Scientists Created the First Successful Human-Pig Hybrid

Scientists have revealed that they have managed to create a hybrid of a human and animal in the lab. They said that the success of the project proves that the cells of a human being can be introduced into an organism that is non-human and they can survive and go on to grow in a host animal, which in this instance is a pig.

This is a biomedical advancement that scientists have always dreamed about but at the same time has left scientists in a quandary as they have hoped to be able to reach a solution to the shortage of donor organs, which is now at a critical level. Scientists said that every ten minutes someone is put on the national waiting list to have an organ transplant. Every day 22 people who are waiting on that list pass away as they have not been given the organ they need. They posed the question of what if people did not have to rely on the death of another and a donor as custom organs could be grown inside a host animal.

While this might sound far-fetched and something out of a movie, scientists are now one step closer to making this become reality. Researchers from the Salk Institute said that they have created a chimera: an organism that is able to contain cells that come from two separate species.

In the past, this is something that has been out of reach of the scientists. At the moment experiments such as these are not eligible to receive funding in the US. Up to this point, Salk and the rest of the team have had to rely on private donations. Another factor that hampers organism creation that is part animal and part human is the opinion of the public.

Jun Wu, the lead study author at the Salk Institute believes that people should look at it from a different perspective and pointed to mythical chimeras which he said included human-bird hybrids that people call angels. He went on to say that ancient civilizations always linked chimeras with God. Ancestors believed that a chimera will guard over a human and he pointed out that this is what the scientists hope for with the human-animal hybrid in the future.

Basically, there are two different ways to make a chimera. The first way relies on introducing organs from one animal to another and this is the riskiest due to the fact that the immune system of the host could reject the organ. The other way starts back at an embryonic level when one of the cells of one animal is introduced to the embryo of the other and they then fuse and grow into the hybrid. While this might sound strange it does happen to be one way of eventually being able to solve some of the most puzzling of biological issues with organs that are grown in the lab.

When stem cells were first discovered by scientists it looked as though they contained a scientific promise that was infinite. However, being able to convince the cells to grow into the organs and tissues that were right was another matter and very difficult to achieve. The cells need to be able to survive in Petri dishes and the scientists used what they termed “scaffolds” to try to ensure that the organs would grow into the correct shapes. Patients would also have to undergo procedures that were not only invasive but painful too to harvest the tissues that were needed to start the process.

Juan Carlos Izpisua Belmonte, a professor at the Salk Institute Gene Expression Laboratory said that the idea of using a host embryo so that organs could be grown seemed at first to be something that was straightforward. This, in fact, turned out not to be so and it took Belmonte and his team over 40 years to work out how to get a human-animal chimera.

Scientists had already found a way of taking a mouse and growing pancreatic tissue belonging to a rat. They revealed that the pancreas had been used to successfully treat diabetes as parts of the organs had been transplanted into mice that were diseased.

This is a concept that was taken one step further by the researchers of the Salk group and they made use of CRISPR, the genome editing tool, to get into the blastocysts of the mouse. They then deleted the genes belonging to the mice that need to grow certain organs. The scientists then introduced the stem cells from rats that would be capable of producing the organs and found that the cells flourished. The resulting mice lived to become adult mice and some of them grew chimeric gallbladders that were rat and mouse cells, despite the fact that rats do not have that organ.

The researchers then took the stem cells from the rats and they were injected into the blastocysts of pigs but it failed as pigs and rats have gestation times that are very different.

Pigs, on the other hand, do have a similarity to humans and their organs look a great deal like those of humans. The task was still not easy as scientists had to get the timing perfect when introducing the cells of humans to the pigs so that they did not kill them.

Ju Wu said that they had tried three types of cells from humans during the experimental process. Finally, they found that naïve pluripotent cells would not last as long as ones with more development. The embryos survived when they injected the human cells that were just right into the pig embryos. These were then put into the adult pigs, which were left to carry them for about four weeks before being removed and then analyzed.

186 late stage chimeric embryos survived with each of them having about 1 in 100,000 cells from humans.

Scientists are now trying to work out if it is going to be possible to boost the number of human cells as the number is low right now. It is thought that it might take many more years before human organs that are functioning will be seen, but the work has been described as being a breakthrough.

Credits: National Geographic  via


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