Abstract
Given the increasing number of people living with OA, due to population aging and rising rates of obesity, there is an urgent need to identify effective treatment and preventions. Two top risk factors for OA, age and obesity, are associated with ER stress. The I-ERS mouse, an ER stress driven model of primary OA, was developed to study the role of ER stress in primary OA susceptibility. The I-ERS mouse has the unique ability to induce ER stress in healthy adult I-ERS mouse articular chondrocytes and cartilage, driving joint degeneration that mimics early primary OA. ER stress-induced damage occurred gradually and stimulated joint degeneration with OA characteristics including increased matrix metalloproteinase activity, inflammation, senescence, chondrocyte death, decreased proteoglycans, autophagy block and gait dysfunction. Consistent with human OA, intense exercise hastened and increased the level of ER stress-induced joint damage. Notably, loss of a critical ER stress response protein (CHOP), largely ameliorated ER stress-stimulated OA outcomes including preserving proteoglycan content, reducing inflammation and relieving autophagy block. Resveratrol diminished ER stress-induced joint degeneration by decreasing CHOP, TNFα, IL-1β, MMP-13, pS6, number of TUNEL positive chondrocytes and senescence marker p16 INK4a. The finding that a dietary supplement can prevent ER stressed-induced joint degeneration in mice, provides a preclinical foundation to potentially develop a prevention strategy for those at high risk to develop OA.
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