Age-dependent increase of oxidative stress regulates microRNA-29 family preserving cardiac health

The short-lived turquoise killifish Nothobranchius furzeri (Nfu) is a valid model for aging studies. Here, we investigated its age-associated cardiac function. We observed oxidative stress accumulation and an engagement of microRNAs (miRNAs) in the aging heart. MiRNA-sequencing of 5 week (young), 12-21 week (adult) and 28-40 week (old) Nfu hearts revealed 23 up-regulated and 18 down-regulated miRNAs with age. MiR-29 family turned out as one of the most up-regulated miRNAs during aging. MiR-29 family increase induces a decrease of known targets like collagens and DNA methyl transferases (DNMTs) paralleled by 5´methyl-cytosine (5mC) level decrease. To further investigate miR-29 family role in the fish heart we generated a transgenic zebrafish model where miR-29 was knocked-down. In this model we found significant morphological and functional cardiac alterations and an impairment of oxygen dependent pathways by transcriptome analysis leading to hypoxic marker up-regulation. To get insights the possible hypoxic regulation of miR-29 family, we exposed human cardiac fibroblasts to 1% O2 levels. In hypoxic condition we found miR-29 down-modulation responsible for the accumulation of collagens and 5mC. Overall, our data suggest that miR-29 family up-regulation might represent an endogenous mechanism aimed at ameliorating the age-dependent cardiac damage leading to hypertrophy and fibrosis.

短寿命绿松石鳉（Nothobranchius furzeri，以下简称Nfu）是衰老研究的可靠模型生物。本研究针对其与年龄相关的心脏功能展开探究。我们在衰老心脏中观测到氧化应激积累，以及微小RNA（microRNAs，miRNAs）的参与调控。对5周龄（年轻个体）、12~21周龄（成年个体）及28~40周龄（老年个体）的Nfu心脏进行小RNA测序后发现，随年龄增长共有23种miRNA上调、18种miRNA下调。miR-29家族是衰老过程中上调幅度最显著的miRNA之一。miR-29家族的表达上调会使其已知靶标（如胶原蛋白与DNA甲基转移酶（DNA methyl transferases，DNMTs））的水平降低，同时伴随5'-甲基胞嘧啶（5´methyl-cytosine，5mC）水平下降。为进一步探究miR-29家族在鳉鱼心脏中的功能，我们构建了miR-29敲低的转基因斑马鱼模型。通过该模型，我们观测到显著的心脏形态与功能异常；转录组分析显示氧依赖通路受损，进而导致缺氧标志物的表达上调。为探究miR-29家族是否受缺氧调控，我们将人心脏成纤维细胞置于1%氧浓度的培养环境中。在缺氧条件下，我们观测到miR-29的表达下调，该变化会引发胶原蛋白与5mC的积累。综合本研究所有结果，我们认为miR-29家族的表达上调可能代表一种内源性保护机制，旨在减轻年龄依赖性心脏损伤，进而预防心肌肥厚与纤维化。