Cytotoxicity of human peripheral blood monocytes

Native tumoricidal activity of human peripheral blood mononuclear cells was examined before and after their separation by counterflow centrifugation elutriation (CCE). Tumoricidal activity was found in the subpopulation of small mononuclear cells but not within the relatively pure subpopulation of large monocytes. Addition of lymphokine and/or lipopolysaccharide demonstrated that large monocytes were resistant to activation for tumor killing, in contrast to small mononuclear cells. However, cryopreservation or simply exposure to dimethyl sulfoxide (DMSO) rendered the large monocytes sensitive to activating agents without altering their unstimulated tumoricidal activity. Cryopreservation was not detrimental to small or large monocytes either in number or tumoricidal function but did decrease the number of large granular lymphocytes (LGL). The small mononuclear cell fraction was enriched for small monocytes to 80% by combining CCE with Percoll gradient separation. HNK-1 mouse monoclonal antibody against human LGL was used with complement to remove virtually all LGL from cryopreserved cells as judged by morphology and tumoricidal activity against K-562 human lymphoblastoid cells. Such treatment actually augmented rather than suppressed tumoricidal activity against P-815 mastocytoma cells. Therefore, we conclude that small monocytes but not large monocytes possess native tumoricidal activity distinct from that attributed to LGL or natural killer lymphocytes. Further, small monocytes are readily activated for tumor killing and can be cryopreserved without loss of tumoricidal activity.     

Human monocytes infected with Yersinia pestis express cell surface TLR9 and differentiate into dendritic cells

TLR9 recognizes DNA sequences containing hypomethylated CpG motifs and is a component of the innate immune system highly conserved during eukaryotic evolution. Previous reports suggested that the expression of TLR9 is restricted to plasmacytoid dendritic cells and B lymphocytes. Our results indicate that low levels of TLR9 are present on the cell surface of freshly isolated human monocytes, and expression is greatly increased by infection with Yersinia pestis. Enhanced cell surface TLR9 coincided with elevated levels of cytoplasmic TLR9 and recruitment of MyD88. Infected monocytes differentiated into mature dendritic cells, expressed IFN-alpha, and stimulated proliferative and cytotoxic T cell responses specific to Y. pestis. Furthermore, uninfected B cells and monocytes both increased cell surface TLR9, CD86, and HLA-DR in response to treatment with CpG-containing oligonucleotides, whereas cell surface TLR9 was down-modulated on infected dendritic cells by the addition of agonist oligonucleotide. Our results suggest that increased expression of TLR9 on the surface of infected cells may serve a role as an activation signal to other cells of the immune system.     

FoxO1 inhibition promotes differentiation of human embryonic stem cells into insulin producing cells

Insulin-producing cells (IPCs) derived from human embryonic stem cells (hESCs) hold great potential for cell transplantation therapy in diabetes. Tremendous progress has been made in inducing differentiation of hESCs into IPCs in vitro, of which definitive endoderm (DE) protocol mimicking foetal pancreatic development has been widely used. However, immaturity of the obtained IPCs limits their further applications in treating diabetes. Forkhead box O1 (FoxO1) is involved in the differentiation and functional maintenance of murine pancreatic β cells, but its role in human β cell differentiation is under elucidation. Here, we showed that although FoxO1 expression level remained consistent, cytoplasmic phosphorylated FoxO1 protein level increased during IPC differentiation of hESCs induced by DE protocol. Lentiviral silencing of FoxO1 in pancreatic progenitors upregulated the levels of pancreatic islet differentiation-related genes and improved glucose-stimulated insulin secretion response in their progeny IPCs, whereas overexpression of FoxO1 showed the opposite effects. Notably, treatment with the FoxO1 inhibitor AS1842856 displayed similar effects with FoxO1 knockdown in pancreatic progenitors. These effects were closely associated with the mutually exclusive nucleocytoplasmic shuttling of FoxO1 and Pdx1 in the AS1842856-treated pancreatic progenitors. Our data demonstrated a promising effect of FoxO1 inhibition by the small molecule on gene expression profile during the differentiation, and in turn, on determining IPC maturation via modulating subcellular location of FoxO1 and Pdx1. Therefore, we identify a novel role of FoxO1 inhibition in promoting IPC differentiation of hESCs, which may provide clues for induction of mature β cells from hESCs and clinical applications in regenerative medicine.     

Human umbilical vein endothelium-derived cells retain potential to differentiate into smooth muscle-like cells

Mouse embryonic stem-derived cells were recently shown to differentiate into endothelial and smooth muscle cells. In the present study, we investigated whether human umbilical vein endothelium-derived cells retain the potential to differentiate into smooth muscle cells. Examination of biochemical markers, including basic calponin, SM22alpha, prostaglandin E synthase, von Willebrand factor, and PECAM-1, as well as cell contractility, showed that whereas endothelium-derived cells cultured with fibroblast growth factor can be characterized as endothelial cells, when deprived of fibroblast growth factor, a significant fraction differentiates into smooth muscle-like cells. Reapplication of fibroblast growth factor reversed this differentiation. Activin A was up-regulated in fibroblast growth factor-deprived, endothelium-derived cells; moreover, the inhibitory effects of exogenous follistatin and overexpressed Smad7 on smooth muscle-like differentiation confirmed that the differentiation was driven by activin A signaling. These findings indicate that when deprived of fibroblast growth factor, human umbilical vein endothelium-derived cells are capable of differentiating into smooth muscle-like cells through activin A-induced, Smad-dependent signaling, and that maintenance of the endothelial cell phenotype and differentiation into smooth muscle-like cells are reciprocally controlled by fibroblast growth factor-1 and activin A.     

Equine bronchial epithelial cells differentiate into ciliated and mucus producing cells in vitro

We describe a method for creating differentiated equine bronchial epithelial cell cultures that can be used for in vitro studies including airway disease mechanisms and pathogen–host interactions. Our method is based on the culturing of human tracheobronchial epithelial cells at an air–liquid interface (ALI) in specific serum-free, hormone-supplemented medium. Bronchial epithelial cells are isolated and grown on T-Clear® insert membranes. Within 2 to 3 wk, cells differentiate into ciliated and mucus producing cells as demonstrated by confocal and electron microscopy. Furthermore, the demonstration of the two major gel-forming mucin species, Muc5ac and Muc5b, in our bronchial epithelial cell culture system validates this method for studies of respiratory tract disease of the horse.     

Human erythroid cells produced ex vivo at large scale differentiate into red blood cells in vivo

New sources of red blood cells (RBCs) would improve the transfusion capacity of blood centers. Our objective was to generate cells for transfusion by inducing a massive proliferation of hematopoietic stem and progenitor cells, followed by terminal erythroid differentiation. We describe here a procedure for amplifying hematopoietic stem cells (HSCs) from human cord blood (CB) by the sequential application of specific combinations of growth factors in a serum-free culture medium. The procedure allowed the ex vivo expansion of CD34+ progenitor and stem cells into a pure erythroid precursor population. When injected into nonobese diabetic, severe combined immunodeficient (NOD/SCID) mice, the erythroid cells were capable of proliferation and terminal differentiation into mature enucleated RBCs. The approach may eventually be useful in clinical transfusion applications.     

Dendritic cells derived from peripheral monocytes express endothelial markers and in the presence of angiogenic growth factors differentiate into endothelial-like cells

CD14-positive monocytes obtained from human peripheral blood were cultured with GM-CSF and IL-4. During the early culture phase immature dendritic cells (DCs) developed which not only expressed CD1a, HLA-DR and CD86, but also expressed the endothelial cell markers von Willebrand factor (vWF), VE-cadherin and VEGF receptors Flt-1 and Flt-4. Further maturation of DCs was achieved by prolonged cultivation with TNFalpha. These cells showed typical DC morphology and like professional antigen-presenting cells (APCs) expressed CD83 and high levels of HLA-DR and CD86. However, if immature DCs were grown with VEGF, bFGF and IGF-1 on fibronectin/vitronectin-coated culture dishes, a marked change in morphology into caudated or oval cells occurred. In the presence of these angiogenic growth factors the cultured cells developed into endothelial-like cells (ELCs), characterized by increased expression of vWF, KDR and Flt-4 and a disappearance of CD1a and CD83. Addition of IL-4 and Oncostatin M also increased VE-cadherin expression, and the loosely adherent cells formed clusters, cobblestones and network-like structures. vWF- expressing ELCs mainly originated from CD1a-positive cells, and VEGF was responsible for the decrease in the expression of the DC markers CD1a and CD83. In mixed leukocyte cultures, mature DCs were more potent APCs than ELCs. Moreover, Ac-LDL uptake, and the formation of tubular structures on a plasma matrix was restricted to ELCs. These results suggest that in the presence of specific cytokines immature DCs have the potential to differentiate along different lineages, i.e. into a cell type resembling ELCs.     

CD56bright human NK cells differentiate into CD56dim cells: role of contact with peripheral fibroblasts

Human NK cells are divided into CD56(bright)CD16(-) cells and CD56(dim)CD16(+) cells. We tested the hypothesis that CD56(bright) NK cells can differentiate into CD56(dim) cells by prospectively isolating and culturing each NK subset in vitro and in vivo. Our results show that CD56(bright) cells can differentiate into CD56(dim) both in vitro, in the presence of synovial fibroblasts, and in vivo, upon transfer into NOD-SCID mice. In vitro, this differentiation was inhibited by fibroblast growth factor receptor-1 Ab, demonstrating a role of the CD56 and fibroblast growth factor receptor-1 interaction in this process. Differentiated CD56(dim) cells had reduced IFN-gamma production but increased perforin expression and cytolysis of cell line K562 targets. Flow cytometric fluorescent in situ hybridization demonstrated that CD56(bright) NK cells had longer telomere length compared with CD56(dim) NK cells, implying the former are less mature. Our data support a linear differentiation model of human NK development in which immature CD56(bright) NK cells can differentiate into CD56(dim) cells.     

Adenosine deaminase activity during in vitro culture of human peripheral blood monocytes and pulmonary alveolar macrophages

Adenosine deaminase (ADA) undergoes changes in specific activity during in vitro culture of human peripheral blood monocytes and pulmonary alveolar macrophages. Monocyte adenosine deaminase activity increases during the first 3 days of culture; after 3 days the specific activity decreases below the levels observed for freshly isolated cells. In contrast, ADA activity of pulmonary alveolar macrophages increases throughout the 14-day culture period studied. Based on pH optima, starch gel electrophoresis and gel filtration column chromatography, the changes in adenosine deaminase activity in monocyte-macrophage cultures are related to changes in the molecular form of the enzyme. Freshly isolated monocytes contain mainly ES, while at day 14, starch gel and gel filtration experiments demonstrate the appearance of EI. Human pulmonary macrophages contain primarily EI or EL; following several days in culture, there is an increase in the amount of ES present.     

In vitro differentiation of human multilineage differentiating stress-enduring (Muse) cells into insulin producing cells

Mesenchymal stem cells (MSCs) is a heterogeneous population. Muse cells is a rare pluripotent subpopulation within MSCs. This study aims to evaluate the pulirpotency and the ability of Muse cells to generate insulin producing cells (IPCs) after in vitro differentiation protocol compared to the non-Muse cells. Muse cells were isolated by FACSAria III cell sorter from adipose-derived MSCs and were evaluated for its pluripotency. Following in vitro differentiation, IPCs derived from Muse and non-Muse cells were evaluated for insulin production. Muse cells comprised 3.2?±?0.7% of MSCs, approximately 82% of Muse cells were positive for anti stage-specific embryonic antigen-3 (SSEA-3). Pluripotent markers were highly expressed in Muse versus non-Muse cells. The percentage of generated IPCs by flow cytometric analysis was higher in Muse cells. Under confocal microscopy, Muse cells expressed insulin and c-peptide while it was undetected in non-Muse cells. Our results introduced Muse cells as a new adult pluripotent subpopulation, which is capable to produce higher number of functional IPCs.     

Human bone marrow-derived mesenchymal stem cells differentiate into epidermal-like cells in vitro

Human bone marrow-derived mesenchymal stem cells (hMSCs) are a population of pluripotent cells. They can differentiate into different embryonic layer cells as osteoblasts, adipocytes, chondrocytes, myoblasts, neurocytes, etc. However, there are only few reports with regard to differentiate hMSCs into epidermal cells in vitro. In this study, we want to investigate the feasibility of inducing hMSCs into epidermal-like cells under specific medium in vitro. hMSCs in specific inducing medium expressed the early markers of epidermal cell lineage, P63, cytokeratin19 (CK19), the late differentiated marker, the pan-cytokeratin, and another early marker, the beta1-integrin, which up-regulated remarkably in inducing medium. Their morphologies were changed from spindle-like fibroblastic appearances to oblate or irregular shapes under phase contrast microscopy. The hemidesmosome structure was found using the transmission electron microscope. All these data suggested that, under certain conditions, hMSCs have the potential to differentiate into epidermal-like cells. It will be of great accordance in the study of the multipotential property of hMSCs.     

Co-expression of chemotactic ligand receptors on human peripheral blood monocytes

Directed migration of monocytes is dependent upon interaction of cell surface receptors and specific chemotactic ligands. To determine whether circulating human monocytes express multiple chemotactic ligand receptors or whether subpopulations of monocytes exist with a single receptor specificity, nonoverlapping fluorescent probes for two chemotactic ligands, N-formyl methionyl leucyl phenylalanine (FMLP) and C5a, were developed to simultaneously evaluate the expression of receptors for these ligands on individual monocytes. The subsequent incubation with different fluorochrome labeled C5a and FMLP probes and monoclonal antibodies specific for antigenic determinants on distinct subsets of mononuclear cells followed by analysis with dual parameter flow microfluorometry indicated that cells that express C5a and FMLP receptors are the OKM1, Mac-1, and Fc gamma receptor positive population. Furthermore, it was demonstrated that approximately 90% of peripheral blood monocytes expressed FMLP receptors, and the majority of FMLP+ cells were also C5a receptor positive. In addition, a parallel spectrum of chemotactic ligand receptor density from low to high levels was demonstrated for both C5a and FMLP. Additional analysis revealed that the density of chemotactic ligand receptors on resting peripheral blood monocytes did not correlate with monocyte maturation levels measured by HLA-DR expression. Elucidation of the monocyte chemotactic receptor-ligand interactions that lead to migration and/or activation may provide insight into the regulation of monocyte function in inflammation.     

Synthesis of prostaglandins by subpopulations of human peripheral blood monocytes

The ability of monocytes/macrophages to regulate various aspects of immunologic responses may in part depend on their release of soluble substances such as prostaglandins. Using quantitative gas-liquid chromatography/mass spectrometry, prostaglandin E₂ was found to be the major prostaglandin synthesized in culture by human peripheral blood monocytes. Subjecting these cells to discontinuous density gradient fractionation demonstrated significant differences in the synthesis of prostaglandins E₂ and E₁ among the resulting monocyte subpopulations.     

Isolation of functional subsets of human peripheral blood monocytes.

Monocytes were isolated by counterflow centrifugation of Ficoll-Hypaque separated peripheral blood mononuclear cells. The monocytes formed a bimodal volume distribution of "large" and "small" phagocytic esterase-positive, peroxidase-positive cells with peaks at 470 and 410 mu3, respectively. The large monocytes were predominately Fc receptor positive, and were able to lyse both sensitized human and chicken erythrocyte targets in ADCC assays, whereas the small monocytes were largely FcR negative and were inactive against sensitized human erythrocyte targets. However, ADCC against chicken erythrocyte targets was seen in some fractions containing small monocytes and was probably due to FcR+ lymphocytes (K cells) in those fractions. These experiments establish that monocytes are effectors of ADCC against both human and chicken erythrocyte targets and that the peripheral blood monocyte is heterogeneous in size, function, and surface receptor distribution.     

Erythromyeloid tumor cells (K562) induce PGE synthesis in human peripheral blood monocytes

Human peripheral blood monocytes were found to spontaneously produce prostaglandin of the E series (PGE) in culture medium (0.5 ng to 3.0 ng/7.5 X 10(5) cells), and the addition of K562 tumor cells enhanced the production by five- to 15-fold after 18 hr of incubation. PGE2 (10(-6) M) inhibited the cytolytic activity of freshly isolated peripheral blood monocytes against K562 target cells by 50%. The PGE production was inhibited by inhibitors of cyclo-oxygenase (indomethacin, aspirin, and ETYA) when present during the incubation. However, pretreatment of monocytes with these cyclo-oxygenase inhibitors was ineffective in preventing PGE production. Kinetic experiments showed that appreciable stimulation of PGE production occurred only after 6 hr of co-culture. Other human tumor cell lines (HSB, SB, and CEM) enhanced PGE production upon co-culture with monocytes but to a lesser extent (twofold to threefold). Monocytes treated with 0.4% formaldehyde or heat (56 degrees C) were not capable of producing PGE when cultured alone or with K526 tumor cells. In contrast, formaldehyde-treated, but not heat-treated, K562 tumor cells were able to induce monocytes to produce PGE. By using a single cell conjugation assay, K562 tumor cells were found to bind equally well to treated or untreated monocytes. In contrast, the lytic activity of treated monocytes against K562 target cells was abolished. The presence of protein synthesis inhibitor, cycloheximide, was found to inhibit PGE production by monocytes cultured alone or with K562 tumor cells. Supernatants from K562 tumor cell cultures were also capable of inducing monocytes to produce PGE, and their effect on PGE production from monocytes was suppressed by cycloheximide. In addition, pretreatment of either K562 tumor cells or monocytes with an irreversible protein synthesis inhibitor, emetine, also suppressed the production of PGE upon co-culture with the untreated counterpart. The production of PGE by monocytes in response to exposure to tumor cells may represent a mechanism whereby tumor cells subvert host immune defense against them.     

TNF-alpha drives human CD14+ monocytes to differentiate into CD70+ dendritic cells evoking Th1 and Th17 responses

Many mechanisms involving TNF-alpha, Th1 responses, and Th17 responses are implicated in chronic inflammatory autoimmune disease. Recently, the clinical impact of anti-TNF therapy on disease progression has resulted in re-evaluation of the central role of this cytokine and engendered novel concept of TNF-dependent immunity. However, the overall relationship of TNF-alpha to pathogenesis is unclear. Here, we demonstrate a TNF-dependent differentiation pathway of dendritic cells (DC) evoking Th1 and Th17 responses. CD14(+) monocytes cultured in the presence of TNF-alpha and GM-CSF converted to CD14(+) CD1a(low) adherent cells with little capacity to stimulate T cells. On stimulation by LPS, however, they produced high levels of TNF-alpha, matrix metalloproteinase (MMP)-9, and IL-23 and differentiated either into mature DC or activated macrophages (M phi). The mature DC (CD83(+) CD70(+) HLA-DR (high) CD14(low)) expressed high levels of mRNA for IL-6, IL-15, and IL-23, induced naive CD4 T cells to produce IFN-gamma and TNF-alpha, and stimulated resting CD4 T cells to secret IL-17. Intriguingly, TNF-alpha added to the monocyte culture medium determined the magnitude of LPS-induced maturation and the functions of the derived DC. In contrast, the M phi (CD14(high)CD70(+)CD83(-)HLA-DR(-)) produced large amounts of MMP-9 and TNF-alpha without exogenous TNF stimulation. These results suggest that the TNF priming of monocytes controls Th1 and Th17 responses induced by mature DC, but not inflammation induced by activated M phi. Therefore, additional stimulation of monocytes with TNF-alpha may facilitate TNF-dependent adaptive immunity together with GM-CSF-stimulated M phi-mediated innate immunity.