Early Pregnancy In Mice Research Articles

Signaling via retinoic acid receptors mediates decidual angiogenesis in mice and human stromal cell decidualization.

At the maternal-fetal interface, tightly regulated levels of retinoic acid (RA), the physiologically active metabolite of vitamin A, are required for embryo implantation and pregnancy success. Herein, we utilize mouse models, primary human cells, and pharmacological tools to demonstrate how depletion of RA signaling via RA receptor (RAR) disrupts implantation and progression of early pregnancy. To inhibit RAR signaling during early pregnancy, BMS493, an inverse pan-RAR agonist that prevents RA-induced differentiation, was administered to pregnant mice during the peri-implantation period. Attenuation of RA/RAR signaling prior to embryo implantation results in implantation failure, whereas attenuation of RA/RAR signaling after embryo implantation disrupts the post-implantation decidual vasculature and results in pregnancy failure by mid-gestation. To inhibit RAR signaling during human endometrial stromal cell (HESC) decidualization, primary HESCs and decidualized primary HESCs were transfected with silencing RNA specific for human RARA. Inhibition of RA/RARA signaling prevents initiation of HESC decidualization, but not maintenance of the decidualized HESC phenotype. These data show that RA/RAR signaling is required for maintenance of the decidual vasculature that supports early pregnancy in mice, and distinct RAR signaling is required for initiation, but not maintenance of primary HESC decidualization invitro.

Determination of vaginal cytology and MMP-9 expression during early pregnancy in mice

Precise pregnancy detection is critical for optimizing reproductive efficiency in animals. In mice, the conventional copulation plug method for pregnancy confirmation lacks reliability, particularly in inbred strains, with false-pregnancy rates exceeding 50 %. Here, to improve pregnancy detection efficiency in mice, we examined vaginal cell population changes using vaginal smear technique and analyzed MMP-9 expression in vaginal tract from day 0.5 to 6.5 of pregnancy. A total of forty-four female mice in the estrus stage were paired with sexually mature male mice for natural mating. The morning after mating was considered as embryonic day 0.5 (E0.5). Vaginal cytology was used to determine the vaginal cells of pregnant and non-pregnant mice from day 0.5 to 6.5. Furthermore, the protein and gene expression of MMP-9 were assessed through the utilization of immunohistochemistry and real-time PCR. Our findings reveal that pregnant mice display the higher number of leukocytes but the low number of nucleated/cornified epithelial cells in vagina compared to the non-pregnant counterparts. Furthermore, MMP-9 protein consistently presents in vaginal epithelial cells throughout the experimental period, with increased protein expression on day 4.5 of pregnancy followed by a decline on day 6.5 of pregnancy. This result is similar to MMP-9 gene expression, reaching the peak on day 5.5 of pregnancy. In conclusion, vaginal cytology proves effective for mouse pregnancy determination, while MMP-9 can serve as a potential biomarker for detecting pregnancy in mice.

Benzo(a)pyrene promotes autophagy to impair endometrial decidualization via inhibiting CXCL12/CXCR4 axis

Benzo(a)pyrene (BaP), a pervasive environmental pollutant with endocrine-disrupting properties, has been associated with detrimental effects on pregnancy. During early pregnancy, the endometrial decidualization process is critical for embryo implantation. Abnormal decidualization can lead to implantation failure, aberrant placental formation, and pregnancy loss. We previously revealed that BaP exposure impaired decidualization and implantation in mice, yet the underlying mechanisms remained elusive. Autophagy, a cellular mechanism pivotal for energy and material recycling, contributes to the decidualization process. The chemokine C-X-C motif chemokine ligand 12 (CXCL12), secreted by endometrium stromal cells (ESCs), is involved in regulating endometrial decidualization and autophagy. Therefore, this study aimed to explore the hypothesis that BaP disrupts the decidualization process by interfering with autophagic pathways via the CXCL12/CXCR4 axis during early pregnancy. We found that BaP inhibited CXCL12/CXCR4 expression, and induced autophagy by promoting autophagosome formation, which in turn impaired the decidualization in early pregnant mice uterus and decidual stromal cells (DSCs). Using autophagy inhibitors 3-methyladenine and chloroquine in combination with BaP to treat DSCs, successfully weakened BaP-induced autophagy, and relieved decidual injury. Additionally, activation of CXCL12/CXCR4 by recombinant protein CXCL12 attenuated BaP-induced autophagy, inhibited the PI3K/AKT signal activation caused by BaP, and partly rescued the expression of decidualization-related genes. In summary, this study demonstrates that BaP induces autophagy in DSCs by inhibiting the CXCL12/CXCR4 axis, leading to damage in endometrial decidualization during early pregnancy. The findings provide a critical chemokine-mediated regulatory mechanism involved in embryo implantation and contribute valuable knowledge to the reproductive toxicology of BaP.

Clusterin from endometrial glands plays a critical role in decidualization via Trem2

BackgroundDecidualization is a critical step in establishing pregnancy in mammals. Successful decidualization depends on intricate gland-stromal crosstalk. Clusterin (Clu) is a ubiquitously secreted protein in physiological fluids that is involved in numerous physiological functions. However, the role of Clu in decidualization is not fully understood.ResultsIn this study, we examined the expression pattern of Clu during early pregnancy in mice and explored its potential function in decidualization. Our results revealed that Clu was expressed in the uterine glands on Days 1–2 of early pregnancy and on Days 5–8 during decidualization after embryo implantation, as well as in glands at the interimplantation site. Additionally, ovariectomized mice exhibited significant upregulation of Clu expression in the uterine glands 3 h after in vivo estrogen injection. Trem2, a receptor for Clu, was detected in the decidual region of mice on Days 5–8 of early pregnancy, where it mediates Clu to regulate the decidual region. Furthermore, we observed that recombinant CLU protein increased the expression of the decidualization marker molecules insulin-like growth factor binding protein 1 (IGFBP1) and prolactin (PRL) in decidual cells. However, this upregulation was not observed when Trem2 expression was inhibited with siRNA.ConclusionsUterine gland-derived Clu, a new paracrine modulator, may participate in early pregnancy by influencing the decidualization process mediated by Trem2 in mice.

Deciphering the role of rapamycin in modulating decidual senescence: implications for decidual remodeling and implantation failure.

Physiological decidual senescence promotes embryo implantation, whereas pathological decidual senescence causes many pregnancy pathologies. The aim of this study was to evaluate the effect of rapamycin on decidual cell subpopulations and endometrial function in physiological and induced senescence and to investigate the decidual cell subpopulations present in physiological conditions during early pregnancy and implantation in mice. Control, physiological decidualization (0.5mM cAMP and 1μM MPA added), and induced senescence (0.1mM HU added) models with and without 200nM rapamycin treatment were established using a human endometrial stromal cell line, and decidual cell subpopulations were analyzed by immunofluorescence and flow cytometry. The human extravillous trophoblast cell line AC-1M88 was also cultured in decidualization models, and spheroid expansion analysis was performed. In in vivo studies, decidual cell subpopulations were analyzed by immunofluorescence during early mouse pregnancy. The results revealed that rapamycin decreased DIO2 and β-GAL expressions in physiological and induced senescence without FOXO1. Notably, in induced senescence, increased fragmentation was observed in AC-1M88 cells, and rapamycin treatment successfully attenuated the fragmentation of spheroids. We showed that the FOXO1-DIO2 signaling axis can trigger decidual senescence during early gestation and days of implantation in mice. Our study underlines the importance of rapamycin in modulating decidual cell subpopulations and endometrial tissue function during decidual senescence. The information obtained may provide insight into the pathologies of pregnancy seen due to decidual senescence and guide better treatment strategies for reproductive problems.

The potential role of the prolyl isomerase Pin1 during blastocyst implantation and uterine decidualization in mice.

During early pregnancy in mice, the establishment of uterine receptivity and endometrial decidualization require the extensive proliferation and differentiation of endometrial epithelial cells or stromal cells. Pin1 has been suggested to act as a molecular 'timer' of the cell cycle and is involved in the regulation of cellular proliferation and differentiation by binding many cell-cycle regulatory proteins. However, its physiological role during early pregnancy is still not fully understood. Here, we employed immunohistochemistry to determine the spatiotemporal pattern of Pin1 expression during early pregnancy. We found that Pin1 was mainly localized in subluminal stromal cells on day 4, in the decidual zone on days 5 to 8 of pregnancy and in artificial decidualization. Using a uterine stromal cell culture system, we found that progesterone, but not estrogen, induced the expression of Pin1 in a progesterone receptor-dependent manner. Inhibition of Pin1 in the uterus leads to impaired embryo implantation and decidualization in mice. Notably, a decrease in Pin1 activation affected the functional execution of several implantation- or decidualization-related factors. These findings provide new evidence for a previously unknown function of Pin1 in mediating embryo implantation and decidualization during successful pregnancy establishment and maintenance.

SLO2.1/NALCN Functional Complex Activity in Mouse Myometrial Smooth Muscle Cells During Pregnancy.

At the end of pregnancy, the uterus transitions from a quiescent to a highly contractile state. This is partly due to depolarization of the resting membrane potential in uterine (myometrial) smooth muscle cells (MSMCs). Experiments with human MSMCs showed that the membrane potential is regulated by a functional complex between the sodium (Na+)-activated potassium (K+) channel SLO2.1 and the Na+ Leak Channel Non-Selective (NALCN). In human MSMCs, Na+ entering through NALCN activates SLO2.1, leading to K+ efflux, membrane hyperpolarization (cells become more negative inside), and reduced contractility. Decreased SLO2.1/NALCN activity results in reduced K+ efflux, leading to membrane depolarization, Ca2+ influx via voltage-dependent calcium channels, and increased MSMC contractility. However, all of these experiments were performed with MSMCs isolated from women at term, so the role of the SLO2.1/NALCN complex early in pregnancy was speculative. To address this question here, we examined the role of the SLO2.1/NALCN complex in regulating mouse MSMC membrane potential across pregnancy. We report that Slo2.1 and Nalcn expression change along pregnancy, being more highly expressed in MSMCs from non-pregnant and early pregnant mice than in those from late-pregnant mice. Functional studies revealed that SLO2.1 channels mediate a significant portion of the K+ current in mouse MSMCs, particularly in cells from non-pregnant and early pregnant mice. Activation of SLO2.1 by Na+ influx through NALCN led to membrane hyperpolarization in MSMCs from early pregnancy but not in MSMCs from later pregnancy. Moreover, we found that the NALCN/SLO2.1 complex regulates intracellular Ca2+ responses more in MSMCs from non-pregnant and early pregnancy mice than in MSMCs from late pregnancy. Together, these findings reveal that the SLO2.1/NALCN functional complex is conserved between mouse and humans and functions throughout pregnancy. This work could open avenues for targeted pharmacological interventions in pregnancy-related complications.

B(a)P induces ovarian granulosa cell apoptosis via TRAF2-NFκB-Caspase1 axis during early pregnancy

Benzo(a)pyrene [B(a)P] is an environmental endocrine disruptor with reproductive toxicity. The corpus luteum (CL) of the ovary plays an important role in embryo implantation and pregnancy maintenance. Our previous studies have shown that B(a)P exposure affects embryo implantation and endometrial decidualization in mouse, but its effects and mechanisms on CL function remain unclear. In this study, we explore the mechanism of ovarian toxicity of B(a)P using a pregnant mouse model and an in vitro model of human ovarian granulosa cells (GCs) KGN. Pregnant mice were gavaged with corn oil or 0.2 mg/kg.bw B(a)P from pregnant day 1 (D1) to D7, while KGN cells were treated with DMSO, 1.0IU/mL hCG, or 1.0IU/mL hCG plus benzo(a)pyrene-7,8-dihydrodiol-9,10-epoxide (BPDE), a B(a)P metabolite. Our findings revealed that B(a)P exposure damaged embryo implantation and reduced estrogen and progesterone levels in early pregnant mice. Additionally, in vitro, BPDE impaired luteinization in KGN cells. We observed that B(a)P/BPDE promoted oxidative stress (OS) and inflammation, leading to apoptosis rather than pyroptosis in ovaries and luteinized KGN cells. This apoptotic response was mediated by the activation of inflammatory Caspase1 through the cleavage of BID. Furthermore, B(a)P/BPDE inhibited TRAF2 expression and suppressed NFκB signaling pathway activation. The administration of VX-765 to inhibit the Caspase1 activation, over-expression of TRAF2 using TRAF2-pcDNA3.1 (+) plasmid, and BetA-induced activation of NFκB signaling pathway successfully alleviated BPDE-induced apoptosis and cellular dysfunction in luteinized KGN cells. These findings were further confirmed in the KGN cell treated with H2O2 and NAC. In conclusion, this study elucidated that B(a)P/BPDE induces apoptosis rather than pyroptosis in GCs via TRAF2-NFκB-Caspase1 during early pregnancy, and highlighting OS as the primary contributor to B(a)P/BPDE-induced ovarian toxicity. Our results unveil a novel role of TRAF2-NFκB-Caspase1 in B(a)P-induced apoptosis and broaden the understanding of mechanisms underlying unexplained luteal phase deficiency.

Effect of beta-cypermethrin on the reproductive capacity of female mice in advanced age

The aim of the present study was to investigate whether exposure to pesticides beta-cypermethrin (β-CYP) harms the reproductive capacity of advanced-age female mice. The results evidenced that peri-implantation β-CYP exposure significantly reduced the number of fetuses per advanced-age female in the first litter, and the number and weight of implantation sites. The levels of decidualization markers were significantly reduced in β-CYP-administered advanced-age mice. Lower expression of Pcna, Cdk6, Foxo1, Ki67, and p62 protein and mRNA was found in the decidua of β-CYP-treated advanced-age mice. The levels of Bax, cleaved caspase-3, Lc3a/b, Atg, mTOR, and p-mTOR protein, and the ratio of p-mTOR/mTOR protein expression were clearly downregulated by peri-implantation β-CYP exposure. These results indicated that peri-implantation β-CYP exposure may elevate the decline in reproductive capacity of early pregnant mice in advanced age.

Lipopolysaccharides of Brucella suis S2 Impaired the Process of Decidualization in Early Pregnancy in Mice.

Brucellosis is a notorious zoonotic disease caused by Brucella, which can lead to reproductive diseases in humans and animals, such as infertility and abortion. Lipopolysaccharides (LPS) are the main virulence factor of Brucella. LPS derived from Brucella are different and non-classical and are less toxic and less active than LPS isolated from E. coli. However, the effects and possible mechanisms of Brucella LPS-caused pregnancy loss remain to be revealed. In the present study, we investigated the effects of Brucella suis S2 LPS on early pregnancy loss in mice. The results indicated that embryo implantation failure was induced by Brucella LPS treatment in a dose-dependent manner. The injection of Brucella LPS mainly resulted in fibrinolysis in the decidual area of the uterus on the 6th day post coition (dpc), infiltration of large granular cells among the decidual cells near the embryo on the 8th dpc, a large number of gaps in the decidual area, and cell necrosis around the embryo. In addition, the expression of Cyclin D3 mRNA in the uterus on the 7th and 8th dpc and IGFBP-1 mRNA and the progesterone receptor in the uterus on the 6th and 7th dpc were also inhibited. Moreover, the expression of decidualization marker Cyclin D3 and decidualization prolactin-associated protein (dPRP) in endometrial stromal cells were also inhibited by Brucella LPS treatment in vitro. In summary, Brucella LPS affect the process of endometrial decidualization in mice by affecting the structure of the decidua and the expression of decidual marker factors in endometrial stromal cells.

Spatiotemporal insight into early pregnancy governed by immune-featured stromal cells

Endometrial decidualization connecting embryo implantation and placentation is transient but essential for successful pregnancy, which, however, is not systematically investigated. Here, we use a scStereo-seq technology to spatially visualize and define the dynamic functional decidual hubs assembled by distinct immune, endothelial, trophoblast, and decidual stromal cells (DSCs) in early pregnant mice. We unravel the DSC transdifferentiation trajectory and surprisingly discover a dual-featured type of immune-featured DSCs (iDSCs). We find that immature DSCs attract immune cells and induce decidual angiogenesis at the mesenchymal-epithelial transition hub during decidualization initiation. iDSCs enable immune cell recruitment and suppression, govern vascularization, and promote cytolysis at immune cell assembling and vascular hubs, respectively, to establish decidual homeostasis at a later stage. Interestingly, dysfunctional and spatially disordered iDSCs cause abnormal accumulation of immune cells in the vascular hub, which disrupts decidual hub specification and eventually leads to pregnancy complications in DBA/2-mated CBA/J mice.

Leptin increases nitric oxide level via increase in iNOS expression in early pregnant mouse uterus

Leptin increases nitric oxide level via increase in iNOS expression in early pregnant mouse uterus

Expressions of Notch signalling pathway members during early pregnancy in mice.

Although pregnancy is initiated and maintained through highly complex mechanisms, it is essential to understand the events that occur before and during early pregnancy to understand a healthy implantation process. The Notch signal, thought to be involved in this process, is frequently the subject of research with its different aspects. To better understand the role of Notch signaling in the peri-implantation period of the mouse uterus, we investigated the state of expression and localization of Notch 3, Notch 4, Rbp-J, Hes1, Hes7, Hey2, HeyL, and Fbw7 in the uterus and implantation sites in early pregnancy. Balb/C mice were divided into groups D1, D4, D5, D6, and D8. For D5 and D6 groups, implantation sites were identified by intravenous injection of Chicago blue. IHC, WB, and QRT-PCR methods were used. Notch 3 was very strong positive on the 4th day of pregnancy. Notch 4 was highly expressed on days 4, 5, 6, and 8 of pregnancy when P4 levels were high. Hes 1 level was at the lowest on the 4th day of pregnancy. Hes 7 protein expression gradually increased from D1 to D8 in the uteri and implantation sites. Hey 2 expression was at the highest level on the 1st and 4th days. Hey L expression was on the apical of the glands. Fbxw7 that expression was high on the 1st and 4th days of pregnancy. Notch signaling may play an essential role in regulating endometrial receptivity. In addition, our Hes7 results are new to the literature.

The Uterine Melatonergic Systems of AANAT and Melatonin Membrane Receptor 2 (MT2) Are Essential for Endometrial Receptivity and Early Implantation in Mice.

In the current study, using Aanat and Mt2 KO mice, we observed that the preservation of the melatonergic system is essential for successful early pregnancy in mice. We identified that aralkylamine N-acetyltransferase (AANAT), melatonin receptor 1A (MT1), and melatonin receptor 1B (MT2) were all expressed in the uterus. Due to the relatively weak expression of MT1 compared to AANAT and MT2, this study focused on AANAT and MT2. Aanat and Mt2 KO significantly reduced the early implantation sites and the abnormal morphology of the endometrium of the uterus. Mechanistical analysis indicated that the melatonergic system is the key player in the induction of the normal nidatory estrogen (E2) response for endometrial receptivity and functions by activating the STAT signaling pathway. Its deficiency impaired the interactions between the endometrium, the placenta, and the embryo. The reduction in melatonin production caused by Aanat KO and the impairment of signal transduction caused by Mt2 KO reduced the uterine MMP-2 and MMP-9 activity, resulting in a hyperproliferative endometrial epithelium. In addition, melatonergic system deficiency also increased the local immunoinflammatory reaction with elevated local proinflammatory cytokines leading to early abortion in the Mt2 KO mice compared to the WT mice. We believe that the novel data obtained from the mice might apply to other animals including humans. Further investigation into the interaction between the melatonergic system and reproductive effects in different species would be worthwhile.

Toxicity mechanism of peri-implantation pesticide beta-cypermethrin exposure on endometrial remodeling in early pregnant mice

Beta-cypermethrin (β-CYP) is a universally used pyrethroid pesticide with adverse effects on human health. β-CYP may impair endometrial remodeling in mice; however, the mechanism remains largely unknown. Endometrial remodeling plays a vital role in embryonic development and the maintenance of pregnancy. Therefore, we explored the mechanism by which peri-implantation β-CYP administration reduces uterine remodeling in pregnant mice. The C57BL/6 J pregnant mice were administered a dose of 20 mg/kg.bw. d β-CYP via oral gavage once daily from day 1 of gestation (GD1) to GD7. Molecular markers of endometrial remodeling, stromal cell proliferation, cell cycle regulation, and the PI3K/Akt/mTOR signaling pathway were evaluated in the decidual tissue of the uterus on GD7. An in vivo pseudopregnancy mouse model, a pregnant mouse model treated with an mTOR activator and an mTOR inhibitor and an in vitro decidualization model of mouse endometrial stromal cells were used to confirm β-CYP-induced defective endometrial remodeling and the key molecules expression of PI3K/Akt/mTOR signaling pathway. The results showed that β-CYP decreased the expression of the endometrial remodeling markers MMP9 and LIF in the uterine decidua. Peri-implantation β-CYP treatment markedly downregulated the expression of endometrial proliferation markers PCNA and Ki67 and decreased decidua thickness. Correspondingly, peri-implantation β-CYP exposure upregulated the expression of FOXO1, P57 and p-4E-BP1 in the decidua. Further experiments showed β-CYP significantly inhibited key molecules in the PI3K/Akt/mTOR pathway: PI3K, p-Akt/Akt, p-mTOR, and p-P70S6K in the uterine decidua. Additional experiments showed that aberrant endometrial remodeling induced by β-CYP was aggravated by rapamycin (an mTOR inhibitor) and partially reversed by MHY1485 (an mTOR agonist). In summary, our results indicated that a reduction in the PI3K/Akt/mTOR pathway may enhance defective endometrial remodeling by downregulating the proliferation and differentiation of endometrial stromal cells in early pregnant mice exposed to β-CYP. Our study elucidates the mechanism of defective endometrial remodeling induced by peri-implantation β-CYP exposure.

Dysregulated glycolysis underpins high-fat-associated endometrial decidualization impairment during early pregnancy in mice

Pregnancy complications are more likely to occur in obese women because of defective decidualization. However, the specific mechanism of glycolysis in decidual modulation associated with obesity remains unknown. Therefore, we explored the role of glycolysis in the endometrium of obese pregnant mice during decidualization. C57BL/6J mice were fed a high-fat diet (HFD) to induce obesity. All obesity related parameters were significantly higher in the HFD mice than control. Furthermore, the HFD mice had fewer implantation sites, a smaller decidual area growth, and decreased decidualization marker protein expression than control. The HFD mice also had significantly decreased lactate production and glycolytic enzyme expression. To confirm the functional role of glycolysis during the decidual period in obese pregnant mice, we extracted endometrial stromal cells (ESCs) and treated them with oleic acid (OA) and palmitic acid (PA) to mimic a high-fat environment. Decidualization and glycolysis were significantly restricted in the OA-and PA-treated groups. Moreover, we administered a glycolytic inhibitor, 2-DG, and an agonist, pioglitazone. 2-DG treatment considerably decreased the cells' glycolysis and decidualization. However, pioglitazone treatment improved glycolysis and alleviated defective decidualization. In conclusion, obesity-induced endometrial glycolysis modifications and key glycolytic enzyme downregulation during early pregnancy might cause abnormal decidualization, leading to an unsustainable pregnancy.

Effect of Disulfiram on the Reproductive Capacity of Female Mice.

In the process of assisted reproduction, the high-oxygen in vitro environment can easily cause oxidative damage to oocytes. Disulfiram (DSF) can play an anti-oxidant or pro-oxidant role in different cells, and the effect of DSF on oocytes remains unclear. Moreover, it remains unclear whether the use of DSF in the early stages of pregnancy has a negative impact on the fetus. In this study, we found that DSF increased serum FSH levels and increased the ovulation rate in mice. Moreover, DSF enhanced the antioxidant capacity of oocytes and contributed to the success rate of in vitro fertilization. Moreover, the use of DSF in early pregnancy in mice increased the uterine horn volume and the degree of vascularization, which contributed to a successful pregnancy. In addition, it was found that DSF regulated the mRNA expression of angiogenesis-related genes (VEGF), follicular development-related genes (C1QTNF3, mTOR and PI3K), ovulation-related genes (MAPK1, MAPK3 and p38 MAPK) and antioxidant-related genes (GPX4 and CAT). These results indicate that DSF is helpful for increasing the antioxidant capacity of oocytes and the ovulation rate. In early pregnancy in mice, DSF promotes pregnancy by increasing the degree and volume of uterine vascularization.

Correction to: Magnetic Resonance Imaging Reveals Distinct Roles for Tissue Transglutaminase and Factor XIII in Maternal Angiogenesis During Early Mouse Pregnancy.

Correction to: Magnetic Resonance Imaging Reveals Distinct Roles for Tissue Transglutaminase and Factor XIII in Maternal Angiogenesis During Early Mouse Pregnancy.

Early pregnancy exposure to beta-cypermethrin compromises endometrial decidualisation in mice via downregulation of cyclin D3, CDK4/6, and p21.

Beta-cypermethrin (β-CYP) is a highly effective broad-spectrum insecticide that can potentially affect female reproduction. However, little is known about the effect of β-CYP on uterine decidualisation, which is a vital process by which the uterus provides a suitable microenvironment for pregnancy maintenance. Therefore, we focused on the effect and mechanism of β-CYP on endometrial decidualisation during early pregnancy in mice. The results indicated that the expression levels of HOXA10, BMP2, and IGFBP1 was significantly downregulated in the decidual tissue and primary endometrial stromal cells of pregnant and pseudopregnant mice following β-CYP treatment. Serum E2 concentration was significantly increased, whereas P4 concentration and oestrogen receptor (ERα) and progesterone receptor (PRA) expression were significantly downregulated following β-CYP exposure. The number of polyploid decidual cells was lower in the β-CYP-treated group. Furthermore, β-CYP significantly downregulated the protein expression levels of CDK4 and CDK6, and the mRNA expression levels of cyclin D3 and p21. The number of foetuses per female in the first litter was markedly reduced following exposure to β-CYP. In summary, early pregnancy exposure to β-CYP may result in defective endometrial decidualisation via compromised proliferation of uterine stromal cells and reduced expressions of cyclin D3, CDK4/6, and p21 in mice.

Maternal IL-33 critically regulates tissue remodeling and type 2 immune responses in the uterus during early pregnancy in mice

The pregnant uterus is an immunologically rich organ, with dynamic changes in the inflammatory milieu and immune cell function underlying key stages of pregnancy. Recent studies have implicated dysregulated expression of the interleukin-1 (IL-1) family cytokine, IL-33, and its receptor, ST2, in poor pregnancy outcomes in women, including recurrent pregnancy loss, preeclampsia, and preterm labor. How IL-33 supports pregnancy progression invivo is not well understood. Here, we demonstrate that maternal IL-33 signaling critically regulates uterine tissue remodeling and immune cell function during early pregnancy in mice. IL-33-deficient dams exhibit defects in implantation chamber formation and decidualization, and abnormal vascular remodeling during early pregnancy. These defects coincide with delays in early embryogenesis, increased resorptions, and impaired fetal and placental growth by late pregnancy. At a cellular level, myometrial fibroblasts, and decidual endothelial and stromal cells, are the main IL-33+ cell types in the uterus during decidualization and early placentation, whereas ST2 is expressed by uterine immune populations associated with type 2 immune responses, including ILC2s, Tregs, CD4+ T cells, M2- and cDC2-like myeloid cells, and mast cells. Early pregnancy defects in IL-33-deficient dams are associated with impaired type 2 cytokine responses by uterine lymphocytes and fewer Arginase-1+ macrophages in the uterine microenvironment. Collectively, our data highlight a regulatory network, involving crosstalk between IL-33-producing nonimmune cells and ST2+ immune cells at the maternal-fetal interface, that critically supports pregnancy progression in mice. This work has the potential to advance our understanding of how IL-33 signaling may support optimal pregnancy outcomes in women.