Repair of injured spinal cord using biomaterial scaffolds and stem cells

Cellular and Transcriptional Response of Human Astrocytes to Hybrid Protein Materials

Collagen is a major component of the tissue matrix, and soybean can regulate the tissue immune response. Both materials have been used to fabricate biomaterials for tissue repair. In this study, adult and fetal human astrocytes were grown in a soy protein isolate (SPI)-collagen hybrid gel or on the surface of a cross-linked SPI-collagen membrane. Hybrid materials reduced the cell proliferation rate compared to materials generated by collagen alone. However, the hybrid materials did not significantly change the cell motility compared to the control collagen material. RNA-sequencing (RNA-Seq) analysis showed downregulated genes in the cell cycle pathway, including CCNA2, CCNB1, CCNB2, CCND1, CCND2, and CDK1, which may explain lower cell proliferation in the hybrid material. This study also revealed the downregulation of genes encoding extracellular matrix (ECM) components, including HSPG2, LUM, SDC2, COL4A1, COL4A5, COL4A6, and FN1, as well as genes encoding chemokines, including CCL2, CXCL1, CXCL2, CX3CL1, CXCL3, and LIF, for adult human astrocytes grown on the hybrid membrane compared with those grown on the control collagen membrane. The study explored the cellular and transcriptional responses of human astrocytes to the hybrid material and indicated a potential beneficial function of the material in the application of neural repair.

Local Spinal Cord Injury Treatment Using a Dental Pulp Stem Cell Encapsulated H2S Releasing Multifunctional Injectable Hydrogel

Spinal cord injury (SCI) commonly induces nerve damage and nerve cell degeneration. In this work, a novel dental pulp stem cells (DPSCs) encapsulated thermoresponsive injectable hydrogel with sustained hydrogen sulfide (H2S) delivery is demonstrated for SCI repair. For controlled and sustained H2S gas therapy, a clinically tested H2S donor (JK) loaded octysilane functionalized mesoporous silica nanoparticles (OMSNs) are incorporated into the thermosensitive hydrogel made from Pluronic F127 (PF-127). The JK-loaded functionalized MSNs (OMSF@JK) promote preferential M2-like polarization of macrophages and neuronal differentiation of DPSCs in vitro. OMSF@JK incorporated PF-127 injectable hydrogel (PF-OMSF@JK) has a soft consistency similar to that of the human spinal cord and thus, shows a high cytocompatibility with DPSCs. The cross-sectional micromorphology of the hydrogel shows a continuous porous structure. Last, the PF-OMSF@JK composite hydrogel considerably improves the in vivo SCI regeneration in Sprague-Dawley rats through a reduction in inflammation and neuronal differentiation of the incorporated stem cells as confirmed using western blotting and immunohistochemistry. The highly encouraging in vivo results prove that this novel design on hydrogel is a promising therapy for SCI regeneration with the potential for clinical translation.

Schwann Cell-Derived Exosomal Vesicles: A Promising Therapy for the Injured Spinal Cord

Exosomes are nanoscale-sized membrane vesicles released by cells into their extracellular milieu. Within these nanovesicles reside a multitude of bioactive molecules, which orchestrate essential biological processes, including cell differentiation, proliferation, and survival, in the recipient cells. These bioactive properties of exosomes render them a promising choice for therapeutic use in the realm of tissue regeneration and repair. Exosomes possess notable positive attributes, including a high bioavailability, inherent safety, and stability, as well as the capacity to be functionalized so that drugs or biological agents can be encapsulated within them or to have their surface modified with ligands and receptors to imbue them with selective cell or tissue targeting. Remarkably, their small size and capacity for receptor-mediated transcytosis enable exosomes to cross the blood-brain barrier (BBB) and access the central nervous system (CNS). Unlike cell-based therapies, exosomes present fewer ethical constraints in their collection and direct use as a therapeutic approach in the human body. These advantageous qualities underscore the vast potential of exosomes as a treatment option for neurological injuries and diseases, setting them apart from other cell-based biological agents. Considering the therapeutic potential of exosomes, the current review seeks to specifically examine an area of investigation that encompasses the development of Schwann cell (SC)-derived exosomal vesicles (SCEVs) as an approach to spinal cord injury (SCI) protection and repair. SCs, the myelinating glia of the peripheral nervous system, have a long history of demonstrated benefit in repair of the injured spinal cord and peripheral nerves when transplanted, including their recent advancement to clinical investigations for feasibility and safety in humans. This review delves into the potential of utilizing SCEVs as a therapy for SCI, explores promising engineering strategies to customize SCEVs for specific actions, and examines how SCEVs may offer unique clinical advantages over SC transplantation for repair of the injured spinal cord.

Challenges and progress of neurodrug: bioactivities, production and delivery strategies of nerve growth factor protein

Nerve growth factor (NGF) is a vital cytokine that plays a crucial role in the development and regeneration of the nervous system. It has been extensively studied for its potential therapeutic applications in various neural diseases. However, as a protein drug, limited natural source seriously hinders its translation and clinical applications. Conventional extraction of NGF from mouse submandibular glands has a very high cost and potentially induces immunogenicity; total synthesis and semi-synthesis methods are alternatives, but have difficulty in obtaining correct protein structure; gene engineering of plant cells is thought to be non-immunogenic, bioactive and economical. Meanwhile, large molecular weight, high polarity, and negative electrical charge make it difficult for NGF to cross the blood brain barrier to reach therapeutic targets. Current delivery strategies mainly depend on the adenovirus and cell biodelivery, but the safety and efficacy remain to be improved. New materials are widely investigated for the controllable, safe and precise delivery of NGF. This review illustrates physiological and therapeutic effects of NGF for various diseases. Moreover, new progress in production and delivery technologies for NGF are summarized. Bottlenecks encountered in the development of NGF as therapeutics are also discussed with the countermeasures proposed.

Acute spinal cord injury in Africa: exploring the long-term outcomes and future directions of acute spinal cord injury - short communication

Acute spinal cord injury (ASCI), a key factor behind serious sensory, motor, and autonomic dysfunctions, holds on as a fundamental cause of morbidity, psychological disturbances, and high socioeconomic burden. This study sheds light, particularly on the African countries where it is found that traumatic ASCI, mainly due to road traffic accidents, remains the leading cause, with 130 cases per million in this part of the world. Moreover, limited resources, with the lack of funds and equipment, as well as widespread poverty, restrict the availability of suitable diagnostic, management, and treatment options. The weight of the evidence suggests that there is an ultimate need for well-developed infrastructure embracing a multidisciplinary approach to rehabilitation in Africa. Furthermore, international collaborations, posing a significantly wide background for evidence-based information and resources, are indispensable for ASCI prospects and future studies among the African population. The purpose of this study is to fill a part of the persistent gap in the research era regarding the ASCI in Africa and direct future research toward investigating its different aspects as well as exploring its interventional needs.

Potential injectable hydrogels as biomaterials for central nervous system injury: A narrative review

Numerous modalities exist through which the central nervous system (CNS) may sustain injury or impairment, encompassing traumatic incidents, stroke occurrences, and neurodegenerative diseases such as Alzheimer's disease and Parkinson's disease. Presently available pharmacological and therapeutic interventions are incapable of restoring or regenerating damaged CNS tissue, leading to substantial unmet clinical needs among patients with CNS ailments or injuries. To address and facilitate the recovery of the impaired CNS, cell-based repair strategies encompass multiple mechanisms, such as neuronal replacement, therapeutic factor secretion, and the promotion of host brain plasticity. Despite the progression of cell-based CNS reparation as a therapeutic strategy throughout the years, substantial barriers have impeded its widespread implementation in clinical settings. The integration of cell technologies with advancements in regenerative medicine utilizing biomaterials and tissue engineering has recently facilitated the surmounting of several of these impediments. This comprehensive review presents an overview of distinct CNS conditions necessitating cell reparation, in addition to exploring potential biomaterial methodologies that enhance the efficacy of treating brain injuries.

The Promising Role of a Zebrafish Model Employed in Neural Regeneration Following a Spinal Cord Injury

Spinal cord injury (SCI) is a devastating event that results in a wide range of physical impairments and disabilities. Despite the advances in our understanding of the biological response to injured tissue, no effective treatments are available for SCIs at present. Some studies have addressed this issue by exploring the potential of cell transplantation therapy. However, because of the abnormal microenvironment in injured tissue, the survival rate of transplanted cells is often low, thus limiting the efficacy of such treatments. Many studies have attempted to overcome these obstacles using a variety of cell types and animal models. Recent studies have shown the utility of zebrafish as a model of neural regeneration following SCIs, including the proliferation and migration of various cell types and the involvement of various progenitor cells. In this review, we discuss some of the current challenges in SCI research, including the accurate identification of cell types involved in neural regeneration, the adverse microenvironment created by SCIs, attenuated immune responses that inhibit nerve regeneration, and glial scar formation that prevents axonal regeneration. More in-depth studies are needed to fully understand the neural regeneration mechanisms, proteins, and signaling pathways involved in the complex interactions between the SCI microenvironment and transplanted cells in non-mammals, particularly in the zebrafish model, which could, in turn, lead to new therapeutic approaches to treat SCIs in humans and other mammals.

Application of stem cells in regeneration medicine

Regeneration is a complex process affected by many elements independent or combined, including inflammation, proliferation, and tissue remodeling. Stem cells is a class of primitive cells with the potentiality of differentiation, regenerate with self-replication, multidirectional differentiation, and immunomodulatory functions. Stem cells and their cytokines not only inextricably linked to the regeneration of ectodermal and skin tissues, but also can be used for the treatment of a variety of chronic wounds. Stem cells can produce exosomes in a paracrine manner. Stem cell exosomes play an important role in tissue regeneration, repair, and accelerated wound healing, the biological properties of which are similar with stem cells, while stem cell exosomes are safer and more effective. Skin and bone tissues are critical organs in the body, which are essential for sustaining life activities. The weak repairing ability leads a pronounced impact on the quality of life of patients, which could be alleviated by stem cell exosomes treatment. However, there are obstacles that stem cells and stem cells exosomes trough skin for improved bioavailability. This paper summarizes the applications and mechanisms of stem cells and stem cells exosomes for skin and bone healing. We also propose new ways of utilizing stem cells and their exosomes through different nanoformulations, liposomes and nanoliposomes, polymer micelles, microspheres, hydrogels, and scaffold microneedles, to improve their use in tissue healing and regeneration.

Bibliometric analysis of stem cells for spinal cord injury: current status and emerging frontiers

Background: This study aimed to conduct a bibliometric analysis of the literature on stem cell therapy for spinal cord injury to visualize the research status, identify hotspots, and explore the development trends in this field. Methods: We searched the Web of Science Core Collection database using relevant keywords ("stem cells" and "spinal cord injury") and retrieved the published literature between 2000 and 2022. Data such as journal title, author information, institutional affiliation, country, and keywords were extracted. Afterwards, we performed bibliometric analysis of the retrieved data using Bibliometrix, VOSviewer, and CiteSpace. Results: A total of 5375 articles related to stem cell therapy for spinal cord injury were retrieved, and both the annual publication volume and the cumulative publication volume showed an upward trend. neural regeneration research was the journal with the most publications and the fastest cumulative publication growth (162 articles), Okano Hideyuki was the author with the highest number of publications and citations (114 articles), Sun Yat-sen University was the institution with the highest number of publications (420 articles), and China was the country with the highest number of publications (5357 articles). However, different authors, institutions, and countries need to enhance their cooperation in order to promote the generation of significant academic achievements. Current research in this field has focused on stem cell transplantation, neural regeneration, motor function recovery, exosomes, and tissue engineering. Meanwhile, future research directions are primarily concerned with the molecular mechanisms, safety, clinical trials, exosomes, scaffolds, hydrogels, and inflammatory responses of stem cell therapy for spinal cord injuries. Conclusion: In summary, this study provided a comprehensive analysis of the current research status and frontiers of stem cell therapy for spinal cord injury. The findings provide a foundation for future research and clinical translation efforts of stem cell therapy in this field.

Composite Fibrin/Carbon Microfiber Implants for Bridging Spinal Cord Injury: A Translational Approach in Pigs

Biomaterials may enhance neural repair after spinal cord injury (SCI) and testing their functionality in large animals is essential to achieve successful clinical translation. This work developed a porcine contusion/compression SCI model to investigate the consequences of myelotomy and implantation of fibrin gel containing biofunctionalized carbon microfibers (MFs). Fourteen pigs were distributed in SCI, SCI/myelotomy, and SCI/myelotomy/implant groups. An automated device was used for SCI. A dorsal myelotomy was performed on the lesion site at 1 day post-injury for removing cloths and devitalized tissue. Bundles of MFs coated with a conducting polymer and cell adhesion molecules were embedded in fibrin gel and used to bridge the spinal cord cavity. Reproducible lesions of about 1 cm in length were obtained. Myelotomy and lesion debridement caused no further neural damage compared to SCI alone but had little positive effect on neural regrowth. The MFs/fibrin gel implant facilitated axonal sprouting, elongation, and alignment within the lesion. However, the implant also increased lesion volume and was ineffective in preventing fibrosis, thus precluding functional neural regeneration. Our results indicate that myelotomy and lesion debridement can be advantageously used for implanting MF-based scaffolds. However, the implants need refinement and pharmaceuticals will be necessary to limit scarring.

Application of Conductive Hydrogels on Spinal Cord Injury Repair: A Review

Spinal cord injury (SCI) causes severe motor or sensory damage that leads to long-term disabilities due to disruption of electrical conduction in neuronal pathways. Despite current clinical therapies being used to limit the propagation of cell or tissue damage, the need for neuroregenerative therapies remains. Conductive hydrogels have been considered a promising neuroregenerative therapy due to their ability to provide a pro-regenerative microenvironment and flexible structure, which conforms to a complex SCI lesion. Furthermore, their conductivity can be utilized for noninvasive electrical signaling in dictating neuronal cell behavior. However, the ability of hydrogels to guide directional axon growth to reach the distal end for complete nerve reconnection remains a critical challenge. In this Review, we highlight recent advances in conductive hydrogels, including the incorporation of conductive materials, fabrication techniques, and cross-linking interactions. We also discuss important characteristics for designing conductive hydrogels for directional growth and regenerative therapy. We propose insights into electrical conductivity properties in a hydrogel that could be implemented as guidance for directional cell growth for SCI applications. Specifically, we highlight the practical implications of recent findings in the field, including the potential for conductive hydrogels to be used in clinical applications. We conclude that conductive hydrogels are a promising neuroregenerative therapy for SCI and that further research is needed to optimize their design and application.

Open-Spaced Ridged Hydrogel Scaffolds Containing TiO2-Self-Assembled Monolayer of Phosphonates Promote Regeneration and Recovery Following Spinal Cord Injury

The spinal cord has a poor ability to regenerate after an injury, which may be due to cell loss, cyst formation, inflammation, and scarring. A promising approach to treating a spinal cord injury (SCI) is the use of biomaterials. We have developed a novel hydrogel scaffold fabricated from oligo(poly(ethylene glycol) fumarate) (OPF) as a 0.08 mm thick sheet containing polymer ridges and a cell-attractive surface on the other side. When the cells are cultured on OPF via chemical patterning, the cells attach, align, and deposit ECM along the direction of the pattern. Animals implanted with the rolled scaffold sheets had greater hindlimb recovery compared to that of the multichannel scaffold control, which is likely due to the greater number of axons growing across it. The immune cell number (microglia or hemopoietic cells: 50-120 cells/mm² in all conditions), scarring (5-10% in all conditions), and ECM deposits (Laminin or Fibronectin: approximately 10-20% in all conditions) were equal in all conditions. Overall, the results suggest that the scaffold sheets promote axon outgrowth that can be guided across the scaffold, thereby promoting hindlimb recovery. This study provides a hydrogel scaffold construct that can be used in vitro for cell characterization or in vivo for future neuroprosthetics, devices, or cell and ECM delivery.

Injectable hydrogels in central nervous system: Unique and novel platforms for promoting extracellular matrix remodeling and tissue engineering

Repairing central nervous system (CNS) is difficult due to the inability of neurons to recover after damage. A clinically acceptable treatment to promote CNS functional recovery and regeneration is currently unavailable. According to recent studies, injectable hydrogels as biodegradable scaffolds for CNS tissue engineering and regeneration have exceptionally desirable attributes. Hydrogel has a biomimetic structure similar to extracellular matrix, hence has been considered a 3D scaffold for CNS regeneration. An interesting new type of hydrogel, injectable hydrogels, can be injected into target areas with little invasiveness and imitate several aspects of CNS. Injectable hydrogels are being researched as therapeutic agents because they may imitate numerous properties of CNS tissues and hence reduce subsequent injury and regenerate neural tissue. Because of their less adverse effects and cost, easier use and implantation with less pain, and faster regeneration capacity, injectable hydrogels, are more desirable than non-injectable hydrogels. This article discusses the pathophysiology of CNS and the use of several kinds of injectable hydrogels for brain and spinal cord tissue engineering, paying particular emphasis to recent experimental studies.

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.

Motor functional recovery efficacy of scaffolds with bone marrow stem cells in rat spinal cord injury: a Bayesian network meta-analysis

STUDY DESIGN

A Bayesian network meta-analysis.

OBJECTIVE

Spinal cord injury (SCI) can profoundly influence human health and has been linked to lifelong disability. More high-level evidence-based medical research is expected to evaluate the value of stem cells and biomaterial scaffold material therapy for SCI.

METHODS

We performed a comprehensive search of Web of Science, Cochrane databases, Embase, and PubMed databases. 18 randomized controlled trials including both scaffolds and BMSCs were included. We performed a Bayesian network meta-analysis to compare the motor functional recovery efficacy of different scaffolds with BMSCs in rat SCI.

RESULTS

In our Bayesian network meta-analysis, the motor functional recovery was found to benefit from scaffolds, BMSCs, and BMSCs combined with scaffolds, but the scaffold and BMSC groups had similar motor functional recovery efficacy, and the BMSCs combined with scaffolds group appeared to show better efficacy than BMSCs and scaffolds alone. Subgroup analysis showed that BMSCs+fibrin, BMSCs+ASC, BMSCs+gelatine, and BMSCs+collagen were the best four treatments for SCI in rat models.

CONCLUSIONS

These Bayesian network meta-analysis findings strongly indicated that BMSCs combined with scaffolds is more effective to improve motor functional recovery than BMSCs and scaffolds alone. The fibrin, gelatine, ASC, and collagen may be favourable scaffolds for the injured spinal cord and that scaffolds with BMSCs could be a promising option in regeneration therapy for patients with SCI.

Oligo (Poly (Ethylene Glycol) Fumarate)-Based Multicomponent Cryogels for Neural Tissue Replacement

Synthetic hydrogels provide a promising platform to produce neural tissue analogs with improved control over structural, physical, and chemical properties. In this study, oligo (poly (ethylene glycol) fumarate) (OPF)-based macroporous cryogels were developed as a potential next-generation alternative to a non-porous OPF hydrogel previously proposed as an advanced biodegradable scaffold for spinal cord repair. A series of OPF cryogel conduits in combination with PEG diacrylate and 2-(methacryloyloxy) ethyl-trimethylammonium chloride (MAETAC) cationic monomers were synthesized and characterized. The contribution of each component to viscoelastic and hydration behaviors and porous structure was identified, and concentration relationships for these properties were revealed. The rheological properties of the materials corresponded to those of neural tissues and scaffolds, according to the reviewed data. A comparative assessment of adhesion, migration, and proliferation of neuronal cells in multicomponent cryogels was carried out to optimize cell-supporting characteristics. The results show that OPF-based cryogels can be used as a tunable synthetic scaffold for neural tissue repair with advantages over their hydrogel counterparts.

Silk-Elastin-like Polymers for Acute Intraparenchymal Treatment of the Traumatically Injured Spinal Cord: A First Systematic Experimental Approach

Despite the promising potential of hydrogel-based therapeutic approaches for spinal cord injury (SCI), the need for new biomaterials to design effective strategies for SCI treatment and the outstanding properties of silk-elastin-like polymers (SELP), the potential use of SELPs in SCI is currently unknown. In this context, we assessed the effects elicited by the in vivo acute intraparenchymal injection of an SELP named (EIS)₂-RGD6 in a clinically relevant model of SCI. After optimization of the injection system, the distribution, structure, biodegradability, and cell infiltration capacity of (EIS)₂-RGD6 were assessed. Finally, the effects exerted by the (EIS)₂-RGD6 injection-in terms of motor function, myelin preservation, astroglial and microglia/macrophage reactivity, and fibrosis-were evaluated. We found that (EIS)₂-RGD6 can be acutely injected in the lesioned spinal cord without inducing further damage, showing a widespread distribution covering all lesioned areas with a single injection and facilitating the formation of a slow-degrading porous scaffold at the lesion site that allows for the infiltration and/or proliferation of endogenous cells with no signs of collapse and without inducing further microglial and astroglial reactivity, as well as even reducing SCI-associated fibrosis. Altogether, these observations suggest that (EIS)₂-RGD6-and, by extension, SELPs-could be promising polymers for the design of therapeutic strategies for SCI treatment.

Additively manufactured metallic biomaterials

Metal additive manufacturing (AM) has led to an evolution in the design and fabrication of hard tissue substitutes, enabling personalized implants to address each patient's specific needs. In addition, internal pore architectures integrated within additively manufactured scaffolds, have provided an opportunity to further develop and engineer functional implants for better tissue integration, and long-term durability. In this review, the latest advances in different aspects of the design and manufacturing of additively manufactured metallic biomaterials are highlighted. After introducing metal AM processes, biocompatible metals adapted for integration with AM machines are presented. Then, we elaborate on the tools and approaches undertaken for the design of porous scaffold with engineered internal architecture including, topology optimization techniques, as well as unit cell patterns based on lattice networks, and triply periodic minimal surface. Here, the new possibilities brought by the functionally gradient porous structures to meet the conflicting scaffold design requirements are thoroughly discussed. Subsequently, the design constraints and physical characteristics of the additively manufactured constructs are reviewed in terms of input parameters such as design features and AM processing parameters. We assess the proposed applications of additively manufactured implants for regeneration of different tissue types and the efforts made towards their clinical translation. Finally, we conclude the review with the emerging directions and perspectives for further development of AM in the medical industry.

Nerve implants with bioactive interfaces enhance neurite outgrowth and nerve regeneration in vivo

Nerve implants functionalized with growth factors and stem cells are critical to promote neurite outgrowth, regulate neurodifferentiation, and facilitate nerve regeneration. In this study, human umbilical cord mesenchymal stem cells (hUCMSCs) and 3,4-hydroxyphenalyalanine (DOPA)-containing insulin-like growth factor 1 (DOPA-IGF-1) were simultaneously applied to enhance the bioactivity of poly(lactide-co-glycolide) (PLGA) substrates which will be potentially utilized as nerve implants. In vitro and in vivo evaluations indicated that hUCMSCs and DOPA-IGF-1 could synergistically regulate neurite outgrowth of PC12 cells, improve intravital recovery of motor functions, and promote conduction of nerve electrical signals in vivo. The enhanced functional and structural nerve regeneration of injured spinal cord might be mainly attributable to the synergistically enhanced biofunctionality of hUCMSCs and DOPA-IGF-1/PLGA on the bioactive interfaces. Findings from this study demonstrate the potential of hUCMSC-seeded, DOPA-IGF-1-modified PLGA implants as promising candidates for promoting axonal regeneration and motor functional recovery in spinal cord injury treatment.

The Role of Tissue Geometry in Spinal Cord Regeneration

Unlike peripheral nerves, axonal regeneration is limited following injury to the spinal cord. While there may be reduced regenerative potential of injured neurons, the central nervous system (CNS) white matter environment appears to be more significant in limiting regrowth. Several factors may inhibit regeneration, and their neutralization can modestly enhance regrowth. However, most investigations have not considered the cytoarchitecture of spinal cord white matter. Several lines of investigation demonstrate that axonal regeneration is enhanced by maintaining, repairing, or reconstituting the parallel geometry of the spinal cord white matter. In this review, we focus on environmental factors that have been implicated as putative inhibitors of axonal regeneration and the evidence that their organization may be an important determinant in whether they inhibit or promote regeneration. Consideration of tissue geometry may be important for developing successful strategies to promote spinal cord regeneration.

3D printed collagen/silk fibroin scaffolds carrying the secretome of human umbilical mesenchymal stem cells ameliorated neurological dysfunction after spinal cord injury in rats

Although implantation of biomaterials carrying mesenchymal stem cells (MSCs) is considered as a promising strategy for ameliorating neural function after spinal cord injury (SCI), there are still some challenges including poor cell survival rate, tumorigenicity and ethics concerns. The performance of the secretome derived from MSCs was more stable, and its clinical transformation was more operable. Cytokine antibody array demonstrated that the secretome of MSCs contained 79 proteins among the 174 proteins analyzed. 3D printed collagen/silk fibroin scaffolds carrying MSCs secretome improved hindlimb locomotor function according to the BBB scores, the inclined-grid climbing test and electrophysiological analysis. Parallel with locomotor function recovery, 3D printed collagen/silk fibroin scaffolds carrying MSCs secretome could further facilitate nerve fiber regeneration, enhance remyelination and accelerate the establishment of synaptic connections at the injury site compared to 3D printed collagen/silk fibroin scaffolds alone group according to magnetic resonance imaging (MRI), diffusion Tensor imaging (DTI), hematoxylin and eosin (HE) staining, Bielschowsky’s silver staining immunofluorescence staining and transmission electron microscopy (TEM). These results indicated the implantation of 3D printed collagen/silk fibroin scaffolds carrying MSCs secretome might be a potential treatment for SCI.

Mesenchymal Stromal Cells Preconditioning: A New Strategy to Improve Neuroprotective Properties

Neurological diseases represent one of the main causes of disability in human life. Consequently, investigating new strategies capable of improving the quality of life in neurological patients is necessary. For decades, researchers have been working to improve the efficacy and safety of mesenchymal stromal cells (MSCs) therapy based on MSCs’ regenerative and immunomodulatory properties and multilinear differentiation potential. Therefore, strategies such as MSCs preconditioning are useful to improve their application to restore damaged neuronal circuits following neurological insults. This review is focused on preconditioning MSCs therapy as a potential application to major neurological diseases. The aim of our work is to summarize both the in vitro and in vivo studies that demonstrate the efficacy of MSC preconditioning on neuronal regeneration and cell survival as a possible application to neurological damage.

Fabrication Techniques of Nerve Guidance Conduits for Nerve Regeneration

Neuronal loss and axonal degeneration after spinal cord injury or peripheral injury result in the loss of sensory and motor functions. Nerve regeneration is a complicated and medical challenge that requires suitable guides to bridge nerve injury gaps and restore nerve function. Due to the hostility of the microenvironment in the lesion, multiple conditions should be fulfilled to achieve improved functional recovery. Many nerve conduits have been fabricated using various natural and synthetic polymers. The design and material of the nerve guide conduits were carefully reviewed. A detailed review was conducted on the fabrication method of the nerve guide conduit for nerve regeneration. The typical fabrication methods used to fabricate nerve conduits are dip coating, solvent casting, micropatterning, electrospinning, and additive manufacturing. The advantages and disadvantages of the fabrication methods were reported, and research to overcome these limitations was reviewed. Extensive reviews have focused on the biological functions and in vivo performance of polymeric nerve conduits. In this paper, we emphasize the fabrication method of nerve conduits by polymers and their properties. By learning from the existing candidates, we can advance the strategies for designing novel polymeric systems with better properties for nerve regeneration.

Management of Acute Traumatic Spinal Cord Injury: A Review of the Literature

Traumatic spinal cord injury (TSCI) is a debilitating disease that poses significant functional and economic burden on both the individual and societal levels. Prognosis is dependent on the extent of the spinal injury and the severity of neurological dysfunction. If not treated rapidly, patients with TSCI can suffer further secondary damage and experience escalating disability and complications. It is important to quickly assess the patient to identify the location and severity of injury to make a decision to pursue a surgical and/or conservative management. However, there are many conditions that factor into the management of TSCI patients, ranging from the initial presentation of the patient to long-term care for optimal recovery. Here, we provide a comprehensive review of the etiologies of spinal cord injury and the complications that may arise, and present an algorithm to aid in the management of TSCI.

Diamond Concept as Principle for the Development of Spinal Cord Scaffold: A Literature Review

INTRODUCTION: Spinal cord injury (SCI) has been bringing detrimental impacts on the affected individuals. However, not only that, it also brings a tremendous effect on the socioeconomic and health-care system. Treatment regimen and strategy for SCI patient have been under further research. DISCUSSION: The main obstacles of regeneration on neuronal structure are the neuroinflammatory process and poor debris clearance, causing a longer healing process and an extensive inflammation process due to this particular inflammatory process. To resolve all of the mentioned significant issues in SCIs neuronal regeneration, a comprehensive model is necessary to analyze each step of progressive condition in SCI. In this review, we would like to redefine a comprehensive concept of the “Diamond Concept” from previously used in fracture management to SCI management, which consists of cellular platform, cellular inductivity, cellular conductivity, and material integrity. The scaffolding treatment strategy for SCI has been widely proposed due to its flexibility. It enables the physician to combine another treatment method such as neuroprotective or neuroregenerative or both in one intervention. CONCLUSION: Diamond concept perspective in the implementation of scaffolding could be advantageous to increase the outcome of SCI treatment.

PLGA-PEG-PLGA hydrogel with NEP1-40 promotes the functional recovery of brachial plexus root avulsion in adult rats

Adult brachial plexus root avulsion can cause serious damage to nerve tissue and impair axonal regeneration, making the recovery of nerve function difficult. Nogo-A extracellular peptide residues 1-40 (NEP1-40) promote axonal regeneration by inhibiting the Nogo-66 receptor (NgR1), and poly (D, L-lactide-co-glycolide)-poly (ethylene glycol)-poly (D, L-lactide-co-glycolide) (PLGA-PEG-PLGA) hydrogel can be used to fill in tissue defects and concurrently function to sustain the release of NEP1-40. In this study, we established an adult rat model of brachial plexus nerve root avulsion injury and conducted nerve root replantation. PLGA-PEG-PLGA hydrogel combined with NEP1-40 was used to promote nerve regeneration and functional recovery in this rat model. Our results demonstrated that functional recovery was enhanced, and the survival rate of spinal anterior horn motoneurons was higher in rats that received a combination of PLGA-PEG-PLGA hydrogel and NEP1-40 than in those receiving other treatments. The combined therapy also significantly increased the number of fluorescent retrogradely labeled neurons, muscle fiber diameter, and motor endplate area of the biceps brachii. In conclusion, this study demonstrates that the effects of PLGA-PEG-PLGA hydrogel combined with NEP1-40 are superior to those of other therapies used to treat brachial plexus nerve root avulsion injury. Therefore, future studies should investigate the potential of PLGA-PEG-PLGA hydrogel as a primary treatment for brachial plexus root avulsion.

A multi-channel collagen scaffold loaded with neural stem cells for the repair of spinal cord injury

Collagen scaffolds possess a three-dimensional porous structure that provides sufficient space for cell growth and proliferation, the passage of nutrients and oxygen, and the discharge of metabolites. In this study, a porous collagen scaffold with axially-aligned luminal conduits was prepared. In vitro biocompatibility analysis of the collagen scaffold revealed that it enhances the activity of neural stem cells and promotes cell extension, without affecting cell differentiation. The collagen scaffold loaded with neural stem cells improved the hindlimb motor function in the rat model of T8 complete transection and promoted nerve regeneration. The collagen scaffold was completely degraded in vivo within 5 weeks of implantation, exhibiting good biodegradability. Rectal temperature, C-reactive protein expression and CD68 staining demonstrated that rats with spinal cord injury that underwent implantation of the collagen scaffold had no notable inflammatory reaction. These findings suggest that this novel collagen scaffold is a good carrier for neural stem cell transplantation, thereby enhancing spinal cord repair following injury. This study was approved by the Animal Ethics Committee of Nanjing Drum Tower Hospital (the Affiliated Hospital of Nanjing University Medical School), China (approval No. 2019AE02005) on June 15, 2019.

Spinal Cord Repair: From Cells and Tissue Engineering to Extracellular Vesicles

Spinal cord injury (SCI) is a debilitating condition, often leading to severe motor, sensory, or autonomic nervous dysfunction. As the holy grail of regenerative medicine, promoting spinal cord tissue regeneration and functional recovery are the fundamental goals. Yet, effective regeneration of injured spinal cord tissues and promotion of functional recovery remain unmet clinical challenges, largely due to the complex pathophysiology of the condition. The transplantation of various cells, either alone or in combination with three-dimensional matrices, has been intensively investigated in preclinical SCI models and clinical trials, holding translational promise. More recently, a new paradigm shift has emerged from cell therapy towards extracellular vesicles as an exciting "cell-free" therapeutic modality. The current review recapitulates recent advances, challenges, and future perspectives of cell-based spinal cord tissue engineering and regeneration strategies.

NeuroRegen Scaffolds Combined with Autologous Bone Marrow Mononuclear Cells for the Repair of Acute Complete Spinal Cord Injury: A 3-Year Clinical Study

Spinal cord injury (SCI) remains among the most challenging pathologies worldwide and has limited therapeutic possibilities and a very bleak prognosis. Biomaterials and stem cell transplantation are promising treatments for functional recovery in SCI. Seven patients with acute complete SCI diagnosed by a combination of methods were included in the study, and different lengths (2.0–6.0 cm) of necrotic spinal cord tissue were surgically cleaned under intraoperative neurophysiological monitoring. Subsequently, NeuroRegen scaffolds loaded with autologous bone marrow mononuclear cells (BMMCs) were implanted into the cleaned site. All patients participated in 6 months of rehabilitation and at least 3 years of clinical follow-up. No adverse symptoms associated with stem cell or functional scaffold implantation were observed during the 3-year follow-up period. Additionally, partial shallow sensory and autonomic nervous functional improvements were observed in some patients, but no motor function recovery was observed. Magnetic resonance imaging suggested that NeuroRegen scaffold implantation supported injured spinal cord continuity after treatment. These findings indicate that implantation of NeuroRegen scaffolds combined with stem cells may serve as a safe and promising clinical treatment for patients with acute complete SCI. However, determining the therapeutic effects and exact application methods still requires further study.

Induction of Neurogenesis and Angiogenesis in a Rat Hemisection Spinal Cord Injury Model With Combined Neural Stem Cell, Endothelial Progenitor Cell, and Biomimetic Hydrogel Matrix Therapy

Acute spinal cord injury is a devastating injury that may lead to loss of independent function. Stem-cell therapies have shown promise; however, a clinically efficacious stem-cell therapy has yet to be developed. Functionally, endothelial progenitor cells induce angiogenesis, and neural stem cells induce neurogenesis. In this study, we explored using a multimodal therapy combining endothelial progenitor cells with neural stem cells encapsulated in a bioactive biomimetic hydrogel matrix to facilitate stem cell-induced neurogenesis and angiogenesis in a rat hemisection spinal cord injury model.

DESIGN

Laboratory experimentation.

SETTING

University laboratory.

SUBJECTS

Female Fischer 344 rats.

INTERVENTIONS

Three groups of rats: 1) control, 2) biomimetic hydrogel therapy, and 3) combined neural stem cell, endothelial progenitor cell, biomimetic hydrogel therapy underwent right-sided spinal cord hemisection at T9-T10. The blinded Basso, Beattie, and Bresnahan motor score was obtained weekly; after 4 weeks, observational histologic analysis of the injured spinal cords was completed.

MEASUREMENTS AND MAIN RESULTS

Blinded Basso, Beattie, and Bresnahan motor score of the hind limb revealed significantly improved motor function in rats treated with combined neural stem cell, endothelial progenitor cell, and biomimetic hydrogel therapy (p < 0.05) compared with the control group. The acellular biomimetic hydrogel group did not demonstrate a significant improvement in motor function compared with the control group. Immunohistochemistry evaluation of the injured spinal cords demonstrated de novo neurogenesis and angiogenesis in the combined neural stem cell, endothelial progenitor cell, and biomimetic hydrogel therapy group, whereas, in the control group, a gap or scar was found in the injured spinal cord.

CONCLUSIONS

This study demonstrates proof of concept that multimodal therapy with endothelial progenitor cells and neural stem cells combined with a bioactive biomimetic hydrogel can be used to induce de novo CNS tissue in an injured rat spinal cord.

LncRNA-GAS5 promotes spinal cord repair and the inhibition of neuronal apoptosis via the transplantation of 3D printed scaffold loaded with induced pluripotent stem cell-derived neural stem cells

Background

Stem cell transplantation has been increasingly used for spinal cord repair, and some achievements have been made. However, limited stem cell sources as well as immune rejection and ethical issues have restricted its wide application. Therefore, to achieve further breakthroughs regarding the application of stem cell transplantation to treat spinal cord injury (SCI), it is important to develop a stem cell line that can effectively avoid immune rejection and ethical issues.

Methods

Urine cells (UCs) were induced to differentiate into induced pluripotent stem cells (iPSCs), which then further differentiated into neural stem cells (NSCs). Relevant tests were performed, and three-dimensional (3D) printed scaffolds were prepared. Thirty C57BL/6 mice were divided into 5 groups based on a random number table: a sham group, an SCI group, an SCI + control group, an SCI + siNC group, and an SCI + siGAS5 group (n=6). The latter 4 groups replicated SCI models. Mice in the SCI + control group were transplanted with 3D scaffolds loaded with iPSC-derived NSCs (iPSd-NSCs). Mice in the SCI + siNC group and the SCI + siGAS5 group were transplanted with scaffolds loaded with iPSd-NSCs-siNC and 3D scaffolds loaded with iPSd-NSCs-siGAS5, respectively. Mice in the other groups were injected with the same amount of normal saline. Hematoxylin-eosin staining was used to observe the histopathology of the injured spinal cord, the Basso-Mouse Scale was used to assess the motor function of the hind limbs of the mice, and Western blot was used to detect the expression of apoptosis-related proteins after SCI.

Results

iPSd-NSCs were successfully induced and differentiated, and 3D printed heparin sulfate-collagen scaffolds were prepared, inside which a 3D loose porous structure was shown by electron microscopy. Morphological observations showed that iPSd-NSC transplantation improved SCI in mice, while GAS5 silencing inhibited the reparative effect of iPSd-NSC transplantation on SCI in mice. Western blot results indicated that iPSd-NSC transplantation significantly increased the expression level of B cell lymphoma/leukemia-2 (Bcl-2) (P<0.01) but decreased the expression levels of Bcl-2 associated X protein, cytochrome C, and cleaved caspase-3 (P<0.001).

Conclusions

The overexpression of lncRNA-GAS5 can promote spinal cord repair and inhibit neural apoptosis via the transplantation of 3D printed scaffolds loaded with iPSd-NSCs.

IL-10 lentivirus-laden hydrogel tubes increase spinal progenitor survival and neuronal differentiation after spinal cord injury

A complex cellular cascade characterizes the pathophysiological response following spinal cord injury (SCI) limiting regeneration. Biomaterial and stem cell combination therapies together have shown synergistic effects, compared to the independent benefits of each intervention, and represent a promising approach towards regaining function after injury. In this study, we combine our polyethylene glycol (PEG) cell delivery platform with lentiviral-mediated overexpression of the anti-inflammatory cytokine interleukin (IL)-10 to improve mouse embryonic Day 14 (E14) spinal progenitor transplant survival. Immediately following injury in a mouse SCI hemisection model, five PEG tubes were implanted followed by direct injection into the tubes of lentivirus encoding for IL-10. Two weeks after tube implantation, mouse E14 spinal progenitors were injected directly into the integrated tubes, which served as a soft substrate for cell transplantation. Together, the tubes with the IL-10 encoding lentivirus improved E14 spinal progenitor survival, assessed at 2 weeks posttransplantation (4 weeks postinjury). On average, 8.1% of E14 spinal progenitors survived in mice receiving IL-10 lentivirus-laden tubes compared with 0.7% in mice receiving transplants without tubes, an 11.5-fold difference. Surviving E14 spinal progenitors gave rise to neurons when injected into tubes. Axon elongation and remyelination were observed, in addition to a significant increase in functional recovery in mice receiving IL-10 lentivirus-laden tubes with E14 spinal progenitor delivery compared to the injury only control by 4 weeks postinjury. All other conditions did not exhibit increased stepping until 8 or 12 weeks postinjury. This system affords increased control over the transplantation microenvironment, offering the potential to improve stem cell-mediated tissue regeneration.

Application of Autologous Peripheral Blood Mononuclear Cells into the Area of Spinal Cord Injury in a Subacute Period: A Feasibility Study in Pigs

Simple Summary

Spinal cord injury is a medical and social issue causing severe disability. The potential to overcome the consequences of spinal cord injury is related to cell therapy. Peripheral blood is a prospective and available source of cells for further clinical use. In our study, we have evaluated the therapeutic potential of peripheral blood mononuclear cells (PBMCs) on the model of spinal cord injury in pigs. In the subacute period (6 weeks after injury), PBMCs enclosed in fibrin glue were applied into the dorsal area of the injured spinal cord. In this study, we observed that the tissue integrity increased in the area adjacent to the epicenter of injury, and conduction along spinal axons was partially restored after cell therapy in pigs.

Abstract

Peripheral blood presents an available source of cells for both fundamental research and clinical use. In our study, we have evaluated the therapeutic potential of peripheral blood mononuclear cells (PBMCs) excluding the preliminary sorting or mobilization of peripheral blood stem cells. We have evaluated the regenerative potential of PBMCs embedded into a fibrin matrix (FM) in a model of pig spinal cord injury. The distribution of transplanted PBMCs in the injured spinal cord was evaluated; PBMCs were shown to penetrate into the deep layers of the spinal cord and concentrate mainly in the grey matter. The results of the current study revealed an increase in the tissue integrity in the area adjacent to the epicenter of injury and the partially restored conduction along posterior columns of the spinal cord in animals after FM+PBMC application. The multiplex analysis of blood serum and cerebrospinal fluid showed the cytokine imbalance to occur without significantly shifting toward pro-inflammatory or anti-inflammatory cytokine cascades.

Designing Enzyme-responsive Biomaterials

Enzymes are a class of protein that catalyze a wide range of chemical reactions, including the cleavage of specific peptide bonds. They are expressed in all cell types, play vital roles in tissue development and homeostasis, and in many diseases, such as cancer. Enzymatic activity is tightly controlled through the use of inactive pro-enzymes, endogenous inhibitors and spatial localization. Since the presence of specific enzymes is often correlated with biological processes, and these proteins can directly modify biomolecules, they are an ideal biological input for cell-responsive biomaterials. These materials include both natural and synthetic polymers, cross-linked hydrogels and self-assembled peptide nanostructures. Within these systems enzymatic activity has been used to induce biodegradation, release therapeutic agents and for disease diagnosis. As technological advancements increase our ability to quantify the expression and nanoscale organization of proteins in cells and tissues, as well as the synthesis of increasingly complex and well-defined biomaterials, enzyme-responsive biomaterials are poised to play vital roles in the future of biomedicine.

TGFβ3 is neuroprotective and alleviates the neurotoxic response induced by aligned poly-l-lactic acid fibers on naïve and activated primary astrocytes

Following spinal cord injury, astrocytes at the site of injury become reactive and exhibit a neurotoxic (A1) phenotype, which leads to neuronal death. In addition, the glial scar, which is composed of reactive astrocytes, acts as a chemical and physical barrier to subsequent axonal regeneration. Biomaterials, specifically electrospun fibers, induce a migratory phenotype of astrocytes and promote regeneration of axons following acute spinal cord injury in preclinical models. However, no study has examined the potential of electrospun fibers or biomaterials in general to modulate neurotoxic (A1) or neuroprotective (A2) astrocytic phenotypes. To assess astrocyte reactivity in response to aligned poly-l-lactic acid microfibers, naïve spinal cord astrocytes or spinal cord astrocytes primed towards the neurotoxic phenotype (A1) were cultured on fibrous scaffolds. Gene expression analysis of the pan-reactive astrocyte makers (GFAP, Lcn2, SerpinA3), A1 specific markers (H2-D1, SerpinG1), and A2 specific makers (Emp1, S100a10) was done using quantitative polymerase chain reaction (qPCR). Electrospun fibers mildly increased the expression of the pan-reactive and A1-specific markers, showing the ability of fibrous materials to induce a more reactive, A1 phenotype. However, when naïve or activated astrocytes were cultured on fibers in the presence of transforming growth factor β3 (TGFβ3), the expression of A1-specific markers was greatly reduced, which in turn improved neuronal survival in culture.

Biomimetic Hybrid Systems for Tissue Engineering

Tissue engineering approaches appear nowadays highly promising for the regeneration of injured/diseased tissues. Biomimetic scaffolds are continuously been developed to act as structural support for cell growth and proliferation as well as for the delivery of cells able to be differentiated, and also of bioactive molecules like growth factors and even signaling cues. The current research concerns materials employed to develop biological scaffolds with improved features as well as complex preparation techniques. In this work, hybrid systems based on natural polymers are discussed and the efforts focused to provide new polymers able to mimic proteins and DNA are extensively explained. Progress on the scaffold fabrication technique is mentioned, those processes based on solution and melt electrospinning or even on their combination being mainly discussed. Selection of the appropriate hybrid technology becomes vital to get optimal architecture to reasonably accomplish the final applications. Representative examples of the recent possibilities on tissue regeneration are finally given.

Pharmacologic and cellular therapies in the treatment of traumatic spinal cord injuries: A systematic review

OBJECTIVE

The objective of this review is to synthesize and consolidate the existing literature on the treatment of SCI, focusing on drugs in development and cellular therapeutics, including stem-cell treatments.

METHODS

Studies were identified through a systemic search of PubMed, Ovid MEDLINE, Embase and the Cochrane database from their respective inceptions through January 1, 2020. We used the keywords "spinal cord injuries", "therapeutics", "stem cells", and "pharmacology."

STUDY SELECTION

Studies that assessed treatment strategies for SCI were included.

DATA EXTRACTION AND SYNTHESIS

Data on SCIs were processed according to the Preferred Reporting Items for Systematic Reviews and meta-Analyses (PRISMA) guidelines.

FINDINGS

In total, 62 articles were found in the literature search and 13 clinical trials were identified and included in this study. This review article discusses the management and treatment of SCI with an emphasis on the pharmacology, molecular approaches, and the use of stem cells. Presently, none of the treatments examined has shown to be clearly effective.

CONCLUSIONS

Present management strategies of SCI are focused on improving spinal cord perfusion and decreasing secondary injuries such as hypoxia, inflammation, edema, excitotoxicity and disturbances of ion homeostasis. This review hopes to demonstrate the significant advances made in the field of SCI and the new methodologies and practices being employed by researchers to improve our knowledge of the pathology. Our hope is that by consolidating the past and current research, improvements can be made in the management, treatment, and outcomes for these patients and other who suffer from spinal pathologies.

A combinatorial approach for spinal cord injury repair using multifunctional collagen-based matrices: development, characterization and impact on cell adhesion and axonal growth

Spinal cord injury is a devastating condition of the central nervous system, in which traditional treatments are largely ineffective due to the complex nature of the injured tissue. Therefore, biomaterial-based systems have been developed as possible alternative strategies to repair the damaged tissue. In the present study, we aimed to design bioactive agent loaded scaffolds composed of two layers with distinct physical properties to improve tissue regeneration. An electrospun layer with aligned nanofibers was made of collagen (Col) Type-I, poly(lactide-co-glycolide) (PLGA) and laminin to promote cell attachment of mesenchymal-like stem cells towards the direction of fibers, while a Col-based second layer was fabricated by plastic compression to act as a releasing system for NT-3 and chondroitinase ABC, so that axonal growth could be stimulated. Results showed that a source of mesenchymal stem cell (MSC)-like cells, adipose tissue-derived stem cells cultured on the fibrous layer of the matrices were able to adhere and proliferate, where the aligned fibers promoted the cell growth in an organized way. Furthermore, the bilayered matrices also promoted dorsal root ganglion neurite outgrowth. The bilayered matrice with Col/PLGA + laminin top layer appears to promote higher neurite growth. Collectively, the designed constructs show promising structural properties and biological performance for being employed as a scaffold for engineering the spinal cord tissue.

Subarachnoid transplantation of human umbilical cord mesenchymal stem cell in rodent model with subacute incomplete spinal cord injury: Preclinical safety and efficacy study

Functional multipotency renders human umbilical cord mesenchymal stem cell (hUC-MSC) a promising candidate for the treatment of spinal cord injury (SCI). However, its safety and efficacy have not been fully understood for clinical translation. In this study, we performed cellular, kinematic, physiological, and anatomical analyses, either in vitro or in vivo, to comprehensively evaluate the safety and efficacy associated with subarachnoid transplantation of hUC-MSCs in rats with subacute incomplete SCI. Concerning safety, hUC-MSCs were shown to have normal morphology, excellent viability, steady proliferation, typical biomarkers, stable karyotype in vitro, and no tumorigenicity both in vitro and in vivo. Following subarachnoid transplantation of hUC-MSCs in the subject rodents, the biodistribution of hUC-MSCs was restricted to the spinal cord, and no toxicity to immune system or organ function was observed. Body weight, organ weight, and the ratio of the latter upon the former between stem cell-transplanted rats and placebo-injected rats revealed no statistical differences. Regarding efficacy, hUC-MSCs could differentiate into osteoblasts, chondrocytes, adipocytes and neural progenitor cells in vitro. While in vivo studies revealed that subarachnoid transplantation of stem cells resulted in significant improvement in locomotion, earlier automatic micturition recovery and reduced lesion size, which correlated with increased regeneration of tracking fiber and reduced parenchymal inflammation. In vivo luminescence imaging showed that a few of the transplanted luciferase-labeled hUC-MSCs tended to migrate towards the lesion epicenter. Shortened latency and enhanced amplitude were also observed in both motor and sensory evoked potentials, indicating improved signal conduction in the damaged site. Immunofluorescent staining confirmed that a few of the administrated hUC-MSCs integrated into the spinal cord parenchyma and differentiated into astrocytes and oligodendrocytes, but not neurons. Moreover, decreased astrogliosis, increased remyelination, and neuron regeneration could be observed. To the best of our knowledge, this preclinical study provides detailed safety and efficacy evidence regarding intrathecal transplantation of hUC-MSCs in treating SCI for the first time and thus, supports its initiation in the following clinical trial.

Stem Cell Therapy for Neurogenic Bladder After Spinal Cord Injury: Clinically Possible?

Neurogenic bladder (NB) after spinal cord injury (SCI) is a common complication that inhibits normal daily activities and reduces the quality of life. Regrettably, the current therapeutic methods for NB are inadequate. Therefore, numerous studies have been conducted to develop new treatments for NB associated with SCI. Moreover, a myriad of preclinical and clinical trials on the effects and safety of stem cell therapy in patients with SCI have been performed, and several studies have demonstrated improvements in urodynamic parameters, as well as in sensory and motor function, after stem cell therapy. These results are promising; however, further high-quality clinical studies are necessary to compensate for a lack of randomized trials, the modest number of participants, variation in the types of stem cells used, and inconsistency in routes of administration.

Bioinspired Nanofiber Scaffold for Differentiating Bone Marrow-Derived Neural Stem Cells to Oligodendrocyte-Like Cells: Design, Fabrication, and Characterization

BACKGROUND

Researchers are trying to study the mechanism of neural stem cells (NSCs) differentiation to oligodendrocyte-like cells (OLCs) as well as to enhance the selective differentiation of NSCs to oligodendrocytes. However, the limitation in nerve tissue accessibility to isolate the NSCs as well as their differentiation toward oligodendrocytes is still challenging.

PURPOSE

In the present study, a hybrid polycaprolactone (PCL)-gelatin nanofiber scaffold mimicking the native extracellular matrix and axon morphology to direct the differentiation of bone marrow-derived NSCs to OLCs was introduced.

MATERIALS AND METHODS

In order to achieve a sustained release of T3, this factor was encapsulated within chitosan nanoparticles and chitosan-loaded T3 was incorporated within PCL nanofibers. Polyaniline graphene (PAG) nanocomposite was incorporated within gelatin nanofibers to endow the scaffold with conductive properties, which resemble the conductive behavior of axons. Biodegradation, water contact angle measurements, and scanning electron microscopy (SEM) observations as well as conductivity tests were used to evaluate the properties of the prepared scaffold. The concentration of PAG and T3-loaded chitosan NPs in nanofibers were optimized by examining the proliferation of cultured bone marrow-derived mesenchymal stem cells (BMSCs) on the scaffolds. The differentiation of BMSCs-derived NSCs cultured on the fabricated scaffolds into OLCs was analyzed by evaluating the expression of oligodendrocyte markers using immunofluorescence (ICC), RT-PCR and flowcytometric assays.

RESULTS

Incorporating 2% PAG proved to have superior cell support and proliferation while guaranteeing electrical conductivity of 10.8 × 10-5 S/cm. Moreover, the scaffold containing 2% of T3-loaded chitosan NPs was considered to be the most biocompatible samples. Result of ICC, RT-PCR and flow cytometry showed high expression of O4, Olig2, platelet-derived growth factor receptor-alpha (PDGFR-α), O1, myelin/oligodendrocyte glycoprotein (MOG) and myelin basic protein (MBP) high expressed but low expression of glial fibrillary acidic protein (GFAP).

CONCLUSION

Considering surface topography, biocompatibility, electrical conductivity and gene expression, the hybrid PCL/gelatin scaffold with the controlled release of T3 may be considered as a promising candidate to be used as an in vitro model to study patient-derived oligodendrocytes by isolating patient's BMSCs in pathological conditions such as diseases or injuries. Moreover, the resulted oligodendrocytes can be used as a desirable source for transplanting in patients.

Local Serpin Treatment via Chitosan-Collagen Hydrogel after Spinal Cord Injury Reduces Tissue Damage and Improves Neurologic Function

Spinal cord injury (SCI) results in massive secondary damage characterized by a prolonged inflammation with phagocytic macrophage invasion and tissue destruction. In prior work, sustained subdural infusion of anti-inflammatory compounds reduced neurological deficits and reduced pro-inflammatory cell invasion at the site of injury leading to improved outcomes. We hypothesized that implantation of a hydrogel loaded with an immune modulating biologic drug, Serp-1, for sustained delivery after crush-induced SCI would have an effective anti-inflammatory and neuroprotective effect. Rats with dorsal column SCI crush injury, implanted with physical chitosan-collagen hydrogels (CCH) had severe granulomatous infiltration at the site of the dorsal column injury, which accumulated excess edema at 28 days post-surgery. More pronounced neuroprotective changes were observed with high dose (100 µg/50 µL) Serp-1 CCH implanted rats, but not with low dose (10 µg/50 µL) Serp-1 CCH. Rats treated with Serp-1 CCH implants also had improved motor function up to 20 days with recovery of neurological deficits attributed to inhibition of inflammation-associated tissue damage. In contrast, prolonged low dose Serp-1 infusion with chitosan did not improve recovery. Intralesional implantation of hydrogel for sustained delivery of the Serp-1 immune modulating biologic offers a neuroprotective treatment of acute SCI.

Vascularization of self-assembled peptide scaffolds for spinal cord injury repair

The disruption of the blood-spinal cord barrier (BSCB) following spinal cord injury contributes to inflammation and glial scarring that inhibits axon growth and diminishes the effectiveness of conduits transplanted to the injury site to promote this growth. The purpose of this study is to evaluate whether scaffolds containing microvessels that exhibit BSCB integrity reduce inflammation and scar formation at the injury site and lead to increased axon growth. For these studies, a self-assembling peptide scaffold, RADA-16I, is used due to its established permissiveness to axon growth and ability to support vascularization. Immunocytochemistry and permeability transport assays verify the formation of tight-junction containing microvessels within the scaffold. Peptide scaffolds seeded with different concentrations of microvascular cells are then injected into a spinal contusion injury in rats to evaluate how microvessels affect axon growth and neurovascular interaction. The effect of the vascularized scaffold on inflammation and scar formation is evaluated by quantifying histological sections stained with ED-1 and GFAP, respectively. Our results indicate that the peptide scaffolds containing microvessels reduce inflammation and glial scar formation and increase the density of axons growing into the injury/transplant site. These results demonstrate the potential benefit of scaffold vascularization to treat spinal cord injury. STATEMENT OF SIGNIFICANCE: This study evaluates the benefit of transplanting microvascular cells within a self-assembling peptide scaffold, RADA-16I, that has shown promise for facilitating regeneration in the central nervous system in previous studies. Our results indicate that vasculature featuring tight junctions that give rise to the blood-spinal cord barrier can be formed within the peptide scaffold both in vitro and in a rat model of a subacute contusion spinal cord injury. Histological analysis indicates that the presence of the microvessels encourages axon infiltration into the site of injury and reduces the area of astrocyte activation and inflammation. Overall, these results demonstrate the potential of vascularizing scaffolds for the repair of spinal cord injury.

Novel cytokine-loaded PCL-PEG scaffold composites for spinal cord injury repair

Severe spinal cord injury (SCI) always leads to permanent sensory and motor dysfunction. However, the therapeutic effects of current treatment methods, including high dose methylprednisolone, surgical interventions and rehabilitative care, are far from satisfactory. In recent years, cellular, molecular, tissue engineering and rehabilitative training have shown promising results in animal models. Poly-ε-caprolacton (PCL) - based hydrogel composite system has been considered as a promising strategy to direct the axon growth and mimic the properties of natural extracellular matrix. In this study, we found the addition of the fibroblast growth factor 2 (FGF2) and epidermal growth factor (EGF) to the hydrogel induces the production of axon growth-supportive substrates. The addition of the glial-derived neurotrophic factor (GDNF) to the hydrogel further induces axon directional growth. This "five-in-one" composite scaffold, referred to as PCL/PEG/FGF2/EGF/GDNF, improved the locomotor function in rats 8 weeks after spinal cord injury (SCI) after implantation in transected spinal cord. Furthermore, histological assessment indicated that the designed composite scaffold guided the neuronal regeneration and promoted the production of axon growth-supportive substrates, providing a favorable biological microenvironment. Our novel composite scaffold provides a promising therapeutic method for SCI.

3D Printed Neural Regeneration Devices

Neural regeneration devices interface with the nervous system and can provide flexibility in material choice, implantation without the need for additional surgeries, and the ability to serve as guides augmented with physical, biological (e.g., cellular), and biochemical functionalities. Given the complexity and challenges associated with neural regeneration, a 3D printing approach to the design and manufacturing of neural devices could provide next-generation opportunities for advanced neural regeneration via the production of anatomically accurate geometries, spatial distributions of cellular components, and incorporation of therapeutic biomolecules. A 3D printing-based approach offers compatibility with 3D scanning, computer modeling, choice of input material, and increasing control over hierarchical integration. Therefore, a 3D printed implantable platform could ultimately be used to prepare novel biomimetic scaffolds and model complex tissue architectures for clinical implants in order to treat neurological diseases and injuries. Further, the flexibility and specificity offered by 3D printed in vitro platforms have the potential to be a significant foundational breakthrough with broad research implications in cell signaling and drug screening for personalized healthcare. This progress report examines recent advances in 3D printing strategies for neural regeneration as well as insight into how these approaches can be improved in future studies.