Intravital Imaging of Liver Function: Moving Beyond Microcirculation

The liver is a favorable organ for intravital microscopy. After anesthesia and laparotomy, the liver can be gently pulled from the abdomen and placed in the view of a microscope lens. Bright field microscopy has long allowed identification of most hepatic cell types and revealed directly sinusoidal movement of blood cells, including margination of leukocytes after various stresses. Based on microanatomy, regions within liver lobules can also be identified and compared. Fluorescence microscopy shows that stellate cells have a unique autofluorescence signature and fluoresce blue with UV excitation, which bleaches rapidly. Hepatocytes display a more robust autofluorescence under visible light. Using introduced fluorophores and GFP‐expressing transgenic mice, many other functional parameters may be monitored. Confocal and multiphoton fluorescence microscopy increases effective resolution compared to widefield microscopy. Red/infrared excitation used in multiphoton microscopy allows deeper tissue penetration with less photodamage and more efficient collection of fluorescence in a scattering environment. Intravital confocal/multiphoton micrographs rival in quality and resolution the corresponding images collected from cell culture monolayers. Examples will be shown illustrating use of intravital microscopy to document changes of microcirculation, leukocyte adherence, mitochondrial function, and cell viability in models of ischemia/reperfusion stress.