Papain is a proteolytic enzyme. When injected into the knee and hip joints of rabbits with subsequent local immobilization, it induces degenerative changes in articular cartilage. Yang et al. injected 0.3 mL of 1.6% papain into the temporomandibular joints of Japanese big-ear rabbits. Pathological examinations at 2, 4, and 6 weeks revealed a series of pathological changes, including thinning of articular cartilage, surface erosion and corrosion, chondrocyte necrosis, and destruction of the cartilage matrix. This model closely resembles the pathological features of human osteoarthritis (OA) and is easy to establish and replicate.

SD rats (male, 6 weeks old)
Modeling method: A mixture of papain and cysteine was injected into the right knee joint cavity of rats. Osteoarthritis model was successfully established 2 days later.
Evaluation indicators: ELISA, HE staining, toluidine blue staining

ELISA

HE staining of the knee joint

Toluidine blue staining of the knee joint