrosis.

Effects of nifedipine and interleukin-1alpha on the expression of collagen, matrix metalloproteinase-1, and tissue inhibitor of metalloproteinase-1 in human gingival fibroblasts

BACKGROUND AND OBJECTIVE

Nifedipine-induced gingival overgrowth is known to be characterized by fibrosis and some degree of inflammation. However, the molecular mechanism of the fibrosis is not fully understood. The purpose of this study was to investigate in vitro the effects of nifedipine and interleukin-1alpha on the molecules involved in fibrosis, namely type I collagen, matrix metalloproteinase-1 (MMP-1), and tissue inhibitor of metalloproteinase-1 (TIMP-1).

MATERIAL AND METHODS

Four human gingival fibroblast strains, derived from four healthy volunteers, were cultured in media containing nifedipine (1 microg/ml), with or without interleukin-1alpha (0.05 ng/ml). The mRNAs of type I collagen, MMP-1, and TIMP-1 were measured by reverse transcription-polymerase chain reaction (RT-PCR). The proteins of MMP-1 and TIMP-1 were examined by enzyme-linked immunosorbent assay (ELISA), and the ratios of MMP-1 to TIMP-1 proteins were calculated.

RESULTS

The mRNA expression of type I collagen showed no significant change. Both mRNA expression and protein production of MMP-1 were up-regulated by interleukin-1alpha, either alone or in combination with nifedipine, whereas those of TIMP-1 were up-regulated by nifedipine alone or in combination with interleukin-1alpha. The ratio of MMP-1 to TIMP-1 was not changed by nifedipine alone, but it was increased by interleukin-1alpha alone or in combination with nifedipine. However, in two of the four cell strains tested, nifedipine reduced the ratio of MMP-1 to TIMP-1 compared with that for interleukin-1alpha alone.

CONCLUSION

These results suggest that nifedipine may predispose to fibrosis in some individuals in situations where interleukin-1 levels are raised.

CCN2, connective tissue growth factor, stimulates collagen deposition by gingival fibroblasts via module 3 and alpha6- and beta1 integrins

CCN2, (connective tissue growth factor, CTGF) is a matricellular factor associated with fibrosis that plays an important role in the production and maintenance of fibrotic lesions. Increased collagen deposition and accumulation is a common feature of fibrotic tissues. The mechanisms by which CCN2/CTGF contributes to fibrosis are not well understood. Previous studies suggest that CTGF exerts some of its biological effects at least in part by integrin binding, though this mechanism has not been previously shown to contribute to fibrosis. Utilizing full length CCN2/CTGF, CCN2/CTGF fragments, and integrin neutralizing antibodies, we provide evidence that the effects of CCN2/CTGF to stimulate extracellular matrix deposition by gingival fibroblasts are mediated by the C-terminal half of CCN2/CTGF, and by alpha6 and beta1 integrins. In addition, a synthetic peptide corresponding to a region of CCN2/CTGF domain 3 that binds alpha6beta1 inhibits the collagen-deposition assay. These studies employed a new and relatively rapid assay for CCN2/CTGF-stimulated collagen deposition based on Sirius Red staining of cell layers. Data obtained support a pathway in which CCN2/CTGF could bind to alpha6beta1 integrin and stimulate collagen deposition. These findings provide new experimental methodologies applicable to uncovering the mechanism and signal transduction pathways of CCN2/CTGF-mediated collagen deposition, and may provide insights into potential therapeutic strategies to treat gingival fibrosis and other fibrotic conditions.

Heterogeneous presence of myofibroblasts in hereditary gingival fibromatosis

BACKGROUND/AIM

Hereditary gingival fibromatosis (HGF) fibroblasts are characterized by an increased production of collagen and transforming growth factor-beta1 (TGF-beta1), resulting in a fibrotic enlargement of the gingiva of affected patients. A common feature of interstitial fibrosis is the occurrence of myofibroblasts, which are regarded as the predominant cells in matrix synthesis. The goal of this article is to describe the presence of myofibroblasts in HGF in order to elucidate the mechanisms underlying HGF gingival overgrowth.

MATERIALS AND METHODS

Fibroblast cell lines and gingival samples from patients of two distinct families affected by HGF and from normal gingiva (NG) were included in this study. To characterize the presence of myofibroblasts, the expression of specific myofibroblast marker smooth muscle isoform of alpha-actin (alpha-SMA) was examined by semi-quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), Western blot, immunofluorescence, and flow cytometric analysis. Immunohistochemistry against the alpha-SMA antigen was performed in the gingival tissue samples.

RESULTS

Our results demonstrated a significant increase in the expression of the myofibroblast marker alpha-SMA in cells from one HGF family (designed as HGF Family 2), which are also characterized by an elevated expression of type I collagen, TGF-beta1 and connective tissue growth factor (CTGF). Additionally, alpha-SMA-positive cells were broadly detected in the gingival tissue samples from HGF Family 2 patients. In contrast, alpha-SMA expression by HGF Family 1 cells was quite similar to NG cells and no myofibroblasts were detected immunohistochemically, despite the higher levels of TGF-beta1 and type I collagen in HGF Family 1 fibroblasts than in NG cells. The expression of CTGF, which has been considered a key molecule to promote the transdifferentiation of myofibroblasts via TGF-beta1 activation, by HGF Family 1 cultures was significantly lower compared with HGF Family 2 and similar to NG control cells.

CONCLUSIONS

Our results suggest that the presence of myofibroblasts in HGF could be dependent on CTFG expression levels, and different biological mechanisms may account for the gingival overgrowth observed in HGF patients. This could be an underlying reason for the high variable clinical expressivity of disease.

Transforming growth factor beta-induced connective tissue growth factor and chronic allograft rejection

Late loss of allograft function is primarily attributed to chronic rejection (CR). There are no effective treatments for CR and the underlying cause of the disease is unknown. This study compared events that occurred within cardiac allografts placed in mice that received either anti-CD4 therapy and develop CR or anti-CD40L therapy and do not develop CR. Both TGFbeta and connective tissue growth factor (CTGF), which is induced by TGFbeta, were expressed in grafts with CR but were not expressed in grafts without CR. TGFbeta transfection of allografts in anti-CD40L-treated recipients resulted in CTGF expression and CR. However, TGFbeta transfection of syngeneic grafts did not result in CTGF expression or CR. These data indicate that TGFbeta alone is insufficient to induce CR and that CTGF is required. Further, antigenic stimulation is required for TGFbeta induction of CTGF. Thus, CTGF may serve as a therapeutic target for CR.

Impaired degradation of matrix collagen in human gingival fibroblasts by the antiepileptic drug phenytoin

BACKGROUND

Gingival overgrowth (GO) is a serious adverse effect associated with the administration of phenytoin (PHT), with PHT-induced GO characterized by a massive accumulation of extracellular matrix components, especially collagen, in gingival connective tissues. However, the etiology of such collagen accumulation is still largely unknown. We examined the effects of PHT on the collagen degradation process leading to collagen accumulation in human gingival fibroblasts (HGF).

METHODS

HGFs were cultured with various concentrations of PHT and viable cell numbers and collagen amounts were determined. Gene and protein expressions of matrix metalloproteinases (MMP) and tissue inhibitors of MMPs (TIMP) were quantified with reverse transcription-polymerase chain reaction (RT-PCR) analyses and Western blotting, respectively. Cellular endocytosis of collagen was assayed using flow-cytometric analysis. The effects of PHT on extracellular signal-regulated kinase 1/2 (ERK1/2) and inhibitor kappaB-alpha (IkappaB-alpha) were assayed.

RESULTS

The proliferation of HGFs was not affected by PHT, whereas it significantly increased collagen accumulation. Further, the expressions of MMP-1, -2, and -3 were markedly suppressed by PHT, whereas that of TIMP-1 was induced in a dose- and time-dependent manner. PHT also markedly prevented collagen endocytosis by HGFs, which was associated with the suppression of alpha2beta1-integrin expression. In addition, the phosphorylation of ERK1/2 and IkappaB-alpha degradation were suppressed by PHT.

CONCLUSIONS

These results suggest that PHT causes an impaired degradation of collagen by suppression of enzymatic degradation with MMPs/TIMP-1 and alpha2beta1-integrin-mediated endocytosis. Those alterations are likely mediated through the cellular signaling pathways of ERK1/2 and nuclear factor kappaB. These synergistic effects may cause collagen accumulation, leading to GO.

Connective tissue growth factor and vascular endothelial growth factor from airway smooth muscle interact with the extracellular matrix

Airway remodeling describes the structural changes that occur in the asthmatic airway that include airway smooth muscle hyperplasia, increases in vascularity due to angiogenesis, and thickening of the basement membrane. Our aim in this study was to examine the effect of transforming growth factor-beta on the release of connective tissue growth factor and vascular endothelial growth factor from human airway smooth muscle cells derived from asthmatic and nonasthmatic patients. In addition we studied the immunohistochemical localization of these cytokines in the extracellular matrix after stimulating bronchial rings with transforming growth factor-beta. Connective tissue growth factor and vascular endothelial growth factor were released from both cell types and colocalized in the surrounding extracellular matrix. Prostaglandin E2 inhibited the increase in connective tissue growth factor mRNA but augmented the release of vascular endothelial growth factor. Matrix metalloproteinase-2 decreased the amount of connective tissue growth factor and vascular endothelial growth factor, but not fibronectin deposited in the extracellular matrix. This report provides the first evidence that connective tissue growth factor may anchor vascular endothelial growth factor to the extracellular matrix and that this deposition is decreased by matrix metalloproteinase-2 and prostaglandin E2. This relationship has the potential to contribute to the changes that constitute airway remodeling, therefore providing a novel focus for therapeutic intervention in asthma.