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The ability to isolate and characterize different hematopoietic stem cell (HSC) or progenitor cell populations opens avenues to understand how hematopoiesis is regulated during development, homeostasis, and regeneration as well as in age-related conditions such as clonal hematopoiesis and leukemogenesis. Significant progress has been made in the past few decades in determining the composition of the cell types that exist in this system, but the most significant advances have come from mouse studies. However, recent breakthroughs have made significant strides that have enhanced the resolution of the human primitive hematopoietic compartment. Therefore, we aim to review this subject not only from a historical perspective but also to discuss the progress made in the characterization of the human postnatal CD34+ HSC-enriched populations. This approach will enable us to shed light on the potential future translational applicability of human HSCs.
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Transplante de Células-Tronco Hematopoéticas , Leucemia , Humanos , Camundongos , Animais , Células-Tronco Hematopoéticas/metabolismo , Antígenos CD34/metabolismo , Hematopoese , Leucemia/metabolismoRESUMO
The present study investigated the involvement of key molecular regulators of oxidative stress in amoebic gill disease (AGD), a parasitic infestation in Atlantic salmon. In addition, the study evaluated how these molecular biomarkers responded when AGD-affected fish were exposed to a candidate chemotherapeutic peracetic acid (PAA). Atlantic salmon were experimentally infected with the parasite Neoparameoba perurans, the causative agent of AGD, by bath exposure and after 2 weeks, the fish were treated with three commercial PAA products (i.e., Perfectoxid, AquaDes and ADDIAqua) at a dose of 5 ppm. Two exposure durations were evaluated - 30 min and 60 min. Sampling was performed 24 h and 2 weeks after PAA treatment (equivalent to 2- and 4-weeks post infection). At each sampling point, the following parameters were evaluated: gross gill pathology, gill parasitic load, plasma reactive oxygen species (ROS) and total antioxidant capacity (TAC), histopathology and gene expression profiling of genes with key involvement in oxidative stress in the gills and olfactory organ. AGD did not result in systemic oxidative stress as ROS and TAC levels remained unchanged. There were no clear patterns of AGD-mediated regulation of the oxidative stress biomarkers in both the gills and olfactory organ; significant changes in the expression were mostly related to time rather than infection status. However, the expression profiles of the oxidative stress biomarkers in AGD-affected salmon, following treatment with PAA, revealed that gills and olfactory organ responded differently - upregulation was prominent in the gills while downregulation was more frequent in the olfactory organ. The expression of catalase, glutathione S-transferase and thioredoxin reductase 2 was significantly affected by the treatments, both in the gills and olfactory organ, and these alterations were influenced by the duration of exposure and PAA product type. Parasitic load in the gills did significantly increase after treatment regardless of the product and exposure duration; the parasite was undetectable in some fish treated with AquaDes for 30 mins. However, PAA treated groups for 30 min showed lower macroscopic gill scores than the infected-untreated fish. Histology disclosed the classic pathological findings such as multifocal hyperplasia and increased number of mucous cells in AGD-affected fish. Microscopic scoring of gill injuries showed that AGD-infected-PAA-treated fish had lower scores, however, an overall trend could not be established. The morphology and structural integrity of the olfactory organ were not significantly altered by parasitism or PAA treatment. Collectively, the results indicate that AGD did not affect the systemic and mucosal oxidative status of Atlantic salmon. However, such a striking profile was changed when AGD-affected fish were exposed to oxidative chemotherapeutics. Moreover, the gills and olfactory organ demonstrated distinct patterns of gene expression of oxidative stress biomarkers in AGD-infected-PAA-treated fish. Lastly, PAA treatment did not fully resolve the infection, but appeared not to worsen the mucosal health either.
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Amebíase , Doenças dos Peixes , Parasitos , Salmo salar , Amebíase/tratamento farmacológico , Amebíase/parasitologia , Amebíase/veterinária , Animais , Antioxidantes/metabolismo , Biomarcadores/metabolismo , Catalase/metabolismo , Doenças dos Peixes/genética , Brânquias/metabolismo , Glutationa Transferase/metabolismo , Estresse Oxidativo , Ácido Peracético , Espécies Reativas de Oxigênio/metabolismo , Salmo salar/genética , Salmo salar/metabolismo , Tiorredoxina Redutase 2/metabolismoRESUMO
The aquaculture growth can be followed by the occurrence of more and new pathogenic agents, since the production leads to higher fish densities in confined areas more appropriate to the appearance and propagation of pathologies. Copper sulfate has been widely used in preventing and controlling fish parasites. The objective of this study is to investigate the effects of copper treatments in the fish tissues (bioaccumulation and histological changes in different organs), mortality and evaluate what happens during the recovery period. White sea bream (Diplodus sargus) were exposed to copper sulfate (0.25 and 0.5 mg L-1) during 60 days followed with a 75-day recovery period. The results showed that the concentration of copper in fish liver was significantly higher in the 0.5 mg L-1 treatment than in the 0.25 mg L-1 treatment. Conversely, copper load in the muscle did not differ significantly between treatments and control. Copper levels in muscle, and especially in liver, increased during copper exposure (up to 60 days). In summary, at higher concentrations copper sulfate treatment (0.5 mg L-1) might be toxic to fish, which showed histological alterations and copper accumulation in their tissues, mainly in the liver. Nevertheless, individuals returned to their original state after a 75-day recovery period and the tested copper concentrations does not represents risk for food safety.
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Antiparasitários/toxicidade , Sulfato de Cobre/toxicidade , Cobre/toxicidade , Exposição Ambiental/análise , Perciformes/fisiologia , Animais , Aquicultura , Bioacumulação , Relação Dose-Resposta a Droga , Longevidade/efeitos dos fármacos , Distribuição TecidualRESUMO
The ataxia telangiectasia mutated (ATM)-interacting protein ATMIN mediates noncanonical ATM signaling in response to oxidative and replicative stress conditions. Like ATM, ATMIN can function as a tumor suppressor in the hematopoietic system: deletion of Atmin under the control of CD19-Cre results in B-cell lymphomas in aging mice. ATM signaling is essential for lymphopoiesis and hematopoietic stem cell (HSC) function; however, little is known about the role of ATMIN in hematopoiesis. We thus sought to investigate whether the absence of ATMIN would affect primitive hematopoietic cells in an ATM-dependent or -independent manner. Apart from its role in B-cell development, we show that ATMIN has an ATM-independent function in the common myeloid progenitors (CMPs) by deletion of Atmin in the entire hematopoietic system using Vav-Cre. Despite the lack of lymphoma formation, ATMIN-deficient mice developed chronic leukopenia as a result of high levels of apoptosis in B cells and CMPs and induced a compensatory mechanism in which HSCs displayed enhanced cycling. Consequently, ATMIN-deficient HSCs showed impaired regeneration ability with the induction of the DNA oxidative stress response, especially when aged. ATMIN, therefore, has multiple roles in different cell types, and its absence results in perturbed hematopoiesis, especially during stress conditions and aging.
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Envelhecimento , Apoptose/genética , Hematopoese/genética , Células-Tronco Hematopoéticas , Estresse Oxidativo/genética , Fatores de Transcrição , Envelhecimento/genética , Envelhecimento/metabolismo , Envelhecimento/patologia , Animais , Proteínas Mutadas de Ataxia Telangiectasia/genética , Proteínas Mutadas de Ataxia Telangiectasia/metabolismo , Linfócitos B/metabolismo , Linfócitos B/patologia , Doença Crônica , Deleção de Genes , Células-Tronco Hematopoéticas/metabolismo , Células-Tronco Hematopoéticas/patologia , Leucopenia/genética , Leucopenia/metabolismo , Leucopenia/patologia , Camundongos , Camundongos Knockout , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismoRESUMO
Chemokine signaling is important for the seeding of different sites by hematopoietic stem cells (HSCs) during development. Serum response factor (SRF) controls multiple genes governing adhesion and migration, mainly by recruiting members of the myocardin-related transcription factor (MRTF) family of G-actin-regulated cofactors. We used vav-iCre to inactivate MRTF-SRF signaling early during hematopoietic development. In both Srf- and Mrtf-deleted animals, hematopoiesis in fetal liver and spleen is intact but does not become established in fetal bone marrow. Srf-null HSC progenitor cells (HSC/Ps) fail to effectively engraft in transplantation experiments, exhibiting normal proximal signaling responses to SDF-1, but reduced adhesiveness, F-actin assembly, and reduced motility. Srf-null HSC/Ps fail to polarize in response to SDF-1 and cannot migrate through restrictive membrane pores to SDF-1 or Scf in vitro. Mrtf-null HSC/Ps were also defective in chemotactic responses to SDF-1. Srf-null HSC/Ps exhibit substantial deficits in cytoskeletal gene expression. MRTF-SRF signaling is thus critical for expression of genes required for the response to chemokine signaling during hematopoietic development.
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Medula Óssea/embriologia , Medula Óssea/fisiologia , Células-Tronco Hematopoéticas/fisiologia , Fator de Resposta Sérica/fisiologia , Nicho de Células-Tronco , Transativadores/fisiologia , Fatores de Transcrição/fisiologia , Animais , Medula Óssea/crescimento & desenvolvimento , Movimento Celular/genética , Células Cultivadas , Regulação da Expressão Gênica no Desenvolvimento , Hematopoese/genética , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Transdução de Sinais/genética , Nicho de Células-Tronco/genéticaRESUMO
The strategy of enzymatic degradation of amino acids to deprive malignant cells of important nutrients is an established component of induction therapy of acute lymphoblastic leukemia. Here we show that acute myeloid leukemia (AML) cells from most patients with AML are deficient in a critical enzyme required for arginine synthesis, argininosuccinate synthetase-1 (ASS1). Thus, these ASS1-deficient AML cells are dependent on importing extracellular arginine. We therefore investigated the effect of plasma arginine deprivation using pegylated arginine deiminase (ADI-PEG 20) against primary AMLs in a xenograft model and in vitro. ADI-PEG 20 alone induced responses in 19 of 38 AMLs in vitro and 3 of 6 AMLs in vivo, leading to caspase activation in sensitive AMLs. ADI-PEG 20-resistant AMLs showed higher relative expression of ASS1 than sensitive AMLs. This suggests that the resistant AMLs survive by producing arginine through this metabolic pathway and ASS1 expression could be used as a biomarker for response. Sensitive AMLs showed more avid uptake of arginine from the extracellular environment consistent with their auxotrophy for arginine. The combination of ADI-PEG 20 and cytarabine chemotherapy was more effective than either treatment alone resulting in responses in 6 of 6 AMLs tested in vivo. Our data show that arginine deprivation is a reasonable strategy in AML that paves the way for clinical trials.
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Antineoplásicos/farmacologia , Hidrolases/farmacologia , Leucemia Mieloide Aguda/metabolismo , Polietilenoglicóis/farmacologia , Animais , Arginina/metabolismo , Argininossuccinato Sintase/biossíntese , Argininossuccinato Sintase/genética , Western Blotting , Células Cultivadas , Cromatografia Líquida de Alta Pressão , Humanos , Imuno-Histoquímica , Leucemia Mieloide Aguda/genética , Espectrometria de Massas , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Reação em Cadeia da Polimerase em Tempo Real , Ensaios Antitumorais Modelo de XenoenxertoRESUMO
Acute myeloid leukemia (AML) induces bone marrow (BM) failure in patients, predisposing them to life-threatening infections and bleeding. The mechanism by which AML mediates this complication is unknown but one widely accepted explanation is that AML depletes the BM of hematopoietic stem cells (HSCs) through displacement. We sought to investigate how AML affects hematopoiesis by quantifying residual normal hematopoietic subpopulations in the BM of immunodeficient mice transplanted with human AML cells with a range of genetic lesions. The numbers of normal mouse HSCs were preserved whereas normal progenitors and other downstream hematopoietic cells were reduced following transplantation of primary AMLs, findings consistent with a differentiation block at the HSC-progenitor transition, rather than displacement. Once removed from the leukemic environment, residual normal hematopoietic cells differentiated normally and outcompeted steady-state hematopoietic cells, indicating that this effect is reversible. We confirmed the clinical significance of this by ex vivo analysis of normal hematopoietic subpopulations from BM of 16 patients with AML. This analysis demonstrated that the numbers of normal CD34(+)CD38(-) stem-progenitor cells were similar in the BM of AML patients and controls, whereas normal CD34(+)CD38(+) progenitors were reduced. Residual normal CD34(+) cells from patients with AML were enriched in long-term culture, initiating cells and repopulating cells compared with controls. In conclusion the data do not support the idea that BM failure in AML is due to HSC depletion. Rather, AML inhibits production of downstream hematopoietic cells by impeding differentiation at the HSC-progenitor transition.
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Células da Medula Óssea/patologia , Diferenciação Celular/fisiologia , Células-Tronco Hematopoéticas/fisiologia , Leucemia Mieloide Aguda/fisiopatologia , ADP-Ribosil Ciclase 1/metabolismo , Animais , Antígenos CD34/metabolismo , Proliferação de Células , Citometria de Fluxo , Imunofluorescência , Humanos , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Microscopia Confocal , Estatísticas não ParamétricasRESUMO
Immunodeficient mouse models are widely used for the assessment of human normal and leukemic stem cells. Despite the advancements over the years, reproducibility, as well as the differences in the engraftment of human cells in recipient mice remains to be fully resolved. Here, we used various immunodeficient mouse models to characterize the effect of donor-recipient sex on the engraftment of the human leukemic and healthy cells. Donor human cells and recipient immunodeficient mice demonstrate sex-specific engraftment levels with significant differences observed in the lineage output of normal CD34+ hematopoietic stem and progenitor cells upon xenotransplantation. Intriguingly, human female donor cells display heightened sensitivity to the recipient mice's gender, influencing their proliferation and resulting in significantly increased engraftment in female recipient mice. Our study underscores the intricate interplay taking place between donor and recipient characteristics, shedding light on important considerations for future studies, particularly in the context of pre-clinical research.
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BACKGROUND: Hematopoietic stem/progenitor cells (HSPCs) maintain the hematopoietic system by balancing their self-renewal and differentiation events. Hematopoietic stem cells also migrate to various sites and interact with their specific microenvironment to maintain the integrity of the system. Rho GTPases have been found to control the migration of hematopoietic cells and other cell types. Although the role of RAC1, RAC2 and CDC42 has been studied, the role of RHOA in human hematopoietic stem cells is unclear. RESULTS: By utilizing constitutively active and dominant negative RHOA, we show that RHOA negatively regulates both in vitro and in vivo migration and dominant negative RHOA significantly increased the migration potential of human HSC/HPCs. Active RHOA expression favors the retention of hematopoietic stem/progenitor cells in the niche rather than migration and was found to lock the cells in the G0 cell cycle phase thereby affecting their long-term self-renewal potential. CONCLUSION: The current study demonstrates that down-regulation of RHOA might be used to facilitate the migration and homing of hematopoietic stem cells without affecting their long-term repopulating ability. This might be of interest especially for increasing the homing of ex vivo expanded HSPC.
Assuntos
Diferenciação Celular , Regulação da Expressão Gênica , Células-Tronco Hematopoéticas/fisiologia , Proteína rhoA de Ligação ao GTP/genética , Animais , Sangue Fetal/metabolismo , Humanos , Camundongos , Camundongos Endogâmicos NOD , Reação em Cadeia da Polimerase em Tempo Real , Proteína rhoA de Ligação ao GTP/metabolismoRESUMO
In vitro exposure of haematopoietic stem and progenitor cells (HSPC) to cytokines in expansion or gene therapy protocols reduces homing and engraftment in vivo. We have previously reported that this is related in part to altered tissue specificity of short-term homing, leading to loss of cells in non-haematopoietic tissues. Here we demonstrate that defective engraftment persists when cultured HSPC are transplanted by intrabone injection. Changes in engraftment function occur within 24 h of cytokine exposure, and are evident when engraftment is analysed solely in the injected bone. A novel ex vivo model of the bone marrow was developed, in which the attachment of infused HSPC in rodent long bones is reduced following culture with cytokines. Finally, cultured HSPC demonstrated reduced adhesion to N-cadherin, osteopontin and vascular cell-adhesion molecule-1, ligands present in bone marrow niches. These changes in adhesive function occur rapidly, and are not related to downregulation of the relevant receptors. Our findings suggest that cytokine exposure of adult human HSPC results in altered adhesion within bone marrow niches, further leading to reduced engraftment potential in vivo.
Assuntos
Medula Óssea/patologia , Adesão Celular/fisiologia , Fatores Estimuladores de Colônias/farmacologia , Sobrevivência de Enxerto/fisiologia , Mobilização de Células-Tronco Hematopoéticas , Transplante de Células-Tronco Hematopoéticas , Células-Tronco Hematopoéticas/patologia , Nicho de Células-Tronco/fisiologia , Adulto , Animais , Antígenos CD34/análise , Células Cultivadas/efeitos dos fármacos , Células Cultivadas/transplante , Células-Tronco Hematopoéticas/efeitos dos fármacos , Humanos , Masculino , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Ratos , Ratos Sprague-Dawley , Proteínas Recombinantes/farmacologia , Organismos Livres de Patógenos EspecíficosRESUMO
BACKGROUND: Fish encounter oxidative stress several times during their lifetime, and it has a pervasive influence on their health and welfare. One of the triggers of oxidative stress in fish farming is the use of oxidative disinfectants to improve rearing conditions, especially in production systems employing recirculation technology. Here we report the physiological and morphological adaptive responses of Atlantic salmon (Salmo salar L.) post-smolts to intermittent exposure to a potent oxidative agent peracetic acid (PAA). Fish reared in semi-commercial scale brackish water recirculating aquaculture system (RAS) were exposed to 1 ppm PAA every 3 days over 6 weeks. Mucosal and systemic responses were profiled before exposure, 22 and 45 days during the intermittent PAA administration. RESULTS: Oxidative stress was likely triggered as plasma antioxidant capacity increased significantly during the exposure period. Adaptive stress response to the periodic oxidant challenge was likewise demonstrated in the changes in plasma glucose and lactate levels. PAA-induced alterations in the transcription of antioxidants, cytokines, heat shock proteins and mucin genes showed a tissue-specific pattern: downregulation was observed in the gills and olfactory rosette, upregulation occurred in the skin, and no substantial changes in the liver. Further, PAA exposure resulted in histological changes in key mucosal organs (i.e. olfactory rosette, skin and gills); pathological alterations were predominant in the gills where cases of epithelial lifting, hypertrophy and clubbing were prevalent. In addition, intermittent PAA administration resulted in an apparent overproduction of mucus in the nasal mucosa. Lastly, PAA did not dramatically alter the ability of salmon to mount a physiological stress response in the presence of a secondary stressor, though some subtle interference was documented in the kinetics and magnitude of plasma cortisol and glucose response post-stress. CONCLUSIONS: The present study collectively demonstrated that intermittent oxidant exposure was a mild environmental stressor that salmon could mount strong adaptive responses at systemic and mucosal levels. The results will be valuable in optimising the rearing conditions of post-smolts in RAS, especially in adopting water treatment strategies that do not considerably interfere with fish health and welfare.
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The heterogeneous nature of human CD34+ hematopoietic stem cells (HSCs) has hampered our understanding of the cellular and molecular trajectories that HSCs navigate during lineage commitment. Using various platforms including single cell RNA-sequencing and extensive xenotransplantation, we have uncovered an uncharacterized human CD34+ HSC population. These CD34+EPCR+(CD38/CD45RA)- (simply as EPCR+) HSCs have a high repopulating and self-renewal abilities, reaching a stem cell frequency of ~1 in 3 cells, the highest described to date. Their unique transcriptomic wiring in which many gene modules associated with differentiated cell lineages confers their multilineage lineage output both in vivo and in vitro. At the single cell level, EPCR+ HSCs are the most transcriptomically and functionally homogenous human HSC population defined to date and can also be easily identified in post-natal tissues. Therefore, this EPCR+ population not only offers a high human HSC resolution but also a well-structured human hematopoietic hierarchical organization at the most primitive level.
Assuntos
Células-Tronco Hematopoéticas , Análise de Célula Única , Antígenos CD34 , Moléculas de Adesão Celular , Linhagem da Célula , Receptor de Proteína C Endotelial , HumanosRESUMO
Immunodeficient mice are increasingly used to assay human hematopoietic repopulating cells as well as leukemia-initiating cells. One method commonly used to isolate these rare cells is to sort cells stained with fluorochrome-conjugated antibodies into fractions, then transplant the different fractions into immunodeficient mice to test their repopulating ability. The antibodies are generally treated as being neutral in terms of their effects on the experiment. Human repopulating cells are thought to express CD34 and lack CD38. Here we present evidence that anti-CD38 antibodies have a profound inhibitory effect on engraftment of cord blood and leukemia cells. We show that this effect is Fc-mediated and can be overcome by treating mice with immunosuppressive antibodies. When this inhibitory effect is prevented, we demonstrate that the CD34(+)CD38(+) fraction of certain acute myeloid leukemia samples contains all, or at least most, leukemia-initiating cell capacity. This study highlights the potential pitfall of antibody-mediated clearance of repopulating cells and is important for any groups working with this model. More importantly, the work suggests that there is greater variation in the phenotypes of leukemia-initiating cells than previously suggested.
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ADP-Ribosil Ciclase 1 , Anticorpos/farmacologia , Leucemia Mieloide Aguda/patologia , ADP-Ribosil Ciclase 1/imunologia , Animais , Antígenos CD34 , Células Cultivadas , Transplante de Células-Tronco de Sangue do Cordão Umbilical , Sangue Fetal/citologia , Sobrevivência de Enxerto/efeitos dos fármacos , Humanos , Camundongos , Camundongos SCID , Transplante de NeoplasiasRESUMO
Immunotherapy has established itself as a promising tool for cancer treatment. There are many challenges that remain including lack of targets and some patients across various cancers who have not shown robust clinical response. One of the major problems that have hindered the progress in the field is the dearth of appropriate mouse models that can reliably recapitulate the complexity of human immune-microenvironment as well as the malignancy itself. Immunodeficient mice reconstituted with human immune cells offer a unique opportunity to comprehensively evaluate immunotherapeutic strategies. These immunosuppressed and genetically modified mice, with some overexpressing human growth factors, have improved human hematopoietic engraftment as well as created more functional immune cell development in primary and secondary lymphoid tissues in these mice. In addition, several new approaches to modify or to add human niche elements to further humanize these immunodeficient mice have allowed a more precise characterization of human hematopoiesis. These important refinements have opened the possibility to evaluate not only human immune responses to different tumor cells but also to investigate how malignant cells interact with their niche and most importantly to test immunotherapies in a more preclinically relevant setting, which can ultimately lead to better success of these drugs in clinical trials.
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Modelos Animais de Doenças , Hematopoese , Sistema Imunitário/imunologia , Imunoterapia/métodos , Neoplasias/imunologia , Animais , Humanos , Camundongos , Neoplasias/terapiaRESUMO
Juvenile myelomonocytic leukemia (JMML) is a rare aggressive myelodysplastic/myeloproliferative neoplasm of early childhood, initiated by RAS-activating mutations. Genomic analyses have recently described JMML mutational landscape; however, the nature of JMML-propagating cells (JMML-PCs) and the clonal architecture of the disease remained until now elusive. Combining genomic (exome, RNA-seq), Colony forming assay and xenograft studies, we detect the presence of JMML-PCs that faithfully reproduce JMML features including the complex/nonlinear organization of dominant/minor clones, both at diagnosis and relapse. Further integrated analysis also reveals that although the mutations are acquired in hematopoietic stem cells, JMML-PCs are not always restricted to this compartment, highlighting the heterogeneity of the disease during the initiation steps. We show that the hematopoietic stem/progenitor cell phenotype is globally maintained in JMML despite overexpression of CD90/THY-1 in a subset of patients. This study shed new lights into the ontogeny of JMML, and the identity of JMML-PCs, and provides robust models to monitor the disease and test novel therapeutic approaches.
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Células-Tronco Hematopoéticas/patologia , Leucemia Mielomonocítica Juvenil/patologia , Células-Tronco Neoplásicas/patologia , Adolescente , Animais , Criança , Pré-Escolar , Feminino , Xenoenxertos , Humanos , Lactente , Leucemia Mielomonocítica Juvenil/genética , Masculino , Camundongos , MutaçãoRESUMO
An amendment to this paper has been published and can be accessed via a link at the top of the paper.
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Subversion of transcription factor (TF) activity in hematopoietic stem/progenitor cells (HSPCs) leads to the development of therapy-resistant leukemic stem cells (LSCs) that drive fulminant acute myeloid leukemia (AML). Using a conditional mouse model where zinc-finger TF Gata2 was deleted specifically in hematopoietic cells, we show that knockout of Gata2 leads to rapid and complete cell-autonomous loss of adult hematopoietic stem cells. By using short hairpin RNAi to target GATA2, we also identify a requirement for GATA2 in human HSPCs. In Meis1a/Hoxa9-driven AML, deletion of Gata2 impedes maintenance and self-renewal of LSCs. Ablation of Gata2 enforces an LSC-specific program of enhanced apoptosis, exemplified by attenuation of anti-apoptotic factor BCL2, and re-instigation of myeloid differentiation--which is characteristically blocked in AML. Thus, GATA2 acts as a critical regulator of normal and leukemic stem cells and mediates transcriptional networks that may be exploited therapeutically to target key facets of LSC behavior in AML.
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Fator de Transcrição GATA2/genética , Células-Tronco Hematopoéticas/metabolismo , Animais , Apoptose , Autorrenovação Celular , Modelos Animais de Doenças , Fator de Transcrição GATA2/antagonistas & inibidores , Fator de Transcrição GATA2/metabolismo , Hematopoese , Transplante de Células-Tronco Hematopoéticas , Células-Tronco Hematopoéticas/citologia , Humanos , Estimativa de Kaplan-Meier , Leucemia Mieloide Aguda/mortalidade , Leucemia Mieloide Aguda/patologia , Leucemia Mieloide Aguda/terapia , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Células-Tronco Neoplásicas/citologia , Células-Tronco Neoplásicas/metabolismo , Proteínas Proto-Oncogênicas c-bcl-2/metabolismo , Interferência de RNA , RNA Interferente Pequeno/metabolismoRESUMO
Treatment for acute myeloid leukemia (AML) remains suboptimal and many patients remain refractory or relapse upon standard chemotherapy based on nucleoside analogs plus anthracyclines. The crosstalk between AML cells and the BM stroma is a major mechanism underlying therapy resistance in AML. Lenalidomide and pomalidomide, a new generation immunomodulatory drugs (IMiDs), possess pleiotropic anti-leukemic properties including potent immune-modulating effects and are commonly used in hematological malignances associated with intrinsic dysfunctional BM such as myelodysplastic syndromes and multiple myeloma. Whether IMiDs may improve the efficacy of current standard treatment in AML remains understudied. Here, we have exploited in vitro and in vivo preclinical AML models to analyze whether IMiDs potentiate the efficacy of AraC/Idarubicin-based standard AML chemotherapy by interfering with the BM stroma-mediated chemoresistance. We report that IMiDs do not exert cytotoxic effects on either non-del5q/5q- AML cells nor BM-MSCs, but they enhance the immunomodulatory properties of BM-MSCs. When combined with AraC/Idarubicin, IMiDs fail to circumvent BM stroma-mediated resistance of non-del5q/5q- AML cells in vitro and in vivo but induce robust extramedullary mobilization of AML cells. When administered as a single agent, lenalidomide specifically mobilizes non-del5q/5q- AML cells, but not healthy CD34+ cells, to peripheral blood (PB) through specific downregulation of CXCR4 in AML blasts. Global gene expression profiling supports a migratory/mobilization gene signature in lenalidomide-treated non-del5q/5q- AML blasts but not in CD34+ cells. Collectively, IMiDs mobilize non-del5q/5q- AML blasts to PB through CXCR4 downregulation, but fail to potentiate AraC/Idarubicin activity in preclinical models of non-del5q/5q- AML.
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PURPOSE OF REVIEW: Understanding the signaling pathways that govern hematopoietic stem and progenitor cells (HSPCs) is fundamental to uncover their regulation and how this is skewed in hematological malignancies. Whether Notch is necessary for the regulation of mammalian HSPCs is still unclear. We therefore critically review the current literature on the role of Notch in HSPCs. RECENT FINDINGS: HSPCs have shown different requirements for Notch signals in vitro and in vivo and at different stages of differentiation. Additionally, bone marrow niche cells activate Notch signaling in HSPCs enhancing their regenerative and self-renewal capacity. SUMMARY: Despite the controversy, adequate levels of Notch signaling appear necessary to avoid the development of hematological malignancies. Contrary to early studies, recent research suggests that Notch signaling may play a role in homeostatic and regenerative hematopoiesis but further investigation is necessary to understand how it is regulated by the different ligand/receptor pairings and the molecular mechanisms that are triggered.
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Conventional dendritic cells (cDCs) are thought to descend from a DC precursor downstream of the common myeloid progenitor (CMP). However, a mouse lymphoid-primed multipotent progenitor has been shown to generate cDCs following a DC-specific developmental pathway independent of monocyte and granulocyte poiesis. Similarly, here we show that, in humans, a large fraction of multipotent lymphoid early progenitors (MLPs) gives rise to cDCs, in particular the subset known as cDC1, identified by co-expression of DNGR-1 (CLEC9A) and CD141 (BDCA-3). Single-cell analysis indicates that over one-third of MLPs have the potential to efficiently generate cDCs. cDC1s generated from CMPs or MLPs do not exhibit differences in transcriptome or phenotype. These results demonstrate an early imprinting of the cDC lineage in human hematopoiesis and highlight the plasticity of developmental pathways giving rise to human DCs.