Functional adaptation through changes in regional biochemical characteristics during maturation of equine superficial digital flexor tendons.

This article studies how the superficial digital flexor tendons (SDFT) in horses change and develop as they age from neonatal stage to adulthood, with a focus on the biochemical characteristics of the extracellular matrix. It suggests these tendons are not homogeneous at birth, meaning they have variations, but then undergo changes due to functional adaptation, potentially helping avoid tendon injuries later in life.

Methodology

• Tendon specimens were collected post-mortem from 40 juvenile horses of varying ages (0, 5, 12, and 36 months old). These horses showed no visible signs of tendonitis.
• Specimens were harvested from the central parts of both the mid-metacarpal and mid-sesamoid regions, which are both loaded sites in the tendon.
• Using a specialized biopsy tool, researchers performed a detailed analysis of the biochemical characteristics of these specimens.

Quantifying Biochemical Characteristics

• Researchers examined both the collagenous and noncollagenous components of the extracellular matrix (ECM), a three-dimensional network of macromolecules that provide structural and biochemical support to cells.
• For the collagenous component, the researchers measured the concentrations of collagen, hydroxylysylpyridinoline crosslink, and pentosidine crosslink, as well as the percentage of degraded collagen.
• For the noncollagenous components, the team noted the percentage of water and glycosaminoglycans, DNA, and hyaluronic acid concentrations present.

Findings and conclusions

• The biochemical composition of the equine SDFT was not homogeneous at birth with decisive differences in terms of DNA, glycosaminoglycans, and pentosidine concentrations.
• The amounts present at birth were found to be dissimilar to those present in mature horses, indicating substantial development and maturation of these tendons over time.
• This process of maturation involves rapid and significant changes in all components of the matrix in the period of growth and development after birth, attributed to functional adaptation.
• Unlike cartilage, tendon tissue in horses is not biochemically identical or “blank” at birth, and it undergoes significant changes before reaching maturity.
• The study concludes that understanding the maturation process of the juvenile equine SDFT could aid in designing exercise programs that minimize tendon injuries resulting from overuse in adult horses.