title: Sequential analysis of myofibroblast differentiation and transforming growth factor-β1/Smad pathway activation in murine pulmonary fibrosis.
abstract: Myofibroblasts play a critical role in tissue fibrosis. However, the intracellular signaling pathways in myofibroblast differentiation are poorly understood. Here, we studied the relationship between transforming growth factor-β (TGF-β)/Smad pathway activation and myofibroblast differentiation in both in vivo and in vitro experiments. In murine bleomycin-induced pulmonary fibrosis, nuclear localization of phosphorylated Smad2/3 (p-Smad2/3) was observed in pulmonary fibrotic lesions 7 days after bleomycin injection, whereas α-smooth muscle actin (ASMA)-positive myofibroblasts appeared in the lesions at 14 days, when the cytoplasmic localization of p-Smad2/3 was observed. We also compared the effects of TGF-β1 on myofibroblast differentiation and on type I collagen expression in a murine lung fibroblast cell line (MLg2908). TGF-β1 induced rapid expression of p-Smad2/3 in nuclei, after which ASMA organization in the cytoplasm of fibroblasts was observed. However, TGF-β1 produced no effect on the quantity of ASMA, either in mRNA levels or protein levels, even after the phosphorylation of Smad2/3. In contrast, TGF-β1 upregulated the expression of type I collagen mRNA. These findings suggest that in pulmonary fibrosis the molecular mechanism of myofibroblast differentiation is complex and that the difference between ASMA expression and type I collagen expression is mediated by the TGF-β/Smad pathway.
authors.affiliation: Division of Pulmonary Medicine, Infection Diseases and Oncology, Graduate School of Medicine, Nippon Medical School, Tokyo, Japan. usukij@nms.ac.jp
authors.forename: Jiro
authors.initials: J
authors.lastname: Usuki
authors.forename: Kuniko
authors.initials: K
authors.lastname: Matsuda
authors.forename: Arata
authors.initials: A
authors.lastname: Azuma
authors.forename: Shoji
authors.initials: S
authors.lastname: Kudoh
authors.forename: Akihiko
authors.initials: A
authors.lastname: Gemma
mesh_terms: D016475:3T3 Cells; D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D001761:Bleomycin; D002454:Cell Differentiation / Q000187:drug effects; D024042:Collagen Type I / Q000235:genetics / Q000378:metabolism; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D007150:Immunohistochemistry; D008168:Lung / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D058628:Myofibroblasts / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology*; D011658:Pulmonary Fibrosis / Q000235:genetics / Q000473:pathology*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D051785:Smad Proteins / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors; D053773:Transforming Growth Factor beta1 / Q000378:metabolism* / Q000494:pharmacology
chemical_list: D000199:Actins; D024042:Collagen Type I; D012333:RNA, Messenger; D051785:Smad Proteins; D053773:Transforming Growth Factor beta1; D001761:Bleomycin