Abstract 409: Ex-vivo Targeting Of Insulin-like Growth Factor-1 Gene To The Heart Promotes Mobilization And Homing Of Stem Cells Through Paracrine Release Of Stromal Cell Derived Factor-1α
Background: We hypothesize that genetic modification of mesenchymal stem cells (MSCs) to overexpress IGF-1 enhances their survival and engraftment in the infarcted heart and promotes recruitment of stem cells through paracrine release of SDF-1α
Methods and Results: MSCs from male rat were either used as non-transduced (Non-TransMSCs) or transduced with adenoviral null-vector (NullMSCs) or vector encoding for IGF-1 (IGF-1MSCs). IGF-1 mRNA and protein levels in IGF-1MSCs were higher until 12 days as compared with NullMSCs (p<0.001). Molecular studies revealed higher levels of phosphorylated (p) p-Akt (2-fold), p-P27 (>20-fold), and p-P21 (>30-fold) together with SDF-1α(>24-fold), all of which increased in parallel with IGF-1 expression (200-fold) in IGF-1 MSCs as compared with NullMSCs. For in vivo studies, coronary artery was ligated in female rats and 70μl DMEM without cells (group-1) or containing 3x106 NullMSCs (group-2) or IGF-1MSCs (group-3) were implanted into infarct and peri-infarct areas. One week later, immunoblot showed elevated myocardial levels of IGF-1, p-Akt, and p-P27 accompanied by higher survival of IGF-1MSCs (p<0.05 vs NullMSCs) as determined by real-time PCR for sry-gene. Enhanced cell proliferation was observed after immunostaining for Ki67+in group-3 (p<0.05 vs all groups). SDF-1α protein was increased in group-3 animal hearts (20-fold vs group-2), with massive mobilization and homing of ckit + GATA4 +, MDR1 + GATA4−, ckit + GATA4−, and CXCR4 + cells into infarcted heart. Animals harvested at six weeks showed significantly reduced infarction size in groups-2 & 3 as compared with group-1. Confocal imaging after immunostaining for myosin heavy chain, troponin-I, actinin, connexin-43, vonWilbrand factor-VIII and smooth muscle actin showed extensive myogenic regeneration and angiogenesis in the infarcted heart. Indices of left ventricle function including ejection fraction and fractional shortening were significantly improved in group-3 as compared with group-1 (p<0.05).
Conclusions: Ex-vivo delivery of IGF-1 activated pro-survival and proliferation signaling. Moreover, paracrine release of SDF-1α subsequent to IGF-1 overexpression caused extensive mobilization and homing of stem cells into infarcted heart.