Melanie Kwan

Introduction: Survival of cardiac stem cells (CSCs) after transplantation is necessary to facilitate cardiac repair following damage to the heart due to their potential ability to regenerate cardiomyocytes. The current best estimate of post-transplantation survival of CSCs is only approximately 10%.¹ The primary cause of transplanted CSC death is oxidative stress induced by ischemia-reperfusion injury during cardiac surgery.¹ Over-production of hydrogen peroxide (H₂O₂; one of the physiological oxidants in cells) caused by ischemia-reperfusion can induce further cardiac damage during surgery.² Discovery of mechanisms that promote CSC survival under oxidative stress is needed to establish CSC transplantation as a viable treatment option. Previous studies used carbon monoxide (CO) pretreatment to induce a delayed cardioprotective effect by activating pro-survival signaling pathways in cardiomyocytes.³ Cai et. al. extended this concept to pretreatment with a heme oxygenase 1 inducer (CoPP), which induced endogenous CO generation to protect against ischemia-reperfusion injury.⁴ Teng et. al. expanded this further by pretreating CSCs with a nitric oxide (NO) donor to promote cell survival after CSC transplantation.² Methods: Teng et. al. preconditioned CSCs with diethylenetriamine nitric oxide adduct (DETA-NO), a NO donor.² The effect of H₂O₂-induced cellular damage was measured by lactate dehydrogenase (LDH) levels. To evaluate the functional role of DETA-NO preconditioning in promoting CSC survival, they stained cells with Annexin V-VITC and PI. to examine cell apoptosis.² Results: DETA-NO pretreatment showed a time- and dose-dependent decrease of LDH release under H₂O₂-induced oxidative stress.² The greatest reduction was seen with 12 h of preconditioning, and remained cytoprotective up to 24 h.² The most effective time and dose combination in preventing cell death under oxidative stress was determined to be preconditioning CSCs for 12 h with 250 mM DETA-NO. Preconditioned cells, compared to controls, exhibited a reduction of 50% of total cell death when examining H₂O₂-induced apoptosis.² Conclusion: Preconditioning CSCs with DETA-NO stimulates cell survival by activating multiple cell survival signaling pathways against oxidative stress, such as the NFkB, ERK, AKT, and STAT3 pathways.² This promotes gene expression of the anti-apoptotic genes MCL, BCL-2, BCL-xL, and HO-1, leading to cytoprotection against oxidative stress and subsequently to increased CSC survival.²

1. Cai C, Guo Y, Teng L, et al. Preconditioning Human Cardiac Stem Cells with an HO-1 Inducer Exerts Beneficial Effects After Cell Transplantation in the Infarcted Murine Heart. Stem Cells. 2015;33(12):3596-3607.
2. Teng L, Bennett E, Cai C. Preconditioning c-Kit-positive Human Cardiac Stem Cells with a Nitric Oxide Donor Enhances Cell Survival through Activation of Survival Signaling Pathways. J Biol Chem. 2016;291(18):9733-9747.
3. Stein AB, Bolli R, Dawn B, et al. Carbon monoxide induces a late preconditioning-mimetic cardioprotective and antiapoptotic milieu in the myocardium. J Mol Cell Cardiol. 2012;52(1):228-236.
4. Cai C, Teng L, Vu D, et al. The heme oxygenase 1 inducer (CoPP) protects human cardiac stem cells against apoptosis through activation of the extracellular signal-regulated kinase (ERK)/NRF2 signaling pathway and cytokine release. J Biol Chem. 2012;287(40):33720-33732.