BACKGROUND: Knee osteoarthritis (OA) is still challenging to prevent or treat. Enhanced endoplasmic reticulum (ER) stress and increased pyroptosis in chondrocytes may be responsible for cartilage degeneration. This study aims to investigate the effect of ER stress on chondrocyte pyroptosis and the upstream regulatory mechanisms, which have rarely been reported. METHODS: The expression of the histone methyltransferase enhancer of zeste homolog 2 (EZH2), microRNA-142-3p (miR-142-3p), and high mobility group box 1 (HMGB1) and the levels of ER stress, pyroptosis, and metabolic markers in normal and OA chondrocytes were investigated by western blotting, quantitative polymerase chain reaction, immunohistochemistry, fluorescence in situ hybridization, fluorescein amidite-tyrosine-valine-alanine-aspartic acid-fluoromethyl ketone (FAM-YVAD-FMK)/Hoechst 33342/propidium iodide (PI) staining, lactate dehydrogenase (LDH) release assays, and cell viability assessments. The effects of EZH2, miR-142-3p, and HMGB1 on ER stress and pyroptosis and the hierarchical regulatory relationship between them were analyzed by chromatin immunoprecipitation, luciferase reporters, gain/loss-of-function assays, and rescue assays in interleukin (IL)-1β-induced OA chondrocytes. The mechanistic contribution of EZH2, miR-142-3p, and HMGB1 to chondrocyte ER stress and pyroptosis and therapeutic prospects were validated radiologically, histologically, and immunohistochemically in surgically induced OA rats. RESULTS: Increased EZH2 and HMGB1, decreased miR-142-3p, enhanced ER stress, and activated pyroptosis in chondrocytes were associated with OA occurrence and progression. EZH2 and HMGB1 exacerbated and miR-142-3p alleviated ER stress and pyroptosis in OA chondrocytes. EZH2 transcriptionally silenced miR-142-3p via H3K27 trimethylation, and miR-142-3p posttranscriptionally silenced HMGB1 by targeting the 3'-UTR of the HMGB1 gene. Moreover, ER stress mediated the effects of EZH2, miR-142-3p, and HMGB1 on chondrocyte pyroptosis. In vivo experiments mechanistically validated the hierarchical regulatory relationship between EZH2, miR-142-3p, and HMGB1 and their effects on chondrocyte ER stress and pyroptosis. CONCLUSIONS A novel EZH2/miR-142-3p/HMGB1 axis mediates chondrocyte pyroptosis and cartilage degeneration by regulating ER stress in OA, contributing novel mechanistic insights into OA pathogenesis and providing potential targets for future therapeutic research.
Enhancer of Zeste Homolog 2 Protein/genetics* ; Osteoarthritis, Knee/pathology* ; Chondrocytes/metabolism* ; Pyroptosis/physiology* ; HMGB1 Protein/genetics* ; MicroRNAs/metabolism* ; Endoplasmic Reticulum Stress/genetics* ; Humans ; Animals ; Rats ; Male ; Rats, Sprague-Dawley ; Middle Aged

This study aims to integrate data mining techniques of single cell transcriptomics and spatial transcriptomics, along with animal experiment validation, so as to systematically characterize the protective effects of Jianpi Tongluo Formula(JTF) on the cartilage in knee osteoarthritis(KOA) and elucidate the underlying molecular mechanisms. Single cell transcriptomics and spatial transcriptomics datasets(GSE254844 and GSE255460) of the cartilage tissue obtained from KOA patients were analyzed to map the single cell-spatial heterogeneity and identify key pathogenic factors. After that, a KOA rat model was established via knee joint injection of papain. The intervention effects of JTF on the expression features of these key factors were assessed through real-time quantitative polymerase chain reaction(PCR), Western blot, and immunohistochemical staining. As a result, the integrated single cell and spatial transcriptomics data identified distinct cell subsets with different pathological changes in different regions of the inflamed cartilage tissue in KOA, and their differentiation trajectories were closely related to the inflammatory fibrosis-like pathological changes of chondrocytes. Accordingly, the expression levels of the two key effect targets, namely nuclear receptor coactivator 4(NCOA4) and high mobility group box 1(HMGB1) were significantly reduced in the articular surface and superficial zone of the inflamed joints when JTF effectively alleviated various pathological changes in KOA rats, thus reversing the abnormal chondrocyte autophagy level, relieving the inflammatory responses and fibrosis-like pathological changes, and promoting the repair of chondrocyte function. Collectively, this study revealed the heterogeneous characteristics and dynamic changes of inflamed cartilage tissue in different regions and different cell subsets in KOA patients. It is worth noting that NCOA4 and HMGB1 were crucial in regulating chondrocyte autophagy and inflammatory reaction, while JTF could reverse the regulation of NCOA4 and HMGB1 and correct the abnormal molecular signal axis in the target cells of the inflamed joints. The research can provide a new research idea and scientific basis for developing a personalized therapeutic schedule targeting the spatiotemporal heterogeneity characteristics of KOA.
Animals ; Drugs, Chinese Herbal/administration & dosage* ; Rats ; Osteoarthritis, Knee/pathology* ; Humans ; Male ; Cartilage, Articular/metabolism* ; Chondrocytes/metabolism* ; Rats, Sprague-Dawley ; Female ; Protective Agents/administration & dosage* ; Single-Cell Analysis ; Middle Aged ; HMGB1 Protein/metabolism*

With the deepening understanding of the pathogenesis of osteoarthritis (OA), therapeutic strategies targeting oxidative stress in chondrocytes have gradually become a research hotspot. This article summarizes the important role of oxidative stress in the development of OA, pointing out that it is closely related to chondrocyte senescence, inflammatory cascade reaction, and cartilage matrix degradation. Given the central role of oxidative stress in the pathological process of OA, inhibiting oxidative stress and the generation of reactive oxygen species (ROS) is considered the key to alleviating chondrocyte damage and senescence, and preventing the progression of OA. Although some progress has been made in current OA research, there are still many challenges, such as the in-depth understanding of the etiology of OA and the limited selection of therapeutic drugs. Future research will focus on a more comprehensive understanding of the mechanism of oxidative stress in OA, exploring new biomarkers and therapeutic targets, and developing new drugs or treatment methods targeting oxidative stress pathways. These efforts are expected to bring more effective treatment options to OA patients, thereby improving their quality of life and prognosis.
Humans ; Oxidative Stress ; Osteoarthritis/pathology* ; Chondrocytes/pathology* ; Animals ; Reactive Oxygen Species/metabolism*

OBJECTIVES: Osteoarthritis (OA) is one of the most common chronic degenerative diseases, with chondrocyte apoptosis and extracellular matrix (ECM) degradation as the major pathological changes. The mechanical stimulation can attenuate chondrocyte apoptosis and promote ECM synthesis, but the underlying molecular mechanisms remain unclear. This study aims to investigate the role of primary cilia (PC) in mediating the effects of mechanical stimulation on OA progression. METHODS: In vivo, conditional knockout mice lacking intraflagellar transport 88 (IFT88^flox/flox IFT88 knockout; i.e., primary cilia-deficient mice) were generated, with wild-type mice as controls. OA models were established via anterior cruciate ligament transection combined with destabilization of the medial meniscus, followed by treadmill exercise intervention. OA progression was evaluated by hematoxylin-eosin staining, safranin O-fast green staining, and immunohistochemistry; apoptosis was assessed by TUNEL staining; and limb function by rotarod testing. In vitro, primary articular chondrocytes were isolated from mice and transfected with lentiviral vectors to suppress IFT88 expression, thereby constructing a primary cilia-deficient cell model. Interleukin-1β (IL-1β) was used to induce an inflammatory environment, while cyclic tensile strain (CTS) was applied via a cell stretcher to mimic mechanical loading on chondrocytes. Immunofluorescence and Western blotting were used to detect the protein expression levels of type II collagen α1 chain (COL2A1), primary cilia, IFT88, and caspase-12; reverse transcription polymerase chain reaction was performed to assess COL2A1 mRNA levels; and flow cytometry was used to evaluate apoptosis. RESULTS: In vivo, treadmill exercise significantly reduced Osteoarthritis Research Society International (OARSI) scores and apoptotic cell rates, and improved balance ability in wild-type OA mice, whereas IFT88-deficient OA mice showed no significant improvement. In vitro, CTS inhibited IL-1β-induced ECM degradation and apoptosis in primary chondrocytes; however, this protective effect was abolished in cells with suppressed primary cilia expression. CONCLUSIONS Mechanical stimulation delays OA progression by mediating signal transduction through primary cilia, thereby inhibiting cartilage degeneration and chondrocyte apoptosis.
Animals ; Chondrocytes/cytology* ; Apoptosis/physiology* ; Mice ; Cilia/metabolism* ; Osteoarthritis/pathology* ; Extracellular Matrix/metabolism* ; Mice, Knockout ; Disease Progression ; Interleukin-1beta ; Male ; Cells, Cultured

Objective To explore the effect of rehmanniae radix extract(RRE)on chondrocyte apoptosis in the rabbit model of knee osteoarthritis(KOA)by regulating the miR-485-5p/heat shock protein 90 beta family member 1(Hsp90b1)axis.Methods New Zealand rabbits were randomly assigned into control,KOA,low-dose RRE,medium-dose RRE,high-dose RRE,celecoxib,high-dose RRE+antagonist control,and high-dose RRE+miR-485-5p antagonist groups,with 12 rabbits in each group.Rabbits in other groups except the control group were modeled for KOA with the improved Hulth method.After modeling for 8 weeks,the rabbits were administrated with corresponding agents for 4 weeks.The changes in the activity rating of rabbits were recorded.ELISA was employed to measure the levels of tumor necrosis factor-α(TNF-α)and interleukin(IL)-6 in the serum.Safranine O-fast green staining was conducted to reveal the pathological changes in the cartilage tissue and Mankin scoring was performed.TUNEL was employed to detect chondrocyte apoptosis.Real-time fluorescence quantitative PCR was performed to determine the expression of miR-485-5p in the cartilage tissue.Western blot was employed to determine the protein levels of Hsp90b1,cleaved cysteinyl aspartate-specific proteinase-3(Caspase-3),and Bcl2-associated-X(Bax)in the cartilage tissue.The dual-luciferase reporter assay was employed to examine the relationship between miR-485-5p and Hsp90b1.Results Compared with the control group,the KOA group showed down-regulated expression of miR-485-5p,elevated levels of TNF-α and IL-6 in the serum,cartilage erosion and losses,and increases in activity rating,Mankin score,chondrocyte apoptosis rate,and protein levels of Hsp90b1,cleaved Caspase-3,and Bax(all P<0.001).Compared with the KOA group,RRE at low,medium,and high doses,and celecoxib up-regulated the expression of miR-485-5p,lowered the levels of TNF-α and IL-6 in the serum,alleviated the pathological damage to the cartilage tissue,and decreased the activity rating,Mankin score,chondrocyte apoptosis rate,and protein levels of Hsp90b1,cleaved Caspase-3,and Bax(all P<0.05).Compared with the high-dose RRE group and the high-dose RRE+antagonist control group,high-dose RRE+miR-485-5p antagonist down-regulated the expression of miR-485-5p,elevated the levels of TNF-α and IL-6 in the serum,exacerbated the pathological damage to the cartilage tissue,and increased the activity rating,Mankin score,chondrocyte apoptosis rate,and protein levels of Hsp90b1,cleaved Caspase-3,and Bax(all P<0.05).The results indicated that there was a targeted regulatory relationship between miR-485-5p and Hsp90b1.Conclusion RRE may inhibit the expression of Hsp90b1 by up-regulating miR-485-5p,thereby inhibiting chondrocyte apoptosis in the rabbit model of KOA.
Animals ; Rabbits ; Apoptosis/drug effects* ; Chondrocytes/pathology* ; Osteoarthritis, Knee/drug therapy* ; MicroRNAs/metabolism* ; Rehmannia/chemistry* ; Disease Models, Animal ; Tumor Necrosis Factor-alpha/blood* ; Plant Extracts/pharmacology* ; Interleukin-6/blood* ; HSP90 Heat-Shock Proteins/metabolism* ; Male ; Drugs, Chinese Herbal/pharmacology*

OBJECTIVES: To investigate the effect of nuclear protein (Nupr) 1 on the pathological progression of osteoarthritis and its relationship with ferroptosis of chondrocytes. METHODS: Chondrocytes from mouse knees were divided into small interfering RNA (siRNA) control group, small interfering RNA targeting Nupr1 (siNupr1) group, siRNA control+IL-1β group (siRNA control interference for 24 h followed by 10 ng/mL IL-1β) and siNupr1+IL-1β group (siNupr1 interference for 24 h followed by 10 ng/mL IL-1β). The protein and mRNA expressions of Nupr1 were detected by Western blotting and quantitative reverse transcription polymerase chain reaction (qRT-PCR). Cell proliferation viabilities were measured using the cell counting kit-8 method. The levels of ferrous ions were detected by FerroOrange staining. Lipid peroxidation levels were detected by C11-BODIPY-591 fluorescence imaging. The contents of malondialdehyde (MDA) and glutathione (GSH) were detected by enzyme-linked immunosorbent assay. The protein expressions of acyl-CoA synthetase long-chain family (ACSL) 4, P53, glutathione peroxidase (GPX) 4 and solute carrier family 7 member 11 gene (SLC7A11) were detected by Western blotting. The osteoarthritis model was constructed by destabilization of the medial meniscus (DMM) surgery in 7-week-old male C57BL/6J mice. The mice were randomly divided into four groups with 10 animals in each group: sham surgery (Sham)+adeno-associated virus serotype 5 (AAV5)-short hairpin RNA (shRNA) control group, Sham+AAV5-shRNA control targeting Nupr1 (shNupr1) group, DMM+AAV5-shRNA control group, and DMM+AAV5-shNupr1 group. Hematoxylin and eosin staining and Safranin O-Fast Green staining were used to observe the morphological changes in cartilage tissue. The Osteoarthritis Research Society International (OARSI) osteoarthritis cartilage histopathology assessment system was used to evaluate the degree of cartilage degeneration in mice. The mRNA expressions of matrix metallopeptidase (MMP) 13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) 5, cyclooxy-genase (COX) 2, and GPX4 were detected by qRT-PCR. RESULTS: In vitro experiments showed that knocking down Nupr1 alleviated the decrease of chondrocyte proliferation activity induced by IL-1β, reduced iron accumulation in mouse chondrocytes, lowered lipid peroxidation, downregulated ACSL4 and P53 protein expression and upregulated GPX4 and SLC7A11 protein expression (all P<0.01), thereby inhibiting ferroptosis in mouse chondrocytes. Meanwhile, in vivo animal experiments demonstrated that knocking down Nupr1 delayed the degeneration of articular cartilage in osteoarthritis mice, improved the OARSI score, slowed down the degradation of the extracellular matrix in osteoarthritis cartilage, and reduced the expression of the key ferroptosis regulator GPX4 (all P<0.01). CONCLUSIONS Knockdown of Nupr1 can delay the pathological progression of osteoarthritis through inhibiting ferroptosis in mouse chondrocytes.
Animals ; Ferroptosis ; Mice ; Chondrocytes/metabolism* ; Osteoarthritis/pathology* ; RNA, Small Interfering/genetics* ; Basic Helix-Loop-Helix Transcription Factors/genetics* ; Interleukin-1beta/metabolism* ; Phospholipid Hydroperoxide Glutathione Peroxidase/genetics* ; Coenzyme A Ligases/genetics* ; Tumor Suppressor Protein p53/metabolism* ; Mice, Inbred C57BL ; DNA-Binding Proteins ; Neoplasm Proteins ; Amino Acid Transport System y+ ; Nuclear Receptor Subfamily 1, Group D, Member 1

To investigate the mechanism by which Cangxi Tongbi Capsules promote chondrocyte autophagy to inhibit knee osteoarthritis(KOA) progression by regulating the circRNA＿0008365/miR-1271/p38 mitogen-activated protein kinase(MAPK) pathway. The cell and animal models of KOA were established and intervened with Cangxi Tongbi Capsules, si-circRNA＿0008365, si-NC, and Cangxi Tongbi Capsules combined with si-circRNA＿0008365. Flow cytometry and transmission electron microscopy were employed to determine the level of apoptosis and observe autophagosomes, respectively. Western blot was employed to reveal the changes in the protein levels of microtubule-associated protein light chain 3(LC3)Ⅱ/Ⅰ, Beclin-1, selective autophagy junction protein p62/sequestosome 1, collagen Ⅱ, a disintegrin and metalloproteinase with thrombospondin motifs 5(ADAMTS-5), and p38 MAPK. The mRNA levels of circRNA＿0008365, miR-1271, collagen Ⅱ, and ADAMTS-5 were determined by qRT-PCR. Hematoxylin-eosin staining was employed to reveal the pathological changes of the cartilage tissue of the knee, and enzyme-linked immunosorbent assay to measure the levels of interleukin-1β(IL-1β) and tumor necrosis factor-alpha(TNF-α). The chondrocytes treated with IL-1β showed down-regulated expression of circRNA＿0008365, up-regulated expression of miR-1271 and p38 MAPK, lowered autophagy level, increased apoptosis rate, and accelerated catabolism of extracellular matrix. The intervention with Cangxi Tongbi Capsules up-regulated the expression of circRNA＿0008365, down-regulated the expression of miR-1271 and p38 MAPK, increased the autophagy level, decreased the apoptosis rate, and weakened the catabolism of extracellular matrix. However, the effect of Cangxi Tongbi Capsules was suppressed after interfering with circRNA＿0008365. The in vivo experiments showed that Cangxi Tongbi Capsules dose-dependently inhibited the p38 MAPK pathway, enhanced chondrocyte autophagy, and mitigated articular cartilage damage and inflammatory response, thereby inhibiting the progression of KOA in rats. This study indicated that Cangxi Tongbi Capsules promoted chondrocyte autophagy by regulating the circRNA＿0008365/miR-1271/p38 MAPK pathway to inhibit the development of KOA.
Rats ; Animals ; Chondrocytes ; Osteoarthritis, Knee/pathology* ; RNA, Circular/pharmacology* ; p38 Mitogen-Activated Protein Kinases/metabolism* ; MicroRNAs/metabolism* ; Apoptosis ; Autophagy/genetics* ; Collagen/metabolism*

Osteoarthritis (OA) is a prevalent degenerative joint disease characterized by cartilage loss and accounts for a major source of pain and disability worldwide. However, effective strategies for cartilage repair are lacking, and patients with advanced OA usually need joint replacement. Better comprehending OA pathogenesis may lead to transformative therapeutics. Recently studies have reported that exosomes act as a new means of cell-to-cell communication by delivering multiple bioactive molecules to create a particular microenvironment that tunes cartilage behavior. Specifically, exosome cargos, such as noncoding RNAs (ncRNAs) and proteins, play a crucial role in OA progression by regulating the proliferation, apoptosis, autophagy, and inflammatory response of joint cells, rendering them promising candidates for OA monitoring and treatment. This review systematically summarizes the current insight regarding the biogenesis and function of exosomes and their potential as therapeutic tools targeting cell-to-cell communication in OA, suggesting new realms to improve OA management.
Apoptosis ; Cartilage/pathology* ; Cartilage, Articular/metabolism* ; Cell Communication ; Chondrocytes/metabolism* ; Exosomes/pathology* ; Humans ; Osteoarthritis/therapy*

The progressive destruction of condylar cartilage is a hallmark of the temporomandibular joint (TMJ) osteoarthritis (OA); however, its mechanism is incompletely understood. Here, we show that Kindlin-2, a key focal adhesion protein, is strongly detected in cells of mandibular condylar cartilage in mice. We find that genetic ablation of Kindlin-2 in aggrecan-expressing condylar chondrocytes induces multiple spontaneous osteoarthritic lesions, including progressive cartilage loss and deformation, surface fissures, and ectopic cartilage and bone formation in TMJ. Kindlin-2 loss significantly downregulates the expression of aggrecan, Col2a1 and Proteoglycan 4 (Prg4), all anabolic extracellular matrix proteins, and promotes catabolic metabolism in TMJ cartilage by inducing expression of Runx2 and Mmp13 in condylar chondrocytes. Kindlin-2 loss decreases TMJ chondrocyte proliferation in condylar cartilages. Furthermore, Kindlin-2 loss promotes the release of cytochrome c as well as caspase 3 activation, and accelerates chondrocyte apoptosis in vitro and TMJ. Collectively, these findings reveal a crucial role of Kindlin-2 in condylar chondrocytes to maintain TMJ homeostasis.
Aggrecans/metabolism* ; Animals ; Cartilage, Articular/metabolism* ; Chondrocytes/pathology* ; Cytoskeletal Proteins/metabolism* ; Mice ; Muscle Proteins/metabolism* ; Osteoarthritis/pathology* ; Temporomandibular Joint/pathology*

Osteoarthritis (OA) is a prevalent joint disease with no effective treatment strategies. Aberrant mechanical stimuli was demonstrated to be an essential factor for OA pathogenesis. Although multiple studies have detected potential regulatory mechanisms underlying OA and have concentrated on developing novel treatment strategies, the epigenetic control of OA remains unclear. Histone demethylase JMJD3 has been reported to mediate multiple physiological and pathological processes, including cell differentiation, proliferation, autophagy, and apoptosis. However, the regulation of JMJD3 in aberrant force-related OA and its mediatory effect on disease progression are still unknown. In this work, we confirmed the upregulation of JMJD3 in aberrant force-induced cartilage injury in vitro and in vivo. Functionally, inhibition of JMJD3 by its inhibitor, GSK-J4, or downregulation of JMJD3 by adenovirus infection of sh-JMJD3 could alleviate the aberrant force-induced chondrocyte injury. Mechanistic investigation illustrated that aberrant force induces JMJD3 expression and then demethylates H3K27me3 at the NR4A1 promoter to promote its expression. Further experiments indicated that NR4A1 can regulate chondrocyte apoptosis, cartilage degeneration, extracellular matrix degradation, and inflammatory responses. In vivo, anterior cruciate ligament transection (ACLT) was performed to construct an OA model, and the therapeutic effect of GSK-J4 was validated. More importantly, we adopted a peptide-siRNA nanoplatform to deliver si-JMJD3 into articular cartilage, and the severity of joint degeneration was remarkably mitigated. Taken together, our findings demonstrated that JMJD3 is flow-responsive and epigenetically regulates OA progression. Our work provides evidences for JMJD3 inhibition as an innovative epigenetic therapy approach for joint diseases by utilizing p5RHH-siRNA nanocomplexes.
Cartilage, Articular/pathology* ; Chondrocytes/metabolism* ; Down-Regulation ; Epigenesis, Genetic ; Humans ; Jumonji Domain-Containing Histone Demethylases/metabolism* ; Nuclear Receptor Subfamily 4, Group A, Member 1/metabolism* ; Osteoarthritis/pathology* ; RNA, Small Interfering/pharmacology*