title: Constitutive thrombospondin-1 overexpression contributes to autocrine transforming growth factor-beta signaling in cultured scleroderma fibroblasts.
abstract: The extracellular matrix (ECM) glycoprotein thrombospondin-1 (TSP-1) has been reported to activate the latent complex of transforming growth factor-beta (TGF-beta), the major effects of which in mesenchymal cells is stimulation of the synthesis of ECM. Previous reports suggested the involvement of an autocrine TGF-beta loop in the pathogenesis of scleroderma. In this study, we examined whether TSP-1 plays a role in maintaining the autocrine TGF-beta loop in scleroderma. TSP-1 expression was increased in scleroderma patients compared with in healthy controls in vivo and in vitro. TGF-beta blocking antibody or TGF-beta1 antisense oligonucleotide markedly reduced the up-regulated TSP-1 expression in scleroderma fibroblasts but had little effect on normal fibroblasts. The expression of TSP-1 is up-regulated in scleroderma fibroblasts, possibly at the post-transcriptional level just like in normal fibroblasts stimulated with exogenous TGF-beta1. TSP-1 blocking peptide or antisense oligonucleotide had an inhibitory effect on the up-regulated alpha2I collagen and phosopho-Smad3 levels in scleroderma fibroblasts but had little effects on normal fibroblasts. The transient overexpression of TSP-1 up-regulated alpha2I collagen and phospho-Smad3 levels in normal fibroblasts but had no major effect on scleroderma fibroblasts. Furthermore, these effects of transiently overexpressed TSP-1, which possibly occurred via the activation of latent TGF-beta1, were abolished by the TGF-beta1 antisense oligonucleotide. These results indicate that the constitutive overexpression of TSP-1 may play an important role in autocrine TGF-beta signaling and accumulation of ECM in scleroderma fibroblasts.
authors.affiliation: Department of Dermatology, Faculty of Medicine, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8655, Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Mimura
authors.forename: Hironobu
authors.initials: H
authors.lastname: Ihn
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Jinnin
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Asano
authors.forename: Kenichi
authors.initials: K
authors.lastname: Yamane
authors.forename: Kunihiko
authors.initials: K
authors.lastname: Tamaki
mesh_terms: D019898:Autocrine Communication; D016022:Case-Control Studies; D002478:Cells, Cultured; D003094:Collagen / Q000235:genetics / Q000378:metabolism; D024042:Collagen Type I / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D010766:Phosphorylation; D011401:Promoter Regions, Genetic / Q000187:drug effects; D012333:RNA, Messenger / Q000378:metabolism; D012595:Scleroderma, Systemic / Q000378:metabolism / Q000503:physiopathology*; D015398:Signal Transduction; D012867:Skin / Q000378:metabolism; D051900:Smad3 Protein; D019700:Thrombospondin 1 / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism* / Q000494:pharmacology; D053773:Transforming Growth Factor beta1; D015854:Up-Regulation
chemical_list: D024042:Collagen Type I; D004268:DNA-Binding Proteins; D012333:RNA, Messenger; C497790:SMAD3 protein, human; D051900:Smad3 Protein; C508960:TGFB1 protein, human; D019700:Thrombospondin 1; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1; D003094:Collagen