Tight Junction Transmembrane Protein Claudin Subtypes Expression and Distribution in hTERT Immortalized Conjunctival Epithelium and in vivo Human Conjunctival Epithelium

Abstract

Purpose:: To investigate the expression and cellular distribution of the tight junction transmembrane protein claudin subtypes in hTERT immortalized conjunctival epithelium and in vivo human conjunctival epithelium.

Methods:: Conjunctival epithelial cells immortalized by preventing telomere shortening by transduction with hTERT (the generous gift of Dr. I. K. Gipson, Schepens Eye Research Institute, Boston, MA) were cultured on 12 mm Transwell filters (Corning Co., Acton, MA) at a density of 4 x 10⁵ cells/cm². Human conjunctival tissue extirpated from patients with conjunctivochalasis during conjunctivoplasty surgery was also examined. All conjunctiva was obtained with consent of the patients and the procedures followed the Tenets of the Declaration of Helsinki. Reverse transcription-polymerase chain reaction was used to reveal the claudin mRNA expression. Immunohistochemistry was used to determine the tissue distribution of claudins and Mac5AC.

Results:: The transcripts for claudin-1, -2, -3, -4, -7, -9, -10, and -14 were identified in hTERT immortalized conjunctival epithelium. The transcripts for claudin-1, -2, -7, -9, -10, and -14 were identified in in vivo human conjunctival epithelium. By light immunohistochemistry, claudin-1, -4, and -7 were localized at the membrane of epithelial cells, but claudin-2 staining was limited in the nucleus in both conjunctival epithelia. In in vivo human conjunctival epithelium, 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. On the other hand, there was no staining with anti-Muc5AC and anti-Claudin-10 antibody in hTERT immortalized conjunctival epithelium.

Conclusions:: Many subtypes of claudin are expressed in both conjunctival epithelia.hTERT immortalized conjunctival epithelium has the potential to differentiate goblet cells under special conditions. However, there was no goblet cell differentiation under the conditions of our study. Claudin-10, which does not exist in our cultured conjunctival epithelium, is most prominent at the apical epithelial cell to goblet cell junctions in in vivo human conjunctival epithelium. Each claudin subtype may serve a different function within the conjunctival epithelium and claudin-10, especially, may have a particular function.

Keywords: cell adhesions/cell junctions • conjunctiva