Beijing, April 21 (CNBC) -- According to the "News Hyperlink" of the Voice of China of the Central Radio and Television Corporation, a blockbuster study was recently published in the top international journal "Cell": scientists from China's Kunming University of Science and Technology and the Salk Institute of Biology in the United States have created "human-monkey embryos" with high survival rates for the first time.
Human-monkey chimeric embryo, red for human cells (photo by Ji Weizhi, Kunming University of Science and Technology)
"Human-monkey embryos", in simple terms, are the injection of human extended pluripotent stem cells into in vitro cultured crab-eating monkey embryos. This embryo, which contains cells of different species of origin, is called a "chimeric embryo". The scientific community expects chimeric animals to "grow" human organs to solve the real problem of organ transplantation.
In this experiment, human-monkey chimeric embryos were cultured only to the 20th day, all embryos died, and the in vitro culture of embryos ended here, avoiding larger ethical issues.
In 2010, Japanese scientists had achieved rat-mouse chimeras, allowing mice to grow rat pancreas. But when it comes to the chimera of human cells and monkey embryos, things become more sensitive. Can the public accept the future growth of organs needed by humans on other species? Even if it is used to cure diseases and save people, ethical issues will remain the biggest obstacles.
What is a chimeric embryo? Why eat crab monkeys?
Chimeric embryos are meant to allow cells from different species to survive in the same embryo. In this experiment, what are the advantages of choosing a crab-eating monkey as an embryo compared to the previous experiment?
Professor Tan Tao of the Institute of Primate Translational Medicine of Kunming University of Science and Technology, one of the corresponding authors of the study paper, said that scientists have long been studying chimeras across species. Before the human-monkey chimeric embryo, human-mouse chimeric embryos and human-pig chimeric embryos were also made.
Monkeys and humans have 95% similar genomes, and early embryonic development is also similar. In contrast, there is a wide gap between the embryonic morphology, structure and development of early organs in pigs and mice. Experiments with monkey embryos, a near-source species, help rule out situations where species differences affect embryonic development.
Gorillas or chimpanzees are more "close" to people, why choose crab-eating monkeys? This is because knowledge of their basic embryonic development as well as early embryonic development is relatively absent. The study of cynobial monkeys has a history of 30 years. Crab-eating monkeys are small and can retrieve their eggs all year round, with no limit on the duration of experiments.
Professor Tan Tao said that the main purpose of this project is to use near-source species to study heterogeneous chimerism, which has positive significance for future organ replacement therapy, organ reconstruction and clinical application.
It is worth noting that the human-monkey chimera embryo is not a fusion of genes, but the cells of humans and monkeys coexist in the embryo of the crab-eating monkey at the same time, and there is no process of gene exchange. In simple terms, the embryo is the "house" of the monkey, the monkey's cells are equivalent to the "master", and the human cells are equivalent to the "guest".
20 days, natural death? Or is it an experimental requirement?
Human-monkey chimeric embryos are only cultured until day 20 and all embryos die. Is this human action or natural death?
Professor Tan Tao said that the experiment chose to cultivate embryos in vitro to facilitate the "control" of cell development and reduce the ethical issues involved. At present, in vitro culture technology does not allow embryos to grow in vitro for a long time, which is an international problem. Secondly, after 20 days, the embryo's nervous system begins to develop. For ethical reasons, the scientists terminated the experiment on day 20.
Theoretically, if such a chimeric embryo is fully developed, it will become a living organism. Professor Tan Tao said that whether this kind of experiment needs to continue to be carried out or whether to continue to study, it also needs to be discussed by scientists, ethicists and all sectors of society in China and the world.
Is the direction of chimera development controllable?
Human expanded pluripotent stem cells are powerful. In the course of the experiment, can the position of human cells in the chimeric embryo be strictly controlled to prevent the development of sensitive parts such as the brain and sexual organs?
Professor Tan Tao said that it is still difficult for the construction of chimeras. Currently, there is no particularly perfect technique to control the direction of differentiation of human cells in chimeric embryos. If it is only in vitro cultured cells, it can be directed by adding some chemical molecules, cytokines, proteins, etc.; but the embryonic environment is complex, and it is uncertain what can be bred in the embryonic environment, which is one of the main reasons for the experiment.
In the future, the team's research direction is to find answers to some basic scientific questions, such as how "human-monkey embryos" develop, and may also use basic scientific problems to achieve technological breakthroughs, such as extending the length of in vitro culture embryos.
Producer: Bai Zhonghua
Reporter: Hejia
Editor: Yang Yang Bi Liwei