32 The kidneys developed striking vascular abnormalities and prominent striped fibrosis. These findings highlight

the important roles of Dicer and Bortezomib price miRNAs in renal physiology and pathology, although the extent to which such genetic studies reveal an essential and fundamental role of Dicer in cellular function, as opposed to a specific role in renin secreting cells, is arguable. The importance of Dicer in cellular function is further highlighted by Wei’s study.33 They established a mouse model with targeted Dicer deletion in renal proximal tubules. These mice had normal renal function and histology despite a global downregulation of miRNAs in the renal cortex. However, these mice were strikingly resistant to renal ischaemia-reperfusion injury, showing significantly better renal function, less tissue damage, lower tubular apoptosis and improved survival compared with their wild-type

counterparts.33 Diabetic nephropathy is the leading cause of end-stage kidney disease but our understanding of the disease mechanisms is incomplete. Studies of miRNA expression BMS-354825 purchase in diabetic nephropathy have so far emerged predominantly from animal models of diabetes and the effects of hyperglycaemia. In one study, miR-192 levels were shown to be increased in glomeruli isolated from streptozotocin-injected diabetic mice and diabetic mice db/db when compared with non-diabetic mice.34 In this study, miR-192 was shown to regulate E-box repressors that are responsible for controlling the expression of TGF-β-induced

Rebamipide extracellular matrix proteins, collagen 1-α 1 and 2 (Col1a1 and 2). Col1a1 and 2 were shown to accumulate during diabetic nephropathy; therefore, these results suggest a potential role of miR-192 in diabetic nephropathy or that miR-192 can be an effector of TGF-β. However, discordantly a recent study demonstrated that miR-192 expression is decreased in proximal tubular epithelial cells in response to TGF-β.35 The loss of miR-192 correlates with tubulointerstitial fibrosis and reduction in eGFR in renal biopsies from patients with established diabetic nephropathy. This suggests that mesangial cell and proximal tubular epithelial cell miRNA expression may exhibit different responses to TGF-β. Recently, Akt kinase, a key mediator of diabetic nephropathy, was found to be activated through downregulation of phosphatase and tensin homolog deleted on chromosome 10 (PTEN), which is targeted by miR-216a and miR-217. In turn, these miRNAs are upregulated by TGF-β, and indirectly by miR-192, in mouse mesangial cells.36,37 In other animal studies, Zhang et al. showed miR-21 expression was downregulated in response to early diabetic nephropathy in vitro and in vivo.