Microglia inhibition is a target of mild hypothermic treatment after the spinal cord injury

A prospective multi-center study comparing the complication profile of modest systemic hypothermia versus normothermia for acute cervical spinal cord injury

STUDY DESIGN

Prospective multi-center trial.

OBJECTIVES

To characterize the complication profile associated with modest systemic hypothermia after acute cervical SCI in a prospective multi-center study.

SETTING

Five trauma centers in the United States.

METHODS

We analyzed data from a prospective, multi-center trial on the use of modest systemic hypothermia for acute cervical SCI. Patients with acute cervical SCI were assigned to receive modest systemic hypothermia (33 C) or standard of care medical treatment. Patients in the hypothermia group were cooled to 33 C and maintained at the target temperature for 48 h. Complication profile and the rate of complications within the first 6 weeks after injury were compared between the two groups. Multiple regression analysis was performed to determine risk factors for complications after injury.

RESULTS

Fifty patients (hypothermia: 27, control: 23) were analyzed for this study. Median age was significantly lower in the hypothermia arm (39 vs 59 years, p = 0.02). Respiratory complications were the most common (hypothermia: 55.6% vs control: 52.2%, p = 0.81). The rate of deep vein thrombosis was not significantly different between the two groups (hypothermia: 14.8% vs control 17.4%, p = 0.71). The rate of complications was not statistically different between the two groups.

CONCLUSION

In this prospective multi-center controlled trial, preliminary data show that modest systemic hypothermia was not associated with increased risk of complications within the first 6 weeks after acute cervical SCI.

TRIAL INFORMATION

The study is registered on clinicaltrials.gov NCT02991690. University of Miami IRB (Central IRB) approval No.: 20160758. Emory University IRB #IRB00093786.

A Direct Comparison of Physical Versus Dihydrocapsaicin-Induced Hypothermia in a Rat Model of Traumatic Spinal Cord Injury

Spinal cord injury (SCI) is a devastating neurological condition with no effective treatment. Hypothermia induced by physical means (cold fluid) is established as an effective therapy in animal models of SCI, but its clinical translation to humans is hampered by several constraints. Hypothermia induced pharmacologically may be noninferior or superior to physically induced hypothermia for rapid, convenient systemic temperature reduction, but it has not been investigated previously in animal models of SCI. We used a rat model of SCI to compare outcomes in three groups: (1) normothermic controls; (2) hypothermia induced by conventional physical means; (3) hypothermia induced by intravenous (IV) dihydrocapsaicin (DHC). Male rats underwent unilateral lower cervical SCI and were treated after a 4-hour delay with physical cooling or IV DHC (∼0.60 mg/kg total) cooling (both 33.0 ± 1.0°C) lasting 4 hours; controls were kept normothermic. Telemetry was used to monitor temperature and heart rate during and after treatments. In two separate experiments, one ending at 48 hours, the other at 6 weeks, “blinded” investigators evaluated rats in the three groups for neurological function followed by histopathological evaluation of spinal cord tissues. DHC reliably induced systemic cooling to 32–33°C. At both the time points examined, the two modes of hypothermia yielded similar improvements in neurological function and lesion size compared with normothermic controls. Our results indicate that DHC-induced hypothermia may be comparable with physical hypothermia in efficacy, but more clinically feasible to administer than physical hypothermia.

Hypothermia as a potential remedy for canine and feline acute spinal cord injury: a review

Severe spinal cord injury (SCI) resulting in permanent sensory-motor and autonomic dysfunction caudal to a damaged spinal cord (SC) segment is a catastrophic event in human as well as in veterinary medicine. The situation of paraplegic/tetraplegic people or animals is further impaired by serious complications and often displays an image of permanent suffering. Therapeutic hypothermia (TH) has shown neuroprotective capacity in numerous experimental and several clinical studies or case reports. Hence, the method draws increasing attention of neuroscientists as well as health care workers. While systemic TH is a too complex procedure for veterinary practice, local application of TH with a reduced risk of the whole body temperature fluctuations and minimal side effects can become one of the therapeutic tools considered in the treatment of acute traumatic SCIs in bigger animals, especially when surgical decompression of spinal medulla and vertebral column reconstruction is indicated. Still, additional large prospective randomized studies are essential for the standardization of therapeutic protocols and the introduction of the method into therapeutic armamentarium in canine and feline spinal traumatology. The research strategy involved a PubMed, MEDLINE (Ovid), EMBASE (Ovid), and ISI Web of Science search from January 2000 to July 2021 using the terms “canine and feline spinal cord injuryˮ, “hypothermiaˮ, and “targeted temperature managementˮ in the English language literature; also references from selected studies were scanned and relevant articles included.

Increasing Severity of Spinal Cord Injury Results in Microglia/Macrophages With Annular-Shaped Morphology and No Change in Expression of CD40 and Tumor Growth Factor-β During the Chronic Post-injury Stage

Determination of the quantitative composition of phenotypically and morphologically different populations of resident microglia and infiltrating macrophages in spinal cord injury (SCI) of various degrees of severity could lead to much needed novel therapeutic interventions in neurotrauma. In this regard, we investigated the CD40 and TGF-β expressing populations of microglia/macrophages and their morphological states in a rat model of SCI of varying severity. We are the first to describe the annular-shaped microglia/macrophages, the morphology of which was formed due to the spatial orientation of the processes that form round or oval micro-territories, which include disintegrating myelin fibers. This type of cell morphology was found only in the injured spinal cord and mainly in the white matter. At the same time, an assessment of the number of annular-shaped microglia/macrophages and the diameter of micro-territories formed by their processes showed an elevation in these indicators as the severity of SCI increased. While we did not find significant quantitative changes in the populations of Iba1⁺/CD40⁺ and Iba1⁺/TGF-β⁺ microglia/macrophages with increased severity of SCI in the chronic period (60 dpi), we did determine changes in the expression of cytokines and mRNAs of genes-encoding microglial marker proteins, finding the greatest changes on days 7 and 14 after SCI between experimental groups with varying severity.

Hypothermia for Acute Spinal Cord Injury

Neuroprotection after acute spinal cord injury is an important strategy to limit secondary injury. Animal studies have shown that systemic hypothermia is an effective neuroprotective strategy that can be combined with other therapies. Systemic hypothermia affects several processes at the cellular level to reduce metabolic activity, oxidative stress, and apoptotic neuronal cell death. Modest systemic hypothermia has been shown to be safe and feasible in the acute phase after cervical spinal cord injury. These data have provided the impetus for an active multicenter randomized controlled trial for modest systemic hypothermia in acute cervical spinal cord injury.

Neuroimmunological therapies for treating spinal cord injury: Evidence and future perspectives

Spinal cord injury (SCI) has a complex pathophysiology. Following the initial physical trauma to the spinal cord, which may cause vascular disruption, hemorrhage, mechanical injury to neural structures and necrosis, a series of biomolecular cascades is triggered to evoke secondary injury. Neuroinflammation plays a major role in the secondary injury after traumatic SCI. To date, the administration of systemic immunosuppressive medications, in particular methylprednisolone sodium succinate, has been the primary pharmacological treatment. This medication is given as a complement to surgical decompression of the spinal cord and maintenance of spinal cord perfusion through hemodynamic augmentation. However, the impact of neuroinflammation is complex with harmful and beneficial effects. The use of systemic immunosuppressants is further complicated by the natural onset of post-injury immunosuppression, which many patients with SCI develop. It has been hypothesized that immunomodulation to attenuate detrimental aspects of neuroinflammation after SCI, while avoiding systemic immunosuppression, may be a superior approach. To accomplish this, a detailed understanding of neuroinflammation and the systemic immune responses after SCI is required. Our review will strive to achieve this goal by first giving an overview of SCI from a clinical and basic science context. The role that neuroinflammation plays in the pathophysiology of SCI will be discussed. Next, the positive and negative attributes of the innate and adaptive immune systems in neuroinflammation after SCI will be described. With this background established, the currently existing immunosuppressive and immunomodulatory therapies for treating SCI will be explored. We will conclude with a summary of topics that can be explored by neuroimmunology research. These concepts will be complemented by points to be considered by neuroscientists developing therapies for SCI and other injuries to the central nervous system.

Therapeutic Hypothermia Improves Hind Limb Motor Outcome and Attenuates Oxidative Stress and Neuronal Damage in the Lumbar Spinal Cord Following Cardiac Arrest

Hypothermia enhances outcomes of patients after resuscitation after cardiac arrest (CA). However, the underlying mechanism is not fully understood. In this study, we investigated effects of hypothermic therapy on neuronal damage/death, microglial activation, and changes of endogenous antioxidants in the anterior horn in the lumbar spinal cord in a rat model of asphyxial CA (ACA). A total of 77 adult male Sprague–Dawley rats were randomized into five groups: normal, sham ACA plus (+) normothermia, ACA + normothermia, sham ACA + hypothermia, and ACA + hypothermia. ACA was induced for 5 min by injecting vecuronium bromide. Therapeutic hypothermia was applied after return of spontaneous circulation (ROSC) via rapid cooling with isopropyl alcohol wipes, which was maintained at 33 ± 0.5 °C for 4 h. Normothermia groups were maintained at 37 ± 0.2 °C for 4 h. Neuronal protection, microgliosis, oxidative stress, and changes of endogenous antioxidants were evaluated at 12 h, 1 day, and 2 days after ROSC following ACA. ACA resulted in neuronal damage from 12 h after ROSC and evoked obvious degeneration/loss of spinal neurons in the ventral horn at 1 day after ACA, showing motor deficit of the hind limb. In addition, ACA resulted in a gradual increase in microgliosis with time after ACA. Therapeutic hypothermia significantly reduced neuronal loss and attenuated hind limb dysfunction, showing that hypothermia significantly attenuated microgliosis. Furthermore, hypothermia significantly suppressed ACA-induced increases of superoxide anion production and 8-hydroxyguanine expression, and significantly increased superoxide dismutase 1 (SOD1), SOD2, catalase, and glutathione peroxidase. Taken together, hypothermic therapy was found to have a substantial impact on changes in ACA-induced microglia activation, oxidative stress factors, and antioxidant enzymes in the ventral horn of the lumbar spinal cord, which closely correlate with neuronal protection and neurological performance after ACA.

Clinical Neurorestorative Therapeutic Guidelines for Spinal Cord Injury (IANR/CANR version 2019)

Functional restoration after spinal cord injury (SCI) is one of the most challenging tasks in neurological clinical practice. With a view to exploring effective neurorestorative methods in the acute, subacute, and chronic phases of SCI, “Clinical Therapeutic Guidelines of Neurorestoration for Spinal Cord Injury (China Version 2016)” was first ​proposed in 2016 by the Chinese Association of Neurorestoratology (CANR). Given the rapid advances in this field in recent years, the International Association of Neurorestoratology (IANR) and CANR formed and approved the “Clinical Neurorestorative Therapeutic Guidelines for Spinal Cord Injury (IANR/CANR version 2019)”. These guidelines mainly introduce restoring damaged neurological structure and functions by varying neurorestorative strategies in acute, subacute, and chronic phases of SCI. These guidelines can provide a neurorestorative therapeutic standard or reference for clinicians and researchers in clinical practice to maximally restore functions of patients with SCI and improve their quality of life.

The translational potential of this article

This guideline provided comprehensive management strategies for SCI, which contains the evaluation and diagnosis, pre-hospital first aid, treatments, rehabilitation training, and complications management. Nowadays, amounts of neurorestorative strategies have been demonstrated to be benefit in promoting the functional recovery and improving the quality of life for SCI patients by clinical trials. Also, the positive results of preclinical research provided lots of new neurorestorative strategies for SCI treatment. These promising neurorestorative strategies are worthy of translation in the future and can promote the advancement of SCI treatments.

Hypothermic treatment after computer-controlled compression in minipig: A preliminary report on the effect of epidural vs. direct spinal cord cooling

The aim of the present study was to investigate the therapeutic efficacy of local hypothermia (beginning 30 min post-injury persisting for 5 h) on tissue preservation along the rostro-caudal axis of the spinal cord (3 cm cranially and caudally from the lesion site), and the prevention of injury-induced functional loss in a newly developed computer-controlled compression model in minipig (force of impact 18N at L3 level), which mimics severe spinal cord injury (SCI). Minipigs underwent SCI with two post-injury modifications (durotomy vs. intact dura mater) followed by hypothermia through a perfusion chamber with cold (epidural t≈15°C) saline, DMEM/F12 or enriched DMEM/F12 (SCI/durotomy group) and with room temperature (t≈24°C) saline (SCI-only group). Minipigs treated with post-SCI durotomy demonstrated slower development of spontaneous neurological improvement at the early postinjury time points, although the outcome at 9 weeks of survival did not differ significantly between the two SCI groups. Hypothermia with saline (t≈15°C) applied after SCI-durotomy improved white matter integrity in the dorsal and lateral columns in almost all rostro-caudal segments, whereas treatment with medium/enriched medium affected white matter integrity only in the rostral segments. Furthermore, regeneration of neurofilaments in the spinal cord after SCI-durotomy and hypothermic treatments indicated an important role of local saline hypothermia in the functional outcome. Although saline hypothermia (24°C) in the SCI-only group exhibited a profound histological outcome (regarding the gray and white matter integrity and the number of motoneurons) and neurofilament protection in general, none of the tested treatments resulted in significant improvement of neurological status. The findings suggest that clinically-proven medical treatments for SCI combined with early 5 h-long saline hypothermia treatment without opening the dural sac could be more beneficial for tissue preservation and neurological outcome compared with hypothermia applied after durotomy.

Hypothermia Used in Medical Applications for Brain and Spinal Cord Injury Patients

Despite more than 80 years of animal experiments and clinical practice, efficacy of hypothermia in improving treatment outcomes in patients suffering from cell and tissue damage caused by ischemia is still ongoing. This review will first describe the history of utilizing cooling in medical treatment, followed by chemical and biochemical mechanisms of cooling that can lead to neuroprotection often observed in animal studies and some clinical studies. The next sections will be focused on current cooling approaches/devices, as well as cooling parameters recommended by researchers and clinicians. Animal and clinical studies of implementing hypothermia to spinal cord and brain tissue injury patients are presented next. This section will review the latest outcomes of hypothermia in treating patients suffering from traumatic brain injury (TBI), spinal cord injury (SCI), stroke, cardiopulmonary surgery, and cardiac arrest, followed by a summary of available evidence regarding both demonstrated neuroprotection and potential risks of hypothermia. Contributions from bioengineers to the field of hypothermia in medical treatment will be discussed in the last section of this review. Overall, an accumulating body of clinical evidence along with several decades of animal research and mathematical simulations has documented that the efficacy of hypothermia is dependent on achieving a reduced temperature in the target tissue before or soon after the injury-precipitating event. Mild hypothermia with temperature reduction of several degrees Celsius is as effective as modest or deep hypothermia in providing therapeutic benefit without introducing collateral/systemic complications. It is widely demonstrated that the rewarming rate must be controlled to be lower than 0.5 °C/h to avoid mismatch between local blood perfusion and metabolism. In the past several decades, many different cooling methods and devices have been designed, tested, and used in medical treatments with mixed results. Accurately designing treatment protocols to achieve specific cooling outcomes requires collaboration among engineers, researchers, and clinicians. Although this problem is quite challenging, it presents a major opportunity for bioengineers to create methods and devices that quickly and safely produce hypothermia in targeted tissue regions without interfering with routine medical treatment.

Extended magnetic resonance imaging studies on the effect of classically activated microglia transplantation on white matter regeneration following spinal cord focal injury in adult rats

Spinal cord injuries are still a serious problem for regenerative medicine. Previous research has demonstrated that activated microglia accumulate in spinal lesions, influencing the injured tissues in various ways. Therefore, transplantation of activated microglia may have a beneficial role in the regeneration of the nervous system. The present study examined the influence of transplanted activated microglial cells in adult rats with injured spinal cords. Rats were randomly divided into an experimental (M) and control (C) group, and were subjected to non-laminectomy focal injury of spinal cord white matter by means of a high-pressured air stream. In group M, activated cultured microglial cells were injected twice into the site of injury. Functional outcome and morphological features of regeneration were analyzed during a 12-week follow-up. The lesions were characterized by means of magnetic resonance imaging (MRI). Neurons in the brain stem and motor cortex were labeled with FluoroGold (FG). A total of 12 weeks after surgery, spinal cords and brains were collected and subjected to histopathological and immunohistochemical examinations. Lesion sizes in the spinal cord were measured and the number of FG-positive neurons was counted. Rats in group M demonstrated significant improvement of locomotor performance when compared with group C (P<0.05). MRI analysis demonstrated moderate improvement in water diffusion along the spinal cord in the group M following microglia treatment, as compared with group C. The water diffusion perpendicular to the spinal cord in group M was closer to the reference values for a healthy spinal cord than it was in group C. The sizes of lesions were also significantly smaller in group M than in the group C (P<0.05). The number of brain stem and motor cortex FG-positive neurons in group M was significantly higher than in group C. The present study demonstrated that delivery of activated microglia directly into the injured spinal cord gives some positive effects for the regeneration of the white matter.

Neuroprotective effect of local hypothermia in a computer-controlled compression model in minipig: Correlation of tissue sparing along the rostro-caudal axis with neurological outcome

This study investigated the neuroprotective efficacy of local hypothermia in a minipig model of spinal cord injury (SCI) induced by a computer-controlled impactor device. The tissue integrity observed at the injury epicenter, and up to 3 cm cranially and caudally from the lesion site correlated with motor function. A computer-controlled device produced contusion lesions at L3 level with two different degrees of tissue sparing, depending upon pre-set impact parameters (8N- and 15N-force impact). Hypothermia with cold (4°C) saline or Dulbecco's modified Eagle's medium (DMEM)/F12 culture medium was applied 30 min after SCI (for 5 h) via a perfusion chamber (flow 2 ml/min). After saline hypothermia, the 8N-SCI group achieved faster recovery of hind limb function and the ability to walk from one to three steps at nine weeks in comparison with non-treated animals. Such improvements were not observed in saline-treated animals subjected to more severe 15N-SCI or in the group treated with DMEM/F12 medium. It was demonstrated that the tissue preservation in the cranial and caudal segments immediately adjacent to the lesion, and neurofilament protection in the lateral columns may be essential for modulation of the key spinal microcircuits leading to a functional outcome. Tissue sparing observed only in the caudal sections, even though significant, was not sufficient for functional improvement in the 15N-SCI model.

Promising neuroprotective strategies for traumatic spinal cord injury with a focus on the differential effects among anatomical levels of injury

Traumatic spinal cord injury (SCI) is a devastating condition of motor, sensory, and autonomic dysfunction. The significant cost associated with the management and lifetime care of patients with SCI also presents a major economic burden. For these reasons, there is a need to develop and translate strategies that can improve outcomes following SCI. Given the challenges in achieving regeneration of the injured spinal cord, neuroprotection has been at the forefront of clinical translation. Yet, despite many preclinical advances, there has been limited translation into the clinic apart from methylprednisolone (which remains controversial), hypertensive therapy to maintain spinal cord perfusion, and early decompressive surgery. While there are several factors related to the limited translational success, including the clinical and mechanistic heterogeneity of human SCI, the misalignment between animal models of SCI and clinical reality continues to be an important factor. Whereas most clinical cases are at the cervical level, only a small fraction of preclinical research is conducted in cervical models of SCI. Therefore, this review highlights the most promising neuroprotective and neural reparative therapeutic strategies undergoing clinical assessment, including riluzole, hypothermia, granulocyte colony-stimulating factor, glibenclamide, minocycline, Cethrin (VX-210), and anti-Nogo-A antibody, and emphasizes their efficacy in relation to the anatomical level of injury. Our hope is that more basic research will be conducted in clinically relevant cervical SCI models in order to expedite the transition of important laboratory discoveries into meaningful treatment options for patients with SCI.

The role of therapeutic hypothermia in the management of acute spinal cord injury

This review paper investigates the history, efficacy, and administration of systemic and local hypothermia for spinal cord injury (SCI). It summarizes the published experimental and clinical evidence on hypothermia for SCI and analyzes the potential for further research. Early experimental animal research showed that local hypothermia improved recovery and gain of function after acute SCI. However, in the early 1970s, clinical research findings did not coincide with results of these animal trials, which led to a loss of interest in local hypothermia. Since the 1980s, systemic hypothermia has been successfully used to treat SCI in both animals and humans. An abundance of positive evidence suggests that clinical trials are needed to determine the effectiveness of hypothermia for SCI. As a first step, we investigated the published clinical and experimental evidence on the use of hypothermia for SCI patients, who have few available treatment options. We searched PubMed for English-language reports published from 1940 to 2016 containing terms related to SCI treatment using hypothermia. We reviewed all articles on local hypothermia and acute SCI or on systemic hypothermia and acute SCI. Bibliographies of retrieved publications were also screened for additional citations. Ninety-six papers were selected. The clinical use of hypothermia is most successful if applied according to certain optimized parameters (e.g., duration, temperature, time from injury to initiation of cooling, and rewarming time). Preliminary data suggest that modest systemic hypothermia applied for 48h provides the best therapeutic value, but the parameters for use of local hypothermia vary greatly. Experimental evidence and some clinical evidence suggest that both local hypothermia and systemic hypothermia are beneficial for acute SCI. Future research should focus on defining the optimal levels of parameters. Large, multicenter, controlled clinical trials are needed to investigate its therapeutic potential.

Beneficial effects of local profound hypothermia and the possible mechanism after experimental spinal cord injury in rats

OBJECTIVE

The primary focus of this study was to investigate the effects of local profound hypothermia and to explore the possible mechanism in adult rats with spinal cord injury.

STUDY DESIGN AND METHODS

Spinal cord injury models were established by placing aneurysm clips on T10. An epidural perfusion device was applied to maintain a steady temperature (18 °C) for 120 min with gradual rewarming to 37 °C Total hypothermic duration lasted up to about 170 min. The expression of axon regeneration inhibitors was tested by Western blot and real-time PCR. Luxol Fast Blue (LFB) stain and Bielschowsky silver stain were used to observe spinal cord morphology. Motor function of the hind limbs (BBB score) was monitored for 21 days.

RESULTS

The expressions of RhoA, ROCK-II, NG2, Neurocan, Brevican, and Nogo-A were downregulated by regional hypothermia (RH) after spinal cord injury. Subsequent observation showed that rats that had received RH had an alleviated demyelinating condition and a greater number of nerve fibers. Furthermore, the RH group achieved higher BBB scores than the spinal cord injury (SCI) group.

CONCLUSIONS

Recovery of hind limb function in rats can be promoted by local profound hypothermia; this may be caused by the suppression of axon regeneration inhibitors.

Therapeutic Hypothermia in Spinal Cord Injury: The Status of Its Use and Open Questions

Spinal cord injury (SCI) is a major health problem and is associated with a diversity of neurological symptoms. Pathophysiologically, dysfunction after SCI results from the culmination of tissue damage produced both by the primary insult and a range of secondary injury mechanisms. The application of hypothermia has been demonstrated to be neuroprotective after SCI in both experimental and human studies. The myriad of protective mechanisms of hypothermia include the slowing down of metabolism, decreasing free radical generation, inhibiting excitotoxicity and apoptosis, ameliorating inflammation, preserving the blood spinal cord barrier, inhibiting astrogliosis, promoting angiogenesis, as well as decreasing axonal damage and encouraging neurogenesis. Hypothermia has also been combined with other interventions, such as antioxidants, anesthetics, alkalinization and cell transplantation for additional benefit. Although a large body of work has reported on the effectiveness of hypothermia as a neuroprotective approach after SCI and its application has been translated to the clinic, a number of questions still remain regarding its use, including the identification of hypothermia's therapeutic window, optimal duration and the most appropriate rewarming rate. In addition, it is necessary to investigate the neuroprotective effect of combining therapeutic hypothermia with other treatment strategies for putative synergies, particularly those involving neurorepair.

Protection and Repair After Spinal Cord Injury: Accomplishments and Future Directions

It was an honor for me to present the 2014 G. Heiner Sell Memorial Lecture at the annual American Spinal Injury Association (ASIA) meeting in San Antonio. For this purpose, I provided a comprehensive review of the scope of research targeting discovery and translational and clinical investigations into spinal cord injury (SCI) research. Indeed, these are exciting times in the area of spinal cord research and clinical initiatives. Many laboratories and clinical programs throughout the world are publishing data related to the pathophysiology of SCI and new strategies for protecting and promoting recovery in both animal models and humans. For this lecture, several topics were discussed including neuroprotective and reparative strategies, neurorehabilitation, quality of life issues, and future directions. In the area of neuroprotection, pathophysiological events that may be targeted with therapeutic strategies, including pharmacological and targeted temperature management were reviewed. For reparative approaches, the importance of both intrinsic and extrinsic mechanisms of axonal regeneration was highlighted. Various cell therapies currently being tested in preclinical and clinical arenas were reviewed as well as ongoing US Food and Drug Administration approved trials for SCI patients. Neurorehabilitation is an evolving research field with locomotive training strategies, electrical stimulation, and brain-machine interface programs targeting various types of SCI. The importance of testing combination approaches including neuroprotective, reparative, and rehabilitative strategies to maximize recovery mechanisms was therefore emphasized. Finally, quality of life issues that affect thousands of individuals living with paralysis were also presented. Future directions and specific obstacles that require attention as we continue to move the SCI field forward were discussed.

Effects of hypothermia combined with neural stem cell transplantation on recovery of neurological function in rats with spinal cord injury

The microenvironment of the injured spinal cord is hypothesized to be involved in driving the differentiation and survival of engrafted neural stem cells (NSCs). Hypothermia is known to improve the microenvironment of the injured spinal cord in a number of ways. To investigate the effect of NSC transplantation in combination with hypothermia on the recovery of rat spinal cord injury, 60 Sprague-Dawley female rats were used to establish a spinal cord hemisection model. They were divided randomly into three groups: A, spinal cord injury group; B, NSC transplantation group; and C, NSC transplantation + hypothermia group. At 1, 2, 4, 6 and 8 weeks post-injury, the motor function of all animals was evaluated using the Basso, Beattie and Besnaham locomotor scoring system and the inclined plane test. At 4 weeks post-transplantation, histological analysis and immunocytochemistry were performed. At 8 weeks post-transplantation, horseradish peroxidase nerve tracing and transmission electron microscopy were conducted to observe axonal regeneration. The outcome of hind limb motor function recovery in group C significantly surpassed that in group B at 4 weeks post-injury (P<0.05). Recovery was also observed in group A, but to a lesser degree. For the pathological sections no neural axonal were observed in group A. A few axon-like structures were observed in group B and more in group C. Horseradish peroxidase-labeled neurofibers and bromodeoxyuridine-positive cells were observed in the spinal cords of group C. Fewer of these cells were found in group B and fewer still in group A. The differences among the three groups were significant (P<0.05). Using transmission electron microscopy, newly formed nerve fibers and myelinated nerve fibers were observed in the central transverse plane in groups B and C, although these nerve fibers were not evident in group A. In conclusion, NSC transplantation promoted the recovery of hind limb function in rats, and combination treatment with hypothermia produced synergistic effects.

Mild hypothermia as a treatment for central nervous system injuries: Positive or negative effects

Besides local neuronal damage caused by the primary insult, central nervous system injuries may secondarily cause a progressive cascade of related events including brain edema, ischemia, oxida-tive stress, excitotoxicity, and dysregulation of calcium homeostasis. Hypothermia is a beneficial strategy in a variety of acute central nervous system injuries. Mild hypothermia can treat high intra-cranial pressure following traumatic brain injuries in adults. It is a new treatment that increases sur-vival and quality of life for patients suffering from ischemic insults such as cardiac arrest, stroke, and neurogenic fever following brain trauma. Therapeutic hypothermia decreases free radical produc-tion, inflammation, excitotoxicity and intracranial pressure, and improves cerebral metabolism after traumatic brain injury and cerebral ischemia, thus protecting against central nervous system dam-age. Although a series of pathological and physiological changes as well as potential side effects are observed during hypothermia treatment, it remains a potential therapeutic strategy for central nervous system injuries and deserves further study.

The effect of hypothermia on sensory-motor function and tissue sparing after spinal cord injury

BACKGROUND CONTEXT

In recent years, hypothermia has been described as a therapeutic approach that leads to potential protective effects via minimization of secondary damage consequences, reduction of neurologic deficit, and increase of motor performance after spinal cord injury (SCI) in animal models and humans.

PURPOSE

The objective of this study was to determine the therapeutic efficacy of hypothermia treatment on sensory-motor function and bladder activity outcome correlated with the white and gray matter sparing and neuronal survival after SCI in adult rats.

STUDY DESIGN

A standardized animal model of compression SCI was used to test the hypothesis that hypothermia could have a neuroprotective effect on neural cell death and loss of white and/or gray matter.

METHODS

Animals underwent spinal cord compression injury at the Th8-Th9 level followed by systemic hypothermia of 32.0°C with gradual re-warming to 37.0°C. Motor function of hind limbs (BBB score) and mechanical allodynia (von Frey hair filaments) together with function of urinary bladder was monitored in all experimental animals throughout the whole survival period.

RESULTS

Present results showed that hypothermia had beneficial effects on urinary bladder activity and on locomotor function recovery at Days 7 and 14 post-injury. Furthermore, significant increase of NeuN-positive neuron survival within dorsal and ventral horns at Days 7, 14, and 21 were documented.

CONCLUSIONS

Our conclusions suggest that hypothermia treatment may not only promote survival of neurons, which can have a significant impact on the improvement of motor and vegetative functions, but also induce mechanical allodynia.

From basics to clinical: a comprehensive review on spinal cord injury

Spinal cord injury (SCI) is a devastating neurological disorder that affects thousands of individuals each year. Over the past decades an enormous progress has been made in our understanding of the molecular and cellular events generated by SCI, providing insights into crucial mechanisms that contribute to tissue damage and regenerative failure of injured neurons. Current treatment options for SCI include the use of high dose methylprednisolone, surgical interventions to stabilize and decompress the spinal cord, and rehabilitative care. Nonetheless, SCI is still a harmful condition for which there is yet no cure. Cellular, molecular, rehabilitative training and combinatorial therapies have shown promising results in animal models. Nevertheless, work remains to be done to ascertain whether any of these therapies can safely improve patient's condition after human SCI. This review provides an extensive overview of SCI research, as well as its clinical component. It starts covering areas from physiology and anatomy of the spinal cord, neuropathology of the SCI, current clinical options, neuronal plasticity after SCI, animal models and techniques to assess recovery, focusing the subsequent discussion on a variety of promising neuroprotective, cell-based and combinatorial therapeutic approaches that have recently moved, or are close, to clinical testing.

Systematic review and meta-analysis of therapeutic hypothermia in animal models of spinal cord injury

Background

Therapeutic hypothermia is a clinically useful neuroprotective therapy for cardiac arrest and neonatal hypoxic ischemic encephalopathy and may potentially be useful for the treatment of other neurological conditions including traumatic spinal cord injury (SCI). The pre-clinical studies evaluating the effectiveness of hypothermia in acute SCI broadly utilise either systemic hypothermia or cooling regional to the site of injury. The literature has not been uniformly positive with conflicting studies of varying quality, some performed decades previously.

Methods

In this study, we systematically review and meta-analyse the literature to determine the efficacy of systemic and regional hypothermia in traumatic SCI, the experimental conditions influencing this efficacy, and the influence of study quality on outcome. Three databases were utilised; PubMed, ISI Web of Science and Embase. Our inclusion criteria consisted of the (i) reporting of efficacy of hypothermia on functional outcome (ii) number of animals and (iii) mean outcome and variance in each group.

Results

Systemic hypothermia improved behavioural outcomes by 24.5% (95% CI 10.2 to 38.8) and a similar magnitude of improvement was seen across a number of high quality studies. The overall behavioural improvement with regional hypothermia was 26.2%, but the variance was wide (95% CI −3.77 to 56.2). This result may reflect a preponderance of positive low quality data, although a preferential effect of hypothermia in ischaemic models of injury may explain some of the disparate data. Sufficient heterogeneity was present between studies of regional hypothermia to reveal a number of factors potentially influencing efficacy, including depth and duration of hypothermia, animal species, and neurobehavioural assessment. However, these factors could reflect the influence of earlier lower quality literature.

Conclusion

Systemic hypothermia appears to be a promising potential method of treating acute SCI on the basis of meta-analysis of the pre-clinical literature and the results of high quality animal studies.

Microglial physiopathology: how to explain the dual role of microglia after acute neural disorders?

Microglia are the resident macrophages of the central nervous system (CNS). In physiological conditions, resting microglia maintain tissue integrity by scanning the entire CNS parenchyma through stochastic and complex movements of their long processes to identify minor tissue alterations. In pathological conditions, over-activated microglia contribute to neuronal damage by releasing harmful substances, including inflammatory cytokines, reactive oxygen species, and proteinases, but they can provide tissue repair by releasing anti-inflammatory cytokines and neurotrophic factors. The reasons for this apparent paradox are unknown. In this paper, we first review the physiological role as well as both detrimental and beneficial actions of microglial during acute CNS disorders. Further, we discuss the possible reasons for this microglial dual role following CNS insults, considering that the final microglial phenotype is a direct consequence of both noxious and beneficial stimuli released into the extracellular space during the pathological insult. The nature of these micro-glial ligands is unknown, but we hypothesize that harmful and beneficial stimuli may be preferentially located at specific anatomical niches along the pathological environment triggering both beneficial and deleterious actions of these glial cells. According to this notion, there are no natural populations of detrimental microglia, but is the pathological environment that determines the final microglial phenotype.

Potential long-term benefits of acute hypothermia after spinal cord injury: assessments with somatosensory-evoked potentials

OBJECTIVE

Neuroprotection by hypothermia has been an important research topic over last two decades. In animal models of spinal cord injury, the primary focus has been assessing the effects of hypothermia on behavioral and histologic outcomes. Although a few studies have investigated electrophysiological changes in descending motor pathways with motor-evoked potentials recorded during cooling, we report here hypothermia induced increased electrical conduction in the ascending spinal cord pathways with somatosensory-evoked potentials in injured rats. In our experiments, these effects lasted long after the acute hypothermia and were accompanied by potential long-term improvements in motor movement.

DESIGN

Laboratory investigation.

SETTING

University medical school.

SUBJECTS

Twenty-one female Lewis rats.

INTERVENTIONS

Hypothermia.

MEASUREMENTS AND MAIN RESULTS

All animals underwent spinal cord contusion with the NYU-Impactor by a 12.5-mm weight drop at thoracic vertebra T8. A group (n = 10) was randomly assigned for a systemic 2-hr hypothermia episode (32 ± 0.5°C) initiated approximately 2.0 hrs postinjury. Eleven rats were controls with postinjury temperature maintained at 37 ± 0.5°C for 2 hrs. The two groups underwent preinjury, weekly postinjury (up to 4 wks) somatosensory-evoked potential recordings and standard motor behavioral tests (BBB). Three randomly selected rats from each group were euthanized for histologic analysis at postinjury day 3 and day 28. Compared with controls, the hypothermia group showed significantly higher postinjury somatosensory-evoked potential amplitudes with longer latencies. The BBB scores were also higher immediately after injury and 4 wks later in the hypothermia group. Importantly, specific changes in the Basso, Beattie, Bresnahan scores in the hypothermia group (not seen in controls) indicated regained functions critical for motor control. Histologic evaluations showed more tissue preservation in the hypothermia group.

CONCLUSIONS

After spinal cord injury, early systemic hypothermia provided significant neuroprotection weeks after injury through improved sensory electrophysiological signals in rats. This was accompanied by higher motor behavioral scores and more spared tissue in acute and postacute periods after injury.

The antinociceptive effect of the asthma drug ibudilast in rat models of peripheral and central neuropathic pain

Ibudilast, an asthma drug, has demonstrated antinociceptive effects in several rat models of peripheral neuropathic pain, and a proposed mechanism of action is the inhibition of release of the cytokine tumor necrosis factor-α (TNF-α) from activated spinal microglia. Spinal glial activation has also been demonstrated in rat models of central neuropathic pain following spinal cord injury (SCI). The current study evaluated the effect of a short course of treatment with ibudilast on SCI-induced pain, and for comparison, following a chronic constriction injury (CCI; the Bennett model) of the sciatic nerve in rats. The effects of ibudilast treatment on spinal (SCI and CCI rats), and nerve tissue (CCI only) TNF-α content were also evaluated. Following an acute midthoracic SCI with a microvascular clip (20-g force), hindpaw withdrawal thresholds were significantly decreased, indicating below-level cutaneous tactile hypersensitivity. Likewise, unilateral loose ligation of the sciatic nerve led to a robust ipsilateral tactile hypersensitivity. Rats were treated with either ibudilast (10 mg/kg IP) or vehicle (2 mL/kg) during the period of robust and steady hindpaw hypersensitivity for each model--CCI rats were treated 14-16 days post-surgery, and SCI rats were treated 30-32 days post-surgery--and tested daily. Ibudilast ameliorated hindpaw hypersensitivity in both SCI and CCI rats, whereas vehicle treatment had no effect. Interestingly, repeated treatment led to increased baseline thresholds, beyond the duration of the drug half-life, suggesting persistent changes in neuropathic pain processing. In SCI rats, an increase in TNF-α content in spinal tissue rostral to the SCI was observed. Ibudilast treatment did not significantly alter this increase. In rats with a CCI, TNF-α content was markedly increased in the ipsilateral sciatic nerve and was partially reduced following ibudilast, but not vehicle, treatment. Ibudilast could be useful for the treatment of neuropathic pain of central as well as peripheral origin.

A systematic review of non-invasive pharmacologic neuroprotective treatments for acute spinal cord injury

An increasing number of therapies for spinal cord injury (SCI) are emerging from the laboratory and seeking translation into human clinical trials. Many of these are administered as soon as possible after injury with the hope of attenuating secondary damage and maximizing the extent of spared neurologic tissue. In this article, we systematically review the available pre-clinical research on such neuroprotective therapies that are administered in a non-invasive manner for acute SCI. Specifically, we review treatments that have a relatively high potential for translation due to the fact that they are already used in human clinical applications, or are available in a form that could be administered to humans. These include: erythropoietin, NSAIDs, anti-CD11d antibodies, minocycline, progesterone, estrogen, magnesium, riluzole, polyethylene glycol, atorvastatin, inosine, and pioglitazone. The literature was systematically reviewed to examine studies in which an in-vivo animal model was utilized to assess the efficacy of the therapy in a traumatic SCI paradigm. Using these criteria, 122 studies were identified and reviewed in detail. Wide variations exist in the animal species, injury models, and experimental designs reported in the pre-clinical literature on the therapies reviewed. The review highlights the extent of investigation that has occurred in these specific therapies, and points out gaps in our knowledge that would be potentially valuable prior to human translation.

Body cooling ameliorating spinal cord injury may be neurogenesis-, anti-inflammation- and angiogenesis-associated in rats

BACKGROUND

Body cooling (BC) or mild hypothermia therapy (about 33°C) is reportedly effective for spinal cord injury (SCI). However, the mechanisms underlying the beneficial effects of BC remain unclear, so does BC ameliorating SCI via promoting neurogenesis, anti-inflammation, and angiogenesis.

METHODS

The standard rat compression SCI model was tested hypothetically in two groups: one receiving BC (33°C) and the other, normothermia (37°C). Afterward, the effects of BC therapy on the hind limb locomotion, spinal cord infarction and apoptosis, angiogenesis, neurogenesis, and inflammation in these two groups of SCI were assessed. The other group of sham SCI was used as controls.

RESULTS

Apoptosis (evidenced by higher numbers of terminal deoxynucleotidyl- transferase-mediated and duDP-biotin nick end-labeling-positive cells), infarct, activated inflammation (evidenced by higher levels of tumor necrosis factor-α, interleukin-1β, and myeloperoxidase), and hind limb locomotor dysfunction were inspected in the untreated (37°C) SCI rats 4 days after SCI. When compared with those of untreated SCI rats, SCI rats receiving BC (33°C) displayed lower levels of apoptosis, infarct volume, activated inflammation, and hind limb locomotor dysfunction. In addition, that BC promoted both angiogenesis (evidenced by increased numbers of both vascular endothelial growth factors and bromodeoxyuridine-positive endothelial cells) and neurogenesis (evidenced by increased numbers of both glial cell line-derived neurotrophic growth factors and bromodeoxyuridine-neuronal-specific nuclear protein double positive cells) in the injured spinal cord was evaluated 4 days after SCI.

CONCLUSION

BC (33°C) improved SCI outcomes by promoting angiogenesis, neurogenesis, and anti-inflammation in a rat SCI model.

Hypothermic treatment for acute spinal cord injury

Spinal cord injury (SCI) is a devastating condition that affects approximately 11,000 patients each year in the United States. Although a significant amount of research has been conducted to clarify the pathophysiology of SCI, there are limited therapeutic interventions that are currently available in the clinic. Moderate hypothermia has been used in a variety of experimental and clinical situations to target several neurological disorders, including traumatic brain and SCI. Recent studies using clinically relevant animal models of SCI have reported the efficacy of therapeutic hypothermia (TH) in terms of promoting long-term behavioral improvement and reducing histopathological damage. In addition, several clinical studies have demonstrated encouraging evidence for the use of TH in patients with a severe cervical spinal cord injury. Moderate hypothermia (33°C) introduced systemically by intravascular cooling strategies appears to be safe and provides some improvement of long-term recovery of function. TH remains an experimental clinical approach and randomized multicenter trials are needed to critically evaluate this potentially exciting therapeutic intervention targeting this patient population.

Spinal cord injury therapies in humans: an overview of current clinical trials and their potential effects on intrinsic CNS macrophages

INTRODUCTION

Macrophage activation is a hallmark of spinal cord injury (SCI) pathology. CNS macrophages, derived from resident microglia and blood monocytes, are ubiquitous throughout the injured spinal cord, and respond to signals in the lesion environment by changing their phenotype and function. Depending on their phenotype and activation status, macrophages may initiate secondary injury mechanisms and/or promote CNS regeneration and repair.

AREAS COVERED

This review provides a comprehensive overview of current SCI clinical trials that are intended to promote neuroprotection, axon regeneration or cell replacement. None of these potential therapies were developed with the goal of influencing macrophage function; however, it is likely that each will have direct or indirect effects on CNS macrophages. The potential impact of each trial is discussed in the context of CNS macrophage biology.

EXPERT OPINION

Activation of CNS macrophages is an inevitable consequence of traumatic SCI. Given that these cells are exquisitely sensitive to changes in microenvironment, any intervention that affects tissue integrity and/or the composition of the cellular milieu will undoubtedly affect CNS macrophages. Thus, it is important to understand how current clinical trials will affect intrinsic CNS macrophages.

Clinical Outcomes Using Modest Intravascular Hypothermia After Acute Cervical Spinal Cord Injury

BACKGROUND

Although a number of neuroprotective strategies have been tested after spinal cord injury (SCI), no treatments have been established as a standard of care.

OBJECTIVE

We report the clinical outcomes at 1-year median follow-up, using endovascular hypothermia after SCI and a detailed analysis of the complications.

METHODS

We performed a retrospective analysis of American Spinal Injury Association and International Medical Society of Paraplegia Impairment Scale (AIS) scores and complications in 14 patients with SCI presenting with a complete cervical SCI (AIS A). All patients were treated with 48 hours of modest (33°C) intravascular hypothermia. The comparison group was composed of 14 age- and injury-matched subjects treated at the same institution.

RESULTS

Six of the 14 cooled patients (42.8%) were incomplete at final follow-up (50.2 [9.7] weeks). Three patients improved to AIS B, 2 patients improved to AIS C, and 1 patient improved to AIS D. Complications were predominantly respiratory and infectious in nature. However, in the control group, a similar number of complications was observed. Adverse events such as coagulopathy, deep venous thrombosis, and pulmonary embolism were not seen in the patients undergoing hypothermia.

CONCLUSION

This study is the first phase 1 clinical trial on the safety and outcome with the use of endovascular hypothermia in the treatment of acute cervical SCI. In this small cohort of patients with SCI, complication rates were similar to those of normothermic patients with an associated AIS A conversion rate of 42.8%.

Protection in animal models of brain and spinal cord injury with mild to moderate hypothermia

For the past 20 years, various laboratories throughout the world have shown that mild to moderate levels of hypothermia lead to neuroprotection and improved functional outcome in various models of brain and spinal cord injury (SCI). Although the potential neuroprotective effects of profound hypothermia during and following central nervous system (CNS) injury have long been recognized, more recent studies have described clinically feasible strategies for protecting the brain and spinal cord using hypothermia following a variety of CNS insults. In some cases, only a one or two degree decrease in brain or core temperature can be effective in protecting the CNS from injury. Alternatively, raising brain temperature only a couple of degrees above normothermia levels worsens outcome in a variety of injury models. Based on these data, resurgence has occurred in the potential use of therapeutic hypothermia in experimental and clinical settings. The study of therapeutic hypothermia is now an international area of investigation with scientists and clinicians from every part of the world contributing to this important, promising therapeutic intervention. This paper reviews the experimental data obtained in animal models of brain and SCI demonstrating the benefits of mild to moderate hypothermia. These studies have provided critical data for the translation of this therapy to the clinical arena. The mechanisms underlying the beneficial effects of mild hypothermia are also summarized.