PBS News Hour

AMNA NAWAZ: In an historic first, a kidney from a genetically modified pig has been successfully transplanted into a human.

As William Brangham reports, the technique used in the surgery last weekend is a big step forward and could have wide implications.

WILLIAM BRANGHAM: The patient here is a 62-year-old Black man whose kidneys were failing, and he was on dialysis for years.

This kind of human-to-animal transplant, known as xenotransplantation, is one that researchers hope to do more of because there aren't nearly enough human organs for the thousands of people in need.

But putting animal tissue into a human body is complicated.

The body often rejects foreign tissue.

So, in this case, scientists removed several genes from the pig that can trigger that rejection.

To help us understand this brave new world, we are joined by Dr. Leonardo Riella.

He's the medical director for kidney transplantation at Massachusetts General Hospital, where this historic event took place.

Dr. Riella, so good to have you on the program.

Congratulations on this historic successful first.

I take it is still successful, right?

The patient is doing well?

DR. LEONARDO RIELLA, Massachusetts General Hospital: The patient is doing extremely well.

Thank you for asking.

WILLIAM BRANGHAM: And what is his - - so, his prognosis -- normally, if you had a kidney transplant, how soon would he be getting out of the hospital?

And do you know what his -- when he will be getting out?

DR. LEONARDO RIELLA: Yes, so most patients remain in the hospital after a kidney transplant for about five to six days.

On his case, we're probably going to keep about a week or nine days just to make sure everything's OK.

But all the signs that we had so far, particularly the blood tests and things that we follow, are extremely positive.

So, and he has been off dialysis since he got his transplant last Saturday.

WILLIAM BRANGHAM: It's amazing.

Before we get into some of the complexities here, we were all very struck by seeing how moved you were at the press conference when you announced this breakthrough.

And I just wonder, if I had talked to you back when you were a younger man in medical school, and I had told you that you could have cured someone's end-stage renal disease with a pig kidney, what would younger you have thought about that?

DR. LEONARDO RIELLA: That that was just a dream, a big dream, and maybe it would never happen.

WILLIAM BRANGHAM: And what is it, again -- for people who might have thought, well, I have heard that we can put parts of pig hearts into people or other animal transplantations, what is it that has been the challenge thus far that you were able to surmount here?

DR. LEONARDO RIELLA: So, if we go back 20, 30 years, when xenotransplants started, there had been so many challenges, in particular, what was mentioned before about these incompatibilities.

And changing the DNA to make animals more compatible was extremely difficult.

I think what really changed -- was a game-changer was the development of the CRISPR-Cas technology, and so the discovery and then the application of that in xenotransplantation, because then scientists were able to modify multiple genes at the same time in a short period of time, which before was impossible.

And that permitted us to overcome all these barriers and make organs that were really more compatible with humans.

WILLIAM BRANGHAM: And is that why you think that this case was successful, when other previous attempts have not been?

DR. LEONARDO RIELLA: Well, that's one point that is very important, is the type of donor organ that we're going to get.

What type of gene-modified pigs are donating these kidneys, so that we can do a successful transplant.

I think the second aspect is, what are the medications that we're going to be giving this patient in order to prevent it from rejecting?

What we have learned from all preclinical models, so animal studies, is that the usual immune-suppressive drugs, anti-rejection medications that we use in the clinic do not seem to be effective in the case of xenotransplantation.

And what we had to do is then adapt some of the new drugs that were being developed.

And, for the first time, we used one of these medications on the current patient.

And I think that that was so far a success.

Of course, rejection takes time, so we have to follow this patient carefully.

And -- but the initial impression is only positive from our team.

WILLIAM BRANGHAM: Can you help me understand a little bit the potential that you and your colleagues see for this type of thing, given the enormous need, tens of thousands of people, and we know the big disparities in racial minorities in the country?

DR. LEONARDO RIELLA: Yes, those are huge.

The disparity in kidney transplantation keeps increasing, and as well as the organ shortage.

So patients don't get referred for transplant, and when they do get referred, they have to wait on a waiting list years before getting a transplant.

And, unfortunately, while they're still on dialysis, their health deteriorates.

So while they were initial candidates for kidney transplant when they first entered the list, if they wait four or five years, many of them will not be candidates anymore.

So I think what we hope to be able to do is that one first step in getting more organs for these patients, so they can be transplanted in a timely manner.

WILLIAM BRANGHAM: There have been a series of concerns that have been raised about using gene-edited organs in humans, about the potential for spreading animal viruses from animals to humans.

How do you weigh those risks versus the potential that you're talking about here?

DR. LEONARDO RIELLA: That's always a major debate in the entire field of xenotransplantation.

So how high are the risks?

And what we have learned over the past 20 years with many animal studies is that, if these pigs are grown in a very isolated manner, with frequent testing, you're able to actually have a very low risk of infections.

And I think what was unique about the pig that donated the kidney for our patient was that, in addition to the improvements in compatibility that we just mentioned, they also did 59 modifications in the gene, in particular, in some retroviruses that are present endogenously on the pig.

And so that creates an extra level of safety in terms of minimizing infections coming from the pig.

And then we tested for all the other pathogens, bacteria and viruses that could be present on the pig to make sure that they were negative prior to transplantation.

And that reassures.

So, the risk overall, we consider very low, but, of course, this is the first time we're doing this in humans, so we're going to be monitoring this very carefully.

WILLIAM BRANGHAM: All right, Leonardo Riella of Massachusetts General Hospital, thank you so much.

And, again, congratulations on this historic breakthrough.

DR. LEONARDO RIELLA: Thank you so much.

I appreciate it.