Platelet function assays

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.

Platelet function testing: Update on determinant variables and permissive windows using a platelet-count-based device

While there are various aspects of platelet biology that can be studied in the lab (i.e. adhesion, degranulation, integrin activation), the master test for platelet function is that which gives a measure of the platelet aggregation capacity upon stimulation with an agonist. Platelet function testing is necessary for the diagnosis of platelet disorders and the monitoring of patients receiving anti-platelet treatments. Furthermore, it becomes relevant in the quality control of platelet concentrates for transfusion purposes, especially considering the global concern about long term storage, other forms of storage (i.e. cryopreservation, lyophilization), and the impact of Pathogen Reduction Treatments (PRTs) on platelet performance upon transfusion. However, it has been acknowledged as technically difficult and demanding, since a fine platelet function test must be carried out under specific conditions. Still, there might be occasions that preclude the platelet function testing abiding to the gold standard requirements, thus, leaving us with the necessity to redefine which variables may condition or limit the analysis of platelet function testing. In the present manuscript, we test different variables (such as the anticoagulant used or the time elapsed since extraction) and the possibility to reconstitute blood prior to platelet function analysis. This study aims to provide windows of action at the diagnostics lab, especially when not all of the recommended procedures and conditions can be followed: for example, when a sample is sent from a long distance, when there is a limitation on blood extraction volume or when certain parameters (platelet count) preclude reliable test results.

Current Strategies to Guide the Antiplatelet Therapy in Acute Coronary Syndromes

The role of antiplatelet therapy in patients with acute coronary syndromes is a moving target with considerable novelty in the last few years. The pathophysiological basis of the treatment depends on platelet biology and physiology, and the interplay between these aspects and clinical practice must guide the physician in determining the best therapeutic options for patients with acute coronary syndromes. In the present narrative review, we discuss the latest novelties in the antiplatelet therapy of patients with acute coronary syndromes. We start with a description of platelet biology and the role of the main platelet signal pathways involved in platelet aggregation during an acute coronary syndrome. Then, we present the latest evidence on the evaluation of platelet function, focusing on the strengths and weaknesses of each platelet's function test. We continue our review by describing the role of aspirin and P2Y12 inhibitors in the treatment of acute coronary syndromes, critically appraising the available evidence from clinical trials, and providing current international guidelines and recommendations. Finally, we describe alternative therapeutic regimens to standard dual antiplatelet therapy, in particular for patients at high bleeding risk. The aim of our review is to give a comprehensive representation of current data on antiplatelet therapy in patients with acute coronary syndromes that could be useful both for clinicians and basic science researchers to be up-to-date on this complex topic.

The evolving knowledge on primary hemostasis in patients with cirrhosis: A comprehensive review

Patients with cirrhosis develop complex alterations in primary hemostasis that include both hypocoagulable and hypercoagulable features. This includes thrombocytopenia, multiple alterations of platelet function, and increased plasma levels of von Willebrand factor. Contrary to the historical view that platelet dysfunction in cirrhosis might be responsible for an increased bleeding tendency, the current theory posits a rebalanced hemostasis in patients with cirrhosis. Severe thrombocytopenia is not indicative of the bleeding risk in patients undergoing invasive procedures and does not dictate per se the need for pre-procedural prophylaxis. A more comprehensive and individualized risk assessment should combine hemostatic impairment, the severity of decompensation and systemic inflammation, and the presence of additional factors that may impair platelet function, such as acute kidney injury and bacterial infections. Although there are multiple, complex alterations of platelet function in cirrhosis, their net effect is not yet fully understood. More investigations evaluating the association between alterations of platelet function and bleeding/thrombosis may improve risk stratification in patients with decompensated cirrhosis. Besides hemostasis, the assessment of von Willebrand factor Ag and ADP-induced, whole-blood platelet aggregation normalized by platelet count (VITRO score and PLT ratio) are promising biomarkers to predict the risk of hepatic decompensation and survival in both compensated and decompensated patients. Further investigations into the in vivo interplay between platelets, circulating blood elements, and endothelial cells may help advance our understanding of cirrhotic coagulopathy. Here, we review the complex changes in platelets and primary hemostasis in cirrhosis and their potential clinical implications.

Effect of platelet content on occurrence and prognosis of distal radius fracture

Fractures of the distal radius are a common fracture with an increasing incidence. However, the underlying factors for distal radius fractures (DRFs) remain unclear. A total of 123 patients with distal radial fractures were recruited. To document clinical and follow-up data, and measure the levels of white blood cells, hemoglobin, platelets, and red blood cells in the bloodstream for qualitative observation of their expression effects within the human body, specifically assessing whether the magnitudes of these indicators are associated with potential factors influencing DRF. Pearson chi-square test and Spearman correlation were used to analyze the relationship between DRF and related parameters. Univariate and multivariate logistic regression and multivariate Cox proportional risk regression were used for further analysis. Pearson chi-square test and Spearman correlation analysis showed a significant correlation between platelet and red blood cell levels and the occurrence of DRFs. Univariate logistic regression analysis demonstrated a significant correlation between platelet count (OR [odds ratio] = 6.286, 95% CI [confidence interval]: 2.862-13.808, P < .001) and red blood cell count (OR = 2.780, 95% CI: 1.322-5.843, P = .007) with DRFs. Increasing levels of both indicators were associated with a higher susceptibility to DRFs. Multivariate logistic regression showed that platelets (OR = 6.344, 95% CI: 2.709-14.855, P < .001) were significantly associated with DRFs. Multivariate Cox regression analysis showed sex (HR [hazard ratio] = 0.596, 95% CI: 0.381-0.931, P = .023) and platelet (HR = 3.721, 95% CI: 2.364-5.855, P < .001) were significantly associated with maintenance time from recovery to recurrence (MTRR) of DRFs. In other words, the platelet content in the body of different genders is different, and the MTRR of DRF is different. Platelets were significantly associated with DRFs. The higher the platelet count, the higher the risk of DRF and the shorter the time of DRF recurrence.

Comprehensive multiparameter evaluation of platelet function using a highly sensitive membrane capacitance sensor

An accurate and comprehensive assessment of platelet function is essential for managing patients who receive antiplatelet therapies or require platelet transfusion either for treating active bleeding or for prophylaxis. Platelets contribute to clotting by undergoing a series of highly regulated functional responses including adhesion, spreading, granular secretion, aggregation, and cytoskeletal contraction. However, current platelet function assays evaluate only partial aspects of this intricate process and often under non-physiological testing conditions. Herein, we describe the development of a new approach to measure multiple key platelet function-related parameters, in a more physiologically relevant ex vivo semi-rigid microenvironment using a membrane capacitance sensor (MCS). MCS response to clotting provided three sensing parameters with sensitivities towards platelet counts, stimulation strengths, and activation pathways. Live confocal fluorescent imaging of stimulated platelets on MCS suggests that the presented system can readily and accurately convert the dynamics of cytoskeletal reorganization into analyzable electrical signals. Together, this new completely electrical sensing platform can be a promising diagnostic venue to recognize the impairment of primary hemostatic functions, evaluate the efficacy of therapeutic interventions, and gain further insights into the mechanisms of platelets in hemostasis and thrombosis.

Prospective, randomized, controlled, trial to assess ASA DOSing by body mass index in HEalthy volunteers (DOSE study)

STUDY OBJECTIVE: Aspirin (ASA) has demonstrated inconsistent results in primary prevention of cardiovascular disease (CVD). Guidelines are also inconsistent in the recommendation of routine ASA use for primary prevention of CVD, but advocate dosing as a "one-size-fits-all" approach.

DESIGN

An intention-to-treat, double-blind, randomized, controlled, clinical trial comparing three treatment arms of ASA 81, 325, and 500 mg daily dosed for 14 days were evenly randomized across the dosing categories to measure the impact of dosing by body mass index (BMI) (20-24.9, 25-29.9, ≥30 kg/m² ) on ASA anti-platelet effects.

SETTING

University Ambulatory Clinic.

PATIENTS

Healthy volunteers defined as individuals who were medication free without acute or chronic significant health problems.

INTERVENTION

Change in ASA reactivity unit (ARU), salicylate levels, and thromboxane B2 (TxB2) levels were measured across BMI dosing categories and time. MAIN RESULTS: Fifty-four participants with a mean (±SD) age of 34.4 ± 10.9 years (M:F; 23:31) completed the study. Baseline ARU and TxB2 levels were not significantly different between obese and non-obese individuals. BMI was not a predictor of platelet inhibition. There was no interaction between gender and platelet activation at baseline or following ASA treatment. ASA 81 mg was associated with a lower ARU response (approximate 50% lower response) than either the 325-mg or the 500-mg doses of ASA. TxB2 and salicylate levels exhibited lower trends at 81 mg compared with higher doses.

CONCLUSIONS

In healthy male and female participants administered ASA for 14 days, obesity is not associated with increased basal platelet activation or ASA resistance. ASA 81 mg was significantly less effective in reducing platelet aggregation compared with ASA 325 and 500 mg, independent of BMI.

Fibrinogen, Coagulation, and Ageing

The World Health Organization estimates that the world's population over 60 years of age will nearly double in the next 30 years. This change imposes increasing demands on health and social services with increased disease burden in older people, hereafter defined as people aged 60 years or more. An older population will have a greater incidence of cardiovascular disease partly due to higher levels of blood fibrinogen, increased levels of some coagulation factors, and increased platelet activity. These factors lead to a hypercoagulable state which can alter haemostasis, causing an imbalance in appropriate coagulation, which plays a crucial role in the development of cardiovascular diseases. These changes in haemostasis are not only affected by age but also by gender and the effects of hormones, or lack thereof in menopause for older females, ethnicity, other comorbidities, medication interactions, and overall health as we age. Another confounding factor is how we measure fibrinogen and coagulation through laboratory and point-of-care testing and how our decision-making on disease and treatment (including anticoagulation) is managed. It is known throughout life that in normal healthy individuals the levels of fibrinogen and coagulation factors change, however, reference intervals to guide diagnosis and management are based on only two life stages, paediatric, and adult ranges. There are no specific diagnostic guidelines based on reference intervals for an older population. How ageing relates to alterations in haemostasis and the impact of the disease will be discussed in this chapter. Along with the effect of anticoagulation, laboratory testing of fibrinogen and coagulation, future directions, and implications will be presented.

PLATELET FUNCTION IN TRAUMA: IS CURRENT TECHNOLOGY IN FUNCTION TESTING MISSING THE MARK IN INJURED PATIENTS?

ABSTRACT

Platelets are subcellular anucleate components of blood primarily responsible for initiating and maintaining hemostasis. After injury to a blood vessel, platelets can be activated via several pathways, resulting in changed shape, adherence to the injury site, aggregation to form a plug, degranulation to initiate activation in other nearby platelets, and acceleration of thrombin formation to convert fibrinogen to fibrin before contracting to strengthen the clot. Platelet function assays use agonists to induce and measure one or more of these processes to identify alterations in platelet function that increase the likelihood of bleeding or thrombotic events. In severe trauma, these assays have revealed that platelet dysfunction is strongly associated with poor clinical outcomes. However, to date, the mechanism(s) causing clinically significant platelet dysfunction remain poorly understood. We review the pros, cons, and evidence for use of many of the popular assays in trauma, discuss limitations of their use in this patient population, and present approaches that can be taken to develop improved functional assays capable of elucidating mechanisms of trauma-induced platelet dysfunction. Platelet dysfunction in trauma has been associated with need for transfusions and mortality; however, most of the current platelet function assays were not designed for evaluating trauma patients, and there are limited data regarding their use in this population. New or improved functional assays will help define the mechanisms by which platelet dysfunction occurs, as well as help optimize future treatment.

The role of thromboxane prostanoid receptor signaling in gastric ulcer healing

The process of gastric ulcer healing includes cell migration, proliferation, angiogenesis and re-epithelialization. Platelets contain angiogenesis stimulating factors that induce angiogenesis. Thromboxane A2 (TXA2 ) not only induces platelet activity but also angiogenesis. This study investigated the role of TXA2 in gastric ulcer healing using TXA2 receptor knockout (TPKO) mice. Gastric ulcer healing was suppressed by treatment with the TXA2 synthase inhibitor OKY-046 and the TXA2 receptor antagonist S-1452 compared with vehicle-treated mice. TPKO showed delayed gastric ulcer healing compared with wild-type mice (WT). The number of microvessels and CD31 expression were lower in TPKO than in WT mice, and TPKO suppressed the expression of transforming growth factor beta (TGF-β) and vascular endothelial growth factor A (VEGF-A) in areas around gastric ulcers. Immunofluorescence assays showed that TGF-β and VEGF-A co-localized with platelets. Gastric ulcer healing was significantly reduced in WT mice transplanted with TPKO compared with WT bone marrow. These results suggested that TP signalling on platelets facilitates gastric ulcer healing through TGF-β and VEGF-A.

Role of Platelet Function Test in Predicting Postoperative Bleeding Risk after Coronary Artery Bypass Grafting: A Prospective Observational Study

Patients undergoing cardiac surgery are at risk of excessive bleeding and its associated complications. Excessive bleeding during and after cardiac surgery has an incidence of ~20%. Massive bleeding and subsequent requirement for blood product administration and mediastinal reexploration are associated with significant morbidity and mortality. Postoperative, nonsurgical bleeding in cardiac surgical patients is often multifactorial. Platelet dysfunction, excessive fibrinolysis, hypothermia, preoperative anemia, and deficiency of coagulation factors or their dilution are all suggested etiologies of postoperative bleeding. In the Arachidonic Acid Thromboelastometry (ARATEM) test, platelets are activated with arachidonic acid; in Adenosine diphosphate Thromboelastometry (ADPTEM) test, platelets are activated with adenosine diphosphate; and in TRAPTEM test, platelets are activated with thrombin receptor-activating peptide 6. Measurement time is 6 minutes, and results are expressed in three different parameters: A6 (amplitude at 6 minutes, in Ohm); MS (maximum slope of the aggregation curve in Ohm/min), and AUC (area under the curve in Ohm.min). Algorithm-based point-of-care platelet function testing helped us to preemptively give the right blood component therapy, avoiding fibrinolytic bleeding in the postoperative period.

A comparative study between light transmission aggregometry and flow cytometric platelet aggregation test for the identification of platelet function defects in patients with bleeding

Background

Platelet aggregation studies using conventional light transmission aggregometry (LTA) have several disadvantages and require strict pre-analytical measures for reliable results. We aimed to examine the utility of flow cytometric platelet aggregation (FCA) assay in detecting platelet function defects (PFDs) in patients with a history of bleeding symptoms.

Methods

Sixty-four participants (24 patients and 40 healthy controls) were included in this study. LTA and FCA assay were performed simultaneously in patients and healthy controls. In the FCA assay, two portions of platelets from the same individual were labeled separately with CD31-FITC and CD31-PE. After mixing and stimulation with agonists, the double-colored platelet aggregates were visualized using a flow cytometer. The results generated using the two techniques were compared and correlated.

Results

The patients’ median age was 17 years (range, 3‒72 yr) with a male-to-female ratio of 11.7. There was substantial agreement between LTA and FCA assay in detecting a PFD (k=0.792). Four patients showing a Glanzmann thrombasthenia-like pattern on LTA exhibited an abnormal FCA. A functional defect in collagen binding was detected on the FCA assay conducted in two immune thrombocytopenic patients with severe bleeding.

Conclusion

FCA assay can be used to identify functional defects in platelets, with potential applications in thrombocytopenic individuals. It also facilitates the diagnosis of inherited bleeding disorders with platelet defects.

Functional Assessment of Platelet Dense Granule ATP Release

OBJECTIVES

This study was undertaken to explore the feasibility of assessing platelet dense granule release in response to platelet stimuli, using less than 1 mL of whole blood (WB).

METHODS

Optimization of the luciferin-luciferase (LL) assay for ATP release, together with additional modifications, was applied to 1:10 diluted WB.

RESULTS

LL assay optimization using nonstirred 1:10 diluted WB resulted in dense granule ATP release in response to thrombin receptor-activating peptide (TRAP) of similar magnitude to that observed using stirred platelet-rich plasma. Stirring of the 1:10 diluted WB restored collagen-induced dense granule secretion. Addition of lyophilized, formalin-fixed platelets, together with stirring, restored dense granule secretion responsiveness to ADP. TRAP, ADP, and collagen all stimulated ATP release in 1:10 diluted WB under the optimized conditions of this study at levels close to those observed using platelet-rich plasma. Blood sample reconstitution experiments offer hope that this assay may prove robust down to WB platelet counts as low as 50 × 103/μL.

CONCLUSIONS

Platelet dense granule release in response to a number of classic stimuli, including ADP, was accomplished from less than 1 mL WB with minimal specimen processing, using widely available reagents and instrumentation.

Autoinducer N-(3-oxododecanoyl)-l-homoserine lactone induces calcium and reactive oxygen species-mediated mitochondrial damage and apoptosis in blood platelets

Acylated homoserine lactones (AHL) such as N-(3-oxododecanoyl)-l-homoserine lactone (3-oxo-C₁₂ HSL) and N-butyryl-l-homoserine lactone (C₄ HSL) are the most common autoinducer molecules in Pseudomonas aeruginosa. These AHL molecules not only regulate the expression of virulence factors but also have been shown to interfere with the host cell and modulate its functions. Recently, we reported that 3-oxo-C₁₂ HSL but not C₄ HSL causes cytosolic Ca²⁺ rise and ROS production in platelets. In this study, we examined the potential of AHLs to induce apoptosis in the human blood platelet. Our result showed that 3-oxo-C₁₂ HSL but not C₄ HSL causes phosphatidylserine (PS) exposure, mitochondrial dysfunction (mitochondrial transmembrane potential loss, and mitochondrial permeability transition pore (mPTP) formation). Besides, 3-oxo-C₁₂ HSL also inhibited thrombin-induced platelet aggregation and clot retraction. The pretreatment of an intracellular calcium chelator BAPTA-AM or ROS inhibitor (DPI) significantly attenuated the 3-oxo-C₁₂ HSL induced apoptotic characters such as PS exposure and mitochondrial dysfunctions. These data, including our previous findings, confirmed that 3-oxo-C₁₂ HSL induced intracellular Ca²⁺ mediated ROS production results in the activation and subsequent induction of apoptotic features in platelets. Our results demonstrated that the 3-oxo-C₁₂ HSL modulates the functions of platelets that may cause severe thrombotic complications in P. aeruginosa infected individuals.

Influence of different methods and anticoagulants on platelet parameter measurement

Platelets are the smallest and perhaps the most versatile components of human blood. Besides their role in coagulation and the maintenance of vascular integrity, they are involved in many physiological processes, ranging from immune response and leukocyte recruitment to the production of antimicrobial peptides and immune-suppressive factors like TGF-β. These versatile abilities make platelets interesting for researchers from different disciplines. However, beside profound investigation into platelets’ physiological role, there is a need for correct, standardized and thus reproducible quantification of platelet parameters. Mean platelet volume (MPV) is a widespread prognostic marker for several conditions, such as, acute coronary syndrome, chronic kidney disease and liver cirrhosis. Platelet activation is regarded as a marker for inflammatory processes, for example in autoimmune diseases such as type-1 diabetes, systemic lupus erythematosus and rheumatoid arthritis. The monitoring of platelet function is relevant for patients receiving antiplatelet medication. Platelet parameter measurement is affected by the choice of in vitro anticoagulant, the measurement technology and the time delay after sampling. This review focuses on the pre-analytical variability that arises as a result of the use of different in vitro anticoagulants and analyzer technologies when determining platelet parameters, since, even approximately 180 years after the discovery of platelets, there is still no standardized procedure.

Current methods of measuring platelet activity: pros and cons

: Platelets play a pivotal role in controlling hemorrhaging from vessels of the human body. The impairment of platelets may lead to the development of bleeding manifestations. Unraveling the precise defects of platelets by means of suitable laboratory methods paves the way for the effective control and management of platelet disorders. Choosing the most appropriate approach for the detection of platelet disorders may be difficult for a researcher or clinical internist when faced with ordering a platelet-function test. The aim of the current study was to provide a user-friendly overview of the advantages and disadvantages of the available detection systems. To reach this goal, 11 commonly used methods of studying platelet activity were evaluated and compared in detail. A literature search, with no time or language limitations, was conducted in Google Scholar and Medline. All publications published before June 2019 were analyzed. The following laboratory methods were compared: number and size of platelets, bleeding time, clot retraction time, platelet function assay 100 & 200, Rapid platelet function assay, flow cytometry, light transmission aggregometry, multiple electrode aggregometry, 96-well plate aggregometry, cone and plate(let) analyzer (Impact-R), and Plateletworks (single platelet counting system). This article provides the reader with a rapid comparison of the different systems used to study platelets activities.

A comparison of three platelet function tests in ischemic stroke patients with antiplatelet therapy

Predicting the effectiveness of antiplatelet drugs is critical to precision antiplatelet therapy. However, there is a lack of an acceptable method, although there are a variety of methods for detecting platelet function. In this study, we compared three major platelet function tests to assess their performance and found better methods for platelet function evaluation after aspirin or clopidogrel treatment in ischemic stroke patients by comparative study. A total of 249 ischemic stroke patients were enrolled who were treated with aspirin or clopidogrel or both. Three platelet function tests including light transmittance aggregometry (LTA), thromboelastography (TEG), platelet function analyzer (PFA) were performed as well as CYP2C19 genotype determination. Correlation analyses and kappa statistics were used. All three methods were effective in evaluating aspirin function. However, only LTA and TEG had good correlation and consistency (r = -0.37, kappa = 0.634). TEG-ADP was the least sensitive for clopidogrel, as the platelet inhibition ratio did not differ between the clopidogrel-user group and the control (P = 0.074), while LTA and PFA were sensitive (P ＜ 0.001). Correlations between platelet assays were poor for clopidogrel (the absolute value of r range from 0.13 to 0.35) and so was the agreement (Kappa from 0.232 to 0.314). LTA and PFA have a good correlation with CYP2C19 genotyping (P = 0.034 and 0.014). In conclusion, all three tests were able to evaluate aspirin effect, LTA-AA and TEG-AA had a good correlation. TEG perform badly for clopidogrel effect detection. The fair-to-modest agreement among assays indicated further study was indispensable.

Calcium chelation: a novel approach to reduce cryopreservation-induced damage to frozen platelets

BACKGROUND

Cryopreserved platelets are phenotypically and functionally different to conventionally stored platelets. Calcium may be released from internal stores during the freeze-thaw process, initiating signaling events which lead to these alterations. It was hypothesized that the addition of a calcium chelator prior to cryopreservation may mitigate some of these changes.

METHODS

Buffy coat-derived platelets that had been pooled and split were tested fresh and following cryopreservation (n = 8 per group). Platelets were cryopreserved using 5%-6% dimethylsulfoxide (DMSO) or were supplemented with increasing concentrations of the internal calcium chelator, BAPTA-AM (100 μM, 200 μM, or 400 μM), prior to storage at -80°C.

RESULTS

Supplementation of platelets with BAPTA-AM prior to freezing improved platelet recovery in a dose response manner (400 μM: 84 ± 2%) compared to standard DMSO cryopreserved platelets (70 ± 4%). There was a loss of GPIbα, GPVI, and GPIIb/IIIa receptors on platelets following cryopreservation, which was rescued when platelets were supplemented with BAPTA-AM (400 μM: p < 0.0001 for all). Platelet activation markers, such as phosphatidylserine and P-selectin, were externalized on platelets following cryopreservation. However, the addition of BAPTA-AM significantly reduced the increase of these activation markers on cryopreserved platelets (400 μM: p < 0.0001 for both). Both cryopreserved platelet groups exhibited similar functionality as assessed by thromboelastography, forming clots at a faster rate than fresh platelets.

CONCLUSIONS

This study demonstrates that calcium plays a crucial role in mediating cryopreservation-induced damage to frozen platelets. The addition of the calcium chelator, BAPTA-AM, prior to cryopreservation reduces this damage.

Development of a Nonradioactive Platelet Serotonin Uptake and Release Assay by Micro-Liquid Chromatography Tandem Mass Spectrometry Using Minimal Blood Volume

OBJECTIVES

Analysis of platelet functional responses to stimuli is presently quite limited with respect to measurement of dense granule secretion. We sought to develop a nonradioactive assay of stimulated serotonin release using liquid chromatography tandem mass spectrometry (LC-MS/MS).

METHODS

Citrated whole blood (200 μL) was incubated with deuterated serotonin (d45-HT). Following uptake by platelets, blood was diluted 10-fold and aliquots were incubated with platelet stimuli. Following stimulation, blood was further diluted, centrifuged, and supernatant was assayed for released d45-HT by micro-LC-MS/MS.

RESULTS

This study demonstrated a broad linear range of 50 to 2,000 pg/mL d45-HT, with a total precision of less than 15.0% coefficient of variation at all quality control levels and a limit of quantitation of 50 pg/mL.

CONCLUSIONS

Quantification of d45-HT by micro-LC-MS/MS assay offers a highly sensitive, nonradioactive methodology for quantitating platelet serotonin uptake and dense granule secretion, requiring only small volumes of patient blood.

Towards increasing shelf life and haemostatic potency of stored platelet concentrates

PURPOSE OF REVIEW

Platelet transfusion is a widely used therapy in treating or preventing bleeding and haemorrhage in patients with thrombocytopenia or trauma. Compared with the relative ease of platelet transfusion, current practice for the storage of platelets is inefficient, costly and relatively unsafe, with platelets stored at room temperature (RT) for upto 5-7 days.

RECENT FINDINGS

During storage, especially at cold temperatures, platelets undergo progressive and deleterious changes, collectively termed the 'platelet storage lesion', which decrease their haemostatic function and posttransfusion survival. Recent progress in understanding platelet activation and host clearance mechanisms is leading to the consideration of both old and novel storage conditions that use refrigeration and/or cryopreservation to overcome various storage lesions and significantly extend platelet shelf-life with a reduced risk of pathogen contamination.

SUMMARY

A review of the advantages and disadvantages of alternative methods for platelet storage is presented from both a clinical and biological perspective. It is anticipated that future platelet preservation involving cold, frozen and/or pathogen reduction strategies in a proper platelet additive solution will enable longer term and safer platelet storage.

Role of Thromboelastography and Rotational Thromboelastometry in the Management of Cardiovascular Diseases

The monitoring of coagulation by viscoelastometric methods—thromboelastography and rotational thromboelastometry—may detect the contributions of cellular and plasma components of hemostasis. These methods might overcome some of the serious limitations of conventional laboratory tests. Viscoelastic testing can be repeatedly performed during and after surgery and thus provides a dynamic picture of the coagulation process during these periods. Several experiences with the use of these methods in cardiovascular surgery have been reported, but there is perspective for more frequent use of these assays in the assessment of platelet response to antiplatelet therapy and in the assessment of coagulation in patients on long-term dabigatran therapy. This article reviews the current role and future perspectives of thromboelastography and thromboelastometry in the management of cardiovascular diseases.

Mass Cytometry Reveals Distinct Platelet Subtypes in Healthy Subjects and Novel Alterations in Surface Glycoproteins in Glanzmann Thrombasthenia

Mass cytometry (MC) uses mass spectrometry to simultaneously detect multiple metal-conjugated antibodies on single cells, thereby enabling the detailed study of cellular function. Here, for the first time, we applied MC to the analysis of platelets. We developed a panel of 14 platelet-specific metal-tagged antibodies (targeting cluster of differentiation [CD] 9, CD29, CD31, CD36, CD41, CD42a, CD42b, CD61, CD62P, CD63, CD107a, CD154, glycoprotein [GP] VI and activated integrin αIIbβ3) and compared this panel with two fluorescence flow cytometry (FFC) panels (CD41, CD42b, and CD61; or CD42b, CD62P, and activated integrin αIIbβ3) in the evaluation of activation-dependent changes in glycoprotein expression on healthy subject and Glanzmann thrombasthenia (GT) platelets. High-dimensional analysis of surface markers detected by MC identified previously unappreciated subpopulations of platelets in healthy donors. As expected, MC and FFC revealed that GT platelets had significantly reduced CD41, CD61, and activated integrin αIIbβ3 surface expression. MC also revealed that surface expression of CD9, CD42a and CD63 were elevated, CD31, CD154 and GPVI were reduced and CD29, CD36, CD42b, CD62P and CD107a were similar on GT platelets compared to healthy donor platelets. In summary, MC revealed distinct platelet subtypes in healthy subjects and novel alterations in surface glycoproteins on GT platelets.

Synthesis of a series of benzothiazole amide derivatives and their biological evaluation as potent hemostatic agents

A series of benzothiazole amide derivatives were synthesized through a facile and efficient method via a nucleophilic acyl substitution reaction between 2-aminobenzothiazole and various cinnamic acid compounds. The obtained products exhibited good thermal stabilities. All compounds were evaluated for their in vitro hemostatic activities using the commercially available standard drug etamsylate as a positive control. The results showed that compound Q2 had a significant partial coagulation activity, reduced capillary permeability at 5, 10 and 50 μmol L⁻¹, activated thrombin activity, and a more potent platelet aggregation activity than the positive control group (etamsylate, up to 1283.9 times in the nanomole range). A molecular modeling study revealed that compound Q2 was a competitive thrombin activator. Therefore, Q2 may be a potential lead for further biological screening and for the generation of drug molecules. Moreover, the structure–activity relationship of the prepared compounds is also discussed herein.

New benzothiazole amide derivative Q2 is a potential hemostatic drug molecule with good hemostatic activity.

Impact of levosimendan on platelet function

Levosimendan has been developed for treatment of severe heart failure. The favorable hemodynamic effect of levosimendan is related to its unique dual mechanism of action - increase of the contractile force of the myocardium caused by enhanced sensitivity of myofilaments to calcium combined with vasodilatation caused by the opening of adenosine triphosphate - dependent potassium channels. Due to the structural similarities to phosphodiesterase inhibitors it may partly exert its action via inhibition of phosphodiesterase inhibitors III. Inhibition of the phosphodiesterase inhibitors III leads to an increase of intracellular concentration of cyclic adenosine monophosphate causing an anti-aggregatory effect. There are some contradictory or indirect and inconclusive reports related to the impact of levosimendan on platelet function. The aim of this systematic review was to critically discuss the impact of levosimendan on platelet function according to currently available knowledge based on the findings of experimental as well as observational and randomized clinical studies.

Significant Risk Factors for Postoperative Enlargement of Basal Ganglia Hematoma after Frameless Stereotactic Aspiration: Antiplatelet Medication and Concomitant IVH

OBJECTIVE

Frameless stereotactic aspiration of a hematoma can be the one of the treatment options for spontaneous intracerebral hemorrhage in the basal ganglia. Postoperative hematoma enlargement, however, can be a serious complication of intracranial surgery that frequently results in severe neurological deficit and even death. Therefore, it is important to identify the risk factors of postoperative hematoma growth.

METHODS

During a 13-year period, 101 patients underwent minimally invasive frameless stereotactic aspiration for basal ganglia hematoma. Patients were classified into two groups according to whether or not they had postoperative hematoma enlargement in a computed tomography scan. Baseline demographic data and several risk factors, such as hypertension, preoperative hematoma growth, antiplatelet medication, presence of concomitant intraventricular hemorrhage (IVH), were analysed via a univariate statistical study.

RESULTS

Nine of 101 patients (8.9%) showed hematoma enlargement after frameless stereotactic aspiration. Among the various risk factors, concomitant IVH and antiplatelet medication were found to be significantly associated with postoperative enlargement of hematomas.

CONCLUSION

In conclusion, our study revealed that aspirin use and concomitant IVH are factors associated with hematoma enlargement subsequent to frameless stereotactic aspiration for basal ganglia hematoma.

Point-of-Care-Testing in Acute Stroke Management: An Unmet Need Ripe for Technological Harvest

Stroke, the second highest leading cause of death, is caused by an abrupt interruption of blood to the brain. Supply of blood needs to be promptly restored to salvage brain tissues from irreversible neuronal death. Existing assessment of stroke patients is based largely on detailed clinical evaluation that is complemented by neuroimaging methods. However, emerging data point to the potential use of blood-derived biomarkers in aiding clinical decision-making especially in the diagnosis of ischemic stroke, triaging patients for acute reperfusion therapies, and in informing stroke mechanisms and prognosis. The demand for newer techniques to deliver individualized information on-site for incorporation into a time-sensitive work-flow has become greater. In this review, we examine the roles of a portable and easy to use point-of-care-test (POCT) in shortening the time-to-treatment, classifying stroke subtypes and improving patient's outcome. We first examine the conventional stroke management workflow, then highlight situations where a bedside biomarker assessment might aid clinical decision-making. A novel stroke POCT approach is presented, which combines the use of quantitative and multiplex POCT platforms for the detection of specific stroke biomarkers, as well as data-mining tools to drive analytical processes. Further work is needed in the development of POCTs to fulfill an unmet need in acute stroke management.

Synthesis and biological evaluation of a new series of cinnamic acid amide derivatives as potent haemostatic agents containing a 2-aminothiazole substructure

Ten new cinnamic acid derivatives containing a 2-aminothiazole substructure were designed and synthesized. This series of compounds exhibited good thermostabilities as demonstrated by thermogravimetric analysis. In coagulation assays (prothrombin time, activated partial thromboplastin time and thrombin time) in vitro, most compounds demonstrated excellent activities to promote blood coagulation. Among the studied series, compounds N1, N4, N5 and W5 exhibited a significant coagulation activity. Further studies indicated that compound N5 (IC₅₀=1.87μmol/L) displayed the most suitable efficacy of promoting platelet aggregation than the clinically used haemostatic drug etamsylate (IC₅₀=46.22μmol/L). Furthermore, the relationship between the functional groups of the compounds and the corresponding blood coagulant activity was explored in this study.

Hereditary Blood Coagulation Disorders: Management and Dental Treatment

Patients with hereditary hemostatic disorders, characterized by a tendency to bleeding or thrombosis, constitute a serious challenge in the dental practice. Advances in the medical diagnosis of hemostatic disorders have exposed dental professionals to new patients not amenable to the application of the management protocols associated with other, more well-known, disorders. It is the aim of this paper to review the evidence, to highlight the areas of major concern, and to suggest management regimens for patients with hereditary hemostatic disorders. An extensive review has been made (PubMed, Science Direct, Web of Knowledge, etc.) of literature pertaining to hereditary disorders affecting blood coagulation factors and how they affect the practice of dentistry. Several aspects relating to the care of such patients must be recognized and taken into consideration when dental treatment is planned. Replacement of deficient coagulation factors ensures that safe dental treatment will be carried out. However, the half-life of such coagulation factors requires that dental treatment be specifically planned and adapted to the type of pathology involved.

The Effect of Hyperparathyroid State on Platelet Functions and Bone Loss

Objective:

Coagulation and fibrinolysis defects were reported in primary hyperparathyroid patients. However, there are not enough data regarding platelet functions in this group of patients. Our aim was to evaluate the platelet functions in primary and secondary hyperparathyroid patients and to compare them with healthy subjects.

Materials and Methods:

In our study 25 subjects with primary hyperparathyroidism (PHPT), 25 subjects with secondary hyperparathyroidism (SHPT), and 25 healthy controls were included. Platelet functions of the subjects were evaluated by using platelet-rich plasma and platelet aggregation tests induced with epinephrine, adenosine diphosphate (ADP), collagen, and ristocetin. Serum P selectin levels, which indicate platelet activation level, were measured in all subjects. Bone mineral densitometry was performed for all patients.

Results:

There was no significant difference between the groups with PHPT and SHPT and the control group regarding the platelet aggregation tests and serum P selectin levels. There was also no significant correlation between parathormone levels and aggregation parameters (ristocetin, epinephrine, collagen, and ADP: respectively p=0.446, 0.537, 0.346, and 0.302) and between P selectin (p=0.516) levels. When we separated the patients according to serum calcium levels, there was also no significant difference between aggregation parameters and serum P selectin levels between the patients with hypercalcemia and the patients with normocalcemia. We could not find any significant correlation between aggregation parameters, P selectin levels, and serum calcium levels in this group of patients. Bone loss was greater in patients with PHPT.

Conclusion:

There is no significant effect of PHPT or SHPT and serum calcium levels on platelet functions when evaluated by aggregation tests.

Functional recovery of stored platelets after transfusion

BACKGROUND

Platelet (PLT) concentrates are prophylactically given to prevent major bleeding complications. The corrected count increment (CCI) is currently the only tool to monitor PLT transfusion efficacy. PLT function tests cannot be performed in patients with thrombocytopenia. Therefore, an optimized agonist-induced assay was used to determine PLT function, in patients with severe thrombocytopenia before and after transfusion.

STUDY DESIGN AND METHODS

PLT reactivity toward adenosine diphosphate (ADP), thrombin receptor-activating peptide SFLLRN (TRAP), and convulxin (CVX) was assessed by flow cytometry. P-selectin expression was measured on PLTs from 11 patients with thrombocytopenia before and 1 hour after transfusion, on stored PLTs, and on stored PLTs incubated for 1 hour in whole blood from patients ex vivo.

RESULTS

The mean (±SEM) CCI after 1 hour was 11.4 (±1.5). After transfusion, maximal agonist-induced PLT P-selectin expression was on average 29% higher for ADP (p = 0.02), 25% higher for TRAP (p = 0.007), and 24% higher for CVX (p = 0.0008). ADP-induced reactivity of stored PLTs increased with 46% after ex vivo incubation (p = 0.007). These PLTs also showed an overall higher P-selectin expression compared to PLTs 1 hour after transfusion (p = 0.005). After normalization for this background expression, a similar responsiveness was observed.

CONCLUSIONS

Our study shows recovery of PLT function after transfusion in patients with thrombocytopenia. The majority of functional PLTs measured after transfusion most likely represents stored transfused PLTs that regained functionality in vivo. The difference in baseline P-selectin expression in vivo versus ex vivo suggests a rapid clearance from circulation of PLTs with increased P-selectin expression.

Control of bleeding in surgical procedures: critical appraisal of HEMOPATCH (Sealing Hemostat)

The need for advanced hemostatic agents increases with the complexity of surgical procedures and use of anticoagulation and antiplatelet treatments. HEMOPATCH (Sealing Hemostat) is a novel, advanced hemostatic pad that is composed of a synthetic, protein-reactive monomer and a collagen backing. The active side is covered with a protein-reactive monomer: N-hydroxysuccinimide functionalized polyethylene glycol (NHS-PEG). NHS-PEG rapidly affixes the collagen pad to tissue to promote and maintain hemostasis. The combined action of the NHS-PEG and collagen is demonstrated to have benefit relative to other hemostatic agents in surgery and preclinical surgical models. This paper reviews the published investigations and case reports of the hemostatic efficacy of HEMOPATCH, wherein HEMOPATCH is demonstrated to be an effective, easy-to-use hemostatic agent in open and minimally invasive surgery of patients with thrombin- or platelet-induced coagulopathies.

Kinetics and mechanics of clot contraction are governed by the molecular and cellular composition of the blood

Platelet-driven blood clot contraction (retraction) is thought to promote wound closure and secure hemostasis while preventing vascular occlusion. Notwithstanding its importance, clot contraction remains a poorly understood process, partially because of the lack of methodology to quantify its dynamics and requirements. We used a novel automated optical analyzer to continuously track in vitro changes in the size of contracting clots in whole blood and in variously reconstituted samples. Kinetics of contraction was complemented with dynamic rheometry to characterize the viscoelasticity of contracting clots. This combined approach enabled investigation of the coordinated mechanistic impact of platelets, including nonmuscle myosin II, red blood cells (RBCs), fibrin(ogen), factor XIIIa (FXIIIa), and thrombin on the kinetics and mechanics of the contraction process. Clot contraction is composed of 3 sequential phases, each characterized by a distinct rate constant. Thrombin, Ca(2+), the integrin αIIbβ3, myosin IIa, FXIIIa cross-linking, and platelet count all promote 1 or more phases of the clot contraction process. In contrast, RBCs impair contraction and reduce elasticity, while increasing the overall contractile stress generated by the platelet-fibrin meshwork. A better understanding of the mechanisms by which blood cells, fibrin(ogen), and platelet-fibrin interactions modulate clot contraction may generate novel approaches to reveal and to manage thrombosis and hemostatic disorders.

Novel whole blood assay for phenotyping platelet reactivity in mice identifies ICAM-1 as a mediator of platelet-monocyte interaction

Testing of platelet function is central to the cardiovascular phenotyping of genetically modified mice. Traditional platelet function tests have been developed primarily for testing human samples and the volumes required make them highly unsuitable for the testing of mouse platelets. This limits research in this area. To address this problem, we have developed a miniaturized whole blood aggregometry assay, based on a readily accessible 96-well plate format coupled with quantification of single platelet depletion by flow cytometric analysis. Using this approach, we observed a concentration-dependent loss of single platelets in blood exposed to arachidonic acid, collagen, U46619 or protease activated receptor 4 activating peptide. This loss was sensitive to well-established antiplatelet agents and genetic manipulation of platelet activation pathways. Observations were more deeply analyzed by flow cytometric imaging, confocal imaging, and measurement of platelet releasates. Phenotypic analysis of the reactivity of platelets taken from mice lacking intercellular adhesion molecule (ICAM)-1 identified a marked decrease in fibrinogen-dependent platelet-monocyte interactions, especially under inflammatory conditions. Such findings exemplify the value of screening platelet phenotypes of genetically modified mice and shed further light upon the roles and interactions of platelets in inflammation.

Platelet geometry sensing spatially regulates α-granule secretion to enable matrix self-deposition

Although the biology of platelet adhesion on subendothelial matrix after vascular injury is well characterized, how the matrix biophysical properties affect platelet physiology is unknown. Here we demonstrate that geometric orientation of the matrix itself regulates platelet α-granule secretion, a key component of platelet activation. Using protein microcontact printing, we show that platelets spread beyond the geometric constraints of fibrinogen or collagen micropatterns with <5-µm features. Interestingly, α-granule exocytosis and deposition of the α-granule contents such as fibrinogen and fibronectin were primarily observed in those areas of platelet extension beyond the matrix protein micropatterns. This enables platelets to "self-deposit" additional matrix, provide more cellular membrane to extend spreading, and reinforce platelet-platelet connections. Mechanistically, this phenomenon is mediated by actin polymerization, Rac1 activation, and αIIbβ3 integrin redistribution and activation, and is attenuated in gray platelet syndrome platelets, which lack α-granules, and Wiskott-Aldrich syndrome platelets, which have cytoskeletal defects. Overall, these studies demonstrate how platelets transduce geometric cues of the underlying matrix geometry into intracellular signals to extend spreading, which endows platelets spatial flexibility when spreading onto small sites of exposed subendothelium.

Laboratory diagnostics of inherited platelet disorders

Abstract Inherited platelet disorders (IPDs) are the general and common denomination of a broad number of different rare and congenital pathologies affecting platelets. Even if these disorders are characterized by widely heterogeneous clinical presentations, all of them are commonly present as defects in hemostasis. Platelet number and/or function are affected by a wide spectrum of severity. IPDs might be associated with defects in bone marrow megakaryocytopoiesis and, rarely, with somatic defects. Although in the last few years new insights in the genetic bases and pathophysiology of IPDs have greatly improved our knowledge of these disorders, much effort still needs to be made in the field of laboratory diagnosis. This review discusses the laboratory approach for the differential diagnosis of the most common IPDs, suggesting a common multistep flowchart model which starts from the simpler test (platelet count) ending with the more selective and sophisticated analyses.

Clinical phenotype in heterozygote and biallelic Bernard-Soulier syndrome--a case control study

Bernard-Soulier syndrome (BSS) is a rare severe autosomal recessive bleeding disorder. To date heterozygous carriers of BSS mutations have not been shown to have bleeding symptoms. We assessed bleeding using a semi-quantitative questionnaire, platelet parameters, PFA-100 closure times, ristocetin response, GP Ib/IX expression and VWF antigen in 14 BSS patients, 30 heterozygote carriers for related mutations and 29 controls. Eight mutations in GP1BA, GP1BB or GP9 were identified including four previously unknown pathogenic mutations. Subjects with BSS reported markedly more mucocutaneous bleeding than controls. Increased bleeding was also observed in heterozygotes. Compared to controls, patients with BSS had lower optical platelet counts (P < 0.001), CD61-platelet counts (P < 0.001) and higher mean platelet volume (17.7 vs. 7.8 fL, P < 0.001) and ristocetin response and closure times were unmeasurable. Heterozygotes had higher MPV (9.7 fL, P < 0.001) and lower platelet counts (P < 0.001) than controls but response to ristocetin and closure times were normal. The VWF was elevated in both BSS and in heterozygotes (P = 0.005). We conclude that heterozygotes for BSS mutations have lower platelet counts than controls and show a bleeding phenotype albeit much milder than in BSS. Both patients with BSS and heterozygote carriers of pathogenic mutations have raised VWF.

Reduced IL-35 levels are associated with increased platelet aggregation and activation in patients with acute graft-versus-host disease after allogeneic hematopoietic stem cell transplantation

Acute graft-versus-host disease (aGVHD) is a major complication associated with allogeneic hematopoietic stem cell transplantation (allo-HSCT). Interleukin (IL)-35 is a novel anti-inflammatory cytokine that suppresses the immune response. This prospective study explored IL-35 plasma levels in 65 patients after HSCT. The results revealed that the peripheral blood of patients with grades III-IV aGVHD (23.46 ng/ml) had reduced IL-35 compared to transplanted patients with grades I-II aGVHD (40.26 ng/ml, p < 0.01) or patients without aGVHD (41.40 ng/ml, p < 0.05). Allografts, including granulocyte colony-stimulating factor (G-CSF)-mobilized peripheral blood progenitor cell (PBPC) and G-CSF-primed bone marrow (GBM), from 38 patients were analyzed for IL-35 levels with respect to aGVHD. The patients who received lower levels of IL-35 cells in the GBM (28.0 ng/ml, p = 0.551) or lower levels of IL-35 in PBPC (53.46 ng/ml, p = 0.03) exhibited a higher incidence of aGVHD. Patients with aGVHD have increased platelet aggregation. IL-35 was added to patient blood in vitro, and platelet aggregation was inhibited by IL-35 in a dose-dependent manner. The markers of platelet activation (CD62P/PAC-1) can also be inhibited by IL-35. The results indicate that IL-35 may affect the development of aGVHD by inhibiting platelet activation and aggregation. Our data suggests that IL-35 represents a potentially effective therapeutic agent against aGVHD after allo-HSCT.

Assessment of platelet function: Laboratory and point-of-care methods

In the event of blood vessel damage, human platelets are promptly recruited on the site of injury and, after their adhesion, activation and aggregation, prevent blood loss with the formation of a clot. The consequence of abnormal regulation can be either hemorrhage or the development of thrombosis. Qualitative and/or quantitative defects in platelets promote bleeding, whereas the residual reactivity of platelets, despite antiplatelet therapies, play an important role in promoting arterial thrombotic complications. Platelet function is traditionally assessed to investigate the origin of a bleeding syndrome, to predict the risk of bleeding prior surgery or during pregnancy or to monitor the efficacy of antiplatelet therapy in thrombotic syndromes that, now, can be considered a new discipline. “Old” platelet function laboratory tests such as the evaluation of bleeding time and the platelet aggregation analysis in platelet-rich plasma are traditionally utilized to aid in the diagnosis and management of patients with platelet and hemostatic disorders and used as diagnostic tools both in bleeding and thrombotic diathesis in specialized laboratories. Now, new and renewed automated systems have been introduced to provide a simple, rapid assessment of platelet function including point of care methods. These new methodologies are also suitable for being used in non-specialized laboratories and in critical area for assessing platelet function in whole blood without the requirement of sample processing. Some of these methods are also beginning to be incorporated into routine clinical use and can be utilized as not only as first panel for the diagnosis of platelet dysfunction, but also for monitoring anti-platelet therapy and to potentially assess risk of both bleeding and/or thrombosis.

ACE and platelet aggregation inhibitors from Tamarix hohenackeri Bunge (host plant of Herba Cistanches) growing in Xinjiang

Background:

Tamarix hohenackeri Bunge is a salt cedar that grows widespread in the desert mountains in Xinjiang. T. hohenackeri has not been investigated earlier, although there are many reports of phytochemical work on other Tamarix species.

Materials and Methods:

To find out natural angiotensin-converting enzyme (ACE) inhibitor and platelet aggregation inhibitors, the bioactive extract (ethyl acetate [EtOAc] fraction) from the dried aerial parts of T. hohenackeri were investigated. The active fraction was purified by repeated column chromatography, including silica gel, Sephadex LH-20 column, medium-pressure liquid chromatography (MPLC) (polyamide column) and high-performance liquid chromatography (HPLC). The isolated major constituents were tested for their anti-platelet aggregation activity.

Results:

Bioassay-directed separation of the EtOAc fraction of the 70% ethanol extract from the air-dried aerial parts of T. hohenackeri led to the isolation of a new triterpenoid lactone (1), together with 13 known compounds (2-14). It was the first time to focus on screening bioactive constituents for this plant. The chemical structures were established on the basis of spectral data (ESI-MS and NMR). The results showed that the flavonoid compounds (7 and 8) and phenolic compounds (9, 10, 11, and 14) were potential ACE inhibitors. And the flavonoid compounds (5 and 7) showed significant anti-platelet aggregation activities.

Conclusion:

On the basis of the chemical and biological data, the material basis of ACE inhibitory activity for the active part was the phenolic constituents. However, the flavonoid compounds were responsible for the anti-platelet aggregation. The primary structure and activity relationship were also discussed respectively.

Perioperative coagulopathy monitoring

Coagulopathy is common in orthopedic surgery patients either due to acquired factors, such as surgery, trauma, medications, or hemorrhage. Perioperative monitoring of blood coagulation is critical to diagnose the causes of hemorrhage, guide hemostatic therapies, predict the risk of bleeding during surgical procedures, and reduce risk of postoperative cardiac and thromboembolic events. In contrast to previous interventions that measure specific portions of the clotting cascade (such as intrinsic or extrinsic pathways or platelet aggregation), "Point-of-care" coagulation monitoring devices assess the viscoelastic properties of whole blood. These techniques have the potential to measure the entire clotting process, starting with fibrin formation, clot retraction, and fibrinolysis. Furthermore, the coagulation status of patients is assessed in whole blood, allowing the plasmatic coagulation system to interact with platelets and red cells, and thereby providing useful additional information on platelet function. Improved monitoring of coagulopathy is particularly important as new anticoagulant drugs emerge that affect the clotting cascade in novel ways, including the inhibition of intrinsic and extrinsic pathways and platelet function. It is important for orthopedic surgeons to understand the pharmacology and reversal of these drugs in the perioperative setting. The purpose of this review is to review the current techniques to monitoring perioperative coagulopathy and to identify the manner in which novel anticoagulant medications affect the clotting cascade with particular interest in trauma and spine surgery.

Comprehensive Evaluation of Hemostasis in Normal Women

Women with mild bleeding disorders (MBDs) pose a diagnostic challenge and menorrhagia, the most common presenting symptom that remains underreported. We tested the hypothesis that screening apparently normal females using general and gynecological bleeding assessment tools and a global hemostatic assay together with platelet aggregation can help predict MBDs. We assessed 47 women using electronic bleeding assessment tools; e-bleeding questionnaire; and e-Pictorial Bleeding Assessment Chart (e-PBAC) based on previously validated methods, thrombelastography (TEG), and platelet aggregation together with basic coagulation testing. Three women had elevated bleeding score with von Willebrand disease diagnosis confirmed in one case and eleven cases had elevated e-PBAC. We report normal ranges for TEG and platelet aggregation in women during the first half of the menstrual cycle and show 23.4% of apparently normal women may have general or heavy menstrual bleeding. This is a prelude to a larger study to determine the validity of bleeding assessment tools in screening for MBDs in women.