Name: correlative light and electron microscopy to study microglial interactions with &#946;-amyloid plaques
Uploaded: 2016-06-01T15:00:00
Description: Watch this Scientific Journal Video about Correlative Light and Electron Microscopy to Study Microglial Interactions with ÃŽÂ²-Amyloid Plaques at JoVE.com

We are grateful to Dr. Sachiko Sato and Julie-Christine L&#233;vesque at the Bioimaging Platform of the Centre de recherche du CHU de Qu&#233;bec for their technical assistance. Grants from the Natural Sciences and Engineering Research Council of Canada (NSERC) RGPIN-2014-05308, The Banting Research Foundation, and The Scottish Rite Charitable Foundation of Canada to M.E.T supported this work.
H.E.H. is recipient of a scholarship from the Lebanese Ministry of Education and Higher Education, and K.B. from the Facult&#233; de m&#233;decine of Universit&#233; Laval.

Note: All experiments were approved and performed under the guidelines of the Institutional animal ethics committee, in conformity with the Canadian Council on Animal Care guidelines as administered by the Animal Care Committee of Universit&#233; Laval. APP-PS1 male mice between 4 and 21 months of age were used. These animals were housed under a 12&#160;hr light-dark cycle at 22 - 25 &#176;C with free access to food and water.
1. Methoxy-X04 Solution Preparation
<ol>
	<li>Prepare a 5 mg/ml s...

<ol>
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This protocol explains a correlative approach for targeting dense core A&#946; plaques with EM. Methoxy-X04 in vivo injection allows rapid selection of brain sections that contain A&#946; plaques within particular regions and layers of interest, for instance the hippocampus CA1, strata radiatum, and lacunosum-moleculare. In the present example, methoxy-X04 pre-screening was combined with pre-embedding immunostaining for IBA1 to study how different microglial phenotypes interact with synapses at the ultrastructur...

Amyloid A&#946; plaque formation is the main neuropathological hallmark of Alzheimer&#39;s disease (AD). However increasing evidence suggests important roles of the immune system in disease progression1,2. In particular, new data from preclinical and clinical studies established immune dysfunction as a main driver and contributor to AD pathology. With these findings, central and peripheral immune cells have emerged as promising therapeutic targets for AD3. The following protocol combines light and electron microscopy (EM) to generate new insights into the relationship between A&#946; plaque deposition and microglial phenotypic alterations in AD. This protocol allows the labeling of A&#946; plaques in mouse models of AD using in vivo injection of the fluorescent dye methoxy-X04. Methoxy-X04 is a Congo Red derivative that can easily cross the blood-brain barrier to enter the brain parenchyma and bind &#946;-pleated sheets with high affinity. Since the dye is fluorescent, it can be used for in vivo detection of A&#946; plaque deposition with two-photon microscopy4. Once bound to A&#946;, methoxy-X04 does not dissociate or redistribute away from plaques, and it retains its fluorescence over time. It is generally administered peripherally to allow for non-invasive imaging of brain dynamics5. The fluorescence also remains following aldehyde fixation, allowing for correlative post-mortem analyses, including investigation of neuronal death in the vicinity of A&#946; plaques6.
This protocol takes advantage of the properties of methoxy-X04 to select brain sections from APPSWE/PS1A246E mice (APP-PS1; coexpressing a double mutation at APP gene Lys670Asn/Met671Leu, and human presenilin PS1-A264E variant)7 that exhibit A&#946; plaques in specific regions of interest (hippocampus CA1, strata radiatum, and lacunosum-moleculare) prior to pre-embedding immunostaining against the microglial marker ionized calcium-binding adapter molecule 1 (IBA1) to visualize microglial cell bodies and processes with EM. The mice are given intraperitoneal injection of methoxy-X04 solution, 24 hr&#160;prior to brain fixation through transcardial perfusion. Coronal brain sections are obtained using a vibratome. Sections containing the hippocampus CA1 are screened under a fluorescent microscope for the presence of A&#946; plaques in strata radiatum and lacunosum-moleculare. Immunostaining for IBA1, osmium tetroxide post-fixation, and plastic resin embedding are then performed on the selected brain sections. At the end of this protocol, the sections can be archived without further ultrastructural degradation, ready for ultrathin sectioning and ultrastructural examination. Importantly, the plaques are still fluorescent after immunostaining with different antibodies, for instance IBA1 as in the present protocol. They become darker than their surrounding neuropil following osmium tetroxide post-fixation, independently of methoxy-X04 staining, which helps to accurately identify the regions of interest, generally down to a few square millimeters, to be examined with the transmission electron microscope.
This correlative approach offers an efficient way to identify specific brain sections to examine at the ultrastructural level. This is particularly helpful when studying early AD pathology, within specific brain regions or layers that may only contain a few A&#946; plaques, present in only a small fraction of tissue sections. During these times especially, it would be inefficient to use immunostaining for A&#946; (and dual labeling for other cellular markers such as IBA1) on several brain sections simply to yield a small fraction containing A&#946; plaques at the right location. In addition, injection of live mice with methoxy-X04 prior to sacrifice and tissue processing does not compromise the ultrastructural preservation. Alternative methods such as post-mortem staining with Congo Red, Thioflavin S, Thioflavin T or methoxy-X04 on fixed tissue sections require staining differentiation in ethanol,8-11 which causes osmotic stress and disrupts the ultrastructure. Congo Red is also a known human carcinogen12.

<table border="0" cellpadding="0" cellspacing="0" width="1006">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:523px;">Methoxy-X04</td>
			<td style="width:197px;">Tocris Bioscience</td>
			<td style="width:119px;">4920</td>
			<td style="width:167px;">10 mg substrate per tablet</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Propylene glycol</td>
			<td>Sigma Aldrich</td>
			<td>W294004&#160;</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dimethyl sulfoxide (DMSO)</td>
			<td>Fisher BioReagents</td>
			<td>BP231-1</td>
			<td>Caution: toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium Chloride NaCl</td>
			<td>Sigma</td>
			<td>S9625</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium phosphate monobasic monohydrate</td>
			<td>Sigma</td>
			<td>S9638</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium phosphate dibasic</td>
			<td>Sigma</td>
			<td>S0876</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tris Hydrochloride</td>
			<td>Fisher BioReagents</td>
			<td>BP153500</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Acrolein&#160;</td>
			<td>Sigma</td>
			<td>110221</td>
			<td>Caution: Toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Paraformaldehyde Granular</td>
			<td>Electron Microscopy Sciences</td>
			<td>19210</td>
			<td>Caution: Toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Filter paper</td>
			<td>Fisher</td>
			<td>09-790-14F</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Peristaltic Pump with Tubing</td>
			<td>ColeParmer</td>
			<td>cp.78023-00</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Excel Winged blood Collection Set Needles 25G&#160;</td>
			<td>Becton Dickinson</td>
			<td>367341</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Extrafine Forceps</td>
			<td>F.S.T</td>
			<td>11152-10</td>
			<td>Tip shape: curved</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Scissors</td>
			<td>F.S.T</td>
			<td>14090-09</td>
			<td>Tip shape: straight</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hartman Hemostats</td>
			<td>F.S.T</td>
			<td>13003-10</td>
			<td>Tip shape: curved</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Surgical Scissors</td>
			<td>F.S.T</td>
			<td>14004-16</td>
			<td>Tip shape: straight</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Micro Dissecting Scissors</td>
			<td>ROBOZ surgical store</td>
			<td>5818</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glass scintillation vials</td>
			<td>Fisher Scientific</td>
			<td>74515-20</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vibrating Blade Michrotome Leica VT1000 S</td>
			<td>Leica Biosystems&#160;</td>
			<td>14047235612</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Vibratome blades</td>
			<td>Electron microscopy Sciences</td>
			<td>71990</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Microscope Slides</td>
			<td>Fisher Scientific</td>
			<td>12-550-15</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">24-well Tissue Culture Plates</td>
			<td>Fisher Scientific</td>
			<td>353047</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethylene Glycol</td>
			<td>Fisher BioReagents</td>
			<td>BP230-4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Glycerol</td>
			<td>Fisher BioReagents</td>
			<td>BP229-4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Hydrogen Peroxide, 30%</td>
			<td>J.T.BAKER</td>
			<td>cat: 2186-01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Sodium borohydride</td>
			<td>Sigma</td>
			<td>480886</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Tris HCl</td>
			<td>Fisher</td>
			<td>BP153-500ML</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fetal bovine Serum (FBS)</td>
			<td>Sigma Aldrich</td>
			<td>F1051</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Bovine serum albumin (BSA), fraction V</td>
			<td>Thomas Scientific</td>
			<td>C001H24</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Triton X-100</td>
			<td>Sigma</td>
			<td>T8787</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Anti IBA1, Rabbit&#160;</td>
			<td>WAKO</td>
			<td>019-19741</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Goat Anti-Rabbit IgG</td>
			<td>Jackson Immunoresearch</td>
			<td>111066046</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">VECTASTAIN Elite ABC Kit (Standard)</td>
			<td>Vector Labs</td>
			<td>PK-6100</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">3.3&#39;-Diaminobenzidine tetra-hydrochloride (DAB)</td>
			<td>Sigma</td>
			<td>D5905-50TAB</td>
			<td>Caution: toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Osmium tetroxide, 4% solution</td>
			<td>Electron Microscopy Sciences</td>
			<td>19150</td>
			<td>Caution: toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:523px;">Durcupan&#8482; ACM single component A</td>
			<td>Sigma</td>
			<td>44611</td>
			<td>Resin Caution: Toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:523px;">Durcupan&#8482; ACM single component B</td>
			<td>Sigma</td>
			<td>44612</td>
			<td>Hardener Caution: Toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:523px;">Durcupan&#8482; ACM single component C</td>
			<td>Sigma</td>
			<td>44613</td>
			<td>Plasticizer Caution: Toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:523px;">Durcupan&#8482; ACM single component D</td>
			<td>Sigma</td>
			<td>44614</td>
			<td>Accelerator Caution: Toxic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Ethanol</td>
			<td>LesAlcoolsdeComerce</td>
			<td>151-01-15N</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Propylene oxide</td>
			<td>Sigma</td>
			<td>110205</td>
			<td>Caution: corrosive</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Aluminum weigh dishes</td>
			<td>Electron Microscopy Sciences</td>
			<td>70048-01</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">ACLAR&#174;&#8211;Fluoropolymer Films</td>
			<td>Electron Microscopy Sciences</td>
			<td>50425</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Oven/Incubator</td>
			<td>VWR</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

correlative light and electron microscopy to study microglial interactions with &#946;-amyloid plaques

A detailed protocol is provided here to identify amyloid A&#946; plaques in brain sections from Alzheimer&#39;s disease mouse models before pre-embedding immunostaining (specifically for ionized calcium-binding adapter molecule 1 (IBA1), a calcium binding protein expressed by microglia) and tissue processing for electron microscopy (EM). Methoxy-X04 is a fluorescent dye that crosses the blood-brain barrier and selectively binds to &#946;-pleated sheets found in dense core A&#946; plaques. Injection of the animals with methoxy-X04 prior to sacrifice and brain fixation allows pre-screening and selection of the plaque-containing brain sections for further processing with time-consuming manipulations. This is particularly helpful when studying early AD pathology within specific brain regions or layers that may contain very few plaques, present in only a small fraction of the sections. Post-mortem processing of tissue sections with Congo Red, Thioflavin S, and Thioflavin T (or even with methoxy-X04) can label &#946;-pleated sheets, but requires extensive clearing with ethanol to remove excess dye and these procedures are incompatible with ultrastructural preservation. It would also be inefficient to perform labeling for A&#946; (and other cellular markers such as IBA1) on all brain sections from the regions of interest, only to yield a small fraction containing A&#946; plaques at the right location. Importantly, A&#946; plaques are still visible after tissue processing for EM, allowing for a precise identification of the areas (generally down to a few square millimeters) to examine with the electron microscope.

This section illustrates the results that can be obtained at different critical steps of the protocol. In particular the results show examples of brain sections containing methoxy-X04 stained plaques in specific region and layers of interest: the hippocampus CA1, strata radiatum, and lacunosum-moleculare. The plaques and regional/lamellar organization of the hippocampus are successively visualized using a combination of UV and bright field filters (Figure 1). The selected...

Watch this Scientific Journal Video about Correlative Light and Electron Microscopy to Study Microglial Interactions with ÃŽÂ²-Amyloid Plaques at JoVE.com

Correlative Light and Electron Microscopy to Study Microglial Interactions with ÃƒÅ½Ã‚Â²-Amyloid Plaques

This article describes a protocol for visualizing amyloid A&#946; plaques in Alzheimer&#39;s disease mouse models using methoxy-X04, which crosses the blood-brain barrier and selectively binds to &#946;-pleated sheets found in dense core A&#946; plaques. It allows pre-screening of plaque-containing tissue sections prior to immunostaining and processing for electron microscopy.

Correlative Light and Electron Microscopy to Study Microglial Interactions with &#946;-Amyloid Plaques

A detailed protocol is provided here to identify amyloid A&#946; plaques in brain sections from Alzheimer&#39;s disease mouse models before pre-embedding ...

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Neuroscience

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