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Updated: Jun 3, 2026
A Murine Closed-chest Model of Myocardial Ischemia and Reperfusion
Published on: July 17, 2012
Role of miR-1 and miR-133a in myocardial ischemic postconditioning
Bin He1, Jian Xiao, An-Jing Ren
1Department of Anesthesiology, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, Kongjiang Road, Shanghai, China.
Background:
Ischemic postconditioning (IPost) has aroused much attention since 2003 when it was firstly reported. The role of microRNAs (miRNAs or miRs) in IPost has rarely been reported. The present study was undertaken to investigate whether miRNAs were involved in the protective effect of IPost against myocardial ischemia-reperfusion (IR) injury and the probable mechanisms involved.
Methods:
Thirty SD rats weighing 250-300 g were equally randomized to three groups: Control group, where the rats were treated with thoracotomy only; IR group, where the rats were treated with ischemia for 60 min and reperfusion for 180 min; and IPost group, where the rats were treated with 3 cycles of transient IR just before reperfusion. The extent of myocardial infarction, LDH and CK activities were measured immediately after treatment. Myocardial apoptosis was detected by TUNEL assay. The myocardial tissue was collected after IR or IPost stimulation to evaluate the miRNAs expression level by miRNA-microarray and quantitative real-time RT-PCR. Real-time PCR was conducted to identify changes in mRNA expression of apoptosis-related genes such as Bcl-2, Bax and Caspase-9 (CASP9), and Western blot was used to compare the protein expression level of CASP9 in the three groups. The miRNA mimics and anti-miRNA oligonucleotides (AMO) were transferred into the cultured neonatal cardiomyocytes and myocardium before they were treated with IR. The effect of miRNAs on apoptosis was determined by flow cytometry and TUNEL assay. CASP9, as one of the candidate target of miR-133a, was compared during IR after the miR-133a mimic or AMO-133a was transferred into the myocardium.
Results:
IPost reduced the IR-induced infarct size of the left ventricle, and decreased CK and LDH levels. TUNEL assay showed that myocardial apoptosis was attenuated by IPost compared with IR. MiRNA-microarray and RT-PCR showed that myocardial-specific miR-1 and miR-133a were down-regulated by IR, and up-regulated by IPost compared with IR. Furthermore, IPost up-regulated the mRNA expression of Bcl-2, down-regulated that of Bax and CASP9. Western blot showed that IPost also down-regulated the CASP9 protein expression compared with IR. The results of flow cytometry and TUNEL assay showed that up-regulation of miR-1 and miR-133a decreased apoptosis of cardiomyocytes. MiR-133a mimic down-regulated CASP9 protein expression and attenuated IR-induced apoptosis.
Conclusion:
MiRNAs are associated with the protective effect of IPost against myocardial IR injury. IPost can up-regulate miR-1 and miR-133a, and decrease apoptosis of cardiomyocyte. Myocardial-specific miR-1 and miR-133a may play an important role in IPost protection by regulating apoptosis-related genes. MiR-133a may attenuate apoptosis of myocardiocytes by targeting CASP9.
Insights
Ischemic postconditioning (IPost) protects the heart from injury by increasing miR-1 and miR-133a levels, which reduces cardiomyocyte apoptosis. This study reveals miRNAs
Area of Science:
- Cardiovascular Science
- Molecular Biology
- Regenerative Medicine
Background:
- Ischemic postconditioning (IPost) is a protective strategy against myocardial ischemia-reperfusion (IR) injury.
- The role of microRNAs (miRNAs) in IPost-mediated cardioprotection remains largely unexplored.
- This study investigates the involvement of miRNAs in the protective mechanisms of IPost against myocardial IR injury.
Purpose of the Study:
- To determine if miRNAs are involved in the protective effects of IPost against myocardial IR injury.
- To elucidate the molecular mechanisms by which IPost confers cardioprotection, focusing on miRNA regulation of apoptosis.
Main Methods:
- Rats were divided into Control, IR, and IPost groups.
- Myocardial infarction size, cardiac enzyme levels (LDH, CK), and apoptosis were assessed.
- miRNA expression profiling (miRNA-microarray, RT-PCR) and analysis of apoptosis-related genes (Bcl-2, Bax, Caspase-9) were performed.
- In vitro studies using miRNA mimics and anti-miRNA oligonucleotides (AMO) in cardiomyocytes investigated the functional role of specific miRNAs.
Main Results:
- IPost significantly reduced infarct size, LDH, and CK levels, and attenuated myocardial apoptosis compared to IR.
- IR downregulated myocardial-specific miR-1 and miR-133a, while IPost upregulated them.
- IPost increased Bcl-2 mRNA and decreased Bax and Caspase-9 (CASP9) mRNA and protein expression.
- Overexpression of miR-1 and miR-133a reduced cardiomyocyte apoptosis; miR-133a mimic downregulated CASP9 and attenuated IR-induced apoptosis.
Conclusions:
- miRNAs are integral to the cardioprotective effects of IPost against myocardial IR injury.
- IPost enhances miR-1 and miR-133a expression, leading to decreased cardiomyocyte apoptosis.
- Myocardial-specific miR-1 and miR-133a likely mediate IPost protection by regulating apoptosis-related genes, with miR-133a potentially targeting CASP9.