Mitotic activity of keratinocytes in nifedipine- and immunosuppressive medication-induced gingival overgrowth

Background: The purpose of the study was to compare mitotic activity in the basal cell layer of normal human gingiva and in nifedipine- and immunosupp ressive medication-induced gingival overgrowth. Methods: Gingival samples were collected from 19 generally healthy individu als, 12 nifedipine-medicated cardiac patients, and 22 immunosuppression-med icated (azathioprine, prednisolone, and cyclosporin A) organ transplant rec ipients. The transplant recipients were divided into those not taking nifed ipine and those taking nifedipine. Cryostat sections were stained with mono clonal antibody for Ki-67, using an avidin-biotin-enzyme complex method. Th e mitotic activities of epithelial cells were determined as percentages of Ki-67 labeled cells in relation to total numbers of epithelial cells in the basal layer of oral, oral sulcular, and sulcular epithelium. Results: Mitotic activities were significantly higher in all 3 medication g roups in the oral epithelium (P less than or equal to0.003), and in the imm unosuppression group in the sulcular epithelium (P = 0.032) than in the con trols. In the oral sulcular epithelium, mitotic activity was fairly similar in all medication groups. In the nifedipine group a significant negative c orrelation was found between duration of nifedipine medication and the perc entage of Ki-67 labeled cells in the oral epithelium (P = 0.025). Conclusions: The results suggest that the increased epithelial thickness ob served in nifedipine- and cyclosporin A-induced gingival overgrowth is asso ciated with increased mitotic activity, especially in the oral epithelium.