Bone Abstracts

Aims: To investigate the role of interleukin-6 (IL-6) as a modulator of osteoclastic resorption in vitro in acute Charcot osteoarthropathy.

Material and methods: Peripheral blood mononuclear cells were isolated from six patients with acute Charcot osteoarthropathy, five diabetic and five healthy controls and cultured in vitro on bovine bone disks for 21 days in the presence of i) macrophage-colony stimulating factor (M-CSF) and receptor activator of nuclear factor κβ ligand (RANKL) and ii) M-CSF, RANKL and neutralising antibody to IL-6 (anti-IL-6). Bone discs in duplicate were stained with toluidine blue. Resorption was measured by two methods: i) median area of resorption at the surface by image analysis (%) and ii) median area of resorption under the surface (μm²) measured by Dektak 150 surface profiler and calculated using OriginPro 8.6. Ten scans each 1000 μm long per disc were carried out.

Results: In patients with acute Charcot osteoarthropathy, the addition of anti-IL-6 to cultures treated with M-CSF+RANKL, led to a reduction in the median area of resorption on the surface by image analysis (M-CSF+RANKL vs M-CSF+RANKL+anti-IL-6: 39% (12.9) vs 31% (6.8), P=0.028, median (interquartile range)) but not in the median area of resorption under the surface after profilometry (7.7×10³ μm² (6.9×10³) vs 5.4 (3.3×10³), P=0.2). In diabetic patients, there was no difference in the median area of resorption on the surface (P=0.251) and under the surface (P=0.249) in cultures treated with M-CSF+RANKL compared with cultures treated with M-CSF+RANKL+anti-IL6. Similarly, in healthy subjects, there was no difference in the median area of resorption on the surface (P=0.251) and under the surface (P=0.753) between the two culture treatments.

Conclusion: In acute Charcot osteoarthropathy, IL-6 modulates osteoclastic resorption on the surface but does not influence the extent of resorption under the surface.