Osteoblasts express claudins and tight junction-associated proteins

Histochem Cell Biol. 2008 Jul;130(1):79-90. doi: 10.1007/s00418-008-0419-6. Epub 2008 Mar 26.


Osteoblasts 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 approximately 110-180 Omegacm(2), 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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bone and Bones / metabolism*
  • Bone and Bones / ultrastructure
  • Cells, Cultured
  • Female
  • Gene Expression
  • Membrane Proteins / biosynthesis*
  • Microscopy, Electron, Scanning
  • Occludin
  • Osteoblasts / metabolism*
  • Osteoblasts / ultrastructure
  • Rats
  • Rats, Sprague-Dawley
  • Tight Junctions / metabolism*
  • Tight Junctions / ultrastructure


  • Membrane Proteins
  • Occludin
  • Ocln protein, rat