Altered spinal microRNA-146a and the microRNA-183 cluster contribute to osteoarthritic pain in knee joints

MicroRNA-125b mediates Interferon-γ-induced downregulation of the vitamin D receptor in systemic lupus erythematosus

BACKGROUND

The inflammatory factor interferon (IFN)-γ is related to the occurrence and development of systemic lupus erythematosus (SLE). The vitamin D receptor (VDR) has an anti-inflammatory effect and its downregulation is involved in the onset of SLE. Our previous studies have confirmed that the expression of VDR in SLE peripheral blood mononuclear cells (PBMCs) is downregulated, which is negatively correlated with disease activity and inflammation. However, the mechanism underlying VDR downregulation in SLE is unknown.

METHODS

Based on the results of computer simulation analysis, the expression of VDR and four microRNAs (miR-17-3p, miR-34a, miR-346, and miR-125b) in SLE PBMC cells was analyzed under proinflammatory cytokine IFN‑γ treatment, and miR-125b was identified as the target miRNA. The relationship between IFN‑γ, miR-125b, and VDR was further assessed in THP‑1 cells.

RESULTS

We showed that IFN‑γ inhibited the expression of VDR and miR-125b. Further study revealed that VDR mRNA was positively correlated with miR-125b in THP‑1 cells after IFN‑γ intervention. After transfection of miR-125b mimic or inhibitor, the expression of VDR in the miR-125b inhibitor group was lower than in the control group and miR-125b mimic group, while expression in the control group was lower than in miR-125b mimic group. Transfection of miR-125b inhibitor into THP‑1 cells could further promote the ability of IFN‑γ to inhibit VDR.

CONCLUSION

The decrease in VDR expression promotes development of inflammation and SLE. These data suggest that miR-125b may mediate inflammatory factor IFN-γ-induced downregulation of VDR in the pathogenesis of SLE.

Circulating miR-146b and miR-27b are efficient biomarkers for early diagnosis of Equidae osteoarthritis

One of the most orthopedic problems seen in the equine is osteoarthritis (OA). The present study tracks some biochemical, epigenetic, and transcriptomic factors along different stages of monoiodoacetate (MIA) induced OA in donkeys in serum and synovial fluid. The aim of the study was the detection of sensitive noninvasive early biomarkers. OA was induced by a single intra-articular injection of 25 mg of MIA into the left radiocarpal joint of nine donkeys. Serum and synovial samples were taken at zero-day and different intervals for assessment of total GAGs and CS levels as well as miR-146b, miR-27b, TRAF-6, and COL10A1 gene expression. The results showed that the total GAGs and CS levels increased in different stages of OA. The level of expression of both miR-146b and miR-27b were upregulated as OA progressed and then downregulated at late stages. TRAF-6 gene was upregulated at the late stage while synovial fluid COL10A1 was over-expressed at the early stage of OA and then decreased at the late stages (P < 0.05). In conclusion, both miR-146b and miR-27b together with COL10A1 could be used as promising noninvasive biomarkers for the very early diagnosis of OA.

The temporal expression of circulating microRNAs after acute experimental pain in humans

BACKGROUND

MicroRNAs (miRNAs) can modulate several biological systems, including the pain system. This study aimed to evaluate the temporal expression of circulating miRNAs in the plasma of healthy volunteers as a marker for epigenetic changes before and after an acute, experimental, pain provocation by intramuscular hypertonic saline injection.

METHODS

Twenty volunteers were randomly allocated into two groups and received either hypertonic (pain) or isotonic (control) saline injection in the first dorsal interosseous muscle of their dominant hand. Pain intensity was continuously recorded for 20 minutes after injection on a VAS scale from 0 to 100 (0 indicates no pain and 100 the worst imaginable pain). Blood samples were taken at baseline, 30 minutes, 3 hours, and 24 hours post-injection, and plasma was separated. MiRNA extracts were used for RNA sequencing with the Illumina NextSeq platform. MiRNA transcripts were compared between the pain and the no-pain, control group at every time point. Significant differences were considered when folds were >2 and the False Discovery Rate was p < 0.05.

RESULTS

After 30 minutes, 4 miRNAs were significantly altered in the pain group compared to controls, which increased to 24 after 3 hours and to 42 after 24 hours from baseline (p < 0.0001). Two miRNAs were consistently upregulated throughout the experiment. Enrichment analysis showed significant miRNAs involved in brain perception of pain, brain signalling and response to stimuli.

CONCLUSIONS

This exploratory study is the first to report on the temporal expression of circulating miRNAs after an acute, human experimental muscle pain model.

SIGNIFICANCE

This exploratory study evaluated the temporal profile of circulating miRNAs in the plasma of healthy subjects after acute experimental pain. Several miRNAs were altered in subjects at the times of follow-up after the acute pain model when compared to controls. MiRNAs previously associated with pain processes were altered in the pain group. Our results, by showing the fast and prolonged modifications of miRNA elicited by the acute experimental pain model, add new perspectives to the topic of epigenetics and pain.

MicroRNAs in spinal cord injury: A narrative review

Spinal cord injury (SCI) is a global medical problem with high disability and mortality rates. At present, the diagnosis and treatment of SCI are still lacking. Spinal cord injury has a complex etiology, lack of diagnostic methods, poor treatment effect and other problems, which lead to the difficulty of spinal cord regeneration and repair, and poor functional recovery. Recent studies have shown that gene expression plays an important role in the regulation of SCI repair. MicroRNAs (miRNAs) are non-coding RNA molecules that target mRNA expression in order to silence, translate, or interfere with protein synthesis. Secondary damage, such as oxidative stress, apoptosis, autophagy, and inflammation, occurs after SCI, and differentially expressed miRNAs contribute to these events. This article reviews the pathophysiological mechanism of miRNAs in secondary injury after SCI, focusing on the mechanism of miRNAs in secondary neuroinflammation after SCI, so as to provide new ideas and basis for the clinical diagnosis and treatment of miRNAs in SCI. The mechanisms of miRNAs in neurological diseases may also make them potential biomarkers and therapeutic targets for spinal cord injuries.

Silencing miR-146a-5p Protects against Injury-Induced Osteoarthritis in Mice

Osteoarthritis (OA), the most prevalent joint disease and the leading cause of disability, remains an incurable disease largely because the etiology and pathogenesis underlying this degenerative process are poorly understood. Low-grade inflammation within joints is a well-established factor that disturbs joint homeostasis and leads to an imbalance between anabolic and catabolic processes in articular cartilage; however, the complexity of the network between inflammatory factors that often involves positive and negative feedback loops makes current anti-cytokine therapy ineffective. MicroRNAs (miRNAs) have emerged as key regulators to control inflammation, and aberrant miRNAs expression has recently been linked to OA pathophysiology. In the present study, we characterized transcriptomic profiles of miRNAs in primary murine articular chondrocytes in response to a proinflammatory cytokine, IL-1β, and identified miR-146a-5p as the most responsive miRNA to IL-1β. miR-146a-5p was also found to be upregulated in human OA cartilage. We further demonstrated that knockdown of miR-146a-5p antagonized IL-1β-mediated inflammatory responses and IL-1β-induced catabolism in vitro, and silencing of miR-146a in chondrocytes ameliorated articular cartilage destruction and reduced OA-evoked pain in an injury-induced murine OA model. Moreover, parallel RNA sequencing revealed that differentially expressed genes in response to IL-1β were enriched in pathways related to inflammatory processes, cartilage matrix homeostasis, and cell metabolism. Bioinformatic analyses of putative miR-146a-5p gene targets and following prediction of protein-protein interactions suggest a functional role of miR-146a-5p in mediating inflammatory processes and regulation of cartilage homeostasis. Our genetic and transcriptomic data define a crucial role of miR-146a-5p in OA pathogenesis and implicate modulation of miR-146a-5p in articular chondrocytes as a potential therapeutic strategy to alleviate OA.

The emerging power and promise of non-coding RNAs in chronic pain

Chronic pain (CP) is an unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage lasting longer than 3 months. CP is the main reason why people seek medical care and exerts an enormous economic burden. Genome-wide expression analysis has revealed that diverse essential genetic elements are altered in CP patients. Although many possible mechanisms of CP have been revealed, we are still unable to meet all the analgesic needs of patients. In recent years, non-coding RNAs (ncRNAs) have been shown to play essential roles in peripheral neuropathy and axon regeneration, which is associated with CP occurrence and development. Multiple key ncRNAs have been identified in animal models of CP, such as microRNA-30c-5p, ciRS-7, and lncRNA MRAK009713. This review highlights different kinds of ncRNAs in the regulation of CP, which provides a more comprehensive understanding of the pathogenesis of the disease. It mainly focuses on the contributions of miRNAs, circRNAs, and lncRNAs to CP, specifically peripheral neuropathic pain (NP), diabetic NP, central NP associated with spinal cord injury, complex regional pain syndrome, inflammatory pain, and cancer-induced pain. In addition, we summarize some potential ncRNAs as novel biomarkers for CP and its complications. With an in-depth understanding of the mechanism of CP, ncRNAs may provide novel insight into CP and could become new therapeutic targets in the future.

Microvascular Barrier Protection by microRNA-183 via FoxO1 Repression: A Pathway Disturbed in Neuropathy and Complex Regional Pain Syndrome

Blood nerve barrier disruption and edema are common in neuropathic pain as well as in complex regional pain syndrome (CRPS). MicroRNAs (miRNA) are epigenetic multitarget switches controlling neuronal and non-neuronal cells in pain. The miR-183 complex attenuates hyperexcitability in nociceptors, but additional non-neuronal effects via transcription factors could contribute as well. This study explored exosomal miR-183 in CRPS and murine neuropathy, its effect on the microvascular barrier via transcription factor FoxO1 and tight junction protein claudin-5, and its antihyperalgesic potential. Sciatic miR-183 decreased after CCI. Substitution with perineural miR-183 mimic attenuated mechanical hypersensitivity and restored blood nerve barrier function. In vitro, serum from CCI mice und CRPS patients weakened the microvascular barrier of murine cerebellar endothelial cells, increased active FoxO1 and reduced claudin-5, concomitant with a lack of exosomal miR-183 in CRPS patients. Cellular stress also compromised the microvascular barrier which was rescued either by miR-183 mimic via FoxO1 repression or by prior silencing of Foxo1. PERSPECTIVE: Low miR-183 leading to barrier impairment via FoxO1 and subsequent claudin-5 suppression is a new aspect in the pathophysiology of CRPS and neuropathic pain. This pathway might help untangle the wide symptomatic range of CRPS and nurture further research into miRNA mimics or FoxO1 inhibitors.

The plasma microRNA levels and their relationship with the general health and functional status in female patients with fibromyalgia syndrome

Objectives: The aim of this study was to identify the plasma level of micro-ribonucleic acid (microRNA) expressions and the relationship between plasma microRNA levels with the general health and functional status in female patients with fibromyalgia syndrome (FMS).

Patients and methods: Thirty-five female patients (mean age: 42.0±11.8 years; range, 21 to 62 years) diagnosed as FMS and 35 sex-and age-matched healthy controls (mean age: 43.7±8.8 years; range, 21 to 56 years) were enrolled in the study. MicroRNA measurements of the participants in plasma were carried out by using the quantitative polymerase chain reaction (qPCR). A total of 11 plasma levels of microRNA expressions were examined in both groups. The general health and functional status of the patients and controls were assessed by the Fibromyalgia Impact Questionnaire (FIQ) and the Short Form-36 (SF-36) scale.

Results: No significant difference was observed between the plasma levels of microRNA expressions in patients with FMS and healthy controls. The plasma level of miR-320a expression was found to be negatively correlated with the total FIQ score in female patients with FMS (p=0.05, r=-0.34). Negative correlations were also detected between the plasma level of miR-320a and miR-320b expressions and the subscale score of SF-36 physical function in female patients with FMS (p=0.01, r=-0.43 and p=0.01, r=-0.43, respectively). A strong positive correlation was found between miR-142-3p and the subscale score of SF-36 mental symptom score in female patients with FMS (p<0.001, r=1.00).

Conclusion: The expression levels of microRNAs in plasma between female patients with FMS and controls were not significantly different. Only plasma levels of miR-320a, miR-320b, and miR-142-3p expressions were associated with the general health, functional status, and mental symptom score in female patients with FMS.

MiR-183 regulates the differentiation of osteoblasts in the development of osteoporosis by targeting Smad4

OBJECTIVE

To discuss the effect of miR-183 on osteoblast differentiation in the osteoporosis progression via targeting Smad4.

METHODS

Osteoporosis models were constructed on ovariectomized (OVX) mice to determine the expression of miR-183 and Smad4. Then, MC3T3-E1 cells and primary osteoblasts were divided into Mock, miR-control, miR-183 mimic, miR-183 inhibitor, siSmad4 and miR-183 inhibitor + siSmad4 groups. Alkaline phosphatase (ALP) staining were performed to determine ALP activity, alizarin red staining to evaluate the calcium deposit, while qRT-PCR and Western blotting were used to determine the expression of related molecules. Besides, MC3T3-E1 cells transfected with miR-control or miR-183 mimic were cultured with or without TGF-β1 to verify whether miR-183 regulates the TGF-β signaling pathway.

RESULTS

MiR-183 was up-regulated with decreased Smad4 in the femur of OVX mice, and dual luciferase reporter gene assay showed that Smad4 was a target of miR-183. As compared to Mock group, MC3T3-E1 cells and primary osteoblasts in the miR-183 mimic group and siSmad4 group had significant reductions of OCN, OPN, Runx2 and Osx, as well as decreased ALP activity and calcium deposit. Contrarily, miR-183 and Smad4 were up-regulated and down-regulated respectively. However, cells in the miR-183 inhibitor group manifested the opposite changes. Besides, osteoblast differentiation in the miR-183 inhibitor + siSmad4 group was weakened evidently when compared to miR-183 inhibitor group. Pathway analysis indicated that miR-183 regulated osteogenic differentiation via TGF-β signaling pathway.

CONCLUSION

MiR-183 was up-regulated in osteoporosis, and miR-183 overexpression can inhibit osteoblast differentiation by targetedly down-regulating TGF-β pathway member Smad4 to trigger osteoporosis.

NEAT1/miR-146a-3p/TrkB/ShcB axis regulates the development and function of chondrocyte

The current study aimed to explored the regulatory effect of Tropomyosin-related kinases B (TrkB) in the development and function of chondrocyte. Correlation between clinicopathological characteristics and osteoarthritis (OA) were analyzed. The expressions of TrkA, brain-derived neurotrophic factor (BDNF), TrkB, Src homolog and collagen homolog B (ShcB), and ShcC in OA cartilage tissue and IL-1β-stimulated chondrocytes from normal cartilage were determined by Western blot/qRT-PCR. After manipulating the expressions of TrkA, shTrkB, ShcB, miR-146a-3p and nuclear paraspeckle assembly transcript 1 (NEAT1), the differentiation-related molecules, and apoptosis-related molecules were examined by Western blot/qRT-PCR, and migration, invasion, proliferation, tube formation, and apoptosis rate in IL-1β-stimulated chondrocyte were examined by scratch, Transwell, colony formation, and tube formation, and flow cytometry assays, respectively. Bioinformatics, dual-luciferase and Spearman were used to analyze the binding and correlation of target genes. The findings showed that OA was related to body mass Index (BMI). The expressions of TrkA, TrkB and ShcB and NEAT1 were up-regulated in OA and IL-1β-stimulated chondrocytes, while miR-146a-3p was donwnregulated and was negatively correlated with TrkB or NEAT1. NEAT1 competed with TrkB in chondrocytes for miR-146a-3p binding. ShTrkB reversed the decrease in expressions of differentiation-related molecules, migration, invasion and proliferation, and the increase in ShcB expression and tube formation, of IL-1β-stimulated chondrocytes. Overexpressed ShcB reversed effect of shTrkB on the functions of IL-1β-stimulated chondrocytes. MiR-146a-3p inhibitor reversed effects of shTrkB on the function and apoptosis-related molecules on IL-1β-stimulated chondrocytes, while NEAT1 reversed role of miR-146a-3p. This paper demonstrated that NEAT1/miR-146a-3p/TrkB/ShcB axis regulates the development and function of chondrocyte.

Dexamethasone-loaded thermo-sensitive hydrogel attenuates osteoarthritis by protecting cartilage and providing effective pain relief

Background

We utilized the destabilization of medial meniscus (DMM)-induced mice to illustrate the osteoarthritis (OA) suppressing and pain-relieving effects of a novel prolonged-release intra-articular (IA)-dexamethasone-loaded thermo-sensitive hydrogel (DLTH).

Methods

The effects of temperature and pH on DLTH formation and in vitro DLTH release profile were assessed. C57BL/6J mice were randomly divided into three groups: Ctrl group, Model group and DLTH group. The DLTH group received joint injections of 10 µL DLTH (1 mg/kg) into the right knee once a week from week 2 to week 11. We performed micro-computed tomography (Micro-CT) and histological analyses of safranin O-fast green, hematoxylin and eosin, and tartrate-resistant acid phosphatase in knee joints. We also carried out immunohistochemical (IHC) staining for matrix metalloproteinase-9 (MMP-9), MMP-13, and a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS-5) in cartilage and Ki-67 in synovia. Pain behavioral testing was carried out in all mice. The serum content of prostaglandin E2 (PGE2) and real-time polymerase chain reaction (PCR) of inflammatory cytokines and pain-related factors in dorsal root ganglia (DRGs) were evaluated.

Results

It took 20 minutes to form DLTH at pH 7.0 and 37 °C. The cumulative release profiles of dexamethasone (Dex) from DLTH at 37 °C revealed a rapid release in the first 24 h and a sustained slow release for 7 days. In vivo study illustrated that DLTH attenuated OA bone destruction and ameliorated synovitis and progression of OA in DMM-induced mice. The chondroprotective effects of DLTH were mediated by decreased expressions of MMP-9, MMP-13, and ADAMTS-5. The results showed that IA-DLTH exerted pain-relieving effects in OA mice. Upregulation of nociceptive response time (NRT) and downregulations of serum PGE2, inflammatory factors, and pain-related mediators in DRGs of mice in the DLTH group were recorded.

Conclusions

Data presented in this study elucidated that DLTH exhibited a long and lasting Dex release and it is a potential sustainable drug delivery system (DDS) to treat OA locally. IA-DLTH injection exerted chondroprotective and pain-relieving effects in DMM-induced arthritis. The involvement of MMP-9, MMP-13, ADAMTS-5, and inflammatory and pain-related factors, may account for the suppression of OA progression and pain.

Preoperative serum circulating microRNAs as potential biomarkers for chronic postoperative pain after total knee replacement

Background

Chronic postoperative pain affects approximately 20% of patients with knee osteoarthritis after total knee replacement. Circulating microRNAs can be found in serum and might act as biomarkers in a variety of diseases. The current study aimed to investigate the preoperative expression of circulating microRNAs as potential predictive biomarkers for the development of chronic postoperative pain in the year following total knee replacement.

Methods

Serum samples, collected preoperatively from 136 knee osteoarthritis patients, were analyzed for 21 circulatory microRNAs. Pain intensity was assessed using a visual analog scale before and one year after total knee replacement. Patients were divided into a low-pain relief group (pain relief percentage <30%) and a high-pain relief group (pain relief percentage >30%) based on their pain relief one year after total knee replacement, and differences in microRNAs expression were analyzed between the two groups.

Results

We found that three microRNAs were preoperatively dysregulated in serum in the low-pain relief group compared with the high-pain relief group. MicroRNAs hsa-miR-146a-5p, -145-5p, and -130 b-3p exhibited fold changes of 1.50, 1.55, and 1.61, respectively, between the groups (all P values < 0.05). Hsa-miR-146a-5p and preoperative pain intensity correlated positively with postoperative pain relief (respectively, R = 0.300, P = 0.006; R = 0.500, P < 0.001).

Discussion

This study showed that patients with a low postoperative pain relief present a dysregulation of circulating microRNAs. Altered circulatory microRNAs expression correlated with postoperative pain relief, indicating that microRNAs can serve as predictive biomarkers of pain outcome after surgery and hence may foster new strategies for preventing chronic postoperative pain after total knee replacement (TKR).

EZH2 Mediates miR-146a-5p/HIF-1α to Alleviate Inflammation and Glycolysis after Acute Spinal Cord Injury

Acute spinal cord injury (ASCI) is a severe traumatic disease of the central nervous system, the underlying mechanism of which is unclear. This study was intended to study the role of EZH2 and miR-146a-5p/HIF-1α in inflammation and glycolysis after ASCI, providing reference and basis for the clinical treatment and prognosis of ASCI injury. We used lipopolysaccharide (LPS) to induce inflammation of microglia, and we constructed the ASCI animal model. qRT-PCR detected the relative expression levels of EZH2, HIF-1α, miR-146a-5p, IL-6, TNF-α, IL-17, PKM2, GLUT1, and HK2 in cells and tissues. Western blot was performed to detect the expression levels of EZH2, HIF-1α, H3K27me3, IL-6, TNF-α, IL-17, PKM2, GLUT1, and HK2. ChIP verified the enrichment of H3K27me3 in the miR-146a-5p promoter region. Bioinformatics predicted the binding sites of HIF-1α and miR-146a-5p, and dual-luciferase reporter assay verified the binding of HIF-1α and miR-146a-5p. ELISA detects the levels of inflammatory factors IL-6, TNF-α, and IL-17 in the cerebrospinal fluid of rats. The GC-TOFMS was used to detect the changes of glycolytic metabolites in the cerebrospinal fluid of rats. EZH2 could mediate inflammation and glycolysis of microglia. EZH2 regulates inflammation and glycolysis through HIF-1α. EZH2 indirectly regulated the HIF-1α expression by mediating miR-146a-5p. EZH2 mediates miR-146a-5p/HIF-1α to alleviate inflammation and glycolysis in ASCI rats. In the present study, our results demonstrated that EZH2 could mediate miR-146a-5p/HIF-1α to alleviate the inflammation and glycolysis after ASCI. Therefore, EZH2/miR-146a-5p/HIF-1α might be a novel potential target for treating ASCI.

miR-122/SIRT1 axis regulates chondrocyte extracellular matrix degradation in osteoarthritis

Background/Aims: MicroRNAs (miRNAs) are involved in the pathogenesis of osteoarthritis (OA). The present study aimed to investigate the potential function of miR-122 in the development of OA and its potential molecular mechanisms. Methods: The expression of miR-122, silent information regulator 1 (SIRT1), collagen II, aggrecan, matrix metalloproteinase (MMP) 13 (MMP13) and ADAMTS4 in OA cartilage was detected by RT-qPCR. Target gene prediction and screening, luciferase reporter assay were used to verify downstream target genes of miR-122. Results: Compared with osteonecrosis, the expression of miR-122 was significantly increased in OA cartilage, while the expression of SIRT1 was significantly decreased. Overexpression of miR-122 increased the expression of extracellular matrix (ECM) catabolic factors, for example disintegrins, MMPs and metalloproteinases with platelet reaction protein motifs, and inhibited the expression of synthetic metabolic genes such as collagen II and aggregating proteoglycan. Inhibition of miR-122 expression had the opposite effect. Furthermore, SIRT1 was identified as a direct target of miR-122. SIRT1 was significantly inhibited by miR-122 overexpression. Knockdown of SIRT1 reversed the degradation of chondrocyte ECM by miR-122 inhibitors. Conclusion: The miR-122/SIRT1 axis can regulate the degradation of ECM in OA, thus providing new insights into the treatment of OA.

Circ_DHRS3 positively regulates GREM1 expression by competitively targeting miR-183-5p to modulate IL-1β-administered chondrocyte proliferation, apoptosis and ECM degradation

BACKGROUND

Osteoarthritis (OA) is a chronic inflammatory disease caused by degenerative changes of articular cartilage, involving in the expression changes of special circular RNAs (circRNAs). This study aimed to explore the role of circ_DHRS3 in OA cell models and provide a potential mechanism.

METHODS

OA cell models were constructed using human chondrocytes with Interleukin-1 beta (IL-1β) treatment. The expression of circ_DHRS3, microRNA (miR)-183-5p and Gremlin 1 (GREM1) mRNA was detected using real-time quantitative polymerase chain reaction (RT-qPCR). Cell proliferation was identified using 3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyl tetrazolium bromide (MTT) assay. Cell apoptosis was investigated using flow cytometry assay. The protein levels of proliferation- and apoptosis-related proteins were quantified by western blot. The levels of extracellular matrix (ECM)-associated proteins were quantified by western blot to assess ECM degradation. The relationship between miR-183-5p and circ_DHRS3 or GREM1 was predicted and then verified by dual-luciferase reporter assay.

RESULTS

Circ_DHRS3 expression was elevated in OA cartilage tissues and IL-1β-treated chondrocytes. Circ_DHRS3 was resistant to RNase R and Actinomycin D. Circ_DHRS3 knockdown promoted chondrocyte proliferation inhibited by IL-1β, and alleviated IL-1β-induced apoptosis and ECM degradation, which were reversed by the inhibition of miR-183-5p, a target of circ_DHRS3. MiR-183-5p restoration also enhanced IL-1β-blocked cell proliferation, and relieved IL-1β-induced cell apoptosis and ECM degradation, while GREM1 (a target of miR-183-5p) overexpression abolished the effects of miR-183-5p restoration. Moreover, circ_DHRS3 regulated GREM1 expression by targeting miR-183-5p.

CONCLUSION

Circ_DHRS3 mediated IL-1β-administered chondrocyte proliferation, apoptosis and ECM degradation by positively regulating GREM1 expression via competitively targeting miR-183-5p.

Behavioral, Histopathologic, and Molecular Biological Responses of Nanoparticle- and Solution-Based Formulations of Vincristine in Mice

Clinical use of the chemotherapeutic agent vincristine (VCR) is limited by chemotherapy-induced peripheral neuropathy (CiPN). A new formulation of VCR encapsulated by nanoparticles has been proposed and developed to alleviate CiPN. We hypothesized in nonclinical animals that the nanoparticle drug would be less neurotoxic due to different absorption and distribution properties to the peripheral nerve from the unencapsulated free drug. Here, we assessed whether VCR encapsulation in nanoparticles alleviates CiPN using behavioral gait analysis (CatWalk), histopathologic and molecular biological (RT-qPCR) approaches. Adult male C57BL/6 mice were assigned to 3 groups (empty nanoparticle, nano-VCR, solution-based VCR, each n = 8). After 15 days of dosing, animals were euthanized for tissue collection. It was shown that intraperitoneal administration of nano-VCR (0.15 mg/kg, every other day) and the empty nanoparticle resulted in no changes in gait parameters; whereas, injection of solution-based VCR resulted in decreased run speed and increased step cycle and stance (P < 0.05). There were no differences in incidence and severity of degeneration in the sciatic nerves between the nano-VCR-dosed and solution-based VCR-dosed animals. Likewise, decreased levels of a nervous tissue-enriched microRNA-183 in circulating blood did not show a significant difference between the nano- and solution-based VCR groups (P > 0.05). Empty nanoparticle administration did not cause any behavioral, microRNA, or structural changes. In conclusion, this study suggests that the nano-VCR formulation may alleviate behavioral changes in CiPN, but it does not improve the structural changes of CiPN in peripheral nerve. Nanoparticle properties may need to be optimized to improve biological observations.

Downregulation of microRNA‑29c reduces pain after child delivery by activating the oxytocin‑GABA pathway

A significant decrease in the expression of spinal microRNA-29c (miR-29c), which is responsible for the regulation of oxytocin receptor (OXTR) expression, was observed in nerve injury pain during childbirth. The present study investigates whether spinal miR-29c could be a potential target for the treatment of pain, via the oxytocin (OT)-γ-aminobutyric acid (GABA) pathway. A spared nerve injury (SNI) rat model was established to induce neuropathic pain, simulating hyperalgesia. Spinal neurons were treated with OT to mimic the hormonal changes in the central nervous system after delivery. A change in the neuronal miniature inhibitory postsynaptic currents (mIPSCs) was observed in neurons, following the silencing of miR-29c or OT treatment with or without OXTR antagonist. The Von-Frey apparatus was used to measure the animal behaviors. Molecular biological experiments and electrophysical recordings in vivo and in vitro were performed to reveal the potential analgesic mechanisms. miR-29c was significantly downregulated (more than 8-fold) in the spinal dorsal horn of delivery+SNI rats compared with the SNI rats. The silencing of miR-29c resulted in increased pain threshold in SNI rats. Bioinformatics analysis indicated that OXTR was a potential target gene of miR-29c. The delivery+SNI rats presented with higher levels of OT in the cerebrospinal fluid compared with SNI rats, which indicated that the OT signaling pathway may participate in pain relief response. The increased expression of OXTR and GABA in delivery+SNI rats were observed in the miR-29c-silenced SNI rat model, suggesting that the silencing of miR-29c can mediate pain relief by enhancing the OT-GABA pathway. In addition, an electrophysiology assay was performed to assess the mIPSCs in neurons. The silencing of miR-29c in neurons increased the frequency and amplitude of mIPSCs but there was no influence on the decay time, which suggested that the spinal inhibitory neurons became more active, subsequently reducing the feeling of pain. The inhibition of OXTR reversed the enhanced inhibitory postsynaptic currents, indicating a crucial role for OXTR in the miR-29c-associated pain regulation. Taken together, the results of the present study suggested that spinal oxytocinergic inhibitory control plays an important role in pain relief in the neuropathic pain rat model undergoing vaginal delivery. Silencing spinal miR-29c may be a potential target for pain relief through the OT-GABA pathway.

Interleukin-4 Gene Transfection and Spheroid Formation Potentiate Therapeutic Efficacy of Mesenchymal Stem Cells for Osteoarthritis

Osteoarthritis (OA) is a painful intractable disease that significantly affects patients' quality of life. However, current therapies, such as pain killers and joint replacement surgery, do not lead to cartilage protection. Mesenchymal stem cells (MSCs) have been proposed as an alternative strategy for OA therapy because MSCs can secrete chondroprotective and anti-inflammatory factors. However, interleukin-4 (IL-4), a potent anti-inflammatory cytokine, is barely produced by MSCs, and MSC therapy suffers from rapid MSC death following intra-articular implantation. MSCs in spheroids survive better than naïve MSCs in vitro and in vivo. IL-4-transfected MSCs in spheroids (IL-4 MSC spheroid) show increased chondroprotective and anti-inflammatory effects in an OA chondrocyte model in vitro. Following intra-articular implantation in OA rats, IL-4 MSC spheroids show better cartilage protection and pain relief than naïve MSCs. Thus, IL-4 MSC spheroid may potentiate the therapeutic efficacy of MSCs for OA.

Endosomal TLR-8 Senses microRNA-1294 Resulting in the Production of NFḱB Dependent Cytokines

The primary function of toll-like receptor 8 (TLR-8) is the detection of viruses and other microbial pathogens. Recent evidence suggests that TLR-8 also senses host microRNAs (miRNAs) and implicate TLR-8 in autoimmune disorders. This study examined the interaction between miR-1294 and TLR-8. We first performed a BLAST search to identify miRNAs with the same sequences as two core motifs of miR-1294. Next, we examined NFḱB activation induced by the binding of miR-1294 mimic to endosomal TLR-8. HEK-Blue™ hTLR-8 cells (Invivogen), a HEK293 cell line co-transfected with human TLR-8 gene, were incubated with miR-1294 mimic. A TLR-8 agonist ssRNA40, was used as a positive control. Using the same experimental set up, we also examined the effects of miR-1294 and its two core motifs (Integrated DNA Technologies) on IL-8, IL-1β, and TNFα. Data were analyzed using t-test or one-way ANOVA and Dunnets post-hoc test. Using miRCarta we identified 29 other mature human miRNAs or their precursors which contain the same core motifs as miR-1294. Our data show that miR-1294 activates NFḱB in cells expressing TLR-8 (p < 0.05). miR-1294, and its core motifs induce expression of IL-8, IL-1β, and TNFα via TLR8 activation (p < 0.05). This constitutes a novel mechanism by which endosomal TLR-8 senses host miRNAs resulting in the release of pro-inflammatory cytokines and thus potentially contributing to autoimmune disorders.

Targeting Extracellular miR-21-TLR7 Signaling Provides Long-Lasting Analgesia in Osteoarthritis

Osteoarthritis (OA) is the most prevalent joint disorder associated with severe chronic pain. Although synovial inflammation is well correlated with pain severity, the molecular mechanism responsible for OA pain remains unclear. Here, we show that extracellular miR-21 released from synovial tissue mediates knee OA pain in surgical OA model rats. miR-21 was the most abundant among increased microRNAs (miRNAs) in the synovial tissue. miR-21 was released into extracellular space from the synovial tissue and increased in the synovial fluid. A single intra-articular injection of miR-21 inhibitor exerted long-term analgesia of knee OA pain, whereas miR-21 injection in naive rats caused knee joint pain. miR-21 mutant, which lacks the Toll-like receptor (TLR) binding motif, but not in the seed sequence, did not cause joint pain, suggesting a non-canonical mode of action different from translational repression. Consistent with this, the algesic effect of miR-21 was blocked by antagonizing TLR7. The TLR7 antagonist also exerted a long-lasting analgesic effect on knee OA pain. Therefore, extracellular miR-21 released from synovial tissue mediates knee OA pain through TLR7 activation in surgical OA model rats. Extracellular miRNA in the joint may be a plausible target for pain therapy, providing a novel analgesic strategy for OA.

MiR-125a-5p Regulates Vitamin D Receptor Expression in a Mouse Model of Experimental Autoimmune Encephalomyelitis

Multiple sclerosis (MS) is a chronic and incurable autoimmune neurodegenerative disease of the central nervous system. Although the symptoms of MS can be managed by vitamin D3 treatment alone, this condition cannot be completely eradicated. Thus, there might be unknown factors capable of regulating the vitamin D receptor (VDR). Genome-wide analysis showed that miRNAs were associated with VDRs. We sought to determine the role and mechanism of action of miRNA-125a-5p and VDRs in a model of MS, mice with experimental autoimmune encephalomyelitis (EAE), which was induced by myelin oligodendrocyte glycoprotein 35-55 peptides. EAE mice showed decreased mean body weight but increased mean clinical scores compared with vehicle or control mice. And inflammatory infiltration was found in the lumbosacral spinal cord of EAE mice. In addition, VDR expression was significantly lower while the expression of miR-125a-5p was markedly higher in the spinal ventral horn of EAE mice than in vehicle or control mice. Importantly, activation of VDRs by paricalcitol or inhibition of miR-125a-5p by its antagomir markedly decreased the mean clinical scores in EAE mice. Interestingly, VDR and miR-125a-5p were co-localized in the same neurons of the ventral horn. More importantly, inhibition of miR-125a-5p remarkably blocked the decrease of VDRs in EAE mice. These results support a critical role for miR-125a-5p in modulating VDR activity in EAE and suggest potential novel therapeutic interventions.

TLR4 participates in the transmission of ethanol-induced neuroinflammation via astrocyte-derived extracellular vesicles

BACKGROUND

Current evidence indicates that extracellular vesicles (EVs) participate in intercellular signaling, and in the regulation and amplification of neuroinflammation. We have previously shown that ethanol activates glial cells through Toll-like receptor 4 (TLR4) by triggering neuroinflammation. Here, we evaluate if ethanol and the TLR4 response change the release and inflammatory content of astrocyte-derived EVs, and whether these vesicles are capable of communicating with neurons by spreading neuroinflammation.

METHODS

Cortical neurons and astrocytes in culture were used. EVs were isolated from the extracellular medium of the primary culture of the WT and TLR4-KO astrocytes treated with or without ethanol (40 mM) for 24 h. Flow cytometry, nanoparticle tracking analysis technology, combined with exosomal molecular markers (tetraspanins) along with electron microscopy, were used to characterize and quantify EVs. The content of EVs in inflammatory proteins, mRNA, and miRNAs was analyzed by Western blot and RT-PCR in both astrocyte-derived EVs and the neurons incubated or not with these EVs. Functional analyses of miRNAs were also performed.

RESULTS

We show that ethanol increases the number of secreted nanovesicles and their content by raising the levels of both inflammatory-related proteins (TLR4, NFκB-p65, IL-1R, caspase-1, NLRP3) and by changing miRNAs (mir-146a, mir-182, and mir-200b) in the EVs from the WT-astrocytes compared with those from the untreated WT cells. No changes were observed in either the number of isolated EVs or their content between the untreated and ethanol-treated TLR4-KO astrocytes. We also show that astrocyte-derived EVs could be internalized by naïve cortical neurons to increase the neuronal levels of inflammatory protein (COX-2) and miRNAs (e.g., mir-146a) and to compromise their survival. The functional analysis of miRNAs revealed the regulatory role of the expressed miRNAs in some genes involved in several inflammatory pathways.

CONCLUSIONS

These results suggest that astrocyte-derived EVs could act as cellular transmitters of inflammation signaling by spreading and amplifying the neuroinflammatory response induced by ethanol through TLR4 activation.

MicroRNA-146a regulates the transformation from liver fibrosis to cirrhosis in patients with hepatitis B via interleukin-6

The aim of the present study was to measure the expression of microRNA (miR)-146a in liver tissues, peripheral blood mononuclear cells (PMBC) and serum from patients with Hepatitis B and either liver fibrosis or cirrhosis, as well as to determine the regulatory mechanism of miR-146a. A total of 36 patients with Hepatitis B and liver fibrosis and 25 patients with hepatitis B and liver cirrhosis admitted to Linyi People's Hospital (Shandong, China) between June 2012 and February 2016 were included in the present study. Reverse transcription-quantitative polymerase chain reaction was performed to determine the expression of miR-146a and interleukin (IL)-6 mRNA in the liver tissue, PBMCs and serum. Western blotting was used to assess the expression of IL-6 in liver tissues and PBMCs. An enzyme-linked immunosorbent assay was conducted to measure IL-6 levels in serum. To identify the direct interaction between IL-6 and miR-146a, a dual luciferase reporter assay was performed. IL-6 mRNA expression in liver tissues, PBMCs and serum from patients with liver cirrhosis was significantly higher than that from patients with liver fibrosis (P<0.05). Furthermore, IL-6 expression in liver tissues and PBMCs from patients with liver cirrhosis was enhanced and levels of IL-6 protein in the serum of patients with liver cirrhosis were significantly elevated compared with patients with liver fibrosis (P<0.05). By contrast, levels of miR-146a in liver tissues, PBMCs and serum from patients with liver cirrhosis were significantly downregulated (P<0.05) compared with patients with liver fibrosis. miR-146a regulated the expression of IL-6 by binding to its 3'-untranslated region. Thus, in the transformation from liver fibrosis to cirrhosis, the upregulation of IL-6 in liver tissues, PBMCs and serum may be associated with the downregulation of miR-146a. miR-146a directly targets IL-6, which may regulate the occurrence and immune responses of Hepatitis B.

Deep sequencing and miRNA profiles in alcohol-induced neuroinflammation and the TLR4 response in mice cerebral cortex

Alcohol abuse can induce brain injury and neurodegeneration, and recent evidence shows the participation of immune receptors toll-like in the neuroinflammation and brain damage. We evaluated the role of miRNAs as potential modulators of the neuroinflammation associated with alcohol abuse and the influence of the TLR4 response. Using mice cerebral cortex and next-generation sequencing (NGS), we identified miRNAs that were differentially expressed in the chronic alcohol-treated versus untreated WT or TLR4-KO mice. We observed a differentially expression of miR-183 Cluster (C) (miR-96/-182/-183), miR-200a and miR-200b, which were down-regulated, while mirR-125b was up-regulated in alcohol-treated WT versus (vs.) untreated mice. These miRNAs modulate targets genes related to the voltage-gated sodium channel, neuron hyperexcitability (Nav1.3, Trpv1, Smad3 and PP1-γ), as well as genes associated with innate immune TLR4 signaling response (Il1r1, Mapk14, Sirt1, Lrp6 and Bdnf). Functional enrichment of the miR-183C and miR-200a/b family target genes, revealed neuroinflammatory pathways networks involved in TLR4 signaling and alcohol abuse. The changes in the neuroinflammatory targets genes associated with alcohol abuse were mostly abolished in the TLR4-KO mice. Our results show the relationship between alcohol intake and miRNAs expression and open up new therapeutically targets to prevent deleterious effects of alcohol on the brain.

Inhibition of lncRNA X inactivate-specific transcript ameliorates inflammatory pain by suppressing satellite glial cell activation and inflammation by acting as a sponge of miR-146a to inhibit Nav 1.7

Long noncoding RNAs (lncRNA) has been validated to participate in nociception in inflammatory pain, presenting as a potential target against anesthesia. Previous research work confirmed the correlation between lncRNA X inactivate-specific transcript (XIST) and inflammation. However, its role in inflammatory pain is undefined. In animal pain models, voltage-gated sodium channels (VGSCs) reportedly participate in neural excitation. In this study, we observed the high expression of XIST and VGSC 1.7 (Na_v 1.7) in the dorsal root ganglion (DRG) of the complete Freund's adjuvant (CFA)-induced rat inflammatory pain model. Furthermore, XIST inhibition alleviated pain behavior and the activation of DRG satellite glial cells by suppressing glial fibrillary acidic protein (GFAP) expression, as well as inflammatory cytokine levels of interleukin-6 and tumor necrosis factor-α. XIST downregulation increased the mechanical pain threshold in an inflammatory pain model. Moreover, the expression of miR-146a was decreased in CFA rats. In vitro, XIST acted as a sponge of miR-146a, which targeted Na_v 1.7 via bioinformatic prediction, luciferase reporter, and pull-down assay. More importantly, activation of the Na_v 1.7 pathway or miR-146 depression both reversed XIST knockdown-inhibited satellite glial cell activation and inflammatory pain in CFA rats. These results suggest that cessation of XIST may ameliorate inflammatory pain by acting as a sponge of miR-146a to inhibit Nav1.7, implying a promising strategy against inflammatory pain.

Chronic constriction injury-induced microRNA-146a-5p alleviates neuropathic pain through suppression of IRAK1/TRAF6 signaling pathway

Background

microRNA-146a-5p (miRNA-146a-5p) is a key molecule in the negative regulation pathway of TLRs and IL-1 receptor (TIR) signaling. Our recent study demonstrated that MyD88-dependent signaling pathway of TIR in the dorsal root ganglion (DRG) and spinal dorsal horn (SDH) plays a role in peripheral nerve injury-induced neuropathic pain. However, it was not clear whether and how miRNA-146a-5p regulates the TIR pathway of DRG and SDH in the development of neuropathic pain.

Methods

The sciatic nerve chronic constriction injury (CCI) model of rat was used to induce chronic neuropathic pain. The levels and cellular distribution of miRNA-146a-5p were detected with quantitative real-time PCR (qPCR) and fluorescent in situ hybridization (FISH). The RNA level, protein level, and cellular distribution of IRAK1 and TRAF6 that is targeted by miRNA-146a-5p were detected with qPCR, western blot, and immunofluorescent. The pain-related behavioral effect of miRNA-146a-5p was accessed after intrathecal administration. Mechanical stimuli and radiant heat were used to evaluate mechanical allodynia and thermal hyperalgesia.

Results

We found that the level of miRNA-146a-5p significantly increased in L4-L6 DRGs and SDH after CCI surgery; meanwhile, the protein level of IRAK1 and TRAF6 in DRGs was significantly increased after CCI. Intrathecal injection of miR146a-5p agomir or miRNA-146a-5p antagomir regulates miRNA-146a-5p level of L4-L6 DRGs and SDH. We found that intrathecal injection of miR146a-5p agomir can alleviate mechanical and thermal hyperalgesia in CCI rats and reverse the upregulation of IRAK1 and TRAF6 of L4-L6 DRGs and SDH induced by CCI. We furthermore found that intrathecal injection of miRNA-146a-5p antagomir can exacerbate the mechanical and thermal pain-related behavior of CCI rats and meanwhile increase IRAK1 and TRAF6 of L4-L6 DRGs and SDH expression even further.

Conclusions

miRNA-146a-5p of DRG and SDH can modulate the development of CCI-induced neuropathic pain through inhibition of IRAK1 and TRAF6 in the TIR signaling pathway. Hence, miRNA-146a-5p may serve as a potential therapeutic target for neuropathic pain.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1215-4) contains supplementary material, which is available to authorized users.

Lung injury caused by paraquat poisoning results in increased interleukin-6 and decreased microRNA-146a levels

The aim of the present study was to investigate the expression of microRNA (miR)-146a in the pulmonary macrophages, peripheral blood mononuclear cells and serum of patients with lung injury caused by paraquat poisoning, as well as the underlying mechanism of its regulation in the disease. A total of 26 patients with lung injury caused by paraquat poisoning were included in the present study. In addition, 33 healthy subjects were included as the control group. The expression levels of interleukin (IL)-6 mRNA and miR-146a was determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Western blotting was used to measure IL-6 protein expression, while enzyme-linked immunosorbent assay was also performed to determine the secretion of IL-6 protein. A dual-luciferase reporter assay was conducted to examine whether IL-6 mRNA is a direct target of miR-146a. Patients with lung injury caused by paraquat poisoning exhibited higher IL-6 mRNA and protein levels as compared with those in healthy subjects. In addition, miR-146a expression in patients with paraquat poisoning-induced lung injury was significantly reduced in comparison with that in healthy subjects. Notably, the overexpression of miR-146a by mimic transfection downregulated the expression of IL-6 in pulmonary macrophages. The results of dual-luciferase reporter assay demonstrated that IL-6 mRNA was a direct target of miR-146a. Therefore, the present study demonstrated that increased expression of IL-6 in patients with lung injury caused by paraquat poisoning is associated with decreased expression of miR-146a. Furthermore, miR-146a may regulate the occurrence and immune response of lung injury caused by paraquat poisoning and this process is possibly achieved via IL-6, an important cytokine that mediates inflammation.

Zhenbao pill protects against acute spinal cord injury via miR-146a-5p regulating the expression of GPR17

The aim of the present study was to observe the effect of zhenbao pill on the motor function of acute spinal cord injury (ASCI) rats and the molecular mechanisms involving miR-146a-5p and G-protein-coupled receptor 17 (GPR17). ASCI rat model was established by modified Allen method, and then the rats were divided into three groups. SH-SY5Y cells were cultured overnight in hypoxia condition and transfected with miR-146a-5p mimic or miR-146a-5p inhibitor. The hind limb motor function of the rats was evaluated by Basso, Beattie, Bresnahan (BBB) scoring system. Quantitative real-time PCR (qRT-PCR) and Western blot were used to detect the expression of miR-146a-5p, GPR17, inducible nitric oxide synthase (iNOS), interleukin 1β (IL-1β), and tumor necrosis factor α (TNF-α). Neuronal apoptosis was measured using flow cytometry assay. Luciferase reporter assay was performed to determine the regulation of miR-146a-5p on GPR17. Zhenbao pill could enhance hind limb motor function and attenuate the inflammatory response caused by ASCI. Moreover, zhenbao pill increased the level of miR-146a-5p and decreased GPR17 expression in vivo and in vitro Bioinformatics software predicted that GPR17 3'-UTR had a binding site with miR-146a-5p Luciferase reporter assay showed that miR-146a-5p had a negative regulatory effect on GPR17 expression. Knockdown of miR-146a-5p could reverse the effect of zhenbao pill on the up-regulation of GPR17 induced by hypoxia, reversed the inhibitory effect of zhenbao pill on the cell apoptosis induced by hypoxia and the recovery of zhenbao pill on hind limb motor function in ASCI rats. Zhenbao pill could inhibit neuronal apoptosis by regulating miR-146a-5p/GPR17 expression, and then promoting the recovery of spinal cord function.

Termination of cell-type specification gene programs by miR-183 cluster determines the population sizes of low threshold mechanosensitive neurons

Touch and mechanical sensations require the development of several different kinds of sensory neurons dedicated to respond to certain types of mechanical stimuli. The transcription factor Shox2 (short stature homeobox 2) is involved in the generation of TRKB+ low-threshold mechanoreceptors (LTMRs), but mechanisms terminating this program and allowing for alternative fates are unknown. Here, we show that the conditional loss of miR-183-96-182 cluster leads to a failure of extinction of Shox2 during development and an increase in the proportion of Aδ LTMRs (TRKB+/NECAB2+) neurons at the expense of Aβ slowly adapting (SA)-LTMRs (TRKC+/Runx3−) neurons. Conversely, overexpression of miR-183 cluster that represses Shox2 expression, or loss of Shox2, both increases the Aβ SA-LTMRs population at expense of Aδ LTMRs. Our results suggest that the miR-183 cluster determines the timing of Shox2 expression by direct targeting during development, and through this determines the population sizes of Aδ LTMRs and Aβ SA-LTMRs.

Changes in microRNA expression in the brachial plexus avulsion model of neuropathic pain

The present study aimed to perform microRNA (miRNA/miR) expression profiling of the thalamus (T), the anterior cingulate (AC), the dorsal horn of the spinal cord (DHSC) and the blood (B) in post‑complete brachial plexus avulsion (CBPA) pain model, and analyze biological functions. Neuropathic pain was induced in Sprague‑Dawley rats by CBPA. Animal behavioral tests were performed to differentiate the pain and control groups. DHSC, T, AC and B tissues were collected from the two groups for miRNA array analysis. The predicted mRNA targets were investigated by Gene Ontology analysis and pathway analysis. The results revealed that in the post‑CBPA pain model, there were 10 differentially expressed miRNAs revealed among 4 different tissues. A total of 4 microRNAs in the AC and 3 microRNAs in the T were shown to be significantly upregulated. The functions of the differentially expressed miRNAs in the AC and T were synergetic in the aspect of positive regulation of neuron apoptotic process, inhibition of long‑term potentiation and formation of synapse plasticity. miR‑30c‑1‑3p and its predicted genes [calcium/calmodulin dependent protein kinase IIβ (Camk2b) and protein kinase Cγ (Prkcg)] existed in the AC and T groups with significant changes in expression. There were 2 miRNAs in the DHSC and B groups, respectively, with significant downregulation. The function of the change in miRNAs in the DHSC group was opposite to that in the AC and T groups. The differentially expressed microRNAs in the B group were revealed to be negative for the regulation of cell apoptosis. In conclusion, the central nerve groups (AC and T) and the peripheral nerve group (DHSC) exhibited contrasting effects on synapse plasticity and neuron apoptosis. miR‑30c‑1‑3p and its predicted genes (Camk2b and Prkcg) existed in the AC and T groups with significant changes in expression.

Aberrant microRNA expression in patients with painful peripheral neuropathies

Changes in the neuro-immune balance play a major role in the induction and maintenance of neuropathic pain. We recently reported pathophysiologically relevant alterations in skin and sural nerve cytokine expression in peripheral neuropathies of different etiologies. Immune processes and cytokine expression are under tight control of microRNAs (miRNAs). To identify potential master switches in the neuro-immune balance, we aimed at characterizing inflammation-regulating miRNA profiles in patients with peripheral neuropathies. In an unselected patient cohort with polyneuropathies of different etiologies seen at our neuromuscular center between 2014 and 2015, we determined the systemic and local relative expression of miR-21-5p, miR-146a, and miR-155. In white blood cells we found higher miR-21 (p<0.001) and miR-146a (p<0.001) expression and lower miR-155 (p<0.001) expression when compared to healthy controls. In sural nerve, miR-21 (p<0.02) was increased in painful compared to painless neuropathies. In painful neuropathies, skin biopsies from the lower leg had reduced miR-146a (p<0.001) and miR-155 (p<0.001) expression compared to the thigh. Thus, peripheral neuropathies are associated with aberrant miRNA expression in white blood cells, sural nerve, and skin. These miRNA patterns may help to identify factors that determine the painfulness of peripheral neuropathies and lead to druggable targets.

miR-183 cluster scales mechanical pain sensitivity by regulating basal and neuropathic pain genes

Nociception is protective and prevents tissue damage but can also facilitate chronic pain. Whether a general principle governs these two types of pain is unknown. Here, we show that both basal mechanical and neuropathic pain are controlled by the microRNA-183 (miR-183) cluster in mice. This single cluster controls more than 80% of neuropathic pain-regulated genes and scales basal mechanical sensitivity and mechanical allodynia by regulating auxiliary voltage-gated calcium channel subunits α2δ-1 and α2δ-2. Basal sensitivity is controlled in nociceptors, and allodynia involves TrkB+ light-touch mechanoreceptors. These light-touch-sensitive neurons, which normally do not elicit pain, produce pain during neuropathy that is reversed by gabapentin. Thus, a single microRNA cluster continuously scales acute noxious mechanical sensitivity in nociceptive neurons and suppresses neuropathic pain transduction in a specific, light-touch-sensitive neuronal type recruited during mechanical allodynia.

MicroRNA-29a Counteracts Synovitis in Knee Osteoarthritis Pathogenesis by Targeting VEGF

Synovitis contributes to the development of osteoarthritis (OA) of the knee. MicroRNAs regulate joint microenvironment homeostasis and deterioration. This study was undertaken to characterize the actions of microRNA-29a (miR-29a) to synovial remodeling in OA joints. Synovial specimens isolated from patients with end-stage OA knees showed abundant fibrotic matrix and vessel histopathology concomitant with weak miR-29a expression. In vitro, miR-29a knockdown caused synovial fibroblasts to exhibit high expressions of collagen III, TGF-β1, MMP9, MMP13, and ADAMTS5, whereas miR-29a overexpression diminished these joint-deleterious factors. In collagenase-mediated OA pathogenesis, miR-29a-overexpressing transgenic mice showed minor responses to hyperplasia, macrophage infiltration, fibrosis, hyperangiogenesis, and VEGF expression in synovial lesions. These effects mitigated articular cartilage loss and gait aberrance of injured joints. Intra-articular administration of miR-29a precursor lessened the collagenase aggravation of excessive synovial remodeling reactions and thereby sustained joint tissue integrity. miR-29a lowered VEGF production and angiogenic activities in synovial fibroblasts through targeting the 3′-UTR of VEGF. Taken together, miR-29a deficiency exacerbated synovitis pathogenesis in the end-stage OA knees. miR-29a signaling fends off excessive synovial angiogenesis and fibrosis, which delays joint destruction. This study sheds new light on the protective effects against synovial deterioration and the therapeutic advantage of miR-29a in OA knees.

Gender-specific differential expression of exosomal miRNA in synovial fluid of patients with osteoarthritis

The pathogenesis of osteoarthritis (OA) is poorly understood, and therapeutic approaches are limited to preventing progression of the disease. Recent studies have shown that exosomes play a vital role in cell-to-cell communication, and pathogenesis of many age-related diseases. Molecular profiling of synovial fluid derived exosomal miRNAs may increase our understanding of OA progression and may lead to the discovery of novel biomarkers and therapeutic targets. In this article we report the first characterization of exosomes miRNAs from human synovial fluid. The synovial fluid exosomes share similar characteristics (size, surface marker, miRNA content) with previously described exosomes in other body fluids. MiRNA microarray analysis showed OA specific exosomal miRNA of male and female OA. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis identified gender-specific target genes/signaling pathways. These pathway analyses showed that female OA specific miRNAs are estrogen responsive and target TLR (toll-like receptor) signaling pathways. Furthermore, articular chondrocytes treated with OA derived extracellular vesicles had decreased expression of anabolic genes and elevated expression of catabolic and inflammatory genes. In conclusion, synovial fluid exosomal miRNA content is altered in patients with OA and these changes are gender specific.

Effects of microRNA-146a on the proliferation and apoptosis of human osteoarthritis chondrocytes by targeting TRAF6 through the NF-κB signalling pathway

The present study aims to investigate the effects of miR-146a on the proliferation and apoptosis of human osteoarthritis (OA) chondrocytes by targeting tumour necrosis factor receptor-associated factor 6 (TRAF6) through nuclear factor-κB (NF-κB) signalling pathway. Human normal and OA chondrocytes were selected and divided into the normal group, blank group, negative control (NC) group, miR-146a mimics group, miR-146a inhibitors, miR-146a inhibitor + si-TRAF6 group and si-TRAF6 group. Quantitative real-time PCR (qRT-PCR) was applied to detect the expressions of miR-146a, TRAF6 mRNA and NF-κB mRNA. Western blotting was used to detect the protein expressions of TRAF6 and NF-κB. CCK-8 assay and flow cytometry were used to detect cell proliferation and apoptosis. Compared with normal chondrocytes, the expression of miR-146a decreased, while the mRNA and protein expressions of TRAF6 and NF-κB increased in OA chondrocytes. OA chondrocytes had a lower proliferation rate and a higher apoptosis rate than the normal chondrocytes. Compared with the blank, NC and si-TRAF6 groups, the expression of miR-146a increased in the miR-146a mimics group, but decreased in the miR-146a inhibitors and miR-146a inhibitor + si-TRAF6 groups. Compared with the blank, NC and miR-146a inhibitor + si-TRAF6 groups, the mRNA and protein expressions of TRAF6 and NF-κB decreased, cell proliferation rate increased and cell apoptosis rate decreased in the miR-146a mimics and si-TRAF6 groups, while opposite trends were observed in the miR-146a inhibitors group. Our study suggests that miR-146a could promote proliferation and inhibit apoptosis of OA chondrocytes by inhibiting TRAF6 expression and suppressing the activation of NF-κB signalling pathway.

miR-146a facilitates osteoarthritis by regulating cartilage homeostasis via targeting Camk2d and Ppp3r2

Osteoarthritis (OA), characterized by insufficient extracellular matrix synthesis and cartilage degeneration, is known as an incurable disease because its pathogenesis is poorly elucidated. Thus far, limited information is available regarding the pathophysiological role of microRNAs (miRNAs) in OA. In this study, we investigated the specific function of miR-146a in OA pathophysiology using mouse OA models. We found that the articular cartilage degeneration of miR-146a knockout (KO) mice was alleviated compared with that of the wild-type (WT) mice in spontaneous and instability-induced OA models. We demonstrate that miR-146a aggravated pro-inflammatory cytokines induced suppressing the expression of cartilage matrix-associated genes. We further identified calcium/calmodulin-dependent protein kinase II delta (Camk2d) and protein phosphatase 3, regulatory subunit B, beta isoform (Ppp3r2, also known as calcineurin B, type II) were essential targets of miR-146a in regulating cartilage homeostasis. Moreover, we found that surgical-induced OA mice treated with a miR-146a inhibitor significantly alleviated the destruction of articular cartilage via targeting Camk2d and Ppp3r2. These results suggested that miR-146a has a crucial role in maintaining cartilage homeostasis. MiR-146a inhibition in chondrocytes can be a potential therapeutic strategy to ameliorate OA.

Review of Prospects of Biological Fluid Biomarkers in Osteoarthritis

Osteoarthritis (OA) is a degenerative disease of the joints and is one of the leading causes of disability in adults. However, there are no key therapeutics for OA and medical treatment is based on managing the symptoms and slowing down progression of the disease. Diagnostics based on clinical examination and radiography have provided little information about metabolic changes in joint tissues, disease onset and progression. Due to lack of effective methods for early detection and evaluation of treatment outcome, the measurement of biochemical markers (biomarkers) shows promise as a prospective method aiding in disease monitoring. OA biomarkers that are present in biological fluids such as blood, urine and synovial fluid, sources that are easily isolated from body, are of particular interest. Moreover, there are increasingly more studies identifying and developing new biomarkers for OA. In this review, efforts have been made to summarize the biomarkers that have been reported in recent studies on patients. We also tried to classify biomarkers according to tissue metabolism (bone, cartilage and synovial metabolism markers), pathological pathways (inflammatory and genetic markers) and biological function (chemokines, growth factors, acute phase proteins, etc.).

MicroRNA-146a Ameliorates Inflammation via TRAF6/NF-κB Pathway in Intervertebral Disc Cells

Background

Intervertebral disc degeneration (IDD) has been widely recognized as a major contributor to low back pain. Accumulating evidence suggests that IDD is linked to various pro-inflammatory cytokines and metabolites. Recently, numerous studies have demonstrated that microRNAs (miRNAs) play a pivotal role in the development of most disorders, including degenerative disc diseases. Previous reports have revealed that miRNA-146a (miR-146a) could attenuate neuropathic pain in the spinal cord. The aim of this study was to investigate the role of miR-146a in the inflammatory response of IDD.

Material/Methods

Quantitative real-time (RT)-PCR was performed to investigate the levels of miR-146a in the PBMCs (peripheral blood mononuclear cells) of patients with IDD. Human nucleus pulposus (NP) cells were transiently transfected with miR-146a mimic; control NP cell transfections lacked miR-146a. Then all NP cells were treated with LPS (10 μM) to induce inflammation. The mRNA levels of miR-146a in NP cells were determined by RT-PCR. In addition, the mRNA and protein expression levels of tumor necrosis factor (TNF), receptor-associated factor 6 (TRAF6), and nuclear factor (NF)-κB in NP cells were evaluated by quantitative RT-PCR and Western blot analysis, respectively.

Results

We found that miR-146a was significantly downregulated in the PBMCs of patients. Moreover, overexpression of miR-146a significantly decreased the levels of pro-inflammatory cytokines in LPS-stimulated NP cells. The mRNA and protein levels of TRAF6 and NF-κB were downregulated by miR-146a overexpression.

Conclusions

These results suggest that overexpression of miR-146a could promote IDD through the TRAF/NF-κB pathway. Our findings also highlight miR-146a as a novel possible therapeutic target for IDD.

The synovial microenvironment of osteoarthritic joints alters RNA-seq expression profiles of human primary articular chondrocytes

Osteoarthritis (OA) is a disabling degenerative joint disease that prompts pain and has limited treatment options. To permit early diagnosis and treatment of OA, a high resolution mechanistic understanding of human chondrocytes in normal and diseased states is necessary. In this study, we assessed the biological effects of OA-related changes in the synovial microenvironment on chondrocytes embedded within anatomically intact cartilage from joints with different pathological grades by next generation RNA-sequencing (RNA-seq). We determined the transcriptome of primary articular chondrocytes derived from anatomically unaffected knees and ankles, as well as from joints affected by OA. The GALAXY bioinformatics platform was used to facilitate biological interpretations. Comparisons of patient samples by k-means, hierarchical clustering and principal component analyses together reveal that primary chondrocytes exhibit OA grade-related differences in gene expression, including genes involved in cell-adhesion, ECM production and immune response. We conclude that diseased synovial microenvironments in joints with different histopathological OA grades directly alter gene expression in chondrocytes. One ramification of this finding is that anatomically intact cartilage from OA joints is not an ideal source of healthy chondrocytes, nor should these specimens be used to generate a normal baseline for the molecular characterization of diseased joints.

miRNAs Related to Skeletal Diseases

miRNAs as non-coding, short, double-stranded RNA segments are important for cellular biological functions, such as proliferation, differentiation, and apoptosis. miRNAs mainly contribute to the inhibition of important protein translations through their cleavage or direct repression of target messenger RNAs expressions. In the last decade, miRNAs got in the focus of interest with new publications on miRNAs in the context of different diseases. For many types of cancer or myocardial damage, typical signatures of local or systemically circulating miRNAs have already been described. However, little is known about miRNA expressions and their molecular effect in skeletal diseases. An overview of published studies reporting miRNAs detection linked with skeletal diseases was conducted. All regulated miRNAs were summarized and their molecular interactions were illustrated. This review summarizes the involvement and interaction of miRNAs in different skeletal diseases. Thereby, 59 miRNAs were described to be deregulated in tissue, cells, or in the circulation of osteoarthritis (OA), 23 miRNAs deregulated in osteoporosis, and 107 miRNAs deregulated in osteosarcoma (OS). The molecular influences of miRNAs regarding OA, osteoporosis, and OS were illustrated. Specific miRNA signatures for skeletal diseases are described in the literature. Some overlapped, but also unique ones for each disease exist. These miRNAs may present useful targets for the development of new therapeutic approaches and are candidates for diagnostic evaluations.

Osteoclast-derived microRNA-containing exosomes selectively inhibit osteoblast activity

MicroRNAs have an important role in bone homeostasis. However, the detailed mechanism of microRNA-mediated intercellular communication between bone cells remains elusive. Here, we report that osteoclasts secrete microRNA-enriched exosomes, by which miR-214 is transferred into osteoblasts to inhibit their function. In a coculture system, inhibition of exosome formation and secretion prevented miR-214 transportation. Exosomes specifically recognized osteoblasts through the interaction between ephrinA2 and EphA2. In osteoclast-specific miR-214 transgenic mice, exosomes were secreted into the serum, and miR-214 and ephrinA2 levels were elevated. Therefore, these exosomes have an inhibitory role in osteoblast activity. miR-214 and ephrinA2 levels in serum exosomes from osteoporotic patients and mice were upregulated substantially. These exosomes may significantly inhibit osteoblast activity. Inhibition of exosome secretion via Rab27a small interfering RNA prevented ovariectomized-induced osteoblast dysfunction in vivo. Taken together, these findings suggest that exosome-mediated transfer of microRNA plays an important role in the regulation of osteoblast activity. Circulating miR-214 in exosomes not only represents a biomarker for bone loss but could selectively regulate osteoblast function.

MicroRNAs: exploring new horizons in osteoarthritis

INTRODUCTION

Osteoarthritis (OA) is a common disease worldwide leading to significant morbidity. The underlying disease process is multifactorial however there is increasing focus on molecular mechanisms. MicroRNAs are small non-coding segments of RNA that have important regulatory functions at a cellular level. These molecules are readily detectable in human tissues and circulation. They are increasingly recognised as having a major role in many disease processes - including malignancy and inflammatory processes.

OBJECTIVE

This review paper aims to provide a comprehensive update on the evidence for miRNA roles in OA.

DESIGN

A comprehensive literature search was performed using key medical subject headings (MeSH) terms 'microRNA' and 'osteoarthritis'.

RESULTS

Several miRNAs have been identified as having aberrant expression levels in OA. Some of these include miR-9, miR-27, miR-34a, miR-140, miR-146a, miR-558 and miR-602. Many of the dysregulated miRNAs have been shown to regulate expression of inflammatory pathways such as interleukin-mediated or matrix metalloproteinase-13 (MMP-13)-mediated degradation of the articular cartilage extracellular matrix (ECM). MiRNAs may also play a role in pain pathways and hence expression of clinical symptoms.

CONCLUSIONS

Recent evidence has shown that miRNAs in the circulation may reflect underlying disease states and hence serve as potential markers for disease activity. These findings may represent possible future therapeutic applications in the management of OA.