Abstract 15302: Genetic Enhancement of Insulin-Like Growth Factor-1 in Human Cardiac Stem Cells Prevents Cell Death and Enhances Ischemic Myocardial Repair
Insulin-like growth factor (IGF-1) activates pro-survival pathways and improves post ischemic cardiac function but this key cytokine is not expressed by ex vivo proliferated human cardiac stem cells (CSCs). Here, we explore the influence of an IGF-1 enhanced paracrine signature on CSC-mediated cardiac repair.
Methods/Results: To rationalize the timing of IGF-1 delivery to infarcted myocardium, the expression of the IGF-1 receptor (IGF-1R) transcript was screened in myocardial samples from C57 mice taken 1, 7, 14 and 21 days after experimental myocardial infarction (MI). Seven days after LAD ligation, IGF-1R expression was increased by 1.4±0.7 and 3.0±0.8 fold in the infarct and border zones (p≤0.05) and remained elevated throughout the sampling period. Based on these data, human CSCs underwent lentivirus-mediated somatic gene transfer to overexpress human IGF-1 (CSCIGF-1) or the GFP reporter alone (CSCGFP). Genetic engineering enhanced the IGF-1 content within hypoxic conditioned media by 8.1±1.9 fold (p=0.01) with no discernible effects on population doubling time (1.1±0.3 vs. 1.2±0.1 days, p=ns). With the exception of enhanced IGF-1, a proteomic array of 59 cardioprotective/pro-angiogenic cytokines demonstrated that CSCIGF-1 engineering improved the secretion of additional cytokines compared to CSCGFP. Culture of CSCIGF-1 within conditions designed to mimic the ischemic border zone improved proliferation and reduced the expression of annexin V compared to CSCGFP or non-transduced CSCs (proliferation: 30±13% vs. -14±15% or -19±12% change in cell numbers, p≤0.05; annexin V: 30±6% vs. 74±9% or 77±1%, respectively; p≤0.05). These results may be partially explained through the enhancement of downstream activators within the AKT, ERK and MAPK pro-survival pathways (p≤0.05 vs. CSCGFP). Intra-myocardial injection of CSCIGF-1 into immunodeficient mice one week after MI enhanced cardiac repair as compared to CSCGFP and vehicle controls. (echocardiographic left ventricular ejection fraction 28 days post LAD ligation: 41±1% vs. 37±1% or 25±1%, respectively; p<0.05).
Conclusions: Paracrine engineering of CSCs to over-express IGF-1 boosts CSC resistance to hypoxia and improves cell-mediated cardiac repair.
- © 2013 by American Heart Association, Inc.