Background Osteoarthritis (OA) is a chronic joint disease characterized by progressive loss of articular cartilage and abnormal bone formation. Furthermore, there are changes in periarticular muscles, such as loss of muscle mass, strength and function. These features may contribute to functional impairment among patients.

Objectives To study the effects of OA induced by anterior cruciate ligament transection (ACLT) on muscle histopathology in rat.

Methods Female Wistar rat underwent ACLT surgery (n=9) or sham surgery (n=8) (1) on the right knee only. Body weight and spontaneous exploratory locomotion were evaluated weekly. Twenty weeks after the surgery, animals were euthanized. Joints from the right knee were collected for histological analyses. Gastrocnemius muscles from the right paw were collected for weighing and histological and molecular analyses. Data were analyzed with ANOVA Two-Way followed by Bonferroni and independent samples t-test and p<0.05 was considered significant.

Results Body weight and spontaneous exploratory locomotion were not statistically different between groups, during the experimental period. Histological evaluation of the right knee joint proved the development of OA in animals which underwent ACLT surgery (p<0,01), accordingly to OARSI histologic scoring system (2). The weight of gastrocnemius muscle was not statistically different between groups at the end of the experimental period (p<0,14). Histological evaluation of gastrocnemius muscle fiber cross-sectional area (CSA) (3) showed a reduction in muscle fiber CSA in ACLT animals (p=0,0006).

Conclusions ACLT induced chronic degenerative articular changes and muscle fiber CSA reduction in rats. It is yet to be studied what factors are related to atrophy, evaluating the expression of muscle factors related to muscle growth, differentiation, and mass regulation.

References

1. Elsaid KA, Machan JT, Waller K, Fleming BC, Jay GD. The Impact of Anterior Cruciate Ligament Injury on Lubricin Metabolism and the Effect of Inhibiting Tumor Necrosis Factor alpha on Chondroprotection in an Animal Model. Arthritis and Rheumatism. 2009;60(10):2997-3006.

2. Gerwin N, Bendele AM, Glasson S, Carlson CS. The OARSI histopathology initiative - recommendations for histological assessments of osteoarthritis in the rat. Osteoarthritis and Cartilage. 2010;18:S24-S34.

3. Filippin LI, Teixeira VN, Viacava PR, Lora PS, Xavier LL, Xavier RM. Temporal development of muscle atrophy in murine model of arthritis is related to disease severity. Journal of Cachexia Sarcopenia and Muscle. 2013;4(3):231-8.

Acknowledgements Financial support: CAPES, FIPE-HCPA.

Disclosure of Interest None declared