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

Este trabalho foi apoiado pelo Christopher e Dana Reeve Foundation International Research Consortium na lesão da medula espinhal, o Dr. Miriam e Sheldon G. Adelson Medical Research Foundation, Fundação JPB, o Instituto Novartis de pesquisas básicas, contribuições generosas de Vincent e Stella Coates e o Damon Runyon Cancer Research Foundation (DRG-2125-12).

Todos os procedimentos envolvendo roedores em conformidade com as diretrizes da Universidade de Stanford, que estejam em conformidade com políticas e leis estaduais e nacional. Todos os procedimentos de animais foram aprovados pelo painel administrativo da Universidade de Stanford no cuidado do Animal de laboratório.
Nota: Todas as composições de buffer e solução são fornecidas na Tabela de materiais.
1. preparar um prato de Petri para Immunopa...

     

<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>

Porque microglia servem como as células imunes Sentinela do SNC, eles são altamente sensíveis às mudanças ambientais; Portanto, muito cuidado é necessário para minimizar as respostas inflamatórias dentro das células durante seu isolamento e cultura8. Isso é feito no presente protocolo através de velocidade e temperatura. Sempre que possível reduz a ativação, para que todas as etapas de centrifugação ocorrem a 4 ° C, mantendo as células no gelo ou a 4 ° C, os animais são pintado...

Como os macrófagos do parênquima CNS, microglia interagir com uma vasta gama de circuitos neuronais e gliais redes de sinalização. Eles desempenham um papel vital no desenvolvimento e na homeostase do cérebro através de poda sináptica, afastamento de célula apoptótica e transitórias interações com processos neuronais1,2. Microglia são primeiros respondentes a lesões neurológicas, estendendo seus processos longos e finos para sites de lesão para coordenar as respostas inflamatórias e limitar o sangramento3,4. Alterações na função e morfologia microglial são onipresentes em lesões de CNS agudas e crônicas, e microglia exposição alterou a expressão de mediadores inflamatórios em uma variada gama de Estados de doença1, localização e morfologia. Estudos de genéticos humanos indicam que mutações que alteram o risco para doenças neurodegenerativas são frequentemente predominantemente ou exclusivamente expressa pela micróglia no SNC intacta, apontando para um papel crucial para microglia na patogênese da doença ou progressão5 . Dada sua proeminência em ferimentos e doenças, promover a compreensão da biologia microglial é uma alta prioridade para o desenvolvimento de novas abordagens terapêuticas.
Muitos avanços importantes para a compreensão da biologia microglial surgiram extrapolando as técnicas e mecanismos descobertos em estudos de outras populações de macrófagos, incluindo métodos de cultura, perfis de expressão de gene e definições de funcional / morfológica dos Estados. Embora generalizada macrófago funções muitas vezes jogar em formas surpreendentes dentro da paisagem do CNS, microglia são eles próprios altamente especializado, exibindo uma morfologia ramificada e uma assinatura de expressão de gene único que os distingue de outros tecidos os macrófagos6. Microglia tem uma linhagem que é diferente da maioria dos outros macrófagos de tecido; Eles colonizam o CNS durante uma onda de embrionária precoce da hematopoiese primitivo e auto renovam ao longo da vida, independente de contribuições de hematopoiese definitivo7. A assinatura de expressão de gene totalmente maduro do adulto microglia não é alcançada até a segunda semana pós-parto8. Dicas ambientais no tecido circundante desempenham um papel importante em ditar o macrófago tecido-específica características6, que no SNC inclui limitada exposição a fatores transmitidas pelo sangue, concedido pelo barreira hemato - encefálica,9.
Um obstáculo para compreender plenamente microglial contribuições para a homeostase do CNS e doença é a dificuldade de sintetizando as propriedades especializadas do maduro microglia visto na vivo com células purificadas in vitro. Muitos métodos têm sido desenvolvidos para isolar e cultura microglia intacta, mas a maioria das abordagens dependem de soro para apoiar a sobrevivência da pilha. Mostramos que além de soro, que é um reagente inerentemente variável que contém uma vasta gama de moléculas bioativas, é especialmente problemática quando trabalhar com microglia porque promove uma morfologia ameboide, aumentou a proliferação, e aumento da fagocitose9 muitas vezes visto em vivo quando microglia são expostas ao sangue a cargo de fatores após o rompimento da barreira do sangue - cérebro. Por essas métricas, células expostas ao soro se assemelham a micróglia em lesões ou doenças, mas tais alterações são reduzidas quando microglia são cultivadas em meio de crescimento definidos contendo CSF-1 (ou IL-34), TGF-β, colesterol e Selenito.
Este protocolo fornece detalhes sobre cultivo microglia juvenil rato sob condições isento de soro, relacionadas com o trabalho recentemente publicado9. Este protocolo foi racionalizado para ratos de pós-Natal dia 21-30 (P21 - P30), mas pode ser adaptado para isolar microglia de ratos e camundongos, de qualquer idade, embora o rendimento e a viabilidade global irão variar dependendo da espécie e idade do animal. Máximo rendimento e viabilidade ideal é alcançada quando usando um pouco imaturo microglia (~ P9), com rendimentos e viabilidade gradualmente afilado, um pouco mais baixos níveis em animais adultos. Microglia também pode ser isolado de ratos, mas achamos que pilhas do rato mostram significativamente mais elevados rendimentos, viabilidade e complexidade de morfologias ramificadas, quando comparado com as pilhas do rato em culturas isento de soro. Animais com idade superior a P50 não foram avaliadas com este protocolo. Este procedimento de isolamento de immunopanning foi otimizado para minimizar as alterações nos perfis transcriptional microglial durante o isolamento e para maximizar a jusante viabilidade das células. Usando estas técnicas e formulações de mídia, alta-viabilidade culturas primárias podem ser sustentadas por semanas. Microglia cultivada sob essas condições apresentam uma morfologia altamente ramificada envolvendo rápida extensão e retração dos processos e relativamente baixas taxas de proliferação. Podemos destacar a importância do soro-exposição sobre essas propriedades e discutir os pontos fortes e fraquezas deste método em relação a outras abordagens.

<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 representam 5-10% de todas as células do sistema nervoso central (SNC) e são cada vez mais atenção devido a suas contribuições durante o desenvolvimento, homeostase e doença. Embora os macrófagos têm sido estudados em detalhe por décadas, recursos especializados de micróglia, os macrófagos de tecido-residente do SNC, mantiveram-se em grande parte misteriosa, em parte devido às limitações na habilidade de recapitular microglial maduro Propriedades em cultura. Aqui, podemos ilustrar um procedimento simples para o isolamento rápido de puro microglia no cérebro de roedor maduro. Descrevemos também condições de cultura livre de soro que suportam níveis elevados de microglial viabilidade ao longo do tempo. Microglia cultivada sob essas condições definidas e médias apresentam elaborados processos ramificados e comportamento dinâmico de vigilância. Podemos ilustrar alguns efeitos de exposição de soro na microglia culta e discutir como essas culturas isento de soro comparam com culturas expostas ao soro, bem como micróglia em vivo.

Este protocolo descreve um método de cultura alta pureza ramificada microglia de ratos jovens. Resultados semelhantes podem ser obtidos usando animais imaturos, perinatais e adultos, como discutido abaixo. Desde que os isolamentos de célula frequentemente incluem nuances sutis e muitas oportunidades para as células a morrer, usamos pontos de verificação de controle de qualidade para ajudar a determinar o sucesso em várias etapas. Nós normalmente monitorados suspensões celulares us...

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

Esforços para entender a função microglial no detalhe tem sido prejudicados pela falta de modelos de cultura microglial que recapitular as propriedades de micróglia maduro na vivo . Este protocolo descreve uma abordagem de isolamento e cultura projetada para manter a sobrevivência robusta de rato maduro altamente ramificados microglia sob condições definidas e médias.

Isolamento e cultura de roedor Microglia para promover uma dinâmica ramificada morfologia em meio livre de soro

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.

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