British scientists have, for the first time, used regenerative medicine to fully restore an organ in a living animal, a discovery they say may pave the way for similar techniques to be used in humans in future.
The University of Edinburgh team rebuilt the thymus — an organ central to the immune system and found in front of the heart — of very old mice by reactivating a natural mechanism that gets shut down with age.
The regenerated thymus was not only similar in structure and genetic detail to one in a young mouse, the scientists said, but also able to function again, with the treated mice beginning to make more T-cells, a type of white blood cell key to fighting infections.
"By targeting a single protein, we have been able to almost completely reverse age-related shrinking of the thymus," said research leader Clare Blackburn from Edinburgh’s Medical Research Council Centre for Regenerative Medicine.
"Our results suggest that targeting the same pathway in humans may improve thymus function and ... boost immunity in elderly patients, or those with a suppressed immune system."
However, she said, while the treated mice were making T-cells, her research could not yet establish whether the immune systems of the older mice were strengthened. And before the technique could be tested in humans, researchers would need to conduct more animal experiments to make sure the process could be tightly controlled.
The thymus is the first organ to deteriorate as people age. This shrinking is one of the main reasons the immune system becomes less effective and people lose the ability to fight off new infections as they get older.
Prof Blackburn’s team, whose work was published on Tuesday in the journal Development, said it targeted a part of the process by which the thymus degenerates — a protein called FOXN1 that helps control how key genes in the thymus are switched on.
They used genetically modified mice to enable them to increase levels of this protein using chemical signals. By doing so, they managed to instruct immature cells in the thymus to rebuild the organ in the older mice.
