Changes in extracellular matrix macromolecules in human gingiva after treatment with drugs inducing gingival overgrowth

Hereditary gingival fibromatosis associated with the missense mutation of the KCNK4 gene

Hereditary gingival fibromatosis (HGF) is a rare oral condition that may appear as an isolated entity or as part of a genetic disease or syndrome. Molecular and biochemical mechanisms that trigger this pathologic process are not completely understood. In this article, we present a rare case of hereditary gingival fibromatosis in conjunction with a syndromic phenotype, associated with a rare missense mutation of the KCNK4 gene. This mutation induces a change in the structure of the TRAAK channel belonging to the 2-pore potassium channels. The gain of function promoted by the mutation could represent the pathogenetic basis of gingival fibromatosis.

REST Final-Exon-Truncating Mutations Cause Hereditary Gingival Fibromatosis

Hereditary gingival fibromatosis (HGF) is the most common genetic form of gingival fibromatosis that develops as a slowly progressive, benign, localized or generalized enlargement of keratinized gingiva. HGF is a genetically heterogeneous disorder and can be transmitted either as an autosomal-dominant or autosomal-recessive trait or appear sporadically. To date, four loci (2p22.1, 2p23.3-p22.3, 5q13-q22, and 11p15) have been mapped to autosomes and one gene (SOS1) has been associated with the HGF trait observed to segregate in a dominant inheritance pattern. Here we report 11 individuals with HGF from three unrelated families. Whole-exome sequencing (WES) revealed three different truncating mutations including two frameshifts and one nonsense variant in RE1-silencing transcription factor (REST) in the probands from all families and further genetic and genomic analyses confirmed the WES-identified findings. REST is a transcriptional repressor that is expressed throughout the body; it has different roles in different cellular contexts, such as oncogenic and tumor-suppressor functions and hematopoietic and cardiac differentiation. Here we show the consequences of germline final-exon-truncating mutations in REST for organismal development and the association with the HGF phenotype.

Nifedipine and Cyclosporin Affect Fibroblast Calcium and Gingiva

It has been stated that cyclosporin and nifedipine produce gingival overgrowth. However, the specific pathogenic mechanism remains uncertain. We used an experimental rat model to test the hypothesis that changes in collagen metabolism and numbers of gingival blood vessels are not mediated by intracellular calcium concentration (ratiometric Fura-2 AM measurement) in gingival fibroblasts. In the cyclosporin group, both width (364.2 ± 67.5 μm) and microvessel density (number of vessels/mm2, stained with anti-CD34 antibody) (41.6 ± 5.1) of gingiva were statistically different when compared with those in the control group (width = 184.3 ± 35.2 μm, microvessel density = 19.6 ± 2.4). The nifedipine group showed the highest content of collagen (proportion of total stroma occupied by collagen, stained with Picro-Mallory) (nifedipine group = 66.3 ± 9.4, cyclosporin group = 55.2 ± 7.9, control group = 30.1 ± 10.2). Freshly cultured fibroblasts from the cyclosporin group exhibited higher ratiometric values of fluorescence than did both the control and nifedipine groups (p = 0.03). Our results support the hypothesis that changes in gingival collagen metabolism are not mediated by calcium intracellular oscillations.

Gingival fibromatosis: clinical, molecular and therapeutic issues

Gingival fibromatosis is a rare and heterogeneous group of disorders that develop as slowly progressive, local or diffuse enlargements within marginal and attached gingiva or interdental papilla. In severe cases, the excess tissue may cover the crowns of the teeth, thus causing functional, esthetic, and periodontal problems, such as bone loss and bleeding, due to the presence of pseudopockets and plaque accumulation. It affects both genders equally. Hereditary, drug-induced, and idiopathic gingival overgrowth have been reported. Hereditary gingival fibromatosis can occur as an isolated condition or as part of a genetic syndrome. The pathologic manifestation of gingival fibromatosis comprises excessive accumulation of extracellular matrix proteins, of which collagen type I is the most prominent example. Mutation in the Son-of-Sevenless-1 gene has been suggested as one possible etiological cause of isolated (non-syndromic) hereditary gingival fibromatosis, but mutations in other genes are also likely to be involved, given the heterogeneity of this condition. The most attractive concept of mechanism for drug-induced gingival overgrowth is epithelial-to-mesenchymal transition, a process in which interactions between gingival cells and the extracellular matrix are weakened as epithelial cells transdifferentiate into fibrogenic fibroblast-like cells. The diagnosis is mainly made on the basis of the patient's history and clinical features, and on histopathological evaluation of affected gingiva. Early diagnosis is important, mostly to exclude oral malignancy. Differential diagnosis comprises all pathologies in the mouth with excessive gingival overgrowth. Hereditary gingival fibromatosis may present as an autosomal-dominant or less commonly autosomal-recessive mode of inheritance. If a systemic disease or syndrome is suspected, the patient is directed to a geneticist for additional clinical examination and specialized diagnostic tests. Treatments vary according to the type of overgrowth and the extent of disease progression, thus, scaling of teeth is sufficient in mild cases, while in severe cases surgical intervention is required. Prognosis is precarious and the risk of recurrence exists.

Mechanism of drug-induced gingival overgrowth revisited: a unifying hypothesis

Drug-induced gingival overgrowth (DIGO) is a disfiguring side effect of anti-convulsants, calcineurin inhibitors, and calcium channel blocking agents. A unifying hypothesis has been constructed which begins with cation flux inhibition induced by all three of these drug categories. Decreased cation influx of folic acid active transport within gingival fibroblasts leads to decreased cellular folate uptake, which in turn leads to changes in matrix metalloproteinases metabolism and the failure to activate collagenase. Decreased availability of activated collagenase results in decreased degradation of accumulated connective tissue which presents as DIGO. Studies supporting this hypothesis are discussed.

Nifedipine-induced histological changes in the parotid glands of hypertensive rats

Nifedipine is a widely used anti-anginal and anti-hypertensive agent. It is associated with significant gingival changes attributed more to collagen hyperplasia than to enhancement of protein synthesis. We investigated the influence of nifedipine on morphological changes in the parotid glands of rats in a model of hypertension. Twenty-eight male Wistar rats (8-10 weeks; 200±15 g) were divided into four groups (A-D). Hypertension was induced by surgical means in groups C and D. Animals in groups B and D were treated with nifedipine (0.85 mg/kg) via a gastroesophageal catheter the day after surgery (experimental day-1) for 2 weeks. A significant difference was observed between the control group and nifedipine group and between the control group and hypertension group with regard to the weight of the parotid gland and its surface area. Histological findings demonstrated changes in the parotid glands of hypertensive animals with mild vessel dilatation and infiltration of inflammatory cells. These histological findings seemed to be due more to changes in venous function than to alterations in gland architecture.

Extracellular matrix molecules: potential targets in pharmacotherapy

The extracellular matrix (ECM) consists of numerous macromolecules classified traditionally into collagens, elastin, and microfibrillar proteins, proteoglycans including hyaluronan, and noncollagenous glycoproteins. In addition to being necessary structural components, ECM molecules exhibit important functional roles in the control of key cellular events such as adhesion, migration, proliferation, differentiation, and survival. Any structural inherited or acquired defect and/or metabolic disturbance in the ECM may cause cellular and tissue alterations that can lead to the development or progression of disease. Consequently, ECM molecules are important targets for pharmacotherapy. Specific agents that prevent the excess accumulation of ECM molecules in the vascular system, liver, kidney, skin, and lung; alternatively, agents that inhibit the degradation of the ECM in degenerative diseases such as osteoarthritis would be clinically beneficial. Unfortunately, until recently, the ECM in drug discovery has been largely ignored. However, several of today's drugs that act on various primary targets affect the ECM as a byproduct of the drugs' actions, and this activity may in part be beneficial to the drugs' disease-modifying properties. In the future, agents and compounds targeting directly the ECM will significantly advance the treatment of various human diseases, even those for which efficient therapies are not yet available.

Comparison of Azithromycin and Oral Hygiene Program in the Treatment of Cyclosporine-Induced Gingival Hyperplasia

BACKGROUND

It has been shown that azithromycin improves cyclosporine-induced gingival hyperplasia (GH), but its efficacy was never compared against an efficient oral hygiene program (OHP). The aim of this study was to analyze the effects of azithromycin plus OHP versus OHP alone in patients with cyclosporine-induced GH.

METHODS

After periodontal evaluation, 20 renal transplant recipients received detailed oral hygiene instructions and a complete OHP, and were randomized to control (OHP) or azithromycin groups (OHP plus azithromycin). Patients were re-evaluated after 15 and 30 days. Both groups were similar in time after transplant, age, gender, cyclosporine dose, and cyclosporine through level and serum creatinine. The control group had fewer patients using calcium cannel blockers (10% vs. 70%, p = 0.02).

RESULTS

All patients improved in pain, halitosis, and gum bleeding after OHP. The control group did not improve plaque index (PI) or GH. In contrast, baseline PI decreased from 1.52 +/- 0.28 to 0.50 +/- 0.16 on day 15 (p < 0.01) and to 0.46 +/- 0.14 on day 30 (p < 0.01) in the azithromycin group, and the GH score decreased from 1.9 +/- 0.27 to 0.90 +/- 0.27 on day 15 (p < 0.05) and to 0.70 +/- 0.21 on day 30 (p < 0.01).

CONCLUSION

Azithromycin associated to efficient OHP induced a striking reduction in cyclosporine-induced GH, while efficient OHP alone improved oral symptoms but did not decrease cyclosporine-induced GH.

Cyclosporine A inhibits the expression of membrane type-I matrix metalloproteinase in gingiva

BACKGROUND AND OBJECTIVE

Membrane type-I matrix metalloproteinase (MMP) and tissue inhibitor of metalloproteinase-2 (TIMP-2) regulate the activation of MMP-2; however, their roles in the activation of MMP-2 in gingiva during treatment with cyclosporine A are still unknown. Therefore, the expressions of membrane type-I MMP and TIMP-2, as well as MMP-2, in gingivae upon treatment with cyclosporine A were examined in vivo and in vitro.

MATERIAL AND METHODS

Thirty-four rats were divided into two groups after edentulous ridges were established. The experimental group received 30 mg/kg/d of cyclosporine A and the control group received vehicle. At the end of the experimental period, the rats were killed, the gingivae were obtained and the expression of mRNA and protein of membrane type-I MMP, TIMP-2 and MMP-2 in gingiva were examined using real-time polymerase chain reaction and immunohistochemistry. In human gingival fibroblasts, the activity of MMP-2 and the expression of MMP-2, membrane type-I MMP and TIMP-2 mRNAs were examined (using zymography and reverse transcription-polymerase chain reaction, respectively) after treatment with cyclosporine A.

RESULTS

In gingivae of rats, cyclosporine A significantly decreased the expression of mRNA and protein of membrane type-I MMP, but not of TIMP-2. The expression of MMP-2 mRNA was unaffected but the expression of MMP-2 protein showed a significant decrease upon treatment with cyclosporine A. In fibroblast culture medium, the presence of cyclosporine A induced a decrease in MMP-2 activity in a dose-dependent manner. The expression of MMP-2, membrane type-I MMP and TIMP-2 mRNAs in fibroblasts was not significantly affected by cyclosporine A; however, in fibroblasts the ratio of mRNA expression of membrane type-I MMP to that of TIMP-2 decreased as the cyclosporine A dose was increased.

CONCLUSION

Cyclosporine A inhibits the expression of membrane type-I MMP in gingiva and it may further reduce the activation of MMP-2.

Mechanism of Azithromycin Treatment on Gingival Overgrowth

Azithromycin is effective for the remission of cyclosporine A-induced gingival overgrowth (CIGO) in persons who have undergone renal transplant. To explain its mechanism in alleviating the clinical symptoms of these indivduals, we examined the effect of azithromycin on cell proliferation and collagen turnover modified by cyclosporin A in human gingival fibroblasts from healthy persons and from persons who had undergone renal transplant. Cyclosporin A-induced proliferation of renal transplant fibroblasts and normal fibroblasts was inhibited by azithromycin. Azithromycin elevated the reduced metalloproteinase (MMP)-1 and MMP-2 activities in cyclosporine A-treated renal transplant fibroblasts and normal fibroblasts. In cyclosporine A-treated renal transplant fibroblasts, azithromycin blocked the accumulation of total collagen in culture media and the increase in type I collagen mRNA level, but recovered the reduced MMP-2 mRNA level to the control. These results suggest that azithromycin may improve CIGO by blocking cyclosporine A-induced cell proliferation and collagen synthesis, and by activating MMP-2 in gingival fibroblasts of persons with cyclosporine A-induced gingival overgrowth.

The clinical effect of topical phenytoin on wound healing: a systematic review

BACKGROUND

Oral phenytoin was first introduced as an antiseizure medication in 1937. Over 60 years investigators have shown an interest in how topical phenytoin may be used to promote wound healing in a variety of chronic wounds.

OBJECTIVES

Systematically to identify, summarize and critically appraise the clinical evidence available on the effects of topical phenytoin on wound healing.

METHODS

Systematic searches were carried out in PubMed (1963-2005), Medline (1966-2005) and Cinahl (1982-2005) for the years listed and in the Cochrane Library and the University of York NHS Centre for Reviews and Dissemination. The search terms used the following key words alone and in combination: phenytoin, wounds and injuries, wound healing, and wound care. Secondary hand searching was also carried out using relevant journal articles and reference lists, historical books, conference proceedings and theses in the area of wound healing. Papers were included if they described randomized controlled trials (RCTs) on humans and if the primary aim was wound closure, with a secondary aim of measuring wound healing over time. The methodological quality of the papers in this systematic review was assessed using the van Tulder method and in addition best-evidence synthesis was carried out. The magnitude of the effect of phenytoin therapy in the studies included in the systematic review was investigated in four of the 14 trials.

RESULTS

Fourteen RCTs were included in the systematic review. Two papers were of high and 12 papers of low to moderate methodological quality. Most papers failed to describe randomization, treatment allocation and blinding techniques adequately. There was moderate evidence presented to support the use of phenytoin for the treatment of leg ulcers, leprosy wounds, chronic wounds and diabetic foot ulcers. There was a positive percentage treatment effect in favour of the phenytoin-treated group in one study investigating diabetic foot wounds and one study on chronic wounds. There was limited evidence for the use of phenytoin on burns and war wounds.

CONCLUSIONS

Overall it would appear that studies investigating the effect of topical phenytoin on wound healing are of moderate methodological quality, and these suggest that there may be a positive effect on wound healing in a variety of wounds.

Increased expression of collagen prolyl 4-hydroxylases in Chinese patients with hereditary gingival fibromatosis

OBJECTIVES

Hereditary gingival fibromatosis (HGF) is characterized by excess accumulation of interstitial collagen. However, until now, there has been controversy about the mechanism of collagen accumulation in HGF gingivae. The present study aimed to clarify the pathogenic mechanisms potentially involved.

DESIGN

Gingival fibroblasts from three Chinese HGF patients and three healthy subjects were cultured. Cell proliferation was assessed by MTT assay. The mRNA levels of type I collagen, MMP-1, MMP-3, TIMP-1, prolyl 4-hydroxylase (P4H)alpha(I), alpha(II), alpha(III) and P4Hbeta were analyzed in gingival fibroblasts by RT-PCR. The protein production of type I collagen and P4H was examined respectively by ELISA and Western blot.

RESULTS

In culture, HGF gingival fibroblasts showed similar growth characteristics to fibroblasts isolated from control gingivae. The mRNA and protein levels of type I collagen and P4Halpha in HGF fibroblasts were higher than those in controls. There were no detected differences in mRNA expression levels of MMP-1, MMP-3, TIMP-1, P4Halpha(II), alpha(III) and P4Hbeta between HGF and control fibroblasts.

CONCLUSIONS

These data suggest that increased collagen post-translational modification by P4H may be one mechanism by which increased collagen accumulation occurs in some forms of HGF.

Drug-induced gingival overgrowth--a review

Drug-induced gingival overgrowth is a side effect associated with 3 types of drugs: anticonvulsants (phenytoin), immunosuppressive agents (cyclosporine A), and various calcium channel blockers for cardiovascular diseases. Gingival overgrowth is characterized by the accumulation of extracellular matrix in gingival connective tissues, particularly collagenous components with various degrees of inflammation. Although the mechanisms of these disorders have not been elucidated, recent studies suggest that these disorders seem to be induced by the disruption of homeostasis of collagen synthesis and degradation in gingival connective tissue, predominantly through the inhibition of collagen phagocytosis of gingival fibroblasts. The integrins are a large family of heterodimeric transmembrane receptors for extracellular matrix molecules. alpha2beta1 integrin serves as a specific receptor for type I collagen on fibroblasts, and alpha2 integrin has been shown to play a crucial role in collagen phagocytosis. Actin filaments, which are assembled from monomers and oligomers, are involved in collagen internalization after binding to integrins. Furthermore, the implication of intracellular calcium in the regulation of integrin-mediated binding activity and gelsolin activity, known as a calcium-dependent actin-severing protein, is also described. In this review, we focus on collagen metabolism in drug-induced gingival overgrowth, focusing on the regulation of collagen phagocytosis in fibroblasts.

Inhibition of growth of human gingival fibroblasts by chimeric DNA-RNA hammerhead ribozyme targeting transforming growth factor-beta 1

BACKGROUND

Transforming growth factor (TGF)-beta1 is involved in the pathogenesis of both drug-induced gingival overgrowth and hereditary gingival fibromatosis. Ribozymes enzymatically cleave target mRNAs and are expected to be utilized as the basis of novel nucleic acid-based therapies. We designed a chimeric DNA-RNA ribozyme targeting TGF-beta1 mRNA and examined its effect on growth of gingival fibroblasts in culture.

METHODS

Chimeric DNA-RNA hammerhead ribozyme with sequence complementary to the loop structure of human TGF-beta1 mRNA was used. We evaluated transfer of the chimeric ribozyme by hemagglutinating virus of Japan (HVJ)-envelope into cultured human gingival fibroblasts in vitro and rat gingival tissues in vivo. We then examined effects of the chimeric ribozyme to TGF-beta1 on proliferation and DNA synthesis in human gingival fibroblasts. We also examined effects of the chimeric ribozyme to TGF-beta1 on expression of TGF-beta1, type IV collagens, and fibronectin mRNAs and expression of TGF-beta1 protein in human gingival fibroblasts.

RESULTS

Chimeric ribozyme was sufficiently distributed into human fibroblasts in vitro and rat gingivae in vivo. Chimeric ribozyme to TGF-beta1 significantly inhibited expression of TGF-beta1, type IV collagen, and fibronectin mRNAs and TGF-beta1 protein in human gingival fibroblasts. Mismatch ribozyme had no effect on expression of these molecules. Chimeric ribozyme to TGF-beta1 also significantly inhibited proliferation and DNA synthesis in gingival fibroblasts.

CONCLUSION

Chimeric DNA-RNA ribozyme targeting TGF-beta1 may be a useful gene therapy agent for treatment of gingival hyperplasia.

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.

Ultrastructure of the gingiva in cardiac patients treated with or without calcium channel blockers

OBJECTIVES

In the last few years, several studies have suggested that periodontal diseases are related to the development of atherosclerosis and its complications. Our objective was to study the ultrastructural morphology of the gingiva from cardiac patients, some of whom were treated and some not with calcium channel blockers compared to a control group.

MATERIAL AND METHODS

Fifty-five patients were studied and grouped in the following way: (a) healthy group (HG) (n=12) healthy patients with at least two pockets between 3 and 5 mm; (b) cardiac group (CG) (n=12) patients with cardiac disease untreated with calcium channel blockers; (c) diltiazem group (DG) (n=13) cardiac patients treated with diltiazem; (d) nifedipine group (NG) (n=18) cardiac patients treated with nifedipine.

RESULTS

Ultrastructural studies in the CG showed inflammatory cells, collagen fibers disruption and a more extended morphologically compromised fibroblast mitochondria. Morphometric studies in CG showed mitochondria that were impaired in number but increased in volume, suggesting metabolic cell suffering. In DG and NG, morphometric data were similar to HG. The presence of myofibroblasts and collagen neosynthesis was detected in DG and NG.

CONCLUSIONS

Our data showed differences in the ultrastructure of the gingival fibroblasts between the studied groups; the DG and NG showed features that could be interpreted as an attempt to restore the cellular metabolic function.

Macrophage subpopulations in gingival overgrowth induced by nifedipine and immunosuppressive medication

BACKGROUND

The immunomodulating effects of both immunosuppressive and nifedipine medication have been associated with drug-induced gingival overgrowth. The aim of the study reported here was to evaluate the presence of macrophage subpopulations in normal human gingiva and in gingival overgrowth induced by nifedipine and immunosuppressive medication.

METHODS

Gingival samples were taken from 11 nifedipine-medicated cardiac outpatients (nifedipine group), 11 triple-medicated organ-transplant recipients also taking nifedipine (immunosuppression plus nifedipine group), 12 triple-medicated organ-transplant recipients (immunosuppression group), and 20 generally healthy individuals (control group). Cryostat sections were stained with mAbs for inflammatory 27E10, reparative RM3/1, and resident 25F9 macrophages using an avidin-biotin enzyme complex method. Total numbers of mAb-labeled cells were determined in connective tissue beneath sulcular epithelium, connective tissue beneath oral epithelium, and middle connective tissue. Expression of 27E10 was determined in keratinocytes in the oral epithelium. Statistics analyses were undertaken using the chi-square test, the Mann-Whitney U test, the independent samples t test, analysis of variance, and analysis of covariance.

RESULTS

Greater numbers of inflammatory 27E10-positive macrophages were found in all 3 medicated groups and counting zones than in the control group except in connective tissue beneath sulcular epithelium in the immunosuppression group. The incidence of specimens expressing 27E10 antigen throughout the oral epithelium was significantly higher in the immunosuppression group (8 of 12) than in the control group (4 of 20) and the nifedipine group (2 of 11). Numbers of reparative RM3/1-positive macrophages were significantly greater in the immunosuppression group in connective tissue beneath oral epithelium than in the control group. The effect was markedly associated with degree of inflammation. Numbers of resident 25F9-positive macrophages were lower in connective tissue beneath sulcular epithelium in the immunosuppression group, and higher in middle connective tissue in the nifedipine group than in the control group.

CONCLUSION

Our results show that the nature of drug-induced gingival overgrowth differs somewhat between immunosuppressive and nifedipine medications.

A new locus for hereditary gingival fibromatosis (GINGF2) maps to 5q13-q22

Gingival fibromatosis (GINGF) is an oral disorder characterized by enlargement of the gingiva. It occurs either as the sole phenotype or combined with other symptoms. Thus far, one GINGF locus has been mapped on chromosome 2, at 2p21, and a second possible locus has been mapped to 2p13. However, the genes responsible for this disorder have not been elucidated. We identified a four-generation Chinese GINGF family in which the disease manifests within 1 year after birth. After exclusion of the two known GINGF loci in this family, we performed a genome-wide search to map the chromosome location of the responsible gene. We identified a new locus, GINGF2, on chromosome 5q13-q22 with a maximum two-point lod score of 4.31 at D5S1721 (theta = 0.00). Haplotype analysis placed the critical region in the interval defined by D5S1491 and D5S1453. Within this region, calcium/calmodulin-dependent protein kinase IV (CAMK4) is a strong candidate.

Cyclosporin A-induced gingival overgrowth in the rat: a histological, ultrastructural and histomorphometric evaluation

This investigation was undertaken to further study cyclosporin A (CsA)-induced gingival overgrowth. Thirty mg/kg/d of vehicle or CsA solutions were given orally to 6-wk-old male Sprague-Dawley rats. After 4, 9, 14 and 19 wk 2 control and 2 experimental rats were anaesthetized, tissues fixed by intracardiac perfusion of fixative solution and jaws processed for Epon inclusion. Histological and ultrastructural studies conducted in a gingival portion (free gingiva) revealed the presence of hyalinization areas and of multinucleated cells (MCs) containing collagen fibrils (connective tissue), of amorphous areas and disorders of keratinization (epithelia). Histomorphometric evaluation indicated that in the CsA rats the mean cross-sectional area of the free gingiva was 2.52-fold increased compared to the controls. The connective tissue comprised 41.43% of this area (instead of 31.49% in controls). Additional histomorphometric evaluation was performed in 3 groups of free gingival portions: control (C group), CsA-non-respondent (CsA-nR) and CsA-respondent (CsA-R). The cross-sectional gingival areas studied were slightly lower than the mean area of all the control sites previously defined (groups C and CsA-nR) or showed the higher degrees of enlargement (CsA-R). In the CsA-R group the mean cross-sectioned area of the vessel profiles was increased and the number of fibroblast profiles decreased. In the CsA-nR group the number of vessel profiles and that of MCs profiles were increased. In the epithelia of the CsA-R group were increased (a) keratinized epithelia: thickness; thickness of the inner and of the outer compartments; surface area of spinous cell profiles; (b) oral gingival epithelium: number of cell layers (inner compartment); (c) oral sulcular epithelium: surface area of granular cell profiles; (d) junctional epithelium: thickness; number of cell layers. These results indicate that (a) the CsA induced modifications are not limited to enlarged gingiva (b) the overgrowth of the GCT is the result of a vasodilatation and of an increase in the volume of the extracellular matrix and (c) the increase of the epithelial thickness is mainly the result of a cell hypertrophy in the keratinized epithelia and of a cell hyperplasia in the junctional epithelium.

Pre-transplant gingival hyperplasia predicts severe cyclosporin-induced gingival overgrowth in renal transplant patients

The relationship between the pre-transplant periodontal status and the development of post-transplant gingival overgrowth was investigated in a longitudinal study. The periodontal condition of 35 patients was examined on 2 occasions while they were on the transplant waiting list and then at 4-6, 10-12, 16 and 20 weeks post-transplant. At each visit the plaque index, the bleeding index and a pocket index (CPITN) were measured. Dental impressions were taken of the pre- and post-transplant gingival condition and used to make stone models which were used to score the gingival overgrowth index (GOI). The patients divided into 3 distinct groups having severe (n=13), mild (n=16) or no post-transplant gingival overgrowth (n=6). Only 1 of the patients had taken cyclosporin prior to inclusion into the study. All the patients who developed severe overgrowth had evidence of gingival hyperplasia before the transplant. There was no difference in the serum cyclosporin levels between the three groups (chi2<2.28, p>0.319). Furthermore, there was no statistical difference for any of the periodontal indices. This study indicates that the hyperplastic gingival inflammatory response of some individuals appears to be potentiated by cyclosporin resulting in severe post-transplant overgrowth. In other patients the same reaction may allow the fibroblastic activity to occur to an extent where it produces a mild clinically apparent overgrowth.

Lack of influence of cyclosporin A on levels of gingival procollagen types I and III mRNAs in rats of different ages

Previous studies showed that gingival overgrowth following cyclosporin A (CsA) administration is not associated with an increase in interstitial collagen. It also was shown that CsA causes a significant decrease in collagen content within the gingival stroma. In order to determine whether this decrease is caused by down-regulation of collagen mRNA, the procollagen mRNA level in gingiva of young and old rats was measured correlated with the ratio of interstitial collagen to DNA in these regions. Hybridization of 32P-labelled cDNA probes for procollagen types I and III with total RNA extracted from the molar gingiva showed that administration of Csa did not change the steady-state levels of mRNAs for both procollagens in the gingiva of either young or old rats. The ratio of gingival interstitial collagen to DNA was significantly reduced in the CsA-treated animals (4.2 +/- 0.85) relative to the controls (7.8 +/- 1.6). It is concluded that the reduction in interstitial collagen following CsA treatment is not age-related, and is most probably caused by increased degradation rather by decreased biosynthesis.