BACKGROUND: Myoblast transplantation (Tx) is promising for the improvement of 
cardiac function in ischemic cardiomyopathy. Insulin-like growth factor-1 
(IGF-1) has anti-apoptotic and angiogenic effects, and induces myocyte 
hypertrophy. Our hypothesis is that topical and slow-release IGF-1 enhances the 
efficacy of Tx through its multiple functions.
METHODS: Four weeks after coronary artery ligation, Lewis rats were divided into 
four groups: (1) IGF-1+Tx, injection of 6 x 10(6) myoblasts into the infarcted 
area with placement of an IGF-1-impregnated sheet on the left ventricular (LV) 
free wall; (2) Tx, Tx alone; (3) IGF-1, IGF-1 sheet alone; and (4) control. We 
measured cardiac function and performed immunohistochemical examinations.
RESULTS: At 4 weeks after treatment, LV diastolic dimension was the smallest, 
end-systolic elastance was the highest, and tau was the smallest in the IGF-1+Tx 
group. The graft volume in the IGF-1+Tx group was 3-fold larger than in the Tx 
group. One day after transplantation, TUNEL-positive donor cells were fewer in 
the IGF-1+Tx than in the Tx group. Western blot analysis demonstrated that the 
phosphorylation of Akt increased and the expression of Bax decreased in the 
transplanted area of IGF-1+Tx rats compared with Tx rats. The vascular density 
in the peri-infarcted area was larger in IGF-1+Tx than in Tx rats. The mean 
diameter of graft-derived myotubes was larger in IGF-1+Tx than in Tx animals.
CONCLUSIONS: IGF-1 increases the graft volume and enhances the efficacy of Tx in 
the chronic myocardial infarction model due to its multiple effects of 
preventing apoptosis, inducing angiogenesis, and promoting myoblast growth.