Transplantation of Schwann cells and/or olfactory ensheathing glia into the contused spinal cord: Survival, migration, axon association, and functional recovery

A comparison between neurally induced bone marrow derived mesenchymal stem cells and olfactory ensheathing glial cells to repair spinal cord injuries in rat

Cell therapy has proven to be a highly promising method in clinical applications, raising so much hope for the treatment of injured tissues with low, if any, self regeneration potential such as central and peripheral nervous system. Neurally induced bone marrow derived mesenchymal stem cells (NIMSCs) as well as olfactory ensheathing cells (OECs) were transplanted in a rat model of sub-acute spinal cord injury and the behavioral and histological analyses were conducted. A balloon-compression technique was used to produce an injury at T8-T9 level of spinal cord. After a week post injury, rats were injected with either NIMSCs or OECs at the center of developing lesion cavity, 3mm cranial and 3mm caudal to the cavity. Weekly behavioral assessment using BBB score was done over five-week period post transplantation and finally histological assessment was performed to locate labeled cells in the tissue in order to evaluate the reduction of cavity formation and axonal regeneration. Evaluation of locomotor performance showed significant behavioral improvement in NIMSC group over OEC and control groups. The histological analyses revealed the presence of transplanted cells in the spinal cord parenchyma. Volume of injured area that was occupied with syrinx cavity in NIMSC group was significantly less than control group. In addition, meanwhile neurofilament-positive axons significantly showed higher expression in rats receiving NIMSC compared to the other two groups. In conclusion NIMSC caused both behavioral and histological improvement that potentially makes them a promising candidate for cell therapy approaches of spinal cord injuries.

Extensive cell migration, axon regeneration, and improved function with polysialic acid-modified Schwann cells after spinal cord injury

Schwann cell (SC) implantation after spinal cord injury (SCI) promotes axonal regeneration, remyelination repair, and functional recovery. Reparative efficacy, however, may be limited because of the inability of SCs to migrate outward from the lesion-implant site. Altering SC cell surface properties by overexpressing polysialic acid (PSA) has been shown to promote SC migration. In this study, a SCI contusion model was used to evaluate the migration, supraspinal axon growth support, and functional recovery associated with polysialyltransferase (PST)-overexpressing SCs [PST-green fluorescent protein (GFP) SCs] or controls (GFP SCs). Compared with GFP SCs, which remained confined to the injection site at the injury center, PST-GFP SCs migrated across the lesion:host cord interface for distances of up to 4.4 mm within adjacent host tissue. In addition, with PST-GFP SCs, there was extensive serotonergic and corticospinal axon in-growth within the implants that was limited in the GFP SC controls. The enhanced migration of PST-GFP SCs was accompanied by significant growth of these axons caudal to lesion. Animals receiving PST-GFP SCs exhibited improved functional outcome, both in the open-field and on the gridwalk test, beyond the modest improvements provided by GFP SC controls. This study for the first time demonstrates that a lack of migration by SCs may hinder their reparative benefits and that cell surface overexpression of PSA enhances the ability of implanted SCs to associate with and support the growth of corticospinal axons. These results provide further promise that PSA-modified SCs will be a potent reparative approach for SCI. © 2012 Wiley Periodicals, Inc.

Oligodendrocyte-protection and remyelination post-spinal cord injuries: a review

In the past four decades, the main focus of investigators in the field of spinal cord regeneration has been to devise therapeutic measures that enhance neural regeneration. More recently, emphasis has been placed on enhancing remyelination and providing oligodendrocyte-protection after a spinal cord injury (SCI). Demyelination post-SCI is part of the cascading secondary injury that takes place immediately after the primary insult; therefore, therapeutic measures are needed to reduce oligodendrocyte death and/or enhance remyelination during the acute stage, preserving neurological functions that would be lost otherwise. In this review a thorough investigation of the oligodendrocyte-protective and remyelinative molecular therapies available to date is provided. The advent of new biomaterials shown to promote remyelination post-SCI is discussed mainly in the context of a combinatorial approach where the biomaterial also provides drug delivery capabilities. The aim of these molecular and biomaterial-based therapies is twofold: (1) oligodendrocyte-protective therapy, which involves protecting already existing oligodendrocytes from undergoing apoptosis/necrosis; and (2) inductive remyelination, which involves harnessing the remyelinative capabilities of endogenous oligodendrocyte precursor cells (OPCs) at the lesion site by providing a suitable environment for their migration, survival, proliferation and differentiation. From the evidence reported in the literature, we conclude that the use of a combinatorial approach including biomaterials and molecular therapies would provide advantages such as: (1) sustained release of the therapeutic molecule, (2) local delivery at the lesion site, and (3) an environment at the site of injury that promotes OPC migration, differentiation and remyelination.

Astrocyte-Schwann-cell coculture systems

Schwann cells are one of the cellular candidates used in repair strategies following trauma and demyelination of the spinal cord. One of the major obstacles in the use of Schwann cells is their limited migratory ability within the astrocytic environment of the CNS and boundary formation between the Schwann cells of the graft and the host astrocytes. This boundary creates an abrupt obstacle for regenerating axons attempting to exit the Schwann cell graft back to the CNS. To facilitate the study of mechanisms underlying these interactions, in vitro coculture assays of Schwann-Astrocytes have been developed. In this chapter, we have described the methodology for two commonly used coculture systems known as the Schwann-Astrocyte boundary assay and the inverted coverslip migration assay.

The Utility of 3D Ultramicroscopy for Evaluating Cellular Therapies After Spinal Cord Injury

Cell therapies have shown promise for repairing the injured spinal cord in experimental models and are now being evaluated in clinical trials for the treatment of human spinal cord injury (SCI). To date, experimental evaluation of implanted cell survival, migration, and integration within the injured central nervous system (CNS) of animals has been technically demanding, requiring tissue sectioning, staining, imaging, and manual reconstruction of 2-dimensional (2D) specimens in 3 dimensions (3D). Not only are these histological procedures laborious and fraught with processing artifacts during manual 3D reconstruction, but they are time-intensive. Herein we describe the utility of 3D ultramicroscopy for assessment of cell therapies after SCI, a new state-of-the-art imaging modality in which whole brain and spinal cord samples are optically sectioned to allow evaluation of intact, macroscopic specimens with microscopic resolution.

Realizing the maximum potential of Schwann cells to promote recovery from spinal cord injury

Transplantation of Schwann cells (SCs) has been extensively investigated as a therapeutic intervention in rodent models of spinal cord injury (SCI). Here we review both strengths and weaknesses of this approach and discuss additional strategies for maximizing the potential of SCs to repair the injured spinal cord. With no additional treatments, SCs were consistently shown to provide a bridge across the lesion site, supporting the ingrowth of sensory and propriospinal axons, to myelinate axons and to decrease the size of cavities formed after injury. Supraspinal axons did not, however, grow onto the bridge, axons failed to traverse the caudal SC-host cord interface and transplanted SC survival was poor. More recent studies have shown that the potential of SC transplantation as a therapeutic approach can be strongly enhanced by combining additional strategies . For example, combining SC transplantation with elevation of cAMP levels resulted in growth of brainstem axons into the SC graft and caudal to the lesion and in significant improvements in locomotion. Axon growth (and functional improvement) have been increased by strategies to raise neurotrophin levels, either by injection or by genetic modification of the SCs before transplantation. A major problem in maximizing SC potential in injured cord has been in achieving good integration of the transplanted cells with the adjacent cord parenchyma. Several previous studies suggested an ability of SCs to migrate extensively in CNS tissue when astroctyes were absent and to myelinate CNS axons. Furthermore, in some cases involving very limited injury, SCs migrated and integrated well even in the presence of host astrocytes. Consistent with these observations, treatments with an enzyme, chondroitinase, to modify the SC-astrocyte interface surrounding the graft, have shown much promise. Very new studies have shown that SCs derived from SC precursors show a higher ability to survive, integrate well with host tissue and support brainstem axon growth into and beyond the graft, confirming the innate promise of SCs in spinal cord repair. We review one clinical trial already underway in Iran testing SC transplantation in patients with SCI. Finally, we briefly describe a protocol, adaptable to the principles of good manufacturing practice, for generating large numbers of human SCs. Overall, the available evidence suggests that SCs, especially when used in combination with other treatments, offer one of the best hopes we have today of devising an effective treatment for spinal cord repair.

Spinal cord bypass surgery with intercostal and spinal accessory nerves: an anatomical feasibility study in human cadavers

OBJECT

Despite extensive study, no meaningful progress has been made in encouraging healing and recovery across the site of spinal cord injury (SCI) in humans. Spinal cord bypass surgery is an unconventional strategy in which intact peripheral nerves rostral to the level of injury are transferred into the spinal cord below the injury. This report details the feasibility of using spinal accessory nerves to bypass cervical SCI and intercostal nerves to bypass thoracolumbar SCI in human cadavers.

METHODS

Twenty-three human cadavers underwent cervical and/or lumbar laminectomy and dural opening to expose the cervical cord and/or conus medullaris. Spinal accessory nerves were harvested from the Erb point to the origin of the nerve's first major branch into the trapezius. Intercostal nerves from the T6-12 levels were dissected from the lateral border of paraspinal muscles to the posterior axillary line. The distal ends of dissected nerves were then transferred medially and sequentially inserted 4 mm deep into the ipsilateral cervical cord (spinal accessory nerve) or conus medullaris (intercostals). The length of each transferred nerve was measured, and representative distal and proximal cross-sections were preserved for axonal counting.

RESULTS

Spinal accessory nerves were consistently of sufficient length to be transferred to caudal cervical spinal cord levels (C4-8). Similarly, intercostal nerves (from T-7 to T-12) were of sufficient length to be transferred in a tension-free manner to the conus medullaris. Spinal accessory data revealed an average harvested nerve length of 15.85 cm with the average length needed to reach C4-8 of 4.7, 5.9, 6.5, 7.1, and 7.8 cm. The average length of available intercostal nerve from each thoracic level compared with the average length required to reach the conus medullaris in a tension-free manner was determined to be as follows (available, required in cm): T-7 (18.0, 14.5), T-8 (18.7, 11.7), T-9 (18.8, 9.0), T-10 (19.6, 7.0), T-11 (18.8, 4.6), and T-12 (15.8, 1.5). The number of myelinated axons present on cross-sectional analysis predictably decreased along both spinal accessory and intercostal nerves as they coursed distally.

CONCLUSIONS

Both spinal accessory and intercostal nerves, accessible from a posterior approach in the prone position, can be successfully harvested and transferred to their respective targets in the cervical spinal cord and conus medullaris. As expected, the number of axons available to grow into the spinal cord diminishes distally along each nerve. To maximize axon "bandwidth" in nerve bypass procedures, the most proximal section of the nerve that can be transferred in a tension-free manner to a spinal level caudal to the level of injury should be implanted. This study supports the feasibility of SAN and intercostal nerve transfer as a means of treating SCI and may assist in the preoperative selection of candidates for future human clinical trials of cervical and thoracolumbar SCI bypass surgery.

Olfactory and respiratory lamina propria transplantation after spinal cord transection in rats: effects on functional recovery and axonal regeneration

Spinal cord injury (SCI) has very poor clinical prospects, resulting in irreversible loss of function below the injury site. Although applied in clinical trials, olfactory ensheathing cells transplantation (OEC) derived from lamina propria (OLP) is still a controversial repair strategy. The present study explored the efficacy of OLP or respiratory lamina propria (RLP) transplantation and the optimum period after SCI for application of this potential therapy. Adult male rats were submitted to spinal cord transection and underwent acute, 2-week or 4-week post-injury transplantation with pieces of OLP (containing OECs) or RLP (without OECs). After grafting, animals with OLP and RLP showed discrete and similar hindlimb motor improvement, with comparable spinal cord tissue sparing and sprouting in the lesion area. Acute transplantation of OLP and RLP seems to foster limited supraspinal axonal regeneration as shown by the presence of neurons stained by retrograde tracing in the brainstem nuclei. A larger number of 5-HT positive fibers were found in the cranial stump of the OLP and RLP groups compared to the lesion and caudal regions. Calcitonin gene-related peptide fibers were present in considerable numbers at the SCI site in both types of transplantation. Our results failed to verify differences between acute, 2-week and 4-week delayed transplantation of OLP and RLP, suggesting that the limited functional and axon reparative effects observed could not be exclusively related to OECs. A greater understanding of the effects of these tissue grafts is necessary to strengthen the rationale for application of this treatment in humans.

Cellular treatments for spinal cord injury: the time is right for clinical trials

More than 1 million people in the United States live with a spinal cord injury (SCI). Despite medical advances, many patients with SCIs still experience substantial neurological disability, with loss of motor, sensory, and autonomic function. Cell therapy is ideally suited to address the multifactorial nature of the secondary events following SCI. Remarkable advances in our understanding of the pathophysiology of SCI, structural and functional magnetic resonance imaging, image-guided micro-neurosurgical techniques, and transplantable cell biology have enabled the use of cell-based regenerative techniques in the clinic. It is important to note that there are more than a dozen recently completed, ongoing, or recruiting cell therapy clinical trials for SCI that reflect the views of many key stakeholders. The field of regenerative neuroscience has reached a stage in which the clinical trials are scientifically and ethically justified. Although experimental models and analysis methods and techniques continue to evolve, no model will completely replicate the human condition. It is recognized that more work with cervical models of contusive/compressive SCI are required in parallel with clinical trials. It is also important that the clinical translation of advances made through well-established and validated experimental approaches in animal models move forward to meet the compelling needs of individuals with SCI and to advance the field of regenerative neuroscience. However, it is imperative that such efforts at translation be done in the most rigorous and informed fashion to determine safety and possible efficacy, and to provide key information to clinicians and basic scientists, which will allow improvements in regenerative techniques and the validation and refinement of existing preclinical animal models and research approaches. The field of regenerative neuroscience should not be stalled at the animal model stage, but instead the clinical trials need to be focused, safe, and ethical, backed up by a robust, translationally relevant preclinical research strategy.

Neurotrophins: potential therapeutic tools for the treatment of spinal cord injury

Spinal cord injury permanently disrupts neuroanatomical circuitry and can result in severe functional deficits. These functional deficits, however, are not immutable and spontaneous recovery occurs in some patients. It is highly likely that this recovery is dependent upon spared tissue and the endogenous plasticity of the central nervous system. Neurotrophic factors are mediators of neuronal plasticity throughout development and into adulthood, affecting proliferation of neuronal precursors, neuronal survival, axonal growth, dendritic arborization and synapse formation. Neurotrophic factors are therefore excellent candidates for enhancing axonal plasticity and regeneration after spinal cord injury. Understanding growth factor effects on axonal growth and utilizing them to alter the intrinsic limitations on regenerative growth will provide potent tools for the development of translational therapeutic interventions for spinal cord injury.

A calpain inhibitor enhances the survival of Schwann cells in vitro and after transplantation into the injured spinal cord

Despite the diversity of cells available for transplantation into sites of spinal cord injury (SCI), and the known ability of transplanted cells to integrate into host tissue, functional improvement associated with cellular transplantation has been limited. One factor potentially limiting the efficacy of transplanted cells is poor cell survival. Recently we demonstrated rapid and early death of Schwann cells (SCs) within the first 24 h after transplantation, by both necrosis and apoptosis, which results in fewer than 20% of the cells surviving beyond 1 week. To enhance SC transplant survival, in vitro and in vivo models to rapidly screen compounds for their ability to promote SC survival are needed. The current study utilized in vitro models of apoptosis and necrosis, and based on withdrawal of serum and mitogens and the application of hydrogen peroxide, we screened several inhibitors of apoptosis and necrosis. Of the compounds tested, the calpain inhibitor MDL28170 enhanced SC survival both in vitro in response to oxidative stress induced by application of H2O2, and in vivo following delayed transplantation into the moderately contused spinal cord. The results support the use of calpain inhibitors as a promising new treatment for promoting the survival of transplanted cells. They also suggest that in vitro assays for cell survival may be useful for establishing new compounds that can then be tested in vivo for their ability to promote transplanted SC survival.

Safety of intramedullary Schwann cell transplantation for postrehabilitation spinal cord injuries: 2-year follow-up of 33 cases

OBJECT

Many experimental studies on spinal cord injuries (SCIs) support behavioral improvement after Schwann cell treatment. This study was conducted to evaluate safety issues 2 years after intramedullary Schwann cell transplantation in 33 consecutively selected patients with SCI.

METHODS

Of 356 patients with SCIs who had completed at least 6 months of a conventional rehabilitation program and who were screened for the study criteria, 33 were enrolled. After giving their informed consent, they volunteered for participation. They underwent sural nerve harvesting and intramedullary injection of a processed Schwann cell solution. Outcome assessments included a general health questionnaire, neurological examination, and functional recordings in terms of American Spinal Injury Association (ASIA) and Functional Independence Measure scoring, which were documented by independent observers. There were 24 patients with thoracic and 9 with cervical injuries. Sixteen patients were categorized in ASIA Grade A, and the 17 remaining participants had ASIA Grade B.

RESULTS

There were no cases of deep infection, and the follow-up MR imaging studies obtained at 2 years did not reveal any deformity related to the procedure. There was no case of permanent neurological worsening or any infectious or viral complications. No new increment in syrinx size or abnormal tissue and/or tumor formation were observed on contrast-enhanced MR imaging studies performed 2 years after the treatment.

CONCLUSIONS

Preliminary results, especially in terms of safety, seem to be promising, paving the way for future cell therapy trials.

Adipose tissue and bone marrow-derived stem cells react similarly in an ischaemia-like microenvironment

Mesenchymal stem cells (MSCs) from adipose tissue and bone marrow are promising cell sources for autologous cell therapy of nerve injuries, as demonstrated by their intrinsic neurotrophic potential. However, extensive death of transplanted cells limits their full benefits. This study investigated the effects of ischaemia (metabolically induced by sodium azide and 2-deoxyglucose) and serum-derived mitogens on the viability and functional profile of MSCs in vitro. MSCs were more susceptible to combined, rather than individual, blockade of glycolysis and oxidative phosphorylation. Apoptosis and autophagy were involved in ischaemia-induced cell death. Chemical ischaemia alone and serum withdrawal alone induced a similar amount of cell death, with significantly different intracellular ATP maintenance. Combined ischaemia and serum deprivation had additive effects on cell death. Expression of the extracellular matrix (ECM) molecules laminin and fibronectin was attenuated under ischaemia and independent of serum level; however, BDNF and NGF levels remained relatively constant. Strong upregulation of VEGF and to a lesser extent angiopoietin-1 was observed under ischaemia but not in serum withdrawal conditions. Importantly, this study demonstrated similar reactions of MSCs derived from adipose and bone marrow tissue, in ischaemia-like and mitogen-deprived microenvironments in terms of viability, cellular energetics, cell death mechanisms and expression levels of various growth-promoting molecules. Also, the results suggest that ischaemia has a larger impact on the ability of MSCs to survive transplantation than withdrawal of mitogens.

Human Schwann cells retain essential phenotype characteristics after immortalization

Schwann cells (SCs) play an important role in the pathogenesis of peripheral nerve diseases and represent a potential target for development of therapies. However, use of primary human SCs (hSCs) for in vitro models is limited because these cells are difficult to prepare and maintain in high yield and purity under common cell culture conditions. To circumvent this obstacle, we immortalized primary human fetal SCs using the SV40 large T-antigen and human telomerase reverse transcriptase expression vectors. After cloning, selection, and purification, we evaluated several immortalized SC lines for their ability to express extracellular matrix (ECM) molecules and myelinate embryonic rat sensory axons. In addition, we established a gene expression profile and explored their sensitivity to oxidative stress in a simple in vitro assay. Immortalized hSC clones expressed common glial markers and a broad variety of growth factors, receptors, and ECM molecules as determined by immunocytochemistry, microarray, and quantitative reverse transcription-polymerase chain reaction. In neuron-SC co-cultures, these cells were able to myelinate rat dorsal root ganglia neurons, although their effectiveness was lower in comparison to primary rat SCs. In toxicity assays, immortalized hSCs remain susceptible to oxidative stress induced by H(2)O(2). This study shows that, using specific immortalization techniques, it is possible to establish hSC lines that retain characteristics of typical primary hSCs. These cells are particularly useful for drug screening and studies aimed at disease mechanisms involving SCs.

Axon regeneration can facilitate or suppress hindlimb function after olfactory ensheathing glia transplantation

Reports based primarily on anatomical evidence suggest that olfactory ensheathing glia (OEG) transplantation promotes axon regeneration across a complete spinal cord transection in adult rats. Based on functional, electrophysiological, and anatomical assessments, we found that OEG promoted axon regeneration across a complete spinal cord transection and that this regeneration altered motor responses over time. At 7 months after transection, 70% of OEG-treated rats showed motor-evoked potentials in hindlimb muscles after transcranial electric stimulation. Furthermore, a complete spinal cord retransection performed 8 months after injury demonstrated that this axon regeneration suppressed locomotor performance and decreased the hypersensitive hindlimb withdrawal response to mechanical stimulation. OEG transplantation alone promoted reorganization of lumbosacral locomotor networks and, when combined with long-term training, enhanced some stepping measures. These novel findings demonstrate that OEG promote regeneration of mature axons across a complete transection and reorganization of spinal circuitry, both of which contribute to sensorimotor function.

Transplantation of Olfactory Ensheathing Cells as Adjunct Cell Therapy for Peripheral Nerve Injury

Traumatic events, such as work place trauma or motor vehicle accident violence, result in a significant number of severe peripheral nerve lesions, including nerve crush and nerve disruption defects. Transplantation of myelin-forming cells, such as Schwann cells (SCs) or olfactory ensheathing cells (OECs), may be beneficial to the regenerative process because the applied cells could mediate neurotrophic and neuroprotective effects by secretion of chemokines. Moreover, myelin-forming cells are capable of bridging the repair site by establishing an environment permissive to axonal regeneration. The cell types that are subject to intense investigation include SCs and OECs either derived from the olfactory bulb or the olfactory mucosa, stromal cells from bone marrow (mesenchymal stem cells, MSCs), and adipose tissue-derived cells. OECs reside in the peripheral and central nervous system and have been suggested to display unique regenerative properties. However, so far OECs were mainly used in experimental studies to foster central regeneration and it was not until recently that their regeneration-promoting activity for the peripheral nervous system was recognized. In the present review, we summarize recent experimental evidence regarding the regenerative effects of OECs applied to the peripheral nervous system that may be relevant to design novel autologous cell transplantation therapies.

A Neuroregenerative Human Ensheathing Glia Cell Line with Conditional Rapid Growth

Ensheathing glia have been demonstrated to have neuroregenerative properties but this cell type from human sources has not been extensively studied because tissue samples are not easily obtained, primary cultures are slow growing, and human cell lines are not available. We previously isolated immortalized ensheathing glia by gene transfer of BMI1 and telomerase catalytic subunit into primary cultures derived from olfactory bulbs of an elderly human cadaver donor. These cells escape the replicative senescence characteristic of primary human cells while conserving antigenic and neuroregenerative properties of ensheathing glia, but their low proliferative rate in culture complicates their utility as cell models and their application for preclinical cell therapy experiments. In this study we describe the use of a conditional SV40 T antigen (TAg) transgene to generate human ensheathing glia cell lines, which are easy to maintain due to their robust growth in culture. Although these fast growing clones exhibited polyploid karyotypes frequently observed in cells immortalized by TAg, they did not acquire a transformed phenotype, all of them maintaining neuroregenerative capacity and antigenic markers typical of ensheathing glia. These markers were also retained even after elimination of the TAg transgene using Cre/LoxP technology, although the cells died shortly after, confirming that their survival depended on the presence of the immortalizing genes. We have also demonstrated here the feasibility of using these human cell lines in animal models by genetically marking the cells with GFP and implanting them into the injured spinal cord of immunosuppressed rats. Our conditionally immortalized human ensheathing glia cell lines will thus serve as useful tools for advancing cell therapy approaches and understanding neuroregenerative mechanisms of this unique cell type.

Increased expression of the close homolog of the adhesion molecule L1 in different cell types over time after rat spinal cord contusion

The close homolog of the adhesion molecule L1 (CHL1) is important during CNS development, but a study with CHL1 knockout mice showed greater functional recovery after spinal cord injury (SCI) in its absence. We investigated CHL1 expression from 1 to 28 days after clinically relevant contusive SCI in Sprague-Dawley rats. Western blot analysis showed that CHL1 expression was significantly up-regulated at day 1 and further increased over 4 weeks after SCI. Immunohistochemistry of tissue sections showed that CHL1 in the intact spinal cord was expressed at low levels. By 1 day and through 4 weeks after SCI, CHL1 became highly expressed in NG2(+) cells. Hypertrophic GFAP(+) astrocytes also expressed CHL1 by 1 week after injury. The increase in CHL1 protein paralleled that of NG2 in the first week and GFAP between 1 and 4 weeks after injury. At 4 weeks, NG2(+) /CHL1(+) cells and GFAP(+) /CHL1(+) astrocytes were concentrated at the boundary between residual spinal cord tissue and the central lesion. NF200(+) spinal cord axons approached but did not penetrate this boundary. In contrast, CHL1(+) cells in the central lesion at 1 week and later colabeled with p75 and NG2 and were chronically associated with many NF200(+) axons, presumably axons that had sprouted in association with CHL1(+) Schwann cells infiltrating the cord after contusion. Thus, our study demonstrates up-regulation of CHL1 in multiple cell types and locations in a rat model of contusion injury and suggests that this molecule may be involved both in inhibition of axonal regeneration and in recovery processes after SCI.

Promoting survival, migration, and integration of transplanted Schwann cells by over-expressing polysialic acid

The poor survival and migration of transplanted Schwann cells (SCs) are major drawbacks for their clinical application in cell therapy for neurotrauma. To overcome such drawbacks we genetically modified SCs to over-express polysialic acid (PSA) by lentiviral delivery of polysialyltransferase (PST) to study whether over-expression of PSA could enhance their survival, migration, and integration when transplanted into the spinal cord. It was found that more PSA-expressing SCs (PST/SCs) survived than GFP-expressing SCs (GFP/SCs) after transplantation, although cell loss was still quite significant. PSA expression did not enhance the motility of transplanted SCs in uninjured spinal cord. However, in a spinal cord crush injury model PST/SCs transplanted caudal to the lesion showed that increased number of PST/SCs migrated to the injury site compared with that of GFP/SCs. Induced expression of PSA in spinal cord can further facilitate the infiltration of PST/SCs into the lesion site. PST/SCs were also shown to intermingle well with host spinal cells while GFP/SCs formed boundaries with host tissue. This was confirmed by an in vitro confrontation assay showing that more PST/SCs crossed over to astrocyte territory than GFP/SCs. Furthermore, PST/SCs induced much less expression of glial fibrillary acidic protein and chondroitin sulfate proteoglycan in the surrounding tissues than GFP/SCs, indicating that expression of PSA on SCs do not cause significant stress response of astrocytes. These results demonstrate that expression of PSA on SCs significantly changes their biological properties and makes them more feasible for neural repair after neurotrauma.

Suspension matrices for improved Schwann-cell survival after implantation into the injured rat spinal cord

Trauma to the spinal cord produces endogenously irreversible tissue and functional loss, requiring the application of therapeutic approaches to achieve meaningful restoration. Cellular strategies, in particular Schwann-cell implantation, have shown promise in overcoming many of the obstacles facing successful repair of the injured spinal cord. Here, we show that the implantation of Schwann cells as cell suspensions with in-situ gelling laminin:collagen matrices after spinal-cord contusion significantly enhances long-term cell survival but not proliferation, as well as improves graft vascularization and the degree of axonal in-growth over the standard implantation vehicle, minimal media. The use of a matrix to suspend cells prior to implantation should be an important consideration for achieving improved survival and effectiveness of cellular therapies for future clinical application.

17β-estradiol protects Schwann cells against H2O2-induced cytotoxicity and increases transplanted Schwann cell survival in a cervical hemicontusion spinal cord injury model

Schwann cell (SC) transplantation is a promising repair strategy after spinal cord injury (SCI); however, a large number of SCs do not survive following transplantation. Previous studies have shown that 17β-estradiol (E2) protects several cell types against cytotoxicity. Thus, this study evaluated the protective potential of E2 on SCs in vitro and investigated the effect of E2 on transplanted SC survival in a rat model of SCI. Primary SC cultures were found to robustly express estrogen receptors (ER) and incubation with E2 protected SCs against hydrogen peroxide-induced cell death. This protection was not inhibited by the ER antagonist ICI 182,780, suggesting that genomic signaling is not necessary for protection. In a subsequent experiment, cervical hemicontusion SCI was induced in male rats followed by sustained administration of E2 or placebo. Eight days after SCI, SCs were transplanted into the injury epicenter. E2 treatment significantly increased the number of surviving labeled transplanted SCs evaluated 7 days after transplantation. These data demonstrate that E2 protects SCs against oxidative stress and improves transplanted SC survival, which suggests that E2 administration may be an intervention of choice for enhancing survival of transplanted SCs after SCI.

Feasibility of combination allogeneic stem cell therapy for spinal cord injury: a case report

Cellular therapy for spinal cord injury (SCI) is overviewed focusing on bone marrow mononuclear cells, olfactory ensheathing cells, and mesenchymal stem cells. A case is made for the possibility of combining cell types, as well as for allogeneic use. We report the case of 29 year old male who suffered a crush fracture of the L1 vertebral body, lacking lower sensorimotor function, being a score A on the ASIA scale. Stem cell therapy comprised of intrathecal administration of allogeneic umbilical cord blood ex-vivo expanded CD34 and umbilical cord matrix MSC was performed 5 months, 8 months, and 14 months after injury. Cell administration was well tolerated with no adverse effects observed. Neuropathic pain subsided from intermittent 10/10 to once a week 3/10 VAS. Recovery of muscle, bowel and sexual function was noted, along with a decrease in ASIA score to "D". This case supports further investigation into allogeneic-based stem cell therapies for SCI.

Efficacy of olfactory ensheathing cells to support regeneration after spinal cord injury is influenced by method of culture preparation

Olfactory ensheathing cells (OEC) have been shown to stimulate regeneration, myelination and functional recovery in different spinal cord injury models. However, recent reports from several laboratories have challenged this treatment strategy. The discrepancy in results could be attributed to many factors including variations in culture protocols. The present study investigates whether the differences in culture preparation could influence neuroprotective and growth-promoting effects of OEC after transplantation into the injured spinal cord. Primary OEC cultures were purified using method of differential cell adhesion (a-OEC) or separated with immunomagnetic beads (b-OEC). After cervical C4 hemisection in adult rats, short-term (3 weeks) or long-term (7 weeks) cultured OEC were transplanted into the lateral funiculus at 1mm rostral and caudal to the transection site. At 3-8 weeks after transplantation, labeled OEC were mainly found in the injection sites and in the trauma zone. Short-term cultured a-OEC supported regrowth of rubrospinal, raphaespinal and CGRP-positive fibers, and attenuated retrograde degeneration in the red nucleus. Short-term cultured b-OEC failed to promote axonal regrowth but increased the density of rubrospinal axons within the dorsolateral funiculus and provided significant neuroprotection for axotomized rubrospinal neurons. In addition, short-term cultured OEC attenuated sprouting of rubrospinal terminals. In contrast, long-term cultured OEC neither enhanced axonal growth nor prevented retrograde cell death. The results suggest that the age of OEC in culture and the method of cell purification could affect the efficacy of OEC to support neuronal survival and regeneration after spinal cord injury. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair.

Muscle injection of AAV-NT3 promotes anatomical reorganization of CST axons and improves behavioral outcome following SCI

Here we propose the use of adeno-associated virus (AAV) vectors as a non-invasive vehicle for the nervous system to deliver genes to spinal motoneurons, based on their retrograde transport from muscle. Long-term protein expression in lower cervical motoneurons was achieved after injections of AAV into the triceps, independently of serotypes 1, 2, or 5. Muscle injections of AAV5-neurotrophin 3 (NT3) resulted in a significant increase in the levels of NT3 in the cervical enlargement, compared to those obtained after injections of AAV5-GFP. Following a dorsal lesion at C4/C5, animals injected with AAV5-NT3 made fewer errors (footslips) in the horizontal ladder test compared to those injected with AAV5-GFP. In parallel, the number and length of corticospinal tract (CST) fibers circumventing the injury site were significantly increased in rats injected with AAV5-NT3. Compared to controls, we observed less astrogliosis and less CST axonal retraction and/or enhanced sprouting in animals injected with AAV5-NT3. In sum, we demonstrate here that the delivery of nt3 via retrograde transport of AAV from triceps to cervical motoneurons leads to reduced functional loss and anatomical reorganization of the CST following injury, without introducing additional injury to the spinal cord.

A new rating scale for open-field evaluation of behavioral recovery after cervical spinal cord injury in rats

The Basso, Beattie, Bresnahan (BBB) locomotor rating scale has proven a reliable tool to evaluate impairments of hindlimb locomotor skills after thoracic spinal cord injury (SCI). With the increasing use of cervical SCI rat models, there is a critical need to develop scoring scales designed to more precisely examine alteration and recovery of forelimb functions. The main goal of the present study was to elaborate and evaluate a new rating scale for open-field testing of the fore- and hindlimb locomotor functions after cervical SCI. We also assessed the effectiveness of this rating scale for discriminating the functional consequences of dorsolateral (Hdl group), lateral (Hl group), or complete C4 unilateral hemisections (Hc group). Our findings show that the new rating scale can be considered as a sensitive and reliable descriptor of the postoperative time course of deficits affecting differentially the fore- and hindlimb sensorimotor functions following injuries of various severities. This new method provides reproducible data and can be used reliably by non-expert examiners. The proposed rating scale appears to be a useful tool for the assessment of various treatments designed to promote functional recovery after SCI. See online Supplementary Material (scoring spreadsheet and videotape recordings) at www.liebertonline.com.

Olfactory ensheathing cells enhance Schwann cell-mediated anatomical and functional repair after sciatic nerve injury in adult rats

Sciatic nerve injury results in axon damage, muscle degeneration, and loss of function. We compared the potential of Schwann cell (SC), olfactory ensheathing cell (OEC), or mixed SC/OEC transplants for anatomical and functional restoration after adult rat sciatic nerve transection. The cells were seeded into a 20mm long macroporous poly(dl-lactide-co-glycolide) acid conduit and grafted between the sciatic nerve stumps. Some rats received a conduit without cells (controls) or an autologous nerve graft, the clinical standard of care. Compared with SC transplants, axon regeneration was 25% less with OEC transplants but 28% more with SC/OEC transplants. Gastrocnemius muscle restoration was similar with a SC or OEC transplant and 35% better with a SC/OEC transplant. With SC transplants, motor and sensory function recovery and electrophysiological outcomes were similar as with OEC transplants and 33% better with SC/OEC transplants. Compared with the mixed SC/OEC transplants, axon regeneration was 21% better and gastrocnemius muscle restoration was 18% better with autologous peripheral nerve transplants, but these improvements did not translate into increased function and electrophysiological outcomes. Our results revealed that OEC synergistically improve SC mediated sciatic nerve repair. The data emphasized the promise of SC/OEC transplants as artificial nerves for peripheral nerve repair. This article is part of a Special Issue entitled: Understanding olfactory ensheathing glia and their prospect for nervous system repair.

BD™ PuraMatrix™ peptide hydrogel seeded with Schwann cells for peripheral nerve regeneration

This study investigated the effects of a membrane conduit filled with a synthetic matrix BD™ PuraMatrix™ peptide (BD) hydrogel and cultured Schwann cells on regeneration after peripheral nerve injury in adult rats. After sciatic axotomy, a 10mm gap between the nerve stumps was bridged using ultrafiltration membrane conduits filled with BD hydrogel or BD hydrogel containing Schwann cells. In control experiments, the nerve defect was bridged using either membrane conduits with alginate/fibronectin hydrogel or autologous nerve graft. Axonal regeneration within the conduit was assessed at 3 weeks and regeneration of spinal motoneurons and recovery of muscle weight evaluated at 16 weeks postoperatively. Schwann cells survived in the BD hydrogel both in culture and after transplantation into the nerve defect. Regenerating axons grew significantly longer distances within the conduits filled with BD hydrogel when compared with the alginate/fibronectin hydrogel and alginate/fibronectin with Schwann cells. Addition of Schwann cells to the BD hydrogel considerably increased regeneration distance with axons crossing the injury gap and entering into the distal nerve stump. The conduits with BD hydrogel showed a linear alignment of nerve fibers and Schwann cells. The number of regenerating motoneurons and recovery of the weight of the gastrocnemius muscle was inferior in BD hydrogel and alginate/fibronectin groups compared with nerve grafting. Addition of Schwann cells did not improve regeneration of motoneurons or muscle recovery. The present results suggest that BD hydrogel with Schwann cells could be used within biosynthetic conduits to increase the rate of axonal regeneration across a nerve defect.

Therapeutic potential of appropriately evaluated safe-induced pluripotent stem cells for spinal cord injury

Various types of induced pluripotent stem (iPS) cells have been established by different methods, and each type exhibits different biological properties. Before iPS cell-based clinical applications can be initiated, detailed evaluations of the cells, including their differentiation potentials and tumorigenic activities in different contexts, should be investigated to establish their safety and effectiveness for cell transplantation therapies. Here we show the directed neural differentiation of murine iPS cells and examine their therapeutic potential in a mouse spinal cord injury (SCI) model. "Safe" iPS-derived neurospheres, which had been pre-evaluated as nontumorigenic by their transplantation into nonobese diabetic/severe combined immunodeficiency (NOD/SCID) mouse brain, produced electrophysiologically functional neurons, astrocytes, and oligodendrocytes in vitro. Furthermore, when the safe iPS-derived neurospheres were transplanted into the spinal cord 9 d after contusive injury, they differentiated into all three neural lineages without forming teratomas or other tumors. They also participated in remyelination and induced the axonal regrowth of host 5HT(+) serotonergic fibers, promoting locomotor function recovery. However, the transplantation of iPS-derived neurospheres pre-evaluated as "unsafe" showed robust teratoma formation and sudden locomotor functional loss after functional recovery in the SCI model. These findings suggest that pre-evaluated safe iPS clone-derived neural stem/progenitor cells may be a promising cell source for transplantation therapy for SCI.

Schwann cell migration is integrin-dependent and inhibited by astrocyte-produced aggrecan

Schwann cells transplantation has considerable promise in spinal cord trauma to bridge the site of injury and for remyelination in demyelinating conditions. They support axonal regeneration and sprouting by secreting growth factors and providing a permissive surface and matrix molecules while shielding axons from the inhibitory environment of the central nervous system. However, following transplantation Schwann cells show limited migratory ability and they are unable to intermingle with the host astrocytes. This in turn leads to formation of a sharp boundary and an abrupt transition between the Schwann cell graft and the host tissue astrocytes, therefore preventing regenerating axons from exiting the graft. The objective of this study was to identify inhibitory elements on astrocytes involved in restricting Schwann cell migration. Using in vitro assays of cell migration, we show that aggrecan produced by astrocytes is involved in the inhibition of Schwann cell motility on astrocytic monolayers. Knockdown of this proteoglycan in astrocytes using RNAi or digestion of glycosaminglycan chains on aggrecan improves Schwann cell migration. We further show aggrecan mediates its effect by disruption of integrin function in Schwann cells, and that the inhibitory effects of aggrecan can overcome by activation of Schwann cell integrins.

Effects of human OEC-derived cell transplants in rodent spinal cord contusion injury

Numerous reports indicate that rodent olfactory ensheathing cells (OECs) assist in spinal cord repair and clinical trials have been undertaken using autologous transplantation of human olfactory ensheathing cells (hOECs) as a treatment for spinal cord injury. However, there are few studies investigating the efficacy of hOECs in animal models of spinal cord injury. In this study hOECs were derived from biopsies of human olfactory mucosa, purified by culture in a serum-free medium containing neurotrophin-3, genetically labelled with EGFP, and stored frozen. These hOEC-derived cells were thawed and transplanted into the spinal cord injury site 7 days after a moderate contusion injury of the spinal cord at thoracic level T10 in the athymic rat. Six weeks later the animals receiving the hOEC-derived transplants had greater functional improvement in their hindlimbs than controls, assessed using open field (BBB scale) and horizontal rung walking tests. Histological analysis demonstrated beneficial effects of hOEC-derived cell transplantation: reductions in the volume of the lesion and the cavities within the lesion. The transplanted cells were located at the periphery of the lesion where they integrated with GFAP-positive astrocytes resulting in a significant reduction of GFAP staining intensity adjacent to the lesion. Although their mechanism of action is unclear we conclude that hOEC-derived cell transplants improved functional recovery after transplantation into the contused spinal cord, probably by modulating inflammatory responses and reducing secondary damage to the cord.

Astrocyte-produced ephrins inhibit schwann cell migration via VAV2 signaling

Schwann cells are a promising candidate for bridging spinal cord injuries and remyelinating axons. However, grafted Schwann cells show little intermingling with host astrocytes and therefore limited migration from transplant sites. This leads to the formation of a sharp border between host astrocytes and Schwann cells, which results in axons stalling at the graft-host interface and failing to exit the graft. We investigated the possibility that Eph/ephrin interactions are involved in the segregation of Schwann cells and astrocytes and in limiting Schwann cell migration. Using reverse transcription-PCR, we have characterized the ephrin and Eph profile in cultured Schwann cells and astrocytes, showing that astrocytes produce all the ephrinAs and Schwann cells produce the receptors EphA2, EphA4, and EphA7. Several ephrinAs inhibit Schwann cell migration on laminin, with ephrinA5 being the most effective. Blocking the EphA receptors with excess EphA4-Fc increases Schwann cell migration on astrocytes and improves Schwann-astrocyte intermingling. We show that the action of ephrinA5 on Schwann cells is mediated via VAV2. Both clustered ephrinA5 and astrocyte contact increases the phosphorylation of VAV2 in Schwann cells. Knockdown of VAV2 abrogates the inhibitory effect of clustered ephrinA5 on migration and increases the ability of Schwann cells to migrate on astrocytes. In addition, we found a role for ephrinA5 in inhibiting Schwann cell integrin signaling and function. Overall, we suggest that Eph/ephrin interactions inhibit Schwann cell migration and intermingling with astrocytes via VAV signaling affecting integrin function.

A systematic review of cellular transplantation therapies for spinal cord injury

Cell transplantation therapies have become a major focus in pre-clinical research as a promising strategy for the treatment of spinal cord injury (SCI). In this article, we systematically review the available pre-clinical literature on the most commonly used cell types in order to assess the body of evidence that may support their translation to human SCI patients. These cell types include Schwann cells, olfactory ensheathing glial cells, embryonic and adult neural stem/progenitor cells, fate-restricted neural/glial precursor cells, and bone-marrow stromal cells. Studies were included for review only if they described the transplantation of the cell substrate into an in-vivo model of traumatic SCI, induced either bluntly or sharply. Using these inclusion criteria, 162 studies were identified and reviewed in detail, emphasizing their behavioral effects (although not limiting the scope of the discussion to behavioral effects alone). Significant differences between cells of the same "type" exist based on the species and age of donor, as well as culture conditions and mode of delivery. Many of these studies used cell transplantations in combination with other strategies. The systematic review makes it very apparent that cells derived from rodent sources have been the most extensively studied, while only 19 studies reported the transplantation of human cells, nine of which utilized bone-marrow stromal cells. Similarly, the vast majority of studies have been conducted in rodent models of injury, and few studies have investigated cell transplantation in larger mammals or primates. With respect to the timing of intervention, nearly all of the studies reviewed were conducted with transplantations occurring subacutely and acutely, while chronic treatments were rare and often failed to yield functional benefits.

Labeling of olfactory ensheathing glial cells with fluorescent tracers for neurotransplantation

Development of cell-based treatment strategies for repair of the injured nervous system requires cell tracing techniques to follow the fate of transplanted cells and their interaction with the host tissue. The present study investigates the efficacy of fluorescent cell tracers Fast Blue, PKH26, DiO and CMFDA for long-term labeling of olfactory ensheathing glial cells (OEC) in culture and following transplantation into the rat spinal cord. All tested dyes produced very efficient initial labeling of p75-positive OEC in culture. The number of Fast Blue-positive cells remained largely unchanged during the first 4 weeks but only about 21% of the cells retained tracer 6 weeks after labeling. In contrast, the number of cells labeled with PKH26 and DiO was reduced to 51-55% after 2 weeks in culture and reached 8-12% after 4-6 weeks. CMFDA had completely disappeared from the cells 2 weeks after labeling. AlamarBlue assay showed that among four tested tracers only CMFDA reduced proliferation rate of the OEC. After transplantation into spinal cord, Fast Blue-labeled OEC survived for at least 8 weeks but demonstrated very limited migration from the injection sites. Additional immunostaining with glial and neuronal markers revealed signs of dye leakage from the transplanted cells resulted in weak labeling of microglia and spinal neurons. The results show that Fast Blue is an efficient cell marker for cultured OEC. However, transfer of the dye from the transplanted cells to the host tissue should be considered and correctly interpreted.

Chronic spinal injury repair by olfactory bulb ensheathing glia and feasibility for autologous therapy

Olfactory bulb ensheathing glia (OB-OEG) promote repair of spinal cord injury (SCI) in rats after transplantation at acute or subacute (up to 45 days) stages. The most relevant clinical scenario in humans, however, is chronic SCI, in which no more major cellular or molecular changes occur at the injury site; this occurs after the third month in rodents. Whether adult OB-OEG grafts promote repair of severe chronic SCI has not been previously addressed. Rats with complete SCI that were transplanted with OB-OEG 4 months after injury exhibited progressive improvement in motor function and axonal regeneration from different brainstem nuclei across and beyond the SCI site. A positive correlation between motor outcome and axonal regeneration suggested a role for brainstem neurons in the recovery. Functional and histological outcomes did not differ after transplantation at subacute or chronic stages. Thus, autologous transplantation is a feasible approach as there is a time frame for patient stabilization and OEG preparation; moreover, the healing effects of OB-OEG on established injuries may offer new therapeutic opportunities for chronic SCI patients.

Olfactory ensheathing cells reduce duration of autonomic dysreflexia in rats with high spinal cord injury

Autonomic dysreflexia is a common complication in high spinal cord injury and can result in serious consequences and death. Here we have examined the effect of acute transplantation of olfactory ensheathing cells on cardiovascular functions in rats. After T4 transection, radio-telemetric recording in conscious animals was used to study blood pressure and heart rate at rest and during autonomic dysreflexia for up to 8 weeks post-injury. Olfactory ensheathing cells from syngeneic rats were transplanted at the injury site; control animals received culture medium only. At the study end point, we examined morphometric features of sympathetic preganglionic neurons above and below the injury. T4 transection resulted in a fall in resting mean arterial pressure and an increase in resting heart rate. Colorectal distension, used to trigger autonomic dysreflexia, caused episodic hypertension and bradycardia. Although the cell transplantation had no effect on resting cardiovascular parameters, it led to a significantly faster recovery from hypertension, with the recovery time shortened by approximately 25%. The transection resulted in an increase in soma size of sympathetic preganglionic neurons above and below the injury. OEC transplantation normalised this change below the injury and increased dendritic length of preganglionic neurons above the injury, compared to controls. It has been proposed that changes in sympathetic preganglionic neurons following spinal cord transection may be related to the development of autonomic dysreflexia. Our results suggest that olfactory ensheathing cells may alter the morphology of these neurons, and hence modify their activity in the neuronal networks responsible for the dysreflexic reaction.

Strategies to restore motor functions after spinal cord injury

This review presents recent advances in the development of strategies to restore posture and locomotion after spinal cord injury (SCI). A set of strategies focusing on the lesion site includes prevention of secondary damages, promotion of axonal sprouting/regeneration, and replacement of lost cells. Other strategies focus on spinal central pattern generators (CPGs). Training promotes functional recovery by enhancing the plasticity of CPGs and these sublesional networks can be reactivated by means of pharmacological or electrical stimulation. It is now clear that substantial functional recovery will require a combination of strategies adapted to each phase following SCI. Finally, improvements in the understanding of the mechanisms underlying spasticity may lead to new treatments of this disabling complication affecting patients with SCI.

Dose and chemical modification considerations for continuous cyclic AMP analog delivery to the injured CNS

In this investigation, two cell-permeable synthetic analogs of cAMP, dibutyryl-cAMP (db-cAMP) and 8-bromo-cAMP, which are widely used to elevate intracellular cAMP levels under experimental conditions, were investigated for their ability to dose-dependently improve histological and functional outcomes following continuous delivery in two models of incomplete spinal cord injury (SCI). The cAMP analogs were delivered via osmotic minipumps at 1-250 mM through an indwelling cortical cannula or by intrathecal infusion for up to 4 weeks after either a T8 unilateral over-hemisection or a C2-3 dorsolateral quadrant lesion, respectively. In both SCI models, continuous db-cAMP delivery was associated with histopathological changes that included sporadic micro-hemorrhage formation and cavitation, enhanced macrophage infiltration and tissue damage at regions beyond the immediate application site; no deleterious or beneficial effect of agent delivery was observed at the spinal injury site. Furthermore, these changes were accompanied by pronounced behavioral deficits that included an absence of progressive locomotor recovery, increased extensor tone, paralysis, and sensory abnormalities. These deleterious effects were not observed in saline-treated animals, in animals in which the db-cAMP dose did not exceed 1 mM, or in those animals that received a high dose (250 mM) of the alternative cAMP analog, 8-bromo-cAMP. These results demonstrate that, for continuous intraparenchymal or intrathecal administration of cAMP analogs for the study of biological or therapeutic effects within the central nervous system (CNS), consideration of the effective concentration applied as well as the potential toxicity of chemical moieties on the parent molecule and/or their activity needs to be taken into account.

A comparative examination of biomarkers for olfactory ensheathing cells in cats and guinea pigs

We investigated the neurochemical characteristics of olfactory ensheathing cells (OECs) in adult cats and in adult guinea pigs. Three conventional biomarkers for OECs, p75 neurotrophin receptor (p75NTR), S100, and glial fibrillary acidic protein (GFAP), as well as two recently identified biomarkers, smooth muscle alpha-actin (SMA) and calponin, were used. We found that 1) antibodies against SMA and S100 yielded positive immunostaining of mucosal and bulbar OECs in cats and guinea pigs; 2) antibodies against GFAP gave positive immunostaining of mucosal and bulbar OECs in cats; and 3) antibodies against calponin yielded positive immunostaining of bulbar OECs in adult cats. Unexpectedly, antibodies against p75NTR failed to positively stain mucosal and bulbar OECs in cats and guinea pigs, and antibodies against GFAP and calponin failed to positively stain mucosal and bulbar OECs in guinea pigs. These findings show the importance for empirical testing of all biomarkers for OECs among different mammalian species when attempting to identify these cells in vivo, in vitro, and following intraspinal implantation.

Analysis of olfactory ensheathing glia transplantation-induced repair of spinal cord injury by electrophysiological, behavioral, and histochemical methods in rats

This study examined the efficacy of transplanting olfactory ensheathing glia (OEG) in repairing spinal cord injury (SCI) using behavioral tests, retrograde labeling, as well as somatosensory and motor evoked potentials in rats. One week after surgery, motor function in OEG-treated rats was significantly superior to untreated controls (P < 0.05). Also, we found that up to 8 weeks following surgery to induce SCI, somatosensory and motor evoked potentials were found in the OEG-treated groups, but not in the transplantation and damage control groups. Retrograde labeling from the area distal to the SCI produced a higher number of labeled neurons in the ventrolateral division of red nucleus and motor cortex of OEG-treated rats compared to controls, which showed no retrograde labeling (P < 0.05). We believe that this study has important implications for characterizing the mechanisms of OEG transplantation as a treatment for SCI.

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

Olfactory ensheathing cells (OECs) are cells that display Schwann cell or astrocyte-like properties. They are a source of growth factors and adhesion molecules which play a very important role as neuronal support enhancing cellular survival. Over the past 10 years, OECs have emerged as a leading reparative candidate, when transplanted into the injured spinal cord, having shown significant promise in the regeneration of spinal cord lesions. In this study we assessed the efficacy of OECs on the survival and neurite outgrowth of hippocampal neurons in vitro. Co-cultures of OECs and hippocampal of postnatal rats were successfully established and cells were immunocytochemically characterized. Some hippocampal cultures were added with growth factors, as bFGF, NGF and GDNF. Furthermore, conditioned medium from OECs cultures was used to feed some hippocampal neurons coverslips. Our results show that in co-cultures of hippocampal neurons and OECs the number of neurons and their neurite outgrowth were significantly increased in comparison with controls. Moreover, we showed that NGF and GDNF promoted a more positive effect in both neuronal survival and neurite outgrowth than bFGF. OEC-conditioned media stimulated both the neuronal survival and dense neurite outgrowth. These data indicate that OECs, as a source of growth factors, can promote the survival and the neurite outgrowth of hippocampal neurons in vitro and that bFGF, NGF and GDNF support them differently. Therefore, as OECs and their secreted growth factors appear to exert a neuroprotective effect for functional restoration and for neural plasticity in neurodegenerative disorders, they might be considered an approach for functional recovery.