A new medical record was set on Monday as a man struggling with heart disease received a genetically modified heart from a pig, raising fresh hopes for animal to human organ swap.
The operation by surgeons at the University of Maryland Medical Centre is the first successful transplant of a pig’s heart to human and the patient is doing well, according to the New York Times.
Scientists have worked anxiously to develop pigs whose organs would not be rejected by the human body, with research accelerated in the past decade by new gene editing and cloning technologies. The heart transplant comes just months after surgeons in New York successfully attached the kidney of a genetically engineered pig to a brain-dead person.
Researchers hope procedures like this will usher in a new era in medicine in the future when organs for replacement are no longer in short supply for the more than half a million Americans who are waiting for kidneys and other organs.
“This is a watershed event,” said Dr. David Klassen, the chief medical officer of the United Network for Organ Sharing and a transplant physician. “Doors are starting to open that will lead, I believe, to major changes in how we treat organ failure.”
But he added that there were many hurdles to overcome before such a procedure could be broadly applied, noting that rejection of organs occurs even when a well-matched human donor kidney is transplanted.
“Events like these can be dramatised in the press, and it’s important to maintain perspective,” Dr. Klassen said. “It takes a long time to mature a therapy like this.”
Bennett decided to gamble on the experimental treatment because he would have died without a new heart, had exhausted other treatments, and was too sick to qualify for a human donor heart, family members and doctors said.
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His prognosis is uncertain. Bennett is still connected to a heart-lung bypass machine, which was keeping him alive before the operation, but that is not unusual for a new heart transplant recipient, experts said.
The new heart is functioning and already doing most of the work, and his doctors said he could be taken off the machine on Tuesday. Bennett is being closely monitored for signs that his body is rejecting the new organ, but the first 48 hours, which are critical, passed without incident.
He is also being monitored for infections, including porcine retrovirus, a pig virus that may be transmitted to humans, although the risk is considered low.
Xenotransplantation
Xenotransplantation, the process of grafting or transplanting organs or tissues from animals to humans, has a long history. Efforts to use the blood and skin of animals go back hundreds of years.
In the 1960s, chimpanzee kidneys were transplanted into some human patients, but the longest a recipient lived was nine months. In 1983, a baboon heart was transplanted into an infant known as Baby Fae, but she died 20 days later.
Pigs offer advantages over primates for organ procurements, because they are easier to raise and achieve adult human size in six months. Pig heart valves are routinely transplanted into humans, and some patients with diabetes have received porcine pancreas cells. Pig skin has also been used as a temporary graft for burn patients.
Two newer technologies — gene editing and cloning — have yielded genetically altered pig organs less likely to be rejected by humans.
Pig hearts have been transplanted successfully into baboons by Muhammad Mohiuddin, a professor of surgery at the University of Maryland School of Medicine who established the cardiac xenotransplantation programme with Griffith and is its scientific director.
But safety concerns and fear of setting off a dangerous immune response that can be life-threatening precluded their use in humans until recently.
