The heart makers

How do you make a working human heart? Scientists can turn stem cells into beating heart cells, but getting them to organize into a 3D heart requires a scaffold. 

At the Massachusetts General Hospital in Boston, Harald Ott and his team are reusing the scaffold that nature provides. They're stripping away all the living cells from dead hearts, before filling in the leftover matrix with healthy new cells. 

In this video, Brendan Maher finds out how the technique could be used to develop parts of the heart, like the aortic root and valve, for transplant.