This work was supported by&#160;The New Frontiers in Research Fund (NFRFE201901326), the Canadian Institutes of Health Research (162211, 461274, 461275), the Canadian Foundation for Innovation (37439), Canada Research Chair program (950-231859), Natural Sciences and Engineering Research Council of Canada (RGPIN-2019-06824), and the Fonds de Recherche du Qu&#233;bec Nature et technologies (253380).

The Institutional Animal Care and Use Committees of Universit&#233; de Montr&#233;al (#22053, #22054) approved all animal procedures. See Table 1 for a list of solutions and their composition and the Table of Materials for a list of materials, equipment, and reagents used in this protocol.
1. NK cell isolation, culture, and stimulation
<ol>
	<li>Generate nociceptor neuron intact (littermate control; TRPV1wt::DTAfl/wt) and ablated (TRPV1cre::DTAfl/wt) mice by crossing lox-stop-lox-diphtheria toxin mice (DTAfl/fl) with TRPV1cre/wt mice.</li>
	<li>Using CO2 inhalation, euthanize a na&#239;ve littermate control (TRPV1wt::DTAfl/wt) mouse.</li>
	<li>Collect the spleen in a 1.5 mL microcentrifuge tube containing 500 &#181;L of sterile phosphate-buffered saline (PBS).</li>
	<li>Homogenize the spleen using a pestle.</li>
	<li>Dilute the cells with 1 mL of sterile PBS.</li>
	<li>Filter the mixture through a 50 &#181;m cell strainer into a 15 mL conical tube.</li>
	<li>Top up the volume (10 mL) with sterile PBS.</li>
	<li>Collect 10 &#181;L and count the cells using a hemocytometer.</li>
	<li>Centrifuge the cells (500 &#215; g, 5 min) and remove the supernatant.</li>
	<li>Resuspend the cells at a concentration of 108 cells/mL in supplemented RPMI 1640 medium.</li>
	<li>Follow the manufacturer&#39;s instructions to magnetically purify spleen NK cells using a mouse NK cell isolation kit. Confirm NK cell purity using flow cytometry11.</li>
	<li>Collect 10 &#181;L and count the cells using a hemocytometer.</li>
	<li>Centrifuge the cells (500 &#215; g, 5 min) and remove the supernatant.</li>
	<li>Resuspend the NK cells in supplemented RPMI 1640 culture medium (containing IL-2 and IL-15).</li>
	<li>Culture 2 &#215; 106 NK cells/mL in a 96-well U-bottom plate for 48 h.</li>
</ol>
2. DRG neuron isolation and culture
<ol>
	<li>At 24 h prior to the end of the NK cell stimulation (step 1.15), coat a 96-well plate with 100 &#181;L/well of laminin (1 ng/mL) and incubate for 45 min (37 &#176;C).</li>
	<li>After incubation, remove the solution and allow the wells to air-dry in a&#160;biosafety cabinet.</li>
	<li>Using CO2 inhalation, euthanize nociceptor neuron intact (littermate control; TRPV1wt::DTAfl/wt) or ablated (TRPV1cre::DTAfl/wt) mice. 
	NOTE: CO2 inhalation is preferred to cervical dislocation as it avoids disrupting the spinal nerves connected to the DRG.</li>
	<li>Secure the mouse on the board in a prone position, lift the skin, and incise the skin along the dorsal column. Refer to Perner et al. for a detailed video12.</li>
	<li>Cut off the lumbosacral joint and separate the sacrum from the lumbar spine with scissors.</li>
	<li>Separate the spine by cutting the muscles and ribs on both sides of the spine in the cranial direction until the base of the skull is reached.</li>
	<li>Using scissors, cut off the spine at the atlanto-occipital joint.</li>
	<li>Remove muscle and fatty tissue from the spine.</li>
	<li>Pin and open the vertebral column to remove the spinal cord and gain access to the DRG. Look for the DRG in the intervertebral foramina connected to the spinal cord through the dorsal root but separated from the meninges.</li>
	<li>Harvest the DRGs into a 15 mL conical tube filled with 10 mL of ice-cold supplemented DMEM.</li>
	<li>Centrifuge the preparation (200 &#215; g, 5 min, room temperature) and remove the supernatant.</li>
	<li>Add 250 &#181;L of PBS containing Collagenase IV (1 mg/mL) and Dispase II (2.4 U/mL).</li>
	<li>Incubate the DRG with Collagenase IV/Dispase II (C/D) solution (80 min, 37 &#176;C, mild agitation). When pooling ganglia from several mice, maintain a ratio of 125 &#181;L of C/D solution per ganglion.</li>
	<li>To inactivate the enzymes, add 5 mL of supplemented DMEM medium.</li>
	<li>Centrifuge the solution (200 &#215; g, 5 min) and gently remove the supernatant using a pipette.</li>
	<li>To avoid unwanted cell loss, leave ~100 &#181;L of the supernatant.</li>
	<li>Add 1 mL of supplemented DMEM medium.</li>
	<li>Using a pipette gun and three glass Pasteur pipettes of decreasing sizes, gently triturate (~10 up/down per Pasteur pipette size) the DRG into a single-cell preparation.</li>
	<li>In a biosafety cabinet, dilute bovine serum albumin (BSA) in sterile PBS to a final concentration of 15%. Store 1 mL aliquots at &#8722;20 &#176;C.</li>
	<li>Create a BSA gradient in a 15 mL conical tube by adding 2 mL of sterile PBS and slowly dispensing 1 mL of 15% BSA solution at the bottom of the tube. Avoid disrupting the gradient by gently removing the pipette.</li>
	<li>Using a P200 pipette, slowly pipette the triturated ganglia suspension (which contains the neurons) onto the side of the tube into the gradient.</li>
	<li>Centrifuge the neuron-containing BSA gradient (200 &#215; g, 12 min, room temperature). Set the acceleration and deceleration of the centrifuge to the minimum speed. 
	NOTE: After centrifugation, the neurons will be at the bottom of the tube while the cell debris will be trapped in the BSA gradient.</li>
	<li>Gently remove all of the supernatant using a pipette.</li>
	<li>Resuspend the cells in 500 &#181;L of Neurobasal.</li>
	<li>Plate 104 neurons per well (200 &#181;L of neurobasal/well) in a laminin-coated, flat-bottom 96-well plate. 
	NOTE: On average, an investigator will be able to fill ~8 wells per mouse.</li>
	<li>Culture the neurons (37 &#176;C, overnight) to allow attachment.</li>
</ol>
3. Co-culture and flow cytometry
<ol>
	<li>Slowly remove the neurobasal from the neuron culture.</li>
	<li>After 48 h stimulation with IL-2 and IL-15 (see steps 1.14-1.15), resuspend the NK cells and add 105 NK cells/well to the neuron culture (96-well flat bottom plate). 
	NOTE: On average, the investigator will be able to fill ~6 wells per mouse.</li>
	<li>Co-culture the cells in supplemented neurobasal MX (37 &#176;C, 48 h).</li>
	<li>Collect the cells, wash with PBS (3x), and centrifuge (500 &#215; g, 5 min, 4 &#176;C).</li>
	<li>Discard the supernatant and stain the cells with Viability Dye eFlour-780 (1:1,000, 15 min, 4 &#176;C).</li>
	<li>Collect the cells, wash with PBS (3x), and centrifuge (500 &#215; g, 5 min, 4 &#176;C).</li>
	<li>Block nonspecific sites on the cells with CD16/32 (1:100, 15 min, 4 &#176;C).</li>
	<li>Collect the cells, wash with PBS (3x), and centrifuge (500 &#215; g, 5 min, 4 &#176;C).</li>
	<li>Stain (15 min, 4 &#176;C) the cells with BV421 anti-NK-1.1 (1:100), fluorescein isothiocyanate (FITC) anti-NKp46 (1:100), and phycoerythrin (PE) anti-GM-CSF (1:100).</li>
	<li>Collect the cells, wash with PBS (3x), and centrifuge (500 &#215; g, 5 min, 4 &#176;C).</li>
	<li>Discard the supernatant, resuspend the cells in FACS buffer (500 &#181;L) and immunophenotype the NK cells by flow cytometry11. See Figure 1A for the gating strategy.</li>
</ol>

<ol>
	<li>Berta, T., Qadri, Y., Tan, P. H., Ji, R. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Targeting+dorsal+root+ganglia+and+primary+sensory+neurons+for+the+treatment+of+chronic+pain.">Targeting dorsal root ganglia and primary sensory neurons for the treatment of chronic pain.</a> Expert Opinion on Therapeutic Targets. 21 (7), 695-703 (2017).</li><li>Baral, 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=Nociceptor+sensory+neurons+suppress+neutrophil+and+gammadelta+T+cell+responses+in+bacterial+lung+infections+and+lethal+pneumonia.">Nociceptor sensory neurons suppress neutrophil and gammadelta T cell responses in bacterial lung infections and lethal pneumonia.</a> Nature Medicine. 24, 417-426 (2018).</li><li>Binshtok, A. 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=Nociceptors+are+interleukin-1beta+sensors.">Nociceptors are interleukin-1beta sensors.</a> Journal of Neuroscience. 28 (52), 14062-14073 (2008).</li><li>Chesne, J., Cardoso, V., Veiga-Fernandes, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuro-immune+regulation+of+mucosal+physiology.">Neuro-immune regulation of mucosal physiology.</a> Mucosal Immunology. 12 (1), 10-20 (2019).</li><li>Samad, T. 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=Interleukin-1beta-mediated+induction+of+Cox-2+in+the+CNS+contributes+to+inflammatory+pain+hypersensitivity.">Interleukin-1beta-mediated induction of Cox-2 in the CNS contributes to inflammatory pain hypersensitivity.</a> Nature. 410 (6827), 471-475 (2001).</li><li>Godinho-Silva, C., 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=Light-entrained+and+brain-tuned+circadian+circuits+regulate+ILC3s+and+gut+homeostasis.">Light-entrained and brain-tuned circadian circuits regulate ILC3s and gut homeostasis.</a> Nature. 574, 254-258 (2019).</li><li>Talbot, J., 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=Feeding-dependent+VIP+neuron-ILC3+circuit+regulates+the+intestinal+barrier.">Feeding-dependent VIP neuron-ILC3 circuit regulates the intestinal barrier.</a> Nature. 579, 575-580 (2020).</li><li>Raulet, D. H., Gasser, S., Gowen, B. G., Deng, W., Jung, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulation+of+ligands+for+the+NKG2D+activating+receptor.">Regulation of ligands for the NKG2D activating receptor.</a> Annual Review of Immunology. 31, 413-441 (2013).</li><li>Vivier, 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=Innate+or+adaptive+immunity?+The+example+of+natural+killer+cells.">Innate or adaptive immunity? The example of natural killer cells.</a> Science. 331, 44-49 (2011).</li><li>Davies, A. J., 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=Natural+Killer+Cells+Degenerate+Intact+Sensory+Afferents+following+Nerve+Injury.">Natural Killer Cells Degenerate Intact Sensory Afferents following Nerve Injury.</a> Cell. 176, 716-728 (2019).</li><li>Perner, C., Sokol, C. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protocol+for+dissection+and+culture+of+murine+dorsal+root+ganglia+neurons+to+study+neuropeptide+release.">Protocol for dissection and culture of murine dorsal root ganglia neurons to study neuropeptide release.</a> STAR Protocols. 2, 100333 (2021).</li><li>Goswami, S. C., 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=Molecular+signatures+of+mouse+TRPV1-lineage+neurons+revealed+by+RNA-Seq+transcriptome+analysis.">Molecular signatures of mouse TRPV1-lineage neurons revealed by RNA-Seq transcriptome analysis.</a> Journal of Pain. 15, 1338-1359 (2014).</li><li>Mishra, S. K., Tisel, S. M., Orestes, P., Bhangoo, S. K., Hoon, M. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=TRPV1-lineage+neurons+are+required+for+thermal+sensation.">TRPV1-lineage neurons are required for thermal sensation.</a> EMBO J. 30, 582-593 (2011).</li><li>Kim, H. 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=Attenuation+of+natural+killer+cell+functions+by+capsaicin+through+a+direct+and+TRPV1-independent+mechanism.">Attenuation of natural killer cell functions by capsaicin through a direct and TRPV1-independent mechanism.</a> Carcinogenesis. 35, 1652-1660 (2014).</li></ol>

The authors have no conflicts of interest to disclose.

Davies et al.11 found that injured neurons upregulate RAE1. Via cell-cell contact, NKG2D-expressing NK cells were then able to identify and eliminate RAE1+ neurons, which in turn limit chronic pain11. Given that NK cells also express various neuropeptide receptors, and that those neuropeptides are known for their immunomodulatory capabilities, it appears increasingly important to study the interaction between NK cells and nociceptor neurons in vitro<...

The cell bodies of sensory neurons originate in the dorsal root ganglia (DRG). The DRG are located in the peripheral nervous system (PNS), between the dorsal horn of the spinal cord and the peripheral nerve terminals. The pseudo-unipolar nature of DRG neurons allows the transfer of information from the peripheral branch, which innervates the target tissue, to the central branch, which carries the somatosensory information to the spinal cord1. Using specialized ion channel receptors, first-order neurons sense threats posed by pathogens, allergens, and pollutants2, leading to the influx of cations (Na+, Ca2+) and the generation of an action potential3,4,5.
These neurons also send antidromic action potential toward the periphery, where the initial danger sensing had occurred, which leads to the local release of neuropeptides1,4. Therefore, the nociceptor neurons serve as a protective mechanism, alerting the host to environmental danger4,5,6,7.&#160;
To communicate with second-order neurons, the nociceptors release various neurotransmitters (e.g., glutamate) and neuropeptides (e.g., calcitonin gene-related peptide (CGRP), substance P (SP), and vasoactive intestinal peptide (VIP))6,7.These peptides act on capillaries and promote plasma extravasation, edema, and the local influx and modulation of immune cells2,4,7.
The somatosensory and immune systems utilize a shared communication system composed of cytokines and neuropeptides, and their respective cognate receptors4. While this bidirectional communication helps protect from danger and preserve homeostasis, it can also contribute to disease pathophysiology4.&#160;
NK cells are classified as innate lymphoid cells and are specialized to eliminate virally infected cells. NK cell function is governed by a balance of stimulatory and inhibitory receptors, including the activating receptor NKG2D8. The endogenous ligand of NKG2D, retinoic acid early inducible1 (RAE1), is expressed by cells undergoing stress such as tumorigenesis and infection8,9.
Recent investigations have shown that peripheral nerve injury drives sensory neurons to express maladaptive molecules such as stathmin 2 (STMN2) and RAE1. Thus, via cell-cell contact, NKG2D-expressing NK cells were activated by interaction with RAE1-expressing neurons. In turn, NK cells were able to eliminate injured nociceptor neurons and blunt pain hypersensitivity normally associated with nerve injury10. In addition to the NKG2D-RAE1 axis, NK cells express the cognate receptors for various nociceptor-produced mediators. It is therefore possible that these mediators modulate NK cell activity. This paper presents a co-culture method to investigate the biology of the nociceptor neuron-NK cell interaction. This approach will help advance the understanding of how nociceptor neurons modulate innate immune cell responses to injury, infection, or malignancy.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Anti-mouse CD16/32</td>
			<td>Jackson Laboratory</td>
			<td>Cat no: 017769</td>
			<td></td>
		</tr>
		<tr>
			<td>B-27</td>
			<td>Jackson Laboratory</td>
			<td>Cat no: 009669</td>
			<td></td>
		</tr>
		<tr>
			<td>Bovine Serum Albumin (BSA) culture grade</td>
			<td>World Precision Instruments</td>
			<td>Cat no: 504167</td>
			<td></td>
		</tr>
		<tr>
			<td>BV421 anti-mouse NK-1.1</td>
			<td>Fisher Scientific</td>
			<td>Cat no: 12430112</td>
			<td></td>
		</tr>
		<tr>
			<td>Cell strainer (50 &#956;m)</td>
			<td>Fisher Scientific</td>
			<td>Cat no: A3160702</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagenase IV</td>
			<td>Fisher Scientific</td>
			<td>Cat no: 15140148</td>
			<td></td>
		</tr>
		<tr>
			<td>Diphteria toxinfl/fl</td>
			<td>Fisher Scientific</td>
			<td>Cat no: SH3057402</td>
			<td></td>
		</tr>
		<tr>
			<td>Dispase II</td>
			<td>Fisher Scientific</td>
			<td>Cat no: 13-678-20B</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle Medium (DMEM)</td>
			<td>Fisher Scientific</td>
			<td>Cat no: 07-200-95</td>
			<td></td>
		</tr>
		<tr>
			<td>EasySep Mouse NK Cell Isolation Kit</td>
			<td>Sigma</td>
			<td>Cat no: CLS2595</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethylenediaminetetraacetic acid (EDTA)</td>
			<td>Sigma</td>
			<td>Cat no: C0130</td>
			<td></td>
		</tr>
		<tr>
			<td>FACSAria III</td>
			<td>Sigma</td>
			<td>Cat no: 04942078001</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum (FBS)</td>
			<td>Sigma</td>
			<td>Cat no: 806552</td>
			<td></td>
		</tr>
		<tr>
			<td>FITC anti-mouse NKp46</td>
			<td>Sigma</td>
			<td>Cat no: L2020</td>
			<td></td>
		</tr>
		<tr>
			<td>Flat bottom 96-well plate</td>
			<td>Sigma</td>
			<td>Cat no: 03690</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass Pasteur pipette</td>
			<td>Sigma</td>
			<td>Cat no: 470236-274</td>
			<td></td>
		</tr>
		<tr>
			<td>Glial cell line-derived neurotrophic factor (GDNF)</td>
			<td>VWR</td>
			<td>Cat no: 02-0131</td>
			<td></td>
		</tr>
		<tr>
			<td>Laminin</td>
			<td>Cedarlane</td>
			<td>Cat no: 03-50/31</td>
			<td></td>
		</tr>
		<tr>
			<td>L-Glutamine</td>
			<td>Gibco</td>
			<td>Cat no: A14867-01</td>
			<td></td>
		</tr>
		<tr>
			<td>Mouse recombinant IL-15</td>
			<td>Gibco</td>
			<td>Cat no: 22400-089</td>
			<td></td>
		</tr>
		<tr>
			<td>Mouse recombinant IL-2</td>
			<td>Gibco</td>
			<td>Cat no: 21103-049</td>
			<td></td>
		</tr>
		<tr>
			<td>Nerve Growth Factor (NGF)</td>
			<td>Life Technologies</td>
			<td>Cat no: 13257-019</td>
			<td></td>
		</tr>
		<tr>
			<td>Neurobasal media</td>
			<td>PeproTech</td>
			<td>Cat no: 450-51-10</td>
			<td></td>
		</tr>
		<tr>
			<td>PE anti-mouse GM-CSF</td>
			<td>PeproTech</td>
			<td>Cat no: 212-12</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin and Streptomycin</td>
			<td>PeproTech</td>
			<td>Cat no: 210-15</td>
			<td></td>
		</tr>
		<tr>
			<td>Pestles</td>
			<td>Stem Cell Technology</td>
			<td>Cat no: 19855</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate Buffered Saline (PBS)</td>
			<td>Biolegend</td>
			<td>Cat no: 108732</td>
			<td>Clone PK136</td>
		</tr>
		<tr>
			<td>RPMI 1640 media</td>
			<td>Biolegend</td>
			<td>Cat no: 137606</td>
			<td>Clone 29A1.4</td>
		</tr>
		<tr>
			<td>TRPV1Cre</td>
			<td>Biolegend</td>
			<td>Cat no: 505406</td>
			<td>Clone MP1-22E9</td>
		</tr>
		<tr>
			<td>Tweezers and dissection tools.</td>
			<td>Biolegend</td>
			<td>Cat no: 65-0865-14</td>
			<td></td>
		</tr>
		<tr>
			<td>U-Shaped-bottom 96-well plate</td>
			<td>Biolegend</td>
			<td>Cat no: 101319</td>
			<td></td>
		</tr>
		<tr>
			<td>Viability Dye eFlour-780</td>
			<td>Becton Dickinson</td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

teasing out the interplay between natural killer cells and nociceptor neurons

Somatosensory neurons have evolved to detect noxious stimuli and activate defensive reflexes. By sharing means of communication, nociceptor neurons also tune host defenses by controlling the activity of the immune system. The communication between these systems is mostly adaptive, helping to protect homeostasis, it can also lead to, or promote, the onset of chronic diseases. Both systems co-evolved to allow for such local interaction, as found in primary and secondary lymphoid tissues and mucosa. Recent studies have demonstrated that nociceptors directly detect and respond to foreign antigens, immune cell-derived cytokines, and microbes.
Nociceptor activation not only results in pain hypersensitivity and itching, but lowers the nociceptor firing threshold, leading to the local release of neuropeptides. The peptides that are produced by, and released from, the peripheral terminals of nociceptors can block the chemotaxis and polarization of lymphocytes, controlling the localization, duration, and type of inflammation. Recent evidence shows that sensory neurons interact with innate immune cells via cell-cell contact, for example, engaging group 2D (NKG2D) receptors on natural killer (NK) cells.
Given that NK cells express the cognate receptors for various nociceptor-produced mediators, it is conceivable that nociceptors use neuropeptides to control the activity of NK cells. Here, we devise a co-culture method to study nociceptor neuron-NK cell interactions in a dish. Using this approach, we found that lumbar nociceptor neurons decrease NK cell cytokine expression. Overall, such a reductionist method could be useful to study how tumor-innervating neurons control the anticancer function of NK cells and how NK cells control the elimination of injured neurons.

NK cells were magnetically purified from littermate control (TRPV1wt::DTAfl/wt) mice splenocytes and stimulated (48 h) with IL-2 and IL-15. The NK cells were then cultured alone or co-cultured with DRG neurons harvested from nociceptor neuron intact (littermate control; TRPV1wt::DTAfl/wt) or ablated (TRPV1cre::DTAfl/wt) mice. The cells were then exposed to the TRPV1 agonist capsaicin (1 &#181;M) or its vehicle. After 24 h of co-culture, the NK cells were F...

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Teasing Out the Interplay Between Natural Killer Cells and Nociceptor Neurons

Nociceptor neurons and NK cells actively interact in an inflammatory context. A co-culture approach enables studying this interplay.

Somatosensory neurons have evolved to detect noxious stimuli and activate defensive reflexes. By sharing means of communication, nociceptor neurons also ...

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2.0K Views.  Université de Montréal. Nociceptor neurons and NK cells actively interact in an inflammatory context. A co-culture approach enables studying this interplay.

Video: Teasing Out the Interplay Between Natural Killer Cells and Nociceptor Neurons

Neuromodulation and Mitochondrial Transport: Live Imaging in Hippocampal Neurons over Long Durations

To understand the relationship between mitochondrial transport and neuronal function, it is critical to observe mitochondrial behavior in live cultured neurons for extended durations1-3. This is now possible through the use of vital dyes and fluorescent proteins with which cytoskeletal components, organelles, and other structures in living cells can be labeled and then visualized via dynamic fluorescence microscopy. For example, in embryonic chicken sympathetic neurons, mitochondrial movement was characterized using the vital dye rhodamine 1234. In another study, mitochondria were visualized in rat forebrain neurons by transfection of mitochondrially targeted eYFP5. However, imaging of primary neurons over minutes, hours, or even days presents a number of issues. Foremost among these are: 1) maintenance of culture conditions such as temperature, humidity, and pH during long imaging sessions; 2) a strong, stable fluorescent signal to assure both the quality of acquired images and accurate measurement of signal intensity during image analysis; and 3) limiting exposure times during image acquisition to minimize photobleaching and avoid phototoxicity.
Here, we describe a protocol that permits the observation, visualization, and analysis of mitochondrial movement in cultured hippocampal neurons with high temporal resolution and under optimal life support conditions. We have constructed an affordable stage-top incubator that provides good temperature regulation and atmospheric gas flow, and also limits the degree of media evaporation, assuring stable pH and osmolarity. This incubator is connected, via inlet and outlet hoses, to a standard tissue culture incubator, which provides constant humidity levels and an atmosphere of 5-10% CO2/air. This design offers a cost-effective alternative to significantly more expensive microscope incubators that don't necessarily assure the viability of cells over many hours or even days. To visualize mitochondria, we infect cells with a lentivirus encoding a red fluorescent protein that is targeted to the mitochondrion. This assures a strong and persistent signal, which, in conjunction with the use of a stable xenon light source, allows us to limit exposure times during image acquisition and all but precludes photobleaching and phototoxicity. Two injection ports on the top of the stage-top incubator allow the acute administration of neurotransmitters and other reagents intended to modulate mitochondrial movement. In sum, lentivirus-mediated expression of an organelle-targeted red fluorescent protein and the combination of our stage-top incubator, a conventional inverted fluorescence microscope, CCD camera, and xenon light source allow us to acquire time-lapse images of mitochondrial transport in living neurons over longer durations than those possible in studies deploying conventional vital dyes and off-the-shelf life support systems.

We describe a protocol that allows imaging of mitochondria in living neurons via fluorescence microscopy over long durations. Imaging over extended periods is accomplished through lentivirus-mediated expression of a mitochondrially targeted fluorescent protein and use of an inexpensive stage-top incubator that was designed and built in our laboratory.

To understand the relationship between mitochondrial transport and neuronal function, it is critical to observe mitochondrial behavior in live cultured ...

Live-cell Imaging of Sensory Organ Precursor Cells in Intact Drosophila Pupae

Since the discovery of Green Fluorescent Protein (GFP), there has been a revolutionary change in the use of live-cell imaging as a tool for understanding fundamental biological mechanisms. Striking progress has been particularly evident in Drosophila, whose extensive toolkit of mutants and transgenic lines provides a convenient model to study evolutionarily-conserved developmental and cell biological mechanisms. We are interested in understanding the mechanisms that control cell fate specification in the adult peripheral nervous system (PNS) in Drosophila. Bristles that cover the head, thorax, abdomen, legs and wings of the adult fly are individual mechanosensory organs, and have been studied as a model system for understanding mechanisms of Notch-dependent cell fate decisions. Sensory organ precursor (SOP) cells of the microchaetes (or small bristles), are distributed throughout the epithelium of the pupal thorax, and are specified during the first 12 hours after the onset of pupariation. After specification, the SOP cells begin to divide, segregating the cell fate determinant Numb to one daughter cell during mitosis. Numb functions as a cell-autonomous inhibitor of the Notch signaling pathway.
Here, we show a method to follow protein dynamics in SOP cell and its progeny within the intact pupal thorax using a combination of tissue-specific Gal4 drivers and GFP-tagged fusion proteins 1,2.This technique has the advantage over fixed tissue or cultured explants because it allows us to follow the entire development of an organ from specification of the neural precursor to growth and terminal differentiation of the organ. We can therefore directly correlate changes in cell behavior to changes in terminal differentiation. Moreover, we can combine the live imaging technique with mosaic analysis with a repressible cell marker (MARCM) system to assess the dynamics of tagged proteins in mitotic SOPs under mutant or wildtype conditions. Using this technique, we and others have revealed novel insights into regulation of asymmetric cell division and the control of Notch signaling activation in SOP cells (examples include references 1-6,7 ,8).

Live-cell Imaging of Sensory Organ Precursor Cells in Intact Drosophila Pupae

In this video, we describe a method for live cell imaging of asymmetrically dividing sensory organ progenitor cells and epidermal cells in intact Drosophila pupae

Since the discovery of Green Fluorescent Protein (GFP), there has been a revolutionary change in the use of live-cell imaging as a tool for understanding ...

Cut-loading: A Useful Tool for Examining the Extent of Gap Junction Tracer Coupling Between Retinal Neurons

In addition to chemical synaptic transmission, neurons that are connected by gap junctions can also communicate rapidly via electrical synaptic transmission. Increasing evidence indicates that gap junctions not only permit electrical current flow and synchronous activity between interconnected or coupled cells, but that the strength or effectiveness of electrical communication between coupled cells can be modulated to a great extent1,2. In addition, the large internal diameter (~1.2 nm) of many gap junction channels permits not only electric current flow, but also the diffusion of intracellular signaling molecules and small metabolites between interconnected cells, so that gap junctions may also mediate metabolic and chemical communication. The strength of gap junctional communication between neurons and its modulation by neurotransmitters and other factors can be studied by simultaneously electrically recording from coupled cells and by determining the extent of diffusion of tracer molecules, which are gap junction permeable, but not membrane permeable, following iontophoretic injection into single cells. However, these procedures can be extremely difficult to perform on neurons with small somata in intact neural tissue.
Numerous studies on electrical synapses and the modulation of electrical communication have been conducted in the vertebrate retina, since each of the five retinal neuron types is electrically connected by gap junctions3,4. Increasing evidence has shown that the circadian (24-hour) clock in the retina and changes in light stimulation regulate gap junction coupling3-8. For example, recent work has demonstrated that the retinal circadian clock decreases gap junction coupling between rod and cone photoreceptor cells during the day by increasing dopamine D2 receptor activation, and dramatically increases rod-cone coupling at night by reducing D2 receptor activation7,8. However, not only are these studies extremely difficult to perform on neurons with small somata in intact neural retinal tissue, but it can be difficult to adequately control the illumination conditions during the electrophysiological study of single retinal neurons to avoid light-induced changes in gap junction conductance.
Here, we present a straightforward method of determining the extent of gap junction tracer coupling between retinal neurons under different illumination conditions and at different times of the day and night. This cut-loading technique is a modification of scrape loading9-12, which is based on dye loading and diffusion through open gap junction channels. Scrape loading works well in cultured cells, but not in thick slices such as intact retinas. The cut-loading technique has been used to study photoreceptor coupling in intact fish and mammalian retinas7, 8,13, and can be used to study coupling between other retinal neurons, as described here.

An easy and convenient method to determine the extent of gap junction tracer coupling between retinal neurons is described. This technique enables one to investigate the function of the electrical synapses between neurons in the intact retina under different illumination conditions and at different times of the day and night.

In addition to chemical synaptic transmission, neurons that are connected by gap junctions can also communicate rapidly via electrical synaptic ...

Patch Clamp Recordings in Inner Ear Hair Cells Isolated from Zebrafish

Patch clamp analyses of the voltage-gated channels in sensory hair cells isolated from a variety of species have been described previously1-4 but this video represents the first application of those techniques to hair cells from zebrafish. Here we demonstrate a method to isolate healthy, intact hair cells from all of the inner ear end-organs: saccule, lagena, utricle and semicircular canals. Further, we demonstrate the diversity in hair cell size and morphology and give an example of the kinds of patch clamp recordings that can be obtained. The advantage of the use of this zebrafish model system over others stems from the availability of zebrafish mutants that affect both hearing and balance. In combination with the use of transgenic lines and other techniques that utilize genetic analysis and manipulation, the cell isolation and electrophysiological methods introduced here should facilitate greater insight into the roles hair cells play in mediating these sensory modalities.

The purpose of this video is to demonstrate procedures for obtaining healthy, intact hair cells from the inner ear organs of adult zebrafish and then using them for patch clamp studies aimed at characterizing the biophysical properties of their voltage-gated channels.

Patch  clamp analyses of the voltage-gated channels in sensory hair cells isolated  from a variety of species have been described previously1-4 but this  ...

The Specification of Telencephalic Glutamatergic Neurons from Human Pluripotent Stem Cells

Here, a stepwise procedure for efficiently generating telencephalic glutamatergic neurons from human pluripotent stem cells (PSCs) has been described. The differentiation process is initiated by breaking the human PSCs into clumps which round up to form aggregates when the cells are placed in a suspension culture. The aggregates are then grown in hESC medium from days 1-4 to allow for spontaneous differentiation. During this time, the cells have the capacity to become any of the three germ layers. From days 5-8, the cells are placed in a neural induction medium to push them into the neural lineage. Around day 8, the cells are allowed to attach onto 6 well plates and differentiate during which time the neuroepithelial cells form. These neuroepithelial cells can be isolated at day 17. The cells can then be kept as neurospheres until they are ready to be plated onto coverslips. Using a basic medium without any caudalizing factors, neuroepithelial cells are specified into telencephalic precursors, which can then be further differentiated into dorsal telencephalic progenitors and glutamatergic neurons efficiently. Overall, our system provides a tool to generate human glutamatergic neurons for researchers to study the development of these neurons and the diseases which affect them.

This procedure yields telencephalic neurons by going through checkpoints which are similar to those observed during human development. The cells are allowed to spontaneously differentiate, are exposed to factors which push them towards the neural lineage, are isolated, and are plated onto coverslips to allow for terminal differentiation and maturation.

Here, a stepwise procedure for efficiently generating telencephalic glutamatergic neurons from human pluripotent stem cells (PSCs) has been described. The ...

Lineage-reprogramming of Pericyte-derived Cells of the Adult Human Brain into Induced Neurons

Direct lineage-reprogramming of non-neuronal cells into induced neurons (iNs) may provide insights into the molecular mechanisms underlying neurogenesis and enable new strategies for in vitro modeling or repairing the diseased brain. Identifying brain-resident non-neuronal cell types amenable to direct conversion into iNs might allow for launching such an approach in situ, i.e. within the damaged brain tissue. Here we describe a protocol developed in the attempt of identifying cells derived from the adult human brain that fulfill this premise. This protocol involves: (1) the culturing of human cells from the cerebral cortex obtained from adult human brain biopsies; (2) the in vitro expansion (approximately requiring 2-4 weeks) and characterization of the culture by immunocytochemistry and flow cytometry; (3) the enrichment by fluorescence-activated cell sorting (FACS) using anti-PDGF receptor-&#946; and anti-CD146 antibodies; (4) the retrovirus-mediated transduction with the neurogenic transcription factors sox2 and ascl1; (5) and finally the characterization of the resultant pericyte-derived induced neurons (PdiNs) by immunocytochemistry (14 days to 8 weeks following retroviral transduction). At this stage, iNs can be probed for their electrical properties by patch-clamp recording. This protocol provides a highly reproducible procedure for the in vitro lineage conversion of brain-resident pericytes into functional human iNs.

Targeting brain-resident cells for direct lineage-reprogramming offers new perspectives for brain repair. Here we describe a protocol of how to prepare cultures enriched for brain-resident pericytes from the adult human cerebral cortex and convert these into induced neurons by retrovirus-mediated expression of the transcription factors Sox2 and Ascl1.

Direct lineage-reprogramming of non-neuronal cells into induced neurons (iNs) may provide insights into the molecular mechanisms underlying neurogenesis ...

An Engulfment Assay: A Protocol to Assess Interactions Between CNS Phagocytes and Neurons

Phagocytosis is a process in which a cell engulfs material (entire cell, parts of a cell, debris, etc.) in its surrounding extracellular environment and subsequently digests this material, commonly through lysosomal degradation. Microglia are the resident immune cells of the central nervous system (CNS) whose phagocytic function has been described in a broad range of conditions from neurodegenerative disease (e.g., beta-amyloid clearance in Alzheimer&#8217;s disease) to development of the healthy brain (e.g., synaptic pruning)1-6. The following protocol is an engulfment assay developed to visualize and quantify microglia-mediated engulfment of presynaptic inputs in the developing mouse retinogeniculate system7. While this assay was used to assess microglia function in this particular context, a similar approach may be used to assess other phagocytes throughout the brain (e.g., astrocytes) and the rest of the body (e.g., peripheral macrophages) as well as other contexts in which synaptic remodeling occurs (e.g. ,brain injury/disease).

Microglia are the resident immune cells of the central nervous system (CNS) with a high capacity to phagocytose or engulf material in their extracellular environment. Here, a broadly applicable, reliable, and highly quantitative assay for visualizing and measuring microglia-mediated engulfment of synaptic components is described.

Phagocytosis is a process in which a cell engulfs material (entire cell, parts of a cell, debris, etc.) in its surrounding extracellular environment and ...

Isolation and Culture of Dissociated Sensory Neurons From Chick Embryos

Neurons are multifaceted cells that carry information essential for a variety of functions including sensation, motor movement, learning, and memory. Studying neurons in vivo can be challenging due to their complexity, their varied and dynamic environments, and technical limitations. For these reasons, studying neurons in vitro can prove beneficial to unravel the complex mysteries of neurons. The well-defined nature of cell culture models provides detailed control over environmental conditions and variables. Here we describe how to isolate, dissociate, and culture primary neurons from chick embryos. This technique is rapid, inexpensive, and generates robustly growing sensory neurons. The procedure consistently produces cultures that are highly enriched for neurons and has very few non-neuronal cells (less than 5%). Primary neurons do not adhere well to untreated glass or tissue culture plastic, therefore detailed procedures to create two distinct, well-defined laminin-containing substrata for neuronal plating are described. Cultured neurons are highly amenable to multiple cellular and molecular techniques, including co-immunoprecipitation, live cell imagining, RNAi, and immunocytochemistry. Procedures for double immunocytochemistry on these cultured neurons have been optimized and described here.

Cell culture models provide detailed control over environmental conditions and thus provide a powerful platform to elucidate numerous aspects of neuronal cell biology. We describe a rapid, inexpensive, and reliable method to isolate, dissociate, and culture sensory neurons from chick embryos. Details of substrata preparation and immunocytochemistry are also provided.

Neurons are multifaceted cells that carry information essential for a variety of functions including sensation, motor movement, learning, and memory. ...

Dorsal Root Ganglia Neurons and Differentiated Adipose-derived Stem Cells: An In Vitro Co-culture Model to Study Peripheral Nerve Regeneration

Dorsal root ganglia (DRG) neurons, located in the intervertebral foramina of the spinal column, can be used to create an in vitro system facilitating the study of nerve regeneration and myelination. The glial cells of the peripheral nervous system, Schwann cells (SC), are key facilitators of these processes; it is therefore crucial that the interactions of these cellular components are studied together. Direct contact between DRG neurons and glial cells provides additional stimuli sensed by specific membrane receptors, further improving the neuronal response. SC release growth factors and proteins in the culture medium, which enhance neuron survival and stimulate neurite sprouting and extension. However, SC require long proliferation time to be used for tissue engineering applications and the sacrifice of an healthy nerve for their sourcing. Adipose-derived stem cells (ASC) differentiated into SC phenotype are a valid alternative to SC for the set-up of a co-culture model with DRG neurons to study nerve regeneration. The present work presents a detailed and reproducible step-by-step protocol to harvest both DRG neurons and ASC from adult rats; to differentiate ASC towards a SC phenotype; and combines the two cell types in a direct co-culture system to investigate the interplay between neurons and SC in the peripheral nervous system. This tool has great potential in the optimization of tissue-engineered constructs for peripheral nerve repair.

Dorsal Root Ganglia Neurons and Differentiated Adipose-derived Stem Cells: An In Vitro Co-culture Model to Study Peripheral Nerve Regeneration

Dorsal root ganglia (DRG) are structures containing the sensory neurons of the peripheral nervous system. When dissociated, they can be co-cultured with SC-like adipose-derived stem cells (ASC), providing a valuable model to study in vitro nerve regeneration and myelination, mimicking the in vivo environment at the injury site.

Dorsal root ganglia (DRG) neurons, located in the intervertebral foramina of the spinal column, can be used to create an in vitro system facilitating the ...

Visualizing Axonal Growth Cone Collapse and Early Amyloid &#946; Effects in Cultured Mouse Neurons

Amyloid-&#946; (A&#946;) causes memory impairments in Alzheimer's disease (AD). Although therapeutics have been shown to reduce A&#946; levels in the brains of AD patients, these do not improve memory functions. Since A&#946; aggregates in the brain before the appearance of memory impairments, targeting A&#946; may be inefficient for treating AD patients who already exhibit memory deficits. Therefore, downstream signaling due to A&#946; deposition should be blocked before AD development. A&#946; induces axonal degeneration, leading to the disruption of neuronal networks and memory impairments. Although there are many studies on the mechanisms of A&#946; toxicity, the source of A&#946; toxicity remains unknown. To help identify the source, we propose a novel protocol that uses microscopy, gene transfection, and live cell imaging to investigate early changes caused by A&#946; in axonal growth cones of cultured neurons. This protocol revealed that A&#946; induced clathrin-mediated endocytosis in axonal growth cones followed by growth cone collapse, demonstrating that inhibition of endocytosis prevents A&#946; toxicity. This protocol will be useful in studying the early effects of A&#946; and may lead to more efficient and preventative AD treatment.

Visualizing Axonal Growth Cone Collapse and Early Amyloid &amp;#946; Effects in Cultured Mouse Neurons

Here a protocol to investigate the early effects of amyloid-&#946; (A&#946;) in the brain is presented. This shows that A&#946; induces clathrin-mediated endocytosis and collapse of axonal growth cones. The protocol is useful in studying early effects of A&#946; on axonal growth cones and may facilitate prevention of Alzheimer's disease.

Amyloid-&#946; (A&#946;) causes memory impairments in Alzheimer's disease (AD). Although therapeutics have been shown to reduce A&#946; levels in the ...