Tuesday, August 11, 2009

A Genetic Link For ACL Injuries?

One of the more hotly debated questions in soccer is why do female athletes suffer more ACL injuries than males. Researchers have proposed a whole host of possible explanations ranging from muscular strength to hormonal changes. For the first time, a preliminary study headed by researchers at the University of Cape Town, South Africa, has found a possible genetic link. It seems that a gene variant in one of the many genes that responsible for the production of collagen (the primary component of ligaments and tendons) may affect the risk of suffering an ACL injury.

A gene variant is a small variation in the genetic code. In many cases, gene variants affect health and may increase the risk of developing various diseases. The COL5A1 gene is responsible for the production of type V collagen. Collagen is the major protein found in ligaments and tendons. It gives these tissues, strength and elasticity. Compared to type I collagen, Type V collagen is a relatively minor component. However, it is necessary for organizing and strengthening Type I fibers. In an earlier study, this research group found the absence of what is called the CC genotype of COL5A1 BstUI RFLP to associated with increased risk of chronic tendinopathy (pain and swelling of the Achilles tendon). Based on this, they set out to determine if this same genetic variant was associated with increased risk of ACL injuries.

The investigators examined a total of 345 athletes from various sports. Of these 38 women and 91 men had suffered an ACL tear. Care was taken to match the injured and non-injured athletes in terms of age, weight, height as well as participation in contact, non-contact, non-jumping and skiing sports. A blood sample was taken and analyzed for variants in the COL5A1 gene.

Two key findings emerged from the results. First, women who possessed the CC gene variant were less likely to have suffered an ACL injury. Second, women who had a sibling with an ACL rupture were twice as likely to have had their own ACL torn. Interestingly, the risk of ACL injury in men was not affected by their gene variant.

This study if the first to suggest that there is a genetic component for ACL injury in women. Possessing a variant in one of the genes responsible for Type V collagen production seems to affect the female athlete’s risk of suffering an ACL rupture. Athletes who have the CC variant have reduced risk while those with other variants seem to have increased risk of injury.

What does this study mean for female athletes? First, this is a relatively small and preliminary study. More confirmation is needed to verify the results. Second the degree of risk associated with this gene variant is not clear. There are several examples of preliminary studies that initially showed a link between various factors and ACL injury risk. Subsequent studies failed to confirm the initial results or indicated that the risks were very small. So, further research is needed before we draw firm conclusions.

Third, let’s assume that the results are true and that this gene variant greatly affects risk of ACL injury. Then the importance of the study lies in the possibility of identifying “at risk” athletes before an injury occurs. A blood test could tell athletes, physicians and trainers which athletes are more likely to suffer a ligament tear. This information could then be to provide preventative measures to reduce the risk of injury. Those athletes without the CC variant of the COL5A1 gene might be given targeted training programs, special diets or preventative bracing / taping.

For the first time, researchers have identified a genetic risk factor for ACL ruptures in female athletes. While more research is needed to confirm these preliminary results, it may soon be possible to identify “at risk” individuals and design programs to counter this risk.

Reference:

Posthumus M, September AV, O’Cuinneagain D, van der Merwe W, Schwellnus MP, Collins M (2009) The COL5A1 gene is associated with increased risk of anterior cruciate ligament ruptures in female participants. American Journal of Sports Medicine, DOI: 10.1177/0363546509338266