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Cyclosportne a (csa) is a widely used immunosuppressant for transplant patients and is also used for the treatment of a wide variety of systemic diseases with immunologic components. A prominent side effect of CSA administration is gingival overgrowth (hyperplasia). It has been postulated that CSA alters fibroblast activity through effects on various growth factors/cytokines. However, as yet, data concerning the molecular mechanisms involved in pathologic connective tissue proliferation are preliminary in nature. Our previous investigations concerning phenytoin‐induced effects on platelet‐derived growth factor B (PDGF‐B) gene expression have demonstrated that other drugs which cause gingival overgrowth can upregulate macrophage PDGF‐B gene expression in vitro and in vivo. The purpose of the present study was to evaluate PDGF‐B gene expression in gingival tissues of patients receiving CSA therapy and exhibiting gingival overgrowth to determine if similar PDGF‐B upregulation occurs in response to CSA and to identify PDGF‐B producing cells in these tissues. Quantitative competitive reverse transcription polymerase chain reaction (QC‐RTPCR) techniques were utilized to measure PDGF‐B mRNA levels in CSA overgrowth patients and normal controls (N = 6/group). Results were expressed as mean ± mRNA copy number and tested for significance using unpaired t‐tests. Gingival samples were harvested (standardized for local inflammation at the sample site), total RNA was extracted, and QC‐RTPCR was performed using specific PDGF‐B primers and a corresponding competitive internal standard. CSA‐treated patients exhibiting gingival overgrowth demonstrated approximately 48‐fold increase in PDGF‐B mRNA (7667.1 ± 477.4 copies for CSA patients vs. 158.2 ± 37.1 copies for controls; P < 0.001). Additionally, dual fluorescence immunohistochemistry for mature macrophage marker antigen (CD51) and intracellular PDGF‐B was utilized to identify and localize PDGFB producing cells in hyperplastic gingiva of CSA‐treated patients. PDGF‐B producing cells were demonstrated to be macrophages distributed in a non‐uniform manner throughout the papillary connective tissue. These results further support the hypothesis that the molecular mechanisms responsible for drug‐induced gingival overgrowth may involve upregulation of PDGF‐B macrophage gene expression. We continue to investigate specific CSA‐induced alterations of macrophage PDGF‐B gene expression in vitro and in vivo. J Periodontol 1996;67:271–278.

It has been proposed that healthy gingiva is in a continuous state of wound repair. Thus, one might expect to find cells in normal gingiva producing growth factors associated with wound healing such as platelet-derived growth factor B chain (PDGF-B). One might also expect to find increased numbers of these cells or increased amounts of these growth factors in conditions which involve increased tissue volume such as drug-induced gingival overgrowth (DGO). The purpose of this study was to quantify PDGF-B gene expression and identify cells producing PDGF-B in normal gingiva and DGO. Cyclosporine A (CSA) was selected as a prototype of the overgrowth condition. Twelve patients with clinical CSA DGO and 12 patients with no DGO or history of drugs known to cause DGO were selected for study. Frozen sections of gingival specimens from these patients were subjected to in situ hybridization for PDGF-B mRNA. Positive cells were counted and expressed as mean +/- SEM cells/mm2 of lamina propria. Morphometric analysis revealed 6.2 +/- 1.9 cells/mm2 for control gingiva and 10.3 +/- 3.4 cells/mm2 for CSA DGO samples. There was no statistically significant difference between groups. PDGF-B gene expression was measured in these cells and expressed as mean +/- SEM silver grains/cells. There was a significant upregulation of PDGF-B gene expression in cells from the CSA DGO group (39.5 +/- 14.7 silver grains/cell for normal gingiva vs. 255.3 +/- 77.1 silver grains/cell for CSA DGO samples; P < 0.001). The presence of PDGF-B in these cells was confirmed in all cases by immunocytochemical localization. Additionally, PDGF-B producing cells were identified as macrophages in sections taken from an additional patient with CSA DGO by double immunofluorescence labeling of the CD51 membrane marker for macrophages and intracellular PDGF-B. These findings are consistent with the concept that healthy gingiva is in a continuous state of wound repair and support the hypothesis that CSA DGO is associated with enhanced macrophage PDGF-B gene expression rather than an increase in the number of PDGF-B producing macrophages.