Uterine receptivity, embryo attachment, and embryo invasion: Multistep processes in embryo implantation

Abstract Progesterone receptor (PGR) is indispensable for pregnancy in mammals. Uterine PGR responds to the heightened levels of ovarian progesterone (P4) after ovulation and regulates uterine gene transcription for successful embryo implantation. Although epithelial and stromal P4-PGR signaling may interact with each other to form appropriate endometrial milieu for uterine receptivity and the subsequent embryo attachment, it remains unclear what the specific roles of epithelial P4-PGR signaling in the adult uterus are. Here we generated mice with epithelial deletion of Pgr in the adult uterus (Pgrfl/flLtfCre/+ mice) by crossing Pgr-floxed and Ltf-Cre mice. Pgrfl/flLtfCre/+ mice are infertile due to the impairment of embryo attachment. Pgrfl/flLtfCre/+ uteri did not exhibit epithelial growth arrest, suggesting compromised uterine receptivity. Both epithelial and stromal expressions of P4-responsive genes decreased in Pgrfl/flLtfCre/+ mice during the peri-implantation period, indicating that epithelial Pgr deletion affects not only epithelial but stromal P4 responsiveness. In addition, uterine LIF, an inducer of embryo attachment, was decreased in Pgrfl/flLtfCre/+ mice. The RNA-seq analysis using luminal epithelial specimens dissected out by laser capture microdissection revealed that the signaling pathways related to extracellular matrix, cell adhesion, and cell proliferation are altered in Pgr fl/flLtf Cre/+ mice. These findings suggest that epithelial PGR controls both epithelial and stromal P4 responsiveness and epithelial cell differentiation, which provides normal uterine receptivity and subsequent embryo attachment.

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Differential roles of uterine epithelial and stromal STAT3 coordinate uterine receptivity and embryo attachment

Scientific Reports ◽

10.1038/s41598-020-72640-0 ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Takehiro Hiraoka ◽

Yasushi Hirota ◽

Yamato Fukui ◽

Mona Gebril ◽

Tetsuaki Kaku ◽

...

Keyword(s):

Cell Proliferation ◽

Embryo Implantation ◽

Uterine Receptivity ◽

Uterine Lumen ◽

Female Mice ◽

Attachment Sites ◽

Transcription 3 ◽

Estrogenic Responses ◽

Embryo Attachment

Abstract Although it has been reported that uterine signal transducer and activator of transcription 3 (STAT3) is essential for embryo implantation, the exact roles of uterine epithelial and stromal STAT3 on embryo implantation have not been elucidated. To address this issue, we generated Stat3-floxed/Ltf-iCre (Stat3-eKO), Stat3-floxed/Amhr2-Cre (Stat3-sKO), and Stat3-floxed/Pgr-Cre (Stat3-uKO) mice to delete Stat3 in uterine epithelium, uterine stroma, and whole uterine layers, respectively. We found that both epithelial and stromal STAT3 have critical roles in embryo attachment because all the Stat3-eKO and Stat3-sKO female mice were infertile due to implantation failure without any embryo attachment sites. Stat3-eKO uteri showed indented structure of uterine lumen, indicating the role of epithelial STAT3 in slit-like lumen formation in the peri-implantation uterus. Stat3-sKO uteri exhibited hyper-estrogenic responses and persistent cell proliferation of the epithelium in the peri-implantation uterus, suggesting the role of stromal STAT3 in uterine receptivity. In addition, Stat3-uKO female mice possessed not only the characteristic of persistent epithelial proliferation but also that of indented structure of uterine lumen. These findings indicate that epithelial STAT3 controls the formation of slit-like structure in uterine lumen and stromal STAT3 suppresses epithelial estrogenic responses and cell proliferation. Thus, epithelial and stromal STAT3 cooperatively controls uterine receptivity and embryo attachment through their different pathways.

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Influence of hyaluronan on endometrial receptivity and embryo attachment in sheep

Reproduction Fertility and Development ◽

10.1071/rd16232 ◽

2017 ◽

Vol 29 (9) ◽

pp. 1763 ◽

Cited By ~ 3

Author(s):

Waleed F. A. Marei ◽

D. Claire Wathes ◽

Kabir A. Raheem ◽

Omnia Mohey-Elsaeed ◽

Fataneh Ghafari ◽

...

Keyword(s):

Embryo Implantation ◽

Endometrial Receptivity ◽

Uterine Receptivity ◽

Female Reproduction ◽

Mucin 1 ◽

Synthesis Inhibitor ◽

The Impact ◽

Hyaluronidase 2 ◽

Embryo Attachment

An increasing number of reports suggests a role of hyaluronan (HA) in female reproduction and interest in its application in assisted reproduction is rising. However, there are contrasting data about the effectiveness of adding HA to the embryo-transfer medium on improving pregnancy rates. Using sheep as an experimental model, the studies reported here analysed the impact of HA infusion into the uterus on embryo attachment to uterine luminal epithelium (LE) and expression of selected markers of uterine receptivity. On Day 14 after natural mating (pre-attachment), uterine horns were infused with either (n = 4 each): PBS (control), HA (1 mg mL–1), HA + hyaluronidase 2 (Hyal2; 300 IU mL–1) or 4-methyl-umbelliferone (HA-synthesis inhibitor; 4MU, 1 mM). HA immunostaining on uterine sections collected on Day 17 was negative in the 4MU group and weak in the HA+Hyal2 group. In contrast to 4MU, which resulted in 100% attachment, HA infusion blocked embryo attachment in all treated animals. This was accompanied by the disappearance of mucin 1 and increased expression of osteopontin and CD44v6 in the LE of uteri with attached embryos. In conclusion, the presence of HA at the embryo–maternal interface during embryo implantation resulted in reduced endometrial receptivity and inhibited the interaction of trophoblasts with the LE, whereas clearance of HA favoured embryo attachment.

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Heparan Sulfate Proteoglycan Sulfation Regulates Uterine Differentiation and Signaling During Embryo Implantation

Endocrinology ◽

10.1210/en.2018-00105 ◽

2018 ◽

Vol 159 (6) ◽

pp. 2459-2472 ◽

Cited By ~ 2

Author(s):

Yan Yin ◽

Adam Wang ◽

Li Feng ◽

Yu Wang ◽

Hong Zhang ◽

...

Keyword(s):

Signal Transduction ◽

Heparan Sulfate ◽

Signaling Pathways ◽

Reproductive Tract ◽

Ovarian Function ◽

Embryo Implantation ◽

Uterine Epithelium ◽

Female Reproductive Tract ◽

Uterine Receptivity ◽

Mouse Uterus

Abstract To prepare for embryo implantation, the uterus must undergo a series of reciprocal interactions between the uterine epithelium and the underlying stroma, which are orchestrated by ovarian hormones. During this process, multiple signaling pathways are activated to direct cell proliferation and differentiation, which render the uterus receptive to the implanting blastocysts. One important modulator of these signaling pathways is the cell surface and extracellular matrix macromolecules, heparan sulfate proteoglycans (HSPGs). HSPGs play crucial roles in signal transduction by regulating morphogen transport and ligand binding. In this study, we examine the role of HSPG sulfation in regulating uterine receptivity by conditionally deleting the N-deacetylase/N-sulfotransferase (NDST) 1 gene (Ndst1) in the mouse uterus using the Pgr-Cre driver, on an Ndst2- and Ndst3-null genetic background. Although development of the female reproductive tract and subsequent ovarian function appear normal in Ndst triple-knockout females, they are infertile due to implantation defects. Embryo attachment appears to occur but the uterine epithelium at the site of implantation persists rather than disintegrates in the mutant. Uterine epithelial cells continued to proliferate past day 4 of pregnancy, accompanied by elevated Fgf2 and Fgf9 expression, whereas uterine stroma failed to undergo decidualization, as evidenced by lack of Bmp2 induction. Despite normal Indian hedgehog expression, transcripts of Ptch1 and Gli1, both components as well as targets of the hedgehog (Hh) pathway, were detected only in the subepithelial stroma, indicating altered Hh signaling in the mutant uterus. Taken together, these data implicate an essential role for HSPGs in modulating signal transduction during mouse implantation.

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Uterine Insulin Sensitivity Defects Induced Embryo Implantation Loss Associated with Mitochondrial Dysfunction-Triggered Oxidative Stress

Oxidative Medicine and Cellular Longevity ◽

10.1155/2021/6655685 ◽

2021 ◽

Vol 2021 ◽

pp. 1-18

Author(s):

Meixia Chen ◽

Jie Li ◽

Bo Zhang ◽

Xiangfang Zeng ◽

Xiangzhou Zeng ◽

...

Keyword(s):

Oxidative Stress ◽

Insulin Sensitivity ◽

Mitochondrial Dysfunction ◽

Insulin Signaling ◽

Embryo Implantation ◽

Fetal Loss ◽

Enrichment Analysis ◽

Uterine Receptivity ◽

Resistant Mouse

Scope. Implantation loss is a considerable cause of early pregnancy loss in humans and mammalian animals. It is not addressed how proliferative uterine defects implicate in implantation loss. Methods and Results. Herein, a comprehensive proteomic analysis was conducted on proliferative endometria from sows with low and normal reproductive performance (LRP and NRP, respectively). Enrichment analysis of differentially expressed proteins revealed alterations in endometrial remodeling, substance metabolism (mainly lipid, nitrogen, and retinol metabolism), immunological modulation, and insulin signaling in LRP sows. Importantly, aberrant lipid metabolite accumulation and dysregulation of insulin signaling were coincidently confirmed in endometria of LPR sows, proving an impaired insulin sensitivity. Furthermore, established high-fat diet- (HFD-) induced insulin-resistant mouse models revealed that uterine insulin resistance beginning before pregnancy deteriorated uterine receptivity and decreased implantation sites and fetal numbers. Mitochondrial biogenesis and fusion were decreased, and reactive oxygen species was overproduced in uteri from the HFD group during the implantation period. Ishikawa and JAR cells directly demonstrated that oxidative stress compromised implantation in vitro. Conclusions. This study demonstrated that uterine insulin sensitivity impairment beginning before pregnancy resulted in implantation and fetal loss associated with oxidative stress induced by mitochondrial dysfunction.

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Uterine aquaporin expression is dynamically regulated by estradiol and progesterone and ovarian stimulation disrupts embryo implantation without affecting luminal closure

MHR Basic science of reproductive medicine ◽

10.1093/molehr/gaaa007 ◽

2020 ◽

Vol 26 (3) ◽

pp. 154-166 ◽

Cited By ~ 2

Author(s):

Vanessa de Oliveira ◽

Jennifer Schaefer ◽

Basim Abu-Rafea ◽

George A Vilos ◽

Angelos G Vilos ◽

...

Keyword(s):

Embryo Development ◽

Ovarian Stimulation ◽

Embryo Implantation ◽

Pathological State ◽

Implantation Failure ◽

Uterine Receptivity ◽

Spatial Expression ◽

Aqp4 Expression ◽

Abnormal Expression ◽

Aquaporin Gene

Abstract The study investigated the effect of normal and supraphysiological (resulting from gonadotropin-dependent ovarian stimulation) levels of estradiol (E2) and progesterone (P4) on mouse uterine aquaporin gene/protein (Aqp/AQP) expression on Day 1 (D1) and D4 of pregnancy. The study also examined the effect of ovarian stimulation on uterine luminal closure and uterine receptivity on D4 of pregnancy and embryo implantation on D5 and D7 of pregnancy. These analyses revealed that the expression of Aqp3, Aqp4, Aqp5 and Aqp8 is induced by E2 while the expression of Aqp1 and Aqp11 is induced by P4. Additionally, P4 inhibits E2 induction of Aqp3 and Aqp4 expression while E2 inhibits Aqp1 and Aqp11 expression. Aqp9, however, is constitutively expressed. Ovarian stimulation disrupts Aqp3, Aqp5 and Aqp8 expression on D4 and AQP1, AQP3 and AQP5 spatial expression on both D1 and D4, strikingly so in the myometrium. Interestingly, while ovarian stimulation has no overt effect on luminal closure and uterine receptivity, it reduces implantation events, likely through a disruption in myometrial activity and embryo development. The wider implication of this study is that ovarian stimulation, which results in supraphysiological levels of E2 and P4 and changes (depending on the degree of stimulation) in the E2:P4 ratio, triggers abnormal expression of uterine AQP during pregnancy, and this is associated with implantation failure. These findings lead us to recognize that abnormal expression would also occur under any pathological state (such as endometriosis) that is associated with changes in the normal E2:P4 ratio. Thus, infertility among these patients might in part be linked to abnormal uterine AQP expression.

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MicroRNAs in Small Extracellular Vesicles Indicate Successful Embryo Implantation during Early Pregnancy

Cells ◽

10.3390/cells9030645 ◽

2020 ◽

Vol 9 (3) ◽

pp. 645 ◽

Cited By ~ 4

Author(s):

Qiang Tan ◽

Shuang Shi ◽

Jingjie Liang ◽

Xiaowei Zhang ◽

Dingren Cao ◽

...

Keyword(s):

Expression Profiles ◽

Embryo Implantation ◽

Extracellular Vesicle ◽

Synchronous Communication ◽

Normal Embryo ◽

Multivesicular Bodies ◽

Uterine Receptivity ◽

Database Analysis ◽

Mirna Expression Profiles ◽

Future Practice

Synchronous communication between the developing embryo and the receptive endometrium is crucial for embryo implantation. Thus, uterine receptivity evaluation is vital in managing recurrent implantation failure (RIF). The potential roles of small extracellular vesicle (sEV) miRNAs in pregnancy have been widely studied. However, the systematic study of sEVs derived from endometrium and its cargos during the implantation stage have not yet been reported. In this study, we isolated endometrium-derived sEVs from the mouse endometrium on D2 (pre-receptive phase), D4 (receptive phase), and D5 (implantation) of pregnancy. Herein, we reveal that multivesicular bodies (MVBs) in the endometrium increase in number during the window of implantation (WOI). Moreover, our findings indicate that CD63, a well-known sEV marker, is expressed in the luminal and glandular epithelium of mouse endometrium. The sEV miRNA expression profiles indicated that miR-34c-5p, miR-210, miR-369-5p, miR-30b, and miR-582-5p are enriched during WOI. Further, we integrated the RIF’s database analysis results and found out that miR-34c-5p regulates growth arrest specific 1 (GAS1) for normal embryo implantation. Notably, miR-34c-5p is downregulated during implantation but upregulated in sEVs. An implication of this is the possibility that sEVs miR-34c-5p could be used to evaluate uterine states. In conclusion, these findings suggest that the endometrium derived-sEV miRNAs are potential biomarkers in determining the appropriate period for embryo implantation. This study also has several important implications for future practice, including therapy of infertility.

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

Endocrinology ◽

10.1210/endocr/bqz005 ◽

2019 ◽

Vol 161 (2) ◽

Cited By ~ 4

Author(s):

Mitsunori Matsuo ◽

Yasushi Hirota ◽

Yamato Fukui ◽

Hidetoshi Fujita ◽

Tomoko Saito-Fujita ◽

...

Keyword(s):

Leukemia Inhibitory Factor ◽

Embryo Implantation ◽

Infertility Treatment ◽

Vehicle Control ◽

Inhibitory Factor ◽

Wild Type ◽

Attachment Sites ◽

Attachment Inhibition ◽

Evening Administration ◽

Embryo Attachment

Abstract 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.

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Uterine Receptivity

Reproduction Fertility and Development ◽

10.1071/rd9920645 ◽

1992 ◽

Vol 4 (6) ◽

pp. 645 ◽

Cited By ~ 3

Author(s):

PAW Rogers

Keyword(s):

Ovulation Induction ◽

Embryo Implantation ◽

Morphological Markers ◽

Human Uterus ◽

Uterine Receptivity ◽

Morphometric Measurement ◽

New Techniques ◽

Cellular Processes ◽

Functional Capabilities ◽

Human Implantation

Reduced uterine receptivity can play a major role in human infertility, particularly following ovarian stimulation as occurs during ovulation induction and IVF. Many of the conventional histological and morphological markers used to identify normal progestational changes in the human uterus are inadequate as markers of uterine receptivity for implantation, and new techniques including ultrasound and morphometric measurement will be required. At the same time, a'better understanding of the cellular processes involved in human implantation is required if we are to identify markers of uterine receptivity. Recent observations suggest that the uterus is normally a barrier to embryo implantation and that uterine receptivity is in fact the loss of this barrier function, rather than the acquisition of new structural or functional capabilities.

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Follistatin is critical for mouse uterine receptivity and decidualization

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1620903114 ◽

2017 ◽

Vol 114 (24) ◽

pp. E4772-E4781 ◽

Cited By ~ 7

Author(s):

Paul T. Fullerton ◽

Diana Monsivais ◽

Ramakrishna Kommagani ◽

Martin M. Matzuk

Keyword(s):

Molecular Mechanisms ◽

Recurrent Miscarriage ◽

Embryo Implantation ◽

Bmp Signaling ◽

Conditional Knockout ◽

Uterine Receptivity ◽

Vitro Fertilization ◽

Morphogenetic Protein ◽

Proliferation And Differentiation

Embryo implantation remains a significant challenge for assisted reproductive technology, with implantation failure occurring in ∼50% of in vitro fertilization attempts. Understanding the molecular mechanisms underlying uterine receptivity will enable the development of new interventions and biomarkers. TGFβ family signaling in the uterus is critical for establishing and maintaining pregnancy. Follistatin (FST) regulates TGFβ family signaling by selectively binding TGFβ family ligands and sequestering them. In humans, FST is up-regulated in the decidua during early pregnancy, and women with recurrent miscarriage have lower endometrial expression of FST during the luteal phase. Because global knockout of Fst is perinatal lethal in mice, we generated a conditional knockout (cKO) of Fst in the uterus using progesterone receptor-cre to study the roles of uterine Fst during pregnancy. Uterine Fst-cKO mice demonstrate severe fertility defects and deliver only 2% of the number of pups delivered by control females. In Fst-cKO mice, the uterine luminal epithelium does not respond properly to estrogen and progesterone signals and remains unreceptive to embryo attachment by continuing to proliferate and failing to differentiate. The uterine stroma of Fst-cKO mice also responds poorly to artificial decidualization, with lower levels of proliferation and differentiation. In the absence of uterine FST, activin B expression and signaling are up-regulated, and bone morphogenetic protein (BMP) signals are impaired. Our findings support a model in which repression of activin signaling by FST enables uterine receptivity by preserving critical BMP signaling.

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