Background: The "key regulator" of protection of ischemic heart has yet to be identified. We assess whether nestin-640, a truncated active form of endogenous intermediate filament protein nestin, is essential for mediating effective protection of infarcted heart. Methods: Permanent ligation of the left descending coronary artery was performed in 21 adult male Winstar rats. After 60 minutes, the rats were randomized for injection into the left ventricular (LV) infarct border zone (BZ) of AAV9-Nest640 (10¹², n=9) or AAV9-green fluorescent protein (AAV9-GFP, 10¹², n=6) or saline (PBS, n=6). The LV performance was investigated by echocardiography and histology. The pro-survival effect of Nest640 was explored by TUNEL assay in colture of rodent cardiomyocytes transduced with AAV6-Nest640 (10¹²) and exposed for 1 hour to 100mM of H₂O₂.Results: At 4 weeks both control groups (AAV9-GFP, PBS) showed a dim increase of local expression of nestin in the BZ in presence of all hallmarks of myocardial remodeling. AAV9-Nest640 preserved LV ejection fraction compared to AAV9-GFP (60.7±4.97 vs 37.13±2.2%, p<0.05). Accordingly, the LV end-diastolic thickness was preserved in the BZ of AAV9-Nest640 compared to AAV9-GFP (1.3±0.1 vs 0.7±0.07mm, P<0.05), and the LV scar size was significantly reduced by 40.6±7% in treated rats. Nestin overexpression was restricted to non proliferating cardiomyocytes. The apoptotic index was significantly reduced by 50±1% in LVBZ. In vitro, we confirmed a significant preservation of apoptosis in AAV6-Nest640-transduced cells. Conclusions: We show that nestin is essential for cardiomyocyte survival and delivery of Nest640 vector preserves function of infarcted heart.