The same method that helped clone Dolly the Sheep almost 22 years ago helped Chinese scientists clone monkeys, illuminating science with models that could be beneficial for understanding human medical issues.

The scientists announced that two long-tailed macaque monkeys were successfully cloned, the first monkey was born in November 2017 and the second one, ten days later, in December 2017 at a Shanghai laboratory.

Zhong Zhong (ZZ) and Hua Hua (HH), Zhong Zhong and Hua Hua, Cloned monkeys from China
Cloned monkeys from China. Image credit: China Daily via Reuters

Although the process is still not ideal, the scientists are very excited since it means, according to Mu-ming Poo of the Chinese Academy of Science, a “breakthrough for biomedicine.”

What is SCNT and its highlights on the study

Somatic Cell Nuclear Transfer (SCNT) is the name of the method used for the cloning process. The study was made by Zhen Liu, Yijun Cai, Yan Wang, Yanhong Nie, Chenchen Zhang, Yuting Xu, Xiaotong Zhang, Yong Lu, Zhanyang Wang, Mu-ming Poo and Qiang Sun.

The SCNT involves removing the nucleus of the somatic cell, being the one that contains the DNA o the organism.This nucleus is inserted into an egg cell (that has had its nucleus removed before to give its place to the new one), and this new nucleus is reprogrammed by the host cell.

The egg cell is stimulated with a shock with the purpose of beginning its mitotic division. After many of those divisions, the cell forms an embryo with about 100 cells, a blastocyst, which has a DNA almost identical to the original organism, according to Science Daily.

The study, published in the journal Cell, successfully achieves the SCNT using fetal fibroblasts, the cell that synthesizes the extracellular matrix and collagen, and also the most common cell of connective tissue in animals. It also explains the promoted development and pregnancy rate of SCNT due to epigenetic modulators, and the births of the monkeys achieved using adult cumulus cells during the SCNT.

SCNT Using Fetal Monkey Fibroblasts and Adult Monkey Cumulus Cells

According to the scientists, Fetal Fibroblasts selected thanks to their potential in obtaining a large number of nuclei with uniform genetic background were derived from an aborted female monkey. The cells were prepared using a specific method from the SCNT protocol, transferring them to a total of 21 female monkey surrogates.

A total of 6 pregnancies were confirmed among the surrogates after a month, during an ultrasound examination, sadly two of them were only gestational sacs and other two aborted within two months.

The success came 140 days after when one of the female monkeys gave birth to a living baby. The second one was born on the mark of the 155th day. The scientists named them Zhong Zhong (ZZ) and Hua Hua (HH), gave them human care, and unlike other baby monkeys born from natural fertilization, these SCNT obtained ones did not show hypertrophy of umbilical cord at birth. They showed normal postnatal temperature regulation and sucking reflex during feeding just as the normal growth rate in head circumference and body weight, explain the scientists in their report.

Zhong Zhong (ZZ) and Hua Hua (HH), Zhong Zhong and Hua Hua, Cloned monkeys from China
Zhong Zhong and Hua Hua. Image credit: Associated Press

The second part of the project didn’t have such a great outcome. Adult Cumulus Cells (cluster of cells that surround the oocyte in the ovarian follicle and also after ovulation) of female monkeys, were also used for attempting the SCNT. In this case, the embryos were transferred to 42 female monkey surrogates.

The pregnancies were confirmed after a month as well in 22 monkeys, but only 12 had living creatures on them. Sadly, 8 of them aborted within two months and other two later on. The last two pregnant monkeys could carry their babies beyond 130 days, and two baby monkeys were born via cesarean, but the first one died 3 hours later due to impaired body development and the second one following him, died 30 hours later due to respiratory failure.

The analysis of the genetic code was performed to examine the nuclear DNAs and the mitochondria of baby ZZ and HH. The ear tissues matched perfectly the original organism regarding the STR (Short Tandem Repeat), and the SNP (Single Nucleotide Polymorphisms) of the ND3 gene of the mitochondria DNA was identical to of the one obtained from the oocyte donor monkeys. This confirms the success of the clone project and the clonal origin of the two baby monkeys generated by the SCNT Method.

A Breakthrough For Biomedicine

Besides from demonstrating, just as they explained on their discussion fragment on their study, that cloning on non-human primates is possible thanks to SCNT, they also highlight the massive step that this represents for biomedicine, and science overall as well.

Since monkeys are creatures developmentally close to human being, as Mu-ming Poo explains, the primate cloning can be used for laboratory created models to develop “basic research in primate biology” and studying the mechanisms and treatments that could be used to help fight human diseases.

The scientists declared:

“There is no aim for us to apply this strategy to people.”

Source: USA Today