The SARS-CoV-2 receptor, angiotensin-converting enzyme 2, is required for human endometrial stromal cell decidualization†.

The coronavirus disease 2019 (COVID-19) first appeared in December 2019 and rapidly spread throughout the world. The SARS-CoV-2 virus enters the host cells by binding to the angiotensin-converting enzyme 2 (ACE2). Although much of the focus is on respiratory symptoms, recent reports suggest that SARS-CoV-2 can cause pregnancy complications such as pre-term birth and miscarriages; and women with COVID-19 have had maternal vascular malperfusion and decidual arteriopathy in their placentas. Here, we report that the ACE2 protein is expressed in both endometrial epithelial and stromal cells in the proliferative phase of the menstrual cycle, and the expression increases in stromal cells in the secretory phase. It was observed that the ACE2 mRNA and protein abundance increased during primary human endometrial stromal cell (HESC) decidualization. Furthermore, HESCs transfected with ACE2-targeting siRNA impaired the full decidualization response, as evidenced by a lack of morphology change and lower expression of the decidualization markers PRL and IGFBP1. Additionally, in mice during pregnancy, the ACE2 protein was expressed in the uterine epithelial cells, and stromal cells increased through day 6 of pregnancy. Finally, progesterone induced Ace2 mRNA expression in mouse uteri more than vehicle or estrogen. These data establish a role for ACE2 in endometrial physiology, suggesting that SARS-CoV-2 may be able to enter endometrial stromal cells and elicit pathological manifestations in women with COVID-19, including an increased risk of early pregnancy loss.

Microtubule depolymerization attenuates WNT4/CaMKIIα signaling in mouse uterus and leads to implantation failure.

Microtubule (MT) dynamics plays a crucial role in fertilization and early embryonic development; however its involvement in uterus during embryo implantation remains unclear. Herein, we report the effect of microtubule depolymerization during embryo implantation in BALB/c mice. Intrauterine treatment with depolymerizing agent nocodazole at pre-implantation phase (D4, 07:00 h) in mice resulted into mitigation in receptivity markers viz. LIF, HoxA10, Integrin-ß3, IHH, WNT4 and led to pregnancy failure. MT depolymerization in endometrial epithelial cells (EECs) also inhibited the blastocyst attachment and the adhesion. The decreased expression of MT polymerization-related proteins TPPP and α/ß-tubulin in luminal and glandular epithelial cells along with the alteration in morphology of pinopodes in the luminal epithelium was observed in nocodazole receiving uteri. Nocodazole treatment also led to increased intracellular Ca+2 levels in EECs, which indicated that altered Ca+2 homeostasis might be responsible for implantation failure. Microtubule depolymerization inhibited WNT4 and Fz-2 interaction, thereby suppressing the downstream WNT4/CaMKIIα signaling cascades calmodulin and calcineurin which led to attenuation of NF-κB transcriptional promoter activity in EECs. MT depolymerization or CaMKIIα knockdown inhibited the transcription factor NFAT and NF-κB expression along with reduced secretion of prostaglandins PGE2 and PGF2α in mouse EECs. Overall, MT depolymerization impaired the WNT4/CaMKIIα signaling and suppressed the secretion of PGE2 and PGF2α in EECs which may be responsible for implantation failure in mice.

Uterine TPPP3 plays important role in embryo implantation via modulation of ß-catenin.

Tubulin polymerization promoting protein 3 (TPPP3) is known to be expressed in the endometrium in a cyclic manner, and its functional role in the physiology of implantation remains unknown. Here we demonstrate a novel function of TPPP3 during the window of implantation and in the establishment of pregnancy using a mouse model. The increased protein expression of TPPP3 and ß-catenin during peri-implantation period, i.e. D5 (receptive phase, 0800 h), was observed as compared to that on D1 (nonreceptive phase, 0800 h). SiRNATPPP3-mediated knockdown of uterine TPPP3 resulted in implantation failure and inhibited the expression of receptivity markers: LIF, Integrin-ß3, IHH, and Wnt4. TPPP3 silencing in mouse endometrial epithelial cells also prevented blastocyst attachment and the adhesion reaction. In delayed implantation experiment, expression of TPPP3 was increased in active implantation group (E2 + P4) compared to delayed implantation group (P4). The increased expression of TPPP3 in E2 + P4-treated Ishikawa cells compared to vehicle or P4 or E2 alone-treated Ishikawa cells also revealed its upregulation by E2. The suppression of ß-catenin in uterus under the condition of transient knockdown of TPPP3 and the co-immunoprecipitation experiment revealed that regulation of ß-catenin was mediated via TPPP3 during implantation. Additionally, in order to gain insight into TPPP3 collaborators, we identified TPPP3 interacting proteins by nanoLC-MS analysis in mouse uterus which might be involved during implantation. In conclusion, our study suggests that TPPP3 is important for embryo implantation and for the establishment of early pregnancy through modulation of ß-catenin.

The autophagy protein, ATG14 safeguards against unscheduled pyroptosis activation to enable embryo transport during early pregnancy.

Recurrent pregnancy loss (RPL), characterized by two or more failed clinical pregnancies, poses a significant challenge to reproductive health. In addition to embryo quality and endometrial function, proper oviduct function is also essential for successful pregnancy establishment. Therefore, structural abnormalities or inflammation resulting from infection in the oviduct may impede the transport of embryos to the endometrium, thereby increasing the risk of miscarriage. However, the precise cellular mechanisms that maintain the structural and functional integrity of the oviduct are not studied yet. Here, we report that autophagy is critical for maintaining the oviduct homeostasis and keeping the inflammation under check to enable embryo transport. Specifically, the loss of the autophagy-related gene, Atg14 in the oviduct causes severe structural abnormalities compromising its cellular plasticity and integrity leading to the retention of embryos. Interestingly, the selective loss of Atg14 in oviduct ciliary epithelial cells did not impact female fertility, highlighting the specificity of ATG14 function in distinct cell types within the oviduct. Mechanistically, loss of Atg14 triggered unscheduled pyroptosis leading to inappropriate embryo retention and impeded embryo transport in the oviduct. Finally, pharmacological activation of pyroptosis in pregnant mice led to an impairment in embryo transport. Together, we found that ATG14 safeguards against unscheduled pyroptosis activation to enable embryo transport from the oviduct to uterus for the successful implantation. Of clinical significance, these findings provide possible insights on the underlying mechanism(s) of early pregnancy loss and might aid in developing novel prevention strategies using autophagy modulators.

A GREB1-steroid receptor feedforward mechanism governs differential GREB1 action in endometrial function and endometriosis.

Cellular responses to the steroid hormones, estrogen (E2), and progesterone (P4) are governed by their cognate receptor's transcriptional output. However, the feed-forward mechanisms that shape cell-type-specific transcriptional fulcrums for steroid receptors are unidentified. Herein, we found that a common feed-forward mechanism between GREB1 and steroid receptors regulates the differential effect of GREB1 on steroid hormones in a physiological or pathological context. In physiological (receptive) endometrium, GREB1 controls P4-responses in uterine stroma, affecting endometrial receptivity and decidualization, while not affecting E2-mediated epithelial proliferation. Of mechanism, progesterone-induced GREB1 physically interacts with the progesterone receptor, acting as a cofactor in a positive feedback mechanism to regulate P4-responsive genes. Conversely, in endometrial pathology (endometriosis), E2-induced GREB1 modulates E2-dependent gene expression to promote the growth of endometriotic lesions in mice. This differential action of GREB1 exerted by a common feed-forward mechanism with steroid receptors advances our understanding of mechanisms that underlie cell- and tissue-specific steroid hormone actions.

Autophagy is required for stem-cell-mediated endometrial programming and the establishment of pregnancy.

Autophagy plays an important role in the normal growth and morphogenesis of a variety of tissues. Its role in uterine maturation, however, is not fully characterized. Recently, we reported that BECN1 (Beclin1)-dependent autophagy, but not apoptosis, is crucial for stem cell-mediated endometrial programming and the establishment of pregnancy in mice. Upon genetic and pharmacological inhibition of BECN1-mediated autophagy, female mice displayed severe endometrial structural and functional defects leading to infertility. Specifically, conditional loss of Becn1 in the uterus induces apoptosis and results in the gradual loss of endometrial progenitor stem cells. Importantly, the restoration of BECN1-driven autophagy, but not apoptosis in Becn1 conditionally ablated mice promoted normal uterine adenogenesis and morphogenesis. Overall, our findings emphasize the critical role of intrinsic autophagy in endometrial homeostasis and on the molecular underpinnings of uterine differentiation.

SF3B1-dependent alternative splicing is critical for maintaining endometrial homeostasis and the establishment of pregnancy.

The remarkable potential of human endometrium to undergo spontaneous remodeling is shaped by controlled spatiotemporal gene expression patterns. Although hormone-driven transcription shown to govern these patterns, the post-transcriptional processing of these mRNA transcripts, including the mRNA splicing in the endometrium is not studied yet. Here, we report that the splicing factor, SF3B1 is central in driving alternative splicing (AS) events that are vital for physiological responses of the endometrium. We show that loss of SF3B1 splicing activity impairs stromal cell decidualization as well as embryo implantation. Transcriptomic analysis revealed that SF3B1 depletion decidualizing stromal cells led to differential mRNA splicing. Specifically, a significant upregulation in mutually exclusive AS events (MXEs) with SF3B1 loss resulted in the generation of aberrant transcripts. Further, we found that some of these candidate genes phenocopy SF3B1 function in decidualization. Importantly, we identify progesterone as a potential upstream regulator of SF3B1-mediated functions in endometrium possibly via maintaining its persistently high levels, in coordination with deubiquitinating enzymes. Collectively, our data suggest that SF3B1-driven alternative splicing plays a critical role in mediating the endometrial-specific transcriptional paradigms. Thus, the identification of novel mRNA variants associated with successful pregnancy establishment may help to develop new strategies to diagnose or prevent early pregnancy loss.

Beclin-1-dependent autophagy, but not apoptosis, is critical for stem-cell-mediated endometrial programming and the establishment of pregnancy.

The human endometrium shows a remarkable regenerative capacity that enables cyclical regeneration and remodeling throughout a woman's reproductive life. Although early postnatal uterine developmental cues direct this regeneration, the vital factors that govern early endometrial programming are largely unknown. We report that Beclin-1, an essential autophagy-associated protein, plays an integral role in uterine morphogenesis during the early postnatal period. We show that conditional depletion of Beclin-1 in the uterus triggers apoptosis and causes progressive loss of Lgr5+/Aldh1a1+ endometrial progenitor stem cells, with concomitant loss of Wnt signaling, which is crucial for stem cell renewal and epithelial gland development. Beclin-1 knockin (Becn1 KI) mice with disabled apoptosis exhibit normal uterine development. Importantly, the restoration of Beclin-1-driven autophagy, but not apoptosis, promotes normal uterine adenogenesis and morphogenesis. Together, the data suggest that Beclin-1-mediated autophagy acts as a molecular switch that governs the early uterine morphogenetic program by maintaining the endometrial progenitor stem cells.

Gut microbiota and microbiota-derived metabolites promotes endometriosis.

Endometriosis is a pathological condition of the female reproductive tract characterized by the existence of endometrium-like tissue at ectopic sites, affecting 10% of women between the age 15 and 49 in the USA. However, currently there is no reliable non-invasive method to detect the presence of endometriosis without surgery and many women find hormonal therapy and surgery as ineffective in avoiding the recurrences. There is a lack of knowledge on the etiology and the factors that contribute to the development of endometriosis. A growing body of recent evidence suggests an association between gut microbiota and endometriosis pathophysiology. However, the direct impact of microbiota and microbiota-derived metabolites on the endometriosis disease progression is largely unknown. To understand the causal role of gut microbiota and endometriosis, we have implemented a novel model using antibiotic-induced microbiota-depleted (MD) mice to investigate the endometriosis disease progression. Interestingly, we found that MD mice showed reduced endometriotic lesion growth and, the transplantation of gut microbiota by oral gavage of feces from mice with endometriosis rescued the endometriotic lesion growth. Additionally, using germ-free donor mice, we indicated that the uterine microbiota is dispensable for endometriotic lesion growth in mice. Furthermore, we showed that gut microbiota modulates immune cell populations in the peritoneum of lesions-bearing mice. Finally, we found a novel signature of microbiota-derived metabolites that were significantly altered in feces of mice with endometriosis. Finally, we found one the altered metabolite, quinic acid promoted the survival of endometriotic epithelial cells in vitro and lesion growth in vivo, suggesting the disease-promoting potential of microbiota-derived metabolites. In summary, these data suggest that gut microbiota and microbiota-derived metabolome contribute to lesion growth in mice, possibly through immune cell adaptations. Of translational significance, these findings will aid in designing non-invasive diagnostics using stool metabolites for endometriosis.

The Multifaceted Role of Autophagy in Endometrium Homeostasis and Disease.

Autophagy is a conserved fundamental cellular process with a primary function of catabolizing harmful or surplus cellular contents such as protein aggregates, dysfunctional/long-lived organelles, intracellular pathogens, and storage nutrients. An increasing body of evidence reveals that basal autophagy is essential for maintaining endometrial homeostasis and mediating endometrial-specific functions, including menstrual cycle, embryo implantation, and decidualization. However, perturbed levels of autophagy can lead to severe endometrial pathologies, including endometriosis, endometrial hyperplasia, endometrial cancer, adenomyosis, and leiomyoma. This review highlights the most recent findings on the activity, regulation, and function of autophagy in endometrium physiology and pathology. Understanding the mechanistic roles of autophagy in endometrium homeostasis and disease is key to developing novel therapeutic strategies for endometrium-related infertility and malignancies.

Peroxiredoxin 6 Plays Essential Role in Mediating Fertilization and Early Embryonic Development in Rabbit Oviduct.

The oviduct is a site for early reproductive events including gamete maturation, fertilization, and early embryo development. Secretory cells lining the oviduct lumen synthesize and secrete proteins that interact with gametes and developing embryos. Although previous studies have identified some of the secretory proteins in the oviduct, however, knowledge and their precise specific functions in the oviduct are poorly understood. In this study, by using proteomic approach, we identified a secretory protein, Peroxiredoxin 6 (PRDX6), and evaluated its role in mediating early pregnancy events, fertilization, and embryo development in rabbit oviduct. The expression of PRDX6 was significantly higher in ampulla and isthmus sections of the oviduct in mated animal groups compared to non-mated controls. Furthermore, significant reduction in number of embryos recovered from PRDX6 siRNA-transfected oviductal horn was observed compared to the control contralateral horn. Moreover, in animals receiving PRDX6 siRNA in their oviductal horn, the number of implanted blastocysts was significantly less in the uterus as observed on day 9 post-coital (p.c.). Further, during embryo-rabbit oviduct epithelial cell (ROEC) co-culture, siRNA-mediated PRDX6 silencing attenuated the early embryonic development. Mechanistically, increased levels of ROS and expression of oxidative stress- and inflammation-related proteins were found in PRDX6 siRNA-treated ROEC cells as compared to control cells, implicating that ablation of PRDX6 in the oviduct creates a stress-induced micro-environment detrimental to early embryonic development in oviduct. Taken together, our data suggest that PRDX6 maintains an optimal micro-environment conducive to successful embryo development and can be considered as a candidate to evaluate its therapeutic potential in IVF strategies.

A genome-wide CRISPR-Cas9 knockout screen identifies essential and growth-restricting genes in human trophoblast stem cells.

The recent derivation of human trophoblast stem cells (hTSCs) provides a scalable in vitro model system of human placental development, but the molecular regulators of hTSC identity have not been systematically explored thus far. Here, we utilize a genome-wide CRISPR-Cas9 knockout screen to comprehensively identify essential and growth-restricting genes in hTSCs. By cross-referencing our data to those from similar genetic screens performed in other cell types, as well as gene expression data from early human embryos, we define hTSC-specific and -enriched regulators. These include both well-established and previously uncharacterized trophoblast regulators, such as ARID3A, GATA2, and TEAD1 (essential), and GCM1, PTPN14, and TET2 (growth-restricting). Integrated analysis of chromatin accessibility, gene expression, and genome-wide location data reveals that the transcription factor TEAD1 regulates the expression of many trophoblast regulators in hTSCs. In the absence of TEAD1, hTSCs fail to complete faithful differentiation into extravillous trophoblast (EVT) cells and instead show a bias towards syncytiotrophoblast (STB) differentiation, thus indicating that this transcription factor safeguards the bipotent lineage potential of hTSCs. Overall, our study provides a valuable resource for dissecting the molecular regulation of human placental development and diseases.

Gut microbiota-derived short-chain fatty acids protect against the progression of endometriosis.

Worldwide, ∼196 million are afflicted with endometriosis, a painful disease in which endometrial tissue implants and proliferates on abdominal peritoneal surfaces. Theories on the origin of endometriosis remained inconclusive. Whereas up to 90% of women experience retrograde menstruation, only 10% develop endometriosis, suggesting that factors that alter peritoneal environment might contribute to endometriosis. Herein, we report that whereas some gut bacteria promote endometriosis, others protect against endometriosis by fermenting fiber to produce short-chain fatty acids. Specifically, we found that altered gut microbiota drives endometriotic lesion growth and feces from mice with endometriosis contained less of short-chain fatty acid and n-butyrate than feces from mice without endometriosis. Treatment with n-butyrate reduced growth of both mouse endometriotic lesions and human endometriotic lesions in a pre-clinical mouse model. Mechanistic studies revealed that n-butyrate inhibited human endometriotic cell survival and lesion growth through G-protein-coupled receptors, histone deacetylases, and a GTPase activating protein, RAP1GAP. Our findings will enable future studies aimed at developing diagnostic tests, gut bacteria metabolites and treatment strategies, dietary supplements, n-butyrate analogs, or probiotics for endometriosis.

The SARS-CoV-2 receptor, Angiotensin converting enzyme 2 (ACE2) is required for human endometrial stromal cell decidualization.

STUDY QUESTION: Is SARS-CoV-2 receptor, angiotensin-converting enzyme 2 (ACE 2) expressed in the human endometrium during the menstrual cycle, and does it participate in endometrial decidualization? SUMMARY ANSWER: ACE2 protein is highly expressed in human endometrial stromal cells during the secretory phase and is essential for human endometrial stromal cell decidualization. WHAT IS KNOWN ALREADY: ACE2 is expressed in numerous human tissues including the lungs, heart, intestine, kidneys and placenta. ACE2 is also the receptor by which SARS-CoV-2 enters human cells. STUDY DESIGN SIZE DURATION: Proliferative (n = 9) and secretory (n = 6) phase endometrium biopsies from healthy reproductive-age women and primary human endometrial stromal cells from proliferative phase endometrium were used in the study. PARTICIPANTS/MATERIALS SETTING METHODS: ACE2 expression and localization were examined by qRT-PCR, Western blot, and immunofluorescence in both human endometrial samples and mouse uterine tissue. The effect of ACE2 knockdown on morphological and molecular changes of human endometrial stromal cell decidualization were assessed. Ovariectomized mice were treated with estrogen or progesterone to determine the effects of these hormones on ACE2 expression. MAIN RESULTS AND THE ROLE OF CHANCE: In human tissue, ACE2 protein is expressed in both endometrial epithelial and stromal cells in the proliferative phase of the menstrual cycle, and expression increases in stromal cells in the secretory phase. The ACE2 mRNA ( P < 0.0001) and protein abundance increased during primary human endometrial stromal cell (HESC) decidualization. HESCs transfected with ACE2 -targeting siRNA were less able to decidualize than controls, as evidenced by a lack of morphology change and lower expression of the decidualization markers PRL and IGFBP1 ( P < 0.05). In mice during pregnancy, ACE2 protein was expressed in uterine epithelial and stromal cells increased through day six of pregnancy. Finally, progesterone induced expression of Ace2 mRNA in mouse uteri more than vehicle or estrogen ( P < 0.05). LARGE SCALE DATA: N/A. LIMITATIONS REASONS FOR CAUTION: Experiments assessing the function of ACE2 in human endometrial stromal cell decidualization were in vitro . Whether SARS-CoV-2 can enter human endometrial stromal cells and affect decidualization have not been assessed. WIDER IMPLICATIONS OF THE FINDINGS: Expression of ACE2 in the endometrium allow SARS-CoV-2 to enter endometrial epithelial and stromal cells, which could impair in vivo decidualization, embryo implantation, and placentation. If so, women with COVID-19 may be at increased risk of early pregnancy loss. STUDY FUNDINGS/COMPETING INTERESTS: This study was supported by National Institutes of Health / National Institute of Child Health and Human Development grants R01HD065435 and R00HD080742 to RK and Washington University School of Medicine start-up funds to RK. The authors declare that they have no conflicts of interest.

Splicing factor SF3B1 promotes endometrial cancer progression via regulating KSR2 RNA maturation.

Although endometrial cancer is the most common cancer of the female reproductive tract, we have little understanding of what controls endometrial cancer beyond the transcriptional effects of steroid hormones such as estrogen. As a result, we have limited therapeutic options for the ~62,000 women diagnosed with endometrial cancer each year in the United States. Here, in an attempt to identify new prognostic and therapeutic targets, we focused on a new area for this cancer-alternative mRNA splicing-and investigated whether splicing factor, SF3B1, plays an important role in endometrial cancer pathogenesis. Using a tissue microarray, we found that human endometrial tumors expressed more SF3B1 protein than non-cancerous tissues. Furthermore, SF3B1 knockdown reduced in vitro proliferation, migration, and invasion of the endometrial cancer cell lines Ishikawa and AN3CA. Similarly, the SF3B1 inhibitor, Pladienolide-B (PLAD-B), reduced the Ishikawa and AN3CA cell proliferation and invasion in vitro. Moreover, PLAD-B reduced tumor growth in an orthotopic endometrial cancer mouse model. Using RNA-Seq approach, we identified ~2000 differentially expressed genes (DEGs) with SF3B1 knockdown in endometrial cancer cells. Additionally, alternative splicing (AS) events analysis revealed that SF3B1 depletion led to alteration in multiple categories of AS events including alternative exon skipping (ES), transcript start site usage (TSS), and transcript termination site (TTS) usage. Subsequently, bioinformatics analysis showed KSR2 as a potential candidate for SF3B1-mediated functions in endometrial cancer. Specifically, loss of SF3B1 led to decrease in KSR2 expression, owing to reduced maturation of KSR2 pre-mRNA to a mature RNA. Importantly, we found rescuing the KSR2 expression with SF3B1 knockdown partially restored the cell growth of endometrial cancer cells. Taken together, our data suggest that SF3B1 plays a crucial oncogenic role in the tumorigenesis of endometrial cancer and hence may support the development of SF3B1 inhibitors to treat this disease.

The Autophagy Gene Atg16L1 is Necessary for Endometrial Decidualization.

Uterine receptivity is critical for establishing and maintaining pregnancy. For the endometrium to become receptive, stromal cells must differentiate into decidual cells capable of secreting factors necessary for embryo survival and placental development. Although there are multiple reports of autophagy induction correlated with endometrial stromal cell (ESC) decidualization, the role of autophagy in decidualization has remained elusive. To determine the role of autophagy in decidualization, we utilized 2 genetic models carrying mutations to the autophagy gene Atg16L1. Although the hypomorphic Atg16L1 mouse was fertile and displayed proper decidualization, conditional knockout in the reproductive tract of female mice reduced fertility by decreasing the implantation rate. In the absence of Atg16L1, ESCs failed to properly decidualize and fewer blastocysts were able to implant. Additionally, small interfering RNA knock down of Atg16L1 was detrimental to the decidualization response of human ESCs. We conclude that Atg16L1 is necessary for decidualization, implantation, and overall fertility in mice. Furthermore, considering its requirement for human endometrial decidualization, these data suggest Atg16L1 may be a potential mediator of implantation success in women.

Derivation of trophoblast stem cells from naïve human pluripotent stem cells.

Naïve human pluripotent stem cells (hPSCs) provide a unique experimental platform of cell fate decisions during pre-implantation development, but their lineage potential remains incompletely characterized. As naïve hPSCs share transcriptional and epigenomic signatures with trophoblast cells, it has been proposed that the naïve state may have enhanced predisposition for differentiation along this extraembryonic lineage. Here we examined the trophoblast potential of isogenic naïve and primed hPSCs. We found that naïve hPSCs can directly give rise to human trophoblast stem cells (hTSCs) and undergo further differentiation into both extravillous and syncytiotrophoblast. In contrast, primed hPSCs do not support hTSC derivation, but give rise to non-self-renewing cytotrophoblasts in response to BMP4. Global transcriptome and chromatin accessibility analyses indicate that hTSCs derived from naïve hPSCs are similar to blastocyst-derived hTSCs and acquire features of post-implantation trophectoderm. The derivation of hTSCs from naïve hPSCs will enable elucidation of early mechanisms that govern normal human trophoblast development and associated pathologies.

The placenta is one of the most important human organs, but it is perhaps the least understood. The first decision the earliest human cells have to make, shortly after the egg is fertilized by a sperm, is whether to become part of the embryo or part of the placenta. This choice happens before a pregnancy even implants into the uterus. The cells that commit to becoming the embryo transform into 'naïve pluripotent' cells, capable of becoming any cell in the body. Those that commit to becoming the placenta transform into 'trophectoderm' cells, capable of becoming the two types of cell in the placenta. Placental cells either invade into the uterus to anchor the placenta or produce hormones to support the pregnancy. Once a pregnancy implants into the uterus, the naïve pluripotent cells in the embryo become 'primed'. This prevents them from becoming cells of the placenta, and it poses a problem for placental research. In 2018, scientists in Japan reported conditions for growing trophectoderm cells in the laboratory, where they are known as "trophoblast stem cells". These cells were capable of transforming into specialized placental cells, but needed first to be isolated from the human embryo or placenta itself. Dong et al. now show how to reprogram other pluripotent cells grown in the laboratory to produce trophoblast stem cells. The first step was to reset primed pluripotent cells to put them back into a naïve state. Then, Dong et al. exposed the cells to the same concoction of nutrients and chemicals used in the 2018 study. This fluid triggered a transformation in the naïve pluripotent cells; they started to look like trophoblast stem cells, and they switched on genes normally active in trophectoderm cells. To test whether these cells had the same properties as trophoblast stem cells, Dong et al. gave them chemical signals to see if they could mature into placental cells. The stem cells were able to transform into both types of placental cell, either invading through a three-dimensional gel that mimics the wall of the uterus or making pregnancy hormones. There is a real need for a renewable supply of placental cells in pregnancy research. Animal placentas are not the same as human ones, so it is not possible to learn everything about human pregnancy from animal models. A renewable supply of trophoblast stem cells could aid in studying how the placenta forms and why this process sometimes goes wrong. This could help researchers to better understand miscarriage, pre-eclampsia and other conditions that affect the growth of an unborn baby. In the future, it may even be possible to make custom trophoblast stem cells to study the specific fertility issues of an individual.

Sonic hedgehog protects endometrial hyperplasial cells against oxidative stress via suppressing mitochondrial fission protein dynamin-like GTPase (Drp1).

Hh/Gli1 cascade as well as Gsk3ß-Gli1 crosstalk play crucial role in estrogen-dependent progression of endometrial hyperplasia (EH). However, the underlying mechanisms involved in progression of disease still remain unclear. In the present study, we explored the role of Hh signaling in protection of endometrial hyperplasial cells against oxidative stress and the underlying mechanism involved therein. EH cells were found to be more resistant towards H2O2-induced oxidative stress (IC50: ~ 3×) as compared with normal endometrial cells. Estrogen (E2) pre-treatment followed by cytotoxic dose of H2O2, almost rescued the EH cells from apoptosis and caused the increased expression of downstream Shh signaling molecules i.e., Smo, Ptch and Gli1. Whereas pretreatment with cyclopamine was not able to curtail H2O2-induced effects indicating that estrogen protects these cells via activation of Shh pathway. Further, H2O2-induced ROS and lipid peroxidation alongwith decreased activities of antioxidant enzymes glutathione peroxidase and superoxide dismutase were found to be reversed in EH cells pre-exposed to E2 or rShh. The rShh suppressed H2O2-induced cell death and caused attenuation of mitochondrial apoptotic mediators and prevented disruption in mitochondrial morphology and mitochondrial membrane potential in EH cells. The functional blockage of signaling by Shh siRNA or Gli1siRNA led to significantly increased expression of mitochondrial fission protein dynamin-like GTPase (Drp1). The H2O2-treated EH cells showed diminished Gli1 and increased Drp1 expression, concurrent with reduced p-Drp1-(serine637). Whereas rShh pre-treated EH cells presented normal mitochondrial dynamics with dense, long networks of mitochondria alongwith nuclear accumulation of Gli1 and the decreased expression of Drp1. Overall, our results implicated that Shh signaling modulates antioxidant defense system and stabilizes mitochondrial dynamics by suppressing Drp1 protein which maintains survival of EH cells against oxidative stress.

Sorcin is involved during embryo implantation via activating VEGF/PI3K/Akt pathway in mice.

Our earlier studies have demonstrated the cyclic variation and also the altered expression of sorcin in endometrium during early-to-mid-secretory phase transition in women with unexplained infertility. The current study was undertaken to establish the functional role of sorcin in endometrial receptivity in mice. Results indicated that sorcin was highly expressed during the window of implantation in mice and functional blockage of sorcin caused significant reduction in number of implanted blastocyst. The receptivity markers (i.e.Integrin ß3, HBEGF, IGFBP1, WNT4 and Cyclin E)) were found to be downregulated in sorcin knocked down uterine horn on day 5 as compared to untreated horn. The reduced attachment and expansion of BeWo spheroids on RL95-2 endometrial cells with sorcin knock down, in in vitro model of endometrium-trophoblast interaction further supported these findings. Uterine sorcin expression pattern during estrous cycle and in delayed implantation mice model suggested the upregulation of sorcin by estrogen. The functional blockade of sorcin induced the intracellular Ca+2 levels in endometrial epithelial cells (EECs), which indicated that altered Ca+2 homeostasis might be responsible for implantation failure. Sorcin silencing led to significant reduction in the expression of angiogenic factor VEGF and its downstream effector molecules i.e. PI3K, Akt and NOS. The migratory and invasive properties of HUVECs were abrogated by anti-VEGF or by adding culture media from sorcin blocked EECs, which indicated that sorcin might mediate angiogenesis during implantation. Taken together, sorcin is involved in the regulation of Ca+2-mediated angiogenesis via VEGF/PI3K/Akt pathway in endometrial cells and plays a crucial role in preparing the endometrium for implantation.

The regulation of Hh/Gli1 signaling cascade involves Gsk3ß- mediated mechanism in estrogen-derived endometrial hyperplasia.

The present study was undertaken to explore the functional involvement of Hh signaling and its regulatory mechanism in endometrial hyperplasia. Differential expression of Hh signaling molecules i.e., Ihh, Shh, Gli1 or Gsk3ß was observed in endometrial hyperplasial (EH) cells as compared to normal endometrial cells. Estradiol induced the expression of Hh signaling molecules and attenuated the expression of Gsk3ß whereas anti-estrogen (K1) or progestin (MPA) suppressed these effects in EH cells. Cyclopamine treatment or Gli1 siRNA knockdown suppressed the growth of EH cells and reduced the expression of proliferative markers. Estradiol also induced the nuclear translocation of Gli1 which was suppressed by both MPA and K1 in EH cells. While exploring non-canonical mechanism, LY-294002 (Gsk3ß activator) caused a decrease in Gli1 expression indicating the involvement of Gsk3ß in Gli1 regulation. Further, Gsk3ß silencing promoted the expression and nuclear translocation of Gli1 demonstrating that Gsk3ß serves as a negative kinase regulator of Gli1 in EH cells. Similar attenuation of Hh signaling molecules was observed in rats with uterine hyperplasia undergoing anti-estrogen treatment. The study suggested that Hh/Gli1 cascade (canonical pathway) as well as Gsk3ß-Gli1 crosstalk (non-canonical pathway) play crucial role in estrogen-dependent cell proliferation in endometrial hyperplasia.