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