Abuse liability assessment of the JUUL system in two nicotine concentrations compared to combustible cigarette, nicotine gum and comparator electronic nicotine delivery system.

BACKGROUND: To assess the abuse liability of the JUUL System (JS) in 5.0 % (59 mg/mL) and 3.0 % (35 mg/mL) nicotine concentrations. METHODS: Adult smokers (N = 146; 45.9 % female; mean age = 41.29 years) were randomized to one of four study flavor arms and then to a within-subjects cross-over sequence for five test product categories: (1) JS 5.0 % nicotine concentration; (2) JS 3.0 % nicotine; (3) usual brand (UB) cigarette; (4) 4 mg mint nicotine gum; (5) comparator ENDS (VUSE Alto 5.0 % nicotine). Products were tested by ad libitum use (5 min for ENDS and cigarette; 30 min for gum); nicotine pharmacokinetic (PK) parameters and subjective effects were assessed following use. RESULTS: Maximum plasma nicotine concentration (Cmax-BL), rate of plasma nicotine rise and total nicotine exposure (AUC0-60-BL) of UB cigarette were significantly greater than all other test products. The comparator ENDS was significantly greater than 5.0 % and 3.0 % JS and nicotine gum on Cmax-BL, rate of plasma nicotine rise, and AUC0-60-BL; Cmax-BL of JS 5.0 % was significantly greater than JS 3.0 % and nicotine gum. Product liking and satisfying effects were significantly highest for the UB cigarette; JS products and comparator ENDS did not significantly differ and were rated higher than nicotine gum on most subjective measures. CONCLUSIONS: These results suggest that the abuse liability of both 5.0 % and 3.0 % JS is: (1) substantially lower than UB cigarette; (2) somewhat lower than comparator ENDS; and (3) higher than nicotine gum. Additionally, the abuse liability of JS 5.0 % is somewhat higher than JS 3.0 %.

Optimization and testing of dried antibody tube: The EuroFlow LST and PIDOT tubes as examples.

Within EuroFlow, we recently developed screening tubes for hematological malignancies and immune deficiencies. Pipetting of antibodies for such 8-color 12-marker tubes however is time-consuming and prone to operational mistakes. We therefore evaluated dried formats of the lymphocytosis screening tube (LST) and of the primary immune deficiency orientation tube (PIDOT). Both tubes were evaluated on normal and/or on patient samples, comparing the mean fluorescence intensity of specific lymphocyte populations. Our data show that the dried tubes and liquid counterparts give highly comparable staining results, particularly when analyzed in multidimensional plots. In addition, the use of dried tubes may result in a reduced staining variability between different samples and thereby contributes to the generation of more robust data. Therefore, by using ready-to-use reagents in a dried single test tube format, the laboratory efficiency and quality will be improved.

Phosphorylation of NEUROG3 Links Endocrine Differentiation to the Cell Cycle in Pancreatic Progenitors.

During pancreatic development, proliferating pancreatic progenitors activate the proendocrine transcription factor neurogenin 3 (NEUROG3), exit the cell cycle, and differentiate into islet cells. The mechanisms that direct robust NEUROG3 expression within a subset of progenitor cells control the size of the endocrine population. Here we demonstrate that NEUROG3 is phosphorylated within the nucleus on serine 183, which catalyzes its hyperphosphorylation and proteosomal degradation. During progression through the progenitor cell cycle, NEUROG3 phosphorylation is driven by the actions of cyclin-dependent kinases 2 and 4/6 at G1/S cell-cycle checkpoint. Using models of mouse and human pancreas development, we show that lengthening of the G1 phase of the pancreatic progenitor cell cycle is essential for proper induction of NEUROG3 and initiation of endocrine cell differentiation. In sum, these studies demonstrate that progenitor cell-cycle G1 lengthening, through its actions on stabilization of NEUROG3, is an essential variable in normal endocrine cell genesis.

PEGylated IL-10 Activates Kupffer Cells to Control Hypercholesterolemia.

Interleukin-10 (IL-10) is a multifunctional cytokine that exerts potent context specific immunostimulatory and immunosuppressive effects. We have investigated the mechanism by which PEGylated rIL-10 regulates plasma cholesterol in mice and humans. In agreement with previous work on rIL-10, we report that PEGylated rIL-10 harnesses the myeloid immune system to control total plasma cholesterol levels. We have discovered that PEG-rMuIL-10's dramatic lowering of plasma cholesterol is dependent on phagocytotic cells. In particular, PEG-rHuIL-10 enhances cholesterol uptake by Kupffer cells. In addition, removal of phagocytotic cells dramatically increases plasma cholesterol levels, suggesting for the first time that immunological cells are implicitly involved in regulating total cholesterol levels. These data suggest that treatment with PEG-rIL-10 potentiates endogenous cholesterol regulating cell populations not currently targeted by standard of care therapeutics. Furthermore, we show that IL-10's increase of Kupffer cell cholesterol phagocytosis is concomitant with decreases in liver cholesterol and triglycerides. This leads to the reversal of early periportal liver fibrosis and facilitates the restoration of liver health. These data recommend PEG-rIL-10 for evaluation in the treatment of fatty liver disease and preventing its progression to non-alcoholic steatohepatitis. In direct confirmation of our in vivo findings in the treatment of hypercholesterolemic mice with PEG-rMuIL-10, we report that treatment of hypercholesterolemic cancer patients with PEG-rHuIL-10 lowers total plasma cholesterol by up to 50%. Taken together these data suggest that PEG-rIL-10's cholesterol regulating biology is consistent between mice and humans.

Simultaneous flow cytometric analysis of IFN-γ and CD4 mRNA and protein expression kinetics in human peripheral blood mononuclear cells during activation.

The application of fluorescently-labeled antibodies for flow cytometric identification and characterization of specific cell types within heterogeneous populations by their protein expression profile is well established. While detection of proteins is informative, concomitant transcript analysis in the same cells would provide a more complete and comprehensive view of intracellular signaling events. We recently reported on the efficient detection of RNA in suspension cells for flow cytometric analysis. The improved RNA flow cytometry procedure described here allows for the specific labeling of multiple RNA species, and is compatible with antibody-based targeting of extracellular and intracellular antigens for multiplexing purposes. To show proof of concept, human peripheral blood mononuclear cells were stimulated with phorbol 12-myristate 13-acetate and ionomycin for a maximum of 5 h, during which their CD4 and interferon-gamma (IFN-γ) transcript and protein levels were monitored. Substantial and increasing numbers of IFN-γ mRNA+ cells were detected within 30 min after initiation of induction, while IFN-γ protein+ cells could only be discerned at 1 h and beyond. Surprisingly, resting lymphocytes contained less CD4 mRNA but more of the protein per cell compared with monocytes, revealing a difference in the relationship of transcript and protein levels in these two cell types. We additionally applied monensin, which is commonly used to block cytokine secretion, and found that IFN-γ mRNA can still be analyzed consistently using the improved RNA flow cytometry staining method. Notably, a subset of IFN-γ mRNA(-)/protein+ cells that were not observed in the absence of monensin became apparent at the 5-h mark. This subset probably represents cells that have accumulated IFN-γ protein, but no longer transcribe mRNA. Collectively, the results described here exemplify how the improved RNA flow cytometry labeling procedure can be applied to simultaneously assess mRNA and protein dynamics to gain insight into the regulation of gene transcription and translation in individual cells.

Directed differentiation of human pluripotent stem cells along the pancreatic endocrine lineage.

Many research groups are engaged in using human pluripotent stem cells (hPSCs) to generate surrogate pancreatic ß-cells for transplantation into diabetic patients. However, to our knowledge, there is no report on the successful generation of glucose-responsive insulin-producing ß-cells from hPSCs in vitro. Below, we outline a method that is based on published protocols as well as our own experience by which one can differentiate hPSCs along the pancreatic lineage to generate insulin-producing ß-cell-like cells. The protocol, which spans five distinct stages, is an attempt to recapitulate the derivation of pancreatic ß-cells in vitro as they form in the developing embryo. We included details on materials and techniques, suggest ways to customize it to your hPSC line of choice, added notes on how to monitor and analyze the cells during differentiation, and indicate what results can be expected.

Proteomic analysis of stem cell differentiation and early development.

Genomics methodologies have advanced to the extent that it is now possible to interrogate the gene expression in a single cell but proteomics has traditionally lagged behind and required much greater cellular input and was not quantitative. Coupling protein with gene expression data is essential for understanding how cell behavior is regulated. Advances primarily in mass spectrometry have, however, greatly improved the sensitivity of proteomics methods over the last decade and the outcome of proteomic analyses can now also be quantified. Nevertheless, it is still difficult to obtain sufficient tissue from staged mammalian embryos to combine proteomic and genomic analyses. Recent developments in pluripotent stem cell biology have in part addressed this issue by providing surrogate scalable cell systems in which early developmental events can be modeled. Here we present an overview of current proteomics methodologies and the kind of information this can provide on the biology of human and mouse pluripotent stem cells.

Chromatin insulator elements block transgene silencing in engineered human embryonic stem cell lines at a defined chromosome 13 locus.

Lineage reporters of human embryonic stem cell (hESC) lines are useful for differentiation studies and drug screening. Previously, we created reporter lines driven by an elongation factor 1 alpha (EF1α) promoter at a chromosome 13q32.3 locus in the hESC line WA09 and an abnormal hESC line BG01V in a site-specific manner. Expression of reporters in these lines was maintained in long-term culture at undifferentiated state. However, when these cells were differentiated into specific lineages, reduction in reporter expression was observed, indicating transgene silencing. To develop an efficient and reliable genetic engineering strategy in hESCs, we used chromatin insulator elements to flank single-copy transgenes and integrated the combined expression constructs via PhiC31/R4 integrase-mediated recombination technology to the chromosome 13 locus precisely. Two copies of cHS4 double-insulator sequences were placed adjacent to both 5' and 3' of the promoter reporter constructs. The green fluorescent protein (GFP) gene was driven by EF1α or CMV early enhancer/chicken ß actin (CAG) promoter. In the engineered hESC lines, for both insulated CAG-GFP and EF1α-GFP, constitutive expression at the chromosome 13 locus was maintained during prolonged culture and in directed differentiation assays toward diverse types of neurons, pancreatic endoderm, and mesodermal progeny. In particular, described here is the first normal hESC fluorescent reporter line that robustly expresses GFP in both the undifferentiated state and throughout dopaminergic lineage differentiation. The dual strategy of utilizing insulator sequences and integration at the constitutive chromosome 13 locus ensures appropriate transgene expression. This is a valuable tool for lineage development study, gain- and loss-of-function experiments, and human disease modeling using hESCs.

Differentiation of human embryonic stem cells into pancreatic endoderm in patterned size-controlled clusters.

Pancreatic ß-cells function optimally when clustered in islet-like structures. However, nutrient and oxygen deprivation limits the viability of cells at the core of excessively large clusters. Hence, production of functional ß-cells from human embryonic stem cells (hESCs) for patients with diabetes would benefit from the growth and differentiation of these cells in size-controlled aggregates. In this study, we controlled cluster size by seeding hESCs onto glass cover slips patterned by the covalent microcontact-printing of laminin in circular patches of 120 µm in diameter. These were used as substrates to grow and differentiate hESCs first into SOX17-positive/SOX7-negative definitive endoderm, after which many clusters released and formed uniformly sized three-dimensional clusters. Both released clusters and those that remained attached differentiated into HNF1ß-positive primitive gut tube-like cells with high efficiency. Further differentiation yielded pancreatic endoderm-like cells that co-expressed PDX1 and NKX6.1. Controlling aggregate size allows efficient production of uniformly-clustered pancreatic endocrine precursors for in vivo engraftment or further in vitro maturation.

Identification of cell surface proteins for antibody-based selection of human embryonic stem cell-derived cardiomyocytes.

The absence of identified cell surface proteins and corresponding antibodies to most differentiated derivatives of human embryonic stem cells (hESCs) has largely limited selection of specific cell types from mixed cell populations to genetic approaches. Here, we describe the use of mass spectrometry (MS)-based proteomics on cell membrane proteins isolated from hESCs that were differentiated into cardiomyocytes to identify candidate proteins for this particular lineage. Quantitative MS distinguished cardiomyocyte-specific plasma membrane proteins that were highly enriched or detected only in cardiomyocytes derived from hESCs and human fetal hearts compared with a heterogeneous pool of hESC-derived differentiated cells. For several candidates, cardiomyocyte-specific expression and cell surface localization were verified by conventional antibody-based methodologies. Using an antibody against elastin microfibril interfacer 2 (EMILIN2), we demonstrate that cardiomyocytes can be sorted from live cell populations. Besides showing that MS-based membrane proteomics is a powerful tool to identify candidate proteins that allow purification of specific cell lineages from heterogeneous populations, this approach generated a plasma membrane proteome profile suggesting signaling pathways that control cell behavior.

Derivation of insulin-producing cells from human embryonic stem cells.

The potential of pluripotent human cells, such as human embryonic stem cells (hESCs) and induced pluripotent stem (iPS) cells, to differentiate into any adult cell type makes them ideally suited for the generation of various somatic cells and tissues in vitro. This remarkable differentiation capacity permits analyzing aspects of human embryonic development in the laboratory, as well as generating specialized adult human cells for screening drugs, and for replacing tissues damaged by injury or degenerative diseases, such as diabetes. Understanding and controlling the fundamental processes that drive the differentiation of specialized cells are the keys to the eventual application of this technology to patients. In this review, we discuss the different protocols developed that are aimed at deriving beta-cells from hESCs. Despite many differences, successful strategies share a general adherence to the normal differentiation pathway through definitive endoderm. Mimicking normal pancreagenesis offers the best strategy for producing glucose-responsive insulin-producing cells in vitro for people with diabetes.

Phosphorylation dynamics during early differentiation of human embryonic stem cells.

Pluripotent stem cells self-renew indefinitely and possess characteristic protein-protein networks that remodel during differentiation. How this occurs is poorly understood. Using quantitative mass spectrometry, we analyzed the (phospho)proteome of human embryonic stem cells (hESCs) during differentiation induced by bone morphogenetic protein (BMP) and removal of hESC growth factors. Of 5222 proteins identified, 1399 were phosphorylated on 3067 residues. Approximately 50% of these phosphosites were regulated within 1 hr of differentiation induction, revealing a complex interplay of phosphorylation networks spanning different signaling pathways and kinase activities. Among the phosphorylated proteins was the pluripotency-associated protein SOX2, which was SUMOylated as a result of phosphorylation. Using the data to predict kinase-substrate relationships, we reconstructed the hESC kinome; CDK1/2 emerged as central in controlling self-renewal and lineage specification. The findings provide new insights into how hESCs exit the pluripotent state and present the hESC (phospho)proteome resource as a complement to existing pluripotency network databases.

A practical guide for the identification of membrane and plasma membrane proteins in human embryonic stem cells and human embryonal carcinoma cells.

The identification of (plasma) membrane proteins in cells can provide valuable insights into the regulation of their biological processes. Pluripotent cells such as human embryonic stem cells and embryonal carcinoma cells are capable of unlimited self-renewal and share many of the biological mechanisms that regulate proliferation and differentiation. The comparison of their membrane proteomes will help unravel the biological principles of pluripotency, and the identification of biomarker proteins in their plasma membranes is considered a crucial step to fully exploit pluripotent cells for therapeutic purposes. For these tasks, membrane proteomics is the method of choice, but as indicated by the scarce identification of membrane and plasma membrane proteins in global proteomic surveys it is not an easy task. In this minireview, we first describe the general challenges of membrane proteomics. We then review current sample preparation steps and discuss protocols that we found particularly beneficial for the identification of large numbers of (plasma) membrane proteins in human tumour- and embryo-derived stem cells. Our optimized assembled protocol led to the identification of a large number of membrane proteins. However, as the composition of cells and membranes is highly variable we still recommend adapting the sample preparation protocol for each individual system.

Feeder-free monolayer cultures of human embryonic stem cells express an epithelial plasma membrane protein profile.

Human embryonic stem cells (hESCs) are often cocultured on mitotically inactive fibroblast feeder cells to maintain their undifferentiated state. Under these growth conditions, hESCs form multilayered colonies of morphologically heterogeneous cells surrounded by flattened mesenchymal cells. In contrast, hESCs grown in feeder cell-conditioned medium on Matrigel instead tend to grow as monolayers with uniform morphology. Using mass spectrometry and immunofluorescence microscopy, we showed that hESCs under these conditions primarily express proteins belonging to epithelium-related cell-cell adhesion complexes, including adherens junctions, tight junctions, desmosomes, and gap junctions. This indicates that monolayers of hESCs cultured under feeder-free conditions retain a homogeneous epithelial phenotype similar to that of the upper central cell layer of colonies maintained on feeder cells. Notably, feeder-free hESCs also coexpressed vimentin, which is usually associated with mesenchyme, suggesting that these cells may have undergone epithelium-to-mesenchyme transitions, indicating differentiation. However, if grown on a "soft" substrate (Hydrogel), intracellular vimentin levels were substantially reduced. Moreover, when hESCs were transferred back to feeder cells, expression of vimentin was again absent from the epithelial cell population. These results imply that on tissue culture substrates, vimentin expression is most likely a stress-induced response, unrelated to differentiation. Disclosure of potential conflicts of interest is found at the end of this article.

Plasma membrane proteomics of human embryonic stem cells and human embryonal carcinoma cells.

Human embryonic stem cells (hESCs) are of immense interest in regenerative medicine as they can self-renew indefinitely and can give rise to any adult cell type. Human embryonal carcinoma cells (hECCs) are the malignant counterparts of hESCs found in testis tumors. hESCs that have acquired chromosomal abnormalities in culture are essentially indistinguishable from hECC. Direct comparison of karyotypically normal hESCs with hECCs could lead to understanding differences between their mechanisms of growth control and contribute to implementing safe therapeutic use of stem cells without the development of germ cell cancer. While several comparisons of hECCs and hESCs have been reported, their cell surface proteomes are largely unknown, partly because plasma membrane proteomics is still a major challenge. Here, we present a strategy for the identification of plasma membrane proteins that has been optimized for application to the relatively small numbers of stem cells normally available, and that does not require tedious cell fractionation. The method led to the identification of 237 and 219 specific plasma membrane proteins in the hESC line HUES-7 and the hECC line NT2/D1, respectively. In addition to known stemness-associated cell surface markers like ALP, CD9, and CTNNB, a large number of receptors, transporters, signal transducers, and cell-cell adhesion proteins were identified. Our study revealed that several Hedgehog and Wnt pathway members are differentially expressed in hESCs and hECCs including NPC1, FZD2, FZD6, FZD7, LRP6, and SEMA4D, which play a pivotal role in stem cell self-renewal and cancer growth. Various proteins encoded on chromosome 12p, duplicated in testicular cancer, were uniquely identified in hECCs. These included GAPDH, LDHB, YARS2, CLSTN3, CSDA, LRP6, NDUFA9, and NOL1, which are known to be upregulated in testicular cancer. Distinct HLA molecules were revealed on the surface of hESCs and hECCs, despite their low abundance. Results were compared with genomic and proteomic data sets reported previously for mouse ESCs, hECCs, and germ cell tumors. Our data provides a surface signature for HUES-7 and NT2/D1 cells and distinguishes normal hESCs from hECCs, helping explain their 'benign' versus 'malignant' nature.

Proteomics and human embryonic stem cells.

The derivation of human embryonic stem cells (hESCs) brought cell therapy-based regenerative medicine significantly closer to clinical application. However, expansion of undifferentiated cells and their directed differentiation in vitro have proven difficult to control. This is mainly because of a lack of knowledge of the intracellular signaling events that direct these complex processes. Additionally, extracellular factors, either secreted by feeder cells that support self-renewal and maintain pluripotency or present in serum supplementing proprietary culture media, that influence hESC behavior are largely unknown. Xeno-free media that effectively support long-term hESC self-renewal and differentiation to specific types of specialized cells are only slowly becoming available. Microarray-based transcriptome analyses have produced valuable gene expression profiles of hESCs and indicated changes in transcription that occur during differentiation. However, proteins are the actual effectors of these events and changes in their levels do not always match changes in their corresponding mRNA. Furthermore, information on posttranslational modifications that influence the activity of pivotal proteins is still largely missing. Over the years, mass spectrometry has experienced major breakthroughs in high-throughput identification of proteins and posttranslational modifications in cells under different conditions. Mass spectrometry-based proteomic techniques are being applied with increasing frequency to analyze hESCs, as well as media conditioned by feeder cells, and have generated proteome profiles that not only support, but also complement, existing microarray data. In this review, the various proteomic studies on hESCs and feeder cells are discussed. In a meta-analysis, comparison of published data sets distinguished 32 intracellular proteins and 16 plasma membrane proteins that are present in multiple hESC lines but not in differentiated cells, which were therefore likely to include proteins important for hESCs. In addition, 13 and 24 proteins, respectively, were commonly found in different feeder cell lines of mouse and human origin, some of which may be extracellular signaling molecules that play a key role in the undifferentiated propagation of hESCs. These findings underscore the power of mass spectrometry-based techniques to identify novel proteins associated with hESCs by studying these cells in an unbiased, discovery-oriented manner on a proteome-wide scale.

Concise review: trends in stem cell proteomics.

Gene expression analyses of stem cells (SCs) will help to uncover or further define signaling pathways and molecular mechanisms involved in the maintenance of self-renewal, pluripotency, and/or multipotency. In recent years, proteomic approaches have produced a wealth of data identifying proteins and mechanisms involved in SC proliferation and differentiation. Although many proteomics techniques have been developed and improved in peptide and protein separation, as well as mass spectrometry, several important issues, including sample heterogeneity, post-translational modifications, protein-protein interaction, and high-throughput quantification of hydrophobic and low-abundance proteins, still remain to be addressed and require further technical optimization. This review summarizes the methodologies used and the information gathered with proteome analyses of SCs, and it discusses biological and technical challenges for proteomic study of SCs. Disclosure of potential conflicts of interest is found at the end of this article.

Embryonic stem cell proteomics.

Human embryonic stem cells potentially represent an unlimited source of cells and tissues for regenerative medicine. Understanding signaling events that drive proliferation and specialization of these cells into various differentiated derivatives is of utmost importance for controlling their behavior in vitro. Major progress has been made in unraveling these signaling events with large-scale studies at the transcriptional level, but analysis of protein expression, interaction and modification has been more limited, since it requires different strategies. Recent advances in mass spectrometry-based proteomics indicate that proteome characterization can contribute significantly to our understanding of embryonic stem cell biology. In this article, we review mass spectrometry-based studies of human and mouse embryonic stem cells and their differentiated progeny, as well as studies of conditioned media that have been reported to support self-renewal of the undifferentiated cells in the absence of the more commonly used feeder cells. In addition, we make concise comparisons with related transcriptome profiling reports.

A quest for human and mouse embryonic stem cell-specific proteins.

Embryonic stem cells (ESCs) are of immense interest as they can proliferate indefinitely in vitro and give rise to any adult cell type, serving as a potentially unlimited source for tissue replacement in regenerative medicine. Extensive analyses of numerous human and mouse ESC lines have shown generic similarities and differences at both the transcriptional and functional level. However, comprehensive proteome analyses are missing or are restricted to mouse ESCs. Here we have used an extensive proteomic approach to search for ESC-specific proteins by analyzing the differential protein expression profiles of human and mouse ESCs and their differentiated derivatives. The data sets comprise 1,775 non-redundant proteins identified in human ESCs, 1,532 in differentiated human ESCs, 1,871 in mouse ESCs, and 1,552 in differentiated mouse ESCs with a false positive rate of <0.2%. Comparison of the data sets distinguished 191 proteins exclusively identified in both human and mouse ESCs but not in their differentiated derivatives. Besides well known ESC benchmarks, this subset included many uncharacterized proteins, some of which may be novel ESC-specific markers. To complement the mass spectrometric approach, differential expression of a selection of these proteins was confirmed by Western blotting, immunofluorescence confocal microscopy, and fluorescence-activated cell sorting. Additionally two other independently isolated and cultured human ESC lines as well as their differentiated derivatives were monitored for differential expression of selected proteins. Some of these proteins were identified exclusively in ESCs of all three human lines and may thus serve as generic ESC markers. Our wide scale proteomic approach enabled us to screen thousands of proteins rapidly and select putative ESC-associated proteins for further analysis. Validation by three independent conventional protein analysis techniques shows that our methodology is robust, provides an excellent tool to characterize ESCs at the protein level, and may disclose novel ESC-specific benchmarks.