Platelet biology and function: plaque erosion vs. rupture

The leading cause of heart disease in developed countries is coronary atherosclerosis, which is not simply a result of ageing but a chronic inflammatory process that can lead to acute clinical events upon atherosclerotic plaque rupture or erosion and arterial thrombus formation. The composition and location of atherosclerotic plaques determine the phenotype of the lesion and whether it is more likely to rupture or to erode. Although plaque rupture and erosion both initiate platelet activation on the exposed vascular surface, the contribution of platelets to thrombus formation differs between the two phenotypes. In this review, plaque phenotype is discussed in relation to thrombus composition, and an overview of important mediators (haemodynamics, matrix components, and soluble factors) in plaque-induced platelet activation is given. As thrombus formation on disrupted plaques does not necessarily result in complete vessel occlusion, plaque healing can occur. Therefore, the latest findings on plaque healing and the potential role of platelets in this process are summarized. Finally, the clinical need for more effective antithrombotic agents is highlighted.

Endothelial dysfunction and immunothrombosis in sepsis

Sepsis is a life-threatening clinical syndrome characterized by multiorgan dysfunction caused by a dysregulated or over-reactive host response to infection. During sepsis, the coagulation cascade is triggered by activated cells of the innate immune system, such as neutrophils and monocytes, resulting in clot formation mainly in the microcirculation, a process known as immunothrombosis. Although this process aims to protect the host through inhibition of the pathogen’s dissemination and survival, endothelial dysfunction and microthrombotic complications can rapidly lead to multiple organ dysfunction. The development of treatments targeting endothelial innate immune responses and immunothrombosis could be of great significance for reducing morbidity and mortality in patients with sepsis. Medications modifying cell-specific immune responses or inhibiting platelet–endothelial interaction or platelet activation have been proposed. Herein, we discuss the underlying mechanisms of organ-specific endothelial dysfunction and immunothrombosis in sepsis and its complications, while highlighting the recent advances in the development of new therapeutic approaches aiming at improving the short- or long-term prognosis in sepsis.

Mental Stress-Induced Change in Plasma Stromal Cell-Derived Factor-1 and Adverse Cardiovascular Outcomes: A Cohort Study

Background

Acute psychological stress can provoke mental stress-induced myocardial ischemia (MSIMI) in coronary artery disease (CAD). Stromal cell-derived factor 1 (SDF1) is released in response to hypoxia, and higher levels of SDF1 are associated with adverse outcomes. We examined whether an increase in SDF1 level in response to mental stress predicts adverse outcomes in CAD patients.

Methods

A total of 554 patients with stable CAD (mean age 63 years; 76% male; 26% Black) underwent standardized mental stress testing. Plasma SDF1 levels were measured at rest and 90 minutes after mental stress, and MSIMI was evaluated by 99mTc-sestamibi perfusion imaging. Participants were followed for 5 years for the primary endpoint of composite of death and myocardial infarction (MI) and the secondary endpoint of composite of death, MI, and heart failure hospitalization. Cox hazard models were used to assess the association between SDF1 change and incident adverse events.

Results

Mean (standard deviation) SDF1 change with mental stress was +56.0 (230) pg/mL. During follow-up, a rise of 1 standard deviation in SDF1 with mental stress was associated with a 32% higher risk for the primary endpoint of death and MI (95% confidence interval, 6%-64%), independent of the resting SDF1 level, demographic and clinical risk factors, and presence of ischemia. A rise of 1 standard deviation in SDF1 was associated with a 33% (95% confidence interval, 11%-59%) increase in the risk for the secondary endpoint, independent of the resting SDF1 level, demographic, and clinical risk factors and presence of ischemia.

Conclusions

An increase in SDF1 level in response to mental stress is associated with a higher risk of adverse events in stable CAD, independent of MSIMI.

Human platelets release TGFBIp in acute myocardial infarction

Transforming growth factor-β-induced protein (TGFBIp) is released from activated platelets and promotes pro-thrombotic complications like pulmonary embolism. The role of TGFBIp in acute coronary syndrome, especially with a focus on platelets, has not been investigated so far. Using ELISA and immunoblotting, we demonstrate platelet TGFBIp release in patients with myocardial infarction (MI). We investigated TGFBIp-induced platelet adhesion and rolling by flow chamber and chemotactic effects of TGFBIp in transwell experiments. Immunochemistry staining of arterial vessels detected TGFBIp and the platelet-specific protein GPVI in the vessel wall.We demonstrate for the first time that platelet TGFBIp release is significantly increased in MI and correlates with the severity of acute coronary syndromes (STEMI, NSTEMI). After activation with TRAP, platelets release TGFBIp and TGFBIp itself activates platelets. Under flow, TGFBIp-mediated platelet rolling and adherence similarly to collagen. TGFBIp significantly increased platelet transmigration and we demonstrate TGFBIp deposits in the wall of human arteries. In this study, we add novel aspects to the role of TGFBIp in acute coronary syndrome by demonstrating that TGFBIp is partially released from platelets during MI and has activating, pro-adhesive and pro-migratory effects on platelets that could contribute to the disease development of coronary vascular inflammation and MI.

Atypical Roles of the Chemokine Receptor ACKR3/CXCR7 in Platelet Pathophysiology

The manifold actions of the pro-inflammatory and regenerative chemokine CXCL12/SDF-1α are executed through the canonical GProteinCoupledReceptor CXCR4, and the non-canonical ACKR3/CXCR7. Platelets express CXCR4, ACKR3/CXCR7, and are a vital source of CXCL12/SDF-1α themselves. In recent years, a regulatory impact of the CXCL12-CXCR4-CXCR7 axis on platelet biogenesis, i.e., megakaryopoiesis, thrombotic and thrombo-inflammatory actions have been revealed through experimental and clinical studies. Platelet surface expression of ACKR3/CXCR7 is significantly enhanced following myocardial infarction (MI) in acute coronary syndrome (ACS) patients, and is also associated with improved functional recovery and prognosis. The therapeutic implications of ACKR3/CXCR7 in myocardial regeneration and improved recovery following an ischemic episode, are well documented. Cardiomyocytes, cardiac-fibroblasts, endothelial lining of the blood vessels perfusing the heart, besides infiltrating platelets and monocytes, all express ACKR3/CXCR7. This review recapitulates ligand induced differential trafficking of platelet CXCR4-ACKR3/CXCR7 affecting their surface availability, and in regulating thrombo-inflammatory platelet functions and survival through CXCR4 or ACKR3/CXCR7. It emphasizes the pro-thrombotic influence of CXCL12/SDF-1α exerted through CXCR4, as opposed to the anti-thrombotic impact of ACKR3/CXCR7. Offering an innovative translational perspective, this review also discusses the advantages and challenges of utilizing ACKR3/CXCR7 as a potential anti-thrombotic strategy in platelet-associated cardiovascular disorders, particularly in coronary artery disease (CAD) patients post-MI.

Interleukin-17A Triggers the Release of Platelet-Derived Factors Driving Vascular Endothelial Cells toward a Pro-Angiogenic State

Platelets comprise a highly interactive immune cell subset of the circulatory system traditionally known for their unique haemostatic properties. Although platelets are considered as a vault of growth factors, cytokines and chemokines with pivotal role in vascular regeneration and angiogenesis, the exact mechanisms by which they influence vascular endothelial cells (ECs) function remain underappreciated. In the present study, we examined the role of human IL-17A/IL-17RA axis in platelet-mediated pro-angiogenic responses. We reveal that IL-17A receptor (IL-17RA) mRNA is present in platelets transcriptome and a profound increase is documented on the surface of activated platelets. By quantifying the protein levels of several factors, involved in angiogenesis, we identified that IL-17A/IL17RA axis selectively induces the release of vascular endothelial growth factor, interleukin -2 and -4, as well as monocyte chemoattractant protein -1 from treated platelets. However, IL-17A exerted no effect on the release of IL-10, an anti-inflammatory factor with potentially anti-angiogenic properties, from platelets. Treatment of human endothelial cell two-dimensional tubule networks or three-dimensional spheroid and mouse aortic ring structures with IL-17A-induced platelet releasate evoked pro-angiogenic responses of ECs. Our findings suggest that IL-17A may critically affect platelet release of pro-angiogenic factors driving ECs towards a pro-angiogenic state.

Human Platelets Take up Anti-VEGF Agents

Purpose

Growing evidence suggests different systemic exposure of anti-vascular endothelial growth factor (anti-VEGF) agents with repeated intravitreal application. Since the penetration of anti-VEGF agents through vascular barrier was reported, the interaction of anti-VEGF with nonresident platelets has become a topic of interest. The purpose of this study was to evaluate, with the help of visualization techniques, whether platelets take up the anti-VEGF agents ranibizumab, aflibercept, and bevacizumab.

Methods

The uptake of anti-VEGF agents with or without VEGF treatment was investigated using immunofluorescence and immunogold staining in human platelets. The role of actin filaments and clathrin-coated vesicles in the transport of ranibizumab, aflibercept, and bevacizumab was evaluated by two pharmacologic inhibitors: staurosporine (protein kinase C inhibitor) and cytochalasin D.

Results

All three anti-VEGF agents were taken up by platelets and colocalized with VEGF. Ranibizumab and aflibercept were mainly detected in alpha-granules; however, bevacizumab was equally localized in alpha-granules and in platelet vesicles. Both staurosporine and cytochalasin D completely inhibited the uptake of aflibercept into platelets. Both pharmacological inhibitors also decreased the transport of ranibizumab and bevacizumab into platelets. Bevacizumab was significantly more frequently colocalized within clathrin-coated vesicles than ranibizumab and aflibercept.

Conclusion

All three anti-VEGF agents are taken up by platelets and internalized in alpha-granules, which may result in a higher local exposure of anti-VEGF after the activation of platelets, potentially contributing to arterial thromboembolic events. Clathrin-coated vesicles seem to be more prominent in the transport of bevacizumab than ranibizumab and aflibercept. Nevertheless, whether the different localization and transport of bevacizumab are truly related to specific differences of receptor-mediated endocytosis has to be revealed by further research.

Associations between handgrip strength and hypertension in relation to circulating CD34-positive cell levels among Japanese older men: a cross-sectional study

Background

A positive association between handgrip strength and blood pressure has been reported. Since these factors are linked to the condition of the endothelium, the activity of endothelial repair might influence the association between handgrip strength and hypertension.

Methods

A cross-sectional study was conducted with 257 Japanese men aged 60–69 years who underwent an annual health checkup. As individuals with high level of circulating CD34-positive cells might show active endothelial repair, which plays an important role in vascular homeostasis, participants were stratified by circulating CD34-positive cell levels, using the median value of this population (0.96 cells/μL) as the cutoff.

Results

Independent of known cardiovascular risk factors, for participants with a high CD34-positive cell, handgrip strength is significantly positively associated with hypertension (odds ratio and 95% confidence interval of hypertension for 1 standard deviation increment of handgrip strength were 1.85 (1.19, 2.88) but not for participants with a low CD34-positive cell (0.91 (0.61, 1.37)).

Conclusion

The positive association between handgrip strength and hypertension is limited to high CD34-positive cells. This result may help clarify the role of vascular homeostasis in maintaining muscle strength.

The chemokine CXCL14 mediates platelet function and migration via direct interaction with CXCR4

AIMS

Beyond classical roles in thrombosis and haemostasis, it becomes increasingly clear that platelets contribute as key players to inflammatory processes. The involvement of platelets in these processes is often mediated through a variety of platelet-derived chemokines which are released upon activation and act as paracrine and autocrine factors. In this study, we investigate CXCL14, a newly described platelet chemokine and its role in thrombus formation as well as monocyte and platelet migration. In addition, we examine the chemokine receptor CXCR4 as a possible receptor for CXCL14 on platelets. Furthermore, with the use of artificially generated platelets derived from induced pluripotent stem cells (iPSC), we investigate the importance of CXCR4 for CXCL14-mediated platelet functions.

METHODS AND RESULTS

In this study, we showed that CXCL14 deficient platelets reveal reduced thrombus formation under flow compared with wild-type platelets using a standardized flow chamber. Addition of recombinant CXCL14 normalized platelet-dependent thrombus formation on collagen. Furthermore, we found that CXCL14 is a chemoattractant for platelets and mediates migration via CXCR4. CXCL14 promotes platelet migration of platelets through the receptor CXCR4 as evidenced by murine CXCR4-deficient platelets and human iPSC-derived cultured platelets deficient in CXCR4. We found that CXCL14 directly interacts with the CXCR4 as verified by immunoprecipitation and confocal microscopy.

CONCLUSIONS

Our results reveal CXCL14 as a novel platelet-derived chemokine that is involved in thrombus formation and platelet migration. Furthermore, we identified CXCR4 as principal receptor for CXCL14, an interaction promoting platelet migration.

Influence of height on endothelial maintenance activity: a narrative review

Recent studies have revealed an inverse association between height and cardiovascular disease. However, the background mechanism of this association has not yet been clarified. Height has also been reported to be positively associated with cancer. Therefore, well-known cardiovascular risk factors, such as increased oxidative stress and chronic inflammation, are not the best explanations for this inverse association because these risk factors are also related to cancer. However, impaired blood flow is the main pathological problem in cardiovascular disease, while glowing feeding vessels (angiogenesis) are the main characteristic of cancer pathologies. Therefore, endothelial maintenance activity, especially for the productivity of hematopoietic stem cells such as CD34-positive cells, could be associated with the height of an individual because this cell contributes not only to the progression of atherosclerosis but also to the development of angiogenesis. In addition, recent studies have also revealed a close connection between bone marrow activity and endothelial maintenance; bone marrow-derived hematopoietic stem cells contribute towards endothelial maintenance. Since the absolute volume of bone marrow is positively associated with height, height could influence endothelial maintenance activity. Based on these hypotheses, we performed several studies. The aim of this review is not only to discuss the association between height and bone marrow activity, but also to describe the potential mechanism underlying endothelial maintenance. In addition, this review also aims to explain some of the reasons that implicate hypertension as a major risk factor for stroke among the Japanese population. The review also aims to clarify the anthropological reasons behind the high risk of atherosclerosis progression in Japanese individuals with acquired genetic characteristics.

Association between serum sodium level within normal range and handgrip strength in relation to hypertension status: a cross-sectional study

Serum sodium concentration within the normal range could act as an indicator of age-related changes such as decrease in muscle strength and impairment of capillary function. Since endothelial injury stimulates endothelial repair by enhancing CD34-positive cell production, the level of serum sodium may be inversely associated with that of circulating CD34-positive cells, thus indicating the degree of age-related endothelial injury. We conducted a cross-sectional study of 246 elderly Japanese men aged 60–69 years. Subjects were stratified by hypertension status because hypertension should act as a strong confounding factor for the analyses performed in this study. Serum sodium concentration was positively associated with handgrip strength in non-hypertensive subjects [standardized parameter estimate (β) = 0.29; p = 0.003], but not for hypertensive subjects (β = 0.01; p = 0.878), while it was inversely associated with circulating CD34-positive cell levels in non-hypertensive subjects [simple correlation coefficient (r) = − 0.28; p = 0.002] but not for hypertensive subjects (r = − 0.07; p = 0.454). For non-hypertensive elderly subjects, serum sodium concentration within the normal range is positively associated with handgrip strength and inversely associated with CD34-positive cells, thus partly indicating the degree of age-related endothelium injury. These associations could prove to be an efficient tool for clarifying the background mechanism governing the decrease in age-related muscle strength.

Relationships of handgrip strength with the presence of cerebral microbleeds and platelet count in older Japanese adults

Introduction: Lower handgrip strength is a manifestation of sarcopenia and frailty, and has been reported to be associated with cerebral microbleeds (CMBs), which appear on T2^*-weighted magnetic resonance scans as low-intensity spots. However, the underlying mechanism is unknown. We hypothesized that vascular endothelial injury could be the common factor in loss of handgrip strength and CMBs. We aimed to clarify the relationship between handgrip strength and CMBs, with reference to a marker of vascular repair capability.

Materials and Methods: We conducted a cross-sectional study of 95 60- to 87-year-old Japanese people who underwent brain magnetic resonance imaging in 2016–2017. Baseline information was obtained by trained interviewers regarding the age, sex, smoking status, nutrient intake, cognition, medical history, education, and household income of the participants. Physical activity was assessed using a tri-axial accelerometer. We used the Fried frailty phenotype definition. Multivariable linear regression analysis was performed.

Results: Handgrip strength was independently associated with the presence of CMB after adjustment for age, sex, body mass index, classical cardiovascular risk factors, protein intake, and daily activity (B = −3.43, p = 0.027). This association was shown in participants with a low (B = −4.05, p = 0.045) but not high platelet count (B=−2.23, p = 0.479). Frailty was also independently associated with the presence of CMB after adjustment for confounders (B = 0.57, p = 0.014). Although this association was not present in participants a high platelet count, there was a positive trend in those with a low platelet count (B = 0.50, p = 0.135).

Conclusions: Platelet count, a marker of vascular repair capability, appears to modify the relationship between handgrip strength and CMBs.

Circulating CD34+ cells and active arterial wall thickening among elderly men: A prospective study

Age-related physical changes, such as low-grade inflammation and increased oxidative stress, induce endothelial repair and cause active arterial wall thickening by stimulating the production of CD34+ cells (the principal mediators of atherosclerosis). Despite this, aggressive endothelial repair (progressing atherosclerosis) might cause a wasting reduction in CD34+ cells, which could result in a lower capacity of endothelial repair and hypertension. As yet, no prospective study has clarified the association of circulating CD34+ cells with active arterial wall thickening. We conducted a prospective study of 363 men aged 60-69 years who participated in a general health check-up at least twice from 2014-2017. The circulating CD34+ cell count was significantly positively associated with active arterial wall thickening among subjects without hypertension (n = 236), but not among subjects with hypertension (n = 127). The fully adjusted odds ratios (ORs) of active arterial wall thickening for the logarithmic circulating CD34+ cell count were 1.83 (1.19, 2.84) and 0.69 (0.36, 1.32) for subjects without and with hypertension, respectively. Circulating CD34+ cells are positively associated with active arterial wall thickening in subjects without hypertension. This study demonstrates a means to clarify the mechanisms of endothelial repair in elderly subjects.

Hypoxia-Inducible Factor-1α: The Master Regulator of Endothelial Cell Senescence in Vascular Aging

Aging is one of the hottest topics in biomedical research. Advances in research and medicine have helped to preserve human health, leading to an extension of life expectancy. However, the extension of life is an irreversible process that is accompanied by the development of aging-related conditions such as weakness, slower metabolism, and stiffness of vessels. It also debated that aging can be considered an actual disease with aging-derived comorbidities, including cancer or cardiovascular disease. Currently, cardiovascular disorders, including atherosclerosis, are considered as premature aging and represent the first causes of death in developed countries, accounting for 31% of annual deaths globally. Emerging evidence has identified hypoxia-inducible factor-1α as a critical transcription factor with an essential role in aging-related pathology, in particular, regulating cellular senescence associated with cardiovascular aging. In this review, we will focus on the regulation of senescence mediated by hypoxia-inducible factor-1α in age-related pathologies, with particular emphasis on the crosstalk between endothelial and vascular cells in age-associated atherosclerotic lesions. More specifically, we will focus on the characteristics and mechanisms by which cells within the vascular wall, including endothelial and vascular cells, achieve a senescent phenotype.

The Integrin Activating Protein Kindlin-3 Is Cleaved in Human Platelets during ST-Elevation Myocardial Infarction

Kindlins are important proteins for integrin signaling and regulation of the cytoskeleton, but we know little about their precise function and regulation in platelets during acute ischemic events. In this work, we investigated kindlin-3 protein levels in platelets isolated from patients with ST-elevation myocardial infarction (STEMI) compared to patients with non-ischemic chest pain. Platelets from twelve patients with STEMI and twelve patients with non-ischemic chest pain were isolated and analyzed for kindlin-3 protein levels and intracellular localization by immunoblotting and two-dimensional gel electrophoresis. Platelet proteome analysis by two-dimensional gel electrophoresis and protein sequencing identified kindlin-3 as a protein that is cleaved in platelets from patients with myocardial infarction. Kindlin-3 full-length protein was significantly decreased in patients with STEMI compared to patients with non-ischemic chest pain (1.0 ± 0.2 versus 0.28 ± 0.2, p < 0.05) by immunoblotting. Kindlin-3 showed a differential distribution and was primarily cleaved in the cytosolic and membrane compartment of platelets in myocardial infarction. Platelet activation with thrombin alone did not affect kindlin-3 protein levels. The present study demonstrates that kindlin-3 protein levels become significantly reduced in platelets of patients with myocardial infarction compared to controls. The results suggest that kindlin-3 cleavage in platelets is associated with the ischemic event of myocardial infarction.

CXCL12/CXCR4 signal transduction in diseases and its molecular approaches in targeted-therapy

Chemokines are small molecules called "chemotactic cytokines" and regulate many processes like leukocyte trafficking, homing of immune cells, maturation, cytoskeletal rearrangement, physiology, migration during development, and host immune responses. These proteins bind to their corresponding 7-membrane G-protein-coupled receptors. Chemokines and their receptors are anti-inflammatory factors in autoimmune conditions, so consider as potential targets for neutralization in such diseases. They also express by cancer cells and function as angiogenic factors, and/or survival/growth factors that enhance tumor angiogenesis and development. Among chemokines, the CXCL12/CXCR4 axis has significantly been studied in numerous cancers and autoimmune diseases. CXCL12 is a homeostatic chemokine, which is acts as an anti-inflammatory chemokine during autoimmune inflammatory responses. In cancer cells, CXCL12 acts as an angiogenic, proliferative agent and regulates tumor cell apoptosis as well. CXCR4 has a role in leukocyte chemotaxis in inflammatory situations in numerous autoimmune diseases, as well as the high levels of CXCR4, observed in different types of human cancers. These findings suggest CXCL12/CXCR4 as a potential therapeutic target for therapy of autoimmune diseases and open a new approach to targeted-therapy of cancers by neutralizing CXCL12 and CXCR4. In this paper, we reviewed the current understanding of the role of the CXCL12/CXCR4 axis in disease pathology and cancer biology, and discuss its therapeutic implications in cancer and diseases.

Stromal cell derived factor-1 and long-term prognosis in acute coronary syndrome

Aim: To explore long-term prognostic value of SDF-1 in acute coronary syndrome (ACS). Materials & methods: We included 254 patients with ACS. Plasma SDF-1 was measured and patients were classified into tertiles of SDF-1. Results: Multivariate analysis showed third tertile of SDF-1 as an independent predictor of all-cause death (HR: 2.5; 95% CI: 1.2-5.2; p = 0.011) and the composite of major adverse cardiovascular and cerebrovascular events (HR: 1.8; 95% CI: 1.1-3.1; p = 0.031). SDF-1 added to a clinical model can improve all-cause death prediction (net reclassification improvement 0.362; 95% CI: 0.423-0.681; p = 0.027). Conclusion: SDF-1 is an independent predictor of all-cause mortality and major adverse cardiovascular and cerebrovascular events in long-term follow-up of patients with ACS and adds prognostic information beyond traditional cardiovascular risks factors.

Circulating Proangiogenic Cells and Proteins in Patients with Glioma and Acute Myocardial Infarction: Differences in Neovascularization between Neoplasia and Tissue Regeneration

Although extensive angiogenesis takes place in glial tumors, antiangiogenic therapies have remained without the expected success. In the peripheral circulation of glioma patients, increased numbers of endothelial precursor cells (EPCs) are present, potentially offering targets for antiangiogenic therapy. However, for an antiangiogenic therapy to be successful, the therapy should specifically target glioma-related EPC subsets and secreted factors only. Here, we compared the EPC subsets and plasma factors in the peripheral circulation of patients with gliomas to acute myocardial infarctions. We investigated the five most important EPC subsets and 21 angiogenesis-related plasma factors in peripheral blood samples of 29 patients with glioma, 14 patients with myocardial infarction, and 20 healthy people as controls, by FACS and Luminex assay. In GBM patients, all EPC subsets were elevated as compared to healthy subjects. In addition, HPC and KDR⁺ cell fractions were higher than in MI, while CD133⁺ and KDR⁺CD133⁺ cell fractions were lower. There were differences in relative EPC fractions between the groups: KDR⁺ cells were the largest fraction in GBM, while CD133⁺ cells were the largest fraction in MI. An increase in glioma malignancy grade coincided with an increase in the KDR⁺ fraction, while the CD133⁺ cell fraction decreased relatively. Most plasma angiogenic factors were higher in GBM than in MI patients. In both MI and GBM, the ratio of CD133⁺ HPCs correlated significantly with elevated levels of MMP9. In the GBM patients, MMP9 correlated strongly with levels of all HPCs. In conclusion, the data demonstrate that EPC traffic in patients with glioma, representing neoplasia, is different from that in myocardial infarction, representing tissue regeneration. Glioma patients may benefit from therapies aimed at lowering KDR⁺ cells and HPCs.

Autologous activated platelet-rich plasma injection into adult human ovary tissue: molecular mechanism, analysis, and discussion of reproductive response

In clinical infertility practice, one intractable problem is low (or absent) ovarian reserve which in turn reflects the natural oocyte depletion associated with advancing maternal age. The number of available eggs has been generally thought to be finite and strictly limited, an entrenched and largely unchallenged tenet dating back more than 50 years. In the past decade, it has been suggested that renewable ovarian germline stem cells (GSCs) exist in adults, and that such cells may be utilized as an oocyte source for women seeking to extend fertility. Currently, the issue of whether mammalian females possess such a population of renewable GSCs remains unsettled. The topic is complex and even agreement on a definitive approach to verify the process of 'ovarian rescue' or 're-potentiation' has been elusive. Similarities have been noted between wound healing and ovarian tissue repair following capsule rupture at ovulation. In addition, molecular signaling events which might be necessary to reverse the effects of reproductive ageing seem congruent with changes occurring in tissue injury responses elsewhere. Recently, clinical experience with such a technique based on autologous activated platelet-rich plasma (PRP) treatment of the adult human ovary has been reported. This review summarizes the present state of understanding of the interaction of platelet-derived growth factors with adult ovarian tissue, and the outcome of human reproductive potential following PRP treatment.

Co-culture of Platelets with Monocytes Induced M2 Macrophage Polarization and Formation of Foam Cells: Shedding Light on the Crucial Role of Platelets in Monocyte Differentiation

Objective

Far beyond hemostasis and thrombosis, significant evidence has indicated the critical role of platelets in atherosclerosis. SDF-1 is among the pro-inflammatory chemokines that are increased in platelets of patients with coronary artery disease (CAD). The goal of the current work is to identify the in vitro effect of platelets from either CAD patients or healthy volunteers on the induction of macrophages and foam cells.

Materials and Methods

The expression of SDF-1 on platelet surfaces in CAD patients and healthy volunteers was investigated using flow cytometry. We also evaluated the CXCR4/CXCR7 expression on monocytes from buffy coats of healthy volunteers. The effect of platelets from CAD patients and healthy volunteers on differentiation of monocytes and foam cell formation was evaluated using Oil Red O (ORO) staining. Flow cytometry and real-time PCR were also employed to evaluate surface markers and mRNA expression of genes involved in this process after co-culture of platelets with monocytes.

Results

Monocytes in co-culture with platelets acquired a spindleshape appearance and ORO-positive lipid droplets. In addition, platelets could induce CD163 expression, as an important marker of M2 macrophage, and upregulate the mRNA expression of the SRB, CD36, ACAT, LXR-α, and ABCA1 genes in monocytes. Notably, platelets of CAD patients with higher expression of SDF-1, increased the expression of genes encoding SRB and CD36 as compared to platelets of healthy volunteers.

Conclusion

Our results indicate that platelets from CAD patients could provoke monocyte differentiation into macrophages with an M2 phenotype, which in turn may participate in an atheroprotective process.

Effects of pulmonary artery banding in doxorubicin-induced left ventricular cardiomyopathy

OBJECTIVE

Central pulmonary banding has been proposed as a novel alternative for the treatment of left ventricular dilated cardiomyopathy in children. We sought to investigate the effects of central pulmonary banding in an experimental model of doxorubicin-induced left ventricular dilated cardiomyopathy.

METHODS

Four-month-old sheep (n = 28) were treated with intermittent intracoronary injections of doxorubicin (0.75 mg/kg/dose) into the left main coronary artery. A total dose of up to 2.15 mg/kg of doxorubicin was administered until signs of left ventricular dilation with functional impairment occurred by transthoracic echocardiography evaluation. Animals that survived were treated with surgical central pulmonary banding through a left anterior thoracotomy or sham surgery. Transthoracic echocardiography and pressure-volume loop measurements were used to compare left ventricular function preoperatively and 3 months later. Macroscopic and microscopic histologic examinations followed after hearts were harvested.

RESULTS

Nine animals from the central pulmonary banding group and 8 animals from the sham group survived and were included in the final analysis. Both groups showed similar inflammation and fibrosis upon histologic examination consistent with the toxic myocardial effects of doxorubicin. There were no differences in the echocardiographic measurements before central pulmonary banding or sham operation. Baseline measurements before the central pulmonary banding/sham operation were considered as 100%. The central pulmonary banding group had better left ventricular ejection fraction (102.5% ± 21.6% vs 76.7% ± 11.7%, P = .01), with a tendency for smaller left ventricular end-diastolic (101.2% ± 7.4% vs 120.4% ± 10.8%, P = .18) and significantly smaller end-systolic (100.3% ± 12.9% vs 116.5 ± 9.6%, P = .02) diameter of the left ventricle in comparison with the sham animals at 3 months. The end-systolic volume (101.4% ± 31.6% vs 143.4% ± 28.6%, P = .02) was significantly lower in the central pulmonary banding group 3 months postoperatively. Fractional shortening in the long axis (118.5% ± 21.5% vs 85.2% ± 22.8%, P = .016) and short axis (122.5% ± 18% vs 80.9% ± 13.6%, P = .0005) revealed significantly higher values in the central pulmonary banding group. In the conductance catheter measurements, no significant differences were seen between the groups for the parameters of systolic and diastolic function.

CONCLUSIONS

Central pulmonary artery banding in the setting of experimental toxic left ventricular dilated cardiomyopathy improved left ventricular echocardiographic function and dimensions.

Association between chronic kidney disease and carotid intima-media thickness in relation to circulating CD34-positive cell count among community-dwelling elderly Japanese men

BACKGROUND AND AIMS

Endothelial injury is well-known as a process that can lead to chronic kidney disease (CKD) and atherosclerosis. Hematopoietic activity is known to be associated inversely with CKD and positively with atherosclerosis. Since bone-derived progenitor cells (CD34-positive cells) contribute to endothelial repair (including the progression of atherosclerosis), understanding the association between CKD and carotid intima-media thickness (CIMT), in relation to circulating CD34-positive cell count, may be an efficient means of clarifying the mechanisms underlying endothelial activity.

METHODS

We conducted a cross-sectional study of 570 elderly Japanese men aged 60-69 years, who underwent a general health check-up. Participants were stratified as per a median circulating CD34-positive cell count (1.01 cells/μL).

RESULTS

Independent of the known cardiovascular risk factors, CIMT was found to be positively associated with CKD in the participants with high circulating CD34-positive cell counts but not in participants with low counts. Odds ratios were 1.40 (1.04, 1.89) for participants with high and 1.01 (0.72, 1.43) for participants with low circulating CD34-positive cell counts after adjustment for known cardiovascular risk factors at 95% confidence intervals for CKD with one standard deviation increment of CIMT.

CONCLUSIONS

A positive association between CIMT and CKD was observed among participants with high circulating CD34-positive cell counts but not among participants with low counts. Endothelial repair activity might determine the association between CKD and CIMT.

Relative survival potential of platelets is associated with platelet CXCR4/CXCR7 surface exposure and functional recovery following STEMI

BACKGROUND AND AIMS

Platelets are critically involved in tissue repair and regeneration, which depend on their inflammatory properties and survival. SDF-1 ligates to CXCR4 and CXCR7 and contributes to the regulation of platelet survival. Platelet CXCR4/CXCR7 are involved in myocardial regeneration after infarction and are associated with outcomes in patients with symptomatic coronary artery disease. This study investigates the CXCR4/CXCR7 platelet survival axis ex vivo.

METHODS

87 patients with ST-segment elevation myocardial infarction (STEMI) were included and analyzed for platelet surface exposure of CXCR4, CXCR7, Annexin V binding and tetramethylrhodamine ethyl ester (TMRE) response. Serum of 38 patients was analyzed for FasL, TNFα, TNF RI, TNF RII and TRAIL with Bioplex^®. The majority of patients received sequential cardiac MRI (intrahospital, 6-month follow-up).

RESULTS

We found a strong and positive correlation between surface exposure of CXCR4 and CXCR7 (ρ = 0.856, p<0.001). Relative survival potential correlated significantly with both platelet surface exposure of CXCR4 and CXCR7 (ρ = 0.365, p = 0.019; ρ = 0.417, p = 0.006) and furthermore with improvement of myocardial left ventricular ejection fraction (LVEF) (ρ = 0.490, p = 0.013). High relative survival potential showed significantly higher levels for both CXCR4 and CXCR7 surface exposure (MFI 87.3 vs. 69.0, p = 0.037; MFI 71.4 vs. 59.3, p = 0.045). We found a significant change in absolute LVEF% over the course of 6 months in patients with high CXCR7 platelet surface exposure (LVEF% 44.3 vs. 60.0, p≤0.001).

CONCLUSIONS

Platelet survival is associated with platelet surface exposure of CXCR4 and CXCR7 in STEMI patients and contributes to functional recovery after STEMI.

Association between tongue pressure and subclinical carotid atherosclerosis in relation to platelet levels in hypertensive elderly men: a cross-sectional study

Background

Age-related low-grade inflammation causing endothelial disruption influences sarcopenia, hypertension, and atherosclerosis. We reported previously that maintenance of muscle strength in elderly hypertensive men with high platelet levels is positively associated with subclinical atherosclerosis but not in those with low platelet levels. Since reduced tongue pressure is related to sarcopenia, tongue pressure may be associated with subclinical carotid atherosclerosis in hypertensive elderly subjects, and platelet levels may function as an indicator of the association between tongue pressure and subclinical carotid atherosclerosis.

Methods

We conducted a cross-sectional study of 342 hypertensive elderly Japanese men aged 60–89 who participated in an annual health check-up in 2015 and 2016. Subclinical carotid atherosclerosis was defined as a common carotid intima-media thickness (CIMT) of 1.1 mm or more.

Results

In the overall study population, 171 subjects demonstrated low platelets (< 21.4 × 10⁴/μL). Tongue pressure was significantly inversely associated with subclinical carotid atherosclerosis in these subjects, but not in subjects with high platelets. The known cardiovascular risk factor adjusted odds ratios (ORs) and 95% confidence intervals (CIs) of subclinical carotid atherosclerosis for a 1 standard deviation (SD) increment in tongue pressure (10.4 kPa) were 0.54 (0.35, 0.85) and 1.31 (0.87, 1.96), respectively.

Conclusion

Tongue pressure is inversely associated with subclinical carotid atherosclerosis in hypertensive elderly men with low platelet levels, but not in those with high levels. This finding may thus constitute an efficient tool for clarifying the background mechanism of age-related diseases such as sarcopenia, hypertension, and atherosclerosis.

The homing of bone marrow stem cells is differentially activated in ischemic and valvular heart diseases and influenced by beta-blockers

Background

Cell homing is the mechanism by which an injury releases signaling molecules that cause recruitment, proliferation, migration and differentiation of progenitor cells. Stromal derived factor-1 (SDF-1) and its receptor CXCR4 are key molecules involved in homing and little is known about their activation in cardiopathies. Here, we assessed the homing activation status of bone marrow cells (BMC) concerning the SDF-1 and CXCR4 expression in ischemic (IHD) and valvular (VHD) heart diseases.

Methods

The SDF-1 and inflammatory profile were analyzed by ELISA from plasma obtained bone marrow of ischemic heart patients (IHD, n = 41), valvular heart patients (VHD, n = 30) and healthy controls (C, n = 9). Flow cytometry was used to evaluate CXCR4 (CD184) expression on the surface of bone marrow cells, and the CXCR4 expression was estimated by real-time quantitative PCR.

Results

The SDF-1 levels in the groups IHD, VHD and control were, respectively, 230, 530 and 620 pg/mL (P = 0.483), and was decreased in VHD patients using beta-blockers (263 pg/mL) when compared with other (844 pg/mL) (P = 0.023). Compared with IHD, the VHD group showed higher CXCR4 (P = 0.071) and CXCR7 (P = 0.082) mRNA expression although no difference in the level of CXCR4⁺ bone marrow cells was found between groups (P = 0.360).

Conclusion

In conclusion, pathophysiological differences between IHD and VHD can affect the molecules involved in the activation of homing. In addition, the use of beta-blockers appears to interfere in this mechanism, a fact that should be considered in protocols that use BMC.

Myocardial Ischemia and Mobilization of Circulating Progenitor Cells

Background

The response of progenitor cells (PCs) to transient myocardial ischemia in patients with coronary artery disease remains unknown. We aimed to investigate the PC response to exercise‐induced myocardial ischemia (ExMI) and compare it to flow mismatch during pharmacological stress testing.

Methods and Results

A total of 356 patients with stable coronary artery disease underwent 99mTc‐sestamibi myocardial perfusion imaging during exercise (69%) or pharmacological stress (31%). CD34⁺ and CD34⁺/chemokine (C‐X‐C motif) receptor 4 PCs were enumerated by flow cytometry. Change in PC count was compared between patients with and without myocardial ischemia using linear regression models. Vascular endothelial growth factor and stromal‐derived factor‐1α were quantified. Mean age was 63±9 years; 76% were men. The incidence of ExMI was 31% and 41% during exercise and pharmacological stress testing, respectively. Patients with ExMI had a significant decrease in CD34⁺/chemokine (C‐X‐C motif) receptor 4 (−18%, P=0.01) after stress that was inversely correlated with the magnitude of ischemia (r=−0.19, P=0.003). In contrast, patients without ExMI had an increase in CD34⁺/chemokine (C‐X‐C motif) receptor 4 (14.7%, P=0.02), and those undergoing pharmacological stress had no change. Plasma vascular endothelial growth factor levels increased (15%, P<0.001) in all patients undergoing exercise stress testing regardless of ischemia. However, the change in stromal‐derived factor‐1α level correlated inversely with the change in PC counts in those with ExMI (P=0.03), suggesting a greater decrease in PCs in those with a greater change in stromal‐derived factor‐1α level with exercise.

Conclusions

ExMI is associated with a significant decrease in circulating levels of CD34⁺/chemokine (C‐X‐C motif) receptor 4 PCs, likely attributable, at least in part, to stromal‐derived factor‐1α–mediated homing of PCs to the ischemic myocardium. The physiologic consequences of this uptake of PCs and their therapeutic implications need further investigation.

Platelets as an indicator of vascular repair in elderly Japanese men

Platelets and circulating CD34-positive cells have been reported to contribute to vascular repair (endothelial repair and developing atherosclerosis). And because hypertension is known to be a strong vascular impairment factors, it should also influence the respective numbers of these factors. To clarify the clinical importance of platelets on vascular repair, we conducted a cross-sectional study of 567 Japanese men aged 60-69 who underwent an annual health check-up between 2013 and 2015. Multiple linear regression analysis of non-hypertensive subjects adjusting for classical cardiovascular risk factors showed that although platelet count did not significantly correlate with carotid intima media thickness (β = −0.05, p = 0.356), it did positively correlate significantly with the natural log of the number of circulating CD34-positive cells (β = 0.26, p < 0.001). In hypertensive subjects, a significant positive correlation was seen between platelets and intima media thickness (β = 0.19, p = 0.008), whereas no significant correlation was seen between platelet count and the natural log of the number of circulating CD34-positive cells (β = 0.11, p = 0.119). Our results indicate that platelet count is an indicator of vascular repair activity (endothelial repair and developing atherosclerosis). Additionally, hypertension might mask the beneficial effects of circulating CD34-positive cells.

Metabolic syndrome, inflammation and atherothrombosis

Extensive research of the past decades altered our traditional concept about the genesis of atherosclerosis fundamentally. Today, the crucial role of inflammation in the formation and progression of atherosclerotic plaques is indisputable. Patients at high risk for developing cardiovascular disease, owing to poor diet, obesity and low physical activity have been shown to exhibit a particular inflammatory pattern.

Therefore, the present review highlights the crosslink between the metabolic syndrome (MetS), adipose tissue, adipokines and selected inflammatory cytokines in the context of atherothrombosis and cardiovascular disease.

Possible mechanism underlying the association between height and vascular remodeling in elderly Japanese men

Height is reported to be inversely associated with cardiovascular disease. And platelets play an important role in vascular remodeling by supporting CD34-positive cells. To clarify the association between height and platelet, we conducted a cross-sectional study of 219 elderly Japanese men. Since hemoglobin concentration is influenced by vascular remodeling activity, an analysis stratified by hemoglobin level was performed. An inverse association was seen between height and platelet count in subjects with a high hemoglobin concentration (≥ 14.5 g/dL), but not in subjects with a low hemoglobin concentration (< 14.5 g/dL). The standardized parameter estimates (β) were β = -0.22, p = 0.019 for subjects with high hemoglobin, and β = -0.01, p = 0.931 for subjects with low hemoglobin. We also found a positive association between platelets and carotid intima media thickness (CIMT) and circulating CD34-positive cells in subjects with high hemoglobin (partial correlation coefficient (r) = 0.21, p = 0.037 and r = 0.40, p =< 0.001), but not in subjects with low hemoglobin (r = 0.04, p = 0.710 and r = 0.06, p = 0.544). In subjects with a high hemoglobin concentration, platelets were inversely associated with height, and positively associated with CIMT and circulating CD34-positive cells. These results indicate that subjects with a short stature activate vascular remodeling to a much greater extent than subjects with a tall stature.

The influence of low-grade inflammation on platelets in patients with stable coronary artery disease

Inflammation is likely to be involved in all stages of atherosclerosis. Numerous inflammatory biomarkers are currently being studied, and even subtle increases in inflammatory biomarkers have been associated with increased risk of cardiovascular events in patients with coronary artery disease (CAD). Low-grade inflammation may influence both platelet production and platelet activation potentially leading to enhanced platelet aggregation. Thrombopoietin is considered the primary regulator of platelet production, but it likely acts in conjunction with numerous cytokines, of which many have altered levels in CAD. Previous studies have shown that high-sensitive C-reactive protein (CRP) independently predicts increased platelet aggregation in stable CAD patients. Increased levels of CRP, fibrinogen, interleukin-6, stromal cell-derived factor-1, CXC motif ligand 16, macrophage migration inhibitory factor, RANTES, calprotectin, and copeptin have been associated with increased risk of cardiovascular events in CAD patients. Additionally, some of these inflammatory markers have been associated with enhanced platelet activation and aggregation. However, CRP and other inflammatory markers provide only limited additional predictive value to classical risk factors such as smoking, blood pressure, and cholesterol levels. Existing data do not clarify whether inflammation simply accompanies CAD and increased production and aggregation of platelets, or whether a causal relationship exists. In this review, we provide a comprehensive overview of inflammatory markers in stable CAD with particular emphasis on platelet production, activation, and aggregation in CAD patients.

Handgrip strength and subclinical carotid atherosclerosis in relation to platelet levels among hypertensive elderly Japanese

Age-related disruption of microvascular endothelium exacerbates hypertension and sarcopenia; and atherosclerosis is a well-known biological response to vascular endothelial injury. Therefore, prevalence of atherosclerosis among hypertensive elderly subjects may partly indicate the presence of an appropriate response to endothelial injury. We conducted a cross-sectional study of 795 elderly hypertensive Japanese subjects aged 60-89 years. Since platelet level is an indicator of vascular repair activity, subjects were stratified by platelet counts. No significant association between handgrip strength and subclinical carotid atherosclerosis (carotid intima-media thickness (CIMT) ≥1.1mm) was observed for subjects with lower platelet counts, while a significant positive association was observed for subjects with higher platelets. Adjusted odds and 95% confidence intervals of subclinical carotid atherosclerosis for 1 standard deviation increments in handgrip strength were 0.86 (0.61, 1.22) for subjects with lower platelets and 1.82 (1.26, 2.64) for subjects with higher platelets. A positive association between handgrip strength and subclinical carotid atherosclerosis exists in hypertensive elderly subjects with higher, but not lower, platelet counts. These results lead us to speculate that subjects with a beneficial influence on prevention of sarcopenia (maintenance of handgrip strength) may possess the capacity of active endothelial repair that causes atherosclerosis.

SDF-1α/CXCR4 Signaling in Lipid Rafts Induces Platelet Aggregation via PI3 Kinase-Dependent Akt Phosphorylation

Stromal cell-derived factor-1α (SDF-1α)-induced platelet aggregation is mediated through its G protein-coupled receptor CXCR4 and phosphatidylinositol 3 kinase (PI3K). Here, we demonstrate that SDF-1α induces phosphorylation of Akt at Thr308 and Ser473 in human platelets. SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the CXCR4 antagonist AMD3100 or the PI3K inhibitor LY294002. SDF-1α also induces the phosphorylation of PDK1 at Ser241 (an upstream activator of Akt), GSK3β at Ser9 (a downstream substrate of Akt), and myosin light chain at Ser19 (a downstream element of the Akt signaling pathway). SDF-1α-induced platelet aggregation is inhibited by pretreatment with the Akt inhibitor MK-2206 in a dose-dependent manner. Furthermore, SDF-1α-induced platelet aggregation and Akt phosphorylation are inhibited by pretreatment with the raft-disrupting agent methyl-β-cyclodextrin. Sucrose density gradient analysis shows that 35% of CXCR4, 93% of the heterotrimeric G proteins Gαi-1, 91% of Gαi-2, 50% of Gβ and 4.0% of PI3Kβ, and 4.5% of Akt2 are localized in the detergent-resistant membrane raft fraction. These findings suggest that SDF-1α/CXCR4 signaling in lipid rafts induces platelet aggregation via PI3K-dependent Akt phosphorylation.

Novel Biomarker MicroRNAs for Subtyping of Acute Coronary Syndrome: A Bioinformatics Approach

Acute coronary syndrome (ACS) is a life-threatening disease that affects more than half a million people in United States. We currently lack molecular biomarkers to distinguish the unstable angina (UA) and acute myocardial infarction (AMI), which are the two subtypes of ACS. MicroRNAs play significant roles in biological processes and serve as good candidates for biomarkers. In this work, we collected microRNA datasets from the Gene Expression Omnibus database and identified specific microRNAs in different subtypes and universal microRNAs in all subtypes based on our novel network-based bioinformatics approach. These microRNAs were studied for ACS association by pathway enrichment analysis of their target genes. AMI and UA were associated with 27 and 26 microRNAs, respectively, nine of them were detected for both AMI and UA, and five from each subtype had been reported previously. The remaining 22 and 21 microRNAs are novel microRNA biomarkers for AMI and UA, respectively. The findings are then supported by pathway enrichment analysis of the targets of these microRNAs. These novel microRNAs deserve further validation and will be helpful for personalized ACS diagnosis.

SDF1 Polymorphisms Influence Outcome in Patients with Symptomatic Cardiovascular Disease

Background

SDF1 and its cognate receptors CXCR4 and CXCR7 are involved in myocardial repair and are associated with outcome in cardiovascular patients. Hence, we aimed to investigate clinically significant SDF1 SNPs for their prognostic impact in patients with cardiovascular disease.

Methods and Results

Genotyping for selected SDF1 variants (rs1065297, rs2839693, rs1801157, rs266087, rs266085 and rs266089 was performed in patients (n = 872) who underwent percutaneous coronary intervention. Carriers of variant rs2839693 and rs266089 showed significantly higher cumulative event-free survival compared with non-carriers. All other polymorphisms had no relevant influence on outcome. Multivariate Cox regression analysis showed a significant correlation of these SNPs with cardiovascular outcome after inclusion of clinical and prognostic relevant variables (hazard ratio (HR) 0.51 (95% CI 0.30–0.88), p = 0.015 and [HR 0.51 (95% CI 0.30–0.88), p = 0.016, respectively). In addition, multivariate Cox regression with SDF1 haplotypes revealed a significantly reduced risk for the haplotype carrying the minor alleles of rs2839693 and rs266089 (HR 0.47 (95% CI 0.27–0.84), p = 0.011).

Conclusion

Distinct SDF1 polymorphisms are associated with improved cardiovascular prognosis in CAD patients. Further studies are warranted to validate these results and to better describe the endogenous regeneration potential in carriers of these SNPs. Targeted, genotype guided therapeutic approaches to foster myocardial regeneration and thus cardiovascular prognosis should be evaluated in future.

Platelet surface expression of SDF-1 is associated with clinical outcomes in the patients with cardiovascular disease

Platelet surface expression levels of stromal cell derived factor 1 (SDF-1) are elevated in acute coronary syndrome and associated with LVEF% improvement after myocardial infarction (MI). Platelet SDF-1 might facilitate thrombus formation and endomyocardial expression of SDF-1 is enhanced in inflammatory cardiomyopathy and positively correlates with myocardial fibrosis. The influence of platelet SDF-1 on outcome in the patients with symptomatic coronary artery disease (CAD) is to the best of our knowledge unknown. Blood samples of 608 consecutive CAD patients were collected during the percutaneous coronary intervention and analyzed for surface expression of SDF-1 by flow cytometry. The primary combined endpoint was defined as the composite of either MI, or ischemic stroke, or all-cause death. Secondary endpoints were defined as the aforementioned single events. The patients with baseline platelet SDF-1 levels above the third quartile showed a significantly worse cumulative event-free survival when compared to the patients with lower baseline SDF-1 levels (first to third quartile) (log rank 0.009 for primary combined endpoint and log rank 0.016 for secondary endpoint all-cause death). Multivariate Cox regression analysis showed that SDF-1 levels above the third quartile were independently associated with the primary combined endpoint and the secondary endpoint all-cause death. We provide first clinical evidence that high platelet expression levels of SDF-1 influence clinical outcomes in CAD patients in a negative way.

Evidence of an interaction between TGF-β1 and the SDF-1/CXCR4/CXCR7 axis in human platelets

BACKGROUND

TGF-β1, SDF-1 and its cognate receptors CXCR4 and CXCR7 are expressed on the surface of human platelets and their expression levels are differently regulated in symptomatic coronary artery disease (CAD). All these proteins and receptors influence outcome in patients with symptomatic CAD. There might be a crosstalk between TGF-β1 and the SDF-1/CXCR4/CXCR7 axis. Interrelations in CAD, especially in the context of platelets, are poorly understood. Therefore, we aimed to provide clinical and experimental evidence of interactions between TGF-β1 and the SDF-1/CXCR4/CXCR7 axis in human platelets.

METHODS AND RESULTS

Blood samples of the complete cohort (n=284) were analysed for platelet surface expression levels of TGF-β1, SDF-1, CXCR4 and CXCR7 by flow cytometry. For stimulation assays platelet rich plasma was treated with TGF-β1 or SDF-1 and then analysed by flow cytometry. Multiple regression analyses were run to show independent associations of TGF-β1 with SDF-1, CXCR4, CXCR7 and clinical cofactors. Both, CXCR4 and CXCR7 significantly predicted TGF-β1 (p<0.001 and p<0.001, respectively). After stimulation with SDF-1, surface expression of TGF-β1 increased significantly when compared to resting platelets [mean TGF-β1 MFI 19.01 vs. mean TGF-β1 MFI 14.01, p<0.001]. Upon receptor blocking with either anti-CXCR4 or anti-CXCR7 monoclonal antibodies the enhancing effect of SDF-1 on TGF-β1 surface expression was significantly blunted. Stimulation with TGF-β1 did not alter SDF-1, CXCR4 or CXCR7 expression significantly.

CONCLUSIONS

We provide first clinical and experimental data suggesting a cross-talk between TGF-β and the SDF-1/CXCR4/CXCR7 axis in platelets which does not involve transcriptional modulation as shown previously for other cellular systems.

CXCL12 regulates platelet activation via the regulator of G-protein signaling 16

The regulators of G protein signaling (RGS) protein superfamily negatively controls G protein-coupled receptor signal transduction pathways. One of the members of this family, RGS16, is highly expressed in megakaryocytes and platelets. Studies of its function in platelet and megakaryocyte biology have been limited, in part, due to lack of pharmacological inhibitors. For example, RGS16 overexpression inhibited CXC chemokine receptor 4 (CXCR4)-mediated megakaryocyte migration. More recent studies showed that the chemokine stromal cell-derived factor (SDF1α or CXCL12) regulates platelet function via CXCR4. Based on these considerations, the present study investigated the capacity of RGS16 to regulate CXCL12-dependent platelet function, using the RGS16 knockout mouse model (Rgs16(-/-)). RGS16-deficient platelets had increased protease activated receptor 4 and collagen-induced aggregation, as well as increased CXCL12-dependent agonist-induced aggregation, dense and alpha granule secretion, integrin αIIbβ3 activation and phosphatidylserine exposure compared to those from WT littermates. CXCL12 alone did not stimulate aggregation or secretion in either RGS16-deficient or WT platelets. Furthermore, platelets from Rgs16(-/-) mice displayed enhanced phosphorylation of ERK and Akt following CXCL12 stimulation relative to controls. Finally, we also found that PKCδ is involved in regulating CXCL12-dependent activation of ERK and Akt, in the Rgs16-deficient platelets. Collectively, our findings provide the first evidence that RGS16 plays an important role in platelet function by modulating CXCL12-dependent platelet activation.

Platelet-derived CXCL12 regulates monocyte function, survival, differentiation into macrophages and foam cells through differential involvement of CXCR4-CXCR7

Platelets store and release CXCL12 (SDF-1), which governs differentiation of hematopoietic progenitors into either endothelial or macrophage-foam cells. CXCL12 ligates CXCR4 and CXCR7 and regulates monocyte/macrophage functions. This study deciphers the relative contribution of CXCR4-CXCR7 in mediating the effects of platelet-derived CXCL12 on monocyte function, survival, and differentiation. CXCL12 and macrophage migration inhibitory factor (MIF) that ligate CXCR4-CXCR7 induced a dynamic bidirectional trafficking of the receptors, causing CXCR4 internalization and CXCR7 externalization during chemotaxis, thereby influencing relative receptor availability, unlike MCP-1. In vivo we found enhanced accumulation of platelets and platelet-macrophage co-aggregates in peritoneal fluid following induction of peritonitis in mice. The relative surface expression of CXCL12, CXCR4, and CXCR7 among infiltrated monocytes was also enhanced as compared with peripheral blood. Platelet-derived CXCL12 from collagen-adherent platelets and recombinant CXCL12 induced monocyte chemotaxis specifically through CXCR4 engagement. Adhesion of monocytes to immobilized CXCL12 and CXCL12-enriched activated platelet surface under static and dynamic arterial flow conditions were mediated primarily through CXCR7 and were counter-regulated by neutralizing platelet-derived CXCL12. Monocytes and culture-derived-M1-M2 macrophages phagocytosed platelets, with the phagocytic potential of culture-derived-M1 macrophages higher than M2 involving CXCR4-CXCR7 participation. CXCR7 was the primary receptor in promoting monocyte survival as exerted by platelet-derived CXCL12 against BH3-mimetic induced apoptosis (phosphatidylserine exposure, caspase-3 activation, loss of mitochondrial transmembrane potential). In co-culture experiments with platelets, monocytes predominantly differentiated into CD163(+) macrophages, which was attenuated upon CXCL12 neutralization and CXCR4/CXCR7 blocking antibodies. Moreover, OxLDL uptake by platelets induced platelet apoptosis, like other platelet agonists TRAP and collagen-related peptide (CRP). CXCL12 facilitated phagocytosis of apoptotic platelets by monocytes and M1-M2 macrophages, also promoted their differentiation into foam cells via CXCR4 and CXCR7. Thus, platelet-derived CXCL12 could regulate monocyte-macrophage functions through differential engagement of CXCR4 and CXCR7, indicating an important role in inflammation at site of platelet accumulation.

Injection of Human Cord Blood Cells With Hyaluronan Improves Postinfarction Cardiac Repair in Pigs

Recent clinical trials using autologous bone marrow or peripheral blood cells to treat myocardial infarction (MI) show controversial results, although the treatment has a good safety profile. These discrepancies are likely caused by factors such as aging, systemic inflammation, and cell processing procedures, all of which might impair the regenerative capability of the cells used. Here, we tested whether injection of human cord blood mononuclear cells (CB-MNCs) combined with hyaluronan (HA) hydrogel improves cell therapy efficacy in a pig MI model. A total of 34 minipigs were divided into 5 groups: sham operation (Sham), surgically induced-MI plus injection with normal saline (MI+NS), HA only (MI+HA), CB-MNC only (MI+CB-MNC), or CB-MNC combined with HA (MI+CB-MNC/HA). Two months after the surgery, injection of MI+CB-MNC/HA showed the highest left ventricle ejection fraction (51.32%±0.81%) compared with MI+NS (42.87%±0.97%, p<.001), MI+HA (44.2%±0.63%, p<.001), and MI+CB-MNC (46.17%±0.39%, p<.001) groups. The hemodynamics data showed that MI+CB-MNC/HA improved the systolic function (+dp/dt) and diastolic function (-dp/dt) as opposed to the other experimental groups, of which the CB-MNC alone group only modestly improved the systolic function (+dp/dt). In addition, CB-MNC alone or combined with HA injection significantly decreased the scar area and promoted angiogenesis in the infarcted region. Together, these results indicate that combined CB-MNC and HA treatment improves heart performance and may be a promising treatment for ischemic heart diseases.

SIGNIFICANCE

This study using healthy human cord blood mononuclear cells (CB-MNCs) to treat myocardial infarction provides preclinical evidence that combined injection of hyaluronan and human CB-MNCs after myocardial infarction significantly increases cell retention in the peri-infarct area, improves cardiac performance, and prevents cardiac remodeling. Moreover, using healthy cells to replace dysfunctional autologous cells may constitute a better strategy to achieve heart repair and regeneration.

MicroRNAs; easy and potent targets in optimizing therapeutic methods in reparative angiogenesis

The age‐related senescence of adult tissues is associated with the decreased level of angiogenic capability and with the development of a degenerative disease such as atherosclerosis which thereafter result in the deteriorating function of multiple systems. Findings indicate that tissue senescence not only diminishes repair processes but also promotes atherogenesis, serving as a double‐edged sword in the development and prognosis of ischaemia‐associated diseases. Evidence evokes microRNAs (miRNAs) as molecular switchers that underlie cellular events in different tissues. Here, miRNAs would promote new potential targets for optimizing therapeutic methods in blood flow recovery to the ischaemic area. Effectively beginning an ischaemia therapy, a more characteristic of miRNA changes in adult tissues is prerequisite and in the forefront. It may also be a preliminary phase in treatment strategies by stem cell‐based therapy.

Chemokines and their receptors in Atherosclerosis

Atherosclerosis, a chronic inflammatory disease of the medium- and large-sized arteries, is the main underlying cause of cardiovascular diseases (CVDs) most often leading to a myocardial infarction or stroke. However, atherosclerosis can also develop without this clinical manifestation. The pathophysiology of atherosclerosis is very complex and consists of many cells and molecules interacting with each other. Over the last years, chemokines (small 8-12 kDa cytokines with chemotactic properties) have been identified as key players in atherogenesis. However, this remains a very active and dynamic field of research. Here, we will give an overview of the current knowledge about the involvement of chemokines in all phases of atherosclerotic lesion development. Furthermore, we will focus on two chemokines that recently have been associated with atherogenesis, CXCL12, and macrophage migration inhibitory factor (MIF). Both chemokines play a crucial role in leukocyte recruitment and arrest, a critical step in atherosclerosis development. MIF has shown to be a more pro-inflammatory and thus pro-atherogenic chemokine, instead CXCL12 seems to have a more protective function. However, results about this protective role are still quite debatable. Future research will further elucidate the precise role of these chemokines in atherosclerosis and determine the potential of chemokine-based therapies.

Role of chemokine receptors CXCR4 and CXCR7 for platelet function

Platelet-derived SDF-1α (stromal cell derived factor-α) mediates inflammation, immune defence and repair mechanisms at site of tissue injury. This review summarizes the relative expression of CXC chemokine receptor 4 (CXCR4) and CXCR7 in platelets, their dynamic trafficking in presence of ligands like chemokine C-X-C-motif ligand 11 (CXCL11), CXCL12 and MIF (macrophage migration inhibitory factor); how these receptors differentially mediate the functional and survival response to the chemokines CXCL11, CXCL12 and MIF. We further elaborate and emphasize the prognostic significance of platelet surface expression of CXCR4-CXCR7 in the context of coronary artery disease (CAD). SDF-1α/CXCL12, CXCL11, MIF effects mediated through CXCR4 and CXCR7 may play a regulatory role at the site of vascular and tissue inflammation, immune defence and repair where activated platelets reach as forerunners and function as critical players.

HMGB1 binds to activated platelets via the receptor for advanced glycation end products and is present in platelet rich human coronary artery thrombi

High mobility group box 1 (HMGB1) acts as both a nuclear protein that regulates gene expression, as well as a pro-inflammatory alarmin that is released from necrotic or activated cells. Recently, HMGB1-expression in human atherosclerotic plaques was identified. Therapeutic blockade of HMGB1 reduced the development of diet-induced atherosclerosis in ApoE knockout mice. Thus, we hypothesised an interaction between HMGB1 and activated platelets. Binding of recombinant HMGB1 to platelets was assessed by flow cytometry. HMGB1 bound to thrombin-activated human platelets (MFI 2.49 vs 25.01, p=0.0079). Blood from wild-type, TLR4 and RAGE knockout mice was used to determine potential HMGB1 receptors on platelets. HMGB1 bound to platelets from wild type C57Bl6 (MFI 2.64 vs 20.3, p< 0.05), and TLR4-/- mice (MFI 2.11 vs 25.65, p< 0.05) but failed to show binding to platelets from RAGE-/- mice (p > 0.05). RAGE expression on human platelets was detected by RT-PCR with mRNA extracted from highly purified platelets and confirmed by Western blot and immunofluorescence microscopy. Platelet activation increased RAGE surface expression (MFI 4.85 vs 6.74, p< 0.05). Expression of HMGB1 in human coronary artery thrombi was demonstrated by immunohistochemistry and revealed high expression levels. Platelets bind HMGB1 upon thrombin-induced activation. Platelet specific expression of RAGE could be detected at the mRNA and protein level and is involved in the binding of HMGB1. Furthermore, platelet activation up-regulates platelet surface expression of RAGE. HMGB1 is highly expressed in platelet-rich human coronary artery thrombi pointing towards a central role for HMGB1 in atherothrombosis, thereby suggesting the possibility of platelet targeted anti-inflammatory therapies for atherothrombosis.