*4.11. Statistical Analysis*

Data are presented as means ± standard deviation (SD). Statistical significance was assessed by student's *t*-test to compare between the two groups. *p* < 0.05 was considered statically significant.

#### **5. Conclusions**

Pretreatment with histochrome (sodium salt of echinochrome A—a common sea urchin pigment) enhances cell survival under oxidative stress conditions by regulating the apoptosis signaling pathway and preventing DNA damage. Furthermore, histochrome attenuates cellular senescence in hCPCs. Our results suggest that pretreating c-kit-positive hCPCs with histochrome before transplantation might be a potential therapeutic strategy in treating ischemic heart disease.

**Author Contributions:** J.H.P. conception and design, conducted the experiments, data analysis and manuscript writing; N.-K.L., H.J.L., S.M., conducted the experiments, V.K.R., Y.-J.K., W.B.J., S.T.J., S.K., D.Y.K., L.T.H.V., L.T.T.G., D.H.K., J.S.H., J.Y. data analysis, H.T.K., provide cardiac tissue, N.P.M., S.A.F., E.A.V., J.H. prepared histochrome, S.H.B. and S.M.K. financial support, manuscript writing, and final approval of manuscript.

**Funding:** This research was funded by the National Research Foundation (NRF - 2018R1A2B6006380, NRF - 2015M3A9B4066493, NRF – 2015R1A5A2009656), the Korean Health Technology R&D Project, Ministry of Health and Welfare (HI18C2459, HI18C2458, HI17C1662) funded by the Korean government, and the Ministry of Science and Higher Education of the Russian Federation (RFMEFI61317X0076).

**Acknowledgments:** We thanks the students, Jun Bum Heo, Chae Ra Ahn, Hee Jeen Kim, and Geon Uk Ha, who participated in the experiment.

**Conflicts of Interest:** The authors declare no conflict of interest.
