HSP20-mediated cardiomyocyte exosomes improve cardiac function in mice with myocardial infarction by activating Akt signaling pathway.

OBJECTIVE: To explore the role of heat shock protein 20 (HSP20)-mediated cardiomyocyte exosomes in the cardiac function in mice with myocardial infarction via the activation of the protein kinase B (Akt) signaling pathway.
MATERIALS AND METHODS: A total of 30 mice were enrolled to establish the model of myocardial infarction. Next, these mice were divided into three groups, namely Blank group (healthy mice), Model group (mouse models of myocardial infarction), and HSP20 group (mouse models of myocardial infarction transfected with lentivirus to overexpress HSP20). After that, terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) staining assay was performed to detect myocardial apoptosis. Reactive oxygen species (ROS) accumulation in myocardial tissues was determined via dihydroethidium (DHE) staining assay. Western blotting was employed to analyze the expression level of Akt. The expression levels of inflammatory factors tumor necrosis factor-alpha (TNF-α) and interleukin 1 beta (IL-1β) in HSP20-mediated cardiomyocyte exosomes were measured through quantitative real time polymerase chain reaction (qRT-PCR).
RESULTS: Compared with that in Blank group, the number of cardiomyocyte exosomes was increased in Model group and HSP20 group under anoxic conditions (p<0.05). The results of quantitative Real Time-Polymerase Chain Reaction (qRT-PCR) proved that the HSP20 messenger ribonucleic acid (mRNA) expression in mediated cardiomyocyte exosomes was significantly lower in Model group than that in Blank group (p<0.05), while in HSP20 group, it was overtly higher than that in Model group but clearly lowered compared with that in Blank group (p<0.05). The protein expression of Akt in cardiomyocyte exosomes was evidently decreased in Model group compared with that in Blank group (p<0.05), while it was notably increased in HSP20 group compared with that in Model group (p<0.05). In comparison with Blank group, Model group had significantly elevated mRNA expression levels of TNF-α and IL-1β. The mRNA expression levels of TNF-α and IL-1β in HSP20 group were remarkably lower than those in Model group (p<0.05). The results of TUNEL assay revealed that the overexpression of HSP20 affected myocardial apoptosis. The myocardial apoptosis index in Model group [(38.42±2.52) %] was higher than that in Blank group [(9.74±1.21) %], HSP20 group had a significantly decreased myocardial apoptosis index [(22.36±2.13) %] in comparison with Model group (p<0.05). In accordance with DHE staining comparison, the accumulation of ROS in myocardial tissues in Model group was significantly higher than that in Blank group (p<0.05) and HSP20 group (p<0.05).
CONCLUSIONS: We demonstrated that HSP20-mediated cardiomyocyte exosomes activate the AKT signaling pathway, repress TNF-α and IL-1β factors, and alleviate myocardial infarction.