The effects of culture environment on the response of human gingival fibroblasts to cyclosporin A

Effect of cyclosporin A on proliferation and differentiation of human periodontal ligament cells

OBJECTIVE

Cyclosporin A (CsA) is widely used to prevent rejection after organ transplantation. However, it also causes several side-effects, including gingival overgrowth and bone resorption. Cellular mechanisms underlying the effect of CsA on periodontal tissue remain unclear. In this study, we investigated the effect of CsA on the proliferation and expression of characteristic markers in periodontal ligament cells (PDLs).

MATERIAL AND METHODS

The proliferation and viability of PDLs were measured by direct cell counting and 3,4,5-dimethylthiazol-2-yl-2,5-diphenyl tetrazolium bromide assay, respectively. mRNA expression levels of the specific proteins alkaline phosphatase (ALP), osteocalcin (OC) and collagen type 1 (Coll-1) were quantified using real-time polymerase chain reaction. Finally, ALP activity of PDLs was investigated using a specific colorimetric assay.

RESULTS

We found that proliferation of PDLs was stimulated by 0.01–0.1 μg/ml CsA and unaffected by 1 μg/ml CsA. The viability of PDLs was increased by 0.1 μg/ml CsA and not affected by 0.01 μg/ml and 1 μg/ml CsA. Furthermore, the mRNA expression levels of ALP, OC and Coll-1 in PDLs were significantly increased upon stimulation with 0.1 μg/ml CsA for 24 h or by stimulation with 0.01 μg/ml CsA for 48 h. In contrast, significantly lower expression levels of all three proteins in PDLs were observed upon stimulation with 1 μg/ml CsA for 48 h. The ALP activity of PDLs exhibited a similar pattern of changes upon CsA stimulation.

CONCLUSION

Our data demonstrated that CsA may influence both the proliferation and differentiation of human PDLs, which may play an important role in the homeostasis of periodontal tissue.

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.

Influence of Cyclosporin A on human gingival keratinocytes in vitro

PURPOSE

Gingival hyperplasia is a well known side effect of Cyclosporine A therapy. The aetiology of this is not totally understood and there is debate whether it is hyperplasia of the gingival epithelium or of the submucosal connective tissue, or both, and what roles play factors like age and gender of the patients, duration and dosage of the drug.

MATERIAL AND METHODS

The influence of different Cyclosporine A concentrations (10(-6) g/ml; 5 x 10(-7) g/ml; 10(-9) g/ml) and of no medication (controls) on growth and proliferation of cultured human gingival keratinocytes was investigated after a culture period of 3, 6 and 9 days. Cell proliferation was assessed by counting anti Ki-67 stained nuclei, cell growth by counting total number of nuclei and by the EZ4U-assay.

RESULTS

There was no significant correlation of the cell proliferation rate and cellular growth with either gender (p > 0.568) or duration of medication (p > 0.876); but Cyclosporine A concentration showed a highly significant influence on cellular growth (p = 0.0001). Inhibition of cell growth was dependent on drug dosage, but a low concentration of 10(-9) g/ml even stimulated cell growth.

CONCLUSIONS

There is evidence that Cyclosporine A in low concentrations (10(-9) g/ml as applied in long-term therapy) stimulates gingival keratinocyte growth and therefore might be related to hyperplasia of the gingiva. However, high Cyclosporine A concentrations may inhibit cell growths and factors like gender of the patient did not show any influence in-vitro.

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.

Gingival tissue proteoglycan and chondroitin-4-sulphate levels in cyclosporin A-induced gingival overgrowth and the effects of initial periodontal treatment

OBJECTIVES

Cyclosporin A (CsA) is a potent immunosuppressive drug used in organ transplant patients to prevent graft rejection. CsA-induced gingival overgrowth is one of the side effects of this drug and its pathogenesis is still unclear. The present study was planned to comparatively analyse total proteoglycan (PG) and chondroitin-4-sulphate (C4S) levels in CsA-induced overgrown gingival tissue samples obtained before and after initial periodontal treatment and to compare these findings with the situation in healthy gingiva.

MATERIAL AND METHODS

Gingival tissue samples were obtained from nine patients with CsA-induced gingival overgrowth before and 4 weeks after initial periodontal treatment including oral hygiene instruction and scaling and also from 10 healthy control subjects. Total PG and C4S levels were determined by biochemical techniques. PG levels were analysed using modified Bitter and Muir method. C4S assay was carried out using chondroitin sulphate lyase AC and chondroitin-6 sulphate sulphohydrolase enzymes. The results were tested statistically using non-parametric tests.

RESULTS

All clinical measurements in the CsA-induced gingival overgrowth group demonstrated significant reductions 4 weeks after initial periodontal treatment (p<0.05). There was no significant difference between the levels of baseline total PG in CsA-induced gingival overgrowth and healthy control groups (p>0.05). The gingival tissue levels of PG in CsA-induced gingival overgrowth group decreased significantly 4 weeks after treatment (p=0.043). Gingival tissue C4S levels in the overgrowth group were significantly higher than the healthy control group at baseline (p=0.000). C4S levels of the overgrowth group were significantly reduced after treatment (p=0.033), but these levels were still significantly higher than the healthy control group (p=0.000).

CONCLUSION

The observed prominent increase in gingival tissue C4S levels may be interpreted as a sign of an increase in C4S synthesis in CsA-induced gingival overgrowth. Furthermore, remission of clinical inflammation by means of initial periodontal treatment had a positive effect on tissue levels of these extracellular matrix molecules.

Cyclosporin A promotes mineralization by human cementoblastoma-derived cells in culture

OBJECTIVE

The immunosuppressive drug cyclosporin A has been shown to induce cementum deposition in vivo in experimental animals. Using cementoblastoma-derived cells, we have studied whether this drug will be useful to study cementum mineralization and differentiation in vitro.

METHODS

Human cementoblastoma cells and gingival fibroblasts (controls) were cultured and treated with 0.5, 1.0 and 5.0 microg/ml of cyclosporin A. Cell proliferation was evaluated by MTT (tetrazolium) assay and cell number, and cell viability was assessed by trypan blue dye exclusion. Induction of mineralization was evaluated by alizarin red S staining to detect mineralized nodules and by reverse transcription-polymerase chain reaction (RT-PCR) to assess the expression of bone differentiation markers alkaline phosphatase, osteocalcin, bone sialoprotein and core-binding factor a1 (Cbfa1).

RESULTS

Cyclosporin A at 5.0 microg/ml concentration reduced significantly the increase in the number of cementoblastoma cells. A dose-dependent increase in the number of mineralized nodules occurred in cultures of cementoblastoma-derived cells treated with cyclosporin A, and RT-PCR analyses showed significantly higher levels of expression of alkaline phosphatase, bone sialoprotein, type I collagen, matrix metalloproteinase-1, osteocalcin, osteopontin, and Cbfa1. Human gingival fibroblast proliferation and cell number were not affected. Mineralized nodules were not detected in gingival fibroblasts and bone specific proteins were not expressed.

CONCLUSIONS

Presence of cyclosporin A during 14-day culture period appears to suppress the proliferation of cementoblastoma cells and induce the formation mineralized-like tissue by these cells.

Inhibition of cyclosporin A-induced gingival overgrowth by azithromycin through phagocytosis: an in vivo and in vitro study

BACKGROUND

The objective of the present study was to investigate the effect of cyclosporin A (CsA) and azithromycin (AZI) on collagen metabolism in the gingiva of rats.

METHODS

Fifty 6-week-old male Sprague-Dawley (SD) rats (weight 120 to 150 g) were randomly distributed into five groups. All groups received various drugs via gastric feeding for 7 weeks. The first group (Mo group) received mineral oil for 7 weeks as a control; the CsA group received CsA in mineral oil for 7 weeks (dosage 30 mg/kg); the CsA/Mo group received CsA in mineral oil for 6 weeks and mineral oil only for the seventh week; the CsA/AZI group received CsA in mineral oil for 6 weeks and AZI (dosage 10 mg/kg) in mineral oil simultaneously with CsA in the seventh week; and the Mo/AZI group received mineral oil for 6 weeks and AZI in mineral oil for the seventh week. All animals were sacrificed for clinical and histological analyses. Gingival fibroblasts were cultured at the fourth passage, and the amount of collagen was measured. Type I collagen and collagenase mRNA were measured by reverse transcription-polymerase chain reaction. Collagen phagocytosis assay also was performed.

RESULTS

Clinically, CsA induced gingival overgrowth in rats, whereas AZI reduced gingival overgrowth. Histological results of the CsA group showed a marked increase of tissue volume compared to the other groups. High collagen amounts were found when gingival overgrowth was induced. However, type I collagen mRNA and collagenase mRNA expressions did not statistically differ among groups. Phagocytosis assay showed that CsA decreased phagocytic activity of gingival fibroblasts, whereas AZI increased the activity. These results suggest that the induction and reduction of CsA-induced gingival overgrowth were closely associated with phagocytic activity.

CONCLUSION

Cyclosporin A decreases collagen degradation by lowering phagocytic activity of rat gingival fibroblasts. Azithromycin partially compensates for this lowered phagocytic activity.

Geometric Control of Fibroblast Growth on Proton Beam-Micromachined Scaffolds

Circular three-dimensional (3D) micropatterns with grooves and ridges of various sizes on the circumference of the structure were micromachined in polymethylmethacrylate, using proton beam micromachining. Fibroblasts were seeded in the center smooth nonpatterned surface of the circle. The circumference grooves could retard the outward spreading of cells after they became confluent in the central smooth surface. The fibroblasts eventually migrated across the grooves and ridges several days later. Wider and deeper grooves were more effective in retarding fibroblast spreading. Our results indicate that groove structures in cellular dimensions can effectively retard fibroblasts invasion. Proton beam micromachining, which has the unique advantage of being the only technique capable of manufacturing direct-write precise 3D microstructure at cellular dimensions, has great potential in generating 3D microscaffolds for studying cell behavior in a 3D microenvironment, which is important for tissue engineering.

Gene Expression of Extracellular Matrix Proteoglycans in Human Cyclosporin-Induced Gingival Overgrowth

BACKGROUND

Gingival overgrowth is one of the side effects associated with the systemic use of cyclosporin A (CsA). In vitro studies on the extracellular matrix of gingival tissues have demonstrated an altered composition, particularly an accumulation of proteoglycans and collagen. We investigated the gene expression of extracellular matrix proteoglycans in CsA-induced gingival tissue alterations.

METHODS

mRNA expression of the proteoglycans perlecan, decorin, biglycan, and versican was analyzed by reverse transcription polymerase chain reaction (RT-PCR) in gingival samples obtained from 12 individuals, six with CsA-induced gingival overgrowth (CsA group) and six with a normal gingiva (control group). The RT-PCR products were subjected to 1% agarose gel electrophoresis containing ethidium bromide and analyzed qualitatively and semiquantitatively by densitometry. Density values were normalized by determining the expression of the housekeeping gene beta-actin in the same sample. Groups were compared by the Student's t test.

RESULTS

Perlecan expression showed a marked increase (54%) in the CsA group compared to the control group (P < 0.01), while no significant differences were observed for the other proteoglycans.

CONCLUSION

CsA-induced gingival overgrowth seems to be associated with increased expression of perlecan, a typical basement membrane proteoglycan, but not decorin, biglycan, or versican.

The effects of cyclosporin on the collagenolytic activity of gingival fibroblasts

BACKGROUND

The immunosuppressive agent cyclosporin is associated with a number of major side-effects including the development of gingival overgrowth. Although the pathogenesis of cyclosporin-induced gingival overgrowth remains unclear, it has been suggested that the finely regulated balance between extracellular matrix synthesis and degradation may be disturbed, resulting in an accumulation of excess connective tissue components within the gingival tissue. The aim of this study was to investigate the effect of cyclosporin on matrix metalloproteinases (MMP)-1 and tissue inhibitors of MMP (TIMP)-1 expression at the mRNA, protein, and enzyme activity levels.

METHODS

Gingival fibroblasts were grown to confluence and then cultured in serum-free medium supplemented with cyclosporin over the concentration range of 0 to 2000 ng/ml. MMP-1 and TIMP-1 mRNA levels in cultures were determined by reverse transcription polymerase chain reaction (RT-PCR), protein levels in whole conditioned medium were assessed by enzyme-linked immunosorbent assay (ELISA), and collagenolytic activity determined using a 3H-acetylated type I collagen degradation assay. Tissue mRNA levels in normal and overgrown gingiva were also determined by RT-PCR.

RESULTS

Results indicated that cyclosporin inhibited MMP-1 expression at both the mRNA and protein level in a dose- and time-dependent fashion. The effects on TIMP-1 expression were less clear, cyclosporin inhibiting mRNA expression, but having no effect on TIMP-1 protein levels at any concentration studied. Addition of the drug resulted in reduced levels of collagenolytic activity in the culture medium. MMP-1 mRNA expression was significantly reduced in overgrown compared to normal tissue.

CONCLUSIONS

These results add support to the hypothesis that the accumulation of collagen seen in gingival overgrowth can be explained by a cyclosporin-induced inhibition of collagenolytic activity within the gingival tissues.

The influence of transforming growth factor-beta1 gene polymorphisms on the severity of gingival overgrowth associated with concomitant use of cyclosporin A and a calcium channel blocker

BACKGROUND

The purpose of this study was to determine whether the prevalence and severity of gingival overgrowth in renal transplant recipients concomitantly treated with cyclosporin and a calcium channel blocker was associated with functional polymorphisms within the signal sequence of the transforming growth factor-(TGF)beta1 gene.

METHODS

The extent and severity of gingival overgrowth for 164 renal transplant recipients immunosuppressed with cyclosporin A and concomitantly taking a calcium channel blocker since transplant were entered into the study (86 in Manchester, 78 in Belfast). Two biallelic polymorphisms of the TGF-beta1 gene were studied at position +869, codon 10 (leucine to proline substitution), and position +915, codon 25 (arginine to proline substitution).

RESULTS

Subjects who were homozygous for proline at codon 10 had significantly higher overgrowth scores than those who were heterozygous (P= 0.03) or homozygous for leucine (P= 0.01). Subjects who were heterozygous (arginine/proline) at codon 25 had a significantly higher (P= 0.04) gingival overgrowth score than those who were homozygous for arginine. Logistic regression analysis indicated that for codon 25 independent predictors of severe gingival overgrowth were the heterozygous arginine/proline genotype (P= 0.009) and whether the individual was young (P= 0.05).

CONCLUSIONS

Polymorphisms in the TGF-beta1 gene influence the expression of gingival overgrowth in renal transplant recipients concomitantly treated with cyclosporin and a calcium channel blocker. The polymorphism in the TGF-beta1 gene at codon 25 represented an independent genetic determinant of severe gingival overgrowth in the susceptible subjects studied.

Cyclosporin A decreases the degradation of type I collagen in rat gingival overgrowth

Cyclosporin A (CsA) is used as an immunosuppressive agent and its prominent side effect is the induction of fibrous gingival overgrowth. The purpose of this study was to investigate the effect of CsA on the type I collagen metabolism in the gingiva of rats fed a powdered diet either containing or lacking CsA. Immunohistochemical analysis revealed that type I collagen was more prevalent in the connective tissue of CsA-treated gingiva than in those of control rats on days 15, 30, and 55 after the start of feeding. Total RNAs were isolated from mandibular molar gingiva on days 0, 3, 8, 15, 30, and 55. Quantitative analysis of mRNA by reverse transcriptase-polymerase chain reaction revealed that the CsA-treated groups showed a gradual decrease in expression of type I collagen and collagenase mRNAs, 0.4% and 18.0% on day 55 compared with those on day 0, respectively. In the control groups, type I collagen and collagenase mRNAs also decreased to 19.7% and 63.0%, respectively, however, both mRNA expressions were significantly lower in the CsA-treated group than in the controls. An electron microscopic analysis of fibroblasts was performed to count the number of cells with collagen fibrils in the cytoplasm, a marker of phagocytosis of collagen by fibroblasts. The collagen fibrils were detected in 4.7% +/- 2.7% and 24.3% +/- 13.7% of fibroblasts in the overgrown gingiva treated with CsA rat for 8 days and 30 days, but in 57.0% +/- 5.3% and 81.3% +/- 9.2% of fibroblasts in the each control group gingiva, respectively. Furthermore, in vitro analysis was performed to measure the phagocytosis of cultured fibroblasts by flow cytometry using collagen-coated latex beads. Fibroblasts isolated from CsA-treated gingiva on day 8 and day 30 contained 5.7% +/- 0.6% and 9.9% +/- 1.5% phagocytic cells, whereas control fibroblasts contained 50.3% +/- 5.5% and 33.3% +/- 4.9% phagocytic cells, respectively. The inhibition rate of phagocytic activity was similar between in vivo and in vitro assays. These findings suggest that the decrease of the collagen degradation due to the lower phagocytosis and the lower collagenase mRNA expression are closely associated with the increase of type I collagen accumulation in CsA-treated rat gingiva.

Signal recognition particle receptor (SRPR) is downregulated in a rat model of cyclosporin A-induced gingival overgrowth

Differential display is a powerful technique which can be used to identify those genes whose expression is altered between two or more tissues under investigation. We have applied differential display to a rat model of cyclosporin A-induced gingival overgrowth (CIGO) to identify genes which are differentially expressed as a result of drug treatment. Ten weanling Wistar rats were fed with a pelleted diet containing cyclosporin A (CsA) at 120 mg/kg for 10 d and then 200 mg/kg for a further 30 d prior to culling. Experimental rats were compared with 10 age/sex-matched rats on a control diet. Significant evidence of overgrowth was observed in the interdental papilla between the mandibular first and second molar teeth in the CsA group. Differential display was performed on total cellular RNA extracted from the mandibular buccal gingiva. A cDNA product was isolated which was underexpressed in the overgrowth tissue and demonstrated a 95% sequence homology to the human signal recognition particle receptor (Human Docking Protein). Preliminary studies indicate that this gene is also underexpressed in human CIGO tissue. The method of approach and the potential implications of our findings are discussed.

Cyclosporin A regulates interleukin-1beta and interleukin-6 expression in gingiva: implications for gingival overgrowth

BACKGROUND

Gingival overgrowth is a common side effect following the administration of cyclosporin A (CsA); however, the cellular mechanisms remain poorly understood. CsA's immunosuppressant properties involve the regulation of synthesis and cellular response to cytokines. A CsA-induced alteration in the cytokine profile within gingival tissue could provide a mechanism for gingival hyperplasia. The aim of this study was to investigate the effects of CsA on the production of 2 cytokines - interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) - by both gingival fibroblasts and peripheral blood mononuclear cells (PBMC).

METHODS

Cells were stimulated for 24 hours in the presence of CsA over a concentration range of 100 to 2,000 ng/ml and the resultant cytokine production determined by ELISA. In addition, levels of both cytokines within normal, inflamed, and overgrown gingival tissue were determined.

RESULTS

CsA inhibited IL-6 production by gingival fibroblasts in a dose-dependent manner. In contrast, at a concentration of 2,000 ng/ml, CsA stimulated IL-6 production by PBMC (P <0.05). Fibroblasts derived from overgrown gingiva produced significantly higher levels of IL-6 than their normal counterparts (P <0.05). CsA inhibited IL-1beta production by PBMC over the whole concentration range (P <0.05). IL-1beta was not found in measurable quantities in any of the fibroblast cultures. Levels of IL-6 extracted from overgrown gingival tissue were significantly higher than in inflamed or normal tissue. In contrast IL-1beta levels in overgrown tissue were not statistically significantly greater than those in inflamed tissue.

CONCLUSIONS

These results show that CsA does regulate cytokine expression in gingival tissue. This effect may play an important role in the pathogenesis of CsA-induced gingival overgrowth.

Medication induced gingival overgrowth

A number of idiopathic, pathological and pharmacological reactions may result in an overgrowth of the gingiva. This review concentrates on those overgrowths associated with various pharmacological agents. The pharmaco-kinetics and side effects of each drug associated with gingival overgrowth are discussed along with the clinical and histological features and treatment. By examining the possible pathogeneses for these overgrowths we propose a unifying hypothesis for the causation based around inhibition of apoptosis and decreased collagenase activity modulated by cytoplasmic calcium.

Gingival fibroblast response to cyclosporin A and transforming growth factor beta 1

This study investigates a potential role for TGF beta 1 in the pathogenesis of cyclosporin A-induced gingival overgrowth (CsA-OG). TGF beta 1 was localized immunohistochemically in the connective tissue of both normal gingiva and CsA-OG. Intense staining for TGF beta 1 was detected at the tips of the dermal papillae of the overgrown gingiva. In addition, fibroblasts derived from healthy gingiva and fibroblasts derived from CsA-OG were cultured both as monolayers or embedded in a 3D-collagen gel. Fibroblast activity was monitored in terms of protein and collagen production in the presence of (i) 1 ng/ml TGF beta 1, (ii) 500 ng/ml CsA, or (iii) 500 ng/ml CsA and 1 ng/ml TGF beta 1. In monolayer culture TGF beta 1 significantly increased protein and collagen production in all cell strains (p < 0.05); however, there was no difference in response between fibroblasts from overgrown and healthy tissue. The production of both protein and collagen was significantly lower in the presence of the combination of CsA and TGF beta 1 when compared with the maximal stimulation produced by TGF beta 1 alone. In gel, TGF beta 1 significantly elevated matrix production by all overgrown cell strains (p < 0.05) but had little or no effect on the normal cell strains. The combination of CsA and TGF beta 1 in gel cultures reduced protein and collagen production by overgrown cell strains compared with TGF beta 1 alone. It is concluded that the cellular activity of gingival fibroblasts is dependent on culture conditions and that fibroblasts derived from overgrown gingival tissue are more responsive to TGF beta 1 than normal gingival fibroblasts when cultured in type I collagen gel.

Comparative effects of cyclosporin on glycosaminoglycan synthesis by gingival fibroblasts

Histological studies show that drug-induced gingival overgrowth results from an accumulation of the connective tissue component. Despite comprising a major part of gingival connective tissue, a role for glycosaminoglycans (GAGs) in the pathogenesis of gingival overgrowth has received scant attention. By analyzing the metabolism of 3H-glucosamine, we have compared GAG and hyaluronan synthesis by fibroblasts derived from normal and overgrown gingival tissue, and the effects of cyclosporin on GAG output. GAG production was cell density-dependent, fibroblasts cultured at low density synthesizing significantly increased quantities in comparison to confluent cultures. The effects of cyclosporin on GAG synthesis was also found to be both cell density- and cell strain-dependent. However, cyclosporin-stimulated GAG synthesis by 2/3 overgrown cell strains and 1/3 normal strains. These results suggest that a direct promotion of GAG synthesis by gingival fibroblasts in response to cyclosporin may play a role in the pathogenesis of gingival 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.