High YKL-40 serum levels and its expression in the muscle tissues of patients with antisynthetase syndrome

Background The protein chitinase-3-like-1 (YKL-40) is rarely analyzed in patients with myositis. Therefore, we aimed to evaluate YKL-40 serum levels; correlate them with laboratory and clinical parameters, disease status, and treatment schemes; and analyze the YKL-40 expression in the muscle tissues of patients with antisynthetase syndrome (ASSD). Methods This cross-sectional single-center study included 64 adult patients with ASSD who were age-, gender-, and ethnicity-matched to 64 healthy control individuals. Their YKL-40 serum levels were analyzed using the Enzyme-Linked Immunosorbent Assay (ELISA) kit method, while YKL-40 expression in muscle tissues was analyzed using an immunohistochemical technique. Disease status was assessed using the International Myositis Assessment and Clinical Studies Group (IMACS) set scores. Results The patients' mean age was 44.8 +/- 11.8 years, and median disease duration was 1.5 (0.0-4.0) years. These patients were predominantly female (82.8%) and Caucasian (73.4%). Most patients had stable disease. The median YKL-40 serum level was significantly higher in patients with ASSD when compared to the healthy individuals: 538.4 (363.4-853.1) pg/mL versus 270.0 (201.8-451.9) pg/mL, respectively; P < 0.001. However, YKL-40 serum levels did not correlate with any clinical, laboratory, disease status, or therapeutic parameters (P > 0.050), except tumor necrosis factor alpha (TNF-alpha) serum levels (Spearman's correlation, rho = 0.382; P = 0.007). YKL-40 was highly expressed by inflammatory cells found in muscle biopsy specimens. Conclusions High YKL-40 serum levels were observed in patients with ASSD and correlated positively with TNF-alpha serum levels. Moreover, YKL-40 was expressed by the inflammatory cells of the muscle tissue.

Automated summary

The study found that serum levels of the protein YKL-40 were significantly elevated in patients with ASSD and were positively correlated with TNF-alpha serum levels. YKL-40 was highly expressed by inflammatory cells in muscle tissue.