@chalkahlom I'd heard something about this on another podcast. I think heart parts have been produced experimentally by taking the collagen from the heart of another individual (pig?) and building cells onto that framework. Not sure what cells exactly, but I believe they did generate the physical structure which showed some heart behaviour (contraction?).
All from memory so probably flawed...
@chalkahlom Collagen being a protein that doesn't trigger an immune response? Or not a strong one? Not sure.