Blood groups and HLA antigens in patients with abdominal aortic aneurysms

Blood groups and acute aortic dissection type III

INTRODUCTION

Acute aortic type III dissection is one of the most catastrophic events, with in-hospital mortality ranging between 10% and 12%. The majority of patients are treated medically, but complicated dissections, which represent 15% to 20% of cases, require surgical or thoracic endovascular aortic repair (TEVAR). For the best outcomes adequate blood transfusion support is required. Interest in the relationship between blood type and vascular disease has been established. The aim of our study is to evaluate distribution of blood groups among patients with acute aortic type III dissection and to identify any kind of relationship between blood type and patient's survival.

MATERIAL AND METHODS

From January 2005 to December 2014, 115 patients with acute aortic type III dissection were enrolled at the Clinic of Vascular and Endovascular Surgery in Belgrade, Serbia and retrospectively analyzed. Patients were separated into two groups. The examination group consisted of patients with a lethal outcome, and the control group consisted of patients who survived.

RESULTS

The analysis of the blood groups and RhD typing between groups did not reveal a statistically significant difference (p = 0.220).

CONCLUSIONS

Our results indicated no difference between different blood groups and RhD typing with respect to in-hospital mortality of patients with acute aortic dissection type III.

Genes and abdominal aortic aneurysm

Abdominal aortic aneurysm (AAA) is a multifactorial disease with a strong genetic component. Since the first candidate gene studies were published 20 years ago, approximately 100 genetic association studies using single nucleotide polymorphisms (SNPs) in biologically relevant genes have been reported on AAA. These studies investigated SNPs in genes of the extracellular matrix, the cardiovascular system, the immune system, and signaling pathways. Very few studies were large enough to draw firm conclusions and very few results could be replicated in another sample set. The more recent unbiased approaches are family-based DNA linkage studies and genome-wide genetic association studies, which have the potential of identifying the genetic basis for AAA, only when appropriately powered and well-characterized large AAA cohorts are used. SNPs associated with AAA have already been identified in these large multicenter studies. One significant association was of a variant in a gene called contactin-3, which is located on chromosome 3p12.3. However, two follow-up studies could not replicate this association. Two other SNPs, which are located on chromosome 9p21 and 9q33, were replicated in other samples. The two genes with the strongest supporting evidence of contribution to the genetic risk for AAA are the CDKN2BAS gene, also known as ANRIL, which encodes an antisense ribonucleic acid that regulates expression of the cyclin-dependent kinase inhibitors CDKN2A and CDKN2B, and DAB2IP, which encodes an inhibitor of cell growth and survival. Functional studies are now needed to establish the mechanisms by which these genes contribute toward AAA pathogenesis.

Association of fatal aneurysmal subarachnoid hemorrhage with human leukocyte antigens in the Finnish population

Human leukocyte antigens (HLA) have been reported to associate with the risk of aneurysmal subarachnoid hemorrhage (SAH) and poor outcome after SAH. Our aim was to identify HLA antigens that associate with the risk of fatal SAH in the Finnish population. Medical records of 600 cadaveric organ donors were reviewed to find organ donors that succumbed to SAH (n = 232) or brain trauma (n = 151). HLA antigen frequencies in these groups were compared with HLA frequencies in a reference population of 10,000 bone marrow donors. Chi-Square test with Bonferroni correction and multiplicative logistic regression models were used and false positive result probabilities (FPRP) were calculated. Alpha-level was 0.01. HLA-A3 associated with fatal SAH (p = 0.0014, OR 1.3 and 95%CI 1.1-1.6) and HLA-DR7 inversely associated with fatal SAH (p = 0.0040, OR 0.3 and 95%CI 0.2-0.6). HLA-A3 but not HLA-DR7 showed also a positive trend in donors with brain trauma. FPRP was below 0.5 for HLA-A3, but clearly above 0.5 for HLA-DR7. HLA-A3 seems to associate with fatal SAH in the Finnish population. Further studies are needed to reveal the pathobiologic mechanisms for how HLA-A3 associates with the risk of fatal SAH in Finns.

Evidence for association between the HLA-DQA locus and abdominal aortic aneurysms in the Belgian population: a case control study

BACKGROUND

Chronic inflammation and autoimmunity likely contribute to the pathogenesis of abdominal aortic aneurysms (AAAs). The aim of this study was to investigate the role of autoimmunity in the etiology of AAAs using a genetic association study approach with HLA polymorphisms.

METHODS

HLA-DQA1, -DQB1, -DRB1 and -DRB3-5 alleles were determined in 387 AAA cases (180 Belgian and 207 Canadian) and 426 controls (269 Belgian and 157 Canadian) by a PCR and single-strand oligonucleotide probe hybridization assay.

RESULTS

We observed a potential association with the HLA-DQA1 locus among Belgian males (empirical p = 0.027, asymptotic p = 0.071). Specifically, there was a significant difference in the HLA-DQA1*0102 allele frequencies between AAA cases (67/322 alleles, 20.8%) and controls (44/356 alleles, 12.4%) in Belgian males (empirical p = 0.019, asymptotic p = 0.003). In haplotype analyses, marginally significant association was found between AAA and haplotype HLA-DQA1-DRB1 (p = 0.049 with global score statistics and p = 0.002 with haplotype-specific score statistics).

CONCLUSION

This study showed potential evidence that the HLA-DQA1 locus harbors a genetic risk factor for AAAs suggesting that autoimmunity plays a role in the pathogenesis of AAAs.

Smooth muscle cell migration and proliferation is enhanced in abdominal aortic aneurysms

BACKGROUND

The aetiology of abdominal aortic aneurysms (AAA) is as yet undetermined. Smooth muscle cells (SMC) have been implicated in the pathogenesis of AAA as a result of their ability to produce elastin degrading proteases. The present study was undertaken to examine AAA SMC and aortic occlusive disease (AOD) SMC in terms of their respective migration and proliferation in vitro, in order to identify intrinsic differences between these cells.

METHODS

Five AAA specimens, four AOD and five inferior mesenteric artery (IMA) specimens were established in culture. The cultures were examined for the extent and the rate of SMC outgrowth and proliferation. Cells were counted following trypsinization using a haemocytometer.

RESULTS

For the AAA explants, the cellular outgrowths were first seen at 6.7 days, after culture initiation, while the corresponding outgrowth in the AOD group required 8.8 days (P < 0.05) and the IMA group 11.4 days (P < 0.05). AAA cells reached confluency at a mean of 22.4 days while AOD SMC required 28.6 days (P < 0.05) and IMA 31 days (P < 0.05). In the first passage, the time for AAA SMC doubling was 5.3 days compared to 6.2 days for AOD (P < 0.05) and 8.1 days for the IMA group (P < 0.05). Greater than 98% of the cells, in both groups, stained positive to SMC alpha-actin.

CONCLUSION

From these data it is clear that there are intrinsic differences in cellular kinetics between SMC from the two disease states, supporting the hypothesis that AAA are not the result of atherosclerosis.

Pathogenesis of acquired aneurysms of the abdominal aorta

The incidence of abdominal aortic aneurysm has recently increased. There is still no accurate definition of abdominal aortic aneurysm. The diameter of abdominal aortic aneurysms is the only factor permitting evaluation of the risk of rupture of aneurysms whose growth remains unpredictable. Abdominal aortic aneurysm is a multi-factorial disease associated with aortic aging and atheroma. It differs from stenotic disease by the intensity of degenerative or destructive phenomena in the media. Particular hemodynamic conditions in the infrarenal abdominal aorta seem to enhance the development of aneurysm at this level. While certain constitutional anomalies of the extracellular matrix of proteins seem to enhance the development of abdominal aortic aneurysm, protease activity of as yet undetermined origin also seems to play a prominent role. Family cases of abdominal aortic aneurysms have been reported but the mechanisms responsible remain to be determined. Several genetic markers have been suggested. The most reliable marker of aortic aneurysm is arteriomegaly.

Incidence and etiology of abdominal aortic aneurysms

Unlike coronary artery disease and cerebrovascular disease, the incidence of abdominal aortic aneurysms has increased dramatically over the past three decades. There appears to be a correlation between both hypertension and smoking and the development of aneurysms, and there is a substantial predominance of white men among the patients. Recent studies have also documented a strong genetic component to this disease. Several biochemical abnormalities have been noted in those with aortic aneurysms, including increased proteolysis (elastolysis and collagenolysis). At present, the precise etiology of aneurysmal disease remains unclear, but it will most likely turn out to be a heterogenous disease with several molecular forms.

Ultrasonographic screening of the abdominal aorta among siblings of patients with abdominal aortic aneurysms

To evaluate the prevalence of abdominal aortic dilatations among asymptomatic brothers and sisters of patients with abdominal aortic aneurysms (AAAs), an ultrasonographic screening study was performed. One hundred and two siblings of patients operated on for AAAs at two Swedish hospitals were invited to attend, and 87 of them (35 men and 52 women) from 32 different families, accepted the invitation. Their median age was 63 years (range 39-82 years). Aortic dilatation was diagnosed in ten of the brothers (29 per cent) and three of the sisters (6 per cent). In ten cases (eight men and two women) there was a localized dilatation caudal to the coeliac axis, and in three a general dilatation of the abdominal aorta with the diameter at the coeliac axis greater than 29 mm. None of the aortic dilatations had been known before this study was performed. The conclusion is that the prevalence of asymptomatic aortic dilatations among brothers of patients with AAAs seems to be high and that this group should be selected for further screening studies.

Co-existence of abdominal aortic aneurysms and intracranial aneurysms

The occurrence of abdominal aortic aneurysms (AAAs) and intracranial aneurysms (IAs) in the same patient and in the same family was studied among 89 patients with AAAs and 485 patients with IAs. Among the AAA-patients two had IAs themselves and five had IAs in the family, whereas three IA-patients had AAAs themselves and eight had AAAs in the family. Moreover, one of the patients with both AAA and IA had a blood relative with AAA, and in six of the families with both types of aneurysms there were more than two subjects with aneurysms. The results indicate, that AAAs and IAs may have a common aetiologic factor.