Stephen F. Badylak DVM, PhD, MD|
May 5, 2014 —Damaged leg muscles grew stronger and partially regenerated in three out of five men who were implanted with extracellular matrix (ECM) derived from pig bladder, according to a paper just published in the journal Science. The study was conducted by researchers at the University of Pittsburgh School of Medicine (UPMC) and the McGowan Institute for Regenerative Medicine.
Pig bladder ECM, which has long been used as the basis for medical products, is the structural scaffold remaining after urinary bladder tissue of a pig has been stripped of cells.
When a large volume of muscle is lost, the body cannot repair the damage on its own, explained senior investigator UPMC's Stephen F. Badylak, D.V.M., Ph.D., M.D. Instead, scar tissue forms, which impairs strength and function. Previous research conducted in Badylak’s lab suggested ECM could be used to regenerate lost muscle.
“This new study is the first to show replacement of new functional muscle tissue in humans, and we’re very excited by its potential,” Badylak said. “These are patients who can’t walk anymore, can’t get out of a car, can’t get up and down from a chair, can’t take steps without falling. Now we might have a way of helping them get better.”
The five men participating had at least six months earlier lost at least 25 percent of leg muscle volume and function compared to the uninjured limb. They first underwent physical therapy for 12 to 26 weeks until their function and strength had plateaued for a minimum of two weeks.
Then, study lead surgeon J. Peter Rubin, M.D., UPMC Professor and chair of plastic surgery, surgically implanted a quilt of compressed ECM sheets designed to fill in their injury sites. Within 48 hours of the operation, the participants resumed physical therapy for up to 26 additional weeks.
The researchers found that three of the participants, two of whom had thigh injuries and one a calf injury, were stronger by 20 percent or more six months after the surgery. One thigh-injured patient improved on the “single hop test” by 1,820 percent, and the other had a 352 percent improvement in a chair lift test and a 417 percent improvement in the single-leg squat test. Biopsies and scans all indicated that muscle growth had occurred. Two other participants with calf injuries did not have such dramatic results, but both improved on at least one functional measure and said they felt better.
“This work represents an important step forward in our ability to repair tissues and improve function with materials derived from natural proteins,” Rubin said.
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