It was only a year ago that ACell's "miracle powder" was sprinkled on amputated fingers and shown to stimulate the regeneration of fingertips. The world was both awed and skeptical of the powder's regenerative power, touting that it would revolutionize regenerative medicine or calling it was quack science.
A fingertip is one thing. A thigh, quite another.
After losing most of his thigh muscle in a battlefield explosion, one marine was given a second chance when another such miracle powder caused much of his thigh to grow back. It's not only a wonderful feel-good story, but demonstrating that the same substance can grow back different tissues suggests that we may have only seen a small part of its full regenerative potential.
October 12, 2004, Afghanistan
At the time the mortar exploded, U.S. Marine Corporal Isaias Hernandez and his companion were working to repair a truck. If he hadn’t been carrying a television at that moment he, like his companion, would have been killed. The TV absorbed most of the shrapnel, but what it missed tore through Hernandez’s arms and legs. His right thigh got the worst of it: 70 percent of its muscle was sheered off and the femur was fractured. For the next four years the Corporal underwent multiple surgeries and constant physical therapy, but his leg wasn’t getting stronger. His only option was amputation, as is the fate of the vast majority of limbs with severe muscle damage.
Enter Dr. Stephen Badylak, Director of Tissue Engineering at the University of Pittsburg’s McGowan Institute for Regenerative Medicine. Dr. Badylak and colleagues offered Corporal Hernandez an alternative to amputation: regrow the muscle. The key to this seemingly miraculous procedure is a material obtained from pig bladders. As the material’s name, the extracellular matrix implies, it is the mix of chemicals that fills the space surrounding the body’s cells. It’s a complex mixture of hormones, structural proteins, and other molecules that maintain the health and function of the cells, as well as mediates cell-to-cell communication. It also guides tissue growth. Following an intense physical therapy program to strengthen the 30 percent of muscle he had left, doctors made an incision deep into Hernandez’s thigh and applied the extracellular matrix. Instead of a powder like ACell's, Dr. Badylak's group turned the material into a gel form. "You can't use a powder to replace a tendon," remarked Dr. Badylak. It went to work, spurring not only the growth of muscle tissue but tendons, as he mentioned, and the proper vasculature as well. About six weeks after the surgery the Marine began to feel his strength returning. What’s more, he saw muscle bulking up in the area that the extracellular matrix had been applied. “I used to have a hard time walking and going up and down stairs,” he told Purdue alumnus magazine in a feature story on star alum Dr. Badylak. “I can pretty much walk and do stairs fine now.”
After more than a decade since Dr. Badylak first treated a patient with the extracellular matrix material he still doesn’t quite know how it does what it does. A few things researchers do know: the extracellular matrix becomes part of the tissue it is placed into; as part of the tissue it can grow and heal; it somehow recruits the body’s own stem cells to its location; and it changes the body’s immune response from attacking to “constructive remodeling.”
The decision to use extracellular matrix from pig bladders was not a scientific one, but an economic one. Pig parts were in abundance in butcher-happy Indiana near Purdue University where Dr. Badylak first began the research.
The fact that the extracellular matrix recruits the body’s own stem cells is huge because it obviates the need to introduce stem cells from an outside source. As we’ve discussed before, even genetically-identical cells derived from the patient can be problematic. Reprogramming skin cells, for instance, into heart cells requires significant molecular manipulation, and these manipulations can lead to side effects such as rejection or cancer. The fact that the extracellular matrix puts the body’s own stem cells to work is simpler and safer. It may also get Dr. Badylak’s treatment into clinics sooner. “It...simplifies treatment because it’s much easier to get FDA approval with stem cell research when you don’t have to harvest them,” he told Purdue alumnus.
As Dr. Badylak and his colleagues know, every little bit helps. Their ‘MiracleGro For Muscles’ wasn’t always seen as such. Even after years of watching the extracellular matrix successfully morph into whatever tissue it was inserted into–from nerve cells to muscle and bone–the research stubbornly refused to get funded. As Dr. Badylak told the Purdue alumnus, “Nobody thought it was worth funding because it was such a crazy idea. Why would anyone want to put pig tissue in a human?” But profit-minded entrepreneurialism saved the day from pundit-advised conservatism. Eli Lilly and Co. and DuPuy, an orthopedic company in Indiana, put real money into the idea. With the help of drug company coffers Dr. Badylak’s research took off and eventually Washington came aboard. The current study that gave Corporal Hernandez much of his thigh back is a trial in collaboration with the U.S. government. As part of a $70 million government program for regenerative medicine, it’s hoped that Hernandez’s will be the first of many such success stories.
Given that the U.S. is currently fighting two wars, the victory for regenerative medicine couldn’t have come at a better time. “I get six to eight emails a day (from potential patients),” Dr. Badylak said in December of last year, long before news of Corporal Hernandez’s regrown thigh. Let’s hope that this treatment makes it to the clinic soon, so that Dr. Badylak can answer not only their emails, but their prayers as well.