Blechschmidt Collection: Revisiting specimens from a historical collection of serially sectioned human embryos and fetuses using modern imaging techniques

Recent advances in understanding cell types during human gastrulation

Gastrulation is a fundamental process during embryonic development, conserved across all multicellular animals [1]. In the majority of metazoans, gastrulation is characterised by large scale morphogenetic remodeling, leading to the conversion of an early pluripotent embryonic cell layer into the three primary 'germ layers': an outer ectoderm, inner endoderm and intervening mesoderm layer. The morphogenesis of these three layers of cells is closely coordinated with cellular diversification, laying the foundation for the generation of the hundreds of distinct specialized cell types in the animal body. The process of gastrulation has for a long time attracted tremendous attention in a broad range of experimental systems ranging from sponges to mice. In humans the process of gastrulation starts approximately 14 days after fertilization and continues for slightly over a week. However our understanding of this important process, as it pertains to human, is limited. Donations of human fetal material at these early stages are exceptionally rare, making it nearly impossible to study human gastrulation directly. Therefore, our understanding of human gastrulation is predominantly derived from animal models such as the mouse [2,3] and from studies of limited collections of fixed whole samples and histological sections of human gastrulae [4-7], some of which date back to over a century ago. More recently we have been gaining valuable molecular insights into human gastrulation using in vitro models of hESCs [8-12] and increasingly, in vitro cultured human and non-human primate embryos [13-16]. However, while methods have been developed to culture human embryos into this stage (and probably beyond), current ethical standards prohibit the culture of human embryos past 14 days again limiting our ability to experimentally probe human gastrulation. This review discusses recent molecular insights from the study of a rare CS 7 human gastrula obtained as a live sample and raises several questions arising from this recent study that it will be interesting to address in the future using emerging models of human gastrulation.

The return process of physiological umbilical herniation in human fetuses: The possible role of the vascular tree and umbilical ring

The human intestine elongates during the early fetal period, herniates into the extraembryonic coelom (EC), and subsequently returns to the abdominal cavity (AC). The process by which the intestinal loop returns to the abdomen remains unclear. This study aimed to document positional changes in the intestinal tract with the superior mesenteric artery (SMA) and branches in 3D to elucidate the intestinal loop return process (transition phase). Serial histological cross-sections from human fetuses (crown-rump length [CRL] range: 30-50 mm) in the herniation (n = 1), transition (n = 7), and return (n = 2) phases were selected from the Blechschmidt Collection. The distribution of the SMA trunk and all intestinal and sister branches entering the intestines was visualized so that positional changes in branches were continuous from the herniation to return phases. Positional changes in SMA branches proceeded in an orderly and structured manner; this is essential for continuous blood supply via the SMA to the intestine during transition and for safe intestinal return. Changes in the SMA distribution proceeded prior to the detection of initiation of intestinal tract return, which might start earlier and last much longer than our consensus (i.e., that the return of the herniated intestine begins when the CRL is approximately 40 mm and ends within a short time). In the cross-section of the umbilical ring in the herniation and transition phases, one proximal limb and one distal limb were observed with SMA intestinal branches, which were fully packed in the umbilical ring. The SMA branches were aligned from inferior to superior along the SMA main trunk. In the herniation phase, the distribution of 3rd-13th branches aligned from proximal inferior medial to distal superior left with a slight spiral in the EC, the tips of which suggested an orderly running course of the small intestine. In the transition phase, SMA branches running across the umbilical ring that fed the small intestine were observed, suggesting that the intestine was uncoiled and ran across the umbilical ring almost vertically. The estimated curvature value supported the phenomenon of uncoiling at the umbilical ring; the value at the umbilical ring was lesser than that in the AC and EC. During the transition phase, the proximal and distal limbs transversely ran side by side in the AC, umbilical ring, limbs on the cranial side, and mesentery on the caudal side. The SMA trunk and its branches ran in parallel, cranially to caudally aligned in the mesentery. This layout of the umbilical ring was maintained during the transition phase. In the return phase, the SMA trunk was gently curved from the upper left to the lower right of the AC; around 12 branches spread with a winding staircase appearance. The intestinal tract reached its definitive position immediately after all tissues crossed the umbilical ring and released any restriction. Each SMA branch and the corresponding region of the intestinal tract form a unit and change their position, though the conformation may change within each unit when running across the umbilical ring. We suggest that the slide-stack model requires revision.

Early development of the cortical layers in the human brain

The cortical plate (CP) first appears at seven postconceptional weeks (pcw), when it splits the preexisting preplate into two layers, the marginal zone and the presubplate (pSP). Although three-dimensional (3D) analysis using fetal magnetic resonance imaging and two-dimensional tissue observations have been reported, there have been no studies analyzing the early development of the layer structure corresponding to the pSP stage in 3D. Here, we reconstructed 3-D models of the brain with a focus on the cortical layers in pSP stage. To achieve this, we digitized serial tissue sections of embryos between CS20 and CS23 from the Kyoto Collection (n = 7, approximately 7-8.5 pcw), and specimens at early fetal phase from the Blechschmidt Collection (n = 2, approximately 9.5-12 pcw, crown rump length [CRL] 39 and 64 mm). We observed tissue sections and 3D images and performed quantitative analysis of the thickness, surface area, and volume. Because the boundary between pSP and the intermediate zone (IZ) could not be distinguished in hematoxylin and eosin-stained sections, the two layers were analyzed together as a single layer in this study. The histology of the layers was observed from CS21 and became distinct at CS22. Subsequently, we observed the 3-D models; pSP-IZ was present in a midlateral region of the cerebral wall at CS21, and an expansion centered around this region was observed after CS22. We observed it over the entire cerebral hemisphere at early fetal phase (CRL 39 mm). The thickness of pSP-IZ was visible in 3D and was greater in the midlateral region. At the end of the pSP stage (CRL 64 mm), the thick region expanded to lateral, superior, and posterior regions around the primordium of the insula. While, the region near the basal ganglia was not included in the thickest 10% of the pSP-IZ area. Middle cerebral artery was found in the midlateral region of the cerebral wall, near the area where pSP-IZ was observed. Feature of layer structure growth was revealed by quantitative assessment as thickness, surface area, and volume. The maximum thickness value of pSP-IZ and CP increased significantly according to CRL, whereas the median value increased slightly. The layer structure appeared to grow and spread thin, rather than thickening during early development, which is characteristic during pSP stages. The surface area of the cerebral total tissue, CP, and pSP-IZ increased in proportion to the square of CRL. The surface area of CP and pSP-IZ approached that of the total tissue at the end of the pSP stage. Volume of each layer increased in proportion to the cube of CRL. pSP-IZ and CP constituted over 50% of the total tissue in volume at the end of the pSP stages. We could visualize the growth of pSP-IZ in 3D and quantify it during pSP stage. Our approach allowed us to observe the process of rapid expansion of pSP-IZ from the midlateral regions of the cerebral wall, which subsequently becomes the insula.

The Embryonic re-Development of an Anatomy Museum : Visualising Anatomical Collections: Human Female Reproductive Anatomy and Biology and Foetal Development

This chapter discusses the history of the Museum of Anatomy at the University of Glasgow in the context of a planned themed display on obstetrics and pregnancy, centred around human female reproductive anatomy, to support a showcase of Plaster Casts made and used by William Hunter. This exhibition aims to enhance the audience's experience with an educational display of historical specimens as well as anatomical artwork and medical models. It is anticipated that the resultant exhibition will include a series of visualisations and diagrams for use within the collection display to support the audience's understanding of the biological processes involved in reproduction, foetal development and women's experiences of childbirth. The chapter considers historical and contemporary methods of visualising embryos, as well as the developing discourse around menstruation, the gendered body and the lack of diverse representation in gynaecological images, and reflects on some of the historical, scientific, situational and societal considerations needed to achieve an inclusive and accessible exhibition. It also reflects on the artist's role in the embryonic development of this exhibition. The artworks in this chapter and the more that are planned should guide viewers with intentionally inclusive visual content. The project requires considerable further development and discussion with the team of experts involved. It is hoped that this intervention will broaden the impact of the collections in this space and provide opportunities to improve audience engagement by creating content that reflects and includes the voices of society in its creation.

Ethical Aspects of Human Embryo Collections: A Historically Grounded Approach to the Blechschmidt Collection at the University of Göttingen

Human body donation and tissue collections are nowadays grounded on a legal framework centered around the concept of informed consent in most countries. Comparable regulations did not exist prior to the second half of the 20th century, when several of the most important collections of human embryos were established. As a particularly prominent example, the Human Embryology Collection ("Blechschmidt Collection") at the Center of Anatomy, University Medical Center Göttingen, Germany, is described here with regard to how to approach a human specimen collection from the perspective of both collection ethics and the history of science. The methods and concepts used as well as the outcome in terms of historical and ethical knowledge will be discussed as a model for future projects of similar scope at other collection sites. It it also shown that general ethical recommendations published by museum and collection experts are of value only if they are related to profound knowledge about the history of the particular collection in focus.

"Inform the Head, Give Dexterity to the Hand, Familiarise the Heart": Seeing and Using Digitised Eighteenth-Century Specimens in a Modern Medical Curriculum

Recent years have seen an explosion of interest in digitising museum collections. Among the objects of interest are anatomical and pathological specimens found in medical museums. As researchers increasingly produce digital replicas of these preparations, ways of integrating these resources into the medical curriculum must be explored. This article takes a medical humanities approach to this topical question, comparing the historic use of anatomical specimens to modern intentions, and exploring the potential for using digital anatomy to help integrate humanities into the curriculum. The use of anatomical specimens by William Hunter (1718-1783), whose collection is now kept at the Hunterian in the University of Glasgow, provides a key historic focus. The teaching intentions for his private courses of anatomy are examined, to investigate how specimens were used in an eighteenth-century "curriculum". The motivations behind digitisation and the use of digital anatomy in modern curriculums are then examined and compared. Many of these motivations are shared with Hunter's: the desire to maintain a unique anatomical resource, the need to provide multisensory engagement in learning, and a desire to attempt to show "natural" anatomy without the interference of human processes. The balance between fostering empathy and maintaining detachment is also key for both. Using digital replicas of historic specimens to teach anatomy also opens up a unique opportunity to educate students in the medical humanities in a fully integrated way. Understanding the full story of the specimens they use, as explored in the first half of the article, allows students to place themselves, their dissection subjects, and healthcare as a whole in a historical context. As well as fostering empathy in the dissection lab, the stories behind the specimens can be used to introduce key humanities topics, including ethics, institutional bias, and social aspects of health and disease. It is essential that this potential is explored now while digital anatomy is still a relatively young field, and therefore collaborations between anatomists and medical humanities practitioners can be built and included from the ground up.

[Modelled Development. Practices of Human Embryology at Göttingen University in the Second Half of the Twentieth Century]

The Human Embryology Collection at the Centre of Anatomy Göttingen, created between 1942 and 1970, represents a unique interrelation of histological sectional series of human embryos and large-format physical models open to the public based on them. The collection was established long after the heyday of human embryology. It is also remarkable in another aspect: while usually models within the discipline are considered research objects, Göttingen embryologist Erich Blechschmidt (1904-1992) based his understanding on a pedagogical impetus. The article highlights the distinctive and unconventional features of Blechschmidt's undertaking against its disciplinary background. My focus lies on the two practices that are central to human embryology-collecting and modelling-, as well as the derived collection stocks. The special tension between individuality and universality that already characterized the process of their creation is also reflected in the later use of the collection. This tension allowed Blechschmidt to utilize the models in embryological research and anatomical teaching as well as in the broad social debate on abortion and the ethical status of human embryos.

Ethical Rationales and Guidelines for the Continued Use of Archival Collections of Embryonic and Fetal Specimens

Benefits from the use of cadavers in anatomical education are well described. Historically, human embryos and fetal cadavers were used in anatomy education to understand development and congenital malformations. Recently, three-dimensional printed models produced from archival fetal specimens, and online repositories of images from archival collections of embryos and fetuses, have been used as an educational tool in human development courses. Given that the archival specimens were likely obtained prior to the era of informed consent, this raises questions about their appropriate and ethical use. Because some institutions in the United States retain archival collections of embryonic and fetal specimens that were once used as educational tools, their existence and utility require frequent reexamination against contemporary ethical frameworks to guide appropriate use or utilization. Four ethical rationales for uses of these collections are examined, including destruction, indefinite storage, use in research, and use in health professions education. Guidelines for the use of archival collections of human embryos and fetuses are presented. Indefinite storage and use in health professions education are supported, while use in research is also permitted, however, such use is limited and dependent on circumstance and purpose. The development of current digital repositories and three-dimensionally printed models based on archival collections that were collected without informed consent, or those promoting commercial opportunity, are not supported. New embryonic and fetal donations obtained with informed consent should include reference to potential uses with new technology and virtual, genetic, or imaging applications.

The Hinrichsen Embryology Collection: Digitization of Historical Histological Human Embryonic Slides and MRI of Whole Fetuses

The number of human embryology collections is very limited worldwide. Some of these comprise the Carnegie Collection, Kyoto Collection, and the Blechschmidt Collection. One further embryonic collection is the Hinrichsen Collection of the Ruhr University Bochum, Germany, which also contains very well-preserved embryos/fetuses, along with approximately 16,000 histological sections. The digitization of this collection is indispensable to enable conservation of the collection for the future and to provide a large group of embryologists, researchers, and physicians access to these histological slides. A small selection of these scans is available at the website of the Digital Embryology Consortium [https://-human-embryology.org/wiki/Main_Page].