Scientists in China have achieved a groundbreaking experiment, resulting in the birth of a one-of-a-kind primate. This lab-born male monkey, a long-tailed macaque, displayed extraordinary observable features such as glowing yellow fingertips and green-shining eyes. However, the true marvel lied within its genes and the composition of its cells. Through the fusion of pluripotent stem cells from two genetically distinct fertilized eggs from the same monkey species, researchers were able to create a chimeric monkey with cells and tissues originating from two separate stem cell lines. This groundbreaking creation has far-reaching implications for neurological disease research and biomedicine studies.
In the field of science, a “chimera” refers to an organism composed of cells that derive from more than two parents. In this case, the chimeric monkey’s body exhibited cells and tissues originating from both a donor embryo and a host embryo. These cells were apparent in various organs and systems of the monkey, including the brain, heart, kidney, liver, gastrointestinal tract, testes, and the cells that develop into its sperm. Researchers measured 26 different tissue types in the live monkey, with contributions from extra donated stem cells ranging from 21 percent to a striking 92 percent. The highest percentage was observed in brain tissues, indicating the presence of chimeric cells. This surpasses previous studies, which showed low donor cell contributions of only 0.1 to 4.5 percent.
The survival of the chimeric monkey for only ten days raises concerns about the ongoing health of chimeric monkeys. However, the creation of such an extensive chimeric primate opens doors to generate more precise monkey models for studying neurological diseases and other areas of biomedicine. The ability to generate accurate models for disease testing and therapy development is highly valuable. By genetically editing donor stem cells, biomedical researchers can potentially test various disease outcomes in monkey models. The greater the contribution of donor stem cells in the target tissue, the more accurate the disease model becomes. For egg and sperm cells, even a low percentage of chimerism, such as 10 percent, can serve as a useful model as these germ lines can theoretically transfer to offspring.
The first live chimeric monkeys were reported in 2012, but the donor cells’ contribution to their tissues was limited to around 4 percent and mostly present in organs rich in blood. The extensive chimerism observed in the newest chimeric monkey provides a significant advancement in the field. To achieve this, the researchers injected a set of pluripotent stem cells, capable of differentiating into all cell types, into week-old monkey blastocyst embryos. By labeling the donated stem cells with green fluorescent protein, they could identify the specific tissues or cells that originated from the donor stem cell line. This meticulous engineering resulted in six live births, with only one male monkey displaying stem-cell-derived tissue in multiple regions of its body. Although the overall efficiency of the process remains low compared to traditional in vitro fertilization, it represents a promising step forward in creating chimeric monkeys.
The efficiency of the process could be attributed to how the stem cells or embryos are cultured in the lab. Many cells undergo programmed cell death when donor stem cells are injected into a host embryo, which affects the survival rate. Improving the survival rate of both the embryo and fetus presents an ongoing challenge that the research team aims to address. Additionally, the research has the potential to enhance our understanding of the early stages of stem cell differentiation in primates, an area that remains less understood than in mice.
The birth of the chimeric monkey represents a significant breakthrough in the field of science and biological research. Through innovative techniques and genetic engineering, scientists in China have created an extraordinary primate with cells and tissues derived from two separate stem cell lines. While the challenges of creating healthy and long-lasting chimeric monkeys persist, this achievement offers hope for more precise monkey models for studying neurological diseases and biomedicine. Despite ethical concerns surrounding chimeric animal research, the potential benefits of accurate disease models and therapeutic testing cannot be disregarded. As research continues, this field holds immense potential for advancing our understanding of genetic and cellular processes in primates.