title: Tissue-type plasminogen activator is not necessary for platelet-derived growth factor-c activation.
abstract: Platelet-derived growth factors (PDGFs) are critical for development; their over-expression is associated with fibrogenesis. Full-length PDGF-C is secreted as an inactive dimer, requiring cleavage to allow receptor binding. Previous studies indicate that tissue-type plasminogen activator (tPA) is the specific protease that performs this cleavage; in vivo confirmation is lacking. We demonstrate that primary hepatocytes from tpa KO mice produce less cleaved active PDGF-CC than do wild type hepatocytes, suggesting that tPA is critical for in vitro activation of this growth factor. We developed mice that over-express full-length human PDGF-C in the liver; these mice develop progressive liver fibrosis. To test whether tPA is important for cleavage and activation of PDGF-C in vivo, we intercrossed PDGF-C transgenic (Tg) and tpa knock-out (KO) mice, anticipating that lack of tPA would result in decreased fibrosis due to lack of hPDGF-C cleavage. To measure levels of cleaved, dimerized PDGF-CC in sera, we developed an ELISA that specifically detects cleaved PDGF-CC. We report that the absence of tpa does not affect the phenotype of `PDGF-C Tg mice. PDGF-C Tg mice lacking tPA have high serum levels of cleaved growth factor, significant liver fibrosis, and gene expression alterations similar to those of PDGF-C Tg mice with intact tPA. Furthermore, urokinase plasminogen activator and plasminogen activator inhibitor-1 expression are increased in PDGF-C Tg; tpa KO mice. Our ELISA data suggest a difference between in vitro and in vivo activation of this growth factor, and our mouse model confirms that multiple proteases cleave and activate PDGF-C in vivo.
authors.affiliation: Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195, USA; Department of Surgery, University of Washington School of Medicine, Seattle, WA 98195, USA.
authors.forename: Kimberly J
authors.initials: KJ
authors.lastname: Riehle
authors.affiliation: Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195, USA.
authors.forename: Melissa M
authors.initials: MM
authors.lastname: Johnson
authors.affiliation: Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195, USA.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Johansson
authors.affiliation: Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195, USA.
authors.forename: Renay L
authors.initials: RL
authors.lastname: Bauer
authors.affiliation: Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195, USA.
authors.forename: Brian J
authors.initials: BJ
authors.lastname: Hayes
authors.affiliation: Bristol Meyers Squibb, 1201 Eastlake Avenue East, Seattle, WA 98102, USA.
authors.forename: Debra G
authors.initials: DG
authors.lastname: Gilbertson
authors.affiliation: Bristol Meyers Squibb, 1201 Eastlake Avenue East, Seattle, WA 98102, USA.
authors.forename: Aaron C
authors.initials: AC
authors.lastname: Haran
authors.affiliation: Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195, USA.
authors.forename: Nelson
authors.initials: N
authors.lastname: Fausto
authors.affiliation: Department of Pathology, University of Washington School of Medicine, Seattle, WA 98195, USA. Electronic address: campjs@u.washington.edu.
authors.forename: Jean S
authors.initials: JS
authors.lastname: Campbell
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004797:Enzyme-Linked Immunosorbent Assay; D020869:Gene Expression Profiling; D022781:Hepatocytes / Q000166:cytology / Q000378:metabolism*; D006801:Humans; D008099:Liver / Q000378:metabolism / Q000473:pathology; D008103:Liver Cirrhosis / Q000235:genetics* / Q000378:metabolism; D008222:Lymphokines / Q000097:blood / Q000235:genetics* / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000235:genetics* / Q000378:metabolism; D059748:Proteolysis; D020133:Reverse Transcriptase Polymerase Chain Reaction; D010959:Tissue Plasminogen Activator / Q000235:genetics* / Q000378:metabolism; D014568:Urokinase-Type Plasminogen Activator / Q000235:genetics / Q000378:metabolism
chemical_list: D008222:Lymphokines; D017395:Plasminogen Activator Inhibitor 1; D010982:Platelet-Derived Growth Factor; C411423:platelet-derived growth factor C; D010959:Tissue Plasminogen Activator; D014568:Urokinase-Type Plasminogen Activator
keywords: BrdU; CUB; ECM; H&E; HCC; IP; KO; Liver fibrosis; NPC; PAI-1; PDGF; Plasminogen activator; Platelet-derived growth factor; Tg; bromodeoxyuridine; complement subcomponents Clr/Cls, Uegf, Bmp1; extracellular matrix; hematoxylin & eosin; hepatocellular carcinoma; intraperitoneally; knock-out; non-parenchymal cell; plasminogen activator inhibitor-1; platelet-derived growth factor; tPA; tissue-type plasminogen activator; transgenic; uPA; urokinase plasminogen activator