Repairing hearts with stem cell muscle patches

Scientists in Germany have found that damaged hearts can be repaired using small "patches" of heart muscle grown in the lab. The findings - which have been published in Nature - could give new hope to millions of people with advanced heart failure. Sanjay Sinha - a professor of cardiovascular regenerative medicine at the University of Cambridge - has been telling me how it works…

Sanjay - It's trying to tackle the problem of heart failure, and that's when hearts are damaged, often by a heart attack, and we've got about a million people in Britain who have heart failure. They can't do the things that you and I would want to do, walking upstairs, whatever, they get very short of breath and they have a shortened lifespan. We don't have a good treatment for these patients that will bring their hearts back to normal, so the idea here is to use stem cells to try and mend that gap.

Chris - And what shape does that mend take? What actually is the application of the stem cells? What do they do?

Sanjay - So stem cells are cells that can turn into any cells in the body, and what this group have done is they've used stem cells to make heart muscle cells, and then they've seeded these heart muscle cells into a patch. They made a cardiac patch, basically, so it looks like a piece of heart muscle that's contracting away, and they've used it to actually stitch onto the hearts of monkeys who have had heart attacks, and then to see whether that improves heart function.

Chris - Does it?

Sanjay - Yeah, absolutely. Even six months after it's applied, the heart function has improved in these monkeys. The heart cells that they put in are still alive and beating and contributing to heart function. It's absolutely wonderful to see.

Chris - Is it a meaningful contribution, though? So if that was a patient, the thing they would say is, I can't get up the stairs, and now I can get up the stairs. Do the monkeys show a significant improvement, or is it just, yeah, it's working, but it's not making much of a difference to their quality of life?

Sanjay - Yeah, that's a great question. It's certainly improving heart function. Quality of life is a bit more difficult to measure, and I think those studies will actually happen once we start to do this work in patients, and that's when we'll really know how well it works.

Chris - When you look at the heart that's had this done to it, what does that patch actually do? Does it wire itself in? Because the heart's an electrical organ, isn't it? And there's electrical signals flowing all over it that make all the cells beat in synchrony and so on. So does that work the way we would hope it would when you do this?

Sanjay - What's interesting is that the patch, it doesn't electrically couple to the heart, but it does contract in synchrony to the heart. We don't know exactly how that does it, but it might be mechanical forces. That means that the patch and the heart work together, and we think that contracting together helps the heart to function better. But there's probably other factors as well. We think the patch probably releases substances that make the rest of the damaged heart contract better as well. So there's probably many different things going on here.

Chris - When you look at a heart that's been damaged by a heart attack, often the area that was affected, it forms a tough scar, which makes the heart very stiff. So do you have to remove that and then put the patch in, or does the patch slowly get rid of that? What does it look like when they look down the microscope in the aftermath of doing this?

Sanjay - Yeah, there is a scar there. You're absolutely right. You put the patch actually on the surface of the heart, so on top of the damaged area, so you don't remove the scar. So it doesn't change what's underlying, but it just adds extra muscle on top of the damaged area to try and help the heart to contract.

Chris - And how long did they look for with these monkeys?

Sanjay - Oh, for six months after they implanted them. And even at six months, the heart was showing better function, the transplanted cells were present and working away.

Chris - So it looks like it does have the potential to have long-term contribution. It's not one of those things where the cells are going to expire pretty quickly or get removed by the immune system or something.

Sanjay - That's exactly right. This is one of the nice things and very promising things about this is that it suggests there will be long-term benefits.

Chris - Where did the stem cells come from? Were they the monkey's own cells that got reprogrammed, or was this sort of an off-the-shelf batch of stem cells that got turned into heart cells?

Sanjay - So they did both. They did some studies where they took skin cells and turned them into stem cells. So the monkey got its own heart cells back, in other words. That monkey didn't need any immunosuppression. But other studies they did, they just used generic stem cells where it was given to different monkeys. And those monkeys had to have their immune response suppressed. But that's the same sort of immunosuppression that a patient who has a cardiac transplant might have. So it's the kind of immunosuppression that we're familiar with and we can use clinically in the future.

Chris - What does this add then? Because people have been trying to build these patches for a long time. They've done this sort of thing in small animals like rats. This is the first time they've done it in monkeys, isn't it? I think I'm right in saying that, aren't I? So what does this add then? Does this give us confidence to go into the clinic now?

Sanjay - Yeah, absolutely. It shows that it's safe. It shows that it's effective. It's the springboard for going to clinical studies. And in fact, this group who have done the work in the monkeys, they've used this to get approval for clinical trials. And in fact, the paper shows one patient who's had a patch, who then subsequently went on to have a heart transplant. So they were able to look at the heart. And they could show that that patch in the patient still had a heart cell surviving. So there's a clinical trial now ongoing to see how well these patches work in patients. So that's the impact of this piece of work.