The labs growing human embryos for longer than ever before

A tridimensional atlas of the developing human head

The evolution and development of the head have long captivated researchers due to the crucial role of the head as the gateway for sensory stimuli and the intricate structural complexity of the head. Although significant progress has been made in understanding head development in various vertebrate species, our knowledge of early human head ontogeny remains limited. Here, we used advanced whole-mount immunostaining and 3D imaging techniques to generate a comprehensive 3D cellular atlas of human head embryogenesis. We present detailed developmental series of diverse head tissues and cell types, including muscles, vasculature, cartilage, peripheral nerves, and exocrine glands. These datasets, accessible through a dedicated web interface, provide insights into human embryogenesis. We offer perspectives on the branching morphogenesis of human exocrine glands and unknown features of the development of neurovascular and skeletomuscular structures. These insights into human embryology have important implications for understanding craniofacial defects and neurological disorders and advancing diagnostic and therapeutic strategies.

Ethical, legal, regulatory, and policy issues concerning embryoids: a systematic review of the literature

Recent advances in methods to culture pluripotent stem cells to model human development have resulted in entities that increasingly have recapitulated advanced stages of early embryo development. These entities, referred to by numerous terms such as embryoids, are becoming more sophisticated and could resemble human embryos ever more closely as research progresses. This paper reports a systematic review of the ethical, legal, regulatory, and policy questions and concerns found in the literature concerning human embryoid research published from 2016 to 2022. We identified 56 papers that use 53 distinct names or terms to refer to embryoids and four broad categories of ethical, legal, regulatory, or policy considerations in the literature: research justifications/benefits, ethical significance or moral status, permissible use, and regulatory and oversight challenges. Analyzing the full range of issues is a critical step toward fostering more robust ethical, legal, and social implications research in this emerging area and toward developing appropriate oversight.

Electrically-driven handling of gametes and embryos: taking a step towards the future of ARTs

Electrical stimulation of gametes and embryos and on-chip manipulation of microdroplets of culture medium serve as promising tools for assisted reproductive technologies (ARTs). Thus far, dielectrophoresis (DEP), electrorotation (ER) and electrowetting on dielectric (EWOD) proved compatible with most laboratory procedures offered by ARTs. Positioning, entrapment and selection of reproductive cells can be achieved with DEP and ER, while EWOD provides the dynamic microenvironment of a developing embryo to better mimic the functions of the oviduct. Furthermore, these techniques are applicable for the assessment of the developmental competence of a mammalian embryo in vitro. Such research paves the way towards the amelioration and full automation of the assisted reproduction methods. This article aims to provide a summary on the recent developments regarding electrically stimulated lab-on-chip devices and their application for the manipulation of gametes and embryos in vitro.

Miscarriage Can Kill … But it Usually Does Not: Evaluating Inconsistency Arguments

Recent publications debate the value of inconsistency arguments. Here, I argue that 'Cause of Death Arguments' - inconsistency arguments that claim miscarriage causes death far more often than induced abortion - are unsound or invalid. 'Miscarriage' ambiguously refers both to intrauterine death, an outcome that does not itself cause death, and preterm delivery, which only sometimes causes death. The referential ambiguity also obscures actions people do take to prevent 'miscarriage.' When using the most plausible versions of each premise, these arguments equivocate. Thus, they cannot prove anything. However, missing the equivocation also causes those responding to Cause of Death Arguments to make unconvincing arguments; they inadvertently make or grant false claims themselves. To avoid such mistakes and expose the merely rhetorical power of Cause of Death Arguments, philosophers should replace 'miscarriage' with disambiguated terms. Doing so should lead people across the abortion debate to finally abandon the Cause of Death Argument.

[The pre-gastrulation embryonic human development: future models and societal concerns]

Infertility, early miscarriages and congenital malformations are major public health issues that are frequent and poorly understood. Until now, what is known about early human development originates from two main sources: studies of human embryos and studies of model animals. Although some molecular mechanisms are conserved, there are specific human features. Thus, it is necessary to study model animals that are close to humans in the phylogenetic classification, which led to the use of pre-established primate cell lineages. Currently, the only human embryos available come from In Vitro Fertilization, which leads to important limitations: these embryos are relatively few and must be destroyed after 14 days. This has led researchers to develop new strategies. Several teams used Embryonic Stem Cells or Induced Pluripotent Stem Cells and their in vitro auto-organization properties to recreate "embryos" and thereby study their development. These new strategies allow a reduced use of human embryos but new questions arise about the legal status of these new research "models". In the future, it would be important to update the different legislations and recommendations of the International Society for Stem Cell Research as science progresses to avoid any failing drift. The respect of recommendations as well as the maintenance of discussions between specialists and the general public will allow a better understanding of early human development and the establishment of innovative strategies to target health challenges.

Pluripotent Stem Cell-Based Models: A Peephole into Virus Infections during Early Pregnancy

The rubella virus (RV) was the first virus shown to be teratogenic in humans. The wealth of data on the clinical symptoms associated with congenital rubella syndrome is in stark contrast to an incomplete understanding of the forces leading to the teratogenic alterations in humans. This applies not only to RV, but also to congenital viral infections in general and includes (1) the mode of vertical transmission, even at early gestation, (2) the possible involvement of inflammation as a consequence of an activated innate immune response, and (3) the underlying molecular and cellular alterations. With the progress made in the development of pluripotent stem cell-based models including organoids and embryoids, it is now possible to assess congenital virus infections on a mechanistic level. Moreover, antiviral treatment options can be validated, and newly emerging viruses with a potential impact on human embryonal development, such as that recently reflected by the Zika virus (ZIKV), can be characterized. Here, we discuss human cytomegalovirus (HCMV) and ZIKV in comparison to RV as viruses with well-known congenital pathologies and highlight their analysis on current models for the early phase of human development. This includes the implications of their genetic variability and, as such, virus strain-specific properties for their use as archetype models for congenital virus infections. In this review, we will discuss the use of induced pluripotent stem cells (iPSC) and derived organoid systems for the study of congenital virus infections with a focus on their prominent aetiologies, HCMV, ZIKV, and RV. Their assessment on these models will provide valuable information on how human development is impaired by virus infections; it will also add new insights into the normal progression of human development through the analysis of developmental pathways in the context of virus-induced alterations. These are exciting perspectives for both developmental biology and congenital virology.