Name: cell membrane repair assay using a two-photon laser microscope
Uploaded: 2018-01-02T15:00:00
Description: Watch this Scientific Journal Video about Cell Membrane Repair Assay Using a Two-photon Laser Microscope at JoVE.com

This work was supported by University of Alberta Faculty of Medicine and Dentistry, The Friends of Garrett Cumming Research Chair Fund, HM Toupin Neurological Science Research Chair Fund, Muscular Dystrophy Canada, Canada Foundation for Innovation (CFI), Alberta Advanced Education and Technology (AET), Canadian Institutes of Health Research (CIHR), Jesse's Journey - The Foundation for Gene and Cell Therapy, the Women and Children's Health Research Institute (WCHRI), and Alberta Innovates Health Solutions (AIHS).
We would like to thank Dr. Steven Laval for supplying us with the full-length dysferlin plasmid. We would also like to thank Dr. Katsuya Miyake for technical advice.

Human fibroblast cells used in this study were used with approval from the Human Ethics Committee of the Faculty of Medicine and Dentistry at the University of Alberta.
1. Transfection of cells with full-length DYSF plasmid
<ol>
	<li>Culture fibroblast cells in a T225 flask containing 40 mL of growth media - 36 mL Dulbecco&#39;s Modified Eagle Medium (DMEM), 4 mL of fetal bovine serum (FBS), and 20 &#181;L of penicillin/streptomycin (P/S) - in a CO2 incubator at 37&#176;C. 
	...

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Two-photon laser wounding of the cell membrane is a precise and versatile technique for assessing the dynamics of membrane resealing in vitro. In this article, we described a protocol for determining cell membrane resealing ability in dysferlinopathy patient cells using the two-photon laser wounding assay. Our results show that dysferlinopathy patient cells are defective in cell membrane resealing, which is consistent with findings by other researchers and which further highlights the striking similarities in ce...

The cell membrane of eukaryotic cells consists of a double-layer of protein-studded phospholipids which defines the intra/extracellular environment of the cell and is essential for maintaining cellular homeostasis and cell survival. Cell membrane injuries arising from mechanical or chemical insults are commonplace in various mammalian cell types, including skeletal and cardiac muscle, stomach, and lung cells1,2,3,4. In addition to injuries consequent to daily physiological function, cell membranes can also be damaged by environmental insults, bacterial toxins, and ischemic reperfusion5. Failure to reseal ruptures in the cell membrane leads to an unregulated influx of extracellular Ca2+- along with other potentially toxic extracellular components - into the cell, triggering downstream signal cascades which can quickly result in cell death1,4,5,6.
To date, there have been several proposed models for membrane repair in cells. Different repair mechanisms may be activated depending on the size and nature of the membrane rupture. For example, it is suggested that cell membranes may utilize lateral flow or protein clogging to repair small disruptions (&#60;1 nm). The lateral fusion model proposes that membrane ruptures are rapidly mended through lateral recruitment of dysferlin-containing membrane7, while the protein clogging model suggests that small perforations are mended through protein aggregations (mostly annexins)8. Conversely, larger membrane lesions trigger Ca2+-dependent, dysferlin-mediated vesicle fusion and formation of a repair patch. In the repair patch model, a rapid Ca2+ influx into the cell triggers the recruitment of multiple proteins (dysferlin, annexins, mitsugumin-53, and EDH proteins) which form a complex or &#34;patch&#34;, along with a fusion of intracellular vesicles or lysosomes at the site of membrane damage4,9,10,11,12. It is important to note that these models are not necessarily mutually exclusive and may work in concert to facilitate membrane repair. Failure to properly reseal cell membrane damage is associated with multiple disease states, including muscular dystrophy (dysferlinopathy - including Miyoshi myopathy, limb-girdle muscular dystrophy type IIB, and distal myopathy with anterior tibial onset)13, cardiomyopathy14, and Chediak-Higashi syndrome (CHS)15.
Given that proper cell membrane integrity and resealing plays such an important role in health and disease, a deeper understanding of the underlying molecular mechanisms of cell membrane repair would be beneficial in the search for novel therapeutic strategies. It is, therefore, necessary to possess appropriate experimental techniques to&#160;monitor the kinetics and evaluate the ability of cell membrane repair. Several in vitro methods for modeling membrane repair have been designed. One strategy involves mechanical injury, which can be facilitated through cell scraping with a pipette/surgical blade/razor or by rolling glass beads over the cells16. However, this type of mechanical injury generates larger lesions, and creates a high degree of variation in cell injury, both within and between cultures.
Another method of generating membrane wounds is laser ablation by two-photon microscopy. In contrast to traditional laser confocal microscopy that employs single photon excitation, the two-photon laser simultaneously uses two long-wavelength, low-energy photons to facilitate the excitation of a high-energy electron17. This non-linear process results in excitation exclusively within the focal plane and not along the entire light path17 (Figure 1). This reduced excitation volume helps to minimize photodamage when imaging live cells18,19. Researchers are therefore able to generate precise lesions in the cell membrane and monitor membrane resealing in real time by using fluorescent dyes and observing changes in the fluorescence intensity as the cell membrane ruptures and then reseals.
This approach has been used repeatedly to study membrane wounding in vitro and in vivo and in multiple cell types20,21. For example, membrane repair defects in fibroblasts and myotubes derived from dysferlinopathy patients were assessed using this technique22,23. Also, single muscle fibers isolated from mice were used to monitor repair patch formation13,24,25. The movement of fluorescently tagged proteins can also be observed during membrane repair in single muscle fibers9. Furthermore, the process of sarcolemmal repair following two-photon laser wounding in zebrafish embryos can be observed in real-time in vivo26.
In this article, we outline a methodology for assessing cell membrane repair dynamics in fibroblasts using two-photon laser wounding, although this methodology can be applied to various cell types for the purpose of quantifying plasma membrane resealing ability in vitro. In this method, cells are incubated with FM4-64, a lipophilic, cell-impermeable dye which quickly fluoresces as it binds to negatively charged phospholipids within the cytoplasm upon entering the cell through the membrane lesion (Figure 2&#38;3). Quantification of dye fluorescence adjacent to the membrane lesion allows for monitoring the time that it takes for the cell membrane to reseal itself. To exemplify the utility of this method, we use dysferlinopathy patient fibroblasts transfected with GFP-conjugated full-length dysferlin (DYSF) plasmids to assess the rescue of cell membrane repair.

<table border="0" cellpadding="0" cellspacing="0" width="600">
	<tbody>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Dulbecco&#39;s Modified Eagle Medium (DMEM)</td>
			<td style="width:71px;">Thermo Fisher</td>
			<td style="width:119px;">11320033</td>
			<td style="width:167px;"></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Fetal Bovine Serum</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">F1051</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Penicillin-Streptomycin (10,000 U/mL)</td>
			<td style="width:71px;">Thermo Fisher</td>
			<td style="width:119px;">15140122</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Trypsin-EDTA (0.05%), phenol red</td>
			<td style="width:71px;">Thermo Fisher</td>
			<td style="width:119px;">25300062</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Dulbecco&#8217;s Phosphate Buffered Saline</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">D8537</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">35mm collagen-coated glass-bottom dishes</td>
			<td style="width:71px;">MatTek</td>
			<td style="width:119px;">P53GCOL-1.5-14-C</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Serum-deprived media</td>
			<td style="width:71px;">Thermo Fisher</td>
			<td style="width:119px;">31985070</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Transfection reagent</td>
			<td style="width:71px;">Thermo Fisher</td>
			<td style="width:119px;">15338100</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">FM 4-64 Dye</td>
			<td style="width:71px;">Invitrogen</td>
			<td style="width:119px;">T13320</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Tyrode&#8217;s Salts Solution</td>
			<td style="width:71px;">Sigma-Aldrich</td>
			<td style="width:119px;">T2397</td>
			<td></td>
		</tr>
		<tr height="42">
			<td height="42" style="height:42px;width:243px;">Confocal laser scanning microscope</td>
			<td style="width:71px;">Carl Zeiss</td>
			<td style="width:119px;">NA</td>
			<td></td>
		</tr>
		<tr height="21">
			<td height="21" style="height:21px;width:243px;">Chameleon Two-photon laser</td>
			<td style="width:71px;">Coherent</td>
			<td style="width:119px;">NA</td>
			<td></td>
		</tr>
	</tbody>
</table>

cell membrane repair assay using a two-photon laser microscope

Numerous pathophysiological insults can cause damage to cell membranes and, when coupled with innate defects in cell membrane repair or integrity, can result in disease. Understanding the underlying molecular mechanisms surrounding cell membrane repair is, therefore, an important objective to the development of novel therapeutic strategies for diseases associated with dysfunctional cell membrane dynamics. Many in vitro and in vivo studies aimed at understanding cell membrane resealing in various disease contexts utilize two-photon laser ablation as a standard for determining functional outcomes following experimental treatments. In this assay, cell membranes are subjected to wounding with a two-photon laser, which causes the cell membrane to rupture and fluorescent dye to infiltrate the cell. The intensity of fluorescence within the cell can then be monitored to quantify the cell's ability to reseal itself. There are several alternative methods for assessing cell membrane response to injury, as well as great variation in the two-photon laser wounding approach itself, therefore, a single, unified model of cell wounding would beneficially serve to decrease the variation between these methodologies. In this article, we outline a simple two-photon laser wounding protocol for assessing cell membrane repair in vitro in both healthy and dysferlinopathy patient fibroblast cells transfected with or without a full-length dysferlin plasmid.

Healthy human fibroblasts, non-treated dysferlinopathy patient fibroblasts, and patient fibroblasts transfected with a plasmid containing the full-length dysferlin sequence were subjected to two-photon laser wounding to assess membrane resealing ability in real time. Healthy human fibroblast cells displayed low levels of FM 4-64 fluorescence activation following laser wounding and non-treated patient fibroblasts exhibited a high degree of relative fluorescence intensity following injury (...

Watch this Scientific Journal Video about Cell Membrane Repair Assay Using a Two-photon Laser Microscope at JoVE.com

Cell Membrane Repair Assay Using a Two-photon Laser Microscope

Cell membrane wounding via two-photon laser is a widely used method for assessing membrane resealing ability and can be applied to multiple cell types. Here, we describe a protocol for in vitro live-imaging of membrane resealing in dysferlinopathy patient cells following two-photon laser ablation.

Numerous pathophysiological insults can cause damage to cell membranes and, when coupled with innate defects in cell membrane repair or integrity, can ...

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