Abstract
We tested the hypothesis that simultaneous transgenic overexpression of a select quartet of growth factors activates diverse signaling pathways for mobilization and participation of various stem/progenitor cells for cardiogenesis in the infarcted heart. Human insulin growth factor-1 (IGF-1), vascular endothelial growth factor (VEGF), stromal cell-derived factor-1 (SDF-1a), and hepatocyte growth factor (HGF) plasmids were synthesized and transfected into skeletal myoblasts (SM) from young male wild-type or transgenic rats expressing green fluorescent protein (GFP). Overexpression of growth factors in transfected SM ((Trans)SM) was confirmed by reverse transcription polymerase chain reaction, western blotting, and fluorescence immunostaining. Using our custom-made growth factor array and western blotting, multiple angiogenic and prosurvival factors were detected in (Trans)SM, including secreted frizzled related protein-1,2,4,5, matrix metalloproteinases-3 and 9, connexin-43, netrin-1, Nos-2, Wnt-3, Akt, MAPK42/44, Stat3, nuclear factor kappa B (NFκB), hypoxia-inducible factor 1 (HIF-1α), and protein kinase C (PKC). The conditioned medium (CM) from (Trans)SM was cytoprotective for cardiomyocytes following H(2)O(2) treatment [P<0.01 vs. CM from native SM ((Nat)SM)], promoted a higher transwell migration of human umbilical cord vein endothelial cells (223.3±1.8, P<0.01) and in vitro tube formation (47.8±1.9, P<0.01). Intramyocardial transplantation of 1.5×10(6) (Trans)SM (group-3) in a rat model of acute myocardial infarction induced extensive mobilization of cMet(+), ckit(+), ckit(+)/GATA(4+), CXCR4(+), CD44(+), CD31(+), and CD59(+) cells into the infarcted heart on day 7 and improved integration of (Trans)SM in the heart compared to (Nat)SM (group 2) (P<0.05). Extensive neomyogenesis and angiogenesis in group-3 (P<0.01 vs. group-2), with resultant attenuation of infarct size (P<0.01 vs. group-2) and improvement in global heart function (P<0.01 vs. group-2) was observed at 8 weeks. In conclusion, simultaneous activation of diverse signaling pathways by overexpression of multiple growth factors caused massive mobilization and homing of stem/progenitor cells from peripheral circulation, the bone marrow, and the heart for accelerated repair of the infarcted myocardium.