Multi-omics analysis of synovial fluid: a promising approach in the study of osteoarthritis.

Osteoarthritis (OA), affecting 250 million individuals worldwide, is a significant social health problem. Therefore, the search for synovial fluid (SF) biomarkers that could anticipate the diagnosis of OA is gaining increasing importance in orthopaedics. This review summarizes the recent progresses preformed in the multi-omics approach to OA, mainly focusing on proteome and metabolome analysis of SF. Proteomics of the SF has shown the up-regulation of several components of the classic complement pathway in OA samples, including C1, C2, C3, C4A, C4B, C5 and C4 C4BPA, thus depicting that complement is involved in the pathogenesis of OA. Moreover, proteomics has displayed that some pro-inflammatory cytokines, namely IL-6, IL-8 and IL-18, have a role in OA. The metabolomic profiling of the SF in OA has identified some metabolites as potential biomarkers of OA and has shown the existence of metabolically different OA subgroups. However, further studies with larger samples sizes and matched-control groups are needed to identify SF biomarkers that could be useful in the diagnosis, treatment and follow-up of OA.