Expression of RANKL and OPG in middle ear cholesteatoma tissue

Objective. The objective of this study was to investigate how the expression of the RANK-RANKL-OPG system mediates the formation and differentiation of osteoclasts and causes bone resorption in cholesteatoma. Methods. An immunohistochemical analysis was carried out in 22 cholesteatoma tissues obtained during middle ear surgery and 15 normal postauricular skin tissues to examine the expression of RANKL and OPG. Results. All 22 cases of cholesteatoma and the 15 cases of normal postauricular skin expressed RANKL and OPG. The count and rate of RANKL-positive cells in cholesteatoma was significantly higher than in normal postauricular skin. The count and rate of OPG-positive cells in normal postauricular skin was significantly higher than in cholesteatoma. The ratio of the positive expression rates of RANKL and OPG in cholesteatoma was statistically higher than in normal postauricular skin. Conclusions. We provide evidence suggesting that RANKL, which activates osteoclasts, plays a significant role in the mechanism of bone destruction in cholesteatoma, and that the ratio of RANKL to OPG may be a reliable indicator of bone destruction in cholesteatoma.