Preimplantation Embryo Development

This volume contains the Proceedings of the Serono Symposium on Pre implantation Embryo Development, held in Newton, Massachusetts, in 1991. The idea for the symposium grew out of the 1989 Serono Symposium on Fertilization in Mammals* at which preimplantation development was the predominant suggestion for a follow-up topic. This was indeed a timely subject in view of the recent resurgence of interest in this funda mental phase of embryogenesis and its relevance to basic research and applied fertility studies in humans, food-producing animals, and endangered species. The symposium brought together speakers from a broad range of disciplines in order to focus on key regulatory mechanisms in embryo development, using a wide variety of animal models, and on representative topics in human preimplantation embryogenesis. The culmination of preimplantation development is a blastocyst con taining the first differentiated embryonic tissues and capable of initiating and sustaining pregnancy. The central objective of the symposium was to throw light on the regulation of cellular and molecular events underlying blastocyst formation. It was particularly appropriate that the date of the symposium marked the 20th anniversary of the publication of the classic volume Biology of the Blastocyst, the proceedings of an international workshop held in 1970. This book, which summarized most of the information then available on this topic in mammals, was edited by the pioneer in blastocyst research, Dr. Richard B1andau, who was the guest speaker at the symposium.

With a few notable exceptions, mammalian preimplantation embryos grown in vitro are likely to exhibit sub-optimal or retarded development. This may be manifested in different ways, depending on the species and on the stage(s) of embryonic development that are being examined. For example, bovine embryos often experience difficulty in cleaving under in vitro conditions, and usually cease development at about the 8-cell stage (Wright and Bondioli, 1981). The block to development is stage-dependent; embryos cultured for 24 hr from the I-cell stage are much more capable of developing into viable blastocysts after transfer to oviducts than embryos cultured for 24 hr from the 4-cell stage prior to transfer (Eyestone et oZ. , 1985). Similar problems with in vitro embryo development are encountered in other species. Pig embryos can be grown up to the 4-cell stage in vitro but usually no further (Davis and Day, 1978). In the golden hamster, in the rat and in many outbred strains of mice, development of zygotes in vitro is blocked at the 2-cell stage (Yanagimachi and Chang, 1964; Whittingham, 1975). Even with some inbred mouse strains, embryo development is reduced if very early cleavage stages are used as the starting point for in vitro culture (Spielmann et oZ. , 1980). A common finding is that embryos grown in vitro have reduced cell counts (Harlow and Quinn, 1982; Kane, 1985) and their viability is reduced (Bowman and McLaren, 1970; Papaioannou and Ebert, 1986) compared to equivalent developmental stages recovered from mated animals.

This volume contains the Proceedings of the Serono Symposium on Pre implantation Embryo Development, held in Newton, Massachusetts, in 1991. The idea for the symposium grew out of the 1989 Serono Symposium on Fertilization in Mammals* at which preimplantation development was the predominant suggestion for a follow-up topic. This was indeed a timely subject in view of the recent resurgence of interest in this funda mental phase of embryogenesis and its relevance to basic research and applied fertility studies in humans, food-producing animals, and endangered species. The symposium brought together speakers from a broad range of disciplines in order to focus on key regulatory mechanisms in embryo development, using a wide variety of animal models, and on representative topics in human preimplantation embryogenesis. The culmination of preimplantation development is a blastocyst con taining the first differentiated embryonic tissues and capable of initiating and sustaining pregnancy. The central objective of the symposium was to throw light on the regulation of cellular and molecular events underlying blastocyst formation. It was particularly appropriate that the date of the symposium marked the 20th anniversary of the publication of the classic volume Biology of the Blastocyst, the proceedings of an international workshop held in 1970. This book, which summarized most of the information then available on this topic in mammals, was edited by the pioneer in blastocyst research, Dr. Richard B1andau, who was the guest speaker at the symposium.

The most profound dilemma in assisted reproduction to date is the inability to recognize potentially viable embryos before their replacement into the reproductive tract. Application of increasingly advanced new technology has allowed the field of embryo evaluation to evolve rapidly and dramatically over the past five years.Human Preimplantation Emb

Mammalian Preimplantation Development, the latest volume in the Current Topics in Developmental Biology series covers mammalian preimplantation development, and includes contributions from an international board of authors. The book's chapters provide a comprehensive set of reviews covering such topics as cell proliferation, cell differentiation, and biological significance. Covers the area of mammalian preimplantation development Includes contributions from an International board of authors Provides a comprehensive set of reviews covering such topics as cell proliferation, cell differentiation, and biological significance

In recent years, the advancing science and increasing availability of assisted reproduction have given new hope to infertile couples. However, the use of IVF and ART has also led to marked increases in the number of multiple-infant live births. This poses a public health concern, as these neonates have a higher rate of pre-term delivery, compromising their survival chances and increasing their risk of lifelong disability. By optimizing the selection of gametes and embryos with high probabilities of implantation, it is possible to reduce the number of embryos transferred and, by extension, the number of high-risk multiple gestations, while maintaining or increasing pregnancy rates. Human Gametes and Preimplantation Embryos: Assessment and Diagnosis provides a broad yet concise overview of established and developing methodologies for assessment of gamete and embryo viability in assisted reproduction. This book elucidates the best practices for precisely selecting viable specimens based on morphology and cleavage rate and covers the spectrum of emerging adjunctive technologies for predicting reproductive potential. The authors present their extensive knowledge of “omics” approaches (genomics, transcriptomics, proteomics, and metabolomics), with unbiased delineation of the associated advantages and potential pitfalls. This valuable clinical resource is well suited to infertility specialists, Ob/Gyn physicians, IVF laboratory technicians, and researchers in the fields of embryology and reproductive medicine.

Because of the recent advances in embryo modeling techniques, and at the request of the Office of Science Policy in the Office of the Director at the National Institutes of Health, the National Academies of Sciences, Engineering, hosted a 1-day public workshop that would explore the state of the science of mammalian embryo model systems. The workshop, which took place on January 17, 2020, featured a combination of presentations, panels, and general discussions, during which panelists and participants offered a broad range of perspectives. Participants considered whether embryo model systems - especially those that use nonhuman primate cells - can be used to predict the function of systems made with human cells. Presentations provided an overview of the current state of the science of in vitro development of human trophoblast. This publication summarizes the presentation and discussion of the workshop.

The book considers signaling events from the zygote embryo through to the blastocyst with relevant data from embryonic stem (ES) cells, including dialogue with the extracellular environment and with the maternal tract during the implantation process. Application of the knowledge described to improve the success of human and animal assisted conception is considered where appropriate, but the focus is largely on fundamental rather than applied cell/molecular biology, as this is the area that has historically been neglected. While the general features of metabolism during preimplantation development are well established, especially in terms of nutrient requirements, uptake and fate, remarkably little is known about early embryo signaling events, intracellular or intercellular, between individual embryos in vitro or with the female reproductive tract in vivo. This contrasts with the wealth of information on cell signaling in somatic cells and tissues, as a glance at any textbook of biochemistry illustrates. This lack of information is such that our understanding of the molecular cell biology of early embryos -- a prerequisite to defining the mechanisms which regulate development at this critical stage of the life cycle -- is seriously incomplete. This volume is the first to address this issue by describing the current state of knowledge on cell signaling during mammalian early embryo development and highlighting priority areas for research.