Embryonic stem (ES) cells have the potential to differentiate into various progenitor cells. Here we investigated the capacity of mouse ES cells to differentiate into renal tubular cells both in vitro and in vivo. After stably transfecting Wnt4 cDNA to mouse ES cells (Wnt4-ES cells), undifferentiated ES cells were incubated by the hanging drop culture method to induce differentiation to embryoid bodies (EBs). During culturing of the EBs derived from the Wnt4-ES cells, aquaporin-2 (AQP2) mRNA and protein were expressed within 15-20 days. The expression of AQP2 in Wnt4-EBs was enhanced in the presence of hepatocyte growth factor (HGF) and activin A. We next performed in vivo experiments by transplanting the Wnt4-EBs into the mouse renal cortex. Four weeks after transplantation, some portions of the EB-derived cells expressing AQP2 in the kidney assembled into tubular-like formations. In conclusion, our in vitro and in vivo experiments revealed two new findings: first, that cultured Wnt4-EBs have an ability to differentiate into renal tubular cells; and second, that Wnt4, HGF, and activin A may promote the differentiation of ES cells to renal tubular cells. (c) 2005 Elsevier Inc. All rights reserved.