title: Matrix Metalloproteinase-3 (MMP-3) Is an Endogenous Activator of the MMP-9 Secreted by Placental Leukocytes: Implication in Human Labor.
abstract: BACKGROUND
  The activity of matrix degrading enzymes plays a leading role in the rupture of the fetal membranes under normal and pathological human labor, and matrix metalloproteinase-9 (MMP-9) it is considered a biomarker of this event. To gain further insight into local MMP-9 origin and activation, in this study we analyzed the contribution of human placental leukocytes to MMP-9 secretion and explored the local mechanisms of the pro-enzyme activation.
  
  
  METHODS
  Placental blood leukocytes were obtained from women at term gestation without labor and maintained in culture up to 72 h. MMP-9 activity in the culture supernatants was determined by zymography and using a specific substrate. The presence of a potential pro-MMP-9 activator in the culture supernatants was monitored using a recombinant biotin-labeled human pro-MMP-9. To characterize the endogenous pro-MMP-9 activator, MMP-1, -3, -7 and -9 were measured by multiplex assay in the supernatants, and an inhibition assay of MMP-9 activation was performed using an anti-human MMP-3 and a specific MMP-3 inhibitor. Finally, production of MMP-9 and MMP-3 in placental leukocytes obtained from term pregnancies with and without labor was assessed by immunofluorescence.
  
  
  RESULTS
  Placental leukocytes spontaneously secreted pro-MMP-9 after 24 h of culture, increasing significantly at 48 h (P≤0.05), when the active form of MMP-9 was detected. Culture supernatants activated the recombinant pro-MMP-9 showing that placental leukocytes secrete the activator. A significant increase in MMP-3 secretion by placental leukocytes was observed since 48 h in culture (P≤0.05) and up to 72 h (P≤0.001), when concentration reached its maximum value. Specific activity of MMP-9 decreased significantly (P≤0.005) when an anti-MMP-3 antibody or a specific MMP-3 inhibitor were added to the culture media. Placental leukocytes from term labor produced more MMP-9 and MMP-3 compared to term non-labor cells.
  
  
  CONCLUSIONS
  In this work we confirm that placental leukocytes from human term pregnancies are able to secrete large amounts of MMP-9, and that the production of the enzyme it is enhanced by labor. We also demonstrate for the first time that endogenous MMP-3 plays a major role in MMP-9 activation process. These findings support the contribution of placental leukocytes to create the collagenolytic microenvironment that induces the rupture of the fetal membranes during human labor.
authors.affiliation: Instituto Nacional de Perinatologia Isidro Espinosa de los Reyes, Mexico City, Mexico.
authors.forename: Arturo
authors.initials: A
authors.lastname: Flores-Pliego
authors.affiliation: Instituto Nacional de Perinatologia Isidro Espinosa de los Reyes, Mexico City, Mexico.
authors.forename: Aurora
authors.initials: A
authors.lastname: Espejel-Nuñez
authors.affiliation: Unidad de Vinculacion de la Facultad de Medicina, UNAM en el Instituto Nacional de Medicina Genomica, Mexico City, Mexico.
authors.forename: Marisol
authors.initials: M
authors.lastname: Castillo-Castrejon
authors.affiliation: Unidad de Vinculacion de la Facultad de Medicina, UNAM en el Instituto Nacional de Medicina Genomica, Mexico City, Mexico.
authors.forename: Noemi
authors.initials: N
authors.lastname: Meraz-Cruz
authors.affiliation: Instituto Nacional de Perinatologia Isidro Espinosa de los Reyes, Mexico City, Mexico.
authors.forename: Jorge
authors.initials: J
authors.lastname: Beltran-Montoya
authors.affiliation: Instituto Nacional de Perinatologia Isidro Espinosa de los Reyes, Mexico City, Mexico.
authors.forename: Veronica
authors.initials: V
authors.lastname: Zaga-Clavellina
authors.affiliation: Instituto Nacional de Perinatologia Isidro Espinosa de los Reyes, Mexico City, Mexico.
authors.forename: Sonia
authors.initials: S
authors.lastname: Nava-Salazar
authors.affiliation: Instituto Nacional de Perinatologia Isidro Espinosa de los Reyes, Mexico City, Mexico.
authors.forename: Maribel
authors.initials: M
authors.lastname: Sanchez-Martinez
authors.affiliation: Unidad de Vinculacion de la Facultad de Medicina, UNAM en el Instituto Nacional de Medicina Genomica, Mexico City, Mexico.
authors.forename: Felipe
authors.initials: F
authors.lastname: Vadillo-Ortega
authors.affiliation: Instituto Nacional de Perinatologia Isidro Espinosa de los Reyes, Mexico City, Mexico.
authors.forename: Guadalupe
authors.initials: G
authors.lastname: Estrada-Gutierrez
mesh_terms: D002470:Cell Survival; D003094:Collagen / Q000378:metabolism; D004789:Enzyme Activation; D004792:Enzyme Precursors / Q000378:metabolism; D005260:Female; D006801:Humans; D007743:Labor, Obstetric / Q000097:blood* / Q000378:metabolism*; D007962:Leukocytes / Q000166:cytology / Q000201:enzymology / Q000378:metabolism*; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism*; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism*; D010920:Placenta / Q000166:cytology*; D011247:Pregnancy
chemical_list: D004792:Enzyme Precursors; D003094:Collagen; C120487:pro-matrix metalloproteinase 9; C511768:MMP3 protein, human; D019278:Matrix Metalloproteinase 3; C579270:MMP9 protein, human; D020780:Matrix Metalloproteinase 9