3D printing a mini heart

Cells in dishes are one thing, but how close is science to growing a whole new, fully functional organ like a heart? Before we hear about this, here's Phil Sansom with another quick fire science...

Last year there were seven and a half thousand heart transplants across the world. Each of those hearts went to someone whose own heart was failing and for whom all other treatments had failed. These people who received a transplant are the lucky ones because cardiovascular disease is the number one cause of death globally, meaning there are millions of people who die of heart failure without any prospect of a transplant.

Most of those are older people because if you're over 65, other health problems like diabetes or lung disease can render a transplant impossible. However, many people who are good candidates still die waiting for a transplant. Last year in the UK, about 200 people got heart transplants, but almost 300 were still on the waiting list. While someone's on that waiting list, they might be kept alive by a ventricular assist device, a mechanical pump in their chest that helps pump blood around their body. Then even if they do finally get a heart transplant, that is a major operation with potentially life threatening complications. And you're not guaranteed a long life after the transplant, only about 50% of people live for another decade afterwards.

One US biotech company - BioLife4D - have just announced they’ve bioprinted a mini human heart. Steven Morris, CEO of BioLife4D, spoke to Chris Smith...

史蒂文,我们已经能够生物,bioprintwhat we call our mini heart. So what our mini heart is really about a cherry-size version of a human heart, scaled down, with all of the different components; valves, atriums chambers, things like that. So it's actually more representative of an organ than your previous guest who was talking more about organoids, which are small groupings of cells.

Chris - Where do you get the cells from?

Steven - So what we would do is we would take a patient's own cells and basically reprogramme them to the different cell types that make up the heart and then use those to bioprint ultimately an organ viable for transplantation. For the mini heart though, you don't need to have a patient's own cells because it's not designed to be implanted back into a human. It's a little bit lower of a bar than the complexity and the functionality of an organ to keep an animal alive for the longterm.

Steven - The mini heart is really designed for pharmaceutical testing and drug discovery testing, to give a better predictive model to test the potential cardiotoxic effects of whatever it is, therapies, that they're working on.

Chris - And how do you actually do the bioprinting?

Steven - It's an incredible process. We'd start out with white blood cells and then we literally reprogramme them into induced adult stem cells. And then once we do that, we reprogramme them again into the different cell types that make up the heart. So there's cardiomyocyte cells that beat and different cells that make up the structure of the heart and the different components of the heart. And once we've been able to reprogramme enough of each of those cells, we put them in what we call our bio-ink, like little balls of hydro gel. And in that hydro-gel, you have the cells as well as nutrients, growth factors and other secret sauce that we put in there in order to keep everything viable for the 3D bioprinting process.

Steven - We load that into a bio-printer, and then what we do is we literally bioprint an organ, our heart. So layer by layer 3D bioprinting is very similar to normal 3D printing, but normal 3D printing, you melt one layer to another. You can't do that with cells or you'll kill the cells. So what we do is we place all of the cells in the appropriate place as we're constructing the heart. And then we also lay down what we call scaffolding. So material to hold everything in place, because the cells have not self assembled yet. And after a couple of days, the cells all self assemble, form networks and join together and then we are able to melt away that scaffolding and be left with the organ.

Chris - Does it work though? That's the crucial question. Can you actually get this thing pumping blood?

Steven - We have not got it to the point where it's pumping blood. That's what our next milestone is. You know, we're well on our way towards doing that, so we're now capable of printing all of the different components of the heart separately, the valves and the chambers and even vascularization and things like that. But when we're laying it down layer by layer, it's not like a normal crossword puzzle where you take the pieces and just plug them in. We have to be printing layers of each of those different components at a time. So even though we're able to print these functional components, we have not bee n able to get them together in this construct so that they're fully functional.