This work is a component of the National Cooperative Reprogrammed Cell Research Groups (NCRCRG) to study mental illness and was supported by NIH grant U19MH107367. Initial work was also supported by NIH grant NS070297. We thank Drs. Carol Marchetto and Fred Gage, The Salk Institute, for providing the WT 126 line of neural progenitor cells, and Drs. Eugene Yeo and Lawrence Goldstein, UC San Diego for providing the CVB WT24 line of neural progenitor cells. We thank Deborah Pre in the laboratory of Dr. Anne Bang, Sanford Burnham Prebys Medical Discovery Institute, for useful discussions.

1. Differentiation Period Prior to Replating
<ol>
	<li>Differentiate neurons on 10 cm dishes, using a protocol of choice7,8 until neurons have formed a thick network with their processes and express not only early neuronal markers such as MAP2 or TuJ1, but also late markers such as NeuN.</li>
	<li>Change half the medium of choice every 4 days during the neuronal differentiation process. 
	NOTE: More extensive or frequent medium changes dil...

<ol>
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E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=CellProfiler:+image+analysis+software+for+identifying+and+quantifying+cell+phenotypes.">CellProfiler: image analysis software for identifying and quantifying cell phenotypes.</a> Genome Biology. 7 (10), 100 (2006).</li><li>Gupta, S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Deriving+Dorsal+Spinal+Sensory+Interneurons+from+Human+Pluripotent+Stem+Cells.">Deriving Dorsal Spinal Sensory Interneurons from Human Pluripotent Stem Cells.</a> Stem Cell Reports. 10 (2), 390-405 (2018).</li><li>Ogura, T., Sakaguchi, H., Miyamoto, S., Takahashi, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Three-dimensional+induction+of+dorsal,+intermediate+and+ventral+spinal+cord+tissues+from+human+pluripotent+stem+cells.">Three-dimensional induction of dorsal, intermediate and ventral spinal cord tissues from human pluripotent stem cells.</a> Development. 145, (2018).</li><li>Playne, R., Jones, K., Connor, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Generation+of+dopamine+neuronal-like+cells+from+induced+neural+precursors+derived+from+adult+human+cells+by+non-viral+expression+of+lineage+factors.">Generation of dopamine neuronal-like cells from induced neural precursors derived from adult human cells by non-viral expression of lineage factors.</a> Journal of Stem Cells and Regenerative Medicine. 14 (1), 34-44 (2018).</li><li>Rao, M. S., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Illustrating+the+potency+of+current+Good+Manufacturing+Practice-compliant+induced+pluripotent+stem+cell+lines+as+a+source+of+multiple+cell+lineages+using+standardized+protocols.">Illustrating the potency of current Good Manufacturing Practice-compliant induced pluripotent stem cell lines as a source of multiple cell lineages using standardized protocols.</a> Cytotherapy. 20 (6), 861-872 (2018).</li><li>Suga, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differentiation+of+pluripotent+stem+cells+into+hypothalamic+and+pituitary+cells.">Differentiation of pluripotent stem cells into hypothalamic and pituitary cells.</a> Neuroendocrinology. 101 (1), 18-24 (2015).</li><li>Endaya, B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Isolating+dividing+neural+and+brain+tumour+cells+for+gene+expression+profiling.">Isolating dividing neural and brain tumour cells for gene expression profiling.</a> Journal of Neuroscience Methods. 257, 121-133 (2016).</li><li>Sergent-Tanguy, S., Chagneau, C., Neveu, I., Naveilhan, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fluorescent+activated+cell+sorting+(FACS):+a+rapid+and+reliable+method+to+estimate+the+number+of+neurons+in+a+mixed+population.">Fluorescent activated cell sorting (FACS): a rapid and reliable method to estimate the number of neurons in a mixed population.</a> Journal of Neuroscience Methods. 129 (1), 73-79 (2003).</li><li>Frega, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Rapid+Neuronal+Differentiation+of+Induced+Pluripotent+Stem+Cells+for+Measuring+Network+Activity+on+Micro-electrode+Arrays.">Rapid Neuronal Differentiation of Induced Pluripotent Stem Cells for Measuring Network Activity on Micro-electrode Arrays.</a> Journal of Visualized Experiments. (119), e54900 (2017).</li><li>Grainger, A. I., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=In+vitro+Models+for+Seizure-Liability+Testing+Using+Induced+Pluripotent+Stem+Cells.">In vitro Models for Seizure-Liability Testing Using Induced Pluripotent Stem Cells.</a> Frontiers in Neuroscience. 12, 590 (2018).</li><li>Daub, A., Sharma, P., Finkbeiner, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-content+screening+of+primary+neurons:+ready+for+prime+time.">High-content screening of primary neurons: ready for prime time.</a> Current Opinion in Neurobiology. 19 (5), 537-543 (2009).</li></ol>

We have demonstrated a straight-forward procedure for the resuspension and replating of human neuronal cultures that optimizes viability, differentiation success, and subcellular imaging in a manner that is compatible with high content screening platforms, and other assays relevant to drug discovery. Figure 6 illustrates the overall workflow and examples of such applications.
Although here we focused on hiPSC-derived neurons that are directed toward a cortical neu...

Human pluripotent stem cell (hiPSC)-derived neurons are increasingly relevant in the areas of basic research, drug development, and regenerative medicine. Workflows and procedures to optimize their culture and maintenance, and improve the efficiency of differentiation into specific neuronal subtypes, are evolving rapidly1,2. To improve the utility and cost-effectiveness of human stem cell-derived neurons as model systems amenable to high-content analyses in drug discovery and target validation, it is useful to decrease the culturing time required to generate mature, functional neurons, while retaining maximum robustness, reproducibility, and phenotype relevance. Although 3-dimensional organoid cultures are driving breakthroughs in neurodevelopment research3, 2-dimensional monolayer cultures are especially compatible with automated imaging-based applications due to their minimal tissue thickness.
However, the adaptation of imaging-based screening methods to models of human neurological and neurodevelopmental disease faces a major challenge. The protracted timeframe over which the human nervous system matures in vivo necessitates extended time in culture to accommodate natural programs of gene expression and achieve neuronal maturation.
One practical consequence of the lengthy neuronal differentiation program is that the maintenance of hiPSC-derived monolayer cultures must be sustained for many weeks to achieve adequate synapse maturity. During this time, neural progenitors that remain undifferentiated continue to divide. These can quickly overgrow the culture and usurp the nutrient content required to maintain viable postmitotic neurons. Vigorously dividing neural progenitor cells (NPCs) can also compete with neurons for the growth substrate. This can render such cultures subject to problems of poor adhesion, a condition unsuitable for imaging-based assays. Moreover, many investigators find that the smaller the culture volume, the greater the difficulty in maintaining healthy populations of differentiated neurons long enough to observe the late stages of neuronal differentiation. In other words, assays of synapse maturation using high content screening (HCS) approaches can be very challenging for human-derived neurons.
To circumvent some of these problems, a procedure of resuspending and replating previously differentiated hiPSC-derived neurons has been used. Firstly, it allows the study of neurite outgrowth (or, more accurately, neurite regeneration) in a population of fully committed neurons. Secondly, the replating of previously differentiated neurons from a large volume format (like 10 cm plates or larger), down to small volume formats (like HCS-compatible 96- or 384-well microtiter plates) enables a significant reduction in total culturing time in the small volume condition. This facilitates the study of synapse assembly and maturation over subsequent weeks in vitro.
However, the replating of mature neurons that have already established long neurites and a complex connectivity network presents several challenges, one of which is the sometimes high and variable rate of cell death. Here, we describe a replating procedure that results in excellent cell survival and reproducibility. Commonly, neurons are exposed to proteolytic enzymes for short incubation periods (typically ~3-10 min) in order to detach cells from the substrate prior to trituration. This brief proteolysis time is customarily used for resuspending and passaging many types of dividing cells, including non-neuronal cells and undifferentiated progenitors4,5,6. However, for differentiated neurons bearing long, interconnected neurites, it is essential not only to detach cells from the substrate but also to disrupt the dendritic and axonal network in order to isolate individual cells while minimizing damage. Indeed, a thick meshwork of neurons usually tends to detach from the substrate as a single sheet, rather than as individual cells. If care is not taken to loosen the thick network of neurites, neurons not only become irreversibly damaged during trituration, but many of them fail to pass through the filter used to remove clumps, resulting in poor cell yield. Below we describe a simple modification to a widely-used protease incubation procedure to counter these difficulties.
In the protocol described below, neurons are incubated for 40-45 min with a mild protease, such as the proteolytic enzyme (e.g., Accutase). During the first 5-10 min after adding the enzyme, the neuronal network lifts off from the substrate as a sheet. Incubation with the protease proceeds for an additional 30-40 min before proceeding with gentle trituration and filtering. This extra incubation time helps ensure that the digestion of the material relaxes the intercellular network, thereby ensuring that subsequent trituration produces a suspension of individual cells. This procedure maximizes the uniformity of cell distribution upon replating while minimizing cell death. We have successfully applied this replating method to hiPSC-derived neuronal cultures generated by various differentiation protocols7,8 and from various lines of hiPSCs. The procedure is nominally suitable for use with most or all lines of stem cell-derived neurons. We have observed that an extended protease incubation time is not absolutely essential for replating cultures from small format plates (e.g., 35 mm diameter); however, as we show here, it provides a significant benefit when replating from large diameter plates (e.g., 10 cm diameter or larger), probably because neurites in such plates can extend very long processes and form a densely interconnected array.
Here we demonstrate this method and briefly illustrate its application in assays for early neuritogenesis and for synapse maturation, which involves clustering of pre- and postsynaptic proteins along the dendrites and axons, followed by their later colocalization at synaptic sites. The examples highlight the advantages this protocol offers in preserving cell viability and reproducibility. First, it permits investigators to study early steps in human neuritogenesis. The experimental setting is similar to the commonly used primary cultures of rodent cortical or hippocampal neurons, where cells are extracted from late fetal or early postnatal brain, dissociated by trituration after gentle protease treatment, and allowed to initiate neurites or to regenerate neurites that were severed in the procedure9,10. Similar to such rodent primary neurons, hiPSC-derived neurons begin to form or regenerate their neurites within hours after replating, allowing imaging of growth cones and neurite morphology in an environment optimal for high spatiotemporal imaging with fewer surrounding undifferentiated cells. We have observed that neurite outgrowth is more synchronized compared to the variable delays and different outgrowth rates seen when neurons first begin to differentiate from a progenitor population. In addition, replating enables assays of neurons expressing neuronal subtype markers that typically appear later in neural development, such as the cortical layer 5/6 transcription factor CTIP2 (Chicken ovalbumin upstream promoter transcription factor-interacting protein 2), or the pan-neuronal marker NeuN11. An especially useful feature of the replating approach is that synaptogenesis proceeds within a time frame compatible with HCS.

<table border="0" cellpadding="0" cellspacing="0" style="width:1076px;" width="1076">
	<colgroup>
		<col />
		<col />
		<col />
		<col />
	</colgroup>
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Post Replating Media</td>
			<td style="width:276px;"></td>
			<td style="width:119px;"></td>
			<td style="width:377px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">L-Ascorbic Acid</td>
			<td style="width:276px;">Sigma</td>
			<td>A4403</td>
			<td>Add 1ml of 200mM stock to 1L of N2B27 media</td>
		</tr>
		<tr height="20">
			<td height="20" style="height:20px;">dibutyryl-cAMP</td>
			<td>Sigma</td>
			<td>D0627</td>
			<td>Add 1 &#181;M</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Human BDNF</td>
			<td style="width:276px;">Peprotech</td>
			<td style="width:119px;">450-02</td>
			<td>10 ng/ml final concentration</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">B27 (50X)</td>
			<td style="width:276px;">Thermofisher Scientific</td>
			<td style="width:119px;">17504044</td>
			<td>Add 20 ml to 1L N2B27 media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">DMEM/F12 with Glutamax</td>
			<td style="width:276px;">Thermofisher Scientific</td>
			<td>31331093</td>
			<td>Add N2 and distribute in 50 mL conicals; parafilm wrap lids</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Human GDNF</td>
			<td style="width:276px;">Peprotech</td>
			<td>450-10</td>
			<td>10 ng/ml final concentration</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Glutamax</td>
			<td style="width:276px;">Thermofisher Scientific</td>
			<td>35050038</td>
			<td>Add 10 ml to 1L N2B27 media; glutamine supplement</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Mouse Laminin</td>
			<td style="width:276px;">Sigma</td>
			<td>P3655-10mg</td>
			<td>Add 100 &#181;l to 50 mL N2B27</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">MEM Nonessential Amino Acids</td>
			<td style="width:276px;">Thermofisher Scientific</td>
			<td style="width:119px;">11140035</td>
			<td>Add 5ml to 1L N2B27 media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">N2 (100X) Supplement</td>
			<td style="width:276px;">Life Technologies</td>
			<td>17502048</td>
			<td>Add 5ml to 500mL media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Neurobasal A Media</td>
			<td style="width:276px;">Thermofisher Scientific</td>
			<td>10888022</td>
			<td>Combine with DMEM/F12 to generate N2B27 media for CVB wt cells; neural basal A media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Neurobasal Media</td>
			<td style="width:276px;">Thermofisher Scientific</td>
			<td>21103049</td>
			<td>for WT126 cells; neural basal media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">SM1 Supplement</td>
			<td style="width:276px;">StemCell Technologies</td>
			<td>5711</td>
			<td>Add 1:50 to media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">sodium bicarbonate</td>
			<td style="width:276px;">Thermofisher Scientific</td>
			<td>25080-094</td>
			<td>Add 10ml to 1L N2B27 media</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Plate Preparation</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">10cm Tissue Culture Dishes</td>
			<td style="width:276px;">Fisher Scientific</td>
			<td>08772-E</td>
			<td>Plastic TC-treated dishes</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">6-well Tissue Culture Dishes</td>
			<td style="width:276px;">Thomas Scientific</td>
			<td>1194Y80</td>
			<td>NEST plates</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Mouse Laminin</td>
			<td style="width:276px;">Life Technologies</td>
			<td>23017-015</td>
			<td>Add 1:400 on plastic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Poly-Ornithine</td>
			<td style="width:276px;">Sigma</td>
			<td>P3655-10mg</td>
			<td>Add 1:1000 on plastic</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">UltraPure Distilled Water</td>
			<td style="width:276px;">Life Technologies</td>
			<td style="width:119px;">10977-015</td>
			<td>To dilute Poly-L-Ornithine</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Replating Reagents</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">100mM Cell Strainer</td>
			<td style="width:276px;">Corning</td>
			<td style="width:119px;">431752</td>
			<td>Sterile, individually wrapped</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">384-well plate, uncoated</td>
			<td style="width:276px;">PerkinElmer</td>
			<td>6007550</td>
			<td>Coat with PLO and Laminin</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">DPBS</td>
			<td style="width:276px;">Life Technologies</td>
			<td style="width:119px;">14190144</td>
			<td>Dulbecco&#39;s phosphate-buffered saline</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Poly-D-Lysine-Precoated 384-well Plates</td>
			<td style="width:276px;">PerkinElmer</td>
			<td>6057500</td>
			<td>Rinse before coating with laminin</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">StemPro Accutase</td>
			<td style="width:276px;">Life Technologies</td>
			<td>A1110501</td>
			<td>Apply 1mL/10cm plate for 30-45 minutes; proteolytic enzyme</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Fixation Materials</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">37% Formaldehyde</td>
			<td style="width:276px;">Fisher Scientific</td>
			<td style="width:119px;">F79-1</td>
			<td>Dissolved in PBS</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Sucrose</td>
			<td style="width:276px;">Fisher Scientific</td>
			<td style="width:119px;">S5-12</td>
			<td>0.8 g per 10 ml of fixative</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Immunostaining Materials</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Alexa Fluor 488 Goat anti-mouse</td>
			<td style="width:276px;">Invitrogen</td>
			<td>A-11001</td>
			<td>secondary antibody</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Alexa Fluor 568 Goat anti-chicken</td>
			<td style="width:276px;">Invitrogen</td>
			<td>A-11041</td>
			<td>secondary antibody</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Alexa Fluor 647 Goat anti-chicken</td>
			<td style="width:276px;">Invitrogen</td>
			<td>A-21449</td>
			<td>secondary antibody</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Alexa Fluor 561 Goat anti-rat</td>
			<td style="width:276px;">Invitrogen</td>
			<td>A-11077</td>
			<td>secondary antibody</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">DAPI</td>
			<td style="width:276px;">Biotium</td>
			<td>40043</td>
			<td>visualizes DNA</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">mouse antibody against b3-tubulin (TuJ-1)</td>
			<td style="width:276px;">Neuromics</td>
			<td>MO15013</td>
			<td>early stage neuronal marker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">rat antibody against CTIP2</td>
			<td style="width:276px;">Abcam</td>
			<td>ab18465</td>
			<td>layer 5/6 cortical neurons</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">chicken antibody against MAP2</td>
			<td style="width:276px;">LifeSpan Biosciences</td>
			<td>LS-B290</td>
			<td>early stage neuronal marker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">chicken antibody against NeuN</td>
			<td style="width:276px;">Millipore</td>
			<td>ABN91</td>
			<td>late stage neuronal marker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">rabbit antibody against MAP2</td>
			<td style="width:276px;">Shelley Halpain</td>
			<td>N/A</td>
			<td>early stage neuronal marker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">mouse antibody against PSD-95</td>
			<td style="width:276px;">Sigma</td>
			<td>P-246</td>
			<td>post-synaptic marker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">rabbit antibody against Synapsin 1</td>
			<td style="width:276px;">Millipore</td>
			<td>AB1543</td>
			<td>pre-synaptic marker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Bovine serum albumin (BSA)</td>
			<td style="width:276px;">GE Healthcare Life Sciences</td>
			<td>SH30574.02</td>
			<td>10% in PBS for blocking</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Titon X-100</td>
			<td style="width:276px;">Sigma</td>
			<td style="width:119px;">9002931</td>
			<td>Dilute to 0.2% on PBS for permeabilization</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Viability Markers</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Vivafix 649/660</td>
			<td style="width:276px;">Biorad</td>
			<td style="width:119px;">135-1118</td>
			<td>cell death marker</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Calcium Imaging</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">Name of Reagent/ Equipment</td>
			<td style="width:276px;">Company</td>
			<td style="width:119px;">Catalog Number</td>
			<td>Comments/Description</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">AAV8-syn-jGCAMP7f-WPRE</td>
			<td>THE SALK INSTITUTE, GT3 Core Facility</td>
			<td style="width:119px;">N/A</td>
			<td>calcium reporter in a viral delivery system</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">hiPSC-derived NPCs</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">WT 126 (Y2610)</td>
			<td style="width:276px;">Gage lab</td>
			<td style="width:119px;">N/A</td>
			<td>Marchetto et al., 2010</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:304px;">CVB WT24</td>
			<td style="width:276px;">Yeo and Goldstein labs</td>
			<td style="width:119px;">N/A</td>
			<td>unpublished</td>
		</tr>
	</tbody>
</table>

post-differentiation replating of human pluripotent stem cell-derived neurons for high-content screening of neuritogenesis and synapse maturation

Neurons differentiated in two-dimensional culture from human pluripotent stem-cell-derived neural progenitor cells (NPCs) represent a powerful model system to explore disease mechanisms and carry out high content screening (HCS) to interrogate compound libraries or identify gene mutation phenotypes. However, with human cells the transition from NPC to functional, mature neuron requires several weeks. Synapses typically start to form after 3 weeks of differentiation in monolayer culture, and several neuron-specific proteins, for example the later expressing pan-neuronal marker NeuN, or the layer 5/6 cerebral cortical neuron marker CTIP2, begin to express around 4-5 weeks post-differentiation. This lengthy differentiation time can be incompatible with optimal culture conditions used for small volume, multi-well HCS platforms. Among the many challenges are the need for well-adhered, uniformly distributed cells with minimal cell clustering, and culture procedures that foster long-term viability and functional synapse maturation. One approach is to differentiate neurons in a large volume format, then replate them at a later time point in HCS-compatible multi-wells. Some main challenges when using this replating approach concern reproducibility and cell viability, due to the stressful disruption of the dendritic and axonal network. Here we demonstrate a detailed and reliable procedure for enzymatically resuspending human induced pluripotent stem cell (hiPSC)-derived neurons after their differentiation for 4-8 weeks in a large-volume format, transferring them to 384-well microtiter plates, and culturing them for a further 1-3 weeks with excellent cell survival. This replating of human neurons not only allows the study of synapse assembly and maturation within two weeks from replating, but also enables studies of neurite regeneration and growth cone characteristics. We provide examples of scalable assays for neuritogenesis and synaptogenesis using a 384-well platform.

The replating of hiPSCs-derived neurons that have been differentiated for multiple weeks offers several advantages. However, detaching and replating differentiated neurons that have long, interconnected dendrites and axons (Figure 1A) can result in a high fraction of irreversibly damaged neurons.
As described in the protocol section, we used incubation with a proteolytic enzyme to detach the neurons from the substrate. Typically, due to their thic...

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Post-differentiation Replating of Human Pluripotent Stem Cell-derived Neurons for High-content Screening of Neuritogenesis and Synapse Maturation

This protocol describes a detailed procedure for resuspending and culturing human stem cell derived neurons that were previously differentiated from neural progenitors in vitro for multiple weeks. The procedure facilitates imaging-based assays of neurites, synapses, and late-expressing neuronal markers in a format compatible with light microscopy and high-content screening.

Neurons differentiated in two-dimensional culture from human pluripotent stem-cell-derived neural progenitor cells (NPCs) represent a powerful model ...

This protocol facilitates the use of human pluripotent stem cell-derived neurons for high content screening applications. It is particularly well suited for assaying synapses, which in human neurons require lengthy culture periods. We demonstrate the replating of neurons from large format dishes into HCS-compatible multi wells in a way that preserves their viability.Counter-intuitively, we show that extending protease incubation prior to resuspending and replating yields improved neuronal survival. Human pluripotent stem cell-derived neurons are increasingly relevant in the areas of basic research, drug development, and degenerative medicine. This gentle titration method can be used to resuspend any large mono-layer of cells having a thick network of processes.In addition to human iPSCs, it can be used to replate culture of primary neurons or to resuspend them for fact sorting or single cell sequencing. It is important to follow the protocols steps carefully and frequently monitor the protease mediated detachment of the neurons from the plate. The optimal incubation time may vary, depending on the culture.Visual demonstration enables even inexperienced investigators to reproduce this procedure. Start by gently rinsing the plate of differentiated neurons with PBS. Disperse the PBS down the wall of the plate and not directly onto the cells to avoid disrupting them.Aspirate the PBS from the edge of the dish while tipping it, taking care not to touch the cells. Apply at least one milliliter of proteolytic enzyme per 10-centimeter plate. And return the cells to the incubator for 40 to 45 minutes.During the incubation, check neurons on a phased contrast microscope and continue the protease treatment until the neural network completely detaches from the plate and starts to break apart. When the neurons have detached, stop digestion by adding five milliliters of fresh DEMEM media for every one milliliter of protease. Use a serological pipette to gently titrate the cells against the plate five to eight times, making sure to not apply too much pressure.Strain the cells through a 100 micrometer mesh into a 50 milliliter conical tube, drop by drop. And rinse the strainer with an additional five milliliters of fresh DMEM media. Use a bench-top centrifuge to spin the cells down at 1000 times G for five minutes.After centrifugation, return the conical tube to the biosafety cabinet and aspirate most of the media, leaving 250 microliters to keep the cells moist. Gently resuspend the cells in two milliliters of fresh DMEM media then pass them through the end of a five milliliter serological pipette. Finally, invert the tube two to three times.Use a hemocytometer and tripan blue to count the viable cells. And then DMEM to the desired concentration. Add appropriate supplements to the tube, depending on the requirements of the specific cell line and gently mix the cells by tilting the conical tube two to three times.Aspirate laminin coating from a 24-well plate and rinse it once with PBS. Aspirate the PBS. And apply cell solution to each well in a figure eight motion to avoid clumping.When finished plating the cells, return the plate to the incubator set at 37 degrees Celsius and 5%carbon dioxide. Briefly vortex the stock solution of the early cell death reporter and add it to the wells according to the manuscript directions. Wait 20 minutes.And then image the live and dead cells on glass bottom multi wells. Prolonging the protease incubation allows loosening of the neuronal network within the lifted sheet of cells. This results in reduced cell death at the time of dissociation as well as results in more efficient recovery over the following days.Using the extended enzyme incubation procedure, the cultures exhibit an approximate doubling of cell viability during the days after replating and a lower density of dead or dying cells. The transition phase of neuronal differentiation takes place over several days, during which the cells gradually express late-stage neuronal markers. These markers are immediately detected in cultures that were replated after four weeks of pre-differentiation.The extended protease protocol also moderately enhances neuride outgrowth. Both total neuride length and dendrite growth are improved. Replating is also useful for studying synapses.Just one week after replating, markers for pre-and post-synaptic proteins were observed. Moreover, electrical activity from spontaneous depolarization and synaptically-driven currents is detectable using calcium imaging or multielectrode arrays. This replating procedure can be adapted to many types of applications.In addition to high content screening to identify potential therapeutic compounds, it could be used for imaging growth cones or multielectrode array recordings. Mechanical dissociation of neurons that have already formed long processes is stressful. Elongated enzymatic incubation and gentle titration of cells are essential steps for the success of this procedure.

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Research

JoVE Journal

Neuroscience

9.1K visualizações.  University of California, San Diego. Este protocolo facilita o uso de neurônios pluripotentes humanos derivados de células-tronco para aplicações de triagem de alto conteúdo. É particularmente adequado para avaliar sinapses, que em neurônios humanos requerem longos períodos de cultura. Demonstramos a replação de neurônios de pratos de grande formato em multi-poços compatíveis com HCS de forma a preservar sua viabilidade.Contra-intuitivamente, mostramos que estender a incubação de protease antes de resuscupa...

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