Cell transplantation therapy for stroke

REVIEW: "ISCHEMIC STROKE: From Fibrinolysis to Functional Recovery" Nanomedicine: emerging approaches to treat ischemic stroke

Stroke is responsible for 11% of all deaths worldwide, the majority of which are caused by ischemic strokes, thus making the need to urgently find safe and effective therapies. Today, these can be cured either by mechanical thrombectomy when the thrombus is accessible, or by intravenous injection of fibrinolytics. However, the latter present several limitations, such as potential severe side effects, few eligible patients and low rate of partial and full recovery. To design safer and more effective treatments, nanomedicine appeared in this medical field a few decades ago. This review will explain why nanoparticle-based therapies and imaging techniques are relevant for ischemic stroke management. Then, it will present the different nanoparticle types that have been recently developed to treat this pathology. It will also study the various targeting strategies used to bring nanoparticles to the stroke site, thereby limiting side effects and improving the therapeutic efficacy. Finally, this review will present the few clinical studies testing nanomedicine on stroke and discuss potential causes for their scarcity.

Stem Cell Therapy and Thiamine Deficiency-Induced Brain Damage

Wernicke's encephalopathy (WE) is a major central nervous system disorder resulting from thiamine deficiency (TD) in which a number of brain regions can develop serious damage including the thalamus and inferior colliculus. Despite decades of research into the pathophysiology of TD and potential therapeutic interventions, little progress has been made regarding effective treatment following the development of brain lesions and its associated cognitive issues. Recent developments in our understanding of stem cells suggest they are capable of repairing damage and improving function in different maladys. This article puts forward the case for the potential use of stem cell treatment as a therapeutic strategy in WE by first examining the effects of TD on brain functional integrity and its consequences. The second half of the paper will address the future benefits of treating TD with these cells by focusing on their nature and their potential to effectively treat neurodegenerative diseases that share some overlapping pathophysiological features with TD. At the same time, some of the obstacles these cells will have to overcome in order to become a viable therapeutic strategy for treating this potentially life-threatening illness in humans will be highlighted.

An update on stem cell therapy for stroke patients: Where are we now?

With a foundation built upon initial work from the 1980s demonstrating graft viability in cerebral ischemia, stem cell transplantation has shown immense promise in promoting survival, enhancing neuroprotection and inducing neuroregeneration, while mitigating both histological and behavioral deficits that frequently accompany ischemic stroke. These findings have led to a number of clinical trials that have thoroughly supported a strong safety profile for stem cell therapy in patients but have generated variable efficacy. As preclinical evidence continues to expand through the investigation of new cell lines and optimization of stem cell delivery, it remains critical for translational models to adhere to the protocols established through basic scientific research. With the recent shift in approach towards utilization of stem cells as a conjunctive therapy alongside standard thrombolytic treatments, key issues including timing, route of administration, and stem cell type must each be appropriately translated from the laboratory in order to resolve the question of stem cell efficacy for cerebral ischemia that ultimately will enhance therapeutics for stroke patients towards improving quality of life.

Ischemic and hemorrhagic stroke lesion environments differentially alter the glia repair potential of neural progenitor cell and immature astrocyte grafts

Using cell grafting to direct glia-based repair mechanisms in adult CNS injuries represents a potential therapeutic strategy for supporting functional neural parenchymal repair. However, glia repair directed by neural progenitor cell (NPC) grafts is dramatically altered by increasing lesion size, severity, and mode of injury. To address this, we studied the interplay between astrocyte differentiation and cell proliferation of NPC in vitro to generate proliferating immature astrocytes (ImA) using hysteretic conditioning. ImA maintain proliferation rates at comparable levels to NPC but showed robust immature astrocyte marker expression including Gfap and Vimentin. ImA demonstrated enhanced resistance to myofibroblast-like phenotypic transformations upon exposure to serum enriched environments in vitro compared to NPC and were more effective at scratch wound closure in vitro compared to quiescent astrocytes. Glia repair directed by ImA at acute ischemic striatal stroke lesions was equivalent to NPC but better than quiescent astrocyte grafts. While ischemic injury environments supported enhanced survival of grafts compared to healthy striatum, hemorrhagic lesions were hostile towards both NPC and ImA grafts leading to poor survival and ineffective modulation of natural wound repair processes. Our findings demonstrate that lesion environments, rather than transcriptional pre-graft states, determine the survival, cell-fate, and glia repair competency of cell grafts applied to acute CNS injuries.

Targeting blood-brain barrier for sepsis-associated encephalopathy: Regulation of immune cells and ncRNAs

Sepsis causes significant morbidity and mortality worldwide, most surviving patients show acute or chronic mental disorders, which are known as sepsis-associated encephalopathy (SAE). SAE involves many pathological processes, including the blood-brain barrier (BBB) damage. The BBB is located at the interface between the central nervous system and the surrounding environment, which protects the central nervous system (CNS) from the invasion of exogenous molecules, harmful substances or microorganisms in the blood. Recently, a growing number of studies have indicated that the BBB destruction was involved in SAE and played an important role in SAE-induced brain injury. In the present review, we firstly reveal the pathological processes of SAE such as the neurotransmitter disorders, oxidative stress, immune dysfunction and BBB destruction. Moreover, we introduce the structure of BBB, and describe the immune cells including microglia and astrocytes that participate in the BBB destruction after SAE. Furthermore, in view of the current research on non-coding RNAs (ncRNAs), we explain the regulatory mechanism of ncRNAs including long noncoding RNAs (lncRNAs), microRNAs (miRNAs) and circular RNAs (circRNAs) on BBB in the processes of SAE. Finally, we propose some challenges and perspectives of regulating BBB functions in SAE. Hence, on the basis of these effects, both immune cells and ncRNAs may be developed as therapeutic targets to protect BBB for SAE patients.

Efficacy of redox nanoparticles for improving survival of transplanted cells in a mouse model of ischemic stroke

The success of cell transplantation therapy for ischemic stroke is hindered by the low cell survival rate in poststroke brain, due in part to high free radical production and ensuing oxidative stress. We have developed redox nanoparticles to eliminate reactive oxygen species. In this study, we tested the protective efficacy of these redox nanoparticles in cell culture and a mouse model of ischemic stroke. Induced human dental pulp stem cells were subjected to oxygen-glucose deprivation and reoxygenation to recapitulate ischemia and reperfusion in the penumbra surrounding a cerebral infarct. Cell viability using WST-8 assay, apoptosis using TUNEL, free radicals using MitoSOX, and inflammatory cytokines using ELISA kit were measured in the presence and absence of redox nanoparticles after oxygen-glucose deprivation and reoxygenation. The scavenging activity of redox nanoparticles against reactive oxygen species was detected by electron spin resonance. Moreover, induced cells were transplanted intracerebrally into to the distal middle cerebral artery occlusion model with and without redox nanoparticles, and the survival rate measured. Cell viability was enhanced, while apoptosis, free radical generation, and inflammatory cytokine expression levels were reduced in cultures with redox nanoparticles. Further, reduced redox nanoparticles were detected in the cytoplasm, indicating free radical scavenging. Addition of redox nanoparticles also improved the survival rate of transplanted cells after 6 weeks in vivo. These redox nanoparticles may increase the applicability and success of induced stem cell therapy for ischemic stroke patents by promoting long-term survival.

Towards human organ generation using interspecies blastocyst complementation: Challenges and perspectives for therapy

Millions of people suffer from end-stage refractory diseases. The ideal treatment option for terminally ill patients is organ transplantation. However, donor organs are in absolute shortage, and sadly, most patients die while waiting for a donor organ. To date, no technology has achieved long-term sustainable patient-derived organ generation. In this regard, emerging technologies of chimeric human organ production via blastocyst complementation (BC) holds great promise. To take human organ generation via BC and transplantation to the next step, we reviewed current emerging organ generation technologies and the associated efficiency of chimera formation in human cells from the standpoint of developmental biology.

Optimal therapeutic conditions for the neural stem cell-based management of ischemic stroke: a systematic review and network meta-analysis based on animal studies

BACKGROUND

In order to promote the clinical translation of preclinical findings, it is imperative to identify the most optimal therapeutic conditions and adopt them for further animal and human studies. This study aimed to fully explore the optimal conditions for neural stem cell (NSC)-based ischemic stroke treatment based on animal studies.

METHODS

The PubMed, Ovid-Embase, and Web of Science databases were searched in December 2021. The screening of search results, extraction of relevant data, and evaluation of study quality were performed independently by two reviewers.

RESULTS

In total, 52 studies were included for data analysis. Traditional meta-analysis showed that NSCs significantly reduced the modified neurological severity score (mNSS) and volume of cerebral infarct in animal models of ischemic stroke. Network meta-analysis showed that allogeneic embryonic tissue was the best source of NSCs. Further, intracerebral transplantation was the most optimal route of NSC transplantation, and the acute phase was the most suitable stage for intervention. The optimal number of NSCs for transplantation was 1-5×10⁵ in mouse models and 1×10⁶ or 1.8×10⁶ in rat models.

CONCLUSIONS

We systematically explored the therapeutic strategy of NSCs in ischemic stroke, but additional research is required to develop optimal therapeutic strategies based on NSCs. Moreover, it is necessary to further improve and standardize the design, implementation, measuring standards, and reporting of animal-based studies to promote the development of better animal experiments and clinical research.

Lipid Microcapsules Promoted Neural Stem Cell Survival in the Infarcted Area of Mice with Ischemic Stroke by Inducing Autophagy

Intracerebral transplantation of neural stem cells (NSCs) for ischemic stroke treatment has been demonstrated to be inefficient, with only <5% of delivered cells being retained. Microcapsules may be a good carrier for NSC delivery; however, the current microcapsules do not fully meet the demands for cell survival after transplantation. In the present study, we designed a strategy for the encapsulation of NSCs in a novel lipid-alginate (L-A) microcapsule based on a two-step method. The protective effect of a L-A microcapsule on oxygen-glucose deprivation (OGD) was investigated by using the CCK8 test, the LDH release test, and flow cytometry. Mechanisms underlying the prosurvival effect were investigated by detecting autophagy markers like P62, LC3-I, and LC3-II, and autophagy flux analysis was also performed. Lastly, the ability of the L-A microcapsule to support NSCs delivery for ischemic stroke was investigated in the middle cerebral artery occlusion (MCAO) model. We found that L-A microcapsules exerted a good protective effect against OGD compared with control and alginate microcapsules. The L-A microcapsules were found to promote cell survival by not only providing a "physical" barrier but also altering autophagy markers like P62 and LC3-II, which enhanced autophagy flux. This novel microcapsule was confirmed to be suitable for NSC delivery in vivo, which alleviated transplanted NSC apoptosis, reduced the infarct volume, decreased brain edema, improved neurological deficit scores, and lastly, improved survival rate. The findings of this study may provide a new method for stem cell delivery, raising the prospect that intracerebral cell transplantation may be used to treat, for instance, ischemic stroke, traumatic brain injury, and so on.

Translating Therapeutic Microgels into Clinical Applications

Microgels are crosslinked, water-swollen networks with a 10 nm to 100 µm diameter and can be modified chemically or biologically to render them biocompatible for advanced clinical applications. Depending on their intended use, microgels require different mechanical and structural properties, which can be engineered on demand by altering the biochemical composition, crosslink density of the polymer network, and the fabrication method. Here, the fundamental aspects of microgel research and development, as well as their specific applications for theranostics and therapy in the clinic, are discussed. A detailed overview of microgel fabrication techniques with regards to their intended clinical application is presented, while focusing on how microgels can be employed as local drug delivery materials, scavengers, and contrast agents. Moreover, microgels can act as scaffolds for tissue engineering and regeneration application. Finally, an overview of microgels is given, which already made it into pre-clinical and clinical trials, while future challenges and chances are discussed. This review presents an instructive guideline for chemists, material scientists, and researchers in the biomedical field to introduce them to the fundamental physicochemical properties of microgels and guide them from fabrication methods via characterization techniques and functionalization of microgels toward specific applications in the clinic.

Exploring the Role of Stem Cell Therapy in Treating Neurodegenerative Diseases: Challenges and Current Perspectives

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Several human neurological disorders, such as Parkinson’s disease, Alzheimer’s disease, amyotrophic lateral sclerosis, Huntington’s disease, spinal cord injury, multiple sclerosis, and brain stroke, are caused by the injury to neurons or glial cells. The recent years have witnessed the successful generation of neurons and glia cells driving efforts to develop stem-cell-based therapies for patients to combat a broad spectrum of human neurological diseases. The inadequacy of suitable cell types for cell replacement therapy in patients suffering from neurological disorders has hampered the development of this promising therapeutic approach. Attempts are thus being made to reconstruct viable neurons and glial cells from different stem cells, such as embryonic stem cells, mesenchymal stem cells, and neural stem cells. Dedicated research to cultivate stem cell-based brain transplantation therapies has been carried out. We aim at compiling the breakthroughs in the field of stem cell-based therapy for the treatment of neurodegenerative maladies, emphasizing the shortcomings faced, victories achieved, and the future prospects of the therapy in clinical settings.

CD200 -dependent and -independent immune-modulatory functions of neural stem cells

Neural stem/precursor cells (NPC) exhibit powerful immune-modulatory properties. Attenuation of neuroinflammation by intra-cerebroventricular transplantation of NPC, protects from immune-mediated demyelination and axonal injury. The immune modulatory properties of NPC are mediated by a non-species-specific, multiple bystander effect, mediated by both direct cell-cell contact, and by soluble factor(s). CD200 is a cell-surface molecule, with important roles in regulating diverse immune responses, and shown also to limit neuroinflammatory processes. We hypothesized that CD200 may play a role in mediating immune-modulatory effects of NPC. We used wild type and CD200-deficient NPC to examine the role of CD200 in mediating two vital aspects of NPC -immune modulatory properties: (1) Attenuation of autoimmune neuroinflammation; and (2) Suppression of immune rejection response towards transplanted allogeneic NPC from the host CNS. We found that CD200 is dispensable for attenuating acute experimental autoimmune neuroinflammation, but is required for protecting transplanted allogeneic NPC from immune rejection by the host tissue. CD200 deficient NPC showed similar growth, differentiation and survival properties as wild type NPC. CD200-deficient NPC attenuated efficiently T cell activation and proliferation, but exhibited reduced ability to inhibit macrophages. We conclude that CD200 plays a partial role in mediating the immune-modulatory properties of NPC. The differential effect on T cells versus macrophages may underlie the observed discrepancy in their function in vivo.

Neural Stem Cells for Early Ischemic Stroke

Clinical treatments for ischemic stroke are limited. Neural stem cell (NSC) transplantation can be a promising therapy. Clinically, ischemia and subsequent reperfusion lead to extensive neurovascular injury that involves inflammation, disruption of the blood-brain barrier, and brain cell death. NSCs exhibit multiple potentially therapeutic actions against neurovascular injury. Currently, tissue plasminogen activator (tPA) is the only FDA-approved clot-dissolving agent. While tPA’s thrombolytic role within the vasculature is beneficial, tPA’s non-thrombolytic deleterious effects aggravates neurovascular injury, restricting the treatment time window (time-sensitive) and tPA eligibility. Thus, new strategies are needed to mitigate tPA’s detrimental effects and quickly mediate vascular repair after stroke. Up to date, clinical trials focus on the impact of stem cell therapy on neuro-restoration by delivering cells during the chronic stroke stage. Also, NSCs secrete factors that stimulate endogenous repair mechanisms for early-stage ischemic stroke. This review will present an integrated view of the preclinical perspectives of NSC transplantation as a promising treatment for neurovascular injury, with an emphasis on early-stage ischemic stroke. Further, this will highlight the impact of early sub-acute NSC delivery on improving short-term and long-term stroke outcomes.

Reliable generation of glial enriched progenitors from human fibroblast-derived iPSCs

White matter stroke (WMS) occurs as small infarcts in deep penetrating blood vessels in the brain and affects the regions of the brain that carry connections, termed the subcortical white matter. WMS progresses over years and has devastating clinical consequences. Unlike large grey matter strokes, WMS disrupts the axonal architecture of the brain and depletes astrocytes, oligodendrocyte lineage cells, axons and myelinating cells, resulting in abnormalities of gait and executive function. An astrocytic cell-based therapy is positioned as a strong therapeutic candidate after WMS. In this study we report, the reliable generation of a novel stem cell-based therapeutic product, glial enriched progenitors (GEPs) derived from human induced pluripotent stem cells (hiPSCs). By transient treatment of hiPSC derived neural progenitors (hiPSC-NPCs) with the small molecule deferoxamine, a prolyl hydroxylase inhibitor, for three days hiPSC-NPCs become permanently biased towards an astrocytic fate, producing hiPSC-GEPs. In preparation for clinical application, we have developed qualification assays to ensure identity, safety, purity, and viability of the cells prior to manufacture. Using tailored q-RT-PCR-based assays, we have demonstrated the lack of pluripotency in our final therapeutic candidate cells (hiPSC-GEPs) and we have identified the unique genetic profile of hiPSC-GEPs that is clearly distinct from the parent lines, hiPSCs and iPSC-NPCs. After completion of the viability assay, we have stablished the therapeutic window of use for hiPSC-GEPs in future clinical applications (7 h). Lastly, we were able to reliably and consistently produce a safe therapeutic final product negative for contamination by any human or murine viral pathogens, selected bacteria, common laboratory mycoplasmas, growth of any aerobes, anaerobes, yeast, or fungi and 100 times less endotoxin levels than the maximum acceptable value. This study demonstrates the reliable and safe generation of patient derived hiPSC-GEPs that are clinically ready as a cell-based therapeutic approach for WMS.

Transplantation of Human Cortically-Specified Neuroepithelial Progenitor Cells Leads to Improved Functional Outcomes in a Mouse Model of Stroke

Stroke is a leading cause of death and long-term disability worldwide. Current therapeutic options are limited in terms of their time for implementation and efficacy in promoting recovery. Cell transplantation has been shown to have promise in several animal models however significant challenges remain, including the optimal source of cells to promote neural repair. Here, we report on the use of a population of human ESC derived, cortically specified, neuroepithelial precursor cells (cNEPs) that are neurally restricted in their lineage potential. CNEPs have the potential to give rise to mature neural cell types following transplantation, including neurons, astrocytes and oligodendrocytes. With a view towards translation, we sought to determine whether this human cell source was effective in promoting improved functional outcomes following stroke. Undifferentiated cNEPs were transplanted in a pre-clinical endothelin-1 (ET-1) model of ischemic motor cortical stroke in immunocompromised SCID-beige mice and cellular and functional outcomes were assessed. We demonstrate that cNEP transplantation in the acute phase (4 days post-stroke) improves motor function as early as 20 days post-stroke, compared to stroke-injured, non-transplanted mice. At the time of recovery, a small fraction (<6%) of the transplanted cNEPs are observed within the stroke injury site. The surviving cells expressed the immature neuronal marker, doublecortin, with no differentiation into mature neural phenotypes. At longer survival times (40 days), the majority of recovered, transplanted mice had a complete absence of surviving cNEPS. Hence, human cNEPs grafted at early times post-stroke support the observed functional recovery following ET-1 stroke but their persistence is not required, thereby supporting a by-stander effect rather than cell replacement.

Photoreceptor precursor cell integration into rodent retina after treatment with novel glycopeptide PKX-001

Cell replacement therapy is emerging as an important approach in novel treatments for neurodegenerative diseases. Many problems remain, in particular improvements are needed in the survival of transplanted cells and increasing functional integration into host tissue. These problems arise because of immune rejection, suboptimal precursor cell type, trauma during cell transplantation, and toxic compounds released by dying tissues and nutritional deficiencies. We recently developed an ex vivo system to facilitate identification of factors contributing to the death of transplanted neuronal (photoreceptor) and showed 2.8-fold improvement in transplant cell survival after pretreatment with a novel glycopeptide (PKX-001). In this study, we extended these studies to look at cell survival, maturation, and functional integration in an in vivo rat model of rhodopsin-mutant retinitis pigmentosa causing blindness. We found that only when human photoreceptor precursor cells were preincubated with PKX-001 prior to transplantation, did the cells integrate and mature into cone photoreceptors expressing S-opsin or L/M opsin. In addition, ribbon synapses were observed in the transplanted cells suggesting they were making synaptic connections with the host tissue. Furthermore, optokinetic tracking and electroretinography responses in vivo were significantly improved compared to cell transplants without PKX-001 pre-treatment. These data demonstrate that PKX-001 promotes significant long-term stem cell survival in vivo, providing a platform for further investigation towards the clinical application to repair damaged or diseased retina.

Evaluation of the Effect of Hyaluronic Acid-Based Biomaterial Enriched With Tenascin-C on the Behavior of the Neural Stem Cells

One of the most important natural extracellular constituents is hyaluronic acid (HA) with the potential to develop a highly organized microenvironment. In the present study, we enriched HA hydrogel with tenascin-C (TN-C) and examined the viability and survival of mouse neural stem cells (NSCs) using different biological assays. Following NSCs isolation and expansion, their phenotype was identified using flow cytometry analysis. Cell survival was measured using MTT assay and DAPI staining after exposure to various concentrations of 50, 100, 200, and 400 nM TN-C. Using acridine orange/ethidium bromide staining, we measured the number of live and necrotic cells after exposure to the combination of HA and TN-C. MTT assay revealed the highest NSCs viability rate in the group exposed to 100 nM TN-C compared to other groups, and a combination of 1% HA + 100 nM TN-C increased the viability of NSCs compared to the HA group after 24 hours. Electron scanning microscopy revealed the higher attachment of these cells to the HA + 100 nM TN-C substrate relative to the HA substrate. Epifluorescence imaging and DAPI staining of loaded cells on HA + 100 nM TN-C substrate significantly increased the number of NSCs per field over 72 hours compared to the HA group (P < 0.05). Live and dead assay revealed that the number of live NSCs significantly increased in the HA + 100 TN-C group compared to HA and control groups. The enrichment of HA substrate with TN-C promoted viability and survival of NSCs and could be applied in neural tissue engineering approaches and regenerative medicine.

Prospects of Therapeutic Target and Directions for Ischemic Stroke

Stroke is a serious, adverse neurological event and the third leading cause of death and disability worldwide. Most strokes are caused by a block in cerebral blood flow, resulting in neurological deficits through the death of brain tissue. Recombinant tissue plasminogen activator (rt-PA) is currently the only immediate treatment medication for stroke. The goal of rt-PA administration is to reduce the thrombus and/or embolism via thrombolysis; however, the administration of rt-PA must occur within a very short therapeutic timeframe (3 h to 6 h) after symptom onset. Components of the pathological mechanisms involved in ischemic stroke can be used as potential biomarkers in current treatment. However, none are currently under investigation in clinical trials; thus, further studies investigating biomarkers are needed. After ischemic stroke, microglial cells can be activated and release inflammatory cytokines. These cytokines lead to severe neurotoxicity via the overactivation of microglia in prolonged and lasting insults such as stroke. Thus, the balanced regulation of microglial activation may be necessary for therapy. Stem cell therapy is a promising clinical treatment strategy for ischemic stroke. Stem cells can increase the functional recovery of damaged tissue after post-ischemic stroke through various mechanisms including the secretion of neurotrophic factors, immunomodulation, the stimulation of endogenous neurogenesis, and neovascularization. To investigate the use of stem cell therapy for neurological diseases in preclinical studies, however, it is important to develop imaging technologies that are able to evaluate disease progression and to “chase” (i.e., track or monitor) transplanted stem cells in recipients. Imaging technology development is rapidly advancing, and more sensitive techniques, such as the invasive and non-invasive multimodal techniques, are under development. Here, we summarize the potential risk factors and biomarker treatment strategies, stem cell-based therapy and emerging multimodal imaging techniques in the context of stroke. This current review provides a conceptual framework for considering the therapeutic targets and directions for the treatment of brain dysfunctions, with a particular focus on ischemic stroke.

Bone marrow-derived NCS-01 cells for ischemic stroke

Stroke stands as one of the most common causes of death among adults worldwide. Currently, tissue plasminogen activator serves as the only approved drug by the Food and Drug Administration for the treatment of acute ischemic stroke. Stem cell therapy serves as a viable treatment option and has been deemed as a safe and effective treatment for stroke patients. Adult human bone marrow-derived NCS-01 cells serve as a potential treatment for stroke given their ability to reduce stroke-induced pathological deficits by increasing cell viability and mitochondrial activity. Recently, we demonstrated the use of adult bone marrow-derived NCS-01 cells both on both in vitro and in vivo models. Using NCS-01 cells in rat stroke models subjected to middle cerebral artery occlusion, an effective dosage of 7.5 × 10⁶ cells/ml, administered through the intracarotid artery within 3 days poststroke, was shown to display significant improvements in motor and neurological behaviors, reductions in infarct area, and peri-infarct cell loss. NCS-01 cells, in comparison with other lines of stem cells (Li cells), are shown to produce greater therapeutic effects, most likely due to the observed filopodia formation that allows the stem cells to extend and target the ischemic cells. Given these findings, NCS-01 stem cells serve as a potential treatment for stroke through the demonstration of profound efficacy and further research that favors their filopodia-mediated mechanism of action.

The Neuronal Regeneration of Adult Zebrafish After Spinal Cord Injury Is Enhanced by Transplanting Optimized Number of Neural Progenitor Cells

Cell transplantation is commonly used to study the regeneration and repair of the nervous system in animals. However, a technical platform used to evaluate the optimum number of transplanted cells in the recipient’s spinal cord is little reported. Therefore, to develop such platform, we used a zebrafish model, which has transparent embryos, and transgenic line huORFZ, which generates green fluorescent protein (GFP)-expressing cells in the central nervous system under hypoxic stress. After GFP-expressing cells, also termed as hypoxia-responsive recovering cells, were obtained from hypoxia-exposed huORFZ embryos, we transplanted these GFP-(+) cells into the site of spinal cord injury (SCI) in adult wild-type zebrafish, followed by assessing the relationship between number of transplanted cells and the survival rate of recipients. When 100, 300, 500, and 1,000 GFP-(+) donor cells were transplanted into the lesion site of SCI-treated recipients, we found that recipient adult zebrafish transplanted with 300 donor cells had the highest survival rate. Those GFP-(+) donor cells could undergo proliferation and differentiation into neuron in recipients. Furthermore, transplantation of GFP-(+) cells into adult zebrafish treated with SCI was able to enhance the neuronal regeneration of recipients. In contrast, those fish transplanted with over 500 cells showed signs of inflammation around the SCI site, resulting in higher mortality. In this study, we developed a technological platform for transplanting cells into the lesion site of SCI-treated adult zebrafish and defined the optimum number of successfully transplanted cells into recipients, as 300, and those GFP-(+) donor cells could enhance recipient’s spinal cord regeneration. Thus, we provided a practical methodology for studying cell transplantation therapy in neuronal regeneration of zebrafish after SCI.

Therapeutic Potential of Umbilical Cord Stem Cells for Liver Regeneration

The liver is a vital organ for life and the only internal organ that is capable of natural regeneration. Although the liver has high regeneration capacity, excessive hepatocyte death can lead to liver failure. Various factors can lead to liver damage including drug abuse, some natural products, alcohol, hepatitis, and autoimmunity. Some models for studying liver injury are APAP-based model, Fas ligand (FasL), D-galactosamine/endotoxin (Gal/ET), Concanavalin A, and carbon tetrachloride-based models. The regeneration of the liver can be carried out using umbilical cord blood stem cells which have various advantages over other stem cell types used in liver transplantation. UCB-derived stem cells lack tumorigenicity, have karyotype stability and high immunomodulatory, low risk of graft versus host disease (GVHD), low risk of transmitting somatic mutations or viral infections, and low immunogenicity. They are readily available and their collection is safe and painless. This review focuses on recent development and modern trends in the use of umbilical cord stem cells for the regeneration of liver fibrosis.

Stem Cell Repair of the Microvascular Damage in Stroke

Stroke is a life-threatening disease that leads to mortality, with survivors subjected to long-term disability. Microvascular damage is implicated as a key pathological feature, as well as a therapeutic target for stroke. In this review, we present evidence detailing subacute diaschisis in a focal ischemic stroke rat model with a focus on blood–brain barrier (BBB) integrity and related pathogenic processes in contralateral brain areas. Additionally, we discuss BBB competence in chronic diaschisis in a similar rat stroke model, highlighting the pathological changes in contralateral brain areas that indicate progressive morphological brain disturbances overtime after stroke onset. With diaschisis closely approximating stroke onset and progression, it stands as a treatment of interest for stroke. Indeed, the use of stem cell transplantation for the repair of microvascular damage has been investigated, demonstrating that bone marrow stem cells intravenously transplanted into rats 48 h post-stroke survive and integrate into the microvasculature. Ultrastructural analysis of transplanted stroke brains reveals that microvessels display a near-normal morphology of endothelial cells and their mitochondria. Cell-based therapeutics represent a new mechanism in BBB and microvascular repair for stroke.

Intracerebral transplantation of HLA-homozygous human iPSC-derived neural precursors ameliorates the behavioural and pathological deficits in a rodent model of ischaemic stroke

OBJECTIVES

Human-induced pluripotent stem cells (hiPSCs) are a promising cell source for treating ischaemic stroke. Although autologous hiPSCs provide the advantage of avoiding immune rejection, their practical limitations, such as substantial amount of time and costs to generate individual iPSC lines, have hampered their widespread application in clinical settings. In this study, we investigated the therapeutic potential of neural precursor cells derived from human HLA-homozygous induced pluripotent stem cells (hiPSC-NPCs) following intracerebral transplantation into a rodent model of middle cerebral artery occlusion (MCAo).

MATERIALS AND METHODS

We differentiated a GMP-grade HLA-homozygous hiPSC line (CMC-hiPSC-004) into neural precursor cells for transplantation into rats at the subacute stage of ischaemic stroke (ie at 7 days after the induction of MCAo). To investigate functional recovery, the transplanted animals were subjected to five behavioural tests, namely the rotarod, stepping, mNSS, staircase and apomorphine-induced rotation tests, for up to 12 weeks, followed by histological analyses.

RESULTS

We observed that the hiPSC-NPC transplantation produced significant behavioural improvements. At 12 weeks post-transplantation, a high proportion of transplanted cells survived and had differentiated into MAP2⁺ mature neurons, GABAergic neurons and DARPP32⁺ medium spiny neurons. The transplanted cells formed neuronal connections with striatal neurons in the host brain. In addition, hiPSC-NPC transplantation gave rise to enhanced endogenous repair processes, including decreases of post-stroke neuroinflammation and glial scar formation and an increase of proliferating endogenous neural stem cells in the subventricular zone as well as the perilesional capillary networks.

CONCLUSIONS

These results strongly suggest that HLA-homozygous hiPSC-NPCs may be useful for treating ischaemic stroke patients.

Cortical Transplantation of Brain-Mimetic Glycosaminoglycan Scaffolds and Neural Progenitor Cells Promotes Vascular Regeneration and Functional Recovery after Ischemic Stroke in Mice

Stroke causes significant mortality and morbidity. Currently, there are no treatments which can regenerate brain tissue lost to infarction. Neural progenitor cells (NPCs) are at the forefront of preclinical studies for regenerative stroke therapies. NPCs can differentiate into and replace neurons and promote endogenous recovery mechanisms such as angiogenesis via trophic factor production and release. The stroke core is hypothetically the ideal location for replacement of neural tissue since it is in situ and develops into a potential space where injections may be targeted with minimal compression of healthy peri-infarct tissue. However, the compromised perfusion and tissue degradation following ischemia create an inhospitable environment resistant to cellular therapy. Overcoming these limitations is critical to advancing cellular therapy. In this work, the therapeutic potential of mouse-induced pluripotent stem cell derived NPCs is tested encapsulated in a basic fibroblast growth factor (bFGF) binding chondroitin sulfate-A (CS-A) hydrogel transplanted into the infarct core in a mouse sensorimotor cortex mini-stroke model. It is shown that CS-A encapsulation significantly improves vascular remodeling, cortical blood flow, and sensorimotor behavioral outcomes after stroke. It is found these improvements are negated by blocking bFGF, suggesting that the sustained trophic signaling endowed by the CS-A hydrogel combined with NPC transplantation can promote tissue repair.

Multiparametric classification of sub-acute ischemic stroke recovery with ultrafast diffusion, 23 Na, and MPIO-labeled stem cell MRI at 21.1 T

MRI leverages multiple modes of contrast to characterize stroke. High-magnetic-field systems enhance the performance of these MRI measurements. Previously, we have demonstrated that individually sodium and stem cell tracking metrics are enhanced at ultrahigh field in a rat model of stroke, and we have developed robust single-scan diffusion-weighted imaging approaches that utilize spatiotemporal encoding (SPEN) of the apparent diffusion coefficient (ADC) for these challenging field strengths. Here, we performed a multiparametric study of middle cerebral artery occlusion (MCAO) biomarker evolution focusing on comparison of these MRI biomarkers for stroke assessment during sub-acute recovery in rat MCAO models at 21.1 T. T₂ -weighted MRI was used as the benchmark for identification of the ischemic lesion over the course of the study. The number of MPIO-induced voids measured by gradient-recalled echo, the SPEN measurement of ADC, and ²³ Na MRI values were determined in the ischemic area and contralateral hemisphere, and relative performances for stroke classification were compared by receiver operator characteristic analysis. These measurements were associated with unique time-dependent trajectories during stroke recovery that changed the sensitivity and specificity for stroke monitoring during its evolution. Advantages and limitations of these contrasts, and the use of ultrahigh field for multiparametric stroke assessment, are discussed.

Translating intracarotid artery transplantation of bone marrow-derived NCS-01 cells for ischemic stroke: Behavioral and histological readouts and mechanistic insights into stem cell therapy

The present study used in vitro and in vivo stroke models to demonstrate the safety, efficacy, and mechanism of action of adult human bone marrow‐derived NCS‐01 cells. Coculture with NCS‐01 cells protected primary rat cortical cells or human neural progenitor cells from oxygen glucose deprivation. Adult rats that were subjected to middle cerebral artery occlusion, transiently or permanently, and subsequently received intracarotid artery or intravenous transplants of NCS‐01 cells displayed dose‐dependent improvements in motor and neurological behaviors, and reductions in infarct area and peri‐infarct cell loss, much better than intravenous administration. The optimal dose was 7.5 × 10⁶ cells/mL when delivered via the intracarotid artery within 3 days poststroke, although therapeutic effects persisted even when administered at 1 week after stroke. Compared with other mesenchymal stem cells, NCS‐01 cells ameliorated both the structural and functional deficits after stroke through a broad therapeutic window. NCS‐01 cells secreted therapeutic molecules, such as basic fibroblast growth factor and interleukin‐6, but equally importantly we observed for the first time the formation of filopodia by NCS‐01 cells under stroke conditions, characterized by cadherin‐positive processes extending from the stem cells toward the ischemic cells. Collectively, the present efficacy readouts and the novel filopodia‐mediated mechanism of action provide solid lab‐to‐clinic evidence supporting the use of NCS‐01 cells for treatment of stroke in the clinical setting.

Neural stem cell therapy for neurovascular injury in Alzheimer's disease

Alzheimer's disease (AD), the most common form of dementia, is characterized by progressive neurodegeneration leading to severe cognitive decline and eventual death. AD pathophysiology is complex, but neurotoxic accumulation of amyloid-β (Aβ) and hyperphosphorylation of Tau are believed to be main drivers of neurodegeneration in AD. The formation and deposition of Aβ plaques occurs in the brain parenchyma as well as in the cerebral vasculature. Thus, proper blood-brain barrier (BBB) and cerebrovascular functioning are crucial for clearance of Aβ from the brain, and neurovascular dysfunction may be a critical component of AD development. Further, neuroinflammation and dysfunction of angiogenesis, neurogenesis, and neurorestorative capabilities play a role in AD pathophysiology. Currently, there is no effective treatment to prevent or restore loss of brain tissue and cognitive decline in patients with AD. Based on multifactorial and complex pathophysiological cascades in multiple Alzheimer's disease stages, effective AD therapies need to focus on targeting early AD pathology and preserving cerebrovascular function. Neural stem cells (NSCs) participate extensively in mammalian brain homeostasis and repair and exhibit pleiotropic intrinsic properties that likely make them attractive candidates for the treatment of AD. In the review, we summarize the current advances in knowledge regarding neurovascular aspects of AD-related neurodegeneration and discuss multiple actions of NSCs from preclinical studies of AD to evaluate their potential for future clinical treatment of AD.

A NeuroD1 AAV-Based Gene Therapy for Functional Brain Repair after Ischemic Injury through In Vivo Astrocyte-to-Neuron Conversion

Adult mammalian brains have largely lost neuroregeneration capability except for a few niches. Previous studies have converted glial cells into neurons, but the total number of neurons generated is limited and the therapeutic potential is unclear. Here, we demonstrate that NeuroD1-mediated in situ astrocyte-to-neuron conversion can regenerate a large number of functional new neurons after ischemic injury. Specifically, using NeuroD1 adeno-associated virus (AAV)-based gene therapy, we were able to regenerate one third of the total lost neurons caused by ischemic injury and simultaneously protect another one third of injured neurons, leading to a significant neuronal recovery. RNA sequencing and immunostaining confirmed neuronal recovery after cell conversion at both the mRNA level and protein level. Brain slice recordings found that the astrocyte-converted neurons showed robust action potentials and synaptic responses at 2 months after NeuroD1 expression. Anterograde and retrograde tracing revealed long-range axonal projections from astrocyte-converted neurons to their target regions in a time-dependent manner. Behavioral analyses showed a significant improvement of both motor and cognitive functions after cell conversion. Together, these results demonstrate that in vivo cell conversion technology through NeuroD1-based gene therapy can regenerate a large number of functional new neurons to restore lost neuronal functions after injury.

Concise Review: Stem Cell Therapy for Stroke Patients: Are We There Yet?

Four decades of preclinical research demonstrating survival, functional integration, and behavioral effects of transplanted stem cells in experimental stroke models have provided ample scientific basis for initiating limited clinical trials of stem cell therapy in stroke patients. Although safety of the grafted cells has been overwhelmingly documented, efficacy has not been forthcoming. Two recently concluded stroke clinical trials on mesenchymal stem cells (MSCs) highlight the importance of strict adherence to the basic science findings of optimal transplant regimen of cell dose, timing, and route of delivery in enhancing the functional outcomes of cell therapy. Echoing the Stem Cell Therapeutics as an Emerging Paradigm for Stroke and Stroke Treatment Academic Industry Roundtable call for an NIH‐guided collaborative consortium of multiple laboratories in testing the safety and efficacy of stem cells and their derivatives, not just as stand‐alone but preferably in combination with approved thrombolytic or thrombectomy, may further increase the likelihood of successful fruition of translating stem cell therapy for stroke clinical application. The laboratory and clinical experience with MSC therapy for stroke may guide the future translational research on stem cell‐based regenerative medicine in neurological disorders. stem cells translational medicine2019;8:983&988

D-mannose-Coating of Maghemite Nanoparticles Improved Labeling of Neural Stem Cells and Allowed Their Visualization by ex vivo MRI after Transplantation in the Mouse Brain

Magnetic resonance imaging (MRI) of superparamagnetic iron oxide-labeled cells can be used as a non-invasive technique to track stem cells after transplantation. The aim of this study was to (1) evaluate labeling efficiency of D-mannose-coated maghemite nanoparticles (D-mannose(γ-Fe2O3)) in neural stem cells (NSCs) in comparison to the uncoated nanoparticles, (2) assess nanoparticle utilization as MRI contrast agent to visualize NSCs transplanted into the mouse brain, and (3) test nanoparticle biocompatibility. D-mannose(γ-Fe2O3) labeled the NSCs better than the uncoated nanoparticles. The labeled cells were visualized by ex vivo MRI and their localization subsequently confirmed on histological sections. Although the progenitor properties and differentiation of the NSCs were not affected by labeling, subtle effects on stem cells could be detected depending on dose increase, including changes in cell proliferation, viability, and neurosphere diameter. D-mannose coating of maghemite nanoparticles improved NSC labeling and allowed for NSC tracking by ex vivo MRI in the mouse brain, but further analysis of the eventual side effects might be necessary before translation to the clinic.

Therapeutic strategy against ischemic stroke with the concept of neurovascular unit

Stroke is one of the leading causes of death and disability globally. Although thrombolytic therapy by t-PA and mechanical thrombectomy have improved outcomes of ischemic stroke patients, both of these approaches are applicable to limited numbers of patients owing to their time constraints. Therefore, development of other treatment approaches such as developing neuroprotective drugs and nerve regeneration therapy is required to overcome ischemic stroke. The concept of the neurovascular unit (NVU) was formalized by the Stroke Progress Review Group of the National Institute of Neurological Disorders and Stroke in 2001. This concept emphasizes the importance not just of neurons but of the interactions between neurons, endothelial cells, astroglia, microglia and associated tissue matrix proteins to investigate the pathological condition of ischemic stroke. Many reports have been published about these interactions. This review focuses on the roles of cells that surround cerebral vasculature, especially endothelial cells, and reports therapeutic strategies against ischemic stroke from four points of view including angiogenesis, neurotrophic effects, protection of NVU components and regenerative therapy.

SUMOylation promotes survival and integration of neural stem cell grafts in ischemic stroke

Background

Neural stem cell (NSC)-based therapies hold great promise for treating diseases of the central nervous system (CNS). However, several fundamental problems still need to be overcome to fully exploit the clinical potential of NSC therapeutics. Chief among them is the limited survival of NSC grafts within hostile microenvironments.

Methods

Herein, we sought to engineer NSCs in an effort to increase graft survival within ischemic brain lesions via upregulation of global SUMOylation, a post-translational modification critically involved in mediating tolerance to ischemia/reperfusion.

Findings

NSCs overexpressing the SUMO E2-conjugase Ubc9 displayed resistance to oxygen-glucose-deprivation/restoration of oxygen/glucose (OGD/ROG) and enhanced neuronal differentiation in vitro, as well as increased survival and neuronal differentiation when transplanted in mice with transient middle cerebral artery occlusion in vivo.

Interpretation

Our work highlights a critical role for SUMOylation in NSC biology and identifies a biological pathway that can be targeted to increase the effectiveness of exogenous stem cell medicines in ischemic stroke.

Fund

Intramural Research Program of the NINDS/NIH, the Italian Multiple Sclerosis Foundation (FISM), the Bascule Charitable Trust, NIH-IRTA-OxCam and Wellcome Trust Research Training Fellowships.

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Ubc9-overexpressing NSCs demonstrate enhanced neuronal differentiation.

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Upregulating SUMOylation in NSCs increases resistance to ischemia/reperfusion in vitro.

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Ubc9-overexpressing NSC grafts robustly integrate within the brain of mice post-stroke.

Intra-arterial administration of cell-based biological agents for ischemic stroke therapy

INTRODUCTION

Ischemic stroke is becoming a primary cause of disability and death worldwide. To date, therapeutic options remain limited focusing on mechanical thrombolysis or administration of thrombolytic agents. However, these therapies do not promote neuroprotection and neuro-restoration of the ischemic area of the brain.

AREAS COVERED

This review highlights the option of minimal invasive, intra-arterial, administration of biological agents for stroke therapy. The authors provide an update of all available studies, discuss issues that influence outcomes and describe future perspectives which aim to improve clinical outcomes. New therapeutic options based on cellular and molecular interactions following an ischemic brain event, will be highlighted.

EXPERT OPINION

Intra-arterial administration of biological agents during trans-catheter thrombolysis or thrombectomy could limit neuronal cell death and facilitate regeneration or neurogenesis following ischemic brain injury. Despite the initial progress, further meticulous studies are needed in order to establish the clinical use of stem cell-induced neuroprotection and neuroregeneration.

Vascularization and Engraftment of Transplanted Human Cerebral Organoids in Mouse Cortex

Neural stem cells (NSCs) hold great promise for neural repair in cases of CNS injury and neurodegeneration; however, conventional cell-based transplant methods face the challenges of poor survival and inadequate neuronal differentiation. Here, we report an alternative, tissue-based transplantation strategy whereby cerebral organoids derived from human pluripotent stem cells (PSCs) were grafted into lesioned mouse cortex. Cerebral organoid transplants exhibited enhanced survival and robust vascularization from host brain as compared to transplants of dissociated neural progenitor cells (NPCs). Engrafted cerebral organoids harbored a large NSC pool and displayed multilineage neurodifferentiation at two and four weeks after grafting. Cerebral organoids therefore represent a promising alternative source to NSCs or fetal tissues for transplantation, as they contain a large set of neuroprogenitors and differentiated neurons in a structured organization. Engrafted cerebral organoids may also offer a unique experimental paradigm for modeling human neurodevelopment and CNS diseases in the context of vascularized cortical tissue.

Transplantation of human dental pulp stem cells ameliorates brain damage following acute cerebral ischemia

AIMS

Numerous experimental studies have shown that cellular therapy, including human dental pulp stem cells (DPSCs), is an attractive strategy for ischemic brain injury. Herein, we examined the effects of intravenous DPSC administration after transient middle cerebral artery occlusion in rats.

METHODS

Male Sprague-Dawley rats received a transient 90 min middle cerebral artery occlusion. DPSCs (1 × 10⁶ cells) or vehicle were administered via the femoral vein at 0 h or 3 h after ischemia-reperfusion. PKH26, a red fluorescent cell linker, was used to track the transplanted cells in the brain. Infarct volume, neurological deficits, and immunological analyses were performed at 24 h and 72 h after reperfusion.

RESULTS

PKH26-positive cells were observed more frequently in the ipsilateral than the contralateral hemisphere. DPSCs transplanted at 0 h after reperfusion significantly reduced infarct volume and reversed motor deficits at 24 h and 72 h recovery. DPSCs transplanted at 3 h after reperfusion also significantly reduced infarct volume and improved motor function compared with vehicle groups at 24 h and 72 h recovery. Further, DPSC transplantation significantly inhibited microglial activation and pro-inflammatory cytokine expression compared with controls at 72 h after reperfusion. Moreover, DPSCs attenuated neuronal degeneration in the cortical ischemic boundary area.

CONCLUSIONS

Systemic delivery of human DPSCs after reperfusion reduced ischemic damage and improved functional recovery in a rodent ischemia model, with a clinically relevant therapeutic window. The neuroprotective action of DPSCs may relate to the modulation of neuroinflammation during the acute phase of stroke.

Neuroglobin promotes neurogenesis through Wnt signaling pathway

Neuroglobin (Ngb) has been demonstrated by our lab and others to be neuroprotective against neurological disorders including stroke. However, the roles of Ngb in neurogenesis remain elusive. Neurogenesis can occur in adulthood and can be induced by pathological conditions in the brain such as stroke, and significantly contributes to functional recovery, thus enhancing endogenous neurogenesis may be a promising therapeutic strategy for neurodegenerative diseases. In this study we aimed to investigate the roles of Ngb in neurogenesis using Lentivirus overexpressing Ngb (Lv-Ngb). We show that Ngb overexpression promoted the proliferation of neural progenitor cells (NPC) marked by increased neurosphere number and size. Ngb overexpression also enhanced neuronal differentiation of cultured NPC under differentiation conditions. Moreover, subventricular injection of Lv-Ngb in mice after middle cerebral artery occlusion (MCAO) increased PSA-NCAM positive neuroblasts and Tuj1 positive immature neurons, suggesting that Ngb overexpression promotes neurogenesis in mice brain after stroke. We further show that the pro-neurogenesis effect of Ngb overexpression might be mediated through Dvl1 up-regulation, and subsequent activation of Wnt signaling, indicated by increased nuclear localization of beta-catenin. These results suggest that Ngb may play an important role in promoting neurogenesis in neurodegenerative diseases such as stroke, which may eventually benefit the development of stroke therapeutics targeting neurogenesis through Ngb upregulation.

Safety and Optimization of Metabolic Labeling of Endothelial Progenitor Cells for Tracking

Metabolic labeling is one of the most powerful methods to label the live cell for in vitro and in vivo tracking. However, the cellular mechanisms by modified glycosylation due to metabolic agents are not fully understood. Therefore, metabolic labeling has not yet been widely used in EPC tracking and labeling. In this study, cell functional properties such as proliferation, migration and permeability and gene expression patterns of metabolic labeling agent-treated hUCB-EPCs were analyzed to demonstrate cellular effects of metabolic labeling agents. As the results, 10 μM Ac4ManNAz treatment had no effects on cellular function or gene regulations, however, higher concentration of Ac4ManNAz (>20 μM) led to the inhibition of functional properties (proliferation rate, viability and rate of endocytosis) and down-regulation of genes related to cell adhesion, PI3K/AKT, FGF and EGFR signaling pathways. Interestingly, the new blood vessel formation and angiogenic potential of hUCB-EPCs were not affected by Ac4ManNAz concentration. Based on our results, we suggest 10 μM as the optimal concentration of Ac4ManNAz for in vivo hUCB-EPC labeling and tracking. Additionally, we expect that our approach can be used for understanding the efficacy and safety of stem cell-based therapy in vivo.

Human umbilical cord tissue stem cells and neuronal lineages in an injectable caffeic acid-bioconjugated gelatin hydrogel for transplantation

Present-day scaffolds are useful in cell therapy to a reasonable extent, but in pursuit of improvising the scaffold to improve the outcome, we tested a new injectable caffeic acid-bioconjugated gelatin hydrogel scaffold (CBGH; with tunable stiffness -10%). Two-dimensional (2D) form of human umbilical cord tissue-derived mesenchymal stem cells (HUCMSCs) culture performed based on our previously reported methods and characterized by using multipotent and pluripotent analysis. In addition, neurogenesis was induced in the presence of retinoic acid or neural growth factor or epidermal growth factor categorized by neuronal markers. The viability, proliferation rate, and vascular endothelial growth factor expression of HUCMSCs increased significantly in the CBGH scaffold. In addition, there was an increase in CD90 and TRA-1-81 phenotypic expressions and SOX-2, MAP-2, TAU, NeuN, and NF, which confirmed the neurogenesis of encapsulated HUCMSCs. Topographical elucidation by scanning electron microscopy data showed that the HUCMSCs proliferated and migrated inside the construct. Hematoxylin and eosin staining demonstrated a more viable structural pattern and cresyl violet staining showed the Nissl synthesis, confirming the presence of functional neurons in the encapsulated form. The molecular-level analysis further substantiated that HUCMSCs cultured in CBGH expressed significantly greater upregulation of stemness, neuronal genes, and protein expression compared with the adherent culture. Correspondingly, this is the first time that we have measured the fluorescence intensity variation of the HUCMSCs-stained cell segmentation process using customized MATLAB code execution to reduce the background noise and autofluorescence. We conclude that this novel CBGH scaffold increases the viability, proliferation, stemness, and also neuronal transdifferentiation of HUCMSCs in a three-dimensional culture than the 2D plastic adherent culture.

Preconditioning and Cellular Engineering to Increase the Survival of Transplanted Neural Stem Cells for Motor Neuron Disease Therapy

Despite the extensive research effort that has been made in the field, motor neuron diseases, namely, amyotrophic lateral sclerosis and spinal muscular atrophies, still represent an overwhelming cause of morbidity and mortality worldwide. Exogenous neural stem cell-based transplantation approaches have been investigated as multifaceted strategies to both protect and repair upper and lower motor neurons from degeneration and inflammation. Transplanted neural stem cells (NSCs) exert their beneficial effects not only through the replacement of damaged cells but also via bystander immunomodulatory and neurotrophic actions. Notwithstanding these promising findings, the clinical translatability of such techniques is jeopardized by the limited engraftment success and survival of transplanted cells within the hostile disease microenvironment. To overcome this obstacle, different methods to enhance graft survival, stability, and therapeutic potential have been developed, including environmental stress preconditioning, biopolymers scaffolds, and genetic engineering. In this review, we discuss current engineering techniques aimed at the exploitation of the migratory, proliferative, and secretive capacity of NSCs and their relevance for the therapeutic arsenal against motor neuron disorders and other neurological disorders.

Impact of Dental Pulp Stem Cells Overexpressing Hepatocyte Growth Factor after Cerebral Ischemia/Reperfusion in Rats

Hepatocyte growth factor (HGF) has neuroprotective effects against ischemia-induced injuries. Dental pulp stem cell (DPSC) transplantation attenuates tissue injury in the brain of rats with post-transient middle cerebral artery occlusion. We sought to determine whether DPSCs that overexpress HGF can enhance their therapeutic effects on brain damage post-ischemia/reperfusion injury. Treatment with DPSCs overexpressing HGF reduced infarct volumes compared to unmodified DPSC treatment at 3 and 7 days post-transient middle cerebral artery occlusion. The use of unmodified DPSCs and DPSCs overexpressing HGF was associated with improved motor function compared to that with administration of vehicle at 7 days post-transient middle cerebral artery occlusion. DPSCs overexpressing HGF significantly inhibited microglial activation and pro-inflammatory cytokine production along with suppression of neuronal degeneration. Post-reperfusion, DPSCs overexpressing HGF attenuated the decreases in tight junction proteins, maintained blood-brain barrier integrity, and increased microvessel density in peri-infarct areas. The administration of DPSCs overexpressing HGF during the acute phase of stroke increased their neuroprotective effects by modulating inflammation and blood-brain barrier permeability, thereby promoting improvements in post-ischemia/reperfusion brain injury.

In Vivo Long-Term Tracking of Neural Stem Cells Transplanted into an Acute Ischemic Stroke model with Reporter Gene-Based Bimodal MR and Optical Imaging

Transplantation of neural stem cells (NSCs) is emerging as a new therapeutic approach for stroke. Real-time imaging of transplanted NSCs is essential for successful cell delivery, safety monitoring, tracking cell fate and function, and understanding the interactions of transplanted cells with the host environment. Magnetic resonance imaging (MRI) of magnetic nanoparticle-labeled cells has been the most widely used means to track stem cells in vivo. Nevertheless, it does not allow for the reliable discrimination between live and dead cells. Reporter gene-based MRI was considered as an alternative strategy to overcome this shortcoming. In this work, a class of lentiviral vector-encoding ferritin heavy chain (FTH) and enhanced green fluorescent protein (EGFP) was constructed to deliver reporter genes into NSCs. After these transgenic NSCs were transplanted into the contralateral hemisphere of rats with acute ischemic stroke, MRI and fluorescence imaging (FLI) were performed in vivo for tracking the fate of transplanted cells over a long period of 6 wk. The results demonstrated that the FTH and EGFP can be effectively and safely delivered to NSCs via the designed lentiviral vector. The distribution and migration of grafted stem cells could be monitored by bimodal MRI and FLI. FTH can be used as a robust MRI reporter for reliable reporting of the short-term viability of cell grafts, whereas its capacity for tracking the long-term viability of stem cells remains dependent on several confounding factors such as cell death and the concomitant reactive inflammation.

Age of donor of human mesenchymal stem cells affects structural and functional recovery after cell therapy following ischaemic stroke

Cell transplantation therapy offers great potential to improve impairments after stroke. However, the importance of donor age on therapeutic efficacy is unclear. We investigated the regenerative capacity of transplanted cells focusing on donor age (young vs. old) for ischaemic stroke. The quantities of human mesenchymal stem cell (hMSC) secreted brain-derived neurotrophic factor in vitro and of monocyte chemotactic protein-1 at day 7 in vivo were both significantly higher for young hMSC compared with old hMSC. Male Sprague-Dawley rats subjected to transient middle cerebral artery occlusion that received young hMSC (trans-arterially at 24 h after stroke) showed better behavioural recovery with prevention of brain atrophy compared with rats that received old hMSC. Histological analysis of the peri-infarct cortex showed that rats treated with young hMSC had significantly fewer microglia and more vessels covered with pericytes. Interestingly, migration of neural stem/progenitor cells expressing Musashi-1 positively correlated with astrocyte process alignment, which was more pronounced for young hMSC. Aging of hMSC may be a critical factor that affects cell therapy outcomes, and transplantation of young hMSC appears to provide better functional recovery through anti-inflammatory effects, vessel maturation, and neurogenesis potentially by the dominance of trophic factor secretion.

Engineered stem cell mimics to enhance stroke recovery

Currently, no medical therapies exist to augment stroke recovery. Stem cells are an intriguing treatment option being evaluated, but cell-based therapies have several challenges including developing a stable cell product with long term reproducibility. Since much of the improvement observed from cellular therapeutics is believed to result from trophic factors the stem cells release over time, biomaterials are well-positioned to deliver these important molecules in a similar fashion. Here we show that essential trophic factors secreted from stem cells can be effectively released from a multi-component hydrogel system into the post-stroke environment. Using our polymeric system to deliver VEGF-A and MMP-9, we improved recovery after stroke to an equivalent degree as observed with traditional stem cell treatment in a rodent model. While VEGF-A and MMP-9 have many unique mechanisms of action, connective tissue growth factor (CTGF) interacts with both VEGF-A and MMP-9. With our hydrogel system as well as with stem cell delivery, the CTGF pathway is shown to be downregulated with improved stroke recovery.

Neural stem cell therapy for subacute and chronic ischemic stroke

Neural stem cells (NSCs) play vital roles in brain homeostasis and exhibit a broad repertoire of potentially therapeutic actions following neurovascular injury. One such injury is stroke, a worldwide leading cause of death and disability. Clinically, extensive injury from ischemic stroke results from ischemia-reperfusion (IR), which is accompanied by inflammation, blood-brain barrier (BBB) damage, neural cell death, and extensive tissue loss. Tissue plasminogen activator (tPA) is still the only US Food and Drug Administration-approved clot-lysing agent. Whereas the thrombolytic role of tPA within the vasculature is beneficial, the effects of tPA (in a non-thrombolytic role) within the brain parenchyma have been reported as harmful. Thus, new therapies are needed to reduce the deleterious side effects of tPA and quickly facilitate vascular repair following stroke. The Stroke Treatment Academic Industry Roundtable (STAIR) recommends that stroke therapies "focus on drugs/devices/treatments with multiple mechanisms of action and that target multiple pathways". Thus, based on multifactorial ischemic cascades in various stroke stages, effective stroke therapies need to focus on targeting and ameliorating early IR injury as well as facilitating angiogenesis, neurogenesis, and neurorestorative mechanisms following stroke. This review will discuss the preclinical perspectives of NSC transplantation as a promising treatment for neurovascular injury and will emphasize both the subacute and chronic phase of ischemic stroke.

Human neural stem cells dispersed in artificial ECM form cerebral organoids when grafted in vivo

Human neural stem cells (hNSC) derived from induced pluripotent stem cells can be differentiated into neurons that could be used for transplantation to repair brain injury. In this study we dispersed such hNSC in a three-dimensional artificial extracellular matrix (aECM) and compared their differentiation in vitro and following grafting into the sensorimotor cortex (SMC) of postnatal day (P)14 rat pups lesioned by localised injection of endothelin-1 at P12. After 10-43 days of in vitro differentiation, a few cells remained as PAX6⁺ neuroprogenitors but many more resembled post-mitotic neurons expressing doublecortin, β-tubulin and MAP2. These cells remained dispersed throughout the ECM, but with extended long processes for over 50 μm. In vivo, by 1 month post grafting, cells expressing human specific markers instead organised into cerebral organoids: columns of tightly packed PAX6 co-expressing progenitor cells arranged around small tubular lumen in rosettes, with a looser network of cells with processes around the outside co-expressing markers of immature neurons including doublecortin, and CTIP2 characteristic of corticofugal neurons. Host cells also invaded the graft including microglia, astrocytes and endothelial cells forming blood vessels. By 10 weeks post-grafting, the organoids had disappeared and the aECM had started to break down with fewer transplanted cells remaining. In vitro, cerebral organoids form in rotating incubators that force oxygen and nutrients to the centre of the structures. We have shown that cerebral organoids can form in vivo; intrinsic factors may direct their organisation including infiltration by host blood vessels.

Syngeneic Transplantation of Olfactory Ectomesenchymal Stem Cells Restores Learning and Memory Abilities in a Rat Model of Global Cerebral Ischemia

Stem cells are considered as promising tools to repair diverse tissue injuries. Among the different stem cell types, the “olfactory ectomesenchymal stem cells” (OE-MSCs) located in the adult olfactory mucosa stand as one of the best candidates. Here, we evaluated if OE-MSC grafts could decrease memory impairments due to ischemic injury. OE-MSCs were collected from syngeneic F344 rats. After a two-step global cerebral ischemia, inducing hippocampal lesions, learning abilities were evaluated using an olfactory associative discrimination task. Cells were grafted into the hippocampus 5 weeks after injury and animal's learning abilities reassessed. Rats were then sacrificed and the brains collected for immunohistochemical analyses. We observed significant impairments in learning and memory abilities following ischemia. However, 4 weeks after OE-MSC grafts, animals displayed learning and memory performances similar to those of controls, while sham rats did not improve them. Immunohistochemical analyses revealed that grafts promoted neuroblast and glial cell proliferation, which could permit to restore cognitive functions. These results demonstrated, for the first time, that syngeneic transplantations of OE-MSCs in rats can restore cognitive abilities impaired after brain injuries and provide support for the development of clinical studies based on grafts of OE-MSCs in amnesic patients following brain injuries.

Human Neural Stem/Progenitor Cells Derived From Epileptic Human Brain in a Self-Assembling Peptide Nanoscaffold Improve Traumatic Brain Injury in Rats

Traumatic brain injury (TBI) is a disruption in the brain functions following a head trauma. Cell therapy may provide a promising treatment for TBI. Among different cell types, human neural stem cells cultured in self-assembling peptide scaffolds have been suggested as a potential novel method for cell replacement treatment after TBI. In the present study, we accessed the effects of human neural stem/progenitor cells (hNS/PCs) derived from epileptic human brain and human adipose-derived stromal/stem cells (hADSCs) seeded in PuraMatrix hydrogel (PM) on brain function after TBI in an animal model of brain injury. hNS/PCs were isolated from patients with medically intractable epilepsy undergone epilepsy surgery. hNS/PCs and hADSCs have the potential for proliferation and differentiation into both neuronal and glial lineages. Assessment of the growth characteristics of hNS/PCs and hADSCs revealed that the hNS/PCs doubling time was significantly longer and the growth rate was lower than hADSCs. Transplantation of hNS/PCs and hADSCs seeded in PM improved functional recovery, decreased lesion volume, inhibited neuroinflammation, and reduced the reactive gliosis at the injury site. The data suggest the transplantation of hNS/PCs or hADSCs cultured in PM as a promising treatment option for cell replacement therapy in TBI.

Preconditioning of bone marrow mesenchymal stem cells with hydrogen sulfide improves their therapeutic potential

Bone marrow mesenchymal stem cells (BMSCs) transplantation has shown great promises for treating various brain diseases. However, poor viability of transplanted BMSCs in injured brain has limited the therapeutic efficiency. Hypoxia-ischemic injury is one of major mechanisms underlying the survival of transplanted BMSCs. We investigated the mechanism of preconditioning of BMSCs with hydrogen sulfide (H2S), which has been proposed as a novel therapeutic strategy for hypoxia-ischemic injury. In this study, we demonstrated that preconditioning of NaHS, a H2S donor, effectively suppressed hypoxia-ischemic-induced apoptosis whereby the rise in Bax/Bcl-2 ratio. Further analyses revealed Akt and ERK1/2 pathways were involved in the protective effects of NaHS. In addition, NaHS preconditioning increased secretion of BDNF and VEGF in BMSCs. Consistent with in vitro data, transplantation of NaHS preconditioned BMSCs in vivo further enhanced the therapeutic effects of BMSCs on neuronal injury and neurological recovery, associated with increased vessel density and upregulation of BDNF and VEGF in the ischemic tissue. These findings suggest that H2S could enhance the therapeutic effects of BMSCs. The underlying mechanisms might be due to enhanced capacity of BMSCs and upregulation of protective cytokines in the hypoxia tissue.

Hydrogels-Assisted Cell Engraftment for Repairing the Stroke-Damaged Brain: Chimera or Reality

The use of advanced biomaterials as a structural and functional support for stem cells-based therapeutic implants has boosted the development of tissue engineering applications in multiple clinical fields. In relation to neurological disorders, we are still far from the clinical reality of restoring normal brain function in neurodegenerative diseases and cerebrovascular disorders. Hydrogel polymers show unique mechanical stiffness properties in the range of living soft tissues such as nervous tissue. Furthermore, the use of these polymers drastically enhances the engraftment of stem cells as well as their capacity to produce and deliver neuroprotective and neuroregenerative factors in the host tissue. Along this article, we review past and current trends in experimental and translational research to understand the opportunities, benefits, and types of tentative hydrogel-based applications for the treatment of cerebral disorders. Although the use of hydrogels for brain disorders has been restricted to the experimental area, the current level of knowledge anticipates an intense development of this field to reach clinics in forthcoming years.

Potential of Stem Cell-Based Therapy for Ischemic Stroke

Ischemic stroke is one of the major health problems worldwide. The only FDA approved anti-thrombotic drug for acute ischemic stroke is the tissue plasminogen activator. Several studies have been devoted to assessing the therapeutic potential of different types of stem cells such as neural stem cells (NSCs), mesenchymal stem cells, embryonic stem cells, and human induced pluripotent stem cell-derived NSCs as treatments for ischemic stroke. The results of these studies are intriguing but many of them have presented conflicting results. Additionally, the mechanism(s) by which engrafted stem/progenitor cells exert their actions are to a large extent unknown. In this review, we will provide a synopsis of different preclinical and clinical studies related to the use of stem cell-based stroke therapy, and explore possible beneficial/detrimental outcomes associated with the use of different types of stem cells. Due to limited/short time window implemented in most of the recorded clinical trials about the use of stem cells as potential therapeutic intervention for stroke, further clinical trials evaluating the efficacy of the intervention in a longer time window after cellular engraftments are still needed.