DOCSLIB.ORG

A Model of Human Embryo Implantation

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A Model of Human Embryo Implantation RESEARCH NEWS & VIEWS DEVELOPMENTAL BIOLOGY hESCs and hiPSCs) that are grown in conven- tional culture conditions in the laboratory are molecularly equivalent to cells in an early-stage embryo that are ready to undergo gastrulation7. A model of human Thus, hESCs and hiPSCs can be grown indefi- nitely in this state in a tissue-culture incubator, or cryopreserved in liquid nitrogen and thawed embryo implantation and cultured again many years later. Currently, hESCs and hiPSCs are used in An innovative microfluidic device has enabled the modelling of the events that different ways to study the various types of occur in human embryos when they implant in the wall of the uterus. It could be cell that make up human embryos and fetuses. used to help understand early pregnancy loss. See Letter p.421 They can be allowed to spontaneously differ- entiate to create aggregates of cells known as embryoid bodies8. Alternatively, their differ- AMANDER T. CLARK of cell-differentiation events in the human entiation can be directed by incubation with embryo around the time of implantation. The specific cocktails of growth factors, to create ach year, millions of women around the events involved include the formation of the simplified 3D models of fetal organs or spe- world experience early pregnancy loss1. amniotic sac and a disc of cells inside it called cific germ layers9,10. hiPSC lines derived from Most pregnancy losses occur in the first the epiblast; the initial specification of pri- patients can be used for ‘disease in a dish’ mod- Etrimester, around the time that the embryo mordial germ cells (PGCs; the eventual sperm elling. Such strategies give rise to the same implants in the lining of the uterus. Our lack of or egg cells); and the start of a process called cell types as those found in late-stage embryos understanding of why some early pregnancies gastrulation. In gastrulation, the epiblast dif- and fetuses; however, the initial germ-layer fail is frustrating to women and their partners. ferentiates into the three germ layers of cells differentiation seen in these models is dis- To fill this fundamental gap in our knowledge, — the ectoderm, mesoderm and endoderm organized, and bears no resemblance to the models of human embryo implantation are — that will form the fetus. spatially organized differentiation seen in greatly needed. On page 421, Zheng et al.2 Crucially, this model does not involve the human embryos during implantation. There- report the creation of an advanced model of use of intact human embryos or an in vitro fore, such models have not been very helpful human embryo development that recapitulates attachment system for human embryos6. for studying the peri-implantation stage of many of the key events that happen around the Instead, it relies on a simple bioengineered human pregnancy. time of implantation (that is, during the peri- microfluidic device and on the differentiation To create a 3D environment in which the implantation stage). of pluripotent cells — which can differentiate stem cells could develop into embryonic- The authors’ model involves the genera- into any type of cell in the body. These pluri- like sac structures, Zheng and colleagues tion of synthetic structures resembling the potent cells can be derived from human engineered a microfluidic device containing embryonic sac — which, later in development, embryos (human embryonic stem cells; three channels: a central channel for loading a becomes a fluid-filled bag and the embryo. It hESCs) or generated through the conversion matrix material, another for loading hESCs or is a substantial advance on previous exciting of differentiated human cells (human induced hiPSCs, and a third containing flowing liquids models developed by this group3 and others4,5 pluripotent stem cells; hiPSCs). carrying molecules called morphogens that because it reveals the spatial coordination Human pluripotent stem cells (including induce stem-cell differentiation (Fig. 1a). The a b c Anteriorized Amniotic hESC Embryonic-sac-like ectoderm-like cell Pluripotent structure cell Morphogens hESC 18 h 36 h Matrix Matrix pouch Posteriorized PGC-like cell Primitive- streak-like cell Figure 1 | Modelling human embryo development during implantation. influence the development of pluripotent cells on either side of each sac. a, Zheng et al.2 developed a three-channel microfluidic device containing c, After 36 hours of exposure to various morphogens, the sacs show signs a cell-loading channel, a matrix-filled channel and an induction channel of anteriorization or posteriorization — that is, features of the anterior or through which morphogens (molecules that affect development and growth) posterior ends of an embryo. Anteriorized and posteriorized sacs have cells can be pumped. Human pluripotent cells (which can differentiate into all resembling those that form the developing amniotic membrane (amniotic the cell types of the body) that are fed into the cell-loading channel settle ectoderm-like cells), and posteriorized sacs show cells that resemble in matrix pouches. b, After 18 hours, the pluripotent cells (in this case, primordial germ cells (PGCs; the eventual fetus’s sperm or egg cells) and cells human embryonic stem cells; hESCs) form embryonic-like sac structures. of the posterior primitive streak (which, in human embryos, form the basis of Morphogens pumped through the induction and cell-loading channels the body’s bilateral symmetry). 350 | NATURE | VOL 573 | 19 SEPTEMBER 2019©2019 Spri nger Nature Li mited. All ri ghts reserved. ©2019 Spri nger Nature Li mited. All ri ghts reserved. NEWS & VIEWS RESEARCH microfluidic device was lined with trapezium- neuronal cells would have formed. Therefore, extra information about embryonic develop- shaped posts 80 micrometres apart that created Zheng and colleagues’ micro fluidic model ment. In turn, we might be able to use this evenly spaced matrix pouches in which the might technically be exempt from the 14-day information to help millions of women around stem cells could grow and differentiate. rule because it does not represent an intact the world to better understand or even avoid The authors loaded stem cells into the device embryo in the way that we consider an embryo early pregnancy loss. ■ and, 18 hours later, pumped morphogen-con- donated for research from an in vitro fertili- taining fluids into either the liquid-containing zation clinic to be intact. However, the eth- Amander T. Clark is in the Department channel on one side or the cell-loading channel ics of running experiments using human of Molecular, Cell and Developmental on the other (Fig. 1b). After 36 hours, struc- embryonic-like sacs for longer than 14 days Biology, and the Broad Stem Cell Research tures with 3D organization that mimicked should be evaluated, with particular focus on Center, University of California Los Angeles, a peri-implantation human embryonic sac whether the structure should at any point be Los Angeles, California 90095, USA. had formed in each pocket. Furthermore, considered a human being. e-mail: [email protected] the authors could use different morphogens Finally, I urge policymakers to consider 1. Wang, X. et al. Fertil. Steril. 79, 577–584 (2003). to induce anteriorization or posterioriza- this device to be a useful addition to the 2. Zheng, Y. et al. Nature 573, 421–425 (2019). tion — that is, the development of character- human-stem-cell toolbox, as it can be used 3. Shao, Y. et al. Nature Commun. 8, 208 (2017). 4. Christodoulou, N. et al. Nature Cell Biol. 20, istic features of the anterior or posterior ends to examine a period of human embryonic 1278–1289 (2018). of a normal embryo (Fig. 1c). However, the development that is currently inaccessible for 5. Simunovic, M. et al. Nature Cell Biol. 21, 900–910 embryonic-like sacs did not anteriorize and in vivo research. The model can be scaled up (2019). 6. Deglincerti, A. et al. Nature 533, 251–254 (2016). posteriorize at the same time, which is crucial to become high throughput, and thus could be 7. Nakamura, T. et al. Nature 537, 57–62 (2016). for further embryo development. invaluable to environmental toxicologists. The 8. Itskovitz-Eldor, J. et al. Mol. Med. 6, 88–95 (2000). In posteriorized embryonic-like sacs meas- length of time for which these structures can 9. Spence, J. R. et al. Nature 470, 105–109 (2011). 10. Irie, N. et al. Cell 160, 253–268 (2015). uring just over 100 micrometres in diameter, be studied in the device is relatively short; cur- 11. Aach, J., Lunshof, J., Iyer, E. & Church, G. M. eLife 6, the authors observed cell populations that rently, most of them collapse within a few days. e20674 (2017). resembled a developing amniotic membrane In future, if these embryonic-like sacs could be (the membrane that lines the walls of the cultured for longer, they could provide crucial This article was published online on 11 September 2019. amniotic-fluid-filled sac), a posterior primi- tive streak (which forms the basis of the body’s bilateral symmetry), mesoderm-like cells and, COMPUTING remarkably, PGC-like cells. In the anteriorized embryonic-like sacs, the authors saw anterior primitive streak-like cells and endoderm-like cells. Thus, this is one of the first humanized Stochastic magnetic bits models that can enable study of the awesome complexity of spatial relationships between cells in the peri-implantation window of rival quantum bits development. At this point, readers might be asking Circuits based on the stochastic evolution of nanoscale magnets have been used to whether these embryonic-like sacs are, in fact, split large numbers into prime-number factors — a problem that only quantum human embryos. The structures can be consid- computers were previously expected to solve efficiently. See Letter p.390 ered imitations of the real things, but crucially, they are not viable (they could not develop into a normal fetus) and do not have certain DMITRI E.
Load more

Recommended publications
  • 3 Embryology and Development
    BIOL 6505 − INTRODUCTION TO FETAL MEDICINE 3. EMBRYOLOGY AND DEVELOPMENT Arlet G. Kurkchubasche, M.D. INTRODUCTION Embryology – the field of study that pertains to the developing organism/human Basic embryology –usually taught in the chronologic sequence of events. These events are the basis for understanding the congenital anomalies that we encounter in the fetus, and help explain the relationships to other organ system concerns. Below is a synopsis of some of the critical steps in embryogenesis from the anatomic rather than molecular basis. These concepts will be more intuitive and evident in conjunction with diagrams and animated sequences. This text is a synopsis of material provided in Langman’s Medical Embryology, 9th ed. First week – ovulation to fertilization to implantation Fertilization restores 1) the diploid number of chromosomes, 2) determines the chromosomal sex and 3) initiates cleavage. Cleavage of the fertilized ovum results in mitotic divisions generating blastomeres that form a 16-cell morula. The dense morula develops a central cavity and now forms the blastocyst, which restructures into 2 components. The inner cell mass forms the embryoblast and outer cell mass the trophoblast. Consequences for fetal management: Variances in cleavage, i.e. splitting of the zygote at various stages/locations - leads to monozygotic twinning with various relationships of the fetal membranes. Cleavage at later weeks will lead to conjoined twinning. Second week: the week of twos – marked by bilaminar germ disc formation. Commences with blastocyst partially embedded in endometrial stroma Trophoblast forms – 1) cytotrophoblast – mitotic cells that coalesce to form 2) syncytiotrophoblast – erodes into maternal tissues, forms lacunae which are critical to development of the uteroplacental circulation.
    [Show full text]
  • Reproductive System, Day 2 Grades 4-6, Lesson #12
    Family Life and Sexual Health, Grades 4, 5 and 6, Lesson 12 F.L.A.S.H. Reproductive System, day 2 Grades 4-6, Lesson #12 Time Needed 40-50 minutes Student Learning Objectives To be able to... 1. Distinguish reproductive system facts from myths. 2. Distinguish among definitions of: ovulation, ejaculation, intercourse, fertilization, implantation, conception, circumcision, genitals, and semen. 3. Explain the process of the menstrual cycle and sperm production/ejaculation. Agenda 1. Explain lesson’s purpose. 2. Use transparencies or your own drawing skills to explain the processes of the male and female reproductive systems and to answer “Anonymous Question Box” questions. 3. Use Reproductive System Worksheets #3 and/or #4 to reinforce new terminology. 4. Use Reproductive System Worksheet #5 as a large group exercise to reinforce understanding of the reproductive process. 5. Use Reproductive System Worksheet #6 to further reinforce Activity #2, above. This lesson was most recently edited August, 2009. Public Health - Seattle & King County • Family Planning Program • © 1986 • revised 2009 • www.kingcounty.gov/health/flash 12 - 1 Family Life and Sexual Health, Grades 4, 5 and 6, Lesson 12 F.L.A.S.H. Materials Needed Classroom Materials: OPTIONAL: Reproductive System Transparency/Worksheets #1 – 2, as 4 transparencies (if you prefer not to draw) OPTIONAL: Overhead projector Student Materials: (for each student) Reproductive System Worksheets 3-6 (Which to use depends upon your class’ skill level. Each requires slightly higher level thinking.) Public Health - Seattle & King County • Family Planning Program • © 1986 • revised 2009 • www.kingcounty.gov/health/flash 12 - 2 Family Life and Sexual Health, Grades 4, 5 and 6, Lesson 12 F.L.A.S.H.
    [Show full text]
  • Female Reproductive System External Female Reproductive Organs Internal Female Reproductive Organs Menstrual Cycle
    Prevention and Recognition of Obstetric Fistula Training Package Module 3: Female Reproductive System External female reproductive organs Internal female reproductive organs Menstrual cycle • Menstruation usually starts when a girl is between 11-15 years of age (menarche) and continues until 50-60 years of age (menopause) • Monthly cycle if a woman is not pregnant or breastfeeding (can also be affected by some methods of family planning) • Controlled by hormone cycles – Follicular stimulating hormone (FSH) and Luteinizing hormone (LH) from the pituitary gland – Estrogen and progesterone from the ovaries • After the egg is released from the ovary (ovulation) if there is no fertilization with sperm, there is a discharge of blood and mucous from the uterus and the cycle repeats Changes during pregnancy • A woman can get pregnant if she has sex during or near the time of ovulation • Symptoms of pregnancy women may notice: missed menstruation, soreness and enlargement of breasts, nausea, frequent urination and fatigue • As the fetus grows inside the uterus, it stretches and extends above the pelvic bones Impact of nutrition on reproduction • Inadequate nutrition interferes with physical growth – height and weight – of children • Young women who had inadequate nutrition as children may be short in stature, undernourished and have pelvic bones not well developed for pregnancy and childbirth • Under-nutrition can also interfere with reproductive hormones and increase risk of anemia. Women who are undernourished may not have normal menstrual cycles and may have difficulty getting pregnancy and staying healthy during pregnancy.
    [Show full text]
  • Gastrulation
    Embryology of the spine and spinal cord Andrea Rossi, MD Neuroradiology Unit Istituto Giannina Gaslini Hospital Genoa, Italy [email protected] LEARNING OBJECTIVES: LEARNING OBJECTIVES: 1) To understand the basics of spinal 1) To understand the basics of spinal cord development cord development 2) To understand the general rules of the 2) To understand the general rules of the development of the spine development of the spine 3) To understand the peculiar variations 3) To understand the peculiar variations to the normal spine plan that occur at to the normal spine plan that occur at the CVJ the CVJ Summary of week 1 Week 2-3 GASTRULATION "It is not birth, marriage, or death, but gastrulation, which is truly the most important time in your life." Lewis Wolpert (1986) Gastrulation Conversion of the embryonic disk from a bilaminar to a trilaminar arrangement and establishment of the notochord The three primary germ layers are established The basic body plan is established, including the physical construction of the rudimentary primary body axes As a result of the movements of gastrulation, cells are brought into new positions, allowing them to interact with cells that were initially not near them. This paves the way for inductive interactions, which are the hallmark of neurulation and organogenesis Day 16 H E Day 15 Dorsal view of a 0.4 mm embryo BILAMINAR DISK CRANIAL Epiblast faces the amniotic sac node Hypoblast Primitive pit (primitive endoderm) faces the yolk sac Primitive streak CAUDAL Prospective notochordal cells Dias Dias During
    [Show full text]
  • Massive Subchorionic Haemorrhage: a Rare Case Report Associated with Secondary PPH Due to Uterine Artery Pseudoaneurysm
    International Journal of Reproduction, Contraception, Obstetrics and Gynecology Arumaikannu J et al. Int J Reprod Contracept Obstet Gynecol. 2017 Oct;6(10):4723-4726 www.ijrcog.org pISSN 2320-1770 | eISSN 2320-1789 DOI: http://dx.doi.org/10.18203/2320-1770.ijrcog20174475 Case Report Massive subchorionic haemorrhage: a rare case report associated with secondary PPH due to uterine artery pseudoaneurysm J. Arumaikannu*, S. Usha Rani, T. S. Aarifa Thasleem Institute of Obstetrics and Gynecology, Egmore, Chennai, Tamil Nadu, India Received: 08 August 2017 Accepted: 04 September 2017 *Correspondence: Dr. J. Arumaikannu, E-mail: [email protected] Copyright: © the author(s), publisher and licensee Medip Academy. This is an open-access article distributed under the terms of the Creative Commons Attribution Non-Commercial License, which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. ABSTRACT Massive subchorionic hemorrhage is a rare but serious condition in pregnancy in which a large amount of blood, mainly maternal collects between the uterine wall and the chorionic membrane and may leak through the cervical canal. Although many associations have been reported, an underlying etiology has not been elucidated. Association of massive subchorionic hemorrhage with thrombophilias have been reported in few articles. We are reporting a case of massive subchorionic hemorrhage presented at 13 weeks of gestation associated with secondary post-partum hemorrhage due to uterine artery pseudoaneurysm. Keywords: Massive subchorionic haemorrhage, Secondary PPH, Uterine artery pseudoaneurysm INTRODUCTION hemorrhage in the second trimester may also compromise maternal health.2,3 During pregnancy, minor degrees of haemorrhage on the chorionic plate surface of the placenta are commonly A subchorionic hemorrhage can be considered large or identified on ultrasound assessment.
    [Show full text]
  • Segmentation and Specification of the Drosophila Mesoderm
    Downloaded from genesdev.cshlp.org on September 25, 2021 - Published by Cold Spring Harbor Laboratory Press Segmentation and specification of the Drosophila mesoderm Natalia Azpiazu, 1,3 Peter A. Lawrence, 2 Jean-Paul Vincent, 2 and Manfred Frasch 1'4 1Brookdale Center for Molecular Biology, Mount Sinai School of Medicine, New York, New York 10029 USA; 2Medical Research Council Laboratory of Molecular Biology, Cambridge CB2 2QH, UK Patterning of the developing mesoderm establishes primordia of the visceral, somatic, and cardiac tissues at defined anteroposterior and dorsoventral positions in each segment. Here we examine the mechanisms that locate and determine these primordia. We focus on the regulation of two mesodermal genes: bagpipe (hap), which defines the anlagen of the visceral musculature of the midgut, and serpent (srp), which marks the anlagen of the fat body. These two genes are activated in specific groups of mesodermal cells in the anterior portions of each parasegment. Other genes mark the anlagen of the cardiac and somatic mesoderm and these are expressed mainly in cells derived from posterior portions of each parasegment. Thus the parasegments appear to be subdivided, at least with respect to these genes, a subdivision that depends on pair-rule genes such as even-skipped (eve). We show with genetic mosaics that eve acts autonomously within the mesoderm. We also show that hedgehog (hh) and wingless (wg) mediate pair-rule gene functions in the mesoderm, probably partly by acting within the mesoderm and partly by inductive signaling from the ectoderm, hh is required for the normal activation of hap and srp in anterior portions of each parasegment, whereas wg is required to suppress bap and srp expression in posterior portions.
    [Show full text]
  • Mesoderm Induction and the Control of Gastrulation in Xenopus Laevis:The
    Development 108, 229-238 (1990) 229 Printed in Great Britain ©The Company of Biologists Limited 1990 Mesoderm induction and the control of gastrulation in Xenopus laevis: the roles of fibronectin and integrins J. C. SMITH1, K. SYMESH, R. O. HYNES2'3 and D. DeSIMONE3* ' Laboratory of Embryogenesis, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW71AA, UK ^Howard Hughes Medical Institute and ^Center for Cancer Research, Department of Biology, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA * Present address: University of Virginia, Health Sciences Center, Department of Anatomy and Cell Biology, Box 439, School of Medicine, Charlottesville, VA 22908, USA t Present address: Department of Cell and Molecular Biology, 385 LSA, University of California, Berkeley, CA 94720, USA Summary Exposure of isolated Xenopus animal pole ectoderm to diated cell migration is not required for convergent the XTC mesoderm-inducing factor (XTC-MIF) causes extension. the tissue to undergo gastrulation-like movements. In We have investigated the molecular basis of XTC- this paper, we take advantage of this observation to MIF-induced gastrulation-like movements by measuring investigate the control of various aspects of gastrulation rates of synthesis of fibronectin and of the integrin f}y in Xenopus. chain in induced and control explants. No significant Blastomcres derived from induced animal pole regions differences were observed, and this suggests that gastru- are able, like marginal zone cells, but unlike control lation is not initiated simply by control of synthesis of animal pole blastomeres, to spread and migrate on a these molecules. In future work, we intend to investigate fibronectin-coated surface.
    [Show full text]
  • A Guide to Obstetrical Coding Production of This Document Is Made Possible by Financial Contributions from Health Canada and Provincial and Territorial Governments
    ICD-10-CA | CCI A Guide to Obstetrical Coding Production of this document is made possible by financial contributions from Health Canada and provincial and territorial governments. The views expressed herein do not necessarily represent the views of Health Canada or any provincial or territorial government. Unless otherwise indicated, this product uses data provided by Canada’s provinces and territories. All rights reserved. The contents of this publication may be reproduced unaltered, in whole or in part and by any means, solely for non-commercial purposes, provided that the Canadian Institute for Health Information is properly and fully acknowledged as the copyright owner. Any reproduction or use of this publication or its contents for any commercial purpose requires the prior written authorization of the Canadian Institute for Health Information. Reproduction or use that suggests endorsement by, or affiliation with, the Canadian Institute for Health Information is prohibited. For permission or information, please contact CIHI: Canadian Institute for Health Information 495 Richmond Road, Suite 600 Ottawa, Ontario K2A 4H6 Phone: 613-241-7860 Fax: 613-241-8120 www.cihi.ca [email protected] © 2018 Canadian Institute for Health Information Cette publication est aussi disponible en français sous le titre Guide de codification des données en obstétrique. Table of contents About CIHI ................................................................................................................................. 6 Chapter 1: Introduction ..............................................................................................................
    [Show full text]
  • Drug Use and Pregnancy
    Rochester Institute of Technology RIT Scholar Works Theses 7-28-1999 Drug use and pregnancy Kimberly Klapmust Follow this and additional works at: https://scholarworks.rit.edu/theses Recommended Citation Klapmust, Kimberly, "Drug use and pregnancy" (1999). Thesis. Rochester Institute of Technology. Accessed from This Thesis is brought to you for free and open access by RIT Scholar Works. It has been accepted for inclusion in Theses by an authorized administrator of RIT Scholar Works. For more information, please contact [email protected]. ROCHESTER INSTITUTE OF TECHNOLOGY A Thesis Submitted to the Faculty of The College of Imaging Arts and Sciences In Candidacy for the Degree of MASTER OF FINE ARTS Drug Use and Pregnancy by Kimberly A. Klapmust July 28, 1999 Approvals Adviser: Robert Wabnitz Date: Associate Adviser. Dr. Nancy Wanek ~)14 Date: \\.\,, c Associate Advisor: Glen Hintz Date ]I-I, zJ Cf9 I 7 Department ChaiIWrson: _ Dale: 1//17._/c; '1 I, , hereby deny permission to the Wallace Memorial library of RIT to reproduce my thesis in whole or in part. Any reproduction will not be for commercial use or profit. INTRODUCTION Human development is a remarkably complex process whereby the union of two small cells can after a period of time give rise to a new human being, complete with vital organs, bones, muscles, nerves, blood vessels, and much more. Considering the intricacy of the developmental process, it is indeed miraculous that most babies are born healthy. Some children, however, are born with abnormalities. Environmental agents, such as drugs, are responsible for some of these abnormalities.
    [Show full text]
  • Stages of Embryonic Development of the Zebrafish
    DEVELOPMENTAL DYNAMICS 2032553’10 (1995) Stages of Embryonic Development of the Zebrafish CHARLES B. KIMMEL, WILLIAM W. BALLARD, SETH R. KIMMEL, BONNIE ULLMANN, AND THOMAS F. SCHILLING Institute of Neuroscience, University of Oregon, Eugene, Oregon 97403-1254 (C.B.K., S.R.K., B.U., T.F.S.); Department of Biology, Dartmouth College, Hanover, NH 03755 (W.W.B.) ABSTRACT We describe a series of stages for Segmentation Period (10-24 h) 274 development of the embryo of the zebrafish, Danio (Brachydanio) rerio. We define seven broad peri- Pharyngula Period (24-48 h) 285 ods of embryogenesis-the zygote, cleavage, blas- Hatching Period (48-72 h) 298 tula, gastrula, segmentation, pharyngula, and hatching periods. These divisions highlight the Early Larval Period 303 changing spectrum of major developmental pro- Acknowledgments 303 cesses that occur during the first 3 days after fer- tilization, and we review some of what is known Glossary 303 about morphogenesis and other significant events that occur during each of the periods. Stages sub- References 309 divide the periods. Stages are named, not num- INTRODUCTION bered as in most other series, providing for flexi- A staging series is a tool that provides accuracy in bility and continued evolution of the staging series developmental studies. This is because different em- as we learn more about development in this spe- bryos, even together within a single clutch, develop at cies. The stages, and their names, are based on slightly different rates. We have seen asynchrony ap- morphological features, generally readily identi- pearing in the development of zebrafish, Danio fied by examination of the live embryo with the (Brachydanio) rerio, embryos fertilized simultaneously dissecting stereomicroscope.
    [Show full text]
  • Understanding Paraxial Mesoderm Development and Sclerotome Specification for Skeletal Repair Shoichiro Tani 1,2, Ung-Il Chung2,3, Shinsuke Ohba4 and Hironori Hojo2,3
    Tani et al. Experimental & Molecular Medicine (2020) 52:1166–1177 https://doi.org/10.1038/s12276-020-0482-1 Experimental & Molecular Medicine REVIEW ARTICLE Open Access Understanding paraxial mesoderm development and sclerotome specification for skeletal repair Shoichiro Tani 1,2, Ung-il Chung2,3, Shinsuke Ohba4 and Hironori Hojo2,3 Abstract Pluripotent stem cells (PSCs) are attractive regenerative therapy tools for skeletal tissues. However, a deep understanding of skeletal development is required in order to model this development with PSCs, and for the application of PSCs in clinical settings. Skeletal tissues originate from three types of cell populations: the paraxial mesoderm, lateral plate mesoderm, and neural crest. The paraxial mesoderm gives rise to the sclerotome mainly through somitogenesis. In this process, key developmental processes, including initiation of the segmentation clock, formation of the determination front, and the mesenchymal–epithelial transition, are sequentially coordinated. The sclerotome further forms vertebral columns and contributes to various other tissues, such as tendons, vessels (including the dorsal aorta), and even meninges. To understand the molecular mechanisms underlying these developmental processes, extensive studies have been conducted. These studies have demonstrated that a gradient of activities involving multiple signaling pathways specify the embryonic axis and induce cell-type-specific master transcription factors in a spatiotemporal manner. Moreover, applying the knowledge of mesoderm development, researchers have attempted to recapitulate the in vivo development processes in in vitro settings, using mouse and human PSCs. In this review, we summarize the state-of-the-art understanding of mesoderm development and in vitro modeling of mesoderm development using PSCs. We also discuss future perspectives on the use of PSCs to generate skeletal tissues for basic research and clinical applications.
    [Show full text]
  • The Law of Placenta
    The Law of Placenta Mathilde Cohent ABSTRACT: Of the forms of reproductive labor in which legal scholars have been interested, placenta, the organ developed during pregnancy, has been overlooked. As placenta becomes an object of value for a growing number of individuals, researchers, clinicians, biobanks, and biotech companies, among others, its cultural meaning is changing. At the same time, these various constituencies may be at odds. Some postpartum parents and their families want to repossess their placenta for personal use, while third parties use placentas for a variety of research, medical, and commercial purposes. This Article contributes to the scholarship on reproductive justice and agency by asking who should have access to placentas and under what conditions. The Article emphasizes the insufficient protection the law affords pregnant people wishing to decide what happens to their placenta. Generally considered clinical waste under federal and state law, placental tissue is sometimes made inaccessible to its producers on the ground that it is infectious at the same time as it is made available to third parties on the ground that placenta is discarded and de-identified tissue. Less privileged people who lack the ability to shop for obstetric and other pregnancy-related services that allow them to keep their placentas are at a disadvantage in this chain of supply and demand. While calling for further research on the modus operandi of placenta markets and how pregnant people think about them, this Article concludes that lawmakers should take steps to protect decision-making autonomy over placental labor and offers a range of proposals to operationalize this idea.
    [Show full text]