Role of MT1-MMP in Estrogen-Mediated Cellular Processes of Intimal Hyperplasia

Background. Hormone replacement therapy increases intimal hyperplasia (IH) following vascular intervention. Matrix metalloproteinases (MMPs) play a role in IH development. We have shown estrogen up-regulates MT1-MMP expression, a transmembrane protein that activates MMP-2, and increases vascular smooth muscle cell (VSMC) collagen invasion via increased MMP-2 activity. Here we hypothesize inhibition of MT1-MMP will prevent hormonally-stimulated increased MMP-2 activation and the downstream cellular processes of IH pathogenesis. Methods. VSMCs from a postmenopausal donor were transfected with MT1-MMP or negative control siRNAs, treated with estrogen (Est), analyzed by qPCR, Western blot, zymography, migration, invasion, and proliferation assays. Results. Est treatment of MT1-MMP silenced cells still resulted in increased MT1-MMP expression (C = 41% +/- 4%; Est = 52% +/- 2%; P < 0.05). Silencing of MT1MMP decreased basal MMP-2 activity (nonsilenced = 100%; MT1-silenced= 87% +/- 3%; P < 0.05) but had no effect on basal invasion or proliferation. Est treatment of MT1-MMP silenced cells still resulted in increased MMP-2 activity (C = 87% +/- 3%; Est = 101% +/- 4%; P < 0.05) and invasion (C = 89% +/- 6%; Est = 109% +/- 3%; P < 0.05) compared with MT1-MMP silenced control cells. However, silencing of MT1-MMP did inhibit Estand serum-stimulated proliferation (C = 106% +/- 18%; Est = 104% +/- 16%; FBS = 121% +/- 24%; P = NS). Conclusion. Silencing of MT1-MMP in aged VSMCs results in impaired but not complete inhibition of basal and Est-stimulated increases inMMP-2 activity. Other mechanisms appear to be playing a role in hormonally-regulated cellular processes of IH pathogenesis. Future studieswill target other signaling cascades, with the goal of identifying mechanisms responsible for hormonally-modulated unbalanced MMPs. In vivo manipulation of the expression patterns ofMT1-MMPwill be examined for the prevention of IH in animal models of vascular disease. (C) 2012Elsevier Inc. All rights reserved.