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Hematopoiesis
Prospective isolation of radiation induced erythroid stress progenitors reveals unique transcriptomic and epigenetic signatures enabling increased erythroid output
Ferrata Storti Foundation
Haematologica 2020 Volume 105(11):2561-2571
Sofie Singbrant,1 Alexander Mattebo,1 Mikael Sigvardsson,2 Tobias Strid2 and Johan Flygare1
1Division of Molecular Medicine and Gene Therapy, Lund Stem Cell Center, Lund University and 2Division of Molecular Hematology, Lund Stem Cell Center, Lund University, Lund, Sweden
ABSTRACT
Massive expansion of erythroid progenitor cells is essential for sur- viving anemic stress. Research towards understanding this critical process, referred to as stress-erythropoiesis, has been hampered due to the lack of specific marker-combinations enabling analysis of the dis- tinct stress-progenitor cells capable of providing radioprotection and enhanced red blood cell production. Here we present a method for the pre- cise identification and in vivo validation of progenitor cells contributing to both steady-state and stress-erythropoiesis, enabling for the first time in- depth molecular characterization of these cells. Differential expression of surface markers CD150, CD9 and Sca1 defines a hierarchy of splenic stress- progenitors during irradiation-induced stress recovery in mice, and provides high-purity isolation of the functional stress erythroid burst-forming-units (stress-BFU-E) with a 100-fold improved enrichment compared to the state- of-the-art. By transplanting purified stress-progenitors expressing the fluo- rescent protein Kusabira Orange, we determined their kinetics in vivo and demonstrated that CD150+CD9+Sca1– stress-BFU-E provide a massive but transient radioprotective erythroid wave, followed by multi-lineage recon- stitution from CD150+CD9+Sca1+ multi-potent stem/progenitor cells. Whole genome transcriptional analysis revealed that stress-BFU-E express gene sig- natures more associated with erythropoiesis and proliferation compared to steady-state BFU-E, and are bone morphogenetic protein 4-responsive. Evaluation of chromatin accessibility through ATAC sequencing reveals enhanced and differential accessibility to binding sites of the chromatin- looping transcription factor CTCF in stress-BFU-E compared to steady-state BFU-E. Our findings offer a molecular insight into the unique capacity of stress-BFU-E to rapidly form erythroid cells in response to anemia and con- stitute an important step towards identifying novel erythropoiesis stimulat- ing agents.
Introduction
Steady-state erythropoiesis is regulated mainly by changes in erythropoietin (EPO) levels that fine-tune survival and proliferation of erythroid colony-forming- units (CFU-E) and downstream precursor cells. In contrast, acute anemia induces a broader physiological response referred to as stress-erythropoiesis, which involves stimulation also of earlier progenitors to further increase the out-put of erythro- cytes. This process is less characterized and mainly occurs in the murine spleen1 after seeding of progenitors from the bone marrow (BM).2,3 Stress-erythropoiesis is differentially regulated, including increased responsiveness to additional factors like hypoxia, corticosteroids and bone morphogenetic protein 4 (BMP4).1,4-7 Importantly, stress-erythroid progenitors have the capacity to generate larger num- bers of red blood cells than steady-state progenitors, and precise identification and enhanced understanding of their regulation are important steps towards discovering potential new erythroid-enhancing drugs for anemia treatment.
Correspondence:
JOHAN FLYGARE
johan.flygare@med.lu.se
SOFIE SINGBRANT
sofie.singbrant@med.lu.se
Received: August 14, 2019. Accepted: January 2, 2020. Pre-published: January 9, 2020.
doi:10.3324/haematol.2019.234542 ©2020 Ferrata Storti Foundation
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haematologica | 2020; 105(11)
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