Background/Aims: Reperfusion after an ischaemic insult might cause infarct extension. Mesenchymal stem cell (MSC)-derived exosomes could attenuate myocardial remodelling in animal models of myocardial ischaemia reperfusion injury (MIRI), and the present study aimed to explore the related mechanisms. Methods: In vitro, rat H9C2 cardiomyocytes (H9C2s) were exposed to H2O2. Cell viability was detected by the CCK-8 assay, apoptosis was detected by Annexin V-PE/7-AAD staining, ROS production was detected by fluorescence microscopy and flow cytometry, and apoptosis-related proteins and signalling pathway-related proteins were detected by western blot analysis. Autophagic flux was measured using the tandem fluorescent mRFG-GFP-LC3 assay. MSC-derived exosomes were extracted using the total exosome isolation reagent. Apoptosis, myocardial infarction size, heart function and myocardial LC3B expression were examined in an in vivo I/R model by the TUNEL assay, TTC/Evan blue staining, echocardiography and immunohistochemicalstaining, respectively. Results: In vitro, H2O2 dose-dependently increased ROS production and cell apoptosis in H9C2s and blocked autophagic flux after 3 h of exposure; autophagy gradually decreased thereafter, and the lowest level was detected at 12 h after exposure. MSC-derived exosomes reduced H2O2-induced ROS production and cell apoptosis and enhanced autophagy at 12 h after exposure. In H9C2 cells exposed to H2O2 for 12 h, treatment with exosomes enhanced autophagy via the AMPK/mTOR and Akt/mTOR pathways. Likewise, in vivo exosome injections in rats that underwent I/R injury significantly reduced apoptosis and the myocardial infarct size and upregulated myocardial LC3B expression as well as improved heart function. Conclusions: Our results indicate that MSC-derived exosomes could reduce MIRI by inducing cardiomyocyte autophagy via AMPK/mTOR and Akt/mTOR pathways.
Cardiac fibrosis (CF), a main process of ventricular remodeling after myocardial infarction (MI), plays a crucial role in the pathogenesis of heart failure (HF) post-MI. It is known that amphiregulin (AR) is involved in fibrosis of several organs. However, the expression of AR and its role post-MI are yet to be determined. This study aimed to investigate the impact of AR on CF post-MI and related mechanisms. Significantly upregulated AR expression was evidenced in the infarct border zone of MI mice in vivo and the AR secretion was enhanced in macrophages, but not in cardiac fibroblasts. In vitro, treatment with AR increased cardiac fibroblast migration, proliferation and collagen synthesis, and upregulated the expression of epidermal growth factor receptor (EGFR) and the downstream genes such as Akt, ERK1/2 and Samd2/3 on cardiac fibroblasts. All these effects could be abrogated by pretreatment with a specific EGFR inhibitor. To verify the functions of AR in MI hearts, lentivirus-AR-shRNA and negative control vectors were delivered into the infarct border zone. After 28 days, knock-down of AR increased the survival rate and improved cardiac function, while decreasing the extent of myocardial fibrosis of MI mice. Moreover, EGFR and the downstream genes were significantly downregulated in lentivirus-AR-shRNA treated MI mice. Our results thus indicate that AR plays an important role in promoting CF after MI partly though activating the EGFR pathway. Targeting AR might be a novel therapeutic option for attenuating CF and improve cardiac function after MI.
The Editor in Chief has retracted this article because of multiple concerns regarding figures presented here. Specifically:• Three figures in sh-AR panel and three figures in sh-NC panel look more similar than expected in Fig. 5A. • The two figures in MI border panel and two figures in MI-shNC border panel in Fig. 6C show similarities.• In Fig. 9, the Smad2/3 and Akt rows of Western Blots have 9 bands instead of 8.
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