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First-Ever Embryos With Monkey And Human Cells; Scientists Divided Over The Creation

For the first time, scientists have successfully grown monkey embryos containing human cells, marking a milestone in a rapidly advancing field that has raised ethical concerns.

Human stem cells may one day be used to grow new organs for people with failing hearts or kidneys by slipping them into the embryos of other animals. To achieve this goal, researchers have created the first embryos that contain human and monkey cells.

Researchers may be able to refine techniques for growing human tissue in species better suited for transplantation, such as pigs, by studying these chimaeras [1].

In genetics, a chimaera is an organism or tissue that contains at least two sets of DNA, most commonly resulting from the fusion of several zygotes (fertilized eggs). In Greek mythology, the term Chimera refers to a fire-breathing monster that was part lion, part goat, and part dragon [2].

First-Ever Monkey-Human Cells Embryo: Study Findings

According to the study published in the journal Cell, researchers in the United States and China injected 25 pluripotent stem cells (pluripotent stem cells of the body are capable of self-renewal and give rise to all cells of the body's tissues) from humans into monkey embryos.

After one day, researchers detected the development of human cells in 132 embryos, and the embryos ultimately survived for 19 days.

"The paper is a landmark in the stem cell and interspecies chimaera fields. The findings hint at mechanisms by which cells of one species can adjust to survive in the embryo of another", added experts [3].

According to the researchers, a third of the chimaeras had human cells present after 13 days. There appears to be an integration of human cells with monkey cells, and the human cells have begun to specialize into different types of cells that will develop into different organ types. A few previous studies by researchers in the same study group had explored embryo development along the same lines:

  • According to research published in 2017, mouse stem cells were inserted into rat embryos to grow the pancreas. The disease was eradicated when the organs were transplanted into mice with diabetes. Human and pig cells, however, have not been able to get along as well as cells from more distantly related species [4].
  • During the same year, Juan Carlos Izpisúa Belmonte of the Salk Institute for Biological Studies and colleagues reported injecting human stem cells into pig embryos. In surrogate mother pig embryos, only about one in 100,000 of the cells were human after three to four weeks of development [5].
  • In the new study, Izpisúa Belmonte, reproductive biologist Weizhi Ji, and colleagues tested those more capable cells in a closely related species to humans, the cynomolgus monkey. 132 monkey embryos were implanted with 25 human EPS cells, and the chimaeras were raised for 20 days in culture dishes [6].

Researchers identified molecular pathways that were turned on or up in the chimaeras, possibly promoting the integration of human and monkey cells. Researchers believe that manipulating some of these pathways may allow human cells to survive in embryos of species more suitable for regenerative medicine for health problems.

However, the findings also stated that the human and monkey cells did not mesh perfectly. Human cells often stuck together, leading researchers to wonder if there is another barrier they are unaware of that would prevent human cells from thriving if the embryos mature further.

Some Researchers Raise Ethical Concerns

Chimaeras consisting of humans and monkeys do raise some concerns.

Last week, the National Academies of Sciences, Engineering, and Medicine released a report suggesting that human nerve cells may enter the brains of animals and alter their mental capabilities [7].

In this study, however, there are no nervous systems in the chimaeras. Therefore, it is impossible for them to experience pain and not be conscious. However, experts believe the story would be very different if human-monkey chimaeras were permitted to develop further - suggesting that it could go out of their hands.

"My first question is: Why?" Kirstin Matthews, a science and technology fellow at Rice University's Baker Institute, said, "I think the public is going to be concerned, and I am as well, that we're just kind of pushing forward with science without having a proper conversation about what we should or should not do" [8].

According to the researchers, they do not intend to implant any hybrid embryos into monkeys. Instead, the goal is to better understand how different cells communicate with one another during the early stages of embryonic development.

Several scientists question the need for such experiments using closely related primates - these animals are unlikely to be used as model animals in the same way as mice and rodents. Researchers are concerned that such work may stoke public opposition as non-human primates are protected by stricter research ethics rules than rodents [9][10].

On A Final Note...

Although there are concerns, scientists hope that these human-animal hybrids, known as chimaeras, can provide better models for testing drugs and growing human organs for transplantation.

Story first published: Tuesday, August 9, 2022, 16:35 [IST]
Read more about: embryo monkey cells transplant
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