title: Human platelets inhibit liver fibrosis in severe combined immunodeficiency mice.
abstract: OBJECTIVE
  To investigate the role of human platelets in liver fibrosis.
  
  
  METHODS
  Severe combined immunodeficiency (SCID) mice were administered CCl4 and either phosphate-buffered saline (PBS group) or human platelet transfusions (hPLT group). Concentrations of hepatocyte growth factor (HGF), matrix metallopeptidases (MMP)-9, and transforming growth factor-β (TGF-β) in the liver tissue were compared between the PBS and the hPLT groups by enzyme-linked immunosorbent assay (ELISA) and Western blotting. The effects of a human platelet transfusion on liver fibrosis included the fibrotic area, hydroxyproline content, and α-smooth muscle actin (α-SMA) expression, which were evaluated by picrosirius red staining, ELISA, and immunohistochemical staining using an anti-mouse α-SMA antibody, respectively. Phosphorylations of mesenchymal-epithelial transition factor (Met) and SMAD3, downstream signals of HGF and TGF-β, were compared between the two groups by Western blotting and were quantified using densitometry. Hepatocyte apoptosis was evaluated by terminal deoxynucleotidyl transferase dUTP nick end labeling. Furthermore, the accumulation of human platelets in the liver 2 h after platelet transfusion was compared between normal and fibrotic livers by immunohistochemical staining using an anti-human CD41 antibody.
  
  
  RESULTS
  The fibrotic area and hydroxyproline content in the liver were both significantly lower in the hPLT group when compared to the PBS group (fibrotic area, 1.7% ± 0.6% vs 2.5% ± 0.6%, P = 0.03; hydroxyproline content, 121 ± 26 ng/g liver vs 156 ± 47 ng/g liver, P = 0.04). There was less α-smooth muscle actin staining in the hPLT group than in the PBS group (0.5% ± 0.1% vs 0.8% ± 0.3%, P = 0.02). Hepatic expression levels of mouse HGF and MMP-9 were significantly higher in the hPLT group than in the PBS group (HGF, 109 ± 13 ng/g liver vs 88 ± 22 ng/g liver, P = 0.03; MMP-9, 113% ± 7%/GAPDH vs 92% ± 11%/GAPDH, P = 0.04). In contrast, the concentration of mouse TGF-β in the liver tissue was significantly lower in the hPLT group than in the PBS group (22 ± 5 ng/g liver vs 39 ± 6 ng/g liver, P = 0.02). Phosphorylation of Met was more prevalent in the hPLT group than in the PBS group (37% ± 4%/GAPDH vs 20% ± 8%/GAPDH, P = 0.03). Phosphorylation of SMAD3 was weaker in the hPLT group than in the PBS group (60% ± 12%/GAPDH vs 84% ± 12%/GAPDH, P = 0.1), although this difference was not significant. Furthermore, a lower rate of hepatocyte apoptosis was observed in the hPLT group than in the PBS group (5.9% ± 1.7% vs 2.9% ± 2.1%, P = 0.02). Significant human platelet accumulation was observed in the fibrotic liver tissues, whereas few platelets accumulated in the normal liver.
  
  
  CONCLUSIONS
  Human platelets inhibit liver fibrosis in SCID mice. Increased concentration of HGF in the liver suppresses hepatic stellate cell activation, induces MMPs, and inhibits hepatocyte apoptosis.
authors: Department of Surgery, University of Tsukuba, Tsukuba 3058575, Japan.
authors: Kazuhiro
authors: K
authors: Takahashi
authors: Soichiro
authors: S
authors: Murata
authors: Kiyoshi
authors: K
authors: Fukunaga
authors: Nobuhiro
authors: N
authors: Ohkohchi
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002251:Carbon Tetrachloride; D053148:Caspase 3 / Q000378:metabolism; D017228:Hepatocyte Growth Factor / Q000378:metabolism; D022781:Hepatocytes / Q000378:metabolism / Q000473:pathology*; D006801:Humans; D006909:Hydroxyproline / Q000378:metabolism; D008099:Liver / Q000378:metabolism / Q000473:pathology*; D008106:Liver Cirrhosis, Experimental / Q000139:chemically induced / Q000378:metabolism / Q000473:pathology / Q000517:prevention & control*; D008297:Male; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D051379:Mice; D016513:Mice, SCID; D010766:Phosphorylation; D017713:Platelet Transfusion; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D019859:Proto-Oncogene Proteins c-met / Q000378:metabolism; D015398:Signal Transduction; D051900:Smad3 Protein / Q000378:metabolism; D013997:Time Factors; D016212:Transforming Growth Factor beta / Q000378:metabolism
chemical_list: D000199:Actins; D015415:Biomarkers; C553307:HGF protein, mouse; D019253:Proto-Oncogene Proteins c-bcl-2; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; D016212:Transforming Growth Factor beta; C544013:alpha-smooth muscle actin, mouse; C052617:Bcl2 protein, mouse; D017228:Hepatocyte Growth Factor; D002251:Carbon Tetrachloride; D019859:Proto-Oncogene Proteins c-met; C505409:Casp3 protein, mouse; D053148:Caspase 3; D020780:Matrix Metalloproteinase 9; C501830:Mmp9 protein, mouse; D006909:Hydroxyproline
keywords: Hepatocyte apoptosis; Hepatocyte growth factor; Human platelet; Liver fibrosis; Matrix metallopeptidases; Transforming growth factor-β
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