Alessandra Ludovico, Oscar Moran and Debora Baroni*
Osteoarthritis, the most common joint disease worldwide, refers to a heterogeneous group of conditions that share symptoms and signs of compromised articular cartilage integrity and alterations in bone and joint margins. The pathophysiology of osteoarthritis is not comprehensively understood and its treatment is mainly symptomatic. Intra-articular injections of corticosteroids and hyaluronic acid-based preparations are commonly employed to mitigate pain and enhance joint function by replenishing damaged synovial fluid. This study aimed to evaluate the microrheological properties of the synovial fluid under conditions that mimic in vitro the healthy and the oxidized condition, which characterizes the synovial fluid in osteoarthritic subjects. Additionally, the microviscosity properties of the synovial fluid were evaluated after administration of two pharmaceutical agents for the treatment of osteoarthritis, namely the corticosteroid triamcinolone acetonide and a cross-linked hyaluronic acid. The analysis was carried out using the multiple particle technique, a type of functional microscopy that is widely used to study the structural rearrangements and the viscoelastic properties of different types of inorganic and organic fluids, which revealed that triamcinolone acetonide protects the synovial fluid from oxidation without affecting synovial fluid microviscosity. Contrarily, hyaluronic acid acts as a viscosupplement, improving the microviscosity of synovial fluid. However it proved to be ineffective against synovial fluid oxidation. These results highlighted that corticosteroids and hyaluronic acid-based formulations exert different effects on oxidised synovial fluid, and that, therefore, their administration should be chosen on a case-by-case basis.
