HUMAN-ANIMAL CHIMERAS

According to Greek mythology, a chimera is known to be a hybrid creature represented by a lion with a goat’s head protruding from its back and a tail terminating with a snake’s head.

Science has been successful in preserving the mythological roots of a chimera but this research has also been quite transgressive in its approach.

A chimera is a single organism which has been made of cells from different individuals, meaning it contains two different sets of DNAs. For example, tissue chimera may result from organ transplant or tissue transplant such as that of bone marrow. Not only restricted to being a lab experiment, it is known to occur naturally as well. This may happen when the mother and the fetus swap cell during pregnancy via placenta (micro chimerism) or when in a case of fraternal twins, if the two embryos somehow fuse together to form a single fetus having genetically distinct cells (tetragametic chimerism).

The total number of chimeras in the world isn’t known but there have only been 100 cases recorded so far making it a very rare condition.

Most often, chimeras have been a result of lab experiments performed by humans for genetic research. With advancements in science and technology and an increasing need for performing organ transplantation, scientists have developed a technique called xenotransplantation which can be understood as the implantation of live cells, tissues or organs from a non-human animal source into human body. Hiromitsu Nakauchi, a Japanese stem-cell scientist has been the first person to receive government support after the ban on this practice was uplifted recently. The team headed by him aims to produce animals with organs made of human cells that can be used to facilitate organ transplantation. This research has been active in other countries as well such the United States but has not been brought to terms because of the prohibition on its funding since 2015 imposed by the National Institutes of Health.

The first interspecies chimera sheep-human chimera was created by scientists in which human stem cells were introduced into sheep embryos resembling 99% sheep but also showing a tiny bit similarity to humans.

Bioethicists have argued against this idea because there may be a possibility that human cells may go beyond the development of the targeted organ and may reach other organs of the animal such as the brain and interfere in its cognition.

The main strategy of the scientists working on this research is to perform only targeted organ generation, so the cells do not sway away from their original path and penetrate other organs. The necessary concerns need to be taken into consideration regarding this research. Nakauchi plans to address the issue and plans to maintain a dialogue with the public so as to eradicate all of their concerns.