Liver sinusoidal endothelial TGF-β signaling accelerates partial endothelial-mesenchymal transition and MASH through Notch.

BACKGROUND &

aimsAs the global prevalence of obesity continues to rise, metabolic dysfunction-associated steatohepatitis (MASH) has emerged as a significant burden on healthcare systems worldwide. Liver sinusoidal endothelial cells (LSECs) are recognized as crucial regulators of hepatic homeostasis. However, their role in the progression of MASH remains poorly understood, particularly given their early capillarization during disease onset. In this study, we sought to investigate the specific role of LSECs in MASH progression and the underlying molecular mechanisms driving their dysfunction.

methodsWe analyzed single-cell RNA sequencing of the liver from advanced MASH mice (from 6 mice/condition) and conducted in vivo experiments using various LSEC-specific transgenic mouse models (n = 3-10 mice/condition). Primary LSECs (n = 3-6 mice/condition) and human umbilical vein endothelial cells (HUVECs) were used for in vitro experiments.

resultsUsing single-cell RNA sequencing data from MASH-affected livers, we identified a unique population of biphenotypic cells co-expressing markers of both LSECs and mesenchymal cells. Through lineage tracing in LSEC-specific reporter mice, we demonstrated that these biphenotypic cells arose from LSECs undergoing partial endothelial-mesenchymal transition (EndMT) in MASH (p <0.05-0.0001; n = 3 mice/condition, depending on the parameter). Mechanistically, we found that differentiation of these biphenotypic cells was regulated by TGF-β signaling. Inhibition of TGF-β signaling in LSECs suppressed partial EndMT and attenuated MASH progression (p <0.01-0.0001; n = 10 mice/condition). In addition, we discovered that Notch signaling in LSECs, which is activated in response to MASH, was positively regulated by TGF-β signaling and had a crucial role in both the generation of biphenotypic cells and MASH progression (p <0.01-0.0001; n = 3-10 samples/condition).

conclusionsOur findings reveal that a pathogenic TGF-β/Notch axis drives MASH progression by inducing partial EndMet in LSECs, thereby establishing LSEC-targeted intervention as a promising therapeutic strategy for this disease. IMPACT AND IMPLICATIONS: This study reveals a novel biphenotypic LSEC population generated via TGF-β-driven partial EndMT, establishing LSEC dysfunction as an active driver of MASH progression. By elucidating the TGF-β/Notch crosstalk in LSEC partial EndMT, our findings provide new mechanistic insights into MASH pathogenesis. Thus, these results highlight TGF-β signaling in LSECs as a promising therapeutic target. Future work should focus on LSEC-specific delivery systems and validation in cohorts of patients with MASH.