Experimentally Increasing the Compliance of Titin Through RNA Binding Motif-20 (RBM20) Inhibition Improves Diastolic Function In a Mouse Model of Heart Failure With Preserved Ejection Fraction.
Experimentally Increasing the Compliance of Titin Through RNA Binding Motif-20 (RBM20) Inhibition Improves Diastolic Function In a Mouse Model of Heart Failure With Preserved Ejection Fraction.
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DOI：
10.1161/circulationaha.116.023003
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发表时间：
2016-10-11
期刊：
影响因子：
37.8
通讯作者：
Granzier H
中科院分区：
文献类型：
--
作者：
Methawasin M;Strom JG;Slater RE;Fernandez V;Saripalli C;Granzier H
左心室（LV）硬化导致射血分数保留性心力衰竭（HFpEF），这是一种没有有效治疗方案的综合征。最近，通过抑制剪接因子RBM 20，增加肌联蛋白在心脏中的顺应性已成为可能。在这里，我们研究了增加肌联蛋白的顺应性舒张功能障碍小鼠的影响。使用RBM 20等位基因之一的RNA识别基序（RRM）被floxed并在αMHC启动子控制下表达MerCreMer转基因的小鼠（称为cRbm 20 ΔRRM小鼠）。小鼠经历了横向主动脉缩窄（TAC）手术和醋酸脱氧皮质酮（DOCA）颗粒植入（TAC/DOCA）。通过注射雷洛昔芬（cRbm 20 ΔRRM-raloxifene）触发成年小鼠中的RRM缺失，注射DMSO的小鼠（cRbm 20 ΔRRM-DMSO）作为对照。舒张功能进行了研究，使用超声心动图和压力容积分析;被动刚度进行了研究，在左心室肌条和分离的心肌细胞之前和之后消除肌联蛋白为基础的刚度。还研究了跑步机运动性能。用琼脂糖凝胶评价肌联蛋白亚型表达。cRbm 20 Δ RRM-雷洛昔芬小鼠在心脏中表达大滴蛋白，称为超顺应性滴蛋白（N2 BAsc），在雷洛昔芬注射后3周内，其占总滴蛋白的约45%。如压力-容积分析和超声心动图所示，TAC/DOCA cRbm 20 ΔRRM-DMSO小鼠出现LV肥大和LV腔室僵硬度显著增加。在表达N2 BAsc的TAC/DOCA cRbm 20 ΔRRM-raloxifene小鼠中，LV室僵硬度标准化。从LV游离壁分离的肌条的被动刚度测量显示，两组TAC/DOCA小鼠（cRbm 20 ΔRRM-DMSO和cRbm 20 ΔRRM-raloxifene）的细胞外基质（ECM）刚度增加相同。然而，在表达N2 BAsc的小鼠中，基于肌联蛋白的肌肉硬度降低（TAC/DOCA cRbm 20 ΔRRM-raloxifene）。运动测试表明表达N2 BAsc的TAC/DOCA小鼠的运动耐量显著改善。抑制基于RBM 20的肌联蛋白剪接系统上调顺应性肌联蛋白，这改善了TAC/DOCA模型中的舒张功能和运动耐量。Titin有望成为HFpEF的治疗靶点。
Left Ventricular (LV) stiffening contributes to Heart Failure with preserved Ejection Fraction (HFpEF), a syndrome with no effective treatment options. Increasing titin’s compliance in the heart has become possible recently through inhibition of the splicing factor RBM20. Here we investigated the effects of increasing titin’s compliance in mice with diastolic dysfunction. Mice in which the RNA recognition motif (RRM) of one of the RBM20 alleles was floxed and which expressed the MerCreMer transgene under control of the αMHC promoter (referred to as cRbm20ΔRRM mice) were used. Mice underwent transverse aortic constriction (TAC) surgery and deoxycorticosterone acetate (DOCA) pellet implantation (TAC/DOCA). RRM deletion in adult mice was triggered by injecting raloxifene (cRbm20ΔRRM-raloxifene) with DMSO injected mice (cRbm20ΔRRM-DMSO) as the control. Diastolic function was investigated using echocardiography and pressure volume analysis; passive stiffness was studied in LV muscle strips and isolated cardiac myocytes before and after elimination of titin-based stiffness. Treadmill exercise performance was also studied. Titin isoform expression was evaluated with Agarose gels. cRbm20ΔRRM-raloxifene mice expressed large titins in the hearts, named super compliant titin (N2BAsc), which, within 3 weeks after raloxifene injection, made up ~45% of total titin. TAC/DOCA cRbm20ΔRRM-DMSO mice developed LV hypertrophy and a marked increase in LV chamber stiffness as shown by both pressure-volume analysis and echocardiography. LV chamber stiffness was normalized in TAC/DOCA cRbm20ΔRRM-raloxifene mice that expressed N2BAsc. Passive stiffness measurements on muscle strips isolated from the LV free wall revealed that extracellular matrix (ECM) stiffness was equally increased in both groups of TAC/DOCA mice (cRbm20ΔRRM-DMSO and cRbm20ΔRRM-raloxifene). However, titin-based muscle stiffness was reduced in the mice that expressed N2BAsc (TAC/DOCA cRbm20ΔRRM-raloxifene). Exercise testing demonstrated significant improvement in exercise tolerance in TAC/DOCA mice that expressed N2BAsc. Inhibition of the RBM20-based titin splicing system upregulates compliant titins, which improves diastolic function and exercise tolerance in the TAC/DOCA model. Titin holds promise as a therapeutic target for HFpEF.