Our work is supported by the Swiss National Science Foundation (SNF), the Swiss Initiative in Systems Biology (SystemsX.ch), the Muscular Dystrophy Association USA (MDA), the Association Fran&ccedil;aise contre les Myopathies (AFM), the United Mitochondrial Disease Foundation (UMDF), the Gebert-R&uuml;f Foundation Rare Diseases Programme (GRF), the Swiss Society for Research of the Muscle Diseases (SSEM/FSRMM), the Swiss Life "Jubil&auml;umsstiftung f&uuml;r Volksgesundheit und medizinische Forschung", the Roche Research Foundation and the University of Basel.

1. Preparation of the Primary Human Muscle Cell Culture
<ol>
 <li>Establish the human muscle cell cultures according to the explantation-re-explantation technique4. First, remove non-muscle tissue from the biopsies. Then, embed 1 mm3 muscle explants in a coagulum of plasma, which allows fibroblasts to emerge from the explants.</li>
 <li>The embedded explants are transferred onto a plasma-gelatin coated dish and let them grow in normal growth medium (MEM supplemented with 25% medium 199, 10% fetal bovine serum [FBS], 1% penicillin/streptomycin, 10 &mu;g/ml insulin, 10 ng/ml human epidermal growth factor [EGF], 12.5 ng/ml human fibroblast growth factor [FGF]) in a monolayer. The cells that emerge from the explants under those conditions are muscle cells. These cells will continue to grow in a monolayer after removal of the explants.</li>
 <li>Culture the cells aneurally on 0.1% gelatin-coated plates in normal growth medium. The cells can be aneurally cultured and amplified as needed. It is better to use muscle cells at a passage between 3 and 8 to perform the co-cultures. It is critical to innervate young myotubes; after this point, the co-cultures have a high risk of failing. Furthermore, myotubes should not be too large and too thick.</li>
 <li>Two days before the innervation is planned, plate the muscle cells on 35 mm tissue culture dishes (or 6 well plates) at a density of 500,000 cells per dish in normal growth medium. At that density, the cells are at the proper confluency to start the fusion on the following day, and subsequent innervation the day after that. Using those conditions, the myotubes are at the right stage for optimal innervation and hence subsequent fiber contraction.</li>
 <li>On the next day, replace the normal growth medium with a fusion medium composed of MEM supplemented with 25% medium 199, 5% FBS, 10 &mu;g/ml insulin and 1% of penicillin/streptomycin.</li>
</ol>
2. Isolation of the Rat Embryonic Spinal Cord Explants
The whole procedure to isolate the spinal cord explants is performed under a binocular microscope, in Hank's Balanced Salt Solution (HBSS, Gibco/Invitrogen ref 14170) containing 10% Fetal Bovine Serum (FBS).
<ol>
 <li>It is crucial that the rat embryos are between ED 13 and 14 as a different development stage would jeopardize the whole procedure. Sacrifice a pregnant female with CO2 and collect the whole embryo chain in HBSS medium. Isolate each embryo and decapitate them for euthanasia.</li>
 <li>Dissect the embryo spinal cord from the rest of the body in one piece and remove surrounding muscle and connective tissue. Be very careful to keep the dorsal root ganglions (DRGs) attached to the spinal cord to ensure functional innervation.</li>
 <li>Slice each spinal cord transversally in a way that each explant contains at least 2 DRG attached to it (explants of 1 mm3).</li>
</ol>
3. Innervation of the Human Muscle cells with Embryonic Rat Spinal Cord Explants
<ol>
 <li>Remove the fusion medium on the muscle cell culture, leaving a fine layer of medium on the monolayer.</li>
 <li>Place the explants carefully on the muscle cell layer, five evenly spaced explants per 35 mm dish.</li>
 <li>Add very slowly, drop wise, fusion medium onto each explant. It is necessary to add medium for the muscle cells to survive, but not too much to allow the explants to adhere first and make contact with the cells. If the medium is not added properly (too strongly or too much medium), the explants will float and will fail to innervate the muscle cells.</li>
 <li>Once the explants start to adhere, top the fusion medium to 2 ml per 35 mm dish, and put the dishes very carefully back into the incubator.</li>
</ol>
4. Maintenance of the Heterologous Nerve-muscle Co-cultures
<ol>
 <li>Change the fusion medium twice a week.</li>
</ol>
5. Representative Results
As soon as two days after the innervation, it is possible to see the neurites emerging from each explant and establishing contacts with the muscle cells, represented by the button-like structures (Fig 1).
As early as 4-6 days after the innervation, a few individual fibers will start to contract.
The contractions persist for many months, maintained simply by changing the culture medium twice a week.
After about 2 weeks, the spinal cord explant itself degenerates, but the innervation is conserved. This is normal. A fine layer of nerve component stays at the surface of the muscle cell layer. This nervous network is sufficient to maintain the functionality of the motor unit.
If the explants float in the medium the day after innervation, they will never adhere. This happens when the muscle cell layer is not sufficiently confluent, or when the medium is added too roughly. Sometimes, the explant adheres but no neurites will emerge. This is likely due to the lack of DRG attached to it. In that case as well, the innervation will not be established. Manipulate the dishes very carefully the first week, as the explants can still detach easily. To exchange the fusion media, add the liquid drop-wise with a minimal speed to avoid cell detachment.
<img alt="Figure 1" src="/files/ftp_upload/3616/3616fig1.jpg" /> 
Figure 1. Spinal cord explants -muscle cell co-cultures from day 1 to day 15.

<ol>
	<li>Delaporte, C., Dautreaux, B., Fardeau, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+myotube+differentiation+in+vitro+in+different+culture+conditions.">Human myotube differentiation in vitro in different culture conditions.</a> Biol. Cell. 57, 17-22 (1986).</li><li>Kobayashi, T., Askanas, V., Engel, W. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Human+muscle+cultured+in+monolayer+and+cocultured+with+fetal+rat+spinal+cord:+importance+of+dorsal+root+ganglia+for+achieving+successful+functional+innervation.">Human muscle cultured in monolayer and cocultured with fetal rat spinal cord: importance of dorsal root ganglia for achieving successful functional innervation.</a> J. Neurosci. 7, 3131-3141 (1987).</li><li>Braun, S., Croizat, B., Lagrange, M. C., Warter, J. M., Poindron, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Constitutive+muscular+abnormalities+in+culture+in+spinal+muscular+atrophy.">Constitutive muscular abnormalities in culture in spinal muscular atrophy.</a> Lancet. 345, 694-695 (1995).</li><li>Askanas, V., Engel, W. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+program+for+investigating+adult+human+skeletal+muscle+grown+aneurally+in+tissue+culture.">A new program for investigating adult human skeletal muscle grown aneurally in tissue culture.</a> Neurology. 25, 58-67 (1975).</li><li>Guettier-Sigrist, S., Coupin, G., Warter, J. M., Poindron, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+types+required+to+efficiently+innervate+human+muscle+cells+in+vitro.">Cell types required to efficiently innervate human muscle cells in vitro.</a> Exp. Cell Res. 259, 204-212 (2000).</li><li>Lefebvre, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Identification+and+characterization+of+a+spinal+muscular+atrophy-determining+gene.">Identification and characterization of a spinal muscular atrophy-determining gene.</a> Cell. 80, 155-165 (1995).</li><li>Schrank, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Inactivation+of+the+survival+motor+neuron+gene,+a+candidate+gene+for+human+spinal+muscular+atrophy,+leads+to+massive+cell+death+in+early+mouse+embryos.">Inactivation of the survival motor neuron gene, a candidate gene for human spinal muscular atrophy, leads to massive cell death in early mouse embryos.</a> Proc. Natl. Acad. Sci. U.S.A. 94, 9920-9925 (1997).</li><li>Hsieh-Li, H. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+mouse+model+for+spinal+muscular+atrophy.">A mouse model for spinal muscular atrophy.</a> Nat. Genet. 24, 66-70 (2000).</li><li>Monani, U. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+human+centromeric+survival+motor+neuron+gene+(SMN2)+rescues+embryonic+lethality+in+Smn(-/-)+mice+and+results+in+a+mouse+with+spinal+muscular+atrophy.">The human centromeric survival motor neuron gene (SMN2) rescues embryonic lethality in Smn(-/-) mice and results in a mouse with spinal muscular atrophy.</a> Hum. Mol. Genet. 9, 333-339 (2000).</li><li>Sleigh, J. N., Gillingwater, T. H., Talbot, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+contribution+of+mouse+models+to+understanding+the+pathogenesis+of+spinal+muscular+atrophy.">The contribution of mouse models to understanding the pathogenesis of spinal muscular atrophy.</a> Dis. Model. Mech. 4, 457-467 (2011).</li><li>Durbeej, M., Campbell, K. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Muscular+dystrophies+involving+the+dystrophin-glycoprotein+complex:+an+overview+of+current+mouse+models.">Muscular dystrophies involving the dystrophin-glycoprotein complex: an overview of current mouse models.</a> 12, 349-361 (2002).</li><li>Schnabel, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuroscience:+Standard+model.">Neuroscience: Standard model.</a> Nature. 454, 682-685 (2008).</li><li>Benatar, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lost+in+translation:+treatment+trials+in+the+SOD1+mouse+and+in+human+ALS.">Lost in translation: treatment trials in the SOD1 mouse and in human ALS.</a> Neurobiol. Dis. 26, 1-13 (2007).</li><li>Dorchies, O. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Normal+innervation+and+differentiation+of+X-linked+myotubular+myopathy+muscle+cells+in+a+nerve-muscle+coculture+system.">Normal innervation and differentiation of X-linked myotubular myopathy muscle cells in a nerve-muscle coculture system.</a> Neuromuscul. Disord. 11, 736-746 (2001).</li><li>McFerrin, J., Engel, W. K., Askanas, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impaired+innervation+of+cultured+human+muscle+overexpressing+betaAPP+experimentally+and+genetically:+relevance+to+inclusion-body+myopathies.">Impaired innervation of cultured human muscle overexpressing betaAPP experimentally and genetically: relevance to inclusion-body myopathies.</a> Neuroreport. 9, 3201-3205 (1998).</li></ol>

We have nothing to disclose.

A physiological in vitro tool to study muscle cell function in normal and pathological context is of highest interest for the myologists, because muscle cell cultures usually do not recapitulate the importance of multiple cells and cell-type connections. The addition of purified motor neurons to muscle cells is not enough to achieve a functional motor unit since the presence of Schwann cells is required for the innervation to be efficient5 and it is not topologically (3D + special distribution) releva...

<table border="1">
 <tbody>
 <tr>
 <td>Name of reagent</td>
 <td>Company</td>
 <td>Catalog Number</td>
 </tr>
 
 <tr>
 <td>HBSS</td>
 <td>Gibco/Invitrogen</td>
 <td>14170</td>
 </tr>

 <tr>
 <td>MEM</td>
 <td>Gibco/Invitrogen</td>
 <td>31095</td>
 </tr>

 <tr>
 <td>Medium 199 </td>
 <td>Gibco/Invitrogen</td>
 <td>31153</td>
 </tr>

 <tr>
 <td>Fetal Bovine Serum</td>
 <td>Fetal Clone Perbio</td>
 <td>SH30066.03</td>
 </tr>

 <tr>
 <td>Insuline</td>
 <td>Sigma</td>
 <td>I9278</td>
 </tr>

 <tr>
 <td>Human EGF</td>
 <td>Sigma</td>
 <td>E9644</td>
 </tr>

 <tr>
 <td>Human FGF</td>
 <td>Sigma</td>
 <td>F0291</td>
 </tr>

 <tr>
 <td>Penicillin/streptomycin solution</td>
 <td>Gibco</td>
 <td>15140</td>
 </tr>
 </tbody>
</table>

a functional motor unit in the culture dish: co-culture of spinal cord explants and muscle cells

Human primary muscle cells cultured aneurally in monolayer rarely contract spontaneously because, in the absence of a nerve component, cell differentiation is limited and motor neuron stimulation is missing1. These limitations hamper the in vitro study of many neuromuscular diseases in cultured muscle cells. Importantly, the experimental constraints of monolayered, cultured muscle cells can be overcome by functional innervation of myofibers with spinal cord explants in co-cultures.
Here, we show the different steps required to achieve an efficient, proper innervation of human primary muscle cells, leading to complete differentiation and fiber contraction according to the method developed by Askanas2. To do so, muscle cells are co-cultured with spinal cord explants of rat embryos at ED 13.5, with the dorsal root ganglia still attached to the spinal cord slices. After a few days, the muscle fibers start to contract and eventually become cross-striated through innervation by functional neurites projecting from the spinal cord explants that connecting to the muscle cells. This structure can be maintained for many months, simply by regular exchange of the culture medium.
The applications of this invaluable tool are numerous, as it represents a functional model for multidisciplinary analyses of human muscle development and innervation. In fact, a complete de novo neuromuscular junction installation occurs in a culture dish, allowing an easy measurement of many parameters at each step, in a fundamental and physiological context.
Just to cite a few examples, genomic and/or proteomic studies can be performed directly on the co-cultures. Furthermore, pre- and post-synaptic effects can be specifically and separately assessed at the neuromuscular junction, because both components come from different species, rat and human, respectively. The nerve-muscle co-culture can also be performed with human muscle cells isolated from patients suffering from muscle or neuromuscular diseases3, and thus can be used as a screening tool for candidate drugs. Finally, no special equipment but a regular BSL2 facility is needed to reproduce a functional motor unit in a culture dish. This method thus is valuable for both the muscle as well as the neuromuscular research communities for physiological and mechanistic studies of neuromuscular function, in a normal and disease context.

Watch this Scientific Journal Video about A Functional Motor Unit in the Culture Dish: Co-culture of Spinal Cord Explants and Muscle Cells at JoVE.com

A Functional Motor Unit in the Culture Dish: Co-culture of Spinal Cord Explants and Muscle Cells

Cultured muscle cells are an inadequate model to recapitulate innervated muscle in vivo. A functional motor unit can be reproduced in vitro by innervation of differentiated human primary muscle cells using rat embryo spinal cord explants. This article describes how co-cultures of spinal cord explants and muscle cells are established.

Human primary muscle cells cultured  aneurally in monolayer rarely contract spontaneously because, in the absence of  a nerve component, cell ...

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15.2K Views.  University of Basel. Cultured muscle cells are an inadequate model to recapitulate innervated muscle in vivo. A functional motor unit can be reproduced in vitro by innervation of differentiated human primary muscle cells using rat embryo spinal cord explants. This article describes how co-cultures of spinal cord explants and muscle cells are established.

Video: A Functional Motor Unit in the Culture Dish: Co-culture of Spinal Cord Explants and Muscle Cells

Dissection and Culture of Commissural Neurons from Embryonic Spinal Cord

Commissural neurons have been widely used to investigate the mechanisms underlying axon guidance during embryonic spinal cord development. The cell bodies of these neurons are located in the dorsal spinal cord and their axons follow stereotyped trajectories during embryonic development. Commissural axons initially project ventrally towards the floorplate. After crossing the midline, these axons turn anteriorly and project towards the brain. Each of these steps is regulated by the action of several guidance cues. Cultures highly enriched in commissural neurons are ideally suited for many experiments addressing the mechanisms of axon pathfinding, including turning assays, immunochemistry and biochemistry. Here, we describe a method to dissect and culture commissural neurons from E13 rat dorsal spinal cord. First, the spinal cord is isolated and dorsal strips are dissected out. The dorsal tissue is then dissociated into a cell suspension by trypsinization and mechanical disruption. Neurons are plated onto poly-L-lysine-coated glass coverslips or tissue-culture dishes. After 30 hours in vitro, most neurons have extended an axon. The purity of the culture (Yam et al. 2009), typically over 90%, can be assessed by immunolabeling with the commissural neuron markers DCC, LH2 and TAG1 (Helms and Johnson, 1998). This neuronal preparation is a useful tool for in vitro studies of the cellular and molecular mechanisms of commissural axon growth and guidance during spinal cord development.

This video demonstrates a method to dissect and culture commissural neurons from E13 rat dorsal spinal cord. Dissociated commissural neurons are useful to study the cellular and molecular mechanisms of axon growth and guidance.

Commissural neurons have been widely used to investigate the mechanisms underlying axon guidance during embryonic spinal cord development. The cell bodies ...

Dissection and Culture of Chick Statoacoustic Ganglion and Spinal Cord Explants in Collagen Gels for Neurite Outgrowth Assays

The sensory organs of the chicken inner ear are innervated by the peripheral processes of statoacoustic ganglion (SAG) neurons. Sensory organ innervation depends on a combination of axon guidance cues1 and survival factors2 located along the trajectory of growing axons and/or within their sensory organ targets. For example, functional interference with a classic axon guidance signaling pathway, semaphorin-neuropilin, generated misrouting of otic axons3. Also, several growth factors expressed in the sensory targets of the inner ear, including Neurotrophin-3 (NT-3) and Brain Derived Neurotrophic Factor (BDNF), have been manipulated in transgenic animals, again leading to misrouting of SAG axons4. These same molecules promote both survival and neurite outgrowth of chick SAG neurons in vitro5,6.
Here, we describe and demonstrate the in vitro method we are currently using to test the responsiveness of chick SAG neurites to soluble proteins, including known morphogens such as the Wnts, as well as growth factors that are important for promoting SAG neurite outgrowth and neuron survival. Using this model system, we hope to draw conclusions about the effects that secreted ligands can exert on SAG neuron survival and neurite outgrowth. 
SAG explants are dissected on embryonic day 4 (E4) and cultured in three-dimensional collagen gels under serum-free conditions for 24 hours. First, neurite responsiveness is tested by culturing explants with protein-supplemented medium. Then, to ask whether point sources of secreted ligands can have directional effects on neurite outgrowth, explants are co-cultured with protein-coated beads and assayed for the ability of the bead to locally promote or inhibit outgrowth. We also include a demonstration of the dissection (modified protocol7) and culture of E6 spinal cord explants. We routinely use spinal cord explants to confirm bioactivity of the proteins and protein-soaked beads, and to verify species cross-reactivity with chick tissue, under the same culture conditions as SAG explants. These in vitro assays are convenient for quickly screening for molecules that exert trophic (survival) or tropic (directional) effects on SAG neurons, especially before performing studies in vivo. Moreover, this method permits the testing of individual molecules under serum-free conditions, with high neuron survival8.

We demonstrate how to dissect and culture chick E4 statoacoustic ganglion and E6 spinal cord explants. Explants are cultured under serum-free conditions in 3D collagen gels for 24 hours. Neurite responsiveness is tested with growth factor-supplemented medium and with protein-coated beads.

The sensory organs of the chicken inner ear are innervated by the peripheral processes of statoacoustic ganglion (SAG) neurons. Sensory organ innervation ...

Chicken Embryo Spinal Cord Slice Culture Protocol

Slice cultures can facilitate the manipulation of embryo development both pharmacologically and through gene manipulations. In this reduced system, potential lethal side effects due to systemic drug applications can be overcome. However, culture conditions must ensure that normal development proceeds within the reduced environment of the slice. We have focused on the development of the spinal cord, particularly that of spinal motor neurons. We systematically varied culture conditions of chicken embryo slices from the point at which most spinal motor neurons had been born. We assayed the number and type of motor neurons that survived during the culture period and the position of those motor neurons compared to that in vivo. We found that serum type and neurotrophic factors were required during the culture period and were able to keep motor neurons alive for at least 24 hr and allow those motor neurons to migrate to appropriate positions in the spinal cord. We present these culture conditions and the methodology of preparing the embryo slice cultures using eviscerated chicken embryos embedded in agarose and sliced using a vibratome.

Slice cultures facilitate the manipulation of embryo development by gene and pharmacological perturbations. However, culture conditions must ensure that normal development can proceed within the reduced environment of the slice. We illustrate a protocol that facilitates normal spinal cord development to proceed for at least 24 hr.

Slice cultures can facilitate the manipulation of  embryo development both pharmacologically and through gene manipulations. In  this reduced system, ...

Analysis of Developing Tooth Germ Innervation Using Microfluidic Co-culture Devices

Innervation plays a key role in the development, homeostasis and regeneration of organs and tissues. However, the mechanisms underlying these phenomena are not well understood yet. In particular, the role of innervation in tooth development and regeneration is neglected.
Several in vivo studies have provided important information about the patterns of innervation of dental tissues during development and repair processes of various animal models. However, most of these approaches are not optimal to highlight the molecular basis of the interactions between nerve fibres and target organs and tissues.
Co-cultures constitute a valuable method to investigate and manipulate the interactions between nerve fibres and teeth in a controlled and isolated environment. In the last decades, conventional co-cultures using the same culture medium have been performed for very short periods (e.g., two days) to investigate the attractive or repulsive effects of developing oral and dental tissues on sensory nerve fibres. However, extension of the culture period is required to investigate the effects of innervation on tooth morphogenesis and cytodifferentiation.
Microfluidics systems allow co-cultures of neurons and different cell types in their appropriate culture media. We have recently demonstrated that trigeminal ganglia (TG) and teeth are able to survive for a long period of time when co-cultured in microfluidic devices, and that they maintain in these conditions the same innervation pattern that they show in vivo.
On this basis, we describe how to isolate and co-culture developing trigeminal ganglia and tooth germs in a microfluidic co-culture system.This protocol describes a simple and flexible way to co-culture ganglia/nerves and target tissues and to study the roles of specific molecules on such interactions in a controlled and isolated environment.

Co-cultures represent a valuable method to study the interactions between nerves and target tissues and organs. Microfluidic systems allow co-culturing ganglia and whole developing organs or tissues in different culture media, thus representing a valuable tool for the in vitro study of the crosstalk between neurons and their targets.

Innervation plays a key role in the development, homeostasis and regeneration of organs and tissues. However, the mechanisms underlying these phenomena ...

Zebrafish In Situ Spinal Cord Preparation for Electrophysiological Recordings from Spinal Sensory and Motor Neurons

Zebrafish, first introduced as a developmental model, have gained popularity in many other fields. The ease of rearing large numbers of rapidly developing organisms, combined with the embryonic optical clarity, served as initial compelling attributes of this model. Over the past two decades, the success of this model has been further propelled by its amenability to large-scale mutagenesis screens and by the ease of transgenesis. More recently, gene-editing approaches have extended the power of the model.
For neurodevelopmental studies, the zebrafish embryo and larva provide a model to which multiple methods can be applied. Here, we focus on methods that allow the study of an essential property of neurons, electrical excitability. Our preparation for the electrophysiological study of zebrafish spinal neurons involves the use of veterinarian suture glue to secure the preparation to a recording chamber. Alternative methods for recording from zebrafish embryos and larvae involve the attachment of the preparation to the chamber using a fine tungsten pin1,2,3,4,5. A tungsten pin is most often used to mount the preparation in a lateral orientation, although it has been used to mount larvae dorsal-side up4. The suture glue has been used to mount embryos and larvae in both orientations. Using the glue, a minimal dissection can be performed, allowing access to spinal neurons without the use of an enzymatic treatment, thereby avoiding any resultant damage. However, for larvae, it is necessary to apply a brief enzyme treatment to remove the muscle tissue surrounding the spinal cord. The methods described here have been used to study the intrinsic electrical properties of motor neurons, interneurons, and sensory neurons at several developmental stages6,7,8,9.

Zebrafish In Situ Spinal Cord Preparation for Electrophysiological Recordings from Spinal Sensory and Motor Neurons

This manuscript describes methods for electrophysiological recordings from spinal neurons of zebrafish embryos and larvae. The preparation maintains neurons in situ and often involves minimum dissection. These methods allow for the electrophysiological study of a variety of spinal neurons, from the initial electrical excitability acquisition through the early larval stages.

Zebrafish, first introduced as a developmental model, have gained popularity in many other fields. The ease of rearing large numbers of rapidly developing ...

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 ...

Identifying Cell Surface Markers of Primary Neural Stem and Progenitor Cells by Metabolic Labeling of Sialoglycan

Neural stem and progenitor cells (NSPCs) are the cellular basis for the complex structures and functions of the brain. They are located in specialized niches in vivo and can be isolated and expanded in vitro, serving as an important resource for cell transplantation to repair brain damage. However, NSPCs are heterogeneous and not clearly defined at the molecular level or purified due to a lack of specific cell surface markers. The protocol presented, which has been previously reported, combines a neural-endothelial co-culture system with a metabolic glycan labeling method to identify the surface sialoglycoproteome of primary NSPCs. The NSPC-endothelial co-culture system allows self-renewal and expansion of primary NSPCs in vitro, generating a sufficient number of NSPCs. Sialoglycans in cultured NSPCs are labeled using an unnatural sialic acid metabolic reporter with bioorthogonal functional groups. By comparing the sialoglycoproteome from self-renewing NSPCs expanded in an endothelial co-culture with differentiating neural culture, we identify a list of membrane proteins that are enriched in NSPCs. In detail, the protocol involves: 1) set-up of an NSPC-endothelial co-culture and NSPC differentiating culture; 2) labeling with azidosugar per-O-acetylated N-azidoacetylmannosamine (Ac4ManNAz); and 3) biotin conjugation to modified sialoglycan for imaging after fixation of neural culture or protein extraction from neural culture for mass spectrometry analysis. Then, the NSPC-enriched surface marker candidates are selected by comparative analysis of mass spectrometry data from both the expanded NSPC and differentiated neural cultures. This protocol is highly sensitive for identifying membrane proteins of low abundance in the starting materials, and it can be applied to marker discovery in other systems with appropriate modifications

Presented here is a protocol that combines an in vitro neural-endothelial co-culture system and metabolic incorporation of sialoglycan with bioorthogonal functional groups to expand primary neural stem and progenitor cells and label their surface sialoglycoproteins for imaging or mass-spectrometry analysis of cell surface markers.

Neural stem and progenitor cells (NSPCs) are the cellular basis for the complex structures and functions of the brain. They are located in specialized ...

Direct Injection of a Lentiviral Vector Highlights Multiple Motor Pathways in the Rat Spinal Cord

Introducing proteins of interest into cells in the nervous system is challenging due to innate biological barriers that limit access to most molecules. Injection directly into spinal cord tissue bypasses these barriers, providing access to cell bodies or synapses where molecules can be incorporated. Combining viral vector technology with this method allows for introduction of target genes into nervous tissue for the purpose of gene therapy or tract tracing. Here a virus engineered for highly efficient retrograde transport (HiRet) is introduced at the synapses of propriospinal interneurons (PNs) to encourage specific transport to neurons in the spinal cord and brainstem nuclei. Targeting PNs takes advantage of the numerous connections they receive from motor pathways such as the rubrospinal and reticulospinal tracts, as well as their interconnection with each other throughout spinal cord segments. Representative tracing using the HiRet vector with constitutively active green fluorescent protein (GFP) shows high fidelity details of cell bodies, axons and dendritic arbors in thoracic PNs and in reticulospinal neurons in the pontine reticular formation. HiRet incorporates well into brainstem pathways and PNs but shows age dependent integration into corticospinal tract neurons. In summary, spinal cord injection using viral vectors is a suitable method for introduction of proteins of interest into neurons of targeted tracts.

This protocol demonstrates injection of a retrogradely transportable viral vector into rat spinal cord tissue. The vector is taken up at the synapse and transported to the cell body of target neurons. This model is suitable for retrograde tracing of important spinal pathways or targeting cells for gene therapy applications.

Introducing proteins of interest into cells in the nervous system is challenging due to innate biological barriers that limit access to most molecules. ...

Conversion of Human Induced Pluripotent Stem Cells (iPSCs) into Functional Spinal and Cranial Motor Neurons Using PiggyBac Vectors

We describe here a method to obtain functional spinal and cranial motor neurons from human induced pluripotent stem cells (iPSCs). Direct conversion into motor neuron is obtained by ectopic expression of alternative modules of transcription factors, namely Ngn2, Isl1 and Lhx3 (NIL) or Ngn2, Isl1 and Phox2a (NIP). NIL and NIP specify, respectively, spinal and cranial motor neuron identity. Our protocol starts with the generation of modified iPSC lines in which NIL or NIP are stably integrated in the genome via a piggyBac transposon vector. Expression of the transgenes is then induced by doxycycline and leads, in 5 days, to the conversion of iPSCs into MN progenitors. Subsequent maturation, for 7 days, leads to homogeneous populations of spinal or cranial MNs. Our method holds several advantages over previous protocols: it is extremely rapid and simplified; it does not require viral infection or further MN isolation; it allows generating different MN subpopulations (spinal and cranial) with a remarkable degree of maturation, as demonstrated by the ability to fire trains of action potentials. Moreover, a large number of motor neurons can be obtained without purification from mixed populations. iPSC-derived spinal and cranial motor neurons can be used for in vitro modeling of Amyotrophic Lateral Sclerosis and other neurodegenerative diseases of the motor neuron. Homogeneous motor neuron populations might represent an important resource for cell type specific drug screenings.

Conversion of Human Induced Pluripotent Stem Cells iPSCs into Functional Spinal and Cranial Motor Neurons Using PiggyBac Vectors

This protocol allows rapid and efficient conversion of induced pluripotent stem cells into motor neurons with a spinal or cranial identity, by ectopic expression of transcription factors from inducible piggyBac vectors.

We describe here a method to obtain functional spinal and cranial motor neurons from human induced pluripotent stem cells (iPSCs). Direct conversion into ...

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 ...