Genetic link found in superficial digital flexor tendon injuries

© Mike Bain
© Mike Bain

A genetic link in tendon injuries in thoroughbred racehorses has been identified in research in Britain.

Superficial digital flexor tendon injuries are common among thoroughbred hurdlers and steeplechasers in Britain, leading to training and racing days lost and early retirement.

Various factors have been identified as increasing the risk of tendon injury, including gender, age, exercise regimen, trainer, and track surface.

But could some horses have an inherited predisposition toward such injuries?

The latest issue of Equine Science Update reports on research by Lucinda Tully and her colleagues, who set about exploring whether genetic susceptibility is a potential risk factor for superficial digital flexor tendon damage in thorougbred racehorses.

Their research, funded by Britain’s Horserace Betting Levy Board, compared the genotype of horses with and without superficial digital flexor tendinitis in a case-control study.

A report of the work has been published in the Equine Veterinary Journal.

Tully looked specifically at single nucleotide polymorphisms (SNPs) in seven genes that are involved in tendon structure, function, and remodelling or are known to be involved in Achilles tendinopathy (an equivalent condition in humans).

Genetic material for the study was derived from mane hair, or peripheral blood cells, collected from 270 horses with a history of superficial digital flexor tendon strains, and 270 unaffected control samples, chosen at random from among the other horses at yards with affected cases.

The study’s findings suggest that sequence variants in TNC and COL5A1 genes are associated with these tendon strains in racehorses.

A SNP in COL5A1 significantly increased the odds of having SDF tendinitis. Racehorses having two copies of the COL5A1 COL5A1_01 variant allele were nearly three times more likely to have superficial digital flexor tendinopathy than those homozygous for the wild-type allele.

Conversely, a SNP in the TNC gene was associated with significantly lower odds of such injury. Racehorses heterozygous for the TNC BIEC2-696469 polymorphism were less likely to have such tendon injuries compared to those with two copies of the wild-type allele.

TNC plays an important role in regulating the tendon cell-matrix. It encodes Glycoprotein tenascin C, which is highly expressed during tissue remodelling and is regulated by mechanical loading.

Tully explains that low levels of glycoprotein tenascin C are present in healthy adult tendon tissue with increased expression in acute tendinopathy.

The researchers suggest that further studies in a larger group of horses are needed to determine the significance of these findings at the population level.

In the future it may be possible to use genetic markers to identify horses at risk of tendinopathy affecting the superficial digital flexor tendon.

Polymorphisms in TNC and COL5A1 genes are associated with risk of superficial digital flexor tendinopathy in National Hunt Thoroughbred racehorses

L.J. Tully, A.M. Murphy, R.K.W. Smith, S.L. Hulin-Curtis, K.L.P. Verheyen, J.S. Price,
Equine Vet J 2013
DOI: 10.1111/evj.12134

Equine Science Update

Latest research and information from the horse world.

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