This work was supported by NIH Grants R01-DC010146 and R01-DC010397. Its content is solely the responsibility of the authors and does not necessarily represent the official view of the National Institutes of Health.

1. Cell Culture
Note: All cell culturing protocols must be performed using proper cell culture techniques (for reference see the first 3 Chapters of Cell Biology: A Laboratory Handbook, Volume I 10). HEI-OC1 cells do not require any additional coating or treatment of the cell culture dishes for proper adherence and growth. Very important: do not use glassware dishes for cell culture purposes; the phenotype and biological response of the cells to pharmacological drugs will change (G Kalinec &#38; F Kalinec, unpublished); conventional plastic cell culture dishes are recommended (see Table of Materials/Equipment). Pay special attention to aseptic techniques to avoid contaminations, but never use antibiotics (e.g., ampicillin or streptomycin) with HEI-OC1 cells. If necessary, use amphotericin B. While HeLa and HEK-293 cells have been used as control in previous studies with HEI-OC1 8, any other cell line could be acceptable for this purpose.
<ol>
	<li>Resuscitation of Frozen HEI-OC1 Cells 
	Note: This protocol can also be used with other cell lines from the same transgenic mouse developed in our laboratory, such as OC-k3, from organ of Corti 11,12, and SV-k1, from stria vascularis 13,14.
	<ol>
		<li>Remove a vial of cryopreserved HEI-OC1 cells from liquid N2, and place it in a water bath at 37 &#176;C. Submerge only the lower half of the vial, and allow it to thaw until only a small amount of ice remains in the vial. Wipe the outside of the vial with 70% alcohol.</li>
		<li>Pipette the cells from the vial and deliver the entire volume (~ 1.5 x 105 cells/ml) slowly, drop by drop, into a 15 ml conical tube containing 10 ml of a pre-warmed growth medium, like Dulbecco&#39;s Modified Eagle&#39;s Medium (DMEM), supplemented with 10% fetal bovine serum (FBS).</li>
		<li>Remove DMSO by centrifuging the tube at 300-500 x g for 5 min, discarding the supernatant and re-suspending the cells in 9 ml of fresh growth medium (DMEM + 10% FBS). Disaggregate clumps or sheets of cells by flux and reflux of the suspended cells, from the pipette to the medium and vice-versa, three to four times with the tip of the pipette touching the bottom of the tube.</li>
		<li>Place the total volume of cells suspended in growth medium in 100 mm-diameter untreated, plastic cell culture dishes.</li>
		<li>Incubate the cells at 33 &#176;C with 10% CO2 (permissive conditions).</li>
	</ol>
	</li>
	<li>Subculture of HEI-OC1 Cells 
	Note: Prior to confluence (~80%) the cells should be brought into suspension and sub-cultured in order to prevent the culture dying. This protocol can also be used with other cell lines developed in our laboratory from the same transgenic mouse, such as OC-k3, from organ of Corti 11,12, and SV-k1, from stria vascularis 13,14.
	<ol>
		<li>Remove old medium and wash the cells with 2 ml of PBS.</li>
		<li>Cover the cell monolayer with a solution of 0.25% trypsin, using 1 ml per 25 cm2 of surface area. To move onto the next step more than 40% of the cells must be detached. Examine the cells using an inverted microscope and, if necessary, &#34;slap or tap&#34; the culture dishes gently to release any remaining attached cells. 
		Note: Take care as trypsinization for long periods can cause cell death; not enough and the transferred cells will insufficient for the planned studies.</li>
		<li>Resuspend the cells, following the procedure described in 1.1.3, and transfer them to a 15 ml conical tube.</li>
		<li>Centrifuge for 5 min at 300-500 x g, discard the medium, collect the cells with fresh growth medium and seed them in, at least, four 100 mm-diameter cell culture dishes. The number of cells per dish will depend on the amount of cells recovered. Incubate the cells at 33 &#176;C with 10% CO2 (P-HEI-OC1) and divide again as many times as necessary for the planned experiments or for generating a new stock.</li>
		<li>For stock preparation, replace 100 mm-diameter dishes by 250-550 ml cell culture flasks; for experiments, smaller dishes or multi-wells plates may be more adequate.</li>
		<li>For differentiation, incubate HEI-OC1 cells at permissive conditions until they reach ~80% confluence; then move the dishes to 39 &#176;C with 5% CO2 (NP-HEI-OC1) for 2 to 3 weeks. 
		Note: Cells will progressively stop proliferating and dying. Change the medium every other day to remove dead cells. Depending on the original number of cells, usually after ~ 4 weeks no more cells will be available for experiments. Differentiation starts as soon as the cells are placed at NP conditions, but not every cell differentiate at the same pace. Importantly, prestin expression and membrane localization increases during the differentiation process (see Representative Results, Figure 4), providing a qualitative and quantitative indication of the level of differentiation.</li>
	</ol>
	</li>
</ol>
2. Drug Cytotoxicity Studies
Note: HEI-OC1 cells grown at permissive conditions (P-HEI-OC1) are recommended for these studies (see Representative Results, Figure 1).
<ol>
	<li>Cell Viability (MTT Assay)
	<ol>
		<li>Collect P-HEI-OC1 cells by following the procedure described in 1.2, and count them with either an automatic cell counter or hemocytometer. Adjust the concentration to 2.0 x 105 cells/ml.</li>
		<li>Seed the cells on 96-well clear flat bottom plates (100 &#181;l per well), incubate overnight for attachment to the substrate, and then treat them with the drugs of interest. Do not forget to include blanks and non-treated cells (control)!</li>
		<li>After drug treatment (usually 24 or 48 hr at 33 &#176;C), perform the MTT assay following the manufacturer&#39;s protocol. In general, the protocols for this assay have the following steps:
		<ol>
			<li>Add 10 &#181;l of MTT reagent to each well.</li>
			<li>Incubate the plate at 37 &#176;C for 2 to 4 hr until purple dye is visible, and then add 100 &#181;l of the MTT Detergent Reagent to each well. Do not shake the plate.</li>
			<li>Cover the plate and leave it in the dark for 2 to 4 hr at 37 &#176;C.</li>
			<li>Use a microplate plate reader to measure absorbance at 570 nm in each well, including the blanks (growth medium alone). Normalize data using the average OD in control cells as 100% of viability.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Caspase 3/7 Activation Assay 
	Note: HEI-OC1 cells grown at permissive conditions (P-HEI-OC1) are recommended for these studies.
	<ol>
		<li>Collect HEI-OC1 cells by following the procedure described in 1.2, and count them with either an automatic cell counter or a hemocytometer. Adjust the concentration to 2.0 x 105 cells/ml.</li>
		<li>Seed the cells on white-walled 96-well plates (100 &#181;l per well), incubate overnight for attachment to the substrate, and then treat them with the drugs of interest. Do not forget to include blanks and non-treated cells (control)!</li>
		<li>After drug treatment (usually 24 or 48 hr at 33 &#176;C), perform the caspase assay following the respective manufacturer&#39;s protocol. In general, the protocols for this assay have the following steps:
		<ol>
			<li>Prepare the reagents, mix them well, and allow them to equilibrate to room temperature.</li>
			<li>Remove the cells from the incubator and allow the plates to equilibrate to room temperature.</li>
			<li>Add the indicated amount of reagent to each well, being careful to avoid cross-contamination by not touching wells containing different samples with the same pipette tips.</li>
			<li>Cover the plate and mix for 30 sec using a plate shaker at 300-500 rpm.</li>
			<li>Incubate the plate at room temperature for a period of, at least, 30 min. Determine the optimal incubation period empirically. If the room temperature fluctuates use a constant-temperature incubator, because temperature fluctuations will affect luminescence reading.</li>
			<li>Measure luminescence in each well, and normalize values using average luminescence in control cells as 100% of caspase activation.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Cell Division (Proliferation)
	<ol>
		<li>Collect HEI-OC1 cells by following the procedure described in 1.2, and count them with either an automatic cell counter or a hemocytometer. Adjust the concentration to 2.0 x 105 cells/ml.</li>
		<li>Seed the cells on 96-well clear flat bottom plates (100 &#181;l per well), incubate overnight at permissive conditions for attachment to the substrate, and then treat them with the drugs of interest. Don&#39;t forget to include blanks and non-treated cells (control)!</li>
		<li>One hour after treatment, add to each well 1 &#181;l of prepared 100x BrdU (5-Bromo-2&#8242;-deoxyuridine) solution, and return the plates to the incubator at 33 &#176;C.</li>
		<li>After 12, 24 and 48 hr, remove the existing medium from the corresponding plates and wash each well once with PBS.</li>
		<li>Perform the cell proliferation assay following the manufacturer&#39;s protocol. In general, the protocols for this assay have the following steps:
		<ol>
			<li>Prepare the reagents, including fixing/denaturing solution, wash buffer, primary antibody detection solution, secondary antibody detection solution, and BrdU solution as indicated in the manufacturer&#39;s protocol.</li>
			<li>Add the fixing/denaturing solution to each well, in the amounts indicated in the manufacturer&#39;s protocol, and keep the plate at room temperature for 30 min.</li>
			<li>Remove the fixing/denaturing solution and add the primary antibody at the concentration indicated in the manufacturer&#39;s protocol. Keep the plate at room temperature for 1 hr.</li>
			<li>Remove the solution with the primary antibody, wash the plate 3 times with wash buffer, and then add the secondary antibody at the concentration indicated in the manufacturer&#39;s protocol. Keep the plate with the secondary antibody at room temperature for 30 min.</li>
			<li>Remove the solution with the secondary antibody, wash the plate 3 times with wash buffer, and add the substrate. After 10 min incubation at room temperature, add the STOP solution. Be careful: Control the change in color; if the solution becomes very dark, stop the reaction prior to the standard development time of 10 min.</li>
			<li>Read absorbance at 450 nm within 30 min of adding the STOP Solution.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Cytotoxicity 
	Note: HEI-OC1 cells grown at permissive conditions (P-HEI-OC1) are recommended for these studies.
	<ol>
		<li>Incubate at permissive conditions, usually for 24-48 hr, HEI-OC1 cells in cell culture medium alone (control) or medium plus the drugs of interest.</li>
		<li>At the end of the treatment, wash the cells three times with PBS, and detach using 1 ml per 25 cm2 of surface area of a non-enzymatic cell dissociation solution for 3 min.</li>
		<li>After detaching, collect and pellet the cells by centrifugation at 3,000 x g for 5 min, remove the supernatant, and stain the cells for 15 min in the dark with the reagent included in cytotoxicity assay.</li>
		<li>Determine the number of live HEI-OC1 cells by flow cytometry as indicated by the manufacturer of the flow cytometer.</li>
	</ol>
	</li>
	<li>Senescence
	<ol>
		<li>Incubate at permissive conditions, usually for 24-48 hr, HEI-OC1 cells in cell culture medium alone (control) or medium plus the drugs of interest.</li>
		<li>Determine the number of senescence-associated beta-galactosidase positive cells using flow cytometry with the protocol described by Debacq-Chainiaux et al. 15 or other method known to provide reliable results. A brief protocol for flow cytometry is the following:
		<ol>
			<li>At the end of the experimental treatments, wash the cells three times with PBS and then incubate them with 100 nM Bafilomycin A1 in cell culture medium for 1 hr at permissive conditions.</li>
			<li>Add C12FDG at a final concentration of ~33 &#181;M, and continue incubating the cells for 1-2 hr.</li>
			<li>Wash the cells twice with PBS, harvest them using 1 ml per 25 cm2 of surface area of a non-enzymatic cell dissociation solution for 3 min, and pellet them by centrifugation at 3,000 x g for 5 min.</li>
			<li>Resuspend the cells in ice-cold PBS and determine the number of positive HEI-OC1 cells by flow cytometry as indicated by the manufacturer of the flow cytometer.</li>
		</ol>
		</li>
	</ol>
	</li>
	<li>Autophagy
	<ol>
		<li>Collect HEI-OC1 cells control and starved (deprived of serum for 48 hr) by following the procedure described in 1.2, and process them for Western blot following standard protocols. In general, the protocols for Western blot have the following steps:
		<ol>
			<li>Seed HEI-OC1 cells in 6-well plates at a concentration of 1.0 x 105 cells/ml. After 24 and/or 48 hr, wash the cells with ice-cold PBS.</li>
			<li>Lyse with 200 &#181;l of TNESV buffer (1% NP40, 50 mM Tris-HCl pH 7.5, 100 mM NaCl, 2mM EDTA, 1 mM Na3VO4) with protease inhibitor cocktail and 1 mM PMSF for 5 min on ice.</li>
			<li>Collect the cells (by scraping the bottom of each well), transfer to microcentrifuge tubes and centrifuge at 16,800 x g for 5 min at 4 &#176;C.</li>
			<li>Collect the supernatants and quantify the protein concentration using the BCA Assay.</li>
			<li>Add 5x loading buffer and 1 mM DTT to each sample and boil for 5 min to denature the proteins.</li>
			<li>Run the samples using SDS-PAGE on a 4-12% gel, and transfer to PVDF membranes.</li>
			<li>Block the membranes with 5% nonfat dried milk in TBS-T with 0.1% Tween 20 for 60 min at RT.</li>
			<li>Incubate the membranes overnight at 4 &#176;C with primary antibodies.</li>
			<li>The next day, wash the membranes extensively with TBS-T, and incubate with a secondary IgG antibody conjugated to horseradish peroxidase (HRP) (1:1,500) for 1 hr.</li>
			<li>Detect immunoreactivity with an enhanced chemiluminescence (ECL) detection system. Normalize protein expression levels using GAPDH (1:2,000 in TBS-T with in 10% nonfat dried milk) as standard.</li>
		</ol>
		</li>
		<li>In the Western blots investigate the expression of, at least, two different markers of autophagy such as Beclin-1 and LC3B (usually at 1:1,000 dilution in TBS-T with 2.5% BSA). Do not forget to look for a control of protein expression such as GAPDH or actin.</li>
		<li>Evaluate the expression of the protein of interest by densitometry using a digital Blot scanner or computer software such as the public domain NIH Image or ImageJ (http://rsb.info.nih.gov/nih-image/).</li>
	</ol>
	</li>
</ol>
3. Electrophysiology Experiments with HEI-OC1 Cells
<ol>
	<li>Harvesting Cells 
	Note: Use cells growing in 100 mm diameter culture dishes at 50%-80% confluency. Trypsin, Accutase, enzyme-free solution, or phosphate- buffered saline + ethylene diamine tetra acetic acid (PBS-EDTA) may be used for lifting the cells without significant effects on the number and quality of the gigaseals. In some cases, however, trypsin treatment makes the cells more fragile. In these cases, allow the cells to recover for approximately 30 minutes before starting the experiments.
	<ol>
		<li>Wash the cells twice with 10 ml PBS without Ca2+ and Mg2+.</li>
		<li>Add 2 ml of an enzyme-free detacher solution, such as non-enzymatic cell dissociation solution, and incubate the dishes for 3 min at 37 &#176;C with 5% CO2.</li>
		<li>Use an inverted microscope to check the detachment of the cells. If necessary, move the cell culture dish to detach more cells, but do it gently. 
		Note: Do not shake the dish.</li>
		<li>Add 10 ml of DMEM+10% FBS and pipette the cells gently up and down five times with a 10-ml pipette.</li>
		<li>Look at the cells under a microscope. If &#62; 80% of the cells are already separated (single), no further pipetting is needed. If the cells are still in clusters, repeat the gently pipetting until more than 80% cells are single.</li>
		<li>Place the ~10 ml of suspended cells into a 15 ml conical tube, centrifuge for 2 min at 100 x g, and discard the supernatant.</li>
		<li>Use ~200 &#181;l of external recording solution (Leibovitz&#39;s L-15 medium adjusted to 305 - 310 mOsm with distilled water) to resuspend the cells. An optical control of the cells should show many single, round cells with smooth membrane edges.</li>
	</ol>
	</li>
	<li>Patch-clamp and NLC Measurements
	<ol>
		<li>Perform patch-clamp and measurements of voltage-dependent nonlinear capacitance (NLC) using adequate amplifiers and software, as well as standard electrophysiological techniques. As internal (intrapipette) solution use 150 mM KCl, 1 mM MgCl2, 0.1 mM EGTA, 2 mM ATP-Mg, 0.1 mM GTP-Na, and 10 mM HEPES; adjust pH to 7.2 with Tris.</li>
		<li>Under the microscope, select a single, healthy cell, with round and smooth membrane edges. Attach the tip of the glass pipette to the cell surface and check membrane resistance. This should be around 3-6 megaOhms, corresponding to an internal diameter (ID) of the tip of the pipette of ~2 &#181;m.</li>
		<li>Gently press the micropipette tip against the cell plasma membrane and then apply suction. A portion of the cell membrane will be suctioned into the pipette, generating an electrical resistance in the order of 10 - 100 gigaOhms (gigaseal).</li>
		<li>Establish the whole-cell condition by disrupting the plasma membrane with suction pulses.</li>
		<li>Use cells that do not express prestin, such as HEK-293, as a control 9. 
		Note: Current responses should be filtered at 5 kHz, and corrections made for the effects of residual series resistance. All data collection and most analyses can be performed using the software usually included with the lock-in amplifiers. Capacitance function can be fitted to the first derivative of a two state Boltzmann function relating nonlinear charge to membrane voltage 16. 
		 
		&#160;</li>
	</ol>
	</li>
</ol>

<ol>
	<li>Jat, P. 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=Direct+derivation+of+conditionally+immortall+cell+lines+from+an+H-2Kb-tsA58+transgenic+mouse.">Direct derivation of conditionally immortall cell lines from an H-2Kb-tsA58 transgenic mouse.</a> Proc. Natl. Acad. Sci. 88, 5096-5100 (1991).</li><li>Kalinec, G. M., Webster, P., Lim, D. J., Kalinec, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+cochlear+cell+line+as+an+in+vitro+system+for+drug+ototoxicity+screening.">A cochlear cell line as an in vitro system for drug ototoxicity screening.</a> Audiol. Neurootol. 8, 177-189 (2003).</li><li>Devarajan, P., 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=Cisplatin-induced+apoptosis+in+auditory+cells:+role+of+death+receptor+and+mitochondrial+pathways.">Cisplatin-induced apoptosis in auditory cells: role of death receptor and mitochondrial pathways.</a> Hear Res. 174, 45-54 (2002).</li><li>Chen, F. Q., Hill, K., Guan, Y. J., Schacht, J., Sha, S. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Activation+of+apoptotic+pathways+in+the+absence+of+cell+death+in+an+inner-ear+immortomouse+cell+line.">Activation of apoptotic pathways in the absence of cell death in an inner-ear immortomouse cell line.</a> Hear Res. 284, 33-41 (2012).</li><li>Hayashi, K., 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=The+autophagy+pathway+maintained+signaling+crosstalk+with+the+Keap1-Nrf2+system+through+p62+in+auditory+cells+under+oxidative+stress.">The autophagy pathway maintained signaling crosstalk with the Keap1-Nrf2 system through p62 in auditory cells under oxidative stress.</a> Cell Signal. 27, 382-393 (2015).</li><li>Tsuchihashi, N. A., 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=Autophagy+through+4EBP1+and+AMPK+regulates+oxidative+stress-induced+premature+senescence+in+auditory+cells.">Autophagy through 4EBP1 and AMPK regulates oxidative stress-induced premature senescence in auditory cells.</a> Oncotarget. 6, 3644-3655 (2015).</li><li>Youn, C. K., Kim, J., Park, J. H., Do, N. Y., Cho, S. I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Role+of+autophagy+in+cisplatin-induced+ototoxicity.">Role of autophagy in cisplatin-induced ototoxicity.</a> Int J Pediatr Otorhinolaryngol. 79, 1814-1819 (2015).</li><li>Kalinec, G., Thein, P., Park, C., Kalinec, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HEI-OC1+cells+as+a+model+for+investigating+drug+cytotoxicity.">HEI-OC1 cells as a model for investigating drug cytotoxicity.</a> Hear Res. 335, 105-117 (2016).</li><li>Park, C., Thein, P., Kalinec, G., Kalinec, F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=HEI-OC1+cells+as+a+model+for+investigating+prestin+function.">HEI-OC1 cells as a model for investigating prestin function.</a> Hear Res. 335, 9-17 (2016).</li><li>Celis, J. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Cell Biology: A Laboratory Handbook. 1, (2006).</li><li>Bertolaso, L., 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=Apoptosis+in+the+OC-k3+immortalized+cell+line+treated+with+different+agents.">Apoptosis in the OC-k3 immortalized cell line treated with different agents.</a> Audiology. 40, 327-335 (2001).</li><li>Kalinec, F., Kalinec, G., Boukhvalova, M., Kachar, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Establishment+and+characterization+of+conditionally+immortalized+organ+of+corti+cell+lines.">Establishment and characterization of conditionally immortalized organ of corti cell lines.</a> Cell Biol Int. 23, 175-184 (1999).</li><li>Belyantseva, I., Kalinec, G. M., Kalinec, F., Kachar, B. <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+differentiation+of+two+immortalized+cell+lines+derived+from+the+stria+vascularis+of+a+transgenic+mouse.">In vitro differentiation of two immortalized cell lines derived from the stria vascularis of a transgenic mouse.</a> 21st Midwinter Meeting Association for Research in Otolaryngology. 620a, (1998).</li><li>Gratton, M. A., Meehan, D. T., Smyth, B. J., Cosgrove, D. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Strial+marginal+cells+play+a+role+in+basement+membrane+homeostasis:+in+vitro+and+in+vivo+evidence.">Strial marginal cells play a role in basement membrane homeostasis: in vitro and in vivo evidence.</a> Hear Res. 163, 27-36 (2002).</li><li>Debacq-Chainiaux, F., Erusalimsky, J. D., Campisi, J., Toussaint, O. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Protocols+to+detect+senescence-associated+beta-galactosidase+(SA-betagal)+activity,+a+biomarker+of+senescent+cells+in+culture+and+in+vivo.">Protocols to detect senescence-associated beta-galactosidase (SA-betagal) activity, a biomarker of senescent cells in culture and in vivo.</a> Nat Protoc. 4, 1798-1806 (2009).</li><li>Santos-Sacchi, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reversible+inhibition+of+voltage-dependent+outer+hair+cell+motility+and+capacitance.">Reversible inhibition of voltage-dependent outer hair cell motility and capacitance.</a> J. Neurosci. 11, 3096-3110 (1991).</li><li>Fink, S. L., Cookson, B. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Apoptosis,+pyroptosis,+and+necrosis:+mechanistic+description+of+dead+and+dying+eukaryotic+cells.">Apoptosis, pyroptosis, and necrosis: mechanistic description of dead and dying eukaryotic cells.</a> Infect Immun. 73, 1907-1916 (2005).</li><li>Majno, G., Joris, I. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Apoptosis,+oncosis,+and+necrosis.+An+overview+of+cell+death.">Apoptosis, oncosis, and necrosis. An overview of cell death.</a> Am J Pathol. 146, 3-15 (1995).</li><li>Vanden Berghe, T., Linkermann, A., Jouan-Lanhouet, S., Walczak, H., Vandenabeele, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Regulated+necrosis:+the+expanding+network+of+non-apoptotic+cell+death+pathways.">Regulated necrosis: the expanding network of non-apoptotic cell death pathways.</a> Nat Rev Mol Cell Biol. 15, 135-147 (2014).</li><li>Sun, L., Wang, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+new+kind+of+cell+suicide:+mechanisms+and+functions+of+programmed+necrosis.">A new kind of cell suicide: mechanisms and functions of programmed necrosis.</a> Trends Biochem Sci. 39, 587-593 (2014).</li><li>Chan, F. K., Luz, N. F., Moriwaki, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Programmed+necrosis+in+the+cross+talk+of+cell+death+and+inflammation.">Programmed necrosis in the cross talk of cell death and inflammation.</a> Annu Rev Immunol. 33, 79-106 (2015).</li><li>Vercammen, D., 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=Dual+signaling+of+the+Fas+receptor:+initiation+of+both+apoptotic+and+necrotic+cell+death+pathways.">Dual signaling of the Fas receptor: initiation of both apoptotic and necrotic cell death pathways.</a> J Exp Med. 188, 919-930 (1998).</li><li>Campisi, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Aging,+cellular+senescence,+and+cancer.">Aging, cellular senescence, and cancer.</a> Annu Rev Physiol. 75, 685-705 (2013).</li><li>Bian, S., Koo, B. W., Kelleher, S., Santos-Sacchi, J., Navaratnam, D. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+highly+expressing+Tet-inducible+cell+line+recapitulates+in+situ+developmental+changes+in+prestin's+Boltzmann+characteristics+and+reveals+early+maturational+events.">A highly expressing Tet-inducible cell line recapitulates in situ developmental changes in prestin's Boltzmann characteristics and reveals early maturational events.</a> Am J Physiol Cell Physiol. 299, C828-C835 (2010).</li><li>Abe, T., 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=Developmental+expression+of+the+outer+hair+cell+motor+prestin+in+the+mouse.">Developmental expression of the outer hair cell motor prestin in the mouse.</a> J Membr Biol. 215, 49-56 (2007).</li><li>Oliver, D., Fakler, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Expression+density+and+functional+characteristics+of+the+outer+hair+cell+motor+protein+are+regulated+during+postnatal+development+in+rat.">Expression density and functional characteristics of the outer hair cell motor protein are regulated during postnatal development in rat.</a> J Physiol. 519 Pt 3, 791-800 (1999).</li><li>Tsunoo, M., Perlman, H. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cochlear+Oxygen+Tension:+Relation+to+Blood+Flow+and+Function.">Cochlear Oxygen Tension: Relation to Blood Flow and Function.</a> Acta Otolaryngol. 59, 437-450 (1965).</li></ol>

The authors declare no existing or potential conflict of interest.

In this report we describe how to culture HEI-OC1 cells and use them to evaluate mechanisms of drug-induced cytotoxicity and to investigate functional properties of prestin, the molecular motor of cochlear OHCs. The technical procedures, however, are general enough to be easily adapted to different studies.
All the protocols described here require the correct use of well-established cell culture techniques 10. Just like with any other cell line, working with HEI-OC1 cells requires a...

House Ear Institute-Organ of Corti 1 (HEI-OC1) cells are derived from the auditory organ of a transgenic mouse 1,2. Incubation of any cell from this transgenic mouse at 33 &#176;C/10% CO2 (permissive conditions) induces expression of an immortalizing gene that triggers de-differentiation and accelerated proliferation; moving the cells to 39 &#176;C/5% CO2 (non-permissive conditions) lead to decreased proliferation, differentiation and, at least in the case of HEI-OC1, cell death 2,3.
HEI-OC1 cells were cloned and characterized in our laboratory over a decade ago, and initial studies indicated that they express specific markers of cochlear hair cells, such as prestin, myosin 7a, Atoh1, BDNF, calbindin and calmodulin, but also markers of supporting cells like connexin 26 and fibroblast growth factor receptor (FGF-R) 2. Therefore, it was suggested that HEI-OC1 could represent a common progenitor for sensory and supporting cells of the organ of Corti 2. Parallel studies provided strong evidence that archetypal ototoxic drugs like cisplatin, gentamicin and streptomycin induced caspase-3 activation in these cells, while drugs considered non-ototoxic, like penicillin, did not 2,3. Therefore, this cell line was proposed as an in vitro system to investigate the cellular and molecular mechanisms involved in ototoxicity and for screening of the potential ototoxicity or otoprotective properties of new pharmacological drugs. It is estimated that HEI-OC1 cells have been used in more than one hundred and fifty studies published in the last ten years.
Whereas looking at the potential pro-apoptotic effect of different drugs was the major goal of most of the studies involving this cell line, other important cell processes like autophagy and senescence have just started to be investigated in HEI-OC1 cells4-7. In a recent study from our laboratory 8, we used HEI-OC1 cells to collect a comprehensive set of data about cell death, survival, proliferation, senescence and autophagy induced by different pharmacological drugs frequently used in the clinic. We also compared some of the responses of HEI-OC1 cells with those from HEK-293 (human embryonic kidney cells) and HeLa (human epithelial cells) receiving identical treatment. Our results indicated that HEI-OC1 cells respond to the each drug in a characteristic way, with a distinctive dose- and time-dependent sensitivity to at least one of the mechanisms under study. We also emphasized in that study that a correct interpretation of the experimental results will require performing parallel studies with more than one technique 8.
In a different study we investigated the use of HEI-OC1 cells to evaluate the functional response of prestin, the motor protein of cochlear outer hair cells (OHCs) 9. We reported flow cytometry and confocal laser scanning microscopy studies on the pattern of prestin expression, as well as nonlinear capacitance (NLC) and whole cell-patch clamping studies in HEI-OC1 cells cultured at permissive (P-HEI-OC1) and non-permissive (NP-HEI-OC1) conditions. Our results indicated that both total prestin expression and plasma membrane localization increase in a time-dependent manner in NP-HEI-OC1 cells. Interestingly, we also found that the increase in prestin localization at the plasma membrane of NP-HEI-OC1 cells correlated with a decrease in Na+K+ATPase, which translocated from the plasma membrane to the cytoplasm without significant changes in total cell expression. In addition, we demonstrated that P-HEI-OC1 cells have a robust NLC associated to prestin motor function, which decreased when the density of prestin molecules present at the plasma membrane increased. Altogether, these results strongly support the usefulness of HEI-OC1 cells to investigate auditory proteins.
In this video article we describe how to culture HEI-OC1 cells, why it is convenient to use cells growing at permissive conditions (P-HEI-OC1) for cytotoxicity studies, how to evaluate the mechanism/s of drug-induced cytotoxicity and how to perform electrophysiological studies (e.g., patch-clamp, non-linear capacitance (NLC)) to investigate functional properties of prestin, the molecular motor of cochlear OHCs.

<table border="0" cellpadding="0" cellspacing="0" width="1447">
	<tbody>
		<tr height="21">
			<td height="21" style="height:21px;width:905px;">HEI-OC1 cells</td>
			<td style="width:143px;"></td>
			<td style="width:139px;"></td>
			<td style="width:260px;">ALL THE ASSAY KITS, EQUIPMENTS&#160;</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Class II Biological Safety cabinet</td>
			<td>The Baker Company</td>
			<td>Sterilgard III</td>
			<td>AND COMPANIES INDICATED IN THE</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Refrigerated centrifuge</td>
			<td>Eppendorf</td>
			<td>5810R</td>
			<td>PREVIOUS 2 COLUMNS ARE ONLY</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Inverted microscope</td>
			<td>Zeiss</td>
			<td>Axiovert 25</td>
			<td>EXAMPLES, AND ANY OTHER SIMILAR</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Waterbath</td>
			<td>Stovall</td>
			<td>HWB115</td>
			<td>PRODUCT COULD BE USED.</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cell counter</td>
			<td>Nexcelom</td>
			<td>Cellometer Auto T4</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Two (2) Cell incubators, one at 33&#176;C/10% CO2 and other at 39&#176;C/5% CO2</td>
			<td>Forma Scientific</td>
			<td>3110</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cell culture dishes, PS, 100 x 20 mm with vents</td>
			<td>Greinier Bio-One</td>
			<td>664-160</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cell culture dishes , PS,&#160; 60 x 15 mm with vents&#160;</td>
			<td>Greiner Bio-One</td>
			<td>628160</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cellstar tissue culture flasks&#160; 250 mL</td>
			<td>Greiner Bio-One</td>
			<td>658-175</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cellstar tissue cultur&#160; flasks 550 mL</td>
			<td>Greiner Bio-One</td>
			<td>660-175</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">&#160;6 well cell culture plate, with lid-Cellstar</td>
			<td>Greiner Bio-One</td>
			<td>657-160</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Microtest Tissue culture plate, 96 well,flat bottom with lid</td>
			<td>Becton Dickinson</td>
			<td>353072</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Micro-Assay-Plate, Chimmey, 96-well white,clear botton</td>
			<td>Greiner Bio-One</td>
			<td>655098</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">50 ml Polypropylene conical tube with cap Cellstars</td>
			<td>Becton Dickinson&#160;</td>
			<td>352070</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">15 ml Polypropylene conical tubes with cap-Cellstars</td>
			<td>Greiner Bio-One</td>
			<td>188-271</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">PBS pH 7.4 (1X)&#160;</td>
			<td>Life Technologies</td>
			<td>10010-023</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Dulbecco&#8217;s Modified Eagle&#8217;s Medium (DMEM)</td>
			<td>Life Technologies</td>
			<td>11965-084</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Fetal bovine serum (FBS)&#160;</td>
			<td>Hyclone</td>
			<td>SH10073.1</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Leibovitz&#39;s L-15 Medium, no phenol red</td>
			<td>Gibco/Invitrogen</td>
			<td>21083-027</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Trypsin, 0.25%&#160;</td>
			<td>Life Technologies</td>
			<td>25200-056</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">TACS MTT Cell Proliferation Assay Kit</td>
			<td>Trevigen</td>
			<td>4890-25-K</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Caspase-Glo 3/7 Assay&#160; kit</td>
			<td>Promega</td>
			<td style="width:139px;">&#160; G8091&#160;</td>
			<td style="width:260px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">BrdU Cell Proliferation Assay Kit&#160;</td>
			<td>Cell Signaling</td>
			<td>6813</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Non-enzymatic cell dissociation solution&#160;</td>
			<td>Sigma-Aldrich</td>
			<td>C5789</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Cell-Tox Green Cytotoxicity Assay Kit</td>
			<td>Promega</td>
			<td style="width:139px;">&#160; G8741&#160;</td>
			<td style="width:260px;"></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">FACSAriaIII instrument&#160;</td>
			<td>BD Biosciences</td>
			<td>&#160;FACSAriaIII</td>
			<td>With 488 nm excitation (blue laser)</td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Digital Blot Scanner</td>
			<td>LI-COR</td>
			<td>C-DiGit</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Electrophoresis and Blotting Unit</td>
			<td>Hoefer</td>
			<td>SE300 miniVE</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Spectra Max 5 Plate Reader with Soft Max Pro 5.2 Software</td>
			<td>Molecular Devices</td>
			<td>SpectraMax 5</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Patch-clamp amplifier</td>
			<td>HEKA</td>
			<td>EPC-10</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;">Puller for preparing patch electrodes</td>
			<td>Sutter Instruments</td>
			<td>P-97</td>
			<td></td>
		</tr>
	</tbody>
</table>

working with auditory hei-oc1 cells

HEI-OC1 is one of the few mouse auditory cell lines available for research purposes. Originally proposed as an in vitro system for screening of ototoxic drugs, these cells have been used to investigate drug-activated apoptotic pathways, autophagy, senescence, mechanism of cell protection, inflammatory responses, cell differentiation, genetic and epigenetic effects of pharmacological drugs, effects of hypoxia, oxidative and endoplasmic reticulum stress, and expression of molecular channels and receptors. Among other several important markers of cochlear hair cells, HEI-OC1 cells endogenously express prestin, the paradigmatic motor protein of outer hair cells. Thus, they can be very useful to elucidate novel functional aspects of this important auditory protein. HEI-OC1 cells are very robust, and their culture usually does not present big complications. However, they require some special conditions such as avoiding the use of common anti-bacterial cocktails containing streptomycin or other antibiotics as well as incubation at 33 &#176;C to stimulate cell proliferation and incubation at 39 &#176;C to trigger cell differentiation. Here, we describe how to culture HEI-OC1 cells and how to use them in some typical assays, such as cell proliferation, viability, death, autophagy and senescence, as well as how to perform patch-clamp and non-linear capacitance measurements.

In a couple of recent publications we reported a comprehensive set of studies aimed at evaluating the response of HEI-OC1 cells to several commonly used pharmacological drugs as well as investigating prestin function 8,9. In these studies we made use of all the protocols described in the previous sections.
One of the results of these previous studies was that HEI-OC1 cells cultured at non-permissive conditions (39 &#1...

Watch this Scientific Journal Video about Working with Auditory HEI-OC1 Cells at JoVE.com

Working with Auditory HEI-OC1 Cells

House Ear Institute-Organ of Corti 1 (HEI-OC1) is one of the few mouse auditory cell lines currently available for research purposes. This protocol describes how to work with HEI-OC1 cells to investigate the cytotoxic effects of pharmacological drugs as well as functional properties of inner ear proteins.

HEI-OC1 is one of the few mouse auditory cell lines available for research purposes. Originally proposed as an in vitro system for screening of ototoxic ...

Research

JoVE Journal

Biology

14.9K Views.  University of California, Los Angeles. House Ear Institute-Organ of Corti 1 (HEI-OC1) is one of the few mouse auditory cell lines currently available for research purposes. This protocol describes how to work with HEI-OC1 cells to investigate the cytotoxic effects of pharmacological drugs as well as functional properties of inner ear proteins.

Video: Working with Auditory HEI-OC1 Cells

Transfecting Human Neural Stem Cells with the Amaxa Nucleofector

Transfection of primary mammalian neural cells, such as human neural stem/precursor cells (hNSPCs), with commonly used cationic lipid transfection reagents has often resulted in poor cell viability and low transfection efficiency.  Other mechanical methods of introducing a gene of interest, such as a &#8220;gene gun&#8221; or microinjection, are also limited by poor cell viability and low numbers of transfected cells.  The strategy of using viral constructs to introduce an exogenous gene into primary cells has been constrained by both the amount of time and labor required to create viral vectors and potential safety concerns.  We describe here a step-by-step protocol for transfecting hNSPCs using Amaxa's Nucleofector device and technology with electrical current parameters and buffer solutions specifically optimized for transfecting neural stem cells.  Using this protocol, we have achieved initial transfection efficiencies of ~35% and ~70% after stable transfection.  The protocol entails combining a high number of hNSPCs with the DNA to be transfected in the appropriate buffer followed by electroporation with the Nucleofector device.

Introducing a gene of interest into a cell is a powerful method for elucidating its function in vivo. This protocol describes an efficient method of transfecting a culture of human neural stem/precursor cells (hNSPCs) using the Nucleofector electroporation apparatus made by Amaxa.

Transfection of primary mammalian neural cells, such as human neural stem/precursor cells (hNSPCs), with commonly used cationic lipid transfection ...

Labeling Stem Cells with Fluorescent Dyes for non-invasive Detection with Optical Imaging

Optical imaging (OI) is an easy, fast and inexpensive tool for in vivo monitoring of new stem cell based therapies. The technique is based on ex vivo labeling of stem cells with a fluorescent dye, subsequent intravenous injection of the labeled cells and visualization of their accumulation in specific target organs or pathologies. The presented technique demonstrates how we label human mesenchymal stem cells (hMSC) by simple incubation with the lipophilic fluorescent dye DiD (C67H103CIN2O3S) and how we label human embryonic stem cells (hESC) with the FDA approved fluorescent dye Indocyanine Green (ICG). The uptake mechanism is via adherence and diffusion of the lypophilic dye across the phospholipid cell membrane bilayer. The labeling efficiency is usually improved if the cells are incubated with the dye in serum-free media as opposed to incubation in serum-containing media. Furthermore, the addition of the transfection agent Protamine Sulfate significantly improves contrast agent uptake.

This video shows techniques for labeling of human embryonic stem cells and mesenchymal stem cells with fluorescent dyes. This technique can be used for an in vivo tracking of transplanted stem cells with optical imaging and for histopathological correlations with fluorescence microscopy.

Optical imaging (OI) is an easy, fast and inexpensive tool for in vivo monitoring of new stem cell based therapies. The technique is based on ex vivo ...

Imaging Exocytosis in Retinal Bipolar Cells with TIRF Microscopy

Total internal reflectance fluorescence (TIRF) microscopy is a technique that allows the study of events happening at the cell membrane, by selective imaging of fluorescent molecules that are closest to a high refractive index substance such as glass1. In this article, we apply this technique to image exocytosis of synaptic vesicles in retinal bipolar cells isolated from the goldfish retina. These neurons are very suitable for this kind of study due to their large axon terminals. By simultaneously patch clamping the bipolar cells, it is possible to investigate the relationship between pre-synaptic voltage and synaptic release2,3. Synaptic vesicles inside the bipolar cell terminals are loaded with a fluorescent dye (FM 1-43&reg;) by co-puffing the dye and a ringer solution containing a high K+ concentration onto the synaptic terminals. This depolarizes the cells and stimulates endocytosis and consequent dye uptake into the glutamatergic vesicles. After washing the excess dye away for around 30 minutes, cells are ready for being patch clamped and imaged simultaneously with a 488 nm laser. The patch pipette solution contains a rhodamine-based peptide that binds selectively to the synaptic ribbon protein RIBEYE4, thereby labeling ribbons specifically when terminals are imaged with a 561 nm laser. This allows the precise localization of active zones and the separation of synaptic from extra-synaptic events.

In this video, we demonstrate how to label and visualize single synaptic vesicle exocytosis and trafficking in goldfish retinal bipolar cells using total internal reflectance fluorescence (TIRF) microscopy.

Total internal reflectance fluorescence (TIRF) microscopy is a technique that allows the study of events happening at the cell membrane, by selective ...

Mapping the After-effects of Theta Burst Stimulation on the Human Auditory Cortex with Functional Imaging

Auditory cortex pertains to the processing of sound, which is at the basis of speech or music-related processing1. However, despite considerable recent progress, the functional properties and lateralization of the human auditory cortex are far from being fully understood. Transcranial Magnetic Stimulation (TMS) is a non-invasive technique that can transiently or lastingly modulate cortical excitability via the application of localized magnetic field pulses, and represents a unique method of exploring plasticity and connectivity. It has only recently begun to be applied to understand auditory cortical function 2. 
An important issue in using TMS is that the physiological consequences of the stimulation are difficult to establish. Although many TMS studies make the implicit assumption that the area targeted by the coil is the area affected, this need not be the case, particularly for complex cognitive functions which depend on interactions across many brain regions 3. One solution to this problem is to combine TMS with functional Magnetic resonance imaging (fMRI). The idea here is that fMRI will provide an index of changes in brain activity associated with TMS. Thus, fMRI would give an independent means of assessing which areas are affected by TMS and how they are modulated 4. In addition, fMRI allows the assessment of functional connectivity, which represents a measure of the temporal coupling between distant regions. It can thus be useful not only to measure the net activity modulation induced by TMS in given locations, but also the degree to which the network properties are affected by TMS, via any observed changes in functional connectivity.
Different approaches exist to combine TMS and functional imaging according to the temporal order of the methods. Functional MRI can be applied before, during, after, or both before and after TMS. Recently, some studies interleaved TMS and fMRI in order to provide online mapping of the functional changes induced by TMS 5-7. However, this online combination has many technical problems, including the static artifacts resulting from the presence of the TMS coil in the scanner room, or the effects of TMS pulses on the process of MR image formation. But more importantly, the loud acoustic noise induced by TMS (increased compared with standard use because of the resonance of the scanner bore) and the increased TMS coil vibrations (caused by the strong mechanical forces due to the static magnetic field of the MR scanner) constitute a crucial problem when studying auditory processing. 
This is one reason why fMRI was carried out before and after TMS in the present study. Similar approaches have been used to target the motor cortex 8,9, premotor cortex 10, primary somatosensory cortex 11,12 and language-related areas 13, but so far no combined TMS-fMRI study has investigated the auditory cortex. The purpose of this article is to provide details concerning the protocol and considerations necessary to successfully combine these two neuroscientific tools to investigate auditory processing. 
Previously we showed that repetitive TMS (rTMS) at high and low frequencies (resp. 10 Hz and 1 Hz) applied over the auditory cortex modulated response time (RT) in a melody discrimination task 2. We also showed that RT modulation was correlated with functional connectivity in the auditory network assessed using fMRI: the higher the functional connectivity between left and right auditory cortices during task performance, the higher the facilitatory effect (i.e. decreased RT) observed with rTMS. However those findings were mainly correlational, as fMRI was performed before rTMS. Here, fMRI was carried out before and immediately after TMS to provide direct measures of the functional organization of the auditory cortex, and more specifically of the plastic reorganization of the auditory neural network occurring after the neural intervention provided by TMS. 
Combined fMRI and TMS applied over the auditory cortex should enable a better understanding of brain mechanisms of auditory processing, providing physiological information about functional effects of TMS. This knowledge could be useful for many cognitive neuroscience applications, as well as for optimizing therapeutic applications of TMS, particularly in auditory-related disorders.

Auditory processing is the basis of speech and music-related processing. Transcranial Magnetic Stimulation (TMS) has been used successfully to study cognitive, sensory and motor systems but has rarely been applied to audition. Here we investigated TMS combined with functional Magnetic Resonance Imaging to understand the functional organization of auditory cortex.

Auditory cortex pertains to the processing of sound, which is at the basis of speech or music-related processing1. However, despite considerable recent ...

Induction and Analysis of Epithelial to Mesenchymal Transition

Epithelial to mesenchymal transition (EMT) is essential for proper morphogenesis during development. Misregulation of this process has been implicated as a key event in fibrosis and the progression of carcinomas to a metastatic state. Understanding the processes that underlie EMT is imperative for the early diagnosis and clinical control of these disease states. Reliable induction of EMT in vitro is a useful tool for drug discovery as well as to identify common gene expression signatures for diagnostic purposes. Here we demonstrate a straightforward method for the induction of EMT in a variety of cell types. Methods for the analysis of cells pre- and post-EMT induction by immunocytochemistry are also included. Additionally, we demonstrate the effectiveness of this method through antibody-based array analysis and migration/invasion assays.

A straightforward method is described for the induction of epithelial to mesenchymal transition (EMT) in a variety of cell types. Methods for the analysis of cells in EMT states by immunocytochemistry are included.

Epithelial  to mesenchymal transition (EMT) is essential for proper morphogenesis during  development. Misregulation of this  process has been implicated ...

Efficient Generation Human Induced Pluripotent Stem Cells from Human Somatic Cells with Sendai-virus

A few years ago, the establishment of human induced pluripotent stem cells (iPSCs) ushered in a new era in biomedicine. Potential uses of human iPSCs include modeling pathogenesis of human genetic diseases, autologous cell therapy after gene correction, and personalized drug screening by providing a source of patient-specific and symptom relevant cells. However, there are several hurdles to overcome, such as eliminating the remaining reprogramming factor transgene expression after human iPSCs production. More importantly, residual transgene expression in undifferentiated human iPSCs could hamper proper differentiations and misguide the interpretation of disease-relevant in vitro phenotypes. With this reason, integration-free and/or transgene-free human iPSCs have been developed using several methods, such as adenovirus, the piggyBac system, minicircle vector, episomal vectors, direct protein delivery and synthesized mRNA. However, efficiency of reprogramming using integration-free methods is quite low in most cases.
Here, we present a method to isolate human iPSCs by using Sendai-virus (RNA virus) based reprogramming system. This reprogramming method shows consistent results and high efficiency in cost-effective manner.

Here, we present our established method to reprogram human somatic cells into transgene-free human iPSCs with Sendai virus, which shows consistent outcome and enhanced efficiency.

A few years ago, the establishment of human induced pluripotent stem cells (iPSCs) ushered in a new era in biomedicine. Potential uses of human iPSCs ...

Fluorescence Imaging with One-nanometer Accuracy (FIONA)

Fluorescence imaging with one-nanometer accuracy (FIONA) is a simple but useful technique for localizing single fluorophores with nanometer precision in the x-y plane. Here a summary of the FIONA technique is reported and examples of research that have been performed using FIONA are briefly described. First, how to set up the required equipment for FIONA experiments, i.e., a total internal reflection fluorescence microscopy (TIRFM), with details on aligning the optics, is described. Then how to carry out a simple FIONA experiment on localizing immobilized Cy3-DNA single molecules using appropriate protocols, followed by the use of FIONA to measure the 36 nm step size of a single truncated myosin Va motor labeled with a quantum dot, is illustrated. Lastly, recent effort to extend the application of FIONA to thick samples is reported. It is shown that, using a water immersion objective and quantum dots soaked deep in sol-gels and rabbit eye corneas (&#62;200 &#181;m), localization precision of 2-3 nm can be achieved.

Fluorescence Imaging with One-nanometer Accuracy FIONA

Single fluorophores can be localized with nanometer precision using FIONA. Here a summary of the FIONA technique is reported, and how to carry out FIONA experiments is described.

Fluorescence imaging with one-nanometer accuracy (FIONA) is a simple but useful technique for localizing single fluorophores with nanometer precision in ...

Transfecting RAW264.7 Cells with a Luciferase Reporter Gene

Transfection of desired genetic materials into cells is an inevitable procedure in biomedical research studies. While numerous methods have been described, certain types of cells are resistant to many of these methods and yield low transfection efficiency1, potentially hindering research in those cell types. In this protocol, we present an optimized transfection procedure to introduce luciferase reporter genes as a plasmid DNA into the RAW264.7 macrophage cell line. Two different types of transfection reagents (lipid-based and polyamine-based) are described, and important notes are given throughout the protocol to ensure that the RAW264.7 cells are minimally altered by the transfection procedure and any experimental data obtained are the direct results of the experimental treatment. While transfection efficiency may not be higher compared to other transfection methods, the described procedure is robust enough for detecting luciferase signal in RAW264.7 without changing the physiological response of the cells to stimuli.

Transfection into the macrophage cell line, RAW264.7, is difficult due to the cell&#8217;s natural response against foreign materials. We described here a gentle yet robust procedure for transfecting luciferase reporter genes into RAW264.7 cells.

Transfection of desired genetic materials into cells is an inevitable procedure in biomedical research studies. While numerous methods have been ...

Rodent Working Heart Model for the Study of Myocardial Performance and Oxygen Consumption

Isolated working heart models have been used to understand the effects of loading conditions, heart rate and medications on myocardial performance in ways that cannot be accomplished in vivo. For example, inotropic medications commonly also affect preload and afterload, precluding load-independent assessments of their myocardial effects in vivo. Additionally, this model allows for sampling of coronary sinus effluent without contamination from systemic venous return, permitting assessment of myocardial oxygen consumption. Further, the advent of miniaturized pressure-volume catheters has allowed for the precise quantification of markers of both systolic and diastolic performance. We describe a model in which the left ventricle can be studied while performing both volume and pressure work under controlled conditions. 
In this technique, the heart and lungs of a Sprague-Dawley rat (weight 300-500 g) are removed en bloc under general anesthesia. The aorta is dissected free and cannulated for retrograde perfusion with oxygenated Krebs buffer. The pulmonary arteries and veins are ligated and the lungs removed from the preparation. The left atrium is then incised and cannulated using a separate venous cannula, attached to a preload block. Once this is determined to be leak-free, the left heart is loaded and retrograde perfusion stopped, creating the working heart model. The pulmonary artery is incised and cannulated for collection of coronary effluent and determination of myocardial oxygen consumption. A pressure-volume catheter is placed into the left ventricle either retrograde or through apical puncture. If desired, atrial pacing wires can be placed for more precise control of heart rate. This model allows for precise control of preload (using a left atrial pressure block), afterload (using an afterload block), heart rate (using pacing wires) and oxygen tension (using oxygen mixtures within the perfusate).

Isolated working heart models can be used to measure the effect of loading conditions, heart rate, and medications on myocardial performance and oxygen consumption. We describe methods for preparation of a rodent left heart working model that permits study of systolic and diastolic performance and oxygen consumption under various conditions.

Isolated working heart models have been used to understand the effects of loading conditions, heart rate and medications on myocardial performance in ways ...

Nephrotoxin Microinjection in Zebrafish to Model Acute Kidney Injury

The kidneys are susceptible to harm from exposure to chemicals they filter from the bloodstream. This can lead to organ injury associated with a rapid decline in renal function and development of the clinical syndrome known as acute kidney injury (AKI). Pharmacological agents used to treat medical circumstances ranging from bacterial infection to cancer, when administered individually or in combination with other drugs, can initiate AKI. Zebrafish are a useful animal model to study the chemical effects on renal function in vivo, as they form an embryonic kidney comprised of nephron functional units that are conserved with higher vertebrates, including humans. Further, zebrafish can be utilized to perform genetic and chemical screens, which provide opportunities to elucidate the cellular and molecular facets of AKI and develop therapeutic strategies such as the identification of nephroprotective molecules. Here, we demonstrate how microinjection into the zebrafish embryo can be utilized as a paradigm for nephrotoxin studies.

Renal injuries incurred from nephrotoxins, which include drugs ranging from antibiotics to chemotherapeutics, can result in complex disorders whose pathogenesis remains incompletely understood. This protocol demonstrates how zebrafish can be used for disease modeling of these conditions, which can be applied to the identification of renoprotective measures.

The kidneys are susceptible to harm from exposure to chemicals they filter from the bloodstream. This can lead to organ injury associated with a rapid ...