Associations between serum IL-8 and knee symptoms, joint structures, and cartilage or bone biomarkers in patients with knee osteoarthritis

Objective The aim of this study was to investigate cross-sectional associations between serum levels of IL-8 and the above outcomes in patients with knee osteoarthritis (OA). Methods A total of 160 subjects with clinical knee OA were included. Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score and Lequesne index were used to assess the joint symptom. Magnetic resonance imaging was used to measure knee structural abnormalities including infrapatellar fat pad (IPFP) signal intensity alternation. Knee radiographic OA was assessed by radiography using the Kellgren-Lawrence (K-L) grading system. Enzyme-linked immunosorbent assay was used to measure the serum levels of IL-8 and cartilage or bone biomarkers. Results In multivariable analyses, serum IL-8 was positively associated with WOMAC weight-bearing pain (beta 2.85, P = 0.028), WOMAC physical dysfunction (beta 12.71, P = 0.048), and Lequesne index (beta 1.65, P = 0.015), and had positive associations with IPFP signal intensity alteration (OR 3.18, P = 0.011) and serum levels of N-telopeptide of type I collagen (NTXI), N-terminal procollagen III propeptide (PIIINP), matrix metalloproteinase (MMP)3, and MMP13 (beta 0.24-1.44, all P < 0.05) in patients with clinical knee OA. Furthermore, there were positive associations between IL-8 and WOMAC score (beta 22.49, P = 0.037), K-L grades (OR 3.88, P = 0.013), and IPFP signal intensity alteration (OR 3.20, P = 0.033) in patients with radiographic OA. Conclusions Serum levels of IL-8 were positively associated with increased knee symptoms, IPFP signal intensity alteration, and serum levels of bone and/or cartilage biomarkers, suggesting that IL-8 may have a role to play in knee OA.