This work was funded by grants from the National Multiple Sclerosis Society (RG4179 to A.N.), the National Institutes of Health (NIH R01NS073425 and R01NS074870 to A.N.) and the National Science Foundation (A.N.). We thank Dr. Frank Kirchhoff (University of Saarland, Homburg Germany) for providing PLPDsRed transgenic mice. We thank Youfen Sun for her assistance in maintaining the transgenic mouse colony.

NOTE: All animal procedures are following the guidelines and have been approved by the Institutional Animal Care and Use Committee (IACUC) at the University of Connecticut.
NOTE: For these experiments constitutive NG2cre18 (JAX#008533) and inducible NG2creER16 (JAX#008538) transgenic mice crossed to Z/EG19 (JAX#003920) or gtRosa26:YFP reporter20 (JAX#006148) lines respectively were used to image NG2 cells and their progeny. To image mature oligodendrocytes, PLPDsRed transgenic mice21 were used. For consistent survival, slices can be isolated from mice up to postnatal day 10 from both the forebrain and cerebellum.
1. Slice Preparation
<ol>
	<li>In a culture hood, place tissue culture inserts in six well plates and add 1 ml slice culture medium (recipe in reagents section). Put the plates in the cell culture incubator at 37 &#176;C with 5% CO2 at least 2 hr prior to dissection.</li>
	<li>Sterilize all tools and tissue chopper with 70% ethanol.</li>
	<li>Bubble dissection buffer (recipe in reagents section) with 95% &#160;O2, 5% CO2 on ice for at least 15 min&#160;prior to the start of dissection.</li>
	<li>Anesthetize mouse pups by placing them on ice for 5-10 min according to approved animal protocols. Ascertain the appropriate depth of anesthesia by confirming that the mice do not respond to tail and toe pinching.</li>
	<li>Decapitate animals using sharp scissors following animal protocols. Quickly remove the skull over the forebrain and cerebellum by first making a sagittal cut followed by lateral incision, using sterilized tools. Cut cranial nerves from the ventral surface of the brain and cerebellum by carefully rolling the tissue to the side.</li>
	<li>Place tissue in a sterile 35 mm dish containing ice-cold oxygenated dissection buffer.</li>
	<li>Using a razor blade, sever the cerebellum and forebrain. Then make a mid-sagittal cut through the forebrain and cerebellum, separating the hemispheres.</li>
	<li>Cut 300 &#956;m-thick coronal and sagittal sections of the forebrain and cerebellum with a manual tissue chopper. NOTE: A manual tissue chopper allows rapid processing from dissection to culture incubation without the need for agarose embedding. A vibratome can also be used as described previously9.</li>
	<li>Transfer separated slices into freshly bubbled cold dissection buffer on ice.</li>
	<li>Use small dissecting or weighing spatulas to separate individual sections and transfer them to preincubated six well dishes with culture inserts.</li>
	<li>Remove any excess dissection buffer from the surface of the culture insert using a disposable transfer pipette or a P 200 pipet tip. Two to three forebrain or three cerebellar slices can be placed on one culture insert. 
	NOTE: For consistent results with forebrain cultures, it is ideal to take slices spanning the anterior one-third of the corpus callosum (Figure 1A) in order to study both gray and white matter regions in the same slice. Each animal usually yields 6 forebrain slices and 6 cerebellum slices.</li>
	<li>Place the six well plates in the incubator and replace the slice medium with 1 ml of slice medium 1 day after slice preparation and then every other day until slice fixation.</li>
	<li>Depending on the experiment, use slices after 5-7 days in culture. Use only slices that become transparent after the first few days and discard those that have uneven opaque regions. NOTE: Opaque regions within slices are visible by eye and appear as a clump of dark cells under phase contrast. After the technique has been mastered, dead opaque slices occur rarely, in less than 1-5% of slices.</li>
</ol>
2. Time-Lapse Imaging of NG2 cell Division and Oligodendrocyte Differentiation
NOTE: To perform time lapse imaging of NG2 cell proliferation and differentiation we use NG2cre:ZEG mice16 which express EGFP in NG2 cells and their progeny (Figure 1C-E). Reporter expression in this line is sufficiently robust to obtain live images of GFP+ cells in slices immediately after sectioning for a time period of at least four weeks. The clearest images are obtained after the initial thinning period of the slice, which occurs over the first 3-5 days in culture.
<ol>
	<li>Throughout the experiment, keep the slices in a cell culture incubator at 37 &#176;C and remove only for brief periods of time (less than 15 min per slice), keeping the lid on the six well plate while imaging.</li>
	<li>Using an inverted fluorescence microscope equipped with a digital camera, capture images at the first time point using a 10X objective. NOTE: First time points will vary by experiment and can be the day when the slices were prepared or any time point after.</li>
	<li>Capture images from multiple regions at time point one in both gray and white matter areas of the slice. Note the region imaged by specific landmarks within the slice and by mapping the image location on a schematic that can be used for subsequent imaging sessions. Useful landmarks can include edges of the slices and/or orientation of white matter tracts. Image four to eight locations on each slice at each time point.</li>
	<li>Capture subsequent images at an interval of 4-6 hr if examining NG2 cell division and oligodendrocyte differentiation, ideally over 5-7 days.</li>
	<li>Capture a final image of all regions and fix the slices immediately. Add 1 ml of fixative (4% PFA with 0.1M l-lysine 0.01 M sodium meta-periodate) to the bottom of the culture insert, then add another 1 ml on top of the slices. Take care not to squirt the fixative directly on the slice as it can detach from the membrane. Fix the tissue for 30 min &#160;and proceed with immunohistochemistry using developmental stage-specific markers as described in section 4.</li>
	<li>Wash slices with 0.2 M sodium phosphate buffer 3 x 10 min. If necessary, store slices at 4 &#176;C in 0.2 M sodium phosphate buffer for 1-3 days before immunostaining but ideally perform staining within 24 hr. Proceed with immunohistochemistry as described below in section 4 to determine the proportion of cells that have differentiated into oligodendrocytes (Figure 2D-F).</li>
</ol>
3. Fate Mapping of NG2 cell Progeny Using Inducible Reporter Transgenic Mice in Slice Cultures
NOTE: To track the fate of NG2 cells from a particular time point in the culture, inducible NG2creER:YFP transgenic mice can be used.
<ol>
	<li>Induce Cre recombination and reporter expression by adding 100 nM 4OHT dissolved in ethanol to the culture medium. NOTE: Reporter positive cells should appear within 1-2 days at an induction efficiency of ~20-25% YFP+NG2+/NG2+ cells and at this time point will all be cells at the NG2 cell stage (Figure 2A-C)</li>
	<li>Fix and wash the slices at different time points after various manipulations (described in sections 2.5 and 2.6).</li>
</ol>
4. Slice Immunohistochemistry
<ol>
	<li>Cut the membranes with the slices attached out of the inserts using a scalpel.</li>
	<li>Transfer slices to individual wells of a 24 well plate containing phosphate buffered saline (PBS) using a set of tweezers, taking care not to disrupt the composition of the slice when picking up the membrane.</li>
	<li>Transfer the slices to a 24 well plate with blocking solution containing 5% normal goat serum (NGS) and 0.1% Triton-X100 in PBS for 1 hr.</li>
	<li>Incubate the slices in primary antibody O/N in 5% NGS in PBS at 4 &#176;C. For identifying cells in the NG2 cell stage, use antibodies to NG2 and PDGFR&#945;. For identifying differentiated oligodendrocytes, use an antibody to the adenomatous polyposis coli antigen (APC; clone CC1).</li>
	<li>On the second day wash slices in PBS 3 x15 min, then incubate in secondary antibodies in 5% NGS in PBS for 1 hr at RT. Wash slices in PBS 3 x15 min and mount on slides. Mount with slices up and membrane facing the slide so that the membrane will not be between the objective and the tissue.</li>
</ol>

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The authors declare that they have no competing financial interests

Myelination in the central nervous system is essential for efficient neuronal communication and axonal survival22. NG2 cells continuously generate myelinating oligodendrocytes into adulthood while maintaining a resident population in most brain regions16,23&#8211;25. Some genetic and molecular mechanisms regulating the differentiation of these cells have been described but much remains to be discovered. Organotypic slice cultures are a convenient tool to investigate these mecha...

Organoytpic slice cultures of the central nervous system have proven to be extremely useful for studying neuron and glial cell biology in a semiintact system1&#8211;4. These cultures are relatively simple to adopt and retain many benefits of primary dissociated cell cultures such as manipulation of the extracellular environment and easy access for repeated long-term live cell imaging and electrophysiological recordings5&#8211;9. In addition, slice cultures maintain 3-dimensional tissue cytoarchitecture, regional neural connectivity, and most major cell types are present in the system. These properties make these cultures a unique and convenient system to investigate single cell behavior and physiology with cellular and environmental interactions.
NG2 cells are a population of glial cells in the mammalian central nervous system that continue to proliferate and generate myelinating oligodendrocytes during embryonic and postnatal development10. They have been extensively studied in dissociated primary cell cultures, and recent development of transgenic mouse lines with NG2 cell-specific expression of fluorescent proteins has facilitated in vivo fate mapping and electrophysiological recordings in acute slice preparations. Even with these studies, little is known about the temporal dynamics of NG2 cell proliferation and oligodendrocyte differentiation. Although dissociated cell culture is widely used for the relative facility in pharmacological and genetic manipulations, it is not suitable for interrogating functional differences of these cells in different brain regions particularly when it is desirable to maintain the context of the cellular microenvironment. Slice cultures provide a simple alternative that is amenable to pharmacological manipulations and have been used to investigate oligodendrocyte myelination11,12, cellular response after lysolecithin (LPC) or antibody induced demyelination13,14, and induction of remyelination via pharmacological treatment15.
A method to investigate and perform live imaging and fixed tissue (or postfixation) analysis of NG2 cell proliferation and oligodendrocyte differentiation in organotypic slice cultures taken from both the forebrain and cerebellum is described. This is a powerful method that can be used to study the cell fate of single NG2 cells after division16 and to discover region- and age-dependent differences in growth factor induced NG2 cell proliferation17. This relatively simple technique is widely accessible to further investigate cell intrinsic and/or environmental mechanisms regulating the physiology of these glial cells and their response to neuronal activity or myelin damage.

<table border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Slice Culture Medium</td>
		</tr>
		<tr>
			<td>Minimum Essential Medium</td>
			<td>Invitrogen</td>
			<td>11090</td>
			<td>50%</td>
		</tr>
		<tr>
			<td>Hank&#8217;s Balanced Salt Solution</td>
			<td>Invitrogen</td>
			<td>14175</td>
			<td>25%</td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Sigma-Aldrich</td>
			<td>H-4034</td>
			<td>25mM</td>
		</tr>
		<tr>
			<td>L-Glutamine</td>
			<td>Invitrogen</td>
			<td>25030</td>
			<td>1mM</td>
		</tr>
		<tr>
			<td>Insulin</td>
			<td>Sigma-Aldrich</td>
			<td>I6634</td>
			<td>1mg/L</td>
		</tr>
		<tr>
			<td>Ascorbic Acid</td>
			<td>Sigma-Aldrich</td>
			<td>A-0278</td>
			<td>0.4mM</td>
		</tr>
		<tr>
			<td>Horse Serum</td>
			<td>Hyclone</td>
			<td>SH30074.03</td>
			<td>25%</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Titrate to pH 7.22 with NaOH, filter with bottle top filter, and store at 4 degrees Celsius</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Dissection Buffer</td>
		</tr>
		<tr>
			<td>NaCl</td>
			<td>Sigma-Aldrich</td>
			<td>S3014</td>
			<td>124mM</td>
		</tr>
		<tr>
			<td>KCl</td>
			<td>Sigma-Aldrich</td>
			<td>P5405</td>
			<td>3.004mM</td>
		</tr>
		<tr>
			<td>KH2PO4</td>
			<td>Sigma-Aldrich</td>
			<td>P5655</td>
			<td>1.25mM</td>
		</tr>
		<tr>
			<td>MgSO4 (anhydrous)</td>
			<td>Sigma-Aldrich</td>
			<td>M7506</td>
			<td>4.004mM</td>
		</tr>
		<tr>
			<td>CaCl2 2H2O</td>
			<td>Sigma-Aldrich</td>
			<td>C7902</td>
			<td>2mM</td>
		</tr>
		<tr>
			<td>NaHCO3</td>
			<td>Sigma-Aldrich</td>
			<td>S5761</td>
			<td>26mM</td>
		</tr>
		<tr>
			<td>D-(+)-Glucose</td>
			<td>Sigma-Aldrich</td>
			<td>G7021</td>
			<td>10mM</td>
		</tr>
		<tr>
			<td>Ascorbic Acid</td>
			<td>Sigma-Aldrich</td>
			<td>A-0278</td>
			<td>2.0mM</td>
		</tr>
		<tr>
			<td>Adenosine</td>
			<td>Sigma-Aldrich</td>
			<td>A4036</td>
			<td>0.075mM</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Filter with bottle top filter and store at 4 degrees Celsius, oxygenate with 95%O2 5%CO2 before use</td>
		</tr>
		<tr>
			<td></td>
			<td></td>
			<td></td>
			<td>Other Reagents and Supplies</td>
		</tr>
		<tr>
			<td>4-hydroxy tamoxifen (4OHT)</td>
			<td>Sigma-Aldrich</td>
			<td>H7904</td>
			<td>100nM</td>
		</tr>
		<tr>
			<td>Paraformaldehyde (PFA)</td>
			<td>EM Sciences</td>
			<td>19200</td>
			<td>4%</td>
		</tr>
		<tr>
			<td>L-Lysine</td>
			<td>Sigma-Aldrich</td>
			<td>L-6027</td>
			<td>0.1M</td>
		</tr>
		<tr>
			<td>Sodium Metaperiodate</td>
			<td>Sigma-Aldrich</td>
			<td>S-1878</td>
			<td>0.01M</td>
		</tr>
		<tr>
			<td>Rabbit anti NG2 antibody</td>
			<td>Chemicon (Millipore)</td>
			<td>AB5320</td>
			<td>1:500</td>
		</tr>
		<tr>
			<td>Mouse anti CC1 antibody</td>
			<td>Calbiochem (Millipore)</td>
			<td>OP80</td>
			<td>1:200</td>
		</tr>
		<tr>
			<td>Mouse anti Ki67 antibody</td>
			<td>Vision Biosystems</td>
			<td>NCL-Ki67-MM1</td>
			<td>1:300</td>
		</tr>
		<tr>
			<td>Mouse anti NeuN antibody</td>
			<td>Chemicon (Millipore)</td>
			<td>MAB377</td>
			<td>1:500</td>
		</tr>
		<tr>
			<td>Species specific secondary antibodies</td>
			<td>Jackson Immunoresearch</td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Normal Goat Serum (NGS)</td>
			<td></td>
			<td></td>
			<td>5%</td>
		</tr>
		<tr>
			<td>Triton X-100</td>
			<td></td>
			<td></td>
			<td>0.10%</td>
		</tr>
		<tr>
			<td>Mounting medium with DAPI</td>
			<td>Vector Labs</td>
			<td>H-1200</td>
			<td></td>
		</tr>
		<tr>
			<td>Millicell culture membrane inserts 0.45&#956;m pore size</td>
			<td>Fisher Scientific</td>
			<td>PICM03050</td>
			<td></td>
		</tr>
		<tr>
			<td>Bottle top filters</td>
			<td>Fisher Scientific</td>
			<td>09-740-25E</td>
			<td></td>
		</tr>
		<tr>
			<td>Ethanol</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>95% O2 5% CO2 gas mix</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Phosphate Buffered Saline (PBS)</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Sterile six well plates</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Dissecting (hippocampal) or weighing spatulas</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Manual or automatic tissue chopper</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Razor blades</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Disposable transfer pipettes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>35mm and 60mm sterile Petri dishes</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Inverted Phase Microscope</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Laminar Flow Hood</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue Culture Incubator</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Inverted Fluorescence Microcope</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

organotypic slice cultures to study oligodendrocyte dynamics and myelination

NG2 expressing cells (polydendrocytes, oligodendrocyte precursor cells) are the fourth major glial cell population in the central nervous system. During embryonic and postnatal development they actively proliferate and generate myelinating oligodendrocytes. These cells have commonly been studied in primary dissociated cultures, neuron cocultures, and in fixed tissue. Using newly available transgenic mouse lines slice culture systems can be used to investigate proliferation and differentiation of oligodendrocyte lineage cells in both gray and white matter regions of the forebrain and cerebellum. Slice cultures are prepared from early postnatal mice and are kept in culture for up to 1 month. These slices can be imaged multiple times over the culture period to investigate cellular behavior and interactions. This method allows visualization of NG2 cell division and the steps leading to oligodendrocyte differentiation while enabling detailed analysis of region-dependent NG2 cell and oligodendrocyte functional heterogeneity. This is a powerful technique that can be used to investigate the intrinsic and extrinsic signals influencing these cells over time in a cellular environment that closely resembles that found in vivo.

Examples of representative data are given below that have been obtained using slice cultures from both the forebrain and cerebellum of P8 NG2cre:ZEG, NG2creER:YFP and PLPDsRed transgenic mouse lines. NG2 cells can be imaged over days in forebrain and cerebellum slices (Figure 1B-D, Video 1) and the phenotype of these cells can be determined after fixation and immunostaining with NG2 and CC1 antibodies (Figure 1E). In addition to live imaging, cell proliferation can also be assessed using...

Watch this Scientific Journal Video about Organotypic Slice Cultures to Study Oligodendrocyte Dynamics and Myelination at JoVE.com

Organotypic Slice Cultures to Study Oligodendrocyte Dynamics and Myelination

A technique to study NG2 cells and oligodendrocytes using a slice culture system of the forebrain and cerebellum is described. This method allows examination of the dynamics of proliferation and differentiation of cells within the oligodendrocyte lineage where the extracellular environment can be easily manipulated while maintaining tissue cytoarchitecture.

NG2 expressing cells (polydendrocytes, oligodendrocyte precursor cells) are the fourth major glial cell population in the central nervous system. During ...

organotypic-slice-cultures-to-study-oligodendrocyte-dynamics

Research

JoVE Journal

Neuroscience

18.2K Views.  University of Connecticut. A technique to study NG2 cells and oligodendrocytes using a slice culture system of the forebrain and cerebellum is described. This method allows examination of the dynamics of proliferation and differentiation of cells within the oligodendrocyte lineage where the extracellular environment can be easily manipulated while maintaining tissue cytoarchitecture.

Video: Organotypic Slice Cultures to Study Oligodendrocyte Dynamics and Myelination

The Organotypic Hippocampal Slice Culture Model for Examining Neuronal Injury

Organotypic hippocampal slice culture is an in vitro method to examine mechanisms of neuronal injury in which the basic architecture and composition of the hippocampus is relatively preserved 1. The organotypic culture system allows for the examination of neuronal, astrocytic and microglial effects, but as an ex vivo preparation, does not address effects of blood flow, or recruitment of peripheral inflammatory cells. To that end, this culture method is frequently used to examine excitotoxic and hypoxic injury to pyramidal neurons of the hippocampus, but has also been used to examine the inflammatory response. Herein we describe the methods for generating hippocampal slice cultures from postnatal rodent brain, administering toxic stimuli to induce neuronal injury, and assaying and quantifying hippocampal neuronal death.

The organoptypic hippocampal slice culture model is an in vitro model used to examine neuronal injury in a variety of paradigms. In this article, we describe the methods for generating slice cultures and quantifying neuronal injury.

Organotypic hippocampal slice culture is an in vitro method to examine mechanisms of neuronal injury in which the basic architecture and composition of ...

Organotypic Hippocampal Slice Cultures

The hippocampus, a component of the limbic system, plays important roles in long-term memory and spatial navigation 1. Hippocampal neurons can modify the strength of their connections after brief periods of strong activation. This phenomenon, known as long-term potentiation (LTP) can last for hours or days and has become the best candidate mechanism for learning and memory 2. In addition, the well defined anatomy and connectivity of the hippocampus 3 has made it a classical model system to study synaptic transmission and synaptic plasticity4.
As our understanding of the physiology of hippocampal synapses grew and molecular players became identified, a need to manipulate synaptic proteins became imperative. Organotypic hippocampal cultures offer the possibility for easy gene manipulation and precise pharmacological intervention but maintain synaptic organization that is critical to understanding synapse function in a more naturalistic context than routine culture dissociated neurons methods.
Here we present a method to prepare and culture hippocampal slices that can be easily adapted to other brain regions. This method allows easy access to the slices for genetic manipulation using different approaches like viral infection 5,6 or biolistics 7. In addition, slices can be easily recovered for biochemical assays 8, or transferred to microscopes for imaging 9 or electrophysiological experiments 10.

We describe a method to prepare organotypic hippocampal slices that can be easily adapted to other brain regions. Brain slices are laid on porous membranes and culture media is allowed to form an interface. This method preserves the gross architecture of the hippocampus for up to 2 weeks in culture.

The hippocampus, a component of the limbic system, plays important roles in long-term memory and spatial navigation 1. Hippocampal neurons can modify the ...

Organotypic Cerebellar Cultures: Apoptotic Challenges and Detection

Organotypic cultures of neuronal tissue were first introduced by Hogue in 1947 1,2 and have constituted a major breakthrough in the field of neuroscience. Since then, the technique was developed further and currently there are many different ways to prepare organotypic cultures. The method presented here was adapted from the one described by Stoppini et al. for the preparation of the slices and from Gogolla et al. for the staining procedure 3,4.
A unique feature of this technique is that it allows you to study different parts of the brain such as hippocampus or cerebellum in their original structure, providing a big advantage over dissociated cultures in which all the cellular organization and neuronal networks are disrupted. In the case of the cerebellum it is even more advantageous because it allows the study of Purkinje cells, extremely difficult to obtain as dissociated primary culture. This method can be used to study certain developmental features of the cerebellum in vitro, as well as for electrophysiological and pharmacological experiments in both wild type and mutant mice.
The method described here was designed to study the effect of apoptotic stimuli such as Fas ligand in the developing cerebellum, using TUNEL staining to measure apoptotic cell death. If TUNEL staining is combined with cell type specific markers, such as Calbindin for Purkinje cells, it is possible to evaluate cell death in a cell population specific manner. The Calbindin staining also serves the purpose of evaluating the quality of the cerebellar cultures.

This method describes the generation of organotypic cerebellar cultures and the effect of certain apoptotic stimuli on the viability of different cerebellar cell types.

Organotypic cultures of neuronal tissue were first introduced by Hogue in 1947 1,2 and have constituted a major breakthrough in the field of neuroscience. ...

Whole Cell Recording from an Organotypic Slice Preparation of Neocortex

We have been studying the expression and functional roles of voltage-gated potassium channels in pyramidal neurons from rat neocortex. Because of the lack of specific pharmacological agents for these channels, we have taken a genetic approach to manipulating channel expression. We use an organotypic culture preparation (16) in order to maintain cell morphology and the laminar pattern of cortex. We typically isolate acute neocortical slices at postnatal days 8-10 and maintain the slices in culture for 3-7 days. This allows us to study neurons at a similar age to those in our work with acute slices and minimizes the development of exuberant excitatory connections in the slice. We record from visually-identified pyramidal neurons in layers II/III or V using infrared illumination (IR-) and differential interference contrast microscopy (DIC) with whole cell patch clamp in current- or voltage-clamp. We use biolistic (Gene gun) transfection of wild type or mutant potassium channel DNA to manipulate expression of the channels to study their function. The transfected cells are easily identified by epifluorescence microscopy after co-transfection with cDNA for green fluorescent protein (GFP). We compare recordings of transfected cells to adjacent, untransfected neurons in the same layer from the same slice.

This is a protocol to prepare and maintain a neocortical slice preparation in organotypic culture for the purpose of making electrical recordings from pyramidal neurons.

We have been studying the expression and functional roles of voltage-gated potassium channels in pyramidal neurons from rat neocortex.  Because of the ...

Multi-electrode Array Recordings of Neuronal Avalanches in Organotypic Cultures

The cortex is spontaneously active, even in the absence of any particular input or motor output. During development, this activity is important for the migration and differentiation of cortex cell types and the formation of neuronal connections1. In the mature animal, ongoing activity reflects the past and the present state of an animal into which sensory stimuli are seamlessly integrated to compute future actions. Thus, a clear understanding of the organization of ongoing i.e. spontaneous activity is a prerequisite to understand cortex function. 
Numerous recording techniques revealed that ongoing activity in cortex is comprised of many neurons whose individual activities transiently sum to larger events that can be detected in the local field potential (LFP) with extracellular microelectrodes, or in the electroencephalogram (EEG), the magnetoencephalogram (MEG), and the BOLD signal from functional magnetic resonance imaging (fMRI). The LFP is currently the method of choice when studying neuronal population activity with high temporal and spatial resolution at the mesoscopic scale (several thousands of neurons). At the extracellular microelectrode, locally synchronized activities of spatially neighbored neurons result in rapid deflections in the LFP up to several hundreds of microvolts. When using an array of microelectrodes, the organizations of such deflections can be conveniently monitored in space and time. 
Neuronal avalanches describe the scale-invariant spatiotemporal organization of ongoing neuronal activity in the brain2,3. They are specific to the superficial layers of cortex as established in vitro4,5, in vivo in the anesthetized rat 6, and in the awake monkey7. Importantly, both theoretical and empirical studies2,8-10 suggest that neuronal avalanches indicate an exquisitely balanced critical state dynamics of cortex that optimizes information transfer and information processing.
In order to study the mechanisms of neuronal avalanche development, maintenance, and regulation, in vitro preparations are highly beneficial, as they allow for stable recordings of avalanche activity under precisely controlled conditions. The current protocol describes how to study neuronal avalanches in vitro by taking advantage of superficial layer development in organotypic cortex cultures, i.e. slice cultures, grown on planar, integrated microelectrode arrays (MEA; see also 11-14).

A robust way to study neuronal avalanches, i.e. scale-invariant spatio-temporal activity bursts, indicative of critical state dynamics in cortex. Avalanches emerge spontaneously in developing superficial layers of cultured cortex which allows for long-term measurements of the activity with planar integrated multi-electrode arrays (MEA) under precisely controlled conditions.

The cortex is spontaneously active, even in the absence of any particular input or motor output.  During development, this activity is important for the ...

Derivation of Enriched Oligodendrocyte Cultures and Oligodendrocyte/Neuron Myelinating Co-cultures from Post-natal Murine Tissues

Identifying the molecular mechanisms underlying OL development is not only critical to furthering our knowledge of OL biology, but also has implications for understanding the pathogenesis of demyelinating diseases such as Multiple Sclerosis (MS). Cellular development is commonly studied with primary cell culture models. Primary cell culture facilitates the evaluation of a given cell type by providing a controlled environment, free of the extraneous variables that are present in vivo. While OL cultures derived from rats have provided a vast amount of insight into OL biology, similar efforts at establishing OL cultures from mice has been met with major obstacles. Developing methods to culture murine primary OLs is imperative in order to take advantage of the available transgenic mouse lines. 
Multiple methods for extraction of OPCs from rodent tissue have been described, ranging from neurosphere derivation, differential adhesion purification and immunopurification 1-3. While many methods offer success, most require extensive culture times and/or costly equipment/reagents. To circumvent this, purifying OPCs from murine tissue with an adaptation of the method originally described by McCarthy &amp; 
de Vellis 2 is preferred. This method involves physically separating OPCs from a mixed glial culture derived from neonatal rodent cortices. The result is a purified OPC population that can be differentiated into an OL-enriched culture. This approach is appealing due to its relatively short culture time and the unnecessary requirement for growth factors or immunopanning antibodies. 
While exploring the mechanisms of OL development in a purified culture is informative, it does not provide the most physiologically relevant environment for assessing myelin sheath formation. Co-culturing OLs with neurons would lend insight into the molecular underpinnings regulating OL-mediated myelination of axons. For many OL/neuron co-culture studies, dorsal root ganglion neurons (DRGNs) have proven to be the neuron type of choice. They are ideal for co-culture with OLs due to their ease of extraction, minimal amount of contaminating cells, and formation of dense neurite beds. While studies using rat/mouse myelinating xenocultures have been published 4-6, a method for the derivation of such OL/DRGN myelinating co-cultures from post-natal murine tissue has not been described. Here we present detailed methods on how to effectively produce such cultures, along with examples of expected results. These methods are useful for addressing questions relevant to OL development/myelinating function, and are useful tools in the field of neuroscience.

This article describes methods to derive enriched populations of murine oligodendrocyte precursor cells (OPCs) in primary culture, which differentiate to produce mature oligodendrocytes (OLs). In addition, this report describes techniques to produce murine myelinating co-cultures by seeding mouse OPCs onto a neurite bed of mouse dorsal root ganglion neurons (DRGNs).

Identifying the molecular mechanisms underlying OL development is not only critical to furthering our knowledge of OL biology, but also has implications ...

Organotypic Slice Cultures of Embryonic Ventral Midbrain: A System to Study Dopaminergic Neuronal Development in vitro

The mouse is an excellent model organism to study mammalian brain development due to the abundance of molecular and genetic data. However, the developing mouse brain is not suitable for easy manipulation and imaging in vivo since the mouse embryo is inaccessible and opaque. Organotypic slice cultures of embryonic brains are therefore widely used to study murine brain development in vitro. Ex-vivo manipulation or the use of transgenic mice allows the modification of gene expression so that subpopulations of neuronal or glial cells can be labeled with fluorescent proteins. The behavior of labeled cells can then be observed using time-lapse imaging. Time-lapse imaging has been particularly successful for studying cell behaviors that underlie the development of the cerebral cortex at late embryonic stages 1-2. Embryonic organotypic slice culture systems in brain regions outside of the forebrain are less well established. Therefore, the wealth of time-lapse imaging data describing neuronal cell migration is restricted to the forebrain 3,4. It is still not known, whether the principles discovered for the dorsal brain hold true for ventral brain areas. In the ventral brain, neurons are organized in neuronal clusters rather than layers and they often have to undergo complicated migratory trajectories to reach their final position. The ventral midbrain is not only a good model system for ventral brain development, but also contains neuronal populations such as dopaminergic neurons that are relevant in disease processes. While the function and degeneration of dopaminergic neurons has been investigated in great detail in the adult and ageing brain, little is known about the behavior of these neurons during their differentiation and migration phase 5. We describe here the generation of slice cultures from the embryonic day (E) 12.5 mouse ventral midbrain. These slice cultures are potentially suitable for monitoring dopaminergic neuron development over several days in vitro. We highlight the critical steps in generating brain slices at these early stages of embryonic development and discuss the conditions necessary for maintaining normal development of dopaminergic neurons in vitro. We also present results from time lapse imaging experiments. In these experiments, ventral midbrain precursors (including dopaminergic precursors) and their descendants were labeled in a mosaic manner using a Cre/loxP based inducible fate mapping system 6.

Organotypic Slice Cultures of Embryonic Ventral Midbrain: A System to Study Dopaminergic Neuronal Development in vitro

A method to generate organotypic slices from the E12.5 murine embryonic midbrain is described. The organotypic slice cultures can be used to observe the behavior of dopaminergic neurons or other ventral midbrain neurons.

The  mouse is an excellent model organism to study mammalian brain development due  to the abundance of molecular and genetic data. However, the ...

The Analysis of Purkinje Cell Dendritic Morphology in Organotypic Slice Cultures

Purkinje cells are an attractive model system for studying dendritic development, because they have an impressive dendritic tree which is strictly oriented in the sagittal plane and develops mostly in the postnatal period in small rodents 3. Furthermore, several antibodies are available which selectively and intensively label Purkinje cells including all processes, with anti-Calbindin D28K being the most widely used. For viewing of dendrites in living cells, mice expressing EGFP selectively in Purkinje cells 11 are available through Jackson labs. Organotypic cerebellar slice cultures cells allow easy experimental manipulation of Purkinje cell dendritic development because most of the dendritic expansion of the Purkinje cell dendritic tree is actually taking place during the culture period 4. We present here a short, reliable and easy protocol for viewing and analyzing the dendritic morphology of Purkinje cells grown in organotypic cerebellar slice cultures. For many purposes, a quantitative evaluation of the Purkinje cell dendritic tree is desirable. We focus here on two parameters, dendritic tree size and branch point numbers, which can be rapidly and easily determined from anti-calbindin stained cerebellar slice cultures. These two parameters yield a reliable and sensitive measure of changes of the Purkinje cell dendritic tree. Using the example of treatments with the protein kinase C (PKC) activator PMA and the metabotropic glutamate receptor 1 (mGluR1) we demonstrate how differences in the dendritic development are visualized and quantitatively assessed. The combination of the presence of an extensive dendritic tree, selective and intense immunostaining methods, organotypic slice cultures which cover the period of dendritic growth and a mouse model with Purkinje cell specific EGFP expression make Purkinje cells a powerful model system for revealing the mechanisms of dendritic development.

We present a protocol that permits to view and to quantitatively asses the morphology of the dendritic tree of individual Purkinje cells grown in organotypic cerebellar slice cultures. This protocol is intended to promote studies on the mechanisms of Purkinje cell dendritic development.

Purkinje cells are an attractive model system for studying dendritic development, because they have an impressive dendritic tree which is strictly ...

The Analysis of Neurovascular Remodeling in Entorhino-hippocampal Organotypic Slice Cultures

Ischemic brain injury is among the most common and devastating conditions compromising proper brain function and often leads to persisting functional deficits in the affected patients. Despite intensive research efforts, there is still no effective treatment option available that reduces neuronal injury and protects neurons in the ischemic areas from delayed secondary death. Research in this area typically involves the use of elaborate and problematic animal models. Entorhino-hippocampal organotypic slice cultures challenged with oxygen and glucose deprivation (OGD) are established in&#160;vitro models which mimic cerebral ischemia. The novel aspect of this study is that changes of the brain blood vessels are studied in addition to neuronal changes and the reaction of both the neuronal compartment and the vascular compartment can be compared and correlated. The methods presented in this protocol substantially broaden the potential applications of the organotypic slice culture approach. The induction of OGD or hypoxia alone can be applied by rather simple means in organotypic slice cultures and leads to reliable and reproducible damage in the neural tissue. This is in stark contrast to the complicated and problematic animal experiments inducing stroke and ischemia in vivo. By broadening the analysis to include the study of the reaction of the vasculature could provide new ways on how to preserve and restore brain functions. The slice culture approach presented here might develop into an attractive and important tool for the study of ischemic brain injury and might be useful for testing potential therapeutic measures aimed at neuroprotection.

A protocol for entorhino-hippocampal organotypic slice cultures, which allows reproducing many aspects of ischemic brain injury, is presented. By studying changes of the neurovasculature in addition to changes in the neurons, this protocol is a versatile tool to study plastic changes in neural tissue after injury.

Ischemic brain injury is among the most common and devastating conditions compromising proper brain function and often leads to persisting functional ...

Organotypic Hippocampal Slice Cultures As a Model to Study Neuroprotection and Invasiveness of Tumor Cells

In organotypic hippocampal slice cultures (OHSC), the morphological and functional characteristics of both neurons and glial cells are well preserved. This model is suitable for addressing different research questions that involve studies on neuroprotection, electrophysiological experiments on neurons, neuronal networks or tumor invasion. The hippocampal architecture and neuronal activity in multisynaptic circuits are well conserved in OHSC, even though the slicing procedure itself initially lesions and leads to formation of a glial scar. The scar formation alters presumably the mechanical properties and diffusive behavior of small molecules, etc. Slices allow the monitoring of time dependent processes after brain injury without animal surgery, and studies on interactions between various brain-derived cell types, namely astrocytes, microglia and neurons under both physiological and pathological conditions. An ambivalent aspect of this model is the absence of blood flow and immune blood cells. During the progression of the neuronal injury, migrating immune cells from the blood play an important role. As those cells are missing in slices, the intrinsic processes in the culture may be observed without external interference. Moreover, in OHSC the composition of the medium-external environment is precisely controlled. A further advantage of this method is the lower number of sacrificed animals compared to standard preparations. Several OHSC can be obtained from one animal making simultaneous studies with multiple treatments in one animal possible. For these reasons, OHSC are well suited to analyze the effects of new protective therapeutics after tissue damage or during tumor invasion. 
The protocol presented here describes a preparation method of OHSC that allows generating highly reproducible, well preserved slices that can be used for a variety of experimental research, like neuroprotection or tumor invasion studies.

Organotypic hippocampal slice cultures (OHSC) represent an in vitro model that simulates the in vivo situation very well. Here we describe a vibratome-based improved slicing protocol to obtain high quality slices for use in assessing the neuroprotective potential of novel substances or the biological behavior of tumor cells.

In organotypic hippocampal slice cultures (OHSC), the morphological and functional characteristics of both neurons and glial cells are well preserved. ...