Name: imaging serotonergic fibers in the mouse spinal cord using the clarity/cubic technique
Uploaded: 2016-02-26T14:00:00
Description: Watch this Scientific Journal Video about Imaging Serotonergic Fibers in the Mouse Spinal Cord Using the CLARITY/CUBIC Technique at JoVE.com

This work was supported by the Australian Research Council Centre of Excellence for Integrative Brain Function (ARC Centre Grant CE140100007), an NHMRC project grant (#1086643). Prof. George Paxinos is supported by a Senior Principal Research Fellow NHMRC grant (#1043626).

Ethics Statement: All procedures involving animal subjects follow the guidelines of the Animal Care and Ethics Committee (ACEC) at The University of New South Wales (the approved ACEC number is 14/94A).
1. Preparation of the Transparent Mouse Spinal Cord
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	<li>Preparation of Ice Cold Hydrogel Solution
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		<li>Preparation of 16% paraformaldehyde solution (PFA)
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			<li>Add 16 g paraformaldehyde powder into 70 ml pre-warmed distilled water (50-55 &#176;C) and stir on a heated magn...

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	<li>Rivot, J. P., Chaouch, A., Besson, 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=Nucleus+raphe+magnus+modulation+of+response+of+rat+dorsal+horn+neurons+to+unmyelinated+fiber+inputs:+partial+involvement+of+serotonergic+pathways.">Nucleus raphe magnus modulation of response of rat dorsal horn neurons to unmyelinated fiber inputs: partial involvement of serotonergic pathways.</a> J Neurophysiol. 44 (6), 1039-1057 (1980).</li><li>Liang, H., Paxinos, G., Watson, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Projections+from+the+brain+to+the+spinal+cord+in+the+mouse.">Projections from the brain to the spinal cord in the mouse.</a> Brain Struct Funct. 215 (3-4), 159-186 (2011).</li><li>Sorkin, L. S., McAdoo, D. J., Willis, W. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Raphe+magnus+stimulation-induced+anti-nociception+in+the+cat+is+associated+with+release+of+amino+acids+as+well+as+serotonin+in+the+lumbar+dorsal+horn.">Raphe magnus stimulation-induced anti-nociception in the cat is associated with release of amino acids as well as serotonin in the lumbar dorsal horn.</a> Brain Res. 618 (1), 95-108 (1993).</li><li>Rivot, J. P., Chiang, C. Y., Besson, 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=Increase+of+serotonin+metabolism+within+the+dorsal+horn+of+the+spinal+cord+during+nucleus+raphe+magnus+stimulation,+as+revealed+by+in+vivo+electrochemical+detection.">Increase of serotonin metabolism within the dorsal horn of the spinal cord during nucleus raphe magnus stimulation, as revealed by in vivo electrochemical detection.</a> Brain Res. 238 (1), 117-126 (1982).</li><li>Hentall, I. D., Pinzon, A., Noga, B. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Spatial+and+temporal+patterns+of+serotonin+release+in+the+rat's+lumbar+spinal+cord+following+electrical+stimulation+of+the+nucleus+raphe+magnus.">Spatial and temporal patterns of serotonin release in the rat's lumbar spinal cord following electrical stimulation of the nucleus raphe magnus.</a> Neuroscience. 142 (3), 893-903 (2006).</li><li>Bullitt, E., Light, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Intraspinal+course+of+descending+serotoninergic+pathways+innervating+the+rodent+dorsal+horn+and+lamina+X.">Intraspinal course of descending serotoninergic pathways innervating the rodent dorsal horn and lamina X.</a> J Comp Neurol. 286 (2), 231-242 (1989).</li><li>Jones, S. L., Light, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Termination+patterns+of+serotoninergic+medullary+raphespinal+fibers+in+the+rat+lumbar+spinal+cord:+an+anterograde+immunohistochemical+study.">Termination patterns of serotoninergic medullary raphespinal fibers in the rat lumbar spinal cord: an anterograde immunohistochemical study.</a> J Comp Neurol. 297 (2), 267-282 (1990).</li><li>Marlier, L., Sandillon, F., Poulat, P., Rajaofetra, N., Geffard, M., Privat, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Serotonergic+innervation+of+the+dorsal+horn+of+rat+spinal+cord:+light+and+electron+microscopic+immunocytochemical+study.">Serotonergic innervation of the dorsal horn of rat spinal cord: light and electron microscopic immunocytochemical study.</a> J Neurocytol. 20 (4), 310-322 (1991).</li><li>Morrison, S. F., Gebber, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Axonal+branching+patterns+and+funicular+trajectories+of+raphespinal+sympathoinhibitory+neurons.">Axonal branching patterns and funicular trajectories of raphespinal sympathoinhibitory neurons.</a> J Neurophysiol. 53 (3), 759-772 (1985).</li><li>Barman, S. M., Gebber, G. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+axons+of+raphespinal+sympathoinhibitory+neurons+branch+in+the+cervical+spinal+cord.">The axons of raphespinal sympathoinhibitory neurons branch in the cervical spinal cord.</a> Brain Res. 441 (1-2), 371-376 (1988).</li><li>Martin, G. F., Cabana, T., Ditirro, F. J., Ho, R. H., Humbertson, A. O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Raphespinal+projections+in+the+North+American+opossum:+evidence+for+connectional+heterogeneity.">Raphespinal projections in the North American opossum: evidence for connectional heterogeneity.</a> J Comp Neurol. 208 (1), 67-84 (1982).</li><li>Bowker, R. M., Westlund, K. N., Coulter, J. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Origins+of+serotonergic+projections+to+the+lumbar+spinal+cord+in+the+monkey+using+a+combined+retrograde+transport+and+immunocytochemical+technique.">Origins of serotonergic projections to the lumbar spinal cord in the monkey using a combined retrograde transport and immunocytochemical technique.</a> Brain Res Bull. 9 (1-6), 271-278 (1982).</li><li>Watkins, L. R., Griffin, G., Leichnetz, G. R., Mayer, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+and+somatotopic+organization+of+nuclei+projecting+via+the+dorsolateral+funiculus+in+rats:+a+retrograde+tracing+study+using+HRP+slow-release+gels.">Identification and somatotopic organization of nuclei projecting via the dorsolateral funiculus in rats: a retrograde tracing study using HRP slow-release gels.</a> Brain Res. 223 (2), 237-255 (1981).</li><li>Chung, K., 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=Structural+and+molecular+interrogation+of+intact+biological+systems.">Structural and molecular interrogation of intact biological systems.</a> Nature. 497 (7449), 332-337 (2013).</li><li>Tomer, R., Ye, L., Hsueh, B., Deisseroth, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Advanced+CLARITY+for+rapid+and+high-resolution+imaging+of+intact+tissues.">Advanced CLARITY for rapid and high-resolution imaging of intact tissues.</a> Nature Protoc. 9 (7), 1682-1697 (2014).</li><li>Susaki, E. A., 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=Whole-brain+imaging+with+single-cell+resolution+using+chemical+cocktails+and+computational+analysis.">Whole-brain imaging with single-cell resolution using chemical cocktails and computational analysis.</a> Cell. 157 (3), 726-739 (2014).</li><li>Ke, M. T., Fujimoto, S., Imai, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SeeDB:+a+simple+and+morphology-preserving+optical+clearing+agent+for+neuronal+circuit+reconstruction.">SeeDB: a simple and morphology-preserving optical clearing agent for neuronal circuit reconstruction.</a> Nature Neurosci. 16 (8), 1154-1161 (2013).</li><li>Ert&#252;rk, A., 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=Three-dimensional+imaging+of+solvent-cleared+organs+using+3DISCO.">Three-dimensional imaging of solvent-cleared organs using 3DISCO.</a> Nature Protoc. 7 (11), 1983-1995 (2012).</li><li>Hama, H., 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=Scale:+a+chemical+approach+for+fluorescence+imaging+and+reconstruction+of+transparent+mouse+brain.">Scale: a chemical approach for fluorescence imaging and reconstruction of transparent mouse brain.</a> Nature Neurosci. 14 (11), 1481-1488 (2011).</li><li>Kuwajima, T., Sitko, A. A., Bhansali, P., Jurgens, C., Guido, W., Mason, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=ClearT:+a+detergent-+and+solvent-free+clearing+method+for+neuronal+and+non-neuronal+tissue.">ClearT: a detergent- and solvent-free clearing method for neuronal and non-neuronal tissue.</a> Development. 140 (6), 1364-1368 (2013).</li><li>Ert&#252;rk, A., Bradke, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-resolution+imaging+of+entire+organs+by+3-dimensional+imaging+of+solvent+cleared+organs+(3DISCO).">High-resolution imaging of entire organs by 3-dimensional imaging of solvent cleared organs (3DISCO).</a> Exp Neurol. 242, 57-64 (2013).</li><li>Kim, S. Y., Chung, K., Deisseroth, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Light+microscopy+mapping+of+connections+in+the+intact+brain.">Light microscopy mapping of connections in the intact brain.</a> Trends Cogn Sci. 17 (12), 596-599 (2013).</li><li>Spence, R. 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=Bringing+CLARITY+to+gray+matter+atrophy.">Bringing CLARITY to gray matter atrophy.</a> NeuroImage. 101, 625-632 (2014).</li><li>Ando, K., 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=Inside+Alzheimer+brain+with+CLARITY:+senile+plaques,+neurofibrillary+tangles+and+axons+in+3-D.">Inside Alzheimer brain with CLARITY: senile plaques, neurofibrillary tangles and axons in 3-D.</a> Acta Neuropathol. 128 (3), 457-459 (2014).</li><li>Zhang, H., Rinaman, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Simplified+CLARITY+for+visualizing+immunofluorescence+labeling+in+the+developing+rat+brain.">Simplified CLARITY for visualizing immunofluorescence labeling in the developing rat brain.</a> Brain Struct Funct. , (2015).</li><li>Lee, H., Park, J. H., Seo, I., Park, S. H., Kim, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Improved+application+of+the+electrophoretic+tissue+clearing+technology,+CLARITY,+to+intact+solid+organs+including+brain,+pancreas,+liver,+kidney,+lung,+and+intestine.">Improved application of the electrophoretic tissue clearing technology, CLARITY, to intact solid organs including brain, pancreas, liver, kidney, lung, and intestine.</a> BMC Dev Biol. 14, 781 (2015).</li><li>Yang, 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=Single-cell+phenotyping+within+transparent+intact+tissue+through+whole-body+clearing.">Single-cell phenotyping within transparent intact tissue through whole-body clearing.</a> Cell. 158 (4), 945-958 (2014).</li><li>Rosset, A., Spadola, L., Ratib, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=OsiriX:+an+open-source+software+for+navigating+in+multidimensional+DICOM+images.">OsiriX: an open-source software for navigating in multidimensional DICOM images.</a> J Digit Imaging. 17, 205-216 (2004).</li></ol>

The protocol described shows how to image serotonergic fibers in the mouse spinal cord with the combined CLARITY and CUBIC techniques. It introduces a faster clearing process compared to the passive clearing protocol developed by Cheung et al.14 and Tomer et al.15 and allows the spinal cord tissue to be well supported by the hydrogel during clearing.
An important step during fixation of the mouse spinal cord, as reported by Cheung et al.14 ...

Supraspinal projections are responsible for the modulation of diverse behaviors such as pain perception. One of the projections carrying nociceptive information contains serotoninergic fibers, which originate from the hindbrain raphe and adjacent reticular nuclei1,2. Physiological and pharmacological studies have demonstrated an increased release of serotonin in the dorsal horn of the spinal cord after electrical stimulation of the raphe nuclei in the hindbrain3-5. In the rat and opossum, serotonergic raphespinal fibers have dense terminals, not only in the dorsal horn6-8, but also in the intermediate zone7,9,10, the ventral horn7,11, and even lamina 1012,13. There are no similar studies in the mouse. The present study aimed to map the termination pattern of serotonergic fibers arising from the hindbrain raphe nuclei and their adjacent reticular nuclei in the mouse spinal cord using the recently published CLARITY14 method and its modification - CUBIC15. 
Conventional fluorescence or peroxidase immunohistochemistry of the spinal cord clearly shows the distribution of serotonergic fibers in the gray matter of the spinal cord in 30-40 &#181;m thick cross-sections. However, this approach does not show the continuity of the serotonergic fiber tracts in the white matter and their collaterals in the gray matter. Although the 3D reconstruction of histological sections has advanced our knowledge of fiber tracts, it remains a challenge for histologists and anatomists to follow a single tract due to small distortions in the tissue caused by cutting. To circumvent this obstacle a number of researchers have developed various protocols for making the whole tissue structure transparent, and collecting an image of unaltered tissue in a single video file17-21. So far, the clear, lipid-exchanged, acrylamide-hybridized rigid, imaging/ immunostaining compatible, tissue hydrogel (CLARITY) technique, developed by Deisseroth's group14,15, as well as CUBIC, developed by Susaki et al16 are the most successful. Since the publication of the protocols, many researchers have started using these techniques to investigate various aspects of biological tissues, including, not only the brain22-25, but also the heart, kidneys, intestine, and the lungs26,27. 
By fixing the mouse spinal cord with the hydrogel solution (CLARITY) and clearing with the CUBIC reagents (which is a much faster method than that described by the original CLARITY protocol14,15), a spinal cord tissue block of 2-3 mm long was cleared within two weeks and immunofluorescence staining for serotonin completed in eight days. With just a combination of chemical agents, conventional immunohistochemistry can be used to create an image of individual fiber tracts in a 3D video file in approximately one month.

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			<td height="22" style="height:22px;width:495px;">Photoinitiator VA044</td>
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			<td style="width:807px;">http://www.wako-chem.co.jp/specialty/waterazo/VA-044.htm</td>
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			<td height="21" style="height:21px;">40% acrylamide solution</td>
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			<td>Bio Rad</td>
			<td>161-0142</td>
			<td>http://www.bio-rad.com/en-au/sku/161-0142-2-bis-solution?parentCategoryGUID=5e7a4f31-879c-4d63-ba0b-82556a0ccf1d</td>
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			<td>http://www.merckmillipore.com/AU/en/product/Urea---CAS-57-13-6---Calbiochem,EMD_BIO-66612</td>
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			<td height="21" style="height:21px;">N,N,N&#8217;,N&#8217;-tetrakis (2-hydroxypropyl) ethylenediamine</td>
			<td>Merck Millipore</td>
			<td align="right">821940</td>
			<td>http://www.merckmillipore.com/AU/en/product/Ethylenediamine-N,N,N&#39;,N&#39;-tetra-2-propanol,MDA_CHEM-821940</td>
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			<td height="21" style="height:21px;">Triton-X 100</td>
			<td>Merck Millipore</td>
			<td align="right">648462</td>
			<td>http://www.merckmillipore.com/AU/en/product/TRITON&#174;-X-100-Detergent---CAS-9002-93-1---Calbiochem,EMD_BIO-648462</td>
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			<td>Sigma</td>
			<td>S0389</td>
			<td>http://www.sigmaaldrich.com/catalog/product/sigma/s0389?lang=en&#38;region=AU</td>
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			<td height="21" style="height:21px;">2,2&#8217;,2&#8217;&#8217;- nitrilotriethanol</td>
			<td>Merck Millipore</td>
			<td align="right">137002</td>
			<td>http://www.merckmillipore.com/AU/en/product/Triethanolamine-(Trolamine),MDA_CHEM-137022</td>
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			<td height="21" style="height:21px;">serotonin antibody</td>
			<td>Merck Millipore</td>
			<td>AB938</td>
			<td>http://www.merckmillipore.com/AU/en/product/Anti-Serotonin-Antibody,MM_NF-AB938</td>
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			<td height="21" style="height:21px;">goat anti rabbit IgG (H+L) Secondary Antibody, Alexa Fluor&#174; 594 conjugate</td>
			<td>Life Technologies</td>
			<td>&#160;A-11012</td>
			<td>https://www.lifetechnologies.com/order/genome-database/antibody/Rabbit-IgG-H-L-Secondary-Antibody-Polyclonal/A-11012</td>
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			<td height="21" style="height:21px;">multi-photon microscope</td>
			<td>Leica</td>
			<td>Leica TCS SP5 MP STED</td>
			<td>http://www.leica-microsystems.com/products/confocal-microscopes/details/product/leica-tcs-sp5-mp/</td>
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imaging serotonergic fibers in the mouse spinal cord using the clarity/cubic technique

Long descending fibers to the spinal cord are essential for locomotion, pain perception, and other behaviors. The fiber termination pattern in the spinal cord of the majority of these fiber systems have not been thoroughly investigated in any species. Serotonergic fibers, which project to the spinal cord, have been studied in rats and opossums on histological sections and their functional significance has been deduced based on their fiber termination pattern in the spinal cord. With the development of CLARITY and CUBIC techniques, it is possible to investigate this fiber system and its distribution in the spinal cord, which is likely to reveal previously unknown features of serotonergic supraspinal pathways. Here, we provide a detailed protocol for imaging the serotonergic fibers in the mouse spinal cord using the combined CLARITY and CUBIC techniques. The method involves perfusion of a mouse with a hydrogel solution and clarification of the tissue with a combination of clearing reagents. Spinal cord tissue was cleared in just under two weeks, and the subsequent immunofluorescent staining against serotonin was completed in less than ten days. With a multi-photon fluorescent microscope, the tissue was scanned and a 3D image was reconstructed using Osirix software.

This section shows results from serotonin antibody staining in the transparent mouse spinal cord using a combination of the CLARITY and CUBIC protocols. We show that serotonergic fibers are present in all laminae of the spinal cord with a predominance in the ventral portion of the ventral horn (Figure 1, also see Video 1). The control tissue did not have positive fibers (result was not shown). In the ventral horn, densely packed serotonergic fibers are pr...

Watch this Scientific Journal Video about Imaging Serotonergic Fibers in the Mouse Spinal Cord Using the CLARITY/CUBIC Technique at JoVE.com

Imaging Serotonergic Fibers in the Mouse Spinal Cord Using the CLARITY/CUBIC Technique

Supraspinal projections are important for pain perception and other behaviors, and serotonergic fibers are one of these fiber systems. The present study focused on the application of the combined CLARITY/CUBIC protocol to the mouse spinal cord in order to investigate the termination of these serotonergic fibers.

Long descending fibers to the spinal cord are essential for locomotion, pain perception, and other behaviors. The fiber termination pattern in the spinal ...

The overall goal of this CLARITY/CUBIC experiment is to reveal the 3D features of serotonergic fibers in the mouse spinal cord, which are not observable by traditional histology. This method can help answer key questions in the neuroanatomy field, such as how are serotonergic fibers distributed throughout the spinal cord? The main advantages of this technique are that it allows serotonergic fibers to be observed in situ, along with identification of vectors that are not observable by traditional histology.Although this method can provide insight into the organization of the central nervous system, it can also be applied to other systems, such as the cardiovascular system. We first sought to use this method when we reached limitations using a traditional tracing method to analyze serotonergic fibers in the mouse spinal cord. Begin by fixing the limbs of an anesthetized mouse to a plastic dissection stage in a fume hood.Confirm a lack of response to toe pinch and use a pair of scissors to open the skin over the chest. Next, open the chest to expose the heart and insert a 25 gauge needle attached to a peristaltic pump tubing into the left ventricle. Snip the right atrium to create an exit point for the blood.Then, wash the heart with 40 milliliters of 9 percent saline at approximately 10 milliliters per minute. When all of the blood has been flushed, perfuse the animal with 35 milliliters of freshly prepared, ice cold hydrogel at the same perfusion rate. Then, incise the skin over the back of the mouse and dissect the muscles nest to the vertebrae.After cutting the vertebral arches on one side and flipping them to the other, excise the spinal cord from the vertebral column with fine scissors. Immediately after harvesting, place the spinal cord in 15 milliliters of freshly prepared hydrogel solution overnight at four degrees Celsius. The next day, remove 10 milliliters of the hydrogel and pour the rest of the solution and spinal cord into a five milliliter tube.Add fresh hydrogel solution until the tube is full and then stretch a small piece of parafilm over the top of the tube, taking care that the parafilm contacts the hyrdogel and that there are no bubbles between the solution and the film. Removing air from the tube is the most difficult step. To make sure there are no bubbles, take care to fill the tube slowly with the hydrogel solution and then carefully place the parafilm across the top of the tube, without spilling the gel.Now, wrap a second piece of parafilm around the neck of the tube and incubate the spinal cord in a 37 degree Celsius oven overnight. When the hydrogel solution becomes a gel, use a spanner to remove the gel and neural tissue from the tube. To remove the hydrogel from the spinal cord, briefly press a course tissue against the gel.The gel will stick to the tissue as it is removed. When the spinal cord is clean, place it in PBS for four, six hour washes on a shaker. After 24 hours, use a razor blade to cut the spinal cord coronally into two to three millimeter long segments and transfer the tissue pieces into five milliliters of freshly prepared CUBIC clearing solution.Shake the pieces in the 37 degree Celsius oven for 72 hours and then replace the three day old clearing solution with freshly prepared clearing solution. Two to three days later, check the transparency of the tissue against the paper with font size 8 letters. When the letters can be observed through the cleared tissue, replace the CUBIC clearing solution with four milliliters of fresh PBST for four, six hour washes.To stain the spinal cord segments for fluorescent imaging, incubate the tissue in the appropriate primary antibody solution for three days on a shaker in the 37 degree Celsius oven. At the end of the primary antibody staining, immerse the tissue in four milliliters of PBST for four, six hour washes in the 37 degree Celsius oven. Then, replace the PBST with the appropriate secondary antibody solution for three more days on the shaker in the 37 degree Celsius oven.On the fourth day, wash away the unbound secondary antibody with PBST, as just demonstrated. To image the segments, replace the last PBST wash with four milliliters of 85 percent glycerol to make the refractive index of the tissue even. After about an hour, check the transparency of the tissue.When the tissue is clear, transfer the spinal cord segments on to a large, thin glass slide. Next, place a few drops of 85 percent glycerol next to the spinal cord tissue and cover the tissue with a 22 by 50 millimeter glass cover slip. Place the slide into the holding frame of the microscope and move the tissue into the light path.Then, select the Helium Neon laser and check the brightness of the positive signal in the live image to adjust the intensity of the laser. With the laser at the optimal intensity, use a 20x objective to select the scanning area of the spinal cord tissue. Then, set the instrument to create a z-stack with the depth of each stack at three microns.Finally, scan the tissue from the top to the bottom of the z-stack, first, under the 20x objective, followed by a z-stack scan under the 63x objective. 3D software can then be used to reconstruct the appropriate 3D videos. Here, the presence of serotonergic fibers in all of the laminae of the spinal cord, with a predominance in the ventral portion of the ventral horn, can be observed.In the ventral horn, densely packed serotonergic fibers are present in the ventral medial area, extending toward the lateral portion of the ventral horn, with some of the immunopositive fibers also extending from the ventral horn, toward the dorsal horn, or central canal. Immunopositive fibers are present in all of the laminae of the dorsal horn, but there is a small gap between the positive fibers in laminae two and four, particularly, in the lateral part of the dorsal horn. In a horizontal section, densely packed sertonergic fibers in ventral horn along the longitudinal axis of the spinal cord, can be observed issuing branches regularly along the axis perpendicular to the fiber bundle.These branches further diverge along their paths, to the lateral portion of the ventral horn. Compared with these branches, those extending toward the midline are more irregular and smaller. Under the 63x objective, the serotonergic fibers in the dorsal horn, are observed to travel along the axis of the spinal cord and to terminate at various points along the path of the tract with thick fibers, sporadically distributed among the thin fibers.Once mastered, this technique can be completed in less than three weeks, if it is performed properly. Following this procedure, other methods, like double labeling with choline acetyltransferase antibody, can be performed to answer additional questions about whether serotonergic fibers terminate motor neurons. After its development, this technique paved the way for researchers in the field of biomedical imaging to explore the complex spatial relationships between various cell types in animal specimens or human tissues.After watching this video, you should have a good understanding of how to clarify the mouse spinal cord tissue for 3D imaging after immunofluorescent staining.

imaging-serotonergic-fibers-mouse-spinal-cord-using-claritycubic

Research

JoVE Journal

Neuroscience

Spinal Cord Electrophysiology II: Extracellular Suction Electrode Fabrication

Development of neural circuitries and locomotion can be studied using neonatal rodent spinal cord central pattern generator (CPG) behavior. We demonstrate a method to fabricate suction electrodes that are used to examine CPG activity, or fictive locomotion, in dissected rodent spinal cords. The rodent spinal cords are placed in artificial cerebrospinal fluid and the ventral roots are drawn into the suction electrode. The electrode is constructed by modifying a commercially available suction electrode. A heavier silver wire is used instead of the standard wire given by the commercially available electrode. The glass tip on the commercial electrode is replaced with a plastic tip for increased durability. We prepare hand drawn electrodes and electrodes made from specific sizes of tubing, allowing consistency and reproducibility. Data is collected using an amplifier and neurogram acquisition software. Recordings are performed on an air table within a Faraday cage to prevent mechanical and electrical interference, respectively.

A demonstration of the fabrication and use of an extracellular suction electrode used to measure electrophysiological recordings of neonatal rodent spinal cords in vitro

Development of neural circuitries and locomotion can be studied using neonatal rodent spinal cord central pattern generator (CPG) behavior. We demonstrate ...

In vivo Imaging of the Mouse Spinal Cord Using Two-photon Microscopy

In vivo imaging using two-photon microscopy 1 in mice that have been genetically engineered to express fluorescent proteins in specific cell types 2-3 has significantly broadened our knowledge of physiological and pathological processes in numerous tissues in vivo 4-7. In studies of the central nervous system (CNS), there has been a broad application of in vivo imaging in the brain, which has produced a plethora of novel and often unexpected findings about the behavior of cells such as neurons, astrocytes, microglia, under physiological or pathological conditions 8-17. However, mostly technical complications have limited the implementation of in vivo imaging in studies of the living mouse spinal cord. In particular, the anatomical proximity of the spinal cord to the lungs and heart generates significant movement artifact that makes imaging the living spinal cord a challenging task.
We developed a novel method that overcomes the inherent limitations of spinal cord imaging by stabilizing the spinal column, reducing respiratory-induced movements and thereby facilitating the use of two-photon microscopy to image the mouse spinal cord in vivo. This is achieved by combining a customized spinal stabilization device with a method of deep anesthesia, resulting in a significant reduction of respiratory-induced movements. This video protocol shows how to expose a small area of the living spinal cord that can be maintained under stable physiological conditions over extended periods of time by keeping tissue injury and bleeding to a minimum. Representative raw images acquired in vivo detail in high resolution the close relationship between microglia and the vasculature. A timelapse sequence shows the dynamic behavior of microglial processes in the living mouse spinal cord. Moreover, a continuous scan of the same z-frame demonstrates the outstanding stability that this method can achieve to generate stacks of images and/or timelapse movies that do not require image alignment post-acquisition. Finally, we show how this method can be used to revisit and reimage the same area of the spinal cord at later timepoints, allowing for longitudinal studies of ongoing physiological or pathological processes in vivo.

In vivo Imaging of the Mouse Spinal Cord Using Two-photon Microscopy

A minimally invasive protocol to stabilize the mouse spinal column and perform repetitive in vivo spinal cord imaging using two-photon microscopy is described. This method combines a spinal stabilization device and an anesthetic regimen to minimize respiratory-induced movements and produce raw imaging data that require no alignment or other post-processing.

In vivo imaging using two-photon microscopy 1 in mice that have been genetically engineered to express fluorescent proteins in specific cell types 2-3 has ...

Spinal Cord Transection in the Larval Zebrafish

Mammals fail in sensory and motor recovery following spinal cord injury due to lack of axonal regrowth below the level of injury as well as an inability to reinitiate spinal neurogenesis. However, some anamniotes including the zebrafish Danio rerio exhibit both sensory and functional recovery even after complete transection of the spinal cord. The adult zebrafish is an established model organism for studying regeneration following spinal cord injury, with sensory and motor recovery by 6&#160;weeks post-injury. To take advantage of in vivo analysis of the regenerative process available in the transparent larval zebrafish as well as genetic tools not accessible in the adult, we use the larval zebrafish to study regeneration after spinal cord transection. Here we demonstrate a method for reproducibly and verifiably transecting the larval spinal cord. After transection, our data shows sensory recovery beginning at 2&#160;days post-injury (dpi), with the C-bend movement detectable by 3 dpi and resumption of free swimming by 5 dpi. Thus we propose the larval zebrafish as a companion tool to the adult zebrafish for the study of recovery after spinal cord injury.

After spinal transection, adult zebrafish have functional recovery by six weeks post-injury. To take advantage of larval transparency and faster recovery, we present a method for transecting the larval spinal cord. After transection, we observe sensory recovery beginning at 2&#160;days post-injury, and C-bend movement by 3 days post-injury.

Mammals fail in sensory and motor recovery following spinal cord injury due to lack of axonal regrowth below the level of injury as well as an inability ...

A Procedure for Implanting a Spinal Chamber for Longitudinal In Vivo Imaging of the Mouse Spinal Cord

Studies in the mammalian neocortex have enabled unprecedented resolution of cortical structure, activity, and response to neurodegenerative insults by repeated, time-lapse in vivo imaging in live rodents. These studies were made possible by straightforward surgical procedures, which enabled optical access for a prolonged period of time without repeat surgical procedures. In contrast, analogous studies of the spinal cord have been previously limited to only a few imaging sessions, each of which required an invasive surgery. As previously described, we have developed a spinal chamber that enables continuous optical access for upwards of 8 weeks, preserves mechanical stability of the spinal column, is easily stabilized externally during imaging, and requires only a single surgery. Here, the design of the spinal chamber with its associated surgical implements is reviewed and the surgical procedure is demonstrated in detail. Briefly, this video will demonstrate the preparation of the surgical area and mouse for surgery, exposure of the spinal vertebra and appropriate tissue debridement, the delivery of the implant and vertebral clamping, the completion of the chamber, the removal of the delivery system, sealing of the skin, and finally, post-operative care. The procedure for chronic in vivo imaging using nonlinear microscopy will also be demonstrated. Finally, outcomes, limitations, typical variability, and a guide for troubleshooting are discussed.

A Procedure for Implanting a Spinal Chamber for Longitudinal In Vivo Imaging of the Mouse Spinal Cord

In this video, we describe a procedure for implanting a chronic optical imaging chamber over the dorsal spinal cord of a live mouse. The chamber, surgical procedure, and chronic imaging are reviewed and demonstrated.

Studies in the mammalian neocortex have enabled unprecedented resolution of cortical structure, activity, and response to neurodegenerative insults by ...

Diffusion Imaging in the Rat Cervical Spinal Cord

Magnetic resonance imaging (MRI) is the state of the art approach for assessing the status of the spinal cord noninvasively, and can be used as a diagnostic and prognostic tool in cases of disease or injury. Diffusion weighted imaging (DWI), is sensitive to the thermal motion of water molecules and allows for inferences of tissue microstructure. This report describes a protocol to acquire and analyze DWI of the rat cervical spinal cord on a small-bore animal system. It demonstrates an imaging setup for the live anesthetized animal and recommends a DWI acquisition protocol for high-quality imaging, which includes stabilization of the cord and control of respiratory motion. Measurements with diffusion weighting along different directions and magnitudes (b-values) are used. Finally, several mathematical models of the resulting signal are used to derive maps of the diffusion processes within the spinal cord tissue that provide insight into the normal cord and can be used to monitor injury or disease processes noninvasively.

The goal of this protocol is to obtain high-quality diffusion weighted magnetic resonance imaging (DWI) of the rat spinal cord for noninvasive characterization of tissue microstructure. This protocol describes optimizations of the MRI sequence, radiofrequency coil, and analysis methods to enable DWI images free from artifacts.

Magnetic resonance imaging (MRI) is the state of the art approach for assessing the status of the spinal cord noninvasively, and can be used as a ...

Two-photon Imaging of Cellular Dynamics in the Mouse Spinal Cord

Two-photon (2P) microscopy is utilized to reveal cellular dynamics and interactions deep within living, intact tissues. Here, we present a method for live-cell imaging in the murine spinal cord. This technique is uniquely suited to analyze neural precursor cell (NPC) dynamics following transplantation into spinal cords undergoing neuroinflammatory demyelinating disorders. NPCs migrate to sites of axonal damage, proliferate, differentiate into oligodendrocytes, and participate in direct remyelination. NPCs are thereby a promising therapeutic treatment to ameliorate chronic demyelinating diseases. Because transplanted NPCs migrate to the damaged areas on the ventral side of the spinal cord, traditional intravital 2P imaging is impossible, and only information on static interactions was previously available using histochemical staining approaches. Although this method was generated to image transplanted NPCs in the ventral spinal cord, it can be applied to numerous studies of transplanted and endogenous cells throughout the entire spinal cord. In this article, we demonstrate the preparation and imaging of a spinal cord with enhanced yellow fluorescent protein-expressing axons and enhanced green fluorescent protein-expressing transplanted NPCs.

A new ex vivo preparation for imaging the mouse spinal cord. This protocol allows for two-photon imaging of live cellular interactions throughout the spinal cord.

Two-photon (2P) microscopy is utilized to reveal cellular dynamics and interactions deep within living, intact tissues. Here, we present a method for ...

Imaging Neural Activity in the Primary Somatosensory Cortex Using Thy1-GCaMP6s Transgenic Mice

The mammalian brain exhibits marked symmetry across the sagittal plane. However, detailed description of neural dynamics in symmetric brain regions in adult mammalian animals remains elusive. In this study, we describe an experimental procedure for measuring calcium dynamics through dual optical windows above bilateral primary somatosensory corticies (S1) in Thy1-GCaMP6s transgenic mice using 2-photon (2P) microscopy. This method enables recordings and quantifications of neural activity in bilateral mouse brain regions one at a time in the same experiment for a prolonged period in vivo. Key aspects of this method, which can be completed within an hour, include minimally invasive surgery procedures for creating dual optical windows, and the use of 2P imaging. Although we only demonstrate the technique in the S1 area, the method can be applied to other regions of the living brain facilitating the elucidation of structural and functional complexities of brain neural networks.

Imaging Neural Activity in the Primary Somatosensory Cortex Using Thy1-GCaMP6s Transgenic Mice

We describe an experimental procedure for measuring neuronal activity through dual optical windows above bilateral primary somatosensory corticies (S1) in Thy1-GCaMP6s transgenic mice using 2-photon (2P) microscopy in vivo.

The mammalian brain exhibits marked symmetry across the sagittal plane. However, detailed description of neural dynamics in symmetric brain regions in ...

Laminectomy and Spinal Cord Window Implantation in the Mouse

This protocol describes a method for spinal cord laminectomy and glass window implantation for in vivo imaging of the mouse spinal cord. An integrated digital vaporizer is utilized to achieve a stable plane of anesthesia at a low-flow rate of isoflurane. A single vertebral spine is removed, and a commercially available cover-glass is overlaid on a thin agarose bed. A 3D-printed plastic backplate is then affixed to the adjacent vertebral spines using tissue adhesive and dental cement. A stabilization platform is used to reduce motion artifact from respiration and heartbeat. This rapid and clamp-free method is well-suited for acute multi-photon fluorescence microscopy. Representative data are included for an application of this technique to two-photon microscopy of the spinal cord vasculature in transgenic mice expressing eGFP:Claudin-5 &#8212; a tight junction protein.

This protocol describes implantation of a glass window onto the spinal cord of a mouse to facilitate visualization by intravital microscopy.

This protocol describes a method for spinal cord laminectomy and glass window implantation for in vivo imaging of the mouse spinal cord. An integrated ...

Diffusion Tensor Magnetic Resonance Imaging in Chronic Spinal Cord Compression

Chronic spinal cord compression is the most common cause of spinal cord impairment in patients with nontraumatic spinal cord damage. Conventional magnetic resonance imaging (MRI) plays an important role in both confirming the diagnosis and evaluating the degree of compression. However, the anatomical detail provided by conventional MRI is not sufficient to accurately estimate neuronal damage and/or assess the possibility of neuronal recovery in chronic spinal cord compression patients. In contrast, diffusion tensor imaging (DTI) can provide quantitative results according to the detection of water molecule diffusion in tissues. In the present study, we develop a methodological framework to illustrate the application of DTI in chronic spinal cord compression disease. DTI fractional anisotropy (FA), apparent diffusion coefficients (ADCs), and eigenvector values are useful for visualizing microstructural pathological changes in the spinal cord. Decreased FA and increases in ADCs and eigenvector values were observed in chronic spinal cord compression patients compared to healthy controls. DTI could help surgeons understand spinal cord injury severity and provide important information regarding prognosis and neural functional recovery. In conclusion, this protocol provides a sensitive, detailed, and noninvasive tool to evaluate spinal cord compression.

Here, we present a protocol for the application of diffusion tensor imaging parameters to evaluate spinal cord compression.

Chronic spinal cord compression is the most common cause of spinal cord impairment in patients with nontraumatic spinal cord damage. Conventional magnetic ...

Intra-Arterial Delivery of Neural Stem Cells to the Rat and Mouse Brain: Application to Cerebral Ischemia

Neural stem cell (NSC) therapy is an emerging innovative treatment for stroke, traumatic brain injury and neurodegenerative disorders. As compared to intracranial delivery, intra-arterial administration of NSCs is less invasive and produces a more diffuse distribution of NSCs within the brain parenchyma. Further, intra-arterial delivery allows the first-pass effect in the brain circulation, lessening the potential for trapping of cells in peripheral organs, such as liver and spleen, a complication associated with peripheral injections. Here, we detail the methodology, in both mice and rats, for delivery of NSCs through the common carotid artery (mouse) or external carotid artery (rat) to the ipsilateral hemisphere after an ischemic stroke. Using GFP-labeled NSCs, we illustrate the widespread distribution achieved throughout the rodent ipsilateral hemisphere at 1 d, 1 week and 4 weeks after postischemic delivery, with a higher density in or near the ischemic injury site. In addition to long-term survival, we show evidence of differentiation of GFP-labeled cells at 4 weeks. The intra-arterial delivery approach described here for NSCs can also be used for administration of therapeutic compounds, and thus has broad applicability to varied CNS injury and disease models across multiple species.

A method for delivering neural stem cells, adaptable for injecting solutions or suspensions, through the common carotid artery (mouse) or external carotid artery (rat) after ischemic stroke is reported. Injected cells are distributed broadly throughout the brain parenchyma and can be detected up to 30 d after delivery.

Neural stem cell (NSC) therapy is an emerging innovative treatment for stroke, traumatic brain injury and neurodegenerative disorders. As compared to ...