WASHINGTON — Scientists implanted thin sheets of scaffolding-like material from pigs into a few young men with disabling leg injuries, and they say the experimental treatment coaxed the men's own stem cells to grow new muscle.
The research, funded by the Defense Department, included just five patients, a small first step in the complex quest for regenerative medicine.
But the researchers said some of the men improved enough that they no longer need canes or they can ride a bicycle again, after years of living with injuries that today have no good treatment.
"The real rush for someone like myself is to see this patient being able to do these things and not struggle and have a smile on his face," said Dr. Stephen Badylak of the University of Pittsburgh School of Medicine. He led the study, which was reported Wednesday in the journal Science Translational Medicine.
Muscles have some natural ability to regenerate after small injuries. But if too much is lost — from a car accident, a sports injury or, for soldiers, a bomb blast — the body can't heal properly. Hard scar tissue fills the gaps instead. Called volumetric muscle loss, a severe enough injury can leave an arm or leg essentially useless.
The new experiment combined bioengineering with a heavy dose of physical therapy to spur stem cells that are roaming the body to settle on the injury and turn into the right kind of tissue to repair it.
Three patients were officially deemed a success because their legs were stronger by 20 percent or more after the surgery. They had dramatic improvements in tests showing they could hop or squat on the injured leg. Badylak said the two other men had some improvement in balance and quality of life, but not enough to meet the study's definition of success.
Nick Clark, 34, of Youngwood, Pa., suffered severe muscle loss after he broke his lower leg in a skiing accident. He had a hard time balancing and using stairs, and he sometimes needed a cane. He tried to ride his bike, but his left leg was too weak to pedal far.
He received the experimental therapy in 2012. It didn't restore him to normal, but he now reports biking "quite a distance" and playing table tennis, his left leg finally strong enough to pivot around the table.
"This strategy obviously has some merit," said professor George Christ of the Wake Forest Institute for Regenerative Medicine, who wasn't involved with the new study. While larger studies must verify the findings, "the concept of physical therapy coupled with these regenerative strategies is going to be really important."