The feat makes the headlines. A 57 year old American was transplanted on Friday from a genetically modified pig’s heart. If this is an achievement, it is mainly because the patient is doing well three days later and there is, for the time being, no sign of rejection by his body. The operation potentially opens the door to great breakthroughs thanks to xenografting.
How did that happen ?
The operation is still recent. It was conducted Friday on David Bennett. The 57-year-old American was declared ineligible to receive a human transplant. “It was either death or this transplant. I want to live. I know it’s quite risky, but it was my last option, ”he said before the intervention, according to comments reported by University of Maryland School of Medicine, who led this incredible operation.
The patient had been hospitalized six weeks earlier with a life-threatening arrhythmia (an irregular heartbeat). He had only lived since thanks to the establishment of extracorporeal oxygenation.
The intervention took place in several stages. Surgeons “operated” on the pig to remove its heart and transport it to the patient to whom it was transplanted. To accompany the operation, a new anti-rejection drug was used in addition to the drugs traditionally used. These must make it possible to neutralize the immune system to prevent the transplant from being considered as a foreign body by the body. A video posted on YouTube by the university shows the meticulous execution of surgeons as well as the pig’s heart beating inside the human body.
How was the operation made possible?
The “donor” pig is not an ordinary pig: it is of an animal genetically modified for these purposes. “10 unique genetic modifications made in donor pigs,” summarizes the University of Maryland School of Medicine. Thus, three genes usually responsible for the rapid rejection of pig organs by the human organism have been “deleted” from the animal and replaced by six human genes which are supposed to aid in the “immune acceptance” of the animal organ by the animal organism. ‘man. One of the genes was also deleted “to prevent excessive growth of pig heart tissue”. “The pig’s genome has been purified”, summarizes the Parisian Benoit Averland, deputy director of sampling and transplantation at the Biomedicine Agency.
It is a pig with identical genetic modifications which allowed the transplant of an animal kidney on a human last September, in New York, on a brain dead patient. “Urine production and creatinine levels, key indicators of a properly functioning kidney, were normal and equivalent to those observed during a human kidney transplant”, the scientists had rejoiced, explaining not to have observed no sign of rejection. The experiment only lasted 54 hours, after which it was decided to cut off the patient’s artificial respiration.
“The heart of the pig has a morphology quite similar to ours and it is the animal which has the closest genetic proximity to humans”, explains Benoit Averland. Other advantages: they grow easily, it only takes a few months for them to reach the ideal size for transplantation to the human body and there is no problem with the possible disappearance of the species, close or future. It is also for these reasons that transplants in humans of their heart valves, which are not organs, have been common practice for years.
Why is it a feat?
Xenografting (the transplant of an organ from one species to another) is nothing new. The last famous case dates back to 1984 when a baby of a few days, nicknamed “Baby Fae”, born with a heart problem, was transplanted with a baboon heart. This was already a feat: the child had survived three weeks, after which his immune system rejected the transplant. “The feat was more a matter of research than of the hope of life,” explains Benoit Averland.
The feat of David Bennett’s operation is therefore based on the non-rejection by the human organism of the animal transplant. “Not having had a rejection in the hours following the transplant is incredible,” says Benoit Averland. One has managed to trick the organism to ensure that it does not determine the heart as to destroy. “
It remains to be seen how long this will last, “but two days is already a feat”. An experiment, the results of which had been published in 2016, had determined that the survival of a baboon transplanted with a pig heart similar to that used for the David Bennett transplant had reached up to 945 days (with a duration of median survival of nearly 300 days).
Three days after the operation, David Bennett was “still doing well”. His case will be “closely watched over the next few days and weeks” to see if the solution is viable. “We are proceeding with caution, but we are also optimistic that this world’s first surgery will provide an important new option for patients in the future,” added Bartley Griffith, the surgeon who operated on the American patient. Benoit Averland says: “If he does not reject, he will be able to live like any transplant patient. “And give hope to many people waiting for a transplant.