Expression and distribution of claudin subtypes in human corneal endothelium

To investigate the expression pattern of claudins in human corneal endothelium, and to evaluate the functional role of the claudin-10b subtype.

Corneal endothelium with Descemet's membrane and the corneal epithelium were stripped from donor human corneal stroma. Reverse transcription-polymerase chain reaction (RT-PCR) was performed to evaluate the claudin subtypes expressed in corneal endothelium, stroma, and epithelium. Immunohistochemistry was performed to confirm the expression of claudin subtypes in corneal endothelium, and the expression pattern was compared to that of corneal epithelium. Finally, transendothelial resistance (TER), short-circuit current (SCC), and potential difference (PD) were measured in human corneal endothelial cell line B4G12 cells with or without claudin-10 small interfering RNA (siRNA) transfection by Ussing chamber system.

Transcripts for claudin-1, -2, -3, -4, -7, -10b, -11, -15, -22, -23, and -24 were identified in corneal endothelium sample by RT-PCR. Immunohistochemistry confirmed the expression of claudin-1, -2, -4, -7, -10, -11 -15, -22, and -23 in corneal endothelium. In corneal stroma, claudin-1, -2, -3, -4, -5, -6, -7, -8, -10b, -11, -12, -14, -15, -22, -23, and -24 were identified by RT-PCR. In corneal epithelium, claudin-1, -3, -4, -7, -11, -14, and -23 were identified by immunohistochemistry and RT-PCR. Downregulation of claudin-10b by siRNA resulted in the decrease of SCC and PD, but not TER, in B4G12 cells.

The expression pattern of claudin-10b(+)/claudin-14(-) was specific in corneal endothelium among the three corneal layers. Claudin-10b may play an important role in the tight junction of corneal endothelium.