Increased expression of type VI collagen genes in drug-induced gingival enlargement

Nifedipine and phenytoin induce matrix synthesis, but not proliferation, in intact human gingival connective tissue ex vivo

Drug-induced gingival enlargement (DIGE) is a fibrotic condition that can be caused by the antihypertensive drug nifedipine and the anti-seizure drug phenytoin, but the molecular etiology of this type of fibrosis is not well understood and the role of confounding factors such as inflammation remains to be fully investigated. The aim of this study was to develop an ex vivo gingival explant system to allow investigation of the effects of nifedipine and phenytoin alone on human gingival tissue. Comparisons were made to the histology of human DIGE tissue retrieved from individuals with DIGE. Increased collagen, fibronectin, and proliferating fibroblasts were evident, but myofibroblasts were not detected in DIGE samples caused by nifedipine and phenytoin. In healthy gingiva cultured in nifedipine or phenytoin-containing media, the number of cells positive for p-SMAD2/3 increased, concomitant with increased CCN2 and periostin immunoreactivity compared to untreated explants. Collagen content assessed through hydroxyproline assays was significantly higher in tissues cultured with either drug compared to control tissues, which was confirmed histologically. Matrix fibronectin levels were also qualitatively greater in tissues treated with either drug. No significant differences in proliferating cells were observed between any of the conditions. Our study demonstrates that nifedipine and phenytoin activate canonical transforming growth factor-beta signaling, CCN2 and periostin expression, as well as increase collagen density, but do not influence cell proliferation or induce myofibroblast differentiation. We conclude that in the absence of confounding variables, nifedipine and phenytoin alter matrix homeostasis in gingival tissue explants ex vivo, and drug administration is a significant factor influencing ECM accumulation in gingival enlargement.

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.

Gingival overgrowth in children: epidemiology, pathogenesis, and complications. A literature review

Gingival overgrowth is the enlargement of the attached gingiva due to an increased number of cells. The most prevalent types of gingival overgrowth in children are drug-induced gingival overgrowth, hereditary gingival fibromatosis (HGF), and neurofibromatosis I (von Recklinghausen disease). Gingival overgrowth induced by drugs such as phenytoin, nifedipine, and cyclosporin develops due to an increase in the connective tissue extracellular matrix. According to epidemiologic studies, it is more prevalent in male children and adolescents. There is an additive effect of those drugs on the degree of gingival overgrowth. Genetic heterogeneity seems to play an important role in the development of the disease. Functional difficulties, disfigurement, increased caries, and delayed eruption of permanent teeth are the main complications of drug-induced gingival overgrowth. HGF is the most common syndromic gingival enlargement in children. This autosomal dominant disease usually appears at the time of eruption of permanent dentition. Histologically, it is characterized by highly collagenized connective tissue. The most important complications are drifting of teeth, prolonged retention of primary dentition, diastemata, and poor plaque control. Neurofibromatosis I is an autosomal dominant disease more common in mentally handicapped individuals. Gingival overgrowth is caused by the formation of plexiform neurofibromas in the connective tissue of the gingiva. Plexiform neurofibromas are pathognomonic of the disease and consist of hypertrophic nerves arranged as lobules in the connective tissue. Complications of the disease are multiple and severe due to neurofibromas and their occasional malignant transformation.

Synergistic enhancement of collagenous protein synthesis by human gingival fibroblasts exposed to nifedipine and TNF-alpha in vitro

BACKGROUND

Gingival overgrowth occurs in patients receiving nifedipine. Gingival inflammation may be an etiologic factor.

METHODS

Gingival fibroblasts were either exposed to (i) 0-500 ng/ml TNF-alpha or 10(-7) M nifedipine or (ii) 0-500 ng/ml TNF-alpha + 10(-7) M nifedipine for 7 days. 3H-proline was used to quantify collagenous protein synthesis.

RESULTS

Both TNF-alpha and 10(-7) M nifedipine significantly decreased cell proliferation, and 10(-7) M nifedipine + 500 ng/ml TNF-alpha reversed these effects. Collagenous protein synthesis was significantly reduced by TNF-alpha and was significantly enhanced by either 10(-7) M nifedipine or 5-500 ng/ml TNF-alpha + 10(-7) M nifedipine.

CONCLUSIONS

Our data report that nifedipine reverses the primary effects of TNF-alpha on collagenous protein synthesis. Patients with gingivitis could be susceptible to gingival overgrowth during nifedipine therapy as a result of synergistic effects of these agents on fibroblast metabolism, which occurs irrespective of reduced cell numbers.

Pharmacogenomics - it's not just pharmacogenetics

New technologies in both combinatorial chemistry and combinatorial biology promise to unlock new opportunities for drug discovery and lead optimisation. Using such genome-based technologies to measure the dynamic properties of pharmacological systems, pharmacogenomics can now provide an objective measure of a drug's biological efficacy, including its potential adverse effects.

Nifedipine-induced gingival overgrowth in rats: brief review and experimental study

The first case report of gingival overgrowth induced by nifedipine (NIF), a calcium-beta blocker, was in 1984. However, the association between gingival alterations and the drug therapy of sodium diphenyl hydantoinate was initially described in 1939. The purpose of the experimental study was to examine the effect of NIF on gingival morphology in an animal model. Forty-five male Sprague-Dawley rats were randomly divided into 3 groups. Animals in each group daily received NIF in dimethyl sulfoxide by gastric feeding at a dosage of 0 (control), 30, or 50 mg/kg body weight for 9 weeks. Gingival gross morphology was assessed tri-weekly from stone models obtained from the mandibular incisal region. Animals were sacrificed at the end of study and tissue blocks were processed for histopathologic and histometric evaluation. Histometric analysis was performed at 5 selected tissue levels. Macro- and microscopic significantly increased gingival dimensions were demonstrated in NIF-treated animals compared to control. Although a fibrovascular tissue was observed in the tooth-gingiva interface for both NIF-treated and control animals, it was thicker and appeared earlier in NIF-treated animals. The results of the present study suggest that gingival overgrowth can be induced by NIF in rats and that the gingival overgrowth appears dose dependent.

Immunohistochemical localization of transforming growth factor beta, basic fibroblast growth factor and heparan sulphate glycosaminoglycan in gingival hyperplasia induced by nifedipine and phenytoin

Although drug-induced gingival hyperplasia has been extensively studied, the pathogenesis of this disorder has not been clarified to date. Transforming growth factor beta (TGF beta) and basic fibroblast growth factor (bFGF) have been shown to be implicated in diverse fibrotic and hyperplastic diseases. Heparan sulphate proteoglycan (HSPG), which is composed of heparan sulphate glycosaminoglycan (HSGAG), has also been shown to play an important role in the pathogenesis of tissue overgrowth by enhancing the functions of bFGF. However, the possible implication of these growth factors in gingival hyperplasia has not been studied. Immunohistochemical localization of TGF beta, bFGF, their receptors and HSGAG was studied in 4 nifedipine-induced and 5 phenytoin-induced hyperplastic gingival tissues, and 5 non-hyperplastic control gingival tissues to elucidate the pathogenesis of this disease. Significant immunostaining against TGF beta, bFGF, the receptors of these two growth factors and HSGAG was observed in the lamina propria of hyperplastic gingival tissues while less immunostaining was observed in the controls. The mean numbers of immunostained cells against TGF beta, bFGF, their receptors in a square unit (0.1 x 0.1 mm) of the lamina propria, which were counted to 10 units of each hyperplastic gingival tissue, were significantly higher than those of the controls. The results suggest that the increased synthesis of TGF beta, bFGF, their receptors and HSGAG may be related to the pathogenesis of drug-induced gingival hyperplasia.

Pathogenesis of drug-induced gingival overgrowth. A review of studies in the rat model

Drug-induced gingival overgrowth is a side effect associated principally with 3 types of drugs: anticonvulsant (phenytoin), immunosuppressant (cyclosporine A), and various calcium channel blockers (nifedipine, verapamil, diltiazem). In this review, we describe the features of phenytoin-, cyclosporine A- and nifedipine-induced gingival overgrowth in rats and discuss factors influencing the onset and severity of these disorders. There are several features common to the gingival overgrowth induced by these drugs: 1) gingival overgrowth is more conspicuous in the buccal than in the lingual gingiva and less severe in the maxilla than in the mandible; 2) once the blood concentration of the drug reaches a certain level as a result of increasing the dose, the incidence of gingival overgrowth is 100% and its severity is dependent on the blood level, the most severe overgrowth being induced by cyclosporine A; 3) the duration of drug administration for maximal gingival overgrowth to develop is about 40 days; 4) the gingival overgrowth regresses spontaneously after discontinuing the drug; 5) accumulation of dental plaque is not essential for the onset of overgrowth, but plays a role in its severity; and 6) more severe overgrowth is induced in young than in old rats. Furthermore, male rats are more susceptible than females to nifedipine-induced gingival overgrowth. These results suggest that drug-induced gingival overgrowth in rats is dependent on the oral drug dose, blood drug level, age, and sex and that preexisting gingival inflammation is a factor relevant to its severity. Since these factors have also been suggested to be important determinants for human drug-induced gingival overgrowth, the rat model may prove valuable in the future for elucidating the molecular pathogenesis of the disorder.

The pathogenesis of drug-induced gingival overgrowth

Gingival overgrowth is a well-documented unwanted effect, associated with phenytoin, cyclosporin, and the calcium channel blockers. The pathogenesis of drug-induced gingival overgrowth is uncertain, and there appears to be no unifying hypothesis that links together the 3 commonly implicated drugs. In this review, we consider a multifactorial model which expands on the interaction between drug and/or metabolite, with the gingival fibroblasts. Factors which impact upon this model include age, genetic predisposition, pharmacokinetic variables, plaque-induced inflammatory and immunological changes and activation of growth factors. Of these, genetic factors which give rise to fibroblast heterogeneity, gingival inflammation, and pharmacokinetic variables appear to be significant in the expression of gingival overgrowth. A more thorough understanding of the pathogenesis of this unwanted effect will hopefully elucidate appropriate mechanisms for its control.

Influence of the extracellular matrix on fibroblast responsiveness to phenytoin using in vitro wound healing models

Recent reports indicate that the topical administration of phenytoin to cutaneous wounds can promote repair. However, isolated skin cells (keratinocytes and fibroblasts) in vitro have varied in their response to phenytoin, giving rise to apparently contradictory results. We have examined how the structure of the extracellular matrix in which human dermal fibroblasts are grown in vitro can influence the response of these cells to phenytoin. The results indicate that, when fibroblasts are embedded within freely-contracting, relaxed, types I collagen matrices, they are insensitive to phenytoin treatment. However, if fibroblasts are grown in collagen matrices which are nonretracting and under tension, phenytoin (5-50 micrograms/ml) significantly (P < 0.01) stimulates cell proliferation, and inhibits collagenase activity in a dose- and time-dependent manner. The fact that the effects of phenytoin on dermal fibroblasts are biphasic and influenced by the surrounding matrix may help to explain why in vitro investigations with phenytoin give rise to inconsistent data. It also suggests that the matrix alterations which accompany wound healing may modulate the effects of phenytoin on dermal fibroblasts.

Factors influencing nifedipine-induced gingival overgrowth in rats

Factors such as age, the dose of nifedipine administered in the diet, serum drug level, duration of drug administration, and sex which may influence nifedipine-induced gingival overgrowth were examined in a rat model using 20-, 50-, and 90-days-old male and female rats. Oral administration of nifedipine (50 to 250 mg/kg diet) increased the serum level of the drug in a dose-dependent manner in both males and females. However, a higher serum level was required in females than males to attain the same degree of gingival overgrowth. The minimum dietary concentrations of the drug required to elicit gingival overgrowth in males and females were 150 and 100 mg/kg, respectively, which gave respective minimum serum levels of 800 and 1100 ng/ml. The degree of overgrowth depended on the serum concentration of the drug after it had reached the required minimum in male and female animals. Administration of nifedipine (250 mg/kg diet) for 20 days was enough to induce maximal overgrowth, but this induction occurred only in rats that started to receive the drug when they were 20 days old, not in those that started at 50 and 90 days of age for the same administration period of 55 days, and the overgrowth regressed and the gingiva were normal 40 days after ceasing drug administration. These results suggest that gingival overgrowth occurred in accordance with the drug concentration in the diet, as well as that in the serum, and was more likely to occur in males and younger individuals.