The proteins attract human stem cells to migrate to the limb area and start creating skeletal muscle cells.
A new tissue regeneration technique has been developed to re-grow large amounts of skeletal tissue.
The method could give new hope to people who face amputation.
For the first time, scientists have figured out how re-grow big chunks of human skeletal muscle by tricking the human body into accepting a biological matrix of pig proteins. If successful, this cellular regeneration method promises new life for injured war veterans and other trauma victims who are missing more than 25 percent of a limb and/or who face amputation.
The researchers base their optimism on 20 years of clinical research, animal trials and a single "human guinea pig" patient, a U.S. Marine who nearly had his legs blown off in Iraq seven years ago, but who is now playing softball and jogging three years after surgery.
"This offers the possibility of creating new functional tissue," said Stephen Badylak, deputy director of the McGowan Center for Regenerative Medicine at the University of Pittsburgh Medical Center. Badylak has been credited with performing this treatment for the first time on a human.
Badylak said the regenerative technique uses proteins taken from pig intestines, which are inserted into the damaged human tissue. The proteins attract human stem cells to migrate to the limb and start creating matching bone and tissue cells.
"We put a homing device inside and it recruits (human) stem cells on its own," Badylak said. "It's a shortcut."
Since the regenerative technique uses "decellularized" material around the cells, Badylak says he's able to avoid conflicts with the human body's immune system, which normally would attack cells and other recognizable biological material from another species.
Badylak's team is now screening patients for a Pentagon-funded clinical trial that will launch at Pittsburgh and four other medical centers across the country later this year with 80 subjects. A separate study that is also being done at the Pitt Medical Center will be trying to re-grow bone material in patients with head injuries, according to a university spokeswoman, using a special "bone cement."
What's new here is the promise of re-growing skeletal muscle and bones, something that hasn't been done before in human subjects. Badylak and other researchers say they are optimistic at the results of animal studies in which it worked, but they need to test how it works in patients that have lost at least 25 percent of their muscle tissue in an arm or leg. Other experts in this field say that it's still early days, even though they agree the experiments are promising.
"We know this technique works with soft tissue," said Anthony Atala, who is director of the Institute for Regenerative Medicine at Wake Forest University and a member of the scientific advisory board of Acell, a Pittsburgh-based company that manufactures the pig protein matrix. "The question is whether it will be able to regenerate bone tissue as well. With all these technologies, we have to look at them long term and assess the functionality of the patients," said Atala.
One patient who's already happy with the results is 25-year-old Marine Cpl. Isaias Hernandez of San Antonio. While deployed in Iraq's dangerous Al-Anbar province back in 2004, Hernandez was carrying a TV set from a base store to his truck when a mortar landed nearby. Shrapnel from the explosion killed a man next to him and sliced through Hernandez's legs. The 12-inch TV monitor protected his upper body and probably saved his life.
Hernandez was severely injured and lost more than a quarter of his right thigh. He has undergone more than 50 surgeries since then to repair tissue, remove infections and insert or fix screws holding his damaged leg together. In 2008, Hernandez volunteered to be the first human subject in Badylak's new experimental tissue regeneration therapy.
"They cut a little slit into my thigh where they were going to put the material," Hernandez told Discovery News. "It was like blood in an envelope."
This envelope was a cellular matrix taken from a pigs' intestine, which then grew and formed human skeletal muscle, according to Badylak. Hernandez has been the only human patient so far.
"It feels pretty good," Hernandez said. "I've been losing weight and playing sports."
Hernandez has been on medical leave while he awaits a second surgery in Pittsburgh. He says he's been trying to get fit enough to re-join the Marines.