Laboratory Investigation advance online publication 9 August 2010; doi: 10.1038/labinvest.2010.147
Thiago de Almeida Pereira 1,6, Rafal P Witek 1, Wing-Kin Syn 1, Steve S Choi 1, Shelton Bradrick 2, Gamze F Karaca 1, Kolade M Agboola 1, Youngmi Jung 1, Alessia Omenetti 1, Cynthia A Moylan 1, Liu Yang 4, Martin E Fernandez-Zapico 4,5, Ravi Jhaveri 2,3, Vijay H Shah 4, Fausto E Pereira 6 and Anna M Diehl 1
1 Division of Gastroenterology, Duke University, Durham, NC, USA
2 Department of Molecular Genetics and Microbiology, Duke University, Durham, NC, USA
3 Department of Pediatrics, Duke University, Durham, NC, USA
4 Division of Gastroenterology and Hepatology, Division of Oncology Research, Mayo Clinic, Rochester, MN, USA
5 Schulze Center for Novel Therapeutics, Division of Oncology Research, Mayo Clinic, Rochester, MN, USA
6 Núcleo de Doenças Infecciosas, Centro de Ciências da Saúde, Universidade Federal do Espírito Santo, Vitória, ES, Brazil
Correspondence: Dr AM Diehl, MD, Florence McAlister Professor and Chief, Division of Gastroenterology, Duke University, Snyderman Building (GSRB-1), 595 LaSalle Street, Suite 1073, Durham, NC 27710, USA. E-mail: email@example.com
Received 10 May 2010; Revised 6 July 2010; Accepted 7 July 2010; Published online 9 August 2010.
Hedgehog (Hh) pathway activation promotes many processes that occur during fibrogenic liver repair. Whether the Hh pathway modulates the outcomes of virally mediated liver injury has never been examined. Gene-profiling studies of human hepatocellular carcinomas (HCCs) demonstrate Hh pathway activation in HCCs related to chronic infection with hepatitis B virus (HBV) or hepatitis C virus (HCV). Because most HCCs develop in cirrhotic livers, we hypothesized that Hh pathway activation occurs during fibrogenic repair of liver damage due to chronic viral hepatitis, and that Hh-responsive cells mediate disease progression and hepatocarciongenesis in chronic viral hepatitis. Immunohistochemistry and qRT-PCR analysis were used to analyze Hh pathway activation and identify Hh-responsive cell types in liver biopsies from 45 patients with chronic HBV or HCV. Hh signaling was then manipulated in cultured liver cells to directly assess the impact of Hh activity in relevant cell types. We found increased hepatic expression of Hh ligands in all patients with chronic viral hepatitis, and demonstrated that infection with HCV stimulated cultured hepatocytes to produce Hh ligands. The major cell populations that expanded during cirrhosis and HCC (ie, liver myofibroblasts, activated endothelial cells, and progenitors expressing markers of tumor stem/initiating cells) were Hh responsive, and higher levels of Hh pathway activity associated with cirrhosis and HCC. Inhibiting pathway activity in Hh-responsive target cells reduced fibrogenesis, angiogenesis, and growth. In conclusion, HBV/HCV infection increases hepatocyte production of Hh ligands and expands the types of Hh-responsive cells that promote liver fibrosis and cancer.
Keywords: fibrosis; Hedgehog pathway; hepatitis B; hepatitis C; liver progenitors; morphogens