Proliferation Of Ependymal Cells Research Articles

Treatment of Syringomyelia Characterized by Focal Dilatation of the Central Canal Using Mesenchymal Stem Cells and Neural Stem Cells.

Syringomyelia is a progressive chronic disease that leads to nerve pain, sensory dissociation, and dyskinesia. Symptoms often do not improve after surgery. Stem cells have been widely explored for the treatment of nervous system diseases due to their immunoregulatory and neural replacement abilities. In this study, we used a rat model of syringomyelia characterized by focal dilatation of the central canal to explore an effective transplantation scheme and evaluate the effect of mesenchymal stem cells and induced neural stem cells for the treatment of syringomyelia. The results showed that cell transplantation could not only promote syrinx shrinkage but also stimulate the proliferation of ependymal cells, and the effect of this result was related to the transplantation location. These reactions appeared only when the cells were transplanted into the cavity. Additionally, we discovered that cell transplantation transformed activated microglia into the M2 phenotype. IGF1-expressing M2 microglia may play a significant role in the repair of nerve pain. Cell transplantation can promote cavity shrinkage and regulate the local inflammatory environment. Moreover, the proliferation of ependymal cells may indicate the activation of endogenous stem cells, which is important for the regeneration and repair of spinal cord injury.

P2X7 receptor activation awakes a dormant stem cell niche in the adult spinal cord.

The ependyma of the spinal cord is a latent stem cell niche that is reactivated by injury, generating new cells that migrate to the lesion site to limit the damage. The mechanisms by which ependymal cells are reactivated after injury remain poorly understood. ATP has been proposed to act as a diffusible "danger signal" to alert about damage and start repair. Indeed, spinal cord injury (SCI) generates an increase in extracellular ATP around the lesion epicenter that lasts for several hours and affects the functional outcome after the damage. The P2X7 receptor (P2X7r) has functional properties (e.g., low sensitivity for ATP, high permeability for Ca2+) that makes it a suitable candidate to act as a detector of tissue damage. Because ependymal cells express functional P2X7r that generate an inward current and regenerative Ca2+ waves, we hypothesize that the P2X7r has a main role in the mechanisms by which progenitor-like cells in the ependyma react to tissue damage. To test this possibility, we simulated the P2X7r activation that occurs after SCI by in vivo intraspinal injection of the selective agonist BzATP nearby the central canal. We found that BzATP rescued ependymal cells from quiescence by triggering a proliferative response similar to that generated by injury. In addition, P2X7r activation by BzATP induced a shift of ependymal cells to a glial fibrillary acidic protein (GFAP) phenotype similar to that induced by injury. However, P2X7r activation did not trigger the migration of ependyma-derived cells as occurs after tissue damage. Injection of BzATP induced the expression of connexin 26 (Cx26) in ependymal cells, an event needed for the proliferative reaction after injury. BzATP did not induce these changes in ependymal cells of P2X7-/- mice supporting a specific action on P2X7r. In vivo blockade of P2X7r with the potent antagonist AZ10606120 reduced significantly the injury-induced proliferation of ependymal cells. Our data indicate that P2X7r has a key role in the "awakening" of the ependymal stem cell niche after injury and suggest purinergic signaling is an interesting target to improve the contribution of endogenous progenitors to repair.

Rspo1 and Rspo3 are required for sensory lineage neural crest formation in mouse embryos.

R-spondins (Rspos) are secreted proteins that modulate Wnt/β-catenin signaling. At the early stages of spinal cord development, Wnts (Wnt1, Wnt3a) and Rspos (Rspo1, Rspo3) are co-expressed in the roof plate, suggesting that Rspos are involved in development of dorsal spinal cord and neural crest cells in cooperation with Wnt ligands. Here, we found that Rspo1 and Rspo3, as well as Wnt1 and Wnt3a, maintained roof-plate-specific expression until late embryonic stages. Rspo1- and Rspo3-double-knock-out (dKO) embryos partially exhibited the phenotype of Wnt1 and Wnt3a dKO embryos. While the number of Ngn2-positive sensory lineage neural crest cells is reduced in Rspo-dKO embryos, development of dorsal spinal cord, including its size and dorso-ventral patterning in early development, elongation of the roof plate, and proliferation of ependymal cells, proceeded normally. Consistent with these slight defects, Wnt/β-catenin signaling was not obviously changed in developing spinal cord of dKO embryos. Our results show that Rspo1 and Rspo3 are dispensable for most developmental processes involving roof plate-derived Wnt ligands, except for specification of a subtype of neural crest cells. Thus, Rspos may modulate Wnt/β-catenin signaling in a context-dependent manner.

Suppression of TGFβR-Smad3 pathway alleviates the syrinx induced by syringomyelia

BackgroundSyringomyelia is a cerebrospinal fluid (CSF) disorder resulted in separation of pain and temperature, dilation of central canal and formation of syrinx in central canal. It is unclear about mechanisms of the dilation and syrinx formation. We aimed to investigate roles of ependymal cells lining central canal on the dilation, trying to reduce syrinx formation in central canal.MethodsWe employed 78 Sprague–Dawley (SD) rats totally with syringomyelia to detect the contribution of ependymal cells to the dilation of central canal. Immunofluorescence was used to examine the activation of ependymal cells in 54 syringomyelia rat models. BrdU was used to indicate the proliferation of ependymal cells through intraperitoneal administration in 6 syringomyelia rat models. 18 rats with syringomyelia were injected with SIS3, an inhibitor of TGFβR-Smad3, and rats injected with DMSO were used as control. Among the 18 rats, 12 rats were used for observation of syrinx following SIS3 or DMSO administration by using magnetic resonance imaging (MRI) on day 14 and day 30 under syringomyelia without decompression. All the data were expressed as mean ± standard deviation (mean ± SD). Differences between groups were compared using the two-tailed Student’s t-test or ANOVA. Differences were considered significant when *p < 0.05.ResultsOur study showed the dilation and protrusions of central canal on day 5 and enlargement from day 14 after syringomyelia induction in rats with activation of ependymal cells lining central canal. Moreover, the ependymal cells contributed to protrusion formation possibly through migration along with central canal. Furthermore, suppression of TGFβR-Smad3 which was crucial for migration reversed the size of syrnix in central canal without treatment of decompression, suggesting TGFβR-Smad3 signal might be key for dilation of central canal and formation of syrinx.ConclusionsThe size of syrinx was decreased after SIS3 administration without decompression. Our study depicted the mechanisms of syrinx formation and suggested TGFβR-Smad3 signal might be key for dilation of central canal and formation of syrinx.

Radial Glia and Neuronal-like Ependymal Cells Are Present within the Spinal Cord of the Trunk (Body) in the Leopard Gecko (Eublepharis macularius).

As is the case for many lizards, leopard geckos (Eublepharis macularius) can self-detach a portion of their tail to escape predation, and then regenerate a replacement complete with a spinal cord. Previous research has shown that endogenous populations of neural stem/progenitor cells (NSPCs) reside within the spinal cord of the original tail. In response to tail loss, these NSPCs are activated and contribute to regeneration. Here, we investigate whether similar populations of NSPCs are found within the spinal cord of the trunk (body). Using a long-duration 5-bromo-2′-deoxyuridine pulse-chase experiment, we determined that a population of cells within the ependymal layer are label-retaining following a 20-week chase. Tail loss does not significantly alter rates of ependymal cell proliferation within the trunk spinal cord. Ependymal cells of the trunk spinal cord express SOX2 and represent at least two distinct cell populations: radial glial-like (glial fibrillary acidic protein- and Vimentin-expressing) cells; and neuronal-like (HuCD-expressing) cells. Taken together, these data demonstrate that NSPCs of the trunk spinal cord closely resemble those of the tail and support the use of the tail spinal cord as a less invasive proxy for body spinal cord injury investigations.

Interleukin-17A regulates ependymal cell proliferation and functional recovery after spinal cord injury in mice

Ependymal cells have been suggested to act as neural stem cells and exert beneficial effects after spinal cord injury (SCI). However, the molecular mechanism underlying ependymal cell regulation after SCI remains unknown. To examine the possible effect of IL-17A on ependymal cell proliferation after SCI, we locally administrated IL-17A neutralizing antibody to the injured spinal cord of a contusion SCI mouse model, and revealed that IL-17A neutralization promoted ependymal cell proliferation, which was paralleled by functional recovery and axonal reorganization of both the corticospinal tract and the raphespinal tract. Further, to test whether ependymal cell-specific manipulation of IL-17A signaling is enough to affect the outcomes of SCI, we generated ependymal cell-specific conditional IL-17RA-knockout mice and analyzed their anatomical and functional response to SCI. As a result, conditional knockout of IL-17RA in ependymal cells enhanced both axonal growth and functional recovery, accompanied by an increase in mRNA expression of neurotrophic factors. Thus, Ependymal cells may enhance the regenerative process partially by secreting neurotrophic factors, and IL-17A stimulation negatively regulates this beneficial effect. Molecular manipulation of ependymal cells might be a viable strategy for improving functional recovery.

High mobility group box 1 promotes the differentiation of spinal ependymal cells into astrocytes rather than neurons.

Spinal ependymal cells are involved in proliferation, differentiation and migration after spinal cord injury (SCI) and represent an endogenous source of repair cells for treating SCI. However, 95% of activated ependymal cells eventually differentiate into astrocytes after SCI and ultimately contribute more than half of the new astrocytes that form glial scars in vivo. The factors that regulate the fate of ependymal cells after SCI remain unclear. High mobility group box 1 (HMGB1) is regarded as an important proinflammatory factor in nerve injury, and recent studies have shown that HMGB1 can regulate the fate of stem cells after injury. In this study, we investigated whether HMGB1 released from reactive astrocytes after SCI regulates the proliferation and differentiation of ependymal cells in vitro. Ependymal cells extracted and cultured from the spinal cord of mice were separately treated with astrocyte culture medium (ACM), IL-1β, ACM (IL-1β) and the HMGB1 protein, and the proliferation and differentiation of ependymal cells were detected. Additionally, an HMGB1-neutralizing antibody (anti-HMGB1) was added to further verify the regulatory effect of HMGB1 on ependymal cells. The results showed that HMGB1 released from reactive astrocytes promoted ependymal cell differentiation into astrocytes and inhibited ependymal cell differentiation into neurons in vitro; however, the effect disappeared after the addition of anti-HMGB1. HMGB1 had no significant effect on ependymal cell proliferation. Our findings demonstrate that HMGB1 can regulate the differentiation of ependymal cells after SCI. These results provide a new strategy for the treatment of SCI.

Intracellular signaling similarity reveals neural stem cell-like properties of ependymal cells in the adult rat spinal cord.

Proliferation of ependymal cells of the adult spinal cord (SCEp cells) in the intact condition has been considered as a quite rare event. To visualize proliferating/proliferated SCEp cells, we used the intensive 5-bromo-2'-deoxyuridine (BrdU) administration method to find that about two cells in the ependymal layer incorporated BrdU in a 10-μm-thick section. Because these two cells were not considered to undergo further proliferation, we analyzed the positioning and motility of two neighboring BrdU-incorporated proliferated cells and elucidated the tendency of the movement of SCEp cells to the outer side inside the ependymal layer. Even if it was rare, one of the proliferated cells in the ependymal layer differentiated into astrocytes. Gene introduction of Notch intracellular domain (NICD), a constitutively active form of Notch1, into SCEp cells demonstrated both increase in proliferation and induction of differentiation into astrocytes. Overexpression of Sox2 promoted proliferation in SCEp cells. The reaction of gene introduction of NICD and Sox2 indicates the similarity of intracellular signaling between SCEp cells and neural stem cells. Also, considering the fact that SCEp cells express these two factors in the intact condition, Notch and Sox2 are important for the cell fate control of SCEp cells in the intact condition.

Wnt/β-catenin signaling regulates ependymal cell development and adult homeostasis

In the adult mouse spinal cord, the ependymal cell population that surrounds the central canal is thought to be a promising source of quiescent stem cells to treat spinal cord injury. Relatively little is known about the cellular origin of ependymal cells during spinal cord development, or the molecular mechanisms that regulate ependymal cells during adult homeostasis. Using genetic lineage tracing based on the Wnt target gene Axin2, we have characterized Wnt-responsive cells during spinal cord development. Our results revealed that Wnt-responsive progenitor cells are restricted to the dorsal midline throughout spinal cord development, which gives rise to dorsal ependymal cells in a spatially restricted pattern. This is contrary to previous reports that suggested an exclusively ventral origin of ependymal cells, suggesting that ependymal cells may retain positional identities in relation to their neural progenitors. Our results further demonstrated that in the postnatal and adult spinal cord, all ependymal cells express the Wnt/β-catenin signaling target gene Axin2, as well as Wnt ligands. Genetic elimination of β-catenin or inhibition of Wnt secretion in Axin2-expressing ependymal cells in vivo both resulted in impaired proliferation, indicating that Wnt/β-catenin signaling promotes ependymal cell proliferation. These results demonstrate the continued importance of Wnt/β-catenin signaling for both ependymal cell formation and regulation. By uncovering the molecular signals underlying the formation and regulation of spinal cord ependymal cells, our findings thus enable further targeting and manipulation of this promising source of quiescent stem cells for therapeutic interventions.

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.

Nestin expression and invivo proliferative potential of tanycytes and ependymal cells lining the walls of the third ventricle in the adult rat brain.

There is a disagreement in the literature concerning the degree of proliferation of cells in the walls of the third ventricle (3rdV) under normal conditions in the adult mammalian brain. To address this issue, we mapped the cells expressing the neural stem/progenitor cell marker nestin along the entire rostrocaudal extent of the 3rdV in adult male rats and observed a complex distribution. Abundant nestin was present in tanycyte cell bodies and processes and also was observed in patches of ependymal cells as well as in isolated ependymal cells throughout the walls of the 3rdV. However, we observed very limited ependymal cell or tanycyte proliferation in normal adult rats as determined by bromodeoxyuridine (BrdU) incorporation or the expression of Ki-67. Moreover, fewer than 13% of the cells that were BrdU-positive (BrdU+) or Ki-67-positive (Ki-67+) expressed nestin. These observations stand in contrast to those made in the subventricular zone of the lateral ventricle (SVZ) and subgranular zone of the hippocampal formation (SGZ), where cell proliferation measured by BrdU incorporation or Ki-67 expression is observed frequently in cells that also express nestin. Thus, while ependymal cell or tanycyte cell proliferation can be promoted by the addition of mitogens, dietary modifications or other invivo manipulations, the proliferation of ependymal cells and tanycytes in the walls of the 3rdV is very limited in the normal adult male rat brain.

Wnts Are Expressed in the Ependymal Region of the Adult Spinal Cord.

The Wnt family of proteins plays key roles during central nervous system development and in several physiological processes during adulthood. Recently, experimental evidence has linked Wnt-related genes to regulation and maintenance of stem cells in the adult neurogenic niches. In the spinal cord, the ependymal cells surrounding the central canal form one of those niches, but little is known about their Wnt expression patterns. Using microdissection followed by TaqMan® low-density arrays, we show here that the ependymal regions of young, mature rats and adult humans express several Wnt-related genes, including ligands, conventional and non-conventional receptors, co-receptors, and soluble inhibitors. We found 13 genes shared between rats and humans, 4 exclusively expressed in rats and 9 expressed only in humans. Also, we observed a reduction with age on spontaneous proliferation of ependymal cells in rats paralleled by a decrease in the expression of Fzd1, Fzd8, and Fzd9. Our results suggest a role for Wnts in the regulation of the adult spinal cord neurogenic niche and provide new data on the specific differences in this region between humans and rodents.

PATHOLOGY IN CHRONIC ENCEPHALITIS OPIUM ADDICTION IN THE DIFFERENTIAL DIAGNOSIS RATIO WITH OTHER FOCAL BRAIN LESIONS

The analysis of morphological studies of the brain in 33 cases of acute poisoning with opiates in 20 cases of stroke at a young age with a fatal outcome. In the first group drug encephalitis was detected in 23.0% of the observed cases. Studies suggest that, along with morphological signs of encephalopathy (ischemia neuronal proliferation of ependymal cells of the ventricles of the brain, perivascular and pericellular edema, etc.) take place with the formation of neuronophagia microglial nodules at the site of nerve cells lysed. There was a special kind of encephalitis in chronic addiction — ventriculitis histologically manifested plethora subependimarnyh vessels ependymal destruction, infiltration of the ventricular wall and the vascular plexus polymorphonuclear leukocytes. In forensic practice there is a need to differentiate drugs ventriculitis with secondary changes in the ventricles of the brain, which are often accompanied by encephalopathy. When forensic histological examination identified some morphological differences opium encephalitis and focal brain lesions, including vascular origin. Also found that in chronic opiate poisoning characterized by morphological changes in the brain that are not a manifestation of sepsis and associated with primary infection of the brain and can be attached to the drug encephalopathy. Particular attention is paid to specific features, informative for determining the pathological changes of the internal elastic membrane of brain vessels. Identify options tanatogenesis encephalitis drugs, including bacterial, viral and fungal etiology, cerebrovascular disease, and demyelinating diseases.

Contribution of purinergic receptors to spinal cord injury repair: stem cell-based neuroregeneration.

Traumatic spinal cord injury (SCI), defined as physical trauma to the spinal column yielding altered motor, sensory, or autonomic function, is a devastating neurological disease causing major impact at both personal and societal level. SCI is characterized by a primary insult (compression, contusion or laceration) followed by a secondary pathological cascade that propagates further injury disrupting motor, sensory and/or autonomic functions. The primary mechanical trauma produces necrosis, edema, hemorrhage and vasospasm. Afterwards, a cascade of secondary pathophysiological mechanisms is induced, including ischemia, apoptosis, fluid and electrolyte disturbances, excitotoxicity, lipid peroxidation, production of free radicals, and an inflammatory response, resulting in further damage due to swelling and blood flow reduction (Tator et al., 2012). Worldwide incidence of SCI is 15–40 cases per million people annually and affects predominantly to young adults. SCI often involves a lifelong disability including paralysis distal to the lesion, loss of sensation, neuropathic pain, and bowel/bladder dysfunction as a result of axonal damage, demyelination, and death of oligodendrocytes, astrocytes, interneurons, and motor neurons. Unfortunately, to date no effective treatment exists for the major neurological deficits of SCI. However, there are several hopeful neuroprotective agents being currently investigated in ongoing preclinical and clinical trials (Tator et al., 2012). The aim of neuroprotective treatments is not only to reduce cell death and reduce mechanisms of secondary injury, but also to promote regeneration and tissue repair. One of these promising therapeutic strategies consists on cell transplantation to replace dead or damaged cells and provide trophic support. In particular, adult neural stem/progenitor cells (NSPCs) are especially attractive to promote tissue repair after SCI, since they can readily expand in vitro to form colonies of undifferentiated cells called neurospheres, and are committed to the neural lineage. Adult NSPCs may have advantages over embryonic or fetal cells: 1) in some cases it will be possible to harvest them in an autologous fashion; 2) they may have less oncogenic potential than embryonic stem cells; and 3) the avoidance of some of the ethical issues surrounding the use of stem cells of embryonic or fetal origin. NSPCs consist primarily of progenitor cells and a small percentage of stem cells. Neural stem cells are multipotent cells that continuously proliferate and divide to self-renew and generate daughter committed to differentiation into neurons, oligodendrocytes, and astrocytes. In contrast, neural progenitor cells are more restricted, with a limited proliferative capacity and differentiation potential (Mothe and Tator, 2012). In the adult brain, NSPCs are found within specific niches including the subventricular zone (SVZ) lining the lateral ventricles of the forebrain and the subgranular layer of the dentate gyrus of the hippocampus (Kriegstein and Alvarez-Buylla, 2009). The periventricular region containing the central canal of the adult spinal cord also contains NSPCs called ependymal progenitor/stem cells (epSPCs), which have the ability to rapidly proliferate, migrate, and differentiate into neurons and glia to regenerate the injured cord in lower vertebrates. In mammals, including humans, proliferation of epSPCs and their progeny is a frequent event during embryonic and early postnatal periods of development. The turnover of epSPCs declines significantly in the postnatal period, but extensive epSPCs proliferation has been observed in response to SCI. SCI induces proliferation of ependymal cells and migration of their progeny towards the site of injury, where they differentiate and give rise mainly to astrocytes as well as myelinating oligodendrocytes (Meletis et al., 2008). Using specific differentiation protocol, 90% of differentiated cultures of epSPCs obtained after SCI stain positive for the motor neuron-specific marker HB9, with 32% of these motor neurons displaying electrophysiological properties that resemble those of functional spinal motor neurons (Moreno-Manzano et al., 2009).

Cholinergic Enhancement of Cell Proliferation in the Postnatal Neurogenic Niche of the Mammalian Spinal Cord.

The region surrounding the central canal (CC) of the spinal cord is a highly plastic area, defined as a postnatal neurogenic niche. Within this region are ependymal cells that can proliferate and differentiate to form new astrocytes and oligodendrocytes following injury and cerebrospinal fluid contacting cells (CSFcCs). The specific environmental conditions, including the modulation by neurotransmitters that influence these cells and their ability to proliferate, are unknown. Here, we show that acetylcholine promotes the proliferation of ependymal cells in mice under both in vitro and in vivo conditions. Using whole cell patch clamp in acute spinal cord slices, acetylcholine directly depolarized ependymal cells and CSFcCs. Antagonism by specific nicotinic acetylcholine receptor (nAChR) antagonists or potentiation by the α7 containing nAChR (α7*nAChR) modulator PNU 120596 revealed that both α7*nAChRs and non‐α7*nAChRs mediated the cholinergic responses. Using the nucleoside analogue EdU (5‐ethynyl‐2'‐deoxyuridine) as a marker of cell proliferation, application of α7*nAChR modulators in spinal cord cultures or in vivo induced proliferation in the CC region, producing Sox‐2 expressing ependymal cells. Proliferation also increased in the white and grey matter. PNU 120596 administration also increased the proportion of cells coexpressing oligodendrocyte markers. Thus, variation in the availability of acetylcholine can modulate the rate of proliferation of cells in the ependymal cell layer and white and grey matter through α7*nAChRs. This study highlights the need for further investigation into how neurotransmitters regulate the response of the spinal cord to injury or during aging. Stem Cells 2015;33:2864–2876

Nicotine modulates neurogenesis in the central canal during experimental autoimmune encephalomyelitis

Nicotine has been shown to attenuate experimental autoimmune encephalomyelitis (EAE) through inhibiting inflammation in microglial populations during the disease course. In this study, we investigated whether nicotine modified the regenerative process in EAE by examining nestin-expressing neural stem cells (NSCs) in the spinal cord, which is the primary area of demyelination and inflammation in EAE. Our results show that the endogenous neurogenic responses in the spinal cord after EAE are limited and delayed: while nestin expression is increased, the proliferation of ependymal cells is inhibited compared to healthy animals. Nicotine application significantly reduced nestin expression and partially allowed for the proliferation of ependymal cells. We found that reduction of ependymal cell proliferation correlated with inflammation in the same area, which was relieved by the administration of nicotine. Further, increased numbers of oligodendrocytes (OLs) were observed after nicotine treatment. These findings give a new insight into the mechanism of how nicotine functions to attenuate EAE.

Dynamic expression of ATF3 as a novel tool to study activation and migration of endogenous spinal stem cells and their role in neural repair.

One of the major problems of modern neurobiology is how to replace dead or damaged neurons in the human brain or spinal cord after injury or as a consequence of neurodegenerative diseases. In fact, because adult mammalian neurons are post-mitotic cells that cannot divide to replace dead cells, loss due to lesion or disease is permanent. Furthermore, surviving neurons have modest capacity to regenerate their damaged axons and re-establish functional connections. Thus, a gradual neurodegenerative scenario with certain similarities in stroke, brain or spinal cord injuries and neurological diseases like Alzheimer's disease is produced. These conditions represent the major disease burden of the modern world in terms of mortality, disability, productivity loss and health-care costs (World Health Organization, 2008). While much effort has been directed to understand the molecular and cellular mechanisms involved in the pathology of these diseases to set new effective treatments, many neuroprotective and regenerative approaches, although showing positive results in preclinical studies, have so far failed to provide strong benefit to patients.

ATF3 is a novel nuclear marker for migrating ependymal stem cells in the rat spinal cord

The present study identified ATF3 as a novel dynamic marker for ependymal stem/progenitor cells (nestin, vimentin and SOX2 positive) around the central canal of the neonatal or adult rat spinal cord. While quiescent ependymal cells showed cytoplasmic ATF3 expression, during 6–24h in vitro these cells mobilized and acquired intense nuclear ATF3 staining. Their migratory pattern followed a centrifugal pathway toward the dorsal and ventral funiculi, reminiscent of the rostral migratory stream of the brain subventricular stem cells. Thus, the chain cell formation was, by analogy, termed funicular migratory stream (FMS). The FMS process preceded the strong proliferation of ependymal cells occurring only after 24h in vitro. Pharmacological inhibition of MAPK-p38 and JNK/c-Jun (upstream effectors of ATF3 activation) prevented the FMS mobilization of ATF3 nuclear-positive cells. Excitotoxicity or ischemia-like conditions, reported to evoke neuronal and glial injury, did not further enhance migration of ependymal cells at 24h, suggesting that, at this early stage of damage, the FMS phenomenon had peaked and that more extensive repair processes are delayed beyond this time point. ATF3 is, therefore, useful to identify activation and migration of endogenous stem cells of the rat spinal cord in vitro.

Central Canal Ependymal Cells Proliferate Extensively in Response to Traumatic Spinal Cord Injury but Not Demyelinating Lesions

The adult mammalian spinal cord has limited regenerative capacity in settings such as spinal cord injury (SCI) and multiple sclerosis (MS). Recent studies have revealed that ependymal cells lining the central canal possess latent neural stem cell potential, undergoing proliferation and multi-lineage differentiation following experimental SCI. To determine whether reactive ependymal cells are a realistic endogenous cell population to target in order to promote spinal cord repair, we assessed the spatiotemporal dynamics of ependymal cell proliferation for up to 35 days in three models of spinal pathologies: contusion SCI using the Infinite Horizon impactor, focal demyelination by intraspinal injection of lysophosphatidylcholine (LPC), and autoimmune-mediated multi-focal demyelination using the active experimental autoimmune encephalomyelitis (EAE) model of MS. Contusion SCI at the T9–10 thoracic level stimulated a robust, long-lasting and long-distance wave of ependymal proliferation that peaked at 3 days in the lesion segment, 14 days in the rostral segment, and was still detectable at the cervical level, where it peaked at 21 days. This proliferative wave was suppressed distal to the contusion. Unlike SCI, neither chemical- nor autoimmune-mediated demyelination triggered ependymal cell proliferation at any time point, despite the occurrence of demyelination (LPC and EAE), remyelination (LPC) and significant locomotor defects (EAE). Thus, traumatic SCI induces widespread and enduring activation of reactive ependymal cells, identifying them as a robust cell population to target for therapeutic manipulation after contusion; conversely, neither demyelination, remyelination nor autoimmunity appears sufficient to trigger proliferation of quiescent ependymal cells in models of MS-like demyelinating diseases.

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.