title: Extrahepatic platelet-derived growth factor-β, delivered by platelets, promotes activation of hepatic stellate cells and biliary fibrosis in mice.
abstract: OBJECTIVE
  Platelet-derived growth factor-β (PDGFB) is a mitogen for hepatic stellate cells (HSCs). We studied the cellular sources of PDGFB and the effects of a high-affinity monoclonal antibody against PDGFB (MOR8457) in mouse models of biliary fibrosis.
  
  
  METHODS
  Cellular sources of PDGFB were identified using quantitative reverse-transcription polymerase chain reaction, biochemical, and immunohistologic methods. Mice with advanced biliary fibrosis, MDR2(Abcb4)-null mice, and C57Bl/6 (control) mice were placed on 3,5-diethoxycarbonyl-1,4-dihydrocollidine (DDC)-supplemented diets and were given weekly intraperitoneal injections of MOR8457. Platelets were depleted from MDR2-null mice by injection of an antibody against CD41, or inhibited with diets containing low-dose aspirin. Liver tissues were collected and analyzed by quantitative reverse-transcription PCR and histologic and biochemical analyses.
  
  
  RESULTS
  Levels of PDGFB protein, but not messenger RNA, were increased in fibrotic livers of MDR2-null mice, compared with control mice. Platelet clusters were detected in the hepatic endothelium, in close proximity to HSCs, and were identified as a source of PDGFB protein in MDR2-null mice. Levels of the PDGFB were increased in serum samples from patients with early stages of liver fibrosis of various etiologies (F1-2, n = 16; P < .05), compared with nonfibrotic liver tissue (F0, n = 12). Depletion of platelets from MDR2-null mice normalized hepatic levels of PDGFB within 48 hours, reducing levels of a marker of HSC activation (α-smooth muscle actin) and expression of genes that promote fibrosis. Diets supplemented with low-dose aspirin reduced circulating serum and hepatic levels of PDGFB and significantly reduced progression of fibrosis in MDR2-null mice over 1 year. MOR8457 produced a dose-dependent decrease in liver fibrosis in MDR2-null mice, reducing collagen deposition by 45% and expression of fibrosis-associated genes by 50%, compared with mice given a control antibody. In vitro, platelets activated freshly isolated HSCs (induction of α-smooth muscle actin and fibrosis-associated genes) via a PDGFB-dependent mechanism. MOR8457 also reduced liver fibrosis in mice placed on DDC-supplemented diets.
  
  
  CONCLUSIONS
  Platelets produce PDGFB to activate HSC and promote fibrosis in MDR2-null mice and mice on DDC-supplemented diets. Antiplatelet therapy or selective inhibition of PDGFB might reduce biliary fibrosis in patients with liver disease.
authors.affiliation: Division of Gastroenterology and Hepatology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
authors.forename: Shuhei
authors.initials: S
authors.lastname: Yoshida
authors.affiliation: Division of Gastroenterology and Hepatology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
authors.forename: Naoki
authors.initials: N
authors.lastname: Ikenaga
authors.affiliation: Division of Gastroenterology and Hepatology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
authors.forename: Susan B
authors.initials: SB
authors.lastname: Liu
authors.affiliation: Division of Gastroenterology and Hepatology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
authors.forename: Zhen-Wei
authors.initials: ZW
authors.lastname: Peng
authors.affiliation: Division of Gastroenterology and Hepatology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
authors.forename: Jeanhee
authors.initials: J
authors.lastname: Chung
authors.affiliation: Division of Gastroenterology and Hepatology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
authors.forename: Deanna Y
authors.initials: DY
authors.lastname: Sverdlov
authors.affiliation: Division of Gastroenterology and Hepatology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts.
authors.forename: Makoto
authors.initials: M
authors.lastname: Miyamoto
authors.affiliation: Institute of Translational Immunology, University Medical Center, Mainz, Germany.
authors.forename: Yong Ook
authors.initials: YO
authors.lastname: Kim
authors.affiliation: Pfizer, Inc, Cambridge, Massachusetts.
authors.forename: Shinji
authors.initials: S
authors.lastname: Ogawa
authors.affiliation: Pfizer, Inc, Cambridge, Massachusetts.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Arch
authors.affiliation: Division of Gastroenterology and Hepatology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts; Institute of Translational Immunology, University Medical Center, Mainz, Germany.
authors.forename: Detlef
authors.initials: D
authors.lastname: Schuppan
authors.affiliation: Division of Gastroenterology and Hepatology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts. Electronic address: ypopov@bidmc.harvard.edu.
authors.forename: Yury
authors.initials: Y
authors.lastname: Popov
mesh_terms: D018435:ATP Binding Cassette Transporter, Subfamily B / Q000235:genetics; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000818:Animals; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D057134:Antibodies, Neutralizing / Q000494:pharmacology; D001241:Aspirin / Q000494:pharmacology; D017734:Bile Ducts, Extrahepatic / Q000378:metabolism*; D001792:Blood Platelets / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D004195:Disease Models, Animal; D005260:Female; D055166:Hepatic Stellate Cells / Q000378:metabolism*; D006801:Humans; D008103:Liver Cirrhosis / Q000188:drug therapy / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008875:Middle Aged; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology; D020574:Proto-Oncogene Proteins c-sis / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D012333:RNA, Messenger / Q000378:metabolism; D000097202:ATP-Binding Cassette Sub-Family B Member 4
chemical_list: D018435:ATP Binding Cassette Transporter, Subfamily B; D000911:Antibodies, Monoclonal; D057134:Antibodies, Neutralizing; D001241:Aspirin; D010975:Platelet Aggregation Inhibitors; D020574:Proto-Oncogene Proteins c-sis; D012333:RNA, Messenger; D000097202:ATP-Binding Cassette Sub-Family B Member 4
keywords: Chronic Liver Injury; Mouse Model; PBC; PSC