Researchers in China have developed a chimeric macaque in an experimental setting. The animal exhibited unusual physical characteristics, including green eyes and fluorescent fingers, resulting from the presence of a fluorescent protein. The team states that this study aims to support animal experimentation in medical research on stem cells.
In science, a chimera is a creature resulting from two or more different zygotes, typically created by scientists for research purposes. In a laboratory in Shanghai, China, Jing Cao and her team “designed” a genuine chimeric monkey.
According to the researchers, while this is not the first time such a chimera has been produced, theirs possessed the highest level of cell mixing from different cell lineages. The study details have been published in the journal Cell.
Steps of the Experiment
In this experiment, researchers used stem cells taken from 7-day-old “donor” monkey embryos of the same species called crab-eating macaques. From these cells, Cao and her team created nine cell lines that, once reaching a state of “naivety” or “pluripotence,” were reintegrated into 4 to 5-day-old “host” embryos. When pluripotent, cells can develop into any type of body cell.
The host embryos were implanted into several female monkeys. 12 of them became pregnant, and 6 monkeys were born alive, with only one being largely chimeric. It was recognizable by notable differences in appearance, including green eyes and partially yellow or fluorescent distal phalanges.
Integration of a Green Fluorescent Protein
To track the development of these injected stem cells, researchers marked them with a green fluorescent protein before their integration into host embryos. The protein allows the stem cells and the tissues they form to glow under certain light conditions. Among the six monkeys born, only one male showed the green color, indicating that some parts of his body were derived from the (modified) injected stem cells.
Following analysis, it became clear that stem cell-derived tissues helped the monkey’s brain, heart, kidneys, liver, gastrointestinal tract, testicles, and sperm cells form, among other vital organs.
Moreover, out of the 26 types of tissues analyzed, the presence of introduced stem cells ranged from 21% to 92%. In contrast, other chimeric monkeys from previous experiments, whether alive or deceased, showed that only 0.1% to 4.5% of their tissues consisted of cells from external donors.
Goals in Biomedical Research
According to the researchers, the objective of this chimera study is to develop animal models that can be used to more precisely study human diseases, especially neurological disorders. They emphasize the essential role of animals in biomedical research to understand disease development and progression.
However, the Chinese researchers acknowledge that they are still far from their goal. They recognize that the success rate of chimera creation is relatively low compared to ordinary laboratory conception through in vitro fertilization (IVF). This low efficiency could be attributed to the cell culture techniques used in the laboratory. Additionally, the chimeric monkey died after only 10 days.