Expression of neuropeptides and cytokines at the extensor carpi radialis brevis muscle origin

To reveal whether neuropeptides and cytokines affect the pathogenesis of tennis elbow, expressions of substance P, calcitonin gene–related peptide, interleukin 1α, and transforming growth factor β1 at the origin of the extensor carpi radialis brevis muscle were investigated in patients with tennis elbow (n = 10). Innervation in the origin was determined with use of the protein gene product 9.5. Substance P–like immunoreactivity and calcitonin gene–related peptide–like immunoreactivity were observed in the nerve fibers around small vessels without apparent infiltration of inflammatory cells. Cells showing positive interleukin 1α or transforming growth factor β1 immunoreactivity were noted in small vessels and the dense collagen meshwork in 5 of 10 cases. The results suggested that these neuropeptides and cytokines might promote inflammation and stimulate proliferation and matrix synthesis of fibroblasts, contributing to the pathology of tennis elbow. (J Shoulder Elbow Surg 2002;11:570-5)