Long-Distance Axonal Growth and Protracted Functional Maturation of Neurons Derived from Human Induced Pluripotent Stem Cells After Intracerebral Transplantation

Loading neural stem cells on hydrogel scaffold improves cell retention rate and promotes functional recovery in traumatic brain injury

Neural stem cell (NSC) has gained considerable attention in traumatic brain injury (TBI) treatment because of their ability to replenish dysfunctional neurons and stimulate endogenous neurorestorative processes. However, their therapeutic effects are hindered by the low cell retention rate after transplantation into the dynamic brain. In this study, we found cerebrospinal fluid (CSF) flow after TBI is an important factor associated with cell loss following NSC transplantation. Recently, several studies have shown that hydrogels could serve as a beneficial carrier for stem cell transplantation, which provides a solution to prevent CSF flow-induced cell loss after TBI. For this purpose, we evaluated three different hydrogel scaffolds and found the gelatin methacrylate (GelMA)/sodium alginate (Alg) (GelMA/Alg) hydrogel scaffold showed the best capabilities for NSC adherence, growth, and differentiation. Additionally, we detected that pre-differentiated NSCs, which were loaded on the GelMA/Alg hydrogel and cultured for 7 days in neuronal differentiation medium (NSC [7d]), had the highest cell retention rate after CSF impact. Next, the neuroprotective effects of the NSC-loaded GelMA/Alg hydrogel scaffold were evaluated in a rat model of TBI. NSC [7d]-loaded GelMA/Alg markedly decreased microglial activation and neuronal death in the acute phase, reduced tissue loss, alleviated astrogliosis, promoted neurogenesis, and improved neurological recovery in the chronic phase. In summary, we demonstrated that the integration with the GelMA/Alg and modification of NSC differentiation could inhibit the influence of CSF flow on transplanted NSCs, leading to increased number of retained NSCs and improved neuroprotective effects, providing a promising alternative for TBI treatment.

Extracellular Vesicles and Cellular Ageing

Ageing is a complex process characterized by deteriorated performance at multiple levels, starting from cellular dysfunction to organ degeneration. Stem cell-based therapies aim to administrate stem cells that eventually migrate to the injured site to replenish the damaged tissue and recover tissue functionality. Stem cells can be easily obtained and cultured in vitro, and display several qualities such as self-renewal, differentiation, and immunomodulation that make them suitable candidates for stem cell-based therapies. Current animal studies and clinical trials are being performed to assess the safety and beneficial effects of stem cell engraftments for regenerative medicine in ageing and age-related diseases.Since alterations in cell-cell communication have been associated with the development of pathophysiological processes, new research is focusing on the modulation of the microenvironment. Recent research has highlighted the important role of some microenvironment components that modulate cell-cell communication, thus spreading signals from damaged ageing cells to neighbor healthy cells, thereby promoting systemic ageing. Extracellular vesicles (EVs) are small-rounded vesicles released by almost every cell type. EVs cargo includes several bioactive molecules, such as lipids, proteins, and genetic material. Once internalized by target cells, their specific cargo can induce epigenetic modifications and alter the fate of the recipient cells. Also, EV's content is dependent on the releasing cells, thus, EVs can be used as biomarkers for several diseases. Moreover, EVs have been proposed to be used as cell-free therapies that focus on their administration to slow or even reverse some hallmarks of physiological ageing. It is not surprising that EVs are also under study as next-generation therapies for age-related diseases.

Long-Term Evaluation of Intranigral Transplantation of Human iPSC-Derived Dopamine Neurons in a Parkinson's Disease Mouse Model

Parkinson's disease (PD) is a neurodegenerative disorder associated with loss of dopaminergic (DA) neurons in the substantia nigra pars compacta (SNpc). One strategy for treating PD is transplantation of DA neuroblasts. Significant advances have been made in generating midbrain DA neurons from human pluripotent stem cells. Before these cells can be routinely used in clinical trials, extensive preclinical safety studies are required. One of the main issues to be addressed is the long-term therapeutic effectiveness of these cells. In most transplantation studies using human cells, the maturation of DA neurons has been analyzed over a relatively short period not exceeding 6 months. In present study, we generated midbrain DA neurons from human induced pluripotent stem cells (hiPSCs) and grafted these neurons into the SNpc in an animal model of PD. Graft survival and maturation were analyzed from 1 to 12 months post-transplantation (mpt). We observed long-term survival and functionality of the grafted neurons. However, at 12 mpt, we observed a decrease in the proportion of SNpc DA neuron subtype compared with that at 6 mpt. In addition, at 12 mpt, grafts still contained immature neurons. Our results suggest that longer-term evaluation of the maturation of neurons derived from human stem cells is mandatory for the safe application of cell therapy for PD.

The mechanisms of Chuanxiong Rhizoma in treating spinal cord injury based on network pharmacology and experimental verification

Background

Chuanxiong Rhizoma (CR) is a common traditional Chinese medicine (TCM) that has been widely used in the treatment of spinal cord injury (SCI). However, the underlying molecular mechanism of CR is still largely unknown. This study was designed to explore the bioactive components and the mechanism of CR in treating SCI based on a network pharmacology approach and experimental validation.

Methods

First, the active compounds and related target genes in CR were screened from the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database. Subsequently, the corresponding target genes of SCI were collected by the Therapeutic Target Database (TTD) and GeneCards database. A protein-protein interaction (PPI) network was constructed using the STRING database. Furthermore, GO function and KEGG enrichment analysis of the targets were analyzed using DAVID tools. Subsequently, the AutoDock software for molecular docking was adopted to verify the above network pharmacology analysis results between the active components and key targets. Finally, an SCI rat model animal validation experiment was assessed to verify the reliability of the network pharmacology results.

Results

There were 7 active ingredients identified in CR and 246 SCI-related targets were collected. Then, 4 core nodes (ALB, AKT1, MAPK1, and EGFR) were discerned via construction of a PPI network of 111 common targets. The KEGG enrichment analysis results indicated that the Ras signaling pathway, estrogen signaling pathway, and vascular endothelial growth factor (VEGF) signaling pathway were enriched in the development of SCI. The results of molecular docking demonstrated that the effects of CR have a strong affinity with the 4 pivotal targets. Experimental validation in a rat model showed that CR could effectively improve the recovery of motor function and mechanical pain threshold after SCI.

Conclusions

In summary, it revealed the mechanism of CR treatment for SCI involve active ingredients, targets and signaling pathways, providing a scientific basis for future investigations into the mechanism underlying CR treating for SCI.

Transplantation of a vascularized pedicle of hemisected spinal cord to establish spinal cord continuity after removal of a segment of the thoracic spinal cord: A proof-of-principle study in dogs

Introduction

Glial scar formation impedes nerve regeneration/reinnervation after spinal cord injury (SCI); therefore, removal of scar tissue is essential for SCI treatment.

Aims

To investigate whether removing a spinal cord and transplanting a vascularized pedicle of hemisected spinal cord from the spinal cord caudal to the transection can restore motor function, to aid in the treatment of future clinical spinal cord injuries. We developed a canine model. After removal of a 1‐cm segment of the thoracic (T10–T11) spinal cord in eight beagles, a vascularized pedicle of hemisected spinal cord from the first 1.5 cm of the spinal cord caudal to the transection (cut along the posterior median sulcus of the spinal cord) was transplanted to bridge the transected spinal cord in the presence of a fusogen (polyethylene glycol, PEG) in four of the eight dogs. We used various forms of imaging, electron microscopy, and histologic data to determine that after our transplantation of a vascular pedicled hemisection to bridge the transected spinal cord, electrical continuity across the spinal bridge was restored.

Results

Motor function was restored following our transplantation, as confirmed by the re‐establishment of anatomic continuity along with interfacial axonal sprouting.

Conclusion

Taken together, our findings suggest that SCI patients—who have previously been thought to have irreversible damage and/or paralysis—may be treated effectively with similar operative techniques to re‐establish electrical and functional continuity following SCI.

One Raft to Guide Them All, and in Axon Regeneration Inhibit Them

Central nervous system damage caused by traumatic injuries, iatrogenicity due to surgical interventions, stroke and neurodegenerative diseases is one of the most prevalent reasons for physical disability worldwide. During development, axons must elongate from the neuronal cell body to contact their precise target cell and establish functional connections. However, the capacity of the adult nervous system to restore its functionality after injury is limited. Given the inefficacy of the nervous system to heal and regenerate after damage, new therapies are under investigation to enhance axonal regeneration. Axon guidance cues and receptors, as well as the molecular machinery activated after nervous system damage, are organized into lipid raft microdomains, a term typically used to describe nanoscale membrane domains enriched in cholesterol and glycosphingolipids that act as signaling platforms for certain transmembrane proteins. Here, we systematically review the most recent findings that link the stability of lipid rafts and their composition with the capacity of axons to regenerate and rebuild functional neural circuits after damage.

Generation of Neural Progenitor Cells From Canine Induced Pluripotent Stem Cells and Preliminary Safety Test in Dogs With Spontaneous Spinal Cord Injuries

Advances in stem cell technology, including the use of induced pluripotent stem cells (iPSC) to produce neurons and glial cells, offer new hope for patients with neurological disease and injuries. Pet dogs with spinal cord injuries provide an important spontaneous animal model for evaluating new approaches to stem cell therapy. Therefore, studies were conducted to identify optimal conditions for generating neural progenitor cells (NPC) from canine induced pluripotent stem cells (iPSC) for preliminary evaluation in animals with spinal cord injury. We found that canine NPC could be induced to differentiate into mature neural cells, including glia and neurons. In addition, canine NPC did not form teratomas when injected in NOD/SCID mice. In a pilot study, two dogs with chronic spinal cord injury underwent fluoroscopically guided intrathecal injections of canine NPC. In follow-up MRI evaluations, tumor formation was not observed at the injection sites. However, none of the animals experienced meaningful clinical or electrophysiological improvement following NPC injections. These studies provide evidence that canine iPSC can be used to generate NPC for evaluation in cellular therapy of chronic spinal cord injury in the dog spontaneous injury model. Further refinements in the cell implantation procedure are likely required to enhance stem cell treatment efficacy.

Optogenetically transduced human ES cell-derived neural progenitors and their neuronal progenies: Phenotypic characterization and responses to optical stimulation

Optogenetically engineered human neural progenitors (hNPs) are viewed as promising tools in regenerative neuroscience because they allow the testing of the ability of hNPs to integrate within nervous system of an appropriate host not only structurally, but also functionally based on the responses of their differentiated progenies to light. Here, we transduced H9 embryonic stem cell-derived hNPs with a lentivirus harboring human channelrhodopsin (hChR2) and differentiated them into a forebrain lineage. We extensively characterized the fate and optogenetic functionality of hChR2-hNPs in vitro with electrophysiology and immunocytochemistry. We also explored whether the in vivo phenotype of ChR2-hNPs conforms to in vitro observations by grafting them into the frontal neocortex of rodents and analyzing their survival and neuronal differentiation. Human ChR2-hNPs acquired neuronal phenotypes (TUJ1, MAP2, SMI-312, and synapsin 1 immunoreactivity) in vitro after an average of 70 days of coculturing with CD1 astrocytes and progressively displayed both inhibitory and excitatory neurotransmitter signatures by immunocytochemistry and whole-cell patch clamp recording. Three months after transplantation into motor cortex of naïve or injured mice, 60–70% of hChR2-hNPs at the transplantation site expressed TUJ1 and had neuronal cytologies, whereas 60% of cells also expressed ChR2. Transplant-derived neurons extended axons through major commissural and descending tracts and issued synaptophysin⁺ terminals in the claustrum, endopiriform area, and corresponding insular and piriform cortices. There was no apparent difference in engraftment, differentiation, or connectivity patterns between injured and sham subjects. Same trends were observed in a second rodent host, i.e. rat, where we employed longer survival times and found that the majority of grafted hChR2-hNPs differentiated into GABAergic neurons that established dense terminal fields and innervated mostly dendritic profiles in host cortical neurons. In physiological experiments, human ChR2⁺ neurons in culture generated spontaneous action potentials (APs) 100–170 days into differentiation and their firing activity was consistently driven by optical stimulation. Stimulation generated glutamatergic and GABAergic postsynaptic activity in neighboring ChR2^- cells, evidence that hChR2-hNP-derived neurons had established functional synaptic connections with other neurons in culture. Light stimulation of hChR2-hNP transplants in vivo generated complicated results, in part because of the variable response of the transplants themselves. Our findings show that we can successfully derive hNPs with optogenetic properties that are fully transferrable to their differentiated neuronal progenies. We also show that these progenies have substantial neurotransmitter plasticity in vitro, whereas in vivo they mostly differentiate into inhibitory GABAergic neurons. Furthermore, neurons derived from hNPs have the capacity of establishing functional synapses with postsynaptic neurons in vitro, but this outcome is technically challenging to explore in vivo. We propose that optogenetically endowed hNPs hold great promise as tools to explore de novo circuit formation in the brain and, in the future, perhaps launch a new generation of neuromodulatory therapies.

Stem cell therapy for neurological disorders: A focus on aging

Age-related neurological disorders continue to pose a significant societal and economic burden. Aging is a complex phenomenon that affects many aspects of the human body. Specifically, aging can have detrimental effects on the progression of brain diseases and endogenous stem cells. Stem cell therapies possess promising potential to mitigate the neurological symptoms of such diseases. However, aging presents a major obstacle for maximum efficacy of these treatments. In this review, we discuss current preclinical and clinical literature to highlight the interactions between aging, stem cell therapy, and the progression of major neurological disease states such as Parkinson's disease, Huntington's disease, stroke, traumatic brain injury, amyotrophic lateral sclerosis, multiple sclerosis, and multiple system atrophy. We raise important questions to guide future research and advance novel treatment options.

Harnessing stem cells and biomaterials to promote neural repair

With the limited capacity for self-repair in the adult CNS, efforts to stimulate quiescent stem cell populations within discrete brain regions, as well as harness the potential of stem cell transplants, offer significant hope for neural repair. These new cells are capable of providing trophic cues to support residual host populations and/or replace those cells lost to the primary insult. However, issues with low-level adult neurogenesis, cell survival, directed differentiation and inadequate reinnervation of host tissue have impeded the full potential of these therapeutic approaches and their clinical advancement. Biomaterials offer novel approaches to stimulate endogenous neurogenesis, as well as for the delivery and support of neural progenitor transplants, providing a tissue-appropriate physical and trophic milieu for the newly integrating cells. In this review, we will discuss the various approaches by which bioengineered scaffolds may improve stem cell-based therapies for repair of the CNS.

Abnormal DNA Methylation in Thoracic Spinal Cord Tissue Following Transection Injury

Background

Spinal cord injury (SCI) is a serious disease with high disability and mortality rates, with no effective therapeutic strategies available. In SCI, abnormal DNA methylation is considered to be associated with axonal regeneration and cell proliferation. However, the roles of key genes in potential molecular mechanisms of SCI are not clear.

Material/Methods

Subacute spinal cord injury models were established in Wistar rats. Histological observations and motor function assessments were performed separately. Whole-genome bisulfite sequencing (WGBS) was used to detect the methylation of genes. Gene ontology (GO) term enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were performed using the DAVID database. Protein–protein interaction (PPI) networks were analyzed by Cytoscape software.

Results

After SCI, many cavities, areas of necrotic tissue, and many inflammatory cells were observed, and motor function scores were low. After the whole-genome bisulfite sequencing, approximately 96 DMGs were screened, of which 50 were hypermethylated genes and 46 were hypomethylated genes. KEGG pathway analysis highlighted the Axon Guidance pathway, Endocytosis pathway, T cell receptor signaling pathway, and Hippo signaling pathway. Expression patterns of hypermethylated genes and hypomethylated genes detected by qRT-PCR were the opposite of WGBS data, and the difference was significant.

Conclusions

Abnormal methylated genes and key signaling pathways involved in spinal cord injury were identified through histological observation, behavioral assessment, and bioinformatics analysis. This research can serve as a source of additional information to expand understanding of spinal cord-induced epigenetic changes.

Polycaprolactone electrospun fiber scaffold loaded with iPSCs-NSCs and ASCs as a novel tissue engineering scaffold for the treatment of spinal cord injury

Background

Spinal cord injury (SCI) is a traumatic disease of the central nervous system, accompanied with high incidence and high disability rate. Tissue engineering scaffold can be used as therapeutic systems to provide effective repair for SCI.

Purpose

In this study, a novel tissue engineering scaffold has been synthesized in order to explore the effect of nerve repair on SCI.

Patients and methods

Polycaprolactone (PCL) scaffolds loaded with actived Schwann cells (ASCs) and induced pluripotent stem cells -derived neural stem cells (iPSC-NSCs), a combined cell transplantation strategy, were prepared and characterized. The cell-loaded PCL scaffolds were further utilized for the treatment of SCI in vivo. Histological observation, behavioral evaluation, Western-blot and qRT-PCR were used to investigate the nerve repair of Wistar rats after scaffold transplantation.

Results

The iPSCs displayed similar characteristics to embryonic stem cells and were efficiently differentiated into neural stem cells in vitro. The obtained PCL scaffolds werê0.5 mm in thickness with biocompatibility and biodegradability. SEM results indicated that the ASCs and (or) iPS-NSCs grew well on PCL scaffolds. Moreover, transplantation reduced the volume of lesion cavity and improved locomotor recovery of rats. In addition, the degree of spinal cord recovery and remodeling maybe closely related to nerve growth factor and glial cell-derived neurotrophic factor. In summary, our results demonstrated that tissue engineering scaffold treatment could increase tissue remodeling and could promote motor function recovery in a transection SCI model.

Conclusion

This study provides preliminary evidence for using tissue engineering scaffold as a clinically viable treatment for SCI in the future.

An update on intracerebral stem cell grafts

INTRODUCTION

Primary neurological disorders are notoriously debilitating and deadly, and over the past four decades stem cell therapy has emerged as a promising treatment. Translation of stem cell therapies from the bench to the clinic requires a better understanding of delivery protocols, safety profile, and efficacy in each disease. Areas covered: In this review, benefits and risks of intracerebral stem cell transplantation are presented for consideration. Milestone discoveries in stem cell applications are reviewed to examine the efficacy and safety of intracerebral stem cell transplant therapy for disorders of the central nervous system and inform design of translatable protocols for clinically feasible stem cell-based treatments. Expert commentary: Intracerebral administration, compared to peripheral delivery, is more invasive and carries the risk of open brain surgery. However, direct cell implantation bypasses the blood-brain barrier and reduces the first-pass effect, effectively increasing the therapeutic cell deposition at its intended site of action. These benefits must be weighed with the risk of graft-versus-host immune response. Rigorous clinical trials are underway to assess the safety and efficacy of intracerebral transplants, and if successful will lead to widely available stem cell therapies for neurologic diseases in the coming years.

Peptide-Based Scaffolds Support Human Cortical Progenitor Graft Integration to Reduce Atrophy and Promote Functional Repair in a Model of Stroke

Stem cell transplants offer significant hope for brain repair following ischemic damage. Pre-clinical work suggests that therapeutic mechanisms may be multi-faceted, incorporating bone-fide circuit reconstruction by transplanted neurons, but also protection/regeneration of host circuitry. Here, we engineered hydrogel scaffolds to form "bio-bridges" within the necrotic lesion cavity, providing physical and trophic support to transplanted human embryonic stem cell-derived cortical progenitors, as well as residual host neurons. Scaffolds were fabricated by the self-assembly of peptides for a laminin-derived epitope (IKVAV), thereby mimicking the brain's major extracellular protein. Following focal ischemia in rats, scaffold-supported cell transplants induced progressive motor improvements over 9 months, compared to cell- or scaffold-only implants. These grafts were larger, exhibited greater neuronal differentiation, and showed enhanced electrophysiological properties reflective of mature, integrated neurons. Varying graft timing post-injury enabled us to attribute repair to both neuroprotection and circuit replacement. These findings highlight strategies to improve the efficiency of stem cell grafts for brain repair.

In Vivo Imaging of CNS Injury and Disease

In vivo optical imaging has emerged as a powerful tool with which to study cellular responses to injury and disease in the mammalian CNS. Important new insights have emerged regarding axonal degeneration and regeneration, glial responses and neuroinflammation, changes in the neurovascular unit, and, more recently, neural transplantations. Accompanying a 2017 SfN Mini-Symposium, here, we discuss selected recent advances in understanding the neuronal, glial, and other cellular responses to CNS injury and disease with in vivo imaging of the rodent brain or spinal cord. We anticipate that in vivo optical imaging will continue to be at the forefront of breakthrough discoveries of fundamental mechanisms and therapies for CNS injury and disease.

BMP4/LIF or RA/Forskolin Suppresses the Proliferation of Neural Stem Cells Derived from Adult Monkey Brain

Monkeys are much closer to human and are the most common nonhuman primates which are used in biomedical studies. Neural progenitor cells can originate from the hippocampus of adult monkeys. Despite a few reports, the detailed properties of monkey neural stem cells (NSCs) and their responses to cytokine are still unclear. Here, we derive NSCs from an adult monkey brain and demonstrate that BMP4 inhibits cell proliferation and affects cell morphology of monkey NSCs. Combined treatment of BMP4 and LIF or RA and Forskolin represses the proliferation of monkey NSCs. We also show that BMP4 may promote monkey NSC quiescence. Our study therefore provides implications for NSC-based cell therapy of brain injury in the future.

A PITX3-EGFP Reporter Line Reveals Connectivity of Dopamine and Non-dopamine Neuronal Subtypes in Grafts Generated from Human Embryonic Stem Cells

Development of safe and effective stem cell-based therapies for brain repair requires an in-depth understanding of the in vivo properties of neural grafts generated from human stem cells. Replacing dopamine neurons in Parkinson's disease remains one of the most anticipated applications. Here, we have used a human PITX3-EGFP embryonic stem cell line to characterize the connectivity of stem cell-derived midbrain dopamine neurons in the dopamine-depleted host brain with an unprecedented level of specificity. The results show that the major A9 and A10 subclasses of implanted dopamine neurons innervate multiple, developmentally appropriate host targets but also that the majority of graft-derived connectivity is non-dopaminergic. These findings highlight the promise of stem cell-based procedures for anatomically correct reconstruction of specific neuronal pathways but also emphasize the scope for further refinement in order to limit the inclusion of uncharacterized and potentially unwanted cell types.