Scientists led by two Harvard University geneticists, George Church and Luhan Yang, have genetically modified porcine embryos in order to make their organs compatible for human transplantation in the future.
Their study, published in the Science journal on 10 August, explains the procedure. Using CRISPR, they sliced out genes causing viruses  capable of infecting humans, from the porcine genome. Such viruses are the main technical obstacle to xenotransplantation . As this initial step was carried out on cells, the latter were then cloned to produce pig embryos and transferred to a surrogate sow. Thirty-seven piglets were born through these experiments with “potentially suitable organs for xenotransplantation”. Fifteen are still alive today. The eldest is four months old.
The heart valves and pancreas of pigs are already used in human transplant surgery. Based on this recent study, scientists hope, in the future, to transplant “larger pig organs”, which “can reach an ideal size for humans” and thus resolve the organ donor shortage. However, as far as other scientists are concerned, pig organs remain a risk for man because viruses could still be present in the pig genome.
 Porcine endogen retrovirus or PERVs
 Organ transplantation where the donor is a different biological species from the recipient
AFP (10/08/2017); New scientist, Clare Wilson (10/08/2017)