miR-200 family and targets, ZEB1 and ZEB2, modulate uterine quiescence and contractility during pregnancy and labor

Abstract

Throughout most of pregnancy, uterine quiescence is maintained by increased progesterone receptor (PR) transcriptional activity, whereas spontaneous labor is initiated/facilitated by a concerted series of biochemical events that activate inflammatory pathways and have a negative impact on PR function. In this study, we uncovered a previously undescribed regulatory pathway whereby micro-RNAs (miRNAs) serve as hormonally modulated and conserved mediators of contraction-associated genes in the pregnant uterus in the mouse and human. Using miRNA and gene expression microarray analyses of uterine tissues, we identified a conserved family of miRNAs, the miR-200 family, that is highly induced at term in both mice and humans as well as two coordinately downregulated targets, zinc finger E-box binding homeobox proteins ZEB1 and ZEB2, which act as transcriptional repressors. We also observed up-regulation of the miR-200 family and down-regulation of ZEB1 and ZEB2 in two different mouse models of preterm labor. We further demonstrated that ZEB1 is directly up-regulated by the action of progesterone (P 4 )/PR at the ZEB1 promoter. Excitingly, we observed that ZEB1 and ZEB2 inhibit expression of the contractionassociated genes, oxytocin receptor and connexin-43, and block oxytocin-induced contractility in human myometrial cells. Together, these findings implicate the miR-200 family and their targets, ZEB1 and ZEB2, as unique P 4 /PR-mediated regulators of uterine quiescence and contractility during pregnancy and labor and shed light on the molecular mechanisms involved in preterm birth.A lthough premature labor is the leading cause of neonatal morbidity and mortality in developed countries, the signaling mechanisms that maintain uterine quiescence during pregnancy and promote increased uterine contractility leading to labor at term and preterm remain incompletely defined (1). In mammalian pregnancy, uterine quiescence is maintained by elevated circulating progesterone (P 4 ) acting via the progesterone receptor (PR). Conversely, parturition is associated with a decline in maternal circulating P 4 and/or a decrease in the function of the PR, termed "functional P 4 withdrawal," (2, 3) and an increased inflammatory response within the uterus and cervix (4). Studies from a number of laboratories, including our own, suggest that P 4 and PR maintain uterine quiescence until term by inhibiting expression of contraction-associated genes [e.g., connexin-43 (CXN-43), oxytocin receptor (OXTR), cyclooxygenase 2 (COX-2)] in the myometrium, in part, via anti-inflammatory actions. For example, P 4 and PR inhibit activation of COX-2 expression in myometrial cells through direct interaction of PR with NF-κB p65 (5) and by P 4 -induced expression of the NF-κB inhibitor, IκB-α (6).Recently, it has been shown that micro-RNAs (miRNAs) play especially powerful roles in vascular smooth muscle cells and in female reproduction, wherein they have been implicated in proliferation, differentiation, and hormone responsiveness (7-9). The identification o...

Progesterone and preterm birth prevention: translating clinical trials data into clinical practice

“…While the exact mechanism of action of progestogens in preventing preterm birth is unknown, several possibilities have been proposed. (Table 1) (9)(10)(11)(12)(13)(14)(15)(16)(17) In general, the evidence seems to favor 2 mechanisms: an anti-inflammatory effect that counteracts the inflammatory process leading to PTB, and a local increase in progesterone in gestational tissues that counteracts the functional decrease in progesterone leading to PTB. (Table 1) (9)(10)(11)(12)(13)(14)(15)(16)(17) Regarding safety, several studies failed to detect any long term effect from the intrauterine exposure of the fetus to pharmacologic progestogens, even when given in the first trimester.…”

“…Algorithm for use of progestogens in prevention of preterm birth in clinical care Table 1 Proposed mechanisms of action reported for progestogens to prevent preterm birth [9][10][11][12][13][14][15][16][17] Mechanisms Stimulate transcription of ZEB1 and ZEB2, which inhibit connexin 43 ( a gap-junction protein that helps synchronize contractile activity) and the oxytocin-receptor gene Decrease prostaglandin synthesis, infection-mediated cytokine production (antiinflammatory effects) by the fetal membranes/placenta Changes in progesterone receptor (PR)-A and PR-B expression (decreased PR-A/PR-B ratio keeps uterus quiescent) Membrane-bound PR in myometrium Progesterone receptors, when stimulated by progesterone, help selected gene promotion, or prevent the binding of other factors Interfere with cortisol-mediated regulation of placental gene expression Non-genomic pathways Reduce cervical stromal degradation in the cervix Alter barrier to ascending inflammation/infection in the cervix Reduce contraction frequency in the myometrium Attenuate response to hemorrhage/inflammation in the decidua Alter estrogen synthesis in the fetal membranes/placenta Alter fetal endocrine-mediated effects ZEB1 and ZEB2, zinc finger E-box binding homeobox proteins 1 and 2. …”

MicroRNAs, immune cells and pregnancy

“…We are only beginning to discover the roles of miRNAs in reproduction. miRNAs have been implicated in endometrial receptivity, [34][35][36] implantation, 37-42 labor [43][44][45][46][47] and even spontaneous fetal loss in the pig. 48,49 In the uterus, most of the physiological changes occurring over the estrous/menstrual cycle and during pregnancy are driven by the ovarian hormones.…”

Maternal serum progesterone, estradiol and estriol levels in successful dinoprostone-induced labor

“…In a recent study, regarding successful labor induction, most women were nulliparous and parity was noted to be the single best predictor of subsequent vaginal delivery (27). Progesterone withdrawal has been considered a major determinant of labor initiation, since it relaxes the myometrium by repressing the expression of genes that encode factors collectively called contraction-associated proteins, which include connexin43 (28), cyclooxygenase-2 (29) and oxytocin receptor (28). Moreover, increased progesterone activity is associated with increased 15-hydroxyprostaglandin dehydrogenase expression, which catalyzes the conversion of PGE 2 and PGF 2 a to their biologically inactive 15-keto derivatives in term trophoblasts (30).…”