Human iPSC for Therapeutic Approaches to the Nervous System: Present and Future Applications

Neuroprotection of Stem Cells Against Ischemic Brain Injury: From Bench to Clinic

Neurological injuries can have numerous debilitating effects on functional status including sensorimotor deficits, cognitive impairment, and behavioral symptoms. Despite the disease burden, treatment options remain limited. Current pharmacological interventions are targeted at symptom management but are ineffective in reversing ischemic brain damage. Stem cell therapy for ischemic brain injury has shown promising preclinical and clinical results and has attracted attention as a potential therapeutic option. Various stem cell sources (embryonic, mesenchymal/bone marrow, and neural stem cells) have been investigated. This review provides an overview of the advances made in our understanding of the various types of stem cells and progress made in the use of these stem cells for the treatment of ischemic brain injuries. In particular, the use of stem cell therapy in global cerebral ischemia following cardiac arrest and in focal cerebral ischemia after ischemic stroke are discussed. The proposed mechanisms of stem cells' neuroprotective effects in animal models (rat/mice, pig/swine) and other clinical studies, different routes of administration (intravenous/intra-arterial/intracerebroventricular/intranasal/intraperitoneal/intracranial) and stem cell preconditioning are discussed. Much of the promising data on stem cell therapies after ischemic brain injury remains in the experimental stage and several limitations remain unsettled. Future investigation is needed to further assess the safety and efficacy and to overcome the remaining obstacles.

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.

Exploring the promising potential of induced pluripotent stem cells in cancer research and therapy

The advent of iPSCs has brought about a significant transformation in stem cell research, opening up promising avenues for advancing cancer treatment. The formation of cancer is a multifaceted process influenced by genetic, epigenetic, and environmental factors. iPSCs offer a distinctive platform for investigating the origin of cancer, paving the way for novel approaches to cancer treatment, drug testing, and tailored medical interventions. This review article will provide an overview of the science behind iPSCs, the current limitations and challenges in iPSC-based cancer therapy, the ethical and social implications, and the comparative analysis with other stem cell types for cancer treatment. The article will also discuss the applications of iPSCs in tumorigenesis, the future of iPSCs in tumorigenesis research, and highlight successful case studies utilizing iPSCs in tumorigenesis research. The conclusion will summarize the advancements made in iPSC-based tumorigenesis research and the importance of continued investment in iPSC research to unlock the full potential of these cells.

Use of Brain-Derived Stem/Progenitor Cells and Derived Extracellular Vesicles to Repair Damaged Neural Tissues: Lessons Learned from Connective Tissue Repair Regarding Variables Limiting Progress and Approaches to Overcome Limitations

Pluripotent neural stem or progenitor cells (NSC/NPC) have been reported in the brains of adult preclinical models for decades, as have mesenchymal stem/stromal cells (MSC) been reported in a variety of tissues from adults. Based on their in vitro capabilities, these cell types have been used extensively in attempts to repair/regenerate brain and connective tissues, respectively. In addition, MSC have also been used in attempts to repair compromised brain centres. However, success in treating chronic neural degenerative conditions such as Alzheimer's disease, Parkinson's disease, and others with NSC/NPC has been limited, as have the use of MSC in the treatment of chronic osteoarthritis, a condition affecting millions of individuals. However, connective tissues are likely less complex than neural tissues regarding cell organization and regulatory integration, but some insights have been gleaned from the studies regarding connective tissue healing with MSC that may inform studies attempting to initiate repair and regeneration of neural tissues compromised acutely or chronically by trauma or disease. This review will discuss the similarities and differences in the applications of NSC/NPC and MSC, where some lessons have been learned, and potential approaches that could be used going forward to enhance progress in the application of cellular therapy to facilitate repair and regeneration of complex structures in the brain. In particular, variables that may need to be controlled to enhance success are discussed, as are different approaches such as the use of extracellular vesicles from stem/progenitor cells that could be used to stimulate endogenous cells to repair the tissues rather than consider cell replacement as the primary option. Caveats to all these efforts relate to whether cellular repair initiatives will have long-term success if the initiators for neural diseases are not controlled, and whether such cellular initiatives will have long-term success in a subset of patients if the neural diseases are heterogeneous and have multiple etiologies.

An Alternate Approach to Generate Induced Pluripotent Stem Cells with Precise CRISPR/Cas9 Tool

The induced pluripotent stem cells (iPSCs) are considered powerful tools in pharmacology, biomedicine, toxicology, and cell therapy. Multiple approaches have been used to generate iPSCs with the expression of reprogramming factors. Here, we generated iPSCs by integrating the reprogramming cassette into a genomic safe harbor, CASH-1, with the use of a precise genome editing tool, CRISPR/Cas9. The integration of cassette at CASH-1 into target cells did not alter the pattern of proliferation and interleukin-6 secretion as a response to ligands of multiple signaling pathways involving tumor necrosis factor-α receptor, interleukin-1 receptor, and toll-like receptors. Moreover, doxycycline-inducible expression of OCT4, SOX2, and KLF4 reprogrammed engineered human dermal fibroblasts and human embryonic kidney cell line into iPSCs. The generated iPSCs showed their potential to make embryoid bodies and differentiate into the derivatives of all three germ layers. Collectively, our data emphasize the exploitation of CASH-1 by CRISPR/Cas9 tool for therapeutic and biotechnological applications including but not limited to reprogramming of engineered cells into iPSCs.

Thioethers: An Overview

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Spreading rapidly in recent years, cancer has become one of the causes of the highest mor-tality rates after cardiovascular diseases. The reason for cancer development is still not clearly under-stood despite enormous research activities in this area. Scientists are now working on the biology of cancer, especially on the root cause of cancer development. The aim is to treat the cancer disease and thus cure the patients. The continuing efforts for the development of novel molecules as potential anti-cancer agents are essential for this purpose. The main aim of this review was to present a survey on the medicinal chemistry of thioethers and provide practical data on their cytotoxicities against various cancer cell lines. The research articles published between 2001-2020 were consulted to pre-pare this review article; however, patent literature has not been included. The thioether-containing heterocyclic compounds may emerge as a new class of potent and effective anti-cancer agents in the future.

The Application of Brain Organoid Technology in Stroke Research: Challenges and Prospects

Stroke is a neurological disease responsible for significant morbidity and disability worldwide. However, there remains a dearth of effective therapies. The failure of many therapies for stroke in clinical trials has promoted the development of human cell-based models, such as brain organoids. Brain organoids differ from pluripotent stem cells in that they recapitulate various key features of the human central nervous system (CNS) in three-dimensional (3D) space. Recent studies have demonstrated that brain organoids could serve as a new platform to study various neurological diseases. However, there are several limitations, such as the scarcity of glia and vasculature in organoids, which are important for studying stroke. Herein, we have summarized the application of brain organoid technology in stroke research, such as for modeling and transplantation purposes. We also discuss methods to overcome the limitations of brain organoid technology, as well as future prospects for its application in stroke research. Although there are many difficulties and challenges associated with brain organoid technology, it is clear that this approach will play a critical role in the future exploration of stroke treatment.

Optimizing Stem Cell Therapy after Ischemic Brain Injury

Stem cells have been used for regenerative and therapeutic purposes in a variety of diseases. In ischemic brain injury, preclinical studies have been promising, but have failed to translate results to clinical trials. We aimed to explore the application of stem cells after ischemic brain injury by focusing on topics such as delivery routes, regeneration efficacy, adverse effects, and in vivo potential optimization. PUBMED and Web of Science were searched for the latest studies examining stem cell therapy applications in ischemic brain injury, particularly after stroke or cardiac arrest, with a focus on studies addressing delivery optimization, stem cell type comparison, or translational aspects. Other studies providing further understanding or potential contributions to ischemic brain injury treatment were also included. Multiple stem cell types have been investigated in ischemic brain injury treatment, with a strong literature base in the treatment of stroke. Studies have suggested that stem cell administration after ischemic brain injury exerts paracrine effects via growth factor release, blood-brain barrier integrity protection, and allows for exosome release for ischemic injury mitigation. To date, limited studies have investigated these therapeutic mechanisms in the setting of cardiac arrest or therapeutic hypothermia. Several delivery modalities are available, each with limitations regarding invasiveness and safety outcomes. Intranasal delivery presents a potentially improved mechanism, and hypoxic conditioning offers a potential stem cell therapy optimization strategy for ischemic brain injury. The use of stem cells to treat ischemic brain injury in clinical trials is in its early phase; however, increasing preclinical evidence suggests that stem cells can contribute to the down-regulation of inflammatory phenotypes and regeneration following injury. The safety and the tolerability profile of stem cells have been confirmed, and their potent therapeutic effects make them powerful therapeutic agents for ischemic brain injury patients.

Transplanting neural progenitor cells to restore connectivity after spinal cord injury

Spinal cord injury remains a scientific and therapeutic challenge with great cost to individuals and society. The goal of research in this field is to find a means of restoring lost function. Recently we have seen considerable progress in understanding the injury process and the capacity of CNS neurons to regenerate, as well as innovations in stem cell biology. This presents an opportunity to develop effective transplantation strategies to provide new neural cells to promote the formation of new neuronal networks and functional connectivity. Past and ongoing clinical studies have demonstrated the safety of cell therapy, and preclinical research has used models of spinal cord injury to better elucidate the underlying mechanisms through which donor cells interact with the host and thus increase long-term efficacy. While a variety of cell therapies have been explored, we focus here on the use of neural progenitor cells obtained or derived from different sources to promote connectivity in sensory, motor and autonomic systems.

Stem Cell Extracellular Vesicles and their Potential to Contribute to the Repair of Damaged CNS Cells

Neurological diseases and disorders are leading causes of death and disability worldwide. Many of these pathologies are associated with high levels of neuroinflammation and irreparable tissue damage. As the global burden of these pathologies continues to rise there is a significant need for the development of novel therapeutics. Due to their multipotent properties, stem cells have broad applications for tissue repair; additionally, stem cells have been shown to possess both immunomodulatory and neuroprotective properties. It is now believed that paracrine factors, such as extracellular vesicles (EVs), play a critical role in the functionality associated with stem cells. The diverse biological cargo contained within EVs are proposed to mediate these effects and, to date, the reparative and regenerative effects of stem cell EVs have been demonstrated in a wide range of cell types. While a high potential for their therapeutic use exists, there is a gap of knowledge surrounding their characterization, mechanisms of action, and how they may regulate cells of the CNS. Here, we report the isolation, characterization, and functional assessment of EVs from two sources of human stem cells, mesenchymal stem cells and induced pluripotent stem cells. We demonstrate the ability of these EVs to enhance the processes of cellular migration and angiogenesis, which are critical for both normal cellular development as well as cellular repair. Furthermore, we investigate their reparative effects on damaged cells, specifically those with relevance to the central nervous system. Collectively, our data highlight the similarities and differences among these EV populations and support the view that stem cells EV can be used to repair or partially reverse cellular damage. Graphical Abstract Stem cell-derived Extracellular Vesicles (EVs) for repair of damaged cells. EVs isolated from human induced pluripotent stem cells and mesenchymal stem cells contribute to the partial reversal of phenotypes induced by different sources of cellular damage.

Tissue Engineered Neural Constructs Composed of Neural Precursor Cells, Recombinant Spidroin and PRP for Neural Tissue Regeneration

We have designed a novel two-component matrix (SPRPix) for the encapsulation of directly reprogrammed human neural precursor cells (drNPC). The matrix is comprised of 1) a solid anisotropic complex scaffold prepared by electrospinning a mixture of recombinant analogues of the spider dragline silk proteins - spidroin 1 (rS1/9) and spidroin 2 (rS2/12) - and polycaprolactone (PCL) (rSS-PCL), and 2) a "liquid matrix" based on platelet-rich plasma (PRP). The combination of PRP and spidroin promoted drNPC proliferation with the formation of neural tissue organoids and dramatically activated neurogenesis. Differentiation of drNPCs generated large numbers of βIII-tubulin and MAP2 positive neurons as well as some GFAP-positive astrocytes, which likely had a neuronal supporting function. Interestingly the SPRPix microfibrils appeared to provide strong guidance cues as the differentiating neurons oriented their processes parallel to them. Implantation of the SPRPix matrix containing human drNPC into the brain and spinal cord of two healthy Rhesus macaque monkeys showed good biocompatibility: no astroglial and microglial reaction was present around the implanted construct. Importantly, the human drNPCs survived for the 3 month study period and differentiated into MAP2 positive neurons. Tissue engineered constructs based on SPRPix exhibits important attributes that warrant further examination in spinal cord injury treatment.

Differentiation of induced pluripotent stem cells for future olfactory repair using an indirect co-culture technique

This study was to investigate the differentiation potential of iPSCs into olfactory receptor neurons and mitral/tufted cells in vitro. We extracted mouse embryonic fibroblast and prepared feeding layer, where mouse iPSCs were inoculated on; RT-PCR were used to identify iPSCs pluripotency genes Oct4, Nanog and Sox2. Then, we separated the olfactory epithelium and olfactory bulb from mice, which contained respectively olfactory receptor neurons and mitral/tufted cells, co-cultured iPSCs with olfactory epithelium cell and olfactory bulb, and identified differentiated cells with the olfactory receptor neurons markers (OMP, GAP43, NCAM), mitral/tufted cells markers (TBX21, Iba1) after 14 days co-culturing by immunofluorescence and RT-PCR. We successfully established a stable culture system of mouse iPSCs and RT-PCR showed that pluripotency genes (Oct4, Nanog, Sox2) were expressed in mouse iPSCs. Immunocytochemical analysis or RT-PCR results indicated that the differentiated iPSCs can express olfactory receptor neurons markers (OMP, GAP43, NCAM) and mitral/tufted cells markers (TBX21, Iba1) after being co-culture with olfactory epithelium or olfactory bulb. We conclude that Mouse iPSCs can be differentiated into olfactory receptor neuron-like cells and mitral/tufted-like cells in vitro.

Advances in translational inner ear stem cell research

Stem cell research is expanding our understanding of developmental biology as well as promising the development of new therapies for a range of different diseases. Within hearing research, the use of stem cells has focused mainly on cell replacement. Stem cells however have a broad range of other potential applications that are just beginning to be explored in the ear. Mesenchymal stem cells are an adult derived stem cell population that have been shown to produce growth factors, modulate the immune system and can differentiate into a wide variety of tissue types. Potential advantages of mesenchymal/adult stem cells are that they have no ethical constraints on their use. However, appropriate regulatory oversight seems necessary in order to protect patients from side effects. Disadvantages may be the lack of efficacy in many preclinical studies. But if proven safe and efficacious, they are easily translatable to clinical trials. The current review will focus on the potential application on mesenchymal stem cells for the treatment of inner ear disorders.

Cell therapies administered in the chronic phase after stroke: a meta-analysis examining safety and efficacy

Aim: To assess the safety and efficacy of cell therapies for chronic stroke. Methodology: Five databases were searched for treatments administered >90 days post-stroke. Reporting quality, adherence to research guidelines, treatment safety (risk ratios/pooled incidence rates) and neurological/functional efficacy (Hedge’s g) were all evaluated. Results: Twenty-three studies examined 17 treatments. Reporting quality scores were medium to high, but adherence to recommended guidelines was lower. Three treatments resulted in serious adverse events; four improved outcomes more than standard care. However, many studies were under-powered and individual patients varied in their response to some treatments. Conclusion: Preliminary findings suggest that some cell therapies may be relatively safe and effective, but larger double-blinded placebo-controlled studies are needed to establish the long-term risks and benefits.

Ethical clinical translation of stem cell interventions for neurologic disease

The application of stem cell transplants in clinical practice has increased in frequency in recent years. Many of the stem cell transplants in neurologic diseases, including stroke, Parkinson disease, spinal cord injury, and demyelinating diseases, are unproven-they have not been tested in prospective, controlled clinical trials and have not become accepted therapies. Stem cell transplant procedures currently being carried out have therapeutic aims, but are frequently experimental and unregulated, and could potentially put patients at risk. In some cases, patients undergoing such operations are not included in a clinical trial, and do not provide genuinely informed consent. For these reasons and others, some current stem cell interventions for neurologic diseases are ethically dubious and could jeopardize progress in the field. We provide discussion points for the evaluation of new stem cell interventions for neurologic disease, based primarily on the new Guidelines for Stem Cell Research and Clinical Translation released by the International Society for Stem Cell Research in May 2016. Important considerations in the ethical translation of stem cells to clinical practice include regulatory oversight, conflicts of interest, data sharing, the nature of investigation (e.g., within vs outside of a clinical trial), informed consent, risk-benefit ratios, the therapeutic misconception, and patient vulnerability. To help guide the translation of stem cells from the laboratory into the neurosurgical clinic in an ethically sound manner, we present an ethical discussion of these major issues at stake in the field of stem cell clinical research for neurologic disease.

Synergistic and Superimposed Effect of Bone Marrow-Derived Mesenchymal Stem Cells Combined with Fasudil in Experimental Autoimmune Encephalomyelitis

Bone marrow-derived mesenchymal stem cells (MSCs) are the ideal transplanted cells of cellular therapy for promoting neuroprotection and neurorestoration. However, the optimization of transplanted cells and the improvement of microenvironment around implanted cells are still two critical challenges for enhancing therapeutic effect. In the current study, we observed the therapeutic potential of MSCs combined with Fasudil in mouse model of experimental autoimmune encephalomyelitis (EAE) and explored possible mechanisms of action. The results clearly show that combined intervention of MSCs and Fasudil further reduced the severity of EAE compared with MSCs or Fasudil alone, indicating a synergistic and superimposed effect in treating EAE. The addition of Fasudil inhibited MSC-induced inflammatory signaling TLR-4/MyD88 and inflammatory molecule IFN-γ, IL-1β, and TNF-α but did not convert M1 microglia to M2 phenotype. The delivery of MSCs enhanced the expression of glial cell-derived neurotrophic factor (GDNF) and brain-derived neurotrophic factor (BDNF) compared with that of Fasudil. Importantly, combined intervention of MSCs and Fasudil further increased the expression of BDNF and GDNF compared with the delivery of MSCs alone, indicating that combined intervention of MSCs and Fasudil synergistically contributes to the expression of neurotrophic factors which should be related to the expression of increased galactocerebroside (GalC) compared with mice treated with Fasudil and MSCs alone. However, a lot of investigation is warranted to further elucidate the cross talk of MSCs and Fasudil in the therapeutic potential of EAE/multiple sclerosis.

The Vegetative State and Stem Cells: Therapeutic Considerations

The vegetative state (VS), also known as “unresponsive wakefulness syndrome,” is considered one of the most devastating outcomes of acquired brain injury. While diagnosis of this condition is generally well-defined clinically, patients often appear to be awake despite an absence of behavioral signs of awareness, which to the family can be confusing, leading them to believe the loved one is aware of their surroundings. This inequality of agreement can be very distressing. Currently, no cure for the VS is available; as a result, patients may remain in this condition for the rest of their lives, which in some cases amount to decades. Recent advances in stem cell approaches for the treatment of other neurological conditions may now provide an opportunity to intervene in this syndrome. This mini review will address the development of VS, its diagnosis, affected cerebral structures, and the underlying basis of how stem cells can offer therapeutic promise that would take advantage of the often long-term features associated with this maladie to effect a repair of the severely damaged circuitry. In addition, current limitations of this treatment strategy, including a lack of animal models, few long-term clinical studies that might identify benefits of stem cell treatment, and the potential for development of tumors are considered.

Strategies to Optimize Adult Stem Cell Therapy for Tissue Regeneration

Stem cell therapy aims to replace damaged or aged cells with healthy functioning cells in congenital defects, tissue injuries, autoimmune disorders, and neurogenic degenerative diseases. Among various types of stem cells, adult stem cells (i.e., tissue-specific stem cells) commit to becoming the functional cells from their tissue of origin. These cells are the most commonly used in cell-based therapy since they do not confer risk of teratomas, do not require fetal stem cell maneuvers and thus are free of ethical concerns, and they confer low immunogenicity (even if allogenous). The goal of this review is to summarize the current state of the art and advances in using stem cell therapy for tissue repair in solid organs. Here we address key factors in cell preparation, such as the source of adult stem cells, optimal cell types for implantation (universal mesenchymal stem cells vs. tissue-specific stem cells, or induced vs. non-induced stem cells), early or late passages of stem cells, stem cells with endogenous or exogenous growth factors, preconditioning of stem cells (hypoxia, growth factors, or conditioned medium), using various controlled release systems to deliver growth factors with hydrogels or microspheres to provide apposite interactions of stem cells and their niche. We also review several approaches of cell delivery that affect the outcomes of cell therapy, including the appropriate routes of cell administration (systemic, intravenous, or intraperitoneal vs. local administration), timing for cell therapy (immediate vs. a few days after injury), single injection of a large number of cells vs. multiple smaller injections, a single site for injection vs. multiple sites and use of rodents vs. larger animal models. Future directions of stem cell-based therapies are also discussed to guide potential clinical applications.