IL-1 Receptor Antagonist Anakinra Inhibits the Effect of IL-1β- Mediated Osteoclast Formation by Periodontal Ligament Fibroblasts

Rheumatoid arthritis and periodontitis are comorbidities that share mutual pathways. IL-1β is a pro-inflammatory cytokine that plays a crucial role in both diseases. One of the treatment options for rheumatoid arthritis is the use of an IL-1 receptor antagonist (IL-1RA) such as anakinra. Anakinra tempers the disease by decreasing bone resorption and it could possibly stimulate bone formation. Here, we investigate the effect of anakinra in a periodontal disease setting on osteoclastogenesis by co-culturing periodontal ligament fibroblasts (PDLFs) and peripheral blood mononuclear cells (PBMCs) that contain monocytes, a source of osteoclast precursors, as well as by culturing PBMCs alone. The effect of anakinra on PDLF-mediated osteogenesis was studied under mineralization conditions. To mimic a chronic infection such as that prevalent in periodontitis, 10 ng/mL of IL-1β was added either alone or with 10 µg/mL of anakinra. Osteoclastogenesis experiments were performed using co-cultures of PDLF and PBMCs and PBMCs only. Osteoclastogenesis was determined through the formation of multinucleated cells in co-cultures of PDLF and PBMCs, as well as PBMCs alone, at day 21, and gene expression through qPCR at day 14. Osteogenesis was determined by measuring alkaline phosphatase activity (ALP) per cell at day 14. Anakinra is effective in downregulating IL-1β mediated leukocyte clustering and osteoclastogenesis in the co-cultures of both PDLF and PMBCs and PBMCs alone. Gene expression analysis shows that IL-1β increases the expression of the osteoclastogenic marker RANKL and its own expression. This higher expression of IL-1β at the RNA level is reduced by anakinra. Moreover, IL-1β downregulates OPG expression, which is upregulated by anakinra. No effects of anakinra on osteogenesis were seen. Clinically, these findings suggest that anakinra could have a beneficial systemic effect on periodontal breakdown in rheumatoid arthritis patients taking anakinra.