Olfactory ensheathing cells represent an optimal substrate for hippocampal neurons: an in vitro study

Zinc-a2-Glycoprotein Acts as a Component of PNN to Protect Hippocampal Neurons from Apoptosis

In the adult mouse brain, perineuronal net (PNN), a highly structured extracellular matrix, surrounds subsets of neurons. The AZGP1 gene encodes zinc-2-glycoprotein (ZAG) is a lipid-mobilizing factor. However, its expression and distribution in the adult brain have been controversial. Here, for the first time, we demonstrate that the secreted ZAG is localized to Wisteria floribunda agglutinin (WFA)-positive PNNs around parvalbumin (PV)-expressing interneurons in the hippocampus, cortex, and a number of other PNN-bearing neurons and co-localizes with aggrecan, one of the components of PNNs. Few ZAG-positive nets were seen in the area without WFA staining by chondroitinase ABC (ChABC) which degrades glycosaminoglycans (GAGs) from the chondroitin sulfate proteoglycans (CSPGs) in the PNN. Reanalysis of single-cell sequencing data revealed that ZAG mRNA was mainly expressed in oligodendrocyte lineages, specifically in olfactory sheathing cells. The ZAG receptor β3 adrenergic receptor (β3AR) is also selectively co-localized with PV interneurons and CA2 pyramidal neurons in the hippocampus. In addition, molecular docking provides valuable new insights on how GAGs interfere with ZAG and ZAG/β3AR complex. Finally, our results indicated that human recombinant ZAG could significantly inhibit serum derivation-induced cell apoptosis in HT22 cells. Our combined experimental and theoretical approach raises a unique hypothesis namely that ZAG may be a crucial functional attribute of PNNs in the brain to protect neuronal cell from apoptosis.

Melatonin Enhances Neural Differentiation of Adipose-Derived Mesenchymal Stem Cells

Adipose-derived mesenchymal stem cells (ASCs) are adult multipotent stem cells, able to differentiate toward neural elements other than cells of mesodermal lineage. The aim of this research was to test ASC neural differentiation using melatonin combined with conditioned media (CM) from glial cells. Isolated from the lipoaspirate of healthy donors, ASCs were expanded in a basal growth medium before undergoing neural differentiation procedures. For this purpose, CM obtained from olfactory ensheathing cells and from Schwann cells were used. In some samples, 1 µM of melatonin was added. After 1 and 7 days of culture, cells were studied using immunocytochemistry and flow cytometry to evaluate neural marker expression (Nestin, MAP2, Synapsin I, GFAP) under different conditions. The results confirmed that a successful neural differentiation was achieved by glial CM, whereas the addition of melatonin alone did not induce appreciable changes. When melatonin was combined with CM, ASC neural differentiation was enhanced, as demonstrated by a further improvement of neuronal marker expression, whereas glial differentiation was attenuated. A dynamic modulation was also observed, testing the expression of melatonin receptors. In conclusion, our data suggest that melatonin's neurogenic differentiation ability can be usefully exploited to obtain neuronal-like differentiated ASCs for potential therapeutic strategies.

Primary neurons lacking the SNAREs vti1a and vti1b show altered neuronal development

BACKGROUND

Neurons are highly specialized cells with a complex morphology generated by various membrane trafficking steps. They contain Golgi outposts in dendrites, which are formed from somatic Golgi tubules. In trafficking membrane fusion is mediated by a specific combination of SNARE proteins. A functional SNARE complex contains four different helices, one from each SNARE subfamily (R-, Qa, Qb and Qc). Loss of the two Qb SNAREs vti1a and vti1b from the Golgi apparatus and endosomes leads to death at birth in mice with massive neurodegeneration in peripheral ganglia and defective axon tracts.

METHODS

Hippocampal and cortical neurons were isolated from Vti1a^-/- Vti1b^-/- double deficient, Vti1a^-/- Vti1b^+/-, Vti1a^+/- Vti1b^-/- and Vti1a^+/- Vti1b^+/- double heterozygous embryos. Neurite outgrowth was determined in cortical neurons and after stimulation with several neurotrophic factors or the Rho-associated protein kinase ROCK inhibitor Y27632, which induces exocytosis of enlargeosomes, in hippocampal neurons. Moreover, postsynaptic densities were isolated from embryonic Vti1a^-/- Vti1b^-/- and Vti1a^+/- Vti1b^+/- control forebrains and analyzed by western blotting.

RESULTS

Golgi outposts were present in Vti1a^-/- Vti1b^+/- and Vti1a^+/- Vti1b^-/- dendrites of hippocampal neurons but not detected in the absence of vti1a and vti1b. The length of neurites was significantly shorter in double deficient cortical neurons. These defects were not observed in Vti1a^-/- Vti1b^+/- and Vti1a^+/- Vti1b^-/- neurons. NGF, BDNF, NT-3, GDNF or Y27632 as stimulator of enlargeosome secretion did not increase the neurite length in double deficient hippocampal neurons. Vti1a^-/- Vti1b^-/- postsynaptic densities contained similar amounts of scaffold proteins, AMPA receptors and NMDA receptors compared to Vti1a^+/- Vti1b^+/-, but much more TrkB, which is the receptor for BDNF.

CONCLUSION

The absence of Golgi outposts did not affect the amount of AMPA and NMDA receptors in postsynaptic densities. Even though TrkB was enriched, BDNF was not able to stimulate neurite elongation in Vti1a^-/- Vti1b^-/- neurons. Vti1a or vti1b function as the missing Qb-SNARE together with VAMP-4 (R-SNARE), syntaxin 16 (Qa-SNARE) and syntaxin 6 (Qc-SNARE) in induced neurite outgrowth. Our data show the importance of vti1a or vti1b for two pathways of neurite elongation.

Effects of exosomes on adult hippocampal neurogenesis and neuropsychiatric disorders

Exosomes are extracellular vesicles originating from the endosomal system, which are involved in intercellular substance transfer and cell waste elimination. Recent studies implicate the roles of exosomes in adult hippocampal neurogenesis, a process through which new granule cells are generated in the dentate gyrus, and which is closely related to mood and cognition, as well as psychiatric disorders. As such, exosomes are recognized as potential biomarkers of neurologic and psychiatric disorders. This review briefly introduces the synthesis and secretion mechanism of exosomes, and discuss the relationship between exosomes and hippocampal neurogenesis, and their roles in regulating depression, epilepsy and schizophrenia. Finally, we discuss the prospects of their application in diagnosing disorders of the central nervous system (CNS).

A phosphoproteomics study reveals a defined genetic program for neural lineage commitment of neural stem cells induced by olfactory ensheathing cell-conditioned medium

Since both Olfactory ensheathing cells (OECs) and neural stem cells (NSCs) have shown certain efficacy in the cellular therapy of nerve injury and disease, there have been a series of investigations in recent years looking at the co-culture of NSCs and OECs. Protein phosphorylation forms the basis for identifying a variety of cellular signaling pathways responsible for regulating the self-renewal and differentiation of NSCs induced by OECs. To better understand the signaling cascades in the early phases of OEC-induced NSC differentiation, changes in the NSC proteome and phosphoproteome during the first 24 h were determined using dimethyl labeling and TiO₂ phosphorylation enrichment coupled with Liquid chromatography-tandem mass spectrometry (LC-MS/MS). A total of 565 proteins and 2511 phosphorylation sites were identified. According to quantitative phosphoproteomics analyses of NSC differentiation induced by OECs during the first 12 and 24 h, it was speculated that there were at least two different signal waves: one peaking within 12 h after stimulation and the second upsurge after 24 h. In addition to understanding the dynamics of the proteome and phosphoproteome in the early stages of NSC differentiation, our analyses identified a key role of the TGF-β3 protein secreted by OECs, which may be an initiating factor that promotes differentiation of NSCs into neurons induced by OECs. These findings not only redemonstrated a OECs-based therapeutic strategy in cell therapy, but also added a node to the regulatory network for the neural lineage commitment of NSCs induced by OECs.

Amyloid-Beta Induces Different Expression Pattern of Tissue Transglutaminase and Its Isoforms on Olfactory Ensheathing Cells: Modulatory Effect of Indicaxanthin

Herein, we assessed the effect of full native peptide of amyloid-beta (Aβ) (1-42) and its fragments (25-35 and 35-25) on tissue transglutaminase (TG2) and its isoforms (TG2-Long and TG2-Short) expression levels on olfactory ensheathing cells (OECs). Vimentin and glial fibrillary acid protein (GFAP) were also studied. The effect of the pre-treatment with indicaxanthin from Opuntia ficus-indica fruit on TG2 expression levels and its isoforms, cell viability, total reactive oxygen species (ROS), superoxide anion (O₂⁻), and apoptotic pathway activation was assessed. The levels of Nestin and cyclin D1 were also evaluated. Our findings highlight that OECs exposure to Aβ(1-42) and its fragments induced an increase in TG2 expression levels and a different expression pattern of its isoforms. Indicaxanthin pre-treatment reduced TG2 overexpression, modulating the expression of TG2 isoforms. It reduced total ROS and O₂⁻ production, GFAP and Vimentin levels, inhibiting apoptotic pathway activation. It also induced an increase in the Nestin and cyclin D1 expression levels. Our data demonstrated that indicaxanthin pre-treatment stimulated OECs self-renewal through the reparative activity played by TG2. They also suggest that Aβ might modify TG2 conformation in OECs and that indicaxanthin pre-treatment might modulate TG2 conformation, stimulating neural regeneration in Alzheimer’s disease.

Ghrelin peptide improves glial conditioned medium effects on neuronal differentiation of human adipose mesenchymal stem cells

The influences of ghrelin on neural differentiation of adipose-derived mesenchymal stem cells (ASCs) were investigated in this study. The expression of typical neuronal markers, such as protein gene product 9.5 (PGP9.5) and Microtubule Associated Protein 2 (MAP2), as well as glial Fibrillary Acid Protein (GFAP) as a glial marker was evaluated in ASCs in different conditions. In particular, 2 µM ghrelin was added to control ASCs and to ASCs undergoing neural differentiation. For this purpose, ASCs were cultured in Conditioned Media obtained from Olfactory Ensheathing cells (OEC-CM) or from Schwann cells (SC-CM). Data on marker expression were gathered after 1 and 7 days of culture by fluorescence immunocytochemistry and flow cytometry. Results show that only weak effects were induced by the addition of only ghrelin. Instead, dynamic ghrelin-induced modifications were detected on the increased marker expression elicited by glial conditioned media. In fact, the combination of ghrelin and conditioned media consistently induced a further increase of PGP9.5 and MAP2 expression, especially after 7 days of treatment. The combination of ghrelin with SC-CM produced the most evident effects. Weak or no modifications were found on conditioned medium-induced GFAP increases. Observations on the ghrelin receptor indicate that its expression in control ASCs, virtually unchanged by the addition of only ghrelin, was considerably increased by CM treatment. These increases were enhanced by combining ghrelin and CM treatment, especially at 7 days. Overall, it can be assumed that ghrelin favors a neuronal rather than a glial ASC differentiation.

Olfactory ensheathing cells: Unique glial cells promising for treatments of spinal cord injury

Spinal cord injury (SCI) is generally the consequence of physical damage, which may result in devastating consequences such as paraplegia or paralysis. Some certain candidates for SCI repair are olfactory ensheathing cells (OECs), which are unique glial cells located in the transition region of the peripheral nervous system and central nervous system and perform neuron regeneration in the olfactory system throughout life. Culture studies have clarified many properties of OECs, but their mechanisms of actions are not fully understood. Successful results achieved in animal models showcased that SCI treatment with OEC transplants is suitable for clinical trials. However, clinical trials are limited by difficulties like cell acquisition for autograft transplantation. Despite the improvements in both animal and clinical studies so far, there is still insufficient information about the mechanism of actions, adverse effects, proper application methods, effective subtypes, and sources of cells. This review summarizes pre-clinical and clinical literature focused on the cellular characterization of both OECs in vitro and post-transplantation. We highlight the roles and effects of OECs on (a) the injury-induced glial milieu, (b) neuronal growth/regeneration, and (c) functional recovery after injury. Due to the shown benefits of OECs with in vitro and animal studies and a limited number of clinical trials, where safety and effectivity were shown, it is necessary to conduct more studies on OECs to obtain effective and feasible treatment methods.

Effects of Ghrelin on Olfactory Ensheathing Cell Viability and Neural Marker Expression

Ghrelin (Ghre), a gut-brain peptide hormone, plays an important role in the entire olfactory system and in food behavior regulation. In the last years, it has aroused particular interest for its antioxidant, anti-inflammatory, and anti-apoptotic properties. Our previous research showed that Ghre and its receptor are expressed by peculiar glial cells of the olfactory system: Olfactory Ensheathing Cells (OECs). These cells are able to secrete different neurotrophic factors, promote axonal growth, and show stem cell characteristics. The aim of this work was to study, in an in vitro model, the effect of Ghre on both cell viability and the expression of some neural markers, such as Nestin (Ne), Glial Fibrillary Acid Protein (GFAP), Neuregulin (Neu), and β-III-tubulin (Tuj1), in primary mouse OEC cultures. The MTT test and immunocytochemical procedures were used to highlight cell viability and marker expression, respectively. Our results demonstrate that Ghre, after 7 days of treatment, exerted a positive effect, stimulating OEC viability compared with cells without Ghre treatment. In addition, Ghre was able to modify the expression of some biomarkers, increasing Neu and Tuj1 expression, while GFAP was constant; on the contrary, the presence of positive Ne cells was drastically reduced after 7 days, and this showed a loss of stem cell characteristic and therefore the possible orientation towards an adult neural phenotype.

Conditioned Media From Glial Cells Promote a Neural-Like Connexin Expression in Human Adipose-Derived Mesenchymal Stem Cells

The expression of neuronal and glial connexins (Cxs) has been evaluated in adipose-derived mesenchymal stem cells (ASCs) whose neural differentiation was promoted by a conditioned medium (CM) obtained from cultures of olfactory ensheathing cells (OECs) or Schwann cells (SCs). By immunocytochemistry and flow cytometer analysis it was found that Cx43 was already considerably expressed in naïve ASCs and further increased after 24 h and 7 days from CM exposition. Cx32 and Cx36 were significantly improved in conditioned cultures compared to control ASCs, whereas a decreased expression was noticed in the absence of CM treatments. Cx47 was virtually absent in any conditions. Altogether, high basal levels and induced increases of Cx43 expression suggest a potential attitude of ASCs toward an astrocyte differentiation, whereas the lack of Cx47 would indicate a poor propensity of ASCs to become oligodendrocytes. CM-evoked Cx32 and Cx36 increases showed that a neuronal- or a SC-like differentiation can be promoted by using this strategy. Results further confirm that environmental cues can favor an ASC neural differentiation, either as neuronal or glial elements. Of note, the use of glial products present in CM rather than the addition of chemical agents to achieve such differentiation would resemble "more physiological" conditions of differentiation. As a conclusion, the overexpression of typical neural Cxs would indicate the potential capability of neural-like ASCs to interact with neighboring neural cells and microenvironment.

Bioprocessing strategies to enhance the challenging isolation of neuro-regenerative cells from olfactory mucosa

Olfactory ensheathing cells (OECs) are a promising potential cell therapy to aid regeneration. However, there are significant challenges in isolating and characterizing them. In the current study, we have explored methods to enhance the recovery of cells expressing OEC marker p75NTR from rat mucosa. With the addition of a 24-hour differential adhesion step, the expression of p75NTR was significantly increased to 73 ± 5% and 46 ± 18% on PDL and laminin matrices respectively. Additionally, the introduction of neurotrophic factor NT-3 and the decrease in serum concentration to 2% FBS resulted in enrichment of OECs, with p75NTR at nearly 100% (100 ± 0% and 98 ± 2% on PDL and laminin respectively), and candidate fibroblast marker Thy1.1 decreased to zero. Culturing OECs at physiologically relevant oxygen tension (2-8%) had a negative impact on p75NTR expression and overall cell survival. Regarding cell potency, co-culture of OECs with NG108-15 neurons resulted in more neuronal growth and potential migration at atmospheric oxygen. Moreover, OECs behaved similarly to a Schwann cell line positive control. In conclusion, this work identified key bioprocessing fundamentals that will underpin future development of OEC-based cell therapies for potential use in spinal cord injury repair. However, there is still much work to do to create optimized isolation methods.

Neural differentiation of human adipose-derived mesenchymal stem cells induced by glial cell conditioned media

Adipose-derived mesenchymal stem cells (ASCs) may transdifferentiate into cells belonging to mesodermal, endodermal, and ectodermal lineages. The aim of this study was to verify whether a neural differentiation of ASCs could be induced by a conditioned medium (CM) obtained from cultures of olfactory ensheathing cells (OECs) or Schwann cells (SCs). ASCs were isolated from the stromal vascular fraction of adipose tissue and expanded for 2-3 passages. They were then cultured in OEC-CM or SC-CM for 24 hr or 7 days. At each stage, the cells were tested by immunocytochemistry and flow cytometer analysis to evaluate the expression of typical neural markers such as Nestin, PGP 9.5, MAP2, Synapsin I, and GFAP. Results show that both conditioned media induced similar positive effects, as all tested markers were overexpressed, especially at day 7. Overall, an evident trend toward neuronal or glial differentiation was not clearly detectable in many cases. Nevertheless, a higher tendency toward a neuronal phenotype was recognized for OEC-CM (considering MAP2 increases). On the other hand, SC-CM would be responsible for a more marked glial induction (considering GFAP increases). These findings confirm that environmental features can induce ASCs toward a neural differentiation, either as neuronal or glial elements. Rather than supplementing the culture medium by adding chemical agents, a "more physiological" condition was obtained here by means of soluble factors (cytokines/growth factors) likely released by glial cells. This culture strategy may provide valuable information in the development of cell-based therapeutic approaches for pathologies affecting the central/peripheral nervous system.

Cell therapy for spinal cord injury with olfactory ensheathing glia cells (OECs)

The prospects of achieving regeneration in the central nervous system (CNS) have changed, as most recent findings indicate that several species, including humans, can produce neurons in adulthood. Studies targeting this property may be considered as potential therapeutic strategies to respond to injury or the effects of demyelinating diseases in the CNS. While CNS trauma may interrupt the axonal tracts that connect neurons with their targets, some neurons remain alive, as seen in optic nerve and spinal cord (SC) injuries (SCIs). The devastating consequences of SCIs are due to the immediate and significant disruption of the ascending and descending spinal pathways, which result in varying degrees of motor and sensory impairment. Recent therapeutic studies for SCI have focused on cell transplantation in animal models, using cells capable of inducing axon regeneration like Schwann cells (SchCs), astrocytes, genetically modified fibroblasts and olfactory ensheathing glia cells (OECs). Nevertheless, and despite the improvements in such cell-based therapeutic strategies, there is still little information regarding the mechanisms underlying the success of transplantation and regarding any secondary effects. Therefore, further studies are needed to clarify these issues. In this review, we highlight the properties of OECs that make them suitable to achieve neuroplasticity/neuroregeneration in SCI. OECs can interact with the glial scar, stimulate angiogenesis, axon outgrowth and remyelination, improving functional outcomes following lesion. Furthermore, we present evidence of the utility of cell therapy with OECs to treat SCI, both from animal models and clinical studies performed on SCI patients, providing promising results for future treatments.

Phenotypic Modulation and Neuroprotective Effects of Olfactory Ensheathing Cells: a Promising Tool for Cell Therapy

Olfactory Ensheathing Cells (OECs), exhibiting phenotypic characteristics of both astrocytes and Schwann Cells, show peculiar plasticity. In vitro, OECs promote axonal growth, while in vivo they promote remyelination of damaged axons. We decided to further investigate OEC potential for regeneration and functional recovery of the damaged Central Nervous System (CNS). To study OEC antigen modulation, OECs prepared from postnatal mouse olfactory bulbs were grown in different culture conditions: standard or serum-free media with/without Growth Factors (GFs) and analyzed for different neural specific markers. OEC functional characterizations were also achieved. Resistance of OECs to the neurotoxin 6-hydroxydopamine (6-OHDA) was analyzed by evaluating apoptosis and death. OEC neuroprotective properties were investigated by in vitro co-cultures or by addition of OEC conditioned medium to the neuroblastoma SH-SY5Y cells exposed to 6-OHDA. We observed: 1) modification of OEC morphology, reduced cell survival and marker expression in serum-free medium; 2) GF addition to serum-free medium condition influenced positively survival and restored basal marker expression; 3) no OEC apoptosis after a prolonged exposition to 6-OHDA; 4) a clear OEC neuroprotective tendency, albeit non statistically significant, on 6-OHDA treated SH-SY5Y cells. These peculiar properties of OECs might render them potential clinical agents able to support injured CNS.

Transplanted olfactory ensheathing cells restore retinal function in a rat model of light-induced retinal damage by inhibiting oxidative stress

There is still not an effective treatment for continuous retinal light exposure and subsequent photoreceptor degeneration. Olfactory ensheathing cell (OEC) transplantation has been shown to be neuroprotective in spinal cord, and optic nerve injury and retinitis pigmentosa. However, whether OECs protect rat photoreceptors against light-induced damage and how this may work is unclear. Thus, to elucidate this mechanism, purified rat OECs were grafted into the subretinal space of a Long-Evans rat model with light-induced photoreceptor damage. Light exposure decreased a- and b- wave amplitudes and outer nuclear layer (ONL) thickness, whereas the ONL of rats exposed to light for 24 h after having received OEC transplants in their subretinal space was thicker than the PBS control and untreated groups. A- and b- wave amplitudes from electroretinogram of OEC-transplanted rats were maintained until 8 weeks post OEC transplantation. Also, transplanted OECs inhibited formation of reactive oxygen species in retinas exposed to light. In vitro experiments showed that OECs had more total antioxidant capacity in a co-cultured 661W photoreceptor cell line, and cells were protected from damage induced by hydrogen-peroxide. Thus, transplanted OECs preserved retinal structure and function in a rat model of light-induced degeneration by suppressing retinal oxidative stress reactions.

Hypoxic Culture Promotes Dopaminergic-Neuronal Differentiation of Nasal Olfactory Mucosa Mesenchymal Stem Cells via Upregulation of Hypoxia-Inducible Factor-1α

Olfactory mucosa mesenchymal stem cells (OM-MSCs) display significant clonogenic activity and may be easily propagated for Parkinson's disease therapies. Methods of inducing OM-MSCs to differentiate into dopaminergic (DAergic) neurons using olfactory ensheathing cells (OECs) are thus an attractive topic of research. We designed a hypoxic induction protocol to generate DAergic neurons from OM-MSCs using a physiological oxygen (O2) level of 3% and OEC-conditioned medium (OCM; HI group). The normal induction (NI) group was cultured in O2 at ambient air level (21%). The role of hypoxia-inducible factor-1α (HIF-1α) in the differentiation of OM-MSCs under hypoxia was investigated by treating cells with an HIF-1α inhibitor before induction (HIR group). The proportions of β-tubulin- and tyrosine hydroxylase (TH)-positive cells were significantly increased in the HI group compared with the NI and HIR groups, as shown by immunocytochemistry and Western blotting. Furthermore, the level of dopamine was significantly increased in the HI group. A slow outward potassium current was recorded in differentiated cells after 21 d of induction using whole-cell voltage-clamp tests. A hypoxic environment thus promotes OM-MSCs to differentiate into DAergic neurons by increasing the expression of HIF-1α and by activating downstream target gene TH. This study indicated that OCM under hypoxic conditions could significantly upregulate key transcriptional factors involved in the development of DAergic neurons from OM-MSCs, mediated by HIF-1α. Hypoxia promotes DAergic neuronal differentiation of OM-MSCs, and HIF-1α may play an important role in hypoxia-inducible pathways during DAergic lineage specification and differentiation in vitro.

The protective effect of curcumin in Olfactory Ensheathing Cells exposed to hypoxia

Curcumin, a phytochemical component derived from the rhizomes of Curcuma longa, has shown a great variety of pharmacological activities, such as anti-inflammatory, anti-tumor, anti-depression and anti-oxidant activity. Therefore, in the last years it has been used as a therapeutic agent since it confers protection in different neurodegenerative diseases, cerebral ischemia and excitotoxicity. Olfactory Ensheathing Cells (OECs) are glial cells of the olfactory system. They are able to secrete several neurotrophic growth factors, promote axonal growth and support the remyelination of damaged axons. OEC transplantation has emerged as a possible experimental therapy to induce repair of spinal cord injury, even if the functional recovery is still limited. Since hypoxia is a secondary effect in spinal cord injury, this in vitro study investigates the protective effect of curcumin in OECs exposed to hypoxia. Primary OECs were obtained from neonatal rat olfactory bulbs and placed both in normal and hypoxic conditions. Furthermore, some cells were grown with basic Fibroblast Growth Factor (bFGF) and/or curcumin at different concentration and times. The results obtained through immunocytochemical procedures and MTT test show that curcumin stimulates cell viability in OECs grown in normal and hypoxic conditions. Furthermore, the synergistic effect of curcumin and bFGF is the most effective exerting protection on OECs. Since spinal cord injury is often accompanied by secondary insults, such as ischemia or hypoxia, our results suggest that curcumin in combination with bFGF might be considered a possible approach for restoration in injuries.

Olfactory Ensheathing Cell-Conditioned Medium Reverts Aβ25-35-Induced Oxidative Damage in SH-SY5Y Cells by Modulating the Mitochondria-Mediated Apoptotic Pathway

Olfactory ensheathing cells (OECs) are a type of glia from the mammalian olfactory system, with neuroprotective and regenerative properties. β-Amyloid peptides are a major component of the senile plaques characteristic of the Alzheimer brain. The amyloid beta (Aβ) precursor protein is cleaved to amyloid peptides, and Aβ_25-35 is regarded to be the functional domain of Aβ, responsible for its neurotoxic properties. It has been reported that Aβ_25-35 triggers reactive oxygen species (ROS)-mediated oxidative damage, altering the structure and function of mitochondria, leading to the activation of the mitochondrial intrinsic apoptotic pathway. Our goal is to investigate the effects of OECs on the toxicity of aggregated Aβ_25-35, in human neuroblastoma SH-SY5Y cells. For such purpose, SH-SY5Y cells were incubated with Aβ_25-35 and OEC-conditioned medium (OECCM). OECCM promoted the cell viability and reduced the apoptosis, and decreased the intracellular ROS and the lipid peroxidation. In the presence of OECCM, mRNA and protein levels of antioxidant enzymes (SOD1 and SOD2) were upregulated. Concomitantly, OECCM decreased mRNA and the protein expression levels of cytochrome c, caspase-9, caspase-3, and Bax in SH-SY5Y cells, and increased mRNA and the protein expression level of Bcl-2. However, OECCM did not alter intracellular Ca²⁺ concentration in SH-SY5Y cells. Taken together, our data suggest that OECCM ameliorates Aβ_25-35-induced oxidative damage in neuroblastoma SH-SY5Y cells by inhibiting the mitochondrial intrinsic pathway. These data provide new insights into the functional actions of OECCM on oxidative stress-induced cell damage.

Effect of Some Growth Factors on Tissue Transglutaminase Overexpression Induced by β-Amyloid in Olfactory Ensheathing Cells

Herein, we assessed in a particular glial cell type, called olfactory ensheathing cells (OECs), the effect of some growth factors (GFs) on tissue transglutaminase (TG2) overexpression induced by amyloid-beta (Aβ) with native full-length peptide 1-42 or by fragments, 25-35 or 35-25, as control. Previously, we demonstrated that TG2 overexpression induced by some stressors was down-regulated by GFs exposure in OECs. To monitor cell viability, an MTT test was used, while TG2 expression was examined using immunocytochemical and Western blot analysis. We also considered the involvement of the TG2-mediated apoptotic pathway. Vimentin expression was evaluated as well. Reactive oxygen species and reduced glutathione levels were utilized to test the oxidative intracellular status. Lactate dehydrogenase released into the medium, as a marker of necrotic cell death, was evaluated. We found that in OECs exposed to Aβ(1-42) or Aβ(25-35) for 24 h, TG2 expression increased, and we observed that the protein appeared prevalently localized in the cytosol. The pre-treatment with GFs, basic fibroblast growth factor (bFGF) or glial-derived neurotrophic factor (GDNF), down-regulated the TG2 level, which was prevalently limited to the nuclear compartment. Vimentin expression and caspase cleavage showed a significant enhancement in Aβ(1-42) and Aβ(25-35) exposed cells. The pre-treatment with bFGF or GDNF was able to restore the levels of the proteins to control values, and the intracellular oxidative status modified by the exposure to Aβ(1-42) or Aβ(25-35). Our data suggest that both bFGF or GDNF could be an innovative mechanism to contrast TG2 expression, which plays a key role in Alzheimer's disease.

Stem cell therapy in spinal cord injury: Hollow promise or promising science?

Spinal cord injury (SCI) remains one of the most physically, psychologically and socially debilitating conditions worldwide. While rehabilitation measures may help limit disability to some extent, there is no effective primary treatment yet available. The efficacy of stem cells as a primary therapeutic option in spinal cord injury is currently an area under much scrutiny and debate. Several laboratory and some primary clinical studies into the use of bone marrow mesenchymal stem cells or embryonic stem cell-derived oligodentrocyte precursor cells have shown some promising results in terms of remyelination and regeneration of damaged spinal nerve tracts. More recently,laboratory and early clinical experiments into the use of Olfactory Ensheathing Cells, a type of glial cell derived from olfactory bulb and mucosa have provided some phenomenal preliminary evidence as to their neuroregenerative and neural bridging capacity. This report compares and evaluates some current research into selected forms of embryonic and mesenchymal stem cell therapy as well as olfactory ensheathing cell therapy in SCI, and also highlights some legal and ethical issues surrounding their use. While early results shows promise, more rigorous large scaleclinical trials are needed to shed light on the safety, efficacy and long term viability of stem cell and cellular transplant techniques in SCI.

Olfactory ensheathing cell-neurite alignment enhances neurite outgrowth in scar-like cultures

The regenerative capacity of adult CNS neurons after injury is strongly inhibited by the spinal cord lesion site environment that is composed primarily of the reactive astroglial scar and invading meningeal fibroblasts. Olfactory ensheathing cell (OEC) transplantation facilitates neuronal survival and functional recovery after a complete spinal cord transection, yet the mechanisms by which this recovery occurs remain unclear. We used a unique multicellular scar-like culture model to test if OECs promote neurite outgrowth in growth-inhibitory areas. Astrocytes were mechanically injured and challenged by meningeal fibroblasts to produce key inhibitory elements of a spinal cord lesion. Neurite outgrowth of postnatal cerebral cortical neurons was assessed on three substrates: quiescent astrocyte control cultures, reactive astrocyte scar-like cultures, and scar-like cultures with OECs. Initial results showed that OECs enhanced total neurite outgrowth of cortical neurons in a scar-like environment by 60%. We then asked if the neurite growth-promoting properties of OECs depended on direct alignment between neuronal and OEC processes. Neurites that aligned with OECs were nearly three times longer when they grew on inhibitory meningeal fibroblast areas and twice as long on reactive astrocyte zones compared to neurites not associated with OECs. Our results show that OECs can independently enhance neurite elongation and that direct OEC-neurite cell contact can provide a permissive substrate that overcomes the inhibitory nature of the reactive astrocyte scar border and the fibroblast-rich spinal cord lesion core.

Characterization of glial cell models and in vitro manipulation of the neuregulin1/ErbB system

The neuregulin1/ErbB system plays an important role in Schwann cell behavior both in normal and pathological conditions. Upon investigation of the expression of the neuregulin1/ErbB system in vitro, we explored the possibility to manipulate the system in order to increase the migration of Schwann cells, that play a fundamental role in the peripheral nerve regeneration. Comparison of primary cells and stable cell lines shows that both primary olfactory bulb ensheathing cells and a corresponding cell line express ErbB1-ErbB2 and neuregulin1, and that both primary Schwann cells and a corresponding cell line express ErbB2-ErbB3, while only primary Schwann cells express neuregulin1. To interfere with the neuregulin1/ErbB system, the soluble extracellular domain of the neuregulin1 receptor ErbB4 (ecto-ErbB4) was expressed in vitro in the neuregulin1 expressing cell line, and an unexpected increase in cell motility was observed. In vitro experiments suggest that the back signaling mediated by the transmembrane neuregulin1 plays a role in the migratory activity induced by ecto-ErbB4. These results indicate that ecto-ErbB4 could be used in vivo as a tool to manipulate the neuregulin1/ErbB system.

Viability of olfactory ensheathing cells after hypoxia and serum deprivation: Implication for therapeutic transplantation

Olfactory ensheathing cells (OECs) represent glial cells supporting neuronal turnover in the olfactory system. In vitro, OECs promote axonal growth as a source of neurotrophic growth factors; in vivo, they produce myelin, promoting remyelination of damaged axons. Consequently, OEC transplantation appears to be a promising treatment for spinal cord injury, although the functional recovery is limited. This might be ascribed to the microenvironment at the lesion site, lacking growth factors (GFs), nutrients, and oxygen. To mimic this condition, we used an in vitro approach by growing primary neonatal mouse OECs under hypoxic conditions and/or serum deprivation. In addition, we compared OECs survival/proliferation with that of primary cultures of Schwann cells (SCs) and astrocytes under the same experimental conditions. Cultures were analyzed by immunocytochemistry, and cell viability was evaluated by MTT assay. Different GFs, such as NGF, bFGF, and GDNF, and their combination were used to rescue cells from serum and/or oxygen deprivation. We show that the cell types were differently sensitive to the tested stress conditions and that OECs were the most sensitive among them. Moreover, OEC viability was rescued by bFGF under serum-deprived or hypoxic condition but not under conditions of drastic serum deprivation and hypoxia. bFGF was effective also for the other cell types, whereas the effect of the other GFs was negligible. This model suggests that administration of bFGF might be considered useful to sustain cell survival/proliferation after transplantation of OECs either alone or in combination with other glial cell types.

Neuroprotective potentials of neurotrophin rich olfactory ensheathing cell's conditioned media against 6OHDA-induced oxidative damage

On the basis of recent reports, we propose that impaired neurotrophin signaling (PI3k/Akt), low antioxidant levels, and generation of reactive oxygen species (ROS) conjointly participate in the progressive events responsible for the dopaminergic cell loss in Parkinson's disease (PD). In the present study we tried to target these deficits collectively through multiple neurotrophic factors (NTFs) support in the form of Olfactory Ensheathing Cell's Conditioned Media (OEC CM) using human SH-SY5Y neuroblastoma cell line exposed to 6 hydroxydopamine (6OHDA). 6OHDA exposure induced, oxidative stress-mediated apoptotic cell death viz. enhanced ROS generation, diffused cytosolic cytochrome c (cyt c), impaired Bcl-2: Bax levels along with decrease in GSH content. These changes were accompanied by loss in Akt phosphorylation and TH levels in SH-SY5Y cells. OEC CM significantly checked apoptotic cell death by preserving pAkt levels which coincided with enhanced GSH and suppressed oxidative injury. Functional integrity of OEC CM supported cells was evident by maintained tyrosine hydroxylase (TH) expression. Intercepting Akt signaling by specific inhibitor LY294002 blocked the protective effect. Taken together our findings provide important evidence that the key to protective effect of multiple NTF support via OEC CM is enhanced Akt survival signaling which promotes antioxidant defense leading to suppression of oxidative damage.

Nose-to-brain delivery: evaluation of polymeric nanoparticles on olfactory ensheathing cells uptake

The nasal route has received a great deal of attention as a convenient and reliable method for the brain target on administration of drugs. When drugs are loaded into nanoparticles (NPs) the interaction with mucosa transports directly into the brain, skipping the blood-brain barrier and achieving rapid cerebrospinal fluid levels. Poly-lactic acid (PLA), poly-lactic-co-glycolic acid (PLGA), and chitosan (CS) were chosen to prepare NPs. After optimization of CS nanocarriers, our goal was to evaluate the different type of NPs uptake into olfactory ensheathing cells (OECs). We then correlated obtained biological data to zeta potential measurements of cells treated with NPs. Rodhamine-loaded NPs were used to study the uptake of OECs carried out by confocal microscopy at different times (1, 2, and 4 h). Our results showed that uptake of rodhamine-NPs by OECs was time dependent and it was influenced by the carrier charge. Confocal imaging of OECs demonstrated that NPPLGA showed a higher increase in uptake compared with NPPLA and NPCS after 1 h and it increased at 2-4 h. Zeta potential values of treated cells were more amplified with respect to untreated cells. The highest values were showed by unloaded NPPLGA, confirming microscopy data.

Selective neuronal differentiation of neural stem cells induced by nanosecond microplasma agitation

An essential step for therapeutic and research applications of stem cells is their ability to differentiate into specific cell types. Neuronal cells are of great interest for medical treatment of neurodegenerative diseases and traumatic injuries of central nervous system (CNS), but efforts to produce these cells have been met with only modest success. In an attempt of finding new approaches, atmospheric-pressure room-temperature microplasma jets (MPJs) are shown to effectively direct in vitro differentiation of neural stem cells (NSCs) predominantly into neuronal lineage. Murine neural stem cells (C17.2-NSCs) treated with MPJs exhibit rapid proliferation and differentiation with longer neurites and cell bodies eventually forming neuronal networks. MPJs regulate ~75% of NSCs to differentiate into neurons, which is a higher efficiency compared to common protein- and growth factors-based differentiation. NSCs exposure to quantized and transient (~150 ns) micro-plasma bullets up-regulates expression of different cell lineage markers as β-Tubulin III (for neurons) and O4 (for oligodendrocytes), while the expression of GFAP (for astrocytes) remains unchanged, as evidenced by quantitative PCR, immunofluorescence microscopy and Western Blot assay. It is shown that the plasma-increased nitric oxide (NO) production is a factor in the fate choice and differentiation of NSCs followed by axonal growth. The differentiated NSC cells matured and produced mostly cholinergic and motor neuronal progeny. It is also demonstrated that exposure of primary rat NSCs to the microplasma leads to quite similar differentiation effects. This suggests that the observed effect may potentially be generic and applicable to other types of neural progenitor cells. The application of this new in vitro strategy to selectively differentiate NSCs into neurons represents a step towards reproducible and efficient production of the desired NSC derivatives.

Differentiation of human adipose stem cells into neural phenotype by neuroblastoma- or olfactory ensheathing cells-conditioned medium

Olfactory ensheathing cells (OECs) are known to be capable of continuous neurogenesis throughout lifetime and are a source of multiple trophic factors important in central nervous system regeneration. B104 neuroblastoma cells are recognized to induce differentiation of neural stem cells into oligodendrocyte precursor cells. Therefore, the aim of this study was to verify if conditioned medium (CM) obtained from OECs or B104 cells was capable of inducing differentiation of adipose tissue-derived mesenchymal stem cells (AT-MSCs) to a neuronal phenotype. In order to this goal, immunocytochemical procedures and flow cytometry analysis were used and some neural markers, as nestin, protein gene product 9.5 (PGP 9.5), microtubule-associated protein 2 (MAP2), glial fibrillary acidic protein (GFAP), and neuron cell surface antigen (A2B5) were examined 24 h and 7 days after the treatment. The results showed that both OECs- or B104-CM treated AT-MSCs express markers of progenitor and mature neurons (nestin, PGP 9.5 and MAP2) in time-dependent manner, display morphological features resembling neuronal cells, and result negative for GFAP and A2B5, astrocyte and oligodendrocyte markers, respectively. This study demonstrated that AT-MSCs can be influenced by the environment, indicating that these cells can respond to environmental cues also versus a neuronal phenotype.

A multilevel screening strategy defines a molecular fingerprint of proregenerative olfactory ensheathing cells and identifies SCARB2, a protein that improves regenerative sprouting of injured sensory spinal axons

Olfactory ensheathing cells (OECs) have neuro-restorative properties in animal models for spinal cord injury, stroke, and amyotrophic lateral sclerosis. Here we used a multistep screening approach to discover genes specifically contributing to the regeneration-promoting properties of OECs. Microarray screening of the injured olfactory pathway and of cultured OECs identified 102 genes that were subsequently functionally characterized in cocultures of OECs and primary dorsal root ganglion (DRG) neurons. Selective siRNA-mediated knockdown of 16 genes in OECs (ADAMTS1, BM385941, FZD1, GFRA1, LEPRE1, NCAM1, NID2, NRP1, MSLN, RND1, S100A9, SCARB2, SERPINI1, SERPINF1, TGFB2, and VAV1) significantly reduced outgrowth of cocultured DRG neurons, indicating that endogenous expression of these genes in OECs supports neurite extension of DRG neurons. In a gain-of-function screen for 18 genes, six (CX3CL1, FZD1, LEPRE1, S100A9, SCARB2, and SERPINI1) enhanced and one (TIMP2) inhibited neurite growth. The most potent hit in both the loss- and gain-of-function screens was SCARB2, a protein that promotes cholesterol secretion. Transplants of fibroblasts that were genetically modified to overexpress SCARB2 significantly increased the number of regenerating DRG axons that grew toward the center of a spinal cord lesion in rats. We conclude that expression of SCARB2 enhances regenerative sprouting and that SCARB2 contributes to OEC-mediated neuronal repair.

Salsolinol induced apoptotic changes in neural stem cells: amelioration by neurotrophin support

Salsolinol (SAL), a catechol isoquinoline has invited considerable attention due to its structural similarity with dopaminergic neurotoxin 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Its high endogenous presence in Parkinsonian brain implicated its possible association with the disease process. SAL is also present in alcohol beverages and certain food materials and can get access to brain especially in conditions of immature or impaired BBB. Besides this, the effect of SAL on neural stem cells (NSCs) which are potential candidates for adult neurogenesis and transplantation mediated rejuvenating attempts for Parkinson's disease (PD) brain has not been known so far. NSCs in both the cases have to overcome suppressive cues of diseased brain for their survival and function. In this study we explored the toxicity of SAL toward NSCs focusing on apoptosis and status of PI3K survival signaling. NSCs cultured from embryonic day 11 rat fetal brain including those differentiated to TH(+ve) colonies, when challenged with SAL (1-100μM), elicited a concentration and time dependent cell death/loss of mitochondrial viability. 10μM SAL on which significant mitochondrial impairment initiated was further used to study mechanism of toxicity. Morphological impairment, enhanced TUNEL positivity, cleaved caspase-3 and decreased Bcl-2:Bax suggested apoptosis. Sal toxicity coincided with reduced pAkt level and its downstream effectors: pCREB, pGSK-3β, Bcl-2 and neurotrophins GDNF, BDNF suggesting repressed PI3K/Akt signaling. Multiple neurotrophic factor support in the form of Olfactory Ensheathing Cell's Conditioned Media (OEC CM) potentially protected NSCs against SAL through activating PI3K/Akt pathway. This was confirmed on adding LY294002 the PI3K inhibitor which abolished the protection. We inferred that SAL exerts substantial toxicity toward NSCs. These findings will lead to better understanding of endogenous threats that might affect the fate of transplanted NSCs and their probable antidotes.

Olfactory ensheathing cell neurorestorotherapy for amyotrophic lateral sclerosis patients: benefits from multiple transplantations

Our previous series of studies have proven that olfactory ensheathing cell (OEC) transplantation appears to be able to slow the rate of clinical progression after OEC transplantation in the first 4 months and cell intracranial (key points for neural network restoration, KPNNR) and/or intraspinal (impaired segments) implants provide benefit for patients (including both the bulbar onset and limb onset subtypes) with amyotrophic lateral sclerosis (ALS). Here we report the results of cell therapy in patients with ALS on the basis of long-term observation following multiple transplants. From March of 2003 to January of 2010, 507 ALS patients received our cellular treatment. Among them, 42 patients underwent further OEC therapy by the route of KPNNR for two or more times (two times in 35 patients, three times in 5 patients, four times in 1 patient, and five times in 1 patient). The time intervals are 13.1 (6-60) months between the first therapy and the second one, 15.2 (8-24) months between the second therapy and the third one, 16 (6-26) months between the third therapy and the fourth one, and 9 months between the fourth therapy and the fifth time. All of the patients exhibited partial neurological functional recovery after each cell-based administration. Firstly, the scores of the ALS Functional Rating Scale (ALS-FRS) and ALS Norris Scale increased by 2.6 + 2.4 (0-8) and 4.9 + 5.2 (0-20) after the first treatment, 1.1 + 1.3 (0-5) and 2.3 + 2.9 (0-13) after the second treatment, 1.1 + 1.5 (0-4), and 3.4 + 6.9 (0-19) after the third treatment, 0.0 + 0.0 (0-0), and 2.5 + 3.5 (0-5) after the fourth treatment, and 1 point after the fifth cellular therapy, which were evaluated by independent neurologists. Secondly, the majority of patients have achieved improvement in electromyogram (EMG) assessments after the first, second, third, and fourth cell transplantation. After the first treatment, among the 42 patients, 36 (85.7%) patients' EMG test results improved, the remaining 6 (14.3%) patients' EMG results showed no remarkable change. After the second treatment, of the 42 patients, 30 (71.4%) patients' EMG results improved, 11 (26.2%) patients showed no remarkable change, and 1 (2.4%) patient became worse. After the third treatment, out of the 7 patients, 4 (57.1%) patients improved, while the remaining 3 (42.9%) patients showed no change. Thirdly, the patients have partially recovered their breathing ability as demonstrated by pulmonary functional tests. After the first treatment, 20 (47.6%) patients' pulmonary function ameliorated. After the second treatment, 18 (42.9%) patients' pulmonary function improved. After the third treatment, 2 (28.6%) patients recovered some pulmonary function. After the fourth and fifth treatment, patients' pulmonary function did not reveal significant change. The results show that multiple doses of cellular therapy definitely serve as a positive role in the treatment of ALS. This repeated and periodic cell-based therapy is strongly recommended for the patients, for better controlling this progressive deterioration disorder.

Expression of tissue transglutaminase on primary olfactory ensheathing cells cultures exposed to stress conditions

Tissue transglutaminase (TG2), a multifunctional enzyme implicated in cellular proliferation and differentiation processes, plays a modulatory role in the cell response to stressors. Herein, we used olfactory ensheathing cells (OECs), representing an unusual population of glial cells to promote axonal regeneration and to provide trophic support, as well as to assess whether the effect of some Growth Factors (GFs), NGF, bFGF or GDNF, on TG2 overexpression induced by stress conditions, such as glutamate or lipopolysaccaride (LPS). Glial Fibrillary Acidic Protein (GFAP) and vimentin were used as markers of astroglial differentiation and cytoskeleton component, respectively. Glutamate or LPS treatment induced a particular increase of TG2 expression. A pre-treatment of the cells with the GFs restored the levels of the protein to that of untreated ones. Our results demonstrate that the treatment of OECs with the GFs was able to restore the OECs oxidative status as modified by stress, also counteracting TG2 overexpression. It suggests that, in OECs, TG2 modulation or inhibition induced by GFs might represent a therapeutic target to control the excitotoxicity and/or inflammation, which are involved in several acute and chronic brain diseases.

Electrophysiological characterization of NSCs after differentiation induced by OEC conditioned medium

PURPOSE

We induced neural stem cells (NSCs) to neurons by olfactory ensheathing cell (OEC) conditioned medium and characterized their electrophysiological properties after neuronal differentiation.

METHODS

Fetal NSCs and OECs were cultured from embryonic day 14 SD rats and the conditioned medium was collected and stored at -20°C when the cell number was up to 80% of the culture flasks. The experiment groups were divided into a control group (cultured with DMEM/F12 without FBS) and an OECs induction group (cultured with OEC conditioned medium and DMEM/F12 without FBS). Immunocytochemistry staining was carried out to identify the neurons derived from NSCs and their electrophysiological properties were characterized after neuronal differentiation using a patch-clamp technique.

RESULTS

The NSCs divided rapidly in the expansion medium, forming small proliferating spheres after 7 days. The OECs induction group presented an evident neuron-like type 7 days after adding OEC conditioned medium, and the nestin immunochemistry staining was positive. The electrophysiological characterization showed that the derived neurons presented a transient inward sodium current and slow outward potassium current under proper electric stimulus, which were blocked by tetrodotoxin (TTX) and tetraethylammonium (TEA).

CONCLUSION

OEC conditioned medium can induce NSCs to form neurons, and electrophysiological characterization demonstrated that the derived neurons presented active electrophysiological properties which are essential for nervous excitation.

A meta-analysis of microarray-based gene expression studies of olfactory bulb-derived olfactory ensheathing cells

Genome wide transcriptional profiling and large scale proteomics have emerged as two powerful methods to dissect the molecular properties of specific neural tissues or cell types on a global scale. Several genome-wide transcriptional profiling and proteomics studies have been published on cultured olfactory ensheathing cells (OEC). In this article we present a meta-analysis of all five published and publicly available micro-array gene expression datasets of cultured early-passage-OB-OEC with other cell types (Schwann cells, late-passage-OB-OEC, mucosa-OEC, an OEC cell line, and acutely dissected OEC). The aim of this meta-analysis is to identify genes and molecular pathways that are found in multiple instead of one isolated study. 454 Genes were detected in at least three out of five microarray datasets. In this "Top-list", genes involved in the biological processes "growth of neurites", "blood vessel development", "migration of cells" and "immune response" were strongly overrepresented. By applying network analysis tools, molecular networks were constructed and Hub-genes were identified that may function as key genes in the above mentioned interrelated processes. We also identified 7 genes (ENTPD2, MATN2, CTSC, PTHLH, GLRX1, COL27A1 and ID2) with uniformly higher or lower expression in early-passage-OB-OEC in all five microarray comparisons. These genes have diverse but intriguing roles in neuroprotection, neurite extension and/or tissue repair. Our meta-analysis provides novel insights into the molecular basis of OB-OEC-mediated neural repair and can serve as a repository for investigators interested in the molecular biology of OEC. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair.

Transplantation of olfactory ensheathing cells promotes axonal regeneration and functional recovery of peripheral nerve lesion in rats

INTRODUCTION

Olfactory ensheathing cells (OECs) hold promise for cell therapy because they may promote regeneration of the central nervous system. However, OECs have been less studied after peripheral nerve injury (PNI). The purpose of this investigation was to determine the effect of OEC transplantation on a severe sciatic nerve (SN) lesion.

METHODS

OECs were injected in rats after section and 2-cm resection of the SN.

RESULTS

Three months after therapy, muscle strength and morphometric studies showed complete restoration of the contractile properties of the gastrocnemius and complete repair of the SN. Immunohistochemistry and RT-PCR studies indicated an increase in the presence of neurotrophic factors. Interestingly, tracking of green fluorescent protein (GFP)-positive OECs showed that no OECs were present in the SN.

DISCUSSION

Our results demonstrate that, after severe PNI, OECs have remarkable potential for nerve regeneration by creating a favorable microenvironment.

From the periphery to the brain: Wiring the olfactory system

The olfactory system represents a perfect model to study the interactions between the central and peripheral nervous systems in order to establish a neural circuit during early embryonic development. In addition, another important feature of this system is the capability to integrate new cells generated in two neurogenic zones: the olfactory epithelium in the periphery and the wall of the lateral ventricles in the CNS, both during development and adulthood. In all these processes the combination and sequence of specific molecular signals plays a critical role in the wiring of the olfactory axons, as well as the precise location of the incoming cell populations to the olfactory bulb. The purpose of this review is to summarize recent insights into the cellular and molecular events that dictate cell settling position and axonal trajectories from their origin in the olfactory placode to the formation of synapses in the olfactory bulb to ensure rapid and reliable transmission of olfactory information from the nose to the brain.

Cell Therapy From Bench to Bedside Translation in CNS Neurorestoratology Era

Recent advances in cell biology, neural injury and repair, and the progress towards development of neurorestorative interventions are the basis for increased optimism. Based on the complexity of the processes of demyelination and remyelination, degeneration and regeneration, damage and repair, functional loss and recovery, it would be expected that effective therapeutic approaches will require a combination of strategies encompassing neuroplasticity, immunomodulation, neuroprotection, neurorepair, neuroreplacement, and neuromodulation. Cell-based restorative treatment has become a new trend, and increasing data worldwide have strongly proven that it has a pivotal therapeutic value in CNS disease. Moreover, functional neurorestoration has been achieved to a certain extent in the CNS clinically. Up to now, the cells successfully used in preclinical experiments and/or clinical trial/treatment include fetal/embryonic brain and spinal cord tissue, stem cells (embryonic stem cells, neural stem/progenitor cells, hematopoietic stem cells, adipose-derived adult stem/precursor cells, skin-derived precursor, induced pluripotent stem cells), glial cells (Schwann cells, oligodendrocyte, olfactory ensheathing cells, astrocytes, microglia, tanycytes), neuronal cells (various phenotypic neurons and Purkinje cells), mesenchymal stromal cells originating from bone marrow, umbilical cord, and umbilical cord blood, epithelial cells derived from the layer of retina and amnion, menstrual blood-derived stem cells, Sertoli cells, and active macrophages, etc. Proof-of-concept indicates that we have now entered a new era in neurorestoratology.

Morphological and biomolecular characterization of the neonatal olfactory bulb ensheathing cell line

Cell transplantation therapy has raised a great interest in the perspective of its employment for nerve tissue repair. Among the various cell populations proposed, olfactory ensheathing glial cells have raised great interest over recent years, especially in the perspective of their employment for neural repair because of their homing capacity in both central and peripheral nervous system. This paper is aimed to provide an in vitro characterization of the NOBEC (neonatal olfactory bulb ensheathing cell) line that was obtained from primary cells dissociated from rat neonatal olfactory bulb (OB) and immortalized by retroviral transduction of SV40 large T antigen. Light and electron microscopy investigation showed that NOBECs are a homogeneous cell population both at structural and ultrastructural level. RT-PCR, Western blotting and immunocytochemistry showed that NOBECs express the glial markers S100, GFAP (Glial Fibrillar Acid Protein) and p75NGFR as well as NRG1 (neuregulin-1) and ErbB1-2-3 receptors; while they are negative for ErbB4. Yet, NOBECs exhibit a high proliferation and migration basal activity and can be transducted with vectors carrying GFP (green fluorescent protein) and NRG1 cDNA. Functional stimulation by means of NRG1-III-beta3 overexpression through viral transduction induced a significant increase in cell proliferation rate while it had no effect on cell migration. Altogether, these results show that NOBEC cell line retain glial features both morphologically and functionally, responding to the NRG1/ErbB-mediated gliotrophic stimulus, and represents thus a good tool for in vitro assays of glial cell manipulation and for in vivo experimental studies of glial cell transplantation in the central and peripheral nervous system.