Scientists create hybrid human and monkey embryos, which may help 'build' organs for transplantation and study cancer and ageing
Posted on April 16, 2021
The experiment makes it possible to advance in the knowledge of the first stages of pregnancy and paves the way for obtaining, in the future, organs for transplantation in animals.
An international team of researchers, led by the Spanish Juan Carlos Izpisúa, from the Salk Institute in the United States, and with the collaboration of the Kunming University of Science and Technology in Yunnan, China (led by Weizhi Ji), has generated hybrid human and macaque embryos in the laboratory. The chimeric organism developed for 19 days, a significant period. The results, published in the journal 'Cell', represent an important advance in the understanding of the beginnings of life, in the study of ageing and serious diseases such as cancer and, above all, in the possibility of 'manufacturing' in other human organ species to end transplant waiting lists.
Chimeras refer to the mythological monster that is represented with the head of a lion, the body of a goat and the tail of a dragon. Those made between mammals have been known since the 1970s, but the breakthrough that made the current work possible came last year, when the teams of Izpisúa and Weizhi Ji generated a technology that allowed monkey embryos to grow outside the mother's body for about three weeks.
On this occasion, the researchers inserted 25 human pluripotent stem cells - cells that are capable of becoming all cell types in the body - into laboratory-created monkey embryos six days earlier. The cells were tagged with a fluorescent protein in order to follow their development. A day later, they were detected in 132 embryos. Ten days later, 103 of the chimeric embryos were still developing. Survival soon began to decline and by day 19 only three chimeras were still alive. Still, they were better integrated than in previous similar experiments carried out in pigs, in which the human contribution was quite low. To identify the molecular communication pathways between the two species, the scientists analysed the transcriptome of the generated chimera, that is, a reading of which genes and molecules were active.
The team makes it clear that it does not intend to use human-macaque chimeras for the generation of organs for transplantation. The reason is that being two species much closer to each other, these hybrids are very useful to better understand how human cells are integrated. Izpisúa compares him to two people trying to understand each other in different languages: between human and pig cells the communication would be similar to Chinese and Spanish. Between human and macaque cells, it would be like Spanish and Italian. By improving 'translation', researchers could increase the integration of human cells into hosts such as pigs, better suited for on-demand human organ farms for ethical, social and economic reasons, among others.
According to the Spanish biologist, these chimeras are "really very useful to advance biomedical research". In the future, in addition to generating human cells, tissues or organs, they could also be used to study how some diseases such as cancer arise or how ageing occurs. "We don't know if all organs age at the same rate, or if perhaps one organ drives that of the others. We could grow the organ of a common rat into a longer-lived species, such as the naked mole-rat, and investigate which organs may be key to ageing", says the scientist.
A human-monkey hybrid may sound disturbing, but the team says they consulted with all relevant regulatory bodies and independent bioethicists to ensure the work meets all current legal and ethical standards. "The way to carry out these studies, with the utmost rigour in ethical considerations, is as important as the results obtained", says Izpisúa.
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