Smooth muscle cell-specific Notch1 haploinsufficiency restricts the progression of abdominal aortic aneurysm by modulating CTGF expression

Abstract

AimsInfiltration of macrophages and apoptosis of vascular smooth muscle cells (VSMCs) promote the development of abdominal aortic aneurysm (AAA). Previously, we demonstrated that global Notch1 deficiency prevents the formation of AAA in a mouse model. Herein, we sought to explore the cell-specific roles of Notch1 in AAA development.Methods and resultsCell-specific Notch1 haploinsufficient mice, generated on Apoe-/- background using Cre-lox technology, were infused with angiotensin II (1000 ng/min/kg) for 28 days. Notch1 haploinsufficiency in myeloid cells (n = 9) prevented the formation of AAA attributed to decreased inflammation. Haploinsufficiency of Notch1 in SMCs (n = 14) per se did not prevent AAA formation, but histoarchitectural traits of AAA including elastin degradation and aortic remodeling, were minimal in SMC-Notch1+/-;Apoe-/- mice compared to Apoe-/- mice (n = 33). Increased immunostaining of the contractile SMC-phenotype markers and concomitant decreased expression of synthetic SMC-phenotype markers were observed in the aortae of SMC-Notch1+/-;Apoe-/- mice. Expression of connective tissue growth factor (CTGF), a matrix-associated protein that modulates the synthetic VSMC phenotype, increased in the abdominal aorta of Apoe-/- mice and in the adventitial region of the abdominal aorta in human AAA. Notch1 haploinsufficiency decreased the expression of Ctgf in the aorta and in vitro cell culture system. In vitro studies on SMCs using the Notch1 intracellular domain (NICD) plasmid, dominant negative mastermind-like (dnMAML), or specific siRNA suggest that Notch1, not Notch3, directly modulates the expression of CTGF.ConclusionsOur data suggest that lack of Notch1 in SMCs limits dilation of the abdominal aorta by maintaining contractile SMC-phenotype and preventing matrix-remodeling.

Vascular ADAM17 (a Disintegrin and Metalloproteinase Domain 17) Is Required for Angiotensin II/β-Aminopropionitrile–Induced Abdominal Aortic Aneurysm

“…Other ADAM17 substrates including TNFα, Notch1 and angiotensin converting enzyme 2 may also participate in AAA pathology according to literature 17, 24, 25 . Note that while the protein expression analysis of TNFα did not show any enhancement in AAA, the experiment did not measure the potential conversion of pro-TNFα to mature and active TNFα by ADAM17.…”

“…However, our study provides new information that AngII-dependent AAA development and rupture are markedly prevented in mice lacking VSMC ADAM17 and that pharmacological intervention of ADAM17 can attenuate AAA in a mouse model. Limited VSMC-specific mechanisms are known to contribute to AAA in animal models, which includes decreased catalase 16 and activation of Notch1 17 , whereas induction of hypoxia-inducible factor-1α in VSMCs appears protective 18 .…”

Factor XII blockade inhibits aortic dilatation in angiotensin II-infused apolipoprotein E-deficient mice

“…The EGFR-ADAM-17 pathway was focussed on since this has previously been implicated in AAA in other experimental models. Other ADAM-17 substrates, such as Notch1 and angiotensin-converting enzyme 2, may also be important but these were not investigated [10,16,38]. Finally, conclusions regarding the effect of intervention using samples from the study end-point have limitations and analyses of serum and aortic tissue taken from earlier time points may have provided additional mechanistic insight.…”

Connective tissue growth factor (CTGF) in age-related vascular pathologies

“…It also binds growth factors (e.g., bone morphogenetic protein-4 (BMP4), transforming growth factor-β (TGFβ), and vascular endothelial growth factor (VEGF), thereby regulating their functions) and ECM proteins. CTGF has important roles in diverse biological processes in multiple tissue types, including cell adhesion, migration (Fan et al 2000), angiogenesis (Brigstock 2002), wound repair, and ECM remodeling (Ponticos 2013;Sachdeva et al 2017). Expression of CTGF is regulated by growth factors and cytokines (including angiotensin II (Gao et al 2007), bone morphogenetic proteins, endothelin (Shi-Wen et al 2007)), and mechanical stimuli, including hemodynamic forces (shear stress, high pressure/ wall tension) (Ponticos 2013).…”

“…In adulthood, CTGF likely plays a role in the pathogenesis of several diseases affecting the heart, including heart failure, cardiac fibrosis, and scar formation postmyocardial infarction (Ponticos 2013). In the vasculature, upregulated CTGF expression has been linked to atherogenesis (Cicha et al 2005(Cicha et al , 2006Oemar et al 1997), smooth muscle cell apoptosis (Hishikawa et al 1999), and aneurysm formation (Branchetti et al 2013;Meng et al 2014;Muratoglu et al 2013;Sachdeva et al 2017;Wang et al 2006). Experimental studies indicate that angiotensin II and increased pressure/wall tension result in upregulation of CTGF, which promote changes in the synthetic phenotype in vascular smooth muscle cells (Branchetti et al 2013).…”