The world's first organ grown in a laboratory has been successfully implanted in humans, heralding a new era in transplant surgery.
Seven patients given new bladders grown from their own cells have functioning organs that have performed as well as those conventionally repaired but with none of the ill effects, scientists reveal.
Experts hailed the "stunning" development, which marks a new frontier in the search for replacement body parts. Scientists behind the breakthrough are now trying to grow up to 20 other organs and tissues.
Throughout the Western world, thousands of people die every year waiting for donor organs and thousands more never make it on to the waiting lists, so the potential benefits are enormous.
In Britain, about 6,700 people are waiting for an organ and 2,180 transplants were done last year, according to UK Transplant. The number of donor organs available has declined as a result of improved road safety and fewer accidents.
Instead of relying on organs from other bodies, doctors are investigating ways of harvesting specially grown replacements by farming human tissue.
Anthony Atala, director of the Institute for Regenerative Medicine at Wake Forest University School of Medicine, North Carolina, who led the trial, said it was a vital step towards the goal of replacing damaged organs. "We have shown regenerative medicine techniques can be used to generate functional bladders that are durable," he said. "This suggests regenerative medicine may one day be a solution to the shortage of donor organs in this country for those needing transplants."
Professor Atala is working on growing 20 tissues and organs, including blood vessels and hearts, in the laboratory, the university said in a statement.
Catherine Kielty, professor of medical biochemistry at the UK Centre for Tissue Engineering at Manchester University, said: "It is an exciting development. To my knowledge, a whole organ grown in the laboratory has not been tested in humans before. It is an engineered organ which has proved functional."
The development could be useful in other areas such as growing small blood vessels and "plumbing in" kidney transplants where there is a need for elastic tissue , Professor Kielty said. But longer-term studies were necessary of the bladder wall to see if it continued to grow normally.
Professor John Dark, a cardiac surgeon at the Freeman Hospital, Newcastle, described the result as stunning but said it would be a big step to grow more complex organs. "The liver grows itself like the tail of a lizard," he said. "But growing organs with complex different parts is much more difficult. The key thing about the heart is getting it all to beat together in synchrony. I would be cautious about the potential of this."
In the trial, the seven patients, all aged between four and 19, had engineered bladders grown from their own cells so there was no risk of rejection. A tiny sample of cells was taken from each patient's bladder by biopsy and grown on a biodegradeable "scaffold". Elastic, smooth muscle cells were grown on the outside, with epithelial cells forming the bladder lining on the inside. After seven to eight weeks in the laboratory, the fully grown bladder was transplanted and stitched to the patient's existing bladder to create an enlarged organ. After up to seven years of follow-up, results published in the online edition of The Lancet show the new bladders functioned well and did not have the side-effects such as kidney stone formation associated with conventional repair with intestinal tissue.
Professor Atala said: "We wanted to go slowly and carefully and make sure we did it the right way. This is a small, limited experience but it has enough follow-up to show that tissue engineering is a viable tool." All the patients were born with a congenital defect, spina bifida, which is associated with poor bladders.
Scientists have already grown human skin, cartilage, bone and liver outside the body. Heart valves have been grown and transplanted into animals with human trials due to start soon. Stem cells have been injected into failing hearts to regenerate them.
In the 1990s, scientists pinned their hopes on xenotransplantation - the use of organs from genetically engineered pigs - to overcome the organ shortage. But the research ran into the sand when it became clear that the rejection problems were too deep-seated to be overcome and there was an additional risk of transmitting animal viruses to the human population, which could trigger new diseases.
First kidney transplant operation carried out on 23-year-old identical twins Richard and Ronald Herrick in the US.
First UK kidney transplant by Sir Michael Woodruff in the Royal Infirmary, Edinburgh, on twin brothers.
World's first liver transplant performed on a three-year-old boy in the US. The boy died, but doctors gained crucial knowledge about preventing rejection of donor organs.
World's first heart transplant was carried out by Dr Christiaan Barnard in Cape Town, South Africa. The 55-year-old patient lived for 18 days after the transplant.
Europe's first bone marrow transplant performed on Ian Cuneen, aged 7, at the Royal Marsden Hospital in London.
UK's first heart and lung transplant performed at Harefield Hospital in London. The patient died after 13 hours.
World's first liver, heart and lung transplant performed in Cambridge. The patient survived 10 years.
Two women received pig livers until human livers could be found for permanent transplant. One patient survived to receive a human liver. The other patient died before a human transplant was found.
World's first hand transplant done by surgeons in France, who grafted the hand and forearm from an anonymous donor on to the right arm of 45-year-old Clint Hallam.
Isabelle Dinoire, 38, received world's first face transplant in France on 27 November after being mauled by her dog.