TAp73甲基化通过Dicer1调控MDS-MSC细胞衰老的机制研究

Bone marrow mesenchymal stem cell (MSC) is an important part of the hematopoietic stem cell niche. Many studies have shown that the hematopoiesis support function of MSC from patients with MDS is impaired. But the specific mechanism is unclear. Our previous studies showed that the senescence cells in MDS-MSC are significantly higher than that of normal controls, whereas the expression of Dicer1 gene is lower. Dicer1 knockdown promoted cell senescence， reduced the MSC osteogenetic differentiation and hematopoiesis support ability. By analysis of Dicer1 gene, we found that its promoter regions harbored TAp73 binding sites. TAp73 hypermethylation existed in MDS-MSC. TAp73 expression was reduced and was associated with Dicer1 expression. We speculated that TAp73 methylation may participate in cell senescence through reducing Dicer1 expression, then affecting the hematopoiesis support functions. Based on these, we will further explore the role of TAp73 in cell senescence, microRNA changes and MSC hematopoiesis support functions by building Dicerl promoter luciferase reporter gene vector, CHIP, establishing TAp73 silence and overexpression cell lines, miRNA array and cell functional assay. The study will help to clarify the mechanism of cell senescence in MDS-MSC and the role of cell senescence in abnormal hematopoiesis in MDS.

骨髓间充质干细胞（MSC）是造血干细胞龛的重要成员。研究表明MDS患者MSC（MDS-MSC）造血支持功能受损，但具体机制尚不清楚。我们前期研究显示MDS-MSC细胞衰老显著高于正常对照， Dicer1基因表达降低，下调Dicer1促进了MSC衰老，降低了其成骨分化及造血支持能力；进一步分析发现Dicer1启动子存在TAp73结合位点，而MDS-MSC中TAp73基因存在高甲基化，并介导基因沉默，与Dicer1表达相关联。我们推测TAp73可能通过调控Dicer1参与MDS-MSC衰老。本研究通过荧光报告基因、CHIP、慢病毒介导的干扰/过表达技术、miRNA芯片及功能学实验，阐述TAp73-Dicer1-p21通路在MDS-MSC衰老中的作用、导致的miRNA改变及其对MSC造血支持功能的影响。该项目有助于阐明MDS-MSC衰老机制，明确MDS-MSC细胞衰老在MDS异常造血中的作用。

骨髓间充质干细胞（MSC）是造血干细胞龛的重要成员。研究表明MDS患者MSC（MDS-MSC）造血支持功能受损，但具体机制尚不清楚。我们研究发现MDS-MSC存在TAp73启动子异常高甲基化，通过地西他滨去甲基化诱导了TAp73及Dicer1表达；进一步研究证实TAp73可作用于Dicer1启动子调控后者基因表达；TAp73及Dicer1在MDS-MSC均低表达，下调Dicer1促进了MSC衰老，降低了其成骨分化及造血支持能力，而在MDS-MSC中上调Dicer1的表达可部分逆转MSC衰老；进一步机制研究发现Dicer1可通过调控miRNA-17家族，靶向于p21基因，从而导致细胞衰老。该项目阐明了MDS-MSC衰老机制，明确MDS-MSC细胞衰老在MDS异常造血中的作用。