This work was supported by US National Institutes of Health grants HL082798 and HL111580.

1. Kidney Tissue Sections
<ol>
	<li>Formalin-fixed (10%) paraffin-embedded kidney sections are cut onto microscope slides at 5 mm thickness using a Microm HM 355 S. The slides can be stored for several months before analysis.</li>
</ol>
2. Solution Preparation
<ol>
	<li>Prepare 1 L of 1x PBS in ddH2O in an autoclavable screw top bottle. Fill another bottle with 1 L of ddH2O. Add 1 ml of DEPC to each bottle, cover and shake vigorously. Let the solutions sit overnight at ro...

<ol>
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U.S.A. 104 (4), 3432-3437 (2007).</li><li>Krupa, A., Jenkins, R., Luo, D. D., Lewis, A., Phillips, A., Fraser, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Loss+of+microRNA-192+promotes+fibrogenesis+in+diabetic+nephropathy.">Loss of microRNA-192 promotes fibrogenesis in diabetic nephropathy.</a> J. Am. Soc. Neph. 21 (3), 438-447 (2010).</li><li>Wang, B., Herman-Edelstein, M., Koh, P., Burns, W., Jandeleit-Dahm, K., Watson, A., Saleem, M., Goodall, G. J., Twigg, S. M., Cooper, M. 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G., Ferracin, M., Calin, G. A., Fassan, M., Bassi, P., Sevignani, C., Byrne, D., Negrini, M., Pagano, F., Gomella, L. G., Croce, C. M., Baffa, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Micro-RNA+profiling+in+kidney+and+bladder+cancers.">Micro-RNA profiling in kidney and bladder cancers.</a> Urol. Oncol. 25 (5), 387-392 (2007).</li><li>Juan, D., Alexe, G., Antes, T., Liu, H., Madabhushi, A., Delisi, C., Ganesan, S., Bhanot, G., Liou, L. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+of+a+microRNA+panel+for+clear-cell+kidney+cancer.">Identification of a microRNA panel for clear-cell kidney cancer.</a> Urol. 75 (4), 835-841 (2010).</li><li>Xu, X., Kriegel, A. 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H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+situ+detection+of+miRNAs+in+animal+embryos+using+LNA-moidified+oligonucleotide+probes.">In situ detection of miRNAs in animal embryos using LNA-moidified oligonucleotide probes.</a> Nat. Methods. 3 (1), 27-29 (2006).</li><li>Nelson, P. T., Baldwin, D. A., Kloosterman, W. P., Kauppinen, S., Plasterk, R. H., Mourelatos, Z. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=RAKE+and+LNA-ISH+reveal+microRNA+expression+and+localization+in+archival+human+brain+tissue.">RAKE and LNA-ISH reveal microRNA expression and localization in archival human brain tissue.</a> RNA. 12 (2), 187-191 (2006).</li><li>Obernosterer, G., Martinez, J., Alenius, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Locked+nucleic+acid-based+in+situ+detection+of+microRNAs+in+mouse+tissue+sections.">Locked nucleic acid-based in situ detection of microRNAs in mouse tissue sections.</a> Nat. Protocols. 2 (6), 1508-1514 (2007).</li><li>Kriegel, A. J., Liu, Y., Cohen, B., Usa, K., Liu, Y., Liang, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MiR-382+targeting+of+kallikrein+5+contributes+to+renal+inner+medullary+interstitial+fibrosis.">MiR-382 targeting of kallikrein 5 contributes to renal inner medullary interstitial fibrosis.</a> Physiol. Genomics. 44 (4), 259-267 (2012).</li></ol>

There is nothing to disclose.

The goal of this article was to describe a protocol for miRNA in situ hybridization that works well in formalin fixed kidney tissues. While working out this protocol several important sources of staining artifact have been identified. Careful attention to these points can help avoid staining artifact and increase the likelihood of a successful ISH run.
One of the most avoidable causes of staining artifact can occur when tissue sections become dried out during long incubations. When th...

MicroRNA are small (approximately 22 nucleotides long) noncoding RNAs that are endogenously produced. They generally function to suppress protein expression through translational repression or mRNA degradation. miRNAs bind to mRNA targets with incomplete complementarity, making it possible for a single miRNA to suppress multiple targets.
Understanding which cell types and structures express miRNAs is an important part of understanding the mechanisms through which alterations in miRNA expression influence cell and tissue phenotypes. While methods such as miRNA sequencing, qPCR and Northern blotting can be used for detection of miRNAs in whole tissues, this approach does not allow one to determine which specific cell type they came from within a given tissue. Dissection of cellular and structural components prior to analysis using these methods can be very difficult and the conditions needed to achieve adequate isolations can lead to alterations in gene expression or degradation of RNAs. microRNA in situ hybridization is a method used to visualize microRNA location and expression levels in tissues. This technique is especially valuable in tissues composed of heterogeneous structures, such as the kidney.
MicroRNAs have been shown to play an regulatory role in kidney development2,3 and physiology4. microRNA expression alterations have also been shown to be involved with renal pathology such as fibrosis5-10, diabetic nephropathy7, renal carcinoma11,12, and acute kidney injury13. In our research, we have found that optimizing microRNA in situ hybridization for kidney tissues was valuable for determining the exact structural locations of miRNA expression in both health and disease14. Determination of the tubular and cellular expression of different microRNAs is important because their regulation of targets may be dependent on cellular functions. In diseased states it is also important to determine how alterations in miRNA expression may be impacting function.
The goal of the method described here was to build upon existing ISH methodologies developed by Kloosterman et al.15, other investigators16,17, and those suggested by Exiqon1 and optimize the method for formalin fixed kidney tissues. We have successfully used this method to identify distinct regional differences in renal microRNA miR-382 expression with unilateral ureteral obstruction18. This approach can be used with other tissues as well, with additional optimization.

<table border="0" cellpadding="0" cellspacing="0" width="481">
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	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Paraformaldehyde</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">P6148</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">PBS</td>
			<td style="width:71px;">Gibco</td>
			<td style="width:137px;">70011044</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Diethyl Pyrocarbonate</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">D5758</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Tween-20</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">P1379</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Xylenes</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">534056</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">Ethanol</td>
			<td style="width:71px;">Ultra Pure</td>
			<td style="width:137px;">200CSPTP</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:195px;">Tris-HCl</td>
			<td style="width:71px;">Life Technologies</td>
			<td style="width:137px;">15506-017</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">CaCl2</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">C2536</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">Glycine</td>
			<td style="width:71px;">J.T. Baker</td>
			<td style="width:137px;">4059-00</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Citric Acid</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">C2404</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Formamide</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">F9037</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:195px;">20x SSC Buffer</td>
			<td style="width:71px;">Life Technologies</td>
			<td style="width:137px;">15557-044</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">Heparin</td>
			<td style="width:71px;">SAGENT</td>
			<td style="width:137px;">25021-400-30</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:195px;">Yeast RNA</td>
			<td style="width:71px;">Life Technologies</td>
			<td style="width:137px;">AM7118</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">MgCl2</td>
			<td style="width:71px;">Sigma</td>
			<td style="width:137px;">M8266-1004</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">NaCl</td>
			<td style="width:71px;">J.T. Baker</td>
			<td style="width:137px;">4058-01</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">Proteinase K</td>
			<td style="width:71px;">Fermentas</td>
			<td style="width:137px;">EO0491</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">3&#8217; DIG- miRNA probe</td>
			<td style="width:71px;">Exiqon</td>
			<td style="width:137px;">miR dependent-05</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">3&#8217; DIG- Scrambled miR probe</td>
			<td style="width:71px;">Exiqon</td>
			<td style="width:137px;">99004-05</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">3&#8217; DIG- U6 miR probe</td>
			<td style="width:71px;">Exiqon</td>
			<td style="width:137px;">99002-05</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Anti-Digoxigenin-Ab Fab</td>
			<td rowspan="2" style="width:71px;">Roche</td>
			<td rowspan="2" style="width:137px;">11093274910</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Fragments</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">NBT/BCIP</td>
			<td style="width:71px;">Roche</td>
			<td style="width:137px;">11681451001</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Permount</td>
			<td style="width:71px;">Fisher</td>
			<td style="width:137px;">SP15-500</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Coverslips</td>
			<td style="width:71px;">Fisher</td>
			<td style="width:137px;">Fit to tissue size</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="60">
			<td height="60" style="height:60px;width:195px;">Microtom HM 355 S</td>
			<td style="width:71px;">Thermo Scientific</td>
			<td style="width:137px;">23-900-672</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">In-slide Out Hybridization Oven</td>
			<td style="width:71px;">Boekel</td>
			<td style="width:137px;">241000</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:195px;">Aluminum Tray Assembly</td>
			<td style="width:71px;">Boekel</td>
			<td style="width:137px;">C2403973</td>
			<td style="width:79px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:195px;">Stainless Steel Rack Insert</td>
			<td style="width:71px;">Boekel</td>
			<td style="width:137px;">C2403754</td>
			<td style="width:79px;"></td>
		</tr>
	</tbody>
</table>

microrna in situ 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 probes. This protocol, originally developed by Kloosterman and colleagues for broad use with Exiqon miRNA probes1, has been modified to overcome challenges inherent in miRNA analysis in kidney tissues. These include issues such as structure identification and hard to remove residual probe and antibody. Use of relatively thin, 5 mm thick, tissue sections allowed for clear visualization of kidney structures, while a strong probe signal was retained in cells. Additionally, probe concentration and incubation conditions were optimized to facilitate visualization of microRNA expression with low background and nonspecific signal. Here, the optimized protocol is described, covering the initial tissue collection and preparation through the mounting of slides at the end of the procedure. The basic components of this protocol can be altered for application to other tissues and cell culture models.

The areas of a tissue section that become dried out during the hybridizations, incubations or wash steps generally end up staining more darkly during the NBT/BCIP development. Figure 1 shows a portion of a kidney section in which the HybriSlip slipped off of the edge of the tissue, allowing it to become partially dehydrated. Despite rehydration and coverage in the remaining steps, the signal in the dehydrated portion is artificially high.
The importance of controlling the time...

Watch this Scientific Journal Video about MicroRNA In situ Hybridization for Formalin Fixed Kidney Tissues at JoVE.com

MicroRNA In situ Hybridization for Formalin Fixed Kidney Tissues

This article describes an in situ hybridization protocol optimized for colormetric detection of microRNA expression in formalin fixed kidney sections.

MicroRNA In situ 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 ...

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14.8K Views.  Medical College of Wisconsin. This article describes an in situ hybridization protocol optimized for colormetric detection of microRNA expression in formalin fixed kidney sections.