title: Role of MT1-MMP in estrogen-mediated cellular processes of intimal hyperplasia.
abstract: 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 q-PCR, 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 MT1-MMP 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 Est- and serum-stimulated proliferation (C = 106% ± 18%; Est = 104% ± 16%; FBS = 121% ± 24%; P = NS).
  
  
  CONCLUSIONS
  Silencing of MT1-MMP in aged VSMCs results in impaired but not complete inhibition of basal and Est-stimulated increases in MMP-2 activity. Other mechanisms appear to be playing a role in hormonally-regulated cellular processes of IH pathogenesis. Future studies will target other signaling cascades, with the goal of identifying mechanisms responsible for hormonally-modulated unbalanced MMPs. In vivo manipulation of the expression patterns of MT1-MMP will be examined for the prevention of IH in animal models of vascular disease.
authors.affiliation: Department of Surgery, University of Tennessee Graduate School of Medicine, Knoxville, Tennessee 37920, USA.
authors.forename: Deidra J H
authors.initials: DJ
authors.lastname: Mountain
authors.forename: Stacy S
authors.initials: SS
authors.lastname: Kirkpatrick
authors.forename: Michael B
authors.initials: MB
authors.lastname: Freeman
authors.forename: Scott L
authors.initials: SL
authors.lastname: Stevens
authors.forename: Mitchell H
authors.initials: MH
authors.lastname: Goldman
authors.forename: Oscar H
authors.initials: OH
authors.lastname: Grandas
mesh_terms: D002465:Cell Movement; D049109:Cell Proliferation; D002478:Cells, Cultured; D024141:Collagen Type IV; D015914:Estrogen Replacement Therapy; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D006801:Humans; D006965:Hyperplasia / Q000201:enzymology / Q000209:etiology; D053511:Matrix Metalloproteinase 14 / Q000378:metabolism*; D020778:Matrix Metalloproteinase 2 / Q000378:metabolism*; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000201:enzymology*; D017698:Postmenopause / Q000378:metabolism*; D034622:RNA Interference; D019715:Tissue Inhibitor of Metalloproteinase-1 / Q000378:metabolism; D019716:Tissue Inhibitor of Metalloproteinase-2 / Q000378:metabolism; D017539:Tunica Intima / Q000201:enzymology*
chemical_list: D024141:Collagen Type IV; D004967:Estrogens; C560822:TIMP1 protein, human; C560823:TIMP2 protein, human; D019715:Tissue Inhibitor of Metalloproteinase-1; D019716:Tissue Inhibitor of Metalloproteinase-2; C522361:MMP2 protein, human; D020778:Matrix Metalloproteinase 2; C507086:MMP14 protein, human; D053511:Matrix Metalloproteinase 14