Abstract: Objective: To investigate the expression of nuclear factor-kappa B ligand (RANKL) and osteoprotegerin (OPG) in human cholesteatoma tissues. Method: Thirty cholesteatoma samples and twenty normal auditory canal skin specimens were enrolled in this study, and expressions of RANKL and OPG were determined by reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry. Results: The mRNA level of RANKL, but not OPG was significantly increased in the cholesteatoma group compared with the control group（t=4.315,P<0.05；t=0.578，P>0.05）. Meanwhile, the ratio of OPG/RANKL was increased (t=6.127；P<0.05). Expression of the cytokine RANKL was increased in infiltrated lymphocytes in the cholesteatoma tissues compared with the normal external meatal skins（t=7.758，P<0.05）, however, expression of OPG was not significantly changed in the cholesteatoma tissues compared with the normal external meatal skins（t=0.623；P>0.05）. Ratio of OPG/RANKL was decreased in the cholesteatoma tissues compared with the normal external meatal skins（t=8.183；P<0.05）. Conclusion: This study reveals that the expression level of RANKL is markedly increased in the perimatrix of cholesteatoma and is closely related to bone resorption induced by cholesteatoma. The decreased OPG/ RANKL is probable a risk factor of the bone resorption induced by cholesteatoma.

Key words: Cholesteatoma, Nuclear factor-kappa B ligand, Osteoprotegerin