TBX18 overexpression enhances pacemaker function in a rat subsidiary atrial pacemaker model of sick sinus syndrome.
TBX18 overexpression enhances pacemaker function in a rat subsidiary atrial pacemaker model of sick sinus syndrome.
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DOI：
10.1113/jp276508
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发表时间：
2018-12
期刊：
影响因子：
--
通讯作者：
Morris GM
中科院分区：
文献类型：
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作者：
Choudhury M;Black N;Alghamdi A;D'Souza A;Wang R;Yanni J;Dobrzynski H;Kingston PA;Zhang H;Boyett MR;Morris GM
窦房结（SAN）是心脏的主要起搏器。SAN功能障碍，或“病态窦性综合征”，会导致心率过慢和停顿，导致运动受限和晕厥，目前通过植入电子起搏器治疗。“生物起搏器制造”利用基因疗法通过操纵基因表达来恢复起搏器的活性。过表达HCN起搏器离子通道已被广泛应用，但收效甚微。我们利用心动过缓的大鼠辅助心房起搏器组织来评估其他基因靶点：Na+/Ca2+交换器NCX1，以及已知参与SAN胚胎发育的转录因子TBX3和TBX18。TBX18过表达恢复了正常的SAN功能，通过增加心率、改善心率稳定性和恢复异丙肾上腺素反应来评估。TBX3和NCX1对辅助心房起搏器组织的加速无明显作用。因此，针对TBX18的基因治疗有可能恢复人类病态窦综合征患者的起搏器功能，从而避免使用电子起搏器。窦房结（SAN）是心脏的主要起搏器。SAN疾病，病态窦性综合征，以心动过缓和停顿的形式引起心率不稳定，导致运动受限和晕厥。生物合成旨在通过操纵基因表达来恢复起搏器的活性，利用HCN通道过表达的方法已被广泛使用。我们利用Na+/Ca2+交换器NCX1和转录因子TBX3和TBX18，评估了在慢性辅助心房起搏器（SAP）组织中恢复正常SAN起搏器生理的生物合成的替代基因靶点。TBX18在SAP组织中的表达恢复了正常的SAN功能，提高了心率（SAN 267.5±13.6 bpm, SAP 144.1±8.6 bpm, SAP‐TBX18 214.4±14.4 bpm, P < 0.001），改善了心率稳定性(RR间隔的标准差从39.3±7.2 ms降至6.9±0.8 ms, P < 0.01； RR间隔的连续差异的均方根从41.7±8.2 ms降至6.1±1.2 ms, P < 0.01；垂直于poincar<e:1>地块的点的标准差（SD1）从29.5±5.8 ms降至7.9±2.0 ms, P < 0.05)，异丙肾上腺素反应恢复（SAN增加65.5±1.3%，SAP增加28.4±3.4%，SAP‐TBX18增加103.3±10.2%,P < 0.001）。这些变化是由TBX18诱导的SAP组织中显性HCN亚型的开关驱动的，HCN2显著上调（从1.01 × 10−5±2.2 × 10−6到2.8 × 10−5±4.3 × 10−6任意单位，P < 0.001）。结合同种异构体特异性HCN通道电生理学的生物物理详细计算机模型证实，测量到的HCN丰度变化可以解释观察到的心率变化。TBX3和NCX1对SAP组织的加速无明显作用。窦房结（SAN）是心脏的主要起搏器。SAN功能障碍，或“病态窦性综合征”，会导致心率过慢和停顿，导致运动受限和晕厥，目前通过植入电子起搏器治疗。“生物起搏器制造”利用基因疗法通过操纵基因表达来恢复起搏器的活性。过表达HCN起搏器离子通道已被广泛应用，但收效甚微。我们利用心动过缓的大鼠辅助心房起搏器组织来评估其他基因靶点：Na+/Ca2+交换器NCX1，以及已知参与SAN胚胎发育的转录因子TBX3和TBX18。TBX18过表达恢复了正常的SAN功能，通过增加心率、改善心率稳定性和恢复异丙肾上腺素反应来评估。TBX3和NCX1对辅助心房起搏器组织的加速无明显作用。因此，针对TBX18的基因治疗有可能恢复人类病态窦综合征患者的起搏器功能，从而避免使用电子起搏器。
The sinoatrial node (SAN) is the primary pacemaker of the heart. SAN dysfunction, or ‘sick sinus syndrome’, can cause excessively slow heart rates and pauses, leading to exercise limitation and syncope, currently treated by implantation of an electronic pacemaker. ‘Biopacemaking’ utilises gene therapy to restore pacemaker activity by manipulating gene expression. Overexpressing the HCN pacemaker ion channel has been widely used with limited success. We utilised bradycardic rat subsidiary atrial pacemaker tissue to evaluate alternative gene targets: the Na+/Ca2+ exchanger NCX1, and the transcription factors TBX3 and TBX18 known to be involved in SAN embryonic development. TBX18 overexpression restored normal SAN function, as assessed by increased rate, improved heart rate stability and restoration of isoprenaline response. TBX3 and NCX1 were not effective in accelerating the rate of subsidiary atrial pacemaker tissue. Gene therapy targeting TBX18 could therefore have the potential to restore pacemaker function in human sick sinus syndrome obviating electronic pacemakers. The sinoatrial node (SAN) is the primary pacemaker of the heart. Disease of the SAN, sick sinus syndrome, causes heart rate instability in the form of bradycardia and pauses, leading to exercise limitation and syncope. Biopacemaking aims to restore pacemaker activity by manipulating gene expression, and approaches utilising HCN channel overexpression have been widely used. We evaluated alternative gene targets for biopacemaking to restore normal SAN pacemaker physiology within bradycardic subsidiary atrial pacemaker (SAP) tissue, using the Na+/Ca2+ exchanger NCX1, and the transcription factors TBX3 and TBX18. TBX18 expression in SAP tissue restored normal SAN function, as assessed by increased rate (SAN 267.5 ± 13.6 bpm, SAP 144.1 ± 8.6 bpm, SAP‐TBX18 214.4 ± 14.4 bpm; P < 0.001), improved heart rate stability (standard deviation of RR intervals fell from 39.3 ± 7.2 ms to 6.9 ± 0.8 ms, P < 0.01; root mean square of successive differences of RR intervals fell from 41.7 ± 8.2 ms to 6.1 ± 1.2 ms, P < 0.01; standard deviation of points perpendicular to the line of identity of Poincaré plots (SD1) fell from 29.5 ± 5.8 ms to 7.9 ± 2.0 ms, P < 0.05) and restoration of isoprenaline response (increases in rates of SAN 65.5 ± 1.3%, SAP 28.4 ± 3.4% and SAP‐TBX18 103.3 ± 10.2%; P < 0.001). These changes were driven by a TBX18‐induced switch in the dominant HCN isoform in SAP tissue, with a significant upregulation of HCN2 (from 1.01 × 10−5 ± 2.2 × 10−6 to 2.8 × 10−5 ± 4.3 × 10−6 arbitrary units, P < 0.001). Biophysically detailed computer modelling incorporating isoform‐specific HCN channel electrophysiology confirmed that the measured changes in HCN abundance could account for the observed changes in beating rates. TBX3 and NCX1 were not effective in accelerating the rate of SAP tissue. The sinoatrial node (SAN) is the primary pacemaker of the heart. SAN dysfunction, or ‘sick sinus syndrome’, can cause excessively slow heart rates and pauses, leading to exercise limitation and syncope, currently treated by implantation of an electronic pacemaker. ‘Biopacemaking’ utilises gene therapy to restore pacemaker activity by manipulating gene expression. Overexpressing the HCN pacemaker ion channel has been widely used with limited success. We utilised bradycardic rat subsidiary atrial pacemaker tissue to evaluate alternative gene targets: the Na+/Ca2+ exchanger NCX1, and the transcription factors TBX3 and TBX18 known to be involved in SAN embryonic development. TBX18 overexpression restored normal SAN function, as assessed by increased rate, improved heart rate stability and restoration of isoprenaline response. TBX3 and NCX1 were not effective in accelerating the rate of subsidiary atrial pacemaker tissue. Gene therapy targeting TBX18 could therefore have the potential to restore pacemaker function in human sick sinus syndrome obviating electronic pacemakers.