Olfactory ensheathing cells - another miracle cure for spinal cord injury?

Several recent publications describe remarkably promising effects of transplanting olfactory ensheathing cells as a potential future method to repair human spinal cord injuries. But why were cells from the nose transplanted into the spinal cord? What are olfactory ensheathing cells, and how might they produce these beneficial effects? And more generally, what do we mean by spinal cord injury? To what extent can we compare repair in an animal to repair in a human?     

Treatments for spinal cord injury: is there hope in neurosteroids?

In this review, we describe the current therapeutic strategies to find a cure for paralysis. We use the example of DHEA, a neurosteroid normally produced in the developing neural tube, to raise the hypothesis that such a class of molecules, capable of modulating proliferation of committed neural precursors, could serve as an environmental cue in the adult injured spinal cord to promote re-population of CNS lesion with endogenous dormant precursor cells. Such mechanism may be a part of the natural response to heal the injured CNS and promote recovery of function, suggesting that neurosteroid-treatment could be a promising and novel therapeutic avenue for SCI. We will review pertinent biological activities of DHEA supporting this hypothesis, demonstrate that such activities, dependent on an intact sonic-hedgehog pathway, are responsible for the motor and bladder functional recovery observed after DHEA-treatment in the adult injured spinal cord. We will also raise the current limitations to further development of DHEA- or other neurosteroid-treatments as drug candidates, including the urgent need to further document DHEA long-term safety in CNS indications.     

Is obesity a risk factor for deep tissue injury in patients with spinal cord injury?

Deep tissue injury (DTI) is a severe form of pressure ulcers that occur in subcutaneous tissue under intact skin by the prolonged compression of soft tissues overlying bony prominences. Pressure ulcers and DTI in particular are common in patients with impaired motosensory capacities, such as those with a spinal cord injury (SCI). Obesity is also common among subjects with SCI, yet there are contradicting indications regarding its potential influence as a risk factor for DTI in conditions where these patients sit in a wheelchair without changing posture for prolonged times. It has been argued that high body mass may lead to a greater risk for DTI due to increase in compressive forces from the bones on overlying deep soft tissues, whereas conversely, it has been argued that the extra body fat associated with obesity may reduce the risk by providing enhanced subcutaneous cushioning that redistributes high interface pressures. No biomechanical evaluation of this situation has been reported to date. In order to elucidate whether obesity can be considered a risk factor for DTI, we developed computational finite element (FE) models of the seated buttocks with 4° of obesity, quantified by body mass index (BMI) values of 25.5, 30, 35 and 40 kg/m². We found that peak principal strains, strain energy densities (SED) and von Mises stresses in internal soft tissues (muscle, fat) overlying the ischial tuberosities (ITs) all increased with BMI. With a rise in BMI from 25.5 to 40 kg/m², values of these parameters increased 1.5 times on average. Moreover, the FE simulations indicated that the bodyweight load transferred through the ITs has a greater effect in increasing internal tissue strains/stresses than the counteracting effect of thickening of the adipose layer which is concurrently associated with obesity. We saw that inducing some muscle atrophy (30% reduction in muscle volume, applied to the BMI=40 kg/m² model) which is also characteristic of chronic SCI resulted in further substantial increase in all biomechanical measures reflecting geometrical distortion of muscle tissue, that is, SED, tensile stress, shear stress and von Mises stress. This result highlights that obesity and muscle atrophy, which are both typical of the chronic phase of SCI, contribute together to the state of elevated tissue loads, which consequently increases the likelihood of DTI in this population.     

Can regenerating axons recapitulate developmental guidance during recovery from spinal cord injury?

The precise wiring of the adult mammalian CNS originates during a period of stunning growth, guidance and plasticity that occurs during and shortly after development. When injured in adults, this intricate system fails to regenerate. Even when the obstacles to regeneration are cleared, growing adult CNS fibres usually remain misdirected and fail to reform functional connections. Here, we attempt to fill an important niche related to the topics of nervous system development and regeneration. We specifically contrast the difficulties faced by growing fibres within the adult context to the precise circuit-forming capabilities of developing fibres. In addition to focusing on methods to stimulate growth in the adult, we also expand on approaches to recapitulate development itself.     

Upregulation of casein kinase 1ε in dorsal root ganglia and spinal cord after mouse spinal nerve injury contributes to neuropathic pain

Glycine receptors (GlyRs) play important roles in regulating hippocampal neural network activity and spinal nociception. Here we show that, in cultured rat hippocampal (HIP) and spinal dorsal horn (SDH) neurons, 17-β-estradiol (E₂) rapidly and reversibly reduced the peak amplitude of whole-cell glycine-activated currents (I _Gly). In outside-out membrane patches from HIP neurons devoid of nuclei, E₂ similarly inhibited I _Gly, suggesting a non-genomic characteristic. Moreover, the E₂ effect on I _Gly persisted in the presence of the calcium chelator BAPTA, the protein kinase inhibitor staurosporine, the classical ER (i.e. ERα and ERβ) antagonist tamoxifen, or the G-protein modulators, favoring a direct action of E₂ on GlyRs. In HEK293 cells expressing various combinations of GlyR subunits, E₂ only affected the I _Gly in cells expressing α2, α2β or α3β subunits, suggesting that either α2-containing or α3β-GlyRs mediate the E₂ effect observed in neurons. Furthermore, E₂ inhibited the GlyR-mediated tonic current in pyramidal neurons of HIP CA1 region, where abundant GlyR α2 subunit is expressed. We suggest that the neuronal GlyR is a novel molecular target of E₂ which directly inhibits the function of GlyRs in the HIP and SDH regions. This finding may shed new light on premenstrual dysphoric disorder and the gender differences in pain sensation at the CNS level.     

Quantifying the internal deformation of the rodent spinal cord during acute spinal cord injury – the validation of a method

Visualization and analysis of the rodent spinal cord subject to experimental spinal cord injury (SCI) has almost completely been limited to naked-eye observations, and a single measure of gross spinal cord motion due to injury. This study introduces a novel method which utilizes MRI to quantify the deformation of the rodent spinal cord due to imposed, clinically-relevant injuries – specifically, cervical contusion and dislocation mechanisms. The image registration methods were developed using the Advanced Normalization Tools package, which incorporate rigid, affine and deformable registration steps. The proposed method is validated against a fiducial-based, ‘gold-standard’ measure of spinal cord tissue motion. The validation analysis yielded accuracy (and precision) values of 62 μm (49 μm), 73 μm (79 μm) and 112 μm (110 μm), for the medio-lateral, dorso-ventral and cranio-caudal directions, respectively. The internal morphological change of the spinal cord has never before been quantified, experimentally. This study demonstrates the capability of this method and its potential for future application to in vivo rodent models of SCI.     

Regenerative medicine for the treatment of spinal cord injury: more than just promises?

Spinal cord injury triggers a complex set of events that lead to tissue healing without the restoration of normal function due to the poor regenerative capacity of the spinal cord. Nevertheless, current knowledge about the intrinsic regenerative ability of central nervous system axons, when in a supportive environment, has made the prospect of treating spinal cord injury a reality. Among the range of strategies under investigation, cell‐based therapies offer the most promising results, due to the multifactorial roles that these cells can fulfil. However, the best cell source is still a matter of debate, as are clinical issues that include the optimal cell dose as well as the timing and route of administration. In this context, the role of biomaterials is gaining importance. These can not only act as vehicles for the administered cells but also, in the case of chronic lesions, can be used to fill the permanent cyst, thus creating a more favourable and conducive environment for axonal regeneration in addition to serving as local delivery systems of therapeutic agents to improve the regenerative milieu. Some of the candidate molecules for the future are discussed in view of the knowledge derived from studying the mechanisms that facilitate the intrinsic regenerative capacity of central nervous system neurons. The future challenge for the multidisciplinary teams working in the field is to translate the knowledge acquired in basic research into effective combinatorial therapies to be applied in the clinic.     

Lithium chloride contributes to blood–spinal cord barrier integrity and functional recovery from spinal cord injury by stimulating autophagic flux

Blood–spinal cord barrier (BSCB) disruption following spinal cord injury (SCI) significantly compromises functional neuronal recovery. Autophagy is a potential therapeutic target when seeking to protect the BSCB. We explored the effects of lithium chloride (LiCl) on BSCB permeability and autophagy-induced SCI both in a rat model of SCI and in endothelial cells subjected to oxygen–glucose deprivation. We evaluated BSCB status using the Evans Blue dye extravasation test and measurement of tight junction (TJ) protein levels; we also assessed functional locomotor recovery. We detected autophagy-associated proteins in vivo and in vitro using both Western blotting and immunofluorescence staining. We found that, in a rat model of SCI, LiCl attenuated the elevation in BSCB permeability, improved locomotor recovery, and inhibited the degradation of TJ proteins including occludin and claudin-5. LiCl significantly induced the extent of autophagic flux after SCI by increasing LC3-II and ATG-5 levels, and abolishing p62 accumulation. In addition, a combination of LiCl and the autophagy inhibitor chloroquine not only partially eliminated the BSCB-protective effect of LiCl, but also exacerbated TJ protein degradation both in vivo and in vitro. Together, these findings suggest that LiCl treatment alleviates BSCB disruption and promotes locomotor recovery after SCI, partly by stimulating autophagic flux.     

What is the potential of oligodendrocyte progenitor cells to successfully treat human spinal cord injury?

Background  

Spinal cord injury is a serious and debilitating condition, affecting millions of people worldwide. Long seen as a permanent injury, recent advances in stem cell research have brought closer the possibility of repairing the spinal cord. One such approach involves injecting oligodendrocyte progenitor cells, derived from human embryonic stem cells, into the injured spinal cord in the hope that they will initiate repair. A phase I clinical trial of this therapy was started in mid 2010 and is currently underway.     

Nuclear translocation of PKM2 modulates astrocyte proliferation via p27 and β-catenin pathway after spinal cord injury

Aberrant functionality of the cell cycle has been implicated in the pathology of traumatic SCI. Although it has been reported that the expressions of various cell cycle related proteins were altered significantly following SCI, detailed information on the subject remains largely unclear. The embryonic pyruvate kinase M2 (PKM2) is an important metabolic kinase in aerobic glycolysis or the warburg effect, however, its functions in central nervous system (CNS) injury remains elusive. Here we demonstrate that PKM2 was not only significantly upregulated by western blot and immunohistochemistry but certain traumatic stimuli also induced translocation of PKM2 into the nucleus in astrocytes following spinal cord injury (SCI). Furthermore, the expression levels and localization of p-β-catenin, p27, cyclin D1 and PCNA were correlated with PKM2 after SCI. In vitro, we also found that PKM2 co-immunoprecipitation with p-β-catenin and p27 respectively. Knockdown of PKM2 apparently decreased the level of PCNA, cyclinD1, p27 in primary astrocyte cells. Taken together, our findings indicate that nuclear translocation of PKM2 promotes astrocytes proliferation after SCI through modulating cell cycle signaling. These discoveries firstly uncovered the role of PKM2 in spinal cord injury and provided a potential therapeutic target for CNS injury and repair.     

Stress-induced phosphoprotein 1 restrains spinal cord ischaemia-reperfusion injury by modulating NF-κB signalling

Spinal cord injury (SCI), a major cause of disability, causes high global disease and economic burdens. Stress-induced phosphoprotein 1 (STIP1) has been identified to be involved in spinal cord ischaemia-reperfusion injury (SCII); however, the effect of STIP1 on SCII remains unclear until now. This study aimed to examine the role of STIP1 in SCII and unravel the possible mechanisms. Western blotting and immunohistochemical staining showed that STIP1 expression rapidly increased and then decreased in rat spinal cord following SCII treatment. Neurological function scoring, HE staining, immunohistochemical staining and Western blotting revealed that STIP1 overexpression alleviated SCII-induced motor dysfunction of hind limbs, neuronal loss and inflammation in spinal cord, and inhibited activity of nuclear factor kappa B (NF-κB) signalling in rats. Immunoprecipitation identified that STIP1 was co-located with Iba-1. In addition, STIP1 was found to ameliorate oxygen and glucose deprivation (OGD)-induced inflammation and activation of NF-κB signalling in mouse microglia BV2 cells, and STIP1 resulted in decrease of heat shock protein family A member 8 (HSPA8), increase of IκBβ expression and reduced binding of IκBβ to HSPA8 in BV2 cells. The results of the present study demonstrate that STIP1 alleviates ischaemia/reperfusion-induced neuronal injury and inflammation in rat spinal cord and mouse microglial cells by deactivating NF-κB signalling. These findings may provide novel insights for the clinical diagnosis and treatment of SCI.     

Construction of rat spinal cord injury model based on Allen’s animal model

The aim of this study is to explore the construction of rat spinal cord injury model guided by Allen's model. Methods: Male rats aged 4–5 weeks and weighing about 250 g are selected as subjects in the Animal Laboratory Center of XX Hospital. Rats are divided into two groups, which are experimental group 1 and experimental group 2, respectively, so as to construct spinal cord injury model in rats. The first group is given 300 g.cm hitting force of T10 spinal cord, and the second group is given 500 g.cm hitting force of T10 spinal cord. Within 25 days after spinal cord injury in Allen's rats, the survival, neurological function, diet, motor ability, tactile ability and auditory ability of the two groups are monitored and evaluated daily. Results: In terms of survival, the survival rate of rats in group 1 is 85%, while that of rats in group 2 is 21%, and there is a concentrated death phenomenon in group 2. In terms of neurological function recovery, experimental group 1 is stable and gets 7 points and experimental group 2 is stable and gets 3 points. In terms of diet, the experimental group 1 is stable and gets 5 points and the experimental group 2 is stable and gets 2 points. In terms of motor ability, the experimental group 1 is stable and gets 5 points and the experimental group 2 is stable and gets 2 points. In tactile sense, experimental group 1 is stable and gets 17 points and experimental group 2 is stable and gets 12 points. It can be seen that the post-operative recovery ability of the experimental group 1 is better than that of the experimental group 2. Conclusion: Under the guidance of Allen's model, compared with the group 2, the experimental group 1 of the rat spinal cord injury model has better recovery in each index. It can be seen that the smaller impact strength is more beneficial to the recovery of rats after spinal cord injury surgery.     

Are induced pluripotent stem cells the future of cell‐based regenerative therapies for spinal cord injury?

Despite advances in medical and surgical care, current clinical therapies for spinal cord injury (SCI) are limited. During the last two decades, the search for new therapies has been revolutionized by the discovery of stem cells, inspiring scientists and clinicians to search for stem cell‐based reparative approaches for many disorders, including neurotrauma. Cell‐based therapies using embryonic and adult stem cells in animal models of these disorders have provided positive outcome results. However, the availability of clinically suitable cell sources for human application has been hindered by both technical and ethical issues. The recent discovery of induced pluripotent stem (iPS) cells holds the potential to revolutionize the field of regenerative medicine by offering the option of autologous transplantation, thus eliminating the issue of host rejection. Herein, we will provide the rationale for the use of iPS cells in SCI therapies. In this review, we will evaluate the recent advancements in the field of iPS cells including their capacity for differentiation toward neural lineages that may allow iPS cells transplantation in cell‐based therapy for spinal cord repair. J. Cell. Physiol. 222: 515–521, 2010. © 2009 Wiley‐Liss, Inc.     

ifn-γ-dependent secretion of IL-10 from Th1 cells and microglia/macrophages contributes to functional recovery after spinal cord injury

Transfer of type-1 helper T-conditioned (Th1-conditioned) cells promotes functional recovery with enhanced axonal remodeling after spinal cord injury (SCI). This study explored the molecular mechanisms underlying the beneficial effects of pro-inflammatory Th1-conditioned cells after SCI. The effect of Th1-conditioned cells from interferon-γ (ifn-γ) knockout mice (ifn-γ^−/− Th1 cells) on the recovery after SCI was reduced. Transfer of Th1-conditioned cells led to the activation of microglia (MG) and macrophages (MΦs), with interleukin 10 (IL-10) upregulation. This upregulation of IL-10 was reduced when ifn-γ^−/− Th1 cells were transferred. Intrathecal neutralization of IL-10 in the spinal cord attenuated the effects of Th1-conditioned cells. Further, IL-10 is robustly secreted from Th1-conditioned cells in an ifn-γ-dependent manner. Th1-conditioned cells from interleukin 10 knockout (il-10^−/−) mice had no effects on recovery from SCI. These findings demonstrate that ifn-γ-dependent secretion of IL-10 from Th1 cells, as well as native MG/MΦs, is required for the promotion of motor recovery after SCI.