Spatially segregated defects and IGF1-responsiveness of hilar and peripheral biliary organoids from a model of Alagille syndrome

Abstract

Background & aims: Alagille syndrome (ALGS) manifests with peripheral intrahepatic bile duct (IHBD) paucity, which can spontaneously resolve. In a model for ALGS, Jag1^Ndr/Ndr mice, this occurs with distinct architectural mechanisms in hilar and peripheral IHBDs. Here, we investigated region-specific IHBD characteristics and addressed whether IGF1, a cholangiocyte mitogen that is downregulated in ALGS and in Jag1^Ndr/Ndr mice, can improve biliary outcomes.

Methods: Intrahepatic cholangiocyte organoids (ICOs) were derived from hilar and peripheral adult Jag1^+/+ and Jag1^Ndr/Ndr livers (hICOs and pICOs, respectively). ICOs were grown in Matrigel or microwell arrays, and characterized using bulk RNA sequencing, immunofluorescence, and high throughput analyses of nuclear sizes. ICOs were treated with IGF1, followed by analyses of growth, proliferation, and death. CellProfiler and Python scripts were custom written for image analyses. Key results were validated in vivo by immunostaining.

Results: Cell growth assays and transcriptomics demonstrated that Jag1^Ndr/Ndr ICOs were less proliferative than Jag1^+/+ ICOs. IGF1 specifically rescued survival and growth of Jag1^Ndr/Ndr pICOs. Jag1^Ndr/Ndr hICOs were the least proliferative, with lower Notch signalling and an enrichment of hepatocyte signatures and IGF uptake/transport pathways. In vitro (Jag1^Ndr/Ndr hICOs) and in vivo (Jag1^Ndr/Ndr hilar portal tracts) analyses revealed ectopic HNF4a⁺ hepatocytes.

Conclusions: Hilar and peripheral Jag1^Ndr/Ndr ICOs exhibit differences in Notch signalling status, proliferation, and cholangiocyte commitment which may result in cholangiocyte-to-hepatocyte transdifferentiation. While Jag1^Ndr/Ndr pICOs can be rescued by IGF1, hICOs are unresponsive, perhaps due to their hepatocyte-like state and/or expression of IGF transport components. IGF1 represents a potential therapeutic for peripheral bile ducts.

Keywords: Jag1; Notch; bile duct paucity; biliary epithelial cells (BECs); cholangiocytes.