The inhibitory effect of microRNA-146a expression on bone destruction in collagen-induced arthritis

MicroRNA, a class of noncoding RNA, play a role in human diseases. MicroRNA-146a (miR-146a) is a negative regulator of immune and inflammatory responses, and is strongly expressed in rheumatoid arthritis (RA) synovium and peripheral blood mononuclear cells (PBMCs). This study was undertaken to examine whether miR-146a expression inhibits osteoclastogenesis, and whether administration of miR-146a prevents joint destruction in mice with collagen-induced arthritis (CIA).

PBMCs from healthy volunteers were isolated and seeded in culture plates. The following day, double-stranded miR-146a was transfected and cultured in the presence of macrophage colony-stimulating factor and either tumor necrosis factor α or RANKL. After 3 weeks, tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells were counted. Three days after miR-146a culture, the expression of c-Jun, nuclear factor of activated T cells c1 (NF-ATc1), PU.1, and TRAP was evaluated by quantitative reverse transcriptase-polymerase chain reaction. After the onset of distinct arthritis in mice with CIA, double-stranded miR-146a or nonspecific double-stranded RNA was administered twice by intravenous injection. Radiographic and histologic examinations were performed at 4 weeks.

The number of TRAP-positive multinucleated cells in human PBMCs was significantly reduced by miR-146a in a dose-dependent manner. The expression of c-Jun, NF-ATc1, PU.1, and TRAP in PBMCs was significantly down-regulated by miR-146a. Administration of miR-146a prevented joint destruction in mice with CIA, although it did not completely ameliorate inflammation.

Our findings indicate that expression of miR-146a inhibits osteoclastogenesis and that administration of double-stranded miR-146a prevents joint destruction in arthritic mice. Administration of miR-146a has potential as a novel therapeutic target for bone destruction in RA.