title: Modulation of transforming growth factor beta response and signaling during transdifferentiation of rat hepatic stellate cells to myofibroblasts.
abstract: Activation of hepatic stellate cells (HSCs) is the key step in liver fibrogenesis. Increased transforming growth factor beta (TGF-beta) expression and extracellular matrix production in patients with hepatic fibrosis and experimental models of liver fibrogenesis support implication of TGF-beta in the pathogenesis of this disease. However, a causative role for TGF-beta during transdifferentiation of HSCs has not been delineated in molecular detail. Using a rat cell culture model of HSC transdifferentiation, we analyzed TGF-beta signal transduction and identified changes between stellate cells and their transdifferentiated phenotype. Fully transdifferentiated myofibroblasts, opposed to HSCs, were not inhibited in proliferation activity on treatment with TGF-beta1. Furthermore, stimulation of alpha2 (I) collagen and Smad7 messenger RNA (mRNA) expression by TGF-beta1 was achieved in stellate cells but not in myofibroblasts. Northern and Western blot analyses indicated significant expression of TGF-beta receptors I and II in both cell types. In contrast, [(125)I]-TGF-beta1 receptor affinity labeling displayed strongly reduced types I, II, and III receptor presentation at the cell surface of myofibroblasts. Moreover, myofibroblasts did not display DNA-binding SMAD proteins in electrophoretic mobility shift assays with a CAGA box. These data indicate that stellate cells are responsive to TGF-beta1 treatment and transduce a signal that may play an important role in liver fibrogenesis. Myofibroblasts display decreased availability of surface receptors for TGF-beta, which could be based on autocrine stimulation. However, lack of activated SMAD complexes with DNA-binding activity and absence of alpha2 (I) collagen transcription inhibition by latency-associated peptide (LAP)/anti-TGF-beta antibody raise the possibility of TGF-beta signaling independent receptor down-regulation in myofibroblasts.
authors.affiliation: Institute of Clinical Chemistry and Pathobiochemistry, RWTH-University Hospital, Aachen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Dooley
authors.forename: B
authors.initials: B
authors.lastname: Delvoux
authors.forename: B
authors.initials: B
authors.lastname: Lahme
authors.forename: K
authors.initials: K
authors.lastname: Mangasser-Stephan
authors.forename: A M
authors.initials: AM
authors.lastname: Gressner
mesh_terms: D030201:Activin Receptors, Type I; D000818:Animals; D002454:Cell Differentiation / Q000187:drug effects; D003094:Collagen / Q000235:genetics; D004247:DNA / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D005347:Fibroblasts / Q000166:cytology; D008099:Liver / Q000166:cytology*; D008297:Male; D017346:Protein Serine-Threonine Kinases / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000235:genetics; D015398:Signal Transduction; D051906:Smad7 Protein; D015534:Trans-Activators / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
chemical_list: D004268:DNA-Binding Proteins; D018125:Receptors, Transforming Growth Factor beta; D051906:Smad7 Protein; C497808:Smad7 protein, rat; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D003094:Collagen; D004247:DNA; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; C000625843:Tgfbr1 protein, rat