Implantation of dendritic cells in injured adult spinal cord results in activation of endogenous neural stem/progenitor cells leading to de novo neurogenesis and functional recovery

Role of dendritic cells in spinal cord injury

BACKGROUND

Inflammation can worsen spinal cord injury (SCI), with dendritic cells (DCs) playing a crucial role in the inflammatory response. They mediate T lymphocyte differentiation, activate microglia, and release cytokines like NT-3. Moreover, DCs can promote neural stem cell survival and guide them toward neuron differentiation, positively impacting SCI outcomes.

OBJECTIVE

This review aims to summarize the role of DCs in SCI-related inflammation and identify potential therapeutic targets for treating SCI.

METHODS

Literature in PubMed and Web of Science was reviewed using critical terms related to DCs and SCI.

RESULTS

The study indicates that DCs can activate microglia and astrocytes, promote T-cell differentiation, increase neurotrophin release at the injury site, and subsequently reduce secondary brain injury and enhance functional recovery in the spinal cord.

CONCLUSIONS

This review highlights the repair mechanisms of DCs and their potential therapeutic potential for SCI.

Schwann cells promote the capability of neural stem cells to differentiate into neurons and secret neurotrophic factors

The present study investigated whether co-culturing Schwann cells (SCs) with neural stem cells (NSCs) improves viability, direction of differentiation and secretion of brain-derived neurotrophic factor (BDNF) and glial cell-derived neurotrophic factor (GDNF) in NSCs. The three groups assessed were as follows: SCs, NSCs, and a co-culture of SCs and NSCs. Cellular morphological changes were observed under an inverted phase contrast microscope and quantified. Cells were identified by immunofluorescence staining: S100 for SCs, Nestin for NSCs, microtubule associated protein (Map) 2 and NeuN for neurons and glial fibrillary acidic protein for astrocytes. Cell viability was evaluated by MTT assay. Secretion of BDNF and GDNF was quantified; mRNA expression was quantified by reverse transcription-quantitative polymerase chain reaction. The majority of NSCs in the co-cultured group differentiated into neurons. The cell survival rate of the co-culture group was significantly higher than the other groups on days 3, 5 and 10 (P<0.01). The secretion of BDNF in the co-culture group was significantly higher than NSCs on days 3, 5 and 7 (P<0.05), while the amount of GDNF in co-culture was significantly higher than both NSCs and SCs on day 1 (P<0.05). BDNF and GDNF gene expression in the co-culture group was significantly higher than SCs (P<0.01). Gene expression of Map2 in co-culture group was also significantly higher than both NSC and SC groups (P<0.01). Therefore, co-cultured SCs and NSCs promote differentiation of NSCs into neurons and secrete higher levels of neurotropic factors including BDNF and GDNF.

Human class I major histocompatibility complex alleles determine central nervous system injury versus repair

BACKGROUND

We investigated the role of human HLA class I molecules in persistent central nervous system (CNS) injury versus repair following virus infection of the CNS.

METHODS

Human class I A11+ and B27+ transgenic human beta-2 microglobulin positive (Hβ2m+) mice of the H-2 b background were generated on a combined class I-deficient (mouse beta-2 microglobulin deficient, β2m0) and class II-deficient (mouse Aβ0) phenotype. Intracranial infection with Theiler's murine encephalomyelitis virus (TMEV) in susceptible SJL mice results in acute encephalitis with prominent injury in the hippocampus, striatum, and cortex.

RESULTS

Following infection with TMEV, a picornavirus, the Aβ0.β2m0 mice lacking active immune responses died within 18 to 21 days post-infection. These mice showed severe encephalomyelitis due to rapid replication of the viral genome. In contrast, transgenic Hβ2m mice with insertion of a single human class I MHC gene in the absence of human or mouse class II survived the acute infection. Both A11+ and B27+ mice significantly controlled virus RNA expression by 45 days and did not develop late-onset spinal cord demyelination. By 45 days post-infection (DPI), B27+ transgenic mice showed almost complete repair of the virus-induced brain injury, but A11+ mice conversely showed persistent severe hippocampal and cortical injury.

CONCLUSIONS

The findings support the hypothesis that the expression of a single human class I MHC molecule, independent of persistent virus infection, influences the extent of sub frequent chronic neuronal injury or repair in the absence of a class II MHC immune response.

Tissue-engineered regeneration of completely transected spinal cord using induced neural stem cells and gelatin-electrospun poly (lactide-co-glycolide)/polyethylene glycol scaffolds

Tissue engineering has brought new possibilities for the treatment of spinal cord injury. Two important components for tissue engineering of the spinal cord include a suitable cell source and scaffold. In our study, we investigated induced mouse embryonic fibroblasts (MEFs) directly reprogrammed into neural stem cells (iNSCs), as a cell source. Three-dimensional (3D) electrospun poly (lactide-co-glycolide)/polyethylene glycol (PLGA-PEG) nanofiber scaffolds were used for iNSCs adhesion and growth. Cell growth, survival and proliferation on the scaffolds were investigated. Scanning electron microscopy (SEM) and nuclei staining were used to assess cell growth on the scaffolds. Scaffolds with iNSCs were then transplanted into transected rat spinal cords. Two or 8 weeks following transplantation, immunofluorescence was performed to determine iNSC survival and differentiation within the scaffolds. Functional recovery was assessed using the Basso, Beattie, Bresnahan (BBB) Scale. Results indicated that iNSCs showed similar morphological features with wild-type neural stem cells (wt-NSCs), and expressed a variety of neural stem cell marker genes. Furthermore, iNSCs were shown to survive, with the ability to self-renew and undergo neural differentiation into neurons and glial cells within the 3D scaffolds in vivo. The iNSC-seeded scaffolds restored the continuity of the spinal cord and reduced cavity formation. Additionally, iNSC-seeded scaffolds contributed to functional recovery of the spinal cord. Therefore, PLGA-PEG scaffolds seeded with iNSCs may serve as promising supporting transplants for repairing spinal cord injury (SCI).

Dysregulated production of leukemia inhibitory factor in immune cells of relapsing remitting multiple sclerosis patients

Leukemia inhibitory factor (LIF) is known to potentiate the differentiation and survival of neuronal and oligodendrocyte precursors. Systemic therapy with LIF reportedly ameliorated the severity of experimental autoimmune encephalomyelitis and prevented oligodendrocyte death. We studied the secreted LIF levels from immune cells of relapsing remitting multiple sclerosis (RR-MS) patients compared to age- and gender-matched healthy controls (HCs). LIF was barely detected in the supernatants when the cells were not stimulated. After stimulation with anti-CD3/CD28 monoclonal antibody, LIF levels were up-regulated in both patients and controls, although to a significantly lower extent in RR-MS patients compared to HC. There were no significant differences between untreated patients and interferon-β1a treated patients. This is a heretofore unreported aspect of immune dysregulation in patients with RR-MS that may be related to insufficient remyelination and neurogenesis in MS lesions.

Modulating inflammatory cell responses to spinal cord injury: all in good time

Spinal cord injury can have a range of debilitating effects, permanently impacting a patient's quality of life. Initially thought to be an immune privileged site, the spinal cord is able to mount a timely and well organized inflammatory response to injury. Intricate immune cell interactions are triggered, typically consisting of a staggered multiphasic immune cell response, which can become deregulated if left unchecked. Although several immunomodulatory compounds have yielded success in experimental rodent spinal cord injury models, their translation to human clinical studies needs further consideration. Because temporal differences between rodent and human inflammatory responses to spinal cord injury do exist, drug delivery timing will be a crucial component in recovery from spinal cord injury. Given too early, immunomodulatory therapies may impede beneficial inflammatory reactions to the injured spinal cord or even miss the opportunity to dampen delayed harmful autoimmune processes. Therefore, this review aims to summarize the temporal inflammatory response to spinal cord injury, as well as detailing specific immune cell functions. By clearly defining the chronological order of inflammatory events after trauma, immunomodulatory drug delivery timing can be better optimized. Further, we compare spinal cord injury-induced inflammatory responses in rodent and human studies, enabling clinicians to consider these differences when initiating clinical trials. Improved understanding of the cellular immune response after spinal cord injury would enhance the efficacy of immunomodulatory agents, enabling combined therapies to be considered.

Spinal cord transection in the larval zebrafish

Mammals fail in sensory and motor recovery following spinal cord injury due to lack of axonal regrowth below the level of injury as well as an inability to reinitiate spinal neurogenesis. However, some anamniotes including the zebrafish Danio rerio exhibit both sensory and functional recovery even after complete transection of the spinal cord. The adult zebrafish is an established model organism for studying regeneration following spinal cord injury, with sensory and motor recovery by 6 weeks post-injury. To take advantage of in vivo analysis of the regenerative process available in the transparent larval zebrafish as well as genetic tools not accessible in the adult, we use the larval zebrafish to study regeneration after spinal cord transection. Here we demonstrate a method for reproducibly and verifiably transecting the larval spinal cord. After transection, our data shows sensory recovery beginning at 2 days post-injury (dpi), with the C-bend movement detectable by 3 dpi and resumption of free swimming by 5 dpi. Thus we propose the larval zebrafish as a companion tool to the adult zebrafish for the study of recovery after spinal cord injury.

The role of the immune system in central nervous system plasticity after acute injury

Acute brain injuries cause rapid cell death that activates bidirectional crosstalk between the injured brain and the immune system. In the acute phase, the damaged CNS activates resident and circulating immune cells via the local and systemic release of soluble mediators. This early immune activation is necessary to confine the injured tissue and foster the clearance of cellular debris, thus bringing the inflammatory reaction to a close. In the chronic phase, a sustained immune activation has been described in many CNS disorders, and the degree of this prolonged response has variable effects on spontaneous brain regenerative processes. The challenge for treating acute CNS damage is to understand how to optimally engage and modify these immune responses, thus providing new strategies that will compensate for tissue lost to injury. Herein we have reviewed the available information regarding the role and function of the innate and adaptive immune responses in influencing CNS plasticity during the acute and chronic phases of after injury. We have examined how CNS damage evolves along the activation of main cellular and molecular pathways that are associated with intrinsic repair, neuronal functional plasticity and facilitation of tissue reorganization.

Novel method for analyzing locomotor ability after spinal cord injury in rats: technical note

In the research for the treatment of spinal cord injury (SCI), the evaluation of motor function in model rats must be as objective, noninvasive, and ethical as possible. The maximum speed and acceleration of a mouse measured using a SCANET system were previously reported to vary significantly according to severity of SCI. In the present study, the motor performance of SCI model rats was examined with SCANET and assessed for Basso-Beattie-Bresnahan (BBB) score to determine the usefulness of the SCANET system in evaluating functional recovery after SCI. Maximum speed and acceleration within the measurement period correlated significantly with BBB scores. Furthermore, among several phased kinematic factors used in BBB scores, the capability of “plantar stepping” was associated with a drastic increase in maximum speed and acceleration after SCI. Therefore, evaluation of maximum speed and acceleration using a SCANET system is a useful method for rat models of SCI and can complement open field scoring scales.

Immunopharmacological intervention for successful neural stem cell therapy: New perspectives in CNS neurogenesis and repair

The pharmacological support and stimulation of endogenous and transplanted neural stem cells (NSCs) is a major challenge in brain repair. Trauma to the central nervous system (CNS) results in a distinct inflammatory response caused by local and infiltrating immune cells. This makes NSC-supported regeneration difficult due to the presence of inhibitory immune factors which are upregulated around the lesion site. The continual and dual role of the neuroinflammatory response leaves it difficult to decipher upon a single modulatory strategy. Therefore, understanding the influence of cytokines upon regulation of NSC self-renewal, proliferation and differentiation is crucial when designing therapies for CNS repair. There is a plethora of partially conflicting data in vitro and in vivo on the role of cytokines in modulating the stem cell niche and the milieu around NSC transplants. This is mainly due to the pleiotropic role of many factors. In order for cell-based therapy to thrive, treatment must be phase-specific to the injury and also be personalized for each patient, i.e. taking age, sex, neuroimmune and endocrine status as well as other key parameters into consideration. In this review, we will summarize the most relevant information concerning interleukin (IL)-1, IL-4, IL-10, IL-15, IFN-γ, the neuropoietic cytokine family and TNF-α in order to extract promising therapeutic approaches for further research. We will focus on the consequences of neuroinflammation on endogenous brain stem cells and the transplantation environment, the effects of the above cytokines on NSCs, as well as immunopharmacological manipulation of the microenvironment for potential therapeutic use.

The stimulation of dendritic cells by amyloid beta 1-42 reduces BDNF production in Alzheimer's disease patients

Dendritic cells (DCs), the main actors of immune responses and inflammation, may play a role in Alzheimer's disease (AD). Recent studies demonstrate that monocyte-derived DCs (MDDCs), generated in vitro in the presence of amyloid β1-42 peptide (Aβ1-42), show a functional alteration and an increased production of inflammatory molecules. Accordingly, MDDCs from AD patients show a more pronounced pro-inflammatory profile than DCs obtained from control subjects. In this study, we aimed at further investigating DC role in AD. Thus, we analyzed the in vitro effect of Aβ1-42 treatment on already differentiated DCs from AD patients, as compared to control subjects. We found that Aβ1-42 significantly decreases the expression of brain-derived neurotrophic factor (BDNF) in DCs derived from AD patients but not from control subjects. Thus, possibly due to their Aβ-induced reduction of neurotrophic support to neurons, DCs from AD patients might contribute to brain damage by playing a part in Aβ-dependent neuronal toxicity.

Bone marrow-derived mesenchymal stem cell transplantation for chronic spinal cord injury in rats: comparative study between intralesional and intravenous transplantation

STUDY DESIGN

Animal experimental study.

OBJECTIVE

To present experimental evidence for mesenchymal cell therapy for spinal cord injury (SCI).

SUMMARY OF BACKGROUND DATA

Prior to clinical application of stem cell therapy for SCI, many critical issues have to be addressed including efficiency, safety, method of transplantation, and differentiation of the transplanted cells.

METHODS

Chronic contusive SCI was induced in 36 Sprague-Dawley rats and randomly assigned to the intralesional (IL), intravenous (IV), or control groups. At 6 weeks post injury, allogenic mesenchymal stem cells (MSCs, 1 × 10 cells) were transplanted either intralesionally or intravenously for the intervention groups. Engraftment of the transplanted MSCs was evaluated with PKH 26 staining. Differentiation was evaluated using double stain with neuronal and glial cell markers. Brain-derived neurotrophic factor and nerve growth factor (NGF) were used for neurotrophic factor expression. Basso, Beattie, and Bresnahan locomotor rating scale was used for evaluation of functional recovery.

RESULTS

The estimated engraftment percentage of the transplanted cells in the IL group and IV group were 36.5%, and 15.5%, respectively. The engraftment of the transplanted MSCs was higher in the IL group than in the IV group. Most of the transplanted MSCs were colocalized with GFAP in both transplantation groups. Brain-derived neurotrophic factor and NGF expression (Western blot and real-time polymerase chain reaction) in the injured spinal cord was higher in both transplanted groups compared with those in the control group. At 6 weeks post transplantation, the mean Basso, Beattie, and Bresnahan locomotor scales in the IL, IV, and control groups were 5.63 ± 0.89, 5.63 ± 1.03, and 2.88 ± 0.44, respectively. The functional recovery seen in the rats that underwent transplantation was significantly better than that in the control group (P < 0.05).

CONCLUSION

Although the number of engrafted cells and expression of neurotrophic factors were lower in the IV group than those in the IL group, both IL and IV transplantation of MSC in the chronic SCI gave a significant clinical improvement. However, there were no differences in differentiation of the transplanted cells between the IL group and IV group. Astrocytic differentiation of the transplanted cells was predominant.

LEVEL OF EVIDENCE

N/A.

Neurotoxic or Neuroprotective? Current Controversies in SCI-Induced Autoimmunity

Controversy exists regarding the autoimmune response that has been observed following traumatic spinal cord injury (SCI). It is not clear if this represents a protective response by the immune system to prevent further tissue damage, a pathological reaction of the immune system to central nervous system antigens released by the injury, or a combination of both. Experimental evidence indicates that B cells produce auto-antibodies following SCI and that the presence of self-reactive antibodies is associated with tissue damage. Conversely, other studies suggest T cell activity at the site of the injury promotes tissue regeneration. Vaccination with dendritic cells exposed to central nervous system (CNS) antigens dramatically improves recovery of motor function in spinal cord injured rats. Further research is required to determine the nature of post-SCI B cell and T cell responses and to establish efficacy of dendritic cell vaccination therapy in clinical studies. This information is critical for the development of therapies to either suppress or promote immune responses following neurotrauma to improve neurological outcomes.

Neural stem cell survival factors

Neural stem and progenitor cells (NSCs and NPs) give rise to the central nervous system (CNS) during embryonic development. NSCs and NPs differentiate into three main cell-types of the CNS; astrocytes, oligodendrocytes, and neurons. NSCs are present in the adult CNS and are important in maintenance and repair. Adult NSCs hold great promise for endogenous or self-repair of the CNS. Intriguingly, NSCs have been implicated as the cells that give rise to brain tumors. Thus, the balance between survival, growth and differentiation is a critical aspect of NSC biology, during development, in the adult, and in disease processes. In this review, we survey what is known about survival factors that control both embryonic and adult NSCs. We discuss the neurosphere culture system as this is widely used to measure NSC activity and behavior in vitro and emphasize the importance of clonality. We define here NSC survival factors in their broadest sense to include any factor that influences survival and proliferation of NSCs and NPs. NSC survival factors identified to date include growth factors, morphogens, proteoglycans, cytokines, hormones, and neurotransmitters. Understanding NSC and NP interaction in response to these survival factors will provide insight to CNS development, disease and repair.

Macrophage migration inhibitory factor (MIF) promotes cell survival and proliferation of neural stem/progenitor cells

In a previous study, we showed that murine dendritic cells (DCs) can increase the number of neural stem/progenitor cells (NSPCs) in vitro and in vivo. In the present study, we identified macrophage migration inhibitory factor (MIF) as a novel factor that can support the proliferation and/or survival of NSPCs in vitro. MIF is secreted by DCs and NSPCs, and its function in the normal brain remains largely unknown. It was previously shown that in macrophages, MIF binds to a CD74-CD44 complex. In the present study, we observed the expression of MIF receptors in mouse ganglionic-eminence-derived neurospheres using flow cytometry in vitro. We also found CD74 expression in the ganglionic eminence of E14 mouse brains, suggesting that MIF plays a physiological role in vivo. MIF increased the number of primary and secondary neurospheres. By contrast, retrovirally expressed MIF shRNA and MIF inhibitor (ISO-1) suppressed primary and secondary neurosphere formation, as well as cell proliferation. In the neurospheres, MIF knockdown by shRNA increased caspase 3/7 activity, and MIF increased the phosphorylation of Akt, Erk, AMPK and Stat3 (Ser727), as well as expression of Hes3 and Egfr, the products of which are known to support cell survival, proliferation and/or maintenance of NSPCs. MIF also acted as a chemoattractant for NSPCs. These results show that MIF can induce NSPC proliferation and maintenance by multiple signaling pathways acting synergistically, and it may be a potential therapeutic factor, capable of activating NSPC, for the treatment of degenerative brain disorders.

The use of cellular magnetic resonance imaging to track the fate of iron-labeled multipotent stromal cells after direct transplantation in a mouse model of spinal cord injury

PURPOSE

The objective of this study was to track the fate of iron-labeled, multipotent stromal cells (MSC) after their direct transplantation into mice with spinal cord injuries using magnetic resonance imaging (MRI).

PROCEDURES

Mice with spinal cord injuries received a direct transplant of (1) live MSC labeled with micron-sized iron oxide particles (MPIO); (2) dead, MPIO-labeled MSC; (3) unlabeled MSC; or (4) free MPIO and were imaged at 3 T for 6 weeks after transplantation.

RESULTS

Live, iron-labeled MSC appeared as a well-defined region of signal loss in the mouse spinal cord at the site of transplant. However, the MR appearance of dead, iron-labeled MSC and free iron particles was similar and persisted for the 6 weeks of the study.

CONCLUSIONS

Iron-labeled stem cells can be detected and monitored in vivo after direct transplantation into the injured spinal cord of mice. However, the fate of the iron label is not clear. Our investigation indicates that caution should be taken when interpreting MR images after direct transplantation of iron-labeled cells.

A single dose of neuron-binding human monoclonal antibody improves spontaneous activity in a murine model of demyelination

Our laboratory demonstrated that a natural human serum antibody, sHIgM12, binds to neurons in vitro and promotes neurite outgrowth. We generated a recombinant form, rHIgM12, with identical properties. Intracerebral infection with Theiler's Murine Encephalomyelitis Virus (TMEV) of susceptible mouse strains results in chronic demyelinating disease with progressive axonal loss and neurologic dysfunction similar to progressive forms of multiple sclerosis. To study the effects of rHIgM12 on the motor function of TMEV-infected mice, we monitored spontaneous nocturnal activity over many weeks. Nocturnal behavior is a sensitive measure of rodent neurologic function because maximal activity changes are expected to occur during the normally active night time monitoring period. Mice were placed in activity boxes eight days prior to treatment to collect baseline spontaneous activity. After treatment, activity in each group was continuously recorded over 8 weeks. We chose a long 8-week monitoring period for two reasons: (1) we previously demonstrated that IgM induced remyelination is present by 5 weeks post treatment, and (2) TMEV-induced demyelinating disease in this strain progresses very slowly. Due to the long observation periods and large data sets, differences among treatment groups may be difficult to appreciate studying the original unfiltered recordings. To clearly delineate changes in the highly fluctuating original data we applied three different methods: (1) binning, (2) application of Gaussian low-pass filters (GF) and (3) polynomial fitting. Using each of the three methods we showed that compared to control IgM and saline, early treatment with rHIgM12 induced improvement in both horizontal and vertical motor function, whereas later treatment improved only horizontal activity. rHIgM12 did not alter activity of normal, uninfected mice. This study supports the hypothesis that treatment with a neuron-binding IgM not only protects neurons in vitro, but also influences functional motor improvement.

Reduced ErbB4 Expression in Immune Cells of Patients with Relapsing Remitting Multiple Sclerosis

Background. There is an insufficient remyelination in the lesions of multiple sclerosis (MS). One of the factor that was found to promote remyelination is neuregulin-1 which is the ligand of ErbB4. Immune cells have been implicated in neurogenesis and oligodendrogenesis. Aims. We studied the expression of ErbB4 in the immune cells of patients with relapsing remitting (RR) multiple sclerosis (MS) and healthy controls. Methods. ErB4 expression in immune cells was studied by flow cytometry without stimulation or with stimulation with anti-CD3 and anti-CD28 monoclonal antibodies or in the presence of interferon-g or TNF-α as well as by immunoprecipitation and Western blot, and its mRNA was studied by real-time PCR. Results. We found reduced levels of ErbB4 in the total PBMCs and in T cells, monocytes, and B cells of RR MS patients. Similarly, the ErbB4 RNA levels were reduced in the immune cells of patients with RR-MS. Stimulation via CD3 and CD28 significantly upregulated the expression of ErbB4 on immune cells healthy individuals. This effect was weaker in the patients group. Conclusion. ErbB4 may play a role in the proliferation of oligodendrocyte progenitor cells, differentiation of oligodendrocytes, and remyelination, and, therefore, the reduced ErbB4 expression in immune cells of patients with RR-MS may contribute to insufficient remyelination that occurs in the disease.

Chemical priming for spinal cord injury: a review of the literature part II-potential therapeutics

INTRODUCTION

Spinal cord injury is a complex cascade of reactions secondary to the initial mechanical trauma that puts into action the innate properties of the injured cells, the circulatory, inflammatory, and chemical status around them, into a non-permissive and destructive environment for neuronal function and regeneration. Priming means putting a cell, in a state of "arousal" towards better function. Priming can be mechanical as trauma is known to enhance activity in cells.

MATERIALS AND METHODS

A comprehensive review of the literature was performed to better understand the possible chemical primers used for spinal cord injuries.

CONCLUSIONS

Taken together, many studies have shown various promising results using the substances outlined herein for treating SCI.

Modulation of dendritic cell function by PGE2 and DHA: a framework for understanding the role of dendritic cells in neuroinflammation

Neuroinflammation characterizes various neurological disorders. Peripheral immune cells and CNS-resident glia contribute to neuroinflammation and impact CNS degeneration, recovery and regeneration. Recently, the role of dendritic cells in neuroinflammation received special attention. The function of infiltrating immune cells and resident glia is affected by various factors, including lipid mediators. Polyunsaturated fatty acids, especially n-6 arachidonic acid and n-3 docosahexaenoic acid (DHA), the most abundant in the CNS, play an important role in neuroinflammation. The major arachidonic acid bioactive derivative in immune cells, PGE2, and DHA have been reported to have opposite effects on dendritic cells in terms of cytokine production and activation/differentiation of CD4(+) T cells. Here we review the existing information on PGE2 and DHA modulation of dendritic cell function and the potential impact of these lipid mediators of dendritic cells in CNS inflammatory disorders.

Flt3 ligand synergizes with granulocyte-colony-stimulating factor in bone marrow mobilization to improve functional outcome after spinal cord injury in the rat

BACKGROUND AIMS

The effect of granulocyte-colony-stimulating factor (G-CSF) and/or the cytokine fms-like thyrosin kinase 3 (Flt3) ligand on functional outcome and tissue regeneration was studied in a rat model of spinal cord injury (SCI).

METHODS

Rats with a balloon-induced compression lesion were injected with G-CSF and/or Flt3 ligand to mobilize bone marrow cells. Behavioral tests (Basso-Beattie-Bresnahan and plantar test), blood counts, morphometric evaluation of the white and gray matter, and histology were performed 5 weeks after SCI.

RESULTS

The mobilization of bone marrow cells by G-CSF, Flt3 ligand and their combination improved the motor and sensory performance of rats with SCI, reduced glial scarring, increased axonal sprouting and spared white and gray matter in the lesion. The best results were obtained with a combination of G-CSF and Flt3. G-CSF alone or in combination with Flt3 ligand significantly increased the number of white blood cells, but not red blood cells or hemoglobin content, during and after the time-course of bone marrow stimulation. The combination of factors led to infiltration of the lesion by CD11b(+) cells.

CONCLUSIONS

The observed improvement in behavioral and morphologic parameters and tissue regeneration in animals with SCI treated with a combination of both factors could be associated with a prolonged time-course of mobilization of bone marrow cells. The intravenous administration of G-CSF and/or Flt3 ligand represents a safe and effective treatment modality for SCI.

Novel concept of motor functional analysis for spinal cord injury in adult mice

In basic research on spinal cord injury (SCI), behavioral evaluation of the SCI animal model is critical. However, it is difficult to accurately evaluate function in the mouse SCI model due to the small size of mice. Although the open-field scoring scale is an outstanding appraisal method, supplementary objective tests are required. Using a compact SCANET system, in which a mouse carries out free movement for 5 min, we developed a novel method to detect locomotor ability. A SCANET system samples the horizontal coordinates of a mouse every 0.1 s, and both the speed and acceleration of its motion are calculated at each moment. It was found that the maximum speed and acceleration of motion over 5 min varied by injury severity. Moreover, these values were significantly correlated with open-field scores. The maximum speed and acceleration of SCI model mice using a SCANET system are objective, easy to obtain, and reproducible for evaluating locomotive function.

Reduced production of noggin by immune cells of patients with relapsing-remitting multiple sclerosis

Multiple sclerosis (MS) plaques are characterized by neurodegeneration, astrogliolis, the presence of immature oligodendrocytes and infiltrating immune cells. Recent studies revealed a putative role for noggin in both neurogenesis and oligodenrocytes development. In order to study the potential of peripheral immune cells to contribute to neurogenesis in MS, we studied the mRNA expression, protein secretion and regulation profile of noggin in peripheral blood mononuclear cells (PBMCs) of untreated patients with relapsing-remitting MS (RR-MS), interferon-β (IFN-β) treated RR-MS patients compared to matched healthy controls (HC). Basal levels of noggin mRNA expression, determined by quantitative real-time PCR were lower in untreated patients than in HC. No differences were found between untreated patients and IFN-β treated patients. Similarly, the secreted levels of noggin, detected in 24h PBMCs supernatants by ELISA, were decreased in untreated RR-MS patients than in HC. Again no significant differences were found between untreated patients and IFN-β treated patients. Stimulation with anti-CD3/CD28 mAbs increased noggin mRNA expression in untreated patients but not in HC. However, noggin mRNA levels in untreated patients PBMCs stimulated with anti-CD3/CD28 did not reach noggin levels in unstimulated PBMCs of HC. Purification of monocytes (CD14+) and T cells (CD3+ cells) by magnet-activated cell separation has demonstrated that noggin mRNA is predominantly expressed in CD3(+) cells in both HC and in RR-MS patients. This pattern also appeared in protein level of noggin, tested by Western blot. The incubation of the PBMCs with TNF-α increased the expression of noggin only in HC group. In conclusion, T cells possess the potential to participate in the induction of neurogeneration by the production of noggin. This potential seems to be defective in immune cells of RR-MS patients as there is reduced mRNA expression and protein secretion levels of noggin, insufficient stimulatory effect of CD3/CD28 stimulation and unresponsiveness to TNF-α in these patients PBMCs.

Comparative study of methods for administering neural stem/progenitor cells to treat spinal cord injury in mice

To investigate potential cures for spinal cord injury (SCI), several researchers have transplanted neural stem/progenitor cells (NS/PCs) into the injured spinal cord by different procedures, including intralesional (IL), intrathecal (IT), and intravenous (IV) injection. However, there are no reports quantifying or comparing the number of cells successfully transplanted to the lesion site by each procedure in vivo. The purpose of the present study was to determine the optimal method of cell transplantation to the SCI site in terms of grafted cell survival and safety. For this purpose, we developed mouse NS/PCs that expressed a novel Venus-luciferase fusion protein that enabled us to detect a minimum of 1,000 grafted cells in vivo by bioluminescence imaging (BLI). After inducing contusive SCI at the T10 level in mice, NS/PCs were transplanted into the injured animals three different ways: by IL, IT, or IV injection. Six weeks after the transplantation, BLI analysis showed that in the IL group, the luminescence intensity of the grafted cells had decreased to about 10% of its initial level, and appeared at the site of injury. In the IT group, the luminescence of the grafted cells, which was distributed throughout the entire subarachnoid space immediately after transplantation, was detected at the injured site 1 week later, and by 6 weeks had gradually decreased to about 0.3% of its initial level. In the IV group, no grafted cells were detected at the site of injury, but all of these mice showed luminescence in the bilateral chest, suggesting pulmonary embolism. In addition, one third of these mice died immediately after the IV injection. In terms of grafted cell survival and safety, we conclude that the IL application of NS/PCs is the most effective and feasible method for transplanting NS/PCs into the SCI site.

Activated spinal cord ependymal stem cells rescue neurological function

Spinal cord injury (SCI) is a major cause of paralysis. Currently, there are no effective therapies to reverse this disabling condition. The presence of ependymal stem/progenitor cells (epSPCs) in the adult spinal cord suggests that endogenous stem cell-associated mechanisms might be exploited to repair spinal cord lesions. epSPC cells that proliferate after SCI are recruited by the injured zone, and can be modulated by innate and adaptive immune responses. Here we demonstrate that when epSPCs are cultured from rats with a SCI (ependymal stem/progenitor cells injury [epSPCi]), these cells proliferate 10 times faster in vitro than epSPC derived from control animals and display enhanced self renewal. Genetic profile analysis revealed an important influence of inflammation on signaling pathways in epSPCi after injury, including the upregulation of Jak/Stat and mitogen activated protein kinase pathways. Although neurospheres derived from either epSPCs or epSPCi differentiated efficiently to oligodendrocites and functional spinal motoneurons, a better yield of differentiated cells was consistently obtained from epSPCi cultures. Acute transplantation of undifferentiated epSPCi or the resulting oligodendrocyte precursor cells into a rat model of severe spinal cord contusion produced a significant recovery of motor activity 1 week after injury. These transplanted cells migrated long distances from the rostral and caudal regions of the transplant to the neurofilament-labeled axons in and around the lesion zone. Our findings demonstrate that modulation of endogenous epSPCs represents a viable cell-based strategy for restoring neuronal dysfunction in patients with spinal cord damage.

Repair effect of Wnt3a protein on the contused adult rat spinal cord

OBJECTIVE

To explore the repair effect of Wnt3a on injured spinal cord in rats.

METHODS

Moderate spinal cord contusion injury was made in 40 adult Sprague-Dawley rats at T10. Fifteen rats served as contusion controls (Group 1). Fifteen rats were treated with Wnt3a 3 days after injury (Group 2). Ten additional rats received only T10 laminectomies to serve as non-injured controls (Group 0). The functional recovery of the rats was observed through Basso-Beattie-Bresnahan (BBB) open field locomotor score. Rats were killed at 14 or 28 days after injury, then spinal cords were removed for histopathologic examinations, and the expression of the bromodeoxyuridine (BrdU) plus neural cell markers was stained with immunohistochemical method.

RESULTS

After an initial complete hindlimb paralysis, rats of all groups receiving a contusive injury recovered substantial function within 1 week. By 28 days, the BBB score for rats in Group 2 is better than that for rats in Group 1 by 7 points (Group 2 = 16.94, after 28 days versus Group 1 = 9.89 points; p < 0.05). Light and electron microscopic works showed that the Wnt3a-treated group had moderate repair effect of myelin and axons. Immunohistochemical analysis showed a significant increase in the number of the inducing differentiated neurons in Wnt3a-treated rats compared with control rats 2 weeks after injury.

CONCLUSIONS

Exogenous Wnt3a administration can improve axonal conduction and spinal cord function in the injured spinal cord, and the administration of Wnt3a result in the increase in the populations of neurons, suggesting that these cells may be derived from neural precursors and stem cells.

CD11c/EYFP transgene illuminates a discrete network of dendritic cells within the embryonic, neonatal, adult, and injured mouse brain

The CD11c enhanced yellow fluorescent protein (EYFP) transgenic mouse was constructed to identify dendritic cells in the periphery (Lindquist et al. [2004] Nat. Immunol. 5:1243-1250). In this study, we used this mouse to characterize dendritic cells within the CNS. Our anatomic results showed discrete populations of EYFP(+) brain dendritic cells (EYFP(+) bDC) that colocalized with a small fraction of microglia immunoreactive for Mac-1, Iba-1, CD45, and F4/80 but not for NeuN, Dcx, NG2 proteoglycan, or GFAP. EYFP(+) bDC, isolated by fluorescent activated cell sorting (FACS), expressed mRNA for the Itgax (CD11c) gene, whereas FACS anlaysis of EYFP(+) bDC cultures revealed the presence of CD11c protein. Light microscopy studies revealed that EYFP(+) bDC were present in the embryonic CNS when the blood-brain barrier is formed and postnatally when brain cells are amenable to culturing. In adult male mice, EYFP(+) bDC distribution was prominent within regions of the CNS that 1) are subject to structural plasticity and neurogenesis, 2) receive sensory and humoral input from the external environment, and 3) lack a blood-brain barrier. Ultrastructural analysis of EYFP(+) bDC in adult neurogenic niches showed their proximity to developing neurons and a morphology characteristic of immune/microglia cells. Kainic acid-induced seizures revealed that EYFP(+) bDC responded to damage of the hippocampus and displayed morphologies similar to those described for seizure-activated EGFP(+) microglia in the hippocampus of cfms (CSF-1R) EGFP mice. Collectively, these findings suggest a new member of the dendritic cell family residing among the heterogeneous microglia population.

Stem and progenitor cell therapies: recent progress for spinal cord injury repair

Mechanical trauma to the spinal cord is often accompanied by irreversible tissue damage, limited endogenous repair and permanent loss of motor, sensory and autonomic function. The implantation of exogenous cells or the stimulation of endogenous cells, to repopulate and replace or to provide a conducive environment for repair, offers a promising therapeutic direction for overcoming the multitude of obstacles facing successful recovery from spinal cord injury. Although relatively new to the scene of cell based therapies for reparative medicine, stem cells and their progenitors have been labeled as the 'cell of the future' for revolutionizing the treatment of CNS injury and neurodegenerative disorders. The following review examines the different types of stem cells and their progenitors, their utility in experimental models of spinal cord injury and explores the outstanding issues that still need to be addressed before they move towards clinical implementation.

Delayed accumulation of activated macrophages and inhibition of remyelination after spinal cord injury in an adult rodent model

OBJECT

Inhibition of remyelination is part of the complex problem of persistent dysfunction after spinal cord injury (SCI), and residual myelin debris may be a factor that inhibits remyelination. Phagocytosis by microglial cells and by macrophages that migrate from blood vessels plays a major role in the clearance of myelin debris. The object of this study was to investigate the mechanisms underlying the failure of significant remyelination after SCI.

METHODS

The authors investigated macrophage recruitment and related factors in rats by comparing a contusion model (representing contusive SCI with residual myelin debris and failure of remyelination) with a model consisting of chemical demyelination by lysophosphatidylcholine (representing multiple sclerosis with early clearance of myelin debris and remyelination). The origin of infiltrating macrophages was investigated using mice transplanted with bone marrow cells from green fluorescent protein-transfected mice. The changes in levels of residual myelin debris and the infiltration of activated macrophages in demyelinated lesions were investigated by immunostaining at 2, 4, and 7 days postinjury. To investigate various factors that might be involved, the authors also investigated gene expression of macrophage chemotactic factors and adhesion factors.

RESULTS

Activated macrophages coexpressing green fluorescent protein constituted the major cell population in the lesions, indicating that the macrophages in both models were mainly derived from the bone marrow, and that very few were derived from the intrinsic microglia. Immunostaining showed that in the contusion model, myelin debris persisted for a long period, and the infiltration of macrophages was significantly delayed. Among the chemotactic factors, the levels of monocyte chemoattractant protein-1 and granulocyte-macrophage colony-stimulating factor were lower in the contusion model at 2 and 4 days postinjury.

CONCLUSIONS

The results suggest that the delayed infiltration of activated macrophages is related to persistence of myelin debris after contusive SCI, resulting in the inhibition of remyelination.

Remyelination-promoting human IgMs: developing a therapeutic reagent for demyelinating disease

Promoting remyelination following injury to the central nervous system (CNS) promises to be an effective neuroprotective strategy to limit the loss of surviving axons and prevent disability. Studies confirm that multiple sclerosis (MS) and spinal cord injury lesions contain myelinating cells and their progenitors. Recruiting these endogenous cells to remyelinate may be of therapeutic value. This review addresses the use of antibodies reactive to CNS antigens to promote remyelination. Antibody-induced remyelination in a virus-mediated model of chronic spinal cord injury was initially observed in response to treatment with CNS reactive antisera. Monoclonal mouse and human IgMs, which bind to the surface of oligodendrocytes and myelin, were later identified that were functionally equivalent to antisera. A recombinant form of a human remyelination-promoting IgM (rHIgM22) targets areas of CNS injury and promotes maximal remyelination within 5 weeks after a single low dose (25 microg/kg). The IgM isoform of this reparative antibody is required for in vivo function. We hypothesize that the IgM clusters membrane domains and associated signaling molecules on the surface of target cells. Current therapies for MS are designed to modulate inflammation. In contrast, remyelination promoting IgMs are the first potential therapeutic molecules designed to induce tissue repair by acting within the CNS at sites of damage on the cells responsible for myelin synthesis.

Isolation and characterization of dendritic cells from common marmosets for preclinical cell therapy studies

Dendritic cells (DCs) have important functions as modulators of immune responses, and their ability to activate T cells is of great value in cancer immunotherapy. The isolation of DCs from the peripheral blood of rhesus and African green monkeys has been reported, but the immune system in the common marmoset remains poorly characterized, although it offers many potential advantages for preclinical studies. In the present study, we devised methods, based on techniques developed for mouse and human DC preparation, for isolating DCs from three major tissue sources in the common marmoset: bone marrow (BM), spleen and peripheral blood. Each set of separated cells was analysed using the cell surface DC-associated markers CD11c, CD80, CD83, CD86 and human leucocyte antigen (HLA)-DR, all of which are antibodies against human antigens, and the cells were further characterized both functionally and morphologically as antigen-presenting cells. BM proved to be an excellent cell source for the isolation of DCs intended for preclinical studies on cell therapy, for which large quantities of cells are required. In the BM-derived CD11c(+) cell population, cells exhibiting the characteristic features of DCs were enriched, with the typical DC morphology and the abilities to undergo endocytosis, to secrete interleukin (IL)-12, and to stimulate Xenogenic T cells. Moreover, BM-derived DCs produced the neurotrophic factor NT-3, which is also found in murine splenic DCs. These results suggest that BM-derived DCs from the common marmoset may be useful for biological analysis and for preclinical studies on cell therapy for central nervous system diseases and cancer.

The effect of dendritic cells on the retinal cell transplantation

The potential of bone marrow cell-derived immature dendritic cells (myeloid iDCs) in modulating the efficacy of retinal cell transplantation therapy was investigated. (1) In vitro, myeloid iDCs but not BMCs enhanced the survival and proliferation of embryonic retinal cells, and the expression of various neurotrophic factors by myeloid iDCs was confirmed with RT-PCR. (2) In subretinal transplantation, neonatal retinal cells co-transplanted with myeloid iDCs showed higher survival rate compared to those transplanted without myeloid iDCs. (3) CD8 T-cells reactive against donor retinal cells were significantly increased in the mice with transplantation of retinal cells alone. These results suggested the beneficial effects of the use of myeloid iDCs in retinal cell transplantation therapy.

Glial cell loss, proliferation and replacement in the contused murine spinal cord

Studies in the rat have shown that contusive spinal cord injury (SCI) results in devastating pathology, including significant loss of mature oligodendrocytes and astrocytes even in spared white matter. Subsequently, there is increased proliferation of endogenous NG2(+) cells, postulated to contribute to replacement of mature glia chronically, which is important for functional recovery. Studies of mechanisms that stimulate endogenous progenitor cells would be facilitated by using mouse models with naturally occurring and genetically engineered mutations. To determine whether the murine response is similar to that in the rat, we performed contusive SCI on adult female C57Bl/6 mice at the T8-9 level. Animals received bromodeoxyuridine injections in the first week following injury and were killed at 1, 3, 4, 7 or 28 days postinjury (DPI). The overall loss of macroglia and the temporal-spatial response of NG2(+) cells after SCI in the (C57Bl/6) mouse was very similar to that in the (Sprague-Dawley) rat. By 24 h after SCI nearly half of the macroglia in spared ventral white matter had been lost. Cell proliferation was increased at 1-7 DPI, peaking at 3-4 DPI. Dividing cells included NG2(+) cells and Cd11b(+) macrophages and microglia. Furthermore, cells dividing in the first week expressed markers of mature glia at 28 DPI. The similarities in endogenous progenitor cell response to SCI in the mouse and rat suggest that this is a fundamental injury response, and that transgenic mouse models may be used to further probe how this cellular response to SCI might be enhanced to improve recovery after SCI.

An overview of tissue engineering approaches for management of spinal cord injuries

Severe spinal cord injury (SCI) leads to devastating neurological deficits and disabilities, which necessitates spending a great deal of health budget for psychological and healthcare problems of these patients and their relatives. This justifies the cost of research into the new modalities for treatment of spinal cord injuries, even in developing countries. Apart from surgical management and nerve grafting, several other approaches have been adopted for management of this condition including pharmacologic and gene therapy, cell therapy, and use of different cell-free or cell-seeded bioscaffolds. In current paper, the recent developments for therapeutic delivery of stem and non-stem cells to the site of injury, and application of cell-free and cell-seeded natural and synthetic scaffolds have been reviewed.

Novel nerve guidance material prepared from bovine aponeurosis

Spinal cord injury (SCI) creates an adverse environment for axon regeneration. As a result, the axons at the injury sites begin to be atrophy, retract and lose their functions. Several strategies to promote axon regeneration at the injury site have been tested, but the progress is very limited. One of the major reasons is that the regenerated axons often extend randomly and do not reach the proper place. Fabricating linearly ordered materials as nerve guidance would be important to solve such problems. In this study, a novel type of nerve guidance material was prepared from the bovine aponeurosis, which mainly consisted of ordered collagen fibers. The processed material showed good cell compatibility and low immunogenisity. Moreover, the processed material guided the neurites outgrowth of in vitro cultured cortical neurons along its fibers. The results suggested that the processed aponeurosis would be a proper nerve guidance biomaterial for SCI repair.

Growth factor treatment and genetic manipulation stimulate neurogenesis and oligodendrogenesis by endogenous neural progenitors in the injured adult spinal cord

Neurons and oligodendrocytes are highly vulnerable to various insults, and their spontaneous replacement occurs to only a limited extent after damage in the adult spinal cord. The environment of injured tissue is thus thought to restrict the regenerative capacity of endogenous neural stem/progenitor cells; strategies for overcoming such restrictions remain to be developed. Here, we combined growth factor treatment and genetic manipulation to stimulate neurogenesis and oligodendrogenesis by endogenous progenitors in vivo. The recombinant retrovirus pMXIG, which was designed to coexpress green fluorescent proteins (GFPs) and a neurogenic/gliogenic transcription factor, was directly injected into the injured spinal cord parenchyma to manipulate proliferative cells in situ. We found that cells expressing Olig2, Nkx2.2, and NG2 were enriched among virus-infected, GFP-positive (GFP+) cells. Moreover, a fraction of GFP+ cells formed neurospheres and differentiated into neurons, astrocytes, and oligodendrocytes in vitro, demonstrating that GFP retroviruses indeed infected endogenous neural progenitors in vivo. Neuronal differentiation of control virus-infected cells did not occur at a detectable level in the injured spinal cord. We found, however, that direct administration of fibroblast growth factor 2 and epidermal growth factor into lesioned tissue could induce a significant fraction of GFP-labeled cells to express immature neuronal markers. Moreover, retrovirus-mediated overexpression of the basic helix-loop-helix transcription factors Neurogenin2 and Mash1, together with growth factor treatment, enhanced the production and maturation of new neurons and oligodendrocytes, respectively. These results demonstrate that endogenous neural progenitors can be manipulated to replace neurons and oligodendrocytes lost to insults in the injured spinal cord.

Inflammation and Spinal Cord Injury: Infiltrating Leukocytes as Determinants of Injury and Repair Processes

The immune response that accompanies spinal cord injury contributes to both injury and reparative processes. It is this duality that is the focus of this review. Here we consider the complex cellular and molecular immune responses that lead to the infiltration of leukocytes and glial activation, promote oxidative stress and tissue damage, influence wound healing, and subsequently modulate locomotor recovery. Immunomodulatory strategies to improve outcomes are gaining momentum as ongoing research carefully dissects those pathways, which likely mediate cell injury from those, which favor recovery processes. Current therapeutic strategies address divergent approaches including early immunoblockade and vaccination with immune cells to prevent early tissue damage and support a wound-healing environment that favors plasticity. Despite these advances, there remain basic questions regarding how inflammatory cells interact in the injured spinal cord. Such questions likely arise as a result of our limited understanding of immune cell/neural interactions in a dynamic environment that culminates in progressive cell injury, demyelination, and regenerative failure.

Synergy between immune cells and adult neural stem/progenitor cells promotes functional recovery from spinal cord injury

The well regulated activities of microglia and T cells specific to central nervous system (CNS) antigens can contribute to the protection of CNS neural cells and their renewal from adult neural stem/progenitor cells (aNPCs). Here we report that T cell-based vaccination of mice with a myelin-derived peptide, when combined with transplantation of aNPCs into the cerebrospinal fluid (CSF), synergistically promoted functional recovery after spinal cord injury. The synergistic effect was correlated with modulation of the nature and intensity of the local T cell and microglial response, expression of brain-derived neurotrophic factor and noggin protein, and appearance of newly formed neurons from endogenous precursor-cell pools. These results substantiate the contention that the local immune response plays a crucial role in recruitment of aNPCs to the lesion site, and suggest that similar immunological manipulations might also serve as a therapeutic means for controlled migration of stem/progenitor cells to other acutely injured CNS sites.

Intracarotid injection of granulocyte-macrophage colony-stimulating factor induces neuroprotection in a rat transient middle cerebral artery occlusion model

Granulocyte-macrophage colony-stimulating factor (GM-CSF) was found to promote collateral flow in patients with coronary artery disease and also to induce arteriogenesis in a rat hypoperfusion brain model. Activated macrophages have been shown to induce vascular proliferation and play an important role in ischemic stroke. In this study, we examined the therapeutic effect of GM-CSF on the ischemic brain by activating microglia/macrophages. Rats were subjected to 1-h intraluminal middle cerebral artery occlusion (MCAO) and received an intracarotid injection of GM-CSF (5 ng) or saline immediately after reperfusion. Infarct volume, neurological function and histological findings were assessed 48 h later. An intracarotid injection of GM-CSF reduced the infarct volume and improved neurological function at 48 h after reperfusion. Histological analysis revealed that the number of activated microglia/macrophages to be increased and the number of apoptotic cells to be decreased in the area of the penumbra. These results suggest that intracarotid injection of GM-CSF may have a therapeutic effect on brain ischemia via activation of microglia/macrophages.

Immune-Based Therapy for Spinal Cord Repair: Autologous Macrophages and Beyond

Spinal cord injury is a devastating condition of the central nervous system (CNS), often resulting in severe loss of tissue, functional impairment, and only limited repair. Studies over the last few years have shown that response to the insult and spontaneous attempts at repair are multiphasic processes, with varying and sometimes conflicting requirements. This knowledge has led to novel strategies of therapeutic intervention. Our view is that a pivotal role in repair, maintenance, healing, and cell renewal in the CNS, as in other tissues, is played by the immune system. The mode and timing of intervention must be carefully selected, however, as the capacity of the CNS to tolerate local repair mechanisms is limited. Studies have shown that the spontaneously evoked early innate response to CNS injury is characterized by invasion of neutrophils and is unfavorable for cell survival. This is followed by a response of the resident innate immune cells (microglia), which however cannot supply all the needs of the damaged tissue; moreover, once evoked, and for as long as the damage persists, the microglial response remains beyond the capacity of the CNS to tolerate it. Immune-based clinical intervention is most effective in improving functional and morphological recovery when delayed for a certain period. Effective intervention might be in the form of (1) local injection of "alternatively activated" macrophages, (2) systemic injection of dendritic cells specific to CNS antigens, or (3) T-cell-based vaccination. The treatment of choice depends on the severity of the insult, the site of injury, the therapeutic window, and safety considerations.

Targeted expression of anti-apoptotic protein p35 in oligodendrocytes reduces delayed demyelination and functional impairment after spinal cord injury

Functional impairment after spinal cord injury (SCI) is attributed to neuronal cell necrosis death and axonotmesis, with further worsening caused by the accompanying apoptosis of myelin-forming oligodendrocytes (OLGs). However, it is unclear as to how much OLG apoptosis contributes to functional impairment. To address this issue, we used transgenic mice characterized by the targeted expression of p35, a broad-spectrum caspase inhibitor, in OLGs using the cre/loxP system (referred to as cre/p35 transgenic mice). In this study, we examined the motor function and histopathologic changes after a contusive thoracic spinal cord injury in the cre/p35 transgenic mice. A larger number of OLGs and a lesser extent of demyelination were observed after SCI in the cre/p35 transgenic mice than in the control cre mice, which did not carry the p35 transgene. Furthermore, the motor function of the hindlimbs recovered to a significantly better degree in the cre/p35 transgenic mice than in the control cre mice. Thus, the inhibition of OLG apoptosis decreased the extent of functional impairment after SCI. These findings suggest that the inhibition of OLG apoptosis may be a potential treatment for SCI.

A versatile, low-cost adaptor for stereotaxic and electrophysiologic spinal preparations in juvenile and adult rodents

Rats and mice provide excellent models for normal spinal cord physiology, traumatic spinal cord injury, and various disease states. Alternative and improved methodologies for experimental spinal preparations are desirable, particularly in the wake of expanding neuroscience technology, such as the diverse array of transgenic mice now available, and exciting new therapeutic approaches, including transplantation and gene therapy. This report describes a simple, low-cost instrument for spinal preparations in rodents of different sizes, including rat pups. The device adapts to standard small animal stereotaxic instruments, precluding the need for additional stereotaxic apparatus. Surgical methods utilizing the device are presented demonstrating the instrument's capacity for precise alignment and stabilization of the spinal column that is reproducible from animal to animal. Proof of concept is demonstrated with results from spinal cord injections and electrophysiologic recordings.