Clinical applicability of reticulated platelets

Platelets and the Atherosclerotic Process: An Overview of New Markers of Platelet Activation and Reactivity, and Their Implications in Primary and Secondary Prevention

The key role played by platelets in the atherosclerosis physiopathology, especially in the acute setting, is ascertained: they are the main actors during thrombus formation and, thus, one of the major investigated elements related to atherothrombotic process involving coronary arteries. Platelets have been studied from different points of view, according with the technology advances and the improvement in the hemostasis knowledge achieved in the last years. Morphology and reactivity constitute the first aspects investigated related to platelets with a significant body of evidence published linking a number of their values and markers to coronary artery disease and cardiovascular events. Recently, the impact of genetics on platelet activation has been explored with promising findings as additional instrument for patient risk stratification; however, this deserves further confirmations. Moreover, the interplay between immune system and platelets has been partially elucidated in the last years, providing intriguing elements that will be basic components for future research to better understand platelet regulation and improve cardiovascular outcome of patients.

Platelet-Acute Leukemia Interactions

Acute leukemia (AL) is a hematological malignancy with high morbidity and mortality that is caused by abnormal hematopoietic stem cells. AL can change the parameters, quality, and function of platelets through numerous mechanisms, resulting in bleeding and even death in AL patients. Hence, AL patients are often clinically treated using normal platelet transfusion. However, studies have found that platelets can also affect AL cells. This review discusses the changes occurring in platelet count, mean platelet volume, platelet distribution width, reticulated platelets, platelet membrane glycoprotein, platelet aggregation, and activation in AL patients, the causes of these changes, and the possible significance of these changes for patient prognosis. The effects of platelets on the proliferation and drug resistance of AL cells are also discussed.

Primary immune thrombocytopenia: a 'diagnosis of exclusion'?

Current diagnosis of primary immune thrombocytopenia (ITP) is presumptive, centered on excluding other causes of thrombocytopenia. The diagnosis of ITP is challenging because of the wide range of potential inherited and acquired causes of thrombocytopenia. The treatment of ITP is empiric with steroids, high-dose immunoglobulin, immunosuppressants and thrombopoietin agonists with potential side effects. We searched Medline and Cochrane databases, reviewed the study data and analyzed the individual diagnostic tests for their evidence-based role in the diagnosis of ITP. We then analyzed the strength of the scientific evidence for each diagnostic test in the diagnosis of ITP and identified gaps in the diagnostic accuracy. The diagnostic challenges in ITP include: insufficient evidence for the individual test for diagnosis of ITP, no standardized protocol/guideline for diagnosis, hurdles in accessing the available resources and failure to correlate the clinical data while reviewing the blood smear. We did not identify a diagnostic test that clinicians can use to confirm the diagnosis of ITP. In the absence of a diagnostic test of proven value in ITP, the clinician is best served by a comprehensive history and physical examination, complete blood count and review of the peripheral blood smear in evaluating thrombocytopenia.

Changes in Platelet Function in Preterm Newborns with Prematurity Related Morbidities

Platelet indices represent useful biomarkers to express the thromboembolic status, inflammatory response, and oxidative stress in preterm newborns. Our study presented platelet count and function changes in prematurity-related morbidities such as respiratory distress syndrome, intraventricular bleeding, and anemia of prematurity in preterm newborn cases reported to healthy full-term newborns by flow cytometry and hematological methods. The platelet volume represents the average size of platelets in the blood samples, showing the significantly increased values in preterm newborns compared with healthy full-term newborns due to increasing activated platelet production. Flow cytometric analysis of immature platelet fractions (IPF) made using thiazole orange staining to detect their mRNA content and a glycoprotein (anti-GPIIIa) antibody for platelet gating. CD61-TO expression from premature newborns was significantly lower compared to healthy full-term neonates. Preterm newborn cases with respiratory distress syndrome and a need for respiratory support (RDS+) were characterized by a significantly increased platelet volume and a decreased immature platelet fraction reported in RDS− cases. Evaluating the platelet function in the newborn is difficult because the laboratory methodologies work with small quantities of newborn blood samples. The immature platelet fractions and platelet volume promise to be diagnostic biomarkers for diseases.

A novel mechanism of thrombocytopenia by PS exposure through TMEM16F in sphingomyelin synthase 1 deficiency

Membrane SM reduction by SMS1deficiency enhances PS exposure and thrombocytopenia.

Depression of membrane SM potentiates Ca²⁺ influx and PS externalization through TMEM16F.

Sphingomyelin synthase 1 (SMS1) contributes to the generation of membrane sphingomyelin (SM) and affects SM-mediated physiological functions. Here, we describe the hematologic phenotypes, such as reduced circulating platelets and dysfunctional hemostasis, in SMS1-deficient (SMS1-KO) mice. SMS1-KO mice display pathologic manifestations related to idiopathic thrombocytopenia (ITP), including relatively high amounts of peripheral blood reticulated platelets, enhanced megakaryopoiesis in the bone marrow and spleen, and splenomegaly. Deficiency of SMS1, but not SMS2, prevented SM production and enhanced phosphatidylserine (PS) externalization on the plasma membranes of platelets and megakaryocytes. Consequently, SMS1-KO platelets were excessively cleared by macrophages in the spleen. Multimer formation in the plasma membrane of TMEM16F, a known calcium (Ca²⁺)-activated nonselective ion channel and Ca²⁺-dependent PS scramblase, was enhanced; the result was PS externalization to outer leaflets through increased Ca²⁺ influx in immortalized mouse embryonic fibroblasts established from SMS1-KO mice (SMS1-KO tMEFs), as seen with SMS1-KO platelets. Thus, SMS1 deficiency changed the TMEM16F distribution on the membrane microdomain, regulating Ca²⁺ influx-dependent PS exposure. SMS1-KO tMEFs in which TMEM16F was knocked out by using the CRISPR/Cas9 system lacked both the Ca²⁺ influx and excess PS exposure seen in SMS1-KO tMEFs. Therefore, SM depletion on platelet membrane microdomains due to SMS1 deficiency enhanced PS externalization via a Ca²⁺ influx through TMEM16F activation, leading to elevated platelet clearance and causing hemostasis dysfunction through thrombocytopenia. Our current findings show that the SM-rich microdomain generated by SMS1 is a potent regulator of thrombocytopenia through TMEM16F, suggesting that its dysfunction may be a novel additional mechanism of ITP.

Evaluation of immature platelet fraction as a marker of dengue fever progression

OBJECTIVES

Progression of dengue is often associated with thrombocytopenia resulting from viral-induced bone marrow suppression and immune-mediated peripheral platelet consumption. Immature platelet fraction (IPF), which can be measured using a haematology analyser, is a precursor indicating platelet formation in the bone marrow. This study evaluated the trend of IPF as an early recovery indicator of platelets in dengue patients with thrombocytopenia, and its relationship with severe dengue in conjunction with reticulocyte count.

METHODS

Hospitalized patients with dengue were enrolled and followed-up daily until discharge. Blood investigations included daily full blood counts and IPF measured using a haematology analyser.

RESULTS

In total, 287 patients with confirmed dengue were enrolled in this study, 25 of whom had severe dengue. All patients had a decreasing trend in platelet count in the first week of illness, concomitant with an increasing trend in the percentage of immature platelets to total platelets (IPF%) for more than 3 days prior to platelet recovery. IPF% was significantly increased in patients with severe dengue compared with patients with non-severe dengue on days 3-5 after the onset of fever. Reticulocyte count increased significantly in patients with severe dengue on day 5.

CONCLUSIONS

IPF can be utilized as an early recovery indicator of platelets in patients with dengue and thrombocytopenia.

Immature Platelet Dynamics in Immune-Mediated Thrombocytopenic States

A major challenge encountered by clinicians is differentiating presentations characterized by significant thrombocytopenia due to overlapping clinical symptoms and signs in the setting of ambiguous laboratory results. Immature platelets represent the youngest platelets that can be measured in peripheral blood by current hematology analyzers. These young platelets are larger, with higher RNA content recently released from the bone marrow. Thrombocytopenic presentations caused directly or indirectly by immune responses can lead to compensatory bone marrow responses seeking to normalize the platelet count; thus obtaining absolute immature platelet counts may be informative while triaging patients. Over the last decade, their use has expanded beyond being an early biomarker of bone marrow reconstitution post-hematopoietic stem cell transplantation to being used to establish bone marrow responses to infection and thrombocytopenias due to immune etiologies. Its accessibility as part of more detailed platelet indices obtained with routine laboratories makes it a promising option to understand the bone marrow's real-time response to disease states characterized by thrombocytopenia. This review will look at the immature platelet count as a biomarker, while presenting current attempts trying to understand how it could be used in thrombocytopenias occurring secondary to a given immune etiology.

Impact of uric acid on immature platelet fraction in patients undergoing percutaneous coronary intervention

INTRODUCTION

Reticulated platelets have been involved in the pathophysiology of coronary artery disease (CAD). Immature platelet fraction (IPF) allows their measurement in daily clinical practice, although the factors conditioning their elevation are still largely unexplored. Serum uric acid (SUA) is the end product of purine metabolism, displaying a pro-oxidant and pro-inflammatory action and increasing the cardiovascular risk. The aim of our study was to investigate the impact of SUA on IPF levels in patients undergoing percutaneous coronary intervention (PCI), and their relationship with CAD.

METHODS

We enrolled a cohort of consecutive patients undergoing coronary angiography in a single center. Hyperuricemia was defined by SUA ≥ 6.5 mg/dl. Significant CAD was defined as at least 1 vessel stenosis >50%, while severe CAD was defined as left main and/or three-vessel disease. IPF was measured at admission by routine blood cells count (A Sysmex XE-2100).

RESULTS

We included in our study 2217 patients, of whom 544 had high levels of SUA, while 1673 had normal levels. Hyperuricemics were older, with higher percentage of renal failure, hypertension, dilated cardiomyopathy or valvular disease as indication to angiography, higher levels of creatinine and C-reactive protein (p < 0.001, respectively) when compared to normouricemics. Immature platelet fraction (IPF) was significant higher in hyperuricemic patients (3.96% vs 3.59%, p = 0.004). A progressive direct increase in the IPF values was observed in relation to SUA levels (r = 0.101, p < 0.001), although at multivariate analysis, hyperuricemia did not result as an independent predictor of IPC in 3rd tertile (adjusted OR [95%CI] = 1.21 [0.85-1.71] P = 0.288). When stratifying hyperuricemics and normouricemics according to IPF tertiles (<2.3%; 2.3-3.9%; ≥ 4%), reticulated platelets were not associated to the prevalence of CAD (SUA ≥6.5:80.9 vs 79.3% vs 78.6%, p = 0.60; SUA < 6.5: 79.3% vs 81.3% vs 78.9%, p = 0.878) or severe CAD (SUA ≥6.5: 34.9% vs 38.9% vs 35.2%, p = 0.99; SUA < 6.5: 30.4% vs 33.5% vs 34%, p = 0.192), and the results were confirmed at multivariate analysis for CAD (SUA ≥6.5: adjusted OR [95%CI] = 1.11 [0.81-1.51] P = 0.524, SUA < 6.5: adjusted OR [95%CI] = 0.89 [0.75-1.05] P = 0.170) or severe CAD (SUA ≥6.5: adjusted OR [95%CI] = 1.03 [0.81-1.31] P = 0.795; SUA < 6.5: adjusted OR [95%CI] = 1.10 [0.96-1.26] P = 0.192).

CONCLUSIONS

In the present study we found a direct relationship between SUA levels and IPF values; however, hyperuricemia did not result as an independent predictor of higher IPF tertile values. Neither in hyperuricemics nor in normouricemics higher IPF were independently associated to the prevalence of CAD or severe CAD.

Impact of active smoking on the immature platelet fraction and its relationship with the extent of coronary artery disease

INTRODUCTION

Smoking represents a major cardiovascular risk factor, due to the induction of oxidative stress and low-grade, continuous, inflammation that contribute to promote atherothrombosis. However, the mechanisms leading to increased platelet aggregability associated with smoking are only partially defined. A potential role has been hypothesized for immature platelets, a younger and potentially more reactive fraction, previously associated with the main determinants of coronary artery disease (CAD). Therefore, the aim of our study was to define the impact of smoking on the immature platelet fraction (IPF) and its relationship with prevalence and extent of coronary artery disease.

METHODS

We enrolled a cohort of consecutive patients undergoing coronary angiography in a single centre. Significant CAD was defined as at least 1 vessel stenosis >50%, while severe CAD was defined as left main and/or three-vessel disease. IPF was measured at admission by routine blood cell count (Sysmex XE-2100).

RESULTS

We included in our study 2553 patients who were divided according to smoking status (active smokers: 512; nonactive smokers: 2041). Smokers were younger, more frequent males, with lower rate of diabetes mellitus, previous PCI and previous CABG (P < .001, respectively) and were in treatment less often with ARB, BB, nitrates, statins, ASA, clopidogrel, CCB and diuretics (P < .001, respectively) as compared to nonactive smokers. Higher percentage of smokers was observed in patients with higher IPF values, and at multivariate analysis, active smoking resulted as an independent predictor of higher IPF (adjusted OR [95% CI] = 1.59[1.03-2.45], P = .035). Among smokers, higher IPF was associated with lower ejection fraction (P = .034), percentage of acute coronary syndrome (P = .002) and platelet count (P < .001) compared to ones with lower IPF. However, the IPF (according to quartiles values) was not associated with the prevalence and extent of CAD (82.5%, 80.4%, 86.1% and 80.9%, from 1st to 4th quartile, respectively, adjusted OR[95% CI] = 0.98[0.79-1.23], P = .89) and severe CAD (31%, 31.1%, 39.1% and 35.2%, from 1st to 4th quartile, respectively, adjusted OR[95% CI] = 1.03[0.86-1.23], P = .76).

CONCLUSION

The present study shows an independent association between active smoking and the levels of immature platelet fraction in patients undergoing coronary angiography. However, among active smokers, IPF did not result as an independent predictor of CAD or severe CAD.

Impact of aging on immature platelet count and its relationship with coronary artery disease

Despite the fact that elderly patients represent a prevalent and challenging population in the current practice, few data exist on the impact of platelet parameters on cardiovascular risk in these patients. Therefore, the aim of the present study was to evaluate the impact of age on the immature platelet count (IPC) and their relationship with CAD. We included a total of 2236 consecutive patients undergoing coronary angiography in a single center. Elderly patients (age ≥ 75 years) were 756 (33.7%). IPC was measured at admission. Elderly patients were more often females (p < .001), with lower BMI and prevalence of smokers (p < .001), and a more complex cardiovascular risk profile and coronary disease (p = .02). Platelet count decreased with aging (p = .05), whereas no difference in the mean IPC was found between patients < or ≥75 years. In fact, advanced age did not emerge as an independent predictor of IPC above III tertile (≥8.6*10^6/ml), (adjusted OR[95%CI] = 0.97[0.78-1.21], p = .79). When considering elderly patients according to tertiles values of IPC (<5.1,5.1-8.59; ≥8.6*10^6/ml), we found no impact of IPC on the prevalence of CAD (81.1% vs 84.5% vs 81.5%, p = .92; adjusted OR[95%CI] = 1.08[0.67-1.72], p = .75) and its extent (37.7% vs 34.5% vs 40.2%, p = .57; adjusted OR[95%CI] = 1.22[0.85-1.73], p = .28). However, we observed a higher rate of calcified and type C lesions in elderly patients with higher IPC (p = .03 and p < .001, respectively). Therefore, advanced age is not associated with higher immature platelet count and the prevalence and severity of CAD. Moreover, IPC does not contribute to explain the higher prevalence and extent of coronary artery disease observed in elderly patients.

Reticulated Platelets as Predictor of Myocardial Injury and 30 Day Mortality After Non-cardiac Surgery

OBJECTIVE

A pre-operative marker for identification of patients at risk of peri-operative adverse events and 30 day mortality might be the percentage of young, reticulated platelets (pRP). This study aimed to determine the predictive value of pre-operative pRP on post-operative myocardial injury (PMI) and 30 day mortality, in patients aged ≥ 60 years undergoing moderate to high risk non-cardiac surgery.

METHODS

The incidence of PMI (troponin I > 0.06 μg/L) and 30 day mortality was compared for patients with normal and high pRP (≥2.82%) obtained from The Utrecht Patient Orientated Database. The predictive pRP value was assessed using logistic regression. A prediction model for PMI or 30 day mortality with known risk factors was compared with a model including increased pRP using the area under the receiving operator characteristics curve (AUROC).

RESULTS

In total, 26.5% (607/2289) patients showed pre-operative increased pRP. Increased pRP was associated with more PMI and 30 day mortality compared with normal pRP (36.1% vs. 28.3%, p < .001 and 8.6% vs. 3.6%, p < .001). The median pRP was higher in patients suffering PMI and 30 day mortality compared with not (2.21 [IQR: 1.57-3.11] vs. 2.07 [IQR: 1.52-1.78], p = .002, and 2.63 [IQR: 1.76-4.15] vs. 2.09 [IQR: 1.52-3.98], p < .001). pRP was independently related to PMI (OR: 1.28 [95% CI: 1.04-1.59], p = .02) and 30 day mortality (OR: 2.35 [95% CI: 1.56-3.55], p < .001). Adding increased pRP to the predictive model of PMI or 30 day mortality did not increase the AUROC 0.71 vs. 0.72, and 0.80 vs. 0.81.

CONCLUSION

In patients undergoing major non-cardiac surgery, increased pre-operative pRP is related to 30 day mortality and PMI.

Impact of platelet turnover on long-term adverse cardiovascular outcomes in patients undergoing percutaneous coronary intervention

BACKGROUND

Increased platelet turnover and high platelet reactivity are associated with short-term major adverse cardiovascular events (MACE) after percutaneous coronary intervention (PCI) for acute coronary syndrome (ACS) or stable coronary artery disease (SCAD). We investigated the impact of platelet turnover on long-term MACE.

METHODS

Consecutive patients presenting with ACS or SCAD undergoing PCI between 2009 and 2010 were included. All patients received clopidogrel and aspirin as dual antithrombotic therapy regimen. Multivariable Cox proportional hazard models were applied to assess the prognostic impact of platelet turnover (reticulated platelet count [RPC], mean platelet volume [MPV]) and function on long-term MACE, a composite of cardiovascular death, nonfatal myocardial infarction and nonfatal stroke.

RESULTS

In total, 477 patients were eligible. Mean age was 64.3 ± 12.7 years, 68.8% were male. Median follow-up was 5.8 (IQR 4.2-6.5) years. Median RPC was 7.6 (IQR 5.6-10.4) g/L and median MPV was 10.7 (IQR 10.1-11.3) fL. In univariable analysis, RPC was associated with MACE, both as continuous (HR 1.064 [95%CI 1.021-1.111]; P = .006) and dichotomized (HR 1.693 [95%CI 1.156-2.481]; P = .006) variable. After adjustment, continuous RPC (HR 1.055 [95%CI 1.012-1.099]; P = .010) and dichotomized RPC (HR 1.716 [95%CI 1.152-2.559]; P = .007) remained significantly associated with MACE. Neither MPV nor platelet function testing was associated with long-term adverse outcome.

CONCLUSION

Increased platelet turnover is associated with long-term adverse outcome in patients with coronary artery disease undergoing PCI. Platelet turnover represents a new marker of atherothrombotic risk and might help to guide composition or duration of antiplatelet therapy.

Immature Platelet Count Levels as a Novel Quality Marker in Plateletpheresis

The efficiency of plateletpheresis was improved owing to new developments in automated cell separators in the past decades. Nowadays multiple units of plateletpheresis products can be taken per collection from single donor and new parameters such as immature platelet fraction (IPF), immature platelet count (IPC) can be detected practically by automated hematology analyzers. Our aim is to find out a new quality parameter for evaluation of plateletpheresis by analyzing the platelet indices of donor and also to predict platelet recovery in recipients thereby preventing unnecessary platelet transfusion. In this study 104 platelet apheresis procedures were performed on the Trima Accel cell separator. Complete blood counts of donors and recipients were analyzed by Sysmex XN-1000 automated blood cell counter by means of quality parameters such as platelet count, IPF, IPC, mean platelet volume, platelet distribution width. We analyzed these parameters in the follow up after the transfusion of plateletpheresis and evaluated them as quality markers in the assessment of plateletpheresis effectiveness. For recipients of both single and double unit apheresis platelet transfusions, the pre-apheresis donor IPC correlated significantly with 1st and 24th hour recipient IPC values (p values < 0.05 for all comparisons). A-IPC as well as % change in IPF can be used to determine the quality of plateletpheresis in conjunction with platelet number in terms of evaluation of donors and also in the follow up of recipients undergoing platelet transfusion.

Biological variation of platelet parameters determined by the Sysmex XN hematology analyzer

BACKGROUND

This study was aimed to define the short- and medium-term biological variation (BV) estimates, the index of individuality and the reference change value (RCV) of platelet count, platelet distribution width, mean platelet volume, platelet larger cell ratio, plateletcrit and immature platelet fraction.

METHODS

The study population consisted of 43 health subjects, who participated to the assessment of medium-term (21 subjects; blood sampling once a week for 5 consecutive weeks) and short-term (22 subjects; blood sampling once a day for 5 consecutive days) BV study, using Sysmex XN-module. Eight subjects were also scheduled to participate to both phases. The data were subject to outlier analysis prior to CV-ANOVA, to determine the BV estimates with the relative confidence intervals.

RESULTS

The medium-term and short-term within-subject BV (CV_I) was comprised between 2.3 and 7.0% and 1.1-8.6%, whereas the medium-term and short-term between-subjects BV (CV_G) was comprised between 7.1 and 20.7% and 6.8-48.6%. The index of individuality and index of heterogeneity were always respectively <0.6 and >0.63 for all the parameters, in both arms of the study. The RCVs were similar for all parameters, in both arms of the study.

CONCLUSION

This study allowed to define the BV estimates of many platelet parameters, some of them unavailable in literature. The kinetics of platelet turnover suggests the use of short-term BV data for calculating analytical goals and RCV. The correct clinical interpretation of platelet parameters also necessitates that each laboratory estimates local RCV values.

Imetelstat, a telomerase inhibitor, differentially affects normal and malignant megakaryopoiesis

Imetelstat (GRN163L) is a specific telomerase inhibitor that has demonstrated clinical activity in patients with myeloproliferative neoplasms (MPN) and in patients with solid tumors. The antitumor effects were associated with the development of thrombocytopenia, one of the common side effects observed in patients treated with imetelstat. The events underlying these adverse effects are not apparent. In this report, we investigated the potential mechanisms that account for imetelstat's beneficial effects in MPN patients and the manner by which imetelstat treatment leads to a reduction in platelet numbers. Using a well-established system of ex vivo megakaryopoiesis, we demonstrated that imetelestat treatment affects normal megakaryocyte (MK) development by exclusively delaying maturation of MK precursor cells. By contrast, additional stages along MPN MK development were affected by imetelstat resulting in reduced numbers of assayable colony-forming unit MK and impaired MK maturation. In addition, treatment with imetelstat inhibited the secretion of fibrogenic growth factors by malignant but not by normal MK. Our results indicate that the delay observed in normal MK maturation may account for imetelstat-induced thrombocytopenia, while the more global effects of imetelstat on several stages along the hierarchy of MPN megakaryopoiesis may be responsible for the favorable clinical outcomes reported in MPN patients.

The Centenary of Immune Thrombocytopenia-Part 2: Revising Diagnostic and Therapeutic Approach

Primary immune thrombocytopenia (ITP) is the most common cause of thrombocytopenia in children and adolescents and can be considered as a paradigmatic model of autoimmune disease. This second part of our review describes the clinical presentation of ITP, the diagnostic approach and overviews the current therapeutic strategies. Interestingly, it suggests an algorithm useful for differential diagnosis, a crucial process to exclude secondary forms of immune thrombocytopenia (IT) and non-immune thrombocytopenia (non-IT), which require a different therapeutic management. Advances in understanding the pathogenesis led to new therapeutic targets, as thrombopoietin receptor agonists, whose role in treatment of ITP will be discussed in this work.

Time-Dependent Decay of mRNA and Ribosomal RNA during Platelet Aging and Its Correlation with Translation Activity

Previous investigations have indicated that RNAs are mostly present in the minor population of the youngest platelets, whereas translation in platelets could be biologically important. To attempt to solve this paradox, we studied changes in the RNA content of reticulated platelets, i.e., young cells brightly stained by thiazole orange (TO^bright), a fluorescent probe for RNAs. We provoked in mice strong thrombocytopenia followed by dramatic thrombocytosis characterized by a short period with a vast majority of reticulated platelets. During thrombocytosis, the TO^bright platelet count rapidly reached a maximum, after which TO^dim platelets accumulated, suggesting that most of the former were converted into the latter within 12 h. Experiments on platelets, freshly isolated or incubated ex vivo at 37°C, indicated that their “RNA content”, here corresponding to the amounts of extracted RNA, and the percentage of TO^bright platelets were positively correlated. The “RNA Content” normalized to the number of platelets could be 20 to 40 fold higher when 80–90% of the cells were reticulated (20–40 fg/platelet), than when only 5–10% of control cells were TO^bright (less than 1fg/platelet). TO^bright platelets, incubated ex vivo at 37°C or transfused into mice, became TO^dim within 24 h. Ex vivo at 37°C, platelets lost about half of their ribosomal and beta actin RNAs within 6 hours, and more than 98% of them after 24 hours. Accordingly, fluorescence in situ hybridization techniques confirmed the presence of beta actin mRNAs in most reticulated-enriched platelets, but detected them in only a minor subset of control platelets. In vitro, constitutive translation decreased considerably within less than 6 hours, questioning how protein synthesis in platelets, especially in non-reticulated ones, could have a biological function in vivo. Nevertheless, constitutive transient translation in young platelets under pathological conditions characterized by a dramatic increase in circulating reticulated platelets could deserve to be investigated.

Drug delivery and therapeutic impact of extended-release acetylsalicylic acid

Current treatment guidelines recommend once-daily, low-dose acetylsalicylic acid (ASA; aspirin) for secondary prevention of cardiovascular events. However, the anti-thrombotic benefits of traditional ASA formulations may not extend over a 24-h period, especially in patients at high risk for a recurrent cardiovascular event. A next-generation, extended-release ASA formulation (ER-ASA) has been developed to provide 24-h anti-thrombotic coverage with once-daily dosing. The pharmacokinetics of ER-ASA indicates slower absorption and prolonged ASA release versus immediate-release ASA, with a favorable safety profile. ER-ASA minimizes systemic ASA absorption and provides sustained antiplatelet effects over a 24-h period.