Increased clusterin expression in Fuchs' endothelial dystrophy.

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 presecretory CLU (pre-sCLU), secretory (s)CLU, and nuclear (n)CLU were compared between normal and FED HCEC-DM by Western blot analysis. Expression of CLU mRNA was compared by using RT-PCR. Subcellular localization of CLU was compared in corneal wholemounts from normal eyes and eyes with FED by immunocytochemistry followed by confocal microscopy.

RESULTS: Proteomic analysis revealed an apparent increase in CLU expression in FED HCEC-DM compared with the normal control. Western blot analysis demonstrated that pre-sCLU protein expression was 5.2 times higher in FED than in normal samples (P = 3.52E-05), whereas the mature form modified for secretion (sCLU) was not significantly elevated (P = 0.092). Expression of nCLU protein was significantly elevated in FED (P = 0.013). RT-PCR analysis revealed that CLU mRNA was significantly increased (P = 0.002) in FED samples, but not in PBK samples. CLU also had a distinctive localization in FED samples with enhanced intracellular staining around the guttae and in the nuclei of endothelial cells.

CONCLUSIONS: CLU expression is markedly elevated in FED-affected tissue, pointing to a yet undiscovered form of dysregulation of endothelial cell function involved in FED pathogenesis.