Systemic vasculopathy with altered vasoreactivity in a transgenic mouse model of scleroderma.
BACKGROUND
Vasculopathy, including altered vasoreactivity and abnormal large vessel biomechanics, is a hallmark of systemic sclerosis (SSc). However, the pathogenic link with other aspects of the disease is less clear. To assess the potential role of transforming growth factor beta (TGF-beta) overactivity in driving these cardiovascular abnormalities, we studied a novel transgenic mouse model characterized by ligand-dependent activation of TGF-beta signaling in fibroblasts.


METHODS
The transgenic mouse strain Tbeta RIIDeltak-fib is characterized by balanced ligand-dependent upregulation of TGF-beta signaling. Aortic and cardiac tissues were examined with histologic, biochemical, and isolated organ bath studies. Vascular and perivascular architecture was examined by hematoxylin and eosin (H&E) and special stains including immunostaining for TGF-beta1 and phospho-Smad2/3 (pSmad2/3). Confirmatory aortic smooth muscle cell proliferation, phenotype, and functional assays, including signaling responses to exogenous TGF-beta and endothelin-1, were performed. Aortic ring contractile responses to direct and receptor-mediated stimulation were assessed.


RESULTS
Aortic ring contractility and relaxation were diminished compared with wild-type controls, and this was associated with aortic adventitial fibrosis confirmed histologically and with Sircol assay. TGF-beta1 and pSmad 2/3 expression was increased in the adventitia and smooth muscle layer of the aorta. Aortic smooth muscle cells from transgenic animals showed significant upregulation of TGF-beta- responsive genes important for cytoskeletal function, such as transgelin and smoothelin, which were then resistant to further stimulation with exogenous TGF-beta1. These cells promoted significantly more contraction of free floating type I collagen lattices when compared with the wild-type, but were again resistant to exogenous TGF-beta1 stimulation. Aortic ring responses to receptor-mediated contraction were reduced in the transgenic animals. Specifically, bosentan reduced endothelin-mediated contraction in wild-type animals, but had no effect in transgenic animals, and endothelin axis gene expression was altered in transgenic animals. Transgenic mice developed cardiac fibrosis.


CONCLUSIONS
The histologic, biochemical, and functional phenotype of this transgenic mouse model of scleroderma offers insight into the altered biomechanical properties previously reported for large elastic arteries in human SSc and suggests a role for perturbed TGF-beta and endothelin activity in this process.
Derrett-Smith
Emma C
EC
Centre for Rheumatology and Connective Tissue Diseases, UCL Medical School, Royal Free Campus, Rowland Hill Street, London, NW3 2PF, UK.
Dooley
Audrey
A
Khan
Korsa
K
Shi-wen
Xu
X
Abraham
David
D
Denton
Christopher P
CP
D000818:Animals; D001013:Aorta, Thoracic / Q000187:drug effects / Q000473:pathology* / Q000503:physiopathology; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism; D004195:Disease Models, Animal; D016232:Endothelins / Q000235:genetics / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology; D005355:Fibrosis; D008297:Male; D051379:Mice; D008822:Mice, Transgenic; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000503:physiopathology; D032389:Myocytes, Smooth Muscle / Q000187:drug effects / Q000378:metabolism / Q000473:pathology*; D012595:Scleroderma, Systemic / Q000235:genetics / Q000473:pathology*; D015398:Signal Transduction / Q000235:genetics; D051899:Smad2 Protein / Q000378:metabolism; D056647:Systemic Vasculitis / Q000235:genetics / Q000473:pathology*; D016212:Transforming Growth Factor beta / Q000235:genetics / Q000378:metabolism
D016232:Endothelins; D051899:Smad2 Protein; C497783:Smad2 protein, mouse; D016212:Transforming Growth Factor beta; D003094:Collagen
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