The composition of collagen in the aneurysm wall of men and women

Biomarkers and Social Determinants in Atherosclerotic Arterial Diseases: A Scoping Review

BACKGROUND

Arterial diseases like coronary artery disease (CAD), carotid stenosis (CS), peripheral artery disease (PAD), and abdominal aortic aneurysm (AAA) have high morbidity and mortality, making them key research areas. Their multifactorial nature complicates patient treatment and prevention. Biomarkers offer insights into the biochemical and molecular processes, while social factors also significantly impact patients' health and quality of life. This scoping review aims to search the literature for studies that have linked the biological mechanisms of arterial diseases through biomarkers with social issues and to analyze them, supporting the interdependence of biological and social sciences.

METHODS

After a rigorous selection process, adhering to the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines for Scoping Reviews, 30 articles were identified through Scopus, Web of Science, and PubMed. Inclusion and exclusion criteria were based on the population, intervention, comparator, outcome, time, and setting framework. Inclusion criteria were studies involving human subjects that explored the relationships among arterial diseases, biomarkers, and psychosocial factors, with no restrictions on publication date. Nonhuman studies, purely biological or medical analyses without psychosocial dimensions, and non-English publications were excluded. Eligible study types included experimental, observational, and review articles published in peer-reviewed journals. Data extraction focused on study characteristics, such as authors, publication year, country, methods, population, and findings. Results were synthesized narratively, as this format was deemed the most suitable for summarizing diverse findings. The quality or methodological rigor of the included studies was not formally assessed, consistent with the scoping review methodology.

RESULTS

In CAD, biomarkers such as high-sensitivity C-reactive protein are strongly associated with psychological stress, whereas lipoprotein (a) and the apolipoprotein B/apolipoprotein A1 ratio reflect lipid profiles that are influenced by socioeconomic factors and ethnicity. In CS, increased carotid intima-media thickness is linked to psychiatric conditions like attention deficit/hyperactivity disorder, and heat shock protein-70 levels are associated with socioeconomic status and gender. In PAD, inflammatory markers, including interleukin-6, intracellular adhesion molecule-1, and high-sensitivity C-reactive protein, mediate the connection between depression and disease severity, with gender and ethnicity influencing the expression of biomarkers and clinical outcomes. In AAA, factors like smoking and exposure to air pollution have increased matrix metalloproteinase levels and other inflammatory markers. Additionally, estradiol provides partial protection in women, underscoring the role of hormones and environmental influences in disease progression. Social determinants such as socioeconomic status, healthcare access, and ethnicity significantly affect biomarker levels and arterial disease progression.

CONCLUSIONS

These findings are crucial for the assumption that social determinants of health modulate the levels of inflammatory biomarkers involved in the progression of arterial diseases such as CAD, CS, PAD, and AAA. This highlights the need to integrate highly predictive mathematical systems into clinical practice, combining biological sciences with social sciences to achieve advanced standards in precision medicine. However, further studies are needed to validate these approaches fully.

Distribution and Maturity of Medial Collagen Fibers in Thoracoabdominal Post-Dissection Aortic Aneurysms: A Comparative Study of Marfan and Non-Marfan Patients

Thoracoabdominal aortic aneurysms (TAAAs) are rare but serious conditions characterized by dilation of the aorta characterized by remodeling of the vessel wall, with changes in the elastin and collagen content. Individuals with Marfan syndrome have a genetic predisposition for elastic fiber fragmentation and elastin degradation and are prone to early aneurysm formation and progression. Our objective was to analyze the medial collagen characteristics through histological, polarized light microscopy, and electron microscopy methods across the thoracic and abdominal aorta in twenty-five patients undergoing open surgical repair, including nine with Marfan syndrome. While age at surgery differed significantly between the groups, maximum aortic diameter and aneurysm extent did not. Collagen content increased from thoracic to infrarenal segments in both cohorts, with non-Marfan patients exhibiting higher collagen percentages, notably in the infrarenal aorta (729.3 nm vs. 1068.3 nm, p = 0.02). Both groups predominantly displayed mature collagen fibers, with the suprarenal segment containing the highest proportion of less mature fibers. Electron microscopy revealed comparable collagen fibril diameters across segments irrespective of Marfan status. Our findings underscore non-uniform histological patterns in TAAAs and suggest that ECM remodeling involves mature collagen deposition, albeit with lower collagen content observed in the infrarenal aorta of Marfan patients.

Medical treatments for abdominal aortic aneurysm: an overview of clinical trials

INTRODUCTION

Abdominal aortic aneurysm is a progressive, segmental, abdominal aortic dilation associated with a high mortality rate. Abdominal aortic aneurysms with diameters larger than 55 mm are associated with a high risk of rupture, and the most effective treatment options are surgical repair. Close observation and lifestyle adjustments are recommended for smaller abdominal aortic aneurysms with lower rupture risk. The development of medical therapies that limit or prevent the progression, expansion, and eventual rupture of abdominal aortic aneurysms remains an unmet clinical need.

AREAS COVERED

This review provides an overview of completed and ongoing clinical trials examining the efficacies of various drug classes, including antibiotics, antihypertensive drugs, hypolipidemic drugs, hypoglycemic drugs, and other potential therapies for abdominal aortic aneurysms. A search of PubMed, Web of Science, Clinical Trials, and another six clinical trial registries was conducted in January 2024.

EXPERT OPINION

None of the drugs have enough evidence to indicate that they can effectively inhibit the dilation of abdominal aortic aneurysm. More clinical trial data is required to support the efficacy of propranolol. Future research should also explore different drug delivery mechanisms, such as nanoparticles, to elevate drug concentration at the aneurysm wall.

Investigating the influence of collagen cross-linking on mechanical properties of thoracic aortic tissue

Vascular diseases, such as abdominal aortic aneurysms, are associated with tissue degeneration of the aortic wall, resulting in variations in mechanical properties, such as tissue ultimate stress and a high slope. Variations in the mechanical properties of tissues may be associated with an increase in the number of collagen cross-links. Understanding the effect of collagen cross-linking on tissue mechanical properties can significantly aid in predicting diseased aortic tissue rupture and improve the clarity of decisions regarding surgical procedures. Therefore, this study focused on increasing the density of the aortic tissue through cross-linking and investigating the mechanical properties of the thoracic aortic tissue in relation to density. Uniaxial tensile tests were conducted on the porcine thoracic aorta in four test regions (anterior, posterior, distal, and proximal), two loading directions (circumferential and longitudinal), and density increase rates (0%-12%). As a result, the PPC (Posterior/Proximal/Circumferential) group experienced a higher ultimate stress than the PDC (Posterior/Distal/Circumferential) group. However, this relationship reversed when the specimen density exceeded 3%. In addition, the ultimate stress of the ADC (Anterior/Distal/Circumferential) and PPC group was greater than that of the APC (Anterior/Proximal/Circumferential) group, while these findings were reversed when the specimen density exceeded 6% and 9%, respectively. Finally, the high slope of the PDL (Posterior/Distal/Longitudinal) group was lower than that of the ADL (Anterior/Distal/Longitudinal) group, but the high slope of the PDL group appeared larger due to the stabilization treatment. This highlights the potential impact of density variations on the mechanical properties of specific specimen groups.

Treatment With Small Molecule Inhibitors of Advanced Glycation End-Products Formation and Advanced Glycation End-Products-Mediated Collagen Cross-Linking Promotes Experimental Aortic Aneurysm Progression in Diabetic Mice

Background Although diabetes attenuates abdominal aortic aneurysms (AAAs), the mechanisms by which diabetes suppresses AAAs remain incompletely understood. Accumulation of advanced glycation end- (AGEs) reduces extracellular matrix (ECM) degradation in diabetes. Because ECM degradation is critical for AAA pathogenesis, we investigated whether AGEs mediate experimental AAA suppression in diabetes by blocking AGE formation or disrupting AGE-ECM cross-linking using small molecule inhibitors. Methods and Results Male C57BL/6J mice were treated with streptozotocin and intra-aortic elastase infusion to induce diabetes and experimental AAAs, respectively. Aminoguanidine (AGE formation inhibitor, 200 mg/kg), alagebrium (AGE-ECM cross-linking disrupter, 20 mg/kg), or vehicle was administered daily to mice from the last day following streptozotocin injection. AAAs were assessed via serial aortic diameter measurements, histopathology, and in vitro medial elastolysis assays. Treatment with aminoguanidine, not alagebrium, diminished AGEs in diabetic AAAs. Treatment with both inhibitors enhanced aortic enlargement in diabetic mice as compared with vehicle treatment. Neither enhanced AAA enlargement in nondiabetic mice. AAA enhancement in diabetic mice by aminoguanidine or alagebrium treatment promoted elastin degradation, smooth muscle cell depletion, mural macrophage accumulation, and neoangiogenesis without affecting matrix metalloproteinases, C-C motif chemokine ligand 2, or serum glucose concentration. Additionally, treatment with both inhibitors reversed suppression of diabetic aortic medial elastolysis by porcine pancreatic elastase in vitro. Conclusions Inhibiting AGE formation or AGE-ECM cross-linking enhances experimental AAAs in diabetes. These findings support the hypothesis that AGEs attenuate experimental AAAs in diabetes. These findings underscore the potential translational value of enhanced ECM cross-linking as an inhibitory strategy for early AAA disease.

Sex difference in early mortality after abdominal aortic aneurysm repair

OBJECTIVE

Although female patients have a lower prevalence of abdominal aortic aneurysm (AAA), they seem to have a worse treatment outcome compared with male patients. Both maximum aneurysm diameter and aortic size index (ASI) are important indicators of the risk of AAA rupture, among which ASI has been shown capable of equalizing sex-related anatomical differences. Our study aimed to investigate whether sex is an independent risk factor for early postoperative mortality and how the diameter or ASI affects the association between sex and mortality.

METHODS

We performed a retrospective analysis of patients who enrolled in the AAA registry of the German Society of Vascular Surgery from 2013 to 2019. The patients were treated by either open surgical repair (OSR) or endovascular aneurysm repair (EVAR). The association between sex and 30-day mortality was investigated using logistic regression analysis. The interaction and mediating effects of maximum aneurysm diameter and ASI were investigated to verify their roles in the effect of sex on mortality. The relationships between the diameter (or ASI) and the risk of 30-day mortality in different sexes were demonstrated by the restricted cubic spline.

RESULTS

Overall, 23,275 cases were included in our analysis, with 20,130 male (86.5%) and 3139 female (13.5%) patients. Female patients had a smaller maximum aneurysm diameter (OSR, 55.23 ± 10.29 mm vs 58.05 ± 11.28 mm [P < .001]; EVAR, 54.06 ± 9.08 mm vs 56.11 ± 9.38 mm [P < .001]), but a higher ASI (OSR, 3.16 ± 0.71 vs 2.92 ± 0.69 [P < .001]; EVAR, 3.05 ± 0.66 vs 2.80 ± 0.59 [P < .001]) compared with male patients. The 30-day mortality rate was higher for female patients in both OSR (6.6% vs 4.2%; P = .002) and EVAR groups (1.8% vs 0.8%; P < .001). Logistic regression confirmed a significantly higher risk of 30-day mortality for female patients compared with male patients (odds ratio, 1.55; 95% confidence interval, 1.21-1.99; P = .001). No interaction was found between sex and diameter or ASI, but there were mediating effects for diameter and ASI in the effect of sex on 30-day mortality. For female patients, the risk of 30-day mortality linearly increased with the increase of diameter (P_Nonlinear = .089) or ASI (P_Nonlinear = .888), whereas the risk for male patients was U-shaped (for diameter, P_Nonlinear < .001; for ASI, P_Nonlinear = .020).

CONCLUSIONS

Sex is an independent risk factor for 30-day mortality after AAA repair. Both diameter and ASI are mediating factors for the effect of sex on 30-day mortality. The relationship between diameter or ASI and the risk of 30-day mortality is different for male and female patients.

Deficiency of cystathionine gamma-lyase promotes aortic elastolysis and medial degeneration in aged mice

Enzymatic degradation of elastin by matrix metalloproteinases (MMPs) leads to the permanent dilation of aortic wall and constitutes the most prominent characters of aortic aneurysm and aging-related medial degeneration. Hydrogen sulfide (H₂S) as a gasotransmitter exhibits a wide variety of cardio-protective functions through its anti-inflammatory and anti-oxidative actions. Cystathionine gamma-lyase (CSE) is a main H₂S-generating enzyme in cardiovascular system. The regulatory roles of CSE/H₂S system on elastin homeostasis and blood vessel degeneration have not yet been explored. Here we found that aged CSE knockout mice had severe aortic dilation and elastic degradation in abdominal aorta and were more sensitive to angiotensin II-induced aortic elastolysis and medial degeneration. Administration of NaHS would protect the mice from angiotensin II-induced inflammation, gelatinolytic activity, elastin fragmentation, and aortic dilation. In addition, human aortic aneurysm samples had higher inflammatory infiltration and lower expression of CSE. In cultured smooth muscle cells (SMCs), TNFα-induced MMP2/9 hyperactivity and elastolysis could be attenuated by exogenously applied NaHS or CSE overexpression while further deteriorated by complete knockout of CSE. It was further found that H₂S inhibited MMP2 transcription by posttranslational modification of Sp1 via S-sulfhydration. H₂S also directly suppressed MMP hyperactivity by S-sulfhydrating the cysteine switch motif. Taken together, this study revealed the involvement of CSE/H₂S system in the pathogenesis of aortic elastolysis and medial degeneration by maintaining the inactive form of MMPs, suggesting that CSE/H₂S system can be a target for the prevention of age-related medial degeneration and treatment of aortic aneurysm.

Aortic aneurysm evaluation by scanning acoustic microscopy and Raman spectroscopy

Aortic aneurysm is observed as a result of the extensive alteration in the elasticity of the aortic wall due to the breakdown of elastin and collagen. In this study, we studied the feasibility of scanning acoustic microscopy (SAM) and Raman spectroscopy (RS) in characterizing the dilated segments of the aorta from male and female patients with aortic aneurysm. SAM determined the acoustic property variation in the aorta by calculating the acoustic impedance values of aorta samples of 18 patients. RS determined the disease states by analyzing the chemical variation especially in the peaks related to elastin and collagen using the k-means classification method. Consequently, we assume that combining these two techniques in clinics will help to investigate the dilated segment of the aorta with micrometer resolution, which will reduce the possibility of new aneurysm formation due to a segment not excised during the surgery.

Lysyl hydroxylase 1 (LH1) deficiency promotes angiotensin II (Ang II)-induced dissecting abdominal aortic aneurysm

Rationale: The progressive disruption of extracellular matrix (ECM) proteins, particularly early elastin fragmentation followed by abnormalities in collagen fibril organization, are key pathological processes that contribute to dissecting abdominal aortic aneurysm (AAA) pathogenesis. Lysyl hydroxylase 1 (LH1) is essential for type I/III collagen intermolecular crosslinking and stabilization. However, its function in dissecting AAA has not been explored. Here, we investigated whether LH1 is significantly implicated in dissecting AAA progression and therapeutic intervention. Methods and Results: Sixteen-week-old male LH1-deficient and wild-type (WT) mice on the C57Bl/6NCrl background were infused with angiotensin II (Ang II, 1000 ng/kg per minute) via subcutaneously implanted osmotic pumps for 4 weeks. Ang II increased LH1 levels in the abdominal aortas of WT mice, whereas mice lacking LH1 developed dissecting AAA. To evaluate the related mechanism, we performed whole-transcriptomic analysis, which demonstrated that LH1 deficiency aggravated gene transcription alterations; in particular, the expression of thrombospondin-1 was markedly upregulated in the aortas of LH1-deficient mice. Furthermore, targeting thrombospondin-1 with TAX2 strongly inhibited the proinflammatory process, matrix metalloproteinase (MMP) activity and vascular smooth muscle cells (VSMCs) apoptosis, ultimately decreasing the incidence of dissecting AAA. Restoration of LH1 protein expression in LH1-deficient mice by intraperitoneal injection of an adeno-associated virus normalized thrombospondin-1 levels, subsequently alleviating dissecting AAA formation and preserving aortic structure and function. Consistently, in human AAA specimens, decreased LH1 expression was associated with increased thrombospondin-1 levels. Conclusions: LH1 deficiency contributes to dissecting AAA pathogenesis, at least in part, by upregulating thrombospondin-1 expression, which subsequently enables proinflammatory processes, MMP activation and VSMCs apoptosis. Our study provides evidence that LH1 is a potential critical therapeutic target for AAA.

Sex Hormones in Men with Abdominal Aortic Aneurysm

BACKGROUND

Abdominal aortic aneurysm (AAA) primarily affects elderly men. The impact of sex on aneurysm development has been associated with an effect of sex hormones, through mechanisms that are not fully understood. This study aimed to examine the association between levels of sex hormones and the occurrence of AAA in elderly men.

METHODS

A prospective case-control study was conducted including 452, 65-year old men participating in screening for AAA, 2013-2019; 230 men with AAA and 222 men with an aortic diameter<30mm (controls). Questionnaires and blood samples were collected and stored consecutively. Serum levels of total testosterone, estradiol, progesterone, luteinizing hormone and sex hormone binding globulin were analyzed by electrochemiluminescent immunoassays. Multivariable logistic regression analysis was used to assess the association of sex hormones with AAA.

RESULTS

The median aneurysm diameter was 33mm. Men with AAA had higher estradiol and progesterone levels than controls (93pmol/L vs. 84pmol/L, p=.003 and 0.41nmol/L vs. 0.17nmol/L, p<.001). Testosterone levels were lower in men with AAA than in controls (13nmol/L vs. 14nmol/L, p=.026). AAA was associated with detectable levels of progesterone(OR 6.69, 95%CI 3.86-11.47), smoking(OR 5.26, 95%CI 3.12-8.85), coronary heart disease(OR 4.06, 95%CI 1.92-8.58) and body mass index>25(OR 2.26, 95%CI 1.34-3.82).

CONCLUSION

The observed higher levels of estradiol and progesterone in men with AAA, suggest an impact of sex hormones on aneurysm development. The association between progesterone levels and aortic diameter, stress the importance of focusing on the potential effect of this unconsidered female sex hormone on aneurysm formation.

Sex-Based Differences Among Experimental Swine Abdominal Aortic aneurysms

BACKGROUND

Female sex protects against abdominal aortic aneurysms (AAAs); however, the mechanisms behind these sex-based differences remain unknown. The purpose of this study was to explore the role of sex and sex hormones in AAA formation among swine.

MATERIALS AND METHODS

Using a previous validated model, infrarenal AAA were surgically created in uncastrated male (n = 8), female (n = 5), and castrated male (n = 4) swine. Aortic dilation was measured on postoperative day 28 during the terminal procedure and compared to initial aortic diameter measured during the index procedure. Tissue was analyzed for immunohistochemistry, cytokine array, gelatin zymography, serum 17β-estradiol, and testosterone assay.

RESULTS

Uncastrated males had significantly larger maximal aortic dilation compared to castrated males (113.5% ± 11.4% versus 38.1% ± 4.5%, P = 0.0012). Females had significantly higher mean aortic dilation compared to castrated males (96.2% ± 7.5% versus 38.1% ± 4.5%, P = 0.0004). Aortic diameters between females and uncastrated males were not significantly different on day 28. Female swine had significantly higher concentrations of 17β-estradiol compared with uncastrated males (1590 ± 873.3 ng/mL versus 95.2 ± 2.3 ng/mL, P = 0.047), with no significant difference between females and castrated males. Uncastrated male AAA demonstrated significantly more elastin degradation compared with female and castrated males (P = 0.01 and <0 .01, respectively). No differences existed for T-cells or smooth muscle cells between groups. Multiple proinflammatory cytokines were elevated within uncastrated male aortic walls compared to females and castrated males.

CONCLUSIONS

Sex hormones, specifically 17β-estradiol and testosterone, influence experimental swine AAA formation as demonstrated by increased aneurysm size, collagen turnover, and elastolysis in uncastrated males in processes reflective of human disease.

Sex-Related Outcomes After Endovascular Aneurysm Repair Within the Global Registry for Endovascular Aortic Treatment

BACKGROUND

Abdominal aortic aneurysms (AAAs) are more common in men. However, women have been shown to have more short- and long-term adverse outcomes after endovascular aneurysm repair. This disparity is thought to be multifactorial, including anatomical differences, hormonal differences, older age of presentation, and a greater degree of preoperative comorbidities.

METHODS

A retrospective analysis that included data for 3,758 patients from the Global Registry for Endovascular Aortic Treatment (GREAT) was conducted. Patients were recruited into GREAT between August 2010 and October 2016 and received the Gore Excluder stent graft for infrarenal AAAs repair. Cox multivariate regression analyses were performed to analyze any reintervention and device-related intervention rates.

RESULTS

Of the 3,758 patients, 3,220 were male (mean age 73 years) and 538 were female (mean age 75 years). Women had higher prevalence rates of chronic obstructive pulmonary disease (P < 0.0001) and renal insufficiency (P = 0.03), whereas men had higher rates of cardiovascular comorbidities. The AAAs in women were smaller in diameter with shorter and more angulated necks. Women did not experience a significantly higher rate of endoleaks but did exhibit higher reintervention rates, including reintervention for device-related issues. In terms of mortality, aorta-related mortality was most prevalent within the first 30 days after procedure in both sexes.

CONCLUSIONS

Women were treated at an older age and had a more hostile aneurysmal anatomy. Although the mortality rates were lower in women, they had significantly higher rates of reintervention, and thus higher morbidity rates after endovascular aneurysm repair.

A large proportion of patients with small ruptured abdominal aortic aneurysms are women and have chronic obstructive pulmonary disease

Objective

In a population-based cohort of ruptured abdominal aortic aneurysms (rAAAs), our aim was to investigate clinical, morphological and biomechanical features in patients with small rAAAs.

Methods

All patients admitted to an emergency department in Stockholm and Gotland, a region with a population of 2.1 million, between 2009–2013 with a CT-verified rupture (n = 192) were included, and morphological measurements were performed. Patients with small rAAAs, maximal diameter (Dmax) ≤ 60 mm were selected (n = 27), and matched 2:1 by Dmax, sex and age to intact AAA (iAAAs). For these patients, morphology including volume and finite element analysis-derived biomechanics were assessed.

Results

The mean Dmax for all rAAAs was 80.8 mm (SD = 18.9 mm), women had smaller Dmax at rupture (73.4 ± 18.4 mm vs 83.1 ± 18.5 mm, p = 0.003), and smaller neck and iliac diameters compared to men. Aortic size index (ASI) was similar between men and women (4.1 ± 3.1 cm/m² vs 3.8 ± 1.0 cm/m²). Fourteen percent of all patients ruptured at Dmax ≤ 60 mm, and a higher proportion of women compared to men ruptured at Dmax ≤ 60 mm: 27% (12/45) vs. 10% (15/147), p = 0.005. Also, a higher proportion of patients with a chronic obstructive pulmonary disease ruptured at Dmax ≤ 60 mm (34.6% vs 14.6%, p = 0.026). Supra-renal aortic size index (14.0, IQR 13.3–15.3 vs 12.8, IQR = 11.4–14.0) and peak wall rupture index (PWRI, 0.35 ± 0.08 vs 0.43 ± 0.11, p = 0.016) were higher for small rAAAs compared to matched iAAAs. Aortic size index, peak wall stress and aneurysm volume did not differ.

Conclusion

More than one tenth of ruptures occur at smaller diameters, women continuously suffer an even higher risk of presenting with smaller diameters, and this must be considered in surveillance programs. The increased supra-renal aortic size index and PWRI are potential markers for rupture risk, and patients under surveillance with these markers may benefit from increased attention, and potentially from timely repair.

Should Abdominal Aortic Aneurysms in Women be Repaired at a Lower Diameter Threshold?

Abdominal aortic aneurysm (AAA) primarily affects male patients; however, female patients with AAA have a faster rate of aneurysm growth, have higher risk of rupture even at smaller diameters, and have worse outcomes following repair of ruptured and intact aneurysms. Furthermore, early natural history studies and randomized controlled trials evaluating surveillance versus repair in small aneurysms were conducted primarily in male patients. Therefore, there are limited data regarding the ideal threshold for elective repair of AAA in women, either by aortic diameter or by alternative measures. We review the existing literature regarding AAA in women and consider the most appropriate threshold for repair.

Sex differences in abdominal aortic aneurysms

Abdominal aortic aneurysm (AAA) is a vascular disorder with a high case fatality rate in the instance of rupture. AAA is a multifactorial disease, and the etiology is still not fully understood. AAA is more likely to occur in men, but women have a greater risk of rupture and worse prognosis. Women are reportedly protected against AAA possibly by premenopausal levels of estrogen and are, on average, diagnosed at older ages than men. Here, we review the present body of research on AAA pathophysiology in humans, animal models, and cultured cells, with an emphasis on sex differences and sex steroid hormone signaling.