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

Gelatin Methacrylic Acid Hydrogel-Based Nerve Growth Factors Enhances Neural Stem Cell Growth and Differentiation to Promote Repair of Spinal Cord Injury

Background

The challenge in treating irreversible nerve tissue damage has resulted in suboptimal outcomes for spinal cord injuries (SCI), underscoring the critical need for innovative treatment strategies to offer hope to patients.

Methods

In this study, gelatin methacrylic acid hydrogel scaffolds loaded with nerve growth factors (GMNF) were prepared and used to verify the performance of SCI. The physicochemical and biological properties of the GMNF were tested. The effect of GMNF on activity of neuronal progenitor cells (NPCs) was investigated in vitro. Histological staining and motor ability was carried out to assess the ability of SCI repair in SCI animal models.

Results

Achieving nerve growth factors sustained release, GMNF had good biocompatibility and could effectively penetrate into the cells with good targeting permeability. GMNF could better enhance the activity of NPCs and promote their directional differentiation into mature neuronal cells in vitro, which could exert a good neural repair function. In vivo, SCI mice treated with GMNF recovered their motor abilities more effectively and showed better wound healing by macroscopic observation of the coronal surface of their SCI area. Meanwhile, the immunohistochemistry demonstrated that the GMNF scaffolds effectively promoted SCI repair by better promoting the colonization and proliferation of neural stem cells (NSCs) in the SCI region and targeted differentiation into mature neurons.

Conclusion

The application of GMNF composite scaffolds shows great potential in SCI treatment, which are anticipated to be a potential therapeutic bioactive material for clinical application in repairing SCI in the future.

Bispecific FpFs: a versatile tool for preclinical antibody development

We previously described FpFs 1̲ (Fab-PEG-Fab) as binding mimetics of IgGs. FpFs are prepared with di(bis-sulfone) conjugation reagents 3̲ that undergo disulfide rebridging conjugation with the accessible disulfide of each Fab (Scheme 1). We have now prepared bispecific FpFs 2̲ (bsFpF and Fab1-PEG-Fab2) as potential bispecific antibody mimetics with the intent that bsFpFs could be used in preclinical antibody development since sourcing bispecific antibodies may be challenging during preclinical research. The di(bis-sulfone) reagent 3̲ was first used to prepare a bsFpF 2̲ by the sequential conjugation of a first Fab and then a second Fab to another target (Scheme 2). Seeking to improve bsFpF synthesis, the asymmetric conjugation reagent, bis-sulfone bis-sulfide 1̲6̲, with different thiol conjugation reactivities at each terminus (Scheme 4) was examined and the bsFpFs appeared to be formed at similar conversion to the di(bis-sulfone) reagent 3̲. To explore the advantages of using common intermediates in the preparation of bsFpF families, we investigated bsFpF synthesis with a protein conjugation-ligation approach (Scheme 5). Reagents with a bis-sulfone moiety for conjugation on one PEG terminus and a ligation moiety on the other terminus were examined. Bis-sulfone PEG trans-cyclooctene (TCO) 2̲8̲ and bis-sulfone PEG tetrazine (Tz) 3̲0̲ were used to prepare several bsFpFs targeting various therapeutic targets (TNF-α, IL6R, IL17, and VEGF) and tissue affinity targets (hyaluronic acid and collagen II). Surface plasmon resonance (SPR) binding studies indicated that there was little difference between the dissociation rate constant (k d) for the unmodified Fab, mono-conjugated PEG-Fab and the corresponding Fab in a bsFpF. The Fab association rate (k a) in the bsFpF was slower than for PEG-Fab, which may be because of mass differences that influence SPR results. These observations suggest that each Fab will bind to its target independently of the other Fab and that bsFpF binding profiles can be estimated using the corresponding PEG-Fab conjugates.

Carbohydrates and neurotrophic factors: A promising partnership for spinal cord injury rehabilitation

Spinal cord injury (SCI) leaves a temporary or enduring motor, sensory, and autonomic function loss, significantly impacting the patient's quality of life. Given their biocompatibility, bioactivity, and tunable attributes, three-dimensional scaffolds frequently employ carbohydrates to facilitate spinal cord regeneration. These scaffolds have also been engineered to be novel local delivery platforms that present distinct advantages in the targeted transportation of drug candidates to the damaged spinal cord, ensuring the right dosage and duration of administration. Neurotrophic factors have emerged as promising therapeutic candidates, preserved neuron survival and encouraged severed axons repair, although their local and continuous delivery is believed to produce considerable spinal cord rehabilitation. This study aims to discuss breakthroughs in scaffold engineering, exploiting carbohydrates as an essential part of their structure, and highlight their impact on spinal cord regeneration and sustained neurotrophic factors delivery to treat SCI.

Acellular spinal cord scaffold containing quercetin-encapsulated nanoparticles plays an anti-inflammatory role in functional recovery from spinal cord injury in rats

Inflammatory responses play a crucial role in the pathophysiology of spinal cord injury (SCI) and developing new approaches to establish an anti-inflammatory environment for the promotion of neuroregeneration holds promise as a potential approach. In this study, our aim was to investigate the potential of combining an acellular spinal cord scaffold (ASCS) with quercetin-loaded bovine serum albumin (Qu/BSA) nanoparticles (NPs) for the treatment of SCI. The ASCS was prepared using physical and chemical methods, while the Qu/BSA NPs were prepared through a desolvation technique. The NPs exhibited favorable characteristics, including a mean size of 203 nm, a zeta potential of -38, and an encapsulation efficiency of 96%. Microscopic evaluation confirmed the successful distribution of NPs on the walls of ASCS. Animal studies revealed that Qu/BSA NPs group exhibited a significant decrease in NLRP3, ASC, and Casp1 gene expression compared to the SCI group (p < 0.0001). The findings indicated a significant decrease in the NLRP3, ASC, and Casp1 protein level between the Qu/BSA/ASCS group and the SCI group (p < 0.0001). Moreover, treatment with ASCS containing either blank BSA (B/BSA) NPs or Qu/BSA NPs effectively promoted functional recovery via increasing the amount of nestin- and glial fibrillary acidic protein (GFAP)-positive cells in the site of injury. Notably, Qu/BSA/ASCS exhibited superior outcomes compared to B/BSA/ASCS. Overall, the combination of ASCS with the Qu delivery system presents a promising therapeutic approach for SCI by inhibiting inflammatory responses and promoting neuroregeneration, leading to the restoration of motor function in animals. This study demonstrates the potential of utilizing biomaterials and NPs to enhance the effectiveness of SCI treatment.

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.

Research hotspots and trends of microRNAs in spinal cord injury: a comprehensive bibliometric analysis

Background

Spinal cord injury (SCI) is a nervous system disease leading to motor and sensory dysfunction below the injury level, and can result in paralysis. MicroRNAs (miRNAs) play a key role in SCI treatment, and related research provides insights for SCI diagnosis and treatment. Bibliometrics is an important tool for literature statistics and evaluation, objectively summarizing multidimensional information. This study comprehensively overviews the field through bibliometric analysis of miRNA and SCI research, providing contemporary resources for future collaboration and clinical treatment.

Materials and methods

In this study, we searched the Web of Science Core Collection (WOSCC) database. After careful screening and data import, we extracted annual publications, citation counts, countries, institutions, authors, journals, highly cited articles, co-cited articles, keywords, and H-index. Bibliometrics and visualization analyses employed VOSviewer, CiteSpace, the R package "bibliometrix," and online analytic platforms. Using Arrowsmith, we determined miRNA-SCI relationships and discussed potential miRNA mechanisms in SCI.

Results

From 2008 to 2024, the number of related papers increased annually, reaching 754. The number of yearly publications remained high and entered a period of rapid development. Researchers from 50 countries/regions, 802 institutions, 278 journals, and 3,867 authors participated in the field. Currently, China has advantages in the number of national papers, citations, institutions, and authors. However, it is necessary to strengthen cooperation among different authors, institutions, and countries to promote the production of important academic achievements. The research in the field currently focuses on nerve injury, apoptosis, and gene expression. Future research directions mainly involve molecular mechanisms, clinical trials, exosomes, and inflammatory reactions.

Conclusion

Overall, this study comprehensively analyzes the research status and frontier of miRNAs in SCI. A systematic summary provides a complete and intuitive understanding of the relationship between SCI and miRNAs. The presented findings establish a basis for future research and clinical application in this field.

Injectable, self-healing hyaluronic acid-based hydrogels for spinal cord injury repair

The cystic cavity that develops following spinal cord injury is a major obstacle for repairing spinal cord injury (SCI). The injectable self-healing biomaterials treatment is a promising strategy to enhance tissue repair after traumatic spinal cord injury. Herein, a natural extracellular matrix (ECM) biopolymer hyaluronic acid-based hydrogel was developed based on multiple dynamic covalent bonds. The hydrogels exhibited excellent injectable and self-healing properties, could be effectively injected into the injury site, and filled the lesion cavity to accelerate the tissue repair of traumatic SCI. Moreover, the hydrogels were compatible with cells and various tissues and possessed proper stiffness matched with nervous tissue. Additionally, when implanted into the injured spinal cord site, the hyaluronic acid-based hydrogel promoted axonal regeneration and functional recovery by accelerating remyelination, axon regeneration, and angiogenesis. Overall, the injectable self-healing hyaluronic acid-based hydrogels are ideal biomaterials for treating traumatic SCI.

Injectable Hydrogels for Nervous Tissue Repair-A Brief Review

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

Zeolitic imidazole framework-8 loaded gelatin methacryloyl microneedles: A transdural and controlled-release drug delivery system attenuates neuroinflammation after spinal cord injury

Spinal cord injury (SCI) is a matter of significant clinical concern, often treated through early surgical decompression along with methylprednisolone sodium succinate (MPSS). However, the side effects and the unsatisfactory focal concentration of MPSS have limited its further applications. To address this limitation, herein, a versatile drug delivery system of zeolitic imidazole framework-8 (ZIF-8) and gelatin methacryloyl microneedles (GelMA MNs) was developed for stable, transdural, and controlled sustained release of drugs in SCI. The microneedles were used to create tiny pores in the dura mater, allowing for the direct administration of drugs into the spinal cord. ZIF-8 provided a secondary extended release once they were separated from the microneedles. To attenuate the neuroinflammation, MPSS was selected. Such a combination of ZIF-8 and GelMA MNs was able to prolong the release period of MPSS to five days. The system showed transdural capacity, reduction of M1 polarization, and decrease in NLRP3-positive inflammasome and proinflammatory cytokines. In vivo studies indicated that this novel drug delivery strategy could constrict the inflammatory microenvironment, reduce glial scar formation, and promote neural regeneration. Thus, this versatile drug delivery system provides an up-and-coming alternative for stable, transdural, and controlled sustained release of drugs to those suffering from SCI.

Hydrogel-encapsulated extracellular vesicles for the regeneration of spinal cord injury

Spinal cord injury (SCI) is a critical neurological condition that may impair motor, sensory, and autonomous functions. At the cellular level, inflammation, impairment of axonal regeneration, and neuronal death are responsible for SCI-related complications. Regarding the high mortality and morbidity rates associated with SCI, there is a need for effective treatment. Despite advances in SCI repair, an optimal treatment for complete recovery after SCI has not been found so far. Therefore, an effective strategy is needed to promote neuronal regeneration and repair after SCI. In recent years, regenerative treatments have become a potential option for achieving improved functional recovery after SCI by promoting the growth of new neurons, protecting surviving neurons, and preventing additional damage to the spinal cord. Transplantation of cells and cells-derived extracellular vesicles (EVs) can be effective for SCI recovery. However, there are some limitations and challenges related to cell-based strategies. Ethical concerns and limited efficacy due to the low survival rate, immune rejection, and tumor formation are limitations of cell-based therapies. Using EVs is a helpful strategy to overcome these limitations. It should be considered that short half-life, poor accumulation, rapid clearance, and difficulty in targeting specific tissues are limitations of EVs-based therapies. Hydrogel-encapsulated exosomes have overcome these limitations by enhancing the efficacy of exosomes through maintaining their bioactivity, protecting EVs from rapid clearance, and facilitating the sustained release of EVs at the target site. These hydrogel-encapsulated EVs can promote neuroregeneration through improving functional recovery, reducing inflammation, and enhancing neuronal regeneration after SCI. This review aims to provide an overview of the current research status, challenges, and future clinical opportunities of hydrogel-encapsulated EVs in the treatment of SCI.