Phenotypic analysis and isolation of murine hematopoietic stem cells and lineage-committed progenitors

Chronic LCMV infection regulates the effector T cell response by inducing the generation of less immunogenic dendritic cells

Chronic viral infection impairs systemic immunity in the host; however, the mechanism underlying the dysfunction of immune cells in chronic viral infection is incompletely understood. In this study, we studied the lineage differentiation of hematopoietic stem cells (HSCs) during chronic viral infection to elucidate the changes in dendritic cell (DC) differentiation and subsequent impact on T cell functionality using a chronic lymphocytic choriomeningitis virus (LCMV) infection model. We first investigated the lineage differentiation of HSCs in the bone marrow (BM) to elucidate the modulation of immune cell differentiation and found that the populations highly restrained in their differentiation were common myeloid progenitors (CMPs) and common dendritic cell progenitors (CDPs). Of interest, the main immune cells infected with LCMV Clone 13 (CL13) in the BM were CD11b/c⁺ myeloid DCs. We next characterized CD11b⁺ DCs that differentiated during chronic LCMV infection. These DCs displayed a less immunogenic phenotype than DCs in naive or acutely infected mice, showing low expression of CD80 but high expression of PD-L1, B7-H4, IDO, TGF-β, and IL-10. Consequently, these CD11b⁺ DCs induced less effective CD8⁺ T cells and more Foxp3⁺ regulatory T (Treg) cells. Furthermore, CD11b⁺ DCs generated during CL13 infection could not induce effective CD8⁺ T cells specific to the antigens of newly invading pathogens. Our findings demonstrate that DCs generated from the BM during chronic viral infection cannot activate fully functional effector CD8⁺ T cells specific to newly incoming antigens as well as persistent antigens themselves, suggesting a potential cause of the functional alterations in the T cell immune response during chronic viral infection.

Analysis of Radiation-Induced Changes in Cell Cycle and DNA Damage of Murine Hematopoietic Stem Cells by Multi-Color Flow Cytometry

Exposure of bone marrow to genotoxic stress such as ionizing radiation (IR) results in a rapid decline of peripheral blood cells and stimulates entry of the normally quiescent hematopoietic stem cells (HSCs) into the cell cycle to reconstitute the hematopoietic system. While several protocols have employed flow cytometry analysis of bone marrow cells to study changes in specific cell populations with respect to cell cycle proliferation and/or expression of γ-H2AX, a marker of DNA damage, these parameters were examined in separate panels. Here, we describe a flow cytometry-based method specifically designed to examine cell cycle distribution using Ki-67 and FXCycle violet in combination with γ-H2AX in HSCs and hematopoietic progenitor cells (HPCs) within the same sample. This method is very useful, particularly in studies involving genotoxic stresses such as IR, which substantially reduce the absolute numbers of HSCs and HPCs available for staining. Additionally, we describe several important considerations for the analysis of markers of HSCs in irradiated versus unirradiated samples. Examples include the use of fluorescence minus one (FMO) controls, the gating strategy for markers whose expression is typically impacted by IR such as Sca1, tips for staining of intracellular antigens like Ki67, and ensuring the detection of signal from at least 500 events in each gate to ensure robustness of the results. © 2021 Wiley Periodicals LLC. Basic Protocol: Immunostaining protocol for bone marrow mononuclear cells using a multi-fluorophore panel.

Stem Cell Therapy in Dengue Virus-Infected BALB/C Mice Improves Hepatic Injury

Extensive clinical efforts have been made to control the severity of dengue diseases; however, the dengue morbidity and mortality have not declined. Dengue virus (DENV) can infect and cause systemic damage in many organs, resulting in organ failure. Here, we present a novel report showing a tailored stem-cell-based therapy that can aid in viral clearance and rescue liver cells from further damage during dengue infection. We administered a combination of hematopoietic stem cells and endothelial progenitor cells in a DENV-infected BALB/c mouse model and found that delivery of this cell cocktail had improved their liver functions, confirmed by hematology, histopathology, and next-generation sequencing. These stem and progenitor cells can differentiate into target cells and repair the damaged tissues. In addition, the regime can regulate endothelial proliferation and permeability, modulate inflammatory reactions, enhance extracellular matrix production and angiogenesis, and secrete an array of growth factors to create an enhanced milieu for cell reparation. No previous study has been published on the treatment of dengue infection using stem cells combination. In conclusion, dengue-induced liver damage was rescued by administration of stem cell therapy, with less apoptosis and improved repair and regeneration in the dengue mouse model.

The lysine methyltransferase SMYD2 is required for normal lymphocyte development and survival of hematopoietic leukemias

The 5 membered SET and MYND Domain-containing lysine methyltransferase (SMYD) family plays pivotal roles in development and proliferation. Initially characterized within the cardiovascular system, one such member, SMYD2, has been implicated as an oncogene in leukemias deriving from flawed hematopoietic stem cell (HSC) differentiation. We show here that conditional SMYD2 loss disrupts hematopoiesis at and downstream of the HSC via both apoptotic loss and transcriptional deregulation of HSC proliferation and disruption of Wnt-β-Catenin signaling. Yet previously documented SMYD2 cell cycle targets were unscathed. Turning our analysis to human leukemias, we observed that SMYD2 is highly expressed in CML, MLLr-B-ALL, AML, T-ALL and B-ALL leukemias and its levels in B-ALL correlate with poor survival. SMYD2 knockdown results in apoptotic death and loss of anchorage-independent transformation of each of these hematopoietic leukemias. These data provide an underlying mechanism by which SMYD2 acts during normal hematopoiesis and as a proto-oncogene in leukemia.

Flow Cytometric Analysis of Mitochondrial Reactive Oxygen Species in Murine Hematopoietic Stem and Progenitor Cells and MLL-AF9 Driven Leukemia

We present a flow cytometric approach for analyzing mitochondrial ROS in various live bone marrow (BM)-derived stem and progenitor cell populations from healthy mice as well as mice with AML driven by MLL-AF9. Specifically, we describe a two-step cell staining process, whereby healthy or leukemia BM cells are first stained with a fluorogenic dye that detects mitochondrial superoxides, followed by staining with fluorochrome-linked monoclonal antibodies that are used to distinguish various healthy and malignant hematopoietic progenitor populations. We also provide a strategy for acquiring and analyzing the samples by flow cytometry. The entire protocol can be carried out in a timeframe as short as 3-4 h. We also highlight the key variables to consider as well as the advantages and limitations of monitoring ROS production in the mitochondrial compartment of live hematopoietic and leukemia stem and progenitor subpopulations using fluorogenic dyes by flow cytometry. Furthermore, we present data that mitochondrial ROS abundance varies among distinct healthy HSPC sub-populations and leukemia progenitors and discuss the possible applications of this technique in hematologic research.

HuR regulates telomerase activity through TERC methylation

Telomerase consists of the catalytic protein TERT and the RNA TERC. Mutations in TERC are linked to human diseases, but the underlying mechanisms are poorly understood. Here we report that the RNA-binding protein HuR associates with TERC and promotes the assembly of the TERC/TERT complex by facilitating TERC C106 methylation. Dyskeratosis congenita (DC)-related TERC U100A mutation impair the association of HuR with TERC, thereby reducing C106 methylation. Two other TERC mutations linked to aplastic anemia and autosomal dominant DC, G107U, and GC107/108AG, likewise disrupt methylation at C106. Loss-of-HuR binding and hence lower TERC methylation leads to decreased telomerase activity and telomere shortening. Furthermore, HuR deficiency or mutation of mTERC HuR binding or methylation sites impair the renewal of mouse hematopoietic stem cells, recapitulating the bone marrow failure seen in DC. Collectively, our findings reveal a novel function of HuR, linking HuR to telomerase function and TERC-associated DC.

Mutations in the RNA component TERC can cause telomerase dysfunction but the underlying mechanisms are largely unknown. Here, the authors show that RNA-binding protein HuR regulates telomerase function by enhancing the methylation of TERC, which is impaired by several disease-relevant TERC mutations.

Treatment of MCPT8DTR mice with high- or low-dose diphtheria toxin leads to differential depletion of basophils and granulocyte-macrophage progenitors

Basophils have been recently recognized to play important roles in type 2 immune responses during allergies and parasitic infection, largely due to the development of novel tools for the in vivo study of these cells. As such, the genetically-engineered MCPT8^DTR mouse line has been used to specifically deplete basophils following treatment with diphtheria toxin (DT). In this study, we showed that DT-injected MCPT8^DTR mice exhibited a striking decrease of eosinophils and neutrophils in skin when subjected to a hapten fluorescein isothiocyanate (FITC)-induced allergic contact dermatitis (ACD) experimental protocol. Unexpectedly, we found that loss of skin eosinophils and neutrophils was not due to a lack of basophil-mediated recruitment, as DT injection caused a systemic reduction of eosinophils and neutrophils in MCPT8^DTR mice in a time-dependent manner. Furthermore, we found that hematopoietic stem-cell-derived granulocyte-macrophage progenitors (GMPs) expressed MCPT8 gene, and that these cells were depleted upon DT injection. Finally, we optimized a protocol in which a low-dose DT achieved a better specificity for depleting basophils, but not GMPs, in MCPT8^DTR mice, and demonstrate that basophils do not play a major role in recruiting eosinophils and neutrophils to ACD skin. These data provide new and valuable information about functional studies of basophils.

Effect of testosterone and hypoxia on the expansion of umbilical cord blood CD34+ cells in vitro

Successfully expanding hematopoietic stem cells (HSCs) is advantageous for clinical HSC transplantation. The present study investigated the influence of testosterone on the proliferation, antigen phenotype and expression of hematopoiesis-related genes in umbilical cord blood-derived cluster of differentiation (CD)34⁺ cells under normoxic or hypoxia conditions. Cord blood (CB) CD34⁺ cells were separated using magnetic activated cell sorting. A cytokine cocktail and feeder cells were used to stimulate the expansion of CD34⁺ cells under normoxic (20% O₂) and hypoxic (1% O₂) conditions for 7 days and testosterone was added accordingly. Cells were identified using flow cytometry and reconstruction capacity was determined using a colony-forming unit (CFU) assay. The effects of oxygen concentration and testosterone on the expression of hematopoietic-related genes, including homeobox (HOX)A9, HOXB2, HOXB4, HOXC4 and BMI-1, were measured using reverse transcription-quantitative polymerase chain reaction. The results indicated that the number of CFUs and total cells in the testosterone group increased under normoxic and hypoxic conditions compared with the corresponding control groups. Furthermore, the presence of testosterone increased the number of CFU-erythroid colonies. In liquid culture, the growth of CD34⁺ cells was rapid under normoxic conditions compared with under hypoxic conditions, however CD34⁺ cells were maintained in an undifferentiated state under hypoxic conditions. The addition of testosterone under hypoxia promoted the differentiation of CD34⁺ cells into CD34⁺CD38⁺CD71⁺ erythroid progenitor cells. Furthermore, it was determined that the expression of hematopoietic-related genes was significantly increased (P<0.05) in the hypoxia testosterone group compared with the other groups. Therefore, the results of the current study indicate that a combination of hypoxia and testosterone may be a promising cultivation condition for HSC/hemopoietic progenitor cell expansion ex vivo.

Fan1 deficiency results in DNA interstrand cross-link repair defects, enhanced tissue karyomegaly, and organ dysfunction

Thongthip et al. describe a FANCD2/FANCI-associated nuclease 1 (Fan1)-deficient mouse and show that FAN1 is required for cellular and organismal resistance to DNA interstrand cross-links. Karyomegaly becomes prominent in the kidneys and livers of Fan1-deficient mice with age, and mice develop liver dysfunction.

Deficiency of FANCD2/FANCI-associated nuclease 1 (FAN1) in humans leads to karyomegalic interstitial nephritis (KIN), a rare hereditary kidney disease characterized by chronic renal fibrosis, tubular degeneration, and characteristic polyploid nuclei in multiple tissues. The mechanism of how FAN1 protects cells is largely unknown but is thought to involve FAN1's function in DNA interstrand cross-link (ICL) repair. Here, we describe a Fan1-deficient mouse and show that FAN1 is required for cellular and organismal resistance to ICLs. We show that the ubiquitin-binding zinc finger (UBZ) domain of FAN1, which is needed for interaction with FANCD2, is not required for the initial rapid recruitment of FAN1 to ICLs or for its role in DNA ICL resistance. Epistasis analyses reveal that FAN1 has cross-link repair activities that are independent of the Fanconi anemia proteins and that this activity is redundant with the 5′–3′ exonuclease SNM1A. Karyomegaly becomes prominent in kidneys and livers of Fan1-deficient mice with age, and mice develop liver dysfunction. Treatment of Fan1-deficient mice with ICL-inducing agents results in pronounced thymic and bone marrow hypocellularity and the disappearance of c-kit⁺ cells. Our results provide insight into the mechanism of FAN1 in ICL repair and demonstrate that the Fan1 mouse model effectively recapitulates the pathological features of human FAN1 deficiency.

Rosiglitazone Promotes Bone Marrow Adipogenesis to Impair Myelopoiesis under Stress

Objective

The therapeutic use of thiazolidinediones (TZDs) causes unwanted hematological side effects, although the underlying mechanisms of these effects are poorly understood. This study tests the hypothesis that rosiglitazone impairs the maintenance and differentiation of hematopoietic stem/progenitor cells, which ultimately leads to hematological abnormalities.

Methods

Mice were fed a rosiglitazone-supplemented diet or a normal diet for 6 weeks. To induce hematopoietic stress, all mice were injected once with 250 mg/kg 5-fluorouracil (5-Fu) intraperitoneally. Next, hematopoietic recovery, hematopoietic stem/progenitor cells (HSPCs) subsets, and myeloid differentiation after 5-Fu treatment were evaluated. The adipogenesis induced by rosiglitazone was assessed by histopathology and oil red O staining. The effect of adipocytes on HSPCs was studied with an in vitro co-culture system.

Results

Rosiglitazone significantly enhanced bone marrow adipogenesis and delayed hematopoietic recovery after 5-Fu treatment. Moreover, rosiglitazone inhibited proliferation of a granulocyte/monocyte progenitor (GMP) cell population and granulocyte/macrophage colony-stimulating factor (GM-CSF) colonies, although the proliferation and mobilization of Lin-c-kit+Sca-1+ cells (LSK) was maintained following hematopoietic stress. These effects could be partially reversed by the selective PPARγ antagonist BADGE. Finally, we demonstrated in a co-culture system that differentiated adipocytes actively suppressed the myeloid differentiation of HSPCs.

Conclusion

Taken together, our results demonstrate that rosiglitazone inhibits myeloid differentiation of HSPCs after stress partially by inducing bone marrow adipogenesis. Targeting the bone marrow microenvironment might be one mechanism by which rosiglitazone impairs stress-induced hematopoiesis.

Hematopoietic stem and multipotent progenitor cells produce IL-17, IL-21 and other cytokines in response to TLR signals associated with late apoptotic products and augment memory Th17 and Tc17 cells in the bone marrow of normal and lupus mice

We studied effects of early and late apoptotic (necroptotic) cell products, related damage associated alarmins and TLR agonists, on hematopoietic stem and progenitor cells (HSPC). Surprisingly, normal HSPC themselves produced IL-17 and IL-21 after 1½days of stimulation, and the best stimulators were TLR 7/8 agonist; HMGB1-DNA; TLR 9 agonist, and necroptotic B cells. The stimulated HSPC expressed additional cytokines/mediators, directly causing rapid expansion of IL-17(+) memory CD4 T (Th17), and CD8 T (Tc17) cells, and antigen-experienced IL-17(+) T cells with "naïve" phenotype. In lupus marrow, HSPC were spontaneously pre-stimulated by endogenous signals to produce IL-17 and IL-21. In contrast to HSPC, megakaryocyte progenitors (MKP) did not produce IL-17, and unlike HSPC, they could process and present particulate apoptotic autoantigens to augment autoimmune memory Th17 response. Thus abnormally stimulated primitive hematopoietic progenitors augment expansion of IL-17 producing immune and autoimmune memory T cells in the bone marrow, which may affect central tolerance.

Identifying DNA mutations in purified hematopoietic stem/progenitor cells

In recent years, it has become apparent that genomic instability is tightly related to many developmental disorders, cancers, and aging. Given that stem cells are responsible for ensuring tissue homeostasis and repair throughout life, it is reasonable to hypothesize that the stem cell population is critical for preserving genomic integrity of tissues. Therefore, significant interest has arisen in assessing the impact of endogenous and environmental factors on genomic integrity in stem cells and their progeny, aiming to understand the etiology of stem-cell based diseases. LacI transgenic mice carry a recoverable λ phage vector encoding the LacI reporter system, in which the LacI gene serves as the mutation reporter. The result of a mutated LacI gene is the production of β-galactosidase that cleaves a chromogenic substrate, turning it blue. The LacI reporter system is carried in all cells, including stem/progenitor cells and can easily be recovered and used to subsequently infect E. coli. After incubating infected E. coli on agarose that contains the correct substrate, plaques can be scored; blue plaques indicate a mutant LacI gene, while clear plaques harbor wild-type. The frequency of blue (among clear) plaques indicates the mutant frequency in the original cell population the DNA was extracted from. Sequencing the mutant LacI gene will show the location of the mutations in the gene and the type of mutation. The LacI transgenic mouse model is well-established as an in vivo mutagenesis assay. Moreover, the mice and the reagents for the assay are commercially available. Here we describe in detail how this model can be adapted to measure the frequency of spontaneously occurring DNA mutants in stem cell-enriched Lin(-)IL7R(-)Sca-1(+)cKit(++)(LSK) cells and other subpopulations of the hematopoietic system.