Osteoarthritis Model Research Articles

Small heterodimer partner-interacting leucine zipper protein suppresses pain and cartilage destruction in an osteoarthritis model by modulating the AMPK/STAT3 signaling pathway

Abstract Objective Osteoarthritis (OA) is a degenerative joint disease caused by the breakdown of joint cartilage and adjacent bone. Joint injury, being overweight, differences in leg length, high levels of joint stress, abnormal joint or limb development, and inherited factors have been implicated in the etiology of OA. In addition to physical damage to the joint, a role for inflammatory processes has been identified as well. Small heterodimer partner-interacting leucine zipper protein (SMILE) regulates transcription and many cellular functions. Among the proteins activated by SMILE is the peroxisome proliferator-activated receptor (PPAR) γ, which mediates the activities of CD4 + T helper cells, including Th1, Th2, and Th17, as well as Treg cells. PPAR-γ binds to STAT3 to inhibit its transcription, thereby suppressing the expression of the NF-κB pathway, and in turn, the expression of the inflammatory cytokines interferon (IFN), interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α, which are sub-signals of STAT3 and NF-κB. Methods OA was induced in control C57BL/6 mice and in C57BL/6-derived SMILE-overexpressing transgenic (SMILE Tg) mice. The protein expression levels in the joint and spleen tissues were analyzed by immunohistochemistry and immunofluorescence images. In addition, flow cytometry was performed for detecting changes of the changes of immune cells. Results Less cartilage damage and significantly reduced levels of OA biomarkers (MMP13, TIMP3 and MCP-1) were observed in SMILE Tg mice. Immunohistochemistry performed to identify the signaling pathway involved in the link between SMILE expression and OA revealed decreased levels of IL-1β, IL-6, TNF-α, and phosphorylated AMPK in synovial tissues as well as a significant decrease in phosphorylated STAT3 in both cartilage and synovium. Changes in systemic immune cells were investigated via flow cytometry to analyze splenocytes isolated from control and SMILE Tg mice. SMILE Tg mice had elevated proportions of CD4 + IL-4 + cells (Th2) and CD4 + CD25 + Foxp3 + cells (Treg) and a notable decrease in CD4 + IL-17 + cells (Th17). Conclusion Our results show that overexpressed SMILE attenuates the symptoms of OA, by increasing AMPK signaling and decreasing STAT3, thus reducing the levels of inflammatory immune cells.

Correction: Giunta et al. Ameliorative Effects of PACAP against Cartilage Degeneration. Morphological, Immunohistochemical and Biochemical Evidence from in Vivo and in Vitro Models of Rat Osteoarthritis. Int. J. Mol. Sci. 2015, 16, 5922–5944

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Comparison of effects of intra‐articular diclofenac etalhyaluronate and hyaluronic acid in a monoiodoacetate rat osteoarthritis model

AbstractDiclofenac etalhyaluronate (DF‐HA) sustained diclofenac release with the effects of hyaluronic acid (HA), offering long‐term analgesia in osteoarthritis. In this study, the effects of DF‐HA on pain improvement and osteoarthritis were evaluated in a rat knee monoiodoacetate‐induced osteoarthritis model compared to HA. Eight rats per group had been injected with monoiodoacetate (2.0 mg) or saline in the right knee for 4 weeks and were injected with either DF‐HA (1.25 mg/kg; 0.5 mg), HA (0.5 mg), vehicle which was a substrate without DF‐HA (50 μL), or saline and followed for 4 weeks. Mechanical plantar skin sensitivity was assessed weekly using the von Frey assay. Osteoarthritis changes were monitored with Larsen scores via CT imaging at every 2 weeks. The articular cartilage was analyzed using OARSI scores through H&E, Safranin‐O staining at 8 weeks. The percentage of Iba‐1 positive microglia in the spinal dorsal horn and of FG + CGRP‐labeled cells among FG‐positive cells in the dorsal root ganglion were evaluated by immunohistochemical staining. TNF‐α and IL‐6 mRNA expression levels in the knee synovium were evaluated by PCR. The DF‐HA showed significantly improved pain hypersensitivity compared with the HA at 6–8 weeks. The percentage of Iba‐1‐positive microglia was significantly lower than that in the vehicle and the percentage of FG + CGRP/FG was significantly lower than that in the HA. OARSI scores did not differ among treatment groups, Larsen scores indicated lower in the DF‐HA than in the vehicle. DF‐HA was as effective as HA in joint protection and significantly improved inflammatory pain compared to HA.

Salmon Nasal Cartilage-Derived Proteoglycans Alleviate Monosodium Iodoacetate-Induced Osteoarthritis in Rats

Osteoarthritis is a chronic inflammatory condition characterized by the degeneration of joint cartilage and underlying bone, resulting in pain, swelling, and reduced mobility. This study evaluates the efficacy of salmon nasal cartilage-derived proteoglycans in mitigating osteoarthritis symptoms and investigates the underlying molecular mechanisms. This study employed a rat model of osteoarthritis induced by monosodium iodoacetate (MIA) injection. The rats were orally administered salmon nasal cartilage-derived proteoglycans or ibuprofen. Key aspects of osteoarthritis pathology, including impaired exercise ability, inflammation, extracellular matrix degradation, and chondrocyte apoptosis, were assessed using histological analysis, micro-CT, treadmill testing, serum assays, and mRNA/protein expression studies. The MIA injection caused significant cartilage damage, reduced bone mineral density, and impaired exercise ability. Additionally, it elevated serum levels of prostaglandin E2 and nitric oxide, increased the mRNA and protein levels of inflammation-related factors, and activated apoptosis signaling pathways in cartilage. Treatment with salmon nasal cartilage-derived proteoglycans significantly improved cartilage morphology and mineralization, reduced inflammation, and inhibited apoptosis signaling pathways, with effects comparable to those observed with ibuprofen treatment. These findings highlight the potential of salmon nasal cartilage-derived proteoglycans as a therapeutic agent for managing osteoarthritis by effectively reducing inflammation, preventing cartilage degradation, and inhibiting chondrocyte apoptosis.

RIP1 inhibition reduces chondrocyte apoptosis through downregulating nuclear factor-kappa B signaling in a mouse osteoarthritis model.

Excessive chondrocyte death is a critical player in the process of osteoarthritis (OA). The present study was aimed to study the role of receptor-interacting serine/threonine kinase (RIP) 1-mediated signaling for programmed cell death in OA. In the present study, RIP1 protein expression was evaluated in mouse OA cartilage and cultured primary murine chondrocytes exposed to tumor necrosis factor-alpha (TNF-α). Protein expression involved in necroptosis and apoptosis and chondrocyte-derived extracellular matrix were examined. Inhibition of RIP1 was conducted using the RNAi technique and pharmacological inhibition. Western blot, immunohistochemistry, and immunofluorescence examination were applied. The protein presence of RIP1, but not RIP3, was increased in the mouse OA tissue and cultured chondrocytes exposed to TNF-α. Knockdown of RIP1 increased protein expression of collagen II and sex-determining region Y-box transcription factor 9, and reduced protein expression of matrix metallopeptidases 13 and a disintegrin and metalloproteinase with thrombospondin motifs 5. Inhibition of RIP1 reduced the phosphorylated NF-κB signals, decreased cell apoptosis, and restored extracellular matrix expression in cultured chondrocytes. Both RNAi and pharmacological inhibition of RIP1 decelerated the progress of OA in mice. RIP1 regulates chondrocyte apoptosis through NF-κB signaling. Inhibition of RIP1 provides a novel therapeutic approach for OA therapy.

Astaxanthin mediated repair of tBHP-Induced cellular injury in chondrocytes

ABSTRACT Objective This study investigates how astaxanthin (AST) counters tert-butyl hydroperoxide (tBHP)-induced cellular damage in C28/I2 chondrocytes, focusing on the circ-HP1BP3/miR-139-5p/SOD1 signaling pathway and its use in sustained-release microspheres for osteoarthritis treatment. Methods We employed a variety of techniques including real-time quantitative PCR, Western blot, ELISA, and dual-luciferase reporter gene assays to explore AST's molecular effects. Additionally, the efficacy of AST-loaded sustained-release microspheres was evaluated in vitro and in a mouse model of osteoarthritis. Results AST significantly enhanced SOD1 expression, reducing apoptosis and inflammation in damaged cells. The AST-loaded microspheres showed promising in vitro drug release, improved cell viability, and reduced oxidative stress. In the osteoarthritis mouse model, they effectively decreased joint inflammation and increased the expression of chondrocyte markers. Conclusion Astaxanthin effectively mitigates oxidative stress and inflammation in chondrocytes via the circ-HP1BP3/miR-139-5p/SOD1 pathway. The development of AST-loaded microspheres offers a novel and promising approach for osteoarthritis therapy, potentially extending to osteoarthritis treatment.

Intra-Articular Injection of Human Umbilical Cord-Derived Mesenchymal Stromal Cells Reduces Radiographic Osteoarthritis in an Ovine Model.

To determine if mesenchymal stromal cells (MSCs) derived from human umbilical cords (hUC) could reduce degeneration developing when injected into the knee of a large animal model of osteoarthritis (OA). Ten million culture-expanded UC-MSCs (pooled from 3 human donors) were injected in 50 μL of tissue culture medium into the left stifle joints of 7 sheep whose medial meniscus was transected 4 weeks previously. Seven other sheep had only 50 μL of medium injected as the no treatment "control" group. After 8 weeks the sheep underwent euthanasia, the joints were excised and examined macroscopically, via x-ray and magnetic resonance imaging (MRI), both via histology for degenerative and inflammatory changes and immunohistochemically to identify any human cells within the joint tissues. Activity monitoring both before meniscus transection and euthanasia was also undertaken. There was a significant reduction in the Kellgren-Lawrence x-ray score for joints injected with hUC-MSCs compared with the control joints. Likewise, macroscopic, MRI, synovitis and OARSI histology scores were all lower (better) in the joints injected with hUC-MSCs than in the control arm, but not significantly. Activity levels and synovitis scores were similar in both groups of animals. hUC-MSCs appear to modify and reduce the development of osteoarthritic changes in the ovine stifle joint after meniscal destabilization, an injury which commonly leads to OA in humans. These results are encouraging for the potential benefit of culture expanded UC-MSCs as an allogeneic cell therapy in patients who may have early OA following a meniscal injury of the knee.

Gelatin microcarriers as an effective adipose-derived stem cells delivery strategy in osteoarthritis treatment

Despite their clinical success, stem cells (SCs) in the treatment of osteoarthritis (OA) are limited by lower retention efficiency and restricted paracrine function. The development of effective SCs culture and delivery systems to maintain or promote SCs paracrine function is urgently needed. In this study, we focused on gelatin microcarriers with different sizes as SCs culture scaffold for OA therapy. The effect of culturing adipose-derived stem cells (ADSCs) on different size microcarriers (180 μm and 320 μm) to promote paracrine function was evaluated. The secretome of ADSCs cultured on microcarriers more effectively regulated macrophages and chondrocytes in a direction favorable to OA healing compared to culture plates. In particular, microcarriers with ADSCs effectively reduced the coefficient of friction at the cartilage interface. Injection low-dose ADSCs without and with different size microcarriers into the knee joints in rats' OA model was achieved. Even better OA therapeutic effects were achieved by using smaller size (higher curvature) microcarriers to deliver ADSCs at low doses. Microcarrier-based cell delivery strategies offer potential solution method for OA therapy.

A drug-loaded nano chitosan/hyaluronic acid hydrogel system as a cartilage tissue engineering scaffold for drug delivery

Cartilage lesions, especially osteoarthritis (OA), usually arise from aging, trauma, or obesity and require medical intervention due to the damaged site's inflammation and the cartilage tissue's poor self-healing capacity. This study aimed to prepare a drug-loaded nanoparticle hydrogel system with anti-inflammatory and chondroprotective effects to treat OA. First, hyaluronic acid (HA) was oxidized to create aldehyde functional groups and then cross-linked with adipic acid dihydrazide (ADH) to form a hydrogel. Next, chitosan nanoparticles (CS NPs) loaded with an anti-inflammatory molecule (fisetin) and or a chondrogenic and chondroprotective agent (kartogenin) were incorporated into the hyaluronan hydrogel to improve the release profile of the drug and increase its retention time in the joint cavity. Incorporating drug-loaded NPs into the hyaluronan hydrogel provided the hydrogel with controlled release features and improved properties. In addition, the real-time PCR (Polymerase chain reaction) results showed that the hyaluronan hydrogel containing both drug-loaded NPs performed better than either constituent alone on an in vitro model of OA. Finally, based on the results of in vitro evaluation, this drug-loaded nanoparticle hydrogel system can be a promising technique for treating OA by rapidly suppressing inflammation and supporting cartilage regeneration and requires further investigation in an animal model of OA. Meanwhile, this study investigated, for the first time, the effect of the simultaneous use of fisetin and kartogenin together with a nano CS/HA hydrogel system to treat OA.

4-octyl itaconate inhibits synovitis in the mouse model of post-traumatic osteoarthritis and alleviates pain

4-octyl itaconate inhibits synovitis in the mouse model of post-traumatic osteoarthritis and alleviates pain

Matrikine stimulation of equine synovial fibroblasts and chondrocytes results in an in vitro osteoarthritis phenotype.

Osteoarthritis (OA) is a debilitating disease that impacts millions of individuals and has limited therapeutic options. A significant hindrance to therapeutic discovery is the lack of in vitro OA models that translate reliably to in vivo preclinical animal models. An alternative to traditional inflammatory cytokine models is the matrikine stimulation model, in which fragments of matrix proteins naturally found in OA tissues and synovial fluid, are used to stimulate cells of the joint. The objective of this study was to determine if matrikine stimulation of equine synovial fibroblasts and chondrocytes with fibronectin fragments (FN7-10) would result in an OA phenotype. We hypothesized that FN7-10 stimulation of equine articular cells would result in an OA phenotype with gene and protein expression changes similar to those previously described for human chondrocytes stimulated with FN7-10. Synovial fibroblasts and chondrocytes isolated from four horses were stimulated in monolayer culture for 6 or 18 h with 1 µM purified recombinant 42 kD FN7-10 in serum-free media. At the conclusion of stimulation, RNA was collected for targeted gene expression analysis and media for targeted protein production analysis. Consistent with our hypothesis, FN7-10 stimulation resulted in significant alterations to many important genes that are involved in OA pathogenesis including increased expression of IL-1β, IL-4, IL-6, CCL2/MCP-1, CCL5/RANTES, CXCL6/GCP-2, MMP-1, MMP-3, and MMP13. The results of this study suggest that the equine matrikine stimulation model of OA may prove useful for in vitro experiments leading up to preclinical trials.

Increased Rab1a accelerates osteoarthritis by inhibiting autophagy via activation of the mTORC1-S6K pathway

IntroductionCartilage degradation is a critical alteration in the progression of osteoarthritis (OA) due to the disorder of chondrocyte metabolic homeostasis. Autophagy plays an important role in maintaining intracellular homeostasis. Recent investigations have increasingly underscored the importance of autophagy in modulating the pathological mechanisms underlying OA. Ras-related protein Rab-1a (Rab1a) has been illustrated to regulate autophagy in many diseases but not in OA. ObjectivesThis study aims to elucidate whether Rab1a could regulate the development of OA through modulation of chondrocyte autophagy and apoptosis. MethodsProteomic sequencing, Western blotting, and immunohistochemistry were applied to detect the expression level of Rab1a in vitro and in vivo. Gene Ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways were rigorously identified. The effects of Rab1a and the interaction between Rab1a, mTORC1, autophagy and apoptosis were explored by qPCR, Western blotting, and immunofluorescence. An experimental mouse OA model was also performed to confirm the role of Rab1a in OA pathogenesis in vivo. Histological analysis was employed to demonstrate cartilage damage. ResultsRab1a expression was significantly upregulated in inflamed chondrocytes and knee OA cartilage. Inhibition of Rab1a partially attenuated the degradation of the extracellular matrix and cell apoptosis both in vitro and in vivo, whereas overexpression of Rab1a intensified cartilage matrix degradation and cellular apoptosis. Additionally, elevated Rab1a levels were observed to suppress autophagy and activate the mTORC1-S6K signaling pathway, thereby aggravating OA pathogenesis. ConclusionThe augmentation of Rab1a expression impairs autophagy and promotes apoptosis through the activation of the mTORC1-S6K signaling pathway, further exacerbating OA pathogenesis. This finding suggests that Rab1a serves as a promising and innovative therapeutic target for the prevention and treatment of OA.

TissueGene-C induces anti-inflammatory activity and M2 macrophage polarization via activation of prostaglandin E2 signaling

Osteoarthritis (OA) is the most common form of degenerative joint disease that commonly affects the knees, hips, and hands. OA is a mechano-inflammatory disease characterized by low-grade inflammation, which results in the breakdown of the cartilage extracellular matrix (ECM) within joints, leading to pain, stiffness, and inflammation. TissueGene-C (TG-C) is a cell and gene therapy investigational drug for treating knee OA that comprises human allogenic chondrocytes and an irradiated modified cell line stably expressing transforming growth factor-β1 (TGF-β1). Previous preclinical animal studies have shown that TG-C provides pain relief via its anti-inflammatory effects and cartilage structural improvement in rat OA model. The goal of this study was to investigate the mechanism of action of TG-C, explore its anti-inflammatory activity, and identify the TG-C-derived active factor(s) responsible for its efficacy. Our results showed that TG-C induces the polarization of M2 macrophages and the upregulation of interleukin-10 (IL-10) and interleukin-1 receptor antagonist (IL-1ra) while inhibiting tumor necrosis factor alpha (TNF-α) expression. Additionally, this study identified prostaglandin E2 (PGE2) as the main bioactive factor responsible for the anti-inflammatory activity of TG-C. Our results demonstrated that PGE2 is expressed by the TG-C chondrocyte component and modulated by TGF-β1 derived from the second component of TG-C. Finally, the present study provides insight into the mechanism of action of TG-C in the treatment of OA.

Exploring the mechanism of tetramethylpyrazine in the treatment of osteoarthritis based on network pharmacology

BackgroundOsteoarthritis (OA) is the most common joint disease, which mainly damages articular cartilage and involves the whole joint tissue. It has the characteristics of long course, repeated symptoms and high disability rate, and the incidence trend is gradually increasing. Tetramethylpyrazine (TMP) is the main alkaloid active substance in Ligusticum wallichii, a traditional Chinese medicine, which has the effect of promoting blood circulation and dredging collaterals, and has a good effect on the treatment of early OA, but its molecular mechanism has not been fully clarified so far. Based on network pharmacology, molecular docking simulation and animal experiments, this study explored the target and molecular mechanism of TMP in the treatment of OA.MethodsWe used PubChem, SwissTargetPrediction, and PharmMapper databases to predict the molecular structure and potential targets of TMP. GeneCards and DisGeNET databases were used to predict the relevant targets of OA. Apply UniProt database to convert targets into unified gene names, and proofread and remove duplicate gene names. The intersection targets of TMP and OA obtained on venny2.1.0 website were submitted to the STRING database to construct a PPI network. CytoScape 3.8.2 software was used to analyze the PPI network and obtain the sub-network modules and 10 key targets. The intersection targets of TMP and OA were analyzed by Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) enrichment using DAVID 6.8 database. The intersecting targets of TMP and OA, the biological process of GO enrichment, and KEGG signaling pathway were imported into Cytoscape 3.8.2 software to construct the TMP-target-pathway network diagram. Use molecular docking technology to simulate the interaction between TMP molecules and key targets, and predict the binding mode and binding ability. Animal models of rabbit knee osteoarthritis were prepared, and magnetic resonance imager (MRI) and fluorescence quantitative PCR (RT-qPCR) were used to observe the effect of TMP in treating OA as well as the expression of key target genes.Results585 potential targets of TMP, 3,857 potential targets of OA, and 49 intersecting targets of TMP and OA were obtained. The top 10 key target genes were obtained, in order of ranking: ALB, ESR1, IL10, CAT, F2, MPO, C3, CYP3A4, CYP2C9, ANXA1. GO and KEGG analysis implied that the key targets might act on OA by affecting endothelial cell permeability, peri-articular microcirculatory status, NETs production, activation of complement system and coagulation pathway, regulation of immune function of macrophages and T cells, and substance metabolism pathway in vivo, etc. The molecular mechanism might involve the formation of neutrophil extracellular trap, regulation of the actin cytoskeleton, complement and coagulation cascades, and T cell receptor signaling pathways, etc. Molecular docking simulations showed that the binding energy of IL10 and ANXA1 to TMP was greater than -5Kal/mol, but the other key target proteins showed better binding to TMP, and the binding energy was less than -5 kcal/mol. Animal experiments showed that TMP had a significant therapeutic effect on OA. The TMP group had significantly reduced knee joint effusion and bone marrow damage compared to the OA group (p < 0.05). The qRT-PCR results showed that compared with the OA group, the mRNA expression of ESR1, CAT, C3, CYP3A4, CYP2C9, and ANXA1 in the TMP group increased (p < 0.05), while there was no significant difference in mRNA expression of ALB, IL-10, F2, MPO, etc. (p > 0.05).ConclusionTMP is effective in the treatment of OA, with multi-target and multi-pathway interactions. ESR1, CAT, C3, CYP3A4, CYP2C9, and ANXA1 may be potential targets for TMP treatment of OA. The molecular mechanism mainly involves the formation of neutrophil extracellular trap, regulation of the actin cytoskeleton, complement and coagulation cascades, and T cell receptor signaling pathways, etc.

The role of m5C RNA methylation regulators in the diagnosis and immune microenvironment of osteoarthritis

The 5-methylcytosine (m5C) is a common post-transcriptional RNA methylation modification and is involved in the pathological process of many diseases. However, little is known about the role of m5C in osteoarthritis (OA). OA gene data and the corresponding information were downloaded from the Gene Expression Omnibus database. Based on 36 m5C regulators, we constructed the landscape and diagnostic model for OA. Later, two m5C modification patterns were identified, and functional analyses were performed to evaluate whether these patterns were related to endoplasmic reticulum (ER) stress and mitochondrial autophagy. We further comprehensively analyzed the immune cell infiltration characteristics in different modification patterns in OA. We also established the post-transcriptional regulatory networks and drug-gene networks. Our findings suggested that m5C regulators were differentially expressed between OA and normal samples and could serve as novel biomarkers for the diagnosis of OA. Besides, m5C regulators may be involved in regulating ER stress, mitochondrial autophagy, and immune infiltration in OA. The m5C modification can influence the sensitivity to drugs and the potential post-transcriptional regulatory mechanisms might provide promising targets.

The Therapeutic Potential of Exosomes vs. Matrix-Bound Nanovesicles from Human Umbilical Cord Mesenchymal Stromal Cells in Osteoarthritis Treatment

Osteoarthritis (OA) is a degenerative joint disease with limited therapeutic options, where inflammation plays a critical role in disease progression. Extracellular vesicles (EV) derived from mesenchymal stromal cells (MSC) have shown potential as a therapeutic approach for OA by modulating inflammation and alleviating degenerative processes in the joint. This study evaluated the therapeutic effects for the treatment of OA of two types of EV—exosomes and matrix-bound nanovesicles (MBV)—both derived from the human umbilical cord MSC (UC-MSC) via differential ultracentrifugation. Different phenotypes of human monocyte-derived macrophages (MDM) were used to study the anti-inflammatory properties of EV in vitro, and the medial meniscectomy-induced rat model of knee osteoarthritis (MMx) was used in vivo. The study found that both EV reduced pro-inflammatory cytokines IL-6 and TNF-α in MDM. However, exosomes showed superior results, preserving the extracellular matrix (ECM) of hyaline cartilage, and reducing synovitis more effectively than MBVs. Additionally, exosomes downregulated inflammatory markers (TNF-α, iNOS) and increased Arg-1 expression in macrophages and synovial fibroblasts, indicating a stronger anti-inflammatory effect. These results suggest UC-MSC exosomes as a promising therapeutic option for OA, with the potential for modulating inflammation and promoting joint tissue regeneration.

IRF1-mediated upregulation of PARP12 promotes cartilage degradation by inhibiting PINK1/Parkin dependent mitophagy through ISG15 attenuating ubiquitylation and SUMOylation of MFN1/2

Osteoarthritis (OA) is an age-related cartilage-degenerating joint disease. Mitochondrial dysfunction has been reported to promote the development of OA. Poly (ADP-ribose) polymerase family member 12 (PARP12) is a key regulator of mitochondrial function, protein translation, and inflammation. However, the role of PARP12 in OA-based cartilage degradation and the underlying mechanisms are relatively unknown. Here, we first demonstrated that PARP12 inhibits mitophagy and promotes OA progression in human OA cartilage and a monosodium iodoacetate-induced rat OA model. Using mass spectrometry and co-immunoprecipitation assay, PARP12 was shown to interact with ISG15, upregulate mitofusin 1 and 2 (MFN1/2) ISGylation, which downregulated MFN1/2 ubiquitination and SUMOylation, thereby inhibiting PINK1/Parkin-dependent chondrocyte mitophagy and promoting cartilage degradation. Moreover, inflammatory cytokine-induced interferon regulatory factor 1 (IRF1) activation was required for the upregulation of PARP12 expression, and it directly bound to the PARP12 promoter to activate transcription. XAV-939 inhibited PARP12 expression and suppressed OA pathogenesis in vitro and in vivo. Clinically, PARP12 can be used to predict the severity of OA; thus, it represents a new target for the study of mitophagy and OA progression. In brief, the IRF1-mediated upregulation of PARP12 promoted cartilage degradation by inhibiting PINK1/Parkin-dependent mitophagy via ISG15-based attenuation of MFN1/2 ubiquitylation and SUMOylation. Our data provide new insights into the molecular mechanisms underlying PARP12-based regulation of mitophagy and can facilitate the development of therapeutic strategies for the treatment of OA.

Establishment of rabbit knee osteoarthritis model by simple anterior cruciate ligament disruption

The rabbit knee osteoarthritis(KOA) model was established by simple anterior cruciate ligament disruption. The selected 40 adult white rabbits were randomly divided into two groups, blank group with 6 rabbits and model group with 34 rabbits. The rabbits in model group were given the disruption of anterior cruciate ligament of right knee joint. In the fourth, eighth and the twelfth weeks of modeling, different degrees of degenerative changes have been observed on the rabbits articular cartilages from both macroscopic and microscopic aspects. At 4, 8 and 12 weeks after modeling, the articular cartilage of the rabbits in the model group showed degenerative changes in different degrees. At 8 and 12 weeks, the typical pathological manifestations of KOA in the middle and late stages were found in the infrapatellar fat pad and synovium, respectively. There were no changes in articular cartilage, infrapatellar fat pad and synovial membrane in the blank group at the same time. There were significant differences in the gross score between the model group and the blank group at 4 weeks [(1.300±0.674) vs 0.000], 8 weeks [(2.400±0.516) vs 0.000] and 12 weeks [(3.583±0.668) vs 0.000] (P<0.05), the histopathological scores were significantly different, at 4 weeks [(2.900±0.567) vs 0.000], 8 weeks [(7.500±1.178) vs (0.500±0.707)], 12 weeks[(11.833±1.337) vs (1.500±0.707)], (P<0.05). The establishment of rabbit knee arthritis model by simply cutting the anterior cruciate ligament is simple and feasible, with good stability, high success rate, small trauma, short modeling cycle and less changes in animal physiological structure. The rabbit knee arthritis model established by simply cutting the anterior cruciate ligament has good modeling effect on different stages and grades of knee osteoarthritis, and the postoperative infection and trauma can be controlled, which can meet the test requirements.

IGF1 drives Wnt-induced joint damage and is a potential therapeutic target for osteoarthritis

Osteoarthritis is the most common joint disease and a global leading cause of pain and disability. Current treatment is limited to symptom relief, yet there is no disease-modifying therapy. Its multifactorial etiology includes excessive activation of Wnt signaling, but how Wnt causes joint destruction remains poorly understood. Here, we identify that Wnt signaling promotes the transcription of insulin-like growth factor 1 (IGF1) in articular chondrocytes and that IGF1 is a major driver of Wnt-induced joint damage. Male mice with cartilage-specific Igf1 deficiency are protected from Wnt-triggered joint disease. Mechanistically, Wnt-induced IGF1 transcription depends on β-catenin and binding of Wnt transcription factor TCF4 to the IGF1 gene promoter. In a clinically relevant mouse model of post-traumatic osteoarthritis, cartilage-specific deletion of Igf1 protects against the disease in male mice. IGF1 silencing in chondrocytes from patients with osteoarthritis restores a healthy molecular profile. Our findings reveal that reducing Wnt-induced IGF1 is a potential therapeutic strategy for osteoarthritis.

The collagenase-induced osteoarthritis (CIOA) model: Where mechanical damage meets inflammation

ObjectiveTo characterize inflammatory and mechanical changes in the collagenase-induced OA (CIOA) model in rats. DesignSkeletally mature, 6-month-old Wistar rats received unilateral intraarticular injections of saline, 500 U or 1000 U of collagenase on days 0 and 2 of the study. Joint tissues were harvested on either day 4 or 70 to evaluate the acute and long-term changes. Blood biomarkers, gait asymmetry and mechanical hyperalgesia were assessed repeatedly up until day 70. ResultsThe intraarticular injection of collagenase triggered an increase in cartilage degeneration and bone resorption over time, particularly for 1000 U. Similarly, mild synovitis was observed on day 70 with an increased number of synovial lining cells, increased fibrosis, and infiltration of peripheral macrophages. Mechanistically, these findings were linked to a dose-related mechanical weakening of the anterior cruciate ligament (ACL), which caused persistent joint destabilization throughout the study. Furthermore, the collagenase injection triggered acute inflammation and swelling of the synovium on day 4 and an acute systemic inflammatory response with increased cytokine and peripheral blood immune cell levels. While mild synovitis persisted until day 70, the systemic inflammatory response returned to control levels after 8 days. Similarly, the observed acute changes in gait and mechanical hyperalgesia also returned to baseline after 21 days. ConclusionBy evaluating inflammatory and mechanical factors at different doses and timepoints, our characterization enables a more targeted study design and increases the clinical relevance of future studies involving the CIOA model.