Name: thoracic spinal cord hemisection surgery and open-field locomotor assessment in the rat
Uploaded: 2019-06-26T14:30:00
Description: Watch this Scientific Journal Video about Thoracic Spinal Cord Hemisection Surgery and Open-Field Locomotor Assessment in the Rat at JoVE.com

This work was supported by the Canadian Institutes for Health Research (CIHR; MOP-142288) to M.M. M.M. was supported by a salary award from Fonds de Recherche Qu&#233;bec Sant&#233; (FRQS), and A.R.B was supported by a fellowship from FRQS.

The experiments described in this article were performed in compliance with the guidelines of the Canadian Council on Animal Care and were approved by the ethics committee at the Universit&#233; de Montr&#233;al.
1. Thoracic hemisection surgery
<ol>
	<li>Wear appropriate protective equipment (gloves, mask, and gown) to maintain an aseptic environment for surgery. Clean the surgical area with alcohol wipes, and place sterile surgical drapes over the surgical field. Sterilize surgical tools an...

A major strength of the hemisection technique is the selectivity and reproducibility of the lesion which leads to reduced variability in histological and behavioral phenotypes between animals25. In order to ensure a unilateral lesion at the appropriate spinal level, accurate identification of both the proper vertebral segment and spinal cord midline is critical. As there can be a tendency for the spinal cord to rotate in the direction of the cut during the hemisection procedure, it can be benefici...

Spinal cord injury (SCI) is associated with severe disturbances in motor, sensory, and autonomic function. Experimental animal models of SCI are valuable tools to understand the anatomical and physiological events involved in SCI pathology, to investigate the neural mechanisms in repair and recovery, and to screen for efficacy and safety of potential therapeutic interventions. The rat is the most commonly used species in SCI research1. Rat models are low cost, easy to reproduce, and a large battery of behavioral tests are available to assess functional outcomes2. Despite some differences in tract locations, the rat spinal cord shares overall similar sensorimotor functions with larger mammals, including primates3,4. Rats also share analogous physiological and behavioral consequences to SCI that relate to humans5. Non-human primate and large animal models can provide a closer approximation of human SCI6 and are essential to prove treatment safety and efficacy prior to human experimentation, but are less commonly used due to ethical and animal welfare considerations, expenses, and regulatory requirements7.
Rat transection SCI models are performed by the targeted interruption of the spinal cord with a selective lesion using a dissection knife or iridectomy scissors after a laminectomy. Compared to a complete transection, partial transection in the rat results in a less severe injury, easier postoperative animal care, spontaneous locomotor recovery, and more closely models SCI in humans which is predominately incomplete with partial sparing of tissue connecting the spinal cord and supraspinal structures8. A unilateral hemisection disrupts all ascending and descending tracts on one side only, and produces quantifiable and highly reproducible locomotor deficits, enhancing exploration of the underlying biological mechanisms. The most prominent functional consequence of the hemisection is an initial limb paralysis on the same side and below the level of the lesion with graded spontaneous recovery of locomotor function over several weeks9,10,11,12. The hemisection model is particularly useful to investigate neural plasticity of damaged and residual tracts and circuits associated with functional recovery9,11,12,13,14,15,16,17,18. Specifically, hemisection performed at the thoracic level, i.e., above the spinal circuits that control hindlimb locomotion, is particularly useful for investigating changes in locomotor control. As a non-linear relationship exists between lesion severity and locomotor recovery after SCI19, appropriate behavioral testing to assess functional outcomes is paramount in experimental models.
A comprehensive battery of behavioral tests are available to assess specific aspects of functional locomotor recovery in the rat2,20. Many locomotor tests do not provide reliable measures early after SCI as rats are too disabled to support their body weight. A measure of spontaneous locomotor performance that is sensitive to deficits early after injury, and does not require preoperative training or specialized equipment, is beneficial in order to monitor locomotor recovery for appropriate time points in which to supplement specialized behavioral testing. The Martinez open-field assessment score10, originally developed for evaluating locomotor performance after cervical SCI in the rat, is a 20-point ordinal score assessing global locomotor performance during spontaneous overground locomotion in an open-field. Scoring is conducted separately for each limb using a rubric that evaluates specific parameters of a range of locomotor measures including articular limb movement, weight support, digit position, stepping abilities, forelimb-hindlimb coordination, and tail position. The assessment score is derived from the Basso, Beattie and Bresnahan (BBB) open-field rating scale designed to evaluate locomotor performance after thoracic contusion21. It is adapted to accurately and reliably evaluate both forelimb and hindlimb locomotor function, allows for independent assessment of the different scoring parameters that is not amenable with the hierarchical scoring of the BBB, and provides a linear recovery profile10. Additionally, in comparison to the BBB, the assessment score is sensitive and reliable in more severe injury models10,11,20,22. The assessment score has been used to assess locomotor impairment in the rat following cervical10,12 and thoracic9 SCI alone and in combination with traumatic brain injury23.
We present here a detailed step-by-step protocol for performing a thoracic hemisection SCI at the T8 vertebral level in the female Long-Evans rat, and for assessing hindlimb locomotor recovery in the open-field.

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thoracic spinal cord hemisection surgery and open-field locomotor assessment in the rat

Spinal cord injury (SCI) causes disturbances in motor, sensory, and autonomic function below the level of the lesion. Experimental animal models are valuable tools to understand the neural mechanisms involved in locomotor recovery after SCI and to design therapies for clinical populations. There are several experimental SCI models including contusion, compression, and transection injuries that are used in a wide variety of species. A hemisection involves the unilateral transection of the spinal cord and disrupts all ascending and descending tracts on one side only. Spinal hemisection produces a highly selective and reproducible injury in comparison to contusion or compression techniques that is useful for investigating neural plasticity in spared and damaged pathways associated with functional recovery. We present a detailed step-by-step protocol for performing a thoracic hemisection at the T8 vertebral level in the rat that results in an initial paralysis of the hindlimb on the side of the lesion with graded spontaneous recovery of locomotor function over several weeks. We also provide a locomotor scoring protocol to assess functional recovery in the open-field. The locomotor assessment provides a linear recovery profile and can be performed both early and repeatedly after injury in order to accurately screen animals for appropriate time points in which to conduct more specialized behavioral testing. The hemisection technique presented can be readily adapted to other transection models and species, and the locomotor assessment can be used in a variety of SCI and other injury models to score locomotor function.

Reproducible lesions with a high degree of consistency can be generated with the hemisection technique. To assess and compare lesions sizes between experimental groups, the maximal area of the lesion as a percentage of the total cross-section of the spinal cord can be readily calculated with histological staining of spinal cord sections. Figure 1 shows a representative lesion of the left hemicord and an overlay of the proportion of maximal lesion area shared between rats with a mean lesion s...

Watch this Scientific Journal Video about Thoracic Spinal Cord Hemisection Surgery and Open-Field Locomotor Assessment in the Rat at JoVE.com

Thoracic Spinal Cord Hemisection Surgery and Open-Field Locomotor Assessment in the Rat

The rat thoracic spinal hemisection is a valuable and reproducible model of unilateral spinal cord injury to investigate the neural mechanisms of locomotor recovery and treatment efficacy. This article includes a detailed step-by-step guide to perform the hemisection procedure and to assess locomotor performance in an open-field arena.

Spinal cord injury (SCI) causes disturbances in motor, sensory, and autonomic function below the level of the lesion. Experimental animal models are ...

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