Fibrosis, vascular activation, and immune abnormalities resembling systemic sclerosis in bleomycin-treated Fli-1-haploinsufficient mice.
OBJECTIVE
Fli-1, a potential predisposing factor for systemic sclerosis (SSc), is constitutively down-regulated in the lesional skin of patients with SSc by an epigenetic mechanism. To investigate the impact of Fli-1 deficiency on the induction of an SSc phenotype in various cell types, we generated bleomycin-induced skin fibrosis in Fli-1(+/-) mice and investigated the molecular mechanisms underlying its phenotypic alterations.


METHODS
Messenger RNA (mRNA) levels and protein expression of target molecules were examined by quantitative reverse transcription-polymerase chain reaction and immunostaining. Transforming growth factor β (TGFβ) bioassay was used to evaluate the activation of latent TGFβ. The binding of Fli-1 to the target gene promoters was assessed with chromatin immunoprecipitation.


RESULTS
Bleomycin induced more severe dermal fibrosis in Fli-1(+/-) mice than in wild-type mice. Fli-1 haploinsufficiency activated dermal fibroblasts via the up-regulation of αvβ3 and αvβ5 integrins and activation of latent TGFβ. Dermal fibrosis in Fli-1(+/-) mice was also attributable to endothelial-to-mesenchymal transition, which is directly induced by Fli-1 deficiency and amplified by bleomycin. Th2/Th17-skewed inflammation and increased infiltration of mast cells and macrophages were seen, partly due to the altered expression of cell adhesion molecules in endothelial cells as well as the induction of the skin chemokines. Fli-1(+/-) mouse macrophages preferentially differentiated into an M2 phenotype upon stimulation with interleukin-4 (IL-4) or IL-13.


CONCLUSIONS
Our findings provide strong evidence for the fundamental role of Fli-1 deficiency in inducing SSc-like phenotypic alterations in dermal fibroblasts, endothelial cells, and macrophages in a manner consistent with human disease.
University of Tokyo Graduate School of Medicine, Tokyo, Japan.
Takashi
T
Taniguchi
Yoshihide
Y
Asano
Kaname
K
Akamata
Shinji
S
Noda
Takehiro
T
Takahashi
Yohei
Y
Ichimura
Tetsuo
T
Toyama
Maria
M
Trojanowska
Shinichi
S
Sato
D000818:Animals; D001761:Bleomycin / Q000009:adverse effects*; D002465:Cell Movement / Q000502:physiology; D016207:Cytokines / Q000378:metabolism; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000473:pathology / Q000503:physiopathology*; D058750:Epithelial-Mesenchymal Transition / Q000502:physiology; D005260:Female; D005355:Fibrosis; D057895:Haploinsufficiency / Q000235:genetics*; D007107:Immune System / Q000473:pathology / Q000503:physiopathology*; D016023:Integrins / Q000378:metabolism; D008264:Macrophages / Q000473:pathology; D008407:Mast Cells / Q000473:pathology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D051789:Proto-Oncogene Protein c-fli-1 / Q000172:deficiency / Q000235:genetics* / Q000502:physiology; D012595:Scleroderma, Systemic / Q000139:chemically induced* / Q000473:pathology / Q000503:physiopathology*; D012867:Skin / Q000378:metabolism / Q000473:pathology*; D016212:Transforming Growth Factor beta / Q000378:metabolism
D016207:Cytokines; C497426:Fli1 protein, mouse; D016023:Integrins; D051789:Proto-Oncogene Protein c-fli-1; D016212:Transforming Growth Factor beta; D001761:Bleomycin