BACKGROUND: Granulocyte stimulating factor (G-CSF) and bone marrow mononuclear cells (BM-MNC) were reported to improve cardiac function after myocardial infarction (MI). This study was to examine their combined beneficial effects and mechanisms of actions in reperfused MI, which have not been verified yet. METHODS:Fifteen pigs were divided into 3 groups after a 1-hour balloon occlusion and reperfusion of the left anterior descending coronary artery. G1 (n=5) was a control, G2 (n=5) was a G-CSF injected group (10 ug/kg/day, from day1 to day7 after MI), and G3 (n=5) was an autologous intracoronary BM-MNC infused group after G-CSF treatment RESULTS:Modified wall motion indices by echocardiography were similar among 3 groups at 24 hours after MI. However, they improved significantly in G2 and G3 at 35days after MI (p<0.05). The percentage of infarct area/left ventricular myocardial area measured from a triphenyltetrazolium chloride (TTC) stain was lower in G3 than in G1 or G2 (p=0.026). The number of vWF-positive vessels and the expressions of vWF and VE cardherin by RT-PCR were higher in G3 and G2 than in G1 (p<0.05). The number of TUNEL-positive cells and bcl2/bax ratio were not significantly different among 3 groups. CONCLUSION: This study suggests that intracoronary BM-MNC infusion with G-CSF treatment in reperfused MI reduced infarct size, improved left ventricular function and prevented ventricular remodeling.