Hhex Is a Critical Gene In The Development Of Normal and Malignant Lymphoid Cells

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3788-3788
Author(s):  
Charnise Goodings ◽  
Stephen B. Smith ◽  
Elizabeth Mathias ◽  
Elizabeth Smith ◽  
Rati Tripathi ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cell ◽  
Transgenic Mice ◽  
Conflicts Of Interest ◽  
Lymphoid Cells ◽  
Conditional Knockout ◽  
Hematopoietic Stem ◽  
Direct Transcriptional Target ◽  
Cell Counts ◽  
Transcriptional Target

Abstract Hematopoietically expressed homeobox (Hhex) is a T-cell oncogene. It is frequently deregulated in murine retroviral insertional mutagenesis screens and its enforced expression induces T-cell leukemia in bone marrow transduction and transplantation experiments. We discovered that HHEX is a direct transcriptional target of an LIM domain Only-2 (LMO2)-associated protein complex. HHEX clusters with LMO2-overexpressing T-ALLs and is especially overexpressed in Early T-cell Precursor (ETP) – ALL where it is a direct transcriptional target of LMO2. To further understand Hhex's function, we induced a conditional knockout in floxed Hhex mice with the Vav-iCre transgene. Mice were viable and showed normal blood cell counts with highly efficient deletion of Hhex in all hematopoietic tissues. Thymocytes from conditional knockouts showed a normal pattern of development. Most impressively, Hhex conditional knockout markedly prolonged the latency of T-ALL onset in CD2-Lmo2 transgenic mice (figure 1). Hhex conditional knockouts (Hhex cKOs) also had a significant decrease in mature B cells in the spleen and bone marrow. Interestingly, hematopoietic stem and progenitor cells plated on OP9-GFP or OP9-DL1 stromal cells showed proliferative defects and incomplete differentiation towards both B and T lineage. Also under stress conditions such as sublethal irradiation and competitive bone marrow transplants, Hhex conditional knockouts show a marked defect in both B and T lineages but an increase in early progenitor populations. Our experiments show that Hhex is a critical transcription factor in lymphoid development and in LMO2-induced T-ALL.Figure 1Hhex conditional knockout markedly prolonged the latency of T-ALL onset in CD2-Lmo2 transgenic miceFigure 1. Hhex conditional knockout markedly prolonged the latency of T-ALL onset in CD2-Lmo2 transgenic mice Disclosures: No relevant conflicts of interest to declare.

scholarly journals Lmo2's Oncogenic Function in T-Cell Leukemia Requires Ldb1

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 3663-3663
Author(s):  
Liqi Li ◽  
Justin H. Layer ◽  
Claude Warzecha ◽  
Rati Tripathi ◽  
Paul Love ◽  
...  
Keyword(s):  
T Cell ◽  
Transgenic Mice ◽  
Conflicts Of Interest ◽  
Protein Complexes ◽  
Lymphoblastic Leukemia ◽  
Conditional Knockout ◽  
Lim Domain ◽  
Double Positive ◽  
Hematopoietic Stem ◽  
T Cell Progenitors

Abstract LIM domain Only-2 (LMO2) is one of the most frequently deregulated oncogenes in T-cell acute lymphoblastic leukemia (T-ALL). LMO2 encodes a small protein with 2 LIM domains that is part of a large multiprotein complex in hematopoietic stem and progenitor cells, where it is required for HSC specification and maintenance. Many of LMO2's protein partners in HSPCs are expressed in T-ALL implying that protein complexes similar to those nucleated by LMO2 in HSPCs also play a role in leukemia. In this study, we analyzed a critical component of the LMO2 associated complex, LIM domain binding1 (LDB1). LDB1 appears to be an obligate partner of LMO2 in HSPCs but it is not required for T-cell development from committed progenitors. LDB1 is concordantly expressed with LMO2 in human T-ALL although its expression is more widespread than LMO2. To further define Ldb1's role in leukemia, we induced its conditional knockout in CD2-Lmo2 transgenic mice. CD2-Lmo2 transgenic mice develop T-ALL with high penetrance and closely model the human disease. We discovered that Lmo2-induced T-ALL was markedly attenuated in penetrance and latency by Ldb1 deletion. Since Lmo2 induces a distinct differentiation arrest in T-cell progenitors prior to leukemic transformation, we analyzed the differentiation of T-cell progenitors in CD2-Lmo2 transgenic/floxed-Ldb1/Lck-Cre mice and in non-Lmo2 transgenics: floxed-Ldb1/Lck-Cre mice. Ldb1 deletion by Lck-Cre was efficient in double negative and double positive T-cell progenitors. In striking contrast, Ldb1 deletion could not be induced in CD2-Lmo2 transgenic T-cell progenitors. Consistent with this finding, T-ALLs that developed in CD2-Lmo2/floxed-Ldb1/Lck-Cre mice had incomplete deletion of Ldb1. These results imply that Ldb1 is a required factor for Lmo2 to induce T-ALL. Lastly, gene expression analysis of Lmo2-induced T-ALLs and ChIP-exonuclease analysis of Ldb1 occupancy in T-ALL suggested that the Lmo2/Ldb1 complex enforced a gene signature similar to that seen in HSPCs and in Early T-cell Precursor ALL. In conclusion, Ldb1 is a required partner for Lmo2 to induce T-ALL. Additionally, the HSPC function of Lmo2/Ldb1 complexes may be recapitulated in T-cell progenitors prior to T-ALL. Disclosures No relevant conflicts of interest to declare.

PDK1 Controls the Differentiation of Hematopoietic Stem Cells Via Modulating ROS Levels

Blood ◽  
2015 ◽  
Vol 126 (23) ◽  
pp. 896-896
Author(s):  
Tianyuan Hu ◽  
Cong Li ◽  
Le Wang ◽  
Yingchi Zhang ◽  
Luyun Peng ◽  
...  
Keyword(s):  
Stem Cells ◽  
Bone Marrow ◽  
Hematopoietic Stem Cells ◽  
Conflicts Of Interest ◽  
Conditional Knockout ◽  
Quiescent State ◽  
Self Renewal ◽  
Hematopoietic Stem ◽  
Hematopoietic System ◽  
Cell Counts

Abstract Hematopoietic stem cells (HSCs) exist as a rare population with two essential properties of self-renewal and differentiation. HSCs can give rise to all hematopoietic progenitor and mature cells. While critical for a full understanding of the hematopoietic process and HSC-related clinical applications, the mechanisms of self-renewal and differentiation of HSCs remain elusive. The PI3K-Akt signaling pathway plays essential roles in the regulation of hematopoiesis. 3-Phosphoinositide-dependent protein kinase 1 (PDK1) activates multiple AGC kinases including Akt and is a pivotal regulator in this pathway. PDK1 phosphorylates Akt at its T308 residue and regulates the functional development of B and T cells during hematopoiesis. However, the role of PDK1 in HSCs has not been fully defined. In this study, we generated PDK1 conditional knockout mice Vav-Cre;PDK1fl/fl (PDK1Δ/Δ) to explore the roles of PDK1 in HSCs. While PDK1Δ/Δ mice have reduced B and T cell counts as previously described, their LT-HSCs and ST-HSCs were significantly increased in comparison with WT mice while MPPs and CMPs were decreased after PDK1 deletion, indicating that the loss of PDK1 perturbed the steady-state hematopoiesis. Furthermore, although deletion of PDK1 increased the frequency of HSCs, PDK1-deficient HSCs fail to reconstitute the hematopoietic system when PDK1-deficient HSCs were used in bone marrow transplantation and competitive transplantation experiments in comparison to the WT HSCs, indicating that PDK1 is vital for hematopoiesis. To explore the mechanisms by which PDK1 regulates HSC function, we examined the cell cycle status and found the percentage of PDK1Δ/Δ HSCs was decreased significantly in G0 stage while increased in G1 and S/G2/M phases. This suggests an increase in HSC exit from a quiescent state. Since MPPs were significantly decreased in bone marrow, we examined the percentage of Annexin V+ DAPI- PDK1Δ/Δ and WT MPPs and found that they are comparable. This indicates that apoptosis did not cause the decrease in MPPs. In addition, a total of 300 LT-HSCs from PDK1Δ/Δ or WT mice and competitor cells were transplanted into lethally irradiated recipient mice to examine whether the decrease in MPPs is due to a defect in HSC differentiation. We found that less than 1% of MPPs arose from PDK1Δ/Δ HSCs 12 weeks after transplantation, indicating that PDK1 is required for the differentiation from LT-HSCs to MPPs. Because the full activation of Akt requires cooperative phosphorylation at its S473 and T308 residues by mTORC2 and PDK1, respectively, we also investigated the function of HSCs in RictorΔ/Δ PDK1Δ/Δ (DKO) mice in conjunction with RictorΔ/Δ or PDK1Δ/Δ mice to explore how mTORC2 and/or PDK1 influence Akt function in HSCs. The flow cytometric analyses of peripheral blood and bone marrow samples revealed very similar parameters of RictorΔ/Δ PDK1Δ/Δ and PDK1Δ/Δ mice. Interestingly, Rictor seemed to exert a minimal impact on HSCs and MPPs. More importantly, in contrast to RictorΔ/Δ, RictorΔ/Δ PDK1Δ/Δ HSCs failed to reconstitute the hematopoietic system after transplantation as PDK1Δ/Δ HSCs, suggesting that PDK1 plays a dominant role in the Akt-mediated regulation of HSC function. To explore the mechanism that leads to the defect in HSCs due to loss of PDK1, we assessed ROS levels in PDK1-deficient HSCs and found that PDK1-deficient LSKs and HSCs exhibit greatly reduced ROS levels when compared with the control HSCs. Treating PDK1-deficient BM cells with BSO in vitro increased cellular ROS levels and the colony counts of PDK1-deficient BM cells significantly. Notably, the recovery effect was only observed with BSO concentrations lower than 0.03 mM. This suggests that ROS levels are precisely controlled in HSCs. Higher or lower ROS levels beyond the normal range are both harmful to normal HSC functions. Since increased SDFα expression is associated with cellular ROS levels in various cells including hematopoietic cells, we also treated PDK1Δ/Δ mice with SDFα and found that it couldpartially rescue the defective differentiation ability of PDK1-deficient HSCs. In addition, we found that PDK1 deletion could significantly prolong the life span and inhibit the leukemia development in murine T-ALL model via altering leukemic cell differentiation and proliferation. Taken together, PDK1 controls HSC differentiation via regulating cellular ROS levels and regulates malignant hematopoiesis. Disclosures No relevant conflicts of interest to declare.

scholarly journals LIM Domain Protein 1 (Ldb1) Is Required for Lmo2 Oncogene-Induced Thymocyte Self-Renewal and T-Cell Leukemia in a Mouse Model of Human T-ALL

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 2538-2538
Author(s):  
Liqi Li ◽  
Apratim Mitra ◽  
Bin Zhao ◽  
Seeyoung Choi ◽  
Jan Lee ◽  
...  
Keyword(s):  
T Cell ◽  
Mouse Model ◽  
Transgenic Mice ◽  
Progenitor Cells ◽  
Conflicts Of Interest ◽  
Lymphoblastic Leukemia ◽  
Conditional Knockout ◽  
Lim Domain ◽  
Self Renewal ◽  
Hematopoietic Stem

LIM domain Only-2 (LMO2) is one of the most frequently deregulated oncogenes in T-cell acute lymphoblastic leukemia (T-ALL) and is generally expressed in the clinically aggressive Early Thymocyte Precursor ALL. LMO2 encodes a small protein with 2 LIM domains that is part of a large multiprotein complex in hematopoietic stem and progenitor cells (HSPC), where it is required for HSC specification and maintenance. Many of LMO2's protein partners in HSPCs are expressed in T-ALL implying that protein complexes like those scaffolded by LMO2 in HSPCs also play a role in leukemia. LDB1 is concordantly expressed with LMO2 in human T-ALL although its expression is more widespread than LMO2. In this study, we analyzed a critical component of the Lmo2 associated complex, LIM domain binding 1 (Ldb1), in the CD2-Lmo2 transgenic mouse model of human T-ALL. To further define Ldb1's role in leukemia, we induced its conditional knockout in CD2-Lmo2 transgenic mice with the use of Lck-Cre, Rag1-Cre, and Il7r-Cre transgenic mice. CD2-Lmo2 transgenic mice develop T-ALL with high penetrance and closely model the human disease. We discovered that the penetrance and latency of Lmo2-induced T-ALL were markedly attenuated in the Lck-Cre model and T-ALL onset was completely abrogated in the Rag1-Cre and Il7r-Cre models. The latter two models induced more efficient deletions of Ldb1, earlier in the T-cell differentiation program compared to Lck-Cre. Interestingly, Lck-Cre deletion was efficient in thymocytes without the Lmo2 transgene. In striking contrast, Ldb1 deletion could not be induced in CD2-Lmo2 transgenic T-cell progenitors. Consistent with this finding, T-ALLs that developed in CD2-Lmo2/floxed-Ldb1/Lck-Cre mice had incomplete deletion of Ldb1. These results imply that Ldb1 is a required factor for Lmo2 to induce T-ALL. To further probe the pathogenesis of Lmo2-induced T-ALL, we analyzed preleukemic phenotypes in the Rag1-Cre (or Il7r-Cre) conditional knockout models. Our results showed that Ldb1 is required for the induction of thymocyte self-renewal and radioresistance. Ldb1 was also required for the acquisition of the pre-leukemic ETP gene expression signature observed in immature CD2-Lmo2 transgenic thymocytes. Detailed biochemical experiments show that LMO2 protein is directly stabilized by LDB1 in leukemia cells perhaps on chromatin. In conclusion, these results support a model where Lmo2-induced T-ALL is caused by a failure to downregulate Ldb1/Lmo2 nucleated transcription complexes that normally function to enforce self-renewal in bone marrow hematopoietic progenitor cells. Disclosures No relevant conflicts of interest to declare.

scholarly journals CongenitalSTAT3mutation Mediates Primary Persistent Polymorphic Inflammatory Activation and T Cell Leukemogenesis

Blood ◽  
2019 ◽  
Vol 134 (Supplement_1) ◽  
pp. 1054-1054 ◽  
Author(s):  
Hongxing Liu
Keyword(s):  
Bone Marrow ◽  
Flow Cytometry ◽  
T Cell ◽  
Lymph Nodes ◽  
Conflicts Of Interest ◽  
Sh2 Domain ◽  
Janus Kinase ◽  
Gingival Hyperplasia ◽  
Hematopoietic Stem ◽  
T Cell Leukemogenesis

Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathways play a pivotal role in inflammation and immunity, among which, JAK/STAT3 pathway is the most potent and leads the crosstalk of immunity and oncogenesis. Somatic STAT3 activatingmutations have been found in about 40% of T cell large granular lymphocytic leukemia (T-LGLL) patients, most of which are located in exon 21 which encodes Src homology 2 (SH2) domain leading to the increased activity of aberrant STAT3 protein and the upregulation of its transcriptional targets. While germline STAT3activatingmutations represent a newly defined entity of immune dysregulations named infantile-onset multisystem autoimmune disease-1 (ADMIO1, #MIM 615952). Both the two diseases are rare and poorly understood. Here, we report a pedigree including a proband, a six-year-old girl, primarily manifesting as thrombocytopenia and lymphadenopathy and her father diagnosed as T-LGLL with pure red cell aplastic anemia without autoimmune disorders preceding or during his disease course. Morphology of the bone marrow smears of the proband indicated normal hyperplasia without evident dyspepsia or increased blast cells. However, the vacuoles in monocytes and the density and size of granules in neutrophils increased, and megaloblast transformation was observed in some neutrophils. (Fig. 1A, 1B) Biopsy of an enlarged lymph node showed the reactive follicular hyperplasia. (Fig. 1C) Whole exon sequencing and pedigree analysis of the family revealed the germline STAT3 c.833G>A/p.R278Hmutation harbored by the proband which originated de novo from her father who additionally carried a germline TAL1G62Rmutation and somatically accumulated an FLT3-ITD mutation. (Fig. 2) Through single-cell RNA sequencing, we also found the increase of circulating CD8+ T cells and the decrease of NK cells of the proband. (Fig. 3) The STAT3 target genes were generally overactivated, and the expression of cytokines decreased in transcription level. In the genes participating in JAK/STATs pathways, the expression of JAK3, STAT1, and STAT3was up-regulated significantly. (data not shown) Immunophenotype of the proband by flow cytometry confirmed change in immunocyte compartments, (Fig. 4) but the serum cytokine concentrations measured by flow cytometry yielded controversial results, that most of cytokines were moderately elevated, and IL-1β, IL-5, TNF-α, and IFN-γ were of the most evident. (data not shown) During the treatment and follow-up, Cyclosporin A (CsA) was efficient in maintaining her circulating platelets in the range of 166×109/L to 302×109/L, but the enlarged lymph nodes and hepatosplenomegaly had no response. Eleven months later, CsA was replaced by tacrolimusfor the severe gingival hyperplasia, which has efficiently stabilized her platelets count and normalized the enlarged lymph nodes, liver, and spleen. On the contrary, in the three and a half years' span of illness, the father was refractory to CsA and methotrexate (MTX), moreover, lethal bone marrow suppression was induced by one course of fludarabine. For the high level of HLA-I and HLA-II antibodies in the circulation, plantlets transfusions were only efficient after plasmapheresis. The father eventually died from pulmonary and gastrointestinal infection due to the failure of maternal HLA-haploidentical hematopoietic stem cell transplantation (HSCT). We comprehensively elaborated the immunophenotype of the proband and thoroughly elucidated the genetic alternations of the father which led to the T cell leukemogenesis, which brought new insight on these two rare diseases and highlighted a more scrupulous therapeutic strategy in T-LGLL with congenital mutations. Figure 1 Disclosures No relevant conflicts of interest to declare.

RhoA Is An Essential Regulator of Mitosis and Survival During Hematopoietic Stem Cell Differentiation to Multipotent Progenitors

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1273-1273
Author(s):  
Xuan Zhou ◽  
Jaime Meléndez ◽  
Yuxin Feng ◽  
Richard Lang ◽  
Yi Zheng
Keyword(s):  
Cell Cycle ◽  
Bone Marrow ◽  
Intracellular Signaling ◽  
Conflicts Of Interest ◽  
Stem Cell Differentiation ◽  
Conditional Knockout ◽  
Hematopoietic Progenitors ◽  
Hematopoietic Stem ◽  
Differentiated Cells ◽  
Multipotent Progenitors

Abstract Abstract 1273 The maintenance and differentiation of hematopoietic stem cells (HSC) are critical for blood cell homeostasis, which is tightly regulated by a variety of factors. In spite of extensive investigation of HSC biology, however, the mechanism of regulation of HSC and progenitor cell division, particularly the unique molecular events controlling the mitosis process during HSC differentiation, remains unclear. RhoA GTPase is a critical intracellular signaling nodal that has been implicated in signal transduction from cytokines, chemokines, wnt/notch/shh, and adhesion molecules to impact on cell adhesion, migration, cell cycle progression, survival and gene expression. Recent mouse genetic studies in keratinocytes and embryonic fibroblast cells showed that RhoA is a key regulator of mitosis. By using an interferon-inducible RhoA conditional knockout mouse model (Mx-cre;RhoAlox/lox), we have made the discovery that RhoA plays an indispensible role in primitive hematopoietic progenitor differentiation through the regulation of mitosis and survival. RhoA deficient mice die at ∼10 days because of hematopoietic failure, as evidenced by a loss of bone marrow, splenocyte and PB blood cells. Syngenic as well as reverse transplant experiments demonstrate that these effects are intrinsic to the hematopoietic compartment. RhoA loss results in pancytopenia associated with a rapid exhaustion of the lin−c-kit+ (LK) phenotypic progenitor population (within 4 days after two polyI:C injections). Meanwhile, the lin−c-kit+sca1+ (LSK) primitive cell compartment is transiently increased in BM after RhoA deletion due to a compensatory loss of quiescence and increased cell cycle. Interestingly, we find that within the LSK population, there is a significant accumulation of LSKCD34+Flt2− short-term HSCs (ST-HSC) and a corresponding decrease in frequency of LSKCD34+Flt2+ multipotent progenitors (MPPs). Consistent with these phenotypes, the LK and more differentiated hematopoietic cell populations of RhoA knockout mice show an increased apoptosis while the survival activities of LSK and more primitive compartments of WT and RhoA KO mice remain comparable. These data suggest that RhoA plays an indispensible role in the step of ST-HSCs differentiation to MPP cells, possibly through the regulation of MPP cell survival. This hypothesis is further supported by a competitive transplantation experiment. Deletion of RhoA in a competitive transplantation model causes an extinction of donor derived (CD45.2+) differentiated cells (myeloid, erythroid, T and B cells) in the peripheral blood. Interestingly, bone marrow CD45.2+ LSK cells are only marginally affected by deletion of RhoA and RhoA−/− LSK cells are able to engraft into 2nd recipient, whereas CD45.2+ LK and more differentiated cells are mostly eliminated after RhoA deletion. This effect is associated with a decrease in the survival of CD45.2+ RhoA−/− LK, but not LSK cells. Further in vitro culture of isolated lin− progenitors demonstrates that RhoA deficiency results in a failure of cytokinesis, causing an accumulation of multinucleated cells, further suggesting that RhoA is essential for the cytokinesis of hematopoietic progenitors. Surprisingly, the well-defined Rho downstream target, actomyosin machinery, does not appear to be affected by RhoA knockout. We are further exploring the mechanism of RhoA contribution to the differentiation of HSCs by dissecting the signaling and functional relationship of RhoA regulated survival activity and cell cycle mitosis in early hematopoietic progenitors. Disclosures: No relevant conflicts of interest to declare.

“RUNX1-IRES-GFP Knock-in” Mice Lack Expression of Runx1a: A Versatile Tool for Hematopoietic Stem Cell Analysis

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2329-2329
Author(s):  
Yukiko Komeno ◽  
Ming Yan ◽  
Shinobu Matsuura ◽  
Miao-Chia Lo ◽  
James R. Downing ◽  
...  
Keyword(s):  
Body Weight ◽  
Conflicts Of Interest ◽  
Lymphoid Cells ◽  
Hematopoietic Stem ◽  
Blood Indices ◽  
Cell Counts ◽  
Significant Difference ◽  
Versatile Tool ◽  
Exon 4 ◽  
Runx1 Expression

Abstract Abstract 2329 Previously reported “RUNX1-IRES-GFP knock-in mice” (Blood 2004;103:2522) (KI mice) were generated by replacing exon 4 of runx1 gene with cDNA of Runx1b/c from exon 4 to exon 8 followed by IRES-GFP, aiming to evaluate Runx1 expression in specific lineages and developmental stages during adult hematopoiesis. They are phenotypically normal, fertile, and blood indices are normal. GFP intensity correlates with Runx1 expression level, and shows lineage-specific changes during maturation in myeloid, erythroid, and lymphoid cells. However, the behavior in the hematopoietic stem cells (HSCs) had not been carefully examined. Interestingly, we discovered that this knock-in strategy eliminated Runx1a expression. Since Runx1a expression is relatively higher in HSCs than in differentiated cells, we analyzed HSCs in these mice to evaluate its roles in stable and stress hematopoiesis. We found that LSK fraction in bone marrow (BM) was significantly decreased in KI mice compared to wild type (WT) mice (0.043% vs 0.085%, p = 0.001). Among subpopulations in LSK, short-term HSC and multipotent progenitor fractions were significantly decreased (0.024% vs 0.046%, p = 0.003, 0.0021% vs 0.0026%, p = 0.001, respectively). SLAM marker staining using CD150 and CD48 showed similar results. Competitive repopulation assay showed less functional HSCs in KI mice. However, there was no significant difference in recovery of cell counts after single-dose 5-FU intraperitoneal injection (150 mg/kg body weight) or sublethal irradiation (5 Gy), or survival after weekly 5-FU injection. After G-CSF subcutaneous injection (125 μg/kg body weight, twice daily for 5 days), mobilized WBC or neutrophil in PB showed no difference. However, LSK and long-term HSC in PB were significantly less in KI mice (0.078% vs 0.135%, p = 0.010, 0.043% vs 0.092%, p = 0.029, respectively) while those in BM did not show significant difference (increased to 0.295% and 0.346% in KI and WT mice, respectively). In conclusion, Runx1a plays some non-redundant roles in stable hematopoiesis, while it is dispensable for tested stress hematopoiesis. RUNX1-GFP KI mice are a versatile tool to evaluate roles of Runx1a in normal hematopoiesis and leukemogenesis when combined with other genetic modifications. Disclosures: No relevant conflicts of interest to declare.

Comparative Analysis on Cellular Components of Bone Marrow Microenvironment in Normal and Aberrant Hematopoiesis

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 4808-4808
Author(s):  
Young-Ho Lee ◽  
Young-hee Kwon ◽  
Kyoujung Hwang ◽  
Hyunju Jun ◽  
Byungbae Park ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cell ◽  
Conflicts Of Interest ◽  
T Cell Subsets ◽  
Hematopoietic Stem ◽  
Cd34 Cells ◽  
Significant Difference ◽  
Stromal Cell Derived Factor ◽  
And Control ◽  
Cellular Components

Abstract Abstract 4808 Background: It is now evident that hematopoietic stem cells (HSCs) reside preferentially at the endosteal region within the bone marrow (BM) where bone-lining osteoblasts are a key cellular component of the HSC niche that directly regulates HSC fate. We investigated the microenvironmental differences including osteoblastic activities and HSC components in myeloproliferative (chronic myeloid leukemia, CML) and hypogenerative disease (aplastic anemia, AA) as well as normal control (NC). Methods: The immunohistochemistry for osteonectin, osteocalcin, stromal cell derived factor (SDF, CXCL12), T cell, T helper/inducer cell, T suppressor/cytotoxic cell, hematopoietic stem/progenitor (CD34, CD117) and megakaryocytes was performed on BM biopsy specimens from 10 AA patients, 10 CML patients and 10 NC (lymphoma without BM involvement). The positive cells for immunohistochemical stainings except osteocalcin on each slide were calculated on 10 high power fields (HPF, ×400), and then corrected by the cellularity. The positive cells for osteocalcin were counted on the peritrabecular line on each slide, and then corrected by the mean length measured. Results: The CD34+ cells (p=0.012) and megakaryocytes (p<0.0001) were significantly lower in AA than in NC, but CD117+ cells was comparable in AA, CML, and control samples. The osteonectin+ cells (p=0.0003) were lower in CML than in AA and NC, however the osteocalcin+ cells showed wide variation (0-903/2035um) and no significant difference. The SDF+ cells (p<0.0001) was significantly higher in AA and very lower in CML, compared with NC. The counts for T cell and T cell subsets were significantly lower in CML than in NC, and higher in AA than in NC (p<0.0001). Conclusions: Cellular components of BM microenvironment in 2 hematologic diseases representative of myeloproliferation (CML) and hyporegeneration (AA) respectively are quite different. Further studies would be required to explore the role of these components for hematopoiesis and the rationale for therapeutic application. Disclosures: No relevant conflicts of interest to declare.

Prolonged Thrombocytopenia After Allogeneic Hematopoietic Stem Cell Transplantation (allo-HSCT) and Its Association with an Increase in CD8+ CX3CR1+ Cells in Bone Marrow.

Blood ◽  
2012 ◽  
Vol 120 (21) ◽  
pp. 3077-3077
Author(s):  
Xiao-hui Zhang ◽  
Guo-xiang Wang ◽  
Yan-rong Liu ◽  
Lan-Ping Xu ◽  
Kai-Yan Liu ◽  
...  
Keyword(s):  
Bone Marrow ◽  
T Cells ◽  
T Cell ◽  
Cd8 T Cells ◽  
Surface Expression ◽  
T Cell Subsets ◽  
Control Group ◽  
Hematopoietic Stem ◽  
Cell Counts

Abstract Abstract 3077 Background: Since prolonged thrombocytopenia (PT) is an independent risk factor for poor clinical outcome after allogeneic hematopoietic stem cell transplantation (allo-HSCT), the underlying mechanisms need to be understood in order to develop selective treatments. Previous studies1–4 have suggested that abnormalities in B cells may play a role in the pathogenesis of PT. However, abnormalities in B cells alone do not fully explain the complete pathogenic mechanisms of PT. Our previous studies5 showed that the frequency of megakaryocytes with a ploidy value ≤ 8N was significantly increased in patients who developed PT after allo-HSCT compared to the control group. Mechanisms concerning the megakaryocyte hypoplasia in PT after allo-HSCT are not well understood. Design and Methods: PT was defined as a platelet count ≤80 × 109/L for more than 3 months after HSCT, recovery of all other cell counts, and no apparent cause for thrombocytopenia, such as aGVHD, disease recurrence, CMV infection, or antiviral drug treatment at three months post-HSCT when all other blood cell counts had return to normal.5 We analyzed T cell subsets in bone marrow (BM) and peripheral blood (PB) from allo-HSCT recipients with and without PT (n = 23 and 17, respectively) and investigated the expression characteristics of homing receptors CX3CR1, CXCR4 and VLA-4 by flow cytometry. Futhermore, Mononuclear cells (MNCs) from PT patients and controls were cultured with and without autologous CD8+ T cells in vitro, and clarify the effect of activated CD8+ T cells on the ploidy and apoptosis of megakaryocytes in the bone marrow. Results: The results demonstrated that the percentage of CD3+ T cells in the BM was significantly higher in PT patients than the experimental controls (76.00 ± 13.04% and 57.49 ± 9.11%, respectively, P < 0.001), whereas this difference was not significant for the PB (71.01 ± 11.49% and 70.49 ± 12.89%, respectively, P = 0.911). While, some T cell subsets in the BM and PB from allo-HSCT recipients with PT were not significantly different from that of the experimental control group, such as CD8+ T cells, CD4+ T cells, CD4+ CD25bright T cells (regulatory T cells), CD44hi CD62Llo CD8+ T cells and naive T cells (CD11a+ CD45RA+). Furthermore, the surface expression of homing receptor CX3CR1 on BM T cells (64.16 ± 14.07% and 37.45 ± 19.66%, respectively, P < 0.001) and CD8+ T cells (56.25 ± 14.54% and 35.16 ± 20.81%, respectively, P = 0.036), but not in blood, were significantly increased in PT patients compared to controls. For these two groups of patients, the surface expression of CXCR4 and VLA-4 on T cells and CD8+ T cells from both BM and PB did not show significant differences. Through the study in vitro, we found that the activated CD8+ T cells in bone marrow of patients with PT might suppress apoptosis (MNC group and Co-culture group: 18.02 ± 3.60% and 13.39 ± 4.22%, P < 0.05, respectively) and Fas expression (MNC group and Co-culture group: 21.10 ± 3.93 and 15.10 ± 2.33, P <0.05, respectively) of megakaryocyte. In addition, megakaryocyte with a ploidy value ≤ 8N (MNC group: 40.03 ± 6.42% and 24.54 ± 4.31%, respectively, P < 0.05) was significantly increased in patients with PT compared to the control group. Conclusions: In conclusion, an increased surface expression of CX3CR1 on T cells may mediate the recruitment of CD8+ T cells into the bone marrow in patients with PT who received an allo-HSCT. Moreover, CD8+CX3CR1+ T cells, which can have significantly increased numbers in bone marrow of patients with PT, likely caused a reduction in the megakaryocyte ploidy, and suppressed megakaryocyte apoptosis via CD8+ T cell-mediated cytotoxic effect, possibly leading to impaired platelet production. Therefore, treatment targeting CX3CR1 should be considered as a reasonable therapeutic strategy for PT following allo-HSCT. Disclosures: No relevant conflicts of interest to declare.

scholarly journals IL-6 Deficiency Reverses Leukemic Transformation in an MDS Mouse Model

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 36-36
Author(s):  
Yang Mei ◽  
Yijie Liu ◽  
Xu Han ◽  
Jing Yang ◽  
Peng Ji
Keyword(s):  
Bone Marrow ◽  
Mouse Model ◽  
Inflammatory Cytokines ◽  
Conflicts Of Interest ◽  
Double Knockout ◽  
Leukemic Transformation ◽  
Hematopoietic Stem ◽  
Cell Counts ◽  
Age Related

Myelodysplastic syndromes (MDS) are a group of age-related myeloid malignancies that are characterized by ineffective hematopoiesis and increased incidence of developing acute myeloid leukemia (AML). The mechanisms of MDS to AML transformation are poorly understood, which is partially due to the scarcity of leukemia transformation mouse models. Recently, we established a mDia1/miR146a double knockout (DKO) mouse model mimicking human del(5q) MDS. DKO mice present with pancytopenia with aging due to myeloid suppressive cell (MDSC) expansion and over-secretion of pro-inflammatory cytokines including TNF-a and interlukine-6 (IL-6). In the current study, we found that most of the DKO mice underwent leukemic transformation at 12-14 months of age. The bone marrow of these mice was largely replaced by c-Kit+ blasts in a background of fibrosis. Flow cytometry analysis and in vitro colony formation assay demonstrated that hematopoietic stem progenitor cells (HSPCs) in DKO bone marrow were dramatically declined. The leukemic DKO mice had elevated white blood cell counts and circulating blasts, which contributes to the myeloid cell infiltration in non-hematopoietic organs including liver and lung. Moreover, the splenocytes from DKO old mice efficiently reconstitute the hematopoiesis, but led to a 100% disease occurrence with rapid lethality in gramma irradiated recipient mice, suggesting the leukemic stem cells enriched in DKO spleen were transplantable. Given the significant roles of the inflammatory cytokines in the pathogenesis of the DKO mice, we crossed DKO mice with IL-6 knockout mice and generated mDia1/miR-146a/IL-6 triple knockout (TKO) mice. Strikingly, the TKO mice showed dramatic rescue of the leukemic transformation of the DKO mice in that all the aforementioned leukemic phenotypes were abolished. In addition, IL-6 deficiency normalized the cell comparts and prevented leukemic transplantation ability in TKO spleen. Single cell RNA sequencing analyses indicated that DKO leukemic mice had increased monocytic blast population with upregulation of Fn1, Csf1r, and Lgals1, that was completely diminished with IL-6 knockout. Through a multiplex ELISA, we found IL-6 deficiency attenuated the levels of multiple inflammatory cytokines in TKO serum. In summary, we report a mouse model with MDS leukemic transformation during aging, which could be reverted with the depletion of IL-6. Our data indicate that IL-6 could be a potential target in high risk MDS. Disclosures No relevant conflicts of interest to declare.

scholarly journals Engraftment Effects of Intra Bone Marrow Compared to Intravenous Transplantation of Allogeneic Hematopoietic Stem Cells Following a Reduced Intensity Conditioning in a DLA-Identical Canine Littermate Model

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 1089-1089
Author(s):  
Juliane Werner ◽  
Stephanie Schaefer ◽  
Sandra Lange ◽  
Christoph Machka ◽  
Gudrun Knuebel ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Conflicts Of Interest ◽  
Control Group ◽  
Reduced Intensity Conditioning ◽  
Hematopoietic Stem ◽  
Platelet Recovery ◽  
Time Points ◽  
Donor Chimerism ◽  
Cell Counts ◽  
Reduced Intensity

Abstract Introduction: Successful engraftment following hematopoietic stem cell transplantation (HSCT) depends on factors like immunosuppression, graft composition and number of infused HSC. Whereas the immunosuppression as well as the type and composition of the graft are influenceable low numbers of available HSCs i.e. “weak grafts” remain a clinical challenge. Weak grafts are accompanied by increased graft failure rates and longer cytopenias associated with increased morbidity. Intra bone marrow (IBM) infusion of HSC might be an approach to overcome these problems. Studies in rodents demonstrated faster engraftment with an IBM HSCT approach compared to intravenous (IV) HSCT following myeloablative conditioning. Studies of IBM HSCT following non-myeloablative or reduced intensity conditioning (RIC) are missing. Aims: Exploring the feasibility and efficiency of IBM allogeneic HSCT in comparison to IV HSCT in dog leukocyte antigen (DLA) identical canine littermates using a RIC regimen. Methods: DLA-identical siblings were used as donor/recipient pairs for HSCT. Recipient dogs were conditioned with 4.5 Gy total body irradiation before HSCT (d0) and received 15 mg/kg Cyclosporin A BID as pre- and postgrafting immunosuppression (d-1 to d+35). BM grafts were harvested at d0. In the control group (CON, n=7) unmodified BM was transplanted IV. In the IBM group (n=7) BM harvests were centrifuged and buffy coat of the BM was then transfused simultaneously into the recipient humeri and femura (50 ml, 10 min). 10 dogs are currently evaluable. Chimerism of the peripheral blood mononuclear cells (PBMC) and granulocytes (G) were tested weekly until week 8 and afterwards in larger intervals. Blood cell counts and clinical toxicities such as weight loss were monitored. Results: Infusion of BM directly into the bone was feasible. All animals engrafted. Median number of infused total nucleated cells was 4.0*108/kg (range 2.3-6.0*108/kg, IBM) and 3.3*108/kg (range 1.9-5.0*108/kg, CON, IBM vs CON: p=0.4). Median CD34+ numbers infused were 3.1*106/kg (range:1.2-10.0*106/kg, IBM) and 3.9*106/kg (range: 1.0-7.2*106/kg, CON; IBM vs CON: p= 0.8). Hematopoietic recovery in the IBM and CON groups were similar. Leukocytes recovery (>1.0*109/l) occurred at median d+11 (range: d+10 - d+16, IBM) and d+10 (range: d+9-d+12, CON; IBM vs CON: p=0.3). Median leukocytes nadirs amounted to 0.23*109/l (IBM) and 0.28*109/l (CON; IBM vs CON: p=0.3) and median duration of leukopenia (<1.0*109/l) were 6 days (range: 5.0–11.0, IBM) and 4 days (range: 3.0–6.0, CON; IBM vs CON: p=0.1). Median platelet nadir after IBMT was 10.0*109/l (range: 0.0 - 25.0*109/l) and 6.0*109/l (range: 3.0-15.0*109/l, CON; IBM vs CON: p=0.8). Period of thrombocytopenia (≤50.0*109/l) lasted for 12 days in both groups (p=0.7). Chimerism analyses showed an early and fast increase in donor chimerism in both groups. The PBMC donor chimerism at d+14, d+28 and d+56 were 46% (range: 30-53%), 57% (range: 40-73%), 64% (range: 60-83%) for IBM. Results in CON were 37% (range: 17-93%), 60% (range: 49-100%), 57% (range: 40-100%) (IBM vs CON, p=n.s. (all time points)). The G chimerism values at that specific points were 95% (range: 53-100%), 100% (range: 53-100%), 96% (range: 88-100%) for IBM and 100% (range: 93-100%), 99% (range: 92-100%), 98% (range: 93-100%) for CON (IBM vs CON, p=n.s. (all time points)). Primary goal of the study was the feasibility of the IBM approach. Ethics regulations did not allow to use weak grafts (≤2.0*106/kg) intentionally. However, 4 animals received weak grafts (CON n=2, 1.0 and 2.0*106/kg; IBM n=2, 1.2 and 1.3 *106/kg). Of interest, comparing data of these dogs showed that durations of leukopenia were similar (median 10 days, both groups), but duration of thrombocytopenia were different (median 8 days, IBM vs 22 days, CON). Additionally, long term donor chimerism was higher in the IBM (median 80% PBMC, 100% G) vs CON (median 61% PBMC, 42% G). Conclusion: First, IBM HSCT is a feasible and effective method to deliver HSC directly into the bone marrow following RIC in a canine HSCT model. Second, our preliminary data suggest that IBM HSCT reveals advantageous engraftment differences in regards to platelet recovery and donor chimerism kinetics compared to the IV HSCT when grafts with low HSC numbers were infused. Follow up data of this study and future studies will have to clarify these observations further. Disclosures No relevant conflicts of interest to declare.

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