Background: Arthritis is the most common joint disorder. The most significant structural change seen in arthritis is the degeneration of the articular cartilage. Numerous animal models are used to reproduce arthritis. In this paper, we assessed the ability of complete Freund's adjuvant (CFA) to induce degenerative changes of hyaline articular cartilage in rat chronic arthritis model.
Methods: In this study, 42 adult male albino rats were used, divided into: control group I (18 rats) and arthritis group II (24 rats). Arthritis was induced unilaterally by a single intra-articular injection of 125 μl of CFA in the right knee joint of each rat. The samples were collected 2, 6, and 10 weeks post-injection. Hematoxylin & Eosin (H&E) stain, Masson's trichrome stain, Safranin O (S.O) stain were used to assess articular cartilage degeneration during inflammation.
Results: The articular cartilage of rats of arthritis group II showed progressive inflammatory cell infiltration in the synovial membrane. Chondrocytes showed degeneration, hypertrophy and extensive proliferation. Moreover, the matrix exhibited fibrillations, fissuring, delamination and denudation with fibrous tissue within the denuded surface. The thickness of the articular cartilage, the collagen content and the proteoglycan content showed significant decrease in rats sacrificed after 10 weeks compared to rats sacrificed after 2 weeks and 6 weeks from the onset of the experiment.
Conclusions: Intra-articular injection of complete Freund's adjuvant induces progressive degeneration of the hyaline articular cartilage of the knee joint of rats. It can be useful for studies on mechanisms and strategy of treatment of knee joint arthritis.