Embryonic intermediate filament, nestin, expression following traumatic spinal cord injury in adult rats

Mechanism Analysis of Selenium-Containing Compounds in Alleviating Spinal Cord Injury Based on Network Pharmacology and Molecular Docking Technology

Spinal cord injury (SCI) is a severe traumatic condition in spinal surgery characterized by nerve damage in and below the injured area. Despite advancements in understanding the pathophysiology of SCI, effective clinical treatments remain elusive. Selenium compounds have become a research hotspot due to their diverse medicinal activities. Previously, our group synthesized a selenium-containing Compound 34# with significant anti-inflammatory activity. This study aimed to explore the anti-SCI effects of selenium-containing compounds using network pharmacology, molecular docking (MD), and ADMET methods. To identify SCI-related targets and those associated with 34#, GeneCards, NCBI, and SEA databases were employed. Eight overlapping targets were considered candidate targets, and molecular docking was performed using the PDB database and AutoDock software. The STRING database was used to obtain protein-protein interactions (PPI). Molecular dynamics simulation, MM/GBSA binding free energy score, and ADMET prediction were used to evaluate the potential targets and drug properties of 34#. Finally, experiments on NSC34 cells and mice were to verify the effects of 34# on SCI. Our results revealed eight candidate targets for 34# in the treatment of SCI. PPI and MD identified ADRB2 and HTR1F as the highest connectivity with 34#. ADMET analysis confirmed the low toxicity and safety of 34#. In vitro and in vivo models validated the anti-SCI effects. Our study elucidated candidate targets for alleviating SCI with 34#, explored PPI and target-related signaling pathways, and validated its anti-SCI effects. These findings enhance our understanding of 34#'s mechanism in treating SCI, positioning it as a potential candidate for SCI prevention.

Harnessing developmental dynamics of spinal cord extracellular matrix improves regenerative potential of spinal cord organoids

Neonatal spinal cord tissues exhibit remarkable regenerative capabilities as compared to adult spinal cord tissues after injury, but the role of extracellular matrix (ECM) in this process has remained elusive. Here, we found that early developmental spinal cord had higher levels of ECM proteins associated with neural development and axon growth, but fewer inhibitory proteoglycans, compared to those of adult spinal cord. Decellularized spinal cord ECM from neonatal (DNSCM) and adult (DASCM) rabbits preserved these differences. DNSCM promoted proliferation, migration, and neuronal differentiation of neural progenitor cells (NPCs) and facilitated axonal outgrowth and regeneration of spinal cord organoids more effectively than DASCM. Pleiotrophin (PTN) and Tenascin (TNC) in DNSCM were identified as contributors to these abilities. Furthermore, DNSCM demonstrated superior performance as a delivery vehicle for NPCs and organoids in spinal cord injury (SCI) models. This suggests that ECM cues from early development stages might significantly contribute to the prominent regeneration ability in spinal cord.

Electrical stimulation promotes functional recovery after spinal cord injury by activating endogenous spinal cord-derived neural stem/progenitor cell: an in vitro and in vivo study

BACKGROUND CONTEXT

Electrical stimulation is a noninvasive treatment method that has gained popularity in the treatment of spinal cord injury (SCI). Activation of spinal cord-derived neural stem/progenitor cell (SC-NSPC) proliferation and differentiation in the injured spinal cord may elicit considerable neural regenerative effects.

PURPOSE

This study aimed to explore the effect of electrical stimulation on the neurogenesis of SC-NSPCs.

STUDY DESIGN

This study analyzed the effects of electrical stimulation on neurogenesis in rodent SC-NSPCs in vitro and in vivo and evaluated functional recovery and neural circuitry improvements with electrical stimulation using a rodent SCI model.

METHODS

Rats (20 rats/group) were assigned to sham (Group 1), SCI only (Group 2), SCI + electrode implant without stimulation (Group 3), and SCI + electrode with stimulation (Group 4) groups to count total SC-NSPCs and differentiated neurons and to evaluate morphological changes in differentiated neurons. Furthermore, the Basso, Beattie, and Bresnahan scores were analyzed, and the motor- and somatosensory-evoked potentials in all rats were monitored.

RESULTS

Biphasic electrical currents enhanced SC-NSPC proliferation differentiation and caused qualitative morphological changes in differentiated neurons in vitro. Electrical stimulation promoted SC-NSPC proliferation and neuronal differentiation and improved functional outcomes and neural circuitry in SCI models. Increased Wnt3, Wnt7, and β-catenin protein levels were also observed after electrical stimulation.

CONCLUSIONS

Our study proved the beneficial effects of electrical stimulation on SCI. The Wnt/β-catenin pathway activation may be associated with this relationship between electrical stimulation and neuronal regeneration after SCI.

CLINICAL SIGNIFICANCE

The study confirmed the benefits of electrical stimulation on SCI based on cellular, functional, electrophysiological, and histological evidence. Based on these findings, we expect electrical stimulation to make a positive and significant difference in SCI treatment strategies.

Cortical Pathology in Vanishing White Matter

Vanishing white matter (VWM) is classified as a leukodystrophy with astrocytes as primary drivers in its pathogenesis. Magnetic resonance imaging has documented the progressive thinning of cortices in long-surviving patients. Routine histopathological analyses, however, have not yet pointed to cortical involvement in VWM. Here, we provide a comprehensive analysis of the VWM cortex. We employed high-resolution-mass-spectrometry-based proteomics and immunohistochemistry to gain insight into possible molecular disease mechanisms in the cortices of VWM patients. The proteome analysis revealed 268 differentially expressed proteins in the VWM cortices compared to the controls. A majority of these proteins formed a major protein interaction network. A subsequent gene ontology analysis identified enrichment for terms such as cellular metabolism, particularly mitochondrial activity. Importantly, some of the proteins with the most prominent changes in expression were found in astrocytes, indicating cortical astrocytic involvement. Indeed, we confirmed that VWM cortical astrocytes exhibit morphological changes and are less complex in structure than control cells. Our findings also suggest that these astrocytes are immature and not reactive. Taken together, we provide insights into cortical involvement in VWM, which has to be taken into account when developing therapeutic strategies.

Improvement of Rat Spinal Cord Injury Following Lentiviral Vector-Transduced Neural Stem/Progenitor Cells Derived from Human Epileptic Brain Tissue Transplantation with a Self-assembling Peptide Scaffold

Spinal cord injury (SCI) is a disabling neurological disorder that causes neural circuit dysfunction. Although various therapies have been applied to improve the neurological outcomes of SCI, little clinical progress has been achieved. Stem cell-based therapy aimed at restoring the lost cells and supporting micromilieu at the site of the injury has become a conceptually attractive option for tissue repair following SCI. Adult human neural stem/progenitor cells (hNS/PCs) were obtained from the epileptic human brain specimens. Induction of SCI was followed by the application of lentiviral vector-mediated green fluorescent protein-labeled hNS/PCs seeded in PuraMatrix peptide hydrogel (PM). The co-application of hNS/PCs and PM at the SCI injury site significantly enhanced cell survival and differentiation, reduced the lesion volume, and improved neurological functions compared to the control groups. Besides, the transplanted hNS/PCs seeded in PM revealed significantly higher migration abilities into the lesion site and the healthy host tissue as well as a greater differentiation into astrocytes and neurons in the vicinity of the lesion as well as in the host tissue. Our data suggest that the transplantation of hNS/PCs seeded in PM could be a promising approach to restore the damaged tissues and improve neurological functions after SCI.

Lineage tracing reveals the origin of Nestin-positive cells are heterogeneous and rarely from ependymal cells after spinal cord injury

Nestin is expressed extensively in neural stem/progenitor cells during neural development, but its expression is mainly restricted to the ependymal cells in the adult spinal cord. After spinal cord injury (SCI), Nestin expression is reactivated and Nestin-positive (Nestin⁺) cells aggregate at the injury site. However, the derivation of Nestin⁺ cells is not clearly defined. Here, we found that Nestin expression was substantially increased in the lesion edge and lesion core after SCI. Using a tamoxifen inducible CreER(T2)-loxP system, we verified that ependymal cells contribute few Nestin⁺ cells either to the lesion core or the lesion edge after SCI. In the lesion edge, GFAP⁺ astrocytes were the main cell type that expressed Nestin; they then formed an astrocyte scar. In the lesion core, Nestin⁺ cells expressed αSMA or Desmin, indicating that they might be derived from pericytes. Our results reveal that Nestin⁺ cells in the lesion core and edge came from various cell types and rarely from ependymal cells after complete transected SCI, which may provide new insights into SCI repair.

Methylprednisolone inhibits the proliferation of endogenous neural stem cells in nonhuman primates with spinal cord injury

OBJECTIVE

The aim of this work was to investigate the effects of methylprednisolone on the proliferation of endogenous neural stem cells (ENSCs) in nonhuman primates with spinal cord injury (SCI).

METHODS

A total of 14 healthy cynomolgus monkeys (Macaca fascicularis) (4–5 years of age) were randomly divided into 3 groups: the control group (n = 6), SCI group (n = 6), and methylprednisolone therapy group (n = 2). Only laminectomy was performed in the control animals at T-10. SCI was induced in monkeys using Allen’s weight-drop method (50 mm × 50 g) to injure the posterior portion of the spinal cord at T-10. In the methylprednisolone therapy group, monkeys were intravenously infused with methylprednisolone (30 mg/kg) immediately after SCI. All animals were intravenously infused with 5-bromo-2-deoxyuridine (BrdU) (50 mg/kg/day) for 3 days prior to study end point. The small intestine was dissected for immunohistochemical examination. After 3, 7, and 14 days, the spinal cord segments of the control and SCI groups were dissected to prepare frozen and paraffin sections. The proliferation of ENSCs was evaluated using BrdU and nestin immunofluorescence staining.

RESULTS

Histological examination showed that a larger number of mucosa epithelial cells in the small intestine of all groups were BrdU positive. Nestin-positive ependymal cells are increased around the central canal after SCI. After 3, 7, and 14 days of SCI, BrdU-positive ependymal cells in the SCI group were significantly increased compared with the control group, and the percentage of BrdU-positive cells in the left/right ventral horns and dorsal horn was significantly higher than that of the control group. Seven days after SCI, the percentages of both BrdU-positive ependymal cells around the central canal and BrdU– and nestin–double positive cells in the left/right ventral horns and dorsal horn were significantly lower in the methylprednisolone therapy group than in the SCI group.

CONCLUSIONS

While ENSCs proliferate significantly after SCI in nonhuman primates, methylprednisolone can inhibit the proliferation of ependymal cells after SCI.

Cytoplasmic Intermediate Filaments in Cell Biology

Intermediate filaments (IFs) are one of the three major elements of the cytoskeleton. Their stability, intrinsic mechanical properties, and cell type-specific expression patterns distinguish them from actin and microtubules. By providing mechanical support, IFs protect cells from external forces and participate in cell adhesion and tissue integrity. IFs form an extensive and elaborate network that connects the cell cortex to intracellular organelles. They act as a molecular scaffold that controls intracellular organization. However, IFs have been revealed as much more than just rigid structures. Their dynamics is regulated by multiple signaling cascades and appears to contribute to signaling events in response to cell stress and to dynamic cellular functions such as mitosis, apoptosis, and migration.

Curcumin Increase the Expression of Neural Stem/Progenitor Cells and Improves Functional Recovery after Spinal Cord Injury

Objective

To investigates the effect of curcumin on proliferation of spinal cord neural stem/progenitor cells (SC-NSPCs) and functional outcome in a rat spinal cord injury (SCI) model.

Methods

Sixty adult male Sprague-Dawley rats were randomly and blindly allocated into three groups (sham control group; curcumin treated group after SCI; vehicle treated group after SCI). Functional recovery was evaluated by the Basso, Beattie, and Bresnahan (BBB) scale during 6 weeks after SCI. The expression of SC-NSPC proliferation and astrogliosis were analyzed by nestin/Bromodeoxyuridine (BrdU) and Glial fibrillary acidic protein (GFAP) staining. The injured spinal cord was then examined histologically, including quantification of cavitation.

Results

The BBB score of the SCI-curcumin group was better than that of SCI-vehicle group up to 14 days (p<0.05). The co-immunoreactivity of nestin/BrdU in the SCI-curcumin group was much higher than that of the SCI-vehicle group 1 week after surgery (p<0.05). The GFAP immunoreactivity of the SCI-curcumin group was remarkably lower than that of the SCI-vehicle group 4 weeks after surgery (p<0.05). The lesion cavity was significantly reduced in the curcumin group as compared to the control group (p<0.05).

Conclusion

These results indicate that curcumin could increase the expression of SC-NSPCs, and reduce the activity of reactive astrogliosis and lesion cavity. Consequently curcumin could improve the functional recovery after SCI via SC-NSPC properties.

Neural progenitor cells but not astrocytes respond distally to thoracic spinal cord injury in rat models

Traumatic spinal cord injury (SCI) is a detrimental condition that causes loss of sensory and motor function in an individual. Many complex secondary injury cascades occur after SCI and they offer great potential for therapeutic targeting. In this study, we investigated the response of endogenous neural progenitor cells, astrocytes, and microglia to a localized thoracic SCI throughout the neuroaxis. Twenty-five adult female Sprague-Dawley rats underwent mild-contusion thoracic SCI (n = 9), sham surgery (n = 8), or no surgery (n = 8). Spinal cord and brain tissues were fixed and cut at six regions of the neuroaxis. Immunohistochemistry showed increased reactivity of neural progenitor cell marker nestin in the central canal at all levels of the spinal cord. Increased reactivity of astrocyte-specific marker glial fibrillary acidic protein was found only at the lesion epicenter. The number of activated microglia was significantly increased at the lesion site, and activated microglia extended to the lumbar enlargement. Phagocytic microglia and macrophages were significantly increased only at the lesion site. There were no changes in nestin, glial fibrillary acidic protein, microglia and macrophage response in the third ventricle of rats subjected to mild-contusion thoracic SCI compared to the sham surgery or no surgery. These findings indicate that neural progenitor cells, astrocytes and microglia respond differently to a localized SCI, presumably due to differences in inflammatory signaling. These different cellular responses may have implications in the way that neural progenitor cells can be manipulated for neuroregeneration after SCI. This needs to be further investigated.

Thermosensitive heparin-poloxamer hydrogels enhance the effects of GDNF on neuronal circuit remodeling and neuroprotection after spinal cord injury

Traumatic spinal cord injury (SCI) results in paraplegia or quadriplegia, and currently, therapeutic interventions for axonal regeneration after SCI are not clinically available. Animal studies have revealed that glial cell-derived neurotrophic factor (GDNF) plays multiple beneficial roles in neuroprotection, glial scarring remodeling, axon regeneration and remyelination in SCI. However, the poor physicochemical stability of GDNF, as well as its limited ability to cross the blood-spinal cord barrier, hampers the development of GDNF as an effective therapeutic intervention in clinical practice. In this study, a novel temperature-sensitive heparin-poloxamer (HP) hydrogel with high GDNF-binding affinity was developed. HP hydrogels showed a supporting scaffold for GDNF when it was injected into the lesion epicenter after SCI. GDNF-HP by orthotopic injection on lesioned spinal cord promoted the beneficial effects of GDNF on neural stem cell proliferation, reactive astrogliosis inhibition, axonal regeneration or plasticity, neuroprotection against cell apoptosis, and body functional recovery. Most interestingly, GDNF demonstrated a bidirectional regulation of autophagy, which inhibited cell apoptosis at different stages of SCI. Furthermore, the HP hydrogel promoted the inhibition of autophagy-induced apoptosis by GDNF in SCI. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2816-2829, 2017.

Optical Imaging of the Motor Cortex Following Antidromic Activation of the Corticospinal Tract after Spinal Cord Injury

Spinal cord injury (SCI) disrupts neuronal networks of ascending and descending tracts at the site of injury, leading to a loss of motor function. Restoration and new circuit formation are important components of the recovery process, which involves collateral sprouting of injured and uninjured fibers. The present study was conducted to determine cortical responses to antidromic stimulation of the corticospinal tracts, to compare changes in the reorganization of neural pathways within normal and spinal cord-injured rats, and to elucidate differences in spatiotemporal activity patterns of the natural progression and reorganization of neural pathways in normal and SCI animals using optical imaging. Optical signals were recorded from the motor cortex in response to electrical stimulation of the ventral horn of the L1 spinal cord. Motor evoked potentials (MEPs) were evaluated to demonstrate endogenous recovery of physiological functions after SCI. A significantly shorter N1 peak latency and broader activation in the MEP optical recordings were observed at 4 weeks after SCI, compared to 1 week after SCI. Spatiotemporal patterns in the cerebral cortex differed depending on functional recovery. In the present study, optical imaging was found to be useful in revealing functional changes and may reflect conditions of reorganization and/or changes in surviving neurons after SCI.

Molecular imaging of nestin in neuroinflammatory conditions reveals marked signal induction in activated microglia

Background

Nestin is a known marker of neuronal progenitor cells in the adult brain. Following neuro- and gliogenesis, nestin is replaced by cell type-specific intermediate filaments, e.g., neurofilaments for panneuronal expression and glial fibrillary acidic protein as a specific marker of mature astrocytes. While previous work have been mostly focused on the neuronal fate of nestin-positive progenitors, in the present study, we sought to investigate in real time how nestin signals and cellular expression patterns are controlled in the context of neuroinflammatory challenge and ischemic brain injury.

Methods

To visualize effects of neuroinflammation on neurogenesis/gliogenesis, we created a transgenic model bearing the dual reporter system luciferase and GFP under transcriptional control of the murine nestin promoter. In this model, transcriptional activation of nestin was visualized from the brains of living animals using biophotonic/bioluminescence molecular imaging and a high resolution charged coupled device camera. Nestin induction profiles in vivo and in tissue sections were analyzed in two different experimental paradigms: middle cerebral artery occlusion and lipopolysaccharide-induced innate immune stimuli.

Results

We report here a context- and injury-dependent induction and cellular expression profile of nestin. While in the baseline conditions the nestin signal and/or GFP expression was restricted to neuronal progenitors, the cellular expression patterns of nestin following innate immune challenge and after stroke markedly differed shifting the cellular expression patterns towards activated microglia/macrophages and astrocytes.

Conclusions

Our results suggest that nestin may serve as a context-dependent biomarker of inflammatory response in glial cells including activated microglia/macrophages.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-017-0816-7) contains supplementary material, which is available to authorized users.

Does vitamin C have the ability to augment the therapeutic effect of bone marrow-derived mesenchymal stem cells on spinal cord injury?

Methylprednisolone (MP) is currently the only drug confirmed to exhibit a neuroprotective effect on acute spinal cord injury (SCI). Vitamin C (VC) is a natural water-soluble antioxidant that exerts neuroprotective effects through eliminating free radical damage to nerve cells. Bone marrow mesenchymal stem cells (BMMSCs), as multipotent stem cells, are promising candidates in SCI repair. To evaluate the therapeutic effects of MP, VC and BMMSCs on traumatic SCI, 80 adult male rats were randomly divided into seven groups: control, SCI (SCI induction by weight-drop method), MP (SCI induction, followed by administration of 30 mg/kg MP via the tail vein, once every other 6 hours, for five times), VC (SCI induction, followed by intraperitoneal administration of 100 mg/kg VC once a day, for 28 days), MP + VC (SCI induction, followed by administration of MP and VC as the former), BMMSCs (SCI induction, followed by injection of 3 × 10⁶ BMMSCs at the injury site), and BMMSCs + VC (SCI induction, followed by BMMSCs injection and VC administration as the former). Locomotor recovery was assessed using the Basso Mouse Scale. Injured spinal cord tissue was evaluated using hematoxylin-eosin staining and immunohistochemical staining. Expression of transforming growth factor-beta, tumor necrosis factor-alpha, and matrix metalloproteinase-2 genes was determined using real-time quantitative PCR. BMMSCs intervention better promoted recovery of nerve function of rats with SCI, mitigated nerve cell damage, and decreased expression of transforming growth factor-beta, tumor necrosis factor-alpha, and matrix metalloproteinase-2 genes than MP and/or VC. More importantly, BMMSCs in combination with VC induced more obvious improvements. These results suggest that VC can enhance the neuroprotective effects of BMMSCs against SCI.

Thermo-sensitive hydrogels combined with decellularised matrix deliver bFGF for the functional recovery of rats after a spinal cord injury

Because of the short half-life, either systemic or local administration of bFGF shows significant drawbacks to spinal injury. In this study, an acellular spinal cord scaffold (ASC) was encapsulated in a thermo-sensitive hydrogel to overcome these limitations. The ASC was firstly prepared from the spinal cord of healthy rats and characterized by scanning electronic microscopy and immunohistochemical staining. bFGF could specifically complex with the ASC scaffold via electrostatic or receptor-mediated interactions. The bFGF-ASC complex was further encapsulated into a heparin modified poloxamer (HP) solution to prepare atemperature-sensitive hydrogel (bFGF-ASC-HP). bFGF release from the ASC-HP hydrogel was more slower than that from the bFGF-ASC complex alone. An in vitro cell survival study showed that the bFGF-ASC-HP hydrogel could more effectively promote the proliferation of PC12 cells than a bFGF solution, with an approximate 50% increase in the cell survival rate within 24 h (P < 0.05). Compared with the bFGF solution, bFGF-ASC-HP hydrogel displayed enhanced inhibition of glial scars and obviously improved the functional recovery of the SCI model rat through regeneration of nerve axons and the differentiation of the neural stem cells. In summary, an ASC-HP hydrogel might be a promising carrier to deliver bFGF to an injured spinal cord.

Neuronal regeneration after acute spinal cord injury in adult rats

BACKGROUND CONTEXT

The most common causes of spinal cord injury (SCI) are traumatic traffic accidents, falls, and violence. Spinal cord injury greatly affects a patient's mental and physical conditions and causes substantial economic impact to society. There are many methods, such as high doses of corticosteroids, surgical stabilization, decompression, and stem cell transplantation, for functional recovery after SCI, but the effect is still not satisfactory.

PURPOSE

This study investigated the role of neuronal regeneration and the location of the neuronal regeneration after SCI in rats.

STUDY DESIGN

This is an experimental animal study of acute spinal cord injury investigating the neuronal regeneration after SCI. Double immunofluorescence staining of NF-200 and BrdU was performed to detect the location of the neuronal regeneration.

METHODS

Forty-five adult Wistar rats were tested. Allen hit model (10 g) induced acute SCI sites targeted at the T10 segments. Nestin expression was detected via immunohistochemistry. Double immunofluorescence staining of neurofilament 200 (NF-200) and 5-bromo-2'-deoxyuridine (BrdU) was performed 10 mm away from the spinal cord center. Neural functional recovery was determined using the Basso, Beattie, and Bresnahan (BBB) score and electro-physiological examination. The study was funded by the Natural Science Foundation of China (NSFC, 81272172). The funder of this study had no capacity to influence the scholarly conduct of the research, interpretation of results, or dissemination of study outcomes.

RESULTS

BrdU- and NF-200-positive cells were rarely detected and absent at 3 weeks and 4 weeks, respectively. We also detected the BrdU and NF-200 co-expressed cells are at 3 to 5 mm away from the injured site, and no co-expressed cells were detected at the injured site in this SCI model. The BBB score and electro-physiological examination of the nervous system were significantly different at 4 weeks.

CONCLUSIONS

To our knowledge, this is the first study to demonstrate that neurons are regenerated 3 to 5 mm away from the injured site, and no neurons are regenerated at the injured site in this SCI model, which suggests a novel train of thought on SCI treatment.

"Targeting astrocytes in CNS injury and disease: A translational research approach"

Astrocytes are a major constituent of the central nervous system. These glia play a major role in regulating blood-brain barrier function, the formation and maintenance of synapses, glutamate uptake, and trophic support for surrounding neurons and glia. Therefore, maintaining the proper functioning of these cells is crucial to survival. Astrocyte defects are associated with a wide variety of neuropathological insults, ranging from neurodegenerative diseases to gliomas. Additionally, injury to the CNS causes drastic changes to astrocytes, often leading to a phenomenon known as reactive astrogliosis. This process is important for protecting the surrounding healthy tissue from the spread of injury, while it also inhibits axonal regeneration and plasticity. Here, we discuss the important roles of astrocytes after injury and in disease, as well as potential therapeutic approaches to restore proper astrocyte functioning.

Temporal Response of Endogenous Neural Progenitor Cells Following Injury to the Adult Rat Spinal Cord

A pool of endogenous neural progenitor cells (NPCs) found in the ependymal layer and the sub-ependymal area of the spinal cord are reported to upregulate Nestin in response to traumatic spinal cord injury (SCI). These cells could potentially be manipulated within a critical time period offering an innovative approach to the repair of SCI. However, little is known about the temporal response of endogenous NPCs following SCI. This study used a mild contusion injury in rat spinal cord and immunohistochemistry to determine the temporal response of ependymal NPCs following injury and their correlation to astrocyte activation at the lesion edge. The results from the study demonstrated that Nestin staining intensity at the central canal peaked at 24 h post-injury and then gradually declined over time. Reactive astrocytes double labeled by Nestin and glial fibrillary acidic protein (GFAP) were found at the lesion edge and commenced to form the glial scar from 1 week after injury. We conclude that the critical time period for manipulating endogenous NPCs following a spinal cod injury in rats is between 24 h when Nestin expression in ependymal cells is increased and 1 week when astrocytes are activated in large numbers.

Substance P stimulates proliferation of spinal neural stem cells in spinal cord injury via the mitogen-activated protein kinase signaling pathway

BACKGROUND CONTEXT

Substance P (SP) is a neuropeptide that can influence neural stem/progenitor cell (NSPC) proliferation and neurogenesis in the brain. However, we could not find any experimental study that investigates SP action in the spinal cord.

PURPOSE

The aims of our study were to investigate the potential of the neuropeptide SP in promoting the proliferation of spinal cord-derived NSPCs (SC-NSPCs) after spinal cord injury (SCI) and to clarify the roles of the mitogen-activated protein (MAP) kinase signaling pathway in the process.

STUDY DESIGN

This is a randomized animal study.

METHODS

The SC-NSPCs were suspended in 100 μL of a neurobasal medium containing SP (binds neurokinin-1 receptor [NK1R]) or L-703,606 (NK1R antagonist) and cultured in a 96-well plate for 5 days. A cell proliferation assay was performed using a 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay. A cord clipping method was used for the SCI model. Substance P and the NK1R antagonist (L-703,606) were infused intrathecally in SCI and sham models. Neural stem/progenitor cell proliferation was evaluated with immunostaining for bromodeoxyuridine (BrdU) and the immature neural marker nestin. An immunoblotting method was used for evaluating the MAP kinase signaling protein that contains extracellular signal-regulated kinases (ERKs and p38) and β-actin as the control group.

RESULTS

In vitro, SP (0.01-10 μmol/L) increased the proliferation of cultured SC-NSPCs, with a peak increase of 35±2% at the 0.1 μmol/L concentration. Substance P of 0.1 μmol/L continuously increased SC-NSPC proliferation from 6 hours to 5 days, whereas the proliferation decreased from 18% to 98% with L-703,606 (1-10 μM). Intrathecal infusion of SP (1 μmol/L) for 7 days significantly increased the number of proliferating NPSCs (cells positive for both BrdU and nestin) in the spinal cord (by 120±17%, p<.05) in adult rats, but infusion of L-703,606 (10 μmol/L) significantly decreased the post-SCI induction of NPSC proliferation in the spinal cord (by 87±4%). Also, SP stimulates proliferation of SC-NSPCs via the MAP kinase signaling pathway, especially the phosphorylated ERK and phosphorylated p38 proteins. The phosphorylated ERK and phosphorylated p38 protein levels increased with SP (0.1 μmol/L, p<.05).

CONCLUSIONS

These data indicate that SP can promote proliferation of SC-NSPCs in SCI and normal conditions and have important roles in neuronal regeneration after SCI. Also, ERKs and p38 MAP kinases are important signaling proteins in this process.

Roles of microglia in brain development, tissue maintenance and repair

The emerging roles of microglia are currently being investigated in the healthy and diseased brain with a growing interest in their diverse functions. In recent years, it has been demonstrated that microglia are not only immunocentric, but also neurobiological and can impact neural development and the maintenance of neuronal cell function in both healthy and pathological contexts. In the disease context, there is widespread consensus that microglia are dynamic cells with a potential to contribute to both central nervous system damage and repair. Indeed, a number of studies have found that microenvironmental conditions can selectively modify unique microglia phenotypes and functions. One novel mechanism that has garnered interest involves the regulation of microglial function by microRNAs, which has therapeutic implications such as enhancing microglia-mediated suppression of brain injury and promoting repair following inflammatory injury. Furthermore, recently published articles have identified molecular signatures of myeloid cells, suggesting that microglia are a distinct cell population compared to other cells of myeloid lineage that access the central nervous system under pathological conditions. Thus, new opportunities exist to help distinguish microglia in the brain and permit the study of their unique functions in health and disease.

Neurogenic potential of spinal cord organotypic culture

There are several neurogenic niches in the adult mammalian central nervous system. In the central nervous system, neural stem cells (NSC) localize not only to the periventricular area, but are also diffusely distributed in the parenchyma. Here, we assessed neurogenic potential of organotypic cultures prepared from adult mouse spinal cord. Slices were placed on Millipore inserts for organotypic culture and incubated in neurobasal media supplemented with B27 and N2 for up to 9 weeks. After 3-4 weeks, the cell's aggregates formed in the slices. The aggregate's cells were BrdU-uptake, nestin and alkaline phosphatase positive. At the later stage of incubation, we observed Oct3/4 in the inner mass of the neurospheres as well as expression of Dppa1, which is an Oct-4 downstream target gene and a marker for pluripotency. To check differentiation, the formed neurospheres were isolated and cultured for several days in differentiation media. The obtained data demonstrated the cells from isolated neurospheres differentiate into astrocytes and MAP2-positive neurons. Immunostaining for HB9 and Lim2 revealed subsequent differentiation of MAP2-positive cells into motor neurons and interneurons, respectively. We hypothesized neuronal loss and/or long-term culturing of spinal cord slices may trigger a reset of the internal cell program and promote proliferation and further differentiation of NSC.

Cell transcriptional state alters genomic patterns of DNA double-strand break repair in human astrocytes

The misrepair of DNA double-strand breaks in close spatial proximity within the nucleus can result in chromosomal rearrangements that are important in the pathogenesis of haematopoietic and solid malignancies. It is unknown why certain epigenetic states, such as those found in stem or progenitor cells, appear to facilitate neoplastic transformation. Here we show that altering the transcriptional state of human astrocytes alters patterns of DNA damage repair from ionizing radiation at a gene locus-specific and genome-wide level. Astrocytes induced into a reactive state exhibit increased DNA repair, compared with non-reactive cells, in actively transcribed chromatin after irradiation. In mapping these repair sites, we identify misrepair events and repair hotspots that are unique to each state. The precise characterization of genomic regions susceptible to mutation in specific transcriptional states provides new opportunities for addressing clonal evolution in solid cancers, in particular those where double-strand break induction is a cornerstone of clinical intervention.

Astrocyte transplantation for spinal cord injury: current status and perspective

Spinal cord injury (SCI) often causes incurable neurological dysfunction because axonal regeneration in adult spinal cord is rare. Astrocytes are gradually recognized as being necessary for the regeneration after SCI as they promote axonal growth under both physiological and pathophysiological conditions. Heterogeneous populations of astrocytes have been explored for structural and functional restoration. The results range from the early variable and modest effects of immature astrocyte transplantation to the later significant, but controversial, outcomes of glial-restricted precursor (GRP)-derived astrocyte (GDA) transplantation. However, the traditional neuron-centric view and the concerns about the inhibitory roles of astrocytes after SCI, along with the sporadic studies and the lack of a comprehensive review, have led to some confusion over the usefulness of astrocytes in SCI. It is the purpose of the review to discuss the current status of astrocyte transplantation for SCI based on a dialectical view of the context-dependent manner of astrocyte behavior and the time-associated characteristics of glial scarring. Critical issues are then analyzed to reveal the potential direction of future research.

A spatiotemporal study of gliosis in relation to depth electrode tracks in drug-resistant epilepsy

Key questions remain regarding the processes governing gliogenesis following central nervous system injury that are critical to understanding both beneficial brain repair mechanisms and any long-term detrimental effects, including increased risk of seizures. We have used cortical injury produced by intracranial electrodes (ICEs) to study the time-course and localization of gliosis and gliogenesis in surgically resected human brain tissue. Seventeen cases with ICE injuries of 4–301 days age were selected. Double-labelled immunolabelling using a proliferative cell marker (MCM2), markers of fate-specific transcriptional factors (PAX6, SOX2), a microglial marker (IBA1) and glial markers (nestin, GFAP) was quantified in three regions: zone 1 (immediate vicinity: 0–350 μm), zone 2 (350–700 μm) and zone 3 (remote ≥2000 μm) in relation to the ICE injury site. Microglial/macrophage cell densities peaked at 28–30 days post-injury (dpi) with a significant decline in proliferating microglia with dpi in all zones. Nestin-expressing cells (NECs) were concentrated in zones 1 and 2, showed the highest regenerative capacity (MCM2 and PAX6 co-expression) and were intimately associated with capillaries within the organizing injury cavity. There was a significant decline in nestin/MCM2 co-expressing cells with dpi in zones 1 and 2. Nestin-positive fibres remained in the chronic scar, and NECs with neuronal morphology were noted in older injuries. GFAP-expressing glia were more evenly distributed between zones, with no significant decline in density or proliferative capacity with dpi. Colocalization between nestin and GFAP in zone 1 glial cells decreased with increasing dpi. In conclusion, NECs at acute injury sites are a proliferative, transient cell population with capacity for maturation into astrocytes with possible neuronal differentiation observed in older injuries.

Valproic Acid increases expression of neuronal stem/progenitor cell in spinal cord injury

Objective

This study investigates the effect of valproic acid (VPA) on expression of neural stem/progenitor cells (NSPCs) in a rat spinal cord injury (SCI) model.

Methods

Adult male rats (n=24) were randomly and blindly allocated into three groups. Laminectomy at T9 was performed in all three groups. In group 1 (sham), only laminectomy was performed. In group 2 (SCI-VPA), the animals received a dose of 200 mg/kg of VPA. In group 3 (SCI-saline), animals received 1.0 mL of the saline vehicle solution. A modified aneurysm clip with a closing force of 30 grams was applied extradurally around the spinal cord at T9, and then rapidly released with cord compression persisting for 2 minutes. The rats were sacrificed and the spinal cord were collected one week after SCI. Immunohistochemistry (IHC) and western blotting sample were obtained from 5 mm rostral region to the lesion and prepared. We analyzed the nestin immunoreactivity from the white matter of ventral cord and the ependyma of central canal. Nestin and SOX2 were used for markers for NSPCs and analyzed by IHC and western blotting, respectively.

Results

Nestin and SOX2 were expressed significantly in the SCI groups but not in the sham group. Comparing SCI groups, nestin and SOX2 expression were much stronger in SCI-VPA group than in SCI-saline group.

Conclusion

Nestin and SOX2 as markers for NSPCs showed increased expression in SCI-VPA group in comparison with SCI-saline group. This result suggests VPA increases expression of spinal NSPCs in SCI.

Biciliated ependymal cell proliferation contributes to spinal cord growth

Two neurogenic regions have been described in the adult brain, the lateral ventricle subventricular zone and the dentate gyrus subgranular zone. It has been suggested that neural stem cells also line the central canal of the adult spinal cord. Using transmission and scanning electron microscopy and immunostaining, we describe here the organization and cell types of the central canal epithelium in adult mice. The identity of dividing cells was determined by 3D ultrastructural reconstructions of [(3) H]thymidine-labeled cells and confocal analysis of bromodeoxyuridine labeling. The most common cell type lining the central canal had two long motile (9+2) cilia and was vimentin+, CD24+, FoxJ1+, Sox2+, and CD133+, but nestin- and glial fibrillary acidic protein (GFAP)-. These biciliated ependymal cells of the central canal (Ecc) resembled E2 cells of the lateral ventricles, but their basal bodies were different from those of E2 or E1 cells. Interestingly, we frequently found Ecc cells with two nuclei and four cilia, suggesting they are formed by incomplete cytokinesis or cell fusion. GFAP+ astrocytes with a single cilium and an orthogonally oriented centriole were also observed. The majority of dividing cells corresponded to biciliated Ecc cells. Central canal proliferation was most common during the active period of spinal cord growth. Pairs of labeled Ecc cells were observed within the central canal in adult mice 2.5 weeks post labeling. Our work suggests that the vast majority of postnatal dividing cells in the central canal are Ecc cells and their proliferation is associated with the growth of the spinal cord.

Concise review: the potential of stromal cell-derived factor 1 and its receptors to promote stem cell functions in spinal cord repair

Transplanted stem cells provide beneficial effects on regeneration/recovery after spinal cord injury (SCI) by the release of growth-promoting factors, increased tissue preservation, and provision of a permissive environment for axon regeneration. A rise in chemokine stromal cell-derived factor 1 (SDF-1/CXCL12) expression levels in central nervous system (CNS) injury sites has been shown to play a central role in recruiting transplanted stem cells. Although technically more challenging, it has been shown that after SCI few endogenous stem cells are recruited via SDF-1/CXCR4 signaling. Evidence is accumulating that increasing SDF-1 levels at the injury site (e.g., by exogenous application or transfection methods) further enhances stem cell recruitment. Moreover, SDF-1 might, in addition to migration, also influence survival, proliferation, differentiation, and cytokine secretion of stem cells. Here, we discuss the experimental data available on the role of SDF-1 in stem and progenitor cell biology following CNS injury and suggest strategies for how manipulation of the SDF-1 system could facilitate stem cell-based therapeutic approaches in SCI. In addition, we discuss challenges such as how to circumvent off-target effects in order to facilitate the transfer of SDF-1 to the clinic.

Nestin- and doublecortin-positive cells reside in adult spinal cord meninges and participate in injury-induced parenchymal reaction

Adult spinal cord has little regenerative potential, thus limiting patient recovery following injury. In this study, we describe a new population of cells resident in the adult rat spinal cord meninges that express the neural stem/precursor markers nestin and doublecortin. Furthermore, from dissociated meningeal tissue a neural stem cell population was cultured in vitro and subsequently shown to differentiate into functional neurons or mature oligodendrocytes. Proliferation rate and number of nestin- and doublecortin-positive cells increased in vivo in meninges following spinal cord injury. By using a lentivirus-labeling approach, we show that meningeal cells, including nestin- and doublecortin-positive cells, migrate in the spinal cord parenchyma and contribute to the glial scar formation. Our data emphasize the multiple roles of meninges in the reaction of the parenchyma to trauma and indicate for the first time that spinal cord meninges are potential niches harboring stem/precursor cells that can be activated by injury. Meninges may be considered as a new source of adult stem/precursor cells to be further tested for use in regenerative medicine applied to neurological disorders, including repair from spinal cord injury. Stem Cells 2011;29:2062–2076.

Increased expression of nestin in the major pelvic ganglion following cavernous nerve injury

In an effort to identify neuronal repair mechanisms of the major pelvic ganglion (MPG), we evaluated changes in the expression of nestin, an intermediate filament protein and neural stem cell marker following cavernous nerve crush injury (CNI). We utilized two groups of Sprague Dawley rats: (i) sham and (ii) bilateral CNI. Erectile responses to cavernous nerve stimulation (CNS) were determined at 48 h in a subset of rats. The MPG was isolated and removed at 48 h after CNI, and nestin immunolocalization, protein levels and RNA expression were evaluated. At 48 h, erectile responses to CNS in CNI rats were substantially reduced (P<0.05; ∼70% decrease in intracavernous pressure/mean arterial pressure) compared with sham surgery controls. This coincided with a dramatic 10-fold increase (P<0.05) in nestin messenger RNA expression and protein levels in the MPG of rats with CNI. Immunoflourescence microscopy demonstrated that nestin upregulation after CNI occurred within the ganglion cell bodies and nerve fibers of the MPG. In conclusion, CNI induces nestin in the MPG. These data suggest that nestin may be involved in the regenerative process of the cavernous nerve following crush injury.

Clinical and pathological effects of intrathecal injection of mesenchymal stem cell-derived neural progenitors in an experimental model of multiple sclerosis

Multiple sclerosis (MS) is associated with irreversible disability in a significant proportion of patients. At present, there is no treatment to halt or reverse the progression of established disability. In an effort to develop cell therapy-based strategies for progressive MS, we investigated the pre-clinical efficacy of bone marrow mesenchymal stem cell-derived neural progenitors (MSC-NPs) as an autologous source of stem cells. MSC-NPs consist of a subpopulation of bone marrow MSCs with neural progenitor and immunoregulatory properties, and a reduced capacity for mesodermal differentiation, suggesting that this cell population may be appropriate for clinical application in the CNS. We investigated whether MSC-NPs could promote repair and recovery after intrathecal injection into mice with EAE. Multiple injections of MSC-NPs starting at the onset of the chronic phase of disease improved neurological function compared to controls, whereas a single injection had no effect on disease scores. Intrathecal injection of MSC-NPs correlated with reduced immune cell infiltration, reduced area of demyelination, and increased number of endogenous nestin-positive progenitor cells in EAE mice. These observations suggest that MSC-NPs may influence the rate of repair through effects on endogenous progenitors in the spinal cord. This study supports the use of autologous MSC-NPs in MS patients as a means of promoting CNS repair.

Insights into intermediate filament regulation from development to ageing

Intermediate filament (IF) proteins comprise a large family with more than 70 members. Initially, IFs were assumed to provide only structural reinforcement for the cell. However, IFs are now known to be dynamic structures that are involved in a wide range of cellular processes during all stages of life, from development to ageing, and during homeostasis and stress. This Commentary discusses some lesser-known functional and regulatory aspects of IFs. We specifically address the emerging roles of nestin in myogenesis and cancer cell migration, and examine exciting evidence on the regulation of nestin and lamin A by the notch signalling pathway, which could have repercussions for our understanding of the roles of IF proteins in development and ageing. In addition, we discuss the modulation of the post-translational modifications of neuronally expressed IFs and their protein-protein interactions, as well as IF glycosylation, which not only has a role in stress and ageing, but might also regulate IFs during development. Although many of these recent findings are still preliminary, they nevertheless open new doors to explore the functionality of the IF family of proteins.

Blood-brain barrier modeling with co-cultured neural progenitor cell-derived astrocytes and neurons

In vitro blood-brain barrier (BBB) models often consist of brain microvascular endothelial cells (BMECs) that are co-cultured with other cells of the neurovascular unit, such as astrocytes and neurons, to enhance BBB properties. Obtaining primary astrocytes and neurons for co-culture models can be laborious, while yield and heterogeneity of primary isolations can also be limiting. Neural progenitor cells (NPCs), because of their self-renewal capacity and ability to reproducibly differentiate into tunable mixtures of neurons and astrocytes, represent a facile, readily scalable alternative. To this end, differentiated rat NPCs were co-cultured with rat BMECs and shown to induce BBB properties such as elevated trans-endothelial electrical resistance, improved tight junction continuity, polarized p-glycoprotein efflux, and low passive permeability at levels indistinguishable from those induced by primary rat astrocyte co-culture. An NPC differentiation time of 12 days, with the presence of 10% fetal bovine serum, was found to be crucial for generating NPC-derived progeny capable of inducing the optimal response. This approach could also be extended to human NPC-derived astrocytes and neurons which similarly regulated BBB induction. The distribution of rat or human NPC-derived progeny under these conditions was found to be a roughly 3 : 1 mixture of astrocytes to neurons with varying degrees of cellular maturity. BMEC gene expression analysis was conducted using a BBB gene panel, and it was determined that 23 of 26 genes were similarly regulated by either differentiated rat NPC or rat astrocyte co-culture while three genes were differentially altered by the rat NPC-derived progeny. Taken together, these results demonstrate that NPCs are an attractive alternative to primary neural cells for use in BBB co-culture models.

Adult spinal cord radial glia display a unique progenitor phenotype

Radial glia (RG) are primarily embryonic neuroglial progenitors that express Brain Lipid Binding Protein (Blbp a.k.a. Fabp7) and Glial Fibrillary Acidic Protein (Gfap). We used these transcripts to demarcate the distribution of spinal cord radial glia (SCRG) and screen for SCRG gene expression in the Allen Spinal Cord Atlas (ASCA). We reveal that neonatal and adult SCRG are anchored in a non-ventricular niche at the spinal cord (SC) pial boundary, and express a “signature” subset of 122 genes, many of which are shared with “classic” neural stem cells (NSCs) of the subventricular zone (SVZ) and SC central canal (CC). A core expressed gene set shared between SCRG and progenitors of the SVZ and CC is particularly enriched in genes associated with human disease. Visualizing SCRG in a Fabp7-EGFP reporter mouse reveals an extensive population of SCRG that extend processes around the SC boundary and inwardly (through) the SC white matter (WM), whose abundance increases in a gradient from cervical to lumbar SC. Confocal analysis of multiple NSC-enriched proteins reveals that postnatal SCRG are a discrete and heterogeneous potential progenitor population that become activated by multiple SC lesions, and that CC progenitors are also more heterogeneous than previously appreciated. Gene ontology analysis highlights potentially unique regulatory pathways that may be further manipulated in SCRG to enhance repair in the context of injury and SC disease.

In vivo stem cell tracking in neurodegenerative therapies

INTRODUCTION

Cell transplants to replace cells lost due to injury or degenerative diseases, for which there are currently no cures, are being pursued in a wide range of experimental models. Thus, the application of stem cell-based therapies to treat neurodegenerative and traumatic injuries is now a clinical reality. However, the monitoring of cellular grafts, non-invasively, is an important aspect of the ongoing efficacy and safety assessment of cell-based therapies. Hence, there is a need for non-invasive imaging techniques to ensure that transplants are not only administered to the relevant site, but also allow the monitoring of inappropriate cellular migration to improve our understanding of stem cell migration in the context of the whole organism.

AREAS COVERED

This review provides an up to date overview of molecular imaging approaches that have been used for visualizing and tracking transplanted stem cells, in vivo.

EXPERT OPINION

It's important to emphasize that the application of molecular imaging to interrogate transplanted cells may require one or even two imaging modalities to provide a reasonable assessment of transplanted cells in specific organs.

Defective glial maturation in vanishing white matter disease

Vanishing white matter (VWM) disease is a genetic leukoencephalopathy linked to mutations in the eukaryotic translation initiation factor 2B. It is a disease of infants, children, and adults who experience a slowly progressive neurologic deterioration with episodes of rapid clinical worsening triggered by stress and eventually leading to death. Characteristic neuropathologic findings include cystic degeneration of the white matter with scarce reactive gliosis, dysmorphic astrocytes, and paucity of myelin despite an increase in oligodendrocytic density. To assess whether a defective maturation of macroglia may be responsible for the feeble gliosis and lack of myelin, weinvestigated the maturation status of astrocytes and oligodendrocytes in the brains of 8 VWM patients, 4 patients with other white matter disorders and 6 age-matched controls with a combination of immunocytochemistry, histochemistry, scratch-wound assays, Western blot, and quantitative polymerase chain reaction. We observed increased proliferation and a defect in the maturation of VWM astrocytes. They show an anomalous composition of their intermediate filament network with predominance of the δ-isoform of the glial fibrillary acidic protein and an increase in the heat shock protein αB-crystallin, supporting the possibility that a deficiency in astrocyte function may contribute to the loss of white matter in VWM. We also demonstrated a significant increase in numbers of premyelinating oligodendrocyte progenitors in VWM, which may explain the coexistence of oligodendrocytosis and myelin paucity in the patients' white matter.

Reaction of endogenous progenitor cells in a rat model of posttraumatic syringomyelia

OBJECT

Endogenous stem cells theoretically could replace lost tissue and repair deficits caused by syringes. In this study the authors quantitatively examined 1) whether neural progenitor cells exist in an adult rat model of posttraumatic syringomyelia (PTS); 2) and if so, how long an active population of progenitor cells can persist; 3) whether the cell population's location is associated with the syrinx; 4) the degree of differentiation of the progenitor cells; and 5) the phenotypic fate of the progenitor cells.

METHODS

Wistar rats were divided into intact, sham-operated, and experimental syrinx groups. Animals in each group were equally subdivided according to 4 time points: 7, 14, 28, and 56 days post-syrinx induction. Rats in the experimental syrinx group underwent a C-7 and T-1 laminectomy and then received 0.5 μl of a 24-mg/ml quisqualic acid spinal cord injection at the C-8 level to mimic an excitotoxic injury with an initial cyst, and 10 μl of a 250-mg/ml kaolin injection into the subarachnoid space at the C-8 level to create arachnoiditis. The proliferation, distribution, and differentiation of endogenous progenitor cells were identified immunocytochemically.

RESULTS

The authors observed a 20-fold increase in progenitor cells excluding inflammatory cells in the 1st 2 weeks post-syrinx induction. The cells persisted for at least 56 days, and 80% of them were located in the gray matter along the border of cysts. They included neural multipotential progenitor cells, oligodendroglial progenitor cells, and astrocytes.

CONCLUSIONS

Data in this study provide evidence for proliferation, distribution, and differentiation of endogenous progenitor cells in a model of PTS in adult rats. These progenitor cells proliferate rapidly, extend for long periods, and are mainly located in the gray matter along the border of syringes. Neural multipotential progenitor cells are expected to be associated with reparative and regenerative mechanisms of PTS. Glial cells are involved in the formation of a glial scar barrier that surrounds the syrinx and may prevent cyst enlargement. The authors' findings suggest that neural progenitor cells play a protective role in PTS.

Deciphering the oligodendrogenic program of neural progenitors: cell intrinsic and extrinsic regulators

In the developing and adult CNS, neural stem/progenitor cells (NSPCs) and oligodendroglial progenitor cells (OPCs) follow an oligodendrogenic process with the aim of myelinating axons. This process is to a high degree regulated by an oligodendrogenic program (OPr) composed of intrinsic and extrinsic factors that modulate the different steps required for NSPCs to differentiate into myelinating oligodendrocytes. Even though NSPCs and OPCs are present in the diseased CNS and have the capacity to generate oligodendrocytes, sparse remyelination of axons constitutes a major constraint in therapies toward multiple sclerosis (MS) and spinal cord injury (SCI). Lack of pro-oligodendrogenic factors and presence of anti-oligodendrogenic activities are thought to be the main reasons for this limitation. Thus, molecular and cellular strategies aiming at remyelination and at targeting such pro- and anti-oligodendrogenic mechanisms are currently under investigation. The present review summarizes the current knowledge on the OPr; it implements our own findings on mesenchymal stem cell-derived pro-oligodendroglial factors and on the role of p57/kip2 in oligodendroglial differentiation. Moreover, it describes molecular and cellular approaches for the development of future therapies toward remyelination.

Inducible expression of stem cell associated intermediate filament nestin reveals an important role in glioblastoma carcinogenesis

The intermediate filament nestin is transiently expressed in neural stem/progenitor cells during the development of central nervous system. Recently, increasing evidence has shown that upregulation of nestin is related to malignancy of several cancers, especially glioblastoma. However, the function of nestin in carcinogenesis remains unclear. In this study, we investigated the role of nestin in glioblastoma carcinogenesis by comparing subclones of rat C6 glioblastoma cells that were either high or low for nestin expression. We found that while nestin expression did not influence the in vitro proliferation of glioblastoma cells, subclones characterized by high levels of nestin formed tumors in vivo at significantly faster rates than subclones with low expression. Importantly, C6 subclones that expressed nestin at low levels in vitro were also found to give rise to tumors highly positive for the protein, suggesting that induction of nestin plays an important role in glioblastoma carcinogenesis. Derivation of nestin positive tumors from nestin negative human U87 glioblastoma cells in immunodeficient mice further confirmed that a switch to positive expression of nestin is fundamental to the course of glioblastoma development. Blocking the expression of nestin in glioblastoma tumors via intratumor injection of shRNA significantly slowed tumor growth and volume. These results demonstrated that nestin plays a crucial role in development of glioblastoma and may potentially be targeted for treatment of the disease.

Chemokine expression in the white matter spinal cord precursor niche after force-defined spinal cord contusion injuries in adult rats

Inflammatory cascades induced by spinal cord injuries (SCI) are localized in the white matter, a recognized neural stem- and progenitor-cell (NSPC) niche of the adult spinal cord. Chemokines, as integrators of these processes, might also be important determinants of this NSPC niche. CCL3/CCR1, CCL2/CCR2, and SDF-1alpha/CXCR4 were analyzed in the ventrolateral white matter after force defined thoracic SCI: Immunoreactivity (IR) density levels were measured 2 d, 7 d, 14 d, and 42 d on cervical (C 5), thoracic (T 5), and lumbar (L 5) levels. On day post operation (DPO) 42, chemokine inductions were further evaluated by real-time RT-PCR and Western blot analyses. Cellular phenotypes were confirmed by double labeling with markers for major cell types and NSPCs (nestin, Musashi-1, NG2, 3CB2, BLBP). Mitotic profiles were investigated in parallel by BrdU labeling. After lesion, chemokines were induced in the ventrolateral white matter on IR-, mRNA-, and protein-level. IR was generally more pronounced after severe lesions, with soaring increases of CCL2/CCR2 and continuous elevations of CCL3/CCR1. SDF-1alpha and CXCR4 IR induction was focused on thoracic levels. Chemokines/-receptors were co-expressed with astroglial, oligodendroglial markers, nestin, 3CB2 and BLBP by cells morphologically resembling radial glia on DPO 7 to DPO 42, and NG2 or Musashi-1 on DPO 2 and 7. In the white matter BrdU positive cells were significantly elevated after lesion compared with sham controls on all investigated time points peaking in the early time course on thoracic level: Here, chemokines were co-expressed by subsets of BrdU-labeled cells. These findings suggest an important role of chemokines/-receptors in the subpial white matter NSPC niche after SCI.

Nestin action during insulin-secreting cell differentiation

Nestin, which was initially identified as a marker of neural stem cells, has been reported in regenerating pancreas as well as in early embryonic stem (ES) cell derivatives. However, little is known about its specific roles in stem cells as a functional regulator. We investigated the source of the action of nestin in ES and adult pancreatic ductal stem (PDS) cells in regard to the neogenesis of insulin-secreting beta-cells. In ES cells, suppression of nestin by gene silencing led to an increased expression of the pluripotency-associated genes, including Oct 4, Nanog, and SSEA-1, before embryoid body (EB) formation, whereas it reduced endodermal and pancreatic transcription factors in EBs. Inhibition of nestin expression in adult PDS cells caused a low expression of pancreatic transcription factors and islet hormones, leading to poor beta-cell development and insulin secretion. These data may indicate not only that nestin is a simple stem cell marker, but also that it constitutes a functional factor at the time of stem cell differentiation. We suggest that nestin plays pivotal roles as an intermediate regulator governing both stemness and differentiation of stem cells in the process of their differentiation into insulin-secreting cells.

DHP-derivative and low oxygen tension effectively induces human adipose stromal cell reprogramming

BACKGROUND AND METHODS

In this study, we utilized a combination of low oxygen tension and a novel anti-oxidant, 4-(3,4-dihydroxy-phenyl)-derivative (DHP-d) to directly induce adipose tissue stromal cells (ATSC) to de-differentiate into more primitive stem cells. De-differentiated ATSCs was overexpress stemness genes, Rex-1, Oct-4, Sox-2, and Nanog. Additionally, demethylation of the regulatory regions of Rex-1, stemnesses, and HIF1alpha and scavenging of reactive oxygen species were finally resulted in an improved stem cell behavior of de-differentiate ATSC (de-ATSC). Proliferation activity of ATSCs after dedifferentiation was induced by REX1, Oct4, and JAK/STAT3 directly or indirectly. De-ATSCs showed increased migration activity that mediated by P38/JUNK and ERK phosphorylation. Moreover, regenerative efficacy of de-ATSC engrafted spinal cord-injured rats and chemical-induced diabetes animals were significantly restored their functions.

CONCLUSIONS/SIGNIFICANCE

Our stem cell remodeling system may provide a good model which would provide insight into the molecular mechanisms underlying ATSC proliferation and transdifferentiation. Also, these multipotent stem cells can be harvested may provide us with a valuable reservoir of primitive and autologous stem cells for use in a broad spectrum of regenerative cell-based disease therapy.

Intermediate filaments take the heat as stress proteins

Intermediate filament (IF) proteins and heat shock proteins (HSPs) are large multimember families that share several features, including protein abundance, significant upregulation in response to a variety of stresses, cytoprotective functions, and the phenocopying of several human diseases after IF protein or HSP mutation. We are now coming to understand that these common elements point to IFs as important cellular stress proteins with some roles akin to those already well-characterized for HSPs. Unique functional roles for IFs include protection from mechanical stress, whereas HSPs are characteristically involved in protein folding and as chaperones. Shared IF and HSP cytoprotective roles include inhibition of apoptosis, organelle homeostasis, and scaffolding. In this report, we review data that corroborate the view that IFs function as highly specialized cytoskeletal stress proteins that promote cellular organization and homeostasis.

Downregulation of thymosin beta4 in neural progenitor grafts promotes spinal cord regeneration

Thymosin beta4 (Tbeta4) is an actin-binding peptide whose expression in developing brain correlates with migration and neurite extension of neurons. Here, we studied the effects of the downregulation of Tbeta4 expression on growth and differentiation of murine neural progenitor cells (NPCs), using an antisense lentiviral vector. In differentiation-promoting medium, we found twice the number of neurons derived from the Tbeta4-antisense-transduced NPCs, which showed enhanced neurite outgrowth accompanied by increased expression of the adhesion complex N-cadherin-beta-catenin and increased ERK activation. Importantly, when the Tbeta4-antisense-transduced NPCs were transplanted in vivo into a mouse model of spinal cord injury, they promoted a significantly greater functional recovery. Locomotory recovery correlated with increased expression of the regeneration-promoting cell adhesion molecule L1 by the grafted Tbeta4-antisense-transduced NPCs. This resulted in an increased number of regenerating axons and in sprouting of serotonergic fibers surrounding and contacting the Tbeta4-antisense-transduced NPCs grafted into the lesion site. In conclusion, our data identify a new role for Tbeta4 in neuronal differentiation of NPCs by regulating fate determination and process outgrowth. Moreover, NPCs with reduced Tbeta4 levels generate an L1-enriched environment in the lesioned spinal cord that favors growth and sprouting of spared host axons and enhances the endogenous tissue-repair processes.

Neural stem cell- and Schwann cell-loaded biodegradable polymer scaffolds support axonal regeneration in the transected spinal cord

Biodegradable polymer scaffolds provide an excellent approach to quantifying critical factors necessary for restoration of function after a transection spinal cord injury. Neural stem cells (NSCs) and Schwann cells (SCs) support axonal regeneration. This study examines the compatibility of NSCs and SCs with the poly-lactic-co-glycolic acid polymer scaffold and quantitatively assesses their potential to promote regeneration after a spinal cord transection injury in rats. NSCs were cultured as neurospheres and characterized by immunostaining for nestin (NSCs), glial fibrillary acidic protein (GFAP) (astrocytes), betaIII-tubulin (immature neurons), oligodendrocyte-4 (immature oligodendrocytes), and myelin oligodendrocyte (mature oligodendrocytes), while SCs were characterized by immunostaining for S-100. Rats with transection injuries received scaffold implants containing NSCs (n=17), SCs (n=17), and no cells (control) (n=8). The degree of axonal regeneration was determined by counting neurofilament-stained axons through the scaffold channels 1 month after transplantation. Serial sectioning through the scaffold channels in NSC- and SC-treated groups revealed the presence of nestin, neurofilament, S-100, and betaIII tubulin-positive cells. GFAP-positive cells were only seen at the spinal cord-scaffold border. There were significantly more axons in the NSC- and SC- treated groups compared to the control group. In conclusion, biodegradable scaffolds with aligned columns seeded with NSCs or SCs facilitate regeneration across the transected spinal cord. Further, these multichannel biodegradable polymer scaffolds effectively serve as platforms for quantitative analysis of axonal regeneration.

Neural stem cells and new neurons in the cerebral cortex of stroke-prone spontaneously hypertensive rats after stroke

Stroke-prone spontaneously hypertensive rats (SHRSP) are the only animal model that suffers from spontaneous cerebral stroke. In this study, we investigated the appearance of neural stem cells (NSCs) and new neurons in the penumbra and the subventricular zone (SVZ) after cerebral stroke in SHRSP. SHRSP before cerebral stroke were intraperitoneally injected with 5-bromo-2'-deoxyuridine (BrdU). SHRSP were divided into acute and chronic phase groups after cerebral stroke. Brain sections from both groups were studied with cell-specific markers such as BrdU, a cell division and proliferation marker, sex-determining region Y-box 2, a marker of NSCs, nestin, an NSC and immature astrocyte marker, doublecortin, an immature new neuron marker, and neuron-specific nuclear protein, a marker of mature neurons. NSCs and new neurons appeared in the penumbra in the early stages after cerebral stroke, and these cells differentiated into mature neurons in the chronic phase. Furthermore, soon after being affected by a cerebral stroke, there were many new neurons and immature cells, which appear to be NSCs, in the ipsilateral SVZ. Immature cells and new neurons from the ipsilateral SVZ might migrate into the penumbra after cerebral stroke, and this is the first report of their observation after a spontaneous cerebral stroke.