Synovial fluid alpha-melanocyte-stimulating hormone may act as a protective biomarker for primary knee osteoarthritis.

Objective: The current study was carried out to investigate the serum and synovial fluid (SF) alpha-melanocyte-stimulating hormone (alpha-MSH) levels in correlation with disease severity in primary knee osteoarthritis (OA). Methods: This study comprised of 105 primary knee OA patients and 98 healthy controls. The radiographic severity was verified according to the Kellgren-Lawrence radiographic grading criteria. The symptomatic severity of knee OA was assessed by the Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index. Serum alpha-MSH concentrations were measured by ELISA. The inflammation markers IL-6 and TNF-alpha, as well as cartilage damage markers MMP-3 (matrix metalloproteinase 3) and COMP (cartilage oligomeric matrix protein), were also measured. The receiver operating characteristic (ROC) curve was used to evaluate the diagnostic value between alpha-MSH and other four markers with regard to the radiographic progression. Results: SF alpha-MSH concentrations were negatively related to Kellgren-Lawrence grades and WOMAC index. SF alpha-MSH levels in knee OA patients were negatively associated with inflammation markers IL-6, TNF-alpha, and cartilage damage factors COMP and MMP-3. In addition, ROC analysis implied that attenuated alpha-MSH levels may serve as a favorable diagnostic marker for the radiographic progression. The difference of serum alpha-MSH concentration was not significant between knee OA patients and healthy controls. Conclusions: Reduced SF alpha-MSH expression may be a characteristic of OA patients. Attenuated alpha-MSH level in SF may serve as a potential biomarker for disease severity of knee OA, and further studies are needed to identify its potential application for monitoring the course of the disease and the efficacy of therapies in OA patients.