Role of the Cell Cycle Regulator Cdh1 in Physiology and Pathology of Hematopoiesis

Abstract Abstract 2419 Various key molecules for cell cycle, especially G0/G1 regulators, have effects not only on cell proliferation but also on cell differentiation. Cdh1, one of the co-activators for anaphase-promoting complex/cyclosome, plays a crucial role in the mitotic phase, but has recently been identified as a G0/G1 regulator, suggesting that the role of Cdh1 in cell differentiation. Because there are only few reports about Cdh1 from this point of view, we focused on Cdh1 functions on the hematopoietic system, in which distinct populations of cells can be precisely identified by their cell surface markers, in physiology and pathology. For this purpose, we generated Cdh1 conditional gene-trap (GT) mice, by overcoming the embryonic lethality of Cdh1 homozygous GT mice. We introduced the Cdh1 cDNA replacing vector into ES cells derived from Cdh1 heterozygous GT mice. The resulted construct contains the floxed Cdh1 cDNA allele which is cleaved under the existence of Cre recombinases. We crossed mice carrying this Cdh1 transgene in homozygous (Cdh1f/f) with Mx1-Cre transgenic mice to obtain Mx1-Cre (+) / Cdh1f/f mice, in which Cre recombinases are induced in vivo by administration of pIpC. In this system, we found that the Cdh1-deficient mice 4 months after pIpC treatment, compared to Cdh1-intact mice (Mx1-Cre (-) / Cdh1f/f mice), exhibited a subtle but significant decrease in absolute number of mature lineage progenitor cells (4.3 ± 0.31 × 107 vs 3.2 ± 0.10 × 107 /femurs and tibiae; p=0.009). Furthermore, this phenomenon was conspicuous by irradiation as short as 7 days after pIpC treatment. In 48 hours post-irradiation, the absolute number of mature lineage progenitor cells decreased markedly in the Cdh1-deficient mice (7.4 ± 0.82 × 106 vs 3.6 ± 0.46 × 106; p=0.0023) and in addition, both of CD34+ and CD34- LSK cells were also decreased (absolute number of CD34- cells: 905 ± 194 vs 344 ± 223; p= 0.03). These results indicate that the loss of Cdh1 induces genotoxic fragility especially in these two subpopulations, the mature lineage progenitors and the stem cells. We also confirmed that the increased cell loss induced by irradiation in Cdh1-deficient mice is the result of mitotic catastrophe following G2/M checkpoint slippage due to loss of Cdh1 by DNA content analysis. We next focused on how oncogenic stress, as another genotoxic stress, effects on the cell fragility by Cdh1 loss. We performed retroviral transduction of N-myc into Cdh1-intact and Cdh1-deficient bone marrow mononuclear cells (BM-MNCs) and transplanted those into irradiated wild type mice. In this system, which our laboratory has established recently, the transplanted mice develop precursor B cell lymphoblastic leukemia (pre-B ALL) phenotype in high frequency (more than 80%) when wild type BM-MNCs were used as cell source. Our hypothesis at that time was that oncogenic stress due to N-myc induces the loss of stem/progenitor cell function, and in result, that Cdh1 loss reveals negative effects on leukemogenesis or changes its lineage phenotype by affecting pseudodifferentiation due to N-myc. However, against our speculation, 70% (7 out of 10) of mice transplanted with N-myc transduced Cdh1-deficient BM-MNCs developed pre-B ALL, which was the same frequency and the same phenotype as in Cdh1-intact cell sources. Of note, Cdh1 loss did not have a great impact on the prognosis of these pre-B ALL mice (median survival: 80 days in Cdh1-intact group vs 95 days in Cdh1-deficient group; p= 0.049). In conclusion, our results suggest that Cdh1 regulates the pool sizes of the hematopoietic stem cells and mature lineage progenitor cells both physiologically and pathologically; especially under irradiation stress. In contrast, Cdh1 is dispensable for B cell leukemogenesis and does not have a great impact on the natural prognosis of non-treated pre-B ALL. It is interesting that oncomine mRNA microarray database and other few reports indicate that human pre-B ALL cases are also divided into two groups according to the expression level of Cdh1, and it is the matter remained to be solved whether Cdh1 expression level affects the prognosis of treated patients. We propose that our Cdh1-deficient pre-B ALL mice have a potential as promising mouse model in order to assess this proposition and to prove that Cdh1 affects the sensitivity of pre-B ALL to treatments which causes the genotoxic stress, such as radiotherapy and genotoxic agents. Disclosures: Saya: Kyowa Hakko Kirin, Co., Ltd.: Research Funding.

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The role of stem cells/progenitor cells in liver carcinogenesis in glycine N-methyltransferase deficient mice

Experimental and Molecular Pathology ◽

10.1016/j.yexmp.2010.01.004 ◽

2010 ◽

Vol 88 (2) ◽

pp. 234-237 ◽

Cited By ~ 8

Author(s):

M.L. Martinez-Chantar ◽

S.C. Lu ◽

J.M. Mato ◽

Z. Luka ◽

C. Wagner ◽

...

Keyword(s):

Stem Cells ◽

Progenitor Cells ◽

Liver Carcinogenesis ◽

Deficient Mice

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Deficiency of Bone Marrow Stromal Cx43 Expression Induces Hematopoietic Progenitor Homing Deficiency and Cell-Cycle Arrest of Hematopoietic Stem Cells and Progenitors.

Blood ◽

10.1182/blood.v108.11.349.349 ◽

2006 ◽

Vol 108 (11) ◽

pp. 349-349

Author(s):

Lina Li ◽

Cynthia A. Presley ◽

Bryan Kastl ◽

Jose A. Cancelas

Keyword(s):

Cell Cycle ◽

S Phase ◽

Chimeric Mice ◽

Wild Type ◽

Hematopoietic Progenitor ◽

Cx43 Expression ◽

Hematopoietic Stem ◽

M Phase ◽

Deficient Mice

Abstract Contact between bone marrow (BM) hematopoietic stem cells (HSC) and osteoblast/stromal (OS) cells has been shown to be critical in the regulation of hematopoiesis. However, very little is known about the regulatory mechanisms of direct cell-to-cell communication in the hematopoietic microenvironment. BM cells are directly connected through gap junctions (GJs) which consist of narrow channels between contacting cells and are composed by connexins. Connexin 43 (Cx43) is expressed by BM OS cells. Multiple osteogenic defects have been reported in human Cx43 mutations and Cx43 has been shown to be essential in controlling osteoblast functions. Due to the perinatal death of Cx43 germline null mice, an interferon-inducible, conditional genetic approach (Mx1-Cre), expressed by both hematopoietic and stromal BM cells, was used to study the role of Cx43 in stem cell function. We have previously reported that Cx43 is critical for the interaction between stroma and HSC in CAFC assays (Cancelas J.A. et al., Blood 2000) and in adult hematopoiesis after 5-fluorouracil (5-FU) administration (Presley C, et al., Cell Comm. Adh., 2005). Here, we observed that after 5-FU administration, Cx43 expression is predominantly located in the endosteum. To study the role of stroma-dependent Cx43 in hematopoiesis, we developed hematopoietic chimeras by BM transplantation of wild-type Cx43 HSC into stromal Cx43-deficient mice. Stromal Cx43 deficiency induced a severe impairment of blood cell formation during the recovery phase after 5-FU administration compared to stromal Mx1-Cre-Tg wild-type controls (Table 1), as well as a significant decrease in BM cellularity (~60% reduction) and progenitor cell content (~83% reduction). Cell cycle analysis of 5-FU-treated BM progenitors from stromal Cx43-deficient mice showed an S-phase arrest (S phase: 63.5%; G2/M phase: <1%) compared to wild-type chimeric mice (S phase: 38.6%, G2/M phase: 7.8%, p=0.01) suggesting a cell division blockade. Unlike Cx43-deficient primary mice, a differentiation arrest at the HSC compartment was observed in 5-FU-treated, stromal Cx43-deficient mice, since the content of competitive repopulating units (CRU) at 1 month, of 14-day post-5-FU BM of stromal Cx43-deficient mice was increased (27.7 ± 0.67) compared to recipients of HSC from stromal wild-type counterparts (26.5 ± 0.92 CRU, p < 0.01). Interestingly, wild-type hematopoietic progenitor homing in stromal Cx43-deficient BM was severely impaired with respect to wild-type BM (5.1% vs10.4 %, respectively, p < 0.01), while hematopoietic Cx43-deficient BM progenitors normally homed into the BM, suggesting a differential role for Cx43 in stromal and HSC. In conclusion, expression of Cx43 in osteoblasts and stromal cells appears to play a crucial role in the regulation of HSC homing in BM and hematopoietic regeneration after chemotherapy. Peripheral blood counts of WT and stromal Cx43-deficient chimeric mice after 5-FU administration (150 mg/Kg) Neutrophil counts (×10e9/L) Reticulocyte count (%) Day post-5-FU WT Cx43-deficient WT Cx43-deficient * p < 0.05 Day +8 2.89 ± 0.06 0.81 ± 0.02* 2.0 ± 0.6 3.0 ± 0.9 Day +11 9.11 ± 2.5 3.13 ± 0.8* 6.1 ± 0.6 2.7 ± 0.3* Day +14 6.22 ± 5.7 7.58 ± 8.2 7.5 ± 0.5 2.5 ± 0.5*

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Sox4 Is Required for the Formation and Maintenance of Multipotent Progenitors

Blood ◽

10.1182/blood.v124.21.1577.1577 ◽

2014 ◽

Vol 124 (21) ◽

pp. 1577-1577 ◽

Cited By ~ 1

Author(s):

Hong Zhang ◽

Min Ye ◽

Robert S. Welner ◽

Daniel G. Tenen

Keyword(s):

Progenitor Cells ◽

Absolute Number ◽

Brdu Incorporation ◽

Binding Motif ◽

Wild Type ◽

Hematopoietic Stem ◽

Genetic Ablation ◽

Qpcr Analysis ◽

Multipotent Progenitors ◽

Deficient Mice

Abstract Introduction Hematopoiesis is maintained by a hierarchical system, whereas aberrant control of hematopoiesis is the underlying cause of many diseases. Within the hematopoietic hierarchy, hematopoietic stem cells (HSCs) give rise to multipotent progenitors that have lost their self-renewal capacity but remain multipotent to differentiate into mature blood cells. However, the precise molecular mechanisms that modulate this transition are not fully understood yet. Results We recently discovered that genetic ablation of SRY sex determining region Y-box 4 gene (Sox4) in the murine hematopoietic system resulted in dramatic loss of multipotent progenitor population (CD48+CD150-Lin-kit+Sca1+, or CD48+CD150-LSK) both relatively (to the total LSK population) and in absolute number. Interestingly, the absolute number of HSCs (CD48-CD150+Lin-kit+Sca1+, or SLAM+LSK) in these conditional Sox4-deficient mice was comparable to their wild-type counterparts. Transcriptional factor Sox4 belongs to the high-mobility group (HMG) domain superfamily which also includes other Sox proteins, TCF-1 (T-cell factor 1) and LEF-1 (lymphoid enhancer factor 1). Sox4 has been implicated in leukemogenesis and may potentially contribute to stem cell properties. Nevertheless, the precise roles of Sox4 in hematopoietic stem/progenitor cells and the underlying mechanisms have not been defined yet. Further analysis of stem/progenitor compartment defined by Flt3 and CD34 expression demonstrated a major loss in lymphoid-primed multipotent progenitors (LMPPs) (CD34+Flt3+LSK) with relatively normal formation of LT-HSCs (CD34-Flt3-LSK) and ST-HSCs (CD34+Flt3-LSK) upon the loss of Sox4, suggesting that Sox4 is essential for the development from HSCs to multipotent progenitors. Such observation is in line with the expression pattern of Sox4. Quantitative PCR (qPCR) analysis of wild-type mice revealed that expression of Sox4 increased from HSCs to multipotent progenitors which expressed Sox4 at the highest level among all the hematopoietic compartments. Studies of biological behaviors further indicateed that disruption of Sox4 had no effect on proliferative capacity of HSCs and multipotent progenitors, as evidenced by BrdU incorporation assay. However, Annexin V/propidium iodide staining revealed an increased frequency of apoptotic multipotent progenitors, but not that of HSCs upon the ablation of Sox4. In a transplantation setting, although Sox4-deficient LSKs homed appropriately to the bone marrow, they exhibited severely impaired ability to give rise to multipotent progenitors, but contributed normally to HSCs compared to the wild-type donors. Among a set of genes crucial to the biological properties of stem/progenitor cells, qPCR analysis revealed that upon the loss of Sox4, only the levels of Ikaros1 and Ikaros2, the two major Ikaros isoforms in stem/progenitor cells, were downregulated specifically in multipotent progenitors, but remained normal in HSCs. Intriguingly, in a reminiscent manner of Sox4-deficient mice, mice lacking both Ikaros 1 and Ikaros 2 proteins, also exhibited disrupted B cell development and selectively impaired LMPPs. Previous study identified an enhancer of Ikaros locus as the only cis-regulatory element that was capable of stimulating reporter expression in the LMPPs. Our sequence analysis revealed a highly conserved Sox4 binding motif within this enhancer, therefore potentially connecting Sox4 with the known regulatory networks that modulate the differentiation of HSCs. Currently, we are working on (1) confirming the direct transcriptional regulation of Ikaros by Sox4; (2) assessing whether Ikaros mediates the functions of Sox4 in the formation or maintenance of the multipotent progenitors population in vivo; and (3) delineating the downstream regulatory network of Sox4 in stem/progenitor cells. Conclusion In summary, out study reveals a novel role for Sox4 gene in early hematopoiesis and brings important insights into the regulatory mechanisms underlying the commitment of HSCs toward multipotent progenitors. Disclosures No relevant conflicts of interest to declare.

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Inflammatory Niche Signalling Drives Genotoxic Stress in Hematopoietic Stem Cells and Predicts Leukemic Evolution in Human Leukemia Predisposition Syndromes

Blood ◽

10.1182/blood.v128.22.428.428 ◽

2016 ◽

Vol 128 (22) ◽

pp. 428-428

Author(s):

Si Chen ◽

Noemi A. Zambetti ◽

Zhen Ping ◽

Keane Kenswil ◽

Maria Mylona ◽

...

Keyword(s):

Cell Cycle ◽

Dna Damage ◽

Progenitor Cells ◽

Transcriptional Activation ◽

Genotoxic Stress ◽

Wild Type ◽

Hematopoietic Stem ◽

Skeletal Defects ◽

Bona Fide

Abstract Primary alterations of the mesenchymal niche can induce myelodysplasia and acute myeloid leukemia in mouse models, introducing a concept of niche-driven leukemogenesis (Raaijmakers et al, Nature 2010). The molecular mechanisms and human relevance of this concept, however, have remained elusive. We addressed these key questions by modelling Shwachman-Diamond-Syndrome (SDS), a human monogenic congenital disorder caused by loss-of function mutation in the SBDS gene and characterized by skeletal defects, bone marrow failure and a striking propensity for leukemic evolution. Targeted Sbds deletion from mesenchymal progenitor cells (MPCs) in mice (OsxCre/+Sbdsf/f; OCSf/f) resulted in bone abnormalities faithfully recapitulating human disease, including short stature and early-onset osteoporosis. Skeletal defects were associated with genotoxic stress in hematopoietic stem and progenitor cells (HSPCs) as demonstrated by mitochondrial membrane hyperpolarization, oxidative stress, DNA damage and cell cycle checkpoint activation (transcriptional modulation of DNA damage response/repair pathways and G0-G1 cell cycle arrest). DNA damage could be partially rescued by in vivo administration of the ROS scavenger N-acetylcysteine supporting the notion of niche induced DNA damage in HSPCs induced by mitochondria-derived superoxide radicals. Mechanistically, Sbds deficiency caused activation of the p53 tumor suppressorpathway in MPCs (upregulation of P53 and transcriptional activation of downstream targets (GSEA). Genetic deletion of Trp53 from MPCs (Osxcre/+Sbdsf/fTrp53f/f mice) rescued the skeletal phenotype and genotoxic stress in HSPCs. Comparison of the transcriptome of MPCs from OCSf/f mice to their highly FACS-purified mesenchymal (CD45-CD235-7AAD-CD31-CD271+CD105+) human equivalents from SDS patients (RNAseq; n=5) demonstrated a striking overlap in disrupted gene programs (GSEA), including ribosome biogenesis and significant overexpression of the proinflammatory molecules such as S100A8 and S100A9, bona fide p53 downstream targets. Activation of p53 and inflammatory molecules was an MPC-autonomous consequence of Sbds depletion as demonstrated by ex vivo knockdown of the gene in OP9 cells. S100A8/A9 overexpression and secretion from MPCs from OCSf/f mice was confirmed by FCM and serum ELISA. Exposure of HSPCs to recombinant murine S100A8/9 resulted in increased DNA damage and apoptosis associated with transcriptional activation of TLR4 downstream signaling, a bona fide S100A8A9 receptor. In vivo TLR4 blockade by neutralizing antibodies resulted in reduced γH2AX foci in HSPCs from OCSf/f mice, in support of the existence of a Tpr53-S100A8/A9-TLR4 axis driving genotoxic stress. Formal demonstration that niche-derived S100A8/9 is sufficient to drive genotoxic stress in HSPCs was provided by transplantation of wild-type hematopoietic cells into recipient S100A8/A9 transgenic mice (Cheng et al., 2008) resulting in accumulation of mitochondrial superoxide radicals and DNA-damage in wild-type HSPCs. Finally, to further define the clinical relevance of this inflammatory MPC-HSPC axis to human disease, we performed massive parallel RNA-sequencing of FACS purified mesenchymal cells from homogeneously treated low-risk MDS patients (n=45). Overexpression of S100A8 and S100A9 in MPCs(confirmed by IHC) was found in a considerable subset of patients (17/45; 38%). S100A8/9+ mesenchymal cells displayed transcriptional activation of p53 and TLR programs, in line with findings in the mouse model. Strikingly, patients in the niche-S100A8/9+ group displayed a higher frequency of leukemia evolution (29.4% vs. 14.2%) with significantly shorter evolution time (average 3.4 (1-7.5) vs 18.5 (7-40); p=.03) and progression-free survival (median 11.5 vs. 53 months, p=.03), independent of established prognostic factors and risk classification systems. Collectively, the data define niche-HSPC inflammatory signaling through the p53-S100A8/A9-TLR axis as an actionable determinant of genotoxic stress and disease outcome in human preleukemia, opening the way to niche-instructed, therapeutic targeting to attenuate leukemic evolution. Disclosures No relevant conflicts of interest to declare.

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Myeloid Progenitor Cells from Gadd45a and Gadd45b-Deficient Mice Are Sensitized to Genotoxic-Stress Induced Apoptosis.

Blood ◽

10.1182/blood.v104.11.4239.4239 ◽

2004 ◽

Vol 104 (11) ◽

pp. 4239-4239

Author(s):

Mamta Gupta ◽

Shiv K. Gupta ◽

Arthur G. Balliet ◽

Barbara Hoffman ◽

Dan A. Lieberman

Keyword(s):

Bone Marrow ◽

Progenitor Cells ◽

Bone Marrow Cells ◽

Genotoxic Stress ◽

Wild Type ◽

Myeloid Progenitor ◽

Myeloid Progenitor Cells ◽

Induced Apoptosis ◽

Deficient Mice ◽

Marrow Cells

Abstract GADD45 (Growth arrest and DNA damge) regulates cell growth following exposure to diverse stimuli. It has been shown that, mice lacking the gadd45a gene exhibit genomic instability and increased carcinogenesis, but the exact role of the gadd45 family genes still remains unclear. In this study we have aimed at determining the effect of gadd45a or gadd45b deficiency on the response of bone marrow derived myeloid cells to genotoxic stress agents by using gadd45a or gadd45b null mice. We have found that myeloid progenitor cells from gadd45a or gadd45b-null mice are more sensitive to ultraviolet-radiation (UV), VP-16 or daunorubicin induced apoptosis. Introduction of wild-type gadd45 into gadd45-deficient bone marrow cells restored the wild-type apoptotic phenotype. In-vitro colony formation following stress responses has shown that bone marrow cells from gadd45a or gadd45b-deficient mice have a decreased ability to form haematopoetic colonies. Gadd45a or gadd45b-deficient bone marrow cells also displayed defective G2/M cell cycle checkpoint following exposure to either UV and V-16 but were still able to undergo G2/M arrest following exposure to daunorubicin, indicating the existence of different G2/M checkpoints in response to these anticancer agents. Taken together these findings identify gadd45a or gadd45b as anti-apoptotic gene(s), and suggests that the absence of gadd45a or gadd45b results in higher susceptibility of haematopoetic cells to UV radiation and certain anticancer drugs.

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Loss of Gfi1 Impedes Development of T-Cell Lymphoma upon Exposure to N-ethyl-N-nitrosourea but Predisposes to Severe Myleodysplastic Changes.

Blood ◽

10.1182/blood.v110.11.2221.2221 ◽

2007 ◽

Vol 110 (11) ◽

pp. 2221-2221

Author(s):

Cyrus Khandanpour ◽

Ulrich Duehrsen ◽

Tarik Möröy

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Dna Damage ◽

T Cell ◽

Bone Marrow Cells ◽

Cell Lymphoma ◽

Wild Type ◽

Hematopoietic Stem ◽

Deficient Mice

Abstract Exogenous toxic substances often cause the initiation and development of leukemia and lymphoma by acting as mutagens. N-ethyl-N-nitrosourea (ENU) is a paradigmatic example for such a substance, which introduces point mutations in the genome through DNA damage and repair pathways. ENU is widely used to experimentally induce T-cell lymphomas in mice. We have used ENU to investigate whether the hematopoietic transcription factor Gfi1 is required for lymphomagenesis. The Gfi1 gene was originally discovered as a proviral target gene and a series of experiments with transgenic mice had suggested a role of Gfi1 as a dominant oncogene with the ability to cooperate with Myc and Pim genes in the generation of T-cell lymphoma. In addition, Gfi1 deficient mice showed a defect in T-cell maturation but also aberration in myeloid differentiation and an accumulation of myelomonocytic cells. ENU was administered i.p. once a week for three weeks with a total dose of 300mg/kg to wild type (wt) and Gfi1 null mice. Wild type mice (12/12) predominantly developed T-cell tumors and rarely acute myeloid leukemia, as expected. However, only 2/8 Gfi1 −/− mice succumbed to lymphoid neoplasia; they rather showed a severe dysplasia of the bone marrow that was more pronounced than in wt controls. These changes in Gfi1 null mice were accompanied by a dramatic decrease of the LSK (Lin-, Sca1- and c-Kit+) bone marrow fraction that contains hematopoietic stem cells and by a higher percentage (18%) of bone marrow cells, not expressing any lineage markers (CD4, CD 8, Ter 119, Mac1, Gr1, B220, CD3). In particular, we found that the LSK subpopulation of Gfi1 deficient mice showed a noticeable increase in cells undergoing apoptosis suggesting a role of Gfi1 in hematopoietic stem cell survival. In addition, Gfi1−/− bone marrow cells and thymic T-cells were more sensitive to DNA damage such as radiation and exposure to ENU than their wt counterparts pointing to a role of Gfi1 in DNA damage response. Our results indicate that Gfi1 is required for development of T-cell tumors and that a loss of Gfi1 may sensitize hematopoietic cells and possibly hematopoietic stem cells for programmed cell death. Further studies have to show whether interfering with Gfi1 expression or function might represent a tool in the therapy of leukemia.

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Homeostatic Role of the Krüppel-Like Factor 4 (KLF4) in Proliferation and Differentiation of Primitive Hematopoietic Progenitor Cells.

Blood ◽

10.1182/blood.v114.22.1497.1497 ◽

2009 ◽

Vol 114 (22) ◽

pp. 1497-1497 ◽

Cited By ~ 2

Author(s):

Chun Shik Park ◽

Takeshi Yamada ◽

H. Daniel Lacorazza

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Progenitor Cells ◽

Peripheral Blood ◽

Blood Cells ◽

Proliferative Potential ◽

Dependent Manner ◽

Hematopoietic Stem ◽

Deficient Mice

Abstract Abstract 1497 Poster Board I-520 KLF4 is a tumor suppressor in the gastrointestinal tract known to induce cell cycle arrest in a cell context dependent manner. We recently reported that KLF4 maintains quiescence of T lymphocytes downstream of T-cell receptor signaling (Yamada et al., Nature Immunology, 2009). The role of KLF4 in reprogramming adult somatic cells into pluripotent stem cells along with Oct3/4, c-Myc and Sox2 suggests that KLF4 restricts proliferation of undifferentiated cells. In spite of a redundant role of KLF4 in fetal liver hematopoietic stem cells (HSC), its role in the maintenance of adult bone marrow HSCs has not been studied yet. To study the role of KLF4 in the hematopoietic system we used gain- and loss-of-function mouse models. Retroviral transfer of KLF4 into wild type bone marrow (BM) cells led to significant reduction of colony forming units (CFU) in methylcellulose cultures due to increased apoptosis and lower proliferation. Then, Mx1-Cre was used to induce deletion of Klf4-floxed mice by polyI:C administration. Analysis of peripheral blood cells up to 6-9 months post polyI:C administration showed significant reduction of monocytes, as previously reported, and expansion of CD8+CD44+ T cells due to their increased proliferative potential. BM cells from Klf4-deficient mice exhibited increased number of myeloid progenitor cells measured by flow cytometry (Lin-Sca-1-c-kit+FcRII/III+CD34+ cells), CFU and CFU-S8. Cytoablation with 5-fluorouracil (5-FU) showed lower nadir of peripheral white blood cells in Klf4-deficient mice compared to control mice. In spite of normal multilineage reconstitution in BM transplants experiments, competitive reconstitution with Klf4-deficient and normal BM cells resulted in reduced contribution of Klf4-deficient cells to peripheral blood, likely due to homing and proliferative differences. Collectively, our data shows that KLF4 has an important role in function of hematopoietic stem and progenitor cells. Disclosures: No relevant conflicts of interest to declare.

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CXCR4-SDF-1 Signaling Mediated up-Regulation of Survivin Expression In Mesenchymal Progenitor Cells Is Critical for Their Proliferation and Maintenance of Osteoblastic Niche

Blood ◽

10.1182/blood.v116.21.941.941 ◽

2010 ◽

Vol 116 (21) ◽

pp. 941-941

Author(s):

Pratibha Singh ◽

Jennifer Speth ◽

Peirong Hu ◽

Louis M. Pelus

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Flow Cytometry ◽

Stem Cell ◽

Progenitor Cells ◽

Survivin Expression ◽

Wild Type ◽

Hematopoietic Stem ◽

Cxcr4 Signaling

Abstract Abstract 941 Hematopoietic stem cells reside in osteoblastic and vascular niches within the bone marrow. The osteoblastic niche is composed of mesenchymal stem cell derived progenitor cells (MPC) and osteoblasts and are the main sources of the CXC chemokine CXCL12/SDF-1 in the bone marrow microenvironment. Several published studies suggest that the interaction between CXCR4 expressed on hematopoietic stem cells with SDF-1 produced in the bone marrow microenvironment is important for their retention in the bone-marrow. However, the role of SDF-CXCR4 signaling in formation and maintenance of osteoblastic niches in the bone marrow is not known. In this study, we examined the role of CXCR4 signaling in MPC proliferation and differentiation and its effects on hematopoietic stem cell (HSC) function. Flow cytometry analysis demonstrated that CXCR4 is expressed on the phenotypically defined MPC. Deletion of CXCR4 in tamoxifen cre inducible CXCR4flox-flox mice (verified by PCR and flow cytometry; 90% gene deletion and surface CXCR4 expression) results in significantly decreased numbers of Lin- CD45- CD31- Sca-1+ ALCAM- MPC (39±4.2%) and Lin- CD45- CD31- Sca-1-CD51+ osteoblasts (25±2.6%) in bone marrow 15 days after tamoxifen treatment. SDF-1 induced proliferation of CXCR4 deficient MPC was decreased by 4-fold compared to control, measured by the colony forming unit-fibroblast (CFU-F) assay. To determine, whether CXCR4 deficiency in bone marrow stromal cells affects SDF-1 induced HSC proliferation, we cultured FACS sorted wild-type SLAM SKL (103 cells) on CXCR4 deficient stroma for 5 days and total SLAM SKL cell numbers were counted by flow-cytometey analysis. CXCR4 deficient stroma failed to support optimal HSC proliferation and 48±5.2% less SLAM KSL cells was observed on CXCR4 deficient stroma compared to wild-type stroma. To investigate the mechanisms through which CXCR4-SDF-1 signaling regulates MPC proliferation, we evaluated the effect of SDF-1 treatment on expression of the anti-apoptotic and cell-cycle regulator protein, Survivin, in MPC. Multivariate intracellular flow cytometry demonstrated that Survivin expression increased by 23±4.2% in wild-type MPC after SDF-1 treatment (50ng/ml), however no significant increased was demonstrated in CXCR4 deficient MPC cells. CFU-F formation was reduced by 2.5 fold when the Survivin gene was conditionally deleted in MPC. Moreover, fewer SLAM SKL cells were detected on Survivin deficient stroma compared to wild-type stroma after SDF-1 treatment for 5 days. In conclusion, our data suggest that CXCR4-SDF-1 signaling mediated Survivin expression in MPC is important for their proliferation and maintenance of the bone-marrow hematopoietic niche. Disclosures: No relevant conflicts of interest to declare.

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Further Evidence That HO-1 Regulates SDF-1 Expression in the Bone Marrow Microenvironment and That HO-1-Deficient Mice Show a Defect in the SDF-1–CXCR4 Retention Axis of Hematopoietic Stem/Progenitor Cells in Bone Marrow and Thus Are Easy Mobilizers - Studies in HO-1 Mutant Mice, Irradiation Chimeras, and the Effect of in Vivo Pharmacological Inhibition of HO-1

Blood ◽

10.1182/blood.v120.21.344.344 ◽

2012 ◽

Vol 120 (21) ◽

pp. 344-344

Author(s):

Marcin Wysoczynski ◽

Janina Ratajczak ◽

Gregg Rokosh ◽

Roberto Bolli ◽

Mariusz Z Ratajczak

Keyword(s):

Bone Marrow ◽

Progenitor Cells ◽

Crucial Role ◽

Conflicts Of Interest ◽

Wild Type ◽

Hematopoietic Stem ◽

Cell Counts ◽

Deficient Mice

Abstract Abstract 344 Background: Stromal derived factor-1 (SDF-1), which binds to the CXCR4 receptor expressed on the surface of hematopoietic stem/progenitor cells (HSPCs), plays an important role in the retention of HSPCs in BM niches. Heme oxygenase (HO-1) is a stress-responsive enzyme that catalyzes the degradation of heme and plays an important function in various physiological and pathophysiological states associated with cellular stress, such as ischemic/reperfusion injury, atherosclerosis, and cancer. Interestingly, it has also been reported that HO-1 regulates the expression of SDF-1 in myocardium (J Mol Cell Cardiol. 2008;45:44–55). Aim of study: Since SDF-1 plays a crucial role in retention and survival of HSPCs in BM, we become interested in whether HO-1 is expressed by BM stromal cells and whether deficiency of HO-1 affects normal hematopoiesis and retention of HSPCs in BM. Experimental approach: To address this issue, we employed several complementary strategies to investigate HO-1–/–, HO-1+/–, and wild type (wt) mouse littermates for i) the expression level of SDF-1 in BM, ii) the number of clonogenic progenitors from major hematopoietic lineages in BM, iii) peripheral blood (PB) cell counts, iv) the chemotactic responsiveness of HSPCs to an SDF-1 gradient as well as to other chemoattractants, including sphingosine-1-phosphate (S1P), ceramide-1-phosphate (C1P), and extracellular nucleotiodes (ATP, UTP), iv) the adhesiveness of clonogenic progenitors to immobilized SDF-1 and stroma, v) the number of circulating HSPCs in PB, and vi) the degree of mobilization in response to granulocyte-colony stimulating factor (G-CSF) or AMD3100, assessed by enumerating the number of CD34–SKL cells and clonogeneic progenitors (CFU-GM) circulating in PB. We also exposed mice to the small HO-1 molecular inhibitor tin protoporphyrin IX (SnPP) and studied the effect of this treatment on G-CSF- or AMD3100-induced mobilization of HSPCs. Finally, to prove an environmental HSPC retention defect in HO-1-deficient mice, we created radiation chimeras, wild type mice transplanted with HO-1-deficient BM cells, and, vice versa, HO-1-deficient mice reconstituted with wild type BM cells. Results: Our data indicate that under normal, steady-state conditions, HO-1–/– and HO+/– mice have normal PB cell counts and numbers of circulating CFU-GM, while a lack of HO-1 leads to an increase in the number of erythroid (BFU-E) and megakaryocytic (CFU-GM) progenitors in BM. However, while BMMNCs from HO-1–/– have normal expression of the SDF-1-binding receptor, CXCR4, we observed that the mRNA level for SDF-1 in BM-derived fibroblasts was ∼4 times lower. This corresponded with the observation in vitro that HSPCs from HO-1–/– animals respond more robustly to an SDF-1 gradient, and HO-1–/– animals mobilized a higher number of CD34–SKL cells and CFU-GM progenitors into PB in response to G-CSF and AMD3100. Both G-CSF and AMD3100 mobilization were also significantly enhanced in normal wild type mice after in vivo administration of HO-1 inhibitor. Finally, mobilization studies in irradiation chimeras confirmed the crucial role of the microenvironmental SDF-1-based retention mechanism of HSPCs in BM niches. Conclusions: Our data demonstrate for the first time that HO-1 plays an important and underappreciated role in modulating the SDF-1 level in the BM microenvironment and thus plays a role in retention of HSPCs in BM niches. Furthermore, our recent data showing a mobilization effect by a small non-toxic molecular inhibitor of HO-1 (SnPP), suggest that blockage of HO-1 could be a promising strategy to facilitate mobilization of HSPCs. Further studies are also needed to evaluate the role of HO-1 in homing of HSPCs after transplantation to BM stem cell niches. Disclosures: No relevant conflicts of interest to declare.

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Laminin α4 Deficiency Results in Impaired Hematopoietic Recovery Accompanied with Altered Bone Marrow Niche after Myelosuppression

Blood ◽

10.1182/blood.v128.22.27.27 ◽

2016 ◽

Vol 128 (22) ◽

pp. 27-27

Author(s):

Makoto Kondo ◽

Pingnan Xiao ◽

Lakshmi Sandhow ◽

Monika Dolinska ◽

Thibault Bouderlique ◽

...

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Endothelial Cells ◽

Steady State ◽

Progenitor Cells ◽

Wild Type ◽

Post Irradiation ◽

Colony Forming Unit ◽

Hematopoietic Recovery

Abstract Myelosuppression is a life-threatening complication of anti-cancer therapy including irradiation. Rapid and complete hematopoietic recovery after therapy-induced myelosuppression is required for a successful treatment outcome. This process relies on efficient regeneration of hematopoietic stem cells (HSCs) and is tightly controlled by bone marrow (BM) microenvironment consisting of mesenchymal stem/progenitor cells, endothelial cells as well as secreted factors including cytokines and extracellular matrix proteins (ECM). However, the extrinsic factors critical for promoting the hematopoietic recovery remain poorly understood. Laminins are heterotrimetric ECM composed of α, β, and γ chains. Laminin α4 chain (LAMA4) is an active component for laminin-411 and -421, which are located in vascular basement membrane. LAMA4 plays an important role for HSC homing after transplantation via interaction with laminin receptor integrin α6 (Qian H et al., Blood 2006). However, the role of LAMA4 in normal hematopoiesis and HSC reconstitution after irradiation-induced myelosuppression is not known. In this study, we first detected Lama4 gene expression in BM endothelial cells (CD31+), mesenchymal stem cells (MSC: CD45-Ter119-CD31-CD44-Sca1+CD51+), and mesenchymal progenitor cells (MPC: CD45-Ter119-CD31-CD44-Sca1-CD51+) in young adult mice. By using Lama4 deficient (Lama4-/-) mice, we analyzed the functional role of LAMA4 on hematopoietic activity at steady state. We found the lower number of platelets (PLTs) (p = 0.03), and neutrophils (Gr1+CD11b+) (p = 0.03) in the peripheral blood (PB) of Lama4-/- mice, but a higher frequency of common myeloid progenitor (Lin-Sca1-Kit+CD34+FcRlow) (p < 0.01) in the Lama4-/- BM at steady state, indicating that LAMA4 plays a role in the maintenance of physiological hematopoiesis. The important role of LAMA4 in hematopoietic recovery was demonstrated by delayed and incomplete recoveries of mature red blood cells, PLTs, and Gr1+CD11b+ cells in PB following sublethal irradiation (7Gy). The impaired recovery of erythropoiesis was also indicated by the higher values of mean corpuscular hemoglobin and mean corpuscular volume in PB as well as the higher frequency of megakaryocyte-erythrocyte progenitor (Lin-Sca1-Kit+CD34-FcR-) (p < 0.01) and colony-forming unit-erythrocyte (CFU-E) (p = 0.03) in the BM of the Lama4-/- mice at 6 weeks after irradiation, suggesting blocked erythrocyte maturation. In keeping with the refractory neutropenia, the frequency of colony-forming unit-granulocyte-macrophage (CFU-GM) was lower in the Lama4-/- BM compared to that in the age- and gender-matched wild type mice (p = 0.04). These data indicate that LAMA4 is critical for multiple hematopoietic lineage reconstitution post irradiation. To investigate the cellular and molecular mechanisms underlying the critical role of LAMA4 in hematopoietic recovery after the irradiation, we characterized the BM niche by colony assay, flow cytometry immunophenotyping, quantitative real time PCR (qPCR), and histological analysis. The number of colony-forming unit-fibroblast (CFU-F) was comparable between wild type and Lama4-/- in steady state. Interestingly, the proportion of BM MPCs, a population containing osteoblast progenitors, was significantly lower in the Lama4-/- mice compared to that in the wild type controls at steady state (p < 0.01). qPCR analysis showed downregulation of Il6 (p < 0.05) in the MSC and Angpt1 (p = 0.02) in the MPC of the Lama4-/-mice post irradiation. These data suggest that Lama4 deficiency alters BM stromal cell composition and gene expressions, which may be related to the impaired hematopoietic reconstitution. The recovery of BM vascular structure is essential for efficient reconstitution of hematopoiesis. We observed uniquely dilated blood vessels in Lama4-/- BM at 6-week post irradiation. This might be caused by the lower Angpt1 expression in Lama4-/- MPC since Angpt1/Tie2 signaling is required for vascular regeneration (Kopp HG et al., Blood 2005, Zhou BO et al., eLife 2015). The functional consequences of this phenotype are still under investigation. Altogether, LAMA4 is required for rapid and complete hematopoietic recovery post irradiation-induced myelosuppression. Therapeutic strategies to upregulate Lama4 may facilitate the recovery of hematopoiesis following HSC transplantation under preconditioning using irradiation. Disclosures No relevant conflicts of interest to declare.

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