The regenerative capacity of the myocardium and its blood vessels has now been 
well demonstrated. The cytokines granulocyte colony-stimulating factor, 
erythropoietin, and stem cell factor may play a role in helping to stimulate 
cell regeneration under normal physiologic conditions and in patients with 
myocardial injury. After an ischemic insult, cytokines are released into the 
peripheral circulation and signal for the mobilization of stem cells. In 
experimental cardiac injury models, the addition of cytokines has been shown to 
improve myocardial function with and without the concurrent use of stem cell 
therapy. Preliminary studies in humans using cytokine therapy alone for treating 
myocardial infarction have been disappointing. Future studies in patients with 
myocardial injury need to examine the use of various combinations of cytokines, 
with and without the addition of intravascular stem cell infusions or direct 
stem cell injections.