A British boy who made medical history by having a new windpipe built from his own stem cells is still doing well two years after the operation.
Doctors say Ciaran Finn-Lynch, who is now 13, from Northern Ireland, has grown 11 centimetres in height and returned to school.
He is continuing to live a normal life, free from medication to stop his immune system rejecting the transplant.
Ciaran was the first child in the world to undergo the pioneering tracheal transplant.
The procedure involved seeding stem cells taken from Ciaran's bone marrow into the collagen "skeleton" of a donor windpipe stripped of its own cells.
Once the structure was implanted, the stem cells matured, grew and divided to create a new organ.
A groundbreaking feature of the treatment was that the stem cells were allowed to mature in Ciaran's body, rather than in a laboratory "bioreactor".
Ciaran, a keen drummer, underwent the operation at London's Great Ormond Street Hospital in March 2010.
The surgery was a desperate attempt to save his life after earlier treatment failed.
Ciaran was born with a condition called Long Segment Tracheal Stenosis which left him with a very narrow windpipe, making it hard to breathe.
A follow-up report published in The Lancet medical journal today said the new organ had strengthened and showed no signs of rejection.
Doctors called for more research to speed up the recovery of future patients and increase the availability of donor windpipes, or tracheas.
Martin Birchall, Professor of Laryngology at University College Hospital Ear Institute, said: "Since the treatment plan for Ciaran was devised in an emergency, we used a novel mix of techniques that have proved successful in treating other conditions.
"To minimise delays, we bypassed the usual process of growing cells in the laboratory over a period of weeks, and instead opted to grow the cells inside the body, in a similar manner to treatments currently being trialled with patients who have had heart attacks.
"We need more research on stem cells grown deliberately inside the body, rather than grown first in a laboratory over a long time. This research should help to convert one-off successes such as this into more widely available clinical treatments for thousands of children with severe tracheal problems worldwide."