However, our approach of combining Hedera-saponin-B angiogenic growth factors and overexpressing them in nanofiber expanded stem cells, resulted in significant enhancement of neovascularization and improvement of cardiac function compared to stem cell injection alone. In addition, to the proangiogenic effect of VEGF, this marked improvement of neovascularization may also be due to enhanced maturating effect and inhibition of apoptosis by PDGF. To further elucidate the precise mechanisms of the improved effects of angiogenic growth factors overexpressed in nanofiber expanded stem cells on neovascularization and cardiac function, we evaluated the role of signaling molecules in ischemic rat hearts. We observed a significant increase in the production of VEGF, pNOS3 and NOS2 and decrease in the production of MMP9 in rat heart Obtusifolin tissues treated with stem cells overexpressing VEGF and PDGF genes. Since the contribution of angiogenic factors from transfected genes are limited, this type of transfection does not sustain greater than two weeks and only transiently produces these gene products. We, in our current study, noted a similar lower degree of tissue expression of VEGF and NOS2 in tissues harvested after six weeks of stem cell therapy in the Exp group, thereby indicating that stem cell therapy itself induces host tissue production of angiogenic factors, which in turn leads to neovascularization of ischemic tissues. In addition, animals in the VIP group had enhanced tissue production of angiogenic factors, which may have been due to initiation of the signaling cascade and initial effects of VEGF and PDGF produced by the stem cells, further contributing to angiogenesis in the host tissue. Finally, the concern that transient overexpression leads to tumor formation was addressed by testing for molecules of oncogenic potential and their signaling pathways. As we did not detect enhanced production of these molecules or their signaling pathways of oncogenesis, these results are encouraging for potential clinical use of nanofiber-expanded stem cells.