MicroRNA-155 suppresses the catabolic effect induced by TNF-α and IL-1β by targeting C/EBPβ in rat nucleus pulposus cells

MicroRNA-targeting nanomedicines for the treatment of intervertebral disc degeneration

Low back pain stands as a pervasive global health concern, afflicting almost 80% of adults at some point in their lives with nearly 40% attributable to intervertebral disc degeneration (IVDD). As only symptomatic relief can be offered to patients there is a dire need for innovative treatments.Given the accumulating evidence that multiple microRNAs (miRs) are dysregulated during IVDD, they could have a huge potential against this debilitating condition. The way miRs can profoundly modulate signaling pathways and influence several cellular processes at once is particularly exciting to tackle this multifaceted disorder. However, miR delivery encounters extracellular and intracellular biological barriers. A promising technology to address this challenge is the vectorization of miRs within nanoparticles, providing both protection and enhancing their uptake within the scarce target cells of the degenerated IVD. This comprehensive review presents the diverse spectrum of miRs' connection with IVDD and demonstrates their therapeutic potential when vectorized in nanomedicines.

MicroRNA-155 suppressed cholesterol-induced matrix degradation, pyroptosis and apoptosis by targeting RORα in nucleus pulposus cells

Intervertebral disc degeneration (IDD) is associated with low back pain, yet its inherent mechanism remains obscure. Hypercholesteremia was regarded as a risk factor for IDD, and our previous study showed that cholesterol accumulation could elicit matrix degradation in the nucleus pulposus (NP). MicroRNA-155 (miR-155) was substantiated as protective in IDD, but its role in cholesterol-induced IDD was unclear. The present study investigated whether miR-155 could mediate cholesterol-related IDD and its internal mechanisms. In vivo experiments revealed high-fat diet-induced hypercholesteremia in wild-type (WT) mice along with the occurrence of IDD, whereas Rm155LG transgenic mice showed milder NP degeneration, as evidenced by Safranin O-fast green (SF) staining and immunohistochemistry (IHC). Meanwhile, IHC showed that NLRP3 and Bax expression was also suppressed in Rm155LG mice. In vitro studies using Western blotting (WB) and immunofluorescence (IF) confirmed that the miR-155 mimic could alleviate cholesterol-induced matrix degradation, apoptosis and pyroptosis in NP. Moreover, RORα was upregulated in severely degenerated NP compared to mild IDD. It was also noted that RORα was suppressed in Rm155LG mice. In this study, we demonstrated that miR-155 could target RORα and that inhibition of RORα could prevent cholesterol-induced matrix degradation, apoptosis, and pyroptosis in NP, indicating the protective effect of miR-155 in cholesterol-induced IDD by targeting RORα.

Tetrahedral-Framework Nucleic Acid Loaded with MicroRNA-155 Enhances Immunocompetence in Cyclophosphamide-Induced Immunosuppressed Mice by Modulating Dendritic Cells and Macrophages

Nanomaterials are often used as immunomodulators because they can be tailored by a controllable process. In this work, a complex based on a tetrahedral framework nucleic acid delivery system and MicroRNA-155, known as T-155, is synthesized for the modulation of immunosuppression. In vivo, T-155 ameliorated spleen and thymus damage and hematopoiesis suppression in cyclophosphamide-induced immunosuppressed mice by promoting T-cell proliferation to resist oxidative stress. In vitro, T-155 induced immature dendritic cells (DCs) to differentiate into mature DCs by the ERK1/2 pathway and converted M0 macrophages (Mφ) into the M1 type by the NF-κB pathway to enhance the surveillance capabilities of antigen-presenting cells. The experimental results suggest that T-155 has therapeutic potential as an immunomodulator for immunosuppression.

Lipid nanocapsules for intracellular delivery of microRNA: a first step towards intervertebral disc degeneration therapy

Approximately 40% of cases of lower back pain are caused by disc degeneration disease (DDD). It is well established that microRNA (miR) dysregulation is a key player in various diseases, and its impact on DDD has recently been highlighted. RNAi (miR in particular) is increasingly being considered as a novel therapeutic tool. However, free miR is degraded rapidly in vivo, and its protection is thus a prerequisite. Nanoparticular platforms, such as lipid nanocapsules (LNC), could be specifically adapted for miR delivery, allowing the transfer and release of miR in the cell cytoplasm. The objective of the current study was to formulate and characterize miR-loaded LNC to establish their in vitro potential (cell internalization, bioactivity) as well as to determine the safety and feasibility of in situ intervertebral disc (IVD) injection of miR LNC in a healthy sheep model. Using a miR library, miR-155 was clearly identified as being involved in the DDD process and was selected for further assessment. miR-155-loaded LNC (miR-155 LNC) were successfully formulated using a phase inversion process, with the addition of lipoplexes in the cooling step. Following purification, miR-155 LNC were fully characterized, and the optimized formulation had an average diameter of 75 nm, a polydispersity index below 0.1, and a positive zeta potential. By fluorescence spectroscopy, an encapsulation efficiency (EE) of 75.6% and a drug loading (DL) of 0.6% were obtained, corresponding to a sufficient amount of miR per mL of LNC to potentially have a biological effect. The sustained release of miR-155 from LNC was demonstrated compared with free miR-155: only 22% was released after 2 h and 58% after 24 h. miR-155 protection against endonuclease degradation by LNC was confirmed by gel electrophoresis, a sine qua non condition for it to be administered in vivo. Cell viability assays were performed on human adipose stromal cells (hASCs) and ovine Nucleus pulposus cells (oNP), and a cytotoxicity of less than 30% was obtained at the considered concentrations. Additionally, miR-155 LNC cell internalization was demonstrated by flow cytometry and confocal imaging. Moreover, downregulation of total ERK1/2 in hASCs and oNP cells, after miR-155 LNC treatment, was demonstrated by Western blot and quantitative reverse-transcription PCR (qRT-PCR), thus confirming maintenance of its bioactivity after formulation and internalization. Finally, the feasibility and safety of miR-155 LNC in situ injection (compared to control groups: blank LNC and sham condition) was demonstrated in healthy sheep by imaging (MRI and T2wsi measurement) and histology (Boos' scoring) analysis. T2wsi was measured, and no significant difference was observed three months after the injection between the different conditions. No histological impact was observed, with no significant difference in Boos' scoring between the different conditions. All these results suggest LNC may be a potent strategy for the encapsulation and delivery of miR (particularly miR-155) and can be considered as a first step towards IVD regenerative medicine.

Treatment of Intervertebral Disc Degeneration

Intervertebral disc degeneration (IDD) causes a variety of signs and symptoms, such as low back pain (LBP), intervertebral disc herniation, and spinal stenosis, which contribute to high social and economic costs. IDD results from many factors, including genetic factors, aging, mechanical injury, malnutrition, and so on. The pathological changes of IDD are mainly composed of the senescence and apoptosis of nucleus pulposus cells (NPCs), the progressive degeneration of extracellular matrix (ECM), the fibrosis of annulus fibrosus (AF), and the inflammatory response. At present, IDD can be treated by conservative treatment and surgical treatment based on patients' symptoms. However, all of these can only release the pain but cannot reverse IDD and reconstruct the mechanical function of the spine. The latest research is moving towards the field of biotherapy. Mesenchymal stem cells (MSCs) are regard as the potential therapy of IDD because of their ability to self-renew and differentiate into a variety of tissues. Moreover, the non-coding RNAs (ncRNAs) are found to regulate many vital processes in IDD. There have been many successes in the in vitro and animal studies of using biotherapy to treat IDD, but how to transform the experimental data to real therapy which can apply to humans is still a challenge. This article mainly reviews the treatment strategies and research progress of IDD and indicates that there are many problems that need to be solved if the new biotherapy is to be applied to clinical treatment of IDD. This will provide reference and guidance for clinical treatment and research direction of IDD.

miRNA-Based Potential Biomarkers and New Molecular Insights in Ulcerative Colitis

Ulcerative colitis (UC) is a chronic non-specific inflammatory bowel disease, which usually manifests as abdominal pain, diarrhea and hematochezia. The disease often recurs and is difficult to cure. At present, the pathogenesis is not clear, but it is believed that the disease is caused by a complex interaction among immunity, heredity, environment and intestinal microflora disorders. MicroRNA (miRNA) is endogenous single-stranded non-coding RNA of 17–25 nucleotides (nts). They target the 3'Untranslated Region of a target gene and inhibit or degrade the target gene according to the extent of complementary bases. As important gene expression regulators, miRNAs are involved in regulating the expression of most human genes, and play an important role in the pathogenesis of many autoimmune diseases including UC. Studies in recent years have illustrated that abnormal expression of miRNA occurs very early in disease pathogenesis. Moreover, this abnormal expression is highly related to disease activity of UC and colitis-associated cancer, and involves virtually all key UC-related mechanisms, such as immunity and intestinal microbiota dysregulation. Recently, it was discovered that miRNA is highly stable outside the cell in the form of microvesicles, exosomes or apoptotic vesicles, which raises the possibility that miRNA may serve as a novel diagnostic marker for UC. In this review, we summarize the biosynthetic pathway and the function of miRNA, and summarize the usefulness of miRNA for diagnosis, monitoring and prognosis of UC. Then, we described four types of miRNAs involved in regulating the mechanisms of UC occurrence and development: 1) miRNAs are involved in regulating immune cells; 2) affect the intestinal epithelial cells barrier; 3) regulate the homeostasis between gut microbiota and the host; and 4) participate in the formation of tumor in UC. Altogether, we aim to emphasize the close relationship between miRNA and UC as well as to propose that the field has value for developing potential biomarkers as well as therapeutic targets for UC.

Role of microRNAs in intervertebral disc degeneration (Review)

The incidence of lower back pain caused by intervertebral disc degeneration (IDD) is gradually increasing. IDD not only affects the quality of life of the patients, but also poses a major socioeconomic burden. There is currently no optimal method for delaying or reversing IDD, mainly due to its unknown pathogenesis. MicroRNAs (miRNAs/miRs) participate in the development of a number of diseases, including IDD. Abnormal expression of miRNAs in the intervertebral disc is implicated in various pathological processes underlying the development of IDD, including nucleus pulposus (NP) cell (NPC) proliferation, NPC apoptosis, extracellular matrix remodeling, inflammation and cartilaginous endplate changes, among others. The focus of the present review was the advances in research on the involvement of miRNAs in the mechanism underlying IDD. Further research is expected to identify markers for early diagnosis of IDD and new targets for delaying or reversing IDD.

Bromodomain-containing protein 7 regulates matrix metabolism and apoptosis in human nucleus pulposus cells through the BRD7-PI3K-YAP1 signaling axis

Intervertebral disc degeneration (IDD) results from dysregulated metabolism of the extracellular matrix of the nucleus pulposus (NP) and involves the participation of inflammatory factors such as TNF-α. Bromodomain-containing protein 7 (BRD7) shows considerable potential for anti-inflammatory applications. Herein, we investigated the role of BRD7 in IDD. The immunohistochemistry results demonstrated decreased BRD7 expression in severely degenerated human NP tissues compared to those showing mild degeneration. Lentiviruses and adenoviruses were used to knock down or overexpress BRD7 and YAP1, respectively. Our results revealed that BRD7 knockdown promoted matrix degradation and suppressed PI3K and YAP1 expression, while BRD7 overexpression alleviated matrix degradation and promoted YAP1 and PI3K expression. In addition, PI3K inhibition augmented matrix degradation, enhanced apoptosis, and reduced YAP1 expression, whereas YAP1 overexpression promoted matrix synthesis, suppressed apoptosis and promoted PI3K expression. Besides, BRD7 overexpression reversed the reductions in sulfated glycosaminoglycan levels induced by TNF-α, but this effect was blocked by PI3K or YAP1 inhibitors. Moreover, YAP1 and PI3K were shown to interact through coimmunoprecipitation analysis. In summary, our results demonstrate that BRD7 can regulate matrix metabolism and apoptosis in human NP cells through the BRD7-PI3K-YAP1 signaling axis. This study might provide new insights into the prevention and treatment of IDD.

microRNA-155-3p attenuates intervertebral disc degeneration via inhibition of KDM3A and HIF1α

OBJECTIVE

Intervertebral disc degeneration (IDD) is a key element resulting in low back pain, but the mechanisms underlying IDD remain largely unknown. The purpose of the study was to investigate the influence of microRNA-155-3p (miR-155-3p) on proliferation and autophagy of nucleus pulposus (NP) cells in IDD with the involvement of hypoxia-inducible factor 1 α (HIF1α)/histone lysine demethylase 3A (KDM3A) axis.

METHODS

IDD NP tissues of patients with lumbar disc herniation and traumatic intervertebral disc NP tissues from patients with traumatic lumbar fracture were collected. Apoptosis in NP tissues was observed, and autophagy marker proteins in NP tissues were detected. NP cells in IDD were transfected with miR-155-3p mimic or KDM3A-siRNA to explore their roles in cell proliferation, autophagy and apoptosis. MiR-155-3p, KDM3A and HIF1α expression in NP tissues and cells were detected.

RESULTS

Decreased miR-155-3p, and elevated HIF1α and KDM3A were presented in NP tissues and cells of IDD. Elevated miR-155-3p or silenced KDM3A promoted the proliferation and autophagy, and inhibited the apoptosis of NP cells of IDD. Moreover, elevated miR-155-3p decreased KDM3A and HIF1α expression, while silenced KDM3A decreased HIF1α expression in NP cells with IDD.

CONCLUSION

The study concludes that up-regulated miR-155-3p or silenced KDM3A promotes the proliferation, autophagy, and restrains the apoptosis of NP cells of IDD via inhibition of HIF1α, which may be a promising approach for the treatment of IDD.

New insights into the interplay between miRNAs and autophagy in the aging of intervertebral discs

Intervertebral disc degeneration (IDD) has been widely known as a main contributor to low back pain which has a negative socioeconomic impact worldwide. However, the underlying mechanism remains unclear. MicroRNAs (miRNAs) are a class of small noncoding RNAs that post-transcriptionally regulate gene expression and serve key roles in the ageing process of intervertebral disc. Autophagy is an evolutionarily conserved process that maintains cellular homeostasis through recycling of nutrients and degradation of damaged or aged cytoplasmic organelles. Autophagy has been proposed as a "double-edged sword" and autophagy dysfunction of IVD cells is considered as a crucial reason of IDD. A rapidly growing number of recent studies demonstrate that both miRNAs and autophagy play important roles in the progression of IDD. Furthermore, accumulated research has indicated that miRNAs target autophagy-related genes and influence the onset and development of IDD. Hence, this review focuses mainly on the current findings regarding the correlations between miRNA, autophagy, and IDD and provides new insights into the role of miRNA-autophagy pathway involved in IDD pathophysiology.

MiR-155 promotes interleukin-1β-induced chondrocyte apoptosis and catabolic activity by targeting PIK3R1-mediated PI3K/Akt pathway

Osteoarthritis (OA) is a common joint disease characterized by progressive cartilage degradation, in which elevated chondrocyte apoptosis and catabolic activity play an important role. MicroRNA-155 (miR-155) has recently been shown to regulate apoptosis and catabolic activity in some pathological circumstances, yet, whether and how miR-155 is associated with OA pathology remain unexplored. We report here that miR-155 level is significantly up-regulated in human OA cartilage biopsies and also in primary chondrocytes stimulated by interleukin-1β (IL-1β), a pivotal pro-catabolic factor promoting cartilage degradation. Moreover, miR-155 inhibition attenuates and its overexpression promotes IL-1β-induced apoptosis and catabolic activity in chondrocytes in vitro. We also demonstrate that the PIK3R1 (p85α regulatory subunit of phosphoinositide 3-kinase (PI3K)) is a target of miR-155 in chondrocytes, and more importantly, PIK3R1 restoration abrogates miR-155 effects on chondrocyte apoptosis and catabolic activity. Mechanistically, PIK3R1 positively regulates the transduction of PI3K/Akt pathway, and a specific Akt inhibitor reverses miR-155 effects on promoting chondrocyte apoptosis and catabolic activity, phenocopying the results obtained via PIK3R1 knockdown, hence establishing that miR-155 promotes chondrocyte apoptosis and catabolic activity through targeting PIK3R1-mediated PI3K/Akt pathway activation. Altogether, our study discovers novel roles and mechanisms of miR-155 in regulating chondrocyte apoptosis and catabolic activity, providing an implication for therapeutically intervening cartilage degradation and OA progression.

Circulating miR-155-5p as a Novel Biomarker of Lumbar Degenerative Disc Disease

MINI: Circulating microRNAs provide an insight into current disease states. Comparing patients with degenerative disc disease to healthy controls, patients with disc disease were found to have significantly downregulated levels of miR-155-5p. This marker was found to be an accurate diagnostic predictor for the presence of degeneration (P = 0.006).

STUDY DESIGN

Case-control study measuring differential gene expression of circulating microRNA (miRNA) in patients with degenerative disc disease (DDD).

OBJECTIVE

To identify miRNA dysregulation in serum samples of patients with DDD compared to healthy controls (HC).

SUMMARY OF BACKGROUND DATA

Early DDD can be a difficult diagnosis to make clinically, with lack of positive and specific findings on physical exam or advanced imaging. miRNAs are a class of molecules that act as gene regulators and have been shown to be dysregulated in local degenerative disc tissue. However, to date no studies have identified dysregulation of serum miRNA in patients with DDD.

METHODS

Whole blood samples were obtained from 69 patients with DDD and 16 HC. Patient-reported outcomes were collected preoperatively and degree of DDD was classified using Pfirrmann grade on preoperative imaging. Differential gene expression analysis using a screening assay for several hundred miRNAs and further characterization for five specific miRNAs (miR-16-5p, miR-21-5p, miR-142-3p, miR-146a-5p, and miR-155-5p) was performed. In addition, a pro-inflammatory cytokine multiplex assay and bioinformatics analysis were done.

RESULTS

The initial screening assay showed 13 miRNA molecules that were significantly dysregulated in DDD patients, with miR-155-5p showing significant downregulation (p = 0.027) and direct interactions with the pro-inflammatory cytokine IL-1β, and the tumor suppressor genes p53 and BRAF. Analyzing the whole cohort, miR-155 showed an almost four-fold downregulation in DDD patients (-3.94-fold, P < 0.001) and was the sole miRNA that accurately predicted the presence of disc degeneration (P = 0.006). Downregulation of miR-155 also correlated with increased leg pain (P = 0.018), DDD (P = 0.006), and higher Pfirrmann grade (P = 0.039). On cytokine analysis, TNF-α (0.025) and IL-6 (P < 0.001) were significantly higher in DDD patients.

CONCLUSION

Serum miR-155-5p is significantly downregulated in patients with DDD and may be a diagnostic marker for degenerative spinal disease.

LEVEL OF EVIDENCE

N/A.

Non-Coding RNAs in Cartilage Development: An Updated Review

In the development of the skeleton, the long bones are arising from the process of endochondral ossification (EO) in which cartilage is replaced by bone. This complex process is regulated by various factors including genetic, epigenetic, and environmental elements. It is recognized that DNA methylation, higher-order chromatin structure, and post-translational modifications of histones regulate the EO. With emerging understanding, non-coding RNAs (ncRNAs) have been identified as another mode of EO regulation, which is consist of microRNAs (miRNAs or miRs) and long non-coding RNAs (lncRNAs). There is expanding experimental evidence to unlock the role of ncRNAs in the differentiation of cartilage cells, as well as the pathogenesis of several skeletal disorders including osteoarthritis. Cutting-edge technologies such as epigenome-wide association studies have been employed to reveal disease-specific patterns regarding ncRNAs. This opens a new avenue of our understanding of skeletal cell biology, and may also identify potential epigenetic-based biomarkers. In this review, we provide an updated overview of recent advances in the role of ncRNAs especially focus on miRNA and lncRNA in the development of bone from cartilage, as well as their roles in skeletal pathophysiology.