Ethanol extract of Magnoliae cortex (EEMC) limits teratoma formation of pluripotent stem cells by selective elimination of undifferentiated cells through the p53-dependent mitochondrial apoptotic pathway.

Induced pluripotent stem cells (iPSCs) are regarded as the best potential cell source for cell-based regenerative medicine. To develop a safe and efficient iPSC-based cell therapy, it is very important to avoid possible teratoma formation, which can arise from undifferentiated iPSCs (USCs) remaining among differentiated cell products. Dried bark of Magnolia officinalis (Magnolia cortex, MC) has long been used in traditional medicine to treat gastrointestinal ailments and allergic diseases, and has shown have various pharmacological activities, including anti-bacterial, anti-inflammatory, and anti-cancer effects. However, its effects on iPSCs have not yet been examined.In this study, we investigated the selective cytotoxic effects of ethanol extract of MC (EEMC) on undifferentiated iPSCs and elucidated the underlying apoptotic mechanisms in detail. We also investigated the inhibitory effects of EEMC on teratoma formation via in ovo experiments.We found that EEMC greatly reduced cell growth and induced apoptotic cell death in USCs, but not in differentiated or normal cells. EEMC caused G2/M cell cycle arrest, mitochondrial damage, and caspase activation of USCs, accompanied by p53 accumulation. In p53KO human iPSCs, EEMC had no cytotoxicity, reinforcing that EEMC-mediated apoptosis of USCs is p53-dependent. EEMC did not cause DNA damage in iPSC-derived differentiated cells. In ovo teratoma formation assay revealed that EEMC treatment before injection efficiently eliminated USCs and prevented teratoma formation.These results collectively indicate that EEMC has potent anti-teratoma activity, and therefore can be used for the development of safe iPSC-based therapy.