Differentiation characteristics of cholesteatoma epithelium determined by expression of transglutaminase isoenzymes

Transglutaminase (TGase) isoenzymes are involved in the process of the diff erentiation and cornification of keratinocytes in the epidermis. This study investigates the presence and localization of three TGase isoenzymes to el ucidate the nature and differentiation status of the squamous epithelium in human aural cholesteatoma. Twenty cholesteatoma specimens were used. The p resence and localization of three TGase isoenzymes were studied by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry. mRNA expression of three TGase isoenzymes were detected in the tested chole steatomas with variable levels. The immunohistochemical staining patterns o f three TGase isoenzymes showed variations within specimens, relating to ke ratinizing activity. TGase K is the most abundant among three isoenzymes. K eratinizing epithelium of cholesteatoma have similar expression profiles of TGase isoenzymes with those of epidermis of the skin. Other areas, particu larly those showing non-keratinizing epithelium, showed weak immunostaining of TGase E and C, suggesting its different maturation status from keratini zing epithelium. The results of this study indicate that epithelium of chol esteatoma undergoes same direction of maturation and differentiation charac teristics as the epidermis of skin, evidenced by similar expressions of TGa ses both in mRNA level and immunochistochemistry.