With the increasing rate of end-stage renal failure and limited alternatives for its treatment, potential regenerative approaches for kidney damages are urgently needed. Because of the complexity of the organ, the development of stem cell therapies for kidney is still in its infancy. Identifying which cell types are capable of beneficial effects is the critical step required to realize the potential of this therapeutic approach. Three possible sources of stem cells can be envisioned for the development of this type of treatment: (i) bone-marrow-derived stem cells, (ii) renal adult stem cells, and (iii) fetal renal stem cells. The focus of this project is to assess the regenerative potential of stem cells derived from different sources and investigate the possible obstacles to their utilization, as well as their potential side effects in preclinical models of acute and chronic renal failure. Indeed, the clinical usefulness of the treatment, as well as the need to understand currently discrepant results, require comparative experimental studies that have never been performed before either in SC therapy of kidney injury, or in that of other organs. Hopefully, this comparison will allow to set up standardized protocols of SC isolation and administration for phase I/II trials in patients affected by acute and chronic renal failure.