A 10-year-old British boy has become the first child to undergo a windpipe transplant with an organ crafted from his own stem cells.
It is hoped that using the boy's own tissue in the nine-hour operation at Great Ormond Street Hospital will cut the risk of rejection.
The world's first tissue-engineered windpipe transplant was done in Spain in 2008 but with a shorter graft.
Doctors say the boy is doing well and breathing normally.
He has a rare condition called Long Segment Congenital Tracheal Stenosis, in which patients are born with an extremely narrow airway.
At birth his airway was just one millimetre across.
Doctors had previously operated to expand his airway but in November last year he suffered complications from erosion of a metal stent in his windpipe or trachea.
In order to build him a new airway, doctors took a donor trachea, stripped it down to the collagen scaffolding, and then injected stem cells taken from his bone marrow.
The organ was then implanted in the boy and over the next month, doctors expect the stem cells to transform into specialised cells which form the inside and outside of the trachea.
Two years ago, Claudia Castillo, a 30-year-old mother of two, became the first person to receive a transplant organ created from stem cells.
She received a new section of trachea after her own had been damaged by tuberculosis.
The latest operation is a significant advance on that pioneering work, as it is the first time a whole tissue engineered windpipe has been transplanted.
Also in Ms Castillo's case, doctors grew the new tissue from her stem cells in the laboratory.
But in the UK operation, the donor windpipe was treated with a cocktail of chemicals designed to prompt the stem cells to grow into new tissue once inside the body.
Professor Martin Birchall, head of translational regenerative medicine at University College London, who was part of the team behind the operation, said it was a "real milestone".
"It is the first time a child has received stem cell organ treatment, and it's the longest airway that has ever been replaced.
"I think the technique will allow not just highly specialised hospitals to carry out stem cell organ transplants."
He said more clinical trials were needed to prove the technique worked but that the team was also thinking about transplanting other organs, such as the oesophagus.
Professor Anthony Hollander, ARC professor of rheumatology and tissue engineering at the University of Bristol, said: "The advantage of the new approach is that it can be performed quickly and cheaply and so if successful it could be made available to large numbers of patients at relatively low cost."
But he said the technique was more unpredictable than that done in the laboratory because there is less control of the type of stem cells being used and a very short time between seeding the cells onto the scaffold and implantation.
Stem cell pioneer Professor Paolo Macchiarini, from Careggi University Hospital in Florence was involved in both the Spanish and UK transplants.
He had also carried out the stem cell procedure on a 53-year-old Italian woman.