Inflammatory signals from fatty bone marrow support DNMT3a-driven clonal hematopoiesis (Dnmt3A KI heterozygote subset). Inflammatory signals from fatty bone marrow support DNMT3a-driven clonal hematopoiesis (Dnmt3A KI heterozygote subset)

Accumulation of fatty bone marrow (FBM) is one of the key age related changes possibly influencing the blood system. While a link between obesity and cancer evolution has been reported it remains unknown whether FBM can modify the evolution of the early stages of leukemia and clonal hematopoiesis (CH). To address this question, we established different FBM mouse models in immunodeficient mice in whom we can study both mouse and human cells. We focused our studies on two FBM models: 1) after sublethal irradiation; 2) after castration; and in both we used an adipogenesis inhibitor as a control (PPARγ inhibitor). We transplanted both human and mice hematopoietic stem cells (HSCs) carrying DNMT3A mutations into immunodeficient mice with FBM. A significant increase in self-renewal was found when DNMT3AMut-HSCs were exposed to FBM. To better understand the mechanisms of the FBM-CH interaction, we performed single cell RNA-sequencing on HSPCs after FBM exposure in vivo. A 6-10 fold increase in DNMT3AMut-HSCs was observed under FBM conditions in comparison to normal bone marrow. Mutated HSCs from mice exposed to FBM exhibited an activated inflammatory signaling (IL-6 and IFNγ). Cytokine analysis of BM fluid and BM derived adipocytes grown in vitro demonstrated increased IL-6 levels under FBM conditions. Anti-IL-6 neutralizing antibodies significantly reduced the selective advantage of mice derived DNMT3AMut-HSCs exposed to FBM. Overall, paracrine FBM inflammatory signals promote DNMT3A-driven clonal hematopoiesis, which can be inhibited by blocking the IL-6 receptor.

脂肪骨髓（fatty bone marrow, FBM）蓄积是与年龄相关的关键改变之一，可能对血液系统产生影响。尽管已有研究报道肥胖与肿瘤发生发展存在关联，但目前尚不清楚FBM是否能够影响白血病及克隆性造血（clonal hematopoiesis, CH）的早期进程。为解答这一科学问题，我们在免疫缺陷小鼠中构建了多种FBM小鼠模型，可同时研究小鼠及人类细胞。本研究聚焦于两种FBM模型：1）亚致死剂量照射造模；2）去势造模；且两组均采用脂肪生成抑制剂（PPARγ抑制剂）作为对照。我们将携带DNMT3A突变的人类及小鼠造血干细胞（hematopoietic stem cells, HSCs）移植至构建了FBM的免疫缺陷小鼠体内。当DNMT3A突变型造血干细胞（DNMT3AMut-HSCs）暴露于FBM环境时，其自我更新能力显著增强。为进一步阐明FBM与克隆性造血的相互作用机制，我们对体内暴露于FBM环境的造血干祖细胞（hematopoietic stem and progenitor cells, HSPCs）进行了单细胞RNA测序。与正常骨髓环境相比，FBM环境下DNMT3AMut-HSCs的数量增加了6~10倍。暴露于FBM环境的小鼠体内的突变型造血干细胞，表现出炎症信号通路的激活，涉及白细胞介素6（interleukin-6, IL-6）及干扰素γ（interferon-γ, IFNγ）通路。对骨髓液及体外培养的骨髓源性脂肪细胞进行细胞因子分析后发现，FBM环境下IL-6的表达水平显著升高。抗IL-6中和抗体可显著降低暴露于FBM环境的小鼠源性DNMT3AMut-HSCs的选择优势。综上，FBM通过旁分泌炎性信号促进DNMT3A驱动的克隆性造血，该过程可通过阻断IL-6受体予以抑制。