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Figure 2. Summary of functional interactions in drug-induced gingival overgrowth. Fibrogenic drugs (phenytoin, nifedipine, cyclosporin A) are envisioned to alter the phenotypes of inflammatory cells (principally lymphocytes and macrophages), resulting in the observed abnormal balances of cytokines and inflammatory mediators. This would result in distortion of normal responses to bacterial insults and injury, as follows: A subset of cytokines would influence gingival fibroblast extracellular matrix metabolism and proliferation. For example, in the case of TGF-ß1 overexpression in phenytoin-induced gingival overgrowth, fibroblasts produce and accumulate CTGF that has direct and indirect effects on extracellular matrix production, cell/extracellular matrix (ECM) interactions, and activity of other growth factors and cytokines, and gingival fibroblast extracellular matrix production (block arrows). By contrast, increased FGF-2 is seen as principally a mitogenic factor that stimulates gingival fibroblast proliferation. In addition, unique aspects of gingival fibroblast metabolism are believed to confer tissue-specific features of extracellular matrix metabolism in gingiva.
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