Achilles tendon injuries in elite athletes: lessons in pathophysiology from their equine counterparts.

The research article explores the similarities between Achilles tendon injuries in elite human athletes and superficial digital flexor tendon injuries in horses. The study highlights the importance of equine models in understanding the accumulation of microdamage, aging, the effect of specific exercises, and other factors related to these tendon injuries.

Relevance of Equine Models

• A key contention of the study is that understanding the injuries of the superficial digital flexor tendon (SDFT) in horses – elite equine athletes, offers significant insights into similar injuries in human athletes, notably the Achilles tendon (AT) injuries.
• The article suggests that no comparably suitable models exist in rodents, rabbits, or other animals. Hence, studying equine tissues has led to substantial progress in understanding tendon maturation and aging, exercise effects, and even early stages of subclinical pathology.

Understanding Human Surgeries to Advanced Phases of Disease

• The researchers used information from human surgical biopsies, which further aided understanding of the more advanced stages of these diseases. However, they underline that equine SDFT injuries only serve as a model for acute ruptures in athletes, and not the entire spectrum of human tendinopathy, which also includes chronic tendon pain.
• The study emphasizes that in both humans and horses, tendon pathology starts with a phase of accumulating microdamage, which might remain subclinical for a prolonged period.

Exploring Genetic Risk Factors and Cell Responses

• Recent developments have revealed strikingly similar genetic risk factors in both species and have further strengthened the idea of the active role of tenocyte dysfunction in these diseases.
• The researchers call for more comprehensive studies to understand the response of tendon cells to different combinations of exercise-associated stresses, and underline the necessity for a more thorough investigation of key stress pathway auditors common to both species.

Limitations of Mouse Models and Importance of Horses

• This research highlights the limitations of using mice as models for multiple diseases, particularly at the cellular level. Molecular evidence suggests a poor performance of mouse models for understanding these tendon injuries.
• Horses, on the other hand, might provide a more accurate model. Justifying the use of horses aligns with comparable species longevity, lifestyle factors, and evolutionary pressures due to similar infectious agents such as herpesviruses impacting general cell stress pathway evolution.