Researchers recently reported initial success in a transplant of decellularized lungs in pigs, though there is still a way to go in order to prove the ability to produce a completely functional lung in this way. In the decellularization process, donor lungs are stripped of their cells, leaving behind the extracellular matrix and its chemical cues for cell growth. The lung is then repopulated with cells derived from samples taken from the eventual recipient of the transplant. This minimizes the risk of transplant rejection.
Decellularization is a short-cut technology, a way to work around the present inability to produce sufficiently structured and chemically correct scaffolds for tissue engineering of complex organs. It will allow for a higher fraction of donor organs to be transplanted than is currently the case, make the logistics of organ transplant somewhat easier, as decellularized tissue is much more amenable to longer term storage, and also opens the door for the development of viable xenotransplantation, such as from pigs to humans.
Researchers have transplanted bioengineered lungs into pigs successfully for the first time. The team harvested lungs from dead pigs to construct a scaffold for the bioengineered lung to hold fast to. They used a solution of soap and sugar to wear away all the cells of the lungs, leaving behind only collagen, a protein that forms the support structure of the organ. Next, they removed one lung from every recipient pig, and used cells from those lungs, together with the collagen scaffold, growth factors, and media, to grow a new lung in a bioreactor. After a month, the lungs were transplanted into the recipient pigs.
As the cells came from the same animal that then received a bioengineered lung, there was no organ rejection. The researchers euthanized the recipient animals and tested their lungs 10 hours, two weeks, and one and two months following transplantation. The team found that before the pigs were euthanized, the transplanted lungs developed without any outside help, building blood vessels they needed for survival. However, even the two-month-old transplanted lung, while not showing any fluid collection that would indicate an underdeveloped organ, had not developed enough to independently supply the animal with oxygen. The researchers hope that bioengineered lung transplants will be feasible in humans within a decade. But first the team will "need to prove that the animals can survive on the oxygen provided by the engineered lung alone."