Building a scaffold for the bladder is one thing, building one for the heart is far more complicated. One of the problems when you move to larger organs is the getting the blood supply to work, connecting arteries, capillaries and veins to keep the organ alive.

It is why some researchers are investigating "decellularisation" - taking an existing donated organ, stripping out the original cells and replacing them with new cells from the patient who will receive the organ.

Prof Martin Birchall, a surgeon at University College London, has been involved in a number of windpipe transplants performed in this way.