Expression of a Cathelicidin antimicrobial peptide is augmented in cholesteatoma

Objectives/Hypothesis: Antimicrobial peptides are active defense components of innate immunity. Their importance was confirmed at epithelial surfaces as immediate barrier effectors in preventing infection. Cathelicidins are peptide antibiotics that are receiving increasing attention. Several studies have shown that overexpression of cathelicidin results in augmented protection against bacterial infection and prevention of local infection and systemic invasion of microbes. The goal of the study was to investigate whether cathelicidin is upregulated in cholesteatoma epithelium compared with normal skin. Study Design: Twenty patients from a prospective study of cholesteatoma tissues and normal skins were enrolled in the study. The specimens were divided into two portions. One portion was used for subsequent RNA studies; the other was used for immunohistochemical staining. Methods: Reverse transcriptase-polymerase chain reaction was used to assess the expression levels of cathelicidin messenger RNA (mRNA) both in cholesteatoma and in normal skin. Presumptive concentration of cathelicidin mRNA and β₂-microglobulin mRNA was evaluated. Ratio of β₂-microglobulin to cathelicidin was analyzed in each group. The expressions of cathelicidin in cholesteatoma and normal skin epithelium were investigated by an immunohistochemical technique. Results: Cathelicidin mRNA in cholesteatoma epithelium was increased 5.5-fold compared with normal skin of the ear canal. In cholesteatoma epithelium, cathelicidin was located in all the layers, but in the normal skin it was expressed only in the granular and prickle cell layers. Conclusions: Cathelicidin is augmented in cholesteatoma epithelium, and the data in the present study are in agreement with the hypothesis that cathelicidin is likely to act as a key component in the first line of defense at the surface epithelium.