For some time, cardiac researchers have been able to grow beating heart cells in a laboratory dish. They have even grown thin layers of heart tissue. But they have not been able to create anything resembling an actual organ, until now.
U of M researchers say they have succeeded where others failed by using the framework of a dead heart.
Team leader Doris Taylor says the process is much easier than creating a heart from scratch. "Our philosophy is give nature the tools and get out of the way," says Taylor. "We're never going to understand everything about how this works. We don't need to."
Taylor directs the Center for Cardiovascular Repair. Her team created its new heart by flushing the dead organ to remove every existing cell in it.
What remains is a snow white shell that Taylor says is essentially the same material as the gristle on a steak. "So what that means is for the first time we have what we call a scaffold that looks like a heart and we can use that scaffold now to start to build a new organ."
In research circles this work is called tissue engineering.
Taylor's team then collects new living heart cells from a donor animal and re-seeds the empty organ scaffolding. "When we put heart cells in there they begin to know how to line up, the begin to know how to go to the blood vessels and form new blood vessels and line the blood vessels again," says Taylor. "We can hook a pacemaker up to this and the heart cells start to beat and contract and over time it matures."
"For the first time we have what we call a scaffold that looks like a heart and we can use that scaffold now to start to build a new organ."
As the organ matures, it grows layers of muscle in the heart walls. It also appears to get stronger when researchers increase the volume of blood flowing through the organ. And the heart continues to beat even after the pacemaker is turned off.
So if U of M researchers can regenerate a pig heart, which is close in size to a human heart, does that mean this technique could be applied to humans one day? Taylor says it is possible, but not imminent. "You really can't move to anything remotely like a clinical scenario until you've worked out all the details in a way that you're willing to do it on your mom, you know? And we're not quite there yet."
Taylor says the progress so far has been good. But her team still is not sure that they have every type of cell that they need to make a fully functioning heart.
Robert Nerem, a tissue engineer at Georgia Tech, says the U of M's challenge is making sure the right cells grow in the right places in the heart. "The issue is how to get those cells to home in where you want them to home in and there's just a lot more work that needs to be done in that area," says Nerem. "But do I think it's possible? Yes, I think it's possible."
Nerem says his Georgia Tech research group will likely adopt the U of M's approach to engineering tissues in the future.
That is exactly what Doris Taylor hopes her research will do. "We hope that we've opened a door that will let us and a number of other people take this and just really change the way that we begin to think about building organs."
Taylor says her lab has already had some success applying its technique to other animal organs.The process works on kidneys, lungs, the liver, pancreas and any other organ that depends on a blood supply.
If the technology can be applied to human organs, Taylor says it would mean that patients could get a heart built from their very own cells, instead of an organ from someone else.
The study is published in the latest edition of the journal "Nature Medicine."