This work was supported by grants from the National Institute on Deafness and Other communication Disorders (R21DC010806 to C.A.M. and J.C.S and R01DC011285 to C.A.M.).

Use male Fischer 344-Brown Norway rats at 6 and 30 months of age for this protocol. Rats were obtained from the National Institute of Aging rodent colony. We used rats for this study because the structure of the rat larynx is similar to that of the human, functionally serving for airway protection and species-specific vocalizations This study was performed in accordance with the PHS Policy on Humane Care and Use of Laboratory Animals, the NIH Guide for the Care and Use of Laboratory Animals, and the Animal Welfare Act (7 U.S.C. et seq.); the animal use protocol was approved by the Institutional Animal Care and Use Committee (IACUC) of the University of Kentucky.
1. Anesthesia of Rats
<ol>
	<li>Prepare the anesthetics by mixing ketamine hydrochloride (dissociative anesthetic) and xylazine hydrochloride (sedative and analgesic) in buffered saline. The concentrations of ketamine and xylazine in the final solution are 100 mg/8 mg per kg body weight respectively.</li>
	<li>Inject the anesthetics into the rat by intraperitoneal administration using a syringe with a 25 G needle.</li>
	<li>Determine that the rat is sufficiently anesthetized by pinching the toe or foot with forceps. If the rat does not react to the pinch, then surgery can begin. If the rat reacts to the toe pinch with reflex or muscle contractions, then wait 1-2 min and repeat the pinch test. If the rat reacts again, replace the rat with a new animal and repeat procedure beginning from step 1.2.</li>
	<li>Apply ophthalmic ointment to the rat&#39;s eyes, after the rat is immobile, to prevent the corneas from drying out.</li>
</ol>
2. Osmotic Pump Implantation
<ol>
	<li>Place the rat ventral on the aseptic surgical area. &#160;Administer meloxicam as a preanesthetic medication. Administer intraperitoneally at a dosage of 1-4 mg/kg of body weight using a syringe with a 25 G needle.</li>
	<li>&#160;Use clippers to remove an approximately 1&#34; x 1&#34; square of fur from back of neck, and approximately 1&#34; caudal of space between shoulders. Shave as close to the skin as possible.</li>
	<li>Wet the back and neck with disinfecting ethanol (70%).</li>
	<li>After shaving, scrub the dorsal aspect of the neck with&#160;3 scrubs in succession of iodine-alcohol finishing with alcohol.</li>
	<li>Maintain the body temperature of the rat by placing it on a heating pad set to 34 &#176;C.</li>
	<li>Fill aseptically prepared osmotic pumps with either 50 &#181;L of NTF4 or saline for systemic NTF4 treatment (Figure 1).
	<ol>
		<li>Use a scalpel to make a horizontal incision approximately 2 cm wide through the skin, just cranial&#160;to the space between the scapulae. Lift the posterior edge of the incision with forceps with one hand while inserting the tip of hemostats and gently pushing posterior to the incision.</li>
		<li>After the tip of the hemostats is approximately 2 cm cranial&#160;to the incision, open the handles on the hemostats, expanding the tips to form a hollow &#34;pocket&#34; subcutaneous to the incision site. This will be the placement site for the pump.</li>
	</ol>
	</li>
	<li>Orient the pump delivery portal end first upon insertion to minimize any interaction of the NTF4 and the healing of the pocket incision site.</li>
	<li>Deliver 50 &#181;L of NTF4 saline for either 7 14 days. The 7 day group received 6.72 mg/day of NTF4 for a total dose of 47.04 mg. The 14-day group received 6.72 mg/day for a total dose of 94.08 mg of NTF425.</li>
	<li>Use 5-0 nylon suture thread, hemostats and forceps to close the incision made for pump placement.</li>
	<li>Observe the rats for a minimum of 30 min as they recover from anesthesia. Criteria for completion of monitoring include the animal becoming active, moving about the cage, drinking water, and beginning other normal activities such as grooming.</li>
	<li>Monitor animals daily for the first week by observing the healing of surgical site, normal feed and water consumption and passing of urine/feces, and any abnormal behavioral signs of stress, pain, or other post-operative complications.</li>
	<li>If the rat appears to be in pain or distress, provide the rat with a 5 mg/kg subcutaneous injection of carprofen once every 24 h for up to 5 days to relieve pain.</li>
	<li>If there appears to be an infection, consult a veterinarian to ensue that the wound heals properly.</li>
	<li>Depending on which experimental group the rat in in, remove the 5-0 nylon suture 7-10 days following surgery to prevent irritation from the thread.</li>
</ol>
3. Anesthesia of Rats for Direct Injection
<ol>
	<li>Withhold food from the rats the night before the procedure. This ensures that there is no food to block the endoscope or injection needle.</li>
	<li>Weigh rats and prepare acepromazine 1-2 mg/kg body weight. Inject intramuscularly (the IM location is the left thyroarytenoid muscle).</li>
	<li>Place the rat in the induction box. Induce anesthesia in the induction box with 5% isoflurane and 1 L O2.</li>
	<li>Move the rat to a nose cone with 2% isoflurane and 600 mL O2.</li>
	<li>Determine that the rat is sufficiently anesthetized by pinching the toe or foot with forceps. If the rat does not react to the pinch, then the injection protocol can begin. If the rat reacts to the toe pinch with reflex or muscle contractions, then wait 1-2 min and repeat the pinch test. If the rat reacts again, replace the rat with a new animal and repeat procedure beginning from step 3.4.</li>
</ol>
4. Direct Injection and Visualization
<ol>
	<li>Place aseptically prepared 50-&#181;L dosages containing NTF4 or saline in a H2O bath set to 25&#176; C for 30 min before injection.</li>
	<li>Place the rat in a supine and reclined position on a plexiglass platform (Figure 2). Suspend the rat in the reclined posture from their frontal top incisors via a guide wire strung across the top of the platform.</li>
	<li>Attach a 50 mm, 30 gauge, 100 &#181;L syringe to a 1.9 mm, 30&#176; sinus endoscope (Figure 3). 
	NOTE: The syringe assembly is attached via a jig that holds the cannula firmly to the outer wall of the endoscope. The endoscope allows for visualization of the vocal folds and guidance of the syringe intraorally. The position of the cannula tip is adjusted prior to each animal to ensure that the tip is fully and clearly visible via the endoscopic view (Figure 4).</li>
	<li>Use a rubber-tipped pair of forceps to extend the tongue and move it laterally. Afterward, insert a plastic speculum to maintain oral patency. Make the speculum from a 5 mL plastic syringe barrel that is cut to a length of 1.5 to 2 cm, with the cut edges deburred and polished smooth.</li>
	<li>Turn off the lights in the room and attach a halogen light source to the endoscope. Turn on the video recorder to capture the procedure.</li>
	<li>Immerse the distal end of the endoscope in warm water for a few seconds to minimize the development of condensation on the glass tip when inserted into the mouth of the rat.</li>
	<li>Using visual feedback from the monitor, carefully guide the needle to the area of the left vocal fold.</li>
	<li>Time the injection of the solution with the inspiratory phase of the animals&#39; respiration cycle to fully access the vocal fold. During the inspiratory phase of respiration, the vocal fold is fully exposed.
	<ol>
		<li>Once the vocal fold is fully visible, insert the needle into the left thyroarytenoid, found lateral to the white medial edge of the vocal fold. With the needle in place, deliver the injectate through depression of the syringe.</li>
	</ol>
	</li>
	<li>Turn off the halogen light source on the endoscope and the video player, and turn back on the room lights.</li>
	<li>Return the rat to its home cage and place on a heating pad.</li>
	<li>Allow the rat to recover before removal from the heating pad. Replace food and water in the cage.</li>
	<li>Monitor rats for 7 days after the injection and then euthanize. Remove the larynges for cryosectioning24.</li>
</ol>
5. Euthanization of Rats
<ol>
	<li>Anesthetize rats with ketamine hydrochloride and xylazine hydrochloride (100 mg/8 mg per kg body weight injected intraperitoneal injection).</li>
	<li>Euthanize by exsanguination following a medial thoracotomy.</li>
</ol>

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The authors have nothing to disclose.

Laryngeal muscles are vulnerable to the unfavorable effects of aging. Previous studies have demonstrated changes in aging laryngeal muscles that include changes in fiber size, total number of fibers, regenerative ability, NMJ size and quantity changes, in addition to variations in contractile function and myosin isoform shifts 4,11,27,30,31. Aging laryngeal mu...

Laryngeal muscles contract rapidly and consistently, and are vulnerable to the adverse effects of aging. This constant activity is thought to contribute to voice problems or dysphagia observed in persons over 65 years of age 1,2,3,4,5,6,7. Several molecular and pathophysiologic mechanisms contribute to this age-related dysfunction. These mechanisms can include remodeling of laryngeal mucosa, muscle fiber atrophy or loss, lack of muscle fiber regeneration or atrophy which causes bowing of the vocal folds and inability of glottis closure 8,9,10,11. There is no proven medical therapy at this time that can completely prevent or rehabilitate these age-related changes in these muscles.
Modulation of the effectiveness of neuromuscular transmission can greatly influence neuromotor performance. The family of neurotrophins include nerve growth factor (NGF), brain derived nerve growth factor (BDNF), neurotrophin 3 (NTF3) and NTF4 12,13. Neurotrophins have been shown to modulate synaptic efficacy1,4. Hepatocyte growth factor, transforming growth factor beta and fibroblast growth factor have recently been used in humans for the treatment of vocal fold scarring 15-17. NTF4 also regulates NMJ effectiveness; mice lacking NTF4 show disassembled NMJs 11,18,19. These studies lead to promising effects of treatment of aging laryngeal muscle disorders and denervation with growth factors.
Direct injection therapeutics to the tissues of the vocal folds are not unprecedented in humans. For example, local injections of botulinum toxin are currently used as an effective treatment for neurological movement disorders that affect the muscles in the larynx, such as spasmodic dysphonia and bilateral recurrent laryngeal nerve paralysis 20,21. Hyaluronic acid hydrogel is another injectable, which is used to treat vocal fold scaring and glottal insufficiency 22,23. Injection laryngoplasty can be used to treat a variety of communication disorders 24. These direct injection methods hold promise to improve vocal function and swallowing in aging populations.

<table><tbody><tr><td>Neurotrophin 4</td><td>Pepro Tech</td><td>450-04</td><td>200 ng in 50 &amp;mu;L</td></tr><tr><td>Alzet Osmotic Pump</td><td>DURECT Corporation</td><td>2001D</td><td></td></tr><tr><td>30 &amp;deg; endoscope</td><td>Stoltz</td><td>61029D</td><td></td></tr><tr><td>50 mm 30 gauge 100-&amp;mu;L syringe</td><td>Hamilton</td><td>84850 and 201812</td><td></td></tr><tr><td>saline (sodium chloride solution)</td><td>Sigma-Aldrich</td><td>S8776</td><td></td></tr><tr><td>ketamine hydrochloride</td><td>Henry Schein</td><td>56344</td><td></td></tr><tr><td>xylazine hydrochloride</td><td>Henry Schein</td><td>33198</td><td></td></tr><tr><td>25 G 5/8 needle</td><td>Becton-Dickinson</td><td>305901</td><td></td></tr><tr><td>1 mL syringe</td><td>Becton-Dickinson</td><td>309659</td><td></td></tr><tr><td>ophthalmic ointment</td><td>Henry Schein</td><td>8897</td><td></td></tr><tr><td>clippers</td><td>Oster</td><td>44-018</td><td></td></tr><tr><td>ethanol</td><td>Decon</td><td>2716</td><td></td></tr><tr><td>iodine (Betadine)</td><td>Purdue Pharma L.P.</td><td>606404</td><td></td></tr><tr><td>heating pad</td><td>Sunbeam</td><td>731-5</td><td></td></tr><tr><td>5-0 nylon suture thread</td><td>AD Surgical</td><td>PMN-518R6</td><td></td></tr><tr><td>crile hemostat</td><td>Fine Science Tools</td><td>13005-14</td><td></td></tr><tr><td>delicate suture tying forceps</td><td>Fine Science Tools</td><td>11063-07</td><td></td></tr><tr><td>meloxicam</td><td>Henry Schein</td><td>49756</td><td></td></tr><tr><td>carprofen</td><td>Merritt Veterinary Supplies</td><td>148700</td><td></td></tr><tr><td>antibiotic ointment</td><td>Henry Schein</td><td>57110</td><td></td></tr><tr><td>acepromizine Aceproject</td><td>Henry Schein</td><td>3845</td><td></td></tr><tr><td>isoflurane Isothesia</td><td>Henry Schein</td><td>50033</td><td></td></tr><tr><td>induction box (anesthetizing box)</td><td>Harvard Apparatus</td><td>50-0116</td><td></td></tr><tr><td>oxygen compressed tank</td><td>Scott Gross</td><td>UN1072</td><td></td></tr><tr><td>plexiglas platform</td><td>Small Parts Inc (Amazon)</td><td></td><td></td></tr><tr><td>rubber tipped forceps</td><td>Fine science tools rubber</td><td>11075-00</td><td></td></tr><tr><td>liquid rubber for forceps above</td><td>Lowe&#039;s</td><td>42518</td><td></td></tr><tr><td>plastic spectula (BD syringe cut to length)</td><td>Becton-Dickinson</td><td>309659</td><td></td></tr><tr><td>halogen light source rhino-laryngeal stroboscope</td><td>Kay-Pentax</td><td>RLS 9100 B</td><td></td></tr><tr><td>video recorder</td><td>Kay-Pentax</td><td></td><td></td></tr><tr><td>sucrose</td><td>Sigma-Aldrich</td><td>S0389-500G</td><td></td></tr><tr><td>phosphate buffered saline</td><td>Sigma-Aldrich</td><td>P4417-100TAB</td><td></td></tr><tr><td>cryostat Mictotom HM525</td><td>Thermo Scientific</td><td>HM 525</td><td></td></tr><tr><td>Gill 1 hematoxylin</td><td>VWR</td><td>10143-142</td><td></td></tr><tr><td>Shandon eosin-Y alcoholic</td><td>Thermo Fisher Scientific</td><td>6766007</td><td></td></tr><tr><td>anti-sodium channel Nav1.5 antibody produced in rabbit</td><td>Sigma-Aldrich</td><td>S0819</td><td></td></tr><tr><td>Texas red-X phalloidin</td><td>Sigma-Aldrich</td><td>T7471</td><td></td></tr><tr><td>alpha- bungarotoxin alexa fluor 488 conjugate</td><td>Thermo Fisher Scientific</td><td>B-13422</td><td></td></tr><tr><td>Small animal anaesthesia machine</td><td>Smiths Medical</td><td>CDS 9000</td><td></td></tr></tbody></table>

subcutaneous neurotrophin 4 infusion using osmotic pumps or direct muscular injection enhances aging rat laryngeal muscles

Laryngeal dysfunction in the elderly is a major cause of disability, from voice disorders to dysphagia and loss of airway protective reflexes. Few, if any, therapies exist that target age-related laryngeal muscle dysfunction. Neurotrophins are involved in muscle innervation and differentiation of neuromuscular junctions (NMJs). It is thought that neurotrophins enhance neuromuscular transmission by increasing neurotransmitter release. The neuromuscular junctions (NMJs) become smaller and less abundant in aging rat laryngeal muscles, with evidence of functional denervation. We explored the effects of NTF4 for future clinical use as a therapeutic to improve function in aging human laryngeal muscles. Here, we provide the detailed protocol for systemic application and direct injection of NTF4 to investigate the ability of aging rat laryngeal muscle to remodel in response to NTF4 application. In this method, rats either received NTF4 either systemically via osmotic pump or by direct injection through the vocal folds. Laryngeal muscles were then dissected and used for histological examination of morphology and age-related denervation.

The rats were euthanized after 2 weeks of osmotic pump infusion or 1 week after direct injection of NTF4. Larynges were harvested, placed in cryoprotectant (30% sucrose and 70% phosphate buffered saline) and then serially sectioned in 10- &#181;m widths with a cryostat. Aging laryngeal muscles are affected by administration of NTF4 25. In addition to young and old rat, we compared the injected and non-injected side of the thyroarytenoid muscles. Typically we see a ...

Watch this Scientific Journal Video about Subcutaneous Neurotrophin 4 Infusion Using Osmotic Pumps or Direct Muscular Injection Enhances Aging Rat Laryngeal Muscles at JoVE.com

Subcutaneous Neurotrophin 4 Infusion Using Osmotic Pumps or Direct Muscular Injection Enhances Aging Rat Laryngeal Muscles

Here, we present a protocol to describe the use of neurotrophin 4 (NTF4) systemically and directly to remodel rat aging laryngeal muscles.

Laryngeal dysfunction in the elderly is a major cause of disability, from voice disorders to dysphagia and loss of airway protective reflexes. Few, if ...

subcutaneous-neurotrophin-4-infusion-using-osmotic-pumps-or-direct

Research

JoVE Journal

Developmental Biology

8.3K Views.  University of Kentucky. Here, we present a protocol to describe the use of neurotrophin 4 (NTF4) systemically and directly to remodel rat aging laryngeal muscles.

Video: Subcutaneous Neurotrophin 4 Infusion Using Osmotic Pumps or Direct Muscular Injection Enhances Aging Rat Laryngeal Muscles

Intraspinal Cell Transplantation for Targeting Cervical Ventral Horn in Amyotrophic Lateral Sclerosis and Traumatic Spinal Cord Injury

Respiratory compromise due to phrenic motor neuron loss is a debilitating consequence of a large proportion of human traumatic spinal cord injury (SCI) cases 1 and is the ultimate cause of death in patients with the motor neuron disorder, amyotrophic laterals sclerosis (ALS) 2.
ALS is a devastating neurological disorder that is characterized by relatively rapid degeneration of upper and lower motor neurons. Patients ultimately succumb to the disease on average 2-5 years following diagnosis because of respiratory paralysis due to loss of phrenic motor neuron innnervation of the diaphragm 3. The vast majority of cases are sporadic, while 10% are of the familial form. Approximately twenty percent of familial cases are linked to various point mutations in the Cu/Zn superoxide dismutase 1 (SOD1) gene on chromosome 21 4. Transgenic mice 4,5 and rats 6 carrying mutant human SOD1 genes (G93A, G37R, G86R, G85R) have been generated, and, despite the existence of other animal models of motor neuron loss, are currently the most highly used models of the disease.
Spinal cord injury (SCI) is a heterogeneous set of conditions resulting from physical trauma to the spinal cord, with functional outcome varying according to the type, location and severity of the injury 7. Nevertheless, approximately half of human SCI cases affect cervical regions, resulting in debilitating respiratory dysfunction due to phrenic motor neuron loss and injury to descending bulbospinal respiratory axons 1. A number of animal models of SCI have been developed, with the most commonly used and clinically-relevant being the contusion 8.
Transplantation of various classes of neural precursor cells (NPCs) is a promising therapeutic strategy for treatment of traumatic CNS injuries and neurodegeneration, including ALS and SCI, because of the ability to replace lost or dysfunctional CNS cell types, provide neuroprotection, and deliver gene factors of interest 9.
Animal models of both ALS and SCI can model many clinically-relevant aspects of these diseases, including phrenic motor neuron loss and consequent respiratory compromise 10,11. In order to evaluate the efficacy of NPC-based strategies on respiratory function in these animal models of ALS and SCI, cellular interventions must be specifically directed to regions containing therapeutically relevant targets such as phrenic motor neurons. We provide a detailed protocol for multi-segmental, intraspinal transplantation of NPCs into the cervical spinal cord ventral gray matter of neurodegenerative models such as SOD1G93A mice and rats, as well as spinal cord injured rats and mice 11.

Neural precursor transplantation is a promising strategy for protecting and/or replacing lost/dysfunctional cervical phrenic motor neurons in spinal cord injury (SCI) and the motor neuron disorder, amyotrophic laterals sclerosis (ALS). We provide a protocol for cell delivery to cervical spinal cord ventral horn in rodent models of ALS and SCI.

Respiratory compromise due to phrenic motor neuron loss is a debilitating consequence of a large proportion of human traumatic spinal cord injury (SCI) ...

Medicine

A Murine Model of Muscle Training by Neuromuscular Electrical Stimulation

Neuromuscular electrical stimulation (NMES) is a common clinical modality that is widely used to restore1, maintain2 or enhance3-5 muscle functional capacity. Transcutaneous surface stimulation of skeletal muscle involves a current flow between a cathode and an anode, thereby inducing excitement of the motor unit and the surrounding muscle fibers. 
NMES is an attractive modality to evaluate skeletal muscle adaptive responses for several reasons. First, it provides a reproducible experimental model in which physiological adaptations, such as myofiber hypertophy and muscle strengthening6, angiogenesis7-9, growth factor secretion9-11, and muscle precursor cell activation12 are well documented. Such physiological responses may be carefully titrated using different parameters of stimulation (for Cochrane review, see 13). In addition, NMES recruits motor units non-selectively, and in a spatially fixed and temporally synchronous manner14, offering the advantage of exerting a treatment effect on all fibers, regardless of fiber type. Although there are specified contraindications to NMES in clinical populations, including peripheral venous disorders or malignancy, for example, NMES is safe and feasible, even for those who are ill and/or bedridden and for populations in which rigorous exercise may be challenging. 
Here, we demonstrate the protocol for adapting commercially available electrodes and performing a NMES protocol using a murine model. This animal model has the advantage of utilizing a clinically available device and providing instant feedback regarding positioning of the electrode to elicit the desired muscle contractile effect. For the purpose of this manuscript, we will describe the protocol for muscle stimulation of the anterior compartment muscles of a mouse hindlimb.

A murine model of neuromuscular electrical stimulation (NMES), a safe and inexpensive clinical modality, to the anterior compartment muscles is described. This model has the advantage of modifying a readily available clinical device for the purpose of eliciting targeted and specific muscle contractions in mice.

Neuromuscular electrical stimulation (NMES) is a common clinical modality that is widely used to restore1, maintain2 or enhance3-5 muscle functional ...

Subcutaneous Administration of Muscarinic Antagonists and Triple-Immunostaining of the Levator Auris Longus Muscle in Mice

Hind limb muscles of rodents, such as gastrocnemius and tibialis anterior, are frequently used for in vivo pharmacological studies of the signals essential for the formation and maintenance of mammalian NMJs. However, drug penetration into these muscles after subcutaneous or intramuscular administration is often incomplete or uneven and many NMJs can remain unaffected. Although systemic administration with devices such as mini-pumps can improve the spatiotemporal effects, the invasive nature of this approach can cause confounding inflammatory responses and/or direct muscle damage. Moreover, complete analysis of the NMJs in a hind limb muscle is challenging because it requires time-consuming serial sectioning and extensive immunostaining. 
The mouse LAL is a thin, flat sheet of muscle located superficially on the dorsum of the neck. It is a fast-twitch muscle that functions to move the pinna. It contains rostral and caudal portions that originate from the midline of the cranium and extend laterally to the cartilaginous portion of each pinna. The muscle is supplied by a branch of the facial nerve that projects caudally as it exits the stylomastoid foramen. We and others have found LAL to be a convenient preparation that offers advantages for the investigation of both short and long-term in vivo effects of drugs on NMJs and muscles. First, its superficial location facilitates multiple local applications of drugs under light anesthesia. Second, its thinness (2-3 layers of muscle fibers) permits visualization and analysis of almost all the NMJs within the muscle. Third, the ease of dissecting it with its nerve intact together with the pattern of its innervation permits supplementary electrophysiological analysis in vitro9,5. Last, and perhaps most importantly, a small applied volume (&tilde;50&mu;l) easily covers the entire muscle surface, provides a uniform and prolonged exposure of all its NMJs to the drug and eliminates the need for a systemic approach1,8.

We describe procedures for repeated administration of inhibitors of muscarinic signaling to the levator auris longus (LAL) muscle of young adult mice and for subsequent immunostaining of its neuromuscular junctions (NMJs) in wholemounts. The LAL muscle has unique advantages for revealing in vivo pharmacological effects on NMJs.

Hind limb muscles of rodents, such as gastrocnemius and tibialis anterior, are frequently used for in vivo  pharmacological studies of the signals ...

Neuroscience

Tibial Nerve Transection - A Standardized Model for Denervation-induced Skeletal Muscle Atrophy in Mice

The tibial nerve transection model is a well-tolerated, validated, and reproducible model of denervation-induced skeletal muscle atrophy in rodents. Although originally developed and used extensively in the rat due to its larger size, the tibial nerve in mice is big enough that it can be easily manipulated with either crush or transection, leaving the peroneal and sural nerve branches of the sciatic nerve intact and thereby preserving their target muscles. Thus, this model offers the advantages of inducing less morbidity and impediment of ambulation than the sciatic nerve transection model and also allows investigators to study the physiologic, cellular and molecular biologic mechanisms regulating the process of muscle atrophy in genetically engineered mice. The tibial nerve supplies the gastrocnemius, soleus and plantaris muscles, so its transection permits the study of denervated skeletal muscle composed of fast twitch type II fibers and/or slow twitch type I fibers. Here we demonstrate the tibial nerve transection model in the C57Black6 mouse. We assess the atrophy of the gastrocnemius muscle, as a representative muscle, at 1, 2, and 4 weeks post-denervation by measuring muscle weights and fiber type specific cross-sectional area on paraffin-embedded histologic sections immunostained for fast twitch myosin.

The tibial nerve transection model is a well-tolerated, validated, and reproducible model of skeletal muscle atrophy. The model surgical protocol is described and demonstrated in C57Black6 mice. &#160;

The tibial nerve transection model is a well-tolerated, validated, and reproducible model of denervation-induced skeletal muscle atrophy in rodents. ...

Transplantation of Olfactory Ensheathing Cells to Evaluate Functional Recovery after Peripheral Nerve Injury

Olfactory ensheathing cells (OECs) are neural crest cells which allow growth and regrowth of the primary olfactory neurons. Indeed, the primary olfactory system is characterized by its ability to give rise to new neurons even in adult animals. This particular ability is partly due to the presence of OECs which create a favorable microenvironment for neurogenesis. This property of OECs has been used for cellular transplantation such as in spinal cord injury models. Although the peripheral nervous system has a greater capacity to regenerate after nerve injury than the central nervous system, complete sections induce misrouting during axonal regrowth in particular after facial of laryngeal nerve transection. Specifically, full sectioning of the recurrent laryngeal nerve (RLN) induces aberrant axonal regrowth resulting in synkinesis of the vocal cords. In this specific model, we showed that OECs transplantation efficiently increases axonal regrowth.
OECs are constituted of several subpopulations present in both the olfactory mucosa (OM-OECs) and the olfactory bulbs (OB-OECs). We present here a model of cellular transplantation based on the use of these different subpopulations of OECs in a RLN injury model. Using this paradigm, primary cultures of OB-OECs and OM-OECs were transplanted in Matrigel after section and anastomosis of the RLN. Two months after surgery, we evaluated transplanted animals by complementary analyses based on videolaryngoscopy, electromyography (EMG), and histological studies. First, videolaryngoscopy allowed us to evaluate laryngeal functions, in particular muscular cocontractions phenomena. Then, EMG analyses demonstrated richness and synchronization of muscular activities. Finally, histological studies based on toluidine blue staining allowed the quantification of the number and profile of myelinated fibers.
All together, we describe here how to isolate, culture, identify and transplant OECs from OM and OB after RLN section-anastomosis and how to evaluate and analyze the efficiency of these transplanted cells on axonal regrowth and laryngeal functions.

Olfactory ensheathing cells (OECs) are neural crest cells which allow growth of the primary olfactory neurons. This specific property can be used for cellular transplantation. We present here a model of cellular transplantation based on the use of OECs in a laryngeal nerve injury model.

Olfactory ensheathing cells (OECs) are neural crest cells which allow growth and regrowth of the primary olfactory neurons. Indeed, the primary olfactory ...

Intramuscular Injections Along the Motor End Plates: A Minimally Invasive Approach to Shuttle Tracers Directly into Motor Neurons

Diseases affecting the integrity of spinal cord motor neurons are amongst the most debilitating neurological conditions. Over the last decades, the development of several animal models of these neuromuscular disorders has provided the scientific community with different therapeutic scenarios aimed at delaying or reversing the progression of these conditions. By taking advantage of the retrograde machinery of neurons, one of these approaches has been to target skeletal muscles in order to shuttle therapeutic genes into corresponding spinal cord motor neurons. Although once promising, the success of such gene delivery approach has been hampered by the sub-optimal number of transduced motor neurons it has so far shown to yield. Motor end plates (MEPs) are highly specialized regions on the skeletal musculature that are in direct synaptic contact to the spinal cord &#945; motor neurons. In this regard, it is important to note that, so far, the efforts to retrogradely transfer genes into motor neurons were made without reference to the location of the MEP region in the targeted muscles. Here, we describe a simple protocol 1) to reveal the exact location of the MEPs on the surface of skeletal muscles and 2) to use this information to guide the intramuscular delivery and subsequent optimal retrograde transport of retrograde tracers into motor neurons. We hope to utilize the results from these tracing experiments in further studies into investigating retrograde transport of therapeutic genes to spinal cord motor neurons through the targeting of MEPs.

The efficacy of intramuscular uptake and retrograde transport of molecules to corresponding motor neurons depends on the location of the injection sites with respect to the motor end plates (MEPs). Here, we describe how to locate MEPs on skeletal muscles to optimise retrograde transport of tracers into motor neurons.

Diseases affecting the integrity of spinal cord motor neurons are amongst the most debilitating neurological conditions. Over the last decades, the ...

Nerve Stimulator-guided Injection of Autologous Stem Cells Near the Equine Left Recurrent Laryngeal Nerve

Recurrent laryngeal neuropathy (RLN) commonly affects horses and is characterized by abnormal respiratory sounds and exercise intolerance. The recurrent laryngeal nerve shows lesions of demyelination. The benefit of applying stem cells to demyelinated nerves has been demonstrated in various animal models. The aim of the study was to test the feasibility and safety of a peri-neuronal injection of autologous muscle-derived mesenchymal stem cells to the left recurrent laryngeal nerve in healthy horses by using an electrical nerve stimulator.
Muscle-derived stems cell are obtained from five healthy Standardbred horses by sampling 20 mg of muscle tissue with a semi-automatic 14 G biopsy needle from the triceps muscle. Movements of the larynx are monitored via upper-airway video endoscopy. The left recurrent laryngeal nerve is approached with an insulated nerve block needle. Nerve stimulation is applied, starting at 2 mA, and the successful abduction of the left arytenoid is monitored. The stimulation intensity is reduced progressively. When a loss of the motor response is observed at 0.5 mA, 107 autologous muscle-derived stem cells are injected. Two examiners, who are blinded to the time point, score the laryngeal function of the horses prior to the treatment and at day 1, day 7, and day 28 after the injection of the cells. In a sixth horse, 1 mL of 2% lidocaine is injected to further confirm the correct positioning of the needle. This leads to a temporary paralysis of the left arytenoid cartilage.
This study proves that the recurrent laryngeal nerve can be approached with the help of an electrical nerve stimulator and that the electrical stimulation of the nerve is well tolerated by the horses. No modification of the laryngeal function was observed in any of the horses after the injection of the stem cells. Further studies should be conducted to describe the effects of a peri-neuronal injection of autologous muscle-derived mesenchymal stem cells to horses suffering from RLN.

Here, we present a protocol to inject autologous muscle-derived stem cells in the proximity to the recurrent laryngeal nerve with the help of an electrical nerve stimulator. This novel technique may become useful for the treatment of equine recurrent laryngeal neuropathy.

Recurrent laryngeal neuropathy (RLN) commonly affects horses and is characterized by abnormal respiratory sounds and exercise intolerance. The recurrent ...

An Implantable System For Chronic In Vivo Electromyography

Electromyography (EMG) measures the muscle response to electrical stimulation or spontaneous activity of motor units and plays an important role in assessing neuromuscular function. Chronic recording of EMG activity reflecting a muscle&#8217;s reinnervation status after nerve injury has been limited, due to the invasive nature of traditional EMG recording techniques. In this regard, an implantable system is designed for long-term, in vivo EMG recording and nerve stimulation. It has been applied and tested in a study on reinnervation of laryngeal muscles. This system consists of 1) two bipolar electrode nerve cuffs and leads for stimulating each of two nerves: the recurrent laryngeal nerve (RLN) and internal branch of the superior laryngeal nerve (SLN); 2) two EMG recording electrodes and leads for each of the two laryngeal muscles: posterior cricoarytenoid (PCA) muscle and thyroarytenoid-lateral cricoarytenoid (TA-LCA) muscle complex; and 3) a skin receptacle interfacing all implanted lead terminals to an external recording preamplifier and stimulator using a connection cable. The wire leads are Teflon-coated, multi-filament, type 316 stainless steel. They are coiled and can stretch during body movement of the awake animal to prevent lead breakage and electrode migration. This system is implanted during an aseptic surgery. Afterwards, baseline EMG recordings are performed before the RLN is transected in the second surgery to study muscle reinnervation. Throughout the study, multiple physiological sessions are conducted in the anesthetized animal to obtain evoked and spontaneous EMG activity that reflects the reinnervation status of laryngeal muscles. The system is compact, free of infection over the course of the study, and highly durable. This implantable system can provide a reliable platform for research in which long-term recording or nerve stimulation is required in an anesthetized or freely moving animal.&#160;

Presented here is a protocol for the manufacturing of an implantable system for in vivo chronological recording of evoked and spontaneous electromyographic potentials. The system is applied to the investigation of reinnervation of laryngeal muscles following nerve injury. &#160;&#160;

Electromyography (EMG) measures the muscle response to electrical stimulation or spontaneous activity of motor units and plays an important role in ...

Preparation of the Rat Vocal Fold for Neuromuscular Analyses

The purpose of this tutorial is to describe the preparation of the rat vocal fold for histochemical neuromuscular study. This protocol outlines procedures for rat laryngeal dissection, flash-freezing, and cryosectioning of the vocal folds. This study describes how to cryosection vocal folds in both longitudinal and cross-sectional planes. A novelty of this protocol is the laryngeal tracking during cryosectioning that ensures accurate identification of the intrinsic laryngeal muscles and reduces the chance of tissue loss. Figures demonstrate the progressive cryosectioning in both planes. Twenty-nine rat hemi-larynges were cryosectioned and tracked from the emergence of the thyroid cartilage to the appearance of the first section that included the full vocal fold. The full vocal fold was visualized for all animals in both planes. There was high variability in the distance from the appearance of the thyroid cartilage to the appearance of the full vocal fold in both planes. Weight was not correlated to depth of laryngeal landmarks, suggesting individual variability and other factors related to tissue preparation may be responsible for the high variability in the appearance of landmarks during sectioning. This study details a methodology and presents morphological data for preparing the rat vocal fold for histochemical neuromuscular investigation. Due to high individual variability, laryngeal landmarks should be closely tracked during cryosectioning to prevent oversectioning tissue and tissue loss. The use of a consistent methodology, including adequate tissue preparation and awareness of landmarks within the rat larynx, will assist with consistent results across studies and aid new researchers interested in using the rat vocal fold as a model to investigate laryngeal neuromuscular mechanisms.

This protocol describes methods used to prepare rat vocal folds for histochemical neuromuscular study.

The purpose of this tutorial is to describe the preparation of the rat vocal fold for histochemical neuromuscular study. This protocol outlines procedures ...

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 ...