Is it possible to regenerate cardiac muscle after a heart attack?

            When someone has a myocardial infarction, commonly known as a heart attack, there is typically associated cardiac muscle damage that occurs in response to it.  The damage to the cardiac muscle is specifically to the heart muscle cells, cardiomyocytes, which are the cells that help contribute to the pumping and contraction function of the heart. With the loss of cardiomyocytes, it causes for the heart to be unable to pump as much blood per beat, and can be causative for increased rate of heart disease and mortality associated with it.

            Cardiomyocytes are cells that are known to be unable to regenerate, but the reasoning behind this is unsure. With this being the case, Edward Morrisey, Professor of Medicine and Scientific Director of the Penn Institute of Regenerative medicine in Penn Medicine and his team set out to target the cardiomyocyte proliferation pathway to help repair damaged cardiac cells.

            The team of doctors, researchers, and engineers set out to develop a gel using microRNA’s that target the cardiomyocytes specifically, and prevent their “stop” signals from firing, allowing for continued cell proliferation. The gel is injected and is short-lived with only lasting in the bloodstream for about eight hours. The gel has two characteristics that are ideally used to help to directly inject it to the tissue where needed and prevent proliferation of cells in spots where it is not necessary. These characteristics are that the gel is shear thinning, meaning it breaks under mechanical stress and is able to be administered with a syringe, as well as self-healing so when the stress is removed, the bonds in the gel reform and stay intact with heart muscle.

            The gel was tested in three populations of mice under different conditions but all ultimately showing this gel could be promising for promoting repair of cardiac muscle after a heart attack. The first population of mice was normal, healthy mice that showed increased proliferation of cardiac cells identified with the use of biomarkers. The second group was the “confetti” mice, which were transgenic mice expressing four different fluorescent proteins in four different colors. These mice had heart attacks induced, and afterwards saw that there was proliferation and “clumps” of different fluorescent proteins that were in response to the microRNA-gel. The third population of mice had heart attacks induced as well and were tested to see clinical relevance of the treatment. These mice in comparison to the controls showed improved recovery including a higher ejection fraction, or the amount of blood pumped out of the heart with each beat.

Though this gel has only been tested in mice, the research is looking to be able to apply it to human cardiac cells in vitro next. If this gel continues to show promise, it could ultimately lead to a reduction in numbers of those affected by cardiac disease and the damage that comes from experiencing a heart attack.

Sources:

University of Pennsylvania. (2017, November 29). Injectable gel helps heart muscle

regenerate after heart attack. ScienceDaily. Retrieved December 1, 2017 from

www.sciencedaily.com/releases/2017/11/171129131346.htm