 "Scientists clone first healthy rhesus monkey. Why is this significant?")
Scientists in China have announced that they have cloned the first healthy rhesus monkey (macaca mulatta).
The animal named Retro, who is over three years old, was brought into the world on 16 July, 2020.
The study on how Retro was cloned was published in the journal Nature Communications on Tuesday.
But what happened? How did scientists manage this feat? And why is this significant?
Let’s take a closer look:
What happened?
Remember Dolly the sheep?
The animal, the first mammal to be cloned from an adult cell, was cloned in 1996 using a method known as somatic cell nuclear transfer (SCNT).
As per CNN, SCNT is basically when scientists create an unfertilised egg by melding the nuclear of a somatic cell – not from a sperm or egg – with an egg whose nucleus has been removed.
Since Dolly, over 20 different animals have been created using the process, including dogs, cats, pigs and cattle.
But primates proved particularly difficult to clone.
“In a way we have made much progress in that, after Dolly, many mammalian species were cloned, but the truth is that inefficiency remains a major roadblock,” Miguel Esteban, principal investigator with the Guangzhou Institute of Biomedicine and Health at the Chinese Academy of Sciences told CNN.
Just one to three per cent of such clones are born, as per CBS.
Impact Shorts
More ShortsIt was only two decades later that scientists managed to clone the first primates using SCNT.
A pair of identical crab-eating macaques named Hua Hua and Zhong Zhong were created using SCNT in 2018 by researchers at the Chinese Academy of Sciences Institute of Neuroscience in Shanghai.
But that breakthrough, led by the institute’s Qiang Sun, only resulted in live births in fewer than two percent of attempts.
Qiang was also a senior author of the new research published in the journal Nature Communications.
He told AFP that the team had extensively researched why previous efforts to clone the rhesus monkey (Macaca mulatta) had failed.
In an earlier attempt, one monkey – out of 35 implanted foetuses – was born alive, but it died in less than a day.
Qiang said that one of the “major problems” was that the placentas of cloned embryos were showing abnormalities compared to those from in vitro fertilisation.
Cracking the code
Researchers ultimately cloned Retro by tweaking the SCNT method.
They replaced the cells that later become the placenta, which are called the trophoblast, with those from a healthy, non-cloned embryo.
The trophoblast cells provide nutrients to a growing embryo, and turn into the placenta that supplies oxygen and other life-supporting assistance to the foetus.
The monkey’s name Retro was derived from “trophoblast replacement”, as per BBC.
The technique “greatly improved the success rate of cloning by SCNT” and led to the birth of Retro, Qiang said.
“We have achieved the first live and healthy cloned rhesus monkey, which is a big step forward that has turned impossible to possible, although the efficiency is very low compared to normal fertilised embryos,” Falong Lu, one of the authors of the study told CNN. “Currently, we haven’t had the second live birth yet.”
“They created a combination embryo — one part cloned and another part not cloned,” Rüdiger Behr, a stem cell and embryo researcher at the German Primate Center told DW.
A rhesus monkey named Tetra was cloned in 1999 using a different technique called embryo splitting.
But this simpler technique can only produce four clones at once.
Scientists have focused on SCNT in part because it can create far more clones, with the goal of creating identical monkeys to study a range of diseases as well as test drugs.
“The cloned rhesus monkey has reached the age of 3,” Lu told New Scientist. “So far, we haven’t observed any health issues in it by our routine physical check-ups.”
Why it is significant
Researchers hope their new technique will lead to the creation of identical rhesus monkeys that can be experimented on for medical research including developing treatments for Alzheimer’s and cancer.
“We can produce a large number of genetically uniform monkeys that can be used for drug efficacy tests,” Mu-ming Poo, director of the Institute of Neuroscience in the Chinese Academy of Sciences in Shanghai told Nature.
It is also yet another scientific barrier that has been breached.
Esteban told CNN, “This research is proof of principle that cloning can be done in different non-human primate species and opens the door to new ways of enhancing the efficiency. Cloned monkeys can be genetically engineered in complex ways that wild-type monkeys cannot; this has many implications for disease modelling. There is also a species conservation perspective.”
As per CBS, examining how embryos develop in animals could lend insights into solving issues humans face.
Some people undergoing IVF fail to have embryos implanted in their uterine wall.
“In Australia, one solution at the moment is to essentially transfer more embryos because we often don’t know how to fix this recurrent implantation failure, or the current treatments we have fail,” Jarrod McKenna, a reproductive biologist and science communicator told CBS.
“So having an understanding of what might be going on with those [placenta-forming] cells might have implications on that human side of things too.”
However, outside researchers warned that the success rate for the new method was still very low, as well as raising the usual ethical questions around cloning.
Lu acknowledged this telling CNN, “We think that there might be additional…. abnormalities to be fixed. Strategies to further enhance the success rate of SCNT in primates remains …our main focus in the future.”
Still, Lu told BBC News that ‘’everyone was beaming with happiness’'
Regardless, sceptics abound.
Lluis Montoliu, a scientist at the Spanish National Centre for Biotechnology who was not involved in the research, pointed out that just one out of 113 initial embryos survived, meaning a success rate of less than one per cent.
If human beings were to ever be cloned – the great ethical fear of this field of research – then other primate species would have to be cloned first, he added.
But so far, the poor efficiency of these efforts has “confirmed the obvious: not only was human cloning unnecessary and debatable, but if attempted, it would be extraordinarily difficult – and ethically unjustifiable,” Montoliu said.
“It is extremely difficult to succeed with these experiments, with such low efficiencies,” Montoliu added.
Qiang emphasised that cloning a human being was “unacceptable” in any circumstance.
A spokesperson for the UK’s Royal Society for the Prevention of Cruelty to Animals (RSPCA) told BBC it was concerned.
“There is no immediate application for this study. We are expected to assume that human patients will benefit from these experiments, but any real-life applications would be years away and it is likely that more animal ‘models’ will be necessary in developing these technologies,” a spokesperson said.
“The RSPCA is deeply concerned about the very high numbers of animals who experience suffering and distress in these experiments and the very low success rate. Primates are intelligent and sentient animals, not just research tools”.
With inputs from agencies
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