Effect of experimental genital mycoplasmosis on production of matrix metalloproteinases in membranes and amniotic fluid of Sprague-Dawley rats

Problem: Preterm, premature rupture of membranes (PPROM) is a dire pregnancy outcome that is frequently associated with infection by the genital mycoplasmas, Mycoplasma hominis, Ureaplasma parvum, and U. urealyticum. One potential mechanism by which these microorganisms may cause PPROM is by increasing the concentration of matrix metalloproteinases (MMPs) in the membranes and amniotic fluid. We tested this hypothesis in a well-defined model system of genital infection with M. pulmonis, a natural reproductive pathogen of rats. Method of study: Timed-pregnant, specific pathogen-free, Sprague-Dawley rats were infected with 10⁷ CFU M. pulmonis at gestation day (gd) 14. Controls received an equivalent volume (100 μ L) of sterile medium. At gd 18, rats were euthanized, and membranes and amniotic fluids were harvested and stored at -70°C until analysis. Proteinase activity of amniotic fluid and membranes was resolved on discontinuous 7.5% sodium dodecyl sulfate-polyacrylamide gel electrophoresis gelatin zymography gels. Band intensity was determined using a digital gel documentation system and the manufacturer's software (Kodak). Results: Gelatinolytic activity associated with a band similar in molecular weight to ProMMP-9 (92 kDa, the inactive precursor of MMP-9) was significantly increased in amniotic fluids and membranes harvested from M. pulmonis-treated pups at gd 18 when compared with tissues harvested from control pups. Both ProMMP-9 and ProMMP-2 (72 kDa, the inactive precursor of MMP-2) were increased in infected animals at gd 21. Conclusion: Our study suggests that the genital mycoplasmas can increase MMP-9 production in vivo.