Digital analysis of hepatic sections in mice accurately quantitates triglycerides and selected properties of lipid droplets

We describe a method for the histologic evaluation of lipid accumulation in the livers of various mouse models of hepatic steatosis based on quantitative digital analysis of Oil Red O (ORO) accumulation in fresh-frozen hepatic sections. The process involves two principal steps: identification and digital photographic imaging of areas appropriate for analysis, followed by digital determination of the fraction of the identified area (Area Fraction) exhibiting ORO staining. The Area Fraction, designated the Digital Steatosis Score, is a valuable aspect of the histologic assessment of the liver, especially in various forms of alcoholic and non-alcoholic liver diseases. The method is rapid, requiring similar to 3 min per specimen, and highly reproducible, avoiding the inevitably subjective, semi-quantitative evaluation of lipid content inherent in visual steatosis scoring systems. In normal mice and in six different mouse models of fatty liver, the Area Fraction was highly correlated with hepatic triglyceride content (P < 0.01). The coefficient of variation of repeated determinations of the Area Fraction by two different observers was +/- 6.4%. If made available in clinical settings, rapid, accurate quantitation of liver triglycerides by this method could be very useful in specific conditions such as assessment of donor livers for transplantation.