SnRNA sequencing defines signaling by RBC-derived extracellular vesicles in the murine heart.

Extracellular vesicles (EVs) mediate intercellular signaling by transferring their cargo to recipient cells, but the functional consequences of signaling are not fully appreciated. RBC-derived EVs are abundant in circulation and have been implicated in regulating immune responses. Here, we use a transgenic mouse model for fluorescence-based mapping of RBC-EV recipient cells to assess the role of this intercellular signaling mechanism in heart disease. Using fluorescent-based mapping, we detected an increase in RBC-EV-targeted cardiomyocytes in a murine model of ischemic heart failure. Single cell nuclear RNA sequencing of the heart revealed a complex landscape of cardiac cells targeted by RBC-EVs, with enrichment of genes implicated in cell proliferation and stress signaling pathways compared with non-targeted cells. Correspondingly, cardiomyocytes targeted by RBC-EVs more frequently express cellular markers of DNA synthesis, suggesting the functional significance of EV-mediated signaling. In conclusion, our mouse model for mapping of EV-recipient cells reveals a complex cellular network of RBC-EV-mediated intercellular communication in ischemic heart failure and suggests a functional role for this mode of intercellular signaling.

High-fidelity detection and sorting of nanoscale vesicles in viral disease and cancer.

Biological nanoparticles, including viruses and extracellular vesicles (EVs), are of interest to many fields of medicine as biomarkers and mediators of or treatments for disease. However, exosomes and small viruses fall below the detection limits of conventional flow cytometers due to the overlap of particle-associated scattered light signals with the detection of background instrument noise from diffusely scattered light. To identify, sort, and study distinct subsets of EVs and other nanoparticles, as individual particles, we developed nanoscale Fluorescence Analysis and Cytometric Sorting (nanoFACS) methods to maximise information and material that can be obtained with high speed, high resolution flow cytometers. This nanoFACS method requires analysis of the instrument background noise (herein defined as the "reference noise"). With these methods, we demonstrate detection of tumour cell-derived EVs with specific tumour antigens using both fluorescence and scattered light parameters. We further validated the performance of nanoFACS by sorting two distinct HIV strains to >95% purity and confirmed the viability (infectivity) and molecular specificity (specific cell tropism) of biological nanomaterials sorted with nanoFACS. This nanoFACS method provides a unique way to analyse and sort functional EV- and viral-subsets with preservation of vesicular structure, surface protein specificity and RNA cargo activity.

A rapid single cell sorting verification method using plate-based image cytometry.

Single cell sorting is commonly used for ensuring monoclonality and producing homogenous target cell populations. Current single cell verification methods involve manually confirming the existence of single cells or colonies in a well using a standard light microscope. However, the manual verification method is time-consuming and highly tedious, which prompts a need for an accurate and rapid detection method for verifying single cell sorting capability. Here, we demonstrate a rapid single cell sorting verification method using the Celigo Image Cytometer. Calcein AM-stained Jurkat cells and fluorescent beads are sorted into 96-well half area microplates using the MoFlo Astrios EQ. Whole well bright field and fluorescent images are acquired and analyzed using the image cytometer in less than 8 min. The proposed single cell verification detection method in multi-well microplates can allow for quick optimization of FACS instruments at flow core laboratories, as well as improvement of downstream biological assays by accurately confirming the presence of single cells in each well.

Red Blood Cells: A Source of Extracellular Vesicles.

During their lifetime, like all other cell types, red blood cells (RBCs) release both exosomes and plasma membrane derived EVs (ectosomes). RBC exosomes are formed only during the development of RBCs in bone marrow, and are released following the fusion of microvesicular bodies (MVB) with the plasma membrane. On the other hand, RBC EVs are generated during normal aging of RBCs in circulation by budding of the plasma membrane due to complement -mediated calcium influx, followed by vesicle shedding. This makes red blood cells and stored red cells a reliable source of EVs for basic and clinical research.

Characterization of Extracellular Vesicles by Flow Cytometry.

Here, we describe a comprehensive methodology for the setup and standardization of EV analysis using nanoscale flow cytometry. Controls of different size ranges, fluorescent intensities, and materials can be used to set up distribution curves that are then used for instrument optimization and as a reference guide. Using these controls, flow cytometry instruments can be primed for the detection, analysis, and sorting of specific EV populations. This allows for cross platform comparison and the ability to monitor both quality control (QC) and quality assurance (QA). The method here describes the use of nanoparticles to optimize a flow cytometer for small particle detection. It also outlines the procedures necessary to recover EVs for downstream applications.

Extracellular Microvesicle Production by Human Eosinophils Activated by "Inflammatory" Stimuli.

A key function of human eosinophils is to secrete cytokines, chemokines and cationic proteins, trafficking, and releasing these mediators for roles in inflammation and other immune responses. Eosinophil activation leads to secretion of pre-synthesized granule-stored mediators through different mechanisms, but the ability of eosinophils to secrete extracellular vesicles (EVs), very small vesicles with preserved membrane topology, is still poorly understood. In the present work, we sought to identify and characterize EVs released from human eosinophils during different conditions: after a culturing period or after isolation and stimulation with inflammatory stimuli, which are known to induce eosinophil activation and secretion: CCL11 (eotaxin-1) and tumor necrosis factor alpha (TNF-α). EV production was investigated by nanoscale flow cytometry, conventional transmission electron microscopy (TEM) and pre-embedding immunonanogold EM. The tetraspanins CD63 and CD9 were used as EV biomarkers for both flow cytometry and ultrastructural immunolabeling. Nanoscale flow cytometry showed that human eosinophils produce EVs in culture and that a population of EVs expressed detectable CD9, while CD63 was not consistently detected. When eosinophils were stimulated immediately after isolation and analyzed by TEM, EVs were clearly identified as microvesicles (MVs) outwardly budding off the plasma membrane. Both CCL11 and TNF-α induced significant increases of MVs compared to unstimulated cells. TNF-α induced amplified release of MVs more than CCL11. Eosinophil MV diameters varied from 20 to 1000 nm. Immunonanogold EM revealed clear immunolabeling for CD63 and CD9 on eosinophil MVs, although not all MVs were labeled. Altogether, we identified, for the first time, that human eosinophils secrete MVs and that this production increases in response to inflammatory stimuli. This is important to understand the complex secretory activities of eosinophils underlying immune responses. The contribution of the eosinophil-derived MVs to the regulation of immune responses awaits further investigation.

Diurnal Variations of Circulating Extracellular Vesicles Measured by Nano Flow Cytometry.

The identification of extracellular vesicles (EVs) as intercellular conveyors of biological information has recently emerged as a novel paradigm in signaling, leading to the exploitation of EVs and their contents as biomarkers of various diseases. However, whether there are diurnal variations in the size, number, and tissue of origin of blood EVs is currently not known, and could have significant implications when using EVs as biomarkers for disease progression. Currently available technologies for the measurement of EV size and number are either time consuming, require specialized equipment, or lack sufficient accuracy across a range of EV sizes. Flow cytometry represents an attractive alternative to these methods; however, traditional flow cytometers are only capable of measuring particles down to 500 nm, which is significantly larger than the average and median sizes of plasma EVs. Utilizing a Beckman Coulter MoFlo XDP flow cytometer with NanoView module, we employed nanoscale flow cytometry (termed nanoFCM) to examine the relative number and scatter distribution of plasma EVs at three different time points during the day in 6 healthy adults. Analysis of liposomes and plasma EVs proved that nanoFCM is capable of detecting biologically-relevant vesicles down to 100 nm in size. With this high resolution configuration, we observed variations in the relative size (FSC/SSC distributions) and concentration (proportions) of EVs in healthy adult plasma across the course of a day, suggesting that there are diurnal variations in the number and size distribution of circulating EV populations. The use of nanoFCM provides a valuable tool for the study of EVs in both health and disease; however, additional refinement of nanoscale flow cytometric methods is needed for use of these instruments for quantitative particle counting and sizing. Furthermore, larger scale studies are necessary to more clearly define the diurnal variations in circulating EVs, and thus further inform their use as biomarkers for disease.

NAD+ protects against EAE by regulating CD4+ T-cell differentiation.

CD4(+) T cells are involved in the development of autoimmunity, including multiple sclerosis (MS). Here we show that nicotinamide adenine dinucleotide (NAD(+)) blocks experimental autoimmune encephalomyelitis (EAE), a mouse model of MS, by inducing immune homeostasis through CD4(+)IFNγ(+)IL-10(+) T cells and reverses disease progression by restoring tissue integrity via remyelination and neuroregeneration. We show that NAD(+) regulates CD4(+) T-cell differentiation through tryptophan hydroxylase-1 (Tph1), independently of well-established transcription factors. In the presence of NAD(+), the frequency of T-bet(-/-) CD4(+)IFNγ(+) T cells was twofold higher than wild-type CD4(+) T cells cultured in conventional T helper 1 polarizing conditions. Our findings unravel a new pathway orchestrating CD4(+) T-cell differentiation and demonstrate that NAD(+) may serve as a powerful therapeutic agent for the treatment of autoimmune and other diseases.

Characterization of circulating microparticle-associated CD39 family ecto-nucleotidases in human plasma.

Phosphohydrolysis of extracellular ATP and ADP is an essential step in purinergic signaling that regulates key pathophysiological processes, such as those linked to inflammation. Classically, this reaction has been known to occur in the pericellular milieu catalyzed by membrane bound cellular ecto-nucleotidases, which can be released in the form of both soluble ecto-enzymes as well as being associated with exosomes. Circulating ecto-nucleoside triphosphate diphosphohydrolase 1 (NTPDase 1/CD39) and adenylate kinase 1 (AK1) activities have been shown to be present in plasma. However, other ecto-nucleotidases have not been characterized in depth. An in vitro ADPase assay was developed to probe the ecto-enzymes responsible for the ecto-nucleotidase activity in human platelet-free plasma, in combination with various specific biochemical inhibitors. Identities of ecto-nucleotidases were further characterized by chromatography, immunoblotting, and flow cytometry of circulating exosomes. We noted that microparticle-bound E-NTPDases and soluble AK1 constitute the highest levels of ecto-nucleotidase activity in human plasma. All four cell membrane expressed E-NTPDases are also found in circulating microparticles in human plasma, inclusive of: CD39, NTPDase 2 (CD39L1), NTPDase 3 (CD39L3), and NTPDase 8. CD39 family members and other ecto-nucleotidases are found on distinct microparticle populations. A significant proportion of the microparticle-associated ecto-nucleotidase activity is sensitive to POM6, inferring the presence of NTPDases, either -2 or/and -3. We have refined ADPase assays of human plasma from healthy volunteers and have found that CD39, NTPDases 2, 3, and 8 to be associated with circulating microparticles, whereas soluble AK1 is present in human plasma. These ecto-enzymes constitute the bulk circulating ADPase activity, suggesting a broader implication of CD39 family and other ecto-enzymes in the regulation of extracellular nucleotide metabolism.

Role of endothelial progenitor cells and inflammatory cytokines in healing of diabetic foot ulcers.

BACKGROUND: To evaluate changes in endothelial progenitor cells (EPCs) and cytokines in patients with diabetic foot ulceration (DFU) in association with wound healing. METHODS: We studied healthy subjects, diabetic patients not at risk of DFU, at risk of DFU and with active DFU. We prospectively followed the DFU patients over a 12-week period. We also investigated similar changes in diabetic rabbit and mouse models of wound healing. RESULTS: All EPC phenotypes except the kinase insert domain receptor (KDR)(+)CD133(+) were reduced in the at risk and the DFU groups compared to the controls. There were no major EPC differences between the control and not at risk group, and between the at risk and DFU groups. Serum stromal-cell derived factor-1 (SDF-1) and stem cell factor (SCF) were increased in DFU patients. DFU patients who healed their ulcers had lower CD34(+)KDR(+) count at visits 3 and 4, serum c-reactive protein (CRP) and granulocyte-macrophage colony-stimulating factor (GM-CSF) at visit 1, interleukin-1 (IL-1) at visits 1 and 4. EPCs tended to be higher in both diabetic animal models when compared to their non-diabetic counterparts both before and ten days after wounding. CONCLUSIONS: Uncomplicated diabetes does not affect EPCs. EPCs are reduced in patients at risk or with DFU while complete wound healing is associated with CD34(+)KDR(+) reduction, suggesting possible increased homing. Low baseline CRP, IL-1α and GM-CSF serum levels were associated with complete wound healing and may potentially serve as prognostic markers of DFU healing. No animal model alone is representative of the human condition, indicating the need for multiple experimental models.

CD39 modulates hematopoietic stem cell recruitment and promotes liver regeneration in mice and humans after partial hepatectomy.

OBJECTIVE: To study molecular mechanisms involved in hematopoietic stem cell (HSC) mobilization after liver resection and determine impacts on liver regeneration. BACKGROUND: Extracellular nucleotide-mediated cell signaling has been shown to boost liver regeneration. Ectonucleotidases of the CD39 family are expressed by bone marrow-derived cells, and purinergic mechanisms might also impact mobilization and functions of HSC after liver injury. METHODS: Partial hepatectomy was performed in C57BL/6 wild-type, Cd39 ectonucleotidase-null mice and in chimeric mice after transplantation of wild-type or Cd39-null bone marrow. Bone marrow-derived HSCs were purified by fluorescence-activated cell sorting and administered after hepatectomy. Chemotactic studies were performed to examine effects of purinergic receptor agonists and antagonists in vitro. Mobilization of human HSCs and expression of CD39 were examined and linked to the extent of resection and liver tests. RESULTS: Subsets of HSCs expressing Cd39 are preferentially mobilized after partial hepatectomy. Chemotactic responses of HSCs are increased by CD39-dependent adenosine triphosphate hydrolysis and adenosine signaling via A2A receptors in vitro. Mobilized Cd39 HSCs boost liver regeneration, potentially limiting interleukin 1ß signaling. In clinical studies, mobilized human HSCs also express CD39 at high levels. Mobilization of HSCs correlates directly with the restoration of liver volume and function after partial hepatectomy. CONCLUSIONS: We demonstrate CD39 to be a novel HSC marker that defines a functionally distinct stem cell subset in mice and humans. HSCs are mobilized after liver resection, limit inflammation, and boost regeneration in a CD39-dependent manner. These observations have implications for monitoring and indicate future therapeutic avenues.

Increased plasma levels of microparticles expressing CD39 and CD133 in acute liver injury.

BACKGROUND: We have previously demonstrated that CD133 and CD39 are expressed by hematopoietic stem cells (HSC), which are mobilized after liver injury and target sites of injury, limit vascular inflammation, and boost hepatic regeneration. Plasma microparticles (MP) expressing CD39 can block endothelial activation. Here, we tested whether CD133 MP might be shed in a CD39-dependent manner in a model of liver injury and could potentially serve as biomarkers of liver failure in the clinic. METHODS: Wild-type and Cd39-null mice were subjected to acetaminophen-induced liver injury. Mice were sacrificed and plasma MP were isolated by ultracentrifugation. HSC and CD133 MP levels were analyzed by fluorescence-activated cell sorting. Patients were enrolled with acute (n=5) and acute on chronic (n=5) liver injury with matched controls (n=7). Blood was collected at admission and plasma CD133 and CD39 MP subsets were analyzed by fluorescence-activated cell sorting. RESULTS: HSC and CD133 MP levels were significantly increased only in the plasma of wild-type mice with acetaminophen hepatotoxicity (P<0.05). No increases in CD133 MP were noted in Cd39-null mice. Plasma MP increases were observed in patients with liver injury. These MP were characterized by significantly higher levels of CD39 (P<0.05). CONCLUSIONS: HSC and plasma CD133 MP levels increase in a CD39-dependent manner during experimental acute liver injury. Increased levels of CD39 MP are differentially noted in patients with liver injury. Further research is needed to determine whether MP fluxes are secondary to pathophysiologic insults to the liver or might reflect compensatory responses.

Alternative methods for characterization of extracellular vesicles.

Extracellular vesicles (ECVs) are nano-sized vesicles released by all cells in vitro as well as in vivo. Their role has been implicated mainly in cell-cell communication, but also in disease biomarkers and more recently in gene delivery. They represent a snapshot of the cell status at the moment of release and carry bioreactive macromolecules such as nucleic acids, proteins, and lipids. A major limitation in this emerging new field is the availability/awareness of techniques to isolate and properly characterize ECVs. The lack of gold standards makes comparing different studies very difficult and may potentially hinder some ECVs-specific evidence. Characterization of ECVs has also recently seen many advances with the use of Nanoparticle Tracking Analysis, flow cytometry, cryo-electron microscopy instruments, and proteomic technologies. In this review, we discuss the latest developments in translational technologies involving characterization methods including the facts in their support and the challenges they face.

In vivo tracking of 'color-coded' effector, natural and induced regulatory T cells in the allograft response.

Here we present methods to longitudinally track islet allograft-infiltrating T cells in live mice by endoscopic confocal microscopy and to analyze circulating T cells by in vivo flow cytometry. We developed a new reporter mouse whose T cell subsets express distinct, 'color-coded' proteins enabling in vivo detection and identification of effector T cells (T(eff) cells) and discrimination between natural and induced regulatory T cells (nT(reg) and iT(reg) cells). Using these tools, we observed marked differences in the T cell response in recipients receiving tolerance-inducing therapy (CD154-specific monoclonal antibody plus rapamycin) compared to untreated controls. These results establish real-time cell tracking as a powerful means to probe the dynamic cellular interplay mediating immunologic rejection or transplant tolerance.

Signal sequence is still required in genes downstream of "autocleaving" 2A peptide for secretary or membrane-anchored expression.

2A Peptide sequences are now being widely used to construct multicistronic expression vectors. It is suggested that when only the first 2A-linked protein bears a signal sequence, the signal-less protein(s) downstream of 2A can also be translocated into the mammalian endoplasmic reticulum system through a "slipstreaming" mechanism. By using flow cytometry and cell surface CD90 as a localization indicator, we show here that slipstreaming translocation does not occur in mammalian cells; that is, the second protein downstream of 2A still requires signal sequence for secretary or membrane-anchored expression.