Abstract
Purpose::
Tight junction proteins (TJP) claudin-1 (Cl-1), occludin and zonulae-occludens-1(ZO-1) are expressed at the apical side of the epithelial and endothelial cells of ocular tissues where they control paracellular movement of solutes and macromolecules. In the ciliary processes, TJP are critical to maintaining the blood-aqueous barrier (BAB). The present study was designed to compare expression patterns of TJP in ciliary epithelium of mouse, rabbit cat and human.
Methods::
Briefly, 10 µm thick ocular tissue sections were rehydrated in PBS followed by fixation in chilled acetone or PBS containing ammonium chloride. After washing in 0.1 % triton-X100 the sections were blocked in goat serum for one hour followed by incubation in primary antibody either overnight at 4o C or at room temperature for one hour. The sections were then incubated in secondary antibody, cover-slipped and photographed in Carl Zeiss microscope.
Results::
Each of the three TJ proteins showed a similar expression pattern in mouse, rabbit, cat and human ciliary epithelium. Occludin and ZO-1 are localized along the apico-lateral surfaces of the non-pigmented ciliary epithelium. However, the distribution of occludin was more discrete along the border of the non-pigmented and pigmented epithelium, whereas ZO-1 showed staining also at the adjacent membrane. Claudin-1 was not discrete along the apico-lateral surfaces, but diffused along the boundaries of the non-pigmented epithelial cells. In cat and human the staining was weaker and more diffuse.
Conclusions::
The results show a similar pattern of expression of the TJP in all the species examined. The immunostaining pattern suggests that Cl-1, occludin and ZO-1 are co-localized along the apico-lateral border of the non-pigmented ciliary epithelium. It is not clear whether expression of Cl-1 along the cell boundaries was because of the presence of other cross-reactive epitopes on the cell boundaries or the protein is distributed as such.
Keywords: cell adhesions/cell junctions • immunohistochemistry • ciliary body