UOS Milan Unit, Istituto di Ricerca Genetica e Biomedica (IRGB), CNR, Milan, Italy.
Humanitas Clinical and Research Center - IRCCS, Rozzano, Italy.
Haematologica. 2019 Sep;104(9):1744-1755. doi: 10.3324/haematol.2018.198499. Epub 2019 Feb 21.
The balance between self-renewal and differentiation is crucial to ensure the homeostasis of the hematopoietic system, and is a hallmark of hematopoietic stem cells. However, the underlying molecular pathways, including the role of micro-RNA, are not completely understood. To assess the contribution of micro-RNA, we performed micro-RNA profiling of hematopoietic stem cells and their immediate downstream progeny multi-potent progenitors from wild-type control and Pbx1-conditional knockout mice, whose stem cells display a profound self-renewal defect. Unsupervised hierarchical cluster analysis separated stem cells from multi-potent progenitors, suggesting that micro-RNA might regulate the first transition step in the adult hematopoietic development. Notably, Pbx1-deficient and wild-type cells clustered separately, linking micro-RNAs to self-renewal impairment. Differential expression analysis of micro-RNA in the physiological stem cell-to-multi-potent progenitor transition and in Pbx1-deficient stem cells compared to control stem cells revealed miR-127-3p as the most differentially expressed. Furthermore, miR-127-3p was strongly stem cell-specific, being quickly down-regulated upon differentiation and not re-expressed further downstream in the bone marrow hematopoietic hierarchy. Inhibition of miR-127-3p function in Lineage-negative cells, achieved through a lentiviral-sponge vector, led to severe stem cell depletion, as assessed with serial transplantation assays. miR-127-3p-sponged stem cells displayed accelerated differentiation, which was uncoupled from proliferation, accounting for the observed stem cell reduction. miR-127-3p overexpression in Lineage-negative cells did not alter stem cell pool size, but gave rise to lymphopenia, likely due to lack of miR-127-3p physiological downregulation beyond the stem cell stage. Thus, tight regulation of miR-127-3p is crucial to preserve the self-renewing stem cell pool and homeostasis of the hematopoietic system.
自我更新和分化之间的平衡对于确保造血系统的内稳态至关重要，这也是造血干细胞的标志。然而，其潜在的分子途径，包括 microRNA 的作用，尚未完全了解。为了评估 microRNA 的作用，我们对来自野生型对照和 Pbx1 条件性敲除小鼠的造血干细胞及其直接下游祖细胞多能祖细胞进行了 microRNA 谱分析，这些小鼠的干细胞表现出明显的自我更新缺陷。无监督层次聚类分析将干细胞与多能祖细胞分开，表明 microRNA 可能调节成人造血发育的第一步。值得注意的是，Pbx1 缺失和野生型细胞分别聚类，将 microRNA 与自我更新受损联系起来。与对照组干细胞相比，在生理干细胞向多能祖细胞的过渡以及 Pbx1 缺失的干细胞中，microRNA 的差异表达分析显示 miR-127-3p 的表达差异最大。此外，miR-127-3p 具有很强的干细胞特异性，在分化时迅速下调，并且在骨髓造血层次结构中进一步下游不再表达。通过慢病毒海绵载体抑制 Lineage-negative 细胞中的 miR-127-3p 功能，通过连续移植实验评估导致严重的干细胞耗竭。miR-127-3p 海绵化的干细胞显示出加速分化，与增殖脱耦联，这解释了观察到的干细胞减少。Lineage-negative 细胞中的 miR-127-3p 过表达不会改变干细胞池的大小，但会导致淋巴细胞减少，可能是由于 miR-127-3p 缺乏生理下调超出干细胞阶段所致。因此，miR-127-3p 的紧密调控对于维持自我更新的干细胞池和造血系统的内稳态至关重要。
