Background Clusterin (also known as apolipoprotein J) is a molecular chaperone that participates in inflammatory and apoptotic processes. Recent data indicate its possible protective role in the development of chronic autoimmune disorders.
Objectives The aim of this study was to analyse the skeletal muscle expression of clusterin and its serum levels in patients with idiopathic inflammatory myopathies (IIM) and in healthy donors, and to examine the association of clusterin with disease activity.
Methods Clusterin mRNA expression in skeletal muscle specimens, obtained by muscle biopsy (mini-invasive Bergstrom technique), was determined using qPCR in 10 patients with IIM and 10 healthy subjects. Serum concentrations of clusterin 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. Disease activity was assessed using myositis intention to treat index (MITAX), myositis disease activity assessment visual analogue scales (MYOACT), health assessment questionnaire (HAQ) and global disease assessment evaluated by doctor and patient. Data are presented as mean ± SD.
Results Clusterin mRNA expression in skeletal muscles was increased in patients with IIM compared to healthy donors (p=0.029). In addition, serum clusterin levels were significantly higher in all IIM patients than in healthy subjects (87.1±22.8 vs 68.4±12.4, p<0.0001) and also in individual subsets of patients in comparison to the control group (DM: 87.7±24.7, PM: 86.1±23.2, IMNM: 88.15±18.0, p<0.0001 for all). Clusterin levels in all patients with IIM positively correlated with MYOACT (r=0.337, p=0.008), MITAX (r=0.357, p=0.004) and global disease assessment evaluated by doctor (r=0.309, p=0.015). In patients with DM, positive correlations with MYOACT (r=0.499, p=0.009), MITAX (r=0.491, p=0.009), HAQ (r=0.470, p=0.014), global disease assessment evaluated by doctor (r=0.559, p=0.004), γ-glutamyl transpeptidase and asparate aminotransferase were found (r=0.504, p=0.007; r=0.429, p=0.025, respectively). PM and IMNM subsets showed no significant association.
Conclusions We demonstrate increased local and systemic expression of clusterin in IIM patients compared to healthy individuals and its association with disease activity, especially in dermatomyositis.
Acknowledgements Supported by the project of MHCR for conceptual development of research organization 00023728 and project NV16–33746A.
Disclosure of Interest None declared