Age-related changes in platelet function are more profound in women than in men

Biological processes and factors involved in soft and hard tissue healing

Wound healing is a complex and iterative process involving myriad cellular and biologic processes that are highly regulated to allow satisfactory repair and regeneration of damaged tissues. This review is intended to be an introductory chapter in a volume focusing on the use of platelet concentrates for tissue regeneration. In order to fully appreciate the clinical utility of these preparations, a sound understanding of the processes and factors involved in soft and hard tissue healing. This encompasses an appreciation of the cellular and biological mediators of both soft and hard tissues in general as well as specific consideration of the periodontal tissues. In light of good advances in this basic knowledge, there have been improvements in clinical strategies and therapeutic management of wound repair and regeneration. The use of platelet concentrates for tissue regeneration offers one such strategy and is based on the principles of cellular and biologic principles of wound repair discussed in this review.

Combining diabetes, sex, and menopause as meaningful clinical features associated with NASH and liver fibrosis in individuals with class II and III obesity: A retrospective cohort study

OBJECTIVE

Steatotic liver disease (SLD) is frequent in individuals with obesity. In this study, type 2 diabetes (T2D), sex, and menopausal status were combined to refine the stratification of obesity regarding the risk of advanced SLD and gain further insight into disease physiopathology.

METHODS

This study enrolled 1446 participants with obesity from the ABOS cohort (NCT01129297), who underwent extensive phenotyping, including liver histology and transcriptome profiling. Hierarchical clustering was applied to classify participants. The prevalence of metabolic disorders associated with steatohepatitis (NASH) and liver fibrosis (F ≥ 2) was determined within each identified subgroup and aligned to clinical and biological characteristics.

RESULTS

The prevalence of NASH and F ≥ 2 was, respectively, 9.5% (N = 138/1446) and 11.7% (N = 159/1365) in the overall population, 20.3% (N = 107/726) and 21.1% (N = 106/502) in T2D patients, and 3.4% (N = 31/920) and 6.1% (N = 53/863) in non-T2D patients. NASH and F ≥ 2 prevalence was 15.4% (33/215) and 15.5% (32/206) among premenopausal women with T2D vs. 29.5% (33/112) and 30.3% (N = 36/119) in postmenopausal women with T2D (p < 0.01); and 21.0% (21/100) / 27.0% (24/89) in men with T2D ≥ age 50 years and 17.9% (17/95) / 18.5% (17/92) in men with T2D < age 50 years (NS). The distinct contribution of menopause was confirmed by the interaction between sex and age with respect to NASH among T2D patients (p = 0.048). Finally, several NASH-associated biological traits (lower platelet count; higher serum uric acid; gamma-glutamyl transferase; aspartate aminotransferase) and liver expressed genes AKR1B10 and CCL20 were significantly associated with menopause in women with T2D but not with age in men with T2D.

CONCLUSIONS

This study unveiled a remarkably high prevalence of advanced SLD after menopause in women with T2D, associated with a dysfunctional biological liver profile.

Time- and distance-resolved robotic imaging of fluid flow in vertical microfluidic strips: a new technique for quantitative, multiparameter measurement of global haemostasis

Measuring the complex processes of blood coagulation, haemostasis and thrombosis that are central to cardiovascular health and disease typically requires a choice between high-resolution low-throughput laboratory assays, or simpler less quantitative tests. We propose combining mass-produced microfluidic devices with open-source robotic instrumentation to enable rapid development of affordable and portable, yet high-throughput and performance haematological testing. A time- and distance-resolved fluid flow analysis by Raspberry Pi imaging integrated with controlled sample addition and illumination, enabled simultaneous tracking of capillary rise in 120 individual capillaries (∼160, 200 or 270 μm internal diameter), in 12 parallel disposable devices. We found time-resolved tracking of capillary rise in each individual microcapillary provides quantitative information about fluid properties and most importantly enables quantitation of dynamic changes in these properties following stimulation. Fluid properties were derived from flow kinetics using a pressure balance model validated with glycerol-water mixtures and blood components. Time-resolved imaging revealed fluid properties that were harder to determine from a single endpoint image or equilibrium analysis alone. Surprisingly, instantaneous superficial fluid velocity during capillary rise was found to be largely independent of capillary diameter at initial time points. We tested if blood function could be measured dynamically by stimulating blood with thrombin to trigger activation of global haemostasis. Thrombin stimulation slowed vertical fluid velocity consistent with a dynamic increase in viscosity. The dynamics were concentration-dependent, with highest doses reducing flow velocity faster (within 10 s) than lower doses (10-30 s). This open-source imaging instrumentation expands the capability of affordable microfluidic devices for haematological testing, towards high-throughput multi-parameter blood analysis needed to understand and improve cardiovascular health.

Effect of regular exercise training on platelet function in patients with cardiovascular disease and healthy individuals: A systematic review

INTRODUCTION

Regular exercise training is essential in prevention and treatment of cardiovascular disease (CVD), yet the beneficial effects of exercise remain only partly explained. Platelets play a key role in CVD and may be affected by regular exercise training. We aimed to systematically summarise studies investigating the effect of regular exercise training on platelet function in patients with CVD and in healthy individuals.

METHODS

Studies were identified by PubMed, Embase and Web of Science May 16, 2022. We selected studies investigating markers of platelet function in relation to regular exercise training in patients with CVD and in healthy individuals. Regular exercise was defined as exercise training for four weeks or more.

RESULTS

Of the included studies, 11 investigated patients with CVD and 29 were on healthy individuals. Studies were heterogeneous regarding design, study population and methodology, and the results were ambiguous. In total, 52 different markers of platelet function were investigated with platelet aggregation, soluble P-selectin, and thromboxane B2 (TXB2) as the most frequently examined. When evaluating between-group changes after regular exercise, two studies found a reduced platelet aggregation in the exercise group whilst three studies did not find a difference between groups. With respect to TXB2, three studies reported a reduction and two studies an increase in the exercise group. There were no between-group differences in the seven studies examining soluble P-selectin.

CONCLUSION

Regular exercise training has no clear impact on platelet function in patients with CVD or healthy individuals.

PROSPERO REGISTRATION

CRD42022350539.

The modulation of platelet function by growth hormone in growth hormone deficient Hypopituitary patients

BACKGROUND

Growth hormone deficiency (GHD) has been implicated in increased cardiovascular and cerebrovascular disease risk seen in hypopituitarism, however the mechanism remains speculative. We hypothesise that platelet abnormalities may play a contributory role. Herein we examined platelet behaviour in GHD hypopituitary patients, pre- and post-growth hormone (GH) replacement.

METHODS

This study utilizes a physiological flow-based assay to quantify platelet function in whole blood from patient cohorts under arterial shear. Thirteen GH Naïve hypopituitary adults with GHD and thirteen healthy matched controls were studied. Patients were assessed before and after GH treatment. All other pituitary replacements were optimised before the study. In addition to a full endocrine profile, whole blood was labelled and perfused over immobilised von Willibrand factor (vWF). Seven parameters of dynamic platelet-vWF interactions were recorded using digital image microscopy and analysed by customised platelet tracking software.

RESULTS

We found a significantly altered profile of platelet-vWF interactions in GHD individuals compared to healthy controls. Specifically, we observed a marked increase in platelets shown to form associations such as tethering, rolling and adherence to immobilized vWF, which were reduced post GH treatment. Speed and distance platelets travelled across vWF was similar between controls and pre-therapy GHD patients, however, this was considerably increased post treatment. This may indicate reduced platelet signaling resulting in less stable adhesion of platelets post GH treatment.

CONCLUSIONS

Taken together observed differences in platelet behaviour may contribute to an increased risk of thrombosis in GHD which can in part be reversed by GH therapy.

Effect of Mean Platelet Volume to Platelet Count Ratio on Mortality in Peritoneal Dialysis

Background and Aims

Mean platelet volume to platelet count ratio (MPV/PC) has been found to be an independent risk factor for mortality in various diseases, including cardiovascular disease, cancer, and hemodialysis. We aimed to evaluate the association between MPV/PC and all-cause and cardiovascular (CV) mortality in peritoneal dialysis (PD) patients.

Methods and Results

We conducted a retrospective cohort study at a single center and enrolled 1473 PD patients who were catheterized at our PD center from January 1, 2006, to December 31, 2013. All patients were divided into four groups according to the quartiles of baseline MPV/PC levels and followed up until December 31, 2018. A total of 453 patients died, and 221 deaths were caused by cardiovascular disease during a median follow-up time of 48.0 (21.9-82.2) months. There was a significant interaction by age of association between MPV/PC level and all-cause mortality (P = 0.009), and multivariate Cox regression analysis showed that higher MPV/PC level was related to a decreased risk of all-cause and CV mortality in PD patients aged < 60 years (HR = 0.62, 95%CI = 0.40 − 0.96, P = 0.032; HR = 0.49, 95%CI = 0.26 − 0.93, P = 0.029, respectively), rather than in patients aged ≥ 60 years (HR = 1.37, 95%CI = 0.84 − 2.22, P = 0.208; HR = 1.50, 95%CI = 0.77 − 2.92, P = 0.237, respectively).

Conclusion

Our results indicated that low MPV/PC level was an independent risk factor for all-cause and CV mortality in PD patients aged less than 60 years.

Sex differences at the platelet-vascular interface

Platelets are multifunctional cells that ensure the integrity of the vascular wall and modulate the immune response at the blood/vascular interface. Their pathological activation results in both thrombosis and inflammation and implicates them in the pathogenesis of vascular disease. Vascular diseases are sexually dimorphic in terms of incidence, clinical presentation, outcome, and efficacy of anti-platelet therapy. We here provide an overview of what is known about the role of platelets in the initiation and progression of vascular diseases and summarize what is known about the sex differences in platelet reactivity and in the thromboinflammatory mechanisms that drive these diseases, with a particular focus on atherosclerosis, obstructive and non-obstructive coronary artery disease, and ischemic stroke. Understanding the sex differences at the platelet-vascular interface is clinically relevant as it will enable: (1) to design new therapeutic strategies that prevent the detrimental effects of the immune-modulatory function of platelets taking sex into account, and (2) to evaluate if sex-specific anti-platelet drug regimens should be used to reduce the risk not only of thrombosis but also of vascular disease progression.

Prognostic value of the ADAMTS13-vWF axis in disseminated intravascular coagulation: Platelet count/vWF:Ag ratio as a strong prognostic marker

INTRODUCTION

ADAMTS13 deficiency increases the circulating level of von Willebrand factor (vWF). Low ADAMTS13 and high vWF can provide a milieu for microthrombosis, including disseminated intravascular coagulation (DIC). This study investigated the prognostic values of ADAMTS13-vWF axis markers and their correlation with DIC severity.

METHODS

ADAMTS13-vWF axis markers (vWF antigen (vWF:Ag), vWF ristocetin cofactor (vWF:Rco), ADAMTS13 activity, and anti-ADAMTS13 antibody) were measured in patients (n = 152) suspected of having DIC along with the well-known DIC markers including antithrombin and protein C.

RESULT

The vWF:Ag level was significantly increased, and ADAMTS13 activity was significantly decreased in overt DIC. The vWF:Ag level (hazard ratio 7.365, p = .009), ADAMTS13 activity/vWF:Ag ratio (hazard ratio 3.777, p = .037), ADAMTS13 activity/vWF:Rco ratio (hazard ratio 3.027, p = .028), and platelet count/vWF:Ag ratio (hazard ratio 8.538, p < .001) were significant prognostic markers in Cox regression analysis and correlated well with DIC score and antithrombin and protein C levels.

CONCLUSION

The platelet count/vWF:Ag was the strongest prognostic marker among ADAMTS13-vWF axis markers. The measurement of vWF:Ag may improve prognostic insights of DIC in clinical practice.

The Clot Thickens: Recent Clues on Hematopoietic Stem Cell Contribution to Age-Related Platelet Biology Open New Questions

Platelets provide life-saving functions by halting external and internal bleeding. There is also a dark side to platelet biology, however. Recent reports provide evidence for increased platelet reactivity during aging of mice and humans, making platelets main suspects in the most prevalent aging-related human pathologies, including cardiovascular diseases, stroke, and cancer. What drives this platelet hyperreactivity during aging? Here, we discuss how hematopoietic stem cell differentiation pathways into the platelet lineage offer avenues to understand the fundamental differences between young and old platelets. Recent advances begin to unravel how the cellular and molecular regulation of the parent hematopoietic stem and progenitor cells likely imbue aging characteristics on the resulting Plt progeny. The resulting mechanistic insights into intrinsic platelet reactivity will provide strategies for selectively targeting age-related pathways. This brief viewpoint focuses on current concepts on aging hematopoiesis and the implications for platelet hyperactivity during aging.

Platelets in aging and cancer-"double-edged sword"

Platelets control hemostasis and play a key role in inflammation and immunity. However, platelet function may change during aging, and a role for these versatile cells in many age-related pathological processes is emerging. In addition to a well-known role in cardiovascular disease, platelet activity is now thought to contribute to cancer cell metastasis and tumor-associated venous thromboembolism (VTE) development. Worldwide, the great majority of all patients with cardiovascular disease and some with cancer receive anti-platelet therapy to reduce the risk of thrombosis. However, not only do thrombotic diseases remain a leading cause of morbidity and mortality, cancer, especially metastasis, is still the second cause of death worldwide. Understanding how platelets change during aging and how they may contribute to aging-related diseases such as cancer may contribute to steps taken along the road towards a "healthy aging" strategy. Here, we review the changes that occur in platelets during aging, and investigate how these versatile blood components contribute to cancer progression.

Platelet proteome changes in dogs with congestive heart failure

BACKGROUND

Platelets play a central role in the development of cardiovascular diseases and changes in their proteins are involved in the pathophysiology of heart diseases in humans. There is lack of knowledge about the possible role of platelets in congestive heart failure (CHF) in dogs. Thus, this study aimed to investigate the changes in global platelet proteomes in dogs with CHF, to clarify the possible role of platelets in the physiopathology of this disease. Healthy-dogs (n = 10) and dogs with acute CHF due to myxomatous mitral valve disease (MMVD, n = 10) were used. Acute CHF was defined based on the clinical (increased respiratory rate or difficulty breathing) and radiographic findings of pulmonary edema. Dogs Blood samples were collected into tubes with acid-citrate-dextrose, and platelet-pellets were obtained by centrifuge and washing steps. Platelet-proteomes were identified using LC-MS based label-free differential proteome expression analysis method and matched according to protein database for Canis lupus familiaris.

RESULTS

Totally 104 different proteins were identified in the platelets of the dogs being 4 out of them were significantly up-regulated and 6 down-regulated in acute CHF dogs. Guanine-nucleotide-binding protein, apolipoproteins (A-II and C-III) and clusterin levels increased, but CXC-motif-chemokine-10, cytochrome-C-oxidase-subunit-2, cathepsin-D, serine/threonine-protein-phosphatase-PP1-gamma-catalytic-subunit, creatine-kinase-B-type and myotrophin levels decreased in acute CHF dogs. These proteins are associated with several molecular functions, biological processes, signaling systems and immune-inflammatory responses.

CONCLUSION

This study describes by first time the changes in the protein composition in platelets of dogs with acute CHF due to MMVD. Our findings provide a resource for increase the knowledge about the proteome of canine platelets and their roles in CHF caused by MMVD and could be a tool for further investigations about the prevention and treatment of this disease.

CHADS2 and CHA2DS2-VASc scores as predictors of platelet reactivity in acute coronary syndrome

BACKGROUND

Platelet function testing (PFT) in patients treated with P2Y₁₂ inhibitors has been widely evaluated for the prediction of stent thrombosis, myocardial infarction, and bleeding events following percutaneous coronary intervention (PCI) in acute coronary syndrome (ACS). Thus, PFT-guided treatment could positively affect patient outcomes. Data regarding clinical parameters for predicting platelet reactivity in ACS patients are limited. Therefore, our study aims to evaluate CHADS2 and CHA2DS2-VASc scores as predictors for platelet reactivity in ACS patients.

METHODS

Two hundred and ninety-one consecutive patients who underwent PCI and were treated with aspirin and clopidogrel due to ACS were tested for their CHADS2, CHA2DS2-VASc scores and platelet reactivity using adenosine diphosphate (ADP)-induced aggregation (conventional aggregometry). Patients were classified into groups according to their CHADS2 and CHA2DS2-VASc scores. Low-risk group (0-1 score) for CHADS2 and CHA2DS2-VASc scores and high-risk group (2-6, 2-9) for CHADS2 and CHA2DS2-VASc scores, respectively. Furthermore, platelet reactivity in each group were compared (low CHADS2 group vs high CHADS2 group, and low CHA2DS2-VASc vs high CHA2DS2-VASc). Platelet reactivity was defined as low platelet reactivity (<19 U), optimal platelet reactivity [(OPR); 19-46 U], and high on-treatment platelet reactivity [(HPR); >46 U]. Thereafter receiver operating characteristic curve analysis was conducted to verify whether CHADS2 and CHA2DS2-VASc scores could predict platelet reactivity.

RESULTS

Low CHADS2 and CHA2DS2-VASc scores were significantly correlated with lower mean platelet ADP-induced aggregation as compared with high CHADS2 and CHA2DS2-VASc scores [45.5 U (± 16) vs. 54.8 U (±15) and 44.2 U (±16) vs. 51.0 U (±17), respectively, p = 0.01 for both].

CONCLUSION

In ACS patients treated with clopidogrel following PCI, high CHADS2 and CHA2DS2-VASc scores correlated with HPR and lower scores correlated with OPR. Further studies are needed to evaluate our findings' clinical implications.

Systemic and local factors associated with reduced thrombolysis in myocardial infarction flow in ST-segment elevation myocardial infarction patients with plaque erosion detected by intravascular optical coherence tomography

Local factors of plaque rupture (e.g. lipid burden) are related to preprocedural thrombolysis in myocardial infarction (TIMI) flow grade during primary percutaneous coronary intervention (PCI). However, the pathological mechanism differs between plaque erosion and rupture. We aimed to identify the factors associated with reduced TIMI flow in plaque erosion. A total of 329 ST-segment elevation myocardial infarction (STEMI) patients with optical coherence tomography (OCT) identified plaque erosion were divided into 2 groups by preprocedural TIMI flow grade [TIMI 0-1 group (n = 219) and TIMI 2-3 group (n = 110)]. Patients in TIMI 0-1 group were older (age > 50 years, 68.5% vs. 51.8%, P = 0.003), and had more diabetes mellitus (18.3% vs. 8.2%, P = 0.015). Plaque erosion with TIMI flow 0-1 was less frequently located in the left anterior descending artery (LAD, 58.4% vs. 72.7%, P = 0.011), but more frequently located in the right coronary artery (RCA, 34.2% vs. 7.3%, P = 0.001) than those with TIMI flow 2-3. TIMI 0-1 group had more lipid plaques (53.9% vs. 41.8%, P = 0.039), macrophage accumulation (59.8% vs. 41.8%, P = 0.002), and calcification (34.2% vs. 21.8%, P = 0.020). In the multivariable analysis, age > 50 years, diabetes mellitus, RCA location, and macrophage accumulation were the independent predictors of reduced TIMI flow grade in STEMI patients with plaque erosion. Systemic factors (older age and diabetes mellitus) and local factors (RCA location and macrophage accumulation) were independently associated with reduced coronary flow in STEMI patients with plaque erosion. CLINICAL TRIAL REGISTRATION : ClinicalTrials.gov NCT03084991 May 17, 2017 (retrospectively registered).

Advances in Platelet Function Testing-Light Transmission Aggregometry and Beyond

Platelet function testing is essential for the diagnosis of hemostasis disorders. While there are many methods used to test platelet function for research purposes, standardization is often lacking, limiting their use in clinical practice. Light transmission aggregometry has been the gold standard for over 60 years, with inherent challenges of working with live dynamic cells in specialized laboratories with independent protocols. In recent years, standardization efforts have brought forward fully automated systems that could lead to more widespread use. Additionally, new technical approaches appear promising for the future of specialized hematology laboratories. This review presents developments in platelet function testing for clinical applications.

Platelet Responses in Cardiovascular Disease: Sex-Related Differences in Nutritional and Pharmacological Interventions

Cardiovascular diseases (CVD) represent one of the biggest causes of death globally, and their prevalence, aetiology, and outcome are related to genetic, metabolic, and environmental factors, among which sex- and age-dependent differences may play a key role. Among CVD risk factors, platelet hyperactivity deserves particular mention, as it is involved in the pathophysiology of main cardiovascular events (including stroke, myocardial infarction, and peripheral vascular injury) and is closely related to sex/age differences. Several determinants (e.g., hormonal status and traditional cardiovascular risk factors), together with platelet-related factors (e.g., plasma membrane composition, receptor signaling, and platelet-derived microparticles) can elucidate sex-related disparity in platelet functionality and CVD onset and outcome, especially in relation to efficacy of current primary and secondary interventional strategies. Here, we examined the state of the art concerning sex differences in platelet biology and their relationship with specific cardiovascular events and responses to common antiplatelet therapies. Moreover, as healthy nutrition is widely recognized to play a key role in CVD, we also focused our attention on specific dietary components (especially polyunsaturated fatty acids and flavonoids) and patterns (such as Mediterranean diet), which also emerged to impact platelet functions in a sex-dependent manner. These results highlight that full understanding of gender-related differences will be useful for designing personalized strategies, in order to prevent and/or treat platelet-mediated vascular damage.

Platelets in Amyloidogenic Mice Are Activated and Invade the Brain

Alzheimer’s disease (AD) is a neurodegenerative disease with a complex and not fully understood pathogenesis. Besides brain-intrinsic hallmarks such as abnormal deposition of harmful proteins, i.e., amyloid beta in plaques and hyperphosphorylated Tau in neurofibrillary tangles, blood-derived elements, in particular, platelets have been discussed to be involved in AD pathogenesis. The underlying mechanisms, however, are rather unexplored. Here, we investigate a potential role of platelets in an AD transgenic animal model with severe amyloid plaque formation, the APP-PS1 transgenic mice, and analyzed the presence, spatial location and activation status of platelets within the brain. In APP-PS1 mice, a higher number of platelets were located within the brain parenchyma, i.e., outside the cerebral blood vessels compared to WT controls. Such platelets were activated according to the expression of the platelet activation marker CD62P and to morphological hallmarks such as membrane protrusions. In the brain, platelets were in close contact exclusively with astrocytes suggesting an interaction between these two cell types. In the bloodstream, although the percentage of activated platelets did not differ between transgenic and age-matched control animals, APP-PS1 blood-derived platelets showed remarkable ultrastructural peculiarities in platelet-specific organelles such as the open canalicular system (OCS). This work urges for further investigations on platelets and their yet unknown functional roles in the brain, which might go beyond AD pathogenesis and be relevant for various age-related neurodegenerative diseases.

Elevated Plasma von Willebrand Factor Antigen and Activity Levels Are Associated With the Severity of Coronary Stenosis

von Willebrand factor (VWF) acts as a bridge between platelets and the subendothelial matrix following vessel damage and plays a vital role in coronary artery disease (CAD). The aim of this study was to investigate the association between VWF and the severity of coronary stenosis quantified by the Gensini score in acute myocardial infarction (AMI), the most dangerous complication of CAD. Plasma VWF antigen (VWF: Ag) and VWF-collagen binding (VWF: CB) in normal controls (n = 123) and in patients with AMI (n = 205) were tested, and then the patients were divided based on Gensini scores. The levels of VWF: Ag and VWF: CB in patients with AMI were significantly higher than those in the control group (P < .001). Plasma levels of VWF: Ag and VWF: CB were positively correlated with both Gensini score and the number of affected vessels. Both VWF: Ag and VWF: CB were independent factors for coronary stenosis, adjusting confounding factors. Thus, the levels of VWF: Ag and VWF: CB were positively correlated with the severity of coronary stenosis. Screening of VWF at time of AMI may have prognostic value in terms of the severity of coronary stenosis.

Platelets can reflect the severity of Crohn's disease without the effect of anemia

OBJECTIVES

Anemia and changes in platelets (PLT) are common in inflammatory bowel disease (IBD). In our study, we aimed to verify whether PLT count can independently reflect the severity of IBD.

METHODS

In our hospital, 137 Crohn's Disease (CD), 69 Ulcerative colitis (UC) patients, and 412 healthy controls were included to compare the differences in PLT count. In addition, the effect of anemia, C-reactive protein (CRP), age, CD activity index (CDAI) or Mayo on PLTs was also analyzed. If PLTs independently affected CD or UC, we used the receiver operating characteristic (ROC) curve to verify the diagnostic value and obtain the cut-off value of PLT.

RESULTS

CD and UC patients had higher PLT than controls (p<0.001, p<0.001; respectively). In CD patients, the results showed that patients with anemia (P<0.01), Iron Deficiency Anemia (IDA) (p<0.001), CRP≥8 mg/L (p=0.046), and CDAI≥150 (p<0.001) had higher PLT, while in UC patients, those with anemia (p=0.018), CRP≥8 mg/L (p=0.045), and Mayo≥3 (p=0.029) had higher PLT. Univariate analysis showed that CDAI was positively correlated with PLT count (p<0.001), while hemoglobin (p=0.001) and age (p<0.001) were negatively correlated with PLT in CD. In UC patients, Mayo (p=0.001) and CRP (p<0.001) were positively correlated with PLT, while hemoglobin (p=0.002) was negatively correlated. Finally, by linear stepwise multivariate analysis, we clarified the positive relationship between PLT and CD (p<0.001) by eliminating the interference of hemoglobin, and determined the cut-off value of PLT as 298×109/L. For UC, we did not obtain similar results.

CONCLUSIONS

PLT can be an indicator of disease severity in CD, while there is a lack of evidence regarding this finding in UC.

17β-Estradiol, a potential ally to alleviate SARS-CoV-2 infection

Considering that female sexual hormones may modulate the inflammatory response and also exhibit direct effects on the cells of the immune system, herein, we intend to discuss the sex differences and the role of estradiol in modulating the lung and systemic inflammatory response, focusing on its possible application as a treatment modality for SARS-CoV-2 patients. COVID-19 patients develop severe hypoxemia early in the course of the disease, which is silent most of the time. Small fibrinous thrombi in pulmonary arterioles and a tumefaction of endothelial were observed in the autopsies of fatal COVID-19 cases. Studies showed that the viral infection induces a vascular process in the lung, which included vasodilation and endothelial dysfunction. Further, the proportions of CD4+ T and CD8+ T lymphocytes were strongly reduced in patients with severe SARS-CoV-2 infection. Estradiol is connected with CD4+ T cell numbers and increases T-reg cell populations, affecting immune responses to infection. It is known that estradiol exerts a protective effect on endothelial function, activating the generation of nitric oxide (NO) via endothelial nitric oxide synthase. Estrogen attenuates the vasoconstrictor response to various stimuli and induces vasodilation in the pulmonary vasculature during stress situations like hypoxia. It exerts a variety of rapid actions, which are initiated after its coupling with membrane receptors, which in turn, may positively modulate vascular responses in pulmonary disease and help to maintain microvascular flow. Direct and indirect mechanisms underlying the effects of estradiol were investigated, and the results point to a possible protective effect of estradiol against COVID-19, indicating that it may be considered as an adjuvant therapeutic element for the treatment of patients affected by the novel coronavirus.

Investigating the effect of age on platelet ultrastructure using transmission electron microscopy

In the present study, the age- and sex-related differences in platelet ultrastructure were investigated using transmission electron microscopy (TEM). A total of 15 healthy volunteers were grouped according to age, with 5 people in each of the following groups: young group (25-45 years), middle-aged group (46-65 years), and old-aged group (> 65 years). In the TEM micrographs, the internal components, specifically the α-granules, dense granules, and lysosomal granules, of 20 platelets were counted for each group. Two-way analysis of variance of age and sex variance was used to compare the results. The ultrastructure of the platelets in the old-aged group was observed to be quite different from those of the young and middle-aged groups. Specifically, with ageing, the platelet membrane becomes more irregular in shape and non-smooth, and multiple platelet membrane ruptures are observed. Furthermore, the pseudopodia and protuberances become more numerous and slender, and the number of α-granules is significantly reduced. These morphological changes indicate that ageing may affect the function of platelets, which in turn affects the efficacy of platelet concentrates. Thus, the effects of age should be considered when using platelet concentrates prepared from elderly autologous blood.

Modulators of platelet function in aging

Platelets are small, anucleated effector cells that play an important role in linking the hemostatic and inflammatory processes in the body. Platelet function is known to be altered under various inflammatory conditions including aging. A gain in platelet function during aging can increase the risk of thrombotic events, such as stroke and acute myocardial infarction. Anti-platelet therapy is designed to reduce risk of serious cerebrovascular and cardiovascular events, but the adverse consequences of therapy, such as risk for bleeding increases with aging as well. Age-associated comorbidities such as obesity, diabetes, and hyperlipidemia also contribute to increased platelet activity and thus can enhance the risk of thrombosis. Therefore, identification of unique mechanisms of platelet dysfunction in aging and in age-associated comorbidities is warranted to design novel antiplatelet drugs. This review outlines some of the current areas of research on aging-related mechanisms of platelet hyperactivity and addresses the clinical urgency for designing anti-platelet therapies toward novel molecular targets in the aging population.

Antiplatelet protocol: Effects of ingesting a tomato pomace extract on human platelet aggregation

Consumption of tomato and tomato-based products is associated with risk reduction of cardiovascular disease (CVD). Protective effect of tomato is not clearly understood, but there is an interest in its ability to affect platelet aggregation (coagulation). Therefore, the aim of the present study is to describe the protocol of a single blind, parallel design (3-groups), placebo controlled trial, which will assess acute and "acute upon 5-day repeated dose" effects of ingesting a tomato pomace extract on platelet aggregation. Participants will be randomized to receive a flavoured water either with 1 g tomato pomace extract, 2.5 g tomato pomace extract or placebo negative control. A total of 99 people are required to complete (n = 33/group). Each group will ingest either a treatment or placebo once daily, for 5-days and blood samples will be taken to analyze platelet aggregation. For 14-days preceding the baseline assessment day and for the 5-day period of intervention, participants will have to exclude some foods/beverages from their diet, which are known to affect platelet function. The present study is expected to generate significant information about the effect of tomato pomace extract consumption on platelet function of volunteers.

Altered functions of platelets during aging

PURPOSE OF REVIEW

Platelets are specialized effector cells that rapidly respond to sites of vascular injury. However, emerging data demonstrate that platelets possess diverse functions that also mediate inflammatory responses and neurological diseases. These functions are relevant to disease processes prevalent among older adults and likely influence susceptibility to thrombotic and inflammatory disorders.

RECENT FINDINGS

Platelet counts decrease in aged individuals whereas platelet reactivity increases. The platelet transcriptome is altered in aged individuals resulting in altered platelet function and exaggerated inflammation. Platelet signaling to monocytes in aging results in significantly more cytokines because of increased platelet-derived granzyme A. Platelet activation in aging appears to be driven, in part, because of increased reactive oxygen species and activation of the mammalian target of rapamycin pathway. Increased platelet hyperactivity in diseases is associated with aging, such cardiovascular disease and sepsis, exaggerate inflammation and thrombosis. Noncanonical functions of platelets influence the development of neurological diseases including Alzheimer's disease.

SUMMARY

Although there have been advances dissecting the molecular mechanisms regarding aging-related changes in platelets, many knowledge gaps still remain. Studies filling these gaps are likely to identify new mechanisms driving aging-related changes in platelet gene expression and function, and contributing to injurious thrombo-inflammation in older adults.

Platelet Function in Aging

Aging is associated with an increased incidence of cardiovascular disease and thrombosis. Platelets play a major role in maintaining hemostasis and in thrombus formation, making them a key player in thrombotic disorders. Whereas it is well-known that platelet aggregability is increased in vascular diseases, the contribution of age-related changes in platelet biology to cardiovascular risk is not well-understood. Several lines of evidence support that platelets from older subjects differ in their function and structure, making platelets more prone to activation and less sensitive to inhibition. These age-related changes could lead to platelet hyperactivity and to the development of a prothrombotic state in advanced age. This review will focus on platelet biochemical modifications during aging and on the mechanisms by which these alterations could lead to thrombotic disease.

Blood group alters platelet binding kinetics to von Willebrand factor and consequently platelet function

Blood type O is associated with a lower risk of myocardial infarction. Platelets play a critical role in myocardial infarction. It is not known whether the expression of blood group antigens on platelet proteins alters platelet function; we hypothesized that platelet function would be different between donors with blood type O and those with non-O. To address this hypothesis, we perfused blood from healthy type O donors (n = 33) or non-O donors (n = 54) over pooled plasma derived von Willebrand factor (VWF) protein and purified blood type-specific VWF at arterial shear and measured platelet translocation dynamics. We demonstrate for the first time that type O platelets travel farther at greater speeds before forming stable bonds with VWF. To further characterize these findings, we used a novel analytical model of platelet interaction. Modeling revealed that the kinetics for GPIb/VWF binding rate are significantly lower for type O compared with non-O platelets. Our results demonstrate that platelets from type O donors interact less with VWF at arterial shear than non-O platelets. Our results suggest a potential mechanism for the reduced risk of myocardial infarction associated with blood type O.

Bleeding Complications After Cardiac Arrest and Targeted Temperature Management, a Post Hoc Study of the Targeted Temperature Management Trial

Target Temperature Management (TTM) is standard care following out of hospital cardiac arrest (OHCA). The aim of the study was to evaluate if treatment temperature (33°C or 36°C) or other predefined variables were associated with the occurrence of bleeding in the TTM study. This study is a predefined, post hoc analysis of the TTM trial, a multinational randomized controlled trial comparing treatment at 33°C and 36°C for 24 hours after OHCA with return of spontaneous circulation. Bleeding events from several locations were registered daily. The main outcome measure was occurrence of any bleeding during the first 3 days of intensive care. Risk factors for bleeding, including temperature allocation, were evaluated. Complete data were available for 722/939 patients. Temperature allocation was not associated with bleeding either in the univariable (p = 0.95) or in the primary multivariable analysis (odds ratio [OR] 0.95; 95% confidence interval [CI] 0.64-1.41, p = 0.80). A multiple imputation model, including all patients, was used as a sensitivity analysis, rendering similar results (OR 0.98; 95% CI 0.69-1.38, p = 0.92). Factors associated with bleeding were increasing age, female sex, and angiography with percutaneous coronary intervention (PCI) within 36 hours of cardiac arrest (CA) in both the primary and the sensitivity analysis. TTM at 33°C, when compared to TTM at 36°C, was not associated with an increased incidence of bleeding during the first 3 days of intensive care after CA. Increasing age, female gender, and PCI were independently associated with any bleeding the first 3 days after CA.

The effects of aging, diabetes mellitus, and antiplatelet drugs on growth factors and anti-aging proteins in platelet-rich plasma

As the aged population continues to markedly increase worldwide, the incidences of diabetes mellitus (DM) and cardiovascular disease (CVD) are increasing. In this study, we investigated the effects of aging, DM, and antiplatelet drugs on growth factors and anti-aging proteins in platelet-rich plasma (PRP). The study participants were classified into the following four groups: Group A, healthy individuals aged ≤45 years; Group B, healthy individuals aged >45 years; Group C, DM patients aged >45 years; and Group D, CVD patients aged >45 years taking antiplatelet drugs. The concentrations of epidermal growth factor (EGF), fibroblast growth factor (FGF)-2, platelet-derived growth factor (PDGF)-AA, PDGF-AB/BB, vascular endothelial growth factor (VEGF)-A, tissue inhibitor of metalloproteinase 2 (TIMP2), insulin-like growth factor 1 (IGF-1), growth differentiation factor (GDF)11, and clusterin in PRP samples were determined to analyze the effects of aging, DM, and antiplatelet drugs. Overall, the concentrations of IGF-1, TIMP2, and clusterin did not vary significantly between the four groups. The concentrations of PDGF-AB/BB (P = 0.010), VEGF-A (P = 0.000), and GDF11 (P = 0.026) were significantly different between Group A and Group B. Further, the concentrations of EGF (P = 0.000) and GDF11 (P = 0.000) were significantly different between Groups B and C. The concentrations of EGF (P = 0.001), VEGF-A (P = 0.000), and GDF11 (P = 0.002) significantly differed between Groups A and C. The concentrations of FGF-2 (P = 0.048), PDGF-AA (P = 0.03), and GDF11 (P = 0.001) were significantly different between Groups B and D. The concentrations of PDGF-AB/BB (P = 0.032), VEGF-A (P = 0.010), and GDF11 (P = 0.02) significantly differed between Groups A and D. We found that PRP contains high concentrations of the growth factors, TIMP2 and GDF11. Aging, DM, and antiplatelet drugs can decrease the concentration of some growth factors and GDF11, which weakens the regenerative capacity and anti-aging effects of PRP and reduces the quality of PRP.

Successful kidney transplantation normalizes platelet function

Background

Uraemic platelet dysfunction is not completely understood, in part due to non-physiological platelet function assays. We have developed a physiological flow-based assay that quantifies platelet function in microlitre volumes of blood under arterial shear. The aim of this study was to characterize platelet function before and after kidney transplantation.

Methods

Ten patients scheduled for living donor kidney transplant surgery and nine healthy controls were analysed using the assay. The motional parameters of platelet behaviour on von Willebrand factor (VWF) were recorded using customized platelet tracking software. The assay was repeated 3–8 weeks post-transplant in the transplant group and at an interval of >3 weeks in normal healthy volunteers.

Results

Platelet–VWF interactions were markedly reduced in the 10 pre-transplant patients compared with the healthy controls. In seven patients with immediate graft function, dynamic platelet function returned to normal (despite a small decrease in haemoglobin and haematocrit), but remained markedly abnormal in the three patients with delayed graft function (DGF).

Conclusions

Dynamic platelet function returned to normal following transplantation in those with immediate graft function. This early improvement was not observed in those with DGF. There may be important clinical implications, as patients with DGF are more likely to undergo invasive procedures, including transplant biopsies and insertion of central venous catheters.

Review of biomarkers to assess the effects of switching from cigarettes to modified risk tobacco products

Context: One approach to reducing the harm caused by cigarette smoking, at both individual and population level, is to develop, assess and commercialize modified risk alternatives that adult smokers can switch to. Studies to demonstrate the exposure and risk reduction potential of such products generally involve the measuring of biomarkers, of both exposure and effect, sampled in various biological matrices.Objective: In this review, we detail the pros and cons for using several biomarkers as indicators of effects of changing from conventional cigarettes to modified risk products.Materials and methods: English language publications between 2008 and 2017 were retrieved from PubMed using the same search criteria for each of the 25 assessed biomarkers. Nine exclusion criteria were applied to exclude non-relevant publications.Results: A total of 8876 articles were retrieved (of which 7476 were excluded according to the exclusion criteria). The literature indicates that not all assessed biomarkers return to baseline levels following smoking cessation during the study periods but that nine had potential for use in medium to long-term studies.Discussion and conclusion: In clinical studies, it is important to choose biomarkers that show the biological effect of cessation within the duration of the study.

Entrapment of Autologous von Willebrand Factor on Polystyrene/Poly(methyl methacrylate) Demixed Surfaces

Human platelets play a vital role in haemostasis, pathological bleeding and thrombosis. The haemostatic mechanism is concerned with the control of bleeding from injured blood vessels, whereby platelets interact with the damaged inner vessel wall to form a clot (thrombus) at the site of injury. This adhesion of platelets and their subsequent aggregation is dependent on the presence of the blood protein von Willebrand Factor (vWF). It is proposed here that the entrapment of vWF on a substrate surface offers the opportunity to assess an individual’s platelet function in a clinical diagnostic context. Spin coating from demixed solutions of polystyrene (PS) and poly(methyl methacrylate) (PMMA) onto glass slides has been shown previously to support platelet adhesion but the mechanism by which this interaction occurs, including the role of vWF, is not fully understood. In this work, we report a study of the interaction of platelets in whole blood with surfaces produced by spin coating from a solution of a weight/weight mixture of a 25% PS and 75% PMMA (25PS/75PMMA) in chloroform in the context of the properties required for their use as a Dynamic Platelet Function Assay (DPFA) substrate. Atomic Force Microscopy (AFM) indicates the presence of topographical features on the polymer demixed surfaces in the sub-micron to nanometer range. X-ray Photoelectron Spectroscopy (XPS) analysis confirms that the uppermost surface chemistry of the coatings is solely that of PMMA. The deliberate addition of various amounts of 50 μm diameter PS microspheres to the 25PS/75PMMA system has been shown to maintain the PMMA chemistry, but to significantly change the surface topography and to subsequently effect the scale of the resultant platelet interactions. By blocking specific platelet binding sites, it has been shown that their interaction with these surfaces is a consequence of the entrapment and build-up of vWF from the same whole blood sample.

Risk factors for intracranial lesions and mortality in older patients with mild traumatic brain injuries

PRIMARY OBJECTIVE

To identify risk factors for intracerebral lesion (ICL) in older adults with mild traumatic brain injury (MTBI) and evaluate the influence of comorbidities on outcomes.

RESEARCH DESIGN

Prospective cohort study.

METHODS AND PROCEDURES

Information was gathered on clinical history/examination, cranial computed tomography, admission Glasgow Coma Scale (GCS) score, analytical and coagulation findings, and mortality at 1 week post-discharge. Bivariate and multivariate logistic regression analyses were performed, calculating odds ratios for ICL with 95% confidence interval. P < 0.05 was considered significant.

MAIN OUTCOMES AND RESULTS

Data were analyzed on 504 patients with mean±SD age of 79.37 ± 8.06 years. Multivariate analysis showed that traffic accident, GCS score of 14/15, transient consciousness loss, nausea, and receipt of antiplatelets were predictors of ICL, while SRRI and/or benzodiazepine intake was a protective factor. A score was assigned to patients by rounding OR values, and a score ≥1 indicated moderate/high risk of ICL.

CONCLUSIONS

MTBI management should be distinct in over-60 year-olds, who may not present typical symptoms, with frequent comorbidities. Knowledge of risk factors for post-MTBI ICL, associated with higher mortality, is important to support clinical decision-making. Further research is warranted to verify our novel finding that benzodiazepines and/or SSRI inhibitors may act as neuroprotectors.

Age- and sex-related changes in hematological parameters in healthy Malawians

Aim

The aim of the study was to determine how values for white blood cell (WBC) counts, hemoglobin (Hb), hematocrit (Hct), mean corpuscular volume (mcv), and platelet counts vary with age and sex in healthy Malawians.

Methods

We recruited 660 (316 male and 344 female) participants in 12 different age groups. An ethylenediaminetetraacetic acid-anticoagulated blood sample collected from each participant was analyzed using a hematological analyzer.

Results

WBC counts decreased with age with the lowest counts observed in the 20 to <60 years old group. Median WBC counts for 20 to <60 year old females (5.9×10⁹/L) were significantly higher than those for men (4.7×10⁹/L; p=0.015) of the same age. Hb and Hct increased between 5 and 10 years in males and 10 and 15 years in females to adult levels. Males aged 5 to <10 years had significantly higher Hb (13.05 g/dL) and Hct (42.50%) compared to females of the same age (10.40 g/dL and 32.55%, respectively; p<0.0001 for both parameters). Platelet counts in males, which were highest between 3 and 5 years (376×10⁹/L), decreased to lowest counts among 5 to <10 year olds (238×10⁹/L), while in females these decreased from 402×10⁹/L in 6 to <10 years olds to 226×10⁹/L in 10 to <15 year olds. mcv median values were high in neonates reaching a nadir at 13–18 months and then increased throughout life. Females aged 0 to <6 months had significantly higher mcv values (81.85 fL) than males of the same age (69.3 fL; p<0.0001).

Conclusion

This study provides hematological values according to age and sex that are suitable for reference use in studies among Malawian subjects.

Platelet behaviour on von Willebrand Factor changes in pregnancy: Consequences of haemodilution and intrinsic changes in platelet function

Platelet function in pregnancy is poorly understood. Previous studies of platelet function in pregnancy have used non-physiological assays of platelet function with conflicting results. This study using a physiological assay of platelet function investigated platelet interactions with von Willebrand Factor (VWF) in blood from healthy pregnant women and healthy non-pregnant controls. Blood samples (200 µl) from third-trimester pregnancies (n = 21) and non-pregnant controls (n = 21) were perfused through custom-made parallel-plate flow chambers coated with VWF under arterial shear (1,500 s⁻¹). Multi-parameter measurements of platelet interactions with the immobilized VWF surface were recorded by digital-image microscopy and analysed using custom-designed platelet-tracking software. Platelet interactions with VWF decreased in healthy third-trimester pregnant participants relative to controls. This effect is most likely due to haemodilution which occurs physiologically during pregnancy. Interestingly, platelets in blood from pregnant participants translocated more slowly on VWF under arterial-shear conditions. These decreases in platelet translocation speed were independent of haemodilution, suggesting intrinsic changes in platelet function with pregnancy.

Platelet oxidative stress as a novel target of cardiovascular risk in frail older people

The average lifespan of humans and the percentage of people entering the 65 and older age group are growing rapidly. Within this age group, cardiovascular diseases (CVD) increase steeply and are the most common cause of death. During aging, experimental and clinical studies support the pivotal role played by reactive oxidant species in the mechanism of platelet activation. Frailty has been implicated as a causative and prognostic factor in patients with CVD. Oxidative stress is increased in frail older people, and may lead to accelerated aging and higher incidence of oxidative diseases such as CVD. The present article aims to highlight the relative contribution of platelet oxidative stress as a key target of frailty in elderly people with CVD.

Influences of ABO blood group, age and gender on plasma coagulation factor VIII, fibrinogen, von Willebrand factor and ADAMTS13 levels in a Chinese population

Background

ABO blood group is a hereditary factor of plasma levels of coagulation factor VIII (FVIII) and von Willebrand factor (VWF). Age and gender have been shown to influence FVIII, VWF, fibrinogen (Fbg), and ADAMTS13 (A disintegrin and metalloprotease with thrombospondin type 1 motif, 13). We investigated the effects of ABO type, age, and gender on plasma levels of FVIII, Fbg, VWF, and ADAMTS13 in a Chinese population.

Methods

A total of 290 healthy volunteers were eligible for this study. ABO blood group was determined by indirect technique. FVIII:C and Fbg were measured by clotting assays. VWF antigen (VWF:Ag), collagen-binding activity (VWF:CBA), and ADAMTS13 antigen were assessed by ELISA, whereas VWF ristocetin cofactor activity (VWF:Rcof) was performed by agglutination of platelets with ristocetin.

Results

Mean FVIII:C and VWF levels (VWF:Ag, VWF:CBA, and VWF:Rcof) were significantly higher in non-O than in O type subjects (p < 0.05 for all comparison). ADAMTS13 antigen decreased with increasing age, whereas the other parameters increased. Other than ADAMTS13 (p < 0.01), no gender-related variations were observed in the other parameters. Moreover, FVIII:C, Fbg, VWF:Ag, VWF:CBA, and VWF:Rcof showed significant and positive relationships with age (r = 0.421, 0.445, 0.410, 0.401, and 0.589, resp.; all p < 0.001), whereas a negative relationship was observed for ADAMTS13 antigen (r = 0.306; p = 0.006). Furthermore, FVIII:C were strongly correlated with VWF:Ag, VWF:CBA, and VWF:Rcof (r = 0.746, r = 0.746, and r = 0.576, resp.; p < 0.0001). VWF parameters were also strongly correlated with each other (r = 0.0.847 for VWF:Ag and VWF:CBA; r = 0.722 for VWF:Ag and VWF:Rcof; p < 0.0001).

Conclusions

ABO blood group, age, and gender showed different effects on plasma levels of FVIII:C, Fbg, VWF:Ag, VWF:CBA, VWF:Rcof, and ADAMTS13 antigen. These new data on a Chinese population are quite helpful to compare with other ethnic groups.

Dynamic platelet function on von Willebrand factor is different in preterm neonates and full-term neonates: changes in neonatal platelet function

Essentials It is unclear if platelet function differs between preterm and full-term neonates. Platelet behavior was characterized using a flow-based assay on von Willebrand Factor (VWF). Preterms had increased platelet interaction with VWF and glycoprotein Ibα expression. Platelets from preterm neonates behave differently on VWF compared to full-term neonates.

SUMMARY

Background Very low birth weight (VLBW) preterm neonates have an increased risk of hemorrhage-related morbidity and mortality as compared with their full-term counterparts. It is unclear whether platelet function differs between preterm and full-term neonates. This is partly because of the large volumes of blood required to perform standard platelet function tests, and the difficulty in obtaining such samples in neonates. Objectives This study was designed to characterize platelet behavior in neonates with a physiologic flow-based assay that quantifies platelet function in microliter volumes of blood under arterial shear. Methods Blood from VLBW preterm neonates of ≤ 32 weeks' gestation (n = 15) and full-term neonates (n = 13) was perfused under arterial shear over surface-immobilized von Willebrand factor (VWF). Platelet behavior was recorded by digital-image microscopy and analyzed. Surface expression of platelet glycoprotein (GP) Ibα and GPIIIa of VLBW preterm and full-term neonates was also measured. Results VLBW preterm neonates had increased numbers of platelets interacting with VWF, and increased GPIbα expression on the platelet surface. Despite the increased numbers of VWF interactions as reflected by flow-driven platelet translocation along the protein surface, no significant differences were observed in the numbers of platelets that adhered in a stationary fashion to VWF. Platelets from VLBW preterm neonates and those from full-term neonates behaved differently on VWF. Conclusions These differences in platelet function may contribute to the higher incidence of bleeding observed in VLBW preterm neonatal populations, or may represent a compensatory mechanism to counteract this risk of bleeding.

Platelet function and ageing

There are clear age-related changes in platelet count and function, driven by changes in hematopoietic tissue, the composition of the blood and vascular health. Platelet count remains relatively stable during middle age (25–60 years old) but falls in older people. The effect of age on platelet function is slightly less clear. The longstanding view is that platelet reactivity increases with age in an almost linear fashion. There are, however, serious limitations to the data supporting this dogma. We can conclude that platelet function increases during middle age, but little evidence exists on the changes in platelet responsiveness in old age (>75 years old). This change in platelet function is driven by differential mRNA and microRNA expression, an increase in oxidative stress and changes in platelet receptors. These age-related changes in platelets are particularly pertinent given that thrombotic disease and use of anti-platelet drugs is much more prevalent in the elderly population, yet the majority of platelet research is carried out in young to middle-aged (20–50 years old) human volunteers and young mice (2–6 months old). We know relatively little about exactly how platelets from people over 75 years old differ from those of middle-aged subjects, and we know even less about the mechanisms that drive these changes. Addressing these gaps in our knowledge will provide substantial understanding in how cell signalling changes during ageing and will enable the development of more precise anti-platelet therapies.