Regular heartbeat rhythm at the heartbeat initiation stage is essential for normal cardiogenesis at low temperature.
Regular heartbeat rhythm at the heartbeat initiation stage is essential for normal cardiogenesis at low temperature.
复制标题
DOI：
10.1186/1471-213x-14-12
复制
发表时间：
2014-02-25
影响因子：
--
通讯作者：
Mitani H
中科院分区：
文献类型：
--
作者：
Watanabe-Asaka T;Sekiya Y;Wada H;Yasuda T;Okubo I;Oda S;Mitani H
心脏血流的发展对心脏功能和胚胎存活至关重要。最近的研究揭示了细胞外基质和施加在瓣膜垫上的机械应力在胚胎形成过程中控制血液流动对心脏瓣膜形成的重要性。然而，触发这种阀门形成和机械应力的事件，以及它们对温度的依赖尚未得到完全解释。米达卡（Oryzias latipes）广泛生长在东亚地区，适应各种气候。我们使用不同基因组背景的medaka胚胎，分析了低温培养胚胎的心跳特征，包括来回血流和慢性心律失常。我们还使用高速成像分析来检查这些动物在短暂暴露于低温后的心跳。在15°C孵育后，Hd-rR medaka菌株的胚胎在心脏中表现出来回的血流（血液反流）。这种反流是在心跳起始期前后暴露在低温下引起的，与心房或房室管收缩的维持或模式异常有关。来自日本北部群体的Odate菌株在15°C孵育后显示出正常的血流。心跳的高速延时分析显示，只有在15°C孵育的Hd-rR胚胎中才会出现慢速心律失常。收缩系数，定义为心房收缩期长度除以心房舒张期长度的商，在两种应变中都不受影响。去除心律失常影响后的平均心率在两品系之间没有显著差异，提示无论是否存在心律失常或心率，个体心肌收缩的机械应力与总机械应力可能是相等的。交叉试验表明，这种循环表型是由一个主要的基因组位点引起的。这些结果表明，低温下的心脏发生需要持续的心跳。在心跳开始阶段异常的收缩节律可能导致后期的反流。从进化的角度来看，在低温下发育过程中表现出正常心脏发生的菌株居住在北方环境中。
The development of blood flow in the heart is crucial for heart function and embryonic survival. Recent studies have revealed the importance of the extracellular matrix and the mechanical stress applied to the valve cushion that controls blood flow to the formation of the cardiac valve during embryogenesis. However, the events that trigger such valve formation and mechanical stress, and their temperature dependence have not been explained completely. Medaka (Oryzias latipes) inhabits a wide range of East Asia and adapts to a wide range of climates. We used medaka embryos from different genomic backgrounds and analyzed heartbeat characteristics including back-and-forth blood flow and bradyarrhythmia in embryos incubated at low temperature. We also used high-speed imaging analysis to examine the heartbeat of these animals after transient exposure to low temperature. Embryos of the Hd-rR medaka strain exhibited back-and-forth blood flow in the heart (blood regurgitation) after incubation at 15°C. This regurgitation was induced by exposure to low temperature around the heartbeat initiation period and was related to abnormalities in the maintenance or pattern of contraction of the atrium or the atrioventricular canal. The Odate strain from the northern Japanese group exhibited normal blood flow after incubation at 15°C. High-speed time-lapse analysis of the heartbeat revealed that bradyarrhythmia occurred only in Hd-rR embryos incubated at 15°C. The coefficient of contraction, defined as the quotient of the length of the atrium at systole divided by its length at diastole, was not affected in either strain. The average heart rate after removing the effect of arrhythmia did not differ significantly between the two strains, suggesting that the mechanical stress of individual myocardial contractions and the total mechanical stress could be equivalent, regardless of the presence of arrhythmia or the heart rate. Test-cross experiments suggested that this circulation phenotype was caused by a single major genomic locus. These results suggest that cardiogenesis at low temperature requires a constant heartbeat. Abnormal contraction rhythms at the stage of heartbeat initiation may cause regurgitation at later stages. From the evolutionary viewpoint, strains that exhibit normal cardiogenesis during development at low temperature inhabit northern environments.