Ready for a Human Hybrid? Human-Animal Chimeras May Now Be Possible

Science has always been in the forefront on advancements, whether it is technology or medicine. Even though the primary concern of science is to improve our lives, it still courts controversy ranging from stem cells, mutations, and cloning.

Perhaps, the topic of a human hybrid is the most controversial yet.

According to the National Institute of Health, to gain valuable insights into human biology and disease development, biomedical researchers have created and used animal models containing human cells for decades.

For example, human tumor cells are routinely grown in mice to study cancer disease processes and to evaluate potential treatment. It's a common practice to validate the potency of pluripotent human cells by introducing them into rodents to advance regenerative medicine.

With recent advances in stem cell and gene editing technologies, there's an increasing interest in growing human tissues and organs in animals by introducing pluripotent human cells into early animal embryos.

How to Create a Human Hybrid?

A human hybrid is created by injecting human stem cells into animal embryos. This will create an embryo that has two different sets of cells: an animal set and a human set, something that's known as a chimera, Live Science reported.

"Chimeras" (human-animal organisms) hold tremendous potential for disease modeling, drug testing, and perhaps eventual organ transplant. But what makes it so controversial that research on this is subject to debate?

The effects of human cells on off-target organs and tissues in the chimeric animals are uncertain, particularly in the nervous system. This raises ethical and animal welfare concerns.

To help study human diseases as well as early human development, some researchers are interested in creating new types of animal models with human tissue.

A letter by stem cell scientists published in the journal Science last year explains that by using chimera models, researchers might be able to better study heritable human diseases and find potential cures.

Live Science says that it might be possible "to generate an unlimited supply of therapeutic replacement organs" by using pig or sheep chimeras. However, the most controversial part of this issue is the use of animals as vessels for human organ transplants.  

Ethical and Welfare Concerns

There are calls to lift NIH restrictions on chimera research. Despite the ethical and animal welfare, "continued dialougue between scientists and bioethicists regarding human/non-human chimera studies is critical for advancing human health through basic science."

However, uncertainty about the effects of human cells on off-target organs and tissues in the chimeric animals, particularly in the nervous system, raises ethical and animal welfare concerns.