Osteoclast stimulating and differentiating factors in human cholesteatoma

Objectives. To investigate the expression of osteoclast-activating and differentiating factors and to study the occurrence of osteoclast precursor cells and osteoclasts in acquired human cholesteatoma tissue. Methods. We examined 21 cholesteatoma samples versus 18 normal auditory canal skin specimens for the expression of osteoprotegerin ligand (OPGL), osteoprotegerin (OPG), and macrophage-colony stimulating factor (M-CSF) using reverse transcriptase-polymerase chain reaction (RT-PCR) and inununohistochemistry. Immunohistochemistry and computer-assisted microscopy using markers CD4, CD11a, CD11b, CD14, CD51, CD68, and TRAP obtained the detection of osteoclast cell lineage. Results. An increased expression of the investigated cytokines M-CSF, OPG, and OPGL was demonstrated by immunohistochemistry and RT-PCR in cholesteatoma tissue compared with normal external meatal skin. Several CD4-positive cells exhibited a co-expression for OPGL within the perimatrix of cholesteatoma. The presence of osteoclast precursor cells was confirmed in all samples of cholesteatoma tissue. Conclusions: This study reveals that the number of osteoclast precursor cells is markedly increased in the perimatrix of cholesteatoma tissue. Our results support a concept described for inflammatory arthritis: the inflammation related to cholesteatoma induces bone resorption by release of OPGL from activated T-cells and triggers osteoclastogenesis. This could be a major target for drugs to inhibit osteoclast formation and bone resorption and may be an adjunct in cholesteatoma management.