Microarray-based Gene Expression Profiling of Abdominal Aortic Aneurysm.

OBJECTIVE/BACKGROUND: Microarray-based gene expression profiling studies may detect transcriptional signatures carrying prognostic value in abdominal aortic aneurysms (AAA). A gene expression profiling study was conducted to compare individuals with AAA with screened controls. METHODS: The peripheral blood transcriptome was compared between 12 individuals with AAA and 12 age- and sex-matched controls using microarray. Validation by Taqman real-time quantitative (qPCR) was performed in an independent group as described. Peripheral blood RNA was hybridized to Illumina microarrays, each representing 37,846 genes, allowing comparison of gene expression between cases and controls. Eleven differentially expressed genes were re-quantified by qPCR in the independent group with AAA (n = 95), controls (n = 92), pre- and postendovascular AAA repair (EVAR, n = 31); or open AAA repair (n = 13), AAA wall biopsies (n = 11), and in matched smooth muscle cultures (n = 7). RESULTS: Microarray detected 47 significantly differentially expressed genes in AAA after correction for multiple testing (p < .05). These genes conferred roles in regulation of apoptosis, proteolysis, the electron transport chain, leukocyte migration, and the humoral immune response. Gene quantification in the independent group demonstrated three genes to be downregulated in AAA compared with controls: MSN, PSMB10, and STIM1; however, their expression remained unchanged post-AAA repair. PSMB10 was the only gene conferring a consistent direction of effect in both the discovery and validation analyses (downregulated). EIF3G, SIVA, PUF60, CYC1, FIBP, and CARD8 were downregulated post-EVAR. Expression of all 11 genes of interest was detected in aortic biopsies and matched smooth muscle cultures. CONCLUSION: This study demonstrates differential expression of transcripts in peripheral blood of individuals with AAA, with functional roles in proteolysis, inflammation, and apoptotic processes. These were modulated by aneurysm exclusion from the circulation and expressed in matched aortic biopsies and smooth muscle cultures. These observations further support the key roles for these pathways in the pathogenesis of AAA.

Identification of microRNAs associated with abdominal aortic aneurysms and peripheral arterial disease.

BACKGROUND: MicroRNAs are crucial in the regulation of cardiovascular disease and represent potential therapeutic targets to decrease abdominal aortic aneurysm (AAA) expansion. The aim of this study was to identify circulating microRNAs associated with AAA. METHODS: Some 754 microRNAs in whole-blood samples from 15 men with an AAA and ten control subjects were quantified using quantitative reverse transcriptase-PCR. MicroRNAs demonstrating a significant association with AAA were validated in peripheral blood and plasma samples of men in the following groups (40 in each): healthy controls, controls with peripheral arterial disease (PAD), men with a small AAA (30-54 mm), those with a large AAA (over 54 mm), and those following AAA repair. MicroRNA expression was also assessed in aortic tissue. RESULTS: Twenty-nine differentially expressed microRNAs were identified in the discovery study. Validation study revealed that let-7e (fold change (FC) -1·80; P = 0·001), miR-15a (FC -2·24; P < 0·001) and miR-196b (FC -2·26; P < 0·001) were downregulated in peripheral blood from patients with an AAA, and miR-411 was upregulated (FC 5·90; P = 0·001). miR-196b was also downregulated in plasma from the same individuals (FC -3·75; P = 0·029). The same miRNAs were similarly expressed differentially in patients with PAD compared with healthy controls. Validated and predicted microRNA targets identified through miRWalk revealed that these miRNAs were all regulators of AAA-related genes (vascular cell adhesion molecule 1, intercellular cell adhesion molecule 1, DAB2 interacting protein, α1-antitrypsin, C-reactive protein, interleukin 6, osteoprotegerin, methylenetetrahydrofolate reductase, tumour necrosis factor α). CONCLUSION: In this study, circulating levels of let-7e, miR-15a, miR-196b and miR-411 were differentially expressed in men with an AAA compared with healthy controls, but also differentially expressed in men with PAD. Modulation of these miRNAs and their target genes may represent a new therapeutic pathway to affect the progression of AAA and atherosclerosis.

Low density lipoprotein receptor related protein 1 and abdominal aortic aneurysms.

OBJECTIVES: A recent GWAS demonstrated an association between low density lipoprotein receptor related protein 1 (LRP1) and abdominal aortic aneurysm (AAA). This review aims to identify how LRP1 may be involved in the pathogenesis of abdominal aortic aneurysm. DESIGN AND MATERIALS: A systematic review of the English language literature was undertaken in order to determine whether LRP1 and associated pathways were plausible candidates for contributing to the development and/or progression of AAA. METHODS AND RESULTS: A comprehensive literature search of MEDLINE (since 1948), Embase (since 1980) and Health and Psychological Instruments (since 1985) was conducted in January 2012 identified 50 relevant articles. These studies demonstrate that LRP1 has a diverse range of biological functions and is a plausible candidate for playing a central role in aneurysmogenesis. Importantly, LRP1 downregulates MMP (matrix metalloproteinase) activity in vascular smooth muscle cells and regulates other key pathways involved in extracellular matrix remodelling and vascular smooth muscle migration and proliferation. Crucially animal studies have shown that LRP1 depletion leads to progressive destruction of the vascular architecture and aneurysm formation. CONCLUSIONS: Published evidence suggests that LRP1 may play a key role in the development of AAA.

In vivo and in vitro examination of the functional significances of novel lamin gene mutations in heart failure patients.

CONTEXT: Lamin A/C (LMNA) gene variations have been reported in more than one third of genotyped families with dilated cardiomyopathy (DCM). However, the relationship between LMNA mutation and the development of DCM is poorly understood. METHODS AND RESULTS: We found that end stage DCM patients carrying LMNA mutations displayed either dramatic ultrastructural changes of the cardiomyocyte nucleus (D192G) or nonspecific changes (R541S). Overexpression of the D192G lamin C dramatically increased the size of intranuclear speckles and reduced their number. This phenotype was only partially reversed by coexpression of the D192G and wild type lamin C. Moreover, the D192G mutation precludes insertion of lamin C into the nuclear envelope when co-transfected with the D192G lamin A. By contrast, the R541S phenotype was entirely reversed by coexpression of the R541S and wild type lamin C. As lamin speckle size is known to be correlated with regulation of transcription, we assessed the SUMO1 distribution pattern in the presence of mutated lamin C and showed that D192G lamin C expression totally disrupts the SUMO1 pattern. CONCLUSION: Our in vivo and in vitro results question the relationship of causality between LMNA mutations and the development of heart failure in some DCM patients and therefore, the reliability of genetic counselling. However, LMNA mutations producing speckles result not only in nuclear envelope structural damage, but may also lead to the dysregulation of cellular functions controlled by sumoylation, such as transcription, chromosome organisation, and nuclear trafficking.

A new locus for autosomal dominant dilated cardiomyopathy identified on chromosome 6q12-q16.

Dilated cardiomyopathy (DCM) is a heart-muscle disease characterized by ventricular dilatation and impaired heart contraction and is heterogeneous both clinically and genetically. To date, 12 candidate disease loci have been described for autosomal dominant DCM. We report the identification of a new locus on chromosome 6q12-16 in a French family with 9 individuals affected by the pure form of autosomal dominant DCM. This locus was found by using a genomewide search after exclusion of all reported disease loci and genes for DCM. The maximum pairwise LOD score was 3.52 at recombination fraction 0.0 for markers D6S1644 and D6S1694. Haplotype construction delineated a region of 16.4 cM between markers D6S1627 and D6S1716. This locus does not overlap with two other disease loci that have been described in nonpure forms of DCM and have been mapped on 6q23-24 and 6q23. The phospholamban, malic enzyme 1-soluble, and laminin-alpha4 genes were excluded as candidate genes, using single-strand conformation polymorphism or linkage analysis.

Epidemiology of desmin and cardiac actin gene mutations in a european population of dilated cardiomyopathy.

AIMS: Although dilated cardiomyopathy is the most frequent form of cardiomyopathy, its aetiology is still poorly understood. In about 20-30% of cases the disease is familial with a large predominance of autosomal dominant transmission. Ten different chromosomal loci have been described for autosomal dominant forms of dilated cardiomyopathy. Only two genes have been associated with pure forms (without myopathy and/or conduction disorders) of the disease, the cardiac actin and the desmin genes. Our aim was to determine the proportion of dilated cardiomyopathy affected individuals carrying a mutation in one of these two genes. METHODS AND RESULTS: We performed (1) a systematic polymerase chain reaction-SSCP-sequencing screening of the coding sequences of cardiac actin on DNA samples from 43 probands of dilated cardiomyopathy families and 43 sporadic cases; (2) a systematic polymerase chain reaction-SSCP-sequencing screening of the coding sequences of desmin combined with a search for the described missense mutation (Ile451Met) by restriction fragment length polymorphism analysis on DNA samples from 41 probands of dilated cardiomyopathy families and 22 sporadic cases. CONCLUSION: None of the patients presents a mutation in any of these two genes. Consequently, the proportion of European dilated cardiomyopathy affected individuals bearing a mutation in (1) the cardiac actin gene is less than 1.2%, (2) the desmin gene is less than 1.6%.