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Apolipoprotein A-I and B distribution in the human cornea
F Ashraf1, D G Cogan, H S Kruth
1Clinical Branch, National Eye Institute, National Institutes of Health, Bethesda, MD 20892.
Investigative Ophthalmology & Visual Science
|December 1, 1993
Summary
Lipid deposits in the cornea may lack apolipoprotein B, suggesting altered low-density lipoprotein. Unexpectedly, apolipoprotein A-I associates with corneal cells, indicating potential uptake or synthesis.
Area of Science:
- Ophthalmology
- Lipid Metabolism
- Corneal Biology
Background:
- Apolipoprotein A-I (A-I) is a marker for high-density lipoprotein (HDL).
- Apolipoprotein B (B) is a marker for low-density lipoprotein (LDL).
- Lipid accumulation in the cornea, such as in corneal arcus, is a clinical concern.
Purpose of the Study:
- To determine the presence and localization of apolipoprotein A-I and apolipoprotein B in human cornea.
- To examine the relationship between these apolipoproteins and corneal lipid accumulation.
Main Methods:
- Localization of A-I and B apolipoproteins using monoclonal antibodies and avidin-biotin immunoperoxidase labeling in human corneal frozen sections.
- Colocalization of corneal lipid with apolipoproteins using oil red 0 staining.
Main Results:
- Apolipoprotein B and lipid accumulated in peripheral corneal stroma extracellular spaces, but their distributions were not coincident.
- Lipid was found in the posterior peripheral stroma without detectable apolipoprotein B.
- Apolipoprotein A-I was associated with keratocytes throughout the cornea and extracellularly in the periphery.
Conclusions:
- Corneal lipid deposits lacking apolipoprotein B suggest altered LDL, potentially modified from plasma LDL.
- The association of apolipoprotein A-I with keratocytes suggests these cells may be involved in uptake or synthesis of A-I or a related protein.