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

几十年来，全世界的预期寿命稳步增长。目前，每两个德国公民中就有一个年龄在45岁以上，每五个人中就有一个年龄在66岁以上，而且有上升的趋势。与此同时，老龄化也对癌症、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，心脏的衰老过程是由有害（例如DNA或表观遗传变化，细胞衰老）和修复机制的不平衡驱动的，导致细胞恢复力和完整性的逐渐丧失。这可能导致心脏病的易感性增加，随后出现心功能障碍。尽管两个人的实际年龄相同，但由于分子衰老过程的异质性表达，这两个人的衰老可以以不同的速度进行;因此，将产生两个不同的生物学年龄。通过单细胞RNA测序，可以测量单个细胞的基因表达模式，这允许以高灵敏度表征心脏细胞类型的异质性。为了能够提取不同大小的所有心脏细胞类型（特别是心肌细胞），将在单细胞测量（“单核RNA测序”，snRNA-seq）之前提取细胞核。在snRNA-seq的帮助下，首先以单细胞分辨率绘制了健康和患病的人类心脏。在患有收缩功能障碍的患病心脏中，发现心肌细胞减少，成纤维细胞的分泌表型增加，这促进心脏纤维化发展和“不利的心脏重塑”。除了在单个细胞核中或直接在组织中进行RNA测量之外，还可以在单细胞水平上同时显示染色质可及性，这允许对表观遗传调控进行额外的了解。通过结合这两种模式，将在单细胞水平上表征健康、衰老的人类心脏，以描述i）细胞组成、ii）基因表达和iii）表观遗传模式中与衰老相关的变化。这将有助于过滤导致生物心脏老化的异质速率的分子因素;同时，将确定老化和患病心脏的共同特征。为此，将使用来自健康供体的心脏组织并在单细胞水平上进行测序。结果将与衰老的野生型小鼠相关联并验证。触发衰老相关的负面影响，如“不良心脏重塑”的分子信号将被识别和治疗的“小干扰”RNA（siRNA）首先在体外，然后在体内。

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.