In a new study published in the journal Cell, researchers have made a key breakthrough in stem-cell biology by making an infant chimeric monkey out of two genetically distinct embryos.
Making an Infant Chimeric Monkey: Credit:
Miguel A. Esteban
Study authors describe the baby animal, which had a distinctive green glow, as the first live-born chimera of a primate to show a high share of its cells from donor stem cells. This is a notable milestone because it will better enable researchers to probe human diseases and develop treatments.
Read Also: Chinese Scientists Generate Functioning Blood Cells Using Interspecies Chimerism
However, study outcomes suggest there is a need to better fine-tune the approach used for creating the hybrid monkey and address ethical concerns.
The study was led by researchers from the Chinese Academy of Sciences.
A challenging endeavor
This research was not the first attempt to create chimeras, which are organisms made from cells obtained from two or more genetically distinct sources. Researchers have created chimeric rats and mice in the past. The process involves the use of embryonic stem cells – obtained from the inner region of an embryo – capable of developing into diverse tissues.
The stem cells from an embryo can be edited genetically, say, for mutations, before being combined with the second embryo. This can make it possible for researchers to study how mutations impact health.
Read Also: Scientists Make Embryos That Are Part Human, Part Monkey
A challenge in disease research is that rats and mice are less similar to humans, biologically, compared to monkeys.
However, previous attempts to create chimeric monkeys did not produce impressive results. Less than five percent of the cells in the organs of those animals came from donor stem cells. Such low proportions made them not fitting for studying human diseases.
Breakthrough for disease research
The team of researchers in this Cell study made recipient embryos from the eggs of female cynomolgus monkeys (Macaca fascicularis), which they collected and fertilized. They then edited embryonic stem cells from a-week-old cynomolgus embryos to enable a green fluorescent signal before injecting them into host embryos.
The green fluorescent signal was intended to help the team tell how much of an animal resulting from the process came from donor stem cells.
Those recipient embryos were then implanted into 40 female monkeys, with 12 of them becoming pregnant as a result. However, only one live birth was recorded.
As per the study authors, the baby monkey showed a donor cell expression of roughly 67 percent across 26 tested tissues, including the brain and heart. The highest proportion was observed in the adrenal gland, at 92 percent of all cells.
This level of donor cell expression is the highest reported yet. It raises hope that chimeric monkeys could someday be used to better model diseases in humans. Scientists think the approach might be used to grow human organs in non-human primates.
However, the method still needs to be worked on further for now. For instance, only one baby monkey (a male) came out of this effort despite the implantation of 40 female monkeys. That sole animal also had to be euthanized at just 10 days old due to breathing difficulties and hypothermia.
There are also ethical concerns that would have to be addressed regarding the approach.
References
Cao, J. et al (2023). Live birth of chimeric monkeys with high contribution from embryonic stem cells. Cell https://doi.org/10.1016/j.cell.2023.10.005
