Kannikar WongdeeJantarima PandaranandakaJarinthorn TeerapornpuntakitKukiat TudporJirawan ThongbunchooNarongrit ThongonWalailak JantarajitNateetip KrishnamraNarattaphol CharoenphandhuMahidol UniversityFaculty of Medicine, Thammasat University2018-07-122018-07-122008-07-01Histochemistry and Cell Biology. Vol.130, No.1 (2008), 79-90094861432-s2.0-44449143346https://repository.li.mahidol.ac.th/handle/20.500.14594/18902Osteoblasts were previously reported to form tight junctions, which may play an important role in the regulation of ion transport across the epithelial-like bone membrane. However, the evidence for the presence of tight junction-associated proteins in osteoblasts is lacking. We therefore studied the expression of tight junction-associated genes in primary rat osteoblasts and bone tissues. Quantitative real-time PCR showed that osteoblasts expressed ZO-1, -2, -3, cingulin, occludin, claudin-1 to -12, -14 to -20, -22 and -23. By using western blot analyses of selected claudins, expression of claudin-5, -11, -14 and -15, but not claudin-3, were identified in osteoblasts. A confocal immunofluorescent study in undecalcified tibial sections confirmed that claudin-16 was localized on the trabecular surface, normally covered by osteoblasts and bone-lining cells. In addition, immunohistochemical studies in decalcified tibial sections demonstrated the expression of claudin-5, -11, -14, -15 and -16 in bone-lining cells (inactive osteoblasts). Primary osteoblasts cultured in the Snapwell for 19-26 days were found to form a monolayer with measurable transepithelial resistance of ∼110-180 Ωcm2, confirming the presence of barrier functions of the tight junction. It was concluded that osteoblasts expressed several tight junction-associated proteins, which possibly regulated ion transport across the bone membrane. © 2008 Springer-Verlag.Mahidol UniversityBiochemistry, Genetics and Molecular BiologyHealth ProfessionsMedicineArticleSCOPUS10.1007/s00418-008-0419-6