IT WAS bound to happen, the only questions were when, and which organ would be first. The answers are 1999 and the bladder.
Seven years ago, a team led by Anthony Atala, now at Wake Forest University in Winston-Salem, North Carolina, first implanted an almost entire artificial bladder into a child whose own bladder was failing. The implant was grown in the lab from the child’s own cells. Atala has waited until now to go public to be sure of his procedure’s long-term effects. Seven implants later, the signs are looking good (see “Lab-grown bladder shows big promise”).
Many claims have been made for artificial organs. They will, it is said, usher in an age in which organ transplants and tissue rejection are unknown. Does Atala’s work herald the start of that age?
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By any measure it is astonishing work, the culmination of 16 years of painstaking, ground-breaking lab work, animal testing and surgery. Blood vessels seem to infiltrate the new tissue and possibly some nerves too. If the organs do not yet function as well as natural healthy bladders, they are at least better than what the patients had before.
“If the organs do not yet function as well as natural bladders, they are at least better than what the patients had before”
But Atala has yet to implant an entire organ. The ureters draining the kidneys and the sphincter muscles at the base of the bladder are still the patients’ originals. To replace the organ completely would require a full set of nervous connections, so that when the bladder was full it would send that niggling message of urgency to the brain. During urination the sphincters would have to relax while the wall of the bladder contracted. To get all this working properly is an immense challenge.
What about other transplantable tissues? “Flat” structures such as skin and corneas are already in use or in trials. Tubular structures, such as blood vessels have also been tried out in humans. The bladder is the first “hollow organ” to be implanted successfully. But more complex still are solid organs such as the heart and liver.
Researchers trying to create these organs face huge obstacles. First, can they persuade the necessary cells to grow in a dish? Atala and his colleagues needed several years and plenty of luck to solve that one. They had to concoct the right mix of growth factors and nutrients, and devise the structure and make-up of the “scaffold” on which the organs developed. And a major problem with solid organs is how to make sure enough oxygen and nutrients reach central areas.
Some obstacles may be avoided by alternative approaches. It may prove easier to coax stem cells to generate the right tissues than to persuade specialised adult cells to divide. And the body may turn out to be a far better incubator for artificial organs than the lab. Teeth, hair, bone, even patches of heart muscle are already being grown in vivo.
And what about money? Atala’s procedure costs about $4000 per patient, which compares favourably with a lifetime of care for the kidney problems caused by these kinds of disorders. But the same may not be true for other organs.
It is anybody’s guess when we will see the first implanted heart or liver. The hurdles are high and often invisible from a distance. Safety testing can take years. On the other hand, research into artificial organs is now a huge worldwide endeavour and some problems may be quickly solved. Atala, for example, has grown small segments of kidney that successfully produce urine.
Atala has shown proof of concept: it is possible to create and implant a relatively complex organ. In that sense it is a landmark study. But don’t get too excited about a new age without transplants. You could grow old before that begins.
