Spinal cord injury induced neuropathic pain: Molecular targets and therapeutic approaches

miR-363-5p protects from neuropathic pain in chronic constriction injury (CCI) rat models and regulates Schwann cell injury via negatively modulating SERPING1

OBJECTIVES

Due to the complex and unclear pathogenesis of neuropathic pain, there is a lack of effective therapeutic strategy. miR-363-5p was considered of great potential in mediating the development of neuropathic pain, which has not been confirmed with direct evidence. This study evaluated the role of miR-363-5p in neuropathic pain with animal and cell models, aiming to reveal the potential of miR-363-5p in target therapy of neuropathic pain.

METHODS

Chronic constriction injury (CCI) rat models were established as the neuropathic pain model. The expression of miR-363-5p and its target was evaluated by PCR. The painology behaviors were evaluated to assess the function of miR-363-5p. Schwann cells were induced with LPS mimicking cell injury during neuropathic pain. Inflammation and cell growth were estimated by ELISA and CCK8 assays.

RESULTS

Significant downregulation of miR-363-5p and upregulation of SERPING1 were observed in CCI rats. miR-363-5p negatively regulated SERPING1 in CCI rats and LPS-induced Schwann cells. Overexpressing miR-363-5p could improve pain threshold and alleviate inflammation in CCI rats. It also a ttenuated LPS-induced inflammation and reduced proliferation in Schwann cells. The overexpression of SERPING1 could reverse the protective effect of miR-363-5p on CCI rats and LPS-induced Schwann cell injury.

CONCLUSION

miR-363-5p protected from neuropathic pain via alleviating Schwann cell injury by negatively modulating SERPING1.

Spinal Cord Stimulation for Spinal Cord Injury-Related Pain: A Pilot Study

BACKGROUND

Spinal cord stimulation (SCS) has emerged as an effective treatment for managing chronic pain that is unresponsive to traditional therapies. While SCS is well documented for conditions like failed back surgery syndrome (FBSS) and complex regional pain syndrome (CRPS), its effectiveness in managing pain related to spinal cord injuries (SCI) is less studied. This study aims to assess the efficacy of SCS in alleviating SCI-related pain and improving patients' quality of life, filling a gap in the existing literature.

METHODS

This cohort study included 15 adult patients with traumatic and non-traumatic SCIs, treated between 2016 and 2022. Patients received SCS implants after either a trial or direct implantation. Pain levels were assessed using visual analog scale (VAS) scores, while quality of life was evaluated using the EuroQol five-dimensional (EQ-5D) scale. The SCS devices were implanted at different spinal levels, with various stimulation protocols applied, including high-frequency stimulation (10 kHz).

RESULTS

In patients with traumatic SCI, the mean VAS score decreased from 8.6 to 4.5, with 71% reporting more than 50% pain relief. Non-traumatic SCI patients experienced a reduction from 8.5 to 2.5, with all showing more than 50% pain relief. EQ-5D scores improved in both groups. A 49% reduction in pain medication usage was also observed, though one patient required revision surgery due to an adverse event.

CONCLUSIONS

SCS significantly reduces pain and improves quality of life for SCI patients, particularly with high-frequency protocols. While promising, further research is needed to optimize patient selection and stimulation parameters for better long-term outcomes.

The impact of time from injury to surgery on the risk of neuropathic pain after traumatic spinal cord injury

Traumatic spinal cord injury (SCI) is a devastating neurological disorder often accompanied by neuropathic pain (NeP), significantly affecting patients' quality of life. This retrospective study aimed to investigate the impact of the time from injury to surgery on the development of NeP following traumatic SCI. Medical records of patients with traumatic SCI who underwent surgical intervention between January 2017 and January 2021 at two specialized centers were reviewed. Variables associated with NeP including demographics, injury profiles, medical history, surgical details, and pain assessments were investigated. Independent risk factors related to NeP were identified using multivariate logistic regression analysis. A total of 320 patients met the inclusion criteria, with 245 (76.6%) being male and a mean age of 56.5 ± 13.2 years. NeP was identified in 48.4% of patients (155 of 320). The multivariate analysis identifies age at injury, Injury Severity Score, and the neurological level of injury as independent risk factors for the development of NeP in both AIS A and AIS B, C, and D subgroups. Additionally, a significant association between the time from injury to surgery and NeP was observed in AIS B, C, and D patients, while no such association was found in AIS A patients. This study highlights the benefits of early and ultra-early surgical intervention in preventing NeP in patients with incomplete traumatic SCI (AIS B, C, and D), underscoring the importance of optimizing surgical timing to improve patient outcomes. Prospective studies are warranted to establish evidence-based surgical guidelines for managing traumatic SCI and preventing NeP effectively.

Analysis of Crucial Genes and Pathways Associated with Spared Nerve Injury-Induced Neuropathic Pain

Purpose. The study was aimed at elucidating the molecular mechanism underlying neuropathic pain induced by spared nerve injury (SNI). Methods. The microarray data of GSE30691 were downloaded from the Gene Expression Omnibus database, including sciatic nerve lesion samples at 3, 7, 21, and 40 days after SNI and sham control samples at 3, 7, and 21 days. Differential analysis along with Mfuzz clustering analysis was performed to screen crucial clusters and cluster genes. Subsequently, comprehensive bioinformatic analyses were performed, including functional enrichment analysis, protein-protein interaction (PPI) network and module analysis, and transcription factor- (TF-) gene and miRNA-target interaction predictions. Moreover, the screened differentially expressed genes (DEGs) were corroborated using two other microarray datasets. Results. Three clusters with different change trends over time after SNI were obtained. Protein kinase CAMP-activated catalytic subunit beta (Prkacb), complement C3 (C3), and activating transcription factor 3 (Atf3) were hub nodes in the PPI network, and fibroblast growth factor 9 (Fgf9) was found to interact with more TFs. Prkacb and Fgf9 were significantly enriched in the MAPK signaling pathway. Moreover, rno-miR-3583-5p was targeted by Fgf9, and rno-miR-1912-3p was targeted by neuregulin 1 (Nrg1). Key genes like Nrg1 and Fgf9 in cluster 1, Timp1 in cluster 2, and Atf3 and C3 in cluster 3 were screened out after corroborating microarray data with other microarray data. Conclusions. Key pathways like the MAPK signaling pathway and crucial genes like Prkacb, Nrg1, Fgf9, Timp1, C3, and Atf3 may contribute to SNI-induced neuropathic pain development in rats.

Yoga: Can it be integrated with treatment of neuropathic pain?

Background

Neuropathic pain (NP) is a debilitating condition that may result from spinal cord injury (SCI). Nearly 75% of all SCI results in NP affecting 17,000 new individuals in the United States every year, and an estimated 7–10% of people worldwide. It is caused by damaged or dysfunctional nerve fibers sending aberrant signals to pain centers in the central nervous system causing severe pain that affects daily life and routine. The mechanisms underlying NP are not fully understood, making treatment difficult. Identification of specific molecular pathways that are involved in pain syndromes and finding effective treatments has become a major priority in current SCI research. Yoga has therapeutic applications may prove beneficial in treating subjects suffering chronically with SCI induced NP, chronic back and associated pains if necessary experimental data is generated

Summary

This review aims to discuss the implications of various mechanistic approaches of yoga which can be tested by new study designs around various nociceptive molecules including matrix metalloproteinases (MMPs), cation-dependent chloride transporter (NKCC1) etc in SCI induced NP patients.

Key messages

Thus, yogic practices could be used in managing SCI induced NP pain by regulating the action of various mechanisms and its associated molecules. Modern prescriptive treatment strategies combined with alternative approaches like yoga should be used in rehabilitation centers and clinics in order to ameliorate chronic NP. We recommend practical considerations of careful yoga practice as part of an integrative medicine approach for NP associated with SCI.

Spinal Cord Stimulation for Pain Treatment After Spinal Cord Injury

In addition to restoration of bladder, bowel, and motor functions, alleviating the accompanying debilitating pain is equally important for improving the quality of life of patients with spinal cord injury (SCI). Currently, however, the treatment of chronic pain after SCI remains a largely unmet need. Electrical spinal cord stimulation (SCS) has been used to manage a variety of chronic pain conditions that are refractory to pharmacotherapy. Yet, its efficacy, benefit profiles, and mechanisms of action in SCI pain remain elusive, due to limited research, methodological weaknesses in previous clinical studies, and a lack of mechanistic exploration of SCS for SCI pain control. We aim to review recent studies and outline the therapeutic potential of different SCS paradigms for traumatic SCI pain. We begin with an overview of its manifestations, classification, potential underlying etiology, and current challenges for its treatment. The clinical evidence for using SCS in SCI pain is then reviewed. Finally, future perspectives of pre-clinical research and clinical study of SCS for SCI pain treatment are discussed.

Folic Acid Modulates Matrix Metalloproteinase-2 Expression, Alleviates Neuropathic Pain, and Improves Functional Recovery in Spinal Cord-Injured Rats

BACKGROUND

The molecular underpinnings of spinal cord injury (SCI) associated with neuropathic pain (NP) are unknown. Recent studies have demonstrated that matrix metalloproteinases (MMPs) such as MMP2 play a critical role in inducing NP following SCI. Promoter methylation of MMPs is known to suppress their transcription and reduce NP. In this context, it has been shown in rodents that folic acid (FA), an FDA approved dietary supplement and key methyl donor in the central nervous system (CNS), increases axonal regeneration and repair of injured CNS in part via methylation.

PURPOSE

Based on above observations, in this study, we test whether FA could decrease MMP2 expression and thereby decrease SCI-induced NP.

METHODS

Sprague-Dawley male rats weighing 250-270 g received contusion spinal cord injuries (cSCIs) with a custom spinal cord impactor device that drops a 10 g weight from a height of 12.5 mm. The injured rats received either i.p. injections of FA (80 µg/kg) or water (control) 3 days prior and 17 days post-cSCI (mid phase) or for 3 days pre-cSCI and 14 days post-cSCI ending on the 42nd day of cSCI (late phase). The functional neurological deficits due to cSCI were then assessed by Basso, Beattie, and Bresnahan (BBB) scores either on post-impaction days 0 through 18 post-cSCI (mid phase) or on days 0, 2, 7, 14, 21, 28, 35, and 42 (late phase). Baseline measurements were taken the day before starting treatments. Thermal hyperalgesia (TH) testing for pain was performed on 4 days pre-cSCI (baseline data) and on days 18, 21, 28, 35, and 42 post-cSCI. Following TH testing, animals were euthanized and spinal cords harvested for MMP-2 expression analysis.

RESULT

The FA-treated groups showed higher BBB scores during mid phase (day 18) and in late phase (day 42) of injury compared to controls, suggesting enhanced functional recovery. There is a transient decline in TH in animals from the FA-treated group compared to controls when tested on days 18, 21, 28, and 35, indicative of a decrease in NP. However, when tested 25 days after stopping FA administration on day 42 of cSCI, no significant difference in TH was observed between FA-treated and control animals. Western blot analysis of the injured spinal cord from FA-treated animals showed significant decline in MMP2 expression compared to spinal cord samples from water-treated controls.

CONCLUSION

Together, these data suggest that FA could alleviate NP and improve functional recovery post-SCI, possibly by reducing the expression of MMP2. Further studies will open up a novel and easy natural therapy, ideal for clinical translation with minimal side effects, for managing SCI-induced NP. Such studies might also throw light on a possible epigenetic mechanism in FA-induced recovery after SCI.

Gene expression profiles reveal key pathways and genes associated with neuropathic pain in patients with spinal cord injury

Previous gene expression profiling studies of neuropathic pain (NP) following spinal cord injury (SCI) have predominantly been performed in animal models. The present study aimed to investigate gene alterations in patients with spinal cord injury and to further examine the mechanisms underlying NP following SCI. The GSE69901 gene expression profile was downloaded from the public Gene Expression Omnibus database. Samples of peripheral blood mononuclear cells (PBMCs) derived from 12 patients with intractable NP and 13 control patients without pain were analyzed to identify the differentially expressed genes (DEGs), followed by functional enrichment analysis and protein‑protein interaction (PPI) network construction. In addition, a transcriptional regulation network was constructed and functional gene clustering was performed. A total of 70 upregulated and 61 downregulated DEGs were identified in the PBMC samples from patients with NP. The upregulated and downregulated genes were significantly involved in different Gene Ontology terms and pathways, including focal adhesion, T cell receptor signaling pathway and mitochondrial function. Glycogen synthase kinase 3 β (GSK3B) was identified as a hub protein in the PPI network. In addition, ornithine decarboxylase 1 (ODC1) and ornithine aminotransferase (OAT) were regulated by additional transcription factors in the regulation network. GSK3B, OAT and ODC1 were significantly enriched in two functional gene clusters, the function of mitochondrial membrane and DNA binding. Focal adhesion and the T cell receptor signaling pathway may be significantly linked with NP, and GSK3B, OAT and ODC1 may be potential targets for the treatment of NP.