Mission/Officers

Dr. Gao is a Research Biologist in the Office of Applied Research and Safety Assessment (OARSA) of the Center for Food Safety and Applied Nutrition (CFSAN) at the US Food and Drug Administration (US FDA) where he is the principal investigator for the stem cell research program and for the toxicogenomics research program. His research focuses on toxicity testing and safety assessment of chemicals related to food, cosmetics, and dietary supplements using stem cell-based in vitro models and transcriptomics technologies. He received his doctorate in biotechnology from Jiangnan University (China) in 1995 and was a postdoctoral fellow at the National Autonomous University of Mexico (1997-1999) and at the National Cancer Institute of the National Institutes of Health (NIH) (1999-2005). Dr. Gao has served on a review panel for the Board of Scientific Counselors (BOSC) of the US Environmental Protection Agency (US EPA) and on expert peer reviewer panels for the Office of the Chief Scientist Grants Program of the US FDA. He has also reviewed research proposals for the National Center for Toxicological Research (NCTR).
Dr. Gao has published 56 original research papers, 6 review articles, and contributed 7 book chapters. He has been a member of SOT since 2013 and has served as co-chair for an SOT FDA Colloquium on Emerging Toxicological Science.

Dr. Sebastian Medina is currently an Assistant Professor in the Department of Pharmaceutical Sciences at the University of New Mexico (UNM) Health Sciences Center (HSC). He attained a PhD with distinction in Biomedical Sciences with a concentration in Pharmaceutical Sciences under the mentorship of Dr. Scott Burchiel at the UNM HSC. He then completed a postdoctoral fellowship under the mentorship of Dr. Ke Jian “Jim” Liu at the UNM HSC prior to transitioning to New Mexico Highlands University (NMHU). Dr. Medina’s major research interests are in the toxicology of environmental metals and their impacts on human health. He is particularly interested in understanding mechanisms of metal-induced toxicity to hematopoietic stem and progenitor cells, including the hematotoxicity of inorganic and organic arsenicals. His other major research interests are in elucidating mechanisms of immune dysregulation produced by metal and other toxicant exposures. Dr. Medina is primary author or coauthor of ~20 peer-reviewed articles and/or book chapters. He has received multiple awards for his research and scholastic achievements including, the Gerald Yost Outstanding Graduate Student Award from the Mountain West Society of Toxicology (MWSOT). Dr. Medina has been an active member of the Society of Toxicology and Stem Cells Specialty Section since 2016, including having served as the Graduate Student Representative of MWSOT (2016-2018), Postdoctoral Representative (2018-2021), and Vice President-Elect (2024-present). He is currently Principal Investigator of a National Institute of a General Medical Sciences SuRE Research Award (R16) and former Program Director of two USDA-funded programs focused on increasing the number of students from traditionally underserved populations graduating with degrees in life sciences.

Dr. Xian Wu is a Research Assistant Professor in the Department of Pharmacology and Toxicology at the Brody School of Medicine, East Carolina University. He holds a PhD in Toxicology from the University of Georgia, where he specialized in neurotoxicity screening using human pluripotent stem cell–derived neurons and astrocytes. Dr. Wu has extensive postdoctoral experience, having served as a postdoctoral fellow at the NIEHS and an ORISE fellow at the US FDA. His primary research focuses on the effects of environmental toxins on human health, particularly through the use of stem cell–based models to investigate developmental neurotoxicity and cardiotoxicity. His other research interests include chemotherapy-induced cardiotoxicity and the use of epigenetic regulation as a strategy for heart regeneration. Dr. Wu is the primary author or coauthor of approximately 25 peer-reviewed articles and book chapters. He has received multiple awards for his contributions to toxicology, including the Society of Toxicology Best Postdoctoral Publication Award, the Excellence in Research Award from the Stem Cells Specialty Section, and the Fellows Award for Research Excellence from the National Institutes of Health. Dr. Wu has been an active member of the Society of Toxicology (SOT) since 2014 and has served as the Postdoctoral Representative (2019–2020) and Secretary/Treasurer (2024–2025) of the Stem Cells Specialty Section. He is also actively involved in mentoring and service activities, contributing to various academic committees and editorial boards.

Dr. Rong Li is a Research Biologist in the Office of Chemistry and Toxicology (OCT) within the Human Foods Program (HFP) at the US Food and Drug Administration (US FDA). She serves as the principal investigator for developmental neurotoxicity (DNT) and stem cell research programs, focusing on developing New Approach Methodologies (NAMs) to assess the DNT hazards of chemical compounds in US FDA/HFP-regulated foods and dietary supplements. Dr. Li received her PhD in Pharmacology from Peking Union Medical College and Chinese Academy of Medical Sciences (PUMC & CAMS) and completed postdoctoral training at the National Institutes of Health (NIH)/National Eye Institute (NEI). She then joined the National Center for Advancing Translational Sciences (NCATS), where she supported drug development for the Therapeutics for Rare and Neglected Diseases (TRND) program. Her expertise spans stem cell technology, cellular and molecular biology, pharmacology, and toxicology, with a focus on using human stem cell-derived models—such as retinal pigment epithelial cells, neuronal cells, hepatocytes, and cardiomyocytes—for disease modeling, drug development, toxicology, and regenerative medicine. Dr. Li has participated in peer reviews for multiple biomedical journals and reviewed research grants for ZonMw Translational Research Program: Pluripotent Stem Cells for Inherited Diseases and Embryonic Research (PSIDER). She has published 46 research papers, contributed to two book chapters, and holds two international patents. Her contributions have been recognized with multiple awards, including the NIH Research Award, NCATS Director’s Award, and the CFSAN Honor Award – Exceptional Achievement Award. She has been a member of the Society of Toxicology (SOT) since 2020 and is also a member of the International Society for Stem Cell Research (ISSCR).

Dr. zur Nieden is an Associate Professor of molecular, cell, and systems biology at the University of California Riverside (UCR). There, she is affiliated with the Environmental Toxicology Program and the Stem Cell Center. She initiated her college career at the Ruhr-University of Bochum in Germany and the Whitney Marine Laboratory (USA) and finished summa cum laude with an MSc in 1999. She developed an interest in toxicology and stem cell biology during her PhD, which she pursued at Bayer Healthcare, Wuppertal, Germany, and where she was the first to develop osteogenic differentiation protocols from embryonic stem cells, using these protocols to screen pharmaceutical compounds for embryotoxic effects. After training under Dr. Rancourt as a postdoctoral scholar at the University of Calgary, Canada, in the Institute for Maternal and Child Health from 2002 to 2006, she joined the Fraunhofer Institute for Cell Therapy and Immunology in Leipzig, Germany, as a Group Leader. In her positions at Leipzig and UCR, Dr. zur Nieden developed projects in stem cell expansion and differentiation and predictive assay development and investigates the molecular mechanisms whereby toxicants interfere with bone development and signaling pathways that direct osteoblast differentiation. Her research has been funded by the German Ministry for Science and Education, the Tobacco Related Disease Research Program, the Johns Hopkins University Center for Alternatives to Animal Testing, the National Institutes of Health, and the US Environmental Protection Agency.

Dr. zur Nieden has published 34 original articles and five reviews and contributed 17 book chapters. She has held workshops on stem cell predictive assays and has served as an issue editor on Stem Cells for Osteo-degenerative Diseases in the Humana Press book series Methods in Molecular Biology. Dr. zur Nieden has worked as a toxicologist (using stem cells) for over 20 years and joined SOT in 2018.

Dr. Erik J. Tokar is the Leader of the Stem Cells Toxicology Group in the Mechanistic Toxicology Branch, Division of Translational Toxicology at NIEHS. He received his PhD in Cancer Biology from Michigan State University and completed a Postdoctoral fellowship at the National Cancer Institute at NIEHS, where he studied the role of stem cells and cancer stem cells in carcinogenesis. As head of the Stem Cell Toxicology Group, he develops and uses 2D and 3D (i.e., organoids) models to investigate the involvement of pluripotent stem cells in the pathogenesis of diseases associated with exposure to environmental chemicals. He has trained numerous students and fellows, served on several Postdoctoral science advisory and Doctoral supervisory committees, and served as an expert scientific reviewer on several toxicology-related funding applications and risk assessment documents. He has nearly 100 publications and serves as Associated Editor or on the Editorial Review Boards for multiple scientific journals. Since joining in 2006, Dr. Tokar has remained active in the Society of Toxicology (SOT). He has held positions in the Stem Cells Specialty Section (SCSS) (co-founder; Secretary/Treasurer; President), Metals SS (Postdoctoral Representative; Councilor; President) and the North Carolina Chapter of SOT (Councilor; President). He has also organized and/or presented in several SOT Annual Meeting sessions including symposia and Continuing Education Courses.

Dr. Katherine Zychowski is currently an Assistant Professor at the University of New Mexico where she studies how inhaled toxicants impact the immune system and the hematopoietic niche. She received her doctorate in Toxicology from Texas A&M University in 2014 and was an ASERT-IRACDA Postdoctoral Fellow (an NIH/NIGMS-sponsored program) from 2014-2018 at the University of New Mexico. She has served on multiple study sections (ad hoc) for the National Institutes of Health (NIH), Centers for Disease Control and Prevention (CDC) and Department of Defense (DOD). She has published over 30 peer-reviewed publications and 3 book chapters. She has been a member of the SOT since 2010 and has served the SOT as a member of the SOT Committee for Diversity Initiatives, the Treasurer of the Cardiovascular Specialty Section (2020-2022), and as a Councilor for the Inhalation and Respiratory Specialty Section (2022-2024). Dr. Zychowski is currently funded through an NIH R01 grant and has obtained funding from multiple federal agencies. Dr. Zychowski aims to incorporate mentoring strategies to retain and recruit promising Stem Cell Specialty Section members and disseminate our science to the greater scientific community.

Dr. Tukker is a postdoctoral research associate at Purdue University in the laboratory of Dr. Aaron Bowman. In her research she focuses on understanding how maternal-fetal exposures to metals and pesticides affect vulnerability to later-life exposures in relation to neurodegenerative disease pathology. She uses human induced pluripotent stem cells (hiPSCs) as a model system and differentiates them in cortical cultures as well as trophoblasts to mimic the maternal-fetal brain interface. Anke performed her PhD research at the Institute for Risk Assessment Sciences, Utrecht University (The Netherlands) and received her degree in 2020. Her graduate research focused on the development of an hiPSC-derived neuronal model for in vitro neurotoxicity testing and seizure liability assessment. She is first author on three book chapters as well as nine peer-reviewed articles published in, amongst others, Toxicological Sciences, ALTEX, and Neurotoxicology. Anke became a member of SOT in 2016 and joined the Neurotoxicology Specialty Section, for which she served as Postdoctoral Representative in 2021-2022, and WIT. In 2021 she joined the In Vitro and Alternative Methods and Stem Cells Specialty Sections. Anke served as (vice) Chair for SOT’s Postdoctoral Assembly (2022-2024). In 2019 she presented in the SOT Symposium Session “Perfluoroalkyl Substances (PFAS): Global and Persistent Environmental Contaminants”. In 2020, Anke was chair and presenter of the Symposium Session “Opportunities for human induced pluripotent stem cell-derived neurons in in vitro neurotoxicity safety testing” and chaired the session “Leader’s Digest: the art of scientific leadership” in 2023. In the same year, she presented in the symposium session “Mechanisms of Neurotoxicity, Neurodegeneration, and Neurodevelopmental Dysfunction Induced by Metals and Pesticide.” Currently, she serves as the Postdoctoral Representative for the SOT Career Advancement, Mentoring, and Networking Committee. Anke is honored to run for Postdoctoral Representative because she wants to use her network to expand the reach of SCSS by hosting webinars relevant to the stem cell community, provide practice and feedback opportunities for trainees and help the specialty section grow.