Sports Medicine Research: In the Lab & In the Field: Potential Genetic Marker for Posterior Tibial Tendinopathy (Sports Med Res)
Thursday, May 17, 2012

Potential Genetic Marker for Posterior Tibial Tendinopathy

MMP-8 polymorphism is genetic marker to tendinopathy primary posterior tibial tendon

Godoy-Santos A, Ortiz RT, Mattar Junior R, Fernades TD, Santos MCL. Scand J Med Sci Sports . 2012; 39(11): 2319-2324
Posterior tibial tendinopathy effects many people, especially females, and has several distinctive predisposing risk factors (e.g., flat foot, presence of accessory navicular bone, or impact of osteofibrous tunnel). However, many patients present with posterior tibial tendinopathy without any of the distinctive risk factors, which suggests there could be a genetic influence associated with patients being more prone to this injury. For example, if there is a genetic variation within the gene for MMP-8 (a proteinase that stimulates protein degradation) then the quantity or quality of the MMP-8 protein could be altered. Godoy-Santos et al. examined whether a specific genetic variation of the MMP-8 gene (-799 polymorphism in the promoter region of the gene) was associated with posterior tibial tendinopathy. This study included 150 women patients that were divided into 2 groups: 1) a control group (n = 100), which consisted of women who had normal posterior tibial tendons (based on magnetic resonance imaging) with no signs of degeneration, and 2) a test group (n = 50) with women who were undergoing a surgical procedure due posterior tendon degeneration. Every participant gave a DNA sample via buccal cells (cells on the cheek), which was genotyped for their MMP-8 polymorphism. They could have had the C/C, T/T or C/T genotype (which means there could be three genetic patterns at this location). Furthermore, the researchers assessed the distribution of specific alleles (genotype data explains the genetic sequence or code for a gene or protein, where allelic variation can measure the frequency of a polymorphism at a specific site). The analysis showed that T/T genotype was more frequent in the test group (46% vs 23%) and the C/C genotype was more frequent in the control group (67% vs 19%). There was no significant difference between the 2 groups in regards to the C/T genotype. There was also a significant difference in the frequency of the alleles. The T allele was significantly more frequent in the test group (54% vs 28%) and the C allele was significantly more frequent in the control group (72% vs 46%). This suggests that there may be a genetic association to posterior tibial tendinopathy.

Why are some people more susceptible to injuries than others? This question could be answered via intrinsic factors such as genetics. If a patient carries a different allele (genetic variation) this could alter their proteins. This could then make the patient more susceptible to an injury (or it could protect against an injury as well). In this study, participants with the T/T genotype were more likely to have a posterior tibial tendinopathy, whereas those carrying the C/C genotype were not as susceptible. This suggests that the T allele could be a risk factor for developing degenerative posterior tibial tendinopathy and the C allele could be a potential protective factor against developing degenerative posterior tibial tendinopathy. While this MMP-8 promoter polymorphism may be associated with posterior tibial tendinopathy it cannot be ruled out that there are many other genes that may be associated to posterior tibial tendinopathy. Knowing the genotype of a person could assist medical personnel in more specific treatment leading to better outcomes such as better exercise/rehabilitation programs to prevent degeneration. Do you think knowing genetic variations associated to injuries and diseases will help us develop more specific therapeutic agents and rehabilitation plans to promote patient recovery?

Written by: Jane McDevitt MS, ATC, CSCS
Reviewed by: Jeff Driban

Related Posts:

Godoy-Santos A, Ortiz RT, Junior RM, Fernandes TD, & Santos MC (2012). MMP-8 polymorphism is genetic marker to tendinopathy primary posterior tibial tendon. Scandinavian Journal of Medicine & Science in Sports PMID: 22487237

2 comments:

Kyle Kosik said...

I don't think you can say whether knowing if you had a genetic predisposition to have PTTD is beneficial or not. Until further research comes out looking at specific rehabilitation protocols for the treatment of PTTD in people who have a specific genome, you can't say "yes" or "no". Research needs to prove that a certain intervention is indeed effective for the treatment of PTTD. I think the research is going in the right direction, researchers need to have a better understanding of the genotype and the effects conservative treatment has on PTTD.

Jane McDevitt said...

Kyle,

I agree there is not enough evidence to say that these SNPs in this one gene definitely predisposes you to PTTD let alone if it they can develop a therapy program based on their geneotype. However, I do think gene therapy is the future. Individualized medicine is important especially in rehabilitation, and you cant get more individualized then basing it off one's geneotype. I think this article did a good job and it is one small step going towards that end goal.

There is so much research that needs to be done in genetics overall before we can create rehabilitation programs based on their genotype. Though research like this (association studies) is one of those first steps. After there is enough evidence that these SNPs are strongly associated researchers can do genetic effect studies. Effect studies actually change the DNA which we obviously can not do in people (VERY UNETHICAL!). These studies are done in animals and in vitro. There are also GWAS (genome wide association studies) that are being doing that look at thousands of people with and without the disease and researchers look at their entire genome (the map of all their genes and genetic variations within) to view if there are any genotypes strongly associated to the disease. So researchers are moving forward but have a way to go.

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