High-fat diet-induced obesity exacerbated collagenase-induced tendon injury with upregulation of interleukin-1beta and matrix metalloproteinase-1.

Obesity increases tendinopathy's risk, but its mechanisms remain unclear. This study examined the effect of high-fat diet (HFD)-induced obesity on the outcomes and inflammation of collagenase-induced (CI) tendon injury. Mice were fed with standard chow (SC) or HFD for 12 weeks. Bacterial collagenase I or saline was injected over the patellar tendons of each mouse. At weeks 2 and 8 post-injection, the patellar tendons were harvested for histology, immunohistochemical staining, and gait analysis. The difference (Δ) of limb-idleness index (LII) at the time of post-injury and pre-injury states was calculated. Biomechanical test of tendons was also performed at week 8 post-injection. HFD aggravated CI tendon injury with an increase in vascularity and cellularity compared to SC treatment. The histopathological score (week 2: HFD-induced obesity exacerbated histopathological, functional, and biomechanical changes in the CI tendon injury model, which was associated with an upregulation of IL-1β and MMP-1.