High Frequencies of TNC and COL5A1 Genotypes Associated With Low Risk for Superficial Digital Flexor Tendinopathy in Greek Indigenous Horse Breeds Compared With Warmblood Horses

Tendinopathies constitute a very common category of musculoskeletal disorders, causing economic losses in the equine industry and animal welfare issues in horse populations. Sport and racehorses are in general sensitive to tendinopathies, whereas local indigenous horse populations are often more tolerant to various disorders. Particularly, indigenous Greek horse breeds have evolved and adapted in the rough topographic features of mountainous and semimountainous Greek terrain and are less prone to develop tendinopathies. Susceptibility to tendinopathy has been proposed to be associated with three specific variants in the tenascin-C and collagen type 5 α-1 genes. The present study was designed to analyze these genes and estimate the frequency of the aforementioned variants in three indigenous Greek horse populations, namely the pinia (peneia) breed, the Messara breed, and the nondescript Macedonian pacer, in comparison with a population of warmbloods. Results revealed high frequencies of genotypes with high risk for tendinopathy in the warmblood population and high frequency of low risk genotypes in the Greek breeds. Apart from the three variants, two novel polymorphisms were detected, one of which may also be associated with risk for tendinopathy. Our findings (a) are in agreement with previous ones demonstrating that risk for tendinopathies is associated with particular gene variants and also (b) highlight the value of Greek indigenous horse breeds as a genetic resource that (c) may be used in selective breeding schemes for decreasing the risk for tendinopathies in genetically improved breeds.

Quantitative characterization of viscoelastic properties of synovial fluid from forelimb joints of orthopedically normal Thoroughbreds and warmblood horses

OBJECTIVE

To determine whether differences existed in the viscoelastic properties of synovial fluid samples from the metacarpophalangeal, intercarpal, and distal interphalangeal joints of orthopedically normal athletic horses.

ANIMALS

45 warmblood horses and 30 Thoroughbreds (age range, 4 to 16 years).

PROCEDURES

Synovial fluid samples were aseptically obtained via arthrocentesis from 1 metacarpophalangeal, intercarpal, and distal interphalangeal joint of each horse, and nucleated cell counts were performed. A commercial ELISA was used to measure sample hyaluronic acid concentrations, and full rheological characterization of samples was performed to measure the elastic or storage modulus G' and viscous or loss modulus G" at 37.5°C (representing the body temperature of horses). Findings were compared among joints and between breed groups by means of ANOVA.

RESULTS

Significant differences in synovial fluid G' and G" values were identified between Thoroughbreds and warmblood horses for the metacarpophalangeal joint, between the metacarpophalangeal and intercarpal joints of Thoroughbreds, and between the metacarpophalangeal and distal interphalangeal joints and intercarpal and distal interphalangeal joints of warmblood horses. No significant differences were identified between breed groups or among joints in synovial fluid hyaluronic concentrations or nucleated cell counts.

CONCLUSIONS AND CLINICAL RELEVANCE

Viscoelastic properties of the forelimb joints of orthopedically normal Thoroughbreds and warmblood horses differed within and between these 2 groups, mainly as a function of the evaluated joint. To the authors' knowledge, this was the first study of its kind, and additional research is warranted to better understand the viscoelastic properties of synovial fluid in horses to optimize their locomotive function.