World first: Live birth of a chimeric monkey created with stem cells

A team of Chinese researchers has reported the first live birth of a chimeric monkey, a significant stride in the field of biomedicine and genetic engineering. 

The chimeric monkey, composed of cells from two distinct embryonic stem cell lines of the same monkey species, represents a major advancement. Until now, this had only been achieved in rats and mice. 

Pioneering effort

The research team, led by Zhen Liu of the Chinese Academy of Sciences (CAS), heralds this success as a “long-sought goal in the field.”

“This research not only has implications for understanding naive pluripotency in other primates, including humans, but it also has relevant practical implications for genetic engineering and species conservation,” said Liu.

“Specifically, this work could help us to generate more precise monkey models for studying neurological diseases as well as for other biomedicine studies.”

How the research was conducted 

The team focused on cynomolgus monkeys, which are widely used in biomedical research. By establishing nine stem cell lines from 7-day-old blastocyst embryos and enhancing their pluripotency, the researchers set the stage for a groundbreaking experiment. 

The pluripotent cells, marked with green fluorescent protein, were injected into early monkey morula embryos and implanted in female macaques, leading to 12 pregnancies and six live births.

Successful results

The experts confirmed that one live-born monkey and one fetus that was miscarried were substantially chimeric, containing cells that grew out of the stem cells throughout their bodies. 

These stem cells, present across various tissues including the brain, heart, kidney, liver, and gastrointestinal tract, accounted for 21% to 92% of the live monkey. 

In both animals, the researchers found stem-cell-derived cells in the testes and cells predestined to become sperm, underscoring the comprehensive nature of this chimerism.

Study implications

“In this study, we 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,” said study co-author Miguel Esteban of BGI Research and CAS. “This study deepens our understanding of the developmental potential of pluripotent stem cells in primate species.”

“This work helps us to better understand naive pluripotency in primate cells,” added study co-author Qiang Sun of CAS. “In the future, we will try to increase the efficiency of this method for generating chimeric monkeys by optimizing the culture conditions for the stem cells, the cultures for the blastocysts where the stem cells are inserted, or both.”

More about chimeric monkeys 

A chimeric monkey refers to an individual monkey that is made up of cells from two different embryos, essentially combining genetic material from two distinct sources within the same species. In this context, the term “chimeric” is derived from “chimera,” a creature from Greek mythology that was a combination of different animals. In biological terms, a chimera is an organism that contains cells with different genetic compositions.

In the case of the chimeric monkey discussed in the CAS study, it was created by injecting cells from monkey embryonic stem cell lines into a monkey embryo at an early stage of development. These stem cells were derived from a different individual than the embryo into which they were injected. 

As the embryo developed, it incorporated these stem cells, resulting in an organism where some of the cells have one genetic makeup and others have a different genetic makeup. This process creates a unique individual with a mix of cells from two genetically distinct sources.

Image Credit: Cell/Cao et al.

The study is published in the journal Cell.

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