Name: in vitro phagocytosis of myelin debris by bone marrow-derived macrophages
Uploaded: 2017-12-30T15:00:00
Description: Watch this Scientific Journal Video about In Vitro Phagocytosis of Myelin Debris by Bone Marrow-Derived Macrophages at JoVE.com

The authors would like to thank Glenn Sanger-Hodgson, Media Specialist at the FSU College of Medicine for all his work in video production, editing, and voice-over.
This work was supported by the National Institutes of Health (R01GM100474 and R01GM072611).

The methods described here and in Section 2 have been approved by the Florida State University Institutional Animal Care and Use Committee (IACUC) and follows the guidelines set forth in the Guide for Care and Use of Laboratory Animals, 8th edition. All animals used in this in this protocol are house in a dedicated laboratory animal facility until use. No in vivo experimentation was performed prior to sacrifice. Animal numbers were based on experimental need using average cell and myelin coll...

<ol>
	<li>Wynn, T. A., Chawla, A., Pollard, J. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macrophage+biology+in+development,+homeostasis+and+disease.">Macrophage biology in development, homeostasis and disease.</a> Nature. 496 (7446), 445-455 (2013).</li><li>Unanue, E. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Antigen-presenting+function+of+the+macrophage.">Antigen-presenting function of the macrophage.</a> Annu Rev Immunol. 2, 395-428 (1984).</li><li>Cavaillon, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cytokines+and+macrophages.">Cytokines and macrophages.</a> Biomed Pharmacother. 48 (10), 445-453 (1994).</li><li>Ren, Y., Savill, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Apoptosis:+the+importance+of+being+eaten.">Apoptosis: the importance of being eaten.</a> Cell Death Differ. 5 (7), 563-568 (1998).</li><li>Wang, X., 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=Macrophages+in+spinal+cord+injury:+phenotypic+and+functional+change+from+exposure+to+myelin+debris.">Macrophages in spinal cord injury: phenotypic and functional change from exposure to myelin debris.</a> Glia. 63 (4), 635-651 (2015).</li><li>Goodrum, J. F., Earnhardt, T., Goines, N., Bouldin, T. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fate+of+myelin+lipids+during+degeneration+and+regeneration+of+peripheral+nerve:+an+autoradiographic+study.">Fate of myelin lipids during degeneration and regeneration of peripheral nerve: an autoradiographic study.</a> J Neurosci. 14 (1), 357-367 (1994).</li><li>Greenhalgh, A. D., David, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differences+in+the+Phagocytic+Response+of+Microglia+and+Peripheral+Macrophages+after+Spinal+Cord+Injury+and+Its+Effects+on+Cell+Death.">Differences in the Phagocytic Response of Microglia and Peripheral Macrophages after Spinal Cord Injury and Its Effects on Cell Death.</a> J Neurosci. 34 (18), 6316 (2014).</li><li>Sun, X., 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=Myelin+activates+FAK/Akt/NF-kappaB+pathways+and+provokes+CR3-dependent+inflammatory+response+in+murine+system.">Myelin activates FAK/Akt/NF-kappaB pathways and provokes CR3-dependent inflammatory response in murine system.</a> PLoS One. 5 (2), e9380 (2010).</li><li>Gensel, J. C., Zhang, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macrophage+activation+and+its+role+in+repair+and+pathology+after+spinal+cord+injury.">Macrophage activation and its role in repair and pathology after spinal cord injury.</a> Brain Res. , 1-11 (2015).</li><li>Bourre, J. M., Pollet, S., Daudu, O., Le Saux, F., Baumann, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myelin+consists+of+a+continuum+of+particles+of+different+density+with+varying+lipid+composition:+major+differences+are+found+between+normal+mice+and+quaking+mutants.">Myelin consists of a continuum of particles of different density with varying lipid composition: major differences are found between normal mice and quaking mutants.</a> Biochimie. 59 (10), 819-824 (1977).</li><li>Larocca, J. N., Norton, W. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Current Protocols in Cell Biology. , (2001).</li><li>Norton, W. T., Poduslo, S. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myelination+in+rat+brain:+method+of+myelin+isolation.">Myelination in rat brain: method of myelin isolation.</a> J Neurochem. 21 (4), 749-757 (1973).</li><li>Wang, X. Q., Duan, X. M., Liu, L. H., Fang, Y. Q., Tan, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Carboxyfluorescein+diacetate+succinimidyl+ester+fluorescent+dye+for+cell+labeling.">Carboxyfluorescein diacetate succinimidyl ester fluorescent dye for cell labeling.</a> Acta Biochim Biophys Sin (Shanghai). 37 (6), 379-385 (2005).</li><li>Parish, C. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescent+dyes+for+lymphocyte+migration+and+proliferation+studies.">Fluorescent dyes for lymphocyte migration and proliferation studies.</a> Immunol Cell Biol. 77 (6), 499-508 (1999).</li><li>Deutsch, M. J., Schriever, S. C., Roscher, A. A., Ensenauer, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Digital+image+analysis+approach+for+lipid+droplet+size+quantitation+of+Oil+Red+O-stained+cultured+cells.">Digital image analysis approach for lipid droplet size quantitation of Oil Red O-stained cultured cells.</a> Anal Biochem. 445, 87-89 (2014).</li><li>Kroner, 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=TNF+and+increased+intracellular+iron+alter+macrophage+polarization+to+a+detrimental+M1+phenotype+in+the+injured+spinal+cord.">TNF and increased intracellular iron alter macrophage polarization to a detrimental M1 phenotype in the injured spinal cord.</a> Neuron. 83 (5), 1098-1116 (2014).</li><li>Trouplin, V., 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=Marrow-derived+Macrophage+Production.">Marrow-derived Macrophage Production.</a> J Vis Exp. (81), e50966 (2013).</li><li>Chen, S., So, E. C., Strome, S. E., Zhang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Impact+of+Detachment+Methods+on+M2+Macrophage+Phenotype+and+Function.">Impact of Detachment Methods on M2 Macrophage Phenotype and Function.</a> J Immunol Methods. 426, 56-61 (2015).</li><li>Guo, L., 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=Rescuing+macrophage+normal+function+in+spinal+cord+injury+with+embryonic+stem+cell+conditioned+media.">Rescuing macrophage normal function in spinal cord injury with embryonic stem cell conditioned media.</a> Mol Brain. 9 (1), 48 (2016).</li><li>Bosco, D. B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+synthetic+matrix+metalloproteinase+inhibitor+reduces+human+mesenchymal+stem+cell+adipogenesis.">A new synthetic matrix metalloproteinase inhibitor reduces human mesenchymal stem cell adipogenesis.</a> PLOS ONE. 12 (2), e0172925 (2017).</li><li>Ram&#237;rez-Zacar&#237;as, J. L., Castro-Mu&#241;ozledo, F., Kuri-Harcuch, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Quantitation+of+adipose+conversion+and+triglycerides+by+staining+intracytoplasmic+lipids+with+oil+red+O.">Quantitation of adipose conversion and triglycerides by staining intracytoplasmic lipids with oil red O.</a> Histochem. 97 (6), 493-497 (1992).</li><li>Koopman, R., Schaart, G., Hesselink, M. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimisation+of+oil+red+staining+permits+combination+with+immunofluorescence+and+automated+quantification+of+lipids.">Optimisation of oil red staining permits combination with immunofluorescence and automated quantification of lipids.</a> Histochem Cell Biol. 116 (1), 63-68 (2001).</li><li>Fang, H., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Lipopolysaccharide-Induced+Macrophage+Inflammatory+Response+Is+Regulated+by+SHIP.">Lipopolysaccharide-Induced Macrophage Inflammatory Response Is Regulated by SHIP.</a> J Immunol. 173 (1), (2004).</li><li>Martinez, F. O., Sica, A., Mantovani, A., Locati, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macrophage+activation+and+polarization.">Macrophage activation and polarization.</a> Front Biosci. 13, (2008).</li><li>Mosser, D. M., Edwards, J. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Exploring+the+full+spectrum+of+macrophage+activation.">Exploring the full spectrum of macrophage activation.</a> Nat Rev Immunol. 8 (12), 958-969 (2008).</li></ol>

The procedures described here utilize both freshly isolated crude CNS myelin debris and primary bone marrow-derived macrophages. To reduce animal expenditures, we recommend that both brains and bone marrow cells be harvested from each mouse at the time of sacrifice. Two researchers working together can prepare both materials simultaneously. Alternatively, brains can be stored at -80 &#176;C in PBS supplemented with antibiotics prior to myelin debris isolation. It has been our experience that brains can be maintained in t...

Bone marrow-derived macrophages (BMDMs) are an important link between the innate and adaptive immune systems. As antigen presenting cells (APCs), they can communicate with lymphocytes via both antigen presentation and cytokine release1,2,3. However, as professional phagocytes, their primary function is to clear pathogens, aged cells, and cellular debris1,4. Following a spinal cord injury (SCI), substantial quantities of myelin debris is generated from dying oligodendrocytes, the cell type responsible for CNS axon myelination5. We and others have shown that clearance of myelin debris is primarily the responsibility of infiltrating BMDMs5,6,7. However, within spinal cord injury sites engulfment of myelin debris has been suggested to shift these normally anti-inflammatory cells towards a pro-inflammatory state5,8,9. As key mediators of neuro-inflammation in the injured spinal cord, BMDMs are important clinical targets.
To help investigate the influence of BMDMs in the injured spinal cord, we have developed an in vitro model to directly study how BMDMs respond to myelin debris. To improve biological relevance, both primary murine BMDMs and freshly isolated myelin debris are used in these investigations. As such, the methods presented here also detail the isolation and culture of primary murine BMDMs, and a modified sucrose gradient technique used to isolate murine CNS derived myelin debris10,11,12. Myelin debris can be readily labeled with a fluorescent dye, carboxyfluorescein succinimidyl ester (CFSE), to track its internalization by BMDMs. CFSE is well suited for this application because it is non-cytotoxic, and its narrow fluorescent spectrum permits multiplexing with other fluorescent probes13,14. Following phagocytosis, myelin debris lipids are transported through the lysosomes and packaged as neutral lipids into intracellular lipid droplets5. To quantify this intracellular lipid accumulation, we present an Oil Red O (ORO) staining method optimized for quantitative image analysis. This simple staining method produces robust reproducible results and quantification15. These methods facilitate the study of myelin debris phagocytosis and lipid retention with limited specialized equipment.

<table border="0" cellpadding="0" cellspacing="0" width="669">
	<tbody>
		<tr height="41">
			<td height="41" style="height:42px;width:180px;">DMEM</td>
			<td style="width:149px;">GE Healthcare Life Sciences</td>
			<td style="width:115px;">SH30243.01</td>
			<td style="width:225px;">High glucose with L-glutamine, sodium pyruvate</td>
		</tr>
		<tr height="62">
			<td height="62" style="height:63px;width:180px;">Penicillin-Streptomycin Solution</td>
			<td style="width:149px;">Corning</td>
			<td style="width:115px;">30-002-CI</td>
			<td style="width:225px;">100X Solution</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:42px;width:180px;">New Born Calf Serum (NCS)</td>
			<td style="width:149px;">Rocky Mountain Biologics</td>
			<td style="width:115px;">NBS-BBT-5XM</td>
			<td style="width:225px;">United States Origin</td>
		</tr>
		<tr height="83">
			<td height="83" style="height:83px;width:180px;">NCTC clone 929 [L cell, L-929, derivative of Strain L]&#160;</td>
			<td style="width:149px;">ATCC</td>
			<td style="width:115px;">CCL-1</td>
			<td style="width:225px;">L929 Cell Line of Conditioned Media Preparation</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:42px;width:180px;">24-well Cell Culture Plates</td>
			<td style="width:149px;">VWR</td>
			<td style="width:115px;">10062-896&#160;</td>
			<td style="width:225px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:21px;width:180px;">Cell Culture Dish</td>
			<td style="width:149px;">Greiner Bio-One</td>
			<td style="width:115px;">639960</td>
			<td style="width:225px;">Polystyrine, 145/20mm</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:42px;width:180px;">CFSE Cell Proliferation Kit</td>
			<td style="width:149px;">Thermo Fisher</td>
			<td style="width:115px;">C34570</td>
			<td style="width:225px;">DMSO for Reconsitution Provided</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:42px;width:180px;">Fluoro-gel with Tris Buffer&#160;</td>
			<td style="width:149px;">Electron Microscopy Sciences</td>
			<td style="width:115px;">17985-11</td>
			<td style="width:225px;"></td>
		</tr>
		<tr height="20">
			<td height="20" style="height:21px;width:180px;">Oil Red O</td>
			<td style="width:149px;">Sigma Aldrich</td>
			<td style="width:115px;">O0625</td>
			<td style="width:225px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:180px;">Equipment</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;">Materials</td>
			<td style="width:149px;">Company</td>
			<td style="width:115px;">Catalog Number</td>
			<td style="width:225px;">Comments</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:42px;width:180px;">Ultracentrifuge Tubes</td>
			<td style="width:149px;">Beckman Coulter</td>
			<td style="width:115px;">326823</td>
			<td style="width:225px;">Thinwall, Polypropylene, 38.5 mL, 25 x 89 mm</td>
		</tr>
		<tr height="62">
			<td height="62" style="height:63px;width:180px;">SW 32 Ti Ultracentrifuge Rotor</td>
			<td style="width:149px;">Beckman Coulter</td>
			<td style="width:115px;">369650</td>
			<td style="width:225px;">SW 32 Ti Rotor, Swinging Bucket, Titanium</td>
		</tr>
		<tr height="41">
			<td height="41" style="height:42px;width:180px;">Hand Held Rotary Homogenizer</td>
			<td style="width:149px;">Fisher Science</td>
			<td style="width:115px;">08-451-71</td>
			<td style="width:225px;"></td>
		</tr>
	</tbody>
</table>

in vitro phagocytosis of myelin debris by bone marrow-derived macrophages

Bone marrow-derived macrophages (BMDMs) are mature leukocytes that serve a critical physiological role as professional phagocytes capable of clearing a variety of particles. Normally, BMDMs are restricted from the central nervous system (CNS), but following an injury, they can readily infiltrate. Once within the injured CNS tissue, BMDMs are the primary cell type responsible for the clearance of injury-derived cellular debris, including large quantities of lipid rich myelin debris. The neuropathological ramifications of BMDM infiltration and myelin debris phagocytosis within the CNS are complex and not well understood. The protocols described here, allow for the direct in vitro study of BMDMs in the context of CNS injury. We cover murine BMDM isolation and culture, myelin debris preparation, and assays to assess BMDM myelin debris phagocytosis. These techniques produce robust quantifiable results without the need for significant specialized equipment or materials, yet can be easily customized to meet the needs of researchers.

Treatment of BMDMs with CFSE labeled myelin debris should yield clear internalization (Figure 2). While a 3-hour interaction time is sufficient for BMDMs to phagocytose enough added myelin debris for robust downstream detection, intracellular accumulation can be observed with as little as 1 hour of interaction. However, some myelin debris may still be present on the cell surface after washing. This may be due to insufficient washing, or particles not being fully internalized during the early...

Watch this Scientific Journal Video about In Vitro Phagocytosis of Myelin Debris by Bone Marrow-Derived Macrophages at JoVE.com

In Vitro Phagocytosis of Myelin Debris by Bone Marrow-Derived Macrophages

We present methods to assess the phagocytic capacity of primary murine bone marrow-derived macrophages using fluorescently labeled myelin debris and intracellular lipid droplet staining.

In Vitro Phagocytosis of Myelin Debris by Bone Marrow-Derived Macrophages

Bone marrow-derived macrophages (BMDMs) are mature leukocytes that serve a critical physiological role as professional phagocytes capable of clearing a ...

The overall goal of this protocol is to assess bone marrow-derived macrophage phagocytosis of brain-derived myelin debris. This protocol is designed to answer key questions in the field of neurotrauma. The advantage of this method is that allows for efficient and relatively cost-effective analysis of macrophage responses in vitro, specifically the phagocytic capacity of bone marrow-derived macrophages for myelin debris.This method can easily be adapted to investigate the effects of external modulators. Having saturated the mouse with 70%ethanol, make an opening in the abdominal skin. Pull the skin back to reveal the legs for dissection.Take care not to puncture the peritoneal cavity during this process. Once exposed, remove the legs by cutting at the ankle and the hip. Place the legs in ice-cold PBS supplemented with antibiotics.Repeat for the other leg. Wash the tissue in fresh ice-cold PBS supplemented with antibiotics to dislodge any particulates that may have adhered to the tissue during dissection. A gentle scraping motion applied along at the muscle will dislodge a majority of the unwanted tissue.With a scalpel and tweezers, free the tibia from the muscle and connective tissue. Once freed, remove both ends to expose the marrow cavity. Repeat this process for the femur.Affix a 25-gauge needle to a 20-millimeter syringe filled with complete bone marrow-derived macrophage media. Then flush the bone marrow cavity. The bone will appear white when sufficiently flushed.Agitate the collected marrow aspirates with an 18-gauge needle for 30 to 90 seconds in order to obtain a single cell suspension. Next pass the suspension through a sterile 70-micrometer pore size cell strainer. Evenly divide the cell suspensions in 145-centimeter cell culture dishes.Each mouse will provide enough for a total of three dishes. After seven days of culture, these dishes will typically be between 70 to 80%confluent with mature macrophages. To isolate crude myelin debris from brains, a series of sucrose gradient ultracentrifugation steps are carried out.To begin, 10 to 12 brains are dissected from mice eight to 10 weeks of age. The brains are then homogenized in 0.32 molar sucrose solution, and then layered onto a 0.383 molar sucrose solution cushion to create a discontinuous gradient. Following centrifugation, the crude myelin debris is found at the interface between the layers.This is collected and dispensed into a Tris buffer solution and centrifuged again to pellet the myelin debris. The pellet is resuspended again in Tris buffer solution and split between two tubes for additional cenetrifugation. To begin, remove the entire brain and place it in a dish with ice-cold 0.32 molar sucrose solution.Using sterile surgical scissors, cut the collected brains into pieces approximately five millimeters in size. This step aids in the subsequent homogenization process. Collect the tissue into a 50-milliliter tube.Using a rotary homogenizer, homogenize the tissue into a smooth slurry. Make sure that all large visible brain solids have been thoroughly homogenized. Into an ultracentrifuge tube containing 20 milliliters of 0.83 molar sucrose solution, generate and homogenate, taking care to maintain the separation.Carefully balance each tube using the 0.32 molar sucrose solution. Once finished, transfer the tubes to an appropriate centrifuge rotor and spin for 45 minutes at 100, 000 times gravity, four degrees Celsius. Ensure that acceleration and deceleration are set to their minimum values.Once centrifugation is complete, the myelin debris will be visible between the sucrose density interface. Gently collect the myelin debris. Once collected, add Tris buffer to the myelin debris.Homogenize again with a rotary homogenizer. Divide the homogenate between six clean ultracentrifuge tubes and balance the tubes as needed with additional Tris buffer. Centrifuge the collected myelin debris again at 100, 000 times gravity, four degrees Celsius for 45 minutes, with acceleration and deceleration set to their maximum values.After centrifugation, the myelin will have been pelleted. Using the Tris buffer, resuspend the pellet. Combine the resuspensions and ultracentrifuge again.After centrifugation, a tightly-packed pellet is formed. Decant the supernate. Resuspend the pellet in sterile PBS.Equally divide the resuspended myelin debris into preweighed microcentrifuge tubes. After centrifugation for 10 minutes at 22, 000 times gravity, remove the PBS supernate. After weighing the pellet, resuspend to a concentration of 100 milligrams per milliliter with PBS.The resulting crude myelin debris is now suitable for study of phagocytosis. CFSE labeling myelin debris can be used to track early internalization as well as intracellular trafficking. Unlabeled myelin debris is compatible with Oil Red-O lipid staining to assess the storage and metabolism of the internalized lipids.If you are using myelin debris that has been stored at negative 80 degrees Celsius, you'll first want to resuspend with a 29-gauge needle. Resuspend 10 milligrams of pelleted myelin debris in 200 microliters of PBS. Then add two microliters of five-millimolar CFSE solution.Pipette to mix. After a 30 minute incubation, protected from light and subsequent washing, resuspend the myelin debris to 100 milligrams per milliliter with PBS. Following culture and fixation with 4%paraformaldehyde, add 100%propylene glycol to each well.After incubating for five minutes at room temperature, add Oil Red-O staining solution to each well. Incubate for eight minutes at 60 degrees Celsius with gentle agitation. Gently tilt the plate to allow for complete aspiration of the Oil Red-O stain.To each well add 85%propylene glycol. After five minutes of incubation at room temperature, wash wells with PBS and stain cells with your choice of nuclear dye. Representative light microscopy images of bone marrow cells during culture.24 hours after initial seeding, few adherent cells are present. However, in the presence of macrophage colony-stimulating factor, M-CSF, leukocyte precursor cells begin to undergo differentiation. After seven days of culture in the presence of M-CSF, precursor cells are fully differentiated into mature bone marrow-derived macrophages capable of phagocytosis.Using this method, a single eight-to 10-week-old C57 black 6J mouse will typically yield 18 to 24 million bone marrow macrophages. To visualize internalization, CFSE-labeled myelin debris is added to bone marrow-derived macrophage cultures. Cells were treated with one milligram per milliliter CFSE-labeled myelin debris for one hour prior to washing and fixation with 4%paraformaldehyde.Internalized myelin debris can be visualized using standard GFP filter sets on an epifluorescent-capable microscope. To demonstrate how myelin lipid accumulation changes over time, macrophages were treated with unlabeled myelin debris for 90 minutes, then washed and fixed at various time points. Immediately following washing, few lipid droplets are visible.However, as time progresses, more lipid droplets become visible, reaching a maximum approximately 24 hours after washing. Macrophages will begin to metabolize for efflux to lipid stores, reducing the number of stainable droplets. To quantify Oil Red-O staining, five randomly-obtained images from each time point sample were obtained using an epifluorescent-capable microscope.The Oil Red-O-stained area was determined for each well using images captured in the DsRed channel. The total number of cells is determined by counting the number of nuclei present in each field. This graph shows the resulting quantification.A steady increase in Oil Red-O-positive signal is typical, as the bone marrow-derived macrophages convert internalized myelin lipids into neutral lipids. A decrease in Oil Red-O-positive signal follows the peak at 24 hours as macrophages begin to metabolize or efflux the lipids. Having watched this video, you should have a good idea of how to isolate and culture primary bone marrow-derived macrophages, as well as how to study their interaction with freshly isolated brain-derived myelin debris.The most important part of these procedures is the proper maintenance of aseptic technique at all times. Because macrophages can robustly respond to small quantities of pathogen-associated molecules, it is critical to minimize any potential interaction that can bias results. The main advantage of these techniques is that they make us of biologically relevant primary cells and fresh myelin debris, while eliminating the amount of specialized equipment needed.Additionally, with some user optimization, these methods can be easily adapted to address a wide variety of questions regarding the response of bone marrow-derived macrophages to myelin debris. By making use of both florescently-labeled myelin debris and Oil Red-O staining of myelinated macrophage, it is possible to investigate potential therapeutic interventions for patients suffering from a variety of neurotrauma. The overall goal of such work is for remote macrophage-mediated cellular debris clearance to promote inflammation resolution.

in-vitro-phagocytosis-myelin-debris-bone-marrow-derived

Research

JoVE Journal

Neuroscience

Transfection of Mouse Retinal Ganglion Cells by in vivo Electroporation

The targeting and refinement of RGC projections to the midbrain is a popular and powerful model system for studying how precise patterns of neural connectivity form during development. In mice, retinofugal projections are arranged in a topographic manner and form eye-specific layers in the Lateral Geniculate Nucleus (dLGN) of the thalamus and the Superior Colliculus (SC). The development of these precise patterns of retinofugal projections has typically been studied by labeling populations of RGCs with fluorescent dyes and tracers, such as horseradish peroxidase1-4. However, these methods are too coarse to provide insight into developmental changes in individual RGC axonal arbor morphology that are the basis of retinotopic map formation. They also do not allow for the genetic manipulation of RGCs.
Recently, electroporation has become an effective method for providing precise spatial and temporal control for delivery of charged molecules into the retina5-11. Current retinal electroporation protocols do not allow for genetic manipulation and tracing of retinofugal projections of a single or small cluster of RGCs in postnatal mice. It has been argued that postnatal in vivo electroporation is not a viable method for transfecting RGCs since the labeling efficiency is extremely low and hence requires targeting at embryonic ages when RGC progenitors are undergoing differentiation and proliferation6. 
In this video we describe an in vivo electroporation protocol for targeted delivery of genes, shRNA, and fluorescent dextrans to murine RGCs postnatally. This technique provides a cost effective, fast and relatively easy platform for efficient screening of candidate genes involved in several aspects of neural development including axon retraction, branching, lamination, regeneration and synapse formation at various stages of circuit development. In summary we describe here a valuable tool which will provide further insights into the molecular mechanisms underlying sensory map development.

Transfection of Mouse Retinal Ganglion Cells by in vivo Electroporation

We demonstrate an in vivo electroporation protocol for transfecting single or small clusters of retinal ganglion cells (RGCs) and other retinal cell types in postnatal mice over a wide range of ages. The ability to label and genetically manipulate postnatal RGCs in vivo is a powerful tool for developmental studies.

The targeting and refinement of RGC projections to the midbrain is a popular and powerful model system for studying how precise patterns of neural ...

Simultaneous ex vivo Functional Testing of Two Retinas by in vivo Electroretinogram System

An In vivo electroretinogram (ERG) signal is composed of several overlapping components originating from different retinal cell types, as well as noise from extra-retinal sources. Ex vivo ERG provides an efficient method to dissect the function of retinal cells directly from an intact isolated retina of animals or donor eyes. In addition, ex vivo ERG can be used to test the efficacy and safety of potential therapeutic agents on retina tissue from animals or humans. We show here how commercially available in vivo ERG systems can be used to conduct ex vivo ERG recordings from isolated mouse retinas. We combine the light stimulation, electronic and heating units of a standard in vivo system with custom-designed specimen holder, gravity-controlled perfusion system and electromagnetic noise shielding to record low-noise ex vivo ERG signals simultaneously from two retinas with the acquisition software included in commercial in vivo systems. Further, we demonstrate how to use this method in combination with pharmacological treatments that remove specific ERG components in order to dissect the function of certain retinal cell types.

Simultaneous ex vivo Functional Testing of Two Retinas by in vivo Electroretinogram System

Ex vivo ERG can be used to record electrical activity of retinal cells directly from isolated intact retinas of animals or humans. We demonstrate here how common in vivo ERG systems can be adapted for ex vivo ERG recordings in order to dissect the electrical activity of retinal cells.

An In vivo electroretinogram (ERG) signal is composed of several overlapping components originating from different retinal cell types, as well as noise ...

A Novel In Vitro Live-imaging Assay of Astrocyte-mediated Phagocytosis Using pH Indicator-conjugated Synaptosomes

Astrocytes are the major cell type in the brain and directly contact synapses and blood vessels. Although microglial cells have been considered the major immune cells and only phagocytes in the brain, recent studies have shown that astrocytes also participate in various phagocytic processes, such as developmental synapse elimination and clearance of amyloid beta plaques in Alzheimer&#39;s disease (AD). Despite these findings, the efficiency of astrocyte engulfment and degradation of their targets is unclear compared with that of microglia. This lack of information is mostly due to the lack of an assay system in which the kinetics of astrocyte- and microglia-mediated phagocytosis are easily comparable. To achieve this goal, we have developed a long-term live-imaging in vitro phagocytosis assay to evaluate the phagocytic capacity of purified astrocytes and microglia. In this assay, real-time detection of engulfment and degradation is possible using pH indicator-conjugated synaptosomes, which emit bright red fluorescence in acidic organelles, such as lysosomes. Our novel assay provides simple and effective detection of phagocytosis through live-imaging. In addition, this in vitro phagocytosis assay can be used as a screening platform to identify chemicals and compounds that can enhance or inhibit the phagocytic capacity of astrocytes. As synaptic pruning malfunction and pathogenic protein accumulation have been shown to cause mental disorders or neurodegenerative diseases, chemicals and compounds that modulate the phagocytic capacity of glial cells should be helpful in treating various neurological disorders.

A Novel In Vitro Live-imaging Assay of Astrocyte-mediated Phagocytosis Using pH Indicator-conjugated Synaptosomes

This protocol presents an in vitro live-imaging phagocytosis assay to measure the phagocytic capacity of astrocytes. Purified rat astrocytes and microglia are used along with pH indicator-conjugated synaptosomes. This method can detect real-time engulfment and degradation kinetics and provides a suitable screening platform to identify factors modulating astrocyte phagocytosis.

Astrocytes are the major cell type in the brain and directly contact synapses and blood vessels. Although microglial cells have been considered the major ...

Ocular Kinematics Measured by In Vitro Stimulation of the Cranial Nerves in the Turtle

After animals are euthanized, their tissues begin to die. Turtles offer an advantage because of a longer survival time of their tissues, especially when compared to warm-blooded vertebrates. Because of this, in vitro experiments in turtles can be performed for extended periods of time to investigate the neural signals and control of their target actions. Using an isolated head preparation, we measured the kinematics of eye movements in turtles, and their modulation by electrical signals carried by cranial nerves. After the brain was removed from the skull, leaving the cranial nerves intact, the dissected head was placed in a gimbal to calibrate eye movements. Glass electrodes were attached to cranial nerves (oculomotor, trochlear, and abducens) and stimulated with currents to evoke eye movements. We monitored eye movements with an infrared video tracking system and quantified rotations of the eyes. Current pulses with a range of amplitudes, frequencies, and train durations were used to observe effects on responses. Because the preparation is separated from the brain, the efferent pathway going to muscle targets can be examined in isolation to investigate neural signaling in the absence of centrally processed sensory information.

Ocular Kinematics Measured by In Vitro Stimulation of the Cranial Nerves in the Turtle

This protocol describes how to use an in vitro isolated turtle head preparation to measure the kinematics of their eye movements. After removal of the brain from the cranium, cranial nerves can be stimulated with currents to quantify rotations of the eye and changes in pupil sizes.

After animals are euthanized, their tissues begin to die. Turtles offer an advantage because of a longer survival time of their tissues, especially when ...

Modeling Charcot-Marie-Tooth Disease In Vitro by Transfecting Mouse Primary Motoneurons

Neurodegeneration of spinal motoneurons (MNs) is implicated in a large spectrum of neurological disorders including amyotrophic lateral sclerosis, Charcot-Marie-Tooth disease, and spinal muscular atrophy, which are all associated with muscular atrophy. Primary cultures of spinal MNs have been used widely to demonstrate the involvement of specific genes in such diseases and characterize the cellular consequences of their mutations. This protocol models a primary MN culture derived from the seminal work of Henderson and colleagues more than twenty years ago. First, we detail a method of dissecting the anterior horns of the spinal cord from a mouse embryo and isolating the MNs from neighboring cells using a density gradient. Then, we present a new way of efficiently transfecting MNs with expression plasmids using magnetofection. Finally, we illustrate how to fix and immunostain primary MNs. Using neurofilament mutations that cause Charcot-Marie-Tooth disease type 2, this protocol demonstrates a qualitative approach to expressing proteins of interest and studying their involvement in MN growth, maintenance, and survival.

Modeling Charcot-Marie-Tooth Disease In Vitro by Transfecting Mouse Primary Motoneurons

The goal of this technique is to prepare a highly enriched culture of primary motoneurons (MNs) from murine spinal cord. To evaluate the consequences of mutations causing MN diseases, we describe here the isolation of these isolated MNs and their transfection by magnetofection.

Neurodegeneration of spinal motoneurons (MNs) is implicated in a large spectrum of neurological disorders including amyotrophic lateral sclerosis, ...

Real-time In Vitro Monitoring of Odorant Receptor Activation by an Odorant in the Vapor Phase

Olfactory perception begins with the interaction of odorants with odorant receptors (OR) expressed by olfactory sensory neurons (OSN). Odor recognition follows a combinatorial coding scheme, where one OR can be activated by a set of odorants and one odorant can activate a combination of ORs. Through such combinatorial coding, organisms can detect and discriminate between a myriad of volatile odor molecules. Thus, an odor at a given concentration can be described by an activation pattern of ORs, which is specific to each odor. In that sense, cracking the mechanisms that the brain uses to perceive odor requires the understanding odorant-OR interactions. This is why the olfaction community is committed to &#34;de-orphanize&#34;&#160;these receptors. Conventional in vitro systems used to identify odorant-OR interactions have utilized incubating cell media with odorant, which is distinct from the natural detection of odors via vapor odorants dissolution into nasal mucosa before interacting with ORs. Here, we describe a new method that allows for real-time monitoring of OR activation via vapor-phase odorants. Our method relies on measuring cAMP release by luminescence using the Glosensor assay. It bridges current gaps between in vivo and in vitro approaches and provides a basis for a biomimetic volatile chemical sensor.

Physiologically, odorant receptors are activated by odorant molecules inhaled in the vapor phase. However, most in vitro systems utilize liquid phase odorant stimulation. Here, we present a method that allows real-time in vitro monitoring of odorant receptor activation upon odorant stimulation in vapor phase.

Olfactory perception begins with the interaction of odorants with odorant receptors (OR) expressed by olfactory sensory neurons (OSN). Odor recognition ...

Rapid Isolation of Dorsal Root Ganglion Macrophages

There are growing interests to study the molecular and cellular interactions among immune cells and sensory neurons in the dorsal root ganglia after peripheral nerve injury. Peripheral monocytic cells, including macrophages, are known to respond to a tissue injury through phagocytosis, antigen presentation, and cytokine release. Emerging evidence has implicated the contribution of dorsal root ganglia macrophages to neuropathic pain development and axonal repair in the context of nerve injury. Rapidly phenotyping (or &#8220;rapid isolation of&#8221;) the response of dorsal root ganglia macrophages in the context of nerve injury is desired to identify the unknown neuroimmune factors. Here we demonstrate how our lab rapidly and effectively isolates macrophages from the dorsal root ganglia using an enzyme-free mechanical dissociation protocol. The samples are kept on ice throughout to limit cellular stress. This protocol is far less time consuming compared to the standard enzymatic protocol and has been routinely used for our Fluorescence-activated Cell Sorting analysis.

Here we present a mechanical dissociation protocol to rapidly isolate macrophages from the dorsal root ganglion for phenotyping and functional analysis.

There are growing interests to study the molecular and cellular interactions among immune cells and sensory neurons in the dorsal root ganglia after ...

Positron Emission Tomography Imaging for In Vivo Measuring of Myelin Content in the Lysolecithin Rat Model of Multiple Sclerosis

Multiple sclerosis (MS) is a neuroinflammatory disease with expanding axonal and neuronal degeneration and demyelination in the central nervous system, leading to motor dysfunctions, psychical disability, and cognitive impairment during MS progression. Positron emission tomography (PET) is an imaging technique able to quantify in vivo cellular and molecular alterations.
Radiotracers with affinity to intact myelin can be used for in vivo imaging of myelin content changes over time. It is possible to detect either an increase or decrease in myelin content, what means this imaging technique can detect demyelination and remyelination processes of the central nervous system. In this protocol we demonstrate how to use PET imaging to detect myelin changes in the lysolecithin rat model, which is a model of focal demyelination lesion (induced by stereotactic injection) (i.e., a model of multiple sclerosis disease). 11C-PIB PET imaging was performed at baseline, and 1 week and 4 weeks after stereotaxic injection of lysolecithin 1% in the right striatum (4 &#181;L) and corpus callosum (3 &#181;L) of the rat brain, allowing quantification of focal demyelination (injection site after 1 week) and the remyelination process (injection site at 4 weeks).
Myelin PET imaging is an interesting tool for monitoring in vivo changes in myelin content which could be useful for monitoring demyelinating disease progression and therapeutic response.

Positron Emission Tomography Imaging for In Vivo Measuring of Myelin Content in the Lysolecithin Rat Model of Multiple Sclerosis

This protocol has the aim of monitoring in vivo myelin changes (demyelination and remyelination) by positron emission tomography (PET) imaging in an animal model of multiple sclerosis.

Multiple sclerosis (MS) is a neuroinflammatory disease with expanding axonal and neuronal degeneration and demyelination in the central nervous system, ...

In vitro Quantitative Imaging Assay for Phagocytosis of Dead Neuroblastoma Cells by iPSC-Macrophages

Microglia orchestrate neuroimmune responses in several neurodegenerative diseases, including Parkinson&#39;s disease and Alzheimer&#39;s disease. Microglia clear up dead and dying neurons through the process of efferocytosis, a specialized form of phagocytosis. The phagocytosis function can be disrupted by environmental or genetic risk factors that affect microglia. This paper presents a rapid and simple in vitro&#160;microscopy protocol for studying microglial efferocytosis in an induced pluripotent stem cell (iPSC) model of microglia, using a human neuroblastoma cell line (SH-SY5Y) labeled with a pH-sensitive dye for the phagocytic cargo. The procedure results in a high yield of dead neuroblastoma cells, which display surface phosphatidylserine, recognized as an &#34;eat-me&#34; signal by phagocytes. The 96-well plate assay is suitable for live-cell time-lapse imaging, or the plate can be successfully fixed prior to further processing and quantified by high-content microscopy. Fixed-cell high-content microscopy enables the assay to be scaled up for screening of small molecule inhibitors or assessing the phagocytic function of genetic variant iPSC lines. While this assay was developed to study phagocytosis of whole dead neuroblastoma cells by iPSC-macrophages, the assay can be easily adapted for other cargoes relevant to neurodegenerative diseases, such as synaptosomes and myelin, and other phagocytic cell types.

Neurodegenerative diseases are associated with dysregulated microglia functions. This article outlines an in vitro assay of phagocytosis of neuroblastoma cells by iPSC-macrophages. Quantitative microscopy readouts are described for both live-cell time-lapse imaging and fixed-cell high-content imaging.

Microglia orchestrate neuroimmune responses in several neurodegenerative diseases, including Parkinson&#39;s disease and Alzheimer&#39;s disease. ...

Human Microglia-like Cells: Differentiation from Induced Pluripotent Stem Cells and In Vitro Live-cell Phagocytosis Assay using Human Synaptosomes

Microglia are the resident immune cells of myeloid origin that maintain homeostasis in the brain microenvironment and have become a key player in multiple neurological diseases. Studying human microglia in health and disease represents a challenge due to the extremely limited supply of human cells. Induced pluripotent stem cells (iPSCs) derived from human individuals can be used to circumvent this barrier. Here, it is demonstrated how to differentiate human iPSCs into microglia-like cells (iMGs) for in vitro experimentation. These iMGs exhibit the expected and physiological properties of microglia, including microglia-like morphology, expression of proper markers, and active phagocytosis. Additionally, documentation for isolating and labeling synaptosome substrates derived from human iPSC-derived lower motor neurons (i3LMNs) is provided. A live-cell, longitudinal imaging assay is used to monitor engulfment of human synaptosomes labeled with a pH-sensitive dye, allowing for investigations of iMG's phagocytic capacity. The protocols described herein are broadly applicable to different fields that are investigating human microglia biology and the contribution of microglia to disease.

Human Microglia-like Cells: Differentiation from Induced Pluripotent Stem Cells and In Vitro Live-cell Phagocytosis Assay using Human Synaptosomes

This protocol describes the differentiation process of human induced pluripotent stem cells (iPSCs) into microglia-like cells for in vitro experimentation. We also include a detailed procedure for generating human synaptosomes from iPSC-derived lower motor neurons that can be used as a substrate for in vitro phagocytosis assays using live-cell imaging systems.

Microglia are the resident immune cells of myeloid origin that maintain homeostasis in the brain microenvironment and have become a key player in multiple ...