25 April 2006
Scientists grow bladder replacement in lab

A team of scientists has grown human bladder sacs in the laboratory and successfully transplanted them into people. It is the first time that a complicated internal organ, rather than a scrap of skin or other tissue, has been grown in the lab and placed into people. The researchers say that they are already working on growing tailor-made kidneys, livers or hearts that might bypass the shortage of donor organs and problems with organ rejection. Anthony Atala at Wake Forest University School of Medicine in Winston-Salem, North Carolina, and his colleagues took cells from the malfunctioning bladders of seven children with spina bifida and used them to grow thin sacs of tissue. They grafted the artificial organs, which look a little like hollowed-out grapefruits, on to the patients' own bladders. The team started their work in 1999 and then tracked the progress of the patients for several years before publishing the results in The Lancet.

In the three patients who received the most promising version of the technique, the bladders worked better and leaked less than the current best treatment, in which a poor bladder is patched up with tissue cut from the bowel. "This will definitely generate a lot of excitement for all tissue engineers," says Steve Chung who studies stem cells for bladder repair at the Advanced Urology Institute of Illinois in Spring Valley. Growing a new body part is not easy. Medical researchers must first find a source of cells and coax them into multiplying in the lab. Next, they have to mould the cells into a structure that mimics the normal organ, often by growing them on a scaffold. They also have to ensure that the organ is properly nourished by blood vessels and nerves.

Atala's team did this by slicing a postage-stamp-sized fragment of bladder tissue from each patient and encouraging the cells to proliferate. They spread a layer of muscle cells on the outside of a bladder-shaped, biodegradable mould of synthetic polymer and collagen, and added a separate layer of bladder urothelial cells on the inside. The organ part grew in a soup of nutrients for several weeks before the team sewed it to the patient's bladder. Researchers already use artificially grown skin tissue in surgery, and scientists are working to create patches or full replacements for virtually every other organ in the body. This latest work is a significant step forwards because "they were actually able to do this in humans and show an enhanced function," says David Mooney, an expert in tissue engineering at Harvard University in Cambridge, Massachusetts. But experts caution that the bladder is a relatively simple organ when compared to something like the heart.

Atala says that the team now wants to refine the technique so that they can offer it to patients with numerous bladder diseases and problems. Urologists would particularly like to adopt it for patients with bladder cancer, Chung says. But it could be difficult to grow a new bladder from a sick patient's own cells, because these might also be predisposed to cancer.One way around this is to take stem cells from another part of the body, such as the bone marrow, and persuade these to generate bladder tissue, but such research is less advanced than Atala's.

Nature
April 25, 2006

Original web page at Nature