Organ transplantation, once rare and experimental has become relatively common place in modern society and functions to save and extend the lifetime of many people each year. Just last year for example there were over 100,000 organ transplants performed world wide. However each one of these transplants requires a donor, and for some organs the only way for that to be achieved is for them to pass away (auto mobile accident deaths are a major source of transplantable organs).

With the advent of self driving cars and the reduction in accidents the technology promises, it is likely that our "supply" so to speak of available organs for transplantation will not always be available. This puts a pressing need on the development of technologies allowing for the growth of organs that can be transplanted effectively and directly into humans.

Though I will openly disclose that I am NOT particularly comfortable with this technology being used to create Human chimeras.

What is a Chimera?

When I hear the word chimera I picture the beast from ancient Greek mythology: part lion, part dragon, part goat with a tail that is a snake!

Yeah, that thing!

However, in science a chimera is not a mythical beast but rather an organism (at least for animals) that was grown by combining cells from multiple fertilized eggs. This has been done in mice to create a variety of chimeric creatures.

All of these mice are chimeras (and they just look like mice too, no dragon heads)...Source

In the past scientists had struggled to make chimeric embryos crossing together two species (Source), but thanks to everyone's favorite gene-editing technology CRISPR/Cas9 researchers were able to knock out the genes which allow organs to form in a mouse embryo. The researchers then injected stem cells into the embryo. These stem cells had the necessary genes for organ development, and thus the embryo could grow and organs could develop.

Creation of a Cross Species Chimera

Researchers began by injecting the organ growth deficient mouse embryos with Rat stem cells, and implanted the mouse embryo into a mouse's uterus and allowed it to grow. Interestingly, since the stem cells were the source of the genes allowing for organ development, the organs that grew in the mouse embryo were actually rat organs. The researchers had successfully created a mouse-rat chimeric fetus with rat organs.

Then Things Got Weird

The mouse-rat chimera was exciting and all, but the researchers decided to press forward. They sought to cross two organisms a little further apart. Like Humans and Pigs... (oh boy...).

They created pig embryos that, similar to the mouse variety described above could not develop organs, and injected them with human stem cells. The human stem cells that they used had also already been genetically modified to express a green fluorescent protein (which I have discussed previously in this post) this fluorescent protein would allow the researchers to track whether human cells grew in the pig embryos as the human cells would be green.

This is exactly what they saw, green fluorescent human cells grew in the pig embryo as it developed. Before you get too horrified only 1 out of every 100,000 cells in this pig-human chimera was a human cell, that's really not very many, but they are still there.

The researchers had successfully created a pig-human chimera. Thankfully the chimeras were destroyed after 4 weeks of growth due to ethics regulations, however the technology to create such a creature now officially exists. Research will continue to investigate how functional these human cells are that develop in these pig-human chimeras...

The End Goal Is Noble, BUT...

The goal of this sort of research, to create human organs that can be grown in animals for transplantation is noble, the intention is obviously to save lives.

That said, it makes me uncomfortable that we are creating chimeric organisms that are part human. What do you think about this technology? This isn't science fiction anymore, it's very much real and it's just one of the many large ethical dilemmas which will be plaguing us as we move forward and technological advancements continue.

If you are interested to read more check out this nature.com editorial:

http://www.nature.com/news/hybrid-zoo-introducing-pig-human-embryos-and-a-rat-mouse-1.21378

Or dive directly into the primary article (though I warn you this is a very dense read)

Other Sources

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Hive account@justtryme90. I am a PhD holding biochemist with a love for science. My future science blog posts will cover a range of topics in the biology/chemistry fields.

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Newslink: Scientists Create A Human-Pig Chimeric Fetus