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Thrombopoietin metabolically primes hematopoietic stem cells to megakaryocyte lineage differentiation

ABSTRACT: During acute myelosuppression or thrombocytopenia, bone marrow (BM) hematopoietic cells respond rapidly to replenish peripheral blood platelets. While the cytokine Thrombopoietin (Thpo) concomitantly regulates platelet production and maintains HSC stem cell potential whether Thpo directly controls Mk-lineage differentiation of HSCs is unclear. Stress hematopoiesis requires quiescent HSCs to proliferate, a process which depends on a higher energy production. However, whether this switch of metabolic state relates to lineage differentiation of HSCs is not known. We here show that Thpo rapidly upregulates mitochondrial activity in HSCs which was accompanied by preferential differentiation to Mk-lineage. During unperturbed hematopoiesis, HSCs with high mitochondrial content and activity exhibit Mk-lineage biased differentiation. Furthermore, Thpo rapidly skewed HSCs to express a tetraspanin molecule, CD9, which expression correlated to mitochondria cell content. While highly proliferative, mitochondrial-rich HSCs were resistant to apoptosis and oxidative stress upon Thpo stimulation. Thpo regulated mitochondrial activity did not associate with high levels of cMpl expression but was influenced by non-nuclear mitochondrial translocation of phosphorylated of STAT3 at serine 727. Our data reveals that HSCs are metabolically heterogeneous and higher mitochondrial activity primes HSCs toward the Mk lineage differentiation. We also uncover a pivotal role of Thpo in regulating the rapid Mk-lineage commitment during stress hematopoiesis. Our findings suggest that mitochondria metabolism primes HSCs not only to exit dormancy but toward direct differentiation to Mk lineage.

ORGANISM(S): Mus musculus

PROVIDER: GSE121001 | GEO | 2018/12/31

REPOSITORIES: GEO

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Project description:Hematopoietic stem cells (HSCs) with certain somatic mutations, most commonly in the DNA methyltransferase DNMT3A, gain a clonal growth advantage leading to the development of clonal hematopoiesis (CH). The distinct functional differences that allow DNMT3A-mutant HSCs to gain a fitness advantage and outcompete wild-type HSC in the context of aging are not fully elucidated. We recently discovered that HSC aging is initiated by decline in local production of insulin-like growth factor 1 (IGF1). Here, we used a mouse model of DNMT3A-mutant CH (Dnmt3aR878H/+) to investigate the extent to which decline in IGF1 alters the selective advantage of Dnmt3aR878H/+ HSCs. Upon transplant into IGF1-deficient recipient mice, Dnmt3aR878H/+ HSCs gained enhanced selective advantage over wild-type HSCs and maintained lineage balanced blood production. As IGF1/mTOR signaling is well understood to regulate energy metabolism, we investigated underlying metabolic differences between Dnmt3aR878H/+ and wild-type HSCs. Dnmt3aR878H/+ HSPCs had similar glycolytic capacity as wild-type HSCs but enhanced mitochondrial reserve capacity and mitochondrial activation potential. To evaluate whether mitochondrial function is a targetable dependency of Dnmt3aR878H/+ HSCs, we administered the mitochondrial-targeted molecule MitoQ resulting in the depletion of their mitochondrial reserve capacity. We find that MitoQ reduces the competitive advantage of Dnmt3aR878H/+ hematopoiesis. To identify the mechanism(s) by which MitoQ alters Dnmt3aR878H/+ phenotypic expansion we evaluated transcriptional changes after MitoQ treatment and find altered response to Igf1/mTOR signaling compared to wild-type HSC. The altered response to Igf1/mTOR signaling in part mediates the Dnmt3aR878H/+ hematopoietic selective advantage. Taken together, our work supports that mitochondrial metabolic regulation is a key mechanism by which DNMT3A-mutant HSCs gain a selective advantage. Targeting this mechanism may maintain polyclonal hematopoiesis during aging and reduce the risk of CH-associated disease.

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Thrombopoietin metabolically primes hematopoietic stem cells to megakaryocyte lineage differentiation

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