As there is a global shortage of organs, scientists are experimenting with prolonging people's lives with organs from other species.
A monkey in which a kidney from a genetically engineered pygmy pig was implanted lived for more than two years after the transplant, the news was published in Nature. This experiment is also part of the work aimed at transplanting organs from other species into people due to the global organ shortage. Pig kidneys implanted in monkeys provided many lessons.
In the United States, the demand for new organs to replace damaged or diseased organs far exceeds the supply. Last week, almost 104,000 Americans were on the transplant waiting list, of which about 89,000 people were waiting for a kidney.
"There simply aren't enough kidneys," eGenesis CEO Mike Curtis told Sciencenews.org, adding that most of those waiting never receive a kidney because they die during dialysis. According to Mike Curtis, interspecies organ transplantation - in this case, the transplantation of a pig kidney - could be the solution to the huge organ shortage.
However, the road is full of pitfalls. Pig organs cannot be transplanted directly into humans, as our immune system sees them as foreign - and rejection begins.
The human immune system detects sugars in the pig's cells that should not be in the body. However, after the genetic modification, there is a chance that the body will not attack it, but accept it. Jayme Locke, a transplant surgeon at the University of Alabama in Birmingham, told the scientific portal: the genome of the donor animals is modified in such a way that "the pig kidney is made as human as possible so that our body does not immediately attack it." As part of gene editing, human genes are inserted to prevent organ rejection and eliminate potentially harmful retroviruses embedded in the pig genome.
Researchers have made significant progress in recent years. In 2021, a group of American doctors transplanted a genetically modified pig kidney into a brain-dead woman. In 2022, Jayme Locke's group published the first peer-reviewed study of a genetically engineered pig kidney transplanted into a brain-dead human. In August of this year, they reported that pig kidneys transplanted into brain-dead humans functioned normally and produced urine.
In 2021, doctors also implanted modified pig hearts into two brain-dead people – and even into a living person for the first time in early 2022. David Bennett, 57, of Maryland, survived the transplant by two months. This September, Lawrence Faucette became the second living person to receive a genetically modified pig heart.
Mike Curtis' team also transplanted pig kidneys into monkeys. Because these were genetically engineered pig kidneys, the monkeys had to be given strong immunosuppressive drugs to prevent the animals from rejecting the new organs.
These types of animal experiments are important, according to Jayme Locke, because with this solution researchers can study long-term organ function, which is difficult to demonstrate in people suffering from brain death.
During the team's experiments, eight out of 15 monkeys were given pig kidneys that carried human genes. These animals lived for at least 176 days, but one monkey lasted much longer: 758 days after a kidney transplant. Monkeys implanted with pig kidneys devoid of human genes did not fare nearly as well, living an average of 24 days.
According to experts in the field, this work is a promising element in the process of using other species to address the global organ shortage.
