Introduction:
Overcoming the poor survival of cell grafts is an indispensable mission in cell therapy. Apurinic/apyrimidinic endonuclease/redox factor-1 (APE1) is known as a multifunctional enzyme to encourage cell survival, whereas the role of APE1 in cardiac cell therapy is still unknown.
Hypothesis:
APE1 overexpression in cardiac progenitor cells (CPC) ameliorates the effect of cardiac cell therapy.
Methods:
CPCs from 8-10 week-old C57BL/6 mice hearts were transfected with APE1-DsRed gene (APE1-CPC) or DsRed gene (Control [Ct]-CPC). The apoptosis induced by oxidative stress was assessed in APE1-/Ct-CPCs, and in neonatal rat cardiomyocytes (NRCM) within the co-culture system of APE1-/Ct-CPCs. Western blot analysis indicated the cellular signal to protect CPC via APE1 enzyme. To evaluate the effect of APE1 overexpression in cell therapy, we transplanted APE1-CPCs and Ct-CPCs into the mice myocardial infarction (MI) model and assessed the pathophysiological role of APE1 with functional and histological analysis.
Results:
Under the oxidative stress condition, APE1 overexpression inhibited the apoptosis of CPCs and accelerated TAK1 activation (Ct-CPC : APE1-CPC = 1.5±0.4 : 3.3±1.6 fold, p<0.05), and consequently NfKB phosphorylation in CPCs. In the co-culture system, the apoptosis of NRCMs was inhibited with APE1-CPCs compared to that with Ct-CPCs. In vivo, in the mice MI model, the number of total CPC grafts and cardiac α-actinin-positive graft CPCs were significantly larger in APE1-CPC injected mice (APE1 mice) compared to Ct-CPC injected mice (Ct mice) at 7 days after implantation. Eventually, the left ventricular ejection fraction of APE1 mice was significantly improved compared to Ct mice (Ct mice : APE1 mice = +3.1±6.7 : +11.3±4.0%, p<0.05) and was accompanied with the attenuation of fibrosis at 28 days after implantation.
Conclusions:
APE1 gene inhibited the apoptosis of CPCs and host cells against oxidative stress via the activation of TAK1-NFkB pathway, which is a novel insight into the stress response of APE1 enzyme. Furthermore, APE1-CPC grafts that effectively survived in the ischemic heart restored cardiac dysfunction and attenuated myocardial infarct size, and may be an innovative strategy to reinforce cardiac cell therapy.
Myocardial Restoration: Is It the Cell or the Architecture or Both?
