Acute and delayed transplantation of olfactory ensheathing cells promote partial recovery after complete transection of the spinal cord

The role of olfactory ensheathing cells in the repair of nerve injury

Cell transplantation has brought about a breakthrough in the treatment of nerve injuries, and the efficacy of cell transplantation compared to drug and surgical therapies is very exciting. In terms of transplantation targets, the classic cells include neural stem cells (NSCs) and Schwann cells, while a class of cells that can exist and renew throughout the life of the nervous system - olfactory ensheathing cells (OECs) - has recently been discovered in the olfactory system. OECs not only encircle the olfactory nerves but also act as macrophages and play an innate immune role. OECs can also undergo reprogramming to transform into neurons and survive and mature after transplantation. Currently, many studies have confirmed the repairing effect of OECs after transplantation into injured nerves, and safe and effective results have been obtained in clinical trials. However, the specific repair mechanism of OECs among them is not quite clear. For this purpose, we focus here on the repair mechanisms of OECs, which are summarized as follows: neuroprotection, secretion of bioactive factors, limitation of inflammation and immune regulation, promotion of myelin and axonal regeneration, and promotion of vascular proliferation. In addition, integrating the aspects of harvesting, purification, and prognosis, we found that OECs may be more suitable for transplantation than NSCs and Schwann cells, but this does not completely discard the value of these classical cells. Overall, OECs are considered to be one of the most promising transplantation targets for the treatment of nerve injury disorders.

Effect of multifactorial therapeutic approach on axonal regeneration and cell viability in an in-vitro model of spinal-derived neural injury

The highly debilitated nature of spinal cord injuries (SCI) creates an inhibitory repair environment that limits the recovery rate and therefore single interventional treatment has been resulted in incomplete recovery. A multifactorial approach that combines several therapeutic approaches may address diverse aspects of SCI pathology and enhance the recovery rate over single therapy. Accordingly, in this study, we aimed to investigate the effect of combined olfactory ensheathing cells (OECs) (to transport trophic factor, mediate immunomodulation, provide a suitable environment for cell survival), G-CSF (to establish a favorable environment for cell survival) and lipopolysaccharide (LPS) (to boost the protective activity of OEC) therapy on the cell viability after a scratch injury caused by a cataract knife on cells in an in-vitro model of spinal-derived neural injury. In this study, we used mixed neuronal-glial cultures, which are widely used for an in vitro study of neuronal damage. Scratch insult was made on cells using a cataract knife. The cells were divided into 8 groups (two control groups with and without olfactory ensheathing cells (OECs) treatment, injury group, three injury groups with single therapy by using super low dose of LPS (SLD-LPS) (100 pg/ml), OEC group, and G-CSF (100 ng/ml) group, and two injury groups with combined therapy (OEC with SLD-LPS and with all three treatments)). We found a significant decrease in the survival rate of injured cells (p < 0.001) 24 h after scratching insult. Our results indicated morphological alterations in cells in the acute phase (1, 2 and 6 h) after injury, with significant increased gap size at 6 h after induction of injury. Our combined therapy, significantly prevented cell death and decreased the size of the gap over time. We found that combined therapy promoted cell survival following spinal injury by providing a neuroprotective environment for cells. Therefore, our findings provide new insight into the combined therapy, which can be considered for promising preclinical therapeutic strategy for SCI toward clinical trials.

Application of Human Umbilical Cord Mesenchymal Stem Cells in Rat Spinal Cord Injury Model

The treatment of spinal cord injury (SCI) is a hot topic in clinic. In this study, female rats were selected and randomly divided into four groups (normal, sham, SCI, and mesenchymal stem cells [MSCs] groups). Hemostatic forceps were used to clamp the spinal cord for 1 min to establish the SCI animal model in rats. The levels of proinflammatory factors in the blood of each group were compared 4 h after operation. The motor function of hind limb was estimated by Basso, Beattie & Bresnahan Locomotor rating scale (BBB scale) at 3 months after surgery, the spinal cord tissue from the experimental area was obtained and stained histologically and immunohistochemically. Basso, Beattie & Bresnahan Locomotor rating scale results indicated that human umbilical cord (HUC) MSCs transplantation could improve the walking ability in rats with the SCI. Human umbilical cord mesenchymal stem cells substantially upregulated the secretion of anti-inflammatory factors and downregulated the secretion of proinflammatory factors, and promoted the repair of the SCI and inhibited the increase of glial cells induced by the SCI. Human umbilical cord mesenchymal stem cells transplantation can partially recovered the motor ability of rats with the SCI through promoting the regeneration of nerve cell and the expression of neural related genes, and inhibiting inflammatory reaction.

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.

Neurotrophic and immunomodulatory effects of olfactory ensheathing cells as a strategy for neuroprotection and regeneration

Accumulating evidence sustains glial cells as critical players during central nervous system (CNS) development, homeostasis and disease. Olfactory ensheathing cells (OECs), a type of specialized glia cells sharing properties with both Schwann cells and astrocytes, are of critical importance in physiological condition during olfactory system development, supporting its regenerative potential throughout the adult life. These characteristics prompted research in the field of cell-based therapy to test OEC grafts in damaged CNS. Neuroprotective mechanisms exerted by OEC grafts are not limited to axonal regeneration and cell differentiation. Indeed, OEC immunomodulatory properties and their phagocytic potential encourage OEC-based approaches for tissue regeneration in case of CNS injury. Herein we reviewed recent advances on the immune role of OECs, their ability to modulate CNS microenvironment via bystander effects and the potential of OECs as a cell-based strategy for tissue regeneration.

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.

Considering the Cellular Composition of Olfactory Ensheathing Cell Transplants for Spinal Cord Injury Repair: A Review of the Literature

Olfactory ensheathing cells (OECs) are specialized glia cells of the olfactory system that support the continual regeneration of olfactory neurons throughout adulthood. Owing to their pro-regenerative properties, OECs have been transplanted in animal models of spinal cord injuries (SCI) and trialed in clinical studies on SCI patients. Although these studies have provided convincing evidence to support the continued development of OEC transplantation as a treatment option for the repair of SCI, discrepancies in the reported outcome has shown that OEC transplantation requires further improvement. Much of the variability in the reparative potential of OEC transplants is due to the variations in the cell composition of transplants between studies. As a result, the optimal cell preparation is currently a subject of debate. Here we review, the characterization as well as the effect of the cell composition of olfactory cell transplantation on therapeutic outcome in SCI. Firstly, we summarize and review the cell composition of olfactory cell preparations across the different species studied prior to transplantation. Since the purity of cells in olfactory transplants might affect the study outcome we also examine the effect of the proportions of OECs and the different cell types identified in the transplant on neuroregeneration. Finally, we consider the effect of the yield of cells on neuroregeneration by assessing the cell dose of transplants on therapeutic outcome.

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

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

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.

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

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

Why is olfactory neuroepithelium?

Currently, most cellular therapeutic effects for nervous diseases cannot be proven in a multicenter, randomized, double-blind placebo-control clinical trials, except for a few kinds of cells such as olfactory ensheathing cells. These cells show significant improvements in functional recovery and quality of life for patients with chronic ischemic stroke. Also, olfactory neuron transplantation has promising neurorestorative effects on patients with vascular dementia. Human olfactory neuroepithelium can spontaneously and sustainably regenerate or produce new olfactory neurons and glial cell types for decades or a lifetime. The neurorestorative mechanisms of olfactory ensheathing cells are well known; however, little is known about the neurorestorative mechanisms of olfactory neurons. Therefore, I hypothesize that the neurorestorative mechanisms of olfactory neurons after transplantation: (1) can well migrate where they are needed and become local functional neurons, as they need to compensate or replace; (2) must be regulated by some special molecular factors to elongate their axons, modulate or direct synapses to correctly recognize and connect the target cells, and integrate functions. Based on olfactory neuroepithelium cells displaying the special characterization, neurorestorative mechanisms, clinical therapeutic achievements, and hypotheses of effective mechanisms, they (olfactory ensheathing cells and olfactory neurons) may be the most efficient instruments of neurorestoration.

[Radiotherapy and spinal toxicity: News and perspectives]

Radiation-induced myelopathy is a devastating late effect of radiotherapy. Fortunately, this late effect is exceptional. The clinical presentation of radiation myelopathy is aspecific, typically occurring between 6 to 24 months after radiotherapy, and radiation-induced myelopathy remains a diagnosis of exclusion. Magnetic resonance imaging is the most commonly used imaging tool. Radiation oncologists must be extremely cautious to the spinal cord dose, particularly in stereotactic radiotherapy and reirradiation. Conventionally, a maximum dose of 50Gy is tolerated in normofractionated radiotherapy (1.8 to 2Gy per fraction). Repeat radiotherapies lead to consider cumulative doses above this recommendation to offer individualized reirradiation. Several factors increase the risk of radiation-induced myelopathy, such as concomitant or neurotoxic chemotherapy. The development of predictive algorithms to prevent the risk of radiation-induced myelopathy is promising. However, radiotherapy prescription should be cautious, regarding to ALARA principle (as low as reasonably achievable). As the advent of immunotherapy has improved patient survival data and the concept of oligometastatic cancer is increasing in daily practice, stereotactic treatments and reirradiations will be increasingly frequent indications. Predict the risk of radiation-induced myelopathy is therefore a major issue in the following years, and remains a daily challenge for radiation oncologists.

Gunshot injury to spine: An institutional experience of management and complications from a developing country

PURPOSE

Gunshot wounds are the second leading cause of spinal cord injuries. Surgical intervention for gunshot injury to the spine carries a high rate of complications. There is a scarcity of data on civilian gunshot injuries to the spine in Pakistan. Approximately 60 cases over the last 10 years have been recoded, with unusual presentation and neurological recovery. Thus it is imperative to fill this gap in data, by reviewing cases of civilian gunshot injuries to spine presenting at a tertiary care hospital (Aga Khan University Hospital, Karachi).

METHODS

This is a retrospective cohort study. Patients of all ages who presented to the emergency department of Aga Khan University Hospital, with gunshot injuries to spine between January 2005 and December 2016 were included in the study. Data were collected on neurological status (American Spinal Injury Association score was used for the initial and follow-up neurological assessment), extent of cord transection, motor and sensory deficits. The patients were further grouped into those with cord transection, and those with fractures of the bony spine but an intact spinal cord. These patients were then followed and the outcomes were recorded.

RESULTS

A total of 40 patients were identified. The mean ± SD of patients age was (30.9 ± 9.5) years. Of the 40 patients with gunshot wounds, 31 had the medical imaging performed at the facility, and hence they were included in this categorization. The remaining 9 patients were excluded from this additional grouping. Thirteen patients were managed surgically and 27 patients underwent the conservative management. The mean ± SD of follow-up was (8.7 ± 7.2) months. In our study, the thoracic spine was the most commonly injured region in gunshot injuries. Of the 31 patients with medical imaging performed at our institute, 17 (54.8%) had cord transection, of whom 8 (47%) ultimately developed paraplegia.

CONCLUSION

The prognosis of gunshot injuries to the spine can be varied depending on whether the spinal cord is intact or transected. This will help healthcare providers to plan the further management of the patient and counsel them accordingly.

Stemness and Regenerative Potential of Corneal Stromal Stem Cells and Their Secretome After Long-Term Storage: Implications for Ocular Regeneration

Purpose

To assess the stemness and regenerative potential of cryopreserved corneal stromal stem cells (cryo-CSSCs) after long-term storage. We also used the secretome from these cells to observe the effect on wound-healing capacity of corneal fibroblasts and on the expression of fibrotic markers during wound healing.

Methods

CSSCs were obtained from three donors and stored in liquid nitrogen for approximately 10 years. Post thaw, cryo-CSSCs were characterized for stemness using phenotypic and genotypic markers along with colony-forming efficiency and three-dimensional spheroid formation. Multilineage differentiation was observed by differentiation into osteocytes, adipocytes, neural cells, and keratocytes. Secretome was harvested by culturing cryo-CSSCs in log phase. Wound-healing capacity was observed by live-cell time-lapse microscopy. Statistical analysis was done using 1-way ANOVA and Tukey posttest.

Results

CSSCs displayed good viability post thaw and showed >90% expression of stem cell markers CD90, CD73, CD105, STRO1, and CD166. cryo-CSSCs also expressed stem cell genes OCT4, KLF4, and ABCG2, and could also form colonies and three-dimensional spheroids. Multipotency assessment showed that all three cryo-CSSCs could differentiate into osteocytes, adipocytes, neural cells, as shown by β-III tubulin and neurofilament antibody staining and corneal keratocytes as observed by staining for Kera C, J19, and collagen V antibodies. The secretome derived from these three populations could promote the wound healing of corneal fibroblasts and reduce the expression of fibrotic markers SPARC and fibronectin.

Conclusions

CSSCs maintained their stemness and multipotency after long-term storage, and secretome derived from these cells can be of paramount importance for corneal regeneration and prevention of fibrosis.

Neuroprotective Effects of Combined Treatment with Minocycline and Olfactory Ensheathing Cells Transplantation against Inflammation and Oxidative Stress after Spinal Cord Injury

Objective

Traumatic spinal cord injury (SCI) is considered one of the most devastating injuries leading to neuronal disruption. Olfactory ensheathing cells (OECs) and minocycline have been shown to promote locomotor function after spinal cord injury. In this study, we have tested the efficacy of combined treatment with minocycline and OECs after contusive spinal cord injury.

Materials and Methods

In this experimental study, adult female Wistar rats were randomly divided into five groups. Rats received an intraperitoneal injection of minocycline immediately after SCI, and then 24 hours after the injury. Transplantations were performed 7 days after the injury. Functional recovery was evaluated using the Basso, Beattie and Bresnahan scale (BBB). After that, the animals were sacrificed, and T11 segment of the spinal cord was removed after 5 weeks, and then used for histopathological, immunohistochemical, and biochemical assessments. Western blot analysis was applied to determine the protein expression of tumor necrosis factor alpha (TNF-α), interleukin 1 beta (IL1β) and caspase3.

Results

The results of this study showed that the combination of OECs graft and minocycline reduced the functional deficits and diminished cavitation and astrogliosis in spinal tissue. The analysis of protein expression by western blotting revealed that minocycline treatment along with OECs transplantation further decreased the level of IL-1β, TNF-α, caspase-3, and the oxidative stress as compared with when minocycline or OECs transplantation was used alone.

Conclusion

The combinatory treatment with OECs graft and minocycline induced a more effective response to the repair of spinal cord injury, and it is considered a therapeutic potential for the treatment of SCI.

On the Viability and Potential Value of Stem Cells for Repair and Treatment of Central Neurotrauma: Overview and Speculations

Central neurotrauma, such as spinal cord injury or traumatic brain injury, can damage critical axonal pathways and neurons and lead to partial to complete loss of neural function that is difficult to address in the mature central nervous system. Improvement and innovation in the development, manufacture, and delivery of stem-cell based therapies, as well as the continued exploration of newer forms of stem cells, have allowed the professional and public spheres to resolve technical and ethical questions that previously hindered stem cell research for central nervous system injury. Recent in vitro and in vivo models have demonstrated the potential that reprogrammed autologous stem cells, in particular, have to restore functionality and induce regeneration-while potentially mitigating technical issues of immunogenicity, rejection, and ethical issues of embryonic derivation. These newer stem-cell based approaches are not, however, without concerns and problems of safety, efficacy, use and distribution. This review is an assessment of the current state of the science, the potential solutions that have been and are currently being explored, and the problems and questions that arise from what appears to be a promising way forward (i.e., autologous stem cell-based therapies)-for the purpose of advancing the research for much-needed therapeutic interventions for central neurotrauma.

Exercise intervention alleviates nerve injury by the suppression of inflammatory mediator expression via the TLR4/NF-κB signaling pathway

Spinal cord injury (SCI) may cause changes that have damaging effects on sensation and functionality. However, methods for the significant amelioration of SCI-reduced nerve injury are lacking. Previous studies have indicated that reasonable and effective exercise may promote the recovery of injured nerves. Therefore, the aim of the present study was to investigate the ability of exercise to improve recovery following SCI and the underlying mechanism. A rat model was used to evaluate the effects of two different periods of exercise intervention on recovery following SCI. The exercise intervention comprised 15 or 30 min/day passive walking for 30 days. ELISA measurements were used to analysis the plasma levels of inflammatory cytokines. Reverse transcription-quantitative polymerase chain reaction and western blot analyses were performed to examine the levels of proteins and mRNAs associated with nuclear factor (NF)-κB-related signaling. In addition, histological examination and immunostaining were used to evaluate the neural injury and associated indicators. The results indicated that severe SCI induced a peripheral inflammatory response and increased the expression of inflammatory cytokines. In addition, the SCI-induced nerve injury was associated with increased glial fibrillary acidic protein (GFAP) expression and the upregulation of Toll-like receptor 4 (TLR4)/NF-κB signaling, which may further aggravate the inflammatory responses induced by SCI. However, the exercise intervention decreased SCI-induced GFAP expression and reduced the activation of the TLR4/NF-κB signaling pathway compared with that of SCI model rats that did not exercise. Furthermore, the exercise intervention inhibited the release of inflammatory cytokines into the serum. These results indicate that exercise treatment reduces inflammation and glial activation, and may be beneficial to recovery following SCI.

The Therapeutic Effects after Transplantation of Whole-Layer Olfactory Mucosa in Rats with Optic Nerve Injury

Background

Existing evidence suggests the potential therapy of transplanting olfactory ensheathing cells (OEC) either alone or in combination with neurotrophic factors or other cell types in optic nerve injury (ONI). However, clinical use of autologous OEC in the acute stages of ONI is not possible. On the other hand, acute application of heterologous transplantation may bring the issue of immune rejection. The olfactory mucosa (OM) with OEC in the lamina propria layer is located in the upper region of the nasal cavity and is easy to dissect under nasal endoscopy, which makes it a candidate as autograft material in acute stages of ONI. To investigate the potential of the OM on the protection of injured neurons and on the promotion of axonal regeneration, we developed a transplantation of syngenic OM in rats with ONI model.

Methods

After the right optic nerve was crushed in Lewis rats, pieces of syngenic whole-layer OM were transplanted into the lesion. Rats undergoing phosphate buffered saline (PBS) injection were used as negative controls (NC). The authors evaluated the regeneration of retinal ganglion cells (RGCs) and axons for 3, 7, 14, and 28 days after transplantation. Obtained retinas and optic nerves were analyzed histologically.

Results

Transplantations of OM significantly promoted the survival of retinal ganglion cells (RGCs) and axonal growth of RGCs compared with PBS alone. Moreover, OM group was associated with higher expression of GAP-43 in comparison with the PBS group. In addition to the potential effects on RGCs, transplantations of OM significantly decreased the expression of GFAP in the retinas, suggesting inhibiting astrocyte activation.

Conclusions

Transplantation of whole-layer OM in rats contributes to the neuronal survival and axon regeneration after ONI.

Co-Transplantation of Adipose Tissue-Derived Stromal Cells and Olfactory Ensheathing Cells for Spinal Cord Injury Repair

Patients suffering from spinal cord injury (SCI) still have a dismal prognosis. Despite all the efforts developed in this area, currently there are no effective treatments. Therefore, cell therapies have been proposed as a viable alternative to the current treatments used. Adipose tissue-derived stromal cells (ASCs) and olfactory ensheathing cells (OECs) have been used with promising results in different models of SCI, namely due to the regenerative properties of the secretome of the first, and the guidance capability of the second. Using an in vitro model of axonal growth, the dorsal root ganglia explants, we demonstrated that OECs induce neurite outgrowth mainly through cell-cell interactions, while ASCs' effects are strongly mediated by the release of paracrine factors. A proteomic analysis of ASCs' secretome revealed the presence of proteins involved in VEGF, PI3K, and Cadherin signaling pathways, which may be responsible for the effects observed. Then, the cotransplantation of ASCs and OECs showed to improve motor deficits of SCI-rats. Particular parameters of movement such as stepping, coordination, and toe clearance were improved in rats that received the transplant of cells, in comparison to nontreated rats. A histological analysis of the spinal cord tissues revealed that transplantation of ASCs and OECs had a major effect on the reduction of inflammatory cells close the lesion site. A slight reduction of astrogliosis was also evident. Overall, the results obtained with the present work indicate that the cotransplantation of ASCs and OECs brings important functional benefits to the injured spinal cord. Stem Cells 2018;36:696-708.

Axonal regeneration of different tracts following transplants of human glial restricted progenitors into the injured spinal cord in rats

The goal of this study was to compare the efficacy of human glial restricted progenitors (hGRPs) in promoting axonal growth of different tracts. We examined the potential of hGRPs grafted into a cervical (C4) dorsal column lesion to test sensory axons, and into a C4 hemisection to test motor tracts. The hGRPs, thawed from frozen stocks, were suspended in a PureCol matrix and grafted acutely into a C4 dorsal column or hemisection lesion. Control rats received PureCol only. Five weeks after transplantation, all transplanted cells survived in rats with the dorsal column lesion but only about half of the grafts in the hemisection. In the dorsal column lesion group, few sensory axons grew short distances into the lesion site of control animals. The presence of hGRPs transplants enhanced axonal growth significantly farther into the transplants. In the hemisection group, coerulospinal axons extended similarly into both control and transplant groups with no enhancement by the presence of hGRPs. Rubrospinal axons did not grow into the lesion even in the presence of hGRPs. However, reticulospinal and raphespinal axons grew for a significantly longer distance into the transplants. These results demonstrate the differential capacity of axonal growth/regeneration of the motor and sensory tracts based on their intrinsic abilities as well as their response to the modified environment induced by the hGRPs transplants. We conclude that hGRP transplants can modify the injury site for axon growth of sensory and some motor tracts, and suggest they could be combined with other interventions to restore connectivity.

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.

Stem cells for spinal cord injuries bearing translational potential

Spinal cord injury (SCI) is a highly debilitating neurological disease, which still lacks effective treatment strategies, causing significant financial burden and distress to the affected families. Nevertheless, nanotechnology and regenerative medicine strategies holding promise for the development of novel therapies that would reach from bench to bedside to serve the SCI patients. There has already been significant progress in the field of cell-based therapies, with the clinical application for SCI, currently in phase II of the clinical trial. Stem cells (e.g., induced pluripotent stem cells, fetal stem cells, human embryonic stem cells, and olfactory ensheathing cells) are certainly not to be considered the panacea for neural repair but, especially when combined with rehabilitation or other combinatorial approaches using the help of nanotechnology, they seem to be the source of some of the most promising and clinical translatable cell-based therapies that could help solving impactful problems on neural repair.

Serum-Free Medium Provides a Clinically Relevant Method to Increase Olfactory Ensheathing Cell Numbers in Olfactory Mucosa Cell Culture

There is much evidence to suggest that transplanted olfactory ensheathing cells may ameliorate the functional deficits associated with injuries to the nervous system, especially the spinal cord. For clinical implementation of this strategy it will be necessary to derive large numbers of these cells from an accessible and, preferably, autologous source, implying that olfactory mucosa would be ideal. Although olfactory ensheathing cells can be derived from olfactory mucosa, in routine culture conditions the proportion of these cells is unacceptably low for clinical purposes. This study compared the effect of culturing dissociated olfactory bulb and olfactory mucosa in two different media: one containing serum and one serum free. The results indicate that olfactory ensheathing cell proportion, and absolute cell numbers, is greatly increased in serum-free conditions. Further analysis suggests that serum-free medium has a differential effect on contaminating fibronectin-positive and p75-positive cells from olfactory bulb and olfactory mucosa. This study demonstrates that serum-free culture conditions provide a simple and useful means of deriving a sufficient number of olfactory ensheathing cells for transplantation and reveals a difference in biological behavior of the cells contained within olfactory bulb and olfactory mucosa.

Feasibility of Diffusion Tensor Imaging for Assessing Functional Recovery in Rats with Olfactory Ensheathing Cell Transplantation After Contusive Spinal Cord Injury (SCI)

Background

Olfactory ensheathing cell transplantation is a promising treatment for spinal cord injury. Diffusion tensor imaging has been applied to assess various kinds of spinal cord injury. However, it has rarely been used to evaluate the beneficial effects of olfactory ensheathing cell transplantation. This study aimed to explore the feasibility of diffusion tensor imaging in the evaluation of functional recovery in rats with olfactory ensheathing cell transplantation after contusive spinal cord injury.

Material/Methods

Immunofluorescence staining was performed to determine the purity of olfactory ensheathing cells. Rats received cell transplantation at week 1 after injury. Basso, Beattie, and Bresnahan score was used to assess the functional recovery. Magnetic resonance imaging was applied weekly, including diffusion tensor imaging. Diffusion tensor tractography was reconstructed to visualize the repair process.

Results

The results showed that olfactory ensheathing cell transplantation increased the functional and histological recovery and restrained the secondary injury process after the initial spinal cord injury. The fractional anisotropy values in rats with cell transplantation were significantly higher than those in the control group, while the apparent diffusion coefficient values were significantly lower. Basso, Beattie, and Bresnahan score was positively and linearly correlated with fractional anisotropy value, and it was negatively and linearly correlated with apparent diffusion coefficient value.

Conclusions

These findings suggest that diffusion tensor imaging parameters are sensitive biomarker indices for olfactory ensheathing cell transplantation interventions, and diffusion tensor imaging scan can reflect the functional recovery promoted by the olfactory ensheathing cell transplantation after contusive spinal cord injury.

Glial restricted precursors maintain their permissive properties after long-term expansion but not following exposure to pro-inflammatory factors

Glial restricted precursors (GRP) are a promising cellular source for transplantation therapy of spinal cord injury (SCI), capable of creating a permissive environment for axonal growth and regeneration. However, there are several issues regarding the nature of their permissive properties that remain unexplored. For example, cellular transplantation strategies for spinal cord repair require the preparation of a large number of cells, but it is unknown whether the permissive properties of GRP are maintained following the process of in vitro expansion. We used rat GRP isolated from the embryonic day 13.5 spinal cord to compare the properties of early (10-20 days) and late (120-140 days) passage GRP. We found that late passage GRP showed comparable effects on neurite outgrowth of adult rat DRG to early passage GRP in both in vitro co-culture and conditioned medium experiments. In addition, to further examine the effects of the inflammatory cascade activated in the aftermath of SCI on the microenvironment, we studied the direct effects of strong inflammatory mediators, Lipopolysaccharide and interferon gamma (LPS and IFNɤ, respectively), on the properties of GRP. We showed that exposure to these pro-inflammatory mediators altered GRP phenotype and attenuated their growth-promoting effects on neurite outgrowth in a dose dependent manner. Taken together, our data suggest that GRP maintain their growth-promoting properties following extensive in vitro passaging and underscore the importance of modulating the inflammatory environment at the injured spinal cord.

The Cotransplantation of Olfactory Ensheathing Cells with Bone Marrow Mesenchymal Stem Cells Exerts Antiapoptotic Effects in Adult Rats after Spinal Cord Injury

The mechanisms behind the repairing effects of the cotransplantation of olfactory ensheathing cells (OECs) with bone marrow mesenchymal stromal cells (BMSCs) have not been fully understood. Therefore, we investigated the effects of the cotransplantation of OECs with BMSCs on antiapoptotic effects in adult rats for which the models of SCI are induced. We examined the changes in body weight, histopathological changes, apoptosis, and the expressions of apoptosis-related proteins after 14 days and 28 days after transplantation. We also assessed animal locomotion using BBB test. We found that treatment with OECs and BMSCs had a remissive effect on behavioral outcome and histopathological changes induced SCI. Furthermore, we observed the significant antiapoptotic effect on cotransplant treated group. In addition, cotransplantation of OECs with BMSCs was found to have more significant repairing effect than that of OECs or BMSCs alone. Furthermore, the recovery of hind limb could be related to antiapoptotic effect of OECs and BMSCs through downregulating the apoptotic pathways. Finally, our data suggested the cotransplantation of OECs with BMSCs holds promise for a potential cure after SCI through the ability to incorporate into the spinal cord.

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.

Hydrogels and Cell Based Therapies in Spinal Cord Injury Regeneration

Spinal cord injury (SCI) is a central nervous system- (CNS-) related disorder for which there is yet no successful treatment. Within the past several years, cell-based therapies have been explored for SCI repair, including the use of pluripotent human stem cells, and a number of adult-derived stem and mature cells such as mesenchymal stem cells, olfactory ensheathing cells, and Schwann cells. Although promising, cell transplantation is often overturned by the poor cell survival in the treatment of spinal cord injuries. Alternatively, the therapeutic role of different cells has been used in tissue engineering approaches by engrafting cells with biomaterials. The latter have the advantages of physically mimicking the CNS tissue, while promoting a more permissive environment for cell survival, growth, and differentiation. The roles of both cell- and biomaterial-based therapies as single therapeutic approaches for SCI repair will be discussed in this review. Moreover, as the multifactorial inhibitory environment of a SCI suggests that combinatorial approaches would be more effective, the importance of using biomaterials as cell carriers will be herein highlighted, as well as the recent advances and achievements of these promising tools for neural tissue regeneration.

Complete rat spinal cord transection as a faithful model of spinal cord injury for translational cell transplantation

Spinal cord injury (SCI) results in neural loss and consequently motor and sensory impairment below the injury. There are currently no effective therapies for the treatment of traumatic SCI in humans. Various animal models have been developed to mimic human SCI. Widely used animal models of SCI are complete or partial transection or experimental contusion and compression, with both bearing controversy as to which one more appropriately reproduces the human SCI functional consequences. Here we present in details the widely used procedure of complete spinal cord transection as a faithful animal model to investigate neural and functional repair of the damaged tissue by exogenous human transplanted cells. This injury model offers the advantage of complete damage to a spinal cord at a defined place and time, is relatively simple to standardize and is highly reproducible.

Sponge-mediated lentivirus delivery to acute and chronic spinal cord injuries

The environment within the spinal cord after injury, which changes in the progression from the acute to chronic stages, limits the extent of regeneration. The delivery of inductive factors to promote regeneration following spinal cord injury has been promising, yet, few strategies are versatile to allow delivery during acute or chronic injury that would facilitate screening of candidate therapies. This report investigates the intrathecal delivery of lentiviruses for long-term expression of regenerative factors. Lentivirus-filled sponges were inserted into the intrathecal space surrounding the spinal cord, with transgene expression observed within multiple cell types that persists for 12 weeks for both intact and injured spinal cord, without any apparent damage to the spinal cord tissue. Sponges loaded with lentivirus encoding for Sonic hedgehog (Shh) were investigated for acute (delivered at 0 weeks) and chronic (at 4 weeks) injuries, and for multiple locations relative to the injury. In an acute model, sponges placed directly above the injury increased oligodendrocyte and decreased astrocyte presence. Sponges placed caudal to the injury had reduced impact on oligodendrocytes and astrocytes in the injury. In a chronic model, sponges increased oligodendrocyte and decreased astrocyte presence. Furthermore, the effect of Shh was shown to be mediated in part by reduction of Bmp signaling, monitored with an Msx2-sensitive reporter vector. The implantation of lentivirus-loaded biomaterials intrathecally provides the opportunity to induce the expression of a factor at a specified time without entering the spinal cord, and has the potential to promote gene delivery within the spinal cord, which can influence the extent of regeneration.

Meta analysis of olfactory ensheathing cell transplantation promoting functional recovery of motor nerves in rats with complete spinal cord transection

OBJECTIVE:

To evaluate the effects of olfactory ensheathing cell transplantation on functional recovery of rats with complete spinal cord transection.

DATA SOURCES:

A computer-based online search of Medline (1989–2013), Embase (1989–2013), Cochrane library (1989–2013), Chinese Biomedical Literature Database (1989–2013), China National Knowledge Infrastructure (1989–2013), VIP (1989–2013), Wanfang databases (1989–2013) and Chinese Clinical Trial Register was conducted to collect randomized controlled trial data regarding olfactory ensheathing cell transplantation for the treatment of complete spinal cord transection in rats.

SELECTION CRITERIA:

Randomized controlled trials investigating olfactory ensheathing cell transplantation and other transplantation methods for promoting neurological functional recovery of rats with complete spinal cord transection were included in the analysis. Meta analysis was conducted using RevMan 4.2.2 software.

MAIN OUTCOME MEASURES:

Basso, Beattie and Bresnahan scores of rats with complete spinal cord transection were evaluated in this study.

RESULTS:

Six randomized controlled trials with high quality methodology were included. Meta analysis showed that Basso, Beattie and Bresnahan scores were significantly higher in the olfactory ensheathing cell transplantation group compared with the control group (WMD = 3.16, 95% CI (1.68, 4.65); P < 0.00001).

CONCLUSION:

Experimental studies have shown that olfactory ensheathing cell transplantation can promote the functional recovery of motor nerves in rats with complete spinal cord transection.

Transplantation of Neural Stem/Progenitor Cells at Different Locations in Mice with Spinal Cord Injury

Transplantation of neural stem/progenitor cells (NS/PCs) promotes functional recovery after spinal cord injury (SCI); however, few studies have examined the optimal site of NS/PC transplantation in the spinal cord. The purpose of this study was to determine the optimal transplantation site of NS/PCs for the treatment of SCI. Wild-type mice were generated with contusive SCI at the T10 level, and NS/PCs were derived from fetal transgenic mice. These NS/PCs ubiquitously expressed ffLuc-cp156 protein (Venus and luciferase fusion protein) and so could be detected by in vivo bioluminescence imaging 9 days postinjury. NS/PCs (low: 250,000 cells per mouse; high: 1 million cells per mouse) were grafted into the spinal cord at the lesion epicenter (E) or at rostral and caudal (RC) sites. Phosphate-buffered saline was injected into E as a control. Motor functional recovery was better in each of the transplantation groups (E-Low, E-High, RC-Low, and RC-High) than in the control group. The photon counts of the grafted NS/PCs were similar in each of the four transplantation groups, suggesting that the survival of NS/PCs was fairly uniform when more than a certain threshold number of cells were transplanted. Quantitative RT-PCR analyses demonstrated that brain-derived neurotropic factor expression was higher in the RC segment than in the E segment, and this may underlie why NS/PCs more readily differentiated into neurons than into astrocytes in the RC group. The location of the transplantation site did not affect the area of spared fibers, angiogenesis, or the expression of any other mediators. These findings indicated that the microenvironments of the E and RC sites are able to support NS/PCs transplanted during the subacute phase of SCI similarly. Optimally, a certain threshold number of NS/PCs should be grafted into the E segment to avoid damaging sites adjacent to the lesion during the injection procedure.

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

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

Bone marrow mesenchymal stromal cells and olfactory ensheathing cells transplantation after spinal cord injury--a morphological and functional comparison in rats

Cell therapy for spinal cord injury (SCI) is a promising strategy for clinical application. Both bone marrow mesenchymal stromal cells (MSCs; also known as bone marrow-derived 'mesenchymal stem cells') and olfactory ensheathing cells (OECs) have demonstrated beneficial effects following transplantation in animal models of SCI. However, due to the large number of affecting parameters that determine the therapy success and the lack of methodological consensus, the comparison of different works is difficult. Therefore, we compared the effects of MSC and OEC transplants at early or delayed time after a spinal cord contusion injury in the rat. Functional outcomes for locomotion, sensory perception and electrophysiological responses were assessed. Moreover, the grafted cells survival and the amount of cavity and spared tissue were studied. The findings indicate that grafted cells survived until 7 days post-injection, but markedly disappeared in the following 2 weeks. Despite the low survival of the cells, MSC and OEC grafts provided tissue protection after early and delayed transplantation. Nevertheless, only acute MSC grafts improved locomotion recovery in treadmill condition and electrophysiological outcomes with respect to the other injured groups. These results, together with previous works, indicate that the MSC seem a better option than OEC for treatment of contusion injuries.

Human umbilical cord blood-derived mesenchymal stem cell transplantation for the treatment of spinal cord injury

The aim of the present study was to investigate the effects of human umbilical cord blood-derived mesenchymal stem cell (HUCB-MSC) transplantation on the functional restoration of spinal cord injury (SCI). A total of 46 adult Wistar rats were randomly divided into three groups: Injury (n=15), control (n=15) and transplantation (n=16). A SCI model was established using the modified Allen’s method (vulnerating energy, 25 g/cm). The rats in the control and transplantation groups were injected at the site of the injury with physiological saline and HUCB-MSC suspension, respectively. At week one, two and four following treatment, the behavior of the rats was evaluated using the Basso, Beattie, Bresnahan locomotor rating scale. In addition, immunohistochemistry (IHC) was performed on samples from the rats that had been sacrificed four weeks subsequent to the treatment. Recovery of the spinal cord nerve function was identified to be significantly different at week two and four following treatment (P<0.05), and IHC identified that at week four following treatment novel nerve cells were being produced. Thus, transplantation of HUCB-MSCs promoted the recovery of the damaged function of spinal cord nerves in rats with SCI.

Brief Report: Astrogliosis Promotes Functional Recovery of Completely Transected Spinal Cord Following Transplantation of hESC-Derived Oligodendrocyte and Motoneuron Progenitors

Spinal cord injury results in neural loss and consequently motor and sensory impairment below the injury. Reactive astrocytes contribute to formation of glial scar, thus impeding axonal regeneration, through secretion of extracellular matrix molecules, chondroitin sulfate proteoglycans (CSPGs). In this study, we analyze lesion site tissue to reveal the possible mechanism underlying the functional recovery after cell transplantation of human embryonic stem cell (hESC)-derived oligodendrocyte progenitor cell (OPC) and motoneuron progenitors (MP) and propose that transplanted cells increase astrogliosis through the regenerative signaling pathways activated in the host tissue that may crucial for restoring locomotor ability. We show that the transplantation of hESC-derived OPC and MP promotes astrogliosis, through activation of Jagged1-dependent Notch and Jak/STAT signaling that support axonal survival. The transplanted cells in synergism with reactive astrocytes create permissive environment in which the expression of detrimental genes (Cspg, Tenascins, and genes involved in SLIT/ROBO signaling) was significantly decreased while expression of beneficial ones (Laminins and Fibronectin) was increased. According to our data, this mechanism is activated in all transplantation groups independently of the level of locomotor recovery. These results indicate that modifying the beneficial function of reactive astrocytes could be a feasible therapeutic strategy for spinal cord injury in future. Stem Cells  2014;32:594–599

Cell therapy for spinal cord injuries: what is really going on?

During the last two decades, many experiments have examined the ability of cell transplants to ameliorate the loss of function after spinal cord injuries, with the hope of developing interventions to benefit patients. Although many reports suggest positive effects, there is growing concern over the quality of the available preclinical data. It is therefore important to ask whether this worldwide investigative process is close to defining a cell transplant protocol that could be translated into human patients with a realistic chance of success. This review systematically examines the strength of the preclinical evidence and outlines mechanisms by which transplanted cells may mediate their effects in spinal cord injuries. First, we examined changes in voluntary movements in the forelimb associated with cell transplants after partial cervical lesions. Second, we examined the efficacy of transplanted cells to restore electrophysiological conduction across a complete thoracic lesion. We postulated that cell therapies found to be successful in both models could reasonably have potential to treat human patients. We conclude that although there are data to support a beneficial effect of cell transplantation, most reports provide only weak evidence because of deficits in experimental design. The mechanisms by which transplanted cells mediate their functional effects remain unclear.

Crucial roles for olfactory ensheathing cells and olfactory mucosal cells in the repair of damaged neural tracts

Olfactory ensheathing cells, the glial cells of the olfactory nervous system, exhibit unique growth-promoting and migratory properties that make them interesting candidates for cell therapies targeting neuronal injuries such as spinal cord injury. Transplantation of olfactory cells is feasible and safe in humans; however, functional outcomes are highly variable with some studies showing dramatic improvements and some no improvements at all. We propose that the reason for this is that the identity and purity of the cells is different in each individual study. We have shown that olfactory ensheathing cells are not a uniform cell population and that individual subpopulations of OECs are present in different regions of the olfactory nervous system, with strikingly different behaviors. Furthermore, the presence of fibroblasts and other cell types in the transplant can dramatically alter the behavior of the transplanted glial cells. Thus, a thorough characterization of the differences between olfactory ensheathing cell subpopulations and how the behavior of these cells is affected by the presence of other cell types is highly warranted.

Gene expression changes in the injured spinal cord following transplantation of mesenchymal stem cells or olfactory ensheathing cells

Transplantation of bone marrow derived mesenchymal stromal cells (MSC) or olfactory ensheathing cells (OEC) have demonstrated beneficial effects after spinal cord injury (SCI), providing tissue protection and improving the functional recovery. However, the changes induced by these cells after their transplantation into the injured spinal cord remain largely unknown. We analyzed the changes in the spinal cord transcriptome after a contusion injury and MSC or OEC transplantation. The cells were injected immediately or 7 days after the injury. The mRNA of the spinal cord injured segment was extracted and analyzed by microarray at 2 and 7 days after cell grafting. The gene profiles were analyzed by clustering and functional enrichment analysis based on the Gene Ontology database. We found that both MSC and OEC transplanted acutely after injury induce an early up-regulation of genes related to tissue protection and regeneration. In contrast, cells transplanted at 7 days after injury down-regulate genes related to tissue regeneration. The most important change after MSC or OEC transplant was a marked increase in expression of genes associated with foreign body response and adaptive immune response. These data suggest a regulatory effect of MSC and OEC transplantation after SCI regarding tissue repair processes, but a fast rejection response to the grafted cells. Our results provide an initial step to determine the mechanisms of action and to optimize cell therapy for SCI.

Cotransplantation of Olfactory Ensheathing Cells and Schwann Cells Combined with Treadmill Training Promotes Functional Recovery in Rats with Contused Spinal Cords

The present study investigated the ability of cotransplantation of Schwann cells (SCs) and olfactory ensheathing cells (OECs) combined with treadmill training in facilitating neuronal plasticity and promoting hindlimb function recovery of subacute moderate thoracic (T10) spinal cord contusion in rats. Two weeks postinjury, SCs were injected directly into the lesion, while OECs were injected into the adjacent tissues. The treadmill training with the rats began postinjury on day 7, with each session lasting 20 ± 10 min per day, 5 days per week, for 10 weeks. At the 11th week postinjury, OECs were found migrating longitudinally and laterally from the injection site to the injury site through the gray and white matter, while some traveled along the central canal or pia. The SCs remained densely packed and concentrated at the transplant site. The transplanted SCs supported ingrowth of numerous, densely populated neurofilament-positive (NF+), MBP+ axons. The OECs promoted elongation of moderate NF+, GAP-43+ axons and a few MBP+ axons in parallel with OEC processes. The GFAP immunoreactivity in the spared tissue surrounding the graft of SCs and OECs at the lesion site was less intense than that in the DMEM group. Treadmill training had no effect on GFAP immunoreactivity. Treadmill training increased the number of TH-immunoreactive neurons in the gray matter of L2 spinal cord. Moreover, cotransplantation of OECs and SCs significantly increased the BBB score during 5–8 weeks postinjury alongside treadmill training between 5 and 11 weeks. Cotransplantation of OECs and SCs combined with treadmill training resulted in the highest BBB score at 4 and 11 weeks. The study details the differential mechanisms of neuronal plasticity: ( 1 ) axon growth and remyelination induced by cotransplantation of OECs and SCs and ( 2 ) neuron plasticity below the lesion enhanced by treadmill training. The synergistic effects of the combined strategy enhance functional recovery. This manuscript is published as part of the International Association of Neurorestoratology (IANR) supplement issue of Cell Transplantation.

Implications of olfactory lamina propria transplantation on hyperreflexia and myelinated fiber regeneration in rats with complete spinal cord transection

Transplantation with olfactory ensheathing cells (OECs) has been adopted after several models of spinal cord injury (SCI) with the purpose of creating a favorable environment for the re-growth of injured axons. However, a consensus on the efficacy of this cellular transplantation has yet to be reached. In order to explore alternative parameters that could demonstrate the possible restorative properties of such grafts, the present study investigated the effects of olfactory lamina propria (OLP) transplantation on hyperreflexia and myelinated fiber regeneration in adult rats with complete spinal cord transection. The efficacy of OLP (graft containing OECs) and respiratory lamina propria (RLP, graft without OECs) was tested at different post-injury times (acutely, 2- and 4-week delayed), to establish the optimum period for transplantation. In the therapeutic windows used, OLP and RLP grafts produced no considerable improvements in withdrawal reflex responses or on the low-frequency dependent depression of H-reflex. Both lamina propria grafts produced comparable results for the myelinated fiber density and for the estimated total number of myelinated fibers at the lesion site, indicating that the delayed transplantation approach does not seem to limit the regenerative effects. However, animals transplanted with OLP 2 or 4 weeks after injury exhibit smaller myelin sheath thickness and myelinated fiber area and diameter at the lesion site compared to their respective RLP groups. Despite the ongoing clinical use of OECs, it is important to emphasize the need for more experimental studies to clarify the exact nature of the repair capacity of these grafts in the treatment of SCI.

The migration of olfactory ensheathing cells during development and regeneration

The primary olfactory nervous system is unique in that it continuously renews itself and regenerates after injury. These properties are attributed to the presence of olfactory glia, termed olfactory ensheathing cells (OECs). Evidence is now emerging that individual OEC populations exist with distinct anatomical localisations and physiological properties, but their differential roles have not been determined. Unlike other glia, OECs can migrate from the periphery into the central nervous system, and organised OEC migration can enhance axonal extension after injury. Despite this, the mechanisms regulating OEC migration are largely unknown. Here, we provide an overview of the roles of OECs in development and adulthood. We review the latest research describing the differences between individual OEC subpopulations and discuss potential regulatory mechanisms for OEC guidance and migration. Using advanced time lapse techniques, we have obtained novel insights into how OECs behave in a complex multicellular environment which we discuss here with particular focus on cell-cell interactions. Significantly, transplantation of OECs constitutes a promising novel therapy for nerve injuries, but results are highly variable and the method needs improvement. We here review the roles of transplanted OECs in neural repair of damaged neuronal tracts distinct from the primary olfactory nervous system.

Repair of central nervous system lesions by transplantation of olfactory ensheathing cells

Clinical conditions affecting the central nervous system (CNS) fall into two main categories - degenerative conditions in which nerve cells are lost (Alzheimer's, Parkinson's, Huntington's disease, etc.), and traumatic insults which sever nerve fibers but leave their cell bodies and initial parts of the severed axons intact (spinal cord injury, cerebrovascular accidents, or tumors affecting fiber tracts). After injuries of this second type, the survival of the nerve cell bodies and the local sprouting at the severed ends of the proximal stumps of the axons raise the tantalizing possibility of one day learning how to induce these severed fibers to regenerate to their original targets and restore lost functions. This chapter gives an overview of current research into the strategy of transplantation of olfactory ensheathing cells into axotomizing injuries.