Polymer and nano-technology applications for repair and reconstruction of the central nervous system

Injectable Hydrogels for Nervous Tissue Repair-A Brief Review

The repair of nervous tissue is a critical research field in tissue engineering because of the degenerative process in the injured nervous system. In this review, we summarize the progress of injectable hydrogels using in vitro and in vivo studies for the regeneration and repair of nervous tissue. Traditional treatments have not been favorable for patients, as they are invasive and inefficient; therefore, injectable hydrogels are promising for the treatment of damaged tissue. This review will contribute to a better understanding of injectable hydrogels as potential scaffolds and drug delivery system for neural tissue engineering applications.

Advantages of nanocarriers for basic research in the field of traumatic brain injury

A major challenge for the efficient treatment of traumatic brain injury is the need for therapeutic molecules to cross the blood-brain barrier to enter and accumulate in brain tissue. To overcome this problem, researchers have begun to focus on nanocarriers and other brain-targeting drug delivery systems. In this review, we summarize the epidemiology, basic pathophysiology, current clinical treatment, the establishment of models, and the evaluation indicators that are commonly used for traumatic brain injury. We also report the current status of traumatic brain injury when treated with nanocarriers such as liposomes and vesicles. Nanocarriers can overcome a variety of key biological barriers, improve drug bioavailability, increase intracellular penetration and retention time, achieve drug enrichment, control drug release, and achieve brain-targeting drug delivery. However, the application of nanocarriers remains in the basic research stage and has yet to be fully translated to the clinic.

Customizing 3D Structures of Vertically Aligned Carbon Nanotubes to Direct Neural Stem Cell Differentiation

Neural tissue-related illnesses have a high incidence and prevalence in society. Despite intensive research efforts to enhance the regeneration of neural cells into functional tissue, effective treatments are still unavailable. Here, a novel therapeutic approach based on vertically aligned carbon nanotube forests (VA-CNT forests) and periodic VA-CNT micropillars produced by thermal chemical vapor deposition is explored. In addition, honeycomb-like and flower-like morphologies are created. Initial viability testing reveals that NE-4C neural stem cells seeded on all morphologies survive and proliferate. In addition, free-standing VA-CNT forests and capillary-driven VA-CNT forests are created, with the latter demonstrating enhanced capacity to stimulate neuritogenesis and network formation under minimal differentiation medium conditions. This is attributed to the interaction between surface roughness and 3D-like morphology that mimics the native extracellular matrix, thus enhancing cellular attachment and communication. These findings provide a new avenue for the construction of electroresponsive scaffolds based on CNTs for neural tissue engineering.

Stem Cell Scaffolds for the Treatment of Spinal Cord Injury-A Review

Spinal cord injury (SCI) is a profoundly debilitating yet common central nervous system condition resulting in significant morbidity and mortality rates. Major causes of SCI encompass traumatic incidences such as motor vehicle accidents, falls, and sports injuries. Present treatment strategies for SCI aim to improve and enhance neurologic functionality. The ability for neural stem cells (NSCs) to differentiate into diverse neural and glial cell precursors has stimulated the investigation of stem cell scaffolds as potential therapeutics for SCI. Various scaffolding modalities including composite materials, natural polymers, synthetic polymers, and hydrogels have been explored. However, most trials remain largely in the preclinical stage, emphasizing the need to further develop and refine these treatment strategies before clinical implementation. In this review, we delve into the physiological processes that underpin NSC differentiation, including substrates and signaling pathways required for axonal regrowth post-injury, and provide an overview of current and emerging stem cell scaffolding platforms for SCI.

Advances in Optogenetics Applications for Central Nervous System Injuries

Injuries to the central nervous system (CNS) often lead to severe neurological dysfunction and even death. However, there are still no effective measures to improve functional recovery following CNS injuries. Optogenetics, an ideal method to modulate neural activity, has shown various advantages in controlling neural circuits, promoting neural remapping, and improving cell survival. In particular, the emerging technique of optogenetics has exhibited promising therapeutic methods for CNS injuries. In this review, we introduce the light-sensitive proteins and light stimulation system that are important components of optogenetic technology in detail and summarize the development trends. In addition, we construct a comprehensive picture of the current application of optogenetics in CNS injuries and highlight recent advances for the treatment and functional recovery of neurological deficits. Finally, we discuss the therapeutic challenges and prospective uses of optogenetics therapy by photostimulation/photoinhibition modalities that would be suitable for clinical applications.

Silica Nanoparticles Cause Activation of NLRP3 Inflammasome in-vitro Model-Using Microglia

INTRODUCTION

Silica nanoparticles (SiNPs) have been widely used in food, cosmetics, medicine and other fields; however, there have been growing concerns regarding their potential adverse effects on health. A large number of studies have confirmed that SiNPs with small particle diameters can pass through the blood brain barrier, causing irreversible damage to the nervous system. This study aims to further explore the molecular mechanism of neurotoxicity of SiNPs and provide a toxicological basis for the medical application of SiNPs.

METHODS

We conducted an in vitro study using neuroimmune cells (mouse microglial cells, BV2) of the central nervous system to study inflammation and ferroptosis after exposure to SiNPs. We detected cell viability, morphology and ultrastructure, antioxidant function, inflammation, and ferroptosis-related proteins to explore the role of pyroptosis and ferroptosis in the damage of BV2 cells induced by SiNPs. We further explored the relationship between the inflammatory response and ferroptosis induced by SiNPs by silencing the NOD-like receptor thermal protein domain associated protein 3 (NLRP3) gene and inhibiting ferroptosis.

RESULTS

The results showed that SiNPs could invade the cytoplasm, change the ultrastructure, activate NLRP3 inflammasomes, release a large number of inflammatory factors, and trigger inflammatory reaction. We also found that SiNPs could disrupt cellular antioxidant function, increase intracellular ferrous ion level and induce ferroptosis. In addition, both inflammation and ferroptosis are alleviated in NLRP3 gene-silenced cells.

CONCLUSION

SiNPs could induce BV2 cytotoxicity through inflammatory response and ferroptosis, which may be mediated by the activation of the NLRP3 inflammasomes.

Biomaterial-Mediated Factor Delivery for Spinal Cord Injury Treatment

Spinal cord injury (SCI) is an injurious process that begins with immediate physical damage to the spinal cord and associated tissues during an acute traumatic event. However, the tissue damage expands in both intensity and volume in the subsequent subacute phase. At this stage, numerous events exacerbate the pathological condition, and therein lies the main cause of post-traumatic neural degeneration, which then ends with the chronic phase. In recent years, therapeutic interventions addressing different neurodegenerative mechanisms have been proposed, but have met with limited success when translated into clinical settings. The underlying reasons for this are that the pathogenesis of SCI is a continued multifactorial disease, and the treatment of only one factor is not sufficient to curb neural degeneration and resulting paralysis. Recent advances have led to the development of biomaterials aiming to promote in situ combinatorial strategies using drugs/biomolecules to achieve a maximized multitarget approach. This review provides an overview of single and combinatorial regenerative-factor-based treatments as well as potential delivery options to treat SCIs.

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

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

Nanopharmaceutical-based regenerative medicine: a promising therapeutic strategy for spinal cord injury

Spinal cord injury (SCI) is a neurological disorder that can lead to loss of perceptive and athletic function due to the severe nerve damage. To date, pieces of evidence detailing the precise pathological mechanisms in SCI are still unclear. Therefore, drug therapy cannot effectively alleviate the SCI symptoms and faces the limitations of systemic administration with large side effects. Thus, the development of SCI treatment strategies is urgent and valuable. Due to the application of nanotechnology in pharmaceutical research, nanopharmaceutical-based regenerative medicine will bring colossal development space for clinical medicine. These nanopharmaceuticals (i.e. nanocrystalline drugs and nanocarrier drugs) are designed using different types of materials or bioactive molecules, so as to improve the therapeutic effects, reduce side effects, and subtly deliver drugs, etc. Currently, an increasing number of nanopharmaceutical products have been approved by drug regulatory agencies, which has also prompted more researchers to focus on the potential treatment strategies of SCI. Therefore, the purpose of this review is to summarize and elaborate the research progress as well as the challenges and future of nanopharmaceuticals in the treatment of SCI, aiming to promote further research of nanopharmaceuticals in SCI.

Recent Advances in the Regenerative Approaches for Traumatic Spinal Cord Injury: Materials Perspective

Spinal cord injury (SCI) is a devastating health condition that may lead to permanent disabilities and death. Understanding the pathophysiological perspectives of traumatic SCI is essential to define mechanisms that can help in designing recovery strategies. Since central nervous system tissues are notorious for their deficient ability to heal, efforts have been made to identify solutions to aid in restoration of the spinal cord tissues and thus its function. The two main approaches proposed to address this issue are neuroprotection and neuro-regeneration. Neuroprotection involves administering drugs to restore the injured microenvironment to normal after SCI. As for the neuro-regeneration approach, it focuses on axonal sprouting for functional recovery of the injured neural tissues and damaged axons. Despite the progress made in the field, neural regeneration treatment after SCI is still unsatisfactory owing to the disorganized way of axonal growth and extension. Nanomedicine and tissue engineering are considered promising therapeutic approaches that enhance axonal growth and directionality through implanting or injecting of the biomaterial scaffolds. One of these recent approaches is nanofibrous scaffolds that are used to provide physical support to maintain directional axonal growth in the lesion site. Furthermore, these preferable tissue-engineered substrates can afford axonal regeneration by mimicking the extracellular matrix of the neural tissues in terms of biological, chemical, and architectural characteristics. In this review, we discuss the regenerative approach using nanofibrous scaffolds with a focus on their fabrication methods and their properties that define their functionality performed to heal the neural tissue efficiently.

Recent progress in therapeutic drug delivery systems for treatment of traumatic CNS injuries

Most therapeutics for the treatment of traumatic central nervous system injuries, such as traumatic brain injury and spinal cord injury, encounter various obstacles in reaching the target tissue and exerting pharmacological effects, including physiological barriers like the blood-brain barrier and blood-spinal cord barrier, instability rapid elimination from the injured tissue or cerebrospinal fluid and off-target toxicity. For central nervous system delivery, nano- and microdrug delivery systems are regarded as the most suitable and promising carriers. In this review, the pathophysiology and biomarkers of traumatic central nervous system injuries (traumatic brain injury and spinal cord injury) are introduced. Furthermore, various drug delivery systems, novel combinatorial therapies and advanced therapies for the treatment of traumatic brain injury and spinal cord injury are emphasized.

Valproic acid-labeled chitosan nanoparticles promote recovery of neuronal injury after spinal cord injury

Chitosan nanoparticles have been recognized as a new type of biomaterials for treatment of spinal cord injury (SCI). To develop a novel treatment method targeted delivery injured spinal cord, valproic acid labeled chitosan nanoparticles (VA-CN) were constructed and evaluated in the treatment of SCI. Our results demonstrated that administration of VA-CN significantly promoted the recovery of the function and tissue repair after SCI. Moreover, we found treatment of VA-CN inhibited the reactive astrocytes after SCI. Furthermore, administration of VA-CN enhanced immunoreactions of neuronal related marker NF160, which suggested that VA-CN could promote the neuroprotective function in rats of SCI. The production of IL-1β, IL-6 and TNF-α were significantly decreased following treatment of VA-CN. Meanwhile, administration of VA-CN effectively improved the blood spinal cord barrier (BSCB) disruption after SCI. Administration of VA-CN could enhance the recovery of neuronal injury, suppress the reactive astrocytes and inflammation, and improve the blood spinal cord barrier disruption after SCI in rats. These results provided a novel and promising therapeutic manner for SCI.

Oxidative Toxicity in Diabetes Mellitus: The Role of Nanoparticles and Future Therapeutic Strategies

Diabetes mellitus is one of the most common chronic medical conditions in the world. Increasing evidence suggests that chronic hyperglycemia can cause excessive production of free radicals, particularly reactive oxygen species (ROS). Free radicals play important roles in tissue damage in diabetes. The relationship between exposure to nanoparticles (NPs) and diabetes has been reported in many previous studies. Evaluation of the potential benefits and toxic effects of NPs on diabetic disorders is of importance. This review highlights studies on the relationship between NPs and oxidative stress (OS) as well as the possible mechanisms in diabetic animal models and humans.

An overview of the neuroprotective potential of rosmarinic acid and its association with nanotechnology-based delivery systems: A novel approach to treating neurodegenerative disorders

Neurodegenerative disorders (ND) are characterized by slow and progressive neuronal dysfunction induced by the degeneration of neuronal cells in the central nervous system (CNS). Recently, the neuroprotective effects of natural compounds with anti-inflammatory and antioxidant activities has been clearly demonstrated. This appears to be an attractive therapeutic approach for ND, particularly regarding the use of polyphenols. In this review, we present an overview of the neuroprotective potential of rosmarinic acid (RA) and discuss the use of nanotechnology as a novel approach to treating ND. RA presents a variety of biological important activities, i.e. the modulation of pro-inflammatory cytokine expression, prevention of neurodegeneration and damage reduction. However, its poor bioavailability represents a limitation in terms of pharmacodynamics. In this sense, nanotechnology-based carriers could allow for the administration of higher but still safe amounts of RA, aiming for CNS delivery. Nasal administration could be a pleasant route for delivery to the CNS, as this represents a direct route to the CNS. With these advantages, RA-loaded nanotechnology-based therapy through the nasal route could be promising approach for the treatment of ND.

Immediate and complete restoration of peripheral nerve function after injury is attainable by a combination of surgical and chemical interventions

Despite significant advances in almost every other aspect of medicine, physicians are still unable to restore function after nerve injury with any consistency or reliability. The current standard of care (which involves coaptation of the two ends via epineurial sutures) is largely unchanged from its first description over 400 years ago, and unfortunately leads to a recovery that is at best slow (taking months or years) and partial. Encouragingly, two new conceptual approaches are being developed that separately have been shown to improve outcomes. The first approach involves optimization of the mechanical aspects of nerve coaptation (with an emphasis on exceedingly "clean cuts" of the axon ends and moving any suture material far away from the coaptation site). The second approach involves manipulation of the chemical composition of the local environment at the cut ends of the nerve in order to promote re-establishment of membranous continuity. Though neither approach currently leads to results that reach those of uninjured controls, there is reason to believe that these two approaches can be used concurrently. Thus, we hypothesize that immediate and complete restoration of peripheral nerve function after injury is attainable by a combination of surgical and chemical interventions. The combination could be tested in rodents and non-human primates by assessing histology, electrical activity, intracellular diffusion, and functional status and could likely rapidly move to a clinical trial in humans. If the hypothesis is proven to be true, its impact would be profound, as it would positively affect not only recovery after traumatic nerve injury, but also functional status after allotransplantation, as well as introduce the prospects of advanced interfaces between human nerves and computer circuits.

From Hypothermia to Cephalosomatic Anastomoses: The Legacy of Robert White (1926-2010) at Case Western Reserve University of Cleveland

Dr. Robert J. White (1926-2010) was an eminent neurosurgeon and bioethicist, renowned for his classic work in hypothermia and pioneering mammalian head transplant experiments. He founded the Division of Neurosurgery at the Cleveland Metropolitan General Hospital (currently MetroHealth Medical Center, a level 1 trauma county hospital) and became the youngest full professor at the Case Western Reserve University in Cleveland, Ohio. With over 500 research articles to his credit, he founded the Brain Research Laboratory at what was then the Cleveland Metropolitan General Hospital, which was also home to future leaders in neurosurgery, neurosciences, and allied specialties. He transferred a healthy monkey head onto a surgically beheaded monkey body under deep hypothermic conditions drawing both laurels and criticisms alike. Despite a largely controversial neurosurgical research career, his original contributions to deep hypothermia have found profound clinical applications in modern trauma and vascular neurosurgery. The new fusogens and myelorrhaphy methods being tried in Europe hold promise for a future of reanastomosing 2 homologous or heterologous tracts in the neuraxis.

Neuroprotection by chitosan nanoparticles in oxidative stress-mediated injury

Objective

Oxidative stress is a critical component of nervous system secondary injury. Oxidative stress produces toxic chemical byproducts including reactive aldehydes that traverse intact membranes and attack neighboring healthy cells. This secondary damage often leads to further patho-biochemical cascades that exacerbate the original insult. In this work, we investigate the therapeutic effects of chitosan nanoparticles on cell cultures exposed to oxidative stress.

Results

We found chitosan nanoparticles can rescue BV-2 glial cells from death, but only for cells undergoing necrosis. Necrosis occurred when cultures were challenged with high concentrations of H₂O₂ (> 110 μM) whereas a slow and progressive loss of cultures was observed in more dilute (50–100 μM) peroxide applications. In the latter case, the primary mode of cell death was apoptosis. These studies revealed that while rescue of H₂O₂ challenged cultures was achieved for necrotic cell death, no such sparing was observed in apoptotic cells. Based on the current and cumulative data regarding the membrane fusogenic properties of chitosan, we conclude that chitosan neuroprotection arises from its membrane sealing effects. Consistent with this hypothesis is the observation that apoptotic cells did not exhibit early stage membrane damage. These in vitro results elucidate mechanisms by which membrane fusogens may provide therapeutic benefit.

Electronic supplementary material

The online version of this article (10.1186/s13104-018-3162-7) contains supplementary material, which is available to authorized users.

Electrically conductive nanocomposite hydrogels embedded with functionalized carbon nanotubes for spinal cord injury

Electrically conductive hydrogels incorporated with CNTs support PC12 cell growth and differentiation and hold promise for nerve regeneration.

Nano-hemostats and a Pilot Study of Their Use in a Large Animal Model of Major Vessel Hemorrhage in Endoscopic Skull Base Surgery

Nano-hemostats are synthetic amino acid chains that self-assemble into a scaffold under certain conditions. These have been shown to be effective in stopping bleeding in small animal models of hemorrhage. Proposed mechanisms for their effect are that they form a mesh analogous to the fibrin plug in native hemostasis and that they may potentiate both platelet activation and the coagulation cascade. These may potentially become valuable adjuncts to endoscopic skull base surgery where there is the potential for both major vessel injury and smaller perforator injury to eloquent areas where bipolar cautery may not be suitable. We present a summary of the clinical studies to date and a small pilot study of nano-hemostat in an endoscopic sheep model of major vessel hemorrhage to determine its efficacy in stopping bleeding in this potentially catastrophic complication.

The application of graphene oxidized combining with decellularized scaffold to repair of sciatic nerve injury in rats

This paper combined the decellularized scaffold of sciatic nerve of rats with graphene oxidized (GO), studied and facilitated the regeneration of sciatic nerve of rats, and provided the basis for the clinical application of nanomaterials. GO was prepared through improving Hammer’s Method. Fourier Infrared Spectrum was used to scan and detect the functional groups in GO of sample by using the pellet method, the microcosmic morphological appearance of GO was observed by using the scanning electron microscope. The GO/decellularized scaffold were prepared and operation bridging of injured sciatic nerve was conducted by using the oscillation mixing method. BL-420F Biofunctional Experiment System was used to detect nerve action potential and the maximum tension value of muscles, and the fiber structure of nerve was observed under H-7650 Transmission Electron Microscope (TEM). Scanning electron microscope observed that GO presented a folded and curly single-layer sheet structure. It was soluble in water through ultrasound, brownish, the Fourier Transform Infrared Spectrometer detected the absorption peaks of carbonyl, hydroxy and carboxy, proving that the surface of GO material had many functional groups containing oxygen. Decellularized scaffold combining with GO was applied to repair injury of sciatic nerve, the nerve action potential, maximum tension value of muscle, wet weight value of gastrocnemius, thickness of gastrocnemius, thickness of myelin sheath and diameter of axon of the decellularized scaffold combining with GO group were obviously higher than the decellularized scaffold group and the self-rotating group, approaching to the normal value. All the data were represented by means ± standard deviation (x¯±s) and processed by adopting SPSS 11.0 software. Comparisons among groups were analyzed by variance, and the comparison of two means was detected by student t. The detection level adopted α = 0.05, when P < 0.05, it could be considered that there were significant differences. GO could combine with the biomaterial-decellularized scaffold to repair the injury of sciatic nerve and facilitate the regeneration of injured nerve. This provided new thoughts and theoretical & experimental bases for nanomaterials to be applied to clinic treatment of repair of nerve injury.

The history of head transplantation: a review

Background

Since the turn of the last century, the prospect of head transplantation has captured the imagination of scientists and the general public. Recently, head transplant has regained attention in popular media, as neurosurgeons have proposed performing this procedure in 2017. Given the potential impact of such a procedure, we were interested in learning the history of the technical hurdles that need to be overcome, and determine if it is even technically possible to perform such a procedure on humans today.

Method

We conducted a historical review of available literature on the technical challenges and developments of head transplantation. The many social, psychological, ethical, religious, cultural, and legal questions of head transplantation were beyond the scope of this review.

Results

Our historical review identified the following important technical considerations related to performing a head transplant: maintenance of blood flow to an isolated brain via vessel anastomosis; availability of immunosuppressive agents; spinal anastomosis and fusion following cord transfection; pain control in the recipient. Several animal studies have demonstrated success in maintaining recipient cerebral perfusion and achieving immunosuppression. However, there is currently sparse evidence in favor of successful spinal anastomosis and fusion after transection. While recent publications by an Italian group offer novel approaches to this challenge, research on this topic has been sparse and hinges on procedures performed in animal models in the 1970s. How transferrable these older methods are to the human nervous system is unclear and warrants further exploration.

Conclusions

Our review identified several important considerations related to performing a viable head transplantation. Besides the technical challenges that remain, there are important ethical issues to consider, such as exploitation of vulnerable patients and informed consent. Thus, besides the remaining technical challenges, these ethical issues will also need to be addressed before moving these studies to the clinic.

Entrapping quercetin in silica/polyethylene glycol hybrid materials: Chemical characterization and biocompatibility

Sol-gel synthesis was exploited to entrap quercetin, a natural occurring antioxidant polyphenol, in silica-based hybrid materials, which differed in their polyethylene glycol (PEG) content (6, 12, 24 and 50wt%). The materials obtained, whose nano-composite nature was ascertained by Scanning Electron Microscopy (SEM), were chemically characterized by Fourier Transform InfraRed (FT-IR) and UV-Vis spectroscopies. The results prove that a reaction between the polymer and the drug occurred. Bioactivity tests showed their ability to induce hydroxyapatite nucleation on the sample surfaces. The direct contact method was applied to screen the cytotoxicity of the synthetized materials towards fibroblast NIH 3T3 cells, commonly used for in vitro biocompatibility studies, and three nervous system cell lines (neuroblastoma SH-SY5Y, glioma U251, and pheochromocytoma PC12 cell lines), adopted as models in oxidative stress related studies. Using the MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) assay NIH 3T3 proliferation was assessed and the morphology was not compromised by direct exposure to the materials. Analogously, PC-12, and U-251 cell lines were not affected by new materials. SH-SY5Y appeared to be the most sensitive cell line with cytotoxic effects of 20-35%.

Traumatic Axonal Injury: Mechanisms and Translational Opportunities

Traumatic axonal injury (TAI) is an important pathoanatomical subgroup of traumatic brain injury (TBI) and a major driver of mortality and functional impairment. Experimental models have provided insights into the effects of mechanical deformation on the neuronal cytoskeleton and the subsequent processes that drive axonal injury. There is also increasing recognition that axonal or white matter loss may progress for years post-injury and represent one mechanistic framework for progressive neurodegeneration after TBI. Previous trials of novel therapies have failed to make an impact on clinical outcome, in both TBI in general and TAI in particular. Recent advances in understanding the cellular and molecular mechanisms of injury have the potential to translate into novel therapeutic targets.

Multiple therapeutic targets are emerging that offer the potential to reduce secondary brain injury at a cellular level. These include cytoskeletal and membrane stabilisation, control of calcium flux and calpain activation, optimisation of cellular energetics, and modulation of the inflammatory response.

Wallerian degeneration, as occurs following an axonal injury, is an active, cell-autonomous death pathway that involves failure of axonal transport to deliver key enzymes involved in NAD biosynthesis.

Chronic microglial activation occurs following traumatic brain injury (TBI) and may persist for decades afterwards. This ongoing response has been linked to long-term neurodegeneration, particularly of white matter tracts.

Phagoptosis is the process whereby physiologically stressed but otherwise viable neurons are phagocytosed by microglia in response to a range of eat-me signals induced by tissue injury.

Intraspinal Delivery of Polyethylene Glycol-coated Gold Nanoparticles Promotes Functional Recovery After Spinal Cord Injury

Failure of the mammalian central nervous system (CNS) to regenerate effectively after injury leads to mostly irreversible functional impairment. Gold nanoparticles (AuNPs) are promising candidates for drug delivery in combination with tissue-compatible reagents, such as polyethylene glycol (PEG). PEG administration in CNS injury models has received interest for potential therapy, but toxicity and low bioavailability prevents clinical application. Here we show that intraspinal delivery of PEG-functionalized 40-nm-AuNPs at early stages after mouse spinal cord injury is beneficial for recovery. Positive outcome of hind limb motor function was accompanied by attenuated inflammatory response, enhanced motor neuron survival, and increased myelination of spared or regrown/sprouted axons. No adverse effects, such as body weight loss, ill health, or increased mortality were observed. We propose that PEG-AuNPs represent a favorable drug-delivery platform with therapeutic potential that could be further enhanced if PEG-AuNPs are used as carriers of regeneration-promoting molecules.

From demyelination to remyelination: the road toward therapies for spinal cord injury

Myelin integrity is crucial for central nervous system (CNS) physiology while its preservation and regeneration after spinal cord injury (SCI) is key to functional restoration. Disturbance of nodal organization acutely after SCI exposes the axon and triggers conduction block in the absence of overt demyelination. Oligodendrocyte (OL) loss and myelin degradation follow as a consequence of secondary damage. Here, we provide an overview of the major biological events and underlying mechanisms leading to OL death and demyelination and discuss strategies to restrain these processes. Another aspect which is critical for SCI repair is the enhancement of endogenously occurring spontaneous remyelination. Recent findings have unveiled the complex roles of innate and adaptive immune responses in remyelination and the immunoregulatory potential of the glial scar. Moreover, the intimate crosstalk between neuronal activity, oligodendrogenesis and myelination emphasizes the contribution of rehabilitation to functional recovery. With a view toward clinical applications, several therapeutic strategies have been devised to target SCI pathology, including genetic manipulation, administration of small therapeutic molecules, immunomodulation, manipulation of the glial scar and cell transplantation. The implementation of new tools such as cellular reprogramming for conversion of one somatic cell type to another or the use of nanotechnology and tissue engineering products provides additional opportunities for SCI repair. Given the complexity of the spinal cord tissue after injury, it is becoming apparent that combinatorial strategies are needed to rescue OLs and myelin at early stages after SCI and support remyelination, paving the way toward clinical translation.

Use of polycaprolactone (PCL) as scaffolds for the regeneration of nerve tissue

Adipose tissue is an easily accessible source of stem cells for use in tissue regenerative medicine. In the literature, different methods have been used to stimulate acquisition of neuronal characteristics by adipose-derived stem cells (ADSC). Herein we study the growth and neuronal differentiation potential of ADSC seeded onto a porous polycaprolactone (PCL) scaffold. The objective of this study is to demonstrate that PCL can be used as a scaffold to support reconstruction of new nervous tissue using adipose stem cells. We have previously shown that undifferentiated ADSC adhere and grow on PCL. Herein we show that, after culture on PCL in neuronal differentiation medium, ADSC expressed molecular markers characteristic of neuronal cells (β-tubulin-III, Neuron-Specific Enolase (NSE), Nestin) and secrete brain derived neurotrophic factor (BDNF) and nerve growth factor (NGF). This study suggests that PCL can be used as a scaffold to generate nervous tissue in vitro. PLC has excellent mechanical properties and a slow degradation rate. Moreover, on the basis of our results, we propose that PCL could be used for to make in vitro, scaffold coated with neuronal cells derived from Adipose stem cells (ADSC). Neuronal cells-coated PCL could find several applications to replace damaged area of ​​the body; for example, a possible use could be the generation of nerves.

Action at a distance: functional drug delivery using electromagnetic-field-responsive polypyrrole nanowires

In this work, we introduce a free-standing, vertically aligned conductive polypyrrole (Ppy) architecture that can serve as a high-capacity drug reservoir. This novel geometric organization of Ppy provides a new platform for improving the drug-loading efficiency. Most importantly, we present the first formal evidence that an impregnated drug (dexamethasone, DEX) can be released on demand by a focal, pulsatile electromagnetic field (EMF). This remotely controlled, on-off switchable polymer system provides a framework for implantable constructs that can be placed in critical areas of the body without any physical contact (such as percutaneous electrodes) with the Ppy, contributing to a low "foreign body" footprint. We demonstrate this possibility by using a BV-2 microglia culture model in which reactive oxygen species (ROS) and inducible nitric oxide synthase (iNOS) expression was attenuated in response to DEX released from EMF-stimulated Ppy.

The role of hybrid chitosan membranes on scarring process following lumbar surgery: post-laminectomy experimental model

OBJECTIVES

Post-operative scarring process on lumbar surgery is object of several studies mainly because of the epidural fibrosis formation. Hybrid chitosan have shown promising effect on fibrosis prevention. The aim of this study was to determine the influence of chitosan-silane membrane on the lumbar surgery scarring process. These membranes have improved mechanical strength which makes them suitable to maintain a predefined shape.

METHODS

A two level lumbar laminectomy was performed in 14 New Zealand male rabbits. Laminectomy sites were randomly selected for biomaterial or control. Chitosan membranes were prepared and care was taken in order to make it adapted to the bone defect dimensions covering the totality of the defect including the bone margins. Histological analysis was performed by haematoxylin/eosin and by Masson's trichrome staining four weeks after laminectomy.

RESULTS

Microscope observations revealed the presence of a well-organized regenerating tissue, integrated in the surrounding vertebral bone tissue with a regular and all-site interface on the chitosan sites, in clear contrast with the presence of a disorganized regenerating tissue with aspects consistent with the persistence of a chronic inflammatory condition, on control sites.

DISCUSSION

The results of this study clearly demonstrated that hybrid chitosan had an organizing effect on post-operative scarring process. The presence of the hybrid chitosan membrane resulted on a well-organized tissue integrated in the surrounding vertebral bone tissue with signs of regenerative bone tissue in continuity with native bone. This can be a major feature on the dynamics of epidural fibrosis formation.

PEG-PDLLA micelle treatment improves axonal function of the corpus callosum following traumatic brain injury

The initial pathological changes of diffuse axonal injury following traumatic brain injury (TBI) include membrane disruption and loss of ionic homeostasis, which further lead to dysfunction of axonal conduction and axon disconnection. Resealing the axolemma is therefore a potential therapeutic strategy for the early treatment of TBI. Monomethoxy poly (ethylene glycol)-poly (D, L-lactic acid) di-block copolymer micelles (mPEG-PDLLA) have been shown to restore depressed compound action potentials (CAPs) of spinal axons and promote functional recovery after spinal cord injury. Here, we evaluate the effect of the micelles on repairing the injured cortical axons following TBI. Adult mice subjected to controlled cortical impact (CCI) were treated with intravenous injection of the micelles at 0 h or 4 h after injury. Evoked CAPs were recorded from the corpus callosum of coronal cortical slices at 2 days after injury. The CCI caused significant decreases in the amplitudes of two CAP peaks that were respectively generated by the faster myelinated axons and slower unmyelinated axons. Micelle treatment at both 0 h and 4 h after CCI resulted in significant increases in both CAP peak amplitudes. Injection of fluorescent dye-labeled micelles revealed high fluorescent staining in cortical gray and white matters underneath the impact site. Labeling membrane-perforated neurons by injecting a membrane impermeable dye Texas Red-labeled dextran into lateral ventricles at 2 h post-CCI revealed that immediate micelle injection after CCI did not reduce the number of dye-stained cortical neurons and dentate granule cells of the hippocampus, indicating its ineffectiveness in repairing plasma membrane of neuronal somata. We conclude that intravenous administration of mPEG-PDLLA micelles immediately or at 4 h after TBI allows brain penetration via the compromised blood brain-barrier, and thereby improves the function of both myelinated and unmyelinated axons of the corpus callosum.

Carboxymethylcellulose hydrogels support central nervous system-derived tumor-cell chemotactic migration: Comparison with conventional extracellular matrix macromolecules

The local microenvironment plays an important role in maintaining the dynamics of the extracellular matrix and the cell–extracellular matrix relationship. The extracellular matrix is a complex network of macromolecules with distinct mechanical and biochemical characteristics. Disruptions in extracellular matrix homeostasis are associated with the onset of cancer. The extracellular matrix becomes highly disorganized, and the cell–matrix relationship changes, resulting in altered cell-signaling processes and metastasis. Medulloblastoma is one of the most common malignant pediatric brain tumors in the United States. In order to gain a better understanding of the interplay between cell–extracellular matrix interactions and cell-migratory responses in tumors, eight different matrix macromolecule formulations were investigated using a medulloblastoma-derived cell line: poly-d-lysine, matrigel, laminin, collagen 1, fibronectin, a 10% blend of laminin–collagen 1, a 20% blend of laminin–collagen 1, and a cellulose-derived hydrogel, carboxymethylcellulose. Over time, the average changes in cell morphology were quantified in 2D and 3D, as was migration in the presence and absence of the chemoattractant, epidermal growth factor. Data revealed that carboxymethylcellulose allowed for a cell–extracellular matrix relationship typically believed to be present in tumors, with cells exhibiting a rounded, amoeboid morphology consistent with chemotactic migration, while the other matrices promoted an elongated cell shape as well as both haptotactic and chemotactic motile processes. Therefore, carboxymethylcellulose hydrogels may serve as effective platforms for investigating central nervous system-derived tumor-cell migration in response to soluble factors.

A nanostructured conductive bio-composite of silk fibroin-single walled carbon nanotubes

Silk fibroin (SF), a protein core fibre from the silkworm Bombyx mori, has huge potential to become a sustainable, biocompatible, and biodegradable material platform that can pave the way towards the replacement of plastic in the fabrication of bio-derived materials for a variety of technological and biomedical applications. SF has remarkable mechanical flexibility, controllable biodegradability, biocompatibility and is capable of drug/doping inclusion, stabilization and release. However, the dielectric properties of SF limit its potential as a direct bioelectronic interface in biomedical devices intended to control the bioelectrical activity of the cell for regenerative purposes. In this work, a novel wet templating method is proposed to generate nanostructured, conductive Silk Fibroin (SF) composite films. We combine the unusual properties of SF, such as its mechanical properties, its convenience and biocompatibility with the electrical conductivity and stiffness of Single Walled Carbon Nanotubes (SWCNTs). The presented SF-SWCNT composite displays a periodic architecture where SWCNTs are regularly and homogeneously distributed in the SF protein matrix. The morphological and chemo-physical properties of the nanocomposite are analysed and defined by SEM, Raman Spectroscopy, ATR-IR, UFM and contact angle analyses. Notably, the SF-SWCNT composite film is conductive, showing additional functionality compared to the dielectric properties of the bare SF film. Finally, SF-SWCNT is biocompatible and enables the growth of primary rat Dorsal Root Ganglion (DRG) neurons. Collectively our results demonstrate that the nanostructured, conductive, robust and biocompatible SF-SWCNT composite can be fabricated using a wet templating method, paving the way towards the fabrication and development of silk-based electronic devices for use in bioelectronic and biomedical applications.

Nanoparticulate strategies for the five R’s of traumatic spinal cord injury intervention: restriction, repair, regeneration, restoration and reorganization

Nanomedicinal approaches for spinal cord injury (SCI) intervention encompasses the use of nanoscale materials and devices that prevent primary to secondary injury transition and improvement in the anatomical, physiological and functional outcomes of SCI. This review provides an incursion into the advances in nanoparticle-based neurotherapeutics for SCI and focuses on neuroactive-loaded nanoparticles for localized delivery of therapeutic factors to the severed spinal cord, targeted or nontargeted systemic drug delivery and nanoenclatherated neuroscaffolds. Special emphasis has been placed on the use of metal nanoparticles and functionalized structures as ‘drug-free’ interventions in SCI. Despite the immense advancements in nanoscience, nanointerventions still pose key challenges that need to be resolved in SCI. Several combinatorial strategies are proposed for the reconstruction of spinal architecture via restriction of the secondary injury cascade, reparation of the tethered neural architecture, regeneration of axons, restoration of biochemical functions and reorganization of the topographical and cortical networks of the spinal cord.

Neuroprotective ferulic acid (FA)-glycol chitosan (GC) nanoparticles for functional restoration of traumatically injured spinal cord

An urgent unmet need exists for early-stage treatment of spinal cord injury (SCI). Currently methylprednisolone is the only therapeutic agent used in clinics, for which the efficacy is controversial and the side effect is well-known. We demonstrated functional restoration of injured spinal cord by self-assembled nanoparticles composed of ferulic acid modified glycol chitosan (FA-GC). Chitosan and ferulic acid are strong neuroprotective agents but their systemic delivery is difficult. Our data has shown a prolonged circulation time of the FA-GC nanoparticles allowing for effective delivery of both chitosan and ferulic acid to the injured site. Furthermore, the nanoparticles were found both in the gray matter and white matter. The in vitro tests demonstrated that nanoparticles protected primary neurons from glutamate-induced excitotoxicity. Using a spinal cord contusion injury model, significant recovery in locomotor function was observed in rats that were intravenously administered nanoparticles at 2 h post injury, as compared to non-improvement by methylprednisolone administration. Histological analysis revealed that FA-GC treatment significantly preserved axons and myelin and also reduced cavity volume, astrogliosis, and inflammatory response at the lesion site. No obvious adverse effects of nanoparticles to other organs were found. The restorative effect of FA-GC presents a promising potential for treating human SCIs.

Advances in peripheral nerve regeneration

Rodent models of nerve injury have increased our understanding of peripheral nerve regeneration, but clinical applications have been scarce, partly because such models do not adequately recapitulate the situation in humans. In human injuries, axons are often required to extend over much longer distances than in mice, and injury leaves distal nerve fibres and target tissues without axonal contact for extended amounts of time. Distal Schwann cells undergo atrophy owing to the lack of contact with proximal neurons, which results in reduced expression of neurotrophic growth factors, changes in the extracellular matrix and loss of Schwann cell basal lamina, all of which hamper axonal extension. Furthermore, atrophy and denervation-related changes in target tissues make good functional recovery difficult to achieve even when axons regenerate all the way to the target tissue. To improve functional outcomes in humans, strategies to increase the speed of axonal growth, maintain Schwann cells in a healthy, repair-capable state and keep target tissues receptive to reinnervation are needed. Use of rodent models of chronic denervation will facilitate our understanding of the molecular mechanisms of peripheral nerve regeneration and create the potential to test therapeutic advances.

Electrical stimulation modulates injury potentials in rats after spinal cord injury

An injury potential is the direct current potential difference between the site of spinal cord injury and the healthy nerves. Its initial amplitude is a significant indicator of the severity of spinal cord injury, and many cations, such as sodium and calcium, account for the major portion of injury potentials. This injury potential, as well as injury current, can be modulated by direct current field stimulation; however, the appropriate parameters of the electrical field are hard to define. In this paper, injury potential is used as a parameter to adjust the intensity of electrical stimulation. Injury potential could be modulated to slightly above 0 mV (as the anode-centered group) by placing the anodes at the site of the injured spinal cord and the cathodes at the rostral and caudal sections, or around -70 mV, which is resting membrane potential (as the cathode-centered group) by reversing the polarity of electrodes in the anode-centered group. In addition, rats receiving no electrical stimulation were used as the control group. Results showed that the absolute value of the injury potentials acquired after 30 minutes of electrical stimulation was higher than the control group rats and much lower than the initial absolute value, whether the anodes or the cathodes were placed at the site of injury. This phenomenon illustrates that by changing the polarity of the electrical field, electrical stimulation can effectively modulate the injury potentials in rats after spinal cord injury. This is also beneficial for the spontaneous repair of the cell membrane and the reduction of cation influx.

Vascular endothelial growth factor-loaded injectable hydrogel enhances plasticity in the injured spinal cord

We hypothesized that vascular endothelial growth factor (VEGF)-containing hydrogels that gelify in situ after injection into a traumatized spinal cord, could stimulate spinal cord regeneration. Injectable hydrogels composed of 0.5% Pronova UPMVG MVG alginate, supplemented or not with fibrinogen, were used. The addition of fibrinogen to alginate had no effect on cell proliferation in vitro but supported neurite growth ex vivo. When injected into a rat spinal cord in a hemisection model, alginate supplemented with fibrinogen was well tolerated. The release of VEGF that was incorporated into the hydrogel was influenced by the VEGF formulation [encapsulated in microspheres or in nanoparticles or in solution (free)]. A combination of free VEGF and VEGF-loaded nanoparticles was mixed with alginate:fibrinogen and injected into the lesion of the spinal cord. Four weeks post injection, angiogenesis and neurite growth were increased compared to hydrogel alone. The local delivery of VEGF by injectable alginate:fibrinogen-based hydrogel induced some plasticity in the injured spinal cord involving fiber growth into the lesion site.

HEAVEN: The head anastomosis venture Project outline for the first human head transplantation with spinal linkage (GEMINI)

In 1970, the first cephalosomatic linkage was achieved in the monkey. However, the technology did not exist for reconnecting the spinal cord, and this line of research was no longer pursued. In this paper, an outline for the first total cephalic exchange in man is provided and spinal reconnection is described. The use of fusogens, special membrane-fusion substances, is discussed in view of the first human cord linkage. Several human diseases without cure might benefit from the procedure.

Pushing the science forward: chitosan nanoparticles and functional repair of CNS tissue after spinal cord injury

BACKGROUND

We continue our exploration of the large polysaccharide polymer Chitosan as an acute therapy for severe damage to the nervous system. We tested the action of subcutaneously injected nanoparticles (~ 100 - 200 nanometers in diameter; 1 mg per ml) against control injections (silica particle of the same size and concentration) in a standardized in vivo spinal cord injury model. These functional tests used standardized physiological measurements of evoked potentials arriving at the sensorimotor cortex subsequent to stimulation of the tibial nerve of the contralateral hindlimb. We further explored the degree of acetylation and molecular weight of chitosan on the success of sealing cell damage using specific probes of membrane integrity.

RESULTS

Not one of the control group showed restored conduction of evoked potentials stimulated from the tibial nerve of the hindleg - through the lesion - and recorded at the sensorimotor cortex of the brain. Investigation if the degree of acetylation and molecular weight impacted "membrane sealing" properties of Chitosan were unsuccessful. Dye - exchange membrane probes failed to show a difference between the comparators in the function of Chitosan in ex vivo injured spinal cord tests.

CONCLUSIONS

We found that Chitosan nanoparticles effectively restore nerve impulse transmission through the crushed adult guinea pig spinal cord in vivo after severe crush/compression injury. The tests of the molecular weight (MW) and degree of acetylation did not produce any improvement in Chitosan's membrane sealing properties.

Evaluation of cell function upon nanovector internalization

In vitro toxicity assays based on the evaluation and retention of advanced and specific cellular functions are proposed to investigate mesoporous silicon nanovectors. This approach provides greater insight compared to simple cellular viability and toxicity assays. Electron microscopy images demonstrate internalized nanovectors altering the curvature of the nuclear envelope with minimal effect on viability or biological function.