Rapid in vivo evaluation system for cholestasis-related genes in mice with humanized bile acid profiles

Background:Pediatric cholestatic liver diseases (Ped-CLD) comprise many ultrarare disorders with a genetic basis. Pharmacologic therapy for severe cases of Ped-CLD has not been established. Species differences in bile acid (BA) metabolism between humans and rodents contribute to the lack of phenocopy of patients with Ped-CLD in rodents and hinder the development of therapeutic strategies. We aimed to establish an efficient in vivo system to understand BA-related pathogenesis, such as Ped-CLD. Methods:We generated mice that express spCas9 specifically in the liver (L-Cas9(Tg/Tg) [liver-specific Cas9(Tg/Tg)] mice) and designed recombinant adeno-associated virus serotype 8 encoding small-guide RNA (AAV8 sgRNA) targeting Abcc2, Abcb11, and Cyp2c70. In humans, ABCC2 and ABCB11 deficiencies cause constitutional hyperbilirubinemia and most severe Ped-CLD, respectively. Cyp2c70 encodes an enzyme responsible for the rodent-specific BA profile. Six-week-old L-Cas9(Tg/Tg) mice were injected with this AAV8 sgRNA and subjected to biochemical and histological analysis. Results:Fourteen days after the injection with AAV8 sgRNA targeting Abcc2, L-Cas9(Tg/Tg) mice exhibited jaundice and phenocopied patients with ABCC2 deficiency. L-Cas9(Tg/Tg) mice injected with AAV8 sgRNA targeting Abcb11 showed hepatomegaly and cholestasis without histological evidence of liver injury. Compared to Abcb11 alone, simultaneous injection of AAV8 sgRNA for Abcb11 and Cyp2c70 humanized the BA profile and caused higher transaminase levels and parenchymal necrosis, resembling phenotypes with ABCB11 deficiency. Conclusions:This study provides proof of concept for efficient in vivo assessment of cholestasis-related genes in humanized bile acid profiles. Our platform offers a more time- and cost-effective alternative to conventional genetically engineered mice, increasing our understanding of BA-related pathogenesis such as Ped-CLD and expanding the potential for translational research.