Identification of a Stroma-Mediated Wnt Signal Promoting Self-Renewal of Hematopoietic Stem Cells in the Stem Cell Niche.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 2208-2208
Author(s):  
Young-Ju Kang ◽  
Eek-hoon Jho ◽  
Hanjun Kim ◽  
Gyeongsin Park ◽  
Jae-Seung Shim ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Stem Cell Niche ◽  
Stable Form ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Stromal Component ◽  
Cell Niche

Abstract With contrasting results recently reported on the effects of b-catenin on hematopoietic stem cells (HSCs), the precise role of Wnt on HSC regulation remains in question. Here, we show that Wnt-b-catenin signaling triggers distinct biological effects on HSCs depending on the target of activation within the hematopoietic microenvironment. Retroviral transduction of a stable form of b-catenin into HSCs caused a loss of competitive repopulating units (CRUs) in a limiting-dilution assay, whereas stabilized b-catenin in stromal cells CRU frequencies of co-cultured HSCs with higher preservation of undifferentiated state and caused enhanced levels of reconstitution in a manner dependent on direct contact between HSC and stroma. The enhancing effect of b-catenin stabilized stroma on HSC was also observed for human HSCs exhibiting higher frequencies of lympho-myeloid repopulating cells after transplantation into NOD/SCID mice. Interestingly, gene expression patterns of Wnt signaling molecules revealed compartmentalization in a manner that canonical Wnt ligands were preferentially expressed in the hematopoietic cells while molecules for reception of the signal such as Frizzled receptors or their co-receptors are preferentially expressed in stromal component, suggesting the role of stromal component as a target of Wnt signals in the niche. Furthermore, b-catenin accumulated selectively in the endosteal stroma of the trabecule region in “stressed” marrows, but not in “steady-state” marrows. Taken together, these results suggest stroma-mediated Wnt signals may function as microenvironmental cues for HSC self-renewal in the stem cell niche.

Identification of a Stroma-Mediated Wnt/β-Catenin Signal Promoting Self-Renewal of Hematopoietic Stem Cells in the Stem Cell Niche

Stem Cells ◽  
2009 ◽  
Vol 27 (6) ◽  
pp. 1318-1329 ◽  
Author(s):  
Jin-A Kim ◽  
Young-Ju Kang ◽  
Gyeongsin Park ◽  
Myungshin Kim ◽  
Young-Ok Park ◽  
...  
Keyword(s):  
Stem Cells ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Stem Cell Niche ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Cell Niche

Does primary myelofibrosis involve a defective stem cell niche? From concept to evidence

Blood ◽  
2008 ◽  
Vol 112 (8) ◽  
pp. 3026-3035 ◽  
Author(s):  
Jean-Jacques Lataillade ◽  
Olivier Pierre-Louis ◽  
Hans Carl Hasselbalch ◽  
Georges Uzan ◽  
Claude Jasmin ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Cell Proliferation ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Stem Cell Niche ◽  
Primary Myelofibrosis ◽  
Hematopoietic Stem ◽  
Stem Cell Proliferation ◽  
Cell Niche

Abstract Primary myelofibrosis (PMF) is the rarest and the most severe Philadelphia-negative chronic myeloproliferative syndrome. By associating a clonal proliferation and a mobilization of hematopoietic stem cells from bone marrow to spleen with profound alterations of the stroma, PMF is a remarkable model in which deregulation of the stem cell niche is of utmost importance for the disease development. This paper reviews key data suggesting that an imbalance between endosteal and vascular niches participates in the development of clonal stem cell proliferation. Mechanisms by which bone marrow niches are altered with ensuing mobilization and homing of neoplastic hematopoietic stem cells in new or reinitialized niches in the spleen and liver are examined. Differences between signals delivered by both endosteal and vascular niches in the bone marrow and spleen of patients as well as the responsiveness of PMF stem cells to their specific signals are discussed. A proposal for integrating a potential role for the JAK2 mutation in their altered sensitivity is made. A better understanding of the cross talk between stem cells and their niche should imply new therapeutic strategies targeting not only intrinsic defects in stem cell signaling but also regulatory hematopoietic niche–derived signals and, consequently, stem cell proliferation.

scholarly journals PEDF Can Rescue the Inhibition of Injured Endothelial Cells on Hematopoietic Stem Cell Expansion Ex Vivo

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 5008-5008
Author(s):  
Lingyu Zeng ◽  
Wenyi Lu ◽  
Lan Ding ◽  
Wen Ju ◽  
Jianlin Qiao ◽  
...  
Keyword(s):  
Stem Cells ◽  
Endothelial Cells ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Hematopoietic Stem Cell ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Mesenchymal Transition ◽  
Endothelial To Mesenchymal Transition

Introduction: Endothelial cells (ECs) provide a fertile niche for hematopoietic stem cell (HSC) maintenance, differentiation, and migration.Several studies have indicated that bone marrow (BM) vascular niche was impaired after HSC transplantation and severely inhibited hematopoietic reconstruction. Pigment epithelium-derived factor (PEDF) is an important potential cytoprotection and therapeutic agent for injured cells. The direct role of the injured endothelial cells on hematopoietic stem cells and whether PEDF has protective effect in this system remain unknown. This study aims to observe the influence of enjured ECs on HSCs and to explore the role of PEDF in endothelial-HSC coculture system. Methods: Injury of Endothelial cells by two important preparative regimenconditioning radiation and Busulfan respectively was evaluated with CCK8 assay. The expression of endothelial tight junctions(TJs),adherent junctions related molecules and endothelial to Mesenchymal Transition molecules such as ZO-1, Occludin,VE-cadherin, ICAM, α-SMA, CD31 and VCAM were detected by RT-qPCR, flow cytometry, immunofluorescence and western blot. The effects of injured endothelial cells on HSC self-renewal, differentiation, cell cycle and apoptosis were evaluated by flow cytometry, photography, viable cell count and clone formation assay. Hematopoiesis regulation factors SCF, IL-6, TGF-β and TNF-α were detected by ELISA. The protective effect of PEDF was also explored. Results: Both radiation and Busulfan could decrease cell viability of endothelial cells. The expression level of ZO-1, Occludin, VE-cadherin, ICAM, CD31 and VCAM were decreased and α-SMA was increased when EC exposed to radiation or Busulfan suggesting endothelial activation, impaired EC permeability and endothelial to Mesenchymal Transition after EC injured. Compared with normal endothelial cells and hematopoietic stem cell co-culture group, the HSC% of injured endothelial cells and hematopoietic stem cells co-cultured group were significantly decreased, the cell colony formation ability was decreased, the proportion of mature cells increased, and the damage of endothelial cells could not maintain the characteristics of HSC, weakened the self-renewal and multidirectional differentiation potential of HSC and promoted the maturation of HSC. After the administration of PEDF, endothelial to Mesenchymal Transition of EC was suppressed and the EC permeability was improved. Most importantly, the proportion of HSC was significantly increased, and the proportion of mature cells decreased in the coculture system. Conclusion: Injured endothelial cells can inhibit proliferation of hematopoietic stem cells, self-renewal and promote HSC differentiation. PEDF could ameliorate endothelial injury and promote HSC expansion by suppressing endothelial-mesenchymal transition and protecting TJs and AJs. Disclosures No relevant conflicts of interest to declare.

Thrombopoietin-Mpl Signal Induces Hematopoietic Stem Cells into Quiescent State in the Bone Marrow Niche.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 858-858
Author(s):  
Hiroki Yoshihara ◽  
Fumio Arai ◽  
Kentaro Hosokawa ◽  
Takao Takahashi ◽  
Hiroshi Miyazaki ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Stem Cells ◽  
Stem Cell ◽  
Stem Cell Niche ◽  
Osteoblastic Cells ◽  
Bone Surface ◽  
Hematopoietic Stem ◽  
Cycle Arrest ◽  
Cell Niche

Abstract Hematopoietic stem cells (HSCs) have the ability to self-renew and to differentiate to produce multi-lineage blood cells throughout the lifetime of individuals. Maintenance of these stem cell activities depends on the balance of intrinsic and extrinsic factors. The factors which regulate HSCs are provided by a microenvironment called stem cell niche, and interactions between HSCs and stem cell niche is critical for the maintenance of stem cell activities. Recently, it has been reported that HSCs exist frequently aside of the trabecular bone surface in bone marrow (BM). We have previously reported that side-population (SP) in HSC fraction is in the G0 phase and anti-apoptotic stem cells, and contacts osteoblasts. (Arai et al., Cell 2004). To further investigate the regulation of quiescence, cell adhesion, and survival of HSCs, we tried to clone the quiescent HSCs specific molecules by microarray analysis of c-Kit+Sca-1+Lin− (KSL)-SP vs. non-SP cells. We identified that Mpl, thrombopoietin (Tpo) receptor, was highly expressed in SP cells compared to non-SP cells. Tpo/Mpl signal is known as a physiological regulator of megakaryopoiesis, but the role of Tpo/Mpl signal in the maintenance of HSCs remains elusive. In this study, we investigated the role of Tpo/Mpl signal on the regulation of HSCs in the niche. The frequency of Mpl+ cells in KSL, KSL-SP, and KSL-non SP cells were 50.4 %, 88.9 %, and 44.7 %, respectively. In addition, Tpo was expressed in osteoblastic cells in BM. Immunohistochemical staining of BM showed that Mpl+ HSCs adhered to the bone surface and bone-lining osteoblastic cells produced Tpo. These data suggest that Tpo/Mpl signal contributes to the HSCs-niche interaction. BM transplantation (BMT) assay demonstrated that Mpl+KSL cells showed high long-term reconstitution (LTR)-activity, whereas Mpl−KSL cells did not, suggesting that LTR-HSCs were enriched in Mpl+ fraction. To investigate the function of Tpo/Mpl signal in HSCs, we performed CAFC assay and LTC-IC assay in the presence of anti-Mpl neutralizing antibody (AMM2). Inhibition of Tpo/Mpl signal reduced cobblestone formation and reduced LTC-IC formation. These data suggest that Tpo/Mpl signal maintained immature phenotypes of HSCs in vitro. It was reported that Mpl deficient mice showed the defect of stem cell function. For rapid and transient inhibition of Mpl signaling in vivo, we administrated AMM2 into the adult mice. AMM2 did not affect the frequency of non-SP fraction, but transiently decreased frequency of SP in KSL after 6 days of injection. Moreover, the combination of AMM2 and 5-FU capacitated BMT without irradiation. In contrast, injection of Tpo increased KSL-SP cells. To understand the mechanism of Tpo/Mpl signal, we cultured Mpl+KSL cells in the presence of SCF and/or Tpo, and analyzed the gene expression. We found that Tpo treatment up-regulate β1-integrin and p57, but not p21, p27 or p18. As the up-regulation of p57 is essential for TGF-β induced cell cycle arrest in hematopoiesis, Tpo/Mpl signal may also be related to cell cycle arrest. Altogether, these data suggest that Tpo/Mpl signal regulates HSCs-niche interaction and enhanced the quiescence of HSCs.

Evidence for a Metabolic Stem Cell Niche.

Blood ◽  
2007 ◽  
Vol 110 (11) ◽  
pp. 4046-4046 ◽  
Author(s):  
Michael Cross ◽  
Rudiger Alt ◽  
Lydia Schnapke-Hille ◽  
Thomas Riemer ◽  
Dietger Niederwieser
Keyword(s):  
Stem Cells ◽  
Cell Culture ◽  
Stem Cell ◽  
Stem Cell Niche ◽  
Culture Media ◽  
Self Renewal ◽  
Cell Culture Media ◽  
Hematopoietic Stem ◽  
Cell Niche

Abstract The hematopoietic stem cell niche presents a localised environment supporting the balanced maintenance, self-renewal and occasional expansion of the stem cell pool. These options are widely assumed to be regulated exclusively by signalling from specific combinations of stroma-bound or soluble ligands. However, a consideration of the rare conditions under which absolute numbers of stem cells increase in vivo as well as the selective pressures acting on regenerative systems during evolution has led us to propose a metabolic component to the stem cell niche which serves to limit cumulative damage, to avoid the selection of potentially oncogenic mutations and to tie symmetric division to slow proliferation. This would mean that traditional cell culture media based on “systemic” substrates such as glucose and glutamine may actively prevent the symmetric amplification of high quality stem cells, offering a possible explanation for the limited success in this area to date. To investigate this possibility, we have examined the effects of range of carbon and energy sources on the proliferation and maintenance of stem and progenitor cells. Our strategy is to screen a wide variety of culture conditions using murine FDCPmix cells, which are non-tumorigenic but have an innate tendency to amplify symmetrically in the presence of IL-3, and then to test key observations in human UCB CD133+ cells provided with SCF, TPO and FLT-3L. In both cell systems, we do indeed find an unusually low requirement for the systemic substrates glucose and glutamine normally included as major energy and carbon sources in cell culture media. Reducing glucose reduces the yield of committed cells from CD133+ cultures without affecting the accumulation of CD133+CD34+cKit+ progenitors. When provided with alternative substrates more likely to reflect a “niche” type environment, FDCPmix cells can be maintained for long periods in media containing only the trace levels of glucose or glutamine derived from dialysed serum, and show improved self-renewal under these conditions. We have also found that raising osmolarity reduces glucose dependence and simultaneously favours the maintenance both of self-renewing CFU (FDCPmix culture) and of CAFCweek13 (CD133+ culture). In parallel, the use of NMR and mass spectrometry techniques to profile intracellular metabolites in self-renewing and differentiating FDCPmix cells reveals a shift in the metabolite balance indicating reduced glycolysis in the early cells. Taken together, these results suggest that hematopoietic stem cells do indeed have remarkable metabolic characteristics consistent with adaptation to a metabolically limiting niche environment. It may therefore be necessary to identify niche substrates and to combine these with the relevant signalling environment in vitro in order to effectively increase stem cell numbers for research, stem cell transplantation and tissue engineering applications.

ETO2 Controls Hematopoietic Stem Cell Expansion.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. 396-396
Author(s):  
Stephane Barakat ◽  
Julie Lambert ◽  
Guy Sauvageau ◽  
Trang Hoang
Keyword(s):  
Stem Cells ◽  
Transcription Factor ◽  
Stem Cell ◽  
Hematopoietic Stem Cells ◽  
Short Term ◽  
Self Renewal ◽  
Hematopoietic Stem

Abstract Abstract 396 Hematopoietic stem cells that provide short term reconstitution (ST-HSCs) as well as hematopoietic progenitors expand from a small population of long term hematopoietic stem cells (LT-HSCs) that are mostly dormant cells. The mechanisms underlying this expansion remain to be clarified. SCL (stem cell leukemia), is a bHLH transcription factor that controls HSC quiescence and long term competence. Using a proteomics approach to identify components of the SCL complex in erythroid cells, we and others recently showed that the ETO2 co-repressor limits the activity of the SCL complex via direct interaction with the E2A transcription factor. ETO2/CBF2T3 is highly homologous to ETO/CBFA2T1 and both are translocation partners for AML1. We took several approaches to identify ETO2 function in HSCs. We initially found by Q-PCR that ETO2 is highly expressed in populations of cells enriched in short-term HSC (CD34+Flt3-Kit+Sca+Lin-) and lympho-myeloid progenitors (CD34+Flt3+Kit+Sca+Lin-) and at lower levels in LT-HSCs (CD34-Kit+Sca+Lin- or CD150+CD48-Kit+Sca+Lin-). Next, the role of ETO2 was studied by overexpression or downregulation combined with transplantation in mice. Ectopic ETO2 expression induces a 100 fold expansion of LT-HSCs in vivo in transplanted mice associated with differentiation blockade in all lineages, suggesting that ETO2 overexpression overcomes the mechanisms that limit HSC expansion in vivo. We are currently testing the role of the NHR1 domain of ETO2 in this expansion. Conversely, shRNAs directed against ETO2 knock down ET02 levels in Kit+Sca+Lin- cells, causing a ten-fold decrease in this population after transplantation, associated with reduced short-term reconstitution in mice. Finally, proliferation assays using Hoechst and CFSE indicate that ETO2 downregulation affects cell division (CFSE) and leads to an accumulation of Kit+Sca+Lin-cells in G0/G1 state (Hoescht). In conclusion, we show that ETO2 is highly expressed in ST-HSCs and lymphoid progenitors, and controls their expansion by regulating cell cycle entry at the G1-S checkpoint. In addition, ETO2 overexpression converts the self-renewal of maintenance into self-renewal of expansion in LT-HSCs. Disclosures: No relevant conflicts of interest to declare.

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