microrna-in-situ-hybridization-for-formalin-fixed-kidney-tissues

MicroRNA <em>In situ</em> Hybridization for Formalin Fixed Kidney Tissues

In this article we describe a method for colorimetric detection of miRNA in the kidney through in situ hybridization with digoxigenin tagged microRNA ...

Medical College of Wisconsin

We reported previously an approach for identifying microRNA (miRNA)-target pairs by combining miRNA and proteomic analyses. The approach was applied in the present study to examine human renal epithelial cells treated with transforming growth factor β1 (TGFβ1), a model of epithelial-mesenchymal transition important for the development of renal interstitial fibrosis. Treatment of human renal epithelial cells with TGFβ1 resulted in upregulation of 16 miRNAs and 18 proteins and downregulation of 17 miRNAs and 16 proteins. Of the miRNAs and proteins that exhibited reciprocal changes in expression, 77 pairs met the sequence criteria for miRNA-target interactions. Knockdown of miR-382, which was up-regulated by TGFβ1, attenuated TGFβ1-induced loss of the epithelial marker E-cadherin. miR-382 was confirmed by 3'-untranslated region reporter assay to target five genes that were downregulated at the protein level by TGFβ1, including superoxide dismutase 2 (SOD2). Knockdown of miR-382 attenuated TGFβ1-induced downregulation of SOD2. Overexpression of SOD2 ameliorated TGFβ1-induced loss of the epithelial marker. The study provided experimental evidence in the form of reciprocal expression at the protein level for a large number of predicted miRNA-target pairs and discovered a novel role of miR-382 and SOD2 in the loss of epithelial characteristics induced by TGFβ1.

MicroRNA-target pairs in human renal epithelial cells treated with transforming growth factor beta 1: a novel role of miR-382.

Previously we have shown that microRNA miR-382 can facilitate loss of renal epithelial characteristics in cultured cells. This study examined the in vivo role of miR-382 in the development of renal interstitial fibrosis in a mouse model. Unilateral ureteral obstruction was used to induce renal interstitial fibrosis in mice. With 3 days of unilateral ureteral obstruction, expression of miR-382 in the obstructed kidney was increased severalfold compared with sham-operated controls. Intravenous delivery of locked nucleic acid-modified anti-miR-382 blocked the increase in miR-382 expression and significantly reduced inner medullary fibrosis. Expression of predicted miR-382 target kallikrein 5, a proteolytic enzyme capable of degrading several extracellular matrix proteins, was reduced with unilateral ureteral obstruction. Anti-miR-382 treatment prevented the reduction of kallikrein 5 in the inner medulla. Furthermore, the protective effect of the anti-miR-382 treatment against fibrosis was abolished by renal knockdown of kallikrein 5. Targeting of kallikrein 5 by miR-382 was confirmed by 3'-untranslated region luciferase assay. These data support a completely novel mechanism in which miR-382 targets kallikrein 5 and contributes to the development of renal inner medullary interstitial fibrosis. The study provided the first demonstration of an in vivo functional role of miR-382 in any species and any organ system.

MiR-382 targeting of kallikrein 5 contributes to renal inner medullary interstitial fibrosis.

The human miR-29 family of microRNAs has three mature members, miR-29a, miR-29b, and miR-29c. miR-29s are encoded by two gene clusters. Binding sites for several transcriptional factors have been identified in the promoter regions of miR-29 genes. The miR-29 family members share a common seed region sequence and are predicted to target largely overlapping sets of genes. However, the miR-29 family members exhibit differential regulation in several cases and different subcellular distribution, suggesting their functional relevance may not be identical. miR-29s directly target at least 16 extracellular matrix genes, providing a dramatic example of a single microRNA targeting a large group of functionally related genes. Strong antifibrotic effects of miR-29s have been demonstrated in heart, kidney, and other organs. miR-29s have also been shown to be proapoptotic and involved in the regulation of cell differentiation. It remains to be explored how various cellular effects of miR-29s determine functional relevance of miR-29s to specific diseases and how the miR-29 family members may function cooperatively or separately.

The miR-29 family: genomics, cell biology, and relevance to renal and cardiovascular injury.

MicroRNA research in humans and mammalian model organisms is in a crucial stage of development. Diagnostic and therapeutic values of microRNAs appear promising, but remain to be established. The physiological and pathophysiological significance of microRNAs is generally recognized, but much better understood in some organ systems and disease areas than others. In the present paper, we review several translational studies of microRNAs, including those showing the potential value of therapeutic agents targeting microRNAs and diagnostic or prognostic microRNA markers detectable in body fluids. We discuss the lessons learned and the experience gained from these studies. Several recent studies have begun to explore translational microRNA research in kidney disease and hypertension. Translational research of microRNAs in the kidney faces unique challenges, but provides many opportunities to develop and apply new methods, and to merge complementary basic and clinical approaches.

Translational study of microRNAs and its application in kidney disease and hypertension research.

The SS-16(BN)/Mcwi consomic rat was produced by the introgression of chromosome 16 from the Brown Norway (BN/NHsdMcwi) rat onto the genetic background of the Dahl salt-sensitive (SS/Mcwi) rat by marker-assisted breeding. We have previously shown that the normotensive SS-16(BN)/Mcwi consomic strain is better protected from developing left ventricular dysfunction and fibrosis with aging than the hypertensive SS/Mcwi parental strain; however, the mechanism of this protection was not clear since the SS-16(BN)/Mcwi had both lowered blood pressure and an altered genetic background compared with SS/Mcwi. Microarray analysis of SS-16(BN)/Mcwi and SS/Mcwi left ventricle tissue and subsequent protein pathway analysis were used to identify alterations in gene expression in signaling pathways involved with the observed cardioprotection on the SS background. The SS-16(BN)/Mcwi rats exhibited much higher mRNA levels of expression of transcription factor JunD, a gene found on chromosome 16. Additionally, high levels of differential gene expression were found in pathways involved with angiogenesis, oxidative stress, and growth factor signaling. We tested the physiological relevance of these pathways by experimentally determining the responsiveness of neonatal cardiomyocytes to factors from identified pathways and found that cells isolated from SS-16(BN)/Mcwi rats had a greater growth response to epidermal growth factor and endothelin-1 than those from parental SS/Mcwi. We also demonstrate that the SS-16(BN)/Mcwi is better protected from developing fibrosis with surgically elevated afterload than other normotensive strains, indicating that gene-gene interactions resulting from BN chromosomal substitution confer specific cardioprotection. When combined with our previous findings, these data suggest that that SS-16(BN)/Mcwi may have an increased angiogenic potential and better protection from oxidative stress than the parental SS/Mcwi strain. Additionally, the early transient idiopathic left ventricular hypertrophy in the SS-16(BN)/Mcwi may be related to altered myocyte sensitivity to growth factors.

Mechanisms of cardioprotection resulting from Brown Norway chromosome 16 substitution in the salt-sensitive Dahl rat.

Delayed ischemic preconditioning effectively protects kidneys from ischemia-reperfusion injury but the mechanism underlying renal protection remains poorly understood. Here we examined the in vivo role of microRNA miR-21 in the renal protection conferred by delayed ischemic preconditioning in mice. A 15-min renal ischemic preconditioning significantly increased the expression of miR-21 by 4 h and substantially attenuated ischemia-reperfusion injury induced 4 days later. A locked nucleic acid-modified anti-miR-21 given at the time of ischemic preconditioning knocked down miR-21 and significantly exacerbated subsequent ischemia-reperfusion injury in the mouse kidney. Knockdown of miR-21 resulted in significant upregulation of programmed cell death protein 4, a proapoptotic target gene of miR-21, and substantially increased tubular cell apoptosis. Hypoxia-inducible factor-1α in the kidney was activated after ischemic preconditioning and blockade of its activity with a decoy abolished the upregulation of miR-21 in cultured human renal epithelial cells treated with the inducer cobalt chloride. In the absence of ischemic preconditioning, knockdown of miR-21 alone did not significantly affect ischemia-reperfusion injury in the mouse kidney. Thus, upregulation of miR-21 contributes to the protective effect of delayed ischemic preconditioning against subsequent renal ischemia-reperfusion injury.

Delayed ischemic preconditioning contributes to renal protection by upregulation of miR-21.

Treatment with L-mimosine, which activates hypoxia-inducible factor-α (HIF-α), attenuates renal tubulointerstitial injury and improves renal function in a rat remnant kidney model. The miR-29 family of microRNAs directly targets a large number of extracellular matrix genes and reduces renal interstitial fibrosis. We analyzed microRNA expression profiles in rat remnant kidneys with or without treatment with L-mimosine. The expression of miR-29c was downregulated in rat remnant kidneys compared with sham control and significantly restored by the L-mimosine treatment. In cultured human kidney epithelial HK2 cells, cobalt chloride activated HIF-α and upregulated miR-29c expression. The upregulation of miR-29c expression was significantly attenuated by knockdown of HIF-1α or HIF-2α. Downregulation of miR-29c was associated with significant increases in interstitial fibrosis, collagen type II α1 (COL2A1) protein, and tropomyosin 1α (TPM1) protein in rat remnant kidneys and in kidneys from IgA nephropathy patients. The increases in rat remnant kidneys were attenuated by the L-mimosine treatment. COL2A1 and TPM1 were confirmed to be new, direct targets of miR-29c. In conclusion, miR-29c, an antifibrotic microRNA, is upregulated by HIF-α activation. MiR-29c is downregulated in renal interstitial fibrosis in humans and rats and restored by activation of HIF-α that attenuates fibrosis.

miR-29c is downregulated in renal interstitial fibrosis in humans and rats and restored by HIF-α activation.

Mesenchymal stem cell (MSC) administration is known to enhance the recovery of the kidney following injury. Here we tested the potential of hypoxic-preconditioned-MSC transplantation to enhance the efficacy of cell therapy on acute kidney injury (AKI) by improving MSC migration to the injured kidney. Cobalt was used as hypoxia mimetic preconditioning (HMP). MSC were subjected to HMP through 24 h culture in 200 µmol/L cobalt. Compared to normoxia cultured MSC (NP-MSC), HMP significantly increased the expression of HIF-1α and CXCR4 in MSC and enhanced the migration of MSC in vitro. This effect was lost when MSC were treated with siRNA targeting HIF-1α or CXCR4 antagonist. SPIO labeled MSC were administered to rats with I/R injury followed immediately by magnetic resonance imaging. Imaging clearly showed that HMP-MSC exhibited greater migration and a longer retention time in the ischemic kidney than NP-MSC. Histological evaluation showed more HMP-MSC in the glomerular capillaries of ischemic kidneys than in the kidneys receiving NP-MSC. Occasional tubules showed iron labeling in the HMP group, while no tubules had iron labeling in NP group, indicating the possibility of tubular transdifferentiation after HMP. These results were also confirmed by fluorescence microscopy study using CM-DiI labeling. The increased recruitment of HMP-MSC was associated with reduced kidney injury and enhanced functional recovery. This effect was also related to the increased paracrine action by HMP-MSC. Thus we suggest that by enhancing MSC migration and prolonging kidney retention, hypoxic preconditioning of MSC may be a useful approach for developing AKI cell therapy.

Hypoxic preconditioning with cobalt of bone marrow mesenchymal stem cells improves cell migration and enhances therapy for treatment of ischemic acute kidney injury.

Aminoglycoside antibiotics, especially gentamicin, are widely used to treat Gram-negative infections due to their efficacy and low cost. Nevertheless the use of gentamicin is limited by its major side effect, nephrotoxicity. Xenon (Xe) provided substantial organoprotective effects in acute injury of the brain and the heart and protected against renal ischemic-reperfusion injury. In this study, we investigated whether xenon could protect against gentamicin-induced nephrotoxicity. Male Wistar rats were intermittently exposed to either 70% xenon or 70% nitrogen (N2) balanced with 30% oxygen before and during gentamicin administration at a dose of 100 mg/kg for 7 days to model gentamicin-induced kidney injury. We observed that intermittent exposure to Xe provided morphological and functional renoprotection, which was characterized by attenuation of renal tubular damage, apoptosis, and oxidative stress, but not a reduction in inflammation. We also found that Xe pretreatment upregulated hypoxia-inducible factor 2α (HIF-2α) and its downstream effector vascular endothelial growth factor, but not HIF-1α. With regard to the three HIF prolyl hydroxylases, Xe pretreatment upregulated prolyl hydroxylase domain-containing protein-2 (PHD2), suppressed PHD1, and had no influence on PHD3 in the rat kidneys. Pretreatment with Xe also increased the expression of miR-21, a microRNA known to have anti-apoptotic effects. These results support Xe renoprotection against gentamicin-induced nephrotoxicity.

Intermittent exposure to xenon protects against gentamicin-induced nephrotoxicity.

Knowledge of miRNA expression and function in specific cell types in solid organs is limited because of difficulty in obtaining appropriate specimens. We used laser capture microdissection to obtain nine tissue regions from rats, including the nucleus of the solitary tract, hypoglossal motor nucleus, ventral respiratory column/pre-Bötzinger complex, and midline raphe nucleus from the brainstem, myocardium and coronary artery from the heart, and glomerulus, proximal convoluted tubule, and medullary thick ascending limb from the kidney. Each tissue region consists of or is enriched for a specific cell type. Differential patterns of miRNA expression obtained by deep sequencing of minute amounts of laser-captured cells were highly consistent with data obtained from real-time PCR analysis. miRNA expression patterns correctly clustered the specimens by tissue regions and then by primary tissue types (neural, muscular, or epithelial). The aggregate difference in miRNA profiles between tissue regions that contained the same primary tissue type was as large as one half of the aggregate difference between primary tissue types. miRNAs differentially expressed between primary tissue types are more likely to be abundant miRNAs, while miRNAs differentially expressed between tissue regions containing the same primary tissue type were distributed evenly across the abundance spectrum. The tissue type-enriched miRNAs were more likely to target genes enriched for specific functional categories compared to either cell type-enriched miRNAs or randomly selected miRNAs. These data indicate that the role of miRNAs in determining characteristics of primary tissue types may be different than their role in regulating cell type-specific functions in solid organs.

Alison J. Kriegel

Department of Physiology

Medical College of Wisconsin

MicroRNA In situ Hybridization for Formalin Fixed Kidney Tissues

Alison J. Kriegel

.css-o250i3{font-size:18px;font-family:Open Sans,sans-serif;line-height:21.6px;}Department of Physiology

Medical College of Wisconsin

MicroRNA In situ Hybridization for Formalin Fixed Kidney Tissues

Department of Physiology