Micronized progesterone pretreatment affects the inflammatory response of human gestational tissues and the cervix to lipopolysaccharide stimulation.

INTRODUCTION: Vaginal administration of micronized progesterone (utrogestan capsule, UG) reduces the risk of preterm birth (PTB) in asymptomatic women with a sonographic short cervix at mid-trimester or with a prior history of spontaneous PTB; however, its exact mechanisms remain unclear. We hypothesized that UG limits the inflammatory processes within the gestational tissues and the cervix.

METHODS: Fetal membranes and villous tissues were obtained from normal term placentas from women with cesarean delivery before labor onset. Ectocervical tissues were obtained from premenopausal women undergoing hysterectomies for uterine fibroids. Explant tissue cultures were pretreated with UG for 24 h and then exposed to UG with or without lipopolysaccharide (LPS) for 48 h. Tumor necrosis factor-α, granulocyte-macrophage colony-stimulating factor, monocyte chemotactic protein-1, interleukin (IL)-1β, IL-4, IL-6, IL-8, IL-10, IL-13, interferon-γ, tissue inhibitor of metalloproteinase (TIMP)-1, and TIMP-2 levels in tissue homogenates and culture medium were measured by enzyme-linked immunosorbent assays. Real-time quantitative PCR, Western blot, and gelatine zymography were used to measure matrix metalloproteinase (MMP)-9 and MMP-2 mRNA, protein, and activity levels, respectively.

RESULTS: UG pretreatment did not cause a significant change in basal levels or in LPS-induced production and secretion of cytokines, chemokines, and TIMPs in the three tissues. However, UG pretreatment significantly reduced MMP-9 and MMP-2 expression and activity in fetal membranes stimulated with LPS but not in villous or cervical tissues.

DISCUSSION: UG pretreatment significantly reduced MMP-9 and MMP-2 expression and activity in fetal membranes stimulated with LPS, suggesting a possible protective mechanism of micronized progesterone in preventing infection-associated PTB.