Peripheral Blood Mononuclear Cells Spontaneous Osteoclastogenesis: Mechanisms Driving the Process and Clinical Relevance in Skeletal Disease.

In vitro peripheral blood mononuclear cells differentiate into osteoclasts under the influence of osteoclast-stimulating factors. However, accumulating evidence suggests spontaneous osteoclasts formation and activity in patients affected by local or systemic bone remodeling diseases in comparison with healthy controls. Therefore, within this review, we summarize the studies where spontaneous osteoclastogenesis of peripheral blood mononuclear cells was observed in pathological conditions of the skeletal system. We indicate a linkage between immunoregulation by T cells and spontaneous osteoclasts formation with increased levels of tumor necrosis factors-α, receptor activator of nuclear factor kappa-B ligand and inteleukin-7 production. In the light of these results, it would be of crucial importance to deepen the correlation between systemic bone remodeling diseases and spontaneous osteoclastogenesis as well as to investigate in detail the mechanisms underlying this phenomenon and the clinical relevance in bone remodeling disease diagnosis and monitoring.