Stanford OB/GYN Mourns the Loss of Adjunct Professor Roger Arnold Pedersen, A Pioneering Stem Cell Researcher

It is with great sadness that Stanford Medicine’s Department of Obstetrics and Gynecology announces the passing of Adjunct Professor Roger Arnold Pedersen, PhD, a distinguished and influential figure in stem cell biology and developmental genetics and a beloved and wise faculty member in the Division of Reproductive, Stem Cell, and Perinatal Biology. Pedersen passed away on Wednesday evening, February 5th, 2025, at Stanford Hospital.  

Pedersen’s career spanned over four decades, marked by groundbreaking research and significant contributions to our understanding of early mammalian development and stem cell biology. Pedersen’s research aimed to understand the basic mechanisms underpinning early cell fate decisions, including the identification of factors in the extracellular milieu that activate key signaling pathways, and defining the role of specific transcription factors that implement cell fate changes leading from pluripotency to tissue-specific cell differentiation. He believed that this focus on mammalian embryology and early cell fate decisions would lead to better human health, particularly in the areas of infertility and birth defects.  

Born in San Bernardino, California, Pedersen’s academic journey began at Stanford University, where he earned an A.B. with Distinction in Biology in 1965. He continued his studies at Yale University, receiving his Ph.D. in Biology/Developmental Genetics in 1970. Following a postdoctoral fellowship at The Johns Hopkins University focused on mammalian embryology, he embarked on a distinguished academic career. 

Pedersen held faculty positions at the University of California, San Francisco (UCSF) for many years, rising to the rank of Professor in Residence in the Departments of Radiology & Anatomy and Obstetrics, Gynecology and Reproductive Sciences. In 2002, he moved to the University of Cambridge, where he served as Professor of Regenerative Medicine in the Department of Surgery and later as Professor Emeritus in the Department of Paediatrics. Pedersen’s departure from UCSF was spurred by emerging federal restrictions of the time prohibiting the funding of embryonic stem cell research. While at Cambridge, he was still cited in American debates on the restriction around stem cell research and his vocal advocacy is one reason that California passed Proposition 71, which established the California Institute for Regenerative Medicine to provide funding for researchers in this field. 

In 2018, Pedersen returned to his former alma mater, Stanford University, as an Adjunct Professor and Senior Research Scientist in Obstetrics and Gynecology in the Reproductive, Stem Cell and Perinatal Biology Division (RSCPB).  

“Roger [Pedersen] was a true pioneer in stem cell biology. His groundbreaking work illuminated the fundamental mechanisms of early development and laid the foundation for regenerative medicine as we know it,” says Virginia D. Winn, MD, PhD, Chief of the RSCPB Division. “To me, what I will remember about Roger is his relentless pursuit of knowledge and unwavering belief in the power of science to improve the human condition. It has been an honor to call him a colleague, collaborator, and friend over the last few years.” 

Over the last four decades, he made seminal contributions to the field of stem cell research as one of the early researchers to work with embryonic stem cells.  

• Studying cell potency and fate in pre-implantation and early post-implantation mouse embryos Pedersen revealed the origins of the primary tissue layers and the three-dimensional organization of mammalian embryos. Further investigation led him to discover a new type of stem cell, which he called epiblast stem cells (EpiSCs), in later-stage mouse and rat embryos. EpiSCs share many features with human embryonic stem cells (hESCs), and subsequent work supported the hypothesis that hESCs are the human counterparts of EpiSCs, with similar responses to growth factors and mechanisms of pluripotency regulation and differentiation.
• Pederson’s approach of using transcription factor-based “forward” programming of hPSCs yielded a highly purified and massively expanded population of megakaryocytes, which are now in their preclinical phase of research under license to Platelet Biogenesis, a U.S. company that is moving toward their clinical use.
• With collaborators, he more recently achieved highly efficient reprogramming of hPSCs into neurons, oligodendrocytes and skeletal muscle cells by controlled transcription factor expression from genomic ‘safe harbor’ sites. 
• These discoveries set the stage for a concerted effort to generate multiple components of tissues that could be assembled in vitro and used clinically to repair losses incurred through injury and disease.  

His work has been published in numerous high-impact journals, and he was a highly sought-after speaker at international conferences due to his research and advocacy. He served on the editorial boards of several leading journals, including the International Journal of Developmental Biology, Stem Cells, and Cell Stem Cell, and he served as Associate Editor of Molecular Reproduction and Development. He also held numerous leadership positions, including Director of the Cambridge Stem Cell Consortium, MRC Centre for Stem Cell Biology & Regenerative Medicine, Anne McLaren Laboratory for Regenerative Medicine, Cambridge Centre for Stem Cell Biology & Medicine, Cambridge Programme in Stem Cell Medicine, Reproductive Genetics Unit at UCSF, Transgenic/Targeted Mutagenesis Core at UCSF, and Laboratory Director of the In Vitro Fertilization Program at UCSF. In addition to his research, Pedersen was a dedicated mentor and teacher, having supervised 17 PhD students, 41 postdoctoral fellows, and 5 clinical fellows throughout his career. 

Pedersen was actively involved in the scientific community, holding memberships in the International Society for Stem Cell Research and the Society of Biology. He also contributed his expertise to various organizations, including the UK Stem Cell Bank Management Committee, the Singapore Stem Cell Consortium, East of England Stem Cell Network, UK National Stem Cell Network Steering Committee, Qatar Biomedical Research Institute, Scar-Free Healing Foundation, and Blood Cell Storage Inc. Since 2004, he was a principal scientific advisor for, Stemnion Inc. (now called Noveome Biotherapeutics, Inc.). With Pedersen’s consultation, the company developed a portfolio of wound-healing products from human amniotic epithelium.  

He was an amazing force in science and as a colleague. He lives on through his groundbreaking science...

Pedersen’s legacy extends beyond his scientific achievements. He will be remembered as a scientific leader, a dedicated mentor, and a passionate advocate for stem cell research and its potential to improve human health. His contributions have paved the way for new therapies and have inspired countless scientists to pursue careers in regenerative medicine. 

“When I think of Roger [Pedersen], I see his wry smile, hear his infectious laugh, and remember his curiosity, caring, passion, and innovation,” shares Leslee Subak, MD, Chair of Obstetrics and Gynecology. “He was an amazing force in science and as a colleague. He lives on through his groundbreaking science, his impact on dozens of mentees, and in the fond memories of his colleagues. I will miss him terribly and yet feel grateful to have known him over the decades at both UCSF and Stanford.” 

We extend our deepest condolences to Roger Pedersen’s family, friends, and colleagues.