Chitosan-based hydrogel to support the paracrine activity of mesenchymal stem cells in spinal cord injury treatment

Mesenchymal Stem Cells for Neurological Disorders

Neurological disorders are becoming a growing burden as society ages, and there is a compelling need to address this spiraling problem. Stem cell-based regenerative medicine is becoming an increasingly attractive approach to designing therapies for such disorders. The unique characteristics of mesenchymal stem cells (MSCs) make them among the most sought after cell sources. Researchers have extensively studied the modulatory properties of MSCs and their engineering, labeling, and delivery methods to the brain. The first part of this review provides an overview of studies on the application of MSCs to various neurological diseases, including stroke, traumatic brain injury, spinal cord injury, multiple sclerosis, amyotrophic lateral sclerosis, Alzheimer's disease, Huntington's disease, Parkinson's disease, and other less frequently studied clinical entities. In the second part, stem cell delivery to the brain is focused. This fundamental but still understudied problem needs to be overcome to apply stem cells to brain diseases successfully. Here the value of cell engineering is also emphasized to facilitate MSC diapedesis, migration, and homing to brain areas affected by the disease to implement precision medicine paradigms into stem cell-based therapies.

Biomaterials reinforced MSCs transplantation for spinal cord injury repair

Due to the complex pathophysiological mechanism, spinal cord injury (SCI) has become one of the most intractable central nervous system (CNS) diseases to therapy. Stem cell transplantation, mesenchymal stem cells (MSCs) particularly, appeals to more and more attention along with the encouraging therapeutic results for the functional regeneration of SCI. However, traditional cell transplantation strategies have some limitations, including the unsatisfying survival rate of MSCs and their random diffusion from the injection site to ambient tissues. The application of biomaterials in tissue engineering provides a new horizon. Biomaterials can not only confine MSCs in the injured lesions with higher cell viability, but also promote their therapeutic efficacy. This review summarizes the strategies and advantages of biomaterials reinforced MSCs transplantation to treat SCI in recent years, which are clarified in the light of various therapeutic effects in pathophysiological aspects of SCI.

Dual-enzymatically cross-linked gelatin hydrogel enhances neural differentiation of human umbilical cord mesenchymal stem cells and functional recovery in experimental murine spinal cord injury

Recently, an advanced stem cell and tissue engineering approach has been recognized as an emerging and fascinating strategy to promote neural repair in spinal cord injury (SCI). Hydrogels can be properly engineered to encapsulate cells, enhance cell viability and neural differentiation, and provide the advantage of flexible adaptation to irregular defects. In this study, a dual-enzymatically cross-linked gelatin hydrogel with hydrogen horseradish peroxidase (HRP) and galactose oxidase (GalOx) was proposed to combine human umbilical cord mesenchymal stem cells (hUC-MSCs) for facilitating nerve regeneration post-SCI. In vitro, hUC-MSCs in this 3D gelatin hydrogel displayed good viability, proliferation, and neuronal differentiation. To further evaluate the neural regeneration effect of hUC-MSCs loaded into gelatin hydrogels in vivo, a clinically-relevant and force-controlled contusion model of mouse spinal cords was established. We found that implantation of a hydrogel loaded with hUC-MSCs significantly promoted the motor function recovery evaluated by Basso Mouse Scale (BMS) and footprint tests. Further histological analysis showed that the hydrogel and hUC-MSC combined transplantation dramatically decreased inflammation, inhibited apoptosis and promoted neurogenesis. Overall, implantation of this dual-enzymatically cross-linked and MSC-laden 3D gelatin hydrogel is a promising therapeutic strategy for SCI treatment.

miR-7b-3p Exerts a Dual Role After Spinal Cord Injury, by Supporting Plasticity and Neuroprotection at Cortical Level

Spinal cord injury (SCI) affects 6 million people worldwide with no available treatment. Despite research advances, the inherent poor regeneration potential of the central nervous system remains a major hurdle. Small RNAs (sRNAs) 19-33 nucleotides in length are a set of non-coding RNA molecules that regulate gene expression and have emerged as key players in regulating cellular events occurring after SCI. Here we profiled a class of sRNA known as microRNAs (miRNAs) following SCI in the cortex where the cell bodies of corticospinal motor neurons are located. We identified miR-7b-3p as a candidate target given its significant upregulation after SCI in vivo and we screened by miRWalk PTM the genes predicted to be targets of miR-7b-3p (among which we identified Wipf2, a gene regulating neurite extension). Moreover, 16 genes, involved in neural regeneration and potential miR-7b-3p targets, were found to be downregulated in the cortex following SCI. We also analysed miR-7b-3p function during cortical neuron development in vitro: we observed that the overexpression of miR-7b-3p was important (1) to maintain neurons in a more immature and, likely, plastic neuronal developmental phase and (2) to contrast the apoptotic pathway; however, in normal conditions it did not affect the Wipf2 expression. On the contrary, the overexpression of miR-7b-3p upon in vitro oxidative stress condition (mimicking the SCI environment) significantly reduced the expression level of Wipf2, as observed in vivo, confirming it as a direct miR-7b-3p target. Overall, these data suggest a dual role of miR-7b-3p: (i) the induction of a more plastic neuronal condition/phase, possibly at the expense of the axon growth, (ii) the neuroprotective role exerted through the inhibition of the apoptotic cascade. Increasing the miR-7b-3p levels in case of SCI could reactivate in adult neurons silenced developmental programmes, supporting at the same time the survival of the axotomised neurons.

Enzyme-Responsive Biopolymeric Nanogel Fibers by Extrusion: Engineering of High-Surface-Area Hydrogels and Application in Bacterial Enzyme Detection

The fabrication of covalently cross-linked high-surface-area biopolymeric nanogel fibers by nanopore extrusion is reported for the first time. The biopolymer pullulan was functionalized with tert-butyl acetoacetate via a transesterification reaction to synthesize the water-soluble ketone-rich precursor pullulan acetoacetate (PUAA). PUAA and carbonic dihydrazide (CDH) as cross-linker were extruded through anodic aluminum oxide (AAO) nanoporous membranes, which possessed an average pore diameter of 61 ± 2 nm. By changing the concentration of PUAA, the flow rate, and extrusion time, the step polymerization cross-linking reaction was controlled so that the polymer can be extruded gradually during cross-linking through the membrane, avoiding the formation of macroscopic bulk hydrogels and rupture of the AAO membrane. Fibers with diameters on the order of 250 nm were obtained. This approach was also expanded to functionalized PUAA derivatives together with the fluorogenic substrate 4-methylumbelliferyl-β-d-glucuronide MUGlcU in (PUAA-MUGlcU), which exhibited a mean equilibrium swelling ratio of 5.7 and 9.0 in Milli-Q water and in phosphate-buffered saline, respectively. β-Glucuronidase was sensitively detected via fluorescence of 4-methylumbelliferone, which was liberated in the enzymatic hydrolysis reaction of PUAA-MUGlcU. Compared to hydrogel slabs, the rate of the hydrolysis was >20% higher in the nanogel fibers, facilitating the rapid detection of β-glucuronidase-producing Escherichia coli (E. coli Mach1-T1). Nanopore extruded nanogel fibers are therefore considered a viable approach to enhance the functionality of hydrogels in surface-dominated processes.

Injectable Scaffold-Systems for the Regeneration of Spinal Cord: Advances of the Past Decade

Nowadays, whenever is possible and as an alternative to open spine surgery, minimally invasive procedures are preferred to treat spinal cord injuries (SCI), with percutaneous injections or small incisions, that are faster, less traumatic, and require less recovery time. Injectable repair systems are based on materials that can be injected in the lesion site, can eventually be loaded with drugs or even cells, and act as scaffolds for the lesion repair. The review analyzes papers written from 2010 onward on injectable materials/systems used/proposed for the regenerative and combinatorial therapies of SCI and discusses the in vivo models that have been used to validate them.

Antibiofilm activity of chitosan/epsilon-poly-L-lysine hydrogels in a porcine ex vivo skin wound polymicrobial biofilm model

As antibiotic resistance continues to increase globally, there is an urgency for novel, non-antibiotic approaches to control chronic drug-resistant infections, particularly those associated with polymicrobial biofilm formation in chronic wounds. Also needed are clinically relevant polymicrobial biofilm models that can be utilized to assess the efficacy of innovative therapeutics against mature biofilms. We successfully developed a highly reproducible porcine ex vivo skin wound polymicrobial biofilm model using clinical isolates of multidrug-resistant Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and Candida albicans. This ex vivo biofilm model was then used to assess the antimicrobial and antibiofilm properties of an easily fabricated chitosan hydrogel incorporating the natural antimicrobial peptide epsilon-poly-L-lysine. Antimicrobial activity was evaluated against planktonic cultures in vitro and against mature biofilms ex vivo. The antibiofilm efficiency of the hydrogels was especially pronounced against Pseudomonas aeruginosa, whose counts were reduced by 99.98% after 2 hours in vitro and by 99.94% after treatment for 24 hours when applied to 24 hour ex vivo polymicrobial wound biofilms. The activity of the hydrogels was lower against Staphylococcus aureus and ineffective against Candida albicans. Gram, Hucker-Twort staining of paraffin sections revealed balanced polymicrobial communities in mature 48 hour untreated biofilms. Treatment of 48 or 72 hour biofilms for 2 or 3 days with hydrogels that were applied within 5 hours after inoculation resulted in an impressive 96% and 97% reduction in biofilm thickness compared to untreated biofilms, respectively (P < .001). Likewise, topical gel treatment for 24 hours reduced biofilm thickness by 84% and 70%, respectively, when applied to mature biofilms at 24 and 48 hours after inoculation (P < .001). Thus, this ex vivo wound biofilm model provides a useful means to assess the efficacy of novel treatments to prevent and eradicate polymicrobial biofilms consisting of multidrug-resistant Pseudomonas aeruginosa, methicillin-resistant Staphylococcus aureus, and Candida albicans.

Injectable thermoresponsive hydrogels as drug delivery system for the treatment of central nervous system disorders: A review

The central nervous system (CNS), consisting of the brain, spinal cord, and retina, superintends to the acquisition, integration and processing of peripheral information to properly coordinate the activities of the whole body. Neurodegenerative and neurodevelopmental disorders, trauma, stroke, and brain tumors can dramatically affect CNS functions resulting in serious and life-long disabilities. Globally, the societal and economic burden associated with CNS disorders continues to grow with the ageing of the population thus demanding for more effective and definitive treatments. Despite the variety of clinically available therapeutic molecules, medical interventions on CNS disorders are mostly limited to treat symptoms rather than halting or reversing disease progression. This is attributed to the complexity of the underlying disease mechanisms as well as to the unique biological microenvironment. Given its central importance, multiple barriers, including the blood brain barrier and the blood cerebrospinal fluid barrier, protect the CNS from external agents. This limits the access of drug molecules to the CNS thus contributing to the modest therapeutic successes. Loco-regional therapies based on the deposition of thermoresponsive hydrogels loaded with therapeutic agents and cells are receiving much attention as an alternative and potentially more effective approach to manage CNS disorders. In this work, the current understanding and challenges in the design of thermoresponsive hydrogels for CNS therapy are reviewed. First, the biological barriers that hinder mass and drug transport to the CNS are described, highlighting the distinct features of each barrier. Then, the realization, characterization and biomedical application of natural and synthetic thermoresponsive hydrogels are critically presented. Advantages and limitations of each design and application are discussed with the objective of identifying general rules that could enhance the effective translation of thermoresponsive hydrogel-based therapies for the treatment of CNS disorders.

Design of graphenic nanocomposites containing chitosan and polyethylene glycol for spinal cord injury improvement

Advanced therapeutic strategies include the incorporation of biomaterials, which has been identified as an effective method in treating unsolved diseases, such as spinal cord injury. During the acute phase, cascade responses involving cystic cavitation, fibrous glial scar formation, and myelin-associated dissuasive accumulation occur in the microenvironment of the spinal cord lesion. Graphene oxide (GO)-based materials, due to their extraordinary chemical, electrical and mechanical properties and easy to modify structure, are considered as rising stars in biomaterial and tissue engineering. In order to enhance the biodegradability and biocompatibility of GO, cell proliferation may be appropriately designed and situated at the lesion site. In this study, chitosan (CS) and polyethylene glycol (PEG) were grafted onto GO sheets. CS is a natural non-toxic polymer with good solubility and high biocompatible potential that has been used as an anti-inflammatory and anti-oxidant agent. Furthermore, PEG, a synthetic neuroprotective polymer, was used to develop the pharmacokinetic activity and reduce the toxicity of GO. Herein we report a novel nanocomposite consisting of PEG and CS with a potential advantage in spinal tissue regeneration. The preliminary in vitro study on mesenchymal stem cells (MSCs) has demonstrated that the prepared nanocomposites are not only non-toxic but also increase (by nearly 10%) cell growth. Finally, the use of mixed nanocomposites in the spinal cord injury (SCI) model resulted in good repair and inflammation decline after two weeks, such that walking and functional recovery scores of the hind limbs of mice were improved by an average of 6 points in the treatment group.

Herein we report a novel nanocomposite consisting of PEG and CS with a potential advantage in spinal tissue regeneration.

Hydrogels as delivery systems for spinal cord injury regeneration

Spinal cord injury is extremely debilitating, both at physiological and psychological levels, changing completely the patient's lifestyle. The introduction of biomaterials has opened a new window to develop a therapeutic approach to induce regeneration after injury due to similarities with extracellular matrix. Particularly, hydrogels have the ability to support axonal growth and endogenous regeneration. Moreover, they can also act as potential matrixes in which to load and deliver therapeutic agents at injury site. In this review, we highlight some important characteristics to be considered when designing hydrogels as delivery systems (DS), such as rheology, mesh size, swelling, degradation, gelation temperature and surface charge. Additionally, affinity-based release systems, incorporation of nanoparticles, or ion-mediated interactions are also pondered. Overall, hydrogel DS aim to promote a sustained, controlled and prolonged release at injury site, allowing a targeted oriented action of the therapeutic agent that will be used.

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.

Natural-Based Biomaterials for Peripheral Nerve Injury Repair

Peripheral nerve injury treatment is a relevant problem because of nerve lesion high incidence and because of unsatisfactory regeneration after severe injuries, thus resulting in a reduced patient's life quality. To repair severe nerve injuries characterized by substance loss and to improve the regeneration outcome at both motor and sensory level, different strategies have been investigated. Although autograft remains the gold standard technique, a growing number of research articles concerning nerve conduit use has been reported in the last years. Nerve conduits aim to overcome autograft disadvantages, but they must satisfy some requirements to be suitable for nerve repair. A universal ideal conduit does not exist, since conduit properties have to be evaluated case by case; nevertheless, because of their high biocompatibility and biodegradability, natural-based biomaterials have great potentiality to be used to produce nerve guides. Although they share many characteristics with synthetic biomaterials, natural-based biomaterials should also be preferable because of their extraction sources; indeed, these biomaterials are obtained from different renewable sources or food waste, thus reducing environmental impact and enhancing sustainability in comparison to synthetic ones. This review reports the strengths and weaknesses of natural-based biomaterials used for manufacturing peripheral nerve conduits, analyzing the interactions between natural-based biomaterials and biological environment. Particular attention was paid to the description of the preclinical outcome of nerve regeneration in injury repaired with the different natural-based conduits.

Polymer-Based Scaffold Strategies for Spinal Cord Repair and Regeneration

The injury to the spinal cord is among the most complex fields of medical development. Spinal cord injury (SCI) leads to acute loss of motor and sensory function beneath the injury level and is linked to a dismal prognosis. Currently, while a strategy that could heal the injured spinal cord remains unforeseen, the latest advancements in polymer-mediated approaches demonstrate promising treatment forms to remyelinate or regenerate the axons and to integrate new neural cells in the SCI. Moreover, they possess the capacity to locally deliver synergistic cells, growth factors (GFs) therapies and bioactive substances, which play a critical role in neuroprotection and neuroregeneration. Here, we provide an extensive overview of the SCI characteristics, the pathophysiology of SCI, and strategies and challenges for the treatment of SCI in a review. This review highlights the recent encouraging applications of polymer-based scaffolds in developing the novel SCI therapy.

Role of the CXCR4-SDF1-HMGB1 pathway in the directional migration of cells and regeneration of affected organs

In recent years, several studies have reported positive outcomes of cell-based therapies despite insufficient engraftment of transplanted cells. These findings have created a huge interest in the regenerative potential of paracrine factors released from transplanted stem or progenitor cells. Interestingly, this notion has also led scientists to question the role of proteins in the secretome produced by cells, tissues or organisms under certain conditions or at a particular time of regenerative therapy. Further studies have revealed that the secretomes derived from different cell types contain paracrine factors that could help to prevent apoptosis and induce proliferation of cells residing within the tissues of affected organs. This could also facilitate the migration of immune, progenitor and stem cells within the body to the site of inflammation. Of these different paracrine factors present within the secretome, researchers have given proper consideration to stromal cell-derived factor-1 (SDF1) that plays a vital role in tissue-specific migration of the cells needed for regeneration. Recently researchers recognized that SDF1 could facilitate site-specific migration of cells by regulating SDF1-CXCR4 and/or HMGB1-SDF1-CXCR4 pathways which is vital for tissue regeneration. Hence in this study, we have attempted to describe the role of different types of cells within the body in facilitating regeneration while emphasizing the HMGB1-SDF1-CXCR4 pathway that orchestrates the migration of cells to the site where regeneration is needed.

Delivery of injectable thermo-sensitive hydrogel releasing nerve growth factor for spinal cord regeneration in rat animal model

The main goal of this study was to explore the beneficial effect of nerve growth factor (NGF)-overexpressing of human adipose-derived mesenchymal stem cells (hADSCs) encapsulated in injectable chitosan/β-glycerophosphate/hydroxyethylcellulose (CS/β-GP/HEC) hydrogel for spinal cord regeneration. The CS/β-GP/HEC hydrogel and genetically transduced hADSCs using pseudo-lentiviruses-NGF were prepared. The mechanical properties, morphology and cytotoxicity of the hydrogel were investigated by rheometry, scanning electron microscope (SEM), and MTT assay, respectively. Rats animals were undergone spinal cord injury (SCI), then one-week post-injury, CS/β-GP/HEC hydrogel, transduced hADSCs and transduced hADSCs/CS/β-GP/HEC hydrogel injected into the site of the lesion. Animals with SCI and animals with laminectomy without SCI were considered as negative control and sham groups, respectively. Positive control group received no surgical intervention. At eight weeks post-injection, histological studies indicated a significant increase in cell proliferation, a smaller cavity in size at the SCI site as well as better locomotor functions for transduced hADSCs/CS/β-GP/HEC hydrogel group (P ≤ 0.05) compared to other experimental groups. Our results showed that CS/β-GP/HEC hydrogel in combination with transduced-hADSCs is able to successfully regenerate SCI. These results may be applicable in the selection of the best therapeutic strategy based on gene therapy and tissue engineering for SCI treatment.

Control the fate of human umbilical cord mesenchymal stem cells with dual-enzymatically cross-linked gelatin hydrogels for potential applications in nerve regeneration

Stem-cell-based therapy is a promising strategy to treat challenging neurological diseases, while its application is hindered primarily by the low viability and uncontrolled differentiation of stem cell. Hydrogel can be properly engineered to share similar characteristics with the target tissue, thus promoting cell viability and directing cell differentiation. In this study, we proposed a new dual-enzymatically cross-linked and injectable gelatin hydrogel for regulating survival, proliferation, and differentiation of human umbilical cord mesenchymal stem cells (hUC-MSCs) in a three-dimensional matrix. This injectable gelatin hydrogel was formed by oxidative coupling of gelatin-hydroxyphenyl acid conjugates catalyzed by hydrogen horseradish peroxidase (HRP) and choline oxidase (ChOx). Modulus and H₂ O₂ release can be well controlled by ChOx activity. Results from calcein-AM/PI staining and Ki67 immunofluorescence tests demonstrated that the survival and proliferation behavior of hUC-MSCs were highly enhanced in HRP_1U ChOx_0.25U hydrogel with lower modulus and less H₂ O₂ release compared with other groups. Attractively, the expression of neuron-specific markers β-III tubulin, neurofilament light chain (NFL), and synapsin-1 was significantly increased in HRP_1U ChOx_0.25U hydrogel as well. Additionally, in vitro hemolysis test and in vivo HE staining data highlighted the good biocompatibility. Undoubtedly, this injectable gelatin hydrogel's ability to control hUC-MSCs' fate holds enormous potentials in nervous disorders' therapy and nerve regeneration.

In situ injectable hydrogels for spinal cord regeneration: advances from the last 10 years

Spinal cord injury (SCI) is a tremendously devastating disorder with no effective therapy. Neuroprotective strategies have been applied aiming to prevent secondary cell death but no successful and robust effects have been observed. Recently, combinatorial approaches using biomaterials with cells and/or growth factors have demonstrated promising therapeutic effects because of the improvement of axonal growth and in vivo functional recovery in model organisms. In situ injectable hydrogels are a particularly attractive neuroregenerative approach to improve spinal cord repair and regeneration since they can be precisely injected into the lesion site filling the space prior to gelification, decrease scarring and promote axon growth due to the hydrogel's soft structure. Important advances regarding the use of hydrogels as potential therapeutic approaches has been reported during the last 10 years. Injectable alginate hydrogel loaded with GDNF, thermoresponsives heparin-poloxamer loaded with NGF and imidazole-poly(organophosphazenes) hydrogels are just three examples of biomaterials that can promote neurite, axon growth and improve functional recovery in hemisected and resected rats. Here we will review the status of in situ injectable hydrogels for spinal cord regeneration with special focus in the advantages of using hydrogel scaffolds, the ideal polymers to be used, the gelification process and the cells or growth factors combined. The in vitro and in vivo results reported for those biomaterials will be presented, compared and discussed.

Nanohydroxyapatite Reinforced Chitosan Composite Hydrogel with Tunable Mechanical and Biological Properties for Cartilage Regeneration

With the continuous quest of developing hydrogel for cartilage regeneration with superior mechanobiological properties are still becoming a challenge. Chitosan (CS) hydrogels are the promising implant materials due to an analogous character of the soft tissue; however, their low mechanical strength and durability together with its lack of integrity with surrounding tissues hinder the load-bearing application. This can be solved by developing a composite chitosan hydrogel reinforced with Hydroxyapatite Nanorods (HANr). The objective of this work is to develop and characterize (physically, chemically, mechanically and biologically) the composite hydrogels loaded with different concentration of hydroxyapatite nanorod. The concentration of hydroxyapatite in the composite hydrogel was optimized and it was found that, reinforcement modifies the hydrogel network by promoting the secondary crosslinking. The compression strength could reach 1.62 ± 0.02 MPa with a significant deformation of 32% and exhibits time-dependent, rapid self-recoverable and fatigue resistant behavior based on the cyclic loading-unloading compression test. The storage modulus value can reach nearly 10 kPa which is needed for the proposed application. Besides, composite hydrogels show an excellent antimicrobial activity against Escherichia coli, Staphylococcus aureus bacteria's and Candida albicans fungi and their cytocompatibility towards L929 mouse fibroblasts provide a potential pathway to developing a composite hydrogel for cartilage regeneration.

Progress in research into spinal cord injury repair: Tissue engineering scaffolds and cell transdifferentiation

As with all tissues of the central nervous system, the low regeneration ability of spinal cord tissue after injury decreases the potential for repair and recovery. Initially, in spinal cord injuries (SCI), often the surgeon can only limit further damage by early surgical decompression. However, with the development of basic science, especially the development of genetic engineering, molecular biology, tissue engineering, and materials science, some promising progress has been made in promoting the repair of central nervous system injuries. For example, transplantation of neural stem cells (NSCs), olfactory ensheathing cells (OECs), and gene- mediated transdifferentiation to repair central nervous system injury. This paper summarizes the progress and prospects of SCI repair with tissue engineering scaffold and cell transdifferentiation from an extensive literatures.