Regulation of Hematopoietic Stem Cell Mitochondrial Metabolism

Abstract Hematopoietic stem cells (HSCs) like most, if not all, adult stem cells are primarily quiescent but have the potential to become highly active on demand. HSC quiescence is maintained by glycolytic metabolism and low levels of reactive oxygen species (ROS), which indicate that mitochondria are relatively inactive in quiescent HSC. However, HSC cycling - and exit of quiescence state - require a swift metabolic switch from glycolysis to mitochondrial oxidative phosphorylation. To improve our understanding of mechanisms that integrate energy metabolism with HSC homeostasis, my laboratory has been focused on the transcription factor FOXO3, which is critical for the maintenance of HSC quiescence and redox state and is implicated in HSC aging. We showed recently that FOXO3 is key to HSC mitochondrial metabolism, independent of its inhibition of ROS or mTOR signaling. Mitochondria divide and fuse constantly in part to segregate and dispose of their damaged counterparts. These processes are influenced by and highly linked to mitochondrial metabolism. We have recently developed imaging approaches to study HSC mitochondrial divisions. Mechanisms by which FOXO3 regulates HSC mitochondria and the impact of impaired FOXO3 on the HSC health and activity, and mitochondrial network will be discussed. Detailed understanding of the mitochondrial metabolism and divisions in HSC and their relationship to nuclear transcription are likely to have broad implications for the state of HSC fitness, regenerative capacity and aging. Disclosures No relevant conflicts of interest to declare.

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Impact of Infusion Rate on the Early Engraftment Following Allogeneic Intra Bone Marrow Infusion of Hematopoietic Stem Cells in a Canine DLA-Identical Reduced Intensity Transplantation Model

Blood ◽

10.1182/blood.v126.23.5406.5406 ◽

2015 ◽

Vol 126 (23) ◽

pp. 5406-5406

Author(s):

Stephanie Schaefer ◽

Juliane Werner ◽

Sandra Lange ◽

Katja Neumann ◽

Christoph Machka ◽

...

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Hematopoietic Stem Cells ◽

Infusion Rate ◽

Conflicts Of Interest ◽

Conditioning Regimen ◽

Hematopoietic Stem ◽

Time Points ◽

The Impact ◽

Reduced Intensity

Abstract Introduction: Direct intra bonemarrow (IBM) infusion of hematopoietic stem cells (HSC) is assumed to improve the homing efficiency and to accelerate the early engraftment in comparison to the conventional intravenous application of HSC. Especially for transplantation of low cell numbers i.e. "weak grafts" that is generally associated with delayed engraftment. The direct infusion of HSC in close proximity to the HSC niche by intra bone marrow transplantation (IBMT) might be a promising way. Whether the HSC infusion rate might influence the homing process and therefore the outcome after IBMT is so far unknown. Aims: Herein, we analyzed in a canine DLA-identical littermate model the impact of different graft infusion rates on the hematopoietic recovery as well as on the engraftment kinetics after IBMT following reduced intensity conditioning. Methods: Recipient dogs received IBMT following a 4.5 Gy total body irradiation (TBI). From day (d) -1 until d+35 Cyclosporin A (15mg/kg) was administered orally twice a day as immunosuppression. For IBM transfusion the graft volume was reduced by buffy coat centrifugation and dogs obtained 2x25 ml simultaneously into the humerus and femur. The infusion rate of the graft was 25ml/10 min in group 1 (IBM10, n = 8) and 25 ml/60 min in group 2 (IBM60, n = 7). A 28 day follow-up is currently available for twelve dogs (IBM10 n = 7; IBM60 n = 5). The development of the peripheral blood mononuclear cell (PBMC) and granulocyte chimerism was tested weekly. Blood count, kidney and liver enzymes were monitored routinely. Results: All animals engrafted. One dog of the IBM10 group died at d+15 (infection) and was therefore not included into analysis. The median number of infused total nucleated cells were in IBM10 4.1*108/kg (range 2.3-6.0*108/kg) and in IBM60 3.2*108/kg (range 1.8-4.4*108/kg; p=0.4). The infused CD34+ numbers were median 3.2*106/kg (range: 1.2-10.0*106/kg; IBM10) and 3.6*106/kg (range: 1.5-6.8*106/kg; IBM60; p=0.7). Time of leukocyte recovery was median d+11 after IBMT in both groups (range: d+4 to d+11, IBM10; d+8 to d+14, IBM60; p= 0.5). Median leukocytes nadirs amounted to 0.2*109/l for IBM10 and 0.3*109/l for IBM60 (p= 0.08). The median duration of leukopenia (<1*109/l) were similar (6d, range: 4-11d, IBM10; 3-9d, IBM60) (p= 0.6). Median platelet nadir was 0*109/l for both cohorts (range: 0.0-7.0*109/l, IBM10; 0.0-1.0*109/l, IBM60). The period of thrombocytopenia (≤20.0*109/l) was significantly prolonged in the IBM60 group (median 10d, range) compared to 5d (range: 3-12d) in the IBM10 group (p=0.05). Donor PBMC chimerisms at d+7, d+14 and d+28 were median 22% (range: 8-34%), 50% (range: 29-53%) and 67% (range: 47-73%) in IBM10. The results of PBMC chimerism for IBM60 were 11% (range: 5-34%), 42% (range: 20-42%) and 59% (range: 44-66%) at these time points (p = n.s.). Donor granulocyte chimerisms of median 33% (range: 11-83%), 100% (range: 58-100%) and 100% (range: 82-100%) were detected at d+7, d+14 and d+28 after HSCT in IBM10, respectively. The granulocyte chimerism in IBM60 amounted to 34% (range: 3-87%), 96% (range: 94-100%) and 98% (range: 96-100%) at the above mentioned time points p=n.s. for all time points). Conclusion: Our data suggest that early granulocyte and PBMC engraftment is not influenced by modification of the HSC infusion rate. However, the period of thrombocytopenia seems to be prolonged following a 60 minutes application. Therefore, longer infusion times in an IBMT setting seem not to be beneficial following toxicity reduced conditioning regimen. Disclosures No relevant conflicts of interest to declare.

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Alpha-Catenin Is Dispensable for Normal Hematopoietic Stem Cell Function.

Blood ◽

10.1182/blood.v114.22.1438.1438 ◽

2009 ◽

Vol 114 (22) ◽

pp. 1438-1438

Author(s):

Natallia Mikhalkevich ◽

Michael W. Becker

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Conflicts Of Interest ◽

Fusion Product ◽

Wild Type ◽

Hematopoietic Stem ◽

Myeloid Neoplasms ◽

Increased Risk ◽

Significant Difference ◽

The Impact

Abstract Abstract 1438 Poster Board I-461 We previously demonstrated the loss of expression of alpha-E-Catenin, the product of the CTNNA1 gene, in primary leukemic stem cells isolated from patients with advanced Myelodysplastic Syndrome (MDS) and Acute Myeloid Leukemia (AML) associated with loss of all or part of the long arm of chromosome 5. To formally assess the impact of loss of Ctnna1 expression on hematopoiesis, we employed a murine model for the hematopoietic specific conditional loss of Ctnna1 expression. We demonstrate that Ctnna1 deficiency is associated with normal hematopoietic maturation and proliferation as assessed by peripheral blood examination and methycellulose colony assays. We assessed stem cell and early progenitor frequencies using both flow cytometry and functional assays. Ctnna1 deficiency was associated with equivalent frequencies of Sca1+C-Kit+CD135-Lineage- HSCs in both experimental animals and controls. Short term HSC and MPP frequencies were likewise unaltered. We assessed HSC function using transplantation studies. In competitive repopulation experiments, HSCs deficient for Ctnna1 maintained stable engraftment of recipient mice for up to 1 year. Limiting dilution analyses detected no significant difference in HSC frequency between wild type and Ctnna1 deficient mice. We examined the potential role of Ctnna1 deficient hematopoietic stem cells in two murine models for myeloid neoplasms 1.) exposure to mutagen ENU and 2.) a model for murine AML driven by the HoxA9-Nup98 fusion product. Following exposure of HSCs to ENU, loss of Ctnna1 was not associated with an increased risk of development of a myeloid neoplasm. Expression of the HoxA9-Nup98 fusion product by retroviral infection of Ctnna1 deficient and wild type Sca1+C-Kit+Lineage- cells resulted in no difference in time to development of the previously characterized myeloproliferative disorder or acute leukemia. Taken together, these data demonstrate that in the absence of specific genetic abnormalities, loss of Ctnna1 expression in primary murine HSCs is not associated with aberrant HSC function or the development of myeloid neoplasms. Further studies are necessary to define a role for of loss of Ctnna1 expression in human myeloid malignancies. Disclosures No relevant conflicts of interest to declare.

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Leukemic Hierarchy and Systemic Factors Dictating Disease Evolution In Chronic Myelogenous Leukemia

Blood ◽

10.1182/blood.v116.21.886.886 ◽

2010 ◽

Vol 116 (21) ◽

pp. 886-886

Author(s):

Damien Reynaud ◽

Eric Pietras ◽

Marion Jeanne ◽

Keegan Barry-Holson ◽

Emmanuelle Passegue

Keyword(s):

Stem Cells ◽

Chronic Myelogenous Leukemia ◽

Conflicts Of Interest ◽

Blast Crisis ◽

Lymphoid Cells ◽

Myelogenous Leukemia ◽

Hematopoietic Stem ◽

Disease Evolution ◽

B Lymphoid ◽

The Impact

Abstract Abstract 886 Chronic myelogenous leukemia (CML) is a clonal myeloproliferative neoplasm (MPN) characterized by the t(9;22)(q34;q11) reciprocal translocation, which leads to the expression of the BCR/ABL fusion protein. CML is clinically characterized by the abnormal expansion of the myeloid lineage leading to progressive peripheral neutrophilia. This indolent disease has the propensity to evolve into an acute leukemia-like blastic phase involving either myeloid or B lymphoid cells. As such, CML constitutes a paradigm for understanding cellular and molecular events controlling chronic diseases and their evolution toward frank leukemia. CML arise from a small pool of leukemic stem cells (LSC) that can be operationally defined by their ability to sustain tumor growth over time and to transplant leukemia to recipient mice. Multiple lines of evidence indicate that LSCs originate from abnormally behaving hematopoietic stem cells (HSCs), although it is still largely unknown how BCR/ABL affects the biology of HSCs and the fate of downstream progenitor cells. To study the impact of BCR/ABL expression on these compartments, we used a transgenic mouse model that allows for inducible expression of BCR/ABL in HSCs and downstream progeny (Blood 105: 324, 2005). Induction of BCR/ABL expression in this model recapitulated many features of human CML such as myeloid bone marrow (BM) hyperplasia, myelofibrosis, splenomegaly and myeloid cell infiltration in non-hematopoietic organs. Disease development also correlated with a dramatic reorganization of the stem and progenitor compartments in the BM and their relocation/expansion in the spleen. In the BM, we observed a marked reduction in the number of Lin– Sca1+ c-Kit+ Flk2– CD48– CD150+ long-term (LT) and Lin– Sca1+ c-Kit+ Flk2– CD48– CD150– short-term (ST) HSCs associated with an expansion of several types of non-self-renewing multipotent progenitors (MPP) and myeloid committed progenitors. We confirmed by limited dilution transplantation experiments that BCR/ABL+ LT-HSCs were true LSCs as they were the only cells capable of transferring sustained CML disease in recipient mice with as few as 50 cells injected. We also found that BCR/ABL expression impacts on the biology of the ST-HSC and Lin– Sca1+ c-Kit+ Flk2+ MPP compartments. Transplantation of both populations induced dramatic but transient hyperplasia, which could eventually mimic a leukemic phenotype with high doses of cell injected (4,000 cells per mouse). However, while transplantation of BCR/ABL+ ST-HSCs led to the expected myeloid hyperplasia, transplantation of BCR/ABL+ MPPs led to a massive accumulation of B-cell progenitors in the BM that resembles lymphoid blast crisis. Strikingly, co-transplantation of 4,000 BCR/ABL+ LT- or ST-HSCs with 4,000 BCR/ABL+ MPPs almost always resulted in myeloid hyperplasia suggesting an active inhibition of MPP-derived lymphoid progeny by the leukemic myeloid compartment. We reasoned that the molecular effectors for this lymphoid inhibitory effect could be extracellular signaling molecules that will be detectable in the serum of CML-developing BCR/ABL mice. Using antibody arrays and enzyme-linked immunosorbent assays (ELISA), we found that the serum concentration of the proinflammatory cytokine interleukine-6 (IL-6) correlates with CML progression both in primary and transplanted mice. Moreover, we showed in vitro that IL-6 controls lineage fate decision of leukemic progenitors by promoting myeloid differentiation from MPPs at the expense of the B lymphoid lineage differentiation. As such, IL-6 targets both normal and malignant MPPs thereby providing a positive feedback loops that promote CML development. In summary, our results identify and functionally characterize a pathological hierarchy in CML that includes LSC and immature leukemic progenitors. They uncover a novel fate-regulatory mechanism at the systemic level that controls the differentiation outcome of the leukemic progenitors and can have key implication for disease progression. Taken together, they demonstrate that CML evolution is the result of a balance between BCR/ABL cell intrinsic effects and environmental cues and provide a rational for the paradoxical myeloid-lymphoid conversion that can be observed during lymphoid blast crisis. Disclosures: No relevant conflicts of interest to declare.

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Variant Pcgf-PRC1 Regulates Susceptibility of PRC2 Mediated H3K27me3 to Safeguard B Cell Fate of Hematopoietic Stem/Progenitor Cells

Blood ◽

10.1182/blood-2019-129518 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 3717-3717

Author(s):

Junichiro Takano ◽

Yaeko Nakajima-Takagi ◽

Shinsuke Ito ◽

Haruhiko Koseki ◽

Atsushi Iwama ◽

...

Keyword(s):

Stem Cells ◽

Hematopoietic Stem Cells ◽

B Cell ◽

Progenitor Cells ◽

Molecular Mechanisms ◽

Conflicts Of Interest ◽

Biological Significance ◽

Differentiation Potential ◽

Hematopoietic Stem ◽

The Impact

Polycomb repressive complex (PRC) resides in two major complexes PRC1 and PRC2. They cooperate with each other to coordinate proper developmental process by silencing target genes; PRC1 posits H2AK119ub1 and PRC2 catalyzes trimethylation of H3K27 (H3K27me3). The PRC1 component BMI1/PCGF4 has long been recognized to be essential in the maintenance of normal and malignant hematopoietic stem cells (HSCs). Recently, diversity of PRC1 has been noticed and PRC1 is now classified into six alternative complexes depending on PCGF proteins. In embolic stem cells, PRC1 which contains PCGF1 (PCGF1-PRC1) has been demonstrated to serve upstream of the BMI1/PCGF4-PRC1. However, the impact of BCOR, which is a component of PCGF1-PRC1 on hematopoiesis is clearly different from BMI1/PCGF4; the mice deficient for BCOR exhibited normal HSC activities and BCOR rather prevented leukemic transformation of HSCs, suggesting the previously unappreciated gene control mechanisms of PCGF1-PRC1. To tackle this issue, we focused on the roles of PCGF1 in hematopoiesis. Loss of Pcgf1 in hematopoietic stem cells led to severe reduction of B lineage cells with an expansion of myeloid progenitors due to defects in lymphoid-primed multipotent progenitor (LMPP) cells. To explore the molecular mechanisms, we have established Id3-overexpressing hematopoietic progenitor cells (IdHPs) which correspond to LMPP-like cells (Ikawa et al. 2015) from bone marrow of ERT2-Cre Pcgf1 flox mice. The ChIP-seq analysis of normal IdHPs identified 1274 genes whose promoters were associated with PCGF1 peaks and 37% of them exhibited enrichment of H3K27me3 and binding of SUZ12 (PRC2). Deletion of Pcgf1 destabilized H3K27me3 levels, resulting in re-activation of genes associated with PCGF1 and SUZ12 peaks, whereas the chromatin occupancy of SUZ12 was not affected. Intriguingly, proteomic analysis demonstrated that PCGF1 interacts with key factors responsible for the organization of nucleosomes and PCGF1 loss triggered a decline of nucleosome-densities in promoters of genes occupied by PCGF1 and SUZ12 peaks. Since enzymatic activity of PRC2 is dependent on nucleosome-densities, PCGF1 is likely to regulate the susceptibility of H3K27me3 by PRC2 through determination of the nucleosome-densities. Furthermore, genes which were downregulated by PCGF1-nucleosome-H3K27me3 axis entailed many myeloid-related genes and knock down of one of those myeloid genes partially restored the B cell differentiation potential of Pcgf1-KO hematopoietic stem/progenitor cells (HSPCs), supporting the biological significance of the PCGF1-nucleosome-H3K27me3 axis. Collectively, these results indicate PCGF1 determines cellular fate of HSPCs through stabilization of nucleosomal organization. Disclosures No relevant conflicts of interest to declare.

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Autologous Stem Cell Transfusions on Multiple Days in Patients with Multiple Myeloma - Does It Matter?

Blood ◽

10.1182/blood-2019-127940 ◽

2019 ◽

Vol 134 (Supplement_1) ◽

pp. 3252-3252

Author(s):

Thomas Pabst ◽

Sebastian Moser ◽

Ulrike Bacher ◽

Barbara Jeker ◽

Behrouz Mansouri Taleghani ◽

...

Keyword(s):

Stem Cells ◽

Stem Cell ◽

Hematopoietic Stem Cells ◽

Conflicts Of Interest ◽

High Dose ◽

Hematopoietic Stem ◽

Increased Risk ◽

Cd34 Cells ◽

The Impact

Introduction: Autologous stem cell transplantation (ASCT) following high-dose chemotherapy (HDCT) is a cornerstone in the standard first-line treatment in myeloma (MM) patients. Freezing of the hematopoietic stem cells (HSC) to bypass the time between stem cell collection and completion of HDCT is crucial for this process. Due to the vulnerability of HSC, adding of anti-freezing agents such 5-10 vol% dimethyl-sulfoxide (DMSO) to hematopoietic stem cells is mandatory. DMSO exerts toxic effects after administration, and toxicity of DMSO is dose-related. However, guidelines for this procedure are missing, and transplant centers have implemented varying limitations of maximum total DMSO administration, ranging from 20-70 g per day. At our center, the maximum transplant volume is 300 mL per day with DMSO at 5 vol%. For patients with transfusion volumes above these limits, the transplant procedure is split over several days. Methods: In this single center study, we retrospectively analyzed the impact of multiple day transplantation procedures on survival rates and hematological recovery in 271 patients with MM patients undergoing first melphalan-based ASCT. Results: 244 (90%) received ASCT within a single day, and this group was termed Tx1. The Tx2-3 group comprised 23 patients receiving stem cells on 2 days, and four patients on 3 days. Both groups (Tx1 and Tx2-3) did not differ in clinical characteristics or number/types of induction therapy lines. The remission status pre-transplant was comparable. Plerixafor was given more frequently in Tx2-3 than Tx1 (p=0.0715). At the day of SC collection, peripheral CD34+ counts were lower in Tx2-3. The final administered autograft volume was higher in Tx2-3 patients. The amount of transplanted CD34+ cells/kg b.w. was lower in the Tx2-3 group, mirroring poorer mobilization of CD34+ cells (p<0.0001). The median recovery for neutrophils was 13 days for Tx2-3 and 12 days for Tx1 (p=0.0048), and for platelets 18 versus 14 days (p=0.0004). Tx2-3 patients had longer median hospitalization duration (23 versus 19 days; p=0.0006). The median follow-up was 56 months. Relapse-free survival (RFS) was 39 months, and 169 relapses (62%) occurred so far. Median OS was 91 months, and 82 patients (30%) have died during follow-up. Tx2-3 patients had shorter median RFS (21 versus 40 months for Tx1; p=0.0245), and shorter median OS with 55 versus 93 months (p=0.0134) (Figure 1). Conclusions: Our data suggest that multiple day transplantation is associated with poor CD34+ mobilization and is observed in roughly 10% of myeloma patients. Patients with multiple day transplant procedures had later neutrophil and platelet engraftment, longer hospitalization duration, more febrile episodes, and inferior OS and RFS. This suggests to consider myeloma patients with the need for multiple day transplantation as a patient group at increased risk that needs enhanced surveillance strategies. Disclosures No relevant conflicts of interest to declare.

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Fbxw11 Variants Control the Quiescence of HSCs

Blood ◽

10.1182/blood.v128.22.5052.5052 ◽

2016 ◽

Vol 128 (22) ◽

pp. 5052-5052

Author(s):

Lina Wang ◽

Wenli Feng ◽

Xiao Yang ◽

Feifei Yang ◽

Rong Wang ◽

...

Keyword(s):

Stem Cells ◽

Hematopoietic Stem Cells ◽

Progenitor Cells ◽

Conflicts Of Interest ◽

Hematopoietic Progenitor Cells ◽

Control Vector ◽

Hematopoietic Progenitor ◽

Hematopoietic Stem ◽

The Impact

Abstract Ubiquitination is a posttranslational mechanism that controls diverse cellular processes. Fbxw11, a constituent of the SCF (Skp1-Cul1-F-box) ubiquitin ligase complex, targets for degradation of several important transcription factors, including NF-κB, β-cantenin and ATF4. Fbxw11 may play pivotal roles in many aspects of hematopoiesis through regulating various signal transduction pathways. However, the role of Fbxw11 on HSCs quiescence remains largely unknown. In this study, we cloned three transcript variants (Fbxw11a, Fbxw11c and Fbxw11d) to study the biological function of Fbxw11 in hematopoiesis. To elucidate Fbxw11 distribution in hematopoietic system, hematopoietic cell populations at different stages of differentiation were isolated from bone marrow of 8 week-old mice and Fbxw11 expression was studied by real-time PCR. Expression of Fbxw11 were lower in purified long term hematopoietic stem cells (LT-HSC, LSK CD34- Flt3-), but higher in short term hematopoietic stem cells (ST-HSC, LSK CD34+ Flt3-), hematopoietic stem and progenitor cells (LSK), and various hematopoietic progenitor cells. The results reveal that Fbxw11 is preferentially expressed in more mature progenitor cells. The expression of Fbxw11 in mature blood cells was also studied showing that Fbxw11 was expressed at lower level in neutrophils, higher level in B and T lymphocytes, and moderate level in monocytes. To assess the impact of Fbxw11 on reconstitution capacity of LT-HSCs, we cloned Fbxw11a, Fbxw11c and Fbxw11d into retrovirus system, respectively. LSK cells were infected with MSCV-Fbxw11a/Fbxw11c/Fbxw11d-IRES-GFP or the blank control vector MSCV-GFP. Competitive repopulation assays we performed 48h later after infection, and reconstitution in peripheral blood (PB) was analyzed every 4 weeks. Repopulation of donor cells expressing high level of Fbxw11 variants was significantly lower than those infected with control vector at 1 and 4 months in PB and at 4 months in BM after transplantation. These data indicate that Fbxw11 is negative for the long-term repopulating capacity of HSCs. To further confirm the effects of Fbxw11 variants in hematopoiesis, the effect of Fbxw11 variants on the growth and enumeration of hematopoietic progenitor cells was detected by colony-forming cell assay (CFC). The number of CFU-G, CFU-GM, CFU-GEMM and the total number of CFU were lower in LSK over-expressing Fbxw11 variants when compared with LSK control. To determine the cell-cycle distribution of HSC cells, Hoechst 33342 and Ki67 staining were performed showing that G0 phase LSK cells were decreased when they over-expressing Fbxw11 variants. In conclusion, our data reveal unrecognized roles for Fbxw11 in the regulation of HSPCs. Our findings suggest that Fbxw11 variants have negative effect on reconstitution capacity of LT-HSCs. Fbxw11 variants decrease the reconstitution capacity through promoting cell proliferation, which results in loss of hematopoietic stem cell quiescence. We anticipate that our experiments will facilitate the understanding of hematopoiesis through which Fbxw11-mediated signals control HSC quiescence and functions. The work was supported by the Grants 81300376, 81370634, 81570153 from the National Natural Science Foundation of China (NSFC); 14JCQNJC10600 from the Tianjin Science and Technology Programs; Disclosures No relevant conflicts of interest to declare.

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Microbiota Signals Suppress the Lymphoid Specification of Hematopoietic Stem Cells

Blood ◽

10.1182/blood-2021-151369 ◽

2021 ◽

Vol 138 (Supplement 1) ◽

pp. 204-204

Author(s):

Joseph R. Krambs ◽

Darlene A. Monlish ◽

Feng Gao ◽

Laura G. Schuettpelz ◽

Daniel C. Link

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Hematopoietic Stem Cells ◽

Expression Profiling ◽

Bone Marrow Cells ◽

Conflicts Of Interest ◽

Rna Expression ◽

Hematopoietic Stem ◽

Rna Expression Profiling ◽

The Impact

Abstract Aging is associated with an expansion of phenotypic hematopoietic stem cells (HSCs) with reduced self-renewal capacity and myeloid-skewed lineage differentiation. Signals from commensal flora support basal myelopoiesis in young mice; however, their contribution to hematopoietic aging is largely unknown. Here, we characterize hematopoiesis in young and middle-aged mice housed under specific pathogen free (SPF) and germ-free (GF) conditions. We did not analyze older mice due to the difficulty in maintaining mice in a gnotobiotic facility for more than one year. Consistent with prior studies, there is a shift in hematopoiesis in aged SPF mice towards granulopoiesis, with a significant increase in the percentage of granulocytic cells and a decrease in B lineage cells in the bone marrow. The marked shift from lymphopoiesis to myelopoiesis that develops during aging of SPF mice is mostly abrogated in GF mice. Compared with aged SFP mice, there is a marked expansion of B lymphopoiesis in aged GF mice, which is evident at the earliest stages of B cell development. To investigate the impact of microbiota signals on multipotent HSPCs, we first quantified HSPCs by flow cytometry (Figure 1A-B). In aged SPF mice, the number of lineage - Sca1 + cKit + CD150 + CD48 - (LSK-SLAM) cells and CD34 - LSK-SLAM cells is increased 6.4 ± 1.7-fold and 3.4 ± 1.2-fold, respectively. Similar increases were observed in aged GF mice, with LSK-SLAM increasing 5.3 ± 1.6-fold (p=NS compared to SPF mice) and CD34 - LSK-SLAM cells increasing 2.8 ± 0.31-fold (p=NS). To quantify functional HSCs, limiting dilution transplantation experiments using unsorted bone marrow cells was performed. Although on a per cell basis the repopulating activity of aged HSCs is reduced, due to the large increase in phenotypic HSCs, the number of functional HSCs actually increases with aging, with similar increases in functional HSCs in aged SPF and GF mice (Figure 1C). Finally, to assess lineage-bias, we transplanted a limiting number of sorted HSCs and assessed lineage output. As expected, in young SPF mice, the majority of HSCs displayed a balanced myeloid/lymphoid lineage output, with a significant increase in myeloid-biased HSCs observed with aging (Figure 1D). In young GF mice, the majority of HSCs are lymphoid-biased. Moreover, although the myeloid output increased modestly with aging, the majority of HSCs in aged GF remained lymphoid-biased or balanced. Consistent with these data, RNA expression profiling of phenotypic HSCs from aged GF mice show enrichment for non-myeloid biased HSCs. Surprisingly, the RNA expression profiling data also suggest that inflammatory signaling is increased in aged GF HSCs compared with aged SPF HSCs. Collectively, these data suggest that microbiota-related signals suppress the lymphoid potential of HSCs, contributing to the expansion of myeloid-biased HSCs that occurs with aging. Figure 1 Figure 1. Disclosures No relevant conflicts of interest to declare.

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Analysis of Highly Self-Renewing GPI-80+ Human Fetal Hematopoietic Stem Cells Identifies Novel Regulators of Stemness

Blood ◽

10.1182/blood.v124.21.4314.4314 ◽

2014 ◽

Vol 124 (21) ◽

pp. 4314-4314 ◽

Cited By ~ 1

Author(s):

Vincenzo Calvanese ◽

Sacha L. Prashad ◽

Mattias Magnusson ◽

Hanna K. A. Mikkola

Keyword(s):

Stem Cells ◽

Hematopoietic Stem Cells ◽

Conflicts Of Interest ◽

Fetal Liver ◽

Molecular Signature ◽

Hematopoietic Stem ◽

Human Fetal Liver ◽

Low Levels ◽

Adult Bone

Abstract Achievements in pluripotent stem cell and reprogramming strategies provide hope for generating hematopoietic stem cells (HSC) in culture and for obtaining unlimited sources of transplantable cells. To reach this goal, deeper understanding of the regulatory mechanisms that distinguish the self-renewing HSC from non-self-renewing progenitors during human development is required. We analyzed the molecular signature of GPI-80 (VNN-2) expressing human second trimester fetal liver HSPC, the only population that harbors the truly self-renewing fetal HSC. Microarray and RNAseq analysis comparing CD34+CD38-CD90+GPI-80+ HSC to CD34+CD38-CD90+GPI80- HPC demonstrated remarkable molecular similarity of these two functionally distinct populations, including comparable expression of many key transcription factors involved in HSC development and maintenance (e.g. SCL, RUNX1, MLL1, HOXA9, BMI1, GFI1, ETV6 etc.). Nevertheless, this analysis identified a subset of transcriptional regulators uniquely up-regulated in GPI80+ HSC, such as MYCT1, HLF, MLLT3 and HIF3A. These factors were down-regulated in human fetal liver HSPC upon expansion on MSC stroma culture, during which they become compromised in in vivo engraftment ability despite maintaining HSC surface immunophenotype. multipotency and expression of most known HSC regulators. Moreover, these factors were absent or expressed at low levels in human ES cell derived HPC, which can acquire HSC surface phenotype but are unable to self-renew. The expression of MYCT1, MLLT3 and HLF was also enriched in undifferentiated HSPC subset as compared to progenitors in the adult bone marrow, while HIF3a expression was low post-natally. Altogether, these analyses implied strong correlation of the expression of these factors with HSC self-renewal properties. Strikingly, knockdown of MYCT1, HLF, MLLT3 and HIF3A in human fetal liver HSPC using lentiviral shRNA impaired maintenance of undifferentiated HSPC in MSC stroma co-culture, while their inducible overexpression augmented HSPC expansion and prevented their premature exhaustion. Uncovering how these novel HSC regulators protect the highly self-renewing fetal HSC will help define the pre-requisites for establishing and maintaining stemness in developing human HSC, and for generating HSC for therapeutic use. Disclosures No relevant conflicts of interest to declare.

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The Impact of Age and Gender on Hematopoietic Stem Cells and Immune Contexture of the Bone Marrow Microenvironment

Cells Tissues Organs ◽

10.1159/000510774 ◽

2020 ◽

pp. 1-6

Author(s):

Rebar N. Mohammed

Keyword(s):

Stem Cells ◽

Bone Marrow ◽

Hematopoietic Stem Cells ◽

Immune Cells ◽

Absolute Number ◽

Cell Number ◽

Hematopoietic Stem ◽

The Absolute ◽

And Gender ◽

The Impact

Hematopoietic stem cells (HSCs) are a rare population of cells that reside mainly in the bone marrow and are capable of generating and fulfilling the entire hematopoietic system upon differentiation. Thirty-six healthy donors, attending the HSCT center to donate their bone marrow, were categorized according to their age into child (0–12 years), adolescence (13–18 years), and adult (19–59 years) groups, and gender into male and female groups. Then, the absolute number of HSCs and mature immune cells in their harvested bone marrow was investigated. Here, we report that the absolute cell number can vary considerably based on the age of the healthy donor, and the number of both HSCs and immune cells declines with advancing age. The gender of the donor (male or female) did not have any impact on the number of the HSCs and immune cells in the bone marrow. In conclusion, since the number of HSCs plays a pivotal role in the clinical outcome of allogeneic HSC transplantations, identifying a younger donor regardless the gender is critical.

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The Act of Controlling Adult Stem Cell Dynamics: Insights from Animal Models

Biomolecules ◽

10.3390/biom11050667 ◽

2021 ◽

Vol 11 (5) ◽

pp. 667

Author(s):

Meera Krishnan ◽

Sahil Kumar ◽

Luis Johnson Kangale ◽

Eric Ghigo ◽

Prasad Abnave

Keyword(s):

Stem Cells ◽

Animal Models ◽

Adult Stem Cells ◽

The Body ◽

In Vivo Studies ◽

Self Renewal ◽

Hematopoietic Stem ◽

Organ Systems

Adult stem cells (ASCs) are the undifferentiated cells that possess self-renewal and differentiation abilities. They are present in all major organ systems of the body and are uniquely reserved there during development for tissue maintenance during homeostasis, injury, and infection. They do so by promptly modulating the dynamics of proliferation, differentiation, survival, and migration. Any imbalance in these processes may result in regeneration failure or developing cancer. Hence, the dynamics of these various behaviors of ASCs need to always be precisely controlled. Several genetic and epigenetic factors have been demonstrated to be involved in tightly regulating the proliferation, differentiation, and self-renewal of ASCs. Understanding these mechanisms is of great importance, given the role of stem cells in regenerative medicine. Investigations on various animal models have played a significant part in enriching our knowledge and giving In Vivo in-sight into such ASCs regulatory mechanisms. In this review, we have discussed the recent In Vivo studies demonstrating the role of various genetic factors in regulating dynamics of different ASCs viz. intestinal stem cells (ISCs), neural stem cells (NSCs), hematopoietic stem cells (HSCs), and epidermal stem cells (Ep-SCs).

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