With eyes that shone green and fingertips that glowed yellow, scientists in China have announced the birth of a monkey unlike any other. And those are just the visible characteristics.
Deep below, beneath the surface, this monster was supposedly even more amazing.
Using the pluripotent stem cells of two genetically different fertilized eggs from the same monkey species, an unprecedented experiment produced a male lab-born monkey that was able to develop into a living, breathing long-tailed macaque (Macaca fascicularis).
Though not the first scientifically created living monkey in history, experts from China and the UK claim that this one was the most mixed, or chimera, of all the intentionally created monkeys.
An animal considered a “chimera” in science is a single creature composed of cells originating from more than two parents.
The brain, heart, kidney, liver, gastrointestinal tract, testes, and the cells that become its sperm were among the animal’s bodily tissues made from two distinct stem cell lines—one from a donor embryo and the other from a host embryo.
The percentage of additional given stem cells varied from a low of 21% to 92% of the 26 distinct tissue types that the researchers evaluated in the living monkey. Brain tissues had the highest proportion.
Prior research has produced both liveborn and terminated monkey chimeric fetuses, with the progeny exhibiting minimal contributions of donor cells to diverse tissues, ranging from 0.1 to 4.5 percent.
Those numbers were completely out of the question for the most recent chimp. It only lived for ten days, therefore there is still work to be done in order to address the issue of the chimeric monkeys’ continued health.
“This is a long-sought goal in the field,” remarks Chinese Academy of Sciences (CAS) reproductive engineer and senior author Zhen Liu.
“Specifically, this work could help us to generate more precise monkey models for studying neurological diseases as well as for other biomedicine studies.”
The lead author of the paper, geneticist Jing Cao from CAS, stated in a press conference that this was a fundamental scientific breakthrough since it establishes the possibility of rich non-human primate chimeras for the first time.
Although there are a number of ethical issues with the topic of chimeric animal research, supporters argue that the advantages of precise models in diagnosing illnesses and developing treatments make the work valuable.
In the future, biomedical researchers may use genetically altered donor stem cells to assess specific disease outcomes in monkey models. The more donor stem cells there are in any target tissue, the more accurate the disease model can be—though this will vary depending on the goals of the research.
Immunologist Miguel Esteban of CAS and the Beijing Genomics Institute says that even a 10 percent chimerism in egg and sperm cells can be a valuable model since these germ lines can potentially pass on to kids.
There were reports of the first live chimeric monkeys in 2012, although the percentage of donor cells in these animals’ organs was relatively low (about 4 percent).
Furthermore, the fact that these chimeric tissues were “limited to organs rich in blood,” such as the placenta, liver, and spleen, raises the possibility that “blood mixture, rather than true chimerism in solid tissues,” is at play.
Scientists are ecstatic about this novel chimera monkey’s glowing solid tissues.
A group of scientists in China labeled donor pluripotent stem cells with green fluorescent protein before injecting them into week-old monkey blastocyst embryos. Pluripotent stem cells have the ability to develop into any type of cell.
In this manner, it would be easy to link any tissue or cell that glows green in the progeny to the given stem cell line.
Only six live births resulted from the implantation of these precisely crafted embryos into female macaques, and only one of these live monkeys—a male—exhibited stem-cell-derived tissue in numerous body locations.
Although the amount of chimerism in one of the aborted fetuses was less than in the live chimeric monkey, the fetus did not survive to give birth.
Although Cao and colleagues acknowledge that the process’s overall efficiency “remains low”—roughly half as successful as producing an embryo from in vitro fertilization without chimerism—it’s still a positive step in the right direction.
There are several possible reasons for the low efficiency, including improper lab culture of the embryos or stem cells. Enhancing the survival rate in both the embryo and fetus is a continuous challenge the team aims to refine in the future. For example, many cells suffer programmed cell death when donor stem cells are introduced into a host embryo.
According to Liu, the study may contribute to our understanding of the early phases of stem cell development in primates, a subject that has not received nearly as much attention as it has in mice.
“[W]e have provided strong evidence that naive monkey pluripotent stem cells possess the capability of differentiating in vivo into all the various tissues composing a monkey body,” Esteban states.
“This study deepens our understanding of the developmental potential of pluripotent stem cells in primate species.”
Cell published the research article.