ScienceDaily (Nov. 17, 2008) — A novel protein marker has been found that identifies rare adult liver stem cells, whose ability to regenerate injured liver tissue has the potential for cell-replacement therapy. For the first time, researchers at the University of Pennsylvania School of Medicine led by Linda Greenbaum, MD, Assistant Professor of Medicine in the Division of Gastroenterology, have demonstrated that cells expressing the marker can differentiate into both liver cells and cells that line the bile duct.