Platelet Aggregometry Testing: Molecular Mechanisms, Techniques and Clinical Implications

Physiological platelet aggregation assay to mitigate drug-induced thrombocytopenia using a microphysiological system

Developing a reliable method to predict thrombocytopenia is imperative in drug discovery. Here, we establish an assay using a microphysiological system (MPS) to recapitulate the in-vivo mechanisms of platelet aggregation and adhesion. This assay highlights the role of shear stress on platelet aggregation and their interactions with vascular endothelial cells. Platelet aggregation induced by soluble collagen was detected under agitated, but not static, conditions using a plate shaker and gravity-driven flow using MPS. Notably, aggregates adhered on vascular endothelial cells under gravity-driven flow in the MPS, and this incident increased in a concentration-dependent manner. Upon comparing the soluble collagen-induced aggregation activity in platelet-rich plasma (PRP) and whole blood, remarkable platelet aggregate formation was observed at concentrations of 30 µg/mL and 3 µg/mL in PRP and whole blood, respectively. Moreover, ODN2395, an oligonucleotide, induced platelet aggregation and adhesion to vascular endothelial cells. SYK inhibition, which mediated thrombogenic activity via glycoprotein VI on platelets, ameliorated platelet aggregation in the system, demonstrating that the mechanism of platelet aggregation was induced by soluble collagen and oligonucleotide. Our evaluation system partially recapitulated the aggregation mechanisms in blood vessels and can contribute to the discovery of safe drugs to mitigate the risk of thrombocytopenia.

Advances in Platelet-Dysfunction Diagnostic Technologies

The crucial role of platelets in hemostasis and their broad implications under various physiological conditions underscore the importance of accurate platelet-function testing. Platelets are key to clotting blood and healing wounds. Therefore, accurate diagnosis and management of platelet disorders are vital for patient care. This review outlines the significant advancements in platelet-function testing technologies, focusing on their working principles and the shift from traditional diagnostic methods to more innovative approaches. These improvements have deepened our understanding of platelet-related disorders and ushered in personalized treatment options. Despite challenges such as interpretation of complex data and the costs of new technologies, the potential for artificial-intelligence integration and the creation of wearable monitoring devices offers exciting future possibilities. This review underscores how these technological advances have enhanced the landscape of precision medicine and provided better diagnostic and treatment options for platelet-function disorders.

Non-clinical investigations about cytotoxic and anti-platelet activities of gamma-terpinene

Gamma-terpinene (γ-TPN) is a cyclohexane monoterpene isolated from plant essential oils, such as tea tree (Melaleuca alternifolia), oregano (Origanum vulgare), rosemary (Rosmarinus officinalis L.), thyme (Thymus vulgaris Marchand), and eucalyptus (Eucalyptus sp.). Terpenes are widely studied molecules pharmacologically active on the cardiovascular system, hemostasis, and antioxidant actions. Herein, it was investigated the cytotoxic and antiplatelet activity of γ-TPN using different non-clinical laboratory models. For in silico evaluation, the PreADMET, SwissADME, and SwissTargetPrediction softwares were used. Molecular docking was performed using the AutoDockVina and BIOVIA Discovery Studio databases. The cytotoxicity of γ-TPN was analyzed by the MTT assay upon normal murine endothelial SVEC4-10 and fibroblast L-929 cells. Platelet aggregation was evaluated with platelet-rich (PRP) and platelet-poor (PPP) plasma from spontaneously hypertensive rats (SHR), in addition to SVEC4-10 cells pre-incubated with γ-TPN (50, 100, and 200 µM) for 24 h. SHR animals were pre-treated by gavage with γ-TPN for 7 days and divided into four groups (negative control, 25, 50, and 100 mg/kg). Blood samples were collected to measure nitrite using the Griess reagent. Gamma-TPN proved to be quite lipid-soluble (Log P = +4.50), with a qualified profile of similarity to the drug, good bioavailability, and adequate pharmacokinetics. It exhibited affinity mainly for the P2Y12 receptor (6.450 ± 0.232 Kcal/mol), moderate cytotoxicity for L-929 (CC50 = 333.3 µM) and SVEC 4-10 (CC50 = 366.7 µM) cells. The presence of γ-TPN in SVEC 4-10 cells was also able to reduce platelet aggregation by 51.57 and 44.20% at lower concentrations (50 and 100 µM, respectively). Then, γ-TPN has good affinity with purinergic receptors and an effect on the reversal of platelet aggregation and oxidative stress, being promising and safe for therapeutic targets and subsequent studies on the control of thromboembolic diseases.

Lipoprotein(a), platelet function and cardiovascular disease

Lipoprotein(a) (Lp(a)) is associated with atherothrombosis through several mechanisms, including putative antifibrinolytic properties. However, genetic association studies have not demonstrated an association between high plasma levels of Lp(a) and the risk of venous thromboembolism, and studies in patients with highly elevated Lp(a) levels have shown that Lp(a) lowering does not modify the clotting properties of plasma ex vivo. Lp(a) can interact with several platelet receptors, providing biological plausibility for a pro-aggregatory effect. Observational clinical studies suggest that elevated plasma Lp(a) concentrations are associated with worse long-term outcomes in patients undergoing revascularization. Furthermore, in these patients, those with elevated plasma Lp(a) levels derive more benefit from prolonged dual antiplatelet therapy than those with normal Lp(a) levels. The ASPREE trial in healthy older individuals treated with aspirin showed a reduction in ischaemic events in those who had a single-nucleotide polymorphism in LPA that is associated with elevated Lp(a) levels in plasma, without an increase in bleeding events. In this Review, we re-examine the role of Lp(a) in the regulation of platelet function and suggest areas of research to define further the clinical relevance to cardiovascular disease of the observed associations between Lp(a) and platelet function.

In vitro Hemostatic Functions of Cold-Stored Platelets

Background

Transfusion of platelets is a life-saving medical strategy used worldwide to treat patients with thrombocytopenia as well as platelet function disorders.

Summary

Until the end of 1960s, platelets were stored in the cold because of their superior hemostatic functionality. Cold storage of platelets was then abandoned due to better posttransfusion recovery and survival of room temperature (RT)-stored platelets, demonstrated by radioactive labeling studies. Based on these findings, RT became the standard condition to store platelets for clinical applications. Evidence shows that RT storage increases the risk of septic transfusion reactions associated with bacterial contamination. Therefore, the storage time is currently limited to 4-7 days, according to the national guidelines, causing a constant challenge to cover the clinical request. Despite the enormous efforts made to optimize storage conditions of platelets, the quality and efficacy of platelets still decrease during the short storage time at RT. In this context, during the last years, cold storage has seen a renaissance due to the better hemostatic functionality, reduced risk of bacterial contamination, and potentially longer storage time.

Key Messages

In this review, we will focus on the impact of cold storage on the in vitro platelet functions as promising alternative storage temperature for future medical applications.

Optimizing antithrombotic therapy in patients with coexisting cardiovascular and gastrointestinal disease

Balancing the safety and efficacy of antithrombotic agents in patients with gastrointestinal disorders is challenging because of the potential for interference with the absorption of antithrombotic drugs and for an increased risk of bleeding. In this Review, we address considerations for enteral antithrombotic therapy in patients with cardiovascular disease and gastrointestinal comorbidities. For those with gastrointestinal bleeding (GIB), we summarize a general scheme for risk stratification and clinical evidence on risk reduction approaches, such as limiting the use of concomitant medications that increase the risk of GIB and the potential utility of gastrointestinal protection strategies (such as proton pump inhibitors or histamine type 2 receptor antagonists). Furthermore, we summarize the best available evidence and potential gaps in our knowledge on tailoring antithrombotic therapy in patients with active or recent GIB and in those at high risk of GIB but without active or recent GIB. Finally, we review the recommendations provided by major medical societies, highlighting the crucial role of teamwork and multidisciplinary discussions to customize the antithrombotic regimen in patients with coexisting cardiovascular and gastrointestinal diseases.

The use of scanning electron microscopy and fixation methods to evaluate the interaction of blood with the surfaces of medical devices

Testing the hemocompatibility of medical devices after their interaction with blood entails the need to evaluate the activation of blood elements and the degree of their coagulation and adhesion to the device surface. One possible way to achieve this is to use scanning electron microscopy (SEM). The aim was to develop a novel SEM-based method to assess the thrombogenic potential of medical devices and their adhesiveness to blood cells. As a part of this task, also find a convenient procedure of efficient and non-destructive sample fixation for SEM while reducing the use of highly toxic substances and shortening the fixation time. A polymeric surgical mesh was exposed to blood so that blood elements adhered to its surface. Such prepared samples were then chemically fixed for a subsequent SEM measurement; a number of fixation procedures were tested to find the optimal one. The fixation results were evaluated from SEM images, and the degree of blood elements' adhesion was determined from the images using ImageJ software. The best fixation was achieved with the May-Grünwald solution, which is less toxic than chemicals traditionally used. Moreover, manipulation with highly toxic osmium tetroxide can be avoided in the proposed procedure. A convenient methodology for SEM image analysis has been developed too, enabling to quantitatively evaluate the interaction of blood with the surfaces of various medical devices. Our method replaces the subjective assessment of surface coverage with a better-defined procedure, thus offering more precise and reliable results.

The protective effect and mechanism of piperazine ferulate in rats with 5/6 nephrectomy-caused chronic kidney disease

Chronic kidney disease (CKD) is a type of chronic disease in which multiple factors are responsible for the structural and functional disorders of the kidney. Piperazine ferulate (PF) has anti-platelet and anti-fibrotic effects, and its mechanism of action remains to be elucidated. This study aimed to investigate the protective effect of PF against CKD in rats and to determine its mechanism of action. Network pharmacology was used to predict potential PF action targets in the treatment of CKD and to further validate them. A rat model of CKD was established; blood was collected, etc., for the assessment of the renal function; renal pathologic damage was examined using hematoxylin and eosin (HE) staining and Masson staining; changes in the levels of TGF-β1 and α-SMA were determined with ELISA; EPOR, FN, and COL I expression were detected utilizing immunohistochemistry; and HIF-1α, HIF-2α, and EPO protein molecules were analyzed deploying western blotting. PF reduces Scr, BUN, and 24 h UP levels; decreases FN and COL I expression; and attenuates renal injury. Additionally, PF inhibited TGF-β1 and stimulated the production of HIF-1α and HIF-2α, which downregulated α-SMA and upregulated EPO. PF attenuated the progression of the CKD pathology, and the mechanism of its action is possibly associated with the promotion of HIF-1α/HIF-2α/EPO production and TGF-β1 reduction.

Modular and tunable alternative surfactants for biopharmaceuticals provide insights into Surfactant's Structure-Function relationship

Surface-induced aggregation of protein therapeutics is opposed by employing surfactants, which are ubiquitously used in drug product development, with polysorbates being the gold standard. Since poloxamer 188 is currently the only generally accepted polysorbate alternative, but cannot be ubiquitously applied, there is a strong need to develop surfactant alternatives for protein biologics that would complement and possibly overcome known drawbacks of existing surfactants. Yet, a severe lack of structure-function relationship knowledge complicates the development of new surfactants. Herein, we perform a systematic analysis of the structure-function relationship of three classes of novel alternative surfactants. Firstly, the mode of action is thoroughly characterized through tensiometry, calorimetry and MD simulations. Secondly, the safety profiles are evaluated through cell-based in vitro assays. Ultimately, we could conclude that the alternative surfactants investigated possess a mode of action and safety profile comparable to polysorbates. Moreover, the biophysical patterns elucidated here can be exploited to precisely tune the features of future surfactant designs.

No impact of polymorphism in the phosphodiesterase 5A gene in Cavalier King Charles Spaniels on pimobendan-induced inhibition of platelet aggregation response

BACKGROUND

A variant in the canine phosphodiesterase (PDE) 5A gene (PDE5A:E90K) is associated with decreased concentrations of circulating cyclic guanosine monophosphate (cGMP) and response to PDE5 inhibitor treatment. Pimobendan is a PDE inhibitor recommended for medical treatment of certain stages of myxomatous mitral valve disease (MMVD) in dogs.

HYPOTHESIS

PDE5A:E90K polymorphism attenuates the inhibitory effect of pimobendan on in vitro platelet aggregation and increases basal platelet aggregation in Cavalier King Charles Spaniels (CKCS). Selected clinical variables (MMVD severity, sex, age, hematocrit, platelet count in platelet-rich plasma [PRP], and echocardiographic left ventricular fractional shortening [LV FS]) will not show an association with results.

ANIMALS

Fifty-two privately owned CKCS with no or preclinical MMVD.

METHODS

Using blood samples, we prospectively assessed PDE5A genotype using Sanger sequencing and adenosine diphosphate-induced platelet aggregation response (area under the curve [AUC], maximal aggregation [MaxA], and velocity [Vel]) with and without pimobendan using light transmission aggregometry. Dogs also underwent echocardiography.

RESULTS

Pimobendan inhibited platelet function as measured by AUC, MaxA, and Vel at a concentration of 10 μM (P < .0001) and Vel at 0.03 μM (P < .001). PDE5A:E90K polymorphism did not influence the inhibitory effect of pimobendan or basal platelet aggregation response.

CONCLUSIONS AND CLINICAL IMPORTANCE

The PDE5A:E90K polymorphism did not influence in vitro basal platelet aggregation response or the inhibitory effect of pimobendan on platelet aggregation in CKCS. Dogs with the PDE5A:E90K polymorphism did not appear to have altered platelet function or response to pimobendan treatment.

Management of Microvascular Bleeding after On-Pump Cardiac Surgery in a Patient with Perioperative Diagnosis of Impairment of Platelet Responses to Adenosine Diphosphate: A Case Report and a Literature Review

BACKGROUND

Impairment of platelet responses to adenosine diphosphate (ADP) is typified by mild to severe bleeding diathesis, easy bruising, excessive mucosal and post-operative bleeding. Patients lack full platelet activation and aggregation in response to ADP. Following research of the literature in Scopus, PubMed/MEDLINE, ScienceDirect, and the Cochrane Library, we report only 18 patients described to date with impaired platelet response to ADP, none of whom in the high bleeding-risk surgical setting or exploring potential therapeutic options. Data regarding population, putative genetic mutations, modes of inheritance, functional defects, and related clinical manifestations were retrieved from case series and case reports.

CASE PRESENTATION

A 40-year-old woman was scheduled for on-pump cardiac surgery. Her past medical history included episodes of spontaneous mucocutaneous hemorrhages of the mild entity since childhood. Multiple electrode aggregometry (MEA, Multiplate® Roche Diagnostics, Rotkreuz, Switzerland) was used to evaluate platelet response to thrombin-activated peptide-6 (TRAP), arachidonic acid (ASPI), and ADP. An inadequate platelet aggregation induced using a high concentration of ADP with normal TRAP and ASPI tests was detected preoperatively. Therefore, intravenous desmopressin (DVVAP) 0.3 μg/kg body weight was administered to manage microvascular bleeding developed after weaning from cardiopulmonary bypass (CPB).

CONCLUSIONS

Proper management of impaired platelet response to ADP requires a systematic assessment. The Multiplate analyzer is a valuable tool to promptly detect the disorder when a high clinical suspect is present and obtain insights during high bleeding-risk surgical procedures. DVVAP can be beneficial as first-line therapy in bleeding patients to improve platelet function.

Platelet Function Testing: Update and Future Directions

Platelets play a key role in maintaining normal hemostasis and are also recognized as partners in the development of arterial thrombosis. Today, platelet function testing is used for very different clinical purposes; first, for investigation of platelet dysfunction in acute bleeding and diagnosis of platelet disorders in patients with long-lasting bleeding tendency, and second, for testing the efficacy of antiplatelet therapy in patients with increased thromboembolic risk. Moreover, it has been discussed whether platelet function testing can be used for prediction of bleeding risk (e.g., prior to major surgery). Ever since light transmission aggregometry was introduced, laboratories around the world have worked on testing platelet function, and during the last decades a wide range of new methods has emerged. Besides the clinical utility of platelet function testing, the present review summarizes the test principles and advantages and disadvantages of the different methods, depending on the purpose for which it is to be used. A critical step in investigation of platelet function is the preanalytical factors that can substantially affect test results. Therefore, this review also provides an overview of preanalytical variables that range from patient-related factors such as smoking, coffee, and exercise prior to blood sampling to selection of anticoagulant, needle gauge, and time from blood sampling to analyses. Finally, this review outlines further perspectives on platelet function testing for clinical practice and for research purposes.

Individualized or Uniform De-Escalation Strategies for Antiplatelet Therapy in Acute Coronary Syndrome: A Review of Clinical Trials with Platelet Function Testing and Genetic Testing-Based Protocols

This comprehensive literature review assessed the effectiveness of precision medicine approaches in individualizing P2Y12 de-escalation strategies, such as platelet function testing guidance, genetic testing guidance, and uniform de-escalation, for acute coronary syndrome (ACS) patients undergoing percutaneous coronary intervention (PCI). Analyzing six trials with a total of 13,729 patients, the cumulative analyses demonstrated a significant reduction in major adverse cardiac events (MACE), net adverse clinical events (NACE), and major and minor bleeding events with P2Y12 de-escalation. Specifically, the analysis found a 24% reduction of MACE and a 22% reduction of adverse event risk (relative risk (RR) 0.76, 95% confidence interval (CI): 0.71-0.82, and RR: 0.78, 95% CI 0.67-0.92, respectively). Reductions in bleeding events were highest with uniform unguided de-escalation, followed by guided de-escalations, while ischemic event rates were similarly lower across all three strategies. Although the review highlights the potential of individualized P2Y12 de-escalation strategies to offer a safer alternative to the long-term potent P2Y12 inhibitor-based dual antiplatelet therapy, it also indicates that laboratory-guided precision medicine approaches may not yet offer the expected benefits, necessitating further research to optimize individualized strategies and evaluate the potential of precision medicine approaches in this context.

Platelet Activation and Aggregation Induced by Streptococcus bovis/Streptococcus equinus Complex

Streptococcus bovis/Streptococcus equinus complex (SBSEC) is a common cause of infective endocarditis (IE). For IE-pathogens, the capacity to activate and aggregate platelets is believed to be an important virulence mechanism. While the interactions between bacteria and platelets have been described in detail for many Gram-positive pathogens, little research has been carried out with SBSEC in this respect. Twenty-six isolates of the four most common species and subspecies of SBSEC identified in bacteremia were collected, and interactions with platelets were investigated in platelet rich plasma (PRP) from three donors. Aggregation was studied using light-transmission aggregometry and platelet activation using flow cytometry detecting surface upregulation of CD62P. Platelets and serum were treated with different inhibitors to determine mechanisms involved in platelet aggregation and activation. Twenty-two of 26 isolates induced aggregation in at least one donor, and four isolates induced aggregation in all three donors. In PRP from donor 1, isolate SL1 induced a rapid aggregation with a median time of 70 s to reach 50% aggregation. Blockade of the platelet Fc-receptor or enzymatic cleavage of IgG abolished platelet activation and aggregation. The capacity for bacteria-induced platelet aggregation was also shown to be transferable between donors through serum. SBSEC mediates platelet aggregation in an IgG and IgG-Fc-receptor dependent manner. Bacterial activation of platelets through this pathway is common for many bacteria causing IE and could be a potential therapeutic target for the prevention and treatment of this infection. IMPORTANCE The capacity of bacteria to activate and aggregate platelets is believed to contribute to the pathogenesis of IE. The Streptococcus bovis/Streptococcus equinus complex (SBSEC) contains known IE-pathogens, but there is limited research on the different subspecies ability to interact with platelets and what signaling pathways are involved. This study reports that 22 of 26 tested isolates of different subspecies within SBSEC can induce aggregation, and that aggregation is host dependent. The Fc-IgG-receptor pathway was shown essential for platelet activation and aggregation. To the best of our knowledge, this is the first study that reports on platelet interactions of SBSEC-isolates other than Streptococcus gallolyticus subspecies gallolyticus as well as the first study to report of mechanisms of platelet interaction of SBSEC-isolates. It adds SBSEC to a group of bacteria that activate and aggregate platelets via the platelet Fc-receptor. This could be a potential therapeutic target for prevention of IE.

Dose-Dependent Von Willebrand Factor Inhibition by Aptamer BB-031 Correlates with Thrombolysis in a Microfluidic Model of Arterial Occlusion

Von Willebrand Factor (VWF) plays a critical role in thrombus formation, stabilization, and propagation. Previous studies have demonstrated that targeted inhibition of VWF induces thrombolysis when administered in vivo in animal models of ischemic stroke. The study objective was to quantify dose-dependent inhibition of VWF-platelet function and its relationship with thrombolysis using BB-031, an aptamer that binds VWF and inhibits its function. VWF:Ac, VWF:RCo, T-TAS, and ristocetin-induced impedance aggregometry were used to assess BB-031-mediated inhibition of VWF. Reductions in original thrombus surface area and new deposition during administration of treatment were measured in a microfluidic model of arterial thrombolysis. Rotational thromboelastometry was used to assess changes in hemostasis. BB-031 induced maximal inhibition at the highest dose (3384 nM) in VWF:Ac, and demonstrated dose-dependent responses in all other assays. BB-031, but not vehicle, induced recanalization in the microfluidic model. Maximal lytic efficacy in the microfluidic model was seen at 1692 nM and not 3384 nM BB-031 when assessed by surface area. Minor changes in ROTEM parameters were seen at 3384 nM BB-031. Targeted VWF inhibition by BB-031 results in clinically measurable impairment of VWF function, and specifically VWF-GPIb function as measured by VWF:Ac. BB-031 also induced thrombolysis as measured in a microfluidic model of occlusion and reperfusion. Moderate correlation between inhibition and lysis was observed. Additional studies are required to further examine off-target effects of BB-031 at high doses, however, these are expected to be above the range of clinical targeted dosing.

Platelet-Inspired Intravenous Nanomedicine for Injury-Targeted Direct Delivery of Thrombin to Augment Hemostasis in Coagulopathies

Severe hemorrhage associated with trauma, surgery, and congenital or drug-induced coagulopathies can be life-threatening and requires rapid hemostatic management via topical, intracavitary, or intravenous routes. For injuries that are not easily accessible externally, intravenous hemostatic approaches are needed. The clinical gold standard for this is transfusion of blood products, but due to donor dependence, specialized storage requirements, high risk of contamination, and short shelf life, blood product use faces significant challenges. Consequently, recent research efforts are being focused on designing biosynthetic intravenous hemostats, using intravenous nanoparticles and polymer systems. Here we report on the design and evaluation of thrombin-loaded injury-site-targeted lipid nanoparticles (t-TLNPs) that can specifically localize at an injury site via platelet-mimetic anchorage to the von Willebrand factor (vWF) and collagen and directly release thrombin via diffusion and phospholipase-triggered particle destabilization, which can locally augment fibrin generation from fibrinogen for hemostatic action. We evaluated t-TLNPs in vitro in human blood and plasma, where hemostatic defects were created by platelet depletion and anticoagulation. Spectrophotometric studies of fibrin generation, rotational thromboelastometry (ROTEM)-based studies of clot viscoelasticity, and BioFlux-based real-time imaging of fibrin generation under simulated vascular flow conditions confirmed that t-TLNPs can restore fibrin in hemostatic dysfunction settings. Finally, the in vivo feasibility of t-TLNPs was tested by prophylactic administration in a tail-clip model and emergency administration in a liver-laceration model in mice with induced hemostatic defects. Treatment with t-TLNPs was able to significantly reduce bleeding in both models. Our studies demonstrate an intravenous nanomedicine approach for injury-site-targeted direct delivery of thrombin to augment hemostasis.

Independent association of PCSK9 with platelet reactivity in subjects without statin or antiplatelet agents

Background and aims

Proprotein convertase subtilisin/kexin type 9 (PCSK9) levels could predict cardiovascular event in patients with well-controlled LDL-C levels, suggesting an LDL-independent mechanism of PCSK9 on the cardiovascular system. Accumulating evidence suggests PCSK9 might be associated with increased platelet reactivity. This study aimed to assess the relationship between PCSK9 levels and platelet reactivity in subjects not taking statins or antiplatelet agents.

Methods

A cross-sectional study was conducted to investigate the independent contribution of PCSK9 to platelet activity by controlling for the potential confounding factors. The study population included 89 subjects from a health examination centre who underwent routine annual health check-ups or had an examination before a selective operation. Subjects taking statins or antiplatelet agents were excluded. Adenosine diphosphate (ADP)-induced platelet aggregation was determined by PL-11 platelet analyzer using impedance aggregometry and plasma PCSK9 levels were determined using an ELISA. Serum Lipid profile was assessed by measuring the concentration of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and triglyceride (TG), with low-density lipoprotein cholesterol (LDL-C) being directly measured using enzymatic techniques. The association between PCSK9 and platelet reactivity was investigated.

Results

The study subjects were composed of 53 males and 36 females with an average age of 55 (±11) years old. The univariate correlation analysis showed significant correlation between ADP-induced maximal aggregation rate (MAR) and PCSK9 (r = 0.55, p < 0.001) as well as TC (r = 0.23, p = 0.028), LDL-C (r = 0.27, p < 0.001), and PLT (r = 0.31, p = 0.005). Being male (41.2% vs. 46.6, p = 0.04) and smoking (37.4 vs. 46.2%, p = 0.016) were associated with lower ADP-induced MAR than being female and non-smoking. However, there is no correlation between PCSK9 and AA-induced platelet maximal aggregation rate (r = 0.17, p = 0.12). Multiple regression analysis suggested that PCSK9 contributed independently to ADP-induced maximal aggregation rate (β = 0.08, p = 0.004) after controlling for the effect of TC, LDL-C, PLT, being male, and smoking.

Conclusions

PCSK9 is positively associated with platelet reactivity, which may partly account for the beneficial effect of PCSK9 inhibition in reducing the risk of major adverse cardiovascular events after acute coronary syndrome (ACS).

Increased platelet aggregation in patients with decompensated cirrhosis indicates higher risk of further decompensation and death

BACKGROUND & AIMS

Studies on platelet aggregation in cirrhosis are controversial because interpretation of platelet function is challenged by thrombocytopenia. We conducted a prospective study to investigate whole blood platelet aggregation in cirrhosis and its association with liver-related outcomes.

METHODS

Platelet aggregation was assessed by whole blood aggregometry (Multiplate®). To overcome the influence of platelet count and compare cirrhosis with thrombocytopenia vs. controls with normal platelet count, we calculated a ratio between platelet aggregation and platelet count (PLT ratio). Then, we prospectively followed patients with cirrhosis and ascertained predictors of decompensation, transplantation, and death.

RESULTS

Two-hundred and three patients with cirrhosis were prospectively recruited (77% decompensated). PLT ratio was significantly higher in cirrhosis than in those with chronic hepatitis and healthy individuals (0.44 vs. 0.25 and 0.26, respectively; p <0.0001). In cirrhosis, the ratio increased with disease severity (Child-Pugh class C>B>A) and was particularly elevated in decompensated patients with severe thrombocytopenia. Among decompensated patients, 65 had further decompensation, underwent transplantation, or died during a 6-month follow-up. On multivariate analysis, PLT ratio (odds ratio 1.87; 95% CI 1.23-2.84; p = 0.003) and MELD score (odds ratio 1.05; 95% CI 1.01-1.08; p = 0.01) were independently associated with outcome. The relative risk of events was 7.5-fold higher in patients with PLT ratio >0.75 vs. patients with PLT ratio <0.25 (95% CI 2.5-21.9; p = 0.003). The increased PLT ratio, its discriminative ability for composite outcome, and the prognostic value of PLT ratio >0.75 were confirmed in an independent cohort of hospitalized patients with decompensated cirrhosis (n = 41).

CONCLUSIONS

Patients with cirrhosis, particularly when decompensated, exhibit significantly increased whole blood platelet aggregation. Decompensated patients with a PLT ratio >0.75 have a >80% probability of further decompensation, transplantation, or liver-related death within 6 months.

LAY SUMMARY

In patients with cirrhosis, previous studies have suggested that platelets (i.e. circulating blood cells that help form clots to stop bleeding) are dysfunctional. In particular, these studies suggested that platelet aggregation (the process by which platelets adhere to each other to form clots) is reduced. Since platelet aggregation is important for clot formation, it has been hypothesized that alterations of platelet aggregation may be responsible for the increased risk of bleeding observed in patients with cirrhosis. Our study demonstrates: i) that platelet aggregation in patients with cirrhosis is higher than in healthy individuals; ii) that platelet aggregation in patients with decompensated cirrhosis (i.e. those who have already experienced some complications of cirrhosis) is particularly elevated and associated with risk of further complications and death.

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.

Influence of Trimethylamine N-Oxide on Platelet Activation

Microbiome-derived trimethylamine N-oxide (TMAO) has been associated with platelet hyperreactivity and subsequent atherogenesis. Whether physiological TMAO-levels influence platelet-derived lipid mediators remains unknown. Little is known about pre-analytic factors potentially influencing TMAO concentrations. We aimed at developing a quantitative LC-MS/MS method to investigate in-vivo and in-vitro pre-analytical factors in TMAO analysis to properly assess the proposed activating effect of TMAO on platelets. TMAO, betaine, carnitine, and choline were analyzed by HILIC-ESI-MS/MS within 6 min total run time. Method validation included investigation of reproducibility, recovery, sensitivity, and in-vitro pre-analytical factors. A 24-h monitoring experiment was performed, evaluating in-vivo pre-analytical factors like daytime or diet. Finally, the effects of different TMAO concentrations on platelet activation and corresponding alterations of platelet-derived eicosanoid release were analyzed. The method showed high reproducibility (CVs ≤ 5.3%), good recovery rates (96–98%), and negligible in-vitro pre-analytical effects. The influence of in-vivo pre-analytical factors on TMAO levels was not observable within the applied experimental conditions. We did not find any correlation between TMAO levels and platelet activation at physiological TMAO concentrations, whereas platelet-derived eicosanoids presented activation of the cyclooxygenase and lipoxygenase pathways. In contrast to previously published results, we did not find any indications regarding diet dependency or circadian rhythmicity of TMAO levels. Our results do not support the hypothesis that TMAO increases platelet responsiveness via the release of lipid-mediators.

Bleeding During Veno-Venous ECMO: Prevention and Treatment

Veno-venous extracorporeal membrane oxygenation (vvECMO) has become a routine treatment for severe lung failure in specialized centers. Spontaneous bleeding complications, however, are observed in 30–60% of patients during vvECMO treatment. Bleeding increases mortality by factors 2–3. Anticoagulation in combination with several acquired bleeding disorders caused by the mechanical pump and the foreign layer of the extracorporeal system contribute to the risk of bleeding. In this review, the mechanisms of the underlying pathologies and the route from diagnosis to treatment are described.

Customized low-cost high-throughput amplifier for electro-fluidic detection of cell volume changes in point-of-care applications

Physical parameters of the pathogenic cells, like its volume, shape, and stiffness, are important biomarkers for diseases, chemical changes within the cell, and overall cell health. The response of pathogenic bacteria and viruses to different chemical disinfectants is studied widely. Some of the routinely employed techniques to measure these changes require elaborate and expensive equipment which limits any study to a non-mobile research lab facility. Recently, we showed a micropore-based electro-fluidic technique to have great promise in measuring subtle changes in cell volumes at high throughput and resolution. This method, however, requires commercial amplifiers, which makes this technique expensive and incompatible for in-field use. In this paper, we develop a home-built amplifier to make this technique in-field compatible and apply it to measure changes in bacterial volumes upon exposure to alcohol. First, we introduce our low-cost and portable transimpedance amplifier and characterize the maximum range, absolute error percentage, and RMS noise of the amplifier in the measured current signal, along with the amplifier's bandwidth, and compared these characteristics with the commercial amplifiers. Using our home-built amplifier, we demonstrate a high throughput detection of ~1300 cells/second and resolve cell diameter changes down to 1 μm. Finally, we demonstrate measurement of cell volume changes in E. coli bacteria when exposed to ethanol (5% v/v), which is otherwise difficult to measure via imaging techniques. Our low-cost amplifier (~100-fold lower than commercial alternatives) is battery-run, completely portable for point-of-care applications, and the electro-fluidic devices are currently being tested for in-field applications.

Influencing factors and differences in Born aggregometry in specialized hemostaseological centers – results of a multi-center laboratory comparison

Introduction  Light transmission aggregometry (LTA) is regarded as the gold standard in platelet function diagnostics. However, there is a relevant degree of interlaboratory variability in practical applications.

Objective  The aim of the present study was to develop a practicable laboratory comparison on LTA and to analyze differences and influencing factors in regard to standardization in five specialized hemostaseological centers.

Methods  The study was performed on 30 patients in total. Each center performed LTA on blood samples from six healthy volunteers (three men and three women) using the inductors collagen (Col), adenosine diphosphate (ADP), arachidonic acid (ARA), and ristocetin. The LTA was performed three times using different methods as follows: (1) International Society on Thrombosis and Haemostasis recommendations with identical reagents, (2) in-house protocols and the identical reagents; and (3) in-house protocols and in-house reagents.

Results  A total of 396 measurements of 30 probands were performed. Even after standardization of the protocol and using identical reagents, there were significant differences between the centers regarding the final and maximum aggregation ( p  = 0.002 and <0.001) and further significant differences in the maximum and final aggregation according to the wavelength of the device used to measure the LTA (PAP-8: 430 nm, APACT 4004: 740 nm [ p  < 0.001 each]). Using identical reagents but individual inductor concentrations and laboratory protocols also resulted in different maximum and final aggregation. The largest differences were seen with Col and ristocetin; there were significant influences from the reagents' manufacturers in the results of aggregometry for the inductor Col ( p  < 0.01) but not for ADP, ARA, and ristocetin.

Conclusion  In this study, we proved that there are significant influences from the used aggregometers, inductors concentrations, and manufacturers. These results illustrate the challenges and importance of standardization of LTA.

Study on the Interaction between Deuterium Clopidogrel and Omeprazole

<b><i>Introduction:</i></b> Dual antiplatelet therapy with aspirin in combination with a P2Y₁₂ receptor antagonist is a cornerstone for treating patients with acute coronary syndrome and in percutaneous coronary intervention. However, as this combination of antiplatelet therapy increases the risk of bleeding, proton pump inhibitors (PPIs) are currently recommended to prevent gastrointestinal ulcers and bleeding. The cytochrome P450 (CYP450) isoenzyme system metabolizes both clopidogrel (CLP) and PPIs. Unfortunately, omeprazole (OM) reduce the antiplatelet activity of CLP and increases the probability of recurrence of cardiovascular events by competitively inhibiting the CYP450 isoenzyme CYP2C19. <b><i>Methods:</i></b> To address these abovementioned problems, we designed and synthesized deuterium CLP (D-CL) using selective deuterium technology. Our previous research results showed that D-CL had better pharmacokinetic and pharmacodynamic properties. Thus, the HPLC-MS/MS method, cocktail method, Born method, electro-stimulated thrombus generation, and thrombus elastography were used to detect the production of thiol active metabolites (AM), CYP450 enzyme activities, platelet aggregation, time and length of thrombus formation, and the maximum clot strength after combination therapy. We investigated the pharmacokinetics and pharmacodynamics properties of D-CL combined with OM. <b><i>Results:</i></b> As compared to CLP, D-CL was less affected when combined with OM, which was reflected in lower inhibitory effects of CYP450 enzyme activities, a greater area under the curve of AM, and better antiplatelet and antithrombotic effects. <b><i>Conclusion:</i></b> D-CL may reduce drug-drug interactions and address the clinical disadvantages of CLP.

Personalized pathology test for Cardio-vascular disease: Approximate Bayesian computation with discriminative summary statistics learning

Cardio/cerebrovascular diseases (CVD) have become one of the major health issue in our societies. But recent studies show that the present pathology tests to detect CVD are ineffectual as they do not consider different stages of platelet activation or the molecular dynamics involved in platelet interactions and are incapable to consider inter-individual variability. Here we propose a stochastic platelet deposition model and an inferential scheme to estimate the biologically meaningful model parameters using approximate Bayesian computation with a summary statistic that maximally discriminates between different types of patients. Inferred parameters from data collected on healthy volunteers and different patient types help us to identify specific biological parameters and hence biological reasoning behind the dysfunction for each type of patients. This work opens up an unprecedented opportunity of personalized pathology test for CVD detection and medical treatment.

Global thrombosis test for assessing thrombotic status and efficacy of antithrombotic diet and other conditions

Because of the high mortality from myocardial infarction and stroke, there is a great demand for finding novel methods of diagnosis, prevention and treatment of these diseases. Most of the current tests measure important determinants of thrombosis such as platelet function, coagulation and fibrinolysis in isolation; therefore, a global test measuring the actual thrombotic status would be more useful in clinical conditions. We obtained considerable experience by using the global thrombosis test, which determines the actual thrombotic status by taking into account the measured platelet reactivity, coagulation and fibrinolytic activities. In animal experiments, we found significant correlation between the ex vivo global thrombosis test measurements and the in vivo thrombotic status. The published evidence for the benefit of an antithrombotic diet with regular physical exercise is also described.

There is a great concern in the general population how to detect the risk of thrombotic events and prevent the high mortality from stroke, myocardial infarction, sudden death and cancer-associated thrombosis. Our experience on antithrombotic fruits and vegetables intake and regular exercise assessed by the global thrombosis test suggested a potentially unique way of preventing these life-threatening diseases. In addition, global thrombosis testing may offer some benefit in detecting risk of thrombotic of forthcoming thrombotic events in cancer and COVID-19 virus-infected patients.

A new decade awaits sticky platelet syndrome: where are we now, how do we manage and what are the complications?

INTRODUCTION

Sticky platelet syndrome is a less known platelet function disorder with a familiar occurrence and likely genetic background. Clinically, it is characterized by an increased risk of venous and arterial thromboembolic events and obstetric placenta-mediated complications. The increased aggregation after low-dose ADP and/or epinephrine is its distinctive laboratory feature. Though described for almost 40 years, several issues regarding its etiology, involved pathomechanisms, genetic background, optimal diagnostic and treatment approach remain controversial.

AREAS COVERED

The work aims to summarize published studies, the actual definition of the syndrome, and point out its drawbacks. A literature search on Medline, Embase, and archives from EHA congresses was performed (terms: 'sticky platelet syndrome' - 'platelet hyperreactivity' - 'platelet hyperaggregability'). The authors added in their unpublished data. The introductory overview of the present understanding is followed by the discussion of the pathophysiologic, diagnostic, and therapeutic problems.

EXPERT OPINION

Despite the growing evidence provided by case reports and series, the lack of robust studies limits the decision-making on diagnostics and management. The diagnostic issues, particularly the standardization of light transmission aggregometry, represent the crucial problem for the broader acceptance of the syndrome.

Mitochondrial dysfunction in trauma-related coagulopathy - Is there causality? - Study protocol for a prospective observational study

Hemorrhage control often poses a great challenge for clinicians due to trauma-induced coagulopathy (TIC). The pathogenesis of TIC is not completely revealed; however, growing evidence attributes a central role to altered platelet biology. The activation of thrombocytes and subsequent clot formation are highly energetic processes being tied to mitochondrial activity, and the inhibition of the electron transport chain (ETC) impedes on thrombogenesis, suggesting the potential role of mitochondria in TIC. Our present study protocol provides a guide to quantitatively characterize the derangements of mitochondrial functions in TIC. One hundred eleven severely injured (Injury Severity Score ≥16), bleeding trauma patients with an age of 18 or greater will be included in this prospective observational study. Patients receiving oral antiplatelet agents including cyclooxygenase-1 or adenosine diphosphate receptor inhibitors (aspirin, clopidogrel, prasugrel, and ticagrelor) will be excluded from the final analysis. Hemorrhage will be confirmed and assessed with computer tomography. Conventional laboratory markers of hemostasis such as prothrombin time and international normalized ratio (INR) will be measured and rotational thromboelastometry (ROTEM) will be performed directly upon patient arrival. Platelets will be isolated from venous blood samples and subjected to high-resolution fluororespirometry (Oxygraph-2k, Oroboros Instruments, Innsbruck, Austria) to evaluate the efficacy of mitochondrial respiration. Oxidative phosphorylation (OxPhos), coupling of the ETC, mitochondrial superoxide formation, mitochondrial membrane potential changes and extramitochondrial Ca2+-movement will be recorded. The association between OxPhos capacity of platelet mitochondria and numerical parameters of ROTEM aggregometry will constitute our primary outcome. The relation between OxPhos capacity and results of viscoelastic assays and conventional markers of hemostasis will serve as secondary outcomes. The association of the OxPhos capacity of platelet mitochondria upon patient arrival to the need for massive blood transfusion (MBT) and 24-hour mortality will constitute our tertiary outcomes. Mitochondrial dysfunction and its importance in TIC in are yet to be assessed for the deeper understanding of this common, life-threatening condition. Disclosure of mitochondria-mediated processes in thrombocytes may reveal new therapeutic targets in the management of hemorrhaging trauma patients, thereby leading to a reduction of potentially preventable mortality. The present protocol was registered to ClinicalTrials.gov on 12 August 2021, under the reference number NCT05004844.

Ferulic acid: A review of its pharmacology, pharmacokinetics and derivatives

Ferulic acid, a kind of phenolic substance widely existing in plants, is an important active component of many traditional Chinese medicines. So far, it has been proved that ferulic acid has a variety of biological activities, especially in oxidative stress, inflammation, vascular endothelial injury, fibrosis, apoptosis and platelet aggregation. Many studies have shown that ferulic acid can inhibit PI3K/AKT pathway, the production of ROS and the activity of aldose reductase. The anti-inflammatory effect of ferulic acid is mainly related to the levels of PPAR γ, CAM and NF-κ B and p38 MAPK signaling pathways. Ferulic acid not only protects vascular endothelium by ERK1/2 and NO/ET-1 signal, but also plays an anti-fibrosis role by TGF-β/Smad and MMPs/TIMPs system. Moreover, ferulic acid has ant-apoptotic and anti-platelet effects. In addition to the pharmacological effects of ferulic acid, its pharmacokinetics and derivatives were also discussed in this paper. This review provides the latest summary of the latest research on ferulic acid.

Primary Thrombophilia XVI: A Look at the Genotype of the Sticky Platelet Syndrome Phenotype

The sticky platelet syndrome (SPS) was described by Mammen in 1983. Since then, scientists in several countries have identified the condition and published cases or series of patients, thus enabling the description of the prevalence of the inherited condition, its salient clinical features, and the treatment of the disease. The diagnosis of the SPS phenotype requires fresh blood samples and special equipment which is not available in all coagulation laboratories. In the era of molecular biology, up to now it has not been possible to define a clear association of the SPS phenotype with a specific molecular marker. Some molecular changes which have been described in platelet proteins in some persons with the phenotype of the SPS are here discussed. Nowadays, the SPS phenotype may be considered as a risk factor for thrombosis and most cases of the SPS developing vaso-occlussive episodes are the result of its coexistence with other thrombosis-prone conditions, some of the inherited and some of them acquired, thus leading to the concept of multifactorial thrombophilia. Ignoring all these evidence-based concepts is inappropriate, same as stating that the SPS is a nonentity simply because not all laboratories are endowed with adequate equipment to support the diagnosis.

Plateletworks® as a Point-of-Care Test for ASA Non-Sensitivity

Aspirin (ASA) therapy is proven to be effective in preventing adverse cardiovascular events; however, up to 30% of patients are non-sensitive to their prescribed ASA dosage. In this pilot study, we demonstrated, for the first time, how ASA non-sensitivity can be diagnosed using Plateletworks®, a point-of-care platelet function test. Patients prescribed 81 mg of ASA were recruited in a series of two successive phases-a discovery phase and a validation phase. In the discovery phase, a total of 60 patients were recruited to establish a cut-off point (COP) for ASA non-sensitivity using Plateletworks®. Each sample was simultaneously cross-referenced with a light transmission aggregometer (LTA). Our findings demonstrated that >52% maximal platelet aggregation using Plateletworks® had a sensitivity, specificity, and likelihood ratio of 80%, 70%, and 2.67, respectively, in predicting ASA non-sensitivity. This COP was validated in a secondary cohort of 40 patients prescribed 81 mg of ASA using Plateletworks® and LTA. Our data demonstrated that our established COP had a 91% sensitivity and 69% specificity in identifying ASA non-sensitivity using Plateletworks®. In summary, Plateletworks® is a point-of-care platelet function test that can appropriately diagnose ASA non-sensitive patients with a sensitivity exceeding 80%.

Altered Transcriptional Profile of Mitochondrial DNA-Encoded OXPHOS Subunits, Mitochondria Quality Control Genes, and Intracellular ATP Levels in Blood Samples of Patients with Parkinson's Disease

Mitochondrial dysfunctions are significant contributors to neurodegeneration. One result or a cause of mitochondrial dysfunction might be the disruption of mtDNA transcription. Limited data indicated an altered expression of mtDNA encoded transcripts in Alzheimer's disease (AD) or Parkinson's disease (PD). The number of mitochondria is high in cells with a high energy demand, such as muscle or nerve cells. AD or PD involves increased risk of cardiomyopathy, suggesting that mitochondrial dysfunction might be systemic. If it is systemic, we should observe it in different cell types. Given that, we wanted to investigate any disruption in the regulation of mtDNA encoded gene expression in addition to PINK1, PARKIN, and ATP levels in peripheral blood samples of PD cases who are affected by a neurodegenerative disorder that is very well known by its mitochondrial aspects. Our results showed for the first time that: 1) age of onset > 50 PD sporadic (PDS) cases: mtDNA transcription and quality control genes were affected; 2) age of onset <50 PDS cases: only mtDNA transcription was affected; and 3) PD cases with familial background: only quality control genes were affected. mtDNA copy number was not a confounder. Intracellular ATP levels of PD case subgroups were significantly higher than those of healthy subjects. We suggest that a systemic dysregulation of transcription of mtDNA or mitochondrial quality control genes might result in the development of a sporadic form of the disease. Additionally, ATP elevation might be an independent compensatory and response mechanism. Hyperactive cells in AD and PD require further investigation.

Device-induced platelet dysfunction in patients after left ventricular assist device implantation

BACKGROUND

Non-surgical bleeding (NSB) is a major complication after left ventricular assist device (LVAD) implantation. It has been reported that non-physiological shear stress caused by LVADs could alter platelet receptor expression, which leads to bleeding disorders caused by coagulation dysfunctions.

OBJECTIVES

Because bleeding diathesis could be multifactorial, we focused on the combined characterization of platelet receptor expression patterns and oxidative stress to compare patients with NSB and patients without coagulation disorder in a monocentric, prospective study.

METHODS

Blood samples were obtained from LVAD patients with NSB (bleeder group, n = 19) and without NSB (non-bleeder group, n = 20). The platelet receptors platelet endothelial cell adhesion molecule-1 (PECAM-1), glycoprotein (GP)Ibα, P-selectin, CD63, and GPIIb/IIIa, as well as the production of intraplatelet reactive oxygen species (ROS) were quantified by flow cytometry. Aggregation capacity was evaluated by aggregometry.

RESULTS

The surface expression level of P-selectin and GPIbα on platelets was decreased in bleeders (P-selectin: 465 ± 72 U; GPIbα: 435 ± 41 U) compared to non-bleeders (P-selectin: 859 ± 115 U, P < .01; GPIbα: 570 ± 49 U, p = .04). Additionally, the mean fluorescence intensity of ADP-stimulated P-selectin and PECAM-1 expressing platelets were reduced in bleeders (P-selectin: 944 ± 84 U; PECAM-1: 6722 ± 419 U) compared to non-bleeders (P-selectin: 1269 ± 130 U, P = .04; PECAM-1: 8542 ± 665 U, P = .03). Bleeders showed a higher amount of ROS formation in platelets (88.0 ± 2.6%) than non-bleeders (81.5 ± 2.1%, P = .05).

CONCLUSIONS

These findings suggested that changes of three platelet receptors (GPIbα, P-selectin, and PECAM-1) and elevated oxidative stress may play a role in patients with bleeding complications following LVAD implantation. These results might help to explain the high incidence of spontaneous hemorrhage during LVAD support through an altered platelet function.

Evaluation of latest viscoelastic coagulation assays in the transcatheter aortic valve implantation setting

Background

Point of care viscoelastic measures with thromboelastography (TEG; Haemonetics Corporation, Switzerland) and thromboelastometry (ROTEM, Tem Innovations GmbH, Germany) now supersede laboratory assays in the perioperative assessment and management of coagulation. To the best of our knowledge, this sophisticated coagulation assessment has not been performed to characterise thrombotic changes in the transcatheter aortic valve implantation (TAVI) setting, nor have the two latest iteration cartridge-based systems been directly compared in the elective perioperative period.

Methods

Patients undergoing TAVI were prospectively recruited. Samples (n=44) were obtained at four timepoints (postinduction of anaesthesia, postheparin (100 IU/kg), postprotamine (1 mg/100 IU heparin) and 6 hours postoperatively). Each sample was concurrently assessed with standard laboratory tests (prothrombin time/international normalised ratio, activated partial thromboplastin time, thrombin clotting time, platelet count and direct fibrinogen, ROTEMSigma and TEG6s).

Results

Clot strength showed a statistically significant increase postheparin/TAVI deployment. When considering the subgroup of samples taken following the administration heparin, the heparinase channel of the TEG6s did not yield clotting strength results in 55% of samples and clotting time exceeded the upper limit of normal in 70% of samples. It was retrospectively recognised that the arachidonic acid channel of the TEG6s Platelet Mapping Cartridge had been decommissioned prohibiting assessment of aspirin effect.

Conclusions

This study demonstrated a small intraprocedural prothrombotic change of uncertain clinical importance during the transcatheter aortic valve procedure. Further comparison with percutaneous coronary intervention and aortic valve replacement cohorts are needed to assess the merits of current antithrombotic guidelines, which are extrapolated from the PCI setting. The heparin effect was more consistently quantified by ROTEM.

MicroRNA as Potential Biomarkers of Platelet Function on Antiplatelet Therapy: A Review

MicroRNAs (miRNAs) are small, non-coding RNAs, able to regulate cellular functions by specific gene modifications. Platelets are the major source for circulating miRNAs, with significant regulatory potential on cardiovascular pathophysiology. MiRNAs have been shown to modify the expression of platelet proteins influencing platelet reactivity. Circulating miRNAs can be determined from plasma, serum, or whole blood, and they can be used as diagnostic and prognostic biomarkers of platelet reactivity during antiplatelet therapy as well as novel therapeutic targets in cardiovascular diseases (CVDs). Herein, we review diagnostic and prognostic value of miRNAs levels related to platelet reactivity based on human studies, presenting its interindividual variability as well as the substantial role of genetics. Furthermore, we discuss antiplatelet treatment in the context of miRNAs alterations related to pathways associated with drug response.

Research of spontaneous and stimulated functional activity of platelets in patients with different types of atrial fibrillation

Platelet function testing is widely used to diagnose disorders of the cellular link of hemostasis. The study of platelet aggregation activity is relevant for the prevention of thromboembolic complications in atrial fibrillation and monitoring the effectiveness and safety of therapy. In this study, a comparative analysis of spontaneous and stimulated platelet aggregation in groups of patients with two types of atrial fibrillation was performed - paroxysmal and persistent. The effect of β-adrenoblocker therapy on platelet aggregation activity in patients with atrial fibrillation was also studied. Platelet aggregation activity was studied using the method of G. Born in the modification of Z.A. Gabbasov on a two-channel laser analyzer "Biola". Collagen at a concentration of 2 mg / ml and adrenaline in a concentration range of 2.5-10 μg / ml were used as aggregation-promoting agents. It has been established that spontaneous aggregation potential and collagen-induced platelet aggregation depend on the type of atrial fibrillation, as well as on the presence or absence of β-blockers in therapy. The response of platelets to stimulation with adrenaline depends, first of all, on the type of atrial fibrillation and the concentration of adrenaline in the reaction medium. The most significant changes were noted in the group of patients with a paroxysmal form atrial fibrillation, taking β-blockers in therapy.

Viscoelastic Hemostatic Assays and Platelet Function Testing in Patients with Atherosclerotic Vascular Diseases

Platelets play crucial role in acute vascular atherosclerotic diseases, including myocardial infarction and stroke. Additionally, platelet aggregation is a key target of antiplatelet agents, forming the keystone of pharmacotherapy of various atherosclerotic cardiovascular diseases. Thromboelastography and thromboelastometry, representing currently available viscoelastic hemostatic assays (VHA), are designed as whole blood, real-time analyzers of clot formation and clot resolution. These assays could, in theory, overcome some limitations of currently available platelet function testing assays. This article reviews the current experience with the use of VHA for platelet function testing and for monitoring of the response to antiplatelet therapy.

Pharmacokinetic, pharmacodynamic, and pharmacogenetic assays to monitor clopidogrel therapy

Clopidogrel is the most common and widely used antiplatelet agent for patients with coronary artery disease following confirmation by electrocardiographic studies. The nonresponsiveness of patients to clopidogrel and the possibility of testing for clopidogrel resistance by platelet function assays (PFA) are contentious issues. Light transmission aggregometry (LTA) is considered as the gold standard test among all PFA. In this review, the most commonly used PFA used for monitoring the effect of clopidogrel, LTA, vasodilator-stimulated phosphoprotein assay phosphorylation, rotational thromboelastometry (ROTEM) delta and ROTEM platelet, thromboelastography, PFA-100, VerifyNow P2Y12 assay, Multiplate analyzer, Plateletworks assay and pharmacogenetic studies, are comparatively discussed including their principles of action, advantages, and disadvantages. VerifyNow P2Y12 assay can be accepted as the ideal point of care test out of the discussed assays. However, modified assays are required which could overcome the limitations associated with currently available assays.

Coagulation parameters predictive of repeated implantation failure in Chinese women: A retrospective study

Repeated implantation failure (RIF) greatly influences pregnancy rate after assisted reproductive technologies (ART) with elusive causes. Our study aimed to explore coagulation parameters in association with RIF and establish a model to predict the risk of RIF in Chinese women.Coagulation parameters, including prothrombin time (PT), thrombin time (TT), activated partial prothrombin time (APTT), D-dimer (DD), fibrin degradation products (FDP), fibrinogen (FG), and platelet aggregation induced by arachidonic acid (AA) and adenosine diphosphate (ADP) were measured in RIF patients and controls. A logistic regression model was built by using the purposeful selection to select important factors for the prediction of RIF.Between 92 RIF patients and 47 controls, we found a statistically significant difference in all of the coagulation parameters except APTT, FDP and platelet aggregation induced by ADP. The purposeful selection method selected PT (odds ratio [OR] = 0.28, 95% CI: 0.12-0.66, P = .003), APPT (odds ratio [OR] = 0.76, 95% CI: 0.63-0.91, P = .004), TT (odds ratio [OR] = 0.75, 95% CI: 0.53-1.08, P = .124), and platelet aggregation induced by AA (odds ratio [OR] = 1.27, 95% CI: 1.11-1.44, P = .0003) as important predictors of RIF risk. ROC curve analysis indicated that the area under ROC curve (AUC) of the model was 0.85 with an optimal cut-off point of the predicted probability being P = .65, leading to a sensitivity of 0.83 and a specificity 0.75.We found that coagulation parameters including PT, APTT, TT and platelet aggregation induced by AA are predictive of RIF in Chinese women. Our results highlight the potential of anti-coagulation therapies to lower the risk of RIF.

Programmed Cell Death and Functional Activity of Platelets in Case of Oncohematologic Diseases

Programmed cell death of non-nucleated blood cells - platelets - could be associated with pathophysiology of oncologic and oncohematologic diseases. It contributes to both bleedings (caused by the thrombocytopenia, which is induced by elimination of the platelets) and thrombosis (caused by the processes of blood coagulation on the surface of phosphatidylserine exposing platelets). Here we characterized functional responses of platelets from the patients with various oncological disorders undergoing chemotherapy and compared them to the platelets from the healthy donors and platelets pre-incubated with apoptosis inducer ABT-737. Some patients exhibited diminished capability of platelets to aggregate. Immunophenotyping of these platelets revealed their pre-activation in comparison to the platelets from the healthy donors. Calcium signaling analysis revealed that in the patient-derived platelets, as well as in the apoptotic platelets, intracellular calcium levels were increased in resting cells. However, moderate level of this increase together with weak expression of phosphatidylserine allows us to assume that apoptotic processes in the circulating platelets from the patients are limited.

A geranylated chalcone with antiplatelet activity from the leaves of breadfruit (Artocarpus altilis)

Platelet plays a crucial role in cardiovascular diseases (CVDs) development. Abnormalities in platelet aggregation provokes thromboembolism, eventually leading to death. In Indonesia, breadfruit (Artocarpus altilis) leaf is traditionally used to treat CVDs. This study aimed to evaluate the antiplatelet activity of A. altilis leaf extract (AAE) and to identify its active compound. A. altilis leaves were extracted with ethanol, and the antiplatelet activity was assessed using ADP-induced platelet aggregation. The major compound was isolated with column chromatography followed by preparative TLC, and the structure was determined on the basis of UV, MS, IR, and NMR spectra. The binding mode of the active compound to platelet receptors was characterized in in silico study. AAE exhibited an antiplatelet activity (IC50 of 252.23 µg/mL). A geranylated chalcone, 2-geranyl-2ʹ,3,3,4ʹ-tetrahydroxydihydrochalcone (GTDC) was identified as the antiplatelet compound (IC50 of 9.09 µM). GTDC actions with P2Y12 platelet receptor involving three amino acid residues.

Differences in platelet aggregometers to study platelet function and coagulation dysregulation in xenotransplantation

Xenotransplantation (ie, cross-species transplantation) using genetically engineered pig organs could be a limitless source to solve the shortage of organs and tissues worldwide. However, despite prolonged survival in preclinical pig-to-nonhuman primate xenotransplantation trials, interspecies coagulation dysregulation remains to be overcome in order to achieve continuous long-term success. Different platelet aggregometry methods have been previously used to study the coagulation dysregulation with wild-type and genetically engineered pig cells, including the impact of possible treatment options. Among these methods, while thromboelastography and rotational thromboelastometry measure the change in viscoelasticity, optical aggregometry measures the change in opacity. Recently, impedance aggregometry has been used to measure changes in platelet aggregation in electrical conductance, providing more information to our understanding of coagulation dysregulation in xenotransplantation compared to previous methods. The present study reviews the merits and differences of the above-mentioned platelet aggregometers in xenotransplantation research.

Demonstration of an action pathway in mouse platelets leading to prolongation of bleeding time by fluoxetine

Fluoxetine is one of SSRIs commonly used as first-line antidepressants. It also induces adverse effects, including bleeding events. This study clarified the bleeding effect of fluoxetine and explored the action cascade of this drug leading to a longer bleeding time. A total of 48 male adult mice were evenly distributed into four groups and given fluoxetine in saline at 0, 4, 8, or 16 mg/kg, for 14 days. On day 15, tail bleeding time of 6 mice/group was measured, and their blood samples were collected for analyses of relevant platelet functions. The remained mice were allowed to survive for another 14 days without fluoxetine, and subjected to the same analyses on day 29. A significant effect of fluoxetine was reveled on bleeding time (F _(3,20) = 16.842, P < 0.01) and intraplatelet serotonin (F _(3,20) = 90.967, P < 0.01). Moreover, fluoxetine effectively inhibited platelet aggregation (F_{(3, 20)} = 30.247, P < 0.01), decreased amount of GPIbα (F_{(3, 20)} = 23.855, P < 0.01), suppressed GPIIb/IIIa activation (F_{(3, 20)} = 89.441, P < 0.01), and lowered P-selectin (F_{(3, 20)} = 7.960, P < 0.01) on platelet surface. Negative correlations existed between bleeding time and the aforementioned four indices, whereas correlations between intraplatelet serotonin and the same indices were positive. All changes returned to same levels as Control group after fluoxetine withdrawal. These data suggest an action pathway of fluoxetine starting at binding to serotonin transporter, followed by decreased intraplatelet serotonin, increased GPIbα shedding, suppressed GPIIb/IIIa activation, and inhibited α-granule release, and concluding with prolonged bleeding time in mice.

Comparison of acetylsalicylic acid and clopidogrel non-responsiveness assessed by light transmittance aggregometry and PFA-100® in patients undergoing neuroendovascular procedures

Objectives

Dual platelet inhibition is commonly used for prevention of cardiovascular events in patients undergoing neuroendovascular procedures. Non-responsiveness to platelet inhibitors may be associated with adverse outcomes. The aim of this study was to evaluate the reliability of the platelet function analyzer PFA-100® in comparison to light transmittance aggregometry (LTA) for monitoring clopidogrel and acetylsalicylic acid (ASA) non-responsiveness in a cohort of patients treated for intracranial aneurysm or cranial artery stenosis.

Methods

Non-responsiveness to clopidogrel and ASA was assessed by LTA using adenosine diphosphate (ADP) and arachidonic acid and by PFA-100® with the ADP/prostaglandin E1 (PGE1) and collagen/epinephrine cartridges, respectively.

Results

A total of 203 patients (145 females; median age, 57 years) were analyzed. Agreement between the two tests was poor for clopidogrel non-responsiveness (ƙ=0.19) and not better than chance for ASA non-responsiveness (ƙ=0.01). Clopidogrel non-responsiveness by LTA and PFA-100® was associated with higher von Willebrand factor antigen and activity levels. ADP-induced platelet disaggregation was lower in patients with clopidogrel non-responsiveness as assessed by PFA-100®. Clopidogrel non-responsiveness by LTA was associated with a higher prevalence of diabetes and a higher body mass index (BMI). Adverse outcomes (death, thromboembolism, or in-stent thrombosis) occurred in 13% (n=26) of all patients independently of ASA and clopidogrel non-responsiveness as assessed by both devices.

Conclusions

Our results show that LTA and PFA-100® are not interchangeable in the assessment of ASA and clopidogrel non-responsiveness in patients undergoing neuroendovascular interventions.

The Platelet Concentrates Therapy: From the Biased Past to the Anticipated Future

The ultimate goal of research on platelet concentrates (PCs) is to develop a more predictable PC therapy. Because platelet-rich plasma (PRP), a representative PC, was identified as a possible therapeutic agent for bone augmentation in the field of oral surgery, PRP and its derivative, platelet-rich fibrin (PRF), have been increasingly applied in a regenerative medicine. However, a rise in the rate of recurrence (e.g., in tendon and ligament injuries) and adverse (or nonsignificant) clinical outcomes associated with PC therapy have raised fundamental questions regarding the validity of the therapy. Thus, rigorous evidence obtained from large, high-quality randomized controlled trials must be presented to the concerned regulatory authorities of individual countries or regions. For the approval of the regulatory authorities, clinicians and research investigators should understand the real nature of PCs and PC therapy (i.e., adjuvant therapy), standardize protocols of preparation (e.g., choice of centrifuges and tubes) and clinical application (e.g., evaluation of recipient conditions), design bias-minimized randomized clinical trials, and recognize superfluous brand competitions that delay sound progress. In this review, we retrospect the recent past of PC research, reconfirm our ultimate goals, and discuss what will need to be done in future.