Funded by the intramural program at the Uniformed Services University.

1. Dissection of Neonatal Rat Brain Tissue
<ol>
	<li>Chill Leibovitz's L-15 conditioned media (Leibowitz L-15 + 0.1% BSA + 1% Pen/Strep) to 4 &deg;C. Warm culture media (DMEM + 10% FBS + 1% Penicillin/Streptomycin) to 37 &deg;C. Prepare 4 60x15 mm Petri dishes with 4-5 ml of the conditioned L-15 media on ice. Sterilize all surgical tools with 100% ethanol.</li>
	<li>Rinse the P2 neonatal rap pups with 70% ethanol. (Neonatal rat pups aged between P1-P5 can be used in this protocol.)</li>
	<li>Quickly decapitate a rat pup with sterile sharp scissors and drop the head immediately into 70% ethanol. Repeat for a total of 5 rat pups then transfer heads into saline solution.</li>
	<li>Remove the whole brains from the heads and place into a Petri dish with 4 - 5 ml L-15 solution (Leibowitz L-15 + 0.1% BSA + 1% Pen/Strep) on ice.</li>
	<li>Repeat procedures 1.2 - 1.4 for the remaining pups in the litter.</li>
	<li>Remove the meninges from the brain and transfer the desired brain tissue (i.e., cortex, cerebellum, whole brain, etc.) into a new Petri dish with 4-5 ml of L-15 solution (Leibowitz L-15 + 0.1% BSA + 1% Pen/Strep) on ice.</li>
</ol>
2. Preparation of Mixed Glial Cell Population
<ol>
	<li>Without damaging brain tissue with scissors or a blade, transfer the tissue with a 10 ml pipette to a sterile 50 ml conical tube.</li>
	<li>Centrifuge conical at 2,500 RCF for 5 min at 4 &deg;C.</li>
	<li>Aspirate supernatant. Add 4-5 ml of fresh L-15 media (Leibowitz L-15 + 0.1% BSA + 1% Pen/Strep).</li>
	<li>Pipette tissue up and down 10 times with a sterile 10 ml pipette.</li>
	<li>Place a cell strainer (100 &mu;m pores) onto a fresh 50 ml conical tube. Pipette tissue up and down once with a sterile 5 ml pipette and with the pipette flush to the cell strainer, dispense the material through the cell strainer into the conical tube.</li>
	<li>Rinse the cell strainer with 4-5 ml of fresh L-15 media (Leibowitz L-15 + 0.1% BSA + 1% Pen/Strep).</li>
	<li>Centrifuge conical with strained cells at 2,500 RCF for 5 min at 4 &deg;C.</li>
</ol>
3. Plating and Maintenance of Mixed Glial Cell Cultures
<ol>
	<li>For each rat pup brain processed, prepare 1 sterile T-75 flask by adding 12 ml of culture media (DMEM + 10% FBS + 1% Penicillin/Streptomycin) into each flask.</li>
	<li>Aspirate the supernatant from the pelleted cells and add 5-6 ml of culture media to the cell pellet. Pipette up and down 10 times with a 10 ml pipette.</li>
	<li>Transfer an equal volume of cell suspension to each T-75 flask.</li>
	<li>Incubate flasks in a 5% CO2 incubator at 37 &deg;C for a total of 1-3 weeks.</li>
	<li>Flasks should be first incubated for 5 days, and on the fifth day, replace the culture media in each flask with 12 ml of fresh media and return to the incubator. Then, every 3 days, replace the conditioned media in each flask with 12 ml of fresh media to achieve confluence. This must be done very carefully without touching the bottom of the flasks where the cells attach.</li>
</ol>
4. Isolation and Plating of Primary Microglia
<ol>
	<li>After mixed glial cultures are completely confluent, remove flasks from the incubator and cover flask caps with parafilm to prevent gas exchange with environmental air.</li>
	<li>Shake flasks at 100 rps (Lab Companion SI-600, Jeio Tech) for 1 hr at 37 &deg;C.</li>
	<li>Collect media from all flasks with a 10 ml pipette without disrupting the astrocyte layer on the flask surface. Place the media in 50 ml conical tubes. Add fresh media to the flasks and return flasks to the incubator.</li>
	<li>Centrifuge conical tubes at 2,500 RCF for 5 min at 4 &deg;C.</li>
	<li>Aspirate supernatant from all conical tubes. Cell pellets are high purity microglia cells. Resuspend pellets in 1 ml of microglia plating media (DMEM + 10% FES + 1% Penicillin/Streptomycin).</li>
	<li>Count the cell density in the resuspended media using a hemocytometer.</li>
	<li>Add an appropriate volume of microglia plating media to achieve a 2 x 10e5 cells per ml density. Plate as appropriate for experimental analysis.</li>
	<li>Allow microglia to attach overnight.</li>
</ol>
5. Representative Results
The protocol described above results in high purity primary microglia cultures. As determined by immunohistochemistry for a macrophage/microglia cell specific marker (Iba1), plated microglia cultures are &gt; 90% pure (Figure 2). Additionally, staining for astrocyte, oligodendrocyte and neuron cell specific markers demonstrates minimal contamination (Figure 2). After establishing mixed glial cell cultures, microglia can be isolated by shaking up to 4 successive times. The initial microglia isolation will yield approximately 2.2 x 10&circ;6 cells/ml or approximately 9 million cells per 10 flasks and the expected yield decreases with each successive shake. Microglia isolated by this method have been used successfully to investigate phagocytosis ability, function such as nitric oxide production, and neuronal toxicity (Figure 3) 13-14.
<img alt="Figure 1" src="/files/ftp_upload/3814/3814fig1.jpg" /> 
Figure 1. Overview of the protocol for preparing mixed glial cell cultures and isolation of primary microglia.
<img alt="Figure 2" src="/files/ftp_upload/3814/3814fig2.jpg" /> 
Figure 2. Isolation of high purity microglia as verified by immunohistochemical analysis using microglia (Iba-1, red), astrocyte (GFAP, green), neuron (NeuN, red) and oligodendrocyte (CC1, red) specific markers. Staining for DNA of cells in culture by DAPI (blue) is also shown.
<img alt="Figure 3" src="/files/ftp_upload/3814/3814fig3.jpg" /> 
Figure 3. Microglia isolated in the method described have been used in a number of assays, including, but not limited to, phagocytosis assays, function assays and neurotoxicity studies. In these studies, we have found that microglia (Iba-1 positive, green), when exposed to control (A) or LPS (B) treated media, increase their phagocytosis of fluorescently labeled latex beads (red), which can be quantified (C). Further, LPS (1ng/ml) treatment can increase nitric oxide production in microglia (D). Finally, via both transwell insert-separated or direct microglia-neuron cultures, we have found that microglia incubated with LPS can induce neuronal cell death as measured by lactate dehydrogenase (LDH) release (E, F).

<ol>
	<li>Ransohoff, R. M., Perry, V. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglial+physiology:+unique+stimuli,+specialized+responses.">Microglial physiology: unique stimuli, specialized responses.</a> Annu. Rev. Immunol. 27, 119-145 (2009).</li><li>Raivich, G., Bohatschek, M., Kloss, C. U., Werner, A., Jones, L. L., Kreutzberg, G. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neuroglial+activation+repertoire+in+the+injured+brain:+graded+response,+molecular+mechanisms+and+cues+to+physiological+function.">Neuroglial activation repertoire in the injured brain: graded response, molecular mechanisms and cues to physiological function.</a> Brain Res. Brain Res. Rev. 30, 77-105 (1999).</li><li>Loane, D. J., Byrnes, K. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+microglia+in+neurotrauma.">Role of microglia in neurotrauma.</a> Neurotherapeutics. 7, 245-265 (2010).</li><li>Glass, C. K., Saijo, K., Winner, B., Marchetto, M. C., Gage, F. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mechanisms+underlying+inflammation+in+neurodegeneration.">Mechanisms underlying inflammation in neurodegeneration.</a> Cell. 140, 918-934 (2010).</li><li>Pocock, J. M., Liddle, A. C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microglial+signalling+cascades+in+neurodegenerative+disease.">Microglial signalling cascades in neurodegenerative disease.</a> Prog. Brain Res. 132, 555-565 (2001).</li><li>Block, M. L., Hong, J. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Chronic+microglial+activation+and+progressive+dopaminergic+neurotoxicity.">Chronic microglial activation and progressive dopaminergic neurotoxicity.</a> Biochem. Soc. Trans. 35, 1127-1132 (2007).</li><li>Barger, S. W., Basile, A. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activation+of+microglia+by+secreted+amyloid+percursor+protein+evokes+release+of+glutamate+by+cystine+exchange+and+attenuates+synpatic+function.">Activation of microglia by secreted amyloid percursor protein evokes release of glutamate by cystine exchange and attenuates synpatic function.</a> J. Neurochem. 76, 846-854 (2001).</li><li>Ni, M., Aschner, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Neonatal+rat+primary+microglia:+isolation,+culturing,+and+selected+applications.">Neonatal rat primary microglia: isolation, culturing, and selected applications.</a> Curr. Protoc. Toxicol. Chapter 12, Unit 12.17 (2010).</li><li>Hassan, N. F., Rifat, S., Campbell, D. E., McCawley, L. J., Douglas, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+flow+cytometric+characterization+of+newborn+mouse+brain-derived+microglia+maintained+in+vitro.">Isolation and flow cytometric characterization of newborn mouse brain-derived microglia maintained in vitro.</a> J. Leukoc. Biol. 50, 86-92 (1991).</li><li>Hassan, N. F., Prakash, K., Chehimi, J., McCawley, L. J., Douglas, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+characterization+of+newborn+rabbit+brain-derived+microglia.">Isolation and characterization of newborn rabbit brain-derived microglia.</a> Clin. Immunol. Immunopathol. 59, 426-435 (1991).</li><li>Hassan, N. F., Campbell, D. E., Rifat, S., Douglas, S. D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolation+and+characterization+of+human+fetal+brain-derived+microglia+in+in+vitro+culture.">Isolation and characterization of human fetal brain-derived microglia in in vitro culture.</a> Neuroscience. 41, 149-158 (1991).</li><li>Frank, M. G., Wieseler-Frank, J. L., Watkins, L. R., Maier, S. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+isolation+of+highly+enriched+and+quiescent+microglia+from+adult+rat+hippocampus:+immunophenotypic+and+functional+characteristics.">Rapid isolation of highly enriched and quiescent microglia from adult rat hippocampus: immunophenotypic and functional characteristics.</a> J. Neurosci. Methods. 151, 121-130 (2006).</li><li>Byrnes, K. R., Stoica, B., Loane, D. J., Riccio, A., Davis, M. I., Faden, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Metabotropic+glutamate+receptor+5+activation+inhibits+microglial+associated+inflammation+and+neurotoxicity.">Metabotropic glutamate receptor 5 activation inhibits microglial associated inflammation and neurotoxicity.</a> Glia. 57, 550-560 (2009).</li><li>Loane, D. J., Stoica, B. A., Pajoohesh-Ganji, A., Byrnes, K. R., Faden, A. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activation+of+metabotropic+glutamate+receptor+5+modulates+microglial+reactivity+and+neurotoxicity+by+inhibiting+NADPH+oxidase.">Activation of metabotropic glutamate receptor 5 modulates microglial reactivity and neurotoxicity by inhibiting NADPH oxidase.</a> J. Biol. Chem. 284, 15629-15639 (2009).</li></ol>

No conflicts of interest declared.

While this protocol is routinely utilized to produce pure and healthy microglia for research experiments, careful consideration of technical aspects during critical parts of the procedure will minimize variability in the isolated microglia. First, during the dissection of brain tissue from neonatal rat pups, working in a timely fashion is necessary to minimize hypoxic and ischemic damage to the tissue. However, it is also important to completely remove the meningeal covering from the brain during dissection, beca...

<table border="1">
	<tbody>
 <tr>
 <td>Name of the reagent</td>
 <td>Company</td>
 <td>Catalog number</td>
 <td>Comments</td>
 </tr>
 <tr>
 <td>60 mm x 15 mm Petri dishes</td>
 <td>Fisher brand</td>
 <td>0875713A</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Sharp dissecting scissors</td>
 <td>Fine Science Tools </td>
 <td>14094-11</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Dumont #7b forceps- standard tips, curved, 11cm</td>
 <td>Fine Science Tools</td>
 <td>11270-20</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Dumont #5 forceps-standard tips, straight, 11 cm</td>
 <td>Fine Science Tools</td>
 <td>11251-10</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>50 ml conical centrifuge tubes</td>
 <td>VWR </td>
 <td>89039-656</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>5 ml serological pipettes</td>
 <td>Grenier Bio One</td>
 <td>606180</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>10 ml serological pipettes</td>
 <td>Grenier Bio One</td>
 <td>607180</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>100 &mu;m sterile nylon cell strainer</td>
 <td>Falcon</td>
 <td>35-2360</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>75 cm2 tissue culture flasks</td>
 <td>Corning</td>
 <td>430641</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Dulbecco's minimal essential medium (DMEM)</td>
 <td>Gibco (Invitrogen)</td>
 <td>31053-028</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Leibovitz's L-15 medium</td>
 <td>Gibco (Invitrogen)</td>
 <td>11415064</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Fetal bovine serum</td>
 <td>Gibco(Invitrogen)</td>
 <td>16000-036</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Fetal equine serum</td>
 <td>Fisher</td>
 <td>SH3007402</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Penicillin-Streptomycin</td>
 <td>Gibco (Invitrogen)</td>
 <td>15140163</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>100% Ethanol</td>
 <td>The Warner Graham Company</td>
 <td>64-17-5</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Phosphate buffered saline solution, 10X, pH 7.4 </td>
 <td>Quality Biological, inc. </td>
 <td>119-069-131</td>
 <td>1X in sterile, distilled water</td>
 </tr>
 <tr>
 <td>Biohazard bags</td>
 <td>VWR</td>
 <td>14220-028</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>Haemocytometer</td>
 <td>Hausser Scientific</td>
 <td>1492</td>
 <td>&nbsp;</td>
 </tr>
 <tr>
 <td>6-well cell culture plates with cellBIND surface</td>
 <td>Corning</td>
 <td>3335</td>
 <td>&nbsp;</td>
 </tr>
	 </tbody>
 </table>

primary microglia isolation from mixed glial cell cultures of neonatal rat brain tissue

Microglia account for approximately 12% of the total cellular population in the mammalian brain. While neurons and astrocytes are considered the major cell types of the nervous system, microglia play a significant role in normal brain physiology by monitoring tissue for debris and pathogens and maintaining homeostasis in the parenchyma via phagocytic activity 1,2. Microglia are activated during a number of injury and disease conditions, including neurodegenerative disease, traumatic brain injury, and nervous system infection 3. Under these activating conditions, microglia increase their phagocytic activity, undergo morpohological and proliferative change, and actively secrete reactive oxygen and nitrogen species, pro-inflammatory chemokines and cytokines, often activating a paracrine or autocrine loop 4-6. As these microglial responses contribute to disease pathogenesis in neurological conditions, research focused on microglia is warranted.
	Due to the cellular heterogeneity of the brain, it is technically difficult to obtain sufficient microglial sample material with high purity during in vivo experiments. Current research on the neuroprotective and neurotoxic functions of microglia require a routine technical method to consistently generate pure and healthy microglia with sufficient yield for study. We present, in text and video, a protocol to isolate pure primary microglia from mixed glia cultures for a variety of downstream applications. Briefly, this technique utilizes dissociated brain tissue from neonatal rat pups to produce mixed glial cell cultures. After the mixed glial cultures reach confluency, primary microglia are mechanically isolated from the culture by a brief duration of shaking. The microglia are then plated at high purity for experimental study.
	The principle and protocol of this methodology have been described in the literature 7,8. Additionally, alternate methodologies to isolate primary microglia are well described 9-12. Homogenized brain tissue may be separated by density gradient centrifugation to yield primary microglia 12. However, the centrifugation is of moderate length (45 min) and may cause cellular damage and activation, as well as, cause enriched microglia and other cellular populations. Another protocol has been utilized to isolate primary microglia in a variety of organisms by prolonged (16 hr) shaking while in culture 9-11. After shaking, the media supernatant is centrifuged to isolate microglia. This longer two-step isolation method may also perturb microglial function and activation. We chiefly utilize the following microglia isolation protocol in our laboratory for a number of reasons: (1) primary microglia simulate in vivo biology more faithfully than immortalized rodent microglia cell lines, (2) nominal mechanical disruption minimizes potential cellular dysfunction or activation, and (3) sufficient yield can be obtained without passage of the mixed glial cell cultures.
	It is important to note that this protocol uses brain tissue from neonatal rat pups to isolate microglia and that using older rats to isolate microglia can significantly impact the yield, activation status, and functional properties of isolated microglia. There is evidence that aging is linked with microglia dysfunction, increased neuroinflammation and neurodegenerative pathologies, so previous studies have used ex vivo adult microglia to better understand the role of microglia in neurodegenerative diseases where aging is important parameter. However, ex vivo microglia cannot be kept in culture for prolonged periods of time. Therefore, while this protocol extends the life of primary microglia in culture, it should be noted that the microglia behave differently from adult microglia and in vitro studies should be carefully considered when translated to an in vivo setting.

Watch this Scientific Journal Video about Primary Microglia Isolation from Mixed Glial Cell Cultures of Neonatal Rat Brain Tissue at JoVE.com

Primary Microglia Isolation from Mixed Glial Cell Cultures of Neonatal Rat Brain Tissue

Isolating primary microglia from the cellular heterogeneity of the brain is essential to investigate their role in both physiological and pathological conditions. This protocol describes a mechanical isolation and mixed cell culture technique that provides high yield and high purity, viable primary microglial cells for in vitro study and downstream applications.

Microglia account for approximately 12% of the  total cellular population in the mammalian brain. While neurons and astrocytes are considered  the major ...

primary-microglia-isolation-from-mixed-glial-cell-cultures-neonatal

Research

JoVE Journal

Immunology and Infection

39.1K Views.  Uniformed Services University. Isolating primary microglia from the cellular heterogeneity of the brain is essential to investigate their role in both physiological and pathological conditions. This protocol describes a mechanical isolation and mixed cell culture technique that provides high yield and high purity, viable primary microglial cells for in vitro study and downstream applications.

Video: Primary Microglia Isolation from Mixed Glial Cell Cultures of Neonatal Rat Brain Tissue

A Simple and Efficient Method to Isolate Macrophages from Mixed Primary Cultures of Adult Liver Cells

Kupffer cells are liver-specific resident macrophages and play an important role in the physiological and pathological functions of the liver1-3. Although the isolation methods of liver macrophages have been well-described4-6, most of these methods require sophisticated equipment, such as a centrifugal elutriator and technical skills. Here, we provide a novel method to obtain liver macrophages in sufficient number and purity from mixed primary cultures of adult rat liver cells, as schematically illustrated in Figure 1.
After dissociation of the liver cells by two-step perfusion method7,8,a fraction mostly composed of parenchymal hepatocytes is prepared and seeded into T75 tissue culture flasks with culture medium composed of DMEM and 10% FCS.Parenchymal hepatocytes lose the epithelial cell morphology within a few days in culture, degenerate or transform into fibroblast-like cells (Figure 2). As the culture proceeds, around day 6, phase contrast-bright, round macrophage-like cells start to proliferate on the fibroblastic cell sheet (Figure 2). The growth of the macrophage-like cells continue and reach to maximum levels around day 12, covering the cell sheet on the flask surface. By shaking of the culture flasks, macrophages are readily suspended into the culture medium. Subsequent transfer and short incubation in plastic dishes result in selective adhesion of macrophages(Figure 3), where as other contaminating cells remain suspended. After several rinses with PBS, attached macrophages are harvested. More than 106 cells can be harvested repeatedly from the same T75 tissue culture flask at two to three day intervals for more than two weeks(Figure 3).The purities of the isolated macrophages were 95 to 99%, as evaluated by flow cytometry or immunocytochemistry with rat macrophage-specific antibodies (Figure 4).The isolated cells show active phagocytosis of polystylene beads (Figure 5), proliferative response to recombinant GM-CSF, secretion of inflammatory/anti-inflammatory cytokines upon stimulation with LPS, and formation of multinucleated giant cells9.
In conclusion, we provide a simple and efficient method to obtain liver macrophages in sufficient number and purity without complex equipment and skills.This method might be applicable to other mammalian species.

A novel method to obtain macrophages from primary culture of rat liver cells is described. This method utilizes the proliferation of macrophages in the culture, followed by shaking of culture flasks and purification by selective attachment to plastic dishes. This technique efficiently provides liver macrophages without complex equipment and skills.

Kupffer cells are liver-specific resident macrophages and play an important role in the physiological and pathological functions of the liver1-3. Although ...

Generation of Organotypic Raft Cultures from Primary Human Keratinocytes

The development of organotypic epithelial raft cultures has provided researchers with an efficient in vitro system that faithfully recapitulates epithelial differentiation. There are many uses for this system. For instance, the ability to grow three-dimensional organotypic raft cultures of keratinocytes has been an important milestone in the study of human papillomavirus (HPV)1. The life cycle of HPV is tightly linked to the differentiation of squamous epithelium2. Organotypic epithelial raft cultures as demonstrated here reproduce the entire papillomavirus life cycle, including virus production3,4,5. In addition, these raft cultures exhibit dysplastic lesions similar to those observed upon in vivo infection with HPV. Hence this system can also be used to study epithelial cell cancers, as well as the effect of drugs on epithelial cell differentiation in general. Originally developed by Asselineau and Prunieras6 and modified by Kopan et al.7, the organotypic epithelial raft culture system has matured into a general, relatively easy culture model, which involves the growth of cells on collagen plugs maintained at an air-liquid interface (Figure 1A). Over the course of 10-14 days, the cells stratify and differentiate, forming a full thickness epithelium that produces differentiation-specific cytokeratins. Harvested rafts can be examined histologically, as well as by standard molecular and biochemical techniques. In this article, we describe a method for the generation of raft cultures from primary human keratinocytes. The same technique can be used with established epithelial cell lines, and can easily be adapted for use with epithelial tissue from normal or diseased biopsies8. Many viruses target either the cutaneous or mucosal epithelium as part of their replicative life cycle. Over the past several years, the feasibility of using organotypic raft cultures as a method of studying virus-host cell interactions has been shown for several herpesviruses, as well as adenoviruses, parvoviruses, and poxviruses9. Organotypic raft cultures can thus be adapted to examine viral pathogenesis, and are the only means to test novel antiviral agents for those viruses that are not cultivable in permanent cell lines.

An in vitro method to mimic in vivo epithelial differentiation is described. Many viruses target epithelial cells as part of their viral life cycle, and this method provides a means of examining virus:host interactions that more closely resembles that which occurs in vivo. This technique can be used with primary keratinocytes, established cell lines, as well as normal or diseased biopsy tissue.

The development of organotypic epithelial raft cultures has provided researchers with an efficient in vitro system that faithfully recapitulates ...

Culturing Microglia from the Neonatal and Adult Central Nervous System

Microglia are the resident macrophage-like cells of the central nervous system (CNS) and, as such, have critically important roles in physiological and pathological processes such as CNS maturation in development, multiple sclerosis, and spinal cord injury. Microglia can be activated and recruited to action by neuronal injury or stimulation, such as axonal damage seen in MS or ischemic brain trauma resulting from stroke. These immunocompetent members of the CNS are also thought to have roles in synaptic plasticity under non-pathological conditions. We employ protocols for culturing microglia from the neonatal and adult tissues that are aimed to maximize the viable cell numbers while minimizing confounding variables, such as the presence of other CNS cell types and cell culture debris. We utilize large and easily discernable CNS components (e.g. cortex, spinal cord segments), which makes the entire process feasible and reproducible. The use of adult cells is a suitable alternative to the use of neonatal brain microglia, as many pathologies studied mainly affect the postnatal spinal cord. These culture systems are also useful for directly testing the effect of compounds that may either inhibit or promote microglial activation. Since microglial activation can shape the outcomes of disease in the adult CNS, there is a need for in vitro systems in which neonatal and adult microglia can be cultured and studied.

We outline methods for the efficient and quick isolation/culture of viable microglia from the neonatal cerebral cortex and adult spinal cord. The dissection and plating of cortical microglia can be accomplished within 90 minutes, with the subsequent microglial harvest taking place ~ 10 days following the initial dissection.

Microglia are the resident macrophage-like cells of the central nervous system (CNS) and, as such, have critically important roles in physiological and ...

Isolation of Cortical Microglia with Preserved Immunophenotype and Functionality From Murine Neonates

Isolation of microglia from CNS tissue is a powerful investigative tool used to study microglial biology ex vivo. The present method details a procedure for isolation of microglia from neonatal murine cortices by mechanical agitation with a rotary shaker. This microglia isolation method yields highly pure cortical microglia that exhibit morphological and functional characteristics indicative of quiescent microglia in normal, nonpathological conditions in vivo. This procedure also preserves the microglial immunophenotype and biochemical functionality as demonstrated by the induction of morphological changes, nuclear translocation of the p65 subunit of NF-&#954;B (p65), and secretion of the hallmark proinflammatory cytokine, tumor necrosis factor-&#945; (TNF-&#945;), upon lipopolysaccharide (LPS) and Pam3CSK4 (Pam) challenges. Therefore, the present isolation procedure preserves the immunophenotype of both quiescent and activated microglia, providing an experimental method of investigating microglia biology in ex vivo conditions.

One key to successful investigation of microglial biology is the preservation of microglial immunofunction ex vivo during isolation from CNS tissue. Isolating microglia via rotary shaking results in highly pure and immunofunctional cell cultures as assessed by fluorescent imaging, immunocytochemistry, and ELISA following microglia activation with the proinflammatory stimuli lipopolysaccharide (LPS) and Pam3CSK4 (Pam).

Isolation of microglia from CNS tissue is a powerful investigative tool used to study microglial biology ex vivo. The present method details a procedure ...

Isolation of Sertoli Cells and Peritubular Cells from Rat Testes

The testis, and in particular the male gamete, challenges the immune system in a unique way because differentiated sperm first appear at the time of puberty - more than ten years after the establishment of systemic immune tolerance. Spermatogenic cells express a number of proteins that may be seen as non-self by the immune system. The testis must then be able to establish tolerance to these neo-antigens on the one hand but still be able to protect itself from infections and tumor development on the other hand. Therefore the testis is one of a few immune privileged sites in the body that tolerate foreign antigens without evoking a detrimental inflammatory immune response. Sertoli cells play a key role for the maintenance of this immune privileged environment of the testis and also prolong survival of cotransplanted cells in a foreign environment. Therefore primary Sertoli cells are an important tool for studying the immune privilege of the testis that cannot be easily replaced by established cell lines or other cellular models. Here we present a detailed and comprehensive protocol for the isolation of Sertoli cells - and peritubular cells if desired - from rat testes within a single day.

Primary Sertoli cells are required for studying testis-immune privilege, signal transduction during inflammation or infection, and utilization of their immunoprotective properties. Here we describe an enzyme-based protocol for the isolation of highly purified primary Sertoli cells and peritubular cells from rat testes.

The testis, and in particular the male gamete, challenges the immune system in a unique way because differentiated sperm first appear at the time of ...

Isolation and Flow Cytometric Analysis of Immune Cells from the Ischemic Mouse Brain

Ischemic stroke initiates a robust inflammatory response that starts in the intravascular compartment and involves rapid activation of brain resident cells. A key mechanism of this inflammatory response is the migration of circulating immune cells to the ischemic brain facilitated by chemokine release and increased endothelial adhesion molecule expression. Brain-invading leukocytes are well-known contributing to early-stage secondary ischemic injury, but their significance for the termination of inflammation and later brain repair has only recently been noticed.
Here, a simple protocol for the efficient isolation of immune cells from the ischemic mouse brain is provided. After transcardial perfusion, brain hemispheres are dissected and mechanically dissociated. Enzymatic digestion with Liberase&#160;is followed by density gradient (such as Percoll) centrifugation to remove myelin and cell debris. One major advantage of this protocol is the single-layer density gradient procedure which does not require time-consuming preparation of gradients and can be reliably performed. The approach yields highly reproducible cell counts per brain hemisphere and allows for measuring several flow cytometry panels in one biological replicate. Phenotypic characterization and quantification of brain-invading leukocytes after experimental stroke may contribute to a better understanding of their multifaceted roles in ischemic injury and repair.

Inflammation plays a central role in the pathogenesis of ischemic stroke. Increasing evidence suggests that it acts as a double-edged sword which exacerbates early brain injury, but also contributes to later repair. This protocol describes the isolation of immune cells from the ischemic brain and their subsequent flow cytometric phenotyping.

Ischemic stroke initiates a robust inflammatory response that starts in the intravascular compartment and involves rapid activation of brain resident ...

Induction of an Inflammatory Response in Primary Hepatocyte Cultures from Mice

The liver plays a decisive role in the regulation of systemic inflammation. In chronic kidney disease in particular, the liver reacts in response to the uremic milieu, oxidative stress, endotoxemia and the decreased clearance of circulating proinflammatory cytokines by producing a large number of acute-phase reactants. Experimental tools to study inflammation and the underlying role of hepatocytes are crucial to understand the regulation and contribution of hepatic cytokines to a systemic acute phase response and a prolonged pro-inflammatory scenario, especially in an intricate setting such as chronic kidney disease. Since studying complex mechanisms of inflammation in vivo remains challenging, resource-intensive and usually requires the usage of transgenic animals, primary isolated hepatocytes provide a robust tool to gain mechanistic insights into the hepatic acute-phase response. Since this in vitro technique features moderate costs, high reproducibility and common technical knowledge, primary isolated hepatocytes can also be easily used as a screening approach. Here, we describe an enzymatic-based method to isolate primary murine hepatocytes, and we describe the assessment of an inflammatory response in these cells using ELISA and quantitative real-time PCR.

Here, we show an enzymatic approach to isolate primary hepatocytes from adult mice, and we describe the quantification of an inflammatory response using ELISA and real-time PCR.

The liver plays a decisive role in the regulation of systemic inflammation. In chronic kidney disease in particular, the liver reacts in response to the ...

Assessing Cellular Stress and Inflammation in Discrete Oxytocin-secreting Brain Nuclei in the Neonatal Rat Before and After First Colostrum Feeding

The goal of this protocol is to isolate oxytocin-receptor rich brain nuclei in the neonatal brain before and after first colostrum feeding. The expression of proteins known to respond to metabolic stress was measured in brain-nuclei isolates using Western blotting. This was done to assess whether metabolic stress-induced nutrient insufficiency in the body triggered neuronal stress. We have previously demonstrated that nutrient insufficiency in neonates elicits metabolic stress in the gut. Furthermore, colostrum oxytocin modulates cellular stress response, inflammation, and autophagy markers in newborn rat gut villi prior to and after first feed. Signaling protein markers associated with the endoplasmic reticulum stress [ER chaperone binding immunoglobulin protein (BiP), eukaryotic translation initiation factor 2A (eIF2a), and eIF2a kinase protein kinase R (p-PKR)], as well as two inflammation-signaling proteins [nuclear factor-&#954;B (NF-kB) and inhibitor &#954;B (IkB)], were measured in newborn brain nuclei [nucleus of the solitary tract (NTS), paraventricular nucleus (PVN), supra-optic nucleus (SON), cortex (CX), striatum nuclei (STR), and medial preoptic nucleus (MPO)] before the first feed (unprimed by colostrum) and after the start of nursing (primed by colostrum). Expression of BiP/GRP78 and p-eIF2a were upregulated in unprimed and downregulated in primed NTS tissue. NF-kB was retained (high) in the CX, STR, and MPO cytoplasm, whereas NF-kB was lower and unchanged in NTS, PVN, and SON in both conditions. The collective BiP and p-eIF2 findings are consistent with a stress response. eIf2a was phosphorylated by dsRNA dependent kinase (p-PKR) in the SON, CX, STR, and MPO. However, in the NTS (and to a lesser extent in PVN), eIf2a was phosphorylated by another kinase, general control nonderepressible-2 kinase (GCN2). The stress-modulating mechanisms previously observed in newborn gut enterocytes appear to be mirrored in some OTR-rich brain regions. The NTS and PVN may utilize a different phosphorylation mechanism (under nutrient deficiency) from other regions and be refractory to the impact of nutrient insufficiency. Collectively, this data suggests that brain responses to nutrient insufficiency stress are offset by signaling from colostrum-primed enterocytes.

Here, we present a protocol to isolate brain nuclei in the neonatal rat brain in conjunction with first colostrum feeding. This technique allows the study of nutrient insufficiency stress in the brain as modulated by enterocyte signaling.

The goal of this protocol is to isolate oxytocin-receptor rich brain nuclei in the neonatal brain before and after first colostrum feeding. The expression ...

Concomitant Isolation of Primary Astrocytes and Microglia for Protozoa Parasite Infection

Astrocytes and microglia are the most abundant glial cells. They are responsible for physiological support and homeostasis maintenance in the central nervous system (CNS). The increasing evidences of their involvement in the control of infectious diseases justify the emerging interest in the improvement of methodologies to isolate primary astrocytes and microglia in order to evaluate their responses to infections that affect the CNS. Considering the impact of Trypanosoma cruzi (T. cruzi) and Toxoplasma gondii (T. gondii) infection in the CNS, here we provide a method to extract, maintain, dissociate and infect murine astrocytes and microglia cells with protozoa parasites. Extracted cells from newborn cortices are maintained in vitro for 14 days with periodic differential media replacement. Astrocytes and microglia are obtained from the same extraction protocol by mechanical dissociation. After phenotyping by flow cytometry, cells are infected with protozoa parasites. The infection rate is determined by fluorescence microscopy at different time points, thus enabling the evaluation of differential ability of glial cells to control protozoan invasion and replication. These techniques represent simple, cheap and efficient methods to study the responses of astrocytes and microglia to infections, opening the field for further neuroimmunology analysis.

The overall goal of this protocol is to instruct how to extract, maintain, and dissociate murine astrocyte and microglia cells from the central nervous system, followed by infection with protozoa parasites.

Astrocytes and microglia are the most abundant glial cells. They are responsible for physiological support and homeostasis maintenance in the central ...

Optimizing Stromal Cell Isolation from Thymus and Bone Marrow

Stromal Cell Isolation From Hematopoietic Organs

Single-cell sequencing has enabled the mapping of heterogeneous cell populations in the stroma of hematopoietic organs. These methodologies provide a lens through which to study previously unresolved heterogeneity at steady state, as well as changes in cell type representation induced by extrinsic stresses or during aging. Here, we present step-wise protocols for the isolation of high-quality stromal cell populations from murine and human thymus, as well as murine bone and bone marrow. Cells isolated through these protocols are suitable for generating high-quality single-cell multiomics datasets. The impacts of sample digestion, hematopoietic lineage depletion, FACS analysis/sorting, and how these factors influence compatibility with single-cell sequencing are discussed here. With examples of FACS profiles indicating successful and inefficient dissociation and downstream stromal cell yields in post-sequencing analysis, recognizable pointers for users are provided. Considering the specific requirements of stromal cells is crucial for acquiring high-quality and reproducible results that can advance knowledge in the field.

Author Spotlight: Advancing Hematopoietic Research Using Stromal Cell Isolation for Single Cell Sequencing

Here we present protocols that enable isolation of stromal cells from murine bone, bone marrow, thymus and human thymic tissue compatible with single-cell multiomics.

Single-cell sequencing has enabled the mapping of heterogeneous cell populations in the stroma of hematopoietic organs. These methodologies provide a lens ...