Blockade of interleukin 6 signaling improves the survival rate of transplanted bone marrow stromal cells and increases locomotor function in mice with spinal cord injury

Optical imaging detection of extracellular vesicles of miR-146 modified bone marrow mesenchymal stem cells promoting spinal cord injury repair

Bone Marrow mesenchymal Stem Cells (BMSCs) are considered as an important source of cells for regenerative medicine, In particular, Bone Marrow mesenchymal Stem Cells Exosomes (BMSCs-EXO) have the most significant effect in the treatment of Spinal Cord Injury (SCI), but the mechanism of action is still unknown. This study found that compared with other SCI groups, BMSCs-EXO loaded with miR-146a could significantly improve the functional recovery of the hind limbs of SCI rats. Hematoxylin and eosin (H&E) indicated that the lesion area of spinal cord injury was less, nissl staining indicated that the number of nissl bodies remained more; the mechanism may be through inhibiting the expression of IRAK1 and TRAF6, blocking the activation of NF-κB p65, reducing the expression of TNF-α, IL-1β and IL-6 inflammatory factors and oxidative stress, improving the SCI microenvironment, and promoting the repair of neural function. In general, we found that BMSCs-EXO loaded with miR-146a could reduce the inflammatory response and oxidative stress in SCI by inhibiting the activation of IRAK1/TRAF6/NF-κB p65 signaling pathway, and promote the recovery of neurological function in SCI rats.

Molars to Medicine: A Focused Review on the Pre-Clinical Investigation and Treatment of Secondary Degeneration following Spinal Cord Injury Using Dental Stem Cells

Spinal cord injury (SCI) can result in the permanent loss of mobility, sensation, and autonomic function. Secondary degeneration after SCI both initiates and propagates a hostile microenvironment that is resistant to natural repair mechanisms. Consequently, exogenous stem cells have been investigated as a potential therapy for repairing and recovering damaged cells after SCI and other CNS disorders. This focused review highlights the contributions of mesenchymal (MSCs) and dental stem cells (DSCs) in attenuating various secondary injury sequelae through paracrine and cell-to-cell communication mechanisms following SCI and other types of neurotrauma. These mechanistic events include vascular dysfunction, oxidative stress, excitotoxicity, apoptosis and cell loss, neuroinflammation, and structural deficits. The review of studies that directly compare MSC and DSC capabilities also reveals the superior capabilities of DSC in reducing the effects of secondary injury and promoting a favorable microenvironment conducive to repair and regeneration. This review concludes with a discussion of the current limitations and proposes improvements in the future assessment of stem cell therapy through the reporting of the effects of DSC viability and DSC efficacy in attenuating secondary damage after SCI.

Human motor neurons derived from induced pluripotent stem cells are susceptible to SARS-CoV-2 infection

Introduction

COVID-19 typically causes Q7 respiratory disorders, but a high proportion of patients also reports neurological and neuromuscular symptoms during and after SARSCoV-2 infection. Despite a number of studies documenting SARS-CoV-2 infection of various neuronal cell populations, the impact of SARS-CoV-2 exposure on motor neuronal cells specifically has not been investigated so far.

Methods

Thus, by using human iPSC-derived motor neurons (iPSC-MNs) we assessed: (i) the expression of SARS-CoV-2 main receptors; (ii) iPSC-MN infectability by SARS-CoV-2; and (iii) the effect of SARS-CoV-2 exposure on iPSC-MN transcriptome.

Results

Gene expression profiling and immunofluorescence (IF) analysis of the main host cell receptors recognized by SARS-CoV-2 revealed that all of them are expressed in iPSC-MNs, with CD147 and NRP1 being the most represented ones. By analyzing SARS-CoV-2 N1 and N2 gene expression over time, we observed that human iPSC-MNs were productively infected by SARS-CoV-2 in the absence of cytopathic effect. Supernatants collected from SARS-CoV-2-infected iPSC-MNs were able to re-infect VeroE6 cells. Image analyses of SARS-CoV-2 nucleocapsid proteins by IF confirmed iPSC-MN infectability. Furthermore, SARS-CoV-2 infection in iPSCMNs significantly altered the expression of genes (IL-6, ANG, S1PR1, BCL2, BAX, Casp8, HLA-A, ERAP1, CD147, MX1) associated with cell survival and metabolism, as well as antiviral and inflammatory response.

Discussion

These results suggest for the very first time that SARS-CoV-2 can productively infect human iPSC-derived MNs probably by binding CD147 and NRP1 receptors. Such information will be important to unveil the biological bases of neuromuscular disorders characterizing SARS-CoV-2 infection and the so called long-COVID symptoms.

Adipose-Derived Mesenchymal Stromal Cell Transplantation for Severe Spinal Cord Injury: Functional Improvement Supported by Angiogenesis and Neuroprotection

Mesenchymal stromal cell transplantation alone is insufficient when motor dysfunction is severe; combination therapy with rehabilitation could improve motor function. Here, we aimed to analyze the characteristics of adipose-derived MSCs (AD-MSCs) and determine their effectiveness in severe spinal cord injury (SCI) treatment. A severe SCI model was created and motor function were compared. The rats were divided into AD-MSC-transplanted treadmill exercise-combined (AD-Ex), AD-MSC-transplanted non-exercise (AD-noEx), PBS-injected exercise (PBS-Ex), and no PBS-injected exercise (PBS-noEx) groups. In cultured cell experiments, AD-MSCs were subjected to oxidative stress, and the effects on the extracellular secretion of AD-MSCs were investigated using multiplex flow cytometry. We assessed angiogenesis and macrophage accumulation in the acute phase. Spinal cavity or scar size and axonal preservation were assessed histologically in the subacute phase. Significant motor function improvement was observed in the AD-Ex group. Vascular endothelial growth factor and C-C motif chemokine 2 expression in AD-MSC culture supernatants increased under oxidative stress. Enhanced angiogenesis and decreased macrophage accumulation were observed at 2 weeks post-transplantation, whereas spinal cord cavity or scar size and axonal preservation were observed at 4 weeks. Overall, AD-MSC transplantation combined with treadmill exercise training improved motor function in severe SCI. AD-MSC transplantation promoted angiogenesis and neuroprotection.

Tocilizumab promotes repair of spinal cord injury by facilitating the restoration of tight junctions between vascular endothelial cells

BACKGROUND

Our previous study demonstrated that M1 macrophages could impair tight junctions (TJs) between vascular endothelial cells by secreting interleukin-6 (IL-6) after spinal cord injury (SCI). Tocilizumab, as a humanized IL-6 receptor (IL-6R) monoclonal antibody approved for the clinic, has been applied in the treatment of neurological diseases in recent years, but the treatment effect of Tocilizumab on the TJs restoration of the blood-spinal cord barrier (BSCB) after SCI remains unclear. This study aimed to explore the effect of Tocilizumab on the restoration of TJs between vascular endothelial cells and axon regeneration after SCI.

METHODS

In this study, the mouse complete spinal cord crush injury model was used, and Tocilizumab was continuously injected intrathecally until the day of sample collection. A PBS injection in the same location was included as a control. At 14 days postinjury (dpi) and 28 dpi, spinal cord tissue sections were examined via tissue immunofluorescence. The Basso Mouse Scale (BMS) scores and footprint analysis were used to verify the effect of Tocilizumab on the recovery of motor function in mice after SCI.

RESULTS

We demonstrated that depletion of macrophages has no effect on axon regeneration and motor functional recovery after SCI, but mice subjected to Tocilizumab showed a significant increase in axon regeneration and a better recovery in motor function during the chronic phase after SCI. Moreover, our study demonstrated that at 14 and 28 dpi, the expression of claudin-5 (CLDN5) and zonula occludens-1 (ZO-1) between vascular endothelial cells was significantly increased and the leakage of BSCB was significantly reduced in the injured core after daily intrathecal injection of Tocilizumab. Notably, the infiltration of CD68⁺ macrophages/microglia and the formation of fibrotic scar were decreased in the injured core after Tocilizumab treatment. Tocilizumab treatment could effectively reduce the IL-6 expression in macrophages in the injured core.

CONCLUSION

The application of Tocilizumab to antagonize IL-6R can effectively reduce the expression of IL-6 in macrophages and facilitate TJs restoration of the BSCB, which is beneficial for axon regeneration and motor functional recovery after SCI. Hence, Tocilizumab treatment is a potential therapeutic strategy for SCI.

Hyperbaric Oxygen Therapy-Induced Molecular and Pathway Changes in a Rat Model of Spinal Cord Injury: A Proteomic Analysis

Hyperbaric Oxygen Therapy (HBOT) has definitive therapeutic effects on spinal cord injury (SCI), but its mechanism of action is still unclear. Here, we've conducted a systemic proteomic analysis to identify differentially expressed proteins (DEPs) between SCI rats and HBOT + SCI rats. The function clustering analysis showed that the top enriched pathways of DEPs include oxygen transport activity, oxygen binding, and regulation of T cell proliferation. The results of functional and signal pathway analyses indicated that metabolic pathways, thermogenesis, LXR/RXR activation, acute phase response signaling, and the intrinsic prothrombin pathway in the SCI + HBOT group was higher than SCI group.

Role of IL-6 in the regulation of neuronal development, survival and function

The pleiotropic cytokine interleukin-6 (IL-6) is emerging as a molecule with both beneficial and destructive potentials. It can exert opposing actions triggering either neuron survival after injury or causing neurodegeneration and cell death in neurodegenerative or neuropathic disorders. Importantly, neurons respond differently to IL-6 and this critically depends on their environment and whether they are located in the peripheral or the central nervous system. In addition to its hub regulator role in inflammation, IL-6 is recently emerging as an important regulator of neuron function in health and disease, offering exciting possibilities for more mechanistic insight into the pathogenesis of mental, neurodegenerative and pain disorders and for developing novel therapies for diseases with neuroimmune and neurogenic pathogenic components.

Mesenchymal stem cell conditioned medium increases glial reactivity and decreases neuronal survival in spinal cord slice cultures

Ex vivo spinal cord slice cultures (SCSC) allow study of spinal cord circuitry, maintaining stimuli responses comparable to live animals. Previously, we have shown that mesenchymal stem/stromal cell (MSC) transplantation in vivo reduced inflammation and increased nerve regeneration but MSC survival was short-lived, highlighting that beneficial action may derive from the secretome. Previous in vitro studies of MSC conditioned medium (CM) have also shown increased neuronal growth. In this study, murine SCSC were cultured in canine MSC CM (harvested from the adipose tissue of excised inguinal fat) and cell phenotypes analysed via immunohistochemistry and confocal microscopy. SCSC in MSC CM displayed enhanced viability after propidium iodide staining. GFAP immunoreactivity was significantly increased in SCSC in MSC CM compared to controls, but with no change in proteoglycan (NG2) immunoreactivity. In contrast, culture in MSC CM significantly decreased the prevalence of βIII-tubulin immunoreactive neurites, whilst Ca²⁺ transients per cell were significantly increased. These ex vivo results contradict previous in vitro and in vivo reports of how MSC and their secretome may affect the microenvironment of the spinal cord after injury and highlight the importance of a careful comparison of the different experimental conditions used to assess the potential of cell therapies for the treatment of spinal cord injury.

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Treatment of spinal slices with conditioned medium caused cell phenotypic changes.

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Resident astrocytes become hypertrophic, yet neuronal axonal outgrowth reduced.

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Signalling cells reduced in number but increased their signalling activity.

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Highlights importance of simulation systems and systemic factors in CNS models.

Current evidence on mesenchymal stem cell therapy for traumatic spinal cord injury: systematic review and meta-analysis

BACKGROUND AIMS

The authors aim to analyze the evidence in the literature regarding the efficacy and safety of mesenchymal stem cell (MSC) therapy in human subjects with traumatic spinal cord injury (SCI) and identify its potential role in the management of SCI.

METHODS

The authors conducted independent and duplicate searches of electronic databases, including PubMed, Embase and the Cochrane Library, until May 2020 for studies analyzing the efficacy and safety of stem cell therapy for SCI. American Spine Injury Association (ASIA) impairment scale (AIS) grade improvement, ASIA sensorimotor score, activities of daily living score, residual urine volume, bladder function improvement, somatosensory evoked potential (SSEP) improvement and adverse reactions were the outcomes analyzed. Analysis was performed in R platform using OpenMeta[Analyst] software.

RESULTS

Nineteen studies involving 670 patients were included for analysis. On analysis, the intervention group showed statistically significant improvement in AIS grade (P < 0.001), ASIA sensory score (P < 0.017), light touch (P < 0.001), pinprick (P = 0.046), bladder function (P = 0.012), residual urine volume (P = 0.023) and SSEP (P = 0.002). However, no significant difference was noted in motor score (P = 0.193) or activities of daily living score (P = 0.161). Although the intervention group had a significant increase in complications (P < 0.001), no serious or permanent adverse events were reported. On subgroup analysis, low concentration of MSCs (<5 × 10⁷ cells) and initial AIS grade A presentation showed significantly better outcomes than their counterparts.

CONCLUSIONS

The authors' analysis establishes the efficacy and safety of MSC transplantation in terms of improvement in AIS grade, ASIA sensory score, bladder function and electrophysiological parameters like SSEP compared with controls, without major adverse events. However, further research is needed to standardize dose, timing, route and source of MSCs used for transplantation.

Key differences between olfactory ensheathing cells and Schwann cells regarding phagocytosis of necrotic cells: implications for transplantation therapies

Transplantation of peripheral nervous system glia is being explored for treating neural injuries, in particular central nervous system injuries. These glia, olfactory ensheathing cells (OECs) and Schwann cells (SCs), are thought to aid regeneration by clearing necrotic cells, (necrotic bodies, NBs), as well as myelin debris. The mechanism by which the glia phagocytose and traffic NBs are not understood. Here, we show that OECs and SCs recognize phosphatidylserine on NBs, followed by engulfment and trafficking to endosomes and lysosomes. We also showed that both glia can phagocytose and process myelin debris. We compared the time-course of glial phagocytosis (of both NBs and myelin) to that of macrophages. Internalization and trafficking were considerably slower in glia than in macrophages, and OECs were more efficient phagocytes than SCs. The two glial types also differed regarding their cytokine responses after NB challenge. SCs produced low amounts of the pro-inflammatory cytokine TNF-α while OECs did not produce detectable TNF-α. Thus, OECs have a higher capacity than SCs for phagocytosis and trafficking, whilst producing lower amounts of pro-inflammatory cytokines. These findings suggest that OEC transplantation into the injured nervous system may lead to better outcomes than SC transplantation.

Exosomes secreted from miRNA-29b-modified mesenchymal stem cells repaired spinal cord injury in rats

Exosomes, a kind of extracellular vesicle, are promising therapeutic agents for spinal cord injury (SCI). This article aimed to investigate effects of exosomes secreted from miRNA-29b-modified bone marrow mesenchymal stem cells (BMSCs) on SCI. Exosomes were extracted from BMSCs transfected with miRNA-29b or negative control (miR NC). SCI rats were injected intravenously with exosomes (control exosomes, miRNA-29b exosomes) and BMSCs (miR NC, miRNA-29b) through the tail vein. The expression of miRNA-29b in spinal cord tissues of SCI rats was detected by qRT-PCR. The hind limb motor function was evaluated by Basso Beattie Bresnahan (BBB) score. The histopathological damage and neuronal regeneration in spinal cord tissues was observed by HE staining and immunohistochemistry, respectively. The injection of miRNA-29b exosomes and miRNA-29b BMSCs both significantly increased the expression of miRNA-29b in spinal cord tissues of SCI rats (P<0.05). Compared with SCI rats, rats in the miRNA-29b exosomes and the miRNA-29b groups exhibited improved SCI, including increased BBB score, NF200 and GAP-43 positive neurons, as well as decreased contractile nerve cell numbers and GFAP positive neurons (all P<0.05). The relieving degree of SCI was significantly higher in the miRNA-29b exosomes group than in the miRNA-29b BMSCs group (P<0.05). Exosomes secreted from miRNA-29b-modified BMSCs were effective in the repair of SCI in rats.

Comparison of Mesenchymal Stromal Cells Isolated from Murine Adipose Tissue and Bone Marrow in the Treatment of Spinal Cord Injury

The use of mesenchymal stromal cell (MSC) transplantation to repair the injured spinal cord has shown consistent benefits in preclinical models. However, the low survival rate of grafted MSC is one of the most important problems. In the injured spinal cord, transplanted cells are exposed to hypoxic conditions and exposed to nutritional deficiency caused by poor vascular supply. Also, the transplanted MSCs face cytotoxic stressors that cause cell death. The aim of this study was to compare adipose-derived MSCs (AD-MSCs) and bone marrow-derived MSCs (BM-MSCs) isolated from individual C57BL6/J mice in relation to: (i) cellular characteristics, (ii) tolerance to hypoxia, oxidative stress and serum-free conditions, and (iii) cellular survival rates after transplantation. AD-MSCs and BM-MSCs exhibited a similar cell surface marker profile, but expressed different levels of growth factors and cytokines. To research their relative stress tolerance, both types of stromal cells were incubated at 20.5% O₂ or 1.0% O₂ for 7 days. Results showed that AD-MSCs were more proliferative with greater culture viability under these hypoxic conditions than BM-MSCs. The MSCs were also incubated under H₂O₂-induced oxidative stress and in serum-free culture medium to induce stress. AD-MSCs were better able to tolerate these stress conditions than BM-MSCs; similarly when transplanted into the spinal cord injury region in vivo, AD-MSCs demonstrated a higher survival rate post transplantation Furthermore, this increased AD-MSC survival post transplantation was associated with preservation of axons and enhanced vascularization, as delineated by increases in anti-gamma isotype of protein kinase C and CD31 immunoreactivity, compared with the BM-MSC transplanted group. Hence, our results indicate that AD-MSCs are an attractive alternative to BM-MSCs for the treatment of severe spinal cord injury. However, it should be noted that the motor function was equally improved following moderate spinal cord injury in both groups, but with no significant improvement seen unfortunately following severe spinal cord injury in either group.

Exposing mesenchymal stem cells to chondroitin sulphated proteoglycans reduces their angiogenic and neuro-adhesive paracrine activity

The multifactorial complexity of spinal cord injuries includes the formation of a glial scar, of which chondroitin sulphated proteoglycans (CSPG) are an integral component. Previous studies have shown CSPG to have inhibitory effects on endothelial and neuronal cell growth, highlighting the difficulty of spinal cord regeneration. Mesenchymal stem/stromal cells (MSC) are widely used as a cell therapy, and there is mounting evidence for their angiogenic and neurotrophic paracrine properties. However, in vivo studies have observed poor engraftment and survival of MSC when injected into SCI. Currently, it is not known whether increasing CSPG concentrations seen after SCI may affect MSC; therefore we have investigated the effects of CSPG exposure to MSC in vitro. CSPG-mediated inhibition of MSC adhesion was observed when MSC were cultured on substrates of increasing CSPG concentration, however MSC viability was not affected even up to five days of culture. Culture conditioned medium harvested from these cultures (primed MSC CM) was used as both culture substrata and soluble medium for EA.hy926 endothelial cells and SH-SY5Y neuronal cells. MSC CM was angiogenic, promoting endothelial cell adhesion, proliferation and tubule formation. However, exposing MSC to CSPG reduced the effects of CSPG-primed MSC CM on endothelial cell adhesion and proliferation, but did not reduce MSC-induced endothelial tubule formation. Primed MSC CM also promoted neuronal cell adhesion, which was reduced following exposure to CSPG. There were no marked differences in neurite outgrowth in MSC CM from CSPG primed MSC cultures versus control conditions, although non-primed MSC CM from the same donors was found to significantly enhance neurite outgrowth. Taken together, these studies demonstrate that MSC are resilient to CSPG exposure, but that there is a marked effect of CSPG on their paracrine regenerative activity. The findings increase our understanding of how the wound microenvironment after SCI can mitigate the beneficial effects of MSC transplantation.

Deficiency of Tenascin-C Alleviates Neuronal Apoptosis and Neuroinflammation After Experimental Subarachnoid Hemorrhage in Mice

Tenascin-C (TNC), a matricellular protein, is upregulated in brain parenchyma after experimental subarachnoid hemorrhage (SAH). Recent studies emphasize that early brain injury (EBI) should be overcome to improve post-SAH outcomes. The aim of this study was to investigate effects of TNC knockout (TNKO) on neuronal apoptosis and neuroinflammation, both of which are important constituents of EBI after SAH. C57BL/6 wild-type (WT) mice or TNKO mice underwent sham or filament perforation SAH modeling. Twenty-five WT mice and 25 TNKO mice were randomly divided into sham+WT (n = 10), sham+TNKO (n = 8), SAH+WT (n = 15), and SAH+TNKO (n = 17) groups. Beam balance test, neurological score, terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling staining, immunostaining of Toll-like receptor 4 (TLR4), and Western blotting were performed to evaluate neurobehavioral impairments, neuronal apoptosis, and neuroinflammation at 24 h post-SAH. Deficiency of TNC significantly alleviated post-SAH neurobehavioral impairments and neuronal apoptosis. The protective effects of TNKO on neurons were associated with the inhibition of a caspase-dependent apoptotic pathway, which was at least partly mediated by TLR4/nuclear factor-κB/interleukin-1β and interleukin-6 signaling cascades. This study first provided the direct evidence that TNC causes post-SAH neuronal apoptosis and neuroinflammation, potentially leading to the development of a new molecular targeted therapy against EBI.

Bone marrow mesenchymal stem cells (BMSCs) improved functional recovery of spinal cord injury partly by promoting axonal regeneration

Spinal cord injury (SCI) disrupts the spinal cord and results in the loss of sensory and motor function below the lesion site. The treatment of SCI became a challenge because the injured neurons fail to axon regenerate and repair after injury. Promoting axonal regeneration plays a key role in the treatment strategies for SCI. It would meet the goal of reconstruction the injured spinal cord and improving the functional recovery. Bone marrow mesenchymal stem cells (BMSCs) are attractive therapeutic potential cell sources for SCI, and it could rebuild the injured spinal cord through neuroprotection, neural regeneration and remyelinating. Evidence has demonstrated that BMSCs play important roles in mediating axon regeneration, and glial scar formation after SCI in animal experiments and some clinical trials. We reviewed the role of BMSCs in regulating axon regeneration and glial scar formation after SCI. BMSCs based therapies may provide a therapeutic potential for the injured spinal cord by promoting axonal regeneration and repair.

BDNF Overexpression Exhibited Bilateral Effect on Neural Behavior in SCT Mice Associated with AKT Signal Pathway

Spinal cord injury (SCI), a severe health problem in worldwide, was commonly associated with functional disability and reduced quality of life. As the expression of brain-derived neurotrophic factor (BDNF) was substantial event in injured spinal cord, we hypothesized whether BDNF-overexpression could be in favor of the recovery of both sensory function and hindlimb function after SCI. By using BDNF-overexpression transgene mice [CMV-BDNF 26 (CB26) mice] we assessed the role of BDNF on the recovery of neurological behavior in spinal cord transection (SCT) model. BMS score and tail-flick test was performed to evaluate locomotor function and sensory function, respectively. Immunohistochemistry was employed to detect the location and the expression of BDNF, NeuN, 5-HT, GAP-43, GFAP as well as CGRP, and the level of p-AKT and AKT were examined through western blot analysis. BDNF overexpressing resulted in significant locomotor functional recovery from 21 to 28 days after SCT, compared with wild type (WT)+SCT group. Meanwhile, the NeuN, 5-HT and GAP-43 positive cells were markedly increased in ventral horn in BDNF overexpression animals, compared with WT mice with SCT. Moreover, the crucial molecular signal, p-AKT/AKT has been largely up-regulated, which is consistent with the improvement of locomotor function. However, in this study, thermal hyperpathia encountered in sham (CB26) group and WT+SCT mice and further aggravated in CB26 mice after SCT. Also, following SCT, the significant augment of positive-GFAP astrocytes and CGRP fibers were found in WT+SCT mice, and further increase was seen in BDNF over-expression transgene mice. BDNF-overexpression may not only facilitate the recovery of locomotor function via AKT pathway, but also contributed simultaneously to thermal hyperalgesia after SCT.

Early transplantation of mesenchymal stem cells after spinal cord injury relieves pain hypersensitivity through suppression of pain-related signaling cascades and reduced inflammatory cell recruitment

Bone marrow-derived mesenchymal stem cells (BMSC) modulate inflammatory/immune responses and promote motor functional recovery after spinal cord injury (SCI). However, the effects of BMSC transplantation on central neuropathic pain and neuronal hyperexcitability after SCI remain elusive. This is of importance because BMSC-based therapies have been proposed for clinical treatment. We investigated the effects of BMSC transplantation on pain hypersensitivity in green fluorescent protein (GFP)-positive bone marrow-chimeric mice subjected to a contusion SCI, and the mechanisms of such effects. BMSC transplantation at day 3 post-SCI improved motor function and relieved SCI-induced hypersensitivities to mechanical and thermal stimulation. The pain improvements were mediated by suppression of protein kinase C-γ and phosphocyclic AMP response element binding protein expression in dorsal horn neurons. BMSC transplants significantly reduced levels of p-p38 mitogen-activated protein kinase and extracellular signal-regulated kinase (p-ERK1/2) in both hematogenous macrophages and resident microglia and significantly reduced the infiltration of CD11b and GFP double-positive hematogenous macrophages without decreasing the CD11b-positive and GFP-negative activated spinal-microglia population. BMSC transplants prevented hematogenous macrophages recruitment by restoration of the blood-spinal cord barrier (BSCB), which was associated with decreased levels of (a) inflammatory cytokines (tumor necrosis factor-α, interleukin-6); (b) mediators of early secondary vascular pathogenesis (matrix metallopeptidase 9); (c) macrophage recruiting factors (CCL2, CCL5, and CXCL10), but increased levels of a microglial stimulating factor (granulocyte-macrophage colony-stimulating factor). These findings support the use of BMSC transplants for SCI treatment. Furthermore, they suggest that BMSC reduce neuropathic pain through a variety of related mechanisms that include neuronal sparing and restoration of the disturbed BSCB, mediated through modulation of the activity of spinal-resident microglia and the activity and recruitment of hematogenous macrophages.

Microglia inflict delayed brain injury after subarachnoid hemorrhage

Inflammatory changes have been postulated to contribute to secondary brain injury after aneurysmal subarachnoid hemorrhage (SAH). In human specimens after SAH as well as in experimental SAH using mice, we show an intracerebral accumulation of inflammatory cells between days 4 and 28 after the bleeding. Using bone marrow chimeric mice allowing tracing of all peripherally derived immune cells, we confirm a truly CNS-intrinsic, microglial origin of these immune cells, exhibiting an inflammatory state, and rule out invasion of myeloid cells from the periphery into the brain. Furthermore, we detect secondary neuro-axonal injury throughout the time course of SAH. Since neuronal cell death and microglia accumulation follow a similar time course, we addressed whether the occurrence of activated microglia and neuro-axonal injury upon SAH are causally linked by depleting microglia in vivo. Given that the amount of neuronal cell death was significantly reduced after microglia depletion, we conclude that microglia accumulation inflicts secondary brain injury after SAH.

Transplantation of bone marrow mesenchymal stem cells pretreated with valproic acid in rats with an acute spinal cord injury

This study aimed to investigate whether valproic acid (VPA) pretreatment enhances the therapeutic effectiveness of mesenchymal stem cells derived from bone marrow (BMSCs) transplanted into rats with an acute spinal cord injury (SCI). BMSCs were pretreated with VPA before transplantation and then intravenously injected 1 week after SCI. Before transplantation, levels of CXC chemokine receptor 4 (CXCR4) expression in BMSCs were tested using quantitative real-time PCR and Western blotting. Stromal derived factor-1 (SDF-1), the unique ligand of CXCR4, was quantified using RT-PCR and immunofluorescence. The locomotor function of rats with an SCI was evaluated using the Basso, Beattie, and Bresnahan (BBB) locomotor rating scale. Fluorescence microscopy and hematoxylin-eosin (HE) staining were also performed to evaluate pathophysiological changes after transplantation. On day 7 after SCI, the level of SDF-1 expression peaked. CXCR4 expression increased significantly in BMSCs pretreated with VPA. After intravenous transplantation, BrdU-labeled BMSCs were noted at the spinal injury site, and this was especially true for BMSCs pretreated with VPA. More significant functional improvement was observed in rats receiving BMSCs pretreated with VPA than in other groups of rats. AMD3100 partially inhibited improvement. This study demonstrates that pretreatment with VPA before transplantation enhances the therapeutic benefits of BMSCs in terms of greater cell migration and better neurological outcomes after traumatic SCI. The mechanism of this enhancement may be related to the SDF-1/CXCR4 axis. Therefore, pretreatment of BMSCs with VPA warrants further study in relation to the treatment of traumatic SCI.