The authors would like to thank R&#233;mi Ronzano for his wise advice in manuscript editing. This work was funded by ICM, INSERM, ARSEP foundation grant to NSF, and Bouvet-Labruy&#232;re price.

The care and use of rats in this experiment conforms to institutional policies and guidelines (UPMC, INSERM, and European Community Council Directive 86/609/EEC). The following protocol is established for a standard litter of 12 pups.
1. Preparation of the flasks (~5 min)
NOTE: Perform the following steps the day before dissection in a laminar flow hood under sterile conditions.
<ol>
	<li>Coat the 150 cm2 flasks (T150) with filter cap (1 flask for 2 pups) using 5 mL of polyethylenimine (PEI, 100 mg/L, see protocol in Supplementary File 1).</li>
	<li>Store the flasks at 4 &#176;C overnight.</li>
	<li>Rinse coated flasks 3 times with sterile distilled water on the day of dissection.</li>
</ol>
2. Preparation of media (~10 min)
NOTE: Perform the steps in a laminar flow hood under sterile conditions.
<ol>
	<li>Prepare 500 mL of culture medium, consisting of Dulbecco&#39;s modified Eagle medium (DMEM) supplemented with 10% of fetal calf serum (FCS) and penicillin-streptomycin (100 IU/mL).</li>
	<li>Prepare 20.6 mL of the enzyme digestion medium in a 50 mL tube, consisting of 20 mL of DMEM, 200 &#181;L of DNase (50 &#181;g/mL), 200 &#181;L of papain (30 U/mL) and 200 &#181;L of L-cysteine (0.24 mg/mL).</li>
	<li>Filter-sterilize the media using a 0.22 &#181;m filter.</li>
	<li>Keep the media in the laminar flow hood at room temperature (RT) until dissection.</li>
</ol>
3. Preparation for dissection (~10 min)
NOTE: Perform the steps in a laminar flow hood under sterile conditions.
<ol>
	<li>Prepare 100 mL of phosphate-buffered saline without calcium and magnesium (PBS; 1x). Filter-sterilize using a 0.22 &#181;m filter.</li>
	<li>Prepare 50 mL of ice-cold 1x PBS solution supplemented with 750 &#181;L of 45% glucose. Filter-sterilize using a 0.22 &#181;m filter.</li>
	<li>Fill a 100 mm Petri dish with 1x PBS for cleaning instruments and three 60 mm Petri dishes with ice-cold PBS-glucose for tissue harvesting. Put the petri dishes on ice until dissection.</li>
</ol>
4. Dissection
NOTE: Dissection is performed from male and female Wistar rat pups at postnatal day (P) 2.
<ol>
	<li>In order to provide a sterile environment, make sure to clean the bench with 100% ethanol. Sterilize all surgical tools with 100% ethanol.</li>
	<li>Gently spray the neck of the pup with 70% ethanol.</li>
	<li>Use large surgical scissors to decapitate the animal and place the head in a 100 mm Petri dish containing ice-cold PBS-glucose.</li>
	<li>Use curved forceps to maintain the head of the animal at eye level. Use small surgical scissors to make a small incision at the base of the skull and cut the skull following the brain midline.</li>
	<li>Use forceps to gently peel off the two parts of the skull from the midline.</li>
	<li>Use a small surgical spoon to remove the brain from the head cavity. Put the brain in a 60 mm Petri dish containing ice-cold PBS-glucose on ice.</li>
	<li>Viewing under a steromicroscope, use fine forceps to remove the cerebellum, the brainstem and olfactory bulbs from cerebral hemispheres.</li>
	<li>Use fine forceps to separate the two cerebral hemispheres. Use fine forceps to peel off the meninges. Put the cerebral cortices in a 60 mm-petri dish on ice. 
	NOTE: Ice-cold PBS is critical for correct meninges removal.</li>
</ol>
5. Tissue dissociation
NOTE: Perform the steps in a laminar flow hood under sterile conditions.
<ol>
	<li>Use a sharp scalpel to finely chop the cerebral cortices. Transfer the minced tissue into a 50 mL tube containing enzyme digestion medium.</li>
	<li>Incubate for 30 min in a humidified incubator at 37 &#176;C under 5% CO2.</li>
	<li>Use a p1000 micropipette to gently remove the enzyme digestion medium while making sure that the cortical tissue remains at the bottom of the 50 mL tube.</li>
	<li>Use a p1000 micropipette to add 1 mL of DMEM-10% FCS and gently triturate the tissue.</li>
	<li>Use a 70 &#181;m filter and a piston of a 1 mL syringe to filter the cortical tissue into a 50 mL tube. 
	NOTE: One can rinse residual tissue on the inner tube wall several times with DMEM-10% FCS.</li>
	<li>Fill the 50 mL tube with DMEM-10%FCS. Centrifuge at 423 x g for 5 min at RT. Carefully remove supernatant and resuspend cell pellet with 2 mL of DMEM-10%FCS.</li>
	<li>Gently triturate cell pellet with a p1000 micropipette and then with a p200 micropipette. Dilute the cell suspension with the appropriate volume of DMEM-10%FCS. 
	NOTE: Two brains = one T150 = 5 mL of DMEM-10%FCS.</li>
	<li>Plate 5 mL of the cell suspension on a T150 at a density of 1 x 105 cells/cm2. Add 20 mL of warm DMEM-10%FCS to each T150. Incubate in a humidified incubator at 37 &#176;C under 5% CO2.</li>
	<li>Renew half of the culture medium after 6 days in vitro (DIV) with warm DMEM-10%FCS.</li>
</ol>
6. Shaking preparation
<ol>
	<li>Perform shaking preparation on the day before shaking in a laminar flow hood under sterile conditions.</li>
	<li>Renew half of culture medium by adding fresh warm culture medium into the flask and incubate at 37 &#176;C under 5% CO2.</li>
</ol>
7. Shaking
<ol>
	<li>Coat three 100 mm Petri dishes with PEI. Store them at 4 &#176;C overnight.</li>
	<li>Cover the flasks cap with paraffin film and put the flasks into a plastic bag. Shake flasks containing glial cells overnight at 250 rpm at 37 &#176;C. 
	NOTE: First shaking is performed at 8 DIV and one can perform up to three different shakings (see Figure 1 for timing).</li>
</ol>
8. OL lineage cells harvesting and culture
NOTE: These steps should be performed in a laminar flow hood under sterile conditions.
<ol>
	<li>On the day after shaking, prepare Bottenstein-Sato (BS) medium according to Table 1.</li>
	<li>Rinse coated Petri dishes 3 times with sterile distilled water.</li>
	<li>Harvest flasks&#39; supernatant containing mainly OL lineage cells but also some microglial cells and plate it on non-coated 100 mm Petri dishes. 
	NOTE: This step allows removal of microglial cells through differential fast adhesion on the dish surface.</li>
	<li>Incubate the Petri dishes for 15 min in a humidified incubator at 37 &#176;C under 5% CO2.</li>
	<li>Fill each T150 flask with 25 mL of warm freshly prepared culture medium and incubate in a humidified incubator at 37 &#176;C under 5% CO2 until the second shaking.</li>
	<li>Transfer the supernatant from the Petri dishes into new non-coated 100 mm Petri dishes to allow adhesion of residual microglial cells.</li>
	<li>Incubate the Petri dishes for 15 min in a humidified incubator at 37 &#176;C under 5% CO2.</li>
	<li>Remove the supernatant, which contains non-adherent OL lineage cells, and transfer it into 50 mL tubes (supernatant from 2 Petri dishes for a 50 mL tube). Discard Petri dishes plated with microglia.</li>
	<li>Centrifuge the supernatant for 5 min at 423 x g. Carefully remove supernatant and resuspend cell pellet with 1 mL of BS medium. Pool all pellets in a common 50 mL tube and adjust volume to 10 mL with BS medium.</li>
	<li>Determine cell density counting cells under a microscope. 
	NOTE: A cell density between 3 x 105/mL and 5 x 105/mL should be obtained.</li>
	<li>Add 20 mL of BS if cell density is higher than or equal to 4 x 105/mL to obtain a final volume of 30 mL, or add only 10 mL of BS if cell density is less than 4 x 105/mL to obtain a final volume of 20 mL.</li>
	<li>Plate two or three pre-coated 100 mm Petri dishes with 10 mL of cell suspension. Incubate in a humidified incubator at 37 &#176;C under 5% CO2.</li>
	<li>Clear the debris from the Petri dishes by refreshing all of the BS medium 2 h later. 
	NOTE: Examine the culture under the microscope before and after clearing to verify cell density and efficiency of debris removal.</li>
	<li>Incubate for 2 days in BS medium in a humidified incubator at 37 &#176;C under 5% CO2. 
	NOTE: Examine the culture under the microscope. The confluence should be 70% to 80%.</li>
</ol>
9. OCM production
NOTE: Perform these steps in a laminar flow hood under sterile conditions.
<ol>
	<li>Prepare NB-B27low medium according to Table 2.</li>
	<li>Renew culture medium with 10 mL of warm NB-B27low medium. Incubate for 2 days in a humidified incubator at 37 &#176;C under 5% CO2.</li>
	<li>Harvest the OCM, i.e., supernatant containing OL secreted factors. Filter-sterilize OCM using a 0.22 &#181;m filter. 
	NOTE: Store OCM at 4 &#176;C for a maximum of 2 months.</li>
</ol>
10. OCM addition
NOTE: Steps should be performed in a laminar flow hood under sterile conditions. OCM can be added to purified hippocampal neuron cultures prepared according to the following protocol14, and obtained by adding, 24 h after isolation, the anti-mitotic agents uridine and 5- fluorodeoxyuridine (5 &#181;M) for 36 h.
<ol>
	<li>At 3 DIV, remove all neuron culture medium containing anti-mitotic agents and add 500 &#181;L of fresh warm OCM.</li>
	<li>Renew half of medium every 3 days with freshly made warm NB-B27. 
	NOTE: Such cultures can be maintained up to 21 DIV.</li>
</ol>
11. Addition of OL to purified hippocampal neuron culture
NOTE: Perform the following steps in a laminar flow hood under sterile conditions. OLs can be added to purified hippocampal cultures obtained the same way as described above.
<ol>
	<li>Prepare co-culture medium according to Table 3.</li>
	<li>Retrieve the OL culture at 70% to 80% confluence. Rinse with 2 mL of warm 1x PBS.</li>
	<li>To detach the cells, add 2 mL of 0.25% trypsin to a 100 mm Petri dish.</li>
	<li>Incubate for 5 min in a humidified incubator at 37 &#176;C under 5% CO2.</li>
	<li>Add 2 mL of DMEM-10% FCS to block the enzymatic reaction. Harvest the supernatant containing OL lineage cells.</li>
	<li>Centrifuge at 423 x g for 5 min at RT. Carefully remove supernatant and resuspend the cell pellet in warm co-culture medium to obtain a concentration of 1.25 x 105 cells/mL.</li>
	<li>Add OL to purified hippocampal neurons culture by removing 200 &#181;L of neuron culture medium and adding 200 &#181;L of cell suspension per well (2.5 x 104 cells/well) of a 24-well plate.</li>
	<li>Refresh half of co-culture medium every 2-3 days. 
	NOTE: Co-cultures can be maintained up to 24 DIV.</li>
</ol>

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None of the authors have competing interests or conflicting interests.

Here, we provide a detailed protocol to obtain highly enriched oligodendroglial lineage cell cultures from mixed glial cultures, adapted from a previously published method16, and the subsequent production of OL-conditioned medium. This shaking technique is not expensive, can be repeated three times and is optimal to obtain high quantity of purified OLs, as cells cultured in Bottenstein-Sato (BS) medium containing PDGF&#945; proliferate. Glial cells are prepared using cerebral cortices of Wistar ra...

Oligodendrocytes (OLs) are glial cells of the central nervous system (CNS) that generate myelin wrapping around axons. OLs originate from oligodendrocyte precursor cells (OPCs) which proliferate within the ventricular zones of the embryonic CNS and then migrate and differentiate into fully mature OLs (i.e., myelin-forming cells)1. OPCs are abundant during early development, but also persist in the adult brain where they represent the major proliferative cell population2. A single OL ensheathes multiple axons in non-excitable sections (i.e., internodes), and the edge of each myelin loop attaches to the axon forming the paranodal domain which is crucial for the insulating properties of myelin1,3. In between the paranodes are small unmyelinated gaps called the nodes of Ranvier. These nodes are rich in voltage-gated sodium channels (Nav), allowing the regeneration and rapid propagation of action potentials through saltatory conduction4. This tight interaction also enables axonal energy support through neuronal uptake of lactate from OLs5,6.
The maturation of oligodendroglial lineage cells and the myelination process are tightly regulated by their interactions with neurons7. Indeed, OLs and OPCs, also named NG2 cells, express an array of receptors for neurotransmitters, and can receive input from excitatory and inhibitory neurons, allowing them to sense neuronal activity that can trigger their proliferation and/or differentiation into myelinating cells2. In turn, OPCs/OLs secrete microvesicles and proteins into the extracellular space which alone or synergistically mediate neuromodulative and neuroprotective functions8,9,10,11,12. However, the molecular mechanisms controlling the multiple modes of interactions between oligodendroglial lineage cells and neurons are yet to be fully deciphered.
Moreover, in several CNS pathological conditions, OLs are primarily affected, thus disturbing their interaction with neurons. For instance, in Multiple Sclerosis (MS), neurological dysfunction is caused by focal demyelination in the CNS, secondary to OLs loss that can lead to axonal damage and related disability accumulation. Remyelination can take place, albeit insufficiently in most cases13. Progress in the last decade, due to the development of immunotherapies, have reduce the relapse rate but promoting remyelination remains to date an unmet need. As such, a better understanding of OLs role, functions and influences is of particular interest to the development of new therapies for a wide spectrum of CNS conditions.
Here, we describe the methods of OLs purification and culture. This enables precise examination of intrinsic mechanisms regulating their development and biology. In addition, such highly enriched OLs cultures allow the production of oligodendrocyte-conditioned medium (OCM), which can be added to purified neuron cultures to gain insight into the impact of OLs-secreted factors on neuronal physiology and connectivity. Furthermore, we describe how to implement an in vitro co-culture system where purified oligodendrocytes and neurons are combined together, allowing to address the mechanisms regulating (re)myelination.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>5-fluorodeoxyuridine</td>
			<td>Sigma</td>
			<td>F0503</td>
			<td></td>
		</tr>
		<tr>
			<td>B27 supplement</td>
			<td>ThermoFisher</td>
			<td>17504044</td>
			<td></td>
		</tr>
		<tr>
			<td>D-(+)-Glucose solution</td>
			<td>Sigma</td>
			<td>G8769</td>
			<td></td>
		</tr>
		<tr>
			<td>DNase (Deoxyribonuclease I)</td>
			<td>Worthington</td>
			<td>LS002139</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle Medium</td>
			<td>ThermoFisher</td>
			<td>31966021</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol 100%</td>
			<td>Sigma</td>
			<td>32221-M</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol 70%</td>
			<td>VWR Chemicals</td>
			<td>83801.360</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal Calf Serum</td>
			<td>ThermoFisher</td>
			<td>10082147</td>
			<td></td>
		</tr>
		<tr>
			<td>L-cysteine</td>
			<td>Sigma</td>
			<td>C7352</td>
			<td></td>
		</tr>
		<tr>
			<td>Neurobasal</td>
			<td>ThermoFisher</td>
			<td>21103049</td>
			<td></td>
		</tr>
		<tr>
			<td>Papain</td>
			<td>Worthington</td>
			<td>LS003126</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>ThermoFisher</td>
			<td>15140122</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate Buffered Saline without calcium and magnesium</td>
			<td>ThermoFisher</td>
			<td>A1285601</td>
			<td></td>
		</tr>
		<tr>
			<td>Polyethylenimine(PEI)</td>
			<td>Sigma</td>
			<td>P3143</td>
			<td></td>
		</tr>
		<tr>
			<td>Tetraborate decahydrate</td>
			<td>Sigma</td>
			<td>B9876</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin</td>
			<td>Sigma</td>
			<td>Sigma</td>
			<td></td>
		</tr>
		<tr>
			<td>Uridine</td>
			<td>Sigma</td>
			<td>U3750</td>
			<td></td>
		</tr>
		<tr>
			<td>Bottenstein-Sato (BS) media</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>apo-Transferrin human</td>
			<td>Sigma</td>
			<td>T1147</td>
			<td></td>
		</tr>
		<tr>
			<td>BSA (Bovine Serum Albumin)</td>
			<td>Sigma</td>
			<td>A4161</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle Medium</td>
			<td>ThermoFisher</td>
			<td>31966021</td>
			<td></td>
		</tr>
		<tr>
			<td>Insulin</td>
			<td>Sigma</td>
			<td>I5500</td>
			<td></td>
		</tr>
		<tr>
			<td>PDGF</td>
			<td>Peprotech</td>
			<td>AF-100-13A</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>ThermoFisher</td>
			<td>15140122</td>
			<td></td>
		</tr>
		<tr>
			<td>Progesterone</td>
			<td>Sigma</td>
			<td>P8783</td>
			<td></td>
		</tr>
		<tr>
			<td>Putrescine dihydrochloride</td>
			<td>Sigma</td>
			<td>P5780</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium selenite</td>
			<td>Sigma</td>
			<td>S5261</td>
			<td></td>
		</tr>
		<tr>
			<td>T3 (3,3&#39;,5-Triiodo-L-thyronine sodium salt)</td>
			<td>Sigma</td>
			<td>T6397</td>
			<td></td>
		</tr>
		<tr>
			<td>T4 (L-Thyroxine)</td>
			<td>Sigma</td>
			<td>T1775</td>
			<td></td>
		</tr>
		<tr>
			<td>Co-culture media</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>apo-Transferrin human</td>
			<td>Sigma</td>
			<td>T1147</td>
			<td></td>
		</tr>
		<tr>
			<td>B27 supplement</td>
			<td>ThermoFisher</td>
			<td>17504044</td>
			<td></td>
		</tr>
		<tr>
			<td>Biotin</td>
			<td>Sigma</td>
			<td>B4639</td>
			<td></td>
		</tr>
		<tr>
			<td>BSA (Bovine Serum Albumin)</td>
			<td>Sigma</td>
			<td>A4161</td>
			<td></td>
		</tr>
		<tr>
			<td>Ceruloplasmin</td>
			<td>Sigma</td>
			<td>239799</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle Medium</td>
			<td>ThermoFisher</td>
			<td>31966021</td>
			<td></td>
		</tr>
		<tr>
			<td>Hydrocortisone</td>
			<td>Sigma</td>
			<td>H4001</td>
			<td></td>
		</tr>
		<tr>
			<td>Insulin</td>
			<td>Sigma</td>
			<td>I5500</td>
			<td></td>
		</tr>
		<tr>
			<td>N-Acetyl-L-cysteine</td>
			<td>Sigma</td>
			<td>A8199</td>
			<td></td>
		</tr>
		<tr>
			<td>Neurobasal</td>
			<td>ThermoFisher</td>
			<td>21103049</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin-Streptomycin</td>
			<td>ThermoFisher</td>
			<td>15140122</td>
			<td></td>
		</tr>
		<tr>
			<td>Progesterone</td>
			<td>Sigma</td>
			<td>P8783</td>
			<td></td>
		</tr>
		<tr>
			<td>Putrescin</td>
			<td>Sigma</td>
			<td>P5780</td>
			<td></td>
		</tr>
		<tr>
			<td>Recombinant Human CNTF</td>
			<td>Sigma</td>
			<td>450-13</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium selenite</td>
			<td>Sigma</td>
			<td>S5261</td>
			<td></td>
		</tr>
		<tr>
			<td>T3 (3,3&#39;,5-Triiodo-L-thyronine sodium salt)</td>
			<td>Sigma</td>
			<td>T6397</td>
			<td></td>
		</tr>
		<tr>
			<td>Vitamin B12</td>
			<td>Sigma</td>
			<td>V6629</td>
			<td></td>
		</tr>
		<tr>
			<td>Tools</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>0.22 &#181;m filter</td>
			<td>Sartorius</td>
			<td>514-7010</td>
			<td></td>
		</tr>
		<tr>
			<td>1 mL syringe</td>
			<td>Terumo</td>
			<td>1611127</td>
			<td></td>
		</tr>
		<tr>
			<td>100 mm Petri dish</td>
			<td>Dutscher</td>
			<td>193100</td>
			<td></td>
		</tr>
		<tr>
			<td>15 mL tube</td>
			<td>Corning Life Science</td>
			<td>734-1867</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL tube</td>
			<td>Corning Life Science</td>
			<td>734-1869</td>
			<td></td>
		</tr>
		<tr>
			<td>60 mm Petri dish</td>
			<td>Dutscher</td>
			<td>067003</td>
			<td></td>
		</tr>
		<tr>
			<td>70 &#181;m filter</td>
			<td>Miltenyi Biotec</td>
			<td>130-095-823</td>
			<td></td>
		</tr>
		<tr>
			<td>Binocular microscope</td>
			<td>Olympus</td>
			<td>SZX7</td>
			<td></td>
		</tr>
		<tr>
			<td>Curved forceps</td>
			<td>Fine Science Tools</td>
			<td>11152-10</td>
			<td></td>
		</tr>
		<tr>
			<td>Fine forceps</td>
			<td>Fine Science Tools</td>
			<td>91150-20</td>
			<td></td>
		</tr>
		<tr>
			<td>Large surgical scissors</td>
			<td>Fine Science Tools</td>
			<td>14008-14</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel</td>
			<td>Swann-morton</td>
			<td>233-5528</td>
			<td></td>
		</tr>
		<tr>
			<td>Shaker</td>
			<td>Infors HT</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Small surgical scissors</td>
			<td>Fine Science Tools</td>
			<td>91460-11</td>
			<td></td>
		</tr>
		<tr>
			<td>Small surgical spoon</td>
			<td>Bar Naor Ltd</td>
			<td>BN2706</td>
			<td></td>
		</tr>
		<tr>
			<td>T150 cm2 flask with filter cap</td>
			<td>Dutscher</td>
			<td>190151</td>
			<td></td>
		</tr>
		<tr>
			<td>Animal</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>P2 Wistar rat</td>
			<td>Janvier</td>
			<td>RjHAn:WI</td>
			<td></td>
		</tr>
	</tbody>
</table>

generation of oligodendrocytes and oligodendrocyte-conditioned medium for co-culture experiments

In the central nervous system, oligodendrocytes are well-known for their role in axon myelination, that accelerates the propagation of action potentials through saltatory conduction. Moreover, an increasing number of reports suggest that oligodendrocytes interact with neurons beyond myelination, notably through the secretion of soluble factors. Here, we present a detailed protocol allowing purification of oligodendroglial lineage cells from glial cell cultures also containing astrocytes and microglial cells. The method relies on overnight shaking at 37 &#176;C, which allows selective detachment of the overlying oligodendroglial cells and microglial cells, and the elimination of microglia by differential adhesion. We then describe the culture of oligodendrocytes and production of oligodendrocyte-conditioned medium (OCM). We also provide the kinetics of OCM treatment or oligodendrocytes addition to purified hippocampal neurons in co-culture experiments, studying oligodendrocyte-neuron interactions.

In this protocol, OL lineage cells are purified from glial cultures by shaking off astrocytes and microglia. Purity and phenotypic examination of OL cultures can be assessed by immunostaining with glial markers15. Analysis of the expression of different markers indicated that OL cultures were mostly pre-OLs with 90% &#177; 4% of O4+ cells, 85% &#177; 7% NG2+ cells, and 4.7% &#177; 2.1% of PLP+ cells, while 7.2% &#177; 2.5% of cells ...

Watch this Scientific Journal Video about Generation of Oligodendrocytes and Oligodendrocyte-Conditioned Medium for Co-Culture Experiments at JoVE.com

Generation of Oligodendrocytes and Oligodendrocyte-Conditioned Medium for Co-Culture Experiments

Herein, we display an efficient method for the purification of oligodendrocytes and production of oligodendrocyte-conditioned medium that can be used for co-culture experiments.

In the central nervous system, oligodendrocytes are well-known for their role in axon myelination, that accelerates the propagation of action potentials ...

generation-oligodendrocytes-oligodendrocyte-conditioned-medium-for-co

Research

JoVE Journal

Neuroscience

10.3K Views.  Institut du Cerveau et de la Moelle épinière, ICM. Herein, we display an efficient method for the purification of oligodendrocytes and production of oligodendrocyte-conditioned medium that can be used for co-culture experiments.

Video: Generation of Oligodendrocytes and Oligodendrocyte-Conditioned Medium for Co-Culture Experiments

Bilaminar Co-culture of Primary Rat Cortical Neurons and Glia

This video will guide you through the process of culturing rat cortical neurons in the presence of a glial feeder layer, a system known as a bilaminar or co-culture model. This system is suitable for a variety of experimental needs requiring either a glass or plastic growth substrate and can also be used for culture of other types of neurons.
Rat cortical neurons obtained from the late embryonic stage (E17) are plated on glass coverslips or tissue culture dishes facing a feeder layer of glia grown on dishes or plastic coverslips (known as Thermanox), respectively. The choice between the two configurations depends on the specific experimental technique used, which may require, or not, that neurons are grown on glass (e.g. calcium imaging versus Western blot). The glial feeder layer, an astroglia-enriched secondary culture of mixed glia, is separately prepared from the cortices of newborn rat pups (P2-4) prior to the neuronal dissection.
A major advantage of this culture system as compared to a culture of neurons only is the support of neuronal growth, survival, and differentiation provided by trophic factors secreted from the glial feeder layer, which more accurately resembles the brain environment in vivo. Furthermore, the co-culture can be used to study neuronal-glial interactions1.
At the same time, glia contamination in the neuronal layer is prevented by different means (low density culture, addition of mitotic inhibitors, lack of serum and use of optimized culture medium) leading to a virtually pure neuronal layer, comparable to other established methods1-3. Neurons can be easily separated from the glial layer at any time during culture and used for different experimental applications ranging from electrophysiology4, cellular and molecular biology5-8, biochemistry5, imaging and microscopy4,6,7,9,10. The primary neurons extend axons and dendrites to form functional synapses11, a process which is not observed in neuronal cell lines, although some cell lines do extend processes.
A detailed protocol of culturing rat hippocampal neurons using this co-culture system has been described previously4,12,13. Here we detail a modified protocol suited for cortical neurons. As approximately 20x106 cells are recovered from each rat embryo, this method is particularly useful for experiments requiring large numbers of neurons (but not concerned about a highly homogenous neuronal population). The preparation of neurons and glia needs to be planned in a time-specific manner. We will provide the step-by-step protocol for culturing rat cortical neurons as well as culturing glial cells to support the neurons.

Here we provide a protocol for culturing rat cortical neurons in the presence of a glial feeder layer. The cultured neurons establish polarity and create synapses, and can be separated from the glia for use in various applications, such as electrophysiology, calcium imaging, cell survival assays, immunocytochemistry, and RNA/DNA/protein isolation.

This video will guide you through the process of culturing rat cortical neurons in the presence of a glial feeder layer, a system known as a bilaminar or ...

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.

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 ...

Imaging Analysis of Neuron to Glia Interaction in Microfluidic Culture Platform (MCP)-based Neuronal Axon and Glia Co-culture System

Proper neuron to glia interaction is critical to physiological function of the central nervous system (CNS). This bidirectional communication is sophisticatedly mediated by specific signaling pathways between neuron and glia1,2 . Identification and characterization of these signaling pathways is essential to the understanding of how neuron to glia interaction shapes CNS physiology. Previously, neuron and glia mixed cultures have been widely utilized for testing and characterizing signaling pathways between neuron and glia. What we have learned from these preparations and other in vivo tools, however, has suggested that mutual signaling between neuron and glia often occurred in specific compartments within neurons (i.e., axon, dendrite, or soma)3. This makes it important to develop a new culture system that allows separation of neuronal compartments and specifically examines the interaction between glia and neuronal axons/dendrites. In addition, the conventional mixed culture system is not capable of differentiating the soluble factors and direct membrane contact signals between neuron and glia. Furthermore, the large quantity of neurons and glial cells in the conventional co-culture system lacks the resolution necessary to observe the interaction between a single axon and a glial cell.
	In this study, we describe a novel axon and glia co-culture system with the use of a microfluidic culture platform (MCP). In this co-culture system, neurons and glial cells are cultured in two separate chambers that are connected through multiple central channels. In this microfluidic culture platform, only neuronal processes (especially axons) can enter the glial side through the central channels. In combination with powerful fluorescent protein labeling, this system allows direct examination of signaling pathways between axonal/dendritic and glial interactions, such as axon-mediated transcriptional regulation in glia, glia-mediated receptor trafficking in neuronal terminals, and glia-mediated axon growth. The narrow diameter of the chamber also significantly prohibits the flow of the neuron-enriched medium into the glial chamber, facilitating probing of the direct membrane-protein interaction between axons/dendrites and glial surfaces.

Imaging Analysis of Neuron to Glia Interaction in Microfluidic Culture Platform MCP-based Neuronal Axon and Glia Co-culture System

This study describes the procedures of setting up a novel neuronal axon and (astro)glia co-culture platform. In this co-culture system, manipulation of direct interaction between a single axon (and single glial cell) becomes feasible, allowing mechanistic analysis of the mutual neuron to glial signaling.

Proper  neuron to glia interaction is critical to physiological function of the central  nervous system (CNS). This bidirectional communication is ...

Inhibitory Synapse Formation in a Co-culture Model Incorporating GABAergic Medium Spiny Neurons and HEK293 Cells Stably Expressing GABAA Receptors

Inhibitory neurons act in the central nervous system to regulate the dynamics and spatio-temporal co-ordination of neuronal networks. GABA (&#947;-aminobutyric acid) is the predominant inhibitory neurotransmitter in the brain. It is released from the presynaptic terminals of inhibitory neurons within highly specialized intercellular junctions known as synapses, where it binds to GABAA receptors (GABAARs) present at the plasma membrane of the synapse-receiving, postsynaptic neurons. Activation of these GABA-gated ion channels leads to influx of chloride resulting in postsynaptic potential changes that decrease the probability that these neurons will generate action potentials. 
During development, diverse types of inhibitory neurons with distinct morphological, electrophysiological and neurochemical characteristics have the ability to recognize their target neurons and form synapses which incorporate specific GABAARs subtypes. This principle of selective innervation of neuronal targets raises the question as to how the appropriate synaptic partners identify each other. 
To elucidate the underlying molecular mechanisms, a novel in vitro co-culture model system was established, in which medium spiny GABAergic neurons, a highly homogenous population of neurons isolated from the embryonic striatum, were cultured with stably transfected HEK293 cell lines that express different GABAAR subtypes. Synapses form rapidly, efficiently and selectively in this system, and are easily accessible for quantification. Our results indicate that various GABAAR subtypes differ in their ability to promote synapse formation, suggesting that this reduced in vitro model system can be used to reproduce, at least in part, the in vivo conditions required for the recognition of the appropriate synaptic partners and formation of specific synapses. Here the protocols for culturing the medium spiny neurons and generating HEK293 cells lines expressing GABAARs are first described, followed by detailed instructions on how to combine these two cell types in co-culture and analyze the formation of synaptic contacts.

Inhibitory Synapse Formation in a Co-culture Model Incorporating GABAergic Medium Spiny Neurons and HEK293 Cells Stably Expressing GABAA Receptors

The molecular mechanisms that co-ordinate the formation of inhibitory GABAergic synapses during ontogeny are largely unknown. To study these processes,we have developed a co-culture model system which incorporates embryonic medium spiny GABAergic neurons cultured together with stably transfected human embryonic kidney 293 (HEK293) cells expressing functional GABAA receptors.

Inhibitory neurons act in the central nervous system to regulate the dynamics and spatio-temporal co-ordination of neuronal networks. GABA ...

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 ...

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 ...

Preparing Fresh Retinal Slices from Adult Zebrafish for Ex Vivo Imaging Experiments

The retina is a complex tissue that initiates and integrates the first steps of vision. Dysfunction of retinal cells is a hallmark of many blinding diseases, and future therapies hinge on fundamental understandings about how different retinal cells function normally. Gaining such information with biochemical methods has proven difficult because contributions of particular cell types are diminished in the retinal cell milieu. Live retinal imaging can provide a view of numerous biological processes on a subcellular level, thanks to a growing number of genetically encoded fluorescent biosensors. However, this technique has thus far been limited to tadpoles and zebrafish larvae, the outermost retinal layers of isolated retinas, or lower resolution imaging of retinas in live animals. Here we present a method for generating live ex vivo retinal slices from adult zebrafish for live imaging via confocal microscopy. This preparation yields transverse slices with all retinal layers and most cell types visible for performing confocal imaging experiments using perfusion. Transgenic zebrafish expressing fluorescent proteins or biosensors in specific retinal cell types or organelles are used to extract single-cell information from an intact retina. Additionally, retinal slices can be loaded with fluorescent indicator dyes, adding to the method&#39;s versatility. This protocol was developed for imaging Ca2+ within zebrafish cone photoreceptors, but with proper markers it could be adapted to measure Ca2+ or metabolites in M&#252;ller cells, bipolar and horizontal cells, microglia, amacrine cells, or retinal ganglion cells. The retinal pigment epithelium is removed from slices so this method is not suitable for studying that cell type. With practice, it is possible to generate serial slices from one animal for multiple experiments. This adaptable technique provides a powerful tool for answering many questions about retinal cell biology, Ca2+, and energy homeostasis.

Preparing Fresh Retinal Slices from Adult Zebrafish for Ex Vivo Imaging Experiments

Imaging retinal tissue can provide single-cell information that cannot be gathered from traditional biochemical methods. This protocol describes preparation of retinal slices from zebrafish for confocal imaging. Fluorescent genetically encoded sensors or indicator dyes allow visualization of numerous biological processes in distinct retinal cell types.

The retina is a complex tissue that initiates and integrates the first steps of vision. Dysfunction of retinal cells is a hallmark of many blinding ...

Rapid and Specific Immunomagnetic Isolation of Mouse Primary Oligodendrocytes

The efficient and robust isolation and culture of primary oligodendrocytes (OLs) is a valuable tool for the in vitro study of the development of oligodendroglia as well as the biology of demyelinating diseases such as multiple sclerosis and Pelizaeus-Merzbacher-like disease (PMLD). Here, we present a simple and efficient selection method for the immunomagnetic isolation of stage three O4+ preoligodendrocytes cells from neonatal mice pups. Since immature OL constitute more than 80% of the rodent-brain white matter at postnatal day 7 (P7) this isolation method not only ensures high cellular yield, but also the specific isolation of OLs already committed to the oligodendroglial lineage, decreasing the possibility of isolating contaminating cells such as astrocytes and other cells from the mouse brain. This method is a modification of the techniques reported previously, and provides oligodendrocyte preparation purity above 80% in about 4 h.

We describe the immunomagnetic isolation of primary mouse oligodendrocytes, which allows the rapid and specific isolation of the cells for in vitro culture.

The efficient and robust isolation and culture of primary oligodendrocytes (OLs) is a valuable tool for the in vitro study of the development of ...

Conducting Hyperscanning Experiments with Functional Near-Infrared Spectroscopy

Concurrent brain recordings of two or more interacting persons, an approach termed hyperscanning, are gaining increasing importance for our understanding of the neurobiological underpinnings of social interactions, and possibly interpersonal relationships. Functional near-infrared spectroscopy (fNIRS) is well suited for conducting hyperscanning experiments because it measures local hemodynamic effects with a high sampling rate and, importantly, it can be applied in natural settings, not requiring strict motion restrictions. In this article, we present a protocol for conducting fNIRS hyperscanning experiments with parent-child dyads and for analyzing brain-to-brain synchrony. Furthermore, we discuss critical issues and future directions, regarding the experimental design, spatial registration of the fNIRS channels, physiological influences and data analysis methods. The described protocol is not specific to parent-child dyads, but can be applied to a variety of different dyadic constellations, such as adult strangers, romantic partners or siblings. To conclude, fNIRS hyperscanning has the potential to yield new insights into the dynamics of the ongoing social interaction, which possibly go beyond what can be studied by examining the activities of individual brains.

The present protocol describes how to conduct fNIRS hyperscanning experiments and analyze brain-to-brain synchrony. Further, we discuss challenges and possible solutions.

Concurrent brain recordings of two or more interacting persons, an approach termed hyperscanning, are gaining increasing importance for our understanding ...

Lipid Bilayer Experiments with Contact Bubble Bilayers for Patch-Clampers

Lipid bilayers provide a unique experimental platform for functional studies of ion channels, allowing the examination of channel-membrane interactions under various membrane lipid compositions. Among them, the droplet interface bilayer has gained popularity; however, the large membrane size hinders the recording of low electrical background noise. We have established a contact bubble bilayer (CBB) method that combines the benefits of planar lipid bilayer and patch-clamp methods, such as the ability to vary the lipid composition and to manipulate the bilayer mechanics, respectively. Using the setup for conventional patch-clamp experiments, CBB-based experiments can be readily performed. In brief, an electrolyte solution in a glass pipette is blown into an organic solvent phase (hexadecane), and the pipette pressure is maintained to obtain a stable bubble size. The bubble is spontaneously lined with a lipid monolayer (pure lipids or mixed lipids), which is provided from liposomes in the bubbles. Next, the two monolayer-lined bubbles (~50 &#181;m in diameter) at the tip of the glass pipettes are docked for bilayer formation. Introduction of channel-reconstituted liposomes into the bubble leads to the incorporation of channels in the bilayer, allowing for single-channel current recording with a signal-to-noise ratio comparable to that of patch-clamp recordings. CBBs with an asymmetric lipid composition are readily formed. The CBB is renewed repeatedly by blowing out the previous bubbles and forming new ones. Various chemical and physical perturbations (e.g., membrane perfusion and bilayer tension) can be imposed on the CBBs. Herein, we present the basic procedure for CBB formation.

Here, we present a protocol for the formation of lipid bilayers using a contact bubble bilayer method. A water bubble is blown into an organic solvent, whereby a monolayer is formed at the water-oil interface. Two pipettes are manipulated to dock the bubbles to form a bilayer.

Lipid bilayers provide a unique experimental platform for functional studies of ion channels, allowing the examination of channel-membrane interactions ...

Generation of Oligodendrocytes and Oligodendrocyte-Conditioned Medium for Co-Culture Experiments

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Rapid and Specific Immunomagnetic Isolation of Mouse Primary Oligodendrocytes

Conducting Hyperscanning Experiments with Functional Near-Infrared Spectroscopy

Lipid Bilayer Experiments with Contact Bubble Bilayers for Patch-Clampers