Brain and spinal cord injury repair by implantation of human neural progenitor cells seeded onto polymer scaffolds

Association between neural stem/progenitor cells and biomaterials in spinal cord injury therapies: A systematic review and network meta-analysis

Spinal cord injury (SCI) is associated with substantial healthcare challenges, frequently resulting in enduring sensory and motor deficits alongside various chronic complications. While advanced regenerative therapies have shown promise in preclinical research, their translation into clinical application has been limited. In response, this study utilized a comprehensive network meta-analysis to evaluate the effectiveness of neural stem/progenitor cell (NSPC) transplantation across animal models of SCI. We analyzed 363 outcomes from 55 distinct studies, categorizing the treatments into NSPCs alone (cell only), NSPCs with scaffolds (cell + scaffold), NSPCs with hydrogels (cell + hydrogel), standalone scaffolds (scaffold), standalone hydrogels (hydrogel), and control groups. Our analysis demonstrated significant enhancements in motor recovery, especially in gait function, within the NSPC treatment groups. Notably, the cell only group showed considerable improvements (standardized mean difference [SMD], 2.05; 95 % credible interval [CrI]: 1.08 to 3.10, p < 0.01), as did the cell + scaffold group (SMD, 3.73; 95 % CrI: 2.26 to 5.22, p < 0.001) and the cell + hydrogel group (SMD, 3.37; 95 % CrI: 1.02 to 5.78, p < 0.05) compared to controls. These therapeutic combinations not only reduced lesion cavity size but also enhanced neuronal regeneration, outperforming the cell only treatments. By integrating NSPCs with supportive biomaterials, our findings pave the way for refining these regenerative strategies to optimize their potential in clinical SCI treatment. Although there is no overall violation of consistency, the comparison of effect sizes between individual treatments should be interpreted in light of the inconsistency. STATEMENT OF SIGNIFICANCE: This study presents a comprehensive network meta-analysis exploring the efficacy of neural stem cell (NSC) transplantation, with and without biomaterials, in animal models of spinal cord injury (SCI). We demonstrate that NSCs, particularly when combined with biomaterials like scaffolds or hydrogels, significantly enhance motor and histological recovery post-SCI. These findings underscore the potential of NSC-based therapies, augmented with biomaterials, to advance SCI treatment, offering new insights into regenerative strategies that could significantly impact clinical practices.

Neuritogenic glycosaminoglycan hydrogels promote functional recovery after severe traumatic brain injury

Objective.Severe traumatic brain injury (sTBI) induced neuronal loss and brain atrophy contribute significantly to long-term disabilities. Brain extracellular matrix (ECM) associated chondroitin sulfate (CS) glycosaminoglycans promote neural stem cell (NSC) maintenance, and CS hydrogel implants have demonstrated the ability to enhance neuroprotection, in preclinical sTBI studies. However, the ability of neuritogenic chimeric peptide (CP) functionalized CS hydrogels in promoting functional recovery, after controlled cortical impact (CCI) and suction ablation (SA) induced sTBI, has not been previously demonstrated. We hypothesized that neuritogenic (CS)CP hydrogels will promote neuritogenesis of human NSCs, and accelerate brain tissue repair and functional recovery in sTBI rats.Approach.We synthesized chondroitin 4-Osulfate (CS-A)CP, and 4,6-O-sulfate (CS-E)CP hydrogels, using strain promoted azide-alkyne cycloaddition (SPAAC), to promote cell adhesion and neuritogenesis of human NSCs,in vitro; and assessed the ability of (CS-A)CP hydrogels in promoting tissue and functional repair, in a novel CCI-SA sTBI model,in vivo. Main results.Results indicated that (CS-E)CP hydrogels significantly enhanced human NSC aggregation and migration via focal adhesion kinase complexes, when compared to NSCs in (CS-A)CP hydrogels,in vitro. In contrast, NSCs encapsulated in (CS-A)CP hydrogels differentiated into neurons bearing longer neurites and showed greater spontaneous activity, when compared to those in (CS-E)CP hydrogels. The intracavitary implantation of (CS-A)CP hydrogels, acutely after CCI-SA-sTBI, prevented neuronal and axonal loss, as determined by immunohistochemical analyses. (CS-A)CP hydrogel implanted animals also demonstrated the significantly accelerated recovery of 'reach-to-grasp' function when compared to sTBI controls, over a period of 5-weeks.Significance.These findings demonstrate the neuritogenic and neuroprotective attributes of (CS)CP 'click' hydrogels, and open new avenues for the development of multifunctional glycomaterials that are functionalized with biorthogonal handles for sTBI repair.

Biomaterials and Cell Therapy Combination in Central Nervous System Treatments

Current pharmacological and surgical therapies for the central nervous system (CNS) show a limited capacity to reduce the damage progression; that together with the intrinsic limited capability of the CNS to regenerate greatly reduces the hopes of recovery. Among all the therapies proposed, the tissue engineering strategies supplemented with therapeutic stem cells remain the most promising. Neural tissue engineering strategies are based on the development of devices presenting optimal physical, chemical, and mechanical properties which, once inserted in the injured site, can support therapeutic cells, limiting the effect of a hostile environment and supporting regenerative processes. Thus, this review focuses on the employment of hydrogel and nanofibrous scaffolds supplemented with stem cells as promising therapeutic tools for the central and peripheral nervous systems in preclinical and clinical applications.

Stem cell-based interventions for the treatment of stroke in newborn infants

BACKGROUND

Perinatal stroke refers to a diverse but specific group of cerebrovascular diseases that occur between 20 weeks of fetal life and 28 days of postnatal life. Acute treatment options for perinatal stroke are limited supportive care, such as controlling hypoglycemia and seizures. Stem cell-based therapies offer a potential therapeutic approach to repair, restore, or regenerate injured brain tissue. Preclinical findings have culminated in ongoing human neonatal studies.

OBJECTIVES

To evaluate the benefits and harms of stem cell-based interventions for the treatment of stroke in newborn infants compared to control (placebo or no treatment) or stem-cell based interventions of a different type or source.

SEARCH METHODS

We searched CENTRAL, PubMed, Embase, and three trials registries in February 2023. We planned to search the reference lists of included studies and relevant systematic reviews for studies not identified by the database searches.

SELECTION CRITERIA

We attempted to include randomized controlled trials, quasi-randomized controlled trials, and cluster trials that evaluated any of the following comparisons. • Stem cell-based interventions (any type) versus control (placebo or no treatment) • Mesenchymal stem/stromal cells (MSCs) of a specifictype (e.g. number of doses or passages) or source (e.g. autologous/allogeneic or bone marrow/cord) versus MSCs of another type or source • Stem cell-based interventions (other than MSCs) of a specific type (e.g. mononuclear cells, oligodendrocyte progenitor cells, neural stem cells, hematopoietic stem cells, or induced pluripotent stem cell-derived cells) or source (e.g. autologous/allogeneic or bone marrow/cord) versus stem cell-based interventions (other than MSCs) of another type or source • MSCs versus stem cell-based interventions other than MSCs We planned to include all types of transplantation regardless of cell source (bone marrow, cord blood, Wharton's jelly, placenta, adipose tissue, peripheral blood), type of graft (autologous or allogeneic), and dose.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were all-cause neonatal mortality, major neurodevelopmental disability, and immune rejection or any serious adverse event. Our secondary outcomes included all-cause mortality prior to first hospital discharge, seizures, adverse effects, and death or major neurodevelopmental disability at 18 to 24 months of age. We planned to use GRADE to assess the certainty of evidence for each outcome.

MAIN RESULTS

We identified no completed or ongoing randomized trials that met our inclusion criteria. We excluded three studies: two were phase 1 trials, and one included newborn infants with conditions other than stroke (i.e. cerebral ischemia and anemia). Among the three excluded studies, we identified the first phase 1 trial on the use of stem cells for neonatal stroke. It reported that a single intranasal application of bone marrow-derived MSCs in term neonates with a diagnosis of perinatal arterial ischemic stroke (PAIS) was feasible and apparently not associated with severe adverse events. However, the trial included only 10 infants, and follow-up was limited to three months.

AUTHORS' CONCLUSIONS

No evidence is currently available to evaluate the benefits and harms of stem cell-based interventions for treatment of stroke in newborn infants. We identified no ongoing studies. Future clinical trials should focus on standardizing the timing and method of cell delivery and cell processing to optimize the therapeutic potential of stem cell-based interventions and safety profiles. Phase 1 and large animal studies might provide the groundwork for future randomized trials. Outcome measures should include all-cause mortality, major neurodevelopmental disability and immune rejection, and any other serious adverse events.

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.

Modulating neuroinflammation through molecular, cellular and biomaterial-based approaches to treat spinal cord injury

The neuroinflammatory response that is elicited after spinal cord injury contributes to both tissue damage and reparative processes. The complex and dynamic cellular and molecular changes within the spinal cord microenvironment result in a functional imbalance of immune cells and their modulatory factors. To facilitate wound healing and repair, it is necessary to manipulate the immunological pathways during neuroinflammation to achieve successful therapeutic interventions. In this review, recent advancements and fresh perspectives on the consequences of neuroinflammation after SCI and modulation of the inflammatory responses through the use of molecular-, cellular-, and biomaterial-based therapies to promote tissue regeneration and functional recovery will be discussed.

Stem cell‐based interventions for the treatment of stroke in newborn infants

This is a protocol for a Cochrane Review (intervention). The objectives are as follows:

To evaluate the benefits and harms of stem cell‐based interventions for the treatment of stroke in newborn infants compared to control (placebo or no treatment) or stem‐cell based interventions of a different type or source.

Rosiglitazone Ameliorates Spinal Cord Injury via Inhibiting Mitophagy and Inflammation of Neural Stem Cells

BACKGROUND

Neurodegenerative diseases, such as Alzheimer's disease, and traumatic brain and spinal cord injury (SCI) are prevalent in clinical practice. Inhibition of hyperactive inflammation and proliferation of endogenous neural stem cells (NSCs) is a promising treatment strategy for SCI. Our previous studies demonstrated the beneficial effects of rosiglitazone (Rosi) on SCI, but its roles in inflammation inhibition and proliferation of NSCs are unknown.

METHODS

SCI in a rat model was established, and the effects of Rosi on motor functions were assessed. The effects of Rosi on NSC proliferation and the underlying mechanisms were explored in details.

RESULTS

We showed that Rosi ameliorated impairment of moto functions in SCI rats, inhibited inflammation, and promoted proliferation of NSCs in vivo. Rosi increased ATP production through enhancing glycolysis but not oxidative phosphorylation. Rosi reduced mitophagy by downregulating PTEN-induced putative kinase 1 (PINK1) transcription to promote NSC proliferation, which was effectively reversed by an overexpression of PINK1 in vitro. Through KEGG analysis and experimental validations, we discovered that Rosi reduced the expression of forkhead box protein O1 (FOXO1) which was a critical transcription factor of PINK1. Three FOXO1 consensus sequences (FCSs) were found in the first intron of the PINK1 gene, which could be potentially binding to FOXO1. The proximal FCS (chr 5: 156680169-156680185) from the translation start site exerted a more significant influence on PINK1 transcription than the other two FCSs. The overexpression of FOXO1 entirely relieved the inhibition of PINK1 transcription in the presence of Rosi.

CONCLUSIONS

Besides inflammation inhibition, Rosi suppressed mitophagy by reducing FOXO1 to decrease the transcription of PINK1, which played a pivotal role in accelerating the NSC proliferation.

Hypoxic preconditioning neural stem cell transplantation promotes spinal cord injury in rats by affecting transmembrane immunoglobulin domain-containing

OBJECTIVE

To explore the effects of hypoxic preconditioning neural stem cell (P-NSC) transplantation on rats with spinal cord injury (SCI).

METHODS

After identification, the NSCs were treated with hypoxic preconditioning. The NSCs migration was detected by Transwell method. RT-qPCR was used to detect the mRNA levels of HIF-1α, CXCR4 in NSC. The secretion of representative neurotrophic factors (VEGF, HGF, and BDNF) was checked by Western blot. Forty-six SCI rats were randomly divided into three experimental groups: SCI group (PBS injection, n = 10); N-NSC group (NSC atmospheric normoxic pretreatment injection, n = 18); and P-NSC group (NSC 's hypoxic preconditioning injection, n = 18). The sham operation group was also included (rats underwent laminectomy but not SCI, n = 10). The recovery of hindlimb motor function was evaluated by BBB score. The level of spinal cord inflammation (IL-1β, TNF-α, and IL-6) was determined by ELISA. Western blot was used to detect the content of TMIGD1 and TMIGD3 in spinal cord.

RESULTS

Compared with the N-NSC group, the number of NSC-passing membranes in the P-NSC group increased with the increase of the culture time (p < 0.05). Compared with N-NSC, P-NSC had higher levels of VEGF, HGF, and BDNF after 1 week of culture (p < 0.05). The BBB score of the P-NSC group was significantly higher than that of the N-NSC group at 7 and 28 days (p < 0.05). Compared with the SCI group, the levels of TNF-α, IL-1β, and IL-6 were significantly reduced after NSC treatment, and the P-NSC group was lower than the N-NSC group (p < 0.05). Compared with the SCI group, the levels of TMIGD1 and TMIGD3 increased. Compared with the N-NSC group, and the levels of TMIGD1 and TMIGD3 increased in the P-NSC group (p < 0.05).

CONCLUSION

P-NSC administration could improve SCI injury, and the levels of TMIGD1 and TMIGD3.

Biomaterial and Therapeutic Approaches for the Manipulation of Macrophage Phenotype in Peripheral and Central Nerve Repair

Injury to the peripheral or central nervous systems often results in extensive loss of motor and sensory function that can greatly diminish quality of life. In both cases, macrophage infiltration into the injury site plays an integral role in the host tissue inflammatory response. In particular, the temporally related transition of macrophage phenotype between the M1/M2 inflammatory/repair states is critical for successful tissue repair. In recent years, biomaterial implants have emerged as a novel approach to bridge lesion sites and provide a growth-inductive environment for regenerating axons. This has more recently seen these two areas of research increasingly intersecting in the creation of 'immune-modulatory' biomaterials. These synthetic or naturally derived materials are fabricated to drive macrophages towards a pro-repair phenotype. This review considers the macrophage-mediated inflammatory events that occur following nervous tissue injury and outlines the latest developments in biomaterial-based strategies to influence macrophage phenotype and enhance repair.

Perspectives in the Cell-Based Therapies of Various Aspects of the Spinal Cord Injury-Associated Pathologies: Lessons from the Animal Models

Traumatic injury of the spinal cord (SCI) is a devastating neurological condition often leading to severe dysfunctions, therefore an improvement in clinical treatment for SCI patients is urgently needed. The potential benefits of transplantation of various cell types into the injured spinal cord have been intensively investigated in preclinical SCI models and clinical trials. Despite the many challenges that are still ahead, cell transplantation alone or in combination with other factors, such as artificial matrices, seems to be the most promising perspective. Here, we reviewed recent advances in cell-based experimental strategies supporting or restoring the function of the injured spinal cord with a particular focus on the regenerative mechanisms that could define their clinical translation.

Preparation of decellularized optic nerve grafts

BACKGROUND

Decellularized tissues based on well-conserved extracellular matrices (ECMs) are a common area of research in tissue engineering. Although several decellularization protocols have been suggested for several types of tissues, studies on the optic nerve have been limited.

METHODS

We report decellularization protocol with different detergent for the preparation of acellular optic nerve and tissues were examined. DNA, glycosaminoglycan (GAG), and collagen content of the groups were evaluated with biochemical analyses and examined with histological staining. Mechanical properties, chemical components as well as cytotoxic properties of tissues were compared.

RESULTS

According to the results, it was determined that TX-100 (Triton X-100) was insufficient in decellularization when used alone. In addition, it was noticed that 85% of GAG content was preserved by using TX-100 and TX-100-SD (sodium deoxycholate), while this ratio was calculated as 30% for SDS. In contrast, the effect of the decellularization protocols on ECM structure of the tissues was evaluated by scanning and transmission electron microscopy (SEM and TEM) and determined their mechanical properties. Cytotoxicity analyses were exhibited minimum 95% cell viability for all groups, suggesting that there are no cytotoxic properties of the methods on L929 mouse fibroblast cells.

CONCLUSIONS

The combination of TX-100-SD and TX-100-SDS (sodium dodecyl sulfate) were was determined as the most effective methods to the literature for optic nerve decellularization.

The combination of nanoscaffolds and stem cell transplantation: Paving a promising road for spinal cord injury regeneration

Spinal cord injury (SCI), one of the most devastating traumas, has caused long-term disability in millions of people worldwide. The pathophysiology of SCI primarily occurs in two stages classified as primary injury and secondary injury. Due to the rupture of axons and the apoptosis of neurons, patients lose their motor, sensory, and reflex functions, which also imposes a huge burden on families and society. However, traditional surgery does not facilitate neuronal regeneration. Although neural stem cells (NSCs) have the potential for multidirectional differentiation, the probability of differentiation into neurons and survival are still low. Surprisingly, the unique properties of nanotechnologies enable targeted drug delivery while reducing adverse reactions, assisting NSCs in differentiating into neurons. Here, recent studies on promising nanoscaffolds are highlighted, and their strengths and drawbacks are evaluated. Although the treatment of SCI remains fraught with challenges, the combination of nanoscaffolds and NSCs pave a promising road for SCI regeneration.

Neural stem cell treatment for perinatal brain injury: A systematic review and meta-analysis of preclinical studies

Perinatal brain injury can lead to significant neurological and cognitive deficits and currently no therapies can regenerate the damaged brain. Neural stem cells (NSCs) have the potential to engraft and regenerate damaged brain tissue. The aim of this systematic review was to evaluate the preclinical literature to determine whether NSC administration is more effective than controls in decreasing perinatal brain injury. Controlled interventional studies of NSC therapy using animal models of perinatal brain injury were identified using MEDLINE and Embase. Primary outcomes were brain infarct size, motor, and cognitive function. Data for meta‐analysis were synthesized and expressed as standardized mean difference (SMD) with 95% confidence intervals (CI), using a random effects model. We also reported secondary outcomes including NSC survival, migration, differentiation, and effect on neuroinflammation. Eighteen studies met inclusion criteria. NSC administration decreased infarct size (SMD 1.09; CI: 0.44, 1.74, P = .001; I² = 74%) improved motor function measured via the impaired forelimb preference test (SMD 2.27; CI: 0.85, 3.69, P = .002; I² = 86%) and the rotarod test (SMD 1.88; CI: 0.09, 3.67, P = .04; I² = 95%). Additionally, NSCs improved cognitive function measured via the Morris water maze test (SMD of 2.41; CI: 1.16, 3.66, P = .0002; I² = 81%). Preclinical evidence suggests that NSC therapy is promising for the treatment of perinatal brain injury. We have identified key knowledge gaps, including the lack of large animal studies and uncertainty regarding the necessity of immunosuppression for NSC transplantation in neonates. These knowledge gaps should be addressed before NSC treatment can effectively progress to clinical trial.

Pastable, Adhesive, Injectable, Nanofibrous, and Tunable (PAINT) Biphasic Hybrid Matrices as Versatile Therapeutic Carriers

A critical challenge in many pharmaceutical fields is developing versatile adjuvant devices that can reduce the off-target delivery of therapeutic materials to target lesions. Herein, a biphasic hybrid fibrous system that can manipulate the spatial and temporal delivery of various therapeutic agents to target lesions by integrating multiple distinct systems and technologies such as fluffy coaxial electrospun polycaprolactone (PCL)/polystyrene (PS) fibers, cyclohexane-mediated leaching to remove PS layers selectively, amine display on PCL fibers, conjugation of naturally occurring adhesive gallol molecules onto hyaluronic acid (HA-g), and electrostatically complexing the aminated PCL fibers with the gallol-conjugated HA. In the context of "paintable" systems on target lesions, the resulting system is called a PAINT matrix (abbreviated according to the initial letter of its features: pastable, adhesive, injectable, nanofibrous, and tunable). Its viscoelastic property, which was attributed by coalescing aminated PCL fibers with viscous HA-g, enabled it to be noninvasively injected and fit into any cavity in the body with various morphologies, manually pasted on tissue surfaces, and adhered onto moisture-rich surfaces to ensure the secure delivery of therapeutics toward the target lesions. The PAINT matrix efficiently supplied immunomodulatory human neural stem cells (hNSCs) at rat hemisectioned spinal cord injury (SCI) sites and promoted both locomotive and sensory recovery in SCI models, presumably by protecting hNSCs against host immunosurveillance. The PAINT matrix will be broadly utilized for efficiently delivering therapeutics to difficult-to-reach target lesions by direct infusion or conventional biomaterial-mediated approaches due to their locations, wet surfaces, or complicated ambient environments.

Spinal cord injury in mice impacts central and peripheral pathology in a severity-dependent manner

ABSTRACT

Chronic pain is a common medical complication experienced by those living with spinal cord injury (SCI) and leads to worsened quality of life. The pathophysiology of SCI pain is poorly understood, hampering the development of safe and efficacious therapeutics. We therefore sought to develop a clinically relevant model of SCI with a strong pain phenotype and characterize the central and peripheral pathology after injury. A contusion (50 kdyn) injury, with and without sustained compression (60 seconds) of the spinal cord, was carried out on female C57BL/6J mice. Mice with compression of the spinal cord exhibited significantly greater heat and mechanical hypersensitivity starting at 7 days post-injury, concomitant with reduced locomotor function, compared to those without compression. Immunohistochemical analysis of spinal cord tissue revealed significantly less myelin sparing and increased macrophage activation in mice with compression compared to those without. As measured by flow cytometry, immune cell infiltration and activation were significantly greater in the spinal cord (phagocytic myeloid cells and microglia) and dorsal root ganglia (Ly6C+ monocytes) following compression injury. We also decided to investigate the gastrointestinal microbiome, as it has been shown to be altered in SCI patients and has recently been shown to play a role in immune system maturation and pain. We found increased dysbiosis of the gastrointestinal microbiome in an injury severity-dependent manner. The use of this contusion-compression model of SCI may help advance the preclinical assessment of acute and chronic SCI pain and lead to a better understanding of mechanisms contributing to this pain.

Optimizing Olfactory Ensheathing Cell Transplantation for Spinal Cord Injury Repair

Cell transplantation constitutes an important avenue for development of new treatments for spinal cord injury (SCI). These therapies are aimed at supporting neural repair and/or replacing lost cells at the injury site. To date, various cell types have been trialed, with most studies focusing on different types of stem cells or glial cells. Here, we review commonly used cell transplantation approaches for spinal cord injury (SCI) repair, with focus on transplantation of olfactory ensheathing cells (OECs), the glial cells of the primary olfactory nervous system. OECs are promising candidates for promotion of neural repair given that they support continuous regeneration of the olfactory nerve that occurs throughout life. Further, OECs can be accessed from the nasal mucosa (olfactory neuroepithelium) at the roof of the nasal cavity and can be autologously transplanted. OEC transplantation has been trialed in many animal models of SCI, as well as in human clinical trials. While several studies have been promising, outcomes are variable and the method needs improvement to enhance aspects such as cell survival, integration, and migration. As a case study, we include the approaches used by our team (the Clem Jones Centre for Neurobiology and Stem Cell Research, Griffith University, Nathan, QLD, Australia) to address the current problems with OEC transplantation and discuss how the therapeutic potential of OEC transplantation can be improved. Our approach includes discovery research to improve our knowledge of OEC biology, identifying natural and synthetic compounds to stimulate the neural repair properties of OECs, and designing three-dimensional cell constructs to create stable and transplantable cell structures.

Biomaterial Strategies to Bolster Neural Stem Cell-Mediated Repair of the Central Nervous System

Stem cell therapies have the potential to not only repair, but to regenerate tissue of the central nervous system (CNS). Recent studies demonstrate that transplanted stem cells can differentiate into neurons and integrate with the intact circuitry after traumatic injury. Unfortunately, the positive findings described in rodent models have not been replicated in clinical trials, where the burden to maintain the cell viability necessary for tissue repair becomes more challenging. Low transplant survival remains the greatest barrier to stem cell-mediated repair of the CNS, often with fewer than 1-2% of the transplanted cells remaining after 1 week. Strategic transplantation parameters, such as injection location, cell concentration, and transplant timing achieve only modest improvements in stem cell transplant survival and appear inconsistent across studies. Biomaterials provide researchers with a means to significantly improve stem cell transplant survival through two mechanisms: (1) a vehicle to deliver and protect the stem cells and (2) a substrate to control the cytotoxic injury environment. These biomaterial strategies can alleviate cell death associated with delivery to the injury and can be used to limit cell death after transplantation by limiting cell exposure to cytotoxic signals. Moreover, it is likely that control of the injury environment with biomaterials will lead to a more reliable support for transplanted cell populations. This review will highlight the challenges associated with cell delivery in the CNS and the advances in biomaterial development and deployment for stem cell therapies necessary to bolster stem cell-mediated repair.

Biological Potential of Polyethylene Glycol (PEG)-Functionalized Graphene Quantum Dots in In Vitro Neural Stem/Progenitor Cells

Stem cell therapy is one of the novel and prospective fields. The ability of stem cells to differentiate into different lineages makes them attractive candidates for several therapies. It is essential to understand the cell fate, distribution, and function of transplanted cells in the local microenvironment before their applications. Therefore, it is necessary to develop an accurate and reliable labeling method of stem cells for imaging techniques to track their translocation after transplantation. The graphitic quantum dots (GQDs) are selected among various stem cell labeling and tracking strategies which have high photoluminescence ability, photostability, relatively low cytotoxicity, tunable surface functional groups, and delivering capacity. Since GQDs interact easily with the cell and interfere with cell behavior through surface functional groups, an appropriate surface modification needs to be considered to get close to the ideal labeling nanoprobes. In this study, polyethylene glycol (PEG) is used to improve biocompatibility while simultaneously maintaining the photoluminescent potentials of GQDs. The biochemically inert PEG successfully covered the surface of GQDs. The PEG-GQDs composites show adequate bioimaging capabilities when internalized into neural stem/progenitor cells (NSPCs). Furthermore, the bio-inertness of the PEG-GQDs is confirmed. Herein, we introduce the PEG-GQDs as a valuable tool for stem cell labeling and tracking for biomedical therapies in the field of neural regeneration.

Electrochemical Impedance Spectroscopy as a Tool for Monitoring Cell Differentiation from Floor Plate Progenitors to Midbrain Neurons in Real Time

Here shows that electrical impedance spectroscopy can be used as a non-invasive and real time tool to probe cell adhesion and differentiation from midbrain floor plate progenitors into midbrain neurons on Au electrodes coated with human laminin. The electrical data and equivalent circuit modeling are consistent with standard microscopy analysis and reveal that within the first 6 hours progenitor cells sediment and attach to the electrode within 40 hours. Between 40 and 120 hours, midbrain progenitor cells differentiate into midbrain neurons, followed by an electrochemically stable maturation phase. The ability to sense and characterize non-invasively and in real time cell differentiation opens up unprecedented avenues for implantable therapies and differentiation strategies.

The gut-brain axis and beyond: Microbiome control of spinal cord injury pain in humans and rodents

Spinal cord injury (SCI) is a devastating injury to the central nervous system in which 60 to 80% of patients experience chronic pain. Unfortunately, this pain is notoriously difficult to treat, with few effective options currently available. Patients are also commonly faced with various compounding injuries and medical challenges, often requiring frequent hospitalization and antibiotic treatment. Change in the gut microbiome from the "normal" state to one of imbalance, referred to as gut dysbiosis, has been found in both patients and rodent models following SCI. Similarities exist in the bacterial changes observed after SCI and other diseases with chronic pain as an outcome. These changes cause a shift in the regulation of inflammation, causing immune cell activation and secretion of inflammatory mediators that likely contribute to the generation/maintenance of SCI pain. Therefore, correcting gut dysbiosis may be used as a tool towards providing patients with effective pain management and improved quality of life.

An in situ hydrogel-forming scaffold loaded by PLGA microspheres containing carbon nanotube as a suitable niche for neural differentiation

The cell-extracellular matrix (ECM) interactions are known to have a strong impact on cell behaviors in neural tissues. Due to complex physiology system and limited regenerative capacity of nervous system, neural tissue engineering has attracted attention as a promising strategy. In this study, we designed a hydrogel loaded by poly (lactic-co-glycolic acid) (PLGA) microspheres containing carbon nanotubes (CNT) and the biochemical differentiation factors, as a scaffold, in order to replicate the neural niche for stem cell growth (and/or differentiation). Different formulations from Hyaluronic acid (H), Poloxamer (P), Ethoxy-silane-capped poloxamer (PE), and cross-linked Alginate (Alg) were utilized as an in situ gel structure matrix to mirror the mechanical properties of the ECM of CNS. Subsequently, conductivity, surface morphology, size of microspheres, and CNT dispersion in microsphere were measured using two probes electrical conductometer, scanning electron microscopy (SEM), dynamic light scattering (DLS), and Raman spectroscopy, respectively. According to SEM and fluorescent microscopy images, CNTs increased the porosity of polymeric structure, which, in turn, facilitated the adhesion of stem cells on the surface of microspheres compared with control. Microstructure and rheological behaviors of different gel compositions were investigated using SEM and parallel-plate oscillatory rheometer, respectively. The MTT assay showed the toxicity profile of hydrogels was appropriate for cell transplantation. The confocal images illustrated the 3D platform of P15%H10% and P20%H5% gel formulations containing the PLGA-CNT microspheres, which allows the proliferation of neural stem cells (NSCs) derived from MSC. The results of real-time PCR and immunocytochemistry showed neuronal differentiation capacity of cultured NSCs derived from MSC in the alginate gel that contained PLGA-CNT microspheres as well as other control groups. The dispersion of the CNT-PLGA microspheres, covered by NSCs, into alginate gel in the presence of induction factors was found to notably enhance the expression of Sox2-SYP and β-Tubulin III neuronal markers.

Repair of dural defects with electrospun bacterial cellulose membranes in a rabbit experimental model

To evaluate the advantages and mechanisms involved in repairing rabbit dural defect with a novel electrospun bacterial cellulose (EBC) membrane, a series of experiments were carried out in vitro and in vivo. Compared with common bacterial cellulose (BC) membrane, a more dispersed and regular fiber structure and a better porosity and water holding capacity were found in the EBC membrane, which also had superior degradability. However, the biomechanical properties were slightly decreased. The results demonstrated that BC and EBC membranes had little effect on proliferation and apoptosis of mouse fibroblast cells. There were no complications such as infection, cerebrospinal fluid leakage, epilepsy and brain swelling after BC and EBC membrane repairs in rabbit models. Using real-time quantitative polymerase chain reaction (RT-qPCR) and western blot, the early inflammatory reactions in the EBC group were shown to be lower than in the BC group, and were close to the autologous dura mater group. Histological observations and western blot revealed more collagen fibers evenly distributed on the outer side of EBC membranes than in the BC and unpatched groups, and fewer brain tissue adhesions and epidural scars were found in the EBC group. Compared with common BC membrane, the EBC membrane had better biophysical properties and biocompatibility. It is expected to be a suitable alternative material for the repair of damaged dura mater.

Cellular Response of Ventricular-Subventricular Neural Progenitor/Stem Cells to Neonatal Hypoxic-Ischemic Brain Injury and Their Enhanced Neurogenesis

PURPOSE

To elucidate the brain's intrinsic response to injury, we tracked the response of neural stem/progenitor cells (NSPCs) located in ventricular-subventricular zone (V-SVZ) to hypoxic-ischemic brain injury (HI). We also evaluated whether transduction of V-SVZ NSPCs with neurogenic factor NeuroD1 could enhance their neurogenesis in HI.

MATERIALS AND METHODS

Unilateral HI was induced in ICR neonatal mice. To label proliferative V-SVZ NSPCs in response to HI, bromodeoxyuridine (BrdU) and retroviral particles encoding LacZ or NeuroD1/GFP were injected. The cellular responses of NSPCs were analyzed by immunohistochemistry.

RESULTS

Unilateral HI increased the number of BrdU+ newly-born cells in the V-SVZ ipsilateral to the lesion while injury reduced the number of newly-born cells reaching the ipsilateral olfactory bulb, which is the programmed destination of migratory V-SVZ NSPCs in the intact brain. These newly-born cells were directed from this pathway towards the lesions. HI significantly increased the number of newly-born cells in the cortex and striatum by the altered migration of V-SVZ cells. Many of these newly-born cells differentiated into active neurons and glia. LacZ-expressing V-SVZ NSPCs also showed extensive migration towards the non-neurogenic regions ipsilateral to the lesion, and expressed the neuronal marker NeuN. NeuroD1+/GFP+ V-SVZ NSPCs almost differentiated into neurons in the peri-infarct regions.

CONCLUSION

HI promotes the establishment of a substantial number of new neurons in non-neurogenic regions, suggesting intrinsic repair mechanisms of the brain, by controlling the behavior of endogenous NSPCs. The activation of NeuroD1 expression may improve the therapeutic potential of endogenous NSPCs by increasing their neuronal differentiation in HI.

Stem cell therapies for acute spinal cord injury in humans: a review

Recent advances in stem cell biology present significant opportunities to advance clinical applications of stem cell-based therapies for spinal cord injury (SCI). In this review, the authors critically analyze the basic science and translational evidence that supports the use of various stem cell sources, including induced pluripotent stem cells, oligodendrocyte precursor cells, and mesenchymal stem cells. They subsequently explore recent advances in stem cell biology and discuss ongoing clinical translation efforts, including combinatorial strategies utilizing scaffolds, biogels, and growth factors to augment stem cell survival, function, and engraftment. Finally, the authors discuss the evolution of stem cell therapies for SCI by providing an overview of completed (n = 18) and ongoing (n = 9) clinical trials.

Glial Cell Line-derived Neurotrophic Factor-overexpressing Human Neural Stem/Progenitor Cells Enhance Therapeutic Efficiency in Rat with Traumatic Spinal Cord Injury

Spinal cord injury (SCI) causes axonal damage and demyelination, neural cell death, and comprehensive tissue loss, resulting in devastating neurological dysfunction. Neural stem/progenitor cell (NSPCs) transplantation provides therapeutic benefits for neural repair in SCI, and glial cell linederived neurotrophic factor (GDNF) has been uncovered to have capability of stimulating axonal regeneration and remyelination after SCI. In this study, to evaluate whether GDNF would augment therapeutic effects of NSPCs for SCI, GDNF-encoding or mock adenoviral vector-transduced human NSPCs (GDNF-or Mock-hNSPCs) were transplanted into the injured thoracic spinal cords of rats at 7 days after SCI. Grafted GDNFhNSPCs showed robust engraftment, long-term survival, an extensive distribution, and increased differentiation into neurons and oligodendroglial cells. Compared with Mock-hNSPC- and vehicle-injected groups, transplantation of GDNF-hNSPCs significantly reduced lesion volume and glial scar formation, promoted neurite outgrowth, axonal regeneration and myelination, increased Schwann cell migration that contributed to the myelin repair, and improved locomotor recovery. In addition, tract tracing demonstrated that transplantation of GDNF-hNSPCs reduced significantly axonal dieback of the dorsal corticospinal tract (dCST), and increased the levels of dCST collaterals, propriospinal neurons (PSNs), and contacts between dCST collaterals and PSNs in the cervical enlargement over that of the controls. Finally grafted GDNF-hNSPCs substantially reversed the increased expression of voltage-gated sodium channels and neuropeptide Y, and elevated expression of GABA in the injured spinal cord, which are involved in the attenuation of neuropathic pain after SCI. These findings suggest that implantation of GDNF-hNSPCs enhances therapeutic efficiency of hNSPCs-based cell therapy for SCI.

Research progress and prospects of tissue engineering scaffolds for spinal cord injury repair and protection

Spinal cord injury (SCI) is one of the leading causes of global disability. However, there are currently no effective clinical treatments for SCI. Repair of SCI is essential but poses great challenges. As a comprehensive treatment program combining biological scaffolds, seed cells and drugs or biological factors, tissue engineering has gradually replaced the single transplantation approach to become a focus of research that brings new opportunities for the clinical treatment of SCI.

Use of in vitro electroporation and slice culture for gene function analysis in the mouse embryonic spinal cord

The spinal cord is an important part of the central nervous system (CNS). At present, the expression of the exogenous gene in the spinal cord of the embryonic mouse needs in utero spinal cord electroporation, but the success rate of this technique is very low. In this study, we have demonstrated the expression of an exogenous gene on one side of the spinal cord by combining two methods-in vitro electroporation of embryonic mouse spinal cord and organ spinal cord slices culture. We took 12-day embryonic mice, injected the green fluorescent protein (pCAGGS-GFP) plasmid into the spinal cord cavity in vitro, and then electroporated. The spinal cord was cut into 300-μm slices using a vibratory microtome. After cultured for 48 h, GFP-positive neurons were clearly observed on one side of the spinal cord, indicating that the exogenous gene was successfully transferred. The axon projection direction is basically unanimous from the inside to the lateral edge of the spinal cord. Compared to neurons in vivo, a single neuron in the culturing section has more complete neurites and is conducive to studying changes in the structure and behavior of individual neurons. Based on the above results, we have successfully established a convenient and efficient method for expressing the exogenous gene in the spinal cord of the mouse.

Combinational Treatment of Bioscaffolds and Extracellular Vesicles in Spinal Cord Injury

Spinal cord injury (SCI) can result in an irreversible disability due to loss of sensorimotor function below the lesion. Presently, clinical treatments for SCI mainly include surgery, drugs and postoperative rehabilitation. The prospective roles of bioscaffolds and exosomes in several neurological diseases have been reported. Bioscaffolds can reconnect lesion gaps as well as transport cells and bioactive factors, which in turn can improve axonal and functional regeneration. Herein, we explicate the respective roles of bioscaffolds and exosomes in SCI, and elucidate on the usage of combinational therapy involving bioscaffolds and extracellular vesicles (EVs) in improving SCI.

Biomaterials and Gene Manipulation in Stem Cell-Based Therapies for Spinal Cord Injury

Spinal cord injury (SCI), a prominent health issue, represents a substantial portion of the global health care burden. Stem cell-based therapies provide novel solutions for SCI treatment, yet obstacles remain in the form of low survival rate, uncontrolled differentiation, and functional recovery. The application of engineered biomaterials in stem cell therapy provides a physicochemical microenvironment that mimics the stem cell niche, facilitating self-renewal, stem cell differentiation, and tissue reorganization. Nonetheless, external microenvironment support is inadequate, and some obstacles persist, for example, limited sources, gradual aging, and immunogenicity of stem cells. Targeted stem cell gene manipulation could eliminate many of these drawbacks, allowing safer, more effective use under regulation of intrinsic mechanisms. Additionally, through genetic labeling of stem cells, their role in tissue engineering may be elucidated. Therefore, combining stem cell therapy, materials science, and genetic modification technologies may shed light on SCI treatment. Herein, recent advances and advantages of biomaterials and gene manipulation, especially with respect to stem cell-based therapies, are highlighted, and their joint performance in SCI is evaluated. Current technological limitations and perspectives on future directions are then discussed. Although this combination is still in the early stages of development, it is highly likely to substantially contribute to stem cell-based therapies in the foreseeable future.