Abstract 15217: Intrahepatic Gene Expression Profile Differences in Patients With Fontan Associated Liver Disease

Introduction: Fontan associated liver disease (FALD) develops shortly after the Fontan palliation as the long-term consequence of chronically elevated central venous pressures. The molecular pathways underlying FALD remain largely unknown. We aimed to assess intrahepatic gene expression profile differences among these patients with advanced vs early fibrosis. Hypothesis: Advanced fibrosis in patients with Fontan circulation shows a specific gene expression profile with specific enriched pathways. Methods: This retrospective cohort study included adults with the Fontan circulation who had tissue available from at least one liver biopsy at the UCLA Adult Congenital Heart Disease Center. Clinical, laboratory, imaging and hemodynamic data prior to the liver biopsy were extracted from medical records. Patients were classified into early (F1-F2) or advanced fibrosis (F3-F4). RNA was isolated from formalin-fixed paraffin embedded liver tissue, RNA libraries were constructed using ribosomal RNA depletion method and sequencing was performed on Illumina Novaseq 6000. Differential gene expression and gene ontology analyses were carried out using DESeq2 and Metascape. Results: Seventy-seven patients were included, 53% women, 50% White and 20% Hispanic. Most patients had either a lateral tunnel (40%) or atriopulmonary (24%) Fontan. Four patients had 2 liver biopsies and 1 had hepatocellular carcinoma. Early and advanced fibrosis were present in 43 (54%) and 37 (46%) samples, respectively. Both groups had similar age, comorbidities, NYHA class, liver function tests and liver ultrasound features. Patients with advanced fibrosis had higher BNP, Fontan, mean pulmonary artery and capillary wedge pressures. Samples with advanced fibrosis had 921 up-regulated genes compared to the ones with early fibrosis. The up-regulated genes were enriched in extracellular matrix organization, regulation of cell adhesion, response to wounding, TGF-beta signaling pathway and blood vessel morphogenesis. Conclusions: Advanced fibrosis in patients with Fontan circulation exhibits up-regulated genes compared to early fibrosis, including pathways related to inflammation, congestion and angiogenesis, adding further insight into FALD pathophysiology.