The fear is that gene manipulation can also be applied to try to improve sports performance; in this sense, the World Anti-Doping Agency (WADA) has already taken steps, including genetic doping in the list of prohibited methods and substances.
In theory, all levels of proteins present within our body can be modulated through gene therapy.
The conference on genetic doping which was held in March 2002 by WADA [Pound R, WADA 2002], and the "European Labor Congress on Harmonization and Future Developments of the Anti-Doping Policy" which took place in Arnhem, Holland, in the same year, gave the possibility to scientists, doctors, doctors, governments, anti-doping organizations and pharmaceutical industries, to exchange any type of information on the results of research and detection methods regarding this new doping technique. .
Since January 1, 2003, the International Olympic Committee (IOC) has included genetic doping in the list of prohibited substance classes and methods [WADA, 2007]. Since 2004, WADA has taken responsibility for publishing the international doping list, which is updated annually. The genetic doping method included in this list is defined as the non-therapeutic use of cells, genes, genetic elements or the modulation of gene expression, with the aim of improving athletic performance.
This article aims to:
- to clarify whether in sports it is actually possible to make use of the increasing knowledge deriving from gene therapy, a new and promising branch of traditional medicine;
- identify the possible ways in which gene therapy can be used in order to increase performance.
In this "age of genetics and genomics, it will be possible to identify the genes that determine a person's genetic predisposition for a specific sport [Rankinen T at al., 2004]. The study of genes at a young age can represent the best way to develop a great athlete starting from a child and to create a specific personal training program. This study applied to athletes can also be used to identify specific training methods with the aim of increasing the genetic predisposition for that type of training [Rankinen T at al., 2004].
But will studying genes result in better athletes?
Marion Jones and Tim Montgomery were both 100m speed champions, they had a baby in the summer of 2003. Steffi Graf and Andre Agassi (both World Tennis Championships) also have children. These kids will most likely be favorites. compared to the others, but there are also other factors, such as environmental and psychological ones, which will determine or not the possibility that they become champions.
Gene therapy can be defined as the transfer of gene material into human cells for the treatment or prevention of a disease or dysfunction. This material is represented by DNA, RNA, or by genetically altered cells. The principle of gene therapy is based on the introduction into the cell of a therapeutic gene to compensate for the missing gene or replace the abnormal one. Generally, DNA is used, which codes for the therapeutic protein and is activated when it reaches the nucleus.
"Most athletes take drugs" [De Francesco L, 2004].
A survey by the Drug Research Center concluded that less than 1% of the Dutch population has taken doping products at least once, for a total of about 100,000 people. 40% of these people have been using doping for years and most of them do strength training, or body building. The use of doping substances in elite sport seems to be higher than the 1% indicated for the general population, but the exact figure is not known. The percentage of elite athletes who test positive on doping controls has fluctuated between 1%. 1.3% and 2.0% in recent years [DoCoNed, 2002].
WADA's definition of genetic doping leaves room for questions
- What exactly does non-therapeutic mean?
- Will those patients with muscular dysfunctions treated through gene therapy be admitted to the competitions?
The same consideration applies to cancer patients who have been treated with chemotherapy and who now receive the EPO gene encoding erythropoietin to speed up the recovery of bone marrow function.
Current gene therapy research is also being conducted to speed up the healing process of a wound, or to relieve muscle pain after exercise; such practices may not be regarded by all as "therapeutic" and their performance enhancing properties may be questioned.
From a clinical point of view, it would be more appropriate to specify better the definition of genetic doping, especially in the light of an improper use of gene transfer technologies.
WADA (section M3 of the World Anti-Doping Code (version January 1, 2007) justified the ban on genetic doping through the following points:
- scientific evidence, proven pharmacological effect or experience, that the substances or methods included in the list have the ability to increase sports performance;
- the use of the substance or method causes a real or presumed risk to the athlete's health.
- the use of doping violates the spirit of sport. This spirit is described in the introduction of the Code with reference to a series of values such as ethics, fair play, honesty, health, fun, happiness and compliance with the rules.
There are many uncertainties regarding the long-term effects of gene modification; many of these effects may also never be discovered, either because they have not been thoroughly studied (due to financial problems), or because it is difficult to define reliable samples for studying the side effects of completely new methods or applications.
Unlike somatic cell therapies, the alterations of the germ lines are permanent and are also transmitted to the offspring. In this case, in addition to the possible risk to the health of athletes, there are also risks towards third parties, such as posterity, parents or partners.
In the field of pharmacogenetics, the development of which depends on the combined efforts of science and the pharmaceutical industry, the main objective is to develop medicine "tailored" for each of us. As it is well known, many medicines have a completely different depending on who takes them, this is due to the fact that their development is generic and does not take into account individual genetic characteristics. If pharmacogenetics were to spread in the world of sport, the very idea of competition between apparently equal athletes who train in more or less comparable ways could become obsolete.
The experimental clinical data of gene therapy have shown very encouraging results in patients with severe combined immunodeficiency [Hacein-Bey-Abina S et al., 2002] and haemophilia B [Kay MA, et al. 2000]. Furthermore, angiogenic therapy through vectors expressing vascular endothelial growth factor for the treatment of coronary heart disease has given good results in angina [Losordo DW et al., 2002].
If the transfer of genes encoding tissue growth factors were used [Huard J, Li Y, Peng HR, Fu FH, 2003], the treatment of various damages associated with sports, such as ligament rupture, or muscle tear , could theoretically result in better regeneration. These approaches are now being evaluated on animal models, but clinical trials on humans will certainly be activated in the coming years.
In 1964, Northern Finnish skier Eero Mäntyranta made his opponents' efforts useless by winning two Olympic golds at the Games in Innsbruck, Austria. After a few years, it was shown that Mantyranta carried a rare mutation in the gene for the Erythropoietin receptor which, by compromising the normal feedback control on the number of red blood cells, causes polycythemia with a consequent increase of 25-50% in oxygen transport capacity. Increasing the amount of oxygen to the tissues means increasing resistance to fatigue. Mäntyranta had what every athlete wants: EPO. Athletes of the future may be able to introduce a gene into the body that mimics the effect of the gene mutation that naturally occurred in Mäntyranta and conducive to performance.
Insulin-like growth factor (IGF-1) is produced by both the liver and muscle and its concentration depends on that of human growth hormone (hGH).
Training, Sweeney suggests, stimulates muscle precursor cells, called "satellites", to be more "receptive to IGF-I.
[Lee S. Barton ER, Sweeney HL, Farrar RP, 2004]. Applying this treatment to athletes would mean strengthening the tennis player's brachial muscles, the runner's calf, or the boxer's biceps. Such therapy is thought to be relatively safer than EPO, since the effect is localized only to the target muscle. It is likely that this approach will also be applied to people as early as the next few years.
An isoform of insulin-like growth factor-1 (IGF-1), the mechanical growth factor (MGF), is activated by mechanical stimuli, such as e.g. muscle exercise. This protein, in addition to stimulating muscle growth, plays an important role in the repair of injured muscle tissue (such as occurs after intensive training or competition).
MGF is produced in muscle tissue and does not circulate in the blood.
VEGF represents the growth factor of the vascular endothelium and can be used to facilitate the growth of new blood vessels. VEGF therapy was developed to produce coronary artery bypass grafting in patients with ischemic heart disease, or to help elderly people with peripheral arterial disease. Genes that code for VEGF can promote the growth of new blood vessels by allowing a greater supply of oxygen to the tissues.
So far, gene therapy experiments have been done for diseases such as cardiac ischaemia [Barton-Davis ER et al., 1998; Losordo DW et al., 2002; Tio RA et al., 2005], or peripheral arterial insufficiency [Baumgartner I et al., 1998; Rajagopalan S et al., 2003].
If these treatments were also applied to athletes, the result would be an increase in the oxygen and nutrient content of the tissues, but above all the possibility of postponing the exhaustion of both cardiac and skeletal muscle.
Since VEGF is already used in many clinical trials, genetic doping would already be possible.
The normal differentiation of the musculoskeletal mass it is of fundamental importance for the correct functionality of the organism; this function is made possible thanks to the action of myostatin, a protein responsible for the growth and differentiation of skeletal muscles.
It acts as a negative regulator, inhibiting the proliferation of satellite cells in muscle fibers.
Experimentally, myostatin is used in vivo to inhibit muscle development in different mammalian models.
Myostatin is active both with autocrine and paracrine mechanisms, both at the musculoskeletal and cardiac level. Its physiological role is not yet fully understood, even if the use of myostatin inhibitors, such as follistatin, cause a dramatic and widespread increase in muscle mass [Lee SJ, McPherron AC, 2001]. Such inhibitors can improve the regenerative condition in patients suffering from serious diseases such as Duchenne muscular dystrophy [Bogdanovich S et al., 2002)].
Myostatin belongs to the TGF beta superfamily and was first revealed by the group of Se-Jin Lee [McPherron et al., 1997]. In 2005, Se-Jin Lee of Johns Hopkins University pointed out that mice deprived of the myostatin gene (knock out mice) develop hypertrophic musculature.
These supermice were capable of climbing stairs with heavy weights attached to their tails. During the same year, three other research groups showed that the bovine phenotype commonly called "double-muscle" was due to a mutation of the gene encoding myostatin [Grobet et al., 1997; Kambadur et al., 1997; McPherron & Lee, 1997].
A mutation of the homozygous type mstn - / - was recently discovered in a German child who has developed extraordinary muscle mass. The mutation has been referred to as the effect of inhibiting myostatin expression in humans. The child developed muscles well at birth, but growing up also increased the development of muscle mass and by the age of 4 he was already able to lift weights of 3 kilos; he is the son of a former professional athlete and his grandparents were known as very strong men.
Genetic analyzes of the mother and child revealed a mutation in the myostatin gene resulting in a lack of production of the protein [Shuelke M et al., 2004].
Both in the case of the experiments conducted on the mouse by the Se-Jin Lee group and in that of the child, the muscle had grown both in the cross section (hypertrophy) and in the number of myofibrils (hyperplasia) [McPherron et al., 1997].
Pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage and described in terms of such damage [iasp]. Due to its unpleasantness, the emotion of pain cannot be ignored and induces the subject who tries it to avoid the (noxious) stimuli that are responsible for it; this aspect configures the protective function of pain.
In sports, the use of powerful pain relieving drugs could lead athletes to train and compete beyond the normal pain threshold.
This can cause considerable health risks for the athlete, since the injury can worsen considerably, turning into a permanent injury. The use of these drugs can also lead the athlete to psycho-physical dependence on them.
An "alternative to legal pain relievers could be to use analgesic peptides such as endorphins or enkephalins. Preclinical animal research has shown that the genes encoding these peptides have an effect on the perception of inflammatory pain [Lin CR et al. , 2002; Smith O, 1999].
However, gene therapy for pain relief is still far from its clinical application.
, chemicals, viruses, etc.) and the encoded transgene.Clinical research to date has been relatively safe [Kimmelman J, 2005]. More than 3000 patients have been treated and only one of these died of chronic liver disease and vector overdose [Raper SE et al., 2003]. In three other patients treated for immunodeficiency syndrome, leukemia-like symptoms developed [Hacein-Bey-Abina S et al., 2002] and one of them died. Since then, other research groups have treated similar patients with similar therapeutic results, without any side effects [Cavazzana-Calvo M. Fischer A, 2004]. In this case, research is aimed at treating patients with vectors that can never be used to boost performance.
People who try to increase their EPO levels unnaturally also increase the likelihood of experiencing heart attacks, or acute brain episodes. The increase in red blood cells also determines an increase in blood density which can cause blood clots; it is therefore not wrong to think that the adverse reactions seen in patients can also occur in healthy athletes. [Lage JM et al., 2002].
If EPO were introduced genetically, the level and duration of erythropoietin production would be less controllable, so that the hematocrit would advance almost indefinitely to pathological levels.
It is hypothesized that treatment with IGF-1 may lead to the growth of hormone-dependent tumors.
It is therefore of crucial importance that the use of pharmacogenetically selected vectors has a well known and controlled gene expression model.
The exact methods of detecting genetic doping have not yet been established, also because the DNA that is transferred with gene therapy is of human origin, therefore not different from that of athletes who use it.
Muscle therapies are confined to the injection site or to the tissue in the immediate vicinity, therefore, most of the gene technologies on the muscles will not be able to be detected through the classic anti-doping analysis of urine or blood samples; a muscle biopsy would be necessary, but it is too invasive to be conceived as a normal means of doping control.
Many forms of genetic doping do not require the direct introduction of genes into the desired organ; the EPO gene, for example, can be injected into any part of the body and locally produce the protein that will then enter the circulation. Looking for the EPO injection site would be like looking for a needle in a haystack.
In most cases, however, genetic doping will result in the introduction of a gene that is an exact copy of the endogenous one and capable of giving rise to a protein completely identical to the endogenous one in its post-translational modifications.
A recent publication indicates that it is possible to detect a difference between the innate protein and the gene therapy product based on the different pattern of glycosylation in different cell types, it remains to be seen whether this is the case with all types of genetic doping [ Lasne F et al., 2004].
Public authorities and sports organizations, including the International Olympic Committee, have condemned doping as early as the 1960s. Recent advances made with biologics will have a major impact on the nature of medicines prescribed to patients, and will also change the choice of drugs used to improve athletic performance.
Gene therapy is authorized exclusively for clinical testing of somatic gene therapy products in humans, strictly excluding the possibility of considering any type of human germline gene therapy as feasible.
The prohibition of genetic doping by the World Anti-Doping Agency (WADA) and international sports federations provides a strong basis for its elimination in sport, but it will also depend on how the various regulations are received by athletes.
Most athletes do not have enough knowledge to fully understand the potential negative effect of genetic doping. For this reason it will be very important that they and their support staff are well trained, in order to prevent its use. Athletes must also be aware of the risks associated with the use of genetic doping when used in uncontrolled facilities, without however, compromise the infinite potential offered by official gene therapy for the treatment of serious pathologies.
The pharmaceutical industry is well aware of the possibilities and risks deriving from the use of genetic doping and wants to collaborate in the development of research for the detection of gene products present in its drugs. It should preferably sign a code in which it undertakes never to produce or sell, for any reason, genetic products for non-therapeutic use.
A limited number of people from different disciplines of science and sport were interviewed, in order to get an "idea about the notion and the possible impact of genetic doping on them. Among the interviewees there were three sports doctors, a pharmacist, four elite athletes and five scientists from academia and the pharmaceutical industry; here are the questions:
- Are you familiar with the term genetic doping?
- What do you think this term means?
- Do you believe in improved performance through the use of genetic doping?
- What are, in your opinion, the health risks associated with the use of genetic doping?
- Is genetic doping already used, or will it only be in the future?
- Will it be easy to detect genetic doping?
From the various responses, it is clear that people outside the scientific community have little knowledge about the use of this therapy; a common fear is that gene therapy could affect offspring, or cause cancer. genetic doping will be complex and preventive measures difficult. On the other hand, everyone insists that genetic doping will be used by athletes as soon as it is available and that this will happen in the next few years.
Professionals surrounding elite athletes are very concerned about the possible use of genetic doping and recommend the education of their athletes and their medical support staff to support the development of preventive anti-doping measurement research. These professionals are convinced that the problem of the application of genetic doping to athletes will arise within the next few years and that its detection will be rather difficult.
The world of sport will sooner or later find itself faced with the phenomenon of genetic doping; the exact number of years that will have to elapse for this to happen is difficult to estimate, but it can be assumed that this will happen shortly, in the next few years (2008 Beijing Olympics or at the latest in subsequent ones).
From cycling to weightlifting, swimming to soccer and skiing, all sports could benefit from genetic manipulation: just select the gene that improves the type of performance required! [Bernardini B., 2006].
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