Rodent Models and Behavioral Outcomes of Cervical Spinal Cord Injury

Therapeutic targets and nanomaterial-based therapies for mitigation of secondary injury after spinal cord injury

Spinal cord injury (SCI) and the resulting neurological trauma commonly result in complete or incomplete neurological dysfunction and there are few effective treatments for primary SCI. However, the following secondary SCI, including the changes of microvasculature, inflammatory response and oxidative stress around the injury site, may provide promising therapeutic targets. The advances of nanomaterials hold promise for delivering therapeutics to alleviate secondary SCI and promote functional recovery. In this review, we highlight recent achievements of nanomaterial-based therapy, specifically targeting blood-spinal cord barrier disruption, mitigation of the inflammatory response and lightening of oxidative stress after spinal cord injury.

Fecal transplant prevents gut dysbiosis and anxiety-like behaviour after spinal cord injury in rats

Secondary manifestations of spinal cord injury beyond motor and sensory dysfunction can negatively affect a person's quality of life. Spinal cord injury is associated with an increased incidence of depression and anxiety; however, the mechanisms of this relationship are currently not well understood. Human and animal studies suggest that changes in the composition of the intestinal microbiota (dysbiosis) are associated with mood disorders. The objective of the current study is to establish a model of anxiety following a cervical contusion spinal cord injury in rats and to determine whether the microbiota play a role in the observed behavioural changes. We found that spinal cord injury caused dysbiosis and increased symptoms of anxiety-like behaviour. Treatment with a fecal transplant prevented both spinal cord injury-induced dysbiosis as well as the development of anxiety-like behaviour. These results indicate that an incomplete unilateral cervical spinal cord injury can cause affective disorders and intestinal dysbiosis, and that both can be prevented by treatment with fecal transplant therapy.

Behavioral and histopathological studies of cervical spinal cord contusion injury in rats caused by an adapted weight-drop device

Background

Models of spinal cord injury (SCI) caused by weight-drop devices to cause contusion have been used extensively, and transient behavioral deficits after thoracic injury have been demonstrated. The severity of the injury caused by the device should be mild enough to allow recovery.

Objective

To determine whether our adapted weight-drop device with a small tip can effectively induce mild hemicontusion at the level of the fifth cervical vertebra.

Methods

We divided 15 adult male Sprague Dawley rats into groups of 5 for the following treatments: sham (SH, laminectomy only), mild (MSCI) or severe SCI (SSCI). Behavioral tests and histopathology were used before (day 1) and after the treatment on days 3, 7, 14, 21, 28, and 35 to assess the injury.

Results

Rats with SSCI showed a significant somatosensory deficit on days 3 and 7 compared with rats in the SH group, recovering by day 14. In a horizontal-ladder test of skilled locomotion, rats with SSCI showed a significant increase in error scores and percentage of total rungs used, and a decrease in the percentage of correct paw placement compared with rats in the SH group. There was greater recovery to normal paw placement by rats with MSCI than by rats with SSCI. These behavioral deficits were consistent with histopathology using hematoxylin and eosin counterstained Luxol fast blue, indicating the degree of injury and lesion area.

Conclusions

Mild hemicontusion caused by the adapted device can be used to evaluate SCI and provides a model with which to test the efficacy of translational therapies for SCI.

Experimental spinal cord injury and behavioral tests in laboratory rats

Traumatic spinal cord injury (SCI) results in some serious neurophysiological consequences that alter healthy body functions and devastate the quality of living of individuals. To find a cure for SCI, researchers around the world are working on different neurorepair and neurorehabilitation modalities. To test a new treatment for SCI as well as to understand the mechanism of recovery, animal models are being widely used. Among them, SCI rat models are arguably the most prominent. Furthermore, it is important to select a suitable behavioral test to evaluate both the motor and sensory recovery following any therapeutic intervention. In this paper, we review the rat models of spinal injury and commonly used behavioral tests to serve as a useful guideline for neuroscientists in the field of SCI research.

Spinal cord injury pharmacotherapy: Current research & development and competitive commercial landscape as of 2015

CONTEXT

Current treatment of spinal cord injury (SCI) focuses on cord stabilization to prevent further injury, rehabilitation, management of non-motor symptoms, and prevention of complications. Currently, no approved treatments are available, and limited treatment options exist for symptoms and complications associated with chronic SCI. This review describes the pharmacotherapy landscape in SCI from both commercial and research and development (R&D) standpoints through March 2015.

METHODS

Information about specific compounds has been obtained through drug pipeline monographs in the Pharmaprojects® (Citeline, Inc., New York, New York, USA) drug database (current as of a search on May 30, 2014), websites of individual companies with compounds in development for SCI (current as of March 24, 2015), and a literature search of published R&D studies to validate the Pharmaprojects® source for selected compounds (current as of March 24, 2015).

RESULTS

Types of studies conducted and outcomes measured in earlier phases of development are described for compounds in clinical development Currently four primary mechanisms are under investigation and may yield promising therapeutic targets: 1) neuronal regeneration; 2) neuroprotection (including anti-inflammation); 3) axonal reconnection; and 4) neuromodulation and signal enhancement. Many other compounds are no longer under investigation for SCI are mentioned; however, in most cases, the reason for terminating their development is not clear.

CONCLUSION

There is urgent need to develop disease-modifying therapy for SCI, yet the commercial landscape remains small and highly fragmented with a paucity of novel late-stage compounds in R&D.

Biomimetic hydrogels direct spinal progenitor cell differentiation and promote functional recovery after spinal cord injury

OBJECTIVE

Demyelination that results from disease or traumatic injury, such as spinal cord injury (SCI), can have a devastating effect on neural function and recovery. Many researchers are examining treatments to minimize demyelination by improving oligodendrocyte availability in vivo. Transplantation of stem and oligodendrocyte progenitor cells is a promising option, however, trials are plagued by undirected differentiation. Here we introduce a biomaterial that has been optimized to direct the differentiation of neural progenitor cells (NPCs) toward oligodendrocytes as a cell delivery vehicle after SCI.

APPROACH

A collagen-based hydrogel was modified to mimic the mechanical properties of the neonatal spinal cord, and components present in the developing extracellular matrix were included to provide appropriate chemical cues to the NPCs to direct their differentiation toward oligodendrocytes. The hydrogel with cells was then transplanted into a unilateral cervical contusion model of SCI to examine the functional recovery with this treatment. Six behavioral tests and histological assessment were performed to examine the in vivo response to this treatment.

MAIN RESULTS

Our results demonstrate that we can achieve a significant increase in oligodendrocyte differentiation of NPCs compared to standard culture conditions using a three-component biomaterial composed of collagen, hyaluronic acid, and laminin that has mechanical properties matched to those of neonatal neural tissue. Additionally, SCI rats with hydrogel transplants, with and without NPCs, showed functional recovery. Animals transplanted with hydrogels with NPCs showed significantly increased functional recovery over six weeks compared to the media control group.

SIGNIFICANCE

The three-component hydrogel presented here has the potential to provide cues to direct differentiation in vivo to encourage regeneration of the central nervous system.

Human Embryonic Stem Cell-Derived Oligodendrocyte Progenitor Cells: Preclinical Efficacy and Safety in Cervical Spinal Cord Injury

Cervical spinal cord injury (SCI) remains an important research focus for regenerative medicine given the potential for severe functional deficits and the current lack of treatment options to augment neurological recovery. We recently reported the preclinical safety data of a human embryonic cell‐derived oligodendrocyte progenitor cell (OPC) therapy that supported initiation of a phase I clinical trial for patients with sensorimotor complete thoracic SCI. To support the clinical use of this OPC therapy for cervical injuries, we conducted preclinical efficacy and safety testing of the OPCs in a nude rat model of cervical SCI. Using the automated TreadScan system to track motor behavioral recovery, we found that OPCs significantly improved locomotor performance when administered directly into the cervical spinal cord 1 week after injury, and that this functional improvement was associated with reduced parenchymal cavitation and increased sparing of myelinated axons within the injury site. Based on large scale biodistribution and toxicology studies, we show that OPC migration is limited to the spinal cord and brainstem and did not cause any adverse clinical observations, toxicities, allodynia, or tumors. In combination with previously published efficacy and safety data, the results presented here supported initiation of a phase I/IIa clinical trial in the U.S. for patients with sensorimotor complete cervical SCI. Stem Cells Translational Medicine2017;6:1917–1929

A Unilateral Cervical Spinal Cord Contusion Injury Model in Non-Human Primates (Macaca mulatta)

The development of a non-human primate (NHP) model of spinal cord injury (SCI) based on mechanical and computational modeling is described. We scaled up from a rodent model to a larger primate model using a highly controllable, friction-free, electronically-driven actuator to generate unilateral C6-C7 spinal cord injuries. Graded contusion lesions with varying degrees of functional recovery, depending upon pre-set impact parameters, were produced in nine NHPs. Protocols and pre-operative magnetic resonance imaging (MRI) were used to optimize the predictability of outcomes by matching impact protocols to the size of each animal's spinal canal, cord, and cerebrospinal fluid space. Post-operative MRI confirmed lesion placement and provided information on lesion volume and spread for comparison with histological measures. We evaluated the relationships between impact parameters, lesion measures, and behavioral outcomes, and confirmed that these relationships were consistent with our previous studies in the rat. In addition to providing multiple univariate outcome measures, we also developed an integrated outcome metric describing the multivariate cervical SCI syndrome. Impacts at the higher ranges of peak force produced highly lateralized and enduring deficits in multiple measures of forelimb and hand function, while lower energy impacts produced early weakness followed by substantial recovery but enduring deficits in fine digital control (e.g., pincer grasp). This model provides a clinically relevant system in which to evaluate the safety and, potentially, the efficacy of candidate translational therapies.