Bicuspid aortic valve is the most common congenital heart malformation and the reasons for the aortopathies associated with bicuspid aortic valve remain unclear. NOTCH1 mutations are associated with bicuspid aortic valve and have been found in individuals with various left ventricular outflow tract abnormalities. Notch is a key signaling during cardiac valve formation that promotes the endothelial-to-mesenchymal transition. We address the role of Notch signaling in human aortic endothelial cells from patients with bicuspid aortic valve and aortic aneurysm. Aortic endothelial cells were isolated from tissue fragments of bicuspid aortic valve-associated thoracic aortic aneurysm patients and from healthy donors. Endothelial-to-mesenchymal transition was induced by activation of Notch signaling. Effectiveness of the transition was estimated by loss of endothelial and gain of mesenchymal markers by immunocytochemistry and qPCR. We show that aortic endothelial cells from the patients with aortic aneurysm and bicuspid aortic valve have down regulated Notch signaling and fail to activate Notch-dependent endothelial-to-mesenchymal transition in response to its stimulation by different Notch ligands. Our findings support the idea that bicuspid aortic valve and associated aortic aneurysm is associated with dysregulation of the entire Notch signaling pathway independently on the specific gene mutation.
Thoracic aortic aneurysm develops as a result of complex series of events that alter the cellular structure and the composition of the extracellular matrix of the aortic wall. The purpose of the present work was to study the cellular functions of endothelial and smooth muscle cells from the patients with aneurysms of the thoracic aorta. We studied endothelial and smooth muscle cells from aneurysms in patients with bicuspid aortic valve and with tricuspid aortic valve. The expression of key markers of endothelial (CD31, vWF, and VE-cadherin) and smooth muscle (SMA, SM22α, calponin, and vimentin) cells as well extracellular matrix and MMP activity was studied as well as and apoptosis and cell proliferation. Expression of functional markers of endothelial and smooth muscle cells was reduced in patient cells. Cellular proliferation, migration, and synthesis of extracellular matrix proteins are attenuated in the cells of the patients. We show for the first time that aortic endothelial cell phenotype is changed in the thoracic aortic aneurysms compared to normal aortic wall. In conclusion both endothelial and smooth muscle cells from aneurysms of the ascending aorta have downregulated specific cellular markers and altered functional properties, such as growth rate, apoptosis induction, and extracellular matrix synthesis.
Cellular and molecular mechanisms of thoracic aortic aneurysm are not clear and therapeutic approaches are mostly absent. Thoracic aortic aneurysm is associated with defective differentiation of smooth muscle cells (SMC) of aortic wall. Bicuspid aortic valve (BAV) comparing to tricuspid aortic valve (TAV) significantly predisposes to a risk of thoracic aortic aneurysms. It has been suggested recently that BAV-associated aortopathies represent a separate pathology comparing to TAV-associated dilations. The only proven candidate gene that has been associated with BAV remains NOTCH1. In this study we tested the hypothesis that Notch-dependent and related TGF-β and BMP differentiation pathways are differently altered in aortic SMC of BAV- vs. TAV-associated aortic aneurysms. SMC were isolated from aortic tissues of the patients with BAV- or TAV-associated aortic aneurysms and from healthy donors used as controls. Gene expression was verified by qPCR and Western blotting. For TGF-β induced differentiation SMC were treated with the medium containing TGF-β1. To induce proosteogenic signaling we cultured SMC in the presence of specific osteogenic factors. Notch-dependent differentiation was induced via lentiviral transduction of SMC with activated Notch1 domain. MYOCD expression, a master gene of SMC differentiation, was down regulated in SMC of both BAV and TAV patients. Discriminant analysis of gene expression patterns included a set of contractile genes specific for SMC, Notch-related genes and proosteogenic genes and revealed that control cells form a separate cluster from both BAV and TAV group, while BAV- and TAV-derived SMC are partially distinct with some overlapping. In differentiation experiments TGF-β caused similar patterns of target gene expression for BAV- and TAV derived cells while the induction was higher in the diseased cells than in control ones. Osteogenic induction caused significant change in RUNX2 expression exclusively in BAV group. Notch activation induced significant ACTA2 expression also exclusively in BAV group. We show that Notch acts synergistically with proosteogenic factors to induce ACTA2 transcription and osteogenic differentiation. In conclusion we have found differences in responsiveness of SMC to Notch and to proosteogenic induction between BAV- and TAV-associated aortic aneurysms.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.