| Objective To explore the expression of carbonic anhydrase(CA) and the activity of type Ⅳ collagenase in middle ear cholesteatoma, and to evaluate their roles in the mechanisms of bone resorption associated with cholesteatoma. Methods Tissue specimens from 54 cases(57 ears) of middle ear cholesteatoma and 22 cases of external ear skin were examined by immunohistochemical SABC(StreptAvidin-Biotin Complex) method for CA, another group of specimens from 41 cases of middle ear cholesteatoma and 20 cases of external ear skin were analysed at molecular corresponding to MMP-2 and MMP-9 using Sodium Dodecyl Sulphate Polyacrylamide Gel Electrophoresis(SDS-PAGE) Zymography. Results The rates of positive singal were 98.25% and 63.64% in cholesteatoma and external ear skin, respectively. CA was mainly expressed in cytoplasm. Cholesteatoma showed a significantly stronger expression of CA than external ear skin, P＜0.05. Expression of CA displayed strong staining in the stromal cell, granular cell and basal cell layers in cholesteatoma, while weak in the stratum corneum, and revealed a positive staining in the suprabasal cell and granular cell layers of external ear skin, but weak in the basal cell and the stratum corneum. Expression of CA did not show a significant difference between extensive cholesteatoma and localized cholesteatoma, P＞0.05. The levels of MMP-2 and MMP-9 were 0.954±0.411 and 2.676±0.734 in cholesteatoma and were 0.355±0.160 and 1.166±0.443 area gray-scale/mg/ml in external ear skin, respectively. The activity of MMP-2 and MMP-9 in cholesteatoma was obviously higher than external ear skin and showed close relationship , P＜0.01. The levels of MMP-2 and MMP-9 were 1.062±0.401 and 2.946±0.134 in extensive cholesteatoma and were 0.701±0.318 and 2.193±0.601 area gray-scale/mg/ml in localized cholesteatoma, respectively. The activity of MMP-2 and MMP-9 were significantly increased in extensive cholesteatoma in comparison with localized cholesteatoma, P＜0.01. No significant difference was observed between children and adults, male and female,recurrent cases and first cases, P＞0.05. There was no relationship between expression of CA and activity of MMP-2 and MMP-9 in cholesteatoma. Conclusion Expression of CA in middle ear cholesteatoma was higher than external ear skin. The activity of MMP-2 and MMP-9 in cholesteatoma was significantly higher than external ear skin, extensive cholesteatoma was higher than localized cholesteatoma, which indicated that type Ⅳ collagenase (MMP-2 and MMP-9) played a vital role in the bone destruction associated with cholesteatoma , and that the levels of MMP-2 and MMP-9 was closely related to the extent of bone remodeling in middle ear cholesteatoma.
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