microRNA-138 induces cell survival and reduces WNT/β-catenin signaling of osteoarthritis chondrocytes through NEK2

A brief review of current treatment options for osteoarthritis including disease-modifying osteoarthritis drugs (DMOADs) and novel therapeutics

Osteoarthritis (OA) is a chronic disorder caused by degenerative changes in articular cartilage, which are mainly manifests as degeneration of cartilage, subchondral bone remodeling, as well as synovial inflammation. Over the next few decades, OA and its burden will continue to increase worldwide, posing a major public health challenge for the foreseeable future. Treatment for OA includes non-pharmacological, pharmacological, and surgical treatments. Existing conservative treatments and joint surgery can only alleviate the symptoms and cannot be cured, so new therapies for OA are urgently needed. Since advances in the understanding of OA pathophysiology, researchers have identified some potential therapeutic targets against degeneration of cartilage, subchondral bone remodeling and synovial inflammation, enabling development of the disease-modifying OA drugs (DMOADs). Additionally, a number of new technologies are also being investigated for treating OA, such as RNA interference (RNAi), CRISPR/Cas9 and PROTAC. The goal of this review is to describe the current development status of DMOADs and to discuss the potential of emerging therapeutic approaches for treating OA, thus providing a reference for OA treatments.

P53: A Key Target in the Development of Osteoarthritis

Osteoarthritis (OA), a chronic degenerative disease characterized mainly by damage to the articular cartilage, is increasingly relevant to the pathological processes of senescence, apoptosis, autophagy, proliferation, and differentiation of chondrocytes. Clinical strategies for osteoarthritis can only improve symptoms and even along with side effects due to age, sex, disease, and other factors. Therefore, there is an urgent need to identify new ideas and targets for current clinical treatment. The tumor suppressor gene p53, which has been identified as a potential target for tumor therapeutic intervention, is responsible for the direct induction of the pathological processes involved in OA modulation. Consequently, deciphering the characteristics of p53 in chondrocytes is essential for investigating OA pathogenesis due to p53 regulation in an array of signaling pathways. This review highlights the effects of p53 on senescence, apoptosis, and autophagy of chondrocytes and its role in the development of OA. It also elucidates the underlying mechanism of p53 regulation in OA, which may help provide a novel strategies for the clinical treatment of OA.

Targeting WNT signalling pathways as new therapeutic strategies for osteoarthritis

Osteoarthritis (OA) is a highly prevalent chronic joint disease and the leading cause of disability. Currently, no drugs are available to control joint damage or ease the associated pain. The wingless-type (WNT) signalling pathway is vital in OA progression. Excessive activation of the WNT signalling pathway is pertinent to OA progression and severity. Therefore, agonists and antagonists of the WNT pathway are considered potential drug candidates for OA treatment. For example, SM04690, a novel small molecule inhibitor of WNT signalling, has demonstrated its potential in a recent phase III clinical trial as a disease-modifying osteoarthritis drug (DMOAD). Therefore, targeting the WNT signalling pathway may be a distinctive approach to developing particular agents helpful in treating OA. This review aims to update the most recent progress in OA drug development by targeting the WNT pathway. In this, we introduce WNT pathways and their crosstalk with other signalling pathways in OA development and highlight the role of the WNT signalling pathway as a key regulator in OA development. Several articles have reviewed the Wnt pathway from different aspects. This candid review provides an introduction to WNT pathways and their crosstalk with other signalling pathways in OA development, highlighting the role of the WNT signalling pathway as a key regulator in OA development with the latest research. Particularly, we emphasise the state-of-the-art in targeting the WNT pathway as a promising therapeutic approach for OA and challenges in their development and the nanocarrier-based delivery of WNT modulators for treating OA.

MicroRNA-138: an emerging regulator of skeletal development, homeostasis, and disease

Noncoding microRNAs are powerful epigenetic regulators of cellular processes by their ability to target and suppress expression of numerous protein-coding mRNAs. This multitargeting function is a unique and complex feature of microRNAs. It is now well-described that microRNAs play important roles in regulating the development and homeostasis of many cell/tissue types, including those that make up the skeletal system. In this review, we focus on microRNA-138 (miR-138) and its effects on regulating bone and cartilage cell differentiation and function. In addition to its reported role as a tumor suppressor, miR-138 appears to function as an inhibitor of osteoblast differentiation. This review provides additional information on studies that have attempted to alter miR-138 expression in vivo as a means to dampen ectopic calcification or alter bone mass. However, a review of the published literature on miR-138 in cartilage reveals a number of contradictory and inconclusive findings with respect to regulating chondrogenesis and chondrocyte catabolism. This highlights the need for more research in understanding the role of miR-138 in cartilage biology and disease. Interestingly, a number of studies in other systems have reported miR-138-mediated effects in dampening inflammation and pain responses. Future studies will reveal if a multifunctional role of miR-138 involving suppression of ectopic bone, inflammation, and pain will be beneficial in skeletal conditions such as osteoarthritis and heterotopic ossification.

Phosphate NIMA-Related Kinase 2-Dependent Epigenetic Pathways in Dorsal Root Ganglion Neurons Mediates Paclitaxel-Induced Neuropathic Pain

BACKGROUND

The microtubule-stabilizing drug paclitaxel (PTX) is an important chemotherapeutic agent for cancer treatment and causes peripheral neuropathy as a common side effect that substantially impacts the functional status and quality of life of patients. The mechanistic role for NIMA-related kinase 2 (NEK2) in the progression of PTX-induced neuropathic pain has not been established.

METHODS

Adult male Sprague-Dawley rats intraperitoneally received PTX to induce neuropathic pain. The protein expression levels in the dorsal root ganglion (DRG) of animals were measured by biochemical analyses. Nociceptive behaviors were evaluated by von Frey tests and hot plate tests.

RESULTS

PTX increased phosphorylation of the important microtubule dynamics regulator NEK2 in DRG neurons and induced profound neuropathic allodynia. PTX-activated phosphorylated NEK2 (pNEK2) increased jumonji domain-containing 3 (JMJD3) protein, a histone demethylase protein, to specifically catalyze the demethylation of the repressive histone mark H3 lysine 27 trimethylation (H3K27me3) at the Trpv1 gene, thereby enhancing transient receptor potential vanilloid subtype-1 (TRPV1) expression in DRG neurons. Moreover, the pNEK2-dependent PTX response program is regulated by enhancing p90 ribosomal S6 kinase 2 (RSK2) phosphorylation. Conversely, intrathecal injections of kaempferol (a selective RSK2 activation antagonist), NCL 00017509 (a selective NEK2 inhibitor), NEK2-targeted siRNA, GSK-J4 (a selective JMJD3 inhibitor), or capsazepine (an antagonist of TRPV1 receptor) into PTX-treated rats reversed neuropathic allodynia and restored silencing of the Trpv1 gene, suggesting the hierarchy and interaction among phosphorylated RSK2 (pRSK2), pNEK2, JMJD3, H3K27me3, and TRPV1 in the DRG neurons in PTX-induced neuropathic pain.

CONCLUSIONS

pRSK2/JMJD3/H3K27me3/TRPV1 signaling in the DRG neurons plays as a key regulator for PTX therapeutic approaches.

Advances in understanding effects of miRNAs on apoptosis, autophagy, and pyroptosis in knee osteoarthritis

MicroRNAs (miRNAs) are a class of endogenous small non-coding RNAs. MicroRNAs-mediated signaling pathways play a critical regulatory role in inducing apoptosis, autophagy, and pyroptosis in developing knee osteoarthritis (KOA). Given this, we searched databases, such as PubMed, using keywords including "miRNA," "knee osteoarthritis," "apoptosis," "autophagy," "pyroptosis", and their combinations. Through an extensive literature review, we conclude that miRNAs can be modulated through various signaling pathways, such as Wnt/β-catenin, TGF-β, PI3K/AKT/mTOR, and NLRP3/Caspase-1, to regulate apoptosis, autophagy, and pyroptosis in KOA. Furthermore, we note that P2X7R and HMGB1 may be crucial regulatory molecules involved in the interconnected regulation of apoptosis, autophagy, and pyroptosis in KOA. Additionally, we describe that miR-140-5p and miR-107 can modulate the advancement of KOA chondrocytes by targeting distinct molecules involved in apoptosis, autophagy, and pyroptosis, respectively. Therefore, we conclude that miRNAs may be potential biomarkers and therapeutic targets for the early prediction, diagnosis, and effective therapeutic approaches of KOA.

Role of Wnt signaling pathway in joint development and cartilage degeneration

Osteoarthritis (OA) is a prevalent musculoskeletal disease that affects approximately 500 million people worldwide. Unfortunately, there is currently no effective treatment available to stop or delay the degenerative progression of joint disease. Wnt signaling pathways play fundamental roles in the regulation of growth, development, and homeostasis of articular cartilage. This review aims to summarize the role of Wnt pathways in joint development during embryonic stages and in cartilage maintenance throughout adult life. Specifically, we focus on aberrant mechanical loading and inflammation as major players in OA progression. Excessive mechanical load activates Wnt pathway in chondrocytes, resulting in chondrocyte apoptosis, matrix destruction and other osteoarthritis-related changes. Additionally, we discuss emerging Wnt-related modulators and present an overview of emerging treatments of OA targeting Wnt signaling. Ultimately, this review provides valuable insights towards discovering new drugs or gene therapies targeting Wnt signaling pathway for diagnosing and treating osteoarthritis and other degenerative joint diseases.

The Wnt signaling cascade in the pathogenesis of osteoarthritis and related promising treatment strategies

Osteoarthritis (OA) is the most prevalent joint disease, characterized by the degradation of articular cartilage, synovial inflammation, and changes in periarticular and subchondral bone. Recent studies have reported that Wnt signaling cascades play an important role in the development, growth, and homeostasis of joints. The Wnt signaling cascade should be tightly regulated to maintain the homeostasis of cartilage in either the over-activation or the suppression of Wnt/β-catenin, as this could lead to OA. This review summarizes the role and mechanism of canonical Wnt cascade and noncanonical Wnt cascade experiments in vivo and in vitro. The Wnt cascade is controlled by several agonists and antagonists in the extracellular medium and the cytoplasm. These antagonists and agonists serve as key molecules in drug intervention into the Wnt pathway and may provide potential approaches for the treatment of OA. However, the complexity of the Wnt signaling cascade and the pharmaceutical effects on its mechanism are still not fully understood, which forces us to conduct further research and develop efficient therapeutic approaches to treat OA.

Recent Advances in Pharmacological Intervention of Osteoarthritis: A Biological Aspect

Osteoarthritis (OA) is a degenerative joint disease in the musculoskeletal system with a relatively high incidence and disability rate in the elderly. It is characterized by the degradation of articular cartilage, inflammation of the synovial membrane, and abnormal structure in the periarticular and subchondral bones. Although progress has been made in uncovering the molecular mechanism, the etiology of OA is still complicated and unclear. Nevertheless, there is no treatment method that can effectively prevent or reverse the deterioration of cartilage and bone structure. In recent years, in the field of pharmacology, research focus has shifted to disease prevention and early treatment rather than disease modification in OA. Biologic agents become more and more attractive as their direct or indirect intervention effects on the initiation or development of OA. In this review, we will discuss a wide spectrum of biologic agents ranging from DNA, noncoding RNA, exosome, platelet-rich plasma (PRP), to protein. We searched for key words such as OA, DNA, gene, RNA, exosome, PRP, protein, and so on. From the pharmacological aspect, stem cell therapy is a very special technique, which is not included in this review. The literatures ranging from January 2016 to August 2021 were included and summarized. In this review, we aim to help readers have a complete and precise understanding of the current pharmacological research progress in the intervention of OA from the biological aspect and provide an indication for the future translational studies.

The Interaction between microRNAs and the Wnt/β-Catenin Signaling Pathway in Osteoarthritis

Osteoarthritis (OA) is a chronic disease affecting the whole joint, which still lacks a disease-modifying treatment. This suggests an incomplete understanding of underlying molecular mechanisms. The Wnt/β-catenin pathway is involved in different pathophysiological processes of OA. Interestingly, both excessive stimulation and suppression of this pathway can contribute to the pathogenesis of OA. microRNAs have been shown to regulate different cellular processes in different diseases, including the metabolic activity of chondrocytes and osteocytes. To bridge these findings, here we attempt to give a conclusive overview of microRNA regulation of the Wnt/β-catenin pathway in bone and cartilage, which may provide insights to advance the development of miRNA-based therapeutics for OA treatment.

EZH2 is associated with cartilage degeneration in osteoarthritis by promoting SDC1 expression via histone methylation of the microRNA-138 promoter

Cartilage degeneration has been reported to deteriorate osteoarthritis (OA), a prevalent joint disease caused by intrinsic and epigenetic factors. This study aimed to examine the molecular mechanism of enhancer of zeste 2 polycomb repressive complex 2 subunit (EZH2)/microRNA-138 (miR-138)/syndecan 1 (SDC1) and its epigenetic regulation in cartilage degeneration in OA. An OA cell model was induced by stimulating chondrocytes with interleukin (IL)-1β at a final concentration of 10 ng/mL, followed by alterations in EZH2 and miR-138 expression. Afterwards, cell apoptosis was analyzed using flow cytometry. The expression patterns of cartilage catabolism-related factors (MMP-13, ADAMTS-4, and ADAMTS-5) were determined using RT-qPCR and western blot analyses. The EZH2 and H3K27me3 enrichment at the miR-138 promoter region were determined using ChIP-qPCR. Finally, an OA mouse model was constructed to verify the function of EZH2 in vivo. EZH2 was expressed at high levels in OA models. EZH2 depletion ameliorated OA, as evidenced by reduced cell apoptosis in IL-1β-treated chondrocytes and decreased levels of cartilage catabolism-related factors. Moreover, EZH2 promoted histone methylation at the miR-138 promoter to suppress miR-138 expression, thereby upregulating the expression of SDC1, a target gene of miR-138. Changes in this pathway increased the expression of cartilage catabolism-related factors in vitro while promoting cartilage degeneration in vivo. Our data provided evidence that EZH2 inhibits miR-138 expression by promoting the histone methylation of its promoter, which induces cartilage degeneration in OA models by upregulating SDC1 expression, suggesting a novel mechanistic strategy for OA treatment.

LncRNA SNHG7 alleviates IL-1β-induced osteoarthritis by inhibiting miR-214-5p-mediated PPARGC1B signaling pathways

BACKGROUND

As a common joint disease, osteoarthritis (OA) is the main cause of limited joint mobility and disability. The role of lncRNAs in the regulation of OA is increasingly discovered. Therefore, further exploring the function of SNHG7 in OA is of great significance for understanding its occurrence and development.

METHODS

We used interleukin-1β (IL-1β) to treat to establish an OA model primary on chondrocytes in vitro, and gain- and loss of function assays of SNHG7 and miR-214-5p were conducted. The cell viability and apoptosis of chondrocytes were detected by CCK8 assay, BrdU assay and flow cytometry. The inflammatory cytokines (IL-1β, IL-6 and TNF-α), NLRP3 inflammasome, protein level of PPARGC1B, PPARγ, P38 and NF-κB were determined by RT-PCR and/or western blot.

RESULTS

The results showed that SNHG7 was distinctly downregulated, while miR-214-5p was significantly upregulated in OA patients and primary chondrocytes treated with IL-1β. In addition, SNHG7 enhanced cell viability, inhibited apoptosis and inflammation of IL-1β-mediated chondrocytes. In contrast, miR-214-5p upregulation reduced viability, promoted apoptosis and inflammation of chondrocytes. Mechanistically, SNHG7 served as a competitive endogenous RNA by sponging miR-214-5p, which targeted PPARGC1B. Besides, the results of the compensation experiment affirmed that miR-214-5p attenuates SNHG7-mediated protective effects on IL-1β-mediated chondrocytes against apoptosis and inflammation, and activating PPARγ pathway markedly dampened the cytotoxic effects of miR-214-5p.

CONCLUSIONS

Collectively, The above results confirmed that SNHG7 prevents IL-1β induced OA by inhibiting NLRP3 inflammasome and apoptosis through miR-214-5p/PPARGC1B axis.

MiR-1207-5p/CX3CR1 axis regulates the progression of osteoarthritis via the modulation of the activity of NF-κB pathway

BACKGROUND

Osteoarthritis (OA) is a prevalent chronic diseases characterized by formation of osteophytes and degradation of articular cartilage. Previous evidence has identified the regulatory effects of microRNAs (miRNAs) in OA. The goal of this study is to clearly explore the biological function of miR-1207-5p in OA.

METHODS

MiR-1207-5p and C-X3-C motif chemokine receptor 1 (CX3CR1) expression in OA cartilages were revealed by accessing to Gene Expression Omnibus database. In vitro OA model was established by lipopolysaccharide (LPS) stimulation. Western blot and quantitative real-time polymerase chain reaction were conducted to detect the expression level of genes. Cell counting kit-8 (CCK-8) and flow cytometric experiments were performed to investigate the proliferation and apoptosis capacities of CHON-001 cells. Bioinformatics analysis was applied to predict the binding site of miR-1207-5p and CX3CR1, the connections of which were ascertained using luciferase reporter assay.

RESULTS

MiR-1207-5p expression was decreased while CX3CR1 was increased in OA cartilages. Up-regulation of miR-1207-5p alleviated the LPS-induced damage in the view of cell proliferation, apoptosis and extracellular matrix (ECM) degradation. A target of miR-1207-5p CX3CR1, its down-regulation intensified the impacts of miR-1207-5p mimic, promoted proliferation and mitigated apoptosis. LPS exposure increased the protein expression of the phosphorylated IκBα and P65, and this phenomena was reversed due to miR-1207-5p up-regulation and CX3CR1 knockdown. The treatment of Betulinic acid (BA; an activator of nuclear factor-κB pathway) reversed the miR-1207-5p mimic-induced inhibitory effect on apoptosis in LPS-treated CHON-001.

CONCLUSION

Our results highlight that miR-1207-5p can prevent CHON-001 from LPS-stimulated injury, providing a novel biomarker for OA progression and further advancing treatment of OA.

Hydrostatic Pressure Regulates Oxidative Stress through microRNA in Human Osteoarthritic Chondrocytes

Hydrostatic pressure (HP) modulates chondrocytes metabolism, however, its ability to regulate oxidative stress and microRNAs (miRNA) has not been clarified. The aim of this study was to investigate the role of miR-34a, miR-146a, and miR-181a as possible mediators of HP effects on oxidative stress in human osteoarthritis (OA) chondrocytes. Chondrocytes were exposed to cyclic low HP (1–5 MPa) and continuous static HP (10 MPa) for 3~h. Metalloproteinases (MMPs), disintegrin and metalloproteinase with thrombospondin motif (ADAMTS)-5, type II collagen (Col2a1), miR-34a, miR-146a, miR-181a, antioxidant enzymes, and B-cell lymphoma 2 (BCL2) were evaluated by quantitative real-time polymerase chain reaction qRT-PCR, apoptosis and reactive oxygen species ROS production by cytometry, and β-catenin by immunofluorescence. The relationship among HP, the studied miRNA, and oxidative stress was assessed by transfection with miRNA specific inhibitors. Low cyclical HP significantly reduced apoptosis, the gene expression of MMP-13, ADAMTS5, miRNA, the production of superoxide anion, and mRNA levels of antioxidant enzymes. Conversely, an increased Col2a1 and BCL2 genes was observed. β-catenin protein expression was reduced in cells exposed to HP 1–5 MPa. Opposite results were obtained following continuous static HP application. Finally, miRNA silencing enhanced low HP and suppressed continuous HP-induced effects. Our data suggest miRNA as one of the mechanisms by which HP regulates chondrocyte metabolism and oxidative stress, via Wnt/β-catenin pathway.

microRNA-1236 promotes chondrocyte apoptosis in osteoarthritis via direct suppression of PIK3R3

AIMS

Chondrocyte degeneration is the main cause of osteoarthritis (OA) and increased evidence suggests that miRNAs could have vital roles in the pathology of various cartilage illnesses. miR-1236 has been found to contribute to inflammation in diseases such as pneumonia. However, the exact role of miR-1236 in OA is poorly understood.

MATERIALS AND METHODS

H&E staining and saffron fixation experiments were employed to determine OA tissues. qRT-PCR and immunohistochemistry were used to detect the expression levels of miR-1236 and PIK3R3. Western blot was performed to detect the expression levels of proteins. Luciferase reporter assays were utilized to investigate the interaction between miR-1236 and PIK3R3. Cell counting assays and AO/EB were used to quantify cell growth and apoptosis.

KEY FINDINGS

miR-1236 was up-regulated in OA knee cartilage compared to normal cartilage. Up-regulated expression of miR-1236 suppressed cell proliferation as well as induced apoptosis in chondrocytes. Bioinformatics identified PIK3R3 as a target of miR-1236. Co-transfection with miR-1236 and PIK3R3 could reverse cell apoptosis induced by the miR-1236 mimic.

SIGNIFICANCE

These data enhance our understanding on the role of miR-1236 in OA and identifies miR-1236 as a potential biomarker or possible treatment target within OA.

Regulation of lung endothelial permeability by NEK kinases

Dysregulation of lung endothelial barrier function may lead to lethal outcomes, as demonstrated in the case of the acute respiratory distress syndrome (ARDS). p53 participates in the regulation of the lung endothelial barrier, and it has been associated both in vivo and in vitro with protective effects against the LPS-induced hyperpermeability. Family members of the never in mitosis A-related kinases (NEKs) are crucial mediators of fundamental cellular processes, including mitosis, and have been shown to posttranslationally modify p53. Since such modifications affect p53 stability and activity, it is highly probable that NEK kinases are also regulators of lung endothelial permeability. Thus, they may serve as possible therapeutic targets for treatment of pathologies associated with endothelial barrier dysfunction.

The GSK‑3β/β‑catenin signaling pathway is involved in HMGB1‑induced chondrocyte apoptosis and cartilage matrix degradation

Knee osteoarthritis (KOA) is a common joint disease with a high incidence rate among middle‑aged and elderly individuals. However, the precise underlying pathological mechanisms and effective treatment of this disease remain to be determined. To explore the effect of high mobility group box 1 (HMGB1) on chondrocyte apoptosis and catabolism, the ATDC5 cell line was cultured as an in vitro model for cartilage research. Cultured cells were treated with recombinant HMGB1 at different concentrations. Hoechst staining and flow cytometry demonstrated that HMGB1 administration significantly induced apoptosis of ATDC5 cells, which was the same as the effect of interleukin‑1β treatment. HMGB1 also induced cartilage matrix degradation, as shown by Alcian blue staining. Moreover, HMGB1 markedly upregulated the expression levels of matrix metallopeptidases (MMPs) and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS), while genetic silencing of HMGB1 significantly suppressed their expressions. The glycogen synthase kinase (GSK)‑3β/β‑catenin pathway was activated upon HMGB1 treatment. Pharmacological inhibitors or HMGB1 knockdown inactivated the GSK‑3β/β‑catenin pathway, inhibited the expression levels of downstream genes, including MMPs and ADAMTS, and attenuated the apoptosis of ATDC5 cells. Furthermore, the data demonstrated that HMGB1 promoted chondrocyte dysfunction via the regulation of estrogen sulfotransferase and Runt‑related transcription factor 2. Thus, the findings of the present study demonstrated that HMGB1 induces chondrocyte cell apoptosis via activation of GSK‑3β/β‑catenin and the subsequent expression of multiple targeted genes.

Osteoarthritis from evolutionary and mechanistic perspectives

Developmental osteogenesis and the pathologies associated with tissues that normally are mineralized are active areas of research. All of the basic cell types of skeletal tissue evolved in early aquatic vertebrates. Their characteristics, transcription factors, and signaling pathways have been conserved, even as they adapted to the challenge imposed by gravity in the transition to terrestrial existence. The response to excess mechanical stress (among other factors) can be expressed in the pathologic phenotype described as osteoarthritis (OA). OA is mediated by epigenetic modification of the same conserved developmental gene networks, rather than by gene mutations or new chemical signaling pathways. Thus, these responses have their evolutionary roots in morphogenesis. Epigenetic channeling and heterochrony, orchestrated primarily by microRNAs, maintain the sequence of these responses, while allowing variation in their timing that depends at least partly on the life history of the individual.

Silencing lncRNA HOTAIR declines synovial inflammation and synoviocyte proliferation and promotes synoviocyte apoptosis in osteoarthritis rats by inhibiting Wnt/β-catenin signaling pathway

Osteoarthritis (OA) is a degenerative injury of the articular cartilage and reactive hyperplasia of the articular rim and subchondral bone. Due to its poor prognosis, this study is to research the influences of lncRNA HOTAIR on synovial inflammation and synoviocyte apoptosis and proliferation in OA rats by regulating the Wnt/β-catenin pathway. Rat OA model was constructed by means of cruciate ligament resection, and the successfully modeled rats were injected with sh-HOTAIR, or Wnt/β-catenin pathway activator (LiCl), and synoviocytes were transfected with sh-HOTAIR or LiCl for investigation of the influences of HOTAIR and Wnt/β-catenin pathway on synoviocytes proliferation and apoptosis. ELISA and RT-qPCR were used to detect the levels of IL-1β, IL-6 and TNF-α in serum, synovial tissue and synoviocytes in rats, respectively. The protein levels of bax, bcl-2, wnt1 and β-catenin in synovial tissue and synoviocytes were tested by Western blot analysis. Highly expressed HOTAIR existed in synovial tissue and synoviocytes of rats. There were declining arthritis index, inflammation, synoviocytes proliferation, cycle progression and promoted synoviocytes apoptosis by silencing HOTAIR and inhibited Wnt/β-catenin pathway. Down-regulation of HOTAIR could reverse the effect of LiCl on progression of OA rats. There was strained activation of Wnt/β-catenin pathway via declining HOTAIR. This study suggests that silencing lncRNA HOTAIR and inhibited Wnt/β-catenin pathway decline synovial inflammation and synoviocyte proliferation and promote apoptosis in OA rats.

Regulatory Effects and Interactions of the Wnt and OPG-RANKL-RANK Signaling at the Bone-Cartilage Interface in Osteoarthritis

Cartilage and the bordering subchondral bone form a functionally active regulatory interface with a prominent role in osteoarthritis pathways. The Wnt and the OPG-RANKL-RANK signaling systems, as key mediators, interact in subchondral bone remodeling. Osteoarthritic osteoblasts polarize into two distinct phenotypes: a low secretory and an activated, pro-inflammatory and anti-resorptive subclass producing high quantities of IL-6, PGE2, and osteoprotegerin, but low levels of RANKL, thus acting as putative effectors of subchondral bone sclerosis. Wnt agonists, Wnt5a, Wisp-1 initiate excessive bone remodeling, while Wnt3a and 5a simultaneously cause loss of proteoglycans and phenotype shift in chondrocytes, with decreased expression of COL2A, aggrecan, and Sox-9. Sclerostin, a Wnt antagonist possesses a protective effect for the cartilage, while DKK-1 inhibits VEGF, suspending neoangiogenesis in the subchondral bone. Experimental conditions mimicking abnormal mechanical load, the pro-inflammatory milieu, but also a decreased OPG/RANKL ratio in the cartilage, trigger chondrocyte apoptosis and loss of the matrix via degradative matrix metalloproteinases, like MMP-13 or MMP-9. Hypoxia, an important cofactor exerts a dual role, promoting matrix synthesis via HIF-1α, a Wnt silencer, but turning on HIF-2α that enhances VEGF and MMP-13, along with aberrant collagen expression and extracellular matrix deterioration in the presence of pro-inflammatory cytokines.

Wnt signaling: a promising target for osteoarthritis therapy

Osteoarthritis (OA) is the most common joint disease worldwide and a leading cause of disability. Characterized by degradation of articular cartilage, synovial inflammation, and changes in periarticular and subchondral bone, OA can negatively impact an individual's physical and mental well-being. Recent studies have reported several critical signaling pathways as key regulators and activators of cellular and molecular processes during OA development. Wnt signaling is one such pathway whose signaling molecules and regulators were shown to be abnormally activated or suppressed. As such, agonists and antagonists of those molecules are potential candidates for OA treatment. Notably, a recent phase I clinical trial (NCT02095548) demonstrated the potential of SM04690, a small-molecule inhibitor of the Wnt signaling pathway, as a disease-modifying oseoarthritis drug (DMOAD). This review summarizes the role and mechanism of Wnt signaling and related molecules in regulating OA progression, with a view to accelerating the translation of such evidence into the development of strategies for OA treatment, particularly with respect to potential applications of molecules targeting the Wnt signaling pathway.

TMF inhibits miR-29a/Wnt/β-catenin signaling through upregulating Foxo3a activity in osteoarthritis chondrocytes

Background: miR-29a, a downstream factor of Wnt/β-catenin signaling, promotes the activity of the Wnt/β-catenin signaling in a positive feedback loop. Our previous work showed that 5,7,3ʹ,4ʹ-tetramethoxyflavone (TMF), a major constituent from Murraya exotica L., exhibited chondroprotective activity by inhibiting the activity of Wnt/β-catenin signaling.

Purpose: To investigate whether TMF showed the inhibitory effects on miR-29a/β-catenin signaling by up regulation of Foxo3a expression.

Methods: Rat knee OA models were duplicated by using Hulth’s method. TMF (5 μg/mL and 20 μg/mL) was used for administration to cultured cells, which were isolated from the rat cartilages. Analysis of chondrocytes apoptosis, gene expression, and protein expression were conducted. In addition, miR-29a mimics and pcDNA3.1(+)-Foxo3a vector were used for transfection, luciferase reporter assay for detecting the activity of Wnt/β-catenin signaling, and co-immunoprecipitation for determining proteins interaction.

Results: TMF down regulated miR-29a/β-catenin signaling activity and cleaved caspase-3 expression and up regulated Foxo3a expression in OA rat cartilages. In vitro, miR-29a mimics down regulated the expression of Foxo3a and up regulated the activity of Wnt/β-catenin signaling and cleaved caspase-3 expression. TMF ameliorated miR-29a/β-catenin-induced chondrocytes apoptosis by up regulation of Foxo3a expression.

Conclusion: TMF exhibited chondroprotective activity by up regulating Foxo3a expression and subsequently inhibiting miR-29a/Wnt/β-catenin signaling activity.