Using multiphoton fluorescence lifetime imaging to characterize liver damage and fluorescein disposition in liver in vivo

Liver disease is the fifth most common cause of death and unlike many other major causes of mortality, liver disease rates are increasing rather than decreasing. There is no ideal measurement of liver disease and although biopsies are the gold standard, this only allows for a spot examination and cannot follow dynamic processes of the liver. Intravital imaging has the potential to extract detailed information over a larger sampling area continuously. The aim of this project was to investigate whether multiphoton and fluorescence lifetime imaging microscopy could detect early liver damage and to assess whether it could detect changes in metabolism of fluorescein in normal and diseased livers. Four experimental groups were used in this study: 1) control; 2) ischemia reperfusion injury; 3) steatosis and 4) steatosis with ischemia reperfusion injury. Results showed that multiphoton microscopy could visualize morphological changes such as decreased fluorescence of endogenous fluorophores and the presence of lipid droplets, characteristic of steatosis. Fluorescence lifetime imaging microscopy showed increase in NADPH in steatosis with and without ischemia reperfusion injury and could detect changes in metabolism of fluorescein to fluorescein monoglurcuronide, which was impaired in steatosis with ischemia reperfusion injury. These results concluded that the combination of multiphoton microscopy and fluorescence lifetime imaging is a promising method of assessing early stage liver damage and that it can be used to study changes in drug metabolism in the liver as an indication of liver disease and has the potential to replace the traditional static liver biopsy currently used

Visualization and Modeling of the In Vivo Distribution of Mesenchymal Stem Cells

Copyright © 2017 John Wiley & Sons, Inc. This unit describes a protocol for elucidating the in vivo disposition of administered mesenchymal stem cells (MSCs). Specifically, direct visualization of donor cell spatiotemporal distribution and assessment of donor cell quantity in recipient organs are described. Protocols for data analysis are suggested, with the goal of developing a model to characterize and predict the physiological kinetics of administered MSCs. The use of this model is described, suggesting that it can be applied to abnormal conditions and has potential interspecies and inter-route predictive capability. These universal methods can be employed, regardless of the type of stem cell or disease, to guide future experiments and design treatment protocols. © 2017 by John Wiley & Sons, Inc

Assessing steatotic liver function after ischemia-reperfusion injury by in vivo multiphoton imaging of fluorescein disposition

Ischemia-reperfusion injury, a common complication during liver surgery where steatotic livers are more prone to the injury, may become more prevalent in the growing obese population. This study characterizes liver morphology toward understanding changes in subcellular function in steatotic livers exposed to ischemia-reperfusion injury through quantitative description of fluorescein distribution obtained by minimally invasive in vivo multiphoton microscopy using a physiologic pharmacokinetic model. Rats were fed a high-fat diet for 7 days to induce liver steatosis. Partial ischemia was induced after reperfusion for 4 hours, when fluorescein (10mg/kg) was injected intravenously. Liver images, bile, and blood were collected up to 180 minutes after injection. Ischemia-reperfusion injury was associated with an increase in alanine transaminase levels and apoptosis. In addition, steatosis featured lipid droplets and an increase in fluorescein-associated fluorescence observed in hepato-cytes via multiphoton imaging. Analysis of the hepatic concentration-time profiles has suggested that the steatosis-induced increase in fluorescein-associated fluorescence mainly arises by inducing hepatic fluorescein metabolism. The combination of ischemia-reperfusion with steatosis exacerbates these effects further. This was confirmed by fluorescence lifetime imaging microscopy showing a decreased average fluorescence lifetime of the liver, which is indicative of an increased production of the metabolite. Our results show the potential of noninvasive dye imaging for improving our understanding of liver disease induced by subcellular changes in vivo, providing further quantitative measures of metabolic and biliary liver function, and hence extending the qualitative liver function tests now available