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Implant Lets Patients Regrow Lost Leg Muscle

A new surgical procedure could help people suffering from debilitating wounds.

Five people who suffered serious leg injuries have been able to regrow muscle tissue in their legs thanks to a new regenerative medicine treatment.

The new treatment requires intensive surgery to remove scar tissue, after which a biological scaffold is sutured in. Within two days, the patients began an intensive physical therapy regimen that helps direct the development of stem cells in the body that are drawn to the implant. Once the stem cells reach the implant, they start making new muscle tissue.

The aggressive physical therapy is demanding but critical, said study senior author Stephen Badylak, a regenerative medicine researcher at the University of Pittsburgh, at a teleconference on Tuesday. That’s because mechanical forces are one of the most important cues that tell the recruited stem cells to develop into properly aligned muscle tissue, he said.

Three of the five patients involved in the U.S. Department of Defense-funded study were injured during military service; two of these injuries were the result of IED blasts. The other two participants were injured in skiing accidents. Each injury had taken between 60 and 90 percent of thigh muscle or lower leg muscles, and the participants had already undergone multiple surgeries and physical therapy to try to repair their damaged limbs. “Frankly, most of these patients have been through hell,” said Badylak.

Although the body has a natural ability to regenerate some muscle after injury, extreme trauma can create gaps that are too large for normal processes to fill, so the gaps are instead filled with scar tissue. Such injuries, which can be caused by motorcycle accidents, bomb blasts, and more, lead to “a debilitating condition with limited treatment options,” says Andrés García, a bioengineer at the Georgia Institute of Technology who was not involved in the study.

The new treatment, described in Science Translational Medicine on Wednesday, is “simple yet with significant translational potential,” says García. After the experimental treatment, three of the five patients increased their leg strength by 20 percent or more, and were 25 percent better at physical tests such as standing on one leg and hopping. Biopsies taken six to eight months after the procedure indicated that at least some muscle tissue grew in all five patients, all of whom reported improved quality of life.

The scaffold implant is a commercially available product produced by removing the cells from a pig’s bladder. What remains is a three-dimensional structure of collagen, sugars, and proteins that aren’t attacked by the immune system when implanted. The material is widely used as a passive structural support for abdominal wall hernias, breast reconstruction, and chest wall defects. 

But the compounds in the scaffold can also affect stem cells, said Badylak. As the scaffold starts to break down over several months, it releases biochemical signals that attract the body’s stem cells to the implant.  These stem cells can then help remodel the remaining scaffold and regrow muscle fibers.

The researchers have started treating patients with upper body injuries, and are seeing similar results.