Targeting the IL-17A pathway for therapy in early-stage tendinopathy.

Objectives: Tendinopathy is a frequent clinical problem and represents an extraordinary health economic and socioeconomic burden with high unmet medical needs. Recent clinical evidence suggests blockade of interleukin 17A (IL-17A) for tendinopathy therapy. The present preclinical study elucidates the biological mechanisms of IL-17A pathway stimulation and blockade in tendinopathy.

Methods: We explored whether IL-17A and other IL-17 family members are differentially expressed in biopsies of healthy, early-stage and late-stage tendinopathic human rotator cuff tendons using RT-qPCR. IL-17 pathway signature genes in healthy human tendon-derived cells were identified following IL-17A stimulation using AmpliSeq RNA. The molecular, structural and functional consequences of IL-17A pathway stimulation were explored in healthy human tendon-derived cells and in a rat tendon fascicle model ex vivo. The effects of IL-17A pathway blockade were investigated in a rat model of rotator cuff tendinopathy in vivo.

Results: We provide evidence of differential expression of IL-17A mRNA (IL17A) versus other IL-17 family members in human rotator cuff early-stage tendinopathy. In human tendon-derived cells, stimulation with IL-17A induced the expression of the selected IL-17A pathway signature genes NFKBIZ, ZC3H12A, CXCL1, IL6, MMP3. Expression was inhibited by IL-17A blockade. In the rat ex vivo and in vivo models, IL-17A blockade alleviated inflammatory immune effector release, tendon structural degeneration, tendon inflammation and impaired tendon function.

Conclusion: Our data provide evidence that IL-17A is a key contributor to the pathogenesis of tendinopathy by promoting tendon inflammation and degeneration and that IL-17A blockade may represent a potential therapy in early-stage tendinopathy.