Mast cells are not involved in the development of cyclosporin A-induced gingival hyperplasia: a study with mast cell-deficient mice

Prevention of phenytoin-induced gingival overgrowth by lovastatin in mice

Drug-induced gingival overgrowth is caused by the antiseizure medication phenytoin, calcium channel blockers, and ciclosporin. Characteristics of these drug-induced gingival overgrowth lesions differ. We evaluate the ability of a mouse model to mimic human phenytoin-induced gingival overgrowth and assess the ability of a drug to prevent its development. Lovastatin was chosen based on previous analyses of tissue-specific regulation of CCN2 production in human gingival fibroblasts and the known roles of CCN2 in promoting fibrosis and epithelial to mesenchymal transition. Data indicate that anterior gingival tissue overgrowth occurred in phenytoin-treated mice based on gross tissue observations and histomorphometry of tissue sections. Molecular markers of epithelial plasticity and fibrosis were regulated by phenytoin in gingival epithelial tissues and in connective tissues similar to that seen in humans. Lovastatin attenuated epithelial gingival tissue growth in phenytoin-treated mice and altered the expressions of markers for epithelial to mesenchymal transition. Data indicate that phenytoin-induced gingival overgrowth in mice mimics molecular aspects of human gingival overgrowth and that lovastatin normalizes the tissue morphology and the expression of the molecular markers studied. Data are consistent with characterization of phenytoin-induced human gingival overgrowth in vivo and in vitro characteristics of cultured human gingival epithelial and connective tissue cells. Findings suggest that statins may serve to prevent or attenuate phenytoin-induced human gingival overgrowth, although specific human studies are required.

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.

Mast cell subpopulations in gingival overgrowth induced by immunosuppressive and nifedipine medication

BACKGROUND

An immunohistochemical study was conducted to compare distributions of mast cell subpopulations in normal human gingiva and in gingival overgrowth induced by nifedipine and immunosuppressive medication.

METHODS

Gingival samples were collected from 12 triple-medicated organ transplant recipients (immunosuppression group), 11 triple-medicated organ transplant recipients taking nifedipine (immunosuppression plus nifedipine group), 11 nifedipine-medicated cardiac outpatients (nifedipine group), and 20 generally healthy individuals (control group). Cryostat sections were stained with mAbs for tryptase and chymase, and an avidin-biotin enzyme complex method was used to detect tryptase-positive mast cells (MC(T)), tryptase- and chymase-positive mast cells (MC(TC)), and chymase-positive mast cells (MC(C)). Total numbers of labeled cells were determined in connective tissue beneath the sulcular epithelium, connective tissue beneath the oral epithelium, and middle connective tissue. Statistical analyses were conducted using the Kruskal-Wallis test, the Mann-Whitney U-test, and Pearson's correlation test.

RESULTS

In the three counting zones combined, numbers of MC(TC) cells and MC(C) cells were lower (P = 0.001 and P = 0.048, respectively) in the immunosuppression group than in the control group. The difference in numbers of MC(TC) cells was most marked in the middle connective tissue. Nifedipine medication had no effect on numbers of the mast cell subclasses.

CONCLUSIONS

Immunosuppressive medication without concomitant nifedipine decreases the numbers of MC(TC) and MC(C) in overgrown gingiva. Chymase-positive mast cells may play a role in formation of gingival overgrowth, especially in patients receiving cyclosporin A (CsA) medication with no concomitant nifedipine. In this respect, nifedipine and CsA are different.

Cathepsin-L, a key molecule in the pathogenesis of drug-induced and I-cell disease-mediated gingival overgrowth: a study with cathepsin-L-deficient mice

Drug-induced gingival overgrowth, the chronic side effect of calcium antagonists, is frequently seen due to the increase in patients with hypertension, although the etiology of the disease is largely unknown. I-cell disease, which accompanies gingival overgrowth, is characterized by a deficiency in UDP-N-acetyl-glucosamine and is classified as one of the lysosomal storage diseases. Here, we hypothesized that a common mechanism may underlie the etiology of gingival overgrowth seen in patients treated with calcium antagonist and in patients with I-cell disease. A calcium antagonist, nifedipine, specifically suppressed cathepsin-L activity and mRNA expression, but not that of cathepsin-B in cultured gingival fibroblasts. The activity of cathepsin-L was suppressed up to 50% at 24 hours after treatment of the cells with the reagent. The selective suppression of cathepsin-L activity appeared not to be dependent on Ca(2+), since treatment of the cells with thapsigargin suppressed both cathepsin-B and -L activity. Mice deficient in the cathepsin-L gene manifested enlarged gingivae. Histological observation of the gingivae demonstrated typical features of acanthosis, a phenotype very similar to that of experimentally induced gingival overgrowth. Since cathepsin-L deficiency was reported to be associated with thickening of the skin, impaired cathepsin-L activity may play a key role in the establishment of skin and gingival abnormalities seen in I-cell disease. In addition, reduced cathepsin-L activity may play an important role in inducing drug-induced gingival overgrowth.

Oral mucosa alterations induced by cyclosporin in mice: morphological features

BACKGROUND AND OBJECTIVE

The mechanisms involved in the pathogenesis of cyclosporin A-induced gingival hyperplasia are not well understood. The present work aimed at developing a mouse model with the characteristics of the human process, i.e. time of appearance, dose dependency and the capacity of developing in a variety of genetic backgrounds. This model would present the advantages of using a very well known animal species, small and easy to handle, with a number of experimental reagents (antibodies, etc.) already available against its products.

METHODS

Three different strains of mice were used: CBA, F1(C57Bl x DBA), Balb/c. Groups of mice received different concentrations of cyclosporin A (CSA) (10 mg/kg, 25 mg/kg and 40 mg/kg body weight) intraperitoneally five times a week. Anatomical and histological alterations were recorded at various time intervals.

RESULTS

All strains of mice presented gingival hyperplasia after 8 weeks of CSA treatment. A dose-dependency was observed with regard to the time of first appearance of alterations. Increased redness was seen in all animals at the sixth week, independent of the dosage used. Histologic examination exhibited increased vascularization, epithelial and connective tissue thickening, edema and a mononuclear infiltrate.

CONCLUSIONS

It was possible to develop CSA-induced gingival hyperplasia in mice with the characteristics described in humans and other species. The use of this animal model may help in the elucidation of the process involved in CSA-induced gingival overgrowth.