This is one of the more promising animal studies of heart regeneration that I recall seeing in recent years, particularly given that it is accomplished in pigs, which are a good match in size for human tissues. The heart is one of the least regenerative organs in the mammalian body, and damage, such as that resulting from a heart attack, results in scar tissue and loss of function rather than healing. Here, researchers used a microRNA in order to provoke native cells into regenerative activities that would not normally take place. One of the major goals of the regenerative medicine community over the past two decades has to been to find ways to either deliver cells capable of regrowth or to deliver instructions to native cells that will cause them to heal the damaged tissues.
Myocardial infarction, more commonly known as a heart attack, caused by the sudden blocking of one of the cardiac coronary arteries, is the main cause of heart failure. At present, when a patient survives a heart attack, they are left with permanent structural damage to their heart through the formation of a scar, which can lead to heart failure in the future. This is in contrast to zebrafish and salamanders, which can regenerate the heart throughout life. In a new study, the team of investigators delivered a small piece of genetic material, called microRNA-199, to the heart of pigs, after a myocardial infarction which resulted in the almost complete recovery of cardiac function at one month later.
This is the first demonstration that cardiac regeneration can be achieved by administering an effective genetic drug that stimulates cardiac regeneration in a large animal, with heart anatomy and physiology like that of humans. "It is a very exciting moment for the field. After so many unsuccessful attempts at regenerating the heart using stem cells, which all have failed so far, for the first time we see real cardiac repair in a large animal. It will take some time before we can proceed to clinical trials. We still need to learn how to administer the RNA as a synthetic molecule in large animals and then in patients, but we already know this works well in mice."