This work was supported by a research grant MOP 119271 to JMW by the Canadian Institute of Health Research. The authors would like to thank Ms. Yao Fang Tan for her outstanding technical assistance.

NOTE: All animal procedures conformed to the animal health and welfare guidelines of the Department of Comparative Medicine at the University of Toronto.
1. Preparation of Hippocampal Slices
<ol>
	<li>Sterilize the following instruments using the dry autoclave at 125 &#176;C: Scalpel handle (#3) (2), Standard pattern forceps, large (1), Small dissector scissor (angled to side) (1), Micro spoon (spoon and flat spatula ends) (1), Micro-spatulas (rounded and rounded tapered ends) (2), Fine paintbrush (1), Fire polished Pasteur pipette (2), Gauze squares, 2 x 2 inches (5).</li>
	<li>When sterile, put the instruments into a sterile container and keep covered until use. Immediately before dissection, immerse instruments in a 70% ethanol solution.</li>
	<li>Prepare a 6-well culture plate with culture insert before beginning the dissection procedure by adding 1 ml of culture medium/well and storing the plate in the incubator at 35 &#176;C and 5% CO2.</li>
</ol>
2. Arrange Dissection Tools in Sterile Laminar Flow hood
<ol>
	<li>Spray the laminar flow hood with 70% ethanol and remove sterilized dissection instruments from alcohol. Allow the instruments to dry while resting on a sterile Petri dish to avoid contact between the alcohol and the dissected brain tissue.</li>
	<li>Deposit 5-7 ml of sterilized ice-cold dissecting solution in 2 large sterile Petri dishes. One dish will chill and clean the head (dirty), the other one for cooling and rinsing the scooped out brain (clean). Place a sterilized filter paper in one of the Petri dish lids for dissecting out the brain.</li>
	<li>Place a small, sterilized filter paper in one of the small Petri dish lid for dissecting out the hippocampus. Deposit 3-5 ml of sterilized ice-cold dissecting solution in 2 small, sterile Petri dishes. One dish will hold the scooped out hippocampus, one will hold sections during separation of hippocampal sections under dissection microscope.</li>
	<li>Prepare the tissue chopper by taping a piece of sterilized filter paper to the cutting stage and mounting a sterile razor blade. Wet the filter paper with sterilized dissecting solution.</li>
	<li>Spray a clean bio-bag with alcohol and place it in laminar flow clean bench.</li>
</ol>
3. Hippocampal Dissection
<ol>
	<li>Spray the P7 Sprague Dawley rat pup with 70% ethanol outside of the laminar flow clean bench and quickly decapitate the animal using large sterile surgical scissors inside the laminar flow bench. Let the head drop into ice-cold dissecting solution in one of the Petri dishes.</li>
	<li>In the Petri dish, rinse off the blood and quickly transfer the head to sterilized filter paper, ventral side down.</li>
	<li>Using the scalpel, cut along the dorsal surface in the sagittal plane to expose the underlying skull. Cut through the skin, but not the underlying bone, which is soft and easily penetrable in rats of this age. Set aside this &#8220;dirty&#8221; scalpel and do not use on brain tissue.</li>
	<li>Using the small dissector scissors (angled to side) and forceps, cut open the skull along sagittal suture of the skull to bregma, the anatomical point on the skull where the coronal suture is intersected perpendicularly by the sagittal suture. Use forceps to pull skull flaps up and away from the midline of the skull.</li>
	<li>Place the micro spoon on the underside of the brain, beneath the brain stem, to gently lift the brain out of the skull. Lift the brain to expose the optic nerves and olfactory bulb on basal surface of brain. Cut these structures with small scissors to fully detach the brain from skull. Remove and transfer the intact brain to the other large Petri dish containing ice-cold dissecting solution.</li>
	<li>Using the micro spoon, transfer the brain to a small Petri-dish lid containing sterile filter paper. With a sterile Pasteur pipette, rinse the brain with a few drops of dissecting solution to keep tissue moist.</li>
	<li>Using a &#8220;clean&#8221; scalpel blade cut the two hemispheres apart. Transfer the left hemisphere back to large Petri dish with micro spoon and place hemisphere pia side down in ice-cold dissecting solution for subsequent use.</li>
	<li>View the medial face of the right hemisphere and identify the edge fornix, a prominent band of white matter along the medial edge of the hippocampus. Using a sterile scalpel, make a sagittal cut through the fornix, but take care because only 0.5 cm of the scalpel tip will be sufficient to cut the fornix.</li>
	<li>Using 2 micro-spatulas, remove the first hippocampus from right hemisphere by placing the right-hand-spatula on the brain stem and lifting the overlying cortex with the left-hand spatula. Gently lift the cortex to reveal the lateral ventricle and medial surface of the hippocampus. A white curved line, the fimbria, should now be visible.</li>
	<li>Align the curvature of spatula with the curvature of the fimbria and gently press the spatula under the fimbria. Slide the spatula left and ride along rostral-caudal axis and then lift spatula in dorsal direction to remove hippocampus.</li>
	<li>Transfer the hippocampus to a 2nd small Petri dish with ice-cold dissecting solution. Repeat the same procedure on the left hemisphere to remove the left hippocampus.</li>
	<li>Using a micro spatula, carefully transfer the hippocampi to the tissue chopper stage. Arrange them adjacent and parallel to each other and perpendicular to the axis of the chopper blade. Use a paintbrush to position the tissue and add a few drops of the dissecting solution on top of the hippocampi.</li>
	<li>Cut the tissue in 400 &#956;m slices without pausing to remove individual slices (usually they will not adhere to the blade). After the whole hippocampus has been cut, use the paintbrush to gently transfer the sections to a 2nd small Petri dish with dissection solution.</li>
	<li>Under a dissecting microscope, carefully separate the floating slices using amicro-spatula and paintbrush.</li>
	<li>Remove the pre-prepared culture plate with culture insert from the incubator and place in a laminar flow hood.</li>
	<li>Using a fire-polished Pasteur pipette, draw 4-5 slices into the pipette and transfer slices to the apical surface of culture insert membrane. Next, adjust the positioning with a paintbrush and leave space between individual sections and the border of the culture insert.</li>
	<li>Using a sterile Pasteur pipette, remove the excess dissecting solution from apical surface of membrane. 
	NOTE: While removing solution avoid drawing tissue sections into the pipette. Alternatively, use a regular pipette (P200 or P1000) with sterilized pipette tips to slowly remove solution.</li>
	<li>Place the culture plate with serum-containing culture medium and the hippocampal slices back into the incubator at 35 &#176;C and 5% CO2. 
	NOTE: If experiment calls for generating cultures from multiple animals, thoroughly clean the laminar flow clean bench between dissections. Return instruments to alcohol solution and replace all Petri-dishes, filter papers and sterile razor blades prior to second dissection.</li>
</ol>
4. Feeding and Maintaining Organotypic Slices
<ol>
	<li>Feed cultures in a sterile laminar flow clean bench.</li>
	<li>Perform the first feeding of the cultured sections 2 days post-dissection. Aspirate old culture medium using sterilized glass pipette.</li>
	<li>Use sterile 5 ml serological pipette to add 1 ml of fresh, sterile, serum-containing medium to the wells.</li>
	<li>Gently replace the culture insert and take care to remove any air bubbles that may have formed underneath membrane surface.</li>
	<li>After the first feeding, change medium every other day.</li>
</ol>
5. Incubating Tissue Slices with Thymidine Analogues to Label Newborn Neurons
<ol>
	<li>In order to study the maturation and integration of dentate granule cells in the hippocampus, incubate the organotypic slices with a thymidine analogue, such as Bromodeoxyuridine (BrdU) or Chlorodeoxyuridine (CldU). Here, we use CldU because of its higher solubility in saline.</li>
	<li>After 3DIV, add 1 &#956;l of 10 mg/ml CldU stock solution in saline to 1 ml of culture medium for a final concentration of 10 &#956;g/ml. If BrdU is used, correct the concentration for differences in molecular weight. Add medium with CldU to culture wells and incubate tissue with CldU-containing medium for 2 hr at 35 &#176;C.</li>
	<li>Following 2 hr of incubation at 35 &#176;C, remove the CldU-containing medium and replace with regular feeding medium to resume normal feeding schedule (outlined above).</li>
</ol>
6. Tissue Fixation and Storage
<ol>
	<li>Establish a timeline for applying treatments and fixing tissue samples before starting culture experiments (Figure 2B).</li>
	<li>At a predetermined day post-dissection, prepare the following in a laboratory fume hood: a 10-50 ml beaker containing 4% paraformaldehyde (PFA) in phosphate buffered saline (PBS); an empty beaker for discarded culture medium; small forceps; and a 1,000 ml pipette with disposable tips.</li>
	<li>Remove the culture plate(s) from incubation chamber and transfer to a fume hood. Tilt the individual well plate inserts with forceps. Next, use a pipette to remove culture medium and transfer to a disposal beaker. Tilt the culture plate at an angle to help ensure that all culture medium is removed.</li>
	<li>Finish removing medium for one culture plate at a time. When medium has been removed, add 1 ml of 4% PFA to each culture well and seal well plate with parafilm. Repeat for as many culture plates as necessary and transfer plates to refrigerator at 4 &#176;C for 24 hr.</li>
	<li>After 24 hr, prepare the following in a fume hood: 10-50 ml beaker containing 0.1% Sodium Azide in PBS; an empty beaker for discarded PFA (follow safety precautions when discarding toxic substances); small forceps; and 1,000 ml pipette with disposable tips.</li>
	<li>Follow the procedure outlined in 6.4 for adding PFA, but add 1 ml of PBS with sodium azide instead. Once completely transferred, seal well plates for future use by wrapping edges in parafilm and storing in refrigerator at 4 &#176;C.</li>
</ol>
7. Sectioning Tissue for Immunohistochemistry
<ol>
	<li>Perform tissue sectioning using a vibratome. The following series of steps help maximize the yield of usable tissue sections from organotypic cultures. 
	NOTE: Immediately following hippocampal dissection and plating of slices, the tissue has a thickness of approximately 400 &#956;m. However, after 2-3 weeks in the incubation chamber, tissue slices will begin to flatten, resulting in a final section thickness of 150-300 &#956;m.</li>
	<li>Prepare the following items to section cultured tissue: a #11 scalpel blade and handle, a glass Petri dish containing ice cold PBS, a micro-dissection forceps, and a clean vibratome cutting stage to mount tissue.</li>
	<li>Use a scalpel to carefully cut along the perimeter of the circular insert membrane so that it can be detached from the plastic insert housing. Leave ample space between the cultured slice and the scalpel.</li>
	<li>Transfer the detached insert membrane to a Petri dish containing PBS. After rinsing in PBS, use forceps to transfer the membrane to the vibratome mounting stage.</li>
	<li>Next, use the scalpel to eliminate excess membrane surrounding cultured slices and cut away excess material to create clean edges. This step will ensure the membrane is flat and can easily adhere to the cutting surface.</li>
	<li>Place 1-2 drops of adhesive on the vibratome cutting stage and spread in even layer using a 22 G needle. Spread adhesive into a rectangular shape with the long edge parallel to the cutting blade of the vibratome. Perform this step quickly, to prevent the adhesive from drying.</li>
	<li>Use forceps to transfer the trimmed membrane containing hippocampal slices to the cutting stage and gently position the membrane on glue and ensure that there are no air bubbles.</li>
	<li>As the superglue dries, transfer the vibratome stage with the glued membrane back to the PBS containing Petri dish. Prepare the vibratome blade and a 48 well plate containing sodium azide to store tissue sections.</li>
	<li>Use the vibratome to generate 30 &#956;m sections of the organotypic slice tissue and transfer to a 48 well plate containing sodium azide for storage and subsequent immunohistochemical staining.</li>
	<li>Refer to pre-existing protocols for immunohistochemical staining26,29.</li>
</ol>

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Q. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Embryonic+and+postnatal+injections+of+bromodeoxyuridine+produce+age-dependent+morphological+and+behavioral+abnormalities.">Embryonic and postnatal injections of bromodeoxyuridine produce age-dependent morphological and behavioral abnormalities.</a> The Journal Of Neuroscience : The Official Journal Of The Society For Neuroscience. 19 (6), 2337-2346 (1999).</li><li>Morris, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+genetic+toxicology+of+5-bromodeoxyuridine+in+mammalian+cells.">The genetic toxicology of 5-bromodeoxyuridine in mammalian cells.</a> Mutation Research. 258 (2), 161-188 (1991).</li><li>Bannigan, J., Langman, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+cellular+effect+of+5-bromodeoxyuridine+on+the+mammalian+embryo.">The cellular effect of 5-bromodeoxyuridine on the mammalian embryo.</a> Journal Of Embryology And Experimental Morphology. 50, 123-135 (1979).</li><li>Breunig, J. J., Arellano, J. I., Macklis, J. D., Rakic, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Everything+that+glitters+isn't+gold:+a+critical+review+of+postnatal+neural+precursor+analyses.">Everything that glitters isn't gold: a critical review of postnatal neural precursor analyses.</a> Cell Stem Cell. 1 (6), 612-627 (2007).</li><li>Duque, A., Rakic, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Different+effects+of+bromodeoxyuridine+and+[3H]thymidine+incorporation+into+DNA+on+cell+proliferation,+position,+and+fate.">Different effects of bromodeoxyuridine and [3H]thymidine incorporation into DNA on cell proliferation, position, and fate.</a> The Journal Of Neuroscience : The Official Journal Of The Society For Neuroscience. 31 (42), 15205-15217 (2011).</li><li>Namba, T., Mochizuki, H., Onodera, M., Namiki, H., Seki, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Postnatal+neurogenesis+in+hippocampal+slice+cultures:+early+in+vitro+labeling+of+neural+precursor+cells+leads+to+efficient+neuronal+production.">Postnatal neurogenesis in hippocampal slice cultures: early in vitro labeling of neural precursor cells leads to efficient neuronal production.</a> Journal of Neuroscience Research. 85 (8), 1704-1712 (2007).</li></ol>

The authors declare that they have no competing financial interests.

Following CldU (or BrdU) administration, the timeline of application of pharmacological agents can be chosen to target newborn DGCs during particular developmental windows. For example, a hypothetical agent can be applied during the second week post-CldU injection, which is proposed to coincide with the age of immature neurons that are at a developmental stage where GABA is depolarizing. Future studies using this protocol could adapt the pharmacological agent and the window of exposure to &#8220;tailor&#8221; the approac...

Adult neurogenesis in the mammalian hippocampus represents a remarkable example of the brain&#8217;s innate capacity for adaptability and plasticity. Dentate granule cells (DGCs) are generated from a renewable pool of neural progenitor cells in the hippocampal dentate gyrus, which is one of the two presently well-characterized neurogenic regions in the mammalian brain, and is thought to be particularly important for learning and memory. The hippocampus is part of the limbic system and has a deep location within the mammalian brain, which makes it a difficult target for precise pharmacological manipulation. Additionally, aberrant neurogenesis has been implicated in conditions, such as epilepsy, schizophrenia, and Alzheimer&#8217;s disease, which has prompted interest in understanding the influence of various pharmacological agents during the maturation and survival of newborn neurons. The distinction between postnatal and adult neurogenesis is blurred and previous studies have shown that many features of in vivo neuronal development in the early postnatal period and adulthood are similar25. Here we emphasize postnatal neurogenesis and suggest possible applications to adult neurogenesis.
Organotypic slice cultures provide an efficient in vitro method for studying various physiological properties of the mammalian hippocampus. The value of slice cultures prepared from rodent brains can be summarized in three main qualities: 1) the protocol is straightforward and requires readily available materials; 2) slice cultures allow for pharmacological studies that eliminate complex variables such as the deep anatomic location of the hippocampus and circumvents the blood brain barrier1; and 3) the well characterized structure of the hippocampus and tri-synaptic circuit is preserved2. Previous investigators have used the organotypic hippocampal culture to study synaptic development and physiology3,4, gliogenesis5-7, ischemic brain damage8,9, neuroprotection and neurorepair10-12 as well as epilepsy13-15.The slice cultures could also provide a useful model system allowing for the monitoring of cell development in conjunction with labeling of cells with green fluorescent protein (GFP) or other vital markers.
Slice cultures have also been previously employed to study postnatal hippocampal neurogenesis16-19, but one important factor in the majority of these studies is the well-characterized degeneration that results from explanting tissue from adult animals after approximately 2 weeks in vitro20,21. For this reason, slice cultures are typically prepared from early post-natal (P5-P10) mice or rat pups, which utilizes the improved viability of early postnatal brain tissue for culturing22. While previous studies have shown that the early postnatal and adult hippocampus differ with regards to synaptic physiology and the expression of specific neuronal subtypes23,24, there is substantial conservation of the choreographed developmental program that newborn dentate granule cells proceed through during maturation25. Additionally, recent studies have suggested that the physiological characteristics of newborn DGCs in culture are very similar to immature neurons in the acute hippocampal slice preparation16.

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			<td height="20" style="height:20px;width:265px;">5-chloro-2&#39;-deoxyuridine (CldU)</td>
			<td style="width:131px;">MP Biomedicals</td>
			<td align="right" style="width:135px;">105478</td>
			<td style="width:239px;">Hazardous, Carcinogenic</td>
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		<tr height="80">
			<td height="80" style="height:80px;width:265px;">Cell culture inserts, 30mm diameter, 0.4&#181;m pore size</td>
			<td style="width:131px;">Thermo scientific&#160;</td>
			<td align="right" style="width:135px;">140660</td>
			<td style="width:239px;">Nuclon delta coating on these inserts provides better tissue adhesion and improves slice quality.</td>
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		<tr height="21">
			<td height="21" style="height:21px;width:265px;">Conical Centrifuge tubes (sterile)</td>
			<td style="width:131px;">Fisher Scientific</td>
			<td style="width:135px;">14-432-22</td>
			<td style="width:239px;"></td>
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			<td style="width:135px;">14082-09</td>
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			<td height="20" style="height:20px;width:265px;">Minimum essential medium (MEM)</td>
			<td style="width:131px;">Gibco</td>
			<td style="width:135px;">11095; liquid</td>
			<td style="width:239px;">Store at 4&#176;C</td>
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			<td height="21" style="height:21px;width:265px;">Eclipse Ni-U fluorescent microscope</td>
			<td style="width:131px;">Nikon</td>
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			<td height="80" style="height:80px;width:265px;">Glue for tissue</td>
			<td style="width:131px;">Krazy Glue</td>
			<td style="width:135px;">KG585</td>
			<td style="width:239px;">Use minimum amount of glue to achieve adhesion as any tissue exposed to glue will be unusable for IHC.</td>
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			<td height="40" style="height:40px;width:265px;">Hank&#8217;s Balanced Salt Solution (HBSS) (500 mL)</td>
			<td style="width:131px;">Gibco</td>
			<td style="width:135px;">14025-092</td>
			<td style="width:239px;">Store at 4&#176;C</td>
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			<td height="40" style="height:40px;width:265px;">Horse Serum Heat Inactivated (500 mL)</td>
			<td style="width:131px;">Gibco</td>
			<td style="width:135px;">16050-122</td>
			<td style="width:239px;">Make 50 mL aliquots and store at -20&#176;C</td>
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			<td height="20" style="height:20px;width:265px;">Kimwipes</td>
			<td style="width:131px;">Kimberly-Clarke</td>
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			<td style="width:239px;"></td>
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			<td height="40" style="height:40px;width:265px;">Petri Dish (100mm x 15mm) and (60mm x 15mm)</td>
			<td style="width:131px;">Fisher Brand</td>
			<td style="width:135px;">FB0875712 and FB0875713A</td>
			<td style="width:239px;"></td>
		</tr>
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			<td height="40" style="height:40px;width:265px;">Scalpel blades #11</td>
			<td style="width:131px;">Fine Science Tools</td>
			<td style="width:135px;">10011-00</td>
			<td style="width:239px;"></td>
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		<tr height="40">
			<td height="40" style="height:40px;width:265px;">Scalpel handle #3</td>
			<td style="width:131px;">Fine Science Tools</td>
			<td style="width:135px;">10003-12</td>
			<td style="width:239px;"></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:265px;">Serological Pipettes</td>
			<td style="width:131px;">Sorfa Medical Plastic Co.</td>
			<td style="width:135px;">P8050</td>
			<td></td>
		</tr>
		<tr height="40">
			<td height="40" style="height:40px;width:265px;">Standard Pattern forceps</td>
			<td style="width:131px;">Fine Science Tools</td>
			<td style="width:135px;">11000-12</td>
			<td></td>
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		<tr height="40">
			<td height="40" style="height:40px;width:265px;">Sterile vacuum filter</td>
			<td style="width:131px;">Thermo-Scientific</td>
			<td style="width:135px;">565-0020</td>
			<td></td>
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			<td height="40" style="height:40px;width:265px;">Surgical Scissors</td>
			<td style="width:131px;">Fine Science Tools</td>
			<td style="width:135px;">14054-13</td>
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			<td height="21" style="height:21px;width:265px;">Syringe driven filter unit</td>
			<td style="width:131px;">Millipore-Millex</td>
			<td style="width:135px;">SLGP033RS</td>
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			<td height="40" style="height:40px;width:265px;">Tissue chopper with moveable stage</td>
			<td style="width:131px;">Stoelting&#160;</td>
			<td align="right" style="width:135px;">51425</td>
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			<td height="20" style="height:20px;width:265px;">Fine tip paintbrush</td>
			<td style="width:131px;"></td>
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organotypic slice cultures for studies of postnatal neurogenesis

Here we describe a technique for studying hippocampal postnatal neurogenesis in the rodent brain using the organotypic slice culture technique. This method maintains the characteristic topographical morphology of the hippocampus while allowing direct application of pharmacological agents to the developing hippocampal dentate gyrus. Additionally, slice cultures can be maintained for up to 4 weeks and thus, allow one to study the maturation process of newborn granule neurons. Slice cultures allow for efficient pharmacological manipulation of hippocampal slices while excluding complex variables such as uncertainties related to the deep anatomic location of the hippocampus as well as the blood brain barrier. For these reasons, we sought to optimize organotypic slice cultures specifically for postnatal neurogenesis research.

Determining if organotypic cultures would be suitable for adult neurogenesis research required that they satisfy two main criteria: 1) that slices maintain characteristic morphological features of hippocampal slices after 10-21 days in vitro (DIV), and 2) that newborn DGCs can be quantified using standard immunohistochemical techniques commonly employed in adult neurogenesis research. Regarding the first criterion, Figure 1A and 1B highlight the preserved hippocampal morphology....

Watch this Scientific Journal Video about Organotypic Slice Cultures for Studies of Postnatal Neurogenesis at JoVE.com

Organotypic Slice Cultures for Studies of Postnatal Neurogenesis

Here we describe a technique for studying hippocampal postnatal neurogenesis using the organotypic slice culture technique. This method allows for in vitro manipulation of adult neurogenesis and allows for the direct application of pharmacological agents to the cultured hippocampus.

Here we describe a technique for studying hippocampal postnatal neurogenesis in the rodent brain using the organotypic slice culture technique. This ...

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Developmental Biology

12.2K Views.  University of Toronto. Here we describe a technique for studying hippocampal postnatal neurogenesis using the organotypic slice culture technique. This method allows for in vitro manipulation of adult neurogenesis and allows for the direct application of pharmacological agents to the cultured hippocampus.

Video: Organotypic Slice Cultures for Studies of Postnatal Neurogenesis

Ex Utero Electroporation and Organotypic Slice Culture of Mouse Hippocampal Tissue

Mouse genetics offers a powerful tool determining the role of specific genes during development. Analyzing the resulting phenotypes by immunohistochemical and molecular methods provides information of potential target genes and signaling pathways. To further elucidate specific regulatory mechanisms requires a system allowing the manipulation of only a small number of cells of a specific tissue by either overexpression, ablation or re-introduction of specific genes and follow their fate during development. To achieve this ex utero electroporation of hippocampal structures, especially the dentate gyrus, followed by organotypic slice culture provides such a tool. Using this system to generate mosaic deletions allows determining whether the gene of interest regulates cell-autonomously developmental processes like progenitor cell proliferation or neuronal differentiation. Furthermore it facilitates the rescue of phenotypes by re-introducing the deleted gene or its target genes. In contrast to in utero electroporation the ex utero approach improves the rate of successfully targeting deeper layers of the brain like the dentate gyrus. Overall ex utero electroporation and organotypic slice culture provide a potent tool to study regulatory mechanisms in a semi-native environment mirroring endogenous conditions.

Ex Utero Electroporation and Organotypic Slice Culture of Mouse Hippocampal Tissue

Here we present a protocol providing a tool to examine regulatory mechanisms of specific genes during hippocampal development. Employing ex utero electroporation and organotypic slice culture allows the up- and down-regulation of the expression of genes of interest in single cells and follow their fate during development.

Mouse genetics offers a powerful tool determining the role of specific genes during development. Analyzing the resulting phenotypes by immunohistochemical ...

Generation of Genetically Modified Organotypic Skin Cultures Using Devitalized Human Dermis

Organotypic cultures allow the reconstitution of a 3D environment critical for cell-cell contact and cell-matrix interactions which mimics the function and physiology of their in vivo tissue counterparts. This is exemplified by organotypic skin cultures which faithfully recapitulates the epidermal differentiation and stratification program. Primary human epidermal keratinocytes are genetically manipulable through retroviruses where genes can be easily overexpressed or knocked down. These genetically modified keratinocytes can then be used to regenerate human epidermis in organotypic skin cultures providing a powerful model to study genetic pathways impacting epidermal growth, differentiation, and disease progression. The protocols presented here describe methods to prepare devitalized human dermis as well as to genetically manipulate primary human keratinocytes in order to generate organotypic skin cultures. Regenerated human skin can be used in downstream applications such as gene expression profiling, immunostaining, and chromatin immunoprecipitations followed by high throughput sequencing. Thus, generation of these genetically modified organotypic skin cultures will allow the determination of genes that are critical for maintaining skin homeostasis.

The goal of this paper is to provide a comprehensive and detailed protocol on how to generate genetically modified human organotypic skin from epidermal keratinocytes and devitalized human dermis.

Organotypic cultures allow the reconstitution of a 3D environment critical for cell-cell contact and cell-matrix interactions which mimics the function ...

Generating Primary Fibroblast Cultures from Mouse Ear and Tail Tissues

Primary cells are derived directly from tissue and are thought to be more representative of the physiological state of cells in vivo than established cell lines. However, primary cell cultures usually have a finite life span and need to be frequently re-established. Fibroblasts are an easily accessible source of primary cells. Here, we discuss a simple and quick experimental procedure to establish primary fibroblast cultures from ears and tails of mice. The protocol can be used to establish primary fibroblast cultures from ears stored at RT for up to 10 days. When the protocol is carefully followed, contaminations are unlikely to occur despite the use of non-sterile tissue stored for extended time in some cases. Fibroblasts proliferate rapidly in culture and can be expanded to substantial numbers before undergoing replicative senescence.

We describe a simple and quick experimental procedure for generating primary fibroblasts from the ears and tails of mice. The procedure does not require special animal training and can be used for the generation of fibroblast cultures from ears stored at RT for up to 10 days.

Primary cells are derived directly from tissue and are thought to be more representative of the physiological state of cells in vivo than established cell ...

Imaging Cleared Embryonic and Postnatal Hearts at Single-cell Resolution

Single clonal tracing and analysis at the whole-heart level can determine cardiac progenitor cell behavior and differentiation during cardiac development, and allow for the study of the cellular and molecular basis of normal and abnormal cardiac morphogenesis. Recent emerging technologies of retrospective single clonal analyses make the study of cardiac morphogenesis at single cell resolution feasible. However, tissue opacity and light scattering of the heart as imaging depth is increased hinder whole-heart imaging at single cell resolution. To overcome these obstacles, a whole-embryo clearing system that can render the heart highly transparent for both illumination and detection must be developed. Fortunately, in the last several years, many methodologies for whole-organism clearing systems such as CLARITY, Scale, SeeDB, ClearT, 3DISCO, CUBIC, DBE, BABB and PACT have been reported. This lab is interested in the cellular and molecular mechanisms of cardiac morphogenesis. Recently, we established single cell lineage tracing via the ROSA26-CreERT2; ROSA26-Confetti system to sparsely label cells during cardiac development. We adapted several whole embryo-clearing methodologies including Scale and CUBIC (clear, unobstructed brain imaging cocktails and computational analysis) to clear the embryo in combination with whole mount staining to image single clones inside the heart. The heart was successfully imaged at single cell resolution. We found that Scale can clear the embryonic heart, but cannot effectively clear the postnatal heart, while CUBIC can clear the postnatal heart, but damages the embryonic heart by dissolving the tissue. The methods described here will permit the study of gene function at a single clone resolution during cardiac morphogenesis, which, in turn, can reveal the cellular and molecular basis of congenital heart defects.

We describe a protocol to volumetrically image fluorescent protein labeled cells deep inside intact embryonic and postnatal hearts. Utilizing tissue-clearing methods in combination with whole mount staining, single fluorescent protein-labeled cells inside an embryonic or postnatal heart can be imaged clearly and accurately.

Single clonal tracing and analysis at the whole-heart level can determine cardiac progenitor cell behavior and differentiation during cardiac development, ...

Visualization of Cell Cycle Variations and Determination of Nucleation in Postnatal Cardiomyocytes

Cardiomyocytes are prone to variations of the cell cycle, such as endoreduplication (continuing rounds of DNA synthesis without karyokinesis and cytokinesis) and acytokinetic mitosis (karyokinesis but no cytokinesis). Such atypical cell cycle variations result in polyploid and multinucleated cells rather than in cell division. Therefore, to determine cardiac turnover and regeneration, it is of crucial importance to correctly identify cardiomyocyte nuclei, the number of nuclei per cell, and their cell cycle status. This is especially true for the use of nuclear markers for identifying cell cycle activity, such as thymidine analogues Ki-67, PCNA, or pHH3. Here, we present methods for recognizing cardiomyocytes and their nuclearity and for determining their cell cycle activity. We use two published transgenic systems: the Myh6-H2B-mCh transgenic mouse line, for the unequivocal identification of cardiomyocyte nuclei, and the CAG-eGFP-anillin mouse line, for distinguishing cell division from cell cycle variations. Combined together, these two systems ease the study of cardiac regeneration and plasticity.

To distinguish cell division from cell cycle variations in cardiomyocytes, we present protocols using two transgenic mouse lines: Myh6-H2B-mCh transgenic mice, for the unequivocal identification of cardiomyocyte nuclei, and CAG-eGFP-anillin mice, for distinguishing cell division from cell cycle variations.

Cardiomyocytes are prone to variations of the cell cycle, such as endoreduplication (continuing rounds of DNA synthesis without karyokinesis and ...

Dissection and Coronal Slice Preparation of Developing Mouse Pituitary Gland

The pituitary gland or hypophysis is an important endocrine organ secreting hormones essential for homeostasis. It consists of two glands with separate embryonic origins and functions &#8212; the neurohypophysis and the adenohypophysis. The developing mouse pituitary gland is tiny and delicate with an elongated oval shape. A coronal section is preferred to display both the adenohypophysis and neurohypophysis in a single slice of the mouse pituitary.
The goal of this protocol is to achieve proper pituitary coronal sections with well-preserved tissue architectures from developing mice. In this protocol, we describe in detail how to dissect and process pituitary glands properly from developing mice. First, mice are fixed by transcardial perfusion of formaldehyde prior to dissection. Then three different dissecting techniques are applied to obtain intact pituitary glands depending on the age of mice. For fetal mice aged embryonic days (E) 17.5 - 18.5 and neonates up to 4 days, the entire sella regions including the sphenoid bone, gland, and trigeminal nerves are dissected. For pups aged postnatal days (P) 5 - 14, the pituitary glands connected with trigeminal nerves are dissected as a whole. For mice over 3 weeks old, the pituitary glands are carefully dissected free from the surrounding tissues. We also display how to embed the pituitary glands in a proper orientation by using the surrounding tissues as landmarks to obtain satisfying coronal sections. These methods are useful in analyzing histological and developmental features of pituitary glands in developing mice.

We present a protocol to dissect pituitary glands and prepare pituitary coronal sections from developing mice.

The pituitary gland or hypophysis is an important endocrine organ secreting hormones essential for homeostasis. It consists of two glands with separate ...

Three-dimensional Organotypic Cultures of Vestibular and Auditory Sensory Organs

The sensory organs of the inner ear are challenging to study in mammals due to their inaccessibility to experimental manipulation and optical observation. Moreover, although existing culture techniques allow biochemical perturbations, these methods do not provide a means to study the effects of mechanical force and tissue stiffness during development of the inner ear sensory organs. Here we describe a method for three-dimensional organotypic culture of the intact murine utricle and cochlea that overcomes these limitations. The technique for adjustment of a three-dimensional matrix stiffness described here permits manipulation of the elastic force opposing tissue growth. This method can therefore be used to study the role of mechanical forces during inner ear development. Additionally, the cultures permit virus-mediated gene delivery, which can be used for gain- and loss-of-function experiments. This culture method preserves innate hair cells and supporting cells and serves as a potentially superior alternative to the traditional two-dimensional culture of vestibular and auditory sensory organs.

Three-dimensional organotypic cultures of the murine utricle and cochlea in optically clear collagen I gels preserve innate tissue morphology, allow for mechanical stimulation through adjustment of matrix stiffness, and permit virus-mediated gene delivery.

The sensory organs of the inner ear are challenging to study in mammals due to their inaccessibility to experimental manipulation and optical observation. ...

Single-cell Transcriptomic Analyses of Mouse Pancreatic Endocrine Cells

Pancreatic endocrine cells, which are clustered in islets, regulate blood glucose stability and energy metabolism. The distinct cell types in islets, including insulin-secreting &#946; cells, are differentiated from common endocrine progenitors during the embryonic stage. Immature endocrine cells expand via cell proliferation and mature during a long postnatal developmental period. However, the mechanisms underlying these processes are not clearly defined. Single-cell RNA-sequencing is a promising approach for the characterization of distinct cell populations and tracing cell lineage differentiation pathways. Here, we describe a method for the single-cell RNA-sequencing of isolated pancreatic &#946; cells from embryonic, neonatal and postnatal pancreases.

We describe a method for the isolation of endocrine cells from embryonic, neonatal and postnatal pancreases followed by single-cell RNA sequencing. This method allows analyses of pancreatic endocrine lineage development, cell heterogeneity and transcriptomic dynamics.

Pancreatic endocrine cells, which are clustered in islets, regulate blood glucose stability and energy metabolism. The distinct cell types in islets, ...

Neurogenesis Using P19 Embryonal Carcinoma Cells

The P19 cell line derived from a mouse embryo-derived teratocarcinoma has the ability to differentiate into the three germ layers. In the presence of retinoic acid (RA), the suspension cultured P19 cell line is induced to differentiate into neurons. This phenomenon is extensively investigated as a neurogenesis model in vitro. Therefore, the P19 cell line is very useful for molecular and cellular studies associated with neurogenesis. However, protocols for neuronal differentiation of P19 cell line described in the literature are very complex. The method developed in this study are simple and will play a part in elucidating the molecular mechanisms in neurodevelopmental abnormalities and neurodegenerative diseases.

The P19 mouse embryonic carcinoma cell line (P19 cell line) is widely used for studying the molecular mechanism of neurogenesis with great simplification compared to in vivo analysis. Here, we present a protocol for retinoic acid-induced neurogenesis in the P19 cell line.

The P19 cell line derived from a mouse embryo-derived teratocarcinoma has the ability to differentiate into the three germ layers. In the presence of ...

Real-time Bioluminescence Imaging of Notch Signaling Dynamics during Murine Neurogenesis

Notch signaling regulates the maintenance of neural stem/progenitor cells by cell-cell interactions. The components of Notch signaling exhibit dynamic expression. Notch signaling effector Hes1 and the Notch ligand Delta-like1 (Dll1) are expressed in an oscillatory manner in neural stem/progenitor cells. Because the period of the oscillatory expression of these genes is very short (2 h), it is difficult to monitor their cyclic expression. To examine such rapid changes in the gene expression or protein dynamics, fast response reporters are required. Because of its fast maturation kinetics and high sensitivity, the bioluminescence reporter luciferase is suitable to monitor rapid gene expression changes in living cells. We used a destabilized luciferase reporter for monitoring the promoter activity and a luciferase-fused reporter for visualization of protein dynamics at single cell resolution. These bioluminescence reporters show rapid turnover and generate very weak signals; therefore, we have developed a highly sensitive bioluminescence imaging system to detect such faint signals. These methods enable us to monitor various gene expression dynamics in living cells and tissues, which are important information to help understand the actual cellular states.

Neural stem/progenitor cells exhibit various expression dynamics of Notch signaling components that lead to different outcomes of cellular events. Such dynamic expression can be revealed by real-time monitoring, not by static analysis, using a highly sensitive bioluminescence imaging system that enables visualization of rapid changes in gene expressions.

Notch signaling regulates the maintenance of neural stem/progenitor cells by cell-cell interactions. The components of Notch signaling exhibit dynamic ...