A MnO2 Nanoparticle-Dotted Hydrogel Promotes Spinal Cord Repair via Regulating Reactive Oxygen Species Microenvironment and Synergizing with Mesenchymal Stem Cells

Functional biomaterials for modulating the dysfunctional pathological microenvironment of spinal cord injury

Spinal cord injury (SCI) often results in irreversible loss of sensory and motor functions, and most SCIs are incurable with current medical practice. One of the hardest challenges in treating SCI is the development of a dysfunctional pathological microenvironment, which mainly comprises excessive inflammation, deposition of inhibitory molecules, neurotrophic factor deprivation, glial scar formation, and imbalance of vascular function. To overcome this challenge, implantation of functional biomaterials at the injury site has been regarded as a potential treatment for modulating the dysfunctional microenvironment to support axon regeneration, remyelination at injury site, and functional recovery after SCI. This review summarizes characteristics of dysfunctional pathological microenvironment and recent advances in biomaterials as well as the technologies used to modulate inflammatory microenvironment, regulate inhibitory microenvironment, and reshape revascularization microenvironment. Moreover, technological limitations, challenges, and future prospects of functional biomaterials to promote efficient repair of SCI are also discussed. This review will aid further understanding and development of functional biomaterials to regulate pathological SCI microenvironment.

Exploring the Landscape of Hydrogel Therapy for Spinal Cord Injury: A Bibliometric and Visual Analysis (1991-2023)

BACKGROUND

This study aimed to conduct a bibliometric analysis of the literature on hydrogel therapy for spinal cord injury to visualize the research status, identify hotspots, and explore the development trends in this field.

METHODS

Web of science Core Collection database was searched for relevant studies published between January 1991 and December 2023. Data such as journal title, author information, institutional affiliation, country, citation, and keywords were extracted. Bibliometrix, CiteSpace, and VOSviewer were used to perform bibliometric analysis of the retrieved data.

RESULTS

A total of 1099 articles pertaining to hydrogel therapy for spinal cord injury were retrieved, revealing an upward trajectory in both annual publication volume and cumulative publication volume. Biomaterials emerged as the journal with the highest number of publications and the most rapid cumulative publication growth, contributing 84 articles. Among authors, Shoichet MS stood out with the highest number of publications and citations, totaling 66 articles. The University of Toronto led in institutional contributions with 65 publications, while China dominated in country-specific publications, accounting for 374 articles. However, to foster significant academic achievements, it is imperative for diverse authors, institutions, and countries to enhance collaboration. Current research in this field concentrates on scaffold architecture, nerve growth factor, the fibrotic microenvironment, and guidance channels. Simultaneously, upcoming research directions prioritize 3D bioprinting, injectable hydrogel, inflammation, and nanoparticles within the realm of hydrogel therapy for spinal cord injuries.

CONCLUSIONS

In summary, this study provided a comprehensive analysis of the current research status and frontiers of hydrogel therapy for spinal cord injury. The findings provide a foundation for future research and clinical translation efforts of hydrogel therapy in this field.

Manganese Dioxide-Based Nanomaterials for Medical Applications

Manganese dioxide (MnO2) nanomaterials can react with trace hydrogen peroxide (H2O2) to produce paramagnetic manganese (Mn2+) and oxygen (O2), which can be used for magnetic resonance imaging and alleviate the hypoxic environment of tumors, respectively. MnO2 nanomaterials also can oxidize glutathione (GSH) to produce oxidized glutathione (GSSG) to break the balance of intracellular redox reactions. As a consequence of the sensitivity of the tumor microenvironment to MnO2-based nanomaterials, these materials can be used as multifunctional diagnostic and therapeutic platforms for tumor imaging and treatment. Importantly, when MnO2 nanomaterials are implanted along with other therapeutics, synergetic tumor therapy can be achieved. In addition to tumor treatment, MnO2-based nanomaterials display promising prospects for tissue repair, organ protection, and the treatment of other diseases. Herein, we provide a thorough review of recent progress in the use of MnO2-based nanomaterials for biomedical applications, which may be helpful for the design and clinical translation of next-generation MnO2 nanomaterials.

Biomaterials targeting the microenvironment for spinal cord injury repair: progression and perspectives

Spinal cord injury (SCI) disrupts nerve pathways and affects sensory, motor, and autonomic function. There is currently no effective treatment for SCI. SCI occurs within three temporal periods: acute, subacute, and chronic. In each period there are different alterations in the cells, inflammatory factors, and signaling pathways within the spinal cord. Many biomaterials have been investigated in the treatment of SCI, including hydrogels and fiber scaffolds, and some progress has been made in the treatment of SCI using multiple materials. However, there are limitations when using individual biomaterials in SCI treatment, and these limitations can be significantly improved by combining treatments with stem cells. In order to better understand SCI and to investigate new strategies for its treatment, several combination therapies that include materials combined with cells, drugs, cytokines, etc. are summarized in the current review.

Effect of polydimethylsiloxane surface morphology on osteogenic differentiation of mesenchymal stem cells through SIRT1 signalling pathway

Constructing surface topography with a certain roughness is a widely used, non-toxic, cost-effective and effective method for improving the microenvironment of cells, promoting the proliferation and osteogenic differentiation of mesenchymal stem cells (MSCs), and promoting the osseointegration of grafts and further improving their biocompatibility under clinical environmental conditions. SIRT1 plays an important regulatory role in the osteogenic differentiation of bone marrow-derived MSCs (BM-MSCs). However, it remains unknown whether SIRT1 plays an important regulatory role in the osteogenic differentiation of BM-MSCs with regard to surface morphology. Polydimethylsiloxane (PDMS) with different surface morphologies were prepared using different grits of sandpaper. The value for BMSCs added on different surfaces was detected by cell proliferation assays. RT-qPCR and Western blotting were performed to detect SIRT1 activation and osteogenic differentiation of MSCs. Osteogenesis of MSCs was detected by alkaline phosphatase (ALP) and alizarin red S staining. SIRT1 inhibition experiments were performed to investigate the role of SIRT1 in the osteogenic differentiation of MSCs induced by surface morphology. We found that BM-MSCs have better value and osteogenic differentiation ability on a surface with roughness of PDMS-1000M. SIRT1 showed higher gene and protein expression on a PDMS-1000M surface with a roughness of 13.741 ± 1.388 µm. The promotion of the osteogenic differentiation of MSCs on the PDMS-1000M surface was significantly decreased after inhibiting SIRT1 expression. Our study demonstrated that a surface morphology with certain roughness can activate the SIRT1 pathway of MSCs and promote the osteogenic differentiation of BMSCs via the SIRT1 pathway.

Development of BDNF/NGF/IKVAV Peptide Modified and Gold Nanoparticle Conductive PCL/PLGA Nerve Guidance Conduit for Regeneration of the Rat Spinal Cord Injury

Spinal cord injuries are very common worldwide, leading to permanent nerve function loss with devastating effects in the affected patients. The challenges and inadequate results in the current clinical treatments are leading scientists to innovative neural regenerative research. Advances in nanoscience and neural tissue engineering have opened new avenues for spinal cord injury (SCI) treatment. In order for designed nerve guidance conduit (NGC) to be functionally useful, it must have ideal scaffold properties and topographic features that promote the linear orientation of damaged axons. In this study, it is aimed to develop channeled polycaprolactone (PCL)/Poly-D,L-lactic-co-glycolic acid (PLGA) hybrid film scaffolds, modify their surfaces by IKVAV pentapeptide/gold nanoparticles (AuNPs) or polypyrrole (PPy) and investigate the behavior of motor neurons on the designed scaffold surfaces in vitro under static/bioreactor conditions. Their potential to promote neural regeneration after implantation into the rat SCI by shaping the film scaffolds modified with neural factors into a tubular form is also examined. It is shown that channeled groups decorated with AuNPs highly promote neurite orientation under bioreactor conditions and also the developed optimal NGC (PCL/PLGA G1-IKVAV/BDNF/NGF-AuNP50) highly regenerates SCI. The results indicate that the designed scaffold can be an ideal candidate for spinal cord regeneration.

Quaternary ammonium carboxymethyl chitosan composite hydrogel with efficient antibacterial and antioxidant properties for promoting wound healing

Multifunctional hydrogels have been developed to meet the various requirements of wound healing. Herein, an innovative hydrogel (QCMC-HA-PEG) was formed through the Schiff base reaction, composed of quaternary ammonium-modified carboxymethyl chitosan (QCMC), hyaluronic acid (HA), and 8-arms Polyethylene Glycol aldehyde (8-ARM-PEG-CHO). The resulting hydrogels exhibited good mechanical and adhesive properties with improved antibacterial efficacy against both Gram-positive and Gram-negative bacteria compared to CMC hydrogels. QCMC-HA-PEG hydrogels demonstrated remarkable adhesive ability in lap-shear test. Furthermore, the incorporation of MnO2 nanosheets into the hydrogel significantly enhanced its reactive oxygen species (ROS) scavenging and oxygen generation capabilities. Finally, experimental results from a full-thickness skin wound model revealed that the QCMC-HA-PEG@MnO2 hydrogel promoted skin epithelization, collagen deposition, and inflammatory regulation significantly accelerated the wound healing process. Therefore, QCMC-HA-PEG@MnO2 hydrogel could be a promising wound dressing to promote wound healing.

Advancing Spinal Cord Injury Bioimaging and Repair with Multifunctional Gold Nanodots Tracking

High levels of reactive oxygen species (ROS) are known to play a critical role in the secondary cascade of spinal cord injury (SCI). The scavenging of ROS has emerged as a promising approach for alleviating acute SCI. Moreover, identifying the precise location of the SCI site remains challenging. Enhancing the visualization of the spinal cord and improving the ability to distinguish the lesion site are crucial for accurate and safe treatment. Therefore, there is an urgent clinical need to develop a biomaterial that integrates diagnosis and treatment for SCI. Herein, ultra-small-sized gold nanodots (AuNDs) were designed for dual-mode imaging-guided precision treatment of SCI. The designed AuNDs demonstrate two important functions. First, they effectively scavenge ROS, inhibit oxidative stress, reduce the infiltration of inflammatory cells, and prevent apoptosis. This leads to a significant improvement in SCI repair and promotes a functional recovery after injury. Second, leveraging their excellent dual-mode imaging capabilities, the AuNDs enable rapid and accurate identification of SCI sites. The high contrast observed between the injured and adjacent uninjured areas highlights the tremendous potential of AuNDs for SCI detection. Overall, by integrating ROS scavenging and dual-mode imaging in a single biomaterial, our work on functionalized AuNDs provides a promising strategy for the clinical diagnosis and treatment of SCI.

Nanotechnological Research for Regenerative Medicine: The Role of Hyaluronic Acid

Hyaluronic acid (HA) is a linear, anionic, non-sulfated glycosaminoglycan occurring in almost all body tissues and fluids of vertebrates including humans. It is a main component of the extracellular matrix and, thanks to its high water-holding capacity, plays a major role in tissue hydration and osmotic pressure maintenance, but it is also involved in cell proliferation, differentiation and migration, inflammation, immunomodulation, and angiogenesis. Based on multiple physiological effects on tissue repair and reconstruction processes, HA has found extensive application in regenerative medicine. In recent years, nanotechnological research has been applied to HA in order to improve its regenerative potential, developing nanomedical formulations containing HA as the main component of multifunctional hydrogels systems, or as core component or coating/functionalizing element of nanoconstructs. This review offers an overview of the various uses of HA in regenerative medicine aimed at designing innovative nanostructured devices to be applied in various fields such as orthopedics, dermatology, and neurology.

Perspective insights into versatile hydrogels for stroke: From molecular mechanisms to functional applications

As the leading killer of life and health, stroke leads to limb paralysis, speech disorder, dysphagia, cognitive impairment, mental depression and other symptoms, which entail a significant financial burden to society and families. At present, physiology, clinical medicine, engineering, and materials science, advanced biomaterials standing on the foothold of these interdisciplinary disciplines provide new opportunities and possibilities for the cure of stroke. Among them, hydrogels have been endowed with more possibilities. It is well-known that hydrogels can be employed as potential biosensors, medication delivery vectors, and cell transporters or matrices in tissue engineering in tissue engineering, and outperform many traditional therapeutic drugs, surgery, and materials. Therefore, hydrogels become a popular scaffolding treatment option for stroke. Diverse synthetic hydrogels were designed according to different pathophysiological mechanisms from the recently reported literature will be thoroughly explored. The biological uses of several types of hydrogels will be highlighted, including pro-angiogenesis, pro-neurogenesis, anti-oxidation, anti-inflammation and anti-apoptosis. Finally, considerations and challenges of using hydrogels in the treatment of stroke are summarized.

Bioprinting of inorganic-biomaterial/neural-stem-cell constructs for multiple tissue regeneration and functional recovery

Tissue regeneration is a complicated process that relies on the coordinated effort of the nervous, vascular and immune systems. While the nervous system plays a crucial role in tissue regeneration, current tissue engineering approaches mainly focus on restoring the function of injury-related cells, neglecting the guidance provided by nerves. This has led to unsatisfactory therapeutic outcomes. Herein, we propose a new generation of engineered neural constructs from the perspective of neural induction, which offers a versatile platform for promoting multiple tissue regeneration. Specifically, neural constructs consist of inorganic biomaterials and neural stem cells (NSCs), where the inorganic biomaterials endows NSCs with enhanced biological activities including proliferation and neural differentiation. Through animal experiments, we show the effectiveness of neural constructs in repairing central nervous system injuries with function recovery. More importantly, neural constructs also stimulate osteogenesis, angiogenesis and neuromuscular junction formation, thus promoting the regeneration of bone and skeletal muscle, exhibiting its versatile therapeutic performance. These findings suggest that the inorganic-biomaterial/NSC-based neural platform represents a promising avenue for inducing the regeneration and function recovery of varying tissues and organs.

The Translation of Nanomedicines in the Contexts of Spinal Cord Injury and Repair

PURPOSE OF THIS REVIEW

Manipulating or re-engineering the damaged human spinal cord to achieve neuro-recovery is one of the foremost challenges of modern science. Addressing the restricted permission of neural cells and topographically organised neural tissue for self-renewal and spontaneous regeneration, respectively, is not straightforward, as exemplified by rare instances of translational success. This review assembles an understanding of advances in nanomedicine for spinal cord injury (SCI) and related clinical indications of relevance to attempts to design, engineer, and target nanotechnologies to multiple molecular networks.

RECENT FINDINGS

Recent research provides a new understanding of the health benefits and regulatory landscape of nanomedicines based on a background of advances in mRNA-based nanocarrier vaccines and quantum dot-based optical imaging. In relation to spinal cord pathology, the extant literature details promising advances in nanoneuropharmacology and regenerative medicine that inform the present understanding of the nanoparticle (NP) biocompatibility-neurotoxicity relationship. In this review, the conceptual bases of nanotechnology and nanomaterial chemistry covering organic and inorganic particles of sizes generally less than 100 nm in diameter will be addressed. Regarding the centrally active nanotechnologies selected for this review, attention is paid to NP physico-chemistry, functionalisation, delivery, biocompatibility, biodistribution, toxicology, and key molecular targets and biological effects intrinsic to and beyond the spinal cord parenchyma.

SUMMARY

The advance of nanotechnologies for the treatment of refractory spinal cord pathologies requires an in-depth understanding of neurobiological and topographical principles and a consideration of additional complexities involving the research's translational and regulatory landscapes.

Precise Engineering of Growth Factor Presentation Using Extracellular Microenvironment-Mimicking Microfluidic Microparticles

One of the main challenges in tissue engineering is finding a way to deliver specific growth factors (GFs) with precise spatiotemporal control over their presentation. Here, we report a novel strategy for generating microscale carriers with enhanced affinity for high content loading suitable for the sustained and localized delivery of GFs. Our developed microparticles can be injected locally and sustainably release encapsulated growth factors for up to 28 days. Fine-tuning of particles' size, affinity, microstructures, and release kinetics is achieved using a microfluidic system along with bioconjugation techniques. We also describe an innovative 3D micromixer platform to control the formation of core-shell particles based on superaffinity using a polymer-peptide conjugate for further tuning of release kinetics and delayed degradation. Chitosan shells block the burst release of encapsulated GFs and enable their sustained delivery for up to 10 days. The matched release profiles and degradation provide the local tissues with biomimetic, developmental-biologic-compatible signals to maximize regenerative effects. The versatility of this approach is verified using three different therapeutic proteins, including human bone morphogenetic protein-2 (rhBMP-2), vascular endothelial growth factor (VEGF), and stromal cell-derived factor 1 (SDF-1α). As in vivo morphogenesis is typically driven by the combined action of several growth factors, the proposed technique can be developed to generate a library of GF-loaded particles with designated release profiles.

Injectable hydrogels as promising in situ therapeutic platform for cartilage tissue engineering

Injectable hydrogels are gaining prominence as a biocompatible, minimally invasive, and adaptable platform for cartilage tissue engineering. Commencing with their synthesis, this review accentuates the tailored matrix formulations and cross-linking techniques essential for fostering three-dimensional cell culture and melding with complex tissue structures. Subsequently, it spotlights the hydrogels' enhanced properties, highlighting their augmented functionalities and broadened scope in cartilage tissue repair applications. Furthermore, future perspectives are advocated, urging continuous innovation and exploration to surmount existing challenges and harness the full clinical potential of hydrogels in regenerative medicine. Such advancements are crucial for validating the long-term efficacy and safety of hydrogels, positioning them as a promising direction in regenerative medicine to address cartilage-related ailments.

Recent advances in peptide-based bioactive hydrogels for nerve repair and regeneration: from material design to fabrication, functional tailoring and applications

The injury of both central and peripheral nervous systems can result in neurological disorders and severe nervous diseases, which has been one of the challenges in the medical field. The use of peptide-based hydrogels for nerve repair and regeneration (NRR) provides a promising way for treating these problems, but the effects of the functions of peptide hydrogels on the NRR efficiency have been not understood clearly. In this review, we present recent advances in the material design, matrix fabrication, functional tailoring, and NRR applications of three types of peptide-based hydrogels, including pure peptide hydrogels, other component-functionalized peptide hydrogels, and peptide-modified polymer hydrogels. The case studies on the utilization of various peptide-based hydrogels for NRR are introduced and analyzed, in which the effects and mechanisms of the functions of hydrogels on NRR are illustrated specifically. In addition, the fabrication of medical NRR scaffolds and devices for pre-clinical application is demonstrated. Finally, we provide potential directions on the development of this promising topic. This comprehensive review could be valuable for readers to know the design and synthesis strategies of bioactive peptide hydrogels, as well as their functional tailoring, in order to promote their practical applications in tissue engineering, biomedical engineering, and materials science.

Biosafe Polydopamine-Decorated MnO2 Nanoparticles with Hemostasis and Antioxidative Properties for Postoperative Adhesion Prevention

Surgical bleeding and cumulative oxidative stress are significant factors in the development of postoperative adhesions, which are always associated with adverse patient outcomes. However, effective strategies for adhesion prevention are currently lacking in clinical practice. In this study, we propose a solution using polydopamine-decorated manganese dioxide nanoparticles (MnO2@PDA) with rapid hemostasis and remarkable antioxidant properties to prevent postsurgical adhesion. The PDA modification provides MnO2@PDA with enhanced tissue adhesiveness and hemocompatibility with negligible hemolysis. Furthermore, MnO2@PDA exhibits impressive antioxidant and free radical scavenging properties, protecting cells from the negative effects of oxidative stress. The hemostatic activity of MnO2@PDA is evaluated in a mouse truncated tail model and a liver injury model, with results demonstrating reduced bleeding time and volume. The in vivo test on a mouse cecal abrasion model shows that MnO2@PDA exhibits excellent antiadhesion properties coupled with alleviated inflammation around the damaged tissue. Therefore, MnO2@PDA, which exhibits high biosafety, rapid hemostasis, and beneficial antioxidant capacity, displays exceptional antiadhesion performance, holding great potential for clinical applications to prevent postoperative adhesion.

Sensitive and Selective Dual-Mode Responses to Reactive Oxygen Species by Chiral Manganese Dioxide Nanoparticles for Antiaging Skin

Excessive accumulation of reactive oxygen species (ROS) can lead to oxidative stress and oxidative damage, which is one of the important factors for aging and age-related diseases. Therefore, real-time monitoring and the moderate elimination of ROS is extremely important. In this study, a ROS-responsive circular dichroic (CD) at 553 nm and magnetic resonance imaging (MRI) dual-signals chiral manganese oxide (MnO2 ) nanoparticles (NPs) are designed and synthesized. Both the CD and MRI signals show excellent linear ranges for intracellular hydrogen peroxide (H2 O2 ) concentrations, with limits of detection (LOD) of 0.0027 nmol/106 cells and 0.016 nmol/106 cells, respectively. The lower LOD achieved with CD detection may be attributable to its higher anti-interference capability from the intracellular matrix. Importantly, ROS-induced cell aging is intervened by chiral MnO2 NPs via redox reactions with excessive intracellular ROS. In vivo experiments confirm that chiral MnO2 NPs effectively eliminate ROS in skin tissue, reduce oxidative stress levels, and alleviate skin aging. This approach provides a new strategy for the diagnosis and treatment of age-related diseases.

CD44-targeting hyaluronic acid-selenium nanoparticles boost functional recovery following spinal cord injury

BACKGROUND

Therapeutic strategies based on scavenging reactive oxygen species (ROS) and suppressing inflammatory cascades are effective in improving functional recovery after spinal cord injury (SCI). However, the lack of targeting nanoparticles (NPs) with powerful antioxidant and anti-inflammatory properties hampers the clinical translation of these strategies. Here, CD44-targeting hyaluronic acid-selenium (HA-Se) NPs were designed and prepared for scavenging ROS and suppressing inflammatory responses in the injured spinal cord, enhancing functional recovery.

RESULTS

The HA-Se NPs were easily prepared through direct reduction of seleninic acid in the presence of HA. The obtained HA-Se NPs exhibited a remarkable capacity to eliminate free radicals and CD44 receptor-facilitated internalization by astrocytes. Moreover, the HA-Se NPs effectively mitigated the secretion of proinflammatory cytokines (such as IL-1β, TNF-α, and IL-6) by microglia cells (BV2) upon lipopolysaccharide-induced inflammation. In vivo experiments confirmed that HA-Se NPs could effectively accumulate within the lesion site through CD44 targeting. As a result, HA-Se NPs demonstrated superior protection of axons and neurons within the injury site, leading to enhanced functional recovery in a rat model of SCI.

CONCLUSIONS

These results highlight the potential of CD44-targeting HA-Se NPs for SCI treatment.

Oxygen generating biomaterials at the forefront of regenerative medicine: advances in bone regeneration

Globally, an annual count of more than two million bone transplants is conducted, with conventional treatments, including metallic implants and bone grafts, exhibiting certain limitations. In recent years, there have been significant advancements in the field of bone regeneration. Oxygen tension regulates cellular behavior, which in turn affects tissue regeneration through metabolic programming. Biomaterials with oxygen release capabilities enhance therapeutic effectiveness and reduce tissue damage from hypoxia. However, precise control over oxygen release is a significant technical challenge, despite its potential to support cellular viability and differentiation. The matrices often used to repair large-size bone defects do not supply enough oxygen to the stem cells being used in the regeneration process. Hypoxia-induced necrosis primarily occurs in the central regions of large matrices due to inadequate provision of oxygen and nutrients by the surrounding vasculature of the host tissues. Oxygen generating biomaterials (OGBs) are becoming increasingly significant in enhancing our capacity to facilitate the bone regeneration, thereby addressing the challenges posed by hypoxia or inadequate vascularization. Herein, we discussed the key role of oxygen in bone regeneration, various oxygen source materials and their mechanism of oxygen release, the fabrication techniques employed for oxygen-releasing matrices, and novel emerging approaches for oxygen delivery that hold promise for their potential application in the field of bone regeneration.

VitroGel-loaded human MenSCs promote endometrial regeneration and fertility restoration

Introduction: Intrauterine adhesions (IUA), also known as Asherman's syndrome, is caused by trauma to the pregnant or non-pregnant uterus, which leads to damaged endometrial basal lining and partial or total occlusion of the uterine chambers, resulting in abnormal menstruation, infertility, or recurrent miscarriage. The essence of this syndrome is endometrial fibrosis. And there is no effective treatment for IUA to stimulate endometrial regeneration currently. Recently, menstrual blood-derived stem cells (MenSCs) have been proved to hold therapeutic promise in various diseases, such as myocardial infarction, stroke, diabetes, and liver cirrhosis. Methods: In this study, we examined the effects of MenSCs on the repair of uterine adhesions in a rat model, and more importantly, promoted such therapeutic effects via a xeno-free VitroGel MMP carrier. Results: This combined treatment reduced the expression of inflammatory factors, increased the expression of anti-inflammatory factors, restricted the area of endometrial fibrosis, diminished uterine adhesions, and partially restored fertility, showing stronger effectiveness than each component alone and almost resembling the sham group. Discussion: Our findings suggest a highly promising strategy for IUA treatment.

Hydrogel and Nanomedicine-Based Multimodal Therapeutic Strategies for Spinal Cord Injury

Spinal cord injury (SCI) is a severe neurodegenerative disease caused by mechanical and biological factors, manifesting as a loss of motor and sensory functions. Inhibition of injury expansion and even reversal of injury in the acute damage stage of SCI are important strategies for treating this disease. Hydrogels and nanoparticle (NP)-based drugs are the most effective, widely studied, and clinically valuable therapeutic strategies in the field of repair and regeneration. Hydrogels are 3D flow structures that fill the pathological gaps in SCI and provide a microenvironment similar to that of the spinal cord extracellular matrix for nerve cell regeneration. NP-based drugs can easily penetrate the blood-spinal cord barrier, target SCI lesions, and are noninvasive. Hydrogels and NPs as drug carriers can be loaded with various drugs and biological therapeutic factors for slow release in SCI lesions. They help drugs function more efficiently by exerting anti-inflammatory, antioxidant, and nerve regeneration effects to promote the recovery of neurological function. In this review, the use of hydrogels and NPs as drug carriers and the role of both in the repair of SCI are discussed to provide a multimodal strategic reference for nerve repair and regeneration after SCI.

Engineered Dynamic Hydrogel Niches for the Regulation of Redox Homeostasis in Osteoporosis and Degenerative Endocrine Diseases

Osteoporosis and degenerative endocrine diseases are some of the major causes of disability in the elderly. The feedback loop in the endocrine system works to control the release of hormones and maintain the homeostasis of metabolism, thereby regulating the function of target organs. The breakdown of this feedback loop results in various endocrine and metabolic disorders, such as osteoporosis, type II diabetes, hyperlipidemia, etc. The direct regulation of redox homeostasis is one of the most attractive strategies to redress the imbalance of the feedback loop. The biophysical regulation of redox homeostasis can be achieved through engineered dynamic hydrogel niches, with which cellular mechanics and redox homeostasis are intrinsically connected. Mechanotransduction-dependent redox signaling is initiated by cell surface protein assemblies, cadherins for cell-cell junctions, and integrins for cell-ECM interactions. In this review, we focused on the biophysical regulation of redox homeostasis via the tunable cell-ECM interactions in the engineered dynamic hydrogel niches. We elucidate processes from the rational design of the hydrogel matrix to the mechano-signaling initiation and then to the redox response of the encapsulated cells. We also gave a comprehensive summary of the current biomedical applications of this strategy in several degenerative endocrine disease models.

Nrf2 enhances the therapeutic efficiency of adipose-derived stem cells in the treatment of neurogenic erectile dysfunction in a rat model

BACKGROUND

Erectile dysfunction (ED) caused by intraoperative nerve injury is a major complication of pelvic surgery. Adipose-derived stem cells (ADSCs) have presented therapeutic potential in a rat model of bilateral cavernous nerve injury (BCNI), while inadequate in vivo viability has largely limited their application. Nuclear factor-E2-related Factor (Nrf2) is a key transcription factor that regulates cellular anti-oxidative stress. In this work, we investigated the effect of Nrf2 expression regulation on the viability of ADSCs, and explore its repair potential in a BCNI rat model.

RESULTS

The survival time of tert-Butylhydroquinone (tBHQ)-ADSCs in BCNI model increased obviously. In addition, the tBHQ-ADSCs group presented better restoration of major pelvic ganglion (MPG) nerve contents and fibers, better improvement of erectile function, and less penile fibrosis than the other groups. Moreover, the expression of Nrf2 and superoxide dismutase 1 (SOD1) were higher than those of other groups.

CONCLUSION

Nrf2 could enhance the anti-oxidative stress ability of ADSCs, so as to improve the therapeutic effect of ADSCs on BCNI rat model.

Extracellular Vesicles Derived from Human Umbilical Cord MSC Improve Vascular Endothelial Function in In Vitro and In Vivo Models of Preeclampsia through Activating Arginine Metabolism

Endothelial cell damage is an important feature of preeclampsia (PE). Human umbilical mesenchymal stem-cell-derived extracellular vesicles (HUMSCs-derived EVs) have been shown to have therapeutic effects on a variety of diseases and tissue damage. However, the therapeutic effect of HUMSCs-derived EVs on endothelial injury in PE remains unclear. This study explored the possible mechanism of HUMSCs-derived EVs in the treatment of endothelial cell injury. Tumor necrosis factor α- and lipopolysaccharide-induced endothelial dysfunction models were used to evaluate the therapeutic effect of HUMSCs-derived EVs on endothelial injury. We further constructed PE mouse models to explore the function of HUMSCs-derived EVs in vivo. The changes of metabolites in endothelial cells after HUMSCs-derived EVs treatment were analyzed by metabolomics analysis and further validated by cell experiments. HUMSCs-derived EVs treatment can alleviate endothelial cell injury in PE, involving cell proliferation, migration, angiogenesis, and anti-inflammatory. Importantly, administration of HUMSCs-derived EVs improves hypertension and proteinuria in PE mice, alleviates kidney damage, and promotes vascularization in the placenta. Furthermore, metabolomics analysis found that the arginine metabolic pathway is activated after HUMSCs-derived EVs treatment. We also observed increased arginine level, nitric oxide content, and nitric oxide synthase activity, and further experiments proved that activating the arginine metabolic pathway could alleviate endothelial dysfunction. Our results reveal that HUMSCs-derived EVs could ameliorate PE endothelial dysfunction by activating the arginine metabolic pathway and may serve as a therapeutic method for treating PE.

Artificially reprogrammed stem cells deliver transcytosable nanocomplexes for improved spinal cord repair

Stem cell transplantation holds great promise for restoring function after spinal cord injury (SCI), but its therapeutic efficacy heavily depends on the innate capabilities of the cells and the microenvironment at the lesion site. Herein, a potent cell therapeutic (NCs@SCs) is engineered by artificially reprogramming bone marrow mesenchymal stem cells (BMSCs) with oxidation-responsive transcytosable gene-delivery nanocomplexes (NCs), which endows cells with robust oxidative stress resistance and improved cytokine secretion. NCs@SCs can accumulate in the injured spinal cord after intravenous administration via chemotaxis and boost successive transcytosis to deliver NCs to neurons, augmenting ciliary neurotrophic factor (CNTF) production in both BMSCs and neurons in response to elevated ROS levels. Furthermore, NCs@SCs can actively sense and eliminate ROS and re-educate recruited M1-like macrophages into the anti-inflammatory M2 phenotype via a paracrine pathway, ultimately reshaping the inflammatory microenvironment. Synergistically, NCs@SCs exhibit durable survival and provide neuroprotection against secondary damage, enabling significant locomotor function recovery in SCI rats. Transcriptome analysis reveals that regulation of the ROS/MAPK signaling pathway is involved in SCI therapy by NCs@SCs. This study presents a nanomaterial-mediated cell-reprogramming approach for developing live cell therapeutics, showing significant potential in the treatment of SCI and other neuro-injury disorders.

Neuroprotective Effects of Microglial Membrane-Derived Biomimetic Particles for Spinal Cord Injury

Inhibition of oxidative stress and inflammatory responses caused by secondary injury following traumatic spinal cord injury (SCI) is an attractive strategy in treating traumatic SCI. However, the efficacy of drugs is severely limited owing to the poor penetration of the blood spinal cord barrier (BSCB). Here, inspired by cell chemotaxis and related chemokines production at the lesion sites of SCI, the microglial membrane is selected to construct a drug delivery system with the ability to cross the BSCB and target the lesions. PR@MM is prepared based on the assembly of polylactic-co-glycolic acid (PLGA) and resveratrol (RSV) followed by microglial membrane (MM) coating. Compared to that of the uncoated nanoparticles, the enrichment of PR@MM at the lesion sites of SCI increases, which is beneficial to achieve lesion targeting of RSV and exert therapeutic functions. Both in vitro and in vivo experiments demonstrate that PR@MM has the ability to scavenge reactive oxygen species and anti-inflammatory effects, which ultimately promotes the recovery of locomotory function after SCI. Therefore, this microglial membrane-based drug delivery system provides a promising biomimetic nanomedicine for targeted therapy for SCI.

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

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

Application of Injectable Hydrogels as Delivery Systems in Spinal Cord Injury

Spinal cord injury (SCI) is a severe neurological injury caused by traffic accidents, trauma, or falls, which leads to significant loss of sensory, motor, and autonomous functions and seriously affects the patient's life quality. Although considerable progress has been made in mitigating secondary injury and promoting the regeneration/repair of SCI, the therapeutic effects need to be improved due to drug availability. Given their good biocompatibility, biodegradability, and low immunogenicity, injectable hydrogels can be used as delivery systems to achieve controlled release of drugs and other substances (cells and proteins, etc.), offering new hope for SCI repair. In this article, we summarized the types of injectable hydrogels, analyzed their application as delivery systems in SCI, and further discussed the mechanisms of hydrogels in the treatment of SCI, such as anti-inflammatory, antioxidant, anti-apoptosis, and pro-neurogenesis. Moreover, we highlighted the potential benefits of hydrogels in the treatment of SCI in combination with therapies, including the recent advances and achievements of these promising tools. Our review may offer new strategies for the development of SCI treatments based on injectable hydrogels as delivery systems.

Intranasal delivery of stem cells labeled by nanoparticles in neurodegenerative disorders: Challenges and opportunities

Neurodegenerative disorders occur through progressive loss of function or structure of neurons, with loss of sensation and cognition values. The lack of successful therapeutic approaches to solve neurologic disorders causes physical disability and paralysis and has a significant socioeconomic impact on patients. In recent years, nanocarriers and stem cells have attracted tremendous attention as a reliable approach to treating neurodegenerative disorders. In this regard, nanoparticle-based labeling combined with imaging technologies has enabled researchers to survey transplanted stem cells and fully understand their fate by monitoring their survival, migration, and differentiation. For the practical implementation of stem cell therapies in the clinical setting, it is necessary to accurately label and follow stem cells after administration. Several approaches to labeling and tracking stem cells using nanotechnology have been proposed as potential treatment strategies for neurological diseases. Considering the limitations of intravenous or direct stem cell administration, intranasal delivery of nanoparticle-labeled stem cells in neurological disorders is a new method of delivering stem cells to the central nervous system (CNS). This review describes the challenges and limitations of stem cell-based nanotechnology methods for labeling/tracking, intranasal delivery of cells, and cell fate regulation as theragnostic labeling. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Neurological Disease.

MLL1 inhibits the neurogenic potential of SCAPs by interacting with WDR5 and repressing HES1

Mesenchymal stem cell (MSC)-based therapy has emerged as a promising treatment for spinal cord injury (SCI), but improving the neurogenic potential of MSCs remains a challenge. Mixed lineage leukemia 1 (MLL1), an H3K4me3 methyltransferases, plays a critical role in regulating lineage-specific gene expression and influences neurogenesis. In this study, we investigated the role and mechanism of MLL1 in the neurogenesis of stem cells from apical papilla (SCAPs). We examined the expression of neural markers, and the nerve repair and regeneration ability of SCAPs using dynamic changes in neuron-like cells, immunofluorescence staining, and a SCI model. We employed a coimmunoprecipitation (Co-IP) assay, real-time RT-PCR, microarray analysis, and chromatin immunoprecipitation (ChIP) assay to investigate the molecular mechanism. The results showed that MLL1 knock-down increased the expression of neural markers, including neurogenic differentiation factor (NeuroD), neural cell adhesion molecule (NCAM), tyrosine hydroxylase (TH), βIII-tubulin and Nestin, and promoted neuron-like cell formation in SCAPs. In vivo, a transplantation experiment showed that depletion of MLL 1 in SCAPs can restore motor function in a rat SCI model. MLL1 can combine with WD repeat domain 5 (WDR5) and WDR5 inhibit the expression of neural markers in SCAPs. MLL1 regulates Hairy and enhancer of split 1 (HES1) expression by directly binds to HES1 promoters via regulating H3K4me3 methylation by interacting with WDR5. Additionally, HES1 enhances the expression of neural markers in SCAPs. Our findings demonstrate that MLL1 inhibits the neurogenic potential of SCAPs by interacting with WDR5 and repressing HES1. These results provide a potential therapeutic target for promoting the recovery of motor function in SCI patients.

Nanomedicine innovations in spinal cord injury management: Bridging the gap

Spinal cord injury (SCI) has devastating effects on a person's physical, social, and professional well-being. It is a life-altering neurological condition that significantly impacts individuals and their caregivers on a socioeconomic level. Recent advancements in medical therapy have greatly improved the diagnosis, stability, survival rates, and overall well-being of SCI patients. However, there are still limited options available for enhancing neurological outcomes in these patients. The complex pathophysiology of SCI, along with the numerous biochemical and physiological changes that occur in the damaged spinal cord, contribute to this gradual improvement. Currently, there are no therapies that offer the possibility of recovery for SCI, although several therapeutic approaches are being developed. However, these therapies are still in the early stages and have not yet demonstrated effectiveness in repairing the damaged fibers, which hinders cellular regeneration and the full restoration of motor and sensory functions. Considering the importance of nanotechnology and tissue engineering in treating neural tissue injuries, this review focuses on the latest advancements in nanotechnology for SCI therapy and tissue healing. It examines research articles from the PubMed database that specifically address SCI in the field of tissue engineering, with an emphasis on nanotechnology as a therapeutic approach. The review evaluates the biomaterials used for treating this condition and the techniques employed to create nanostructured biomaterials.

Reactive oxygen nanobiocatalysts: activity-mechanism disclosures, catalytic center evolutions, and changing states

Benefiting from low costs, structural diversities, tunable catalytic activities, feasible modifications, and high stability compared to the natural enzymes, reactive oxygen nanobiocatalysts (RONBCs) have become dominant materials in catalyzing and mediating reactive oxygen species (ROS) for diverse biomedical and biological applications. Decoding the catalytic mechanism and structure-reactivity relationship of RONBCs is critical to guide their future developments. Here, this timely review comprehensively summarizes the recent breakthroughs and future trends in creating and decoding RONBCs. First, the fundamental classification, activity, detection method, and reaction mechanism for biocatalytic ROS generation and elimination have been systematically disclosed. Then, the merits, modulation strategies, structure evolutions, and state-of-art characterisation techniques for designing RONBCs have been briefly outlined. Thereafter, we thoroughly discuss different RONBCs based on the reported major material species, including metal compounds, carbon nanostructures, and organic networks. In particular, we offer particular insights into the coordination microenvironments, bond interactions, reaction pathways, and performance comparisons to disclose the structure-reactivity relationships and mechanisms. In the end, the future challenge and perspectives for RONBCs are also carefully summarised. We envision that this review will provide a comprehensive understanding and guidance for designing ROS-catalytic materials and stimulate the wide utilisation of RONBCs in diverse biomedical and biological applications.

Controlled delivery of a neurotransmitter-agonist conjugate for functional recovery after severe spinal cord injury

Despite considerable unmet medical needs, effective pharmacological treatments that promote functional recovery after spinal cord injury remain limited. Although multiple pathological events are implicated in spinal cord injuries, the development of a microinvasive pharmacological approach that simultaneously targets the different mechanisms involved in spinal cord injury remains a formidable challenge. Here we report the development of a microinvasive nanodrug delivery system that consists of amphiphilic copolymers responsive to reactive oxygen species and an encapsulated neurotransmitter-conjugated KCC2 agonist. Upon intravenous administration, the nanodrugs enter the injured spinal cord due to a disruption in the blood-spinal cord barrier and disassembly due to damage-triggered reactive oxygen species. The nanodrugs exhibit dual functions in the injured spinal cord: scavenging accumulated reactive oxygen species in the lesion, thereby protecting spared tissues, and facilitating the integration of spared circuits into the host spinal cord through targeted modulation of inhibitory neurons. This microinvasive treatment leads to notable functional recovery in rats with contusive spinal cord injury.

Effective Modulation of Inflammation and Oxidative Stress for Enhanced Regeneration of Intervertebral Discs Using 3D Porous Hybrid Protein Nanoscaffold

Degeneration of fibrocartilaginous tissues is often associated with complex pro-inflammatory factors. These include reactive oxygen species (ROS), cell-free nucleic acids (cf-NAs), and epigenetic changes in immune cells. To effectively control this complex inflammatory signaling, it developed an all-in-one nanoscaffold-based 3D porous hybrid protein (3D-PHP) self-therapeutic strategy for treating intervertebral disc (IVD) degeneration. The 3D-PHP nanoscaffold is synthesized by introducing a novel nanomaterial-templated protein assembly (NTPA) strategy. 3D-PHP nanoscaffolds that avoid covalent modification of proteins demonstrate inflammatory stimuli-responsive drug release, disc-mimetic stiffness, and excellent biodegradability. Enzyme-like 2D nanosheets incorporated into nanoscaffolds further enabled robust scavenging of ROS and cf-NAs, reducing inflammation and enhancing the survival of disc cells under inflammatory stress in vitro. Implantation of 3D-PHP nanoscaffolds loaded with bromodomain extraterminal inhibitor (BETi) into a rat nucleotomy disc injury model effectively suppressed inflammation in vivo, thus promoting restoration of the extracellular matrix (ECM). The resulting regeneration of disc tissue facilitated long-term pain reduction. Therefore, self-therapeutic and epigenetic modulator-encapsulated hybrid protein nanoscaffold shows great promise as a novel approach to restore dysregulated inflammatory signaling and treat degenerative fibrocartilaginous diseases, including disc injuries, providing hope and relief to patients worldwide.

Surface-tethered ROS-responsive micelle backpacks for boosting mesenchymal stem cell vitality and modulating inflammation in ischemic stroke treatment

Mesenchymal stem cells (MSCs) exhibited remarkable therapeutic potential in ischemic stroke due to their exceptional immunomodulatory ability and paracrine effect; they have also been regarded as excellent neuroprotectant delivery vehicles with inflammatory tropism. However, the presence of high levels of reactive oxygen species (ROS) and an oxidative stress environment at the lesion site inhibits cell survival and further therapeutic effects. Using bioorthogonal click chemistry, ROS-responsive luteolin-loaded micelles were tethered to the surface of MSCs. As MSCs migrated to the ischemic brain, the micelles would achieve ROS-responsive release of luteolin to protect MSCs from excessive oxidative damage while inhibiting neuroinflammation and scavenging ROS to ameliorate ischemic stroke. This study provided an effective and prospective therapeutic strategy for ischemic stroke and a framework for a stem cell-based therapeutic system to treat inflammatory cerebral diseases.

Coaxial 3D printing of hierarchical structured hydrogel scaffolds for on-demand repair of spinal cord injury

After spinal cord injury (SCI), endogenous neural stem cells (NSCs) near the damaged site are activated, but few NSCs migrate to the injury epicenter and differentiate into neurons because of the harsh microenvironment. It has demonstrated that implantation of hydrogel scaffold loaded with multiple cues can enhance the function of endogenous NSCs. However, programming different cues on request remains a great challenge. Herein, a time-programmed linear hierarchical structure scaffold is developed for spinal cord injury recovery. The scaffold is obtained through coaxial 3D printing by encapsulating a dual-network hydrogel (composed of hyaluronic acid derivatives and N-cadherin modified sodium alginate, inner layer) into a temperature responsive gelatin/cellulose nanofiber hydrogel (Gel/CNF, outer layer). The reactive species scavenger, metalloporphyrin, loaded in the outer layer is released rapidly by the degradation of Gel/CNF, inhibiting the initial oxidative stress at lesion site to protect endogenous NSCs; while the inner hydrogel with appropriate mechanical support, linear topology structure and bioactive cues facilitates the migration and neuronal differentiation of NSCs at the later stage of SCI treatment, thereby promoting motor functional restorations in SCI rats. This study offers an innovative strategy for fabrication of multifunctional nerve regeneration scaffold, which has potential for clinical treatment of SCI. STATEMENT OF SIGNIFICANCE: Two major challenges facing the recovery from spinal cord injury (SCI) are the low viability of endogenous neural stem cells (NSCs) within the damaged microenvironment, as well as the difficulty of neuronal regeneration at the injured site. To address these issues, a spinal cord-like coaxial scaffold was fabricated with free radical scavenging agent metalloporphyrin Mn (III) tetrakis (4-benzoic acid) porphyrin and chemokine N-cadherin. The scaffold was constructed by 3D bioprinting for time-programmed protection and modulation of NSCs to effectively repair SCI. This 3D coaxially bioprinted biomimetic construct enables multi-factor on-demand repair and may be a promising therapeutic strategy for SCI.

Defect-Rich SnO2 Nanofiber as an Oxygen-Defect-Driven Photoenergy Shield against UV Light Cell Damage

Usually, most studies focus on toxic gas and photosensors by using electrospinning and metal oxide polycrystalline SnO2 nanofibers (PNFs), while fewer studies discuss cell-material interactions and photoelectric effect. In this work, the controllable surface morphology and oxygen defect (VO) structure properties were provided to show the opportunity of metal oxide PNFs to convert photoenergy into bio-energy for bio-material applications. Using the photobiomodulation effect of defect-rich polycrystalline SnO2 nanofibers (PNFs) is the main idea to modulate the cell-material interactions, such as adhesion, growth direction, and reactive oxygen species (ROS) density. The VO structures, including out-of-plane oxygen defects (op-VO), bridge oxygen defects (b-VO), and in-plane oxygen defects (ip-VO), were studied using synchrotron analysis to investigate the electron transfer between the VO structures and conduction bands. These intragrain VO structures can be treated as generation-recombination centers, which can convert various photoenergies (365-520 nm) into different current levels that form distinct surface potential levels; this is referred to as the photoelectric effect. PNF conductivity was enhanced 53.6-fold by enlarging the grain size (410 nm2) by increasing the annealing temperature, which can improve the photoelectric effect. In vitro removal of reactive oxygen species (ROS) can be achieved by using the photoelectric effect of PNFs. Also, the viability and shape of human bone marrow mesenchymal stem cells (hMSCs-BM) were also influenced significantly by the photobiomodulation effect. The cell damage and survival rate can be prevented and enhanced by using PNFs; metal oxide nanofibers are no longer only environmental sensors but can also be a bio-material to convert the photoenergy into bio-energy for biomedical science applications.

Combining MSC Exosomes and Cerium Oxide Nanocrystals for Enhanced Dry Eye Syndrome Therapy

Dry eye syndrome (DES) is a prevalent ocular disorder involving diminishe·d tear production and increased tear evaporation, leading to ocular discomfort and potential surface damage. Inflammation and reactive oxygen species (ROS) have been implicated in the pathophysiology of DES. Inflammation is one core cause of the DES vicious cycle. Moreover, there are ROS that regulate inflammation in the cycle from the upstream, which leads to treatment failure in current therapies that merely target inflammation. In this study, we developed a novel therapeutic nanoparticle approach by growing cerium oxide (Ce) nanocrystals in situ on mesenchymal stem cell-derived exosomes (MSCExos), creating MSCExo-Ce. The combined properties of MSCExos and cerium oxide nanocrystals aim to target the "inflammation-ROS-injury" pathological mechanism in DES. We hypothesized that this approach would provide a new treatment option for patients with DES. Our analysis confirmed the successful in situ crystallization of cerium onto MSCExos, and MSCExo-Ce displayed excellent biocompatibility. In vitro and in vivo experiments have demonstrated that MSCExo-Ce promotes corneal cell growth, scavenges ROS, and more effectively suppresses inflammation compared with MSCExos alone. MSCExo-Ce also demonstrated the ability to alleviate DES symptoms and reverse pathological alterations at both the cellular and tissue levels. In conclusion, our findings highlight the potential of MSCExo-Ce as a promising therapeutic candidate for the treatment of DES.

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.

Nanoenzyme-Reinforced Multifunctional Scaffold Based on Ti3C2Tx MXene Nanosheets for Promoting Structure-Functional Skeletal Muscle Regeneration via Electroactivity and Microenvironment Management

The completed volumetric muscle loss (VML) regeneration remains a challenge due to the limited myogenic differentiation as well as the oxidative, inflammatory, and hypoxic microenvironment. Herein, a 2D Ti3C2Tx MXene@MnO2 nanocomposite with conductivity and microenvironment remodeling was fabricated and applied in developing a multifunctional hydrogel (FME) scaffold to simultaneously conquer these hurdles. Among them, Ti3C2Tx MXene with electroconductive ability remarkably promotes myogenic differentiation via enhancing the myotube formation and upregulating the relative expression of the myosin heavy chain (MHC) protein and myogenic genes (MyoD and MyoG) in myogenesis. The MnO2 nanoenzyme-reinforced Ti3C2Tx MXene significantly reshapes the hostile microenvironment by eliminating reactive oxygen species (ROS), regulating macrophage polarization from M1 to M2 and continuously supplying O2. Together, the FME hydrogel as a bioactive multifunctional scaffold significantly accelerates structure-functional VML regeneration in vivo and represents a multipronged strategy for the VML regeneration via electroactivity and microenvironment management.

Nanozyme-Integrated Thermoresponsive In Situ Forming Hydrogel Enhances Mesenchymal Stem Cell Viability and Paracrine Effect for Efficient Spinal Cord Repair

Mesenchymal stem cell (MSC)-based therapy has emerged as a promising strategy for the treatment of spinal cord injury (SCI). However, the hostile microenvironment of SCI, which can adversely affect the survival and paracrine effect of the implanted MSCs, severely limits the therapeutic efficacy of this approach. Here, we report on a ceria nanozyme-integrated thermoresponsive in situ forming hydrogel (CeNZ-gel) that can enable dual enhancement of MSC viability and paracrine effect, leading to highly efficient spinal cord repair. The sol-gel transition property of the CeNZ-gel at body temperature ensures uniform coverage of the hydrogel in injured spinal cord tissues. Our results demonstrate that the CeNZ-gel significantly increases the viability of transplanted MSCs in the microenvironment by attenuating oxidative stress and, more importantly, promotes the secretion of angiogenic factors from MSCs by inducing autophagy of MSCs. The synergy between the oxidative stress-relieving effect of CeNZs and the paracrine effect of MSCs accelerates angiogenesis, nerve repair, and motor function recovery after SCI, providing an efficient strategy for MSC-based SCI therapy.

Cascade and Ultrafast Artificial Antioxidases Alleviate Inflammation and Bone Resorption in Periodontitis

Periodontitis, one of the most common, challenging, and rapidly expanding oral diseases, is an oxidative stress-related disease caused by excessive reactive oxygen species (ROS) production. Developing ROS-scavenging materials to regulate the periodontium microenvironments is essential for treating periodontitis. Here, we report on creating cobalt oxide-supported Ir (CoO-Ir) as a cascade and ultrafast artificial antioxidase to alleviate local tissue inflammation and bone resorption in periodontitis. It is demonstrated that the Ir nanoclusters are uniformly supported on the CoO lattice, and there is stable chemical coupling and strong charge transfer from Co to Ir sites. Benefiting from its structural advantages, CoO-Ir presents cascade and ultrafast superoxide dismutase-catalase-like catalytic activities. Notably, it displays distinctly increased Vmax (76.249 mg L-1 min-1) and turnover number (2.736 s-1) when eliminating H2O2, which surpasses most of the by-far-reported artificial enzymes. Consequently, the CoO-Ir not only provides efficient cellular protection from ROS attack but also promotes osteogenetic differentiation in vitro. Furthermore, CoO-Ir can efficiently combat periodontitis by inhibiting inflammation-induced tissue destruction and promoting osteogenic regeneration. We believe that this report will shed meaningful light on creating cascade and ultrafast artificial antioxidases and offer an effective strategy to combat tissue inflammation and osteogenic resorption in oxidative stress-related diseases.

Recent advance in bioactive hydrogels for repairing spinal cord injury: material design, biofunctional regulation, and applications

Functional hydrogels show potential application in repairing spinal cord injury (SCI) due to their unique chemical, physical, and biological properties and functions. In this comprehensive review, we present recent advance in the material design, functional regulation, and SCI repair applications of bioactive hydrogels. Different from previously released reviews on hydrogels and three-dimensional scaffolds for the SCI repair, this work focuses on the strategies for material design and biologically functional regulation of hydrogels, specifically aiming to show how these significant efforts can promoting the repairing performance of SCI. We demonstrate various methods and techniques for the fabrication of bioactive hydrogels with the biological components such as DNA, proteins, peptides, biomass polysaccharides, and biopolymers to obtain unique biological properties of hydrogels, including the cell biocompatibility, self-healing, anti-bacterial activity, injectability, bio-adhesion, bio-degradation, and other multi-functions for repairing SCI. The functional regulation of bioactive hydrogels with drugs/growth factors, polymers, nanoparticles, one-dimensional materials, and two-dimensional materials for highly effective treating SCI are introduced and discussed in detail. This work shows new viewpoints and ideas on the design and synthesis of bioactive hydrogels with the state-of-the-art knowledges of materials science and nanotechnology, and will bridge the connection of materials science and biomedicine, and further inspire clinical potential of bioactive hydrogels in biomedical fields.

ROS-Scavenging Hydrogels Synergize with Neural Stem Cells to Enhance Spinal Cord Injury Repair via Regulating Microenvironment and Facilitating Nerve Regeneration

Although stem cell-based therapy is recognized as a promising therapeutic strategy for spinal cord injury (SCI), its efficacy is greatly limited by local reactive oxygen species (ROS)-abundant and hyper-inflammatory microenvironments. It is still a challenge to develop bioactive scaffolds with outstanding antioxidant capacity for neural stem cells (NSCs) transplantation. In this study, albumin biomimetic cerium oxide nanoparticles (CeO2 @BSA nanoparticles, CeNPs) are prepared in a simple and efficient manner and dispersed in gelatin methacryloyl to obtain the ROS-scavenging hydrogel (CeNP-Gel). CeNP-Gel synergistically promotes neurogenesis via alleviating oxidative stress microenvironments and improving the viability of encapsulated NSCs. More interestingly, in the presence of CeNP-Gel, microglial polarization to anti-inflammatory M2 subtype are obviously facilitated, which is further verified to be associated with phosphoinositide 3-kinase/protein kinase B pathway activation. Additionally, the injectable ROS-scavenging hydrogel is confirmed to induce the integration and neural differentiation of transplanted NSCs. Compared with the blank-gel group, the survival rate of NSCs in CeNP-Gel group is about 3.5 times higher, and the neural differentiation efficiency is about 2.1 times higher. Therefore, the NSCs-laden ROS-scavenging hydrogel represents a comprehensive strategy with great application prospect for the treatment of SCI through comprehensively modulating the adverse microenvironment.

KDM6B Negatively Regulates the Neurogenesis Potential of Apical Papilla Stem Cells via HES1

Stem cells from the apical papilla (SCAPs) are used to regulate the microenvironment of nerve defects. KDM6B, which functions as an H3K27me3 demethylase, is known to play a crucial role in neurogenesis. However, the mechanism by which KDM6B influences the neurogenesis potential of SCAPs remains unclear. We evaluated the expression of neural markers in SCAPs by using real-time RT-PCR and immunofluorescence staining. To assess the effectiveness of SCAP transplantation in the SCI model, we used the BBB scale to evaluate motor function. Additionally, toluidine blue staining and Immunofluorescence staining of NCAM, NEFM, β-III-tubulin, and Nestin were used to assess nerve tissue remodeling. Further analysis was conducted through Microarray analysis and ChIP assay to study the molecular mechanisms. Our results show that KDM6B inhibits the expression of NeuroD, TH, β-III tubulin, and Nestin. In vivo studies indicate that the SCAP-KDM6Bsh group is highly effective in restoring spinal cord structure and motor function in rats suffering from SCI. Our findings suggest that KDM6B directly binds to the HES1 promoter via regulating H3K27me3 and HES1 expression. In conclusion, our study can help understand the regulatory role of KDM6B in neurogenesis and provide more effective treatments for nerve injury.

Functionalized hydrogels in neural injury repairing

Repairing injuries to the nervous system has always been a prominent topic in clinical research. Direct suturing and nerve displacement surgery are the primary treatment options, but they may not be suitable for long nerve injuries and may require sacrificing the functionality of other autologous nerves. With the emergence of tissue engineering, hydrogel materials have been identified as a promising technology with clinical translation potential for repairing nervous system injuries due to their excellent biocompatibility and ability to release or deliver functional ions. By controlling their composition and structure, hydrogels can be Functionalized and almost fully matched with nerve tissue and even simulate nerve conduction function and mechanical properties. Thus, they are suitable for repairing injuries to both the central and peripheral nervous systems. This article provides a review of recent research progress in functionalized hydrogels for nerve injury repair, highlighting the design differences among various materials and future research directions. We strongly believe that the development of functionalized hydrogels has great potential for improving the clinical treatment of nerve injuries.

Hydrogel scaffolds in the treatment of spinal cord injury: a review

Spinal cord injury (SCI) is a disease of the central nervous system often caused by accidents, and its prognosis is unsatisfactory, with long-term adverse effects on patients' lives. The key to its treatment lies in the improvement of the microenvironment at the injury and the reconstruction of axons, and tissue repair is a promising therapeutic strategy. Hydrogel is a three-dimensional mesh structure with high water content, which has the advantages of biocompatibility, degradability, and adjustability, and can be used to fill pathological defects by injectable flowing hydrophilic material in situ to accurately adapt to the size and shape of the injury. Hydrogels mimic the natural extracellular matrix for cell colonization, guide axon extension, and act as a biological scaffold, which can be used as an excellent carrier to participate in the treatment of SCI. The addition of different materials to make composite hydrogel scaffolds can further enhance their performance in all aspects. In this paper, we introduce several typical composite hydrogels and review the research progress of hydrogel for SCI to provide a reference for the clinical application of hydrogel therapy for SCI.

In situ photo-crosslinking silk fibroin based hydrogel accelerates diabetic wound healing through antibacterial and antioxidant

Bacterial infection and excessive reactive oxygen species (ROS) in diabetic wounds lead to a prolonged inflammatory phase, and injuries are highly susceptible to developing into chronic wounds. Improving the poor microenvironment is vital to achieving effective diabetic wound healing. In this work, methacrylated silk fibroin (SFMA) was combined with ε-polylysine (EPL) and manganese dioxide nanoparticles (BMNPs) to form an SF@(EPL-BM) hydrogel with in situ forming, antibacterial and antioxidant properties. EPL imparted high antibacterial activity (>96 %) to the hydrogel. BMNPs and EPL showed good scavenging activity against a variety of free radicals. SF@(EPL-BM) hydrogel had low cytotoxicity and could alleviate H₂O₂-induced oxidative stress in L929 cells. In diabetic wounds infected with Staphylococcus aureus (S. aureus), the SF@(EPL-BM) hydrogel exhibited better antibacterial properties and reduced wound ROS levels more significantly than that of the control in vivo. In this process, the pro-inflammatory factor TNF-α was down-regulated, and the vascularization marker CD31 was up-regulated. H&E and Masson staining showed a rapid transition from the inflammatory to the proliferative phase of the wounds, with significant new tissue and collagen deposition. These results confirm that this multifunctional hydrogel dressing holds well potential for chronic wound healing.

Cell-instructive biomaterials in tissue engineering and regenerative medicine

The field of biomaterials aims to improve regenerative outcomes or scientific understanding for a wide range of tissue types and ailments. Biomaterials can be fabricated from natural or synthetic sources and display a plethora of mechanical, electrical, and geometrical properties dependent on their desired application. To date, most biomaterial systems designed for eventual translation to the clinic rely on soluble signaling moieties, such as growth factors, to elicit a specific cellular response. However, these soluble factors are often limited by high cost, convoluted synthesis, low stability, and difficulty in regulation, making the translation of these biomaterials systems to clinical or commercial applications a long and arduous process. In response to this, significant effort has been dedicated to researching cell-directive biomaterials which can signal for specific cell behavior in the absence of soluble factors. Cells of all tissue types have been shown to be innately in tune with their microenvironment, which is a biological phenomenon that can be exploited by researchers to design materials that direct cell behavior based on their intrinsic characteristics. This review will focus on recent developments in biomaterials that direct cell behavior using biomaterial properties such as charge, peptide presentation, and micro- or nano-geometry. These next generation biomaterials could offer significant strides in the development of clinically relevant medical devices which improve our understanding of the cellular microenvironment and enhance patient care in a variety of ailments.

Bioactive Spinal Cord Scaffold Releasing Neurotrophic Exosomes to Promote In Situ Centralis Neuroplasticity

Spinal cord injury (SCI), one of the most serious injuries of the central nervous system, causes physical functional dysfunction and even paralysis in millions of patients. As a matter of necessity, redressing the neuroleptic pathologic microenvironment to a neurotrophic microenvironment is essential in order to alleviate this dilemma and facilitate the recovery of the spinal cord. Herein, based on cell-sheet technology, two functional cell types─uninduced and neural-induced stem cells from human exfoliated deciduous teeth─were formed into a composite membrane that subsequently self-assembled to form a bioactive scaffold with a spinal-cord-like structure, called a spinal cord assembly (SCA). In a stable extracellular matrix microenvironment, SCA continuously released SCA-derived exosomes containing various neurotrophic factors, which effectively promoted neuronal regeneration, axonal extension, and angiogenesis and inhibited glial scar generation in a rat model of SCI. Neurotrophic exosomes significantly improved the pathological microenvironment and promoted in situ centralis neuroplasticity, ultimately eliciting a strong repair effect in this model. SCA therapy is a promising strategy for the effective treatment of SCI based on neurotrophic exosome delivery.