Are the black boxes of early human embryo development slowly opening?
Last Update: 2021-03-03
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human life originated in early embryos, but how do human embryos develop after bed? Is there any trace of the development process of fetal formation, i.e. pre-primary embryos and pluripotent stem cells? Scientists have been searching for answers to these life problems.
Nature, a top international journal, recently published online in the form of a long article, Professor Li Tianqing and Ji Weizhi
of Kunming University of Technology's Primate Translational Medicine Research Institute, in collaboration with the First People's Hospital of Yunnan Province, which established a three-dimensional culture system for human embryos for the first time, and for the first time systematically revealed the development process of pre-intestinal embryos and pluripotent stem cells. The panorama of molecular and morphological development they have drawn fills the gaps in the relevant fields and establishes an important research basis for the study of the early development of embryos after bed.
development of human fertilized eggs begins with a series of cleavages and re-discharges in form, forming blastocysts. The advanced blastocyst consists of three different cell linelogies, namely, the upper embryo cell and the inner embryo cell and the two extraterrogenous tissues that nourish the outer embryo layer. After entering the uterus, the upper embryo cells produce three embryonic cells and the entire fetus, which in turn produce the yolk sac and placenta, respectively. Scientists have carried out extensive research into the development of pre-blast embryos, and have achieved
however, on the 7th day of development, human embryos need to be implanted into the mother's womb to survive and develop. This stage of embryo development in the utero three-dimensional space-time by complex and fine regulation, limited by ethical and research techniques, research materials can not be obtained, but also lack of a corresponding in vitro research system, from fertilized eggs on the bed to the 14th day of the formation of the primary embryo, embryo development has long been a mysterious "black box."
" primary intestine began to form, the nervous system began to form, gradually forming a fetus, it is not an embryo. What happened to early embryos in the womb? What kind of molecular mechanism can regulate and maintain its normal development? What factors can affect its normal development? These are all issues that need to be addressed. Li Tianqing told Science and Technology Daily that in fact, the first 2 to 3 weeks of pregnancy is the core key period to ensure fetal development.
Where the production of the blastocyst, about 5 to 6 days, formed the first genealogy differentiation of life; Can grow smoothly into a fetus; the third stage is the formation of the original intestine, if there is a problem in the third embryo layer, then fetal development will certainly appear congenital development defects, in many cases will form neural tube dysplia, cerebral palsy, spinal dysplas and other diseases. The first stage of the current research is more, for the third stage, due to the existence of large ethical problems, it is not possible to carry out related research.
Therefore, the study of the bed-front stage of the primary intestine, the understanding of key events in human embryonic development, as well as the research and application of human stem cells, tissue organ regeneration, and the prevention and treatment of infertility and early developmental diseases are critical.
" In fact, our study is to map the molecular mechanisms of the critical development of pre-human embryos, as well as their morphological development processes, to reflect what changes this process has produced. In other words, our study promises to open up the 'black box' of the early stages of human embryos, promising a breakthrough in the perception of life. Li Tianqing said.
team for the first time cultured human blastocysts in three-dimensional (3D) conditions to the 14th day of the original stage, but did not appear early nervous system development, in line with the international ethical guidelines for embryo research. The breakthrough in the research mainly reveals the dynamics and molecular regulation network of genealogy differentiation and development of upper embryo cells, lower embryo cells and nourishing layer cell lines, and secondly, the study finds that amniotic epithal cells are the first type of cell line isolated by upper embryo cells, unlike rodents, human amniotic epithetical cells occur before the formation of the original strip, but their properties and molecular mechanisms are not clear. The team found that compared with upper embryo cells, amniotic epithal cells significantly reduced the erythromatic gene, the formation of which is significantly related to the absence of substrate membrane, and has a unique molecular expression spectrum. They also shed light for the first time on the differentiation of cell nourishment layers, fluffy outer cell nourishment layers, and co-parenting cells after the embryo bed, as well as the signals and transcription factors that cause differentiation, revealing the function of the fluffy outer cell nourishment layer in early embryos different from the middle and late placenta.
, they also revealed that the upper embryo cells, or erythrocytes, quickly shifted from "primitive" to "origin" when they were bedding. Changes in the expression spectrum of potent stem cells occur mainly in the two stages of inner cell groups to the upper embryo cells in front of the bed and the production of the original strip. Pluripotent stem cells remain relatively stable from bed to day 14, and their development and transformation are determined by the coordination of different pluripotent factors. Through transcriptional group analysis of human and monkey embryos, the team found significant differences in metabolism between monkey and human embryonic cells, while conservative in key molecular and signaling pathways that maintain stem cell pluripotentity and development.
, Li Tianqing, said that through this study, we also have a deeper understanding of human life. In the future, people can improve the success rate of IVF and solve a series of problems in human reproductive development;
As mentioned earlier, previously the academic community could not obtain human embryos in the early post-bed stage after natural conception, so more rodent embryos or non-human primate embryos and other model organisms to replace the study, but this can not accurately reflect the real situation of human molecular regulation and other laws. At the same time, recent results of pre-pregnancy embryo development in humans, including a recent paper published in the journal Science, are still limited by two-dimensional technology platforms that do not simulate in vivo conditions.
Li Tianqing said that under strict ethical permission and informed consent of patients, the research team used clinically donated embryos, first of all, by improving the culture base and culture methods, developed a three-dimensional (3D) human blastocyst culture system, overcome two-dimensional (2D) can not simulate the defects of embryo development, the first time the human blastocyst in 3D conditions to the 14th day of the original stage, to be closer to the real conditions in the body.
" to establish the core of 3D embryos, lies in the cell growth needs to be closest to the human physiological environment of the culture system, which can be understood as the food supplied to cells and embryos and embryo growth space environment. Previously, there are many defects in the research of culture system at home and abroad, resulting in the embryonic cells can not maintain the three-dimensional structure of space, such as a beach of water, the surface collapses, so the cells can only make surface contact with petri dishes, become a 2D environment, so that cells can only one-on-one or only a small number of connections, which further study of cell interaction has major defects. Li Tianqing said that, in fact, the contact between cells and cells, originally a three-dimensional environment, as if we hang a water bead, do not let it collapse. Due to the lack of spatial support structure of 2D conditions, embryos can not develop further at a certain time, so usually 2D embryos can only be about 12 days.
Currently, their self-developed culture system enables the cultivation of 3D embryos and can highly simulate the environment of embryos in the body, where embryos undergo different forms of development and are spontaneously assembled into 3D structures that cannot be produced under 2D conditions, including embryonic double-layer cup discs, amniotic membranes, substrate membranes, primary and primate unique secondary follicles, front and rear axles and primary strips. Li Tianqing is convinced that their independent research and development of the training system will provide a new platform for the academic community to study the frontiers of life related topics.
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