Washington: Scientists have, for the first time, successfully recovered a damaged lung and maintained it outside the body for several days, an advance that could make more donor organs suitable for transplants.
Researchers from the Columbia University in the US used a cross-circulation platform that maintained the viability and function of the donor lung and the stability of the recipient over 36 to 56 hours. They used the advanced support system to fully recover the functionality of lungs injured by ischemia (restricted blood supply), and made them suitable for transplant.
Transplantation remains the only definitive treatment for patients with end-stage lung disease, but the number of donor lungs is much smaller than the number of patients in need, and many patients die while on the wait list. In addition, lungs quickly lose their function outside the body and during transport: four out of five lungs evaluated at transplant centres are rejected.
If these lungs could be kept viable outside the body long enough, it would be possible to improve their function and use them for transplantation. Over the past five years, researchers have been studying how to improve low-quality donor lungs and possibly bioengineer lungs for transplantation.
Rather than attempting to build new lungs, they developed strategies to rescue damaged donor lungs. One approach was to use a stem cell therapy of the lung to replace defective cells with new therapeutic cells derived from the transplant recipient.
While this technique was applicable to low-quality lungs that are rejected for transplantation, there was a problem - the support of the lung outside the body was too short for the therapeutic cells to start improving lung function. As often happens, unmet clinical needs inspire new ideas and drive the development of new technologies.
The team realised that "cross circulation" - an abandoned surgical procedure used in the 1960s to exchange blood flow between two patients - could enable long-term support of living organs outside the body by providing critical systemic
and metabolic factors that are missing from all current technologies. The team embraced this idea and devised an entirely new approach to support lungs outside the body long enough to enable therapeutic interventions needed to recover their health and normal function.
"This is the most complex study we have ever done, and the one with the highest potential for clinical translation," Vunjak-Novakovic said. "The lung is a masterpiece of 'engineering by nature,' with its more than 40 cell types, and a gas exchange surface area of 100 square meters - half a tennis court," he said.
"It is amazing that such an intricate organ can be maintained outside the body and even recovered following injury," he added. The study was published in the journal Nature Biomedical Engineering.
