Clinical Study of NeuroRegen Scaffold Combined With Human Mesenchymal Stem Cells for the Repair of Chronic Complete Spinal Cord Injury

Revisiting the Emerging Role of Light-Based Therapies in the Management of Spinal Cord Injuries

The surge in spinal cord injuries (SCI) attracted many neurobiologists to explore the underlying complex pathophysiology and to offer better therapeutic outcomes. The multimodal approaches to therapy in SCI have proven to be effective but to a limited extent. The clinical basics involve invasive procedures and limited therapeutic interventions, and most preclinical studies and formulations are yet to be translated due to numerous factors. In recent years, photobiomodulation therapy (PBMT) has found many applications in various medical fields. In most PBMT, studies on SCI have employed laser sources in experimental animal models as a non-invasive source. PBMT has been applied in numerous facets of SCI pathophysiology, especially attenuation of neuroinflammatory cascades, enhanced neuronal regeneration, reduced apoptosis and gliosis, and increased behavioral recovery within a short span. Although PBMT is specific in modulating mitochondrial bioenergetics, innumerous molecular pathways such as JAK-STAT, PI3K-AKT, NF-κB, MAPK, JNK/TLR/MYD88, ERK/CREB, TGF-β/SMAD, GSK3β-AKT-β-catenin, and AMPK/PGC-1α/TFAM signaling pathways have been or are yet to be exploited. PMBT has been effective not only in cell-specific actions in SCI such as astrocyte activation or microglial polarization or alterations in neuronal pathology but also modulated overall pathobiology in SCI animals such as rapid behavioral recovery. The goal of this review is to summarize research that has used PBMT for various models of SCI in different animals, including clarifying its mechanisms and prospective molecular pathways that may be utilized for better therapeutic outcomes.

Potential of hyaluronic acid and collagen-based scaffolds in promoting stem cell neuronal differentiation for neuroregenerative therapies: A review

Stem cell therapy has revolutionized neurodegenerative disease treatment by presenting promising medical applications. Despite their potential, stem cell therapy remains constrained by various limitations, including low differentiation efficiency, difficulties in guiding differentiation, proliferation control, shorter half-life of growth factors, experimental reproducibility, etc. The cellular niche environment is pivotal in effective differentiation of stem cells. Neural regeneration ventures require biomaterial-based 3D scaffolds to simulate in-vivo tissue to solve the niche environment problem. Recent breakthroughs in neural regeneration have led to the development of a biomimetic scaffolds made of Hyaluronic acid (HA) and collagen (COL) that imitate the CNS's extracellular matrix (ECM) for better neural regeneration and repair. HA and COL based scaffold creates a favourable microenvironment for cellular migration, proliferation and survival of the embedded stem cells and promotes neural regeneration. HA regulates cellular activities while COL contributes in healing CNS injuries. Therefore, the utilization of HA-COL based scaffolds is appropriate for regulating cellular responses and behaviour for neural regeneration. This review investigates the synergy between HA and COL in the context of neural-specific applications for repair, regeneration, and recovery as well as augmentation of bioactivity through fabrication techniques such as 3D bioprinting, electrospinning, etc. for neural tissue regeneration.

Designing hydrogel for application in spinal surgery

Spinal diseases and injuries are prevalent in clinical settings and impose a substantial burden on healthcare systems. Current treatments for spinal diseases are predominantly limited to surgical interventions, drug injections, and conservative treatments. Generally, these treatment modalities have limited or no long-term benefits. Hydrogel-based treatments have emerged as potentially powerful paradigms for improving therapeutic outcomes and the quality of life of patients. Hydrogels can be injected into target sites, including the epidural, intraspinal, and nucleus pulposus spaces, in a minimally invasive manner and fill defects to provide mechanical support. Hydrogels can be designed for the localized and controlled delivery of pharmacological agents to enhance therapeutic effects and reduce adverse reactions. Hydrogels can act as structural supports for transplanted cells to improve cell survival, proliferation, and differentiation, as well as integration into adjacent host tissues. In this review, we summarize recent advances in the design of hydrogels for the treatment of spinal diseases and injuries commonly found in clinical settings, including intervertebral disc degeneration, spinal cord injury, and dural membrane injury. We introduce the design considerations for different hydrogel systems, including precursor polymers and crosslinking mechanisms. Herein, we discuss the therapeutic outcomes of these hydrogels in terms of providing mechanical support, delivering cells/bioactive agents, regulating local inflammation, and promoting tissue regeneration and functional recovery.

Biomaterial scaffold stiffness influences the foreign body reaction, tissue stiffness, angiogenesis and neuroregeneration in spinal cord injury

Biomaterial scaffold engineering presents great potential in promoting axonal regrowth after spinal cord injury (SCI), yet persistent challenges remain, including the surrounding host foreign body reaction and improper host-implant integration. Recent advances in mechanobiology spark interest in optimizing the mechanical properties of biomaterial scaffolds to alleviate the foreign body reaction and facilitate seamless integration. The impact of scaffold stiffness on injured spinal cords has not been thoroughly investigated. Herein, we introduce stiffness-varied alginate anisotropic capillary hydrogel scaffolds implanted into adult rat C5 spinal cords post-lateral hemisection. Four weeks post-implantation, scaffolds with a stiffness approaching that of the spinal cord effectively minimize the host foreign body reaction via yes-associated protein (YAP) nuclear translocation. Concurrently, the softest scaffolds maximize cell infiltration and angiogenesis, fostering significant axonal regrowth but limiting the rostral-caudal linear growth. Furthermore, as measured by atomic force microscopy (AFM), the surrounding spinal cord softens when in contact with the stiffest scaffold while maintaining a physiological level in contact with the softest one. In conclusion, our findings underscore the pivotal role of stiffness in scaffold engineering for SCI in vivo, paving the way for the optimal development of efficacious biomaterial scaffolds for tissue engineering in the central nervous system.

Advances and New Therapies in Traumatic Spinal Cord Injury

Recovery from traumatic spinal cord injury (tSCI) is challenging due to the limited regenerative capacity of the central nervous system to restore cells, myelin, and neural connections. At the clinical level, the fundamental pillars of treatment are the reduction in secondary damage (neuroprotection) and rehabilitation; these are the tools we have to mitigate the disability caused by spinal cord injury (SCI). To date, the treatments on which neuroprotection has been based are the prevention of acute respiratory failure to avoid hypoxia, early hemodynamic control, neuroprotective drugs and surgical management. Optimizing early hemodynamic control to ensure adequate spinal cord perfusion may be key to the management of SCI. While neuroprotective agents like methylprednisolone have fallen into disuse, several promising therapies are currently being tested in clinical trials. In terms of surgical treatment, although their impact on neurological recovery remains debated, appropriate early bone decompression followed by duroplasty in selected cases is increasingly recommended. Advances in cell therapies hold significant potential for enhancing both clinical and functional outcomes in SCI patients. Moreover, emerging neuromodulation techniques, such as transcutaneous and epidural stimulation, along with innovations in rehabilitation technologies-such as robotic systems and exoskeletons-are becoming indispensable tools for improving locomotion and overall mobility in individuals with SCI. This article provides an update on the advances in neuroprotection against secondary damage caused by tSCI, in cellular therapies, and in new rehabilitation therapies.

Additive manufacturing in spatial patterning for spinal cord injury treatment

Combinatorial treatments integrating cells and biomolecules within scaffolds have been investigated to address the multifactorial nature of spinal cord injury (SCI). Current regenerative treatments have been ineffective as they do not consider the spatial positions of various cell types to effectively form functional neural pathways. Emulating the complex heterogeneity of cells in the native spinal cord requires translating the existing biological understanding of spatial patterning in neural development, as well as the influence of biomolecule and mechanical patterning on regional specification and axonal regeneration, to engineer a scaffold for spinal cord regeneration. This review explores the potential of 3D bioprinting to precisely control material, cell and drug patterns in scaffolds, achieving spatial phenotype specification and providing axonal guidance to form appropriate connections. We also discuss the application of extrusion-based and digital light processing bioprinting in integrating mechanical, chemical and biological cues within a scaffold to advance spatially patterned 3D bioprinted scaffold, as well as current challenges and future perspectives in these bioengineering strategies.

Treatment of spinal cord injury with biomaterials and stem cell therapy in non-human primates and humans

Spinal cord injury results in the loss of sensory, motor, and autonomic functions, which almost always produces permanent physical disability. Thus, in the search for more effective treatments than those already applied for years, which are not entirely efficient, researches have been able to demonstrate the potential of biological strategies using biomaterials to tissue manufacturing through bioengineering and stem cell therapy as a neuroregenerative approach, seeking to promote neuronal recovery after spinal cord injury. Each of these strategies has been developed and meticulously evaluated in several animal models with the aim of analyzing the potential of interventions for neuronal repair and, consequently, boosting functional recovery. Although the majority of experimental research has been conducted in rodents, there is increasing recognition of the importance, and need, of evaluating the safety and efficacy of these interventions in non-human primates before moving to clinical trials involving therapies potentially promising in humans. This article is a literature review from databases (PubMed, Science Direct, Elsevier, Scielo, Redalyc, Cochrane, and NCBI) from 10 years ago to date, using keywords (spinal cord injury, cell therapy, non-human primates, humans, and bioengineering in spinal cord injury). From 110 retrieved articles, after two selection rounds based on inclusion and exclusion criteria, 21 articles were analyzed. Thus, this review arises from the need to recognize the experimental therapeutic advances applied in non-human primates and even humans, aimed at deepening these strategies and identifying the advantages and influence of the results on extrapolation for clinical applicability in humans.

Mesenchymal stromal cell therapies for traumatic neurological injuries

Improved treatment options are urgently needed for neurological injuries resulting from trauma or iatrogenic events causing long-term disabilities that severely impact patients' quality of life. In vitro and animal studies have provided promising proof-of-concept examples of regenerative therapies using mesenchymal stromal cells (MSC) for a wide range of pathological conditions. Over the previous decade, various MSC-based therapies have been investigated in clinical trials to treat traumatic neurological injuries. However, while the safety and feasibility of MSC treatments has been established, the patient outcomes in these studies have not demonstrated significant success in the translation of MSC regenerative therapy for the treatment of human brain and spinal cord injuries. Herein, we have reviewed the literature and ongoing registered trials on the application of MSC for the treatment of traumatic brain injury, traumatic spinal cord injury, and peripheral nerve injury. We have focused on the shortcomings and technological hurdles that must be overcome to further advance clinical research to phase 3 trials, and we discuss recent advancements that represent potential solutions to these obstacles to progress.

Regenerative medicine approaches for the treatment of spinal cord injuries: Progress and challenges

Spinal cord injury (SCI) is a profound medical condition that significantly hampers motor function, imposing substantial limitations on daily activities and exerting a considerable financial burden on patients and their families. The constrained regenerative capacity of endogenous spinal cord tissue, exacerbated by the inflammatory response following the initial trauma, poses a formidable obstacle to effective therapy. Recent advancements in the field, stem cells, biomaterials, and molecular therapy, show promising outcomes. This review provides a comprehensive analysis of tissue engineering and regenerative medicine approaches for SCI treatment, including cell transplantation, tissue-engineered construct implantation, and other potential therapeutic strategies. Additionally, it sheds light on preclinical animal studies and recent clinical trials incorporating these modalities, providing a glimpse into the evolving landscape of SCI management. STATEMENT OF SIGNIFICANCE: The investigation into spinal cord injury (SCI) treatments focuses on reducing long-term impacts by targeting scar inhibition and enhancing regeneration through stem cells, with or without growth factors. Induced pluripotent stem cells (iPSCs) show promise for autologous use, with clinical trials confirming their safety. Challenges include low cell viability and difficulty in targeted differentiation. Biomaterial scaffolds hold potential for improving cell viability and integration, and extracellular vesicles (EVs) are emerging as a novel therapy. While EV research is in its early stages, stem cell trials demonstrate safety and potential recovery. Advancing tissue engineering approaches with biomaterial scaffolds is crucial for human trials.

Biomaterial-mediated delivery of traditional Chinese medicine ingredients for spinal cord injury: a systematic review

Objective

Biomaterials loaded with ingredients derived from traditional Chinese medicine (TCM) are viewed as a promising strategy for treating spinal cord injury (SCI). However, a comprehensive analysis of the existing literature on this topic has not yet been conducted. Therefore, this paper systematically reviews researches related to this approach, aiming to identify gaps and shortcomings in the field.

Methods

PubMed, EMBASE, Web of Science, Chinese Biomedical Literature, Wanfang, and China National Knowledge Infrastructure (CNKI) were searched for retrieving studies on biomaterials loaded with TCM ingredients published from their inception to October 2024. Two reviewers performed screening of search results, information extraction, and literature quality assessment independently.

Results

For this systematic review, 41 publications were included. Six TCM ingredients-paclitaxel, curcumin, tetramethylpyrazine, resveratrol, berberine, and tanshinone IIA were combined with biomaterials for treatment of SCI. Biomaterials were categorized into hydrogels, biodegradable scaffolds, nanoparticles, and microspheres according to the type of scaffold. These drug delivery systems exhibit commendable biocompatibility, drug-loading capacity, and drug-release capabilities, and in combination with TCM ingredients, synergistically contribute to anti-oxidative stress, anti-inflammatory, neuroprotective, and anti-apoptotic effects.

Conclusion

These studies demonstrated the efficacy of biomaterials loaded with TCM ingredients in facilitating motor function recovery and neuroprotection in SCI rats, providing evidence for future research. However, in the complex microenvironment of SCI, achieving the maximum drug loading capacity of TCM ingredients within biomaterials, along with sustained and controlled release to fully exert their pharmacological effects, remains a major challenge for future research.

Systematic Review Registration

https://www.crd.york.ac.uk/PROSPERO/ identifier CRD42024505000.

Progression of mesenchymal stem cell regulation on imbalanced microenvironment after spinal cord injury

Spinal cord injury (SCI) results in significant neural damage and inhibition of axonal regeneration due to an imbalanced microenvironment. Extensive evidence supports the efficacy of mesenchymal stem cell (MSC) transplantation as a therapeutic approach for SCI. This review aims to present an overview of MSC regulation on the imbalanced microenvironment following SCI, specifically focusing on inflammation, neurotrophy and axonal regeneration. The application, limitations and future prospects of MSC transplantation are discussed as well. Generally, a comprehensive perspective is provided for the clinical translation of MSC transplantation for SCI.

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.

Nanomedicine in Neuroprotection, Neuroregeneration, and Blood-Brain Barrier Modulation: A Narrative Review

Nanomedicine is a newer, promising approach to promote neuroprotection, neuroregeneration, and modulation of the blood-brain barrier. This review includes the integration of various nanomaterials in neurological disorders. In addition, gelatin-based hydrogels, which have huge potential due to biocompatibility, maintenance of porosity, and enhanced neural process outgrowth, are reviewed. Chemical modification of these hydrogels, especially with guanidine moieties, has shown improved neuron viability and underscores tailored biomaterial design in neural applications. This review further discusses strategies to modulate the blood-brain barrier-a factor critically associated with the effective delivery of drugs to the central nervous system. These advances bring supportive solutions to the solving of neurological conditions and innovative therapies for their treatment. Nanomedicine, as applied to neuroscience, presents a significant leap forward in new therapeutic strategies that might help raise the treatment and management of neurological disorders to much better levels. Our aim was to summarize the current state-of-knowledge in this field.

Biomimetic Dual-Network Collagen Fibers with Porous and Mechanical Cues Reconstruct Neural Stem Cell Niche via AKT/YAP Mechanotransduction after Spinal Cord Injury

Tissue engineering scaffolds can mediate the maneuverability of neural stem cell (NSC) niche to influence NSC behavior, such as cell self-renewal, proliferation, and differentiation direction, showing the promising application in spinal cord injury (SCI) repair. Here, dual-network porous collagen fibers (PCFS) are developed as neurogenesis scaffolds by employing biomimetic plasma ammonia oxidase catalysis and conventional amidation cross-linking. Following optimizing the mechanical parameters of PCFS, the well-matched Young's modulus and physiological dynamic adaptability of PCFS (4.0 wt%) have been identified as a neurogenetic exciter after SCI. Remarkably, porous topographies and curving wall-like protrusions are generated on the surface of PCFS by simple and non-toxic CO2 bubble-water replacement. As expected, PCFS with porous and matched mechanical properties can considerably activate the cadherin receptor of NSCs and induce a series of serine-threonine kinase/yes-associated protein mechanotransduction signal pathways, encouraging cellular orientation, neuron differentiation, and adhesion. In SCI rats, implanted PCFS with matched mechanical properties further integrated into the injured spinal cords, inhibited the inflammatory progression and decreased glial and fibrous scar formation. Wall-like protrusions of PCFS drive multiple neuron subtypes formation and even functional neural circuits, suggesting a viable therapeutic strategy for nerve regeneration and functional recovery after SCI.

Research progress and prospects of benefit-risk assessment methods for umbilical cord mesenchymal stem cell transplantation in the clinical treatment of spinal cord injury

Over the past decade, we have witnessed the development of cell transplantation as a new strategy for repairing spinal cord injury (SCI). However, due to the complexity of the central nervous system (CNS), achieving successful clinical translation remains a significant challenge. Human umbilical cord mesenchymal stem cells (hUMSCs) possess distinct advantages, such as easy collection, lack of ethical concerns, high self-renewal ability, multilineage differentiation potential, and immunomodulatory properties. hUMSCs are promising for regenerating the injured spinal cord to a significant extent. At the same time, for advancing SCI treatment, the appropriate benefit and risk evaluation methods play a pivotal role in determining the clinical applicability of treatment plans. Hence, this study discusses the advantages and risks of hUMSCs in SCI treatment across four dimensions-comprehensive evaluation of motor and sensory function, imaging, electrophysiology, and autonomic nervous system (ANS) function-aiming to improve the rationality of relevant clinical research and the feasibility of clinical translation.

Decellularized extracellular matrix enriched with GDNF enhances neurogenesis and remyelination for improved motor recovery after spinal cord injury

Motor functional improvement represents a paramount treatment objective in the post-spinal cord injury (SCI) recovery process. However, neuronal cell death and axonal degeneration following SCI disrupt neural signaling, impeding the motor functional recovery. In this study, we developed a multifunctional decellularized spinal cord-derived extracellular matrix (dSECM), crosslinked with glial cell-derived neurotrophic factor (GDNF), to promote differentiation of stem cells into neural-like cells and facilitate axonogenesis and remyelination. After decellularization, the immunogenic cellular components were effectively removed in dSECM, while the crucial protein components were retained which supports stem cells proliferation and differentiation. Furthermore, sustained release of GDNF from the dSECM facilitated axonogenesis and remyelination by activating the PI3K/Akt and MEK/Erk pathways. Our findings demonstrate that the dSECM-GDNF platform promotes neurogenesis, axonogenesis, and remyelination to enhance neural signaling, thereby yielding promising therapeutic effects for motor functional improvement after SCI. STATEMENT OF SIGNIFICANCE: The dSECM promotes the proliferation and differentiation of MSCs or NSCs by retaining proteins associated with positive regulation of neurogenesis and neuronal differentiation, while eliminating proteins related to negative regulation of neurogenesis. After crosslinking, GDNF can be gradually released from the platform, thereby promoting neural differentiation, axonogenesis, and remyelination to enhance neural signaling through activation of the PI3K/Akt and MEK/Erk pathways. In vivo experiments demonstrated that dSECM-GDNF/MSC@GelMA hydrogel exhibited the ability to facilitate neuronal regeneration at 4 weeks post-surgery, while promoting axonogenesis and remyelination at 8 weeks post-surgery, ultimately leading to enhanced motor functional recovery. This study elucidates the ability of neural regeneration strategy to promote motor functional recovery and provides a promising approach for designing multifunctional tissue for SCI treatment.

Construction of functional neural network tissue combining CBD-NT3-modified linear-ordered collagen scaffold and TrkC-modified iPSC-derived neural stem cells for spinal cord injury repair

Induced pluripotent stem cells (iPSCs) can be personalized and differentiated into neural stem cells (NSCs), thereby effectively providing a source of transplanted cells for spinal cord injury (SCI). To further improve the repair efficiency of SCI, we designed a functional neural network tissue based on TrkC-modified iPSC-derived NSCs and a CBD-NT3-modified linear-ordered collagen scaffold (LOCS). We confirmed that transplantation of this tissue regenerated neurons and synapses, improved the microenvironment of the injured area, enhanced remodeling of the extracellular matrix, and promoted functional recovery of the hind limbs in a rat SCI model with complete transection. RNA sequencing and metabolomic analyses also confirmed the repair effect of this tissue from multiple perspectives and revealed its potential mechanism for treating SCI. Together, we constructed a functional neural network tissue using human iPSCs-derived NSCs as seed cells based on the interaction of receptors and ligands for the first time. This tissue can effectively improve the therapeutic effect of SCI, thus confirming the feasibility of human iPSCs-derived NSCs and LOCS for SCI repair and providing a valuable direction for SCI research.

Encapsulation of the growth factor neurotrophin-3 in heparinised poloxamer hydrogel stabilises bioactivity and provides sustained release

Poloxamer-based hydrogels show promise to stabilise and sustain the delivery of growth factors in tissue engineering applications, such as following spinal cord injury. Typically, growth factors such as neurotrophin-3 (NT-3) degrade rapidly in solution. Similarly, poloxamer hydrogels also degrade readily and are, therefore, only capable of sustaining the release of a payload over a small number of days. In this study, we focused on optimising a hydrogel formulation, incorporating both poloxamer 188 and 407, for the sustained delivery of bioactive NT-3. Hyaluronic acid blended into the hydrogels significantly reduced the degradation of the gel. We identified an optimal hydrogel composition consisting of 20 % w/w poloxamer 407, 5 % w/w poloxamer 188, 0.6 % w/w NaCl, and 1.5 % w/w hyaluronic acid. Heparin was chemically bound to the poloxamer chains to enhance interactions between the hydrogel and the growth factor. The unmodified and heparin-modified hydrogels exhibited sustained release of NT-3 for 28 days while preserving the bioactivity of NT-3. Moreover, these hydrogels demonstrated excellent cytocompatibility and had properties suitable for injection into the intrathecal space, underscoring their suitability as a growth factor delivery system. The findings presented here contribute valuable insights to the development of effective delivery strategies for therapeutic growth factors for tissue engineering approaches, including the treatment of spinal cord injury.

Improved Recovery of Complete Spinal Cord Transection by a Plasma-Modified Fibrillar Scaffold

Complete spinal cord injury causes an irreversible disruption in the central nervous system, leading to motor, sensory, and autonomic function loss, and a secondary injury that constitutes a physical barrier preventing tissue repair. Tissue engineering scaffolds are presented as a permissive platform for cell migration and the reconnection of spared tissue. Iodine-doped plasma pyrrole polymer (pPPy-I), a neuroprotective material, was applied to polylactic acid (PLA) fibers and implanted in a rat complete spinal cord transection injury model to evaluate whether the resulting composite implants provided structural and functional recovery, using magnetic resonance (MR) imaging, diffusion tensor imaging and tractography, magnetic resonance spectroscopy, locomotion analysis, histology, and immunofluorescence. In vivo, MR studies evidenced a tissue response to the implant, demonstrating that the fibrillar composite scaffold moderated the structural effects of secondary damage by providing mechanical stability to the lesion core, tissue reconstruction, and significant motor recovery. Histologic analyses demonstrated that the composite scaffold provided a permissive environment for cell attachment and neural tissue guidance over the fibers, reducing cyst formation. These results supply evidence that pPPy-I enhanced the properties of PLA fibrillar scaffolds as a promising treatment for spinal cord injury recovery.

Current status and future perspectives on stem cell transplantation for spinal cord injury

BACKGROUND

Previous assessments of stem cell therapy for spinal cord injuries (SCI) have encountered challenges and constraints. Current research primarily emphasizes safety in early-phase clinical trials, while systematic reviews prioritize effectiveness, often overlooking safety and translational feasibility. This situation prompts inquiries regarding the readiness for clinical adoption.

AIM

To offer an up-to-date systematic literature review of clinical trial results con cerning stem cell therapy for SCI.

METHODS

A systematic search was conducted across major medical databases [PubMed, Embase, Reference Citation Analysis (RCA), and Cochrane Library] up to October 14, 2023. The search strategy utilized relevant Medical Subject Heading (MeSH) terms and keywords related to "spinal cord", "injury", "clinical trials", "stem cells", "functional outcomes", and "adverse events". Studies included in this review consisted of randomized controlled trials and non-randomized controlled trials reporting on the use of stem cell therapies for the treatment of SCI.

RESULTS

In a comprehensive review of 66 studies on stem cell therapies for SCI, 496 papers were initially identified, with 237 chosen for full-text analysis. Among them, 236 were deemed eligible after excluding 170 for various reasons. These studies encompassed 1086 patients with varying SCI levels, with cervical injuries being the most common (42.2%). Bone marrow stem cells were the predominant stem cell type used (71.1%), with various administration methods. Follow-up durations averaged around 84.4 months. The 32.7% of patients showed functional impro vement from American spinal injury association Impairment Scale (AIS) A to B, 40.8% from AIS A to C, 5.3% from AIS A to D, and 2.1% from AIS B to C. Sensory improvements were observed in 30.9% of patients. A relatively small number of adverse events were recorded, including fever (15.1%), headaches (4.3%), muscle tension (3.1%), and dizziness (2.6%), highlighting the potential for SCI recovery with stem cell therapy.

CONCLUSION

In the realm of SCI treatment, stem cell-based therapies show promise, but clinical trials reveal potential adverse events and limitations, underscoring the need for meticulous optimization of transplantation conditions and parameters, caution against swift clinical implementation, a deeper understanding of SCI pathophysiology, and addressing ethical, tumorigenicity, immunogenicity, and immunotoxicity concerns before gradual and careful adoption in clinical practice.

Combined transplantation of hiPSC-NSC and hMSC ameliorated neuroinflammation and promoted neuroregeneration in acute spinal cord injury

BACKGROUND

Spinal cord injury (SCI) is a serious clinical condition that has pathological changes such as increased neuroinflammation and nerve tissue damage, which eventually manifests as fibrosis of the injured segment and the development of a spinal cord cavity leading to loss of function. Cell-based therapy, such as mesenchymal stem cells (MSCs) and neural stem cells (NSCs) are promising treatment strategies for spinal cord injury via immunological regulation and neural replacement respectively. However, therapeutic efficacy is rare reported on combined transplantation of MSC and NSC in acute mice spinal cord injury even the potential reinforcement might be foreseen. Therefore, this study was conducted to investigate the safety and efficacy of co-transplanting of MSC and NSC sheets into an SCI mice model on the locomotor function and pathological changes of injured spinal cord.

METHODS

To evaluate the therapeutic effects of combination cells, acute SCI mice model were established and combined transplantation of hiPSC-NSCs and hMSCs into the lesion site immediately after the injury. Basso mouse scale was used to perform the open-field tests of hind limb motor function at days post-operation (dpo) 1, 3, 5, and 7 after SCI and every week after surgery. Spinal cord and serum samples were collected at dpo 7, 14, and 28 to detect inflammatory and neurotrophic factors. Hematoxylin-eosin (H&E) staining, masson staining and transmission electron microscopy were used to evaluate the morphological changes, fibrosis area and ultrastructure of the spinal cord.

RESULT

M&N transplantation reduced fibrosis formation and the inflammation level while promoting the secretion of nerve growth factor and brain-derived neurotrophic factor. We observed significant reduction in damaged tissue and cavity area, with dramatic improvement in the M&N group. Compared with the Con group, the M&N group exhibited significantly improved behaviors, particularly limb coordination.

CONCLUSION

Combined transplantation of hiPSC-NSC and hMSC could significantly ameliorate neuroinflammation, promote neuroregeneration, and decrease spinal fibrosis degree in safe and effective pattern, which would be indicated as a novel potential cell treatment option.

Biomaterials and Cell Therapy Combination in Central Nervous System Treatments

Current pharmacological and surgical therapies for the central nervous system (CNS) show a limited capacity to reduce the damage progression; that together with the intrinsic limited capability of the CNS to regenerate greatly reduces the hopes of recovery. Among all the therapies proposed, the tissue engineering strategies supplemented with therapeutic stem cells remain the most promising. Neural tissue engineering strategies are based on the development of devices presenting optimal physical, chemical, and mechanical properties which, once inserted in the injured site, can support therapeutic cells, limiting the effect of a hostile environment and supporting regenerative processes. Thus, this review focuses on the employment of hydrogel and nanofibrous scaffolds supplemented with stem cells as promising therapeutic tools for the central and peripheral nervous systems in preclinical and clinical applications.

Mesenchymal Stem Cells for the Treatment of Spinal Cord Injury in Rat Models: A Systematic Review and Network Meta-Analysis

Transplantation of mesenchymal stem cells (MSCs) is one of the hopeful treatments for spinal cord injury (SCI). Most current studies are in animals, and less in humans, and the optimal transplantation strategy for MSCs is still controversial. In this article, we explore the optimal transplantation strategy of MSCs through a network meta-analysis of the effects of MSCs on SCI in animal models. PubMed, Web of Science, Cochrane Library, Embase, China National Knowledge Infrastructure (CNKI), Wanfang Database, China Science and Technology Journal Database (VIP), and Chinese Biomedical Literature Service System (SinoMed) databases were searched by computer for randomized controlled studies on MSCs for SCI. Two investigators independently completed the literature screening and data extraction based on the inclusion and exclusion criteria. RevMan 5.4 software was used to assess the quality of the included literature. Stata 16.0 software was used for standard meta-analysis and network meta-analysis. Standardized mean difference (SMD) was used for continuous variables to combine the statistics and calculate 95% confidence interval (95% CI). P < 0.05 was considered a statistically significant difference. Cochrane's Q test and the I2 value were used to indicate the magnitude of heterogeneity. A random-effects model was used if I2 > 50% and P < 0.10 indicated significant heterogeneity between studies, and conversely, a fixed-effects model was used. Evidence network diagrams were drawn based on direct comparisons between various interventions. The surface under the cumulative ranking curve area (SUCRA) was used to predict the ranking of the treatment effects of each intervention. A total of 32 animal studies were included in this article for analysis. The results of the standard meta-analysis showed that MSCs improved motor ability after SCI. The network meta-analysis showed that the best treatment effect was achieved for adipose tissue-derived mesenchymal stromal cells (ADMSCs) in terms of cell source and intrathecal (IT) in terms of transplantation modality. For transplantation timing, the best treatment effect was achieved when transplantation was performed in the subacute phase. The available literature suggests that IT transplantation using ADMSCs in the subacute phase may be the best transplantation strategy to improve functional impairment after SCI. Future high-quality studies are still needed to further validate the results of this study to ensure the reliability of the results.

Mimicked Spinal Cord Fibers Trigger Axonal Regeneration and Remyelination after Injury

Spinal cord injury (SCI) causes tissue structure damage and composition changes of the neural parenchyma, resulting in severe consequences for spinal cord function. Mimicking the components and microstructure of spinal cord tissues holds promise for restoring the regenerative microenvironment after SCI. Here, we have utilized electrospinning technology to develop aligned decellularized spinal cord fibers (A-DSCF) without requiring synthetic polymers or organic solvents. A-DSCF preserves multiple types of spinal cord extracellular matrix proteins and forms a parallel-oriented structure. Compared to aligned collagen fibers (A-CF), A-DSCF exhibits stronger mechanical properties, improved enzymatic stability, and superior functionality in the adhesion, proliferation, axonal extension, and myelination of differentiated neural progenitor cells (NPCs). Notably, axon extension or myelination has been primarily linked to Agrin (AGRN), Laminin (LN), or Collagen type IV (COL IV) proteins in A-DSCF. When transplanted into rats with complete SCI, A-DSCF loaded with NPCs improves the survival, maturation, axon regeneration, and motor function of the SCI rats. These findings highlight the potential of structurally and compositionally biomimetic scaffolds to promote axonal extension and remyelination after SCI.

Microvascular endothelial cells derived from spinal cord promote spinal cord injury repair

Neural regeneration after spinal cord injury (SCI) closely relates to the microvascular endothelial cell (MEC)-mediated neurovascular unit formation. However, the effects of central nerve system-derived MECs on neovascularization and neurogenesis, and potential signaling involved therein, are unclear. Here, we established a primary spinal cord-derived MECs (SCMECs) isolation with high cell yield and purity to describe the differences with brain-derived MECs (BMECs) and their therapeutic effects on SCI. Transcriptomics and proteomics revealed differentially expressed genes and proteins in SCMECs were involved in angiogenesis, immunity, metabolism, and cell adhesion molecular signaling was the only signaling pathway enriched of top 10 in differentially expressed genes and proteins KEGG analysis. SCMECs and BMECs could be induced angiogenesis by different stiffness stimulation of PEG hydrogels with elastic modulus 50-1650 Pa for SCMECs and 50-300 Pa for BMECs, respectively. Moreover, SCMECs and BMECs promoted spinal cord or brain-derived NSC (SNSC/BNSC) proliferation, migration, and differentiation at different levels. At certain dose, SCMECs in combination with the NeuroRegen scaffold, showed higher effectiveness in the promotion of vascular reconstruction. The potential underlying mechanism of this phenomenon may through VEGF/AKT/eNOS- signaling pathway, and consequently accelerated neuronal regeneration and functional recovery of SCI rats compared to BMECs. Our findings suggested a promising role of SCMECs in restoring vascularization and neural regeneration.

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.

Advances in Microgravity Directed Tissue Engineering

Tissue engineering aims to generate functional biological substitutes to repair, sustain, improve, or replace tissue function affected by disease. With the rapid development of space science, the application of simulated microgravity has become an active topic in the field of tissue engineering. There is a growing body of evidence demonstrating that microgravity offers excellent advantages for tissue engineering by modulating cellular morphology, metabolism, secretion, proliferation, and stem cell differentiation. To date, there have been many achievements in constructing bioartificial spheroids, organoids, or tissue analogs with or without scaffolds in vitro under simulated microgravity conditions. Herein, the current status, recent advances, challenges, and prospects of microgravity related to tissue engineering are reviewed. Current simulated-microgravity devices and cutting-edge advances of microgravity for biomaterials-dependent or biomaterials-independent tissue engineering to offer a reference for guiding further exploration of simulated microgravity strategies to produce engineered tissues are summarized and discussed.

Neuroplasticity and regeneration after spinal cord injury

Spinal cord injury (SCI) is a debilitating condition with significant personal, societal, and economic burden. The highest proportion of traumatic injuries occur at the cervical level, which results in severe sensorimotor and autonomic deficits. Following the initial physical damage associated with traumatic injuries, secondary pro-inflammatory, excitotoxic, and ischemic cascades are initiated further contributing to neuronal and glial cell death. Additionally, emerging evidence has begun to reveal that spinal interneurons undergo subtype specific neuroplastic circuit rearrangements in the weeks to months following SCI, contributing to or hindering functional recovery. The current therapeutic guidelines and standards of care for SCI patients include early surgery, hemodynamic regulation, and rehabilitation. Additionally, preclinical work and ongoing clinical trials have begun exploring neuroregenerative strategies utilizing endogenous neural stem/progenitor cells, stem cell transplantation, combinatorial approaches, and direct cell reprogramming. This review will focus on emerging cellular and noncellular regenerative therapies with an overview of the current available strategies, the role of interneurons in plasticity, and the exciting research avenues enhancing tissue repair following SCI.

Stem cell-based combinatorial therapies for spinal cord injury: a narrative review of current research and future directions

Spinal cord injury (SCI) is a devastating condition that can result in lifelong disability. Despite significant progress in SCI research, current treatments only offer limited functional recovery. Stem cell-based combinatorial therapies have emerged promising to enhance neural repair and regeneration after SCI. Combining stem cells with growth factors, biomaterials, and other therapeutic agents can improve outcomes by providing a multifaceted approach to neural repair. However, several challenges must be addressed before these therapies can be widely adopted in clinical practice. Standardisation of stem cell isolation, characterisation, and production protocols ensures consistency and safety in clinical trials. Developing appropriate animal models that accurately mimic human SCI is crucial for successfully translating these therapies. Additionally, optimal delivery methods and biomaterials that support the survival and integration of stem cells into injured tissue must be identified. Despite these challenges, stem cell-based combinatorial therapies for SCI hold great promise. Innovative approaches such as gene editing and the use of neural tissue engineering may further enhance the efficacy of these therapies. Further research and development in this area are critical to advancing the field and providing effective therapies for SCI patients. This paper discusses the current evidence and challenges from the literature on the potential of stem cell-based combinatorial therapies for SCI.

Mesenchymal Stem Cell Therapy in Traumatic Spinal Cord Injury: A Systematic Review

Recovery from a traumatic spinal cord injury (TSCI) is challenging due to the limited regenerative capacity of the central nervous system to restore cells, myelin, and neural connections. Cell therapy, particularly with mesenchymal stem cells (MSCs), holds significant promise for TSCI treatment. This systematic review aims to analyze the efficacy, safety, and therapeutic potential of MSC-based cell therapies in TSCI. A comprehensive search of PUBMED and COCHRANE databases until February 2023 was conducted, combining terms such as "spinal cord injury," "stem cells," "stem cell therapy," "mesenchymal stem cells," and "traumatic spinal cord injury". Among the 53 studies initially identified, 22 (21 clinical trials and 1 case series) were included. Findings from these studies consistently demonstrate improvements in AIS (ASIA Impairment Scale) grades, sensory scores, and, to a lesser extent, motor scores. Meta-analyses further support these positive outcomes. MSC-based therapies have shown short- and medium-term safety, as indicated by the absence of significant adverse events within the studied timeframe. However, caution is required when drawing generalized recommendations due to the limited scientific evidence available. Further research is needed to elucidate the long-term safety and clinical implications of these advancements. Although significant progress has been made, particularly with MSC-based therapies, additional studies exploring other potential future therapies such as gene therapies, neurostimulation techniques, and tissue engineering approaches are essential for a comprehensive understanding of the evolving TSCI treatment landscape.

Bibliometric analysis of stem cells for spinal cord injury: current status and emerging frontiers

Background: This study aimed to conduct a bibliometric analysis of the literature on stem cell therapy for spinal cord injury to visualize the research status, identify hotspots, and explore the development trends in this field. Methods: We searched the Web of Science Core Collection database using relevant keywords ("stem cells" and "spinal cord injury") and retrieved the published literature between 2000 and 2022. Data such as journal title, author information, institutional affiliation, country, and keywords were extracted. Afterwards, we performed bibliometric analysis of the retrieved data using Bibliometrix, VOSviewer, and CiteSpace. Results: A total of 5375 articles related to stem cell therapy for spinal cord injury were retrieved, and both the annual publication volume and the cumulative publication volume showed an upward trend. neural regeneration research was the journal with the most publications and the fastest cumulative publication growth (162 articles), Okano Hideyuki was the author with the highest number of publications and citations (114 articles), Sun Yat-sen University was the institution with the highest number of publications (420 articles), and China was the country with the highest number of publications (5357 articles). However, different authors, institutions, and countries need to enhance their cooperation in order to promote the generation of significant academic achievements. Current research in this field has focused on stem cell transplantation, neural regeneration, motor function recovery, exosomes, and tissue engineering. Meanwhile, future research directions are primarily concerned with the molecular mechanisms, safety, clinical trials, exosomes, scaffolds, hydrogels, and inflammatory responses of stem cell therapy for spinal cord injuries. Conclusion: In summary, this study provided a comprehensive analysis of the current research status and frontiers of stem cell therapy for spinal cord injury. The findings provide a foundation for future research and clinical translation efforts of stem cell therapy in this field.

Clinical utility of mesenchymal stem/stromal cells in regenerative medicine and cellular therapy

Mesenchymal stem/stromal cells (MSCs) have been carefully examined to have tremendous potential in regenerative medicine. With their immunomodulatory and regenerative properties, MSCs have numerous applications within the clinical sector. MSCs have the properties of multilineage differentiation, paracrine signaling, and can be isolated from various tissues, which makes them a key candidate for applications in numerous organ systems. To accentuate the importance of MSC therapy for a range of clinical indications, this review highlights MSC-specific studies on the musculoskeletal, nervous, cardiovascular, and immune systems where most trials are reported. Furthermore, an updated list of the different types of MSCs used in clinical trials, as well as the key characteristics of each type of MSCs are included. Many of the studies mentioned revolve around the properties of MSC, such as exosome usage and MSC co-cultures with other cell types. It is worth noting that MSC clinical usage is not limited to these four systems, and MSCs continue to be tested to repair, regenerate, or modulate other diseased or injured organ systems. This review provides an updated compilation of MSCs in clinical trials that paves the way for improvement in the field of MSC therapy.

Cell therapies for spinal cord injury: a review of the clinical trials and cell-type therapeutic potential

Spinal cord injury (SCI) is an as yet untreatable neuropathology that causes severe dysfunction and disability. Cell-based therapies hold neuroregenerative and neuroprotective potential, but, although being studied in SCI patients for more than two decades, long-term efficacy and safety remain unproven, and which cell types result in higher neurological and functional recovery remains under debate. In a comprehensive scoping review of 142 reports and registries of SCI cell-based clinical trials, we addressed the current therapeutical trends and critically analysed the strengths and limitations of the studies. Schwann cells, olfactory ensheathing cells (OECs), macrophages and various types of stem cells have been tested, as well as combinations of these and other cells. A comparative analysis between the reported outcomes of each cell type was performed, according to gold-standard efficacy outcome measures like the ASIA impairment scale, motor and sensory scores. Most of the trials were in the early phases of clinical development (phase I/II), involved patients with complete chronic injuries of traumatic aetiology and did not display a randomized comparative control arm. Bone marrow stem cells and OECs were the most commonly tested cells, while open surgery and injection were the main methods of delivering cells into the spinal cord or submeningeal spaces. Transplantation of support cells, such as OECs and Schwann cells, resulted in the highest ASIA Impairment Scale (AIS) grade conversion rates (improvements in ∼40% of transplanted patients), which surpassed the spontaneous improvement rate expected for complete chronic SCI patients within 1 year post-injury (5-20%). Some stem cells, such as peripheral blood-isolated and neural stem cells, offer potential for improving patient recovery. Complementary treatments, particularly post-transplantation rehabilitation regimes, may contribute highly to neurological and functional recovery. However, unbiased comparisons between the tested therapies are difficult to draw, given the great heterogeneity of the design and outcome measures used in the SCI cell-based clinical trials and how these are reported. It is therefore crucial to standardize these trials when aiming for higher value clinical evidence-based conclusions.

Collagen for neural tissue engineering: Materials, strategies, and challenges

Neural tissue engineering (NTE) has made remarkable strides in recent years and holds great promise for treating several devastating neurological disorders. Selecting optimal scaffolding material is crucial for NET design strategies that enable neural and non-neural cell differentiation and axonal growth. Collagen is extensively employed in NTE applications due to the inherent resistance of the nervous system against regeneration, functionalized with neurotrophic factors, antagonists of neural growth inhibitors, and other neural growth-promoting agents. Recent advancements in integrating collagen with manufacturing strategies, such as scaffolding, electrospinning, and 3D bioprinting, provide localized trophic support, guide cell alignment, and protect neural cells from immune activity. This review categorises and analyses collagen-based processing techniques investigated for neural-specific applications, highlighting their strengths and weaknesses in repair, regeneration, and recovery. We also evaluate the potential prospects and challenges of using collagen-based biomaterials in NTE. Overall, this review offers a comprehensive and systematic framework for the rational evaluation and applications of collagen in NTE.

Role of regulatory T cells in spinal cord injury

Spinal cord injury is an intricate process involving a series of multi-temporal and multi-component pathological events, among which inflammatory response is the core. Thus, it is crucial to find a way to prevent the damaging effects of the inflammatory response. The research has found that Treg cells can suppress the activation, proliferation, and effector functions of many parenchymal cells by multiple mechanisms. This review discusses how Treg cells regulate the inflammatory cells to promote spinal cord recovery. These parenchymal cells include macrophages/microglia, oligodendrocytes, astrocytes, and others. In addition, we discuss the adverse role of Treg cells, the status of treatment, and the prospects of cell-based therapies after spinal cord injury. In conclusion, this review provides an overview of the regulatory role of Treg cells in spinal cord injury. We hope to offer new insights into the treatment of spinal cord injury.

Biomimetic engineered approaches for neural tissue engineering: Spinal cord injury

The healing process for spinal cord injuries is complex and presents many challenges. Current advances in nerve regeneration are based on promising tissue engineering techniques, However, the chances of success depend on better mimicking the extracellular matrix (ECM) of neural tissue and better supporting neurons in a three-dimensional environment. The ECM provides excellent biological conditions, including desirable morphological features, electrical conductivity, and chemical compositions for neuron attachment, proliferation and function. This review outlines the rationale for developing a construct for neuron regrowth in spinal cord injury using appropriate biomaterials and scaffolding techniques.

The application of 3D-bioprinted scaffolds for neuronal regeneration after traumatic spinal cord injury - A systematic review of preclinical in vivo studies

BACKGROUND

The implantation of 3D-bioprinted scaffolds represents a promising therapeutic approach for traumatic Spinal Cord Injury (SCI), currently investigating in preclinical in vivo studies. However, a systematic review of the relevant literature has not been performed to date. Hence, we systematically reviewed the outcomes of the application of 3D-bioprinted implants in the treatment of SCI based on studies conducted on experimental animal models.

METHODS

We searched PubMed, Scopus, Web of Science, and Cochrane Library databases. Manuscripts in other designs than in vivo preclinical study and written in other languages than English were excluded. A risk of bias assessment was performed using SYRCLE's tool. The quality of included articles was assessed by ARRIVE guidelines. Extracted data were synthesized only qualitatively because the data were not suitable for conducting the meta-analysis.

RESULTS

Overall, eleven animal studies reporting on the transection SCI rat model were included. Six of included studies investigated 3D-bioprinted scaffolds enriched with stem cells, two studies - 3D-bioprinted scaffolds combined with growth factors, and three studies - stand-alone 3D-bioprinted scaffolds. In all included studies the application of 3D-bioprinted scaffolds led to significant improvement in functional scores compared with no treated SCI rats. The functional recovery corresponded with the changes observed at the injury site in histological analyses. Seven studies demonstrated medium, three studies - high, and one study - low risk of bias. Moreover, some of the included studies were conducted in the same scientific center. The overall quality assessment ratio amounted to 0.60, which was considered average quality.

CONCLUSION

The results of our systematic review suggest that 3D-bioprinted scaffolds may be a feasible therapeutic approach for the treatment of SCI. Further evidence obtained on other experimental SCI models is necessary before the clinical translation of 3D-bioprinted scaffolds.

Clinical Trials Targeting Secondary Damage after Traumatic Spinal Cord Injury

Spinal cord injury (SCI) often causes loss of sensory and motor function resulting in a significant reduction in quality of life for patients. Currently, no therapies are available that can repair spinal cord tissue. After the primary SCI, an acute inflammatory response induces further tissue damage in a process known as secondary injury. Targeting secondary injury to prevent additional tissue damage during the acute and subacute phases of SCI represents a promising strategy to improve patient outcomes. Here, we review clinical trials of neuroprotective therapeutics expected to mitigate secondary injury, focusing primarily on those in the last decade. The strategies discussed are broadly categorized as acute-phase procedural/surgical interventions, systemically delivered pharmacological agents, and cell-based therapies. In addition, we summarize the potential for combinatorial therapies and considerations.

Current Concepts of Biomaterial Scaffolds and Regenerative Therapy for Spinal Cord Injury

Spinal cord injury (SCI) is a catastrophic condition associated with significant neurological deficit and social and financial burdens. It is currently being managed symptomatically, with no real therapeutic strategies available. In recent years, a number of innovative regenerative strategies have emerged and have been continuously investigated in preclinical research and clinical trials. In the near future, several more are expected to come down the translational pipeline. Among ongoing and completed trials are those reporting the use of biomaterial scaffolds. The advancements in biomaterial technology, combined with stem cell therapy or other regenerative therapy, can now accelerate the progress of promising novel therapeutic strategies from bench to bedside. Various types of approaches to regeneration therapy for SCI have been combined with the use of supportive biomaterial scaffolds as a drug and cell delivery system to facilitate favorable cell-material interactions and the supportive effect of neuroprotection. In this review, we summarize some of the most recent insights of preclinical and clinical studies using biomaterial scaffolds in regenerative therapy for SCI and summarized the biomaterial strategies for treatment with simplified results data. One hundred and sixty-eight articles were selected in the present review, in which we focused on biomaterial scaffolds. We conducted our search of articles using PubMed and Medline, a medical database. We used a combination of "Spinal cord injury" and ["Biomaterial", or "Scaffold"] as search terms and searched articles published up until 30 April 2022. Successful future therapies will require these biomaterial scaffolds and other synergistic approaches to address the persistent barriers to regeneration, including glial scarring, the loss of a structural framework, and biocompatibility. This database could serve as a benchmark to progress in future clinical trials for SCI using biomaterial scaffolds.

Systematic Evaluation of Spinal Cord Injury Animal Models in the Field of Biomaterials

The large number of animal models used in spinal cord injury (SCI) research complicates the objective selection of the most appropriate model to investigate the efficacy of biomaterial-based therapies. This systematic review aims to identify a list of relevant animal models of SCI by evaluating the confirmation of SCI and animal survival in all published SCI models used in biomaterials research up until April 2021. A search in PubMed and Embase based on "spinal cord injury," "animal models," and "biomaterials" yielded 4606 papers, 393 of which were further evaluated. A total of 404 individual animal experiments were identified based on type of SCI, level of SCI, and the sex, species, and strain of the animals used. Finally, a total of 149 unique animal models were comparatively evaluated, which led to the generation of an evidence-based list of well-documented mid-thoracic rat models of SCI. These models were used most often, clearly confirmed SCI, and had relatively high survival rates, and therefore could serve as a future starting point for studying novel biomaterial-based therapies for SCI. Furthermore, the review discusses (1) the possible risk of bias in SCI animal models, (2) the difficulty in replication of such experiments due to frequent poor reporting of the methods and results, and (3) the clinical relevance of the currently utilized models. Systematic review registration: The study was prospectively registered in PROSPERO, registration number CRD42019141162. Impact statement Studies on biomaterial-based therapies within the field of spinal cord injury (SCI) research show a large inconsistency concerning the selection of animal models. This review goes beyond summarizing the existing gaps between experimental and clinical SCI by systematically evaluating all animal models used within this field. The models identified by this work were used most often, clearly confirmed SCI, and had a relatively high survival rate. This evidence-based list of well-documented animal models will serve as a practical guideline in future research on innovative biomaterial-based therapies for SCI.

A Biomimetic Nonwoven-Reinforced Hydrogel for Spinal Cord Injury Repair

In clinical trials, new scaffolds for regeneration after spinal cord injury (SCI) should reflect the importance of a mechanically optimised, hydrated environment. Composite scaffolds of nonwovens, self-assembling peptides (SAPs) and hydrogels offer the ability to mimic native spinal cord tissue, promote aligned tissue regeneration and tailor mechanical properties. This work studies the effects of an aligned electrospun nonwoven of P11-8—enriched poly(ε-caprolactone) (PCL) fibres, integrated with a photo-crosslinked hydrogel of glycidylmethacrylated collagen (collagen-GMA), on neurite extension. Mechanical properties of collagen-GMA hydrogel in compression and shear were recorded, along with cell viability. Collagen-GMA hydrogels showed J-shaped stress–strain curves in compression, mimicking native spinal cord tissue. For hydrogels prepared with a 0.8-1.1 wt.% collagen-GMA concentration, strain at break values were 68 ± 1–81 ± 1% (±SE); maximum stress values were 128 ± 9–311 ± 18 kPa (±SE); and maximum force values were 1.0 ± 0.1–2.5 ± 0.1 N (±SE). These values closely mimicked the compression values for feline and porcine tissue in the literature, especially those for 0.8 wt.%. Complex shear modulus values fell in the range 345–2588 Pa, with the lower modulus hydrogels in the range optimal for neural cell survival and growth. Collagen-GMA hydrogel provided an environment for homogenous and three-dimensional cell encapsulation, and high cell viability of 84 ± 2%. Combination of the aligned PCL/P11-8 electrospun nonwoven and collagen-GMA hydrogel retained fibre alignment and pore structure, respectively, and promoted aligned neurite extension of PC12 cells. Thus, it is possible to conclude that scaffolds with mechanical properties that both closely mimic native spinal cord tissue and are optimal for neural cells can be produced, which also promote aligned tissue regeneration when the benefits of hydrogels and electrospun nonwovens are combined.

Clinical translation of stem cell therapy for spinal cord injury still premature: results from a single-arm meta-analysis based on 62 clinical trials

BACKGROUND

How much scientific evidence is there to show that stem cell therapy is sufficient in preclinical and clinical studies of spinal cord injury before it is translated into clinical practice? This is a complicated problem. A single, small-sample clinical trial is difficult to answer, and accurate insights into this question can only be given by systematically evaluating all the existing evidence.

METHODS

The PubMed, Ovid-Embase, Web of Science, and Cochrane databases were searched from inception to February 10, 2022. Two independent reviewers performed the literature search, identified and screened the studies, and performed a quality assessment and data extraction.

RESULTS

In total, 62 studies involving 2439 patients were included in the analysis. Of these, 42 were single-arm studies, and 20 were controlled studies. The meta-analysis showed that stem cells improved the ASIA impairment scale score by at least one grade in 48.9% [40.8%, 56.9%] of patients with spinal cord injury. Moreover, the rate of improvement in urinary and gastrointestinal system function was 42.1% [27.6%, 57.2%] and 52.0% [23.6%, 79.8%], respectively. However, 28 types of adverse effects were observed to occur due to stem cells and transplantation procedures. Of these, neuropathic pain, abnormal feeling, muscle spasms, vomiting, and urinary tract infection were the most common, with an incidence of > 20%. While no serious adverse effects such as tumorigenesis were reported, this could be due to the insufficient follow-up period.

CONCLUSIONS

Overall, the results demonstrated that although the efficacy of stem cell therapy is encouraging, the subsequent adverse effects remain concerning. In addition, the clinical trials had problems such as small sample sizes, poor design, and lack of prospective registration, control, and blinding. Therefore, the current evidence is not sufficiently strong to support the clinical translation of stem cell therapy for spinal cord injury, and several problems remain. Additional well-designed animal experiments and high-quality clinical studies are warranted to address these issues.

Placental-based allograft use for tissue regeneration and scar prevention for neurosurgical wounds

Tweetable abstract Proper wound healing, including internal and surface tissue regeneration with the minimization of scar formation, is one of the most significant topics in surgical discussions and EpiFix^® dehydrated human amnion/chorion membrane allograft promotes healthy healing.

Can a Scaffold Enriched with Mesenchymal Stem Cells Be a Good Treatment for Spinal Cord Injury?

Spinal cord injury (SCI) is a worldwide highly crippling disease that can lead to the loss of motor and sensory neurons. Among the most promising therapies, there are new techniques of tissue engineering based on stem cells that promote neuronal regeneration. Among the different types of stem cells, mesenchymal stem cells (MSCs) seem the most promising. Indeed, MSCs are able to release trophic factors and to differentiate into the cell types that can be found in the spinal cord. Currently, the most common procedure to insert cells in the lesion site is infusion. However, this causes a low rate of survival and engraftment in the lesion site. For these reasons, tissue engineering is focusing on bioresorbable scaffolds to help the cells to stay in situ. Scaffolds do not only have a passive role but become fundamental for the trophic support of cells and the promotion of neuroregeneration. More and more types of materials are being studied as scaffolds to decrease inflammation and increase the engraftment as well as the survival of the cells. Our review aims to highlight how the use of scaffolds made from biomaterials enriched with MSCs gives positive results in in vivo SCI models as well as the first evidence obtained in clinical trials.

Safety and Clinical Efficacy of Mesenchymal Stem Cell Treatment in Traumatic Spinal Cord Injury, Multiple Sclerosis and Ischemic Stroke - A Systematic Review and Meta-Analysis

Background

Mesenchymal stem cells (MSCs) is an attractive candidate in regenerative research and clinical trials have assessed their therapeutic potential in different neurological conditions with disparate etiologies. In this systematic review, we aimed to assess safety and clinical effect of MSC treatment in traumatic spinal cord injury (TSCI), multiple sclerosis (MS) and ischemic stroke (IS).

Methods

A systematic search was performed 2021-12-10 in MEDLINE, EMBASE, Web of Science and Cochrane where clinical studies assessing MSC treatment in TSCI, MS or IS were included. Studies without control group were excluded for efficacy analysis, but included in the safety analysis. For efficacy, AIS score, EDSS score and mRS were used as clinical endpoints and assessed in a meta-analysis using the random effects model.

Findings

Of 5,548 identified records, 54 studies were included. Twenty-six studies assessed MSC treatment in TSCI, 14 in MS and nine in IS, of which seven, seven and five studies were controlled, respectively. There were seven serious adverse events (SAEs), of which four were related to the surgical procedure and included one death due to complications following the implantation of MSCs. Three SAEs were considered directly related to the MSC treatment and all these had a transient course. In TSCI, a meta-analysis showed no difference in conversion from AIS A to C and a trend toward more patients treated with MSCs improving from AIS A to B as compared to controls (p = 0.05). A subgroup analysis performed per protocol, showed more MSC treated patients improving from AIS A to C in studies including patients within 8 weeks after injury (p = 0.04). In MS and IS, there were no significant differences in clinical outcomes between MSC treated patients and controls as measured by EDSS and mRS, respectively.

Interpretation

MSC-treatment is safe in patients with TSCI, MS and IS, although surgical implantation of MSC led to one fatal outcome in TSCI. There was no clear clinical benefit of MSC treatment, but this is not necessarily a proof of inefficacy due to the low number of controlled studies. Future studies assessing efficacy of MSC treatment should aim to do this in randomized, controlled studies.

Application of Collagen-Based Scaffolds for the Treatment of Spinal Cord Injuries in Animal Models: A Literature Update

SCI is regarded as one of the most devastating central nervous system (CNS) injuries, exhibiting an alarmingly rising incidence rate, indirectly connected with the expansion of the global economy. The consequences of SCI are multidimensional: SCI injuries may result in permanent voluntary motor dysfunction and loss of sensation while incurring heavy economic and psychological burdens as part of the treatment. Thus, it is crucial to develop effective and suitable SCI treatment strategies. Collagen-based scaffold application is one of the most promising methods of SCI treatment.

This review compiles newer bibliographical data regarding the application of collagen scaffolds for the treatment of Spinal cord injury (SCI) in animal models. Recently, several relevant studies have been carried out using carefully selected animals with similar pathophysiology to humans. In mouse, rat and canine models that have undergone transection or hemisection, the stump connection, the transplanted cell differentiation, and the elimination of glial scar are promising. Also, encouraging results have been found regarding the increased neuronal growth, the decreased collagen deposition, the behavioral recovery, the improved electrophysiology, and the enhanced axonal regeneration. 

Distinct Glycosylation Responses to Spinal Cord Injury in Regenerative and Nonregenerative Models

Traumatic spinal cord injury (SCI) results in disruption of tissue integrity and loss of function. We hypothesize that glycosylation has a role in determining the occurrence of regeneration and that biomaterial treatment can influence this glycosylation response. We investigated the glycosylation response to spinal cord transection in Xenopus laevis and rat. Transected rats received an aligned collagen hydrogel. The response compared regenerative success, regenerative failure, and treatment in an established nonregenerative mammalian system. In a healthy rat spinal cord, ultraperformance liquid chromatography (UPLC) N-glycoprofiling identified complex, hybrid, and oligomannose N-glycans. Following rat SCI, complex and outer-arm fucosylated glycans decreased while oligomannose and hybrid structures increased. Sialic acid was associated with microglia/macrophages following SCI. Treatment with aligned collagen hydrogel had a minimal effect on the glycosylation response. In Xenopus, lectin histochemistry revealed increased levels of N-acetyl-glucosamine (GlcNAc) in premetamorphic animals. The addition of GlcNAc is required for processing complex-type glycans and is a necessary foundation for additional branching. A large increase in sialic acid was observed in nonregenerative animals. This work suggests that glycosylation may influence regenerative success. In particular, loss of complex glycans in rat spinal cord may contribute to regeneration failure. Targeting the glycosylation response may be a promising strategy for future therapies.