Osteoprotegerin/RANKL system imbalance in active polyarticular‐onset juvenile idiopathic arthritis: a bone damage biomarker?

Abstract

Objective: To evaluate the importance of receptor activator of nuclear factor κB (RANK)/receptor activator of nuclear factor κB ligand (RANKL)/osteoprotegerin (OPG) modulation in active polyarticular juvenile idiopathic arthritis (pJIA) patients with and without bone erosions.

Methods: Thirty female patients (mean age 11.07±3.77 years, range 4–17 years) with active pJIA and 30 healthy gender‐ and age‐matched controls were consecutively selected for this study. All involved articulations were assessed by X‐ray and examined for the presence of bone erosions. The serum levels of RANKL and OPG were measured using an enzyme‐linked immunosorbent assay (ELISA).

Results: Patients with active pJIA had higher levels of serum RANKL than controls [2.90 (0.1–37.4) vs. 0.25 (0.1–5.7) pg/mL, p = 0.007] and a lower OPG/RANKL ratio [21.25 (1.8–897.6) vs. 347.5 (9–947.8), p = 0.005]. However, levels of OPG were comparable in both groups [55.24 (28.34–89.76) vs. 64.42 (30.68–111.28) pg/mL, p = 0.255]. Higher levels of serum RANKL and a lower OPG/RANKL ratio were also observed in active pJIA patients with bone erosions compared to controls [3.49 (0.1–37.4) vs. 0.25 (0.1–5.7) pg/mL, p = 0.0115 and 14.3 (1.8–897.6) vs. 347.5 (9–947.8), p = 0.016]. However, RANKL levels and OPG/RANKL ratio were similar in pJIA patients without bone erosion and controls [1.75 (0.1–10.9) vs. 0.25 (0.1–5.7) pg/mL, p = 0.055 and 29.2 (3.3–756.8) vs. 347.5 (9–947.8), p = 0.281].

Conclusion: These data suggest that active pJIA with bone erosions is associated with high serum levels of RANKL and a low OPG/RANKL ratio, indicating that these alterations may reflect bone damage in this disease.