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Q. Li, A. Verma, P.-Y. Han, Z. Shan, L. Yuan, A. S. Lewin, M. K. Raizada, W. W. Hauswirth; ACE2 Over-Expression Protects Retinal Vascular Dysfunction in an Animal Model of Diabetic Retinopathy. Invest. Ophthalmol. Vis. Sci. 2009;50(13):4296.
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Diabetic retinopathy (DR) is the most common form of diabetic vascular complications, and the leading cause of severe vision loss in people under age of sixty. Increasing evidence indicates that the renin-angiotensin-system (RAS) in the eye plays a significant local role in retinal vascular dysfunction in DR. This coupled with our previous observations that overexpression of angiotensin converting enzyme 2 (ACE2), a recently discovered member of RAS converting Ang II to Ang 1-7, produce beneficial effects on hypertension-induced cardiovascular remodeling, we hypothesize that overexpression of this enzyme would prevent DR. Our objective in this study was to test this hypothesis and identify underlying mechanisms.
A secreted form of human ACE2 gene was cloned into an AAV vector under the control of the CMV promoter and packaged into viral particles. The vector (hsACE2-AAV2) was injected into intravitreal cavity of the eye of streptozocin (STZ) induced diabetic mice. The other eye served as a control. The progression of the retinopathy was followed by fluorescein antiography, retinal vasculature was evaluated by albumin extravasations to quantitatively measure the vascular permeability, fluorescein-isothiocyanate (FITC) conjugated concanavalin A lectin (ConA) perfusion to quantify the adhesive leukocytes and the pericyte/endothelial cell loss was evaluated by trypsin-digested retinal vascular preparation. Cytokine expression profiles and NOS enzymes were examined by real-time PCR, ELISA, and western blotting.
hsACE2-AAV2 treatment resulted in a significant reduction in retinal vascular permeability, and > 40% attenuation of pericyte/endothelial cell loss. In addition, there was a significant protection from DR induced abnormalities of overall vascular structure. Treated eyes also showed significant reduction of VEGF, TNF, MCP-1 levels, and iNOS activation.
Our data demonstrate that increased expression of ACE2 by hACE2-AAV2 gene transfer protects retinal vasculature from dysfunction caused by STZ-induced diabetes. The protective role of ACE2 overexpression is likely mediated by blocking the inflammatory responses and iNOS activation, leading to reduced oxidative stress induced by hyperglycemia. Thus ACE2 gene therapy is extremely encouraging for the treatment of DR and other diabetic complications.
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