Comparative histopathological evaluation of intra-articular therapies in an experimental model of osteoarthritis

Objectives: to perform a histopathological evaluation of osteoarthritis treated with different intra-articular drugs in rats, comparing platelet-rich plasma (PRP), hyaluronic acid (HA), chondroitin sulfate, and triamcinolone. Materials and methods: osteoarthritis was induced in 30 Wistar rats by zymosan injection. Five groups were formed (n = 6): PRP, HA, chondroitin sulfate, triamcinolone, and control. Treatments were administered every 14 days for 60 days. Subsequently, euthanasia was performed, and histopathological analysis of the subchondral cartilage was conducted, evaluating structure, chondrocytes, synovium, and inflammation. The Kruskal–Wallis and Dunn–Bonferroni tests were applied. Results: animals treated with PRP showed mature chondrocytes arranged in columns and signs of regeneration, with moderate inflammation. HA presented minimal erosions, superficial ulcers, high cellular density, and a low inflammatory index, suggesting both chondroprotective and anti-inflammatory effects. Chondroitin sulfate preserved the tidemark, reduced cartilage flaps, and exhibited low inflammation. Triamcinolone achieved better inflammatory control, although with limited regeneration. The control group showed moderate damage, high inflammation, and disorganized chondrocytes. Conclusions: PRP and HA demonstrated greater regenerative capacity: PRP favored chondrocyte maturation, and HA reduced tissue damage and inflammation. Triamcinolone stood out for its anti-inflammatory effect, while chondroitin sulfate exhibited a protective profile.