Cardiovascular risk factors, such as hypertension, have been associated with cognitive decline, potentially due to their impact on brain tissue oxygenation. In this study, high spatial resolution imaging in three dimensions was used to understand changes in brain oxygenation with hypertension. Experiments were performed on Young (WT_Y, 3-4 months, n=8), Old (WT_O, 6-7 months, n=8), and Old with hypertension (HP_O, 6-7 months, n=8) C57bL/6 awake mice. Two photon phosphorescence lifetime microscopy using an O2-sensitive phosphorescent dye PtPC343 was employed to measure two dimensional grids of PO2 in capillary beds (400um*400um, 25*25 pixels, acquired in 4 mins) and decays from arterioles. Scans were obtained continuously at depths from 50 um to 300 um under the brain surface. Using 3D measurements and a 250 um depth stack, we removed the compounding effects on brain oxygenation diffusion from surrounding brain vessels. The entire measurement of each vasculature stack required less than 30 minutes. This study indicates that among vascular risk factors, hypertension can reduce oxygen delivery and could potentially contribute to cognition decline.
Xuecong Lu, Mohammad Moeini, Baoqiang Li, Cong Zhang, Sava Sakadžić, and Frédéric Lesage, "3D brain oxygenation measurements in awake hypertensive mice using two photon phosphorescence lifetime imaging," Proc. SPIE 10498, Multiphoton Microscopy in the Biomedical Sciences XVIII, 104981Y (Presented at SPIE BiOS: January 31, 2018; Published: 23 February 2018); https://doi.org/10.1117/12.2289030.
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