So-called pluripotent stem cells can develop into any type of cell in the body—cells that could especially help in treating human diseases in which tissue loss has occurred. However, the signals that direct pluripotent stem cells to develop into desired cell types aren’t well understood. In a new study published online on January 28 in Differentiation, Sanjeev Gupta, M.D., and colleagues showed that human pluripotent stem cells differentiate into hepatocytes (liver cells) when cultured in a medium in which fetal hepatocytes had been grown. Surprisingly, the signals triggering differentiation were identified as small metabolomics products rather than proteins made by fetal hepatocytes. When the hepatocytes resulting from stem cells were transplanted into mice with acute liver failure, they promoted tissue repair and liver regeneration in the mice, indicating that hepatocytes derived in this way possess therapeutic potential. The U.S. Patent and Trademark Office has allowed claims for a patent to Einstein for Dr. Gupta’s differentiation method. Dr. Gupta is professor of medicine and of pathology and is the Eleazar and Feige Reicher Chair in Translational Medicine at Einstein and is an attending physician and hepatologist at Montefiore.