Atherosclerotic vascular disease becomes a clinical problem when there is 
sufficient atherosclerotic plaque burden and/or endothelial dysfunction to cause 
a limitation of nutrient blood flow to tissues. However, once myocardial 
infarction has occurred, there is little, if any, way to stimulate the growth of 
new blood vessels or cardiac muscle to replace that which has been lost. The 
potential use of hematopoietic stem cells (HSCs) to treat cardiovascular disease 
has recently been suggested from preclinical and clinical studies. HSCs are 
precursors of all the blood cells, but they may also give rise to cells of the 
vascular system, endothelial cells in the form of endothelial progenitor cells 
(EPCs). Clinical trials have been conducted in patients with either acute 
myocardial infarction or limb ischemia to determine the initial effectiveness 
and safety of this treatment approach. These studies demonstrated the potential 
clinical effectiveness of this stem cell approach to the treatment of patients 
with acute myocardial ischemia and limb ischemia. Today, more preclinical 
studies are planned to elucidate the mechanism by which transplanted stem cells 
can home and differentiate into these endothelial cells and cardiac muscle 
cells. At the same time, new clinical trials are planned to evaluate both 
chronic, stable as well as acute myocardial ischemia and limb ischemia with 
CD34+ and CD133+ stem cells, as well as with further selected EPCs and 
mesenchymal stem cells.