LOS ANGELES – Breathe in, breathe out – it may seem simple, but lungs are devilishly complicated structures, boasting more than 40 different cell types and an intricate network of tiny blood vessels and air sacs.
It’s no wonder, then, that engineering lungs in the lab has been extremely challenging.
Reporting Thursday in the journal Science, one research group has now successfully engineered a lung that can sustain a living rat.
The report brings closer the day when artificial lungs might be grown for human transplants, scientists said.
In work colleagues describe as daring, a team led by Dr. Laura Niklason at Yale University grew rat lungs almost from scratch.
Because lungs are so complicated, the group used a scaffold-based approach – they took lungs from adult rats and dissolved away all the cells, leaving behind a fibrous lung “skeleton.”
They seeded these scaffolds with lung cells from newborn rats and – through careful coaxing that included incubation in a “lung bioreactor” that mimicked the fetal lung environment – produced what appeared to be functional lungs.
They then implanted the lungs into four live rats and showed that the engineered lungs were 95 percent as efficient as natural ones.
The same methodology had been used to successfully create beating rat and pig hearts in 2008 – although in those cases, the organs were never transplanted into living animals.
“It’s exciting to see that it’s not just about heart, it works in other organs and tissues too,” said Doris Taylor of the University of Minnesota, who conducted the pioneering heart work. “It really reinforces the belief that these scaffolds are smart. They know how to tell cells what to do, where to go, and how to behave.”
There are still kinks in the process: A few hours after rats received the lung, tiny blood clots began to form, probably due to bare spots on the scaffold. “It’s pointed out to us what worked, but it’s also pointed out to us what needs to be made better,” Niklason said.
And though the work represents a significant leap, Niklason predicts it will be 20 or 25 years before the technology can be used to build lungs for human transplants. Aside from the clotting issue, she also is waiting for stem cell technology to provide the precursor cells needed to grow engineered human lungs.