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.