miR-30c promotes Schwann cell remyelination following peripheral nerve injury

Chitosan/PLGA-based tissue engineered nerve grafts with SKP-SC-EVs enhance sciatic nerve regeneration in dogs through miR-30b-5p-mediated regulation of axon growth

Extracellular vesicles from skin-derived precursor Schwann cells (SKP-SC-EVs) promote neurite outgrowth in culture and enhance peripheral nerve regeneration in rats. This study aimed at expanding the application of SKP-SC-EVs in nerve grafting by creating a chitosan/PLGA-based, SKP-SC-EVs-containing tissue engineered nerve graft (TENG) to bridge a 40-mm long sciatic nerve defect in dogs. SKP-SC-EVs contained in TENGs significantly accelerated the recovery of hind limb motor and electrophysiological functions, supported the outgrowth and myelination of regenerated axons, and alleviated the denervation-induced atrophy of target muscles in dogs. To clarify the underlying molecular mechanism, we observed that SKP-SC-EVs were rich in a variety of miRNAs linked to the axon growth of neurons, and miR-30b-5p was the most important among others. We further noted that miR-30b-5p contained within SKP-SC-EVs exerted nerve regeneration-promoting effects by targeting the Sin3a/HDAC complex and activating the phosphorylation of ERK, STAT3 or CREB. Our findings suggested that SKP-SC-EVs-incorporating TENGs represent a novel type of bioactive material with potential application for peripheral nerve repair in the clinic.

Advances of Schwann cells in peripheral nerve regeneration: From mechanism to cell therapy

Peripheral nerve injuries (PNIs) frequently occur due to various factors, including mechanical trauma such as accidents or tool-related incidents, as well as complications arising from diseases like tumor resection. These injuries frequently result in persistent numbness, impaired motor and sensory functions, neuropathic pain, or even paralysis, which can impose a significant financial burden on patients due to outcomes that often fall short of expectations. The most frequently employed clinical treatment for PNIs involves either direct sutures of the severed ends or bridging the proximal and distal stumps using autologous nerve grafts. However, autologous nerve transplantation may result in sensory and motor functional loss at the donor site, as well as neuroma formation and scarring. Transplantation of Schwann cells/Schwann cell-like cells has emerged as a promising cellular therapy to reconstruct the microenvironment and facilitate peripheral nerve regeneration. In this review, we summarize the role of Schwann cells and recent advances in Schwann cell therapy in peripheral nerve regeneration. We summarize current techniques used in cell therapy, including cell injection, 3D-printed scaffolds for cell delivery, cell encapsulation techniques, as well as the cell types employed in experiments, experimental models, and research findings. At the end of the paper, we summarize the challenges and advantages of various cells (including ESCs, iPSCs, and BMSCs) in clinical cell therapy. Our goal is to provide the theoretical and experimental basis for future treatments targeting peripheral nerves, highlighting the potential of cell therapy and tissue engineering as invaluable resources for promoting nerve regeneration.

[MiR-132-3p negatively regulates CAMTA1 to promote Schwann cell proliferation and migration and alleviates I-125 seeds-induced exacerbation of facial nerve injury in rats]

OBJECTIVE

To investigate the regulatory effect of miR-132-3p on calmodulin-binding transcription activator 1 (CAMTA1) and Schwann cell activity in rats with facial nerve injury (FNI) treated with I-125 seeds.

METHODS

Rat Schwann cells were irradiated with I-125 seeds and transfected with miR-132-3p mimic, miR-132-3p inhibitor or sh-CAMTA1. The expressions of S100B and β-tubulin Ⅲ in the cells were detected with immunofluorescence assay, and the expressions of miR-132-3p and CAMTA1 protein were determined using RT-qPCR and Western blotting, respectively. EdU staining and Transwell assay were used to evaluate the changes in cell proliferation and migration ability. In a rat model of FNI, I-125 seeds were implanted into the facial tissues near the facial nerve 2 weeks before modeling, and miR-132-3p mimic was injected subcutaneously in the face after modeling. The pathologies of the facial nerve was assessed by HE, LFB and immunofluorescence staining. The targeting relationship between miR-132-3p and CAMTA1 was verified using StarBase v2.0 database and dual-luciferase reporter assay.

RESULTS

Rat Schwann cells showed high expressions of S100B and β-tubulin Ⅲ. I-125 seeds radiation significantly decreased miR-132-3p expression and repressed proliferation and migration of the cells (P < 0.001). Overexpression of miR-132-3p or CAMTA1 knockdown obviously enhanced proliferation and migration of the Schwann cells, while miR-132-3p knockdown produced the opposite effect. MiR-132-3p negatively regulated CAMTA1 expression. In the rat models of FNI, miR-132-3p injection significantly inhibited CAMTA1 expression and attenuated I-125 seeds-induced exacerbation of FNI.

CONCLUSION

Overexpression of miR-132-3p suppresses CAMTA1 expression and promotes Schwann cell proliferation and migration to alleviate I-125 seeds-induced exacerbation of FNI in rats.

The role of microRNAs in axon regeneration after peripheral nerve injury: a bibliometric analysis

Objective

This study analyzed the current research hotspots and future development trends of the therapeutic effects of microRNA on PNI axonal regeneration through bibliometric methods. Moreover, the current advantages and disadvantages of this field as well as future development prospects are discussed in depth.

Methods

CiteSpace V and VOSviewer were used as bibliometric tools to complete the analysis of the research focus and direction of the published articles. To supplement, sort out, and summarize, we analyzed the research status of the study on the application of microRNAs for axonal regeneration after peripheral nerve injury from 2013 to 2023.

Results

A total of 207 publications were retrieved from the Web of Science database. After exclusion and screening, a final selection of 174 articles that met the research criteria. These 174 articles were authored by a total of 846 individuals, representing 24 countries and 199 institutions. Additionally, this study presents information on the annual publication output, country distribution, top 5 contributing authors, top 5 most cited articles, and top 10 contributing institutions.

Conclusion

As one of the hottest topics today, microRNAs have become the current research hotspot in neural inflammation, neural cell repair and regeneration, neural protection, and functional recovery. With more investment in research in this field, more high-quality articles will be published in both domestic and international outstanding journals, which will bring a new era for the treatment of peripheral nerve injury.

MiR-30c-5p-Targeted Regulation of GNAI2 Improves Neural Function Injury and Inflammation in Cerebral Ischemia-Reperfusion Injury

MiRNAs are related to neuronal proliferation and apoptosis following cerebral ischemia-reperfusion injury (CIRI). This study focused on miR-30c-5p in the disease. An oxygen-glucose deprivation/re-oxygenation (OGD/R) model was prepared in HT22 cells and transfected to overexpress miR-30c-5p and G Protein Subunit Alpha I2 (GNAI2) respectively or co-transfected to silence miR-30c-5p and GNAI2. Meanwhile, a middle cerebral artery occlusion (MCAO) model was constructed in mice, and miR-30c-5p and GNAI2 were silenced in vivo simultaneously. The mice were evaluated for neurological damage, apoptosis, and inflammation. HT22 cells were tested for cytotoxicity, proliferation, apoptosis, and inflammatory factors. The interaction between miR-30c-5p and GNAI2 was predicted, analyzed, and confirmed. MiR-30c-5p was found to be downregulated in both experimental models. miR-30c-5p reduced lactate dehydrogenase production, inflammatory response, inhibit apoptosis, and enhanced neuronal proliferation, while GNAI2 overexpression showed the opposite results. Downregulated miR-30c-5p worsened neurological function, apoptosis, and inflammation of MCAO mice while silencing GNAI2 attenuated the influence of downregulated miR-30c-5p. MiR-30c-5p can improve neuronal apoptosis and inflammatory response caused by CIRI and is neuroprotective by targeting GNAI2, providing a new target for treating CIRI.

Transcription Factor BCL11A Regulates Schwann Cell Behavior During Peripheral Nerve Regeneration

Nerve injury-induced Schwann cell dedifferentiation helps to construct a favorable microenvironment for axon growth. Transcription factors regulate cell reprogramming and thus may be critical for Schwann cell phenotype switch during peripheral nerve regeneration. Here, we show that transcription factor B-cell lymphoma/leukemia 11A (BCL11A) is up-regulated in Schwann cells of injured peripheral nerves. Bcl11a silencing suppresses Schwann cell viability, decreases Schwann cell proliferation and migration rates, and impairs the debris clearance ability of Schwann cells. Reduced Bcl11a in injured peripheral nerves results in restricted axon elongation and myelin wrapping, leading to recovery failure. Mechanistically, we demonstrate that BCL11A may mediate Schwann cell activity through binding to the promoter of nuclear receptor subfamily 2 group F member 2 (Nr2f2) and regulating Nr2f2 expression. Collectively, we conclude that BCL11A is essential for Schwann cell activation and peripheral nerve regeneration, providing a potential therapeutic target for the treatment of peripheral nerve injury.

Regulation of Schwann cell proliferation and migration via miR-195-5p-induced Crebl2 downregulation upon peripheral nerve damage

Background

Schwann cells acquire a repair phenotype upon peripheral nerve injury (PNI), generating an optimal microenvironment that drives nerve repair. Multiple microRNAs (miRNAs) show differential expression in the damaged peripheral nerve, with critical regulatory functions in Schwann cell features. This study examined the time-dependent expression of miR-195-5p following PNI and demonstrated a marked dysregulation of miR-195-5p in the damaged sciatic nerve.

Methods

CCK-8 and EdU assays were used to evaluate the effect of miR-195-5 on Schwann cell viability and proliferation. Schwann cell migration was tested using Transwell and wound healing assays. The miR-195-5p agomir injection experiment was used to evaluate the function of miR-195-5p in vivo. The potential regulators and effects of miR-195-5p were identified through bioinformatics evaluation. The relationship between miR-195-5p and its target was tested using double fluorescence reporter gene analysis.

Results

In Schwann cells, high levels of miR-195-5p decreased viability and proliferation, while suppressed levels had the opposite effects. However, elevated miR-195-5p promoted Schwann cell migration determined by the Transwell and wound healing assays. In vivo injection of miR-195-5p agomir into rat sciatic nerves promote axon elongation after peripheral nerve injury by affecting Schwann cell distribution and myelin preservation. Bioinformatic assessment further revealed potential regulators and effectors for miR-195-5p, which were utilized to build a miR-195-5p-centered competing endogenous RNA network. Furthermore, miR-195-5p directly targeted cAMP response element binding protein-like 2 (Crebl2) mRNA via its 3'-untranslated region (3'-UTR) and downregulated Crebl2. Mechanistically, miR-195-5p modulated Schwann cell functions by repressing Crebl2.

Conclusion

The above findings suggested a vital role for miR-195-5p/Crebl2 in the regulation of Schwann cell phenotype after sciatic nerve damage, which may contribute to peripheral nerve regeneration.

MiRNA-206 Affects the Recovery of Sciatic Function by Stimulating BDNF Activity through the Down-regulation of Notch3 Expression

OBJECTIVE

To investigate the effects and mechanisms of microRNA 206 (miRNA-206) on neurological recovery through Notch receptor 3 (Notch3).

METHODS

The sciatic functional index (SFI), nerve conduction velocity (NCV), tricipital muscle wet weight (TWW) and cross-sectional area of the muscular fiber, and grip strength of posterior limbs were detected by establishing a model of the sciatic nerve to evaluate the effect of sciatic nerve injury model. miRNA-206 expression in the model was detected by real-time quantitative polymerase chain reaction (qRT-PCR), to regulate the effects of miRNA-206 on the proliferation of gastrocnemius myocytes by Cell Counting Kit-8 (CCK-8).

RESULTS

SFI of the model established by immediate epineurium suture after sciatic nerve resection was in the range of -150% to -100% and TWW, the average area of gastrocnemius myocytes, the NCV, and the grasping power of the hind limbs in the model were all lower than those in the normal group. And in the model, TWW, the average area of gastrocnemius myocytes, NCV, and grip strength of posterior limbs were lower in the normal group, which verified the successful establishment of the model.

CONCLUSION

Over-expression of miRNA-206 can down-regulate Notch3 expression, and then stimulate brain-derived neurotrophic factor (BDNF) activity to promote the repair and functional recovery of sciatic nerve injury.

Emerging Role of MicroRNA-30c in Neurological Disorders

MicroRNAs (miRNAs or miRs) are a class of small non-coding RNAs that negatively regulate the expression of target genes by interacting with 3' untranslated regions of target mRNAs to induce mRNA degradation and translational repression. The miR-30 family members are involved in the development of many tissues and organs and participate in the pathogenesis of human diseases. As a key member of the miR-30 family, miR-30c has been implicated in neurological disorders such as Alzheimer's disease, Parkinson's disease, multiple sclerosis, and stroke. Mechanistically, miR-30c may act as a multi-functional regulator of different pathogenic processes such as autophagy, apoptosis, endoplasmic reticulum stress, inflammation, oxidative stress, thrombosis, and neurovascular function, thereby contributing to different disease states. Here, we review and discuss the biogenesis, gene regulation, and the role and mechanisms of action of miR-30c in several neurological disorders and therapeutic potential in clinics.

miR-140-3p suppresses the proliferation and migration of macrophages

Macrophages benefit myelin debris removal, blood vessel formation, and Schwann cell activation following peripheral nerve injury. Identifying factors that modulate macrophage phenotype may advantage the repair and regeneration of injured peripheral nerves. microRNAs (miRNAs) are important regulators of many physiological and pathological processes, including peripheral nerve regeneration. Herein, we investigated the regulatory roles of miR-140-3p, a miRNA that was differentially expressed in injured rat sciatic nerves, in macrophage RAW264.7 cells. Observations from EdU proliferation assay demonstrated that elevated miR-140-3p decreased the proliferation rates of RAW264.7 cells while suppressed miR-140-3p increased the proliferation rates of RAW264.7 cells. Transwell-based migration assay showed that up-regulated and down-regulated miR-140-3p led to elevated and reduced migration abilities, respectively. However, the abundances of numerous phenotypic markers of M1 and M2 macrophages were not significantly altered by miR-140-3p mimic or inhibitor transfection. Bioinformatic analysis and miR-140-3p-induced gene suppression examination suggested that Smad3 might be the target gene of miR-140-3p. These findings illuminate the inhibitory effects of miR-140-3p on the proliferation and migration of macrophages and contribute to the cognition of the essential roles of miRNAs during peripheral nerve regeneration.

How miRNAs Regulate Schwann Cells during Peripheral Nerve Regeneration-A Systemic Review

A growing body of studies indicate that small noncoding RNAs, especially microRNAs (miRNA), play a crucial role in response to peripheral nerve injuries. During Wallerian degeneration and regeneration processes, they orchestrate several pathways, in particular the MAPK, AKT, and EGR2 (KROX20) pathways. Certain miRNAs show specific expression profiles upon a nerve lesion correlating with the subsequent nerve regeneration stages such as dedifferentiation and with migration of Schwann cells, uptake of debris, neurite outgrowth and finally remyelination of regenerated axons. This review highlights (a) the specific expression profiles of miRNAs upon a nerve lesion and (b) how miRNAs regulate nerve regeneration by acting on distinct pathways and linked proteins. Shedding light on the role of miRNAs associated with peripheral nerve regeneration will help researchers to better understand the molecular mechanisms and deliver targets for precision medicine.

Dysregulated miR-29a-3p/PMP22 Modulates Schwann Cell Proliferation and Migration During Peripheral Nerve Regeneration

Schwann cells switch to a repair phenotype following peripheral nerve injury and create a favorable microenvironment to drive nerve repair. Many microRNAs (miRNAs) are differentially expressed in the injured peripheral nerves and play essential roles in regulating Schwann cell behaviors. Here, we examine the temporal expression patterns of miR-29a-3p after peripheral nerve injury and demonstrate significant up-regulation of miR-29a-3p in injured sciatic nerves. Elevated miR-29a-3p inhibits Schwann cell proliferation and migration, while suppressed miR-29a-3p executes reverse effects. In vivo injection of miR-29a-3p agomir to rat sciatic nerves hinders the proliferation and migration of Schwann cells, delays the elongation and myelination of axons, and retards the functional recovery of injured nerves. Mechanistically, miR-29a-3p modulates Schwann cell activities via negatively regulating peripheral myelin protein 22 (PMP22), and PMP22 extensively affects Schwann cell metabolism. Our results disclose the vital role of miR-29a-3p/PMP22 in regulating Schwann cell phenotype following sciatic nerve injury and shed light on the mechanistic basis of peripheral nerve regeneration.

Involvement of the miR-363-5p/P2RX4 Axis in Regulating Schwann Cell Phenotype after Nerve Injury

Although microRNAs (miRNAs or miRs) have been studied in the peripheral nervous system, their function in Schwann cells remains elusive. In this study, we performed a microRNA array analysis of cyclic adenosine monophosphate (cAMP)-induced differentiated primary Schwann cells. KEGG pathway enrichment analysis of the target genes showed that upregulated miRNAs (mR212-5p, miR335, miR20b-5p, miR146b-3p, and miR363-5p) were related to the calcium signaling pathway, regulation of actin cytoskeleton, retrograde endocannabinoid signaling, and central carbon metabolism in cancer. Several key factors, such as purinergic receptors (P2X), guanine nucleotide-binding protein G(olf) subunit alpha (GNAL), P2RX5, P2RX3, platelet-derived growth factor receptor alpha (PDGFRA), and inositol 1,4,5-trisphosphate receptor type 2 (ITPR2; calcium signaling pathway) are potential targets of miRNAs regulating cAMP. Our analysis revealed that miRNAs were differentially expressed in cAMP-treated Schwann cells; miRNA363-5p was upregulated and directly targeted the P2X purinoceptor 4 (P2RX4)-UTR, reducing the luciferase activity of P2RX4. The expression of miRNA363-5p was inhibited and the expression of P2RX4 was upregulated in sciatic nerve injury. In contrast, miRNA363-5p expression was upregulated and P2RX4 expression was downregulated during postnatal development. Of note, a P2RX4 antagonist counteracted myelin degradation after nerve injury and increased pERK and c-Jun expression. Interestingly, a P2RX4 antagonist increased the levels of miRNA363-5p. This study suggests that a double-negative feedback loop between miRNA363-5p and P2RX4 contributes to the dedifferentiation and migration of Schwann cells after nerve injury.

Engineered axon tracts within tubular biohybrid scaffolds

Injuries to the nervous system that involve the disruption of axonal pathways are devastating to the individual and require specific tissue engineering strategies. Here we analyse a cells-biomaterials strategy to overcome the obstacles limiting axon regenerationin vivo, based on the combination of a hyaluronic acid (HA) single-channel tubular conduit filled with poly-L-lactide acid (PLA) fibres in its lumen, with pre-cultured Schwann cells (SCs) as cells supportive of axon extension. The HA conduit and PLA fibres sustain the proliferation of SC, which enhance axon growth acting as a feeder layer and growth factor pumps. The parallel unidirectional ensemble formed by PLA fibres and SC tries to recapitulate the directional features of axonal pathways in the nervous system. A dorsal root ganglion (DRG) explant is planted on one of the conduit's ends to follow axon outgrowth from the DRG. After a 21 d co-culture of the DRG + SC-seeded conduit ensemble, we analyse the axonal extension throughout the conduit by scanning, transmission electronic and confocal microscopy, in order to study the features of SC and the grown axons and their association. The separate effects of SC and PLA fibres on the axon growth are also experimentally addressed. The biohybrid thus produced may be considered a synthetic axonal pathway, and the results could be of use in strategies for the regeneration of axonal tracts.

Transcriptomic analysis reveals essential microRNAs after peripheral nerve injury

Studies have shown that microRNAs (miRNAs) mediate posttranscriptional regulation of target genes and participate in various physiological and pathological processes, including peripheral nerve injury. However, it is hard to select key miRNAs with essential biological functions among a large number of differentially expressed miRNAs. Previously, we collected injured sciatic nerve stumps at multiple time points after nerve crush injury, examined gene changes at different stages (acute, sub-acute, and post-acute), and obtained mRNA expression profiles. Here, we jointly analyzed mRNAs and miRNAs, and investigated upstream miRNAs of differentially expressed mRNAs using Ingenuity Pathway Analysis bioinformatic software. A total of 31, 42, 30, and 23 upstream miRNAs were identified at 1, 4, 7, and 14 days after rat sciatic nerve injury, respectively. Temporal expression patterns and biological involvement of commonly involved upstream miRNAs (miR-21, let-7, miR-223, miR-10b, miR-132, miR-15b, miR-127, miR-29a, miR-29b, and miR-9) were then determined at multiple time points. Expression levels of miR-21, miR-132, miR-29a, and miR-29b were robustly increased after sciatic nerve injury. Biological processes involving these miRNAs include multicellular organismal response to stress, positive regulation of the epidermal growth factor receptor signaling pathway, negative regulation of epithelial cell differentiation, and regulation of myocardial tissue growth. Moreover, we constructed mechanistic networks of let-7, miR-21, and miR-223, the most significantly involved upstream miRNAs. Our findings reveal that multiple upstream miRNAs (i.e., let-7, miR-21, and miR-223) were associated with gene expression changes in rat sciatic nerve stumps after nerve injury, and these miRNAs play an important role in peripheral nerve regeneration. This study was approved by the Experimental Animal Ethics Committee of Jiangsu Province of China (approval No. 20190303-18) on March 3, 2019.

Emerging Roles of microRNAs as Biomarkers and Therapeutic Targets for Diabetic Neuropathy

Diabetic neuropathy (DN) is the most prevalent chronic complication of diabetes mellitus. The exact pathophysiological mechanisms of DN are unclear; however, communication network dysfunction among axons, Schwann cells, and the microvascular endothelium likely play an important role in the development of DN. Mounting evidence suggests that microRNAs (miRNAs) act as messengers that facilitate intercellular communication and may contribute to the pathogenesis of DN. Deregulation of miRNAs is among the initial molecular alterations observed in diabetics. As such, miRNAs hold promise as biomarkers and therapeutic targets. In preclinical studies, miRNA-based treatment of DN has shown evidence of therapeutic potential. But this therapy has been hampered by miRNA instability, targeting specificity, and potential toxicities. Recent findings reveal that when packaged within extracellular vesicles, miRNAs are resistant to degradation, and their delivery efficiency and therapeutic potential is markedly enhanced. Here, we review the latest research progress on the roles of miRNAs as biomarkers and as potential clinical therapeutic targets in DN. We also discuss the promise of exosomal miRNAs as therapeutics and provide recommendations for future research on miRNA-based medicine.

IcarisideII facilitates the differentiation of ADSCs to SCs via let-7i/STAT3 axis to preserve erectile function

BACKGROUND

IcarisideII (ICAII) could promote the differentiation of adipose tissue-derived stem cells (ADSCs) to Schwann cells (SCs), leading to improvement of erectile function (EF) and providing a realistic therapeutic option for the treatment of erectile dysfunction (ED). However, the underlying molecular mechanisms of ADSCs and ICAII in this process remain largely unclear.

METHODS

ADSCs were treated with different concentrations of ICAII. Cell proliferation was determined by MTT assay. qRT-PCR and western blot were performed to detect expressions of SCs markers, signal transducer and activator of transcription-3 (STAT3), and microRNA-let-7i (let-7i). Luciferase reporter assay was conducted to verify the regulatory relationship between let-7i and STAT3. The detection of intracavernosal pressure (ICP) and the ratio of ICP/mean arterial pressure (MAP) were used to evaluate the EF in bilateral cavernous nerve injury (BCNI) rat models.

RESULTS

ICAII promoted cell proliferation of ADSCs in a dose-dependent manner. The mRNA and protein levels of SCs markers were increased by ICAII treatment in a dose-dependent manner in ADSCs. Moreover, let-7i was significantly decreased in ICAII-treated ADSCs and upregulation of let-7i attenuated ICAII-induced promotion of SCs markers. In addition, STAT3 was a direct target of let-7i and upregulated in ICAII-treated ADSCs. Interestingly, overexpression of STAT3 abated the let-7i-mediated inhibition effect on differentiation of ADSCs to SCs and rescued the ICAII-mediated promotion effect on it. Besides, combination treatment of ADSCs and ICAII preserved the EF of BCNI rat models, which was undermined by let-7i overexpression.

CONCLUSION

ICAII was effective for preserving EF by promoting the differentiation of ADSCs to SCs via modulating let-7i/STAT3 pathway.

Let-7d modulates the proliferation, migration, tubulogenesis of endothelial cells

Endothelial cells are important components of peripheral nerve stumps that contribute to Schwann cell migration and peripheral nerve regeneration. Let-7d modulates the phenotype of Schwann cells and affected peripheral nerve regeneration. However, the regulatory roles of let-7d on endothelial cells remain undetermined. In this study, by transfecting cultured human umbilical vein endothelial cells (HUVECs) with let-7d mimic or let-7d inhibitor, we investigated the biological effects of let-7d on endothelial cells. EdU proliferation assay showed that upregulated let-7d decreased the proliferation rates of HUVECs while downregulated let-7d increased the proliferation rates of HUVECs. Transwell-based migration assay and wound-healing assay demonstrated that let-7d inhibited the migration ability of HUVECs. Matrigel assay suggested that let-7d decreased the numbers of formed meshes and suppressed the tubulogenesis of HUVECs. RNA sequencing, bioinformatic analysis, gene expression validation, and luciferase assay suggested that let-7d directly targeted interferon-induced protein 44 like (IFI44L) gene and negatively regulated the expression of IFI44L. Taken together, our study illuminated the inhibitory roles of let-7d on the proliferation, migration, and tubulogenesis of endothelial cells, identified the target gene of let-7d, and deepened the understanding of the biological effects of let-7d on key elements of peripheral nerve regeneration.

Novel microRNA, miR-sc6, modulates Schwann cell phenotype via targeting ErbB4

MicroRNAs (miRNAs) are non-coding RNAs that regulate various tissues and organs, including the nervous system. Peripheral nerve injury is a common pathology of the nervous system and leads to differential expressions of a variety of miRNAs. Previously, a group of novel miRNAs have been identified in rat proximal nerve segments after sciatic nerve transection. However, the biological functions of these novel miRNAs remain undetermined. The aim of the current study was therefore to identify the function of a novel miRNA, miR-sc6, following nerve injury. Its target genes and effects on phenotypic modulation of Schwann cells were determined using a miR-sc6 mimic transfection. These observations contribute to the understanding of miRNA involvement in peripheral nerve injury and the cognition of regulatory mechanisms in peripheral nerve regeneration.

Increased levels of miR-3099 induced by peripheral nerve injury promote Schwann cell proliferation and migration

MicroRNAs (miRNAs) can regulate the modulation of the phenotype of Schwann cells. Numerous novel miRNAs have been discovered and identified in rat sciatic nerve segments, including miR-3099. In the current study, miR-3099 expression levels following peripheral nerve injury were measured in the proximal stumps of rat sciatic nerves after surgical crush. Real-time reverse transcription-polymerase chain reaction was used to determine miR-3099 expression in the crushed nerve segment at 0, 1, 4, 7, and 14 days post sciatic nerve injury, which was consistent with Solexa sequencing outcomes. Expression of miR-3099 was up-regulated following peripheral nerve injury. EdU and transwell chamber assays were used to observe the effect of miR-3099 on Schwann cell proliferation and migration. The results showed that increased miR-3099 expression promoted the proliferation and migration of Schwann cells. However, reduced miR-3099 expression suppressed the proliferation and migration of Schwann cells. The potential target genes of miR-3099 were also investigated by bioinformatic tools and high-throughput outcomes. miR-3099 targets genes Aqp4, St8sia2, Tnfsf15, and Zbtb16 and affects the proliferation and migration of Schwann cells. This study examined the levels of miR-3099 at different time points following peripheral nerve injury. Our results confirmed that increased miR-3099 level induced by peripheral nerve injury can promote the proliferation and migration of Schwann cells.

Novel miRNA, miR-sc14, promotes Schwann cell proliferation and migration

MicroRNAs refer to a class of endogenous, short non-coding RNAs that mediate numerous biological functions. MicroRNAs regulate various physiological and pathological activities of peripheral nerves, including peripheral nerve repair and regeneration. Previously, using a rat sciatic nerve injury model, we identified many functionally annotated novel microRNAs, including miR-sc14. Here, we used real-time reverse transcription-polymerase chain reaction to examine miR-sc14 expression in rat sciatic nerve stumps. Our results show that miR-sc14 is noticeably altered following sciatic nerve injury, being up-regulated at 1 day and diminished at 7 days. EdU and transwell chamber assay results showed that miR-sc14 mimic promoted proliferation and migration of Schwann cells, while miR-sc14 inhibitor suppressed their proliferation and migration. Additionally, bioinformatic analysis examined potential target genes of miR-sc14, and found that fibroblast growth factor receptor 2 might be a potential target gene. Specifically, our results show changes of miR-sc14 expression in the sciatic nerve of rats at different time points after nerve injury. Appropriately, up-regulation of miR-sc14 promoted proliferation and migration of Schwann cells. Consequently, miR-sc14 may be an intervention target to promote repair of peripheral nerve injury. The study was approved by the Jiangsu Provincial Laboratory Animal Management Committee, China on March 4, 2015 (approval No. 20150304-004).

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.

Effects of RSC96 Schwann Cell-Derived Exosomes on Proliferation, Senescence, and Apoptosis of Dorsal Root Ganglion Cells In Vitro

Background

Stress urinary incontinence is a common condition in women and can be associated with peripheral nerve injury. Exosomes. derived from Schwann cells, can enhance the regeneration of axons of the peripheral nervous system. This study aimed to investigate the effects of RSC96 Schwann cell-derived exosomes in a novel in vitro model of dorsal root ganglion (DRG) cell injury induced by cyclic mechanical strain (CMS).

Material/Methods

RSC96 Schwann cells and DRG cells were cultured in vitro. CMS in DRG cells involved mechanical stretch trauma with 5333 μ strain. ExoQuick-TC polymer was used to precipitate exosomes from RSC96 Schwann cell culture medium and identified by nanoparticle tracking analysis, electron microscopy, and Western blot for detection of CD9 and tumor susceptibility gene 101 (Tsg101) protein. Cultured DRG cells were treated with RSC96 Schwann cell-derived exosomes, followed by measurement of cell viability, proliferation, senescence, and apoptosis using the cell counting kit-8 (CCK-8) assay, senescence-associated beta-galactosidase (SA-β-gal) staining, and Hoechst 33258 (blue) fluorescence nucleic acid staining using flow cytometry.

Results

Mechanical stretch with 5333 μ strain for 8 hours at 1 Hz decreased the activity of cultured DRG cells. RSC96 Schwann cell-derived exosomes promoted cell proliferation and significantly inhibited apoptosis and senescence of DRG cells following injury induced by CMS.

Conclusions

An in vitro model of DRG cell injury induced by CMS, showed that RSC96 Schwann cell-derived exosomes had a protective effect. The effects of Schwann cell-derived exosomes on peripheral nerve injury, including in stress urinary incontinence, require future in vivo studies.

miR-3075 Inhibited the Migration of Schwann Cells by Targeting Cntn2

Peripheral nerve injury is a complex biological process that involves the expression changes of various coding and non-coding RNAs. Previously, a number of novel miRNAs that were dysregulated in rat sciatic nerve stumps after peripheral nerve injury were identified and functionally annotated by Solexa sequencing. In the current study, we studied one of these identified novel miRNAs, miR-3075, in depth. Results of transwell-based cell migration assay showed that increased expression of miR-3075 suppressed the migration rate of Schwann cells while decreased expression of miR-3075 elevated the migration rate of Schwann cells, demonstrating that miR-3075 inhibited Schwann cell migration. Results of BrdU cell proliferation assay showed that neither miR-3075 mimic nor miR-3075 inhibitor would affect Schwann cell proliferation. We further studied candidate target genes of miR-3075 by using bioinformatic tools and analyzing gene expression patterns and found that miR-3075 might target contactin 2 (Cntn2). Previous study showed that Cntn2 regulated cell migration and myelination. Our current observation suggested that the biological effects of miR-3075 on Schwann cell phenotype might by through the negative regulation of Cntn2. Overall, our study revealed the function of a novel miRNA, miR-3075, and expanded our current understanding of the molecular mechanisms underlying peripheral nerve injury and regeneration.

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.

GSK3β inhibitor promotes myelination and mitigates muscle atrophy after peripheral nerve injury

Delay of axon regeneration after peripheral nerve injury usually leads to progressive muscle atrophy and poor functional recovery. The Wnt/β-catenin signaling pathway is considered to be one of the main molecular mechanisms that lead to skeletal muscle atrophy in the elderly. We hold the hypothesis that the innervation of target muscle can be promoted by accelerating axon regeneration and decelerating muscle cell degeneration so as to improve functional recovery of skeletal muscle following peripheral nerve injury. This process may be associated with the Wnt/β-catenin signaling pathway. Our study designed in vitro cell models to simulate myelin regeneration and muscle atrophy. We investigated the effects of SB216763, a glycogen synthase kinase 3 beta inhibitor, on the two major murine cell lines RSC96 and C2C12 derived from Schwann cells and muscle satellite cells. The results showed that SB216763 stimulated the Schwann cell migration and myotube contraction. Quantitative polymerase chain reaction results demonstrated that myelin related genes, myelin associated glycoprotein and cyclin-D1, muscle related gene myogenin and endplate-associated gene nicotinic acetylcholine receptors levels were stimulated by SB216763. Immunocytochemical staining revealed that the expressions of β-catenin in the RSC96 and C2C12 cytosolic and nuclear compartments were increased in the SB216763-treated cells. These findings confirm that the glycogen synthase kinase 3 beta inhibitor, SB216763, promoted the myelination and myotube differentiation through the Wnt/β-catenin signaling pathway and contributed to nerve remyelination and reduced denervated muscle atrophy after peripheral nerve injury.

Transcription factor networks involved in cell death in the dorsal root ganglia following peripheral nerve injury

The peripheral nervous system has the potential to regenerate after nerve injury owing to the intrinsic regrowth ability of neurons and the permissive microenvironment. The regenerative process involves numerous gene expression changes, in which transcription factors play a critical role. Previously, we profiled dysregulated genes in dorsal root ganglion neurons at different time points (0, 3 and 9 hours, and 1, 4 and 7 days) after sciatic nerve injury in rats by RNA sequencing. In the present study, we investigated differentially expressed transcription factors following nerve injury, and we identified enriched molecular and cellular functions of these transcription factors by Ingenuity Pathway Analysis. This analysis revealed the dynamic changes in the expression of transcription factors involved in cell death at different time points following sciatic nerve injury. In addition, we constructed regulatory networks of the differentially expressed transcription factors in cell death and identified some key transcription factors (such as STAT1, JUN, MYC and IRF7). We confirmed the changes in expression of some key transcription factors (STAT1 and IRF7) by quantitative reverse transcription-polymerase chain reaction. Collectively, our analyses provide a global overview of transcription factor changes in dorsal root ganglia after sciatic nerve injury and offer insight into the regulatory transcription factor networks involved in cell death.