Hematopoietic Stem Cell Factors: Their Functional Role in Self-Renewal and Clinical Aspects

Advances in HIV Gene Therapy

Early gene therapy studies held great promise for the cure of heritable diseases, but the occurrence of various genotoxic events led to a pause in clinical trials and a more guarded approach to progress. Recent advances in genetic engineering technologies have reignited interest, leading to the approval of the first gene therapy product targeting genetic mutations in 2017. Gene therapy (GT) can be delivered either in vivo or ex vivo. An ex vivo approach to gene therapy is advantageous, as it allows for the characterization of the gene-modified cells and the selection of desired properties before patient administration. Autologous cells can also be used during this process which eliminates the possibility of immune rejection. This review highlights the various stages of ex vivo gene therapy, current research developments that have increased the efficiency and safety of this process, and a comprehensive summary of Human Immunodeficiency Virus (HIV) gene therapy studies, the majority of which have employed the ex vivo approach.

Increased RUNX1 mutations in breast cancer disease progression

Despite advances in screening, therapy and surveillance, breast cancer remains threatening to women. Worst, patients suffer from side effects of treatments and cancer cells become resistant. The emergence of RUNX1 in breast cancer has put it in a spotlight due to its roles in the disease progression. It also plays important roles in normal mammary glands such as for cell growth, proliferation, migration and stemness. However, mutations in the RUNX1 gene have changed the regulation of these phenotypes and the full spectrum of its implications in breast cancer patients is unknown. In this study therefore, the pattern of RUNX1 mutations in breast cancer patients was examined to understand its fundamental impacts on the disease. The perturbation of RUNX1 and its mutations in breast cancer was elucidated through different studies reported in cBioPortal in the past ten years. From our analyses, the majority of RUNX1 mutations were found in the primary breast cancer, with women constituted most of the mutations, especially on the left side of the breast. Similarly, increased number of mutations was observed in ER-positive breast cancer patients and this was also the case at the early stage of the disease development. The level of RUNX1 mutations also increased gradually as patients got older and the peak was highest in the patients of 60-70 years old. Altogether, these data indicated that the mutated RUNX1 gene contributed to the progression of breast cancer and understanding of its regulatory mechanisms is crucial to therapeutically target this gene in the future.

Multiple Cell Lineages Give Rise to a Cell Type

It has long been assumed that a specific cell type arises following stepwise specification of cells corresponding to the branching of cell lineages. However, accumulating evidence indicates that multiple and even remote cell lineages can lead to the development of the same cells. Four examples giving different yet new insights will be discussed: skeletal muscle development from precursors with distinct initial histories of transcriptional regulation, lens cell development from remote lineages yet sharing basic transcription factors, blood cell development under intersectional pathways, and neural tissue development from cardiac precursors through the manipulation of just one component of epigenetic regulation. These examples provide flexible and nondogmatic perspectives on developmental cell regulation, fundamentally revising the old model relying on cell lineages.

The influence of redox modulation on hypoxic endothelial cell metabolic and proteomic profiles through a small thiol-based compound tuning glutathione and thioredoxin systems

Reduction in oxygen levels is a key feature in the physiology of the bone marrow (BM) niche where hematopoiesis occurs. The BM niche is a highly vascularized tissue and endothelial cells (ECs) support and regulate blood cell formation from hematopoietic stem cells (HSCs). While in vivo studies are limited, ECs when cultured in vitro at low O2 (<5%), fail to support functional HSC maintenance due to oxidative environment. Therefore, changes in EC redox status induced by antioxidant molecules may lead to alterations in the cellular response to hypoxia likely favoring HSC self-renewal. To evaluate the impact of redox regulation, HUVEC, exposed for 1, 6, and 24 h to 3% O2 were treated with N-(N-acetyl-l-cysteinyl)-S-acetylcysteamine (I-152). Metabolomic analyses revealed that I-152 increased glutathione levels and influenced the metabolic profiles interconnected with the glutathione system and the redox couples NAD(P)+/NAD(P)H. mRNA analysis showed a lowered gene expression of HIF-1α and VEGF following I-152 treatment whereas TRX1 and 2 were stimulated. Accordingly, the proteomic study revealed the redox-dependent upregulation of thioredoxin and peroxiredoxins that, together with the glutathione system, are the main regulators of intracellular ROS. Indeed, a time-dependent ROS production under hypoxia and a quenching effect of the molecule were evidenced. At the secretome level, the molecule downregulated IL-6, MCP-1, and PDGF-bb. These results suggest that redox modulation by I-152 reduces oxidative stress and ROS level in hypoxic ECs and may be a strategy to fine-tune the environment of an in vitro BM niche able to support functional HSC maintenance.

Multimodal cartography of human lymphopoiesis reveals B and T/NK/ILC lineages are subjected to differential regulation

The developmental cartography of human lymphopoiesis remains incompletely understood. Here, we establish a multimodal map demonstrating that lymphoid specification follows independent direct or stepwise hierarchic routes converging toward the emergence of newly characterized CD117lo multi-lymphoid progenitors (MLPs) that undergo a proliferation arrest before entering the CD127- (NK/ILC/T) or CD127+ (B) lymphoid pathways. While the differentiation of CD127- early lymphoid progenitors is mainly driven by Flt3 signaling, emergence of their CD127+ counterparts is regulated cell-intrinsically and depends exclusively on the divisional history of their upstream precursors, including hematopoietic stem cells. Further, transcriptional mapping of differentiation trajectories reveals that whereas myeloid granulomonocytic lineages follow continuous differentiation pathways, lymphoid trajectories are intrinsically discontinuous and characterized by sequential waves of cell proliferation allowing pre-commitment amplification of lymphoid progenitor pools. Besides identifying new lymphoid specification pathways and regulatory checkpoints, our results demonstrate that NK/ILC/T and B lineages are under fundamentally distinct modes of regulation. (149 words).

Understanding blood development and leukemia using sequencing-based technologies and human cell systems

Our current understanding of human hematopoiesis has undergone significant transformation throughout the years, challenging conventional views. The evolution of high-throughput technologies has enabled the accumulation of diverse data types, offering new avenues for investigating key regulatory processes in blood cell production and disease. In this review, we will explore the opportunities presented by these advancements for unraveling the molecular mechanisms underlying normal and abnormal hematopoiesis. Specifically, we will focus on the importance of enhancer-associated regulatory networks and highlight the crucial role of enhancer-derived transcription regulation. Additionally, we will discuss the unprecedented power of single-cell methods and the progression in using in vitro human blood differentiation system, in particular induced pluripotent stem cell models, in dissecting hematopoietic processes. Furthermore, we will explore the potential of ever more nuanced patient profiling to allow precision medicine approaches. Ultimately, we advocate for a multiparameter, regulatory network-based approach for providing a more holistic understanding of normal hematopoiesis and blood disorders.

The Role of Box A of HMGB1 in Enhancing Stem Cell Properties of Human Mesenchymal Cells: A Novel Approach for the Pursuit of Anti-aging Therapy

BACKGROUND/AIM

Box A is a highly conserved DNA-binding domain of high-mobility group box 1 (HMGB1) and has been shown to reverse senescence and aging features in many cell models. We investigated whether the activation of box A can influence stem cell properties.

MATERIALS AND METHODS

Human dermal papilla (DP) cells and primary human white pre-adipocytes (HWPc) were employed as mesenchymal cell models. Box A-overexpressing plasmids were used to induce cellular box A expression. mRNA and protein levels of stemness markers POU class 5 homeobox 1 pseudogene 5 (OCT4, HGNC: 9221), Nanog homeobox (NANOG, HGNC: 20857), and SRY-box transcription factor 2 (SOX2, HGNC:11195) in DP cells and HWPc were measured by real-time polymerase chain reaction and immunofluorescence analysis, respectively.

RESULTS

Transfection efficiency of box A-overexpressing plasmid was 80% and 50% in DP cells and HWPc, respectively. The proliferative rate of both cell types significantly increased 72 h after transfection. Levels of OCT4, NANOG and SOX2 mRNA and protein expression were significantly increased in box A-transfected DP cells and HWPc compared to empty plasmid-transfected cells. Immunofluorescence analysis confirmed the induction of OCT4, NANOG and SOX2 protein expression in response to box A in DP cells and HWPc. OCT4 and SOX2 were expressed in both the nuclear and cytoplasmic compartments, while NANOG was intensely located in the nucleus of box A-transfected cells.

CONCLUSION

Our findings suggest that box A may potentially enhance stemness, which may have significant benefits in improving stem cell function due to aging processes and disease. This research may have implications for regenerative medicine applications.

Protein restriction impairs the response activation/responsivity of MAPK signaling pathway of hematopoietic stem cells

Protein restriction (PR) leads to bone marrow hypoplasia with changes in stromal cellularity components of the extracellular matrix in hematopoietic stem cells (HSCs). However, the underlying signaling mechanisms are poorly understood. We hypothesize that PR impairs the HSC mitogen-activated protein kinase (MAPK) signaling pathway response activation. Our aim is to evaluate the activation of MAPK and interleukin-3 (IL-3) proteins in HSC to explain PR-induced bone marrow hypoplasia, which causes altered proliferation and differentiation. C57BL/6 male mice were subjected to a low-protein diet (2% protein) or normoproteic (12% protein). PKC, PLCγ2, CaMKII, AKT, STAT3/5, ERK1/2, JNK, and p38d phosphorylation were evaluated by flow cytometry, and GATA1/2, PU.1, C/EBPα, NF-E2, and Ikz-3 genes (mRNAs) assessed by quantitative real-time-polymerase chain reaction. Pathway proteins, such as PLCγ2, JAK2, STAT3/5, PKC, and RAS do not respond to the IL-3 stimulus in PR, leading to lower activation of ERK1/2 and Ca2+ signaling pathways, consequently lowering the production of hematopoietic transcription factors. Colony forming units granulocyte-macrophage and colony forming units macrophage formation are impaired in PR even after being stimulated with IL-3. Long-term hematopoietic stem cells, short-term hematopoietic stem cells, granulocyte myeloid progenitor, and megakaryocyte-erythroid progenitor cells were significantly reduced in PR animals. This study shows for the first time that activation of MAPK pathway key proteins in HSCs is impaired in cases of PR. Several pathway proteins, such as PLCγ2, JAK2, STAT3, PKC, and RAS do not respond to IL-3 stimulation, leading to lower activation of extracellular signal-regulated protein kinase 1/2 and consequently lower production of hematopoietic transcription factors GATA1/2, PU.1, C/EBPa, NF-E2, and Ikz3. These changes result in a reduction in colony-forming units, proliferation, and differentiation, leading to hypocellularity.

Elucidating the cell metabolic heterogeneity during hematopoietic lineage differentiation based on Met-Flow

Cell metabolism is critically involved in the differentiation of the hematopoietic lineage and, therefore, has attracted the attention of researchers, however, in-depth studies on cellular metabolic activity of hematopoietic cells (HCs) require attention. This investigation compared the metabolic activity of HCs at critical lineage differentiation stages, including hematopoietic stem cells (HSCs), hematopoietic progenitor cells (HPCs), and differentiated blood cells, via multiple methods and basic reference values. Primary metabolic processes of HCs, including anabolism, catabolism, phosphate, and glucose metabolism, were analyzed, and their maps were drawn. The data revealed that GLUT1 expression in HSCs was substantially higher than in all progenitor cells and mature myeloid blood cells, indicating their strong glucose uptake capacity. In myeloid differentiation, the ACAC expression of HPC2 was markedly higher than in neutrophils and monocytes. The ACAC, ASS1, ATP5A, and PRDX2 of HPC2 expression in lymphoid differentiation was substantially greater than in B and Natural-killer cells. CLP, CMP, GMP, MEP, and HPC1 inherit increased glucose uptake stem cell properties. In lymphocyte subsets, the expression of ACAC, ASS1, ATP5A, CPT1A, and PRDX2 in CD4+ T subgroups (naive and memory CD4+ T and nTreg) were elevated than in B subgroups (pro-, pre-, immature and mature Bs) and CD8+ T subgroups. Furthermore, leukemia stem cells (LSCs) had increased levels of ACAC, CPT1A, G6PD, IDH2, and PRDX2 than leukemia cells, indicating a stronger metabolic capacity of LSCs than differentiated leukemia cells.

Inflammatory abrasion of hematopoietic stem cells: a candidate clue for the post-CAR-T hematotoxicity?

Chimeric antigen receptor T-cell (CAR-T) therapy has shown remarkable effects in treating various hematological malignancies. However, hematotoxicity, specifically neutropenia, thrombocytopenia, and anemia, poses a serious threat to patient prognosis and remains a less focused adverse effect of CAR-T therapy. The mechanism underlying lasting or recurring late-phase hematotoxicity, long after the influence of lymphodepletion therapy and cytokine release syndrome (CRS), remains elusive. In this review, we summarize the current clinical studies on CAR-T late hematotoxicity to clarify its definition, incidence, characteristics, risk factors, and interventions. Owing to the effectiveness of transfusing hematopoietic stem cells (HSCs) in rescuing severe CAR-T late hematotoxicity and the unignorable role of inflammation in CAR-T therapy, this review also discusses possible mechanisms of the harmful influence of inflammation on HSCs, including inflammatory abrasion of the number and the function of HSCs. We also discuss chronic and acute inflammation. Cytokines, cellular immunity, and niche factors likely to be disturbed in CAR-T therapy are highlighted factors with possible contributions to post-CAR-T hematotoxicity.

Aging drives Tet2+/- clonal hematopoiesis via IL-1 signaling

Clonal hematopoiesis of indeterminate potential (CHIP), also referred to as aging-related clonal hematopoiesis, is defined as an asymptomatic clonal expansion of mutant mature hematopoietic cells in ≥4% of blood leukocytes. CHIP associates with advanced age and increased risk for hematological malignancy, cardiovascular disease, and all-cause mortality. Loss-of-function somatic mutations in TET2 are frequent drivers of CHIP. However, the contribution of aging-associated cooperating cell-extrinsic drivers, like inflammation, remains underexplored. Using bone marrow (BM) transplantation and newly developed genetic mosaicism (HSC-SCL-Cre-ERT; Tet2+/flox; R26+/tm6[CAG-ZsGreen1]Hze) mouse models of Tet2+/-driven CHIP, we observed an association between increased Tet2+/- clonal expansion and higher BM levels of the inflammatory cytokine interleukin-1 (IL-1) upon aging. Administration of IL-1 to mice carrying CHIP led to an IL-1 receptor 1 (IL-1R1)-dependent expansion of Tet2+/- hematopoietic stem and progenitor cells (HSPCs) and mature blood cells. This expansion was caused by increased Tet2+/- HSPC cell cycle progression, increased multilineage differentiation, and higher repopulation capacity compared with their wild-type counterparts. In agreement, IL-1α-treated Tet2+/- hematopoietic stem cells showed increased DNA replication and repair transcriptomic signatures and reduced susceptibility to IL-1α-mediated downregulation of self-renewal genes. More important, genetic deletion of IL-1R1 in Tet2+/- HPSCs or pharmacologic inhibition of IL-1 signaling impaired Tet2+/- clonal expansion, establishing the IL-1 pathway as a relevant and therapeutically targetable driver of Tet2+/- CHIP progression during aging.

Functionalized 3D scaffolds for engineering the hematopoietic niche

Hematopoietic stem cells (HSCs) reside in a subzone of the bone marrow (BM) defined as the hematopoietic niche where, via the interplay of differentiation and self-renewal, they can give rise to immune and blood cells. Artificial hematopoietic niches were firstly developed in 2D in vitro cultures but the limited expansion potential and stemness maintenance induced the optimization of these systems to avoid the total loss of the natural tissue complexity. The next steps were adopted by engineering different materials such as hydrogels, fibrous structures with natural or synthetic polymers, ceramics, etc. to produce a 3D substrate better resembling that of BM. Cytokines, soluble factors, adhesion molecules, extracellular matrix (ECM) components, and the secretome of other niche-resident cells play a fundamental role in controlling and regulating HSC commitment. To provide biochemical cues, co-cultures, and feeder-layers, as well as natural or synthetic molecules were utilized. This review gathers key elements employed for the functionalization of a 3D scaffold that demonstrated to promote HSC growth and differentiation ranging from 1) biophysical cues, i.e., material, topography, stiffness, oxygen tension, and fluid shear stress to 2) biochemical hints favored by the presence of ECM elements, feeder cell layers, and redox scavengers. Particular focus is given to the 3D systems to recreate megakaryocyte products, to be applied for blood cell production, whereas HSC clinical application in such 3D constructs was limited so far to BM diseases testing.