CYCLOSPORINE-A UP-REGULATES PLATELET-DERIVED GROWTH-FACTOR-B CHAIN INHYPERPLASTIC HUMAN GINGIVA

CYCLOSPORINE A (CSA) IS A WIDELY USED immunosuppressant for transplant patients and is also used for the treatment of a wide variety of syst emic diseases with immunologic components. A prominent side effect of CSA administration is gingival overgrowth (hyperplasia). It has been p ostulated that CSA alters fibroblast activity through effects on vario us growth factors/cytokines. However, as yet, data concerning the mole cular mechanisms involved in pathologic connective tissue proliferatio n are preliminary in nature. Our previous investigations concerning ph enytoin-induced effects on platelet-derived growth factor B (PDGF-B) g ene 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 g ene expression in gingival tissues of patients receiving CSA therapy a nd exhibiting gingival overgrowth to determine if similar PDGF-B upreg ulation occurs in response to CSA and to identify PDGF-B producing cel ls in these tissues. Quantitative competitive reverse transcription po lymerase 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 te sted for significance using unpaired t-tests. Gingival samples were ha rvested (standardized for local inflammation at the sample site), tota l 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 patient s vs. 158.2 +/- 37.1 copies for controls; P < 0.001). Additionally, du al fluorescence immunohistochemistry for mature macrophage marker anti gen (CD51) and intracellular PDGF-B was utilized to identify and local ize PDGF-B producing cells in hyperplastic gingiva of CSA-treated pati ents. PDGF-B producing cells were demonstrated to be macrophages distr ibuted in a non-uniform manner throughout the papillary connective tis sue. These results further support the hypothesis that the molecular m echanisms responsible for drug-induced gingival overgrowth may involve upregulation of PDGF-B macrophage gene expression. We continue to inv estigate specific CSA-induced alterations of macrophage PDGF-B gene ex pression in vitro and in vivo.