Hepatic stellate cells in NASH fibrosis and HCC

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Non-alcoholic steatohepatitis (NASH) is a rising public health threat characterized by progression from steatosis, to hepatocyte injury, inflammation, fibrosis and hepatocellular carcinoma (HCC). A key unanswered question is how inflammation and hepatic fibrosis create a ‘pro-carcinogenic stroma’ that promotes the development of hepatocellular carcinoma (HCC), even without co-existent cirrhosis. Central to these stromal changes is the activation of hepatic stellate cells (HSCs), which are resident perisinusoidal, vitamin A-rich cells that transdifferentiate into myofibroblasts (cancer-associated fibroblasts, or CAFs) to secrete a host of extracellular matrix constituents, growth factors, and cytokines. The objective of this research is to clarify the role of hepatic stellate cells in the pathogenesis of NASH and HCC. We and our collaborators have developed two highly efficient, complementary models of HSC depletion that can address critical gaps in understanding their role in NASH fibrosis and HCC: 1) JEDI (“Just EGFP death inducing”) T-cells, in which CD8+ T cells engineered to kill cells that express green fluorescent protein (GFP) are administered to transgenic mice, in which GFP is driven by the b-PDGF receptor promoter, killing 99% of HSCs; 2) CAR T cells targeting urokinase plasminogen activated receptor (uPAR), which eliminate only senescent HSCs in murine liver. Concurrently, we have created a highly reproducible murine NASH model that faithfully replicates the histology, fibrosis progression and HCCs of human NASH. Our central hypothesis is that activated and senescent HSCs in NASH express unique drivers that contribute to a tumor-prone stromal microenvironment. Thus, this proposal concurrently investigates the dynamics and unique contributions of HSCs to NASH, and the stromal abnormalities they generate that give rise to HCC. We will address this hypothesis in three interrelated, but distinct Specific Aims:1) To define the dynamics, origin and cellular features of HSC repopulation before and after their depletion in normal and NASH mice; 2) To establish the relative contributions of senescent and non-senescent HSCs to NASH fibrosis and HCC; 3) To identify HSC-derived stromal drivers of HCC in murine and human NASH. This innovative approach leveraging unique animal models is significant because it will yield fundamental new insights into HSC biology in health and disease, define specific stromal drivers that they regulate, and link abnormalities from mouse models to human NASH-HCC to establish their clinical relevance as potential therapeutic targets.