Background Clusterin (apolipoprotein J) is an extracellular chaperone involved in the number of biological processes, such as inflammation and apoptosis. Recent data suggest its protective role in autoimmune diseases. The aim of this study was to analyse the serum levels of clusterin and its expression in skeletal muscle specimens in patients with idiopathic inflammatory myopathies (IIM) vs healthy controls, and to investigate the association of clusterin with disease activity.
Materials and methods Clusterin serum levels were measured by ELISA (Biovendor) in 65 patients with IIM (27 dermatomyositis (DM), 28 polymyositis (PM), 10 immune-mediated necrotizing myopathy (IMNM)) and in 54 healthy individuals. Clusterin mRNA expression was analysed in skeletal muscle samples obtained from muscle biopsy (mini-invasive Bergstrom technique) in 10 patients with IIM (DM/PM) and 10 healthy controls by RT-PCR. Disease activity was assessed using myositis disease activity assessment visual analogue scales (MYOACT), myositis intention to treat index (MITAX), health assessment questionnaire (HAQ) and global disease assessment evaluated by patient and doctor. Data are presented as mean ± SD.
Results Serum concentrations of clusterin were significantly higher in all patients with IIM compared with healthy controls (87.1±22.8 vs 68.4±12.4, p<0.0001). There were no differences in the clusterin levels among particular myositis subtypes. Clusterin levels in all IIM patients positively correlated with MITAX (r=0.357, p=0.004), MYOACT (r=0.337, p=0.008) and doctor global disease assessment (r=0.309, p=0.015), but not with muscle enzymes. Moreover, mRNA expression of clusterin in muscle tissues was almost three-times higher in patients with IIM than in healthy individuals (p=0.029).
Conclusions We demonstrate here for the first time increased clusterin expression in myositis patients than in healthy subjects and its association with clinical disease activity.
Acknowledgement Supported by the project of MHCR for conceptual development of research organisation 00023728 and project NV16-33746A.