Ischemic heart disease, also called coronary heart disease, is a leading cause of death worldwide. The term describes what happens when there is a decrease in blood flow to the heart. One of the leading causes of ischemic heart disease is atherosclerosis, which is a build-up of plaque in the coronary arteries. This narrows the arteries and decreases blood flow. In some instances, a piece of atheroma can detach from the wall of the artery and block blood flow completely to the heart. This would cause a heart attack.
Some of the main symptoms of ischemic heart disease are angina, shortness of breath, pain in the body, feeling faint/dizzy, and nausea. The most commonly observed symptom is chest pressure or pain, often on the left side of the body. There is also a condition known as silent ischemia, where the patient does not experience any symptoms.
Mesenchymal stem cells
Stem cells are cells with the ability to differentiate into different types of cells and can self-renew. There are two key types of stem cells with one being embryonic stem cells, collected from a blastocyst. However, there are ethical issues with using embryonic stem cells. Mesenchymal stem cells (MSCs) are a promising alternative with their ability to self-renew and differentiate down multiple lineages. MSCs can be collected from many adult tissues including bone marrow and adipose tissue. They are easily isolated and secrete vesicles that stimulate tissue repair as well as control immune and inflammatory cells.
Mesenchymal stem cells in ischemic heart disease treatment
In ischemic heart disease, the death of heart cells called myocytes can be observed as there is a decrease in oxygen supply. When this happens, the damaged cells and tissue are replaced by scar tissue. Current treatments include revascularisation and pharmaceuticals as heart cells cannot regenerate. An exciting treatment idea is to use MSCs to treat heart disease as they can self-renew and differentiate. It is hoped that these cells can differentiate into cardiac cells to repair the damages cells and tissue. They can also help to protect the heart by decreasing inflammation and stimulating myocardial cells to differentiate. There has been some promising research which has shown that MSCs can improve cardiac repair, however there are some issues with their survival rate.
One way in which MSCs have been shown to have a positive effect on ischemic heart disease is through cardio-protection. Both cardioprotection and a reduction in scar tissue have been shown after MSC transplantation. In one study, there was restoration of the contractive nature of the heart after MSC implantation. The cardio-protective effect could also potentially be increased when a certain gene is overexpressed. Whilst the mechanism of cardio-protection is not currently well understood, there are ideas that inflammatory pathways and signaling pathways are involved.
Often observed in ischemic heart disease is insufficient blood vessel growth, and blood vessel growth is a key factor of tissue repair. MSCs have been shown to be involved in the formation of new blood vessels. There is some evidence to show that when transplanted and differentiated, MSCs can act as perivascular cells, that are key in vascularization as they stimulate other cells involved.
Despite their potential in cardio-protection and revascularization, the most promising application of MSCs in the treatment of heart disease is their ability to stimulate cell growth and differentiation into cardiac cells. This research supports the observation of scarred tissue being replaced with new contractile myocardium. It is thought that this occurs through both the stimulation of cell proliferation and increased cell cycling.
Whilst current research is promising, there is much more needed before MSCs are rendered a safe and effective treatment option for ischemic heart disease.