Curtis E, Martin JR, Gabel B, Sidhu N, Rzesiewicz TK, Mandeville R, Van Gorp S, Leerink M, Tadokoro T, Marsala S, Jamieson C, Marsala M, Ciacci JD. A First-in-Human, Phase I Study of Neural Stem Cell Transplantation for Chronic Spinal Cord Injury. Cell Stem Cell 2018; 22: 941-950. e6. [PMID: 29859175 DOI: 10.1016/j.stem.2018.05.014]

Developmental stage of transplanted neural progenitor cells influences anatomical and functional outcomes after spinal cord injury in mice

Neural progenitor cell (NPC) transplantation is a promising therapeutic strategy for replacing lost neurons following spinal cord injury (SCI). However, how graft cellular composition influences regeneration and synaptogenesis of host axon populations, or recovery of motor and sensory functions after SCI, is poorly understood. We transplanted developmentally-restricted spinal cord NPCs, isolated from E11.5-E13.5 mouse embryos, into sites of adult mouse SCI and analyzed graft axon outgrowth, cellular composition, host axon regeneration, and behavior. Earlier-stage grafts exhibited greater axon outgrowth, enrichment for ventral spinal cord interneurons and Group-Z spinal interneurons, and enhanced host 5-HT+ axon regeneration. Later-stage grafts were enriched for late-born dorsal horn interneuronal subtypes and Group-N spinal interneurons, supported more extensive host CGRP+ axon ingrowth, and exacerbated thermal hypersensitivity. Locomotor function was not affected by any type of NPC graft. These findings showcase the role of spinal cord graft cellular composition in determining anatomical and functional outcomes following SCI.

Profiling spatiotemporal gene expression of the developing human spinal cord and implications for ependymoma origin

The spatiotemporal regulation of cell fate specification in the human developing spinal cord remains largely unknown. In this study, by performing integrated analysis of single-cell and spatial multi-omics data, we used 16 prenatal human samples to create a comprehensive developmental cell atlas of the spinal cord during post-conceptional weeks 5-12. This revealed how the cell fate commitment of neural progenitor cells and their spatial positioning are spatiotemporally regulated by specific gene sets. We identified unique events in human spinal cord development relative to rodents, including earlier quiescence of active neural stem cells, differential regulation of cell differentiation and distinct spatiotemporal genetic regulation of cell fate choices. In addition, by integrating our atlas with pediatric ependymomas data, we identified specific molecular signatures and lineage-specific genes of cancer stem cells during progression. Thus, we delineate spatiotemporal genetic regulation of human spinal cord development and leverage these data to gain disease insight.

Microneurotrophin BNN27 Reduces Astrogliosis and Increases Density of Neurons and Implanted Neural Stem Cell-Derived Cells after Spinal Cord Injury

Microneurotrophins, small-molecule mimetics of endogenous neurotrophins, have demonstrated significant therapeutic effects on various animal models of neurological diseases. Nevertheless, their effects on central nervous system injuries remain unknown. Herein, we evaluate the effects of microneurotrophin BNN27, an NGF analog, in the mouse dorsal column crush spinal cord injury (SCI) model. BNN27 was delivered systemically either by itself or combined with neural stem cell (NSC)-seeded collagen-based scaffold grafts, demonstrated recently to improve locomotion performance in the same SCI model. Data validate the ability of NSC-seeded grafts to enhance locomotion recovery, neuronal cell integration with surrounding tissues, axonal elongation and angiogenesis. Our findings also show that systemic administration of BNN27 significantly reduced astrogliosis and increased neuron density in mice SCI lesion sites at 12 weeks post injury. Furthermore, when BNN27 administration was combined with NSC-seeded PCS grafts, BNN27 increased the density of survived implanted NSC-derived cells, possibly addressing a major challenge of NSC-based SCI treatments. In conclusion, this study provides evidence that small-molecule mimetics of endogenous neurotrophins can contribute to effective combinatorial treatments for SCI, by simultaneously regulating key events of SCI and supporting grafted cell therapies in the lesion site.

Microenvironmental modulation in tandem with human stem cell transplantation enhances functional recovery after chronic complete spinal cord injury

While rapid advancements in regenerative medicine strategies for spinal cord injury (SCI) have been made, most research in this field has focused on the early stages of incomplete injury. However, the majority of patients experience chronic severe injury; therefore, treatments for these situations are fundamentally important. Here, we hypothesized that environmental modulation via a clinically relevant hepatocyte growth factor (HGF)-releasing scaffold and human iPS cell-derived neural stem/progenitor cells (hNS/PCs) transplantation contributes to functional recovery after chronic complete transection SCI. Effective release of HGF from a collagen scaffold induced progressive axonal elongation and increased grafted cell viability by activating microglia/macrophages and meningeal cells, inhibiting inflammation, reducing scar formation, and enhancing vascularization. Furthermore, hNS/PCs transplantation enhanced endogenous neuronal regrowth, the extension of graft axons, and the formation of circuits around the lesion and lumbar enlargement between host and graft neurons, resulting in the restoration of locomotor and urinary function. This study presents an effective therapeutic strategy for severe chronic SCI and provides evidence for the feasibility of regenerative medicine strategies using clinically relevant materials.

Inhibited astrocytic differentiation in neural stem cell-laden 3D bioprinted conductive composite hydrogel scaffolds for repair of spinal cord injury

The emergence of three-dimensional (3D) bioprinting technology has attracted ever-increasing attention in engineered tissue fabrication for stem cell-based tissue repair. However, the in vivo performance of transplanted stem cells in the tissue engineering scaffolds is still a major concern for regenerative medicine researches. Especially for neural stem cell (NSC) transplantation, the uncontrollable differentiation of the NSCs in host often leads to a poor therapeutic effect in nerve tissue repair, such as spinal cord injury (SCI) repair. To address this issue, we have fabricated a conductive composite hydrogel (CCH) scaffold loading with NSCs by 3D bioprinting, for delivering the NSCs to injured spinal cord and repairing the propriospinal nerve circuit. In our strategy, a novel conductive polymer (PEDOT:CSMA,TA) was synthesized and introduced into a photocrosslinkable gelatin/polyethylene glycol physical-gel matrix, thereby forming a composite bioink with well shear-thinning and self-healing properties. The composite bioink we prepared was then printed into the NSC-laden CCH scaffold with high shape fidelity and similar physicochemical properties to native spinal cord tissues. The NSCs encapsulated in the bioprinted CCH scaffold extended their neurites to form superior physical contact with the neighboring cells as well as the electroconductive matrix, and maintained a predominant in vivo neuronal differentiation, accompanying with few astrocytic production in the lesion area after transplantation into the SCI sites. As a result, the removal of glial scar tissues and the regeneration of well-developed nerve fibres sequentially happened, which not only facilitated nerve tissue development, but also accelerated locomotor function recovery in the SCI rats. By exploring the application of conductive biomaterials in stem cell-based SCI therapy, this work represents a feasible, new approach to precisely construct tissue engineering scaffolds for stem cell-based therapy in traumatic SCI and other nervous system diseases.

Spinal Cord-Gut-Immune Axis and its Implications Regarding Therapeutic Development for Spinal Cord Injury

Spinal cord injury (SCI) affects ∼1,300,000 people living in the United States. Most research efforts have been focused on reversing paralysis, as this is arguably the most defining feature of SCI. The damage caused by SCI, however, extends past paralysis and includes other debilitating outcomes including immune dysfunction and gut dysbiosis. Recent efforts are now investigating the pathophysiology of and developing therapies for these more distal manifestations of SCI. One exciting avenue is the spinal cord-gut-immune axis, which proposes that gut dysbiosis amplifies lesion inflammation and impairs SCI recovery. This review will highlight the most recent findings regarding gut and immune dysfunction following SCI, and discuss how the central nervous system (CNS), gut, and immune system all coalesce to form a bidirectional axis that can impact SCI recovery. Finally, important considerations regarding how the spinal cord-gut-immune axis fits within the larger framework of therapeutic development (i.e., probiotics, fecal transplants, dietary modifications) will be discussed, emphasizing the lack of interdepartmental investigation and the missed opportunity to maximize therapeutic benefit in SCI.

Supramolecular Hydrogel Microspheres of Platelet-Derived Growth Factor Mimetic Peptide Promote Recovery from Spinal Cord Injury

Neural stem cells (NSCs) are considered to be prospective replacements for neuronal cell loss as a result of spinal cord injury (SCI). However, the survival and neuronal differentiation of NSCs are strongly affected by the unfavorable microenvironment induced by SCI, which critically impairs their therapeutic ability to treat SCI. Herein, a strategy to fabricate PDGF-MP hydrogel (PDGF-MPH) microspheres (PDGF-MPHM) instead of bulk hydrogels is proposed to dramatically enhance the efficiency of platelet-derived growth factor mimetic peptide (PDGF-MP) in activating its receptor. PDGF-MPHM were fabricated by a piezoelectric ceramic-driven thermal electrospray device, had an average size of 9 μm, and also had the ability to activate the PDGFRβ of NSCs more effectively than PDGF-MPH. In vitro, PDGF-MPHM exerted strong neuroprotective effects by maintaining the proliferation and inhibiting the apoptosis of NSCs in the presence of myelin extracts. In vivo, PDGF-MPHM inhibited M1 macrophage infiltration and extrinsic or intrinsic cells apoptosis on the seventh day after SCI. Eight weeks after SCI, the T10 SCI treatment results showed that PDGF-MPHM + NSCs significantly promoted the survival of NSCs and neuronal differentiation, reduced lesion size, and considerably improved motor function recovery in SCI rats by stimulating axonal regeneration, synapse formation, and angiogenesis in comparison with the NSCs graft group. Therefore, our findings provide insights into the ability of PDGF-MPHM to be a promising therapeutic agent for SCI repair.

Transplantation of A2 type astrocytes promotes neural repair and remyelination after spinal cord injury

BACKGROUND

Limited progress in terms of an effective treatment for spinal cord injury (SCI) emphasizes the urgent need for novel therapies. As a vital central nervous system component, the resident astrocytes play crucial roles in regulating recovery after SCI. In this study, recovery after SCI was compared following the transplantation of either A1 or A2 astrocytes. A1 astrocytes are harmful as they upregulate the neurotoxic classical complement cascade genes. Conversely, A2 astrocytes are characterized as neuroprotective as they upregulate the production of many neurotrophic factors.

METHODS

We used different supernatant obtained from microglia stimulated with lipopolysaccharide or interleukin-4 to generate A1 and A2 astrocytes. We detected the influence of astrocytes on neurons by co-culturing A1 and A2 astrocytes with neurons. We transplanted astrocytes into the lesion site of the spinal cord and assessed lesion progression, neural restoration, glia formation and locomotor recovery.

RESULTS

Astrocytes were polarized into A1 and A2 phenotypes following culture in the supernatant obtained from microglia stimulated with lipopolysaccharide or interleukin-4, respectively. Furthermore, co-culturing A2 astrocytes with neurons significantly suppressed glutamate-induced neuronal apoptosis and promoted the degree of neuron arborization. Transplantation of these A2 astrocytes into the lesion site of the spinal cord of mice significantly improved motor function recovery, preserved spared supraspinal pathways, decreased glia scar deposition, and increased neurofilament formation at the site of injury compared to the transplantation of A1 astrocytes. Additionally, enhanced A2 astrocytes with potentially beneficial A2-like genes were also detected in the A2 group. Moreover, luxol fast blue staining and electron microscopy indicated increased preservation of myelin with organized structure after transplantation of A2 astrocytes than of A1 astrocytes.

CONCLUSIONS

A2 astrocyte transplantation could be a promising potential therapy for SCI. Video abstract.

Human Menstrual Blood-Derived Endometrial Stem Cells Promote Functional Recovery by Improving the Inflammatory Microenvironment in a Mouse Spinal Cord Injury Model

Spinal cord injury (SCI) is a traumatic injury of the central nervous system. Because neurons are damaged and difficult to regenerate after SCI, its repair remains challenging. However, recent research on stem cell therapy have favored its use after SCI. In this study, based on the establishment of a mouse SCI model, human menstrual blood-derived endometrial stem cells (MenSCs) were intrathecally injected to explore the role and molecular mechanism of MenSCs in SCI. MenSCs were transplanted following SCI in the animal model, and behavioral evaluations showed that MenSC transplantation improved functional recovery. Therefore, samples were collected after 7 days, and transcriptome sequencing was performed. Gene Ontology (GO) enrichment analysis revealed that SCI is closely related to immune system processes. After transplantation of MenSCs, the immune response was significantly activated. In the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, MenSC transplantation was found to be closely related to Th1, Th2, and Th17 cell differentiation pathways. Neuronal damage and glial cell proliferation and activation in the different groups were detected by fluorescence immunohistochemistry and Western blotting 7 days after SCI. Simultaneously, the activation of different types of microglia was detected and the expression of pro-inflammatory and anti-inflammatory factors was quantitatively analyzed. The results showed that MenSC transplantation and sonic hedgehog (Shh)-induced MenSCs accelerated neuronal recovery at the injured site, inhibited the formation of glial cells and microglial activation at the injured site, inhibited the expression of inflammatory factors, and improved the inflammatory microenvironment to achieve functional recovery of SCI. This study provides an experimental basis for the study of the role and molecular mechanism of MenSCs in SCI repair, and a reference for the role of Shh-induced MenSCs in SCI repair.

Human spinal GABA neurons survive and mature in the injured nonhuman primate spinal cord

Spinal cord injury (SCI) leads to permanent neural dysfunction without effective therapies. We previously showed that human pluripotent stem cell (hPSC)-derived spinal GABA neurons can alleviate spasticity and promote locomotion in rats after SCI, but whether this strategy can be translated into the clinic remains elusive. Here, a nonhuman primate (NHP) model of SCI was established in rhesus macaques (Macaca mulatta) in which the T10 spinal cord was hemisected, resulting in neural conduction failure and neural dysfunction, including locomotion deficits, pain, and spasms. Grafted human spinal GABA neurons survived for up to 7.5 months in the injured monkey spinal cord and retained their intrinsic properties, becoming mature and growing axons and forming synapses. Importantly, they are functionally alive, as evidenced by designer receptors exclusively activated by designer drug (DREADD) activation. These findings represent a significant step toward the clinical translation of human spinal neuron transplantation for treating SCI.

Cell membrane-targeting NIR fluorescent probes with large Stokes shifts for ultralong-term transplanted neural stem cell tracking

There is an emerging therapeutic strategy to transplant stem cells into diseased host tissue for various neurodegenerative diseases, owing to their self-renewal ability and pluripotency. However, the traceability of long-term transplanted cells limits the further understanding of the mechanism of the therapy. Herein, we designed and synthesized a quinoxalinone scaffold-based near-infrared (NIR) fluorescent probe named QSN, which exhibits ultra-strong photostability, large Stokes shift, and cell membrane-targeting capacity. It could be found that QSN-labeled human embryonic stem cells showed strong fluorescent emission and photostability both in vitro and in vivo. Additionally, QSN would not impair the pluripotency of embryonic stem cells, indicating that QSN did not perform cytotoxicity. Moreover, it is worth mentioning that QSN-labeled human neural stem cells held cellular retention for at least 6 weeks in the mouse brain striatum post transplantation. All these findings highlight the potential application of QSN for ultralong-term transplanted cell tracking.

miR-872-5p/FOXO3a/Wnt signaling feed-forward loop promotes proliferation of endogenous neural stem cells after spinal cord ischemia-reperfusion injury in rats

The activation of endogenous neural stem cells (NSCs) is considered an important mechanism of neural repair after mechanical spinal cord injury; however, whether endogenous NSC proliferation can also occur after spinal cord ischemia-reperfusion injury (SCIRI) remains unclear. In this study, we aimed to verify the existence of endogenous NSC proliferation after SCIRI and explore the underlying molecular mechanism. NSC proliferation was observed after SCIRI in vivo and oxygen-glucose deprivation and reperfusion (OGD/R) in vitro, accompanied by a decrease in forkhead box protein O 3a (FOXO3a) expression. This downward trend was regulated by the increased expression of microRNA-872-5p (miR-872-5p). miR-872-5p affected NSC proliferation by targeting FOXO3a to increase the expression of β-catenin and T-cell factor 4 (TCF4). In addition, TCF4 in turn acted as a transcription factor to increase the expression level of miR-872-5p, and knockdown of FOXO3a enhanced the binding of TCF4 to the miR-872-5p promoter. In conclusion, SCIRI in vivo and OGD/R in vitro stimulated the miR-872-5p/FOXO3a/β-catenin-TCF4 pathway, thereby promoting NSC proliferation. At the same time, FOXO3a affected TCF4 transcription factor activity and miR-872-5p expression, forming a positive feedback loop that promotes NSC proliferation.

Neural stem/progenitor cell-derived extracellular vesicles: A novel therapy for neurological diseases and beyond

As bilayer lipid membrane vesicles secreted by neural stem/progenitor cells (NSCs), NSC-derived extracellular vesicles (NSC-EVs) have attracted growing attention for their promising potential to serve as novel therapeutic agents in treatment of neurological diseases due to their unique physicochemical characteristics and biological functions. NSC-EVs exhibit advantages such as stable physical and chemical properties, low immunogenicity, and high penetration capacity to cross blood-brain barrier to avoid predicaments of the clinical applications of NSCs that include autoimmune responses, ethical/religious concerns, and the problematic logistics of acquiring fetal tissues. More importantly, NSC-EVs inherit excellent neuroprotective and neuroregenerative potential and immunomodulatory capabilities from parent cells, and display outstanding therapeutic effects on mitigating behavioral alterations and pathological phenotypes of patients or animals with neurological diseases. In this review, we first comprehensively summarize the progress in functional research and application of NSC-EVs in different neurological diseases, including neurodegenerative diseases, acute neurological diseases, dementia/cognitive dysfunction, and peripheral diseases. Next, we provide our thoughts on current limitations/concerns as well as tremendous potential of NSC-EVs in clinical applications. Last, we discuss future directions of further investigations on NSC-EVs and their probable applications in both basic and clinical research.

The Dialogue Between Neuroinflammation and Adult Neurogenesis: Mechanisms Involved and Alterations in Neurological Diseases

Adult neurogenesis occurs mainly in the subgranular zone of the hippocampal dentate gyrus and the subventricular zone of the lateral ventricles. Evidence supports the critical role of adult neurogenesis in various conditions, including cognitive dysfunction, Alzheimer's disease (AD), and Parkinson's disease (PD). Several factors can alter adult neurogenesis, including genetic, epigenetic, age, physical activity, diet, sleep status, sex hormones, and central nervous system (CNS) disorders, exerting either pro-neurogenic or anti-neurogenic effects. Compelling evidence suggests that any insult or injury to the CNS, such as traumatic brain injury (TBI), infectious diseases, or neurodegenerative disorders, can provoke an inflammatory response in the CNS. This inflammation could either promote or inhibit neurogenesis, depending on various factors, such as chronicity and severity of the inflammation and underlying neurological disorders. Notably, neuroinflammation, driven by different immune components such as activated glia, cytokines, chemokines, and reactive oxygen species, can regulate every step of adult neurogenesis, including cell proliferation, differentiation, migration, survival of newborn neurons, maturation, synaptogenesis, and neuritogenesis. Therefore, this review aims to present recent findings regarding the effects of various components of the immune system on adult neurogenesis and to provide a better understanding of the role of neuroinflammation and neurogenesis in the context of neurological disorders, including AD, PD, ischemic stroke (IS), seizure/epilepsy, TBI, sleep deprivation, cognitive impairment, and anxiety- and depressive-like behaviors. For each disorder, some of the most recent therapeutic candidates, such as curcumin, ginseng, astragaloside, boswellic acids, andrographolide, caffeine, royal jelly, estrogen, metformin, and minocycline, have been discussed based on the available preclinical and clinical evidence.

Electric field stimulation boosts neuronal differentiation of neural stem cells for spinal cord injury treatment via PI3K/Akt/GSK-3β/β-catenin activation

BACKGROUND

Neural stem cells (NSCs) are considered as candidates for cell replacement therapy in many neurological disorders. However, the propensity for their differentiation to proceed more glial rather than neuronal phenotypes in pathological conditions limits positive outcomes of reparative transplantation. Exogenous physical stimulation to favor the neuronal differentiation of NSCs without extra chemical side effect could alleviate the problem, providing a safe and highly efficient cell therapy to accelerate neurological recovery following neuronal injuries.

RESULTS

With 7-day physiological electric field (EF) stimulation at 100 mV/mm, we recorded the boosted neuronal differentiation of NSCs, comparing to the non-EF treated cells with 2.3-fold higher MAP2 positive cell ratio, 1.6-fold longer neuronal process and 2.4-fold higher cells ratio with neuronal spontaneous action potential. While with the classical medium induction, the neuronal spontaneous potential may only achieve after 21-day induction. Deficiency of either PI3Kγ or β-catenin abolished the above improvement, demonstrating the requirement of the PI3K/Akt/GSK-3β/β-catenin cascade activation in the physiological EF stimulation boosted neuronal differentiation of NSCs. When transplanted into the spinal cord injury (SCI) modelled mice, these EF pre-stimulated NSCs were recorded to develop twofold higher proportion of neurons, comparing to the non-EF treated NSCs. Along with the boosted neuronal differentiation following transplantation, we also recorded the improved neurogenesis in the impacted spinal cord and the significantly benefitted hind limp motor function repair of the SCI mice.

CONCLUSIONS

In conclusion, we demonstrated physiological EF stimulation as an efficient method to boost the neuronal differentiation of NSCs via the PI3K/Akt/GSK-3β/β-catenin activation. Pre-treatment with the EF stimulation induction before NSCs transplantation would notably improve the therapeutic outcome for neurogenesis and neurofunction recovery of SCI.

Hydrogen Promotes the Effectiveness of Bone Mesenchymal Stem Cell Transplantation in Rats with Spinal Cord Injury

Although bone mesenchymal stem cell (BMSC) transplantation has been applied to the treatment of spinal cord injury (SCI), the effect is unsatisfactory due to the specific microenvironment (inflammation and oxidative stress) in the SCI area, which leads to the low survival rate of transplanted cells. Thus, additional strategies are required to improve the efficacy of transplanted cells in the treatment of SCI. Hydrogen possesses antioxidant and anti-inflammatory properties. However, whether hydrogen can enhance the effect of BMSC transplantation in the treatment of SCI has not yet been reported. This study was aimed at investigating whether hydrogen promotes the therapeutic effect of BMSC transplantation in the treatment of SCI in rats. In vitro, BMSCs were cultured in a normal medium and a hydrogen-rich medium to study the effect of hydrogen on the proliferation and migration of BMSCs. BMSCs were treated with a serum-deprived medium (SDM), and the effects of hydrogen on the apoptosis of BMSCs were studied. In vivo, BMSCs were injected into the rat model of SCI. Hydrogen-rich saline (5 ml/kg) and saline (5 ml/kg) were given once a day via intraperitoneal injection. Neurological function was evaluated using the Basso, Beattie, and Bresnahan (BBB) and CatWalk gait analyses. Histopathological analysis, oxidative stress, inflammatory factors (TNF-α, IL-1β, and IL-6), and transplanted cell viability were detected at 3 and 28 days after SCI. Hydrogen can significantly enhance BMSC proliferation and migration and tolerance to SDM. Hydrogen and BMSC codelivery can significantly enhance neurological function recovery by improving the transplant cell survival rate and migration. Hydrogen can enhance the migration and proliferation capacity of BMSCs to repair SCI by reducing the inflammatory response and oxidative stress in the injured area. Hydrogen and BMSC codelivery is an effective method to improve BMSC transplantation in the treatment of SCI.

Pathophysiology of Spinal Cord Injury and Tissue Engineering Approach for Its Neuronal Regeneration: Current Status and Future Prospects

A spinal cord injury (SCI) is a very debilitating condition causing loss of sensory and motor function as well as multiple organ failures. Current therapeutic options like surgery and pharmacotherapy show positive results but are incapable of providing a complete cure for chronic SCI symptoms. Tissue engineering, including neuroprotective or growth factors, stem cells, and biomaterial scaffolds, grabs attention because of their potential for regeneration and ability to bridge the gap in the injured spinal cord (SC). Preclinical studies with tissue engineering showed functional recovery and neurorestorative effects. Few clinical trials show the safety and efficacy of the tissue engineering approach. However, more studies should be carried out for potential treatment modalities. In this review, we summarize the pathophysiology of SCI and its current treatment modalities, including surgical, pharmacological, and tissue engineering approaches following SCI in preclinical and clinical phases.

Injury-Transplantation Interval-Dependent Amelioration of Axonal Degeneration and Motor Deficit in Rats with Penetrating Traumatic Brain Injury

Penetrating traumatic brain injury (pTBI) is increasingly survivable, but permanently disabling as adult mammalian nervous system does not regenerate. Recently, our group demonstrated transplant location-dependent neuroprotection and safety of clinical trial-grade human neural stem cell (hNSC) transplantation in a rodent model of acute pTBI. To evaluate whether longer injury-transplantation intervals marked by chronic inflammation impede engraftment, 60 male Sprague-Dawley rats were randomized to three sets. Each set was divided equally into two groups: 1) with no injury (sham) or 2) pTBI. After either 1 week (groups 1 and 2), 2 weeks (groups 3 and 4), or 4 weeks after injury (groups 5 and 6), each animal received 0.5 million hNSCs perilesionally. A seventh group of pTBI animals treated with vehicle served as the negative control. All animals were allowed to survive 12 weeks with standard chemical immunosuppression. Motor capacity was assessed pre-transplant to establish injury-induced deficit and followed by testing at 8 and 12 weeks after transplantation. Animals were euthanized, perfused, and examined for lesion size, axonal degeneration, and engraftment. Compared to vehicle, transplanted groups showed a trend for reduced lesion size and axonal injury across intervals. Remote secondary axonal injury was significantly reduced in groups 2 and 4, but not in group 6. The majority of animals showed robust engraftment independent of the injury-transplant time interval. Modest amelioration of motor deficit paralleled the axonal injury trend. In aggregate, pTBI-induced remote secondary axonal injury was resolved by early, but not delayed, hNSC transplantation.

Cell therapy for neuropathic pain

Neuropathic pain (NP) is caused by a lesion or a condition that affects the somatosensory system. Pathophysiologically, NP can be ascribed to peripheral and central sensitization, implicating a wide range of molecular pathways. Current pharmacological and non-pharmacological approaches are not very efficacious, with over half of NP patients failing to attain adequate pain relief. So far, pharmacological and surgical treatments have focused primarily on symptomatic relief by modulating pain transduction and transmission, without treating the underlying pathophysiology. Currently, researchers are trying to use cell therapy as a therapeutic alternative for the treatment of NP. In fact, mounting pre-clinical and clinical studies showed that the cell transplantation-based therapy for NP yielded some encouraging results. In this review, we summarized the use of cell grafts for the treatment of NP caused by nerve injury, synthesized the latest advances and adverse effects, discussed the possible mechanisms to inform pain physicians and neurologists who are endeavoring to develop cell transplant-based therapies for NP and put them into clinical practice.

Molecular Mechanisms and Clinical Application of Multipotent Stem Cells for Spinal Cord Injury

Spinal Cord Injury (SCI) is a common neurological disorder with devastating psychical and psychosocial sequelae. The majority of patients after SCI suffer from permanent disability caused by motor dysfunction, impaired sensation, neuropathic pain, spasticity as well as urinary complications, and a small number of patients experience a complete recovery. Current standard treatment modalities of the SCI aim to prevent secondary injury and provide limited recovery of lost neurological functions. Stem Cell Therapy (SCT) represents an emerging treatment approach using the differentiation, paracrine, and self-renewal capabilities of stem cells to regenerate the injured spinal cord. To date, multipotent stem cells including mesenchymal stem cells (MSCs), neural stem cells (NSCs), and hematopoietic stem cells (HSCs) represent the most investigated types of stem cells for the treatment of SCI in preclinical and clinical studies. The microenvironment of SCI has a significant impact on the survival, proliferation, and differentiation of transplanted stem cells. Therefore, a deep understanding of the pathophysiology of SCI and molecular mechanisms through which stem cells act may help improve the treatment efficacy of SCT and find new therapeutic approaches such as stem-cell-derived exosomes, gene-modified stem cells, scaffolds, and nanomaterials. In this literature review, the pathogenesis of SCI and molecular mechanisms of action of multipotent stem cells including MSCs, NSCs, and HSCs are comprehensively described. Moreover, the clinical efficacy of multipotent stem cells in SCI treatment, an optimal protocol of stem cell administration, and recent therapeutic approaches based on or combined with SCT are also discussed.

A Narrative Review of Advances in Neural Precursor Cell Transplantation Therapies for Spinal Cord Injury

A spinal cord injury (SCI) is a destructive event that causes a permanent deficit in neurological function because of poor regenerative potential. Transplantation therapies have attracted attention for restoration of the injured spinal cord, and transplantation of neural precursor cells (NPCs) has been studied worldwide. Several groups have demonstrated functional recovery via this therapeutic intervention due to the multiple beneficial effects of NPC transplantation, such as reconstruction of neuronal circuits, remyelination of axons, and neuroprotection by trophic factors. Our group developed a method to induce NPCs from human induced pluripotent stem cells (hiPSCs) and established a transplantation strategy for SCI. Functional improvement in SCI animals treated with hiPSC-NPCs was observed, and the safety of transplanting these cells was evaluated from multiple perspectives. With selection of a safe cell line and pretreatment of the cells to encourage maturation and differentiation, hiPSC-NPC transplantation therapy is now in the clinical phase of testing for subacute SCI. In addition, a research challenge will be to expand the efficacy of transplantation therapy for chronic SCI. More comprehensive strategies involving combination treatments are required to treat this problematic situation.

Developmentally engineered bio-assemblies releasing neurotrophic exosomes guide in situ neuroplasticity following spinal cord injury

The emerging tissue-engineered bio-assemblies are revolutionizing the regenerative medicine, and provide a potential program to guarantee predictive performance of stem-cell-derived treatments in vivo and hence support their clinical translation. Mesenchymal stem cell (MSC) showed the attractive potential for the therapy of nervous system injuries, especially spinal cord injury (SCI), and yet failed to make an impact on clinical outcomes. Herein, under the guidance of the embryonic development theory that appropriate cellular coarctations or clustering are pivotal initiators for the formation of geometric and functional tissue structures, a developmentally engineered strategy was established to assemble DPMSCs into a bio-assembly termed Spinor through a three-level sequential induction programme including reductant, energy and mechanical force stimulation. Spinor exhibited similar geometric construction with spinal cord tissue and attain autonomy to released exosome with the optimized quantity and quality for suppressing cicatrization and inflammation and promoting axonal regeneration. As a spinal cord fascia and exosome mothership, Spinor guided the in-situ neuroplasticity of spinal cord in vivo, and caused the significant motor improvement, sensory recovery, and faster urinary reflex restoration in rats following SCI, while maintaining a highly favorable biosafety profile. Collectively, Spinor not only is a potentially clinical therapeutic paradigm as a living “exosome mothership” for revisiting Prometheus' Myth in SCI, but can be viewed allowing developmentally engineered manufacturing of biomimetic bio-assemblies with complex topology features and inbuilt biofunction attributes towards the regeneration of complex tissues including nervous system.

Advances in Neural Stem Cell Therapy for Spinal Cord Injury: Safety, Efficacy, and Future Perspectives

Spinal cord injury (SCI) is a devastating central nervous system injury that leads to severe disabilities in motor and sensory functions, causing significant deterioration in patients' quality of life. Owing to the complexity of SCI pathophysiology, there has been no effective treatment for reversing neural tissue damage and recovering neurological functions. Several novel therapies targeting different stages of pathophysiological mechanisms of SCI have been developed. Among these, treatments using stem cells have great potential for the regeneration of damaged neural tissues. In this review, we have summarized recent preclinical and clinical studies focusing on neural stem cells (NSCs). NSCs are multipotent cells with specific differentiation capabilities for neural lineage. Several preclinical studies have demonstrated the regenerative effects of transplanted NSCs in SCI animal models through both paracrine effects and direct neuronal differentiation, restoring synaptic connectivity and neural networks. Based on the positive results of several preclinical studies, phase I and II clinical trials using NSCs have been performed. Despite several hurdles and issues that need to be addressed in the clinical use of NSCs in patients with SCI, gradual progress in the technical development and therapeutic efficacy of NSCs treatments has enhanced the prospects for cell-based treatments in SCI.

Restoration of spinal cord injury: From endogenous repairing process to cellular therapy

Spinal cord injury (SCI) disrupts neurological pathways and impacts sensory, motor, and autonomic nerve function. There is no effective treatment for SCI currently. Numerous endogenous cells, including astrocytes, macrophages/microglia, and oligodendrocyte, are involved in the histological healing process following SCI. By interfering with cells during the SCI repair process, some advancements in the therapy of SCI have been realized. Nevertheless, the endogenous cell types engaged in SCI repair and the current difficulties these cells confront in the therapy of SCI are poorly defined, and the mechanisms underlying them are little understood. In order to better understand SCI and create new therapeutic strategies and enhance the clinical translation of SCI repair, we have comprehensively listed the endogenous cells involved in SCI repair and summarized the six most common mechanisms involved in SCI repair, including limiting the inflammatory response, protecting the spared spinal cord, enhancing myelination, facilitating neovascularization, producing neurotrophic factors, and differentiating into neural/colloidal cell lines.

Stem Cell- and Cell-Based Therapies for Ischemic Stroke

Stroke is the second cause of disability worldwide as it is expected to increase its incidence and prevalence. Despite efforts to increase the number of patients eligible for recanalization therapies, a significant proportion of stroke survivors remain permanently disabled. This outcome boosted the search for efficient neurorestorative methods. Stem cells act through multiple pathways: cell replacement, the secretion of growth factors, promoting endogenous reparative pathways, angiogenesis, and the modulation of neuroinflammation. Although neural stem cells are difficult to obtain, pose a series of ethical issues, and require intracerebral delivery, mesenchymal stem cells are less immunogenic, are easy to obtain, and can be transplanted via intravenous, intra-arterial, or intranasal routes. Extracellular vesicles and exosomes have similar actions and are easier to obtain, also allowing for engineering to deliver specific molecules or RNAs and to promote the desired effects. Appropriate timing, dosing, and delivery protocols must be established, and the possibility of tumorigenesis must be settled. Nonetheless, stem cell- and cell-based therapies for stroke have already entered clinical trials. Although safe, the evidence for efficacy is less impressive so far. Hopefully, the STEP guidelines and the SPAN program will improve the success rate. As such, stem cell- and cell-based therapy for ischemic stroke holds great promise.

Restoring After Central Nervous System Injuries: Neural Mechanisms and Translational Applications of Motor Recovery

Central nervous system (CNS) injuries, including stroke, traumatic brain injury, and spinal cord injury, are leading causes of long-term disability. It is estimated that more than half of the survivors of severe unilateral injury are unable to use the denervated limb. Previous studies have focused on neuroprotective interventions in the affected hemisphere to limit brain lesions and neurorepair measures to promote recovery. However, the ability to increase plasticity in the injured brain is restricted and difficult to improve. Therefore, over several decades, researchers have been prompted to enhance the compensation by the unaffected hemisphere. Animal experiments have revealed that regrowth of ipsilateral descending fibers from the unaffected hemisphere to denervated motor neurons plays a significant role in the restoration of motor function. In addition, several clinical treatments have been designed to restore ipsilateral motor control, including brain stimulation, nerve transfer surgery, and brain–computer interface systems. Here, we comprehensively review the neural mechanisms as well as translational applications of ipsilateral motor control upon rehabilitation after CNS injuries.

GelMA-MXene hydrogel nerve conduits with microgrooves for spinal cord injury repair

Repair of spinal cord injury (SCI) depends on microenvironment improvement and the reconnection between injured axons and regenerated neurons. Here, we fabricate a GelMA-MXene hydrogel nerve conduit with electrical conductivity and internal-facing longitudinal grooves and explore its function in SCI repair. It is found that the resultant grooved GelMA-MXene hydrogel could effectively promote the neural stem cells (NSCs) adhesion, directed proliferation and differentiation in vitro. Additionally, when the GelMA-MXene conduit loaded with NSCs (GMN) is implanted into the injured spinal cord site, effective repair capability for the complete transection of SCI was demonstrated. The GMN group shows remarkable nerve recovery and significantly higher BBB scores in comparison to the other groups. Therefore, GMN with the microgroove structure and loaded with NSCs is a promising strategy in treating SCI.

Intrathecal Cell Therapy with Autologous Bone Marrow Stromal Cells as a New Tool for Neurologic Sequels after Spinal Cord Surgery: A Report of Two Cases

Background aims: The possibility of permanent neurological sequels after surgery of benign lesions affecting the spinal cord is well known. Frequently, they are irreversible, with no effective treatment other than rehabilitation. However, in recent years, intrathecal cell therapy with autologous bone marrow stromal cells (MSCs) in patients with incomplete paraplegia has shown benefits for diverse sequels of spinal cord injury (SCI). Methods: We present two patients with chronic spinal cord sequels after a surgery, who underwent cell therapy treatment with NC1 medicament (repeated intrathecal administrations of MSCs). Results: In both cases, cell therapy achieved a clear improvement in neurological sequels, such as recovery of gait disturbances, bowel dysfunction, or neuropathic pain. Conclusion: Intrathecal cell therapy with autologous MSCs offers a new approach for neurological sequels after spinal cord surgery.

Transplantation of Human-Fetal-Spinal-Cord-Derived NPCs Primed with a Polyglutamate-Conjugated Rho/Rock Inhibitor in Acute Spinal Cord Injury

Neural precursor cell (NPC) transplantation represents a promising therapy for treating spinal cord injuries (SCIs); however, despite successful results obtained in preclinical models, the clinical translation of this approach remains challenging due, in part, to the lack of consensus on an optimal cell source for human neuronal cells. Depending on the cell source, additional limitations to NPC-based therapies include high tumorigenic potential, alongside poor graft survival and engraftment into host spinal tissue. We previously demonstrated that NPCs derived from rat fetal spinal cords primed with a polyglutamate (PGA)-conjugated form of the Rho/Rock inhibitor fasudil (PGA-SS-FAS) displayed enhanced neuronal differentiation and graft survival when compared to non-primed NPCs. We now conducted a similar study of human-fetal-spinal-cord-derived NPCs (hfNPCs) from legal gestational interruptions at the late gestational stage, at 19-21.6 weeks. In vitro, expanded hfNPCs retained neural features, multipotency, and self-renewal, which supported the development of a cell banking strategy. Before transplantation, we established a simple procedure to prime hfNPCs by overnight incubation with PGA-SS-FAS (at 50 μM FAS equiv.), which improved neuronal differentiation and overcame neurite-like retraction after lysophosphatidic-acid-induced Rho/Rock activation. The transplantation of primed hfNPCs into immune-deficient mice (NU(NCr)-Foxn1^nu) immediately after the eighth thoracic segment compression prompted enhanced migration of grafted cells from the dorsal to the ventral spinal cord, increased preservation of GABAergic inhibitory Lbx1-expressing and glutamatergic excitatory Tlx3-expressing somatosensory interneurons, and elevated the numbers of preserved, c-Fos-expressing, activated neurons surrounding the injury epicenter, all in a low percentage. Overall, the priming procedure using PGA-SS-FAS could represent an alternative methodology to improve the capabilities of the hfNPC lines for a translational approach for acute SCI treatment.

Prevention of Oxidative Damage in Spinal Cord Ischemia Upon Aortic Surgery: First-In-Human Results of Shock Wave Therapy Prove Safety and Feasibility

Background Spinal cord ischemia (SCI) remains a devastating complication after aortic dissection or repair. A primary hypoxic damage is followed by a secondary damage resulting in further cellular loss via apoptosis. Affected patients have a poor prognosis and limited therapeutic options. Shock wave therapy (SWT) improves functional outcome, neuronal degeneration and survival in murine spinal cord injury. In this first-in-human study we treated 5 patients with spinal cord ischemia with SWT aiming to prove safety and feasibility. Methods and Results Human neurons were subjected to ischemic injury with subsequent SWT. Reactive oxygen species and cellular apoptosis were quantified using flow cytometry. Signaling of the antioxidative transcription factor NRF2 (nuclear factor erythroid 2-related factor 2) and immune receptor Toll-like receptor 3 (TLR3) were analyzed. To assess whether SWT act via a conserved mechanism, transgenic tlr3^-/- zebrafish created via CRISPR/Cas9 were subjected to spinal cord injury. To translate our findings into a clinical setting, 5 patients with SCI underwent SWT. Baseline analysis and follow-up (6 months) included assessment of American Spinal Cord Injury Association (ASIA) impairment scale, evaluation of Spinal Cord Independence Measure score and World Health Organization Quality of Life questionnaire. SWT reduced the number of reactive oxygen species positive cells and apoptosis upon ischemia via induction of the antioxidative factor nuclear factor erythroid 2-related factor 2. Inhibition or deletion of tlr3 impaired axonal growth after spinal cord lesion in zebrafish, whereas tlr3 stimulation enhanced spinal regeneration. In a first-in-human study, we treated 5 patients with SCI using SWT (mean age, 65.3 years). Four patients presented with acute aortic dissection (80%), 2 of them exhibited preoperative neurological symptoms (40%). Impairment was ASIA A in 1 patient (20%), ASIA B in 3 patients (60%), and ASIA D in 1 patient (20%) at baseline. At follow-up, 2 patients were graded as ASIA A (40%) and 3 patients as ASIA B (60%). Spinal cord independence measure score showed significant improvement. Examination of World Health Organization Quality of Life questionnaires revealed increased scores at follow-up. Conclusions SWT reduces oxidative damage upon SCI via immune receptor TLR3. The first-in-human application proved safety and feasibility in patients with SCI. SWT could therefore become a powerful regenerative treatment option for this devastating injury.

The neural stem cell properties of Pkd2l1+ cerebrospinal fluid-contacting neurons in vivo

The neural stem cells (NSCs) in the ventricular-subventricular zone of the adult mammalian spinal cord may be of great benefit for repairing spinal cord injuries. However, the sources of NSCs remain unclear. Previously, we have confirmed that cerebrospinal fluid-contacting neurons (CSF-cNs) have NSC potential in vitro. In this study, we verified the NSC properties of CSF-cNs in vivo. In mouse spinal cords, Pkd2l1+ CSF-cNs localized around the central canal express NSC markers. In vitro, Pkd2l1+ CSF-cNs form a neurosphere and express NSC markers. Activation and proliferation of CSF-cNs can be induced by injection of the neurotrophic factors basic fibroblast growth factor (bFGF) and vascular endothelial growth factor (VEGF) into the lateral ventricle. Spinal cord injury (SCI) also induces NSC activation and proliferation of CSF-cNs. Collectively, our results demonstrate that Pkd2l1+ CSF-cNs have NSC properties in vivo and may be involved in SCI recovery.

Clinical translation of stem cell therapy for spinal cord injury still premature: results from a single-arm meta-analysis based on 62 clinical trials

BACKGROUND

How much scientific evidence is there to show that stem cell therapy is sufficient in preclinical and clinical studies of spinal cord injury before it is translated into clinical practice? This is a complicated problem. A single, small-sample clinical trial is difficult to answer, and accurate insights into this question can only be given by systematically evaluating all the existing evidence.

METHODS

The PubMed, Ovid-Embase, Web of Science, and Cochrane databases were searched from inception to February 10, 2022. Two independent reviewers performed the literature search, identified and screened the studies, and performed a quality assessment and data extraction.

RESULTS

In total, 62 studies involving 2439 patients were included in the analysis. Of these, 42 were single-arm studies, and 20 were controlled studies. The meta-analysis showed that stem cells improved the ASIA impairment scale score by at least one grade in 48.9% [40.8%, 56.9%] of patients with spinal cord injury. Moreover, the rate of improvement in urinary and gastrointestinal system function was 42.1% [27.6%, 57.2%] and 52.0% [23.6%, 79.8%], respectively. However, 28 types of adverse effects were observed to occur due to stem cells and transplantation procedures. Of these, neuropathic pain, abnormal feeling, muscle spasms, vomiting, and urinary tract infection were the most common, with an incidence of > 20%. While no serious adverse effects such as tumorigenesis were reported, this could be due to the insufficient follow-up period.

CONCLUSIONS

Overall, the results demonstrated that although the efficacy of stem cell therapy is encouraging, the subsequent adverse effects remain concerning. In addition, the clinical trials had problems such as small sample sizes, poor design, and lack of prospective registration, control, and blinding. Therefore, the current evidence is not sufficiently strong to support the clinical translation of stem cell therapy for spinal cord injury, and several problems remain. Additional well-designed animal experiments and high-quality clinical studies are warranted to address these issues.

Extracellular vesicle therapy for traumatic central nervous system disorders

Traumatic central nervous system (CNS) disorders have catastrophic effects on patients, and, currently, there is no effective clinical treatment. Cell transplantation is a common treatment for traumatic CNS injury in animals. In recent years, an increasing number of studies have reported that the beneficial effect of transplanted cells for CNS repair is mediated primarily through the extracellular vesicles (EVs) secreted by the cells, in which microRNAs play a major role. Accordingly, numerous studies have evaluated the roles and applications of EVs secreted by different cell types in neurological diseases. Furthermore, due to their unique biological features, EVs are used as disease biomarkers and drug delivery systems for disease prevention and treatment. We discuss current knowledge related to EVs, focusing on the mechanism underlying their effects on traumatic CNS diseases, and summarize existing research on the potential clinical utility of EVs as disease biomarkers and drug delivery systems.

Transplantation of neuron-inducing grafts embedding positively charged gold nanoparticles for the treatment of spinal cord injury

In this study, we aimed to investigate the recovery after traumatic spinal cord injury (SCI) by inducing cellular differentiation of transplanted neural stem cells (NSCs) into neurons. We dissociated NSCs from the spinal cords of Fisher 344 rat embryos. An injectable gel crosslinked with glycol chitosan and oxidized hyaluronate was used as a vehicle for NSC transplantation. The gel graft containing the NSC and positively charged gold nanoparticles (pGNP) was implanted into spinal cord lesions in Sprague-Dawley rats (NSC-pGNP gel group). Cellular differentiation of grafted NSCs into neurons (stained with β-tubulin III [also called Tuj1]) was significantly increased in the NSC-pGNP gel group (***p < 0.001) compared to those of two control groups (NSC and NSC gel groups) in the SCI conditions. The NSC-pGNP gel group showed the lowest differentiation into astrocytes (stained with glial fibrillary acidic protein). Regeneration of damaged axons (stained with biotinylated dextran amines) within the lesion was two-fold higher in the NSC-pGNP gel group than that in the NSC gel group. The highest locomotor scores were also found in the NSC-pGNP gel group. These outcomes suggest that neuron-inducing pGNP gel graft embedding embryonic spinal cord-derived NSCs can be a useful type of stem cell therapy after SCI.

Monoclonal antibody-mediated immunosuppression enables long-term survival of transplanted human neural stem cells in mouse brain

BACKGROUND

As the field of stem cell therapy advances, it is important to develop reliable methods to overcome host immune responses in animal models. This ensures survival of transplanted human stem cell grafts and enables predictive efficacy testing. Immunosuppressive drugs derived from clinical protocols are frequently used but are often inconsistent and associated with toxic side effects. Here, using a molecular imaging approach, we show that immunosuppression targeting costimulatory molecules CD4 and CD40L enables robust survival of human xenografts in mouse brain, as compared to conventional tacrolimus and mycophenolate mofetil.

METHODS

Human neural stem cells were modified to express green fluorescent protein and firefly luciferase. Cells were implanted in the fimbria fornix of the hippocampus and viability assessed by non-invasive bioluminescent imaging. Cell survival was assessed using traditional pharmacologic immunosuppression as compared to monoclonal antibodies directed against CD4 and CD40L. This paradigm was also implemented in a transgenic Alzheimer's disease mouse model.

RESULTS

Graft rejection occurs within 7 days in non-immunosuppressed mice and within 14 days in mice on a traditional regimen. The addition of dual monoclonal antibody immunosuppression extends graft survival past 7 weeks (p < .001) on initial studies. We confirm dual monoclonal antibody treatment is superior to either antibody alone (p < .001). Finally, we demonstrate robust xenograft survival at multiple cell doses up to 6 months in both C57BL/6J mice and a transgenic Alzheimer's disease model (p < .001). The dual monoclonal antibody protocol demonstrated no significant adverse effects, as determined by complete blood counts and toxicity screen.

CONCLUSIONS

This study demonstrates an effective immunosuppression protocol for preclinical testing of stem cell therapies. A transition towards antibody-based strategies may be advantageous by enabling stem cell survival in preclinical studies that could inform future clinical trials.

The roles and applications of neural stem cells in spinal cord injury repair

Spinal cord injury (SCI), which has no current cure, places a severe burden on patients. Stem cell-based therapies are considered promising in attempts to repair injured spinal cords; such options include neural stem cells (NSCs). NSCs are multipotent stem cells that differentiate into neuronal and neuroglial lineages. This feature makes NSCs suitable candidates for regenerating injured spinal cords. Many studies have revealed the therapeutic potential of NSCs. In this review, we discuss from an integrated view how NSCs can help SCI repair. We will discuss the sources and therapeutic potential of NSCs, as well as representative pre-clinical studies and clinical trials of NSC-based therapies for SCI repair.

The Anti-inflammation Property of Olfactory Ensheathing Cells in Neural Regeneration After Spinal Cord Injury

Neural regeneration has troubled investigators worldwide in the past decades. Currently, cell transplantation emerged as a breakthrough targeted therapy for spinal cord injury (SCI) in the neurotrauma field, which provides a promising strategy in neural regeneration. Olfactory ensheathing cells (OECs), a specialized type of glial cells, is considered as the excellent candidate due to its unique variable and intrinsic regeneration-supportive properties. In fact, OECs could support olfactory receptor neuron turnover and axonal extension, which is essential to maintain the function of olfactory nervous system. Hitherto, an increasing number of literatures demonstrate that transplantation of OECs exerts vital roles in neural regeneration and functional recovery after neural injury, including central and peripheral nervous system. It is common knowledge that the deteriorating microenvironment (ischemia, hypoxia, scar, acute and chronic inflammation, etc.) resulting from injured nervous system is adverse for neural regeneration. Interestingly, recent studies indicated that OECs could promote neural repair through improvement of the disastrous microenvironments, especially to the overwhelmed inflammatory responses. Although OECs possess unusual advantages over other cells for neural repair, particularly in SCI, the mechanisms of OEC-mediated neural repair are still controversial with regard to anti-inflammation. Therefore, it is significant to summarize the anti-inflammation property of OECs, which is helpful to understand the biological characteristics of OECs and drive future studies. Here, we mainly focus on the anti-inflammatory role of OECs to make systematic review and discuss OEC-based therapy for CNS injury.

Mesenchymal Stem Cell-Derived Exosomal MiRNAs Promote M2 Macrophages Polarization: Therapeutic Opportunities for Spinal Cord Injury

Spinal cord injury (SCI) is an enormous public health concern affecting approximately 250,000–500,000 people worldwide each year. It is mostly irreversible considering the limitations of currently available treatments, and its prevention and management have been the prime focus of many studies. Mesenchymal stem cell (MSC) transplantation is one of the most promising treatments for SCI. The role of MSCs in SCI has been studied extensively, and MSCs have been shown to have many limitations. Moreover, the therapeutic effects of MSCs are more likely related to paracrine effects. In SCIs, macrophages from peripheral sources differentiate into M1 macrophages, promoting inflammation and aggravating neuronal damage; however, studies have shown that MSC-derived exosomes can induce the polarization of macrophages from the M1 to the M2 phenotype, thereby promoting nerve function recovery in patients with SCI. In this review, we discussed the research progress of MSC-derived exosomal miRNAs in promoting M2 macrophage differentiation in the SCI, and introduced some exosomal miRNAs that can regulate the differentiation of M2 macrophages in non-SCI; it is hoped that the regulatory role of these exosome-derived miRNAs can be confirmed in SCI.

Assessing fetal human neural stem cells tumorigenicity potential in athymic rats with penetrating traumatic brain injury (pTBI)

Traumatic brain injuries (TBI) often produce disability in survivors due to unresolved inflammation and progressive neurodegeneration. The central nervous system in mammals is incapable of self-repair. Two decades of preclinical studies and clinical trials have provided insights into TBI pathophysiology that could be utilized to develop clinically relevant therapy. Our laboratory recently reported efficacy of clinical trial grade fetal human neural stem cells (hNSCs) in immunosuppressed rats with penetrating traumatic brain injury (pTBI). Next, in compliance with the United States Food and Drug Administration (USFDA) guidance, this study explores safety by assessing the tumorigenicity potential of intracranial hNSC transplants in athymic rats with pTBI. First, the maximum tolerated dose (MTD) was determined. Then, forty athymic pTBI rats were randomized to either: Group A. pTBI + vehicle or Group B. pTBI + hNSCs at MTD one week after injury with 6-months survival, sufficient time to uncover transplant associated tumorigenicity. A board-certified Pathologist examined hematoxylin-eosin (H&E), Ki67 immunostained brain and spinal cord, serial sections along with several abnormal peripheral masses for evidence of lesion, transplant, and oncogenesis. There was no evidence of transplant derived tumors or oncogenic tissue necrosis. Consistent with athymic literature, the lesion remained unchanged even after robust hNSC engraftment. This safety study supports the conclusion that hNSCs are safe for transplantation in pTBI. The differences in lesion expansion between immunosuppressed and athymic rats in the presence of hNSCs suggests an unexpected role for thymus derived cells in resolution of trauma induced inflammation.

Microneedle-based technology for cell therapy: current status and future directions

With the growing technological innovations in medical treatments, cell-based therapies hold great potential as efficient tools against various previously incurable diseases by restoring or altering the function of certain sets of cells. Along this line, an essential factor to determine the success of cell therapy is the choice of cell delivery strategy. In recent years, a novel trend is blooming in the application of microneedle systems, which are based on the miniaturization of multiple needles within a patch to the micrometer dimensions, aimed at the delivery of therapeutic cells to the target site with high efficiency and in a minimally invasive manner. This review aims to demonstrate the advantages of exploiting microneedle-based technology as a new tool for cell therapy. The advancements of microneedle-based strategies for cell delivery are summarized in terms of two categories: cell-free and cell-loaded microneedle systems. The majority of research on microneedle-based cell therapy has shown promising results for tissue regeneration, cancer immunotherapy, skin immune monitoring and targeted cell delivery. Finally, current challenges and future perspectives toward the development and application of microneedles for cell therapy are also discussed.

Strengthening regulations, recent advances and remaining barriers in stem cell clinical translation in China: 2015-2021 in review

A new regulatory regime is being implemented under strict scrutiny for translation of stem cell medical practices since 2015 in China. The new mode of governance is strengthening to curb the marketing of unproven stem cell therapeutic products. This article begins with a brief historical overview of stem cell research and development and then focuses on the policies and country-level guidelines in the past years for stem cell translational research. This study reveals several key observations on the major progress made and the challenges associated with clinical translation of stem cells in China. Given that stem cells or stem cell-based therapeutic products are already considered as biological 'drugs', this study would be conducive to a better understanding of China's approach to stem cell translational research, marketisation and industrialization in progress.

Highly feasible procedure for laparoscopic transplantation of cell sheets under pneumoperitoneum in porcine model

INTRODUCTION

Cell sheet technology is one of the most successful methodologies in regenerative medicine. Various applications of cell sheets have been introduced in first-in-human studies in several clinical fields. When transplanting a cell sheet into internal organs, a relatively large incision is required for delivery due to difficulty handling the sheet. We developed a laparoscopic delivery procedure for safe and easy transplantation of cell sheets in a porcine model.

METHODS

Pneumoperitoneum was established by inflation with CO₂. First, to increase the strength during handling, fibrin was sprayed onto the surface of the cell sheet, and then a myoblast sheet was placed onto the newly developed carrier. The sheets were pinched with laparoscopic forceps to insert into the abdominal cavity through the laparoscopic port. Myoblast sheets were then applied to the surface of the liver, colon, small intestine, and stomach, and procedure times were measured. At three days post transplantation, a histopathological examination was performed to confirm engraftment of the sheet. The function and engraftment were also analyzed in a duodenal endoscopic submucosal dissection (ESD) model.

RESULTS

The fibrin-processed myoblast sheet was able to be managed with conventional laparoscopic forceps without breaking. Despite the drastic change in air pressure by passing through the laparoscopic port, the sheets suffered no apparent damage. The transplantation procedure times did not markedly differ among transplant sites. A histopathological examination revealed thin-layered, desmin-positive cells at each transplant site. With transplantation following ESD, the engrafted myoblast sheets effectively prevented delayed perforation.

CONCLUSIONS

Our procedure is simple, and the system involves a carrier made of medically fit silicon, commercially available fibrin glue and conventional laparoscopic forceps. Our procedure is a powerful tool for laparoscopical cell sheet transplantation.

Stem Cell Therapy in Limb Ischemia: State-of-Art, Perspective, and Possible Impacts of Endometrial-Derived Stem Cells

As an evidence-based performance, the rising incidence of various ischemic disorders has been observed across many nations. As a result, there is a growing need for the development of more effective regenerative approaches that could serve as main therapeutic strategies for the treatment of these diseases. From a cellular perspective, promoted complex inflammatory mechanisms, after inhibition of organ blood flow, can lead to cell death in all tissue types. In this case, using the stem cell technology provides a safe and regenerative approach for ischemic tissue revascularization and functional cell formation. Limb ischemia (LI) is one of the most frequent ischemic disease types and has been shown to have a promising regenerative response through stem cell therapy based on several clinical trials. Bone marrow-derived mononuclear cells (BM-MNCs), peripheral blood CD34-positive mononuclear cells (CD34+ PB-MNCs), mesenchymal stem cells (MSCs), and endothelial stem/progenitor cells (ESPCs) are the main, well-examined stem cell types in these studies. Additionally, our investigations reveal that endometrial tissue can be considered a suitable candidate for isolating new safe, effective, and feasible multipotent stem cells for limb regeneration. In addition to other teams’ results, our in-depth studies on endometrial-derived stem cells (EnSCs) have shown that these cells have translational potential for limb ischemia treatment. The EnSCs are able to generate diverse types of cells which are essential for limb reconstruction, including endothelial cells, smooth muscle cells, muscle cells, and even peripheral nervous system populations. Hence, the main object of this review is to present stem cell technology and evaluate its method of regeneration in ischemic limb tissue.

Human Adipose-Derived Stem Cells Combined with Nano-Hydrogel Promote Functional Recovery after Spinal Cord Injury in Rats

Simple Summary

Nerve regeneration and functional recovery after spinal cord injury (SCI) are worldwide problems. Scientists have achieved encouraging results in the repair of spinal cord injuries using natural or synthetic materials. In this paper, we report that nano-hydrogel combined with human adipose-derived stem cells regulate the inflammatory microenvironment, protect neurons and axons, and promote motor function recovery. In addition, three proteins related to neuronal and axonal growth were screened by Liquid chromatography-mass spectrometry. These results provide evidence for clinical treatment of spinal cord injury.

Abstract

The treatment of spinal cord injury aims to reconstruct the fiber connection and restore the interrupted neural pathways. Adipose mesenchymal stem cells (ADSCs) can promote the recovery of motor functions in spinal cord injury. However, poor survival of ADSCs and leakage outside of the injury site after local transplantation reduce the number of cells, which seriously attenuates the cumulative effect. We performed heterotopic transplantation on rats with severe spinal cord injury using human ADSCs loaded within self-assembly hydrogel RADA16-RGD (R: arginine; A: alanine; D: aspartic acid; G: glycine). Our results indicate that the combined transplantation of human ADSCs with RADA16-RGD improved the survival of ADSCs at the injured site. The inflammatory reaction was inhibited, with improved survival of the neurons and increased residual area of nerve fibers and myelin protein. The functional behaviors were promoted, as determined by the Basso, Beattie, and Bresnahan (BBB) locomotor rating scale score and electrophysiological measurements. ADSCs can promote the repair of spinal cord injury. This study provides new ideas for the treatment of spinal cord injury.