Images of Zhong Zhong (ZZ) and Hua Hua (HH), two clones created via somatic cell nuclear transfer using fetal monkey fibroblasts, at 20 and 34 days after birth, respectively. Liu et al./ Cell, 2018.

Clones of 23 mammal species have been generated using SCNT in the past, yet previous attempts to extend the technique to primates have failed. The challenge lay in correctly programming a single-celled clone egg to act like a normal embryo: Though each contains a full set of DNA, it needs special cues to know which genes to express and which to ignore in order to develop.

The Shanghai team’s breakthrough came when they applied two programming molecules to one-celled clones that were made from the nuclei of early skin cells of other macaque embryos.

Prior experiments using a type of cells found in adult macaque ovaries also led to the birth of clones, but they died shortly after. Of the 21 attempts this time, only two healthy births were achieved.

The next steps will be to ensure that Zhong Zhong and Hua Hua grow and progress normally. As of right now, they are being bottle fed and constantly monitored by staff at the academy’s Nonhuman Primate Research Facility.

If everything proceeds to plan, monkeys like these two will replace the existing populations of primate lab animals used in research for human genetic diseases, cancer, and more.

“It'll be interesting to see how this research shapes the debate over the use of non-human primates as lab animals,” National Geographic science expert Michael Greshko told IFLScience via email. “Will it reduce the number of primates needed to perform medical experiments, as the study's authors hope? How much does that lessen the ethical burden of using primates in the lab at all?”

[H/T: National Geographic]