This work was supported by grants from the scholarship granted by the National Council of Science and Technology (CONACYT) (702361). The authors acknowledge the Ph.D. program in Biological Chemical Sciences of the National School of Biological Sciences of the National Polytechnic Institute.

The study was conducted in accordance with the official Mexican standard NOM-062-ZOO-1999 and the guide for the care and use of laboratory animals. Approval for the study was obtained from the Research, Ethics, and Biosafety Committees of the Mexico Children&#39;s Hospital (HIM/2023/006) and the Research and Bioethics Committee of the General Hospital of Mexico Eduardo Liceaga (DI/21/501/04/62). Three C57BL/6 mice aged 6 to 8 weeks were obtained from the Mexico Children&#39;s Hospital, where they were raised under isolated conditions in ventilated racks, in compliance with institutional animal care and use guidelines.
1. Preparation of materials and reagents
<ol>
	<li>Pre-warm Ca2+ and Mg2+ free PBS as well as Hank&#39;s balanced salt solution (HBSS) to 37 &#176;C.</li>
	<li>Supplement the HBSS solution with 100 &#181;g/mL of Liberase&#160;and 4 &#181;g/mL of DNase (HBSS-LD). Ensure that the solution maintains a physiological pH of 7.4. 
	NOTE: 1 mL of working solution per spinal cord will be necessary.</li>
	<li>Prepare an isotonic 90% solution for density gradient centrifugation (commercially available, see Table of Materials) and prewarm it to 37 &#176;C.</li>
	<li>Prepare the staining buffer by combining 5% heat-inactivated fetal bovine serum (FBS) with PBS, and store the mixture on ice.</li>
	<li>Pre-warm Dulbecco&#39;s Modified Eagle&#39;s Medium-high glucose (1g/L) (DMEM) to 37 &#176;C.</li>
	<li>Supplement the DMEM medium with 10% FBS, 2 mM L-glutamine, 200 U/mL penicillin, 200 &#181;g/mL of streptomycin, and 500 pg/mL of amphotericin B (see Table of Materials) to prepare DMEM-S.</li>
</ol>
2. Dissection and preparation of the spinal cord
<ol>
	<li>Euthanize the mouse with an intraperitoneal overdose of pentobarbital at a dose of 150 mg/kg. Sterilize the mouse&#39;s thorax and back using 70% ethanol. 
	NOTE:&#160;Confirm euthanasia was successful before proceeding with the mouse dissection.</li>
	<li>Shave the thoracolumbar region and secure the extremities to the dissection board using adhesive tape.</li>
	<li>Using a scalpel, make a careful incision along the dorsal midline from the occipital to the sacral region (Figure 2).</li>
	<li>With the assistance of a stereoscopic surgical microscope, dissect in layers until reaching the lumbar spine and identifying the last costal arch. 
	NOTE: The 13 costal arches are articulated in the thoracic vertebrae; when dissected, they become visible superior to the L1 vertebra2.</li>
	<li>Determine the last cervical vertebra and the sacrum, then make a cut to separate the spine (Figure 2).</li>
	<li>Utilizing dissecting forceps, perform a dorsal laminectomy of the vertebrae to extract the spinal cord (Figure 3A-D). 
	NOTE: Except for the first two cervical vertebrae (atlas and axis), all movable vertebrae share a common morphological design in various regions (cervical, thoracic, or lumbar). Each typical movable vertebra features a cylindrical vertebral body at its anterior end. Attached to the back of the body is a bony arch known as the vertebral arch (neural arch), consisting of laminae and spinous processes. Between these structures lies the vertebral foramen15.</li>
	<li>Remove the nerves emerging through the foramina (dorsal and ventral roots) that constitute the peripheral nervous system and may contain infiltrated macrophages (Figure 3D). 
	NOTE: It is unnecessary to remove the pia mater or meninges as the density gradient medium effectively eliminates contaminating astrocytes. Additionally, retaining the meninges reduces purification time and enhances viability.</li>
</ol>
3. Tissue digestion and isolation of microglia
<ol>
	<li>Place the spinal cord on the dissecting board, and using Vannas scissors, cut the spinal cord into 2 mm pieces, yielding an average of 10 pieces.</li>
	<li>Transfer the sections of the spinal cord to a 2 mL flat-bottom microtube (Figure 3E,F).</li>
	<li>Add 1 mL of the HBSS-LD working solution (step 1.2). Incubate at 37 &#176;C for 25 min, vigorously vortexing every 5 min.</li>
	<li>Pass the contents of each digestion through a 40 &#181;m strainer, and then add 7 mL of HBSS with 2% FBS to neutralize the digestion.</li>
	<li>Crush the remaining tissue using a 1 mL syringe plunger. Centrifuge the suspension in a 50 mL conical tube for 5 min at 220 x g, 4 &#176;C.</li>
	<li>Discard the supernatant using a 1 mL micropipette, and resuspend the pellet in 2 mL of HBSS with 2% FBS in a 15 mL conical tube. Combine with 2 mL of 90% isotonic density gradient medium. Centrifuge for 25 min at 160 x g, 18 &#176;C. 
	NOTE: Utilize slow acceleration and avoid using the brake.</li>
	<li>Use a transfer pipette to retrieve the interface and transfer it to a 15 mL conical tube. Wash the cells with 10 mL of PBS and centrifuge for 5 min at 220 x g, 4 &#176;C.</li>
	<li>Resuspend the cells in DMEM-S (step 1.6) and keep them stored on ice.</li>
</ol>
4. Determining purity/viability
<ol>
	<li>For quantifying viable cells using a hemocytometer chamber, employ a 0.4% Trypan blue stain (see Table of Materials). 
	NOTE: On average, a single mouse provides 4-6 million cells.</li>
	<li>To quantify viable cells via a flow cytometer, employ commercially available amine-reactive fluorescent dye staining (see Table of Materials).
	<ol>
		<li>Transfer 1 million cells into a 5 mL polystyrene round-bottom (FACS) tube. Dilute the fluorescent dye with PBS at a ratio of 1:1000 (creating the viability working solution).</li>
		<li>Incubate the samples with the viability solution in the dark at 4 &#176;C for 30 min. Wash the cells with ice-cold PBS twice. Resuspend the cells in 400 &#181;L of staining buffer (step 1.4).</li>
		<li>Block the cells with 2.4G2 anti-FcRIII/I (see Table of Materials) in the ice-cold staining buffer for 15 min at 4 &#176;C.</li>
		<li>Formulate the antibody staining cocktail by adding the fluorescent-labeled monoclonal antibodies CD45-PerCP and CD11b-eFluor 450 to the staining buffer (at a dilution of 1:300) (see Table of Materials). 
		NOTE: While both techniques are available, choose the one that best aligns with the subsequent protocol.</li>
		<li>Incubate the samples with the antibody staining cocktail in the dark at 4 &#176;C for 30 min. Wash the cells with ice-cold staining buffer twice. Resuspend the cells in 400 &#181;L of staining buffer.</li>
		<li>Acquire 250,000 events on a flow cytometer, as outlined by the gating strategy in step 6 (Figure 4).</li>
	</ol>
	</li>
</ol>
5. Immunofluorescent staining
<ol>
	<li>Place a pretreated coverslip into a well of a 6-well plate. 
	NOTE: To treat coverslips, place them in a Petri dish with 500 &#181;L of L-polylysine (0.01 mg/mL, see Table of Materials) solution and incubate for 1 h. Afterward, wash them three times with distilled water and allow them to dry.</li>
	<li>Seed 200,000 cells onto the treated coverslip using 500 &#181;L of DMEM-S solution. Incubate for 24 h.</li>
	<li>Remove the coverslips and fix the cells using 3.7% paraformaldehyde (PFA) for 20 min at room temperature. Wash the coverslips three times with ice-cold PBS.</li>
	<li>Permeabilize the cells with 0.2% Triton X-100 in PBS for 15&#160;min at room temperature. Subsequently, wash the coverslips three times with cold PBS. Block the cells with 0.2% BSA in PBS for 1 h at room temperature.</li>
	<li>Dilute the fluorescence-labeled monoclonal antibodies (at a 1:300 dilution, see Table of Materials) in the blocking solution and incubate for 1 h at room temperature. Wash the coverslips three times with ice-cold PBS.</li>
	<li>Apply mounting medium containing DAPI onto the slide, and then seal it with a coverslip. 
	NOTE: The slides can be immediately analyzed using a fluorescence or confocal microscope, or they can be stored for up to 3 months at -20&#176;C.</li>
</ol>
6. Gating strategy for spinal cord microglia
<ol>
	<li>Generate a dot plot and establish a gate to isolate viable cells based on viability staining and an empty fluorescent channel16. Exclude non-viable cells.</li>
	<li>Produce another plot utilizing forward and side scatter parameters to eliminate debris16.</li>
	<li>Develop an additional dot plot and analyze the expression of CD11b and CD45 to differentiate microglia.</li>
</ol>

Extraction and Enzymatic Purification of Microglia from the Mouse Spinal Cord

<ol>
	<li>Schr&#246;der, H., Schr&#246;der, , Moser, , Huggenberger, , 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> Neuroanatomy of the Mouse. , 59-78 (2020).</li><li>Sengul, G., 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=Cytoarchitecture+of+the+spinal+cord+of+the+postnatal+(P4)+mouse.">Cytoarchitecture of the spinal cord of the postnatal (P4) mouse.</a> Anat Rec. 295, 837-845 (2012).</li><li>Bab, I., 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> Microtomographic atlas of the mouse skeleton. VIII, 205 (2007).</li><li>Nayak, D., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglia+development+and+function.">Microglia development and function.</a> Annu Rev Immunol. 32, 367-402 (2014).</li><li>Martinez, F. O., 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=Macrophage+activation+and+polarization.">Macrophage activation and polarization.</a> Front Biosci. 13, 453-461 (2008).</li><li>Masuda, T., 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=Microglia+heterogeneity+in+the+single-cell+era.">Microglia heterogeneity in the single-cell era.</a> Cell Rep. 30 (5), 1271-1281 (2020).</li><li>Prinz, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglia+biology:+one+century+of+evolving+concepts.">Microglia biology: one century of evolving concepts.</a> Cell. 179 (2), 292-311 (2019).</li><li>de Haas, A. 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=Region-specific+expression+of+immunoregulatory+proteins+on+microglia+in+the+healthy+CNS.">Region-specific expression of immunoregulatory proteins on microglia in the healthy CNS.</a> Glia. 56 (8), 888-894 (2008).</li><li>Xuan, F. 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=Differences+of+microglia+in+the+brain+and+the+spinal+cord.">Differences of microglia in the brain and the spinal cord.</a> Front Cell Neurosci. 13, 504 (2019).</li><li>Paolicelli, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglia+states+and+nomenclature:+A+field+at+its+crossroads.">Microglia states and nomenclature: A field at its crossroads.</a> Neuron. 110 (21), 3458-3483 (2022).</li><li>Li, Q., 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=Spinal+IL-36&#947;/IL-36R+participates+in+the+maintenance+of+chronic+inflammatory+pain+through+astroglial+JNK+pathway.">Spinal IL-36&#947;/IL-36R participates in the maintenance of chronic inflammatory pain through astroglial JNK pathway.</a> Glia. 67 (3), 438-451 (2019).</li><li>Prinz, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglia+and+central+nervous+system-associated+macrophages-from+origin+to+disease+modulation.">Microglia and central nervous system-associated macrophages-from origin to disease modulation.</a> Annu Rev Immunol. 39, 251-277 (2021).</li><li>Yip, P. K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+isolation+and+culture+of+primary+microglia+from+adult+mouse+spinal+cord.">Rapid isolation and culture of primary microglia from adult mouse spinal cord.</a> J Neurosci Methods. 183 (2), 223-237 (2009).</li><li>Akhmetzyanova, E. R., 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=Severity-+and+time-dependent+activation+of+microglia+in+spinal+cord+injury.">Severity- and time-dependent activation of microglia in spinal cord injury.</a> Int J Mo. Sci. 24 (9), 1-16 (2023).</li><li>Mahadevan, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anatomy+of+the+vertebral+column.">Anatomy of the vertebral column.</a> Surgery. 36 (7), 327-332 (2018).</li><li>Krukowski, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Temporary+microglia-depletion+after+cosmic+radiation+modifies+phagocytic+activity+and+prevents+cognitive+deficits.">Temporary microglia-depletion after cosmic radiation modifies phagocytic activity and prevents cognitive deficits.</a> Sci Rep. 8 (1), 1-13 (2018).</li><li>Cardona, 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=Isolation+of+murine+microglial+cells+for+RNA+analysis+or+flow+cytometry.">Isolation of murine microglial cells for RNA analysis or flow cytometry.</a> Nat Protoc. 1, 1947-1951 (2006).</li><li>Schmidt, V. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Comparison+of+the+enzymatic+efficiency+of+Liberase+TM+and+tumor+dissociation+enzyme:+effect+on+the+viability+of+cells+digested+from+fresh+and+cryopreserved+human+ovarian+cortex.">Comparison of the enzymatic efficiency of Liberase TM and tumor dissociation enzyme: effect on the viability of cells digested from fresh and cryopreserved human ovarian cortex.</a> Reprod Biol Endocrinol. 16 (57), 1-14 (2018).</li><li>Kusminski, C. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=MitoNEET-parkin+effects+in+pancreatic+&#945;-+and+&#946;-cells,+cellular+survival,+and+intrainsular+cross+talk.">MitoNEET-parkin effects in pancreatic &#945;- and &#946;-cells, cellular survival, and intrainsular cross talk.</a> Diabetes. 65 (6), 1534-1555 (2016).</li></ol>

The authors declare no conflicts of interest.

Numerous protocols have been developed for the study of microglia due to their significance in brain homeostasis. In these methods, microglia are typically sourced from the cerebral hemispheres of embryonic or neonatal rats and mice17. A limited number of studies have addressed the purification of microglia from the spinal cords of adult mice13,14. These techniques involve enzymatic digestion using collagenase and/or papain along with DNAs...

The defining characteristic of vertebrates is the vertebral column or spine, in which the notochord has been replaced by a sequence of segmented bones called vertebrae, divided by intervertebral discs. This succession of osseous material shapes the spinal canal, a cavity that encloses and protects the spinal cord1. In the genus Rodentia, the spine is usually formed by seven cervical vertebrae, thirteen thoracic vertebrae, six lumbar vertebrae, and a variable number of caudal vertebrae2,3. The length of the spinal cord is similar to that of the spine, and the terminal filum is a non-nervous structure that anchors the spinal cord to the sacrum. Additionally, nerve fibers exit through the intervertebral foramen1.
The development and proper function of the central nervous system in mammals critically depend on the activity of the nervous system&#39;s resident macrophages, called microglia4. Although microglia were initially described as brain resident phagocytes, recent research has attributed many dynamic functions to these cells5,6. Microglia&#39;s size ranges from 7 to 10 &#181;m in homeostasis; they are considered among the most versatile cells in the body and can adapt morphologically and functionally to their constantly changing environment7. These cells exhibit high heterogeneity during both the embryonic and adult stages8,9, while in the adult stage, they also display complex functional heterogeneity based on their spatiotemporal context10. The heterogeneity and multiple functions of microglia allow for differential gene expression and behavior in the spinal cord and brain. It has been shown that CD11b, CD45, CD86, and CCR9 expression is higher in the spinal cord compared to the brain8,9.
Multiple protocols exist for cerebral microglia isolation11,12; however, only a few exist for spinal cord microglia13,14. Optimizing a method for purifying microglia from the spinal cord facilitates the development of multiple studies focused on discovering microglia physiology. This protocol aims to describe a simple and highly reproducible extraction of the mouse spinal cord and the purification of microglia (Figure 1).

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>15 mL collection tubes</td>
			<td>Corning, USA</td>
			<td>430790</td>
			<td></td>
		</tr>
		<tr>
			<td>2 mL microtubes</td>
			<td>Axygen, USA</td>
			<td>MCT-200-G</td>
			<td></td>
		</tr>
		<tr>
			<td>2.4G2 anti-FcR</td>
			<td>BioLegend, USA</td>
			<td>101302</td>
			<td></td>
		</tr>
		<tr>
			<td>50 mL collection tubes</td>
			<td>Corning, USA</td>
			<td>430829</td>
			<td></td>
		</tr>
		<tr>
			<td>70% ethanol</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Antibiotic-Antimycotic (penicillin, streptomycin, amphotericin b)</td>
			<td>Gibco, USA</td>
			<td>15240062</td>
			<td></td>
		</tr>
		<tr>
			<td>Antibody CD11b eFluor 450 anti-mouse</td>
			<td>eBioscience, USA</td>
			<td>48-0112</td>
			<td></td>
		</tr>
		<tr>
			<td>Antibody CD45 PerCP anti-mouse&#160;&#160;</td>
			<td>BioLegend, USA</td>
			<td>103130</td>
			<td></td>
		</tr>
		<tr>
			<td>Balanced salt solution (PBS) calcium- magnesium-free</td>
			<td>Corning, USA</td>
			<td>46-013-CM</td>
			<td></td>
		</tr>
		<tr>
			<td>Blue Cell Strainer 40 &#956;m</td>
			<td>Corning, USA</td>
			<td>352340</td>
			<td></td>
		</tr>
		<tr>
			<td>Costar 6-well Clear Not Treated&#160;</td>
			<td>Corning, USA</td>
			<td>CLS3736</td>
			<td></td>
		</tr>
		<tr>
			<td>Coverslips</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Digital Heating Shaking Drybath&#160;</td>
			<td>Thermo Scientific Digital HS Drybath, USA</td>
			<td>88870001</td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting forceps for microsurgery</td>
			<td>FT by DUMONT</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>DNase</td>
			<td>Roche, USA</td>
			<td>4536282001</td>
			<td></td>
		</tr>
		<tr>
			<td>Dulbecco&#180;s Modified Eagle&#180;s Medium-high glucose (DMEM)&#160;</td>
			<td>Merck, USA</td>
			<td>D6429</td>
			<td></td>
		</tr>
		<tr>
			<td>Electric shaver</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>FACS tube</td>
			<td>Thermo, USA</td>
			<td>352058</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum (FBS)</td>
			<td>PAN Biotech, Alemania</td>
			<td>P30-3306</td>
			<td></td>
		</tr>
		<tr>
			<td>Flow cytometer Cytoflex&#160;</td>
			<td>Beckman Coulter</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Hank&#8217;s balanced salt solution&#160;</td>
			<td>Merck, USA</td>
			<td>H2387</td>
			<td></td>
		</tr>
		<tr>
			<td>L-glutamine</td>
			<td>Corning, USA&#160;</td>
			<td>15393631</td>
			<td></td>
		</tr>
		<tr>
			<td>Liberase TM&#160;</td>
			<td>Roche, USA</td>
			<td>5401119001</td>
			<td></td>
		</tr>
		<tr>
			<td>Neubauer chamber Counting Chambers</td>
			<td>China</td>
			<td>1103</td>
			<td></td>
		</tr>
		<tr>
			<td>Pentobarbital</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Percoll&#160;</td>
			<td>Merck, USA</td>
			<td>17089101</td>
			<td>density gradient centrifugation&#160;</td>
		</tr>
		<tr>
			<td>Poly-L-lysine solution&#160;</td>
			<td>Merck, USA</td>
			<td>P8920</td>
			<td></td>
		</tr>
		<tr>
			<td>Scalpel No. 25&#160;</td>
			<td>HERGOM, Mexico</td>
			<td>H23</td>
			<td></td>
		</tr>
		<tr>
			<td>Snaplock Microcentrifuge Tubes 2 mL</td>
			<td>Axygen, USA</td>
			<td>10011-680</td>
			<td></td>
		</tr>
		<tr>
			<td>Stereoscopic microscope</td>
			<td>Velab, Mexico</td>
			<td>HG927831</td>
			<td></td>
		</tr>
		<tr>
			<td>Straight surgical scissors (10 cm)</td>
			<td>HERGOM, Mexico</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Straight Vannas scissors</td>
			<td>HERGOM, Mexico</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Triton X100</td>
			<td>Merck, USA</td>
			<td>X100</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypan blue Stain 0.4%&#160;</td>
			<td>Merck, USA</td>
			<td>15250-061</td>
			<td></td>
		</tr>
		<tr>
			<td>Vortex mixer</td>
			<td>DLAB, China</td>
			<td>8031102000</td>
			<td></td>
		</tr>
		<tr>
			<td>Zombie Aqua Fixable Viability Kit</td>
			<td>BioLegend, USA</td>
			<td>423102</td>
			<td>amine-reactive fluorescent dye staining&#160;</td>
		</tr>
	</tbody>
</table>

rapid and efficient enrichment of mouse spinal cord microglia

The vertebral column defines a vertebrate and shapes the spinal canal, a cavity that encloses and safeguards the spinal cord. Proper development and function of the mammalian central nervous system rely significantly on the activity of resident macrophages known as microglia. Microglia display heterogeneity and multifunctionality, enabling distinct gene expression and behavior within the spinal cord and brain. Numerous studies have explored cerebral microglia function, detailing purification methods extensively. However, the purification of microglia from the spinal cord in mice lacks a comprehensive description. In contrast, the utilization of a highly purified collagenase, as opposed to an unrefined extract, lacks reporting within central nervous system tissues. In this study, the vertebral column and spinal cord were excised from 8-10 week-old C57BL/6 mice. Subsequent digestion employed a highly purified collagenase, and microglia purification utilized a density gradient. Cells underwent staining for flow cytometry, assessing viability and purity through CD11b and CD45 staining. Results yielded an average viability of 80% and a mean purity of 95%. In conclusion, manipulation of mouse microglia involved digestion with a highly purified collagenase, followed by a density gradient. This approach effectively produced substantial spinal cord microglia populations.

Author Spotlight: Microglia Research on Spinal Cord Heterogeneity and Purification 

Rapid and Efficient Enrichment of Mouse Spinal Cord Microglia

Our research focuses on the heterogeneity of microglia, which can exhibit both pro and anti-inflammatory behaviors across different pathologies and regions like the brain and spinal cord. We aim to enable a deeper understanding of spinal cord microglia behavior in diverse scenarios. The heterogeneity of microglia has made it difficult to classify them.This year, a new and broad classification has been proposed that goes beyond just a pro or anti-inflammatory status. Currently, achieving high purity and gel in isolating spinal cord microglia from animal models of neurological pathologies is a significant experiment and challenge. We identified a novel cytokine signaling pathway in the spinal cord microglia during chronic pain.Our protocol allows for a more controlled and somatic digestion, followed by a density gradient. Both result in less contamination by astrocytes compared to currently employed techniques for the purification of microglia from the spinal cord, brain, or embryos.

Utilizing mouse spinal cord tissue, enzymatic digestion was performed using a mixture highly enriched with collagenase and thermolysin. The resulting digested tissue underwent passage through a 40 &#181;m filter to eliminate undigested material. The collected cells were enriched through a Percoll density gradient, with 90% in the lower portion and 45% in the upper portion. The microglia-enriched cells within the interface were then stained with CD45 and CD11b antibodies and subjected to flow cytometric analysis (<strong ...

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Microglia are regarded as some of the most versatile cells in the body, capable of morphological and functional adaptation. Their heterogeneity and multifunctionality enable the maintenance of brain homeostasis, while also being linked to various neurological pathologies. Here, a technique for purifying spinal cord microglia is described.

The vertebral column defines a vertebrate and shapes the spinal canal, a cavity that encloses and safeguards the spinal cord. Proper development and ...

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Research

JoVE Journal

Neuroscience

Liberase-Based Enzymatic Purification of Microglial Cells Isolated from a Mouse Spinal Cord

To begin, with a scalpel, make an incision along the dorsal midline of a euthanized mouse from the occipital to the sacral region. Using a stereoscopic surgical microscope, carefully dissect through layers until the lumbar spine. Identify the last costal arch.Identify the last cervical vertebra and the sacrum. Then make a cut to separate the spine. With a pair of dissecting forceps, perform a dorsal laminectomy of the vertebra to extract the spinal cord.Remove the nerves emerging through the foramina which constitute the peripheral nervous system. Now, place the extracted spinal cord on a dissecting board. With a pair of vannas scissors, cut it into two-millimeter sized pieces.Then transfer the pieces to a two-milliliter flat-bottomed microtube. Add one milliliter of HBSS-LD working solution to the microtube. Incubate the mixture at 37 degrees Celsius for 25 minutes.Make sure to vigorously vortex the mixture every five minutes. Next, pass the contents of each digestion through a 40-micron-size strainer. Then add seven milliliters of HBSS with 2%FBS to neutralize the digestion and crush the remaining tissue.Transfer the suspension to a 50-milliliter conical tube before centrifuging it at 220 g for five minutes at four degrees Celsius. Now use a one-milliliter micropipette to discard the supernatant. Then resuspend the pellet in two milliliters of HBSS-FBS in a new 15-milliliter conical tube.Add two milliliters of 90%isotonic density gradient medium to the tube, and centrifuge the mixture at 160 g for 25 minutes at 18 degrees Celsius. Finally, with a transfer pipette, retrieve the interphase and transfer it to a 15-milliliter conical tube. Wash the cells with 10 milliliters of PBS, then centrifuge the cells at 220 g for five minutes at five degrees Celsius before further experimentation.The purification of the extracted microglial cells yielded up to 99%cell yield as confirmed by FACS staining. Double positive cells with an average size of 10 micrometers consistent with nonactivated microglia were observed.

1.3K Views.  Mexico Children's Hospital.  Microglia are regarded as some of the most versatile cells in the body, capable of morphological and functional adaptation. Their heterogeneity and multifunctionality enable the maintenance of brain homeostasis, while also being linked to various neurological pathologies. Here, a technique for purifying spinal cord microglia is described.

Extraction and Enzymatic Purification of Microglia from the Mouse Spinal Cord

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