Objectives: This study aims to evaluate the time- and dose-dependent effects of oral hydroxychloroquine (HCQ) on focal full-thickness knee chondral defect healing in a rabbit model.
Materials and methods: Cartilage defects of 4x4 mm2 were created on both medial femoral condyles of 24 New Zealand rabbits. The rabbits were divided into six groups (A-F) according to HCQ administration and sacrifice time: A (three-week control) and B (six-week control) received no additional interventions; C (20 mg/kg HCQ, three weeks); D (20 mg/kg HCQ, six weeks); E (40 mg/kg HCQ, three weeks); and F (40 mg/kg HCQ, six weeks). Osteochondral specimens were evaluated macroscopically, histologically, and immunohistochemically. The terminal deoxynucleotidyl-transferase (TdT)-mediated dUTP nick end labeling (TUNEL) method was used to detect apoptotic cells.
Results: The International Cartilage Repair Society (ICRS) scores were significantly higher in the experimental groups than in the controls (p<0.001). The Wakitani scores in Group D showed a significant improvement compared to those in Group B (p<0.01). The 20 mg/kg HCQ treatment groups showed better recovery than the controls (p<0.01). High-dose HCQ (40 mg/kg) treatment significantly reduced the intensity of collagen type 2 immunoreactivity compared to that in the groups receiving 20 mg/kg of HCQ (p<0.01). Collagen type 2 expression in Group F was significantly lower than that in Group D (p<0.01). There were more TUNEL-positive cells in the repair sites of Groups E and F than in the lower-dose experimental groups and untreated experimental groups (p<0.001).
Conclusion: A low dose of HCQ improved cartilage repair, while higher doses of HCQ exerted a negative effect on cartilage regeneration in rabbits. In the presence of defective cartilage, the use of HCQ at an appropriate dose and time is important for cartilage health.