A side order of stem cells: The SP phenotype

A defining property of murine hematopoietic stein cells (HSCs) is low fluorescence after staining with Hoechst 33342 and Rhodamine 123. These dyes have proven to be remarkably powerful tools in the purification and characterization of HSCs when used alone or in combination with antibodies directed against stem cell epitopes. Hoechst low cells are described as side population (SP) cells by virtue of their typical profiles in Hoechst red versus Hoechst blue bivariate fluorescent-activated cell sorting dot plots. Recently, excitement has been generated by the findings that putative stem cells from solid tissues may also possess this SP phenotype. SP cells have now been isolated from a wide variety of mammalian tissues based on this same dye efflux phenomenon, and in many cases this cell population has been shown to contain apparently multipotent stem cells. What is yet to be clearly addressed is whether cell fusion accounts for this perceived SP multipotency. Indeed, if low fluorescence after Hoechst staining is a phenotype shared by hematopoietic and organ-specific stem cells, do all resident tissue SP cells have bone marrow origins or might the SP phenotype be a property common to all stem cells? Subject to further analysis, the SP phenotype may prove invaluable for the initial isolation of resident tissue stem cells in the absence of definitive cell-surface markers and may have broad-ranging applications in stem cell biology, from the purification of novel stem cell populations to the development of autologous stem cell therapies.

Kidney side population reveals multilineage potential and renal functional capacity but also cellular heterogeneity

Side population (SP) cells in the adult kidney are proposed to represent a progenitor population. However, the size, origin, phenotype, and potential of the kidney SP has been controversial. In this study, the SP fraction of embryonic and adult kidneys represented 0.1 to 0.2% of the total viable cell population. The immunophenotype and the expression profile of kidney SP cells was distinct from that of bone marrow SP cells, suggesting that they are a resident nonhematopoietic cell population. Affymetrix expression profiling implicated a role for Notch signaling in kidney SP cells and was used to identify markers of kidney SP. Localization by in situ hybridization confirmed a primarily proximal tubule location, supporting the existence of a tubular niche, but also revealed considerable heterogeneity, including the presence of renal macrophages. Adult kidney SP cells demonstrated multilineage differentiation in vitro, whereas microinjection into mouse metanephroi showed that SP cells had a 3.5- to 13-fold greater potential to contribute to developing kidney than non-SP main population cells. However, although reintroduction of SP cells into an Adriamycin-nephropathy model reduced albuminuria:creatinine ratios, this was without significant tubular integration, suggesting a humoral role for SP cells in renal repair. The heterogeneity of the renal SP highlights the need for further fractionation to distinguish the cellular subpopulations that are responsible for the observed multilineage capacity and transdifferentiative and humoral activities.

Regrow or repair: Potential regenerative therapies for the kidney

Regenerative medicine is being heralded in a similar way as gene therapy was some 15 yr ago. it is an area of intense excitement and potential, as well as myth and disinformation. However, with the increasing rate of end-stage renal failure and limited alternatives for its treatment, we must begin to investigate seriously potential regenerative approaches for the kidney. This review defines which regenerative options there might be for renal disease, summarizes the progress that has been made to date, and investigates some of the unique obstacles to such treatments that the kidney presents. The options discussed include in situ organ repair via bone marrow recruitment or dedifferentiation; ex vivo stem cell therapies, including both autologous and nonautologous options; and bioengineering approaches for the creation of a replacement organ.

A population of HLA-DR+ immature cells accumulates in the blood dendritic cell compartment of patients with different types of cancer

Dendritic cell (DC) defects are an important component of immunosuppression in cancer. Here, we assessed whether cancer could affect circulating DC populations and its correlation with tumor progression. The blood DC compartment was evaluated in 136 patients with breast cancer, prostate cancer, and malignant glioma. Phenotypic, quantitative, and functional analyses were performed at various stages of disease. Patients had significantly fewer circulating myeloid (CD11c(+)) and plasmacytoid (CD123(+)) DC, and a concurrent accumulation of CD11c(-)CD123(-) immature cells that expressed high levels of HLA-DR+ immature cells (DR+IC). Although DR+IC exhibited a limited expression of markers ascribed to mature hematopoietic lineages, expression of HLA-DR, CD40, and CD86 suggested a role as antigen-presenting cells. Nevertheless, DR+IC had reduced capacity to capture antigens and elicited poor proliferation and interferon-gamma secretion by T-lymphocytes. Importantly, increased numbers of DR+IC correlated with disease status. Patients with metastatic breast cancer showed a larger number of DR+IC in the circulation than patients with local/nodal disease. Similarly, in patients with fully resected glioma, the proportion of DR+IC in the blood increased when evaluation indicated tumor recurrence. Reduction of blood DC correlating with accumulation of a population of immature cells with poor immunologic function may be associated with increased immunodeficiency observed in cancer.

Proliferation in monocyte-derived dendritic cell cultures is caused by progenitor cells capable of myeloid differentiation

Dendritic cells (DC) can be generated by culture of adherent peripheral blood (PB) cells in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). There is controversy as to whether these DC arise from proliferating precursors or simply from differentiation of monocytes. DC were generated from myeloid-enriched PB non-T cells or sorted monocytes. DC generated from either population functioned as potent antigen-presenting cells. Uptake of [H-3]-thymidine was observed in DC cultured from myeloid-enriched non-T cells. Addition of lipopolysaccharide or tumor necrosis factor-alpha led to maturation of the DC, but did not inhibit proliferation. Ki67(+) cells were observed in cytospins of these DC, and by double staining were CD3(-)CD19(-)CD11c(-)CD40(-) and myeloperoxidase(+), suggesting that they were myeloid progenitor cells. Analysis of the starting population by flow cytometry demonstrated small numbers of CD34(+)CD33(-)CD14(-) progenitor cells, and numerous granulocyte-macrophage colony-forming units were generated in standard assays. Thus, production of DC in vitro from adherent PB cells also enriches for progenitor cells that are capable of proliferation after exposure to GM-CSF. Of clinical importance, the yield of DC derived in the presence of GM-CSF and IL-4 cannot be expanded beyond the number of starting monocytes. (C) 1998 by The American Society of Hematology.

Proliferation in monocyte-derived dendritic cell cultures is due to cells capable of myeloid differentiation

Dendritic cells (DC) can be generated by culture of adherent peripheral blood (PB) cells in the presence of granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin-4 (IL-4). There is controversy as to whether these DC arise from proliferating precursors or simply from differentiation of monocytes. DC were generated from myeloid-enriched PB non-T cells or sorted monocytes. DC generated from either population functioned as potent antigen-presenting cells. Uptake of [H-3]-thymidine was observed in DC cultured from myeloid-enriched non-T cells. Addition of lipopolysaccharide or tumor necrosis factor-alpha led to maturation of the DC, but did not inhibit proliferation. Ki67(+) cells were observed in cytospins of these DC, and by double staining were CD3(-)CD19(-)CD11c(-)CD40(-) and myeloperoxidase(+), suggesting that they were myeloid progenitor cells. Analysis of the starting population by flow cytometry demonstrated small numbers of CD34(+)CD33(-)CD14(-) progenitor cells, and numerous granulocyte-macrophage colony-forming units were generated in standard assays. Thus, production of DC in vitro from adherent PB cells also enriches for progenitor cells that are capable of proliferation after exposure to GM-CSF. Of clinical importance, the yield of DC derived in the presence of GM-CSF and IL-4 cannot be expanded beyond the number of starting monocytes. (C) 1998 by The American Society of Hematology.

Population balance model of in vivo neutrophil formation following bone marrow rescue therapy

In this paper, we develop a simple four parameter population balance model of in vivo neutrophil formation following bone marrow rescue therapy. The model is used to predict the number and type of neutrophil progenitors required to abrogate the period of severe neutropenia that normally follows a bone marrow transplant. The estimated total number of 5 billion neutrophil progenitors is consistent with the value extrapolated from a human trial. The model provides a basis for designing ex vivo expansion protocols.

Gene transfer and expression of a non-viral polycation-based vector in CD4(+) cells

CD4-selective targeting of an antibody-polycation-DNA complex was investigated The complex was synthesized with the anti-CD4 monoclonal antibody B-F5, polylysine(268) (pLL) and either the pGL3 control vector containing the luciferase reporter gene or the pGeneGrip vector containing the green fluorescent protein (GFP) gene. B-F5-pLL-DNA complexes inhibited the binding of I-125-B-F5 to CD4(+) Jurkat cells, while complexes synthesised either without B-F5 or using a non-specific mouse IgG1 antibody had little or no effect Expression of the luciferase reporter gene was achieved in Jurkat cells using the B-F5-pLL-pGL3 complex and was enhanced in the presence of PMA. Negligible luciferase activity was defected with the non-specific antibody complex in Jurkat cells or with the B-F5-pLL-pGL3 complex in the CD4(-) K-562 cells. Using complexes synthesised with the pGeneGrip vector, the transfection efficiency in Jurkat and K-562 cells was examined using confocal microscopy. More than 95% of Jurkat cells expressed GFP and the level of this expression was markedly enhanced by PMA. Negligible GFP expression was seen in K-562 cells or when B-F5 was replaced by a nonspecific antibody. Using flow cytometry, fluorescein-labelled complex showed specific targeting to CD4(+) cells in a mixed cell population from human peripheral blood. These studies demonstrate the selective transfection of CD4(+) T-lymphoid cells using a polycation-based gene delivery system. The complex may provide a means of delivering anti-HIV gene therapies to CD4(+) cells in vivo.

Structured modeling of recombinant protein production in batch and fed-batch culture of baculovirus-infected insect cells

The infection of insect cells with baculovirus was described in a mathematical model as a part of the structured dynamic model describing whole animal cell metabolism. The model presented here is capable of simulating cell population dynamics, the concentrations of extracellular and intracellular viral components, and the heterologous product titers. The model describes the whole processes of viral infection and the effect of the infection on the host cell metabolism. Dynamic simulation of the model in batch and fed-batch mode gave good agreement between model predictions and experimental data. Optimum conditions for insect cell culture and viral infection in batch and fed-batch culture were studied using the model.

Immunobiology of liver dendritic cells

Dendritic cells (DC) are rare, bone marrow-derived antigen-presenting cells that play a critical role in the induction and regulation of immune reactivity. In this article, we review the identification and characterization of liver DC, their ontogenic development, in vivo mobilization and population dynamics. In addition, we discuss the functions of DC isolated from liver tissue or celiac lymph, or propagated in vitro from liver-resident haemopoietic stem/progenitor cells. Evidence concerning the role of DC in viral hepatitis. liver tumours, autoimmune liver diseases, granulomatous inflammation and the outcome of liver transplantation is also discussed.

Cytokine expanded myeloid precursors function as regulatory antigen presenting cells and induce tolerance through IL-10 producing regulatory T cells

The initiation of graft vs. host disease (GVHD) after stem cell transplantation is dependent on direct antigen presentation by host antigen presenting cells (APC) while the effect of indirect antigen presentation by donor APC is unknown. We have studied the role of indirect antigen presentation in allogenic responses by adding populations of cytokine-expanded donor APC to haematopoietic grafts that would otherwise induce lethal GVHD. Progenipoietin-1 (a synthetic G-CSF/Flt-3 L molecule) and G-CSF expanded myeloid DC, plasmacytoid DC and a novel granulocyte-monocyte precursor population (GM) that differentiate into class IIpos, CD80/CD86pos, CD40neg APC during GVHD. Whereas addition of plasmacytoid and myeloid donor DC augmented GVHD, GM cells induced transplant tolerance via MHC class II restricted generation of IL-10-secreting regulatory T cells. Thus a population of cytokine expanded granulocyte-monocyte precursors function as regulatory antigen presenting cells, suggesting that G-CSF derivatives may have application in disorders characterised by a loss of self-tolerance.

B, NK and NKT cells contribute to suppression of immunity by dendritic cells

Among the population of antigen presenting cells, dendritic cells (DCs) are considered the sentinels of the immune system. Besides activating naı¨ ve T cells, DC can directly activate naı¨ ve and memory B cells and are also able to regulate effectors of innate immunity such as NK cells and NKT cells. Increasing evidence indicates that DCs are not only decisive for T cell priming, but are also key players to maintain self-tolerance in vivo. Previous results in our lab have shown that DCs treated with a pharmacological NFkB inhibitor (BAY11–7082) confer suppression to a previously immune response. This suppression was IL-10 dependent and results from the induction of Ag specific CD4+ regulatory T cells. To elucidate the mechanism of suppression induced by administration of Bay treated DC, we used a model of infectious tolerance transfer from DC treated mice to primed recipient mice. Our results show that both CD4 + splenic cells and non T cells from animals injected with Bay treated DC, but not from untreated DC, were capable of transferring the suppression. Moreover, sorted B cells and NK cells could transfer antigenspecific infectious tolerance after administration of Bay treated DC. In addition, this suppressive effect could not be seen either in mice depleted of NK cells nor in NKT deficient mice. These observations highlight the role of several immune cells in the maintenance of tolerance, and impact on the design of immunotherapeutic suppression of autoimmune diseases in which NKT cells are deficient or defective, such as diabetes and lupus.

Ca2+-activated K+ channels in rat otic ganglion cells: Role of Ca2+ entry via Ca2+ channels and nicotinic receptors

1. Intracellular recordings were made from neurones in the rat otic ganglion in vitro in order to investigate their morphological, physiological and synaptic properties. We took advantage of the simple structure of these cells to test for a possible role of calcium influx via nicotinic acetylcholine receptors during synaptic transmission. 2. Cells filled with biocytin comprised a homogeneous population with ovoid somata and sparse dendritic trees. Neurones had resting membrane potentials of -53 +/- 0.7 mV (n = 69), input resistances of 112 + 7 M Omega, and membrane time constants of 14 +/- 0.9 ms (n = 60). Upon depolarization, all cells fired overshooting action potentials which mere followed by an apamin-sensitive after-hyperpolarization (AHP). In response to a prolonged current injection, all neurones fired tonically. 3. The repolarization phase of action potentials had a calcium component which was mediated by N-type calcium channels. Application of omega-conotoxin abolished both the repolarizing hump and the after-hgrperpolarization suggesting that calcium influx via N-type channels activates SK-type calcium-activated potassium channels which underlie the AHP. 4. The majority (70%) of neurones received innervation from a single preganglionic fibre which generated a suprathreshold excitatory postsynaptic potential mediated by nicotinic acetylcholine receptors. The other 30% of neurones also had one or more subthreshold nicotinic inputs. 5. Calcium influx via synaptic nicotinic receptors contributed to the AHP current, indicating that this calcium has access to the calcium-activated potassium channels and therefore plays a role in regulating cell excitability.