In a lab at Yale University, a rat inhales. Every breath this rodent takes is a sign of important medical advances looming on the horizon, for only one of its lungs comes from the pair it was born with. The other was built in a laboratory.
This transplanted lung is the work of Thomas Petersen and a large team of US scientists. Their technique isn’t a way of growing a lung from scratch. Instead it takes an existing lung, strips away all the cells and blood vessels to leave behind a scaffold of connective tissues, and re-grows the missing cells in a vat. It’s the medical equivalent of stripping a house down to a frame of beams and struts and rebuilding the rest from scratch. The whole process only took a few days and when the reconstituted lung was transplanted into a rat, it worked.
This is important because the lungs are notoriously bad at regenerating and repairing themselves. If a person’s lungs are severely damaged, the only real solution is a lung transplant. But that’s easier said than done. The procedure is expensive, only 20% of patients at most are still alive ten years later, and the demand for donor lungs far exceeds their supply.
Peterson’s ultimate vision is to solve these problems by fitting patients with a transplanted lung grown using their own stem cells. The scaffold would come from a dead donor, or possibly even a primate or pig. Its own cells would be stripped away and the patient’s stem cells would give the scaffold a personalised makeover, seeding it with the various types of cells in the lungs. The whole process should only take around 1-2 weeks. Laura Niklason, who led the study, says, “The value here is that the resultant lung would not reject, which is the key that limits survival of lung transplant patients right now.”
The team’s latest success in rats is a proof-of-concept – it shows that the technique should eventually be possible. But as Petersen notes, there are many technical hurdles to overcome before it could ever used in humans. That achievement is still years of hard work away. “I think that 20 to 25 years is not a bad time frame,” says Niklason. “I previously developed an engineered artery that will be ready for patients next year. It was first published in 1999. If an artery takes 12 years from first report to patients, then a lung will take 20-25.”
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