Preconditioning (PC) of the heart by sublethal ischemia, mild heat shock, or 
hypoxia has evolved as a powerful experimental tool to discover novel signaling 
mechanisms in cardioprotection. The ultimate goal is to determine novel 
therapeutic targets for potential application in humans to protect the heart 
against ischemia-related injuries. In recent years, there has been a tremendous 
interest in understanding the role of small noncoding RNAs, microRNAs (miRs), in 
cardiovascular diseases. miRs have been recognized as regulators of gene 
expression by destabilization and translational inhibition of target messenger 
RNAs. Studies have shown that several miRs, including miR-1, miR-133, miR-21, 
miR-126, miR-320, miR-92a, and miR-199a, are regulated after preconditioning and 
play an active role in protecting the heart against ischemia/reperfusion injury. 
These miRs also drive the synthesis of important cardioprotective proteins 
including heat shock protein (HSP)-70, endothelial nitric oxide synthase, 
inducible nitric oxide synthase, HSP-20, Sirt1, and hypoxia-inducible factor 1a. 
We believe that identification and targeted delivery of miR(s) in the heart 
could have an immense therapeutic potential in reducing myocardial infarction in 
patients suffering from heart disease.