Hematopoietic Stem Cells (HSC) and Granulocyte Macrophage Progenitors (GMP) are the Oxidative Stress Targets in Low/Intermediate-1 Risk Myelodysplastic Syndromes

Author(s): Valentina Giai, Thea Bensi, Claudia Bertassello, Michela Savio, Dario Ferrero, Maria Matilde Ciriello, Marco Ladetto

Introduction: Myelodysplastic Syndromes (MDS) are a heterogenous group of clonal hematopoietic stem cell malignancies. Previous studies showed that Reactive Oxygen Species (ROS) play a role in the pathogenesis and clinical evolution of MDS, contributing to Hematopoietic Stem and Progenitor Cells (HSPC) genetic instability. Less is known about ROS levels in the various sub-populations of MDS HSPC and how they correlate with clinical data in MDS patients. Our study aims to analyze ROS levels in MDS Hematopoietic Stem Cells (HSC), common myeloid progenitors (CMP), Granulocyte Macrophages Progenitors (GMP) and megakaryocyte-erythrocyte progenitors (MEP); afterwards, we looked at the relationship between ROS levels and clinical data.

Methods: thirty-eight MDS and 27 Normal Bone Marrow (NBM) samples were collected; ROS levels were analyzed via multicolor flow cytometry.

Results: In both NBM and MDS, HSC showed much higher ROS levels than progenitors (3 to 4 folds, p < 0.0001); HSC ROS were significantly more elevated in MDS-no excess blasts versus MDS with excess blasts and versus NBM. GMP from MDS-no excess blasts showed higher ROS compared to NBM GMP. The 3 MDS with Ringed Sideroblasts (RS) showed more elevated ROS in HSC and GMP compared to the not RS low/intermediate-1 MDS; the 2 monosomy 7 patients displayed higher ROS levels in each subpopulation compared to the normal karyotype MDS; the only del(5q) patient did not show relevant differences in ROS levels compared to the median of the normal karyotype MDS ROS. The 9 high transfusion burden patients exhibited higher ROS in HSC and GMP compared to NBM HSC and GMP. These data were not confirmed in low transfusion burden (n:2) and non-transfused patients (n:26). In low/intermediate-1 MDS, a direct correlation between ferritin values and ROS levels in progenitors, but not in HSC, was detected. Interestingly, low/intermediate-1 risk patients that

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