What you're seeing right now is a pig heart beating inside a human being for
the first time ever. This experimental organ transplant is breaking so many boundaries,
but let’s start with the fact that it involves gene editing and…cocaine?
Let’s start simple. Any transfer of cells or tissues across species is called
xenotransplantation. Even though it sounds like science fiction, this is actually nothing new. Pig
heart valves have been replacing worn-out human heart valves for the past 30 years.
That’s because pig hearts are actually very similar in structure and size to human hearts.
But replacing the entire heart with one from another species…
that’s totally uncharted territory.
See, a major roadblock to xenotransplantation
is our immune systems. Pig cells are covered in surface structures that our body recognizes as
non-human. This can trigger something called graft rejection, where the human recipient’s immune
system tries to get rid of the new organ. This even happens with transplants from other humans.
But we need whole hearts, and we need them now. Heart disease is the leading cause of
death worldwide. Even in places that have enough resources to provide valve replacements or heart
transplants, there just aren’t enough organs to go around.
Thousands of people in the U.S. alone are on
the waitlist for a new heart, and an average of 17 people on organ transplant waitlists die everyday.
That’s because, until now, we’ve only had human hearts as our whole
organ transplant option. Pig hearts fit the bill and could help us solve this problem,
but what about that pesky immune response? The answer just might be…genetic modification!
The parent company behind Dolly the sheep,
you know, the world’s first cloned animal,
has also been working on rearing pigs genetically engineered just for organ
transplant. In 2021, these pigs were used to successfully transplant kidneys into two
legally brain dead people whose bodies were being kept alive on ventilators. So, we moved on to hearts.
Scientists used gene-editing technology to make ten major genetic modifications to these pigs:
‘knocking out’ three pig genes behind those cell surface molecules that trigger the human immune
response, removing a tissue proliferation gene, making sure the pig heart won’t keep growing
after it’s inside the recipient, and inserting six human genes that will hopefully help with
immune acceptance of the heart. There are also several other
never-before-used techniques at play here. The doctors are giving the recipient
an experimental drug to suppress his immune system for extra protection against graft rejection. They
also used a brand new machine to pump fluid through the heart while it was awaiting transplant.
And that fluid contained relatively standard cortisol and adrenaline,
with the nonstandard addition of cocaine. It’s not clear exactly how or why, but cocaine seems to
help keep the heart ready for transplant between pig and human.
Getting approval to use the drug apparently caused a bit
of a nightmare, but the team does think it helped. Now, with xenotransplantation, there is also a risk
of transferring diseases across species. There are lots of viruses lurking in pig
genomes. The transplant scientists made ‘precision alterations’ to remove these in the
hopes of making disease transfer less likely. But this is a ‘time will tell’ kind of deal.
So…who would say yes to all this? 57-year old David Bennett was the recipient of
this pig heart. And Bennett’s terminal heart disease eventually made him too sick for
any other option—it was this experimental pig heart surgery or death.
The FDA gave emergency approval for just this one
procedure, making Bennett the only patient allowed to have this surgery. The scientists will keep
testing the procedure in baboons, but they really want to get to clinical trials with even more humans.
And of course, this breakthrough raises all kinds of ethical questions. ‘Farming’ hearts like this
means a reliable supply of these organs could be available as soon as patients need them,
but…raising intelligent animals like pigs just to be slaughtered for organ donation
has many animal rights activists in uproar. There’s also the medical ethics of it all.
Is it even ethical to offer a dangerous procedure with so many unknowns to people who
are terminally ill and maybe desperate, essentially making them human guinea pigs?
As of this writing in February, 2022, Bennett appears to be doing well, with no signs of
rejection yet and he's able to breathe and speak on his own.
It is too early to say if the surgery
will be a long-term success, but it is an exciting first step towards a solution to the world’s organ
shortage. Who knows? Maybe in the future, we could see genetically modified xenotransplantation of organs
become a norm for other organs too. Want more on how to fix a broken heart?
Then check out this video on live heart patches here, and keep coming back to Seeker for all
your groundbreaking biomedical news. If you have another topic like this you want us to cover,
leave us a comment down below, and as always, thanks for watching. I’ll see you next time.