Date of Award

2015

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Neuroscience

College

College of Graduate Studies

First Advisor

Barbel Rohrer

Second Advisor

Carl Atkinson

Third Advisor

Bryan Jones

Fourth Advisor

Craig Crosson

Fifth Advisor

Ann-Charlotte Granholm

Abstract

BACKGROUND: Age-related macular degeneration (AMD), a complex disease involving genetic variants and environmental insults, is among the leading causes of blindness in Western populations. Genetic and histologic evidence implicate the complement system in AMD pathogenesis, and smoking is the major environmental risk factor associated with increased disease risk. Although previous studies have demonstrated that cigarette smoke exposure (CE) causes retinal pigment epithelium (RPE) defects in mice and smoking leads to complement activation in patients, it is unknown whether complement activation is causative in the development of CE pathology; and if so, which complement pathway is required. METHODS: Mice were exposed to cigarette smoke or clean, filtered air for 6 months. The effects of CE were analyzed in wildtype (WT) mice or mice without a functional complement alternative pathway (AP; CFB−/−) using molecular, histological, electrophysiological, and behavioral outcomes. A modified AP inhibitor, CR2-FH, was administered to WT mice for 3 months following CE to determine the effects of anti-complement-based-therapy on smoke-induced ocular pathology. RESULTS: CE in WT mice exhibited a significant reduction in function of rods and cones as determined by electroretinography and contrast sensitivity measurements, concomitant with a thinning of nuclear layers as measured by SD-OCT imaging and histology. Gene expression analyses suggested that alterations in photoreceptors and RPE/choroid may contribute to the observed loss of function, and visualization of complement C3d deposition implies the RPE/Bruch's membrane (BrM) complex as the target of AP activity. RPE/BrM alterations include an increase in mitochondrial size concomitant with an apical shift in mitochondrial distribution within the RPE and a thickening of BrM. CFB−/− mice were protected from developing CE-mediated alterations, and treatment with CR2-FH reversed existing damage in WT mice. CONCLUSIONS: Taken together, these findings provide clear evidence that ocular pathology generated in CE mice is dependent on complement activation and requires the AP. Identifying animal models with RPE/BrM damage and verifying which aspects of pathology are dependent upon complement activation is essential for developing novel complement-based treatment approaches for the treatment of AMD.

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