All experiments using animals were performed at the Penn State College of Medicine, approved by Penn State University&#39;s Institutional Animal Care and Use Committee, and performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments. 12-week-old female C57BL/6 mice were used for this procedure. All surgical tools were autoclaved for sterility prior to experimentation.
1. TA and EDL injection/electroporation preparation
NOTE: These steps are identical for TA and EDL injection/electroporation preparation.
<ol>
	<li>Purify expression plasmid constructs to a concentration of 1 &#181;g/&#181;L diluted in sterile PBS prior to the experiment. For this procedure, a commercially available endotoxin-free purification kit was used to purify pcDNA3-EGFP (GFP) or pcDNA3 empty vector (control).</li>
	<li>Calculate the plasmid concentration to ensure adequate injection volume (TA 50 &#181;g of DNA in 50 &#181;L of sterile PBS; EDL 10 &#181;g of DNA in 10 &#181;L of sterile PBS) and aliquot samples.</li>
	<li>Program the electroporator settings by using the select wheel and depressing the wheel to choose the parameters as follows: Mode - LV, Voltage - 12.5 V/mm (to be adjusted at the time of injection), pulse length - 20 ms, number of pulses - 5, interval - 200 ms, polarity - unipolar.</li>
	<li>Anesthetize the mice using isoflurane gas. Place the mice in an induction box with 5% isoflurane. Confirm the surgical plane of anesthesia by the absence of the toe pinch reflex using forceps and reduce isoflurane to 2% maintenance dose. Transfer mice to an appropriate nose cone resting on a circulating water plate at 37 &#176;C for the rest of the procedure.</li>
	<li>Remove hair from both hindlimbs using small hair clippers. Scrub the lower limbs with alternating 70% ethanol/betadine to sanitize the injection area.</li>
</ol>
2. TA injection/electroporation
<ol>
	<li>With the mouse in a supine position, locate the TA tendon visible through the skin on the lateral side of the lower leg. Using a 50 &#181;L micro-syringe with a detachable 30 G needle, insert the needle 1-2 mm superior to the myotendinous junction at a shallow 5&#176; angle until the needle reaches the superior end of the muscle. 
	NOTE: Injection into the middle of the muscle is the goal.</li>
	<li>Slowly depress the plunger while slowly retracting the needle along the injection path to deliver 50 &#181;L of plasmid solution. The muscle should swell.</li>
	<li>Set the timer for 1 min and measure the thickness of the leg at the TA. Depending on the size of the mouse, this can be from 5-10 mm. Set the caliper electrodes to the measured thickness and set the electroporator voltage to 12.5 V/mm.</li>
	<li>After 1 min, place the caliper electrodes around the lower limb. The electrodes should be snug but not overly tight. Deliver 5 square-wave pulses, with 20 ms duration and 200 ms intervals (the muscle should twitch with each pulse).</li>
	<li>Repeat with the alternate limb using the control vector.</li>
	<li>Remove the mouse from anesthesia and allow it to recover on a heating pad set to 37 &#176;C. Once recovered, return the mouse to its cage.</li>
</ol>
3. EDL injection/electroporation
<ol>
	<li>With the mouse in a supine position, locate the tibia bone anterior crest visually and through gentle palpation.
	<ol>
		<li>Using a scalpel, make a shallow incision through the skin on the lateral side of the tibia anterior crest 5 mm inferior to the knee to 2 mm superior to the TA myotendinous junction.</li>
		<li>Using small scissors, blunt dissect the fascia, exposing the TA muscle.</li>
		<li>Again, using blunt dissection with scissors, separate the TA muscle from the tibia gently by pulling the muscle laterally, exposing the EDL. Small, curved forceps can be used to keep the TA clear from the EDL during the procedure.</li>
	</ol>
	</li>
	<li>Using a 50 &#181;L micro-syringe with a detachable 30 G needle, insert the needle into the EDL longitudinally until the needle reaches the superior end of the muscle.</li>
	<li>Slowly depress the plunger while slowly retracting the needle along the injection path to inject 10 &#181;L of the plasmid solution (muscle should swell).</li>
	<li>Set a timer for 1 min and measure the thickness of the leg at the EDL. Depending on the size of the mouse, this can be from 5-10 mm. Set the caliper electrodes to the measured thickness and set the electroporator voltage to 12.5 V/mm.</li>
	<li>After 1 min, place the caliper electrodes around the lower limb. The electrodes should be snug but not overly tight. Deliver 5 square-wave pulses, with 20 ms duration and 200 ms intervals (muscle should twitch with each pulse).</li>
	<li>Close the incision using disposable 4/0 non-absorbable nylon sutures.</li>
	<li>Repeat with the alternate limb or leave the limb untouched as absolute control.</li>
	<li>Remove the mouse from anesthesia and allow it to recover on a heating pad set to 37 &#176;C. Administer an appropriate subcutaneous analgesic&#160;immediately after surgery and 12-24 h following surgery. Once recovered, return the mouse to its cage. 
	NOTE: Previous studies have shown a muscle contractility deficit in the TA immediately after electroporation and that contractile recovery occurs over the course of 3 days13,15. For this reason, the analysis of both the TA and EDL muscles for histology, protein expression, or muscle contractility is conducted 3-10 days following electroporation. Prolonged expression of EGFP has been observed up to 3 weeks following the procedure13.</li>
</ol>

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	<li>Dodd, S., Hain, B., Judge, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hsp70+prevents+disuse+muscle+atrophy+in+senescent+rats.">Hsp70 prevents disuse muscle atrophy in senescent rats.</a> Biogerontology. 10, 605-611 (2009).</li><li>Dodd, S. L., Gagnon, B. J., Senf, S. M., Hain, B. A., Judge, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Ros-mediated+activation+of+NF-kappaB+and+Foxo+during+muscle+disuse.">Ros-mediated activation of NF-kappaB and Foxo during muscle disuse.</a> Muscle and Nerve. 41 (1), 110-113 (2010).</li><li>Dodd, S. L., Hain, B., Senf, S. M., Judge, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hsp27+inhibits+IKK&#946;-induced+NF-&#954;B+activity+and+skeletal+muscle+atrophy.">Hsp27 inhibits IKK&#946;-induced NF-&#954;B activity and skeletal muscle atrophy.</a> The FASEB Journal. 23 (10), 3415-3423 (2009).</li><li>Hain, B. A., Dodd, S. L., Judge, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=IkappaBalpha+degradation+is+necessary+for+skeletal+muscle+atrophy+associated+with+contractile+claudication.">IkappaBalpha degradation is necessary for skeletal muscle atrophy associated with contractile claudication.</a> American Journal of Physiology Regulatory, Integregrative and Comparative Physiology. 300 (3), 595-604 (2011).</li><li>Houston, F. 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M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=High-efficiency+gene+transfer+into+skeletal+muscle+mediated+by+electric+pulses.">High-efficiency gene transfer into skeletal muscle mediated by electric pulses.</a> Proceedings of the National Academy of Sciences of the United States of America. 96 (8), 4262-4267 (1999).</li><li>Schertzer, J. D., Plant, D. R., Lynch, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Optimizing+plasmid-based+gene+transfer+for+investigating+skeletal+muscle+structure+and+function.">Optimizing plasmid-based gene transfer for investigating skeletal muscle structure and function.</a> Molecular Therapy. 13 (4), 795-803 (2006).</li><li>Hain, B. A., Xu, H., Waning, 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=Loss+of+REDD1+prevents+chemotherapy-induced+muscle+atrophy+and+weakness+in+mice.">Loss of REDD1 prevents chemotherapy-induced muscle atrophy and weakness in mice.</a> Journal of Cachexia, Sarcopenia and Muscle. 12 (6), 1597-1612 (2021).</li><li>Schertzer, J. D., Lynch, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Plasmid-based+gene+transfer+in+mouse+skeletal+muscle+by+electroporation.">Plasmid-based gene transfer in mouse skeletal muscle by electroporation.</a> Methods in Molecular Biology. 433, 115-125 (2008).</li><li>Roche, J. 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=Physiological+and+histological+changes+in+skeletal+muscle+following+in+vivo+gene+transfer+by+electroporation.">Physiological and histological changes in skeletal muscle following in vivo gene transfer by electroporation.</a> American Journal of Physiology: Cell Physiology. 301 (5), 1239-1250 (2011).</li><li>Hain, B. 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=Zoledronic+Acid+Improves+Muscle+Function+in+Healthy+Mice+Treated+with+Chemotherapy.">Zoledronic Acid Improves Muscle Function in Healthy Mice Treated with Chemotherapy.</a> Journal of Bone and Mineral Research. 35 (2), 368-381 (2020).</li><li>Hain, B. 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=REDD1+deletion+attenuates+cancer+cachexia+in+mice.">REDD1 deletion attenuates cancer cachexia in mice.</a> Journal of Applied Physiology. 131 (6), 1718-1730 (2021).</li><li>Hain, B. A., Xu, H., Wilcox, J. R., Mutua, D., Waning, 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=Chemotherapy-induced+loss+of+bone+and+muscle+mass+in+a+mouse+model+of+breast+cancer+bone+metastases+and+cachexia.">Chemotherapy-induced loss of bone and muscle mass in a mouse model of breast cancer bone metastases and cachexia.</a> Journal of Cachexia, Sarcopenia and Muscle Rapid Communications. 2 (1), (2019).</li><li>Waning, D. 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=Excess+TGF-beta+mediates+muscle+weakness+associated+with+bone+metastases+in+mice.">Excess TGF-beta mediates muscle weakness associated with bone metastases in mice.</a> Nature Medicine. 21, 1262-1271 (2015).</li><li>Bonetto, A., Andersson, D. C., Waning, 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=Assessment+of+muscle+mass+and+strength+in+mice.">Assessment of muscle mass and strength in mice.</a> Bonekey Reports. 4, 732 (2015).</li><li>Senf, S. M., Dodd, S. L., Judge, A. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=FOXO+signaling+is+required+for+disuse+muscle+atrophy+and+is+directly+regulated+by+Hsp70.">FOXO signaling is required for disuse muscle atrophy and is directly regulated by Hsp70.</a> American Journal of Physiology Cell Physiology. 298 (1), 38-45 (2010).</li><li>Rana, Z. A., Ekmark, M., Gundersen, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coexpression+after+electroporation+of+plasmid+mixtures+into+muscle+in+vivo.">Coexpression after electroporation of plasmid mixtures into muscle in vivo.</a> Acta Physiologica. 181 (2), 233-238 (2004).</li><li>Sokolowska, E., Blachnio-Zabielska, A. 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B.A.H. and D.L.W claim no conflicts of interest.

In vivo gene transfer in skeletal muscle enhanced by electroporation is a useful and relatively simple tool for modulating protein expression in muscle. We have shown the steps required to achieve efficient gene transfer in the EDL and TA muscles and demonstrated that contractility measurement of the EDL is viable following the procedure. This technique does not require more complicated viral vectors and allows for the comparison of transfected and non-transfected muscle fiber cross-sectional area in a single mu...

Plasmid DNA electroporation into skeletal muscle in vivo is an important tool for assessing changes in skeletal muscle physiology and molecular signaling by modulating gene expression in a variety of physiological and pathophysiological conditions1,2,3,4,5,6,7,8,9. Experimental gene transfer into skeletal muscle was demonstrated as early as 1990 by Wolff et al., where both RNA and DNA were successfully transferred without electroporation, and luciferase expression was maintained for at least 2 months10. The relatively low transfection efficiency with injection only is problematic, and Aihara and Miyazaki demonstrated increased gene transfer with electroporation in 1998 by electroporating a pCAGGS-IL-5 construct into the tibialis anterior (TA) muscle and measuring serum IL-5 expression11. Since that time, many studies have investigated the efficacy of different DNA concentrations, volumes, and electroporation parameters to ensure maximal gene transfer efficiency. Mir et al. tested different electroporation parameters, including voltage, pulse number, pulse duration, and frequency, as well as DNA concentration, and determined that greater voltage, pulse number, and DNA concentration all contributed to increased electroporation efficiency12. A major caveat to high electroporation voltage is that, while it facilitates increased DNA uptake into myofibers, it also causes muscle damage, which can confound results. Schertzer et al. showed that electroporation at 200 V caused damage in around 50% of myofibers 3 days after electroporation, whereas only 10% of myofibers were damaged at 50 V13. We have taken into consideration the variables affecting efficient DNA transfer versus muscle damage and found that a voltage of 125 V per centimeter of caliper width is sufficient to accomplish effective gene transfer.
Analysis of muscle fiber cross-sectional area and whole muscle contractility after electroporation are important aspects of the method for measuring changes in muscle size and function due to gene modulation. We and others have previously demonstrated that electroporation of control vectors alone does not cause a decrease in myofiber area. The green fluorescent protein (EGFP) construct was a useful fluorescent indicator of DNA transfection in these studies13,14. A number of studies have investigated in situ contractility of the TA after electroporation and found varying results. One study showed that 75 V/cm electroporation caused about a 30% reduction in tetanic force 3 days post-electroporation, and by 7 days post-electroporation, tetanic force was back to the control level, while 50 V/cm electroporation did not compromise force13,15. Another study showed that there was a 30% loss of tetanic force 3 h after 180 V/cm electroporation, which recovered to the sham force levels after 7 days16.
In the following detailed procedure, we demonstrate injection and electroporation of a pcDNA3-EGFP plasmid in the TA and extensor digitorum longus (EDL) muscles of mice. We also demonstrate that this method does not affect EDL whole-muscle contractility. The aim is to demonstrate efficient plasmid uptake into myofibers without causing loss of function.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>4-0 Nylon suture (non-absorbable)</td>
			<td>Ethicon</td>
			<td>662G</td>
			<td>Suture to close skin incision</td>
		</tr>
		<tr>
			<td>50&#181;l Hamilton syringe</td>
			<td>Hamilton</td>
			<td>80501</td>
			<td>microsyringe</td>
		</tr>
		<tr>
			<td>C57BLl/6NHsd mice</td>
			<td>Envigo</td>
			<td>044</td>
			<td>12 week-old female mice used for experimentation</td>
		</tr>
		<tr>
			<td>Caliper Electrode</td>
			<td>BTX</td>
			<td>45-0102</td>
			<td>1.0cm x 1.0cm stainless steel</td>
		</tr>
		<tr>
			<td>Dynamic Muscle Control Data Acquisition/analysis</td>
			<td>Aurora Scientific</td>
			<td>605A</td>
			<td>Software used for muscle contractility measurement and analysis</td>
		</tr>
		<tr>
			<td>ECM 830 Electroporation System</td>
			<td>BTX</td>
			<td>45-0662</td>
			<td>electroporator</td>
		</tr>
		<tr>
			<td>EndoFree Plasmid Maxi Kit</td>
			<td>Qiagen</td>
			<td>12362</td>
			<td>Plasmid purification kit</td>
		</tr>
		<tr>
			<td>Extra Narrow Scissors</td>
			<td>Fine Science Tools</td>
			<td>14088-10</td>
			<td>Scissors for blunt dissection</td>
		</tr>
		<tr>
			<td>Force Transducer</td>
			<td>Aurora Scientific</td>
			<td>407A</td>
			<td>To measure force from EDL</td>
		</tr>
		<tr>
			<td>Micro-Masquito Hemastats</td>
			<td>Fine Science Tools</td>
			<td>13010-12</td>
			<td>Hemastats for surturing</td>
		</tr>
		<tr>
			<td>pcDNA3.1 mammalian expression vector</td>
			<td>Fisher Scientific</td>
			<td>V79020</td>
			<td>Control Vector</td>
		</tr>
		<tr>
			<td>pcDNA3-EGFP expression plasmid</td>
			<td>Addgene</td>
			<td>13031</td>
			<td>Plasmid for GFP expression</td>
		</tr>
		<tr>
			<td>Semken curved forceps</td>
			<td>Fine Science Tools</td>
			<td>11009-13</td>
			<td>Forceps for surgery</td>
		</tr>
		<tr>
			<td>Surgical blades stainless steel no. 10</td>
			<td>Becton Dickinson</td>
			<td>37 1210</td>
			<td>Scalpel blades</td>
		</tr>
		<tr>
			<td>Tissue-Tek O.C.T. media</td>
			<td>VWR</td>
			<td>25608-930</td>
			<td>Freezing media for histology</td>
		</tr>
		<tr>
			<td>Wheat Germ Agglutinin- Texas Red</td>
			<td>Thermo-Fisher Scientific</td>
			<td>W21405</td>
			<td>Membrane staining for muscle cross section</td>
		</tr>
	</tbody>
</table>

electroporation of plasmid dna into mouse skeletal muscle

Transient gene expression modulation in murine skeletal muscle by plasmid electroporation is a useful tool for assessing normal and pathological physiology. Overexpression or knockdown of target genes enables investigators to manipulate individual molecular events and, thus, better understand the mechanisms that impact muscle mass, muscle metabolism, and contractility. In addition, electroporation of DNA plasmids that encode fluorescent tags allows investigators to measure changes in subcellular localization of proteins in skeletal muscle in vivo. A key functional assessment of skeletal muscle includes the measurement of muscle contractility. In this protocol, we demonstrate that whole muscle contractility studies are still possible after plasmid DNA injection, electroporation, and gene expression modulation. The goal of this instructional procedure is to demonstrate the step-by-step method of DNA plasmid electroporation into mouse skeletal muscle to facilitate uptake and expression in the myofibers of the tibialis anterior and extensor digitorum longus muscles, as well as to demonstrate that skeletal muscle contractility is not compromised by injection and electroporation.

Electroporation to facilitate gene transfer in skeletal muscle is a useful technique used to evaluate changes in muscle physiology. We have demonstrated a detailed, step-by-step procedure to accomplish efficient gene transfer in both the TA and EDL muscles. Differences in transfection efficiency occur due to a number of variables. Among these variables are electroporation parameters (pulses, voltage, pulse duration, etc.), gene construct size, and concentration/volume of DNA injected. We have previously shown that electr...

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Electroporation of Plasmid DNA into Mouse Skeletal Muscle

Electroporation of plasmid DNA into skeletal muscle is a viable method to modulate gene expression without compromising muscle contractility in mice.

Transient gene expression modulation in murine skeletal muscle by plasmid electroporation is a useful tool for assessing normal and pathological ...

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3.2K Views.  Penn State College of Medicine. Electroporation of plasmid DNA into skeletal muscle is a viable method to modulate gene expression without compromising muscle contractility in mice.

Video: Electroporation of Plasmid DNA into Mouse Skeletal Muscle

Transformation of Plasmid DNA into E. coli Using the Heat Shock Method

Transformation of plasmid DNA into E. coli using the heat shock method is a basic technique of molecular biology. It consists of inserting a foreign plasmid or ligation product into bacteria. This video protocol describes the traditional method of transformation using commercially available chemically competent bacteria from Genlantis. After a short incubation in ice, a mixture of chemically competent bacteria and DNA is placed at 42&deg;C for 45 seconds (heat shock) and then placed back in ice. SOC media is added and the transformed cells are incubated at 37&deg;C for 30 min with agitation. To be assured of isolating colonies irrespective of transformation efficiency, two quantities of transformed bacteria are plated. This traditional protocol can be used successfully to transform most commercially available competent bacteria. The turbocells from Genlantis can also be used in a novel 3-minute transformation protocol, described in the instruction manual.

Transformation of plasmid DNA into E. coli using the heat shock method is a basic technique of molecular biology. It consists of inserting a foreign ...

DNA Transfection of Mammalian Skeletal Muscles using In Vivo Electroporation

A growing interest in cell biology is to express transgenically modified forms of essential proteins (e.g. fluorescently tagged constructs and/or mutant variants) in order to investigate their endogenous distribution and functional relevance. An interesting approach that has been implemented to fulfill this objective in fully differentiated cells is the in vivo transfection of plasmids by various methods into specific tissues such as liver1, skeletal muscle2,3, and even the brain4. We present here a detailed description of the steps that must be followed in order to efficiently transfect genetic material into fibers of the flexor digitorum brevis (FDB) and interosseus (IO) muscles of adult mice using an in vivo electroporation approach. The experimental parameters have been optimized so as to maximize the number of muscle fibers transfected while minimizing tissue damages that may impair the quality and quantity of the proteins expressed in individual fibers. We have verified that the implementation of the methodology described in this paper results in a high yield of soluble proteins, i.e. EGFP and ECFP3, calpain, FKBP12, &beta;2a-DHPR, etc. ; structural proteins, i.e. minidystrophin and &alpha;-actinin; and membrane proteins, i.e. &alpha;1s-DHPR, RyR1, cardiac Na/Ca2+ exchanger , NaV1.4 Na channel, SERCA1, etc., when applied to FDB, IO and other muscles of mice and rats. The efficient expression of some of these proteins has been verified with biochemical3 and functional evidence5. However, by far the most common confirmatory approach used by us are standard fluorescent microscopy and 2-photon laser scanning microscopy (TPLSM), which permit to identify not only the overall expression, but also the detailed intracellular localization, of fluorescently tagged protein constructs. The method could be equally used to transfect plasmids encoding for the expression of proteins of physiological relevance (as shown here), or for interference RNA (siRNA) aiming to suppress the expression of normally expressed proteins (not tested by us yet). It should be noted that the transfection of FDB and IO muscle fibers is particularly relevant for the investigation of mammalian muscle physiology since fibers enzymatically dissociated from these muscles are currently one of the most suitable models to investigate basic mechanisms of excitability and excitation-contraction coupling under current or voltage clamp conditions2,6-8.

DNA Transfection of Mammalian Skeletal Muscles using In Vivo Electroporation

We describe detailed procedures for the efficient transfection of plasmid DNA into the fibers of foot muscles of live mice using electroporation and the subsequent visualization of protein expression using fluorescence microscopy.

 A growing interest in cell biology is to express transgenically modified forms of essential proteins (e.g. fluorescently tagged constructs and/or mutant ...

Primary Culture and Plasmid Electroporation of the Murine Organ of Corti. 

In all mammals, the sensory epithelium for audition is located along the spiraling organ of Corti that resides within the conch shaped cochlea of the inner ear (fig 1). Hair cells in the developing cochlea, which are the mechanosensory cells of the auditory system, are aligned in one row of inner hair cells and three (in the base and mid-turns) to four (in the apical turn) rows of outer hair cells that span the length of the organ of Corti. Hair cells transduce sound-induced mechanical vibrations of the basilar membrane into neural impulses that the brain can interpret. Most cases of sensorineural hearing loss are caused by death or dysfunction of cochlear hair cells.
An increasingly essential tool in auditory research is the isolation and in vitro culture of the organ explant 1,2,9. Once isolated, the explants may be utilized in several ways to provide information regarding normative, anomalous, or therapeutic physiology. Gene expression, stereocilia motility, cell and molecular biology, as well as biological approaches for hair cell regeneration are examples of experimental applications of organ of Corti explants.
This protocol describes a method for the isolation and culture of the organ of Corti from neonatal mice. The accompanying video includes stepwise directions for the isolation of the temporal bone from mouse pups, and subsequent isolation of the cochlea, spiral ligament, and organ of Corti. Once isolated, the sensory epithelium can be plated and cultured in vitro in its entirety, or as a further dissected micro-isolate that lacks the spiral limbus and spiral ganglion neurons. Using this method, primary explants can be maintained for 7-10 days. As an example of the utility of this procedure, organ of Corti explants will be electroporated with an exogenous DsRed reporter gene. This method provides an improvement over other published methods because it provides reproducible, unambiguous, and stepwise directions for the isolation, microdissection, and primary culture of the organ of Corti.

Primary Culture and Plasmid Electroporation of the Murine Organ of Corti.

This procedure describes a method for the isolation and culture of the murine organ of Corti with or without the spiral limbus and spiral ganglion neurons. We also demonstrate a method for the expression of an exogenous reporter gene in the organ of Corti explant by electroporation.

In all mammals, the sensory epithelium for audition is located along the spiraling organ of Corti that resides within the conch shaped cochlea of the ...

Adult and Embryonic Skeletal Muscle Microexplant Culture and Isolation of Skeletal Muscle Stem Cells

Cultured embryonic and adult skeletal muscle cells have a number of different uses. The micro-dissected explants technique described in this chapter is a robust and reliable method for isolating relatively large numbers of proliferative skeletal muscle cells from juvenile, adult or embryonic muscles as a source of skeletal muscle stem cells. The authors have used micro-dissected explant cultures to analyse the growth characteristics of skeletal muscle cells in wild-type and dystrophic muscles. Each of the components of tissue growth, namely cell survival, proliferation, senescence and differentiation can be analysed separately using the methods described here. The net effect of all components of growth can be established by means of measuring explant outgrowth rates. The micro-explant method can be used to establish primary cultures from a wide range of different muscle types and ages and, as described here, has been adapted by the authors to enable the isolation of embryonic skeletal muscle precursors.
Uniquely, micro-explant cultures have been used to derive clonal (single cell origin) skeletal muscle stem cell (SMSc) lines which can be expanded and used for in vivo transplantation. In vivo transplanted SMSc behave as functional, tissue-specific, satellite cells which contribute to skeletal muscle fibre regeneration but which are also retained (in the satellite cell niche) as a small pool of undifferentiated stem cells which can be re-isolated into culture using the micro-explant method.

The micro-dissected explants technique is a robust and reliable method for isolating proliferative skeletal muscle cells from juvenile, adult or embryonic muscles as a source of skeletal muscle stem cells. Uniquely, these cells have been clonally derived to produce skeletal muscle stem cell lines used for in vivo transplantation.

Cultured embryonic and adult skeletal muscle cells have a number of different uses. The micro-dissected explants technique described in this chapter is a ...

Mitochondrial Isolation from Skeletal Muscle

Mitochondria are organelles controlling the life and death of the cell. They participate in key metabolic reactions, synthesize most of the ATP, and regulate a number of signaling cascades2,3. Past and current researchers have isolated mitochondria from rat and mice tissues such as liver, brain and heart4,5. In recent years, many researchers have focused on studying mitochondrial function from skeletal muscles.
Here, we describe a method that we have used successfully for the isolation of mitochondria from skeletal muscles 6. Our procedure requires that all buffers and reagents are made fresh and need about 250-500 mg of skeletal muscle. We studied mitochondria isolated from rat and mouse gastrocnemius and diaphragm, and rat extraocular muscles. Mitochondrial protein concentration is measured with the Bradford assay. It is important that mitochondrial samples be kept ice-cold during preparation and that functional studies be performed within a relatively short time (~1 hr). Mitochondrial respiration is measured using polarography with a Clark-type electrode (Oxygraph system) at 37&deg;C7. Calibration of the oxygen electrode is a key step in this protocol and it must be performed daily. Isolated mitochondria (150 &mu;g) are added to 0.5 ml of experimental buffer (EB). State 2 respiration starts with addition of glutamate (5mM) and malate (2.5 mM). Then, adenosine diphosphate (ADP) (150 &mu;M) is added to start state 3. Oligomycin (1 &mu;M), an ATPase synthase blocker, is used to estimate state 4. Lastly, carbonyl cyanide p-[trifluoromethoxy]-phenyl-hydrazone (FCCP, 0.2 &mu;M) is added to measurestate 5, or uncoupled respiration 6. The respiratory control ratio (RCR), the ratio of state 3 to state 4, is calculated after each experiment. An RCR &ge;4 is considered as evidence of a viable mitochondria preparation.
In summary, we present a method for the isolation of viable mitochondria from skeletal muscles that can be used in biochemical (e.g., enzyme activity, immunodetection, proteomics) and functional studies (mitochondrial respiration).

This protocol describes a procedure to study the respiration of mitochondria isolated from skeletal muscles. This method was adapted from Scorrano et al. (2007). The mitochondrial isolation procedure requires about 2 hours. The mitochondrial respiration can be completed in about 1 hour.

Mitochondria are organelles controlling the life and death of the cell. They participate in key metabolic reactions, synthesize most of the ATP, and ...

Purification of Progenitors from Skeletal Muscle

Skeletal muscle contains multiple progenitor populations of distinct embryonic origins and developmental potential. Myogenic progenitors, usually residing in a "satellite cell position" between the myofiber plasma membrane and the laminin-rich basement membrane that ensheaths it, are self-renewing cells that are solely committed to the myogenic lineage1,2. We have recently described a second class of vessel associated progenitors that can generate myofibroblasts and white adipocytes, which responds to damage by efficiently entering proliferation and provides trophic support to myogenic cells during tissue regeneration3,4. One of the most trusted assays to determine the developmental and regenerative potential of a given cell population relies on their isolation and transplantation5-7. To this end we have optimized protocols for their purification by flow cytometry from enzymatically dissociated muscle, which we will outline in this article. The populations obtained using this method will contain either myogenic or fibro/adipogenic colony forming cells: no other cell types are capable of expanding in vitro or surviving in vivo delivery. However, when these populations are used immediately after the sort for molecular analysis (e.g qRT-PCR) one must keep in mind that the freshly sorted subsets may contain other contaminant cells that lack the ability of forming colonies or engrafting recipients.

Method for the enzymatic dissociation, surface labeling and purification by flow cytometry of fibro/adipogenic and myogenic progenitors from murine skeletal muscle.

Skeletal muscle contains multiple progenitor populations of distinct embryonic origins and developmental potential. Myogenic progenitors, usually residing ...

Laser-inflicted Injury of Zebrafish Embryonic Skeletal Muscle

Various experimental approaches have been used in mouse to induce muscle injury with the aim to study muscle regeneration, including myotoxin injections (bupivacaine, cardiotoxin or notexin), muscle transplantations (denervation-devascularization induced regeneration), intensive exercise, but also murine muscular dystrophy models such as the mdx mouse (for a review of these approaches see 1). In zebrafish, genetic approaches include mutants that exhibit muscular dystrophy phenotypes (such as runzel2 or sapje3) and antisense oligonucleotide morpholinos that block the expression of dystrophy-associated genes4. Besides, chemical approaches are also possible, e.g. with Galanthamine, a chemical compound inhibiting acetylcholinesterase, thereby resulting in hypercontraction, which eventually leads to muscular dystrophy5. However, genetic and pharmacological approaches generally affect all muscles within an individual, whereas the extent of physically inflicted injuries are more easily controlled spatially and temporally1. Localized physical injury allows the assessment of contralateral muscle as an internal control. Indeed, we recently used laser-mediated cell ablation to study skeletal muscle regeneration in the zebrafish embryo6, while another group recently reported the use of a two-photon laser (822 nm) to damage very locally the plasma membrane of individual embryonic zebrafish muscle cells7.
Here, we report a method for using the micropoint laser (Andor Technology) for skeletal muscle cell injury in the zebrafish embryo. The micropoint laser is a high energy laser which is suitable for targeted cell ablation at a wavelength of 435 nm. The laser is connected to a microscope (in our setup, an optical microscope from Zeiss) in such a way that the microscope can be used at the same time for focusing the laser light onto the sample and for visualizing the effects of the wounding (brightfield or fluorescence). The parameters for controlling laser pulses include wavelength, intensity, and number of pulses.
Due to its transparency and external embryonic development, the zebrafish embryo is highly amenable for both laser-induced injury and for studying the subsequent recovery. Between 1 and 2 days post-fertilization, somitic skeletal muscle cells progressively undergo maturation from anterior to posterior due to the progression of somitogenesis from the trunk to the tail8, 9. At these stages, embryos spontaneously twitch and initiate swimming. The zebrafish has recently been recognized as an important vertebrate model organism for the study of tissue regeneration, as many types of tissues (cardiac, neuronal, vascular etc.) can be regenerated after injury in the adult zebrafish10, 11.

The method presented here comprises the precise injury of live zebrafish embryos with high-energy laser pulses and the subsequent analysis of these injuries and their recovery with time. We also show how genetically labeled single or groups of skeletal muscle cells can be tracked during and after laser light induced damage.

Various experimental approaches have been used in mouse to induce muscle injury with the aim to study muscle regeneration, including myotoxin injections ...

Detection and Analysis of DNA Damage in Mouse Skeletal Muscle In Situ Using the TUNEL Method

Terminal deoxynucleotidyl transferase (TdT) deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) is the method of using the TdT enzyme to covalently attach a tagged form of dUTP to 3&#8217; ends of double- and single-stranded DNA breaks in cells. It is a reliable and useful method to detect DNA damage and cell death in situ. This video describes dissection, tissue processing, sectioning, and fluorescence-based TUNEL labeling of mouse skeletal muscle. It also describes a method of semi-automated TUNEL signal quantitation. Inherent normal tissue features and tissue processing conditions affect the ability of the TdT enzyme to efficiently label DNA. Tissue processing may also add undesirable autofluorescence that will interfere with TUNEL signal detection. Therefore, it is important to empirically determine tissue processing and TUNEL labeling methods that will yield the optimal signal-to-noise ratio for subsequent quantitation. The fluorescence-based assay described here provides a way to exclude autofluorescent signal by digital channel subtraction. The TUNEL assay, used with appropriate tissue processing techniques and controls, is a relatively fast, reproducible, quantitative method for detecting apoptosis in tissue. It can be used to confirm DNA damage and apoptosis as pathological mechanisms, to identify affected cell types, and to assess the efficacy of therapeutic treatments in vivo.

Detection and Analysis of DNA Damage in Mouse Skeletal Muscle In Situ Using the TUNEL Method

This video describes dissection, tissue processing, sectioning, and fluorescence-based TUNEL labeling of mouse skeletal muscle. It also describes a method for semi-automated analysis of TUNEL labeling.

Terminal deoxynucleotidyl transferase (TdT) deoxyuridine triphosphate (dUTP) nick end labeling (TUNEL) is the method of using the TdT enzyme to covalently ...

Novel Method of Plasmid DNA Delivery to Mouse Bladder Urothelium by Electroporation

Genetically engineered mouse models (GEMMs) are extremely valuable in revealing novel biological insights into the initiation and progression mechanisms of human diseases such as cancer. Transgenic and conditional knockout mice have been frequently used for gene overexpression or ablation in specific tissues or cell types in vivo. However, generating germline mouse models can be time-consuming and costly. Recent advancements in gene editing technologies and the feasibility of delivering DNA plasmids by viral infection have enabled rapid generation of non-germline autochthonous mouse cancer models for several organs. The bladder is an organ that has been difficult for viral vectors to access, due to the presence of a glycosaminoglycan layer covering the urothelium. Here, we describe a novel method developed in lab for efficient delivery of DNA plasmids into the mouse bladder urothelium in vivo. Through intravesical instillation of pCAG-GFP DNA plasmid and electroporation of surgically exposed bladder, we show that the DNA plasmid can be delivered specifically into the bladder urothelial cells for transient expression. Our method provides a fast and convenient way for overexpression and knockdown of genes in the mouse bladder, and can be applied to building GEMMs of bladder cancer and other urological diseases.

We describe a novel method for the delivery of DNA plasmid into the urothelial cells of mouse bladder in vivo through urethra catheterization and electroporation. It offers a fast and convenient way for generating autochthonous mouse models of bladder diseases.

Genetically engineered mouse models (GEMMs) are extremely valuable in revealing novel biological insights into the initiation and progression mechanisms ...

Isolation of Mitochondria from Mouse Skeletal Muscle for Respirometric Assays

Most of the cell&#39;s energy is obtained through the degradation of glucose, fatty acids, and amino acids by different pathways that converge on the mitochondrial oxidative phosphorylation (OXPHOS) system, which is regulated in response to cellular demands. The lipid molecule Coenzyme Q (CoQ) is essential in this process by transferring electrons to complex III in the electron transport chain (ETC) through constant oxidation/reduction cycles. Mitochondria status and, ultimately, cellular health can be assessed by measuring ETC oxygen consumption using respirometric assays. These studies are typically performed in established or primary cell lines that have been cultured for several days. In both cases, the respiration parameters obtained may have deviated from normal physiological conditions in&#160;any given organ or tissue.
Additionally, the intrinsic characteristics of cultured single fibers isolated from skeletal muscle impede this type of analysis. This paper presents an updated and detailed protocol for the analysis of respiration in freshly isolated mitochondria from mouse skeletal muscle. We also provide solutions to potential problems that could arise at any step of the process. The method presented here could be applied to compare oxygen consumption rates in diverse transgenic mouse models and study the mitochondrial response to drug treatments or other factors such as aging or sex. This is a feasible method to respond to crucial questions about mitochondrial bioenergetics metabolism and regulation.

Here, we describe a detailed method for mitochondria isolation from mouse skeletal muscle and the subsequent analysis of respiration by Oxygen Consumption Rate (OCR) using microplate-based respirometric assays. This pipeline can be applied to study the effects of multiple environmental or genetic interventions on mitochondrial metabolism.

Most of the cell&#39;s energy is obtained through the degradation of glucose, fatty acids, and amino acids by different pathways that converge on the ...