Isolation, characterization, and genetic profiling of subpopulations of olfactory ensheathing cells from the olfactory bulb

Olfactory ensheathing cells as candidate cells for chronic pain treatment

Chronic pain is often accompanied by tissue damage and pain hypersensitivity. It easily relapses and is challenging to cure, which seriously affects the patients' quality of life and is an urgent problem to be solved. Current treatment methods primarily rely on morphine drugs, which do not address the underlying nerve injury and may cause adverse reactions. Therefore, in recent years, scientists have shifted their focus from chronic pain treatment to cell transplantation. This review describes the classification and mechanism of chronic pain through the introduction of the characteristics of olfactory ensheathing cells (OECs), an in-depth discussion of special glial cells through the phagocytosis of nerve debris, receptor-ligand interactions, providing nutrition, and other inhibition of neuroinflammation, and ultimately supporting axon regeneration and mitigation of chronic pain. This review summarizes the potential and limitations of OECs for treating chronic pain by objectively analyzing relevant clinical trials and methods to enhance efficacy and future development prospects.

Olfactory ensheathing cells and neuropathic pain

Damage to the nervous system can lead to functional impairment, including sensory and motor functions. Importantly, neuropathic pain (NPP) can be induced after nerve injury, which seriously affects the quality of life of patients. Therefore, the repair of nerve damage and the treatment of pain are particularly important. However, the current treatment of NPP is very weak, which promotes researchers to find new methods and directions for treatment. Recently, cell transplantation technology has received great attention and has become a hot spot for the treatment of nerve injury and pain. Olfactory ensheathing cells (OECs) are a kind of glial cells with the characteristics of lifelong survival in the nervous system and continuous division and renewal. They also secrete a variety of neurotrophic factors, bridge the fibers at both ends of the injured nerve, change the local injury microenvironment, and promote axon regeneration and other biological functions. Different studies have revealed that the transplantation of OECs can repair damaged nerves and exert analgesic effect. Some progress has been made in the effect of OECs transplantation in inhibiting NPP. Therefore, in this paper, we provided a comprehensive overview of the biology of OECs, described the possible pathogenesis of NPP. Moreover, we discussed on the therapeutic effect of OECs transplantation on central nervous system injury and NPP, and prospected some possible problems of OECs transplantation as pain treatment. To provide some valuable information for the treatment of pain by OECs transplantation in the future.

The Anti-inflammation Property of Olfactory Ensheathing Cells in Neural Regeneration After Spinal Cord Injury

Neural regeneration has troubled investigators worldwide in the past decades. Currently, cell transplantation emerged as a breakthrough targeted therapy for spinal cord injury (SCI) in the neurotrauma field, which provides a promising strategy in neural regeneration. Olfactory ensheathing cells (OECs), a specialized type of glial cells, is considered as the excellent candidate due to its unique variable and intrinsic regeneration-supportive properties. In fact, OECs could support olfactory receptor neuron turnover and axonal extension, which is essential to maintain the function of olfactory nervous system. Hitherto, an increasing number of literatures demonstrate that transplantation of OECs exerts vital roles in neural regeneration and functional recovery after neural injury, including central and peripheral nervous system. It is common knowledge that the deteriorating microenvironment (ischemia, hypoxia, scar, acute and chronic inflammation, etc.) resulting from injured nervous system is adverse for neural regeneration. Interestingly, recent studies indicated that OECs could promote neural repair through improvement of the disastrous microenvironments, especially to the overwhelmed inflammatory responses. Although OECs possess unusual advantages over other cells for neural repair, particularly in SCI, the mechanisms of OEC-mediated neural repair are still controversial with regard to anti-inflammation. Therefore, it is significant to summarize the anti-inflammation property of OECs, which is helpful to understand the biological characteristics of OECs and drive future studies. Here, we mainly focus on the anti-inflammatory role of OECs to make systematic review and discuss OEC-based therapy for CNS injury.

Comparison of the effects of two therapeutic strategies based on olfactory ensheathing cell transplantation and repetitive magnetic stimulation after spinal cord injury in female mice

Spinal cord injury (SCI) is a debilitating condition, which leads to a permanent loss of functions below the injury site. The events which take place after SCI are characterized by cellular death, release of inhibitory factors, and inflammation. Many therapies have been studied to cure SCI, among them magnetic stimulation aims to reduce the secondary damages in particular by decreasing apoptosis, while, cellular transplantation promotes neuroregeneration by enhancing axonal regrowth. In the present study, we compared individually primary olfactory ensheathing cell (OEC) transplantation and repetitive trans‐spinal magnetic stimulation (rTSMS) and then, we combined these two therapeutic approaches on tissue repair and functional recovery after SCI. To do so, SCIs were performed at Th10 level on female C57BL/6 mice, which were randomized into four groups: SCI, SCI + primary bOECs, SCI + STM, SCI + primary bulbar olfactory ensheathing cells (bOECs) + stimulation (STM). On these animals bioluminescence, immunohistological, and behavioral experiments were performed after SCI. Our results show that rTSMS has beneficial effect on the modulation of spinal scar by reducing fibrosis, demyelination, and microglial cell activation and by increasing the astroglial component of the scar, while, primary bOEC transplantation decreases microglial reactivity. At the opposite, locotronic experiments show that both treatments induce functional recovery. We did not observed any additional effect by combining the two therapeutic approaches. Taken together, the present study indicates that primary bOEC transplantation and rTSMS treatment act through different mechanisms after SCI to induce functional recovery. In our experimental paradigm, the combination of the two therapies does not induce any additional benefit.

In vitro, In vivo and Ex vivo Models for Peripheral Nerve Injury and Regeneration

Peripheral Nerve Injuries (PNI) frequently occur secondary to traumatic injuries. Recovery from these injuries can be expectedly poor, especially in proximal injuries. In order to study and improve peripheral nerve regeneration, scientists rely on peripheral nerve models to identify and test therapeutic interventions. In this review, we discuss the best described and most commonly used peripheral nerve models that scientists have and continue to use to study peripheral nerve physiology and function.

Severe Zinc Deficiency Causes the Loss and Apoptosis of Olfactory Ensheathing Cells (OECs) and Olfactory Deficit

Dietary zinc deficiency may lead to olfactory deficits, whose mechanism remains largely elusive. Olfactory ensheathing cells (OECs), a type of glial cells that support the function and neurogenesis in the olfactory bulb (OB), may play a pivotal role in the maintenance of the olfactory system. In the present study, we established a rat model of dietary zinc deficiency and found that severe zinc deficiency, but not marginal zinc deficiency, caused significantly reduced food intake, growth retardation, and apparent olfactory deficit in growing rats. We showed that severe zinc deficiency resulted in the loss of OECs in the olfactory nerve layer (ONL) of the olfactory bulb. In addition, we revealed that the number of TUNEL-positive cells increased markedly in the region, suggesting an involvement of apoptotic cell death in zinc deficiency-induced loss of OECs. Moreover, we found that treatment with zinc chelator N,N,N'N',-tetrakis (2-pyridylmethyl)ethylenediamine (TPEN) triggered the apoptosis of in vitro-cultured primary OECs. The apoptosis of OECs was correlated with significantly elevated expression of p53. Importantly, TUNEL and CCK-8 assays both demonstrated that treatment with p53 antagonist pifithrin-α (PFT-α) markedly attenuated TPEN-induced OEC apoptosis. These findings implicated that p53-triggered apoptosis of OECs might play an integral role in zinc deficiency-induced olfactory malfunction.

Cell therapy assisted autotransplantation of olfactory tract into the optic nerve: A potential treatment for optic neuropathy

Optic neuropathy is an invaliding pathology with diverse clinical manifestation and varying causes. Current understanding of etiopathological aspects of optical neuropathy does not provide an effective treatment protocol. In this article we discuss existing treatment methods, and their effectiveness, evaluated depending on disease etiology. The olfactory tract is a source of olfactory ensheating cells, whose unique properties can have treatment potential in correction of nerve degeneration. Transplantation of an olfactory tract graft into the damaged optic nerve is a technically achievable intervention, though anatomical limitations exist in the proposed surgical access. Optic nerve defects can also be potentially treated with axon growth stimulating therapy (Zymosan and CTP-cAMP). Optic neuropathy can be potentially cured by autotransplantation of a portion of the olfactory tract. Neuroanatomical and histomorphological aspects of olfactory tract autotransplantation into the damaged optic nerve are provided. Feasibility, technical and anatomical features, potential setbacks and limitations are discussed. Anatomical limitations exist, but with current neurosurgical technology can be overcome. Regenerative potential of olfactory tract glial cells plays an important role in nerve restoration and can play a crucial role in further understanding of nerve degeneration treatment.

Olfactory ensheathing cells from the nasal mucosa and olfactory bulb have distinct membrane properties

Transplantation of olfactory ensheathing cells (OECs) is a potential therapy for the regeneration of damaged neurons. While they maintain tissue homeostasis in the olfactory mucosa (OM) and olfactory bulb (OB), their regenerative properties also support the normal sense of smell by enabling continual turnover and axonal regrowth of olfactory sensory neurons (OSNs). However, the molecular physiology of OECs is not fully understood, especially that of OECs from the mucosa. Here, we carried out whole-cell patch-clamp recordings from individual OECs cultured from the OM and OB of the adult rat, and from the human OM. A subset of OECs from the rat OM cultured 1-3 days in vitro had large weakly rectifying K⁺ currents, which were sensitive to Ba²⁺ and desipramine, blockers of Kir4-family channels. Kir4.1 immunofluorescence was detectable in cultured OM cells colabeled for the OEC marker S100, and in S100-labeled cells found adjacent to OSN axons in mucosal sections. OECs cultured from rat OB had distinct properties though, displaying strongly rectifying inward currents at hyperpolarized membrane potentials and strongly rectifying outward currents at depolarized potentials. Kir4.1 immunofluorescence was not evident in OECs adjacent to axons of OSNs in the OB. A subset of human OECs cultured from the OM of adults had membrane properties comparable to those of the rat OM that is dominated by Ba²⁺ -sensitive weak inwardly rectifying currents. The membrane properties of peripheral OECs are different to those of central OECs, suggesting they may play distinct roles during olfaction.

Sublamina-specific organization of the blood brain barrier in the mouse olfactory nerve layer

Astrocytes constitute the main glial component of the mammalian blood brain barrier (BBB). However, in the olfactory bulb (OB), the olfactory nerve layer (ONL) is almost devoid of astrocytes, raising the question which glial cells are part of the BBB. We used mice expressing EGFP in astrocytes and tdTomato in olfactory ensheathing cells (OECs), a specialized type of glial cells in the ONL, to unequivocally identify both glial cell types and investigate their contribution to the BBB in the olfactory bulb. OECs were located exclusively in the ONL, while somata of astrocytes were located in deeper layers and extended processes in the inner sublamina of the ONL. These processes surrounded blood vessels and contained aquaporin-4, an astrocytic protein enriched at the BBB. In the outer sublamina of the ONL, in contrast, blood vessels were surrounded by aquaporin-4-negative processes of OECs. Transcardial perfusion of blood vessels with lanthanum and subsequent visualization by electron microscopy showed that blood vessels enwrapped by OECs possessed intact tight junctions. In acute olfactory bulb preparations, injection of fluorescent glucose 6-NBDG into blood vessels resulted in labeling of OECs, indicating glucose transport from the perivascular space into OECs. In addition, Ca²⁺ transients in OECs in the outer sublamina evoked vasoconstriction, whereas Ca²⁺ signaling in OECs of the inner sublamina had no effect on adjacent blood vessels. Our results demonstrate that the BBB in the inner sublamina of the ONL contains astrocytes, while in the outer ONL OECs are part of the BBB.

Inhibition of ADAMTS-4 Expression in Olfactory Ensheathing Cells Enhances Recovery after Transplantation within Spinal Cord Injury

Spinal cord injury (SCI) induces permanent loss of sensitive and motor functions below the injury level. To date, a wide variety of cells has been used as biotherapies to cure SCI in different animal paradigms. Specifically, olfactory ensheathing cells (OECs) is one of the most promising. Indeed, OECs have been shown to enhance recovery in many animal studies. Moreover, OECs transplantation has been applied to a paraplegic patient and have shown beneficial effects. However, it has been reported that the significant level of recovery varies among different patients. Therefore, it is of primary importance to enhance the regenerative efficiency of OECs for better translations. Recently, it has been shown that inhibiting ADAMTS4 expression in glial cells in vitro increases their synthesis of neurotrophic factors. We hypothesized that the expression of neurotrophic factors secreted by OECs can be increased by the deletion of ADAMTS4. Taking advantage of ADAMTS4^-/- mouse line, we produce ADAMTS4 deficient primary OEC cultures and then we investigated their regenerative potential after SCI. By using quantitative polymerase chain reaction, bioluminescence imaging, measurement of locomotor activity, electrophysiological studies, and immunohistochemistry, our results show that ADAMTS4^-/- olfactory bulb OEC (bOECs) primary cultures upregulate their trophic factor expression in vitro, and that the transplantation of ADAMTS4^-/- bOECs in a severe SCI model increases functional recovery and tissue repair in vivo. Altogether, our study reveals, for the first time, that primary bOEC cultures transplantation can be potentialized by inhibition of the expression of ADAMTS4.

Selective Cre-mediated gene deletion identifies connexin 43 as the main connexin channel supporting olfactory ensheathing cell networks

Many functions of glial cells depend on the formation of selective glial networks mediated by gap junctions formed by members of the connexin family. Olfactory ensheathing cells (OECs) are specialized glia associated with olfactory sensory neuron axons. Like other glia, they form selective networks, however, the connexins that support OEC connectivity in vivo have not been identified. We used an in vivo mouse model to selectively delete candidate connexin genes with temporal control from OECs and address the physiological consequences. Using this model, we effectively abolished the expression of connexin 43 (Cx43) in OECs in both juvenile and adult mice. Cx43-deleted OECs exhibited features consistent with the loss of gap junctions including reduced membrane conductance, largely reduced sensitivity to the gap junction blocker meclofenamic acid and loss of dye coupling. This indicates that Cx43, a typically astrocytic connexin, is the main connexin forming functional channels in OECs. Despite these changes in functional properties, the deletion of Cx43 deletion did not alter the density of OECs. The strategy used here may prove useful to delete other candidate genes to better understand the functional roles of OECs in vivo.

Anatomy of the olfactory mucosa

The classic notion that humans are microsmatic animals was born from comparative anatomy studies showing the reduction in the size of both the olfactory bulbs and the limbic brain relative to the whole brain. However, the human olfactory system contains a number of neurons comparable to that of most other mammals, and humans have exquisite olfactory abilities. Major advances in molecular and genetic research have resulted in the identification of extremely large gene families that express receptors for sensing odors. Such advances have led to a renaissance of studies focused on both human and nonhuman aspects of olfactory physiology and function. Evidence that olfactory dysfunction is among the earliest signs of a number of neurodegenerative and neuropsychiatric disorders has led to considerable interest in the use of olfactory epithelial biopsies for potentially identifying such disorders. Moreover, the unique features of the olfactory ensheathing cells have made the olfactory mucosa a promising and unexpected source of cells for treating spinal cord injuries and other neural injuries in which cell guidance is critical. The olfactory system of humans and other primates differs in many ways from that of other species. In this chapter we provide an overview of the anatomy of not only the human olfactory mucosa but of mucosae from a range of mammals from which more detailed information is available. Basic information regarding the general organization of the olfactory mucosa, including its receptor cells and the large number of other cell types critical for their maintenance and function, is provided. Cross-species comparisons are made when appropriate. The polemic issue of the human vomeronasal organ in both the adult and fetus is discussed, along with recent findings regarding olfactory subsystems within the nose of a number of mammals (e.g., the septal organ and Grüneberg ganglion).

Allogenic Fc Domain-Facilitated Uptake of IgG in Nasal Lamina Propria: Friend or Foe for Intranasal CNS Delivery?

Background: The use of therapeutic antibodies for the treatment of neurological diseases is of increasing interest. Nose-to-brain drug delivery is one strategy to bypass the blood brain barrier. The neonatal Fc receptor (FcRn) plays an important role in transepithelial transcytosis of immunoglobulin G (IgG). Recently, the presence of the FcRn was observed in nasal respiratory mucosa. The aim of the present study was to determine the presence of functional FcRn in olfactory mucosa and to evaluate its role in drug delivery. Methods: Immunoreactivity and messenger RNA (mRNA) expression of FcRn was determined in ex vivo porcine olfactory mucosa. Uptake of IgG was performed in a side-by-side cell and analysed by immunofluorescence. Results: FcRn was found in epithelial and basal cells of the olfactory epithelium as well as in glands, cavernous bodies and blood vessels. Allogenic porcine IgGs were found time-dependently in the lamina propria and along axonal bundles, while only small amounts of xenogenic human IgGs were detected. Interestingly, lymphoid follicles were spared from allogenic IgGs. Conclusion: Fc-mediated transport of IgG across the nasal epithelial barrier may have significant potential for intranasal delivery, but the relevance of immune interaction in lymphoid follicles must be clarified to avoid immunogenicity.

Single-cell profiling of the developing mouse brain and spinal cord with split-pool barcoding

To facilitate scalable profiling of single cells, we developed split-pool ligation-based transcriptome sequencing (SPLiT-seq), a single-cell RNA-seq (scRNA-seq) method that labels the cellular origin of RNA through combinatorial barcoding. SPLiT-seq is compatible with fixed cells or nuclei, allows efficient sample multiplexing, and requires no customized equipment. We used SPLiT-seq to analyze 156,049 single-nucleus transcriptomes from postnatal day 2 and 11 mouse brains and spinal cords. More than 100 cell types were identified, with gene expression patterns corresponding to cellular function, regional specificity, and stage of differentiation. Pseudotime analysis revealed transcriptional programs driving four developmental lineages, providing a snapshot of early postnatal development in the murine central nervous system. SPLiT-seq provides a path toward comprehensive single-cell transcriptomic analysis of other similarly complex multicellular systems.

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.

Morphological study of a connexin 43-GFP reporter mouse highlights glial heterogeneity, amacrine cells, and olfactory ensheathing cells

Connexin 43 (Cx43) is the main astrocytic connexin and forms the basis of the glial syncytium. The morphology of connexin-expressing cells can be best studied in transgenic mouse lines expressing cytoplasmic fluorescent reporters, since immunolabeling the plaques can obscure the shapes of the individual cells. The Cx43kiECFP mouse generated by Degen et al. (FASEBJ 26:4576, 2012) expresses cytosolic ECFP and has previously been used to establish that Cx43 may not be expressed by all astrocytes within a population, and this can vary in a region-dependent way. To establish this mouse line as a tool for future astrocyte and connexin research, we sought to consolidate reporter authenticity, studying cell types and within-region population heterogeneity. Applying anti-GFP, all cell types related to astroglia were positive-namely, protoplasmic astrocytes in the hippocampus, cortex, thalamus, spinal cord, olfactory bulb, cerebellum with Bergmann glia and astrocytes also in the molecular layer, and retinal Müller cells and astrocytes. Labeled cell types further comprise white matter astrocytes, olfactory ensheathing cells, radial glia-like stem cells, retinal pigment epithelium cells, ependymal cells, and meningeal cells. We furthermore describe a retinal Cx43-expressing amacrine cell morphologically reminiscent of ON-OFF wide-field amacrine cells, representing the first example of a mammalian CNS neuron-expressing Cx43 protein. In double staining with cell type-specific markers (GFAP, S100ß, glutamine synthetase), Cx43 reporter expression in the hippocampus and cortex was restricted to GFAP⁺ astrocytes. Altogether, this mouse line is a highly reliable tool for studies of Cx43-expressing CNS cells and astroglial cell morphology. © 2017 Wiley Periodicals, Inc.

Distributed Features of Vimentin-Containing Neural Precursor Cells in Olfactory Bulb of SOD1G93A Transgenic Mice: a Study about Resource of Endogenous Neural Stem Cells

No any effective treatments can prevent from the motor neuron degeneration in amyotrophic lateral sclerosis (ALS) at present. In order to modulating the endogenous neural precursor cells (NPCs) to repairing the degenerative motor neurons in ALS, we studied the alteration of endogenous vimentin-containing NPCs in olfactory bulb (OB) at the different stages of SOD1 wlid-type and G93A transgenic mice. The results showed that the vimentin-containing cells (VCCs) were mainly distributed in the glomerular layer (Gl), the accessory OB (AOB), the OB core, the granular cell layer (GRO) and the mitral cell layer (MI)+the internal plexiform layer (IPL) of the OB of adult mice. Almost all VCCs in Gl, OB core and GRO were the GFAP positive cells. Almost all VCCs in AOB were the Oligo-2 positive cells. Fewer VCCs in MI+IPL were the NeuN positive cells. VCCs significantly increased in the OB core and Gl of adult OB at the pre-onset, onset and progression stages of ALS-like G93A transgenic disease, particularly in OB core. All increased VCCs were the GFAP positive cells. Our data suggested that there extensively existed the endogenous vimentin-containing NPCs in the OB of adult mice, which was a potential resource of neural stem cells, they could differentiate into astrocyte, oligodendrocyte and neuron cells, were a potential astrocyte neuroregenerative response in adult OB in the ALS-like disease, were a potential pathway to repair the degenerated motor neurons.

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.

Voltage-dependent K+ currents contribute to heterogeneity of olfactory ensheathing cells

The olfactory nerve is permissive for axon growth throughout life. This has been attributed in part to the olfactory ensheathing glial cells that encompass the olfactory sensory neuron fascicles. Olfactory ensheathing cells (OECs) also promote axon growth in vitro and when transplanted in vivo to sites of injury. The mechanisms involved remain largely unidentified owing in part to the limited knowledge of the physiological properties of ensheathing cells. Glial cells rely for many functions on the properties of the potassium channels expressed; however, those expressed in ensheathing cells are unknown. Here we show that OECs express voltage-dependent potassium currents compatible with inward rectifier (Kir ) and delayed rectifier (KDR ) channels. Together with gap junction coupling, these contribute to the heterogeneity of membrane properties observed in OECs. The relevance of K(+) currents expressed by ensheathing cells is discussed in relation to plasticity of the olfactory nerve.

Polyurethane/polylactide-based biomaterials combined with rat olfactory bulb-derived glial cells and adipose-derived mesenchymal stromal cells for neural regenerative medicine applications

Research concerning the elaboration and application of biomaterial which may support the nerve tissue regeneration is currently one of the most promising directions. Biocompatible polymer devices are noteworthy group among the numerous types of potentially attractive biomaterials for regenerative medicine application. Polylactides and polyurethanes may be utilized for developing devices for supporting the nerve regeneration, like nerve guide conduits or bridges connecting the endings of broken nerve tracts. Moreover, the combination of these biomaterial devices with regenerative cell populations, like stem or precursor cells should significantly improve the final therapeutic effect. Therefore, the composition and structure of final device should support the proper adhesion and growth of cells destined for clinical application. In current research, the three polymer mats elaborated for connecting the broken nerve tracts, made from polylactide, polyurethane and their blend were evaluated both for physical properties and in vitro, using the olfactory-bulb glial cells and mesenchymal stem cells. The evaluation of Young's modulus, wettability and roughness of obtained materials showed the differences between analyzed samples. The analysis of cell adhesion, proliferation and morphology showed that the polyurethane-polylactide blend was the most neutral for cells in culture, while in the pure polymer samples there were significant alterations observed. Our results indicated that polyurethane-polylactide blend is an optimal composition for culturing and delivery of glial and mesenchymal stem cells.

Olfactory-ensheathing cell transplantation for peripheral nerve repair: update on recent developments

A number of important advances have been made using transplantation of olfactory-ensheathing cells (OECs) to provide therapeutic effects with regard to peripheral nerve repair. In vivo studies have focused on transplanting OECs to stimulate axonal regeneration and sprouting, increase remyelination, confer neuroprotection, enhance neovascularization and replace lost cells. OECs support axonal regeneration and remyelination with appropriate formation of axonal nodes of Ranvier with improvement of nerve conduction velocity. Current work using gene profiling and proteomics is identifying potential therapeutic differences between OECs harvested from nasal mucosa and the olfactory bulb and genes that OECs express that may be conducive to neural repair. OECs derived from nasal mucosa are of clinical interest since the cells could potentially be harvested from a patient and used for autotransplantation. Various nerve scaffolds and materials have been used for nerve repair and recent studies have examined OECs in combination with various supportive materials, including nanoparticles and scaffolds for peripheral nerve substance defects. This review will discuss the use of OECs in nerve repair and nerve defect injuries with specific emphasis on differences between OECs derived from the olfactory bulb and the olfactory mucosa.

Characterization of Olfactory Ensheathing Glial Cells Cultured on Polyurethane/Polylactide Electrospun Nonwovens

The aim of this research was to evaluate novel biomaterials for neural regeneration. The investigated materials were composed of polyurethane (PU) and polylactide (PLDL) blended at three different w/w ratios, that is, 5/5, 6/4, and 8/2 of PU/PLDL. Ultrathin fibrous scaffolds were prepared using electrospinning. The scaffolds were investigated for their applicability for nerve regeneration by culturing rat olfactory ensheathing glial cells. Cells were cultured on the materials for seven days, during which cellular morphology, phenotype, and metabolic activity were analysed. SEM analysis of the fabricated fibrous scaffolds showed fibers of a diameter mainly lower than 600 μm with unimportant volume of protrusions situated along the fibers, with nonsignificant differences between all analysed materials. Cells cultured on the materials showed differences in their morphology and metabolic activity, depending on the blend composition. The most proper morphology, with numerous p75+and GFAP+cells present, was observed in the sample 6/4, whereas the highest metabolic activity was measured in the sample 5/5. However, none of the investigated samples showed cytotoxicity or negatively influenced cellular morphology. Therefore, the novel electrospun fibrous materials may be considered for regenerative medicine applications, and especially when contacting with highly sensitive nervous cells.

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.

Transcription factor Runx1 inhibits proliferation and promotes developmental maturation in a selected population of inner olfactory nerve layer olfactory ensheathing cells

The olfactory system undergoes persistent regeneration throughout life. Olfactory ensheathing cells (OECs) are a specialized class of glia found exclusively in the olfactory system. OECs wrap olfactory sensory neuron axons and support their growth from the olfactory epithelium, and targeting to the olfactory bulb, during development and life-long regeneration. Because of this function and their ability to cross the boundary between central and peripheral nervous systems, OECs are attractive candidates for cell-based regenerative therapies to promote axonal repair in the injured nervous system. OECs are a molecularly, topologically and functionally heterogeneous group of cells and the mechanisms underlying the development and function of specific OEC subpopulations are poorly defined. This situation has affected the outcome and interpretation of OEC-based regenerative strategies. Here we show that the transcription factor Runx1 is selectively expressed in OECs of the inner olfactory nerve layer of the mouse olfactory bulb and in their precursors in the OEC migratory mass. Furthermore, we provide evidence that in vivo knockdown of mouse Runx1 increases the proliferation of the OECs in which Runx1 is expressed. Conversely, Runx1 overexpression in primary cultures of OECs reduces cell proliferation in vitro. Decreased Runx1 activity also leads to an increase in Runx1-expressing OEC precursors, with a parallel decrease in the number of more developmentally mature OECs. These results identify Runx1 as a useful new marker of a distinct OEC subpopulation and suggest that Runx1 is important for the development of this group of OECs. These observations provide an avenue for further exploration into the molecular mechanisms underlying the development and function of specific OEC subpopulations.

Transplantation of olfactory ensheathing cells to evaluate functional recovery after peripheral nerve injury

Olfactory ensheathing cells (OECs) are neural crest cells which allow growth and regrowth of the primary olfactory neurons. Indeed, the primary olfactory system is characterized by its ability to give rise to new neurons even in adult animals. This particular ability is partly due to the presence of OECs which create a favorable microenvironment for neurogenesis. This property of OECs has been used for cellular transplantation such as in spinal cord injury models. Although the peripheral nervous system has a greater capacity to regenerate after nerve injury than the central nervous system, complete sections induce misrouting during axonal regrowth in particular after facial of laryngeal nerve transection. Specifically, full sectioning of the recurrent laryngeal nerve (RLN) induces aberrant axonal regrowth resulting in synkinesis of the vocal cords. In this specific model, we showed that OECs transplantation efficiently increases axonal regrowth. OECs are constituted of several subpopulations present in both the olfactory mucosa (OM-OECs) and the olfactory bulbs (OB-OECs). We present here a model of cellular transplantation based on the use of these different subpopulations of OECs in a RLN injury model. Using this paradigm, primary cultures of OB-OECs and OM-OECs were transplanted in Matrigel after section and anastomosis of the RLN. Two months after surgery, we evaluated transplanted animals by complementary analyses based on videolaryngoscopy, electromyography (EMG), and histological studies. First, videolaryngoscopy allowed us to evaluate laryngeal functions, in particular muscular cocontractions phenomena. Then, EMG analyses demonstrated richness and synchronization of muscular activities. Finally, histological studies based on toluidine blue staining allowed the quantification of the number and profile of myelinated fibers. All together, we describe here how to isolate, culture, identify and transplant OECs from OM and OB after RLN section-anastomosis and how to evaluate and analyze the efficiency of these transplanted cells on axonal regrowth and laryngeal functions.

Possible roles of Robo1+ ensheathing cells in guiding dorsal-zone olfactory sensory neurons in mouse

In the mouse olfactory system, the anatomical locations of olfactory sensory neurons (OSNs) correlate with their axonal projection sites along the dorsoventral axis of the olfactory bulb (OB). We have previously reported that Neuropilin-2 expressed by ventral-zone OSNs contributes to the segregation of dorsal and ventral OSN axons, and that Slit is acting as a negative land mark to restrict the projection of Robo2+, early-arriving OSN axons to the embryonic OB. Here, we report that another guidance receptor, Robo1, also plays an important role in guiding OSN axons. Knockout mice for Robo1 demonstrated defects in targeting of OSN axons to the OB. Although Robo1 is colocalized with dorsal-zone OSN axons, it is not produced by OSNs, but instead by olfactory ensheathing cells. These findings indicate a novel strategy of axon guidance in the mouse olfactory system during development.

Potential of olfactory ensheathing cells from different sources for spinal cord repair

Spinal cord injury (SCI) induces a permanent disability in patients. To this day no curative treatment can be proposed to restore lost functions. Therefore, extensive experimental studies have been conducted to induce recovery after SCI. One of the most promising therapies is based on the use of olfactory ensheathing cells (OECs). OECs can be obtained from either the olfactory bulbs (OB-OECs) or from olfactory mucosa (OM-OECs), involving a less invasive approach for autotransplantation. However the vast majority of experimental transplantations have been focusing on OB-OECs although the OM represents a more accessible source of OECs. Importantly, the ability of OM-OECs in comparison to OB-OECs to induce spinal cord recovery in the same lesion paradigm has never been described. We here present data using a multiparametric approach, based on electrophysiological, behavioral, histological and magnetic resonance imaging experiments on the repair potential of OB-OECs and OM-OECs from either primary or purified cultures after a severe model of SCI. Our data demonstrate that transplantation of OECs obtained from OB or OM induces electrophysiological and functional recovery, reduces astrocyte reactivity and glial scar formation and improves axonal regrowth. We also show that the purification step is essential for OM-OECs while not required for OB-OECs. Altogether, our study strongly indicates that transplantation of OECs from OM represents the best benefit/risk ratio according to the safety of access of OM and the results induced by transplantations of OM-OECs. Indeed, purified OM-OECs in addition to induce recovery can integrate and survive up to 60 days into the spinal cord. Therefore, our results provide strong support for these cells as a viable therapy for SCI.

Spatial and developmental heterogeneity of calcium signaling in olfactory ensheathing cells

Olfactory ensheathing cells (OECs) are specialized glial cells in the mammalian olfactory system supporting growth of axons from the olfactory epithelium into the olfactory bulb. OECs in the olfactory bulb can be subdivided into OECs of the outer nerve layer and the inner nerve layer according to the expression of marker proteins and their location in the nerve layer. In the present study, we have used confocal calcium imaging of OECs in acute mouse brain slices and olfactory bulbs in toto to investigate physiological differences between OEC subpopulations. OECs in the outer nerve layer, but not the inner nerve layer, responded to glutamate, ATP, serotonin, dopamine, carbachol, and phenylephrine with increases in the cytosolic calcium concentration. The calcium responses consisted of a transient and a tonic component, the latter being mediated by store-operated calcium entry. Calcium measurements in OECs during the first three postnatal weeks revealed a downregulation of mGluR(1) and P2Y(1) receptor-mediated calcium signaling within the first 2 weeks, suggesting that the expression of these receptors is developmentally controlled. In addition, electrical stimulation of sensory axons evoked calcium signaling via mGluR(1) and P2Y(1) only in outer nerve layer OECs. Downregulation of the receptor-mediated calcium responses in postnatal animals is reflected by a decrease in amplitude of stimulation-evoked calcium transients in OECs from postnatal days 3 to 21. In summary, the results presented reveal striking differences in receptor responses during development and in axon-OEC communication between the two subpopulations of OECs in the olfactory bulb.

Neural crest and olfactory system: new prospective

Sensory neurons in vertebrates are derived from two embryonic transient cell sources: neural crest (NC) and ectodermal placodes. The placodes are thickenings of ectodermal tissue that are responsible for the formation of cranial ganglia as well as complex sensory organs that include the lens, inner ear, and olfactory epithelium. The NC cells have been indicated to arise at the edges of the neural plate/dorsal neural tube, from both the neural plate and the epidermis in response to reciprocal interactions Moury and Jacobson (Dev Biol 141:243-253, 1990). NC cells migrate throughout the organism and give rise to a multitude of cell types that include melanocytes, cartilage and connective tissue of the head, components of the cranial nerves, the dorsal root ganglia, and Schwann cells. The embryonic definition of these two transient populations and their relative contribution to the formation of sensory organs has been investigated and debated for several decades (Basch and Bronner-Fraser, Adv Exp Med Biol 589:24-31, 2006; Basch et al., Nature 441:218-222, 2006) review (Baker and Bronner-Fraser, Dev Biol 232:1-61, 2001). Historically, all placodes have been described as exclusively derived from non-neural ectodermal progenitors. Recent genetic fate-mapping studies suggested a NC contribution to the olfactory placodes (OP) as well as the otic (auditory) placodes in rodents (Murdoch and Roskams, J Neurosci Off J Soc Neurosci 28:4271-4282, 2008; Murdoch et al., J Neurosci 30:9523-9532, 2010; Forni et al., J Neurosci Off J Soc Neurosci 31:6915-6927, 2011b; Freyer et al., Development 138:5403-5414, 2011; Katoh et al., Mol Brain 4:34, 2011). This review analyzes and discusses some recent developmental studies on the OP, placodal derivatives, and olfactory system.