World's first pig to human lung transplant

Surgeons in China have just reported the first successful transplant of a pig lung into a person. A 39 year old man, who was brain dead at the time of the transplant, was the recipient. The organ functioned for 9 days before the experiment was ended. Xenotransplantation - transplanting organs between species - is being explored as a solution to the ongoing organ shortage crisis. Pigs are a favourite because their organs are very similar in size to our own. Previously, hearts and kidneys have been tested in human transplants, but not lungs, which are judged to be more challenging owing to the fact that the tissue has to handle blood as well as air flow. So what did the experiment reveal, and is this likely to be a feasible approach in the future?

Jas - My name is Jas Parmar. I'm a consultant physician at Royal Papworth Hospital. My specialist interest is lung transplantation and I've been involved in the field for 25 years. So this is the first time that a donor lung from a pig has been implanted into a human recipient and this builds on the background work in renal and cardiac transplantation. This was performed in a hospital in China. They have a laboratory where they have generated these genetically modified pigs and implanted the donor organ into a recipient in a hospital.

Chris - So this is going into a human being, so it gives us a chance to test what happens when you put an animal lung into a person. What are the constraints of doing that first and foremost?

Jas - Yes, so the fact that the recipient was deceased obviously has some implication into the way this organ might behave. But what it did demonstrate was that firstly it was technically feasible to do it and the organ was able to function for a period of time.

Chris - How long did they keep the person going for with the pig lung in there?

Jas - The organ survived for nine days in total. They had a number of challenges which included using some fairly industrial immunosuppressant medication to lower the immune system.

Chris - Did it go in the pig organ into the chest where a lung would normally go, so it behaved to all intents and purposes like the person's own lung?

Jas - Yes, I mean the paper's a little light on detail around that, but that’s the assumption, is that this was placed in the normal anatomical position with the normal connections.

Chris - And how did they actually monitor what was going on?

Jas - So they were using a number of parameters to look at the lungs. They included X-rays, blood tests and function of the lungs in terms of arterial blood gases and with these they had a composite picture of how the organ was performing. And how was it performing? So it appeared to be doing reasonably well up until about day two when it developed a severe immunological-based reaction which then stopped it working well.

Chris - And thereafter?

Jas - Again the paper's a little light on the detail around that, but it seems that the experiment was stopped at nine days and the assumption is that was when the organ actually completely failed.

Chris - You mentioned that the pigs that were the donors for these organs have been genetically modified. In what way?

Jas - Clearly there are species differences in the way in which we handle foreign proteins. And so if a pig organ is transplanted into a human there would be a number of protective mechanisms which would attack the organ. So of the processes they use they use genetic deletion to try and make the pig organ look a bit more like a human organ.

Chris - And does this look like therefore, on the basis of what they present, it is a direction to go in? Does this look promising? Because it's been done for kidneys, it's been done for hearts, okay only in the short term at the moment, this was the first lung. But does this give us hope?

Jas - Yes I think as a proof of concept it demonstrates a number of things. There is still a huge amount of work that needs to go in to make this a durable and sustainable enterprise which can enter the clinical arena. But yes it does demonstrate that this is technically feasible.

Chris - Is this the sort of nuclear fusion of the transplant world where you know it's 10 years away and always will be? Is it the same sort of thing for that?

Jas - Yes I remember conversations around this. We had a very active xenotransplant programme in Cambridge and many of the old sagely people around at that time said this is tomorrow's medicine and will remain tomorrow's medicine.

Chris - But more seriously, does this look like it's going to be practical or do you think that someone bright will come along and be 3D printing organs and we'll be having human-based tissues well before we ever get this problem solved? Is this just too big a nut to crack? The immune system is too hard to defeat when we're doing this?

Jas - Yes I think the biology of the protection against foreign proteins is an immensely basic phenomenon and very strong. And I think if you can get to a point where you can develop organs from stem cells you obviate the need for immunosuppression, the risk of infection goes down and the whole thing is much more attractive. So, if I were to put some money on something it would be on the development of 3D printed organs from stem cells, because I think that's a way more attractive option.

Chris - But there's no doubt there is a big clinical need for this kind of thing isn't there?

Jas - Absolutely, so there's a desperate need in the UK and we have a very large waiting list with a number of patients dying before they receive an organ. So each of these steps are welcome and if they enter the clinical arena they will have a place in treating patients.