OBJECTIVETo examine cytokeratin 18(CK18) and it's gene in jaw odontogenic keratocyst (OKC) epithelial lining.

METHODSThe epithelial linings of 32 cases were subject to monoclonal antibody immunohistochemical staining for CK18, CK8 and CK19. RT-PCR and in situ hybridization for CK18 mRNA were conducted in 12 of 32 cases in keratocyst epithelial cell linings.

RESULTSIn 17 cases, CK18 were observed in keratinized surface layers, though weakly positive. In 27 cases, CK18 were positive in the granular cell layers. CK18 were also positive in the spinous cell layers in 14 cases. In all cases, CK18 was negative in basal cell layers. By RT-PCR, 4 cases expressed CK18 strongly, 8 cases weakly. By in situ hybridization, 8 cases expressed CK18 mRNA positively in both spinous and granular cell layers, and 4 cases positively in basal and keratinized cell layers. CK8 were expressed in basal cell layers of keratocyst epithelial linings. In 23 cases, CK19 were expressed in surface cell layers of keratocyst epithelial linings.

CONCLUSIONThe expression of CK18 in keratocyst epithelial linings transfers from basal cell layer to spinous layer. The expression of CK18 immunohistochemical staining and CK18 mRNA in situ hybridization are different, which shows CK18 might be related to proliferation of OKC epithelial linings. That suggests the existence of regulation of CK18 and CK18 mRNA expression.