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Background In ineffective erythropoiesis, hepcidin synthesis is suppressed by erythroid regulators, namely erythroferrone and growth differentiation factor-15. For the first time, the hypothesis that iron overload in megaloblastic anemia may be related to ineffective erythropoiesis is explored by describing the kinetics of hepcidin, erythroferrone, and growth differentiation factor-15 levels in a patient diagnosed with megaloblastic anemia associated with iron overload. Case presentation An 81-year-old Caucasian male was admitted for fatigue. He had type-2 diabetes previously treated with metformin, ischemic cardiac insufficiency, and stage-3 chronic kidney disease. Vitiligo was observed on both hands. Biological tests revealed normocytic non-regenerative anemia associated with hemolysis, thrombocytopenia, and elevated sideremia, ferritin, and transferrin saturation levels. Megaloblastic anemia was confirmed with undetectable blood vitamin B12 and typical cytological findings like hyper-segmented neutrophils in blood and megaloblasts in bone marrow. The patient received vitamin B12 supplementation. At 3 months, biological parameters reached normal values. Hepcidin kinetics from diagnosis to 3 months inversely correlated with those of erythroferrone and growth differentiation factor-15. Conclusions This case suggests that iron-overload mechanisms of dyserythropoietic anemias may apply to megaloblastic anemias.

International audience; DNA methylation, a major biological process regulating the transcription, contributes to the pathophysiology of hematologic malignancies, and hypomethylating agents are commonly used to treat myelodysplastic syndromes (MDS) and acute myeloid leukemias (AML). In these diseases, bone marrow mesenchymal stromal cells (MSCs) play a key supportive role through the production of various signals and interactions. The DNA methylation status of MSCs, likely to reflect their functionality, might be relevant to understand their contribution to the pathophysiology of these diseases. Consequently, the aim of our study was to analyze the modifications of DNA methylation profiles of MSCs induced by MDS or AML. MSCs from MDS/AML patients were characterized via 5-methylcytosine quantification, gene expression profiles of key regulators of DNA methylation, identification of differentially methylated regions (DMRs) by methylome array, and quantification of DMR-coupled genes expression. MDS and AML-MSCs displayed global hypomethylation and under-expression of DNMT1 and UHRF1. Methylome analysis revealed aberrant methylation profiles in all MDS and in a subgroup of AML-MSCs. This aberrant methylation was preferentially found in the sequence of homeobox genes, especially from the HOX family (HOXA1, HOXA4, HOXA5, HOXA9, HOXA10, HOXA11, HOXB5, HOXC4, and HOXC6), and impacted on their expression. These results highlight modifications of DNA methylation in MDS/AML-MSCs, both at global and focal levels dysregulating the expression of HOX genes well known for their involvement in leukemogenesis. Such DNA methylation in MSCs could be the consequence of the malignant disease or could participate in its development through defective functionality or exosomal transfer of HOX transcription factors from MSCs to hematopoietic cells.

Low reactive oxygen species (ROS) levels are well-established characteristics of mouse hematopoietic stem cells (HSCs). However, little is known about these levels in human HSCs. This study aimed at quantifying ROS levels in human CD34+ CD38low and CD34+ CD38high human progenitors from bone marrow, cord blood and cells mobilized for autologous HSC transplantation. A specifically devised multiparameter flow cytometry method was used to quantify ROS levels (H2 DCFDA staining) in sub-populations of primary cells. Results were confirmed by assessing gene expression level of the ROS scavenger GPX3, a key determinant of HSC self-renewal, in sorted CD34+ CD38low and CD34+ CD38high cells. CD34+ CD38low cells from bone marrow and cord blood displayed significantly lower levels of ROS than CD34+ CD38high cells and other leukocytes. Moreover, the correlation between ROS and GPX3 expression was verified in sorted CD34+ CD38low and CD34+ CD38high cells. These results confirm, in human, data previously reported in mice. Moreover, the flow cytometry assay we developed could allow for a more precise enumeration of repopulating primitive progenitors in the course of HSC transplantation.

Simple Summary Pesticide exposure is a public health concern. Two recent studies reported that exposure of normal primary bone marrow mesenchymal stem/stromal cells (BM-MSCs) to low-dose pesticide mixture induces deleterious consequences, such as oxidative stress, senescence, accelerated aging and increased sensitivity to oncogenic hits. Here, we show that exposure to this mixture decreases aldehyde dehydrogenase-2 (ALDH2) activity, with a concomitant increase in acetaldehyde level and DNA damage and alters the MSC capacity to support primitive hematopoiesis. Similar abnormalities were observed in bone marrow-MSCs from patients suffering from myelodysplastic syndrome (MDS), suggesting a role of pesticide-induced ALDH2 inhibition in the pathophysiology of this pre-leukemic disease. Abstract (1) Background: The impact of occupational exposure to high doses of pesticides on hematologic disorders is widely studied. Yet, lifelong exposure to low doses of pesticides, and more particularly their cocktail effect, although poorly known, could also participate to the development of such hematological diseases as myelodysplastic syndrome (MDS) in elderly patients. (2) Methods: In this study, a cocktail of seven pesticides frequently present in water and food (maneb, mancozeb, iprodione, imazalil, chlorpyrifos ethyl, diazinon and dimethoate), as determined by the European Food Safety Authority, were selected. Their in vitro effects at low-doses on primary BM-MSCs from healthy volunteers were examined. (3) Results: Exposure of normal BM-MSCs to pesticides for 21 days inhibited cell proliferation and promoted DNA damage and senescence. Concomitantly, these cells presented a decrease in aldehyde dehydrogenase 2 (ALDH2: mRNA, protein and enzymatic activity) and an increase in acetaldehyde levels. Pharmacological inhibition of ALDH2 with disulfiram recapitulated the alterations induced by exposure to low doses of pesticides. Moreover, BM-MSCs capacity to support primitive hematopoiesis was significantly altered. Similar biological abnormalities were found in primary BM-MSCs derived from MDS patients. (4) Conclusions: these results suggest that ALDH2 could participate in the pathophysiology of MDS in elderly people long exposed to low doses of pesticides.

The bone marrow (BM) niche impacts the progression of acute myeloid leukemia (AML) by favoring the chemoresistance of AML cells. Intimate interactions between leukemic cells and BM mesenchymal stromal cells (BM-MSCs) play key roles in this process. Direct intercellular communications between hematopoietic cells and BM-MSCs involve connexins, components of gap junctions. We postulated that blocking gap junction assembly could modify cell–cell interactions in the leukemic niche and consequently the chemoresistance. The comparison of BM-MSCs from AML patients and healthy donors revealed a specific profile of connexins in BM-MSCs of the leukemic niche and the effects of carbenoxolone (CBX), a gap junction disruptor, were evaluated on AML cells. CBX presents an antileukemic effect without affecting normal BM-CD34+ progenitor cells. The proapoptotic effect of CBX on AML cells is in line with the extinction of energy metabolism. CBX acts synergistically with cytarabine (Ara-C) in vitro and in vivo. Coculture experiments of AML cells with BM-MSCs revealed that CBX neutralizes the protective effect of the niche against the Ara-C-induced apoptosis of leukemic cells. Altogether, these results suggest that CBX could be of therapeutic interest to reduce the chemoresistance favored by the leukemic niche, by targeting gap junctions, without affecting normal hematopoiesis.

The incidence of myelodysplastic syndrome increases with aging and the early diagnosis enables optimal care of these diseases. The DxH 800 hematology analyzer measures and calculates 126 cytological parameters, but only 23 are used for routine CBC assessment. The goal of this study was to use the 103 unexploited &ldquo, research parameters&rdquo, to develop an algorithm allowing for an early detection of subclinical MDS patients by triggering morphological analysis. Blood sample parameters from 101 MDS patients and 88 healthy volunteers were analyzed to identify the critical &ldquo, with: (i) the most significant differences between MDS patients and healthy volunteers, (ii) the best contributions to principal component analysis (PCA), first axis, and (iii) the best correlations with PCA, first two axes (cos2 &gt, 0.6). Ten critical &ldquo, of white blood cells were identified, allowing for the calculation of an MDS-likelihood score (MDS-LS), based on logistic regression. Automatic calculation of the MDS-LS is easily implementable on the middleware system of the DxH 800 to generate a flag for blood smear review, and possibly early detection of MDS patients in the general population.

The bone marrow (BM) microenvironment plays a crucial role in the development and progression of leukemia (AML). Intracellular reactive oxygen species (ROS) are involved in the regulation of the biology of leukemia-initiating cells, where the antioxidant enzyme GPx-3 could be involved as a determinant of cellular self-renewal. Little is known however about the role of the microenvironment in the control of the oxidative metabolism of AML cells. In the present study, a coculture model of BM mesenchymal stromal cells (MSCs) and AML cells (KG1a cell-line and primary BM blasts) was used to explore this metabolic pathway. MSC-contact, rather than culture with MSC-conditioned medium, decreases ROS levels and inhibits the Nrf-2 pathway through overexpression of GPx3 in AML cells. The decrease of ROS levels also inactivates p38MAPK and reduces the proliferation of AML cells. Conversely, contact with AML cells modifies MSCs in that they display an increased oxidative stress and Nrf-2 activation, together with a concomitant lowered expression of GPx-3. Altogether, these experiments suggest that a reciprocal control of oxidative metabolism is initiated by direct cell&ndash, cell contact between MSCs and AML cells. GPx-3 expression appears to play a crucial role in this cross-talk and could be involved in the regulation of leukemogenesis.

Clonal hematopoiesis (CH) of indeterminate potential has been described in blood samples from large series of patients. Its prevalence and consequences are still not well understood because sequencing methods vary and because most studies were performed in cohorts comprising individuals with nonhematologic diseases. Here, we investigated the frequency of CH in 82 paired bone marrow and blood samples from carefully selected healthy adult volunteers. Forty-one genes known to be mutated in myeloid malignancies were sequenced with a 1% threshold of detection. In bone marrow samples, clones were found in almost 40% of healthy volunteers more than 50 years old. The most frequent mutations were found in DNMT3A and TET2, with 1 individual carrying 3 variants. Variant allele frequencies were highly concordant between blood and bone marrow samples. Blood parameters were normal except for those in 2 individuals: 1 had a mild macrocytosis and 1 had a mild thrombocytosis. Furthermore, no morphologic abnormalities or dysplasia were detected when bone marrow smears were carefully evaluated. Individuals with CH differed from others by age (62.8 vs 38.6 years; P < .0001) and platelet count (294 vs 241 ×109/L; P = .0208), the latter being no more significant when removing the 2 individuals who carried the JAK2 p.V617F mutation. These results confirm that CH is a very common condition in healthy adults over 50 years old. Consequently, the detection of driver myeloid mutations should be interpreted with caution in the absence of cytologic abnormalities in the blood and/or the bone marrow.

INTRODUCTION Cytokines are involved in many processes, including hematopoiesis and inflammation. Aging is associated with the onset of clonal hematopoiesis (CH) of indeterminate potential, putatively associated with a higher risk of progression to hematological malignancies such as myelodysplastic syndromes or acute myeloid leukemia. Moreover, CH may participate to create a pro-inflammatory environment contributing to the pathogenesis of age-related diseases, such as cardiovascular diseases. This is likely to be driven by or translated in changes in bone marrow (BM) and/or peripheral blood (PB) soluble factors for which reference values still remain unclear, because BM cytokines levels have never been determined in strictly selected healthy people. Indeed, control BM samples classically used in studies are from subjects undergoing surgeries for non-hematologic causes, such as total hip replacement or cardiac surgery, patients suffering from immune thrombocytopenic purpura, brain death patients or allogeneic BM donors. In this study, the BM and PB plasma concentrations of 49 hematopoietic and inflammatory cytokines were measured in a representative panel of 94 healthy adult volunteers and the results were analyzed considering their age and presence of CH. METHOD Ninety-four healthy donors aged from 18.6 to 80.1 years old (yo), including 58 women were recruited for this study (HEALTHOX protocol, CPP Tours, AFSSAPS identifier ID-RCB: 2016-A00571-50 and ClinicalTrials.gov # NCT02789839). The presence or absence of CH (>1% of variant allele frequency) in this cohort is already known (Guermouche H, Ravalet N et al, Blood Adv 2020;4(15):3550-3557). BM samples were obtained through sternal aspiration using a classical procedure in France, and PB sampling was performed at the same time by venipuncture. Samples were collected on sodium heparin or EDTA, centrifuged twice (1200 g, 10 min, 20 C°), aliquoted and stored at -80°C. A 48-plex human cytokine panel assay was used to quantify 48 human cytokines in PB and BM plasmas [beta-NGF, CCL2, CCL3, CCL4, CCL5, CCL7, CCL11, CCL27, CLEC11A, CXCL1, CXCL8, CXCL9, CXCL10, CXCL12, FGF-2, G-CSF, GM-CSF, HGF, IFN-alpha-2, IFN-gamma, IL-1 alpha, IL-1 beta, IL-1ra, IL-2, IL-2-RA, IL-3, IL-4, IL-5, IL-6, IL-7, IL-9, IL-10, IL-12, IL-12B, IL-13, IL-15, IL-16, IL-17A, IL-18, KITLG, LIF, LT-alpha, M-CSF, MIF, PDGF subunit B, TNF, TNFSF10, VEGF-A]. MIF and FLT3L quantification were performed by ELISA. Regarding CH, the controls were subjects older than 50 yo without CH. Statistical analyses were performed with the R (3.6.3) and Rstudio version 1.2.5042 (www.rstudio.org) software. Comparisons were computed by Wilcoxon and Kruskal-Wallis tests. All pairwise multiple comparisons were performed using Dunn's-test for multiple comparisons of independent samples (PMCMR package). Correlations between cytokine levels in PB and BM were tested with Pearson and Spearman methods. Correlation matrices were plotted using the "corrplot" package. RESULTS CH was detected in 16 volunteers, mostly in individuals over 50 yo. BM and PB plasma samples were studied in 3 age-groups: 18-40, 40-60 and 60-80 yo. With aging, variations were observed for 18 BM cytokine levels, with 7 increasing (FLT3L, CXCL9, HGF, FGF-2, CCL27, IL-16, IL-18) and 8 decreasing (G-CSF, TNF, IL-2, IL-15, IL-17a, IL-4, LT-alpha, IL-1 alpha). In PB, 10 cytokines significantly increased with age (CXCL9, FLT3L, CCL27, CXCL10, HGF, CCL11, IL-16, IL-6, IL-1 beta, CCL2). CH was associated with significantly higher BM levels of MIF and IL-1 beta, lower BM levels of IL-9 and IL-5 and higher PB levels of IL-15, VEGF-A, IL-2, CXCL8, CXCL1 and G-CSF (Table). CONCLUSION In this study and for the first time, we concomitantly analyzed BM and PB concentrations of a panel of hematopoietic and inflammatory cytokines in a cohort of strictly selected healthy volunteers. In addition to the establishment of reference values, useful for various biological studies, and correlations between blood and BM levels, we identify variations in the BM of key cytokines according to age and CH. The differences in these cytokine concentrations, either as causes or as consequences, may shape both the BM microenvironment and hematopoietic processes, eventually leading to the beginning of age-related myeloid malignancies or inflammatory conditions. Figure 1 Figure 1. Disclosures Hirsch: Daiichi Sankyo Oncology: Consultancy; Novartis Pharma: Consultancy. Suner: Sanofi - Genzyme: Consultancy. Delhommeau: Celgene: Consultancy; BMS: Consultancy; Novartis: Consultancy.

Low reactive oxygen species (ROS) levels are well-established characteristics of mouse hematopoietic stem cells (HSCs). However, little is known about these levels in human HSCs. This study aimed at quantifying ROS levels in human CD34

Myelodysplastic syndromes (MDS) are a heterogeneous group of clonal stem cell disorders with an inherent tendency for transformation in secondary acute myeloid leukemia. This study focused on the redox metabolism of bone marrow (BM) cells from 97 patients compared with 25 healthy controls. The level of reactive oxygen species (ROS) was quantified by flow cytometry in BM cell subsets as well as the expression level of 28 transcripts encoding for major enzymes involved in the antioxidant cellular response. Our results highlight increased ROS levels in BM nonlymphoid cells and especially in primitive CD34posCD38low progenitor cells. Moreover, we identified a specific antioxidant signature, dubbed “antioxidogram,” for the different MDS subgroups or secondary acute myeloblastic leukemia (sAML). Our results suggest that progression from MDS toward sAML could be characterized by 3 successive molecular steps: (1) overexpression of enzymes reducing proteic disulfide bonds (MDS with

7517 Background: Clonal hematopoiesis of indeterminate potential (CHIP) has been described in blood samples from large series of patients. Its prevalence and consequences remain questioned because sequencing methods vary and because most studies were performed in cohorts of individuals suffering from non-hematological diseases (solid cancers, diabetes, cardiovascular or psychiatric diseases). CHIP has been described as a risk factor for blood cancer. However, the diagnosis of most blood cancers relies on morphologic and genetic examination of the bone marrow, and clonal hematopoiesis has never been evaluated in bone marrow samples from healthy individuals. Hence, it is not clear whether the current definition of CHIP is clinically relevant. To address this issue, we studied clonal hematopoiesis in paired peripheral blood and bone marrow samples from an unprecedented cohort of rigorously selected healthy volunteers. Methods: Here, we investigated the frequency of clonal hematopoiesis in 82 paired bone marrow and blood samples from carefully selected healthy adult volunteers (HEALTHOX clinical trial, ClinicalTrials.gov Identifier: NCT02789839). This study was approved by the ethics committees (CPP Tours and AFSSAPS identifier ID-RCB: 2011-A00262-39; CPP Ile-de-France III: 2753). Forty-one genes known to be mutated in myeloid malignancies were sequenced with a 1% threshold of detection. All variants were checked using IGV software v2.3. Statistical analyses were performed using Mann-Whitney, chi-squared, Fisher’s exact, Wilcoxon matched-pairs tests or Spearman correlation using GraphPad Prism 6. Results: In bone marrow samples, clones were found in almost 40 % of healthy volunteers over 50 years-old (yo). The most frequent mutations were found in DNMT3A (48%) and TET2 (28%) and the other mutations were found in ASXL1 (8%), JAK2 (8%), RAD21 (4%) and SRSF2 (4%) with one individual carrying three variants. Blood parameters and bone marrow smears were normal with the exception of two individuals with mild macrocytosis or thrombocytosis. Clonal hematopoiesis cases differed from others by age (62.8 vs. 38.6 years, P < .0001) and platelet count (294 vs. 241 G/L, P < .0208). Conclusions: These results confirm that clonal hematopoiesis is a very common condition in healthy adults over 50 years old. Consequently, the detection of driver myeloid mutations should be interpreted with caution in the absence of cytologic abnormalities in the blood and/or in the bone marrow.

Introduction Moderate anemia affects a substantial fraction of the elderly population and blood smear analysis can help to guide towards a diagnosis of myelodysplastic syndrome (MDS). Nevertheless, in medical laboratories, review of blood smear is realized only if there is quantitative or qualitative flag on the complete blood count (CBC). Consequently, the suspicion of MDS could be delayed because of the absence of systematic blood smear triggering, this smear being crucial to induce the diagnosis process by cytological analysis of bone marrow aspiration. The DxH 800 Hematology Analyzer measures and calculates 126 cytological parameters based on photometry, impedance or light scatter. These parameters regroup 23 standard CBC parameters and 103 unexploited "research parameters". The goal of our study was to create an original mathematical model using "research parameters" to determine a Suspicion Score of MDS which triggers blood smear examination and consequently the process of identification of subclinical patients suffering from MDS. Methods This study compared the 126 parameters measured by the Beckman-Coulter DxH 800 Hematology Analyzer from peripheral blood samples of MDS patients and healthy volunteers. MDS cohort was composed of 101 patients of the university hospital of Tours (9 MDS-SLD, 28 MDS-MLD, 8 MDS-RS-SLD, 8 MDS-RS-MLD, 20 MDS-EB-1, 19 MDS-EB-2, 9 5q-). The cohort of healthy volunteers included 88 aged-matched subjects from HEALTHOX and PLASMYC protocols (ClinicalTrials.gov # NCT02789839 and # NCT02809222, respectively). The "research parameters" contained Research Use Only (RUO) parameters and Cell Population Data (CPD). CPD were composed of 98 parameters measured by Volume Conductivity Scatter (VCS) module. The parameters derived from reticulocytes, which require a specific prescription, were excluded. Statistical analyses were performed using Rstudio version 1.0.153. The normal distribution of values was studied by Shapiro-Wilk tests (p-value0.05). Means comparisons were performed by Wilcoxon and Student tests. Principal component analysis (PCA) was performed using FactoMineR. The logarithmic logistic regression was done thanks to the glm() function of the stats package. The general linear model was obtained by using logistic regression with weighted parameters and was validated by split-sample strategy (10,000 repeats). Samples were divided into two groups ("learning" and "test" groups) randomly mixing MDS patients and healthy volunteers. The "learning" group (n=130) allowed to build the model and the "test" group (n=59) was used to validate it. Results After mono-parametric and multi-parametric comparisons, 10 parameters were selected to establish the model of interest according to the best contributions at the first axe of PCA, the best correlations at two first axes of PCA and the most significant p-values (parameters described in the Table: MN.LALS.NNRBC, MN.LMALS.NNRBC, MN.UMALS.NNRBC, SD.MALS.NE, SD.UMALS.NE, SD.V.NE, MN.MALS.NE, SD.AL2.NE, SD.AL2.MO, SD.V.MO ). In order to determine the Suspicion Score of MDS (SS-MDS), the 10 selected parameters were weighted during split sampling strategy by logistic regression. After repeat of 10,000 split-samples, the SS-MDS determined using weighted parameters was validated with average efficiency of 92.3%. For each parameter, the median of weighting coefficients was used in the mathematical model: "SS-MDS = ΣCi.Pi + intercept" with "Ci: weighting coefficient of parameter i" and "Pi: parameter i value". On the whole cohort, SS-MDS induced "MDS" flag for 11 MDS patients (red points in the Figures) for which conventional CBC algorithms failed to generate flag spreading peripheral blood smear. By fixing the threshold at -1.5, the sensitivity and specificity of SS-MDS were 100% and 92%, respectively. Moreover, the positive and negative predictive values were 93.5% and 100%, respectively. Conclusions The incidence of MDS increases with aging and the early diagnosis enables optimal care of these diseases. The Beckman-Coulter DxH 800 HematologyAnalyzer is widely used over the world. We propose in this study the clinical use of 10 unexploited "research parameters" to early detect subclinical MDS by selective triggering of blood smear examination. A prospective/multicentric study will allow the optimization of SS-MDS. Figure. Figure. Disclosures No relevant conflicts of interest to declare.