The role of cell adhesion in hematopoiesis and leukemogenesis

The cells of the bone marrow microenvironment are emerging as important contributors and regulators of normal hematopoiesis. This microenvironment is perturbed during leukemogenesis, and evidence points toward a bidirectional communication between leukemia cells and the normal cells of the bone marrow, mediated by direct cell–cell contact as well as soluble factors. These interactions are increasingly appreciated to play a role in leukemogenesis and possibly in resistance to chemotherapy. In fact, several compounds that specifically target the bone marrow microenvironment, including inhibitors of cell adhesion, are being tested as adjuncts to leukemia therapy.     

佐剂 DDA 和 MPL 对提高结核杆菌组合DNA 疫苗免疫效果的比较研究

编码结核杆菌 3 种抗原 Ag85B , MPT64 , MPT83 的基因片段插入真核表达载体作为组合疫苗免疫小鼠, DDA 和 MPL 作为佐剂分别提高了此三价苗的免疫原性和免疫保护效果,且相比之下 DDA 优于 MPL. 添加 DDA 后, Ag85B , MPT64 , MPT83 抗原特异的 IFN- γ含量分别为 (265.37±79.2) U/ml , (185.31 ±58.3) U/ml, (108.13±54.4) U/ml ,分别比非佐剂组的高 16 U/ml , 45 U/ml 和 2 U/ml ,与 MPL 组 3 种抗原特异性 IFN- γ的含量无显著差异 . IL-4 的含量在各组中无显著差异 . 攻毒后细菌计数结果显示,添加佐剂的三价苗组小鼠的肺脏和脾脏的载菌量分别比空载体组降低了 2~3 个数量级,且佐剂 DDA 组显著优于佐剂 MPL 组和未加佐剂组 . 病理切片结果与载菌量数据相一致,添加佐剂组,特别是 DDA 组小鼠肺部淋巴细胞相对减少,巨噬细胞增多 . 因此, DDA 作为佐剂能显著提高核酸疫苗的免疫效率,佐剂 MPL 不能提高结核杆菌多价核酸疫苗的免疫效率 .     

Protective role of connexin 32 in steady-state hematopoiesis, regeneration state, and leukemogenesis

The role of gap junctions formed by connexins (Cxs) has been implicated in the homeostatic regulation of multicellular systems. Primitive hematopoietic progenitor cells form a multicellular system, but a previous report states that Cx32 is not expressed in the bone marrow. Thus, a question arises as to why Cx molecules are not detected in the hematopoietic tissue other than in stromal cells. Based on our preliminary study, which suggested a potential impairment of hematopoiesis in Cx32-knockout (KO) mice, the objectives of the present study were to determine whether Cx32 functions in the bone marrow during steady-state hematopoiesis and to examine its possible protective roles during regeneration after chemical abrasions and during leukemogenesis after the administration of a secondary genotoxic chemical, methyl nitrosourea (MNU). As a result, the Cx32 molecule, functioning in the hematopoietic stem cell (HSC) compartment during steady-state hematopoiesis, was observed for the first time; the expressions of Cx32 at the mRNA level, as determined by polymerase chain reaction analysis, and at the protein level, determined using an anti-Cx32 antibody, were observed only in the lin(-)c-kit(+) HSC fraction, using a combination of immunobead-density gradient and immunomagnetic bead separation. Hematopoiesis was impaired in the absence of Cx32, and it was delayed during regeneration after chemical abrasion with 5-fluorouracil at 150 mg/kg body wt in Cx32-KO mice. Cx32-KO mice showed increased leukemogenicity compared with wild-type mice after MNU injection; furthermore, in a competitive assay for leukemogenicity in mice that had been lethally irradiated and repopulated with a mixed population of bone marrow cells from Cx32-KO mice and wild-type mice, the resulting leukemias originated predominantly from Cx32-KO bone marrow cells. In summary, the role of Cx32 in hematopoiesis was not previously recognized, and Cx32 was expressed only in HSCs and their progenitor cells. The results indicate that Cx32 in wild-type mice protects HSCs from chemical abrasion and leukemogenic impacts.     

Fetal Liver Stromal Cells Support Blast Growth in Transient Abnormal Myelopoiesis in Down Syndrome Through GM‐CSF

Transient abnormal myelopoiesis (TAM) in neonates with Down syndrome, which spontaneously resolves within several weeks or months after birth, may represent a very special form of leukemia arising in the fetal liver (FL). To explore the role of the fetal hematopoietic microenvironment in the pathogenesis of TAM, we examined the in vitro influences of stromal cells of human FL and fetal bone marrow (FBM) on the growth of TAM blasts. Both FL and FBM stromal cells expressed mesenchymal cell antigens (vimentin, α‐smooth muscle actin, CD146, and nestin), being consistent with perivascular cells/mesenchymal stem cells that support hematopoietic stem cells. In addition, a small fraction of the FL stromal cells expressed an epithelial marker, cytokeratin 8, indicating that they could be cells in epithelial‐mesenchymal transition (EMT). In the coculture system, stromal cells of the FL, but not FBM, potently supported the growth of TAM blast progenitors, mainly through humoral factors. High concentrations of hematopoietic growth factors were detected in culture supernatants of the FL stromal cells and a neutralizing antibody against granulocyte‐macrophage colony‐stimulating factor (GM‐CSF) almost completely inhibited the growth‐supportive activity of the culture supernatants. These results indicate that FL stromal cells with unique characteristics of EMT cells provide a pivotal hematopoietic microenvironment for TAM blasts and that GM‐CSF produced by FL stromal cells may play an important role in the pathogenesis of TAM. J. Cell. Biochem. 115: 1176–1186, 2014. © 2014 The Authors. Journal of Cellular Biochemistry published by Wiley Periodicals, Inc.     

Role of the thrombopoietin (TPO)/Mpl system: c-Mpl-like molecule/TPO signaling enhances early hematopoiesis in Xenopus laevis

Multiple organs are induced in the primitive embryonic ectoderm excised from blastula stage Xenopus laevis embryos, under the strict control of mesoderm inducing factors. This in vitro system is useful for exploring the mechanisms of development. In this study, the function of thrombopoietin (TPO)/c-Mpl signaling in the development of hematopoietic cells was investigated. An optimal hematopoietic cell induction system was established to evaluate the influence of growth factors on hematopoiesis. It was found that exogenous TPO enhanced hematopoiesis in explants induced by activin and bone morphogenetic protein (BMP)-4 and increased the number of both erythrocytes and leukocytes in a dose-dependent manner. Addition of anti-c-Mpl antibody completely inhibited the expansion of hematopoietic cells stimulated by TPO, and the antibody specifically recognized blood-like cells. These results demonstrate that TPO acts on hematopoietic progenitors induced in explants and the c-Mpl-like molecule in Xenopus mediates the cellular function of TPO. We also found that forced expression of TPO in embryos promoted hematopoiesis in the ventral blood island and the dorsal-- lateral plate mesoderm. These results suggest that hematopoietic stem and progenitor cells are regulated by TPO/c-Mpl signaling from when they appear in their ontogeny. They also suggest that TPO/c-Mpl signaling play a crucial role in the formation of hematopoietic cells in Xenopus.     

Eltrombopag, a thrombopoietin receptor agonist, enhances human umbilical cord blood hematopoietic stem/primitive progenitor cell expansion and promotes multi-lineage hematopoiesis

Umbilical cord blood (UCB) transplantation has emerged as a promising therapy, but it is challenged by scarcity of stem cells. Eltrombopag is a non-peptide, thrombopoietin (TPO) receptor agonist, which selectively activates c-Mpl in humans and chimpanzees. We investigated eltrombopag's effects on human UCB hematopoietic stem cell (HSC) and hematopoietic progenitor cell (HPC) expansion, and its effects on hematopoiesis in vivo. Eltrombopag selectively augmented the expansion of human CD45+, CD34+, and CD41+ cells in bone marrow compartment without effects on mouse bone marrow cells in the NOD/SCID mice xenotransplant model. Consequently, eltrombopag increased peripheral human platelets and white blood cells. We further examined effects in the STAT and AKT signaling pathways in serum-free cultures. Eltrombopag expanded human CD34+ CD38-, CD34+, and CD41+ cells. Both eltrombopag and recombinant human TPO (rhTPO) induced phosphorylation of STAT5 of CD34+ CD41-, CD34- CD41+, and CD34- CD41- cells. rhTPO preferentially induced pSTAT3, pAKT, and more pSTAT5 in CD34- C41+ cells, while eltrombopag had no effects on pSTAT3. In conclusion, eltrombopag enhanced expansion of HSCs/HPCs of human UCB in vivo and in vitro, and promoted multi-lineage hematopoiesis through the expansion of bone marrow HSCs/HPCs of human UCB in vivo. Eltrombopag differed somewhat from rhTPO in the signal transduction pathways by favoring earlier HSC/HPC populations.     

The effects of zoledronic acid in the bone and vasculature support of hematopoietic stem cell niches

Hematopoietic stem cells (HSC) are maintained in a tightly regulated bone microenvironment constituted by a rich milieu of cells. Bone cells such as osteoblasts are associated with niche maintenance as regulators of the endosteal microenvironment. Bone remodeling also plays a role in HSC mobilization although it is poorly defined. The effects of zoledronic acid (ZA), a potent bisphosphonate that inhibits bone resorption, were investigated on bone marrow cell populations focusing on HSCs, and the endosteal and vascular niches in bone. ZA treatment significantly increased bone volume and HSCs in both young and adult mice (4 week and 4 month old, respectively). ZA increased vessel numbers with no overall change in vascular volume in bones of young and had no effect on vasculature in adult mice. Since both young and adult mice had increased HSCs and bone mass with differing vasculature responses, this suggests that ZA indirectly supports HSCs via the osteoblastic niche and not the vascular niche. Additionally, gene expression in Lin‐ cells demonstrated increased expression of self‐renewal‐related genes Bmi1 and Ink4a suggesting a role of ZA in the modulation of cell commitment and differentiation toward a long‐term self‐renewing cell. Genes that support the osteoblastic niche, BMP2 and BMP6 were also augmented in ZA treated mice. In conclusion, ZA‐induced HSC expansion occurs independent of the vascular niche via indirect modulation of the osteoblastic niche. J. Cell. Biochem. 114: 67–78, 2012. © 2012 Wiley Periodicals, Inc.     

The role of the TRAIL/TRAIL receptors system in hematopoiesis and endothelial cell biology

TRAIL is a member of the tumor necrosis factor superfamily that interacts with an unusually complex receptor system, comprising transmembrane (TRAIL-R1, -R2, -R3 and -R4) and soluble (osteoprotegerin) receptors. TRAIL has received considerable attention because of the finding that many cancer cell types are sensitive to TRAIL-induced apoptosis. However, increasing experimental evidence shows that TRAIL exhibits regulatory roles in various normal tissues, as well. Although the best-characterized biological activity of TRAIL is in the homeostatic regulation of the immune system, in this review we have summarized and discussed the physiological function of TRAIL and its receptors, in normal hematopoiesis and vascular physiopathology.     

Normal hematopoiesis and hematologic malignancies: Role of canonical Wnt signaling pathway and stromal microenvironment

Wnts are a family of evolutionary-conserved secreted signaling molecules critically involved in a variety of developmental processes and in cell fate determination. A growing body of evidence suggests that Wnt signaling plays a crucial role in the influence of bone marrow stromal microenvironment on the balance between hematopoietic stem cell self-renewal and differentiation. Emerging clinical and experimental evidence also indicates Wnt signaling involvement in the disruption of the latter balance in hematologic malignancies, where the stromal microenvironment favors the homing of cancer cells to the bone marrow, as well as leukemia stem cell development and chemoresistance. In the present review, we summarize and discuss the role of the canonical Wnt signaling pathway in normal hematopoiesis and hematologic malignancies, with regard to recent findings on the stromal microenvironment involvement in these process and diseases.     

Ikaros in hematopoiesis and leukemia

Ikaros is a gene whose activity is essential for normal hematopoiesis.Ikaros acts as a master regulator of lymphoid and myeloid development as well as a tumor suppressor.In cells,Ikaros regulates gene expression via chromatin remodeling.During the past 15 years tremendous advances have been made in understanding the role of Ikaros in hematopoiesis and leukemogenesis.In this Topic Highlights series of reviews,several groups of international experts in this field summarize the experimental data that is shaping the emerging picture of Ikaros function at the biochemical and cellular levels.The articles provide detailed analyses of recent scientific advancements and present models that will serve as a basis for future studies aimed at developing a better understanding of normal hematopoiesis and hematological malignancies and at accelerating the application of this knowledge in clinical practice.     

The N-acylation-phosphodiesterase pathway and cell signalling

Long-chain N-acylethanolamines (NAEs) elicit a variety of biological and pharmacological effects, Anandamide (20:4n-6 NAE) and other polyunsaturated NAEs bind to the cannabinoid receptor and may thus serve as highly specific lipid mediators of cell signalling. NAEs can be formed by phospholipase D-catalyzed hydrolysis of N-acylethanolamine phospholipids or by direct condensation of ethanolamine and fatty acid, So far, most of the latter biosynthetic activity has been shown to be the reverse reaction of the NAE amidohydrolase that catalyzes NAE degradation. Thus, increasing evidence supports the hypothesis that the N-acylation-phosphodiesterase pathway yields not only saturated-monounsaturated NAEs, but polyunsaturated ones, including anandamide, as well.     

The requirement for pyruvate dehydrogenase in leukemogenesis depends on cell lineage

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The transsulfuration pathway in tetrahymena pyriformis

Four enzymes necessary for the metabolism of methione by the transsulfuration pathway, methionine adenosyltransferase (EC 2.5.1.6), adenosyl-homocysteinase (EC 3.3.1.1), cystathionine β-synthase (EC 4.2.1.22) and cystathionine γ-lyase (EC 4.4.1.1) were identified in Tetrahymean pyriformis. The ability of these cells to transfer ³⁵S from [³⁵S] methionine to form [³⁵S] - cysteine was also observed and taken as direct evidence for the functional existence of this pathway in Tetrahymena. An intermediate in the pathway and an active methyl donor, $\text{S-}\text{adenosylmethionine}$, was qualitatively identified in Tetrahymena and its concentration was found to be greater in late stationary phase cells than in early stationary phase cells.     

The role of stroma in hematopoiesis and dendritic cell development

Development of the immune system is depicted as a hierarchical process of differentiation from hematopoietic stem cells (HSC) to lineage-committed precursors, which further develop into mature immune cells. In the case of dendritic cell (DC) development, this linear precursor-progeny approach has led to a confused picture of relationships between various subsets of DC identifiable in vivo. A possible reconciliation of the diversity of DC precursors and DC subsets in vivo encompasses the role of the microenvironment in DC hematopoiesis. We propose here that various niches for DC hematopoiesis within lymphoid organs could account for the diversity of DC in vivo. A tridimensional space consisting of stromal cells which produce a range of membrane-bound and secreted molecules providing signals to DC progenitors would define these niches.     

壮肝逐瘀煎对肝纤维化大鼠肝脏Fas/FasL表达的影响

目的:研究壮肝逐瘀煎对肝纤维化(HF)大鼠肝脏肝星状细胞(HSC)的凋亡因子Fas/FasL表达的影响,探讨该方抗HF的作用机制。方法:58只SD大鼠随机取14只作为正常对照组,正常饲养。剩余大鼠采用CCl4复合因素法进行HF造模,实验第4周末随机处死造模大鼠4只,证实HF形成。其余随机分为病理模型组、壮肝逐瘀煎组、秋水仙碱组及大黄蛰虫丸组,每组10只。病理模型组给予生理盐水灌胃处理,其他3组分别予对应药物灌胃处理。治疗第6周末,处死所有大鼠,获取肝组织,HE染色光镜观察肝组织结构变化,免疫组化染色分析Fas、FasL分布。结果:与病理模型组大鼠比较,壮肝逐瘀煎治疗组肝小叶结构趋于正常,纤维间隔明显变薄,肝组织Fas、FasL的表达显著表达显著减少(P0.01)。结论:壮肝逐瘀煎能够明显改善HF大鼠肝脏的病理变化,具有明显的抗HF作用,其作用机制可能与壮肝逐瘀煎能调控HSC中凋亡因子Fas/FasL的表达有关。