Abstract 2964: Hsp20-Engineered Mesenchymal Stem Cells Are Resistant to Oxidative Stress via Enhanced Activation of Akt and Secretion of Growth Factors
While heat shock preconditioning has been shown to promote cell survival under oxidative stress, the nature of heat shock response from different cells is variable and complex. Therefore, it remains unclear whether mesenchymal stem cells (MSCs) modified with a single heat-shock protein (Hsp) gene are effective in the repair of a damaged heart. In this study, we genetically engineered rat MSCs with Hsp20 gene (Hsp20-MCSs) and examined cell survival, revascularization, and functional improvement in rat left anterior descending ligation (LAD) model via intra-cardial injection. We observed that overexpression of Hsp20 protected MSCs against oxidative stress-triggered necrosis and apoptosis in vitro, as assessed by lactate dehydrogenase (LDH) release, MTS incorporation, and Annexin-V staining. Transplantation with Hsp20-MSCs increased cell survival by 2.1 fold at 4 days after injection into the infarcted rat heart, compared with vector-MSCs. M-mode echocardiography measurements for left ventricular function demonstrated that left ventricular internal end-systolic (LVIDs), end-diastolic diameters (LVIDd), and LV ejection fraction (LVEF) were improved significantly more in the Hsp20-MSC group (LVIDs: 4.3±0.4 mm; LVIDd: 5.5±0.2mm; LVEF: 71±6.1%) than in the GFP-MSC group (LVIDs: 5.1±0.3 mm; LVIDd: 6.4±0.6mm; LVEF: 59±3.6%, n=8, P<0.05) at 4 weeks after myocardial infarction, which was accompanied with 40% reduction of fibrosis and 42% increase in the vascular density. The mechanisms contributing to the beneficial effects of Hsp20 were associated with enhanced Akt activation and increased secretion of growth factors (VEGF and FGF-2). The paracrine action of Hsp20-MSCs was further validated in vitro by co-cultured adult rat cardiomyocytes with stress-conditioned medium from Hsp20-MSCs. Taken together, these data indicate that Hsp20 may be an important survival factor and new therapeutic candidate for treatment of ischemic heart disease with gene-based cell therapy.