Terminal differentiation of epithelial cells in middle ear cholesteatoma: investigation of patterns of expression of protein kinase C-delta and protein kinase C-eta.
OBJECTIVE
The objective of this study was to elucidate the differentiation mechanism of keratinocytes in cholesteatoma.


METHODS
To achieve the objective, we analyzed the expressions of various cellular proteins: the delta and eta isoforms of protein kinase C (PKCdelta and PKCeta), which are thought to play key roles in signal transduction in differentiation; cytokeratin 1 (CK1) and cytokeratin 10 (CK10) (cytoskeletal constitutive proteins); and involucrin (a marker of differentiation).


METHODS
The materials used in this study were tissue specimens obtained from cholesteatoma epidermis, normal external ear canal skin, normal inguinal skin, and psoriatic skin. Immunohistochemical staining techniques were applied to compare the expressions of the above proteins (i.e., PKCdelta, PKCeta, CK1, CK10 and involucrin) in those various tissues.


RESULTS
No clear differences in the patterns of expression of PKCdelta and PKCeta were found between the cholesteatoma epidermis and the normal external ear canal skin. These proteins were expressed mainly in the stratum spinosum and stratum granulosum, and their patterns of expression were almost the same as those of the CK1, CK10, and involucrin proteins.


CONCLUSIONS
The findings of this study indicate that the terminal differentiation of keratinocytes in the cholesteatoma epidermis is the same as in normal skin tissues. It was concluded that the growth of epidermis which has undergone hyperproliferation of keratinocytes because of increased levels of various cytokines is being regulated by means of normal terminal differentiation.
Miyazaki
H
H
Department of Otorhinolaryngology, Jikei University School of Medicine, Tokyo, Japan.
Kojima
H
H
Tanaka
Y
Y
Shiwa
M
M
Koga
T
T
Moriyama
H
H
D000328:Adult; D002454:Cell Differentiation / Q000502:physiology*; D018424:Cholesteatoma, Middle Ear / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004847:Epithelial Cells / Q000502:physiology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D015603:Keratinocytes / Q000378:metabolism; D008297:Male; D020033:Protein Isoforms; D011493:Protein Kinase C / Q000378:metabolism*; D011498:Protein Precursors / Q000378:metabolism; D015398:Signal Transduction / Q000502:physiology
D003598:Cytoskeletal Proteins; D020033:Protein Isoforms; D011498:Protein Precursors; C032253:involucrin; D011493:Protein Kinase C