Decellularization, or recellularization, is a fairly new technique in tissue engineering wherein a donor organ is chemically stripped of its cells, leaving behind the intricate structure of the extracellular matrix. That structure is then repopulated by stem cells drawn from a patient, which use the matrix as a guide to rebuild the fine structure of the organ. When transplanted, a recellularized organ has few of the issues of immune rejection associated with a normal donor organ transplant, as it is essentially built from a patient's own cells.
Now I see that lungs in rats can be added to the list:
The team started with decellularized adult rat lungs, which retain the organs' branching airways and blood vessel network, and added a mixture of lung cells from newborn rats. Niklason says that the crucial step was nurturing the would-be lungs in a bioreactor that circulates fluid - simulating what would happen during fetal development - or air through them. The cells stuck to the scaffold in the right locations and multiplied. After up to 8 days in the bioreactor, they had coalesced into what the researchers' tests indicated was functional lung tissue.
To determine whether the new organs worked, the researchers removed rats' left lungs and stitched in lab-grown replacements. X-rays showed that the implanted lungs were inflating, though not fully. Tests of gas levels in blood flowing to and from the replacement organs showed that they were taking in oxygen and releasing carbon dioxide at 95% of normal efficiency.
This is an important step forward, as progress on tissue engineering and regenerative medicine for lungs has lagged behind comparable work on other organs in the past decade - lungs are both complex and inaccessible, which is not a helpful combination. Serious lung injuries are hard to treat and have a low survival rate, but these are facts that will change in a near future of engineered replacement lung tissue.