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The first Human-Pig Hybrid Embryo has been created, courtesy of stem cells

Posted by Douglas W. Stoddard MD, M Sp Med, Dip Sport Med, ES on 29 January 2017
The first Human-Pig Hybrid Embryo has been created, courtesy of stem cells

Remember back in mid-August when we foretold - okay, read online somewhere - that animal-human stem cell 'chimera' research was just around the corner?

(See, we did say that.)

Well, it took scientists from the Salk Institute for Biological Studies just five months to take advantage of The National Institutes of Health's (NIH) lifted moratorium on stem cell experimentation, creating the world's first human-pig hybrid embryo.

The embryo, which contains cells from the two-genetically unique species, is a giant first (and controversial) step towards growing human organs in non-human hosts for transplantation.

The Need for Organs

Every ten minutes, another name is added to the U.S.'s national waiting list of organ transplants. And each day, 22 people on the list are crossed off - not because they received a successful transplant, but from death due to the extremely long wait for healthy, compatible human organs.

Instead of waiting and waiting for the perfect donor who may never come, the stem cell technology used to create human-pig embryos can help provide the organs that're the difference between life and death.

Embryonic stem cell research was thought to be way out of reach, at least with the resources at the disposal of researchers today. Add on the ineligibility for public funding in the past, plus a sullied public opinion of the 'controversial' stem cell field, a human-animal hybrid was as plausible as Matt Stone & Trey Parker's ManBearPig.

That negativity didn't deter lead study author Jun Wu from continuing with stem cell experimentation, looking no further than actual chimeras - human-bird hybrids some call angels - for inspiration.

"In ancient civilizations, chimeras were associated with God," he says, and our ancestors thought, "the chimeric form can guard humans."

That's what his team hopes the human-animal hybrids will one day do.

Build-Your-Own-Chimera

Just getting to the initial stage of growing human organs from scratch took tremendous time and resources.

Juan Carlos Izpisua Belmonte, a professor at the Salk Institute's Gene Expression Laboratory, scoffed at the concept of using a host embryo to grow organs - in his eyes, it was simple science.

Flash forward four years, and Belmonte and his team of 40 collaborators from across the globe are only just uncovering the breadth of this stem cell technology's potential.

Before getting to the embryonic level where scientists would introduce animal cells into the embryo of another, Belmonte's team referred to past chimera research done on mice & rats, taking it one step further.

Using CRISPR/Cas9 gene editing, the team extracted the genes for certain organ formation from mouse 'blastocysts', or the cellular stage just before the embryo, like wiping a computer hard drive. Next, rat stem cells were injected into the mouse blastocysts, where they found the stem cells 'filling in the gaps', developing the mice's missing organs like hearts, pancreas', and eyes that were deleted.

Not only were the resulted hybrids healthy enough to live to adulthood, some even grew gall bladders - which haven't been in the species for 18 million years.

Chimeras - Controversial, or Celebrated?

Moving to more genetically-distinct animals, the Salk Institute researchers tried the same process, but with pig blastocysts instead. This trial failed, with the team citing each species differing gestation times as the cause of incompatibility.

So they decided to take a chance, and move onto pigs and humans, who also have dissimilar gestation times, but share similar organs. This was followed by A LOT of trial and error to find stem cells that would develop along a similar timeline as the pig's.
"We tried three different types of human cells, essentially representing three different times," says Wu.

Wu & Co. finally came to the conclusion that native pluripotent stem cells cells heralded for their 'unlimited potential' to differentiate in to any cell type weren't as effective as cells that had more time to develop.

Using the Goldilocks method of selection - not too old, not too premature - the scientists used just-right human cells for injection into the pig embryos.

Amazingly, they survived.

The embryos were carried by adult pigs for about a month, before they removed for testing.

In total, the scientists 'built' 186 successful later-stage chimeric embryos said Wu, and "we estimate [each had] about one in 100,000 human cells."

And therein lies the next challenge for the large research team. While the first step towards creating life-saving organs for people on donor lists is plausible with these findings, the low percentage of human cells could be a problem in the long run.

Researchers must find a solution to the human tissue appearing to impede the growth of the embryo; organs grown from developing embryos like these would likely be rejected by the human body thanks to the overwhelming amount of pig tissue. They'll therefore need to determine whether it's possible to increase the number of human cells an embryo can manage.

The current research is a start, but it remains unknown if that's a barrier that can be overcome.

And while we could be years away from building functioning human organs from cells, the methods used could provide insight in other valuable areas, like the study of human embryo development, or understanding deadly diseases.

"At this point, we wanted to know whether human cells can contribute at all to address the 'yes or no' question," Belmonte said in a press release.

"Now that we know the answer is yes, our next challenge is to improve efficiency and guide the human cells into forming a particular organ in pigs."


While we utilize stem cell treatments & therapies to treat chronic pain & injury, rest assured that RegenerVate's clinics doesn't use pig, swine, or rodent cells in any of our regenerative medicines or injection therapies.

From tendon, muscle, and meniscal tears, to arthritis and other ailments, our treatments utilize your body's own natural healing ability to expedite the recovery process. Call us today at 1-855-847-3975 to schedule an appointment, or stop by one of our RegenerVate locations!

Author: Douglas W. Stoddard MD, M Sp Med, Dip Sport Med, ES
About: Dr. Stoddard is a sport medicine and injection physician in Toronto and is the Medical Director of RegenerVate. After receiving his medical degree from the University of Toronto, he trained in Australia at the Australian Institute of Sport in Canberra, obtaining his Master Degree in Sport Medicine. His injection training, including ultrasound, PRP and Prolotherapy, was primarily done in the USA. He is a diplomat of the Canadian Academy of Sport and Exercise Medicine (CASEM), is married and a proud father of two boys. He is an avid triathlete and occasional guitar player.
Tags: Stem Cell Research

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