Chinese scientists clone a rhesus monkey

Chinese scientists clone a healthy rhesus monkey, Retro, using an improved somatic cell nuclear transfer (SCNT) technique.

Chinese scientists announced a groundbreaking achievement on Tuesday by successfully cloning the first healthy rhesus monkey, a two-year-old named Retro. Utilizing a modified version of the process that produced Dolly the sheep, the researchers overcame previous failures in primate cloning by replacing cloned cells destined to become the placenta with those from a normal embryo. This advancement in somatic cell nuclear transfer (SCNT) techniques raises hopes for the creation of identical rhesus monkeys, serving as valuable subjects for medical research.

Cloning primates has been a formidable challenge, with previous successes limited to animals like dogs, cats, pigs, and cattle since Dolly’s historic cloning in 1996. While identical crab-eating macaques were cloned in 2018 using SCNT, the live birth success rate remained below 2%. The latest breakthrough, led by Qiang Sun from the Chinese Academy of Sciences Institute of Neuroscience, addresses previous failures in cloning rhesus monkeys (Macaca mulatta). A key issue identified was abnormal placental development in cloned embryos compared to those from in vitro fertilization attempts.

To enhance the success rate, researchers replaced the trophoblast cells – the ones destined to become the placenta – with cells from a healthy, non-cloned embryo. This modification significantly improved the cloning success rate, resulting in the birth of Retro. However, caution is warranted as the new method’s success rate remains low, with only one out of 113 initial embryos surviving, translating to less than 1 per cent.

There are numerous ethical considerations surrounding the field. Human cloning, an ethical concern in the realm of cloning research, would require successful cloning in other primate species first. Despite advancements in SCNT, concerns about efficiency and ethical justifiability persist, discouraging the pursuit of human cloning.

Qiang Sun stressed the unacceptability of cloning human beings under any circumstances. The SCNT procedure involves removing the nucleus from a healthy egg and replacing it with another nucleus from a different body cell. This modified embryo grows into a genetically identical organism. While cloning a rhesus monkey named Tetra was achieved in 1999 using a different technique called embryo splitting, SCNT offers the advantage of creating a larger number of clones, facilitating the study of various diseases and drug testing.

The recent success in cloning Retro highlights both the scientific strides made and the challenges that persist in primate cloning, sparking discussions about the ethical boundaries of cloning research.