46 me.engin.umich.edu Advances in Research 47

structure, containing columnar pluripotent symmetry breaking of hPSC cysts, Fu and development,” Fu said. “These are incredi- epiblast cells on one side and flattened, his co-workers developed a microfluidic bly intricate intercellular interactions among squamous amniotic cells on the other. In system to expose half of the hPSC cysts the amniotic cells and between the amnion vivo, the epiblast or the embryonic disc to BMP stimulation. The cells exposed to and the epiblast, and we need to better would eventually develop into the fetus, BMP differentiated; the cells not exposed understand the amnion’s functional role.” while the amniotic cells would eventually retained pluripotency and remained as develop into the amnion, the fluid-filled the epiblast. The microfluidic device Fu’s team devel- membrane sac in which the embryos oped now is also about to be used to develop. screen for drug toxicity and prenatal for- mation of birth defects, or teratogenesis. The team has thus demonstrated for the FUNDAMENTAL SCIENCE AND FIRST “Many compounds have unknown effects first time that without maternal or extraem- APPLICATIONS on pregnancy and human development, bryonic tissues, hPSCs can self-organize and our system is compatible with screen- Fu and collaborators already have begun into an asymmetric structure with amnion- ing assays so it can help us identify them,” investigating fundamental questions that epiblast patterning that resembles the he said. underlie the symmetry-breaking process. core of the implanting human embryo. What are the signals that trigger the The researchers refer to the asymmetrical “I should stress that we’re not trying to symmetry-breaking process? How is the tissue as PASE, post-implantation amniotic grow a complete embryo,” Fu added. tissue boundary between the amnion and sac embryoid. “Our goal is to leverage our synthetic the epiblast determined and maintained? models to advance fundamental under- standing of human development, which The group also is investigating the role of remains largely mysterious. Such efforts Synthetic Models of the amnion in controlling further embryonic CONTROLLING THE PROCESS will be valuable for preventing pregnancy development, including into the embryonic USING MICROFLUIDICS loss, birth defects and teratogenesis and Human Embryonic disc. improving stem cell-based research and The team further identified the involvement therapies. There are many important of signaling molecules, bone morphogenic “We already know from follow-up Development questions about human development that proteins (BMPs), in driving amniotic dif- studies that the amnion serves as a we can study in the near future. I am Many compounds have ferentiation of hPSCs. To further control signaling center and triggers continuous very excited.” hen it comes to human devel- unknown effects on NOVEL MICROSCALE 3D CULTURE opment, our knowledge of the SYSTEM W earliest stages of embryonic pregnancy and human BACKGROUND IMAGE: Bright field image showing many individual The research team developed a bioen- development—especially peri- and post- development, and our cysts containing central cavities developed in 3D culture from human implantation in the maternal uterus—is gineered three-dimensional cell culture embryonic stem cells. Note that most cysts have uniformly squamous sorely limited. Model systems that do exist system is compatible with system that mimics the implantation morphology. All cells contained in these cysts are amnion cells. The center not on humans but on non-primate environment with properly controlled one cyst at the center (above), shows an asymmetrical morphology, screening assays so it can mechanical properties. As in earlier obser- with one side squamous (the amnion) and the other side columnar systems that differ markedly. Associate (the epiblast). The cavities in all cysts are the pro-amniotic cavity. Professor Jianping Fu, who directs the help us identify them. vations, within one day, hPSCs formed Integrated Biosystems and Biomechanics hollow spheres. But soon after, hPSCs in CIRCULAR IMAGES: Immunofluorescence images showing an asym- metrical cyst, with the columnar side (the epiblast) stained positive Laboratory at U-M, is changing that. the implantation-like culture environment Fu’s investigations into this emerging began to look strikingly different from for OCT4 (pink; pluripotency marker), and the squamous side (the amnion) negative for OCT4. The green fluorescence is from staining research area could be described as control cells cultured in standard culture: In a series of papers published recently for some central cavity marker. (Nature Materials, vol. 16, pages 419–425, serendipitous. A few years ago, the lab of On one side of the hollow cyst, the cells 2017; Nature Communications, vol. 8, Dr. Deborah L. Gumucio, a professor in appeared flattened and squamous, while article number 208, 2017), Fu’s research the Department of Cell and Developmental on the other side they appeared columnar. Biology, observed that human pluripotent group has successfully developed novel This research is used in preventing synthetic embryological platforms that can stem cells (hPSCs), a stem cell type equiv- Given the embryonic origin and develop- open up previously inaccessible phases alent to embryonic cells in the implanting mental potential of hPSCs, the research pregnancy loss, of human development to experimental human embryo, possess intrinsic proper- team decided to investigate in greater study, helping advance human embryology ties to form hollow structures with a central detail the identities of the columnar and birth defects and cavity or lumen. But how do hPSCs self- squamous cells by comparing their and reproductive medicine. organize and form such three-dimensional molecular features with data in the teratogenesis Fu’s research on modeling human structures? With Fu’s longstanding interest scientific literature from other primates, and improving stem cell-based development has laid the foundation for in mechanobiology and hPSCs, he and since little to no human data exists. The research and therapies the emerging field of “synthetic embryo,” Gumucio began to collaborate and study team soon realized—with great excitement, which has been selected by the MIT how different mechanical signals and Fu recalled—that what it was observing Technology Review as “10 Breakthrough forces might affect the function and in the implantation-like culture was a Technologies of 2018.” behavior of hPSCs. self-organized asymmetrical embryonic