In-vivo diffusion tensor imaging of rat spinal cord with a phased array coil at 7T

Magnetic resonance imaging (MRI) is a non-invasive technique that offers excellent soft tissue contrast for characterizing soft tissue pathologies. Diffusion tensor imaging (DTI) is an MRI technique that has shown to have the sensitivity to detect subtle pathology that is not evident on conventional MRI. ^ Rats are commonly used as animal models in characterizing the spinal cord pathologies including spinal cord injury (SCI), cancer, multiple sclerosis, etc. These pathologies could affect both thoracic and cervical regions and complete characterization of these pathologies using MRI requires DTI characterization in both the thoracic and cervical regions. Prior to the application of DTI for investigating the pathologic changes in the spinal cord, it is essential to establish DTI metrics in normal animals. ^ To date, in-vivo DTI studies of rat spinal cord have used implantable coils for high signal-to-noise ratio (SNR) and spin-echo pulse sequences for reduced geometric distortions. Implantable coils have several disadvantages including: (1) the invasive nature of implantation, (2) loss of SNR due to frequency shift with time in the longitudinal studies, and (3) difficulty in imaging the cervical region. While echo planar imaging (EPI) offers much shorter acquisition times compared to spin-echo imaging, EPI is very sensitive to static magnetic field inhomogeneities and the existing shimming techniques implemented on the MRI scanner do not perform well on spinal cord because of its geometry. ^ In this work, an integrated approach has been implemented for in-vivo DTI characterization of rat spinal cord in the thoracic and cervical regions. A three element phased array coil was developed for improved SNR and extended spatial coverage. A field-map shimming technique was developed for minimizing the geometric distortions in EPI images. Using these techniques, EPI based DWI images were acquired with optimized diffusion encoding scheme from 6 normal rats and the DTI-derived metrics were quantified. ^ The phantom studies indicated higher SNR and smaller bias in the estimated DTI metrics than the previous studies in the cervical region. In-vivo results indicated no statistical difference in the DTI characteristics of either gray matter or white matter between the thoracic and cervical regions. ^

The association of internet use and depression among spinal cord injury population

The purpose of this study was to exam the relationship between internet use and depression among a population of individuals who have sustained spinal cord injury. This was cross-sectional survey design conducted among spinal cord injury (SCI) patients in the Model Spinal Cord Injury System. We included a total of 1,011 SCI-patients who were interviewed face-to-face or by telephone interview over approximately a three year time period (2004–2006). All data were collected through a telephone survey which included the Patient Health Questionnaire-9 (PHQ-9) to assess depression. We examined various scales of this survey, included a reduced 3-item scale (items 1, 2 and 6) to avoid the presence of somatic symptoms among SCI patients from influencing classification of depression. The frequency of internet usage was grouped as daily/weekly/monthly/non user. Covariates examined as possible confounders included demographic characteristics, occupational status, educational level, injury type, daily function of living, pain level, self-perceived health status and satisfaction with life. We observed a negative association between the frequency of internet use and the level of depression. Daily use of internet was associated with lower PHQ-9 score and depression; however this association did not reach statistical significance after for the mentioned covariates. In conclusion, the factors related to lower depression in SCI patients who use the internet are complicated. Daily internet usage was associated with lower levels of depression. The accuracy of 3-item scale needs further validation and investigation. Further study of internet usage pattern in SCI patient is recommended. ^

In vivo longitudinal studies of spinal cord injury and vascular endothelial growth factor treatment

Approximately 12,000 new cases of spinal cord injury (SCI) are added each year to the estimated 259,000 Americans living with SCI. The majority of these patients return to society, their lives forever changed by permanent loss of sensory and motor function. While there are no FDA approved drugs for the treatment of SCI or a universally accepted standard therapy, the current though controversial treatment includes the delivery of high dosages of the corticosteroid methyliprednisolone sodium succinate, surgical interventions to stabilize the spinal column, and physical rehabilitation. It is therefore critically important to fully understand the pathology of injury and determine novel courses and rationally-based therapies for SCI. ^ Vascular endothelial growth factor (VEGF) is an attractive target for treating central nervous system (CNS) injury and disease because it has been shown to influence angiogenesis and neuroprotection. Preliminary studies have indicated that increased vasculature may be associated with functional recovery; therefore exogenous delivery of a pro-angiogenic growth factor such as VEGF may improve neurobehavioral outcome. In addition, VEGF may provide protection from secondary injury and result in increased survival and axonal sprouting. ^ In these studies, SCI rats received acute intraspinal injections of VEGF, the antibody to VEGF, or vehicle control. The effect of these various agents was investigated using longitudinalmulti-modal magnetic resonance imaging (MRI), neuro- and sensory behavioral assays, and end point immunohistochemistry. We found that rats that received VEGF after SCI had increased tissue sparing and improved white matter integrity at the earlier time points as shown by advanced magnetic resonance imaging (MRI) techniques. However, these favorable effects of VEGF were not maintained, suggesting that additional treatments with VEGF at multiple time points may be more beneficial, Histological examinations revealed that VEGF treatment may result in increased oligodendrogenesis and therefore may eventually lead to remyelination and improved functional outcome. ^ On the neurobehavioral studies, treatments with VEGF and Anti-VEGF did not significantly affect performance on tests of open-field locomotion, grid walk, inclined plane, or rearing. However, VEGF treatment resulted in significantly increased incidence of chronic neuropathic pain. This phenomenon could possibly be attributed to the fact that VEGF treatment may promote axonal sprouting and also results in tissue sparing, thereby providing a substrate for the growth of new axons. New connections made by these sprouting axons may involve components of pathways involved in the transmission of pain and therefore result in increased pain in those animals. ^

Risk factors of pneumonia in traumatic spinal-cord-injured patients

Pneumonia is a well-documented and common respiratory infection in patients with acute traumatic spinal cord injuries, and may recur during the course of acute care. Using data from the North American Clinical Trials Network (NACTN) for Spinal Cord Injury, the incidence, timing, and recurrence of pneumonia were analyzed. The two main objectives were (1) to investigate the time and potential risk factors for the first occurrence of pneumonia using the Cox Proportional Hazards model, and (2) to investigate pneumonia recurrence and its risk factors using a Counting Process model that is a generalization of the Cox Proportional Hazards model. The results from survival analysis suggested that surgery, intubation, American Spinal Injury Association (ASIA) grade, direct admission to a NACTN site and age (older than 65 or not) were significant risks for first event of pneumonia and multiple events of pneumonia. The significance of this research is that it has the potential to identify patients at the time of admission who are at high risk for the incidence and recurrence of pneumonia. Knowledge and the time of occurrence of pneumonias are important factors for the development of prevention strategies and may also provide some insights into the selection of emerging therapies that compromise the immune system. ^

A Pre-Clinical Assessment of Minocycline for Treatment of Chronic Neuropathic Pain after Spinal Cord Injury

Patients living with a spinal cord injury (SCI) often develop chronic neuropathic pain (CNP). Unfortunately, the clinically approved, current standard of treatment, gabapentin, only provides temporary pain relief. This treatment can cause numerous adverse side effects that negatively affect the daily lives of SCI patients. There is a great need for alternative, effective treatments for SCI-dependent CNP. Minocycline, an FDA-approved antibiotic, has been widely prescribed for the treatment of acne for several decades. However, recent studies demonstrate that minocycline has neuroprotective properties in several pre-clinical rodent models of CNS trauma and disease. Pre-clinical studies also show that short-term minocycline treatment can prevent the onset of CNP when delivered during the acute stage of SCI and can also transiently attenuate established CNP when delivered briefly during the chronic stage of SCI. However, the potential to abolish or attenuate CNP via long-term administration of minocycline after SCI is unknown. The purpose of this study was to investigate the potential efficacy and safety of long-term administration of minocycline to abolish or attenuate CNP following SCI. A severe spinal contusion injury was administered on adult, male, Sprague-Dawley rats. At day 29 post-injury, I initiated a three-week treatment regimen of daily administration with minocycline (50 mg/kg), gabapentin (50 mg/kg) or saline. The minocycline treatment group demonstrated a significant reduction in below-level mechanical allodynia and above- level hyperalgesia while on their treatment regimen. After a ten-day washout period of minocycline, the animals continued to demonstrate a significant reduction in below-level mechanical allodynia and above-level hyperalgesia. However, minocycline-treated animals exhibited abnormal weight gain and hepatotoxicity compared to gapabentin-treated or vehicle-treated subjects.The results support previous findings that minocycline can attenuate CNP after SCI and suggested that minocycline can also attenuate CNP via long-term delivery of minocycline after SCI (36). The data also suggested that minocycline had a lasting effect at reducing pain symptoms. However, the adverse side effects of long-term use of minocycline should not be ignored in the rodent model. Gabapentin treatment caused a significant decrease in below-level mechanical allodynia and below-level hyperalgesia during the treatment regimen. Because gabapentin treatment has an analgesic effect at the concentration I administered, the results were expected. However, I also found that gabapentin-treated animals demonstrated a sustained reduction in pain ten days after treatment withdrawal. This result was unexpected because gabapentin has a short half-life of 1.7 hours in rodents and previous studies have demonstrated that pre-drug pain levels return shortly after withdrawal of treatment. Additionally, the gabapentin-treated animals demonstrated a significant and sustained increase in rearing events compared with all other treatment groups which suggested that gabapentin treatment was not only capable of reducing pain long-term but may also significantly improve trunk stability or improve motor function recovery.

Novel Use of Dual Anti-Inflammatory Therapy to Overcome Drug Resistance and Improve Functional Recovery Following Spinal Cord Injury

Over 1.2 million Americans are currently living with a traumatic spinal cord injury (SCI). Despite the need for effective therapies, there are currently no proven effective treatments that can improve recovery of function in SCI patients. Many therapeutic compounds have shown promise in preclinical models of SCI, but all of these have fallen short in clinical trials. P-glycoprotein (Pgp) is an active transporter expressed on capillary endothelial cell membranes at the blood-spinal cord barrier (BSCB). Pgp limits passive diffusion of blood-borne drugs into the CNS, by actively extruding drugs from the endothelial cell membrane. Pgp can become pathologically up-regulated, thus greatly impeding therapeutic drug delivery (‘multidrug resistance’). Importantly, many drugs that have been evaluated for the treatment of SCI are Pgp substrates. We hypothesized that Pgp-mediated drug resistance diminishes the delivery and efficacy of neuroprotective drugs following SCI. We observed a progressive, spatial spread of Pgp overexpression within the injured spinal cord. To assess Pgp function, we examined spinal cord uptake of systemically-delivered riluzole, a drug that is currently being evaluated in clinical trials as an SCI intervention. Blood-to-spinal cord riluzole penetration was reduced following SCI in wild-type but not Pgp-null rats, highlighting a critical role for Pgp in mediating spinal cord drug resistance after injury. Others have shown that pro-inflammatory signaling drives Pgp up-regulation in cancer and epilepsy. We have detected inflammation in both acutely- and chronically-injured spinal cord tissue. We therefore evaluated the ability of the dual COX-/5-LOX inhibitor licofelone to attenuate Pgp-mediated drug resistance following SCI. Licofelone treatment both reduced spinal cord Pgp levels and enhanced spinal cord riluzole bioavailability following SCI. Thus, we propose that licofelone may offer a new combinatorial treatment strategy to enhance spinal cord drug delivery following SCI. Additionally, we assessed the ability of licofelone, riluzole, or both to enhance recovery of locomotor function following SCI. We found that licofelone treatment conferred a significant improvement in hindlimb function that was sustained through the end of the study. In contrast, riluzole did not improve functional outcome. We therefore conclude that licofelone holds promise as a potential neuroprotective intervention for SCI.

TRPV1 Channels Contribute to Behavioral Hypersensitivity and Spontaneous Activity in Nociceptors After Spinal Cord Injury

A majority of persons who have sustained spinal cord injury (SCI) develop chronic pain. While most investigators have assumed that the critical mechanisms underlying neuropathic pain after SCI are restricted to the central nervous system (CNS), recent studies showed that contusive SCI results in a large increase in spontaneous activity in primary nociceptors, which is correlated significantly with mechanical allodynia and thermal hyperalgesia. Upregulation of ion channel transient receptor vanilloid 1 (TRPV1) has been observed in the dorsal horn of the spinal cord after SCI, and reduction of SCI-induced hyperalgesia by a TRPV1 antagonist has been claimed. However, the possibility that SCI enhances TRPV1 expression and function in nociceptors has not been tested. I produced contusive SCI at thoracic level T10 in adult, male rats and harvested lumbar (L4/L5) dorsal root ganglia (DRG) from sham-treated and SCI rats 3 days and 1 month after injury, as well as from age-matched naive control rats. Whole-cell patch clamp recordings were made from small (soma diameter <30 >μm) DRG neurons 18 hours after dissociation. Capsaicin-induced currents were significantly increased 1 month, but not 3 days, after SCI compared to neurons from control animals. In addition, Ca2+ transients imaged during capsaicin application were significantly greater 1 month after SCI. Western blot experiments indicated that expression of TRPV1 protein in DRG is also increased 1 month after SCI. A major role for TRPV1 channels in pain-related behavior was indicated by the ability of a specific TRPV1 antagonist, AMG9810, to reverse SCI-induced hypersensitivity of hindlimb withdrawal responses to heat and mechanical stimuli. Similar reversal of behavioral hypersensitivity was induced by intrathecal delivery of oligodeoxynucleotides antisense to TRPV1, which knocked down TRPV1 protein and reduced capsaicin-evoked currents. TRPV1 knockdown also decreased the incidence of spontaneous activity in dissociated nociceptors after SCI. Limited activation of TRPV1 was found to induce prolonged repetitive firing without accommodation or desensitization, and this effect was enhanced by SCI. These data suggest that SCI enhances TRPV1 expression and function in primary nociceptors, increasing the excitability and spontaneous activity of these neurons, thus contributing to chronic pain after SCI.

External validation study of a clinical prediction rule for ambulation outcomes after traumatic spinal cord injury

The main objective of this study was to determine the external validity of a clinical prediction rule developed by the European Multicenter Study on Human Spinal Cord Injury (EM-SCI) to predict the ambulation outcomes 12 months after traumatic spinal cord injury. Data from the North American Clinical Trials Network (NACTN) data registry with approximately 500 SCI cases were used for this validity study. The predictive accuracy of the EM-SCI prognostic model was evaluated using calibration and discrimination based on 231 NACTN cases. The area under the receiver-operating-characteristics curve (ROC) curve was 0.927 (95% CI 0.894 – 0.959) for the EM-SCI model when applied to NACTN population. This is lower than the AUC of 0.956 (95% CI 0.936 – 0.976) reported for the EM-SCI population, but suggests that the EM-SCI clinical prediction rule distinguished well between those patients in the NACTN population who were able to achieve independent ambulation and those who did not achieve independent ambulation. The calibration curve suggests that higher the prediction score is, the better the probability of walking with the best prediction for AIS D patients. In conclusion, the EM-SCI clinical prediction rule was determined to be generalizable to the adult NACTN SCI population.^

A geographic information science (GIS) approach to conducting comparative area-level community assessments in the Texas CORD Study

This study assessed and compared sociodemographic and income characteristics along with food and physical activity assets (i.e. grocery stores, fast food restaurants, and park areas) in the Texas Childhood Obesity Research Demonstration (CORD) Study intervention and comparison catchment areas in Houston and Austin, Texas. The Texas CORD Study used a quasi-experimental study design, so it is necessary to establish the interval validity of the study characteristics by confirming that the intervention and comparison catchment areas are statistically comparable. In this ecological study, ArcGIS and Esri Business Analyst were used to spatially relate U.S. Census Bureau and other business listing data to the specific school attendance zones within the catchment areas. T-tests were used to compare percentages of sociodemographic and income characteristics and densities of food and physical activity assets between the intervention and comparison catchment areas.^ Only five variables were found to have significant differences between the intervention and comparison catchment areas: Age groups 0-4 and 35-64, the percentage of owner-occupied and renter-occupied households, and the percentage of Asian and Pacific Islander residents. All other variables showed no significant differences between the two groups. This study shows that the methodology used to select intervention and comparison catchment areas for the Texas CORD Study was effective and can be used in future studies. The results of this study can be used in future Texas CORD studies to confirm the comparability of the intervention and comparison catchment areas. In addition, this study demonstrates a methodology for describing detailed characteristics about a geographic area that practitioners, researchers, and educators can use.^

A new feature extraction method for signal classification applied to cat spinal cord signals

In the spinal cord of the anesthetized cat, spontaneous cord dorsum potentials (CDPs) appear synchronously along the lumbo-sacral segments. These CDPs have different shapes and magnitudes. Previous work has indicated that some CDPs appear to be specially associated with the activation of spinal pathways that lead to primary afferent depolarization and presynaptic inhibition. Visual detection and classification of these CDPs provides relevant information on the functional organization of the neural networks involved in the control of sensory information and allows the characterization of the changes produced by acute nerve and spinal lesions. We now present a novel feature extraction approach for signal classification, applied to CDP detection. The method is based on an intuitive procedure. We first remove by convolution the noise from the CDPs recorded in each given spinal segment. Then, we assign a coefficient for each main local maximum of the signal using its amplitude and distance to the most important maximum of the signal. These coefficients will be the input for the subsequent classification algorithm. In particular, we employ gradient boosting classification trees. This combination of approaches allows a faster and more accurate discrimination of CDPs than is obtained by other methods.

A computational model coupling mechanics and electrophysiology in spinal cord injury

Traumatic brain injury and spinal cord injury have recently been put under the spotlight as major causes of death and disability in the developed world. Despite the important ongoing experimental and modeling campaigns aimed at understanding the mechanics of tissue and cell damage typically observed in such events, the differenti- ated roles of strain, stress and their corresponding loading rates on the damage level itself remain unclear. More specif- ically, the direct relations between brain and spinal cord tis- sue or cell damage, and electrophysiological functions are still to be unraveled. Whereas mechanical modeling efforts are focusing mainly on stress distribution and mechanistic- based damage criteria, simulated function-based damage cri- teria are still missing. Here, we propose a new multiscale model of myelinated axon associating electrophysiological impairment to structural damage as a function of strain and strain rate. This multiscale approach provides a new framework for damage evaluation directly relating neuron mechanics and electrophysiological properties, thus provid- ing a link between mechanical trauma and subsequent func- tional deficits.

A data-globe and immersive virtual reality environment for upper limb rehabilitation after spinal cord injury

While a number of virtual data-gloves have been used in stroke, there is little evidence about their use in spinal cord injury (SCI). A pilot clinical experience with nine SCI subjects was performed comparing two groups: one carried out a virtual rehabilitation training based on the use of a data glove, CyberTouch combined with traditional rehabilitation, during 30 minutes a day twice a week along two weeks; while the other made only conventional rehabilitation. Furthermore, two functional indexes were developed in order to assess the patient’s performance of the sessions: normalized trajectory lengths and repeatability. While differences between groups were not statistically significant, the data-glove group seemed to obtain better results in the muscle balance and functional parameters, and in the dexterity, coordination and fine grip tests. Related to the indexes that we implemented, normalized trajectory lengths and repeatability, every patient showed an improvement in at least one of the indexes, either along Y-axis trajectory or Z-axis trajectory. This study might be a step in investigating new ways of treatments and objective measures in order to obtain more accurate data about the patient’s evolution, allowing the clinicians to develop rehabilitation treatments, adapted to the abilities and needs of the patients.

A computational model coupling mechanics and electrophysiology in spinal cord injury

Traumatic brain injury and spinal cord injury have recently been put under the spotlight as major causes of death and disability in the developed world. Despite the important ongoing experimental and modeling campaigns aimed at understanding the mechanics of tissue and cell damage typically observed in such events, the differentiated roles of strain, stress and their corresponding loading rates on the damage level itself remain unclear. More specifically, the direct relations between brain and spinal cord tissue or cell damage, and electrophysiological functions are still to be unraveled. Whereas mechanical modeling efforts are focusing mainly on stress distribution and mechanistic-based damage criteria, simulated function-based damage criteria are still missing. Here, we propose a new multiscale model of myelinated axon associating electrophysiological impairment to structural damage as a function of strain and strain rate. This multiscale approach provides a new framework for damage evaluation directly relating neuron mechanics and electrophysiological properties, thus providing a link between mechanical trauma and subsequent functional deficits

Alloantigen-induced unresponsiveness in cord blood T lymphocytes is associated with defective activation of Ras

Human umbilical cord blood T lymphocytes (CBTL) respond to primary allostimulation but they do not proliferate upon rechallenge with alloantigen. Using PKH-26-labeled cells created a proliferative block that was observed only in CBTL that have divided during primary stimulation (PKH-26dim) but not in unstimulated (PKH-26bright) CBTL. CBTL’s secondary unresponsiveness resembles anergy and can be overcome by treatment with phorbol myristate acetate (PMA) and ionomycin or by high doses (50–100 units/ml) of interleukin 2. Addition of interleukin 2 to the primary cultures does not prevent the induction of secondary unresponsiveness. Defective Ras activation is detected in PKH-26dim CBTL during secondary response to alloantigen or after antibody-mediated T cell receptor stimulation whereas Ras is activated and proliferation is induced in CBTL during primary alloantigenic stimulation. Upon stimulation with PMA plus ionomycin, PMA plus alloantigen, but not alloantigen plus ionomycin, Ras is activated in PKH-26dim CBTL, and the block in proliferation is overcome. Correction of PKH-26dim CBTL’s proliferative defect correlates with PMA-induced Ras activation, suggesting a defect in the signaling pathway leading to Ras. Ras-independent signals, necessary but not sufficient to induce PKH-26dim CBTL proliferation, are provided by alloantigen exposure, as evident by the ability of PMA plus alloantigen but not PMA alone to overcome the proliferative block. Functional signal transduction through CD28 in PKH-26dim CBTL is supported by detectable CD28-mediated PI-3 kinase activation after PKH-26dim CBTL’s exposure to alloantigen or CD28 cross-linking. These results suggest that defective activation of Ras plays a key role in PKH-26dim CBTL’s secondary unresponsiveness and point to a defect along the T cell receptor rather than the CD28 signaling pathway.