Exfoliation syndrome is a systemic disease of the elastic fibers. The manifestation of this disease in the eye is Pseudoexfoliation Glaucoma (XFG), which is the most common identifiable cause of glaucoma, the most aggressive, and the one harder to treat. The disease is characterized by the formation of amyloid-like deposits by various tissues of the anterior segment of the human eye. In particular, the material is more prominently deposited on the anterior surface of the lens, between the iris and the lens, at the pupillary border. The material is easily recognized by the ophthalmologist during a regular examination and it is dubbed as ?a dandruff-like material?. Its presence is the base for the diagnostic of the disease. It is widely accepted that the mechanical friction exerted between the iris and the lens during the opening and closing of the pupil, leads to dislodgement and release of the material into the aqueous humor. During the outflow of this fluid, the material is carried to the trabecular meshwork, causing clogging and a consequent elevated IOP. Proteomics on the composition of the material revealed the presence of a number of components. Among them, some, such as Clusterin (CLU) and ApoE, have been known to be associated with the ?-amyloid plaques characteristic of Alzheimer disease. No many studies on XFG have been conducted To date, seven genes have been linked to the XFG, with LOXL1 being the first and best studied. But very little is known about how this material is formed and no attempts to reproduce its formation are available. Also, the XFM has not been observed in any animal species, including nonhuman primates. In this application, we propose to address this need. Because this material is only formed in humans, we devised a novel strategy to conduct the study on human lens, more precisely on the most anterior region, where the material is clinically observed. This region of the lens is routinely peeled off (and discarded) by ophthalmology surgeons during cataract surgery. Termed ?lens capsule? (LC), it comprises the 14 m lens capsule together with the single layer of epithelial cells underneath. Thus, we will develop and characterize these organotypic cultures form the discarded surgical LCs to begin studying how the XFM is formed. We will focus on two major relevant components, CLU and LOXL1. We will modulate their production by gene transfer, and expose them, not only to XFG stressors, but to conditioned media secreted by the lens proximal tissues, specially by the Iris Pigment Epithelium (IPE). We will evaluate formation of XFG-like deposits by confocal microscopy and their effect on the elastin and fibrillin networks in the insoluble ECM by immunohistochemistry. We have initial feasibility data and although important challenges need to be overcome, we believe that the new system could provide an invaluable tool to the field and render important information about the disease. The understanding gained by this study will also open the door to the search of specific treatments of the pseudoexfoliation glaucoma.

Public Health Relevance

The glaucomas are a group of optic neuropathies caused by the degeneration and death of the retinal ganglion cells. In glaucoma, there is a progressive visual field loss that if left untreated, leads to irreversible blindness. Pseudoexfoliation Glaucoma (XFG) is the most common identifiable cause of glaucoma, the most common glaucoma in many countries, the glaucoma most associated with high pressures and the least responsible to current IOP lowering medications. In the eye, XFG is manifested by amyloid-like deposits of XFmaterial (XFM) on anterior segment tissues, most prominently on the lens anterior capsule at the pupillary border, between the iris and the lens. It is believed that this material gets released into the anterior chamber and obstructs the trabecular meshwork leading to an elevated IOP. In our laboratory we are interested in exploring mechanisms that would lead to the formation of the exfoliation material and its accumulation/ aggregation on the anterior surface of the human lens. The composition of the material is known and proteomics analysis has identified its major components. Among them Clusterin, a ubiquitous chaperone protein that has been extensively associated with the formation of ?-amyloid deposits in Alzheimer?s disease. Genetically, a total of seven genes have been associated with the XFG so far. The first and best studied is LOXL1 a protein that activates tropoelastin for the formation of elastic fibers. LOXL1 is also present in the XFM. Interestingly, the presence of these XFM deposits has only been observed in human and no other animal disease has experienced the disease. Thus, to begin exploring how the XFM material is formed and deposited on the lens, it would be necessary to use human material. For this project, we put together a strategy that involves the use of human lens capsules, a 5 mm piece of tissue which is peeled out and discarded at the time of cataract surgery. We will grow these specimens under controlled conditions, induce the production of proteins that form part of the XFM components, expose them to XFG stresses and evaluate the deposition of their insoluble ECM for fibrillar and elastic abnormalities. We will compare outcomes with those obtained using lens capsules from XFG patients. Our extensive experience on organotypic cultures, gene transfer using viral vectors, and immunohistochemistry, would be able to provide the tools necessary to tackle the development of this project. We expect that findings from these experiments will give a first look on the mechanisms of formation of XFM and would provide the field with a new approach/ model to investigate the numerous conditions associated with this disease

Agency
National Institute of Health (NIH)
Institute
National Eye Institute (NEI)
Type
Exploratory/Developmental Grants (R21)
Project #
1R21EY030608-01
Application #
9808397
Study Section
Biology of the Visual System Study Section (BVS)
Program Officer
Liberman, Ellen S
Project Start
2019-09-01
Project End
2021-08-31
Budget Start
2019-09-01
Budget End
2020-08-31
Support Year
1
Fiscal Year
2019
Total Cost
Indirect Cost
Name
University of North Carolina Chapel Hill
Department
Ophthalmology
Type
Schools of Medicine
DUNS #
608195277
City
Chapel Hill
State
NC
Country
United States
Zip Code
27599