Clinical Outcomes of Transplanted Modified Bone Marrow-Derived Mesenchymal Stem Cells in Stroke: A Phase 1/2a Study

Allogeneic mesenchymal stem cell sheet therapy: A new frontier in drug delivery systems

The evolution of drug discovery exploded in the early 20th century with the advent of critical scientific advancements in organic chemistry, chemical analysis, and purification. Early drug generations focused largely on symptom control and pain management, effective targets for small-molecule drugs. Recently, the attention in drug discovery has shifted to pursuit of radical cures. Cell therapy presents the ideal attributes of a promising new drug, targeting specific tissues based on chemotactic cues and modulating secretion of instructive regenerative molecules in response to dynamic signaling from disease environments. To actuate the therapeutic potential of cell therapy toward worldwide clinical use, cell delivery methods that can effectively localize and engraft mesenchymal stem cells (MSCs) with high disease-site fidelity and enable dynamic MSC bioactive function are paramount. In this review, we discuss the evolution of cell therapies with a focus on stem cell advantages, as well as the limitations to these therapies. This review aims to introduce cell sheet technology as a breakthrough cell therapy with demonstrated therapeutic success across indications for heart, liver, and kidney tissue regeneration. Opportunities and anticipated clinical impacts of cell sheet technology using MSCs are discussed.

Revisiting Stem Cell-Based Clinical Trials for Ischemic Stroke

Stroke is the leading cause of serious long-term disability, significantly reducing mobility in almost half of the affected patients aged 65 years and older. There are currently no proven neurorestorative treatments for chronic stroke. To address the complex problem of restoring function in ischemic brain tissue, stem cell transplantation-based therapies have emerged as potential restorative therapies. Aligning with the major cell types found within the ischemic brain, stem-cell-based clinical trials for ischemic stroke have fallen under three broad cell lineages: hematopoietic, mesenchymal, and neural. In this review article, we will discuss the scientific rationale for transplanting cells from each of these lineages and provide an overview of published and ongoing trials using this framework.

Enhancing Brain Plasticity to Promote Stroke Recovery

Stroke disturbs both the structural and functional integrity of the brain. The understanding of stroke pathophysiology has improved greatly in the past several decades. However, effective therapy is still limited, especially for patients who are in the subacute or chronic phase. Multiple novel therapies have been developed to improve clinical outcomes by improving brain plasticity. These approaches either focus on improving brain remodeling and restoration or on constructing a neural bypass to avoid brain injury. This review describes emerging therapies, including modern rehabilitation, brain stimulation, cell therapy, brain-computer interfaces, and peripheral nervous transfer, and highlights treatment-induced plasticity. Key evidence from basic studies on the underlying mechanisms is also briefly discussed. These insights should lead to a deeper understanding of the overall neural circuit changes, the clinical relevance of these changes in stroke, and stroke treatment progress, which will assist in the development of future approaches to enhance brain function after stroke.

Potential of Cell Surface Engineering with Biocompatible Polymers for Biomedical Applications

The regulation of the cellular surface with biomaterials can contribute to the progress of biomedical applications. In particular, the cell surface is exposed to immunological surveillance and reactions in transplantation therapy, and modulation of cell surface properties might improve transplantation outcomes. The transplantation of therapeutic cells, tissue, and organs is an effective and fundamental treatment and has contributed to saving lives and improving quality of life. Because of shortages, donor cells, tissues, and organs are carefully transplanted with the goal of retaining activity and viability. However, some issues remain to be resolved in terms of reducing side effects, improving graft survival, managing innate and adaptive immune responses, and improving transplant storage and procedures. Given that the transplantation process involves multiple steps and is technically complicated, an engineering approach together with medical approaches to resolving these issues could enhance success. In particular, cell surface engineering with biocompatible polymers looks promising for improving transplantation therapy and has potential for other biomedical applications. Here we review the significance of polymer-based surface modification of cells and organs for biomedical applications, focusing on the following three topics: Cell protection: cellular protection through local immune regulation using cell surface modification with biocompatible polymers. This protection could extend to preventing attack by the host immune system, freeing recipients from taking immunosuppressive drugs, and avoiding a second transplantation. Cell attachment: cell manipulation, which is an important technique for delivery of therapeutic cells and their alignment for recellularization of decellularized tissues and organs in regenerative therapy. Cell fusion: fusion of different cells, which can lead to the formation of new functional cells that could be useful for generating, e.g., immunologically competent or metabolically active cells.

Clinical Trials of Stem Cell Therapy for Cerebral Ischemic Stroke

Despite recent developments in innovative treatment strategies, stroke remains one of the leading causes of death and disability worldwide. Stem cell therapy is currently attracting much attention due to its potential for exerting significant therapeutic effects on stroke patients. Various types of cells, including bone marrow mononuclear cells, bone marrow/adipose-derived stem/stromal cells, umbilical cord blood cells, neural stem cells, and olfactory ensheathing cells have enhanced neurological outcomes in animal stroke models. These stem cells have also been tested via clinical trials involving stroke patients. In this article, the authors review potential molecular mechanisms underlying neural recovery associated with stem cell treatment, as well as recent advances in stem cell therapy, with particular reference to clinical trials and future prospects for such therapy in treating stroke.

The Future of Skull Base Surgery: A View Through Tinted Glasses

In the present report, we have broadly outlined the potential advances in the field of skull base surgery, which might occur within the next 20 years based on the many areas of current research in biology and technology. Many of these advances will also be broadly applicable to other areas of neurosurgery. We have grounded our predictions for future developments in an exploration of what patients and surgeons most desire as outcomes for care. We next examined the recent developments in the field and outlined several promising areas of future improvement in skull base surgery, per se, as well as identifying the new hospital support systems needed to accommodate these changes. These include, but are not limited to, advances in imaging, Raman spectroscopy and microscopy, 3-dimensional printing and rapid prototyping, master-slave and semiautonomous robots, artificial intelligence applications in all areas of medicine, telemedicine, and green technologies in hospitals. In addition, we have reviewed the therapeutic approaches using nanotechnology, genetic engineering, antitumor antibodies, and stem cell technologies to repair damage caused by traumatic injuries, tumors, and iatrogenic injuries to the brain and cranial nerves. Additionally, we have discussed the training requirements for future skull base surgeons and stressed the need for adaptability and change. However, the essential requirements for skull base surgeons will remain unchanged, including knowledge, attention to detail, technical skill, innovation, judgment, and compassion. We believe that active involvement in these rapidly evolving technologies will enable us to shape some of the future of our discipline to address the needs of both patients and our profession.

Mesenchymal stem cells as a multimodal treatment for nervous system diseases

Neurological disorders are a massive challenge for modern medicine. Apart from the fact that this group of diseases is the second leading cause of death worldwide, the majority of patients have no access to any possible effective and standardized treatment after being diagnosed, leaving them and their families helpless. This is the reason why such great emphasis is being placed on the development of new, more effective methods to treat neurological patients. Regenerative medicine opens new therapeutic approaches in neurology, including the use of cell-based therapies. In this review, we focus on summarizing one of the cell sources that can be applied as a multimodal treatment tool to overcome the complex issue of neurodegeneration-mesenchymal stem cells (MSCs). Apart from the highly proven safety of this approach, beneficial effects connected to this type of treatment have been observed. This review presents modes of action of MSCs, explained on the basis of data from vast in vitro and preclinical studies, and we summarize the effects of using these cells in clinical trial settings. Finally, we stress what improvements have already been made to clarify the exact mechanism of MSCs action, and we discuss potential ways to improve the introduction of MSC-based therapies in clinics. In summary, we propose that more insightful and methodical optimization, by combining careful preparation and administration, can enable use of multimodal MSCs as an effective, tailored cell therapy suited to specific neurological disorders.

Woo E, Patten A, Yau SY, Gil-Mohapel J. Beyond the Hippocampus and the SVZ: Adult Neurogenesis Throughout the Brain

Convincing evidence has repeatedly shown that new neurons are produced in the mammalian brain into adulthood. Adult neurogenesis has been best described in the hippocampus and the subventricular zone (SVZ), in which a series of distinct stages of neuronal development has been well characterized. However, more recently, new neurons have also been found in other brain regions of the adult mammalian brain, including the hypothalamus, striatum, substantia nigra, cortex, and amygdala. While some studies have suggested that these new neurons originate from endogenous stem cell pools located within these brain regions, others have shown the migration of neurons from the SVZ to these regions. Notably, it has been shown that the generation of new neurons in these brain regions is impacted by neurologic processes such as stroke/ischemia and neurodegenerative disorders. Furthermore, numerous factors such as neurotrophic support, pharmacologic interventions, environmental exposures, and stem cell therapy can modulate this endogenous process. While the presence and significance of adult neurogenesis in the human brain (and particularly outside of the classical neurogenic regions) is still an area of debate, this intrinsic neurogenic potential and its possible regulation through therapeutic measures present an exciting alternative for the treatment of several neurologic conditions. This review summarizes evidence in support of the classic and novel neurogenic zones present within the mammalian brain and discusses the functional significance of these new neurons as well as the factors that regulate their production. Finally, it also discusses the potential clinical applications of promoting neurogenesis outside of the classical neurogenic niches, particularly in the hypothalamus, cortex, striatum, substantia nigra, and amygdala.

Stem cell treatments for oropharyngeal dysphagia: Rationale, benefits, and challenges

Dysphagia, defined as difficulty swallowing, is a common symptom negatively impacting millions of adults annually. Estimated prevalence ranges from 14 to 33 percent in those over age 65 to over 70 percent in a nursing home setting. The elderly, those with neurodegenerative diseases, head and neck cancer patients, and those with autoimmune conditions such as Sjögren's syndrome are disproportionately affected. Oropharyngeal dysphagia refers specifically to difficulty in initiating a swallow due to dysfunction at or above the upper esophageal sphincter, and represents a large proportion of dysphagia cases. Current treatments are limited and are often ineffective. Stem cell therapy is a new and novel advancement that may fill a much-needed role in our treatment regimen. Here, we review the current literature regarding stem cell treatments for oropharyngeal dysphagia. Topics discussed include tissue regeneration advancements as a whole and translation of these principles into research surrounding tongue dysfunction, xerostomia, cricopharyngeal dysfunction, and finally an overview of the challenges and future directions for investigation. Although this field of study remains in its early stages, initial promising results show potential for the use of stem cell-based therapies to treat oropharyngeal dysphagia and warrant further research.

Intracerebral Transplants of GMP-Grade Human Umbilical Cord-Derived Mesenchymal Stromal Cells Effectively Treat Subacute-Phase Ischemic Stroke in a Rodent Model

In subacute and chronic phases of the stroke, there are no therapeutics available at present to promote functional recovery. Human umbilical cord-derived mesenchymal stromal cells (hUC-MSCs) are one of the candidate cell types for treating subacute-phase stroke. The benefits of cell-based therapy largely depend on the migratory capacity of products administered, as well as their potential for engraftment in targeted tissues and paracrine activities. Timing and delivery modes may also influence the outcomes of stem-cell therapy. Still, the functional recuperative effects of differing hUC-MSC delivery modes, about cell replacement and cell-to-cell paracrine activity levels, have yet to be clarified in subacute phases of stroke.This study was conducted to compare the therapeutic effects of various delivery routes when administering Good Manufacturing Practice (GMP)-grade hUC-MSCs in a rodent model of subacute-phase stroke. Cell aliquots (1 × 10⁶) were given to rats as intravenous (IV) injections or intracerebral (IC) transplants 1 week after middle cerebral artery occlusion (MCAo). Transplanted rats were examined up to 7 weeks later using various behavioral tests and immunohistochemical analyses. Most IC-transplanted cells survived for short periods (i.e., <4 weeks after receipt) and gradually disappeared, whereas IV-injected cells were undetectable in the brain at the same time points (i.e., 3 days, 4 weeks, or 7 weeks after injection). Although short-lived, IC-transplanted cells effectively improved behavioral deficits, serving to reduce infarct volumes and glial scar formation, increase subventricular counts of proliferating neuroblasts, and promote cerebrovascular ingrowth in ischemic penumbra regions. IV injection, however, failed to improve behavioral function or histologic parameters during the same 7-week time frame. These findings overall suggest that IC transplantation is preferable to IV injection for delivery of hUC-MSCs during subacute phases of stroke.

Blowing up Neural Repair for Stroke Recovery: Preclinical and Clinical Trial Considerations

The repair and recovery of the brain after stroke is a field that is emerging in its preclinical science and clinical trials. However, recent large, multicenter clinical trials have been negative, and conflicting results emerge on biological targets in preclinical studies. The coalescence of negative clinical translation and confusion in preclinical studies raises the suggestion that perhaps the field of stroke recovery faces a fate similar to stroke neuroprotection, with interesting science ultimately proving difficult to translate to the clinic. This review highlights improvements in 4 areas of the stroke neural repair field that should reorient the field toward successful clinical translation: improvements in rodent genetic models of stroke recovery, consideration of the biological target in stroke recovery, stratification in clinical trials, and the use of appropriate clinical trial end points.

Communications Between Peripheral and the Brain-Resident Immune System in Neuronal Regeneration After Stroke

Cerebral ischemia may cause irreversible neural network damage and result in functional deficits. Targeting neuronal repair after stroke potentiates the formation of new connections, which can be translated into a better functional outcome. Innate and adaptive immune responses in the brain and the periphery triggered by ischemic damage participate in regulating neural repair after a stroke. Immune cells in the blood circulation and gut lymphatic tissues that have been shaped by immune components including gut microbiota and metabolites can infiltrate the ischemic brain and, once there, influence neuronal regeneration either directly or by modulating the properties of brain-resident immune cells. Immune-related signalings and metabolites from the gut microbiota can also directly alter the phenotypes of resident immune cells to promote neuronal regeneration. In this review, we discuss several potential mechanisms through which peripheral and brain-resident immune components can cooperate to promote first the resolution of neuroinflammation and subsequently to improved neural regeneration and a better functional recovery. We propose that new insights into discovery of regulators targeting pro-regenerative process in this complex neuro-immune network may lead to novel strategies for neuronal regeneration.

Recent Advances in Cell-Based Therapies for Ischemic Stroke

Stroke is the most prevalent cardiovascular disease worldwide, and is still one of the leading causes of death and disability. Stem cell-based therapy is actively being investigated as a new potential treatment for certain neurological disorders, including stroke. Various types of cells, including bone marrow mononuclear cells, bone marrow mesenchymal stem cells, dental pulp stem cells, neural stem cells, inducible pluripotent stem cells, and genetically modified stem cells have been found to improve neurological outcomes in animal models of stroke, and there are some ongoing clinical trials assessing their efficacy in humans. In this review, we aim to summarize the recent advances in cell-based therapies to treat stroke.

From in vitro to in vivo reprogramming for neural transdifferentiation: An approach for CNS tissue remodeling using stem cell technology

Advances in stem cell technology have provided three approaches to address the demanding issue of the treatment of intractable neurological disease. One of the approaches is the screening of compounds attenuating pathological phenotypes in stem-cell based models. A second approach consists of exogenous-targeted cell supplementation to the lesion with stem cell-derived differentiated cells. A third approach involves in vivo direct programming to transdifferentiate endogenous somatic cells and to boost CNS tissue remodeling. In this review, we outline research advances in stem cell technology of direct reprogramming in vitro and in vivo and discuss the future challenge of tissue remodeling by neural transdifferentiation.

Cell Therapies under Clinical Trials and Polarized Cell Therapies in Pre-Clinical Studies to Treat Ischemic Stroke and Neurological Diseases: A Literature Review

Stroke remains a major cause of serious disability because the brain has a limited capacity to regenerate. In the last two decades, therapies for stroke have dramatically changed. However, half of the patients cannot achieve functional independence after treatment. Presently, cell-based therapies are being investigated to improve functional outcomes. This review aims to describe conventional cell therapies under clinical trial and outline the novel concept of polarized cell therapies based on protective cell phenotypes, which are currently in pre-clinical studies, to facilitate functional recovery after post-reperfusion treatment in patients with ischemic stroke. In particular, non-neuronal stem cells, such as bone marrow-derived mesenchymal stem/stromal cells and mononuclear cells, confer no risk of tumorigenesis and are safe because they do not induce rejection and allergy; they also pose no ethical issues. Therefore, recent studies have focused on them as a cell source for cell therapies. Some clinical trials have shown beneficial therapeutic effects of bone marrow-derived cells in this regard, whereas others have shown no such effects. Therefore, more clinical trials must be performed to reach a conclusion. Polarized microglia or peripheral blood mononuclear cells might provide promising therapeutic strategies after stroke because they have pleiotropic effects. In traumatic injuries and neurodegenerative diseases, astrocytes, neutrophils, and T cells were polarized to the protective phenotype in pre-clinical studies. As such, they might be useful therapeutic targets. Polarized cell therapies are gaining attention in the treatment of stroke and neurological diseases.

Magnetic resonance imaging of human neural stem cells in rodent and primate brain

Stem cell transplantation therapies are currently under investigation for central nervous system disorders. Although preclinical models show benefit, clinical translation is somewhat limited by the absence of reliable noninvasive methods to confirm targeting and monitor transplanted cells in vivo. Here, we assess a novel magnetic resonance imaging (MRI) contrast agent derived from magnetotactic bacteria, magneto‐endosymbionts (MEs), as a translatable methodology for in vivo tracking of stem cells after intracranial transplantation. We show that ME labeling provides robust MRI contrast without impairment of cell viability or other important therapeutic features. Labeled cells were visualized immediately post‐transplantation and over time by serial MRI in nonhuman primate and mouse brain. Postmortem tissue analysis confirmed on‐target grft location, and linear correlations were observed between MRI signal, cell engraftment, and tissue ME levels, suggesting that MEs may be useful for determining graft survival or rejection. Overall, these findings indicate that MEs are an effective tool for in vivo tracking and monitoring of cell transplantation therapies with potential relevance to many cellular therapy applications.

Safety and Efficacy of Stem Cell Therapy in Patients With Ischemic Stroke

Stem cell therapy is emerging as a promising treatment strategy to treat patients with stroke. While there are established modes of treatment for stroke patients such as thrombolysis and endovascular intervention, most of the stroke patients frequently end up with major residual deficits or even death. The use of stem cells to treat stroke has been found to be beneficial in the animal models but strict evidence for the same in humans is still lacking. We reviewed 13 clinical trials of stem cell therapy in stroke patients conducted between 2014 and 2020 based on the search using the database PubMed, and the clinical trial registry (www.clinicaltrials.gov). We aimed to assess the safety and efficacy of stem cell treatment in stroke patients who participated in the trials. Quality assessment of the clinical trials revealed a sub-optimal score. We found mixed results regarding the efficacy of stem cells in the treatment of ischemic stroke although we could not do a quantitative analysis of the effect outcomes. Assessment for safety revealed promising results as there were only minor side effects related to cell therapy. Although stem cell therapy seems to be a promising strategy to treat stroke patients in the future, we concluded that the field needs more evidence regarding the safety and efficacy of the use of stem cells in stroke patients before we use them in the clinic.

Efficacy of adipose derived stem cells on functional and neurological improvement following ischemic stroke: a systematic review and meta-analysis

BACKGROUND

The evidence on the efficacy of adipose derived stem cells (ADSCs) in the treatment of stroke is controversial. Therefore, the aim of present systematic review and meta-analysis is to evaluate the efficacy of ADSCs administration in the treatment of animal models of ischemic stroke.

METHODS

An extensive search was performed on electronic databases of Medline, Embase, Scopus, CENTRAL and Web of Science until December 31, 2018. Animal studies that used ADSCs in treatment of ischemic stroke were included. The data were recorded as mean and standard deviation and then a pooled standardized mean difference (SMD) with 95% confidence interval (95% CI) was reported.

RESULTS

Twenty articles were included in the present meta-analysis. It was observed that administration of ADSCs improves motor function (SMD = 2.52, 95% CI: 1.67 to 3.37, p < 0.0001) and neurological status (SMD = 2.05, 95% CI: 1.33 to 2.78, p < 0.0001) in animals following an ischemic stroke. Multivariate meta-regression showed the model of stroke induction (p = 0.017) and the number of transplanted cells (p = 0.007) affect the efficacy of ADSCs administration on motor function improvement following the stroke.

CONCLUSION

Moderate to high levels of evidence indicate a strong efficacy of ADSCs transplantation on motor function and neurological improvement following ischemic stroke in animal models. However, no reports regarding the dose-response effect of ADSCs administration on stroke exist in the literature. As a result, further pre-clinical studies are recommended to be conducted on the matter.

Cell Therapy for Ischemic Stroke: How to Turn a Promising Preclinical Research into a Successful Clinical Story

Stroke is a major public health issue with limited treatment. The pharmacologically or mechanically removing of the clot is accessible to less than 10% of the patients. Stem cell therapy is a promising alternative strategy since it increases the therapeutic time window but many issues remain unsolved. To avoid a new dramatic failure when translating experimental data on the bedside, this review aims to highlight the indispensable checkpoints to make a successful clinical trial based on the current preclinical literature. The large panel of progenitors/ stem cells at the researcher's disposal is to be used wisely, regarding the type of cells, the source of cells, the route of delivery, the time window, since it will directly affect the outcome. Mechanisms are still incompletely understood, although recent studies have focused on the inflammation modulation of most cells types.

Fast-tracking regenerative medicine for traumatic brain injury

Traumatic brain injury remains a global health crisis that spans all demographics, yet there exist limited treatment options that may effectively curtail its lingering symptoms. Traumatic brain injury pathology entails a progression from primary injury to inflammation-mediated secondary cell death. Sequestering this inflammation as a means of ameliorating the greater symptomology of traumatic brain injury has emerged as an attractive treatment prospect. In this review, we recapitulate and evaluate the important developments relating to regulating traumatic brain injury-induced neuroinflammation, edema, and blood-brain barrier disintegration through pharmacotherapy and stem cell transplants. Although these studies of stand-alone treatments have yielded some positive results, more therapeutic outcomes have been documented from the promising area of combined drug and stem cell therapy. Harnessing the facilitatory properties of certain pharmaceuticals with the anti-inflammatory and regenerative effects of stem cell transplants creates a synergistic effect greater than the sum of its parts. The burgeoning evidence in favor of combined drug and stem cell therapies warrants more elaborate preclinical studies on this topic in order to pave the way for later clinical trials.

Insights into the dual role of angiogenesis following stroke

Stroke remains a major cause of serious disability due to the brain's limited capacity to regenerate. Current treatments focus on acute recanalization of the occluded blood vessels; however, currently there are no approved therapy options to regenerate neural circuits and reduce stroke-related disability. To promote recovery, therapeutic angiogenesis has been proposed as a promising target. Although restoration of blood vessels providing oxygen and nutrients to the peri-infarct regions may be beneficial, newly generated capillaries may also carry pathophysiological risk factors that need to be considered. One major concern are adverse effects including edema formation and haemorrhagic transformation due to the comprised endothelial barrier function during vascular remodelling. This brief opinion article will discuss the challenges and the newest advancements of angiogenesis as a therapeutic strategy for ischemic stroke.

Multicolor spectral photon counting CT monitors and quantifies therapeutic cells and their encapsulating scaffold in a model of brain damage

Rationale & aim: Various types of cell therapies are currently under investigation for the treatment of ischemic stroke patients. To bridge the gap between cell administration and therapeutic outcome, there is a need for non-invasive monitoring of these innovative therapeutic approaches. Spectral photon counting computed tomography (SPCCT) is a new imaging modality that may be suitable for cell tracking. SPCCT is the next generation of clinical CT that allows the selective visualization and quantification of multiple contrast agents. The aims of this study are: (i) to demonstrate the feasibility of using SPCCT to longitudinally monitor and quantify therapeutic cells, i.e. bone marrow-derived M2-polarized macrophages transplanted in rats with brain damage; and (ii) to evaluate the potential of this approach to discriminate M2-polarized macrophages from their encapsulating scaffold. Methods: Twenty one rats received an intralesional transplantation of bone marrow-derived M2-polarized macrophages. In the first set of experiments, cells were labeled with gold nanoparticles and tracked for up to two weeks post-injection in a monocolor study via gold K-edge imaging. In the second set of experiments, the same protocol was repeated for a bicolor study, in which the labeled cells are embedded in iodine nanoparticle-labeled scaffold. The amount of gold in the brain was longitudinally quantified using gold K-edge images reconstructed from SPCCT acquisition. Animals were sacrificed at different time points post-injection, and ICP-OES was used to validate the accuracy of gold quantification from SPCCT imaging. Results: The feasibility of therapeutic cell tracking was successfully demonstrated in brain-damaged rats with SPCCT imaging. The imaging modality enabled cell monitoring for up to 2 weeks post-injection, in a specific and quantitative manner. Differentiation of labeled cells and their embedding scaffold was also feasible with SPCCT imaging, with a detection limit as low as 5,000 cells in a voxel of 250 × 250 × 250 µm in dimension in vivo. Conclusion: Multicolor SPCCT is an innovative translational imaging tool that allows monitoring and quantification of therapeutic cells and their encapsulating scaffold transplanted in the damaged rat brain.

Bone Marrow-Derived NCS-01 Cells Advance a Novel Cell-Based Therapy for Stroke

Human mesenchymal stem cells have been explored for their application in cell-based therapies targeting stroke. Identifying cell lines that stand as safe, accessible, and effective for transplantation, while optimizing dosage, timing, and method of delivery remain critical translational steps towards clinical trials. Preclinical studies using bone marrow-derived NCS-01 cells show the cells' ability to confer functional recovery in ischemic stroke. Coculturing primary rat cortical cells or human neural progenitor cells with NCS-01 cells protects against oxygen-glucose deprivation. In the rodent middle cerebral artery occlusion model, intracarotid artery administration of NCS-01 cells demonstrate greater efficacy than other mesenchymal stem cells (MSCs) at improving motor and neurological function, as well as reducing infarct volume and peri-infarct cell loss. NCS-01 cells secrete therapeutic factors, including basic fibroblast growth factor and interleukin-6, while also demonstrating a potentially novel mechanism of extending filopodia towards the site of injury. In this review, we discuss recent preclinical advancements using in vitro and in vivo ischemia models that support the transplantation of NCS-01 in human stroke trials. These results, coupled with the recommendations put forth by the consortium of Stem cell Therapeutics as an Emerging Paradigm for Stroke (STEPS), highlight a framework for conducting preclinical research with the ultimate goal of initiating clinical trials.

Emerging Therapeutic Potential of Mesenchymal Stem/Stromal Cells in Preeclampsia

PURPOSE OF REVIEW

Preeclampsia is a dangerous pregnancy condition affecting both the mother and offspring. It is a multifactorial disease with poorly understood pathogenesis, lacking effective treatments. Maternal immune response, inflammation and oxidative stress leading to endothelial dysfunction are the most prominent pathogenic processes implicated in preeclampsia development. Here, we give a detailed overview of the therapeutic applications and mechanisms of mesenchymal stem/stromal cells (MSCs) as a potential new treatment for preeclampsia.

RECENT FINDINGS

MSCs have gained growing attention due to low immunogenicity, easy cultivation and expansion in vitro. Accumulating evidence now suggests that MSCs act primarily through their secretomes facilitating paracrine signalling that leads to potent immunomodulatory, pro-angiogenic and regenerative therapeutic effects. MSCs have been studied in different animal models of preeclampsia demonstrating promising result, which support further investigations into the therapeutic effects and mechanisms of MSC-based therapies in preeclampsia, steering these therapies into clinical trials.

miR‑210 enhances mesenchymal stem cell‑modulated neural precursor cell migration

The migration of endogenous neural stem cells and neural precursor cells (NPCs) to sites of injury is essential for neuroregeneration following hypoxic‑ischemic events. Bone marrow‑derived mesenchymal stem cells (BMSCs) are a potential therapeutic source of cells following central nervous system damage; however, few studies have investigated the effects of BMSCs on cell migration. Thus, in the present study, the effects of BMSCs on NPC migration were investigated. In the present study, BMSCs and NPCs were isolated and cultured from mice. The effects of BMSCs on the migration of NPCs were analyzed using a Transwell cell migration assay. BMSCs were transfected with microRNA‑210 (miR‑210) mimics and inhibitors to examine the effects of the respective upregulation and downregulation of miR‑210 in BMSCs on the migration of NPCs. Then, miR‑210 expression in BMSCs were quantified and the expression levels of vascular endothelial growth factor‑C (VEGF‑C), brain derived neurotrophic factor (BDNF) and chemokine C‑C motif ligand 3 (CCL3) in the supernatant under hypoxic conditions were investigated via reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR) and ELISA. Subsequently, the expression of VEGF‑C, BDNF and CCL3 in BMSCs overexpressing miR‑210 or BMSCs suppressing miR‑210 was examined by RT‑qPCR and western blot analyses. BMSCs promoted the migration of NPC, particularly when pre‑cultured with BMSCs for 24 h and co‑cultured with NPCs for 24 h; the miR‑210 expression levels increased under hypoxic conditions. Additionally, the migration of NPCs was also increased when the BMSCs overexpressed miR‑210 compared with the BMSCs transfected with a negative control miR and BMSCs with downregulated miR‑210 levels. The expression levels of VEGF‑C increased in the BMSCs that overexpressed miR‑210 and were decreased in BMSCs transfected with a miR‑210 inhibitor. The results of the present study indicated that BMSCs promote the migration of NPCs. Overexpression of miR‑210 in BMSCs enhanced NPC migration and may be associated with increases in VEGF‑C expression levels.

Activity in grafted human iPS cell-derived cortical neurons integrated in stroke-injured rat brain regulates motor behavior

Stem cell transplantation can improve behavioral recovery after stroke in animal models but whether stem cell-derived neurons become functionally integrated into stroke-injured brain circuitry is poorly understood. Here we show that intracortically grafted human induced pluripotent stem (iPS) cell-derived cortical neurons send widespread axonal projections to both hemispheres of rats with ischemic lesions in the cerebral cortex. Using rabies virus-based transsynaptic tracing, we find that at 6 mo after transplantation, host neurons in the contralateral somatosensory cortex receive monosynaptic inputs from grafted neurons. Immunoelectron microscopy demonstrates myelination of the graft-derived axons in the corpus callosum and that their terminals form excitatory, glutamatergic synapses on host cortical neurons. We show that the stroke-induced asymmetry in a sensorimotor (cylinder) test is reversed by transplantation. Light-induced inhibition of halorhodopsin-expressing, grafted neurons does not recreate the impairment, indicating that its reversal is not due to neuronal activity in the graft. However, we find bilateral decrease of motor performance in the cylinder test after light-induced inhibition of either grafted or endogenous halorhodopsin-expressing cortical neurons, located in the same area, and after inhibition of endogenous halorhodopsin-expressing cortical neurons by exposure of their axons to light on the contralateral side. Our data indicate that activity in the grafted neurons, probably mediated through transcallosal connections to the contralateral hemisphere, is involved in maintaining normal motor function. This is an example of functional integration of efferent projections from grafted neurons into the stroke-affected brain's neural circuitry, which raises the possibility that such repair might be achievable also in humans affected by stroke.

Intracerebral implantation of human neural stem cells and motor recovery after stroke: multicentre prospective single-arm study (PISCES-2)

BACKGROUND

Human neural stem cell implantation may offer improved recovery from stroke. We investigated the feasibility of intracerebral implantation of the allogeneic human neural stem cell line CTX0E03 in the subacute-chronic recovery phase of stroke and potential measures of therapeutic response in a multicentre study.

METHODS

We undertook a prospective, multicentre, single-arm, open-label study in adults aged >40 years with significant upper limb motor deficits 2-13 months after ischaemic stroke. 20 million cells were implanted by stereotaxic injection to the putamen ipsilateral to the cerebral infarct. The primary outcome was improvement by 2 or more points on the Action Research Arm Test (ARAT) subtest 2 at 3 months after implantation.

FINDINGS

Twenty-three patients underwent cell implantation at eight UK hospitals a median of 7 months after stroke. One of 23 participants improved by the prespecified ARAT subtest level at 3 months, and three participants at 6 and 12 months. Improvement in ARAT was seen only in those with residual upper limb movement at baseline. Transient procedural adverse effects were seen, but no cell-related adverse events occurred up to 12 months of follow-up. Two deaths were unrelated to trial procedures.

INTERPRETATION

Administration of human neural stem cells by intracerebral implantation is feasible in a multicentre study. Improvements in upper limb function occurred at 3, 6 and 12 months, but not in those with absent upper limb movement at baseline, suggesting a possible target population for future controlled trials.

FUNDING

ReNeuron, Innovate UK (application no 32074-222145).

TRIAL REGISTRATION NUMBER

EudraCT Number: 2012-003482-18.

Neurogenin-1 Overexpression Increases the Therapeutic Effects of Mesenchymal Stem Cells through Enhanced Engraftment in an Ischemic Rat Brain

Background and Objectives

Stem cell therapy is a promising strategy for treating neurological diseases but its effectiveness is influenced by the route of administration and the characteristics of the stem cells. We determined whether neural induction of mesenchymal stem cells (MSCs) was beneficial when the cells were delivered intra-arterially through the carotid artery.

Methods and Results

MSCs were neurally induced using a retroviral vector expressing the neurogenic transcription factor neurogenin-1 (Ngn1). The LacZ gene encoding bacterial β-galactosidase was used as a control. Ischemic stroke was induced by transluminal occlusion of the middle cerebral artery and 3 days later the MSCs were delivered intra-arterially through the internal carotid artery. Magnetic resonance imaging analysis indicated that compared to MSCs expressing LacZ (MSCs/LacZ), MSCs expressing Ngn1 (MSCs/Ngn1) exhibited increased recruitment to the ischemic region and populated this area for a longer duration. Immunohistochemical analysis indicated that compared to MSCs/LacZ, MSCs/Ngn1 more effectively alleviated neurological dysfunction by blocking secondary damage associated with neuronal cell death and brain inflammation. Microarray and real-time PCR analysis indicated that MSCs/Ngn1 exhibited increased expression of chemotactic cytokine receptors, adherence to endothelial cells, and migration ability.

Conclusions

Neural induction with Ngn1 increases the homing ability of MSCs, enhancing their engraftment efficiency in the ischemic rat brain. Intra-arterial delivery of neurally induced MSCs/Ngn1 3 days after ischemic injury blocks neuronal cell death and inflammation, and improves functional recovery. Thus, intra-arterial administration of stem cells with neural properties may be a novel therapy for the treatment of ischemic stroke.

Role of Region-Specific Brain Decellularized Extracellular Matrix on In Vitro Neuronal Maturation

Recent advancements in tissue engineering suggest that biomaterials, such as decellularized extracellular matrix (ECM), could serve to potentiate the localization and efficacy of regenerative therapies in the central nervous system. Still, what factors and which mechanisms are required from these ECM-based biomaterials to exert their effect are not entirely understood. In this study, we use the brain as a novel model to test the effects of particular biochemical and structural properties by evaluating, for the first time, three different sections of the brain (i.e., cortex, cerebellum, and remaining areas) side-by-side and their corresponding decellularized counterparts using mechanical (4-day) and chemical (1-day) decellularization protocols. The three different brain subregions had considerably different initial conditions in terms of cell number and growth factor content, and some of these differences were maintained after decellularization. Decellularized ECM from both protocols was used as a substrate or as soluble factor, in both cases showing good cell attachment and growth capabilities. Interestingly, the 1-day protocol was capable of promoting greater differentiation than the 4-day protocol, probably due to its capacity to remove a similar amount of cell nuclei, while better conserving the biochemical and structural components of the cerebral ECM. Still, some limitations of this study include the need to evaluate the response in other biologically relevant cell types, as well as a more detailed characterization of the components in the decellularized ECM of the different brain subregions. In conclusion, our results show differences in neuronal maturation depending on the region of the brain used to produce the scaffolds. Complex organs such as the brain have subregions with very different initial cellular and biochemical conditions that should be considered for decellularization to minimize exposure to immunogenic components, while retaining bioactive factors conducive to regeneration. [Figure: see text] Impact statement The present study offers new knowledge about the production of decellularized extracellular matrix scaffolds from specific regions of the porcine brain, with a direct comparison of their effect on in vitro neuronal maturation. Our results show differences in neuronal maturation depending on the region of the brain used to produce the scaffolds, suggesting that it is necessary to consider the initial cellular content of the source tissue and its bioactive capacity for the production of an effective regenerative therapy for stroke.

Activated Mesenchymal Stem Cells Induce Recovery Following Stroke Via Regulation of Inflammation and Oligodendrogenesis

Background Brain repair mechanisms fail to promote recovery after stroke, and approaches to induce brain regeneration are scarce. Mesenchymal stem cells (MSC) are thought to be a promising therapeutic option. However, their efficacy is not fully elucidated, and the mechanism underlying their effect is not known. Methods and Results The middle cerebral artery occlusion model was utilized to determine the efficacy of interferon-γ-activated mesenchymal stem cells (aMSCγ) as an acute therapy for stroke. Here we show that treatment with aMSCγ is a more potent therapy for stroke than naive MSC. aMSCγ treatment results in significant functional recovery assessed by the modified neurological severity score and open-field analysis compared with vehicle-treated animals. aMSCγ-treated animals showed significant reductions in infarct size and inhibition of microglial activation. The aMSCγ treatment suppressed the hypoxia-induced microglial proinflammatory phenotype more effectively than treatment with naive MSC. Importantly, treatment with aMSCγ induced recruitment and differentiation of oligodendrocyte progenitor cells to myelin-producing oligodendrocytes in vivo. To elucidate the mechanism underlying high efficacy of aMSCγ therapy, we examined the secretome of aMSCγ and compared it to that of naive MSC. Intriguingly, we found that aMSCγ but not nMSC upregulated neuron-glia antigen 2, an important extracellular signal and a hallmark protein of oligodendrocyte progenitor cells. Conclusions These results suggest that activation of MSC with interferon-γ induces a potent proregenerative, promyelinating, and anti-inflammatory phenotype of these cells, which increases the potency of aMSCγ as an effective therapy for ischemic stroke.

Potential of mesenchymal stem cells alone, or in combination, to treat traumatic brain injury

Traumatic brain injury (TBI) causes death and disability in the United States and around the world. The traumatic insult causes the mechanical injury of the brain and primary cellular death. While a comprehensive pathological mechanism of TBI is still lacking, the focus of the TBI research is concentrated on understanding the pathophysiology and developing suitable therapeutic approaches. Given the complexities in pathophysiology involving interconnected immunologic, inflammatory, and neurological cascades occurring after TBI, the therapies directed to a single mechanism fail in the clinical trials. This has led to the development of the paradigm of a combination therapeutic approach against TBI. While there are no drugs available for the treatment of TBI, stem cell therapy has shown promising results in preclinical studies. But, the success of the therapy depends on the survival of the stem cells, which are limited by several factors including route of administration, health of the administered cells, and inflammatory microenvironment of the injured brain. Reducing the inflammation prior to cell administration may provide a better outcome of cell therapy following TBI. This review is focused on different therapeutic approaches of TBI and the present status of the clinical trials.

Engraftment potential of maternal adipose-derived stem cells for fetal transplantation

Advances in prenatal molecular testing have made it possible to diagnose most genetic disorders early in gestation. In utero mesenchymal stem cell (MSC) therapy can be a powerful tool to cure the incurable. With this in mind, this method could ameliorate potential physical and functional damage. However, the presence of maternal T cells trafficking in the fetus during pregnancy is thought to be the major barrier to achieving the engraftment into the fetus. We investigated the possibility of using maternal adipose-derived stem cells (ADSCs) for in utero transplantation to improve engraftment, thus lowering the risk of graft rejection. Herein, fetal brain engraftment using congenic and maternal ADSC grafts was examined via in utero stem cell transplantation in a mouse model. ADSCs were purified using the mesenchymal stem cell markers, PDGFRα, and Sca-1 via fluorescence-activated cell sorting. The PDGFRα⁺Sca-1⁺ ADSCs were transplanted into the fetal intracerebroventricular (ICV) at E14.5. The transplanted grafts grew for at least 28 days after in utero transplantation with PDGFRα⁺Sca-1⁺ ADSC, and mature neuronal markers were also detected in the grafts. Furthermore, using the maternal sorted ADSCs suppressed the innate immune response, preventing the infiltration of CD8 T cells into the graft. Thus, in utero transplantation into the fetal ICV with the maternal PDGFRα⁺Sca-1⁺ ADSCs may be beneficial for the treatment of congenital neurological diseases because of the ability to reduce the responses after in utero stem cell transplantation and differentiate into neuronal lineages.

Research trends of stem cells in ischemic stroke from 1999 to 2018: A bibliometric analysis

OBJECTIVE

Many studies have evaluated the safety and efficacy of stem cells as therapeutic agents for ischemic stroke. We aimed to quantitatively assess the research trends of stem cell therapy for ischemic stroke.

PATIENTS AND METHODS

We searched the Web of Science Core Collection to identify relevant publications between 1999 and 2018. We used HistCite to summarize the critical information, including yearly records, authors, countries/regions, and institutions. VOSviewer was applied to map the collaborations between studies. Based on the title and abstract of each publication, MeSH terms were obtained using Medical Text Indexer to demonstrate evolutions of topic hotspots.

RESULTS

From 1999-2018, there were a total of 3,741 publications exploring the prospect of stem cells in ischemic stroke. Annual publication outputs grew from six records to 366 records. Stroke was the most high-profile journal because of its ranking first on the top productive and co-cited journal lists. The United States of America and China were the two most contributive countries of stem-cell research of ischemic stroke. Researchers were supposed to follow studies from productive institutions because of their consistent and systematic investigations in this field. Neural stem cells and mesenchymal stem cells were the most recognized cells for clinical translation.

CONCLUSION

With the growth of publications concerning the role of stem cells in ischemic stroke treatment, bibliometrics helps researchers to get insights of academic collaborations, research trends, and hot topics in the study field.

Evaluation of Novel Stereotactic Cannula for Stem Cell Transplantation against Central Nervous System Disease

Cell therapy for central nervous system (CNS) disorders is beginning to prove its safety and efficiency. Intraparenchymal transplantation can be an option for cell delivery; however, one concern regarding this method is that the transplantation cannula may cause additional brain injuries. These include vessel damage, which results in brain hemorrhage, and clogging of the cannula by brain debris and/or cell clusters, which requires replacement of the cannula or forced injection causing jet flow of the cell suspension. We compared cannulas for cell delivery used in clinical trials, the Pittsburg and Mizuho cannulas, to a newly designed one, MK01, to assess their usability. MK01 has a spherical-shaped tip with a fan-like open orifice on the side of the cannula, which prevents vessel damage, clogging of brain debris, and jet flow phenomenon. We compared the extent of rat cervical and abdominal arterial damage with the cannula, the amount of debris in the cannula, the force needed to cause jet flow, and cell viability. While the viability of cells passed through the cannulas was almost the same among cannulas (approximately 95%), the Pittsburg cannula caused cervical arterial injury and subsequent hemorrhage, as it required a significantly smaller force to penetrate the arterial wall. Moreover, the Pittsburg cannula, but not the Mizuho and MK01 cannulas, showed high frequency of brain debris in the needle tip (approximately 80%) after brain puncture. While jet flow of the injection liquid was observed even when using smaller forces in the Pittsburg and Mizuho cannulas, MK01 constantly showed low jet flow occurrence. Thus, MK01 seems to be safer than the previously reported cannulas, although further investigation is necessary to validate its safety for clinical use.

Harnessing the anti-inflammatory properties of stem cells for transplant therapy in hemorrhagic stroke

Hemorrhagic stroke is a global health crisis plagued by neuroinflammation in the acute and chronic phases. Neuroinflammation approximates secondary cell death, which in turn robustly contributes to stroke pathology. Both the physiological and behavioral symptoms of stroke correlate with various inflammatory responses in animal and human studies. That slowing the secondary cell death mediated by this inflammation may attenuate stroke pathology presents a novel treatment strategy. To this end, experimental therapies employing stem cell transplants support their potential for neuroprotection and neuroregeneration after hemorrhagic stroke. In this review, we evaluate experiments using different types of stem cell transplants as treatments for stroke-induced neuroinflammation. We also update this emerging area by examining recent preclinical and clinical trials that have deployed these therapies. While further investigations are warranted to solidify their therapeutic profile, the reviewed studies largely posit stem cells as safe and potent biologics for stroke, specifically owing to their mode of action for sequestering neuroinflammation and promoting neuroregenerative processes.

Systemic conditioned medium treatment from interleukin-1 primed mesenchymal stem cells promotes recovery after stroke

Background

Mesenchymal stem cells (MSCs) hold great potential as a therapy for stroke and have previously been shown to promote recovery in preclinical models of cerebral ischaemia. MSCs secrete a wide range of growth factors, chemokines, cytokines and extracellular vesicles—collectively termed the secretome. In this study, we assessed for the first time the efficacy of the IL-1α-primed MSC-derived secretome on brain injury and functional recovery after cerebral ischaemia.

Methods

Stroke was induced in male C57BL/6 mice using the intraluminal filament model of middle cerebral artery occlusion. Conditioned medium from IL-1α-primed MSCs or vehicle was administered at the time of reperfusion or at 24 h post-stroke by subcutaneous injection.

Results

IL-1α-primed MSC-derived conditioned medium treatment at the time of stroke led to a ~ 30% reduction in lesion volume at 48 h and was associated with modest improvements in body mass gain, 28-point neurological score and nest building. Administration of MSC-derived conditioned medium at 24 h post-stroke led to improved nest building and neurological score despite no observed differences in lesion volume at day 2 post-stroke.

Conclusions

Our results show for the first time that the administration of conditioned medium from IL-1α-primed MSCs leads to improvements in behavioural outcomes independently of neuroprotection.

An Update on the Progress of Isolation, Culture, Storage, and Clinical Application of Human Bone Marrow Mesenchymal Stem/Stromal Cells

Bone marrow mesenchymal stem/stromal cells (BMSCs), which are known as multipotent cells, are widely used in the treatment of various diseases via their self-renewable, differentiation, and immunomodulatory properties. In-vitro and in-vivo studies have supported the understanding mechanisms, safety, and efficacy of BMSCs therapy in clinical applications. The number of clinical trials in phase I/II is accelerating; however, they are limited in the size of subjects, regulations, and standards for the preparation and transportation and administration of BMSCs, leading to inconsistency in the input and outcome of the therapy. Based on the International Society for Cellular Therapy guidelines, the characterization, isolation, cultivation, differentiation, and applications can be optimized and standardized, which are compliant with good manufacturing practice requirements to produce clinical-grade preparation of BMSCs. This review highlights and updates on the progress of production, as well as provides further challenges in the studies of BMSCs, for the approval of BMSCs widely in clinical application.

Toward Functional Restoration of the Central Nervous System: A Review of Translational Neuroscience Principles

Injury to the central nervous system (CNS) can leave patients with devastating neurological deficits that may permanently impair independence and diminish quality of life. Recent insights into how the CNS responds to injury and reacts to critically timed interventions are being translated into clinical applications that have the capacity to drastically improve outcomes for patients suffering from permanent neurological deficits due to spinal cord injury, stroke, or other CNS disorders. The translation of such knowledge into practical and impactful treatments involves the strategic collaboration between neurosurgeons, clinicians, therapists, scientists, and industry. Therefore, a common understanding of key neuroscientific principles is crucial. Conceptually, current approaches to CNS revitalization can be divided by scale into macroscopic (systems-circuitry) and microscopic (cellular-molecular). Here we review both emerging and well-established tenets that are being utilized to enhance CNS recovery on both levels, and we explore the role of neurosurgeons in developing therapies moving forward. Key principles include plasticity-driven functional recovery, cellular signaling mechanisms in axonal sprouting, critical timing for recovery after injury, and mechanisms of action underlying cellular replacement strategies. We then discuss integrative approaches aimed at synergizing interventions across scales, and we make recommendations for the basis of future clinical trial design. Ultimately, we argue that strategic modulation of microscopic cellular behavior within a macroscopic framework of functional circuitry re-establishment should provide the foundation for most neural restoration strategies, and the early involvement of neurosurgeons in the process will be crucial to successful clinical translation.

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.

Clinical diagnostic and therapeutic guidelines of stroke neurorestoration (2020 China version)

Stroke is the main cause of death and disability among Chinese, and neurorestoration is an effective therapeutic strategy for patients with stroke. In recent years, many achievements have been made in stroke neurorestoration, but viewpoints for managing stroke vary per discipline. In order to promote standardization of diagnosis and treatment for stroke neurorestoration, the Chinese Association of Neurorestoratology (CANR; Preparatory) and China Committee of International Association of Neurorestoratology (IANR-China Committee) organized professional experts in the field to integrate fragmented neurorestorative methods and establish clinical diagnostic and therapeutic guidelines for stroke neurorestoration. This guideline includes the diagnosis and staging of stroke and therapeutic recommendations for neurorestoration at different stages of stroke in order to improve survival and quality of life of stroke patients.

Translating concepts of neural repair after stroke: Structural and functional targets for recovery

Stroke is among the most common causes of adult disability worldwide, and its disease burden is shifting towards that of a long-term condition. Therefore, the development of approaches to enhance recovery and augment neural repair after stroke will be critical. Recovery after stroke involves complex interrelated systems of neural repair. There are changes in both structure (at the molecular, cellular, and tissue levels) and function (in terms of excitability, cortical maps, and networks) that occur spontaneously within the brain. Several approaches to augment neural repair through enhancing these changes are under study. These include identifying novel drug targets, implementing rehabilitation strategies, and developing new neurotechnologies. Each of these approaches has its own array of different proposed mechanisms. Current investigation has emphasized both cellular and circuit-based targets in both gray and white matter, including axon sprouting, dendritic branching, neurogenesis, axon preservation, remyelination, blood brain barrier integrity, blockade of extracellular inhibitory signals, alteration of excitability, and promotion of new brain cortical maps and networks. Herein, we review for clinicians recovery after stroke, basic elements of spontaneous neural repair, and ongoing work to augment neural repair. Future study requires alignment of basic, translational, and clinical research. The field continues to grow while becoming more clearly defined. As thrombolysis changed stroke care in the 1990 s and thrombectomy in the 2010 s, the augmentation of neural repair and recovery after stroke may revolutionize care for these patients in the coming decade.

Olfactory ensheathing cells in chronic ischemic stroke: A phase 2, double-blind, randomized, controlled trial

Olfactory ensheathing cells (OECs) have shown promising results for patients with neurologic diseases in non-double-blind, placebo control studies. Thirty patients with a unilateral ischemic stroke of more than a year were enrolled in a phase 2, multicenter, randomized, double-blind, and placebo-controlled cell therapy trial with a subsequent 12-month follow-up. The primary therapeutic objective has shown that after 12 months, there were significant differences in National Institutes of Health Stroke Scale (NIHSS), modified Rankin Scale (mRS) and Barthel Index (BI) assessment scores among the OEC group, Schwann cell group and placebo medium group at one-year follow-up. The second therapeutic objective found that there were significant differences in NIHSS, mRS, and BI assessment scores when comparing the endpoint data with the baseline data in the OEC group. There was neither hypersensitivity reaction nor adverse event. The results of this multicenter, randomized, double-blind, and placebo-controlled study indicate that injecting OECs into the olfactory sub-mucosa have neurorestorative effects, which can improve the quality of life for patients with chronic ischemic strokes without serious side effects.

A novel therapeutic approach using peripheral blood mononuclear cells preconditioned by oxygen-glucose deprivation

Cell therapies that invoke pleiotropic mechanisms may facilitate functional recovery in patients with stroke. Based on previous experiments using microglia preconditioned by oxygen-glucose deprivation, we hypothesized that the administration of peripheral blood mononuclear cells (PBMCs) preconditioned by oxygen-glucose deprivation (OGD-PBMCs) to be a therapeutic strategy for ischemic stroke. Here, OGD-PBMCs were identified to secrete remodelling factors, including the vascular endothelial growth factor and transforming growth factor-β in vitro, while intra-arterial administration of OGD-PBMCs at 7 days after focal cerebral ischemia prompted expression of such factors in the brain parenchyma at 28 days following focal cerebral ischemia in vivo. Furthermore, administration of OGD-PBMCs induced an increasing number of stage-specific embryonic antigen-3-positive cells both in vitro and in vivo. Finally, it was found to prompt angiogenesis and axonal outgrowth, and functional recovery after cerebral ischemia. In conclusion, the administration of OGD-PBMCs might be a novel therapeutic strategy against ischemic stroke.

The effects of cell therapy on seizures in animal models of epilepsy: protocol for systematic review and meta-analysis of preclinical studies

BACKGROUND

Epilepsy is one of the most common and serious brain conditions, characterised by recurrent unprovoked seizures. It affects about 1% of the population worldwide. Despite a range of antiepileptic drugs being available, one third of the patients do not achieve adequate seizure control. Only a minority of these patients may be suitable to undergo surgical resection of the seizure focus, but this is an invasive and not always successful procedure. There is an urgent need to develop more effective treatment options for uncontrolled seizures. With the recent advances in regenerative and translational medicine, cell therapies could prove to be beneficial. Here we describe the protocol for a proposed systematic review and meta-analysis to assess the effects for cell transplantation in animal models of epilepsy.

METHODS

We will include all preclinical animal models of epilepsy that evaluate the effects of cell transplantation compared to the untreated control. The primary outcome will be the change in frequency and duration of seizures from baseline measured by video electroencephalography (EEG). The secondary outcomes will include histological and neurobehavioural assessments. We will perform an electronic search of MEDLINE via PubMed, Web of Science, and EMBASE. Search results will be screened independently by two reviewers and confirmed by a third reviewer. Data from eligible studies will be extracted and pooled, and the summary estimate of effect size will be calculated using DerSimonian and Laird random effects meta-analysis. Heterogeneity will be explored using sub-group meta-analysis, and meta-regression risk of bias will be assessed by using the CAMARADES checklist for study quality tool.

DISCUSSION

The purpose of this systematic review is to assess and summarise the existing literature in the field of cell transplantation as a treatment for epilepsy in animal models. Efficacy will be measured by evaluating the reduction in seizure intervals, number, and duration, within animal models of epilepsy. Analysis of the existing literature will mark the achievement made in the field and locate the existing gaps, a process that will aid in the search for the next needed step.

SYSTEMATIC REVIEW REGISTRATION

CRD42018103628.

Two-year safety and clinical outcomes in chronic ischemic stroke patients after implantation of modified bone marrow-derived mesenchymal stem cells (SB623): a phase 1/2a study

OBJECTIVE

The aim of this study was to evaluate the safety and clinical outcomes associated with stereotactic surgical implantation of modified bone marrow-derived mesenchymal stem cells (SB623) in patients with stable chronic ischemic stroke.

METHODS

This was a 2-year, open-label, single-arm, phase 1/2a study; the selected patients had chronic motor deficits between 6 and 60 months after nonhemorrhagic stroke. SB623 cells were administered to the target sites surrounding the subcortical stroke region using MRI stereotactic image guidance.

RESULTS

A total of 18 patients were treated with SB623 cells. All experienced at least 1 treatment-emergent adverse event (TEAE). No patients withdrew due to adverse events, and there were no dose-limiting toxicities or deaths. The most frequent TEAE was headache related to the surgical procedure (88.9%). Seven patients experienced 9 serious adverse events, which resolved without sequelae. In 16 patients who completed 24 months of treatment, statistically significant improvements from baseline (mean) at 24 months were reported for the European Stroke Scale (ESS) score, 5.7 (95% CI 1.4-10.1, p < 0.05); National Institutes of Health Stroke Scale (NIHSS) score, -2.1 (95% CI -3.3 to -1.0, p < 0.01), Fugl-Meyer (F-M) total score, 19.4 (95% CI 9.9-29.0, p < 0.01); and F-M motor scale score, 10.4 (95% CI 4.0-16.7, p < 0.01). Measures of efficacy reached plateau by 12 months with no decline thereafter. There were no statistically significant changes in the modified Rankin Scale score. The size of transient lesions detected by T2-weighted FLAIR imaging in the ipsilateral cortex at weeks 1-2 postimplantation significantly correlated with improvement in ESS (0.619, p < 0.05) and NIHSS (-0.735, p < 0.01) scores at 24 months.

CONCLUSIONS

In this completed 2-year phase 1/2a study, implantation of SB623 cells in patients with stable chronic stroke was safe and was accompanied by improvements in clinical outcomes.Clinical trial registration no.: NCT01287936 (clinicaltrials.gov).

From the Lab to Patients: a Systematic Review and Meta-Analysis of Mesenchymal Stem Cell Therapy for Stroke

There may be the potential to improve stroke recovery with mesenchymal stem cells (MSCs); however, questions about the efficacy and safety of this treatment remain. To address these issues and inform future studies, we performed a preclinical and clinical systematic review of MSC therapy for subacute and chronic ischemic stroke. MEDLINE, Embase, the Cochrane Register of Controlled Trials, and PubMed were searched. For the clinical review, interventional and observational studies of MSC therapy in ischemic stroke patients were included. For the preclinical review, interventional studies of MSC therapy using in vivo animal models of subacute or chronic stroke were included. Measures of safety and efficacy were assessed. Eleven clinical and 76 preclinical studies were included. Preclinically, MSC therapy was associated with significant benefits for multiple measures of motor and neurological function. Clinically, MSC therapy appeared to be safe, with no increase in adverse events reported (with the exception of self-limited fever immediately following injection). However, the efficacy of treatment was less apparent, with significant heterogeneity in both study design and effect size being observed. Additionally, in the only randomized phase II study to date, efficacy of MSC therapy was not observed. Preclinically, MSC therapy demonstrated considerable efficacy. Although MSC therapy demonstrated safety in the clinical setting, efficacy has yet to be determined. Future studies will need to address the discordance in the continuity of evidence as MSC therapy has been translated from "bench-to-bedside".

A Review of Stem Cell Therapy for Acquired Brain Injuries and Neurodegenerative Central Nervous System Diseases

Cell-based therapies have been the subject of much discussion regarding their potential role in enhancing central nervous system function for a number of pathologic conditions. Much of the current research has been in preclinical trials, with clinical trials in the phase I or I/II stage. Nevertheless, there is considerable interest in the public about the potential regenerative role that stem cells may have in improving function for these neurologic conditions. This review will describe the different types of stem cells that are available, review their possible effects, and discuss some of the variables that investigators need to consider when designing their studies. Current clinical research in the areas of stroke, traumatic brain injury, and neurodegenerative diseases (amyotrophic lateral sclerosis and Parkinson disease) will be reviewed. As this article is aimed at a rehabilitation audience, outcome measures, and the role of concurrent rehabilitation therapies will also be mentioned.