Name: dextran labeling and uptake in live and functional murine cochlear hair cells
Uploaded: 2020-02-08T13:00:00
Description: Watch this Scientific Journal Video about Dextran Labeling and Uptake in Live and Functional Murine Cochlear Hair Cells at JoVE.com

We thank Vincent Schram from the NICHD microscopy and imaging core for assisting in the confocal image acquisition, and Tsg-Hui Chang for invaluable help with colony management and mice care. This research was supported by the Intramural Research Program of the NINDS, NIH, Bethesda, MD, to K.J.S. A.B. was supported by the Intramural Research Program of the NINDS, NIH, and by a Robert Wenthold Postdoctoral Fellowship from the intramural research program of the NIDCD.

The animal care and experimental procedures were performed following the guidelines for the Care and Use of Laboratory Animals, which were approved by the Animal Care and Use Committee of the National Institute of Neurological Disorders and Stroke (Animal protocol #1336 to KJS).
1. Mice
<ol>
	<li>Set a couple of breeding pairs of C57BL/6J wild-type to breed in the animal facility to control the date of birth of the litters and keep track of the age of the pups.</li>
</ol>
<p class="jove_titl...

This protocol describes how to perform uptake experiments in murine organ of Corti explants with 3 kDa dextran Texas Red. The goal of this method is to test whether molecules larger than others previously tested were also able to specifically label auditory hair cells and permeate through the MET channel. Similar experimental protocols have been previously used to evaluate the permeability of hair cells to other fluorescent dyes such as FM1-43 (0.56 kDa)12,19<sup...

The hair cells of the inner ear are the sensory cells that detect sound and covert the mechanically stimuli in electrical signals, which are ultimately interpreted by our brain. These cells have a staircase-shaped bundle of three rows of actin-based filaments, known as stereocilia, which protrude from their apical region1,2. The mechanical stimuli deflect the stereocilia filaments toward the longest row and trigger the opening of the mechanotransduction (MET) channels3. The opening of the MET channels leads to an influx of cations that depolarizes the cell and consequently signals the release of synapse vesicles at the basal region of the hair cell.
The biophysical properties of the MET channel essential for hearing have been extensively characterized. Among other properties, these channels are cationic selective and have a relatively large conductance (150&#8211;300 pS in low Ca2+)4,5,6,7,8,9,10. Remarkably, large fluorescent molecules such as FM1-43 and Texas Red-labeled aminoglycosides are permeant blockers of the MET channel, resulting in their accumulation in the hair cell body that can be visualized using fluorescence microscopy11,12,13,14. Conversely, the molecular identity and the structure of the MET channel and its permeation pathway have remained elusive. Increasing experimental evidence indicates that the transmembrane-like channel protein 1 (TMC1) is a component of the MET channel in mature hair cells15,16,17,18,19. Mutations in the transmembrane-like channel 1 (TMC1) alter the MET channel properties19,20,21,22 and cause deafness. In addition, TMC1 localizes to the site of the MET channel18,23 and interacts with the tip-link responsible for transmitting the mechanical force to the MET channel24,25. Furthermore, recent bioinformatics analysis has identified the TMC proteins as evolutionary related to the mechanosensitive channels TMEM63/OSCA proteins and the TMEM16 proteins, a family of calcium-activated chloride channels and lipid scramblases26,27,28. A structural model of TMC1 based on the relationship between these proteins revealed the presence of a large cavity at the protein-lipid interface27. This cavity harbors the two TMC1 mutations that cause autosomal dominant hearing loss (DFNA36)27,29,30,31,32, and selective modification of cysteine mutants for residues in the cavity alter MET channel properties28, indicating that it could function as the permeation pathway of the MET channel. The large size of this predicted cavity in TMC proteins could explain the ability of large molecules to permeate the MET channel. To test the prediction that the MET channel contains an unusually large permeation pathway and to push the limits of the size of the cavity observed in TMC1, we developed a protocol to perform uptake experiments in the organ of Corti explants with a larger molecule, 3 kDa dextran fluorescently labeled with Texas Red.
Dextran is a complex branched polysaccharide composed of many D-glucose molecules bound by alpha-1,6 glycosidic linkages. Its high solubility in water, low cell toxicity, and bioinertity make it a versatile tool to study several cellular processes. In addition, dextran is available in a wide range of sizes and fluorescently labeled with fluorophores of several colors. Fluorescently labeled dextrans are commonly used in cell and tissue permeability research33,34, to study endocytosis in multiple cellular systems35,36, and for neural tracing37,38. In the auditory field, dextran molecules have also been used to assess the disruption of the cell-cell junction and loss of the auditory sensory epithelium integrity after exposure to intense noise in the chinchilla organ of Corti39,40.
In this work, we exploited the properties of some of the smallest (3 and 10 kDa) fluorescent dextrans to perform uptake experiments in murine inner ear hair cells and explore the size of the permeation pathway of the inner ear hair cell MET channel. In addition, we used a laser-scanning confocal microscope (LSM) 880 equipped with an Airyscan detector to visualize and localize fluorescent dextran at the stereocilia and the cell body of auditory hair cells.

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			<td>64-0714</td>
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			<td>Alexa Fluor 488 Phalloidin</td>
			<td>ThermoFisher</td>
			<td>A12379</td>
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			<td>Alexa Fluor 594 Phalloidin</td>
			<td>ThermoFisher</td>
			<td>A12381</td>
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			<td>alpha Plan-Apochromat 63X/1.4 Oil Corr M27 objective</td>
			<td>Carl Zeiss</td>
			<td>420780-9970-000</td>
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			<td>Amiloride hydrochloride</td>
			<td>EMD MILLIPORE</td>
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			<td>Benchwaver 3-dimensional Rocker</td>
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			<td>B3D5000</td>
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			<td>C57BL/6J wild-type mice</td>
			<td>strain 000664</td>
			<td>The Jackson Laboratory</td>
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			<td>Cell impermeant BAPTA tetrapotassium salt</td>
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			<td>B1204</td>
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			<td>Dextran, Fluorescein, 10,000 MW, Anionic, Lysine Fixable</td>
			<td>ThermoFisher</td>
			<td>D1820</td>
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			<td>Dextran, Texas Red, 10,000 MW, Lysine Fixable</td>
			<td>ThermoFisher</td>
			<td>D1863</td>
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			<td>Dextran, Texas Red, 3000 MW, Lysine Fixable</td>
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			<td>D3328</td>
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			<td>Formaldehyde Aqueous Solution EM Grade</td>
			<td>Electron microscopy science</td>
			<td>15710</td>
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			<td>HBSS, calcium, magnesium, no phenol red</td>
			<td>ThermoFisher</td>
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			<td>HBSS, no calcium, no magnesium, no phenol red</td>
			<td>ThermoFisher</td>
			<td>14170</td>
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			<td>Image J or FIJI</td>
			<td>NIH</td>
			<td><a href="http://fiji.sc/" target="_blank">http://fiji.sc/</a></td>
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			<td>Immersol 518F oil immersion media</td>
			<td>Carl Zeiss</td>
			<td>444970-9000-000</td>
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			<td>Leibovitz&#39;s L-15 Medium, GlutaMAX Supplement</td>
			<td>ThermoFisher</td>
			<td>31415029</td>
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			<td>neomycin trisulfate salt hydrate</td>
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			<td>Phalloidin-CF405M</td>
			<td>Biotium</td>
			<td>00034</td>
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			<td>ProLong Diamond antifade mounting media</td>
			<td>ThermoFisher</td>
			<td>P36970</td>
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			<td>superfrost plus microscope slide</td>
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			<td>22-037-246</td>
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			<td>Triton X-100</td>
			<td>Sigma</td>
			<td>T8787</td>
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			<td>Zen Black 2.3 SP1 software</td>
			<td>Carl Zeiss</td>
			<td><a href="https://www.zeiss.com/microscopy/us/products/microscope-software/zen.html" target="_blank">https://www.zeiss.com/microscopy/us/products/microscope-software/zen.html</a></td>
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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.

We observed robust and specific labeling of hair cells after 2h incubation of organ of Corti explants from wild-type postnatal-day-6 (P6) mice with 3 kDa dextran fluorescently labeled with Texas Red (dextran-TR) (Figure 2A-B). Dextran labeling was observed in both inner and outer hair cells (IHC and OHC) at the basal, middle, and apical regions of the organ of Corti (Figure 2B).
Fluorescently labeled ...

Watch this Scientific Journal Video about Dextran Labeling and Uptake in Live and Functional Murine Cochlear Hair Cells at JoVE.com

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

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 ...

The overall goal of this protocol is to study the uptake of regular dextran fluorescently labeled with Texas Red in live hair cells with functional mechanotransduction channels. The main advantage of this technique is that the three kilodalton Texas Red dextran can be used to assess mechanotransduction channel function in live hair cells. To harvest the cochlea, place the skull of a postnatal day six mouse into a 60 millimeter culture dish containing Leibovitz's L-15 medium and use surgical scissors to make a superficial cut from the anterior end to the posterior end of the skull and across the external auditory canals.Fold the skin toward the nose to expose the cranium and make an incision from the back to the front of the skull and across the eye line. Separate the skull into two halves and use a small spatula to remove the brain. When the temporal bones can be observed, use small scissors to cut around these bones to excise the tissue.Submerge the temporal bones in the 35 millimeter dish containing fresh L-15 medium and place the dish under a stereo microscope equipped with a wide field eyepiece and an external alternating current halogen light source. Use forceps to remove the surrounding cochlear tissue, semi-circular canals and vestibular organs. Once the cochlea has been dissected and placed in a new dish with fresh L-15 media, use surgical forceps to make one puncture wound on the round window and one puncture at the apical cochlear region.When all of the cochleae have been harvested, place the tissue into a well of a nine-well glass depression plate containing 200 microliters of fresh L-15 medium. For dextran labeling of the isolated tissues, replace the medium from each sample well with 200 microliters of fresh L-15 medium supplemented with two milligrams per milliliter of the fluorescence conjugated dextran of interest. Incubate the samples for two hours at room temperature and 25 rotations per minute in a three-dimensional shaker at a tilted angle of 25 degrees protected from light.At the end of the incubation, wash the tissues one time with medium and one time with HBSS for two minutes per wash. After the second wash, fix the specimens in 4%paraformaldehyde for 30 minutes at room temperature followed by two quick and gentle washes in HBSS. After the second wash, use fine tip forceps to remove the cochlear bone, the spiral ligament, and the tectorial membrane and wash the isolated organ of Corti in HBSS.Take extra care when removing the transparent tectorial membrane since the tissue on the hair cells can be easily damaged during this step. To label the F-actin, permeabilize the samples in 0.5%Triton X-100 in PBS supplemented with 100 to 200 dilution of fluorescently labeled phalloidin for 30 minutes at room temperature protected from light. At the end of the incubation, wash the tissues two to three times in fresh HBSS per wash as demonstrated followed by a single wash in PBS.Use an appropriate mounting medium to mount the organ of Corti tissues onto glass microscope slides hair stereocilia sides up and image the samples on a fluorescent confocal microscope using the 63X oil immersion objective. After a two-hour incubation with three kilodalton dextran fluorescently conjugated with Texas Red, organ of Corti explant from wild type postnatal day six mice demonstrate a robust and specific labeling of both inner and outer hair cells. Imaging of the hair cell stereocilia and cell bodies reveals that only those cells that have incorporated three kilodalton dextran Texas Red in their cell body also demonstrated fluorescent labeling of their stereocilia.Importantly, a uniform fluorescent signal is observed along the stereocilia with enrichment at the tips of the shorter stereocilia rows where the mechanotransduction channel is located. Vesicle-like structures in the cell body of the hair cells and the neighboring supporting cells are also observed suggesting that dextran Texas Red can also be taken up by endocytosis. Larger 10 kilodalton dextrans also produced a vesicle-like pattern in the cell body of hair cells and supporting cells.Notably, the presence of a calcium chelator or mechanotransduction channel blockers prevents stereocilia labeling and the uptake of three kilodalton dextran Texas Red in hair cells. The vesicle-like pattern is still observed in the presence of mechanotransduction channel blockade, however, indicating that this pattern of uptake is independent of functional MET channels. It is very important to dissect the organ of Corti tissue carefully and to confirm the proper orientation of the hair cells before mounting the tissue for imaging.After dextran labeling of live and functional hair cells, immunostaining of the fixed tissue can be performed to identify specific cell types of proteins of interest.

dextran-labeling-uptake-live-functional-murine-cochlear-hair

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Bioengineering

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Induced pluripotent stem cell (iPSC)-derived myogenic progenitors are promising candidates for cell therapy strategies to treat muscular dystrophies. This protocol describes transplantation and functional measurements required to evaluate the engraftment and differentiation of iPSC-derived mesoangioblasts (a type of muscle progenitors) in mouse models of acute and chronic muscle regeneration.

Patient-derived iPSCs could be an invaluable source of cells for future autologous cell therapy protocols. iPSC-derived myogenic stem/progenitor cells ...

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Targeted cell delivery is useful in a variety of biomedical applications. The goal of this protocol is to use superparamagnetic iron oxide nanoparticles (SPION) to label cells and thereby enable magnetic cell targeting approaches for a high degree of control over cell delivery and localization.

Targeted delivery of cells and therapeutic agents would benefit a wide range of biomedical applications by concentrating the therapeutic effect at the ...

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An In Vitro Organ Culture Model of the Murine Intervertebral Disc

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Intervertebral disc (IVD) degeneration is a significant contributor to low back pain. The IVD is a fibrocartilaginous joint that serves to transmit and ...

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Imaging the Root Hair Morphology of Arabidopsis Seedlings in a Two-layer Microfluidic Platform

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The Organoid Reconstitution Assay ORA for the Functional Analysis of Intestinal Stem and Niche Cells

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Extracellular mechanical strain is known to elicit cell phenotypic responses and has physiological relevance in several tissue systems. To capture the ...

Generation and Quantitative Characterization of Functional and Polarized Biliary Epithelial Cysts

Cholangiocytes, the epithelial cells that line up the bile ducts in the liver, oversee bile formation and modification. In the last twenty years, in the context of liver diseases, 3-dimensional (3D) models based on cholangiocytes have emerged such as cysts, spheroids, or tube-like structures to mimic tissue topology for organogenesis, disease modeling, and drug screening studies. These structures have been mainly obtained by embedding cholangiocytes in a hydrogel. The main purpose was to study self-organization by addressing epithelial polarity, functional, and morphological properties. However, very few studies focus on cyst formation efficiency. When this is the case, the efficiency is often quantified from images of a single plane. Functional assays and structural analysis are performed without representing the potential heterogeneity of cyst distribution arising from hydrogel polymerization heterogeneities and side effects. Therefore, the quantitative analysis, when done, cannot be used for comparison from one article to another. Moreover, this methodology does not allow comparisons of 3D growth potential of different matrices and cell types. Additionally, there is no mention of the experimental troubleshooting for immunostaining cysts. In this article, we provide a reliable and universal method to show that the initial cell distribution is related to the heterogeneous vertical distribution of cyst formation. Cholangiocyte cells embedded in hydrogel are followed with Z-stacks analysis along the hydrogel depth over the time course of 10 days. With this method, a robust kinetics of cyst formation efficiency and growth is obtained. We also present methods to evaluate cyst polarity and secretory function. Finally, additional tips for optimizing immunostaining protocols are provided in order to limit cyst collapse for imaging. This approach can be applied to other 3D cell culture studies, thus opening the possibilities to compare one system to another.

Three-dimensional (3D) cellular systems are relevant models for investigating organogenesis. A hydrogel-based method for biliary cysts production and their characterization is proposed. This protocol unravels the barriers of 3D characterization, with a straightforward and reliable method to assess cyst formation efficiency, sizes, and to test their functionality.

Cholangiocytes, the epithelial cells that line up the bile ducts in the liver, oversee bile formation and modification. In the last twenty years, in the ...

Near Simultaneous Laser Scanning Confocal and Atomic Force Microscopy (Conpokal) on Live Cells

Techniques available for micro- and nano-scale mechanical characterization have exploded in the last few decades. From further development of the scanning and transmission electron microscope, to the invention of atomic force microscopy, and advances in fluorescent imaging, there have been substantial gains in technologies that enable the study of small materials. Conpokal is a portmanteau that combines confocal microscopy with atomic force microscopy (AFM), where a probe &#8220;pokes&#8221; the surface. Although each technique is extremely effective for the qualitative and/or quantitative image collection on their own, Conpokal provides the capability to test with blended fluorescence imaging and mechanical characterization. Designed for near simultaneous confocal imaging and atomic force probing, Conpokal facilitates experimentation on live microbiological samples. The added insight from paired instrumentation provides co-localization of measured mechanical properties (e.g., elastic modulus, adhesion, surface roughness) by AFM with subcellular components or activity observable through confocal microscopy. This work provides a step by step protocol for the operation of laser scanning confocal and atomic force microscopy, simultaneously, to achieve same cell, same region, confocal imaging, and mechanical characterization.

Near Simultaneous Laser Scanning Confocal and Atomic Force Microscopy Conpokal on Live Cells

Presented here is the protocol of the Conpokal technique, which combines confocal and atomic force microscopy into a single instrument platform. Conpokal provides same cell, same region, near simultaneous confocal imaging and mechanical characterization of live biological samples.

Techniques available for micro- and nano-scale mechanical characterization have exploded in the last few decades. From further development of the scanning ...