This is an interesting approach to organ transplant and regrowth, demonstrated initially in rabbits. The researchers believe it may also provide the basis for xenotransplantation between species, but that remains to be seen:
Researchers have discovered a way of freezing embryonic animal kidneys so that they can later be warmed up and grown into full-size organs without the risk of rejection by their recipient. The team found that when precursor kidney tissue from 16-day-old rabbit embryos is implanted in adult rabbits, it develops into an adult kidney, connecting itself to the host's own blood supply. The host doesn't recognise the organ as strange, and permits it to connect to the blood system. The adult rabbits did not reject the foreign kidneys because the embryonic tissue was transplanted before it had started producing the protein that would alert a host's immune system to foreign cells. Researchers believe that when the protein is eventually produced, it matches that of the host instead.
The team then investigated whether it might be possible to create a biobank of potential organs for transplant. Large organs cannot be frozen to prevent decay because water in them turns to ice as they freeze, destroying delicate call structures. But the embryonic precursor kidneys are much smaller, enabling them to use a cryopreservation process called vitrification that can prevent ice formation by pumping antifreeze into an organ before cooling it to -196 °C. This technique is normally only used to freeze small tissues such as human eggs because it is difficult to get the antifreeze around larger, more complicated organs. The team managed to successfully vitrify and store the precursor kidneys for three months in liquid nitrogen. They then warmed the tissue and transplanted it into adult rabbits. Some 25 per cent of the transplants grew into healthy adult organs in the host - not as high as the 50 per cent success rate they achieved with fresh embryonic tissue, but still good.
The results suggest we may one day be able to create a long-term biobank of animal kidneys that provides an unlimited source of organs for transplanting in people. The team is now trialing a similar experiment between rabbits and goats. More than one kidney could potentially be transplanted into larger animals to make up the mass needed for them to act as a native kidney.