Name: functional and physiological methods of evaluating median nerve regeneration in the rat
Uploaded: 2020-04-18T14:00:00.000+00:00
Duration: 12 min 9 s
Description: Watch this Scientific Journal Video about Functional and Physiological Methods of Evaluating Median Nerve Regeneration in the Rat at JoVE.com

Diogo Casal received a grant from The Program for Advanced Medical Education, which is sponsored by Funda&#231;&#227;o Calouste Gulbenkian, Funda&#231;&#227;o Champalimaud, Minist&#233;rio da Sa&#250;de e Funda&#231;&#227;o para a Ci&#234;ncia e Tecnologia, Portugal. The authors are very grateful to Mr. Filipe Franco for the illustrative drawing in Figure 1. The authors would like to thank the technical help of Mr. Alberto Severino in filming and editing the video. Finally, the authors would like to thank Ms. Sara Marques for her help in all the logistical aspects pertaining to animal acquisition and maintenance.

The authors have nothing to disclose.

This paper presents a protocol to create different types of MN lesions and repair in the rat. Additionally, it illustrates how to evaluate the functional recovery of this nerve using several noninvasive behavioral tests and physiological measurements.
Notably, several of the functional tests described in this paper, namely the Ladder Running Test and the Rope Test, are significantly dependent on the rat&#8217;s willingness to perform the task with the expectation of obtaining the food reward51,52,53. It should be noted that certain rat strains are more amenable to training and performing reproducibly in this type of tests51,52,53. For example, Lewis rats perform poorly in these tests both in the training phase and subsequently51,52,53.
Rat housing should permit ample freedom of movement in agreement with their natural exploratory behavior, in addition to allowing experimental animals to get familiar with some of the elements present in the functional tests19. Therefore, different forms of housing allowing higher freedom of movement are shown. The big cages are personalized with enrichment elements that are later used in the functional tests (e.g., ropes and ladders).
Arguably, these enriching elements as well as the cages with incorporated running wheels and the individual training spheres provide a form of postoperative physiotherapy similar to that offered to human patients operated on the peripheral nervous system10.
Significantly, although some authors advocate dissecting the subcutaneous tissues and muscle fasciae bluntly or by clean cutting with a number 15 scalpel, the use of thermocautery when dissecting these structures is recommended to minimize the risk of postoperative hematoma.
It should be noted that numerous tests have been devised to test different aspects of peripheral nerve repair in the rat, namely axonal regeneration, target reinnervation, and functional recovery, some of which are beyond the scope of this study29,54,55,56. For example, kinematic analysis29,36,55 and histomorphometric assessment29,36,57 are widely employed by multiple authors. Additionally, several of these tests involve variations to maximize efficiency and/or reproducibility54. For example, mechanical algisemetry (i.e., evaluation of responses to mechanical painful stimuli) can be assessed qualitatively using a given von Frey filament, as described in the present paper, or semiquantitatively using successively stronger von Frey filaments, or even quantitatively using electronic devices that apply increasing pressures until a withdrawal response is observed30,54.
Similarly, although several authors use walking track analysis to evaluate forelimb nerve repair in the rat, other authors argue that single MN lesions frequently fail to produce reproducible changes in pawprints10,58,59. Furthermore, some have stated that these changes may not be proportional to muscle recovery10,60. Bearing this in mind, some researchers have advocated the use of walking track analysis in the forepaw mainly when assessing recovery after crushing neve lesions rather than after segmental nerve reconstruction10,50,61.
The Grasping Test is widely used to evaluate motor recovery of the muscles controlled by the MN16,27. To guarantee uniformity and reproducibility of the data obtained with this test, applying the Grasping Test using the well-established methodology proposed by Bertelli et al.16 is recommended. However, the current protocol differs in that it does not routinely immobilize the contralateral paw to prevent undue stress11,27. It should also be noted that other authors, after immobilizing the uninjured paw, quantitatively assess the Grasping Test using a dynamometer or a scale27,56. However, this quantitative evaluation may be affected by the strength the researcher applies to the rat&#8217;s tail26. Furthermore, it is difficult to distinguish between the strength generated by the digital flexor muscles (solely innervated by the MN in the rat and the object of the Grasping Test9) from the strength produced by the wrist flexors, which include the flexor carpi ulnaris that receives its innervation from the ulnar nerve9,10,27. In order to try to circumvent these potential biases, this protocol uses an ordinal scale similar to the Medical Research Council Scale commonly used to grade muscle strength in humans10,11,62. Alternatively, other authors have described detailed assessment of grasping using video analysis and a video-based scoring system11,63.
A potential disadvantage of using the MN compared to the sciatic nerve is that a greater amount of information is available regarding the latter nerve. This, in turn, can make comparison of data obtained with the MN with that of prior experimental works more difficult46,48,64. Additionally, the smaller size of the MN compared to the sciatic nerve makes surgical manipulation more challenging8,12,27,56,65.
Contrary to the methodology described in this paper, the electroneuromyography evaluation can be performed using transcutaneous monopolar electrodes placed in the arm and thenar regions51. Despite being less invasive, this method carries the risk of potential confusion due to the possibility of costimulation of the ulnar nerve in the arm region9,51.
Most authors concur that not all tests used in the rat provide concordant results, as peripheral nerve repair depends on a complex array of factors, comprising neuron survival, axonal elongation and pruning, synaptogenesis, successful recapture of the denervated sensory organs and motor units, and brain plasticity7,10,50,66,67.
Finally, it should be noted that a significant caveat of rodent models is that rat peripheral nerves are much closer to their end organs and have much smaller cross-sectional areas than the homologous human structures. However, this size difference guarantees faster experimental data in rodents, and better overall results in rats in comparison to humans are to be expected68. Indeed, several authors warn that care must be used when trying to extrapolate experimental data obtained in peripheral nerve repair using rodents to humans7,69. Primate models are considered more comparable70. Nevertheless, their use is associated with vexing ethical, logistical, and budget constraints71.
Even though the sciatic nerve is the most commonly used nerve in peripheral nerve research, the rat MN presents multiple advantages. For example, MN lesions are associated with a smaller incidence of joint contractures and automutilation of the affected paw11,12,16,56. Significantly, autotomy subsequent to sciatic nerve transection afflicts 11&#8211;70% of rats. This may make current evaluations like the sciatic index impossible14. This, in turn, makes the estimate of the number of animals required to obtain a given statistical power cumbersome15.
In addition, as the MN is shorter than the sciatic nerve, nerve recovery is observed sooner58,72,73,74,75,76. Furthermore, the MN is not covered by muscle masses, making its dissection technically easier than that of the sciatic nerve16. Additionally, the MN has a parallel path to the ulnar nerve in the arm. Hence, the ulnar nerve can easily be used as nerve graft for repairing MN injuries. Finally, in humans, most peripheral nerve lesions occur in the upper limb, which further supports the use of this nerve in the rat77,78.
Arguably, rodents are the experimental animals most commonly used in the realm of peripheral nerve repair48,79. As shown, the rat MN is a convenient model of peripheral nerve lesion and repair. In fact, there are multiple standardized strategies available to assess motor and sensory recovery, permitting an easier comparison of results36,46,60,80,81,82. Many of these methods are noninvasive, allowing for daily assessment.
Moreover, physiotherapy is part of the standard of care of patients recovering from peripheral nerve injuries. As demonstrated in this paper, there are multiple strategies to provide a postoperative physiotherapy-like environment to rats submitted to MN injuries4,5. Hence, this model is particularly suitable to replicate the clinical scenario, facilitating extrapolation of results to the human species12,27,48,56,58,83.
As shown in this paper, multiple standardized strategies are available to assess motor and sensory recovery in the MN model of the rat. The majority of these are noninvasive procedures, allowing frequent assessment. Moreover, as most peripheral nerve lesions in the human species occur in the upper limb, the mentioned experimental physiotherapy settings can more aptly mimic recovery in the clinical context. Arguably, this can facilitate extrapolation of results to the human species, further validating the use of this nerve in the rat.

Peripheral nerve lesions occur regularly as a result of trauma, infection, vasculitis, autoimmunity, malignancy, and/or radiotherapy1,2. Unfortunately, peripheral nerve repair continues to present clinically unpredictable and frequently disappointing results3,4. There is widespread consensus that considerable basic and translational research is still needed to improve the prospect of those affected4,5,6,7.
The rat MN shows great similarities to that of humans8,9 (Figure 1). Originating from the brachial plexus in the axillary region, this nerve descends into the medial aspect of the arm, reaching the elbow, and branching off to the majority of the muscles in the ventral compartment of the forearm. The MN reaches the hand, where it innervates the thenar muscles and the first two lumbrical muscles as well as to part of the rat&#8217;s hand skin9 (Figure 1).
Using the rat MN, it is possible to adequately replicate peripheral nerve lesions in humans10,11,12. This nerve has several potential research advantages relative to the customarily used sciatic nerve. Because the MN is located in the forelimb of rats (akin to the human upper limbs), it can be damaged experimentally with a much smaller impact on the rat&#8217;s wellbeing, compared to the sciatic nerve, which innervates a substantial portion of the pelvic limb13. Additionally, in humans most clinical lesions occur in the upper limb, which corresponds to the rat&#8217;s forelimb10,11,12,14,15,16.
This paper shows how to produce different types of MN lesions in the rat. Moreover, different ways to simulate postoperative physiotherapy are presented. Finally, tests to evaluate functional recovery of the MN are described. There are multiple standardized strategies available to assess motor and sensory recovery using an MN model of peripheral nerve lesion and repair, thus permitting an easy comparison of results. The MN model is particularly suitable to replicate the clinical scenario, facilitating extrapolation of results to the human species.

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functional and physiological methods of evaluating median nerve regeneration in the rat

The main goal of this investigation is to show how to create and repair different types of median nerve (MN) lesions in the rat. Moreover, different methods of simulating postoperative physiotherapy are presented. Multiple standardized strategies are used to assess motor and sensory recovery using an MN model of peripheral nerve lesion and repair, thus permitting easy comparison of the results. Several options are included for providing a postoperative physiotherapy-like environment to rats that have undergone MN injuries. Finally, the paper provides a method to evaluate the recovery of the MN using several noninvasive tests (i.e., grasping test, pin prick test, ladder rung walking test, rope climbing test, and walking track analysis), and physiological measurements (infrared thermography, electroneuromyography, flexion strength evaluation, and flexor carpi radialis muscle weight determination). Hence, this model seems particularly appropriate to replicate a clinical scenario, facilitating extrapolation of results to the human species.
Although the sciatic nerve is the most studied nerve in peripheral nerve research, analysis of the rat MN presents various advantages. For example, there is a reduced incidence of joint contractures and automutilation of the affected limb in MN lesion studies. Furthermore, the MN is not covered by muscle masses, making its dissection easier than that of the sciatic nerve. In addition, MN recovery is observed sooner, because the MN is shorter than the sciatic nerve. Also, the MN has a parallel path to the ulnar nerve in the arm. Hence, the ulnar nerve can be easily used as the nerve graft for repairing MN injuries. Finally, the MN in rats is located in the forelimb, akin to the human upper limb; in humans, the upper limb is the site of most peripheral nerve lesions.

A total of 34 rats were randomly divided into the following groups: Sham (n = 17), Excision (n = 17), and Nerve Graft (n = 10) for the operation. All rats survived surgery and the postoperative period uneventfully. One week after surgery and for the subsequent 100 days, all animals underwent the functional tests described above once a week. The representative results of each of these tests are described below.
Grasping Test
The percentage of rats with a positive response in the grasping test was highest for the Sham group. This value gradually increased over time in rats from the Crush and Nerve Graft groups (Figure 3).
Pin Prick Test
Rats from the Sham group had the best scores in the cumulative pin prick test relative to rats from the Nerve Graft group. Both had better scores than the rats in the Excision group (Figure 4).
Ladder Running Test
The rats&#8217; velocity in the ladder running test was highest in the Sham group than in the rats submitted to MN lesion. Among the latter, the time to run the ladder tended to decrease over time, paralleling MN recovery (Figure 5).
Rope Test
As in the ladder running test, the time the rats took to climb the rope was shorter in the Sham group compared to the groups in which the MN was injured. The rats&#39; speed in this test increased when the MN was allowed to recover (Figure 6).
Walking Track Analysis
Analysis of walking tracks tended to show changes in the morphology of paw prints (Figure 7). These changes were often more pronounced in crushing injuries than in segmental nerve lesions50.
Infrared Thermography
Thermography was useful when examining temperature differences between the forepaws in the first 30 days after surgery. Temperature differences were more noticeable in rats with a more severely injured MN, such as in those from the Excision group (Figure 8 and Figure 9).
Electroneuromyography
Table 1 summarizes the biological importance of the electroneuromyography measurements, providing representative results for the different experimental groups. Various patterns were observed with electroneuromyography. A normal CMAP was typical of a rat from the Sham group, while a polyphasic CMAP was associated with a variable degree of lesion of the MN, as in the Crush and in the Nerve Graft groups (Figure 10). In the Excision group, no CMAPs were observed.
Wrist Flexion Strength
Given that wrist flexion is mainly dependent on the MN, this test was used to evaluate motor recovery in this nerve&#8217;s territory. Wrist flexion strength was closest to normal when recovery was maximal (Figure 11).
Muscle Weight and Morphology
The weight and morphology of the flexor carpis radialis muscle were dependent on MN recovery, as this muscle is innervated exclusively by the MN9,10. Thus, normal weight and morphology were observed in the Sham group. A loss of weight and muscle trophism was observed in the Crush, Nerve Graft, and Excision groups (Figure 12).
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/59767/59767fig01.jpg" /> 
Figure 1: Schematic representation of the anatomy of the median nerve of the rat. 
(1) Origin and termination of the median nerve in the rat brain (green area = primary motor area; blue area = primary sensory area). (2) Transverse section of the spinal cord at C7 segment level; (3) Axillary nerve; (4) Musculocutaneous nerve; (5) Radial nerve; (6) Median nerve; (7) Ulnar nerve; (8) Medial cutaneous branch of the arm; (9) Medial cutaneous branch of the forearm; (10) Axillary artery; (11) Brachial artery; (12) Median artery; (13) Superficial radial artery; (14) Ulnar artery; (15) Motor branch of the median nerve to the pronator teres muscle; (16) Motor branch of the median nerve to the flexor carpis radialis muscle; (17) Motor branch of the median nerve to the flexor digitorum superficialis muscle; (18) Motor branch of the median nerve to the flexor digitorum profundus muscle; (19) Sensory branch of the median nerve to the thenar region; (20) Common palmar artery of the first interosseous space; (21) Radial palmar digital artery of the first digit; (22) Motor branch of the median nerve to the thenar muscles; (23) Palmar arterial arch; (24) Radial palmar digital nerve of the first digit; (25) Ulnar palmar digital nerve of the first digit; (26) Common palmar artery of the third interosseous space; (27) Motor branches of the terminal divisions of the median nerve to the first three lumbrical muscles; (28) Ulnar palmar digital nerves of the second, third, and fourth digits; (29) Ulnar palmar digital arteries to the fourth and fifth digits; (30) Radial palmar digital nerves of the second, third, and fourth digits; (31) Radial palmar digital artery of the fifth digit; (32) Skin territory of the median nerve in the forepaw (blue-shaded region). <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59767/59767fig01large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/59767/59767fig02.jpg" /> 
Figure 2: Photograph of the right forelimb of the rat showing the surgical anatomy of the median nerve in the arm and axillary regions. 
Cr, cranial; Me, medial <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59767/59767fig02large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/59767/59767fig03.jpg" /> 
Figure 3: Percentage of rats with a positive grasping test in the different experimental group over a period of 100 days after surgery. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59767/59767fig03large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/59767/59767fig04.jpg" /> 
Figure 4: Nociception evaluation using cumulative pin prick test results in the operated forepaw normalized to the contralateral paw in the different experimental groups. 
Vertical bars represent 95% confidence intervals. Horizontal lines in the upper part of the figure indicate statistically significant differences between experimental groups, ***p&#60;0.001. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59767/59767fig04large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/59767/59767fig05.jpg" /> 
Figure 5: Average speed in the ladder running test in the different experimental groups. 
Vertical bars represent 95% confidence intervals. Asterisks in the upper portion of the figure indicate statistically significant differences between groups, *p&#60;0.001. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59767/59767fig05large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/59767/59767fig06.jpg" /> 
Figure 6: Average climbing velocity in the rope test in the Sham and Excision groups. 
Vertical bars represent 95% confidence intervals. Asterisks in the upper portion of the figure show statistically significant differences between groups, *p&#60;0.05; **p&#60;0.01. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59767/59767fig06large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 7" class="xfigimg" src="/files/ftp_upload/59767/59767fig07.jpg" /> 
Figure 7: Walking track parameters in the different experimental groups. 
Values on the operated limb are expressed as percentages of means normalized to the contralateral limb. (A) Stance factor; (B) Print length; (C) Finger spread factor; (D) Intermediate finger spread factor; (E) Stride length; (F) Base of support. Vertical bars represent 95% confidence intervals. Horizontal lines in the upper portion of the figure indicate statistically significant differences between experimental groups. D30, D60, D90 = 30, 60, and 90 days after surgery, *p&#60;0.05; **p&#60;0.01; ***p&#60;0.001. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59767/59767fig07large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 8" class="xfigimg" src="/files/ftp_upload/59767/59767fig08.jpg" /> 
Figure 8: Mean temperature difference registered by infrared thermography. 
The box plots represent the temperature difference between the palmar region of the median nerve on the operated side (right side) and the contralateral side (left) in the Sham (n = 17) and Excision (n = 17) groups, *p&#60;0.05; **p&#60;0.01. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59767/59767fig08large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 9" class="xfigimg" src="/files/ftp_upload/59767/59767fig09.jpg" /> 
Figure 9: Typical infrared thermography pattern of an animal from the excision group during the first 45 days after surgery. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59767/59767fig09large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 10" class="xfigimg" src="/files/ftp_upload/59767/59767fig10.jpg" /> 
Figure 10: Typical patterns of Compound Muscle Action Potentials (CMAPs) from an animal from the Sham and Nerve Graft groups 90 days after surgery. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59767/59767fig10large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 11" class="xfigimg" src="/files/ftp_upload/59767/59767fig11.jpg" /> 
Figure 11: Evaluation of wrist flexion strength on both forepaws 90 days postoperatively in different experimental groups. 
Wrist flexion strength was assessed using the area under the curve (AUC) over a time period of 30 s and using supratetanic stimulation. Vertical lines denote 95% confidence intervals. Horizontal lines in the upper portion of the figure highlight statistically significant differences between groups, **p&#60;0.01. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59767/59767fig11large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 12" class="xfigimg" src="/files/ftp_upload/59767/59767fig12.jpg" /> 
Figure 12: Flexor carpi radialis muscle weight and macroscopic appearance 100 days after surgery. 
(A) Box plots depicting the normalized flexor carpi radialis muscle weight in different experimental groups, **p&#60;0.01; ***p&#60;0.001. (B) Photographs of the muscles on the right and left sides in the Sham and Excision experimental groups. <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/59767/59767fig12large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Parameter</td>
			<td>Parameter significance</td>
			<td>Sham group</td>
			<td>Excision group</td>
			<td>NG group</td>
		</tr>
		<tr>
			<td>Neurological stimulation threshold (%)</td>
			<td>Evaluation of nerve regeneration, as there is a minimal number of nerve fibers required to produce either a CMAP or a visible muscle contraction12</td>
			<td>281.63 &#177; 271.65</td>
			<td>5359.98 &#177; 3466.52</td>
			<td>2108.12 &#177; 2115.13</td>
		</tr>
		<tr>
			<td>Motor stimulation threshold (%)</td>
			<td>Evaluation of nerve regeneration, as there is a minimal number of nerve fibers required to produce either a CMAP or a visible muscle contraction12</td>
			<td>462.52 &#177; 118.91</td>
			<td>1694.10 &#177; 503.24</td>
			<td>1249.50 &#177; 503.24</td>
		</tr>
		<tr>
			<td>Latency (%)</td>
			<td>Assessment of nerve conduction velocity in the fastest nerve fibers, that is to say the largest myelinated fibers44</td>
			<td>113.55 &#177; 25.04</td>
			<td>N/A</td>
			<td>132.80 &#177; 69.95</td>
		</tr>
		<tr>
			<td>Neuromuscular transduction velocity (%)</td>
			<td>Assessment of nerve conduction velocity in the fastest nerve fibers, that is to say the largest myelinated fibers44</td>
			<td>92.01 &#177; 20.88</td>
			<td>N/A</td>
			<td>91.30 &#177; 26.51</td>
		</tr>
		<tr>
			<td>CMAPs amplitude (%)</td>
			<td>Evaluation of the number of reinnervated motor units34</td>
			<td>110.63 &#177;45.66</td>
			<td>N/A</td>
			<td>41.60 &#177; 24.84</td>
		</tr>
		<tr>
			<td>CMAPs duration (%)</td>
			<td>Assessment of synchrony of muscle innervation, which is dependent on the degree of muscle reinnervation and myelination of the innervating motor fibers44,45</td>
			<td>101.12 &#177; 23.92</td>
			<td>N/A</td>
			<td>151.06 &#177; 54.52</td>
		</tr>
		<tr>
			<td colspan="5">NG, nerve graft 
			CMAPs, compound muscle action potential. 
			N/A, non-applicable 
			All parameters are expressed as percentages of the average contralateral values. 
			Numeric variables are expressed as average &#177; standard deviation.</td>
		</tr>
	</tbody>
</table>
Table 1: Electroneuromyographic assessment at the end of the experiment.

Watch this Scientific Journal Video about Functional and Physiological Methods of Evaluating Median Nerve Regeneration in the Rat at JoVE.com

Functional and Physiological Methods of Evaluating Median Nerve Regeneration in the Rat

Presented is a protocol to produce different types of median nerve (MN) lesions and repair in the rat. Additionally, the protocol shows how to evaluate the functional recovery of the nerve using several noninvasive behavioral tests and physiological measurements.

The main goal of this investigation is to show how to create and repair different types of median nerve (MN) lesions in the rat. Moreover, different ...

functional-physiological-methods-evaluating-median-nerve-regeneration

Nanyang Technological University

Research

JoVE Journal

Medicine

12.0K Views.  NOVA Medical School. Met behulp van de mediane zenuw van de rat, is het mogelijk om adequaat te repliceren, perifere zenuwletsels bij de mens. Klinisch, de meeste van deze laesies optreden, in de bovenste extremiteit die ondersteuning biedt aan het gebruik van dit experimentele model. In dit document zullen we laten zien, hoe verschillende soorten mediane zenuwletsels in de rat te produceren.Daarnaast zullen we illustreren, hoe functioneel herstel van deze zenuw te evalueren met behulp van verschillende te...

Video: Functional and Physiological Methods of Evaluating Median Nerve Regeneration in the Rat

Reproducible Mouse Sciatic Nerve Crush and Subsequent Assessment of Regeneration by Whole Mount Muscle Analysis

Regeneration in the peripheral nervous system (PNS) is widely studied both for its relevance to human disease and to understand the robust regenerative response mounted by PNS neurons thereby possibly illuminating the failures of CNS regeneration1. Sciatic nerve crush (axonotmesis) is one of the most common models of peripheral nerve injury in rodents2. Crushing interrupts all axons but Schwann cell basal laminae are preserved so that regeneration is optimal3,4. This allows the investigator to study precisely the ability of a growing axon to interact with both the Schwann cell and basal laminae4. Rats have generally been the preferred animal models for experimental nerve crush. They are widely available and their lesioned sciatic nerve provides a reasonable approximation of human nerve lesions5,4. Though smaller in size than rat nerve, the mouse nerve has many similar qualities. Most importantly though, mouse models are increasingly valuable because of the wide availability of transgenic lines now allows for a detailed dissection of the individual molecules critical for nerve regeneration6, 7. Prior investigators have used multiple methods to produce a nerve crush or injury including simple angled forceps, chilled forceps, hemostatic forceps, vascular clamps, and investigator-designed clamps8,9,10,11,12. Investigators have also used various methods of marking the injury site including suture, carbon particles and fluorescent beads13,14,1. We describe our method to obtain a reproducibly complete sciatic nerve crush with accurate and persistent marking of the crush-site using a fine hemostatic forceps and subsequent carbon crush-site marking. As part of our description of the sciatic nerve crush procedure we have also included a relatively simple method of muscle whole mount we use to subsequently quantify regeneration.

In this report we describe a method to crush mouse sciatic nerve. This method uses readily available hemostatic forceps and easily and reproducibly produces complete sciatic nerve crush. In addition, we describe a method to prepare muscle whole mounts suitable for analysis of nerve regeneration after sciatic nerve crush.

Regeneration in the peripheral nervous system (PNS) is widely studied both for its relevance to human disease and to understand the robust regenerative ...

Neuroscience

The Fibular Nerve Injury Method: A Reliable Assay to Identify and Test Factors That Repair Neuromuscular Junctions

The neuromuscular junction (NMJ) undergoes deleterious structural and functional changes as a result of aging, injury and disease. Thus, it is imperative to understand the cellular and molecular changes involved in maintaining and repairing NMJs. For this purpose, we have developed a method to reliably and consistently examine regenerating NMJs in mice. This nerve injury method involves crushing the common fibular nerve as it passes over the lateral head of the gastrocnemius muscle tendon near the knee. Using 70 day old female mice, we demonstrate that motor axons begin to reinnervate previous postsynaptic targets within 7 days post-crush. They completely reoccupy their previous synaptic areas by 12 days. To determine the reliability of this injury method, we compared reinnervation rates between individual 70 day old female mice. We found that the number of reinnervated postsynaptic sites was similar between mice at 7, 9, and 12 days post-crush. To determine if this injury assay can also be used to compare molecular changes in muscles, we examined levels of the gamma-subunit of the muscle nicotinic receptor (gamma-AChR) and the muscle-specific kinase (MuSK). The gamma-AChR subunit and MuSK to are highly upregulated following denervation and return to normal levels following reinnervation of NMJs. We found a close relationship between transcript levels for these genes and innervation status of muscles. We believe that this method will accelerate our understanding of the cellular and molecular changes involved in repairing the NMJ and other synapses.

We have developed a nerve injury method to reliably examine muscle reinnervation, and thus regeneration of neuromuscular junctions in mice. This technique involves injuring the common fibular nerve via a simple and highly reproducible surgery. Muscle reinnervation in then assessed by whole-mounting the extensor digitorum longus muscle.

The neuromuscular junction (NMJ) undergoes deleterious structural and functional changes as a result of aging, injury and disease. Thus, it is imperative ...

In Vivo Electrophysiological Measurement of the Rat Ulnar Nerve with Axonal Excitability Testing

Electrophysiology enables the objective assessment of peripheral nerve function in vivo. Traditional nerve conduction measures such as amplitude and latency detect chronic axon loss and demyelination, respectively. Axonal excitability techniques &#34;by threshold tracking&#34; expand upon these measures by providing information regarding the activity of ion channels, pumps and exchangers that relate to acute function and may precede degenerative events. As such, the use of axonal excitability in animal models of neurological disorders may provide a useful in vivo measure to assess novel therapeutic interventions. Here we describe an experimental setup for multiple measures of motor axonal excitability techniques in the rat ulnar nerve.
The animals are anesthetized with isoflurane and carefully monitored to ensure constant and adequate depth of anesthesia. Body temperature, respiration rate, heart rate and saturation of oxygen in the blood are continuously monitored. Axonal excitability studies are performed using percutaneous stimulation of the ulnar nerve and recording from the hypothenar muscles of the forelimb paw. With correct electrode placement, a clear compound muscle action potential that increases in amplitude with increasing stimulus intensity is recorded. An automated program is then utilized to deliver a series of electrical pulses which generate 5 specific excitability measures in the following sequence: stimulus response behavior, strength duration time constant, threshold electrotonus, current-threshold relationship and the recovery cycle.
Data presented here indicate that these measures are repeatable and show similarity between left and right ulnar nerves when assessed on the same day. A limitation of these techniques in this setting is the effect of dose and time under anesthesia. Careful monitoring and recording of these variables should be undertaken for consideration at the time of analysis.

In Vivo Electrophysiological Measurement of the Rat Ulnar Nerve with Axonal Excitability Testing

Axonal excitability techniques provide a powerful tool to examine pathophysiology and biophysical changes that precede irreversible degenerative events. This manuscript demonstrates the use of these techniques on the ulnar nerve of anesthetized rats.

Electrophysiology enables the objective assessment of peripheral nerve function in vivo. Traditional nerve conduction measures such as amplitude and ...

Fabrication of the Composite Regenerative Peripheral Nerve Interface (C-RPNI) in the Adult Rat

Recent advances in neuroprosthetics have enabled those living with extremity loss to reproduce many functions native to the absent extremity, and this is often accomplished through integration with the peripheral nervous system. Unfortunately, methods currently employed are often associated with significant tissue damage which prevents prolonged use. Additionally, these devices often lack any meaningful degree of sensory feedback as their complex construction dampens any vibrations or other sensations a user may have previously depended on when using more simple prosthetics. The composite regenerative peripheral nerve interface (C-RPNI) was developed as a stable, biologic construct with the ability to amplify efferent motor nerve signals while providing simultaneous afferent sensory feedback. The C-RPNI consists of a segment of free dermal and muscle graft secured around a target mixed sensorimotor nerve, with preferential motor nerve reinnervation of the muscle graft and sensory nerve reinnervation of the dermal graft. In rats, this construct has demonstrated the generation of compound muscle action potentials (CMAPs), amplifying the target nerve&#39;s signal from the micro- to milli-volt level, with signal to noise ratios averaging approximately 30-50. Stimulation of the dermal component of the construct generates compound sensory nerve action potentials (CSNAPs) at the proximal nerve. As such, this construct has promising future utility towards the realization of the ideal, intuitive prosthetic.

Fabrication of the Composite Regenerative Peripheral Nerve Interface C-RPNI in the Adult Rat

The following manuscript describes a novel method for developing a biologic, closed loop neural feedback system termed the composite regenerative peripheral nerve interface (C-RPNI). This construct has the ability to integrate with peripheral nerves to amplify efferent motor signals while simultaneously providing afferent sensory feedback.

Recent advances in neuroprosthetics have enabled those living with extremity loss to reproduce many functions native to the absent extremity, and this is ...

Bioengineering

Facial Nerve Surgery in the Rat Model to Study Axonal Inhibition and Regeneration

This protocol describes consistent and reproducible methods to study axonal regeneration and inhibition in a rat facial nerve injury model. The facial nerve can be manipulated along its entire length, from its intracranial segment to its extratemporal course. There are three primary types of nerve injury used for the experimental study of regenerative properties: nerve crush, transection, and nerve gap. The range of possible interventions is vast, including surgical manipulation of the nerve, delivery of neuroactive reagents or cells, and either central or end-organ manipulations. Advantages of this model for studying nerve regeneration include simplicity, reproducibility, interspecies consistency, reliable survival rates of the rat, and an increased anatomic size relative to murine models. Its limitations involve a more limited genetic manipulation versus the mouse model and the superlative regenerative capability of the rat, such that the facial nerve scientist must carefully assess time points for recovery and whether to translate results to higher animals and human studies. The rat model for facial nerve injury allows for functional, electrophysiological, and histomorphometric parameters for the interpretation and comparison of nerve regeneration. It thereby boasts tremendous potential toward furthering the understanding and treatment of the devastating consequences of facial nerve injury in human patients.

This protocol describes a reproducible approach to facial nerve surgery in the rat model, including descriptions of various inducible patterns of injury.

This protocol describes consistent and reproducible methods to study axonal regeneration and inhibition in a rat facial nerve injury model. The facial ...

3D Kinematic Analysis for the Functional Evaluation in the Rat Model of Sciatic Nerve Crush Injury

Compared to the Sciatic Functional Index (SFI), kinematic analysis is a more reliable and sensitive method for performing functional evaluations of sciatic nerve injury rodent models. In this protocol, we describe a novel kinematic analysis method that uses a three-dimensional (3D) motion capture apparatus for functional evaluations using a rat sciatic nerve crush injury model. First, the rat is familiarized with treadmill walking. Markers are then attached to the designated bone landmarks and the rat is made to walk on the treadmill at the desired speed. Meanwhile, the posterior limb movements of the rat are recorded using four cameras. Depending on the software used, marker tracings are created using both automatic and manual modes and the desired data are produced after subtle adjustments. This method of kinematic analysis, which uses a 3D motion capture apparatus, offers numerous advantages, including superior precision and accuracy. Many more parameters can be investigated during the comprehensive functional evaluations. This method has several shortcomings that require consideration: The system is expensive, can be complicated to operate, and may produce data deviations due to skin shifting. Nevertheless, kinematic analysis using a 3D motion capture apparatus is useful for performing functional anterior and posterior limb evaluations. In the future, this method may become increasingly useful for generating accurate assessments of various traumas and diseases.

We introduce a kinematic analysis method that uses a three-dimensional motion capture apparatus containing four cameras and data processing software for performing functional evaluations during fundamental research involving rodent models.

Compared to the Sciatic Functional Index (SFI), kinematic analysis is a more reliable and sensitive method for performing functional evaluations of ...

Automated Gait Analysis to Assess Functional Recovery in Rodents with Peripheral Nerve or Spinal Cord Contusion Injury

Peripheral and central nerve injuries are mostly studied in rodents, especially rats, given the fact that these animal models are both cost-effective and a lot of comparative data has been published in the literature. This includes a multitude of assessment methods to study functional recovery following nerve injury and repair. Besides evaluation of nerve regeneration by means of histology, electrophysiology, and other in vivo and in vitro assessment techniques, functional recovery is the most important criterion to determine the degree of neural regeneration. Automated gait analysis allows recording of a vast quantity of gait-related parameters such as Paw Print Area and Paw Swing Speed as well as measures of inter-limb coordination. Additionally, the method provides digital data of the rats&#8217; paws after neuronal damage and during nerve regeneration, adding to our understanding of how peripheral and central nervous injuries affect their locomotor behavior. Besides the predominantly used sciatic nerve injury model, other models of peripheral nerve injury such as the femoral nerve can be studied by means of this method. In addition to injuries of the peripheral nervous systems, lesions of the central nervous system, e.g., spinal cord contusion can be evaluated. Valid and reproducible data assessment is strongly dependent on meticulous adjustment of the hard- and software settings prior to data acquisition. Additionally, proper training of the experimental animals is of crucial importance. This work aims to illustrate the use of computerized automated gait analysis to assess functional recovery in different animal models of peripheral nerve injury as well as spinal cord contusion injury. It also emphasizes the method&#8217;s limitations, e.g., evaluation of nerve regeneration in rats with sciatic nerve neurotmesis due to limited functional recovery. Therefore, this protocol is thought to help researchers interested in peripheral and central nervous injuries to assess functional recovery in rodent models.

Automated gait analysis is a feasible tool to evaluate functional recovery in rodent models of peripheral nerve injury and spinal cord contusion injury. While it requires only one setup to assess locomotor function in various experimental models, meticulous hard- and soft-ware adjustment and training of the animals is highly important.

Peripheral and central nerve injuries are mostly studied in rodents, especially rats, given the fact that these animal models are both cost-effective and ...

Maximum Isometric Tetanic Force Measurement of the Tibialis Anterior Muscle in the Rat

Traumatic nerve injuries result in substantial functional loss and segmental nerve defects often necessitate the use of autologous interposition nerve grafts. Due to their limited availability and associated donor side morbidity, many studies in the field of nerve regeneration focus on alternative techniques to bridge a segmental nerve gap. In order to investigate the outcomes of surgical or pharmacological experimental treatment options, the rat sciatic nerve model is often used as a bioassay. There are a variety of outcome measurements used in rat models to determine the extent of nerve regeneration. The maximum output force of the target muscle remains the most relevant outcome for clinical translation of experimental therapies. Isometric force measurement of tetanic muscle contraction has previously been described as a reproducible and valid technique for evaluating motor recovery after nerve injury or repair in both rat and rabbit models. In this video, we will provide a step-by-step instruction of this invaluable procedure for assessment of functional recovery of the tibialis anterior muscle in a rat sciatic nerve defect model using optimized parameters. We will describe the necessary pre-surgical preparations in addition to the surgical approach and dissection of the common peroneal nerve and tibialis anterior muscle tendon. The isometric tetanic force measurement technique will be detailed. Determining the optimal muscle length and stimulus pulse frequency is explained and measuring the maximum tetanic muscle contraction is demonstrated.

Evaluation of motor recovery remains the benchmark outcome measure in experimental peripheral nerve studies. The isometric tetanic force measurement of the tibialis anterior muscle in the rat is an invaluable tool to assess functional outcomes after reconstruction of sciatic nerve defects. The methods and nuances are detailed in this article.

Traumatic nerve injuries result in substantial functional loss and segmental nerve defects often necessitate the use of autologous interposition nerve ...

Multifactorial Assessment of Motor Behavior in Rats after Unilateral Sciatic Nerve Crush Injury

The induction of a peripheral nerve injury is a widely used method in neuroscience for the assessment of repair and pain mechanisms among others. In addition, in the research field of movement disorders, sciatic crush injury has been employed to trigger a dystonia-like phenotype in genetically predisposed DYT-TOR1A rodent models of dystonia. To achieve consistent, reproducible and comparable results after a sciatic nerve crush injury, a standardized method for inducing the nerve crush is essential, in addition to a standardized phenotypical characterization. Attention must be paid not only to the specific assortment of behavioral tests, but also to the technical requirements, the correct execution and consecutive data analysis. This protocol describes in detail how to perform a sciatic nerve crush injury and provides a behavioral test battery for the assessment of motor deficits in rats that includes the open field test, the CatWalk XT gait analysis, the beam walking task, and the ladder rung walking task.

We provide a protocol for the assessment of motor behavior via a behavioral test battery in rats after sciatic nerve crush injury.

The induction of a peripheral nerve injury is a widely used method in neuroscience for the assessment of repair and pain mechanisms among others. In ...

Modified Spared Nerve Injury Surgery Model of Neuropathic Pain in Mice

Spared nerve injury (SNI) is an animal model that mimics the cardinal symptoms of peripheral nerve injury for studying the molecular and cellular mechanism of neuropathic pain in mice and rats. Currently, there are two types of SNI model, one to cut and ligate the common peroneal and the tibial nerves with intact sural nerve, which is defined as SNIs in this study, and another to cut and ligate the common peroneal and the sural nerves with intact tibial nerve, which is defined as SNIt in this study. Because the sural nerve is purely sensory whereas the tibial nerve contains both motor and sensory fibers, the SNIt model has much less motor deficit than the SNIs model. In the traditional SNIt mouse model, the common peroneal and the sural nerves are cut and ligated separately. Here a modified SNIt surgery method is described to damage both common peroneal and sural nerves with only one ligation and one cut with a shorter procedure time, which is easier to perform and reduces the potential risk of stretching the sciatic or tibial nerves, and produces similar mechanical hypersensitivity as the traditional SNIt model.

The modified surgery is a simplified method for mouse or rat spared nerve injury model that requires only one ligation and one cut to injure both common peroneal and sural nerves.

Functional and Physiological Methods of Evaluating Median Nerve Regeneration in the Rat

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