Name: fluorescence-activated cell sorting-radioligand treated tissue (facs-rtt) to determine the cellular origin of radioactive signal
Uploaded: 2021-09-10T14:30:00
Description: Watch this Scientific Journal Video about Fluorescence-Activated Cell Sorting-Radioligand Treated Tissue FACS-RTT to Determine the Cellular Origin of Radioactive Signal at JoVE.com

This work was supported by the Swiss National Science Foundation (grant no. 320030-184713). Authors BBT and KC are supported by the Velux Foundation (project n. 1123). Author ST received support from the Swiss National Science Foundation (Early Post-Doc Mobility Scholarship, no. P2GEP3_191446), the Prof Dr. Max Cloetta Foundation (Clinical Medicine Plus scholarship), and the Jean and Madeleine Vachoux Foundation.

All experimental procedures were conducted in agreement with the Ethics Committee for Human and Animal Experimentation of the Canton of Geneva, the Cantonal Commission for Research Ethics (CCER), and the General Direction Of The Health Of The Canton Of Geneva (Switzerland), respectively. Data are reported following Animal Research: Reporting In-vivo Experiments (ARRIVE) guidelines.
1. SPECT camera preparation and calibration
<ol>
	<li>Turn on the camera, load the operating software ...

<ol>
	<li>Nichols, E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=regional,+and+national+burden+of+Alzheimer's+disease+and+other+dementias,+1990-2016:+a+systematic+analysis+for+the+Global+Burden+of+Disease+Study+2016.">regional, and national burden of Alzheimer's disease and other dementias, 1990-2016: a systematic analysis for the Global Burden of Disease Study 2016.</a> The Lancet Neurology. 18 (1), 88-106 (2019).</li><li>Kinney, J. W., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inflammation+as+a+central+mechanism+in+Alzheimer's+disease.">Inflammation as a central mechanism in Alzheimer's disease.</a> Alzheimer's &amp; Dementia. 4, 575-590 (2018).</li><li>D'Amelio, M., Puglisi-Allegra, S., Mercuri, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+role+of+dopaminergic+midbrain+in+Alzheimer's+disease:+Translating+basic+science+into+clinical+practice.">The role of dopaminergic midbrain in Alzheimer's disease: Translating basic science into clinical practice.</a> Pharmacological Research. 130, 414-419 (2018).</li><li>D'Amelio, M., Serra, L., Bozzali, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ventral+tegmental+area+in+prodromal+Alzheimer's+disease:+Bridging+the+gap+between+mice+and+humans.">Ventral tegmental area in prodromal Alzheimer's disease: Bridging the gap between mice and humans.</a> Journal of Alzheimer's Disease: JAD. 63 (1), 181-183 (2018).</li><li>Cohen, R. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+transgenic+Alzheimer+rat+with+plaques,+tau+pathology,+behavioral+impairment,+oligomeric+a&#946;,+and+frank+neuronal+loss.">A transgenic Alzheimer rat with plaques, tau pathology, behavioral impairment, oligomeric a&#946;, and frank neuronal loss.</a> The Journal of Neuroscience: The Official Journal of the Society for Neuroscience. 33 (15), 6245-6256 (2013).</li><li>Morrone, C. D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regional+differences+in+Alzheimer's+disease+pathology+confound+behavioural+rescue+after+amyloid-&#946;+attenuation.">Regional differences in Alzheimer's disease pathology confound behavioural rescue after amyloid-&#946; attenuation.</a> Brain: A Journal of Neurology. 143 (1), 359-373 (2020).</li><li>Berkowitz, L. E., Harvey, R. E., Drake, E., Thompson, S. M., Clark, B. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Progressive+impairment+of+directional+and+spatially+precise+trajectories+by+TgF344-Alzheimer's+disease+rats+in+the+Morris+Water+Task.">Progressive impairment of directional and spatially precise trajectories by TgF344-Alzheimer's disease rats in the Morris Water Task.</a> Scientific Reports. 8 (1), 16153 (2018).</li><li>Koulousakis, P., vanden Hove, D., Visser-Vandewalle, V., Sesia, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cognitive+improvements+after+intermittent+deep+brain+stimulation+of+the+nucleus+basalis+of+meynert+in+a+transgenic+rat+model+for+Alzheimer's+disease:+A+preliminary+approach.">Cognitive improvements after intermittent deep brain stimulation of the nucleus basalis of meynert in a transgenic rat model for Alzheimer's disease: A preliminary approach.</a> Journal of Alzheimer's Disease: JAD. 73 (2), 461-466 (2020).</li><li>Tournier, B. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatial+reference+learning+deficits+in+absence+of+dysfunctional+working+memory+in+the+TgF344-AD+rat+model+of+Alzheimer's+disease.">Spatial reference learning deficits in absence of dysfunctional working memory in the TgF344-AD rat model of Alzheimer's disease.</a> Genes, Brain, and Behavior. , 12712 (2020).</li><li>Tournier, B. B., Tsartsalis, S., Ceyz&#233;riat, K., Garibotto, V., Millet, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vivo+TSPO+signal+and+neuroinflammation+in+Alzheimer's+disease.">In vivo TSPO signal and neuroinflammation in Alzheimer's disease.</a> Cells. 9 (9), (2020).</li><li>Backes, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=[11C]raclopride+and+extrastriatal+binding+to+D2/3+receptors.">[11C]raclopride and extrastriatal binding to D2/3 receptors.</a> NeuroImage. 207, 116346 (2020).</li><li>Millet, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantification+of+dopamine+D(2/3)+receptors+in+rat+brain+using+factor+analysis+corrected+[18F]Fallypride+images.">Quantification of dopamine D(2/3) receptors in rat brain using factor analysis corrected [18F]Fallypride images.</a> NeuroImage. 62 (3), 1455-1468 (2012).</li><li>Tsartsalis, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+modified+simplified+reference+tissue+model+for+the+quantification+of+dopamine+D2/3+receptors+with+[18F]Fallypride+images.">A modified simplified reference tissue model for the quantification of dopamine D2/3 receptors with [18F]Fallypride images.</a> Molecular Imaging. 13 (8), (2014).</li><li>Schwarz, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Using+fluorescence-activated+cell+sorting+to+examine+cell-type-specific+gene+expression+in+rat+brain+tissue.">Using fluorescence-activated cell sorting to examine cell-type-specific gene expression in rat brain tissue.</a> Journal of Visualized Experiments: JoVE. (99), e52537 (2015).</li><li>Tournier, B. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescence-activated+cell+sorting+to+reveal+the+cell+origin+of+radioligand+binding.">Fluorescence-activated cell sorting to reveal the cell origin of radioligand binding.</a> Journal of Cerebral Blood Flow &amp; Metabolism. 40 (6), 1242-1255 (2020).</li><li>Tournier, B. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Astrocytic+TSPO+upregulation+appears+before+microglial+TSPO+in+Alzheimer's+disease.">Astrocytic TSPO upregulation appears before microglial TSPO in Alzheimer's disease.</a> Journal of Alzheimer's Disease: JAD. 77 (3), 1043-1056 (2020).</li></ol>

To our knowledge, this technique was the first to describe an approach that allows a better understanding of in vivo binding alterations of a radiotracer at the cellular level. The protocol describes a multiscale method to quantify radiotracer binding at the cellular level using [125I]CLINDE (TSPO) or [125I]R91150 (5HT2AR) as examples.
This technique is robust and sensitive enough to precisely detect the cellular origin of a wide spectrum of glial cell...

Neurodegenerative diseases, such as Alzheimer&#39;s Disease (AD), are characterized by a neuronal loss associated with increased symptoms. AD, the most common cause of dementia, accounting 60%-70% of cases, affects around 50 million people worldwide1. At a neuropathological level, the two major characteristics of AD are the accumulation of extracellular amyloid-&#946; (A&#946;) plaques and intracellular Tau neurofibrillary tangles. Glial cell alterations have also been associated with AD2 and possible disruption of several neurotransmitter systems3,4.
The TgF344-AD rat line has been modified to model AD by expressing human APP and PS1&#916;E9 transgenes, leading to soluble and insoluble A&#946;-40 and A&#946;-42 expression and amyloid plaque formation5. It also presents the accumulation of hyperphosphorylated forms of the Tau protein leading to tauopathy. From the age of 9-24 months, the rats progressively develop the pathological hallmarks of AD and a cognitive impairment5,6,7,8,9.
Positron Emission Tomography (PET), Single-Photon Emission computed Tomography (SPECT), and autoradiography are techniques based on the emission and quantification of &#947; rays. Radiotracers are quantified either in vivo (PET and SPECT) or ex vivo/in vitro (autoradiography). Those sensitive techniques have contributed to the understanding of mechanisms of several brain diseases, such as AD. Indeed, in terms of neuroinflammation, there are a lot of studies assessing 18 kDa Translocator Protein (TSPO), an in vivo neuroinflammation marker, with radiolabeled tracers such as [11C]-(R)-PK11195 or [11C]PBR28 (for review see10). In addition, alterations of neurotransmitter systems have been studied using radiotracers11,12,13.
However, those techniques do not determine the cellular origin of the radioactive signal. This could hamper the interpretation of the biological underpinnings of the alteration in the binding of a radioligand in PET/SPECT. For instance, in the case of TSPO studies of neuroinflammation, understanding whether the increase or decrease of TSPO is due to astrocytic or microglial changes is of paramount importance. The Fluorescence-Activated Cell Sorting to Radioligand Treated Tissue (FACS-RTT) technique was developed to get around these problems, allowing the assessment of radioligand binding in every cell type separately and the quantification of the target-protein density per cell. This innovative technique is consequently complementary and highly compatible with PET and SPECT imaging.
Here, this technique was applied along two axes: the study of neuroinflammation using TSPO-specific radioligands and assessing the serotonergic system. On the first axis, the aim was to understand the cellular origin of the TSPO signal in response to an acute inflammatory reaction. Therefore, FACS-RTT was used on the brain tissues of rats after the induction of neuroinflammation via a lipopolysaccharide (LPS) injection and following an in vivo [125I]CLINDE SPECT imaging study. Further, the same imaging and FACS-RTT protocol were applied on 12- and 24-month-old TgF344-AD rats and matching wild-type (WT) rats. The second axis aimed to determine the origin of serotoninergic system alterations in this rat model via ex vivo 5-HT2AR density assessment by cell type.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Acetic acid</td>
			<td>Sigma-Aldrich</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Acetonitrile</td>
			<td>Sigma-Aldrich</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>BioVet</td>
			<td>BioVet</td>
			<td></td>
			<td>Software for vitals check</td>
		</tr>
		<tr>
			<td>Bondclone C18 reverse-phase column</td>
			<td>Phenomenex, Schlieren, Switzerland</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Des-Sur</td>
			<td>University Hospital of Geneva</td>
			<td></td>
			<td>Virucide</td>
		</tr>
		<tr>
			<td>Fc Block / anti-CD32</td>
			<td>BD Biosciences</td>
			<td>BDB550270</td>
			<td>Reactivity for rat</td>
		</tr>
		<tr>
			<td>FITC-conjugated anti-rat CD90</td>
			<td>Biolegend</td>
			<td>202504</td>
			<td>Reactivity for rat</td>
		</tr>
		<tr>
			<td>Heparin</td>
			<td>B. Braun</td>
			<td>B01AB01</td>
			<td></td>
		</tr>
		<tr>
			<td>HPLC</td>
			<td>Knauer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Insyte-W 24 GA 0.75 IN 0.7 x 19 mm</td>
			<td>BD Biosciences</td>
			<td>321312</td>
			<td>24 G catheter</td>
		</tr>
		<tr>
			<td>Isoflurane</td>
			<td>Baxter</td>
			<td>ZDG9623</td>
			<td></td>
		</tr>
		<tr>
			<td>Lacryvisc</td>
			<td>Alcon</td>
			<td>2160699</td>
			<td></td>
		</tr>
		<tr>
			<td>LS Columns</td>
			<td>Miltenyi Biotec</td>
			<td>130-042-401</td>
			<td></td>
		</tr>
		<tr>
			<td>MACS MultiStand</td>
			<td>Miltenyi Biotec</td>
			<td>130-042-303</td>
			<td></td>
		</tr>
		<tr>
			<td>Micropore soft tape</td>
			<td>3M</td>
			<td>F51DA01</td>
			<td></td>
		</tr>
		<tr>
			<td>MILabs-Uspect II</td>
			<td>MILabs</td>
			<td></td>
			<td>Software for SPECT Camera</td>
		</tr>
		<tr>
			<td>MoFlo Astrios</td>
			<td>Beckman Coulter</td>
			<td></td>
			<td>Cell sorter</td>
		</tr>
		<tr>
			<td>Myelin Removal Beads II</td>
			<td>Miltenyi Biotec</td>
			<td>130-096-733</td>
			<td>Contains beads and myelin removal buffer.</td>
		</tr>
		<tr>
			<td>NaCl 0.9% Sterile solution</td>
			<td>B. Braun</td>
			<td>395202</td>
			<td></td>
		</tr>
		<tr>
			<td>Neural Dissociation Kit (P)</td>
			<td>Miltenyi Biotec</td>
			<td>130-092-628</td>
			<td>Contains the enzyme mixes, pipets 1, 2 and 3.</td>
		</tr>
		<tr>
			<td>Nylon Mesh Sheet</td>
			<td>Amazon</td>
			<td>CMN-0074-10YD</td>
			<td>40 inch width, 80 micron size mesh</td>
		</tr>
		<tr>
			<td>Peracetic acid</td>
			<td>Sigma-Aldrich</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>QuadroMACS Separator</td>
			<td>Miltenyi Biotec</td>
			<td>130-090-976</td>
			<td></td>
		</tr>
		<tr>
			<td>R91150 pr&#233;cursor</td>
			<td>CERMN</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sep-Pak C18 Column</td>
			<td>Waters</td>
			<td></td>
			<td>Concentration column</td>
		</tr>
		<tr>
			<td>Sodium iodide Na125</td>
			<td>PerkinElmer</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tributylin precursor</td>
			<td>CERMN</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>U-SPECT Rec2.38c</td>
			<td>MILabs</td>
			<td>Version Rec2.38c</td>
			<td>Software for SPECT images reconstruction</td>
		</tr>
		<tr>
			<td>USPECT II</td>
			<td>MILabs</td>
			<td></td>
			<td>Spect Camera</td>
		</tr>
		<tr>
			<td>Wizard 3&#34;</td>
			<td>PerkinElmer</td>
			<td></td>
			<td>Gamma counter</td>
		</tr>
	</tbody>
</table>

fluorescence-activated cell sorting-radioligand treated tissue (facs-rtt) to determine the cellular origin of radioactive signal

Glial cells probably have a considerable implication in the pathophysiology of neurodegenerative disorders, such as Alzheimer's disease (AD). Their alterations are perhaps associated with a pro-inflammatory state. The TgF344-AD rat strain has been designed to express human APP and human PS1&#916;E9 genes, encoding for amyloid proteins A&#946;-40 and A&#946;-42 and displays amyloid pathology and cognitive deficits with aging. The TgF344-AD rat model is used in this study to evaluate the cellular origin of the 18 kDa translocator protein (TSPO, a marker of glial cell activation) binding, and the 5HT2A-receptor (5HT2AR) serotonin receptor levels that are possibly disrupted in AD. The technique presented here is Fluorescence-Activated Cell Sorting to Radioligand Treated Tissue (FACS-RTT), a quantitative cell-type-specific technique complementary to in vivo PET or SPECT or ex vivo/in vitro autoradiography techniques. It quantifies the same radiolabeled tracer used prior for imaging, using a &#947; counter after cytometry cell sorting. This allows determining the cellular origin of the radiolabeled protein with high cellular specificity and sensitivity. For example, studies with FACS-RTT showed that (i) the increase in TSPO binding was associated with microglia in a rat model of lipopolysaccharide (LPS)-induced neuroinflammation, (ii) an increase in TSPO binding at 12- and 18-months was associated with astrocytes first, and then microglia in the TgF344-AD rats compared to wild type (WT) rats, and (iii) the striatal density of 5HT2AR decreases in astrocytes at 18 months in the same rat AD model. Interestingly, this technique can be extended to virtually all radiotracers.

WT rats experienced in vivo SPECT scan with [125I]CLINDE radiotracer after a unilateral LPS injection (Figure 2). This scan (using summed data from images of 45-60 min post radiotracer injection) showed higher binding of [125I]CLINDE in the site of the LPS injection (Figure 2A) than in the contralateral region of the brain (Figure 2B). The ex vivo samples that underwent FACS-RTT confirmed thos...

Watch this Scientific Journal Video about Fluorescence-Activated Cell Sorting-Radioligand Treated Tissue FACS-RTT to Determine the Cellular Origin of Radioactive Signal at JoVE.com

Fluorescence-Activated Cell Sorting-Radioligand Treated Tissue FACS-RTT to Determine the Cellular Origin of Radioactive Signal

Fluorescence-Activated Cell Sorting-Radioligand Treated Tissue (FACS-RTT) is a powerful tool to study the role of the 18 kDa translocator protein or Serotonin 5HT2A-receptor expression in Alzheimer&#39;s Disease at a cellular scale. This protocol describes the ex-vivo application of FACS-RTT in the TgF344-AD rat model.

Fluorescence-Activated Cell Sorting-Radioligand Treated Tissue (FACS-RTT) to Determine the Cellular Origin of Radioactive Signal

Glial cells probably have a considerable implication in the pathophysiology of neurodegenerative disorders, such as Alzheimer's disease (AD). Their ...

This protocol is complementary to in vivo imaging. It allows cell type and cellular level quantification of radiotracers, which is a different scale from the one obtained in vivo. The main advantage of this technique is its sensitivity and the cellular resolution given by the use of radioligands and the cell sorting.Turn on the camera and load the operating software. Click on the Home XYZ stage button to perform homing. Set up the experiment composed of one 10-minute scan acquisition.Set the Step mode to fine and the Acquisition mode to the Listmode to record the entire emission spectrum. Set up the bed and ensure that the warming system, breathing sensor, and anesthesia are functional and secure. Then, place a phantom where the animal's head will be positioned.Set the scan area by sliding the cursors for the three dimensions with the help of the three images in the bottom part of the screen. Ensure that the scan volume of the phantom and the animal is the same. Start the phantom scan for subsequent calibration with the previously established parameters.Ensure to work in an appropriate environment, authorized for experiments involving radioactivity. Incubate 100 micrograms of tributylin precursor in 100 microliters of acetic acid with sodium iodide and five microliters of 37%paracetic acid at 70 degrees Celsius for 20 minutes in a thermocycler positioned in a glove box. Dilute the reaction using 50%acetonitrile in water to reach a volume of 500 microliters.Inject the 500 microliters of the diluted reaction onto a reverse-phase column. Isolate the CLINDE with a linear-gradient HPLC run from 5 to 95%ACN in seven-millimolar phosphoric acid for 10 minutes. Dilute the isolate in water to attain a final volume of 10 milliliters and then inject the diluted reaction onto a concentration column.Elute the CLINDE from the column with 300 microliters of absolute ethanol and then evaporate the ethanol by incubating it in a vacuum centrifuge at room temperature for 40 minutes. Dilute the residue containing the CLINDE in 300 microliters of saline to create a stock solution. After measuring its radioactivity, dilute the stock solution in saline to obtain a solution of 0.037 megabecquerel in 500 microliters.Establish the calibration curves with cold reference compounds and resolve the linear regression equation:Y equal to AX plus B to obtain A and B coefficients. X represents the mass of cold compound, and Y represents the area under the curves. Check the area under the curve of the radioligand, measuring ultraviolet absorbance at 450 nanometers based on the calibration curve and the area under the curve of the radioligand.Estimate the mass and measure the activity of the radioligand. Ensure that the specific activity is greater than 1, 000 gigabecquerel per micromole. Click on the Update image button to update the animal position.Set the scan area by sliding the cursors with the help of the three images in the bottom part of the screen for the three dimensions. Set up the experiment on a 60-minute scan constituting 60 frames of one minute. Reuse all other parameters set up initially.Inject 500 microliters of the radioactive radiotracer and then flush the tube with 300 microliters of sterile 0.9%sodium chloride. Simultaneously, click on Start acquisition to start the scan. Open the scan reconstruction software and then open the dataset, looking for the file name parameters file created in the folder of the scan.Select the isotope of interest. Note that the list mode parameter allows multiple isotope selection at this step. Set the different reconstruction parameters like the voxel size, number of subsets, and iterations as described in the manuscript.Select the output format as NIFTI and then select Start SPECT reconstruction. Use a flat metal spatula and a razor blade to dissect the regions of interest of the brain. Place the tissues in a two-milliliter centrifuge tube and weigh the tissue obtained.Put the samples into a two-milliliter centrifuge tube with one milliliter of calcium-and magnesium-free HBSS and then centrifuge at 300 times G for two minutes at room temperature and remove the supernatant without disturbing the pellet. Add 1, 900 microliters of enzyme mix one and incubate it for 15 minutes at 37 degrees Celsius while agitating the tubes by inversion every five minutes. Add 30 microliters of enzyme mix two.Agitate gently with a 1, 000 microliter pipette back and forth 30 times. Then, incubate the mixture for 15 minutes at 37 degrees Celsius while agitating the tubes by inversion every five minutes. Mix gently back and forth with a 200-microliter pipette and then a 10-microliter pipette before incubating the mixture for 10 minutes at 37 degrees Celsius to dissociate the tissues.Filter the cells with a 70-micrometer cell strainer and add 10 milliliters of calcium-and magnesium-free HBSS. Centrifuge at 300 times G for 10 minutes at room temperature and remove the supernatant without disturbing the pellet. For myelin depletion, resuspend the pellet with 400 microliters of myelin removal buffer and then add 100 microliters of myelin removal beads before incubating for 15 minutes at four degrees Celsius.Add five milliliters of myelin removal buffer and centrifuge 300 times G for 10 minutes at room temperature. Add 500 microliters of myelin removal buffer and place the suspended pellets into the magnetic field column. Wash the column with one milliliter of myelin removal buffer four times.Centrifuge at 300 times G for two minutes at room temperature and remove the supernatant without disturbing the pellet. Vortex briefly to dissociate the cells and add five microliters of Fc Block CD32. Add 100 microliters of the mix of primary antibodies of interest and incubate for 20 minutes at four degrees Celsius.Centrifuge at 350 times G for five minutes at four degrees Celsius and remove the supernatant without disturbing the pellet. Blot the tubes upside down on soft paper. Vortex the tube briefly, then add 100 microliters of the secondary antibody mix and incubate for 15 minutes at four degrees Celsius.Add one milliliter of myelin removal buffer and repeat the centrifugation. Discard the supernatant and blot the tubes upside down on soft paper. Resuspend the cells in 250 microliters of sterile PBS and proceed directly to cell sorting.The in vivo SPECT scan of wild-type rats showed higher binding of CLINDE in the site of the lipopolysaccharide injection than in the contra-lateral region of the brain. The ex vivo samples that underwent fluorescence activated cell sorting radioligand-treated tissue, or FACS-RTT, revealed the presence of a higher number of CLINDE binding sites only in microglia, showing that the cellular origin of the CLINDE signal in the ipsilateral side of the brain was microglia. The increase in translocator protein, or TSPO binding, at 12 months in TgF344-AD rats was restricted to astrocytes.In 24-month-old rats, the increase in TSPO binding was observed due to both astrocytic and microglial alterations. In older TgF344-AD rats, striatal astrocytes displayed a decreased 5HT2AR density when compared with wild-type. A cortical overexpression of TSPO was observed in both astrocytes and microglia of AD subjects compared with age-matched controls when FACS-RTT was performed on human AD postmortem samples.When working with radioactivity, follow the instruction of radio-protection and wear appropriate personal protection equipment. Then, after the procedure, make sure to decontaminate the working environment. Protein quantification and gene expression analysis can easily be done after this procedure on isolated cell populations.

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JoVE Journal

Neuroscience

An Optimized Procedure for Fluorescence-activated Cell Sorting (FACS) Isolation of Autonomic Neural Progenitors from Visceral Organs of Fetal Mice

During development neural crest (NC)-derived neuronal progenitors migrate away from the neural tube to form autonomic ganglia in visceral organs like the intestine and lower urinary tract. Both during development and in mature tissues these cells are often widely dispersed throughout tissues so that isolation of discrete populations using methods like laser capture micro-dissection is difficult. They can however be directly visualized by expression of fluorescent reporters driven from regulatory regions of neuron-specific genes like Tyrosine hydroxylase (TH). We describe a method optimized for high yields of viable TH+ neuronal progenitors from fetal mouse visceral tissues, including intestine and lower urogenital tract (LUT), based on dissociation and fluorescence-activated cell sorting (FACS). 
The Th gene encodes the rate-limiting enzyme for production of catecholamines. Enteric neuronal progenitors begin to express TH during their migration in the fetal intestine1 and TH is also present in a subset of adult pelvic ganglia neurons2-4 . The first appearance of this lineage and the distribution of these neurons in other aspects of the LUT, and their isolation has not been described. Neuronal progenitors expressing TH can be readily visualized by expression of EGFP in mice carrying the transgene construct Tg(Th-EGFP)DJ76Gsat/Mmnc1. We imaged expression of this transgene in fetal mice to document the distribution of TH+ cells in the developing LUT at 15.5 days post coitus (dpc), designating the morning of plug detection as 0.5 dpc, and observed that a subset of neuronal progenitors in the coalescing pelvic ganglia express EGFP. 
To isolate LUT TH+ neuronal progenitors, we optimized methods that were initially used to purify neural crest stem cells from fetal mouse intestine2-6. Prior efforts to isolate NC-derived populations relied upon digestion with a cocktail of collagenase and trypsin to obtain cell suspensions for flow cytometry. In our hands these methods produced cell suspensions from the LUT with relatively low viability. Given the already low incidence of neuronal progenitors in fetal LUT tissues, we set out to optimize dissociation methods such that cell survival in the final dissociates would be increased. We determined that gentle dissociation in Accumax (Innovative Cell Technologies, Inc), manual filtering, and flow sorting at low pressures allowed us to achieve consistently greater survival (&gt;70% of total cells) with subsequent yields of neuronal progenitors sufficient for downstream analysis. The method we describe can be broadly applied to isolate a variety of neuronal populations from either fetal or adult murine tissues.

An Optimized Procedure for Fluorescence-activated Cell Sorting FACS Isolation of Autonomic Neural Progenitors from Visceral Organs of Fetal Mice

An optimized procedure to purify neural crest-derived neuronal progenitors from fetal mouse tissues is described. This method takes advantage of expression from fluorescent reporter alleles to isolate discrete populations by fluorescence-activated cell sorting (FACS). The technique can be applied to isolate neuronal subpopulations throughout development or from adult tissues.

During development neural crest (NC)-derived neuronal progenitors migrate away from the neural tube to form autonomic ganglia in visceral organs like the ...

Use of a Caspase Multiplexing Assay to Determine Apoptosis in a Hypothalamic Cell Model

The ability to multiplex assays in studies of complex cellular mechanisms eliminates the need for repetitive experiments, provides internal controls, and decreases waste in costs and reagents. Here we describe optimization of a multiplex assay to assess apoptosis following a palmitic acid (PA) challenge in an in vitro hypothalamic model, using both fluorescent and luminescent based assays to measure viable cell counts and caspase-3/7 activity in a 96-well microtiter plate format. Following PA challenge, viable cells were determined by a resazurin-based fluorescent assay. Caspase-3/7 activity was then determined using a luminogenic substrate, DEVD, and normalized to cell number. This multiplexing assay is a useful technique for determining change in caspase activity following an apoptotic stimulus, such as saturated fatty acid challenge. The saturated fatty acid PA can increase hypothalamic oxidative stress and apoptosis, indicating the potential importance of assays such as that described here in studying the relationship between saturated fatty acids and neuronal function.

Multiplex assays can provide beneficial information for basic cellular mechanisms&#160;and eliminate waste of reagents and unnecessary repetitive experiments. We describe here a multiplex caspase-3/7 activity assay, using fluorescent- and luminescent-based methods, to determine cell viability in an in vitro hypothalamic model following oxidative challenge with palmitic acid.

The ability to multiplex assays in studies of complex cellular mechanisms eliminates the need for repetitive experiments, provides internal controls, and ...

Telomerase Activity in the Various Regions of Mouse Brain: Non-Radioactive Telomerase Repeat Amplification Protocol (TRAP) Assay

Telomerase, a ribonucleoprotein, is responsible for maintaining the telomere length and therefore promoting genomic integrity, proliferation, and lifespan. In addition, telomerase protects the mitochondria from oxidative stress and confers resistance to apoptosis, suggesting its possible importance for the surviving of non-mitotic, highly active cells such as neurons. We previously demonstrated the ability of novel telomerase activators to increase telomerase activity and expression in the various mouse brain regions and to protect motor neurons cells from oxidative stress. These results strengthen the notion that telomerase is involved in the protection of neurons from various lesions. To underline the role of telomerase in the brain, we here compare the activity of telomerase in male and female mouse brain and its dependence on age. TRAP assay is a standard method for detecting telomerase activity in various tissues or cell lines. Here we demonstrate the analysis of telomerase activity in three regions of the mouse brain by non-denaturing protein extraction using CHAPS lysis buffer followed by modification of the standard TRAP assay.
In this 2-step assay, endogenous telomerase elongates a specific telomerase substrate (TS primer) by adding TTAGGG 6 bp repeats (telomerase reaction). The telomerase reaction products are amplified by PCR reaction creating a DNA ladder of 6 bp increments. The analysis of the DNA ladder is made by 4.5% high resolution agarose gel electrophoresis followed by staining with highly sensitive nucleic acid stain.
Compared to the traditional TRAP assay that utilize 32P labeled radioactive dCTP&#39;s for DNA detection and polyacrylamide gel electrophoresis for resolving the DNA ladder, this protocol offers a non-toxic time saving TRAP assay for evaluating telomerase activity in the mouse brain, demonstrating the ability to detect differences in telomerase activity in the various female and male mouse brain region.

Telomerase Activity in the Various Regions of Mouse Brain: Non-Radioactive Telomerase Repeat Amplification Protocol TRAP Assay

Telomerase is expressed in the neonatal brain and also in distinct regions of the adult brain. We present a non-toxic time saving TRAP assay for the analysis of telomerase activity in various regions of the mouse brain and detection of differences in telomerase activity between male and female mouse brains.

Telomerase, a ribonucleoprotein, is responsible for maintaining the telomere length and therefore promoting genomic integrity, proliferation, and ...

An In Vitro Model for the Study of Cellular Pathophysiology in Globoid Cell Leukodystrophy

The precise function of multi-nucleated microglia, called globoid cells, that are uniquely abundant in the central nervous system of globoid cell leukodystrophy (GLD) is unclear. This gap in knowledge has been hindered by the lack of an appropriate in vitro model for study. Herein, we describe a primary murine glial culture system in which treatment with psychosine results in multinucleation of microglia resembling the characteristic globoid cells found in GLD. Using this novel system, we defined the conditions and modes of analysis for study of globoid cells. The potential use of this model system was validated in our previous study, which identified a potential role for matrix metalloproteinase (MMP)-3 in GLD. This novel in vitro system may be a useful model in which to study the formation and function, but also the potential therapeutic manipulation, of these unique cells.

An In Vitro Model for the Study of Cellular Pathophysiology in Globoid Cell Leukodystrophy

Globoid cells are a defining pathological feature of Krabbe disease, a leukodystrophy currently lacking an effective long-term therapy. We have developed a cell culture model to study the innate biology and pathogenic potential of activated microglia and their transformation into globoid cells.

The precise function of multi-nucleated microglia, called globoid cells, that are uniquely abundant in the central nervous system of globoid cell ...

Using Fluorescence Activated Cell Sorting to Examine Cell-Type-Specific Gene Expression in Rat Brain Tissue

The brain is comprised of four primary cell types including neurons, astrocytes, microglia and oligodendrocytes. Though they are not the most abundant cell type in the brain, neurons are the most widely studied of these cell types given their direct role in impacting behaviors. Other cell types in the brain also impact neuronal function and behavior via the signaling molecules they produce. Neuroscientists must understand the interactions between the cell types in the brain to better understand how these interactions impact neural function and disease. To date, the most common method of analyzing protein or gene expression utilizes the homogenization of whole tissue samples, usually with blood, and without regard for cell type. This approach is an informative approach for examining general changes in gene or protein expression that may influence neural function and behavior; however, this method of analysis does not lend itself to a greater understanding of cell-type-specific gene expression and the effect of cell-to-cell communication on neural function. Analysis of behavioral epigenetics has been an area of growing focus which examines how modifications of the deoxyribonucleic acid (DNA) structure impact long-term gene expression and behavior; however, this information may only be relevant if analyzed in a cell-type-specific manner given the differential lineage and thus epigenetic markers that may be present on certain genes of individual neural cell types. The Fluorescence Activated Cell Sorting (FACS) technique described below provides a simple and effective way to isolate individual neural cells for the subsequent analysis of gene expression, protein expression, or epigenetic modifications of DNA. This technique can also be modified to isolate more specific neural cell types in the brain for subsequent cell-type-specific analysis.

The goal of this protocol is to use the fluorescence activated cell sorting (FACS) technique to sort specific types of neural cells for subsequent analysis of cell-type-specific gene expression, epigenetic markers, and or protein expression.

The brain is comprised of four primary cell types including neurons, astrocytes, microglia and oligodendrocytes. Though they are not the most abundant ...

Fluorescence Activated Cell Sorting (FACS) and Gene Expression Analysis of Fos-expressing Neurons from Fresh and Frozen Rat Brain Tissue

The study of neuroplasticity and molecular alterations in learned behaviors is switching from the study of whole brain regions to the study of specific sets of sparsely distributed activated neurons called neuronal ensembles that mediate learned associations. Fluorescence Activated Cell Sorting (FACS) has recently been optimized for adult rat brain tissue and allowed isolation of activated neurons using antibodies against the neuronal marker NeuN and Fos protein, a marker of strongly activated neurons. Until now, Fos-expressing neurons and other cell types were isolated from fresh tissue, which entailed long processing days and allowed very limited numbers of brain samples to be assessed after lengthy and complex behavioral procedures. Here we found that yields of Fos-expressing neurons and Fos mRNA from dorsal striatum were similar between freshly dissected tissue and tissue frozen at -80 &#186;C for 3 - 21 days. In addition, we confirmed the phenotype of the NeuN-positive and NeuN-negative sorted cells by assessing gene expression of neuronal (NeuN), astrocytic (GFAP), oligodendrocytic (Oligo2) and microgial (Iba1) markers, which indicates that frozen tissue can also be used for FACS isolation of glial cell types. Overall, it is possible to collect, dissect and freeze brain tissue for multiple FACS sessions. This maximizes the amount of data obtained from valuable animal subjects that have often undergone long and complex behavioral procedures.

Fluorescence Activated Cell Sorting FACS and Gene Expression Analysis of Fos-expressing Neurons from Fresh and Frozen Rat Brain Tissue

Here we present a Fluorescence Activated Cell Sorting (FACS) protocol to study molecular alterations in Fos-expressing neuronal ensembles from both fresh and frozen brain tissue. The use of frozen tissue allows FACS isolation of many brain areas over multiple sessions to maximize the use of valuable animal subjects.

The study of neuroplasticity and molecular alterations in learned behaviors is switching from the study of whole brain regions to the study of specific ...

In Utero Electroporation Approaches to Study the Excitability of Neuronal Subpopulations and Single-cell Connectivity

The nervous system is composed of an enormous range of distinct neuronal types. These neuronal subpopulations are characterized by, among other features, their distinct dendritic morphologies, their specific patterns of axonal connectivity, and their selective firing responses. The molecular and cellular mechanisms responsible for these aspects of differentiation during development are still poorly understood.
Here, we describe combined protocols for labeling and characterizing the structural connectivity and excitability of cortical neurons. Modification of the in utero electroporation (IUE) protocol allows the labeling of a sparse population of neurons. This, in turn, enables the identification and tracking of the dendrites and axons of individual neurons, the precise characterization of the laminar location of axonal projections, and morphometric analysis. IUE can also be used to investigate changes in the excitability of wild-type (WT) or genetically modified neurons by combining it with whole-cell recording from acute slices of electroporated brains. These two techniques contribute to a better understanding of the coupling of structural and functional connectivity and of the molecular mechanisms controlling neuronal diversity during development. These developmental processes have important implications on axonal wiring, the functional diversity of neurons, and the biology of cognitive disorders.

In Utero Electroporation Approaches to Study the Excitability of Neuronal Subpopulations and Single-cell Connectivity

This manuscript provides protocols that use in utero electroporation (IUE) to describe the structural connectivity of neurons at the single-cell level and the excitability of fluorescently labeled neurons. Histology is used to characterize dendritic and axonal projections. Whole-cell recording in acute slices is used to investigate excitability.

The nervous system is composed of an enormous range of distinct neuronal types. These neuronal subpopulations are characterized by, among other features, ...

A Temperature Gradient Assay to Determine Thermal Preferences of Drosophila Larvae

Many animals, including the fruit fly, Drosophila melanogaster, are capable of discriminating minute differences in&#160;environmental temperature, which enables them to seek out their preferred thermal landscape. To define the temperature preferences of larvae over a defined linear range, we developed an assay using a temperature gradient. To establish a single-directional gradient, two aluminum blocks are connected to independent water baths, each of which controls the temperature of individual blocks. The two blocks set the lower and upper limits of the gradient. The temperature gradient is established by placing an agarose-coated aluminum plate over the two water-controlled blocks so that the plate spans the distance between them. The ends of the aluminum plate that is set on the top of the water blocks defines the minimum and maximum temperatures, and the regions in-between the two blocks form a linear temperature gradient. The gradient assay can be applied to&#160;larvae of different ages and can be used to identify mutants that exhibit phenotypes, such as those with mutations affecting genes encoding TRP channels and opsins, which are required for temperature discrimination.

A Temperature Gradient Assay to Determine Thermal Preferences of Drosophila Larvae

Here, we present a protocol to determine the preferred environmental temperature of Drosophila larvae using a continuous thermal gradient.

Many animals, including the fruit fly, Drosophila melanogaster, are capable of discriminating minute differences in&#160;environmental temperature, which ...

Primary Cell Culture of Purified GABAergic or Glutamatergic Neurons Established through Fluorescence-activated Cell Sorting

The overall goal of this protocol is to generate purified neuronal cultures derived from either GABAergic or glutamatergic neurons. Purified neurons can be cultured in defined media for 16 days in vitro and are amenable to any analyses typically performed on dissociated cultures, including electrophysiological, morphological and survival analyses. The major advantage of these cultures is that specific cell types can be selectively studied in the absence of complex external influences, such as those arising from glial cells or other neuron types. When planning experiments with purified cells, however, it is important to note that neurons strongly depend on glia-conditioned media for their growth and survival. In addition, glutamatergic neurons further depend on glia-secreted factors for the establishment of synaptic transmission. We therefore also describe a method for co-culturing neurons and glial cells in a non-contact arrangement. Using these methods, we have identified major differences between the development of GABAergic and glutamatergic neuronal networks. Thus, studying cultures of purified neurons has great potential for furthering our understanding of how the nervous system develops and functions. Moreover, purified cultures may be useful for investigating the direct action of pharmacological agents, growth factors or for exploring the consequences of genetic manipulations on specific cell types. As more and more transgenic animals become available, labeling additional specific cell types of interest, we expect that the protocols described here will grow in their applicability and potential.

This protocol describes a cell sorting based method for the purification and culture of fluorescent GABAergic or glutamatergic neurons from the neocortex and hippocampus of postnatal mice or rats.

The overall goal of this protocol is to generate purified neuronal cultures derived from either GABAergic or glutamatergic neurons. Purified neurons can ...

Advanced Diffusion Imaging in The Hippocampus of Rats with Mild Traumatic Brain Injury

Mild traumatic brain injury (mTBI) is the most common type of acquired brain injury. Since patients with traumatic brain injury show a tremendous variability and heterogeneity (age, gender, type of trauma, other possible pathologies, etc.), animal models play a key role in unraveling factors that are limitations in clinical research. They provide a standardized and controlled setting to investigate the biological mechanisms of injury and repair following TBI. However, not all animal models mimic the diffuse and subtle nature of mTBI effectively. For example, the commonly used controlled cortical impact (CCI) and lateral fluid percussion injury (LFPI) models make use of a craniotomy to expose the brain and induce widespread focal trauma, which are not commonly seen in mTBI. Therefore, these experimental models are not valid to mimic mTBI. Thus, an appropriate model should be used to investigate mTBI. The Marmarou weight drop model for rats induces similar microstructural alterations and cognitive impairments as seen in patients who sustain mild trauma; therefore, this model was selected for this protocol. Conventional computed tomography and magnetic resonance imaging (MRI) scans commonly show no damage following a mild injury, because mTBI induces often only subtle and diffuse injuries. With diffusion weighted MRI, it is possible to investigate microstructural properties of brain tissue, which can provide more insight into the microscopic alterations following mild trauma. Therefore, the goal of this study is to obtain quantitative information of a selected region-of-interest (i.e., hippocampus) to follow up disease progression after obtaining a mild and diffuse brain injury.

The overall goal of this procedure is to obtain quantitative microstructural information of the hippocampus in a rat with mild traumatic brain injury. This is done using an advanced diffusion-weighted magnetic resonance imaging protocol and region-of-interest based analysis of parametric diffusion maps.