Clinical observation of fetal olfactory ensheathing glia transplantation (OEGT) in patients with complete chronic spinal cord injury

The anti-inflammatory and immunomodulatory effects of olfactory ensheathing cells transplantation in spinal cord injury and concomitant pathological pain

Spinal cord injury (SCI) is a serious and disabling injury that is often accompanied by neuropathic pain (NeP), which severely affects patients' motor and sensory functions and reduces their quality of life. Currently, there is no specific treatment for treating SCI and relieving the accompanying pain, and we can only rely on medication and physical rehabilitation, both of which are ineffective. Researchers have recently identified a novel class of glial cells, olfactory ensheathing cells (OECs), which originate from the olfactory system. Transplantation of OECs into damaged spinal cords has demonstrated their capacity to repair damaged nerves, improve the microenvironment at the point of injury, and They can also restore neural connectivity and alleviate the patient's NeP to a certain extent. Although the effectiveness of OECs transplantation has been confirmed in experiments, the specific mechanisms by which it repairs the spinal cord and relieves pain have not been articulated. Through a review of the literature, it has been established that the ability of OECs to repair and relieve pain is inextricably linked to its anti-inflammatory and immunomodulatory effects. In this regard, it is imperative to gain a deeper understanding of how OECs exert their anti-inflammatory and immunomodulatory effects. The objective of this paper is to provide a comprehensive overview of the mechanisms by which OECs exert anti-inflammatory and immunomodulatory effects. We aim to manipulate the immune microenvironment at the transplantation site through the intervention of cytokines and immune cells, with the goal of enhancing OECs' function or creating a conducive microenvironment for OECs' survival. This approach is expected to improve the therapeutic efficacy of OECs in clinical settings. However, numerous fundamental and clinical challenges remain to be addressed if OEC transplantation therapy is to become a standardized treatment in clinical practice.

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.

Application and challenges of olfactory ensheathing cells in clinical trials of spinal cord injury

Spinal cord injury (SCI) can lead to severe motor, sensory and autonomic nervous dysfunction, cause serious psychosomatic injury to patients. There is no effective treatment for SCI at present. In recent years, exciting evidence has been obtained in the application of cell-based therapy in basic research. These studies have revealed the fact that cells transplanted into the host can exert the pharmacological properties of treating and repairing SCI. Olfactory ensheathing cells (OECs) are a kind of special glial cells. The application value of OECs in the study of SCI lies in their unique biological characteristics, that is, they can survive and renew for life, give full play to neuroprotection, immune regulation, promoting axonal regeneration and myelination formation. The function of producing secretory group and improving microenvironment. This provides an irreplaceable treatment strategy for the repair of SCI. At present, some researchers have explored the possibility of treatment of OECs in clinical trials of SCI. Although OECs transplantation shows excellent safety and effectiveness in animal models, there is still lack of sufficient evidence to prove the effectiveness of their clinical application in clinical trials. There has been an obvious stagnation in the transformation of OECs transplantation into routine clinical practice, and clinical trials of cell therapy in this field are still facing major challenges and many problems that need to be solved. Therefore, this paper summarized and analyzed the clinical trials of OECs transplantation in the treatment of SCI, and discussed the problems and challenges of OECs transplantation in clinical trials.

Spinal cord injury: Olfactory ensheathing cell-based therapeutic strategies

Spinal cord injury (SCI) is a highly disabling neurological disorder that is difficult to treat due to its complex pathophysiology and nerve regeneration difficulties. Hence, effective SCI treatments are necessary. Olfactory ensheathing cells (OECs), glial cells derived from the olfactory bulb or mucosa, are ideal candidates for SCI treatment because of their neuroprotective and regenerative properties, ample supply, and convenience. In vitro, animal model, and human trial studies have reported discoveries on OEC transplantation; however, shortcomings have also been demonstrated. Recent studies have optimized various OEC transplantation strategies, including drug integration, biomaterials, and gene editing. This review aims to introduce OECs mechanisms in repairing SCI, summarize the research progress of OEC transplantation-optimized strategies, and provide novel research ideas for SCI treatment.

Use of Cells, Supplements, and Peptides as Therapeutic Strategies for Modulating Inflammation after Spinal Cord Injury: An Update

Spinal cord injury is a traumatic lesion that causes a catastrophic condition in patients, resulting in neuronal deficit and loss of motor and sensory function. That loss is caused by secondary injury events following mechanical damage, which results in cell death. One of the most important events is inflammation, which activates molecules like proinflammatory cytokines (IL-1β, IFN-γ, and TNF-α) that provoke a toxic environment, inhibiting axonal growth and exacerbating CNS damage. As there is no effective treatment, one of the developed therapies is neuroprotection of the tissue to preserve healthy tissue. Among the strategies that have been developed are the use of cell therapy, the use of peptides, and molecules or supplements that have been shown to favor an anti-inflammatory environment that helps to preserve tissue and cells at the site of injury, thus favoring axonal growth and improved locomotor function. In this review, we will explain some of these strategies used in different animal models of spinal cord injury, their activity as modulators of the immune system, and the benefits they have shown.

Cell therapies for spinal cord injury: a review of the clinical trials and cell-type therapeutic potential

Spinal cord injury (SCI) is an as yet untreatable neuropathology that causes severe dysfunction and disability. Cell-based therapies hold neuroregenerative and neuroprotective potential, but, although being studied in SCI patients for more than two decades, long-term efficacy and safety remain unproven, and which cell types result in higher neurological and functional recovery remains under debate. In a comprehensive scoping review of 142 reports and registries of SCI cell-based clinical trials, we addressed the current therapeutical trends and critically analysed the strengths and limitations of the studies. Schwann cells, olfactory ensheathing cells (OECs), macrophages and various types of stem cells have been tested, as well as combinations of these and other cells. A comparative analysis between the reported outcomes of each cell type was performed, according to gold-standard efficacy outcome measures like the ASIA impairment scale, motor and sensory scores. Most of the trials were in the early phases of clinical development (phase I/II), involved patients with complete chronic injuries of traumatic aetiology and did not display a randomized comparative control arm. Bone marrow stem cells and OECs were the most commonly tested cells, while open surgery and injection were the main methods of delivering cells into the spinal cord or submeningeal spaces. Transplantation of support cells, such as OECs and Schwann cells, resulted in the highest ASIA Impairment Scale (AIS) grade conversion rates (improvements in ∼40% of transplanted patients), which surpassed the spontaneous improvement rate expected for complete chronic SCI patients within 1 year post-injury (5-20%). Some stem cells, such as peripheral blood-isolated and neural stem cells, offer potential for improving patient recovery. Complementary treatments, particularly post-transplantation rehabilitation regimes, may contribute highly to neurological and functional recovery. However, unbiased comparisons between the tested therapies are difficult to draw, given the great heterogeneity of the design and outcome measures used in the SCI cell-based clinical trials and how these are reported. It is therefore crucial to standardize these trials when aiming for higher value clinical evidence-based conclusions.

Clinical results of neurorestorative cell therapies and therapeutic indications according to cellular bio-proprieties

Cell therapies have been explored to treat patients with nervous diseases for over 20 years. Even though most kinds of cell therapies demonstrated neurorestorative effects in non-randomized clinical trials; the effects of the majority type cells could not be confirmed by randomized controlled trials. In this review, clinical therapeutic results of neurorestorative cell therapies according to cellular bio-proprieties or cellular functions were introduced. Currently it was demonstrated from analysis of this review that some indications of cell therapies were not appropriate, they might be reasons why their neurorestorative effects could not be proved by multicenter, randomized, double blind, placebo-controlled clinical trials. Theoretically if one kind of cell therapy has neurorestorative effects according to its cellular bio-proprieties, it should have appropriate indications. The cell therapies with special bio-properties is promising if the indication selections are appropriate, such as olfactory ensheathing cells for chronic ischemic stroke, and their neurorestorative effects can be confirmed by higher level clinical trials of evidence-based medicine.

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.

Efficacy of mesenchymal stromal cells intraspinal transplantation for patients with different degrees of spinal cord injury: A systematic review and meta-analysis

BACKGROUND AIMS

Several studies have reported that mesenchymal stromal cells (MSCs) may improve neurological functions in patients with spinal cord injury (SCI). In this study, we conducted a systematic review and meta-analysis to summarize the effects of MSC treatment on different degrees of severity of SCI.

METHODS

Systematic searching of studies reporting outcomes of MSCs on specific injury severities of patients with SCI was performed in The National Library of Medicine (MEDLINE), Embase and Cochrane for published articles up to the 6 July 2022. Two investigators independently reviewed the included studies and extracted the relevant data. The standardized mean differences of American Spinal Injury Association (ASIA) motor score, ASIA light touch scores, ASIA pinprick scores and the Barthel index between baseline and follow-ups were pooled.

RESULTS

A total of eight studies were included. A large majority focused on patients with ASIA grade A classification. The pooled mean differences of ASIA motor scores, ASIA light touch scores, ASIA pinprick scores and the Barthel index were -2.78 (95% confidence interval [CI] -5.12 to -0.43, P = 0.02), -18.26 (95% CI -26.09 to -10.43, P < 0.01), -17.08 (95% CI -24.10 to -10.07, P < 0.01) and -4.37 (95% CI -10.96 to 2.22, P = 0.19), respectively.

CONCLUSIONS

MSC transplantation was a significantly effective therapy for patients with SCI with ASIA grade A. In the future, further studies are warranted to confirm the potential beneficial effects of MSC therapy.

Clinical Trials Targeting Secondary Damage after Traumatic Spinal Cord Injury

Spinal cord injury (SCI) often causes loss of sensory and motor function resulting in a significant reduction in quality of life for patients. Currently, no therapies are available that can repair spinal cord tissue. After the primary SCI, an acute inflammatory response induces further tissue damage in a process known as secondary injury. Targeting secondary injury to prevent additional tissue damage during the acute and subacute phases of SCI represents a promising strategy to improve patient outcomes. Here, we review clinical trials of neuroprotective therapeutics expected to mitigate secondary injury, focusing primarily on those in the last decade. The strategies discussed are broadly categorized as acute-phase procedural/surgical interventions, systemically delivered pharmacological agents, and cell-based therapies. In addition, we summarize the potential for combinatorial therapies and considerations.

Transplantation of Cryopreserved Olfactory Ensheathing Cells Restores Loss of Functions in an Experimental Model

In the past decades, the properties of olfactory ensheathing cells (OECs) have been widely investigated. Studies have shown that transplantation of OECs cultured from the olfactory bulb mediates axonal regeneration, remyelination and restores lost functions in experimental central nervous system (CNS) injury models. Autologously sourcing the cells from the nasal mucosa or the olfactory bulb to treat patients with spinal cord injuries would be ideal, but the cell yield achieved may be inadequate to cover the surface area of the lesions typically encountered in human spinal cord contusion injuries. Therefore, banking allogenic cryopreserved olfactory bulb cells from donors or generating cell lines could provide a marked increase in cell stock available for transplantation. This study is undertaken in two control and two intervention groups. The control groups have lesions alone and lesions with collagen gel but without cells. The intervention groups have either transplantation of primary cultured olfactory bulb OECs (bOECs) encapsulated in collagen gel or cryopreserved bulb OECs (CbOECs) encapsulated in collagen gel. Here, we report that transplantation of cryopreserved rat bOECs encapsulated in collagen restored the loss of function in a vertical climbing test in a unilateral C6-T1 dorsal root injury model. The loss of function returns in 80% of rats with injuries in about 3 weeks comparable to that we observed after transplantation of primary cultured bOECs. The regeneration axons induced by the transplant are identified by neurofilament antibodies and ensheathed by OECs. Our results indicate that cryopreserved OECs retain their properties of inducing axon regeneration and restoring loss of function in the experimental model. This is a step forward to translate the research into future clinical applications.

Designing a Clinical Trial with Olfactory Ensheathing Cell Transplantation-Based Therapy for Spinal Cord Injury: A Position Paper

Spinal cord injury (SCI) represents an urgent unmet need for clinical reparative therapy due to its largely irreversible and devastating effects on patients, and the tremendous socioeconomic burden to the community. While different approaches are being explored, therapy to restore the lost function remains unavailable. Olfactory ensheathing cell (OEC) transplantation is a promising approach in terms of feasibility, safety, and limited efficacy; however, high variability in reported clinical outcomes prevent its translation despite several clinical trials. The aims of this position paper are to present an in-depth analysis of previous OEC transplantation-based clinical trials, identify existing challenges and gaps, and finally propose strategies to improve standardization of OEC therapies. We have reviewed the study design and protocols of clinical trials using OEC transplantation for SCI repair to investigate how and why the outcomes show variability. With this knowledge and our experience as a team of biologists and clinicians with active experience in the field of OEC research, we provide recommendations regarding cell source, cell purity and characterisation, transplantation dosage and format, and rehabilitation. Ultimately, this position paper is intended to serve as a roadmap to design an effective clinical trial with OEC transplantation-based therapy for SCI repair.

Recovering Voiding and Sex Function in a Patient with Chronic Complete Spinal Cord Injury by Olfactory Ensheathing Cell Transplantation

Spinal cord injury (SCI) is life-altering damage for patients, their family, and society. Transplantation of olfactory ensheathing cells has demonstrated neurorestoration effects for many neurological conditions, including SCI. But voiding and sex dysfunction in patients with chronic complete SCI is still a major issue even though neurorestorative therapies can restore their partial neurological functions. Here we report a case with traumatic complete SCI at the level of C6-C7 one year ago, who received OEC transplantation with intensive neurorehabilitation. The patient started to show clinical improvements within a few days after cell treatment. Six-year follow-up demonstrated his American Spinal Injury Association (ASIA)-Impairment Scale change from ASIA A to become ASIA C. The scores of International Association of Neurorestoratology Spinal Cord Injury Functional Rating Scale changed from 14 (prior to cell therapy) to 31 + 3 (six years after cell therapy). His main improvements in activity of daily life included eating, dressing and writing by himself, standing and walking, and urine control or voiding. His sex function recovered to be normal. He married and had a son through natural sex life. His improving functions and activities of daily life stayed stable in subsequent phone call follow-up. This was one individual case report. In the future, the deep mechanisms of why he got positive results, but other patients with similar condition did not get so much benefits from OEC transplantation should be explored.

Comparing the Efficacy and Safety of Cell Transplantation for Spinal Cord Injury: A Systematic Review and Bayesian Network Meta-Analysis

Objective

To compare the safety and effectiveness of transplanted cells from different sources for spinal cord injury (SCI).

Design

A systematic review and Bayesian network meta-analysis.

Data Sources

Medline, Embase, and the Cochrane Central Register of Controlled Trials.

Study Selection

We included randomized controlled trials, case–control studies, and case series related to cell transplantation for SCI patients, that included at least 1 of the following outcome measures: American Spinal Cord Injury Association (ASIA) Impairment Scale (AIS grade), ASIA motor score, ASIA sensory score, the Functional Independence Measure score (FIM), International Association of Neurorestoratology Spinal Cord Injury Functional Rating Scale (IANR-SCIFRS), or adverse events. Follow-up data were analyzed at 6 and 12 months.

Results

Forty-four eligible trials, involving 1,266 patients, investigated 6 treatments: olfactory ensheathing cells (OECs), neural stem cells/ neural progenitor cells (NSCs), mesenchymal stem cells (MSCs), Schwann cells, macrophages, and combinations of cells (MSCs plus Schwann cells). Macrophages improved the AIS grade at 12 months (mean 0.42, 95% credible interval: 0–0.91, low certainty) and FIM score at 12 months (42.83, 36.33–49.18, very low certainty). MSCs improved the AIS grade at 6 months (0.42, 0.15–0.73, moderate certainty), the motor score at 6 months (4.43, 0.91–7.78, moderate certainty), light touch at 6 (10.01, 5.81–13.88, moderate certainty) and 12 months (11.48, 6.31–16.64, moderate certainty), pinprick score at 6 (14.54, 9.76–19.46, moderate certainty) and 12 months (12.48, 7.09–18.12, moderate certainty), and the IANR-SCIFRS at 6 (3.96, 0.62–6.97, moderate certainty) and 12 months (5.54, 2.45–8.42, moderate certainty). OECs improved the FIM score at 6 months (9.35, 1.71–17.00, moderate certainty). No intervention improved the motor score significantly at 12 months. The certainty of other interventions was low or very low. Overall, the number of adverse events associated with transplanted cells was low.

Conclusions

Patients with SCI who receive transplantation of macrophages, MSCs, NSCs, or OECs may have improved disease prognosis. MSCs are the primary recommendations. Further exploration of the mechanism of cell transplantation in the treatment of SCI, transplantation time window, transplantation methods, and monitoring of the number of transplanted cells and cell survival is needed.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/#recordDetails, identifier: CRD 42021282043.

Are Cell-Based Therapies Safe and Effective in the Treatment of Neurodegenerative Diseases? A Systematic Review with Meta-Analysis

Over the past two decades, significant advances have been made in the field of regenerative medicine. However, despite being of the utmost clinical urgency, there remains a paucity of therapeutic strategies for conditions with substantial neurodegeneration such as (progressive) multiple sclerosis (MS), spinal cord injury (SCI), Parkinson's disease (PD) and Alzheimer's disease (AD). Different cell types, such as mesenchymal stromal cells (MSC), neuronal stem cells (NSC), olfactory ensheathing cells (OEC), neurons and a variety of others, already demonstrated safety and regenerative or neuroprotective properties in the central nervous system during the preclinical phase. As a result of these promising findings, in recent years, these necessary types of cell therapies have been intensively tested in clinical trials to establish whether these results could be confirmed in patients. However, extensive research is still needed regarding elucidating the exact mechanism of action, possible immune rejection, functionality and survival of the administered cells, dose, frequency and administration route. To summarize the current state of knowledge, we conducted a systematic review with meta-analysis. A total of 27,043 records were reviewed by two independent assessors and 71 records were included in the final quantitative analysis. These results show that the overall frequency of serious adverse events was low: 0.03 (95% CI: 0.01-0.08). In addition, several trials in MS and SCI reported efficacy data, demonstrating some promising results on clinical outcomes. All randomized controlled studies were at a low risk of bias due to appropriate blinding of the treatment, including assessors and patients. In conclusion, cell-based therapies in neurodegenerative disease are safe and feasible while showing promising clinical improvements. Nevertheless, given their high heterogeneity, the results require a cautious approach. We advocate for the harmonization of study protocols of trials investigating cell-based therapies in neurodegenerative diseases, adverse event reporting and investigation of clinical outcomes.

Olfactory Stem Cells for the Treatment of Spinal Cord Injury - a new pathway to the cure?

OBJECTIVE

Since full functional recovery after spinal cord injuries (SCI) remains a major challenge, stem cell therapies represent promising strategies to improve neurological functions after SCI. The olfactory mucosa (OM) displays an attractive source of multipotent cells for regenerative approaches and is easily accessible by biopsies due to its exposed location. The regenerative capacity of the resident olfactory stem cells (OSC) has been demonstrated in animal as well as clinical studies. This study aims to demonstrate the feasibility of isolation, purification and cultivation of OSC.

METHODS

OM specimens were taken dorso-posterior from nasal middle turbinate. OSC were isolated and purified using the neurosphere assay. Differentiation capacity of the OSC in neural lineage and their behavior in a plasma clot matrix were investigated.

RESULTS

Our study demonstrated that OSC differentiated into neural lineage and were positive for GFAP as well as β-III tubulin. Furthermore, OSC were viable and proliferated in a plasma clot matrix.

CONCLUSION

Since there are no standard methods for purification, characterization, and delivery of OSC to the injury site, which is a prerequisite for the clinical approval, this study focuses on the establishment of appropriate methods and underlies the high potential of the OM for autologous cell therapeutical approaches.

Human Olfactory Mesenchymal Stem Cells Are a Novel Candidate for Neurological Autoimmune Disease

Background: Human olfactory mesenchymal stem cells (OMSC) have become a novel therapeutic option for immune disorder or demyelinating disease due to their immunomodulatory and regenerative potentials. However, the immunomodulatory effects of OMSC still need to be elucidated, and comparisons of the effects of different MSCs are also required in order to select an optimal cell source for further applications. Results: In animal experiments, we found neural functional recovery and delayed EAE attack in the OMSC treatment group. Compared with umbilical cord-derived mesenchymal stem cells (UMSC) treatment group and the control group, the OMSC treatment group had a better neurological improvement, lower serum levels of IFN-γ, and a lower proportion of CD4+IFN-γ+ T splenic lymphocyte. We also observed OMSC effectively suppressed CD4+IFN-γ+ T cell proportion in vitro when co-cultured with human peripheral blood-derived lymphocytes. The OMSC-mediated immunosuppressive effect on human CD4+IFN-γ+ T cells was attenuated by blocking cyclooxygenase activity. Conclusion: Our results suggest that OMSC treatment delayed the onset and promoted the neural functional recovery in the EAE mouse model possibly by suppressing CD4+IFN-γ+ T cells. OMSC transplantation might become an alternative therapeutic option for neurological autoimmune disease.

Cell Therapy for Neurological Disorders: The Perspective of Promising Cells

Neurological disorders are big public health challenges that are afflicting hundreds of millions of people around the world. Although many conventional pharmacological therapies have been tested in patients, their therapeutic efficacies to alleviate their symptoms and slow down the course of the diseases are usually limited. Cell therapy has attracted the interest of many researchers in the last several decades and has brought new hope for treating neurological disorders. Moreover, numerous studies have shown promising results. However, none of the studies has led to a promising therapy for patients with neurological disorders, despite the ongoing and completed clinical trials. There are many factors that may affect the outcome of cell therapy for neurological disorders due to the complexity of the nervous system, especially cell types for transplantation and the specific disease for treatment. This paper provides a review of the various cell types from humans that may be clinically used for neurological disorders, based on their characteristics and current progress in related studies.

Current Concepts of Stem Cell Therapy for Chronic Spinal Cord Injury

Chronic spinal cord injury (SCI) is a catastrophic condition associated with significant neurological deficit and social and financial burdens. It is currently being managed symptomatically with no real therapeutic strategies available. In recent years, a number of innovative regenerative strategies have emerged and have been continuously investigated in clinical trials. In addition, several more are coming down the translational pipeline. Among ongoing and completed trials are those reporting the use of mesenchymal stem cells, neural stem/progenitor cells, induced pluripotent stem cells, olfactory ensheathing cells, and Schwann cells. The advancements in stem cell technology, combined with the powerful neuroimaging modalities, can now accelerate the pathway of promising novel therapeutic strategies from bench to bedside. Various combinations of different molecular therapies have been combined with supportive scaffolds to facilitate favorable cell–material interactions. In this review, we summarized some of the most recent insights into the preclinical and clinical studies using stem cells and other supportive drugs to unlock the microenvironment in chronic SCI to treat patients with this condition. Successful future therapies will require these stem cells and other synergistic approaches to address the persistent barriers to regeneration, including glial scarring, loss of structural framework, and immunorejection.

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.

Olfactory ensheathing cell transplantation for chronic spinal cord injury: A long-term follow-up study

Spinal cord injury is a serious disabling condition. Transplantation of olfactory ensheathing cells (OECs) is one of the most promising treatments for spinal cord injury (SCI). Thirty-nine patients with chronic SCI received OEC transplantation and completed long-term follow-up, with a minimum follow-up of 7 years. We assessed sensorimotor function with the American Spinal Injury Association (ASIA) Impairment Scale (AIS) and autonomic nervous function by the International Standards to document remaining Autonomic Function after Spinal Cord Injury (ISAFSCI), and sympathetic skin responses (SSR). The scores of each group were significantly higher after OECs transplantation than before treatment. SSR latencies were shorter and response amplitudes increased after treatment. Long-term follow-up showed further improvement only in motor function and autonomic function compared with 3 months postoperatively. No complications occurred in any patient during long-term follow-up. The results indicate that the transplantation of OECs in spinal cord restored function without serious side effects.

Progress in clinical trials of cell transplantation for the treatment of spinal cord injury: how many questions remain unanswered?

Spinal cord injury can lead to severe motor, sensory and autonomic nervous dysfunctions. However, there is currently no effective treatment for spinal cord injury. Neural stem cells and progenitor cells, bone marrow mesenchymal stem cells, olfactory ensheathing cells, umbilical cord blood stem cells, adipose stem cells, hematopoietic stem cells, oligodendrocyte precursor cells, macrophages and Schwann cells have been studied as potential treatments for spinal cord injury. These treatments were mainly performed in animals. However, subtle changes in sensory function, nerve root movement and pain cannot be fully investigated with animal studies. Although these cell types have shown excellent safety and effectiveness in various animal models, sufficient evidence of efficacy for clinical translation is still lacking. Cell transplantation should be combined with tissue engineering scaffolds, local drug delivery systems, postoperative adjuvant therapy and physical rehabilitation training as part of a comprehensive treatment plan to provide the possibility for patients with SCI to return to normal life. This review summarizes and analyzes the clinical trials of cell transplantation therapy in spinal cord injury, with the aim of providing a rational foundation for the development of clinical treatments for spinal cord injury.

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.

A scoping review of trials for cell-based therapies in human spinal cord injury

INTRODUCTION

Spinal cord injury (SCI) is associated with significant and life-long disability. Yet, despite decades of research, no regenerative treatment has reached clinical practice. Cell-based therapies are one possible regenerative strategy beginning to transfer to human trials from a more extensive pre-clinical basis.

METHODS

We therefore conducted a scoping review to synthesise all cell-based trials in SCI to consider the current state of the field and the cell transplant type or strategy with greatest promise. A search strategy of MEDLINE returned 1513 results. All clinical trials including adult human patients with acute or chronic, compete or incomplete SCI and a recorded ASIA score were sought. Exclusion criteria included non-traumatic SCI, paediatric patients and animal studies. A total of 43 studies, treating 1061 patients, were identified. Most trials evaluated cells from the bone marrow (22 papers, 660 patients) or the olfactory bulb (10 papers, 245 patients).

RESULTS

Cell transplantation does appear to be safe, with no serious adverse effects being reported in the short-term. 86% of trials described efficacy as a primary outcome. However, varying degrees of outcome reporting prevented meta-analysis. No emerging cell type or technique was identified. The majority of trials, 53%, took place in developing countries, which may suggest more stringent regulatory requirements within Western countries.

CONCLUSION

We believe cell-based transplantation translation remains in its infancy and that, although further robust clinical research is required, it is an important strategy to consider in the treatment of SCI.

Clinical neurorestorative cell therapies: Developmental process, current state and future prospective

Clinical cell therapies (CTs) for neurological diseases and cellular damage have been explored for more than 2 decades. According to the United States Food and Drug Administration, there are 2 types of cell categories for therapy, namely stem cell-derived CT products and mature/functionally differentiated cell-derived CT products. However, regardless of the type of CT used, the majority of reports of clinical CTs from either small sample sizes based on single-center phase 1 or 2 unblinded trials or retrospective clinical studies showed effects on neurological improvement and the ability to either partially or temporarily thwart the deteriorating cellular processes of the neurodegenerative diseases. There have been only a few prospective, multicenter, randomized, double- blind placebo-control clinical trials of CTs so far in this developing novel area that have shown negative results, and more clinical trials are needed. This will expand our knowledge in exploring the type of cells that yield promising results and restore damaged neurological structure and functions of the central nervous system based on higher level evidence-based medical data. In this review, we briefly introduce the developmental process, current state, and future prospective for clinical neurorestorative CT.

Survival and Integration of Transplanted Olfactory Ensheathing Cells are Crucial for Spinal Cord Injury Repair: Insights from the Last 10 Years of Animal Model Studies

Olfactory ensheathing cells (OECs), the glial cells of the primary olfactory nervous system, support the natural regeneration of the olfactory nerve that occurs throughout life. OECs thus exhibit unique properties supporting neuronal survival and growth. Transplantation of OECs is emerging as a promising treatment for spinal cord injury; however, outcomes in both animals and humans are variable and the method needs improvement and standardization. A major reason for the discrepancy in functional outcomes is the variability in survival and integration of the transplanted cells, key factors for successful spinal cord regeneration. Here, we review the outcomes of OEC transplantation in rodent models over the last 10 years, with a focus on survival and integration of the transplanted cells. We identify the key factors influencing OEC survival: injury type, source of transplanted cells, co-transplantation with other cell types, number and concentration of cells, method of delivery, and time of transplantation after the injury. We found that two key issues are hampering optimization and standardization of OEC transplantation: lack of (1) reliable methods for identifying transplanted cells, and (2) three-dimensional systems for OEC delivery. To develop OEC transplantation as a successful and standardized therapy for spinal cord injury, we must address these issues and increase our understanding of the complex parameters influencing OEC survival.

Application of olfactory ensheathing cells in clinical treatment of spinal cord injury: meta-analysis and prospect

Background:

A number of clinical trials of olfactory ensheathing cells (OECs) for the treatment of chronic spinal cord injury (SCI) have been carried out all over the world. However, their safety and efficacy have not been basically evaluated. Moreover, there are no uniform standards laid out for the use of optimal source, transplantation method and the dosage of OECs.

Objective:

This study evaluated the source, dose, and route of transplantation of OECs for the treatment of chronic SCI.

Methods:

PubMed, Cochrane Library, EMBASE, CNKI, and Wanfang Data were searched for the clinical studies of OECs in the treatment of chronic SCI on July 2018.

Results:

A total of 30 articles on OECs transplantation for chronic SCI were selected for comprehensive evaluation of OECs sources, doses, and transplantation methods. The efficacy of OECs in the treatment of chronic SCI was evaluated using Review Manager 5.3.

Conclusion:

Fetal OECs are the primary source of cells for the treatment of chronic SCI in OECs, with standardized cell-culture and quality-control processes. Fetal OECs can significantly improve the neurological function of patients with chronic SCI. It is an ideal cell therapy for neurorestoration. However to explore more precise and minimally invasive treatment options are required in the future.

Therapeutic abortion and ectopic pregnancy: alternative sources for fetal stem cell research and therapy in Iran as an Islamic country

Regenerative medicine as a background of stem cell research and therapy has a long history. A wide variety of diseases including Parkinson's disease, heart diseases, multiple sclerosis, spinal cord injury, diabetes mellitus and etc. are candidate to be treated using different types of stem cells. There are several sources of stem cells such as bone marrow, umbilical cord, peripheral blood, germ cells and the embryo/fetus tissues. Fetal stem cells (FSCs) and embryonic stem cells (ESCs) have been described as the most potent stem cell source. Although their pluri- or multipotent properties leads to promising reports for their clinical applications, owning to some ethical and legal obstacles in different communities such as Muslim countries, care should be taken for therapeutic applications of FSCs and ESCs. Derivation of these cell types needs termination of pregnancy and embryo or fetus life that is prohibited according to almost all rules and teaches in Muslim communities. Abortion and termination of pregnancy under a normal condition for the procurement of stem cell materials is forbidden by nearly all the major world religions such as Islam. Legislated laws in the most of Muslim countries permit termination of pregnancy and abortion only when the life of the mother is severely threatened or when continuing pregnancy may lead to the birth of a mentally retarded, genetically or anatomically malformed child. Based on the rules and conditions in Islamic countries, finding an alternative and biologically normal source for embryonic or fetal stem cell isolation will be too difficult. On the one hand, Muslim scientists have the feasibility for finding of genetically and anatomically normal embryonic or fetal stem cell sources for research or therapy, but on the other hand they should adhere to the law and related regional and local rules in all parts of their investigation. The authors suggest that the utilization of ectopic pregnancy (EP) conceptus, extra-embryonic tissues, and therapeutic abortion materials as a valuable source of stem cells for research and medical purposes can overcome limitations associated with finding the appropriate stem cell source. Pregnancy termination because of the mentioned subjects is accepted by almost all Islamic laws because of maternal lifesaving. Also, there are no ethical or legal obstacles in the use of extra-embryonic or EP derived tissues which lead to candidate FSCs as a valuable source for stem cell researches and therapeutic applications.

Phenotypic Modulation and Neuroprotective Effects of Olfactory Ensheathing Cells: a Promising Tool for Cell Therapy

Olfactory Ensheathing Cells (OECs), exhibiting phenotypic characteristics of both astrocytes and Schwann Cells, show peculiar plasticity. In vitro, OECs promote axonal growth, while in vivo they promote remyelination of damaged axons. We decided to further investigate OEC potential for regeneration and functional recovery of the damaged Central Nervous System (CNS). To study OEC antigen modulation, OECs prepared from postnatal mouse olfactory bulbs were grown in different culture conditions: standard or serum-free media with/without Growth Factors (GFs) and analyzed for different neural specific markers. OEC functional characterizations were also achieved. Resistance of OECs to the neurotoxin 6-hydroxydopamine (6-OHDA) was analyzed by evaluating apoptosis and death. OEC neuroprotective properties were investigated by in vitro co-cultures or by addition of OEC conditioned medium to the neuroblastoma SH-SY5Y cells exposed to 6-OHDA. We observed: 1) modification of OEC morphology, reduced cell survival and marker expression in serum-free medium; 2) GF addition to serum-free medium condition influenced positively survival and restored basal marker expression; 3) no OEC apoptosis after a prolonged exposition to 6-OHDA; 4) a clear OEC neuroprotective tendency, albeit non statistically significant, on 6-OHDA treated SH-SY5Y cells. These peculiar properties of OECs might render them potential clinical agents able to support injured CNS.

Therapeutic Potential of Olfactory Ensheathing Cells and Mesenchymal Stem Cells in Spinal Cord Injuries

Spinal cord injury (SCI) is a devastating neurological condition that affects individuals worldwide, significantly reducing quality of life, for both patients and their families. In recent years there has been a growing interest in cell therapy potential in the context of spinal cord injuries. The present review aims to discuss and compare the restorative approaches based on the current knowledge, available spinal cord restorative cell therapies, and use of selected cell types. However, treatment options for spinal cord injury are limited, but rehabilitation and experimental technologies have been found to help maintain or improve remaining nerve function in some cases. Mesenchymal stem cells as well as olfactory ensheathing cells seem to show therapeutic impact on damaged spinal cord and might be useful in neuroregeneration. Recent research in animal models and first human trials give patients with spinal cord injuries hope for recovery.

The Use of Cell Transplantation in Spinal Cord Injuries

Acute spinal cord injuries are life-changing events that lead to substantial morbidity and mortality, but the role of cell-based treatment for these injuries is unclear. Cell therapy is a rapidly evolving treatment methodology, with basic science and early phase I/II human trials showing promise. Multiple cell lines can be used in cell therapy, including adult or embryonic stem cells, Schwann cells, olfactory ensheathing cells, and induced pluripotent stem cells. Adult stem cells, Schwann cells, and olfactory ensheathing cells are readily available but lack the ability to differentiate into cells of the central nervous system. Mesenchymal stem cells can decrease cell death by modifying the local environment into which they are introduced. Peripheral nerve cells, such as Schwann cells and olfactory ensheathing cells, can myelinate existing axons and foster axonal growth in the central nervous system, and embryonic stem cells can differentiate into neural progenitor stem cells of the central nervous system. Induced pluripotent stem cells are the basis of an emerging technology that has yet to be implemented in human trials but may offer a means of cell therapy without the ethical dilemmas associated with embryonic cells.

Olfactory bulb transplantation in complete spinal cord injury: axonal regeneration and locomotor recovery

OBJECTIVES: To determine whether the intervention in rats is effective in terms of spinal cord regeneration and locomotor recovery, in order to obtain sufficient evidence to apply the therapy in humans. METHODS: a randomized, controlled, experimental, prospective, randomized trial was conducted, with a sample of 15 adult female Sprague-Dawley rats weighing 250 gr. They were divided into three equal groups, and trained for 2 weeks based on Pavlov's classical conditioning method, to strengthen the muscles of the 4 legs, stimulate the rats mentally, and keep them healthy for the surgery. RESULTS: It was observed that implantation of these cells into the site of injury may be beneficial to the process of spinal cord regeneration after spinal trauma, to mediate secretion of neurotrophic and neuroprotective chemokines, and that the OECs have the ability to bridge the repair site and decrease the formation of gliosis, creating a favorable environment for axonal regeneration. CONCLUSION: It is emphasized that the olfactory ensheathing glial cells possess unique regenerative properties; however, it was not until recently that the activity of promoting central nervous system regeneration was recognized.

A prospective randomized double-blind clinical trial using a combination of olfactory ensheathing cells and Schwann cells for the treatment of chronic complete spinal cord injuries

The aim of this prospective randomized double-blind clinical study is to examine the benefits of using olfactory ensheathing cells (OECs) combined with or without Schwann cells (SCs) in treating chronic complete spinal cord injuries (SCIs). This would offer patients a better alternative for neurological functional recovery. According to the initial design, 28 eligible participants with cervical chronic complete SCI were recruited and randomly allocated into four groups of seven participants each. The neurological assessments were to be performed according to the American Spinal Injury Association (ASIA) and International Association of Neurorestoratology (IANR) Functional Rating Scales, in combination with electrophysiological tests, for example, electromyography (EMG) and paraspinal somatosensory evoked potentials (PSSEPs). Here we have summarized the data from seven patients; three patients received an OEC intraspinal transplantation, one underwent SC implantation, and one received a combination of OECs and SCs. The remaining two patients were used as controls. The scores were evaluated independently by at least two neurologists in a blinded fashion for comparing the neurological functional changes during pre- and post-cell transplantation (6-month follow-up). All patients who received OECs, SCs alone, and a combination of them showed functional improvement. Mild fever occurred in one of the patients with OEC transplant that subsided after symptomatic treatments. All treated patients except one showed improvement in the electrophysiological tests. The functional improvement rate comprises 5/5 (100%) in the treated group, but 0/2 (0%) in the control group (p = 0.008). These preliminary findings show that transplanting OECs, SCs, or a combination of them is well tolerated and that they have beneficial effects in patients. Thus, further studies in larger patient cohorts are warranted to assess the benefits and risks of these intervention strategies. This manuscript is published as part of the IANR special issue of Cell Transplantation.

Consensus of clinical neurorestorative progress in patients with complete chronic spinal cord injury

Currently, there is a lack of effective therapeutic methods to restore neurological function for chronic complete spinal cord injury (SCI) by conventional treatment. Neurorestorative strategies with positive preclinical results have been translated to the clinic, and some patients have gotten benefits and their quality of life has improved. These strategies include cell therapy, neurostimulation or neuromodulation, neuroprosthesis, neurotization or nerve bridging, and neurorehabilitation. The aim of this consensus by 31 experts from 20 countries is to show the objective evidence of clinical neurorestoration for chronic complete SCI by the mentioned neurorestorative strategies. Complete chronic SCI patients are no longer told, "nothing can be done." The clinical translation of more effective preclinical neurorestorative strategies should be encouraged as fast as possible in order to benefit patients with incurable CNS diseases. This manuscript is published as part of the International Association of Neurorestoratology (IANR) special issue of Cell Transplantation.

Fetal stem cell transplantation: Past, present, and future

Since 1928, human fetal tissues and stem cells have been used worldwide to treat various conditions. Although the transplantation of the fetal midbrain substantia nigra and dopaminergic neurons in patients suffering from Parkinson’s disease is particularly noteworthy, the history of other types of grafts, such as those of the fetal liver, thymus, and pancreas, should be addressed as there are many lessons to be learnt for future stem cell transplantation. This report describes previous practices and complications that led to current clinical trials of isolated fetal stem cells and embryonic stem (ES) cells. Moreover, strategies for transplantation are considered, with a particular focus on donor cells, cell processing, and the therapeutic cell niche, in addition to ethical issues associated with fetal origin. With the advent of autologous induced pluripotent stem cells and ES cells, clinical dependence on fetal transplantation is expected to gradually decline due to lasting ethical controversies, despite landmark achievements.

Standard recommendations for the application of Chinese clinical cell therapy for neurorestoration (2012)

Cell therapy has been shown to be a promising alternative therapy for neurorestoration, and more than 30 different types of cells have been shown to possess some capability to restore lost or damaged neurological functions. Chinese physicians have successfully applied cell therapy to many neurological diseases and damages in the clinic and contributed to establish a discipline of neurorestoratology. To standardize the clinical procedures of cell therapy as one of the strategies for treating neurological disorders, the Chinese Branch of the International Association of Neurorestoratology (IANR) and the Preparatory Committee of Chinese Association of Neurorestoratology recently completed the Standard Recommendations (2012) for the Application of Chinese Clinical Cell Therapy for Neurorestoration. We hope these recommendations will guide clinical practice in applying cell therapy for neurorestoration, which will therein offer a reference for both Chinese and other countries' governments to make relevant official regulations. This manuscript is published as part of the International Association of Neurorestoratology (IANR) supplement issue of Cell Transplantation.