The ageing heart: exploring new markers of ageing and investigating new treatment options

几十年来，全世界的预期寿命一直在稳步增长。目前，每两个德国公民中就有超过45岁的人，每五分之一的人超过66岁--而且有上升的趋势。与此同时，老龄化还对癌症、神经退行性疾病或心血管疾病等慢性疾病构成重大风险，后者是最常见的。在分子水平上，心脏的老化过程是由有害物质(如DNA或表观遗传学变化、细胞衰老)和修复机制的不平衡驱动的，导致细胞弹性和完整性的逐渐丧失。这可能会导致更容易患上心脏病并随后出现心脏功能障碍。尽管两个个体的年龄相同，但由于分子衰老过程的不同表达，这两个人的衰老速度可能不同；因此，将产生两个不同的生物年龄。通过单细胞RNA测序，可以测量单个细胞的基因表达模式，这使得心脏细胞类型的异质性能够以高灵敏度表征。为了能够拾取不同大小的所有类型的心脏细胞(尤其是心肌细胞)，在进行单个细胞测量之前将提取细胞核(“单核RNA测序”，SnRNA-seq)。在SNRNA-seq的帮助下，首先是健康的人的心脏，然后是患病的人的心脏，并以单细胞分辨率进行绘制。在有收缩功能障碍的病变心脏中，心肌细胞减少，成纤维细胞的分泌表型增加，这促进了心肌纤维化的发展和“不利的心脏重塑”。除了在单核或直接在组织中进行RNA测量外，还可以在单细胞水平上同时显示染色质的可及性，这使得对表观遗传调控的更多了解成为可能。通过结合这两种模式，健康、老化的人类心脏将在单细胞水平上进行表征，以描绘与衰老相关的变化：i)细胞组成、ii)基因表达和iii)表观遗传模式。这将有助于过滤导致生物心脏老化速率不同的分子因素；同时，将确定老化和患病心脏的共同特征。为此，将使用来自健康捐赠者的心脏组织，并在单细胞水平上对其进行测序。这一结果将在老化的野生型小鼠身上得到关联和验证。触发衰老相关负面效应的分子信号，如“不利的心脏重构”，将首先在体外被“小干扰”RNA(SiRNAs)识别和治疗，然后在体内被识别和治疗。

For decades, the life expectancy worldwide has increased steadily. Currently, every second German citizen is older than 45 and every fifth above 66 – with upward tendency. At the same time, ageing also poses the significant risk for chronic diseases such as cancer, neurodegenerative or cardiovascular diseases, the latter being the most common. At molecular level, the ageing process of the heart is driven by an imbalance of harmful (e.g. DNA or epigenetic changes, cellular senescence) and reparative mechanisms, resulting in a gradual loss of cellular resilience and integrity. This may lead to an increased vulnerability to heart diseases with subsequent cardiac dysfunction. Despite of the same chronological age of two individuals, the ageing of these two can proceed at different speeds due to the heterogeneous expression of molecular ageing processes; thus, two different biological ages will result. With single cell RNA sequencing, the gene expression patterns of individual cells can be measured, which allows the heterogeneity of the cell types of a heart to be characterized with high sensitivity. In order to be able to pick up all heart cell types of different sizes (especially the cardiomyocytes), the cell nucleus will be extracted before single cell measurement (“single nucleus RNA sequencing”, snRNA-seq). With the help of snRNA-seq, first the healthy and later the diseased human heart was mapped at single cell resolution. In diseased hearts with systolic dysfunction, cardiomyocytes were found decreased and a secretory phenotype of fibroblasts was increased, which promotes cardiac fibrosis development and "adverse cardiac remodeling". In addition to the RNA measurement – in single nuclei or directly in tissues – the simultaneous display of chromatin accessibility at single cell level is also possible, which allows additional insights into the epigenetic regulation. By combining these two modalities, the healthy, ageing human heart will be characterized at single-cell level in order to depict ageing-associated changes in i) cellular composition, ii) gene expression and iii) epigenetic patterns. This will help to filter molecular factors that lead to the heterogeneous rates of biological heart ageing; at the same time, common characteristics of the ageing and diseased heart will be determined. For this purpose, heart tissues from healthy donors will be used and sequenced at single cell level. The results will be correlated and validated with ageing wild-type mice. Molecular signals that trigger ageing-associated negative effects such as "adverse cardiac remodeling" will be identified and treated by "small interfering" RNAs (siRNAs) first in vitro and later in vivo.