Retro is a cloned rhesus monkey that was born on July 16, 2020. He is now more than 3 years old and “is doing well and growing strong,” said Falong Lu, one of the authors of the study. study published this week in the magazine Nature Communications that accounts for the scientific feat. It is the first time that a cloned monkey of this species survives to adulthood.
That he has lived this long is what allows the Chinese team to declare his cloning successful. In 2022, researchers cloned a rhesus monkey, but the animal survived less than 12 hours. On that occasion, they used a standard technique known as somatic cell nuclear transfer (SCNT). It is the one that was used to clone the famous Dolly sheep in 1996 and later other mammals, including pigs, cows, horses and dogs.
Cloning with this method is achieved, broadly speaking, when the nucleus of a cell in the body is transferred to an egg whose nucleus has been removed. This technique typically results in extremely low birth and survival rates for cloned embryos.
In the new study, scientists at the Institute of Genetics and Developmental Biology of the Chinese Academy of Sciences have slightly improved the technique. This time, they added placental precursor cells. So, They managed to generate 113 embryos, transferred 11 to seven surrogate mothers, achieved two pregnancies and a single birth: Retro.
Drug testing on cloned monkeys
They named the monkey “Retro,” in honor of the scientific method, called “trophoblast replacement”, used to produce the cloned animal. By replacing the placenta of the cloned embryo with a placenta from embryos produced through in vitro fertilization, scientists were able to reduce developmental defects that hinder the survival of cloned embryos.
Since the first primate was cloned six years ago, scientists have used cloned monkeys to study human diseases, such as depression and anxiety. Also to test various medications.
“We can produce a large number of genetically uniform monkeys that can be used for drug efficacy testing”Mu-ming Poo, director of the Institute of Neuroscience at the Chinese Academy of Sciences in Shanghai, told the magazine Nature. The rhesus monkey is a species widely used in medical research because its physiology is similar to that of humans.
“We are seeing the beginning of the use of these cloned monkeys,” Poo highlighted. “We want to use as few animals as possible to demonstrate the effectiveness of a drug, without the interference of genetic background.” But he clarifies that there are still technological aspects to resolve before the cloning process becomes more agile.
Animal cruelty
A spokesperson for the Royal Society for the Prevention of Cruelty to Animals (RSPCA) in the United Kingdom told the BBC that the animal suffering caused outweighed any immediate benefit to human patients. “There is no immediate application for this study,” a spokesperson highlighted. “We are expected to assume that human patients will benefit from these experiments, but any real-life application would take years.”
The RSPCA said it insisted that a large number of animals experience “suffering and distress” in experiments with a very low success rate. “Primates are intelligent and sensitive animals, not just research tools,” the organization said.