Human adipose stem cell (ASC) transplantation is of therapeutic potential in the treatment of myocardial
infarction (MI). However, little is known with regard to the optimal time of cell transplantation for MI patients. This
study was designed to discover the most beneficial time for cell transplantation with the goal of improving cardiac
function. MI was induced in Sprague-Dawley (SD) rats by permanent ligation of the left anterior descending (LAD)
coronary artery. ASCs (1?0^6) were transplanted directly into the infarcted myocardium 1 -week (n=10), 2 -weeks
(n=10), and 4 -weeks (n=10) post MI. At 2 and 4 weeks after cell transplantation, cardiac function was assessed by
echocardiography. Four weeks after cell transplantation, immunohistochemical staining for fibronectin and troponin
I, and Western blotting for VEGF, bax/bcl-2, and cleaved-caspase-9, were performed. Left ventricular function,
especially ejection fraction (EF), showed a significant improvement in the 1- and 2-week groups compared to the
the PBS group. There were more obvious decreases in the bax/bcl-2 ratio, expression of cleaved-caspase-9, and
increased vascular density and expression of vascular endothelial growth factor (VEGF) in the 1-week group than
1 week after MI exerted the best effect on the recovery of cardiac function in a rat MI model. Decreasing apoptosis
and increasing neovascularization seem to contribute this effect partly.