急性髓系白血病细胞通过外泌体递送GDF15调控骨髓脂肪细胞重塑的机制研究

As an important component of bone marrow microenvironment, adipocytes play an important role in the occurrence and development of leukemia, but little is known about how they are domesticated by leukemia cells. We are the first to find that acute myeloid leukemia (AML) cells regulate the remodeling of bone marrow adipocytes by secreting GDF15. How does GDF15 enter adipocytes as an exogenous factor? Based on the high expression of GDF15 in AML exosomes, we proposed the hypothesis that GDF15 regulates bone marrow adipocyte remodeling through exosomes. In adipocyte culture system, exosomes was combined with protease K blockade experiment to clarify the role of exosomes in adipocyte remodeling through the morphological and functional change of adipocytes. GDF15 gene was further knocked out in AML cells, GDF15 inhibition experiment was used to clarify the role of exosomes in regulating adipocyte remodeling by GDF15. RNA-sequence and gene silencing were used in adipocytes. The target gene and downstream signaling pathway of GDF15 regulating remodeling were identified in adipocytes. Finally, we will verify the results in clinical samples. This project will reveal the molecular mechanism of GDF15 regulating bone marrow adipocyte remodeling from a new perspective of exosomes, and provide new ideas for the treatment of AML.

脂肪细胞作为骨髓微环境的重要组分对白血病的发生发展至关重要，但其如何被白血病细胞驯化以利于后者的生长却知之甚少。我们率先发现急性髓系白血病（AML）细胞通过分泌GDF15调控骨髓脂肪细胞的重塑。而GDF15作为外源性因子如何进入脂肪细胞发挥作用呢？我们在前期发现AML细胞外泌体高表达GDF15的基础上，提出“GDF15通过外泌体转运调控骨髓脂肪细胞重塑”的假说。拟在脂肪细胞培养体系中，将外泌体转运与蛋白酶K阻断实验相结合，通过细胞形态及功能的改变明确外泌体在重塑中的作用；进一步将AML细胞中GDF15基因敲除，通过GDF15抑制实验明确外泌体在GDF15调控脂肪细胞重塑中的作用；在脂肪细胞中通过RNA-seq及基因沉默实验明确GDF15调控重塑的靶基因及下游信号通路，并在临床样本中加以验证。本课题将从外泌体转运的新角度揭示GDF15调控骨髓脂肪细胞重塑的分子机制，为AML的治疗提供新思路。

脂肪细胞作为骨髓微环境中的重要组成成分，通过供能促进白血病细胞生长。我们前期发现急性髓系白血病（AML）患者骨髓脂肪细胞形态重塑与其不良预后密切相关，而生长分化因子15（GDF15）可能是导致这一异常现象的关键分子。然而，目前尚不清楚白血病细胞分泌的GDF15是如何重塑骨髓脂肪细胞。已报道，Ca2+通道在调控脂肪细胞重塑的过程中发挥重要作用，而瞬时受体电位（TRPV4）是调控脂肪细胞能量平衡的重要分子。因此，我们猜测GDF15可能通过调节TRPV4通道调控AML骨髓脂肪细胞重塑。本研究在临床样本中验证了AML骨髓脂肪细胞可重塑为纤维样细胞，通过体内外研究发现骨髓脂肪细胞高表达TRPV4，且抑制TRPV4能够促进骨髓脂肪细胞的脂解，释放更多的游离脂肪酸；白血病细胞分泌的GDF15能够抑制脂肪细胞TRPV4的表达，促进脂肪细胞脂解，GDF15中和抗体能够逆转这种改变；通过生信分析数据库，发现CRHBP是AML潜在的不良预后分子，且可能参与AML的免疫应答。进一步分析显示其与TRPV4的表达呈显著负相关。另外，通过对 TCGA 公共数据库的分析发现，IL-6 受体高表达的AML患者脂代谢通路明显上调，相关系数分析结果显示IL-6参与脂质的转运。由此，我们得出白血病细胞通过外泌体递送GDF15下调骨髓脂肪细胞TRPV4的表达，促进骨髓脂肪细胞脂解进而重塑。CRHBP可能在AML免疫逃逸中发挥重要作用，CRHBP可作为AML的预后生物标志物和潜在的治疗靶点。