Name: imaging cell membrane injury and subcellular processes involved in repair
Uploaded: 2014-03-24T20:45:00
Description: Watch this Scientific Journal Video about Imaging Cell Membrane Injury and Subcellular Processes Involved in Repair at JoVE.com

This work was supported by National Institutes of Health Grants AR055686 and AR060836 and postdoctoral fellowship to AD by French Muscular Dystrophy Association (AFM). The cellular imaging facility utilized in this study is supported by National Institutes of Health Grants HD040677.

1. Imaging Cell Membrane Repair Using Bulk (Glass Bead) Wounding
This protocol allows separately marking the injured cells and those that fail to heal. Quantifying these populations of cells requires use of three conditions: 1. Test (C1) - Cells are allowed to repair in presence of Ca2+, 2. Control 1 (no injury C2) - Cells are incubated in presence of Ca2+, but not injured, and 3. Control 2 (no repair C3) - cells are allowed to repair in absence of Ca2+.
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<ol>
	<li>Bi, G. Q., Alderton, J. M., Steinhardt, R. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Calcium-regulated+exocytosis+is+required+for+cell+membrane+resealing.">Calcium-regulated exocytosis is required for cell membrane resealing.</a> Cell Biol. 131, 1747-1758 (1995).</li><li>Togo, T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Disruption+of+the+plasma+membrane+stimulates+rearrangement+of+microtubules+and+lipid+traffic+toward+the+wound+site.">Disruption of the plasma membrane stimulates rearrangement of microtubules and lipid traffic toward the wound site.</a> Cell Sci. 119, 2780-2786 (2006).</li><li>Miyake, K., McNeil, P. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Vesicle+accumulation+and+exocytosis+at+sites+of+plasma+membrane+disruption.">Vesicle accumulation and exocytosis at sites of plasma membrane disruption.</a> Cell Biol. 131, 1737-1745 (1995).</li><li>Reddy, A., Caler, E. V., Andrews, N. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasma+membrane+repair+is+mediated+by+Ca2+-regulated+exocytosis+of+lysosomes.">Plasma membrane repair is mediated by Ca2+-regulated exocytosis of lysosomes.</a> Cell. 106, 157-169 (2001).</li><li>Babiychuk, E. B., Monastyrskaya, K., Potez, S., Draeger, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Blebbing+confers+resistance+against+cell+lysis.">Blebbing confers resistance against cell lysis.</a> Death Differ. 18, 80-89 .</li><li>Bansal, 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=Defective+membrane+repair+in+dysferlin-deficient+muscular+dystrophy.">Defective membrane repair in dysferlin-deficient muscular dystrophy.</a> Nature. 423, 168-172 (2003).</li><li>Abreu-Blanco, M. T., Verboon, J. M., Parkhurst, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+wound+repair+in+Drosophila+occurs+through+three+distinct+phases+of+membrane+and+cytoskeletal+remodeling.">Cell wound repair in Drosophila occurs through three distinct phases of membrane and cytoskeletal remodeling.</a> Cell Biol. 193, 455-464 (2011).</li><li>Jaiswal, J. K., Chakrabarti, S., Andrews, N. W., Simon, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synaptotagmin+VII+restricts+fusion+pore+expansion+during+lysosomal+exocytosis.">Synaptotagmin VII restricts fusion pore expansion during lysosomal exocytosis.</a> PLoS Biol. 2, 1224-1232 (2004).</li><li>McNeil, P. L., Clarke, M. F., Miyake, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Cell+wound+assays.">Cell wound assays.</a> Protoc. Cell Biol. Chapter 12, (2001).</li><li>McNeil, P. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Direct+introduction+of+molecules+into+cells.">Direct introduction of molecules into cells.</a> Protoc. Cell Biol. Chapter 20, (2001).</li><li>Knight, M. M., Roberts, S. R., Lee, D. A., Bader, D. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Live+cell+imaging+using+confocal+microscopy+induces+intracellular+calcium+transients+and+cell+death.">Live cell imaging using confocal microscopy induces intracellular calcium transients and cell death.</a> J. Physiol. Cell Physiol. 284, C1083-C1089 (2003).</li><li>McNeil, P. L., Miyake, K., Vogel, S. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+endomembrane+requirement+for+cell+surface+repair.">The endomembrane requirement for cell surface repair.</a> Proc. Natl. Acad. Sci. U.S.A. 100, 4592-4597 (2003).</li><li>Benink, H. A., Bement, W. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concentric+zones+of+active+RhoA+and+Cdc42+around+single+cell+wounds.">Concentric zones of active RhoA and Cdc42 around single cell wounds.</a> Cell Biol. 168, 429-439 (2005).</li><li>Schmoranzer, J., Goulian, M., Axelrod, D., Simon, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+constitutive+exocytosis+with+total+internal+reflection+fluorescence+microscopy.">Imaging constitutive exocytosis with total internal reflection fluorescence microscopy.</a> Cell Biol. 149, 23-32 (2000).</li><li>Steyer, J. A., Horstmann, H., Transport Almers, W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=docking+and+exocytosis+of+single+secretory+granules+in+live+chromaffin+cells.">docking and exocytosis of single secretory granules in live chromaffin cells.</a> 388, 474-478 (1997).</li><li>Jaiswal, J. K., Andrews, N. W., Simon, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Membrane+proximal+lysosomes+are+the+major+vesicles+responsible+for+calcium-dependent+exocytosis+in+nonsecretory+cells.">Membrane proximal lysosomes are the major vesicles responsible for calcium-dependent exocytosis in nonsecretory cells.</a> Cell Biol. 159, 625-635 (2002).</li><li>Jaiswal, J. K., Simon, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ch.+4.12.">Ch. 4.12.</a> Current Protocols in Cell Biology. , 4.12.1-4.12.15 (2003).</li><li>Johnson, D. S., Jaiswal, J. K., Simon, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Total+internal+reflection+fluorescence+(TIRF)+microscopy+illuminator+for+improved+imaging+of+cell+surface+events.">Total internal reflection fluorescence (TIRF) microscopy illuminator for improved imaging of cell surface events.</a> Protoc. Cytom. Chapter 12, (2012).</li><li>Jaiswal, J. K., Simon, S. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+single+events+at+the+cell+membrane.">Imaging single events at the cell membrane.</a> Chem. Biol. 3, 92-98 (2007).</li></ol>

Cell membrane injury in vivo occurs due to a variety of physiological stressors and several experimental approaches have been developed to mimic these. These include injuring cell membrane of adherent cells by scraping them off the dish or by passaging through a narrow bore syringe9,10. Following such injuries the cells heal in suspension and not adhered to the extracellular matrix as they normally do in the tissue. Still others, such as use of pore forming toxins chemically alter cell membrane by ext...

Cell membrane maintains the integrity of cells by providing a barrier between the cell and the extracellular environment. A chemical, electrical, or mechanical stimulus that exceeds the normal physiological threshold as well as the presence of invading pathogens can each result in injury to the cell membrane and trigger a subsequent cellular response to repair this injury. To survive these injuries to the cell membrane, cells possess an efficient mechanism for repair. This mechanism is calcium dependent and involves intracellular trafficking of proteins such as annexins and MG53 amongst others as well as subcellular compartments such as endosomes, lysosomes, Golgi derived vesicles and mitochondria to the injured cell membrane1-7. However, the details of the sequence of molecular and subcellular events involved in repairing damaged cell membrane remains poorly understood.
Cell&#39;s repair response can be segregated into early and late responses. Early responses, which occur within seconds to minutes time scale, are tremendously important in determining the nature of late responses leading to successful cell repair or cell death. End point assays based on bulk biochemical and cellular analysis have helped establish the involvement of molecular and cellular processes in repair. But, due to the heterogeneity and rapidity of cellular repair response, end point assays fail to provide the kinetic and spatial details of the sequence of events leading to repair. Approaches that enable controlled injury of cell membrane and allow monitoring the cell membrane repair and associated subcellular responses at high spatial and temporal resolution are ideally suited for such studies. Here, such approaches have been presented. Two of the protocols describe approaches to monitor the real time kinetics of cell membrane repair and the subcellular responses associated with the repair process in live cells following laser injury. As a complement to these live cell imaging based assays, end point assays have also been described that provide a population based measure for monitoring repair of individual cells and the associated subcellular responses. To demonstrate their utility these approaches have been used to monitor trafficking and exocytosis of lysosomes in response to cell membrane injury.

<table border="0" cellpadding="0" cellspacing="0" width="814" fo:keep-together.within-page="always">
	<tbody>
		<tr>
			<td>HBSS</td>
			<td>Sigma</td>
			<td>H1387</td>
			<td>Used to prepare CIM (HBSS/10 mM Hepes/2 mM Ca2+ pH 7.4)</td>
		</tr>
		<tr>
			<td>HEPES</td>
			<td>Fisher</td>
			<td>BP410</td>
			<td>Used to prepare CIM (HBSS/10 mM Hepes/2 mM Ca2+ pH 7.4)</td>
		</tr>
		<tr>
			<td>FITC dextran (Lysine fixable)</td>
			<td>Invitrogen</td>
			<td>D1820</td>
			<td>2 mg/ml in CIM or PBS</td>
		</tr>
		<tr>
			<td>Glass beads</td>
			<td>Sigma</td>
			<td>G8772</td>
			<td></td>
		</tr>
		<tr>
			<td>TRITC dextran (Lysine fixable)</td>
			<td>Invitrogen</td>
			<td>D1818</td>
			<td>2 mg/ml in CIM or PBS</td>
		</tr>
		<tr>
			<td>PFA 16%</td>
			<td>EMS</td>
			<td>15710</td>
			<td>4% in PBS</td>
		</tr>
		<tr>
			<td>Hoechst</td>
			<td>Invitrogen</td>
			<td>H3570</td>
			<td>1/10 000 in PBS</td>
		</tr>
		<tr>
			<td>FM dye</td>
			<td>Invitrogen</td>
			<td>T3163</td>
			<td>1 &#181;g/&#181;l in CIM or PBS</td>
		</tr>
		<tr>
			<td>FITC dextran</td>
			<td>Sigma</td>
			<td>FD40S</td>
			<td>2 mg/ml in growth medium</td>
		</tr>
		<tr>
			<td>LAMP1&#160;</td>
			<td>Santa Cruz</td>
			<td>sc-19992</td>
			<td>1/300 in growth medium</td>
		</tr>
		<tr>
			<td>Alexa Fluor 488 chicken anti-rat IgG</td>
			<td>Invitrogen</td>
			<td>A21470</td>
			<td>1/500 in blocking solution</td>
		</tr>
		<tr>
			<td>Mounting media</td>
			<td>Dako</td>
			<td>S3023</td>
			<td></td>
		</tr>
		<tr>
			<td>Coverslips</td>
			<td>Fisher</td>
			<td>12-545-86</td>
			<td></td>
		</tr>
		<tr>
			<td>Glass bottom petridish</td>
			<td>MatTek corporation</td>
			<td>P35G-1.0-14-C</td>
			<td></td>
		</tr>
		<tr>
			<td>Silicone O ring</td>
			<td>Bellco</td>
			<td>1943-33315</td>
			<td></td>
		</tr>
		<tr>
			<td>Coverslip holder</td>
			<td>Bellco</td>
			<td>1943-11111</td>
			<td></td>
		</tr>
		<tr>
			<td>Invitrogen</td>
			<td>A-7816</td>
			<td></td>
		</tr>
		<tr>
			<td>DMEM</td>
			<td>VWR</td>
			<td>12001-566</td>
			<td></td>
		</tr>
		<tr>
			<td>FBS</td>
			<td>VWR</td>
			<td>MP1400-500H</td>
			<td>Used for growth medium: 10% FBS, 1% P/S in DMEM</td>
		</tr>
		<tr>
			<td>Penicillin/Sreptomycin</td>
			<td>VWR</td>
			<td>12001-350</td>
			<td>Used for growth medium: 10% FBS, 1% P/S in DMEM</td>
		</tr>
		<tr>
			<td>Chicken serum</td>
			<td>Sigma</td>
			<td>C5405</td>
			<td>5% chicken serum in CIM is used for blocking solution during immunostaining</td>
		</tr>
		<tr>
			<td>PBS (Ca2+ and Mg2+ free)</td>
			<td>VWR</td>
			<td>12001-664</td>
			<td></td>
		</tr>
		<tr>
			<td>Epifluorescence microscope</td>
			<td>Olympus America, PA</td>
			<td>IX81</td>
			<td></td>
		</tr>
		<tr>
			<td>TIRF illuminator&#160;</td>
			<td>Olympus America, PA</td>
			<td>Cell^TIRF (IEC60825-1:2007)</td>
			<td></td>
		</tr>
		<tr>
			<td>Epifluorescence illuminator</td>
			<td>Sutter Instruments, Novato CA</td>
			<td>Lambda DG-4 (DG-4 30)</td>
			<td></td>
		</tr>
		<tr>
			<td>CCD Camera</td>
			<td>Photometrics, Tucson, AZ</td>
			<td>Evolve 512 EMCCD&#160;</td>
			<td></td>
		</tr>
		<tr>
			<td>Image acquisition and anaysis software</td>
			<td>Intelligent Imaging Innovations, Inc. Denver, CO</td>
			<td>Slidebook 5</td>
			<td></td>
		</tr>
		<tr>
			<td>Pulsed laser</td>
			<td>Intelligent Imaging Innovations, Inc. Denver, CO</td>
			<td>Ablate (3iL13)</td>
			<td></td>
		</tr>
		<tr>
			<td>Stage top incubator</td>
			<td>Tokaihit, Japan</td>
			<td>INUBG2ASFP-ZILCS</td>
			<td></td>
		</tr>
	</tbody>
</table>

imaging cell membrane injury and subcellular processes involved in repair

The ability of injured cells to heal is a fundamental cellular process, but cellular and molecular mechanisms involved in healing injured cells are poorly understood. Here assays are described to monitor the ability and kinetics of healing of cultured cells following localized injury. The first protocol describes an end point based approach to simultaneously assess cell membrane repair ability of hundreds of cells. The second protocol describes a real time imaging approach to monitor the kinetics of cell membrane repair in individual cells following localized injury with a pulsed laser. As healing injured cells involves trafficking of specific proteins and subcellular compartments to the site of injury, the third protocol describes the use of above end point based approach to assess one such trafficking event (lysosomal exocytosis) in hundreds of cells injured simultaneously and the last protocol describes the use of pulsed laser injury together with TIRF microscopy to monitor the dynamics of individual subcellular compartments in injured cells at high spatial and temporal resolution. While the protocols here describe the use of these approaches to study the link between cell membrane repair and lysosomal exocytosis in cultured muscle cells, they can be applied as such for any other adherent cultured cell and subcellular compartment of choice.

Protocols described here for single cell imaging are to monitor the ability and kinetics of cell membrane repair (Protocols 1 and 2) and the subcellular trafficking and fusion of lysosomes during repair (Protocols 3 and 4).
Protocol 1 shows a bulk assay that allows marking all injured cells and identifying those injured cells that failed to repair. The results in Figure 1 show that while the uninjured cells (Figure 1A) remain unlabeled, cells injured by glass ...

Watch this Scientific Journal Video about Imaging Cell Membrane Injury and Subcellular Processes Involved in Repair at JoVE.com

Imaging Cell Membrane Injury and Subcellular Processes Involved in Repair

The process of healing injured cells involves trafficking of specific proteins and subcellular compartments to the site of cell membrane injury. This protocol describes assays to monitor these processes.

The ability of injured cells to heal is a fundamental cellular process, but cellular and molecular mechanisms involved in healing injured cells are poorly ...

imaging-cell-membrane-injury-subcellular-processes-involved

Research

JoVE Journal

Biology

Visualization of MG53-mediated Cell Membrane Repair Using in vivo and in vitro Systems

Repair of acute injury to the cell membrane is an elemental process of normal cellular physiology, and defective membrane repair has been linked to many degenerative human diseases. The recent discovery of MG53 as a key component of the membrane resealing machinery allows for a better molecular understanding of the basic biology of tissue repair, as well as for potential translational applications in regenerative medicine. Here we detail the experimental protocols for exploring the in vivo function of MG53 in repair of muscle injury using treadmill exercise protocols on mouse models, for testing the ex vivo membrane repair capacity by measuring dye entry into isolated muscle fibers, and for monitoring the dynamic process of MG53-mediated vesicle trafficking and cell membrane repair in cultured cells using live cell confocal microscopy.

Visualization of MG53-mediated Cell Membrane Repair Using in vivo and in vitro Systems

Described here are protocols used to visualize the dynamic process of MG53-mediated cell membrane repair in whole animals and at the cellular level. These methods can be applied to investigate the cell biology of plasma membrane resealing and regenerative medicine.

Repair of acute injury to the cell membrane is an elemental process of normal cellular physiology, and defective membrane repair has been linked to many ...

Rat Mesentery Exteriorization: A Model for Investigating the Cellular Dynamics Involved in Angiogenesis

Microvacular network growth and remodeling are critical aspects of wound healing, inflammation, diabetic retinopathy, tumor growth and other disease conditions1, 2. Network growth is commonly attributed to angiogenesis, defined as the growth of new vessels from pre-existing vessels. The angiogenic process is also directly linked to arteriogenesis, defined as the capillary acquisition of a perivascular cell coating and vessel enlargement. Needless to say, angiogenesis is complex and involves multiple players at the cellular and molecular level3. Understanding how a microvascular network grows requires identifying the spatial and temporal dynamics along the hierarchy of a network over the time course of angiogenesis. This information is critical for the development of therapies aimed at manipulating vessel growth.
The exteriorization model described in this article represents a simple, reproducible model for stimulating angiogenesis in the rat mesentery. It was adapted from wound-healing models in the rat mesentery4-7, and is an alternative to stimulate angiogenesis in the mesentery via i.p. injections of pro-angiogenic agents8, 9. The exteriorization model is attractive because it requires minimal surgical intervention and produces dramatic, reproducible increases in capillary sprouts, vascular area and vascular density over a relatively short time course in a tissue that allows for the two-dimensional visualization of entire microvascular networks down to single cell level. The stimulated growth reflects natural angiogenic responses in a physiological environment without interference of foreign angiogenic molecules. Using immunohistochemical labeling methods, this model has been proven extremely useful in identifying novel cellular events involved in angiogenesis. Investigators can readily correlate the angiogenic metrics during the time course of remodeling with time specific dynamics, such as cellular phenotypic changes or cellular interactions4, 5, 7, 10, 11.

This article describes a simple model for stimulating angiogenesis in the rat mesentery. The model produces dramatic increases in capillary sprouting, vascular area and vascular density over a relatively short time course in a tissue that allows en face visualization of entire microvascular networks down to the single cell level.

Microvacular network growth and remodeling are critical aspects of wound healing, inflammation, diabetic retinopathy, tumor growth and other disease ...

Live Imaging Assay for Assessing the Roles of Ca2+ and Sphingomyelinase in the Repair of Pore-forming Toxin Wounds

Plasma membrane injury is a frequent event, and wounds have to be rapidly repaired to ensure cellular survival. Influx of Ca2+ is a key signaling event that triggers the repair of mechanical wounds on the plasma membrane within ~30 sec. Recent studies revealed that mammalian cells also reseal their plasma membrane after permeabilization with pore forming toxins in a Ca2+-dependent process that involves exocytosis of the lysosomal enzyme acid sphingomyelinase followed by pore endocytosis. Here, we describe the methodology used to demonstrate that the resealing of cells permeabilized by the toxin streptolysin O is also rapid and dependent on Ca2+ influx. The assay design allows synchronization of the injury event and a precise kinetic measurement of the ability of cells to restore plasma membrane integrity by imaging and quantifying the extent by which the liphophilic dye FM1-43 reaches intracellular membranes. This live assay also allows a sensitive assessment of the ability of exogenously added soluble factors such as sphingomyelinase to inhibit FM1-43 influx, reflecting the ability of cells to repair their plasma membrane. This assay allowed us to show for the first time that sphingomyelinase acts downstream of Ca2+-dependent exocytosis, since extracellular addition of the enzyme promotes resealing of cells permeabilized in the absence of Ca2+.

Live Imaging Assay for Assessing the Roles of Ca2+ and Sphingomyelinase in the Repair of Pore-forming Toxin Wounds

Live imaging of cells exposed to the lipophilic dye FM1-43 allows precise determination of the kinetics by which pore-forming toxins are removed from the plasma membrane. This is a sensitive assay that can be used to assess requirements for Ca2+, sphingomyelinase and other factors on plasma membrane repair.

Plasma membrane injury is a frequent event, and wounds have to be rapidly repaired to ensure cellular survival. Influx of Ca2+ is a key signaling event ...

Intravital Microscopy for Imaging Subcellular Structures in Live Mice Expressing Fluorescent Proteins

Here we describe a procedure to image subcellular structures in live rodents that is based on the use of confocal intravital microscopy. As a model organ, we use the salivary glands of live mice since they provide several advantages. First, they can be easily exposed to enable access to the optics, and stabilized to facilitate the reduction of the motion artifacts due to heartbeat and respiration. This significantly facilitates imaging and tracking small subcellular structures. Second, most of the cell populations of the salivary glands are accessible from the surface of the organ. This permits the use of confocal microscopy that has a higher spatial resolution than other techniques that have been used for in vivo imaging, such as two-photon microscopy. Finally, salivary glands can be easily manipulated pharmacologically and genetically, thus providing a robust system to investigate biological processes at a molecular level.
In this study we focus on a protocol designed to follow the kinetics of the exocytosis of secretory granules in acinar cells and the dynamics of the apical plasma membrane where the secretory granules fuse upon stimulation of the beta-adrenergic receptors. Specifically, we used a transgenic mouse that co-expresses cytosolic GFP and a membrane-targeted peptide fused with the fluorescent protein tandem-Tomato. However, the procedures that we used to stabilize and image the salivary glands can be extended to other mouse models and coupled to other approaches to label in vivo cellular components, enabling the visualization of various subcellular structures, such as endosomes, lysosomes, mitochondria, and the actin cytoskeleton.

Intravital microscopy is a powerful tool that enables imaging various biological processes in live animals. In this article, we present a detailed method for imaging the dynamics of subcellular structures, such as the secretory granules, in the salivary glands of live mice.

Here we describe a procedure to image subcellular structures in live rodents that is based on the use of confocal intravital microscopy. As a model organ, ...

Ground State Depletion Super-resolution Imaging in Mammalian Cells

Advances in fluorescent microscopy and cell biology are intimately correlated, with the enhanced ability to visualize cellular events often leading to dramatic leaps in our understanding of how cells function. The development and availability of super-resolution microscopy has considerably extended the limits of optical resolution from ~250-20 nm. Biologists are no longer limited to describing molecular interactions in terms of colocalization within a diffraction limited area, rather it is now possible to visualize the dynamic interactions of individual molecules. Here, we outline a protocol for the visualization and quantification of cellular proteins by ground-state depletion microscopy&#160;for fixed cell imaging. We provide examples from two different membrane proteins, an element of the endoplasmic reticulum translocon, sec61&#946;, and a plasma membrane-localized voltage-gated L-type Ca2+ channel (CaV1.2). Discussed are the specific microscope parameters, fixation methods, photo-switching buffer formulation, and pitfalls and challenges of image processing.

This article outlines a protocol for the detection of one or more plasma and/or intracellular membrane proteins using Ground State Depletion (GSD) super-resolution microscopy in mammalian cells. Here, we discuss the benefits and considerations of using such approaches for the visualization and quantification of cellular proteins.

Advances in fluorescent microscopy and cell biology are intimately correlated, with the enhanced ability to visualize cellular events often leading to ...

Super-Resolution Live Cell Imaging of Subcellular Structures

There has long been a crucial tradeoff between spatial and temporal resolution in imaging. Imaging beyond the diffraction limit of light has traditionally been restricted to be used only on fixed samples or live cells outside of tissue labeled with strong fluorescent signal. Current super-resolution live cell imaging techniques require the use of special fluorescence probes, high illumination, multiple image acquisitions with post-acquisition processing, or often a combination of these processes. These prerequisites significantly limit the biological samples and contexts that this technique can be applied to.
Here we describe a method to perform super-resolution (~140 nm XY-resolution) time-lapse fluorescence live cell imaging in situ. This technique is also compatible with low fluorescent intensity, for example, EGFP or mCherry endogenously tagged at lowly expressed genes. As a proof-of-principle, we have used this method to visualize multiple subcellular structures in the Drosophila testis. During tissue preparation, both the cellular structure and tissue morphology are maintained within the dissected testis. Here, we use this technique to image microtubule dynamics, the interactions between microtubules and the nuclear membrane, as well as the attachment of microtubules to centromeres.
This technique requires special procedures in sample preparation, sample mounting and immobilizing of specimens. Additionally, the specimens must be maintained for several hours after dissection without compromising cellular function and activity. While we have optimized the conditions for live super-resolution imaging specifically in Drosophila male germline stem cells (GSCs) and progenitor germ cells in dissected testis tissue, this technique is broadly applicable to a variety of different cell types. The ability to observe cells under their physiological conditions without sacrificing either spatial or temporal resolution will serve as an invaluable tool to researchers seeking to address crucial questions in cell biology.

Presented here is a protocol for super-resolution live-cell imaging in intact tissue. We have standardized the conditions for imaging a highly sensitive adult stem cell population in its native tissue environment. This technique involves balancing temporal and spatial resolution to allow for the direct observation of biological phenomena in live tissue.

There has long been a crucial tradeoff between spatial and temporal resolution in imaging. Imaging beyond the diffraction limit of light has traditionally ...

Photodiode-Based Optical Imaging for Recording Network Dynamics with Single-Neuron Resolution in Non-Transgenic Invertebrates

The development of transgenic invertebrate preparations in which the activity of specifiable sets of neurons can be recorded and manipulated with light represents a revolutionary advance for studies of the neural basis of behavior. However, a downside of this development is its tendency to focus investigators on a very small number of &#8220;designer&#8221; organisms (e.g., C. elegans and Drosophila), potentially negatively impacting the pursuit of comparative studies across many species, which is needed for identifying general principles of network function. The present article illustrates how optical recording with voltage-sensitive dyes in the brains of non-transgenic gastropod species can be used to rapidly (i.e., within the time course of single experiments) reveal features of the functional organization of their neural networks with single-cell resolution. We outline in detail the dissection, staining, and recording methods used by our laboratory to obtain action potential traces from dozens to ~150 neurons during behaviorally relevant motor programs in the CNS of multiple gastropod species, including one new to neuroscience &#8211; the nudibranch Berghia stephanieae. Imaging is performed with absorbance voltage-sensitive dyes and a 464-element photodiode array that samples at 1,600 frames/second, fast enough to capture all action potentials generated by the recorded neurons. Multiple several-minute recordings can be obtained per preparation with little to no signal bleaching or phototoxicity. The raw optical data collected through the methods described can subsequently be analyzed through a variety of illustrated methods. Our optical recording approach can be readily used to probe network activity in a variety of non-transgenic species, making it well suited for comparative studies of how brains generate behavior.

This protocol presents a method for imaging neuronal population activity with single-cell resolution in non-transgenic invertebrate species using absorbance voltage-sensitive dyes and a photodiode array. This approach enables a rapid workflow, wherein imaging and analysis can be pursued over the course of a single day.

The development of transgenic invertebrate preparations in which the activity of specifiable sets of neurons can be recorded and manipulated with light ...

Isolating and Imaging Live, Intact Pacemaker Regions of Mouse Renal Pelvis by Vibratome Sectioning

The renal pelvis (RP) is a funnel-shaped, smooth muscle structure that facilitates normal urine transport from the kidney to the ureter by regular, propulsive contractions. Regular RP contractions rely on pacemaker activity, which originates from the most proximal region of the RP at the pelvis-kidney junction (PKJ). Due to the difficulty in accessing and preserving intact preparations of the PKJ, most investigations on RP pacemaking have focused on single-cell electrophysiology and Ca2+ imaging experiments. Although important revelations on RP pacemaking have emerged from such work, these experiments have several intrinsic limitations, including the inability to accurately determine cellular identity in mixed suspensions and the lack of in situ imaging of RP pacemaker activity. These factors have resulted in a limited understanding of the mechanisms that underlie normal rhythmic RP contractions. In this paper, a protocol is described to prepare intact segments of mouse PKJ using a vibratome sectioning technique. By combining this approach with mice expressing cell-specific reporters and genetically encoded Ca2+ indicators, investigators may be able to more accurately study the specific cell types and mechanisms responsible for peristaltic RP contractions that are vital for normal urine transport.

The goal of this protocol is to isolate intact pacemaker regions of the mouse renal pelvis using vibratome sectioning. These sections can then be used for in situ Ca2+ imaging to elucidate Ca2+ transient properties of pacemaker cells and other interstitial cells in vibratome slices.

The renal pelvis (RP) is a funnel-shaped, smooth muscle structure that facilitates normal urine transport from the kidney to the ureter by regular, ...

Isolation of Cardiac and Vascular Smooth Muscle Cells from Adult, Juvenile, Larval and Embryonic Zebrafish for Electrophysiological Studies

Zebrafish have long been used as a model vertebrate organism in cardiovascular research. The technical difficulties of isolating individual cells from the zebrafish cardiovascular tissues have been limiting in studying their electrophysiological properties. Previous methods have been described for dissection of zebrafish hearts and isolation of ventricular cardiac myocytes. However, the isolation of zebrafish atrial and vascular myocytes for electrophysiological characterization was not detailed. This work describes new and modified enzymatic protocols that routinely provide isolated juvenile and adult zebrafish ventricular and atrial cardiomyocytes, as well as vascular smooth muscle (VSM) cells from the bulbous arteriosus, suitable for patch-clamp experiments. There has been no literary evidence of electrophysiological studies on zebrafish cardiovascular tissues isolated at embryonic and larval stages of development. Partial dissociation techniques that allow patch-clamp experiments on individual cells from larval and embryonic hearts are demonstrated.

The present protocol describes the acute isolation of viable cardiac and vascular smooth muscle cells from adult, juvenile, larval, and embryonic zebrafish (Danio rerio), suitable for electrophysiological studies.

Zebrafish have long been used as a model vertebrate organism in cardiovascular research. The technical difficulties of isolating individual cells from the ...

Imaging Neutrophil Migration in the Mouse Skin to Investigate Subcellular Membrane Remodeling Under Physiological Conditions

The study of immune cell recruitment and function in tissues has been a very active field over the last two decades. Neutrophils are among the first immune cells to reach the site of inflammation and to participate in the innate immune response during infection or tissue damage. So far, neutrophil migration has been successfully visualized using various in vitro experimental systems based on uniform stimulation, or confined migration under agarose, or micro-fluidic channels. However, these models do not recapitulate the complex microenvironment that neutrophils encounter in vivo. The development of multiphoton microscopy (MPM)-based techniques, such as intravital subcellular microscopy (ISMic), offer a unique tool to visualize and investigate neutrophil dynamics at subcellular resolutions under physiological conditions. In particular, the ear of a live anesthetized mouse provides an experimental advantage to follow neutrophil interstitial migration in real-time due to its ease of accessibility and lack of surgical exposure. ISMic provides the optical resolution, speed, and depth of acquisition necessary to track both cellular and, more importantly, subcellular processes in 3D over time (4D). Moreover, multi-modal imaging of the interstitial microenvironment (i.e., blood vessels, resident cells, extracellular matrix) can be readily accomplished using a combination of transgenic mice expressing select fluorescent markers, exogenous labeling via fluorescent probes, tissue intrinsic fluorescence, and second/third harmonic generated signals. This protocol describes 1) the preparation of neutrophils for adoptive transfer into the mouse ear, 2) different settings for optimal sub-cellular imaging, 3) strategies to minimize motion artifacts while maintaining a physiological response, 4) examples of membrane remodeling observed in neutrophils using ISMic, and 5) a workflow for the quantitative analysis of membrane remodeling in migrating neutrophils in vivo.

Neutrophil migration relies on the rapid and continuous remodeling of the plasma membrane in response to chemoattractant and its interactions with the extracellular microenvironment. Described herein is a procedure based on Intravital Subcellular Microscopy to investigate the dynamic of membrane remodeling in neutrophils injected in the ear of anesthetized mice.

The study of immune cell recruitment and function in tissues has been a very active field over the last two decades. Neutrophils are among the first ...