Cell signalling during blastocyst morphogenesis

Symbiogenesis redicts the monism of the cosmos

Symbiogenesis has been systematically exploited to understand consciousness as the aggregate of our physiology. The Symbiogenic mechanism for assimilation of factors in the environment formulates the continuum from inside the cell to the Cosmos, both consciousness and cosmology complying with the Laws of Nature. Since Symbiogenesis is 'constructive', whereas eliminating what threatens us is 'destructive', why do we largely practice Symbiogenesis? Hypothetically, Symbiogenesis recursively simulates the monism of our origin, recognizing 'something bigger than ourselves'. That perspective explains many heretofore unexplained aspects of consciousness, such as mind, epigenetic inheritance, physiology, behaviors, social systems, mathematics, the Arts, from an a priori perspective. Moreover, there is an energetic continuum from Newtonian to Quantum Mechanics, opening up to a novel way of understanding the 'true nature of our being', not as 'materialism', but instead being the serial homeostatic control of energy. The latter is consistent with the spirit of Claude Bernard and Walter B. Cannon's perspectives on physiology. Such a paradigm shift is overdue, given that materialism is causing the destruction of the Earth and ourselves.

Leucine and Arginine Availability Modulate Mouse Embryonic Stem Cell Proliferation and Metabolism

Amino acids are crucial nutrients involved in several cellular and physiological processes, including fertilization and early embryo development. In particular, Leucine and Arginine have been shown to stimulate implantation, as lack of both in a blastocyst culture system is able to induce a dormant state in embryos. The aim of this work was to evaluate the effects of Leucine and Arginine withdrawal on pluripotent mouse embryonic stem cell status, notably, their growth, self-renewal, as well as glycolytic and oxidative metabolism. Our results show that the absence of both Leucine and Arginine does not affect mouse embryonic stem cell pluripotency, while reducing cell proliferation through cell-cycle arrest. Importantly, these effects are not related to Leukemia Inhibitory Factor (LIF) and are reversible when both amino acids are reconstituted in the culture media. Moreover, a lack of these amino acids is related to a reduction in glycolytic and oxidative metabolism and decreased protein translation in mouse embryonic stem cells (mESCs), while maintaining their pluripotent status.

Bisphenol Exposure Disrupts Cytoskeletal Organization and Development of Pre-Implantation Embryos

The endocrine disrupting activity of bisphenol compounds is well documented, but less is known regarding their impact on cell division and early embryo formation. Here, we tested the effects of acute in vitro exposure to bisphenol A (BPA) and its common substitute, bisphenol F (BPF), during critical stages of mouse pre-implantation embryo development, including the first mitotic division, cell polarization, as well as morula and blastocyst formation. Timing of initial cleavage was determined by live-cell imaging, while subsequent divisions, cytoskeletal organization and lineage marker labeling were assessed by high-resolution fluorescence microscopy. Our analysis reveals that brief culture with BPA or BPF impeded cell division and disrupted embryo development at all stages tested. Surprisingly, BPF was more detrimental to the early embryo than BPA. Notably, poor embryo development was associated with cytoskeletal disruptions of the actomyosin network, apical domain formation during cell polarization, actin ring zippering for embryo sealing and altered cell lineage marker profiles. These results underscore that bisphenols can disrupt cytoskeletal integrity and remodeling that is vital for early embryo development and raise concerns regarding the use of BPF as a 'safe' BPA substitute.

The impact of single-step and sequential embryo culture systems on obstetric and perinatal outcomes in singleton pregnancies: the Massachusetts Outcomes Study of Assisted Reproductive Technology

OBJECTIVE

To compare the obstetric and perinatal outcomes of deliveries conceived with embryos from single-step vs. sequential culture media systems.

DESIGN

Historical cohort of Massachusetts vital records linked to assisted reproductive technology clinic data from the Society for Assisted Reproductive Technology Clinic Outcome Reporting System and laboratory embryology data from two large academic hospital fertility centers.

SETTING

Not applicable.

PATIENTS

Patients with singleton live birth deliveries between 2004 and 2017 conceived with autologous assisted reproductive technology cycles with fresh blastocyst transfer using either single-step (n = 1,058) or sequential (n = 474) culture media systems.

INTERVENTIONS

None.

MAIN OUTCOME MEASURES

Associations of single-step vs. sequential culture with obstetric outcomes (mode of delivery, placental abnormalities, pregnancy-induced hypertension, and gestational diabetes) and perinatal outcomes (preterm birth, low birthweight, small-for-gestational-age, and large-for-gestational-age [LGA]) were assessed with multivariate logistic modeling, adjusted for maternal age, race/ethnicity, education, parity, insurance type, protein supplementation, oxygen concentration, fertilization method, and number of transferred embryos.

RESULTS

Compared with sequential culture, single-step culture was associated with increased odds of LGA (adjusted odds ratio 2.1, 95% confidence interval 1.04-4.22). There were no statistically significant differences between single-step and sequential culture media systems in the odds of placental abnormalities, pregnancy-induced hypertension, gestational diabetes, prematurity, small-for-gestational-age, or low birthweight.

CONCLUSIONS

Single-step culture is associated with increased odds of LGA, indicating that embryo culture media systems may affect perinatal outcomes.

Senescence and Apoptosis During in vitro Embryo Development in a Bovine Model

According to the World Health Organization, infertility affects up to 14% of couples under reproductive age, leading to an exponential rise in the use of assisted reproduction as a route for conceiving a baby. In the same way, thousands of embryos are produced in cattle and other farm animals annually, leading to increased numbers of individuals born. All reproductive manipulations entail deviations of natural phenotypes and genotypes, with in vitro embryo technologies perhaps showing the biggest effects, although these alterations are still emerging. Most of these indications have been provided by animal models, in particular the bovine species, due to its similarities to human early embryo development. Oocytes and embryos are highly sensitive to environmental stress in vivo and in vitro. Thus, during in vitro culture, a number of stressful conditions affect embryonic quality and viability, inducing subfertility and/or long-term consequences that may reach the offspring. A high proportion of the embryos produced in vitro are arrested at a species-specific stage of development during the first cell divisions. These arrested embryos do not show signs of programmed cell death during early cleavage stages. Instead, defective in vitro produced embryos would enter a permanent cell cycle arrest compatible with cellular senescence, in which they show active metabolism and high reactive oxygen species levels. Later in development, mainly during the morula and blastocyst stages, apoptosis would mediate the elimination of certain cells, accomplishing both a physiological role in to balancing cell proliferation and death, and a pathological role preventing the transmission of damaged cells with an altered genome. The latter would acquire relevant importance in in vitro produced embryos that are submitted to stressful environmental stimuli. In this article, we review the mechanisms mediating apoptosis and senescence during early embryo development, with a focus on in vitro produced bovine embryos. Additionally, we shed light on the protective role of senescence and apoptosis to ensure that unhealthy cells and early embryos do not progress in development, avoiding long-term detrimental effects.

Sex Differences in Early Embryogenesis: Inter-Chromosomal Regulation Sets the Stage for Sex-Biased Gene Networks: The dialogue between the sex chromosomes and autosomes imposes sexual identity soon after fertilization

Sex-specific transcriptional and epigenomic profiles are detectable in the embryo very soon after fertilization. I propose that in male (XY) and female (XX) pre-implantation embryos sex chromosomes establish sexually dimorphic interactions with the autosomes, before overt differences become apparent and long before gonadogenesis. Lineage determination restricts expression biases between the sexes, but the epigenetic differences are less constrained and can be perpetuated, accounting for dimorphisms that arise later in life. In this way, sexual identity is registered in the epigenome very early in development. As development progresses, sex-specific regulatory modules are harbored within shared transcriptional networks that delineate common traits. In reviewing this field, I propose that analyzing the mechanisms for sexual dimorphisms at the molecular and biochemical level and incorporating developmental and environmental factors will lead to a greater understanding of sex differences in health and disease. Also see the video abstract here: https://youtu.be/9BPlbrHtkHQ.

AttrActin' Attention to Early Mouse Development

A new study by Zenker et al. uses time-lapse imaging to discover how dynamic actin movements contribute to epithelialization of living mouse embryos. Together with work from other labs, this study presents exciting new ways to think about the emergence of cell fates during mammalian development.

Prolonged Growth Hormone/Insulin/Insulin-like Growth Factor Nutrient Response Signaling Pathway as a Silent Killer of Stem Cells and a Culprit in Aging

The dream of slowing down the aging process has always inspired mankind. Since stem cells are responsible for tissue and organ rejuvenation, it is logical that we should search for encoded mechanisms affecting life span in these cells. However, in adult life the hierarchy within the stem cell compartment is still not very well defined, and evidence has accumulated that adult tissues contain rare stem cells that possess a broad trans-germ layer differentiation potential. These most-primitive stem cells-those endowed with pluripotent or multipotent differentiation ability and that give rise to other cells more restricted in differentiation, known as tissue-committed stem cells (TCSCs) - are of particular interest. In this review we present the concept supported by accumulating evidence that a population of so-called very small embryonic-like stem cells (VSELs) residing in adult tissues positively impacts the overall survival of mammals, including humans. These unique cells are prevented in vertebrates from premature depletion by decreased sensitivity to growth hormone (GH), insulin (INS), and insulin-like growth factor (IGF) signaling, due to epigenetic changes in paternally imprinted genes that regulate their resistance to these factors. In this context, we can envision nutrient response GH/INS/IGF signaling pathway as a lethal factor for these most primitive stem cells and an important culprit in aging.

Vitamin D deficiency: infertility and neurodevelopmental diseases (attention deficit hyperactivity disorder, autism, and schizophrenia)

The process of development depends on a number of signaling systems that regulates the progressive sequence of developmental events. Infertility and neurodevelopmental diseases, such as attention deficit hyperactivity disorder, autism spectrum disorders, and schizophrenia, are caused by specific alterations in these signaling processes. Calcium signaling plays a prominent role throughout development beginning at fertilization and continuing through early development, implantation, and organ differentiation such as heart and brain development. Vitamin D plays a major role in regulating these signaling processes that control development. There is an increase in infertility and an onset of neurodevelopmental diseases when vitamin D is deficient. The way in which vitamin D deficiency acts to alter development is a major feature of this review. One of the primary functions of vitamin D is to maintain the phenotypic stability of both the Ca²⁺ and redox signaling pathways that play such a key role throughout development.

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.

Time to take human embryo culture seriously

STUDY QUESTION

Is it important that end-users know the composition of human embryo culture media?

SUMMARY ANSWER

We argue that there is as strong case for full transparency concerning the composition of embryo culture media intended for human use.

WHAT IS KNOWN ALREADY

Published data suggest that the composition of embryo culture media may influence the phenotype of the offspring.

STUDY DESIGN, SIZE, DURATION

A review of the literature was carried out.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Data concerning the potential effects on embryo development of culture media were assessed and recommendations for users made.

MAIN RESULTS AND THE ROLE OF CHANCE

The safety of ART procedures, especially with respect to the health of the offspring, is of major importance. There are reports from the literature indicating a possible effect of culture conditions, including culture media, on embryo and fetal development. Since the introduction of commercially available culture media, there has been a rapid development of different formulations, often not fully documented, disclosed or justified. There is now evidence that the environment the early embryo is exposed to can cause reprogramming of embryonic growth leading to alterations in fetal growth trajectory, birthweight, childhood growth and long-term disease including Type II diabetes and cardiovascular problems. The mechanism for this is likely to be epigenetic changes during the preimplantation period of development. In the present paper the ESHRE working group on culture media summarizes the present knowledge of potential effects on embryo development related to culture media, and makes recommendations.

LIMITATIONS, REASONS FOR CAUTION

There is still a need for large prospective randomized trials to further elucidate the link between the composition of embryo culture media used and the phenotype of the offspring. We do not presently know if the phenotypic changes induced by in vitro embryo culture represent a problem for long-term health of the offspring.

WIDER IMPLICATIONS OF THE FINDINGS

Published data indicate that there is a strong case for demanding full transparency concerning the compositions of and the scientific rationale behind the composition of embryo culture media.

STUDY FUNDING/COMPETING INTERESTS

This work was funded by The European Society for Human Reproduction and Embryology. No competing interests to declare.