Researchers have used patients' own cells to grow urinary tubes in the lab and have successfully used them to replace damaged tissue in five young boys, showing the potential power of cell-based therapies.
Urine flow tests and tube diameter measurements show the tissue-engineered urethras are still working after six years, said Dr. Anthony Atala, director of the Institute for Regenerative Medicine at Wake Forest University Baptist Medical Center in North Carolina.
The study, published on Monday in the journal Lancet, represents a first in the growing field of regenerative medicine, which doctors hope will eventually lead to ways to repair injuries and eventually replace whole organs.
"Totally grown in the laboratory, these urethras — living tubes which convey urine from the bladder — highlight the power of cell-based therapies," Chris Mason, a regenerative medicine expert at University College London who was not involved in the research, said in an e-mailed statement.
"When an organ or tissue is irreparably damaged or traumatically destroyed, no amount of drugs or mechanical devices will restore the patient back to normal," but he said cell-based therapies offer a potential cure.
Defective urethras can result from injury, disease or birth defects. While short defects in the tube can be repaired, larger defects are treated with a tissue graft, usually taken from skin or the lining of the cheek.
But these grafts fail in half of the cases, often leading to infection, pain, bleeding and trouble urinating.
Previously, Atala's team was the first to grow hollow organs for use as replacement bladders that they implanted in nine children in 1998. The urethras offered a challenge because they were a tubular structure.
In both cases, the technique is similar.
"Basically, the patient presents to us with a diseased or injured organ," Atala said in a telephone interview. "We take a very small piece of tissue, about half the size of a postage stamp."
To that, they add a soup of growth factors that nourish the cells and encourage them to multiply into large quantities.
The team made two cell types: muscle cells for the tube's outer layer and endothelial cells — cells that line blood vessels and other tubular structures — for the inner layer.
Once they grew enough cells, they applied them onto a biodegradable material that gives the cells the right structure. Then they heat the organ in an incubator and the cells start to form sheets. "We basically cook the organ."
The team implanted segments of the home-grown urethras in five boys aged 10 to 14 with damaged urethras.
Once implanted, the sheets of cells started forming new tissue, and after about four weeks, they were able to remove a catheter and the boys were able to urinate through the new urethras. Biopsies showed the engineered urethras had normal layers of epithelial and smooth muscle within three months.
Atala's team has followed the boys for roughly six years. "They continue to do well, which is what was nice to see."
He said larger studies would be needed before the treatment could be widely used.
Mason said using cells as "medicines" offers a major change in the way doctors treat patients.
"Cell-based therapies complement drugs and devices by aiming to cure the large unmet medical needs of our generation including: blindness, diabetes, heart failure, Parkinson's disease and stroke," he said.