Novel fluorescence assay using calcein-AM for the determination of human erythrocyte viability and aging

Necrotic platelets provide a procoagulant surface during thrombosis

A subpopulation of platelets fulfills a procoagulant role in hemostasis and thrombosis by enabling the thrombin burst required for fibrin formation and clot stability at the site of vascular injury. Excess procoagulant activity is linked with pathological thrombosis. The identity of the procoagulant platelet has been elusive. The cell death marker 4-[N-(S-glutathionylacetyl)amino]phenylarsonous acid (GSAO) rapidly enters a subpopulation of agonist-stimulated platelets via an organic anion-transporting polypeptide and is retained in the cytosol through covalent reaction with protein dithiols. Labeling with GSAO, together with exposure of P-selectin, distinguishes necrotic from apoptotic platelets and correlates with procoagulant potential. GSAO(+) platelets form in occluding murine thrombi after ferric chloride injury and are attenuated with megakaryocyte-directed deletion of the cyclophilin D gene. These platelets form a procoagulant surface, supporting fibrin formation, and reduction in GSAO(+) platelets is associated with reduction in platelet thrombus size and fibrin formation. Analysis of platelets from human subjects receiving aspirin therapy indicates that these procoagulant platelets form despite aspirin therapy, but are attenuated by inhibition of the necrosis pathway. These findings indicate that the major subpopulation of platelets involved in fibrin formation are formed via regulated necrosis involving cyclophilin D, and that they may be targeted independent of platelet activation.

Cell-Based Microarrays for In Vitro Toxicology

DNA/RNA and protein microarrays have proven their outstanding bioanalytical performance throughout the past decades, given the unprecedented level of parallelization by which molecular recognition assays can be performed and analyzed. Cell microarrays (CMAs) make use of similar construction principles. They are applied to profile a given cell population with respect to the expression of specific molecular markers and also to measure functional cell responses to drugs and chemicals. This review focuses on the use of cell-based microarrays for assessing the cytotoxicity of drugs, toxins, or chemicals in general. It also summarizes CMA construction principles with respect to the cell types that are used for such microarrays, the readout parameters to assess toxicity, and the various formats that have been established and applied. The review ends with a critical comparison of CMAs and well-established microtiter plate (MTP) approaches.

The protective effect of lactoferrin on ventral mesencephalon neurons against MPP + is not connected with its iron binding ability

Lactoferrin (Lf) can bind to lactoferrin receptor (LfR), leading to iron transport through the plasma membrane. Besides iron transportation, Lf also has antioxidant and anti-inflammatory properties. In the brain, Lf is only synthesized by activated microglia. LfR is present in blood vessels and nigral dopaminergic neurons. Both nigral iron accumulation and microglia activation is believed to be involved in Parkinson’s disease (PD), moreover, increased Lf and LfR in dopaminergic neurons were found in PD cases and MPTP-intoxicated mice. How iron influences microglia to release Lf? Does Lf tend to transport iron to dopaminergic neurons leading to cell death or to protect dopaminergic neuron from neurotoxin? In this study, we observed that iron increased Lf synthesis in activated microglia. In ventral mesencephalon neurons, both iron-free Lf (apo-Lf) and iron-saturated Lf (holo-Lf) exerted neuroprotective effects against MPP⁺ by mechanisms, believed to enhance the mitochondrial transmembrane potential, improve Cu/Zn-superoxide dismutase activity, increase Bcl-2 expression. Although apo-Lf but not holo-Lf chelated cellular iron, there was no difference between the two types of Lf in the neuroprotection. Our data indicate that iron overload increases the activated microglia releasing Lf. Lf plays protective role on ventral mesencephalon neurons against MPP⁺, which is iron-chelating independent.

Review of methods to probe single cell metabolism and bioenergetics

Single cell investigations have enabled unexpected discoveries, such as the existence of biological noise and phenotypic switching in infection, metabolism and treatment. Herein, we review methods that enable such single cell investigations specific to metabolism and bioenergetics. Firstly, we discuss how to isolate and immobilize individuals from a cell suspension, including both permanent and reversible approaches. We also highlight specific advances in microbiology for its implications in metabolic engineering. Methods for probing single cell physiology and metabolism are subsequently reviewed. The primary focus therein is on dynamic and high-content profiling strategies based on label-free and fluorescence microspectroscopy and microscopy. Non-dynamic approaches, such as mass spectrometry and nuclear magnetic resonance, are also briefly discussed.

Fluorescence based cell counting in collagen monolayer cultures of primary hepatocytes

Accurate determination of cell number is essential for the quantitative description of biological processes. The changes should be related to a measurable reference e.g. in the case of cell culture, the viable cell number is a very valuable reference parameter. Indirect methods of cell number/viability measurements may have up to 10 % standard deviation. This can lead to undesirable large deviations in the analysis of "-omics" data as well as time course studies. Such data should be preferably normalized to the exact viable cell number at a given time to allow meaningful interpretation and understanding of the biological processes. Manual counting of cell number is very laborious and not possible in certain experimental setups. We therefore, developed a simple and reliable fluorescence based method with an accuracy of 95-98 % for the determination of the viable cell number in situ. We optimized the seeding cell densities for primary rat hepatocytes for optimal cell adhesion. This will help in efficient use of primary cells which are usually limited in availability. The method will be very useful in the application of "-omics" techniques, especially metabolome analysis where the specific rates of uptake/production of metabolites can be reliably calculated.

SIRT3 interactions with FOXO3 acetylation, phosphorylation and ubiquitinylation mediate endothelial cell responses to hypoxia

This article reports that hypoxia elicits SIRT3 to deacetylate FOXO3 in endothelial cells. This drives an increase in the expression of mitochondrial antioxidant enzymes, reduces accumulation of reactive oxygen species in mitochondria and thereby confers cellular capacity to adapt to hypoxia.

Plasmodium falciparum, but not P. vivax, can induce erythrocytic apoptosis

Background

Apoptosis can occur in red blood cells (RBC) and seems to be involved in hematologic disorders related to many diseases. In malaria it is known that parasitized RBC (pRBC) is involved in the development of anemia and thrombosis; however, non-parasitized RBC (nRBC) apoptosis could amplify these malaria-associated hematologic events. In fact, in experimental malaria, increased levels of apoptosis were observed in nRBC during lethal Plasmodium yoelii 17XL infection, but in human malaria erythrocytic apoptosis has never been studied. The present study was performed to investigate if nRBC apoptosis also occurs in P. vivax and P. falciparum infections.

Findings

Apoptosis of nRBC was evaluated in blood samples of P. vivax malaria patients and clinically healthly individuals living in Manaus, Brazil, both ex vivo and after incubation of RBC for 24 h. Additionally, the capacity of plasma from P. vivax or P. falciparum patients was tested for induction of in vitro apoptosis of normal RBC from a clinically healthy individual living in a non-endemic malaria region. Apoptosis was detected by flow cytometry using annexin V staining. In contrast to experimental malaria that significantly increased the levels of apoptotic nRBC both ex-vivo and after 24 h of incubation, no significant alteration on apoptotic nRBC rates was detected in P. vivax infected patients when compared with non-infected control individuals. Similar results were observed when plasma of these P. vivax patients was incubated with normal RBC. Conversely, plasma from P. falciparum-infected subjects induced significant apoptosis of these cells.

Conclusions

Apoptosis of normal RBC can be induced by plasma from individuals with P. falciparum (but not with P. vivax) malaria. This finding could reflect the existence of erythrocytic apoptosis during infection that could contribute to the pathogenesis of hematological and vascular complications associated with falciparum malaria.

Sorting drops and cells with acoustics: acoustic microfluidic fluorescence-activated cell sorter

We describe a versatile microfluidic fluorescence-activated cell sorter that uses acoustic actuation to sort cells or drops at ultra-high rates. Our acoustic sorter combines the advantages of traditional fluorescence-activated cell (FACS) and droplet sorting (FADS) and is applicable for a multitude of objects. We sort aqueous droplets, at rates as high as several kHz, into two or even more outlet channels. We can also sort cells directly from the medium without prior encapsulation into drops; we demonstrate this by sorting fluorescently labeled mouse melanoma cells in a single phase fluid. Our acoustic microfluidic FACS is compatible with standard cell sorting cytometers, yet, at the same time, enables a rich variety of more sophisticated applications.

Host iron status and iron supplementation mediate susceptibility to erythrocytic stage Plasmodium falciparum

Iron deficiency and malaria have similar global distributions, and frequently co-exist in pregnant women and young children. Where both conditions are prevalent, iron supplementation is complicated by observations that iron deficiency anaemia protects against falciparum malaria, and that iron supplements increase susceptibility to clinically significant malaria, but the mechanisms remain obscure. Here, using an in vitro parasite culture system with erythrocytes from iron-deficient and replete human donors, we demonstrate that Plasmodium falciparum infects iron-deficient erythrocytes less efficiently. In addition, owing to merozoite preference for young erythrocytes, iron supplementation of iron-deficient individuals reverses the protective effects of iron deficiency. Our results provide experimental validation of field observations reporting protective effects of iron deficiency and harmful effects of iron administration on human malaria susceptibility. Because recovery from anaemia requires transient reticulocytosis, our findings imply that in malarious regions iron supplementation should be accompanied by effective measures to prevent falciparum malaria.

Inhibitory action of benzo[α]pyrene on hepatic lipoprotein receptors in vitro and on liver lipid homeostasis in mice

BACKGROUND

Dyslipidemia associated with obesity often manifests as increased plasma LDL and triglyceride-rich lipoprotein levels suggesting changes in hepatic lipoprotein receptor status. Persistent organic pollutants have been recently postulated to contribute to the obesity etiology by increasing adipogenesis, but little information is available on their potential effect on hepatic lipoprotein metabolism.

OBJECTIVE

The objective of this study was to investigate the effect of the common environmental pollutant, benzo[α]pyrene (B[α]P) on two lipoprotein receptors, the LDL-receptor and the lipolysis-stimulated lipoprotein receptor (LSR) as well as the ATP-binding cassette transporter A1 (ABCA1) using cell and animal models.

RESULTS

LSR, LDL-receptor as well as ABCA1 protein levels were significantly decreased by 26-48% in Hepa1-6 cells incubated (<2 h) in the presence of B[α]P (≤1 µM). Real-time PCR analysis and lactacystin studies revealed that this effect was due primarily to increased proteasome, and not lysosomal-mediated degradation rather than decreased transcription. Furthermore, ligand blots revealed that lipoproteins exposed to 1 or 5 µM B[α]P displayed markedly decreased (42-86%) binding to LSR or LDL-receptor. B[α]P-treated (0.5 mg/kg/48 h, i.p. 15 days) C57BL/6J mice displayed higher weight gain, associated with significant increases in plasma cholesterol, triglycerides, and liver cholesterol content, and decreased hepatic LDL-receptor and ABCA1 levels. Furthermore, correlational analysis revealed that B[α]P abolished the positive association observed in control mice between the LSR and LDL-receptor. Interestingly, levels of other proteins involved in liver cholesterol metabolism, ATP-binding cassette transporter G1 and scavenger receptor-BI, were decreased, while those of acyl-CoA:cholesterol acyltransferase 1 and 2 were increased in B[α]P-treated mice.

CONCLUSIONS

B[α]P demonstrates inhibitory action on LSR and LDL-R, as well as ABCA1, which we propose leads to modified lipid status in B[α]P-treated mice, thus providing new insight into mechanisms underlying the involvement of pollutants in the disruption of lipid homeostasis, potentially contributing to dyslipidemia associated with obesity.

Extracellular-controlled breast cancer cell formation and growth using non-UV patterned hydrogels via optically-induced electrokinetics

The culturing of cancer cells on micropatterned substrates can provide insight into the factors of the extracellular environment that enable the control of cell growth. We report here a novel non-UV-based technique to quickly micropattern a poly-(ethylene) glycol diacrylate (PEGDA)-based hydrogel on top of modified glass substrates, which were then used to control the growth patterns of breast cancer cells. Previously, the fabrication of micropatterned substrates required relatively complicated steps, which made it impractical for researchers to rapidly and systematically investigate the effects of different cell growth patterns. The technique presented herein operates on the principle of optically-induced electrokinetics (OEKs) and uses computer-generated projection light patterns to dynamically pattern the hydrogel on a hydrogenated amorphous silicon (a-Si:H) thin-film, atop an indium tin oxide (ITO) glass substrate. This technique allows us to pattern lines, circles, pentagons, and more complex shapes in the hydrogel with line widths below 3 μm and thicknesses of up to 6 μm within 8 s by simply controlling the projected illumination pattern and applying an appropriate AC voltage between the two ITO glass substrates. After separating the glass substrates to expose the patterned hydrogel, we experimentally demonstrate that MCF-7 breast cancer cells will adhere to the bare a-Si:H surface, but not to the hydrogel patterned in various geometric shapes and sizes. Theoretical analysis and finite-element model simulations reveal that the dominant OEK forces in our technique are the dielectrophoresis (DEP) force and the electro-osmosis force, which enhance the photo-initiated cross-linking reaction in the hydrogel. Our preliminary cultures of breast cancer cells demonstrate that this reported technique could be applied to effectively confine the growth of cancer cells on a-Si:H surfaces and affect individual cell geometry during their growth.

Hypoxia and hypoxia mimetic cooperate to counteract tumor cell resistance to glucose starvation preferentially in tumor cells with mutant p53

We demonstrated that exogenous pyruvate promotes survival under glucose depletion in aerobic mutant p53 (R175H) human melanoma cells. Others subsequently indicated that mutant p53 tumor cells undergo p53 degradation and cell death under aerobic glucose-free conditions. Since glucose starvation occurs in hypoxic gradients of poorly vascularized tumors, we investigated the role of p53 siRNA under hypoxia in wt p53 C8161 melanoma using glucose starvation or 5mM physiological glucose. p53 Silencing decreased survival of glucose-starved C8161 melanoma with pyruvate supplementation under hypoxia (≤1% oxygen), but increased resistance to glycolytic inhibitors oxamate and 2-deoxyglucose in 5mM glucose, preferentially under normoxia. Aiming to counteract hypoxic tumor cell survival irrespective of p53 status, genetically-matched human C8161 melanoma harboring wt p53 or mutant p53 (R175H) were used combining true hypoxia (≤1% oxygen) and hypoxia mimetic CoCl2. No significant decrease in metabolic activity was evidenced in C8161 melanoma irrespective of p53 status in 2.5mM glucose after 48h of physical hypoxia. However, combining the latter with 100μM CoCl2 was preferentially toxic for mutant p53 C8161 melanoma, and was enhanced by catalase in wt p53 C8161 cells. Downregulation of MnSOD and LDHA accompanied the toxicity induced by hypoxia and CoCl2 in 5mM glucose, and these changes were enhanced by oxamate or 2-deoxyglucose. Our results show for the first time that survival of malignant cells in a hypoxic microenvironment can be counteracted by hypoxia mimetic co-treatment in a p53 dependent manner.

Ferutinin induces in vitro eryptosis/erythroptosis in human erythrocytes through membrane permeabilization and calcium influx

Ferutinin, isolated from the root of Ferula hermonis and proposed to be used as an antiosteoporosis phytoestrogen, has death promoting activities in a number of cancer cells. However, the effect of ferutinin on the induction of apoptosis in human red blood cells (RBCs), also known as eryptosis or erythroptosis, remains unclear. Given that ferutinin is a small molecule that can induce apoptosis in the cancer cells by opening the mitochondrial permeability transition pores, we therefore hypothesized that the effect of ferutinin to elicit apoptosis in human RBCs devoid of mitochondria would be minimal. This study tried to determine the in vitro effect of ferutinin on the induction of apoptosis in human RBCs. Eryptosis/erythroptosis after ferutinin treatment was examined for phosphatidylserine (PS) externalization, calcein leakage, and other apoptotic feature events by flow cytometry and confocal microscopy. Contrary to our prediction, ferutinin caused eryptosis/erythroptosis in human RBCs and simultaneously increased caspase-3 activity and the cytosolic free Ca(2+) ion level ([Ca(2+)]i). Yet, Ca(2+) seems not to be the sole mediator in ferutinin-mediated eryptosis/erythroptosis because depletion of the external Ca(2+) could not eliminate the apoptotic effect from ferutinin. Subsequent replenishment of the external Ca(2+) was able to promote PS externalization, caspase-3 activation, and rise of [Ca(2+)]i. Also, ferutinin at high dose (40 μM or above) was able to permeabilize the membrane of RBC ghosts in a way similar to that of digitonin. At low dose, ferutinin activated the P- and L-type Ca(2+) channels as the ferutinin-mediated [Ca(2+)]i rise was suppressed by the P-type (ω-agatoxin IVA) and L-type (verapamil and diltiazem) Ca(2+) channel blockers. Taken together, we report here for the first time that ferutinin induces in vitro apoptosis in human RBCs. Mechanistically, eryptosis/erythroptosis is mediated by membrane permeabilization and upregulation of [Ca(2+)]i with the activation of caspase-3.

Caspase-3 is involved in the signalling in erythroid differentiation by targeting late progenitors

A role for caspase activation in erythroid differentiation has been established, yet its precise mode of action remains elusive. A drawback of all previous investigations on caspase activation in ex vivo erythroid differentiation is the lack of an in vitro model producing full enucleation of erythroid cells. Using a culture system which renders nearly 100% enucleated red cells from human CD34(+) cells, we investigated the role of active caspase-3 in erythropoiesis. Profound effects of caspase-3 inhibition were found on erythroid cell growth and differentiation when inhibitors were added to CD34(+) cells at the start of the culture and showed dose-response to the concentration of inhibitor employed. Enucleation was only reduced as a function of the reduced maturity of the culture and the increased cell death of mature cells while the majority of cells retained their ability to extrude their nuclei. Cell cycle analysis after caspase-3 inhibition showed caspase-3 to play a critical role in cell proliferation and highlighted a novel function of this protease in erythroid differentiation, i.e. its contribution to cell cycle regulation at the mitotic phase. While the effect of caspase-3 inhibitor treatment on CD34(+) derived cells was not specific to the erythroid lineage, showing a similar reduction of cell expansion in myeloid cultures, the mechanism of action in both lineages appeared to be distinct with a strong induction of apoptosis causing the decreased yield of myeloid cells. Using a series of colony-forming assays we were able to pinpoint the stage at which cells were most sensitive to caspase-3 inhibition and found activated caspase-3 to play a signalling role in erythroid differentiation by targeting mature BFU-E and CFU-E but not early BFU-E.

Delivery of a granzyme B inhibitor gene using carbamate-mannose modified PEI protects against cytotoxic lymphocyte killing

Cytotoxic T lymphocytes (CTL) and natural killer (NK) cells protect vertebrates by killing infected or transformed cells using granzyme B (GrB) to induce apoptosis. However, GrB-induced apoptosis of target cells causes inflammatory disease and chronic transplant rejection and so is an important disease target. The aim of this study was to prevent apoptosis of the target cells by delivering a plasmid encoding GrB inhibitor proteinase inhibitor-9 (PI-9) using cationic polymers as a non-viral vector. Polyethyleneimine (PEI, branched, Mn 10 kDa) gives a high degree of gene transfection efficiency in many types of cell lines, but it is highly cytotoxic. To reduce this cytotoxicity, we modified PEI by blocking primary amine groups through nucleophilic addition between primary amine and a protected mannose-functionalized cyclic carbonate (MTC-ipman), generating a carbamate linkage through the ring-opening of the cyclic carbonate. Deprotection of the mannose yielded a PEI polymer that is decorated with the carbohydrate. PEI with 7 or 20 of 67 primary amine groups substituted by the carbohydrate had similar gene binding ability compared to unmodified PEI, leading to almost 100% transfection efficiency of a GFP-reporter plasmid in HEK293T human embryonic kidney cells. Furthermore, modification of PEI resulted in a decrease in the cytotoxicity of PEI/DNA complexes. However, PEI with all primary amine groups blocked was unable to form a complex with DNA, and so reporter transfection was negligible. The PI-9 encoding plasmid was transfected into HEK293T cells effectively using the modified PEIs with the optimal degree of primary amine substitution, protecting up to 80% HEK293T cells from killing by human natural killer-like leukemic YT cells. Therefore, these carbamate-mannose modified PEI/PI-9 encoding plasmid complexes have potential clinical utility in the prevention of chronic transplant rejection and inflammatory disease caused by GrB.

Biological validation of bio-engineered red blood cell productions

The generation in vitro of cultured red blood cells (cRBC) could become an alternative to classical transfusion products. However, even when derived from healthy donors, the cRBC generated in vitro from hematopoietic stem cells may display alterations resulting from a poor controlled production process. In this context, we attempted to monitor the quality of the transfusion products arising from new biotechnologies. For that purpose, we developed an in vitro erythrophagocytosis (EP) test with the murine fibroblast cell line MS-5 and human macrophages (reference method). We evaluated 38 batches of cRBC, at the stage of reticulocyte, generated from CD34(+) cells isolated from placental blood or by leukapheresis. We showed that (i) the EP test performed with the MS-5 cell line was sensitive and can replace human macrophages for the evaluation of cultured cells. (ii) The EP tests revealed disparities among the batches of cRBC. (iii) The viability of the cells (determined by calcein-AM test), the expression of CD47 (antiphagocytosis receptor) and the externalization of phosphatidylserine (PS, marker of phagocytosis) were not critical parameters for the validation of the cRBC. (iv) Conversely, the cell deformability determined by ektacytometry was inversely correlated with the intensity of the phagocytic index. Assuming that the culture conditions directly influence the quality of the cell products generated, optimization of the production mode could benefit from the erythrophagocytosis test.

Phosphatidylethanolamine is externalized at the surface of microparticles

Microparticles (MPs) are membrane-bound vesicles shed normally or as a result of various (pathological) stimuli. MPs contain a wealth of bio-active macromolecules. Aminophospholipid phosphatidylserine (PS) is present on the surface of many MPs. As PS and phosphatidylethanolamine (PE) are related, yet distinct aminophospholipids, the purpose of this study was to systematically and directly assess PE exposure on MPs. We examined MPs from various human cellular sources (human breast cancer, endothelial, red and white blood cells) by flow cytometry using a PE-specific probe, duramycin, and two PS-specific probes, annexin V and lactadherin. PS and PE exposure percentage was comparable on vascular and blood cell-derived MPs (80-90% of MP-gated events). However, the percentage of malignant breast cancer MPs exposing PE (~90%) was significantly higher than PS (~50%). Thus, while PS and PE exposure can result from a general loss of membrane asymmetry, there may also be distinct mechanisms of PE and PS exposure on MPs that vary by cellular source.

CTAB-coated gold nanorods elicit allergic response through degranulation and cell death in human basophils

The effect of CTAB (cetyltrimethylammonium bromide)- or PEG (polyethylene glycol)-coated gold-nanorods (Au-NRs) on the non-IgE mediated allergic response was studied. We found that the CTAB-Au-NRs released more allergic mediators such as histamine and β-hexosaminidase from human basophil KU812, a common model for studying allergy, after 20 min incubation. Also, the CTAB-Au-NRs induced more apoptosis than the PEG-Au-NRs in KU812 24 h after treatment. These short- and long-term effects were not solely due to the CTAB residues in the supernatant desorbed from the Au-NRs.

An intact kidney slice model to investigate vasa recta properties and function in situ

Background

Medullary blood flow is via vasa recta capillaries, which possess contractile pericytes. In vitro studies using isolated descending vasa recta show that pericytes can constrict/dilate descending vasa recta when vasoactive substances are present. We describe a live kidney slice model in which pericyte-mediated vasa recta constriction/dilation can be visualized in situ.

Methods

Confocal microscopy was used to image calcein, propidium iodide and Hoechst labelling in ‘live’ kidney slices, to determine tubular and vascular cell viability and morphology. DIC video-imaging of live kidney slices was employed to investigate pericyte-mediated real-time changes in vasa recta diameter.

Results

Pericytes were identified on vasa recta and their morphology and density were characterized in the medulla. Pericyte-mediated changes in vasa recta diameter (10–30%) were evoked in response to bath application of vasoactive agents (norepinephrine, endothelin-1, angiotensin-II and prostaglandin E₂) or by manipulating endogenous vasoactive signalling pathways (using tyramine, L-NAME, a cyclo-oxygenase (COX-1) inhibitor indomethacin, and ATP release).

Conclusions

The live kidney slice model is a valid complementary technique for investigating vasa recta function in situ and the role of pericytes as regulators of vasa recta diameter. This technique may also be useful in exploring the role of tubulovascular crosstalk in regulation of medullary blood flow.

Rapid image-based cytometry for comparison of fluorescent viability staining methods

The ability to accurately measure cell viability is important for any cell-based research. Traditionally, viability measurements have been performed using trypan blue exclusion method on hemacytometer, which allowed researchers to visually distinguish viable from nonviable cells. However, the trypan blue method is often limited to only cell lines or primary cells that have been rigorously purified. In the recent years, small desktop image-based cell counters have been developed for rapid cell concentration and viability measurement due to advances in imaging and optics technologies as well as novel fluorescent stains. In this work, we employed the Cellometer image-based cytometer to demonstrate the ability to simplify viability detection compared to the current methods. We compared various fluorescence viability detection methods using single- or dual-staining technique. Single-staining method using nucleic acid stains including ethidium bromide, propidium iodide, 7AAD, DAPI, Sytox Green and Sytox Red, and enzymatic stains including CFDA and Calcein AM were performed. All stains produced comparable results to trypan blue exclusion method for cell line samples. Dual-staining method using AO/PI, CFDA/PI, Calcein AM/PI and Hoechst 33342/PI that enumerates viable and non-viable cells was tested on primary cell samples with high debris contents. This method allowed exclusion of cellular debris and non-nucleated cells from analysis, which can eliminate the need to perform purification step during sample preparation, and improves the efficiency of viability detection method. Overall, these image-based fluorescent cell counters can simplify assay procedures as well as capture images for visual confirmation.

Salidroside protects human erythrocytes against hydrogen peroxide-induced apoptosis

Rhodiola rosea is a commonly used folk medicine for the treatment of high altitude sickness, mountain malhypoxia, and anoxia. Its active ingredient, salidroside [2-(4-hydroxyphenyl)ethyl β-D-glucopyranoside (1)], has been reported to have a broad spectrum of biological effects. However, the protective role of 1 in human erythrocytes remains unclear. This study therefore has investigated the effects of 1 on oxidative stress-induced apoptosis in human erythrocytes (also known as eryptosis or erythroptosis). Compound 1 increased cell survival significantly and prevented human erythrocytes from undergoing eryptosis/erythroptosis mediated by H(2)O(2), as confirmed by the decreased expression of phosphatidylserine on the cell surface and reduced leakage of calcein through the damaged membrane. Mechanistically, 1 was found to exert its protective effects through its antioxidative activity and the inhibition of caspase-3 activation and stress-induced intracellular Ca(2+) rise in a dose-dependent manner. Compound 1 is a protective agent in human erythrocytes against oxidative stress and may be a good adaptogen to enhance the body's resistance to stress and fatigue.

Polyphyllin D induces apoptosis in human erythrocytes through Ca²⁺ rise and membrane permeabilization

Polyphyllin D (PD) is a potent anticancer agent isolated from a traditional medicinal herb Paris polyphylla that has been used in China for many years to treat cancer. PD is not a substrate of p-glycoprotein, and it can bypass the multi-drug resistance in cancer cell line R-HepG2. However, the effect of PD on the induction of cell death in human erythrocytes remains unknown. Given that PD is a small molecule that can depolarize the mitochondrial membrane potential and release apoptosis-inducing factor (AIF) in isolated mitochondria, we hypothesized that the apoptogenic effect of PD in human erythrocytes devoid of mitochondria would be minimal. This study therefore tried to evaluate the in vitro effect of PD on hemolysis and apoptosis in human erythrocytes. Apoptosis in human red blood cells (RBCs), also known as eryptosis or erythroptosis, after PD treatment was determined by flow cytometry and confocal microscopy for the phosphatidyl-serine externalization and other apoptosis feature events. False to our prediction, PD caused hemolysis and eryptosis/erythroptosis in human RBCs. Mechanistically, elevation in the cytosolic Ca²⁺ ion level seems to be a key but not the only mediator in the PD-mediated eryptosis/erythroptosis because depletion of the external Ca²⁺ could not eliminate the PD effect. Also, PD was able to permeabilize the membrane of RBC ghosts in a way similar to digitonin. Taken together, we report here for the first time the toxicity of PD in human RBCs as well as its underlying mechanism for the hemolysis and eryptosis/erythroptosis.

Physiologically aged red blood cells undergo erythrophagocytosis in vivo but not in vitro

BACKGROUND

The lifespan of red blood cells is terminated when macrophages remove senescent red blood cells by erythrophagocytosis. This puts macrophages at the center of systemic iron recycling in addition to their functions in tissue remodeling and innate immunity. Thus far, erythrophagocytosis has been studied by evaluating phagocytosis of erythrocytes that were damaged to mimic senescence. These studies have demonstrated that acquisition of some specific individual senescence markers can trigger erythrophagocytosis by macrophages, but we hypothesized that the mechanism of erythrophagocytosis of such damaged erythrocytes might differ from erythrophagocytosis of physiologically aged erythrocytes.

DESIGN AND METHODS

To test this hypothesis we generated an erythrocyte population highly enriched in senescent erythrocytes by a hypertransfusion procedure in mice. Various erythrocyte-aging signals were analyzed and erythrophagocytosis was evaluated in vivo and in vitro.

RESULTS

The large cohort of senescent erythrocytes from hypertransfused mice carried numerous aging signals identical to those of senescent erythrocytes from control mice. Phagocytosis of fluorescently-labeled erythrocytes from hypertransfused mice injected into untreated mice was much higher than phagocytosis of labeled erythrocytes from control mice. However, neither erythrocytes from hypertransfused mice, nor those from control mice were phagocytosed in vitro by primary macrophage cultures, even though these cultures were able to phagocytose oxidatively damaged erythrocytes.

CONCLUSIONS

The large senescent erythrocyte population found in hypertransfused mice mimics physiologically aged erythrocytes. For effective erythrophagocytosis of these senescent erythrocytes, macrophages depend on some features of the intact phagocytosing tissue for support.

Single-colour flow cytometric assay to determine NK cell-mediated cytotoxicity and viability against non-adherent human tumor cells

A flow cytometry-based cytotoxicity (FCC) assay was developed using a single fluorophore, calcein-acetoxymethyl diacetylester (calcein-AM), to measure NK cell-mediated cytotoxicity. Non-adherent human K562 and U937 target cells were individually labelled with calcein-AM and co-incubated with effector NK cells to measure calcein loss, and therefore calculate target cell cytotoxicity. This FCC assay also provided a measure of sample viability. Notably, cell viability measured by traditional calcein/7-amino-actinomycin D (7-AAD) double labelling and Trypan Blue methods were comparable to the viability calculated using calcein-loss FCC. This FCC assay may also be used with various effector and target cell types and as a multi-parameter tool to measure viability and immunophenotype cells for tissue engineering purposes.

Integrin-associated protein (CD47) is a putative mediator for soluble fibrinogen interaction with human red blood cells membrane

Fibrinogen is a multifunctional plasma protein that plays a crucial role in several biological processes. Elevated fibrinogen induces erythrocyte hyperaggregation, suggesting an interaction between this protein and red blood cells (RBCs). Several studies support the concept that fibrinogen interacts with RBC membrane and this binding, due to specific and non-specific mechanisms, may be a trigger to RBC hyperaggregation in inflammation. The main goals of our work were to prove that human RBCs are able to specifically bind soluble fibrinogen, and identify membrane molecular targets that could be involved in this process. RBCs were first isolated from blood of healthy individuals and then separated in different age fractions by discontinuous Percoll gradients. After isolation RBC samples were incubated with human soluble fibrinogen and/or with a blocking antibody against CD47 followed by fluorescence confocal microscopy, flow cytometry acquisitions and zeta potential measurements. Our data show that soluble fibrinogen interacts with the human RBC membrane in an age-dependent manner, with younger RBCs interacting more with soluble fibrinogen than the older cells. Importantly, this interaction is abrogated in the presence of a specific antibody against CD47. Our results support a specific and age-dependent interaction of soluble fibrinogen with human RBC membrane; additionally we present CD47 as a putative mediator in this process. This interaction may contribute to RBC hyperaggregation in inflammation.

Distribution and shedding of the membrane phosphatidylserine during maturation and aging of erythroid cells

Maturation and aging of erythroid cells are accompanied by extensive remodeling of the membrane and a marked decrease in cell size, processes that are mediated by externalization and shedding of phosphatidylserine (PS). In the present study, we investigated the redistribution of PS in the plasma membrane of erythroid precursors during their maturation and of mature RBCs during senescence, and the involvement of changes in calcium (Ca)-flux in these processes. Maturation was studied by analyzing normal human bone marrow cells as well as cultured human normal erythroid precursors induced by erythropoietin and murine erythroleukemia cells induced by hexamethylene-bisacetamide. Senescence was studied in normal human peripheral RBCs following density fractionation. PS and Ca were determined by flow cytometry using annexin-V and Flu-3, respectively. The outer, inner and shed PS were quantified by a novel two-step binding inhibitory assay. The results indicate a bi-phasic modulation of intracellular Ca and PS externalization/shedding; both of which decreased during maturation and increased during aging. The role of intracellular Ca in PS externalization/shedding was demonstrated by modulating intracellular Ca: Ca was decreased by incubating the cells with an ion chelator (EDTA) or with decreasing concentrations of Ca, whereas treatment with the ionophore A23187 elevated intracellular Ca. The results showed that low Ca resulted in decreased outer and shed PS, whereas high Ca had the opposite effect. The results suggest that PS externalization and shedding are mediated by increased cellular Ca-flux, and that they play an important role in erythroid maturation and RBC senescence.

Multiphoton imaging of the functioning kidney

Translating discoveries made in isolated renal cells and tubules to the in vivo situation requires the assessment of cellular function in intact live organs. Multiphoton imaging is a form of fluorescence microscopy that is ideally suited to working with whole tissues and organs, but adequately loading cells with fluorescence dyes in vivo remains a challenge. We found that recirculation of fluorescence dyes in the rat isolated perfused kidney (IPK) resulted in levels of intracellular loading that would be difficult to achieve in vivo. This technique allowed the imaging of tubular cell structure and function with multiphoton microscopy in an intact, functioning organ. We used this approach to follow processes in real time, including (1) relative rates of reactive oxygen species (ROS) production in different tubule types, (2) filtration and tubular uptake of low-molecular-weight dextrans and proteins, and (3) the effects of ischemia-reperfusion injury on mitochondrial function and cell structure. This study demonstrates that multiphoton microscopy of the isolated perfused kidney is a powerful technique for detailed imaging of cell structure and function in an intact organ.

Fluoride-induced death of rat erythrocytes in vitro

Although fluoride (F) in low concentrations is essential for teeth and bone development, its excessive consumption causes numerous deleterious abnormalities in cellular metabolism and physiology often leading to cell death. The present study was performed to establish the toxic F effects inducing the death of rat erythrocytes in vitro. The cells were cultured in the presence of 0.5-16 mM NaF for 1, 5 and 24 h. The progression of erythrocyte death was monitored by cell viability (calcein assay), membrane integrity (hemolysis assay), alterations in the cell morphology (light microscopy) and size (flow cytometry forward scatter), plasma membrane scrambling (annexin V binding). To elucidate the molecular mechanisms underlying F-induced cell death, the cytosolic Ca2+ activity (Fluo-3 fluorescence) and ceramide formation (binding of FITC-labeled antibodies) were determined. Exposure of the rat erythrocytes to NaF considerably suppressed their viability and caused partial cell hemolysis within 24 h. The cells underwent dramatic morphological alterations resulted in appearance of shrunken echinocytes after 1h and swollen spherocytes within 24 h. The development of NaF-induced erythrocyte death was accompanied by progressive PS externalization at the outer cell membrane, ∼45% of the cells were annexin V-positive in response to 16 mM NaF within 24 h with a small cell population exhibiting necrotic features. The cell death was preceded by considerable accumulation of the free cytosolic Ca2+, with statistically significant increase in the number of Fluo-3-positive erythrocytes observed as early as during 1-h incubation with 0.5 mM NaF. NaF also induced moderate ceramide formation. Overall, exposure of the rat erythrocytes to NaF triggers rapid progression of their death in a dose- and time-dependent manner, with appearance of apoptotic cells after 1 and 5 h and transition to necrosis within 24 h. An increase in intracellular [Ca2+] appears to be crucial mechanism implicated in development of NaF-induced apoptosis in rat erythrocytes.

A cytometric study of the red blood cells in Gaucher disease reveals their abnormal shape that may be involved in increased erythrophagocytosis

BACKGROUND

Gaucher disease is a sphingolipidosis caused by a deficiency of the enzyme glucocerebrosidase. Macrophages transform into pathogenic Gaucher cells following the phagocytosis of red blood cells (RBCs) and subsequent accumulation of glucosylceramide. Enhanced erythrophagocytosis is one feature of the disease indicating abnormal macrophage-RBC interactions. We hypothesized that the erythrophagocytosis observed in Gaucher disease may be at least partly due to abnormalities in the RBCs themselves.

METHODS

To investigate this hypothesis, we used flow cytometry FSC/SSC to study RBCs sampled from seven patients with Gaucher disease in terms of their shape and the expression of markers of senescence and phagocytosis. Cells from two of the seven patients were evaluated before and 9 months after the start of enzyme-replacement therapy.

RESULTS

Untreated patients were found to have abnormal flow-cytometry profiles suggesting an alteration of Gaucher RBC morphology. Scanning electron microscopy confirmed this finding by revealing many abnormally shaped RBCs. Whereas there was no evidence of desialylation of membrane glycoconjugates or phosphatidylserine exposure, RBC viability (calcein-AM test) and CD47 expression were reduced. These anomalies found in RBCs sampled from two patients before treatment, were no longer present after a 9 month-long enzyme-replacement therapy.

CONCLUSIONS

We report on previously overlooked alterations of Gaucher RBCs that may facilitate erythrophagocytosis in untreated patients. Their potential role in the anemia, the excess of aggregation and rheological anomalies associated with Gaucher disease must now be addressed. RBC anomalies may take part in the abnormal crosstalk between RBCs and macrophages leading to the accumulation of Gaucher cells.

Thin films of functionalized multiwalled carbon nanotubes as suitable scaffold materials for stem cells proliferation and bone formation

In the field of regenerative medicine, human mesenchymal stem cells envisage extremely promising applications, due to their ability to differentiate into a wide range of connective tissue species on the basis of the substrate on which they grow. For the first time ever reported, we investigated the effects of a thin film of pegylated multiwalled carbon nanotubes spray dried onto preheated coverslips in terms of their ability to influence human mesenchymal stem cells' proliferation, morphology, and final differentiation into osteoblasts. Results clearly indicated that the homogeneous layer of functionalized nanotubes did not show any cytotoxicity and accelerated cell differentiation to a higher extent than carboxylated nanotubes or uncoated coverslips, by creating a more viable microenvironment for stem cells. Interestingly, cell differentiation occurred even in the absence of additional biochemical inducing agents, as evidenced by multiple independent criteria at the transcriptional, protein expression, and functional levels. Taken together, these findings suggest that functionalized carbon nanotubes represent a suitable scaffold toward a very selective differentiation into bone.

The antioxidant effect of erythropoietin on thalassemic blood cells

Because of its stimulating effect on RBC production, erythropoietin (Epo) is used to treat anemia, for example, in patients on dialysis or on chemotherapy. In β-thalassemia, where Epo levels are low relative to the degree of anemia, Epo treatment improves the anemia state. Since RBC and platelets of these patients are under oxidative stress, which may be involved in anemia and thromboembolic complications, we investigated Epo as an antioxidant. Using flow-cytometry technology, we found that in vitro treatment with Epo of blood cells from these patients increased their glutathione content and reduced their reactive oxygen species, membrane lipid peroxides, and external phosphatidylserine. This resulted in reduced susceptibility of RBC to undergo hemolysis and phagocytosis. Injection of Epo into heterozygous (Hbb(th3/+)) β-thalassemic mice reduced the oxidative markers within 3 hours. Our results suggest that, in addition to stimulating RBC and fetal hemoglobin production, Epo might alleviate symptoms of hemolytic anemias as an antioxidant.

Mechanism of polymer-induced hemolysis: nanosized pore formation and osmotic lysis

Hemolysis induced by antimicrobial polymers was examined to gain an understanding of the mechanism of polymer toxicity to human cells. A series of cationic amphiphilic methacrylate random copolymers containing primary ammonium groups as the cationic functionality and either butyl or methyl groups as hydrophobic side chains have been prepared by radical copolymerization. Polymers with 0-47 mol % methyl groups in the side chains, relative to the total number of monomeric units, showed antimicrobial activity but no hemolysis. The polymers with 65 mol % methyl groups or 27 mol % butyl groups displayed both antimicrobial and hemolytic activity. These polymers induced leakage of the fluorescent dye calcein trapped in human red blood cells (RBCs), exhibiting the same dose-response curves as for hemoglobin leakage. The percentage of disappeared RBCs after hemolysis increased in direct proportion to the hemolysis percentage, indicating complete release of hemoglobin from fractions of RBCs (all-or-none leakage) rather than partial release from all cells (graded leakage). An osmoprotection assay using poly(ethylene glycol)s (PEGs) as osmolytes indicated that the PEGs with MW > 600 provided protection against hemolysis while low molecular weight PEGs and sucrose had no significant effect on the hemolytic activity of polymers. Accordingly, we propose the mechanism of polymer-induced hemolysis is that the polymers produce nanosized pores in the cell membranes of RBCs, causing an influx of small solutes into the cells and leading to colloid-osmotic lysis.

Active caspases-8 and -3 in circulating human erythrocytes purified on immobilized annexin-V: a cytometric demonstration

Human red blood cells (RBCs) have a normal life span of 120 days in vivo and might be primed in vitro to die in response to apoptotic stimuli through a caspase-independent pathway. It is well known that, in vivo, aging RBCs externalize phosphatidylserine residues but is unknown whether these cells express active caspases at this stage. We isolated RBCs expressing phosphatidylserine on their surface from human blood by applying an original method of affinity chromatography using annexin-V fixed on gelatin or on magnetic beads. The isolated RBCs were then analyzed by flow cytometry for morphological changes (dot-plot forward scatter versus side scatter), phosphatidylserine externalization (annexin-V test), cell viability (calcein-AM test), and caspase activities using fluorescent substrates specific for caspases-3 and -8. In addition, cells were systematically visualized using phase contrast, fluorescence, and confocal microscopy. We found that the population of RBCs fixed on annexin-V is a mixture of discocytes and shrunken cells. This annexin-V-positive population showed a dramatic loss of viability based on esterase activity determination (calcein-AM test). Moreover, we demonstrated that circulating RBCs express both active caspases-8 and -3 in half of the annexin-V-positive cells. All of these results were confirmed by phase contrast, fluorescence, and confocal microscopy. Our results demonstrate active caspases in RBC isolated from blood suggesting that caspases may participate in the regulation of in vivo RBC half-life. This finding open the door to fruitful investigations in the field of RBC pathology.

Differential stimulation of monocytic cells results in distinct populations of microparticles

BACKGROUND

Microparticles (MPs), small vesicles shed from stimulated cells, permit cross-talk between cells within a particular environment. Their composition is thought to reflect their cell of origin, and differs according to whether they are produced by stimulation or by apoptosis. Whether MP properties vary according to stimulus is not yet known.

METHODS

We studied the characteristics of MPs produced from monocytic THP-1 cells upon stimulation with lipopolysaccharide or a soluble P-selectin chimera, using proteomics, flow cytometry, western blotting, and electron microscopy.

RESULTS

Utilizing a novel criterion of calcein-AM staining to define MPs, we found that MP populations were similar with respect to size, presence and organization of cytoskeleton, and expression of certain antigens. The MPs shared the same level of procoagulant activity. We found that MPs also have distinct characteristics, depending on stimuli. These include differences in phosphatidylserine expression and expression of proteins from specific subcellular locations such as the mitochondria, and of unique antigens such as leukocyte-associated immunoglobin-like-receptor (LAIR)-1, which was found only upon stimulation with the soluble P-selectin chimera.

CONCLUSION

We found that the properties of MPs depend on the stimulus that produced them. This supports the concept that monocytic MPs differentially modulate thrombosis, inflammation and immune regulation according to stimulus.

A microwell array device capable of measuring single-cell oxygen consumption rates

Due to interest in cell population heterogeneity, the development of new technology and methodologies for studying single cells has dramatically increased in recent years. The ideal single cell measurement system would be high throughput for statistical relevance, would measure the most important cellular parameters, and minimize disruption of normal cell function. We have developed a microwell array device capable of measuring single cell oxygen consumption rates (OCR). This OCR device is able to diffusionally isolate single cells and enables the quantitative measurement of oxygen consumed by a single cell with fmol/min resolution in a non-invasive and relatively high throughput manner. A glass microwell array format containing fixed luminescent sensors allows for future incorporation of additional cellular parameter sensing capabilities. To demonstrate the utility of the OCR device, we determined the oxygen consumption rates of a small group of single cells (12 to 18) for three different cells lines: murine macrophage cell line RAW264.7, human epithelial lung cancer cell line A549, and human Barrett's esophagus cell line CP-D.

Pathogenesis of osteoarthritis: chondrocyte replicative senescence or apoptosis?

BACKGROUND

The aim of this study was to investigate by flow cytometry cellular viability and apoptosis of human chondrocytes isolated from osteoarthritic cartilage and to correlate replicative senescence with apoptosis of these cells.

METHODS

To understand the mechanisms underlying the process of cell death in cartilage destruction, we investigated by flow cytometry cellular viability (Cell viability calcein-AM assay) and apoptosis (Light scattering properties of chondrocytes, study of chondrocyte death using Annexin-V-FITC and propidium iodide double-labeling, caspase-3 activity determination) of human chondrocytes isolated from osteoarthritic and nonosteoarthritic cartilage. Senescent cells were characterized using the senescence-associated-beta-galactosidase marker (SA-beta-Gal marker) by staining with chromogenic substrate (X-Gal) to produce blue coloration of SA-beta-Gal-positive cells and microscopy analysis.

RESULTS

The results we obtained show that between 25 and 40% of chondrocytes were in apoptosis and all of them were SA-beta-Gal-positive.

CONCLUSIONS

These results demonstrate that the death of osteoarthritic chondrocytes is an apoptotic phenomenon which is preceded by an accelerated mechanism of replicative senescence.

Viability analysis and apoptosis induction of breast cancer cells in a microfluidic device: effect of cytostatic drugs

Breast cancer is the leading cause of cancer deaths among non-smoking women worldwide. At the moment the treatment regime is such that patients receive different chemotherapeutic and/or hormonal treatments dependent on the hormone receptor status, the menopausal status and age. However, in vitro sensitivity testing of tumor biopsies could rationalize and improve the choice of chemo- and hormone therapy. Lab-on-a-Chip devices, using microfluidic techniques, make detailed cellular analysis possible using fewer cells, enabling working with a patients' own cells and performing chemo- and hormone sensitivity testing in an ex vivo setting. This article describes the development of two microfluidic devices made in poly(dimethylsiloxane) (PDMS) to validate the cell culture properties and analyze the chemosensitivity of MCF-7 cells (estrogen receptor positive human breast cancer cells) in response to the drug staurosporine (SSP). In both cases, cell viability was assessed using the life-stain Calcein-AM (CAAM) and the death dye propidium iodide (PI). MCF-7 cells could be statically cultured for up to 7 days in the microfluidic chip. A 30 min flow with SSP and a subsequent 24 h static incubation in the incubator induced apoptosis in MCF-7 cells, as shown by a disappearance of the aggregate-like morphology, a decrease in CAAM staining and an increase in PI staining. This work provides valuable leads to develop a microfluidic chip to test the chemosensitivity of tumor cells in response to therapeutics and in this way improve cancer treatment towards personalized medicine.

Calcium oxalate crystals in fetal bovine serum: implications for cell culture, phagocytosis and biomineralization studies in vitro

Cell culture methods and models are key investigative tools for cell and molecular biology studies. Fetal bovine serum (FBS) is commonly used as an additive during cell culture since its constituents promote cell survival, proliferation and differentiation. Here we report that commercially available FBS from different major suppliers consistently contain precipitated, calcium oxalate crystals-either in the monohydrate (COM) or dihydrate (COD) form. Mineral structure and phase identification of the crystals were determined by X-ray diffraction, chemical composition by energy-dispersive X-ray microanalysis, and imaging and measurement of crystal growth steps by atomic force microscopy-all identified and confirmed crystallographic parameters for COM and COD. Proteins binding to the crystals were identified by immunoblotting, revealing the presence of osteopontin and fetuin-A (alpha(2)HS-glycoprotein)--known regulators of crystal growth found in serum. Macrophage cell cultures exposed to calcium oxalate crystals showed internalization of the crystals by phagocytosis in a process that induced disruption of cell-cell adhesion, release of reactive oxygen species and membrane damage, events that may be linked to the release of inflammatory cytokines by these cells into the culture media. In conclusion, calcium oxalate crystals found in commercially available FBS are toxic to cells, and their presence may confound results from in vitro studies where, amongst others, phagocytosis, biomineralization, renal cell and molecular biology, and drug and biomaterial testing are being examined.

An automatic and quantitative on-chip cell migration assay using self-assembled monolayers combined with real-time cellular impedance sensing

Cell migration is crucial in many physiological and pathological processes including embryonic development, immune response and cancer metastasis. Traditional methods for cell migration detection such as wound healing assay usually involve physical scraping of a cell monolayer followed by an optical observation of cell movement. However, these methods require hand-operation with low repeatability. Moreover, it's a qualitative observation not a quantitative measurement, which is hard to scale up to a high-throughput manner. In this article, a novel and reliable on-chip cell migration detection method integrating surface chemical modification of gold electrodes using self-assembled monolayers (SAMs) and real-time cellular impedance sensing is presented. The SAMs are used to inhibit cell adherence forming an area devoid of cells, which could effectively mimic wounds in a cell monolayer. After a DC electrical signal was applied, the SAMs were desorbed from the electrodes and cells started to migrate. The process of cell migration was monitored by real-time impedance sensing. This demonstrates the first occurrence of integrating cellular impedance sensing and wound-forming with SAMs, which makes cell migration assay being real-time, quantitative and fully automatic. We believe this method could be used for high-throughput anti-migratory drug screening and drug discovery.

Flow cytometry measurement of the labile iron pool in human hematopoietic cells

Iron is important for many biological processes, and its deficiency or excess is involved in pathological conditions. Although most iron is firmly bound (e.g., in hemoglobin), some, the labile iron pool (LIP), is bound to low-affinity ligands. The level of LIP is regulated to meet the cell's requirements for iron but prevent excess. We describe herein a multiparameter flow cytometry procedure for measuring LIP in various human hematopoietic cells. Peripheral blood and bone marrow (BM) cells were loaded with calcein-AM, washed, and then incubated with or without the high-affinity iron-chelator Deferiprone (L1). Specific cell subpopulations were identified based on side-light scattering and expression of surface antigens. LIP was determined based on the ability of L1 to bind and remove iron from calcein and thereby increase the fluorescence emitted by the cells. Blood cells differ in their LIP content in the order monocytes > PMN > RBC > lymphocytes. Analysis of BM cells indicated a similar tendency among precursors of the different lineages. The results also showed that among myeloid precursors, LIP increases along cell maturation. Flow cytometry might be useful for evaluating LIP in various diseases and for studying the efficacy of iron-chelators.

Nouveaux critères d’évaluation de la viabilité des hématies destinées à la transfusion

In light of recent results on the mechanism of programmed cell death of human red blood cells (RBC), the aim of the present study was to solve the enigma of the rapid clearance of transfused RBCs.

MATERIALS AND METHODS

We describe new criteria of RBC viability founded on the use of flow cytometry. They were applied, in association with the classical ones: ATP and hemolysis measurements, to RBCs stored in SAGM medium for 42 days.

RESULTS AND CONCLUSIONS

Application of an original method of flow cytometric quantitation of in vitro erythrophagocytosis showed that an important proportion of stored RBCs were phagocytized although the following classical signals for phagocytosis were absent, i.e.: desialylation, phosphatidylserine exposure in the outer leaflet of the RBC membrane, loss of CD47 receptor, an antiphagocytosis signal. In addition, ATP was still present and hemolysis was very low. This enigma was solved by the use of scanning electron microscopy, which showed the disappearance of discocytes and the presence of an important proportion of spheroechinocytes, which are the phagocytable forms of RBCs. The mechanism of this dramatic morphological transformation remains to be elucidated.

Cordycepin induced eryptosis in mouse erythrocytes through a Ca2+-dependent pathway without caspase-3 activation

Cordyceps sinensis is a prized traditional Chinese medicine and its major component cordycepin is found to have anti-leukemia activities. However, its cytotoxicity in erythrocytes was unclear. To examine the effect of cordycepin on the induction of eryptosis (an apoptosis-like process in enucleated erythrocytes), flow cytometric assays based on membrane integrity and asymmetry were employed. For comparison, analyses were performed in parallel with two other anti-leukemia agents, indirubin 3'-monoxime (IDM) and As2O3. We found that at the IC50 against leukemia HL-60, cordycepin elicited eryptosis while IDM and As2O3 showed no erythrotoxicity in mouse erythrocytes. Mechanistically, cordycepin increased the [Ca2+]i and activated mu-calpain protease in a dose-dependent manner. Yet, no caspase-3 activation was observed in the cordycepin-treated erythrocytes. When extracellular Ca2+ was depleted, both the cordycepin-induced eryptosis and mu-calpain cleavage were suppressed. Our study therefore demonstrated for the first time that cordycepin induces eryptosis through a calcium-dependent pathway in the absence of mitochondria and caspase-3 activation.

A cell nanoinjector based on carbon nanotubes

Technologies for introducing molecules into living cells are vital for probing the physical properties and biochemical interactions that govern the cell's behavior. Here, we report the development of a nanoscale cell injection system (termed the nanoinjector) that uses carbon nanotubes to deliver cargo into cells. A single multiwalled carbon nanotube attached to an atomic force microscope (AFM) tip was functionalized with cargo via a disulfide-based linker. Penetration of cell membranes with this "nanoneedle" was controlled by the AFM. The following reductive cleavage of the disulfide bonds within the cell's interior resulted in the release of cargo inside the cells, after which the nanoneedle was retracted by AFM control. The capability of the nanoinjector was demonstrated by injection of protein-coated quantum dots into live human cells. Single-particle tracking was used to characterize the diffusion dynamics of injected quantum dots in the cytosol. This technique causes no discernible membrane or cell damage, and can deliver a discrete number of molecules to the cell's interior without the requirement of a carrier solvent.