Abstract
Purpose: :
To investigate the expression and cellular distribution of the tight junction–related proteins occludin, claudin, and ZO–1 in human conjunctival epithelium. To evaluate the difference between epithelial cell tight junctions, with those between epithelial cells and goblet cells.
Methods: :
Reverse transcription–polymerase chain reaction was used to reveal claudin mRNA expression in human conjunctival epithelium. Light immunohistochemistry was used to determine tissue distribution of occludin, claudin, and ZO–1 in human conjunctival epithelium.
Results: :
The transcripts for claudin–1 and several other claudin isotypes, such as –2, –7, –9, –10, and –14 were identified. In transverse sections, occludin and ZO–1 were localized at the apical superficial epithelial cell tight junctions, as well as the epithelial cell to goblet cell tight junctions. In en face sections, occludin and ZO–1 antibodies showed as bands that corresponded to the junctional complex. The membrane of epithelial cells through all cell layers was stained by claudin–1, but no staining was observed at goblet cells. Claudin–2 staining was limited in superficial cell nucleus. Both basal and basolateral membranes of superficial epithelial cells and goblet cells were stained by the claudin–7 antibody, but no apical membrane staining was observed. Claudin–9 and –14 staining of superficial cell cytoplasm was observed. Claudin–10 staining was most prominent at the apical epithelial cell to goblet cell junctions, but weak staining was also observed at the apical superficial epithelial cell to epithelial cell junctions.
Conclusions: :
Many subtypes of claudin are expressed in human conjunctival epithelium. Our research indicates that each claudin subtype has different localization, and that the main claudin subtype which exists between superficial epithelial cells differs from those between epithelial cells and goblet cells. For instance, claudin–10, which does not exist in human corneal epithelium, is most prominent at the apical epithelial cell to goblet cell junctions in human conjunctival epithelium. Therefore, we conclude that each claudin subtype may serve a different function within the conjunctival epithelium. Especially, claudin–10 may have a particular function.
Keywords: cell adhesions/cell junctions • conjunctiva • immunohistochemistry