Periodic Reporting for period 4 - EPIROSE (Self-Organising Capacity of Stem Cells during Implantation and Early Post-implantation Development: Implications for Human Development)
Okres sprawozdawczy: 2020-07-01 do 2022-06-30
Implantation is a crucial event in mammalian pregnancy, during which the body axes are established, and the embryonic germ layers are formed. Despite its significance, this remains the most enigmatic stage of development because, upon implantation, the tiny embryo becomes inaccessible within the mother's body. Our aim was to understand how architectural features and signalling events integrate to regulate successive cell fate decisions and tissue morphogenesis during implantation and early post-implantation development. Understanding these processes is essential for comprehending human development and potentially developing new therapeutic approaches in the future.
To bridge the knowledge gap between pre- and post-implantation development, we developed techniques to use stem cells to recapitulate embryo development in vitro. We also aimed to uncover the self-organizing capabilities of stem cells and their ability to mimic embryonic development, which has immense potential for regenerative medicine. Understanding the mechanisms that intertwine lineage specification, developmental plasticity, and tissue morphogenesis at this critical developmental transition in the mouse model will provide insight into pathological embryo lethality and congenital malformations.
We have successfully applied novel techniques and approaches to complete our objectives. Our studies have allowed us to gain a better understanding of the events occurring after the embryo implants. Our research has advanced the field and we have shared our achievements with the scientific community through numerous publications in high-impact journals and also by talks at numerous conferences, often as keynote lectures. The creation of embryo-like structures and other findings from our laboratory generated huge social interest and resulted in many interviews for the general public that have appeared on radio and in magazines and newspapers.
To bridge the knowledge gap between pre- and post-implantation development, we developed techniques to use stem cells to recapitulate embryo development in vitro. We also aimed to uncover the self-organizing capabilities of stem cells and their ability to mimic embryonic development, which has immense potential for regenerative medicine. Understanding the mechanisms that intertwine lineage specification, developmental plasticity, and tissue morphogenesis at this critical developmental transition in the mouse model will provide insight into pathological embryo lethality and congenital malformations.
We have successfully applied novel techniques and approaches to complete our objectives. Our studies have allowed us to gain a better understanding of the events occurring after the embryo implants. Our research has advanced the field and we have shared our achievements with the scientific community through numerous publications in high-impact journals and also by talks at numerous conferences, often as keynote lectures. The creation of embryo-like structures and other findings from our laboratory generated huge social interest and resulted in many interviews for the general public that have appeared on radio and in magazines and newspapers.
Mammalian embryos undergo dramatic shape changes upon implantation, and the cellular and molecular mechanisms underlying this transition were previously largely unknown. We have shown that this transition is directed by cross-talk between the embryonic and extra-embryonic tissues present at that time. We identified signalling pathways responsible for specific fate acquisition, which are required for embryo body and placenta formation in future development.
After the initial step of embryo remodelling during implantation, the embryo breaks symmetry for the first time in its life to define the future anterior and posterior parts of its body. This critical event is required for establishing the correct body plan. We have defined the function of the cells migrating to one side of the embryo during the peri-implantation period that break the embryo’s symmetry and have detailed distinct events, signalling pathways and molecules that are responsible for the correct progression of this process. We have also identified critical changes in the embryonic and extraembryonic parts of the embryo that contribute to the coordination of embryo growth and morphogenesis upon implantation and in early post-implantation development, after the anterior and posterior parts of the embryo are established. We have also shown that distinct adhesion molecules are required for embryo implantation and development, and that modulating their function may lead to unsuccessful implantation and death of the embryo.
Taken together, our above studies provide an in depth characterization of the cellular and molecular mechanisms underlying the transition from the pre- to post-implantation state, which were previously largely unknown. We have shown the significance of cross-talk between the embryonic and extra-embryonic tissues in the regulation and progression of development and future morphogenetic transitions.
An aberrant number of chromosomes in cells may result in cell death or congenital defects, and such cells need to be eliminated during early embryonic development. Using a mouse model, we have shown how cells having an aberrant number of chromosomes are preferentially eliminated from the lineage forming the future embryo body. Moreover, we have shown that healthy cells undertake compensatory divisions during the implantation stages to confer embryonic viability and described self-regulatory mechanisms to ensure its proper size and number of cells. Our results indicate how different processes work together to eliminate cells with genetic instabilities from the lineage forming the embryo body in development and to refine the embryonic cell population, ensuring that only “chromosomally fit” cells proceed through the development of the foetus.
The above findings demonstrate the highly specific regulative mechanisms of early development in mouse embryos, ensuring correct cell number and health during the implantation process and in the formation of embryonic and extra-embryonic structures. This knowledge has potential implications for human development and clinical application.
We have developed a new methodological approach to generate post-implantation mouse embryo-like structures from a mix of stem cells, representing cells present in the preimplantation embryo. Our results demonstrate that these structures can develop in a similar way to natural embryos, forming precursors of the entire brain, a beating heart, and a gut. They are also morphologically similar to natural embryos and form both embryonic and extraembryonic structures, just as is the case in natural mouse embryo development. Therefore, for the first time, we have developed a stem cell-based system that captures mouse embryogenesis in its entirety. In the future, these systems could significantly reduce the use of animals in research. We have already successfully used these systems to address distinct scientific questions about the roles of specific genes in developmental processes.
We have also attempted to translate the stem cell-derived embryo system from mouse to human by modelling early human embryo development with stem cells. However, we have shown that further improvement and research are needed to develop similar model that is as accurate as the mouse model.
After the initial step of embryo remodelling during implantation, the embryo breaks symmetry for the first time in its life to define the future anterior and posterior parts of its body. This critical event is required for establishing the correct body plan. We have defined the function of the cells migrating to one side of the embryo during the peri-implantation period that break the embryo’s symmetry and have detailed distinct events, signalling pathways and molecules that are responsible for the correct progression of this process. We have also identified critical changes in the embryonic and extraembryonic parts of the embryo that contribute to the coordination of embryo growth and morphogenesis upon implantation and in early post-implantation development, after the anterior and posterior parts of the embryo are established. We have also shown that distinct adhesion molecules are required for embryo implantation and development, and that modulating their function may lead to unsuccessful implantation and death of the embryo.
Taken together, our above studies provide an in depth characterization of the cellular and molecular mechanisms underlying the transition from the pre- to post-implantation state, which were previously largely unknown. We have shown the significance of cross-talk between the embryonic and extra-embryonic tissues in the regulation and progression of development and future morphogenetic transitions.
An aberrant number of chromosomes in cells may result in cell death or congenital defects, and such cells need to be eliminated during early embryonic development. Using a mouse model, we have shown how cells having an aberrant number of chromosomes are preferentially eliminated from the lineage forming the future embryo body. Moreover, we have shown that healthy cells undertake compensatory divisions during the implantation stages to confer embryonic viability and described self-regulatory mechanisms to ensure its proper size and number of cells. Our results indicate how different processes work together to eliminate cells with genetic instabilities from the lineage forming the embryo body in development and to refine the embryonic cell population, ensuring that only “chromosomally fit” cells proceed through the development of the foetus.
The above findings demonstrate the highly specific regulative mechanisms of early development in mouse embryos, ensuring correct cell number and health during the implantation process and in the formation of embryonic and extra-embryonic structures. This knowledge has potential implications for human development and clinical application.
We have developed a new methodological approach to generate post-implantation mouse embryo-like structures from a mix of stem cells, representing cells present in the preimplantation embryo. Our results demonstrate that these structures can develop in a similar way to natural embryos, forming precursors of the entire brain, a beating heart, and a gut. They are also morphologically similar to natural embryos and form both embryonic and extraembryonic structures, just as is the case in natural mouse embryo development. Therefore, for the first time, we have developed a stem cell-based system that captures mouse embryogenesis in its entirety. In the future, these systems could significantly reduce the use of animals in research. We have already successfully used these systems to address distinct scientific questions about the roles of specific genes in developmental processes.
We have also attempted to translate the stem cell-derived embryo system from mouse to human by modelling early human embryo development with stem cells. However, we have shown that further improvement and research are needed to develop similar model that is as accurate as the mouse model.
The knowledge and experience gained during this project has resulted in the development of a new methodological approach permitting post-implantation embryo-like structures derived from embryonic stem cells to develop almost half-way through the development to form beating hearts, progenitors for all regions of the brain, formation of somites defining the future spinal column and formation of the gut tube. Moreover, the overall development of the resulting embryo-like structures is very similar to the natural embryo development during these stages with some of the extra-embryonic tissues being also formed, just as in natural development.
At the planning stage of this study, we did not anticipate that we would be able to generate and culture embryo-like structures to this advanced stage from stem cells. We were also uncertain of the extent to which we would be able to obtain structures recapitulating natural development that do not differ at the genetic level. We did not expect to be able to optimize formation of truly embryo-like structures and culture them to the point in which they follow the pathways of natural embryo development to which they show extremely strong similarity both morphologically and at the gene expression level.
At the planning stage of this study, we did not anticipate that we would be able to generate and culture embryo-like structures to this advanced stage from stem cells. We were also uncertain of the extent to which we would be able to obtain structures recapitulating natural development that do not differ at the genetic level. We did not expect to be able to optimize formation of truly embryo-like structures and culture them to the point in which they follow the pathways of natural embryo development to which they show extremely strong similarity both morphologically and at the gene expression level.