Lifelong hematopoiesis is sustained by crosstalk between hematopoietic stem and progenitor cells (HSPCs) and specialized bone marrow niches. Acute myeloid leukemia (AML) upends that balance, as leukemic blasts secrete factors that remodel the bone marrow into a self-reinforcing leukemic niche. The inflammatory secretome behind this compartmental adaptation accounts for a progressive decline in hematopoietic function that leads to diagnosis and persists through early treatment. Not surprisingly, the mediators of an acute inflammatory injury and HSPC suppression have attracted much attention in an effort to alleviate morbidity and improve outcomes. HSPCs typically recover during disease remission and re-expand in the bone marrow (BM), but little is known about potentially lasting consequences for stem cells and progenitors. We recently showed that AML-experienced HSPCs actively participate in the inflammatory process during leukemic progression. HSPCs are constituent components of the innate immune system, and elegant studies of infection and experimental inflammation over the past decade have described the generation of an adoptively transferable, innate immune memory. Building on this paradigm, we discuss the potential translational relevance of a durable legacy in AML-experienced HSPC.

Adoptive immunotherapies that use functional NK cells depend on the availability of sufficient numbers of these cells. We expanded umbilical cord blood (UCB)-CD34+ HSCs for 2 weeks and then differentiated them into NK cells and compared their function to peripheral blood (PB) NK cells. We assessed NKG2D, NKG2A, NKp30, NKp44, NKp46, and the expression of CD107a, CD57, CD69, FasL, PD-1, and IFN-γ level in two groups after co-culture with K562 cell line. We found that UCB-CD34+-derived NK cells express significantly more NKG2D, NKp44, and NKp46 receptors than PB NK cells. PB NK cells expressed significantly higher NKG2A and CD57 than UCB-CD34+-derived NK cells. In addition, UCB-CD34+-derived NK cells significantly expressed CD107a more than PB NK cells. Based on our findings, UCB-CD34+ cells can be a potentially advantageous source with strong cytotoxic function to produce allogeneic NK cells for adoptive cancer immunotherapy.

BACKGROUND: Using natural killer (NK) cells to treat hematopoietic and solid tumors has great promise. Despite their availability from peripheral blood and cord blood, stem cell-derived NK cells provide an \"off-the-shelf\" solution.
METHODS: In this study, we developed two CAR-NK cells targeting PD-L1 derived from lentiviral transduction of human umbilical cord blood (UCB)-CD34+ cells and UCB-CD34+-derived NK cells. The transduction efficiencies and in vitro cytotoxic functions including degranulation, cytokine production, and cancer cell necrosis of both resultants PD-L1 CAR-NK cells were tested in vitro on two different PD-L1 low and high-expressing solid tumor cell lines.
RESULTS: Differentiated CAR‑modified UCB-CD34+ cells exhibited enhanced transduction efficiency. The expression of anti-PD-L1 CAR significantly (P < 0.05) enhanced the cytotoxicity of differentiated CAR‑modified UCB-CD34+ cells and CAR-modified UCB-CD34+-derived NK cells against PD-L1 high-expressing tumor cell line. In addition, CAR-modified UCB-CD34+-derived NK cells significantly (P < 0.05) restored the tumor-killing ability of exhausted PD-1 high T cells.
CONCLUSIONS: Considering the more efficient transduction in stem cells and the possibility of producing CAR-NK cell products with higher yields, this approach is recommended for studies in the field of CAR-NK cells. Also, a pre-clinical study is now necessary to evaluate the safety and efficacy of these two CAR-NK cells individually and in combination with other therapeutic approaches.

Cohesin shapes the chromatin architecture, including enhancer-promoter interactions. Its components, especially STAG2, but not its paralog STAG1, are frequently mutated in myeloid malignancies. To elucidate the underlying mechanisms of leukemogenesis, we comprehensively characterized genetic, transcriptional, and chromatin conformational changes in acute myeloid leukemia (AML) patient samples. Specific loci displayed altered cohesin occupancy, gene expression, and local chromatin activation, which were not compensated by the remaining STAG1-cohesin. These changes could be linked to disrupted spatial chromatin looping in cohesin-mutated AMLs. Complementary depletion of STAG2 or STAG1 in primary human hematopoietic progenitors (HSPCs) revealed effects resembling STAG2-mutant AML-specific changes following STAG2 knockdown, not invoked by the depletion of STAG1. STAG2-deficient HSPCs displayed impaired differentiation capacity and maintained HSPC-like gene expression. This work establishes STAG2 as a key regulator of chromatin contacts, gene expression, and differentiation in the hematopoietic system and identifies candidate target genes that may be implicated in human leukemogenesis.

BACKGROUND: Hematopoietic stem and progenitor cells (HSPCs) mobilize from bone marrow to peripheral blood in response to stress. The impact of alloresponse-induced stress on HSPCs mobilization in human liver transplantation (LTx) recipients remains under-investigated.
METHODS: Peripheral blood mononuclear cell (PBMC) samples were longitudinally collected from pre- to post-LTx for one year from 36 recipients with acute rejection (AR), 74 recipients without rejection (NR), and 5 recipients with graft-versus-host disease (GVHD). 28 PBMC samples from age-matched healthy donors were collected as healthy control (HC). Multi-color flow cytometry (MCFC) was used to immunophenotype HSPCs and their subpopulations. Donor recipient-distinguishable major histocompatibility complex (MHC) antibodies determined cell origin.
RESULTS: Before LTx, patients who developed AR after transplant contained more HSPCs in PBMC samples than HC, while the NR group patients contained fewer HSPCs than HC. After LTx, the HSPC ratio in the AR group sharply decreased and became less than HC within six months, and dropped to a comparable NR level afterward. During the one-year follow-up period, myeloid progenitors (MPs) biased differentiation was observed in all LTx recipients who were under tacrolimus-based immunosuppressive treatment. During both AR and GVHD episodes, the recipient-derived and donor-derived HSPCs mobilized into the recipient\'s blood-circulation and migrated to the target tissue, respectively. The HSPCs percentage in blood reduced after the disease was cured.
CONCLUSIONS: A preoperative high HSPC ratio in blood characterizes recipients who developed AR after LTx. Recipients exhibited a decline in blood-circulating HSPCs after transplant, the cells mobilized into the blood and migrated to target tissue during alloresponse.

The hematopoietic homeostasis in the bone marrow is inextricably intertwined with the immune milieu in peripheral circulation. Researches investigating the pathogenesis of systemic lupus erythematosus (SLE) have defined considerable secretion of inflammatory mediators and activation of pro-inflammatory cells. However, the impacts of \"extrinsic\" factors on hematopoietic stem and progenitor cells (HSPCs) remain unclear, and it is uncertain whether treatments can help coordinate the biased differentiation. In this study, we showed differences in the proportions of common myeloid progenitors (CMP) and myeloid output in the bone marrow of premorbid and morbid MRL/lpr mice using flow cytometry. RNA-seq analysis of lineage-affiliated transcriptional factors and dysregulated genes within lin- HSPCs revealed inflammation potentiation during disease progression. Further, intra-bone marrow mesenchymal stem cells transplantation (IBM-MSCT) partially coordinated myeloid generation and counteracted lupus-associated inflammation gene alterations, compared to intravenous injection. Additionally, co-culturing with umbilical cord mesenchymal stem cells (UC-MSCs) intervened in myeloid lineage tendency, as detected by RT-qPCR of myeloid-related genes. Our research demonstrated enhanced tendency toward myeloid differentiation and highlighted the feasibility of IBM-MSCT for lineage-biased HSPCs in MRL/lpr lupus model, providing novel insight into hematopoiesis and MSC-related treatments for SLE.

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As caretakers of the hematopoietic system, hematopoietic stem cells assure a lifelong supply of differentiated populations that are responsible for critical bodily functions, including oxygen transport, immunological protection and coagulation. Due to the far-reaching influence of the hematopoietic system, hematological disorders typically have a significant impact on the lives of individuals, even becoming fatal. Hematopoietic cell transplantation was the first effective therapeutic avenue to treat such hematological diseases. Since then, key use and manipulation of hematopoietic stem cells for treatments has been aspired to fully take advantage of such an important cell population. Limited knowledge on hematopoietic stem cell behavior has motivated in-depth research into their biology. Efforts were able to uncover their native environment and characteristics during development and adult stages. Several signaling pathways at a cellular level have been mapped, providing insight into their machinery. Important dynamics of hematopoietic stem cell maintenance were begun to be understood with improved comprehension of their metabolism and progressive aging. These advances have provided a solid platform for the development of innovative strategies for the manipulation of hematopoietic stem cells. Specifically, expansion of the hematopoietic stem cell pool has triggered immense interest, gaining momentum. A wide range of approaches have sprouted, leading to a variety of expansion systems, from simpler small molecule-based strategies to complex biomimetic scaffolds. The recent approval of Omisirge, the first expanded hematopoietic stem and progenitor cell product, whose expansion platform is one of the earliest, is predictive of further successes that might arise soon. In order to guarantee the quality of these ex vivo manipulated cells, robust assays that measure cell function or potency need to be developed. Whether targeting hematopoietic engraftment, immunological differentiation potential or malignancy clearance, hematopoietic stem cells and their derivatives need efficient scaling of their therapeutic potency. In this review, we comprehensively view hematopoietic stem cells as therapeutic assets, going from fundamental to translational.

Clonal hematopoiesis of indeterminate potential (CHIP) arises from aging-associated acquired mutations in hematopoietic progenitors, which display clonal expansion and produce phenotypically altered leukocytes. We associated CHIP-DNMT3A mutations with a higher prevalence of periodontitis and gingival inflammation among 4,946 community-dwelling adults. To model DNMT3A-driven CHIP, we used mice with the heterozygous loss-of-function mutation R878H, equivalent to the human hotspot mutation R882H. Partial transplantation with Dnmt3aR878H/+ bone marrow (BM) cells resulted in clonal expansion of mutant cells into both myeloid and lymphoid lineages and an elevated abundance of osteoclast precursors in the BM and osteoclastogenic macrophages in the periphery. DNMT3A-driven clonal hematopoiesis in recipient mice promoted naturally occurring periodontitis and aggravated experimentally induced periodontitis and arthritis, associated with enhanced osteoclastogenesis, IL-17-dependent inflammation and neutrophil responses, and impaired regulatory T cell immunosuppressive activity. DNMT3A-driven clonal hematopoiesis and, subsequently, periodontitis were suppressed by rapamycin treatment. DNMT3A-driven CHIP represents a treatable state of maladaptive hematopoiesis promoting inflammatory bone loss.

The transformative potential of gene editing technologies hinges on the development of safe and effective delivery methods. In this study, we developed a temperature-sensitive and interferon-silent Sendai virus (ts SeV) as a novel delivery vector for CRISPR-Cas9 and for efficient gene editing in sensitive human cell types without inducing IFN responses. ts SeV demonstrates unprecedented transduction efficiency in human CD34+ hematopoietic stem and progenitor cells (HSPCs) including transduction of the CD34+/CD38-/CD45RA-/CD90+(Thy1+)/CD49fhigh stem cell enriched subpopulation. The frequency of CCR5 editing exceeded 90% and bi-allelic CCR5 editing exceeded 70% resulting in significant inhibition of HIV-1 infection in primary human CD14+ monocytes. These results demonstrate the potential of the ts SeV platform as a safe, efficient, and flexible addition to the current gene-editing tool delivery methods, which may help to further expand the possibilities in personalized medicine and the treatment of genetic disorders.