Longitudinal Testing of Retinal Blood Flow in a Mouse Model of Hypertension by Laser Speckle Flowgraphy

Abstract

Purpose: The purpose of this study was to investigate the applicability of laser speckle flowgraphy (LSFG) for a longitudinal study of blood flow parameters in mice before, during, and after continuous infusion of angiotensin-II. Methods: Normotensive C57BL/6J mice were imaged by LSFG at one (n = 22) or three sessions (n = 10). Two additional cohorts were imaged by LSFG before, during, and after continuous infusion of angiotensin-II by minipump for 2 or 4 weeks (n = 6 and 8, respectively). Retinal blood flow, vascular resistance, and total area of retinal vascular flow, a surrogate of vascular remodeling and vasoconstriction, were determined at each time point. Results: During infusion of angiotensin-II for 2 weeks, decreased retinal blood flow and area of vascular flow, as well as increased vascular resistance, were observed. These changes were reversed 1 week after the end of angiotensin-II infusion. In mice infused with angiotensin-II for 4 weeks, decreased retinal blood flow and increased vascular resistance persisted at 6 weeks postinfusion, despite a decrease in blood pressure. Conclusions: Arterial hypertension, induced by continuous angiotensin-II infusion, results in reduced retinal blood flow, increased vascular resistance, and decrease in area of intravascular blood flow within retinal arterioles and venules. Sustained vasoconstriction 6 weeks after the end of a 4-week period of angiotensin-II infusion may indicate vascular remodeling after a period of chronic hypertension. Translational Relevance: Retinal LSFG is useful for serial investigation of blood flow in mouse models and provides a novel approach for translational studies on the microvascular effects of hypertension in vivo.