Adhesion Of Hematopoietic Cells Research Articles

Distinct and Targetable Role of Calcium and Calcium Sensing Receptor in Leukaemia

Calcium, the most abundant mineral in the body, is a key component of bones and is released by bone remodelling. Calcium ions play a role in the localisation, engraftment and the adhesion of normal haematopoietic stem cells (HSC) to extracellular matrix (ECM) proteins in the bone marrow microenvironment (BMM) via the calcium sensing receptor (CaSR), thereby maintaining normal haematopoiesis. However, the role of this heterotrimeric G-protein-coupled receptor and its associated pathways in the local BMM for the development of leukaemia is poorly understood. We hypothesized that calcium ions, subject to a fine balance between osteoblasts and osteoclasts and released from bone, and/or CaSR contribute to development, progression and response to therapy in leukaemia and might be targetable via CaSR. By imaging of a genetically-encoded calcium indicator using intravital microscopy (IVM), we have shown that the local calcium concentration forms a gradient in the BMM with the highest concentrations close to the endosteal area. Furthermore, calcium levels differ between different leukaemias, with the calcium concentration of mice and human patients being highest in acute myeloid leukaemia (AML). Additionally, CaSR was expressed at a higher level on AML compared to chronic myeloid leukaemia (CML) cells. Using genetic deletion or overexpression or pharmacological inhibition of CaSR, we revealed that this receptor influences the localization of CML and AML cells in the BMM. Furthermore, we showed that the secondary messenger intracellular calcium (iCa 2+) can be regulated by CaSR in different leukaemia cell lines which have differential sensitivity to extracellular calcium (eCa 2+). Exposure of the human cell lines K562 (BCR-ABL1 +) and THP1 (MLL-AF9 +) to increasing calcium concentrations revealed that CaSR expression, migration and adhesion to the extracellular matrix (ECM) protein fibronectin were not altered in CML, but significantly increased in AML. Genetic deletion or overexpression of Casr in leukaemia-initiating cells in murine models revealed that CaSR acts as tumour suppressor in BCR-ABL1-driven CML and B-cell acute lymphoblastic leukaemia (B-ALL) and as oncogene in AML. Conversely, overexpression of CaSR in CaSR-deficient AML-initiating cells ‘rescued’ the disease. Limiting dilution transplantation of CaSR-deficient AML-initiating cells to assess leukaemic stem cell number and/or function revealed a 6.5-fold reduction of leukemic stem cells. Treatment of mice with the CaSR agonist cinacalcet and imatinib prolonged survival of mice with CML, while treatment with a CaSR antagonist NPS-2143 significantly reduced tumour burden and prolonged survival of mice with AML in syngeneic and xenogeneic transplantation experiments. In summary, our results suggest that calcium ions, likely originating from the BMM and/or CaSR strongly and differentially influence leukaemia localisation and progression. As an adjunct to existing treatment strategies, targeting of CaSR with specific pharmacologic agonists may be beneficial in CML and B-ALL, while CaSR antagonists may prolong survival of patients with AML.

Measurement of CD166 in Egyptian adult patients with acute lymphoblastic leukemia and its relation to clinical outcome

Abstract Background ALCAM (CD166) is a transmembrane; it has a role in the adhesion and binding of hematopoietic cells. It increases in different solid malignancies and hematological malignancies as multiple myeloma and acute leukemia. CD166 is considered one of the cancer stem cell markers responsible for most cancer recurrences following chemotherapy. Aim The study aimed to assess the expression of CD166 level in adult Egyptian acute lymphoblastic leukemia (ALL) patients, its correlation with disease-free survival, overall survival and relapse rate, as well as correlation with disease prognosis and response to treatment. Patients and methods This was a prospective cohort study conducted on 40 newly diagnosed ALL patients who will be recruited from the Clinical Hematology Department at Ain Shams University Hospital before initiation of chemotherapy in comparison to 15 patients in the control group. Results In comparison between newly diagnosed ALL patient initiation of chemotherapy and control groups, CD166 is elevated in ALL and has high sensitivity and specificity as a diagnostic and prognostic marker for ALL (P=0.000) and ALL patients with a high CD166 score have a higher overall survival rate. Conclusion ALL patients with a high CD166 score have a higher overall.

Physical biomarkers for human hematopoietic stem and progenitor cells

Adhesion of hematopoietic stem and progenitor cells (HSPCs) to the bone marrow niche plays critical roles in the maintenance of the most primitive HSPCs. The interactions of HSPC−niche interactions are clinically relevant in acute myeloid leukemia (AML), because (i) leukemia-initiating cells adhered to the marrow niche are protected from the cytotoxic effect by chemotherapy and (ii) mobilization of HSPCs from healthy donors' bone marrow is crucial for the effective stem cell transplantation. However, although many clinical agents have been developed for the HSPC mobilization, the effects caused by the extrinsic molecular cues were traditionally evaluated based on phenomenological observations. This review highlights the recent interdisciplinary challenges of hematologists, biophysicists and cell biologists towards the design of defined in vitro niche models and the development of physical biomarkers for quantitative indexing of differential effects of clinical agents on human HSPCs.

Exploring Key Genes and Pathways of Cardiac Hypertrophy Based on Bioinformatics

Objective This research is aimed at identifying the key genes and pathways of cardiac hypertrophy using bioinformatics and at providing a new target for the identification of cardiac hypertrophy. Methods Microarray data GSE1621 and GSE18801 were acquired from the GEO database. The DEGs of GSE1621 and GSE18801 were analyzed using the online tool GEO2R. “ggplot2” package of R software was utilized to generate the volcano plots. The top and bottom 10 genes were mapped as a heat map. GO functional annotation analysis and KEGG pathway enrichment analysis were performed separately for DEGs using the online software DAVID. Histograms were plotted using the R “ggplot2” package. The DEGs were imported into the STRING online database for constructing PPI networks and analyzing the DEG interaction relationships. Results In the present study, 469 DEGs were screened in GSE1621 and a total of 793 DEGs were screened in GSE18801. GO analyses indicate that DEGs were mainly involved in cardiac muscle contraction, regulation of blood circulation, regulation of muscle contraction, muscle contraction, striated muscle contraction, regulation of heart contraction, regulation of striated muscle contraction, and tissue remodeling. KEGG analyses indicate that DEGs were mainly involved in Th17 cell differentiation, Th1 and Th2 cell differentiation, HIF-1 signaling pathway, pathways in cancer, hematopoietic cell lineage, Chagas disease and cell adhesion molecules, viral myocarditis, central carbon metabolism in cancer, acute myeloid leukemia, and JAK-STAT signaling pathway. Eight hub genes were screened, including Akt1, Lox, Timp1, Col1al, Spp1, Ccnd1, Mmp3, and Egfr. Conclusions The DEGs associated with cardiac hypertrophy were screened via bioinformatics analysis, and eight hub genes were identified, including Akt1, Lox, Timp1, Col1al, Spp1, Ccnd1, Mmp3, and Egfr, which might be a new target for the identification of cardiac hypertrophy.

The Expression of RTN1 in Lung Adenocarcinoma and Its Effect on Immune Microenvironment

背景与目的网状体家族基因1(Reticulon family gene 1, RTN1)是一种与内质网相关的网状体编码基因。RTN1在神经内分泌细胞的膜运输或神经内分泌分泌中起关键作用，同时RTN1可作为有神经内分泌成分的恶性肿瘤的潜在诊断/治疗标志物。然而在肺腺癌(lung adenocarcinoma, LUAD)患者中RTN1的表达情况及其对免疫微环境影响均未有报道。本研究旨在使用公共数据库和生物信息学网络工具研究RTN1在肺腺癌中的表达及其与肺腺癌中免疫浸润和存活的相关性。方法使用Tumor Immune Estimation Resource 2.0(TIMER 2.0)和Gene Expression Profiling Interactive Analysis 2(GEPIA 2)分析肿瘤和正常组织中RTN1 mRNA的表达水平。使用人类蛋白质图谱检查RTN1蛋白质表达。利用GEPIA2在线工具分析癌症基因组图谱(The Cancer Genome Atlas, TCGA)中RTN1的临床预后意义。为了进一步确认RTN1的潜在功能，使用基因集富集分析对数据进行了分析。此外，我们对来自肿瘤免疫单细胞中心(Tumor Immune Single-cell Hub, TISCH)数据库的两个数据集在单细胞测序水平上进行降维聚类分析，观察RTN1在不同种类免疫细胞的细胞聚类。使用TIMER在线工具分析预测TCGA队列肺腺癌患者免疫微环境中不同种类免疫细胞浸润丰度；使用TIMER和CIBERSORT研究与RTN1共表达基因和其相关肿瘤浸润免疫细胞之间的关系；最后，使用TIMER分析RTN1与免疫检查点之间的相关性。结果我们发现LUAD患者的RTN1表达降低，且与患者的预后密切相关。RTN1参与吞噬体的形成、造血细胞形成和细胞黏附的过程，对T细胞活化起着重要作用，使用cBioPortal与TCGA数据来分析，发现RTN1与BTK、CD4、ECSF1R、MNDA、NCKAP1L和SNX20显著相关。以上基因高表达可能会引起CD4+ T细胞、肥大细胞、单核细胞、髓样树突状细胞和M1型巨噬细胞显著上调。并且，RTN1表达与常见免疫检查点CD274、CTLA4、HAVCR2、LAG3、PDCD1、PDCD1LG2、TIGIT、SIGLEC15密切相关。结论RTN1作为一种肿瘤抑制基因并可能与更好的预后相关。此外，RTN1与可能参与免疫治疗反应的免疫浸润有关。但与其相关的机制需要进一步的研究。

Common Gene Expression Signature of B-Cells of Waldenström Macroglobulinemia (WM) and IgM Monoclonal Gammopathies of Undetermined Significance (IgM MGUS) Compared to Healthy Subjects

We performed a comparative gene expression profiling (GEP) study on B-cells and plasma cells of Waldenström Macroglobulinemia (WM), IgM monoclonal gammopathies of undetermined significance (IgMMGUS), and normal individuals (CTRLs) to identify GEP changes as reliable predictors of progression of IgMMGUS to WM.We analyzed bone marrow B-cells and plasma cells from 36 WM patients, 13 IgMMGUS subjects, and 7 CTRLs by Affymetrix microarray, respectively (Table 1). GEP experiments were performed on the CD19+ and CD138+ cells using GeneChip-HGU133 Plus 2.0. Data were preprocessed and normalized by Robust Multi-Array Average and ComBat. Selection of the different expressed genes was performed separately for CD19+ and CD138+ cells, using Significance Analysis of Microarrays (SAM) on the 3 groups and a false discovery rate threshold of 5%, followed, for significance comparisons, by a pair-wise SAM test corrected for multiple testing.We focused on the comparison of the CD19+ cells of WM vs. IgMMGUS vs. CTRLs which highlighted 2038 unique genes whereas the same comparison of the CD138+ cells determined 29 unique genes (Trojani et.al. Cancers 2021). Among the 2038 DEGs, 115 genes were grouped in KEGG pathways involved in Wnt-signaling, BCR-signaling, calcium signaling, hematopoietic cell antigens, cell adhesion, adherens junctions, coagulation cascade, platelet activation, cytokine receptor, and signaling pathways responsible for cell cycle, apoptosis, and survival.Interestingly, most of the 115 DEGs in B-cells were different expressed in WM vs. IgMMGUS and CTRLs. Only 9/115 DEGs were significantly different expressed in WM vs. CTRLs and in IgMMGUS vs. CTRLs, but no significant expression changes were noted between WM and IgMMGUS (Table 2).To further inspect the similarities and the differences among WM and IgMMGUS, we computed the Euclidean pair-wise distance between subjects and, using this distance as weight, constructed a minimum spanning tree (MST) (Figure 1).Considerably, four probesets identified ADRB2 (transmembrane Beta adrenergic receptor) which was up regulated in WM and IgMMGUS compared to CTRLs. The over expression of ADRB2 was also demonstrated in Mantle Cell Lymphoma cell lines and in Diffuse large B-cell lymphoma (DLBCL) lymphocytes compared to normal B-cells (doi10.1016/j.cellsig.2017.08.002), and in most malignancies (doi10.1007/s11033-021-06250-y) .As far as we know, ADAM23 (ADAM Metallopeptidase Domain23) has not been found in WM, whereas we suggest its possible role in WM patients with Sjogren's syndrome (SS). ADAM23 plays a role in the peripheral neuropathy by controlling the activity of potassium channels in SS (doi10.1007/s10067-016-3499-z). Some authors found that sensory/motor neuropathies were associated with MGUS patients (doi10.1017/s0317167100011483). We strongly believe that the down regulation of ADAM23 in WM and IgMMGUS has a good chance to be associated with clinical neuropathy in WM and IgMMGUS.RASGRP3 (RAS Guanyl Releasing Protein3) and PIK3AP1 (Phosphoinositide 3 Kinase Adaptor Protein1) play crucial roles in BCR signaling pathway: PIK3AP1 activates the PI3K-Akt signaling while RASGRP3 stimulates MAPK signaling pathway.The deregulation of LEF1 (Lymphoid Enhancer Binding Factor1) and genes of Wnt-pathway were previously demonstrated in B-cell disorders and multiple myeloma (doi10.1007/s00277-017-3207-3, doi10.1016/j.pathol.2019.09.009). According to these studies, we showed the under expression of LEF1 in WM and IgMMGUS compared to CTRLs.We identified the down regulation of EZH2 (Enhancer Of Zeste2 Polycomb Repressive Complex2Subunit) in WM and IgMMGUS compared to CTRLs. EZH2 is involved in Follicular lymphoma and DLBCL (doi10.1080/2162402X.2017.1321184).CDHR3 (Cadherin Related Family Member3), CHEK1 (Checkpoint Kinase1), and HIST1H1B (Histone-H1.5) were over expressed in CTRLs compared to IgMMGUS and WM.In conclusion, the common gene-set in WM and IgMMGUS could suggest two-hit hypothesis. First, the gene-set could play a role in the risk of progression of IgMMGUS to WM. Until now, all the IgMMGUS subjects have not been transformed in WM or other NHL, but they have been monitored every 6 months, and their possible transformation to lymphoma could highlight new insights. The second hypothesis suggests their involvement in the biological processes of leukemogenesis in WM and IgMMGUS which will be further investigated. [Display omitted] DisclosuresTedeschi: AbbVie: Honoraria, Speakers Bureau; AstraZeneca: Honoraria, Speakers Bureau; Beigene: Honoraria, Speakers Bureau; Janssen: Honoraria, Speakers Bureau.

Case Report: A Case of Leukocyte Adhesion Deficiency, Type III Presenting With Impaired Platelet Function, Lymphocytosis and Granulocytosis

Fermitin family homolog 3 (FERMT3), alternatively kindlin-3 (KIND3), is an integrin binding protein (of 667 residues) encoded by the FERMT3 gene. The molecule is essential for activating integrin αIIbβ3 (the fibrinogen receptor) on platelets and for the integrin-mediated hematopoietic cell (including platelets, T lymphocytes, B lymphocytes, and granulocytes) adhesion. Its defects are associated with impaired primary hemostasis, described as “Glanzmann's thrombasthenia (MIM#273800)-like bleeding problem.” The defects are also associated with infections, designated as “LAD1 (leukocyte adhesion deficiency, type I; MIM#116920)-like immune deficiency.” The entity that joins the impaired primary hemostasis with the leukocyte malfunction has been termed “leukocyte adhesion deficiency, type III” (LAD3, autosomal recessive, MIM#612840), representing a defective activation of the integrins β1, β2, and β3 on leukocytes and platelets. Here, we report a male toddler with novel compound heterozygous variants, NM_178443.2(FERMT3):c.1800G>A, p.Trp600* (a non-sense variant) and NM_178443.2(FERMT3):c.2001del p.*668Glufs*106 (a non-stop variant). His umbilical cord separated at about 3 weeks of age. A skin rash (mainly petechiae and purpura) and recurrent episodes of severe epistaxis required blood transfusions in early infancy. His hemostatic work-up was remarkable for a normal platelet count, but abnormal platelet function screen with markedly prolonged collagen-epinephrine and collagen-ADP closure times. The impaired platelet function was associated with reduced platelet aggregation with all agonists. The expression of platelet receptors was normal. Other remarkable findings were persistent lymphocytosis and granulocytosis, representing defects in diapedesis due to the integrin dysfunction. The natural history of his condition, structure and sequence analysis of the variations, and comparison with other LAD3 cases reported in the literature are presented.

Expression of RASGRP2 in Lung Adenocarcinoma and Its Effect on Immune Microenvironment

背景与目的肺癌是全球发病率和死亡率的居高不下的恶性肿瘤。近年来，随着新型药物的出现和治疗模式的优化，特别是免疫治疗在临床的应用，肺癌患者的预后已经有了一定的改善。但免疫治疗获益的患者仍然有限，因此我们想要寻找新的生物标志物用于预测肺腺癌患者的预后并探索其对免疫微环境的影响。方法使用癌症基因组图谱（The Cancer Genome Atlas, TCGA）数据库下载肺腺癌患者的测序结果及临床资料。利用人类蛋白质图谱数据库明确RASGRP2在肺腺癌中分布情况，使用Kaplan-Meier Plotter数据库探索RASGRP2表达情况与肺腺癌患者预后之间的联系。对RASGRP2高低表达患者进行KEGG及GO基因富集分析。使用TCGA数据库分析RASGRP2共表达基因并使用TIMER数据库计算RASGRP2及其共表达基因的免疫相关淋巴浸润情况。最后使用TIMER 2.0数据库分析RASGRP2表达量与免疫检查点表达的联系。结果RASGRP2在肺腺癌中低表达，与患者预后密切相关。RASGRP2高表达参与造血细胞形成及细胞黏附，且在T细胞活化进程中有着重要作用。通过TCGA数据库分析发现ZAP70、TBC1D10C、RASAL3、FGD2、CD37、ACAP1与RASGRP2显著相关。以上基因高表达会引起CD8+ T细胞、记忆CD4+ T细胞比例升高以及中性粒细胞和Treg细胞比例降低。最后，我们发现RASGRP2表达量与常见免疫检查点CD274、CTLA4、LAG3、TIGIT等表达量显著相关。结论RASGRP2在肺腺癌中异常表达且影响免疫相关细胞浸润水平，可能会影响免疫治疗疗效。

ALKBH1-8 and FTO: Potential Therapeutic Targets and Prognostic Biomarkers in Lung Adenocarcinoma Pathogenesis.

The AlkB family consists of Fe(II)- and α-ketoglutarate-dependent dioxygenases that can catalyze demethylation on a variety of substrates, such as RNA and DNA, subsequently affecting tumor progression and prognosis. However, their detailed functional roles in lung adenocarcinoma (LUAD) have not been clarified in a comprehensive manner. In this study, several bioinformatics databases, such as ONCOMINE, TIMER, and DiseaseMeth, were used to evaluate the expression profiles and prognostic significance of the AlkB family (ALKBH1-8 and FTO) in LUAD. The expression levels of ALKBH1/2/4/5/7/8 were significantly increased in LUAD tissues, while the expression levels of ALKBH3/6 and FTO were decreased. The main functions of differentially expressed AlkB homologs are related to the hematopoietic system and cell adhesion molecules. We also found that the expression profiles of the AlkB family are highly correlated with infiltrating immune cells (i.e., B cells, CD8 + T cells, CD4 + T cells, macrophages, neutrophils and dendritic cells). In addition, DNA methylation analysis indicated that the global methylation levels of ALKBH1/2/4/5/6/8 and FTO were decreased, while the global methylation levels of ALKBH3/7 were increased. In addition, the patients with upregulated ALKBH2 have significantly poor overall survival (OS) and post-progressive survival (PPS). Taken together, our work could provide insightful information about aberrant AlkB family members as potential biomarkers for the diagnostic and prognostic evaluation of LUAD. Especially, ALKBH2 could be served as a therapeutic candidate for treating LUAD.

Cysteine Cathepsins and Their Prognostic and Therapeutic Relevance in Leukemia

Cysteine cathepsins are lysosomal proteases that require Cys-His ion pair in their catalytic site for enzymatic activity. While their aberrant expression and oncogenic functions have been widely reported in solid tumors, recent findings suggest that these proteases also play an important role in the pathogenesis of hematological malignancies. In this review, we summarize the potential clinical implications of cysteine cathepsins as diagnostic and prognostic markers in leukemia, and present evidences which supports the utility of these proteases as potential therapeutic targets in hematological malignancies. We also highlight the available information on the expression patterns, regulation, and potential functions of cysteine cathepsins in normal hematopoiesis and hematological malignancies. In hematopoiesis, cysteine cathepsins play a variety of physiological roles including regulation of hematopoietic stem cell adhesion in the bone marrow, trafficking, and maturation. They are also involved in several functions of immune cells which include the selection of lymphocytes in the thymus, antigen processing, and presentation. However, the expression of cysteine cathepsins is dysregulated in hematological malignancies where they have been shown to play diverse functions. Interestingly, several pieces of evidence over the past few years have demonstrated overexpression of cathepsins in leukemia and their association with worst survival outcomes in patients. Strategies aimed at altering the expression, activity, and subcellular localization of these cathepsins are emerging as potential therapeutic modalaties in the management of hematological malignancies. Recent findings also suggest the involvement of these proteases in modulating the immune response in leukemia and lymphomas.

Thrombin-Induced Endothelial Cell Damage Is Mitigated By Human Anti-Thrombin III in a Microfluidic Device

Introduction Sickle cell disease (SCD) is a pleiotropic disease that results in a hypercoagulable state due to the depletion of natural anticoagulants and abnormal activation of the coagulation cascade. Vascular inflammation is a characteristic of SCD and can lead to endothelial cell activation and abnormally enhanced adhesion of hematopoietic cells. These adhesive events can lead to vaso-occlusive crises and are thus a target of pharmaceutical exploration. The complex pathophysiology of SCD suggests that there are many potential therapeutic targets, particularly during activation of the coagulation cascade. Presently, we describe the use of a microfluidic device to investigate the effectiveness of anti-thrombin III (AT-III) in mitigating thrombin-mediated effects on and red blood cell adhesion (RBC) to endothelial cells. Our microfluidic device, endothelium-on-a-chip (Fig. 1A), incorporates microchannels functionalized with endothelial cells (ECs), which allows for investigation of SCD pathophysiology under physiological shear stress. Here, we examine the extent to which thrombin causes cellular contraction in human umbilical vein endothelial cells (HUVECs) and the capacity of AT-III to mitigate this contraction. Similarly, we quantify the adhesion of sickle RBCs to thrombin-activated HUVECs and the adhesion to HUVECs pre-treated with AT-III. Methods Microchannels seeded with human umbilical vein endothelial cells (HUVECs) were cultured to confluency under flow for 48 - 72 hrs at 37 °C in a 5% CO2 atmosphere. Culture media containing 10% fetal bovine serum (FBS) was perfused through the microchannels at a shear stress of 1 dyne/cm2 which corresponds to a typical value seen in human post-capillary venules. Approximately 18 hours prior to the start of the experiment, perfused media was exchanged for ITS+1 media in order to condition cells to a low-serum environment and to avoid neutralization of thrombin by residual serum factors. At the start of each experiment, devices were disconnected from the dynamic flow culturing system and incubated with experimental reagents under static conditions. Endothelialized microchannels were treated with one of three conditions: Control channels were incubated with ITS+1 media for 5 hrs; Thrombin channels were incubated with ITS+1 media for 1 hr, followed by 5 IU/mL human alpha thrombin for 4 hrs; Anti-thrombin III channels were incubated with 7 IU/mL human anti-thrombin III (AT-III) for 1 hr, followed by 5 IU/mL human alpha thrombin for 4 hrs. AT-III was donated by Grifols USA (Los Angeles, California). Following each experiment, the endothelialized microchannels were fixed with 3.7% formalin. Microchannels were then imaged and confluency was measured using the FIJI plug-in PHANTAST with default settings. For adhesion experiments, whole blood samples were collected from 6 patients with homozygous SCD (HbSS). RBCs were isolated and suspended at 20% hematocrit in basal media, then perfused through treated, endothelialized microchannels. Microchannels were then imaged and adherent RBCs were quantified. Results The results of contraction and adhesion experiments are shown in Figures 1B&C, respectively. Control channels had an average confluency of 97.9% ± 1.7 (Fig. 1B&D), while thrombin-treated channels resulted in HUVEC contraction causing an average confluency of 63.7% ± 8.9 (Fig. 1B&E). Microchannels treated with AT-III prior to thrombin incubation had an average confluency of 92.5% ± 5.3 (Fig. 1B&F). Adhesion of sickled RBCs followed a similar trend: control channels had an average of 16.0 ± 22.7 RBCs per analyzed region (Fig. 1C&G), thrombin channels had an average of 222.8 ± 86.7 RBCs per analyzed region (Fig. 1C&H), and AT-III channels had an average of 19.6 ± 12.3 RBCs per analyzed region (Fig. 1C&I). Discussion We observed that thrombin treatment resulted in significant endothelial cell contraction. This thrombin induced cell contraction could be mitigated by pre-treating the microchannels with AT-III. Similarly, RBC adhesion significantly increased in thrombin-treated microchannels, and could be similarly mitigated by pre-treatment of the endothelium with AT-III. Taken together, our in vitro model suggests that AT-III may be worthy of investigation as a treatment for SCD associated thromboinflammation and vaso-occlusive crises. Disclosures An: Hemex Health, Inc.: Patents & Royalties. Little:NHLBI: Research Funding; GBT: Membership on an entity's Board of Directors or advisory committees; GBT: Research Funding; Bluebird Bio: Research Funding; BioChip Labs: Patents & Royalties: SCD Biochip (patent, no royalties); Hemex Health, Inc.: Patents & Royalties: Microfluidic electropheresis (patent, no royalties). Key:Novo Nordisk: Other: Chair of Grants Committee; Takeda: Research Funding; Grifols: Research Funding; Uniqure: Consultancy. Gurkan:Hemex Health, Inc.: Consultancy, Current Employment, Patents & Royalties, Research Funding; BioChip Labs: Patents & Royalties; Dx Now Inc.: Patents & Royalties; Xatek Inc.: Patents & Royalties.

Leukemia Stem Cell Release From the Stem Cell Niche to Treat Acute Myeloid Leukemia

Acute myeloid leukemia (AML) is a heterogeneous, complex, and deadly disease, whose treatment has hardly evolved for decades and grounds on the use of intensive chemotherapy regimens. Chemotherapy helps reduce AML bulk, but promotes relapse in the long-run by selection of chemoresistant leukemia stem cells (LSC). These may diversify and result in progression to more aggressive forms of AML. In vivo models suggest that the bone marrow stem cell niche helps LSC stay dormant and protected from chemotherapy. Here, we summarize relevant changes in stem cell niche homing and adhesion of AML LSC vs. healthy hematopoietic stem cells, and provide an overview of clinical trials aiming at targeting these processes for AML treatment and future directions within this field. Promising results with various non-mutation-targeted novel therapies directed to LSC eradication via interference with their anchoring to the stem cell niche have encouraged on-going or future advanced phase III clinical trials. In the coming years, we may see a shift in the focus of AML treatment to LSC-directed therapies if the prospect of improved cure rates holds true. In the future, AML treatment should lean toward personalized therapies using combinations of these compounds plus mutation-targeted agents and/or targeted delivery of chemotherapy, aiming at LSC eradication with reduced side effects.

Retraction: Role of Microvascular endothelial cells on proliferation, migration and adhesion of hematopoietic stem cells.

This Retraction follows an Expression of Concern relating to this article previously published by Portland Press.This article is being retracted from Bioscience Reports at the request of the authors following receipt of a notification from a reader, alerting the authors to the duplications in Figure 4A as well as duplicated figures from another published article by the same authors in Zhongguo Shi Yan Xue Ye Xue Za Zhi (10.19746/j.cnki.issn1009-2137.2019.02.046).The authors wish to retract the article. The Editor-in-Chief and Editorial Board agree with the retraction.

Expression of Concern: Role of Microvascular endothelial cells on proliferation, migration and adhesion of hematopoietic stem cells.

The Editorial Office has been made aware of potential issues surrounding the scientific validity of this paper, hence has issued an expression of concern to notify readers whilst the Editorial Office investigates.

Role of microvascular endothelial cells on proliferation, migration and adhesion of hematopoietic stem cells.

Background: The present study investigated the effects of microvascular endothelial cells (MECs) on the chemotaxis, adhesion and proliferation of bone marrow hematopoietic stem cells (HSCs) ex vivo. Methods and Results: MECs were collected from the lung tissue of C57BL/6 mice, and HSCs were isolated with immunomagnetic beads from bone marrow of GFP mice. MECs and HSCs were co-cultured with or without having direct cell–cell contact in Transwell device for the measurement of chemotaxis and adhesion of MECs to HSCs. Experimental results indicate that the penetration rate of HSCs from the Transwell upper chamber to lower chamber in ‘co-culture’ group was significantly higher than that of ‘HSC single culture’ group. Also, the HSCs in co-culture group were all adherent at 24 h, and the co-culture group with direct cell–cell contact had highest proliferation rate. The HSC number was positively correlated with vascular endothelial growth factor (VEGF) and stromal cell-derived factor-1 (SDF-1) levels in supernatants of the culture. Conclusions: Our study reports that MECs enhance the chemotaxis, adhesion and proliferation of HSCs, which might be related to cytokines SDF-1 and VEGF secreted by MECs, and thus MECs enhance the HSC proliferation through cell–cell contact. The present study revealed the effect of MECs on HSCs, and provided a basis and direction for effective expansion of HSCs ex vivo.

Characterization of a novel decellularized bone marrow scaffold as an inductive environment for hematopoietic stem cells.

Due to the increasing demand for a bone marrow study model, we developed a natural scaffold from decellularized bovine bone marrow (DeBM). The obtained bioscaffold was analyzed after the decellularization process; histological staining, scanning and transmission electron microscopy confirmed the preservation of its native 3D-architecture; including blood vessels and cell niches as well as the integrity of important components of the extracellular matrix; Collagen III, IV and fibronectin. In addition to biochemical composition, physical properties of the bone marrow were also conserved. We evaluated the suitability of this bio-scaffold as a tridimensional culture platform. Seeding experiments with umbilical cord-derived hematopoietic stem cells and human bone marrow stromal cell line HS5 demonstrated that this scaffold is capable of supporting hematopoietic and stromal cell adhesion and proliferation without the need of exogenous factors. DeBM provided an inductive environment for the repopulation of the bone marrow inducing the expression of SDF-1, HGF and SCF by seeded stromal cells. The presence of these potent hematopoietic chemoattractants would be crucial for ex vivo long-term culture of HSCs, and for recreating the natural microenvironment of the bone marrow for bioengineering applications. We conclude that the decellularization process succeeded in preserving the 3D structure and mechanical properties of the bone marrow. The resulting scaffold is suitable for cell culture, representing an advantageous bone marrow experimental model, and potentially an effective platform for CD34+ HSC expansion and differentiation for clinical applications.

Diverging impact of cell fate determinants Scrib and Llgl1 on adhesion and migration of hematopoietic stem cells.

Cell fate determinants Scrib and Llgl1 influence self-renewal capacity of hematopoietic stem cells (HSCs). Scrib-deficient HSCs are functionally impaired and lack sufficient repopulation capacity during serial transplantation and stress. In contrast, loss of Llgl1 leads to increased HSC fitness, gain of self-renewal capacity and expansion of the stem cell pool. Here, we sought to assess for shared and unique molecular functions of Llgl1 and Scrib by analyzing their interactome in hematopoietic cells. Interactome analysis was performed by affinity purification followed by mass spectrometry. Motility, migration and adhesion were assessed on primary murine HSCs, which were isolated by FACS sorting following conditional deletion of Scrib or Llgl1, respectively. Imaging of Scrib-deficient HSCs was performed by intravital 2-photon microscopy. Comparison of Scrib and Llgl1 interactome analyses revealed involvement in common and unique cellular functions. Migration and adhesion were among the cellular functions connected to Scrib but not to Llgl1. Functional validation of these findings confirmed alterations in cell adhesion and migration of Scrib-deficient HSCs in vitro and in vivo. In contrast, genetic inactivation of Llgl1 did not affect adhesion or migratory capacity of hematopoietic stem cells. Our data provide first evidence for an evolutionarily conserved role of the cell fate determinant Scrib in HSC adhesion and migration in vitro and in vivo, a unique function that is not shared with its putative complex partner Llgl1.

Erratum to: Endogenous developmental endothelial locus-1 limits ischaemia-related angiogenesis by blocking inflammation.

We have recently identified endothelial cell-secreted developmental endothelial locus-1 (Del-1) as an endogenous inhibitor of β2-integrin–dependent leukocyte infiltration. Del-1 was previously also implicated in angiogenesis. Here, we addressed the role of endogenously produced Del-1 in ischaemia-related angiogenesis. Intriguingly, Del-1–deficient mice displayed increased neovascularisation in two independent ischaemic models (retinopathy of prematurity and hind-limb ischaemia), as compared to Del-1–proficient mice. On the contrary, angiogenic sprouting in vitro or ex vivo (aortic ring assay) and physiological developmental retina angiogenesis were not affected by Del-1 deficiency. Mechanistically, the enhanced ischaemic neovascularisation in Del-1-deficiency was linked to higher infiltration of the ischaemic tissue by CD45+ haematopoietic and immune cells. Moreover, Del-1-deficiency promoted β2-integrin–dependent adhesion of haematopoietic cells to endothelial cells in vitro, and the homing of hematopoietic progenitor cells and of immune cell populations to ischaemic muscles in vivo. Consistently, the increased hind limb ischaemia-related angiogenesis in Del-1 deficiency was completely reversed in mice lacking both Del-1 and the β2-integrin LFA-1. Additionally, enhanced retinopathy-associated neovascularisation in Del-1-deficient mice was reversed by LFA-1 blockade. Our data reveal a hitherto unrecognised function of endogenous Del-1 as a local inhibitor of ischaemia-induced angiogenesis by restraining LFA-1–dependent homing of pro-angiogenic haematopoietic cells to ischaemic tissues. Our findings are relevant for the optimisation of therapeutic approaches in the context of ischaemic diseases. Supplementary Material to this article is available online at www.thrombosis-online.com.

Ectopic Expression of Snail and Twist in Ph+ Leukemia Cells Upregulates CD44 Expression and Alters Their Differentiation Potential.

Philadelphia chromosome-positive (Ph+) leukemia is characterized by reciprocal translocation between chromosomes 9 and 22. The resultant BCR/ABL fusion protein displays constitutive tyrosine kinase activity, leading to the induction of aberrant proliferation and neoplastic transformation. The bone marrow (BM) microenvironment is tumor-promoting, and contributes to disease recurrence in Ph+ leukemia. Activity in the BM microenvironment is mediated by several cellular compartments, extracellular matrix, various soluble factors including transforming growth factor beta 1 (TGF-β1), and the hypoxic conditions in the BM niche. TGF-β1 is released during bone remodeling and plays a role in maintaining leukemic stem cells, as well as being implicated in the epithelial-mesenchymal transition (EMT) process in most solid tumors. Although EMT is largely implicated in epithelial tumors, recent findings argue for an EMT-like process in leukemia as well. The surface receptor CD44 is involved in cell adhesion, cell migration, and homing of normal and malignant hematopoietic stem cells. Elevation of CD44 expression is considered a marker for a worse prognosis in most hematological malignancies. We explored the functions of Snail and Twist1 in Ph+ leukemia. We showed that ectopic expression of Snail and, to a lesser extent, Twist1, upregulates CD44 expression that is β-catenin-dependent. Moreover, the presence of Snail or Twist1 partially blocked phorbol 12-myristate 13-acetate-induced megakaryocyte differentiation, while that of Twist significantly altered imatinib-induced erythroid differentiation. Thus EMT modulators affected proliferation, CD44 gene expression and differentiation ability of Ph+ leukemia cells.

Endogenous developmental endothelial locus-1 limits ischaemia-related angiogenesis by blocking inflammation.

We have recently identified endothelial cell-secreted developmental endothelial locus-1 (Del-1) as an endogenous inhibitor of β2-integrin-dependent leukocyte infiltration. Del-1 was previously also implicated in angiogenesis. Here, we addressed the role of endogenously produced Del-1 in ischaemia-related angiogenesis. Intriguingly, Del-1-deficient mice displayed increased neovascularisation in two independent ischaemic models (retinopathy of prematurity and hind-limb ischaemia), as compared to Del-1-proficient mice. On the contrary, angiogenic sprouting in vitro or ex vivo (aortic ring assay) and physiological developmental retina angiogenesis were not affected by Del-1 deficiency. Mechanistically, the enhanced ischaemic neovascularisation in Del-1-deficiency was linked to higher infiltration of the ischaemic tissue by CD45+ haematopoietic and immune cells. Moreover, Del-1-deficiency promoted β2-integrin-dependent adhesion of haematopoietic cells to endothelial cells in vitro, and the homing of hematopoietic progenitor cells and of immune cell populations to ischaemic muscles in vivo. Consistently, the increased hind limb ischaemia-related angiogenesis in Del-1 deficiency was completely reversed in mice lacking both Del-1 and the β2-integrin LFA-1. Additionally, enhanced retinopathy-associated neovascularisation in Del-1-deficient mice was reversed by LFA-1 blockade. Our data reveal a hitherto unrecognised function of endogenous Del-1 as a local inhibitor of ischaemia-induced angiogenesis by restraining LFA-1-dependent homing of pro-angiogenic haematopoietic cells to ischaemic tissues. Our findings are relevant for the optimisation of therapeutic approaches in the context of ischaemic diseases.