Deregulation of the IL-1β axis in chronic recurrent multifocal osteomyelitis

BACKGROUND This study aims to investigate the inflammasome response in peripheral blood mononuclear cells (PBMCs) and the expression of inflammasome components in bone biopsies from patients with chronic recurrent multifocal osteomyelitis (CRMO). METHODS The expression of inflammasome components mRNAs was evaluated in PBMCs isolated from 15 CRMO patients and 13 healthy controls by quantitative real-time PCR. The Interleukin (IL)-1β released in the medium of PBMC cultures after treatment with lipopolysaccharides (LPS) alone or LPS and ATP was measured by ELISA. Immunohistochemical staining for Apoptosis-associated Speck-like protein (ASC), caspase-1 (CASP-1), Nod-like receptor protein-3 (NLRP3) and IL-1β expression was performed in bone biopsies from CRMO patients. RESULTS mRNA levels of ASC, CASP-1 and IL-1β were significantly higher in freshly isolated PBMCs from CRMO patients in active disease than in healthy controls. CASP-1 and IL-1β transcript levels were significantly higher also in PBMCs from CRMO patients in remission compared to healthy controls. PBMCs from CRMO patients in active disease stimulated in vitro with LPS showed a significant increase in IL-1β release compared to healthy control cells. Immunohistochemistry staining of bone tissue revealed the expression of inflammasome components in CRMO osteoclasts. CONCLUSIONS Our data suggest that an abnormal regulation of IL-1β axis may be involved in CRMO pathogenesis.