Expression of matrix metalloproteinases in cyclosporin-treated gingival fibroblasts is regulated by transforming growth factor (TGF)-β1 autocrine stimulation

Background: Gingival overgrowth is a common side effect following the administration of cyclosporin A (CsA). The pathogenesis of this condition is not fully understood; however, recent studies show that CsA regulates the transcription of several cytokines including transforming growth factor-beta1 (TGF-beta1). The aim of this study was to investigate the potential role of TGF-beta1 in the pathogenesis of CsA-induced gingival overgrowth, exploring a possible autocrine stimulation of TGF-beta1 as a cellular regulator of synthesis of matrix metalloproteinases (MMPs) and its tissue inhibitors (TIMPs). Methods: Gingival fibroblasts from human normal gingiva were incubated with increasing concentrations of CsA, cultured for 24 hours, and the expression and production of TGF-beta1 determined by semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) and enzyme-linked immunosorbent assay (ELISA), respectively. MMP and TIMP mRNA expression levels were also analyzed by RT-PCR. To determine the effect of TGF-beta1 on the expression of MMP and TIMP by human gingival fibroblasts under CsA treatment, human gingival fibroblast cultures were treated with sense oligonucleotides (SON) or antisense oligonucleotides (AON). Results: CsA simultaneously stimulated TGF-beta1 expression and production and inhibited expression of MMP-1 and MMP-2 by human gingival fibroblasts, whereas CsA has a slight effect on TIMP-1 and TIMP-2 expression. AON reduced TGF-beta1 production as demonstrated by ELISA, whereas TGF-P1 mRNA expression levels were not significantly modified. The inhibition of TGF-beta1 production by AON modulated MMP expression, demonstrating the autocrine inhibitory effect of TGF-beta1 in CsA-treated human gingival fibroblasts. Conclusions: The data presented here suggest that TGF-beta1 in an autocrine fashion may contribute to a reduction of proteolytic activity of human gingival fibroblasts in CsA-induced gingival overgrowth, which favors the accumulation of extracellular matrix.