miR-18a-5p介导的骨髓衰竭的病理生理机制

MicroRNAs are small-noncoding RNA molecules that post-transcriptionally regulate gene expression by degradation or translational repression. Recently, emerging evidence has demonstrated that miRNAs play important roles in a lot of diseases. Through detecting the expression profiles of microRNAs in aplastic anemia (AA) patients and normal controls, we found that miR-18a-5p was significantly lower in AA patients than that of controls. Further bioinformatics analyses showed that the target genes of this microRNA were cell division cycle protein 42 (Cdc42) and ataxia-telangiectasia-mutated (ATM). Cdc42 can regulate many important physiological processes, including cell morphology, migration, cell growth, proliferation, apoptosis, transcriptional activation and so on. Moreover, ATM is also involved in regulations of autophagy, telomere and DNA damage repairmen of hematopoietic stem cells. We hypothesize that miR-18a-5p is involved in AA by regulating Cdc42 and ATM. This project is herein aimed to elucidate the role of miR-18a-5p in pathology of AA, we will focus on the effects of Cdc42 and ATM on physiology of AA and the association between miR-18a-5p and target genes. Furthermore, we will validate the results of in vitro experiments by using AA mouse models, which will provide a theoretical basis of novel treatment strategy for AA.

MicroRNA可在转录后水平调节基因表达，于多种疾病中发挥重要作用。笔者发现 miR-18a-5p 在骨髓衰竭症（BMF）最经典疾病模型-再生障碍性贫血（AA）中表达低下，且预测到其靶基因为细胞分裂周期蛋白42（Cdc42）与共济失调-毛细血管扩张突变基因（ATM）。鉴于Cdc42可调节细胞形态、迁移、生长、增殖、凋亡及其转录激活等，及ATM对细胞自噬和端粒的调节作用，笔者推测miR-18a-5p可能借助调节Cdc42及ATM 参与AA的病理生理过程。本项目中，我们拟研究：①Cdc42介导的AA造血干细胞（HSC）和淋巴细胞各亚群增殖、周期、凋亡及趋化效应；②ATM对AA HSC自噬及端粒的影响；③miR-18a-5p与靶基因间的相互调节作用，以期阐明miR-18a-5p 介导的AA病理生理机制。并于动物模型体内验证上述体外研究结果，为以miR-18a-5p 为靶点的治疗策略提供理论依据

异常免疫介导的造血干/祖细胞损伤仍是再生障碍性贫血（AA）发病的主要环节。AA患者经强烈免疫抑制治疗（immunosuppressive therapy，IST）有效为异常免疫提供确凿证据。MicroRNA（miRNA）是一类短单链非编码RNA分子，可通过与靶基因mRNA的3’UTR （3'-untranslated region）结合抑制基因的转录后翻译而抑制基因的表达。为探究microRNA在AA免疫病理机制中的潜在作用，我们课题组对10个外周血单个核细胞样本（3例超重型再生障碍性贫血（VSAA），4例重型再生障碍性贫血（SAA）和3例健康对照（HC））进行了microRNA芯片检测。依据芯片结果筛选出miR-18a-5p和miR-199a-3p并行进一步验证，明确miR-18a-5p和miR-199a-3p在AA中稳定低表达。我们同时发现共济失调毛细血管扩张突变基因（ATM）和liver kinase B1 (LKB1)分别为miR-18a-5p和miR-199a-3p的靶基因。为明确miR-18a-5p和miR-199a-3p在AA免疫机制中的具体作用，我们通过体外实验上调AA患者miR-18a-5p和miR-199a-3p的表达水平，发现上调上述miRNAs抑制T细胞增殖，此外，上调miR-199a-3p还可诱导T细胞凋亡，此诱导作用在T细胞面临代谢压力时尤为明显。更重要的是，上调miR-199a-3p可抑制CD4+T细胞和CD8+T细胞干扰素-γ的表达，从而减轻造血抑制。因此，本课题研究结果证明，miRNA-18a-5p和miR-199a-3p参与AA的免疫病理机制并发挥关键性作用，应用miRNA mimics上调AA中低表达的miRNAs有望成为AA的新型治疗策略。