Effects of aerobic exercise at different intensities on articular cartilage in mice

Maintaining intrinsic articular cartilage homeostasis is essential for the health of cartilage. However, the impact of aerobic exercise of varying intensities on the articular cartilage homeostasis has never been studied. This study aims to elucidate the influence of different aerobic exercise intensities on the anabolic and catabolic processes within articular cartilage.

Forty-eight male C57BL/6J mice, aged 7 weeks, were divided into 4 aerobic exercise groups and 1 control group. The aerobic exercise groups were subjected to both acute and chronic exercise protocols with varying intensities of 8, 12, 16, 20, and 24 m min-1. Total RNA from the knee joint cartilage was extracted in both phases to quantify mRNA of anabolic (Sox9, Col2a1, and Acan) and catabolic (MMP-13 and ADAMTS5) markers. In the chronic exercise, articular cartilage thickness and chondrocyte density were histologically assessed. Additionally, immunohistochemical staining quantified relevant molecules involved in cartilage metabolism.

In the acute exercise, the 8 m min-1 group exhibited reduced ADAMTS5 expression compared to the control, 16 m min-1, and 24 m min-1 groups. Chronic exercise showed enhanced articular cartilage thickness in both the 8 and 12 m min-1 groups relative to the control group. Moreover, the 8 m min-1 group demonstrated elevated aggrecan levels in comparison to both the control and 24 m min-1 groups. Additionally, the 24 m min-1 group exhibited significantly higher ADAMTS5 levels than the control group.

Our findings suggest that consistent low-intensity aerobic exercise suppresses catabolic molecule expression in articular cartilage, thereby fostering anabolic activity. Conversely, continuous high-intensity aerobic exercise can potentially disrupt cartilage homeostasis by enhancing catabolic processes. This dichotomy underscores the need for balanced exercise regimens to maintain cartilage health.