Critical signaling pathways during Wallerian degeneration of peripheral nerve

Exploring the high-quality ingredients and mechanisms of Da Chuanxiong Formula in the treatment of neuropathic pain based on network pharmacology, molecular docking, and molecular dynamics simulation

Da Chuanxiong Formula (DCXF) is a traditional herbal prescription used for pain management. It consists of Chuanxiong Rhizoma (CR) and Gastrodiae Rhizoma (GR). Despite its long history of use, the underlying therapeutic mechanism of DCXF remains insufficiently understood. Therefore, in this study, key target genes were obtained through network pharmacology research methods and molecular docking techniques, including transient receptor potential vanilloid 1 (TRPV1), adenosine A2a receptor (ADORA2A), nuclear receptor subfamily 3 group C member 1 (NR3C1), and protein kinase C beta (PRKCB). Molecular dynamics simulations demonstrated the favorable binding between all four key genes and their corresponding compounds. Notably, chronic constriction injury (CCI) treatment resulted in a significant decrease in mechanical threshold and thermal latency period for rat foot contraction, which was ameliorated upon administration of DCXF. Furthermore, real-time quantitative reverse transcription PCR (RT-qPCR) and western blot (WB) analyses indicated an upregulation of TRPV1, ADORA2A, NR3C1, and PRKCB expression in the rat dorsal root ganglion following CCI, which was attenuated by treatment with DCXF. The expressions of inflammatory factors, including tumor necrosis factor-α (TNF-α), interleukin 1 beta (IL-1β), and interleukin 6 (IL-6), in the rat dorsal root ganglion were assessed using ELISA, confirming consistent trends with the aforementioned findings. The results of this study offer a promising theoretical foundation for the utilization of DCXF in the treatment of neuropathic pain (NP).

Neuritin accelerates Schwann cell dedifferentiation via PI3K/Akt/mTOR signalling pathway during Wallerian degeneration

Neuritin, also known as candidate plasticity gene 15 (CPG15), was first identified as one of the activity-dependent gene products in the brain. Previous studies have been reported that Neuritin induces neuritogenesis, neurite arborization, neurite outgrowth and synapse formation, which are involved in the development and functions of the central nervous system. However, the role of Neuritin in peripheral nerve injury is still unknown. Given the importance and necessity of Schwann cell dedifferentiation response to peripheral nerve injury, we aim to investigate the molecular mechanism of Neuritin steering Schwann cell dedifferentiation during Wallerian degeneration (WD) in injured peripheral nerve. Herein, using the explants of sciatic nerve, an ex vivo model of nerve degeneration, we provided evidences indicating that Neuritin vividly accelerates Schwann cell dedifferentiation. Moreover, we found that Neuritin promotes Schwann cell demyelination as well as axonal degeneration, phagocytosis, secretion capacity. In summary, we first described Neuritin acts as a positive regulator for Schwann cell dedifferentiation and WD after peripheral nerve injury.

Next-generation RNA sequencing elucidates transcriptomic signatures of pathophysiologic nerve regeneration

The cellular and molecular underpinnings of Wallerian degeneration have been robustly explored in laboratory models of successful nerve regeneration. In contrast, there is limited interrogation of failed regeneration, which is the challenge facing clinical practice. Specifically, we lack insight on the pathophysiologic mechanisms that lead to the formation of neuromas-in-continuity (NIC). To address this knowledge gap, we have developed and validated a novel basic science model of rapid-stretch nerve injury, which provides a biofidelic injury with NIC development and incomplete neurologic recovery. In this study, we applied next-generation RNA sequencing to elucidate the temporal transcriptional landscape of pathophysiologic nerve regeneration. To corroborate genetic analysis, nerves were subject to immunofluorescent staining for transcripts representative of the prominent biological pathways identified. Pathophysiologic nerve regeneration produces substantially altered genetic profiles both temporally and in the mature neuroma microenvironment, in contrast to the coordinated genetic signatures of Wallerian degeneration and successful regeneration. To our knowledge, this study presents as the first transcriptional study of NIC pathophysiology and has identified cellular death, fibrosis, neurodegeneration, metabolism, and unresolved inflammatory signatures that diverge from pathways elaborated by traditional models of successful nerve regeneration.

Effects of Different-Syllable Aggressive Calls on Food Intake and Gene Expression in Vespertilio sinensis

Social animals enjoy colony benefits but are also exposed to social stress, which affects their physiology in many ways, including alterations to their energy intake, metabolism, and even gene expression. Aggressive calls are defined as calls emitted during aggressive conflicts between individuals of the same species over resources, such as territory, food, or mates. Aggressive calls produced by animals in different aggressive states indicate different levels of competitive intentions. However, whether aggressive calls produced in different aggressive states exert different physiological effects on animals has yet to be determined. Importantly, bats live in clusters and frequently produce aggressive calls of different syllables, thus providing an ideal model for investigating this question. Here, we conducted playback experiments to investigate the effects of two types of aggressive calls representing different competitive intentions on food intake, body mass, corticosterone (CORT) concentration, and gene expression in Vespertilio sinensis. We found that the playback of both aggressive calls resulted in a significant decrease in food intake and body mass, and bats in the tonal-syllable aggressive-calls (tonal calls) playback group exhibited a more significant decrease when compared to the noisy-syllable aggressive-calls (noisy calls) playback group. Surprisingly, the weight and food intake in the white-noise group decreased the most when compared to before playback. Transcriptome results showed that, when compared to the control and white-noise groups, differentially expressed genes (DEGs) involved in energy and metabolism were detected in the noisy-calls playback group, and DEGs involved in immunity and disease were detected in the tonal-calls playback group. These results suggested that the playback of the two types of aggressive calls differentially affected body mass, food intake, and gene expression in bats. Notably, bat responses to external-noise playback (synthetic white noise) were more pronounced than the playback of the two aggressive calls, suggesting that bats have somewhat adapted to internal aggressive calls. Comparative transcriptome analysis suggested that the playback of the two syllabic aggressive calls disrupted the immune system and increased the risk of disease in bats. This study provides new insight into how animals differ in response to different social stressors and anthropogenic noise.

Integrative Analysis of Transcriptome and Metabolome Reveals Molecular Responses in Eriocheir sinensis with Hepatopancreatic Necrosis Disease

Hepatopancreatic necrosis disease (HPND) is a highly lethal disease that first emerged in 2015 in Jiangsu Province, China. So far, most researchers believe that this disease is caused by abiotic factors. However, its true pathogenic mechanism remains unknown. In this study, the effects of HPND on the metabolism and other biological indicators of the Chinese mitten crab (Eriocheir sinensis) were evaluated by integrating transcriptomics and metabolomics. Our findings demonstrate that the innate immunity, antioxidant activity, detoxification ability, and nervous system of the diseased crabs were affected. Additionally, metabolic pathways such as lipid metabolism, nucleotide metabolism, and protein metabolism were dysregulated, and energy production was slightly increased. Moreover, the IL-17 signaling pathway was activated and high levels of autophagy and apoptosis occurred in diseased crabs, which may be related to hepatopancreas damage. The abnormal mitochondrial function and possible anaerobic metabolism observed in our study suggested that functional hypoxia may be involved in HPND progression. Furthermore, the activities of carboxylesterase and acetylcholinesterase were significantly inhibited, indicating that the diseased crabs were likely stressed by pesticides such as pyrethroids. Collectively, our findings provide new insights into the molecular mechanisms altered in diseased crabs, as well as the etiology and pathogenic mechanisms of HPND.

SIRT6 Negatively Regulates Schwann Cells Dedifferentiation via Targeting c-Jun During Wallerian Degeneration After Peripheral Nerve Injury

Silent information regulator 6 (SIRT6) is a mammalian homolog of the nicotinamide adenine dinucleotide (NAD)-dependent deacetylase sirtuin family. Previous studies have been reported a pro-regenerative role of SIRT6 in central nervous system injury. However, the role of SIRT6 in peripheral nerve injury is still unknown. Given the importance and necessity of Schwann cell dedifferentiation response to peripheral nerve injury, we aim to investigate the molecular mechanism of SIRT6 steering Schwann cell dedifferentiation during Wallerian degeneration in injured peripheral nerve. Herein, we first examined the expression pattern of SIRT6 after peripheral nerve injury. Using the explants of sciatic nerve, an ex vivo model of nerve degeneration, we provided evidences indicating that SIRT6 inhibitor accelerates Schwann cell dedifferentiation as well as axonal and myelin degeneration, while SIRT6 activator attenuates this process. Moreover, in an in vitro Schwann cell dedifferentiation model, we found SIRT6 inhibitor promotes Schwann cell dedifferentiation through upregulating the expression of c-Jun. In addition, downregulation of c-Jun reverse the effects of SIRT6 inhibition on the Schwann cells dedifferentiation and axonal and myelin degeneration. In summary, we first described SIRT6 acts as a negative regulator for Schwann cells dedifferentiation during Wallerian degeneration and c-Jun worked as a direct downstream partner of SIRT6 in injured peripheral nerve.

The interaction of stem cells and vascularity in peripheral nerve regeneration

The degree of nerve regeneration after peripheral nerve injury can be altered by the microenvironment at the site of injury. Stem cells and vascularity are postulated to be a part of a complex pathway that enhances peripheral nerve regeneration; however, their interaction remains unexplored. This review aims to summarize current knowledge on this interaction, including various mechanisms through which trophic factors are promoted by stem cells and angiogenesis. Angiogenesis after nerve injury is stimulated by hypoxia, mediated by vascular endothelial growth factor, resulting in the growth of pre-existing vessels into new areas. Modulation of distinct signaling pathways in stem cells can promote angiogenesis by the secretion of various angiogenic factors. Simultaneously, the importance of stem cells in peripheral nerve regeneration relies on their ability to promote myelin formation and their capacity to be influenced by the microenvironment to differentiate into Schwann-like cells. Stem cells can be acquired through various sources that correlate to their differentiation potential, including embryonic stem cells, neural stem cells, and mesenchymal stem cells. Each source of stem cells serves its particular differentiation potential and properties associated with the promotion of revascularization and nerve regeneration. Exosomes are a subtype of extracellular vesicles released from cell types and play an important role in cell-to-cell communication. Exosomes hold promise for future transplantation applications, as these vesicles contain fewer membrane-bound proteins, resulting in lower immunogenicity. This review presents pre-clinical and clinical studies that focus on selecting the ideal type of stem cell and optimizing stem cell delivery methods for potential translation to clinical practice. Future studies integrating stem cell-based therapies with the promotion of angiogenesis may elucidate the synergistic pathways and ultimately enhance nerve regeneration.

Exosomal circRNA as a novel potential therapeutic target for multiple myeloma-related peripheral neuropathy

Peripheral neuropathy (PN) is an incurable complication of multiple myeloma (MM) which adversely affects patients' quality of life. The important roles that Circular RNAs (circRNAs) play in tumor progression, and exosome-mediated intracellular communication has been recognized as a crucial factor in the pathogenesis of MM. However, the role of exosome-derived circRNAs (exo-circRNAs) in MM and MM-induced PN remains elusive. In this study, we aimed to investigate the correlation between serum exo-circRNAs and MM to preliminarily explore the role of exo-circRNAs in MM-related PN. A cohort of 25 MM patients and 5 healthy control (HC) individuals were enrolled in the study. High-throughput sequencing and qRT PCR validation of serum exo-circRNAs were used to generate the aberrantly expressed exo-circRNAs profiles. Bioinformatics analysis was done using GO, KEGG, miRanda, Targetscan and Metascape. Correlation analysis was conducted between chr2:2744228-2,744,407+ and clinical characteristics of PN. ROC curve, univariate and multivariate COX regression models were conducted to identify the prognostic potential of chr2:2744228-2,744,407+ in the MM-related PN. 265 upregulated circRNAs and 787 downregulated circRNAs, with at least a two-fold difference in expression level in MM patients vs HC, were screened. Bioinformatics analysis indicated that upregulated circRNAs had the potential to facilitate MM-related PN. Furthermore, PCR validated the abundant expression of chr2:2744228-2,744,407+ in the serum exosomes of 25 MM patients. Bioinformatics analysis indicated that chr2:2744228-2,744,407+ might induce MM related PN via the downstream miRNA and GRIN2B axis. Overexpressed chr2:2744228-2,744,407+ in the serum exosomes of MM patients might lead to the downregulation of hsa-miR-6829-3p, elevation of GRIN2B in the serum and PC12 cells, and inhibited cell viability. The correlation analysis indicated that the expression of chr 2:2744228-2,744,407+ was positively correlated with the clinical characteristics of PN. ROC curve, univariate and multivariate COX regression analysis identified that chr2:2744228-2,744,407+ is an independent prognostic factor in the MM related PN. We identified that the abnormal expression of the serum exo-circRNA was correlated with MM-related PN, implying that exo-circRNA has potential as a novel therapeutic target for MM related PN.

Histological Assessment of Wallerian Degeneration of the Rat Tibial Nerve Following Crush and Transection Injuries

BACKGROUND

 Wallerian degeneration (WD) following peripheral nerve injury (PNI) is an area of growing focus for pharmacological developments. Clinically, WD presents challenges in achieving full functional recovery following PNI, as prolonged denervation of distal tissues for an extended period of time can irreversibly destabilize sensory and motor targets with secondary tissue atrophy. Our objective is to improve upon histological assessments of WD.

METHODS

 Conventional methods utilize a qualitative system simply describing the presence or absence of WD in nerve fibers. We propose a three-category assessment that allows more quantification: A fibers appear normal, B fibers have moderate WD (altered axoplasm), and C fibers have extensive WD (myelin figures). Analysis was by light microscopy (LM) on semithin sections stained with toluidine blue in three rat tibial nerve lesion models (crush, partial transection, and complete transection) at 5 days postop and 5 mm distal to the injury site. The LM criteria were verified at the ultrastructural level. This early outcome measure was compared with the loss of extensor postural thrust and the absence of muscle atrophy.

RESULTS

 The results showed good to excellent internal consistency among counters, demonstrating a significant difference between the crush and transection lesion models. A significant decrease in fiber density in the injured nerves due to inflammation/edema was observed. The growth cones of regenerating axons were evident in the crush lesion group.

CONCLUSION

 The ABC method of histological assessment is a consistent and reliable method that will be useful to quantify the effects of different interventions on the WD process.

Schwann cell reprogramming and lung cancer progression: a meta-analysis of transcriptome data

Schwann cells were identified in the tumor surrounding area prior to initiate the invasion process underlying connective tissue. These cells promote cancer invasion through direct contact, while paracrine signaling and matrix remodeling are not sufficient to proceed. Considering the intertwined structure of signaling, regulatory, and metabolic processes within a cell, we employed a genome-scale biomolecular network. Accordingly, a meta-analysis of Schwann cells associated transcriptomic datasets was performed, and the core information on differentially expressed genes (DEGs) was obtained by statistical analyses. Gene set over-representation analyses was performed on core DEGs to identify significantly functional and pathway enrichment analysis between Schwann cells and, lung adenocarcinoma (LUAD) and lung squamous cell carcinoma (LUSC). DEGs were further integrated with genome-scale human biomolecular networks. miRNAs were proposed by the reconstruction of a transcriptional and post-transcriptional regulatory network. Moreover, microarray-based transcriptome profiling was performed, and the prognostic power of selected dedifferentiated Schwann cell biomolecules was predicted. We observed that pathways associated with Schwann cells dedifferentiation was overexpressed in lung cancer samples. However, genes associated with Schwann cells migration inhibition system were downregulated. Besides, miRNA targeting those pathways were also deregulated. In this study, we report valuable data for further experimental and clinical analysis, because the proposed biomolecules have significant potential as systems biomarkers for screening or for therapeutic purposes in perineural invasion of lung cancer.

Differential gene and protein expression between rat tibial nerve and common peroneal nerve during Wallerian degeneration

Wallerian degeneration and nerve regeneration after injury are complex processes involving many genes, proteins and cytokines. After different peripheral nerve injuries the regeneration rate can differ. Whether this is caused by differential expression of genes and proteins during Wallerian degeneration remains unclear. The right tibial nerve and the common peroneal nerve of the same rat were exposed and completely cut through and then sutured in the same horizontal plane. On days 1, 7, 14, and 21 after surgery, 1–2 cm of nerve tissue distal to the suture site was dissected out from the tibial and common peroneal nerves. The differences in gene and protein expression during Wallerian degeneration of the injured nerves were then studied by RNA sequencing and proteomic techniques. In the tibial and common peroneal nerves, there were 1718, 1374, 1187, and 2195 differentially expressed genes, and 477, 447, 619, and 495 differentially expressed proteins on days 1, 7, 14, and 21 after surgery, respectively. Forty-seven pathways were activated during Wallerian degeneration. Three genes showing significant differential expression by RNA sequencing (Hoxd4, Lpcat4 and Tbx1) were assayed by real-time quantitative polymerase chain reaction. RNA sequencing and real-time quantitative polymerase chain reaction results were consistent. Our findings showed that expression of genes and proteins in injured tibial and the common peroneal nerves were significantly different during Wallerian degeneration at different time points. This suggests that the biological processes during Wallerian degeneration are different in different peripheral nerves after injury. The procedure was approved by the Animal Experimental Ethics Committee of the Second Military Medical University, China (approval No. CZ20160218) on February 18, 2016.

Systemic functional enrichment and ceRNA network identification following peripheral nerve injury

Peripheral nerve injury is a worldwide clinical issue that impacts patients' quality of life and causes huge society and economic burden. Injured peripheral nerves are able to regenerate by themselves. However, for severe peripheral nerve injury, the regenerative abilities are very limited and the regenerative effects are very poor. A better understanding of the mechanisms following peripheral nerve injury will benefit its clinical treatment. In this study, we systematically explored the dynamic changes of mRNAs and long non-coding RNAs (lncRNAs) in the injured sciatic nerve segments after nerve crush, identified significantly involved Gene ontology (GO) terms and Kyoto Enrichment of Genes and Genomes (KEGG) pathways, and innovatively analyzed the correlation of differentially expressed mRNAs and lncRNAs. After the clustering of co-expressed mRNAs and lncRNAs, we performed functional analysis, selected GO term "negative regulation of cell proliferation", and constructed a competing endogenous RNA (ceRNA) network of LIF and HMOX1 gene in this GO term. This study is the first to provide a systematic dissection of mRNA-microRNA (miRNA)-lncRNA ceRNA network following peripheral nerve injury and thus lays a foundation for further investigations of the regulating mechanisms of non-coding RNAs in peripheral nerve repair and regeneration.

Pathophysiological Changes of Physical Barriers of Peripheral Nerves After Injury

Peripheral nerves are composed of complex layered anatomical structures, including epineurium, perineurium, and endoneurium. Perineurium and endoneurium contain many physical barriers, including the blood-nerve barrier at endoneurial vessels and the perineurial barrier. These physical barriers help to eliminate flux penetration and thus contribute to the establishment of a stable microenvironment. In the current review, we introduce the anatomical compartments and physical barriers of peripheral nerves and then describe the cellular and molecular basis of peripheral physical barriers. We also specifically explore peripheral nerve injury-induced changes of peripheral physical barriers, including elevated endoneurial fluid pressure, increased leakage of tracer, decreased barrier-type endothelial cell ratio, and altered distributions and expressions of cellular junctional proteins. The understanding of the pathophysiological changes of physical barriers following peripheral nerve injury may provide a clue for the treatment of peripheral nerve injury.

Strategies to improve nerve regeneration after radical prostatectomy: a narrative review

Peripheral nerves are complex organs that spread throughout the entire human body. They are frequently affected by lesions not only as a result of trauma but also following radical tumor resection. In fact, despite the advancement in surgical techniques, such as nerve-sparing robot assisted radical prostatectomy, some degree of nerve injury may occur resulting in erectile dysfunction with significant impairment of the quality of life. The aim of this review was to provide an overview on the mechanisms of the regeneration of injured peripheral nerves and to describe the potential strategies to improve the regeneration process and the functional recovery. Yet, the recent advances in bio-engineering strategies to promote nerve regeneration in the urological field are outlined with a view on the possible future regenerative therapies which might ameliorate the functional outcome after radical prostatectomy.

Genome-wide analysis of circular RNAs in bovine cumulus cells treated with BMP15 and GDF9

Circular RNAs (circRNAs) are important members of the non-coding RNA family, and those relating to animal physiologies have been widely studied in recent years. This study aimed to explore the roles of circRNAs in the regulation of follicular development. We constructed four bovine cumulus cell cDNA libraries, including a negative control group (NC) and groups treated with BMP15, GDF9 and BMP15 + GDF9, and we sequenced the libraries on the Illumina HiSeq Xten platform. We identified 1706 circRNAs and screened for differential circRNA expression. We conducted a bioinformatics analysis of these circRNAs and screened for differential circRNAs. Functional annotation and enrichment analysis of the host genes showed that the differential circRNAs were related to locomotion, reproduction, biological adhesion, growth, rhythmic processes, biological phases and hormone secretion. According to the differential expression of circRNA between groups, there were 3 up-regulated and 6 down-regulated circRNAs in the BMP15 group as well as 12 up-regulated and 24 down-regulated circRNAs in the GDF9 group. Co-addition of both BMP15 and GDF9 resulted in 15 up-regulated and 13 down-regulated circRNAs. circ_n/a_75,circ_12691_1 and circ_n/a_303 were altered in both the BMP15 and GDF9 groups as well as in the BMP15 + GDF9 combination group. We focused on these three circRNAs because they were potentially associated with the additive effect of BMP15 and GDF9. Quantitative PCR analysis showed that the expression levels of these three circRNAs were consistent with the sequencing results. In addition, the target miRNAs of circ_n/a_75 and circ_n/a_303, miR-339a, miR-2400 and miR-30c, were down-regulated in the experimental group, which was in contrast to the circRNAs trend. These findings demonstrated that BMP15 and GDF9 may regulate the target gene through circRNA, as a miRNA sponge, in order to regulate the status of bovine cumulus cells and affect follicular development.

Transcriptome analysis of adherens junction pathway-related genes after peripheral nerve injury

The neural regeneration process is driven by a wide range of molecules and pathways. Adherens junctions are critical cellular junctions for the integrity of peripheral nerves. However, few studies have systematically characterized the transcript changes in the adherens junction pathway following injury. In this study, a rat model of sciatic nerve crush injury was established by forceps. Deep sequencing data were analyzed using comprehensive transcriptome analysis at 0, 1, 4, 7, and 14 days after injury. Results showed that most individual molecules in the adherens junctions were either upregulated or downregulated after nerve injury. The mRNA expression of ARPC1B, ARPC3, TUBA8, TUBA1C, CTNNA2, ACTN3, MET, HGF, NME1 and ARF6, which are involved in the adherens junction pathway and in remodeling of adherens junctions, was analyzed using quantitative real-time polymerase chain reaction. Most of these genes were upregulated in the sciatic nerve stump following peripheral nerve injury, except for CTNNA2, which was downregulated. Our findings reveal the dynamic changes of key molecules in adherens junctions and in remodeling of adherens junctions. These key genes provide a reference for the selection of clinical therapeutic targets for peripheral nerve injury.