Grant: Operating Grant

Repetitive-use tendon injury (typically called "tendinitis") is a major clinical burden in many Canadian industries. Unfortunately, how and why this condition develops is poorly understood. Improved treatment will require increased knowledge of the causes of this common, costly condition. In everyday clinical medicine, it was presumed that painful 'tendinitis' was due to inflammatory cells damaging tendon tissue. In detailed studies of tendon tissue from patients undergoing surgery for repetitive-use tendon injury, we found that inflammatory cells were very scarce or absent, despite the presence of tendon pain. Instead, we could see a large number of new blood vessels (microvessels) within painful tendons. These microvessels were actively proliferating, and producing a small protein (peptide) that stimulated vessel development (VEGF; vascular endothelial growth factor). Microvessels are associated with pathology in other tissues such as in the eye, where they impair vision, in cancer progression, and in osteoarthritis. These data are of potential importance in understanding the cause of repetitive-use tendon injuries, because clinical imaging techniques have revealed that overgrowth of vessels in tendon is strongly associated with chronic pain. This research is tests the theory that tendon vessels become more prominent during periods of repetitive use as a result of local VEGF production, and that this compromises tendon structure and function. If this is proven, it will provide novel avenues for drug therapies to treat tendon problems.