Connective tissue growth factor causes persistent proalpha2(I) collagen gene expression induced by transforming growth factor-beta in a mouse fibrosis model.
Skin fibrotic disorders such as systemic sclerosis (SSc) are characterized by an excessive production of extracellular matrix (ECM) and understood to develop under the influence of certain growth factors. Connective tissue growth factor (CTGF) is a cysteine-rich mitogenic peptide that is implicated in various fibrotic disorders and induced in fibroblasts after activation with transforming growth factor-beta (TGF-beta). To better understand the mechanisms of persistent fibrosis seen in SSc, we previously established an animal model of skin fibrosis induced by exogenous application of growth factors. In this model, TGF-beta transiently induced subcutaneous fibrosis and serial injections of CTGF after TGF-beta caused persistent fibrosis. To further define the mechanisms of skin fibrosis induced by TGF-beta and CTGF in vivo, we investigated in this study, the effects of growth factors on the promoter activity of the proalpha2 (I) collagen (COL1A2) gene in skin fibrosis. For this purpose, we utilized transgenic reporter mice harboring the -17 kb promoter sequence of the mouse COL1A2 linked to either a firefly luciferase gene or a bacterial beta-galactosidase gene. Serial injections of CTGF after TGF-beta resulted in a sustained elevation of COL1A2 mRNA expression and promoter activity compared with consecutive injection of TGF-beta alone on day 8. We also demonstrated that the number of fibroblasts with activated COL1A2 transcription was increased by serial injections of CTGF after TGF-beta in comparison with the injection of TGF-beta alone. Furthermore, the serial injections recruited mast cells and macrophages. The number of mast cells reached a maximum on day 4 and remained relatively high up to day 8. In contrast to the kinetics of mast cells, the number of macrophages was increased on day 4 and continued to rise during the subsequent consecutive CTGF injections until day 8. These results suggested that CTGF maintains TGF-beta-induced skin fibrosis by sustaining COL1A2 promoter activation and increasing the number of activated fibroblasts. The infiltrated mast cells and macrophages may also contribute to the maintenance of fibrosis.
Chujo
Sonoko
S
Department of Dermatology, Kanazawa University Graduate School of Medical Science, 13-1 Takara-Machi, Kanazawa, Ishikawa 920-8641, Japan.
Shirasaki
Fumiaki
F
Kawara
Shigeru
S
Inagaki
Yutaka
Y
Kinbara
Takuro
T
Inaoki
Makoto
M
Takigawa
Masaharu
M
Takehara
Kazuhiko
K
D000818:Animals; D002634:Chemotaxis, Leukocyte / Q000187:drug effects / Q000502:physiology; D024042:Collagen Type I / Q000096:biosynthesis* / Q000235:genetics; D055513:Connective Tissue Growth Factor; D004195:Disease Models, Animal; D005109:Extracellular Matrix / Q000378:metabolism*; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D005355:Fibrosis / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology*; D017874:Immediate-Early Proteins / Q000494:pharmacology*; D036341:Intercellular Signaling Peptides and Proteins / Q000494:pharmacology*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism; D008407:Mast Cells / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008822:Mice, Transgenic; D011347:Procollagen / Q000096:biosynthesis* / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D012595:Scleroderma, Systemic / Q000235:genetics / Q000378:metabolism* / Q000503:physiopathology; D012871:Skin Diseases / Q000235:genetics / Q000378:metabolism / Q000503:physiopathology; D015533:Transcriptional Activation / Q000187:drug effects / Q000502:physiology; D016212:Transforming Growth Factor beta / Q000378:metabolism / Q000494:pharmacology*; D053782:Transforming Growth Factor beta3; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
C526318:CCN2 protein, mouse; D024042:Collagen Type I; D017874:Immediate-Early Proteins; D036341:Intercellular Signaling Peptides and Proteins; D011347:Procollagen; D012333:RNA, Messenger; C509045:Tgfb3 protein, mouse; D016212:Transforming Growth Factor beta; D053782:Transforming Growth Factor beta3; D055513:Connective Tissue Growth Factor