title: Tensile strain increased COX-2 expression and PGE2 release leading to weakening of the human amniotic membrane.
abstract: BACKGROUND
  There is evidence that premature rupture of the fetal membrane at term/preterm is a result of stretch and tissue weakening due to enhanced prostaglandin E2 (PGE2) production. However, the effect of tensile strain on inflammatory mediators and the stretch sensitive protein connexin-43 (Cx43) has not been examined. We determined whether the inflammatory environment influenced tissue composition and response of the tissue to tensile strain.
  
  
  METHODS
  Human amniotic membranes isolated from the cervix (CAM) or placenta regions (PAM) were examined by second harmonic generation to identify collagen orientation and subjected to tensile testing to failure. In separate experiments, specimens were subjected to cyclic tensile strain (2%, 1 Hz) for 24 h. Specimens were examined for Cx43 by immunofluorescence confocal microscopy and expression of COX-2 and Cx43 by RT-qPCR. PGE2, collagen, elastin and glycosaminoglycan (GAG) levels were analysed by biochemical assay.
  
  
  RESULTS
  Values for tensile strength were significantly higher in PAM than CAM with mechanical parameters dependent on collagen orientation. Gene expression for Cx43 and COX-2 was enhanced by tensile strain leading to increased PGE2 release and GAG levels in PAM and CAM when compared to unstrained controls. In contrast, collagen and elastin content was reduced by tensile strain in PAM and CAM.
  
  
  CONCLUSIONS
  Fibre orientation has a significant effect on amniotic strength. Tensile strain increased Cx43/COX-2 expression and PGE2 release resulting in tissue softening mediated by enhanced GAG levels and a reduction in collagen/elastin content.
  
  
  CONCLUSIONS
  A combination of inflammatory and mechanical factors may disrupt amniotic membrane biomechanics and matrix composition.
authors.affiliation: Institute for Women's Health, University College London, 86-96 Chenies Mews, London WC1E 6HX, UK.
authors.forename: B
authors.initials: B
authors.lastname: Chowdhury
authors.affiliation: Institute for Women's Health, University College London, 86-96 Chenies Mews, London WC1E 6HX, UK.
authors.forename: A L
authors.initials: AL
authors.lastname: David
authors.affiliation: Department of Cell and Developmental Biology, UCL, Gower Street, London WC1E 6BT, UK.
authors.forename: C
authors.initials: C
authors.lastname: Thrasivoulou
authors.affiliation: Lee Kong Chian School of Medicine, Nanyang Technological University, 11, Mandalay Road, Singapore.
authors.forename: D L
authors.initials: DL
authors.lastname: Becker
authors.affiliation: Institute of Bioengineering, School of Engineering and Material Science, Queen Mary University of London, Mile End Road, London E1 4NS, UK; Faculty of Health Sciences, University of Southampton, Southampton General Hospital, Southampton SO16 6YD, UK.
authors.forename: D L
authors.initials: DL
authors.lastname: Bader
authors.affiliation: Institute of Bioengineering, School of Engineering and Material Science, Queen Mary University of London, Mile End Road, London E1 4NS, UK. Electronic address: t.t.chowdhury@qmul.ac.uk.
authors.forename: T T
authors.initials: TT
authors.lastname: Chowdhury
mesh_terms: D000650:Amnion / Q000378:metabolism*; D018031:Connexin 43 / Q000235:genetics / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D015232:Dinoprostone / Q000378:metabolism*; D005260:Female; D005322:Premature Rupture of Fetal Membranes / Q000378:metabolism*; D006801:Humans; D011247:Pregnancy; D013314:Stress, Mechanical; D013718:Tensile Strength / Q000502:physiology*
chemical_list: D018031:Connexin 43; D051546:Cyclooxygenase 2; D015232:Dinoprostone
keywords: Amniotic membrane; Collagen; Connexin 43; Preterm labour; Preterm premature rupture of the membrane; Prostaglandin E(2); Tensile strain