mDia1调控MDS造血干细胞老化的机制研究

Myelodysplastic syndrome(MDS)is a clonal hematopoietic stem cell(HSC)originated malignancy. It is characterized by abnormal hematopoiesis, more apoptosis and genetic instability and has a high risk to transform to leukemia. Due to lack of ideal animal model, the investigation of the biological properties and mechanism of malignant transformation of MDS HSCs has became the "bottle neck" in MDS research. So far, no effective therapy has been development for treatment of human MDS. Our group previously has shown that mice deficient for mammalian diaphanous-related formin 1(mDia1) develop a disease that closely resembles human MDS. The mDia1 deficient MDS HSCs exibit properties of aged HSCs, including lineage shewing towards myeloid, diminished self-renewal repopulation capacity,exsausted HSCs with increased entering of G1 phase of cell cycle and apoptosis but non-productive in peripheral blood. In this proposal, we will investigate the effect of mDia1 deficiency on HSCs aging by evaluating the expression of biomarkers of HSC aging and utilizing high-throughput RNA sequencing to analyze the transcriptome of MDS HSCs. In addition, we will investigate the effect of mDia1 deficiency on the activation of aging-related signaling pathways(such as p53-p21,Wnt/GSK3β signal axis). This proposal will further elucidates the molecular mechanisms whereby mDia1 regulated HSC aging and pathogenesis of MDS and provides new and effective therapeutic intevention to rescue the aging phenotype for new treatment of human MDS.

骨髓增生异常综合征（MDS）是一种起源于造血干细胞（HSC）的恶性克隆性疾病。临床上MDS以病态造血、凋亡亢进为特征，具有遗传不稳定性易向白血病转化。MDS干细胞生物学特性及其恶性转化机制因缺乏理想的动物模型而成为研究"瓶颈"，缺乏有效的干预措施。在课题前期研究中，细胞骨架调节蛋白mDia1基因敲除小鼠表现为类似人MDS的表型，其HSC显著表现为衰老干细胞特征，如偏向髓系的造血失衡、"自新"（self-renewal）能力下降、异常细胞凋亡、细胞周期加速却异常造血。基于此，本课题拟通过检测衰老调控基因在MDS与正常HSC差异表达，建立衰老HSC基因表达谱，探讨mDia1对HSC衰老的影响。同时，拟观察mDia1对HSC衰老相关信号途径（如p53-p21、Wnt/Gsk3β）调控作用，以寻找关键衰老效应分子，逆转MDS衰老表型，寻求人MDS发病机制及治疗措施。

骨髓增生异常综合征（MDS）是一种起源于造血干细胞（HSC）的恶性克隆性疾病。临床上MDS以病态造血、凋亡亢进为特征，具有遗传不稳定性易向白血病转化。MDS干细胞生物学特性及其恶性转化机制因缺乏理想的动物模型而成为研究"瓶颈"，缺乏有效的干预措施。在课题前期研究中，细胞骨架调节蛋白mDia1基因敲除小鼠表现为类似人MDS的表型，其HSC显著表现为衰老干细胞特征，如偏向髓系的造血失衡、"自新"（self-renewal）能力下降、异常细胞凋亡、细胞周期加速却异常造血。基于此，本课题拟通过检测衰老调控基因在MDS与正常HSC差异表达，建立衰老HSC基因表达谱，探讨mDia1对HSC衰老的影响。同时，拟观察mDia1对HSC衰老相关信号途径（如p53-p21、Wnt/Gsk3β）调控作用，以寻找关键衰老效应分子，逆转MDS衰老表型，寻求人MDS发病机制及治疗措施。借助高通量RNA序列分析法 (RNA-Seq，Illumina) 检测衰老HSCs的全基因表达谱，发现共1039个基因表达有显著改变，与WT相比，在mDia1-/- HSC中，513个基因表达下调；526个基因表达上调。DAVID pathway 分析结果显示，主要涉及蛋白磷酸化通路、线粒体内膜通路、呼吸链通路、氧化磷酸化通路等，强烈提示在MDS HSC中，氧化应激、线粒体功能异常等可能与MDS HSC老化表型相关。目前研究证明，体细胞线粒体DNA（mtDNA）突变和氧化损伤的累积是组织老化的重要贡献者。电子传递链反应发生于线粒体内膜的复合体上。在此过程中产生的各种活性氧类（ROS）可氧化线粒体内多种关键的活性物质，使HSCs自新功能下降；同时，本课题还发现，mDia1-/-HSC亦存在AKT/mTOR通路活化，进而活化JAK/STAT/IL-8通路，导致前体细胞过度增殖。课题组通过使用IL8单克隆抗体处理mDia1-/-HSC，发现可逆转其衰老表型，从而为进一步研发靶向MDS HSC衰老表型提供了理论及动物实验基础，具有潜在临床转化意义。