Thank you to Willy Sun for technical assistance and Dr. Kris Gellynck for helpful comments and three anonymous reviewers for their constructive advice. This work was funded by the Sunnybrook Hearing Regeneration Initiative

Mouse tissue was harvested from Sox2EGFP-reporter mice12 maintained and euthanized in accordance with Canadian Council on Animal Care guidelines for the care and use of laboratory animals.
1. Culturing Embryonic Cochleae
<ol>
	<li>Supplement Dulbecco&#8217;s Modified Eagle Medium (DMEM) by mixing 8.89 ml of DMEM, 1 ml of fetal bovine serum (FBS), 100 &#956;l of 100x N2 supplement, and 10 &#956;l of 10 mg/ml ciprofloxacin. Supplement Hank&#8217;s Balanced Salt Solution (HBSS) by mixing 495 ml HBSS with 5 ml of 100% HEPES.</li>
	<li>Prepare glass bottom culture dishes:
	<ol>
		<li>In a laminar flow hood, resuspend 200 &#181;l basement membrane extract substrate in 5 ml DMEM. Prepare 35 mm diameter glass bottom culture dishes with 10 mm wells. Pipette 150 &#181;l substrate/DMEM in to the center of each glass bottomed dish. These dishes can be used after 40 min incubation, or can stored in a CO2 incubator at 35 &#176;C for at least a week. 
		NOTE: Glass bottomed dishes are used for the following reasons: to ensure that the base of the dish is transparent and suitable for imaging, to create a well in the center of the dish that allows the explants to settle in an easily located area and finally so that after an experiment the sample can be processed for immunostaining and subsequent analysis.</li>
	</ol>
	</li>
	<li>Prepare the work-station and tools:
	<ol>
		<li>Turn on the laminar flow clean bench, and spray down with 70% EtOH to create a clean work space. Soak forceps, spoons, and a black 184 silicone elastomer dish (a mix of 184 silicone elastomer (10 parts), curing agent (1 part) and charcoal powder (2.5 g)) in 70% EtOH.</li>
	</ol>
	</li>
	<li>In the clean work station, harvest embryos for the experiment. Collect embryos of the appropriate gestation in ice cold HBSS supplemented with 1% HEPES.
	<ol>
		<li>Determine an external or visible organ that will demonstrate reporter activity and examine the embryos using a fluorescent stereo microscope. Collect the embryos that exhibit reporter activity in ice cold HBSS supplemented with 1% HEPES as these are the subject of the experiment.</li>
	</ol>
	</li>
	<li>Collect temporal bones:
	<ol>
		<li>Working quickly, using a cool light source and fine forceps, collect the heads of the pups. Take care to clip at the cervical vertebrae and below the jaw to avoid damage to the temporal bones.</li>
		<li>Carefully open the skull. Remove the brain, trim off the front of the head, and transfer the posterior skull to fresh ice cold HBSS supplemented with 1% HEPES in a clean dish. Carefully dissect out the peanut shaped temporal bones taking care to keep the vestibular system in tact.</li>
	</ol>
	</li>
	<li>Dissect the cochlea:
	<ol>
		<li>Transfer the temporal bones to a black silicone elastomer coated dish in ice cold HBSS supplemented with 1% HEPES, pin the vestibular region of the bone. Insert insect pins at an oblique angle in order to stabilize the temporal bone and create room for the forceps. Pinning is a crucial step in the process as if the temporal bone is allowed to move too much it is very difficult to harvest an intact cochlea.</li>
		<li>Carefully remove the cartilage surrounding the cochlea. Insert one tine of the forceps into the cartilage at the outer edge of the base of the cochlea and clip a hole into the cartilage.</li>
		<li>Clip a flap up the side, insert the tine of the forceps and gently separate the roof of the duct from the cartilage. Clip horizontally across the top and diagonally, and carefully lift off the front section of the capsule. Insert a prong of the forceps in between the remaining cartilage and the duct and gently clip off the last section. The apical surface of the cochlea is now exposed.</li>
		<li>Starting at the base, catch the area where the roof of the duct meets the cochlear epithelium and open the cochlear duct. Gently peel off the roof, trimming when necessary until it is completely removed. Trim off any portions of membrane left on the medial side of the duct. Clean the duct of excess mesenchymal tissue and detach the duct from the vestibular system.</li>
	</ol>
	</li>
	<li>Culture the explants:
	<ol>
		<li>Place an explant, luminal surface up, in the center of a substrate coated glass bottom culture dish, carefully draw off all of the liquid and leave for two minutes. Add 150 &#181;l supplemented DMEM drop-wise to the explant, taking care not to disturb it. Should the explant float free, reposition with forceps, but take care that the explant settles to the bottom of the dish so that it can attach to the substrate.</li>
		<li>Place the glass bottom dishes in a deep 12 cm diameter Petri dish, with a small dish of sterile water to maintain humidity. Put the cultures in to a 35 &#176;C incubator overnight in order for the explant to attach to the substrate and flatten.</li>
	</ol>
	</li>
</ol>
2. Live Imaging
<ol>
	<li>Select explant samples. Use a fluorescent stereo microscope to evaluate the condition of each explanted cochlea. Only select explants where the duct is intact and attached to the glass from base to apex.</li>
	<li>Set the incubator at 35 &#176;C with 5% CO2 to culture cochlear tissue. Put the cultures into the incubator microscope:
	<ol>
		<li>Gently aspirate off the supplemented DMEM and replace with at least 500 &#956;l fresh media. For imaging up to 6 days, 1-1.5 ml is better. In cases where explants are loosely attached, pipette a ring of media around the edge of the dish. This extra liquid will make a miniature &#8216;humidified chamber&#8217; without disturbing the explant while it continues to attach to the matrix.
		<ol>
			<li>Alternatively, use hinged dish covers to open the lids while the dish stays in its fitting in the microscope if reagents need to be exchanged during intervals between image collections. Hinged dish covers allow the lids to be opened without disturbing the samples or removing the dishes from their settings. This maintains their exact position for subsequent image captures.</li>
		</ol>
		</li>
		<li>Insert the glass bottom dishes containing appropriate samples into the sample dish holder. The microscope in this example has a rotating platform that holds eight 35 mm sample dishes.</li>
		<li>Under the laminar flow hood replace the plastic lids with glass lids and insert the dishes into the sample dish holder. Place the sample dish holder inside the incubator taking care not to dislodge the explants from the bottom of the dish or to disturb the media.</li>
	</ol>
	</li>
	<li>Set up the imaging routine:
	<ol>
		<li>Switch on the microscope, UV lamp and camera and open the imaging software.</li>
		<li>Locate the samples, pick an imaging area, plane of focus and adjust exposure times for each dish in sequence. Choose the plane of focus depending not only on the view of the explant at the time of starting, but also bearing in mind how the tissue will move and how long the time course will run.</li>
		<li>Set a Z stack centering around the selected focal plane in the fluorescence channel. Set the frequency and length of the sampling for the experiment. The frequency of sampling will be limited by the time it takes to collect images, so this should be determined after selecting fields of view and setting a Z stack. In this case sampling takes place every 30 min over five days. The duration of the experiment can be up to 14 days.</li>
	</ol>
	</li>
	<li>Generate a movie:
	<ol>
		<li>At the end of the time lapse period open the image files. In this case Metamorph software that opens sequential collection points is used. Frame by frame pick the best focal plane for showing the cell population of interest.</li>
		<li>Convert these images to an .avi file, or export them as a montage to generate a set of images that can be opened and analyzed in image processing software or converted to multiple formats using video processing software.</li>
	</ol>
	</li>
</ol>

<ol><li>Wu, D. K., Kelley, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Molecular+mechanisms+of+inner+ear+development%5BTitle%5D)+AND+%22Cold+Spring+Harbor+perspectives+in+biology%22%5BJournal%5D)">Molecular mechanisms of inner ear development.</a> Cold Spring Harbor perspectives in biology. 4, (2012).</li>
<li>Shim, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((The+auditory+sensory+epithelium%3A+the+instrument+of+sound+perception%5BTitle%5D)+AND+%22The+international+journal+of+biochemistry+%26+cell+biology%22%5BJournal%5D)">The auditory sensory epithelium: the instrument of sound perception.</a> The international journal of biochemistry & cell biology. 38, 1827-1833 (2006).</li>
<li>Van de Water, T., Ruben, R. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Growth+of+the+inner+ear+in+organ+culture%5BTitle%5D)+AND+%22The+Annals+of+otology%2C+rhinology%2C+and+laryngology%22%5BJournal%5D)">Growth of the inner ear in organ culture.</a> The Annals of otology, rhinology, and laryngology. 83, 1-16 (1974).</li>
<li>Jacques, B. E., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((A+dual+function+for+canonical+Wnt%2Fbeta-catenin+signaling+in+the+developing+mammalian+cochlea%5BTitle%5D)+AND+%22Development%22%5BJournal%5D)">A dual function for canonical Wnt/beta-catenin signaling in the developing mammalian cochlea.</a> Development. 139, 4395-4404 (2012).</li>
<li>Castellano-Munoz, M., Peng, A. W., Salles, F. T., Ricci, A. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Swept+field+laser+confocal+microscopy+for+enhanced+spatial+and+temporal+resolution+in+live-cell+imaging.+Microscopy+and+microanalysis+%3A+the+official+journal+of+Microscopy%5BTitle%5D)+AND+%22Society+of+America%2C+Microbeam+Analysis+Society%2C+Microscopical+Society+of+Canada%22%5BJournal%5D)">Swept field laser confocal microscopy for enhanced spatial and temporal resolution in live-cell imaging. Microscopy and microanalysis : the official journal of Microscopy.</a> Society of America, Microbeam Analysis Society, Microscopical Society of Canada. 18, 753-760 (2012).</li>
<li>Szarama, K. B., Gavara, N., Petralia, R. S., Chadwick, R. S., Kelley, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Thyroid+hormone+increases+fibroblast+growth+factor+receptor+expression+and+disrupts+cell+mechanics+in+the+developing+organ+of+corti%5BTitle%5D)+AND+%22BMC+developmental+biology%22%5BJournal%5D)">Thyroid hormone increases fibroblast growth factor receptor expression and disrupts cell mechanics in the developing organ of corti.</a> BMC developmental biology. 13, 6(2013).</li>
<li>Appler, J. M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Gata3+is+a+critical+regulator+of+cochlear+wiring%5BTitle%5D)+AND+%22The+Journal+of+neuroscience+%3A+the+official+journal+of+the+Society+for+Neuroscience%22%5BJournal%5D)">Gata3 is a critical regulator of cochlear wiring.</a> The Journal of neuroscience : the official journal of the Society for Neuroscience. 33, 3679-3691 (2013).</li>
<li>Wibowo, I., Pinto-Teixeira, F., Satou, C., Higashijima, S., Lopez-Schier, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Compartmentalized+Notch+signaling+sustains+epithelial+mirror+symmetry%5BTitle%5D)+AND+%22Development%22%5BJournal%5D)">Compartmentalized Notch signaling sustains epithelial mirror symmetry.</a> Development. 138, 1143-1152 (2011).</li>
<li>Hashimoto, S., Kato, N., Saeki, K., Morimoto, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Selection+of+high-potential+embryos+by+culture+in+poly%28dimethylsiloxane%29+microwells+and+time-lapse+imaging%5BTitle%5D)+AND+%22Fertility+and+sterility%22%5BJournal%5D)">Selection of high-potential embryos by culture in poly(dimethylsiloxane) microwells and time-lapse imaging.</a> Fertility and sterility. 97, 332-337 (2012).</li>
<li>Matsuoka, F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((Morphology-based+prediction+of+osteogenic+differentiation+potential+of+human+mesenchymal+stem+cells%5BTitle%5D)+AND+%22PloS+one%22%5BJournal%5D)">Morphology-based prediction of osteogenic differentiation potential of human mesenchymal stem cells.</a> PloS one. 8, (2013).</li>
<li>Ma, G. F., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((et+al.Transforming+growth+factor-beta1+and+-beta2+in+gastric+precancer+and+cancer+and+roles+in+tumor-cell+interactions+with+peripheral+blood+mononuclear+cells+in+vitro%5BTitle%5D)+AND+%22PloS+one%22%5BJournal%5D)">et al.Transforming growth factor-beta1 and -beta2 in gastric precancer and cancer and roles in tumor-cell interactions with peripheral blood mononuclear cells in vitro.</a> PloS one. 8, (2013).</li>
<li>Taranova, O. V., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((SOX2+is+a+dose-dependent+regulator+of+retinal+neural+progenitor+competence%5BTitle%5D)+AND+%22Genes+%26+development%22%5BJournal%5D)">SOX2 is a dose-dependent regulator of retinal neural progenitor competence.</a> Genes & development. 20, 1187-1202 (2006).</li>
<li>Chen, P., Segil, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/pubmed?term=((p27%28Kip1%29+links+cell+proliferation+to+morphogenesis+in+the+developing+organ+of+Corti%5BTitle%5D)+AND+%22Development%22%5BJournal%5D)">p27(Kip1) links cell proliferation to morphogenesis in the developing organ of Corti.</a> Development. , 1581-1590 (1999).</li>
</ol>

The authors have nothing to disclose.

There are several technical points to consider when cultures are established and in setting up the time-lapse microscope in order for long-term imaging.
We use basement membrane matrix as a substrate for culturing cochlear explants, but the substrate should be matched to the cell type. For example, to image neuronal cultures, it may be better to provide a fibronectin coating. Incubation temperature and gas composition should also be chosen according to tissue type. Choosing the age of the expl...

The mammalian cochlea is a highly ordered complex organ. In the mouse, between the emergence of the primitive inner ear from the otic vesicle on day E11 and completion of the developmental program at early postnatal stages, multiple waves of cell signaling and coordinated changes in gene expression take place. Running from base to apex of the cochlear duct is the sound detecting sensory epithelium, or organ of Corti. Development of the organ of Corti is exquisitely controlled such that by the end of development, it will consist of a single row of inner hair cells, three rows of outer hair cells interspersed with five rows of supporting cells (two rows of pillar cells, three rows of Deiters&#8217; cells)1. Deviation from this precise order results in hearing loss, highlighting the importance of study&#160;of the genesis and patterning of the sensory epithelium2.
In vitro culturing of the embryonic mouse cochlea is an essential tool in studying the mechanisms of development of the organ of Corti. This technique was established in 1974 and over the last 40 years, has been used to elucidate many of the mechanisms by which the sensory epithelium is specified and the organ of Corti established3. The cochlea is a complex organ with dynamic developmental processes; a manipulation may take as long as seven days to manifest1. For example, when adding GSK 3&#946; inhibitors to a cochlear explant culture at E13, the optimal incubation period to observe a robust effect of the compound is six days4.
Live imaging of the developing cochlea allows investigation into changes in the morphology of the organ of Corti, changes in gene expression, tracking of migrating, proliferating or dying cells, and it allows real-time observation of the results of pharmaceutical agents and disruption of signaling pathways. Until now, live imaging of the cochlea has mainly been performed using confocal microscopy to image small areas of the organ of Corti over short time periods5-8, but this technique has limitations due to explant viability. In imaging of the effects of longer-term manipulations on slow developmental processes, the imaging environment is crucial. Typically a confocal live imaging system uses a humidified plastic box that sits on the microscope. Heat and humidity can escape through the gaps in the incubating box where it meets the microscope table, through the access windows, through the hinged openings and through the gaps around various parts of the microscope- such as the objective or the light source. This is not optimal for maintaining healthy explants for more than two or three days.
We define &#8216;incubator microscope&#8217; as an inverted microscope sealed inside a standard CO2 incubator, rather than an incubator built around the microscope. An incubator microscope extends the life of the experiment such that rather than imaging over two or three days, samples can be imaged for up to two weeks. An incubator microscope provides an excellent environment for cell growth and differentiation, with minimal disturbance to explant cultures and standard controlled conditions. In studies that take place over multiple days it is common to resort to imaging samples on a daily basis by removing them from the incubator and carrying them to an inverted fluorescent microscope. While this approach can work, removing the dishes from the incubator inflicts stress on the sensitive developing tissue. Changes in acidity of the culturing medium and fluctuations in temperature due to removal from the incubator can result in suboptimal development and unhealthy tissue. Imaging the same region at the same focal plane and in the same orientation at every time point is extremely challenging. By using an automated system within an incubator, it is possible to maintain healthy tissue, to collect images at more time points and to ensure that the same area is captured in every frame. In recent years several integrated microscope tissue incubators have been developed, these have been useful not only in clinical practice9 but also in stem cell and cancer research10,11.
Here we present a protocol for long term live imaging of embryonic mouse cochlear explants. We use an automated microscopy system inside a standard CO2 incubator that has the capability to capture images of multiple samples at set time points. The system consists of an inverted microscope set inside an incubator. Samples are placed in a rotating dais that allows imaging of multiple samples at each time point. Illumination, image capture, and rotation of the dais are controlled by an automated system operated through Metamorph software. By setting an imaging routine using the operating software we can set an experiment to run for up to two weeks with minimal human intervention. In this example we use both bright field and fluorescence to show large-scale growth and rearrangement of the cochlea, and specifically, the prosensory region. In this experiment, cochleae will be dissected from Sox2EGFP reporter mice on embryonic day E13. In vitro cultures will be established and then imaged over five days.

<table><tbody><tr><td>Dulbecco&#039;s Modified Eagle media</td><td>Gibco</td><td>12430</td><td>Multiple brands manufacture this</td></tr><tr><td>Basement membrane extract&amp;nbsp;</td><td>Corning</td><td>354230</td><td>Matrigel. Alternative similar products are available from other suppliers.&lt;br/&gt; http://catalog2.corning.com/Lifesciences/en-US/Shopping/Product.aspx?categoryname=Cell+Culture+and+Bioprocess%28Lifesciences%29|Extracellular+Matrix+Proteins+ECMs+and+Attachment+Factors%28Lifesciences%29|Matrigel+Basement+Membrane+Matrix+%28Lifesciences%29</td></tr><tr><td>Fetal bovine serum</td><td>Gibco</td><td>16000044</td><td>Multiple brands manufacture this&lt;br/&gt; http://www.lifetechnologies.com/search/global/searchAction.action?query=fbs&amp;amp;resultPage=1&amp;amp;results PerPage=15&amp;amp;autocomplete=</td></tr><tr><td>HEPES</td><td>Gibco</td><td>5630080</td><td>Multiple brands manufacture this&lt;br/&gt; http://www.lifetechnologies.com/search/global/searchAction.action?query=hepes&amp;amp;resultPage=1&amp;amp;results PerPage=15&amp;amp;autocomplete=</td></tr><tr><td>100 x N2 supplement</td><td>Gibco</td><td>17502-048</td><td>Multiple brands manufacture this&lt;br/&gt; http://www.lifetechnologies.com/search/global/searchAction.action?query=n2&amp;amp;resultPage=1&amp;amp;results PerPage=15&amp;amp;autocomplete=</td></tr><tr><td>Ciprofloxacin</td><td>Sigma Aldrich</td><td>17850-5G-F</td><td>Multiple brands manufacture this&lt;br/&gt; http://www.sigmaaldrich.com/catalog/product/fluka/17850?lang=en&amp;amp;region=CA</td></tr><tr><td>Hank&#039;s balanced salt solution</td><td>Gibco</td><td>14170161</td><td>Multiple brands manufacture this. Should be refidgerated before use.&lt;br/&gt; http://www.lifetechnologies.com/us/en/home/life-science/cell-culture/mammalian-cell-culture/reagents/balanced-salt-solutions/hbss-hanks-balanced-salt-solution.html?s_kwcid=AL!3652!3!26107410508!e!!g!!hbss&amp;amp;ef_id=xoFOglw2s UMAAMU8:20140228185720:s</td></tr><tr><td>Fine Forceps</td><td>Fine Science tools</td><td>11254-20</td><td>Size number 5&lt;br/&gt; http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=350&amp;amp;CategoryId=29</td></tr><tr><td>Curette&amp;nbsp;</td><td>Fine Science Tools</td><td>10080-05</td><td>size 1 mm&amp;nbsp;&lt;br/&gt; http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=91&amp;amp;CategoryId=118</td></tr><tr><td>Insect Pins</td><td>Fine Science Tools</td><td>26001-35</td><td>Must be stainless Steel&lt;br/&gt; http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=124</td></tr><tr><td>50 mm plastic dishes</td><td>Corning/Falcon</td><td>351006</td><td>Multiple brands manufacture this</td></tr><tr><td>charcoal</td><td>Sigma Aldrich</td><td>05105-250G</td><td>Multiple brands manufacture similar items&lt;br/&gt; http://www.sigmaaldrich.com/catalog/product/fluka/05105?lang=en&amp;amp;region=CA</td></tr><tr><td>184 silicone elastomer</td><td>Dow/Corning&amp;nbsp;</td><td>SYLGARD&amp;reg; 184 SILICONE ELASTOMER KIT</td><td>Dishes are home made several weeks in advance.&amp;nbsp; Silicone elastomer can be from any supplier.&lt;a href=&quot;http://www.dowcorning.com/applications/search/products/Details.aspx?prod=01064291&quot;&gt;http://www.dowcorning.com/applications/search/products/Details.aspx?prod=01064291&lt;/a&gt;</td></tr><tr><td>Glass bottom dishes</td><td>MatTek</td><td>P35G-0-10-C</td><td>The dimensions of the dish are determined by the specifications of the imaging system.&amp;nbsp; 35 mm diameter, 10mm well, number 0 coverslip fits Olympus Vivaview FL.&lt;br/&gt; http://glass-bottom-dishes.com/catalog/index.php?main_page=product_info&amp;amp;cPath= 1_4_15&amp;amp;products_id=2</td></tr><tr><td>Stereomicroscope</td><td>Zeiss&amp;nbsp;</td><td>495101-9804-000</td><td>&amp;nbsp;Stemi 2000 model. multiple brands manufacture similar items&lt;br/&gt; http://microscopy.zeiss.com/microscopy/en_de/products/stereo-zoom-microscopes/stemi-2000.html</td></tr><tr><td>Cold Light Source</td><td>Zeiss</td><td>000000-1063-182</td><td>Multiple brands manufacture similar items&lt;br/&gt; http://microscopy.zeiss.com/microscopy/en_de/products/microscope-components/lightsources.html</td></tr><tr><td>Fluorescent Stereomicroscope&amp;nbsp;</td><td>Leica microsystems</td><td>Contact Leica microsystems</td><td>Leica M165-FC. Multiple brands manufacture similar items&lt;br/&gt; http://www.leica-microsystems.com/products/stereo-microscopes-macroscopes/fluorescence/details/product/leica-m165-fc/</td></tr><tr><td>Incubator Microscope +imaging software</td><td>Olympus</td><td>Contact Olympus</td><td>Inverted microcope sealed inside a Co2 incubator. Vivaview FL incubator microscope with proprietry Metamorpoh imaging software.&lt;br/&gt; http://olympuscanada.com/seg_section/product.asp?product=1055&amp;amp;c=0</td></tr><tr><td>Clean bench</td><td>Thermo Scientific</td><td>51029701</td><td>Multiple brands manufacture similar items&lt;br/&gt; http://www.thermoscientific.com/en/product/heraguard-eco-clean-bench.html</td></tr><tr><td>CO2 incubator</td><td>Thermo Scientific</td><td>3310</td><td>Multiple brands manufacture similar items&lt;br/&gt; http://www.thermoscientific.com/en/products/co2-incubators.html</td></tr><tr><td>Laminar Flow hood</td><td>Thermo Scientific</td><td>51026651</td><td>Multiple brands manufacture similar items&lt;br/&gt; http://www.thermoscientific.com/en/products/biological-safety-cabinets-clean-benches.html</td></tr></tbody></table>

long-term time lapse imaging of mouse cochlear explants

Here we present a method for long-term time-lapse imaging of live embryonic mouse cochlear explants. The developmental program responsible for building the highly ordered, complex structure of the mammalian cochlea proceeds for around ten days. In order to study changes in gene expression over this period and their response to pharmaceutical or genetic manipulation, long-term imaging is necessary. Previously, live imaging has typically been limited by the viability of explanted tissue in a humidified chamber atop a standard microscope. Difficulty in maintaining optimal conditions for culture growth with regard to humidity and temperature has placed limits on the length of imaging experiments. A microscope integrated into a modified tissue culture incubator provides an excellent environment for long term-live imaging. In this method we demonstrate how to establish embryonic mouse cochlear explants and how to use an incubator microscope to conduct time lapse imaging using both bright field and fluorescent microscopy to examine the behavior of a typical embryonic day (E) 13 cochlear explant and Sox2, a marker of the prosensory cells of the cochlea, over 5 days.

Here we show a montage (Figure 1) and a movie (Figure 2) demonstrating how a typical organotypic cochlear explant will grow if plated on E13.5. A Sox2 reporter mouse was used to visualize the prosensory region. The movie illustrates that the cochlea undergoes growth and convergence and extension, the cells in the lateral region of the green Sox2 domain do not seem to divide as the tissue surrounding it expands. This is a characteristic of the organ of Corti; on E13 the ...

Watch this Scientific Journal Video about Long-term Time Lapse Imaging of Mouse Cochlear Explants at JoVE.com

Long-term Time Lapse Imaging of Mouse Cochlear Explants

Live imaging of the embryonic mammalian cochlea is challenging because the developmental processes at hand operate on a temporal gradient over ten days. Here we present a method for culturing and then imaging embryonic cochlear explant tissue taken from a fluorescent reporter mouse over five days.

Here we present a method for long-term time-lapse imaging of live embryonic mouse cochlear explants. The developmental program responsible for building ...

long-term-time-lapse-imaging-of-mouse-cochlear-explants

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JoVE Journal

Neuroscience

9.6K Views.  Sunnybrook Research Institute.  Live beeldvorming van de embryonale zoogdieren slakkenhuis is uitdagend omdat de ontwikkelingsprocessen bij de hand werken op een tijdelijke helling van meer dan tien dagen. Hier presenteren we een methode voor het kweken en dan het afbeelden embryonale cochleair explant weefsel afkomstig van een fluorescerende reporter muis over vijf dagen. 

Video: Long-term Time Lapse Imaging of Mouse Cochlear Explants

Culture of Embryonic Mouse Cochlear Explants and Gene Transfer by Electroporation

Auditory hair cells located within the mouse organ of Corti detect and transmit sound information to the central nervous system. The mechanosensory hair cells are aligned in one row of inner hair cells and three rows of outer hair cells that extend along the basal to apical axis of the cochlea. The explant culture technique described here provides an efficient method to isolate and maintain cochlear explants from the embryonic mouse inner ear. Also, the morphology and molecular characteristics of sensory hair cells and nonsensory supporting cells within the cochlear explant cultures resemble those observed in vivo and can be studied within its intrinsic cellular environment. The cochlear explants can serve as important experimental tools for the identification and characterization of molecular and genetic pathways that are involved in cellular specification and patterning. Although transgenic mouse models provide an effective approach for gene expression studies, a considerable number of mouse mutants die during embryonic development thereby hindering the analysis and interpretation of developmental phenotypes. The organ of Corti from mutant mice that die before birth can be cultured so that their in vitro development and responses to different factors can be analyzed. Additionally, we describe a technique for electroporating embryonic cochlear explants ex vivo which can be used to downregulate or overexpress specific gene(s) and analyze their potential endogenous function and test whether specific gene product is necessary or sufficient in a given context to influence mammalian cochlear development1-8.

We present a method that describes isolation and culture of cochlear explants from embryonic mouse inner ear. We also demonstrate a method for gene transfer into cochlear explants via square-wave electroporation. The in vitro explant culture coupled with gene transfer technique enables researchers to study the effects of altering gene expression during development.

Auditory hair cells located within the mouse organ of Corti detect and transmit sound information to the central nervous system. The mechanosensory hair ...

Developmental Biology

Long-term Intravital Immunofluorescence Imaging of Tissue Matrix Components with Epifluorescence and Two-photon Microscopy

Besides being a physical scaffold to maintain tissue morphology, the extracellular matrix (ECM) is actively involved in regulating cell and tissue function during development and organ homeostasis. It does so by acting via biochemical, biomechanical, and biophysical signaling pathways, such as through the release of bioactive ECM protein fragments, regulating tissue tension, and providing pathways for cell migration. The extracellular matrix of the tumor microenvironment undergoes substantial remodeling, characterized by the degradation, deposition and organization of fibrillar and non-fibrillar matrix proteins. Stromal stiffening of the tumor microenvironment can promote tumor growth and invasion, and cause remodeling of blood and lymphatic vessels. Live imaging of matrix proteins, however, to this point is limited to fibrillar collagens that can be detected by second harmonic generation using multi-photon microscopy, leaving the majority of matrix components largely invisible. Here we describe procedures for tumor inoculation in the thin dorsal ear skin, immunolabeling of extracellular matrix proteins and intravital imaging of the exposed tissue in live mice using epifluorescence and two-photon microscopy. Our intravital imaging method allows for the direct detection of both fibrillar and non-fibrillar matrix proteins in the context of a growing dermal tumor. We show examples of vessel remodeling caused by local matrix contraction. We also found that fibrillar matrix of the tumor detected with the second harmonic generation is spatially distinct from newly deposited matrix components such as tenascin C. We also showed long-term (12 hours) imaging of T-cell interaction with tumor cells and tumor cells migration along the collagen IV of basement membrane. Taken together, this method uniquely allows for the simultaneous detection of tumor cells, their physical microenvironment and the endogenous tissue immune response over time, which may provide important insights into the mechanisms underlying tumor progression and ultimate success or resistance to therapy.

The extracellular matrix undergoes substantial remodeling during wound healing, inflammation and tumorigenesis. We present a novel intravital immunofluorescence microscopy approach to visualize the dynamics of fibrillar as well as mesh-like matrix components with high spatial and temporal resolution using epifluorescence or two-photon microscopy.

Besides being a physical scaffold to maintain tissue morphology, the extracellular matrix (ECM) is actively involved in regulating cell and tissue ...

Bioengineering

A Protocol for Decellularizing Mouse Cochleae for Inner Ear Tissue Engineering

In mammals, mechanosensory hair cells that facilitate hearing lack the ability to regenerate, which has limited treatments for hearing loss. Current regenerative medicine strategies have focused on transplanting stem cells or genetic manipulation of surrounding support cells in the inner ear to encourage replacement of damaged stem cells to correct hearing loss. Yet, the extracellular matrix (ECM) may play a vital role in inducing and maintaining function of hair cells, and has not been well investigated. Using the cochlear ECM as a scaffold to grow adult stem cells may provide unique insights into how the composition and architecture of the extracellular environment aids cells in sustaining hearing function. Here we present a method for isolating and decellularizing cochleae from mice to use as scaffolds accepting perfused adult stem cells. In the current protocol, cochleae are isolated from euthanized mice, decellularized, and decalcified. Afterward, human Wharton&#39;s jelly cells (hWJCs) that were isolated from the umbilical cord were carefully perfused into each cochlea. The cochleae were used as bioreactors, and cells were cultured for 30 days before undergoing processing for analysis. Decellularized cochleae retained identifiable extracellular structures, but did not reveal the presence of cells or noticeable fragments of DNA. Cells perfused into the cochlea invaded most of the interior and exterior of the cochlea and grew without incident over a duration of 30 days. Thus, the current method can be used to study how cochlear ECM affects cell development and behavior.

The goal of this protocol is to demonstrate an effective method to decellularize and decalcify mouse cochleae for utilization as scaffolds for tissue engineering applications.

In mammals, mechanosensory hair cells that facilitate hearing lack the ability to regenerate, which has limited treatments for hearing loss. Current ...

Dextran Labeling and Uptake in Live and Functional Murine Cochlear Hair Cells

The hair cell mechanotransduction (MET) channel plays an important role in hearing. However, the molecular identity and structural information of MET remain unknown. Electrophysiological studies of hair cells revealed that the MET channel has a large conductance and is permeable to relatively large fluorescent cationic molecules, including some styryl dyes and Texas Red-labeled aminoglycoside antibiotics. In this protocol, we describe a method to visualize and evaluate the uptake of fluorescent dextrans in hair cells of the organ of Corti explants that can be used to assay for functional MET channels. We found that 3 kDa Texas Red-labeled dextran specifically labels functional auditory hair cells after 1&#8211;2 h incubation. In particular, 3 kDa dextran labels the two shorter stereocilia rows and accumulates in the cell body in a diffuse pattern when functional MET channels are present. An additional vesicle-like pattern of labeling was observed in the cell body of hair cells and surrounding supporting cells. Our data suggest that 3 kDa Texas-Red dextran can be used to visualize and study two pathways for cellular dye uptake; a hair cell-specific entry route through functional MET channels and endocytosis, a pattern also available to larger dextran.

Here, we present a method for visualizing the uptake of 3 kDa Texas Red-labeled dextran in auditory hair cells with functional mechanotransduction channels. In addition, dextrans of 3&#8211;10 kDa can be used to study endocytosis in hair and supporting cells of the organ of Corti.

The hair cell mechanotransduction (MET) channel plays an important role in hearing. However, the molecular identity and structural information of MET ...

Neonatal Murine Cochlear Explant Technique as an In Vitro Screening Tool in Hearing Research

While there have been remarkable advances in hearing research over the past few decades, there is still no cure for Sensorineural Hearing Loss (SNHL), a condition that typically involves damage to or loss of the delicate mechanosensory structures of the inner ear. Sophisticated in vitro and ex vivo assays have emerged in recent years, enabling the screening of an increasing number of potentially therapeutic compounds while minimizing resources and accelerating efforts to develop cures for SNHL. Though homogenous cultures of certain cell types continue to play an important role in current research, many scientists now rely on more complex organotypic cultures of murine inner ears, also known as cochlear explants. The preservation of organized cellular structures within the inner ear facilitates the in situ evaluation of various components of the cochlear infrastructure, including inner and outer hair cells, spiral ganglion neurons, neurites, and supporting cells. Here we present the preparation, culture, treatment, and immunostaining of neonatal murine cochlear explants. The careful preparation of these explants facilitates the identification of mechanisms that contribute to SNHL and constitutes a valuable tool for the hearing research community.

Neonatal Murine Cochlear Explant Technique as an In Vitro Screening Tool in Hearing Research

The goal of this protocol is to demonstrate the preparation, culture, treatment, and immunostaining of neonatal murine cochlear explants. The technique can be utilized as an in vitro screening tool in hearing research.

While there have been remarkable advances in hearing research over the past few decades, there is still no cure for Sensorineural Hearing Loss (SNHL), a ...

Medicine

Cochlear Surface Preparation in the Adult Mouse

Auditory processing in the cochlea depends on the integrity of the mechanosensory hair cells. Over a lifetime, hearing loss can be acquired from numerous etiologies such as exposure to excessive noise, the use of ototoxic medications, bacterial or viral ear infections, head injuries, and the aging process. Loss of sensory hair cells is a common pathological feature of the varieties of acquired hearing loss. Additionally, the inner hair cell synapse can be damaged by mild insults. Therefore, surface preparations of cochlear epithelia, in combination with immunolabeling techniques and confocal imagery, are a very useful tool for the investigation of cochlear pathologies, including losses of ribbon synapses and sensory hair cells, changes in protein levels in hair cells and supporting cells, hair cell regeneration, and determination of report gene expression (i.e., GFP) for verification of successful transduction and identification of transduced cell types. The cochlea, a bony spiral-shaped structure in the inner ear, holds the auditory sensory end organ, the organ of Corti (OC). Sensory hair cells and surrounding supporting cells in the OC are contained in the cochlear duct and rest on the basilar membrane, organized in a tonotopic fashion with high-frequency detection occurring in the base and low-frequency in the apex. With the availability of molecular and genetic information and the ability to manipulate genes by knockout and knock-in techniques, mice have been widely used in biological research, including in hearing science. However, the adult mouse cochlea is miniscule, and the cochlear epithelium is encapsulated in a bony labyrinth, making microdissection difficult. Although dissection techniques have been developed and used in many laboratories, this modified microdissection method using cell and tissue adhesive is easier and more convenient. It can be used in all types of adult mouse cochleae following decalcification.

This article presents a modified cochlear surface preparation method that requires decalcification and use of a cell and tissue adhesive to adhere the pieces of cochlear epithelia to 10 mm round cover slips for immunohistochemistry in adult mouse cochleae.

Auditory processing in the cochlea depends on the integrity of the mechanosensory hair cells. Over a lifetime, hearing loss can be acquired from numerous ...

Stereocilia Bundle Imaging with Nanoscale Resolution in Live Mammalian Auditory Hair Cells

Inner ear hair cells detect sound-induced displacements and transduce these stimuli into electrical signals in a hair bundle that consists of stereocilia that are arranged in rows of increasing height. When stereocilia are deflected, they tug on tiny (~5 nm in diameter) extracellular tip links interconnecting stereocilia, which convey forces to the mechanosensitive transduction channels. Although mechanotransduction has been studied in live hair cells for decades, the functionally important ultrastructural details of the mechanotransduction machinery at the tips of stereocilia (such as tip link dynamics or transduction-dependent stereocilia remodeling) can still be studied only in dead cells with electron microscopy. Theoretically, scanning probe techniques, such as atomic force microscopy, have enough resolution to visualize the surface of stereocilia. However, independent of imaging mode, even the slightest contact of the atomic force microscopy probe with the stereocilia bundle usually damages the bundle. Here we present a detailed protocol for the hopping probe ion conductance microscopy (HPICM) imaging of live rodent auditory hair cells. This non-contact scanning probe technique allows time lapse imaging of the surface of live cells with a complex topography, like hair cells, with single nanometers resolution and without making physical contact with the sample. The HPICM uses an electrical current passing through the glass nanopipette to detect the cell surface in close vicinity to the pipette, while a 3D-positioning piezoelectric system scans the surface and generates its image. With HPICM, we were able to image stereocilia bundles and the links interconnecting stereocilia in live auditory hair cells for several hours without noticeable damage. We anticipate that the use of HPICM will allow direct exploration of ultrastructural changes in the stereocilia of live hair cells for better understanding of their function.

Here we present a protocol for the Hopping Probe Ion Conductance Microscopy (HPICM), a non-contact scanning probe technique that allows nanoscale imaging of stereocilia bundles in live auditory hair cells.

Inner ear hair cells detect sound-induced displacements and transduce these stimuli into electrical signals in a hair bundle that consists of stereocilia ...

In vitro Time-lapse Live-Cell Imaging to Explore Cell Migration toward the Organ of Corti

To study the effects of mesenchymal stem cells (MSCs) on cell regeneration and treatment, this method tracks MSC migration and morphological changes after co-culture with cochlear epithelium. The organ of Corti was immobilized on a plastic coverslip by pressing a portion of the Reissner's membrane generated during the dissection. MSCs confined by a glass cylinder migrated toward cochlear epithelium when the cylinder was removed. Their predominant localization was observed in the modiolus of the organ of Corti, aligned in a direction similarly to that of the nerve fibers. However, some MSCs were localized in the limbus area and showed a horizontally elongated shape. In addition, migration into the hair cell area was increased, and the morphology of the MSCs changed to various forms after kanamycin treatment. In conclusion, the results of this study indicate that the coculture of MSCs with cochlear epithelium will be useful for the development of therapeutics via cell transplantation and for studies of cell regeneration that can examine various conditions and factors.

In this study, we present a real-time imaging method using confocal microscopy to observe cells moving toward damaged tissue by ex vivo incubation with the cochlear epithelium containing the organ of Corti.

To study the effects of mesenchymal stem cells (MSCs) on cell regeneration and treatment, this method tracks MSC migration and morphological changes after ...

Imaging the Aging Cochlea with Light-Sheet Fluorescence Microscopy

Deafness is the most common sensory impairment, affecting approximately 5% or 430 million people worldwide as per the World Health Organization1. Aging or presbycusis is a primary cause of sensorineural hearing loss and is characterized by damage to hair cells, spiral ganglion neurons (SGNs), and the stria vascularis. These structures reside within the cochlea, which has a complex, spiral-shaped anatomy of membranous tissues suspended in fluid and surrounded by bone. These properties make it technically difficult to investigate and quantify histopathological changes. To address this need, we developed a light-sheet microscope (TSLIM) that can image and digitize the whole cochlea to facilitate the study of structure-function relationships in the inner ear. Well-aligned serial sections of the whole cochlea result in a stack of images for three-dimensional (3D) volume rendering and segmentation of individual structures for 3D visualization and quantitative analysis (i.e., length, width, surface, volume, and number). Cochleae require minimal processing steps (fixation, decalcification, dehydration, staining, and optical clearing), all of which are compatible with subsequent high-resolution imaging by scanning and transmission electron microscopy. Since all the tissues are present in the stacks, each structure can be assessed individually or relative to other structures. In addition, since imaging uses fluorescent probes, immunohistochemistry and ligand binding can be used to identify specific structures and their 3D volume or distribution within the cochlea. Here we used TSLIM to examine cochleae from aged mice to quantify the loss of hair cells and spiral ganglion neurons. In addition, advanced analyses (e.g., cluster analysis) were used to visualize local reductions of spiral ganglion neurons in Rosenthal&#39;s canal along its 3D volume. These approaches demonstrate TSLIM microscopy&#39;s ability to quantify structure-function relationships within and between cochleae.

A light-sheet microscope was developed to image and digitize whole cochlea.

Deafness is the most common sensory impairment, affecting approximately 5% or 430 million people worldwide as per the World Health Organization1. Aging or ...

Whole Neonatal Cochlear Explants as an In vitro Model

Untreated hearing loss imposes significant costs on the global healthcare system and impairs individuals' quality of life. Sensorineural hearing loss is characterized by the cumulative and irreversible loss of sensory hair cells and auditory nerves in the cochlea. Entire and vital cochlear explants are one of the fundamental tools in hearing research to detect hair cell loss and to characterize the molecular mechanisms of the inner ear cells. Many years ago, a protocol for neonatal cochlear isolation was developed, and although it has been modified over time, it still holds potential for improvement. 
This paper presents an optimized protocol for isolating and culturing whole neonatal cochlear explants in multi-well culture chambers that enables the study of hair cells and spiral ganglion neuron cells along the entire length of the cochlea. The protocol was tested using cochlear explants from mice and rats. Healthy cochlear explants were obtained to study the interaction between hair cells, spiral ganglion neuron cells, and the surrounding supporting cells. 
One of the main advantages of this method is that it simplifies the organ culture steps without compromising the quality of the explants. All three turns of the organ of Corti are attached to the bottom of the chamber, which facilitates in vitro experiments and the comprehensive analysis of the explants. We provide some examples of cochlear images from different experiments with live and fixed explants, demonstrating that the explants retain their structure despite exposure to ototoxic drugs. This optimized protocol can be widely used for the integrative analysis of the mammalian cochlea.

Whole Neonatal Cochlear Explants as an In vitro Model

The current protocol updates previous protocols and incorporates relatively straightforward approaches for culturing high-quality cochlear explants. This provides reliable data acquisition and high-resolution imaging in live and fixed cells. This protocol supports the ongoing trend of studying inner ear cells.

Untreated hearing loss imposes significant costs on the global healthcare system and impairs individuals' quality of life. Sensorineural hearing loss is ...

Long-term Time Lapse Imaging of Mouse Cochlear Explants

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