Doping scandals have become commonplace in recent sporting history. The battle to curtail the use of illegal substances has become part and parcel of the day-to-day business of high-level sport.
Up to now, the most significant threat has come from the use of anabolic steroids. Recent advances in gene therapy, may however open the door to a whole new, much more profound, way of cheating.
The possibility of athletes using gene therapies to increase their endurance and strengthen their muscles is becoming very real, and is being discussed more and more regularly at conferences.
How gene doping would work
Gene therapies are offering great promise in treating a wide variety of conditions. So-called vectors, in most cases viruses, are used to transfer genetic information into cells. The idea is that the new genetic information can correct the damaged or absent genes associated with the particular genetic condition.
Gene doping would essentially be a form of gene therapy, with the exception that healthy persons would be treated, and rather than curing a disease, the focus would be on enhancing the athletic performance of a healthy body.
In 1998 a study was published in the journal, Proceedings of the National Academy of Sciences, showing that gene therapies could be used to strengthen muscle in mice. The work was done with the eye on future gene therapies to treat the depletion of ageing muscle and conditions such as muscular dystrophy.
The researchers injected a virus containing the gene responsible for the production of the protein, insulin growth factor 1 (IGF1), into mouse muscle. IGF1 has been identified as a crucial protein to the building of muscle.
The researchers found that the muscles of mice injected with the gene withstood the effects of ageing much better than other mice. And in addition, young mice showed increased muscle growth, even without exercising.
The idea is that similar procedures may be used to boost muscle strength in athletes. This form of doping could be very hard to detect, since the proteins may be similar, or very close to similar, to those naturally occurring in the athlete.
Additionally, since the related proteins do not circulate through the body, a biopsy may be the only way to obtain a relevant sample.
Boosting blood genetically
Apart from muscle enhancement, genetic changes to an athlete's blood may also result in improved performance. This would involve inserting a gene into a person's bloodstream to boost production of the hormone erythropoietin (epo).
Epo tells the body to produce more red blood cells, which would enhance the oxygenation of tissue, thereby increasing stamina.
A synthetic form of epo is already being used by some athletes to boost performance. The difference with gene doping, would be that the athlete's body would itself be producing the extra epo.
In 1997 researchers successfully introduced a gene into mice and monkeys to increase production of epo. As yet there is no evidence of similar trials in humans.
Dangers of gene doping
Increased levels of epo leads to a thickening of blood, which in turn, raises the risk of bloodclotting and stroke. When using synthetic epo the risk is only temporary, since the body will flush out the drug over time.
If, however, the orders to produce more epo is given at a genetic level, reversing the process may be much more complicated. Blood may become thicker and thicker, until the body is no longer capable of coping with it.
Similarly, genetically boosting IGF1 levels, may lead to too much muscle growth, which could cause fractures, if muscle growth is out of proportion with the surrounding tendons and bone.
The greatest threat to the athlete's health may well come from as yet unknown risks. Despite its huge potential, gene therapy has delivered very few concrete health benefits so far. And, since inserting genetic material into cells is a very tricky business, the potential for serious side effects is very high.
Gene doping, a real concern
Despite the risks associated with gene doping, experts nevertheless consider the threat as imminent.
"We have seen an interest among individuals who contact gene researchers for the purpose of doping in sport," said Karolinska Institutet's Professor Arne Ljungqvist, Sweden's most well-known anti-doping expert and chairman of WADA's Health, Medical and Research Committee.
And according to WADA chairman Richard W. Pound, "gene doping represents a serious threat to the integrity of sport and the health of athletes." (Marcus Low, Health24)
(Sources: Gene Doping, Science News Online. October 30 2004
Read more: Gene therapy: what you should know
November 2005, updated January 2007