Chinese scientists have unveiled that a rhesus monkey has been successfully cloned, marking the first instance of its kind to reach adulthood. Employing somatic cell nuclear transfer (SCNT) in combination with trophoblast replacement (TR), the researchers accomplished the cloning of the rhesus monkey, similar to the technique employed in cloning Dolly the Sheep over 25 years ago. The resultant clone, named ReTro, is currently three and a half years old and has thrived since birth.
The researchers documented their findings in Nature Communications, a few years subsequent to ReTro's birth in July 2020. They elucidated their utilization of SCNT, wherein the nucleus from the skin tissue of a 62-day-old monkey fetus was transferred into an enucleated egg cell. The resulting embryo was subsequently implanted into a surrogate's uterus, where it matured into a fetus that was a clone of the skin cell donor.
ReTro is not the first monkey to have been successfully cloned through SCNT. In 2018, the same research team reported the successful cloning of Zhong Zhong and Hua Hua, two macaque monkeys who remain alive to this day, utilizing fetal cells and SCNT.
However, rhesus monkeys have proven to be particularly challenging to clone. In an effort to mitigate developmental abnormalities that may impede embryo survival, such as defective placentas, the researchers developed trophoblast replacement. Prior to implantation, they removed the outermost layer of the developing embryo, known as the trophoblast, responsible for placenta formation. This layer was then substituted with a healthy layer sourced from an IVF-generated embryo. Consequently, the cloned fetus developed within a non-cloned placenta, though the researchers confirmed that this did not compromise the genetic integrity of the clone.
The process of cloning has been a contentious subject matter. Despite adhering to Chinese laws and scientific guidelines, the creation of ReTro has reignited concerns regarding animal welfare, ethical considerations, and implications for human reproduction.
Source - Chinese Academy of Sciences - Cloned Rhesus Monkey Grows into Adulthood for First Time: Study----Chinese Academy of Sciences (cas.cn)
