title: Increased MMPs expression and decreased contraction in the rat myometrium during pregnancy and in response to prolonged stretch and sex hormones.
abstract: Normal pregnancy is associated with uterine relaxation to accommodate the stretch imposed by the growing fetus; however, the mechanisms underlying the relationship between pregnancy-associated uterine stretch and uterine relaxation are unclear. We hypothesized that increased uterine stretch during pregnancy is associated with upregulation of matrix metalloproteinases (MMPs), which in turn cause inhibition of myometrium contraction and promote uterine relaxation. Uteri from virgin, midpregnant (day 12), and late-pregnant rats (day 19) were isolated, and myometrium strips were prepared for measurement of isometric contraction and MMP expression and activity using RT-PCR, Western blot analysis, and gelatin zymography. Oxytocin caused concentration-dependent contraction of myometrium strips that was reduced in mid- and late-pregnant rats compared with virgin rats. Pretreatment with the MMP inhibitors SB-3CT (MMP-2/MMP-9 Inhibitor IV), BB-94 (batimastat), or Ro-28-2653 (cipemastat) enhanced contraction in myometrium of pregnant rats. RT-PCR, Western blot analysis, and gelatin zymography demonstrated increased mRNA expression, protein amount, and activity of MMP-2 and MMP-9 in myometrium of late-pregnant>midpregnant>virgin rats. Prolonged stretch of myometrium strips of virgin rats under 8 g basal tension for 18 h was associated with reduced contraction and enhanced expression and activity of MMP-2 and MMP-9, which were reversed by MMP inhibitors. Concomitant treatment of stretched myometrium of virgin rats with 17β-estradiol (E2), progesterone (P4), or E2+P4 was associated with further reduction in contraction and increased MMP expression and activity. MMP-2 and MMP-9 caused significant reduction of oxytocin-induced contraction of myometrium of virgin rat. Thus, normal pregnancy is associated with reduced myometrium contraction and increased MMPs expression and activity. The results are consistent with the possibility that myometrium stretch and concomitant increase in sex hormones during pregnancy are associated with increased expression/activity of specific MMPs, which in turn inhibit uterine contraction and promote uterine relaxation.
authors.affiliation: Vascular Surgery Research Laboratory, Division of Vascular and Endovascular Surgery, Brigham and Women's Hospital, Boston, MA, USA.
authors.forename: Zongzhi
authors.initials: Z
authors.lastname: Yin
authors.forename: Alaa A
authors.initials: AA
authors.lastname: Sada
authors.forename: Ossama M
authors.initials: OM
authors.lastname: Reslan
authors.forename: Neha
authors.initials: N
authors.lastname: Narula
authors.forename: Raouf A
authors.initials: RA
authors.lastname: Khalil
mesh_terms: D000818:Animals; D004790:Enzyme Induction / Q000187:drug effects; D004958:Estradiol / Q000378:metabolism*; D005260:Female; D066298:In Vitro Techniques; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism*; D061965:Matrix Metalloproteinase Inhibitors; D009126:Muscle Relaxation / Q000187:drug effects; D009129:Muscle Tonus / Q000187:drug effects; D009213:Myography; D009215:Myometrium / Q000187:drug effects / Q000201:enzymology* / Q000378:metabolism; D009994:Osmolar Concentration; D010121:Oxytocin / Q000378:metabolism; D010812:Physical Stimulation; D011247:Pregnancy; D011374:Progesterone / Q000378:metabolism*; D011480:Protease Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D014590:Uterine Contraction / Q000187:drug effects
chemical_list: D061965:Matrix Metalloproteinase Inhibitors; D011480:Protease Inhibitors; D012333:RNA, Messenger; D011374:Progesterone; D004958:Estradiol; D010121:Oxytocin; D020778:Matrix Metalloproteinase 2; C522363:Mmp2 protein, rat; D020780:Matrix Metalloproteinase 9; C572337:Mmp9 protein, rat