LONDON -- For athletes, stem cells have much more than the potential to cure disease and save lives -- they may be able to heal injuries, boost strength and endurance, and provide a lasting edge over the competition.
If it sounds like stem cells are next frontier for doping in sports, it's because they very well may be.
"You could potentially find a 40-year-old man with 20-year-old legs."
-- Paul Griffiths, managing director of CryoGenesis International
"There's a spin-off technology from stem cells that could produce super-athletes," said Paul Griffiths, managing director of CryoGenesis International, which stores umbilical cord blood in its bank for potential later therapeutic use.
He thinks injecting stem cells into healthy muscles might increase their size and even restore them to their youthful capacity.
"You could potentially find a 40-year-old man with 20-year-old legs," Griffiths said.
While such applications could be years away, their potential use raises more ethical questions about doping in sports.
Professional sports have grappled with the question this summer after Tour de France winner Floyd Landis and Olympic and world 100-meter champion Justin Gatlin tested positive for banned substances.
Scientists are considering the potential fallout from the new technology, and sports officials will have to decide whether to allow it.
Like gene doping, which involves transferring genes into human cells to blend directly into an athlete's own DNA, it is thought an athlete's stem cells could be injected back into the body. The regenerative powers of stem cells offer countless sporting possibilities, such as increasing endurance, speed, flexibility and strength.
Griffiths' company counts five professional soccer players as clients who have frozen stem cells from their children's umbilical cords in their bank. While Griffiths says the unidentified players' primary goal is to have a type of "biological insurance" for their children, other potential uses cannot be ruled out.
Experimental studies in the United States found that stem cells successfully regenerated all the ligaments in the knees of goats -- their knee structure is believed to be similar to that of humans -- within 12 weeks. Were such techniques possible in humans, athletes would certainly have reason to be tempted.
"Even if it meant only an extra four or five years in their career, for an athlete, that could mean millions," Griffiths said.
Still, stem cell experts note that such technologies are years away from being routinely available.
In their natural environment, stem cells are self-regulated. Scientists hypothesize that the number of stem cells that exist in a muscle might be determined by their need.
"If you inject more stem cells into a healthy muscle, it might not necessarily do a lot," said Dr. Robin Lovell-Badge, of the UK's National Institute for Medical Research.
The process of using stem cells to strengthen muscles will probably not be as straightforward as a simple injection. Desired tissues might need to be first engineered in a laboratory before being implanted into athletes. Years of clinical experience would also be necessary to determine if such a process would be safe and effective.
Though such applications remain highly experimental, anti-doping authorities are already gearing for their arrival in sports. And while experts agree that testing for an individual's own stem cells reintroduced into the body would be virtually impossible, that does not mean that stem cell abuse would be undetectable.
"Our objective is not to detect stem cells, it's to detect the impact of those cells," said Dr. Olivier Rabin, science director at the World Anti-Doping Agency.
Once stem cells are reintroduced into the body, Olivier says that the body's homeostasis, or natural balance, would be disrupted. By looking for the cascade of metabolic events that would inevitably occur following the injection of stem cells, it should be possible to catch athletes using such technologies, Olivier said.
The speculation that using stem cells to enhance performance might have only minimal side effects, since no foreign substances would be involved, raises the issue of whether anti-doping regulations will soon be obsolete.
"Enhancement in sports is only problematic because there are rules against it," said John Harris, a bioethics professor at the University of Manchester.
As Harris points out, many unfair advantages already exist in sports, such as those athletes who can afford such luxuries as high-altitude training or having personal trainers and physiotherapists.
"Using stem cells would just be fine-tuning these advantages," Harris said. "They don't add anything in principle to what is already being done."