Epigenetic control of vascular smooth muscle cells in Marfan and non-Marfan thoracic aortic aneurysms.
OBJECTIVE
Human thoracic aortic aneurysms (TAAs) are characterized by extracellular matrix breakdown associated with progressive smooth muscle cell (SMC) rarefaction. These features are present in all types of TAA: monogenic forms [mainly Marfan syndrome (MFS)], forms associated with bicuspid aortic valve (BAV), and degenerative forms. Initially described in a mouse model of MFS, the transforming growth factor-β1 (TGF-β1)/Smad2 signalling pathway is now assumed to play a role in TAA of various aetiologies. However, the relation between the aetiological diversity and the common cell phenotype with respect to TGF-β signalling remains unexplained.


RESULTS
This study was performed on human aortic samples, including TAA [MFS, n = 14; BAV, n = 15; and degenerative, n = 19] and normal aortas (n = 10) from which tissue extracts and human SMCs and fibroblasts were obtained. We show that all types of TAA share a complex dysregulation of Smad2 signalling, independent of TGF-β1 in TAA-derived SMCs (pharmacological study, qPCR). The Smad2 dysregulation is characterized by an SMC-specific, heritable activation and overexpression of Smad2, compared with normal aortas. The cell specificity and heritability of this overexpression strongly suggest the implication of epigenetic control of Smad2 expression. By chromatin immunoprecipitation, we demonstrate that the increases in H3K9/14 acetylation and H3K4 methylation are involved in Smad2 overexpression in TAA, in a cell-specific and transcription start site-specific manner.


CONCLUSIONS
Our results demonstrate the heritability, the cell specificity, and the independence with regard to TGF-β1 and genetic backgrounds of the Smad2 dysregulation in human thoracic aneurysms and the involvement of epigenetic mechanisms regulating histone marks in this process.
Gomez
Delphine
D
INSERM, U698, Hôpital Xavier Bichat, 46 rue Henri Huchard, FR-75877 Paris Cedex 18, France.
Coyet
Aurélie
A
Ollivier
Véronique
V
Jeunemaitre
Xavier
X
Jondeau
Guillaume
G
Michel
Jean-Baptiste
JB
Vranckx
Roger
R
D000107:Acetylation; D000328:Adult; D000368:Aged; D001013:Aorta, Thoracic / Q000378:metabolism / Q000473:pathology; D017545:Aortic Aneurysm, Thoracic / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D016022:Case-Control Studies; D002478:Cells, Cultured; D042002:Chromatin Assembly and Disassembly; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D020022:Genetic Predisposition to Disease; D040941:Heredity; D006657:Histones / Q000378:metabolism; D006801:Humans; D008382:Marfan Syndrome / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D008875:Middle Aged; D009131:Muscle, Smooth, Vascular / Q000378:metabolism* / Q000473:pathology; D032389:Myocytes, Smooth Muscle / Q000378:metabolism* / Q000473:pathology; D011401:Promoter Regions, Genetic; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D051899:Smad2 Protein / Q000235:genetics / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation; D055815:Young Adult
D006657:Histones; D012333:RNA, Messenger; C497782:SMAD2 protein, human; D051899:Smad2 Protein; C508960:TGFB1 protein, human; D053773:Transforming Growth Factor beta1