THE ROLE OF CARDIOMYOCYTE AND CARDIOFIBROBLAST SENESCENCE IN THE AGING HEART

描述（由申请人提供）：心脏性猝死（SCD）约占心脏病相关死亡的50%，是美国的主要死因;因此，了解导致SCD的致命性心律失常的机制可能会导致预防性药理学和治疗策略，从而增加不断增长的易感人群的预期寿命和生活质量。众所周知，衰老与SCD发病率的增加有关。然而，在细胞和分子水平上，哺乳动物心脏中与年龄相关的促心律变化的机制以及它们如何与心脏发生和SCD发病率增加相关，仍有许多未知之处。到目前为止，我们已经进行了初步的体内EP研究和光学标测实验，揭示了通过希氏-浦肯野系统和心室的传导的老化相关减慢。我们也发现了与年龄相关的室颤诱发率增加，我在石蜡包埋切片上进行了Gomori三色染色，结果显示老年心脏心外膜下区域和同一区域心脏纤维之间的纤维化增加，显示传导缓慢。基于我们的初步数据，我假设衰老不仅与总体心功能降低有关，而且与心肌中衰老样心肌细胞（CM）和衰老的心脏成纤维细胞（CF）的积累有关。此外，我假设CM和CF的进行性衰老与基因表达的改变有关，基因表达的改变将直接导致异常的肌细胞收缩性和异常的细胞兴奋，以及加速纤维化。这些改变将导致心肌收缩力受损、传导速度减慢和室颤诱导阈值降低。为此，我正在寻求一种多层次的方法，通过比较年轻和老年家兔队列以及比较非衰老、按时间顺序衰老和衰老的心脏细胞群，来确定衰老心脏中恶性心律失常的新机制。通过结合体内和体外技术（包括侵入性血流动力学，免疫印迹/qPCR，免疫荧光，流式细胞术和单细胞钙记录），我希望提供生物化学和功能证据，揭示细胞衰老是衰老心脏心律失常的电和结构触发器和底物的基础。

DESCRIPTION (provided by applicant): Accounting for approximately 50% of deaths related to heart disease, sudden cardiac death (SCD) is a leading cause of death in the United States; thus, understanding the mechanisms that underlie deadly arrhythmias that cause SCD could lead to preventative pharmacological and therapeutic strategies that would increase life expectancy and quality of life among a growing susceptible population. It is known that aging is associated with an increase of the incidence of SCD. Yet, much remains unknown about the mechanisms that underlie the age- related, proarrhythmic changes in the mammalian heart at the cellular and molecular level and how they are related to arrhythmogenesis and increased incidence of SCD. Thus far, we have conducted preliminary in vivo EP studies and optical mapping experiments that reveal an aging- related slowing of conduction through the His-Purkinje system and the ventricles. We have also shown an age-related increase in ventricular fibrillation inducibility, and I have performed Gomori trichrome staining on paraffin embedded sections, which revealed increased fibrosis in old hearts at the subepicardial region and between the fibers of the heart in the same area that showed slow conduction. Based on our preliminary data, I hypothesize that aging is not only associated with overall reduced cardiac function but also with the accumulation of senescent- like cardiomyocytes (CMs) and senescent cardiofibroblasts (CFs) in the cardiac muscle. Moreover, I postulate that the progressive senescence of CMs and CFs is associated with alterations in gene expression that will directly lead to abnormal myocyte contractility and abnormal cell excitation, as well as accelerated fibrosis. These alterations would lead to impaired cardiac contractility, a slowing of the conduction velocity, and a decrease in the threshold for induction of ventricular fibrillation. To that end, I am pursuing a multi-leveled approach to identify novel mechanisms that underlie malignant arrhythmias in the aging heart using comparisons between young and old rabbit cohorts, as well as comparisons among non- senescent, chronologically aged, and senescent cardiac cell populations. With a combination of in vivo and in vitro techniques (including invasive hemodynamics, immuoblotting/qPCR, immunofluorescence, flow cytometry, and single-cell calcium recordings), I hope to provide both biochemical and functional evidence revealing that cellular senescence underlies electrical and structural triggers and substrates for arrhythmias in the aging heart.