Name: isolation and culture of rodent microglia to promote a dynamic ramified morphology in serum-free medium
Uploaded: 2018-03-09T14:00:00
Description: Watch this Scientific Journal Video about Isolation and Culture of Rodent Microglia to Promote a Dynamic Ramified Morphology in Serum-free Medium at JoVE.com

Dette arbeidet ble støttet av Christopher og Dana Reeve Foundation International forskning Consortium ryggmargsskade, Dr. Miriam og Sheldon G. Adelson Forskningsstiftelse, JPB stiftelsen, Novartis Institute av grunnleggende forskning, sjenerøse bidrag fra Vincent og Stella Coates og Damon Runyon Cancer Research Foundation (DRG-2125-12).

Alle prosedyrer som involverer gnagere likedannet Stanford University retningslinjer, som i samsvar med nasjonale og statlige lover og retningslinjer. Alle dyr prosedyrer ble godkjent av Stanford University's Administrative Panel på laboratoriet Animal Care.
Merk: Alle løsning og buffer komposisjoner er gitt i Tabellen for materiale.
1. klargjør en Petriskål for CD11b Immunopanning (dag 0)
Merk: Forberede 1 immunopannin...

     

<ol>
	<li>Colonna, M., Butovsky, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglia+Function+in+the+Central+Nervous+System+During+Health+and+Neurodegeneration.">Microglia Function in the Central Nervous System During Health and Neurodegeneration.</a> Annu Rev Immunol. 35, 441-468 (2017).</li><li>Wu, Y., Dissing-Olesen, L., MacVicar, B. A., Stevens, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglia:+Dynamic+Mediators+of+Synapse+Development+and+Plasticity.">Microglia: Dynamic Mediators of Synapse Development and Plasticity.</a> Trends Immunol. 36 (10), 605-613 (2015).</li><li>Lou, N., 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=Purinergic+receptor+P2RY12-dependent+microglial+closure+of+the+injured+blood-brain+barrier.">Purinergic receptor P2RY12-dependent microglial closure of the injured blood-brain barrier.</a> Proc Natl Acad Sci U S A. 113 (4), 1074-1079 (2016).</li><li>Haynes, S. E., 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+P2Y12+receptor+regulates+microglial+activation+by+extracellular+nucleotides.">The P2Y12 receptor regulates microglial activation by extracellular nucleotides.</a> Nat Neurosci. 9 (12), 1512-1519 (2006).</li><li>Gosselin, 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=An+environment-dependent+transcriptional+network+specifies+human+microglia+identity.">An environment-dependent transcriptional network specifies human microglia identity.</a> Science. 356 (6344), (2017).</li><li>Lavin, Y., 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=Tissue-resident+macrophage+enhancer+landscapes+are+shaped+by+the+local+microenvironment.">Tissue-resident macrophage enhancer landscapes are shaped by the local microenvironment.</a> Cell. 159 (6), 1312-1326 (2014).</li><li>Hoeffel, G., Ginhoux, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ontogeny+of+Tissue-Resident+Macrophages.">Ontogeny of Tissue-Resident Macrophages.</a> Front Immunol. 6, 486 (2015).</li><li>Bennett, M. 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=New+tools+for+studying+microglia+in+the+mouse+and+human+CNS.">New tools for studying microglia in the mouse and human CNS.</a> Proc Natl Acad Sci U S A. 113 (12), E1738-E1746 (2016).</li><li>Bohlen, C. 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=Diverse+Requirements+for+Microglial+Survival,+Specification,+and+Function+Revealed+by+Defined-Medium+Cultures.">Diverse Requirements for Microglial Survival, Specification, and Function Revealed by Defined-Medium Cultures.</a> Neuron. 94 (4), 759-773 (2017).</li><li>Herz, J., Filiano, A. J., Smith, A., Yogev, N., Kipnis, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Myeloid+Cells+in+the+Central+Nervous+System.">Myeloid Cells in the Central Nervous System.</a> Immunity. 46 (6), 943-956 (2017).</li></ol>

Fordi microglia fungere som sentinel immunceller av CNS, er de svært responsive til miljøendringer; stor forsiktighet må derfor minimere inflammatorisk svar i cellene under deres isolasjon og kultur8. Dette gjøres i denne protokollen gjennom hastighets- og temperaturinnstillinger. Holde cellene på isen eller i 4 ° C når mulig reduserer aktivisering, så alle sentrifugering trinnene finner sted på 4 ° C, dyrene er parfyme med iskald perfusjon buffer, og protokollen har blitt strømlinjefor...

Som makrofager av CNS parenchyma, microglia samhandle med et stort utvalg av nevrale kretser og glial signalnettverk nettverk. De spiller viktige roller i utviklingen og homeostase i hjernen gjennom synaptic beskjæring, apoptotisk celle klarering og transient interaksjoner med neuronal prosesser1,2. Microglia er tidlig responders for nevrologiske skader, utvide sine lange, tynne prosesser til lesjon steder å koordinere inflammatorisk svar og begrense blødning3,4. Endringene i microglial morfologi og funksjon er allestedsnærværende i både akutte og kroniske CNS skader, og microglia utstillingen endret morfologi, lokalisering og uttrykk for inflammatoriske mediatorer i en rekke ulike sykdom stater1. Menneskelige genetiske studier indikerer at mutasjoner som endrer risiko for nevrodegenerative sykdommer er ofte overveiende eller utelukkende uttrykt av microglia i intakt CNS peker til en avgjørende rolle for microglia i patogenesen ved sykdom eller progresjon5 . Gitt deres framtredende i skader og sykdom, er fremme forståelsen av microglial biologi svært viktig for å utvikle nye terapeutiske metoder.
Mange viktige fremskritt til forståelsen av microglial biologi har oppstått ved å ekstrapolere teknikker og mekanismer i studier av andre macrophage befolkningsgrupper inkludert kultur metoder, gene uttrykket profiler og definisjoner av funksjonell / morfologiske stater. Selv om generalisert macrophage funksjoner ofte spilt på overraskende måter i CNS landskapet, microglia er selv høyt spesialiserte, viser en ramified morfologi og en unik gene expression signatur som skiller dem fra andre vev makrofager6. Microglia har en slektslinje som er forskjellig fra de fleste andre vev makrofager; de kolonisere CNS under en tidlig embryonale bølge av primitive hematopoiesis og selvstendig fornye gjennom livet, uavhengig av bidrag fra definitive hematopoiesis7. Fullt ut modne gene expression signatur voksen microglia oppnås ikke før den andre postnatal uke8. Miljømessige signaler fra de omkringliggende vev spiller en viktig rolle i dikterer vev-spesifikke macrophage funksjoner6, som i CNS inkluderer begrenset eksponering for blodbårne faktorer gitt av blod - hjerne barrieren9.
En helt forstå microglial bidrag til CNS homeostase og sykdom er vanskeligheten av recapitulating spesialiserte egenskapene for eldre microglia sett vivo med renset celler i vitro. Mange metoder har blitt utviklet for å isolere og kultur intakt microglia, men de fleste tilnærminger stole på serum støtte celle overlevelse. Vi har vist at tillegg av serum, som er en iboende variabel reagens som inneholder en rekke bioaktive molekyler, er særlig problematisk når arbeider med microglia fordi den fremmer en amoeboid morfologi, økt spredning, og økt fagocytose9 sett ofte i vivo når microglia er utsatt for blod båret faktorer etter avbrudd av blod - hjerne barrieren. Av disse beregningene, serum-eksponert cellene ligner microglia i skade eller sykdom stater, men slike endringer er redusert når microglia er kultivert i definerte vekstmediet som inneholder CSF-1 (eller IL-34), TGF-β, kolesterol og selenitt.
Denne protokollen gir detaljer for dyrking juvenile rotte microglia under serum-free forhold knyttet til nylig publiserte arbeider9. Denne protokollen er strømlinjeformet for rotter fra postnatal dag 21-30 (P21 - P30), men kan tilpasses å isolere microglia fra rotter og mus i alle aldre, om avkastning og totale levedyktighet vil variere avhengig av arter og alder på dyret. Maksimal gir og optimal levedyktighet oppnås ved litt umoden microglia (~ P9), gir og levedyktighet gradvis avsmalnende til noe lavere nivåer i voksen dyr. Microglia kan også være isolert fra mus, men vi har funnet at rotte celler Vis betydelig høyere avkastning levedyktighet og kompleksiteten i ramified morphologies, sammenlignet med musen celler i serum-free kulturer. Dyr alderen større enn P50 har ikke blitt evaluert med denne protokollen. Denne immunopanning isolasjon prosedyren er blitt optimert å minimere endringer i microglial transcriptional profiler under isolasjon og å maksimere nedstrøms levedyktigheten til cellene. Bruker disse teknikkene og media formuleringer, kan høy-levedyktigheten primære kulturer opprettholdes i uker. Microglia kultivert under disse forholdene viser en svært ramified morfologi med rask utvidelse og retraksjon av prosesser og lave relativt priser spredning. Vi understreke betydningen av serum-eksponering på disse egenskapene, og diskutere styrkene og svakhetene ved denne metoden i forhold til andre tilnærminger.

<table>
	<tbody>
		<tr>
			<td>Rat: Sprague-Dawley</td>
			<td>Charles River</td>
			<td>Cat# 400</td>
			<td></td>
		</tr>
		<tr>
			<td>mouse anti-rat CD11b monoclonal (clone OX42)</td>
			<td>Bio-Rad</td>
			<td>Cat# MCA275R</td>
			<td>Panning: 1:1,000; Staining: 1:500</td>
		</tr>
		<tr>
			<td>Goat polycolonal anti-Iba1&#160;</td>
			<td>Abcam</td>
			<td>Cat# AB5076</td>
			<td>Staining: 1:500</td>
		</tr>
		<tr>
			<td>Rabbit polyclonal anti-Ki67&#160;</td>
			<td>Abcam&#160;</td>
			<td>Cat# AB15580</td>
			<td>Staining: 1:500</td>
		</tr>
		<tr>
			<td>Alexa Fluor Donkey anti-mouse 594</td>
			<td>Invitrogen</td>
			<td>Cat# 11055</td>
			<td>Staining: 1:500</td>
		</tr>
		<tr>
			<td>Alexa Fluor Donkey anti-goat 488</td>
			<td>Invitrogen</td>
			<td>Cat# A-21203</td>
			<td>Staining: 1:500</td>
		</tr>
		<tr>
			<td>Alexa Fluor Donkey anti-Rabbit 647</td>
			<td>Invitrogen</td>
			<td>Cat# A-31573</td>
			<td>Staining: 1:500</td>
		</tr>
		<tr>
			<td>Triton-X (detergent in ICC staining)</td>
			<td>Thermo Fisher</td>
			<td>Cat# 28313</td>
			<td></td>
		</tr>
		<tr>
			<td>Heparan sulfate</td>
			<td>Galen Laboratory Supplies</td>
			<td>Cat# GAG-HS01</td>
			<td></td>
		</tr>
		<tr>
			<td>Heparin</td>
			<td>Sigma&#160;</td>
			<td>Cat# M3149</td>
			<td></td>
		</tr>
		<tr>
			<td>Peptone from milk solids</td>
			<td>Sigma</td>
			<td>Cat# P6838</td>
			<td></td>
		</tr>
		<tr>
			<td>TGF-&#946;2</td>
			<td>Peprotech</td>
			<td>Cat# 100-35B</td>
			<td></td>
		</tr>
		<tr>
			<td>Murine IL-34</td>
			<td>R&#38;D Systems</td>
			<td>Cat# 5195-ML/CF</td>
			<td></td>
		</tr>
		<tr>
			<td>Ovine wool cholesterol</td>
			<td>Avanti Polar Lipids</td>
			<td>Cat# 700000P</td>
			<td></td>
		</tr>
		<tr>
			<td>Collagen IV</td>
			<td>Corning&#160;</td>
			<td>Cat# 354233</td>
			<td></td>
		</tr>
		<tr>
			<td>Oleic acid</td>
			<td>Cayman Chemicals&#160;</td>
			<td>Cat# 90260</td>
			<td></td>
		</tr>
		<tr>
			<td>11(Z)Eicosadienoic (Gondoic) Acid</td>
			<td>Cayman Chemicals&#160;</td>
			<td>Cat# 20606</td>
			<td></td>
		</tr>
		<tr>
			<td>Calcein AM dye</td>
			<td>Invitrogen</td>
			<td>Cat# C3100MP</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethidium homodimer-1</td>
			<td>Invitrogen</td>
			<td>Cat# E1169</td>
			<td></td>
		</tr>
		<tr>
			<td>DNaseI</td>
			<td>Worthington</td>
			<td>Cat# DPRFS</td>
			<td></td>
		</tr>
		<tr>
			<td>Percoll PLUS</td>
			<td>GE Healthcare</td>
			<td>Cat# 17-5445-02</td>
			<td></td>
		</tr>
		<tr>
			<td>Trypsin&#160;</td>
			<td>Sigma</td>
			<td>Cat# T9935</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM/F12</td>
			<td>Gibco</td>
			<td>Cat# 21041-02</td>
			<td></td>
		</tr>
		<tr>
			<td>Penicillin/ Streptomycin</td>
			<td>Gibco</td>
			<td>Cat# 15140-122</td>
			<td></td>
		</tr>
		<tr>
			<td>Glutamine</td>
			<td>Gibco</td>
			<td>Cat# 25030-081</td>
			<td></td>
		</tr>
		<tr>
			<td>N-acetyl cysteine&#160;</td>
			<td>Sigma</td>
			<td>Cat# A9165</td>
			<td></td>
		</tr>
		<tr>
			<td>Insulin</td>
			<td>Sigma</td>
			<td>Cat# 16634</td>
			<td></td>
		</tr>
		<tr>
			<td>Apo-transferrin&#160;</td>
			<td>Sigma</td>
			<td>Cat# T1147</td>
			<td></td>
		</tr>
		<tr>
			<td>Sodium selenite</td>
			<td>Sigma</td>
			<td>Cat# S-5261</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM (high glucose)</td>
			<td>Gibco</td>
			<td>Cat# 11960-044</td>
			<td></td>
		</tr>
		<tr>
			<td>Dapi Fluoromount-G</td>
			<td>Southern Biotech</td>
			<td>Cat# 0100-20&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Poly-D-Lysine&#160;</td>
			<td>Sigma</td>
			<td>Cat# A-003-E</td>
			<td></td>
		</tr>
		<tr>
			<td>Primaria Plates&#160;</td>
			<td>VWR</td>
			<td>Cat# 62406-456</td>
			<td></td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Stock reagents&#160;</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Apo-transferrin</td>
			<td></td>
			<td></td>
			<td>Reconstitution: 10 mg/mL in PBS 
			Concentration used: 1:100 
			Storage: -20&#176;C</td>
		</tr>
		<tr>
			<td>N-acetyl cysteine</td>
			<td></td>
			<td></td>
			<td>Reconstitution: 5 mg/mL in H2O 
			Concentration used: 1:1,000 
			Storage: -20&#176;C</td>
		</tr>
		<tr>
			<td>Sodium selenite</td>
			<td></td>
			<td></td>
			<td>Reconstitution: 2.5 mg/mL in H2O 
			Concentration used: 1:25,000 
			Storage: -20&#176;C</td>
		</tr>
		<tr>
			<td>Collagen IV</td>
			<td></td>
			<td></td>
			<td>Reconstitution: 200 &#956;g/mL in PBS 
			Concentration used: 1:100 
			Storage: -80&#176;C</td>
		</tr>
		<tr>
			<td>TGF-b2</td>
			<td></td>
			<td></td>
			<td>Reconstitution: 2 mg/mL in PBS 
			Concentration used: 1:1,000 
			Storage: -20&#176;C</td>
		</tr>
		<tr>
			<td>IL-34</td>
			<td></td>
			<td></td>
			<td>Reconstitution: 200 &#956;g/mL in PBS 
			Concentration used: 1:1,000 
			Storage: -80&#176;C</td>
		</tr>
		<tr>
			<td>Ovine wool cholesterol</td>
			<td></td>
			<td></td>
			<td>Reconstitution: 1.5 mg/mL in 100% ethanol 
			Concentration used: 1:1,000 
			Storage: -20&#176;C</td>
		</tr>
		<tr>
			<td>Heparan sulfate</td>
			<td></td>
			<td></td>
			<td>Reconstitution: 1 mg/mL in H2O 
			Concentration used: 1:1,000 
			Storage: -20&#176;C</td>
		</tr>
		<tr>
			<td>Oleic acid/Gondoic acid</td>
			<td></td>
			<td></td>
			<td>Reconstitution: Gondoic: 0.001 mg/mL; Oleic: 0.1 mg/mL in 100% ethanol 
			Concentration used: 1:1,000 
			Storage: -20&#176;C</td>
		</tr>
		<tr>
			<td>Heparin</td>
			<td></td>
			<td></td>
			<td>Reconstitution: 50 mg/mL in PBS 
			Concentration used: 1:100 
			Storage: -20&#176;C</td>
		</tr>
		<tr>
			<td>Name</td>
			<td>Company</td>
			<td>Catalog Number</td>
			<td>Comments</td>
		</tr>
		<tr>
			<td>Solutions&#160;</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Perfusion Buffer</td>
			<td></td>
			<td></td>
			<td>Recipe: 50 &#956;g/mL heparin in DPBS++ (PBS with Ca++ and Mg+ +) 
			Comments: Use when ice-cold</td>
		</tr>
		<tr>
			<td>Douncing Buffer</td>
			<td></td>
			<td></td>
			<td>Recipe: 200 &#956;L of 0.4% DNaseI in 50 mL of DPBS++ 
			Comments: Use when ice-cold</td>
		</tr>
		<tr>
			<td>Panning Buffer</td>
			<td></td>
			<td></td>
			<td>Recipe: 2 mg/mL of peptone from milk solids in DPBS++</td>
		</tr>
		<tr>
			<td>Microglia Growth Medium (MGM)</td>
			<td></td>
			<td></td>
			<td>Recipe: DMEM/F12 containing 100 units/mL penicillin, 100 &#956;g/mL streptomycin, 2 mM glutamine, 5 &#956;g/mL N-acetyl cysteine, 5 &#956;g/mL insulin, 100 &#956;g/mL apo-transferrin, and 100 ng/mL sodium selenite 
			Comments: Use ice-cold MGM to pan microglia off of immnopanning dish.</td>
		</tr>
		<tr>
			<td>Collagen IV Coating</td>
			<td></td>
			<td></td>
			<td>Recipe: MGM containing 2 &#956;g/mL collagen IV</td>
		</tr>
		<tr>
			<td>Myelin Seperation Buffer</td>
			<td></td>
			<td></td>
			<td>Recipe: 9 mL Percoll PLUS, 1 mL 10x PBS without Ca++ and Mg++, 9 &#956;L 1 M CaCl2, 5 &#956;L 1 M MgCl2 
			Comments: Mix well after the addition of&#160; CaCl2 and MgCl2</td>
		</tr>
		<tr>
			<td>TGF-b2/IL-34/Cholesterol containing growth media (TIC)&#160;</td>
			<td></td>
			<td></td>
			<td>Recipe: MGM containing human 2 ng/mL TGF-b2, 100 ng/mL murine IL-34, 1.5 &#956;g/mL ovine wool cholesterol, 10 &#956;g/mL heparan sulfate, 0.1 &#956;g/ml oleic acid, and 0.001 &#956;g/ml gondoic acid 
			Comments: Make sure to add cholesterol to media warmed to 37 &#176;C and do not add more than 1.5 &#956;g/mL or it will precipitate out. Do not filter cholesterol-containing media. Equilibrate TIC media with 10% CO2 for 30 min- 1 hr before adding to cells to insure optimal pH.</td>
		</tr>
	</tbody>
</table>

isolation and culture of rodent microglia to promote a dynamic ramified morphology in serum-free medium

Microglia utgjør 5-10% av alle sentralnervesystemet (CNS) celler og økende grad trekker oppmerksomhet deres bidrag under utvikling, homeostase og sykdom. Selv om makrofager har vært studert i detalj for tiår, spesialiserte funksjoner av microglia, vev-resident makrofager av CNS, har vært i stor grad mystisk, delvis på grunn av begrensninger i kunne recapitulate moden microglial egenskaper i kultur. Her viser vi en ukomplisert prosedyre for rask isolering av ren microglia fra modne gnager hjernen. Vi beskriver også serum-free oppdrettsforholdene som støtter høye nivåer av microglial levedyktighet over tid. Microglia kultivert under disse definert mellomstore forholdene utstilling forseggjort ramified prosesser og dynamisk overvåking atferd. Vi illustrerer noen effekter av serum eksponering på kulturperler microglia og diskutere hvordan disse serum-free kulturer i forhold til både serum-eksponerte kulturer samt microglia i vivo.

Denne protokollen beskriver en metode å kultur høy renhetsgrad ramified microglia fra juvenile rotter. Lignende resultater kan oppnås ved hjelp av umodne, perinatal og voksen dyr, som beskrevet nedenfor. Siden cellen isolasjoner ofte inkluderer nyansene og mange muligheter for cellene å dø, brukte vi kvalitetskontroll sjekkpunkter for å finne suksess på trinnene. Vi vanligvis overvåket celle suspensjoner bruker en hemocytometer på flere trinn i isolasjon protokollen (<strong clas...

Watch this Scientific Journal Video about Isolation and Culture of Rodent Microglia to Promote a Dynamic Ramified Morphology in Serum-free Medium at JoVE.com

Isolation and Culture of Rodent Microglia to Promote a Dynamic Ramified Morphology in Serum-free Medium

Innsats for å forstå microglial funksjonen i detalj har blitt hindret av mangelen på microglial kultur modeller som recapitulate egenskapene for eldre i vivo microglia. Denne protokollen beskriver isolasjon og kultur tilnærming beregnet på vedlikeholde robuste overlevelse av svært ramified modent rotta microglia under definert mellomstore forhold.

Isolasjon og kultur av gnager Microglia å fremme en dynamisk Ramified morfologi i Serum-free Medium

Microglia represent 5 - 10% of all central nervous system (CNS) cells and are increasingly drawing attention due to their contributions during ...

The overall goal of this cell culture protocol is to generate highly pure cultures of microglia from developing or adult rodents that can be maintained without exposure to serum. This procedure can help answer key questions in neuroscience related to microglia morphology, fibrous ketosis, and microglia's interaction with other CNS cell types. The main advantage to this protocol is that microglia can be rapidly isolated from rodent tissue of any age and cultured without exposure to serum.To remove the brain, cut the occipital condyle from the spinal cord of an animal on both sides with dissection scissors, being careful not to damage the brain. Then, cut skin along the top of the skull, and cut up one side along the parietal and frontal bone towards the nasal bone. Carefully pull back the top of the skull with forceps, quickly remove the brain, and place it into prechilled DPBS on ice.Repeat the procedure for all remaining animals. After the brains have been collected in cold DPBS, chop each brain into one cube millimeter chunks in a petri dish on ice with a cold scalpel blade and transfer to an ice cold dounce homogenizer with five to seven milliliters of ice cold douncing buffer. Next, use a loose fitting dounce homogenizer to dissociate the tissue with 10 to 20 gentle and incomplete strokes.Take care not to directly crush the tissue at the bottom of the homogenizer. Instead, impel the tissue through the space between the sides of the piston and the homogenizer. It is important to slowly homogenize the tissue with multiple rounds of douncing to preserve microglia viability.Afterward, carefully remove the piston to prevent introducing air bubbles. Allow poorly dissociated tissue chunks to settle to the bottom of the homogenizer and transfer the supernatant to a new, chilled, 50 milliliter conical tube. Subsequently, replace the removed volume with fresh douncing buffer and repeat the dissociation procedure for a total of three to four rounds, or until all tissue has been dissociated.In this procedure, add ice cold douncing buffer to the 50 milliliter conical tube containing the cell suspension and adjust the total volume to 33.5 milliliters. Next, add 10 milliliters of MSB to the cell suspension and mix thoroughly by inverting the tube several times. This will result in a 23%final concentration of MSB in a volume of 43.5 milliliters.After that, centrifuge the cells for 15 minutes at 500 x g at 4 degrees Celsius with slow braking. Then, remove the top layer of myelin and debris and the supernatant with a pipette. Take care when removing the top layer to ensure as much of it is removed as possible.Following that, resuspend the cell pellet in 12 milliliters of panning buffer. Gently triturate the cell suspension to break up any remaining clumps of cells. In this step, pass the cell suspension through a 70 micrometer cell strainer to remove large debris or cell clumps.Rinse the OX42 coated panning dish three times with DPBS. Don't allow the plate to completely dry between washes. Pour off the last DPBS wash and apply the filtered cell suspension to the panning dish.Gently swirl the plate to distribute the cells. Then, incubate the plate on a flat surface at room temperature for 20 minutes to allow cells to adhere. Do not incubate longer than 20 minutes or cells will become very difficult to recover from the dish.Afterward, rinse the panning dish with DPBS 10 times to remove nonadherent cells. Microglia will be firmly attached to the plate, so swirl the plate with each rinse to ensure the removal of other nonadherent cells. Pour off the last DPBS wash and replace with 15 milliliters of DPBS and 200 microliters of trypsin.To trypsinize the cells, incubate the dish for less than or equal to 10 minutes at 37 degrees Celsius. After 10 minutes of trypsinization, microglia will still be stuck to the plate. Pour off the mixture and gently wash the plate two times with DPBS to remove the trypsin.Then, replace with 12 milliliters of ice cold MGM. Subsequently, place the panning dish on ice for two minutes to help weaken cell and substrate interaction and make sure that the dish is flat to prevent areas of the panning dish from drying out. After that, pipette vigorously with a 10 milliliter pipette and pipette controller on high speed to recover cells from the panning dish.Draw a 16 by 16 grid with the stream of liquid from the pipette to try and remove all of the cells. It is important to find a balance between overall cell recovery and the health of your culture. Repeated pipetting of the cell supernatant against the panning dish will result in reduced viability of your culture.Check the cells under a microscope at 20x magnification to make sure that they have detached from the plate. Mark the spots on top of the dish where cells are stuck and repeat pipetting in those areas. Collect the cell suspension and allocate three to four milliliters of supernatant in each 15 milliliter conical tube.Spin it for 15 minutes at 500 x g at four degrees Celsius with slow braking. After 15 minutes, aspirate the supernatant, leaving 0.5 milliliters of MGM with the cell pellet. Then, resuspend each pellet in remaining MGM and pull the cells from all the tubes.Following that, count the cells with a hemocytometer. Now, plate 15 microliters of collagen IV coating directly in the center of a 24 well anionic cationic coated tissue culture plate and incubate for 15 minutes at 37 degrees Celsius. After counting the cells with a hemocytometer, dilute them to 2.3 x 10 to the five per milliliter in MGM.Aspirate collagen IV spot and immediately plate 15 microliters of cell suspension to this spot to yield 3.5 x 10 to the three cells per spot. Next, incubate for five to ten minutes at 37 degrees Celsius to allow the cells to adhere. Then, gently add 500 microliters of CO2 equilibrated TIC to the well.If plating on cover slips, first coat the sterile glass cover slips with 10 micrograms per milliliter PDL in water for one hour at room temperature. Then, wash them three times with water and let them dry in a hood under UV light before proceeding with spot plating on the cover slips. In order to demonstrate successful isolation and culture of highly pure microglia, we isolated microglia from P21 rats and cultured these cells in TIC or TIC supplemented with 10%FCS for eight days.Cells were then fixed and stained with microglial markers and proliferation markers. Cells cultured in TIC show a ramified morphology, low levels of proliferation, and expression of microglia markers. In comparison, cells cultured in TIC supplemented with 10%FCS also stained for microglial markers, but show high levels of proliferation and amoeboid morphology, properties often seen in activated microglia.In addition to staining for cell markers, RNA-Seq on freshly isolated cells can provide a powerful and sensitive tool for evaluating the RNA profile of the cells and can help inform the starting purity of cultures. CD11b micropanning typically results in a small percentage of CD11b positive neutrophils and monocyte carryover, in addition to CD11b positive microglia. These cells will die in TIC after a few days, but can complicate analysis of earlier timepoints.Here is a time lapse movie of P21 rat microglia after 14 DIV in TIC. After two weeks, serum free cultures show dynamic surveillance behavior with rapid process extensions and retractions throughout the dish. Here is a time lapse movie of P21 rat microglia after five DIV in TIC before and after exposure to fetal calf serum.A rapid morphological change is evident after serum exposure. Once mastered, this protocol can be done in four to five hours, if performed properly. Following this procedure, other assays to monitor phagocytosis, chemotaxis, survival, cytokine release, transcriptional responses to stimuli, can be performed in order to answer additional questions about microglia function.After watching this video, you should have a good understanding on how to rapidly isolate microglia from adult rodent tissue and culture them under serum free conditions.

Research

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