The issue of heart disfunction or failure is currently an enormous problem within the United States and stem cells may be the key to regeneration of malfunctioning or lost cardiac tissue.

There are three major types of cardiac cells: (5)

• Cardiomyocytes - These are the cells that make up the contractile cardiac muscle. They proliferate to repair a damaged heart and regain its contractile power.
• Vascular endothelial cells - These cells are located in the inner lining of the heart's newly formed blood vessels.
• Smooth muscle cells - These are located in the wall of the heart's blood vessels

It should also be noted that at this time there is no evidence of true stem cells in the heart.

Is there any evidence that stem cells aid in cardiac tissue regeneration?

Several experiments using mice have been performed in order to regenerate cardiac tissue (specifically, cardiomyocytes):

(Look at a section of cardiac muscle) (Image from http://www.mds.qmw.ac.uk/biomed/kb/microanatomy/muscle_nerve/)

In one experiment, a ligature was placed around the coronary artery, therefore, depriving cardiomyocytes of of oxygen and nutrients. This causes an infarction. (See a cardiac infarction in a mouse) Injecting human hematopoeitic stem cells into the blood stream resulted in repaired heart tissue. In addition, injecting a certain population of mouse derived adult stem cells directly onto the area of infarction, cardiac tissue is also repaired. (Look at these injections) (5)

A second experiment was performed in which the LAD coronary artery was tied off. This induced heart attacks. When Side Population cells (a type of stem cell situated in the bone marrow) were injected into the bone marrow of the mouse, donor derived cardiac muscle as well as vascular endothelial cells were formed. (5)