Spinal Cord Regeneration Research Articles

Biphasic inflammation control by fibroblasts enables spinal cord regeneration in zebrafish.

Spinal cord regeneration remains challenging due to complex inflammatory microenvironments, imbalances in metal ions, and obstacles to neuronal regeneration following spinal cord injury (SCI). Herein, microglial cell membranes coated with zinc sulfide nanoparticles modified with albumin (ZnS@BSA@MM) were designed as an anti-inflammatory combined neuroprotective therapy for SCI. ZnS@BSA@MM NPs were constructed via albumin modification and membrane extrusion and exhibited ROS-scavenging abilities comparable to those of natural products and slow H2S release under acidic conditions. In vitro and in vivo experiments demonstrated the outstanding therapeutic effects of the ZnS@BSA@MM. In detail, the released H2S and Zn2+ not only inhibit microglial activation through the NF-κB signaling axis but also promote the axonal growth of neurons under pathological conditions. Notably, microglial cell membranes effectively deliver ZnS@BSA to the lesion area. Finally, ZnS@BSA@MM facilitated the axonal regeneration of neurons in SCI, suppressed inflammatory responses, and activated multiple pathways, including cytokine-cytokine receptor interactions, neuroactive ligand-receptor interactions, and cAMP signaling. Collectively, this work highlights the anti-inflammatory and neuroprotective effects of ZnS@BSA@MM NPs, featuring satisfactory H2S release and Zn2+ supplementation under membrane-targeting conditions for SCI therapy.

The formation of a functional nervous system during development and its maintenance in adulthood rely on precise regulation of neural stem cell (NSC) proliferation and differentiation. During neurogenesis, progenitor cells use various cellular and molecular mechanisms to balance these processes. Among these, dynamic signal encoding, specifically ultradian oscillations, which are regular protein fluctuations occurring over a few hours, has emerged as a key mechanism underlying NSC fate decisions. In adults, reactivation of quiescent NSCs, proliferation, and differentiation are also controlled by ultradian oscillations. Furthermore, these ultradian dynamics signals are modulated by microRNAs and are considered critical for the ability of neural progenitors to transition between different states. Altogether, these findings may have potential significance for our understanding of NSC reactivation and differentiation in the context of injury or neurodegeneration. The mammalian spinal cord harbours endogenous multipotent NSCs that respond to injury but mostly generate astrocytes and do not undergo neurogenesis. By contrast, many anamniotes regenerate spinal cord neurons from endogenous progenitors, despite the same molecular signalling pathways being activated, suggesting that subtle differences in how these pathways are regulated may result in different regenerative outcomes. Whether oscillatory dynamics could influence the reactivation and differentiation of NSCs upon spinal cord injury remains to be determined. This review explores the role of transcription factor ultradian oscillations in neurogenesis and how microRNAs modulate them. Additionally, we examine evidence for the role of ultradian dynamics in the reactivation of quiescent NSCs and their potential significance for regenerative neurogenesis in the context of spinal cord injury.

Spinal cord injury (SCI) poses a substantial physical, psychological and social burden. Although many therapies are currently available, it is still impossible to fully restore the lost organic functions of SCI patients. An important event in SCI physiopathology is the development of a neuron-repulsive fibrotic scar at the lesion site, a barrier that hampers neuronal growth and contributes to long-term functional impairment. This neuron-repulsive scar is present in severe spinal cord injuries in humans but is absent in some animals capable of natural regeneration. In humans and other mammals, various immune cells take part in the development and maturation of the glial scar, and cytokines and other molecular factors regulate the associated histologic changes. Pro-inflammatory cytokines and complement system proteins tend to be overexpressed early after SCI, but anti-inflammatory cytokines also participate in the remodelling of the injured tissue by regulating the excessively pro-inflammatory environment. This inflammatory regulation is not entirely successful in humans, and inflammation inhibitor drugs offer promising avenues for SCI treatment. Some non-specific immunosuppressor drugs have already been studied, but targeted modulation therapies may be more efficient and less prone to secondary effects. Continued experimental research and clinical trials are vital to advance findings and develop effective treatments, aiming to overcome the barriers to spinal cord regeneration and improve recovery for SCI patients.

The musculoskeletal system, essential for mobility, structural support, and organ protection, is frequently compromised by trauma, degenerative diseases, or tumors, profoundly impacting patients' quality of life. Adhesive hydrogels have emerged as pivotal biomaterials for orthopedic therapies, offering localized treatment with enhanced biocompatibility, tunable mechanics, and sustained bioactive delivery. While systemic drug administration often suffers from off-target effects, adhesive hydrogels enable precise tissue integration and microenvironmental modulation, addressing challenges such as infection control, tissue regeneration, and mechanical reinforcement. However, achieving optimal adhesion strength, dynamic mechanical matching, and selective tissue targeting remains a critical hurdle. Innovative strategies, including dynamic covalent bonds, stimuli-responsive networks, and multifunctional hybridization, have expanded hydrogel applications in diabetic wound healing, load-bearing bone repair, and spinal cord regeneration. For instance, injectable hydrogels with wet adhesion capabilities facilitate minimally invasive delivery, while drug-eluting systems localize chemotherapeutics to tumor sites, reducing systemic toxicity. Despite these advances, scalability, long-term stability, and clinical translation require further exploration. This review systematically examines the design principles, functional mechanisms, and therapeutic applications of adhesive hydrogels in orthopedics, emphasizing their role in bridging biomechanical demands with biological regeneration. We envision that interdisciplinary innovation in smart hydrogels will unlock personalized solutions, transforming the landscape of precision orthopedic medicine.

Abstract The white matter of the spinal cord is essential for sensory and motor signaling, and its proper development is crucial for establishing functional neuronal circuits. However, the mechanisms underlying white matter formation remain incompletely understood. We hypothesized that the extracellular matrix, particularly laminins, plays a key role in this process. The spatiotemporal expression patterns of laminins during spinal cord white matter development have not been fully characterized. Here, we examined the distribution and function of laminins during spinal cord development. Laminin 332 localized to the marginal zone of the spinal cord at embryonic days 12 (E12) and 14 (E14), coinciding with periods of extensive axonal growth. Immunohistochemical analysis revealed an increase in glial fibrillary acidic protein (GFAP)‐positive fibers in laminin 332‐enriched regions. Laminin 332 promoted GFAP expression in astrocyte precursor cells, an effect attenuated by integrin α6β4 blockade, suggesting that laminin 332 signals through integrins to support astrocyte maturation. Our findings indicate that laminin 332 not only serves as a structural component of the extracellular matrix but also actively regulates glial differentiation during spinal cord development. Understanding the signaling pathways mediated by laminin 332 may inform therapeutic strategies aimed at enhancing spinal cord regeneration by modulating astrocyte behavior and promoting axonal growth.

Glial cell crosstalk in the local microenvironment following spinal cord injury.

Neurons in distinct spinal cord segments serve specific functions, raising questions about whether human spinal cord-derived neural stem cells (hscNSCs) retain segment-specific properties crucial for spinal cord injury (SCI) repair. We established a culture system amplifying hscNSCs from cervical, thoracic, and lumbar segments, revealing segment-specific transcriptional profiles and differentiation potentials. Notably, thoracic hscNSCs exhibited elevated hepatocyte growth factor (HGF) expression inherited from the pre-ganglionic column, enhancing their differentiation into motor neurons. Transplantation of thoracic hscNSCs into thoracic SCI rat models demonstrated superior graft survival, neural regeneration, and functional recovery compared with cervical or lumbar counterparts. Thoracic hscNSCs reduced inflammation, minimized glial scar formation, and significantly improved locomotor function post-SCI. Our findings underscore the importance of segment-specific properties of hscNSCs in optimizing SCI repair outcomes, paving the way for tailored therapeutic strategies in spinal cord regeneration.

Spinal cord injury (SCI) leads to myelin breakdown and extensive neuronal loss around the injury site due to increased oxidative stress. This study aims to develop a comprehensive platform incorporating scaffolds, therapeutic agents, and stem cells to restore structures and pathways in SCI. Scaffolds were created through the electrospinning of a PCL/functionalized multi-walled carbon nanotube (f-MWCNTs) composite, which was then coated with liposomal ellagic acid (EA@lip) and seeded with adipose-derived mesenchymal stem cells (ADMSCs). The optimal drug concentration was determined by conducting MTT and DPPH assays through three different time points. After assessing the biocompatibility and anti-inflammatory properties of the scaffolds for ADMSCs, the implant was tested in a rat model of dorsal hemisection. The female Wistar rats were divided into six groups (n = 10): Sham, SCI, SCI + PCL/f-MWCNTs (PCs), SCI + scaffolds + EA@lip (PC/N), SCI + scaffolds + ADMSCs (PC/C), and SCI + scaffolds + EA@lip + ADMSCs (PC/N/C). In the second week, biochemical analyses were conducted to evaluate oxidative stress in the animals’ blood. Throughout the study, the motor function of the animals was monitored. After six weeks, the rats were subjected to real-time PCR and histological analysis, utilizing Cresyl Violet/Luxol Fast Blue staining and evaluating the expression of the genes COX2, GPX1, MBP, and Slc17a6/7. Liposomal encapsulation efficiency was measured to be 33%. The results revealed that EA@lip had the desired size, zeta potential, and lipid concentration. Transmission electron microscopy revealed that f-MWCNTs were well-aligned along nanofibers. EA@lip dramatically enhanced the hydrophilicity of the scaffolds. The MTT assay, DAPI staining, and FE-SEM images confirmed the successful implantation, proliferation, adhesion, and survival of ADMSCs on the liposome-coated scaffold. Additionally, in vitro oxidative stress tests indicated that this platform exhibited superior antioxidant and anti-inflammatory effects for ADMSCs. Histological assessments revealed that the hybrid platform facilitated the regeneration of myelin and neurons, correlating with improved blood levels of oxidative markers. Furthermore, real-time PCR results demonstrated a decrease in COX2 expression and an increase in GPX1, MBP, and Slc17a6/7 expression due to the platform. The findings suggest that the combination of ADMSCs with EA@lip-coated PCL/f-MWCNT scaffolds hold significant promise for applications in spinal cord regeneration.

Spinal cord injuries, whether resulting from traumatic or nontraumatic events, have severe and lasting detrimental effects on individuals, significantly impacting their overall health, mobility, and quality of life. The limited regenerative capacity of the spinal cord is mainly due to neuronal damage, the presence of inhibitory molecules, an impaired immune response, and the formation of glial scars, all of which create a hostile environment for neural repair and functional recovery. The majority of SCIs are caused by traffic accidents and falling objects. The current global treatments used for SCI are surgical methods, steroid medications, physiotherapy, and spinal cord epidural stimulations. However, these approaches offer only temporary relief and have serious adverse effects. Various preclinical approaches have been studied for SCI, including biomaterials, drug delivery, electrical stimulation, and cell-based therapies. Among these, stem cell therapies, such as NSCs, MSCs, and iPSCs, have the potential to significantly improve axonal regrowth, reduce inflammation, and promote neuroprotection. Furthermore, biophysical stimulation methods such as optogenetics, electrical and mechanical stimulation, and biomechanical devices offer encouraging paths toward improving neural plasticity and functional recovery. However, combinational approaches such as biomaterials with cell-based systems, cell-based systems with drug delivery, and biophysical stimulation with biomaterials aim to have more significant potential for functional recovery than a single treatment alone. This review has discussed the current clinical practices for SCI treatment, their limitations, and combinational strategies for spinal cord regeneration. So, this article can give clinicians, bioengineers, and researchers clues to construct preclinical and clinical studies that can have long-term effects on patients.

Background: Lower phylogenetic species are known to rebuild cut-off caudal parts with regeneration of the central nervous system (CNS). In contrast, CNS regeneration in higher vertebrates is often attributed to immaturity, although this has never been conclusively demonstrated. The emergence of stem cells and their effective medical applications has intensified research into spinal cord regeneration. However, despite these advances, the impact of clinical trials involving spinal cord-injured (SCI) patients remains disappointingly low. Long-distance regeneration has yet to be proven. Methods: Our study involved a microsurgical dorsal myelotomy in fetal rats. The development of pioneering long primary afferent axons during early gestation was examined long after birth. Results: A single cut triggered the intrinsic ability of the dorsal root ganglion (DRG) neurons to reprogram. Susceptibility to hypoxia caused the axons to stop developing. However, the residual axonal outgrowth sheds light on the intriguing temporal and spatial events that reveal long-distance CNS regeneration. The altered phenotypes displayed axons of varying lengths and different features, which remained visible throughout life. The previously designed developmental blueprint was crucial for interpreting these enigmatic features. Conclusions: This research into immaturity enabled the exploration of the previously impenetrable domain of early life and the identification of a potential missing link in CNS regeneration research. Central axon regeneration appeared to occur much faster than is generally believed. The paradigm provides a challenging approach for exhaustive intrauterine reprogramming. When the results demonstrate pre-clinical effectiveness in CNS regeneration research, the transformational impact may ultimately lead to improved outcomes for patients with spinal cord injuries.

Vertebrates exhibit a range of regenerative capacities following spinal cord injury. At one end of the spectrum are chief regenerators, including teleost fish and urodele amphibians. At the other end, most mammalian species exhibit limited repair and multicellular complications following spinal cord injury. Pro-regenerative immune, glial and neuronal injury responses underlie innate spinal cord repair in highly regenerative vertebrates. In many instances, fundamental mechanisms of spinal cord repair represent ancestral neuroprotection mechanisms that are conserved but become overwhelmed by anti-regenerative effects in mammals. Reflecting recent advances in the field, we review how fine-tuned immune responses, pro-regenerative glial cell reactivity and multimodal neuronal repair direct innate spinal cord repair.

Spinal cord injury (SCI) is a devastating traumatic condition of the central nervous system (CNS), usually resulting in irreversible motor and sensory deficits that severely compromise patients' quality of life. Harnessing the untapped potential of endogenous neural stem/progenitor cells (NSPCs) may yield revolutionary therapeutic techniques for overcoming the limited NSPC proliferative capacity following SCI in adults. Single-cell sequencing results demonstrated that the limited proliferative capacity of NSPCs after SCI is associated with the upregulation of the p21. Herein, we developed a cationic liposome-based delivery system encapsulating p21 small interfering RNA (P21siRNA@LP) to enhance NSPC proliferation following SCI. P21siRNA@LP significantly increased the primary NSPC proliferation rate (145.4% on day 1 and 144.7% on day 3, respectively) while maintaining differentiation capacity in vitro. Transcriptomic and functional characterization showed that P21siRNA@LP modulated the expression of cyclin-dependent kinases in NSPCs, enhancing cell cycle pathways (enrichment score: 0.6691) and proliferation, with extracellular matrix reorganization (col1a1, col5a1) and gliogenesis (olig1/2) identified as key regulation pathways. Gelatin hydrogels incorporating P21siRNA@LP promoted dense tissue cable formation in T9 SCI rats, facilitating NSPC migration and proliferation at lesion sites, which accelerated locomotor function recovery. These findings emphasize cell cycle manipulation as a promising method to spinal cord regeneration, providing a basis for future therapeutic advances in CNS disorders.

Both mammals and non-mammalian vertebrates display neuroimmune interactions after spinal cord injury (SCI). However, the impact of the immune response on neural regeneration remains unclear as it includes both proregenerative and inhibitory processes. To begin to understand how neuroimmune interactions influence central nervous system (CNS) regeneration, we examined the distribution of microglia/macrophages in relation to regenerating axons in larval sea lamprey (Petromyzon marinus), a non-mammalian vertebrate that exhibits robust axon and synapse regeneration after SCI. The relationship between microglia/macrophages and spinal axons was examined in cryosections of control and transected spinal cords using immunofluorescence. SCI significantly increased microglia/macrophage density within the spinal cord, as shown by isolectin B4 labeling. At 11 weeks post-injury (WPI), microglia/macrophages made physical contacts with regenerating axons, on average a three-fold increase compared to controls. These results are consistent with the conclusion that microglia/macrophage infiltration is associated with axon regeneration. Understanding the importance of these neuroimmune interactions could bring insight into cellular and molecular mechanisms that promote regeneration in the mammalian CNS.

Spinal cord regeneration is a highly intricate physiological process. A material designed for a single function may struggle to swiftly adapt to a delicate regulatory microenvironment, which can cause delays in nerve regeneration and limit functional recovery. To address this, we have devised a multifunctional tissue engineering approach that uses endogenous reactive oxygen species (ROS) production to trigger the on-demand release of hydrogen sulfide (H2S) at the injury site. This targeted delivery aims to facilitate spinal cord repair, neuroprotection, and neuroregeneration. Our delivery system incorporates a H2S donor (peroxyTCM) with ROS-responsive triggers integrated into a zinc-citrate metal-organic framework (Zn-CA MOF) (PTCM@Zn-CA), which is then encapsulated within a composite hydrogel (GelMA@LAMC). This integrated strategy considerably boosts the regeneration of spinal cord injury (SCI) through the physiological benefits of H2S and zinc ions. Specifically, it can mitigate oxidative stress and inflammation, induce macrophage M2 phenotype polarization, protect nerve cells, promote angiogenesis, and restore mitochondrial function to normalcy. Using pleiotropic messengers in tissue regeneration holds great promise for the effective repair of SCI.

Abstract Spinal cord injury (SCI) consists of partial or complete damage to the organ’s functions. Injuries can be traumatic or non-traumatic. New investigations have pointed out different paths in terms of spinal cord regeneration. Among these, the use of scaffolds has grown, structures created based on biomaterials and synthetic materials, aimed at remodelling the injured area, promoting tissue growth, regenerating damaged axons, and vascularizing the affected region. This work developed a fibrous scaffold using a vertical braider to produce Maypole structures from Polyamide 6 fibres, known for their strong mechanical properties, 3D architecture, and porosity, which support cell growth. The scaffold structures were evaluated based on porosity, mechanical strength, and dimensional stability under compression. Among the tested models, the T2/A8B40/E16B50 structure demonstrated superior performance, withstanding a tensile strength of 1,674 N, surpassing other samples. Its external layer of 16 yarns (0.50 mm) and internal layer of 0.40 mm yarns provided greater rigidity and load-bearing capacity. It also showed high elastic recovery (96.47%) after 10 compression cycles, maintaining excellent recovery despite its high load capacity. With 50.7% porosity and 49.3% coverage, the T2/A8B40/E16B50 scaffold balanced mechanical strength with permeability, making it the most promising candidate for SCI treatment and future implant testing.

BackgroundSpinal cord injury (SCI) is a devastating central nervous system disorder that remains a global health challenge. SCI-induced oxidative stress in the postinjury microenvironment limits tissue repair by provoking the excessive production of reactive oxygen species (ROS). Tea polyphenols (TP), as a natural plant polyphenol, could effectively reduce ROS. In recent years, stem cell-based therapy combined with cell sheet technology has been widely used in the treatment of SCI. Therefore, we constructed human umbilical cord mesenchymal stem cell sheet loaded with TP (CS-TP) and evaluated their therapeutic effects and mechanisms both in vitro and in vivo in SCI rats.MethodsHuman umbilical cord mesenchymal stem cell sheet (CS) were prepared by temperature-responsive cell culture method and successfully loaded with TP. The protective effect of CS and CS-TP on cells against oxidative stress was tested by Live/Dead cell staining and CCK-8 assay. CS and CS-TP were co-cultured with PC12 cells and human umbilical vein endothelial cells (HUVECs), respectively, and their effects on reducing ROS production were evaluated using flow cytometry and ROS fluorescence assays. Immune fluorescence (IF) and Western blot analysis of the mechanism by which CS-TP affects PC12 cells and HUVECs in vitro. Wound healing assay, transwell Chamber invasion experiment and tube formation assay were performed to evaluate the effects of CS and CS-TP on the biological behaviors of HUVECs. (Basso-Beattie-Bresnahan) BBB scores and gait analysis were performed to assess the recovery of motor function in rats. Molecular modeling is used to study the affinity between the main active ingredient epigallocatechin gallate (EGCG) in TP and target proteins. Western blot analyzes the mechanism of action of CS and CS-TP in SCI animals and the expression levels of antioxidant proteins. Tissue IF staining was used to evaluate angiogenesis, neuron regeneration and axonal extension.ResultsCompared with CS, CS-TP could effectively reduce cellular ROS production and increase cell viability under high oxidative stress conditions and significantly enhance its biological activity. In vitro, CS-TP can significantly activate the Keap-1/Nrf2/HO-1 pathway, thereby affecting PC12 cells and HUVECs. After transplantation in SCI rats, CS-TP also activates the Keap-1/Nrf2/HO-1 pathway, influencing the repair of SCI and upregulating the expression of SOD1 and SOD2. CS-TP can more effectively promote angiogenesis, neuronal regeneration, and axonal extension in injured spinal cords, greatly improving the motor function of the rats.ConclusionCS-TP not only significantly enhances the resistance of CS to ROS, activates the Keap-1/Nrf2/HO-1 pathway, and regulates the level of antioxidant proteins in the body. Compared to CS, it can also more effectively increase the number of new blood vessels, promote neuron regeneration and axon extension, thereby more effectively repairing SCI.

The endocannabinoid system is a neuromodulatory system implicated in cellular processes during both development and regeneration. The Mexican axolotl, one of only a few vertebrates capable of central nervous system regeneration, was used to examine the role of the endocannabinoid system in the regeneration of the tail and spinal cord following amputation. The endocannabinoid receptor CB1 was upregulated in the regenerating axolotl spinal cord by 4 hours following tail amputation, and this upregulation persisted for at least 14 days. The endocannabinoid receptor CB2 was upregulated later, between 7 and 14 days after tail amputation. Both CB1 and CB2 were located in ependymoglia and neurons within the regenerating spinal cord. Treatment with inverse agonists to inhibit CB1 (AM251) or CB2 (AM630) inhibited spinal cord and tail regeneration. During the first 7 days after injury, CB1 and CB2 expression was also necessary for the proliferation of ependymoglial cells and the regeneration of axons into the newly regenerated tail tissue. However, only CB1 was necessary for the differentiation of ependymoglia into immature neurons. These studies are the first to examine the role of the endocannabinoid system during spinal cord regeneration in a regeneration-competent vertebrate.

The axolotl retains a remarkable capacity for regenerative repair and is one of the few vertebrate species capable of regenerating its brain and spinal cord after injury. To date, studies investigating axolotl spinal cord regeneration have placed particular emphasis on understanding how cells immediately adjacent to the injury site respond to damage to promote regenerative repair. How neurons outside of this immediate injury site respond to an injury remains unknown. Here, we identify a population of dpErk+/etv1+ glutamatergic neurons in the axolotl telencephalon that are activated in response to injury and are essential for tail regeneration. Furthermore, these neurons project to the hypothalamus where they upregulate the neuropeptide neurotensin in response to injury. Together, these findings identify a unique population of neurons in the axolotl brain whose activation is necessary for successful tail regeneration, and sheds light on how neurons outside of the immediate injury site respond to an injury.

JOURNAL/nrgr/04.03/01300535-202602000-00046/figure1/v/2025-05-05T160104Z/r/image-tiff Unlike mammals, zebrafish possess a remarkable ability to regenerate their spinal cord after injury, making them an ideal vertebrate model for studying regeneration. While previous research has identified key cell types involved in this process, the underlying molecular and cellular mechanisms remain largely unexplored. In this study, we used single-cell RNA sequencing to profile distinct cell populations at different stages of spinal cord injury in zebrafish. Our analysis revealed that multiple subpopulations of neurons showed persistent activation of genes associated with axonal regeneration post injury, while molecular signals promoting growth cone collapse were inhibited. Radial glial cells exhibited significant proliferation and differentiation potential post injury, indicating their intrinsic roles in promoting neurogenesis and axonal regeneration, respectively. Additionally, we found that inflammatory factors rapidly decreased in the early stages following spinal cord injury, creating a microenvironment permissive for tissue repair and regeneration. Furthermore, oligodendrocytes lost maturity markers while exhibiting increased proliferation following injury. These findings demonstrated that the rapid and orderly regulation of inflammation, as well as the efficient proliferation and redifferentiation of new neurons and glial cells, enabled zebrafish to reconstruct the spinal cord. This research provides new insights into the cellular transitions and molecular programs that drive spinal cord regeneration, offering promising avenues for future research and therapeutic strategies.