The latest achievement of regenerative medicine has a Spanish stamp. The team of scientists led by the specialist in developmental biology, Juan Carlos Izpisúa , has developed, for the first time in history, chimeras of human and macaque cells. In total, they created 132 chimera embryos in a Chinese laboratory in a controversial experiment, the details of which were made public on Thursday.
What is a genetic chimera?
A genetic chimera, or chimerism, is a unique organism made up of cells from different individuals, containing two sets of DNA.
Three of these hybrid embryos in which the researchers injected human stem cells into primate embryos, of just 10,000 cells, grew for 19 days outside the uterus, at which point the researchers interrupted this experiment, partially funded by the Catholic University Saint Anthony of Murcia.
Previously, six days after the monkey embryos were created, each was injected with 25 human cells. After one day, human cells were detected in 132 embryos. After 10 days, 103 of the chimeric embryos were still developing. However, after this period of time, some of the embryos began to die. As of day 19, only three chimeras were still alive, after which the team destroyed them before they could develop further.
An important point the researchers made was that the percentage of human cells in the embryos remained high throughout the experiment.
According to experts, this work has the potential to provide insight into developmental and evolutionary biology, as well as aid research efforts on cancer treatments, among other things.
“Historically, the generation of human-animal chimeras has suffered low efficiency and failure in the integration of human cells in the host species”, comments Izpisua Belmonte. “Generating a chimera between human and non-human primates , a species more closely related to humans along the evolutionary timeline than all previously used species, will allow us to better understand whether there are evolutionarily imposed barriers to the generation of chimeras and and understand the molecular mechanisms to overcome them “.
The team says the immediate goal is to find which pathways are vital to the development process, and in the long term, the researchers hope to use the chimeras not only to study early human development, but to develop new approaches to drug detection. as well as to generate cells, tissues or organs for transplantation.
“This type of research is important for advancing knowledge about cell communication and biological development during embryogenesis and evolution, as well as for a variety of research applications and regenerative medicine. For example , it may one day result in the ability to to develop replacement human tissue, such as the heart and kidney. It can also help to test candidate drugs for human diseases with greater precision than traditional animal models, “continues the expert.
Is it ethical?
Many scientists question whether these interspecies chimeras should be considered human enough to be treated as people , whether they would have human-like mental capacity, and whether they can actually be used in research.
The Frankenstein element of the study
Would a fully formed mono-human embryo be biologically possible? According to the authors, the goal is not to develop new organisms but to better understand human development.
Referencia: Cell, Tan et al.: “Chimeric contribution of human extended pluripotent stem cells to monkey embryos ex vivo” www.cell.com/cell/fulltext/S0092-8674(21)00305-6 , DOI: 10.1016/j.cell.2021.03.020
