Increase in Clusterin Expression in Fuchs' Endothelial Dystrophy

Abstract

Purpose: : To investigate the differential expression of the glycoprotein clusterin/apoJ (CLU) in normal and Fuchs’ endothelial dystrophy (FED) corneal endothelium and to compare the expression of various forms of CLU in normal and FED tissue.

Methods: : FED and pseudophakic bullous keratopathy (PBK) corneal buttons were removed during transplantation and normal corneas were obtained from tissue banks. Human corneal endothelial cells and Descemet’s membrane (HCEC-DM) complex was dissected from the stroma. Proteins were separated on 2-D gels and subjected to comparative proteomic analysis. Relative expression of pre-secretory CLU (pre-sCLU), secretory CLU (sCLU), and nuclear CLU (nCLU) were compared between normal and FED HCEC-DM by Western blots. Expression of CLU mRNA was compared using RT-PCR. Subcellular localization of CLU was compared in corneal whole mounts from normal and FED patients by immunocytochemistry followed by confocal microscopy.

Results: : Proteomic analysis revealed an apparent increase in CLU expression in FED HCEC-DM compared with normal controls. Western blot analysis demonstrated that pre-sCLU protein expression was 4.5 times higher in FED than in normal samples (p=0.002), while the mature form modified for secretion (sCLU) was not significantly elevated (p=0.29). Expression of nCLU protein was significantly elevated in FED (p=0.006). RT-PCR analysis revealed that CLU mRNA was significantly increased (p= 0.008) in FED samples, but not in PBK samples. CLU had also a distinctive localization in FED samples with enhanced intracellular staining around the guttae and in the nuclei of endothelial cells.

Keywords: cornea: endothelium • degenerations/dystrophies • proteomics