Telomeric Shortening, p53 and miR-34a Condition Senescence of Cardiac Progenitors

描述(由申请人提供)：认识到心脏具有形成心肌细胞和冠状血管的干细胞室，增加了心脏前体细胞(CPC)数量和/或功能的变化导致老年性肌病发生的可能性。CPC的再生能力下降可能与陈旧心肌细胞的积聚和心脏衰老表型有关。CPC的生命周期似乎受端粒酶活性和端粒长度的调节；端粒缩短超过临界长度会触发细胞衰老和死亡。虽然端粒磨损在细胞衰老中的作用已在体外得到证实，但在体内端粒DNA的丢失是否会导致器官和生物的衰老仍有待确定。因此，我们的主要目标是评估：a)在活体心肌老化过程中是否发生端粒缩短；b)端粒过短的CPC经历复制性衰老和凋亡；以及c)端粒缩短导致干细胞和心肌细胞老化，最终导致心力衰竭。我们将尝试通过首先使用一个动物模型来回答这些问题，在该动物模型中，端粒侵蚀依赖于端粒酶的RNA成分的缺失。随后，我们将研究人类CPC中的端粒酶-端粒轴(HCPCS)，并确定端粒酶活性和端粒长度是否调节这些细胞的生长特性。我们实验室的证据表明，IGF-1防止端粒磨损并增强端粒酶活性，而Ang II促进HCPCS的氧化应激。因此，IGF-1受体(IGF-1R)和Ang II受体1(AT1R)将分别用于分离具有长端粒和短端粒的HCPCs。IGF-1R和AT1R在HCPCS中的作用可能是通过它们对P53表达和活性的相反作用来介导的，P53可能在HCPCS的衰老过程中起关键作用。目前尚不清楚P53反应基因是否决定了HCPC衰老和心脏衰老。我们将关注p53、miR-34和miR-34靶基因之间的相互作用；miR-34是p53的下游效应因子，被认为是CPC和心脏老化的重要决定因素。 公共卫生相关性：心脏前体细胞的衰老是老年性肌病的关键决定因素。本文提出了一种新的方法来鉴定可能具有大量心肌细胞分裂和形成能力的前体细胞。如果成功，这一策略可能会对老年人心力衰竭的管理产生重要影响。

DESCRIPTION (provided by applicant): The recognition that the heart possesses a stem cell compartment that forms myocytes and coronary vessels raises the possibility that alterations in number and/or function of cardiac progenitor cells (CPCs) condition the onset of the aging myopathy. The decline in regenerative capacity of resident CPCs may dictate the accumulation of old myocytes and the cardiac senescent phenotype. The life cycle of CPCs appears to be regulated by telomerase activity and telomere length; shortening of telomeres beyond a critical length triggers cellular senescence and death. Although the role of telomere attrition in cellular aging has been documented in vitro, it remains to be determined whether loss of telomere DNA leads to organ and organism aging in vivo. Thus, our major goal is to assess whether: a) telomere shortening occurs during myocardial aging in vivo; b) CPCs with critically short telomeres undergo replicative senescence and apoptosis; and c) telomere shortening causes stem cell and myocyte aging and ultimately heart failure. We will attempt to answer these questions by employing first an animal model in which telomere erosion depends on the deletion of the RNA component of telomerase. Subsequently, we will study the telomerase-telomere axis in human CPCs (hCPCs) and establish whether telomerase activity and telomere length modulate the growth properties of these cells. Evidence in our laboratory suggests that IGF-1 prevents telomere attrition and enhances telomerase activity while Ang II promotes oxidative stress in hCPCs. Therefore, IGF-1 receptor (IGF-1R) and Ang II receptor 1 (AT1R) will be employed to isolate hCPCs with long and short telomeres, respectively. The function of IGF-1R and AT1R in hCPCs may be mediated by their opposite effects on the expression and activity of p53; p53 is expected to be critically involved in hCPC senescence. Whether p53-responsive genes dictate hCPC senescence and cardiac aging is currently unknown. We will focus on the interaction between p53, miR-34 and miR-34 target genes; miR-34 is a downstream effector of p53 and is proposed to be an important determinant of CPC and cardiac aging. PUBLIC HEALTH RELEVANCE: Senescence of cardiac progenitor cells is a critical determinant of the aging myopathy. A new approach is proposed here for the identification of progenitor cells which may have a significant capacity to divide and form a large number of cardiomyocytes. If successful, this strategy may have important implications for the management of human heart failure in the elderly.