Abstract
Purpose:
The primary function of corneal endothelium is to maintain corneal transparency by regulating corneal hydration and nutrition modulated by barrier and metabolic pump function. However, the molecular mechanism of its barrier function is still relatively unknown. Claudins, recently identified main components of tight junctions,are a family of four-transmembrane-spanning proteins. To date, 24 subtype of claudins have been identified in human. Combination of claudin subtypes may contribute not only to the tightness of tight junction strands but also ion-selective channels. In this study, we investigated the expression and pattern of claudins in in vivo human cornea.
Methods:
The experiments in this paper used remained corneal tissue supplied from USA eye bank after the central buttons were used for corneal transplantation. We stripped corneal endothelium with Descemet membrane and corneal epithelium from corneal stroma. Reverse transcription-polymerase (RT-PCR) was performed to evaluate that subtypes of claudins expressed in corneal endothelium, stroma and endothelium. Then, immunohistochemistry was performed for claudins positively expressed in RT-PCR, to confirm whether they would express lateral side of corneal endothelium.
Results:
Transcripts for claudin-1, -2, -3, -4,-7, -10b, -11,-12,-14, -15, -22, -23, and -24 were identified in human corneal endothelium in RT-PCR. Claudin-1, -2, -3, -4, -7 , -11, -12, -14, -15, -22, -23, and -24 expression in corneal endothelium was common to corneal epithelium, and claudin-1, -2,-3,-4, -7, -11,-12,-14, -15, -22,-23,and -24 was common to corneal stroma. Among the claudin subtypes expressed in corneal endothelium, immunohistochemistry revealed the expression of claudin-1,-2, -4, -7, -10 antibodies showed bands that correspond to the junctional complex. Claudin-11 was also expressed in corneal endothelium, however, the expression was not continuous but in a dotlike pattern along cell junctions.
Conclusions:
Claudin-1, -2, -4,-7, -10b and -11 are expressed in corneal endothelium. This combination of claudin subtype may contribute to the uniqueness of barrier integrity and ion sensitivity in corneal endothelium.