In mammals, chronic inflammation can result in scarring of both tissues and organs. Since mesenchymal stem cells (MSCs) have been reported to have immunomodulatory activity, Brazilian scientists P. Semedo et al. from the University of Sào Paulo conducted a study examining the potential of MSCs to reduce fibrosis in chronic kidney diseases. In the September 11th online edition of Stem Cells, the investigators published their experimental results infusing 200,000 bone marrow-derived MSCs into rats undergoing chronic renal failure (remnant model). The animals were intravenously administered MSCs either every other week for 8 weeks or once and followed for 12 weeks. The investigators observed that the rats infused for 8 weeks had improved kidney function, but not in the rats receiving one round of MSCs (12 weeks). Histological analyses revealed that the kidneys from rats receiving multiple rounds of MSCs had reduced vimentin, type I collagen, TGFβ, FSP-1, MCP-1 concomitant with reduced serum levels of IL-6 and TNFα. It was also observed that IL-4 and IL-10 expression levels were increased in the rats receiving multiple treatment cycles of MSCs. The authors concluded that their results suggest that MSCs have immunomodulatory activity following the initial phase of chronic renal injury. The authors also surmise that MSCs may be involved in immunosuppression and remodeling of the diseased organ and modulate fibrogenesis in the chronically inflamed kidney.