Scientists in China created the first living primate chimera using stem cells.

The monkey that was born had fluorescent green eyes and fingers and was created from two genetically different monkey embryos.

This achievement, the researchers said, could benefit medical research and help find ways to conserve endangered species. Chimeras are animals that contain groups of cells from two or more organisms with different types of DNA.

The monkey lived for 10 days before being euthanized, and was created with stem cells from two embryos from the same monkey species. He was born with a high percentage of donor cells – an average of 67% in 26 different tissue types, the scientists said.

“This research could help us create more accurate monkey models for the study of neurological diseases as well as other biomedical studies,” said lead author Zhen Liu, of the Chinese Academy of Sciences.

Chimeras are important for the study of embryonic development, but research has been largely limited to chimeric mice that were first created in the 1960s. Since then, they have been commonly used in biomedical research.

Scientists can observe how normal cells interact with genetically modified or mutant cells in the chimeric mice, so they can understand biological processes and diseases. However, this research has limitations, which is why the researchers turned to monkeys, the scientists said.

“Mice don’t reproduce many aspects of human disease because their physiology is so different from ours. “In contrast, humans and monkeys are evolutionarily close, so human diseases can be modeled more closely in monkeys,” said Liu.

More controversial are the human-animal chimeras, owhich contain human cells as well as cells from other species. In 2021, scientists in the US and China announced that they had developed chimeric human-monkey embryos. The scientific community hopes that chimeras may one day help meet the huge demand for organs for transplant.

The research team cultured nine lines of stem cells using cells removed from 7-day-old monkey embryos. The researchers made the cells pluripotent – ​​giving them the ability to organize into all the different cell types needed to make a living animal. They then injected a subset of the cells into genetically different 4- to 5-day-old embryos from the same monkey species. They also injected the cells with a green fluorescent protein so they could determine which tissues had grown from the stem cells. They then implanted the embryos into female monkeys. This resulted in 12 pregnancies and six live births.

“This is an important study, but I don’t think it’s a breakthrough because the chimeras created are not viable,” said Jun Wu, an associate professor of molecular biology at the University of Texas Southwestern Medical Center.