Targeted disruption of TGF-beta/Smad3 signaling modulates skin fibrosis in a mouse model of scleroderma.
Transforming growth factor-beta (TGF-beta) is a potent stimulus of connective tissue accumulation, and is implicated in the pathogenesis of scleroderma and other fibrotic disorders. Smad3 functions as a key intracellular signal transducer for profibrotic TGF-beta responses in normal skin fibroblasts. The potential role of Smad3 in the pathogenesis of scleroderma was investigated in Smad3-null (Smad3(-/-)) mice using a model of skin fibrosis induced by subcutaneous injections of bleomycin. At early time points, bleomycin-induced macrophage infiltration in the dermis and local TGF-beta production were similar in Smad3(-/-) and wild-type mice. In contrast, at day 28, lesional skin from Smad3(-/-) mice showed attenuated fibrosis, lower synthesis and accumulation of collagen, and reduced collagen gene transcription in situ, compared to wild-type mice. Connective tissue growth factor and alpha-smooth muscle actin expression in lesional skin were also significantly attenuated. Electron microscopy revealed an absence of small diameter collagen fibrils in the dermis from bleomycin-treated Smad3(-/-) mice. Compared to fibroblasts derived from wild-type mice, Smad3(-/-) fibroblasts showed reduced in vitro proliferative and profibrotic responses elicited by TGF-beta. Together, these results indicate that ablation of Smad3 is associated with markedly altered fibroblast regulation in vivo and in vitro, and confers partial protection from bleomycin-induced scleroderma in mice. Reduced fibrosis is due to deregulated fibroblast function, as the inflammatory response induced by bleomycin was similar in wild-type and Smad3(-/-) mice.
Lakos
Gabriella
G
Section of Rheumatology, College of Medicine, University of Illinois at Chicago, 900 S. Ashland Avenue, Chicago, IL 60607, USA.
Takagawa
Shinsuke
S
Chen
Shu-Jen
SJ
Ferreira
Ahalia M
AM
Han
Gangwen
G
Masuda
Koichi
K
Wang
Xiao-Jing
XJ
DiPietro
Luisa A
LA
Varga
John
J
D000199:Actins / Q000096:biosynthesis; D000818:Animals; D001761:Bleomycin / Q000494:pharmacology; D015153:Blotting, Western; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis / Q000187:drug effects; D055513:Connective Tissue Growth Factor; D004195:Disease Models, Animal; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism / Q000473:pathology / Q000648:ultrastructure; D005353:Fibronectins / Q000096:biosynthesis; D005355:Fibrosis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D005434:Flow Cytometry; D005786:Gene Expression Regulation / Q000187:drug effects; D018390:Gene Targeting; D006909:Hydroxyproline / Q000032:analysis; D017874:Immediate-Early Proteins / Q000187:drug effects / Q000378:metabolism; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D036341:Intercellular Signaling Peptides and Proteins / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D012595:Scleroderma, Systemic / Q000378:metabolism* / Q000473:pathology; D015398:Signal Transduction / Q000187:drug effects*; D012867:Skin / Q000737:chemistry / Q000473:pathology / Q000648:ultrastructure; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism* / Q000494:pharmacology
D000199:Actins; C526318:CCN2 protein, mouse; D005353:Fibronectins; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D015534:Trans-Activators; D016212:Transforming Growth Factor beta; D001761:Bleomycin; D055513:Connective Tissue Growth Factor; D003094:Collagen; D006909:Hydroxyproline