TY - JOUR T1 - Thrombospondin 1 acts as a strong promoter of transforming growth factor β effects via two distinct mechanisms in hepatic stellate cells JF - Gut JO - Gut SP - 673 LP - 681 DO - 10.1136/gut.2004.042911 VL - 54 IS - 5 AU - K Breitkopf AU - I Sawitza AU - J H Westhoff AU - L Wickert AU - S Dooley AU - A M Gressner Y1 - 2005/05/01 UR - http://gut.bmj.com/content/54/5/673.abstract N2 - Background and aims: Thrombospondin 1 (TSP-1) is an important activator of latent transforming growth factor β (TGF-β) but little is known of the expression patterns and functions of TSP-1 in liver cells. We therefore analysed if and how TSP-1 acts on TGF-β during fibrogenesis. Methods and results: Using reverse transcription-polymerase chain reaction, we demonstrated that hepatocytes from normal liver expressed no TSP-1 mRNA whereas Kupffer cells and sinusoidal endothelial cells did. TSP-1 mRNA and protein were detected in quiescent and activated cultured hepatic stellate cells (HSC) and TSP-1 expression was highly inducible by platelet derived growth factor BB (PDGF-BB) and, to a lesser extent, by tumour necrosis factor α in activated HSC. Furthermore, addition of PDGF-BB directly led to enhanced TGF-β mRNA expression and a TSP-1 dependent increase in TGF-β/Smad signalling. Using either a peptide specifically blocking the interaction of TSP-1 with latent TGF-β or antibodies against TSP-1 not only abrogated activation of latent TGF-β but also reduced the effects of the active dimer itself. Conclusions: Our data suggest that TSP-1 expression is important for TGF-β effects and that it is regulated by the profibrogenic mediator PDGF-BB in HSC. Furthermore, the presence of TSP-1 seems to be a prerequisite for effective signal transduction by active TGF-β not only in rat HSC but also in other cell types such as human dermal fibroblasts. ER -