Structural Characterization and Lipid Composition of Acquired Cholesteatoma

Abstract

The goal of this work is to characterize the morphology and lipid composition of acquired cholesteatoma. We hypothesize that constitutive lipid membranes are present in the cholesteatoma and resemble those found in human skin stratum corneum. We performed a comparative noninvasive structural and lipid compositional study of acquired cholesteatoma and control human skin using multiphoton excitation fluorescence microscopy-related techniques and high-performance thin-layer chromatography. The structural arrangement of the cholesteatoma is morphologically invariant along a depth of more than 200 μm and resembles the stratum corneum of hyperorthokeratotic skin. Lipid compositional analyses of the cholesteatoma show the presence of all major lipid classes found in normal skin stratum corneum (ceramides, long chain fatty acids, and cholesterol). Consistent with this, evaluation of Nile red and LAURDAN generalized polarization function images of the cholesteatoma show intercellular regions similar to normal skin stratum corneum in terms of lipid membrane packing and local water content. The investigations show the presence of an extremely thickened stratum corneum within the cholesteatoma. The lipid composition and extracellular membranes similar to those of normal skin stratum corneum are present, indicating that a defensive/permeability barrier is present in the cholesteatoma. Finally, it is demonstrated that multiphoton excitation fluorescence microscopy is a suitable noninvasive tool for investigating the morphology and intrinsic physical properties of acquired cholesteatoma.