Liver Sinusoidal Endothelial Cells and Laminin dictate cholangiocytes’ fate in chronic liver disease

BACKGROUND AND AIMS: In chronic liver diseases (CLD), when native hepatocytes enter replicative senescence, new hepatocytes are produced via differentiation of reactive cholangiocytes, also known as ductular reaction - DR - cells. However, this mechanism alone is insufficient to prevent liver failure, emphasizing the need for a deeper understanding to enhance its therapeutic potential. We hypothesize that signals driving DR differentiation into hepatocytes reside in the local niche, particularly extracellular matrix (ECM) composition and neighboring cells. METHOD: injections (3x/week for 6 weeks). Using Opn-iCreERT2; Rosa26RYFP mice, we tracked DR fate, and with Cdh5-iCreERT2; Rosa26RmT/mG mice, we studied LSEC origins. Mouse liver tissues were analyzed using immunohistochemistry (IHC), flow cytometry, RT-qPCR and RESOLVE molecular cartography for spatial transcriptomic. Double-spheroids were used to study ECM effect in vitro. We examined human liver tissues with double IHC and publicly available scRNA-seq datasets were used. RESULTS: We identified two populations of ductular reaction (DR) cells: those surrounded by laminin (Lam-DRs) and those without laminin (NoLam-DRs). Lam-DRs retained a biliary phenotype, while NoLam-DRs showed increased Hnf4α expression. In vitro, a laminin-rich environment maintained cholangiocyte-specific gene expression, supporting laminin's role in preserving the biliary phenotype. Lam-DRs were closely associated with capillarized CD34+ LSECs, which expressed profibrotic and laminin-related genes. Preventing LSEC capillarization reduced laminin deposition and enhanced DR-to-hepatocyte differentiation in chronically injured mice. The CD34+ LSECs-Laminin-DR complex was also present in human liver disease samples. CONCLUSION: Capillarized CD34+ LSECs maintain the biliary phenotype of DR cells by preventing laminin degradation, thereby limiting their differentiation into hepatocytes. Targeting this axis could enhance liver regeneration and improve outcomes in chronic liver disease. IMPACT AND IMPLICATIONS: LSECs and laminin deposition restricts DR plasticity by stabilizing a biliary fate, thereby limiting endogenous regeneration. These findings are relevant for researchers investigating liver regeneration, fibrosis, and cholangiopathies, and for clinicians seeking to understand why regenerative responses remain inefficient in advanced disease. While acknowledging that DR-derived hepatocytes contribute modestly to overall parenchymal renewal, our results suggest that therapeutically modulating LSEC capillarization or ECM remodeling could represent a strategy to enhance regenerative competence in chronic liver disease, warranting further preclinical and translational investigation.