The Effect of iPS-Derived Neural Progenitors Seeded on Laminin-Coated pHEMA-MOETACl Hydrogel with Dual Porosity in a Rat Model of Chronic Spinal Cord Injury

Probing of New Polymer-Based Microcapsules for Islet Cell Immunoisolation

Islet allotransplantation offers a promising cell therapy for type 1 diabetes, but challenges such as limited donor availability and immunosuppression persist. Microencapsulation of islets in polymer-coated alginate microcapsules is a favored strategy for immune protection and maintaining islet viability. This study introduces Poly [2-(methacryloyloxy)ethyl]trimethylammonium chloride (PMETAC) as an innovative coating material for microcapsules. PMETAC enhances biocompatibility and durability, marking a significant advancement in islet encapsulation. Our approach combines alginate with PMETAC to create Langerhans islet microcapsules, simplifying material composition and preparation and ultimately lowering costs and increasing clinical applicability. Our comprehensive evaluation of the stability (including osmotic stability, thermal stability, and culture condition stability) and cytotoxicity of a novel microencapsulation system based on alginate-PMETAC-alginate offers insights into its potential application in islet immunoisolation strategies. Microcapsules with PMETAC content ranging from 0.01 to 1% are explored in the current work. The results indicate that the coatings made with 0.4% PMETAC show the most promising outcomes, remaining stable in the mentioned tests and exhibiting the required permeability. It was shown that the islets encapsulated in this manner retain viability and functional activity. Thus, alginate microcapsules coated with 0.4% PMETAC are suitable for further animal trials. While our findings are promising, further studies, including animal testing, will be necessary to evaluate the clinical applicability of our encapsulation method.

Construction of functional neural network tissue combining CBD-NT3-modified linear-ordered collagen scaffold and TrkC-modified iPSC-derived neural stem cells for spinal cord injury repair

Induced pluripotent stem cells (iPSCs) can be personalized and differentiated into neural stem cells (NSCs), thereby effectively providing a source of transplanted cells for spinal cord injury (SCI). To further improve the repair efficiency of SCI, we designed a functional neural network tissue based on TrkC-modified iPSC-derived NSCs and a CBD-NT3-modified linear-ordered collagen scaffold (LOCS). We confirmed that transplantation of this tissue regenerated neurons and synapses, improved the microenvironment of the injured area, enhanced remodeling of the extracellular matrix, and promoted functional recovery of the hind limbs in a rat SCI model with complete transection. RNA sequencing and metabolomic analyses also confirmed the repair effect of this tissue from multiple perspectives and revealed its potential mechanism for treating SCI. Together, we constructed a functional neural network tissue using human iPSCs-derived NSCs as seed cells based on the interaction of receptors and ligands for the first time. This tissue can effectively improve the therapeutic effect of SCI, thus confirming the feasibility of human iPSCs-derived NSCs and LOCS for SCI repair and providing a valuable direction for SCI research.

Neural stem cell therapies for spinal cord injury repair: an update on recent preclinical and clinical advances

Traumatic spinal cord injury (SCI) is a leading cause of lifelong disabilities. Permanent sensory, motor and autonomic impairments after SCI are substantially attributed to degeneration of spinal cord neurons and axons, and disintegration of neural network. To date, minimal regenerative treatments are available for SCI with an unmet need for new therapies to reconstruct the damaged spinal cord neuron-glia network and restore connectivity with the supraspinal pathways. Multipotent neural precursor cells (NPCs) have a unique capacity to generate neurons, oligodendrocytes and astrocytes. Due to this capacity, NPCs have been an attractive cell source for cellular therapies for SCI. Transplantation of NPCs has been extensively tested in preclinical models of SCI in the past two decades. These studies have identified opportunities and challenges associated with NPC therapies. While NPCs have the potential to promote neuroregeneration through various mechanisms, their low long-term survival and integration within the host injured spinal cord limit the functional benefits of NPC-based therapies for SCI. To address this challenge, combinatorial strategies have been developed to optimize the outcomes of NPC therapies by enriching SCI microenvironment through biomaterials, genetic and pharmacological therapies. In this review, we will provide an in-depth discussion on recent advances in preclinical NPC-based therapies for SCI. We will discuss modes of actions and mechanism by which engrafted NPCs contribute to the repair process and functional recovery. We will also provide an update on current clinical trials and new technologies that have facilitated preparation of medical-grade human NPCs suitable for transplantation in clinical studies.

Spinal cord injury: molecular mechanisms and therapeutic interventions

Spinal cord injury (SCI) remains a severe condition with an extremely high disability rate. The challenges of SCI repair include its complex pathological mechanisms and the difficulties of neural regeneration in the central nervous system. In the past few decades, researchers have attempted to completely elucidate the pathological mechanism of SCI and identify effective strategies to promote axon regeneration and neural circuit remodeling, but the results have not been ideal. Recently, new pathological mechanisms of SCI, especially the interactions between immune and neural cell responses, have been revealed by single-cell sequencing and spatial transcriptome analysis. With the development of bioactive materials and stem cells, more attention has been focused on forming intermediate neural networks to promote neural regeneration and neural circuit reconstruction than on promoting axonal regeneration in the corticospinal tract. Furthermore, technologies to control physical parameters such as electricity, magnetism and ultrasound have been constantly innovated and applied in neural cell fate regulation. Among these advanced novel strategies and technologies, stem cell therapy, biomaterial transplantation, and electromagnetic stimulation have entered into the stage of clinical trials, and some of them have already been applied in clinical treatment. In this review, we outline the overall epidemiology and pathophysiology of SCI, expound on the latest research progress related to neural regeneration and circuit reconstruction in detail, and propose future directions for SCI repair and clinical applications.

A hyaluronic acid/silk fibroin/poly-dopamine-coated biomimetic hydrogel scaffold with incorporated neurotrophin-3 for spinal cord injury repair

Bio-factor stimulation is essential for axonal regeneration in the central nervous system. Thus, persistent and efficient factor delivery in the local microenvironment is an ideal strategy for spinal cord injury repair. We developed a biomimetic hydrogel scaffold to load biofactors in situ and release them in a controlled way as a promising therapeutic modality. Hyaluronic acid and silk fibroin were cross-linked as the basement of the scaffolds, and poly-dopamine coating was used to further increase the loading of factors and endow the hydrogel scaffolds with ideal physical and chemical properties and proper biocompatibility. Notably, neurotrophin-3 release from the hydrogel scaffolds was prolonged to 28 days. A spinal cord injury model was constructed for hydrogel scaffold transplantation. After eight weeks, significant NF200-positive nerve fibers were observed extending across the glial scar to the center of the injured area. Due to the release of neurotrophin-3, spinal cord regeneration was enhanced, and the cavity area of the injury graft site and inflammation associated with CD68 positive cells were reduced, which led to a significant improvement in hind limb motor function. The results show that the hyaluronic acid/silk fibroin/poly-dopamine-coated biomimetic hydrogel scaffold achieved locally slow release of neurotrophin-3, thus facilitating the regeneration of injured spinal cord. STATEMENT OF SIGNIFICANCE: Hydrogels have received great attention in spinal cord regeneration. Current research has focused on more efficient and controlled release of bio-factors. Here, we adopted a mussel-inspired strategy to functionalize the hyaluronic acid/silk fibroin hydrogel scaffold to increase the load of neurotrophin-3 and extend the release time. The hydrogel scaffolds have ideal physiochemical properties, proper release rate, and biocompatibility. Owing to the continuous neurotrophin-3 release from implanted scaffolds, cavity formation is reduced, inflammation alleviated, and spinal cord regeneration enhanced, indicating great potential for bio-factor delivery in soft tissue regeneration applications.

Hydrogel assisted photoreceptor delivery inhibits material transfer

Cell therapy holds tremendous promise for vision restoration; yet donor cell survival and integration continue to limit efficacy of these strategies. Transplanted photoreceptors, which mediate light sensitivity in the retina, transfer cytoplasmic components to host photoreceptors instead of integrating into the tissue. Donor cell material transfer could, therefore, function as a protein augmentation strategy to restore photoreceptor function. Biomaterials, such as hyaluronan-based hydrogels, can support donor cell survival but have not been evaluated for effects on material transfer. With increased survival, we hypothesized that we would achieve greater material transfer; however, the opposite occurred. Photoreceptors delivered to the subretinal space in mice in a hyaluronan and methylcellulose (HAMC) hydrogel showed reduced material transfer. We examined mitochondria transfer in vitro and cytosolic protein transfer in vivo and demonstrate that HAMC significantly reduced transfer in both contexts, which we ascribe to reduced cell-cell contact. Nanotube-like donor cell protrusions were significantly reduced in the hydrogel-transplanted photoreceptors compared to the saline control group, which suggests that HAMC limits the contact required to the host retina for transfer. Thus, HAMC can be used to manipulate the behaviour of transplanted donor cells in cell therapy strategies.

Stem Cell Therapies for Restorative Treatments of Central Nervous System Ischemia-Reperfusion Injury

Ischemic damage to the central nervous system (CNS) is a catastrophic postoperative complication of aortic occlusion subsequent to cardiovascular surgery that can cause brain impairment and sometimes even paraplegia. Over recent years, numerous studies have investigated techniques for protecting and revascularizing the nervous system during intraoperative ischemia; however, owing to a lack of knowledge of the physiological distinctions between the brain and spinal cord, as well as the limited availability of testing techniques and treatments for ischemia-reperfusion injury, the cause of brain and spinal cord ischemia-reperfusion injury remains poorly understood, and no adequate response steps are currently available in the clinic. Given the limited ability of the CNS to repair itself, it is of great clinical value to make full use of the proliferative and differentiation potential of stem cells to repair nerves in degenerated and necrotic regions by stem cell transplantation or mobilization, thereby introducing a novel concept for the treatment of severe CNS ischemia-reperfusion injury. This review summarizes the most recent advances in stem cell therapy for ischemia-reperfusion injury in the brain and spinal cord, aiming to advance basic research and the clinical use of stem cell therapy as a promising treatment for this condition.

Current Concepts of Biomaterial Scaffolds and Regenerative Therapy for Spinal Cord Injury

Spinal cord injury (SCI) is a catastrophic condition associated with significant neurological deficit and social and financial burdens. It is currently being managed symptomatically, with no real therapeutic strategies available. In recent years, a number of innovative regenerative strategies have emerged and have been continuously investigated in preclinical research and clinical trials. In the near future, several more are expected to come down the translational pipeline. Among ongoing and completed trials are those reporting the use of biomaterial scaffolds. The advancements in biomaterial technology, combined with stem cell therapy or other regenerative therapy, can now accelerate the progress of promising novel therapeutic strategies from bench to bedside. Various types of approaches to regeneration therapy for SCI have been combined with the use of supportive biomaterial scaffolds as a drug and cell delivery system to facilitate favorable cell-material interactions and the supportive effect of neuroprotection. In this review, we summarize some of the most recent insights of preclinical and clinical studies using biomaterial scaffolds in regenerative therapy for SCI and summarized the biomaterial strategies for treatment with simplified results data. One hundred and sixty-eight articles were selected in the present review, in which we focused on biomaterial scaffolds. We conducted our search of articles using PubMed and Medline, a medical database. We used a combination of "Spinal cord injury" and ["Biomaterial", or "Scaffold"] as search terms and searched articles published up until 30 April 2022. Successful future therapies will require these biomaterial scaffolds and other synergistic approaches to address the persistent barriers to regeneration, including glial scarring, the loss of a structural framework, and biocompatibility. This database could serve as a benchmark to progress in future clinical trials for SCI using biomaterial scaffolds.

Hydrogels in Spinal Cord Injury Repair: A Review

Traffic accidents and falling objects are responsible for most spinal cord injuries (SCIs). SCI is characterized by high disability and tends to occur among the young, seriously affecting patients' lives and quality of life. The key aims of repairing SCI include preventing secondary nerve injury, inhibiting glial scarring and inflammatory response, and promoting nerve regeneration. Hydrogels have good biocompatibility and degradability, low immunogenicity, and easy-to-adjust mechanical properties. While providing structural scaffolds for tissues, hydrogels can also be used as slow-release carriers in neural tissue engineering to promote cell proliferation, migration, and differentiation, as well as accelerate the repair of damaged tissue. This review discusses the characteristics of hydrogels and their advantages as delivery vehicles, as well as expounds on the progress made in hydrogel therapy (alone or combined with cells and molecules) to repair SCI. In addition, we discuss the prospects of hydrogels in clinical research and provide new ideas for the treatment of SCI.

Circular RNA Hecw1 Regulates the Inflammatory Imbalance in Spinal Cord Injury via miR-3551-3p/LRRTM1 Axis

Spinal cord injury (SCI) is a neurological disease having devastating effect and results in the development of systemic inflammation. However, the molecular mechanisms of SCI remain not entirely elucidated. This study was directed toward exploring the circ Hecw1 involved in the mechanism of lipopolysaccharide (LPS)-triggered inflammation damage in neuronal cells. The in vitro model of SCI based on PC12 cells were established with lipopolysaccharide. The cell proliferation was determined by the use of cell counting kit-8 (CCK8). The expressions of circHecw1, miR-3551-3p, and inflammatory factors were measured by quantitative real-time PCR and ELISA assay. Flow cytometry was used to assess apoptosis. Western blot analysis was performed for the purpose of determining LRRTM1 and NF-kB signaling. The expression of circ Hecw1, TNF-α, IL-6, and IL-1β in LPS-triggered PC12 cells and the expression of miR-3551-3p and IL-10 were significantly decreased. Knockdown of circHecw1 promoted proliferation and inhibited apoptosis and reduction in the inflammatory cytokine expression. Our study revealed that circHecw1 regulates SCI neuronal cell inflammation imbalance by regulating the miR-3551-3p/LRRTM1 signaling.

Multimodal therapy strategies based on hydrogels for the repair of spinal cord injury

Spinal cord injury (SCI) is a serious traumatic disease of the central nervous system, which can give rise to the loss of motor and sensory function. Due to its complex pathological mechanism, the treatment of this disease still faces a huge challenge. Hydrogels with good biocompatibility and biodegradability can well imitate the extracellular matrix in the microenvironment of spinal cord. Hydrogels have been regarded as promising SCI repair material in recent years and continuous studies have confirmed that hydrogel-based therapy can effectively eliminate inflammation and promote spinal cord repair and regeneration to improve SCI. In this review, hydrogel-based multimodal therapeutic strategies to repair SCI are provided, and a combination of hydrogel scaffolds and other therapeutic modalities are discussed, with particular emphasis on the repair mechanism of SCI.

Current Concepts of Neural Stem/Progenitor Cell Therapy for Chronic Spinal Cord Injury

Chronic spinal cord injury (SCI) is a devastating condition that results in major neurological deficits and social burden. It continues to be managed symptomatically, and no real therapeutic strategies have been devised for its treatment. Neural stem/neural progenitor cells (NSCs/NPCs) being used for the treatment of chronic SCI in experimental SCI models can not only replace the lost cells and remyelinate axons in the injury site but also support their growth and provide neuroprotective factors. Currently, several clinical studies using NSCs/NPCs are underway worldwide. NSCs/NPCs also have the potential to differentiate into all three neuroglial lineages to regenerate neural circuits, demyelinate denuded axons, and provide trophic support to endogenous cells. This article explains the challenging pathophysiology of chronic SCI and discusses key NSC/NPC-based techniques having the greatest potential for translation over the next decade.

Construction of a niche-specific spinal white matter-like tissue to promote directional axon regeneration and myelination for rat spinal cord injury repair

Directional axon regeneration and remyelination are crucial for repair of spinal cord injury (SCI), but existing treatments do not effectively promote those processes. Here, we propose a strategy for construction of niche-specific spinal white matter-like tissue (WMLT) using decellularized optic nerve (DON) loaded with neurotrophin-3 (NT-3)-overexpressing oligodendrocyte precursor cells. A rat model with a white matter defect in the dorsal spinal cord of the T10 segment was used. The WMLT transplantation group showed significant improvement in coordinated motor functions compared with the control groups. WMLT transplants integrated well with host spinal cord white matter, effectively addressing several barriers to directional axonal regeneration and myelination during SCI repair. In WMLT, laminin was found to promote development of oligodendroglial lineage (OL) cells by binding to laminin receptors. Interestingly, laminin could also guide linear axon regeneration via interactions with specific integrins on the axon surface. The WMLT developed here utilizes the unique microstructure and bioactive matrix of DON to create a niche rich in laminin, NT-3 and OL cells to achieve significant structural repair of SCI. Our protocol can help to promote research on repair of nerve injury and construction of neural tissues and organoids that form specific cell niches.

Thiolated poly(2-hydroxyethyl methacrylate) hydrogels as a degradable biocompatible scaffold for tissue engineering

Research of degradable hydrogel polymeric materials exhibiting high water content and mechanical properties resembling tissues is crucial not only in drug delivery systems but also in tissue engineering, medical devices, and biomedical-healthcare sensors. Therefore, we newly offer development of hydrogels based on poly(2-hydroxyethyl methacrylate-co-2-(acetylthio) ethyl methacrylate-co-2-methacryloyloxyethyl phosphorylcholine) [P(HEMA-ATEMA-MPC)] and optimization of their mechanical and in vitro and in vivo degradability. P(HEMA-ATEMA-MPC) hydrogels differed in chemical composition, degree of crosslinking, and starting molar mass of polymers (15, 19, and 30 kDa). Polymer precursors were synthesized by a reversible addition fragmentation chain transfer (RAFT) polymerization using 2-(acetylthio)ethyl methacrylate containing protected thiol groups, which enabled crosslinking and gel formation. Elastic modulus of hydrogels increased with the degree of crosslinking (Slaughter et al., 2009) [1]. In vitro and in vivo controlled degradation was confirmed using glutathione and subcutaneous implantation of hydrogels in rats, respectively. We proved that the hydrogels with higher degree of crosslinking retarded the degradation. Also, albumin, γ-globulin, and fibrinogen adsorption on P(HEMA-ATEMA-MPC) hydrogel surface was tested, to simulate adsorption in living organism. Rat mesenchymal stromal cell adhesion on hydrogels was improved by the presence of RGDS peptide and laminin on the hydrogels. We found that rat mesenchymal stromal cells proliferated better on laminin-coated hydrogels than on RGDS-modified ones.

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.

Pluripotent Stem Cells for Spinal Cord Injury Repair

Spinal cord injury (SCI) is a devastating condition of the central nervous system that strongly reduces the patient’s quality of life and has large financial costs for the healthcare system. Cell therapy has shown considerable therapeutic potential for SCI treatment in different animal models. Although many different cell types have been investigated with the goal of promoting repair and recovery from injury, stem cells appear to be the most promising. Here, we review the experimental approaches that have been carried out with pluripotent stem cells, a cell type that, due to its inherent plasticity, self-renewal, and differentiation potential, represents an attractive source for the development of new cell therapies for SCI. We will focus on several key observations that illustrate the potential of cell therapy for SCI, and we will attempt to draw some conclusions from the studies performed to date.

Enhanced neural differentiation of human-induced pluripotent stem cells on aligned laminin-functionalized polyethersulfone nanofibers; a comparison between aligned and random fibers on neurogenesis

Despite the numerous attempts in nerve tissue engineering, no ideal strategy has been translated into effective therapy for neuronal regeneration yet. Here, we designed a novel nerve regeneration scaffold combining aligned laminin-immobilized polyethersulfone (PES) nanofibers and human-induced pluripotent stem cells (hiPSCs) for transplantation strategies. Aligned and random PES nanofibers were fabricated by electrospinning method with a diameter of 95-500 nm and were then modified with covalent laminin bounding subsequent to O₂ plasma treatment. PES-functionalized fibers found to induce a remarkable higher rate of neuronal genes expression as compared to nontreated group. In addition, hiPSCs cultured on aligned pure fibers exhibited the extension of neurites along with fibers direction and an exponentially elevated expression of neuron specific enolase (early neuroectoderm marker), Tuj-1 (axonal marker), and microtubule-associated protein 2 (dendritic marker) in comparison with random pure fibers. The concomitant of increased hydrophilicity and biocompatibility along with exploiting topographical cues and directional guidance make aligned PES-plasma-laminin a versatile scaffold for adhesion, proliferation, spreading, and differentiation of hiPSCs into nerve cells.

Current Concepts of Stem Cell Therapy for Chronic Spinal Cord Injury

Chronic spinal cord injury (SCI) is a catastrophic condition associated with significant neurological deficit and social and financial burdens. It is currently being managed symptomatically with no real therapeutic strategies available. In recent years, a number of innovative regenerative strategies have emerged and have been continuously investigated in clinical trials. In addition, several more are coming down the translational pipeline. Among ongoing and completed trials are those reporting the use of mesenchymal stem cells, neural stem/progenitor cells, induced pluripotent stem cells, olfactory ensheathing cells, and Schwann cells. The advancements in stem cell technology, combined with the powerful neuroimaging modalities, can now accelerate the pathway of promising novel therapeutic strategies from bench to bedside. Various combinations of different molecular therapies have been combined with supportive scaffolds to facilitate favorable cell–material interactions. In this review, we summarized some of the most recent insights into the preclinical and clinical studies using stem cells and other supportive drugs to unlock the microenvironment in chronic SCI to treat patients with this condition. Successful future therapies will require these stem cells and other synergistic approaches to address the persistent barriers to regeneration, including glial scarring, loss of structural framework, and immunorejection.

Stem Cell Therapy for Spinal Cord Injury

Traumatic spinal cord injury (SCI) results in direct and indirect damage to neural tissues, which results in motor and sensory dysfunction, dystonia, and pathological reflex that ultimately lead to paraplegia or tetraplegia. A loss of cells, axon regeneration failure, and time-sensitive pathophysiology make tissue repair difficult. Despite various medical developments, there are currently no effective regenerative treatments. Stem cell therapy is a promising treatment for SCI due to its multiple targets and reactivity benefits. The present review focuses on SCI stem cell therapy, including bone marrow mesenchymal stem cells, umbilical mesenchymal stem cells, adipose-derived mesenchymal stem cells, neural stem cells, neural progenitor cells, embryonic stem cells, induced pluripotent stem cells, and extracellular vesicles. Each cell type targets certain features of SCI pathology and shows therapeutic effects via cell replacement, nutritional support, scaffolds, and immunomodulation mechanisms. However, many preclinical studies and a growing number of clinical trials found that single-cell treatments had only limited benefits for SCI. SCI damage is multifaceted, and there is a growing consensus that a combined treatment is needed.

Biomaterials and strategies for repairing spinal cord lesions

Spinal cord injury (SCI) causes intractable disease and leads to inevitable physical, financial, and psychological burdens on patients and their families. SCI is commonly divided into primary and secondary injury. Primary injury occurs upon direct impact to the spinal cord, which leads to cell necrosis, axon disruption, and vascular loss. This triggers pathophysiological secondary injury, which has several phases: acute, subacute, intermediate, and chronic. These phases are dependent on post-injury time and pathophysiology and have various causes, such as the infiltration of inflammatory cells and release of cytokines that can act as a barrier to neural regeneration. Another unique feature of SCI is the glial scar produced from the reactive proliferation of astrocytes, which acts as a barrier to axonal regeneration. Interdisciplinary research is investigating the use of biomaterials and tissue-engineered fabrication to overcome SCI. In this review, we discuss representative biomaterials, including natural and synthetic polymers and nanomaterials. In addition, we describe several strategies to repair spinal cord injuries, such as fabrication and the delivery of therapeutic biocomponents. These biomaterials and strategies may offer beneficial information to enhance the repair of spinal cord lesions.

Biomaterial-supported MSC transplantation enhances cell-cell communication for spinal cord injury

The spinal cord is part of the central nervous system (CNS) and serves to connect the brain to the peripheral nervous system and peripheral tissues. The cell types that primarily comprise the spinal cord are neurons and several categories of glia, including astrocytes, oligodendrocytes, and microglia. Ependymal cells and small populations of endogenous stem cells, such as oligodendrocyte progenitor cells, also reside in the spinal cord. Neurons are interconnected in circuits; those that process cutaneous sensory input are mainly located in the dorsal spinal cord, while those involved in proprioception and motor control are predominately located in the ventral spinal cord. Due to the importance of the spinal cord, neurodegenerative disorders and traumatic injuries affecting the spinal cord will lead to motor deficits and loss of sensory inputs.

Spinal cord injury (SCI), resulting in paraplegia and tetraplegia as a result of deleterious interconnected mechanisms encompassed by the primary and secondary injury, represents a heterogeneously behavioral and cognitive deficit that remains incurable. Following SCI, various barriers containing the neuroinflammation, neural tissue defect (neurons, microglia, astrocytes, and oligodendrocytes), cavity formation, loss of neuronal circuitry, and function must be overcame. Notably, the pro-inflammatory and anti-inflammatory effects of cell–cell communication networks play critical roles in homeostatic, driving the pathophysiologic and consequent cognitive outcomes. In the spinal cord, astrocytes, oligodendrocytes, and microglia are involved in not only development but also pathology. Glial cells play dual roles (negative vs. positive effects) in these processes. After SCI, detrimental effects usually dominate and significantly retard functional recovery, and curbing these effects is critical for promoting neurological improvement. Indeed, residential innate immune cells (microglia and astrocytes) and infiltrating leukocytes (macrophages and neutrophils), activated by SCI, give rise to full-blown inflammatory cascades. These inflammatory cells release neurotoxins (proinflammatory cytokines and chemokines, free radicals, excitotoxic amino acids, nitric oxide (NO)), all of which partake in axonal and neuronal deficit.

Given the various multifaceted obstacles in SCI treatment, a combinatorial therapy of cell transplantation and biomaterial implantation may be addressed in detail here. For the sake of preserving damaged tissue integrity and providing physical support and trophic supply for axon regeneration, MSC transplantation has come to the front stage in therapy for SCI with the constant progress of stem cell engineering. MSC transplantation promotes scaffold integration and regenerative growth potential. Integrating into the implanted scaffold, MSCs influence implant integration by improving the healing process. Conversely, biomaterial scaffolds offer MSCs with a sheltered microenvironment from the surrounding pathological changes, in addition to bridging connection spinal cord stump and offering physical and directional support for axonal regeneration. Besides, Biomaterial scaffolds mimic the extracellular matrix to suppress immune responses.

Here, we review the advances in combinatorial biomaterial scaffolds and MSC transplantation approach that targets certain aspects of various intercellular communications in the pathologic process following SCI. Finally, the challenges of biomaterial-supported MSC transplantation and its future direction for neuronal regeneration will be presented.

Nanotechnology for the Treatment of Spinal Cord Injury

Spinal cord injury (SCI) affects the central nervous system (CNS) and there is currently no treatment with the potential for rehabilitation. Although several clinical treatments have been developed, they are still at an early stage and have not shown success in repairing the broken fiber, which prevents cellular regeneration and integral restoration of motor and sensory functions. Considering the importance of nanotechnology and tissue engineering for neural tissue injuries, this review focuses on the latest advances in nanotechnology for SCI treatment and tissue repair. The PubMed database was used for the bibliographic survey. Initial research using the following keywords "tissue engineering and spinal cord injury" revealed 970 articles published in the last 10 years. The articles were further analyzed, excluding those not related to SCI or with results that did not pertain to the field of interest, including the reviews. It was observed that a total of 811 original articles used the quoted keywords. When the word "treatment" was added, 662 articles were found and among them, 529 were original ones. Finally, when the keywords "Nanotechnology and spinal cord injury" were used, 102 articles were found, 65 being original articles. A search concerning the biomaterials used for SCI found 700 articles with 589 original articles. A total of 107 articles were included in the discussion of this review and some are used for the theoretical framework. Recent progress in nanotechnology and tissue engineering has shown promise for repairing CNS damage. A variety of in vivo animal testing for SCI has been used with or without cells and some of these in vivo studies have shown successful results. However, there is no translation to humans using nanotechnology for SCI treatment, although there is one ongoing trial that employs a tissue engineering approach, among other technologies. The first human surgical scaffold implantation will elucidate the possibility of this use for further clinical trials. This review concludes that even though tissue engineering and nanotechnology are being investigated as a possibility for SCI treatment, tests with humans are still in the theoretical stage. Impact statement Thousands of people are affected by spinal cord injury (SCI) per year in the world. This type of lesion is one of the most severe conditions that can affect humans and usually causes permanent loss of strength, sensitivity, and motor function below the injury site. This article reviews studies on the PubMed database, assessing the publications on SCI in the study field of tissue engineering, focusing on the use of nanotechnology for the treatment of SCI. The review makes an evaluation of the biomaterials used for the treatment of this condition and the techniques applied for the production of nanostructured biomaterials.

Nanomaterial integration into the scaffolding materials for nerve tissue engineering: a review

The nervous system, which consists of a complex network of millions of neurons, is one of the most highly intricate systems in the body. This complex network is responsible for the physiological and cognitive functions of the human body. Following injuries or degenerative diseases, damage to the nervous system is overwhelming because of its complexity and its limited regeneration capacity. However, neural tissue engineering currently has some capacities for repairing nerve deficits and promoting neural regeneration, with more developments in the future. Nevertheless, controlling the guidance of stem cell proliferation and differentiation is a challenging step towards this goal. Nanomaterials have the potential for the guidance of the stem cells towards the neural lineage which can overcome the pitfalls of the classical methods since they provide a unique microenvironment that facilitates cell-matrix and cell-cell interaction, and they can manipulate the cell signaling mechanisms to control stem cells' fate. In this article, the suitable cell sources and microenvironment cues for neuronal tissue engineering were examined. Afterward, the nanomaterials that impact stem cell proliferation and differentiation towards neuronal lineage were reviewed.

PLG Bridge Implantation in Chronic SCI Promotes Axonal Elongation and Myelination

Spinal cord injury (SCI) is a devastating condition that may cause permanent functional loss below the level of injury, including paralysis and loss of bladder, bowel, and sexual function. Patients are rarely treated immediately, and this delay is associated with tissue loss and scar formation that can make regeneration at chronic time points more challenging. Herein, we investigated regeneration using a poly(lactide-co-glycolide) multichannel bridge implanted into a chronic SCI following surgical resection of necrotic tissue. We characterized the dynamic injury response and noted that scar formation decreased at 4 and 8 weeks postinjury (wpi), yet macrophage infiltration increased between 4 and 8 wpi. Subsequently, the scar tissue was resected and bridges were implanted at 4 and 8 wpi. We observed robust axon growth into the bridge and remyelination at 6 months after initial injury. Axon densities were increased for 8 week bridge implantation relative to 4 week bridge implantation, whereas greater myelination, particularly by Schwann cells, was observed with 4 week bridge implantation. The process of bridge implantation did not significantly decrease the postinjury function. Collectively, this chronic model follows the pathophysiology of human SCI, and bridge implantation allows for clear demarcation of the regenerated tissue. These data demonstrate that bridge implantation into chronic SCI supports regeneration and provides a platform to investigate strategies to buttress and expand regeneration of neural tissue at chronic time points.

Cost-Effective Cosmetic-Grade Hyaluronan Hydrogels for ReNcell VM Human Neural Stem Cell Culture

Hyaluronic acid (HA) is a polysaccharide polymer frequently used as a starting material to fabricate hydrogels, especially for recapitulating the brain's extracellular matrix (ECM) for in vitro neural stem cell (NSC) cultures. Here, we report the successful synthesis of a methacrylated HA (MeHA) polymer from an inexpensive cosmetic-grade hyaluronan starting material. The MeHA polymers synthesized from cosmetic-grade HA yielded similar chemical purity to those from pharmaceutical/research-grade HA reported in the literature. Crosslinked MeHA (x-MeHA) hydrogels were formed using radical polymerization which resulted in mechanical properties matching previously reported mechanical property ranges for enhanced neuronal differentiation of NSCs. We assessed cellular adhesion, spreading, proliferation, and stiffness-dependent neuronal differentiation properties of ReNcell VM human neural stem cells (hNSCs) and compared our results to studies reported in the literature (that utilized non-human and human pluripotent cell-derived NSCs).

Filling the Gap: Neural Stem Cells as A Promising Therapy for Spinal Cord Injury

Spinal cord injury (SCI) can lead to severe motor, sensory and social impairments having a huge impact on patients’ lives. The complex and time-dependent SCI pathophysiology has been hampering the development of novel and effective therapies. Current treatment options include surgical interventions, to stabilize and decompress the spinal cord, and rehabilitative care, without providing a cure for these patients. Novel therapies have been developed targeting different stages during trauma. Among them, cell-based therapies hold great potential for tissue regeneration after injury. Neural stem cells (NSCs), which are multipotent cells with inherent differentiation capabilities committed to the neuronal lineage, are especially relevant to promote and reestablish the damaged neuronal spinal tracts. Several studies demonstrate the regenerative effects of NSCs in SCI after transplantation by providing neurotrophic support and restoring synaptic connectivity. Therefore, human clinical trials have already been launched to assess safety in SCI patients. Here, we review NSC-based experimental studies in a SCI context and how are they currently being translated into human clinical trials.