RANKL and cathepsin K in diffuse sclerosing osteomyelitis of the mandible

Abstract

Diffuse sclerosing osteomyelitis (DSO) of the mandible is characterized by mixed bone resorption and formation. Immunohistopathology of DSO in the clinically acute and subacute phases was compared with healthy bone. Receptor activator of nuclear factor kappaB ligand (RANKL) was found in DSO lesions. When it was used in vitro to stimulate monocytes, cathepsin K expression was observed in mononuclear prefusion precursors and in multinuclear giant cells. Similarly, exacerbations of DSO were characterized by RANKL and induction of cathepsin K in mononuclear precursor cells, which subsequently seem to differentiate into osteoclasts or foreign body giant cells. The proportion of bone to soft tissue increased with the duration of disease. RANKL-driven osteoclastogenesis and acidic cysteine endoproteinase cathepsin K seem to play important roles in DSO as osteoclast-mediated bone resorption may represent the primary disease process later followed by new bone formation.