TGF-β signaling and the development of osteoarthritis

Intra-articular sustained-release of pirfenidone as a disease-modifying treatment for early osteoarthritis

Osteoarthritis (OA) is a major clinical challenge, and effective disease-modifying drugs for OA are still lacking due to the complicated pathology and scattered treatment targets. Effective early treatments are urgently needed to prevent OA progression. The excessive amount of transforming growth factor β (TGFβ) is one of the major causes of synovial fibrosis and subchondral bone sclerosis, and such pathogenic changes in early OA precede cartilage damage. Herein we report a novel strategy of intra-articular sustained-release of pirfenidone (PFD), a clinically-approved TGFβ inhibitor, to achieve disease-modifying effects on early OA joints. We found that PFD effectively restored the mineralization in the presence of excessive amount of TGFβ1 (as those levels found in patients' synovial fluid). A monthly injection strategy was then designed of using poly lactic-co-glycolic acid (PLGA) microparticles and hyaluronic acid (HA) solution to enable a sustained release of PFD (the "PLGA-PFD + HA" strategy). This strategy effectively regulated OA progression in destabilization of the medial meniscus (DMM)- induced OA mice model, including preventing subchondral bone loss in early OA and subchondral bone sclerosis in late OA, and reduced synovitis and pain with cartilage preservation effects. This finding suggests the promising clinical application of PFD as a novel disease-modifying OA drug.

A comprehensive review of phase 2/3 trials in osteoarthritis: an expert opinion

INTRODUCTION

Osteoarthritis (OA) is a chronic, degenerative, and debilitating disease associated with significant long-term morbidity and disability. The pathogenesis of OA is not completely understood but involves an interplay between environmental risk factors, joint mechanics, abnormal pain pathways and upregulation of inflammatory signaling pathways. Current therapeutic options for patients are limited to conservative management, minimal pharmacological options or surgical management, with significant caveats to all approaches.

AREAS COVERED

In this review, we have set out to investigate current phase II/III clinical trials by undertaking a PubMed search. Examined clinical trials have explored a myriad of potential therapeutics from conventional disease-modifying anti-rheumatic drugs and biologics usually used in the treatment of inflammatory arthritides, to more novel approaches targeting inflammatory pathways implicated in OA, cartilage degeneration or pain pathways.

EXPERT OPINION

Unfortunately, most completed phase II/III clinical trials have shown little impact on patient pain scores, with the exception of the traditional DMARD methotrexate and Sprifermin. Methotrexate has been shown to be beneficial when used in the correct patient cohort (MRI proven synovitis). Sprifermin has the longest follow-up data of 5 years and has been shown to reduce loss of MRI-measured cartilage thickness and pain scores.

Is chronic kidney disease associated with osteoarthritis? The United States national health and nutrition examination survey 2011-2020

OBJECTIVE

Chronic kidney disease (CKD) and osteoarthritis (OA) represent two frequently seen disorders among the general population, and they share several similar risk factors. The present work focused on assessing the relation of CKD with OA.

METHODS

This cohort study included 26,280 eligible participants aged ≥ 20 years who had valid data on CKD and OA from the National Health and Nutrition Examination Survey (NHANES) 2011-2020. The association between CKD and OA was studied by logistic regression, adjusting for demographics, body mass index (BMI), socioeconomic factors, physical activity, ever smoking, alcohol using, diabetes status and hypertension status.

RESULTS

Among the participants of this study, 26.69% of OA patients had concurrent CKD, whereas this proportion was only 13.83% among non-OA patients.CKD was related to OA[OR:2.269 (95%CI:2.266-2.271), p < 0.01] and the relation was of significance [OR:1.031 (95%CI:1.030-1.033),p < 0.01] following adjustments. In subgroup analyses based on age, the relation between osteoarthritis and chronic kidney disease remained significant, and in the subgroup analyses based on gender the previously mentioned relation between OA and CKD showed opposite directions in men [OR:0.869(95%CI0.867-0.871), p < 0.01] and women [OR:1.178(95%CI1.177-1.180), p < 0.01].

CONCLUSIONS

In the present 10-year large-scale national-wide survey, OA is closely related to CKD, and women with OA showed a higher risk of developing CKD compared to men. This study suggests that the relationship between OA and CKD deserves further investigation, and we suggest that patients with OA need to pay extra attention to their own kidney health.

Identification of osteoblastic autophagy-related genes for predicting diagnostic markers in osteoarthritis

The development of osteoarthritis (OA) involves subchondral bone lesions, but the role of osteoblastic autophagy-related genes (ARGs) in osteoarthritis is unclear. Through integrated analysis of single-cell dataset, Bulk RNA dataset, and 367 ARGs extracted from GeneCards, 40 ARGs were found. By employing multiple machine learning algorithms and PPI networks, three key genes (DDIT3, JUN, and VEGFA) were identified. Then the RF model constructed from these genes indicated great potential as a diagnostic tool. Furthermore, the model's effectiveness in predicting OA has been confirmed through external validation datasets. Moreover, the expression of ARGs was examined in osteoblasts subject to excessive mechanical stress, human and mouse tissues. Finally, the role of ARGs in OA was confirmed through co-culturing explants and osteoblasts. Thus, osteoblastic ARGs could be crucial in OA development, providing potential diagnostic and treatment strategies.

Proteomic Characterization of Human Placenta: Insights into Potential Therapeutic Applications for Osteoarthritis

Biologics have become increasingly prominent as therapeutics in recent years due to their innate immune-privileged nature, biocompatibility, and high levels of protein biofactors. The aim of the study is to characterise the biologic, lyophilized human placenta (LHP) and explore its therapeutic potential for osteoarthritis (OA). The presence of six bioactive constituents that regulate cell-extracellular matrix interaction was identified by liquid chromatography coupled to electrospray ionization and quadrupole time-of-flight mass spectrometry (LC-ESI-QTOF/MS). Metalloproteinase inhibitor 3 (TIMP3), alpha-1 anti-trypsin (a1AT), basic fibroblast growth factor (bFGF), and transforming growth factor β1 (TGFβ1) were detected and quantified using ELISA. The total protein content present in LHP by Bradford assay was found to be 409.35 ± 0.005 μg/ml. The analytical techniques such as Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR), solid state carbon-13 Nuclear Magnetic Resonance (ssC13 NMR) spectroscopy, and Differential Scanning Calorimetry (DSC) revealed the secondary structure and conformational stability of LHP. X-Ray diffraction (XRD) studies showed its amorphous nature. Bioactivity assessment of LHP was performed in human keratinocytes (HaCaT) and human dermal fibroblasts (HDF) by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The LHP was highly proliferative against skin cells and non-toxic, based on the findings of the bioactivity assay. LHP has the potential to be used as a therapeutic agent for OA, as its characterisation unveiled its physical stability, significant concentration of bioactive components that are pertinent to cartilage repair and its conformational stability.

Elucidation of the key therapeutic targets and potential mechanisms of Andrographolide multi-targets against osteoarthritis via network pharmacological analysis and experimental validation

OBJECTIVE

Our purpose is to unveil Andrographolide's potential multi-target and multi-mechanism therapeutic effects in treating OA via systematic network pharmacological analysis and cell experimental validation.

MATERIALS AND METHODS

Initially, we gathered data from Andrographolide and OA-related databases to obtain information on Andrographolide's biological properties and the targets linked with OA. We developed a bioinformatic network about Andrographolide and OA, whereby we analyzed the network to identify potential therapeutic targets and mechanisms of action of Andrographolide. Subsequently, we used molecular docking to analyze the binding sites of Andrographolide to the target proteins. At the same time, SDF-1 was used to construct an OA cell model to verify the therapeutic effect of Andrographolide on OA and its effect on target proteins.

RESULTS

Our experimental results show that Andrographolide has excellent pharmaceutical properties, by Lipinski's rules for drugs, suggesting that this compound can be considered to have a high therapeutic potential in drug development. 233 targets were preliminarily investigated, the mechanisms through which Andrographolide targets OA primarily involve the TNF signaling pathway, PI3K-AKT signaling pathway, IL-17 signaling pathway, and TLR signaling pathway. These mechanisms target OA by influencing immune and inflammatory responses in the joints, regulating apoptosis to prevent chondrocyte death. Finally, TNF-α, STAT3, TP53, IL-6, JUN, IL-1β, HIF-1α, TGF-β1, and AKT1 were identified as 9 key targets of Andrographolide anti-OA. In addition, our molecular docking analyzes with cell experimental validation further confirm the network pharmacology results. According to our molecular docking results, Andrographolide can bind to all the hub target proteins and has a good binding ability (binding energy < -5 kcal/mol), with the strongest binding affinity to AKT1 of -9.2 kcal/ mol. The results of cell experiments showed that Andrographolide treatment significantly increased the cell viability and the expression of COL2A1 and ACAN proteins. Moreover, 30 μM Andrographolide significantly reversed SDF-1-induced increases in the protein expression of TNF-α, STAT3, TP53, IL-6, JUN, IL-1β, HIF-1α, and TGF-β1, and decreases in the protein expression of AKT1.

CONCLUSION

This study provides a comprehensive understanding of the potential therapeutic targets and mechanisms of action of Andrographolide in OA treatment. Our findings suggest that Andrographolide is a promising candidate for drug development in the management of OA.

Signalling interaction between β-catenin and other signalling molecules during osteoarthritis development

Osteoarthritis (OA) is the most prevalent disorder of synovial joint affecting multiple joints. In the past decade, we have witnessed conceptual switch of OA pathogenesis from a 'wear and tear' disease to a disease affecting entire joint. Extensive studies have been conducted to understand the underlying mechanisms of OA using genetic mouse models and ex vivo joint tissues derived from individuals with OA. These studies revealed that multiple signalling pathways are involved in OA development, including the canonical Wnt/β-catenin signalling and its interaction with other signalling pathways, such as transforming growth factor β (TGF-β), bone morphogenic protein (BMP), Indian Hedgehog (Ihh), nuclear factor κB (NF-κB), fibroblast growth factor (FGF), and Notch. The identification of signalling interaction and underlying mechanisms are currently underway and the specific molecule(s) and key signalling pathway(s) playing a decisive role in OA development need to be evaluated. This review will focus on recent progresses in understanding of the critical role of Wnt/β-catenin signalling in OA pathogenesis and interaction of β-catenin with other pathways, such as TGF-β, BMP, Notch, Ihh, NF-κB, and FGF. Understanding of these novel insights into the interaction of β-catenin with other pathways and its integration into a complex gene regulatory network during OA development will help us identify the key signalling pathway of OA pathogenesis leading to the discovery of novel therapeutic strategies for OA intervention.

Sericin promotes chondrogenic proliferation and differentiation via glycolysis and Smad2/3 TGF-β signaling inductions and alleviates inflammation in three-dimensional models

Knee osteoarthritis is a chronic joint disease mainly characterized by cartilage degeneration. The treatment is challenging due to the lack of blood vessels and nerve supplies in cartilaginous tissue, causing a prominent limitation of regenerative capacity. Hence, we investigated the cellular promotional and anti-inflammatory effects of sericin, Bombyx mori-derived protein, on three-dimensional chondrogenic ATDC5 cell models. The results revealed that a high concentration of sericin promoted chondrogenic proliferation and differentiation and enhanced matrix production through the increment of glycosaminoglycans, COL2A1, COL X, and ALP expressions. SOX-9 and COL2A1 gene expressions were notably elevated in sericin treatment. The proteomic analysis demonstrated the upregulation of phosphoglycerate mutase 1 and triosephosphate isomerase, a glycolytic enzyme member, reflecting the proliferative enhancement of sericin. The differentiation capacity of sericin was indicated by the increased expressions of procollagen12a1, collagen10a1, rab1A, periostin, galectin-1, and collagen6a3 proteins. Sericin influenced the differentiation capacity via the TGF-β signaling pathway by upregulating Smad2 and Smad3 while downregulating Smad1, BMP2, and BMP4. Importantly, sericin exhibited an anti-inflammatory effect by reducing IL-1β, TNF-α, and MMP-1 expressions and accelerating COL2A1 production in the early inflammatory stage. In conclusion, sericin demonstrates potential in promoting chondrogenic proliferation and differentiation, enhancing cartilaginous matrix synthesis through glycolysis and TGF-β signaling pathways, and exhibiting anti-inflammatory properties.

Data-driven identification of predictive risk biomarkers for subgroups of osteoarthritis using interpretable machine learning

Osteoarthritis (OA) is increasing in prevalence and has a severe impact on patients' lives. However, our understanding of biomarkers driving OA risk remains limited. We developed a model predicting the five-year risk of OA diagnosis, integrating retrospective clinical, lifestyle and biomarker data from the UK Biobank (19,120 patients with OA, ROC-AUC: 0.72, 95%CI (0.71-0.73)). Higher age, BMI and prescription of non-steroidal anti-inflammatory drugs contributed most to increased OA risk prediction ahead of diagnosis. We identified 14 subgroups of OA risk profiles. These subgroups were validated in an independent set of patients evaluating the 11-year OA risk, with 88% of patients being uniquely assigned to one of the 14 subgroups. Individual OA risk profiles were characterised by personalised biomarkers. Omics integration demonstrated the predictive importance of key OA genes and pathways (e.g., GDF5 and TGF-β signalling) and OA-specific biomarkers (e.g., CRTAC1 and COL9A1). In summary, this work identifies opportunities for personalised OA prevention and insights into its underlying pathogenesis.

Effect of Low-Intensity Pulsed Ultrasound on Macrophage Properties and Fibrosis in the Infrapatellar Fat Pad in a Carrageenan-Induced Knee Osteoarthritis Rat Model

BACKGROUND

In the progression of knee osteoarthritis (KOA), fibrosis of the infrapatellar fat pad (IFP) is a key pathological change. Low-intensity pulsed ultrasound (LIPUS) inhibits IFP fibrosis by decreasing the gene expression and activity of hypoxia-inducible factor (HIF-1α), which is a protein involved in IFP fibrosis in KOA rat models. On the other hand, macrophages play an important role in the progression of fibrosis in various tissues, and LIPUS irradiation suppresses macrophage infiltration and inflammatory cytokine secretion. However, whether LIPUS suppresses macrophage polarity and IFP fibrosis in KOA remains unclear. Therefore, we investigated the effect of LIPUS on macrophage polarity and IFP fibrosis.

MATERIALS AND METHODS

A KOA model was created by injecting carrageenin into the bilateral knee joints of Wistar rats (eight weeks old). Tissues were harvested over time for histological and molecular biological analysis. The KOA model was also subjected to LIPUS irradiation for two weeks following the injection of carrageenin.

RESULTS

RM-4-positive cells were widely distributed in IFP two weeks after carrageenin administration, but M2 macrophages were significantly increased, and the Sirius red area was decreased in the LIPUS-irradiated group compared with those in the non-irradiated group. The gene expression of M1 macrophage markers was significantly decreased and that of M2 macrophage markers was significantly increased in the LIPUS-irradiated group. The expression of transforming growth factor-β (TGF-β) and type 1 collagen was also significantly decreased.

CONCLUSION

These results suggest that LIPUS may serve as a novel approach for the treatment of KOA through its effect on M1 macrophages and suppression of TGF-β expression.

Deficiency of Cbfβ in articular cartilage leads to osteoarthritis-like phenotype through Hippo/Yap, TGFβ, and Wnt/β-catenin signaling pathways

Osteoarthritis (OA) is the most prevalent degenerative joint disorder, causing physical impairments among the elderly. Core binding factor subunit β (Cbfβ) has a critical role in bone homeostasis and cartilage development. However, the function and mechanism of Cbfβ in articular cartilage and OA remains unclear. We found that Cbfβf/fAggrecan-CreERT mice with Cbfβ-deficiency in articular cartilage developed a spontaneous osteoarthritis-like phenotype with articular cartilage degradation. Immunofluorescence staining showed that Cbfβf/fAggrecan-CreERT mice exhibited a significant increase in the expression of articular cartilage degradation markers and inflammatory markers in the knee joints. RNA-sequencing analysis demonstrated that Cbfβ orchestrated Hippo/Yap, TGFβ/Smad, and Wnt/β-catenin signaling pathways in articular cartilage, and Cbfβ deficiency resulted in the abnormal expression of downstream genes involved in maintaining articular cartilage homeostasis. Immunofluorescence staining results showed Cbfβ deficiency significantly increased active β-catenin and TCF4 expression while reducing Yap, TGFβ1, and p-Smad 2/3 expression. Western blot and qPCR validated gene expression changes in hip articular cartilage of Cbfβ-deficient mice. Our results demonstrate that deficiency of Cbfβ in articular cartilage leads to an OA-like phenotype via affecting Hippo/Yap, TGFβ, and Wnt/β-catenin signaling pathways, disrupting articular cartilage homeostasis and leading to the pathological process of OA in mice. Our results indicate that targeting Cbfβ may be a potential therapeutic target for the design of novel and effective treatments for OA.

Exploring the emerging bidirectional association between inflamm-aging and cellular senescence in organismal aging and disease

There is strong evidence that most individuals in the elderly population are characterized by inflamm-aging which refers to a subtle increase in the systemic pro-inflammatory environment and impaired innate immune activation. Although a variety of distinct factors are associated with the progression of inflamm-aging, emerging research is demonstrating a dynamic relationship between the processes of cellular senescence and inflamm-aging. Cellular senescence is a recognized factor governing organismal aging, and through a characteristic secretome, accumulating senescent cells can induce and augment a pro-inflammatory tissue environment that provides a rationale for immune system-independent activation of inflamm-aging and associated diseases. There is also accumulating evidence that inflamm-aging or its components can directly accelerate the development of senescent cells and ultimately senescent cell burden in tissues in a likely vicious inflammatory loop. The present review is intended to describe the emerging senescence-based molecular etiology of inflamm-aging as well as the dynamic reciprocal interactions between inflamm-aging and cellular senescence. Therapeutic interventions concurrently targeting cellular senescence and inflamm-aging are discussed and limitations as well as research opportunities have been deliberated. An effort has been made to provide a rationale for integrating inflamm-aging with cellular senescence both as an underlying cause and therapeutic target for further studies.

Does Chronic Pancreatitis in Growing Pigs Lead to Articular Cartilage Degradation and Alterations in Subchondral Bone?

Chronic pancreatitis (CP), a progressive inflammatory disease, poses diagnostic challenges due to its initially asymptomatic nature. While CP's impact on exocrine and endocrine functions is well-recognized, its potential influence on other body systems, particularly in young individuals, remains underexplored. This study investigates the hypothesis that CP in growing pigs leads to alterations in articular cartilage and subchondral bone, potentially contributing to osteoarthritis (OA) development. Utilizing a pig model of cerulein-induced CP, we examined the structural and compositional changes in subchondral bone, articular cartilage, and synovial fluid. Histological analyses, including Picrosirius Red and Safranin-O staining, were employed alongside immuno-histochemistry and Western blotting techniques. Our findings reveal significant changes in the subchondral bone, including reduced bone volume and alterations in collagen fiber composition. Articular cartilage in CP pigs exhibited decreased proteoglycan content and alterations in key proteins such as MMP-13 and TGF-β1, indicative of early cartilage degradation. These changes suggest a link between CP and musculoskeletal alterations, underscoring the need for further research into CP's systemic effects. Our study provides foundational insights into the relationship between CP and skeletal health, potentially guiding future pediatric healthcare strategies for early CP diagnosis and management.

Downregulation of extracellular matrix protein 1 effectively ameliorates osteoarthritis progression in vivo

Osteoarthritis (OA) is the most common joint disease whose important pathological feature is degeneration of articular cartilage. Although extracellular matrix protein 1 (ECM1) serves as a central regulator of chondrocyte proliferation and hypertrophy, its role in OA remains largely unknown. This study aims to decipher the roles of ECM1 in OA development and therapy in animal models. In the present study, ECM1 expression was examined in clinical OA samples, experimental OA mice and OA cell models. Mice subjected to destabilised medial meniscus (DMM) surgery were intra-articularly injected with adeno-associated virus (AAV) expressing ECM1 (AAV-ECM1) or AAV containing shECM1 (AAV-shECM1). Histological analysis was performed to determine cartilage damage. mRNA sequencing was performed to explore the molecular mechanism. In addition, the downstream signaling was further confirmed by using specific inhibitors. Our data showed that ECM1 was upregulated in the cartilage of patients with OA, OA mice as well as OA cell models. Moreover, ECM1 over-expressing in knee joints by AAV-ECM1 accelerated OA progression, while knockdown of ECM1 by AAV-shECM1 alleviated OA development. Mechanistically, cartilage destruction increased ECM1 expression, which consequently exacerbated OA progression partly by decreasing PRG4 expression in the TGF-β/PKA/CREB-dependent manner. In conclusion, our study revealed the important role of ECM1 in OA progression. Targeted ECM1 inhibition is a potential strategy for OA therapy.

Integrated Analysis of DNA Methylation and Gene Expression Profiles in a Rat Model of Osteoarthritis

Osteoarthritis (OA) is common and affected by several factors, such as age, weight, sex, and genetics. The pathogenesis of OA remains unclear. Therefore, using a rat model of monosodium iodoacetate (MIA)-induced OA, we examined genomic-wide DNA methylation using methyl-seq and characterized the transcriptome using RNA-seq in the articular cartilage tissue from a negative control (NC) and MIA-induced rats. We identified 170 genes (100 hypomethylated and upregulated genes and 70 hypermethylated and downregulated genes) regulated by DNA methylation in OA. DNA methylation-regulated genes were enriched in functions related to focal adhesion, extracellular matrix (ECM)-receptor interaction and the PI3K-Akt and Hippo signaling pathways. Functions related to extracellular matrix organization, extracellular matrix proteoglycans, and collagen formation were involved in OA. A molecular and protein-protein network was constructed using methylated expression-correlated genes. Erk1/2 was a downstream target of OA-induced changes in DNA methylation and RNA expression. We found that the integrin subunit alpha 2 (ITGA2) gene is important in focal adhesion, alpha6-beta4 integrin signaling, and the inflammatory response pathway in OA. Overall, gene expression changes because DNA methylation influences OA pathogenesis. ITGA2, whose gene expression changes are regulated by DNA methylation during OA onset, is a candidate gene. Our findings provide insights into the epigenetic targets of OA processes in rats.

miR-92a-3p-inspired shRNA exhibits pro-chondrogenic and chondrocyte protective effects in osteoarthritis treatment through targeting SMAD6/7

INTRODUCTION

Osteoarthritis (OA) compromises patients' quality of life and requires further study. Although miR-92a-3p was reported to possess chondroprotective effects, the underlying mechanism requires further clarification. The objectives of this study were to elucidate the mechanism by which miR-92a-3p alleviates OA and to examine the efficacy of shRNA-92a-3p, which was designed based on mature miR-92a-3p.

MATERIALS AND METHODS

TargetScan and luciferase reporter assay were used to predict the target of miR-92a-3p. Adipose-derived stem cells (ADSCs) were transfected with miR-92a-3p/miR-NC mimic for the analysis of chondrogenic biomarkers and SMAD proteins. ADSCs and osteoarthritic chondrocytes were transduced with shRNA-92a-3p for the analysis of chondrogenic biomarkers and SMAD proteins. OA was surgically induced in C57BL/6JJcl mice, and ADSCs with/without shRNA-92a-3p transduction were intra-articularly injected for the assessment of cartilage damage.

RESULTS

SMAD6 and SMAD7 were predicted as direct targets of miR-92a-3p by TargetScan and luciferase reporter assay. Transfection of the miR-92a-3p mimic resulted in a decrease in SMAD6 and SMAD7 levels and an increase in phospho-SMAD2/3, phospho-SMAD1/5/9, SOX9, collagen type II, and aggrecan levels in ADSCs. Furthermore, shRNA-92a-3p decreased SMAD6 and SMAD7 levels, and increased phospho-SMAD2/3, phospho-SMAD1/5/9, SOX9, collagen type II, and aggrecan levels in ADSCs and osteoarthritic chondrocytes. Additionally, ADSC-shRNA-92a-3p-EVs reduced the rate of decrease of SOX9, collagen type II, and aggrecan in osteoarthritic chondrocytes. In mice with surgically induced OA, shRNA-92a-3p-treated ADSCs alleviated cartilage damage more effectively than nontreated ADSCs.

CONCLUSIONS

miR-92a-3p and shRNA-92a-3p exhibit therapeutic effects in treating OA by targeting SMAD6 and SMAD7, thereby enhancing TGF-β signaling.

Directed differentiation of human pluripotent stem cells into articular cartilage reveals effects caused by absence of WISP3, the gene responsible for progressive pseudorheumatoid arthropathy of childhood

OBJECTIVES

Progressive pseudorheumatoid arthropathy of childhood (PPAC), caused by deficiency of WNT1 inducible signalling pathway protein 3 (WISP3), has been challenging to study because no animal model of the disease exists and cartilage recovered from affected patients is indistinguishable from common end-stage osteoarthritis. Therefore, to gain insights into why precocious articular cartilage failure occurs in this disease, we made in vitro derived articular cartilage using isogenic WISP3-deficient and WISP3-sufficient human pluripotent stem cells (hPSCs).

METHODS

We generated articular cartilage-like tissues from induced-(i) PSCs from two patients with PPAC and one wild-type human embryonic stem cell line in which we knocked out WISP3. We compared these tissues to in vitro-derived articular cartilage tissues from two isogenic WISP3-sufficient control lines using histology, bulk RNA sequencing, single cell RNA sequencing and in situ hybridisation.

RESULTS

WISP3-deficient and WISP3-sufficient hPSCs both differentiated into articular cartilage-like tissues that appeared histologically similar. However, the transcriptomes of WISP3-deficient tissues differed significantly from WISP3-sufficient tissues and pointed to increased TGFβ, TNFα/NFκB, and IL-2/STAT5 signalling and decreased oxidative phosphorylation. Single cell sequencing and in situ hybridisation revealed that WISP3-deficient cartilage contained a significantly higher fraction (~4 fold increase, p<0.001) of superficial zone chondrocytes compared with deeper zone chondrocytes than did WISP3-sufficient cartilage.

CONCLUSIONS

WISP3-deficient and WISP3-sufficient hPSCs can be differentiated into articular cartilage-like tissues, but these tissues differ in their transcriptomes and in the relative abundances of chondrocyte subtypes they contain. These findings provide important starting points for in vivo studies when an animal model of PPAC or presymptomatic patient-derived articular cartilage becomes available.

In Vitro Chondrogenesis Induction by Short Peptides of the Carboxy-Terminal Domain of Transforming Growth Factor β1

Τransforming growth factor β1 (TGF-β1) comprises a key regulator protein in many cellular processes, including in vivo chondrogenesis. The treatment of human dental pulp stem cells, separately, with Leu83-Ser112 (C-terminal domain of TGF-β1), as well as two very short peptides, namely, 90-YYVGRKPK-97 (peptide 8) and 91-YVGRKP-96 (peptide 6) remarkably enhanced the chondrogenic differentiation capacity in comparison to their full-length mature TGF-β1 counterpart either in monolayer cultures or 3D scaffolds. In 3D scaffolds, the reduction of the elastic modulus and viscous modulus verified the production of different amounts and types of ECM components. Molecular dynamics simulations suggested a mode of the peptides' binding to the receptor complex TβRII-ALK5 and provided a possible structural explanation for their role in inducing chondrogenesis, along with endogenous TGF-β1. Further experiments clearly verified the aforementioned hypothesis, indicating the signal transduction pathway and the involvement of TβRII-ALK5 receptor complex. Real-time PCR experiments and Western blot analysis showed that peptides favor the ERK1/2 and Smad2 pathways, leading to an articular, extracellular matrix formation, while TGF-β1 also favors the Smad1/5/8 pathway which leads to the expression of the metalloproteinases ADAMTS-5 and MMP13 and, therefore, to a hypertrophic chondrocyte phenotype. Taken together, the two short peptides, and, mainly, peptide 8, could be delivered with a scaffold to induce in vivo chondrogenesis in damaged articular cartilage, constituting, thus, an alternative therapeutic approach for osteoarthritis.

Liposomal aggregates sustain the release of rapamycin and protect cartilage from friction

Liposomes show promise as biolubricants for damaged cartilage, but their small size results in low joint and cartilage retention. We developed a zinc ion-based liposomal drug delivery system for local osteoarthritis therapy, focusing on sustained release and tribological protection from phospholipid lubrication properties. Our strategy involved inducing aggregation of negatively charged liposomes with zinc ions to extend rapamycin (RAPA) release and improve cartilage lubrication. Liposomal aggregation occurred within 10 min and was irreversible, facilitating excess cation removal. The aggregates extended RAPA release beyond free liposomes and displayed irregular morphology influenced by RAPA. At nearly 100 µm, the aggregates were large enough to exceed the previously reported size threshold for increased joint retention. Tribological assessment on silicon surfaces and ex vivo porcine cartilage revealed the system's excellent protective ability against friction at both nano- and macro-scales. Moreover, RAPA was shown to attenuate the fibrotic response in human OA synovial fibroblasts. Our findings suggest the zinc ion-based liposomal drug delivery system has potential to enhance OA therapy through extended release and cartilage tribological protection, while also illustrating the impact of a hydrophobic drug like RAPA on liposome aggregation and morphology.

Separating friend from foe: Inhibition of TGF-β-induced detrimental SMAD1/5/9 phosphorylation while maintaining protective SMAD2/3 signaling in OA chondrocytes

OBJECTIVE

Transforming growth factor-β (TGF-β) signaling via SMAD2/3 is crucial to control cartilage homeostasis. However, TGF-β can also have detrimental effects by signaling via SMAD1/5/9 and thereby contribute to diseases like osteoarthritis (OA). In this study, we aimed to block TGF-β-induced SMAD1/5/9 signaling in primary human OA chondrocytes, while maintaining functional SMAD2/3 signaling.

DESIGN

Human OA chondrocytes were pre-incubated with different concentrations of ALK4/5/7 kinase inhibitor SB-505124 before stimulation with TGF-β. Changes in SMAD C-terminal phosphorylation were analyzed using Western blot and response genes were measured with quantitative Polymerase Chain Reaction. To further explore the consequences of our ability to separate pathways, we investigated TGF-β-induced chondrocyte hypertrophy.

RESULTS

Pre-incubation with 0.5 µM SB-505124, maintained ±50% of C-terminal SMAD2/3 phosphorylation and induction of JUNB and SERPINE1, but blocked SMAD1/5/9-C phosphorylation and expression of ID1 and ID3. Furthermore, TGF-β, in levels comparable to those in the synovial fluid of OA patients, resulted in regulation of hypertrophic and dedifferentiation markers in OA chondrocytes; i.e. an increase in COL10, RUNX2, COL1A1, and VEGF and a decrease in ACAN expression. Interestingly, in a subgroup of OA chondrocyte donors, blocking only SMAD1/5/9 caused stronger inhibition on TGF-β-induced RUNX2 than blocking both SMAD pathways.

CONCLUSION

Our findings indicate that using low dose of SB-505124 we maintained functional SMAD2/3 signaling that blocks RUNX2 expression in a subgroup of OA patients. We are the first to show that SMAD2/3 and SMAD1/5/9 pathways can be separately modulated using low and high doses of SB-505124 and thereby split TGF-β's detrimental from protective function in chondrocytes.

Risk Factors of Loss of Knee Range of Motion after Primary Anterior Cruciate Ligament Reconstruction following Preoperative Recovery of Knee Range of Motion

The loss of knee range of motion (ROM) is not an uncommon complication after anterior cruciate ligament reconstruction (ACLR). However, the risk factors of loss of knee ROM remain debatable. The purpose of this study was to evaluate the incidence and risk factors of loss of knee ROM at 12 months after primary ACLR performed after regaining full knee ROM preoperatively. Consecutive patients who underwent primary ACLR after regaining full ROM between January 2014 and January 2020 were retrospectively reviewed. Patients who received a surgical arthrolysis within 12 months after ACLR or those who had a loss of knee ROM at 12 months postoperatively were defined as the loss of ROM group. Possible risk factors of loss of knee ROM, including patient demographic, preoperative, surgical, and postoperative factors, were assessed. The notch wide index and radiographic parameters of the tibial spines; medial tibial spine height/tibial length (TL), lateral tibial spine height (LTSH)/TL, and tibial spine width (TSW)/TL, were also assessed. A total of 141 patients (141 knees) were included (mean age, 25.8 ± 11.4 years; male/female, 56/85). Of the 141 patients, three received surgical arthrolysis within 12 months, and 23 had a loss of knee ROM at 12 months after ACLR. On comparing patients with and without loss of knee ROM, significant differences were found in the age (p = 0.04), LTSH/TL (p = 0.02), and TSW/TL (p = 0.02). A multivariate regression analysis showed that the age (odds ratio [OR]; 1.05, 95% confidence interval [CI]: 1.01-1.09, p = 0.02), LTSH/TL (OR: 1.44, 95% CI: 1.01-2.1, p = 0.04), and TSW/TL (OR: 0.79, 95% CI: 0.65-0.97, p = 0.02) were identified as significant independent risk predictors of loss of knee ROM. This study showed that the incidence of loss of knee ROM at 12 months after primary ACLR was 18.4% (26/141). An older age, a higher LTSH/TL, and a smaller TSW/TL may be associated with loss of knee ROM at 12 months after ACLR.

Identification of membrane proteins regulated by ADAM15 by SUSPECS proteomics

ADAM15 is a member of the disintegrin-metalloproteinase family of sheddases, which plays a role in several biological processes including cartilage homeostasis. In contrast with well-characterized ADAMs, such as the canonical sheddases ADAM17 and ADAM10, little is known about substrates of ADAM15 or how the enzyme exerts its biological functions. Herein, we used "surface-spanning enrichment with click-sugars (SUSPECS)" proteomics to identify ADAM15 substrates and/or proteins regulated by the proteinase at the cell surface of chondrocyte-like cells. Silencing of ADAM15 by siRNAs significantly altered membrane levels of 13 proteins, all previously not known to be regulated by ADAM15. We used orthogonal techniques to validate ADAM15 effects on 3 of these proteins which have known roles in cartilage homeostasis. This confirmed that ADAM15-silencing increased cell surface levels of the programmed cell death 1 ligand 2 (PDCD1LG2) and reduced cell surface levels of vasorin and the sulfate transporter SLC26A2 through an unknown post-translational mechanism. The increase of PDCD1LG2 by ADAM15 knockdown, a single-pass type I transmembrane protein, suggested it could be a proteinase substrate. However, shed PDCD1LG2 could not be detected even by a data-independent acquisition mass spectrometry, a highly sensitive method for identification and quantification of proteins in complex protein samples, suggesting that ADAM15 regulates PDCD1LG2 membrane levels by a mechanism different from ectodomain shedding.

Equine mesenchymal stem cell derived extracellular vesicle immunopathology biomarker discovery

The use of mesenchymal stem cells (MSCs) in human and veterinary clinical applications has become a subject of increasing importance due to their roles in immunomodulation and regenerative processes. MSCs are especially relevant in equine medicine because they may have the ability to treat prevalent musculoskeletal disorders, among other conditions. However, recent evidence suggests that the components secreted by MSCs, particularly extracellular vesicles (EVs), are responsible for these properties. EVs contain proteins and nucleic acids, which possess an active role in intercellular communication and can be used as therapeutics. However, because the intersection of equine veterinary medicine with EVs remains a relatively new field, there is a demand to identify biomarkers that can discern and enrich for therapeutic EVs, progressing their clinical efficacy. In this study, we identified and characterized 84 miRNAs, between three equine donors involved in immunomodulation in cell and EV subjects. We discovered distinct groups of shared miRNAs, like miR-21-5p and miR-451a, that are abundant and enriched between the donors' EVs, respectively. By mapping and comparing the MSC-EV miRNA expression, we discovered many pathways that are involved in immunomodulation and tissue regenerative processes related to equine clinical applications. Therefore, the miRNAs highlighted in this article can be used as valuable biomarkers for screening MSC-derived EVs for potential equine therapy.

Transcriptomic changes in porcine articular cartilage one year following disruption of the anterior cruciate ligament

To determine the transcriptomic changes seen in early- to mid-stage posttraumatic osteoarthritis (PTOA) development, 72 Yucatan minipigs underwent transection of the anterior cruciate ligament. Subjects were randomized to no further intervention, ligament reconstruction, or ligament repair, followed by articular cartilage harvesting and RNA-sequencing at three different postoperative timepoints (1, 4, and 52 weeks). Six additional subjects received no ligament transection and provided cartilage tissue to serve as controls. Differential gene expression analysis between post-transection cartilage and healthy cartilage revealed an initial increase in transcriptomic differences at 1 and 4 weeks followed by a stark reduction in transcriptomic differences at 52 weeks. This analysis also showed how different treatments genetically modulate the course of PTOA following ligament disruption. Specific genes (e.g., MMP1, POSTN, IGF1, PTGFR, HK1) were identified as being upregulated in the cartilage of injured subjects across all timepoints regardless of treatment. At the 52-week timepoint, 4 genes (e.g., A4GALT, EFS, NPTXR, ABCA3) that-as far as we know-have yet to be associated with PTOA were identified as being concordantly differentially expressed across all treatment groups when compared to controls. Functional pathway analysis of injured subject cartilage compared to control cartilage revealed overarching patterns of cellular proliferation at 1 week, angiogenesis, ECM interaction, focal adhesion, and cellular migration at 4 weeks, and calcium signaling, immune system activation, GABA signaling, and HIF-1 signaling at 52 weeks.

Directed differentiation of human pluripotent stem cells into articular cartilage reveals effects caused by absence of WISP3 , the gene responsible for Progressive Pseudorheumatoid Arthropathy of Childhood

Objectives

Progressive Pseudorheumatoid Arthropathy of Childhood (PPAC), caused by deficiency of WNT1 inducible signaling pathway protein 3 ( WISP3 ), has been challenging to study because no animal model of the disease exists and cartilage recovered from affected patients is indistinguishable from common end-stage osteoarthritis. Therefore, to gain insights into why precocious articular cartilage failure occurs in this disease, we made in vitro derived articular cartilage using isogenic WISP3 -deficient and WISP3 -sufficient human pluripotent stem cells (hPSCs).

Methods

We generated articular cartilage-like tissues from induced-(i)PSCs from 2 patients with PPAC and 1 wild-type human embryonic stem cell line in which we knocked out WISP3. We compared these tissues to in vitro -derived articular cartilage tissues from 2 isogenic WISP3 -sufficient control lines using histology, bulk RNA sequencing, single cell RNA sequencing, and in situ hybridization.

Results

WISP3 -deficient and WISP3 -sufficient hPSCs both differentiated into articular cartilage-like tissues that appeared histologically similar. However, the transcriptomes of WISP3 -deficient tissues differed significantly from WISP3 -sufficient tissues and pointed to increased TGFβ, TNFα/NFkB, and IL-2/STAT5 signaling and decreased oxidative phosphorylation. Single cell sequencing and in situ hybridization revealed that WISP3 -deficient cartilage contained a significantly higher fraction (∼ 4-fold increase, p < 0.001) of superficial zone chondrocytes compared to deeper zone chondrocytes than did WISP3 -sufficient cartilage. Conclusions WISP3 -deficient and WISP3 -sufficient hPSCs can be differentiated into articular cartilage-like tissues, but these tissues differ in their transcriptomes and in the relative abundances of chondrocyte sub-types they contain. These findings provide important starting points for in vivo studies when an animal model of PPAC or presymptomtic patient-derived articular cartilage becomes available.

KEY MESSAGES

What is already known on this topic: Loss-of-function mutations in WISP3 cause Progressive Pseudorheumatoid Arthropathy of Childhood (PPAC), yet the precise function of WISP3 in cartilage is unknown due to the absence of cartilage disease Wisp3 knockout mice and the lack of available PPAC patient cartilage that is not end-stage. Thus, most functional studies of WISP3 have been performed in vitro using WISP3 over-expressing cell lines (i.e., not wild-type) and WISP3 -deficient chondrocytes. What this study adds: We describe 3 new WISP3 -deficient human pluripotent stem cell (hPSC) lines and show they can be differentiated into articular cartilage-like tissue. We compare in vitro -derived articular cartilage made from WISP3 -deficient and isogenic WISP3 - sufficient hPSCs using bulk RNA sequencing, single cell RNA sequencing, and in situ hybridization. We observe significant differences in the expression of genes previously associated with cartilage formation and homeostasis in the TGFβ, TNFα/NFkB, and IL-2/STAT5 signaling pathways. We also observe that WISP3-deficient cartilage-like tissues contain significantly higher fractions of chondrocytes that express superficial zone transcripts. These data suggest precocious cartilage failure in PPAC is the result of abnormal articular cartilage formation, dysregulated homeostatic signaling, or both.How this study might affect research, practice or policy: This study uses in vitro -derived articular cartilage to generate hypotheses for why cartilage fails in children with PPAC. This work prioritizes downstream studies to be performed when pre-symptomatic patient-derived cartilage samples or animal model of PPAC becomes available. It is essential to know how WISP3 functions in cartilage to develop therapies that benefit patients with PPAC and other degenerative joint diseases.

Nanofat lysate ameliorates pain and cartilage degradation of osteoarthritis through activation of TGF-β-Smad2/3 signaling of chondrocytes

Introduction: Nanofat is an effective cell therapy for osteoarthritis (OA). However, it has clinical limitations due to its short half-life. We developed Nanofat lysate (NFL) to overcome the defect of Nanofat and explore its anti-OA efficacy and mechanism. Methods: Monoiodoacetate (MIA) was employed to establish rat OA model. For pain assessment, paw withdrawal latency (PWL) and thermal withdrawal latency (TWL) were evaluated. Degeneration of cartilage was observed by histopathological and immunohistochemical examination. Primary chondrocytes were treated with TNF-α to establish the cellular model of OA. MTT, wound healing, and transwell assays were performed to assess effects of NFL on chondrocytes. RNA-seq, qPCR and Western blot assays were conducted to clarify the mechanism of NFL. Results and Discussion: The animal data showed that PWL and TWL values, Mankin's and OARSI scorings, and the Col2 expression in cartilage were significantly improved in the NFL-treated OA rats. The cellular data showed that NFL significantly improved the proliferation, wound healing, and migration of chondrocytes. The molecular data showed that NFL significantly restored the TNF-α-altered anabolic markers (Sox9, Col2 and ACAN) and catabolic markers (IL6 and Mmp13). The RNA-seq identified that TGF-β-Smad2/3 signaling pathway mediated the efficacy of NFL, which was verified by qPCR and Western blot that NFL significantly restored the abnormal expressions of TGFβR2, phosphorylated-Smad2, phosphorylated-Smad2/3, Col2, Mmp13 and Mmp3. After long-term storage, NFL exerted similar effects as its fresh type, indicating its advantage of storability. In sum, NFL was developed as a new therapeutic approach and its anti-OA efficacy and mechanism that mediated by TGF-β-Smad2/3 signaling was determined for the first time. Besides, the storability of NFL provided a substantial advantage than other living cell-based therapies.

SMAD3 mutation in LDS3 causes bone fragility by impairing the TGF-β pathway and enhancing osteoclastogenesis

Loss-of-function mutations in SMAD3 cause Loeys-Dietz syndrome type 3 (LDS3), a rare autosomal-dominant connective tissue disorder characterized by vascular pathology and skeletal abnormalities. Dysregulation of TGF-β/SMAD signaling is associated with abnormal skeletal features and bone fragility. To date, histomorphometric and ultrastructural characteristics of bone with SMAD3 mutations have not been reported in humans and the exact mechanism by which SMAD3 mutations cause the LDS3 phenotype is poorly understood. Here, we investigated bone histomorphometry and matrix mineralization in human bone with a SMAD3 mutation and explored the associated cellular defect in the TGF-β/SMAD pathway in vitro. The index patient had recurrent fractures, mild facial dysmorphism, arachnodactyly, pectus excavatum, chest asymmetry and kyphoscoliosis. Bone histomorphometry revealed markedly reduced cortical thickness (−68 %), trabecular thickness (−32 %), bone formation rate (−50 %) and delayed mineralization. Quantitative backscattered electron imaging demonstrated undermineralized bone matrix with increased heterogeneity in mineralization. The patient's SMAD3 mutation (c.200 T > G; p.I67S), when expressed from plasmid vectors in HEK293 cells, showed reduced phosphorylation and transcription factor activity compared to normal control and SMAD3 (p.S264Y), a gain-of-function mutation, somatic mosaicism of which causes melorheostosis. Transfection study of the patients' SMAD3 (p.I67S) mutation displayed lower luciferase reporter activity than normal SMAD3 and reduced expression of TGF-β signaling target genes. Patient fibroblasts also demonstrated impaired SMAD3 protein stability. Osteoclastogenic differentiation significantly increased and osteoclast-associated genes, including ACP5 (encoding TRAP), ATP6V0D2, and DCSTAMP, were up-regulated in CD14 (+) peripheral blood mononuclear cells (PBMCs) with the SMAD3 (p.I67S) mutation. Upregulation of osteoclastogenic genes was associated with decreased expression of TGF-β signaling target genes. We conclude that bone with the SMAD3 (p.I67S) mutation features reduced bone formation, and our functional studies revealed decreased SMAD3 activation and protein stability as well as increased osteoclastogenesis. These findings enhance our understanding of the pathophysiology of LDS3 caused by SMAD3 mutations. Emerging therapies targeting in the TGF-β/SMAD pathway also raise hope for treatment of LDS3.

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Increased bone fragility

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Low bone matrix mineralization

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SMAD3 (p.I67S) decreased TGF-b signaling and SMAD3 activity.

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SMAD3 (p.I67S) reduced SMAD3 protein stability.

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SMAD3 (p.I67S) mediated osteoclastogenesis.

Cytokine-primed umbilical cord mesenchymal stem cells enhanced therapeutic effects of extracellular vesicles on osteoarthritic chondrocytes

In recent years, extracellular vesicles (EVs) secreted by mesenchymal stem cells (MSCs) have emerged as a potential cell-free therapy against osteoarthritis (OA). Thus, we investigated the therapeutic effects of EVs released by cytokine-primed umbilical cord-derived MSCs (UCMSCs) on osteoarthritic chondrocyte physiology. Priming UCMSCs individually with transforming growth factor beta (TGFβ), interferon alpha (IFNα), or tumor necrosis factor alpha (TNFα) significantly reduced the sorting of miR-181b-3p but not miR-320a-3p; two negative regulators of chondrocyte regeneration, into EVs. However, the EV treatment did not show any significant effect on chondrocyte proliferation. Meanwhile, EVs from both non-priming and cytokine-primed UCMSCs induced migration at later time points of measurement. Moreover, TGFβ-primed UCMSCs secreted EVs that could upregulate the expression of chondrogenesis markers (COL2 and ACAN) and downregulate fibrotic markers (COL1 and RUNX2) in chondrocytes. Hence, priming UCMSCs with cytokines can deliver selective therapeutic effects of EV treatment in OA and chondrocyte-related disorders.

Analysis of the Anti-Inflammatory and Anti-Osteoarthritic Potential of Flonat Fast®, a Combination of Harpagophytum Procumbens DC. ex Meisn., Boswellia Serrata Roxb., Curcuma longa L., Bromelain and Escin (Aesculus hippocastanum), Evaluated in In Vitro Models of Inflammation Relevant to Osteoarthritis

Osteoarthritis (OA) is a joint disease characterized by inflammation of the synovium, angiogenesis, cartilage degradation, and osteophyte formation. Harpagophytum Procumbens DC. ex Meisn., Boswellia Serrata Roxb., Curcuma longa L., Bromelain and Escin (Aesculus hippocastanum) are plants which extracts, together to Bromelain and Escin (Aesculus hippocastanum) are traditionally used in OA. However, their mechanistic role remains unclear. We aimed to investigate whether these bioactives alone or in combination (as in Flonat Fast^®) can suppress TNF-α-induced inflammation, angiogenesis, and osteophyte formation using two cell models involved in OA: endothelial cells and monocytes. Each plant extract was evaluated for its polyphenol content, antioxidant activity, and toxicity. In endothelial cells and monocytes, expression of genes involved in OA was assessed, functional assays for inflammation and angiogenesis were performed, and impairment of reactive oxygen species production (ROS) was evaluated. Exposure of cells to the bioactives alone and in combination before cytokine stimulation resulted in differential counterregulation of several gene and protein expressions, including those for cyclooxygenases-2, metalloproteinase-9, transforming growth factor β1, and bone morphogenic protein-2. We demonstrated that these bioactives modulated monocyte adhesion to endothelial cells as well as cell migration and endothelial angiogenesis. Consistent with radical scavenging activity in the cell-free system, the bioactives curbed TNF-α-stimulated intracellular ROS production. We confirmed the potential anti-inflammatory and antiangiogenic effects of the combination of Harpagophytum procumbens, Boswellia, Curcuma, Bromelain, and Escin and provided new mechanistic evidence for their use in OA. However, further clinical studies are needed to evaluate the true clinical utility of these bioactives as supportive, preventive, and therapeutic agents.

Inflammation-Driven Secretion Potential Is Upregulated in Osteoarthritic Fibroblast-Like Synoviocytes

Osteoarthritis (OA) is one of the most common joint pathologies and a major cause of disability among the population of developed countries. It manifests as a gradual degeneration of the cartilage and subchondral part of the bone, leading to joint damage. Recent studies indicate that not only the cells that make up the articular cartilage but also the synoviocytes, which build the membrane surrounding the joint, contribute to the development of OA. Therefore, the aim of the study was to determine the response to inflammatory factors of osteoarthritic synoviocytes and to identify proteins secreted by them that may influence the progression of OA. This study demonstrated that fibroblast-like synoviocytes of OA patients (FLS-OA) respond more strongly to pro-inflammatory stimulation than cells obtained from control patients (FLS). These changes were observed at the transcriptome level and subsequently confirmed by protein analysis. FLS-OA stimulated by pro-inflammatory factors [such as lipopolysaccharide (LPS) and tumor necrosis factor alpha (TNFα) were shown to secrete significantly more chemokines (CXCL6, CXCL10, and CXCL16) and growth factors [angiopoietin-like protein 1 (ANGPTL1), fibroblast growth factor 5 (FGF5), and insulin-like growth factor 2 (IGF2)] than control cells. Moreover, the translation of proteolytic enzymes [matrix metalloprotease 3 (MMP3), cathepsin K (CTSK), and cathepsin S (CTSS)] by FLS-OA is increased under inflammatory conditions. Our data indicate that the FLS of OA patients are functionally altered, resulting in an enhanced response to the presence of pro-inflammatory factors in the environment, manifested by the increased production of the previously mentioned proteins, which may promote further disease progression.

SUMOylation in Skeletal Development, Homeostasis, and Disease

The modification of proteins by small ubiquitin-related modifier (SUMO) molecules, SUMOylation, is a key post-translational modification involved in a variety of biological processes, such as chromosome organization, DNA replication and repair, transcription, nuclear transport, and cell signaling transduction. In recent years, emerging evidence has shown that SUMOylation regulates the development and homeostasis of the skeletal system, with its dysregulation causing skeletal diseases, suggesting that SUMOylation pathways may serve as a promising therapeutic target. In this review, we summarize the current understanding of the molecular mechanisms by which SUMOylation pathways regulate skeletal cells in physiological and disease contexts.

HK2: a potential regulator of osteoarthritis via glycolytic and non-glycolytic pathways

Osteoarthritis (OA) is an age-related chronic degenerative joint disease where the main characteristics include progressive degeneration of cartilage, varying degrees of synovitis, and periarticular osteogenesis. However, the underlying factors involved in OA pathogenesis remain elusive which has resulted in poor clinical treatment effect. Recently, glucose metabolism changes provide a new perspective on the pathogenesis of OA. Under the stimulation of external environment, the metabolic pathway of chondrocytes tends to change from oxidative phosphorylation (OXPHOS) to aerobic glycolysis. Previous studies have demonstrated that glycolysis of synovial tissue is increased in OA. The hexokinase (HK) is the first rate limiting enzyme in aerobic glycolysis, participating and catalyzing the main pathway of glucose utilization. An isoform of HKs, HK2 is considered to be a key regulator of glucose metabolism, promotes the transformation of glycolysis from OXPHOS to aerobic glycolysis. Moreover, the expression level of HK2 in OA synovial tissue (FLS) was higher than that in control group, which indicated the potential therapeutic effect of HK2 in OA. However, there is no summary to help us understand the potential therapeutic role of glucose metabolism in OA. Therefore, this review focuses on the properties of HK2 and existing research concerning HK2 and OA. We also highlight the potential role and mechanism of HK2 in OA.

Progress of Noncoding RNA Regulating the Growth and Development of Antler Tissue Research

Antler is the secondary sexual characteristic of deer, which develops on the forehead at puberty. It is the only organ that can be regenerated entirely in mammals. Therefore, it is often used as a research model in the field of organ regeneration and wound repair. Many growth factors and proteins play an active role throughout the developmental process of antler regeneration. With the rapid development of sequencing technology, more and more noncoding RNAs (ncRNAs) have been discovered, and the relationship between ncRNA and antler regeneration has gradually become clear. This paper focuses on the research progress of several ncRNAs (including miRNA and lncRNA) in deer antler tissues, which are helpful to reveal the molecular mechanism of deer antler regeneration at the molecular level.

Multipotential Role of Growth Factor Mimetic Peptides for Osteochondral Tissue Engineering

Articular cartilage is characterized by a poor self-healing capacity due to its aneural and avascular nature. Once injured, it undergoes a series of catabolic processes which lead to its progressive degeneration and the onset of a severe chronic disease called osteoarthritis (OA). In OA, important alterations of the morpho-functional organization occur in the cartilage extracellular matrix, involving all the nearby tissues, including the subchondral bone. Osteochondral engineering, based on a perfect combination of cells, biomaterials and biomolecules, is becoming increasingly successful for the regeneration of injured cartilage and underlying subchondral bone tissue. To this end, recently, several peptides have been explored as active molecules and enrichment motifs for the functionalization of biomaterials due to their ability to be easily chemically synthesized, as well as their tunable physico-chemical features, low immunogenicity issues and functional group modeling properties. In addition, they have shown a good aptitude to penetrate into the tissue due to their small size and stability at room temperature. In particular, growth-factor-derived peptides can play multiple functions in bone and cartilage repair, exhibiting chondrogenic/osteogenic differentiation properties. Among the most studied peptides, great attention has been paid to transforming growth factor-β and bone morphogenetic protein mimetic peptides, cell-penetrating peptides, cell-binding peptides, self-assembling peptides and extracellular matrix-derived peptides. Moreover, recently, phage display technology is emerging as a powerful selection technique for obtaining functional peptides on a large scale and at a low cost. In particular, these peptides have demonstrated advantages such as high biocompatibility; the ability to be immobilized directly on chondro- and osteoinductive nanomaterials; and improving the cell attachment, differentiation, development and regeneration of osteochondral tissue. In this context, the aim of the present review was to go through the recent literature underlining the importance of studying novel functional motifs related to growth factor mimetic peptides that could be a useful tool in osteochondral repair strategies. Moreover, the review summarizes the current knowledge of the use of phage display peptides in osteochondral tissue regeneration.

Protective role of microRNA-23a/b-3p inhibition against osteoarthritis through Gremlin1-depenent activation of TGF-β/smad signaling in chondrocytesa

The changed biomechanical environment of chondrocytes elicited by altered extracellular matrix is reported to accelerate the progression of OA. MicroRNAs (miRNAs or miRs) have emerged as major regulators in chondrocyte function. Hence, we explored effect of miR-23a/b-3p on OA in regulating chondrocyte growth. The medial meniscus and anterior cruciate ligaments of right knee was removed to induce a mouse model of OA. miR-23a/b-3p and Gremlin1 (Grem1) expressions in OA were determined by RT-qPCR. Dual luciferase reporter gene assay was conducted to assess their relationship in the context of OA. Loss- and gain-of-function assays were adopted to clarify their effects on OA by determining the release of pro-inflammatory proteins and the apoptosis of chondrocytes. RT-qPCR determined increased miR-23a/b-3p expression and decreased Grem1 expression in the setting OA. Inhibiting miR-23a/b-3p or overexpressing Grem1 activated transforming growth factor-β/solvated metal atom dispersed 3 (TGF-β/Smad) signaling to prevent OA development. Silencing Grem1 ablated suppressive effects of miR-23a/b-3p inhibitor on the release of pro-inflammatory proteins and the apoptosis of chondrocytes. To conclude, inhibition of miR-23a/b-3p delays OA progression through Grem1-mediated activation of TGF-β/Smad signaling, contributing to deepen understanding of the pathogenesis of OA.

Nangibotide attenuates osteoarthritis by inhibiting osteoblast apoptosis and TGF-β activity in subchondral bone

Osteoarthritis (OA) is a chronic joint disorder that causes cartilage degradation and subchondral bone abnormalities. Nangibotide, also known as LR12, is a dodecapeptide with considerable anti-inflammatory properties, but its significance in OA is uncertain. The aim of the study was to determine whether nangibotide could attenuate the progression of OA, and elucidate the underlying mechanism. In vitro experiments showed that nangibotide strongly inhibited TNF-α-induced osteogenic reduction, significantly enhanced osteoblast proliferation and prevented apoptosis in MC3T3-E1 cells. Male C57BL/6 J mice aged 2 months were randomly allocated to three groups: sham, ACLT, and ACLT with nangibotide therapy. Nangibotide suppressed ACLT-induced cartilage degradation and MMP-13 expression. MicroCT analysis revealed that nangibotide attenuated in vivo subchondral bone loss induced by ACLT. Histomorphometry results showed that nangibotide attenuated ACLT-induced osteoblast inhibition; TUNEL assays and immunohistochemical staining of cleaved-caspase3 further confirmed the in vivo anti-apoptotic effect of nangibotide on osteoblasts. Furthermore, we found that nangibotide exerted protective effects by suppressing TGF-β signaling mediated by Smad2/3 to restore coupled bone remodeling in the subchondral bone. In conclusion, the findings suggest that nangibotide might exert a protective effect on the bone-cartilage unit and maybe an alternative treatment option for OA.

Identification of Transcription Factors Responsible for a Transforming Growth Factor-β-Driven Hypertrophy-like Phenotype in Human Osteoarthritic Chondrocytes

During osteoarthritis (OA), hypertrophy-like chondrocytes contribute to the disease process. TGF-β's signaling pathways can contribute to a hypertrophy(-like) phenotype in chondrocytes, especially at high doses of TGF-β. In this study, we examine which transcription factors (TFs) are activated and involved in TGF-β-dependent induction of a hypertrophy-like phenotype in human OA chondrocytes. We found that TGF-β, at levels found in synovial fluid in OA patients, induces hypertrophic differentiation, as characterized by increased expression of RUNX2, COL10A1, COL1A1, VEGFA and IHH. Using luciferase-based TF activity assays, we observed that the expression of these hypertrophy genes positively correlated to SMAD3:4, STAT3 and AP1 activity. Blocking these TFs using specific inhibitors for ALK-5-induced SMAD signaling (5 µM SB-505124), JAK-STAT signaling (1 µM Tofacitinib) and JNK signaling (10 µM SP-600125) led to the striking observation that only SB-505124 repressed the expression of hypertrophy factors in TGF-β-stimulated chondrocytes. Therefore, we conclude that ALK5 kinase activity is essential for TGF-β-induced expression of crucial hypertrophy factors in chondrocytes.

The Effects of TNF-α Inhibition on the Metabolism of Cartilage: Relationship between KS, HA, HAPLN1 and ADAMTS4, ADAMTS5, TOS and TGF-β1 Plasma Concentrations in Patients with Juvenile Idiopathic Arthritis

We assessed the effect of 24-month anti-tumor necrosis factor alpha (TNF-α) treatment on the remodeling of the cartilage extracellular matrix (ECM) in patients with juvenile idiopathic arthritis (JIA). Methods: Quantitative evaluation of keratan sulfate (KS), hyaluronic acid (HA), hyaluronan and proteoglycan link protein 1 (HAPLN1), as potential biomarkers of joint dysfunction, and the levels of a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) 4 and 5, total oxidative status (TOS) and transforming growth factor (TGF-β1) was performed (using immunoenzymatic methods) in blood obtained from patients before and after 24 months of etanercept (ETA) treatment. Results: When compared to the controls, KS, HA and HAPLN1 levels were significantly higher in patients with an aggressive course of JIA qualified for ETA treatment. An anti-cytokine therapy leading to clinical improvement promotes the normalization only of the HA level. Proteolytic and pro-oxidative factors, present in high concentrations in patients before the treatment, correlated with HAPLN1, but not with KS and HA levels. In these patients, negative correlations were found between the levels of TGF-β1 and KS, HA and HAPLN1. Conclusion: The anti-TNF-α therapy used in patients with JIA has a beneficial effect on ECM cartilage metabolism, but it does not completely regenerate it. The changes in the plasma HA level during the anti-cytokine therapy suggest its potential diagnostic utility in monitoring of disease activity and may be used to assess the efficacy of ETA treatment.

Grem1 accelerates nucleus pulposus cell apoptosis and intervertebral disc degeneration by inhibiting TGF-β-mediated Smad2/3 phosphorylation

Intervertebral disc degeneration (IVDD) is a main cause of low back pain, and inflammatory factors play key roles in its pathogenesis. Gremlin-1 (Grem1) was reported to induce an inflammatory response in other fields. This study aimed to investigate the mechanisms of Grem1 in the degenerative process of intervertebral discs. Dysregulated genes were determined by analyzing microarray profiles. The expression of Grem1 in 17 human disc samples (male:female = 9:8) and rat models (n = 5 each group) was measured by western blotting (WB), real-time quantitative PCR (RT-qPCR), and immunohistochemistry (IHC). The regulatory effects of Grem1 on apoptosis were examined using siRNAs, flow cytometry, immunofluorescence (IF), and WB. The therapeutic effect was evaluated by locally injecting specific Grem1 siRNA into IVDD rats. The expression of Grem1 was significantly increased in human degenerative intervertebral discs; furthermore, the expression of Grem1 positively correlated with the level of intervertebral disc degeneration. Grem1 was significantly overexpressed in tumor necrosis factor (TNF)-α-induced degenerative NP cells. Apoptosis in degenerative NP cells transfected with siRNA targeting Grem1 was significantly lower than that in the control group. Specific Grem1 siRNA markedly repressed the development of IVDD in surgery-induced IVDD rats. These results indicated that the expression of Grem1 was positively correlated with the severity of intervertebral disc degeneration, and Grem1 siRNA could inhibit Grem1-induced apoptosis and extracellular matrix alterations by mediating the TGF-β/Smad signaling pathway. This study may provide a therapeutic strategy for alleviating inflammation-induced apoptosis associated with intervertebral disc degeneration.

Tissue-Specific Methylation Biosignatures for Monitoring Diseases: An In Silico Approach

Tissue-specific gene methylation events are key to the pathogenesis of several diseases and can be utilized for diagnosis and monitoring. Here, we established an in silico pipeline to analyze high-throughput methylome datasets to identify specific methylation fingerprints in three pathological entities of major burden, i.e., breast cancer (BrCa), osteoarthritis (OA) and diabetes mellitus (DM). Differential methylation analysis was conducted to compare tissues/cells related to the pathology and different types of healthy tissues, revealing Differentially Methylated Genes (DMGs). Highly performing and low feature number biosignatures were built with automated machine learning, including: (1) a five-gene biosignature discriminating BrCa tissue from healthy tissues (AUC 0.987 and precision 0.987), (2) three equivalent OA cartilage-specific biosignatures containing four genes each (AUC 0.978 and precision 0.986) and (3) a four-gene pancreatic β-cell-specific biosignature (AUC 0.984 and precision 0.995). Next, the BrCa biosignature was validated using an independent ccfDNA dataset showing an AUC and precision of 1.000, verifying the biosignature’s applicability in liquid biopsy. Functional and protein interaction prediction analysis revealed that most DMGs identified are involved in pathways known to be related to the studied diseases or pointed to new ones. Overall, our data-driven approach contributes to the maximum exploitation of high-throughput methylome readings, helping to establish specific disease profiles to be applied in clinical practice and to understand human pathology.

Cross-Communication Between Knee Osteoarthritis and Fibrosis: Molecular Pathways and Key Molecules

Knee fibrosis is characterized by the presence of excessive connective tissue due to dysregulated fibroblast activation following local or systemic tissue damage. Knee fibrosis constitutes a major clinical problem in orthopaedics due to the severe limitation in the knee range of motion that leads to compromised function and patient disability. Knee osteoarthritis is an extremely common orthopedic condition that is associated with patient disability and major costs to the health-care systems worldwide. Although knee fibrosis and osteoarthritis (OA) have traditionally been perceived as two separate pathologic entities, recent research has shown common ground between the pathophysiologic processes that lead to the development of these two conditions. The purpose of this review was to identify the pathophysiologic pathways as well as key molecules that are implicated in the development of both knee OA and knee fibrosis in order to understand the relationship between the two diagnoses and potentially identify novel therapeutic targets.

Crosstalk Among circRNA/lncRNA, miRNA, and mRNA in Osteoarthritis

Osteoarthritis (OA) is a joint disease that is pervasive in life, and the incidence and mortality of OA are increasing, causing many adverse effects on people's life. Therefore, it is very vital to identify new biomarkers and therapeutic targets in the clinical diagnosis and treatment of OA. ncRNA is a nonprotein-coding RNA that does not translate into proteins but participates in protein translation. At the RNA level, it can perform biological functions. Many studies have found that miRNA, lncRNA, and circRNA are closely related to the course of OA and play important regulatory roles in transcription, post-transcription, and post-translation, which can be used as biological targets for the prevention, diagnosis, and treatment of OA. In this review, we summarized and described the various roles of different types of miRNA, lncRNA, and circRNA in OA, the roles of different lncRNA/circRNA-miRNA-mRNA axis in OA, and the possible prospects of these ncRNAs in clinical application.

Biomimetic Scaffolds Modulate the Posttraumatic Inflammatory Response in Articular Cartilage Contributing to Enhanced Neoformation of Cartilaginous Tissue In Vivo

Focal chondral lesions of the knee are the most frequent type of trauma in younger patients and are associated with a high risk of developing early posttraumatic osteoarthritis. The only current clinical solutions include microfracture, osteochondral grafting, and autologous chondrocyte implantation. Cartilage tissue engineering based on biomimetic scaffolds has become an appealing strategy to repair cartilage defects. Here, a chondrogenic collagen-chondroitin sulfate scaffold is tested in an orthotopic Lapine in vivo model to understand the beneficial effects of the immunomodulatory biomaterial on the full chondral defect. Using a combination of noninvasive imaging techniques, histological and whole transcriptome analysis, the scaffolds are shown to enhance the formation of cartilaginous tissue and suppression of host cartilage degeneration, while also supporting tissue integration and increased tissue regeneration over a 12 weeks recovery period. The results presented suggest that biomimetic materials could be a clinical solution for cartilage tissue repair, due to their ability to modulate the immune environment in favor of regenerative processes and suppression of cartilage degeneration.

Diversity of Vascular Niches in Bones and Joints During Homeostasis, Ageing, and Diseases

The bones and joints in the skeletal system are composed of diverse cell types, including vascular niches, bone cells, connective tissue cells and mineral deposits and regulate whole-body homeostasis. The capacity of maintaining strength and generation of blood lineages lies within the skeletal system. Bone harbours blood and immune cells and their progenitors, and vascular cells provide several immune cell type niches. Blood vessels in bone are phenotypically and functionally diverse, with distinct capillary subtypes exhibiting striking changes with age. The bone vasculature has a special impact on osteogenesis and haematopoiesis, and dysregulation of the vasculature is associated with diverse blood and bone diseases. Ageing is associated with perturbed haematopoiesis, loss of osteogenesis, increased adipogenesis and diminished immune response and immune cell production. Endothelial and perivascular cells impact immune cell production and play a crucial role during inflammation. Here, we discuss normal and maladapted vascular niches in bone during development, homeostasis, ageing and bone diseases such as rheumatoid arthritis and osteoarthritis. Further, we discuss the role of vascular niches during bone malignancy.

Causal effects of inflammatory protein biomarkers on inflammatory diseases

Many circulating proteins are associated with the presence or severity of disease. However, whether these protein biomarkers are causal for disease development is usually unknown. We investigated the causal effect of 21 well-known or exploratory protein biomarkers of inflammation on 18 inflammatory diseases using two-sample Mendelian randomization. We identified six proteins to have causal effects on any of 11 inflammatory diseases (FDR < 0.05, corresponding to P < 1.4 × 10^–3). IL-12B protects against psoriasis and psoriatic arthropathy, LAP-TGF-β-1 protects against osteoarthritis, TWEAK protects against asthma, VEGF-A protects against ulcerative colitis, and LT-α protects against both type 1 diabetes and rheumatoid arthritis. In contrast, IL-18R1 increases the risk of developing allergy, hay fever, and eczema. Most proteins showed protective effects against development of disease rather than increasing disease risk, which indicates that many disease-related biomarkers are expressed to protect from tissue damage. These proteins represent potential intervention points for disease prevention and treatment.

Evaluation of electroacupuncture for symptom modification in a rodent model of spontaneous osteoarthritis

OBJECTIVE

Faced with the frustration of chronic discomfort and restricted mobility due to osteoarthritis (OA), many individuals have turned to acupuncture for relief. However, the efficacy of acupuncture for OA is uncertain, as much of the evidence is inconclusive. The purpose of this study was to evaluate electroacupuncture (EA) in a rodent model of OA such that conclusions regarding its effectiveness for symptom or disease modification could be drawn.

METHODS

Ten 12-month-old male Hartley guinea pigs-which characteristically have moderate to advanced OA at this age-were randomly assigned to receive EA for knee OA (n = 5) or anesthesia only (control group, n = 5). Treatments were performed three times weekly for 3 weeks, followed by euthanasia 2 weeks later. Gait analysis and enclosure monitoring were performed weekly to evaluate changes in movement. Serum was collected for inflammatory biomarker testing. Knee joints were collected for histology and gene expression.

RESULTS

Animals receiving EA had significantly greater changes in movement parameters compared to those receiving anesthesia only. There was a tendency toward decreased serum protein concentrations of complement component 3 (C3) in the EA group compared to the control group. Structural and antioxidant gene transcripts in articular cartilage were increased by EA. There was no significant difference in total joint histology scores between groups.

CONCLUSION

This study provides evidence that EA has a positive effect on symptom, but not disease, modification in a rodent model of OA. Further investigations into mechanistic pathways that may explain the efficacy of EA in this animal model are needed.

FGD5-AS1 Inhibits Osteoarthritis Development by Modulating miR-302d-3p/TGFBR2 Axis

OBJECTIVE

Osteoarthritis (OA) is a common joint disorder, accompanied by extracellular matrix (ECM) degradation. Reportedly, long noncoding RNAs (lncRNAs) are involved in OA pathogenesis. However, the role of lncRNA FYVE, RhoGEF, and PH domain containing 5 antisense RNA 1 (FGD5-AS1) in OA development is still not fully clarified. This study was aimed to clarify the role of FGD5-AS1 in OA.

METHODS

FGD5-AS1 and miR-302d-3p expression levels were determined in cartilage tissues and chondrocytes by quantitative real-time polymerase chain reaction (qRT-PCR). Chondrocytes (C20/A4 cells) were stimulated with interleukin 1β (IL-1β) to mimic the inflammatory environment of OA. Cell viability was detected by cell counting kit-8 and 5-ethynyl-2'-deoxyuridine assays. Cell apoptosis was measured by the caspase-3 activity assay and flow cytometry. Transforming growth factor beta receptors II (TGFBR2), matrix metalloproteinase 13 (MMP-13), and ADAM metallopeptidase with thrombospondin type 1 motif 5 expression levels were examined by qRT-PCR or Western blot. The regulatory relationships among FGD5-AS1, miR-302d-3p, and TGFBR2 were predicted by the StarBase v2.0, miRanda, miRDB, and TargetScan databases, and confirmed by dual-luciferase reporter assay and RNA immunoprecipitation assay.

RESULTS

FGD5-AS1 and TGFBR2 expression levels were downregulated while miR-302d-3p expression was increased in cartilage tissues of OA patients. Knocking down FGD5-AS1 inhibited the viability of C20/A4 cells but induced apoptosis and ECM degradation, while FGD5-AS1 overexpression exerted opposite effects. MiR-302d-3p was identified as a target of FGD5-AS1, and TGFBR2 was identified as a target of miR-302d-3p. FGD5-AS1 positively regulated TGFBR2 expression by repressing miR-302d-3p expression, and miR-302d-3p inhibition or TGFBR2 restoration reversed the changes of cell viability, apoptosis, and ECM degradation induced by FGD5-AS1 knockdown.

CONCLUSION

FGD5-AS1 can probably inhibit OA progression by regulating miR-302d-3p/TGFBR2 axis.

Does Flipping the Tubercle for Improved Cartilage Repair Exposure Increase the Risk for Arthrofibrosis?

OBJECTIVE

We sought to determine whether rates of postoperative arthrofibrosis following tibial tuberosity osteotomy (TTO) with complete mobilization of the fragment (TTO-HD) are comparable to TTOs where the hinge remained intact (TTO-HI).

DESIGN

Patients who underwent TTO with concomitant cartilage repair procedure between January 2007 and May 2017, with at least 2 years of follow-up were included in this study. Postoperative reinterventions following TTO-HD and TTO-HI were assessed and multivariant logistic regression models were used to identify whether postoperative reinterventions can be attributed to either technique when controlled for defect size or defect number.

RESULTS

A total of 127 patients (TTO-HD, n = 80; TTO-HI, n = 47) were included in this study. Significantly more patients in the TTO-HD group (31.2%) developed postoperative arthrofibrosis compared with TTO-HI (6.4%; P < 0.05). Multivariant logistic regression revealed that TTO-HD is an independent risk factor for predicting postoperative arthrofibrosis (OR 6.5, CI = 1.7-24.2, P < 0.05).

CONCLUSION

Patients who underwent TTO with distal hinge detachment and a proximally flipped tubercle for better exposure during concomitant cartilage repair were at a significantly higher risk of postoperative arthrofibrosis than patients with similar size and number of defects treated without mobilization of the tubercle. While certain procedures can benefit from larger exposure, surgeons should be aware of the increased risk of postoperative arthrofibrosis.

LEVEL OF EVIDENCE

Level III, case-control study.

Top-Down Fabricated microPlates for Prolonged, Intra-articular Matrix Metalloproteinase 13 siRNA Nanocarrier Delivery to Reduce Post-traumatic Osteoarthritis

Post-traumatic osteoarthritis (PTOA) associated with joint injury triggers a degenerative cycle of matrix destruction and inflammatory signaling, leading to pain and loss of function. Here, prolonged RNA interference (RNAi) of matrix metalloproteinase 13 (MMP13) is tested as a PTOA disease modifying therapy. MMP13 is upregulated in PTOA and degrades the key cartilage structural protein type II collagen. Short interfering RNA (siRNA) loaded nanoparticles (siNPs) were encapsulated in shape-defined poly(lactic-co-glycolic acid) (PLGA) based microPlates (μPLs) to formulate siNP-μPLs that maintained siNPs in the joint significantly longer than delivery of free siNPs. Treatment with siNP-μPLs against MMP13 (siMMP13-μPLs) in a mechanical load-induced mouse model of PTOA maintained potent (65-75%) MMP13 gene expression knockdown and reduced MMP13 protein production in joint tissues throughout a 28-day study. MMP13 silencing reduced PTOA articular cartilage degradation/fibrillation, meniscal deterioration, synovial hyperplasia, osteophytes, and pro-inflammatory gene expression, supporting the therapeutic potential of long-lasting siMMP13-μPL therapy for PTOA.