Recent research has uncovered the role of a naturally-occurring protein which can promote healing after a heart attack.

Researchers at Toronto General Hospital, University Health Network have discovered the mechanism by which stem cells and some immune cells are activated in order to quickly move to the site of injury in the heart and take part in cell repair.

Dr. Peter Liu, one of the lead researchers of the study, explains how after a heart attack, the damaged heart tissue cannot regenerate, making it difficult for the heart to keep pumping blood with the same strength as before throughout the body. Heart tissue damage can also lead to congestive heart failure, a condition that causes more than half of the patients to die within 5 years of diagnosis.

Dr. Peter Liu considers this study important because it "gives us hope that one day we may be able to stop the damaged heart muscle from dying, and will be able to promote healing soon after any damage, to prevent heart failure".

Dr. Jeffrey Medin of the Ontario Cancer Institute, Princess Margaret Hospital co-authored the research, together with Bill Ayach, PhD candidate at the University of Toronto.

The newer methods of heart cell repair that have been under investigation for several years now, focus on infusing the patient's own cells into the damaged heart muscle to restore its function.

Dr. Liu's approach was to try to find a way to strengthen heart muscle repair by aiding the heart in repairing itself; the research team focused on finding out what types of cells can be mobilized to the site of the injury and how they can be mobilized.

Using mice models and sophisticated gene chip technology, they found that mice that lacked certain specialized proteins had worse heart function and a decreased heart repair capacity after heart attacks as compared to mice that had these proteins, called stem cell factor receptors.

These stem cell factor receptors are frequently found on stem cells in the bone marrow and their role is to activate other "signaling" molecules, which cause stem cells to leave the bone marrow and migrate via the blood stream to the damaged heart tissue.

A further proof that stem cell factor receptor signaling works this way is the fact that once the knock-out mice underwent bone marrow transplantation from normal mouse donors, cardiac function was improved.

Two types of cells are necessary for heart repair, researchers have found: adult stem cells and white blood cells. The latter ones reside in the bone marrow and in the spleen and play an essential role in the immune system defense mechanism, being capable of recognizing and killing bacteria, viruses and abnormal cells. Working together with the stem cells, these cells can help the repair by producing new blood vessels and thus restoring blood flow to the heart. The death rate in mice that were deficient both in stem cell factor receptor protein and white blood cells was double following a heart attack.

Dr. Liu admits, however, that there may be other proteins as well that signal other cells to migrate and help the regeneration of heart cells, adding that the team is currently investigating other possible cell protein signaling mechanisms.

The research paper, entitled "Stem cell factor receptor induces progenitor and natural killer cell-mediated cardiac survival and repair after myocardial infarction" was published on February 6 in the prestigious "Proceedings of the National Academy of Sciences", one of the most cited multidisciplinary scientific journals worldwide.