Publication Date

2016-10-21

Availability

Embargoed

Embargo Period

2018-10-21

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PHD)

Department

Molecular and Cellular Pharmacology (Medicine)

Date of Defense

2016-10-14

First Committee Member

Wei Li

Second Committee Member

Abigail S. Hackam

Third Committee Member

Keith A. Webster

Fourth Committee Member

Zhao-Jun Liu

Fifth Committee Member

Xin-Hai Pei

Abstract

Diabetic retinopathy (DR) is one of the most common diabetic vascular complications. Angiogenic factors, such as VEGF (vascular endothelial growth factor), play important roles in the pathogenesis of vision-threatening DR. A major breakthrough is the recent approval of anti-VEGF therapy for diabetic eye disease however, its limited therapeutic efficacy implicates the involvement of other angiogenic factors in the pathogenesis. Endothelial factors with preferential binding to the diseased vasculature may represent novel targets for alternative ligand-based therapies. In this thesis, I applied a new technology of “comparative ligandomics” to diabetic and healthy mice for the differential mapping of disease-related ligands. Secretogranin III (Scg3) displayed minimal binding to healthy vessels but ~1,731-fold increase in binding to the diabetic endothelium. In contrast, VEGF showed comparable binding to both the diabetic and healthy vasculature. These findings were independently verified using a cornea angiogenesis assay in which Scg3, but not VEGF, preferentially promoted angiogenesis in diabetic mice. Accordingly, Scg3 and VEGF activated distinct receptor signaling pathways. However, both factors were elevated in the diabetic vitreous fluid, suggesting that similar to VEGF, Scg3 may also play a role in DR pathogenesis. The role of Scg3 as a therapeutic target was confirmed using a neutralizing polyclonal antibody (pAb) in a mouse model of diabetic retinal leakage and ocular neovascularization. To demonstrate how the identification of a disease-related factor by comparative ligandomics can impact ligand discovery, we generated a Scg3-neutralizing monoclonal antibody (mAb) and verified its therapeutic efficacy to reduce vascular leakage and angiogenesis in vivo. These findings established Scg3 as a disease-related target for anti-angiogenic therapy and provide a foundation for future mAb humanization and clinical trials. Characterization of Scg3 supports the use of comparative ligandomics for identification of disease-associated ligands.

Keywords

Diabetic retinopathy (DR); wet age-related macular degeneration (wet AMD); angiogenesis, therapy, ligandomics

Available for download on Sunday, October 21, 2018

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