BACKGROUND: Drug-induced gingival overgrowth is a frequent adverse effect 
associated principally with administration of the immunosuppressive drug 
cyclosporin A and also certain antiepileptic and antihypertensive drugs. It is 
characterized by a marked increase in the thickness of the epithelial layer and 
accumulation of excessive amounts of connective tissue. The mechanism by which 
the drugs cause gingival overgrowth is not yet understood. The purpose of this 
study was to compare proliferative activity of normal human gingiva and in 
cyclosporine A-induced gingival overgrowth.
METHODS: Gingival samples were collected from 12 generally healthy individuals 
and 22 Cyclosporin A-medicated renal transplant recipients. Expression of 
proliferating cell nuclear antigen was evaluated in formalin-fixed, 
paraffin-embedded gingival samples using an immunoperoxidase technique and a 
monoclonal antibody for this antigen.
RESULTS: There were differences between the Cyclosporin A group and control 
group in regard to proliferating cell nuclear antigen and epithelial thickness. 
In addition, the degree of stromal inflammation was higher in the Cyclosporin A 
group when compared with the control group.
CONCLUSION: The results suggest that the increased epithelial thickness observed 
in Cyclosporin A-induced gingival overgrowth is associated with increased 
proliferative activity in keratinocytes.