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

Olfactory ensheathing cells from adult female rats are hybrid glia that promote neural repair

Olfactory ensheathing cells (OECs) are unique glial cells found in both central and peripheral nervous systems where they support continuous axonal outgrowth of olfactory sensory neurons to their targets. Previously we reported that following severe spinal cord injury, OECs transplanted near the injury site modify the inhibitory glial scar and facilitate axon regeneration past the scar border and into the lesion. To better understand the mechanisms underlying the reparative properties of OECs, we used single-cell RNA-sequencing of OECs from adult rats to study their gene expression programs. Our analyses revealed five diverse OEC subtypes, each expressing novel marker genes and pathways indicative of progenitor, axonal regeneration, secreted molecules, or microglia-like functions. We found substantial overlap of OEC genes with those of Schwann cells, but also with microglia, astrocytes, and oligodendrocytes. We confirmed established markers on cultured OECs, and localized select top genes of OEC subtypes in olfactory bulb tissue. We also show that OECs secrete Reelin and Connective tissue growth factor, extracellular matrix molecules which are important for neural repair and axonal outgrowth. Our results support that OECs are a unique hybrid glia, some with progenitor characteristics, and that their gene expression patterns indicate functions related to wound healing, injury repair and axonal regeneration.

The Immunological Roles of Olfactory Ensheathing Cells in the Treatment of Spinal Cord Injury

Spinal cord injury (SCI) is a devastating type of neurological disorder of the central nervous system (CNS) with high mortality and disability. The pathological processes of SCI can usually be described as two stages, namely, primary and acute secondary injuries. Secondary injury produces more significant exacerbations of the initial injury. Among all the mechanisms of secondary damage, infection and inflammatory responses, as the principle culprits in initiating the second phase of SCI, can greatly contribute to the severity of SCI and numerous sequelae after SCI. Therefore, effectively antagonizing pro-inflammatory responses may be a promising treatment strategy to facilitate functional recovery after SCI. Olfactory ensheathing cells (OECs), a unique type of glial cells, have increasingly become potential candidates for cell-based therapy in the injured CNS. Strikingly, there is growing evidence that the mechanisms underlying the anti-inflammatory role of OECs are associated with the immune properties and secretory functions of these cells responsible for anti-neuroinflammation and immunoregulatory effects, leading to maintenance of the internal microenvironment. Accordingly, a more profound understanding of the mechanism of OEC immunological functions in the treatment of SCI would be beneficial to improve the therapeutic clinical applications of OECs for SCI. In this review, we mainly summarize recent research on the cellular and molecular immune attributes of OECs. The unique biological functions of these cells in promoting neural regeneration are discussed in relation of the development of novel therapies for CNS injury.

Phagocytosis by Peripheral Glia: Importance for Nervous System Functions and Implications in Injury and Disease

The central nervous system (CNS) has very limited capacity to regenerate after traumatic injury or disease. In contrast, the peripheral nervous system (PNS) has far greater capacity for regeneration. This difference can be partly attributed to variances in glial-mediated functions, such as axon guidance, structural support, secretion of growth factors and phagocytic activity. Due to their growth-promoting characteristic, transplantation of PNS glia has been trialed for neural repair. After peripheral nerve injuries, Schwann cells (SCs, the main PNS glia) phagocytose myelin debris and attract macrophages to the injury site to aid in debris clearance. One peripheral nerve, the olfactory nerve, is unique in that it continuously regenerates throughout life. The olfactory nerve glia, olfactory ensheathing cells (OECs), are the primary phagocytes within this nerve, continuously clearing axonal debris arising from the normal regeneration of the nerve and after injury. In contrast to SCs, OECs do not appear to attract macrophages. SCs and OECs also respond to and phagocytose bacteria, a function likely critical for tackling microbial invasion of the CNS via peripheral nerves. However, phagocytosis is not always effective; inflammation, aging and/or genetic factors may contribute to compromised phagocytic activity. Here, we highlight the diverse roles of SCs and OECs with the focus on their phagocytic activity under physiological and pathological conditions. We also explore why understanding the contribution of peripheral glia phagocytosis may provide us with translational strategies for achieving axonal regeneration of the injured nervous system and potentially for the treatment of certain neurological diseases.

Study on pathogenic genes of dwarfism disease by next-generation sequencing

BACKGROUND

There are many factors that lead to dwarfism, and the mechanism has not yet been elucidated. Next-generation sequencing may identify candidate-related gene mutations, which may clarify the molecular cause.

AIM

To analyze genetic variation by using a constructed panel related to dwarfism by utilizing next-generation sequencing platform sequencing analysis to screen candidate-related gene mutations.

METHODS

Physical and laboratory characteristics, including clinical examination, growth hormone drug challenge test, serum insulin-like growth factor-1 (IGF-1), IGF binding protein 3, other related tests, imaging examination, and chromosome karyotyping, were analyzed. Next-generation sequencing was performed to analyze pathogenicity variability.

RESULTS

In the 39 dwarfism patients, 10 had pathogenicity variability. Gene variation was found in the OBSL1, SLC26A2, PTPN11, COL27AI, HDAC6, CUL7, FGFR3, DYNC2H1, GH1, and ATP7B genes. Of the 10 patients with pathogenicity variability, the related physical characteristics included double breast development and growth hormone deficiency, enuresis and indirect inguinal hernia on the left, two finger distance of 70.2 cm, head circumference of 49.2 cm, ischium/lower body length of 1.8 cm, weak limb muscles, and partial growth hormone deficiency. After 6 mo of growth hormone therapy, the concentrations of IGF-1 and IGF binding protein 3 increased from 215.2 ± 170.3 to 285.0 ± 166.0 and 3.9 ± 1.4 to 4.2 ± 1.1, respectively.

CONCLUSION

OBSL1, SLC26A2, PTPN11, COL27AI, HDAC6, CUL7, FGFR3, DYNC2H1, GH1, and ATP7B genes may be related to the incidence of dwarfism, and more research needs to be performed to elucidate the mechanism.

The role of non-neuronal cells in hypogonadotropic hypogonadism

The hypothalamic-pituitary-gonadal axis is controlled by gonadotropin-releasing hormone (GnRH) released by the hypothalamus. Disruption of this system leads to impaired reproductive maturation and function, a condition known as hypogonadotropic hypogonadism (HH). Most studies to date have focused on genetic causes of HH that impact neuronal development and function. However, variants may also impact the functioning of non-neuronal cells known as glia. Glial cells make up 50% of brain cells of humans, primates, and rodents. They include radial glial cells, microglia, astrocytes, tanycytes, oligodendrocytes, and oligodendrocyte precursor cells. Many of these cells influence the hypothalamic neuroendocrine system controlling fertility. Indeed, glia regulate GnRH neuronal activity and secretion, acting both at their cell bodies and their nerve endings. Recent work has also made clear that these interactions are an essential aspect of how the HPG axis integrates endocrine, metabolic, and environmental signals to control fertility. Recognition of the clinical importance of interactions between glia and the GnRH network may pave the way for the development of new treatment strategies for dysfunctions of puberty and adult fertility.

Insights into olfactory ensheathing cell development from a laser-microdissection and transcriptome-profiling approach

Olfactory ensheathing cells (OECs) are neural crest-derived glia that ensheath bundles of olfactory axons from their peripheral origins in the olfactory epithelium to their central targets in the olfactory bulb. We took an unbiased laser microdissection and differential RNA-seq approach, validated by in situ hybridization, to identify candidate molecular mechanisms underlying mouse OEC development and differences with the neural crest-derived Schwann cells developing on other peripheral nerves. We identified 25 novel markers for developing OECs in the olfactory mucosa and/or the olfactory nerve layer surrounding the olfactory bulb, of which 15 were OEC-specific (that is, not expressed by Schwann cells). One pan-OEC-specific gene, Ptprz1, encodes a receptor-like tyrosine phosphatase that blocks oligodendrocyte differentiation. Mutant analysis suggests Ptprz1 may also act as a brake on OEC differentiation, and that its loss disrupts olfactory axon targeting. Overall, our results provide new insights into OEC development and the diversification of neural crest-derived glia.

Transplantation of cultured olfactory mucosal cells rescues optic nerve axons in a rat glaucoma model

PURPOSE

To determine whether transplantation of olfactory mucosal cells (OMCs) is able to rescue the loss of optic nerve axons after the intraocular pressure (IOP) is elevated in rats.

METHODS

The IOP was raised by injection of magnetic microspheres into the anterior chamber of the eye. OMCs cultured from the adult olfactory mucosa were transplanted into the region of the optic disc.

RESULTS

We demonstrated that although the raised IOP returned to its normal level at six weeks, there was an irreversible 58% loss of optic nerve axons in the control group. However, the loss of the axons was reduced to 23% in the group with the transplanted OMCs. The Pattern Electroretinograms (pERG) showed that the decrement of the voltage amplitudes in association with the raised IOP was significantly alleviated in the group with transplantation of OMC.

CONCLUSIONS

Transplantation of OMCs is able to rescue loss of optic nerve axons induced by raised IOP in the rats. The pERG recording suggested that the functional activities of the axons are also protected.

TRANSLATIONAL RELEVANCE

The results demonstrated the ability of the transplanted OMCs to protect against the loss of the optic nerve axons and the loss of function caused by raised IOPs. The findings provide a basis for future human clinical trials by autografting OMCs from autologous nasal epithelial biopsies to treat or delay glaucoma diseases.

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.

Olfactory Ensheathing Cells Express α7 Integrin to Mediate Their Migration on Laminin

The unique glia located in the olfactory system, called olfactory ensheathing cells (OECs), are implicated as an attractive choice for transplantation therapy following spinal cord injury because of their pro-regenerative characteristics. Adult OECs are thought to improve functional recovery and regeneration after injury by secreting neurotrophic factors and making cell-to-cell contacts with regenerating processes, but the mechanisms are not well understood. We show first that α7 integrin, a laminin receptor, is highly expressed at the protein level by OECs throughout the olfactory system, i.e., in the olfactory mucosa, olfactory nerve, and olfactory nerve layer of the olfactory bulb. Then we asked if OECs use the α7 integrin receptor directly to promote neurite outgrowth on permissive and neutral substrates, in vitro. We co-cultured α7^+/+ and α7^lacZ/lacZ postnatal cerebral cortical neurons with α7^+/+ or α7^lacZ/lacZ OECs and found that genotype did not effect the ability of OECs to enhance neurite outgrowth by direct contact. Loss of α7 integrin did however significantly decrease the motility of adult OECs in transwell experiments. Twice as many α7^+/+ OECs migrated through laminin-coated transwells compared to α7^+/+ OECs on poly-L-lysine (PLL). This is in contrast to α7^lacZ/lacZ OECs, which showed no migratory preference for laminin substrate over PLL. These results demonstrate that OECs express α7 integrin, and that laminin and its α7 integrin receptor contribute to adult OEC migration in vitro and perhaps also in vivo.

A meta-analysis of efficacy in pre-clinical human stem cell therapies for traumatic brain injury

OBJECTIVES

Evaluate the preclinical evidence for human cell therapies for the treatment of traumatic brain injury (TBI), determine behavioral effect sizes for modified and non-modified cells, and identify variables that correlate with greater effect sizes.

METHODS

A literature search identified 58 animal studies of TBI using human stem cells. Each study received a Quality Index (QI) score based on existing guidelines. Effect sizes for cell therapies were determined for the most common behavioral endpoints: Morris Water Maze (MWM) latency/correct quadrant, and modified Neurological Severity Score (mNSS).

RESULTS

50 studies reported significant behavioral and/or histological improvement. The mean effect size for MWM latency was -1.08 for non-modified cells and -3.35 for modified cells. The mean effect size for MWM percent time in the correct quadrant was 1.66 for non-modified cells and 4.36 for modified cells. The mean effect size on the mNSS was -1.56 for non-modified cells and -4.46 for modified cells. No significant associations were found between methodological variables and effect sizes other than route of administration, where intra-lesional delivery resulted in larger effect sizes than i.v. or ventricular delivery. Studies with higher QI had smaller effect sizes; studies with larger effect sizes had greater standard errors. QI was not associated with journal impact factor.

CONCLUSIONS

Although human cell therapy studies report improved behavioral outcomes in the majority of preclinical literature, the methods are too heterogeneous to facilitate direct comparisons and bias was detected. Replication and standardization are needed to identify procedural variables to yield the best results. We encourage the use of quality criteria and rigor for future studies of human cell therapy in animal models of TBI.

Support of positive association in family-based genetic analysis between COL27A1 and Tourette syndrome

Recently, a genome-wide association study has indicated associations between single nucleotide polymorphisms in the Collagen Type XXVII Alpha 1 gene (COL27A1) and Tourette syndrome in several ethnic populations. To clarify the global relevance of the previously identified SNPs in the development of Tourette syndrome, the associations between polymorphisms in COL27A1 and Tourette syndrome were assessed in Chinese trios. PCR-directed sequencing was used to evaluate the genetic contributions of three SNPs in COL27A1(rs4979356, rs4979357 and rs7868992) using haplotype relative risk (HRR) and transmission disequilibrium tests (TDT) with a total of 260 Tourette syndrome trios. The family-based association was significant between Tourette syndrome and rs4979356 (TDT: χ2 = 4.804, P = 0.033; HRR = 1.75, P = 0.002; HHRR = 1.32, P = 0.027), and transmission disequilibrium was suspected for rs4979357 (TDT: χ2 = 3.969, P = 0.053; HRR = 1.84, P = 0.001; HHRR = 1.29, P = 0.044). No statistically significant allele transfer was found for rs7868992 (TDT: χ2 = 2.177, P = 0.158). Although the TDT results did not remain significant after applying the conservative Bonferroni correction (p = 0.005), the significant positive HRR analysis confirmed the possibility of showing transmission disequilibrium, which provides evidence for an involvement of COL27A1in the development of TS. However, these results need to be verified with larger datasets from different populations.

Olfactory ensheathing cells promote differentiation of neural stem cells and robust neurite extension

AIMS

The goal of this study was to gain insight into the signaling between olfactory ensheathing cells (OECs) and neural stem cells (NSCs). We sought to understand the impact of OECs on NSC differentiation and neurite extension and to begin to elucidate the factors involved in these interactions to provide new targets for therapeutic interventions.

MATERIALS AND METHODS

We utilized lines of OECs that have been extremely well characterized in vitro and in vivo along with well studied NSCs in gels to determine the impact of the coculture in three dimensions. To further elucidate the signaling, we used conditioned media from the OECs as well as fractioned components on NSCs to determine the molecular weight range of the soluble factors that was most responsible for the NSC behavior.

RESULTS

We found that the coculture of NSCs and OECs led to robust NSC differentiation and extremely long neural processes not usually seen with NSCs in three dimensional gels in vitro. Through culture of NSCs with fractioned OEC media, we determined that molecules larger than 30 kDa have the greatest impact on the NSC behavior.

CONCLUSIONS

Overall, our findings suggest that cocultures of NSCs and OECs may be a novel combination therapy for neural injuries including spinal cord injury (SCI). Furthermore, we have identified a class of molecules which plays a substantial role in the behavior that provides new targets for investigating pharmacological therapies.

GnRH, anosmia and hypogonadotropic hypogonadism--where are we?

Gonadotropin releasing hormone (GnRH) neurons originate the nasal placode and migrate into the brain during prenatal development. Once within the brain, these cells become integral components of the hypothalamic-pituitary-gonadal axis, essential for reproductive function. Disruption of this system causes hypogonadotropic hypogonadism (HH). HH associated with anosmia is clinically defined as Kallman syndrome (KS). Recent work examining the developing nasal region has shed new light on cellular composition, cell interactions and molecular cues responsible for the development of this system in different species. This review discusses some developmental aspects, animal models and current advancements in our understanding of pathologies affecting GnRH. In addition we discuss how development of neural crest derivatives such as the glia of the olfactory system and craniofacial structures control GnRH development and reproductive function.

Axon plasticity in the mammalian central nervous system after injury

It is widely recognized that severed axons in the adult central nervous system (CNS) have limited capacity to regenerate. However, mounting evidence from studies of CNS injury response and repair is challenging the prevalent view that the adult mammalian CNS is incapable of structural reorganization to adapt to an altered environment. Animal studies demonstrate the potential to achieve significant anatomical repair and functional recovery following CNS injury by manipulating axon growth regulators alone or in combination with activity-dependent strategies. With a growing understanding of the cellular and molecular mechanisms regulating axon plasticity, and the availability of new experimental tools to map detour circuits of functional importance, directing circuit rewiring to promote functional recovery may be achieved.

A panel of protein markers for the early detection of lung cancer with bronchial brushing specimens

BACKGROUND

To date, no robust biomarkers have been available in clinical practice that can provide an early diagnostic evaluation of lung cancer. The objective of this study was to identify potential biomarkers for the early detection of lung cancer using bronchial brushing specimens.

METHODS

Immunocytochemistry was used to investigate the expression of 35 proteins in 880 bronchial brushing specimens from both outpatients and inpatients who had either lung cancer or benign lung lesions. An optimal panel was identified that had high sensitivity and considerable specificity for detecting lung cancer. Associations between protein expression and clinicopathologic parameters were assessed.

RESULTS

Tumor protein 53 (TP53), TP63, Ki67, epidermal growth factor receptor (EGFR), minichromosome maintenance complex component 6 (MCM6), MCM7, uncharacterized proteins KIAA1522 and KIAA0317, and ubiquitin-protein ligase UHR1 (ICBP90) frequently presented high expression in bronchial brushing specimens from patients who had lung cancer compared with patients who had benign lung lesions. A 6-protein panel consisting of TP53, Ki67, MCM6, MCM7, KIAA1522, and KIAA0317 was identified as the best combination, with sensitivity of 81.1% (309 of 381 specimens) for detecting nonsmall cell lung cancer (NSCLC) and 86.8% (145 of 167 specimens) for detecting small cell lung cancer (SCLC) (specificity, 83.3%; 65 of 78 specimens). The combination of cytology and the protein panel significantly improved the sensitivity of bronchial brushing examination for detecting lung cancer (P<.00001), which increased from 49.1% to 81% in early stage NSCLC (stage I and II). In combined analyses, the protein panel was positively associated with patient sex (P=.00033), tumor type (P<.00001), tumor location (P<.00001), and lymph node metastasis (P=.028).

CONCLUSIONS

The 6-protein panel is a potential biomarker for the early detection of lung cancer in bronchial brushings.

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.

Understanding the neural repair-promoting properties of olfactory ensheathing cells

Olfactory ensheathing glial cells (OECs) are a specialized type of glia that form a continuously aligned cellular pathway that actively supports unprecedented regeneration of primary olfactory axons from the periphery into the central nervous system. Implantation of OECs stimulates neural repair in experimental models of spinal cord, brain and peripheral nerve injury and delays disease progression in animal models for neurodegenerative diseases like amyotrophic lateral sclerosis. OECs implanted in the injured spinal cord display a plethora of pro-regenerative effects; they promote axonal regeneration, reorganize the glial scar, remyelinate axons, stimulate blood vessel formation, have phagocytic properties and modulate the immune response. Recently genome wide transcriptional profiling and proteomics analysis combined with classical or larger scale "medium-throughput" bioassays have provided novel insights into the molecular mechanism that endow OECs with their pro-regenerative properties. Here we review these studies and show that the gaps that existed in our understanding of the molecular basis of the reparative properties of OECs are narrowing. OECs express functionally connected sets of genes that can be linked to at least 10 distinct processes directly relevant to neural repair. The data indicate that OECs exhibit a range of synergistic cellular activities, including active and passive stimulation of axon regeneration (by secretion of growth factors, axon guidance molecules and basement membrane components) and critical aspects of tissue repair (by structural remodeling and support, modulation of the immune system, enhancement of neurotrophic and antigenic stimuli and by metabolizing toxic macromolecules). Future experimentation will have to further explore the newly acquired knowledge to enhance the therapeutic potential of OECs.

Tissue sparing, behavioral recovery, supraspinal axonal sparing/regeneration following sub-acute glial transplantation in a model of spinal cord contusion

Background

It has been shown that olfactory ensheathing glia (OEG) and Schwann cell (SCs) transplantation are beneficial as cellular treatments for spinal cord injury (SCI), especially acute and sub-acute time points. In this study, we transplanted DsRED transduced adult OEG and SCs sub-acutely (14 days) following a T10 moderate spinal cord contusion injury in the rat. Behaviour was measured by open field (BBB) and horizontal ladder walking tests to ascertain improvements in locomotor function. Fluorogold staining was injected into the distal spinal cord to determine the extent of supraspinal and propriospinal axonal sparing/regeneration at 4 months post injection time point. The purpose of this study was to investigate if OEG and SCs cells injected sub acutely (14 days after injury) could: (i) improve behavioral outcomes, (ii) induce sparing/regeneration of propriospinal and supraspinal projections, and (iii) reduce tissue loss.

Results

OEG and SCs transplanted rats showed significant increased locomotion when compared to control injury only in the open field tests (BBB). However, the ladder walk test did not show statistically significant differences between treatment and control groups. Fluorogold retrograde tracing showed a statistically significant increase in the number of supraspinal nuclei projecting into the distal spinal cord in both OEG and SCs transplanted rats. These included the raphe, reticular and vestibular systems. Further pairwise multiple comparison tests also showed a statistically significant increase in raphe projecting neurons in OEG transplanted rats when compared to SCs transplanted animals. Immunohistochemistry of spinal cord sections short term (2 weeks) and long term (4 months) showed differences in host glial activity, migration and proteoglycan deposits between the two cell types. Histochemical staining revealed that the volume of tissue remaining at the lesion site had increased in all OEG and SCs treated groups. Significant tissue sparing was observed at both time points following glial SCs transplantation. In addition, OEG transplants showed significantly decreased chondroitin proteoglycan synthesis in the lesion site, suggesting a more CNS tolerant graft.

Conclusions

These results show that transplantation of OEG and SCs in a sub-acute phase can improve anatomical outcomes after a contusion injury to the spinal cord, by increasing the number of spared/regenerated supraspinal fibers, reducing cavitation and enhancing tissue integrity. This provides important information on the time window of glial transplantation for the repair of the spinal cord.

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.

Cell type- and isotype-specific expression and regulation of β-tubulins in primary olfactory ensheathing cells and Schwann cells in vitro

Olfactory ensheathing cells (OECs) and Schwann cells (SCs) are closely-related cell types with regeneration-promoting properties. Comparative gene expression analysis is particularly relevant since it may explain cell type-specific effects and guide the use of each cell type into special clinical applications. In the present study, we focused on β-tubulin isotype expression in primary adult canine glia as a translational large animal model. β-tubulins so far have been studied mainly in non-neuronal tumors and implied in tumorigenic growth. We show here that primary OECs and SCs expressed βII-V isotype mRNA. Interestingly, βIII-tubulin mRNA and protein expression was high in OECs and low in SCs, while fibroblast growth factor-2 (FGF-2) induced its down-regulation in both cell types to the same extent. This was in contrast to βV-tubulin mRNA which was similarly expressed in both cell types and unaltered by FGF-2. Immunocytochemical analysis revealed that OEC cultures contained a higher percentage of βIII-tubulin-positive cells compared to SC cultures. Addition of FGF-2 reduced the number of βIII-tubulin-positive cells in both cultures and significantly increased the percentage of cells with a multipolar morphology. Taken together, we demonstrate cell type-specific expression (βIII) and isotype-specific regulation (βIII, βV) of β-tubulin isotypes in OECs and SCs. While differential expression of βIII-tubulin in primary glial cell types with identical proliferative behaviour argues for novel functions unrelated to tumorigenic growth, strong βIII-tubulin expression in OECs may help to explain the specific properties of this glial cell type.

Olfactory Ensheathing Cells Rescue Optic Nerve Fibers in a Rat Glaucoma Model

PURPOSE

To determine if transplantation of olfactory ensheathing cells (OECs) can reduce loss of optic nerve axons after raised intraocular pressure (IOP) in the rat.

METHODS

OECs cultured from the adult olfactory mucosa were transplanted into the region of the optic disc. The IOP was raised by injection of magnetic microspheres into the anterior chamber.

RESULTS

At 4 weeks after raising the IOP, the transplanted OECs had migrated into the dorsal area of the optic nerve head (ONH) where they surrounded the optic nerve fibers with a non-myelinated ensheathment. The mean amount of damage to the ONH astrocytic area in rats was 51.0% compared with 85.8% in those without OEC transplants (P < 0.02) and the mean loss of axons in the optic nerve was 51.0% compared with 80.3% in the absence of OECs (P < 0.01).

CONCLUSIONS

OECs transplanted into the region of the ONH of the rat can reduce the loss of axons and the damage to ONH astrocytes caused by raised IOP.

TRANSLATIONAL RELEVANCE

Confirmation of these preliminary experimental data, further understanding of possible mechanisms of axonal protection by OECs, and the longer-term time course of protection could provide a basis for future human clinical trials of autografted OECs, which would be available from autologous nasal epithelial biopsies.

Comparison of Schwann cells and olfactory ensheathing cells for peripheral nerve gap bridging

INTRODUCTION

Previously, we introduced the biogenic conduit (BC) as a novel autologous nerve conduit for bridging peripheral nerve defects and tested its regenerative capacity in a short- and long-term setting. The aim of the present study was to clarify whether intraluminal application of regeneration-promoting glial cells, including Schwann cells (SC) and olfactory ensheathing cells (OEC), displayed differential effects after sciatic nerve gap bridging.

MATERIAL AND METHODS

BCs were generated as previously described. The conduits filled with fibrin/SC (n = 8) and fibrin/OEC (n = 8) were compared to autologous nerve transplants (NT; n = 8) in the 15-mm sciatic nerve gap lesion model of the rat. The sciatic functional index was evaluated every 4 weeks. After 16 weeks, histological evaluation followed regarding nerve area, axon number, myelination index and N ratio.

RESULTS

Common to all groups was a continual improvement in motor function during the observation period. Recovery was significantly better after SC transplantation compared to OEC (p < 0.01). Both cell transplantation groups showed significantly worse function than the NT group (p < 0.01). Whereas nerve area and axon number were correlated to function, being significantly lowest in the OEC group (p < 0.001), both cell groups showed lowered myelination (p < 0.001) and lower N ratio compared to the NT group.

DISCUSSION

SC-filled BCs led to improved regeneration compared to OEC-filled BCs in a 15-mm-long nerve gap model of the rat.

Cytokines and olfactory bulb microglia in response to bacterial challenge in the compromised primary olfactory pathway

Background

The primary olfactory pathway is a potential route through which microorganisms from the periphery could potentially access the central nervous system. Our previous studies demonstrated that if the olfactory epithelium was damaged, bacteria administered into the nasal cavity induced nitric oxide production in olfactory ensheathing cells. This study investigates the cytokine profile of olfactory tissues as a consequence of bacterial challenge and establishes whether or not the bacteria are able to reach the olfactory bulb in the central nervous system.

Methods

The olfactory epithelium of C57BL/6 mice was damaged by unilateral Triton X-100 nasal washing, and Staphylococcus aureus was administered ipsilaterally 4 days later. Olfactory mucosa and bulb were harvested 6 h, 24 h and 5 days after inoculation and their cytokine profile compared to control tissues. The fate of S. aureus and the response of bulbar microglia were examined using fluorescence microscopy and transmission electron microscopy.

Results

In the olfactory mucosa, administered S. aureus was present in supporting cells of the olfactory epithelium, and macrophages and olfactory nerve bundles in the lamina propria. Fluorescein isothiocyanate-conjugated S. aureus was observed within the olfactory mucosa and bulb 6 h after inoculation, but remained restricted to the peripheral layers up to 5 days later. At the 24-h time point, the level of interleukin-6 (IL-6) and tumour necrosis factor-α in the compromised olfactory tissues challenged with bacteria (12,466 ± 956 pg/ml and 552 ± 193 pg/ml, respectively) was significantly higher than that in compromised olfactory tissues alone (6,092 ± 1,403 pg/ml and 80 ± 2 pg/ml, respectively). Immunohistochemistry confirmed that IL-6 was present in several cell types including olfactory ensheathing cells and mitral cells of the olfactory bulb. Concurrently, there was a 4.4-, 4.5- and 2.8-fold increase in the density of iNOS-expressing cells in the olfactory mucosa, olfactory nerve and glomerular layers combined, and granule layer of the olfactory bulb, respectively.

Conclusions

Bacteria are able to penetrate the immunological defence of the compromised olfactory mucosa and infiltrate the olfactory bulb within 6 h even though a proinflammatory profile is mounted. Activated microglia may have a role in restricting bacteria to the outer layers of the olfactory bulb.

Myelin-associated proteins block the migration of olfactory ensheathing cells: an in vitro study using single-cell tracking and traction force microscopy

Newly generated olfactory receptor axons grow from the peripheral to the central nervous system aided by olfactory ensheathing cells (OECs). Thus, OEC transplantation has emerged as a promising therapy for spinal cord injuries and for other neural diseases. However, these cells do not present a uniform population, but instead a functionally heterogeneous population that exhibits a variety of responses including adhesion, repulsion, and crossover during cell-cell and cell-matrix interactions. Some studies report that the migratory properties of OECs are compromised by inhibitory molecules and potentiated by chemical gradients. Here, we demonstrated that rodent OECs express all the components of the Nogo receptor complex and that their migration is blocked by myelin. Next, we used cell tracking and traction force microscopy to analyze OEC migration and its mechanical properties over myelin. Our data relate the decrease of traction force of OEC with lower migratory capacity over myelin, which correlates with changes in the F-actin cytoskeleton and focal adhesion distribution. Lastly, OEC traction force and migratory capacity is enhanced after cell incubation with the Nogo receptor inhibitor NEP1-40.

Cellular therapies for treating pain associated with spinal cord injury

Spinal cord injury leads to immense disability and loss of quality of life in human with no satisfactory clinical cure. Cell-based or cell-related therapies have emerged as promising therapeutic potentials both in regeneration of spinal cord and mitigation of neuropathic pain due to spinal cord injury. This article reviews the various options and their latest developments with an update on their therapeutic potentials and clinical trialing.