Remote control of macrophage production by cancer

The communication between tumor and host cells involves signals that act across extended distances in the body. Recent evidence indicates that the hormone angiotensin II is overproduced by lung adenocarcinoma to remotely expand bone marrow-derived hematopoietic stem cells. This process amplifies the supply of tumor-associated macrophages, which promote disease progression.

HLA-C*07:375, a variant of HLA-C*07, detected in a Taiwanese unrelated hematopoietic stem cell donor

One nucleotide exchange in codon 20 of HLA-A*07:02:01:01 results in a novel allele, HLA-C*07:375.

Discrete Notch signaling requirements in the specification of hematopoietic stem cells

Hematopoietic stem cells (HSCs) require multiple molecular inputs for proper specification, including activity of the Notch signaling pathway. A requirement for the Notch1 and dispensability of the Notch2 receptor has been demonstrated in mice, but the role of the remaining Notch receptors has not been investigated. Here, we demonstrate that three of the four Notch receptors are independently required for the specification of HSCs in the zebrafish. The orthologues of the murine Notch1 receptor, Notch1a and Notch1b, are each required intrinsically to fate HSCs, just prior to their emergence from aortic hemogenic endothelium. By contrast, the Notch3 receptor is required earlier within the developing somite to regulate HSC emergence in a non-cell-autonomous manner. Epistatic analyses demonstrate that Notch3 function lies downstream of Wnt16, which is required for HSC specification through its regulation of two Notch ligands, dlc and dld. Collectively, these findings demonstrate for the first time that multiple Notch signaling inputs are required to specify HSCs and that Notch3 performs a novel role within the somite to regulate the neighboring precursors of hemogenic endothelium.

Intercellular network structure and regulatory motifs in the human hematopoietic system

The hematopoietic system is a distributed tissue that consists of functionally distinct cell types continuously produced through hematopoietic stem cell (HSC) differentiation. Combining genomic and phenotypic data with high-content experiments, we have built a directional cell-cell communication network between 12 cell types isolated from human umbilical cord blood. Network structure analysis revealed that ligand production is cell type dependent, whereas ligand binding is promiscuous. Consequently, additional control strategies such as cell frequency modulation and compartmentalization were needed to achieve specificity in HSC fate regulation. Incorporating the in vitro effects (quiescence, self-renewal, proliferation, or differentiation) of 27 HSC binding ligands into the topology of the cell-cell communication network allowed coding of cell type-dependent feedback regulation of HSC fate. Pathway enrichment analysis identified intracellular regulatory motifs enriched in these cell type- and ligand-coupled responses. This study uncovers cellular mechanisms of hematopoietic cell feedback in HSC fate regulation, provides insight into the design principles of the human hematopoietic system, and serves as a foundation for the analysis of intercellular regulation in multicellular systems.

Discovery of HLA-A*11:167, a variant of HLA-A*11, in a Taiwanese unrelated hematopoietic stem cell donor

One nucleotide replacement in codon 57 of HLA-A*11:01:01 results in a novel allele, HLA-A*11:167.

An HLA-A*11 variant, A*11:166, revealed in a Taiwanese unrelated bone marrow hematopoietic stem cell donor

One nucleotide replacement in codon 35 of the human leukocyte antigen HLA-A*11:01:01 results in a new allele, HLA-A*11:166.

The Notch1 transcriptional activation domain is required for development and reveals a novel role for Notch1 signaling in fetal hematopoietic stem cells

Notch1 is required to generate the earliest embryonic hematopoietic stem cells (HSCs), and Notch-deficient embryos die early in gestation. Gerhardt et al. show that, unlike Notch1-deficient mice, mice lacking the Notch1 transcriptional activation domain (TAD) survive until late gestation. Notch1 TAD-deficient HSCs emerge and successfully migrate to the fetal liver but are decreased in frequency by E14.5. The Notch1 TAD is important to properly assemble the Notch1/Rbpj/Maml transcription complex. These results reveal an essential role for the Notch1 TAD in fetal development.

Notch1 is required to generate the earliest embryonic hematopoietic stem cells (HSCs); however since Notch-deficient embryos die early in gestation, additional functions for Notch in embryonic HSC biology have not been described. We used two complementary genetic models to address this important biological question. Unlike Notch1-deficient mice, mice lacking the conserved Notch1 transcriptional activation domain (TAD) show attenuated Notch1 function in vivo and survive until late gestation, succumbing to multiple cardiac abnormalities. Notch1 TAD-deficient HSCs emerge and successfully migrate to the fetal liver but are decreased in frequency by embryonic day 14.5. In addition, TAD-deficient fetal liver HSCs fail to compete with wild-type HSCs in bone marrow transplant experiments. This phenotype is independently recapitulated by conditional knockout of Rbpj, a core Notch pathway component. In vitro analysis of Notch1 TAD-deficient cells shows that the Notch1 TAD is important to properly assemble the Notch1/Rbpj/Maml trimolecular transcription complex. Together, these studies reveal an essential role for the Notch1 TAD in fetal development and identify important cell-autonomous functions for Notch1 signaling in fetal HSC homeostasis.

HLA-A*02:466, a variant of HLA-A*02, discovered in a Taiwanese unrelated hematopoietic stem cell donor

One nucleotide replacement at residue 228 of the human leukocyte antigen HLA-A*02:03:01 results in a novel allele, HLA-A*02:466.

The bone marrow hematopoietic microenvironment is impaired in iron-overloaded mice

OBJECTIVES

Increasing numbers of reports have described hematopoietic improvement after iron chelation therapy in iron-overloaded patients. These observations indicate that excess iron could affect hematopoiesis unfavorably. To investigate how excess iron affects hematopoiesis in vivo, we generated iron-overloaded mice and examined hematopoietic parameters in these mice.

METHODS

We generated iron-overloaded mice by injecting 200 mg of iron dextran into C57BL/6J mice, and immature hematopoietic cells in the bone marrow were evaluated by flow cytometric analyses, colony-forming assays, and bone marrow transplantation analyses. We also examined changes in molecular profiles of the hematopoietic microenvironment.

RESULTS AND CONCLUSIONS

Iron-overloaded (IO) mice did not show significant defects in the hematopoietic data of the peripheral blood. Myeloid progenitor cells in the bone marrow were increased in IO mice, but the number and function of the erythroid progenitors and hematopoietic stem cells were not significantly affected. However, bone marrow transplantation from normal donors to IO recipients showed delayed hematopoietic reconstitution, which indicates that excess iron impacts the hematopoietic microenvironment negatively. Microarray and quantitative RT-PCR analyses on the bone marrow stromal cells demonstrated remarkably reduced expression of CXCL12, VCAM-1, Kit-ligand, and IGF-1 in the iron-overloaded mice. In addition, erythropoietin and thrombopoietin levels were significantly suppressed, and increased oxidative stress was observed in the IO bone marrow and liver. Consequently, our findings indicate that excess iron can damage bone marrow stromal cells and other vital organs, disrupting hematopoiesis presumably by increased oxidative stress.

HLA-A*11:165, a variant of HLA-A*11, discovered in a Taiwanese unrelated hematopoietic stem cell donor

One nucleotide replacement in codon 145 (CGC>AGC) of the human leukocyte antigen HLA-A*11:01:01 results in a novel allele, HLA-A*11:165.

Cigarette Smoke Alters the Hematopoietic Stem Cell Niche

Effects of tobacco smoke on hematologic derangements have received little attention. This study employed a mouse model of cigarette smoke exposure to explore the effects on bone marrow niche function. While lung cancer is the most widely studied consequence of tobacco smoke exposure, other malignancies, including leukemia, are associated with tobacco smoke exposure. Animals received cigarette smoke exposure for 6 h/day, 5 days/week for 9 months. Results reveal that the hematopoietic stem and progenitor cell (HSPC) pool size is reduced by cigarette smoke exposure. We next examined the effect of cigarette smoke exposure on one supporting cell type of the niche, the mesenchymal stromal cells (MSCs). Smoke exposure decreased the number of MSCs. Transplantation of naïve HSPCs into irradiated mice with cigarette smoke exposure yielded fewer numbers of engrafted HSPCs. This result suggests that smoke-exposed mice possess dysfunctional niches, resulting in abnormal hematopoiesis. Co-culture experiments using MSCs isolated from control or cigarette smoke-exposed mice with naïve HSPCs in vitro showed that MSCs from cigarette smoke-exposed mice generated marked expansion of naïve HSPCs. These data show that cigarette smoke exposure decreases in vivo MSC and HSC number and also increases pro-proliferative gene expression by cigarette smoke-exposed MSCs, which may stimulate HSPC expansion. These results of this investigation are clinically relevant to both bone marrow donors with a history of smoking and bone marrow transplant (BMT) recipients with a history of smoking.

Regulation of hematopoiesis by activators and inhibitors of Wnt signaling from the niche

Hematopoietic stem cells (HSCs) are a rare population of somatic stem cells that have the ability to regenerate the entire mature blood system in a hierarchical way for the duration of an adult life. Adult HSCs reside in the bone marrow niche. Different niche cell types and molecules regulate the balance of HSC dormancy and activation as well as HSC behavior in both normal and malignant hematopoiesis. Here, we describe the interplay of HSCs and their niche, in particular the involvement of the Wnt signaling pathway. Although the prevailing notion has been that malignant transformation of HSCs is the main cause of leukemia, evidence is mounting that disruption of niche regulation by transformed hematopoietic cells, which may overexpress Wnt signaling or intrinsic stromal defects in gene expression, is at least a collaborative factor in leukemogenesis. Thus, insights into the normal and altered functions of niche components will help to obtain a better understanding of normal and malignant hematopoiesis and how environmental factors affect these processes.

Hypercholesterolemia induces oxidant stress that accelerates the ageing of hematopoietic stem cells

Background

Clinical studies suggest that hypercholesterolemia may cause ageing in hematopoietic stem cells (HSCs) because ageing‐associated alterations were found in peripheral blood cells and their bone marrow residing precursors in patients with advanced atherosclerosis. We hypothesized that hypercholesterolemia induces oxidant stress in hematopoietic stems cells that accelerates their ageing.

Methods and Results

Here we show that HSCs from ApoE^−/− mice, as well as HSCs from C57Bl/6 mice fed a high cholesterol diet (HCD) accumulated oxLDL and had greater ROS levels. In accordance, the expression pattern of the genes involved in ROS metabolism changed significantly in HSCs from ApoE^−/− mice. Hypercholesterolemia caused a significant reduction in phenotypically defined long‐term HSC compartment, telomere length, and repopulation capacity of KTLS cells, indicating accelerated ageing in these cells. Gene array analysis suggested abnormal cell cycle status, and the key cell cycle regulators including p19^ARF, p27^Kip1 and p21^Waf1 were upregulated in KTLS cells from hypercholesterolemic mice. These effects were p38‐dependent and reversed in vivo by treatment of hypercholesterolemic mice with antioxidant N‐acetylcysteine. The oxidant stress also caused aberrant expression of Notch1 that caused loss of quiescence and proliferation leading to the expansion of KTLS compartment in hypercholesterolemic mice.

Conclusion

Taken together, we provide evidence that hypercholesterolemia can cause oxidant stress that accelerates the ageing and impairs the reconstitution capacity of HSCs.

Physiological problems in patients undergoing autologous and allogeneic hematopoietic stem cell transplantation

OBJECTIVE

Stem cell transplantation is usually performed in an effort to extend the patient's life span and to improve their quality of life. This study was conducted to determine the postoperative physiological effects experienced by patients who had undergone autologous and allogeneic stem cell transplantation.

METHODS

The research is a descriptive study conducted with a sample of 60 patients at Stem Cell Transplantation Units in Ankara. Percentile calculation and chi-square tests were used to evaluate the data.

RESULTS

When a comparison was made between patients who had undergone allogeneic Hematopoietic stem cell transplantation (HSCT) and those who had undergone autologous HSCT, results indicated that problems occurred more often for the allogeneic HSCT patients. The problems included: Digestion (94.3%), dermatological (76.7%), cardiac and respiratory (66.7%), neurological (66.7%), eye (56.7%), infections (26.7%) and Graft Versus Host Disease (5 patients). Furthermore, the problems with pain (50%), numbness and tingling (40%), and speech disorders (3 patients) were observed more often in autologous BMT patients.

CONCLUSION

Autologous and allogeneic patients experienced most of physical problems due to they receive high doses of chemotherapy. Therefore, it is recommended that an interdisciplinary support team approach should be usedtohelp reduce and manage the problems that may arise during patient care.

Hematopoietic stem and progenitor cell activation during chronic dermatitis provoked by constitutively active aryl-hydrocarbon receptor driven by Keratin 14 promoter

Polycyclic aromatic hydrocarbons (PAHs) activate aryl-hydrocarbon receptor (AhR). Because PAHs are known as a risk factor for allergic diseases, PAH-induced AhR activation is expected to be involved in the development of the pathology. We previously generated transgenic mice expressing a constitutively active AhR (AhR-CA) under the control of Keratin 14 (K14) promoter (AhR-CA mouse). The mice develop chronic dermatitis with immune imbalance toward Th2 predominance, indicating that the AhR activation driven by K14 promoter provokes allergic response. Because hematopoietic cells actively participate in the development of allergic inflammation, it is important to understand the hematopoietic status under allergic conditions. To clarify how the K14 promoter-driven AhR activation influences hematopoiesis, we analyzed bone marrow and spleen of AhR-CA mice. We verified that AhR-CA was expressed in keratinocytes and thymic epithelial cells but not in hematopoietic cells. The AhR-CA mice with full-blown dermatitis exhibited leukocytosis and skewed differentiation of hematopoietic progenitor cells toward granulocyte-monocyte lineages. They also showed a significant expansion of short-term hematopoietic stem cells and multipotent progenitors and a subtle reduction in long-term hematopoietic stem cells (LT-HSCs). Their spleens were enlarged and abundantly accumulated hematopoietic stem and progenitor cells. AhR-CA mice at the early stage of dermatitis did not show leukocytosis or splenomegaly but exhibited the granulocyte-monocyte skewing and the reduction in LT-HSCs. Thus, AhR activation driven by K14 promoter already alters the hematopoietic differentiation and reduces LT-HSCs at the initial stage of dermatitis development. These results suggest that nonhematopoietic exposure to PAHs triggers allergic response and concomitantly affects hematopoiesis.

Targeting tumor-stromal interactions in bone metastasis

Bone metastasis is a frequent occurrence in late stage solid tumors, including breast cancers, prostate or lung. However, the causes for this proclivity have only recently been elucidated. Significant progress has been made in the past decade toward understanding the molecular underpinnings of bone metastasis, and much of this research reveals a crucial role of the host stroma in each step of the metastatic cascade. Tumor-stromal interactions are crucial in engineering a pre-metastatic niche, accommodating metastatic seeding, and establishing the vicious cycle of bone metastasis. Current treatments in bone metastasis focus on latter steps of the metastatic cascade, with most treatments targeting the process of bone remodeling; however, emerging research identifies many other candidates as promising targets. Host stromal cells including platelets and endothelial cells are important in the early steps of metastatic homing, attachment and extravasation while a variety of immune cells, parenchymal cells and mesenchymal cells of the bone marrow are important in the establishment of overt, immune-suppressed metastatic lesions. Many participants during these steps have been identified and functionally validated. Significant contributors include integrins, (αvβ3, α2β1, α4β1), TGFβ family members, bone resident proteins (BSP, OPG, SPARC, OPN), RANKL, and PTHrP. In this review, we will discuss the contribution of host stromal cells to pre-metastatic niche conditioning, seeding, dormancy, bone-remodeling, immune regulation, and chemotherapeutic shielding in bone metastasis. Research exploring these interactions between bone metastases and stromal cells has yielded many therapeutic targets, and we will discuss both the current and future therapeutic avenues in treating bone metastasis.

A short history of hemogenic endothelium

Definitive hematopoietic cells are generated de novo during ontogeny from a specialized subset of endothelium, the so-called hemogenic endothelium. In this review we give a brief overview of the identification of hemogenic endothelium, explore its links with the HSC lineage, and summarize recent insights into the nature of hemogenic endothelium and the microenvironmental and intrinsic regulators contributing to its transition into blood. Ultimately, a better understanding of the processes controlling the transition of endothelium into blood will advance the generation and expansion of hematopoietic stem cells for therapeutic purposes.

Erythro-myeloid progenitors: "definitive" hematopoiesis in the conceptus prior to the emergence of hematopoietic stem cells

Erythro-myeloid progenitors (EMP) serve as a major source of hematopoiesis in the developing conceptus prior to the formation of a permanent blood system. In this review, we summarize the current knowledge regarding the emergence, fate, and potential of this hematopoietic stem cell (HSC)-independent wave of hematopoietic progenitors, focusing on the murine embryo as a model system. A better understanding of the temporal and spatial control of hematopoietic emergence in the embryo will ultimately improve our ability to derive hematopoietic stem and progenitor cells from embryonic stem cells and induced pluripotent stem cells to serve therapeutic purposes.

Negative depletion of α/β+ T cells and of CD19+ B lymphocytes: a novel frontier to optimize the effect of innate immunity in HLA-mismatched hematopoietic stem cell transplantation

In recent years, infusion of T-cell depleted hematopoietic stem cells from an HLA-haploidentical relative has been shown to represent a suitable and effective, alternative option in patients in need of an allograft who lack an HLA-identical relative. In particular, this type of allograft is associated with the enormous advantage of offering an immediate transplant treatment to virtually all pediatric patients without an HLA-matched donor, whether related or unrelated, or a suitable umbilical cord blood unit. Several studies have shown that in patients given a T-cell depleted transplant relevant part of the anti-leukemia effect is mediated by alloreactive (i.e. KIR/HLA mismatched) Natural Killer cells originated from donor hematopoietic stem cells. After infusion of positively selected hematopoietic stem cell, fully functioning Natural Killer cells emerge in the recipient peripheral blood, persisting over time, only several weeks after the allograft. We have developed a new method of T-cell depletion (based on the physical elimination of mature T cells carrying α and β chains of the T-cell receptor), which permits to maintain mature donor-derived alloreactive Natural Killer cells and γδ(+) T cells in the graft. We, thus, started a formal study in children with hematological disorders aimed at evaluating the safety and efficacy of this approach. Preliminary results on 60 children transplanted so far after this type of graft manipulation are particularly promising.

Apparent mtDNA sequence heterogeneity in single human blood CD34+ cells is markedly affected by storage and transport

Single CD34(+) cells from adult human peripheral blood show mtDNA sequence heterogeneity. In this study, we compared mtDNA sequence variation in single CD34(+) cells from peripheral blood (PB) mononuclear cells (MNCs) from the same donors but under different conditions of storage and transport: group I, MNCs from heparinized PB that inadvertently required six days to be transported to the testing laboratory; group II, MNCs which were isolated from PB within a day of phlebotomy and frozen prior to transportation and storage. We observed more cell death for MNCs of group I than group II. Concordantly, group I CD34(+) cells had a very low potential for hematopoietic colony formation in vitro compared with group II cells. CD34(+) cells of group II showed an unexpectedly higher level of mtDNA sequence heterogeneity than was present in group I cells. These observations suggest that reduced mtDNA sequence heterogeneity in single CD34(+) cells of group I was likely due to elimination of cells harboring mutations. CD34(+) cells that survive stress ex vivo may be more enriched in quiescent primitive hematopoietic stem cells, with fewer mtDNA mutations than are present in committed progenitors. Technically, attention is required to conditions of preparation of human blood samples for single cell mtDNA analysis.

Phospholipase C-β in immune cells

Great progress has recently been made in structural and functional research of phospholipase C (PLC)-β. We now understand how PLC-β isoforms (β1-β4) are activated by GTP-bound Gαq downstream of G protein-coupled receptors. Numerous studies indicate that PLC-βs participate in the differentiation and activation of immune cells that control both the innate and adaptive immune systems. The PLC-β3 isoform also interplays with tyrosine kinase-based signaling pathways, to inhibit Stat5 activation by recruiting the protein-tyrosine phosphatase SHP-1, with which PLC-β3 and Stat5 form a multi-molecular signaling platform, named SPS complex. The SPS complex has important regulatory roles in tumorigenesis and immune cell activation.

Transcriptional hierarchies regulating early blood cell development

Hematopoiesis represents one of the paradigmatic systems for studying stem cell biology, but our understanding of how the hematopoietic system develops during embryogenesis is still incomplete. While many lessons have been learned from studying the mouse embryo, embryonic stem cells have come to the fore as an alternative and more tractable model to recapitulate hematopoietic development. Here we review what is known about the embryonic origin of blood from these complementary systems and how transcription factor networks regulate the emergence of hematopoietic tissue from the mesoderm. Furthermore, we have performed an integrated analysis of genome-wide microarray and ChIP-seq data sets from mouse embryos and embryonic stem (ES) cell lines deficient in key regulators and demonstrate how this type of analysis can be used to reconstruct regulatory hierarchies that both confirm existing regulatory linkages and suggest additional interactions.

An mRNA atlas of G protein-coupled receptor expression during primary human monocyte/macrophage differentiation and lipopolysaccharide-mediated activation identifies targetable candidate regulators of inflammation

G protein-coupled receptors (GPCRs) are among the most important targets in drug discovery. In this study, we used TaqMan Low Density Arrays to profile the full GPCR repertoire of primary human macrophages differentiated from monocytes using either colony stimulating factor-1 (CSF-1/M-CSF) (CSF-1 Mϕ) or granulocyte macrophage colony stimulating factor (GM-CSF) (GM-CSF Mϕ). The overall trend was a downregulation of GPCRs during monocyte to macrophage differentiation, but a core set of 10 genes (e.g. LGR4, MRGPRF and GPR143) encoding seven transmembrane proteins were upregulated, irrespective of the differentiating agent used. Several of these upregulated GPCRs have not previously been studied in the context of macrophage biology and/or inflammation. As expected, CSF-1 Mϕ and GM-CSF Mϕ exhibited differential inflammatory cytokine profiles in response to the Toll-like Receptor (TLR)4 agonist lipopolysaccharide (LPS). Moreover, 15 GPCRs were differentially expressed between these cell populations in the basal state. For example, EDG1 was expressed at elevated levels in CSF-1 Mϕ versus GM-CSF Mϕ, whereas the reverse was true for EDG6. 101 GPCRs showed differential regulation over an LPS time course, with 65 of these profiles being impacted by the basal differentiation state (e.g. GPRC5A, GPRC5B). Only 14 LPS-regulated GPCRs showed asynchronous behavior (divergent LPS regulation) with respect to differentiation status. Thus, the differentiation state primarily affects the magnitude of LPS-regulated expression, rather than causing major reprogramming of GPCR gene expression profiles. Several GPCRs showing differential profiles between CSF-1 Mϕ and GM-CSF Mϕ (e.g. P2RY8, GPR92, EMR3) have not been widely investigated in macrophage biology and inflammation. Strikingly, several closely related GPCRs displayed completely opposing patterns of regulation during differentiation and/or activation (e.g. EDG1 versus EDG6, LGR4 versus LGR7, GPRC5A versus GPRC5B). We propose that selective regulation of GPCR5A and GPCR5B in CSF-1 Mϕ contributes to skewing toward the M2 macrophage phenotype. Our analysis of the GPCR repertoire expressed during primary human monocyte to macrophage differentiation and TLR4-mediated activation provides a valuable new platform for conducting future functional analyses of individual GPCRs in human macrophage inflammatory pathways.

Biomechanical force in blood development: extrinsic physical cues drive pro-hematopoietic signaling

The hematopoietic system is dynamic during development and in adulthood, undergoing countless spatial and temporal transitions during the course of one's life. Microenvironmental cues in the many unique hematopoietic niches differ, characterized by distinct soluble molecules, membrane-bound factors, and biophysical features that meet the changing needs of the blood system. Research from the last decade has revealed the importance of substrate elasticity and biomechanical force in determination of stem cell fate. Our understanding of the role of these factors in hematopoiesis is still relatively poor; however, the developmental origin of blood cells from the endothelium provides a model for comparison. Many endothelial mechanical sensors and second messenger systems may also determine hematopoietic stem cell fate, self renewal, and homing behaviors. Further, the intimate contact of hematopoietic cells with mechanosensitive cell types, including osteoblasts, endothelial cells, mesenchymal stem cells, and pericytes, places them in close proximity to paracrine signaling downstream of mechanical signals. The objective of this review is to present an overview of the sensors and intracellular signaling pathways activated by mechanical cues and highlight the role of mechanotransductive pathways in hematopoiesis.

The emerging roles of AhR in physiology and immunity

The aryl hydrocarbon receptor (AhR) is traditionally defined as a transcriptional regulator involved in adaptive xenobiotic response, however, emerging evidence supports physiological functions of AhR in normal cell development and immune response. The role of AhR in immunomodulation is multi-dimensional. On the one hand, activation of AhR by TCDD and other ligands leads to profound immunosuppression, potentially via skewed Th1/Th2 cell balance toward Th1 dominance, and boosted Treg cell differentiation. On the other hand, activation of AhR can also induce Th17 cell polarization and increase the severity of autoimmune disease. In addition to T lymphocytes, the AhR also appears to play a vital role in B cell maturation, and regulates the activity of macrophages, dendritic cells and neutrophils following lipopolysaccharide challenge or influenza virus infection. In these scenarios, activation of AhR is associated with decreased host response and reduced survival. Furthermore, gene knock out studies suggest that AhR is indispensable for the postnatal maintenance of intestinal intraepithelial lymphocytes and skin-resident dendritic epidermal gamma delta T cells, providing a potential link between AhR and gut immunity and wound healing. It is well accepted that the magnitude and the type of immune response is dependent on the local cytokine milieu and the AhR appears to be one of the key factors involved in the fine turning of this cytokine balance.

Radiation-dose response of glycophorin A somatic mutation in erythrocytes associated with gene polymorphisms of p53 binding protein 1

Information on individual variations in response to ionizing radiation is still quite limited. Previous studies of atomic-bomb survivors revealed that somatic mutations at the glycophorin A (GPA) gene locus in erythrocytes were significantly elevated with radiation exposure dose, and that the dose response was significantly higher in survivors with subsequent cancer development compared to those without cancer development. Noteworthy in these studies were great inter-individual differences in GPA mutant fraction even in persons with similar radiation doses. It is hypothesized that persistent GPA mutations in erythrocytes of atomic-bomb survivors are derived from those in long-lived hematopoietic stem cell (HSC) populations, and that individual genetic backgrounds, specifically related to DNA double-strand break repair, contribute to individual differences in HSC mutability following radiation exposure. Thus, we examined the relationship between radiation exposure, GPA mutant fraction in erythrocytes, and single nucleotide polymorphisms (SNPs) of the key gene involved in DNA double-strand break repair, p53 binding protein 1 (53BP1). 53BP1 SNPs and inferred haplotypes demonstrated a significant interaction with radiation dose, suggesting that radiation-dose response of GPA somatic mutation is partly dependent on 53BP1 genotype. It is also possible that 53BP1 plays a significant role in DNA double-strand break repair in HSCs following radiation exposure.

Erythropoietin-stimulated endothelial cells support erythroid cell differentiation of CD34(+) haematopoietic progenitors

BACKGROUND AND OBJECTIVES

Endothelial cells provide a unique medium for the proliferation and white lineage differentiation of haematopoietic progenitor cells (HPC). Whether this quality can be exploited to facilitate the differentiation of erythroid precursors is not yet known.

MATERIALS AND METHODS

Haematopoietic progenitor cells derived from cord blood were cultured for 3 weeks in erythropoietin-stimulated supernatants with (n = 6) or without cyclosporine A (CSA, n = 6). Cell count, phenotype and morphology were assessed on a weekly basis, and the haemoglobin content was analysed. These cultures were compared with erythroid differentiation induced by cytokines only (n = 6).

RESULTS

Endothelial supernatants combined with CSA led to equivalent numbers of CD71(+) erythroblasts after 1 week as cytokines only. The purity of glycophorin-positive, CD45-negative cells was higher in cells generated in endothelial supernatants than in cytokine-based media. Additional prostaglandin E2 induced a change from fetal to adult haemoglobin.

CONCLUSION

For the generation of erythroblasts from HPC, endothelial supernatants are a simple and cost-effective alternative to culture conditions based on cytokines.

A stromal-free, serum-free system to expand ex vivo hematopoietic stem cells from mobilized peripheral blood of patients with hematologic malignancies and healthy donors

BACKGROUND AIMS

The number of hematopoietic stem cells (HSCs) is critical for transplantation. The ex vivo expansion of mobilized peripheral blood (MPB) HSCs is of clinical value for reconstitution to meet clinical need.

METHODS

This study proposed a simple, defined, stromal-free and serum-free culture system (SF-HSC medium) for clinical use, which is composed of Iscove's modified Dulbecco's medium, cytokine cocktails and serum substitutes. This study also characterized the cellular properties of expanded MPB CD133(+) HSCs from patients with hematologic malignancies and healthy donors by surface antigen, colony-forming cell, long-term culture-initiating cell, gene expression and in vivo engraftment assays.

RESULTS

The expanded fold values of CD45(+) white blood cells and CD34(+), CD133(+), CD34(+)CD38(-), CD133(+)CD38(-), CD34(+)CD133(+), colony-forming and long-term culture-initiating cells at the end of 7-day culture from CD133(+) MPB of hematologic malignancies were 9.4-fold, 5.9-fold, 4.0-fold, 35.8-fold, 21.9-fold, 3.8-fold, 11.8-fold and 6.7-fold, and values from healthy donor CD133(+) MPB were 20.7-fold, 14.5-fold, 8.5-fold, 83.8-fold, 37.3-fold, 6.2-fold, 19.1-fold and 14.6-fold. The high enrichment of CD38(-) cells, which were either CD34(+) or CD133(+), sustained the proliferation of early uncommitted HSCs. The expanded cells showed high levels of messenger RNA expression of HOBX4, ABCG2 and HTERT and had the in vivo ability to re-populate NOD/SCID mice.

CONCLUSIONS

Our results demonstrated that an initial, limited number of MPB CD133(+) HSCs could be expanded functionally in SF-HSC medium. We believe that this serum-free expansion technique can be employed in both basic research and clinical transplantation.

Cell therapy with autologous mesenchymal stem cells-how the disease process impacts clinical considerations

The prospective clinical use of multipotent mesenchymal stromal cells (MSCs) holds enormous promise for the treatment of a large number of degenerative and age-related diseases. In particular, autologous MSCs isolated from bone marrow (BM) are considered safe and have been extensively evaluated in clinical trials. Nevertheless, different efficacies have been reported, depending on the health status and age of the donor. In addition, the biological functions of BM-MSCs from patients with various diseases may be impaired. Furthermore, medical treatments such as long-term chemotherapy and immunomodulatory therapy may damage the BM microenvironment and affect the therapeutic potential of MSCs. Therefore, a number of practical problems must be addressed before autologous BM-MSCs can be widely applied with higher efficiency in patients. As such, this review focuses on various factors that directly influence the biological properties of BM-MSCs, and we discuss the possible mechanisms of these alterations.

Oral health as a predictive factor for oral mucositis

OBJECTIVES

Oral mucositis is a complication frequently associated with hematopoietic stem cell transplantation, decreasing a patient's quality of life and increasing the occurrence of opportunistic infections. The purpose of this study was to determine the incidence and severity of oral mucositis and to assess the correlation of this disease with the oral health of an individual at the time of hematopoietic stem cell transplantation.

METHODS

Before transplantation, patients' oral health and inflammatory conditions were determined using the gingival index and the plaque index, which are based on gingival bleeding and the presence of dental plaque, respectively. Additionally, the dental health status was determined using the decayed, missing, and filled teeth index. The monitoring of oral mucositis was based on the World Health Organization grading system and was performed for five periods: from Day 0 to D+5, from D+6 to D+10, from D+11 to D+15, from D+16 to D+20, and from D+21 to D+30.

RESULTS

A total of 97 patients (56% male and 44% female) who underwent hematopoietic stem cell transplantation at the Hospital das Clinicas da Faculdade de Medicina da Universidade de Sao Paulo between January 2008 and July 2009 were prospectively examined. The incidence of ulcerative mucositis was highest from days +6 to +10 and from days +11 to +15 in the patients who underwent autologous and allogeneic hematopoietic stem cell transplantation, respectively.

CONCLUSION

The data, including the dental plaque and periodontal status data, showed that these oral health factors were predictive of the incidence and severity of oral mucositis in a cohort of patients with similar conditioning regimens before hematopoietic stem cell transplantation.

Targeting self-renewal pathways in myeloid malignancies

A fundamental property of hematopoietic stem cells (HSCs) is the ability to self-renew. This is a complex process involving multiple signal transduction cascades which control the fine balance between self-renewal and differentiation through transcriptional networks. Key activators/regulators of self-renewal include chemokines, cytokines and morphogens which are expressed in the bone marrow niche, either in a paracrine or autocrine fashion, and modulate stem cell behaviour. Increasing evidence suggests that the downstream signaling pathways induced by these ligands converge at multiple levels providing a degree of redundancy in steady state hematopoiesis. Here we will focus on how these pathways cross-talk to regulate HSC self-renewal highlighting potential therapeutic windows which could be targeted to prevent leukemic stem cell self-renewal in myeloid malignancies.

Gene therapy of primary T cell immunodeficiencies

Gene therapy of severe combined immunodeficiencies has been proven to be effective to provide sustained correction of the T cell immunodeficiencies. This has been achieved for 2 forms of SCID, i.e SCID-X1 (γc deficiency) and adenosine deaminase deficiency. Occurrence of gene toxicity generated by integration of first generation retroviral vectors, as observed in the SCID-X1 trials has led to replace these vectors by self inactivated (SIN) retro(or lenti) viruses that may provide equivalent efficacy with a better safety profile. Results of ongoing clinical studies in SCID as well as in other primary immunodeficiencies, such as the Wiskott Aldrich syndrome, will be thus very informative.

Mixed chimerism and split tolerance: mechanisms and clinical correlations

Establishing hematopoietic mixed chimerism can lead to donor-specific tolerance to transplanted organs and may eliminate the need for long-term immunosuppressive therapy, while also preventing chronic rejection. In this review, we discuss central and peripheral mechanisms of chimerism induced tolerance. However, even in the long-lasting presence of a donor organ or donor hematopoietic cells, some allogeneic tissues from the same donor can be rejected; a phenomenon known as split tolerance. With the current goal of creating mixed chimeras using clinically feasible amounts of donor bone marrow and with minimal conditioning, split tolerance may become more prevalent and its mechanisms need to be explored. Some predisposing factors that may increase the likelihood of split tolerance are immunogenicity of the graft, certain donor-recipient combinations, prior sensitization, location and type of graft and minimal conditioning chimerism induction protocols. Additionally, split tolerance may occur due to a differential susceptibility of various types of tissues to rejection. The mechanisms involved in a tissue's differential susceptibility to rejection include the presence of polymorphic tissue-specific antigens and variable sensitivity to indirect pathway effector mechanisms. Finally, we review the clinical attempts at allograft tolerance through the induction of chimerism; studies that are revealing the complex relationship between chimerism and tolerance. This relationship often displays split tolerance, and further research into its mechanisms is warranted.

Toward minimal conditioning protocols for allogeneic chimerism in tolerance resistant recipients

Mixed chimerism is a promising approach toward generating donor-specific immunological tolerance. However, chimerism induction can be toxic; therefore, there is an effort to develop non-myeloablative, minimal intensity protocols that can generate chimerism without the toxic side effects. Recently, with the goal of creating a minimalistic chimerism induction protocol in the tolerance resistant non-obese diabetic (NOD) mouse model, we identified pre-existing T cells as cells that resist fully allogeneic chimerism. With monoclonals targeting NOD T cells, we showed that long-term chimerism and tolerance toward donor islets could be established. However, this promising new protocol relied on the administration of a single dose of anti-CD40 ligand, which is not clinically applicable. In refining protocols to move even closer to clinical utility, we report here initial success at generating fully allogeneic mixed chimerism in NOD mice by adding cyclophosphamide to the conditioning regimen in place of anti-CD40 ligand antibodies.

The hematopoietic stem cell niche--home for friend and foe?

The hematopoietic stem cell (HSC) niche is involved in the maintainance and regulation of quiescence, self-renewal and differentiation of hematopoietic stem cells and the fate of their progeny in mammals dealing with the daily stresses to the hematopoietic system. From the discovery that perturbations of the HSC niche can lead to hematopoietic disorders, we have now arrived at the prospect that the HSC niche may play a role in hematological malignancies and that this HSC niche may be a target for therapy. This review attempts to capture the discoveries of the last few years regarding the normal and malignant hematopoietic stem cell niche and possible ways to target this niche.

Of blood cells and the nervous system: hematopoiesis in the Drosophila larva

Hematopoiesis is well-conserved between Drosophila and vertebrates. Similar as in vertebrates, the sites of hematopoiesis shift during Drosophila development. Blood cells (hemocytes) originate de novo during hematopoietic waves in the embryo and in the Drosophila lymph gland. In contrast, the hematopoietic wave in the larva is based on the colonization of resident hematopoietic sites by differentiated hemocytes that arise in the embryo, much like in vertebrates the colonization of peripheral tissues by primitive macrophages of the yolk sac, or the seeding of fetal liver, spleen and bone marrow by hematopoietic stem and progenitor cells. At the transition to the larval stage, Drosophila embryonic hemocytes retreat to hematopoietic "niches," i.e., segmentally repeated hematopoietic pockets of the larval body wall that are jointly shared with sensory neurons and other cells of the peripheral nervous system (PNS). Hemocytes rely on the PNS for their localization and survival, and are induced to proliferate in these microenvironments, expanding to form the larval hematopoietic system. In this process, differentiated hemocytes from the embryo resume proliferation and self-renew, omitting the need for an undifferentiated prohemocyte progenitor. Larval hematopoiesis is the first Drosophila model for blood cell colonization and niche support by the PNS. It suggests an interface where innocuous or noxious sensory inputs regulate blood cell homeostasis or immune responses. The system adds to the growing concept of nervous system dependence of hematopoietic microenvironments and organ stem cell niches, which is being uncovered across phyla.

Mutation of STAT1/3 binding sites in gp130(FXXQ) knock-in mice does not alter hematopoietic stem cell repopulation or self-renewal potential

Interleukin (IL)-6 family cytokine signaling through gp130 and signal transducer and activator of transcription (STAT) activation is believed important for early hematopoiesis. To determine whether gp130/STAT1/3 physical interaction is required, we compared hematopoietic repopulating activities of embryonic day (E)14.5 fetal liver cells from gp130(FXXQ/FXXQ) knock-in mice, which have four mutated STAT1/3 binding sites. In hematopoietic cells, failure to tyrosine phosphorylate STAT3 by gp130 did not cause any significant effects on myeloid progenitor colony forming units (CFU) in vitro and or on competitive multilineage hematopoietic reconstitution. Serial transplantation of fetal liver (FL) cells was unaffected throughout primary, secondary, and tertiary transplants indicating normal self-renewal capacity. Even gp130(FXXQ/FXXQ) on the background of STAT5 deficiency, with known hematopoietic stem cell (HSC) repopulating dysfunction, did not further impair HSCs beyond that of STAT5 alone. Overall, the defective gp130-mediated STAT1/3 signaling is surprisingly dispensable for HSC function. However, since these mice lack both STAT1/3 binding sites there are several possible explanations for this result and these are discussed.

The prostate cancer bone marrow niche: more than just 'fertile soil'

The hematopoietic stem cell (HSC) niche in the bone marrow has been studied extensively over the past few decades, yet the bone marrow microenvironment that supports the growth of metastatic prostate cancer (PCa) has only been recently considered to be a specialized 'niche' as well. New evidence supports the fact that disseminated tumor cells (DTCs) of PCa actually target the HSC niche, displace the occupant HSCs and take up residence in the pre-existing niche space. This review describes some of the evidence and mechanisms by which DTCs act as molecular parasites of the HSC niche. Furthermore, the interactions between DTCs, HSCs and the niche may provide new targets for niche-directed therapy, as well as insight into the perplexing clinical manifestations of metastatic PCa disease.

Structure and function of the solid tumor niche

Although the hematopoietic stem cell (HSC) niche has been an active area of study, the concept of the bone marrow microenvironment (BMM) harboring a niche for solid metastatic tumor cells has only recently been considered. The HSC niche and microenvironment that is thought to constitute the solid tumor niche share many of the same structural and functional components, suggesting the possibility that the HSC and tumor niche are one in the same. The osteoblast is a critical component for each of these niches, and is important for regulating cellular processes such homing and migration, growth and survival, and quiescence and dormancy. Current understanding of the HSC niche may provide more insight to better defining the solid tumor niche. As role of the niche in regulating these processes is better understood, new insights to the role of the BMM in metastatic disease may be gained, and provide more potential targets for therapy.

Novel measurements of mammary stem cells in human umbilical cord blood as prospective predictors of breast cancer susceptibility in later life

BACKGROUND

The size of the breast stem-cell pool could underlie the intrauterine roots of breast cancer. We studied whether breast stem cells exist in umbilical cord blood and if they correlate with hematopoietic stem-cell measurements that have been positively associated with perinatal risk factors for breast cancer.

SUBJECTS AND METHODS

We isolated mononuclear cells from umbilical cord blood of 170 singleton full-term pregnancies and determined, by reverse transcription polymerase chain reaction, the presence of genes of putative breast epithelial stem-cell/progenitor markers [including epithelial cell adhesion molecule (EpCAM), CD49f (α6-integrin), CD117 (c-kit receptor), CD24, and CD29 (β1-integrin)]. By immunocytochemistry, we colocalized protein expressions of EpCAM+CD49f+, CD49f+CD24+, and CD24+CD29+. We correlated concentrations of putative breast stem-cell/progenitor subpopulations, quantified by flow cytometry, with concentrations of hematopoietic stem cells.

RESULTS

Mammary stem-cell phenotypes were identified in umbilical cord blood. The measured EpCAM+ subpopulation was positively correlated with concentrations of CD34+ and CD34+CD38- hematopoietic stem cells (both P=0.006). Additionally, EpCAM+CD49f+ and CD49f+CD24+ subpopulations were positively correlated to the CD34+ cells (P=0.03 and 0.008, respectively).

CONCLUSION

The positive association between measurable breast and hematopoietic stem cells in human umbilical cord blood suggests plausible mechanisms for a prenatal influence on breast cancer risk.

Reciprocal upregulation of Notch signaling molecules in hematopoietic progenitor and mesenchymal stromal cells

Although mesenchymal stem cells (MSCs) play pivotal supportive roles in hematopoiesis, how they interact with hematopoietic stem cells (HSCs) is not well understood. We investigated the interaction between HSCs and surrogate MSCs (C3H10T1/2 stromal cells), focusing on the molecular events induced by cell contact of these bipartite populations. C3H10T1/2 is a mesenchymal stromal cell line that can be induced to differentiate into preadipocytes (A54) and myoblasts (M1601). The stromal cell derivatives were cocultured with murine HSCs (Lineage(-)Sca1(+)), and gene expression profiles in stromal cells and HSCs were compared before and after the coculture. HSCs gave rise to cobblestone areas only on A54 cells, with ninefold more progenitors than on M1601 or undifferentiated C3H10T1/2 cells. Microarray-based screening and a quantitative reverse transcriptase directed-polymerase chain reaction showed that the levels of Notch ligands (Jagged1 and Delta-like 3) were increased in A54 cells upon interaction with HSCs. On the other hand, the expression of Notch1 and Hes1 was upregulated in the HSCs cocultured with A54 cells. A transwell assay revealed that the reciprocal upregulation was dependent on cell-to-cell contact. The result suggested that in the hematopoietic niche, HSCs help MSCs to produce Notch ligands, and in turn, MSCs help HSCs to express Notch receptor. Such a reciprocal upregulation would reinforce the downstream signaling to determine the fate of hematopoietic cell lineage. Clarification of the initiating events on cell contact should lead to the identification of specific molecular targets to facilitate HSC engraftment in transplantation therapy.

Embryonic regulation of the mouse hematopoietic niche

Hematopoietic stem cells (HSCs) can differentiate into several types of hematopoietic cells (HCs) (such as erythrocytes, megakaryocytes, lymphocytes, neutrophils, or macrophages) and also undergo self-renewal to sustain hematopoiesis throughout an organism's lifetime. HSCs are currently used clinically as transplantation therapy in regenerative medicine and are typically obtained from healthy donors or cord blood. However, problems remain in HSC transplantation, such as shortage of cells, donor risks, rejection, and graft-versus-host disease (GVHD). Thus, increased understanding of HSC regulation should enable us to improve HSC therapy and develop novel regenerative medicine techniques. HSC regulation is governed by two types of activity: intrinsic regulation, programmed primarily by cell autonomous gene expression, and extrinsic factors, which originate from so-called "niche cells" surrounding HSCs. Here, we focus on the latter and discuss HSC regulation with special emphasis on the role played by niche cells.

Radical reversal of vasoactive intestinal peptide (VIP) receptors during early lymphopoiesis

Successful thymocyte maturation is essential for normal, peripheral T cell function. Vasoactive intestinal peptide (VIP) is a neuropeptide which is highly expressed in the thymus that has been shown to modulate thymocyte development. VIP predominantly binds two G protein coupled receptors, termed vasoactive intestinal peptide receptor 1 (VPAC1) and VPAC2, but their expression profiles in CD4(-)/CD8(-) (double negative, DN) thymocyte subsets, termed DN1-4, have yet to be identified. We hypothesized that a high VPAC1:VPAC2 ratio in the earliest thymocyte progenitors (ETP cells) would be reversed during early lymphopoiesis as observed in activated, peripheral Th(2) cells, as the thymus is rich in Th(2) cytokines. In support of this hypothesis, high VPAC1 mRNA levels decreased 1000-fold, accompanied with a simultaneous increase in VPAC2 mRNA expression during early thymocyte progenitor (ETP/DN1)→DN3 differentiation. Moreover, arrested DN3 cells derived from an Ikaros null mouse (JE-131 cells) failed to completely reverse the VIP receptor ratio compared to wild type DN3 thymocytes. Surprisingly, VPAC2(-/-) mice did not show significant changes in relative thymocyte subset numbers. These data support the notion that both VPAC1 and VPAC2 receptors are dynamically regulated by Ikaros, a master transcriptional regulator for thymocyte differentiation, during early thymic development. Moreover, high VPAC1 mRNA is a novel marker for the ETP population making it enticing to speculate that the chemotactic VIP/VPAC1 signaling axis may play a role in thymocyte movement. Also, despite the results that VPAC2 deficiency did not affect thymic subset numbers, future studies are necessary to determine whether downstream T cell phenotypic changes manifest themselves, such as a propensity for a Th(1) versus Th(2) polarization.

Stem cell therapy for diabetes mellitus

In this review, we present (1) a brief discussion of hematopoietic stem cell transplantation (HSCT) for severe and refractory autoimmune diseases (AIDs) from its beginning in 1996 through recently initiated prospective randomized clinical trials; (2) an update (up to July 2009) of clinical and laboratory outcomes of 23 patients with newly diagnosed type 1 diabetes mellitus (T1DM), who underwent autologous HSCT at the Bone Marrow Transplantation Unit of the Ribeirão Preto Medical School, University of São Paulo, Brazil; (3) a discussion of possible mechanisms of action of HSCT in AIDs, including preliminary laboratory data obtained from our patients; and (4) a discussion of future perspectives of stem cell therapy for T1DM and type 2 DM, including the use of stem cell sources other than adult bone marrow and the combination of cell therapy with regenerative compounds.