Therapeutic miR-21 Silencing Ameliorates Diabetic Kidney Disease in Mice
Johan M. Lorenzen
Diabetic nephropathy is the main cause of end-stage renal disease. MicroRNAs are powerful regulators of the genome, and global expression profiling revealed miR-21 to be among the most highly regulated microRNAs in kidneys of mice with diabetic nephropathy. In kidney biopsies of diabetic patients, miR-21 correlated with tubulointerstitial injury. In situ PCR analysis showed a specific enrichment of miR-21 in glomerular cells. We identified cell division cycle 25a (Cdc25a) and cyclin-dependent kinase 6 (Cdk6) as novel miR-21 targets in mesangial cells. miR-21-mediated repression of Cdc25a and Cdk6 resulted in impaired cell cycle progression and subsequent mesangial cell hypertrophy. miR-21 increased podocyte motility by regulating phosphatase and tensin homolog (Pten). miR-21 antagonism in vitro and in vivo in streptozotocin-induced diabetic mice decreased mesangial expansion, interstitial fibrosis, macrophage infiltration, podocyte loss, albuminuria, and fibrotic- and inflammatory gene expression. In conclusion, miR-21 antagonism rescued various functional and structural parameters in mice with diabetic nephropathy and, thus, might be a viable option in the treatment of patients with diabetic kidney disease.In order to identify miRNAs that are critically involved in the development of diabetic kidney disease, we performed miRNA profiling in kidneys of healthy and streptozotocin-induced diabetic mice, which revealed several deregulated miRNAs in diabetic kidneys (Figure 1A). miR-21 was among the most highly upregulated miRNAs (Figures 1B and 1C). To investigate the specific localization of miR-21 upregulation in the kidney, we performed an in situ PCR on kidney sections of healthy and diabetic mice. In diabetic kidneys, miR-21 was enriched in all parts of the kidney, with the highest change in glomerular cells (Figures 1D–1F).The plasma miR-21 concentration was increased in diabetic patients compared to healthy controls (Figure 1G). Furthermore, we show that urinary miR-21 correlated with proteinuria in patients (Figure 1H). We recently showed that urinary miR-21 concentration is increased in type II diabetic patients.8 Interestingly, in patients with diabetic kidney disease we found a positive correlation of miR-21 expression with chronic tubulointerstitial injury in kidney biopsies (Figure 1I).Patient characteristics are described in Table 1. The ethical committee of the University Hospital Jena approved the study. 26 patients and 20 age-matched healthy controls were included. The diagnosis of diabetic nephropathy (or diabetic kidney disease [DKD]) was histologically confirmed after kidney biopsy in 11 patients. Biopsies were evaluated by an experienced renal pathologist, including the quantification of chronic tubular damage of the renal cortex in percent.We thank Prof. Dr. H.-J. Gröne (German Cancer Research Center (DKFZ), Cellular and Molecular Pathology) for histopathologic diagnosis of kidney biopsies. This work was funded by a grant from the Else Kröner-Fresenius Foundation (to J.M.L. and T.T.), the Else Kröner-Fresenius Memorial scholarship (to J.M.L.), the REBIRTH Excellence Cluster (to T.T.), and the Integrated Research and Treatment Center Transplantation (IFB-Tx) (to T.T. and J.M.L.). T.T. received and licensed a miRNA-based patent about the use of miR-21 inhibitors in fibrotic diseases.Supplemental Information includes five figures and one table and can be found with this article online at http://dx.doi.org/10.1016/j.ymthe.2016.08.001.