"Surgeons in New York have successfully attached a kidney
grown in a genetically altered pig to a human patient and found that the organ
worked normally, a scientific breakthrough that one day may yield a vast new
supply of organs for severely ill patients.
Researchers have long sought to grow organs in pigs that are
suitable for transplantation into humans. Technologies like cloning and genetic
engineering have brought that vision closer to reality in recent years, but
testing these experimental organs in humans has presented daunting ethical
questions.
So surgeons at N.Y.U. Langone Health took an astonishing
step: With the family’s consent, they attached the pig’s kidney to a brain-dead
patient who was kept alive on a ventilator, and then followed the body’s
response while taking measures of the kidney’s function. It is the first operation
of its kind.
The researchers tracked the results for just 54 hours, and
many questions remained to be answered about the long-term consequences of such
an operation. The procedure will not be available to patients any time soon, as
there are significant medical and regulatory hurdles to overcome.
Still, experts in the field hailed the surgery as a
milestone.
The kidney used in the new procedure was obtained by
knocking out a pig gene that encodes a sugar molecule that elicits an
aggressive human rejection response.
The pig was genetically engineered by
Revivicor and approved by the Food and Drug Administration for use as a source
for human therapeutics.
Dr. Montgomery and his team also transplanted the pig’s
thymus, a gland that is involved in the immune system, in an effort to ward off
immune reactions to the kidney.
After attaching the kidney to blood vessels in the upper
leg, the surgeons covered it with a protective shield so they could observe it
and take tissue samples over the 54-hour study period.
Urine and creatinine levels were normal, Dr. Montgomery and
his colleagues found, and no signs of rejection were detected during more than
two days of observation.
“This is a huge breakthrough,” said Dr. Dorry Segev, a
professor of transplant surgery at Johns Hopkins School of Medicine who was not
involved in the research. “It’s a big, big deal.”
A steady supply of organs from pigs — which could eventually
include hearts, lungs and livers — would offer a lifeline to the more than
100,000 Americans currently on transplant waiting lists, including the 90,240
who need a kidney. Twelve people on the waiting lists die each day.
An even larger number of Americans with kidney failure —
more than a half million — depend on grueling dialysis treatments to survive.
In large part because of the scarcity of human organs, the vast majority of
dialysis patients do not qualify for transplants, which are reserved for those
most likely to thrive after the procedure.
The transplanted kidney was obtained from a pig genetically
engineered to grow an organ unlikely to be rejected by the human body. In a close
approximation of an actual transplant procedure, the kidney was attached to
blood vessels in the patient’s upper leg, outside the abdomen.
The organ started functioning normally, making urine and the
waste product creatinine “almost immediately,” according to Dr. Robert
Montgomery, the director of the N.Y.U. Langone Transplant Institute, who
performed the procedure in September.
Although the kidney was not implanted in the body, problems
with so-called xenotransplants — from animals like primates and pigs — usually
occur at the interface of the blood supply and the organ, where human blood
flows through pig vessels, experts said.
After attaching the kidney to blood vessels in the upper
leg, the surgeons covered it with a protective shield so they could observe it
and take tissue samples over the 54-hour study period.
Urine and creatinine levels were normal, Dr. Montgomery and
his colleagues found, and no signs of rejection were detected during more than
two days of observation.
“There didn’t seem to be any kind of incompatibility between
the pig kidney and the human that would make it not work,” Dr. Montgomery said.
“There wasn’t immediate rejection of the kidney.”"