title: Animal model of sclerotic skin. V: Increased expression of alpha-smooth muscle actin in fibroblastic cells in bleomycin-induced scleroderma.
abstract: Scleroderma is a connective tissue disorder with unknown etiology. Myofibroblasts appear during fibrotic processes such as scleroderma, hypertrophic scarring, and wound healing. We previously established a mouse model for scleroderma by local injections of bleomycin. To determine the phenotype of the fibroblasts in sclerotic skin after bleomycin treatment, we examined the expression of alpha-smooth muscle actin (alpha-SMA), a marker for myofibroblasts, in lesional skin as well as in fibrous lung in this model. Dermal sclerosis was induced by daily local injections of bleomycin (100 microg/ml) for 3 weeks in C3H mice. Immunohistochemical examination showed that alpha-SMA-reactive cells were detectable on fibroblastic cells in bleomycin-injected skin at 1 week. There was a significant increase in the immunoreactive fibroblastic cells for alpha-SMA in lesional skin in parallel with the induction of dermal sclerosis. After 3 weeks' treatment with bleomycin, the number of alpha-SMA-reactive fibroblasts showed an 11-fold increase compared with that in control PBS-treated mice. alpha-SMA-positive cells were also detected in lung parenchyma after bleomycin treatment. Following concomitant treatment with anti-transforming growth factor-beta (TGF-beta) antibody with bleomycin, the number of alpha-SMA-positive fibroblastic cells was significantly reduced up to 50%, along with the reduction of dermal sclerosis. To confirm the protein level of alpha-SMA, immunoblotting was carried out. Results showed an increase of alpha-SMA expression in lesional skin at 3 weeks of bleomycin treatment, which was reduced following anti-TGF-beta antibody treatment. These data suggest that fibroblastic cells are phenotypically altered into myofibroblasts during the fibrotic process in the experimental model of bleomycin-induced scleroderma, which was considered mediated, for the most part, by TGF-beta. Blockade of TGF-beta may be a therapeutic intervention for scleroderma.
authors.affiliation: Department of Dermatology, School of Medicine, Tokyo Medical and Dental University, 1-5-45 Yushima, Bunkyo-ku, Tokyo 113-8519, Japan. yamamoto.derm@med.tmd.ac.jp
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Yamamoto
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Nishioka
mesh_terms: D000199:Actins / Q000096:biosynthesis*; D000818:Animals; D001761:Bleomycin / Q000494:pharmacology; D004195:Disease Models, Animal; D005260:Female; D005347:Fibroblasts / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D009130:Muscle, Smooth / Q000737:chemistry / Q000166:cytology / Q000378:metabolism*; D012594:Scleroderma, Localized / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D012595:Scleroderma, Systemic / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology; D012598:Sclerosis / Q000139:chemically induced / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000037:antagonists & inhibitors
chemical_list: D000199:Actins; D016212:Transforming Growth Factor beta; D001761:Bleomycin