Zoledronate inhibits fibroblasts' proliferation and activation via targeting TGF-β signaling pathway

Previous preclinical and clinical studies have demonstrated that zoledronate might inhibit neointimal hyperplasia at least partly by inhibiting the proliferation, adhesion and migration of vascular smooth muscle cells (VSMCs). However, whether zoledronate influences fibroblasts' proliferation and activation, which also play a key role in neointimal hyperplasia and vascular remodeling, remains largely unknown. In the present study, the effect of zoledronate on fibroblasts was investigated and the underlying molecular mechanisms were examined.

After treatment with zoledronate, changes in biological behaviors, including the morphology, proliferation, cell-cycle distribution and migration of fibroblasts (NIH3T3 cells), were observed. The expression of α-SMA, TGF-β1 and TGF-β2 and the level of Smad2/3 phosphorylation in cultured fibroblasts were examined by Western blot. In vivo expression of α-SMA and TGF-β1 was assessed by immunohistochemical staining.

It was shown that the typical fibroblast cell morphology was altered after zoledronate exposure. Cultured fibroblasts treated with zoledronate displayed dose-dependent inhibition of cell proliferation due to cell-cycle arrest in the S phase. Cell migration activities were also dose dependently suppressed by zoledronate treatment. Expression of α-SMA in cultured fibroblasts was significantly reduced by zoledronate treatment. Further analysis showed decreased expression of TGF-β1 and α-SMA by periadventitial delivery of zoledronate in the rat carotid balloon-injury model. The expression of TGF-β1 and TGF-β2 and the phosphorylation of Smad2/3 in cultured fibroblasts were significantly inhibited by zoledronate treatment.

Our findings demonstrated that zoledronate can inhibit the proliferation, migration and activation of fibroblasts via the TGF-β signaling pathway and revealed a novel mechanism of zoledronate action against neointimal hyperplasia.