A standardized, open-source, portable model for noninvasive joint injury in mice

Objective: Preclinical models of osteoarthritis (OA) are crucial for the study of disease mechanisms and development of disease-modifying therapeutics. While surgical OA models, such as destabilization of the medial meniscus (DMM), have been the gold standard in the field for decades, noninvasive joint loading-based models have increased in popularity and utility. To facilitate standardization of the noninvasive anterior cruciate ligament rupture (ACLR) model in mice, we present the Mobile Joint-Injury Operator (MoJO) - an open-source protocol with accompanying fixtures and data, designed for a low-cost, commercially-available, portable, small-footprint uniaxial testing system. Methods: We provide 3d-printable fixture designs and a comprehensive description of the loading protocol, describe the expected mechanical output, and offer various troubleshooting strategies. We validate the mechanical accuracy and inter-operator reproducibility of the procedure and characterize the resultant post-traumatic OA phenotype by knee hyperalgesia testing, flow cytometry, μCT imaging, and histological assessment. Results: Across n ​= ​952 procedures, the MoJO protocol was highly accurate and repeatable, with a >99 ​% rate of successful ACLR and high repeatability between operators and institutions. ACLR-mediated joint injury resulted in the expected post-traumatic OA phenotype in male and female C57Bl/6 mice, including progressive hyperalgesia, histological and μCT evidence of cartilage damage, synovitis, and osteophyte formation, and increased expansion of fibroblasts, endothelial cells, and myeloid cells by flow cytometry. Conclusions: Increased standardization of joint injury is a critical aspect of the overall refinement of animal models of OA. The MoJO represents an affordable and highly reproducible option for implementing the mouse ACLR model of OA.