Effects of uphill and downhill walking on post-traumatic osteoarthritis development in mice.

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Using destabilization of the medial meniscus (DMM) induced models of osteoarthritis (OA), we sought to clarify how flat, uphill, and downhill walking affects OA-related inflammation and articular cartilage degeneration. Thirty-two male C57BL/6J mice of 7 weeks old underwent DMM surgery in their right knee and sham surgery in their left knee, and then were assigned to either the no walking after DMM group or the flat, uphill, or downhill walking after DMM group (n = 8/group). After creating the knee OA model, the mice in the walking groups were subjected to treadmill walking 1 day after surgery, which included walking for 12 m/min, 30 min/day, and 7 days/week, with inclines of 0, 20, or - 20 degrees. Knee joints were harvested at the end of the intervention period. Non-demineralized frozen sections were prepared and samples were examined histologically. Osteoarthritis Research Society International scores were significantly decreased in both the uphill and flat walking groups, compared with the no-walking group. Immunohistochemical staining showed increased levels of aggrecan and Sry-related high mobility group box 9; conversely, decreased levels of Matrix metalloproteinase-13 and A disintegrin and metalloproteinase with thrombospondin motifs 5 in both the uphill and flat walking groups. Micro-CT results showed higher bone volume fraction in the uphill and flat walking groups than that in the no-walking group. Our findings indicate that flat and uphill walking may prevent the progression of OA. KEY POINTS: Flat and uphill treadmill walking can prevent the development of post-traumatic osteoarthritis in mice. Flat and uphill walking increases anabolic proteins and decreases catabolic proteins and inflammatory cytokines in articular cartilage, resulting in protection against cartilage degeneration. Downhill walking increases catabolic proteins and inflammatory cytokines in cartilage, which has negative effects on articular cartilage. Abstract figure legend This study sought to verify how flat, uphill, and downhill walking affects osteoarthritis development. Mice of the post-traumatic osteoarthritis model were subjected to treadmill walking. Flat and uphill walking increased cartilage anabolic proteins (Sry-related high mobility group box 9 [Sox9] and/or Aggrecan) and decreased catabolic proteins (Matrix metalloproteinase-13 [MMP-13] or A disintegrin and metalloproteinase with thrombospondin motifs 5 [ADAMTS5]), resulting in protection against osteoarthritis development. Downhill walking decreased Sox9 protein levels in cartilage compared to uphill walking. In addition, downhill walking increased MMP-13 levels, suggesting negative effects on articular cartilage. This article is protected by copyright. All rights reserved.