Alginate hydrogel cross-linked by Ca2+ to promote spinal cord neural stem/progenitor cell differentiation and functional recovery after a spinal cord injury

Association between neural stem/progenitor cells and biomaterials in spinal cord injury therapies: A systematic review and network meta-analysis

Spinal cord injury (SCI) is associated with substantial healthcare challenges, frequently resulting in enduring sensory and motor deficits alongside various chronic complications. While advanced regenerative therapies have shown promise in preclinical research, their translation into clinical application has been limited. In response, this study utilized a comprehensive network meta-analysis to evaluate the effectiveness of neural stem/progenitor cell (NSPC) transplantation across animal models of SCI. We analyzed 363 outcomes from 55 distinct studies, categorizing the treatments into NSPCs alone (cell only), NSPCs with scaffolds (cell + scaffold), NSPCs with hydrogels (cell + hydrogel), standalone scaffolds (scaffold), standalone hydrogels (hydrogel), and control groups. Our analysis demonstrated significant enhancements in motor recovery, especially in gait function, within the NSPC treatment groups. Notably, the cell only group showed considerable improvements (standardized mean difference [SMD], 2.05; 95 % credible interval [CrI]: 1.08 to 3.10, p < 0.01), as did the cell + scaffold group (SMD, 3.73; 95 % CrI: 2.26 to 5.22, p < 0.001) and the cell + hydrogel group (SMD, 3.37; 95 % CrI: 1.02 to 5.78, p < 0.05) compared to controls. These therapeutic combinations not only reduced lesion cavity size but also enhanced neuronal regeneration, outperforming the cell only treatments. By integrating NSPCs with supportive biomaterials, our findings pave the way for refining these regenerative strategies to optimize their potential in clinical SCI treatment. Although there is no overall violation of consistency, the comparison of effect sizes between individual treatments should be interpreted in light of the inconsistency. STATEMENT OF SIGNIFICANCE: This study presents a comprehensive network meta-analysis exploring the efficacy of neural stem cell (NSC) transplantation, with and without biomaterials, in animal models of spinal cord injury (SCI). We demonstrate that NSCs, particularly when combined with biomaterials like scaffolds or hydrogels, significantly enhance motor and histological recovery post-SCI. These findings underscore the potential of NSC-based therapies, augmented with biomaterials, to advance SCI treatment, offering new insights into regenerative strategies that could significantly impact clinical practices.

Modern advances in spinal cord regeneration: hydrogel combined with neural stem cells

Severe spinal cord injuries (SCI) lead to loss of functional activity of the body below the injury site, affect a person's ability to self-care and have a direct impact on performance. Due to the structural features and functional role of the spinal cord in the body, the consequences of SCI cannot be completely overcome at the expense of endogenous regenerative potential and, developing over time, lead to severe complications years after injury. Thus, the primary task of this type of injury treatment is to create artificial conditions for the regenerative growth of damaged nerve fibers through the area of the SCI. Solving this problem is possible using tissue neuroengineering involving the technology of replacing the natural tissue environment with synthetic matrices (for example, hydrogels) in combination with stem cells, in particular, neural/progenitor stem cells (NSPCs). This approach can provide maximum stimulation and support for the regenerative growth of axons of damaged neurons and their myelination. In this review, we consider the currently available options for improving the condition after SCI (use of NSC transplantation or/and replacement of the damaged area of the SCI with a matrix, specifically a hydrogel). We emphasise the expediency and effectiveness of the hydrogel matrix + NSCs complex system used for the reconstruction of spinal cord tissue after injury. Since such a complex approach (a combination of tissue engineering and cell therapy), in our opinion, allows not only to creation of conditions for supporting endogenous regeneration or mechanical reconstruction of the spinal cord, but also to strengthen endogenous regeneration, prevent the spread of the inflammatory process, and promote the restoration of lost reflex, motor and sensory functions of the injured area of spinal cord.

A review: oligodendrocytes in neuronal axonal conduction and methods for enhancing their performance

OBJECTIVES

This review explores the vital role of oligodendrocytes in axon myelination and efficient neuronal transmission and the impact of dysfunction resulting from neurotransmitter deficiencies related disorders. Furthermore, the review also provides insight into the potential of bionanotechnology for addressing neurodegenerative diseases by targeting oligodendrocytes.

METHODS

A review of literature in the field was conducted using Google scholar. Systematic searches were performed to identify relevant studies and reviews addressing the role of oligodendrocytes in neural function, the influence of neurotransmitters on oligodendrocyte differentiation, and the potential of nanotechnology-based strategies for targeted therapy of oligodendrocytes.

RESULTS

This review indicates the mechanisms underlying oligodendrocyte differentiation and the influence of neurotransmitters on this process. The importance of action potentials and neurotransmission in neural function and the susceptibility of damaged nerve axons to ischemic or toxic damage is provided in detail. The potential of bionanotechnology for targeting neurodegenerative diseases using nanotechnology-based strategies, including polymeric, lipid-based, inorganic, organic, and biomimetic nanoparticles, suggests better management of neurodegenerative disorders.

CONCLUSION

While nanotechnology-based biomaterials show promise for targeted oligodendrocyte therapy in addressing neurodegenerative disorders linked to oligodendrocyte dysfunction, encapsulating neuroprotective agents within nanoparticles offers additional advantages. Nano-based delivery systems effectively protect drugs from degradation and prolong their therapeutic effects, holding promise in overcoming the blood-brain barrier by facilitating drug transport. However, a multifaceted approach is essential to enhance oligodendrocyte differentiation, promote myelin repair, and facilitate myelin dynamics with reduced toxicity. Further research is needed to elucidate the optimal therapeutic approaches and enhance patient outcomes.

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.

Recent Advances in Alginate-Based Hydrogels for Cell Transplantation Applications

With its exceptional biocompatibility, alginate emerged as a highly promising biomaterial for a large range of applications in regenerative medicine. Whether in the form of microparticles, injectable hydrogels, rigid scaffolds, or bioinks, alginate provides a versatile platform for encapsulating cells and fostering an optimal environment to enhance cell viability. This review aims to highlight recent studies utilizing alginate in diverse formulations for cell transplantation, offering insights into its efficacy in treating various diseases and injuries within the field of regenerative medicine.

Decellularized extracellular matrix-based composite scaffolds for tissue engineering and regenerative medicine

Despite the considerable advancements in fabricating polymeric-based scaffolds for tissue engineering, the clinical transformation of these scaffolds remained a big challenge because of the difficulty of simulating native organs/tissues' microenvironment. As a kind of natural tissue-derived biomaterials, decellularized extracellular matrix (dECM)-based scaffolds have gained attention due to their unique biomimetic properties, providing a specific microenvironment suitable for promoting cell proliferation, migration, attachment and regulating differentiation. The medical applications of dECM-based scaffolds have addressed critical challenges, including poor mechanical strength and insufficient stability. For promoting the reconstruction of damaged tissues or organs, different types of dECM-based composite platforms have been designed to mimic tissue microenvironment, including by integrating with natural polymer or/and syntenic polymer or adding bioactive factors. In this review, we summarized the research progress of dECM-based composite scaffolds in regenerative medicine, highlighting the critical challenges and future perspectives related to the medical application of these composite materials.

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.

Recent progress in functional modification and crosslinking of bioprosthetic heart valves

Valvular heart disease (VHD), clinically manifested as stenosis and regurgitation of native heart valve, is one of the most prevalent cardiovascular diseases with high mortality. Heart valve replacement surgery has been recognized as golden standard for the treatment of VHD. Owing to the clinical application of transcatheter heart valve replacement technic and the excellent hemodynamic performance of bioprosthetic heart valves (BHVs), implantation of BHVs has been increasing over recent years and gradually became the preferred choice for the treatment of VHD. However, BHVs might fail within 10-15 years due to structural valvular degeneration (SVD), which was greatly associated with drawbacks of glutaraldehyde crosslinked BHVs, including cytotoxicity, calcification, component degradation, mechanical failure, thrombosis and immune response. To prolong the service life of BHVs, much effort has been devoted to overcoming the drawbacks of BHVs and reducing the risk of SVD. In this review, we summarized and analyzed the research and progress on: (i) modification strategies based on glutaraldehyde crosslinked BHVs and (ii) nonglutaraldehyde crosslinking strategies for BHVs.

Encapsulation of Human Spinal Cord Progenitor Cells in Hyaluronan-Gelatin Hydrogel for Spinal Cord Injury Treatment

Transplanting human induced pluripotent stem cells (iPSCs)-derived spinal cord progenitor cells (SCPCs) is a promising approach to treat spinal cord injuries. However, stem cell therapies face challenges in cell survival, cell localization to the targeted site, and the control of cell differentiation. Here, we encapsulated SCPCs in thiol-modified hyaluronan-gelatin hydrogels and optimized scaffold mechanical properties and cell encapsulation density to promote cell viability and neuronal differentiation in vitro and in vivo. Different compositions of hyaluronan-gelatin hydrogels formulated by varying concentrations of poly(ethylene glycol) diacrylate were mechanically characterized by using atomic force microscopy. In vitro SCPC encapsulation study showed higher cell viability and proliferation with lower substrate Young's modulus (200 Pa vs 580 Pa) and cell density. Moreover, the soft hydrogels facilitated a higher degree of neuronal differentiation with extended filament structures in contrast to clumped cellular morphologies obtained in stiff hydrogels (p < 0.01). When transplanted in vivo, the optimized SCPC-encapsulated hydrogels resulted in higher cell survival and localization at the transplanted region as compared to cell delivery without hydrogel encapsulation at 2 weeks postimplantation within the rat spinal cord (p < 0.01). Notably, immunostaining demonstrated that the hydrogel-encapsulated SCPCs differentiated along the neuronal and oligodendroglial lineages in vivo. The lack of pluripotency and proliferation also supported the safety of the SCPC transplantation approach. Overall, the injectable hyaluronan-gelatin hydrogel shows promise in supporting the survival and neural differentiation of human SCPCs after transplantation into the spinal cord.

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.

Developmental stage of transplanted neural progenitor cells influences anatomical and functional outcomes after spinal cord injury in mice

Neural progenitor cell (NPC) transplantation is a promising therapeutic strategy for replacing lost neurons following spinal cord injury (SCI). However, how graft cellular composition influences regeneration and synaptogenesis of host axon populations, or recovery of motor and sensory functions after SCI, is poorly understood. We transplanted developmentally-restricted spinal cord NPCs, isolated from E11.5-E13.5 mouse embryos, into sites of adult mouse SCI and analyzed graft axon outgrowth, cellular composition, host axon regeneration, and behavior. Earlier-stage grafts exhibited greater axon outgrowth, enrichment for ventral spinal cord interneurons and Group-Z spinal interneurons, and enhanced host 5-HT+ axon regeneration. Later-stage grafts were enriched for late-born dorsal horn interneuronal subtypes and Group-N spinal interneurons, supported more extensive host CGRP+ axon ingrowth, and exacerbated thermal hypersensitivity. Locomotor function was not affected by any type of NPC graft. These findings showcase the role of spinal cord graft cellular composition in determining anatomical and functional outcomes following SCI.

Restoration of spinal cord injury: From endogenous repairing process to cellular therapy

Spinal cord injury (SCI) disrupts neurological pathways and impacts sensory, motor, and autonomic nerve function. There is no effective treatment for SCI currently. Numerous endogenous cells, including astrocytes, macrophages/microglia, and oligodendrocyte, are involved in the histological healing process following SCI. By interfering with cells during the SCI repair process, some advancements in the therapy of SCI have been realized. Nevertheless, the endogenous cell types engaged in SCI repair and the current difficulties these cells confront in the therapy of SCI are poorly defined, and the mechanisms underlying them are little understood. In order to better understand SCI and create new therapeutic strategies and enhance the clinical translation of SCI repair, we have comprehensively listed the endogenous cells involved in SCI repair and summarized the six most common mechanisms involved in SCI repair, including limiting the inflammatory response, protecting the spared spinal cord, enhancing myelination, facilitating neovascularization, producing neurotrophic factors, and differentiating into neural/colloidal cell lines.

Construction of a mineralized collagen nerve conduit for peripheral nerve injury repair

A new nerve guidance conduits (NGCs) named MC@Col containing Type I collagen (Col) and mineralized collagen (MC) was developed, enhancing mechanical and degradation behavior. The physicochemical properties, the mechanical properties and in vitro degradation behavior were all evaluated. The adhesion and proliferation of Schwann cells (SCs) were observed. In the in vivo experiment, MC@Col NGC and other conduits including Col, chitosan (CST) and polycaprolactone (PCL) conduit were implanted to repair a 10-mm-long Sprague-Dawley rat's sciatic nerve defect. Histological analyses, morphological analyses, electrophysiological analyses and further gait analyses were all evaluated after implantation in 12 weeks. The strength and degradation performance of the MC@Col NGC were improved by the addition of MC in comparison with pure Col NGC. In vitro cytocompatibility evaluation revealed that the SCs had good viability, attachment and proliferation in the MC@Col. In in vivo results, the regenerative outcomes of MC@Col NGC were close to those by an autologous nerve graft in some respects, but superior to those by Col, CST and PCL conduits. The MC@Col NGC exhibited good mechanical performance as well as biocompatibility to bridge nerve gap and guide nerve regeneration, thus showing great promising potential as a new type of conduit in clinical applications.