Great excitement greeted the discovery a few years ago that certain cells from mice and humans could be reprogrammed to become inducible pluripotent stem cells (iPS cells), as they hold promise for cell replacement therapy and modeling human disease. Two independent research groups — one led by Ludovic Vallier, at the University of Cambridge, United Kingdom, and the other led by Holger Willenbring, at the University of California San Francisco — have now shown that both possibilities are true for iPS cell–derived liver cells known as hepatocytes.

In the first study, Vallier and colleagues generated iPS cells from patients with various inherited diseases of the liver. These cells were then cultured in a defined way to generate hepatocytes, which were found to recapitulate key features of the diseases affecting the patients from which they were derived. While this study indicates that iPS cells can be used to model diseases of the liver, Willenbring and colleagues showed that iPS cell–derived hepatocytes have both the functional and proliferative capabilities needed for liver regeneration in mice. In an accompanying commentary, Linda Greenbaum, at Thomas Jefferson University School of Medicine, Philadelphia, describes how these studies have extended our understanding of the potential for iPS cells to be used for cell replacement therapy and modeling human disease.