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

Treatment of spinal cord injury by transplantation of cells via cerebrospinal fluid

It is very important to probe into the axonal regeneration and functional recovery of central nervous system (CNS) after implantation of cells into cerebrospinal fluid (CSF) for spinal cord injury (SCI). Transplantation of cells via CSF poses great potentials for SCI in clinic. Studies on administration of cells via CSF indicate that the method is safe and convenient. The method is more suitable to treating multiple lesions of the CNS since it does not produce open lesions. However, there are disputes over its promotion effects on axonal regeneration and functional recovery of spinal cord after injury; and some questions, such as the mechanisms of functional recovery of spinal cord, the proper time window of cell transplantation, and cell types of transplantation, still need to be handled. This review summarized the method of cell transplantation via CSF for treatment of SCI.

Current status of acute spinal cord injury pathophysiology and emerging therapies: promise on the horizon

This review summarizes the current understanding of spinal cord injury pathophysiology and discusses important emerging regenerative approaches that have been translated into clinical trials or have a strong potential to do so. The pathophysiology of spinal cord injury involves a primary mechanical injury that directly disrupts axons, blood vessels, and cell membranes. This primary mechanical injury is followed by a secondary injury phase involving vascular dysfunction, edema, ischemia, excitotoxicity, electrolyte shifts, free radical production, inflammation, and delayed apoptotic cell death. Following injury, the mammalian central nervous system fails to adequately regenerate due to intrinsic inhibitory factors expressed on central myelin and the extracellular matrix of the posttraumatic gliotic scar. Regenerative approaches to block inhibitory signals including Nogo and the Rho-Rho-associated kinase pathways have shown promise and are in early stages of clinical evaluation. Cell-based strategies including using neural stem cells to remyelinate spared axons are an attractive emerging approach.

Transplantation and repair: combined cell implantation and chondroitinase delivery prevents deterioration of bladder function in rats with complete spinal cord injury

STUDY DESIGN

Additional examination. In this study, we report changes in bladder function after a combined treatment that was designed to study axonal regeneration after complete spinal cord injury (SCI) in rats.

OBJECTIVES

To report effects on bladder function following the administration of a combined treatment for complete SCI.

SETTING

University of Alberta, Faculty of Rehabilitation Medicine, Edmonton, Canada.

METHODS

Eight rats received Schwann cells in Matrigel-filled guidance channels, olfactory ensheathing glia and chondroitinase ABC at the lesion site following complete thoracic SCI. Controls (n=7) received Matrigel only. Daily bladder examinations were performed. Analysis of bladder size, wall thickness, actin and collagen type III was performed after 14 weeks.

RESULTS

Following SCI, both groups regained bladder voiding after 3 weeks. However, 2 weeks later, incontinence was observed in all untreated rats and two treated rats. Post-mortem examination of bladders revealed enlarged bladder sizes. Thicker bladder walls were found in untreated rats, which were composed of disorganized bundles of smooth muscle fibers surrounded by high amounts of collagen (type III).

CONCLUSION

We show that the combined treatment prevents collagen deposition in bladder walls and maintains the rat's ability to void efficiently. Although the mechanism responsible for this improvement is unclear, our study shows that the present combinatory therapy can influence bladder function, thus expanding their utility as a broad reparative approach for SCI.

The combination of human neuronal serotonergic cell implants and environmental enrichment after contusive SCI improves motor recovery over each individual strategy

A human neuronal cell line, hNT2.19, which secretes serotonin (5-HT) after differentiation, was used as a transplant source to improve motor dysfunction following severe contusive spinal cord injury (SCI). Also, environmental enrichment (EE) was added to the interspinal transplant treatment paradigm. Motor testing was performed weekly before and following SCI, with and without EE and/or cell transplant conditions. Motor recovery was maximal when both cell transplant and EE were used. Individual treatment paradigms also significantly improved foot rotation and reduced footfall errors but not stride length or base of support dysfunction. This recovery of motor function after SCI suggests that the combinatory use of serotonergic hNT2.19 cell grafts plus EE is a meaningful strategy to modestly improve motor dysfunction that accompanies contusive SCI.

BYHWD rescues axotomized neurons and promotes functional recovery after spinal cord injury in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Buyang Huanwu Decoction (BYHWD), a Chinese prescription that has been used for hundreds of years to treat paralysis, has gained attention recently due to its significant neuroprotective properties.

AIM OF THE STUDY

This study was to investigate whether BYHWD treatment protected axotomized rubrospinal neurons (RN) following spinal cord injury (SCI) in rats.

MATERIALS AND METHODS

Adult rats received a right lateral funiculus transection at the level between C3 and C4, and were either treated with BYHWD or with distilled water (DW) via gastrogavage. Effects on RN viability and atrophy were determined by Nissl staining, axon regeneration was examined by biotinylated dextran amine (BDA) tracing techniques and functional recovery was studied by a test of forelimb usage during spontaneous vertical exploration.

RESULTS

RN cell number and mean somal size were 20% and 29% higher, respectively, in BYHWD-treated rats relative to DW-treated rats. There were a small number of BDA-labeled axons in the caudal of injury site in BYHWD-treated rats, whereas no caudal axonal regeneration was detected in DW-treated rats. BYHWD-treated rats used the injured forelimb more often than rats treated with DW.

CONCLUSIONS

These results indicate that administration of BYHWD following SCI protects injured neurons, promotes regeneration, and enhances functional recovery.

From fish to man: understanding endogenous remyelination in central nervous system demyelinating diseases

In the central nervous system (CNS) of man, evolutionary pressure has preserved some capability for remyelination while axonal regeneration is very limited. In contrast, two efficient programmes of regeneration exist in the adult fish CNS, neurite regrowth and remyelination. The rapidity of CNS remyelination is critical since it not only restores fast conduction of nerve impulses but also maintains axon integrity. If myelin repair fails, axons degenerate, leading to increased disability. In the human CNS demyelinating disease multiple sclerosis (MS), remyelination often takes place in the midst of inflammation. Here, we discuss recent studies that address the innate repair capabilities of the axon-glia unit from fish to man. We propose that expansion of this research field will help find ways to maintain or enhance spontaneous remyelination in man.

Current status of experimental cell replacement approaches to spinal cord injury

Despite advances in medical and surgical care, the current clinical therapies for spinal cord injury (SCI) are largely ineffective. During the last 2 decades, the search for new therapies has been revolutionized by the discovery of stem cells, which has inspired scientists and clinicians to search for a stem cell-based reparative approaches to many diseases, including neurotrauma. In the present study, the authors briefly summarize current knowledge related to the pathophysiology of SCI, including the concepts of primary and secondary injury and the importance of posttraumatic demyelination. Key inhibitory obstacles that impede axonal regeneration include the glial scar and a number of myelin inhibitory molecules including Nogo. Recent advancements in cell replacement therapy as a therapeutic strategy for SCI are summarized. The strategies include the use of pluripotent human stem cells, embryonic stem cells, and a number of adult-derived stem and progenitor cells such as mesenchymal stem cells, Schwann cells, olfactory ensheathing cells, and adult-derived neural precursor cells. Although current strategies to repair the subacutely injured cord appear promising, many obstacles continue to render the treatment of chronic injuries challenging. Nonetheless, the future for stem cell-based reparative strategies for treating SCI appears bright.

[Immunoablation and autologous hematopoietic stem cell transplantation (AHSCT) in multiple sclerosis]

Numerous pathophysiological arguments supporting immunosuppression for multiple sclerosis have been collected during recent years. The relevance of intense immunosuppression, in terms of clinical benefit and early or late risk, remains a matter of discussion. Immunoablation followed by autologous hematopoietic stem cell transplantation (AHSCT) in multiple sclerosis uses intense immunosuppression, followed by reinjection of AHSC, a rescue procedure for the induced aplasia. This method targets disappearance of the immune disorder, and thus, in theory, the interruption of the disease course. Use of AHSCT to treat several types of autoimmune diseases has been performed with contrasted results. In multiple sclerosis, the experience has been gained over the past 10 years through short series of patients treated at a late stage of their disease. This article highlights the recent data of this particular treatment option in multiple sclerosis as well as the therapeutic aims that should be investigated in further trials.

Xenografts of expanded primate olfactory ensheathing glia support transient behavioral recovery that is independent of serotonergic or corticospinal axonal regeneration in nude rats following spinal cord transection

Transplantation of olfactory ensheathing glial cells (OEG) may improve the outcome from spinal cord injury. Proof-of-principle studies in primates are desirable and the feasibility and efficacy of using in vitro expanded OEG should be tested. An intermediate step between the validation of rodent studies and human clinical trials is to study expanded primate OEG (POEG) xenografts in immunotolerant rodents. In this study the time course to generate purified POEG was evaluated as well as their survival, effect on damaged axons of the corticospinal and serotonergic systems, tissue sparing, and chronic locomotor recovery following transplantation. Fifty-seven nude rats underwent T9/10 spinal cord transection. Thirty-eight rats received POEG, 19 controls were injected with cell medium, and 10 received lentivirally-GFP-transfected POEG. Histological evaluation was conducted at 6 weeks, 8 weeks, 14 weeks and 23-24 weeks. Of these 57 rats, 18 were studied with 5-HT immunostaining, 16 with BDA anterograde CST labeling, and six were used for transmission electron microscopy. In grafted animals, behavioral recovery, sprouting and limited regeneration of 5-HT fibers, and increased numbers of proximal collateral processes but not regeneration of CST fibers was observed. Grafted animals had less cavitation in the spinal cord stumps than controls. Behavioral recovery peaked at three months and then declined. Five POEG-transplanted animals that had shown behavioral recovery underwent retransection and behavioral scores did not change significantly, suggesting that long tract axonal regeneration did not account for the locomotor improvement. At the ultrastructural level presumptive POEG were found to have direct contacts with astrocytes forming the glia limitans, distinct from those formed by Schwann cells. At 6 weeks GFP expression was detected in cells within the lesion site and within nerve roots but did not match the pattern of Hoechst nuclear labeling. At 3.5 months only GFP-positive debris in macrophages could be detected. Transplanted POEG support behavioral recovery via mechanisms that appear to be independent of long tract regeneration.

Bioengineering Neural Stem/Progenitor Cell-Coated Tubes for Spinal Cord Injury Repair

The aim of this study was to understand the survival and differentiation of neural stem/progenitor cells (NSPCs) cultured on chitosan matrices in vivo in a complete transection model of spinal cord injury. NSPCs were isolated from the subependyma of lateral ventricles of adult GFP transgenic rat forebrains. The GFP-positive neurospheres were seeded onto the inner lumen of chitosan tubes to generate multicellular sheets ex vivo. These bioengineered neurosphere tubes were implanted into a completely transected spinal cord and assessed after 5 weeks for survival and differentiation. The in vivo study showed excellent survival of NSPCs, as well as differentiation into astrocytes and oligodendrocytes. Importantly, host neurons were identified in the tissue bridge that formed within the chitosan tubes and bridged the transected cord stumps. The excellent in vivo survival of the NSPCs coupled with their differentiation and maintenance of host neurons in the regenerated tissue bridge demonstrates the promise of the chitosan tubes for stem cell delivery and tissue regeneration.

Evaluation of olfactory ensheathing and schwann cells after implantation into a dorsal injury of adult rat spinal cord

Olfactory ensheathing cells (OECs) and Schwann cells (SCs) obtained from adult transgenic rats expressing alkaline phosphatase (AP) were studied following implantation into intact spinal cord and after dorsal column crush (DCC) injury, either within the lesion or near the lesion borders. We observed no evidence of migration of AP OECs or AP SCs after lesion site injections, with most cells remaining in or nearby the injection/lesion site. Acute injection of either cell type outside of the lesion site resulted in the presence of cells in the lesion even two hours after injection. However, after a 2-week delay between DCC injury and cell injection, only OECs injected 2.5-mm outside of a DCC lesion entered the lesion, while SCs did not pass a region of increased astroglial immunoreactivity. GFAP-immunoreactivity also revealed differences in the astroglial scar at the lesion border with openings apparent in this region only in the OEC group. SCs induced greater ingrowth of CGRP-positive axons within the lesion, two weeks post-injury. Equivalent numbers of GAP-43-positive axons grew within the lesion after SC or OEC implantation. These findings show that, although there is no active migration for either cell type, both OECs and SCs are able to support axonal regrowth and/or sprouting into the lesion. The openings in the astroglial boundary at the lesion site may give OECs a potential advantage over SCs in promoting axonal growth through the astroglial scar.

Social and environmental enrichment improves sensory and motor recovery after severe contusive spinal cord injury in the rat

Neuropathic pain and motor dysfunction are difficult problems following spinal cord injury (SCI). Social and environmental enrichment (SEE), which models much of the clinical rehabilitation environment for post-SCI persons, is the focus of the current investigation which examines the effects of multiple-housing and the addition of climbing spaces, improved bedding and crawl toys on the sensory and motor recovery following a severe contusive SCI. Efficacy was determined with sensory testing, open-field motor behavioral testing, lesion volume analysis and quantification of brain-derived neurotrophic factor (BDNF) in the lumbar spinal cord with and without SEE provided during the recovery period. Sensory and motor testing were performed weekly for 12 weeks following SCI. SEE significantly and permanently reversed cutaneous allodynia, but not thermal hyperalgesia, to near normal levels. The gross locomotor performance (BBB [Basso, Beattie, and Bresnahan] motor scores) significantly improved about two points. In addition, the BBB subscale scores were significantly improved nearly seven points by the end of the study. SEE also significantly improved foot rotation to normal levels and reduced gridwalk footfall errors nearly 50%, but had no effect on stride length or base of support dysfunctions. SEE significantly increased the total volume of a thoracic segment of cord encompassing the injury site at 12 weeks, by reducing cavitation and increasing both the volume of grey and white matter spared, compared to SCI alone. When BDNF levels were examined in the injured lumbar spinal cord, SEE significantly returned BDNF levels to near-normal. These data suggest that immediate use of SEE after contusive SCI is able to improve overall spinal cell survival and prevent much of the sensory and motor dysfunction that accompanies contusive SCI.

The function of p75NTR in glia

The p75 neurotrophin receptor (p75(NTR)) is expressed on many cell types and can influence a variety of cellular functions. This receptor can mediate cell survival or cell death, can promote or inhibit axonal growth and can facilitate or attenuate proliferation, depending on the cell context. The emerging picture regarding p75(NTR) indicates that it can partner with different coreceptors to dictate specific responses. It then signals by recruiting intracellular binding proteins to activate different signaling pathways. The function of p75(NTR) has mainly been studied in neurons; however, it is also expressed in a variety of glial populations, especially during development and after injury, where its roles have been poorly defined. In this review, we will examine the potential roles for p75(NTR) in glial function.

Novel combination strategies to repair the injured mammalian spinal cord

Due to the varied and numerous changes in spinal cord tissue following injury, successful treatment for repair may involve strategies combining neuroprotection (pharmacological prevention of some of the damaging intracellular cascades that lead to secondary tissue loss), axonal regeneration promotion (cell transplantation, genetic engineering to increase growth factors, neutralization of inhibitory factors, reduction in scar formation), and rehabilitation. Our goal has been to find effective combination strategies to improve outcome after injury to the adult rat thoracic spinal cord. Combination interventions tested have been implantation of Schwann cells (SCs) plus neuroprotective agents and growth factors administered in various ways, olfactory ensheathing cell (OEC) implantation, chondroitinase addition, or elevation of cyclic AMP. The most efficacious strategy in our hands for the acute complete transection/SC bridge model, including improvement in locomotion [Basso, Beattie, Bresnahan Scale (BBB)], is the combination of SCs, OECs, and chondroitinase administration (BBB 2.1 vs 6.6, 3 times more myelinated axons in the SC bridge, increased serotonergic axons in the bridge and beyond, and significant correlation between the number of bridge myelinated axons and functional improvement). We found the most successful combination strategy for a subacute spinal cord contusion injury (12.5-mm, 10-g weight, MASCIS impactor) to be SCs and elevation of cyclic AMP (BBB 10.4 vs 15, significant increases in white matter sparing, in myelinated axons in the implant, and in responding reticular formation and red and raphe nuclei, and a significant correlation between the number of serotonergic fibers and improvement in locomotion). Thus, in two injury paradigms, these combination strategies as well as others studied in our laboratory have been found to be more effective than SCs alone and suggest ways in which clinical application may be developed.

Olfactory ensheathing glia: Their contribution to primary olfactory nervous system regeneration and their regenerative potential following transplantation into the injured spinal cord

Olfactory ensheathing glia (OEG) are a specialized type of glia that guide primary olfactory axons from the neuroepithelium in the nasal cavity to the brain. The primary olfactory system is able to regenerate after a lesion and OEG contribute to this process by providing a growth-supportive environment for newly formed axons. In the spinal cord, axons are not able to restore connections after an injury. The effects of OEG transplants on the regeneration of the injured spinal cord have been studied for over a decade. To date, of all the studies using only OEG as a transplant, 41 showed positive effects, while 13 studies showed limited or no effects. There are several contradictory reports on the migratory and axon growth-supporting properties of transplanted OEG. Hence, the regenerative potential of OEG has become the subject of intense discussion. In this review, we first provide an overview of the molecular and cellular characteristics of OEG in their natural environment, the primary olfactory nervous system. Second, their potential to stimulate regeneration in the injured spinal cord is discussed. OEG influence scar formation by their ability to interact with astrocytes, they are able to remyelinate axons and promote angiogenesis. The ability of OEG to interact with scar tissue cells is an important difference with Schwann cells and may be a unique characteristic of OEG. Because of these effects after transplantation and because of their role in primary olfactory system regeneration, the OEG can be considered as a source of neuroregeneration-promoting molecules. To identify these molecules, more insight into the molecular biology of OEG is required. We believe that genome-wide gene expression studies of OEG in their native environment, in culture and after transplantation will ultimately reveal unique combinations of molecules involved in the regeneration-promoting potential of OEG.