Formation and regulation of platelet and fibrin hemostatic plug

Steps Toward Recapitulating Endothelium: A Perspective on the Next Generation of Hemocompatible Coatings

Endothelium, the lining in this blood vessel, orchestrates three main critical functions such as protecting blood components, modulating of hemostasis by secreting various inhibitors, and directing clot digestion (fibrinolysis) by activating tissue plasminogen activator. No other surface can perform these tasks; thus, the contact of blood and blood-contacting medical devices inevitably leads to the activation of coagulation, often causing device failure, and thromboembolic complications. This perspective, first, discusses the biological mechanisms of activation of coagulation and highlights the efforts of advanced coatings to recapitulate one characteristic of endothelium, hereafter single functions of endothelium and noting necessity of the synergistic integration of its three main functions. Subsequently, it is emphasized that to overcome the challenges of blood compatibility an endothelium-mimicking system is needed, proposing a synergy of bottom-up synthetic biology, particularly synthetic cells, with passive- and bioactive surface coatings. Such integration holds promise for developing advanced biomaterials capable of recapitulating endothelial functions, thereby enhancing the hemocompatibility and performance of blood-contacting medical devices.

Hard Ticks as Vectors: The Emerging Threat of Tick-Borne Diseases in India

Hard ticks (Ixodidae) play a critical role in transmitting various tick-borne diseases (TBDs), posing significant global threats to human and animal health. Climatic factors influence the abundance, diversity, and vectorial capacity of tick vectors. It is imperative to have a comprehensive understanding of hard ticks, pathogens, eco-epidemiology, and the impact of climatic changes on the transmission dynamics of TBDs. The distribution and life cycle patterns of hard ticks are influenced by diverse ecological factors that, in turn, can be impacted by changes in climate, leading to the expansion of the tick vector's range and geographical distribution. Vector competence, a pivotal aspect of vectorial capacity, involves the tick's ability to acquire, maintain, and transmit pathogens. Hard ticks, by efficiently feeding on diverse hosts and manipulating their immunity through their saliva, emerge as competent vectors for various pathogens, such as viruses, parasites and bacteria. This ability significantly influences the success of pathogen transmission. Further exploration of genetic diversity, population structure, and hybrid tick vectors is crucial, as they play a substantial role in influencing vector competence and complicating the dynamics of TBDs. This comprehensive review deals with important TBDs in India and delves into a profound understanding of hard ticks as vectors, their biology, and the factors influencing their vector competence. Given that TBDs continue to pose a substantial threat to global health, the review emphasizes the urgency of investigating tick control strategies and advancing vaccine development. Special attention is given to the pivotal role of population genetics in comprehending the genetic diversity of tick populations and providing essential insights into their adaptability to environmental changes.

Gluing blood into adhesive gel by oppositely charged polysaccharide dry powder inspired by fibrin fibers coagulation mediator

Hemostatic powders that adapt to irregularly shaped wounds, allowing for easy application and stable storage, have gained popularity for first-aid hemorrhage control. However, traditional powders often provide weak thrombus support and exhibit limited tissue adhesion, making them susceptible to dislodgment by the bloodstream. Inspired by fibrin fibers coagulation mediator, we have developed a bi-component hemostatic powder composed of positively charged quaternized chitosan (QCS) and negatively charged catechol-modified alginate (Cat-SA). Upon application to the wound, the bi-component powders (QCS/Cat-SA) rapidly absorb plasma and dissolve into chains. These chains interact with each other to form a network, which can effectively bind and entraps clustered red blood cells and platelets, ultimately leading to the creation of a durable and robust thrombus. Significantly, these interconnected polymers adhere to the injury site, offering protection against thrombus disruption caused by the bloodstream. Benefiting from these synthetic properties, QCS/Cat-SA demonstrates superior hemostatic performance compared to commercial hemostatic powders like Celox™ in both arterial injuries and non-compressible liver puncture wounds. Importantly, QCS/Cat-SA exhibits excellent antibacterial activity, cytocompatibility, and hemocompatibility. These advantages of QCS/Cat-SA, including strong blood clotting, wet tissue adherence, antibacterial activity, biosafety, ease of use, and stable storage, make it a promising hemostatic agent for emergency situations.

Antithrombotic and prohemorrhagic actions of different concentrations of apixaban in patients exposed to single and dual antiplatelet regimens

We evaluated modifications in the hemostatic balance of different concentrations of apixaban (APIX) in 25 healthy donors and 53 patients treated with aspirin (ASA, n = 21), ASA and clopidogrel (ASA + CLOPI, n = 11), or ASA and ticagrelor (ASA + TICA, n = 21). Blood samples from participants were spiked ex vivo with apixaban 0 (APIX0), 40 (APIX40), and 160 ng/mL (APIX160). We assessed the effects of APIX on (1) clot formation, by ROTEM thromboelastometry; (2) thrombin generation primed by platelets; and (3) platelet and fibrin interactions with a thrombogenic surface, in a microfluidic model with circulating blood. APIX caused dose-related prolongations of clotting time with minimal impact on other ROTEM parameters. Thrombin generation was significantly inhibited by APIX160, with ASA + TICA actions showing the strongest inhibition (p < 0.01 vs APIX0). Microfluidic studies showed that APIX160 was more potent at suppressing platelet and fibrin interactions (p < 0.001 vs. APIX0). APIX40 demonstrated a consistent antithrombotic action but with a favorable protective effect on the structural quality of fibrin. APIX potentiated the antithrombotic effects of current antiplatelet regimens. APIX at 40 ng/mL, enhanced the antithrombotic action of single or dual antiplatelet regimens but was more conservative for hemostasis than the 160 ng/mL concentration.

Heparin Resistance During Cardiopulmonary Bypass in Adult Cardiac Surgery

The use of heparin for anticoagulation has changed the face of cardiac surgery by allowing a bloodless and motionless surgical field throughout the introduction of cardiopulmonary bypass (CPB). However, heparin is a drug with complex pharmacologic properties that can cause significant interpatient differences in terms of responsiveness. Heparin resistance during CPB is a weighty issue due to the catastrophic consequences stemming from inadequate anticoagulation, and the treatment of it necessitates a rationalized stepwise approach due to the multifactorial contributions toward this entity. The widespread use of activated clotting time (ACT) as a measurement of anticoagulation during CPB is examined, as it may be a false indicator of heparin resistance. Heparin resistance also has been repeatedly reported in patients infected with COVID-19, which deserves further exploration in this pandemic era. This review aims to examine the variability in heparin potency, underlying mechanisms, and limitations of using ACT for monitoring, as well as provide a framework towards the current management of heparin resistance.

Endothelium, Platelets, and Coagulation Factors as the Three Vital Components for Diagnosing Bleeding Disorders: A Simplified Perspective with Clinical Relevance

Bleeding disorders are a major group of hematological disorders, which are highly prevalent in the world. Excessive bleeding can result in serious consequences including hypoperfusion and cardiac arrest. The body has its selfmechanism to control excessive bleeding which is termed hemostasis. Hemostasis is achieved in two major steps, the formation of the primary and secondary hemostatic plugs. Endothelium, platelets, and coagulation factors are three components involved in hemostasis. Endothelium and platelets have a major role in forming the primary hemostatic plug. Consequently, the first step in investigating a bleeding disorder is platelet count. Despite normal platelet count, abnormality in the primary hemostatic plug may arise due to functional defects of the platelets including adhesion, activation, and aggregation. Von Willebrand disease (VWD) is an endothelial defect and the most prevalent inherited defect in coagulation. Abnormalities in the secondary hemostatic plug are largely due to coagulation factor deficiencies, and, to a lesser extent, the presence of inhibitors. Techniques involving viscoelastics have been aiding in rapid diagnosis and are useful in point-of-care testing. This article discusses the investigation of bleeding disorders from the perspective of the endothelium, platelet, and coagulation factor physiology. These three components should be properly investigated to achieve the definitive diagnosis of bleeding disorders.

Two Promising Anti-Cancer Compounds, 2-Hydroxycinnaldehyde and 2-Benzoyloxycinnamaldehyde: Where do we stand?

Natural bioactive compounds with anti-carcinogenic activity are gaining tremendous interest in the field of oncology. Cinnamon, an aromatic condiment commonly used in tropical regions, appeared incredibly promising as adjuvant for cancer therapy. Indeed, its whole or active parts (e.g., bark, leaf) exhibited significant anti-carcinogenic activity, which is mainly due to two cinnamaldehyde derivatives, namely 2-hydroxycinnaldehyde (HCA) and 2-benzoyloxycinnamaldehyde (BCA). In addition to their anti-cancer activity, HCA and BCA exert immunomodulatory, anti-platelets, and anti-inflammatory activities. Highly reactive α,ß-unsaturated carbonyl pharmacophore, called Michael acceptor, contribute to their therapeutic effects. The molecular mechanisms, underlying their anti-tumoral and anti-metastatic effects are miscellaneous, strongly suggesting that these compounds are multi-targeting compounds. Nevertheless, unravelling the exact molecular mechanisms of HCA and BCA remain a challenging matter which is necessary for optimal controlled-drug targeting delivery, safety, and efficiency. Eventually, their poor pharmacological properties (e.g., systemic bioavailability and solubility) represent a limitation, and depend both on their administration route (e.g., per os, intravenously) and the nature of the formulation (e.g., free, smart nano-). This concise review focused on the potential of HCA and BCA as adjuvants in Cancer. We described their medicinal effects as well as provide an update about their molecular mechanisms reported either in-vitro, ex-vivo, or in animal models.

Purification, characterization and fibrino(geno)lytic activity of cysteine protease from Tabernaemontana divaricata latex

Protease was isolated and purified from Tabernaemontana divaricata latex and its hemostatic potential was analyzed. Crude latex enzyme was purified through ion exchange and gel filtration chromatography. Purified protease was characterized and its thrombin-like (coagulant assay, fibrinogen polymerizing, and fibrinogenolytic activity) and plasmin-like (blood and plasma clot lysis) activities were assessed accordingly. The homogeneous nature of protease was confirmed with the identification of a single band approximately at 25-kDa molecular weight position. The purified enzyme showed an enhancement of 77.32% in clot inducing ability and 89.86% improvement in blood clot lysis in comparison to that by the crude enzyme. All three subunits (Aα, Bβ and γ chains) of human fibrinogen were hydrolyzed by the purified enzyme. PAGE results of the fibrinolytic activity and blood clot lytic effect by the purified enzyme indicated the plasmin-like activity. The study lays a foundation for the development of enzyme-based approaches for pharmaceutical innovations, in which plant latex proteases can be utilized as a potential natural agent for wound healing applications.

Biofunctionalized fibrin gel co-embedded with BMSCs and VEGF for accelerating skin injury repair

Rapid and effective repair of epithelial tissue is desirable for improving the success rate of operation and reducing postoperative complications. Hydrogel is a widely studied wound repair material, especially as a wound dressing for damaged epithelial tissue. Based on the catalytic effect of thrombin on fibrinogen, in this study, a three-dimensional fibrin gel which of adequate epithelial cell compatibility was constructed by using thrombin and fibrinogen under the cross-linking action of calcium ion. Immunofluorescence staining and hematoxylin-eosin (H&E) staining showed that bone marrow mesenchymal stem cell (BMSC) was embedded in fibrin gel. Furthermore, vascular endothelial growth factor (VEGF) was used to induce BMSC to differentiate into CD31+ and vWF+ endothelial cell (EC) in fibrin gel. The results showed that the fibrin gel surface may effectively promote the adhesion and proliferation of EC and smooth muscle cell (SMC). After 15 days of culture, it was found that the BMSC embedded in the hydrogel had differentiated into EC. The results of in vivo skin wound experiment in rats further proved that the fibrin gel containing BMSC could promote wound healing and repair, and showed the potential to promote neovascularization at the injured site. The construction method of hydrogel materials proposed in this study has potential application value in the field of regenerative medicine.

Short-Term Exposure to Waterpipe/Hookah Smoke Triggers a Hyperactive Platelet Activation State and Increases the Risk of Thrombogenesis

OBJECTIVE

Cardiovascular disease is a major public health problem. Among cardiovascular disease's risk factors, tobacco smoking is considered the single most preventable cause of death, with thrombosis being the main mechanism of cardiovascular disease mortality in smokers. While tobacco smoking has been on the decline, the use of waterpipes/hookah has been rising, mainly due to the perception that they are less harmful than regular cigarettes. Strikingly, there are few studies on the negative effects of waterpipes on the cardiovascular system, and none regarding their direct contribution to thrombus formation. Approach and Results: We used a waterpipe whole-body exposure protocol that mimics real-life human exposure scenarios and investigated its effects, relative to clean air, on platelet function, hemostasis, and thrombogenesis. We found that waterpipe smoke (WPS)-exposed mice exhibited both shortened thrombus occlusion and bleeding times. Further, our results show that platelets from WPS-exposed mice are hyperactive, with enhanced agonist-induced aggregation, dense and α-granule secretion, αIIbβ3 integrin activation, phosphatidylserine expression, and platelet spreading, when compared with clean air-exposed platelets. Finally, at the molecular level, it was found that Akt (protein kinase B) and ERK (extracellular signal-regulated kinases) phosphorylation are enhanced in the WPS and in nicotine-treated platelets.

CONCLUSIONS

Our findings demonstrate that WPS exposure directly modulates hemostasis and increases the risk of thrombosis and that this is mediated, in part, via a state of platelet hyperactivity. The negative health impact of WPS/hookah, therefore, should not be underestimated. Moreover, this study should also help in raising public awareness of the toxic effects of waterpipe/hookah.

Cardiovascular injury induced by tobacco products: assessment of risk factors and biomarkers of harm. A Tobacco Centers of Regulatory Science compilation

Although substantial evidence shows that smoking is positively and robustly associated with cardiovascular disease (CVD), the CVD risk associated with the use of new and emerging tobacco products, such as electronic cigarettes, hookah, and heat-not-burn products, remains unclear. This uncertainty stems from lack of knowledge on how the use of these products affects cardiovascular health. Cardiovascular injury associated with the use of new tobacco products could be evaluated by measuring changes in biomarkers of cardiovascular harm that are sensitive to the use of combustible cigarettes. Such cardiovascular injury could be indexed at several levels. Preclinical changes contributing to the pathogenesis of disease could be monitored by measuring changes in systemic inflammation and oxidative stress, organ-specific dysfunctions could be gauged by measuring endothelial function (flow-mediated dilation), platelet aggregation, and arterial stiffness, and organ-specific injury could be evaluated by measuring endothelial microparticles and platelet-leukocyte aggregates. Classical risk factors, such as blood pressure, circulating lipoproteins, and insulin resistance, provide robust estimates of risk, and subclinical disease progression could be followed by measuring coronary artery Ca2+ and carotid intima-media thickness. Given that several of these biomarkers are well-established predictors of major cardiovascular events, the association of these biomarkers with the use of new and emerging tobacco products could be indicative of both individual and population-level CVD risk associated with the use of these products. Differential effects of tobacco products (conventional vs. new and emerging products) on different indexes of cardiovascular injury could also provide insights into mechanisms by which they induce cardiovascular harm.

A Prospective, Randomized, Phase III Study to Evaluate the Efficacy and Safety of Fibrin Sealant Grifols as an Adjunct to Hemostasis as Compared to Cellulose Sheets in Hepatic Surgery Resections

BACKGROUND

Local hemostatic agents have a role in limiting bleeding complications associated with liver resection.

METHODS

In this randomized, phase III study, we compared the efficacy and safety of Fibrin Sealant Grifols (FS Grifols) with oxidized cellulose sheets (Surgicel®) as adjuncts to hemostasis during hepatic resections. The primary efficacy endpoint was the proportion of patients achieving hemostasis at target bleeding sites (TBS) within 4 min (T₄) of treatment application. Secondary efficacy variables were time to hemostasis (TTH) at a later time point if re-bleeding occurs and cumulative proportion of patients achieving hemostasis by time points T₂, T₃, T₅, T₇, and T₁₀.

RESULTS

The rate of hemostasis by T₄ was 92.8% in the FS Grifols group (n = 163) and 80.5% in the Surgicel® group (n = 162) (p = 0.01). The mean TTH was significantly shorter (p < 0.001) in the FS Grifols group (2.8 ± 0.14 vs. 3.8 ± 0.24 min). The rate of hemostasis by T₂, T₅, and T₇ was higher and statistically superior in the FS Grifols group compared to Surgicel®. No substantial differences in adverse events (AE) were noted between treatment groups. The most common AEs were procedural pain (36.2 vs. 37.7%), nausea (20.9 vs. 23.5%), and hypotension (14.1 vs 6.2%).

CONCLUSIONS

FS Grifols was safe and well tolerated as a local hemostatic agent during liver resection surgeries. Overall, data demonstrate that the hemostatic efficacy of FS Grifols is superior to Surgicel® and support the use of FS Grifols as an effective local hemostatic agent in these surgical procedures.

Prevalence of Low Platelet Count and Identification of Associating Determinants and Genetic Polymorphism in Healthy Individuals of Upper Assam, India

The purpose of the study was to assess the prevalence of low platelet count among the healthy population of upper Assam, India. The impact of socio-demographic features was moreover pointed to evaluate. Additionally, Mean platelet volume (MPV) and Interleukin-6 gene polymorphism (-174 G > C) were also determined to speculate their effect on the basal platelet count. For determination of hematological indices, CBC was done and genetic polymorphism was identified by ARMS-PCR technique. Out of 510 study subjects, 25.3% (n = 129) had low platelet count, and females were recorded with significantly higher mean platelet count as compared to their male counterpart (p < 0.001). A progressive decline in platelet count was observed with ageing and more significantly noticed in females across the various age groups (p < 0.001). The mean MPV was significantly higher in low platelet count group as compared to the normal group (p < 0.001). Both platelet count and MPV differed significantly among the individuals with varied ethnicity. An inverse correlation between platelet count and its volume was reported, and such observation was continued to persist in every age-group under the study. However, no significant differences were observed for other hematological indices between the studied groups except for platelet indices and RBC count. Moreover, the peripheral blood smear examined for cellular morphology and in vitro platelet clumping did not report any significant aberrancy. No significant penetrance of the risk allele was revealed in the studied groups. However, ARMS-PCR confirmed 6% (n = 8/129) of the low platelet count subjects with heterozygous for G allele. This happens to be the first description of low platelet count among the healthy population of upper Assam, where age, gender, ethnicity, and MPV are significantly associated with platelet count variation. Heterozygosity of the risk allele does not contribute to the low platelet count condition.

Platelet-Activation Mechanisms and Vascular Remodeling

This overview article for the Comprehensive Physiology collection is focused on detailing platelets, how platelets respond to various stimuli, how platelets interact with their external biochemical environment, and the role of platelets in physiological and pathological processes. Specifically, we will discuss the four major functions of platelets: activation, adhesion, aggregation, and inflammation. We will extend this discussion to include various mechanisms that can induce these functional changes and a discussion of some of the salient receptors that are responsible for platelets interacting with their external environment. We will finish with a discussion of how platelets interact with their vascular environment, with a special focus on interactions with the extracellular matrix and endothelial cells, and finally how platelets can aid and possibly initiate the progression of various vascular diseases. Throughout this overview, we will highlight both the historical investigations into the role of platelets in health and disease as well as some of the more current work. Overall, the authors aim for the readers to gain an appreciation for the complexity of platelet functions and the multifaceted role of platelets in the vascular system. © 2017 American Physiological Society. Compr Physiol 8:1117-1156, 2018.

Cellular Cyborgs: On the Precipice of a Drug Delivery Revolution

Cell-based drug delivery systems offer the prospect of biocompatibility, large-loading capacity, long in vivo lifespan, and active targeting of diseased sites. However, these opportunities are offset by an array of challenges, including safeguarding the integrity of the drug cargo and the cellular host, as well as ensuring that drug release occurs at the appropriate time and place. Emerging strategies that address these, and related, issues, are described herein.

Fibrin in Reproductive Tissue Engineering: A Review on Its Application as a Biomaterial for Fertility Preservation

In recent years, reproductive medicine has made good use of tissue engineering and regenerative medicine techniques to develop alternatives to restore fertility in cancer patients. For young female cancer patients who cannot undergo any of the currently applied strategies due to the possible presence of malignant cells in their ovaries, the challenge is creating an in vitro or in vivo artificial ovary using carefully selected biomaterials. Thanks to its numerous qualities, fibrin has been widely used as a scaffold material for fertility preservation applications. The goal of this review is to examine and discuss the applications and advantages of this biopolymer for fertility restoration in cancer patients, and consider the main results achieved so far.

In Vitro and Ex Vivo Approaches to Evaluate Next-Generation Tobacco and Non-Tobacco Products on Human Blood Platelets

Human blood platelets are major hemostatic regulators in the circulation and important in the mediation of chronic inflammation and immunomodulation. They are key elements that promote cardiovascular pathogenesis that leads to atherosclerosis, thrombosis, myocardial infarction, and stroke. New information on tobacco use and platelet dysregulation shows that these highly understudied vascular cells are dysregulated by tobacco smoke. Thus, platelet function studies should be an important consideration for the evaluation of existing and next-generation tobacco and non-tobacco products. Novel in vitro approaches are being sought to investigate these products and their influence on platelet function. Platelets are ideally suited for product assessment, as robust and novel in vitro translational methods are available to assess platelet function. Furthermore, the use of human biological systems has the advantage that risk predictions will better reflect the human condition.

Predictors of the success and failure of emergency pelvic artery embolisation for primary postpartum haemorrhage: a 12-year review

INTRODUCTION

This study aimed to identify predictors of the outcome and clinical efficacy of emergency pelvic artery embolisation (PAE) for primary postpartum haemorrhage (PPH) and to assess the post-embolisation fertility of PAE patients in a regional hospital setting.

METHODS

A 12-year retrospective study of patients undergoing emergency PAE was conducted at a regional acute general hospital. Clinical and procedural parameters, clinical outcomes and post-embolisation pregnancy success rates were analysed.

RESULTS

There were 47,221 deliveries at the hospital during the study period, of which 33 patients required urgent PAE for primary PPH. The technical success rate of embolisation was 97.0% (n = 32). Clinically adequate haemostasis was achieved by a single embolisation procedure in 24 (72.7%) patients; the remaining eight eventually required surgery to achieve cessation of bleeding. Among the parameters studied, multivariate logistic regression analysis showed that pre-embolisation platelet count (p = 0.036) and maternal age (p = 0.019) were the only significant independent predictors of embolisation failure. Only two patients successfully conceived after PAE, although one of them had an ectopic pregnancy.

CONCLUSION

Emergency PAE is an effective measure to arrest life-threatening bleeding in patients with primary PPH. As low pre-embolisation platelet count and advanced maternal age are associated with higher odds of embolisation failure, careful post-embolisation monitoring may be required for such patients. Embolisation also allows subsequent pregnancy. However, further studies are required to assess the outcomes of post-embolisation pregnancies.

PolySTAT-modified chitosan gauzes for improved hemostasis in external hemorrhage

Positively-charged chitosan gauzes stop bleeding from wounds by electrostatically interacting with negatively-charged cell membranes of erythrocytes to cause erythrocyte agglutination and by sealing wounds through tissue adhesion. In the following work, nonwoven chitosan gauze was impregnated with PolySTAT, a synthetic polymer that enhances coagulation by cross-linking fibrin, to generate PolySTAT/chitosan gauzes with improved hemostatic efficacy. When comparing nonwoven chitosan and PolySTAT/chitosan to a commercially-available chitosan-containing gauze (Celox® Rapid), no appreciable differences were observed in fiber size, morphology, and pore size. However, PolySTAT/chitosan demonstrated more rapid blood absorption compared to Celox® Rapid. In a rat model of femoral artery injury, PolySTAT/chitosan gauzes reduced blood loss and improved survival rate compared to non-hemostatic controls and Celox® Rapid. While Celox® Rapid had stronger adherence to tissues compared to PolySTAT/chitosan gauzes, blood loss was greater due to hematoma formation under the Celox® dressing. Animals treated with PolySTAT/chitosan gauzes required less saline infusion to restore and maintain blood pressure above the target blood pressure (60mmHg) while other treatment groups required more saline due to continued bleeding from the wound. These results suggest that PolySTAT/chitosan gauzes are able to improve blood clotting and withstand increasing arterial pressure with the addition of a fibrin cross-linking hemostatic mechanism.

STATEMENT OF SIGNIFICANCE

Blood loss remains one of the leading causes of death after traumatic injury in civilian populations and on the battlefield. Advanced biomaterials that interact with blood components and/or accelerate the clotting process to form a hemostatic plug are necessary to staunch bleeding after injury. Chitosan-based gauzes, which stop bleeding by causing red blood cell aggregation, are currently used on the battlefield and have shown variable performance under high pressure arterial blood flow in animal studies, suggesting that red blood cell aggregates require further mechanical stabilization for more reliable performance. In this work, we investigate the binding and cross-linking of fibrin, a major component in blood clots, on chitosan gauze fiber surfaces to structurally reinforce red blood cell aggregates.

Resveratrol preserves the function of human platelets stored for transfusion

Stored platelets undergo biochemical, structural and functional changes that lead to decreased efficacy and safety of platelet transfusions. Not only do platelets acquire markers of activation during storage, but they also fail to respond normally to agonists post-storage. We hypothesized that resveratrol, a cardioprotective antioxidant, could act as a novel platelet storage additive to safely prevent unwanted platelet activation during storage, while simultaneously preserving normal haemostatic function. Human platelets treated with resveratrol and stored for 5 d released less thromboxane B2 and prostaglandin E2 compared to control platelets. Resveratrol preserved the ability of platelets to aggregate, spread and respond to thrombin, suggesting an improved ability to activate post-storage. Utilizing an in vitro model of transfusion and thromboelastography, clot strength was improved with resveratrol treatment compared to conventionally stored platelets. The mechanism of resveratrol's beneficial actions on stored platelets was partly mediated through decreased platelet apoptosis in storage, resulting in a longer half-life following transfusion. Lastly, an in vivo mouse model of transfusion demonstrated that stored platelets are prothrombotic and that resveratrol delayed vessel occlusion time to a level similar to transfusion with fresh platelets. We show resveratrol has a dual ability to reduce unwanted platelet activation during storage, while preserving critical haemostatic function.

Biocompatible and biodegradable fibrinogen microspheres for tumor-targeted doxorubicin delivery

In the development of effective drug delivery carriers, many researchers have focused on the usage of nontoxic and biocompatible materials and surface modification with targeting molecules for tumor-specific drug delivery. Fibrinogen (Fbg), an abundant glycoprotein in plasma, could be a potential candidate for developing drug carriers because of its biocompatibility and tumor-targeting property via arginine–glycine–aspartate (RGD) peptide sequences. Doxorubicin (DOX), a chemotherapeutic agent, was covalently conjugated to Fbg, and the microspheres were prepared. Acid-labile and non-cleavable linkers were used for the conjugation of DOX to Fbg, resulting in an acid-triggered drug release under a mild acidic condition and a slow-controlled drug release, respectively. In vitro cytotoxicity tests confirmed low cytotoxicity in normal cells and high antitumor effect toward cancer cells. In addition, it was discovered that a longer linker could make the binding of cells to Fbg drug carriers easier. Therefore, DOX–linker–Fbg microspheres could be a suitable drug carrier for safer and effective drug delivery.

Drug delivery using platelet cancer cell interaction

PURPOSE

To develop an efficient biocompatible and targeted drug delivery system in which platelets, an essential blood component having a natural affinity for cancer cells, are used as carrier of anticancer drug as delivery of drug to the targeted site is crucial for cancer treatment.

METHODS

Doxorubicin hydrochloride, a potent anti cancer drug, was delivered in lung adenocarcinoma cell line (A549) using platelet as a delivery agent. This delivery mode was also tested in Ehrlich ascites carcinoma (EAC) bearing mice in presence and absence of platelets.

RESULTS

The results show that platelets can uptake the drug and release the same upon activation. The efficiency of drug loaded platelets in inducing cytotoxicity was significantly higher in both in vitro and in vivo model, as compared to the free drug.

CONCLUSIONS

The proposed drug delivery strategy may lead to clinical improvement in the management of cancer treatment as lower drug concentration can be used in a targeted mode. Additionally the method can be personalized as patient's own platelet can be used for deliver various drugs.

Factor v leiden and inflammation

Factor V Leiden, is a variant of human factor V (FV), also known as proaccelerin, which leads to a hypercoagulable state. Along these years, factor V Leiden (FVL) has been studied from the pathophysiologic point of view, and research has been focused on finding clinical approaches for the management of the FVL associated to a trombophilic state. Less attention has been paid about the possible role of FVL in inflammatory conditions known to be present in different disorders such as uremia, cirrhosis, liver transplantation, depression as well as sepsis, infection or, inflammatory bowel disease (IBD). Whether platelet FVL will increase the activation of coagulation and/or in which proportion is able to determine the final outcome in the previously mentioned inflammatory conditions is a subject that remains uncertain. This paper will review the association of FVL with inflammation. Specifically, it will analyze the important role of the endothelium and the contribution of other inflammatory components involved at both the immune and vascular levels. This paper will also try to emphasize the importance of being a FVL carrier in associations to diseases where a chronic inflammation occurs, and how this condition may be determinant in the progression and outcome of a specific clinic situation.

Safety and Efficacy of StarClose SE Vascular Closure System in High-Risk Liver Interventional Oncology Patients

Purpose

To assess the safety and efficacy of the StarClose SE Vascular Closure System (Abbott Vascular, Abbott Park IL, USA) in high-risk thrombocytopenic and coagulopathic interventional oncology (IO) patients.

Methods

In this single institution retrospective study, 63 high-risk thrombocytopenic or coagulopathic IO patients (M:F=51:12, mean age 58 years, range 31–88 years) who underwent 83 common femoral arteriotomy closures using the StarClose device were identified among all IO patients (n=131) undergoing StarClose closure (n=177) between 2008–2011. High-risk thrombocytopenia and coagulopathy were defined as platelet count ≤100 103/mL and international normalized ratio (INR) ≥1.5. Procedures included chemoembolization (n=67), radioembolization (n=8), and hepatic arterial mapping with technetium-99m macroaggrated albumin administration (n=8) for treatment of hepatocellular carcinoma (n=79) or liver metastases (n=4). Measured outcomes included technical success of arterial closure and closure-related adverse events, graded according to the Society of Interventional Radiology classification.

Results

In all cases, 5 French common femoral arterial access was used. Platelet count was ≤100 103/mL in 80/83 (96.4%) cases and INR was ≥1.5 in 35/83 (42.2%) cases. Mean pre-procedure platelet count was 71 (range 26–347) 103/mL and mean INR was 1.4 (range 1.0–2.1). The StarClose device effectively sealed the arteriotomy in 83/83 (100%) cases, 60/83 (72.3%) cases were first-time closures, and 20/83 (24.1%) cases were repeat closures. Small groin hematomas, graded as class A minor complications, developed in 3/83 (3.6%) cases. No other complications were encountered.

Conclusions

The StarClose SE Vascular Closure System confers high technical success and safety in common femoral arteriotomy closure in high-risk IO patients.

A comparative optical aggregometry study of antiplatelet activity of taxanes from Taxus cuspidata

Platelets are highly reactive components of the circulatory system. The cytoskeleton of a platelet is an important structure for platelet aggregation as stimulated by several agonists. An anticancer agent, taxol, has been suggested to exert platelet anti-aggregating activity by stabilizing microtubules during the aggregation process. An activity-guided fractionation was performed with a methanol extract of the leaves and twigs of Taxus cuspidata to isolate taxanes with platelet anti-aggregating effects. Compounds 1 to 7 - taxinine (1), taxinine A (2), taxinine B (3), 2-deacetoxytaxinine B (4), taxacin (5), taxchinin B (6), and taxol (7) - were obtained as the antiplatelet components of this plant. These taxane compounds present the possibility of securing new antiplatelet compounds which differ from currently available antiplatelet agents in chemical structure and possibly in mechanisms of action. All compounds showed stronger inhibitory effects than acetylsalicylic acid (ASA) on platelet aggregation induced by arachidonic acid (AA) (IC(50): 14.4, 64.5, 35.5, 16.0, 21.9, 28.6 and 48.2 versus 63.0microM) or U46619 (IC(50): 34.8, 24.9, 36.2, 35.0, 46.9, 71.9 and 68.7 versus 340microM). Compounds 1, 3, 4 and 5, with a cinnamoyl group at the C(5) position, showed strong inhibitory effects against AA-induced aggregation compared to compound 2 (with an -OH group at C(5)) or compounds with an oxetane ring at C(4),(5), such as compounds 6 and 7. All of the seven compounds were 5-13-fold more strongly inhibitory than ASA against U46619-induced aggregation.

High tissue factor activity and low tissue factor pathway inhibitor concentrations in patients with preterm labor

OBJECTIVE

Preterm labor (PTL) has been associated with an increased thrombin generation in the maternal circulation and amniotic fluid. Tissue factor (TF) is a potent initiator of the coagulation cascade, which can trigger the hemostatic system to generate thrombin. The aims of this study were to determine whether spontaneous PTL with intact membranes is associated with changes in the maternal plasma concentrations and activity of TF as well as tissue factor pathway inhibitor (TFPI).

METHODS

This cross-sectional study included women in the following groups: (1) normal pregnancies (n = 86); (2) term pregnancies in spontaneous labor (TIL) (n = 67) and not in labor (TNL) (n = 88); and (3) patients with spontaneous PTL and intact membranes (n = 136) that were classified into three sub-groups: (a) PTL without intra-amniotic infection and/or inflammation (IAI) who delivered at term (n = 49); (b) PTL without IAI who delivered preterm (n = 54); and (c) PTL with IAI who delivered preterm (n = 33). Plasma concentrations of TF and TFPI were measured by ELISA, and their activity was measured by chromogenic assays. Non-parametric statistics were used for analysis.

RESULTS

(1) Among women at term, those with spontaneous labor had a higher median maternal plasma TF and a lower median TFPI concentration than those without labor. (2) Patients with PTL had a significantly lower median maternal plasma TFPI concentration than that of normal pregnant women, regardless of the presence of IAI. (3) There was no significant difference in the median maternal plasma TF concentration between patients with a normal pregnancy and those with PTL. (4) In contrast, the median maternal plasma TF activity was higher among patients with PTL than in women with normal pregnancies, regardless of the presence of IAI or preterm delivery. (5) However, maternal plasma TFPI activity did not differ among the study groups.

CONCLUSION

Women with preterm parturition, in contrast to those in labor at term, have a higher TF activity and a lower TFPI concentration, without a significant change in the median maternal plasma TF concentration. These observations suggest that the increased thrombin generation reported in patients with PTL may be the result of activation of the extrinsic pathway of the coagulation cascade. In addition, the increased thrombin generation reported in patients with PTL could be due to insufficient anti-coagulation, as reflected by the low maternal plasma TFPI concentration.

In-vitro model for the ultrastructural study of the formation of thrombi in human platelets

Platelets are cell fragments with dynamic properties involved in clot formation after tissue damage. Platelet activation causes a change in shape, secretion of intracellular granules and aggregation with each other through the cytoskeleton components and biochemical changes. Platelet adhesion, considered as the major event in haemostasis, has been studied in several in-vitro and in-vivo models to evaluate the feasible thrombogenicity of some materials, the dynamics of specific receptors, as well as the effect of different buffers and inhibitors in this process. In spite of the numerous reports about platelet activation, to date there is no information available about the fine structure of the platelet-platelet and platelet-substrate interactions. In the present report we describe an in-vitro system that allows the visualization of these interactions: platelets are adhered to an inert substrate, and interactions with suspended platelets as a process to initiate the formation of thrombi was followed by ultramicrotomy and transmission electron microscopy.

An hypothesis on the consolidation and PGE1-induced deconsolidation of a platelet plug

Consolidation is the final stage in haemostasis in which a platelet plug blocking a bleeding area of a vessel: (a) becomes impermeable to circulating plasma proteins and (b) contracts to resist blood pressure.

HYPOTHESIS

The impermeabilization step of consolidation is accomplished through fluid uptake by the platelets from a hydrated intercellular glue formed during thrombin activation. Dehydration occurs through inhibition of the Na+,K+-ATPase of platelets with sodium and water uptake. However, and uniquely, due to the high cellular density of the platelet plug, access of peripheral plasma fluids to the plug is limited forcing the platelets to take up preferentially the fluid of interplatelet space. The increased adhesion properties of the dehydrated glue simultaneously furthers a decreased hydraulic permeability and an improved coupling of the contractile forces among platelets. In 'Deconsolidation', the fluid uptake process can be reversed and amplified by agents that increase cAMP, reactivating the Na+,K+-ATPase and expressing CFTR or equivalent Cl- secretory channels that force the extrusion of fluid from the platelets, with rehydration of the intercellular polymer and a large increase in the interplatelet space.

Physical stability of liposomes bearing hemostatic activity

The physical stability of six liposome systems designed as platelet substitutes was determined on storage at 4 degrees C over a 3-month period under quiescent conditions. Liposomes used were large unilamellar vesicles. Correlation of the n-average mean diameter, polydispersity, zeta-potential and the presence of aminophospholipid on liposome surface (in those preparations which contain phosphatidylethanolamine (PE) and phosphatidylserine (PS)) led to the conclusion that liposomes that mimicked the composition of platelets were the most stable. When a net charge was present in the vesicles (liposomes with PS), the likelihood of aggregation was extremely low. In the period studied, a proportion of 25% of charged lipid (PS) conferred sufficient electrostatic stabilization to prevent vesicle fusion. An increase in this charge did not modify the stability characteristics. PE-containing liposomes behaved in a particular way: when PE content was 50%, the stability of the preparation was limited to 1 month; whereas if the content was 25%, the zeta-potential rose with time, as did the presence of PE in the liposome surface.

Increased prevalence of microthromboses in retinal capillaries of diabetic individuals

In diabetic retinopathy, capillary nonperfusion and eventual obliteration can lead to retinal ischemia and sight-threatening neovascularization. The occurrence of retinal microthrombosis in human diabetes has long been suspected and occasionally observed but never systematically demonstrated. We used trypsin digestion to isolate the intact vascular network from retinas obtained postmortem from nine diabetic donors (age 64 +/- 11 years, duration of diabetes 6 +/- 4 years; mean +/- SD) and eight age-matched nondiabetic donors. Topographically matched sectors (each one-sixth of retina) of diabetic and nondiabetic retinas were tested sequentially with antibodies to fibrin cross-linking factor XIII and platelet glycoprotein (GP)-IIIa to identify fibrin-platelet thrombi. In some trypsin digests, we also examined vascular cell apoptosis. The retina from a nondiabetic donor, 24 years of age, who had died of trauma, was used to exclude confounding influences caused by the postmortem period. When compared with those of nondiabetic donors, the retinas of diabetic donors showed double the number of capillary segments with colocalized immunostaining for factor XIII and GPIIIa (P = 0.02). The total area of the positive segments was fourfold greater in the diabetic than in the nondiabetic donors (P = 0.02) and correlated with the duration of diabetes (r = 0.71, P < 0.05). Large thrombi were six times more frequent in the diabetic donors (P = 0.03), and there was a significant topographical association of microthrombosis with apoptotic cells in both diabetic and nondiabetic vessels (P = 0.0001). Hence, diabetes of short duration was found to be associated with a greater than normal number and size of platelet-fibrin thrombi in the retinal capillaries. These thrombi can contribute to capillary obliteration and retinal ischemia and may be a practical target for early drug intervention.

Discovery of an orally active non-peptide fibrinogen receptor antagonist based on the hydantoin scaffold

Antagonists of the platelet fibrinogen receptor (GP IIb/IIIa receptor) are expected to be a promising new class of antithrombotic agents. The binding of fibrinogen to the fibrinogen receptor depends on an Arg-Gly-Asp-Ser (RGDS) tetrapeptide recognition motif. Structural modifications of the RGDS lead have led to the discovery of a non-peptide RGD mimetic GP IIb/IIIa antagonist 44 (S 1197). Compound 44 inhibited, in a dose dependent and reversible manner, human and dog platelet aggregation as well as 125I-fibrinogen binding to ADP-activated human gel filtered platelets and isolated GP IIb/IIIa with K(i) values of 9 nM and 0.17 nM, respectively. A pharmacophore mapping procedure with QXP and a 3D-QSAR analysis applying the GRID/GOLPE methodology yielded a stable, rather predictive model and revealed structural features which are important for binding. Hydrophobic substitutions both at the hydantoin nucleus and at the C-terminus increase the affinity toward the fibrinogen receptor. The crystalline ethyl ester prodrug 48 (HMR 1794) is an orally active antithrombotic agent which is a promising drug candidate for the treatment of thrombotic diseases in humans.

Increased von Willebrand factor in the endocardium as a local predisposing factor for thrombogenesis in overloaded human atrial appendage

OBJECTIVES

We investigated immunoreactive von Willebrand factor (vWF), a platelet adhesion molecule, in the endocardial endothelium and its relationship to thrombogenesis in the human atrial appendage.

BACKGROUND

Intra-atrial thrombogenesis is generally thought to be induced by blood stasis in the atrial appendage involved with atrial fibrillation (AF). Little attention has been paid to alterations of the endocardial endothelium on which the thrombus develops.

METHODS

Atrial appendage tissue was obtained at heart surgery or at autopsy from AF and non-AF cardiac patients and from noncardiac patients. Immunohistochemistry for endothelial cell markers including vWF, CD31, CD34 and endothelial nitric oxide synthase (eNOS) and platelet glycoprotein Ib/IX or IIb/IIIa was performed and semiquantitatively graded.

RESULTS

In contrast to the apparent immunostaining for CD31, CD34 and eNOS, only focal or little immunoreactive vWF was seen in the endocardium of noncardiac patients. Immunoreactive vWF in the endocardial endothelium was increased in most cardiac patients, particularly in the left, but not in the right, atrial appendage of patients with mitral valvular disease, irrespective of whether AF was present. Platelet adhesion/thrombus formation in the endocardium was found in limited sites in which the overlying endothelium was deficient in eNOS and CD34. When warfarin-treated cases were excluded, there was a significant correlation between the immunohistochemical grade for vWF and the degree of platelet adhesion/thrombus formation in the endocardium.

CONCLUSIONS

Immunoreactive vWF in the endocardial endothelium was increased in overloaded human atrial appendage, which may be a local predisposing factor for intraatrial thrombogenesis.

Minimally invasive endoscopy in the treatment of preterm premature rupture of membranes by application of fibrin sealant

We report only the 3rd case of closure of amniorrhexis following genetic amniocentesis. Our technique is the first to use endoscopic visualization of the rupture site and apply maternal platelets and fibrinogen/thrombin (Hemaseel Haemacure Corp Sarasota F1). The patient underwent repair at 20.6 weeks, 26 days after spontaneous rupture of membranes post-amniocentesis. At the time of the procedure the amniotic fluid index was 1 cm. Patient was delivered at 32.3 weeks secondary to complications of diabetes and severe preeclampsia. The neonate had APGARS of 7 at 1 min and 8 at 5 min and was discharged home on Day 21 of life.

Platelet activation and its role in thrombin generation in platelet-induced thrombin generation time

Platelet-induced thrombin generation time (PITT) is a newly developed global coagulation assay in which a small amount of partially anticoagulated platelet-rich plasma (PRP) is rotated in a disc-shaped cuvette within the light beam of a photometer. The time intervals from onset of rotation until aggregation and coagulation of the sample are registered. The aim of our study was to compare platelet activation with generation of thrombin during rotation of PRP in PITT system. Aliquots of PRP were taken before, 1, 3, and 8 min after the onset of rotation as well as at the beginning of aggregation and shortly before coagulation. Thrombin activity was measured with chromogenic substrate S-2238. We have also measured the level of generated prothrombin activation fragment 1+2 (F1+2), which reflects the concentration of liberated thrombin. Platelet activation was assayed by means of platelet factor 4 (PF4) and beta-thromboglobulin (beta-TG) concentration and registration of the aggregation. The concentrations of the F1+2, PF4, beta-TG increased very slowly from the beginning of the test until aggregation occurred. From the start of aggregation, the levels of F1+2 rose rapidly. In contrast to the F1+2 measurements, thrombin activity has not been detected from onset of rotation until the end of the test. Only trace thrombin activity was detectable just after the plasma sample had been clotted in the cuvette. Our results demonstrate that there exists a close relationship between platelet activation and thrombin generation. Viable platelets, which adhered to the cuvette walls, form an active template on which thrombin can be generated from prothrombin.

von Willebrand disease and pregnancy

von Willebrand Disease (vWD) affects approximately 1% of Americans and as many as 25% of women referred for evaluation of menorrhagia. We briefly review the history of vWD, its molecular defects, and diagnostic criteria for each subtype of disease. We also address obstetric management of the patient with vWD. While there is a significant increased risk for postpartum hemorrhage, patients with vWD should not be discouraged to undertake pregnancy.

Pathophysiology and therapeutic modification of thrombin generation in patients with coronary artery disease

Thrombin plays a central role in thrombogenesis: it activates platelets, converts fibrinogen to fibrin, and activates factor XIII, which then crosslinks and stabilizes the fibrin clot. In addition, thrombin amplifies coagulation by activating factors VIII and V, key cofactors in the generation of activated factor X and thrombin, respectively. Even platelet function is influenced by thrombin. Hence, thrombin generation is most important both in the chronic progression of coronary atherosclerotic disease and in its conversion to acute events. To date, various therapeutic approaches capitalize on this knowledge by targeting specific thrombin-related pathways. Among the successful and carefully documented pharmacologic strategies in acute or chronic coronary heart disease are the use of unfractioned heparin, low-molecular-weight heparin, thrombolysis, hirudin, and/or inhibition of thrombin generation by glycoprotein IIb/IIIa antagonists, most often utilized on top of antiplatelet therapy (e.g., with acetylsalicylic acid) and/or vitamin K antagonism. The present review provides insights into the pathophysiology of thrombin generation in coronary atherosclerosis and gives an overview over the above mentioned therapeutic thrombin modifications.