Platelet olfactory receptor activation limits platelet reactivity and growth of aortic aneurysms

GWAS-based polygenic risk scoring for predicting cerebral artery dissection in the Chinese population

OBJECTIVE

Cerebral artery dissection (CeAD) is a rare but serious disease. Genetic risk assessment for CeAD is lacking in Chinese population. We performed genome-wide association study (GWAS) and computed polygenic risk score (PRS) to explore genetic susceptibility factors and prediction model of CeAD based on patients in Huashan Hospital.

METHODS

A total of 210 CeAD patients and 280 controls were enrolled from June 2017 to September 2022 in Department of Neurology, Huashan Hospital, Fudan University. We performed GWAS to identify genetic variants associated with CeAD in 140 CeAD patients and 210 control individuals according to a case and control 1:1.5 design rule in the training dataset, while the other 70 patients with CeAD and 70 controls were used as validation. Then Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway and Gene Ontology (GO) enrichment analyses were utilized to identify the significant pathways. We constructed a PRS by capturing all independent GWAS SNPs in the analysis and explored the predictivity of PRS, age, and sex for CeAD.

RESULTS

Through GWAS analysis of the 140 cases and 210 controls in the training dataset, we identified 13 leading SNPs associated with CeAD at a genome-wide significance level of P < 5 × 10- 8. Among them, 10 SNPs were annotated in or near (in the upstream and downstream regions of ± 500Kb) 10 functional genes. rs34508376 (OR2L13) played a suggestive role in CeAD pathophysiology which was in line with previous observations in aortic aneurysms. The other nine genes were first-time associations in CeAD cases. GO enrichment analyses showed that these 10 genes have known roles in 20 important GO terms clustered into two groups: (1) cellular biological processes (BP); (2) molecular function (MF). We used genome-wide association data to compute PRS including 32 independent SNPs and constructed predictive model for CeAD by using age, sex and PRS as predictors both in training and validation test. The area under curve (AUC) of PRS predictive model for CeAD reached 99% and 95% in the training test and validation test respectively, which were significantly larger than the age and sex models of 83% and 86%.

CONCLUSIONS

Our study showed that ten risk loci were associated with CeAD susceptibility, and annotated functional genes had roles in 20 important GO terms clustered into biological process and molecular function. The PRS derived from risk variants was associated with CeAD incidence after adjusting for age and sex both in training test and validation.

New insights into the roles of olfactory receptors in cardiovascular disease

Olfactory receptors (ORs) are G protein coupled receptors (GPCRs) with seven transmembrane domains that bind to specific exogenous chemical ligands and transduce intracellular signals. They constitute the largest gene family in the human genome. They are expressed in the epithelial cells of the olfactory organs and in the non-olfactory tissues such as the liver, kidney, heart, lung, pancreas, intestines, muscle, testis, placenta, cerebral cortex, and skin. They play important roles in the normal physiological and pathophysiological mechanisms. Recent evidence has highlighted a close association between ORs and several metabolic diseases. Cardiovascular diseases (CVDs) are the leading cause of morbidity and mortality globally. Furthermore, ORs play an essential role in the development and functional regulation of the cardiovascular system and are implicated in the pathophysiological mechanisms of CVDs, including atherosclerosis (AS), heart failure (HF), aneurysms, and hypertension (HTN). This review describes the specific mechanistic roles of ORs in the CVDs, and highlights the future clinical application prospects of ORs in the diagnosis, treatment, and prevention of the CVDs.

A Divergent Platelet Transcriptome in Patients with Lipedema and Lymphedema

Lipedema and lymphedema are physically similar yet distinct diseases that are commonly misdiagnosed. We previously reported that lipedema and lymphedema are associated with increased risk for venous thromboembolism (VTE). The underlying etiology of the prothrombotic profile observed in lipedema and lymphedema is unclear, but may be related to alterations in platelets. Our objective was to analyze the platelet transcriptome to identify biological pathways that may provide insight into platelet activation and thrombosis. The platelet transcriptome was evaluated in patients with lymphedema and lipedema, then compared to control subjects with obesity. Patients with lipedema were found to have a divergent transcriptome from patients with lymphedema. The platelet transcriptome and impacted biological pathways in lipedema were surprisingly similar to weight-matched comparators, yet different when compared to overweight individuals with a lower body mass index (BMI). Differences in the platelet transcriptome for patients with lipedema and lymphedema were found in biological pathways required for protein synthesis and degradation, as well as metabolism. Key differences in the platelet transcriptome for patients with lipedema compared to BMI-matched subjects involved metabolism and glycosaminoglycan processing. These inherent differences in the platelet transcriptome warrant further investigation, and may contribute to the increased risk of thrombosis in patients with lipedema and lymphedema.

Role of Ectopic Olfactory Receptors in the Regulation of the Cardiovascular-Kidney-Metabolic Axis

Olfactory receptors (ORs) represent one of the largest yet least investigated families of G protein-coupled receptors in mammals. While initially believed to be functionally restricted to the detection and integration of odors at the olfactory epithelium, accumulating evidence points to a critical role for ectopically expressed ORs in the regulation of cellular homeostasis in extranasal tissues. This review aims to summarize the current state of knowledge on the expression and physiological functions of ectopic ORs in the cardiovascular system, kidneys, and primary metabolic organs and emphasizes how altered ectopic OR signaling in those tissues may impact cardiovascular-kidney-metabolic health.

Crosstalk of platelets with macrophages and fibroblasts aggravates inflammation, aortic wall stiffening, and osteopontin release in abdominal aortic aneurysm

AIMS

Abdominal aortic aneurysm (AAA) is a highly lethal disease with progressive dilatation of the abdominal aorta accompanied by degradation and remodelling of the vessel wall due to chronic inflammation. Platelets play an important role in cardiovascular diseases, but their role in AAA is poorly understood.

METHODS AND RESULTS

The present study revealed that platelets play a crucial role in promoting AAA through modulation of inflammation and degradation of the extracellular matrix (ECM). They are responsible for the up-regulation of SPP1 (osteopontin, OPN) gene expression in macrophages and aortic tissue, which triggers inflammation and remodelling and also platelet adhesion and migration into the abdominal aortic wall and the intraluminal thrombus (ILT). Further, enhanced platelet activation and pro-coagulant activity result in elevated gene expression of various cytokines, Mmp9 and Col1a1 in macrophages and Il-6 and Mmp9 in fibroblasts. Enhanced platelet activation and pro-coagulant activity were also detected in AAA patients. Further, we detected platelets and OPN in the vessel wall and in the ILT of patients who underwent open repair of AAA. Platelet depletion in experimental murine AAA reduced inflammation and ECM remodelling, with reduced elastin fragmentation and aortic diameter expansion. Of note, OPN co-localized with platelets, suggesting a potential role of OPN for the recruitment of platelets into the ILT and the aortic wall.

CONCLUSION

In conclusion, our data strongly support the potential relevance of anti-platelet therapy to reduce AAA progression and rupture in AAA patients.

Antiplatelet Therapy, Abdominal Aortic Aneurysm Progression, and Clinical Outcomes

Importance

Preclinical studies suggest a potential role for aspirin in slowing abdominal aortic aneurysm (AAA) progression and preventing rupture. Evidence on the clinical benefit of aspirin in AAA from human studies is lacking.

Objective

To investigate the association of aspirin use with aneurysm progression and long-term clinical outcomes in patients with AAA.

Design, Setting, and Participants

This was a retrospective, single-center cohort study. Adult patients with at least 2 available vascular ultrasounds at the Cleveland Clinic were included, and patients with history of aneurysm repair, dissection, or rupture were excluded. All patients were followed up for 10 years. Data were analyzed from May 2022 to July 2023.

Main Outcomes and Measures

Clinical outcomes were time-to-first occurrence of all-cause mortality, major bleeding, or composite of dissection, rupture, and repair. Multivariable-adjusted Cox proportional-hazard regression was used to estimate hazard ratios (HR) for all-cause mortality, and subhazard ratios competing-risk regression using Fine and Gray proportional subhazards regression was used for major bleeding and composite outcome. Aneurysm progression was assessed by comparing the mean annualized change of aneurysm diameter using multivariable-adjusted linear regression and comparing the odds of having rapid progression (annual diameter change >0.5 cm per year) using logistic regression.

Results

A total of 3435 patients (mean [SD] age 73.7 [9.0] years; 2672 male patients [77.5%]; 120 Asian, Hispanic, American Indian, or Pacific Islander patients [3.4%]; 255 Black patients [7.4%]; 3060 White patients [89.0%]; and median [IQR] follow-up, 4.9 [2.5-7.5] years) were included in the final analyses, of which 2150 (63%) were verified to be taking aspirin by prescription. Patients taking aspirin had a slower mean (SD) annualized change in aneurysm diameter (2.8 [3.0] vs 3.8 [4.2] mm per year; P = .001) and lower odds of having rapid aneurysm progression compared with patients not taking aspirin (adjusted odds ratio, 0.64; 95% CI, 0.49-0.89; P = .002). Aspirin use was not associated with risk of all-cause mortality (adjusted HR [aHR], 0.92; 95% CI, 0.79-1.07; P = .32), nor was aspirin use associated with major bleeding (aHR, 0.88; 95% CI, 0.76-1.03; P = .12), or composite outcome (aHR, 1.16; 95% CI, 0.93-1.45; P = .09) at 10 years.

Conclusions

In this retrospective study of a clinical cohort of 3435 patients with objectively measured changes in aortic aneurysm growth, aspirin use was significantly associated with slower progression of AAA with a favorable safety profile.

Impact of Genetic Variations on Thromboembolic Risk in Saudis with Sickle Cell Disease

BACKGROUND

Sickle cell disease (SCD) is a Mendelian disease characterized by multigenic phenotypes. Previous reports indicated a higher rate of thromboembolic events (TEEs) in SCD patients. A number of candidate polymorphisms in certain genes (e.g., FVL, PRT, and MTHFR) were previously reported as risk factors for TEEs in different clinical conditions. This study aimed to genotype these genes and other loci predicted to underlie TEEs in SCD patients.

METHODOLOGY

A multi-center genome-wide association study (GWAS) involving Saudi SCD adult patients with a history of TEEs (n = 65) and control patients without TEE history (n = 285) was performed. Genotyping used the 10× Affymetrix Axiom array, which includes 683,030 markers. Fisher's exact test was used to generate p-values of TEE associations with each single-nucleotide polymorphism (SNP). The haplotype analysis software tool version 1.05, designed by the University of Göttingen, Germany, was used to identify the common inherited haplotypes.

RESULTS

No association was identified between the targeted single-nucleotide polymorphism rs1801133 in MTHFR and TEEs in SCD (p = 0.79). The allele frequency of rs6025 in FVL and rs1799963 in PRT in our cohort was extremely low (<0.01); thus, both variants were excluded from the analysis as no meaningful comparison was possible. In contrast, the GWAS analysis showed novel genome-wide associations (p < 5 × 10-8) with seven signals; five of them were located on Chr 11 (rs35390334, rs331532, rs317777, rs147062602, and rs372091), one SNP on Chr 20 (rs139341092), and another on Chr 9 (rs76076035). The other 34 SNPs located on known genes were also detected at a signal threshold of p < 5 × 10-6. Seven of the identified variants are located in olfactory receptor family 51 genes (OR51B5, OR51V1, OR51A1P, and OR51E2), and five variants were related to family 52 genes (OR52A5, OR52K1, OR52K2, and OR52T1P). The previously reported association between rs5006884-A in OR51B5 and fetal hemoglobin (HbF) levels was confirmed in our study, which showed significantly lower levels of HbF (p = 0.002) and less allele frequency (p = 0.003) in the TEE cases than in the controls. The assessment of the haplotype inheritance pattern involved the top ten significant markers with no LD (rs353988334, rs317777, rs14788626882, rs49188823, rs139349992, rs76076035, rs73395847, rs1368823, rs8888834548, and rs1455957). A haplotype analysis revealed significant associations between two haplotypes (a risk, TT-AA-del-AA-ins-CT-TT-CC-CC-AA, and a reverse protective, CC-GG-ins-GG-del-TT-CC-TT-GG-GG) and TEEs in SCD (p = 0.024, OR = 6.16, CI = 1.34-28.24, and p = 0.019, OR = 0.33, CI = 0.13-0.85, respectively).

CONCLUSIONS

Seven markers showed novel genome-wide associations; two of them were exonic variants (rs317777 in OLFM5P and rs147062602 in OR51B5), and less significant associations (p < 5 × 10-6) were identified for 34 other variants in known genes with TEEs in SCD. Moreover, two 10-SNP common haplotypes were determined with contradictory effects. Further replication of these findings is needed.

Characterization of small abdominal aortic aneurysms' growth status using spatial pattern analysis of aneurismal hemodynamics

Aneurysm hemodynamics is known for its crucial role in the natural history of abdominal aortic aneurysms (AAA). However, there is a lack of well-developed quantitative assessments for disturbed aneurysmal flow. Therefore, we aimed to develop innovative metrics for quantifying disturbed aneurysm hemodynamics and evaluate their effectiveness in predicting the growth status of AAAs, specifically distinguishing between fast-growing and slowly-growing aneurysms. The growth status of aneurysms was classified as fast (≥ 5 mm/year) or slow (< 5 mm/year) based on serial imaging over time. We conducted computational fluid dynamics (CFD) simulations on 70 patients with computed tomography (CT) angiography findings. By converting hemodynamics data (wall shear stress and velocity) located on unstructured meshes into image-like data, we enabled spatial pattern analysis using Radiomics methods, referred to as "Hemodynamics-informatics" (i.e., using informatics techniques to analyze hemodynamic data). Our best model achieved an AUROC of 0.93 and an accuracy of 87.83%, correctly identifying 82.00% of fast-growing and 90.75% of slowly-growing AAAs. Compared with six classification methods, the models incorporating hemodynamics-informatics exhibited an average improvement of 8.40% in AUROC and 7.95% in total accuracy. These preliminary results indicate that hemodynamics-informatics correlates with AAAs' growth status and aids in assessing their progression.

Thrombosis in the pathogenesis of abdominal aortic aneurysm

Background

Abdominal aortic aneurysms (AAAs) are a relatively common vascular pathology of the elderly with high morbidity potential. Irreversible degeneration of the aortic wall leads to lethal rupture if left untreated. Nearly all AAAs contain intraluminal thrombus (ILT) to a varying degree, yet the mechanisms explaining how thrombosis is disturbed in AAA are relatively unknown. This review examined the thrombotic complications associated with AAA, the impact of thrombosis on AAA surgical outcomes and AAA pathogenesis, and the use of antithrombotic therapy in the management of this disease.

Methods

A literature search of the PubMed database was conducted using relevant keywords related to thrombosis and AAAs.

Results

Thrombotic complications are relatively infrequent in AAA yet carry significant morbidity risks. The ILT can impact endovascular aneurysm repair by limiting anatomic suitability and influence the risk of endoleaks. Many of the pathologic mechanisms involved in AAA development, including hemodynamics, inflammation, oxidative stress, and aortic wall remodeling, contain pathways that interact with thrombosis. Conversely, the ILT can also be a source of biochemical stress and exacerbate these aneurysmal processes. In animal AAA models, antithrombotic therapies have shown favorable results in preventing and stabilizing AAA. Antiplatelet agents may be beneficial for reducing risks of major adverse cardiovascular events in AAA patients; however, neither antiplatelet nor anticoagulation is currently used solely for the management of AAA.

Conclusions

Thrombosis and ILT may have detrimental effects on AAA growth, rupture risk, and patient outcomes, yet there is limited understanding of the pathologic thrombotic mechanisms in aneurysmal disease at the molecular level. Preventing ILT using platelet and coagulation inhibitors may be a reasonable theoretical target for aneurysm progression and stability; however, the practical benefits of current antithrombotic therapies in AAA are unclear. Further research is needed to demonstrate the extent to which thrombosis impacts AAA pathogenesis and to develop novel pharmacologic strategies for the medical management of this disease.

Platelets at the Vessel Wall in Non-Thrombotic Disease

Platelets are small, anucleate entities that bud from megakaryocytes in the bone marrow. Among circulating cells, platelets are the most abundant cell, traditionally involved in regulating the balance between thrombosis (the terminal event of platelet activation) and hemostasis (a protective response to tissue injury). Although platelets lack the precise cellular control offered by nucleate cells, they are in fact very dynamic cells, enriched in preformed RNA that allows them the capability of de novo protein synthesis which alters the platelet phenotype and responses in physiological and pathological events. Antiplatelet medications have significantly reduced the morbidity and mortality for patients afflicted with thrombotic diseases, including stroke and myocardial infarction. However, it has become apparent in the last few years that platelets play a critical role beyond thrombosis and hemostasis. For example, platelet-derived proteins by constitutive and regulated exocytosis can be found in the plasma and may educate distant tissue including blood vessels. First, platelets are enriched in inflammatory and anti-inflammatory molecules that may regulate vascular remodeling. Second, platelet-derived microparticles released into the circulation can be acquired by vascular endothelial cells through the process of endocytosis. Third, platelets are highly enriched in mitochondria that may contribute to the local reactive oxygen species pool and remodel phospholipids in the plasma membrane of blood vessels. Lastly, platelets are enriched in proteins and phosphoproteins which can be secreted independent of stimulation by surface receptor agonists in conditions of disturbed blood flow. This so-called biomechanical platelet activation occurs in regions of pathologically narrowed (atherosclerotic) or dilated (aneurysmal) vessels. Emerging evidence suggests platelets may regulate the process of angiogenesis and blood flow to tumors as well as education of distant organs for the purposes of allograft health following transplantation. This review will illustrate the potential of platelets to remodel blood vessels in various diseases with a focus on the aforementioned mechanisms.

The role of long non-coding RNA in abdominal aortic aneurysm

The abdominal aortic aneurysm (AAA) is characterized by segmental expansion of the abdominal aorta and a high mortality rate. The characteristics of AAA suggest that apoptosis of smooth muscle cells, the production of reactive oxygen species, and inflammation are potential pathways for the formation and development of AAA. Long non-coding RNA (lncRNA) is becoming a new and essential regulator of gene expression. Researchers and physicians are focusing on these lncRNAs to use them as clinical biomarkers and new treatment targets for AAAs. LncRNA studies are beginning to emerge, suggesting that they may play a significant but yet unidentified role in vascular physiology and disease. This review examines the role of lncRNA and their target genes in AAA to increase our understanding of the disease’s onset and progression, which is crucial for developing potential AAA therapies.

Platelet function changes in patients undergoing endovascular aortic aneurysm repair: Review of the literature

Patients with abdominal aortic aneurysm (AAA) have a higher risk of cardiovascular (CV) events, which seems to be associated with disturbed platelet (PLT) function. Endovascular aneurysm repair (EVAR) is an emerging, less-invasive treatment alternative to surgical AAA repair. Both platelet function abnormalities in patients with AAA and the effect of EVAR on platelet function are poorly understood. In this review, we aim to fill the gap regarding the effect of EVAR on PLT function in AAA patients by discussing PLT function disturbances in patients with AAA, PLT function changes after EVAR, evidence from clinical studies regarding PLT function before and after EVAR, and antiplatelet or and antithrombotic treatment in patients undergoing EVAR. The goal of our review is to summarize the contemporary knowledge and initiate further studies to better understand PLT function changes in patients undergoing EVAR, optimize the pharmacotherapy before and after EVAR and further improve outcomes in this group of patients.

The Detrimental Role of Intraluminal Thrombus Outweighs Protective Advantage in Abdominal Aortic Aneurysm Pathogenesis: The Implications for the Anti-Platelet Therapy

Abdominal aortic aneurysm (AAA) is a common cardiovascular disease resulting in morbidity and mortality in older adults due to rupture. Currently, AAA treatment relies entirely on invasive surgical treatments, including open repair and endovascular, which carry risks for small aneurysms (diameter < 55 mm). There is an increasing need for the development of pharmacological intervention for early AAA. Over the last decade, it has been increasingly recognized that intraluminal thrombus (ILT) is involved in the growth, remodeling, and rupture of AAA. ILT has been described as having both biomechanically protective and biochemically destructive properties. Platelets are the second most abundant cells in blood circulation and play an integral role in the formation, expansion, and proteolytic activity of ILT. However, the role of platelets in the ILT-potentiated AAA progression/rupture remains unclear. Researchers are seeking pharmaceutical treatment strategies (e.g., anti-thrombotic/anti-platelet therapies) to prevent ILT formation or expansion in early AAA. In this review, we mainly focus on the following: (a) the formation/deposition of ILT in the progression of AAA; (b) the dual role of ILT in the progression of AAA (protective or detrimental); (c) the function of platelet activity in ILT formation; (d) the application of anti-platelet drugs in AAA. Herein, we present challenges and future work, which may motivate researchers to better explain the potential role of ILT in the pathogenesis of AAA and develop anti-platelet drugs for early AAA.