Revealing the mechanism of fiber promoting sow embryo implantation by altering the abundance of uterine fluid proteins: A proteomic perspective

Many studies have shown that fiber in the diet plays an important role in improving the reproductive performance of sows, but there is rarely research on the impact of fiber on early embryo implantation. This study used 4D-Label free technology to identify and analyze the effect of the fiber composition in the diet on the protein in the early pregnancy uterine fluid (UF) of sows. The results indicate that ratio of insoluble fibers to soluble fibers (ISF/SF) 4.89 can increase the concentration of progesterone (PROG) and reduce tumor necrosis factorα (TNF-α) concentration in sow UF. In addition, through 4D-Label free, we identified a total of 4248 proteins, 38 proteins abundance upregulated and 283 proteins abundance downregulated in UF. Through enrichment analysis of these differential abundance proteins (DAPs), it was found that these differential proteins are mainly related to the docking of extracellular vesicles, vesicular transport, inflammatory response, and insulin resistance. Therefore, the results of this study reveal the possible mechanism by which fiber improves the reproductive performance of sows, laying a theoretical foundation for future research on the effects of diet on reproduction. SIGNIFICANCE: This study demonstrates the importance of dietary fiber for early embryo implantation in sows. The effect of dietary ISF/SF on early embryo implantation in sows was elucidated from a proteomic perspective through 4D-Label free technology. This study not only has significant implications for improving sow reproductive efficiency, but also provides important theoretical references for studying early miscarriage and reproductive nutrition in human pregnancy.

The mammalian preimplantation embryo: Its role in the environmental programming of postnatal health and performance

During formation of the preimplantation embryo several cellular and molecular milestones take place, making the few cells forming the early embryo vulnerable to environmental stressors than can impair epigenetic reprogramming and controls of gene expression. Although these molecular alterations can result in embryonic death, a significant developmental plasticity is present in the preimplantation embryo that promotes full-term pregnancy. Prenatal epigenetic modifications are inherited during mitosis and can perpetuate specific phenotypes during early postnatal development and adulthood. As such, the preimplantation phase is a developmental window where developmental programming can take place in response to the embryonic microenvironment present in vivo or in vitro. In this review, the relevance of the preimplantation embryo as a developmental stage where offspring health and performance can be programmed is discussed, with emphasis on malnutrition and assisted reproductive technologies; two major environmental insults with important implications for livestock production and human reproductive medicine.

Research Progress of Maternal Metabolism on Cardiac Development and Function in Offspring

The developmental origin of health and disease (DOHaD) hypothesis refers to the adverse effects of suboptimal developmental environments during embryonic and early fetal stages on the long-term health of offspring. Intrauterine metabolic perturbations can profoundly impact organogenesis in offspring, particularly affecting cardiac development and giving rise to potential structural and functional abnormalities. In this discussion, we contemplate the existing understanding regarding the impact of maternal metabolic disorders, such as obesity, diabetes, or undernutrition, on the developmental and functional aspects of the offspring's heart. This influence has the potential to contribute to the susceptibility of offspring to cardiovascular health issues. Alteration in the nutritional milieu can influence mitochondrial function in the developing hearts of offspring, while also serving as signaling molecules that directly modulate gene expression. Moreover, metabolic disorders can exert influence on cardiac development-related genes epigenetically through DNA methylation, levels of histone modifications, microRNA expression, and other factors. However, the comprehensive understanding of the mechanistic underpinnings of these phenomena remains incomplete. Further investigations in this domain hold profound clinical significance, as they can contribute to the enhancement of public health and the prevention of cardiovascular diseases.

Maternal Undernutrition Induces Cell Signalling and Metabolic Dysfunction in Undifferentiated Mouse Embryonic Stem Cells

Peri-conceptional environment can induce permanent changes in embryo phenotype which alter development and associate with later disease susceptibility. Thus, mouse maternal low protein diet (LPD) fed exclusively during preimplantation is sufficient to lead to cardiovascular, metabolic and neurological dysfunction in adult offspring. Embryonic stem cell (ESC) lines were generated from LPD and control NPD C57BL/6 blastocysts and characterised by transcriptomics, metabolomics, bioinformatics and molecular/cellular studies to assess early potential mechanisms in dietary environmental programming. Previously, we showed these lines retain cellular and epigenetic characteristics of LPD and NPD embryos after several passages. Here, three main changes were identified in LPD ESC lines. First, their derivation capacity was reduced but pluripotency marker expression was similar to controls. Second, LPD lines had impaired Mitogen-activated protein kinase (MAPK) pathway with altered gene expression of several regulators (e.g., Maff, Rassf1, JunD), reduced ERK1/2 signalling capacity and poorer cell survival characteristics which may contribute to reduced derivation. Third, LPD lines had impaired glucose metabolism comprising reduced upstream enzyme expression (e.g., Gpi, Mpi) and accumulation of metabolites (e.g., glucose-6-P, fructose-6-P) above the phosphofructokinase (PFK) gateway with PFK enzyme activity reduced. ESC lines may therefore permit investigation of peri-conceptional programming mechanisms with reduced need for animal experimentation.

Graphical Abstract

Uterosomes: The lost ring of telegony?

Telegony refers to the appearance of some characteristics of the female's previously mated male in her subsequent offspring by another male. According to evidence, telegony may occur either through the infiltration of sperm into the somatic tissues of the female genital tract or the presence of fetal genes in the mother's blood. It is highlighted that sperm penetrates into the mucosa of the uterine and possibly alters the genetic structure, affecting the embryo and enduring from one pregnancy to the next, which may be one of the potential mechanisms of telegony. Uterine fluid, uterine gland-derived histotroph, supplies key nutrients for successful embryo implantation and it is important during the first trimester, especially, because of its susceptibility to maternal states. The presence of EVs in uterine fluid (uterosomes) was reported in mice, sheep, and humans, including a wide range of biomolecules, such as proteins, and non-coding RNAs. In this review article, we presented a new idea to explain telegony. Based on our idea, after the previous male sperm entry into the female reproductive system, those sperm which do not participate in fertilization penetrate into the somatic cells of the uterus and store their genetic/epigenetic information there. The sperm of the next partner reaches a location in the female reproductive canal where it exchanges information with the uterosomes and obtains the proteins and non-coding RNAs required for fertilization, development, and implantation.

Amino Acid Transport and Metabolism Regulate Early Embryo Development: Species Differences, Clinical Significance, and Evolutionary Implications

In this review we discuss the beneficial effects of amino acid transport and metabolism on pre- and peri-implantation embryo development, and we consider how disturbances in these processes lead to undesirable health outcomes in adults. Proline, glutamine, glycine, and methionine transport each foster cleavage-stage development, whereas leucine uptake by blastocysts via transport system B^0,+ promotes the development of trophoblast motility and the penetration of the uterine epithelium in mammalian species exhibiting invasive implantation. (Amino acid transport systems and transporters, such as B^0,+, are often oddly named. The reader is urged to focus on the transporters’ functions, not their names.) B^0,+ also accumulates leucine and other amino acids in oocytes of species with noninvasive implantation, thus helping them to produce proteins to support later development. This difference in the timing of the expression of system B^0,+ is termed heterochrony—a process employed in evolution. Disturbances in leucine uptake via system B^0,+ in blastocysts appear to alter the subsequent development of embryos, fetuses, and placentae, with undesirable consequences for offspring. These consequences may include greater adiposity, cardiovascular dysfunction, hypertension, neural abnormalities, and altered bone growth in adults. Similarly, alterations in amino acid transport and metabolism in pluripotent cells in the blastocyst inner cell mass likely lead to epigenetic DNA and histone modifications that produce unwanted transgenerational health outcomes. Such outcomes might be avoided if we learn more about the mechanisms of these effects.

Association of maternal pre-pregnancy dietary intake with adverse maternal and neonatal outcomes: A systematic review and meta-analysis of prospective studies

This study aimed to summarize the evidence regarding the effects of dietary intake before conception on pregnancy outcomes by performing a systematic review and meta-analysis of prospective studies. Electronic databases were searched from inception up to August 2021. Overall, 65 studies involving 831 798 participants were included and 38 studies were quantitatively pooled. With regard to maternal outcomes, pre-pregnancy intake of fried food, fast food, red and processed meat, heme iron and a low-carbohydrate dietary pattern was positively associated with the risk of gestational diabetes mellitus (GDM) (all P < 0.05). However, a high dietary fiber intake and folic acid supplementation were negatively associated with GDM risk (both P < 0.05). With regard to neonatal outcomes, maternal caffeine intake before pregnancy significantly increased the risk of spontaneous abortion, while folic acid supplementation had protective effects on total adverse neonatal outcomes, preterm birth, and small-for-gestational age (SGA, all P < 0.05). However, no significant associations were found between adverse pregnancy outcomes (i.e., GDM and SGA) and the pre-pregnancy dietary intake of sugar-sweetened beverages, potato, fish, and carbohydrates and the Healthy Eating Index. Our study suggests that maintaining a healthy diet before conception has significant beneficial effects on pregnancy outcomes.Supplemental data for this article is available online at https://doi.org/10.1080/10408398.2021.1989658.

Interkingdom Comparison of Threonine Metabolism for Stem Cell Maintenance in Plants and Animals

In multicellular organisms, tissue generation, maintenance, and homeostasis depend on stem cells. Cellular metabolic status is an essential component of different differentiated states, from stem to fully differentiated cells. Threonine (Thr) metabolism has emerged as a critical factor required to maintain pluripotent/multipotent stem cells in both plants and animals. Thus, both kingdoms conserved or converged upon this fundamental feature of stem cell function. Here, we examine similarities and differences in Thr metabolism-dependent mechanisms supporting stem cell maintenance in these two kingdoms. We then consider common features of Thr metabolism in stem cell maintenance and predict and speculate that some knowledge about Thr metabolism and its role in stem cell function in one kingdom may apply to the other. Finally, we outline future research directions to explore these hypotheses.

Environmental Exposures around Conception: Developmental Pathways Leading to Lifetime Disease Risk

Environment around conception can influence the developmental programme with lasting effects on gestational and postnatal phenotype and with consequences for adult health and disease risk. Peri-conception exposure comprises a crucial part of the 'Developmental Origins of Health and Disease' (DOHaD) concept. In this review, we consider the effects of maternal undernutrition experienced during the peri-conception period in select human models and in a mouse experimental model of protein restriction. Human datasets indicate that macronutrient deprivation around conception affect the epigenome, with enduring effects on cardiometabolic and neurological health. The mouse model, comprising maternal low protein diet exclusively during the peri-conception period, has revealed a stepwise progression in altered developmental programming following induction through maternal metabolite deficiency. This progression includes differential effects in extra-embryonic and embryonic cell lineages and tissues, leading to maladaptation in the growth trajectory and increased chronic disease comorbidities. The timeline embraces an array of mechanisms across nutrient sensing and signalling, cellular, metabolic, epigenetic and physiological processes with a coordinating role for mTORC1 signalling proposed. Early embryos appear active participants in environmental sensing to optimise the developmental programme for survival but with the trade-off of later disease. Similar adverse health outcomes may derive from other peri-conception environmental experiences, including maternal overnutrition, micronutrient availability, pollutant exposure and assisted reproductive treatments (ART) and support the need for preconception health before pregnancy.

Advanced maternal age perturbs mouse embryo development and alters the phenotype of derived embryonic stem cells

Advanced maternal age (AMA) is known to reduce fertility, increases aneuploidy in oocytes and early embryos and leads to adverse developmental consequences which may associate with offspring lifetime health risks. However, investigating underlying effects of AMA on embryo developmental potential is confounded by the inherent senescence present in maternal body systems further affecting reproductive success. Here, we describe a new model for the analysis of early developmental mechanisms underlying AMA by the derivation and characterisation of mouse embryonic stem cell (mESC-like) lines from naturally conceived embryos. Young (7-8 weeks) and Old (7-8 months) C57BL/6 female mice were mated with young males. Preimplantation embryos from Old dams displayed developmental retardation in blastocyst morphogenesis. mESC lines established from these blastocysts using conventional techniques revealed differences in genetic, cellular and molecular criteria conserved over several passages in the standardised medium. mESCs from embryos from AMA dams displayed increased incidence of aneuploidy following Giemsa karyotyping compared with those from Young dams. Moreover, AMA caused an altered pattern of expression of pluripotency markers (Sox2, OCT4) in mESCs. AMA further diminished mESC survival and proliferation and reduced the expression of cell proliferation marker, Ki-67. These changes coincided with altered expression of the epigenetic marker, Dnmt3a and other developmental regulators in a sex-dependent manner. Collectively, our data demonstrate the feasibility to utilise mESCs to reveal developmental mechanisms underlying AMA in the absence of maternal senescence and with reduced animal use.

Protein O-GlcNAcylation Promotes Trophoblast Differentiation at Implantation

Embryo implantation begins with blastocyst trophectoderm (TE) attachment to the endometrial epithelium, followed by the breaching of this barrier by TE-derived trophoblast. Dynamic protein modification with O-linked β-N-acetylglucosamine (O-GlcNAcylation) is mediated by O-GlcNAc transferase and O-GlcNAcase (OGA), and couples cellular metabolism to stress adaptation. O-GlcNAcylation is essential for blastocyst formation, but whether there is a role for this system at implantation remains unexplored. Here, we used OGA inhibitor thiamet g (TMG) to induce raised levels of O-GlcNAcylation in mouse blastocysts and human trophoblast cells. In an in vitro embryo implantation model, TMG promoted mouse blastocyst breaching of the endometrial epithelium. TMG reduced expression of TE transcription factors Cdx2, Gata2 and Gata3, suggesting that O-GlcNAcylation stimulated TE differentiation to invasive trophoblast. TMG upregulated transcription factors OVOL1 and GCM1, and cell fusion gene ERVFRD1, in a cell line model of syncytiotrophoblast differentiation from human TE at implantation. Therefore O-GlcNAcylation is a conserved pathway capable of driving trophoblast differentiation. TE and trophoblast are sensitive to physical, chemical and nutritive stress, which can occur as a consequence of maternal pathophysiology or during assisted reproduction, and may lead to adverse neonatal outcomes and associated adult health risks. Further investigation of how O-GlcNAcylation regulates trophoblast populations arising at implantation is required to understand how peri-implantation stress affects reproductive outcomes.

Periconception maternal low-protein diet adversely affects male mouse fetal bone growth and mineral density quality in late gestation

Adverse programming of adult non-communicable disease can be induced by poor maternal nutrition during pregnancy and the periconception period has been identified as a vulnerable period. In the current study, we used a mouse maternal low-protein diet fed either for the duration of pregnancy (LPD) or exclusively during the preimplantation period (Emb-LPD) with control nutrition provided thereafter and postnatally to investigate effects on fetal bone development and quality. This model has been shown previously to induce cardiometabolic and neurological disease phenotypes in offspring. Micro 3D computed tomography examination at fetal stages Embryonic day E14.5 and E17.4, reflecting early and late stages of bone formation, demonstrated LPD treatment caused increased bone formation of relative high mineral density quality in males, but not females, at E14.5, disproportionate to fetal growth, with bone quality maintained at E17.5. In contrast, Emb-LPD caused a late increase in male fetal bone growth, proportionate to fetal growth, at E17.5, affecting central and peripheral skeleton and of reduced mineral density quality relative to controls. These altered dynamics in bone growth coincide with increased placental efficiency indicating compensatory responses to dietary treatments. Overall, our data show fetal bone formation and mineral quality is dependent upon maternal nutritional protein content and is sex-specific. In particular, we find the duration and timing of poor maternal diet to be critical in the outcomes with periconceptional protein restriction leading to male offspring with increased bone growth but of poor mineral density, thereby susceptible to later disease risk.

p38-Mitogen Activated Kinases Mediate a Developmental Regulatory Response to Amino Acid Depletion and Associated Oxidative Stress in Mouse Blastocyst Embryos

Maternal starvation coincident with preimplantation development has profound consequences for placental-fetal development, with various identified pathologies persisting/manifest in adulthood; the ‘Developmental Origin of Health and Disease’ (DOHaD) hypothesis/model. Despite evidence describing DOHaD-related incidence, supporting mechanistic and molecular data relating to preimplantation embryos themselves are comparatively meager. We recently identified the classically recognized stress-related p38-mitogen activated kinases (p38-MAPK) as regulating formation of the extraembryonic primitive endoderm (PrE) lineage within mouse blastocyst inner cell mass (ICM). Thus, we wanted to assay if PrE differentiation is sensitive to amino acid availability, in a manner regulated by p38-MAPK. Although blastocysts appropriately mature, without developmental/morphological or cell fate defects, irrespective of amino acid supplementation status, we found the extent of p38-MAPK inhibition induced phenotypes was more severe in the absence of amino acid supplementation. Specifically, both PrE and epiblast (EPI) ICM progenitor populations remained unspecified and there were fewer cells and smaller blastocyst cavities. Such phenotypes could be ameliorated, to resemble those observed in groups supplemented with amino acids, by addition of the anti-oxidant NAC (N-acetyl-cysteine), although PrE differentiation deficits remained. Therefore, p38-MAPK performs a hitherto unrecognized homeostatic early developmental regulatory role (in addition to direct specification of PrE), by buffering blastocyst cell number and ICM cell lineage specification (relating to EPI) in response to amino acid availability, partly by counteracting induced oxidative stress; with clear implications for the DOHaD model.

Epigenetics and human reproduction: the primary prevention of the noncommunicable diseases

Epigenetic regulation of gene expression plays a key role in affecting human health and diseases with particular regard to human reproduction. The major concern in this field is represented by the epigenetic modifications in the embryo and the increased risk of long-life disorders induced by the use of assisted reproduction techniques, able to affect the epigenetic assessment in the first steps of embryo development. In this review, we analyze the correlation between epigenetic modifications and human reproduction, suggesting that the reversibility of the epigenetic processes could represent a novel resource for the treatment of the couple's infertility and that parental lifestyle in periconceptional period could be considered as an important issue of primary prevention.

Maternal and environmental risk factors for neonatal AKI and its long-term consequences

Acute kidney injury (AKI) is a common and life-threatening complication in critically ill neonates. Gestational risk factors for AKI include premature birth, intrauterine growth restriction and low birthweight, which are associated with poor nephron development and are often the consequence of pre-gestational and gestational factors, such as poor nutritional status. Our understanding of how to best optimize renal development and prevent AKI is in its infancy; however, the identification of pre-gestational and gestational factors that increase the risk of adverse neonatal outcomes and the implementation of interventions, such as improving nutritional status early in pregnancy, have the potential to optimize fetal growth and reduce the risk of preterm birth, thereby improving kidney health. The overall risk of AKI among critically ill and premature neonates is exacerbated postnatally as these infants are often exposed to dehydration, septic shock and potentially nephrotoxic medications. Strategies to improve outcomes - for example, through careful evaluation of nephrotoxic drugs - may reduce the incidence of AKI and its consequences among this population. Management strategies and updated technology that will support neonates with AKI are greatly needed. Extremely premature infants and those who survive an episode of AKI should be screened for chronic kidney disease until early adulthood. Here, we provide an overview of our current understanding of neonatal AKI, focusing on its relationship to preterm birth and growth restriction. We describe factors that prevent optimal nephrogenesis during pregnancy and provide a framework for future explorations designed to maximize outcomes in this vulnerable population.

RW-2018-Research Workshop: The Effect of Nutrition on Epigenetic Status, Growth, and Health

The goal of the 2018 American Society for Parenteral and Enteral Nutrition (ASPEN) Research Workshop was to explore the influence of nutrition and dietary exposure to xenobiotics on the epigenome during critical periods in development and how these exposures influence both disease incidence and severity transgenerationally. A growing compendium of research indicates that the incidence and severity of common and costly human diseases may be influenced by dietary exposures and deficiencies that modify the epigenome. The greatest periods of vulnerability to these exposures are the periconception period and early childhood. Xenobiotics in the food chain, protein malnutrition, and methyl donor deficiencies could have a profound bearing on the risk of developing heart disease, diabetes, obesity, hypertension, and mental illness over multiple generations. The financial impact and the life burden of these diseases are enormous. These and other aspects of nutrition, epigenetics, and health are explored in this research workshop.

Periconceptional environment and the developmental origins of disease

The concept emerging from Professor David Barker’s seminal research on the developmental origins of later-life disease has progressed in many directions since it was first published. One critical question being when during gestation might environment alter the developmental programme with such enduring consequences. Here, we review the growing consensus from clinical and animal research that the period around conception, embracing gamete maturation and early embryogenesis might be the most vulnerable period. We focus on four types of environmental exposure shown to modify periconceptional reproduction and offspring development and health: maternal overnutrition and obesity; maternal undernutrition; paternal diet and health; and assisted reproductive technology. These conditions may act through diverse epigenetic, cellular and physiological mechanisms to alter gene expression and cellular signalling and function in the conceptus affecting offspring growth and metabolism leading to increased risk for cardiometabolic and neurological disease in later life.

Mouse maternal protein restriction during preimplantation alone permanently alters brain neuron proportion and adult short-term memory

Maternal protein malnutrition throughout pregnancy and lactation compromises brain development in late gestation and after birth, affecting structural, biochemical, and pathway dynamics with lasting consequences for motor and cognitive function. However, the importance of nutrition during the preimplantation period for brain development is unknown. We have previously shown that maternal low-protein diet (LPD) confined to the preimplantation period (Emb-LPD) in mice, with normal nutrition thereafter, is sufficient to induce cardiometabolic and locomotory behavioral abnormalities in adult offspring. Here, using a range of in vivo and in vitro techniques, we report that Emb-LPD and sustained LPD reduce neural stem cell (NSC) and progenitor cell numbers at E12.5, E14.5, and E17.5 through suppressed proliferation rates in both ganglionic eminences and cortex of the fetal brain. Moreover, Emb-LPD causes remaining NSCs to up-regulate the neuronal differentiation rate beyond control levels, whereas in LPD, apoptosis increases to possibly temper neuron formation. Furthermore, Emb-LPD adult offspring maintain the increase in neuron proportion in the cortex, display increased cortex thickness, and exhibit short-term memory deficit analyzed by the novel-object recognition assay. Last, we identify altered expression of fragile X family genes as a potential molecular mechanism for adverse programming of brain development. Collectively, these data demonstrate that poor maternal nutrition from conception is sufficient to cause abnormal brain development and adult memory loss.

Origins of lifetime health around the time of conception: causes and consequences

Parental environmental factors, including diet, body composition, metabolism, and stress, affect the health and chronic disease risk of people throughout their lives, as captured in the Developmental Origins of Health and Disease concept. Research across the epidemiological, clinical, and basic science fields has identified the period around conception as being crucial for the processes mediating parental influences on the health of the next generation. During this time, from the maturation of gametes through to early embryonic development, parental lifestyle can adversely influence long-term risks of offspring cardiovascular, metabolic, immune, and neurological morbidities, often termed developmental programming. We review periconceptional induction of disease risk from four broad exposures: maternal overnutrition and obesity; maternal undernutrition; related paternal factors; and the use of assisted reproductive treatment. Studies in both humans and animal models have demonstrated the underlying biological mechanisms, including epigenetic, cellular, physiological, and metabolic processes. We also present a meta-analysis of mouse paternal and maternal protein undernutrition that suggests distinct parental periconceptional contributions to postnatal outcomes. We propose that the evidence for periconceptional effects on lifetime health is now so compelling that it calls for new guidance on parental preparation for pregnancy, beginning before conception, to protect the health of offspring.

Maternal intake of milk and milk proteins is positively associated with birth weight: A prospective observational cohort study

BACKGROUND

A striking number of low birth weight (LBW) Indian babies are born annually. Previous studies have confirmed the positive association between milk intake and birth weight. However, the relations between protein and vitamin B₁₂ from milk and birth weight have not been systematically explored.

AIMS

We examined the relations between birth weight and maternal intake of milk, protein from milk and vitamin B₁₂ from milk.

METHODS

This prospective, observational cohort study was conducted in an urban South Indian hospital. The dietary intakes of milk and milk products were assessed using validated food frequency questionnaire and at delivery birth outcomes were measured. The relations between milk products, milk protein, and vitamin B₁₂ from milk with birth weight and gestational weight gain were assessed in 2036 births with first trimester dietary and delivery data.

RESULTS

Median consumption of milk products in the first trimester was 310 g·day^-1 and average birth weight was 2876 g. Birth weight was positively associated with intake of milk products and of % protein from milk products (%milk protein) in the first trimester [β = 86.8, 95% confidence interval (CI): 29.1, 144.6; β = 63.1, 95% CI: 10.8, 115.5; P < 0.001 for both]. Intake of milk products and of %milk protein in the third trimester was positively associated with gestational weight gain (GWG) between the second and third trimester (One-way ANOVA, P < 0.001 and = 0.001, respectively). Neither birth weight nor GWG were associated with %vitamin B₁₂ from milk products.

CONCLUSIONS

These findings indicate that intake of milk products in the first trimester and especially, protein from milk products is positively associated with birth weight in this South Asian Indian population.

Blastocyst-Derived Stem Cell Populations under Stress: Impact of Nutrition and Metabolism on Stem Cell Potency Loss and Miscarriage

Data from in vitro and in vivo models suggest that malnutrition and stress trigger adaptive responses, leading to small for gestational age (SGA) blastocysts with fewer cell numbers. These stress responses are initially adaptive, but become maladaptive with increasing stress exposures. The common stress responses of the blastocyst-derived stem cells, pluripotent embryonic and multipotent placental trophoblast stem cells (ESCs and TSCs), are decreased growth and potency, and increased, imbalanced and irreversible differentiation. SGA embryos may fail to produce sufficient antiluteolytic placental hormone to maintain corpus luteum progesterone secretion that provides nutrition at the implantation site. Myriad stress inputs for the stem cells in the embryo can occur in vitro during in vitro fertilization/assisted reproductive technology (IVF/ART) or in vivo. Paradoxically, stresses that diminish stem cell growth lead to a higher level of differentiation simultaneously which further decreases ESC or TSC numbers in an attempt to functionally compensate for fewer cells. In addition, prolonged or strong stress can cause irreversible differentiation. Resultant stem cell depletion is proposed as a cause of miscarriage via a "quiet" death of an ostensibly adaptive response of stem cells instead of a reactive, violent loss of stem cells or their differentiated progenies.

Insulin and branched-chain amino acid depletion during mouse preimplantation embryo culture programmes body weight gain and raised blood pressure during early postnatal life

Mouse maternal low protein diet exclusively during preimplantation development (Emb-LPD) is sufficient to programme altered growth and cardiovascular dysfunction in offspring. Here, we use an in vitro model comprising preimplantation culture in medium depleted in insulin and branched-chain amino acids (BCAA), two proposed embryo programming inductive factors from Emb-LPD studies, to examine the consequences for blastocyst organisation and, after embryo transfer (ET), postnatal disease origin. Two-cell embryos were cultured to blastocyst stage in defined KSOM medium supplemented with four combinations of insulin and BCAA concentrations. Control medium contained serum insulin and uterine luminal fluid amino acid concentrations (including BCAA) found in control mothers from the maternal diet model (N-insulin + N-bcaa). Experimental medium (three groups) contained 50% reduction in insulin and/or BCAA (L-insulin + N-bcaa, N-insulin + L-bcaa, and L-insulin + N-bcaa). Lineage-specific cell numbers of resultant blastocysts were not affected by treatment. Following ET, a combined depletion of insulin and BCAA during embryo culture induced a non sex-specific increase in birth weight and weight gain during early postnatal life. Furthermore, male offspring displayed relative hypertension and female offspring reduced heart/body weight, both characteristics of Emb-LPD offspring. Combined depletion of metabolites also resulted in a strong positive correlation between body weight and glucose metabolism that was absent in the control group. Our results support the notion that composition of preimplantation culture medium can programme development and associate with disease origin affecting postnatal growth and cardiovascular phenotypes and implicate two important nutritional mediators in the inductive mechanism. Our data also have implications for human assisted reproductive treatment (ART) practice.

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Chronic disease may derive from maternal undernutrition during pregnancy, including the periconceptional period.

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Mouse embryos cultured in medium low in insulin and select amino acids gave rise to offspring with disease symptoms.

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We propose these metabolite deficiencies around conception induce adverse programming of the early embryo leading to increased disease risk in later life.

Early sex-dependent differences in response to environmental stress

Developmental plasticity enables the appearance of long-term effects in offspring caused by exposure to environmental stressors during embryonic and foetal life. These long-term effects can be traced to pre- and post-implantation development, and in both cases, the effects are usually sex specific. During preimplantation development, male and female embryos exhibit an extensive transcriptional dimorphism mainly driven by incomplete X chromosome inactivation. These early developmental stages are crucial for the establishment of epigenetic marks that will be conserved throughout development, making it a particularly susceptible period for the appearance of long-term epigenetic-based phenotypes. Later in development, gonadal formation generates hormonal differences between the sexes, and male and female placentae exhibit different responses to environmental stressors. The maternal environment, including hormones and environmental insults during pregnancy, contributes to sex-specific placental development that controls genetic and epigenetic programming during foetal development, regulating sex-specific differences, including sex-specific epigenetic responses to environmental hazards, leading to long-term effects. This review summarizes several human and animal studies examining sex-specific responses to environmental stressors during both the periconception period (caused by differences in sex chromosome dosage) and placental development (caused by both sex chromosomes and hormones). The identification of relevant sex-dependent trajectories caused by sex chromosomes and/or sex hormones is essential to define diagnostic markers and prevention/intervention protocols.

Breeding animals for quality products: not only genetics

The effect of the Developmental Origins of Health and Disease on the spread of non-communicable diseases is recognised by world agencies such as the United Nations and the World Health Organization. Early environmental effects on offspring phenotype also apply to domestic animals and their production traits. Herein, we show that maternal nutrition not only throughout pregnancy, but also in the periconception period can affect offspring phenotype through modifications of gametes, embryos and placental function. Because epigenetic mechanisms are key processes in mediating these effects, we propose that the study of epigenetic marks in gametes may provide additional information for domestic animal selection.

Non-invasive metabolomics for improved determination of embryonic sex markers in chemically defined culture medium

Metabolic differences between early male and female embryos can be reflected in culture medium (CM). We used a single bovine embryo culture step (24h) supporting improved birth rates under chemically defined conditions (CDC) to investigate biomarker detection of embryonic sex in contrast to classical BSA-containing medium. In vitro matured slaughterhouse oocytes were fertilized in vitro with a single bull. Embryos were initially cultured in synthetic oviduct fluid with BSA. On day-6, morulae were cultured individually in droplets with (BSA) or without protein (CDC). On day-7, expanded blastocysts were sexed (amelogenin gene amplification) and CM was stored at -145°C until metabolomic analysis by UHPLC-TOF MS. N=10 embryos per group (i.e. male-protein; female-protein; male-non-protein; female-non-protein) were produced. Statistical analysis revealed N=6 metabolites with different concentrations in CM, N=5 in male embryos (methionine, tryptophan, N-stearoyl-valine, biotin and pipecolic acid), N=1 in female embryos (threonine) (P<0.05 in BSA; P<10^-7 in CDC). Only the clear threshold between males and females in CDC allowed correct classification of 100% males and 91% females within 5 out of 6 biomarkers (one female outlier showing the male biomarker profile). The use of CDC represents a critical aspect in the efficient detection of embryonic sex biomarkers by metabolomics.

Regulation of ribosomal RNA expression across the lifespan is fine-tuned by maternal diet before implantation

Cells and organisms respond to nutrient deprivation by decreasing global rates of transcription, translation and DNA replication. To what extent such changes can be reversed is largely unknown. We examined the effect of maternal dietary restriction on RNA synthesis in the offspring. Low protein diet fed either throughout gestation or for the preimplantation period alone reduced cellular RNA content across fetal somatic tissues during challenge and increased it beyond controls in fetal and adult tissues after challenge release. Changes in transcription of ribosomal RNA, the major component of cellular RNA, were responsible for this phenotype as evidenced by matching alterations in RNA polymerase I density and DNA methylation at ribosomal DNA loci. Cellular levels of the ribosomal transcription factor Rrn3 mirrored the rRNA expression pattern. In cell culture experiments, Rrn3 overexpression reduced rDNA methylation and increased rRNA expression; the converse occurred after inhibition of Rrn3 activity. These observations define novel mechanism where poor nutrition before implantation irreversibly alters basal rates of rRNA transcription thereafter in a process mediated by rDNA methylation and Rrn3 factor.

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Maternal malnutrition downregulates rDNA transcription in fetal tissues.

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Switch to normal diet permanently upregulates rDNA transcription compared to controls.

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These changes are mediated by DNA methylation and Pol I transcription factor Rrn3.

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This mechanism is activated before implantation.

The Programming Power of the Placenta

Size at birth is a critical determinant of life expectancy, and is dependent primarily on the placental supply of nutrients. However, the placenta is not just a passive organ for the materno-fetal transfer of nutrients and oxygen. Studies show that the placenta can adapt morphologically and functionally to optimize substrate supply, and thus fetal growth, under adverse intrauterine conditions. These adaptations help meet the fetal drive for growth, and their effectiveness will determine the amount and relative proportions of specific metabolic substrates supplied to the fetus at different stages of development. This flow of nutrients will ultimately program physiological systems at the gene, cell, tissue, organ, and system levels, and inadequacies can cause permanent structural and functional changes that lead to overt disease, particularly with increasing age. This review examines the environmental regulation of the placental phenotype with particular emphasis on the impact of maternal nutritional challenges and oxygen scarcity in mice, rats and guinea pigs. It also focuses on the effects of such conditions on fetal growth and the developmental programming of disease postnatally. A challenge for future research is to link placental structure and function with clinical phenotypes in the offspring.

Sex and the preimplantation embryo: implications of sexual dimorphism in the preimplantation period for maternal programming of embryonic development

The developmental program of the embryo displays a plasticity that can result in long-acting effects that extend into postnatal life. In mammals, adult phenotype can be altered by changes in the maternal environment during the preimplantation period. One characteristic of developmental programming during this time is that the change in adult phenotype is often different for female offspring than for male offspring. In this paper, we propose the hypothesis that sexual dimorphism in preimplantation programming is mediated, at least in part, by sex-specific responses of embryos to maternal regulatory molecules whose secretion is dependent on the maternal environment. The strongest evidence for this idea comes from the study of colony-stimulating factor 2 (CSF2). Expression of CSF2 from the oviduct and endometrium is modified by environmental factors of the mother, in particular seminal plasma and obesity. Additionally, CSF2 alters several properties of the preimplantation embryo and has been shown to alleviate negative consequences of culture of mouse embryos on postnatal phenotype in a sex-dependent manner. In cattle, exposure of preimplantation bovine embryos to CSF2 causes sex-specific changes in gene expression, interferon-τ secretion and DNA methylation later in pregnancy (day 15 of gestation). It is likely that several embryokines can alter postnatal phenotype through actions directed towards the preimplantation embryo. Identification of these molecules and elucidation of the mechanisms by which sexually-disparate programming is established will lead to new insights into the control and manipulation of embryonic development.

Cell-Penetrating Peptide as a Means of Directing the Differentiation of Induced-Pluripotent Stem Cells

Protein transduction using cell-penetrating peptides (CPPs) is useful for the delivery of large protein molecules, including some transcription factors. This method is safer than gene transfection methods with a viral vector because there is no risk of genomic integration of the exogenous DNA. Recently, this method was reported as a means for the induction of induced pluripotent stem (iPS) cells, directing the differentiation into specific cell types and supporting gene editing/correction. Furthermore, we developed a direct differentiation method to obtain a pancreatic lineage from mouse and human pluripotent stem cells via the protein transduction of three transcription factors, Pdx1, NeuroD, and MafA. Here, we discuss the possibility of using CPPs as a means of directing the differentiation of iPS cells and other stem cell technologies.

The placenta: phenotypic and epigenetic modifications induced by Assisted Reproductive Technologies throughout pregnancy

Today, there is growing interest in the potential epigenetic risk related to assisted reproductive technologies (ART). Much evidence in the literature supports the hypothesis that adverse pregnancy outcomes linked to ART are associated with abnormal trophoblastic invasion. The aim of this review is to investigate the relationship between epigenetic dysregulation caused by ART and subsequent placental response. The dialogue between the endometrium and the embryo is a crucial step to achieve successful trophoblastic invasion, thus ensuring a non-complicated pregnancy and healthy offspring. However, as described in this review, ART could impair both actors involved in this dialogue. First, ART may induce epigenetic defects in the conceptus by modifying the embryo environment. Second, as a result of hormone treatments, ART may impair endometrial receptivity. In some cases, it results in embryonic growth arrest but, when the development of the embryo continues, the placenta could bring adaptive responses throughout pregnancy. Amongst the different mechanisms, epigenetics, especially thanks to a finely tuned network of imprinted genes stimulated by foetal signals, may modify nutrient transfer, placental growth and vascularization. If these coping mechanisms are overwhelmed, improper maternal-foetal exchanges occur, potentially leading to adverse pregnancy outcomes such as abortion, preeclampsia or intra-uterine growth restriction. But in most cases, successful placental adaptation enables normal progress of the pregnancy. Nevertheless, the risks induced by these modifications during pregnancy are not fully understood. Metabolic diseases later in life could be exacerbated through the memory of epigenetic adaptation mechanisms established during pregnancy. Thus, more research is still needed to better understand abnormal interactions between the embryo and the milieu in artificial conditions. As trophectoderm cells are in direct contact with the environment, they deserve to be studied in more detail. The ultimate goal of these studies will be to render ART protocols safer. Optimization of the environment will be the key to improving the dialogue between the endometrium and embryo, so as to ensure that placentation after ART is similar to that following natural conception.

Centre for human development, stem cells & regeneration

The Centre for Human Development, Stem Cells and Regeneration (CHDSCR) was founded in 2004 as a cross-disciplinary research and translational program within the Faculty of Medicine at the University of Southampton. The Centre undertakes fundamental research into early development and stem cells together with applied translational research for patient benefit. The Centre has vibrant and thriving multidisciplinary research programs that harness the translational strength of the Faculty together with an innovative Stem Cell PhD program, outstanding clinical infrastructure and enterprise to deliver on this vision.

Embryos, DOHaD and David Barker

The early embryo and periconceptional period is a window during which environmental factors may cause permanent change in the pattern and characteristics of development leading to risk of adult onset disease. This has now been demonstrated across small and large animal models and also in the human. Most evidence of periconceptional 'programming' has emerged from maternal nutritional models but also other in vivo and in vitro conditions including assisted reproductive treatments, show consistent outcomes. This short review first reports on the range of environmental in vivo and in vitro periconceptional models and resulting long-term outcomes. Second, it uses the rodent maternal low protein diet model restricted to the preimplantation period and considers the stepwise maternal-embryonic dialogue that comprises the induction of programming. This dialogue leads to cellular and epigenetic responses by the embryo, mainly identified in the extra-embryonic cell lineages, and underpins an apparently permanent change in the growth trajectory during pregnancy and associates with increased cardiometabolic and behavioural disease in adulthood. We recognize the important advice of David Barker some years ago to investigate the sensitivity of the early embryo to developmental programming, an insight for which we are grateful.

Impact of maternal malnutrition during the periconceptional period on mammalian preimplantation embryo development

During episodes of undernutrition and overnutrition the mammalian preimplantation embryo undergoes molecular and metabolic adaptations to cope with nutrient deficits or excesses. Maternal adaptations also take place to keep a nutritional microenvironment favorable for oocyte development and embryo formation. This maternal-embryo communication takes place via several nutritional mediators. Although adaptive responses to malnutrition by both the mother and the embryo may ensure blastocyst formation, the resultant quality of the embryo can be compromised, leading to early pregnancy failure. Still, studies have shown that, although early embryonic mortality can be induced during malnutrition, the preimplantation embryo possesses an enormous plasticity that allows it to implant and achieve a full-term pregnancy under nutritional stress, even in extreme cases of malnutrition. This developmental strategy, however, may come with a price, as shown by the adverse developmental programming induced by even subtle nutritional challenges exerted exclusively during folliculogenesis and the preimplantation period, resulting in offspring with a higher risk of developing deleterious phenotypes in adulthood. Overall, current evidence indicates that malnutrition during the periconceptional period can induce cellular and molecular alterations in preimplantation embryos with repercussions for fertility and postnatal health.

Maternal nutrition modifies trophoblast giant cell phenotype and fetal growth in mice

Mammalian placentation is dependent upon the action of trophoblast cells at the time of implantation. Appropriate fetal growth, regulated by maternal nutrition and nutrient transport across the placenta, is a critical factor for adult offspring long-term health. We have demonstrated that a mouse maternal low-protein diet (LPD) fed exclusively during preimplantation development (Emb-LPD) increases offspring growth but programmes adult cardiovascular and metabolic disease. In this study, we investigate the impact of maternal nutrition on post-implantation trophoblast phenotype and fetal growth. Ectoplacental cone explants were isolated at day 8 of gestation from female mice fed either normal protein diet (NPD: 18% casein), LPD (9% casein) or Emb-LPD and cultured in vitro. We observed enhanced spreading and cell division within proliferative and secondary trophoblast giant cells (TGCs) emerging from explants isolated from LPD-fed females when compared with NPD and Emb-LPD explants after 24 and 48 h. Moreover, both LPD and Emb-LPD explants showed substantial expansion of TGC area during 24–48 h, not observed in NPD. No difference in invasive capacity was observed between treatments using Matrigel transwell migration assays. At day 17 of gestation, LPD- and Emb-LPD-fed conceptuses displayed smaller placentas and larger fetuses respectively, resulting in increased fetal:placental ratios in both groups compared with NPD conceptuses. Analysis of placental and yolk sac nutrient signalling within the mammalian target of rapamycin complex 1 pathway revealed similar levels of total and phosphorylated downstream targets across groups. These data demonstrate that early post-implantation embryos modify trophoblast phenotype to regulate fetal growth under conditions of poor maternal nutrition.

Amino acid composition of human uterine fluid: association with age, lifestyle and gynaecological pathology

STUDY QUESTION

Do the amino acid levels of human uterine fluid vary with age, BMI, phase of menstrual cycle, benign pathology or diet?

SUMMARY ANSWER

The levels of 18 amino acids in human uterine fluid were shown to be affected only by maternal diet.

WHAT IS KNOWN ALREADY

Murine, bovine and ovine uterine amino acid content has been reported, but no reliable data on the human exist. Murine studies have demonstrated that the intrauterine periconceptional nutritional environment is affected by maternal diet.

STUDY DESIGN, SIZE, DURATION

Uterine secretions were aspirated from 56 women aged 18–45 years. The women were recruited preoperatively from gynaecological theatre operating schedules or hysterosalpingo-contrast-sonography (HyCoSy) lists. A proportion of these women had proven fertility; however, the majority were being investigated for subfertility. The BMI, gynaecological history and dietary pattern of these women were also assessed.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Reverse phase high performance liquid chromatography was used to analyse the concentrations of 18 amino acids within the uterine fluid and blood serum. The results were analysed against the women's stage of cycle, age, BMI and diet.

MAIN RESULTS AND THE ROLE OF CHANCE

The profile of 18 amino acids in uterine fluid was described. In total, human uterine fluid was observed to contain an amino acid concentration of 3.54 mM (interquartile range: 2.27–6.24 mM). The relative concentrations of 18 amino acids were not significantly altered by age, BMI, cycle phase or the presence of specific benign gynaecological pathologies. However, a diet identified by a validated scoring system as being less healthy was associated with higher concentrations of asparagine (P = 0.018), histidine (P = 0.011), serine (P = 0.033), glutamine (P = 0.049), valine (P = 0.025), phenylalanine (P = 0.019), isoleucine (P = 0.025) and leucine (P = 0.043) in the uterine fluid compared with a healthier diet, defined as one with a higher intake of fresh vegetables, fruit, whole-grain products and fish and a low intake of red and processed meat and high fat dairy products. There were no significant correlations between serum amino acid concentrations and those in the uterine fluid.

LIMITATIONS, REASONS FOR CAUTION

Our results enabled us to detect the effect of diet on the concentrations of amino acids in human uterine fluid; however, the study may not have had sufficient numbers to detect mild effects of BMI or age.

WIDER IMPLICATIONS OF THE FINDINGS

These findings increase our understanding of the nutritional environment encountered by the preimplantation embryo, and indicate how periconceptional diet may alter this. Given the importance of early embryo environment for programming of development and future health, this information may aid in the development of nutritional interventions aimed at optimizing the preimplantation phase of human embryo development in vivo.

STUDY FUNDING/COMPETING INTEREST(S)

This work was funded by the NIHR, the Medical Research Council (G0701153) and the University of Southampton and was supported by the NIHR BRC in Nutrition and Southampton University NHS Foundation Trust. The authors declare no conflicts of interest.

Epigenetic regulation of histone modifications and Gata6 gene expression induced by maternal diet in mouse embryoid bodies in a model of developmental programming

Background

Dietary interventions during pregnancy alter offspring fitness. We have shown mouse maternal low protein diet fed exclusively for the preimplantation period (Emb-LPD) before return to normal protein diet (NPD) for the rest of gestation, is sufficient to cause adult offspring cardiovascular and metabolic disease. Moreover, Emb-LPD blastocysts sense altered nutrition within the uterus and activate compensatory cellular responses including stimulated endocytosis within extra-embryonic trophectoderm and primitive endoderm (PE) lineages to protect fetal growth rate. However, these responses associate with later disease. Here, we investigate epigenetic mechanisms underlying nutritional programming of PE that may contribute to its altered phenotype, stabilised during subsequent development. We use embryonic stem (ES) cell lines established previously from Emb-LPD and NPD blastocysts that were differentiated into embryoid bodies (EBs) with outer PE-like layer.

Results

Emb-LPD EBs grow to a larger size than NPD EBs and express reduced Gata6 transcription factor (regulator of PE differentiation) at mRNA and protein levels, similar to Emb-LPD PE derivative visceral yolk sac tissue in vivo in later gestation. We analysed histone modifications at the Gata6 promoter in Emb-LPD EBs using chromatin immunoprecipitation assay. We found significant reduction in histone H3 and H4 acetylation and RNA polymerase II binding compared with NPD EBs, all markers of reduced transcription. Other histone modifications, H3K4Me2, H3K9Me3 and H3K27Me3, were unaltered. A similar but generally non-significant histone modification pattern was found on the Gata4 promoter. Consistent with these changes, histone deacetylase Hdac-1, but not Hdac-3, gene expression was upregulated in Emb-LPD EBs.

Conclusions

First, these data demonstrate ES cells and EBs retain and propagate nutritional programming adaptations in vitro, suitable for molecular analysis of mechanisms, reducing animal use. Second, they reveal maternal diet induces persistent changes in histone modifications to regulate Gata6 expression and PE growth and differentiation that may affect lifetime health.

Do little embryos make big decisions? How maternal dietary protein restriction can permanently change an embryo’s potential, affecting adult health

Periconceptional environment may influence embryo development, ultimately affecting adult health. Here, we review the rodent model of maternal low-protein diet specifically during the preimplantation period (Emb-LPD) with normal nutrition during subsequent gestation and postnatally. This model, studied mainly in the mouse, leads to cardiovascular, metabolic and behavioural disease in adult offspring, with females more susceptible. We evaluate the sequence of events from diet administration that may lead to adult disease. Emb-LPD changes maternal serum and/or uterine fluid metabolite composition, notably with reduced insulin and branched-chain amino acids. This is sensed by blastocysts through reduced mammalian target of rapamycin complex 1 signalling. Embryos respond by permanently changing the pattern of development of their extra-embryonic lineages, trophectoderm and primitive endoderm, to enhance maternal nutrient retrieval during subsequent gestation. These compensatory changes include stimulation in proliferation, endocytosis and cellular motility, and epigenetic mechanisms underlying them are being identified. Collectively, these responses act to protect fetal growth and likely contribute to offspring competitive fitness. However, the resulting growth adversely affects long-term health because perinatal weight positively correlates with adult disease risk. We argue that periconception environmental responses reflect developmental plasticity and ‘decisions’ made by embryos to optimise their own development, but with lasting consequences.

Parenting from before conception

At fertilization, the gametes endow the embryo with a genomic blueprint, the integrity of which is affected by the age and environmental exposures of both parents. Recent studies reveal that parental history and experiences also exert effects through epigenomic information not contained in the DNA sequence, including variations in sperm and oocyte cytosine methylation and chromatin patterning, noncoding RNAs, and mitochondria. Transgenerational epigenetic effects interact with conditions at conception to program the developmental trajectory of the embryo and fetus, ultimately affecting the lifetime health of the child. These insights compel us to revise generally held notions to accommodate the prospect that biological parenting commences well before birth, even prior to conception.