A direct-imaging cryo-EM study of shedding extracellular vesicles from leukemic monocytes

The human leukemia monocytic cell line (THP-1) is known to shed extracellular vesicles (EVs) under various stimulations. We studied the effects of two types of common stimulation types, lipopolysaccharide (LPS) and starvation conditions by high resolution cryogenic electron microscopy, namely, cryo-SEM and cryo-TEM. Cryo-SEM data of cells undergoing EV blebbing and shedding is presented here for the first time. The high-resolution images show good agreement with models describing the membrane processes of shedding. Cells that underwent a 48-h starvation treatment exhibited differing morphological features, including shrunken nucleus and elongated membrane protrusions. LPS treated cells, however, showed extensive blebbing originating from the cell membrane, in good agreement with the sizes of EVs imaged by cryo-TEM. EVs isolated from both types of stimulations were measured by nanoparticle tracking analysis (NanoSight), by which LPS-EVs samples exhibited higher concentration and smaller mean diameter, as compared to starvation-EVs. Our results suggest a difference in the effects of the two stimulation types on the shedding process and possibly on the type of EVs shed. Our unique methodologies provide an important and innovative outlook of the shedding process and on its products, paving the way to further discoveries in this developing field of research, in which much is still unknown.

PO-45 - The role of microvesicles in multiple myeloma progression

INTRODUCTION

Multiple myeloma (MM) is an incurable, genetically heterogeneous malignancy of plasma cells that secrete non-functioning immunoglobulins and present high proteasome activity. MM is characterized by bone marrow infiltration leading to multiple lytic bone lesions, cytopenia and increased rate of thrombotic events. Microvesicles (MVs) include exosomes (30-100 nm) and microparticles (0.1-1 micron) shed from various cells and expressing antigens reflecting their cellular origin. MVs are involved in thrombosis, inflammation and cancer.However, the effect of MM-MVs on disease progression and their mechanism of action are unclear. We assume that MVs play a role in the interaction between malignant plasma cells and mesenchymal and endothelial cells (EC).

AIM

To characterize MM-MVs and investigate their effects on microenvironment cells.

MATERIALS AND METHODS

MVs were isolated from MM cell line RPMI 8226 untreated or treated with bortezomib and from peripheral blood (PB) and bone marrow (BM) of MM patients (n=13) and healthy controls (n=14). MM-MV size, concentration and cell origin were measured by Nanosite and FACS. Protein content was evaluated by protein arrays and ELISA. Coagulation and proteasome activity were assessed using chromogenic assays. Migratory capacity (migration assay), proliferative rate (XTT assay) and cell-signaling effects (Western blot analysis) of MVs on BM-mesenchymal and ECs were analyzed.

RESULTS

MM cells exhibited high MV shedding rate, which further increased with the exposure to bortezomib. Significant elevation in MV production was found in MM patients compared to controls. MM-MVs expressed membrane MM markers (syndecan-1/ CD138, CD38), coagulation factor (TF, TFPI, EPCR, TM) and angiogenic factors (VEGFR1, VEGFR2, and CD31). MM-MVs contained high levels of growth factors (Angiogenin, PDGF-BB and VEGF) and displayed procoagulant and proteasome activity. MM-MVs penetrated cells and affected their function. MVs of untreated cells and patient MVs increased EC and mesenchymal cell migration and EC proliferation, while MVs obtained from bortezomib-treated cells decreased these effects. MVs of untreated cells increased ERK1/2 and c-Jun phosphorylation in ECs (by 6.15 and 1.84 fold) but did not affect MAPKAPK-2. MVs of bortezomib-treated cells reduced c-Jun phosphorylation in ECs.

CONCLUSIONS

MM cells are characterized by high shedding rate of MVs. They are pro-coagulants and increase EC thrombogenicity, suggesting their involvement in MM-related thrombosis. MVs contain high levels of angiogenic factors that affect mesenchymal and EC, induce cell migration and proliferation via specific signal transductions. MVs exposed to bortezomib display lower levels of angiogenic factors, which limits proliferation and migration of MVs, reflecting the efficacy of therapy and MM dynamics.

PO-46 - Influence of extracellular vesicles derived from AML patients on stem cells and their microenvironment

INTRODUCTION

Acute myeloid leukemia (AML) is characterized by rapid growth of leukemic blast cells. Extracellular vesicles (EVs) are shed from normal and pathologic cells and express membrane proteins and antigens, reflecting their cellular origin.

AIM

To explore whether bone marrow EVs of AML patients originate from blast cells and are capable of influencing hematopoietic stem cells (HSC) in a pseudo-natural microenvironment obtained by co-culture of HSC with mesenchymal stem cells (MSC).

MATERIALS AND METHODS

Bone marrow (BM) samples were collected from healthy controls and patients with newly diagnosed AML at three time points: diagnosis, nadir and remission. EV concentration, cell origin and expression of coagulation proteins were characterized by FACS. Stem cells were obtained from Ficoll gradient of cord blood (CB) followed by CD34+ isolation. Cord blood stem cells with or without MSC were co-incubated with AML EVs. EV internalization was demonstrated by FACS-AMNIS and confocal microscopy. Mir-125b and -155 expressions in the cells were analyzed by RT-PCR.

RESULTS

AML patients were enrolled in the study. The total BM-EVs number was higher in patients at first remission compared to controls, while blast EV counts (labeled with anti-CD34, CD33, CD117) were higher in patients at diagnosis compared to controls and to patients in remission. Internalization of CD117+/CD33+ BM-EVs to cord blood stem cells in the presence or absence of MSC was evaluated by FACS-AMNIS. Confocal microscopy of CD33+ stained EVs strengthens the findings and shows presence of EVs even in the cytoplasm and the nucleus. Quantitative analysis of mir-125b and mir-155 expression in cord blood stem cells incubated with AML EVs revealed a clear tendency of increased expression in case of cell exposure to AML EVs in comparison to healthy control EVs. This tendency was emphasized in the presence of MSC.

CONCLUSIONS

EVs of AML patients are generated from blast cells. By internalization into naïve stem cells they can influence their differentiation. Moreover, the presence of mesenchymal stem cells is likely to be essential to the process.

Microvesicles of pregnant women receiving low molecular weight heparin improve trophoblast function

INTRODUCTION

Microvesicles including exosomes and microparticles, participate in the placental-maternal crosstalk in normal pregnancies and gestational vascular complications (GVC). Low molecular weight heparin (LMWH) is known to reduce the risk of placenta-mediated pregnancy complications. This study was aimed to characterize microvesicles of pregnant women receiving LMWH and explore microvesicle involvement in trophoblast and endothelial cell function.

MATERIALS AND METHODS

Microvesicles were isolated from blood samples obtained from non-pregnant women, healthy pregnant women (HP) and pregnant woman treated with LMWH. Microvesicle protein contents were assessed by protein array and ELISA. Microvesicle effects on early stage trophoblasts, term trophoblasts and endothelial cell migration, angiogenesis and apoptosis were evaluated.

RESULTS

Microvesicles derived from the group treated with LMWH contained higher levels of several proangiogenic proteins compared to those of HP women. Exposure of endothelial cells to circulating microvesicles derived from HP and LMWH treated groups induced significantly higher cell migration and branch tube formation compared to untreated cells. The effect of microvesicles from HP- and LMWH groups on early-stage trophoblast migration was similar. Microvesicles derived from these two study groups significantly decreased early-stage trophoblast apoptosis, while microvesicles derived from the HP-group (but not from the LMWH-group) significantly increased the term trophoblast apoptosis (TUNEL assay) compared to untreated cells.

CONCLUSION

Therapy with LMWH affects patients' microvesicle content, leading to normalization of invasion, angiogenesis activity and survival of endothelial and trophoblast cells in vitro. The effects of LMWH on microvesicles may point to an additional mechanism of heparin action in high-risk pregnancy.

Disease dynamics in patients with acute myeloid leukemia: new biomarkers

Acute myeloid leukemia (AML) is characterized by rapid growth of leukemic blast cells. Extracellular vesicles (EVs), shedding from various cells, express antigens, reflecting their cellular origin. The current study was designed to explore the role of circulating EVs as potential biomarkers of AML activity and predictors of thrombogenicity in patients with this malignancy. Blood samples were collected from healthy controls and patients with newly diagnosed AML at three time points: diagnosis, nadir, and remission. EV concentration, cell origin, and expression of coagulation proteins were characterized using fluorescence-activated cell sorting. EV cytokine contents were evaluated by protein array. Procoagulant activity was assessed using Factor Xa chromogenic assay. Forty-two AML patients were enrolled in the study. Total EV numbers were higher in patients in first remission compared with controls, whereas blast EV counts were higher in patients at diagnosis compared with controls and patients in remission. Blast EV levels were significantly lower in patients who achieved remission and were alive at 3-year follow up compared with their succumbed counterparts. At all three time points, percentage of endothelial EVs was higher in patients compared with controls. EV procoagulant activity was elevated at diagnosis and in remission, and, unlike controls' EVs, patients' EVs increased endothelial cell thrombogenicity. EVs of AML patients express membrane proteins of blast cells and might serve as biomarkers of leukemia dynamics and presence of minimal residual disease. Increased levels of endothelial EVs and their procoagulant activity may indicate a vascular injury associated with a hypercoagulable state in AML.

Coagulation and placenta-mediated complications

Pregnancy is a physiological hypercoagulable state, preparing the mother for the hemostatic challenge of delivery. However, this is associated with an increased risk of venous thrombosis and placenta-mediated complications, which present major challenges for mother and fetus. Although these conditions are heterogeneous in their pathophysiology, hereditary and acquired thrombophilia has been associated with recurrent pregnancy loss and gestational vascular complications, such as early-onset pre-eclampsia and placental abruption. Prevention of such placenta-mediated complications, which collectively complicate up to 15% of pregnancies, is a major issue for women's health. Prospective interventional studies stratified by current knowledge of pathophysiological mechanisms related to placental and systemic hemostatic alterations will impact on the management of pregnancies at risk of these complications.

Extracellular vesicles in hematological disorders

Extracellular vesicles (EVs), comprised of exosomes, microparticles, apoptotic bodies, and other microvesicles, are shed from a variety of cells upon cell activation or apoptosis. EVs promote clot formation, mediate pro-inflammatory processes, transfer proteins and miRNA to cells, and induce cell signaling that regulates cell differentiation, proliferation, migration, invasion, and apoptosis. This paper will review the contribution of EVs in hematological disorders, including hemoglobinopathies (sickle cell disease, thalassemia), paroxysmal nocturnal hemoglobinuria, and hematological malignancies (lymphomas, myelomas, and acute and chronic leukemias).

Tumor-derived microparticles induce bone marrow-derived cell mobilization and tumor homing: a process regulated by osteopontin

Acute chemotherapy can induce rapid bone-marrow derived pro-angiogenic cell (BMDC) mobilization and tumor homing, contributing to tumor regrowth. To study the contribution of tumor cells to tumor regrowth following therapy, we focused on tumor-derived microparticles (TMPs). EMT/6 murine-mammary carcinoma cells exposed to paclitaxel chemotherapy exhibited an increased number of TMPs and significantly altered their angiogenic properties. Similarly, breast cancer patients had increased levels of plasma MUC-1(+) TMPs following chemotherapy. In addition, TMPs from cells exposed to paclitaxel induced higher BMDC mobilization and colonization, but had no increased effect on angiogenesis in Matrigel plugs and tumors than TMPs from untreated cells. Since TMPs abundantly express osteopontin, a protein known to participate in BMDC trafficking, the impact of osteopontin-depleted TMPs on BMDC mobilization, colonization, and tumor angiogenesis was examined. Although EMT/6 tumors grown in mice inoculated with osteopontin-depleted TMPs had lower numbers of BMDC infiltration and microvessel density when compared with EMT/6 tumors grown in mice inoculated with wild-type TMPs, no significant difference in tumor growth was seen between the two groups. However, when BMDCs from paclitaxel-treated mice were injected into wild-type EMT/6-bearing mice, a substantial increase in tumor growth and BMDC infiltration was detected compared to osteopontin-depleted EMT/6-bearing mice injected with BMDCs from paclitaxel-treated mice. Collectively, our results suggest that osteopontin expressed by TMPs play an important role in BMDC mobilization and colonization of tumors, but is not sufficient to enhance the angiogenic activity in tumors.

Cryogenic transmission electron microscopy nanostructural study of shed microparticles

Microparticles (MPs) are sub-micron membrane vesicles (100–1000 nm) shed from normal and pathologic cells due to stimulation or apoptosis. MPs can be found in the peripheral blood circulation of healthy individuals, whereas elevated concentrations are found in pregnancy and in a variety of diseases. Also, MPs participate in physiological processes, e.g., coagulation, inflammation, and angiogenesis. Since their clinical properties are important, we have developed a new methodology based on nano-imaging that provides significant new data on MPs nanostructure, their composition and function. We are among the first to characterize by direct-imaging cryogenic transmitting electron microscopy (cryo-TEM) the near-to-native nanostructure of MP systems isolated from different cell types and stimulation procedures. We found that there are no major differences between the MP systems we have studied, as most particles were spherical, with diameters from 200 to 400 nm. However, each MP population is very heterogeneous, showing diverse morphologies. We investigated by cryo-TEM the effects of standard techniques used to isolate and store MPs, and found that either high-g centrifugation of MPs for isolation purposes, or slow freezing to –80°C for storage introduce morphological artifacts, which can influence MP nanostructure, and thus affect the efficiency of these particles as future diagnostic tools.

Placenta-derived microparticles

Microparticles (MPs), sub-micron membrane vesicles, participate in the placental and maternal crosstalk in normal pregnancies as well as in gestational vascular complications (GVC). The article will review the effects of MPs on placental physiological processes, including hemostasis, trophoblast migration, invasion, placental vasculature and their involvement in pathologic states such as thrombosis, inflammation and endothelial dysfunction, resulting in GVC.

Microvesicles of women with gestational hypertension and preeclampsia affect human trophoblast fate and endothelial function

Microvesicles shedding from cell membrane affect inflammation, apoptosis, and angiogenesis. We hypothesize that microvesicles of women with gestational vascular complications reflect pathophysiological state of the patients and affect their endothelial and trophoblast cell function. Microvesicles of healthy pregnant women, women with gestational hypertension, mild, or severe preeclampsia/toxemia, were characterized, and their effects on early-stage or term trophoblasts and endothelial cells were evaluated using apoptosis, migration, and tube formation assays. Patient subgroups differed significantly only in proteinuria levels, therefore their microvesicles were assessed as 1 group, demonstrating higher levels of inflammatory and angiogenic proteins compared with those of healthy pregnant women. In endothelial cells, microvesicles of healthy pregnant women reduced caspase 3/7 activity, increased migration, and induced tube formation. These processes were suppressed by microvesicles of women with gestational vascular complications. In early-stage trophoblasts, microvesicles of healthy pregnant women decreased apoptosis compared with untreated cells (6±5% versus 13.8±5.8%; P<0.001) and caspase 3/7 activity and induced higher migration (39.7±10.1 versus 20.3±8.3 mm2; P<0.001). This effect was mediated through extracellular signal-regulated kinase pathway. Conversely, microvesicles of women with gestational vascular complications increased term trophoblast apoptosis compared with cells exposed to microvesicles of healthy pregnant women (15.1±3.3% versus 6.5±2.1%; P<0.001) and inhibited early-stage trophoblasts migration (21.4±18.5 versus 39.7±10.1 mm2; P<0.001). In conclusion, microvesicle content and effects on endothelial and trophoblast cells vary according to the physiological/pathological state of a pregnant woman. Microvesicles seem to play a pivotal role in the course of pregnancy, which could potentially result in gestational vascular complications.

Microparticles and pregnancy complications

Microparticles (MPs) are shed from cell membranes of a variety of cells, promote thrombus formation, mediate pro-inflammatory effects and may cause endothelial dysfunction. Normal pregnancy is characterized by increased levels of MPs compared to non-pregnant healthy women but the prevalence, cell origin and the role of MPs in pregnancy-related complications remain controversial. Normal pregnancy is an acquired hyper-coagulable state due to an increase in procoagulants and decrease in natural anticoagulants. Pregnancy-related complications such as preeclampsia, intrauterine fetal growth restriction (IUGR) and fetal loss are associated with placental dysfunction and may cause significant maternal and fetal morbidity and mortality. This article highlights the role of microparticles in maternal placental crosstalk and the interplay between microparticles, thrombosis and pregnancy complications.

Red wine consumption improves in vitro migration of endothelial progenitor cells in young, healthy individuals

BACKGROUND

Endothelial progenitor cells (EPCs) contribute to the maintenance of vascular endothelial function. The moderate consumption of red wine provides cardiovascular protection.

OBJECTIVE

We investigated the underlying molecular mechanism of EPC migration in young, healthy individuals who drank red wine.

DESIGN

Fourteen healthy volunteers consumed 250 mL red wine daily for 21 consecutive days. Vascular endothelial function, plasma stromal cell-derived factor 1alpha (SDF1alpha) concentrations, and the number, migration, and nitric oxide production of EPCs were determined before and after the daily consumption of red wine. EPCs were glucose stressed to study the effect of red wine on EPC migration, proliferation, and senescence and to study the expressions of CXC chemokine receptor 4 (CXCR4) and members of the Pi3K/Akt/eNOS (phosphatidylinositol 3-kinase/protein kinase B/endothelial nitric oxide synthase) signaling pathway by Western blotting.

RESULTS

Daily red wine consumption for 21 consecutive days significantly enhanced vascular endothelial function. Although plasma SDF1alpha concentrations were unchanged, EPC count and migration were significantly increased after this 21-d consumption period. Red wine increased the migration, proliferation, CXCR4 expression, and activity of the Pi3K/Akt/eNOS signaling pathway and decreased the extent of apoptosis in glucose-stressed EPCs.

CONCLUSIONS

The results of the present study indicate that red wine exerts its effect through the up-regulation of CXCR4 expression and activation of the SDF1alpha/CXCR4/Pi3K/Akt/eNOS signaling pathway, which results in increased EPC migration and proliferation and decreased extent of apoptosis. Our findings suggest that these effects could be linked to the mechanism of cardiovascular protection that is associated with the regular consumption of red wine.

Hyperglycemia and oxidized-LDL exert a deleterious effect on endothelial progenitor cell migration in type 2 diabetes mellitus

INTRODUCTION

Type 2 diabetes mellitus (DM) patients with coronary artery disease (CAD) have elevated plasma oxidized-LDL (OxLDL) levels and impaired neovascularization. Hyperglycemia and hyperlipidemia impair endothelial progenitor cell (EPC) migration, and endothelial nitric oxide (NO) bioavailability and NO synthase (NOS) activity are essential for EPC migration. Stromal-derived factor-1alpha (SDF1alpha) contributes to EPC mobilization and homing by stimulating the CXC receptor-4 (CXCR4) on the EPC plasmalemma to activate the Pi3K/Akt/eNOS signaling pathway. Therefore, we investigated the effect of high glucose (HG) and OxLDL on the migration and NO bioavailability of EPCs from healthy individuals, and then correlated the findings with those of EPCs from type 2 DM patients with and without CAD.

MATERIALS AND METHODS

EPCs from 15 healthy and 55 patients were exposed to HG, OxLDL, or both before evaluating EPC count, migration and NO production, and expression of CXCR4 and members of Pi3K/Akt/eNOS signaling cascade.

RESULTS

Counts, migration, CXCR4 expression, and NO production were significantly reduced in EPCs from DM and CAD patients compared with that obtained in EPCs from healthy, and were further reduced in DM patients with CAD. The expression of CXCR4 and activation of Pi3K/Akt/eNOS signaling cascade were suppressed in OxLDL- and HG-treated EPCs, and this suppression was exacerbated when EPCs were treated simultaneously with HG and OxLDL.

CONCLUSIONS

Hyperglycemia and elevated circulating OxLDL in DM patients with CAD severely impair EPC migration. These results suggest that the underlying mechanism for this impaired EPC migration is linked to the CXCR4/Pi3K/Akt/eNOS signaling pathway.

Nitric oxide and superoxide dismutase modulate endothelial progenitor cell function in type 2 diabetes mellitus

BACKGROUND

The function of endothelial progenitor cells (EPCs), which are key cells in vascular repair, is impaired in diabetes mellitus. Nitric oxide (NO) and reactive oxygen species can regulate EPC functions. EPCs tolerate oxidative stress by upregulating superoxide dismutase (SOD), the enzyme that neutralizes superoxide anion (O2-). Therefore, we investigated the roles of NO and SOD in glucose-stressed EPCs.

METHODS

The functions of circulating EPCs from patients with type 2 diabetes were compared to those from healthy individuals. Healthy EPCs were glucose-stressed, and then treated with insulin and/or SOD. We assessed O2- generation, NO production, SOD activity, and their ability to form colonies.

RESULTS

EPCs from diabetic patients generated more O2-, had higher NAD(P)H oxidase and SOD activity, but lower NO bioavailability, and expressed higher mRNA and protein levels of p22-phox, and manganese SOD and copper/zinc SOD than those from the healthy individuals. Plasma glucose and HbA1c levels in the diabetic patients were correlated negatively with the NO production from their EPCs. SOD treatment of glucose-stressed EPCs attenuated O2- generation, restored NO production, and partially restored their ability to form colonies. Insulin treatment of glucose-stressed EPCs increased NO production, but did not change O2- generation and their ability to form colonies. However, their ability to produce NO and to form colonies was fully restored after combined SOD and insulin treatment.

CONCLUSION

Our data provide evidence that SOD may play an essential role in EPCs, and emphasize the important role of antioxidant therapy in type 2 diabetic patients.

Microparticles, thrombosis and cancer

Microvesicles comprised of exosomes and microparticles are shed from both normal and malignant cells upon cell activation or apoptosis. Microvesicles promote clot formation, mediate pro-inflammatory processes, facilitate cell-to-cell interactions, transfer proteins and mRNA to cells, and induce cell signalling. Microparticles bearing tissue factor play a central role in coagulation initiation and thrombus formation. This chapter will review earlier studies which focus on the role of procoagulant microvesicles in cancer thrombogenicity, and discuss the effects of microvesicles on vascular cell dysfunction and angiogenesis. In addition, this chapter will present new findings which characterize the haemostatic balance of microparticles, and suggest a method that may potentially serve to predict a state of hypercoagulability in cancer patients. This chapter highlights the interplay between microvesicles, coagulation factors and cancer.