Peripheral Blood Gene Expression Profiling Reveals Molecular Pathways Associated with Cervical Artery Dissection

Cervical artery dissection (CeAD) is the primary cause of ischemic stroke in young adults. Monogenic heritable connective tissue diseases account for fewer than 5% of cases of CeAD. The remaining sporadic cases have known risk factors. The clinical, radiological, and histological characteristics of systemic vasculopathy and undifferentiated connective tissue dysplasia are present in up to 70% of individuals with sporadic CeAD. Genome-wide association studies identified CeAD-associated genetic variants in the non-coding genomic regions that may impact the gene transcription and RNA processing. However, global gene expression profile analysis has not yet been carried out for CeAD patients. We conducted bulk RNA sequencing and differential gene expression analysis to investigate the expression profile of protein-coding genes in the peripheral blood of 19 CeAD patients and 18 healthy volunteers. This was followed by functional annotation, heatmap clustering, reports on gene-disease associations and protein-protein interactions, as well as gene set enrichment analysis. We found potential correlations between CeAD and the dysregulation of genes linked to nucleolar stress, senescence-associated secretory phenotype, mitochondrial malfunction, and epithelial-mesenchymal plasticity.

[Clinical characteristics of internal carotid and vertebral arteries dissection]

OBJECTIVE

To compare demographic, clinical, and imaging characteristics of patients with internal carotid artery dissection (ICAD) and vertebral artery dissection (VAD) in a Russian population.

MATERIAL AND METHODS

One hundred fifty-two consecutive patients (74 males, 49%; mean age - 37.0±10.3 years) with cervical artery dissection (ICAD - 85 patients, 56%; VA - 62 patients, 41%; ICA+VA - 5 patients - 3%) verified by MRI/MRA were studied. Five patients with both ICAD and VAD were excluded from analysis.

RESULTS

Patients with ICAD more often were men (63%, p<0.0001), while patients with VAD were women (69%, p<0.0001), age distribution was similar (37.4±11.2 and 36.2±9.4 years, p>0.05). The main precipitating events for VADs were neck movements, prolonged static turning of the head, physical exertion (57% vs 28% in ICAD, p=0.0009). Head trauma within the previous month was more often reported by ICAD patients than VAD patients (21% vs 7%, p=0.0295). Clinically ICADs more frequently manifested by ischemic stroke (IS) then VADs (82% vs 55% p=0.0004), but more rarely by isolated cervical pain/headache (10% vs 35%, p<0.0001). 85% patients with dissections had neck/headache preceding cerebral ischemia: isolated neck pain (27%, p=0.0001) or a combination of neck pain with headache (55%, p=0.0004) were characteristic of VADs while headache was typical for ICADs (71%, р=0.0001). According to MRI, bilateral ICADs were found more rarely than bilateral VADs (10% vs 31% p=0.0029). Arterial occlusion was more common for ICADs (61% vs 20%, p<0.0001), double lumen was found only in VAD patients (6%, p=0.0121), and aneurysms were revealed with similar frequency (ICAD 7%, VAD 5%).

CONCLUSION

There were significant differences between patients with ICAD and VAD in terms of gender distribution, precipitating events, clinical and imaging features. Different embryonic origin of ICA and VA, their anatomical differences, and intramural hematoma location in relation to intima and adventitia may underlay these differences.

Mild Hyperhomocysteinemia and Low Folate Concentrations as Risk Factors for Cervical Arterial Dissection

BACKGROUND AND PURPOSE

Elevated homocysteine (Hcy) plasma levels are associated with an increased risk of spontaneous cervical artery dissection (sCAD). We examined the potential association between Hcy, folate, vitamin B(12) levels and 5,10-methylenetetrahydrofolate reductase (MTHFR) polymorphisms in patients with cerebral infarct caused by sCAD.

PATIENTS AND METHODS

39 patients who survived a cerebral infarct caused by sCAD [20 (51%) women; 24 (61.5%) vertebral and 15 (38.5%) internal carotid arteries], and 76 healthy control subjects were included. Hcy plasma levels (fasting and after methionine load), folate and vitamin B(12) levels were measured. We also performed polymorphisms of MTHFR. Hcy, vitamin B(12), folates and polymorphisms of MTHFR were assessed and any associations were analyzed using multivariate statistics.

RESULTS

Mean plasma fasting Hcy level was 9.81 mumol/l for cases and 6.38 for controls (p = 0.001). The occurrence of sCAD was associated with elevated fasting Hcy levels (>95th percentile over the control group) with an adjusted odds ratio of 7.9 (95% CI 1.66-35). The association between low plasma folate values (<5th percentile) and the presence of CAD was 7.9 (95% CI 1.6-31) after adjusting for confounding variables. The distribution of the MTHFR genotype showed a higher TT mutant frequency among CAD patients (p = 0.034).

CONCLUSIONS

High plasma concentrations of Hcy and low plasma levels of folate were associated with an increased risk of sCAD in the sample studied. We conclude that deficiencies in nutritional status may contribute to the relatively high incidence of CAD in Mexico.

Genetic approaches in the study of risk factors for cervical artery dissection

The familial risk of spontaneous cervical artery dissections (sCAD) and the prevalence of the disease in the general population are not well known, making it difficult to estimate the importance of genetic risk factors in sCAD. sCAD is associated in rare cases with inherited diseases such as Ehlers-Danlos syndrome or osteogenesis imperfecta. In most instances, however, sCAD occurs in the absence of known heritable diseases. Genetic risk factors might play a role in further associated conditions, like the ultrastructural connective tissue alterations that are found in skin biopsies of most patients. Systematic mutation search in genes known for their implication in connective tissue disorders has been disappointing apart from rare missense mutations in the genes encoding type V collagen that were found in a minority of patients with sCAD. Efforts are now focusing on genetic linkage studies scanning the whole genome for markers that cosegregate with the above-mentioned dermal connective tissue alterations. Concomitantly, genetic association studies tested the association between sCAD and candidate genes that were selected a priori on pathophysiological arguments, in particular genes playing a role in the extracellular matrix, endothelial function, or inflammatory processes. Most association studies reported until now were negative, apart from one showing an association with a polymorphism in the MTHFR gene and another with a polymorphism in the ICAM-1 gene. However, the results of the association studies published so far must be interpreted cautiously because of the small sample sizes.

The ICAM-1 E469K gene polymorphism is a risk factor for spontaneous cervical artery dissection

In a primary study on proinflammatory genetic profiles in stroke, the authors found the E469K polymorphism of the intercellular adhesion molecule 1 (ICAM-1) highly represented in the subgroup with spontaneous cervical artery dissection (sCAD). They further investigated the same genetic variant in a second group of 65 patients with sCAD. An association between sCAD and EE genotype was confirmed (odds ratio 3.16; p < 0.01), indicating that a proinflammatory predisposition is a risk factor for sCAD.

Protease Inhibitors in Spontaneous Cervical Artery Dissections

Background and Purpose— Observations in patients with arterial aneurysms, fibromuscular dysplasia, and spontaneous cervical artery dissection (sCAD) indicate that protease inhibitor deficiency might boost the enzymatic destruction of arterial tissue and increase the risk of these arterial wall diseases. Here we present the first large investigation of the protease inhibitor hypothesis in patients with sCAD.

Methods— Eighty patients with sCAD were compared with 80 age- and sex-matched healthy individuals. α 1 -antitrypsin (α 1 -AT) and α 2 -macroglobulin (α 2 -MG) levels, and α 1 -AT genotypes were assessed and compared between groups.

Results— α 1 -AT and α 2 -MG levels as well as α 1 -AT genotypes did not differ significantly between patients and controls. The frequency of Z alleles in the patient group was higher than in the control group and than in other cohorts from Europe; however, the difference remained nonsignificant. All patients with Z alleles had internal carotid artery dissections.

Conclusions— Overall, this data does not support the hypothesis that protease inhibitor levels or α 1 -AT genotypes play an important role in the etiology of sCAD. The present data does not exclude that the Pi-Z allele might have an influence on subgroups of sCAD, such as internal carotid artery dissections.

Plasma homocysteine, MTHFR C677T, CBS 844ins68bp, and MTHFD1 G1958A polymorphisms in spontaneous cervical artery dissections

Mild hyperhomocysteinemia is a probable risk factor for atherosclerotic diseases and stroke. Recently, associations of elevated plasma homocysteine concentrations in the acute phase and of MTHFR 677 TT genotype with spontaneous cervical artery dissections (sCAD) have been reported. The purpose of this study was to test this hypothesis in the currently largest sample of patients with sCAD, taking into account known factors influencing plasma homocysteine levels. Ninety-five patients with past sCAD were compared with 95 age- and sex-matched healthy individuals. Homocysteine, vitamin B6, B12, folate, and polymorphisms of methylenetetrahydrofolate reductase (MTHFR C677T), cystathionine beta-synthase (CBS 844ins68bp) and methylenetetrahydrofolate dehydrogenase/methenyltetrahydrofolate cyclohydrolase/formyltetrahydrofolate synthetase (MTHFD1 G1958A) were assessed and any associations were analysed using multivariate statistics. The occurrence of sCAD was associated with elevated homocysteine levels with an odds ratio of 1.327 per 20 % percentile. Homocysteine levels were influenced by gender, smoking status, occurrence of hypertension, vitamin B12 and folate levels, and by the MTHFR TT genotype. MTHFR, CBS 844ins68bp, and MTHFD1 G1958A genotype were not independently associated with the occurrence of sCAD. These data suggest that elevated homocysteine is associated with the occurrence of sCAD. The MTHFR C677T polymorphism is associated with the homocysteine level.

Alpha-1-antitrypsin deficiency alleles are not associated with cervical artery dissections

The authors searched for the presence of alpha-1-antitrypsin (AAT) deficiency alleles PiZ and PiS in 74 patients with spontaneous cervical artery dissections (sCADs) and in 74 healthy control subjects. In both groups, the authors found four carriers of deficiency alleles. The connective tissue morphology of one additional patient with sCAD with PiZM genotype and her relatives was studied in skin biopsies. The PiZ allele did not segregate with morphologic alterations of the dermal connective tissue in the family. Therefore, AAT deficiency alleles may not play a role in the etiology of sCAD.

MMP-9 Polymorphisms Are Not Associated With Spontaneous Cervical Artery Dissection

Background and Purpose— Cervical artery dissection (CAD) is a common cause of ischemic stroke in young adults. Alteration in the structure of the vascular extracellular matrix has been described in CAD. Matrix metalloproteinases (MMPs) degrade extracellular matrix proteins and can lead to vascular damage.

Methods— We tested 2 different MMP-9 DNA polymorphisms, a CA repeat and a cytosine to thymidine transition in the promotor sequence, for frequency in 52 patients with CAD. We compared the results with those of 52 healthy controls.

Results— No differences were found in the allelic distribution of either polymorphism.

Conclusions— Alleles of these well-characterized functional polymorphisms of MMP-9 gene are not associated with structural alterations in the matrix of vessels of patients with CAD.

Heterozygous carriers of Pseudoxanthoma elasticum were not found among patients with cervical artery dissections

In this study of patients with spontaneous cervical artery dissections (sCAD) we searched for mutations in ABCC6, the candidate gene for Pseudoxanthoma elasticum (PXE). Genomic DNA samples from 12 sCAD patients with pronounced electron microscopic alterations in their dermal connective tissue and from 2 patients with PXE were analysed. One patient with PXE was compound heterozygous for two missense point mutations, in the second patient with PXE we did not find changes in the ABCC6 gene. We observed several missense mutations (H623Q, R3190W and R1268Q) in the patients with sCAD, but these mutations were not disease specific,since they were also detected in a series of 25 healthy control subjects.The finding of several sequence variants in sCAD patients and of disease causing mutations in one of the PXE patients suggests that our strategy of mutation search is reliable. Since we did not find disease causing mutations in our series of patients with sCAD we suggest that ABCC6 is not a candidate gene for sCAD.

Hyperhomocysteinemia: a potential risk factor for cervical artery dissection following chiropractic manipulation of the cervical spine

Despite the increasing incidence of cervical artery dissection (CAD) due to chiropractic manipulation of the cervical spine, risk factors predisposing to vascular damage are still unknown. In the present study we measured fasting total plasma homocysteine (tHcy) concentration in 4 subjects with manipulation-related CAD selected from a larger series of patients with spontaneous dissection of the neck arteries (sCAD) and in a group of 36 control subjects. C677T MTHFR genotypes and 844ins68bp CBS genotypes were also determined. Median tHcy levels were significantly (P = 0.002) higher in patients with manipulation-related CAD (18.2 micromol/l, range 14.3 to 30.0) compared with controls (8.9 micromol/l, range 5 to 17.3) and not significantly different (P = 0.129) from those observed in patients with sCAD (13.9 micromol/l, range 7 to 32.8). No significant difference in the distribution of genotypes was observed in the three groups. Hyperhomocysteinemia may represent a potential risk factor for manipulation-related CAD, leading to structural abnormalities of the arterial wall and increasing the susceptibility to mechanical stress.

Analysis of the COL3A1 gene in patients with spontaneous cervical artery dissections

The etiology of spontaneous cervical artery dissection (sCAD) is unknown. An underlying connective tissue disorder has been suggested. As a collagen disease is conceivable several genes encoding fibrillar collagens have been condsidered as candidate genes for sCAD. We analysed the COL3A1 gene in patients with spontaneous cervical artery dissection (sCAD) and in healthy controls, using three different genetic methods. 1) The promoter region, the 5' and 3' untranscribed regions and the N- and C- peptide encoding regions were studied by direct sequencing analysis of DNA from 12 patients. 2) A possible association of sCAD and the COL3A1 gene was tested for with 5 different DNA polymorphisms in 45 patients and 50 healthy control subjects. 3) DNA samples from a father and his two daughters, all suffering from spontaneous dissections of a cervical artery, were analysed with CA-repeat markers that flank the COL3A1 locus. No disease-causing mutations were found in an extended sequence analysis of the COL3A1 gene in patients with sCAD. However, we identified a single nucleotid polymorphism (SNP) in the promotor region in 2 patients and a 2 bp deletion in the 3' UTR in 7 patients. These sequence variants were also found among 50 healthy subjects. An analysis of multiple DNA polymorphisms of the COL3A1 locus in patients and healthy control persons did not indicate a significant association of sCAD with COL3A1. A deletion polymorphism in the 3' UTR was, however, found more often amongst patients with sCAD. The possible linkage of a hypothetical disease mutation with the COL3A1 locus was tested in a small family with three affected patients. As the affected daughters did not inherit the same COL3A1 allele from their affected father (LOD < - 2.3) COL3A1 was excluded as a disease gene in this family. This study confirms and extends earlier work which suggests that COL3A1 mutations are not a major cause for isolated sCAD.

Sequence analysis of the COL5A2 gene in patients with spontaneous cervical artery dissections

The authors searched for mutations in the gene that codes for the alpha2 chain of type V procollagen in 10 patients with spontaneous cervical artery dissections (sCAD). Two patients carried a missense mutation affecting the predicted C-propeptide (T1227S; D1429V). A third patient carried two mutations (V509A and P830L) in the same alpha2(V) chain. The T1227S mutation and the V509A/P830L haplotype also were detected among 50 healthy subjects. The D1429V substitution was detected neither in a series of 150 healthy control subjects nor among 50 additional patients with sCAD.

Plasma homocysteine concentration, C677T MTHFR genotype, and 844ins68bp CBS genotype in young adults with spontaneous cervical artery dissection and atherothrombotic stroke

BACKGROUND AND PURPOSE

The role of mild hyperhomocysteinemia as a risk factor for cerebral ischemia may depend on stroke subtype. To test this hypothesis, we undertook a prospective case-control study of a group of patients with spontaneous cervical artery dissection (sCAD), a group of patients with atherothrombotic stroke (non-CAD), and a group of control subjects.

METHODS

Fasting total plasma homocysteine (tHcy) concentration, C677T MTHFR genotype, and 844ins68bp CBS genotype were determined in 25 patients with sCAD, 31 patients <45 years of age with non-CAD ischemic stroke, and 36 control subjects. Biochemical data in the patient groups were obtained within the first 72 hours of stroke onset.

RESULTS

Median tHcy levels were significantly higher in patients with sCAD (13.2 micromol/L; range, 7 to 32.8 micromol/L) compared with control subjects (8.9 micromol/L; range, 5 to 17.3 micromol/L; 95% CI, 1.05 to 1.52; P=0.006). Cases with tHcy concentration above the cutoff level of 12 micromol/L were significantly more represented in the group of patients with sCAD compared with control subjects (64% versus 13.9%; 95% CI, 2.25 to 44.23; P=0.003); a significant association between the MTHFR TT genotype and sCAD was also observed (36% versus 11.1%; 95% CI, 1.10 to 19.23; P=0.045). No significant difference in tHcy levels and in the prevalence of thermolabile MTHFR was found between patients with non-CAD ischemic stroke and control subjects and between patients with sCAD and non-CAD ischemic stroke. The distribution of the 844ins68bp CBS genotype and the prevalence of subjects carrying both the TT MTHFR and 844ins68bp CBS genotypes were not significantly different among the 3 groups.

CONCLUSIONS

Our results are consistent with the hypothesis that increased plasma homocysteine levels and the TT MTHFR genotype may represent risk factors for sCAD. In contrast, their role in atherothrombotic strokes remains a contentious issue.