The world's first transplant of a genetically altered pig heart into an ailing human is a landmark for medical science, but the operation and approach raises substantial safety and ethical concerns.
The University of Maryland Medical Center surgeons spent eight hours on Friday evening performing a heart transplant on David Bennett, who had been in the hospital for more than a month with terminal heart failure.
It was a very special procedure. Bennett was too sick to qualify for a human heart transplant. The medical team sought emergency permission from the FDA to transplant a heart from a genetically altered pig.
The pig's heart was created by Revivicor, a spin-out from the UK company that created Dolly the Sheep. Revivicor has pigs that are engineered to avoid immune rejection. Alterations made to the genetics remove a sugar molecule from tissues that cause organ rejection. The FDA approved the operation and the team's proposal to use an experimental drug to prevent Bennett's body from rejecting the organ.
David Bennett is the world's first human recipient of a pig heart. The person is Bartley Griffith/AP.
Bennett was awake and breathing on his own, but it was too soon to say the operation was a success. Doctors are waiting to see how Bennett fares in the coming weeks and months.
The idea of harvesting organs from animals to save human lives has a long and chequered history. The approach is seen as a way to slash waiting lists for desperately ill patients, while animal rights activists see it as dangerous and unethical. In the 1960s, a number of chimp kidneys were used by US doctors, but only one of them died within weeks. A premature baby in California died three weeks after receiving a baboon heart.
Even with human donors, recipients need constant immunosuppression to prevent their bodies from attacking the transplants. Revivicor's pig heart is designed to be less prone to immune rejection than standard animal organs, but it is not certain how well it will be accepted by the body. Bennett will need more potent immunosuppression than usual because it comes from another species.
The pigs are the focus of recent work because their organs are very similar to those of humans. The effort to make pig organs invisible to the human immune system is not the only challenge. Scientists abandoned their work on donor pigs in the 1990s because they realized that the animals' genes could be used to harm humans. The risk of transplant organs spreading infections to vulnerable patients was raised.
The problem is being overcome by taking genome editing to another level. Scientists have made alterations to pig genes to remove retroviruses from pig tissues in order to make the organs safer when they are eventually used.
Clinical trials will decide how well animal organs work. Many companies are starting trials to see if the organs are safe and effective in other animals and humans. The hope for those with failing organs is with the generosity of human donors.
All Rights Reserved © 2024
