Opinions on the preclinical evaluation of novel therapies for spinal cord injury: a comparison between researchers and spinal cord-injured individuals

Automation of training and testing motor and related tasks in pre-clinical behavioural and rehabilitative neuroscience

Testing and training animals in motor and related tasks is a cornerstone of pre-clinical behavioural and rehabilitative neuroscience. Yet manually testing and training animals in these tasks is time consuming and analyses are often subjective. Consequently, there have been many recent advances in automating both the administration and analyses of animal behavioural training and testing. This review is an in-depth appraisal of the history of, and recent developments in, the automation of animal behavioural assays used in neuroscience. We describe the use of common locomotor and non-locomotor tasks used for motor training and testing before and after nervous system injury. This includes a discussion of how these tasks help us to understand the underlying mechanisms of neurological repair and the utility of some tasks for the delivery of rehabilitative training to enhance recovery. We propose two general approaches to automation: automating the physical administration of behavioural tasks (i.e., devices used to facilitate task training, rehabilitative training, and motor testing) and leveraging the use of machine learning in behaviour analysis to generate large volumes of unbiased and comprehensive data. The advantages and disadvantages of automating various motor tasks as well as the limitations of machine learning analyses are examined. In closing, we provide a critical appraisal of the current state of automation in animal behavioural neuroscience and a prospective on some of the advances in machine learning we believe will dramatically enhance the usefulness of these approaches for behavioural neuroscientists.

Clinical Trial Design-A Review-With Emphasis on Acute Intervertebral Disc Herniation

There is a clear need for new methods of treatment of acute disc herniation in dogs, most obviously to address the permanent loss of function that can arise because of the associated spinal cord injury. Clinical trials form the optimal method to introduce new therapies into everyday clinical practice because they are a reliable source of unbiased evidence of effectiveness. Although many designs are available, parallel cohort trials are most widely applicable to acute disc herniation in dogs. In this review another key trial design decision—that between pragmatic and explanatory approaches—is highlighted and used as a theme to illustrate the close relationship between trial objective and design. Acute disc herniation, and acute spinal cord injury, is common in dogs and there is a multitude of candidate interventions that could be trialed. Most current obstacles to large-scale clinical trials in dogs can be overcome by collaboration and cooperation amongst interested veterinarians.

Compressive mechanical characterization of non-human primate spinal cord white matter

The goal of developing computational models of spinal cord injury (SCI) is to better understand the human injury condition. However, finite element models of human SCI have used rodent spinal cord tissue properties due to a lack of experimental data. Central nervous system tissues in non human primates (NHP) closely resemble that of humans and therefore, it is expected that material constitutive models obtained from NHPs will increase the fidelity and the accuracy of human SCI models. Human SCI most often results from compressive loading and spinal cord white matter properties affect FE predicted patterns of injury; therefore, the objectives of this study were to characterize the unconfined compressive response of NHP spinal cord white matter and present an experimentally derived, finite element tractable constitutive model for the tissue. Cervical spinal cords were harvested from nine male adult NHPs (Macaca mulatta). White matter biopsy samples (3 mm in diameter) were taken from both lateral columns of the spinal cord and were divided into four strain rate groups for unconfined dynamic compression and stress relaxation (post-mortem <1-hour). The NHP spinal cord white matter compressive response was sensitive to strain rate and showed substantial stress relaxation confirming the viscoelastic behavior of the material. An Ogden 1st order model best captured the non-linear behavior of NHP white matter in a quasi-linear viscoelastic material model with 4-term Prony series. This study is the first to characterize NHP spinal cord white matter at high (>10/sec) strain rates typical of traumatic injury. The finite element derived material constitutive model of this study will increase the fidelity of SCI computational models and provide important insights for transferring pre-clinical findings to clinical treatments.

STATEMENT OF SIGNIFICANCE

Spinal cord injury (SCI) finite element (FE) models provide an important tool to bridge the gap between animal studies and human injury, assess injury prevention technologies (e.g. helmets, seatbelts), and provide insight into the mechanisms of injury. Although, FE model outcomes depend on the assumed material constitutive model, there is limited experimental data for fresh spinal cords and all was obtained from rodent, porcine or bovine tissues. Central nervous system tissues in non human primates (NHP) more closely resemble humans. This study characterizes fresh NHP spinal cord material properties at high strains rates and large deformations typical of SCI for the first time. A constitutive model was defined that can be readily implemented in finite strain FE analysis of SCI.

Design and testing of a controlled electromagnetic spinal cord impactor for use in large animal models of acute traumatic spinal cord injury

BACKGROUND

Spinal cord injury (SCI) causes debilitating neurological dysfunction and has been observed in warfighters injured in IED blasts. Clinical benefit of SCI treatment remains elusive and better large animal models are needed to assess treatment options. Here, we describe a controlled electromagnetic spinal cord impactor for use in large animal models of SCI.

METHODS

A custom spinal cord impactor and platform were fabricated for large animals (e.g., pig, sheep, dog, etc.). Impacts were generated by a voice coil actuator; force and displacement were measured with a load cell and potentiometer respectively. Labview (National Instruments, Austin, TX) software was used to control the impact cycle and import force and displacement data. Software finite impulse response (FIR) filtering was employed for all input data. Silicon tubing was used a surrogate for spinal cord in order to test the device; repeated impacts were performed at 15, 25, and 40 Newtons.

RESULTS

Repeated impacts demonstrated predictable results at each target force. The average duration of impact was 71.2 ±6.1ms. At a target force of 40N, the output force was 41.5 ±0.7N. With a target of 25N, the output force was 23.5 ±0.6N; a target of 15Newtons revealed an output force of 15.2 ±1.4N. The calculated acceleration range was 12.5-21.2m/s².

CONCLUSIONS

This custom spinal cord impactor reliably delivers precise impacts to the spinal cord and will be utilized in future research to study acute traumatic SCI in a large animal.

Firefighter willingness to participate in a stem cell clinical trial for burns: A mixed methods study

Adult stem cells represent a potentially renewable and autologous source of cells to regenerate skin and improve wound healing. Firefighters are at risk of sustaining a burn and potentially benefiting from a split thickness skin graft (STSG). This mixed methods study examined firefighter willingness to participate in a future stem cell clinical trial, outcome priorities and factors associated with this decision.

METHODS

A sequential explanatory mixed methods design was used. The quantitative phase (online questionnaire) was followed by the qualitative phase (semi-structured interviews). A sample of 149 firefighters completed the online survey, and a purposeful sample of 15 firefighters was interviewed.

RESULTS

A majority (74%) reported they would participate in a future stem cell clinical trial if they experienced burn benefiting from STSG. Hypothetical concerns related to receiving a STSG were pain, itch, scarring/redness and skin durability. Participants indicated willingness to undergo stem cell therapy if the risk of no improvement was 43% or less. Risk tolerance was predicted by perceived social support and having children. Interviews revealed four main themes: a desire to help others, improving clinical outcomes, trusting relationships, and a belief in scientific investigation. Many participants admitted lacking sufficient knowledge to make an informed decision regarding stem cell therapies.

CONCLUSIONS

Firefighters indicated they were largely willing to participate in a stem cell clinical trial but also indicated a lack of knowledge upon which to make a decision. Public education of the role of stem cells in STSG will be increasingly important as clinical trials are developed.

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.

Drug delivery, cell-based therapies, and tissue engineering approaches for spinal cord injury

Spinal cord injury (SCI) results in devastating neurological and pathological consequences, causing major dysfunction to the motor, sensory, and autonomic systems. The primary traumatic injury to the spinal cord triggers a cascade of acute and chronic degenerative events, leading to further secondary injury. Many therapeutic strategies have been developed to potentially intervene in these progressive neurodegenerative events and minimize secondary damage to the spinal cord. Additionally, significant efforts have been directed toward regenerative therapies that may facilitate neuronal repair and establish connectivity across the injury site. Despite the promise that these approaches have shown in preclinical animal models of SCI, challenges with respect to successful clinical translation still remain. The factors that could have contributed to failure include important biologic and physiologic differences between the preclinical models and the human condition, study designs that do not mirror clinical reality, discrepancies in dosing and the timing of therapeutic interventions, and dose-limiting toxicity. With a better understanding of the pathobiology of events following acute SCI, developing integrated approaches aimed at preventing secondary damage and also facilitating neuroregenerative recovery is possible and hopefully will lead to effective treatments for this devastating injury. The focus of this review is to highlight the progress that has been made in drug therapies and delivery systems, and also cell-based and tissue engineering approaches for SCI.

Perspectives on strategies and challenges in the conversation about stem cells for spinal cord injury

STUDY DESIGN

Qualitative study.

OBJECTIVE

To examine how trusted communication between individuals with spinal cord injury (ISCIs) and physicians who care for ISCIs is affected by the discussion of advances in stem cell research and interventions locally and abroad.

SETTING

Canada and the United States (US).

METHODS

Semi-structured interviews with ISCIs and physicians. A thematic analysis approach was applied to more than 12 h of data to derive prominent themes and describe relationships between them.

RESULTS

A convergence of factors involving transparency impact trusted communication between ISCIs and physicians about stem cells and spinal cord injury (SCI). ISCIs expressed that trusted communication is strengthened when physicians exhibit caring, attentive and positive attitudes that are underpinned by domain-specific knowledge and scholarship. Perceived reluctance to communicate or lack of knowledge poses significant challenges. Physicians also emphasised the importance of transparency for trusted communication but expressed that the still limited clinical reality of treatment choices for SCI and the pressures imposed by external resources are significant stressors that complicate the communication landscape. Both groups cited the range and variable quality of information sources, and the difficulty associated with navigating them, as priorities for action that would remediate these tensions.

CONCLUSIONS

(1) Epistemic transparency should be privileged over silence. (2) A new generation of innovations in research and clinical trial dissemination about stem cells for SCI is needed to remedy the perceived inadequacies of existing information content and accessibility.

Large animal and primate models of spinal cord injury for the testing of novel therapies

Large animal and primate models of spinal cord injury (SCI) are being increasingly utilized for the testing of novel therapies. While these represent intermediary animal species between rodents and humans and offer the opportunity to pose unique research questions prior to clinical trials, the role that such large animal and primate models should play in the translational pipeline is unclear. In this initiative we engaged members of the SCI research community in a questionnaire and round-table focus group discussion around the use of such models. Forty-one SCI researchers from academia, industry, and granting agencies were asked to complete a questionnaire about their opinion regarding the use of large animal and primate models in the context of testing novel therapeutics. The questions centered around how large animal and primate models of SCI would be best utilized in the spectrum of preclinical testing, and how much testing in rodent models was warranted before employing these models. Further questions were posed at a focus group meeting attended by the respondents. The group generally felt that large animal and primate models of SCI serve a potentially useful role in the translational pipeline for novel therapies, and that the rational use of these models would depend on the type of therapy and specific research question being addressed. While testing within these models should not be mandatory, the detection of beneficial effects using these models lends additional support for translating a therapy to humans. These models provides an opportunity to evaluate and refine surgical procedures prior to use in humans, and safety and bio-distribution in a spinal cord more similar in size and anatomy to that of humans. Our results reveal that while many feel that these models are valuable in the testing of novel therapies, important questions remain unanswered about how they should be used and how data derived from them should be interpreted.

Lymphocytes and autoimmunity after spinal cord injury

Over the past 15 years an immense amount of data has accumulated regarding the infiltration and activation of lymphocytes in the traumatized spinal cord. Although the impact of the intraspinal accumulation of lymphocytes is still unclear, modulation of the adaptive immune response via active and passive vaccination is being evaluated for its preclinical efficacy in improving the outcome for spinal-injured individuals. The complexity of the interaction between the nervous and the immune systems is highlighted in the contradictions that appear in response to these modulations. Current evidence regarding augmentation and inhibition of the adaptive immune response to spinal cord injury is reviewed with an aim toward reconciling conflicting data and providing consensus issues that may be exploited in future therapies. Opportunities such an approach may provide are highlighted as well as the obstacles that must be overcome before such approaches can be translated into clinical trials.

Neural precursor cell transplantation enhances functional recovery and reduces astrogliosis in bilateral compressive/contusive cervical spinal cord injury

Spinal cord injury has a significant societal and personal impact. Although the majority of injuries involve the cervical spinal cord, few studies of cell transplantation have used clinically relevant models of cervical spinal cord injury, limiting translation into clinical trials. Given this knowledge gap, we sought to examine the effects of neural stem/precursor cell (NPC) transplants in a rodent model of bilateral cervical contusion-compression spinal cord injury. Bilateral C6-level clip contusion-compression injuries were performed in rats, which were then blindly randomized at 2 weeks after injury into groups receiving adult brain-derived NPCs, vehicle, or sham operation. Long-term survival of NPCs was evident at 10 weeks after transplant. Cell grafts were localized rostrocaudally surrounding the lesion, throughout white and gray matter. Graft-derived cells were found within regions of gliotic scar and motor tracts and deposited myelin around endogenous axons. The majority of NPCs developed an oligodendroglial phenotype with greater neuronal profiles in rostral grafts. Following NPC transplantation, white matter was significantly increased compared with control. Astrogliosis and glial scar deposition, measured by GFAP-positive and chondroitin sulfate proteoglycan-positive volume, was significantly reduced. Forelimb grip strength, fine motor control during locomotion, and axonal conduction (by in vivo electrophysiology) was greater in cell-treated animals compared with vehicle controls. Transplantation of NPCs in the bilaterally injured cervical spinal cord results in significantly improved spinal cord tissue and forelimb function, warranting further study in preclinical cervical models to improve this treatment paradigm for clinical translation.

Sex steroids and neuroprotection in spinal cord injury: a review of preclinical investigations

Spinal cord injury (SCI) is a debilitating condition that affects motor, sensory and autonomic functions. Subsequent to the first mechanical trauma, secondary events, which include inflammation and glial activation, exacerbate tissue damage and worsen functional deficits. Although these secondary injury mechanisms are amenable to therapeutic interventions, the efficacy of current approaches is inadequate. Further investigations are necessary to implement new therapies that can protect neural cells and attenuate some of the detrimental effects of inflammation while promoting regeneration. Studies on different animal models of SCI indicated that sex steroids, especially 17β-estradiol and progesterone, exert neuroprotective, anti-apoptotic and anti-inflammatory effects, ameliorate tissue sparing and improve functional deficits in SCI. As sex steroid receptors are expressed in a variety of cells including neurons, glia and immune system-related cells which infiltrate the injury epicenter, sex steroids could impact multiple processes simultaneously and in doing so, influence the outcomes of SCI. However, the translation of these pre-clinical findings into the clinical setting presents challenges such as the narrow therapeutic time window of sex steroid administration, the diversity of treatment regimens that have been employed in animal studies and the lack of sufficient information regarding the persistence of the effects in chronic SCI. The current review will summarize some of the major findings in this field and will discuss the challenges associated with the implementation of sex steroids as a promising treatment in human SCI.

Dissociations in the meaning of risk between health-care professionals and individuals with spinal cord injury

OBJECTIVE

Risks have been a central concern in stem cell research overall, and in clinical trials of individuals with spinal cord injury (ISCIs) in particular. We sought to elucidate how two important stakeholder groups-health-care professionals (HCPs) and ISCIs-view and value both the physical and non-physical risks of stem cell interventions.

SETTING

The study was conducted in Canada, and included participants from both Canada and the United States America.

STUDY DESIGN

We used semi-structured interviews to gain perspectives on risk from HCPs and ISCIs.

METHODS

We applied a constant comparative analytic strategy to derive themes from the discourse collected through the interviews.

RESULTS

We identified three major themes about risk from 12 HCP and 24 ISCI participants: focus, rationale and approach. The salient components of the themes differed: HCPs focus on the physical causes of risks, and the ISCIs on their downstream consequences as well as on non-physical risks; HCPs are concerned about evidence, and ISCIs about experience; and HCPs approach risk narrowly, whereas the approach of ISCIs is more broad and contextualized.

CONCLUSION

Although major themes were common to the two stakeholder groups, the components of the themes were dissociable and illustrate differences in what HCPs and ISCIs worry about, why they worry and how they approach their worries. We draw upon these findings to make recommendations for improving risk communication and informed consent for stem cell research for spinal cord injury.