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

Background: A previous study suggested that mast cells (MC) are involved in the development of cyclosporin A-induced gingival hyperplasia, since an increased number of MC were observed in the tissue sections of enlarged gingiva. To determine the role of MC in gingival hyperplasia, an MC-deficient mouse model was used in the current study. Methods: MC-deficient mice (WBB6F1xW/W-V) and their littermates (+/+) were fed sucrose-containing diets supplemented with or without varying concentrations (300, 400, 500, 600 mg) of cyclosporin A/kg of diet. After 30 days, the mice were sacrificed and the degree of gingival hyperplasia was evaluated by the appearance of the gingiva. Tissue MC were stained with toluidine blue to confirm the presence or absence of MC in the enlarged gingiva. Results: Both W/W-V and +/+ mice, when fed with 600 mg cyclosporin A/kg diet for 30 days, exhibited a similar degree of gingival hyperplasia, while other test mice or control mice did not, Toluidine blue staining of the tissue sections confirmed the presence of MC in the enlarged gingiva of the +/+ mice, but not the W/WV mice. Conclusions: These results indicate that mast cells are not necessary in the development of cyclosporin A-induced gingival hyperplasia, and that the increased number of MC observed in the enlarged gingiva may be a secondary effect of gingival hyperplasia. We also conclude that a study of mice lacking certain molecules or cells would be quite useful in determining the molecules or cell types responsible for the pathogenesis of drug-induced gingival hyperplasia.