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 S...

<ol>
	<li>Wu, D. K., Kelley, M. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Molecular+mechanisms+of+inner+ear+development.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+auditory+sensory+epithelium:+the+instrument+of+sound+perception.">The auditory sensory epithelium: the instrument of sound perception.</a> The international journal of biochemistry &amp; 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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Growth+of+the+inner+ear+in+organ+culture.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+dual+function+for+canonical+Wnt/beta-catenin+signaling+in+the+developing+mammalian+cochlea.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Swept+field+laser+confocal+microscopy+for+enhanced+spatial+and+temporal+resolution+in+live-cell+imaging.+Microscopy+and+microanalysis+:+the+official+journal+of+Microscopy.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Thyroid+hormone+increases+fibroblast+growth+factor+receptor+expression+and+disrupts+cell+mechanics+in+the+developing+organ+of+corti.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gata3+is+a+critical+regulator+of+cochlear+wiring.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Compartmentalized+Notch+signaling+sustains+epithelial+mirror+symmetry.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Selection+of+high-potential+embryos+by+culture+in+poly(dimethylsiloxane)+microwells+and+time-lapse+imaging.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Morphology-based+prediction+of+osteogenic+differentiation+potential+of+human+mesenchymal+stem+cells.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&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.">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/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=SOX2+is+a+dose-dependent+regulator+of+retinal+neural+progenitor+competence.">SOX2 is a dose-dependent regulator of retinal neural progenitor competence.</a> Genes &amp; development. 20, 1187-1202 (2006).</li><li>Chen, P., Segil, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=p27(Kip1)+links+cell+proliferation+to+morphogenesis+in+the+developing+organ+of+Corti.">p27(Kip1) links cell proliferation to morphogenesis in the developing organ of Corti.</a> Development. , 1581-1590 (1999).</li></ol>

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 border="0" cellpadding="0" cellspacing="0">
	<tbody>
		<tr>
			<td>Dulbecco&#39;s Modified Eagle media</td>
			<td>Gibco</td>
			<td>12430</td>
			<td>Multiple brands manufacture this</td>
			<td>http://www.lifetechnologies.com/us/en/home/life-science/cell-culture/mammalian-cell-culture/classical-media/dmem.html</td>
		</tr>
		<tr>
			<td>Basement membrane extract&#160;</td>
			<td>Corning</td>
			<td>354230</td>
			<td>Matrigel. Alternative similar products are available from other suppliers. 
			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 
			http://www.lifetechnologies.com/search/global/searchAction.action?query=fbs&#38;resultPage=1&#38;results PerPage=15&#38;autocomplete=</td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Gibco</td>
			<td>5630080</td>
			<td>Multiple brands manufacture this 
			http://www.lifetechnologies.com/search/global/searchAction.action?query=hepes&#38;resultPage=1&#38;results PerPage=15&#38;autocomplete=</td>
		</tr>
		<tr>
			<td>100 x N2 supplement</td>
			<td>Gibco</td>
			<td>17502-048</td>
			<td>Multiple brands manufacture this 
			http://www.lifetechnologies.com/search/global/searchAction.action?query=n2&#38;resultPage=1&#38;results PerPage=15&#38;autocomplete=</td>
		</tr>
		<tr>
			<td>Ciprofloxacin</td>
			<td>Sigma Aldrich</td>
			<td>17850-5G-F</td>
			<td>Multiple brands manufacture this 
			http://www.sigmaaldrich.com/catalog/product/fluka/17850?lang=en&#38;region=CA</td>
		</tr>
		<tr>
			<td>Hank&#39;s balanced salt solution</td>
			<td>Gibco</td>
			<td>14170161</td>
			<td>Multiple brands manufacture this. Should be refidgerated before use. 
			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&#38;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 
			http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=350&#38;CategoryId=29</td>
		</tr>
		<tr>
			<td>Curette&#160;</td>
			<td>Fine Science Tools</td>
			<td>10080-05</td>
			<td>size 1 mm&#160; 
			http://www.finescience.ca/Special-Pages/Products.aspx?ProductId=91&#38;CategoryId=118</td>
		</tr>
		<tr>
			<td>Insect Pins</td>
			<td>Fine Science Tools</td>
			<td>26001-35</td>
			<td>Must be stainless Steel 
			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 
			http://www.sigmaaldrich.com/catalog/product/fluka/05105?lang=en&#38;region=CA</td>
		</tr>
		<tr>
			<td>184 silicone elastomer</td>
			<td>Dow/Corning&#160;</td>
			<td>SYLGARD&#174; 184 SILICONE ELASTOMER KIT</td>
			<td>Dishes are home made several weeks in advance.&#160; Silicone elastomer can be from any supplier.<a href="http://www.dowcorning.com/applications/search/products/Details.aspx?prod=01064291">http://www.dowcorning.com/applications/search/products/Details.aspx?prod=01064291</a></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.&#160; 35 mm diameter, 10mm well, number 0 coverslip fits Olympus Vivaview FL. 
			http://glass-bottom-dishes.com/catalog/index.php?main_page=product_info&#38;cPath= 1_4_15&#38;products_id=2</td>
		</tr>
		<tr>
			<td>Stereomicroscope</td>
			<td>Zeiss&#160;</td>
			<td>495101-9804-000</td>
			<td>&#160;Stemi 2000 model. multiple brands manufacture similar items 
			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 
			http://microscopy.zeiss.com/microscopy/en_de/products/microscope-components/lightsources.html</td>
		</tr>
		<tr>
			<td>Fluorescent Stereomicroscope&#160;</td>
			<td>Leica microsystems</td>
			<td>Contact Leica microsystems</td>
			<td>Leica M165-FC. Multiple brands manufacture similar items 
			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. 
			http://olympuscanada.com/seg_section/product.asp?product=1055&#38;c=0</td>
		</tr>
		<tr>
			<td>Clean bench</td>
			<td>Thermo Scientific</td>
			<td>51029701</td>
			<td>Multiple brands manufacture similar items 
			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 
			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 
			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

Research

JoVE Journal

Neuroscience

9.4K Views.  Sunnybrook Research Institute.  Immagini dal vivo della coclea embrionale dei mammiferi è impegnativo, perché i processi di sviluppo a portata di mano operano su un gradiente temporale nell'arco di dieci giorni. Qui vi presentiamo un metodo per la coltura e quindi l'imaging embrionale dei tessuti espianto cocleare preso da un topo reporter fluorescente in cinque giorni. 