Abstract 1616: Reconstitution of Embryonic Signaling via Sonic Hedgehog Gene Therapy Ameliorates Aging-induced EPC Dysfunction and Augments EPC-mediated Therapeutic Angiogenesis in Acute Myocardial Infarction
Background: A number of clinical trials using stem/progenitor cell transplantation in ischemic heart diseases are now on-going, however, aging-induced cell dysfunction may impair therapeutic efficacy. We tested the hypothesis that genetic modification of EPCs by sonic hedgehog (Shh), one of the embryonic morphogens, may ameliorate the loss of function in aged EPCs.
Methods and Results: Cultured EPCs were isolated from 3m.o. and 24m.o. mice and cell functions, including cytokine expression, were evaluated by real-time PCR. Proliferation, migration and adhesion activity were significantly decreased and apoptosis was increased in the 24m.o.-EPCs vs. 3m.o.-EPCs. The reduced expression of VEGF, eNOS, and IGF-1 were also observed in the 24m.o.-EPCs. We then evaluated the effect of Shh gene transfer to the 24m.o.-EPCs. Shh gene transfer significantly improved proliferation and anti-apoptosis activities in 24m.o.-EPCs vs. empty vector transfected (EV) 24m.o.-EPCs, up to a similar level of EV 3m.o.-EPCs, and upregulated the eNOS expression in 24m.o.-EPCs. Next, we evaluated the therapeutic effect of genetically modified aged (24m.o.-) EPCs by Shh (Shh-EPC) vs. EV 24m.o.-EPCs (EV-EPC) vs. PBS injection (Control) in the mouse AMI model. One thousand Shh-EPCs or EV-EPCs or equal volume of PBS were injected to the ischemic site just after LAD ligation. The percent of scar length in the infarcted LV 14 days after surgery was significantly reduced in the Shh-EPC group (25±9%) compared to the EV-EPC group (41±5%) and the PBS group (43±7%) with increased capillary density in the peri-infarct area (160±15, 122±9 and 105±12/HPF, respectively). A notable finding is that Ki67 positive cardiomyocytes were observed only in the Shh-EPC group, suggesting that cardiomyocyte proliferation or cardiomyogenesis was induced by transplantation of Shh gene modified EPCs in ischemic myocardium.
Conclusion: Shh gene transfer to aged EPCs ameliorates aging-induced EPC dysfunction. Intramyocardial transplant of Shh-modified aged EPCs augments therapeutic efficacy for repair of ischemic injury. Shh gene modified EPCs may represent second generation-EPC transplantation therapy in ischemic heart disease.