ABSTRACT Background & Aims: The disease course of primary sclerosing cholangitis (PSC) is variable and difficult to predict. MicroRNA-122 (miR-122) is associated with various liver diseases. We investigated the value of miR-122 as a biomarker for the disease course of PSC. Methods: We determined serum miR-122 levels in a long-term, prospective cohort of 114 PSC patients and
a second validation cohort. Results: Based on miR-122 levels, PSC patients were assigned to low or high level miR-122 groups. Kaplan- Meier analysis showed significantly impaired actuarial transplant-free survival for PSC patients in the low miR-122 group (mean: 46.1 ± 4.1 months; 95% confidence intervals [CI]: 38.1–54.2) compared to the high miR- 122 group (mean: 95.2 ± 7.9 months; 95% CI: 79.5–110.8; p = 0.034). Using a multivariate Cox’s proportional hazards model approach, Mayo-Risk score (odds ratio [OR]: 1.47; 95% CI: 1.13‒1.92; p = 0.004), the presence of dominant strictures (OR: 2.62; 95% CI: 1.00‒5.55; p = 0.004), and serum miR-122 levels (OR: 1.19; 95% CI: 1.00‒1.43; p = 0.045) were independent risk factors associated with reduced actuarial transplant-free survival. We were able to confirm this finding in a second, independent cohort of PSC patients (low miR-122 group: mean survival: 13.1 ± 5.2 months; 95% CI: 2.8–23.4; high miR-122 group: mean: 28.62 ± 4.2 months; 95% CI: 20.3–37.0; p = 0.018). Conclusions: We identified miR-122 as a novel, independent prognostic biomarker associated with improved survival in PSC patients. It is unknown whether exogenous miR-122 might influence the disease course of PSC patients. Key words: miR-122 – primary sclerosing cholangitis – actuarial survival free of liver transplantation – biomarker. Abbreviations: AP: alkaline phosphatase; CT: cycle threshold; DS: dominant stenosis; ERC: endoscopic retrograde cholangiography; IBD: inflammatory bowel disease; miR-122: microRNA-122; PSC: primary sclerosing cholangitis; RT-qPCR: quantitative real-time reverse transcription polymerase chain reaction.