Localization of matrix metalloproteinase 1 in cholesteatoma and deep meatal skin

Hypothesis: Matrix metalloproteinase I (MMP-1) is overexpressed in choleste atoma. Background: Cholesteatoma destroys bone, whereas deep meatal skin does not. MMP-1 is a type I collagenase that may be responsible for this destruction . This prospective study was designed to identify overexpression of MMP-1 b y cholesteatoma in comparison with deep mental skin. Methods: Ten cholesteatoma specimens and nine deep meatal skin specimens we re removed during otologic surgery and then fixed in formalin and embedded in paraffin. Immunocytochemistry studies were performed using a monoclonal antibody to MMP-1. A pathologist assessed the slides in a blinded fashion, Expression of MMP-1 protein in epidermis and in stroma was scored from 0 to 10. Five further cholesteatoma specimens and three deep meatal skin specimens u nderwent reverse transcriptase polymerase chain reactions to assess messeng er ribonucleic acid production. Paired and impaired Student's t tests were used to assess the difference in expression levels. Results: Cholesteatoma stroma expressed significantly more MMP-1 protein th an did deep meatal skin stroma (p = 0.04). MMP-1 was localized to stromal f ibroblasts. There was no difference in the epidermal expression levels of t he two tissue types (p = 0.42). The reverse transcriptase polymerase chain reaction showed expression at the messenger ribonucleic acid size of MMP-1 (262 base pair) in all cholesteatoma specimens examined. One deep meatal sk in specimen showed a weak signal; no signal was seen in the other specimens . Conclusions: MMP-1 is overexpressed by the stromal fibroblasts present in c holesteatoma as compared with deep meatal skin. It is possible that these c ells rather than the keratinocytes are responsible for bone destruction in this disease.