北京大学心血管研究所汪南平教授领导的课题组，近日在最新一期的PNAS杂志上发表文章，首次证实血管的层流剪应力调节了miRNA的表达，而其中一个miRNA分子―miR-19a，在cyclin D1表达的流动调节及内皮增殖中扮演了重要角色。
如果血液的生物、化学及物理学性质发生了改变，血管内皮通常能感知到。血流所产生的摩擦力―剪应力，对内皮的结构和功能产生了多种影响。内皮细胞应对了机械力的变化，引起信号网络和细胞功能的调节。稳态层流对内皮细胞的抑制就是一个例子。至于内皮细胞应对血流机械性质改变的分子机制，以及如何经历结构和功能的改变，至今尚不清楚。越来越多的证据表明，剪应力通过调节内皮细胞的基因表达，来施加生理影响。
众所周知，microRNA（miRNA）是～22个核苷酸的小RNA分子，它们在转录后水平负调节了目的基因的表达。近期研究表明miRNA参与了血管发育和体内平衡，至于它和剪应力有什么关联，这也正是研究小组感兴趣的。
汪南平教授的研究小组使用LC Sciences的microRNA芯片，比较了人脐静脉内皮细胞（HUVEC）在有无层流剪切压力（12 dyn/cm2，12小时）下的miRNA表达谱。与对照细胞相比，层流处理过的HUVEC在芯片上的569个miRNA中，有35个miRNA显著上调，而26个显著下调。其中miR-19a在静止状态下以高丰度表达，而暴露在剪应力下12小时后，表达水平大幅提高。
之后，为了筛选miRNA所调节的靶点，他们制备了稳定过表达miR-19a的细胞系。多项分析表明，miR-19a的稳定转染显著减低了报告基因（此报告基因被cyclin D1基因的3’端非翻译保守区所控制）的表达以及cyclin D1的蛋白水平，使细胞周期停滞在G1/S期。当内源miR-19a被抑制后，这种抑制作用减弱。
这项研究的主要发现在于，miR-19直接靶定了cyclin D1的表达。这已经通过报告基因分析和Western blotting分析而证实。重要的是，他们发现了miR-19a的剪切诱导是抑制cyclin D1的表达水平所必需的。过去观察到层流剪应力增加了cyclin D1转录本，却使细胞周期停滞，这项研究结果给出了一个可能的解释。
研究人员通过这一系列分析，证实层流剪应力调节了miRNA的表达，而miR-19a在cyclin D1表达的流动调节及内皮增殖中扮演了重要角色。这些结果揭示出机械力如何调节内皮基因表达的机制。
生物谷推荐原始出处：
PNAS January 27, 2010, doi: 10.1073/pnas.0914825107
Role of microRNA-23b in flow-regulation of Rb phosphorylation and endothelial cell growth
Kuei-Chun Wanga, Lana Xia Garmirea, Angela Younga, Phu Nguyena, Andrew Trinha, Shankar Subramaniama, Nanping Wangb, John YJ Shyyc, Yi-Shuan Lia,1, and Shu Chiena,1
aDepartment of Bioengineering and Institute of Engineering in Medicine, University of California, San Diego, La Jolla, CA 92093;
bKey Laboratory of Molecular Cardiovascular Science, Peking University Health Science Center, Beijing 100191, China; and
cDivision of Biomedical Sciences, University of California, Riverside, CA 92521
MicroRNAs (miRs) can regulate many cellular functions, but their roles in regulating responses of vascular endothelial cells (ECs) to mechanical stimuli remain unexplored. We hypothesize that the physiological responses of ECs are regulated by not only mRNA and protein signaling networks, but also expression of the corresponding miRs. EC growth arrest induced by pulsatile shear (PS) flow is an important feature for flow regulation of ECs. miR profiling showed that 21 miRs are differentially expressed (8 up- and 13 downregulated) in response to 24-h PS as compared to static condition (ST). The mRNA expression profile indicates EC growth arrest under 24-h PS. Analysis of differentially expressed miRs yielded 68 predicted mRNA targets that overlapped with results of microarray mRNA profiling. Functional analysis of miR profile indicates that the cell cycle network is highly regulated. The upregulation of miR-23b and miR-27b was found to correlate with the PS-induced EC growth arrest. Inhibition of miR-23b using antagomir-23b oligonucleotide (AM23b) reversed the PS-induced E2F1 reduction and retinoblastoma (Rb) hypophosphorylation and attenuated the PS-induced G1/G0 arrest. Antagomir AM27b regulated E2F1 expression, but did not affect Rb and growth arrest. Our findings indicate that PS suppresses EC proliferation through the regulation of miR-23b and provide insights into the role of miRs in mechanotransduction.
