Arthritis & Rheumatism
Objective. Our objective was to compare the osteoclastogenic capacity of peripheral blood mononuclear cells (PBMCs) from patients with osteoarthritis (OA) to that of PBMCs from self-reported normal individuals.
Methods. PBMCs from 140 patients with OA and 45 healthy donors were assayed for CD14+ expression and induced to differentiate into osteoclasts (OCs) over 3 weeks in vitro. We assessed the number of the OCs, their resorptive activity, OC apoptosis, and expression of the following cytokine receptors: receptor activator of nuclear factor κB (RANK), interleukin-1 receptor type I (IL-1R1) and IL-1R2. A ridge logistic regression classifier was developed to discriminate OA patients from controls.
Results. PBMCs from OA patients gave rise to more OCs that resorbed more bone surface than did PBMCs from controls. The number of CD14+ precursors was comparable in both groups, but there was less apoptosis in OCs obtained from OA patients. Although no correlation was found between osteoclastogenic capacity and clinical or radiologic scores, levels of IL-1R1 were significantly lower in cultures from patients with OA compared to controls. OC apoptosis and expression levels of IL-1R1 and IL-1R2 were used to build a multivariate predictive model for OA.
Conclusion. During 3 weeks of culture under identical conditions, monocytes from patients with OA display enhanced capacity to generate OCs compared to cells from controls. Enhanced osteoclastogenesis is accompanied by increased resorptive activity, reduced OC apoptosis and diminished IL-1R1 expression. These findings support the possibility that generalized changes in bone metabolism affecting OCs participate in the pathophysiology of OA.