BACKGROUND MicroRNA (miR)-containing exosomes released by acute myeloid leukemia (AML) cells can be delivered into hematopoietic progenitor cells to suppress normal hematopoiesis. Herein, our study was performed to evaluate the effect of exosomal miR-4532 secreted by AML cells on hematopoiesis of hematopoietic stem cells. METHODS Firstly, differentially expressed miRs related to AML were identified using microarray analysis. Subsequently, AML cell lines were collected, and CD34+ HSCs were isolated from healthy pregnant women. Then, miR-4532 expression was measured in AML cells and AML cell-derived exosomes and CD34+ HSCs, together with evaluation of the targeting relationship between miR-4532 and LDOC1. Then, AML cells were treated with miR-4532 inhibitor, and exosomes were separated from AML cells and co-cultured with CD34+ HSCs. Gain- and loss-function approaches were employed in CD34+ HSCs. Colony-forming units (CFU) and expression of dickkopf-1 (DKK1), a hematopoietic inhibiting factor associated with pathogenesis of AML, were determined in CD34+ HSCs, as well as the extents of JAK2 and STAT3 phosphorylation and LDOC1 expression. RESULTS miR-4532 was found to be upregulated in AML cells and AML cell-derived exosomes, while being downregulated in CD34+ HSCs. In addition, exosomes released by AML cells targeted CD34+ HSCs to decrease the expression of CFU and increase the expression of DKK1. miR-4532 was delivered into CD34+ HSCs to target LDOC1 via AML cell-released exosomes. AML cell-derived exosomes containing miR-4532 inhibitor increased CFU but reduced DKK1 in CD34+ HSCs. Inhibition of miR-4532 or JAK2, or ectopic expression of LDOC1 upregulated CFU and downregulated DKK1 expression as well as the extents of JAK2 and STAT3 phosphorylation in CD34+ HSCs. CONCLUSION In conclusion, AML cell-derived exosomes carrying miR-4532 repress normal HSC hematopoiesis via activation of the LDOC1-dependent STAT3 signaling pathway.

中文翻译：

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急性髓细胞性白血病细胞通过激活LDOC1依赖性STAT3信号通路，分泌含microRNA-4532的外来体来介导造血干细胞中的正常造血作用。

背景技术由急性髓细胞性白血病（AML）细胞释放的含MicroRNA（miR）的外来体可以被递送到造血祖细胞中以抑制正常的造血作用。本文中，我们的研究是为了评估AML细胞分泌的外泌体miR-4532对造血干细胞的造血作用的影响。方法首先，使用微阵列分析鉴定与AML相关的差异表达miR。随后，收集AML细胞系，并从健康孕妇中分离出CD34 + HSC。然后，在AML细胞和AML细胞来源的外来体以及CD34 + HSC中测量了miR-4532的表达，并评估了miR-4532和LDOC1之间的靶向关系。然后，用miR-4532抑制剂处理AML细胞，将外泌体从AML细胞中分离出来，并与CD34 + HSCs共培养。在CD34 + HSC中采用了增益和损失函数方法。在CD34 + HSC中测定了菌落形成单位（CFU）和与AML发病相关的造血抑制因子dickkopf-1（DKK1）的表达，以及JAK2和STAT3磷酸化的程度以及LDOC1的表达。结果发现miR-4532在AML细胞和AML细胞来源的外来体中被上调，而在CD34 + HSC中被下调。此外，AML细胞释放的外泌体靶向CD34 + HSC，从而降低CFU的表达并增加DKK1的表达。miR-4532通过AML细胞释放的外泌体被递送到CD34 + HSC中以靶向LDOC1。包含miR-4532抑制剂的AML细胞来源的外来体增加了CD34 + HSC中的CFU，但减少了DKK1。抑制miR-4532或JAK2，CD34 + HSCs中LDOC1的异位表达或上调CFU和DKK1的表达以及JAK2和STAT3磷酸化的程度。结论总之，携带miR-4532的AML细胞来源的外来体通过激活LDOC1依赖性STAT3信号通路抑制正常的HSC造血作用。