Background: Coronary artery disease (CAD) is the leading cause of death worldwide. Recent meta-analyses of genome-wide association studies have identified over 175 loci associated with CAD. The majority of these loci are in noncoding regions and are predicted to regulate gene expression. Given that vascular smooth muscle cells (SMCs) play critical roles in the development and progression of CAD, we aimed to identify the subset of the CAD loci associated with the regulation of transcription in distinct SMC phenotypes. Methods: We measured gene expression in SMCs isolated from the ascending aortas of 151 heart transplant donors of various genetic ancestries in quiescent or proliferative conditions and calculated the association of their expression and splicing with ~6.3 million imputed single-nucleotide polymorphism markers across the genome. Results: We identified 4910 expression and 4412 splicing quantitative trait loci (sQTLs) representing regions of the genome associated with transcript abundance and splicing. A total of 3660 expression quantitative trait loci (eQTLs) had not been observed in the publicly available Genotype-Tissue Expression dataset. Further, 29 and 880 eQTLs were SMC-specific and sex-biased, respectively. We made these results available for public query on a user-friendly website. To identify the effector transcript(s) regulated by CAD loci, we used 4 distinct colocalization approaches. We identified 84 eQTL and 164 sQTL that colocalized with CAD loci, highlighting the importance of genetic regulation of mRNA splicing as a molecular mechanism for CAD genetic risk. Notably, 20% and 35% of the eQTLs were unique to quiescent or proliferative SMCs, respectively. One CAD locus colocalized with a sex-specific eQTL ( TERF2IP ), and another locus colocalized with SMC-specific eQTL ( ALKBH8 ). The most significantly associated CAD locus, 9p21, was an sQTL for the long noncoding RNA CDKN2B-AS1 , also known as ANRIL , in proliferative SMCs. Conclusions: Collectively, our results provide evidence for the molecular mechanisms of genetic susceptibility to CAD in distinct SMC phenotypes.
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Vascular Smooth Muscle Cell Subpopulations and Neointimal Formation in Mouse Models of Elastin Insufficiency
Objective: Using a mouse model of Eln (elastin) insufficiency that spontaneously develops neointima in the ascending aorta, we sought to understand the origin and phenotypic heterogeneity of smooth muscle cells (SMCs) contributing to intimal hyperplasia. We were also interested in exploring how vascular cells adapt to the absence of Eln. Approach and Results: We used single-cell sequencing together with lineage-specific cell labeling to identify neointimal cell populations in a noninjury, genetic model of neointimal formation. Inactivating Eln production in vascular SMCs results in rapid intimal hyperplasia around breaks in the ascending aorta’s internal elastic lamina. Using lineage-specific Cre drivers to both lineage mark and inactivate Eln expression in the secondary heart field and neural crest aortic SMCs, we found that cells with a secondary heart field lineage are significant contributors to neointima formation. We also identified a small population of secondary heart field-derived SMCs underneath and adjacent to the internal elastic lamina. Within the neointima of SMC-Eln knockout mice, 2 unique SMC populations were identified that are transcriptionally different from other SMCs. While these cells had a distinct gene signature, they expressed several genes identified in other studies of neointimal lesions, suggesting that some mechanisms underlying neointima formation in Eln insufficiency are shared with adult vessel injury models. Conclusions: These results highlight the unique developmental origin and transcriptional signature of cells contributing to neointima in the ascending aorta. Our findings also show that the absence of Eln, or changes in elastic fiber integrity, influences the SMC biological niche in ways that lead to altered cell phenotypes.
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- Award ID(s):
- 1662434
- PAR ID:
- 10319309
- Date Published:
- Journal Name:
- Arteriosclerosis, Thrombosis, and Vascular Biology
- Volume:
- 41
- Issue:
- 12
- ISSN:
- 1079-5642
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Key points Vascular oxidative stress increases with advancing age.
We hypothesized that resistance vessels develop resilience to oxidative stress to protect functional integrity and tested this hypothesis by exposing isolated pressurized superior epigastric arteries (SEAs) of old and young mice to H2O2.
H2O2‐induced death was greater in smooth muscle cells (SMCs) than endothelial cells (ECs) and lower in SEAs from old
vs . young mice; the rise in vessel wall [Ca2+]iinduced by H2O2was attenuated with ageing, as was the decline in noradrenergic vasoconstriction; genetic deletion of IL‐10 mimicked the effects of advanced age on cell survival.Inhibiting NO synthase or scavenging peroxynitrite reduced SMC death; endothelial denudation or inhibiting gap junctions increased SMC death; delocalization of cytochrome C activated caspases 9 and 3 to induce apoptosis.
Vascular cells develop resilience to H2O2during ageing by preventing Ca2+overload and endothelial integrity promotes SMC survival.
Abstract Advanced age is associated with elevated oxidative stress and can protect the endothelium from cell death induced by H2O2. Whether such protection occurs for intact vessels or differs between smooth muscle cell (SMC) and endothelial cell (EC) layers is unknown. We tested the hypothesis that ageing protects SMCs and ECs during acute exposure to H2O2(200 µ
m , 50 min). Mouse superior epigastric arteries (SEAs; diameter, ∼150 µm) were isolated and pressurized to 100 cmH2O at 37˚C. For SEAs from young (4 months) mice, H2O2killed 57% of SMCs and 11% of ECs in malesvs . 8% and 2%, respectively, in females. Therefore, SEAs from males were studied to resolve the effect of ageing and experimental interventions. For old (24 months) mice, SMC death was reduced to 10% with diminished accumulation of [Ca2+]iin the vessel wall during H2O2exposure. In young mice, genetic deletion of IL‐10 mimicked the protective effect of ageing on cell death and [Ca2+]iaccumulation. Whereas endothelial denudation or gap junction inhibition (carbenoxolone; 100 µm ) increased SMC death, inhibiting NO synthase (l ‐NAME, 100 µm ) or scavenging peroxynitrite (FeTPPS, 5 µm ) reduced SMC death along with [Ca2+]i. Despite NO toxicity via peroxynitrite formation, endothelial integrity protects SMCs. Caspase inhibition (Z‐VAD‐FMK, 50 µm ) attenuated cell death with immunostaining for annexin V, cytochrome C, and caspases 3 and 9 pointing to induction of intrinsic apoptosis during H2O2exposure. We conclude that advanced age reduces Ca2+influx that triggers apoptosis, thereby promoting resilience of the vascular wall during oxidative stress. -
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1161/ATVBAHA.120.315681
