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>

<ol>
	<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. E., 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=Heat+shock+protein+70+overexpression+does+not+attenuate+atrophy+in+botulinum+neurotoxin+type+A-treated+skeletal+muscle.">Heat shock protein 70 overexpression does not attenuate atrophy in botulinum neurotoxin type A-treated skeletal muscle.</a> Journal of Applied Physiology. 119 (1), 83-92 (2015).</li><li>Reed, S. A., Sandesara, P. 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=Inhibition+of+FoxO+transcriptional+activity+prevents+muscle+fiber+atrophy+during+cachexia+and+induces+hypertrophy.">Inhibition of FoxO transcriptional activity prevents muscle fiber atrophy during cachexia and induces hypertrophy.</a> The FASEB Journal. 26 (3), 987-1000 (2012).</li><li>Senf, S. M., Dodd, S. L., McClung, J. 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=Hsp70+overexpression+inhibits+NF-kappaB+and+Foxo3a+transcriptional+activities+and+prevents+skeletal+muscle+atrophy.">Hsp70 overexpression inhibits NF-kappaB and Foxo3a transcriptional activities and prevents skeletal muscle atrophy.</a> The FASEB Journal. 22 (11), 3836-3845 (2008).</li><li>Blaveri, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Patterns+of+repair+of+dystrophic+mouse+muscle:+studies+on+isolated+fibers.">Patterns of repair of dystrophic mouse muscle: studies on isolated fibers.</a> Developmental Dynamics. 216 (3), 244-256 (1999).</li><li>Fewell, J. G., 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=Gene+therapy+for+the+treatment+of+hemophilia+B+using+PINC-formulated+plasmid+delivered+to+muscle+with+electroporation.">Gene therapy for the treatment of hemophilia B using PINC-formulated plasmid delivered to muscle with electroporation.</a> Molecular Therapy. 3 (4), 574-583 (2001).</li><li>Wolff, 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=Direct+gene+transfer+into+mouse+muscle+in+vivo.">Direct gene transfer into mouse muscle in vivo.</a> Science. 247 (4949), 1465-1468 (1990).</li><li>Aihara, H., Miyazaki, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Gene+transfer+into+muscle+by+electroporation+in+vivo.">Gene transfer into muscle by electroporation in vivo.</a> Nature Biotechnology. 16 (9), 867-870 (1998).</li><li>Mir, L. 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. U. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=A+Critical+Review+of+Electroporation+as+A+Plasmid+Delivery+System+in+Mouse+Skeletal+Muscle.">A Critical Review of Electroporation as A Plasmid Delivery System in Mouse Skeletal Muscle.</a> Integrative Journal of Molecular Science. 20 (11), (2019).</li><li>Molnar, M. J., 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=Factors+influencing+the+efficacy,+longevity,+and+safety+of+electroporation-assisted+plasmid-based+gene+transfer+into+mouse+muscles.">Factors influencing the efficacy, longevity, and safety of electroporation-assisted plasmid-based gene transfer into mouse muscles.</a> Molecular Therapy. 10 (1), 447-455 (2004).</li></ol>

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><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&amp;micro;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...

Watch this Scientific Journal Video about Electroporation of Plasmid DNA into Mouse Skeletal Muscle at JoVE.com

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 ...

electroporation-of-plasmid-dna-into-mouse-skeletal-muscle

Research

JoVE Journal

Biology

3.3K 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

Improved Protocol for Chromatin Immunoprecipitation from Mouse Skeletal Muscle

We describe an efficient and reproducible protocol for the preparation of chromatin from adult mouse skeletal muscle, a physically resistant tissue with a high content of structural proteins. Dissected limb muscles from adult mice are physically disrupted by mechanical homogenisation, or a combination of mincing and douncing, in a hypotonic buffer before formaldehyde fixation of the cell lysate. The fixed nuclei are purified by further cycles of mechanical homogenisation or douncing and sequential filtrations to remove cell debris. The purified nuclei can be sonicated immediately or at a later stage after freezing. The chromatin can be efficiently sonicated and is suitable for chromatin immunoprecipitation experiments, as illustrated by the profiles obtained for transcription factors, RNA polymerase II, and covalent histone modifications. The binding events detected using chromatin prepared by this protocol are predominantly those taking place in the muscle fiber nuclei despite the presence of chromatin from other fiber-associated satellite and endothelial cells. This protocol is therefore adapted to study gene regulation in the adult mouse skeletal muscle.

A novel protocol for the preparation of chromatin from adult mouse skeletal muscle adapted to the study of gene regulation in muscle fibers by chromatin immunoprecipitation is presented.

We describe an efficient and reproducible protocol for the preparation of chromatin from adult mouse skeletal muscle, a physically resistant tissue with a ...

Biochemistry

Transplantation of Induced Pluripotent Stem Cell-derived Mesoangioblast-like Myogenic Progenitors in Mouse Models of Muscle Regeneration

Patient-derived iPSCs could be an invaluable source of cells for future autologous cell therapy protocols. iPSC-derived myogenic stem/progenitor cells similar to pericyte-derived mesoangioblasts (iPSC-derived mesoangioblast-like stem/progenitor cells: IDEMs) can be established from iPSCs generated from patients affected by different forms of muscular dystrophy. Patient-specific IDEMs can be genetically corrected with different strategies (e.g. lentiviral vectors, human artificial chromosomes) and enhanced in their myogenic differentiation potential upon overexpression of the myogenesis regulator MyoD. This myogenic potential is then assessed in vitro with specific differentiation assays and analyzed by immunofluorescence. The regenerative potential of IDEMs is further evaluated in vivo, upon intramuscular and intra-arterial transplantation in two representative mouse models displaying acute and chronic muscle regeneration. The contribution of IDEMs to the host skeletal muscle is then confirmed by different functional tests in transplanted mice. In particular, the amelioration of the motor capacity of the animals is studied with treadmill tests. Cell engraftment and differentiation are then assessed by a number of histological and immunofluorescence assays on transplanted muscles. Overall, this paper describes the assays and tools currently utilized to evaluate the differentiation capacity of IDEMs, focusing on the transplantation methods and subsequent outcome measures to analyze the efficacy of cell transplantation.

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

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

Bioengineering

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 ...

Neonatal Pial Surface Electroporation

Over the past several years the pial surface has been identified as a germinal niche of importance during embryonic, perinatal and adult neuro- and gliogenesis, including after injury. However, methods for genetically interrogating these progenitor populations and tracking their lineages had been limited owing to a lack of specificity or time consuming production of viruses. Thus, progress in this region has been relatively slow with only a handful of investigations of this location. Electroporation has been used for over a decade to study neural stem cell properties in the embryo, and more recently in the postnatal brain. Here we describe an efficient, rapid, and simple technique for the genetic manipulation of pial surface progenitors based on an adapted electroporation approach. Pial surface electroporation allows for facile genetic labeling and manipulation of these progenitors, thus representing a time-saving and economical approach for studying these cells.

The pial surface is a unique progenitor zone in the CNS that is receiving increasing attention. Herein, we detail a method for rapid genetic manipulation of this progenitor zone using a modified electroporation method. This procedure can be used for cellular and molecular investigations of cell lineages and signaling pathways involved in cell differentiation and to elucidate the fate and properties of daughter cells.

Over the past several years the pial surface has been identified as a germinal niche of importance during embryonic, perinatal and adult neuro- and ...

Neuroscience

In Vivo Microinjection and Electroporation of Mouse Testis

This video and article contribution gives a comprehensive description of microinjection and electroporation of mouse testis in vivo. This particular transfection technique for testicular mouse cells allows the study of unique processes in spermatogenesis.
The following protocol focuses on transfection of testicular mouse cells with plasmid constructs. Specifically, we used the reporter vector pEGFP-C1, which expresses enhanced green fluorescent protein (eGFP) and also the pDsRed2-N1 vector expressing red fluorescent protein (DsRed2). Both encoded reporter genes were under the control of the human cytomegalovirus immediate-early promoter (CMV).
For performing gene transfer into mouse testes, the reporter plasmid constructs are injected into testes of living mice. To that end, the testis of an anaesthetized animal is exposed and the site of microinjection is prepared. Our preferred place of injection is the efferent duct, with the ultimately connected rete testis as the anatomical transport route of the spermatozoa between the testis and the epididymis. In this way, the filling of the seminiferous tubules after microinjection is excellently managed and controlled due to the use of stained DNA solutions. After observing a sufficient filling of the testis by its colored tubule structure, the organ is electroporated. This enables the transfer of the DNA solution into the testicular&#160;cells. Following 3 days of incubation, the testis is removed and investigated under the microscope for green or red&#160;fluorescence, illustrating transfection success.
Generally, this protocol can be employed for delivering DNA- or RNA- constructs into living mouse testis in order to (over)express or knock down genes, facilitating in vivo gene function analysis. Furthermore, it is suitable for studying reporter constructs or putative gene regulatory elements. Thus, the main advantages of the electroporation technique are fast performance in combination with low effort as well as the moderate technical equipment and skills required compared to alternative techniques.

In Vivo Microinjection and Electroporation of Mouse Testis

This article describes microinjection and electroporation of mouse testis in&#160;vivo as a&#160;transfection technique for testicular mouse cells to study unique processes of spermatogenesis. The presented protocol involves steps of glass capillary preparation, microinjection via the efferent duct, and transfection by electroporation.

This video and article contribution gives a comprehensive description of microinjection and electroporation of mouse testis in vivo. This particular ...

DNA Electroporation, Isolation and Imaging of Myofibers

Mature muscle has a unique structure that is amenable to live cell imaging. Herein, we describe the experimental protocol for expressing fluorescently labeled proteins in the flexor digitorum brevis (FDB) muscle. Conditions have been optimized to provide a large number of high quality myofibers expressing the electroporated plasmid while minimizing muscle damage. The method employs fluorescent tags on various proteins. Combining this expression method with high resolution confocal microscopy permits live cell imaging, including imaging after laser-induced damage. Fluorescent dyes combined with imaging of fluorescently-tagged proteins provides information regarding the basic structure of muscle and its response to stimuli.

This protocol utilizes electroporation to introduce and express fluorescently labeled proteins in mouse muscle fibers. Following recovery after electroporation, fibers are isolated. Individual fibers are then imaged using high resolution confocal microscopy to visualize muscle structure.

Mature muscle has a unique structure that is amenable to live cell imaging. Herein, we describe the experimental protocol for expressing fluorescently ...

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 ...

Electroporation and Nerve Injury in Mouse Levator Auris Longus Muscle

Combined In Vivo Electroporation and Short&#45;Term Reinnervation of the Cranial Levator Auris Longus Skeletal Muscle

The neuromuscular junction (NMJ) is the peripheral synapse controlling the contraction of skeletal muscle fibers to allow the coordinated movement of many organisms. At the NMJ, a presynaptic motor axon terminal contacts a muscle postsynaptic domain and is covered by terminal Schwann cells. The integrity and function of the NMJ is compromised under several conditions, including aging, neuromuscular diseases, and traumatic injuries. To analyze the potential contribution of muscle-derived proteins to NMJ maintenance and regeneration, an in vivo gene transfer strategy has been combined with the denervation of the cranial levator auris longus (LAL) muscle after mechanical nerve injury. Previous findings showed that the forced expression of control fluorescent proteins does not alter NMJ organization or neurotransmission. This procedure aims to describe a detailed method of in vivo electroporation of the LAL muscle followed by transection or crushing of the specific branch of the facial nerve innervating cranial muscles, leading to NMJ denervation and reinnervation, respectively. The combination of these experimental strategies in the convenient LAL muscle constitutes an efficient method to study the potential contribution of muscle protein overexpression or silencing in the context of short-term NMJ reinnervation.

Author Spotlight: Regenerative Roles of Muscle Proteins at Neuromuscular Junction Post-Nerve Injury

Here, we present a protocol that combines in vivo electroporation and denervation of the cranial levator auris longus (LAL) muscle. This procedure enables the study of the potential role of muscle-derived proteins in the regeneration of the neuromuscular synapse.

The neuromuscular junction (NMJ) is the peripheral synapse controlling the contraction of skeletal muscle fibers to allow the coordinated movement of many ...

Functional Site-Directed Fluorometry in Native Skeletal Muscle Cells

Functional Site-Directed Fluorometry in Native Cells to Study Skeletal Muscle Excitability

Functional site-directed fluorometry has been the technique of choice to investigate the structure-function relationship of numerous membrane proteins, including voltage-gated ion channels. This approach has been used primarily in heterologous expression systems to simultaneously measure membrane currents, the electrical manifestation of the channels&#39; activity, and fluorescence measurements, reporting local domain rearrangements. Functional site-directed fluorometry combines electrophysiology, molecular biology, chemistry, and fluorescence into a single wide-ranging technique that permits the study of real-time structural rearrangements and function through fluorescence and electrophysiology, respectively. Typically, this approach requires an engineered voltage-gated membrane channel that contains a cysteine that can be tested by a thiol-reactive fluorescent dye. Until recently, the thiol-reactive chemistry used for the site-directed fluorescent labeling of proteins was carried out exclusively in Xenopus oocytes and cell lines, restricting the scope of the approach to primary non-excitable cells. This report describes the applicability of functional site-directed fluorometry in adult skeletal muscle cells to study the early steps of excitation-contraction coupling, the process by which muscle fiber electrical depolarization is linked to the activation of muscle contraction. The present protocol describes the methodologies to design and transfect cysteine-engineered voltage-gated Ca2+ channels (CaV1.1) into muscle fibers of the flexor digitorum brevis of adult mice using in vivo electroporation and the subsequent steps required for functional site-directed fluorometry measurements. This approach can be adapted to study other ion channels and proteins. The use of functional site-directed fluorometry of mammalian muscle is particularly relevant to studying basic mechanisms of excitability.

Author Spotlight: Functional Site-Directed Fluorometry in Native Cells to Study Skeletal Muscle Excitability  

Functional site-directed fluorometry is a method to study protein domain motions in real time. Modification of this technique for its application in native cells now allows the detection and tracking of single voltage-sensor motions from voltage-gated Ca2+ channels in murine isolated skeletal muscle fibers.

Functional site-directed fluorometry has been the technique of choice to investigate the structure-function relationship of numerous membrane proteins, ...

Bacterial Transformation: Electroporation

The term &#x201C;transformation&#x201D; refers cellular ingestion of foreign DNA. In nature, transformation can occur in certain types of bacteria. In molecular biology, however, transformation is artificially induced through the creation of pores in the bacterial cell walls. Bacterial cells that are able to take up DNA from the environment are called competent cells. Electrocompetent cells can be produced in the laboratory and transformation of these cells can be achieve via the application of an electrical field that creates pores in the cell wall through which DNA can pass.
The video explains the equipment used in electroporation such as an electroporator and electroporation cuvette. The video also goes through a step-by-step procedure about how to create electrocompetent cells and electroporate cells of interest. 
Prediction of the success of a transformation of an experiment, by observing the time constant, as well as the importance of removing salt from the solutions when electroporating, are also mentioned.

The term &#x201C;transformation&#x201D; refers cellular ingestion of foreign DNA.  In nature, transformation can occur in certain types of bacteria.  In ...

Electroporation of Plasmid DNA into Mouse Skeletal Muscle

Summary

Explore More Videos

Chapters in this video

Improved Protocol for Chromatin Immunoprecipitation from Mouse Skeletal Muscle

Transplantation of Induced Pluripotent Stem Cell-derived Mesoangioblast-like Myogenic Progenitors in Mouse Models of Muscle Regeneration

DNA Transfection of Mammalian Skeletal Muscles using In Vivo Electroporation

Neonatal Pial Surface Electroporation

In Vivo Microinjection and Electroporation of Mouse Testis

DNA Electroporation, Isolation and Imaging of Myofibers

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

Combined In Vivo Electroporation and Short-Term Reinnervation of the Cranial Levator Auris Longus Skeletal Muscle

Functional Site-Directed Fluorometry in Native Cells to Study Skeletal Muscle Excitability

Bacterial Transformation: Electroporation