PROJECT SUMMARY/ABSTRACT We propose to remain a Member of the Childhood Liver Disease Research Network (ChiLDReN). As a Charter Member of the Network, our proposal represents a logical extension of the long-standing commitment of our Center to improve the care of children with chronic liver disease through innovative patient-based research. In the previous grant cycles, we worked collaboratively with investigators from other Centers and with the Scientific Data Coordinating Center to build a strong infrastructure to conduct patient-based studies on biliary atresia, cholestatic syndromes, mitochondrial hepatopathies, and primary sclerosing cholangitis (PSC). Our key contributions in the previous cycle included: 1) leadership and/or partnership in the development of network-wide clinical studies, with data analyses and publication of 34 original manuscripts of which 6 had lead authors from Cincinnati; 2) completion of the PRIME and IMAGINE2 trials; 3) leadership in protocol development and implementation of the PSC Observational Study; 4) leadership in whole exome sequencing analysis of patients with mitochondrial hepatopathy; 5) high enrollment and retention of subjects into prospective studies, including the PSC and FORCE studies; 6) timely processing of liver tissue by the staff of RNA Purification Service and Bile Acid Analysis Service to support Network studies; and 7) development of an MRI Core in collaboration with Perspectum Diagnostics to apply Al based analytics to quantitatively predict biliary damage and liver fibrosis. We completed ancillary studies on the genetic basis of intrahepatic cholestasis, the liver transcriptome in biliary atresia, and proteomic plasma biomarkers of portal hypertension. We look forward to significantly contributing to the scientific goals and operational excellence of ChiLDReN through four aims. In Aim 1, we will enroll subjects into prospective ChiLDReN protocols to enable observational studies and translational science. This will be done by pursuing high enrollment rate of subjects into approved protocols, with the timely collection and submission of data and tissue samples to meet the enrollment goals established by the Network. In Aim 2, we will perform translational studies employing bulk RNA and multiome sequencing of cryopreserved liver tissues, spatially resolved transcriptomics (SRT) on liver sections, and Clink® based proteomics of plasma samples from patients with PSC to elucidate the role of the TNF superfamily ligand TWEAK in the progression of biliary fibrosis in PSC. In Aim 3, we will assess the shortterm efficacy and safety of systemic FXR agonist in the treatment of pediatric PSC. In Aim 4, we will establish a Translational Science Coordination Center to support Network investigators with iPSC-derived model systems. By pursuing the four aims, we will be well positioned to fully execute the new Network aims of pursuing translational science projects and conducting trials to improve the outcome...