A quality by design approach to optimise disulfide-linked hyaluronic acid hydrogels.

In this study, the disulfide-linked hyaluronic acid (HA) hydrogels were optimised for potential application as a scaffold in tissue engineering through the Quality by Design (QbD) approach. For this purpose, HA was first modified by incorporating the cysteine moiety into the HA backbone, which promoted the formation of disulfide cross-linked HA hydrogel at physiological pH. Utilising a Design of Experiments (DoE) methodology, the critical factors to achieve stable biomaterials, i.e. the degree of HA substitution, HA molecular weight, and coupling agent ratio, were explored. To establish a design space, the DoE was performed with 65 kDa, 138 kDa and 200 kDa HA and variable concentrations of coupling agent to optimise conditions to obtain HA hydrogel with improved rheological properties. Thus, HA hydrogel with a 12 % degree of modification, storage modulus of ≈2321 Pa and loss modulus of ≈15 Pa, was achieved with the optimum ratio of coupling agent. Furthermore, biocompatibility assessments in C28/I2 chondrocyte cells demonstrated the non-toxic nature of the hydrogel, underscoring its potential for tissue regeneration. Our findings highlight the efficacy of the QbD approach in designing HA hydrogels with tailored properties for biomedical applications.

Vitamin B6 alleviates osteoarthritis by suppressing inflammation and apoptosis.

BACKGROUND: Although various anti-inflammatory medicines are widely recommended for osteoarthritis (OA) treatment, no significantly clinical effect has been observed. This study aims to examine the effects of vitamin B6, a component that has been reported to be capable of alleviating inflammation and cell death in various diseases, on cartilage degeneration in OA. METHODS: Collagen-induced arthritis (CIA) mice model were established and the severity of OA in cartilage was determined using the Osteoarthritis Research Society International (OARSI) scoring system. The mRNA and protein levels of indicators associated with extracellular matrix (ECM) metabolism, apoptosis and inflammation were detected. The effect of vitamin B6 (VB6) on the mice were assessed using HE staining and masson staining. The apoptosis rate of cells was assessed using TdT-mediated dUTP nick end labeling. RESULTS: Our results showed a trend of improved OARSI score in mice treated with VB6, which remarkably inhibited the hyaline cartilage thickness, chondrocyte disordering, and knees hypertrophy. Moreover, the VB6 supplementation reduced the protein expression of pro-apoptosis indicators, including Bax and cleaved caspase-3 and raised the expression level of anti-apoptosis marker Bcl-2. Importantly, VB6 improved ECM metabolism in both in vivo and in vitro experiments. CONCLUSIONS: This study demonstrated that VB6 alleviates OA through regulating ECM metabolism, inflammation and apoptosis in chondrocytes and CIA mice. The findings in this study provide a theoretical basis for targeted therapy of OA, and further lay the theoretical foundation for studies of mechanisms of VB6 in treating OA.

Inhibition of CC chemokine receptor 1 ameliorates osteoarthritis in mouse by activating PPAR-γ.

BACKGROUND: Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage destruction and inflammation. CC chemokine receptor 1 (CCR1), a member of the chemokine family and its receptor family, plays a role in the autoimmune response. The impact of BX471, a specific small molecule inhibitor of CCR1, on CCR1 expression in cartilage and its effects on OA remain underexplored. METHODS: This study used immunohistochemistry (IHC) to assess CCR1 expression in IL-1ß-induced mouse chondrocytes and a medial meniscus mouse model of destabilization of the medial meniscus (DMM). Chondrocytes treated with varying concentrations of BX471 for 24 h were subjected to IL-1ß (10 ng/ml) treatment. The levels of the aging-related genes P16INK4a and P21CIP1 were analyzed via western blotting, and senescence-associated ß-galactosidase (SA-ß-gal) activity was measured. The expression levels of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), aggrecan (AGG), and the transcription factor SOX9 were determined through western blotting and RT‒qPCR. Collagen II, matrix metalloproteinase 13 (MMP13), and peroxisome proliferator-activated receptor (PPAR)-γ expression was analyzed via western blot, RT‒qPCR, and immunofluorescence. The impact of BX471 on inflammatory metabolism-related proteins under PPAR-γ inhibition conditions (using GW-9662) was examined through western blotting. The expression of MAPK signaling pathway-related molecules was assessed through western blotting. In vivo, various concentrations of BX471 or an equivalent medium were injected into DMM model joints. Cartilage destruction was evaluated through Safranin O/Fast green and hematoxylin-eosin (H&E) staining. RESULTS: This study revealed that inhibiting CCR1 mitigates IL-1ß-induced aging, downregulates the expression of iNOS, COX-2, and MMP13, and alleviates the IL-1ß-induced decrease in anabolic indices. Mechanistically, the MAPK signaling pathway and PPAR-γ may be involved in inhibiting the protective effect of CCR1 on chondrocytes. In vivo, BX471 protected cartilage in a DMM model. CONCLUSION: This study demonstrated the expression of CCR1 in chondrocytes. Inhibiting CCR1 reduced the inflammatory response, alleviated cartilage aging, and retarded degeneration through the MAPK signaling pathway and PPAR-γ, suggesting its potential therapeutic value for OA.

TPX2 upregulates MMP13 to promote the progression of lipopolysaccharide-induced osteoarthritis.

Purpose: This study seeks to identify potential clinical biomarkers for osteoarthritis (OA) using bioinformatics and investigate OA mechanisms through cellular assays. Methods: Differentially Expressed Genes (DEGs) from GSE52042 (four OA samples, four control samples) were screened and analyzed with protein-protein interaction (PPI) analysis. Overlapping genes in GSE52042 and GSE206848 (seven OA samples, and seven control samples) were identified and evaluated using Gene Set Enrichment Analysis (GSEA) and clinical diagnostic value analysis to determine the hub gene. Finally, whether and how the hub gene impacts LPS-induced OA progression was explored by in vitro experiments, including Western blotting (WB), co-immunoprecipitation (Co-IP), flow cytometry, etc. Result: Bioinformatics analysis of DEGs (142 up-regulated and 171 down-regulated) in GSE52042 identified two overlapping genes (U2AF2, TPX2) that exhibit significant clinical diagnostic value. These genes are up-regulated in OA samples from both GSE52042 and GSE206848 datasets. Notably, TPX2, which AUC = 0.873 was identified as the hub gene. In vitro experiments have demonstrated that silencing TPX2 can alleviate damage to chondrocytes induced by lipopolysaccharide (LPS). Furthermore, there is a protein interaction between TPX2 and MMP13 in OA. Excessive MMP13 can attenuate the effects of TPX2 knockdown on LPS-induced changes in OA protein expression, cell growth, and apoptosis. Conclusion: In conclusion, our findings shed light on the molecular mechanisms of OA and suggested TPX2 as a potential therapeutic target. TPX2 could promote the progression of LPS-induced OA by up-regulating the expression of MMP13, which provides some implications for clinical research.

Sericin promotes chondrogenic proliferation and differentiation via glycolysis and Smad2/3 TGF-ß 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-ß signaling pathway by upregulating Smad2 and Smad3 while downregulating Smad1, BMP2, and BMP4. Importantly, sericin exhibited an anti-inflammatory effect by reducing IL-1ß, 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-ß signaling pathways, and exhibiting anti-inflammatory properties.

Glucosamine and Silibinin Alter Cartilage Homeostasis through Glycosylation and Cellular Stresses in Human Chondrocyte Cells.

Osteoarthritis is more prevalent than any other form of arthritis and is characterized by the progressive mechanical deterioration of joints. Glucosamine, an amino monosaccharide, has been used for over fifty years as a dietary supplement to alleviate osteoarthritis-related discomfort. Silibinin, extracted from milk thistle, modifies the degree of glycosylation of target proteins, making it an essential component in the treatment of various diseases. In this study, we aimed to investigate the functional roles of glucosamine and silibinin in cartilage homeostasis using the TC28a2 cell line. Western blots showed that glucosamine suppressed the N-glycosylation of the gp130, EGFR, and N-cadherin proteins. Furthermore, both glucosamine and silibinin differentially decreased and increased target proteins such as gp130, Snail, and KLF4 in TC28a2 cells. We observed that both compounds dose-dependently induced the proliferation of TC28a2 cells. Our MitoSOX and DCFH-DA dye data showed that 1 µM glucosamine suppressed mitochondrial reactive oxygen species (ROS) generation and induced cytosol ROS generation, whereas silibinin induced both mitochondrial and cytosol ROS generation in TC28a2 cells. Our JC-1 data showed that glucosamine increased red aggregates, resulting in an increase in the red/green fluorescence intensity ratio, while all the tested silibinin concentrations increased the green monomers, resulting in decreases in the red/green ratio. We observed increasing subG1 and S populations and decreasing G1 and G2/M populations with increasing amounts of glucosamine, while increasing amounts of silibinin led to increases in subG1, S, and G2/M populations and decreases in G1 populations in TC28a2 cells. MTT data showed that both glucosamine and silibinin induced cytotoxicity in TC28a2 cells in a dose-dependent manner. Regarding endoplasmic reticulum stress, both compounds induced the expression of CHOP and increased the level of p-eIF2α/eIF2α. With respect to O-GlcNAcylation status, glucosamine and silibinin both reduced the levels of O-GlcNAc transferase and hypoxia-inducible factor 1 alpha. Furthermore, we examined proteins and mRNAs related to these processes. In summary, our findings demonstrated that these compounds differentially modulated cellular proliferation, mitochondrial and cytosol ROS generation, the mitochondrial membrane potential, the cell cycle profile, and autophagy. Therefore, we conclude that glucosamine and silibinin not only mediate glycosylation modifications but also regulate cellular processes in human chondrocytes.

TGF-ß2 Induces Ribosome Activity, Alters Ribosome Composition and Inhibits IRES-Mediated Translation in Chondrocytes.

Alterations in cell fate are often attributed to (epigenetic) regulation of gene expression. An emerging paradigm focuses on specialized ribosomes within a cell. However, little evidence exists for the dynamic regulation of ribosome composition and function. Here, we stimulated a chondrocytic cell line with transforming growth factor beta (TGF-ß2) and mapped changes in ribosome function, composition and ribosomal RNA (rRNA) epitranscriptomics. 35S Met/Cys incorporation was used to evaluate ribosome activity. Dual luciferase reporter assays were used to assess ribosomal modus. Ribosomal RNA expression and processing were determined by RT-qPCR, while RiboMethSeq and HydraPsiSeq were used to determine rRNA modification profiles. Label-free protein quantification of total cell lysates, isolated ribosomes and secreted proteins was done by LC-MS/MS. A three-day TGF-ß2 stimulation induced total protein synthesis in SW1353 chondrocytic cells and human articular chondrocytes. Specifically, TGF-ß2 induced cap-mediated protein synthesis, while IRES-mediated translation was not (P53 IRES) or little affected (CrPv IGR and HCV IRES). Three rRNA post-transcriptional modifications (PTMs) were affected by TGF-ß2 stimulation (18S-Gm1447 downregulated, 18S-ψ1177 and 28S-ψ4598 upregulated). Proteomic analysis of isolated ribosomes revealed increased interaction with eIF2 and tRNA ligases and decreased association of eIF4A3 and heterogeneous nuclear ribonucleoprotein (HNRNP)s. In addition, thirteen core ribosomal proteins were more present in ribosomes from TGF-ß2 stimulated cells, albeit with a modest fold change. A prolonged stimulation of chondrocytic cells with TGF-ß2 induced ribosome activity and changed the mode of translation. These functional changes could be coupled to alterations in accessory proteins in the ribosomal proteome.

Cathelicidin-BF regulates the AMPK/SIRT1/NF-κB pathway to ameliorate murine osteoarthritis: In vitro and in vivo studie.

Osteoarthritis (OA) is a chronic degenerative disease with a significant prevalence that causes cartilage damage and can lead to disability. The main factors contributing to the onset and progression of OA include inflammation and degeneration of the extracellular matrix. Cathelicidin-BF (BF-30), a natural peptide derived from Bungarus fasciatus venom, has shown multiple important pharmacological effects. However, the action mechanism of BF-30 in OA treatment remains to be elucidated. In this research, X-ray and Safranin O staining were employed to evaluate the imageology and histomorphology differences in the knee joints of mice in vivo. Techniques such as Western blot analysis, RT-qPCR, ELISA, and immunofluorescence staining were applied to examine gene and protein level changes in in vitro experiments. It was found that BF-30 significantly decreased inflammation and enhanced extracellular matrix metabolism. For the first time, it was demonstrated that the positive effects of BF-30 are mediated through the activation of the AMPK/SIRT1/NF-κB pathway. Moreover, when BF-30 was co-administered with Compound C, an AMPK inhibitor, the therapeutic benefits of BF-30 were reversed in both in vivo and in vitro settings. In conclusion, the findings suggest that BF-30 could be a novel therapeutic agent for OA improvement.

Development and functional evaluation of a hyaluronic acid coated nano-formulation with kaempferol as a novel intra-articular agent for Knee Osteoarthritis treatment.

Knee osteoarthritis (OA) involves articular cartilage degradation driven mainly by inflammation. Kaempferol (KM), known for its anti-inflammatory property, holds potential for OA treatment. This study investigated the potential of hyaluronic acid (HA)-coated gelatin nanoparticles loaded with KM (HA-KM GNP) for treating knee OA. KM was encapsulated into gelatin nanoparticles (KM GNP) and then coated with HA to form HA-KM GNPs. Physical properties were characterized, and biocompatibility and cellular uptake were assessed in rat chondrocytes. Anti-inflammatory and chondrogenic properties were evaluated using IL-1ß-stimulated rat chondrocytes, compared with HA-coated nanoparticles without KM (HA GNP) and KM alone. Preclinical efficacy was tested in an anterior cruciate ligament transection (ACLT)-induced knee OA rat model treated with intra-articular injection of HA-KM GNP. Results show spherical HA-KM GNPs (88.62 ± 3.90 nm) with positive surface charge. Encapsulation efficiency was 98.34 % with a sustained release rate of 18 % over 48 h. Non-toxic KM concentration was 2.5 µg/mL. In IL-1ß-stimulated OA rat chondrocytes, HA-KM GNP significantly down-regulated RNA expression of IL-1ß, TNF-α, COX-2, MMP-9, and MMP-13, while up-regulating SOX9 compared to HA GNP, and KM. In vivo imaging demonstrated significantly higher fluorescence intensity within rat knee joints for 3 hours post HA-KM GNP injection compared with KM GNP (185.2% ± 34.1% vs. 45.0% ± 16.7%). HA-KM GNP demonstrated significant effectiveness in reducing subchondral sclerosis, attenuating inflammation, inhibiting matrix degradation, restoring cartilage thickness, and reducing the severity of OA in the ACLT rat model. In conclusion, HA-KM GNP holds promise for knee OA therapy.

Vitamin K2 ameliorates osteoarthritis by suppressing ferroptosis and extracellular matrix degradation through activation GPX4's dual functions.

Vitamin K2 (VK2) is an effective compound for anti-ferroptosis and anti-osteoporosis, and Semen sojae praeparatum (Dandouchi in Chinese) is the main source of VK2. Chondrocyte ferroptosis and extracellular matrix (ECM) degradation playing a role in the pathogenesis of osteoarthritis (OA). Glutathione peroxidase 4 (GPX4) is the intersection of two mechanisms in regulating OA progression. But no studies have elucidated the therapeutic effects and mechanisms of VK2 on OA. This study utilized an in vivo rat OA model created via anterior cruciate ligament transection (ACLT) and an in vitro chondrocyte oxidative damage model induced by TBHP to investigate the protective effects and mechanisms of action of VK2 in OA. Knee joint pain in mice was evaluated using the Von Frey test. Micro-CT and Safranin O-Fast Green staining were employed to observe the extent of damage to the tibial cartilage and subchondral bone, while immunohistochemistry and PCR were used to examine GPX4 levels in joint cartilage. The effects of VK2 on rat chondrocyte viability were assessed using CCK-8 and flow cytometry assays, and chondrocyte morphology was observed with toluidine blue and alcian blue staining. The impact of VK2 on intracellular ferroptosis-related markers was observed using fluorescent staining and flow cytometry. Protein expression changes were detected by immunofluorescence and Western blot analysis. Furthermore, specific protein inhibitors were applied to confirm the dual-regulatory effects of VK2 on GPX4. VK2 can increase bone mass and cartilage thickness in the subchondral bone of the tibia, and reduce pain and the OARSI score induced by OA. Immunohistochemistry results indicate that VK2 exerts its anti-OA effects by regulating GPX4 to delay ECM degradation. VK2 can inhibit the activation of the MAPK/NFκB signaling pathway caused by reduced expression of intracellular GPX4, thereby decreasing ECM degradation. Additionally, VK2 can reverse the inhibitory effect of RSL3 on GPX4, increase intracellular GSH content and the GSH/GSSG ratio, reduce MDA content, and rescue chondrocyte ferroptosis. The protective mechanism of VK2 may involve its dual-target regulation of GPX4, reducing chondrocyte ferroptosis and inhibiting the MAPK/NFκB signaling pathway to decelerate the degradation of the chondrocyte extracellular matrix.

Tributyltin chloride induces chondrocyte damage through the activation of NLRP3­mediated inflammation and pyroptosis.

Tributyltin chloride (TBTC) is known to have effects and mechanisms in various diseases; however, whether TBTC is detrimental to joints and causes osteoarthritis (OA), as well as its underlying mechanism, has not yet been fully elucidated. The present study explored the effects of TBTC on rat chondrocytes, as well as on mouse OA. The toxicity of TBTC toward rat chondrocytes was detected using a lactate dehydrogenase (LDH) leakage assay and cell viability was evaluated using the Cell Counting Kit­8 assay. The results showed that TBTC decreased the viability of rat chondrocytes and increased the LDH leakage rate in a concentration­dependent manner. Moreover, compared with in the control group, TBTC increased the expression levels of interleukin (IL)­1ß, IL­18, matrix metalloproteinase (MMP)­1, MMP­13, NLR family pyrin domain containing 3 (NLRP3), caspase­1, PYD and CARD domain containing, and gasdermin D in chondrocytes. Furthermore, knockdown of NLRP3 reversed the TBTC­induced increases in LDH leakage and NLRP3 inflammasome­associated protein levels. In vivo, TBTC exacerbated cartilage tissue damage in mice from the OA group, as evidenced by the attenuation of safranin O staining. In conclusion, TBTC may aggravate OA in mice by promoting chondrocyte damage and inducing pyroptosis through the activation of NLRP3 and caspase­1 signaling. The present study demonstrated that TBTC can cause significant damage to the articular cartilage; therefore, TBTC contamination should be strictly monitored.

Botulinum toxin A attenuates osteoarthritis development via inhibiting chondrocyte ferroptosis through SLC7Al1/GPX4 axis.

Osteoarthritis (OA) is a prevalent joint degenerative disease, resulting in a significant societal burden. However, there is currently a lack of effective treatment option available. Previous studies have suggested that Botulinum toxin A (BONT/A), a macromolecular protein extracted from Clostridium Botulinum, may improve the pain and joint function in OA patients, but the mechanism remains elusive. This study was to investigate the impact and potential mechanism of BONT/A on OA in vivo and in vitro experiment. LPS increased the levels of ROS, Fe2+and Fe3+, as well as decreased GSH levels, the ratio of GSH / GSSH and mitochondrial membrane potential. It also enhanced the degeneration of extracellular matrix (ECM) and altered the ferroptosis-related protein expression in chondrocytes. BONT/A rescued LPS-induced decrease in collagen type II (Collagen II) expression and increase in matrix metalloproteinase 13 (MMP13), mitigated LPS-induced cytotoxicity in chondrocytes, abolished the accumulation of ROS and iron, upregulated GSH and the ratio of GSH/ GSSH, improved mitochondrial function, and promoted SLC7A11/GPX4 anti-ferroptosis system activation. Additionally, intra-articular injection of BONT/A inhibited the degradation of cartilage in OA model rats. This chondroprotective effect of BONT/A was reversed by erastin (a classical ferroptosis agonist) and enhanced by liproxstatin-1 (a classic ferroptosis inhibitor). Our research confirms that BONT/A alleviates the OA development by inhibiting the ferroptosis of chondrocytes, which revealed to be a potential therapeutic mechanism for BONT/A treating the OA.

Transforming growth factor-ß1-loaded RADA-16 hydrogel scaffold for effective cartilage regeneration.

Cartilage repair remains a major challenge in clinical trials. These current cartilage repair materials can not effectively promote chondrocyte generation, limiting their practical application in cartilage repair. In this work, we develop an implantable scaffold of RADA-16 peptide hydrogel incorporated with TGF-ß1 to provide a microenvironment for stem cell-directed differentiation and chondrocyte adhesion growth. The longest release of growth factor TGF-ß1 release can reach up to 600 h under physiological conditions. TGF-ß1/RADA-16 hydrogel was demonstrated to be a lamellar porous structure. Based on the cell culture with hBMSCs, TGF-ß1/RADA-16 hydrogel showed excellent ability to promote cell proliferation, directed differentiation into chondrocytes, and functional protein secretion. Within 14 days, 80% of hBMSCs were observed to be directed to differentiate into vigorous chondrocytes in the co-culture of TGF-ß1/RADA-16 hydrogels with hBMSCs. Specifically, these newly generated chondrocytes can secrete and accumulate large amounts of collagen II within 28 days, which can effectively promote the formation of cartilage tissue. Finally, the exploration of RADA-16 hydrogel-based scaffolds incorporated with TGF-ß1 bioactive species would further greatly promote the practical clinical trials of cartilage remediation, which might have excellent potential to promote cartilage regeneration in areas of cartilage damage.

Spinosin ameliorates osteoarthritis through enhancing the Nrf2/HO-1 signaling pathway.

Osteoarthritis (OA) is a common degenerative joint disease in the elderly, while oxidative stress-induced chondrocyte degeneration plays a key role in the pathologic progression of OA. One possible reason is that the expression of nuclear factor erythroid 2-related factor 2 (Nrf2), which acts as the intracellular defense factor against oxidative stress, is significantly inhibited in chondrocytes. Spinosin (SPI) is a potent Nrf2 agonist, but its effect on OA is still unknown. In this study, we found that SPI can alleviate tert-Butyl hydroperoxide (TBHP)-induced extracellular matrix degradation of chondrocytes. Additionally, SPI can effectively activate Nrf2, heme oxygenase-1 (HO-1), and NADPH quinone oxidoreductase 1 (NQO1) in chondrocytes under the TBHP environment. When Nrf2 was silenced by siRNA, the cartilage protective effect of SPI was also weakened. Finally, SPI showed good alleviative effects on OA in mice. Thus, SPI can ameliorate oxidative stress-induced chondrocyte dysfunction and exhibit a chondroprotective effect through activating the Nrf2/HO-1 pathway, which may provide a novel and promising option for the treatment of OA.

Low selenium and T-2 toxin may be involved in the pathogenesis of Kashin-Beck disease by affecting AMPK/mTOR/ULK1 pathway mediated autophagy.

Kashin-Beck disease (KBD) is an endemic, environmentally associated cartilage disease. Previous studies have shown that the environmental suspected pathogenic factors of KBD, T-2 toxin and low selenium, are involved in the regulation of inflammation, oxidative stress and autophagy in some tissues and organs. In cartilage diseases, the level of cellular autophagy determines the fate of the chondrocytes. However, whether autophagy is involved in KBD cartilage lesions, and the role of low selenium and T-2 toxins in KBD cartilage injury and autophagy are still unclear. This work took the classical AMPK/mTOR/ULK1 autophagy regulatory pathway as the entry point to clarify the relationship between the environmental suspected pathogenic factors and chondrocyte autophagy. Transmission electron microscopy was used to observe the autophagy of chondrocytes in KBD patients. qRT-PCR and western blot were used to analyze the expression of AMPK/mTOR/ULK1 pathway and autophagy markers. The rat model of KBD was established by low selenium and T-2 toxin, the autophagy in rat cartilage was detected after 4- and 12-week interventions. Chondrocyte autophagy was found in KBD, and the AMPK/mTOR/ULK1 pathway was down-regulated. In the rat model, the pathway showed an up-regulated trend when low selenium and T-2 toxin, were treated for a short time or low concentration, and autophagy level increased. However, when low selenium and T-2 toxin were treated for a long time or at high concentrations, the pathway showed a down-regulated trend, and the autophagy level was reduced and even defective. In conclusion, in the process of KBD cartilage lesion, chondrocyte autophagy level may increase in the early stage, and decrease in the late stage with the progression of lesion. Low selenium and T-2 toxins may affect autophagy by AMPK/mTOR/ULK1 pathway.

17ß-estradiol activates SOX6 to balance the anabolism and catabolism via estrogen receptor 2 in chondrocyte.

We investigated the influence of 17ß-estradiol (17ß-E2) on cartilage extracellular matrix (ECM) homeostasis in postmenopausal women. We focused on the roles of estrogen receptors (ESR) and SOX6 in 17ß-E2-mediated stimulation of ECM metabolism during chondrocyte (CH) degeneration. We compared the expression of anabolic genes (collagen II and aggrecan) and catabolic genes (MMPs and TIMPs) in IL-1ß-induced CH degeneration in vitro, with and without 17ß-E2 supplementation. We separately silenced the SOX6, ESR1, and ESR2 genes in CHs to determine their impact on 17ß-E2 treatment. Additionally, we used Chromatin immunoprecipitation followed by DNA sequencing (ChIP-seq) and luciferase assays to investigate protein-DNA interactions within ESR2 and SOX6-promoter complexes. After three days of IL-1ß treatment, ESR1/2, SOX6, collagen II, aggrecan, and TIMP1/3 were decreased, while MMP3/9/13 were increased. The addition of 17ß-E2 partially reversed these effects, but silencing SOX6, ESR1, or ESR2 weakened the protective effects of 17ß-E2. Silencing ESR2, but not ESR1, abolished the upregulation of SOX6 induced by 17ß-E2. ESR2 was found to bind the SOX6 promoter and regulate SOX6 expression. 17ß-E2 upregulates SOX6 through ESR2 mediation, and the synergistic effect of 17ß-E2 and ESR2 on SOX6 balances ECM metabolism in CHs.

PI15, a novel secreted WNT-signaling antagonist, regulates chondrocyte differentiation.

PURPOSE/AIM OF STUDY: During the development of the vertebrate skeleton, the progressive differentiation and maturation of chondrocytes from mesenchymal progenitors is precisely coordinated by multiple secreted factors and signaling pathways. The WNT signaling pathway has been demonstrated to play a major role in chondrogenesis. However, the identification of secreted factors that fine-tune WNT activity has remained elusive. Here, in this study, we have identified PI15 (peptidase inhibitor 15, protease Inhibitor 15, SugarCrisp), a member of the CAP (cysteine rich secretory proteins, antigen 5, and pathogenesis related 1 proteins) protein superfamily, as a novel secreted WNT antagonist dynamically upregulated during chondrocyte differentiation. MATERIALS AND METHODS: ATDC5 cells, C3H10T1/2 micromass cultures and primary chondrocyte cells were used as in vitro models of chondrogenesis. PI15 levels were stably depleted or overexpressed by viral shRNA or expression vectors. Chondrogenesis was evaluated by qPCR gene expression analysis and Alcian blue staining. Protein interactions were determined by coimmunoprecipitation assays. RESULTS AND CONCLUSIONS: shRNA-mediated knockdown of PI15 in ATDC5 cells, C3H10T1/2 cells or primary chondrocytes inhibits chondrogenesis, whereas the overexpression of PI15 strongly enhances chondrogenic potential. Mechanistically, PI15 binds to the LRP6 WNT co-receptor and blocks WNT-induced LRP6 phosphorylation, thus repressing WNT-induced transcriptional activity and alleviating the inhibitory effect of WNT signaling on chondrogenesis. Altogether, our findings suggest that PI15 acts as a key regulator of chondrogenesis and unveils a mechanism through which chondrocyte-derived molecules can modulate WNT activity as differentiation proceeds, thereby creating a positive feedback loop that further drives differentiation.

Mume Fructus reduces interleukin-1 beta-induced cartilage degradation via MAPK downregulation in rat articular chondrocytes.

Osteoarthritis is the most prevalent type of degenerative arthritis. It is characterized by persistent pain, joint dysfunction, and physical disability. Pain relief and inflammation control are prioritised during osteoarthritis treatment Mume Fructus (Omae), a fumigated product of the Prunus mume fruit, is used as a traditional medicine in several Asian countries. However, its therapeutic mechanism of action and effects on osteoarthritis and articular chondrocytes remain unknown. In this study, we analyzed the anti-osteoarthritis and articular regenerative effects of Mume Fructus extract on rat chondrocytes. Mume Fructus treatment reduced the interleukin-1ß-induced expression of matrix metalloproteinase 3, matrix metalloproteinase 13, and a disintegrin and metalloproteinase with thrombospondin type 1 motifs 5. Additionally, it enhanced collagen type II alpha 1 chain and aggrecan accumulation in rat chondrocytes. Furthermore, Mume Fructus treatment regulated the inflammatory cytokine levels, mitogen-activated protein kinase phosphorylation, and nuclear factor-kappa B activation. Overall, our results demonstrated that Mume Fructus inhibits osteoarthritis progression by inhibiting the nuclear factor-kappa B and mitogen-activated protein kinase pathways to reduce the levels of inflammatory cytokines and prevent cartilage degeneration. Therefore, Mume Fructus may be a potential therapeutic option for osteoarthritis.

[Mechanism of Tougu Xiaotong Capsules in delaying degeneration of osteoarthritis by regulating cholesterol metabolism in chondrocytes through lncRNA MALAT1].

From the perspective of lncRNA MALAT1 regulating cholesterol metabolism in chondrocytes, this paper explores the effect and mechanism of Tougu Xiaotong Capsules(TGXTC) in delaying the degeneration of osteoarthritis. After one week of adaptive feeding, 48(8-week-old) C57BL/6 mice were randomly divided into a blank group(12 mice) and a model group(36 mice) by random number table method. The mice in the model group were anesthetized by inhalation of 5% isoflurane, and the OA model was induced by Hulth method. The experiment randomly divided the mice into a model group(12 mice), a drug-positive group(taururso-deoxycholic acid)(12 mice), and a TGXTC group(12 mice). The drug-positive group was given 500 mg·kg~(-1) taurodeoxycholic acid by intragastric administration. TGXTC group was given TGXTC 368 mg·kg~(-1) by gavage. The blank group and model group were given the same amount of normal saline for four weeks. After the intervention, the mice in each group were killed under anesthesia, and the knee cartilage tissue was separated and collected. The morphologic changes of knee cartilage were observed. The level of lncRNA MALAT1 in the cartilage tissue was detected by real-time PCR. The protein expressions of ABCA1, ApoA1, LXRß, CHOP, and caspase-3 in mouse articular cartilage were detected by Western blot. Lentivirus-coated plasmid was used to transfect mouse chondrocytes with sh-MALAT1. The gene levels of lncRNA MALAT1 in mouse chondrocytes transfected with sh-MALAT1 were detected by real-time PCR. Western blot was used to detect the effect of TGXTC on the protein content of ABCA1, ApoA1, LXRß, CHOP, and caspase-3 in thapsigargin(TG)-induced mouse chondrocytes after lncRNA MALAT1 knockdown. Flow cytometry was used to detect the effect of TGXTC on apoptosis of TG-induced mouse chondrocytes after lncRNA MALAT1 knockdown. The results of HE and saffranine O staining showed that compared with the model group, the structure of the cartilage layer was basically intact; the damage degree of joint structure was significantly improved, and the cartilage matrix was significantly enhanced by saffranine O staining in the TGXTC group and drug-positive group. Compared with the model group, the lncRNA MALAT1 level was significantly decreased in the TGXTC group and drug-positive group. Compared with the model group, the protein content of ABCA1, ApoA1, and LXRß was significantly increased, while that of CHOP and caspase-3 in the TGXTC group and drug-positive group significantly decreased. Compared with the TG group, the lncRNA MALAT1 level in the TG+sh-MALAT1 group was decreased. The lncRNA MALAT1 level in the TG+sh-MA-LAT1+TGXTC group was increased compared with the TG+TGXTC group. Western blot results showed that compared with the model group, protein expressions of ABCA1, ApoA1, LXRß, CHOP, and caspase-3 in the TGXTC group were significantly decreased, after lncRNA MALAT1 knockdown, the regulation and apoptosis of ABCA1, ApoA1, LXRß, CHOP, and caspase-3 in TG-induced mouse chondrocytes were weakened by TGXTC. TGXTC can improve the disorder of cholesterol metabolism in OA chondrocytes and delay OA degeneration, which is closely related to the regulation of lncRNA MALAT1.

In vitro and in vivo investigation of chitosan/silk fibroin injectable interpenetrating network hydrogel with microspheres for cartilage regeneration.

Articular cartilage is an avascular and almost acellular tissue with limited self-regenerating capabilities. Although injectable hydrogels have garnered a lot of attention as a promising treatment, a biocompatible hydrogel with adequate mechanical properties is yet to be created. In this study, an interpenetrating network hydrogel comprised of chitosan and silk fibroin was created through electrostatic and hydrophobic bonds, respectively. The polymeric network of the scaffold combined an effective microenvironment for cell activity with enhanced mechanical properties to address the current issues in cartilage scaffolds. Furthermore, microspheres (MS) were utilized for a controlled release of methylprednisolone acetate (MPA), around ~75 % after 35 days. The proposed scaffolds demonstrated great mechanical stability with ~0.047 MPa compressive moduli and ~145 kPa compressive strength. Moreover, the degradation rate of the samples (~45 % after 35 days) was optimized to match neo-cartilage formation. Furthermore, the use of natural biomaterials yielded good biocompatibility with ~76 % chondrocyte viability after 7 days. According to gross observation after 12 weeks the defect site of the treated groups was filled with minimally discernible boundary. These results were confirmed by histopathology assays were the treated groups showed higher chondrocyte count and collagen type II expression.