Allergy-induced systemic inflammation impairs tendon quality

Treatment of tendinopathies still present a major challenge, since the aetiology of the disease remains poorly understood. To determine whether the systemic inflammation accompanying predisposing factors including rheumatoid arthritis, diabetes or smoking contributes to the onset of tendinopathy, we studied the effect of a systemic inflammation induced by an allergic episode on tendon properties. To this end, we elicited an allergic response in mice by exposing them to a plant allergen and subsequently analysed both their flexor and Achilles tendons. Biomechanical testing and histological analysis revealed that tendons from allergic mice not only showed a significant reduction of both elastic modulus and tensile stress, but also alterations of the tendon matrix. Moreover, 3D tendon-like constructs treated with sera from allergic mice displayed a matrix-remodelling expression profile and the expression of macrophage-associated markers and matrix metalloproteinase 2 (MMP2) was increased in allergic Achilles tendons. Analysing data from an epidemiologic study comprising data from more than 10.000 persons, we found that persons suffering from an allergic condition appeared to have an increased propensity to develop a tendinopathy. Graphical abstract