DoUble resin casting micro computed tomography (DUCT) reveals biliary and vascular pathology in a mouse model of Alagille syndrome

Abstract

BACKGROUND AND AIMS: Alagille syndrome, like several other liver diseases, is characterized by malformation of lumenized structures, such as the circulatory or biliary systems. Liver architecture has typically been studied through 2D sections and, more recently, using thick tissue sections combined with immunofluorescence. We aimed to develop a robust method to image, digitalize and quantify 3D architecture of the biliary and vascular systems in tandem. METHODS: The biliary and portal vein trees of the mouse liver were injected with Microfil resin, followed by microCT scanning. Tomographic data was segmented and analyzed using a MATLAB script we wrote to investigate length, volume, tortuosity, branching, and the relation between the vascular and biliary systems. Double resin casting micro computed tomography (DUCT) was applied to a mouse model for Alagille syndrome (Jag1 Ndr/Ndr mice), in which the biliary system is absent at postnatal stages, but regenerates by adulthood. Phenotypes discovered using DUCT were validated with cumbersome consecutive liver sections from mouse and human liver including patients with Alagille syndrome. RESULTS: DUCT revealed tortuous bile ducts either placed further from portal veins, or ectopically traversing the parenchyma and connecting two portal areas, in Jag1 Ndr/Ndr mice. Furthermore, bile ducts either ended abruptly, or branched independently of portal vein branching, with bifurcations placed hilar or peripheral to portal vein branches. The branching defects, parenchymal bile ducts, and blunt endings were confirmed in patient samples. CONCLUSION: DUCT is a powerful technique, which provides computerized 3D reconstruction of casted networks. It exposes and quantifies previously unknown vascular and biliary phenotypes in mouse models, revealing new phenotypes in patients.