For going on 30 years, scientists have been trying to grow replacement parts for diseased, defective or damaged tissues and organs. They've had more disappointments than successes. But now and again, they come up with results that rekindle the flame.
The latest involves five Mexican boys between 10 and 14 who suffered terrible damage to their urinary tracts from auto accidents. They were unable to urinate normally.
"When they first came in, they had a leg bag that drains urine, and they have to carry this bag everywhere they go," says Dr. Anthony Atala of Wake Forest University in North Carolina. "It's uncomfortable and painful. So these children were mostly sitting or bed-bound."
Atala and his colleagues, including doctors at Metropolitan Autonomous University in Mexico City, figured out a way to grow these children new urethras, the tube that empties urine from the bladder.
The first thing they did was remove a small patch of each boy's bladder.
"The piece of tissue we take is very small -– less than half the size of a postage stamp," Atala says. The tissue contains two types of cells –- muscle cells and endothelial cells, which form the lining of the urethra and other hollow tubes in the body, such as blood vessels.
The researchers multiplied these cells in the lab until there were 100 million of them. Then they used the cells to "seed" a cylinder made out of biodegradable material. A week or so later, the cells covered the cylinder, creating a tube of tissue about as long as a deck of cards, with a diameter a little bigger than a soda straw.
The researchers stitched these made-to-order tissue tubes into the gaps in the boys' urinary systems. Eventually, the biodegradable "scaffolding" melts away.
That was as long as six years ago. Today, in every case, the boys' re-engineered urinary tracts are functioning normally, the researchers say.
The unusually long follow-up is perhaps the most important aspect of the new report, which appears online in the British journal The Lancet.