Early exercise advances the maturation of glycosaminoglycans and collagen in the extracellular matrix of articular cartilage in the horse.

The study investigated how early age training influences the biochemical composition of the articular cartilage extracellular matrix (ECM) in thoroughbred foals. It found that increased workloads might affect the maturity of glycosaminoglycans and collagen, components of the ECM, and these changes do not appear to increase joint damage.

Objectives

• The primary goal of this research was to determine the impact of a 30% increased workout on thoroughbred foals and its resulting changes in the biochemical composition of the articular cartilage extracellular matrix (ECM).

Methods

• The researchers divided 33 thoroughbred foals into two exercise groups from the age of 10 days to 18 months. One set, called PASTEX (n=15), was reared in a pasture, while the other group, termed CONDEX (n=18), underwent an additional, specific training program which increased their workload by 30%.
• At an average age of 18 months, six foals from each group were euthanized. The researchers analyzed the proximal articular surface of the right hindlimb proximal phalanx for any signs of damage using a cartilage degeneration index (CDI).
• Samples were gathered from two sites with known differing loading patterns, and the slices were tested for levels of DNA, glycosaminoglycans (GAGs), collagen, and post-translational modifications of collagen.

Results

• The CDI showed no differences between the PASTEX and CONDEX groups, which suggests that the increased exercise regimen did not cause additional joint damage.
• There were site-related variations for most biochemical variables, corroborating with previous studies.
• The levels of all biochemical components differed between the PASTEX and CONDEX groups at one of the sites. GAGs and collagen levels were lower in the CONDEX group, whereas levels of hydroxylysine (Hyl), hydroxylysylpyridinoline (HP) crosslinks, and pentosidine crosslinks were higher.

Conclusion

• This research demonstrated that conditioning exercise at early age had a measurable impact on the maturation of the ECM’s components in horse articular cartilage.
• The study suggested that the boundary between too much and too little work during foal training might be narrower than previously thought, implying trainers need to be careful not to over or under-exercise young horses.