β-PDGF Receptor Expressed by Hepatic Stellate Cells Regulates Fibrosis in Murine Liver Injury, but Not Carcinogenesis

BACKGROUND & AIMS: Rapid induction of β-PDGF receptor (β-PDGFR) is a core feature of hepatic stellate cell activation, but its cellular impact in vivo is not well characterized. We explored the contribution of β-PDGFR-mediated pathway activation to hepatic stellate cell responses in liver injury, fibrogenesis, and carcinogenesis in vivo using genetic models with divergent β-PDGFR activity, and assessed its prognostic implications in human cirrhosis. METHODS: The impact of either loss or constitutive activation of β-PDGFR in stellate cells on fibrosis was assessed following carbon tetrachloride (CCl(4)) or bile duct ligation. Hepatocarcinogenesis in fibrotic liver was tracked after a single dose of diethylnitrosamine (DEN) followed by repeated injections of CCl(4). Genome-wide expression profiling was performed from isolated stellate cells that expressed or lacked β-PDGFR to determine deregulated pathways and evaluate their association with prognostic gene signatures in human cirrhosis. RESULTS: Depletion of β-PDGFR in hepatic stellate cells decreased injury and fibrosis in vivo, while its auto-activation accelerated fibrosis. However, there was no difference in development of DEN-induced pre-neoplastic foci. Genomic profiling revealed ERK, AKT, and NF-kB pathways and a subset of a previously identified 186-gene prognostic signature in hepatitis C virus (HCV)-related cirrhosis as downstream of β-PDGFR in stellate cells. In the human cohort, the β-PDGFR signature was not associated with HCC development, but was significantly associated with a poorer outcome in HCV cirrhosis. CONCLUSIONS: β-PDGFR is a key mediator of hepatic injury and fibrogenesis in vivo and contributes to the poor prognosis of human cirrhosis, but not by increasing HCC development.