SJ&#39;s laboratory was established with institutional grants from IITJ and is funded by grants from the Department of Biotechnology (BT/PR12831/MED/30/1489/2015) and Ministry of Electronics and Information Technology Government of India (No.4(16)/2019-ITEA). The human brain tissue sections were obtained from the All India Institute of Medical Sciences (AIIMS) Jodhpur after institutional ethics committee clearance. We thank Mayank Rathor, B.Tech Student member of Design and Arts Society IIT Jodhpur, for videography support.

All tissues were acquired after ethical clearance from the institute ethics committees of Indian Institute of Technology Jodhpur and All India Institute of Medical Sciences (AIIMS) Jodhpur.
1.Tissue acquisition and processing (Day 0)
<ol>
	<li>Collect the tissue in a 50 mL tube containing 10 mL of ice cold artificial cerebrospinal fluid (aCSF) (2 mM CaCl2&#8729;2H2O, 10 mM glucose, 3 mM KCl, 26 mM NaHCO3, 2.5 mM NaH2PO4, 1 mM MgCl2&#8729;6H2O, 202 mM sucrose)20. Ensure that the tube is kept on ice if the tissue needs to be transferred to a different location. 
	NOTE: Prepare aCSF in autoclaved distilled water. Filter it with 0.22 &#181;m syringe filter in the laminar hood. This can be stored for 1 month at 4 &#176;C.</li>
	<li>Wipe the collection tube carefully with 70% alcohol and transfer to an aseptic laminar air flow chamber.</li>
	<li>Discard aCSF carefully and weigh tissue in an aseptic condition. Tissue weight is essential to calculate the volume of trypsin-EDTA needed for subsequent steps.</li>
	<li>Keep the tissue in fresh warm aCSF at 37 &#176;C for 5 minutes. This step is critical to avoid cell death.</li>
	<li>Discard aCSF and wash tissue once with 1x PBS (phosphate buffered saline) at 37 &#176;C. Ensure all blood is washed away with repeated PBS washes (as needed).</li>
	<li>Incubate the tissue in warm PBS, at 37 &#176;C, for 5 min.</li>
	<li>Discard PBS carefully and transfer tissue to a sterilized Petri dish. PBS may be removed with a pipette. This will prevent any loss of tissue.</li>
	<li>Dice the tissue into small (at least 1 mm3) pieces using a sterile scalpel. Finely diced tissue provides higher tissue surface area for tissue dissociation by trypsin-EDTA ensuring higher yield.</li>
	<li>Transfer the diced tissue to a 50 mL tube containing 10 mL/g tissue of 0.25% trypsin-EDTA and mix by pipetting through a 10 mL serological pipette. Add 2 mL of trypsin/EDTA to a Petri dish and wash the plate thoroughly with the help of pipette. Add this trypsin back to the falcon tube. This minimizes loss of tissue and cells while dicing.</li>
	<li>Incubate the tube on a shaker for 30 minutes at 37 &#176;C at 250 rpm. This step increases the dissociation of cells from tissue.</li>
	<li>At the end of the incubation, add 10 mL of neutralizing medium (50% DMEM/50% F12 with glutamine, 1% penicillin-streptomycin, 10% FBS) to neutralize trypsin. Mix with a 10 mL serological pipette. The amount of neutralizing media added should be equal to the amount of trypsin used.</li>
	<li>Centrifuge the tube at 2,000 x g at 4 &#176;C for 10 minutes.</li>
	<li>Discard the supernatant and re-suspend the pellet in 1 mL of culture medium (50% DMEM/50% F12 with glutamine, 1% penicillin-streptomycin, 20% L929 supernatant, 10% FBS). 
	NOTE: L929 cells are culture in DMEM (DMEM with glutamine, 1% penicillin-streptomycin, 10% FBS). ATCC recommended culture method should be followed for cell culture. Supernatant must be collected from the culture flask which is at least 75% confluent. It can be collected in bulk and stored at -80 &#176;C to prevent degradation of growth factors. It is recommended to add L929 supernatant separately in flasks instead of adding to the stock culture medium.</li>
	<li>Plate the cells in a T-25 flask, suited for adherent cells, and add 4 mL of additional culture medium. Incubate the flask at 37 &#176;C with 5% CO2. Carefully shake the flask to homogenously disperse the tissue. Avoid bringing the media to the neck of the flask, while shaking, as this may increase the chances of contamination.</li>
</ol>
2.Cell culture (Day 2)
<ol>
	<li>Collect the media from the T-25 culture flask prepared on day 0 in three 1.5 mL centrifuge tubes by collecting equal volume of media in each tube. Wash the flask once with 1 x PBS. Shake the flask gently to remove any remnant tissue fragments left. Avoid harsh shaking of the flask as any remnant fragments will not adversely affect the culture. Add 5 mL fresh culture media to the flask.</li>
	<li>Centrifuge the collected media at 1,466 x g (4000 rpm) at 4 &#176;C for 4 minutes.</li>
	<li>Discard the supernatant from each tube and add 1 mL of culture medium to one of the tubes. Mix thoroughly with pipette. Serially add the mixed media with cells to other tubes. Mix thoroughly with pipette and pool the cells in one tube.</li>
	<li>Plate the cells in a separate T-25 flask, suited for adherent cells. Add 4 mL of culture medium and incubate the flask at 37 &#176;C with 5% CO2.</li>
</ol>
3.Cell culture (Day 4)
<ol>
	<li>Discard the media from both flasks and add fresh 5 mL of culture media to the flask.</li>
	<li>Incubate the flask at 37 &#176;C with 5% CO2 for 2 days.</li>
</ol>
4. Cell Culture (Day 6)
<ol>
	<li>Cells will be ready for further experiments.</li>
</ol>

<ol>
	<li>Allen, N. J., Barres, B. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glia+-+more+than+just+brain+glue.">Glia - more than just brain glue.</a> Nature. 457 (7230), 675-677 (2009).</li><li>Lenz, K. M., Nelson, L. H. <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+Beyond:+Innate+Immune+Cells+As+Regulators+of+Brain+Development+and+Behavioral+Function.">Microglia and Beyond: Innate Immune Cells As Regulators of Brain Development and Behavioral Function.</a> Frontiers in Immunology. 9 (698), (2018).</li><li>Gordon, S., Pl&#252;ddemann, A., Martinez Estrada, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Macrophage+heterogeneity+in+tissues:+phenotypic+diversity+and+functions.">Macrophage heterogeneity in tissues: phenotypic diversity and functions.</a> Immunological Reviews. 262 (1), 36-55 (2014).</li><li>Li, Q., Barres, B. A. <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+macrophages+in+brain+homeostasis+and+disease.">Microglia and macrophages in brain homeostasis and disease.</a> Nature Reviews Immunology. 18 (4), 225-242 (2018).</li><li>Hansen, D. V., Hanson, J. E., Sheng, 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+in+Alzheimer's+disease:+A+microglial+conundrum.">Microglia in Alzheimer's disease: A microglial conundrum.</a> Journal of Cell Biology. 217 (2), 459-472 (2017).</li><li>Tremblay, M. -. E., Cookson, M. R., Civiero, L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Glial+phagocytic+clearance+in+Parkinson's+disease.">Glial phagocytic clearance in Parkinson's disease.</a> Molecular Neurodegeneration. 14 (1), 16 (2019).</li><li>Qin, C., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dual+Functions+of+Microglia+in+Ischemic+Stroke.">Dual Functions of Microglia in Ischemic Stroke.</a> Neuroscience Bulletin. 35 (5), 921-933 (2019).</li><li>Voet, S., Prinz, M., van Loo, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglia+in+Central+Nervous+System+Inflammation+and+Multiple+Sclerosis+Pathology.">Microglia in Central Nervous System Inflammation and Multiple Sclerosis Pathology.</a> Trends in Molecular Medicine. 25 (2), 112-123 (2019).</li><li>Loane, D. J., Kumar, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglia+in+the+TBI+brain:+The+good,+the+bad,+and+the+dysregulated.">Microglia in the TBI brain: The good, the bad, and the dysregulated.</a> Experimental Neurology. 275 (03), 316-327 (2016).</li><li>Inoue, K., Tsuda, 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+in+neuropathic+pain:+cellular+and+molecular+mechanisms+and+therapeutic+potential.">Microglia in neuropathic pain: cellular and molecular mechanisms and therapeutic potential.</a> Nature Reviews Neuroscience. 19 (3), 138-152 (2018).</li><li>Bellver-Landete, 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=Microglia+are+an+essential+component+of+the+neuroprotective+scar+that+forms+after+spinal+cord+injury.">Microglia are an essential component of the neuroprotective scar that forms after spinal cord injury.</a> Nature Communications. 10 (1), 518 (2019).</li><li>Gutmann, D. H., Kettenmann, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglia/Brain+Macrophages+as+Central+Drivers+of+Brain+Tumor+Pathobiology.">Microglia/Brain Macrophages as Central Drivers of Brain Tumor Pathobiology.</a> Neuron. 104 (3), 442-449 (2019).</li><li>Smith, A. M., Dragunow, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+human+side+of+microglia.">The human side of microglia.</a> Trends in Neurosciences. 37 (3), 125-135 (2014).</li><li>Galatro, T. F., 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=Transcriptomic+analysis+of+purified+human+cortical+microglia+reveals+age-associated+changes.">Transcriptomic analysis of purified human cortical microglia reveals age-associated changes.</a> Nature Neuroscience. 20 (8), 1162-1171 (2017).</li><li>Friedman, B. 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=Diverse+Brain+Myeloid+Expression+Profiles+Reveal+Distinct+Microglial+Activation+States+and+Aspects+of+Alzheimer's+Disease+Not+Evident+in+Mouse+Models.">Diverse Brain Myeloid Expression Profiles Reveal Distinct Microglial Activation States and Aspects of Alzheimer's Disease Not Evident in Mouse Models.</a> Cell Reports. 22 (3), 832-847 (2018).</li><li>Rustenhoven, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PU.1+regulates+Alzheimer's+disease-associated+genes+in+primary+human+microglia.">PU.1 regulates Alzheimer's disease-associated genes in primary human microglia.</a> Molecular Neurodegeneration. 13 (1), 44 (2018).</li><li>Sierra, A., Gottfried-Blackmore, A. C., McEwen, B. S., Bulloch, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglia+derived+from+aging+mice+exhibit+an+altered+inflammatory+profile.">Microglia derived from aging mice exhibit an altered inflammatory profile.</a> Glia. 55 (4), 412-424 (2007).</li><li>Mizee, M. 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=Isolation+of+primary+microglia+from+the+human+post-mortem+brain:+effects+of+ante-+and+post-mortem+variables.">Isolation of primary microglia from the human post-mortem brain: effects of ante- and post-mortem variables.</a> Acta Neuropathologica Communications. 5 (1), 16 (2017).</li><li>Rustenhoven, J., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+of+highly+enriched+primary+human+microglia+for+functional+studies.">Isolation of highly enriched primary human microglia for functional studies.</a> Scientific Reports. 6 (1), 19371 (2016).</li><li>Spaethling, J. 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=Primary+Cell+Culture+of+Live+Neurosurgically+Resected+Aged+Adult+Human+Brain+Cells+and+Single+Cell+Transcriptomics.">Primary Cell Culture of Live Neurosurgically Resected Aged Adult Human Brain Cells and Single Cell Transcriptomics.</a> Cell Reports. 18 (3), 791-803 (2017).</li><li>Olah, 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=An+optimized+protocol+for+the+acute+isolation+of+human+microglia+from+autopsy+brain+samples.">An optimized protocol for the acute isolation of human microglia from autopsy brain samples.</a> Glia. 60 (1), 96-111 (2012).</li><li>Jha, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+Inflammasome+Sensor,+NLRP3,+Regulates+CNS+Inflammation+and+Demyelination+via+Caspase-1+and+Interleukin-18.">The Inflammasome Sensor, NLRP3, Regulates CNS Inflammation and Demyelination via Caspase-1 and Interleukin-18.</a> The Journal of Neuroscience. 30 (47), 15811 (2010).</li><li>Freeman, 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=NLR+members+NLRC4+and+NLRP3+mediate+sterile+inflammasome+activation+in+microglia+and+astrocytes.">NLR members NLRC4 and NLRP3 mediate sterile inflammasome activation in microglia and astrocytes.</a> Journal of Experimental Medicine. 214 (5), 1351-1370 (2017).</li><li>Plant, S. 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=Lymphotoxin+beta+receptor+(Lt+betaR):+dual+roles+in+demyelination+and+remyelination+and+successful+therapeutic+intervention+using+Lt+betaR-Ig+protein.">Lymphotoxin beta receptor (Lt betaR): dual roles in demyelination and remyelination and successful therapeutic intervention using Lt betaR-Ig protein.</a> The Journal of Neuroscience. 27 (28), 7429-7437 (2007).</li><li>Arnett, H. 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=The+Protective+Role+of+Nitric+Oxide+in+a+Neurotoxicant-+Induced+Demyelinating+Model.">The Protective Role of Nitric Oxide in a Neurotoxicant- Induced Demyelinating Model.</a> The Journal of Immunology. 168 (1), 427 (2002).</li><li>Arnett, H. 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&#945;+promotes+proliferation+of+oligodendrocyte+progenitors+and+remyelination.">TNF&#945; promotes proliferation of oligodendrocyte progenitors and remyelination.</a> Nature Neuroscience. 4 (11), 1116-1122 (2001).</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=Bone+marrow-derived+macrophage+production.">Bone marrow-derived macrophage production.</a> Journal of Visualized Experiments. (81), e50966 (2013).</li><li>Boltz-Nitulescu, 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=Differentiation+of+Rat+Bone+Marrow+Cells+Into+Macrophages+Under+the+Influence+of+Mouse+L929+Cell+Supernatant.">Differentiation of Rat Bone Marrow Cells Into Macrophages Under the Influence of Mouse L929 Cell Supernatant.</a> Journal of Leukocyte Biology. 41 (1), 83-91 (1987).</li><li>Englen, M. D., Valdez, Y. E., Lehnert, N. M., Lehnert, B. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Granulocyte/macrophage+colony-stimulating+factor+is+expressed+and+secreted+in+cultures+of+murine+L929+cells.">Granulocyte/macrophage colony-stimulating factor is expressed and secreted in cultures of murine L929 cells.</a> Journal of Immunological Methods. 184 (2), 281-283 (1995).</li></ol>

Authors have nothing to disclose.

Microglia ensure homeostasis in the normal brain and play central roles in the pathophysiology of various neurological diseases4. Microglia are central to neurodevelopment and formation of synapses2. Microglial studies have proven pivotal in understanding the development and progression of diverse neurological diseases4. Rodent microglia are the prevalent model of choice for primary microglial studies, even though, rodent microglia are different from...

The central nervous system (CNS) is constructed of a complex network of neurons and glial cells1. Among the glial cells, microglia function as the innate immune cells of the CNS2,3. Microglia are responsible for maintaining homeostasis in the healthy CNS4. Microglia also play an important role in neurodevelopment, by pruning synapses2. Microglia are central to the pathophysiology of several neurological diseases including but not restricted to; Alzheimer&#39;s disease5, Parkinson&#39;s disease6, stroke7, multiple sclerosis8, traumatic brain injury9, neuropathic pain10, spinal cord injury11 and brain tumors such as gliomas12.
Studies related to CNS homeostasis and diseases utilize rodent microglia due to a dearth of cost efficient and time efficient human primary microglia isolation protocols13. Rodent microglia resemble primary human microglia in expression of genes such as Iba-1, PU.1, DAP12 and M-CSF receptor and have been effective in understanding normal as well as diseased brain13. Interestingly, the expression of several immune related genes such as TLR4, MHC II, Siglec-11 and Siglec-3 varies between human and rodent microglia13. The expression of several genes also varies in temporal expression and in neurodegenerative diseases in both species14,15. These significant differences make human microglia an essential model to study microglia function in homeostasis and disease. Primary human microglia can also be an effective tool for preclinical screening of potential drug candidates16. The above mentioned reasons underline the growing need for cost effective protocols for isolation of primary human microglia.
We have developed a protocol for isolation of primary human microglia from adult human brain tissue collected as a result of surgical window created for tumor resections or other surgical resections. The method here is considerably different from existing methods. We were able to isolate and culture microglia after a transit time of about 75 minutes from the tissue collection site to starting the isolation protocol in the laboratory. We have used the supernatant of L929 fibroblast cells to promote the growth of isolated microglia. This method specifically focuses on the culture and development of only primary microglia. The resulting culture prepared is about 80% microglia. While other protocols provide a enriched culture of microglia by density gradient centrifugation, flow cytometry and magnetic beads, the protocol is a rapid, simple, robust and cost effective way to culture primary human microglia17,18,19,20. The ability to utilize surgically removed live adult brain tissue instead of fixed brain tissues from cadavers proves an added advantage of this method in contrast to existing procedures18,21.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Antibiotic-Antimycotic solution</td>
			<td>Himedia</td>
			<td>A002</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcium chloride</td>
			<td>Sigma</td>
			<td>223506</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge (4 &#176;C)</td>
			<td>Sigma</td>
			<td>146532</td>
			<td></td>
		</tr>
		<tr>
			<td>Centrifuge tubes</td>
			<td>Abdos</td>
			<td>P10203</td>
			<td></td>
		</tr>
		<tr>
			<td>CO2 incubator</td>
			<td>New Brunswik</td>
			<td>Galaxy 170 S</td>
			<td></td>
		</tr>
		<tr>
			<td>D-Glucose</td>
			<td>Himedia</td>
			<td>GRM077</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM medium with glutamine</td>
			<td>Himedia</td>
			<td>AL007S</td>
			<td></td>
		</tr>
		<tr>
			<td>Fetal bovine serum</td>
			<td>Himedia</td>
			<td>RM9955</td>
			<td></td>
		</tr>
		<tr>
			<td>Flacon tube (50 ml)</td>
			<td>Thermo Fsiher Scientific&#160;</td>
			<td>50CD1058</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescein Ricinus communis agglutinin-1</td>
			<td>Vector</td>
			<td>FL-1081</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluorescent microscope</td>
			<td>Leica</td>
			<td>DM2000LED</td>
			<td></td>
		</tr>
		<tr>
			<td>Fluoroshield with DAPI</td>
			<td>Sigma</td>
			<td>F6057</td>
			<td></td>
		</tr>
		<tr>
			<td>GFAP antibody</td>
			<td>GA5</td>
			<td>3670S</td>
			<td></td>
		</tr>
		<tr>
			<td>Incubator shaker</td>
			<td>New Brunswik Scientific</td>
			<td>Innova 42</td>
			<td></td>
		</tr>
		<tr>
			<td>L929 cell line</td>
			<td>ATCC</td>
			<td>NCTC clone 929 [L cell, L-929, derivative of Strain L] (ATCC&#160;CCL-1)</td>
			<td></td>
		</tr>
		<tr>
			<td>Laminar air flow</td>
			<td>Thermo Fsiher Scientific&#160;</td>
			<td>1386</td>
			<td></td>
		</tr>
		<tr>
			<td>Magnesium chloride</td>
			<td>Himedia</td>
			<td>MB040</td>
			<td></td>
		</tr>
		<tr>
			<td>Monosodium phosphate</td>
			<td>Merck</td>
			<td>567545</td>
			<td></td>
		</tr>
		<tr>
			<td>Nutrient Mixture F-12 Ham Medium</td>
			<td>Himedia</td>
			<td>Al106S</td>
			<td></td>
		</tr>
		<tr>
			<td>Petri dish</td>
			<td>Duran Group</td>
			<td>237554805</td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate buffered saline</td>
			<td>Himedia</td>
			<td>ML023</td>
			<td></td>
		</tr>
		<tr>
			<td>Potassium chloride</td>
			<td>Himedia</td>
			<td>MB043</td>
			<td></td>
		</tr>
		<tr>
			<td>Serological pipette</td>
			<td>Labware</td>
			<td>LW-SP1010</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium bicarbonate</td>
			<td>Himedia</td>
			<td>MB045</td>
			<td></td>
		</tr>
		<tr>
			<td>Sucrose</td>
			<td>Himedia</td>
			<td>MB025</td>
			<td></td>
		</tr>
		<tr>
			<td>Syringe filter (0.2&#956;, 25 mm diameter)</td>
			<td>Axiva</td>
			<td>SFPV25R</td>
			<td></td>
		</tr>
		<tr>
			<td>T-25 tissue culture flasks suitable for adherent cell culture.</td>
			<td>Himedia</td>
			<td>TCG4-20X10NO</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin-EDTA (0.25%)</td>
			<td>Gibco&#160;</td>
			<td>25200-056</td>
			<td></td>
		</tr>
	</tbody>
</table>

obtaining human microglia from adult human brain tissue

Microglia are resident innate immune cells of the central nervous system (CNS). Microglia play a critical role during development, in maintaining homeostasis, and during infection or injury. Several independent research groups have highlighted the central role that microglia play in autoimmune diseases, autoinflammatory syndromes and cancers. The activation of microglia in some neurological diseases may directly participate in pathogenic processes. Primary microglia are a powerful tool to understand the immune responses in the brain, cell-cell interactions and dysregulated microglia phenotypes in disease. Primary microglia mimic in vivo microglial properties better than immortalized microglial cell lines. Human adult microglia exhibit distinct properties as compared to human fetal and rodent microglia. This protocol provides an efficient method for isolation of primary microglia from adult human brain. Studying these microglia can provide critical insights into cell-cell interactions between microglia and other resident cellular populations in the CNS including, oligodendrocytes, neurons and astrocytes. Additionally, microglia from different human brains may be cultured for characterization of unique immune responses for personalized medicine and a myriad of therapeutic applications.

By using the above-mentioned protocol (Figure 1), we were able to isolate primary human microglia from live surgically resected brain tissues. Cultured cells were stained with Ricinus communis agglutinin-1 (RCA-1) lectin for microglia (green) and with Glial fibrillary acidic protein (GFAP) for astrocytes (red) (Figure 2) as previously described22,23,<s...

Watch this Scientific Journal Video about Obtaining Human Microglia from Adult Human Brain Tissue at JoVE.com

Obtaining Human Microglia from Adult Human Brain Tissue

This protocol is an efficient, cost effective and robust method of isolating primary microglia from live, adult, human brain tissue. Isolated primary human microglia can serve as a tool for studying cellular processes in homeostasis and disease.

Microglia are resident innate immune cells of the central nervous system (CNS). Microglia play a critical role during development, in maintaining ...

obtaining-human-microglia-from-adult-human-brain-tissue

Microsoft Bing

Research

JoVE Journal

Neuroscience

7.0K Views.  Indian Institute of Technology Jodhpur. This protocol is an efficient, cost effective and robust method of isolating primary microglia from live, adult, human brain tissue. Isolated primary human microglia can serve as a tool for studying cellular processes in homeostasis and disease. 

Video: Obtaining Human Microglia from Adult Human Brain Tissue

Combining Computer Game-Based Behavioural Experiments With High-Density EEG and Infrared Gaze Tracking

Experimental paradigms are valuable insofar as the timing and other parameters of their stimuli are well specified and controlled, and insofar as they yield data relevant to the cognitive processing that occurs under ecologically valid conditions. These two goals often are at odds, since well controlled stimuli often are too repetitive to sustain subjects' motivation. Studies employing electroencephalography (EEG) are often especially sensitive to this dilemma between ecological validity and experimental control: attaining sufficient signal-to-noise in physiological averages demands large numbers of repeated trials within lengthy recording sessions, limiting the subject pool to individuals with the ability and patience to perform a set task over and over again. This constraint severely limits researchers' ability to investigate younger populations as well as clinical populations associated with heightened anxiety or attentional abnormalities. Even adult, non-clinical subjects may not be able to achieve their typical levels of performance or cognitive engagement: an unmotivated subject for whom an experimental task is little more than a chore is not the same, behaviourally, cognitively, or neurally, as a subject who is intrinsically motivated and engaged with the task. A growing body of literature demonstrates that embedding experiments within video games may provide a way between the horns of this dilemma between experimental control and ecological validity. The narrative of a game provides a more realistic context in which tasks occur, enhancing their ecological validity (Chaytor &amp; Schmitter-Edgecombe, 2003). Moreover, this context provides motivation to complete tasks. In our game, subjects perform various missions to collect resources, fend off pirates, intercept communications or facilitate diplomatic relations. In so doing, they also perform an array of cognitive tasks, including a Posner attention-shifting paradigm (Posner, 1980), a go/no-go test of motor inhibition, a psychophysical motion coherence threshold task, the Embedded Figures Test (Witkin, 1950, 1954) and a theory-of-mind (Wimmer &amp; Perner, 1983) task. The game software automatically registers game stimuli and subjects' actions and responses in a log file, and sends event codes to synchronise with physiological data recorders. Thus the game can be combined with physiological measures such as EEG or fMRI, and with moment-to-moment tracking of gaze. Gaze tracking can verify subjects' compliance with behavioural tasks (e.g. fixation) and overt attention to experimental stimuli, and also physiological arousal as reflected in pupil dilation (Bradley et al., 2008). At great enough sampling frequencies, gaze tracking may also help assess covert attention as reflected in microsaccades - eye movements that are too small to foveate a new object, but are as rapid in onset and have the same relationship between angular distance and peak velocity as do saccades that traverse greater distances. The distribution of directions of microsaccades correlates with the (otherwise) covert direction of attention (Hafed &amp; Clark, 2002).

Procedures for recording high-density EEG and gaze data during computer game-based cognitive tasks are described. Using a video game to present cognitive tasks enhances ecological validity without sacrificing experimental control.

Experimental paradigms are valuable insofar as the timing and other parameters of their stimuli are well specified and controlled, and insofar as they ...

A Rapid Approach to High-Resolution Fluorescence Imaging in Semi-Thick Brain Slices

A fundamental goal to both basic and clinical neuroscience is to better understand the identities, molecular makeup, and patterns of connectivity that are characteristic to neurons in both normal and diseased brain. Towards this, a great deal of effort has been placed on building high-resolution neuroanatomical maps1-3. With the expansion of molecular genetics and advances in light microscopy has come the ability to query not only neuronal morphologies, but also the molecular and cellular makeup of individual neurons and their associated networks4. Major advances in the ability to mark and manipulate neurons through transgenic and gene targeting technologies in the rodent now allow investigators to 'program' neuronal subsets at will5-6. Arguably, one of the most influential contributions to contemporary neuroscience has been the discovery and cloning of genes encoding fluorescent proteins (FPs) in marine invertebrates7-8, alongside their subsequent engineering to yield an ever-expanding toolbox of vital reporters9. Exploiting cell type-specific promoter activity to drive targeted FP expression in discrete neuronal populations now affords neuroanatomical investigation with genetic precision.
Engineering FP expression in neurons has vastly improved our understanding of brain structure and function. However, imaging individual neurons and their associated networks in deep brain tissues, or in three dimensions, has remained a challenge. Due to high lipid content, nervous tissue is rather opaque and exhibits auto fluorescence. These inherent biophysical properties make it difficult to visualize and image fluorescently labelled neurons at high resolution using standard epifluorescent or confocal microscopy beyond depths of tens of microns. To circumvent this challenge investigators often employ serial thin-section imaging and reconstruction methods10, or 2-photon laser scanning microscopy11. Current drawbacks to these approaches are the associated labor-intensive tissue preparation, or cost-prohibitive instrumentation respectively.
Here, we present a relatively rapid and simple method to visualize fluorescently labelled cells in fixed semi-thick mouse brain slices by optical clearing and imaging. In the attached protocol we describe the methods of: 1) fixing brain tissue in situ via intracardial perfusion, 2) dissection and removal of whole brain, 3) stationary brain embedding in agarose, 4) precision semi-thick slice preparation using new vibratome instrumentation, 5) clearing brain tissue through a glycerol gradient, and 6) mounting on glass slides for light microscopy and z-stack reconstruction (Figure 1).
For preparing brain slices we implemented a relatively new piece of instrumentation called the 'Compresstome' VF-200 (http://www.precisionary.com/products_vf200.html). This instrument is a semi-automated microtome equipped with a motorized advance and blade vibration system with features similar in function to other vibratomes. Unlike other vibratomes, the tissue to be sliced is mounted in an agarose plug within a stainless steel cylinder. The tissue is extruded at desired thicknesses from the cylinder, and cut by the forward advancing vibrating blade. The agarose plug/cylinder system allows for reproducible tissue mounting, alignment, and precision cutting. In our hands, the 'Compresstome' yields high quality tissue slices for electrophysiology, immunohistochemistry, and direct fixed-tissue mounting and imaging. Combined with optical clearing, here we demonstrate the preparation of semi-thick fixed brain slices for high-resolution fluorescent imaging.

Here we describe a rapid and simple method to image fluorescently labeled cells in semi-thick brain slices. By fixing, slicing, and optically clearing brain tissue we describe how standard epifluorescent or confocal imaging can be used to visualize individual cells and neuronal networks within intact nervous tissue.

A fundamental goal to both basic and clinical neuroscience is to better understand the identities, molecular makeup, and patterns of connectivity that are ...

Fiber-optic Implantation for Chronic Optogenetic Stimulation of Brain Tissue

Elucidating patterns of neuronal connectivity has been a challenge for both clinical and basic neuroscience. Electrophysiology has been the gold standard for analyzing patterns of synaptic connectivity, but paired electrophysiological recordings can be both cumbersome and experimentally limiting. The development of optogenetics has introduced an elegant method to stimulate neurons and circuits, both in vitro1 and in vivo2,3. By exploiting cell-type specific promoter activity to drive opsin expression in discrete neuronal populations, one can precisely stimulate genetically defined neuronal subtypes in distinct circuits4-6. Well described methods to stimulate neurons, including electrical stimulation and/or pharmacological manipulations, are often cell-type indiscriminate, invasive, and can damage surrounding tissues. These limitations could alter normal synaptic function and/or circuit behavior. In addition, due to the nature of the manipulation, the current methods are often acute and terminal. Optogenetics affords the ability to stimulate neurons in a relatively innocuous manner, and in genetically targeted neurons. The majority of studies involving in vivo optogenetics currently use a optical fiber guided through an implanted cannula6,7; however, limitations of this method include damaged brain tissue with repeated insertion of an optical fiber, and potential breakage of the fiber inside the cannula. Given the burgeoning field of optogenetics, a more reliable method of chronic stimulation is necessary to facilitate long-term studies with minimal collateral tissue damage. Here we provide our modified protocol as a video article to complement the method effectively and elegantly described in Sparta et al.8 for the fabrication of a fiber optic implant and its permanent fixation onto the cranium of anesthetized mice, as well as the assembly of the fiber optic coupler connecting the implant to a light source. The implant, connected with optical fibers to a solid-state laser, allows for an efficient method to chronically photostimulate functional neuronal circuitry with less tissue damage9 using small, detachable, tethers. Permanent fixation of the fiber optic implants provides consistent, long-term in vivo optogenetic studies of neuronal circuits in awake, behaving mice10 with minimal tissue damage.

The development of optogenetics now provides the means to precisely stimulate genetically defined neurons and circuits, both in vitro and in vivo. Here we describe the assembly and implantation of a fiber optic for chronic photostimulation of brain tissue.

Elucidating patterns of neuronal connectivity has been a challenge for both clinical and basic neuroscience. Electrophysiology has been the gold standard ...

Simple Generation of a High Yield Culture of Induced Neurons from Human Adult Skin Fibroblasts

Induced neurons (iNs), the product of somatic cells directly converted to neurons, are a way to obtain patient-derived neurons from tissue that is easily accessible. Through this route, mature neurons can be obtained in a matter of a few weeks. Here, we describe a straightforward and rapid one-step protocol to obtain iNs from dermal fibroblasts obtained through biopsy samples from adult human donors. We explain each step of the process, including the maintenance of the dermal fibroblasts, the freezing procedure to build a stock of the cell line, seeding of the cells for reprogramming, as well as the culture conditions during the conversion process. In addition, we describe the preparation of glass coverslips for electrophysiological recordings, long-term coating conditions, and fluorescence activated cell sorting (FACS). We also illustrate examples of the results to be expected. The protocol described here is easy to perform and can be applied to human fibroblasts derived from human skin biopsies from patients with various different diagnoses and ages. This protocol generates a sufficient amount of iNs which can be used for a wide array of biomedical applications, including disease modeling, drug screening, and target validation.

Direct neuronal reprogramming generates neurons that maintain the age of the starting somatic cell. Here, we describe a single vector-based method to generate induced neurons from dermal fibroblasts obtained from adult human donors.

Induced neurons (iNs), the product of somatic cells directly converted to neurons, are a way to obtain patient-derived neurons from tissue that is easily ...

Isolation of Cerebral Capillaries from Fresh Human Brain Tissue

Understanding blood-brain barrier function under physiological and pathophysiological conditions is critical for the development of new therapeutic strategies that hold the promise to enhance brain drug delivery, improve brain protection, and treat brain disorders. However, studying the human blood-brain barrier function is challenging. Thus, there is a critical need for appropriate models. In this regard, brain capillaries isolated from human brain tissue represent a unique tool to study barrier function as close to the human in vivo situation as possible. Here, we describe an optimized protocol to isolate capillaries from human brain tissue at a high yield and with consistent quality and purity. Capillaries are isolated from fresh human brain tissue using mechanical homogenization, density-gradient centrifugation, and filtration. After the isolation, the human brain capillaries can be used for various applications including leakage assays, live cell imaging, and immune-based assays to study protein expression and function, enzyme activity, or intracellular signaling. Isolated human brain capillaries are a unique model to elucidate the regulation of the human blood-brain barrier function. This model can provide insights into central nervous system (CNS) pathogenesis, which will help the development of therapeutic strategies for treating CNS disorders.

Isolated brain capillaries from human brain tissue can be used as a preclinical model to study barrier function under physiological and pathophysiological conditions. Here, we present an optimized protocol to isolate brain capillaries from fresh human brain tissue.

Understanding blood-brain barrier function under physiological and pathophysiological conditions is critical for the development of new therapeutic ...

Isolation and RNA Extraction of Neurons, Macrophages and Microglia from Larval Zebrafish Brains

To gain a detailed understanding of the role of different CNS cells during development or the establishment and progression of brain pathologies, it is important to isolate these cells without changing their gene expression profile. The zebrafish model provides a large number of transgenic fish lines in which specific cell types are labelled; for example neurons in the NBT:DsRed line or macrophages/microglia in the mpeg1:eGFP line. Furthermore, antibodies have been developed to stain specific cells, such as microglia with the 4C4 antibody.
Here, we describe the isolation of neurons, macrophages and microglia from larval zebrafish brains. Central to this protocol is the avoidance of an enzymatic tissue digestion at 37 &#176;C, which could modify cellular profiles. Instead a mechanical system of tissue homogenization at 4 &#176;C is used. This protocol entails homogenization of brains into cell suspension, their immuno-staining and the isolation of neurons, macrophages and microglia by FACS. Afterwards, we extracted RNA from those cells and evaluated their quality/quantity. We managed to obtain RNA of high quality (RNA Integrity Number (RIN) &#62; 7) to perform qPCR on macrophages/microglia and neurons, and transcriptomic analysis on microglia. This approach enables a better characterization of these cells, as well as a clearer understanding about their role in development and pathologies.

We present a protocol to isolate neurons, macrophages and microglia from larval zebrafish brains under physiological and pathological conditions. Upon isolation, RNA is extracted from these cells to analyze their gene expression profile. This protocol allows for the collection of high-quality RNA for performing downstream analysis like qPCR and transcriptomics.

To gain a detailed understanding of the role of different CNS cells during development or the establishment and progression of brain pathologies, it is ...

Short-Term Free-Floating Slice Cultures from the Adult Human Brain

Organotypic, or slice cultures, have been widely employed to model aspects of the central nervous system functioning in vitro. Despite the potential of slice cultures in neuroscience, studies using adult nervous tissue to prepare such cultures are still scarce, particularly those from human subjects. The use of adult human tissue to prepare slice cultures is particularly attractive to enhance the understanding of human neuropathologies, as they hold unique properties typical of the mature human brain lacking in slices produced from rodent (usually neonatal) nervous tissue. This protocol describes how to use brain tissue collected from living human donors submitted to resective brain surgery to prepare short-term, free-floating slice cultures. Procedures to maintain and perform biochemical and cell biology assays using these cultures are also presented. Representative results demonstrate that the typical human cortical lamination is preserved in slices after 4 days in vitro (DIV4), with expected presence of the main neural cell types. Moreover, slices at DIV4 undergo robust cell death when challenged with a toxic stimulus (H2O2), indicating the potential of this model to serve as a platform in cell death assays. This method, a simpler and cost-effective alternative to the widely used protocol using membrane inserts, is mainly recommended for running short-term assays aimed to unravel mechanisms of neurodegeneration behind age-associated brain diseases. Finally, although the protocol is devoted to using cortical tissue collected from patients submitted to surgical treatment of pharmacoresistant temporal lobe epilepsy, it is argued that tissue collected from other brain regions/conditions should also be considered as sources to produce similar free-floating slice cultures.

A protocol to prepare free-floating slice cultures from adult human brain is presented. The protocol is a variation of the widely used slice culture method using membrane inserts. It is simple, cost-effective, and recommended for running short-term assays aimed to unravel mechanisms of neurodegeneration behind age-associated brain diseases.

Organotypic, or slice cultures, have been widely employed to model aspects of the central nervous system functioning in vitro. Despite the potential of ...

Isolation of Region-specific Microglia from One Adult Mouse Brain Hemisphere for Deep Single-cell RNA Sequencing

As resident macrophages in the central nervous system, microglia actively control brain development and homeostasis, and their dysfunctions may drive human diseases. Considerable advances have been made to uncover the molecular signatures of homeostatic microglia as well as alterations of their gene expression in response to environmental stimuli. With the advent and maturation of single-cell genomic methodologies, it is increasingly recognized that heterogenous microglia may underlie the diverse roles they play in different developmental and pathological conditions. Further dissection of such heterogeneity can be achieved through efficient isolation of microglia from a given region of interest, followed by sensitive profiling of individual cells. Here, we provide a detailed protocol for the rapid isolation of microglia from different brain regions in a single adult mouse brain hemisphere. We also demonstrate how to use these sorted microglia for plate-based deep single-cell RNA sequencing. We discuss the adaptability of this method to other scenarios and provide guidelines for improving the system to accommodate large-scale studies.

We provide a protocol for isolation of microglia from different dissected regions of an adult mouse brain hemisphere, followed by semi-automated library preparation for deep single-cell RNA sequencing of full-length transcriptomes. This method will help to elucidate functional heterogeneity of microglia in health and disease.

As resident macrophages in the central nervous system, microglia actively control brain development and homeostasis, and their dysfunctions may drive ...

Isolation of Adult Human Astrocyte Populations from Fresh-Frozen Cortex Using Fluorescence-Activated Nuclei Sorting

The complexity of human astrocytes remains poorly defined in primary human tissue, requiring better tools for their isolation and molecular characterization. Fluorescence-activated nuclei sorting (FANS) can be used to successfully isolate and study human neuronal nuclei (NeuN+) populations from frozen archival tissue, thereby avoiding problems associated with handling&#160;fresh tissue. However, efforts to similarly isolate astroglia from the non-neuronal (NeuN-) element are lacking. A recently developed and validated immunotagging strategy uses three transcription factor antibodies to simultaneously isolate enriched neuronal (NeuN+), astrocyte (paired box protein 6 (PAX6)+NeuN-), and oligodendrocyte progenitor (OLIG2+NeuN-) nuclei populations from non-diseased, fresh (unfixed) snap-frozen&#160;postmortem human temporal neocortex tissue.
This technique was shown to be useful for the characterization of cell type-specific transcriptome alterations in primary pathological epilepsy neocortex. Transcriptomic analyses confirmed that PAX6+NeuN- sorted populations are robustly enriched for pan-astrocyte markers and capture astrocytes in both resting and reactive conditions. This paper describes the FANS methodology for the isolation of astrocyte-enriched nuclei populations from fresh-frozen human cortex, including tissue dissociation into single-nucleus (sn) suspension; immunotagging of nuclei with anti-NeuN and anti-PAX6 fluorescently conjugated antibodies; FANS gating strategies and quality control metrics for optimizing sensitivity and specificity during sorting and for confirming astrocyte enrichment; and recommended procurement for downstream transcriptome and chromatin accessibility sequencing at bulk or sn resolution. This protocol is applicable for non-necrotic, fresh-frozen, human cortical specimens with various pathologies and recommended postmortem tissue collection within 24 h.

We have developed a method that enriches for and isolates human astrocyte populations from fresh-frozen tissue for use in downstream molecular analyses.

The complexity of human astrocytes remains poorly defined in primary human tissue, requiring better tools for their isolation and molecular ...

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 ...