Proteomic profiling of circulating β-thalassaemia/haemoglobin E extra-cellular vesicles reveals that association with immunoglobulin induces membrane vesiculation

Splenectomised β-thalassaemia/haemoglobin E (HbE) patients have increased levels of circulating microparticles or medium extra-cellular vesicles (mEVs). The splenectomised mEVs play important roles in thromboembolic complications in patients since they can induce platelet activation and endothelial cell dysfunction. However, a comprehensive understanding of the mechanism of mEV generation in thalassaemia disease has still not been reached. Thalassaemic mEVs are hypothesised to be generated from cellular oxidative stress in red blood cells (RBCs) and platelets. Therefore, a proteomic analysis of mEVs from splenectomised and non-splenectomised β-thalassaemia/HbE patients was performed by liquid chromatography with tandem mass spectrometry. A total of 171 proteins were identified among mEVs. Interestingly, 72 proteins were uniquely found in splenectomised mEVs including immunoglobulin subunits and cytoskeleton proteins. Immunoglobulin G (IgG)-bearing mEVs in splenectomised patients were significantly increased. Furthermore, complement C1q was detected in both mEVs with IgG binding and mEVs without IgG binding. Interestingly, the percentage of mEVs generated from RBCs with IgG binding was approximately 15-20 times higher than the percentage of RBCs binding with IgG. This suggested that the vesiculation of thalassaemia mEVs could be a mechanism of RBCs to eliminate membrane patches harbouring immune complex and may consequently prevent cells from phagocytosis and lysis.

Increased small extracellular vesicle levels and decreased miR-126 levels associated with atrial fibrillation and coexisting diabetes mellitus

BACKGROUND

Atrial fibrillation (AF) is the most prevalent cardiac arrhythmia. Diabetes mellitus (DM) is one of the risk factors for the development of stroke and thromboembolism in patients with AF. Early identification may reduce the incidence of complications and mortality in AF patients.

HYPOTHESIS

AF patients with DM have different pattern of small extracellular vesicle (sEV) levels and sEV-derived microRNA (miRNA) expression compared with those without DM.

METHODS

We compared sEV levels and sEV-miRNA expression in plasma from AF patients with and without DM using nanoparticle tracking analysis and droplet digital polymerase chain reaction, respectively.

RESULTS

We observed a significant increase in total sEV levels (p = .004) and a significant decrease in sEV-miR-126 level (p = .004) in AF patients with DM. Multivariate logistic regression analysis revealed a positive association between total sEV levels and AF with DM (p = .019), and a negative association between sEV-miR-126 level and AF with DM (p = .031). The combination of clinical data, total sEVs, and sEV-miR-126 level had an area under the curve of 0.968 (p < .0001) for discriminating AF with DM, which was shown to be significantly better than clinical data analysis alone (p = .0368).

CONCLUSIONS

These results suggest that an increased level of total sEV and a decreased sEV-miR-126 level may play a potential role in the pathophysiology and complications of AF with DM, especially endothelial dysfunction, and can be considered as an applied biomarker for distinguishing between AF with and without DM.

Increased expression of six-large extracellular vesicle-derived miRNAs signature for nonvalvular atrial fibrillation

Backgrounds

Non-valvular atrial fibrillation (AF) is the most common type of cardiac arrhythmia. AF is caused by electrophysiological abnormalities and alteration of atrial tissues, which leads to the generation of abnormal electrical impulses. Extracellular vesicles (EVs) are membrane-bound vesicles released by all cell types. Large EVs (lEVs) are secreted by the outward budding of the plasma membrane during cell activation or cell stress. lEVs are thought to act as vehicles for miRNAs to modulate cardiovascular function, and to be involved in the pathophysiology of cardiovascular diseases (CVDs), including AF. This study identified lEV-miRNAs that were differentially expressed between AF patients and non-AF controls.

Methods

lEVs were isolated by differential centrifugation and characterized by Nanoparticle Tracking Analysis (NTA), Transmission Electron Microscopy (TEM), flow cytometry and Western blot analysis. For the discovery phase, 12 AF patients and 12 non-AF controls were enrolled to determine lEV-miRNA profile using quantitative reverse transcription polymerase chain reaction array. The candidate miRNAs were confirmed their expression in a validation cohort using droplet digital PCR (30 AF, 30 controls). Bioinformatics analysis was used to predict their target genes and functional pathways.

Results

TEM, NTA and flow cytometry demonstrated that lEVs presented as cup shape vesicles with a size ranging from 100 to 1000 nm. AF patients had significantly higher levels of lEVs at the size of 101–200 nm than non-AF controls. Western blot analysis was used to confirm EV markers and showed the high level of cardiomyocyte expression (Caveolin-3) in lEVs from AF patients. Nineteen miRNAs were significantly higher (> twofold, p < 0.05) in AF patients compared to non-AF controls. Six highly expressed miRNAs (miR-106b-3p, miR-590-5p, miR-339-3p, miR-378-3p, miR-328-3p, and miR-532-3p) were selected to confirm their expression. Logistic regression analysis showed that increases in the levels of these 6 highly expressed miRNAs associated with AF. The possible functional roles of these lEV-miRNAs may involve in arrhythmogenesis, cell apoptosis, cell proliferation, oxygen hemostasis, and structural remodeling in AF.

Conclusion

Increased expression of six lEV-miRNAs reflects the pathophysiology of AF that may provide fundamental knowledge to develop the novel biomarkers for diagnosis or monitoring the patients with the high risk of AF.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12967-021-03213-6.

Extracellular vesicles from thalassemia patients carry iron-containing ferritin and hemichrome that promote cardiac cell proliferation

Extracellular vesicles (EVs) are bioactive, submicron-sized membrane vesicles released from all cell types upon activation or apoptosis. EVs including microparticles (MPs) and exosomes have emerged as important mediators of cell-to-cell communication in both normal and pathological states including thalassemia (thal). However, the role of EVs derived from β-thal patients with iron overload (+ IO) and without iron overload (-IO) on cardiac cells is unclear. We hypothesized plasma EVs in thal patients containing ferritin (iron storage protein) and a denaturated hemoglobin-hemichrome that induce cardiac cell proliferation. The origins and numbers of EVs isolated from plasma of normal, thal (+ IO), and (- IO) patients were compared and determined for their iron and iron-containing proteins along with their effects on cardiac and endothelial cells. Data shows that MPs were originated from many cell sources with marked numbers of platelet origin. Only the number of RBC-derived MPs in thal (+ IO) patients was significantly high when compared to normal controls. Although MPs derived from both normal and thal patients promoted cardiac cell proliferation in a dose-dependent manner, only exosomes from thal patients promoted cardiac cell proliferation compared to the untreated. Moreover, the exosomes from thal (+ IO) potentially induce higher cardiac cell proliferation and angiogenesis in terms of tube number than thal (- IO) and normal controls. Interestingly, ferritin content in the exosomes isolated from thal (+ IO) was higher than that found in the MPs isolated from the same patient. The exosomes of thal patients with higher serum ferritin level also contained greater level of ferritin inside the exosomes. Apart from ferritin, there were trends of increasing hemichrome and iron presented in the plasma EVs and EV-treated H9C2 cells. Findings from this study support the hypothesis that EVs from β-thal patients carry iron-load proteins that leads to the induction of cardiac cell proliferation.

Enumeration and phenotyping of circulating microvesicles by flow cytometry and nanoparticle tracking analysis: Plasma versus serum

INTRODUCTION

Microvesicles (MVs) are bioactive, submicron-sized (0.01-1000 nm) membrane vesicles released from various types of cells under normal physiological and pathophysiological conditions. MVs have emerged as important mediators of cell-to-cell communication in a diverse range of normal and pathological processes. MVs have been recognized as potential biomarkers in coagulation, inflammation, and cancer. However, for clinical use, minimizing factors which could affect enumeration and phenotypic characterization of MVs during pre-analytical steps is crucial. In this study, we used flow cytometry and nanoparticle tracking analysis (NTA) to investigate the impact of blood collection using with and without anticoagulant on the number and phenotype of MVs in blood samples.

METHODS

Blood from 30 healthy volunteers was collected by venipuncture into 3.2% sodium citrate and clot activator tubes. MV subpopulations and their concentrations were investigated using flow cytometry and NTA. MV morphology was examined by transmission electron microscopy.

RESULTS

Results showed that the concentration of MVs was significantly lower in serum than in plasma and that CD41⁺ MV, CD41⁺ /CD62P⁺ MV, CD45⁺ MV, and CD142⁺ MV levels from serum were significantly lower than those from plasma, whereas no significant differences in Annexin V (Anx V)⁺ MV, CD235a⁺ MV, and CD144⁺ MV levels were found. Interestingly, serum MVs had a higher proportion of small-sized MVs and lower proportion of large-sized MVs than did plasma MVs.

CONCLUSION

Although plasma samples are commonly used, our results suggest that serum can also be used in enumeration of MVs, but care must be taken if coagulation is an aspect of the research.

Altered profile of circulating microparticles in nonvalvular atrial fibrillation

Background

Nonvalvular atrial fibrillation (AF) is the most common cardiac arrhythmia, and it is associated with the prothrombotic state. Circulating microparticles (cMPs) are membrane vesicles that are shed from many cell types in response to cell activation and cell apoptosis. Several studies reported that cMPs may play a role in the hypercoagulable state that can be observed in patients with AF. The aim of this study was to determine the levels of total cMPs and characterize their cellular origins in AF patients.

Methods

Atotal of 66 AF patients and 33 healthy controls were enrolled. This study investigated total cMP levels and their cellular origin in AF patients using polychromatic flow cytometry.

Results

AF patients had significantly higher levels of total cMPs (median 36.38, interquartile range [IQR] 21.16‐68.50 × 10⁵ counts/mL vs median 15.21, IQR 9.91‐30.86 × 10⁵ counts/mL; P = 0.004), platelet‐derived MPs (PMPs) (median 10.61, IQR 6.55‐18.04 × 10⁵ counts/mL vs median 7.83, IQR 4.44‐10.26 × 10/mL; P = 0.009), and endothelial‐derived MPs (EMPs CD31+ CD41−) (median 2.94, IQR 1.78‐0.60 × 10⁵ counts/mL vs median 1.16, IQR 0.71‐2.30 × 10⁵ counts/mL; P = 0.001) than healthy controls after adjusting for potential confounders. Phosphatidylserine positive MP (PS + MP) levels were similar compared between AF patients and healthy controls.

Conclusion

The results of this study revealed a marked increase in total cMP levels, and evidence of elevated endothelial damage and platelet activation, as demonstrated by increased PMP and EMP levels, in AF patients. Additional study is needed to further elucidate the role of cMPs (PMPs and EMPs) in the pathophysiology of and the complications associated with AF.