Targeted inhibition of STAT3 in neural stem cells promotes neuronal differentiation and functional recovery in rats with spinal cord injury

The roles of neural stem cells in myelin regeneration and repair therapy after spinal cord injury

Spinal cord injury (SCI) is a complex tissue injury that results in a wide range of physical deficits, including permanent or progressive disabilities of sensory, motor and autonomic functions. To date, limitations in current clinical treatment options can leave SCI patients with lifelong disabilities. There is an urgent need to develop new therapies for reconstructing the damaged spinal cord neuron-glia network and restoring connectivity with the supraspinal pathways. Neural stem cells (NSCs) possess the ability to self-renew and differentiate into neurons and neuroglia, including oligodendrocytes, which are cells responsible for the formation and maintenance of the myelin sheath and the regeneration of demyelinated axons. For these properties, NSCs are considered to be a promising cell source for rebuilding damaged neural circuits and promoting myelin regeneration. Over the past decade, transplantation of NSCs has been extensively tested in a variety of preclinical models of SCI. This review aims to highlight the pathophysiology of SCI and promote the understanding of the role of NSCs in SCI repair therapy and the current advances in pathological mechanism, pre-clinical studies, as well as clinical trials of SCI via NSC transplantation therapeutic strategy. Understanding and mastering these frontier updates will pave the way for establishing novel therapeutic strategies to improve the quality of recovery from SCI.

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

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

Spinal Cord Injury Management Based on Microglia-Targeting Therapies

Spinal cord injury is a complicated medical condition both from the clinician's point of view in terms of management and from the patient's perspective in terms of unsatisfactory recovery. Depending on the severity, this disorder can be devastating despite the rapid and appropriate use of modern imaging techniques and convenient surgical spinal cord decompression and stabilization. In this context, there is a mandatory need for novel adjunctive therapeutic approaches to classical treatments to improve rehabilitation chances and clinical outcomes. This review offers a new and original perspective on therapies targeting the microglia, one of the most relevant immune cells implicated in spinal cord disorders. The first part of the manuscript reviews the anatomical and pathophysiological importance of the blood-spinal cord barrier components, including the role of microglia in post-acute neuroinflammation. Subsequently, the authors present the emerging therapies based on microglia modulation, such as cytokines modulators, stem cell, microRNA, and nanoparticle-based treatments that could positively impact spinal cord injury management. Finally, future perspectives and challenges are also highlighted based on the ongoing clinical trials related to medications targeting microglia.

Interferon-β deficiency alters brain response to chronic HIV-1 envelope protein exposure in a transgenic model of NeuroHIV

Human immunodeficiency virus-1 (HIV-1) infects the central nervous system (CNS) and causes HIV-associated neurocognitive disorders (HAND) in about half of the population living with the virus despite combination anti-retroviral therapy (cART). HIV-1 activates the innate immune system, including the production of type 1 interferons (IFNs) α and β. Transgenic mice expressing HIV-1 envelope glycoprotein gp120 (HIVgp120tg) in the CNS develop memory impairment and share key neuropathological features and differential CNS gene expression with HIV patients, including the induction of IFN-stimulated genes (ISG). Here we show that knocking out IFNβ (IFNβKO) in HIVgp120tg and non-tg control mice impairs recognition and spatial memory, but does not affect anxiety-like behavior, locomotion, or vision. The neuropathology of HIVgp120tg mice is only moderately affected by the KO of IFNβ but in a sex-dependent fashion. Notably, in cerebral cortex of IFNβKO animals presynaptic terminals are reduced in males while neuronal dendrites are reduced in females. The IFNβKO results in the hippocampal CA1 region of both male and female HIVgp120tg mice in an ameliorated loss of neuronal presynaptic terminals but no protection of neuronal dendrites. Only female IFNβ-deficient HIVgp120tg mice display diminished microglial activation in cortex and hippocampus and increased astrocytosis in hippocampus compared to their IFNβ-expressing counterparts. RNA expression for some immune genes and ISGs is also affected in a sex-dependent way. The IFNβKO abrogates or diminishes the induction of MX1, DDX58, IRF7 and IRF9 in HIVgp120tg brains of both sexes. Expression analysis of neurotransmission related genes reveals an influence of IFNβ on multiple components with more pronounced changes in IFNβKO females. In contrast, the effects of IFNβKO on MAPK activities are independent of sex with pronounced reduction of active ERK1/2 but also of active p38 in the HIVgp120tg brain. In summary, our findings show that the absence of IFNβ impairs memory dependent behavior and modulates neuropathology in HIVgp120tg brains, indicating that its absence may facilitate development of HAND. Moreover, our data suggests that endogenous IFNβ plays a vital role in maintaining neuronal homeostasis and memory function.

[Therapeutic mechanism of basic fibroblast growth factor on spinal cord injury in rats based on the Notch/signal transducer and activator of transcription 3 signaling pathway]

Objective

To explore the therapeutic effect of basic fibroblast growth factor (bFGF) on spinal cord injury (SCI) in rats and the influence of Notch/signal transducer and activator of transcription 3 (STAT3) signaling pathway.

Methods

A total of 40 10-week-old male Sprague Dawley (SD) rats were selected to establish T 10-segment SCI model by a free falling object. Among them, 32 successful models were randomly divided into model group and bFGF group, with 16 in each group. Another 16 SD rats were selected as sham-operation group, with only T 10 processes, dura mater, and spinal cord exposed. After modeling, the rats in bFGF group were intraperitoneally injected with 100 μg/kg bFGF (once a day for 28 days), and the rats in model group and sham-operation group were injected with normal saline in the same way. The survival of rats in each group were observed after modeling. Basso-Beattie-Bresnahan (BBB) scores were performed before modeling and at immediate, 14 days, and 28 days after modeling to evaluate the functional recovery of hind limbs. Then, the spinal cord tissue at the site of injury was taken at 28 days and stained with HE, Nissl, and propidium iodide (PI) to observe the pathological changes, neuronal survival (number of Nissl bodies) and apoptosis (number of PI red stained cells) of the spinal cord tissue; immunohistochemical staining and ELISA were used to detect the levels of astrocyte activation markers [glial fibrillary acidic protein (GFAP)] and inflammatory factors [interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), interferon γ (IFN-γ)] in tissues, respectively. Western blot was used to detect the expressions of Notch/STAT3 signaling pathway related proteins [Notch, STAT3, phosphoryl-STAT3 (p-STAT3), bone morphogenetic protein 2 (BMP-2)] in tissues.

Results

All rats survived until the experiment was completed. At immediate after modeling, the BBB scores in model group and bFGF group significantly decreased when compared to sham-operation group ( P<0.05). At 14 and 28 days after modeling, the BBB scores in model group significantly decreased when compared to sham-operation group ( P<0.05); the bFGF group showed an increase compared to model group ( P<0.05). Compared with before modeling, the BBB scores of model group and bFGF group decreased at immediate after modeling, and gradually increased at 14 and 28 days, the differences between different time points were significant ( P<0.05). The structure of spinal cord tissue in sham-operation group was normal; in model group, there were more necrotic lesions in the spinal cord tissue and fewer Nissl bodies with normal structures; the number of necrotic lesions in the spinal cord tissue of the bFGF group significantly reduced compared to the model group, and some normally structured Nissl bodies were visible. Compared with sham-operation group, the number of Nissl bodies in spinal cord tissue significantly decreased, the number of PI red stained cells, GFAP, IL-1β, TNF-α, IFN-γ, Notch, p-STAT3 /STAT3, BMP-2 protein expression levels significantly increased in model group ( P<0.05). The above indexes in bFGF group significantly improved when compared with model group ( P<0.05).

Conclusion

bFGF can improve motor function and pathological injury repair of spinal cord tissue in SCI rats, improve neuronal survival, and inhibit neuronal apoptosis, excessive activation of astrocytes in spinal cord tissue and inflammatory response, the mechanism of which may be related to the decreased activity of Notch/STAT3 signaling pathway.

Reprogramming of astrocytes to neuronal-like cells in spinal cord injury: a systematic review

STUDY DESIGN

A Systematic Review OBJECTIVES: To determine the therapeutic efficacy of in vivo reprogramming of astrocytes into neuronal-like cells in animal models of spinal cord injury (SCI).

METHODS

PRISMA 2020 guidelines were utilized, and search engines Medline, Web of Science, Scopus, and Embase until June 2023 were used. Studies that examined the effects of converting astrocytes into neuron-like cells with any vector in all animal models were included, while conversion from other cells except for spinal astrocytes, chemical mechanisms to provide SCI models, brain injury population, and conversion without in-vivo experience were excluded. The risk of bias was calculated independently.

RESULTS

5302 manuscripts were initially identified and after eligibility assessment, 43 studies were included for full-text analysis. After final analysis, 13 manuscripts were included. All were graded as high-quality assessments. The transduction factors Sox2, Oct4, Klf4, fibroblast growth factor 4 (Fgf4) antibody, neurogenic differentiation 1 (Neurod1), zinc finger protein 521 (Zfp521), ginsenoside Rg1, and small molecules (LDN193189, CHIR99021, and DAPT) could effectively reprogramme astrocytes into neuron-like cells. The process was enhanced by p21-p53, or Notch signaling knockout, valproic acid, or chondroitin sulfate proteoglycan inhibitors. The type of mature neurons was both excitatory and inhibitory.

CONCLUSION

Astrocyte reprogramming to neuronal-like cells in an animal model after SCI appears promising. The molecular and functional improvements after astrocyte reprogramming were demonstrated in vivo, and further investigation is required in this field.

Metrnl ameliorates diabetic cardiomyopathy via inactivation of cGAS/STING signaling dependent on LKB1/AMPK/ULK1-mediated autophagy

INTRODUCTION

Meteorin-like hormone (Metrnl) is ubiquitously expressed in skeletal muscle, heart, and adipose with beneficial roles in obesity, insulin resistance, and inflammation. Metrnl is found to protect against cardiac hypertrophy and doxorubicin-induced cardiotoxicity. However, its role in diabetic cardiomyopathy (DCM) is undefined.

OBJECTIVES

We aimed to elucidate the potential roles of Metrnl in DCM.

METHODS

Gain- andloss-of-function experimentswere utilized to determine the roles of Metrnl in the pathological processes of DCM.

RESULTS

We found that plasma Metrnl levels, myocardial Metrnl protein and mRNA expressions were significantly downregulated in both streptozotocin (STZ)-induced (T1D) mice and leptin receptor deficiency (db/db) (T2D) mice. Cardiac-specific overexpression (OE) of Metrnl markedly ameliorated cardiac injury and dysfunction in both T1D and T2D mice. In sharp contrast, specific deletion of Metrnl in the heart had the opposite phenotypes. In parallel, Metrnl OE ameliorated, whereas Metrnl downregulation exacerbated high glucose (HG)-elicited hypertrophy, apoptosis and oxidative damage in primary neonatal rat cardiomyocytes. Antibody-induced blockade of Metrnl eliminated the effects of benefits of Metrnl in vitro and in vivo. Mechanistically, Metrnl activated the autophagy pathway and inhibited the cGAS/STING signaling in a LKB1/AMPK/ULK1-dependent mechanism in cardiomyocytes. Besides, Metrnl-induced ULK1 phosphorylation facilitated the dephosphorylation and mitochondrial translocation of STING where it interacted with tumor necrosis factor receptor-associated factor 2 (TRAF2), a scaffold protein and E3 ubiquitin ligase that was responsible for ubiquitination and degradation of STING, rendering cardiomyocytes sensitive to autophagy activation.

CONCLUSION

Thus, Metrnl may be an attractive therapeutic target or regimen for treating DCM.

Modification of Müller Glial Cell Fate and Proliferation with the Use of Small Molecules

In recent years, reprogramming Müller glia by overexpressing Ascl1 and other transcription factors has shown promise for the regeneration of postmitotic retinal neurons, primarily bipolar cells, following injury. Müller glial proliferation and efficiency of neuronal differentiation can be modified by the use of small molecules in various systems. The molecules and pathways studied thus far share remarkable consistency with astrocytes. In this mini review, we provide an overview on the modulation of Müller glial proliferation and cell fate using small molecules in injury and reprogramming. We also compare these observations to what has been observed in astrocytes.

Resveratrol suppresses neuroinflammation to alleviate mechanical allodynia by inhibiting Janus kinase 2/signal transducer and activator of transcription 3 signaling pathway in a rat model of spinal cord injury

Background

Neuropathic pain (NP) is one of intractable complications of spinal cord injury (SCI) and lacks effective treatment. Resveratrol (Res) has been shown to possess potent anti-inflammatory and anti-nociceptive effects. In this study, we investigated the analgesic effect of Res and its underlying mechanism in a rat model of SCI.

Methods

The rat thoracic (T10) spinal cord contusion injury model was established, and mechanical thresholds were evaluated during an observation period of 21 days. Intrathecal administration with Res (300 μg/10 μl) was performed once a day for 7 days after the operation. On postoperative day 7, the expressions of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) and interleukin-6 (IL-6) were determined by enzyme-linked immunosorbent assay (ELISA) and Real-time quantitative PCR (RT-qPCR), the expression of Janus kinase 2/signal transducer and activator of transcription 3 (JAK2/STAT3) signaling pathway was determined by western blot and RT-qPCR, and the co-labeled phospho-STAT3 (p-STAT3) with neuronal nuclear antigen (NeuN), glial fibrillary acidic protein (GFAP), and ionized calcium-binding adapter molecule 1 (Iba-1) were explored by double immunofluorescence staining in the lumbar spinal dorsal horns. The temporal changes of p-STAT3 were investigated by western blot on the 1st, 3rd, 7th, 14th, and 21st days after the operation.

Results

Intrathecal administration with Res for 7 successive days alleviated mechanical allodynia of rats during the observation period. Meanwhile, treatment with Res suppressed the production of pro-inflammatory factors TNF-α, IL-1β and IL-6, and inhibited the expressions of phospho-JAK2 and p-STAT3 in the lumbar spinal dorsal horns on postoperative day 7. Additionally, the protein expression of p-STAT3 was significantly increased on the 1st day following the operation and remained elevated during the next 21 days, immunofluorescence suggested that the up-regulated p-STAT3 was co-located with glial cells and neurons.

Conclusion

Our current results indicated that intrathecal administration with Res effectively alleviated mechanical allodynia after SCI in rats, and its analgesic mechanism might be to suppress neuroinflammation by partly inhibiting JAK2/STAT3 signaling pathway.

Ginsenoside Rg1 promotes astrocyte-to-neuron transdifferentiation in rat and its possible mechanism

INTRODUCTION

Neuronal loss caused by spinal cord injury (SCI) usually contributes to irreversible motor dysfunction. Promoting neuronal regeneration and functional recovery is vital to the repair of SCI.

AIMS

Astrocytes, activated by SCI with high proliferative capacity and proximity to neuronal lineage, are considered ideal cells for neuronal regeneration. As previous studies identified several small molecules for the induction of astrocyte-to-neuron, we confirmed that ginsenoside Rg1, a neuroprotective herb, could promote the direct transdifferentiation of astrocyte-to-neuron in rat.

METHODS AND RESULTS

Immunofluorescence staining showed that 26.0 ± 1.5% of the induced cells exhibited less astroglial properties and more neuronal markers with typical neuronal morphologies, reflecting 20.6 ± 0.9% of cholinergic neurons and 22.3 ± 1.9% of dopaminergic neurons. Western blot and qRT-PCR revealed that the induced cells had better antiapoptotic ability and Rg1-promoted neuronal transdifferentiation of reactive astrocytes might take effect through suppressing Notch/Stat3 signal pathway. In vivo, a revised SCI model treated by Rg1 was confirmed with faster functional recovery and less injury lesion cavity.

CONCLUSION

In summary, our study provided a novel strategy of direct transdifferentiation of endogenous rat reactive astrocytes into neurons with Rg1 and promotion of neuronal regeneration after SCI.

Exploring the mechanism of Buyang Huanwu Decoction in the treatment of spinal cord injury based on network pharmacology and molecular docking

Buyang Huanwu Decoction, a traditional Chinese medicine decoction, is widely used to treat spinal cord injury in China. However, the underlying mechanism of this decoction in treating spinal cord injury is unclear. This study used network pharmacology and molecular docking to examine the pharmacological mechanism of Buyang Huanwu Decoction in prevention and treatment of spinal cord injury. The active compounds and target genes of Buyang Huanwu Decoction were collected from the Traditional Chinese Medicine Systems Pharmacology and the SwissTargetPrediction Database. The network diagram of "traditional Chinese medicine compound target" was constructed by Cytoscape software. Genetic data of spinal cord injury were obtained by GeneCards database. According to the intersection of Buyang Huanwu Decoction's targets and disease targets, the core targets were searched. The protein-protein interaction network were constructed using the STRING and BisoGenet platforms. Meanwhile, gene ontology enrichment and Kyoto encyclopedia of genes, and genome pathway were performed on the intersection targets by Metascape. Molecular docking technology was adopted to verify the combination of main components and core targets. A total of 109 active compounds and 5440 prediction targets were screened from 7 Chinese herbal medicines of Buyang Huanwu Decoction, with 98 active components and 49 related prediction targets being strongly linked to Spinal Cord Injury. By studying protein-protein interaction network, a total of 8 core proteins were identified, primarily interleukin-6, tumor protein P53, epidermal growth factor receptor, and others. Positive regulation of kinase activity regulation of reaction to inorganic chemicals are the basic biological processes. Buyang Huanwu Decoction cures Spinal Cord Injury primarily by moderating immunological inflammation, apoptosis, and oxidative stress, which involves the cancer pathway, the HIF-1 signaling pathway, the p53 signaling pathway, the MAPK signaling pathway, and so on. The results of molecular docking demonstrated that the primary components could attach to the target protein effectively. Finally, the mechanism of Buyang Huanwu Decoction in the treatment of spinal cord injury through multicomponent, multitarget, and multichannel was deeply explored. And it offers new ideas and directions for future research on the mechanism of the treatment of spinal cord injury.

The roles and applications of neural stem cells in spinal cord injury repair

Spinal cord injury (SCI), which has no current cure, places a severe burden on patients. Stem cell-based therapies are considered promising in attempts to repair injured spinal cords; such options include neural stem cells (NSCs). NSCs are multipotent stem cells that differentiate into neuronal and neuroglial lineages. This feature makes NSCs suitable candidates for regenerating injured spinal cords. Many studies have revealed the therapeutic potential of NSCs. In this review, we discuss from an integrated view how NSCs can help SCI repair. We will discuss the sources and therapeutic potential of NSCs, as well as representative pre-clinical studies and clinical trials of NSC-based therapies for SCI repair.

Novel perspectives on the therapeutic role of cryptotanshinone in the management of stem cell behaviors for high-incidence diseases

Cryptotanshinone (CTS), a diterpenoid quinone, is found mostly in Salvia miltiorrhiza Bunge (S. miltiorrhiza) and plays a crucial role in many cellular processes, such as cell proliferation/self-renewal, differentiation and apoptosis. In particular, CTS’s profound physiological impact on various stem cell populations and their maintenance and fate determination could improve the efficiency and accuracy of stem cell therapy for high-incidence disease. However, as much promise CTS holds, these CTS-mediated processes are complex and multifactorial and many of the underlying mechanisms as well as their clinical significance for high-incidence diseases are not yet fully understood. This review aims to shed light on the impact and mechanisms of CTS on the actions of diverse stem cells and the involvement of CTS in the many processes of stem cell behavior and provide new insights for the application of CTS and stem cell therapy in treating high-incidence diseases.

Wogonin inhibits inflammation and apoptosis through STAT3 signal pathway to promote the recovery of spinal cord injury

Spinal cord injury (SCI) is a complex central traumatic disease. STAT3 signal transduction pathway plays an important role in SCI. Wogonin has been reported to exhibit neuroprotection. However, the molecular mechanism of its potential therapeutic effect after SCI remains unclear. In this study, rats were divided into the following groups: Sham; SCI; SCI + wogonin; and SCI + wogonin + colivelin (Colivelin is an effective activator of the STAT3 pathway). Motor function was evaluated by Basso Beattie Bresnahan (BBB) score. Histomorphological changes in the spinal cords were observed by Hematoxylin-eosin (HE) staining and Nissl staining. Western blot, Transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining, and immunofluorescence were used to detect changes in the neuronal inflammation, apoptosis, and STAT3 signal pathway. Western blot and immunofluorescence techniques were also performed to detect the regulatory effect and the underlying mechanism of wogonin on the inflammation and apoptosis of PC12 cells. Experimental results in vivo and in vitro showed that wogonin could promote the recovery of motor function, improve the histopathological morphology, inhibit the activation of the STAT3 signal pathway, and reduce the neuronal inflammation and apoptosis in the rats with SCI. Activation of the STAT3 signal pathway by colivelin reversed the therapeutic effect of wogonin. Therefore, wogonin could inhibit inflammation and apoptosis by inhibiting the STAT3 signal pathway and promote the functional recovery of rats with SCI.

RNA Profiling of Mouse Ependymal Cells after Spinal Cord Injury Identifies the Oncostatin Pathway as a Potential Key Regulator of Spinal Cord Stem Cell Fate

Ependymal cells reside in the adult spinal cord and display stem cell properties in vitro. They proliferate after spinal cord injury and produce neurons in lower vertebrates but predominantly astrocytes in mammals. The mechanisms underlying this glial-biased differentiation remain ill-defined. We addressed this issue by generating a molecular resource through RNA profiling of ependymal cells before and after injury. We found that these cells activate STAT3 and ERK/MAPK signaling post injury and downregulate cilia-associated genes and FOXJ1, a central transcription factor in ciliogenesis. Conversely, they upregulate 510 genes, seven of them more than 20-fold, namely Crym, Ecm1, Ifi202b, Nupr1, Rbp1, Thbs2 and Osmr—the receptor for oncostatin, a microglia-specific cytokine which too is strongly upregulated after injury. We studied the regulation and role of Osmr using neurospheres derived from the adult spinal cord. We found that oncostatin induced strong Osmr and p-STAT3 expression in these cells which is associated with reduction of proliferation and promotion of astrocytic versus oligodendrocytic differentiation. Microglial cells are apposed to ependymal cells in vivo and co-culture experiments showed that these cells upregulate Osmr in neurosphere cultures. Collectively, these results support the notion that microglial cells and Osmr/Oncostatin pathway may regulate the astrocytic fate of ependymal cells in spinal cord injury.

Elucidating the Pivotal Neuroimmunomodulation of Stem Cells in Spinal Cord Injury Repair

Spinal cord injury (SCI) is a distressing incident with abrupt onset of the motor as well as sensory dysfunction, and most often, the injury occurs as result of high-energy or velocity accidents as well as contact sports and falls in the elderly. The key challenges associated with nerve repair are the lack of self-repair as well as neurotrophic factors and primary and secondary neuronal apoptosis, as well as factors that prevent the regeneration of axons locally. Neurons that survive the initial traumatic damage may be lost due to pathogenic activities like neuroinflammation and apoptosis. Implanted stem cells are capable of differentiating into neural cells that replace injured cells as well as offer local neurotrophic factors that aid neuroprotection, immunomodulation, axonal sprouting, axonal regeneration, and remyelination. At the microenvironment of SCI, stem cells are capable of producing growth factors like brain-derived neurotrophic factor and nerve growth factor which triggers neuronal survival as well as axonal regrowth. Although stem cells have proven to be of therapeutic value in SCI, the major disadvantage of some of the cell types is the risk for tumorigenicity due to the contamination of undifferentiated cells prior to transplantation. Local administration of stem cells via either direct cellular injection into the spinal cord parenchyma or intrathecal administration into the subarachnoid space is currently the best transplantation modality for stem cells during SCI.