Serum and synovial fluid concentrations of interleukin-18 and interleukin-20 in patients with osteoarthritis of the knee and their correlation with other markers of inflammation and turnover of joint cartilage
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Department of Arthroscopy, Minimally Invasive Surgery, and Sports Traumatology, Medical University of Lodz, Lodz, Poland
Clinic of Orthopaedic and Traumatology, Polish Mother’s Memorial Hospital Research Institute, Lodz, Poland
Dermatology, Paediatric Dermatology, and Oncology Clinic, Medical University of Lodz, Lodz, Poland
Submission date: 2020-03-30
Final revision date: 2020-05-11
Acceptance date: 2020-05-22
Online publication date: 2020-07-03
Osteoarthritis (OA) is the most common degenerative joint disease, and its aetiology is not entirely known. The aim of the study was to evaluate the involvement of interleukin-18 (IL-18) and interleukin-20 (IL-20) in the pathogenesis of knee OA and their correlations with other markers of inflammation and destruction of joint cartilage, as well as clinical and radiological changes.

Material and methods:
The study included 25 patients with knee OA and a control group. The concentration of IL-18, IL-20, IL-6, MMP-1, MMP-3, COMP, PG-AG, and YKL-40 in serum and synovial fluid (SF) were determined. We also evaluated radiological lesions of the knee joint according to the Kellgren-Lawrence (K-L) scale, and clinical severity of the disease according to Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Lequesne Index.

The concentrations of IL-18 and IL-20 were statistically significantly higher in serum of patients with OA than in the control group (106.00 ±189.76 pg/ml vs. 16.73 ±16.99 pg/ml, p < 0.001, 17.69 ±13.45 pg/ml vs. 9.76 ±9.00 pg/ml, p < 0.014). Serum concentration of IL-18 positively correlated with MMP-3 (R = 0.58; p = 0.006) and YKL-40 (R = 0.48; p = 0.002). The degree of radiological advancement of OA (K-L scale) correlated positively with clinical evaluation (WOMAC, R = 0.74, p ≤ 0.001; Lequesne Index, R = 0.57, p = 0.003).

The analysis of ROC curves showed that IL-20 as well as COMP, MMP-3, and YKL-40 may be diagnostic markers of knee OA. The observations indicate that IL-18 potentially mediates mainly in intra-articular processes and IL-20 could be primarily responsible for the systemic inflammatory reaction.