Acute renal failure (ARF) is a common disease with high morbidity and mortality. Recovery from ARF is dependent on the replacement of necrotic tubular cells with functional tubular epithelium. Recent advancement in developmental biology led to the discovery of immature mesenchymal stem cells (MSCs) in bone marrow and several established organs and to the definition of their potential in the recovery from tissue injury. We investigated the effect of MSCs infusion on the recovery from ARF induced by intramuscle injection of glycerol in C57/BL6 mice. In this model, ARF is associated with an extensive necrosis of tubular epithelial cells due to myoglobin- and hemoglobin-induced injury. MSCs were obtained from bone marrow of transgenic mice expressing green fluorescent protein (GFP). MSC GFP-positive cells (MSC-GFP+) injected intravenously homed to the kidney of mice with glycerol-induced ARF but not to the kidney of normal mice. MSC-GFP+ localized in the context of the tubular epithelial lining and expressed cytokeratin, indicating that MSCs engrafted in the damaged kidney, differentiated into tubular epithelial cells and promoted the recovery of morphological and functional alterations. Moreover, MSCs enhanced tubular proliferation as detected by the increased number of proliferating cell nuclear antigen (PCNA) positive cells. A significant contribution of the engrafted MSCs in the regeneration of tubular epithelial cells was shown by the presence of a consistent number of GFP+ tubular cells 21 days after the induction of injury. In conclusion, these results indicated a tropism of MSCs for the injured kidney and a potential contribution of these cells to tubular regeneration and to the recovery from ARF.

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