Unfolded Protein Response in Fuchs Endothelial Corneal Dystrophy: A Unifying Pathogenic Pathway?
Accepted 11 September 2009.
Purpose
To assess for activation of the unfolded protein response in corneal endothelium of Fuchs endothelial corneal dystrophy patients.
Design
Retrospective, comparative case series of laboratory specimens.
Methods
Corneal specimens of patients with Fuchs dystrophy and controls with corneal pathologic features other than Fuchs dystrophy were evaluated by transmission electron microscopy (TEM) to evaluate for structural changes of the rough endoplasmic reticulum in corneal endothelium. TEM images were evaluated for alterations of rough endoplasmic reticulum as a sign of unfolded protein response. Normal autopsy eyes, Fuchs dystrophy corneas, and keratoconus corneas were used for immunohistochemistry. Immunohistochemistry was performed on formalin-fixed, paraffin-embedded sections of patient corneas for 3 unfolded protein response markers (GRP78, the α subunit of eukaryotic initiation factor 2, C/EBP homologous protein) and 2 apoptosis markers (caspase 3 and 9). Immunohistochemistry signal quantitation of corneal endothelium for evaluation of marker expression was performed using automated software. Corneal sections were assessed quantitatively for levels of immunohistochemistry marker expression.
Results
TEM showed enlargement of rough endoplasmic reticulum in corneal endothelium of all Fuchs dystrophy specimens. Immunohistochemistry quantitation demonstrated a significant increase in mean signal in corneal endothelium from Fuchs dystrophy patients for markers GRP78, the α subunit of eukaryotic initiation factor 2, C/EBP homologous protein, and caspase 9 compared with non-Fuchs dystrophy corneas (P < .05).
Conclusions
Results of both TEM and immunohistochemistry indicate activation of unfolded protein response in Fuchs dystrophy. Unfolded protein response activation leads to endothelial cell apoptosis in Fuchs dystrophy and may play a central pathogenic role in this disease.
Wilmer Eye Institute, The Johns Hopkins Medical Institutions, Baltimore, Maryland
Inquiries to Albert S. Jun, Wilmer Eye Institute, The Johns Hopkins Medical Institutions, Wilmer/Woods 474, 600 North Wolfe Street, Baltimore, MD 21287
ABSTRACT