Chapter 9 The veterinarian perspective: Comparative anatomy, equine models and in vivo bioengineering of tendons

Tendinopathy is common in humans and it is generally accepted that the pathogenesis involves preceding age-related degenerative changes to the tendon associated with repetitive loading that predispose it to injury during exercise. Unfortunately there has a lack of a universally agreed animal model of human tendinopathy because traditional small animal tendons do not have the same structure and function and do not exhibit a similar ageing phenotype to humans. In contrast, investigations have shown remarkable pathophysiological similarities between human and equine tendons, although the most accurate comparison needs to be based on tendon functional correlates, rather than anatomical position, because of the differences between bipedal and quadrupedal locomotion. The size of the horse, and the diverse pathology in different tendons reflecting that seen in humans, makes the horse a highly relevant translational model for evaluating regenerative treatments. These treatments have attempted to harness the potential regenerative capabilities of a number of cell- and growth factor- based preparations to ‘bioengineer’ normal tendon tissue in vivo. Many of these treatments have become established in equine clinical practice, with some showing promising results, but have generally been associated with a modulation of the healing process rather than true regeneration. It is envisaged that the horse will continue to provide an ideal ‘proving ground’ for testing future improved strategies for regenerative therapies.