Effects of STAT3 inhibitors on neural functional recovery after spinal cord injury in rats

Protective Mechanism of Stem Cells from Human Exfoliated Deciduous Teeth in Treating Spinal Cord Injury

Spinal cord injury (SCI) induces devastating permanent deficits. Recently, cell transplantation therapy has become a notable treatment for SCI. Although stem cells from human exfoliated deciduous teeth (SHED) are an attractive therapy, their precise mechanism of action remains to be elucidated. In this study, we explored one of the neuroprotective mechanisms of SHED treatment at the subacute stage after SCI. We used a rat clip compression SCI model. The animals were randomly divided into three groups: SCI, SCI + phosphate-buffered saline (PBS), and SCI + SHED. The SHED or PBS intramedullary injection was administered immediately after SCI. After SCI, we explored the effects of SHED on motor function, as assessed by the Basso-Beattie-Bresnahan score and the inclined plane method, the signal transduction pathway, especially the Janus kinase (JAK) and the signal transducer and activator of transcription 3 (STAT3) pathway, the apoptotic pathway, and the expression of neurocan, one of the chondroitin sulfate proteoglycans. SHED treatment significantly improved functional recovery from Day 14 relative to the controls. Western blot analysis showed that SHED significantly reduced the expression of glial fibrillary acidic protein (GFAP) and phosphorylated STAT3 (p-STAT3) at Tyr705 on Day 10 but not on Day 5. However, SHED had no effect on the expression levels of Iba-1 on Days 5 or 10. Immunohistochemistry revealed that p-STAT3 at Tyr705 was mainly expressed in GFAP-positive astrocytes on Day 10 after SCI, and its expression was reduced by administration of SHED. Moreover, SHED treatment significantly induced expression of cleaved caspase 3 in GFAP-positive astrocytes only in the epicenter lesions on Day 10 after SCI but not on Day 5. The expression of neurocan was also significantly reduced by SHED injection on Day 10 after SCI. Our results show that SHED plays an important role in reducing astrogliosis and glial scar formation between Days 5 and 10 after SCI, possibly via apoptosis of astrocytes, ultimately resulting in improvement in neurological functions thereafter. Our data revealed one of the neuroprotective mechanisms of SHED at the subacute stage after SCI, which improved functional recovery after SCI, a serious condition.

Circ_0006640 transferred by bone marrow-mesenchymal stem cell-exosomes suppresses lipopolysaccharide-induced apoptotic, inflammatory and oxidative injury in spinal cord injury

BACKGROUND

Emerging proofs have shown that differentially expressed circular RNAs (circRNAs) are closely associated with the pathophysiological process of spinal cord injury (SCI). Mesenchymal stem cell (MSC)-exosomes have been demonstrated to possess favorable therapeutic effects in diseases. Herein, this work aimed to investigate the action of circ_0006640 transferred by MSC-exosomes functional recovery after SCI.

METHODS

SCI animal models were established by spinal cord contusion surgery in mice and lipopolysaccharide (LPS)-stimulated mouse microglial cell line BV2. Levels of genes and proteins were detected by qRT-PCR and Western blot. Properties of BV2 cells were characterized using CCK-8 assay, flow cytometry and ELISA analysis. The oxidative stress was evaluated. Dual-luciferase reporter assay was used for verifying the binding between miR-382-5p and circ_0006640 or IGF-1 (Insulin-like Growth Factor 1). Exosome separation was conducted by using the commercial kit.

RESULTS

Circ_0006640 expression was lower in SCI mice and LPS-induced microglial cells. Circ_0006640 overexpression protected microglial cells from LPS-induced apoptotic, inflammatory and oxidative injury. Mechanistically, circ_0006640 directly sponged miR-382-5p, which targeted IGF-1. MiR-382-5p was increased, while IGF-1 was decreased in SCI mice and LPS-induced microglial cells. Knockdown of miR-382-5p suppressed apoptosis, inflammation and oxidative stress in LPS-induced microglial cells, which were reversed by IGF-1 deficiency. Moreover, miR-382-5p up-regulation abolished the protective functions of circ_0006640 in LPS-induced microglial cells. Additionally, circ_0006640 was packaged into MSC-exosomes and could be transferred by exosomes. Exosomal circ_0006640 also had protective effects on microglial cells via miR-382-5p/IGF-1 axis.

CONCLUSION

Circ_0006640 transferred by BMSC-exosomes suppressed LPS-induced apoptotic, inflammatory and oxidative injury via miR-382-5p/IGF-1 axis, indicating a new insight into the clinical application of exosomal circRNA-based therapeutic in the function recovery after SCI.

Identification and Validation of Ferroptosis-Related Genes in Patients with Acute Spinal Cord Injury

Ferroptosis plays crucial roles in the pathology of spinal cord injury (SCI). The purpose of this study was to identify differentially expressed ferroptosis-related genes (DE-FRGs) in human acute SCI by bioinformatics analysis and validate the hub DE-FRGs in non-SCI and SCI patients. The GSE151371 dataset was downloaded from the Gene Expression Omnibus and difference analysis was performed. The differentially expressed genes (DEGs) in GSE151371 overlapped with the ferroptosis-related genes (FRGs) obtained from the Ferroptosis Database. A total of 41 DE-FRGs were detected in 38 SCI samples and 10 healthy samples in GSE151371. Then, enrichment analyses of these DE-FRGs were performed for functional annotation. The GO enrichment results showed that upregulated DE-FRGs were mainly associated with reactive oxygen species and redox reactions, and the KEGG enrichment analysis indicated involvement in some diseases and ferroptosis pathways. Protein-protein interaction (PPI) analysis and lncRNA-miRNA-mRNA regulatory network were performed to explore the correlations between genes and regulatory mechanisms. The relationship between DE-FRGs and differentially expressed mitochondria-related genes (DE-MRGs) was also analyzed. Finally, quantitative real-time polymerase chain reaction (qRT-PCR) was used to verify the hub DE-FRGs in clinical blood samples from acute SCI patients and healthy controls. Consistent with the bioinformatics results, qRT-PCR of the clinical samples indicated similar expression levels of TLR4, STAT3, and HMOX1. This study identified DE-FRGs in blood samples from SCI patients, and the results could improve our understanding of the molecular mechanisms of ferroptosis in SCI. These candidate genes and pathways could be therapeutic targets for SCI.

Hydralazine Promotes Central Nervous System Recovery after Spinal Cord Injury by Suppressing Oxidative Stress and Inflammation through Macrophage Regulation

OBJECTIVE

This study aims to investigate the effects of hydralazine on inflammation induced by spinal cord injury (SCI) in the central nervous system (CNS) and its mechanism in promoting the structural and functional recovery of the injured CNS.

METHODS

A compressive SCI mouse model was utilized for this investigation. Immunofluorescence and quantitative real-time polymerase chain reaction were employed to examine the levels of acrolein, acrolein-induced inflammation-related factors, and macrophages at the injury site and within the CNS. Western blotting was used to evaluate the activity of the phosphoinositide 3-kinase (PI3K)/AKT pathway to study macrophage regulation. The neuropathic pain and motor function recovery were evaluated by glutamic acid decarboxylase 65/67 (GAD65/67), vesicular glutamate transporter 1 (VGLUT1), paw withdrawal response, and Basso Mouse Scale score. Nissl staining and Luxol Fast Blue (LFB) staining were performed to investigate the structural recovery of the injured CNS.

RESULTS

Hydralazine downregulated the levels of acrolein, IL-1β, and TNF-α in the spinal cord. The downregulation of acrolein induced by hydralazine promoted the activation of the PI3K/AKT pathway, leading to M2 macrophage polarization, which protected neurons against SCI-induced inflammation. Additionally, hydralazine promoted the structural recovery of the injured spinal cord area. Mitigating inflammation and oxidative stress by hydralazine in the animal model alleviated neuropathic pain and altered neurotransmitter expression. Furthermore, hydralazine facilitated motor function recovery following SCI. Nissl staining and LFB staining indicated that hydralazine promoted the structural recovery of the injured CNS.

CONCLUSION

Hydralazine, an acrolein scavenger, significantly mitigated SCI-induced inflammation and oxidative stress in vivo, modulated macrophage activation, and consequently promoted the structural and functional recovery of the injured CNS.

CircSmox knockdown alleviates PC12 cell apoptosis and inflammation in spinal cord injury by miR-340-5p/Smurf1 axis

BACKGROUND

Spinal cord injury (SCI) is a traumatic central nervous system disorder that leads to irreversible neurological dysfunction. Emerging evidence has shown that differentially expressed circular RNAs (circRNAs) after SCI is closely associated with the pathophysiological process. Herein, the potential function of circRNA spermine oxidase (circSmox) in functional recovery after SCI was investigated.

METHODS

Differentiated PC12 cells stimulated with lipopolysaccharide (LPS) were employed as an in vitro model for neurotoxicity research. Levels of genes and proteins were detected by quantitative real-time PCR and Western blot analysis. Cell viability and apoptosis were determined by CCK-8 assay and flow cytometry. Western blot analysis was used to detect the protein level of apoptosis-related markers. The levels of interleukin (IL)-1β, IL-6, IL-8, and tumor necrosis factor (TNF)-α. Dual-luciferase reporter, RIP, and pull-down assays were used to confirm the target relationship between miR-340-5p and circSmox or Smurf1 (SMAD Specific E3 Ubiquitin Protein Ligase 1).

RESULTS

LPS elevated the levels of circSmox and Smurf1, but decreased the levels of miR-340-5p in PC12 cells in a dose-dependent manner. Functionally, circSmox silencing alleviated LPS-induced apoptosis and inflammation in PC12 cells in vitro. Mechanistically, circSmox directly sponged miR-340-5p, which targeted Smurf1. Rescue experiments showed that miR-340-5p inhibition attenuated the neuroprotective effect of circSmox siRNA in PC12 cells. Moreover, miR-340-5p suppressed LPS-triggered neurotoxicity in PC12 cells, which was reversed by Smurf1 overexpression.

CONCLUSION

CircSmox enhances LPS-induced apoptosis and inflammation via miR-340-5p/Smurf1 axis, providing an exciting view of the potential involvement of circSmox in SCI pathogenesis.

Ferroptosis related genes participate in the pathogenesis of spinal cord injury via HIF-1 signaling pathway

BACKGROUND

Spinal cord injury (SCI) is a crushing disease without a effective and specific therapeutic strategy. Therefore, it is crucial to uncover underlying mechanism in order to identify potential treatments for SCI. Current studies show ferroptosis might pay important role in SCI.

METHODS

In this study, we aimed to identify the key ferroptosis-related genes providing therapeutic targets for SCI. GSE45006, GSE19890 and GSE156999 from Gene Expression Omnibus (GEO) database were analyzed.

RESULTS

A total of 61 ferroptosis-related DEGs were identified, followed by bioinformatics enrichment analyses and PPI network construction. Ten key ferroptosis-related genes were identified by Cytoscape (Cytohubba), most of which were enriched in the HIF-1 signaling pathway. Then we constructed a clip SCI rat model and qPCR was performed to assess the expressions of five genes enriched in HIF-1 signaling pathway (Stat3, Tlr4, Hmox1, Hif1a and Cybb). Finally, a ceRNA network, Stat3, Tlr4, Hmox1/miR127, miR383, miR485/rno-Mut_0003, rno-Pwwp2a_0002 was constructed and expression of mentioned molecules were validated by chip data.

CONCLUSIONS

Five hub genes from HIF-1 signaling pathway were identified and might play a central role in SCI, which indicated that ferroptosis was correlated with HIF-1 signaling pathway. These results can provide a new insight into molecular mechanisms and identify potential therapeutic targets for SCI.

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.

Exosomes Derived from lncRNA TCTN2-Modified Mesenchymal Stem Cells Improve Spinal Cord Injury by miR-329-3p/IGF1R Axis

Mesenchymal stem cells (MSCs)-derived exosomes play significant roles in alleviating spinal cord injury (SCI). Previous study showed that long non-coding RNA tectonic family member 2 (TCTN2) was able to relieve SCI. Herein, whether TCTN2 exerted its roles in functional recovery after SCI via exosomes derived from MSCs was explored. The SCI model was established in rats, and the neurological function was evaluated using the Basso, Beattie, and Bresnahan (BBB) scoring. Lipopolysaccharide (LPS)-induced differentiated PC12 cells were used as an in vitro model for neurotoxicity research. The expression of genes and proteins was detected by qRT-PCR and Western blot. Exosomes were isolated by ultracentrifugation and qualified by TEM and Western blot. In vitro assays were performed using CCK-8 assay, EdU assay, and flow cytometry, respectively. Dual-luciferase reporter assay and RIP assay were used to confirm the target relationship between miR-329-3p and TCTN2 or insulin-like growth factor1 receptor (IGF1R). TCTN2 expression was down-regulated in SCI model rat and lipopolysaccharide (LPS)-stimulated PC12 cells. MSCs produced exosomes and could package TCTN2 into secreted exosomes. Tail vein injection of TCTN2 exosomes into rats significantly improved functional recovery of SCI. Meanwhile, TCTN2 exosomes treatment alleviated LPS-induced neuronal apoptosis, inflammation, and oxidative stress in vitro. Additionally, TCTN2 targeted miR-329-3p and subsequently regulated the expression of its target IGF1R. Rescue assays suggested that miR-329-3p/IGF1R axis mediated the beneficial effects of TCTN2 exosomes on LPS-treated PC12 cells. In all, exosomes derived from TCTN2-modified MSCs could improve functional recovery of SCI in vivo and attenuate LPS-induced neuronal apoptosis, inflammation, and oxidative stress in vitro via miR-329-3p/IGF1R axis, suggesting a novel insight into the development of MSC-exosomes-based therapy for SCI.

Emerging roles of long non-coding RNAs in spinal cord injury

Spinal cord injury (SCI) is the most serious complication of spinal injury and often leads to severe dysfunction of the limb below the injured segment. SCI causes not only serious physical and psychological harm to the patients, but imposes an enormous economic burden on the whole society. Great efforts have been made to improve the functional outcomes of patients with SCI; however, therapeutic advances have far been limited. Long non-coding RNA (lncRNA) is an important regulator of gene expression and has recently been characterized as a key regulator of central nervous system stabilization. Emerging evidence suggested that lncRNAs are significantly dysregulated and play a key role in the development of SCI. Our review summarizes current researches regarding the roles of deregulated lncRNAs in modulating apoptosis, inflammatory response, neuronal behavior in SCI. These studies suggest that specific regulation of lncRNA or its downstream targets may provide a new therapeutic approach for this desperate disease.

Promoting functions of microRNA-29a/199B in neurological recovery in rats with spinal cord injury through inhibition of the RGMA/STAT3 axis

Background

The prognostic and therapeutic potential of microRNAs (miRNAs) in spinal cord injury (SCI) has aroused increasing concerns. This study aims to research the functions of miR-29a/199B in the neurological function recovery after SCI and the mechanical mechanism.

Methods

A rat model with SCI was induced with sham-operated ones as control. The locomotor function and coordination of rat hindlimbs were determined by a Basso, Beattie, and Bresnahan (BBB) locomotor rating scale and a ladder-climbing test, respectively. Expression of a neurofilament protein NF-200 and synaptophysin in gray matter of rats was determined to evaluate neuronal recovery in a cellular perspective. Binding relationships between miR-29a/199B with RGMA were predicted and validated using luciferase assays. Altered expression of miR-29a/199B and RGMA was introduced to explore their functions in rat neurological functions. The protein level and phosphorylation of STAT3 in gray matter were measured by western blot analysis.

Results

miR-29a and miR-199B were poorly expressed, while RGMA was abundantly expressed in gray matter at injury sites. Either miR-29a or miR-199B could bind to RGMA. Overexpression of miR-29a/199B or silencing of RGMA led to an increase in BBB locomotor scores, hindlimb coordination ability, and the expression of NF-200 and synaptophysin in gray matter. Further inhibition in miR-29a/199B blocked the promoting roles of RGMA silencing in neurological recovery. Upregulation of miR-29a/199B or downregulation of RGMA suppressed the phosphorylation of STAT3.

Conclusion

This study evidenced that miR-29a and miR-199B negatively regulated RGMA to suppress STAT3 phosphorylation, therefore promoting the neurological function recovery in rats following SCI.

Inhibition of JAK1/2 Tyrosine Kinases Reduces Neurogenic Heterotopic Ossification After Spinal Cord Injury

Neurogenic heterotopic ossifications (NHO) are very incapacitating complications of traumatic brain and spinal cord injuries (SCI) which manifest as abnormal formation of bone tissue in periarticular muscles. NHO are debilitating as they cause pain, partial or total joint ankylosis and vascular and nerve compression. NHO pathogenesis is unknown and the only effective treatment remains surgical resection, however once resected, NHO can re-occur. To further understand NHO pathogenesis, we developed the first animal model of NHO following SCI in genetically unmodified mice, which mimics most clinical features of NHO in patients. We have previously shown that the combination of (1) a central nervous system lesion (SCI) and (2) muscular damage (via an intramuscular injection of cardiotoxin) is required for NHO development. Furthermore, macrophages within the injured muscle play a critical role in driving NHO pathogenesis. More recently we demonstrated that macrophage-derived oncostatin M (OSM) is a key mediator of both human and mouse NHO. We now report that inflammatory monocytes infiltrate the injured muscles of SCI mice developing NHO at significantly higher levels compared to mice without SCI. Muscle infiltrating monocytes and neutrophils expressed OSM whereas mouse muscle satellite and interstitial cell expressed the OSM receptor (OSMR). In vitro recombinant mouse OSM induced tyrosine phosphorylation of the transcription factor STAT3, a downstream target of OSMR:gp130 signaling in muscle progenitor cells. As STAT3 is tyrosine phosphorylated by JAK1/2 tyrosine kinases downstream of OSMR:gp130, we demonstrated that the JAK1/2 tyrosine kinase inhibitor ruxolitinib blocked OSM driven STAT3 tyrosine phosphorylation in mouse muscle progenitor cells. We further demonstrated in vivo that STAT3 tyrosine phosphorylation was not only significantly higher but persisted for a longer duration in injured muscles of SCI mice developing NHO compared to mice with muscle injury without SCI. Finally, administration of ruxolitinib for 7 days post-surgery significantly reduced STAT3 phosphorylation in injured muscles in vivo as well as NHO volume at all analyzed time-points up to 3 weeks post-surgery. Our results identify the JAK/STAT3 signaling pathway as a potential therapeutic target to reduce NHO development following SCI.

LncRNA DGCR5 suppresses neuronal apoptosis to improve acute spinal cord injury through targeting PRDM5

Spinal cord injury (SCI) usually results in neurological damage. DGCR5 is closely related to neurological disorders, and this study aims to explore its role in neuronal apoptosis in acute SCI. The ASCI model was established in rats, and the Basso, Beattie, and Bresnahan (BBB) scoring was used to assess the neurological function. The expression of RNA and protein was quantified by quantitative real-time PCR (qRT-PCR) and western blotting, respectively. The oxygenglucose deprivation (OGD) was performed upon neurons and apoptosis was evaluated by flow cytometry. The interaction and binding between DGCR5 and PRDM5 was detected with RNA pull-down and RIP assay, respectively. DGCR5 was down-regulated in ASCI model rat and in neurons treated with hypoxia. Over-expression of DGCR5 inhibited neuronal apoptosis. Interaction between DGCR5 negatively regulated PRDM5 protein expression by binding and interacting with it. DGCR5 inhibited neuronal apoptosis through PRDM5. Over-expressed DGCR5 ameliorated ASCI in rat. DGCR5 suppresses neuronal apoptosis through directly binding and negatively regulating PRDM5, and thereby ameliorating ASCI.