Retro the Rhesus Monkey: First Successful Animal Clone Using a Modified Technique in China

Scientists in China have achieved a significant milestone by successfully cloning a healthy rhesus monkey named Retro.

This achievement was made possible by enhancing the SCNT (Somatic Cell Nuclear Transfer) technique, which had previously been used to clone Dolly the sheep. In this case, scientists overcame the challenges that made primates particularly difficult to clone.

The birth of Retro signifies not just a triumph over technical hurdles but also opens new avenues for medical and scientific research.

By replacing cloned cells that would become the placenta with those from a normal embryo, scientists were able to ensure Retro's health and vitality.

A Breakthrough in Cloning Technology

Somatic cell nuclear transfer, or SCNT, is a technology that has been used to generate over 20 different animals, including dogs, cats, pigs, and cattle, since the historic cloning of Dolly the sheep in 1996.

But it took researchers twenty years to successfully clone the first monkeys using SCNT.

Researchers at the Chinese Academy of Sciences Institute of Neuroscience in Shanghai used SCNT in 2018 to generate Hua Hua and Zhong Zhong, two identical crab-eating macaques.

However, less than 2% of attempts following that breakthrough-led by the institute's Qiang Sun-resulted in live babies. The recent study that was released in the journal Nature Communications also had Qiang as a senior author.

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 fetuses - 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 fertilization.

Therefore, the trophoblast cells-which eventually give rise to the placenta-were substituted by the researchers with cells from a normal, non-cloned embryo.

The trophoblast cells nourish the developing embryo and develop into the placenta, which gives the fetus oxygen and other necessities for survival. According to Qiang, the method "greatly improved the success rate of cloning by SCNT" and produced Retro.

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Implications for Medical Research

The success of cloning Retro raises both excitement and ethical questions around cloning. With this breakthrough, there is potential for creating identical rhesus monkeys that can be used in medical research, offering a consistent model for experimentation.

While this development promises advancements in understanding various diseases and testing treatments, it also brings to light ethical considerations that need addressing. The use of clones in research prompts discussions on animal rights and welfare, regulatory oversight, and the moral boundaries of scientific innovation.

Some experts have expressed concern that cloning monkeys could pave the way for cloning humans, which is widely opposed by the international community.

Qiang said that his team had no intention of cloning humans, and that they followed strict ethical guidelines for animal research. He also said that cloning monkeys was not the ultimate goal, but rather a means to an end.

"Our goal is to produce animal models that are useful for medicine, for human health. That is our goal. Not just to clone a monkey," he said.

Retro, the cloned rhesus monkey, is now more than two years old and lives a "happy and healthy life" with others of the same species, according to Qiang. He said that thus far the researchers have not identified any potential limits on the cloned monkey's lifespan.

Retro's name, which stands for "reprogrammed trophoblast", reflects the innovative technique that made his cloning possible. He is also a symbol of the progress and challenges that lie ahead for cloning research.

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