Treatment with AICAR inhibits blastocyst development, trophectoderm differentiation and tight junction formation and function in mice

Large-scale production of human blastoids amenable to modeling blastocyst development and maternal-fetal cross talk

Recent advances in human blastoids have opened new avenues for modeling early human development and implantation. One limitation of our first protocol for human blastoid generation was relatively low efficiency. We now report an optimized protocol for the efficient generation of large quantities of high-fidelity human blastoids from naive pluripotent stem cells. This enabled proteomics analysis that identified phosphosite-specific signatures potentially involved in the derivation and/or maintenance of the signaling states in human blastoids. Additionally, we uncovered endometrial stromal effects in promoting trophoblast cell survival, proliferation, and syncytialization during co-culture with blastoids and blastocysts. Side-by-side single-cell RNA sequencing revealed similarities and differences in transcriptome profiles between pre-implantation blastoids and blastocysts, as well as post-implantation cultures, and uncovered a population resembling early migratory trophoblasts during co-culture with endometrial stromal cells. Our optimized protocol will facilitate broader use of human blastoids as an accessible, perturbable, scalable, and tractable model for human blastocysts.

Overview of junctional complexes during mammalian early embryonic development

Cell-cell junctions form strong intercellular connections and mediate communication between blastomeres during preimplantation embryonic development and thus are crucial for cell integrity, polarity, cell fate specification and morphogenesis. Together with cell adhesion molecules and cytoskeletal elements, intercellular junctions orchestrate mechanotransduction, morphokinetics and signaling networks during the development of early embryos. This review focuses on the structure, organization, function and expressional pattern of the cell-cell junction complexes during early embryonic development. Understanding the importance of dynamic junction formation and maturation processes will shed light on the molecular mechanism behind developmental abnormalities of early embryos during the preimplantation period.

Capture and metabolomic analysis of the human endometrial epithelial organoid secretome

Suboptimal uterine fluid (UF) composition can lead to pregnancy loss and likely contributes to offspring susceptibility to chronic adult-onset disorders. However, our understanding of the biochemical composition and mechanisms underpinning UF formation and regulation remain elusive, particularly in humans. To address this challenge, we developed a high-throughput method for intraorganoid fluid (IOF) isolation from human endometrial epithelial organoids. The IOF is biochemically distinct to the extraorganoid fluid (EOF) and cell culture medium as evidenced by the exclusive presence of 17 metabolites in IOF. Similarly, 69 metabolites were unique to EOF, showing asymmetrical apical and basolateral secretion by the in vitro endometrial epithelium, in a manner resembling that observed in vivo. Contrasting the quantitative metabolomic profiles of IOF and EOF revealed donor-specific biochemical signatures of organoids. Subsequent RNA sequencing of these organoids from which IOF and EOF were derived established the capacity to readily perform organoid multiomics in tandem, and suggests that transcriptomic regulation underpins the observed secretory asymmetry. In summary, these data provided by modeling uterine luminal and basolateral fluid formation in vitro offer scope to better understand UF composition and regulation with potential impacts on female fertility and offspring well-being.

Roles of AMP-Activated Protein Kinase (AMPK) in Mammalian Reproduction

Reproduction is an energy demanding function and only take place in case of sufficient available energy status in mammals. Metabolic diseases such as anorexia nervosa are clinically associated with reduced fertility. AMP-activated protein kinase (AMPK), as a major regulator of cellular energy homeostasis, is activated in limited energy reserves to ensure the orderly progress of various physiological activities. In recent years, mounting evidence shows that AMPK is involved in the regulation of reproductive function through multiple mechanisms. AMPK is likely to be a metabolic sensor integrating central and peripheral signals. In this review, we aim to explore the preclinical studies published in the last decade that investigate the role of AMP-activated protein kinase in the reproductive field, and its role as a target for drug therapy of reproductive system-related diseases. We also emphasized the emerging roles of AMPK in transcriptional regulation of reproduction processes and metabolisms, which are tightly related to the energy state and fertility of an organism.

Oleic Acid Counters Impaired Blastocyst Development Induced by Palmitic Acid During Mouse Preimplantation Development: Understanding Obesity-Related Declines in Fertility

Obesity is associated with altered fatty acid profiles, reduced fertility, and assisted reproductive technology (ART) success. The effects of palmitic acid (PA), oleic acid (OA), and their combination on mouse preimplantation development, endoplasmic reticulum (ER) stress pathway gene expression, lipid droplet formation, and mitochondrial reactive oxygen species (ROS) were characterized. Two-cell stage mouse embryos collected from superovulated and mated CD1 females were placed into culture with KSOMaa medium, or PA alone or in combination with OA for 46 h. PA significantly reduced blastocyst development in a concentration-dependent manner, which was prevented by co-treatment with OA. PA and OA levels in mouse reproductive tracts were assessed by liquid chromatography coupled to mass spectrometry (LC-MS). LC-MS indicated higher concentrations of PA in the mouse oviduct than the uterus. Transcript analysis revealed that PA alone groups had increased ER stress pathway (ATF3, CHOP, and XBP1 splicing) mRNAs, which was alleviated by OA co-treatment. OA co-treatment significantly increased lipid droplet accumulation and significantly decreased mitochondrial ROS from PA treatment alone. PA treatment for only 24 h significantly reduced its impact on blastocyst development from the 2-cell stage. Thus, PA affects ER stress pathway gene expression, lipid droplet accumulation, and mitochondrial ROS in treated preimplantation embryos. These mechanisms may serve to offset free fatty acid exposure effects on preimplantation development, but their protective ability may be overwhelmed by elevated PA.

Antidiabetic drug metformin affects the developmental competence of cleavage-stage embryos

PURPOSE

Metformin is the most commonly prescribed drug in the management of metabolic disorders such as polycystic ovarian syndrome (PCOS) and gestational diabetes in women of reproductive age. Insulin-sensitizing effect of metformin helps in improving from PCOS features such as hyperandrogenism, anovulation, and infertility. However, its ability to cross placental barrier raises concern about safety of the drug on early embryonic development. In this study, we evaluated the effect of metformin on the ovarian function and embryo development.

METHODS

Adult Swiss albino female mice were administered with metformin (0, 50, 100, and 200 mg/kg body weight) for 4 weeks and assessed for reproductive function and preimplantation embryo development. Further, effect of metformin (0, 10, 25, 50, 100, 250, and 500 μg/mL) exposure to 2-cell-stage embryos was tested under in vitro conditions.

RESULTS

Metformin did not alter the body weight, blood glucose, ovarian weight, and follicular reserve. However, the early embryo development was significantly affected in mice treated with metformin in vivo at highest dose. Moreover, embryos which were exposed to metformin in vitro showed dose-dependent decline in blastocyst rate and hatching rate. Furthermore, at highest concentration of metformin (500 μg/mL), all the embryos were arrested at compaction stage.

CONCLUSION

The study revealed that metformin affects the early embryonic development and raises concern about its use during conception.

Activation of adenosine monophosphate-activated protein kinase (AMPK) enhances energy metabolism, motility, and fertilizing ability of cryopreserved spermatozoa in domestic cat model

PURPOSE

Increasing intracellular energy storage by chemically activating adenosine monophosphate-activated protein kinase (AMPKα) prior to sperm cryopreservation may improve post-thawed sperm function. Using the domestic cat as a biomedical model, the objectives were to (1) confirm the expression of AMPKα and its regulatory kinases in epididymal spermatozoa and (2) assess the influence of AMPK activator, 5'-aminoimidasole-4-carboxamide-1-β-d-ribofuranoside (AICAR) on epididymal sperm function before and after cryopreservation.

METHODS

In study I, sperm samples of different qualities were obtained from cauda epididymides of domestic cats and evaluated for AMPKα expression. In study II, epididymal spermatozoa were equilibrated for either 30 or 60 min in the presence of 0 (control), 0.5, 2.0, and 5.0 mM AICAR and sperm functions were assessed before and after cryopreservation. In study III, epididymal spermatozoa were treated as in study II and evaluated for AMPKα signaling protein expressions (phospho-AMPKα Thr172 and GLUT1) as well as ATP levels.

RESULTS

AMPKα protein expression was higher in high-motility vs poor-motility samples. Thirty-minute equilibration with 0.5 mM AICAR improved motion characteristics and fertilizing ability of cryopreserved sperm to the control. Increased expressions of phospho-AMPKα Thr172 and GLUT1 as well as intracellular ATP level were confirmed in sperm samples equilibrated with 0.5 or 2.0 mM AICAR for 30 min.

CONCLUSIONS

Presence and role of AMPKα protein in cat regulating sperm function were demonstrated before and after cryopreservation. Findings could be used to potentially enhance cryopreserved sperm function in sub-fertile men.

H3K27me3 is an epigenetic barrier while KDM6A overexpression improves nuclear reprogramming efficiency

Aberrant epigenetic reprogramming is a major factor of developmental failure of cloned embryos. Histone H3 lysine 27 trimethylation (H3K27me3), a histone mark for transcriptional repression, plays important roles in mammalian embryonic development and induced pluripotent stem cell (iPSC) generation. The global loss of H3K27me3 marks may facilitate iPSC generation in mice and humans. However, the H3K27me3 level and its role in bovine somatic cell nuclear transfer (SCNT) reprogramming remain poorly understood. Here, we show that SCNT embryos exhibit global H3K27me3 hypermethylation from the 2- to 8-cell stage and that its removal by ectopically expressed H3K27me3 lysine demethylase (KDM)6A greatly improves nuclear reprogramming efficiency. In contrast, H3K27me3 reduction by H3K27me3 methylase enhancer of zeste 2 polycomb repressive complex knockdown or donor cell treatment with the enhancer of zeste 2 polycomb repressive complex-selective inhibitor GSK343 suppressed blastocyst formation by SCNT embryos. KDM6A overexpression enhanced the transcription of genes involved in cell adhesion and cellular metabolism and X-linked genes. Furthermore, we identified methyl-CpG-binding domain protein 3-like 2, which was reactivated by KDM6A, as a factor that is required for effective reprogramming in bovines. These results show that H3K27me3 functions as an epigenetic barrier and that KDM6A overexpression improves SCNT efficiency by facilitating transcriptional reprogramming.-Zhou, C., Wang, Y., Zhang, J., Su, J., An, Q., Liu, X., Zhang, M., Wang, Y., Liu, J., Zhang, Y. H3K27me3 is an epigenetic barrier while KDM6A overexpression improves nuclear reprogramming efficiency.

Metformin in Reproductive Biology

Initially produced in Europe in 1958, metformin is still one of the most widely prescribed drugs to treat type II diabetes and other comorbidities associated with insulin resistance. Metformin has been shown to improve fertility outcomes in females with insulin resistance associated with polycystic ovary syndrome (PCOS) and in obese males with reduced fertility. Metformin treatment reinstates menstrual cyclicity, decreases the incidence of cesareans, and limits the number of premature births. Notably, metformin reduces steroid levels in conditions associated with hyperandrogenism (e.g., PCOS and precocious puberty) in females and improves fertility of adult men with metabolic syndrome through increased testosterone production. While the therapeutical use of metformin is considered to be safe, in the last 10 years some epidemiological studies have described phenotypic differences after prenatal exposure to metformin. The goals of this review are to briefly summarize the current knowledge on metformin focusing on its effects on the female and male reproductive organs, safety concerns, including the potential for modulating fetal imprinting via epigenetics.

Knockdown of p66Shc Alters Lineage-Associated Transcription Factor Expression in Mouse Blastocysts

The p66Shc adaptor protein regulates apoptosis and senescence during early mammalian development. However, p66Shc expression during mouse preimplantation development is upregulated at the blastocyst stage. Our objective was to determine the biological function of p66Shc during mouse blastocyst development. In this study, we demonstrate that a reduced p66Shc transcript abundance following its short interfering RNA (siRNA)-mediated knockdown alters the spatiotemporal expression of cell lineage-associated transcription factors in the inner cell mass (ICM) of the mouse blastocyst. P66Shc knockdown blastocysts restrict OCT3/4 earlier to the inner cells of the early blastocyst and have ICMs containing significantly higher OCT3/4 levels, more GATA4-positive cells, and fewer NANOG-positive cells. P66Shc knockdown blastocysts also show a significantly reduced ability to form ICM-derived outgrowths when explanted in vitro. The increase in cells expressing primitive endoderm markers may be due to increased ERK1/2 activity, as it is reversed by ERK1/2 inhibition. These results suggest that p66Shc may regulate the relative abundance and timing of lineage-associated transcription factor expression in the blastocyst ICM.

Why AMPK agonists not known to be stressors may surprisingly contribute to miscarriage or hinder IVF/ART

Here we examine recent evidence suggesting that many drugs and diet supplements (DS), experimental AMP-activated protein kinase (AMPK) agonists as well as energy-depleting stress, lead to decreases in anabolism, growth or proliferation, and potency of cultured oocytes, embryos, and stem cells in an AMPK-dependent manner. Surprising data for DS and drugs that have some activity as AMPK agonists in in vitro experiments show possible toxicity. This needs to be balanced against a preponderance of evidence in vivo that these drugs and DS are beneficial for reproduction. We here discuss and analyze data that leads to two possible conclusions: First, although DS and drugs that have some of their therapeutic mechanisms mediated by AMPK activity associated with low ATP levels, some of the associated health problems in vivo and in vitro fertilization/assisted reproductive technologies (IVF/ART) may be better-treated by increasing ATP production using CoQ10 (Ben-Meir et al., Aging Cell 14:887-895, 2015). This enables high developmental trajectories simultaneous with solving stress by energy-requiring responses. In IVF/ART, it is ultimately best to maintain handling and culture of gametes and embryos in the quietest state with low metabolic activity (Leese et al., Mol Hum Reprod 14:667-672, 2008; Leese, Bioessays 24 (9):845-849, 2002) using back-to-nature or simplex algorithms to identify optima (Biggers, Reprod Biomed Online 4 Suppl 1:30-38, 2002). Stress markers, such as checkpoint proteins like TRP53 (aka p53) (Ganeshan et al., Exp Cell Res 358:227-233, 2017); Ganeshan et al., Biol Reprod 83:958-964, 2010) and a small set of kinases from the protein kinome that mediate enzymatic stress responses, can also be used to define optima. But, some gametes or embryos may have been stressed in vivo prior to IVF/ART or IVF/ART optimized for one outcome may be suboptimal for another. Increasing nutrition or adding CoQ10 to increase ATP production (Yang et al., Stem Cell Rev 13:454-464, 2017), managing stress enzyme levels with inhibitors (Xie et al., Mol Hum Reprod 12:217-224, 2006), or adding growth factors such as GM-CSF (Robertson et al., J Reprod Immunol 125:80-88, 2018); Chin et al., Hum Reprod 24:2997-3009, 2009) may increase survival and health of cultured embryos during different stress exposure contexts (Puscheck et al., Adv Exp Med Biol 843:77-128, 2015). We define "stress" as negative stimuli which decrease normal magnitude and speed of development, and these can be stress hormones, reactive oxygen species, inflammatory cytokines, or physical stimuli such as hypoxia. AMPK is normally activated by high AMP, commensurate with low ATP, but it was recently shown that if glucose is present inside the cell, AMPK activation by low ATP/high AMP is suppressed (Zhang et al., Nature 548:112-116, 2017). As we discuss in more detail below, this may also lead to greater AMPK agonist toxicity observed in two-cell embryos that do not import glucose. Stress in embryos and stem cells increases AMPK in large stimulation indexes but also direness indexes; the fastest AMPK activation occurs when stem cells are shifted from optimal oxygen to lower or high levels (Yang et al., J Reprod Dev 63:87-94, 2017). CoQ10 use may be better than risking AMPK-dependent metabolic and developmental toxicity when ATP is depleted and AMPK activated. Second, the use of AMPK agonists, DS, and drugs may best be rationalized when insulin resistance or obesity leads to aberrant hyperglycemia and hypertriglyceridemia, and obesity that negatively affect fertility. Under these conditions, beneficial effects of AMPK on increasing triglyceride and fatty acid and glucose uptake are important, as long as AMPK agonist exposures are not too high or do not occur during developmental windows of sensitivity. During these windows of sensitivity suppression of anabolism, proliferation, and stemness/potency due to AMPK activity, or overexposure may stunt or kill embryos or cause deleterious epigenetic changes.

Activating AMPK to Restore Tight Junction Assembly in Intestinal Epithelium and to Attenuate Experimental Colitis by Metformin

Adenosine monophosphate-activated protein kinase (AMPK), a crucial molecule in energy metabolism, is reported to play a potential role in gut epithelial differentiation and barrier function recently; however, its performance and mechanisms in the pathological process of inflammatory bowel diseases remain unidentified. In this study, we have found that the phosphorylation of AMPK in colonic tissues is negatively correlated with severity of disease during the initiation and development of experimental colitis induced by dextran sulfate sodium. Activation of AMPK by metformin significantly controls the progression of colitis, which is associated with the maintenance of tight junction in colonic epithelium in mice. Moreover, our in vitro data in colonic epithelial Caco2 cells shows that metformin promotes expression and assembly of tight junctions via an AMPK-dependent way. Overall, our results suggested that activating AMPK by a clinically safe drug metformin could be a beneficial choice for colitis treatment.