This time around,
surgeons in Alabama transplanted a pig's kidneys into a brain-dead man — a
step-by-step rehearsal for an operation they hope to try in living patients
possibly later this year.
“The organ shortage is
in fact an unmitigated crisis and we've never had a real solution to it,” said
Dr. Jayme Locke of the University of Alabama at Birmingham, who led the newest
study and aims to begin a clinical trial of pig kidney transplants.
Similar experiments have made headlines in
recent months as research into animal-to-human transplants heats up.
Twice this fall, surgeons at New York
University temporarily attached a pig's kidney to blood vessels outside the
body of a deceased recipient to watch them work. And earlier this month,
surgeons at the University of Maryland Medical Center gave a dying man a heart
from a gene-edited pig that so far is keeping him alive.
But scientists still needed to learn more
about how to test such transplants without risking a patient's life. With the
help of a family who donated a loved one's body for science, Locke mimicked the
way human organ transplants are done — from removing the pig “donor” kidneys to
sewing them inside the deceased man's abdomen.
For a little over three days, until the
man's body was removed from life support, the pair of pig kidneys survived with
no sign of immediate rejection, her team reported Thursday in the American
Journal of Transplantation.
That was only one of several key findings.
Locke said it wasn't clear if delicate pig kidney blood vessels could withstand
the pounding force of human blood pressure - but they did. One kidney was
damaged during removal from the pig and didn't work properly but the other
rapidly started producing urine as a kidney should. No pig viruses were
transmitted to the recipient, and no pig cells were found in his bloodstream.
But Locke said the kidney experiment could
have more far-reaching impact - because it shows that a brain-dead body can be
a much-needed human model to test potential new medical treatments.
The research was conducted in September
after Jim Parsons, a 57-year-old Alabama man, was declared brain-dead from a
dirt bike racing accident.
After hearing this kind of research
"had the potential to save hundreds of thousands of lives, we knew without
a doubt that that was something that Jim would have definitely put his seal of
approval on,” said Julie O'Hara, Parsons' ex-wife.
The need for another source of organs is
huge: While more than 41,000 transplants were performed in the US last year, a
record, more than 100,000 people remain on the national waiting list. Thousands
die every year before getting an organ and thousands more never even get added
to the list, considered too much of a long shot.
Animal-to-human transplants, what's called
xenotransplantation, have been attempted without success for decades. People's
immune systems almost instantly attack the foreign tissue. But scientists now
have new techniques to edit pig genes so their organs are more human-like — and
some are anxious to try again.
The recent string of pig experiments “is a
big step forward,” said Dr. David Kaczorowski of the University of Pittsburgh
Medical Center. Moving on to first-stage trials in potentially dozens of people
is “becoming more and more feasible.”
A heart transplant surgeon, Kaczorowski has
done experiments testing pig organs in non-human primates that helped pave the
way but “there are only things we can learn by transplanting them into humans.”
Hurdles remain before formal testing in
people begins, including deciding who would qualify to test a pig organ, said
Karen Maschke, a research scholar at the Hastings Center who will help develop
ethics and policy recommendations for the first clinical trials under a grant
from the National Institutes of Health.
Scientists also still have much to learn
about how long pig organs survive and how best to genetically alter them,
cautioned Dr. Robert Montgomery of NYU Langone Health, who led that centre's
kidney experiments in the fall.
“I think different organs will require
different genetic modifications,” he said in an email.
For the newest kidney experiment, UAB
teamed with Revivicor, the subsidiary of United Therapeutics that also provided
organs for the recent heart transplant in Maryland and the kidney experiment in
New York. Company scientists made 10 genetic changes to these pigs, knocking
out some genes that trigger a human immune attack and make the animals' organs
grow too large — and adding some human genes so the organs look less foreign to
people's immune systems.
Then there are practical questions such as
how to minimise time spent getting pig organs to their destination. UAB housed
the altered pigs in a germ-free facility in Birmingham complete with an
operating room-like space to remove the organs and ready them for transplant.
Revivicor chief scientific officer David
Ayares said future plans include building more such facilities near transplant
centres.