Chondroprotective effects of ozone and hyaluronic acid in rat knee osteoarthritis: Comparison of intra-articular and systemic administration

This study aimed to evaluate the therapeutic efficacy of intra-articular (i.a.) ozone, hyaluronic acid (HA), their combination (ozone-HA), and systemic (intraperitoneal, i.p.) ozone in a rat model of surgically induced knee osteoarthritis (OA). OA was induced by anterior cruciate ligament transection in 60 female Sprague Dawley rats randomized into six groups: i.a. control (saline), i.a. HA, i.a. ozone, i.a. ozone-HA, i.p. control, and i.p. ozone. Treatments were administered weekly for five weeks, starting on day 14 post-surgery. Therapeutic outcomes were assessed using computed tomography, histopathological scoring (Modified Mankin, cartilage degeneration, and matrix loss width), immunohistochemistry (type II collagen, MMP-13), and serum TNF-alpha levels. At week eight, CT imaging revealed reduced structural damage in the i.a. ozone-HA group. The i.a. ozone-HA group had the lowest Modified Mankin score, significantly lower than the i.a. control (p < 0.001) and i.p. control (p = 0.007) groups. Cartilage matrix loss was significantly reduced in treated groups, particularly in the superficial zone (p = 0.010). Cartilage degeneration scores in the Z1 region were significantly improved in the i.a. ozone (p = 0.011) and i.a. ozone-HA (p = 0.004) groups compared to i.a. control. Additionally, type II collagen expression was significantly enhanced in both i.a. ozone and ozone-HA groups (p = 0.010). These results indicate that intraarticular ozone, particularly combined with HA, offers superior chondroprotective and regenerative effects compared to HA alone or systemic ozone, highlighting its potential as a novel therapeutic approach for early-stage osteoarthritis in veterinary medicine.