It sounds like the stuff of Stephen King -- generating body parts, repairing damaged bone and growing back muscle like a gecko's severed tail. But stem cells represent a new wave of medicine that is more science than science fiction. One day they may not only lengthen an athlete's career but also provide the quick healing that Yankees pitcher Andy Pettitte was looking for when he used HGH to recover from elbow tendinitis in 2002.
"Using these cells can really revolutionize how sports injuries and trauma will be treated," says Joshua Hare, director of the Interdisciplinary Stem Cell Institute and chief of cardiology at the University of Miami Medical School.
First things first: The cells scientists are using for this technology aren't extracted from embryos and have nothing to do with cloning. "[President] Bush and the pope like us," says Michael Schuster, project manager of the Australian stem cell company Mesoblast and its U.S.-based sister company, Angioblast. These stem cells come from adults, usually from their bone marrow, and are called mesenchymal precursor cells (MPCs). They are a type of stem cell that is different from the blood-forming/immune-system strengthening hematopoietic stem cells that are used in transplants for leukemia and lymphoma patients. Once extracted, a small number of MPCs are separated from regular blood cells and cultivated, turning those few into millions. Then the cells are injected into the body at the site of injury, where they can generate healthy tissue, bone or cartilage.
Mesoblast says that it injected MPCs into 10 people who had suffered complete breaks of the femur or tibia and that seven healed in less than one third the initially projected recovery time. Says Hare, who has no relationship to Mesoblast and is himself administering a clinical trial for mesenchymal stem cell use in heart attack patients, "A major discovery that was made about these mesenchymal stem cells is that they tell the immune system to be tolerant of this particular cell."
A second type of stem cell therapy that is gaining proponents in sports applications is autologous treatment -- reimplanting the cells extracted from one's own body. Christopher Dalton, 18, a Texas all-state offensive tackle, injured the tendons in his left shoulder last year. He couldn't do a single push-up or lift more than a couple of pounds. Three days after an autologous stem cell treatment -- the cells were extracted from Dalton's tibia -- he had regained 90 percent of his shoulder function, and within a month, the 6'2", 240-pounder was bench-pressing 285 pounds. "His stem cell shoulder was actually stronger than his uninjured shoulder," says his father, Stephen, a family practitioner who sent his son to California for the treatment. But the Daltons took a chance, and it's impossible to prove a causal link between the treatment and his recovery since the treatment has not been proven to work through clinical trials. "When people say they have a magic bullet, I become very dubious," says William Lensch, an instructor in pediatrics at Harvard Medical School and a stem cell researcher. "I don't think there are any easy [answers] left. They're all complex, and they'll all take complex therapies."
But Mesoblast and Angioblast are conducting FDA-approved trials for what they are calling "off-the-shelf" stem cells, which are cultivated from universal donors (volunteers, usually in their 20s, who undergo extensive screening). The hope is that this process will be inexpensive and accessible through a prescription in as little as three years. The treatment is intended for therapeutic use among the general population, but Mesoblast says it has been contacted by at least two Australian Rules Football clubs and several professional athletes from the U.S. "Whether it's football or baseball," says Schuster, "if they're looking for that slight advantage or quick recovery for a rotator-cuff injury or bone repair, this might be that edge."
A study conducted by researchers at the University of Pittsburgh School of Medicine and Sunnybrook Health Sciences Centre in Toronto found that injecting stem cells isolated from the skeletal muscle of women with urinary incontinence into the area surrounding the urethra strengthened their sphincter muscles. Based in part on that study, Johnny Huard, director of the stem cell research center at the Children's Hospital of Pittsburgh at UPMC and professor in the Department of Orthopedic Surgery at the University of Pittsburgh, believes that stem cells could one day relieve the wear and tear on athletes' muscles. "We have shown over the last eight years [and in a published report in the September issue of Nature Biotechnology] that some cells can be tweaked to become muscle cells. We believe right now that we can use this technology immediately after injuries -- take cells from noninfected areas and use them to repair muscle injuries."
What about muscles that aren't injured? What about athletes with healthy muscles who are simply looking to get stronger? Silviu Itescu, Mesoblast's chief scientist and director of transplantation immunology at Columbia University Medical Center in New York City, says, "We've been putting these cells into healthy, normal tissues in animals and haven't seen any amounts of normal tissue growing larger or stronger." But in the same way that injecting a hormone to boost the number of red blood cells has been a method for athletes to increase oxygen capacity, there is potential, Itescu says, as the technology develops for stem cells to be injected into the heart to boost performance. So far, however, studies have not shown that MSCs would work on a healthy heart, nor have they indicated the level of injury that is required for the cells to boost heart function and thus blood flow.
Though stem-cell research is clearly in the early stages, antidoping agencies nevertheless have taken notice. Huard was contacted by the U.S. Anti-Doping Agency (USADA) more than two years ago to help develop tests to detect stem cell doping from both autologous and donor cells. If athletes were to use cells from a donor, detection would be possible, according to Itescu. "You can detect other people's DNA in your bloodstream with routine screening." But the process would be expensive, and testing of an athlete's DNA is a long way off for both practical and ethical reasons. The process also wouldn't work if athletes used their own cells. "We have no way of detecting that you have injected a cell from you to you," says Huard.
Hare, for one, doesn't see athletes abusing stem cell therapy. "I think you'd have to be crazy to inject this into yourself," he says.