© Photo: Wu et al. / Cell 2017
An international team of geneticists for the first time created a full-fledged chimeric embryos, in which pigs combined with human cells and other mammals. This opens the way for growing human organs in animals body, said in an article published in the journal Cell.
«Work on this problem took four years. We clearly underestimated how much effort will be needed to implement this task. This is an important first step toward growing human organs in a pig’s body. Now we need to figure out how to make human cells turn into organs we need to realize our real goal is to learn how to grow transplanted organs,» said Juan Belmonte (Belmonte, Juan) from the Salk Institute in La JOLLA (USA).
About 15 years ago biologists began to actively discuss the possibility of so-called xenotransplantation – the transplant of animal organs into the human body. To implement this idea in life, as it seemed before, it was necessary to solve a simple problem – to force the immune system to reject foreign organs.
This task, as you might guess, is still not solved, but now geneticists are working to create a special gene therapies, making the bodies of pigs and other animals invisible to our immune system. Just last year, the famous American geneticist George Church has approached this task by removing part of the label of «friend or foe» with the help of the genomic editor CRISPR/Cas9.
This editor is DNA used as a «killer» of selectively killing the cells in the embryo at the time when the inside of the embryo begins to form a particular organ. At this point, scientists injected cultured stem cells of another animal species that fill a niche and turn into the body «blank» which was destroyed with the help of CRISPR/Cas9. Other tissues and organs are not affected, which is important for ethical reasons.
To check this technique on mice, growing rat pancreas in their body, scientists have spent almost four years adapting this technique to work with human and pig cells. The problem was that a pig fetus is growing three times faster than his human counterpart, and Belmonte and his colleagues very long to find the right time for implantation of human cells.
Solve this problem, scientists have successfully replaced the future the cells of the muscles in dozens of pig embryos, and implanted them back into the womb of their adoptive mothers. About two-thirds of the embryos successfully developed throughout the month, and then scientists had to stop the experiment for ethical reasons, in accordance with the laws of the United States.
Success in implementing this task, as noted by Belmonte, opens the way to real create a full-fledged human organs ready for transplant and not is shed by our body. Now Belmonte and his colleagues are working on adapting CRISPR/Cas9 for in the body of a pig, and obtaining all necessary permits for such experiments.