Uterine Epithelial LIF Receptors Contribute to Implantation Chamber Formation in Blastocyst Attachment.

Recent studies have demonstrated that the formation of an implantation chamber composed of a uterine crypt, an implantation-competent blastocyst, and uterine glands is a critical step in blastocyst implantation in mice. Leukemia inhibitory factor (LIF) activates signal transducer and activator of transcription 3 (STAT3) precursors via uterine LIF receptors (LIFRs), allowing successful blastocyst implantation. Our recent study revealed that the role of epithelial STAT3 is different from that of stromal STAT3. However, both are essential for blastocyst attachment, suggesting the different roles of epithelial and stromal LIFR in blastocyst implantation. However, how epithelial and stromal LIFR regulate the blastocyst implantation process remains unclear. To investigate the roles of LIFR in the uterine epithelium and stroma, we generated Lifr-floxed/lactoferrin (Ltf)-iCre (Lifr eKO) and Lifr-floxed/antimüllerian hormone receptor type 2 (Amhr2)-Cre (Lifr sKO) mice with deleted epithelial and stromal LIFR, respectively. Surprisingly, fertility and blastocyst implantation in the Lifr sKO mice were normal despite stromal STAT3 inactivation. In contrast, blastocyst attachment failed, and no implantation chambers were formed in the Lifr eKO mice with epithelial inactivation of STAT3. In addition, normal responsiveness to ovarian hormones was observed in the peri-implantation uteri of the Lifr eKO mice. These results indicate that the epithelial LIFR-STAT3 pathway initiates the formation of implantation chambers, leading to complete blastocyst attachment, and that stromal STAT3 regulates blastocyst attachment without stromal LIFR control. Thus, uterine epithelial LIFR is critical to implantation chamber formation and blastocyst attachment.

Levonorgestrel Inhibits Embryo Attachment by Eliminating Uterine Induction of Leukemia Inhibitory Factor.

Progestogens including progesterone (P4) and levonorgestrel (LNG) are clinically used for multiple purposes such as contraception and infertility treatment. The effects of progestogens on the uterus remains to be elucidated. Here we examine the effect of excessive progestogen administration on embryo implantation focusing on the function of uterine leukemia inhibitory factor (LIF), a cytokine that is induced by estrogen and essential for embryo attachment. Treatment of wild-type (WT) female mice with vehicle (control), LNG at the dose of 300 µg/kg/day and P4 at the dose of 10 mg/day from day 1 to day 4 of pregnancy was conducted. LNG-treated and P4-treated mice showed embryo attachment failure on day 5 of pregnancy (The rate of mice with embryo attachment sites [%MAS], 11% and 13%, respectively), while all the control mice had normal attachment sites. Uterine LIF expression was significantly reduced in LNG-treated and P4-treated mice on day 4 evening. Administration of recombinant LIF (rLIF) at the dose of 24 µg/day on day 4 significantly rescued embryo attachment failure in LNG-treated and P4-treated mice (%MAS, 80% and 75%, respectively). Estradiol (E2) administration also rescued embryo attachment failure in LNG-treated mice (%MAS, 83%). Furthermore, excess P4 treatment before implantation decreased decidual P4 receptor (PGR) expression and induced decidualization defect apart from LIF downregulation. These findings indicate that progestogens cause embryo attachment inhibition through downregulation of uterine LIF expression and compromised decidualization through downregulation of PGR independently of LIF reduction. This study may contribute to a better understanding of contraceptive action of progestogens.

Mdm2-p53-SF1 pathway in ovarian granulosa cells directs ovulation and fertilization by conditioning oocyte quality.

Functions of tumor suppressor p53 and its negative regulator mouse double minute 2 homolog (Mdm2) in ovarian granulosa cells remain to be elucidated, and the current study aims at clarifying this issue. Mice with Mdm2 deficiency in ovarian granulosa cells [ Mdm2-loxP/ progesterone receptor ( Pgr)-Cre mice] were infertile as a result of impairment of oocyte maturation, ovulation, and fertilization, and those with Mdm2/p53 double deletion in granulosa cells ( Mdm2-loxP/ p53-loxP/ Pgr-Cre mice) showed normal fertility, suggesting that p53 induction in the ovarian granulosa cells is detrimental to ovarian function by disturbing oocyte quality. Another model of Mdm2 deletion in ovarian granulosa cells ( Mdm2-loxP/ anti-Mullerian hormone type 2 receptor-Cre mice) also showed subfertility as a result of the failure of ovulation and fertilization, indicating critical roles of ovarian Mdm2 in ovulation and fertilization. Mdm2-p53 pathway in cumulus granulosa cells transcriptionally controlled an orphan nuclear receptor steroidogenic factor 1 (SF1), a key regulator of ovarian function. Importantly, MDM2 and SF1 levels in human cumulus granulosa cells were positively associated with the outcome of oocyte maturation and fertilization in patients undergoing infertility treatment. These findings suggest that the Mdm2-p53-SF1 axis in ovarian cumulus granulosa cells directs ovarian function by affecting their neighboring oocyte quality.-Haraguchi, H., Hirota, Y., Saito-Fujita, T., Tanaka, T., Shimizu-Hirota, R., Harada, M., Akaeda, S., Hiraoka, T., Matsuo, M., Matsumoto, L., Hirata, T., Koga, K., Wada-Hiraike, O., Fujii, T., Osuga, Y. Mdm2-p53-SF1 pathway in ovarian granulosa cells directs ovulation and fertilization by conditioning oocyte quality.

HIF2α in the uterine stroma permits embryo invasion and luminal epithelium detachment.

Although it has been reported that hypoxia inducible factor 2 α (Hif2a), a major transcriptional factor inducible by low oxygen tension, is expressed in the mouse uterus during embryo implantation, its role in pregnancy outcomes remains unclear. This study aimed to clarify functions of uterine HIF using transgenic mouse models. Mice with deletion of Hif2a in the whole uterus (Hif2a-uKO mice) showed infertility due to implantation failure. Supplementation with progesterone (P4) and leukemia inhibitory factor (LIF) restored decidual growth arrest and aberrant position of implantation sites in Hif2a-uKO mice, respectively, but did not rescue pregnancy failure. Histological analyses in Hif2a-uKO mice revealed persistence of the intact luminal epithelium, which blocked direct contact between stroma and embryo, inactivation of PI3K-AKT pathway (embryonic survival signal), and failed embryo invasion. Mice with stromal deletion of Hif2a (Hif2a-sKO mice) showed infertility with impaired embryo invasion and those with epithelial deletion of Hif2a (Hif2a-eKO mice) showed normal fertility, suggesting the importance of stromal HIF2α in embryo invasion. This was reflected in reduced expression of membrane type 2 metalloproteinase (MT2-MMP), lysyl oxidase (LOX), VEGF, and adrenomedullin (ADM) in Hif2a-uKO stroma at the attachment site, suggesting that stromal HIF2α regulates these mediators to support blastocyst invasion. These findings provide new insight that stromal HIF2α allows trophoblast invasion through detachment of the luminal epithelium and activation of an embryonic survival signal.

F4/80+ Macrophages Contribute to Clearance of Senescent Cells in the Mouse Postpartum Uterus.

Cellular senescence, defined as an irreversible cell cycle arrest, exacerbates the tissue microenvironment. Our previous study demonstrated that mouse uterine senescent cells were physiologically increased according to gestational days and that their abnormal accumulation was linked to the onset of preterm delivery. We hypothesized that there is a mechanism for removal of senescent cells after parturition to maintain uterine function. In the current study, we noted abundant uterine senescent cells and their gradual disappearance in wild-type postpartum mice. F4/80+ macrophages were present specifically around the area rich in senescent cells. Depletion of macrophages in the postpartum mice using anti-F4/80 antibody enlarged the area of senescent cells in the uterus. We also found excessive uterine senescent cells and decreased second pregnancy success rate in a preterm birth model using uterine p53-deleted mice. Furthermore, a decrease in F4/80+ cells and an increase in CD11b+ cells with a senescence-associated inflammatory microenvironment were observed in the p53-deleted uterus, suggesting that uterine p53 deficiency affects distribution of the macrophage subpopulation, interferes with senescence clearance, and promotes senescence-induced inflammation. These findings indicate that the macrophage is a key player in the clearance of uterine senescent cells to maintain postpartum uterine function.

MicroRNA-200a locally attenuates progesterone signaling in the cervix, preventing embryo implantation.

Although cervical pregnancy and placenta previa, in which the embryo and placenta embed in or adjacent to the cervix, are life-threatening complications that result in massive bleeding and poor pregnancy outcomes in women, the incidence of these aberrant conditions is uncommon. We hypothesized that a local molecular mechanism is normally in place to prevent embryo implantation in the cervix. The ovarian hormones progesterone (P(4)) and estrogen differentially direct differentiation and proliferation of endometrial cells, which confers the receptive state for implantation: P(4) dominance causes differentiation of the luminal epithelium but increases stromal cell proliferation in preparation of the uterus for implantation. In search for the cause of cervical nonresponsiveness to implantation, we found that the statuses of cell proliferation and differentiation between the uterus and cervix during early pregnancy are remarkably disparate under identical endocrine milieu in both mice and humans. We also found that cervical levels of progesterone receptor (PR) protein are low compared with uterine levels during this period, and the low PR protein levels are attributed to elevated levels of microRNA(miR)-200a in the cervix. These changes were associated with up-regulation of the P(4)-metabolizing enzyme 20α-hydroxysteroid dehydrogenase (200α-HSD) and down-regulation of its transcriptional repressor signal transducer and activator of transcription 5 in the cervix. The results provide evidence that elevated levels of miR-200a lead to down-regulation of P(4)-PR signaling and up-regulation of (200α-HSD) in the cervix, rendering it nonresponsive to implantation. These findings may point toward not only the physiological but also the pathological basis of the cervical milieu in embryo implantation.

Combinatory approaches prevent preterm birth profoundly exacerbated by gene-environment interactions.

There are currently more than 15 million preterm births each year. We propose that gene-environment interaction is a major contributor to preterm birth. To address this experimentally, we generated a mouse model with uterine deletion of Trp53, which exhibits approximately 50% incidence of spontaneous preterm birth due to premature decidual senescence with increased mTORC1 activity and COX2 signaling. Here we provide evidence that this predisposition provoked preterm birth in 100% of females exposed to a mild inflammatory insult with LPS, revealing the high significance of gene-environment interactions in preterm birth. More intriguingly, preterm birth was rescued in LPS-treated Trp53-deficient mice when they were treated with a combination of rapamycin (mTORC1 inhibitor) and progesterone (P4), without adverse effects on maternal or fetal health. These results provide evidence for the cooperative contributions of two sites of action (decidua and ovary) toward preterm birth. Moreover, a similar signature of decidual senescence with increased mTORC1 and COX2 signaling was observed in women undergoing preterm birth. Collectively, our findings show that superimposition of inflammation on genetic predisposition results in high incidence of preterm birth and suggest that combined treatment with low doses of rapamycin and P4 may help reduce the incidence of preterm birth in high-risk women.

Attenuated lung fibrosis in interleukin 6 knock-out mice after C-ion irradiation to lung.

There is a great deal of evidence that a cyclic cascade of inflammatory cytokines, together with the activation of macrophages, is initiated very early after irradiation to develop lung fibrosis in a late phase. To understand the persistent effects of cytokines, the cytokine gene of knock out or transgenic mouse is one of the useful tools. In this study, we evaluated a role of a key molecule, interleukin-6 (IL-6), in the late-phase inflammatory response and subsequent fibrotic changes after irradiation using wild-type (WT) and IL-6 knock out (IL-6 KO) mice. The mice underwent thoracic irradiation with 10 Gy of C-ion beam or sham-irradiation and were examined by histology. Immunoreactivity for IL-6 was induced at the site of bronchiolar epithelium, in pneumocytes and in monocytes by C-ion irradiation. At 24 weeks after irradiation, the infiltration of macrophages, detected by positive immunohistological staining with Mac3 antibody, was observed in alveolar spaces both in WT and IL-6 KO mice. The thickening of bronchiolar and alveolar walls exhibited in WT mice, but not KO mice, and fibrotic changes detected by Masson-Trichrome staining, were observed only in the lungs of WT mice, while it was attenuated in IL-6 KO mice. These results indicated that IL-6 might not be essential for activating macrophages in the late phase, but plays an important role for fibrotic changes of the alveolar wall after irradiation.

Pravastatin induces placental growth factor (PGF) and ameliorates preeclampsia in a mouse model.

Preeclampsia is a relatively common pregnancy-related disorder. Both maternal and fetal lives will be endangered if it proceeds unabated. Recently, the placenta-derived anti-angiogenic factors, such as soluble fms-like tyrosine kinase-1 (sFLT1) and soluble endoglin (sENG), have attracted attention in the progression of preeclampsia. Here, we established a unique experimental model to test the role of sFLT1 in preeclampsia using a lentiviral vector-mediated placenta-specific expression system. The model mice showed hypertension and proteinuria during pregnancy, and the symptoms regressed after parturition. Intrauterine growth restriction was also observed. We further showed that pravastatin induced the VEGF-like angiogenic factor placental growth factor (PGF) and ameliorated the symptoms. We conclude that our experimental preeclamptic murine model phenocopies the human case, and the model identifies low-dose statins and PGF as candidates for preeclampsia treatment.