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.
In vitro functional comparison of therapeutically relevant human vasculogenic progenitor cells used for cardiac cell therapy