The regulation of normal and leukemic hematopoietic stem cells by niches

Extracellular vesicle small RNA cargo discriminates non-cancer donors from pediatric B-lymphoblastic leukemia patients

Pediatric B-acute lymphoblastic leukemia (B-ALL) is a disease of abnormally growing B lymphoblasts. Here we hypothesized that extracellular vesicles (EVs), which are nanosized particles released by all cells (including cancer cells), could be used to monitor B-ALL severity and progression by sampling plasma instead of bone marrow. EVs are especially attractive as they are present throughout the circulation regardless of the location of the originating cell. First, we used nanoparticle tracking analysis to compare EVs between non-cancer donor (NCD) and B-ALL blood plasma; we found that B-ALL plasma contains more EVs than NCD plasma. We then isolated EVs from NCD and pediatric B-ALL peripheral blood plasma using a synthetic peptide-based isolation technique (Vn96), which is clinically amenable and isolates a broad spectrum of EVs. RNA-seq analysis of small RNAs contained within the isolated EVs revealed a signature of differentially packaged and exclusively packaged RNAs that distinguish NCD from B-ALL. The plasma EVs contain a heterogenous mixture of miRNAs and fragments of long non-coding RNA (lncRNA) and messenger RNA (mRNA). Transcripts packaged in B-ALL EVs include those involved in negative cell cycle regulation, potentially suggesting that B-ALL cells may use EVs to discard gene sequences that control growth. In contrast, NCD EVs carry sequences representative of multiple organs, including brain, muscle, and epithelial cells. This signature could potentially be used to monitor B-ALL disease burden in pediatric B-ALL patients via blood draws instead of invasive bone marrow aspirates.

AML-derived extracellular vesicles negatively regulate stem cell pool size: A step toward bone marrow failure

PURPOSE OF THE STUDY

Long-term repopulating hematopoietic stem cells (LTR-HSCs) have been previously shown to reside in close proximity to osteoblasts, where they take shelter in the bone marrow (BM) microenvironment against cytotoxic and apoptotic stimuli. Nevertheless, the function of the HSC niche is believed to undergo an adaptive evolutionary modification during leukemogenesis. Recent studies have demonstrated that leukemic clones can impact BM homing through extracellular vesicle (EV) secretion. However, the exact mechanism driving BM conversion is still unclear. In the present study, the human osteoblast cell line (MG-63) were subjected to various concentration of sera-derived EVs of patients with acute myeloid leukemia (AML) and healthy volunteers to assess if they are associated strongly enough to alter the expression pattern of cross-talk molecules involved in niche interactions.

METHOD

To gain a brief insight into the EVs secretion criteria, we first conducted a comparative analysis of sera-derived EVs by dynamic light scattering (DLS), transmission electron microscopy (TEM), and Bradford assay. After incubating MG-63 cell lines with increasing concentrations of the EVs, Trypan-blue and microculture tetrazolium test (MTT) assays were used to evaluate the cell survival, logarithmic growth, and metabolic activity. Finally, the expression levels of OPN, ANGPT-1, and JAG-1 transcripts were evaluated through the qRT-PCR technique.

RESULTS

Here, we report that AML-derived EVs can affect the viability, cell growth, and metabolic activity of the human osteoblasts cell line (MG-63) compared to those that received healthy-derived EVs. We also found that leukemic EVs tend to induce overexpression of OPN but reduce the expression of ANGPT-1 and JAG-1 genes in the osteoblast transcriptome, which may provide a potential context imposing selective suppression of HSC pool size.

CONCLUSION

These findings extend the general concept of a novel mechanism in which leukemic EVs would make it possible to create a specialized pre-metastatic microenvironment in the interest of tumor expansion, allowing leukemic clones to overcome their HSCs counterparts.

Low absolute neutrophil count during induction therapy is an adverse prognostic factor in childhood acute lymphoblastic leukaemia

Variation in normal blood cells during chemotherapy has not been recognised as a risk factor guiding chemotherapy in childhood acute lymphoblastic leukaemia (ALL). This study aims to explore whether variations in normal haematopoiesis determine prognosis as well as to improve risk-stratified treatment in childhood ALL. A retrospective study of 279 cases of ALL treated with the CCCG-ALL-2015 regimen in the Division of Pediatric Blood Diseases Center, Institute of Hematology & Blood Diseases Hospital, Chinese Academy of Medical Sciences & Peking Union Medical College, from May 2015 to January 2017 was performed to analyse the prognostic impact of blood cell levels on day 19 of induction therapy by Kaplan-Meier method. Patients with childhood ALL with absolute neutrophil count (ANC) ≤ 90 cells/μl, absolute monocyte count (AMC) ≤ 10 cells/μl or absolute lymphocyte count (ALC) ≤ 1000 cells/μl on day 19 of induction therapy had a lower event-free survival (EFS) rate than those with higher values (all P < 0.05). Multivariate analysis confirmed that ANC ≤ 90 cells/μl and ALC ≤ 1000 cells/μl were independent adverse prognostic factors (HR = 1.981 and 2.162, respectively, both P < 0.05). Among patients with minimal residual disease (MRD) < 1% on day 19 of induction therapy, those with ANC ≤ 90 cells/μl had lower EFS than those with ANC > 90 cells/μl (70.8 ± 6.1% vs 86.4 ± 3.1%, P = 0.001). In the subgroup with the BCR/ABL1 fusion gene, patients with ANC ≤ 90 cells/μl on day 19 of induction therapy also had lower EFS than those with ANC > 90 cells/μl (34.4 ± 25.2% vs 25.0 ± 21.7%, P = 0.041). ANC and ALC during induction therapy are independent prognostic factors for childhood ALL. ANC contributes to guiding the prognosis of patients with low-level MRD or the BCR/ABL1 fusion gene.

Pathogenesis of pediatric B-cell acute lymphoblastic leukemia: Molecular pathways and disease treatments

B-cell acute lymphoblastic lymphoma (B-ALL) is a disease found mainly in children and in young adults. B-ALL is characterized by the rapid proliferation of poorly differentiated lymphoid progenitor cells inside the bone marrow. In the United States, ~4,000 of these patients are diagnosed each year, accounting for ~30% of childhood cancer types. The tumorigenesis of the disease involves a number of abnormal gene expressions (including TEL-AML1, BCR-ABL-1, RAS and PI3K) leading to dysregulated cell cycle. Risk factors of B-ALL are the history of parvovirus B 19 infection, high birth weight and exposure to environmental toxins. These risk factors can induce abnormal DNA methylation and DNA damages. Treatment procedures are divided into three phases: Induction, consolidation and maintenance. The goal of treatment is complete remission without relapses. Apart from traditional treatments, newly developed approaches include gene targeting therapy, with the aim of wiping out leukemic cells through the inhibition of mitogen-activated protein kinases and via c-Myb inhibition enhancing sensitivity to chemotherapy. To evaluate the efficacy of ongoing treatments, several indicators are currently used. The indicators include the expression levels of microRNAs (miRs) miR-146a, miR-155, miR-181a and miR-195, and soluble interleukin 2 receptor. Multiple drug resistance and levels of glutathione reductase can affect treatment efficacy through the increased efflux of anti-cancer drugs and weakening the effect of chemotherapy through the reduction of intracellular reactive oxygen species. The present review appraised recent studies on B-ALL regarding its pathogenesis, risk factors, treatments, treatment evaluation and causes of disease relapse. Understanding the mechanisms of B-ALL initiation and causes of treatment failure can help physicians improve disease management and reduce relapses.

Niche TWIST1 is critical for maintaining normal hematopoiesis and impeding leukemia progression

The bone marrow microenvironment regulates normal and malignant hematopoiesis, but the underlying molecular mechanisms remain poorly defined. Using a chimeric mice model, we demonstrate that Twist1 deletion in the bone marrow microenvironment results in alteration of multiple niche cells as well as downregulated expression of major hematopoietic stem cell supportive factors. The perturbed microenvironment reduces hematopoietic stem cell homing and retention, impairs hematopoietic stem cell self-renewal and induces myeloid skewing. Nevertheless, it accelerates the progression of MLL-AF9 leukemia, which is partially mediated by Jagged-2-dependent Notch signaling. Our data provide the first demonstration of a pivotal role of TWIST1 in favoring normal hematopoiesis and hampering leukemia development. They also bring new insights into the role of the bone marrow niche in driving the development of acute myeloid leukemia, and suggest possible new avenues, exploiting the niche, to improve leukemia treatments.

Engineering a multicellular vascular niche to model hematopoietic cell trafficking

BACKGROUND

The marrow microenvironment and vasculature plays a critical role in regulating hematopoietic cell recruitment, residence, and maturation. Extensive in vitro and in vivo studies have aimed to understand the marrow cell types that contribute to hematopoiesis and the stem cell environment. Nonetheless, in vitro models are limited by a lack of complex multicellular interactions, and cellular interactions are not easily manipulated in vivo. Here, we develop an engineered human vascular marrow niche to examine the three-dimensional cell interactions that direct hematopoietic cell trafficking.

METHODS

Using soft lithography and injection molding techniques, fully endothelialized vascular networks were fabricated in type I collagen matrix, and co-cultured under flow with embedded marrow fibroblast cells in the matrix. Marrow fibroblast (mesenchymal stem cells (MSCs), HS27a, or HS5) interactions with the endothelium were imaged via confocal microscopy and altered endothelial gene expression was analyzed with RT-PCR. Monocytes, hematopoietic progenitor cells, and leukemic cells were perfused through the network and their adhesion and migration was evaluated.

RESULTS

HS27a cells and MSCs interact directly with the vessel wall more than HS5 cells, which are not seen to make contact with the endothelial cells. In both HS27a and HS5 co-cultures, endothelial expression of junctional markers was reduced. HS27a co-cultures promote perfused monocytes to adhere and migrate within the vessel network. Hematopoietic progenitors rely on monocyte-fibroblast crosstalk to facilitate preferential recruitment within HS27a co-cultured vessels. In contrast, leukemic cells sense fibroblast differences and are recruited preferentially to HS5 and HS27a co-cultures, but monocytes are able to block this sensitivity.

CONCLUSIONS

We demonstrate the use of a microvascular platform that incorporates a tunable, multicellular composition to examine differences in hematopoietic cell trafficking. Differential recruitment of hematopoietic cell types to distinct fibroblast microenvironments highlights the complexity of cell-cell interactions within the marrow. This system allows for step-wise incorporation of cellular components to reveal the dynamic spatial and temporal interactions between endothelial cells, marrow-derived fibroblasts, and hematopoietic cells that comprise the marrow vascular niche. Furthermore, this platform has potential for use in testing therapeutics and personalized medicine in both normal and disease contexts.

The Interaction Between Niche and Hematopoietic Stem Cells

Hematopoietic stem cells (HSCs) are one of the somatic stem cells that have the ability to regenerate the entire blood system in a hierarchical way for the duration of an adult life. HSCs reside in the bone marrow niche which contain different cells and molecules that regulate the balance of HSC dormancy and activation. Here, we describe the interaction between HSCs and their niche, in particularly the involvement of some signaling pathway. Insights into the hematopoietic microenvironment will help to obtain a better understanding of normal hematopoiesis and how environmental factors affect these processes.

Biomodification of PCL Scaffolds with Matrigel, HA, and SR1 Enhances De Novo Ectopic Bone Marrow Formation Induced by rhBMP-2

The de novo formation of ectopic bone marrow was induced using 1.2-mm-thin polycaprolactone (PCL) scaffolds biomodified with several different biomaterials. In vivo investigations of de novo bone and bone marrow formation indicated that subcutaneous implantation of PCL scaffolds coated with recombinant human bone morphogenetic protein-2 (rhBMP-2) plus Matrigel, hydroxyapatite (HA), or StemRegenin 1 (SR1) improved formation of bone and hematopoietic bone marrow as determined by microcomputed tomography, and histological and hematopoietic characterizations. Our study provides evidence that thin PCL scaffolds biomodified with Matrigel, HA, and SR1 mimic the environments of real bone and bone marrow, thereby enhancing the de novo ectopic bone marrow formation induced by rhBMP-2. This ectopic bone marrow model will serve as a unique and essential tool for basic research and for clinical applications of postnatal tissue engineering and organ regeneration.

Novel targeted therapies for eosinophil-associated diseases and allergy

Eosinophil-associated diseases often present with life-threatening manifestations and/or chronic organ damage. Currently available therapeutic options are limited to a few drugs that often have to be prescribed on a lifelong basis to keep eosinophil counts under control. In the past 10 years, treatment options and outcomes in patients with clonal eosinophilic and other eosinophilic disorders have improved substantially. Several new targeted therapies have emerged, addressing different aspects of eosinophil expansion and inflammation. In this review, we discuss available and currently tested agents as well as new strategies and drug targets relevant to both primary and secondary eosinophilic diseases, including allergic disorders.

Mesenchymal stem cells promote leukaemic cells aberrant phenotype from B-cell acute lymphoblastic leukaemia

BACKGROUND AND OBJECTIVES

The role of bone marrow-mesenchymal stem cells (BM-MSC) in leukaemic cell control is controversial. The purpose of this work was to evaluate BM-MSC role regarding the viability, proliferation and immunophenotype of normal B-cell precursors from control (Ct) patients and leukaemic cells from B-acute lymphoblastic leukaemia (B-ALL) patients.

PATIENTS AND METHODS

BM-MSC were isolated and characterised from voluntary donors. Mononuclear cells isolated from Ct and B-ALL bone marrow samples were cultured in the presence or absence of BM-MSC for 7days. Cell viability was determined with LIVE/DEAD and proliferation index evaluated by CFSE labelling. Cell population immunophenotypes were characterised by estimating CD19, CD10, CD20 and CD45 antigens by flow cytometry.

RESULTS

After co-culture, B-ALL cells exhibited higher viability (20-40%) as compared to just cells (3-10%). Ct and B-ALL absolute cell counts were higher in the presence of BM-MSC (Ct: 25/mm(3)cf8/mm(3), B-ALL: 15/mm(3)cf3/mm(3)). Normal B-cell subpopulations in co-culture had increased expression of CD19 and CD10 (Pre-pre B) and CD45 and CD20 antigens (Pre-B). B-ALL cells co-cultured with BM-MSC showed an increase in CD19 and CD20, although the greatest increase was observed in the CD10 antigen.

CONCLUSIONS

Lymphoid cell maintenance, at early stages of differentiation, was significantly promoted by BM-MSC in normal and leukaemic cells. Co-cultures also modulated the expression of antigens associated with the B-ALL asynchronous phenotype as CD10 co-expressed with CD19 and CD20. To our knowledge, this is the first time that CD10, CD19 and CD20 leukaemic antigens have been reported as being regulated by BM-MSC.