Table_1_Multiple Myeloma-Derived Extracellular Vesicles Impair Normal Hematopoiesis by Acting on Hematopoietic Stem and Progenitor Cells.DOCX

Multiple myeloma (MM) is characterized by the abnormal proliferation of clonal plasma cells (PCs) in bone marrow (BM). MM-PCs progressively occupy and likely alter BM niches where reside hematopoietic stem and progenitor cells (HSPCs) whose viability, self-renewal, proliferation, commitment, and differentiation are essential for normal hematopoiesis. Extracellular vesicles (EVs) are particles released by normal and neoplastic cells, such as MM cells. They are important cell-to-cell communicators able to modify the phenotype, genotype, and the fate of the recipient cells. Investigation of mechanisms and mediators underlying HSPC-MM-PC crosstalk is warranted to better understand the MM hematopoietic impairment and for the identification of novel therapeutic strategies against this incurable malignancy. This study is aimed to evaluate whether EVs released by MM-PCs interact with HSPCs, what effects they exert, and the underlying mechanisms involved. Therefore, we investigated the viability, cell cycle, phenotype, clonogenicity, and microRNA profile of HSPCs exposed to MM cell line-released EVs (MM-EVs). Our data showed that: (i) MM cells released a heterogeneous population of EVs; (ii) MM-EVs caused a dose-dependent reduction of HSPCs viability; (iii) MM-EVs caused a redistribution of the HSPC pool characterized by a significant increase in the frequency of stem and early precursors accompanied by a reduction of late precursor cells, such as common myeloid progenitors (CMPs), megakaryocyte erythroid progenitors (MEPs), B and NK progenitors, and a slight increase of granulocyte macrophage progenitors (GMPs); (iv) MM-EVs caused an increase of stem and early precursors in S phase with a decreased number of cells in G0/G1 phase in a dose-dependent manner; (v) MM-EVs reduced the HSPC colony formation; and (vi) MM-EVs caused an increased expression level of C-X-C motif chemokine receptor type 4 (CXCR4) and activation of miRNAs. In conclusion, MM cells through the release of EVs, by acting directly on normal HSPCs, negatively dysregulate normal hematopoiesis, and this could have important therapeutic implications.

多发性骨髓瘤（MM）以骨髓（BM）中克隆性浆细胞（PCs）的异常增殖为特征。MM-PCs逐渐占据并可能改变骨髓微环境，其中居住着造血干细胞和祖细胞（HSPCs），其生存能力、自我更新、增殖、分化及命运决定对于正常的造血至关重要。细胞外囊泡（EVs）是由正常和肿瘤细胞，如MM细胞释放的颗粒。它们是重要的细胞间通讯分子，能够改变受体的表型、基因型和命运。研究HSPC-MM-PC间通讯的机制和介质，对于更好地理解MM的造血损伤以及识别针对这种不可治愈的恶性肿瘤的新疗法具有重要意义。本研究旨在评估MM-PCs释放的EVs是否与HSPCs相互作用，它们产生何种效应，以及涉及的潜在机制。因此，我们研究了暴露于MM细胞系释放的EVs（MM-EVs）的HSPCs的生存能力、细胞周期、表型、克隆性和miRNA谱。我们的数据显示：(i) MM细胞释放了异质性的EVs种群；(ii) MM-EVs导致HSPCs生存能力剂量依赖性下降；(iii) MM-EVs导致HSPC库的重新分布，表现为干细胞和早期前体细胞的频率显著增加，而晚期前体细胞，如常见髓系祖细胞（CMPs）、巨核细胞红系祖细胞（MEPs）、B和NK祖细胞减少，以及粒系巨噬细胞祖细胞（GMPs）的轻微增加；(iv) MM-EVs导致干细胞和早期前体细胞在S期增加，而在G0/G1期的细胞数量剂量依赖性减少；(v) MM-EVs减少了HSPC的集落形成；(vi) MM-EVs导致C-X-C基序趋化因子受体4（CXCR4）表达水平增加和miRNAs的激活。总之，MM细胞通过释放EVs，通过直接作用于正常的HSPCs，负向失调正常的造血过程，这可能具有重要的治疗意义。