Check Up: An advance athletes can cheer

A torn meniscus is among the most common afflictions suffered by athletes who make sudden stops and turns, such as NBA star Blake Griffin, whose injury forced him to pull out of the Olympics.

The usual response is to remove the torn portion of the tissue, to prevent further painful tearing. But because the meniscus cushions the knee joint, removing part of it can lead to osteoarthritis.

A possible treatment, say many in the field of bioengineering, is to replace the torn portion with new tissue, grown from the patient's own cells. Researchers at the University of Pennsylvania's Perelman School of Medicine recently reported a promising advance in that direction, spinning webs of polymer fibers to serve as a "scaffold" for new cells.

The results were published online this month in Proceedings of the National Academy of Sciences.

Scientists have been experimenting with various tissue scaffolds for years, but often the structures are too tightly packed to accommodate much cell growth, said Penn's Robert Mauck, senior author of the new paper.

He and his colleagues got around this problem by creating a composite scaffold from two kinds of polymers. One is water soluble, so it can be easily dissolved to allow space for cell growth.

Mauck said this solution with a "sacrificial" polymer reminds him of the game Jenga, in which players must remove wooden blocks from a tower without wrecking it.

"We've built a polymer scaffold, and we've figured how many little pieces we can pull out without having it collapse," said Mauck.

The two kinds of fibers are "spun" using electrospinning, a process that has long been used in various industries, such as textiles.

In the lab, the Penn team was able to "seed" these scaffolds with adult stem cells, harvested from bone marrow, which then promoted the growth of new cells. The team also has tried the approach without stem cells, implanting "unseeded" scaffolds in the knees of live sheep. The polymer webs became colonized with cells from the animals' surrounding tissue, Mauck said.

"You can let the body heal itself," he said.

If they can get it to work someday in people, athletes like Griffin would consider it a slam dunk.

- Tom Avril