Altered microRNA expression links IL6 and TNF-induced inflammaging with myeloid malignancy [miR146aKO_LSK_WGBS]

Aging is associated with significant changes in the hematopoietic system, including increased inflammation, impaired hematopoietic stem cell (HSC) function, and increased incidence of myeloid malignancy. Inflammation of aging (“inflammaging”) has been proposed as a driver of age-related changes in HSC function and myeloid malignancy, but mechanisms linking these phenomena remain poorly defined. Here, we identify loss of miR-146a as driving aging-associated inflammation in AML patients. miR-146a expression declined in old wild-type mice, and loss of miR-146a promoted premature HSC aging and inflammation in young miR-146a-null mice, preceding development of aging-associated myeloid malignancy. Using single-cell assays of HSC quiescence, stemness, differentiation potential, and epigenetic state to probe HSC function and population structure, we found that loss of miR-146a depleted a subpopulation of primitive, quiescent HSCs. DNA methylation and transcriptome profiling implicated NF-κB, IL6, and TNF as potential drivers of HSC dysfunction, activating an inflammatory signaling relay promoting IL6 and TNF secretion from mature miR-146a-/- myeloid and lymphoid cells. Reducing inflammation by targeting Il6 or Tnf was sufficient to restore single-cell measures of miR-146a-/- HSC function and subpopulation structure, and reduced the incidence of hematological malignancy in miR 146a-/- mice. miR-146a-/- HSCs exhibited enhanced sensitivity to IL6 stimulation, indicating that loss of miR-146a affects HSC function via both cell-extrinsic inflammatory signals and increased cell-intrinsic sensitivity to inflammation. Thus, loss of miR 146a regulates cell-extrinsic and -intrinsic mechanisms linking HSC inflammaging to the development of myeloid malignancy.

衰老与造血系统的显著改变密切相关，包括炎症水平升高、造血干细胞（HSC）功能受损以及髓系恶性肿瘤发病率上升。衰老相关炎症（inflammaging）被认为是驱动造血干细胞功能衰老相关改变及髓系恶性肿瘤发生的关键因素，但连接这些现象的具体机制仍未明确。本研究发现，微小RNA146a（miR-146a）的缺失会驱动急性髓系白血病（AML）患者的衰老相关炎症。老年野生型小鼠体内的miR-146a表达水平显著下降，而在年轻的miR-146a缺失小鼠中，miR-146a的缺失会促进造血干细胞过早衰老与炎症反应，且该现象早于衰老相关髓系恶性肿瘤的发生。通过针对造血干细胞静息状态、干细胞干性、分化潜能及表观遗传状态的单细胞检测技术探究造血干细胞功能与群体结构，我们发现miR-146a的缺失会耗竭原始静息态造血干细胞亚群。DNA甲基化与转录组分析显示，核因子κB（NF-κB）、白细胞介素6（IL6）及肿瘤坏死因子（TNF）可能是造血干细胞功能异常的驱动因子，其激活的炎症信号通路可促进成熟的miR-146a缺失髓系与淋巴样细胞分泌IL6与TNF。通过靶向Il6或Tnf减轻炎症反应，足以恢复miR-146a缺失小鼠造血干细胞的单细胞功能检测指标与亚群结构，并降低该类小鼠血液系统恶性肿瘤的发病率。miR-146a缺失的造血干细胞对IL6刺激的敏感性增强，这表明miR-146a的缺失可通过细胞外源性炎症信号及细胞内源性炎症敏感性升高这两种途径影响造血干细胞功能。综上，miR-146a的缺失通过调控细胞外源性与内源性机制，将造血干细胞的炎症衰老与髓系恶性肿瘤的发生联系起来。