Abstract
Purpose::
To evaluate the presence of prion protein PrPc in human corneas and characterize its distribution among the corneal layers.
Methods::
Microarray analysis using the Affymetrix Hu-133 Plus 2.0 Gene Chips for the presence of PRNP RNA sequences was performed on epithelial cells scraped from human corneas, cultured human stromal fibroblasts, and cultured immortalized E6/E7 human corneal endothelial cells. To confirm the presence of the PrPc protein product in the three corneal layers, immunohistochemistry using a commercially available mouse monoclonal antibody was performed on human corneas obtained from archived pathology specimens. Each layer of the cornea was graded independently using a 0 to 3 scale.
Results::
Microarray analysis demonstrated significant levels of PRNP messenger RNA in all three layers of the human cornea. The mean raw expression values were: epithelium = 5929, stromal fibroblasts = 35,821, endothelium = 5837. Immunohistochemistry also demonstrated the presence of the PRPc protein product in the epithelium, stroma, and endothelium. Based on a 0 to 3 grading, the mean intensity of each individual layer is as follows: epithelium = 1.04, stroma = 0.46, and endothelium = 1.07.
Conclusions::
This data provides evidence for the expression of the native prion protein PRPc in the human cornea. More research is needed to evaluate if the native PRPc is involved in the transmission of Creutzfeldt-Jakob Disease (CJD) by corneal transplantation. This data should also be considered in the ongoing debate about the standards for screening corneal donors for symptoms of the transmissible spongiform encephalopathies (TSEs).
Keywords: transplantation • gene microarray • immunohistochemistry