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.

The Role of Copper-Induced M2 Macrophage Polarization in Protecting Cartilage Matrix in Osteoarthritis.

BACKGROUND The pathological mechanism of osteoarthritis is still unclear. The regulation of the immune microenvironment has been of growing interest in the progression and treatment of osteoarthritis. Macrophages with different phenotypes, producing different cytokines, have been linked to the mechanism of cartilage injury in osteoarthritis. Copper ions play a role in the immune response and are involved in the pathological mechanisms of osteoarthritis by affecting the metabolism of the cartilage matrix. Bioactive glass (BG) is an osteogenic material with superior biocompatibility. Here, we report on the regulatory behavior of macrophages using a copper-based composite BG material. MATERIAL AND METHODS Cu-BGC powder was prepared by sol-gel method, and scaffolds were fabricated and characterized using 3D printing. Macrophage cultures grown with Cu-BGC were examined for cell culture and proliferation. The effect of Cu-BGC on the degradation metabolism of chondrocytes, cultured in the environment of inflammatory cytokine IL-1ß, was determined. In addition, the morphology of macrophages, secretion of inflammatory cytokines, and expression of surface markers were examined. RESULTS The results show that Cu-BGC promotes macrophage proliferation at a range of concentrations and increases the secretion of anti-inflammatory cytokines while inhibiting proinflammatory cytokines. At the same time, M2-type cell surface markers are definitely expressed and the morphology of macrophages is altered. In addition, Cu-BGC inhibited the degradation metabolism of chondrocytes in the inflammatory environment induced by IL-1ß. CONCLUSIONS These results suggest that Cu-BGC induced macrophage polarization into an M2 type anti-inflammatory phenotype, and inhibition of immune injury response may play a role in delaying cartilage matrix damage in osteoarthritis.

HIF-1α in cartilage homeostasis, apoptosis, and glycolysis in mice with steroid-induced osteonecrosis of the femoral head.

With the prevalence of coronavirus disease 2019, the administration of glucocorticoids (GCs) has become more widespread. Treatment with high-dose GCs leads to a variety of problems, of which steroid-induced osteonecrosis of the femoral head (SONFH) is the most concerning. Since hypoxia-inducible factor 1α (HIF-1α) is a key factor in cartilage development and homeostasis, it may play an important role in the development of SONFH. In this study, SONFH models were established using methylprednisolone (MPS) in mouse and its proliferating chondrocytes to investigate the role of HIF-1α in cartilage differentiation, extracellular matrix (ECM) homeostasis, apoptosis and glycolysis in SONFH mice. The results showed that MPS successfully induced SONFH in vivo and vitro, and MPS-treated cartilage and chondrocytes demonstrated disturbed ECM homeostasis, significantly increased chondrocyte apoptosis rate and glycolysis level. However, compared with normal mice, not only the expression of genes related to collagens and glycolysis, but also chondrocyte apoptosis did not demonstrate significant differences in mice co-treated with MPS and HIF-1α inhibitor. And the effects observed in HIF-1α activator-treated chondrocytes were similar to those induced by MPS. And HIF-1α degraded collagens in cartilage by upregulating its downstream target genes matrix metalloproteinases. The results of activator/inhibitor of endoplasmic reticulum stress (ERS) pathway revealed that the high apoptosis rate induced by MPS was related to the ERS pathway, which was also affected by HIF-1α. Furthermore, HIF-1α affected glucose metabolism in cartilage by increasing the expression of glycolysis-related genes. In conclusion, HIF-1α plays a vital role in the pathogenesis of SONFH by regulating ECM homeostasis, chondrocyte apoptosis, and glycolysis.

Collagen short nanofiber-embedded chondroitin sulfate-hyaluronic acid nanocomposite: A cartilage-mimicking in situ-forming hydrogel with fine-tuned properties.

In situ-forming hydrogels that possess the ability to be injected in a less invasive manner and mimic the biochemical composition and microarchitecture of the native cartilage extracellular matrix are desired for cartilage tissue engineering. Besides, gelation time and stiffness of the hydrogel are two interdependent factors that affect cells' distribution and fate and hence need to be optimized. This study presented a bioinspired in situ-forming hydrogel composite of hyaluronic acid (HA), chondroitin sulfate (CS), and collagen short nanofiber (CSNF). HA and CS were functionalized with aldehyde and amine groups to form a gel through a Schiff-base reaction. CSNF was fabricated via electrospinning, followed by fragmentation by ultrasonics. Gelation time (11-360 s) and compressive modulus (1.4-16.2 kPa) were obtained by varying the concentrations of CS, HA, CSNFs, and CSNFs length. The biodegradability and biocompatibility of the hydrogels with varying gelation and stiffness were also assessed in vitro and in vivo. At three weeks, the assessment of hydrogels' chondrogenic differentiation also yields varying levels of chondrogenic differentiation. The subcutaneous implantation of the hydrogels in a mouse model indicated no severe inflammation. Results demonstrated that the injectable CS/HA@CSNF hydrogel was a promising hydrogel for tissue engineering and cartilage regeneration.

Ruscogenin attenuates cartilage destruction in osteoarthritis through suppressing chondrocyte ferroptosis via Nrf2/SLC7A11/GPX4 signaling pathway.

Osteoarthritis (OA) is a common joint degenerative disease, and chondrocyte injury is the main pathological and physiological change. Ruscogenin (Rus), a bioactive compound isolated from Radix Ophiopogon japonicus, exhibits various pharmacological effects. The aim of this research was to test the role and mechanism of Rus on OA both in vivo and in vitro. Destabilized medial meniscus (DMM)-induced OA model was established in vivo and IL-1ß-stimulated mouse chondrocytes was used to explore the role of Rus on OA in vitro. In vivo, Rus exhibited protective effects against DMM-induced OA model. Rus could inhibit MMP1 and MMP3 expression in OA mice. In vitro, IL-1ß-induced inflammation and degradation of extracellular matrix were inhibited by Rus, as confirmed by the inhibition of PGE2, NO, MMP1, and MMP3 by Rus. Also, IL-1ß-induced ferroptosis was suppressed by Rus, as confirmed by the inhibition of MDA, iron, and ROS, as well as the upregulation of GSH, GPX4, Ferritin, Nrf2, and SLC7A11 expression induced by Rus. Furthermore, the suppression of Rus on IL-1ß-induced inflammation, MMPs production, and ferroptosis were reversed when Nrf2 was knockdown. In conclusion, Rus attenuated OA progression through inhibiting chondrocyte ferroptosis via Nrf2/SLC7A11/GPX4 signaling pathway.

Investigation of the efficacy of epidermal growth factor, boric acid and their combination in cartilage injury in rats: An experimental study.

OBJECTIVES: In this study, we aimed to determine the bioefficacy of epidermal growth factor (EGF), boric acid (BA), and their combination on cartilage injury in rats. MATERIALS AND METHODS: In in vitro setting, the cytotoxic effects of BA, EGF, and their combinations using mouse fibroblast cell (L929), human bone osteosarcoma cell (Saos-2), and human adipose derived mesenchymal stem cells (hAD-MSCs) were determined by applying MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] test. In in vivo setting, 72 rats were randomly divided into four groups. A standard chondral defect was created and microfracture was performed in all groups. Group A was determined as the control group. In addition to the standard procedure, Group B received 100 ng/mL of EGF, Group C received a combination of 100 ng/mL of EGF and 10 µg/mL of BA combination, and Group D 20 µg/mL of BA. RESULTS: The cytotoxic effect of the combinations of EGF dilutions (1, 5, 10, 25, 50, 100, 200 ng/mL) with BA (100, 300, 500 µg/mL) was observed only in the 72-h application period and in Saos-2. The cytotoxic effect of BA was reduced when combined with EGF. There was no significant difference in the histopathological scores among the groups (p=0.13). CONCLUSION: Our study showed that EGF and low-dose BA application had a positive effect on cartilage healing in rats. Significant decreases in recovery scores were observed in the other groups. The combination of EGF and BA promoted osteoblast growth. Detection of lytic lesions in the group treated with 20 µg/mL of BA indicates that BA may have a cytotoxic effect.

A single-cell mass cytometry platform to map the effects of preclinical drugs on cartilage homeostasis.

No disease-modifying drug exists for osteoarthritis (OA). Despite success in animal models, candidate drugs continue to fail in clinical trials owing to the unmapped interpatient heterogeneity and disease complexity. We used a single-cell platform based on cytometry by time-of-flight (cyTOF) to precisely outline the effects of candidate drugs on human OA chondrocytes. OA chondrocytes harvested from patients undergoing total knee arthroplasty were treated with 2 drugs, an NF-κB pathway inhibitor, BMS-345541, and a chondroinductive small molecule, kartogenin, that showed preclinical success in animal models for OA. cyTOF conducted with 30 metal isotope-labeled antibodies parsed the effects of the drugs on inflammatory, senescent, and chondroprogenitor cell populations. The NF-κB pathway inhibition decreased the expression of p-NF-κB, HIF2A, and inducible NOS in multiple chondrocyte clusters and significantly depleted 4 p16ink4a-expressing senescent populations, including NOTCH1+STRO1+ chondroprogenitor cells. While kartogenin also affected select p16ink4a-expressing senescent clusters, there was a less discernible effect on chondroprogenitor cell populations. Overall, BMS-345541 elicited a uniform drug response in all patients, while only a few responded to kartogenin. These studies demonstrate that a single-cell cyTOF-based drug screening platform can provide insights into patient response assessment and patient stratification.

Exposure to endocrine disruptors and alterations in mineralized tissues: a narrative review / Exposición a disruptores endocrinos y alteraciones en tejidos mineralizados: revisión narrativa

Background: Endocrine Disrupting Chemicals (EDCs) would cause alterations in organs/systems of exposed individuals or their progeny. Objetive: To identify and analyze the main published findings on the effects of exposure to EDCs on teeth, cartilage, and bone. Material and Methods: Two databases were analyzed: Medline and Web of Science. Only observational studies analyzing the effect of EDCs on mineralized tissues published since 2006 were included in the study. Results: 25 articles were selected, most of them involving EDCs pesticides, plasticizers, or personal care products, highlighting organochlorine compounds, bisphenols, phthalates, dioxins, parabens, and perfluoroalkyls. Thirty-six per cent of the studies reported an accumulation of EDCs in teeth or bones, while 64% reported alterations in their development or morphology, mainly at the bone level, primarily affecting their mineral density and size, as well as that of the bones of exposed individuals or their progeny. The type of effect observed was related to the EDCs analyzed, and it seemed to depend on variables such as age, sex, ethnicity/race, and even the metabolic status of the individuals in the different species analyzed. No evidence associated with effects on cartilage was found. Conclusion: EDCs in the environment, at work, or at home, under different exposure routes, are capable of accumulating in teeth and bone, particularly affecting the latter. It is necessary to study the effect of EDCs on mineralized tissues in agro-industrial areas, especially on teeth.

Antecedentes: Los Químicos Disruptores Endocrinos (EDCs) causarían alteraciones en órganos/sistemas de individuos expuestos, o su progenie. Objetivo: Identificar y analizar los principales hallazgos publicados sobre el efecto de la exposición a EDCs en dientes, cartílago y hueso. Material y Métodos: Se analizaron dos bases de datos: Medline y Web of Science, incluyendo solo estudios observacionales publicados desde el 2006, analizando el efecto de los EDCs sobre tejidos mineralizados. Resultados:25 artículos fueron seleccionados, siendo la mayoría de los EDCs pesticidas, plastificantes o productos de cuidado personal, destacando los compuestos Organo-clorados, Bisfenoles, Ftalatos, Dioxinas, Parabenos y los Perfluoroalquilos. Un 36% de los estudios reportaron un acúmulo de EDCs en dientes o huesos, mientras que un 64% informaron de alteraciones en su desarrollo o morfología, particularmente a nivel de huesos, afectando principalmente su densidad mineral y su tamaño, así como el de los individuos expuestos o su progenie. El tipo de efecto observado tuvo relación con el EDCs analizado, pareciendo depender de variables tales como edad, sexo, etnia/raza e incluso el estado metabólico de los individuos, en las diferentes especies analizadas. No se encontraron evidencias asociadas a efectos en el cartílago. Conclusión: Los EDCs en el medio ambiente, ámbito laboral o doméstico, bajo distintas rutas de exposición, son capaces de acumularse en diente y hueso, afectando particularmente a este último. Es necesario estudiar el efecto de los EDCs en los tejidos mineralizados en zonas agroindustriales, particularmente a nivel de dientes.

Ononin ameliorates inflammation and cartilage degradation in rat chondrocytes with IL-1ß-induced osteoarthritis by downregulating the MAPK and NF-κB pathways.

BACKGROUND: Osteoarthritis (OA) treatment aims to improve inflammation and delay cartilage degeneration. However, there is no effective strategy presently available. Ononin, a representative isoflavone glycoside component extracted from natural Chinese herbs, exerts anti-inflammatory and proliferative effects. However, the therapeutic effect of ononin on chondrocyte inflammation remains unclear. METHODS: In this study, we explored the therapeutic effect and potential mechanism of ononin in OA by establishing an interleukin-1 beta (IL-1ß)-induced chondrocyte inflammation model. RESULTS: Our results verified that ononin alleviated the IL-1ß-induced decrease in chondrocyte viability, attenuated the overexpression of the inflammatory factors tumour necrosis factor α (TNF-α) and interleukin 6 (IL-6), and simultaneously inhibited the expression of cartilage extracellular matrix (ECM)-degrading enzymes such as matrix metalloproteinase-13 (MMP-13). Furthermore, the decomposition of Collagen II protein could be alleviated in the OA model by ononin. Finally, ononin improved chondrocyte inflammation by downregulating the mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) signalling pathways. CONCLUSION: Our findings suggested that ononin could inhibit the IL-1ß-induced proinflammatory response and ECM degradation in chondrocytes by interfering with the abnormal activation of the MAPK and NF-κB pathways, indicating its protective effect against OA.

Engineering osteoarthritic cartilage model through differentiating senescent human mesenchymal stem cells for testing disease-modifying drugs.

Significant cellular senescence has been observed in cartilage harvested from patients with osteoarthritis (OA). In this study, we aim to develop a senescence-relevant OA-like cartilage model for developing disease-modifying OA drugs (DMOADs). Specifically, human bone marrow-derived mesenchymal stromal cells (MSCs) were expanded in vitro up to passage 10 (P10-MSCs). Following their senescent phenotype formation, P10-MSCs were subjected to pellet culture in chondrogenic medium. Results from qRT-PCR, histology, and immunostaining indicated that cartilage generated from P10-MSCs displayed both senescent and OA-like phenotypes without using other OA-inducing agents, when compared to that from normal passage 4 (P4)-MSCs. Interestingly, the same gene expression differences observed between P4-MSCs and P10-MSC-derived cartilage tissues were also observed between the preserved and damaged OA cartilage regions taken from human samples, as demonstrated by RNA Sequencing data and other analysis methods. Lastly, the utility of this senescence-initiated OA-like cartilage model in drug development was assessed by testing several potential DMOADs and senolytics. The results suggest that pre-existing cellular senescence can induce the generation of OA-like changes in cartilage. The P4- and P10-MSCs derived cartilage models also represent a novel platform for predicting the efficacy and toxicity of potential DMOADs on both preserved and damaged cartilage in humans.

Sulfated Hydrogels in Intervertebral Disc and Cartilage Research.

Hydrogels are commonly used for the 3D culture of musculoskeletal cells. Sulfated hydrogels, which have seen a growing interest over the past years, provide a microenvironment that help maintain the phenotype of chondrocytes and chondrocyte-like cells and can be used for sustained delivery of growth factors and other drugs. Sulfated hydrogels are hence valuable tools to improve cartilage and intervertebral disc tissue engineering. To further advance the utilization of these hydrogels, we identify and summarize the current knowledge about different sulfated hydrogels, highlight their beneficial effects in cartilage and disc research, and review the biofabrication processes most suitable to secure best quality assurance through deposition fidelity, repeatability, and attainment of biocompatible morphologies.

Inhibition of SYK and cSrc kinases can protect bone and cartilage in preclinical models of osteoarthritis and rheumatoid arthritis.

The pathophysiology of osteoarthritis (OA) includes the destruction of subchondral bone tissue and inflammation of the synovium. Thus, an effective disease-modifying treatment should act on both of these pathogenetic components. It is known that cSrc kinase is involved in bone and cartilage remodeling, and SYK kinase is associated with the inflammatory component. Thus the aim of this study was to characterize the mechanism of action and efficacy of a small molecule multikinase inhibitor MT-SYK-03 targeting SYK and cSrc kinases among others in different in vitro and in vivo arthritis models. The selectivity of MT-SYK-03 kinase inhibition was assayed on a panel of 341 kinases. The compound was evaluated in a set of in vitro models of OA and in vivo OA and RA models: surgically-induced arthritis (SIA), monosodium iodoacetate-induced arthritis (MIA), collagen-induced arthritis (CIA), adjuvant-induced arthritis (AIA). MT-SYK-03 inhibited cSrc and SYK with IC50 of 14.2 and 23 nM respectively. Only five kinases were inhibited > 90% at 500 nM of MT-SYK-03. In in vitro OA models MT-SYK-03 reduced hypertrophic changes of chondrocytes, bone resorption, and inhibited SYK-mediated inflammatory signaling. MT-SYK-03 showed preferential distribution to joint and bone tissue (in rats) and revealed disease-modifying activity in vivo by halving the depth of cartilage erosion in rat SIA model, and increasing the pain threshold in rat MIA model. Chondroprotective and antiresorptive effects were shown in a monotherapy regime and in combination with methotrexate (MTX) in murine and rat CIA models; an immune-mediated inflammation in rat AIA model was decreased. The obtained preclinical data support inhibition of cSrc and SYK as a viable strategy for disease-modifying treatment of OA. A Phase 2 clinical study of MT-SYK-03 is to be started.

MCC950, the NLRP3 Inhibitor, Protects against Cartilage Degradation in a Mouse Model of Osteoarthritis.

Osteoarthritis (OA), characterized by chronic systemic low-level inflammation and cartilage degeneration, is a type of arthritis closely associated with aging. Inflammation and aging play a pivotal role in the occurrence and progression of OA. NLRP3 inflammasome is involved in many inflammatory and aging diseases, and NLRP3 inhibitor MCC950 has anti-inflammatory and antisenescence effects on some diseases such as Alzheimer's disease. In the present study, we found that NLRP3 protein was upregulated in human and mouse OA cartilage. Moreover, NLRP3 and Caspase1 expression induced by IL-1ß in chondrocytes was blocked by MCC950. In addition, MCC950 inhibited the expression of inflammatory mediators, matrix-degrading enzymes, senescence marker protein P16 (INK4A), and ß-galactosidase, as well as excessive production of ROS. Meanwhile, MCC950 promoted autophagy-related protein expression and autophagy flux under the inflammatory condition. However, autophagy inhibitor 3-MA reversed anti-inflammatory and anticatabolic effects of MCC950. In in vivo experiments, intra-articular administration of MCC950 further showed its protective effect on cartilage degeneration. Bioinformatic analysis and in vitro experimental results revealed that MCC950 might play a protective role in cartilage by regulating Nrf2/HO-1/NQO1, PI3k/Akt/mTOR, P38/MAPK, and JNK/MAPK pathways. In conclusion, our work demonstrated that NLRP3 inhibitor MCC950 might serve as a promising strategy for OA treatment.

Chitosan oligosaccharides packaged into rat adipose mesenchymal stem cells-derived extracellular vesicles facilitating cartilage injury repair and alleviating osteoarthritis.

OBJECTIVES: This study aimed to investigate the roles of adipose mesenchymal stem cell (AMSC)-derived extracellular vesicles (EVs) binding with chitosan oligosaccharides (COS) in cartilage injury, as well as the related mechanisms. RESULTS: IL-1ß treatment significantly inhibited the viability and migration of chondrocytes and enhanced cell apoptosis (P < 0.05), while chitosan oligosaccharides and extracellular vesicles-chitosan oligosaccharide conjugates (EVs-COS/EVs-COS conjugates) reversed the changes induced by IL-1ß (P < 0.05), and the effects of extracellular vesicles-chitosan oligosaccharide conjugates were better than those of chitosan oligosaccharides (P < 0.05). After cartilage damage, IL-1ß, OPN, and p53 were significantly upregulated, COL1A1, COL2A1, OCN, RUNX2, p-Akt/Akt, PI3K, c-Myc, and Bcl2 were markedly downregulated, and extracellular vesicles-chitosan oligosaccharide conjugates reversed the expression induced by cartilage injury. Through sequencing, 760 differentially expressed genes (DEGs) clustered into four expression patterns were associated with negative regulation of the canonical Wnt, PI3K-Akt, AMPK, and MAPK signaling pathways. CONCLUSION: Extracellular vesicles-chitosan oligosaccharide conjugates may serve as a new cell-free biomaterial to facilitate cartilage injury repair and improve osteoarthritis.

Targeted treatment for osteoarthritis: drugs and delivery system.

The management of osteoarthritis (OA) is a clinical challenge due to the particular avascular, dense, and occluded tissue structure. Despite numerous clinical reports and animal studies, the pathogenesis and progression of OA are still not fully understood. On the basis of traditional drugs, a large number of new drugs have been continuously developed. Intra-articular (IA) administration for OA hastens the development of targeted drug delivery systems (DDS). OA drugs modification and the synthesis of bioadaptive carriers contribute to a qualitative leap in the efficacy of IA treatment. Nanoparticles (NPs) are demonstrated credible improvement of drug penetration and retention in OA. Targeted nanomaterial delivery systems show the prominent biocompatibility and drug loading-release ability. This article reviews different drugs and nanomaterial delivery systems for IA treatment of OA, in an attempt to resolve the inconsonance between in vitro and in vivo release, and explore more interactions between drugs and nanocarriers, so as to open up new horizons for the treatment of OA.

Bardoxolone-Methyl Prevents Oxidative Stress-Mediated Apoptosis and Extracellular Matrix Degradation in vitro and Alleviates Osteoarthritis in vivo.

PURPOSE: Oxidative stress-induced chondrocyte apoptosis and extracellular matrix (ECM) degradation plays an important role in the progression of osteoarthritis (OA). Bardoxolone methyl (BM), a semisynthetic triterpenoid, exerts strong effect against oxidative stress. The purpose of the present study was to determine the effectiveness of bardoxolone-methyl (BM) in preventing oxidative stress-induced chondrocyte apoptosis and extracellular ECM degradation in vitro and the role of alleviating OA progression in vivo. METHODS: Oxidative damage was induced by 25 mM tert-butyl hydroperoxide (TBHP) for 24 h in rat chondrocytes. 0.025 and 0.05 µM bardoxolone-methyl (BM) were used in vitro treatment. Ex-vivo cartilage explant model was established to evaluate the effect of BM on oxidative stress-induced ECM degradation. The mouse OA model was induced by surgical destabilization of the medial meniscus. RESULTS: In vitro, 0.025 and 0.05 µM BM reduced TBHP-induced excessive ROS generation, improved cell viability, increased malondialdehyde level and decreased superoxide dismutase level. 0.025 and 0.05 µM BM prevented TBHP-induced mitochondrial damage and apoptosis in chondrocytes BM activated heme oxygenase-1 (HO-1)/NADPH quinone oxidoreductase 1 (NOQ1) signaling pathway through targeting nuclear factor erythroid derived-2-related factor 2 (Nrf2). Additionally, BM treatment enhanced the expression levels of aggrecan and collagen II and inhibited the expression levels of matrix metalloproteinase 9 (MMP 9), MMP 13, Bax and cleaved-caspase-3. BM increased proteoglycan staining area and IOD value in ex vivo cultured experiment cartilage explants and improved the OARSI score, stands, max contact mean intensity, print area and duty cycle in mouse OA model. CONCLUSION: BM prevented oxidative stress-induced chondrocyte apoptosis and ECM degradation in vitro and alleviated OA in vivo, suggesting that BM serves as an effective drug for treatment with OA.

Nootkatone protects cartilage against degeneration in mice by inhibiting NF-κB signaling pathway.

Osteoarthritis is a common chronic disease associated with chondrocyte inflammation and cartilage matrix hydrolyzation. Studies report that IL-1ß plays a critical role in osteoarthritis. Anti-inflammatory effect of nootkatone has been explored in acute and chronic inflammatory disease, thus the current study sought to explore its therapeutic effect in osteoarthritis. Notably, the effect of nootkatone in osteoarthritis has not been elucidated. Therefore, murine primary chondrocytes were extracted and ACLT induced OA mouse model was established in the current study to explore the therapeutic effect of nootkatone in OA both in vitro and in vivo. The findings showed that nootkatone inhibited inflammatory response and protected cartilage balance in murine primary chondrocyte. Further analysis showed that nootkatone suppressed inflammation and protected cartilage against degeneration induced by ACLT surgery in mice. The cellular mechanism of the protective effect of nootkatone in osteoarthritis and associated signaling pathway was identified as the NF-κB signaling pathway. In summary, the findings of the current study indicated that nootkatone is a potential therapeutic agent for OA.

Adipose-Derived Extract Suppresses IL-1ß-Induced Inflammatory Signaling Pathways in Human Chondrocytes and Ameliorates the Cartilage Destruction of Experimental Osteoarthritis in Rats.

We investigated the effects of adipose-derived extract (AE) on cultured chondrocytes and in vivo cartilage destruction. AE was prepared from human adipose tissues using a nonenzymatic approach. Cultured human chondrocytes were stimulated with interleukin-1 beta (IL-1ß) with or without different concentrations of AE. The effects of co-treatment with AE on intracellular signaling pathways and their downstream gene and protein expressions were examined using real-time PCR, Western blotting, and immunofluorescence staining. Rat AE prepared from inguinal adipose tissues was intra-articularly delivered to the knee joints of rats with experimental osteoarthritis (OA), and the effect of AE on cartilage destruction was evaluated histologically. In vitro, co-treatment with IL-1ß combined with AE reduced activation of the p38 and ERK mitogen-activated protein kinase (MAPK) pathway and nuclear translocation of the p65 subunit of nuclear factor-kappa B (NF-κB), and subsequently downregulated the expressions of matrix metalloproteinase (MMP)-1, MMP-3, MMP-13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-4, IL-6, and IL-8, whereas it markedly upregulated the expression of IL-1 receptor type 2 (IL-1R2) in chondrocytes. Intra-articular injection of homologous AE significantly ameliorated cartilage destruction six weeks postoperatively in the rat OA model. These results suggested that AE may exert a chondroprotective effect, at least in part, through modulation of the IL-1ß-induced inflammatory signaling pathway by upregulation of IL-1R2 expression.

Parathyroid hormone promotes cartilage healing after free reduction of mandibular condylar fractures by upregulating Sox9.

After high fractures of the mandibular condyle, the insufficient blood supply to the condyle often leads to poor bone and cartilage repair ability and poor clinical outcome. Parathyroid hormone (PTH) can promote the bone formation and mineralization of mandibular fracture, but its effects on cartilage healing after the free reduction and internal fixation of high fractures of the mandibular condyle are unknown. In this study, a rabbit model of free reduction and internal fixation of high fractures of the mandibular condyle was established, and the effects and mechanisms of PTH on condylar cartilage healing were explored. Forty-eight specific-pathogen-free (SPF) grade rabbits were randomly divided into two groups. In the experimental group, PTH was injected subcutaneously at 20 µg/kg (PTH (1-34)) every other day, and in the control group, PTH was replaced with 1 ml saline. The healing cartilages were assessed at postoperative days 7, 14, 21, and 28. Observation of gross specimens, hematoxylin eosin staining and Safranin O/fast green staining found that every-other-day subcutaneous injection of PTH at 20 µg/kg promoted healing of condylar cartilage and subchondral osteogenesis in the fracture site. Immunohistochemistry and polymerase chain reaction showed that PTH significantly upregulated the chondrogenic genes Sox9 and Col2a1 in the cartilage fracture site within 7-21 postoperative days in the experimental group than those in the control group, while it downregulated the cartilage inflammation gene matrix metalloproteinase-13 and chondrocyte terminal differentiation gene ColX. In summary, exogenous PTH can stimulate the formation of cartilage matrix by triggering Sox9 expression at the early stage of cartilage healing, and it provides a potential therapeutic protocol for high fractures of the mandibular condyle.

Snail/HDAC1/2 mediate skeletal growth retardation in fetuses caused by prenatal nicotine exposure.

Previous findings have confirmed that prenatal nicotine exposure (PNE) leads to retarded cartilage development in the fetal growth plate. It is characterized by insufficient matrix synthesis and decreased expression of matrix phenotype genes aggrecan (ACAN) and Col2A1 in the fetal growth plate chondrocytes; however, the specific molecular mechanism is yet unclear. This study intends to clarify the specific molecular mechanism of fetal osteochondral retardation caused by PNE through animal and cellular experiments. The present study demonstrated that in male offspring of the PNE group (the pregnant rats were subcutaneously administered nicotine 1.0 mg/kg twice per day (2.0 mg/kg.d) at GD11-20), the cartilage matrix of the fetal growth plate was lightly stained, the collagen was reduced, and expression of the matrix phenotype genes, ACAN and Col2A1, was significantly decreased. It was further found that PNE decreased histone acetylation (H3K9/H3K14) levels in the ACAN and Col2A1 promoter regions. Moreover, the expression of Snail and HDAC1/2 was increased in the PNE group. in vitro, the nicotine treatment at different concentrations elevated the expression of Snail/HDAC1/2 while decreasing the H3K9/H3K14 levels in the ACAN and Col2A1 promoter regions. Snail-siRNA transfection partially abolished the nicotine-induced increase in HDAC1/2 expression and decreased the histone acetylation levels in the ACAN and Col2A1 promoter regions. Trichostatin A (TSA) treatment partially reversed the nicotine-induced changes in downstream parameters. In summary, PNE-induced decreased cartilage matrix synthesis in the fetal growth plate of male offspring is effectuated by Snail/HDAC1/2-mediated decreased H3K9/H3K14 levels in the ACAN and Col2A1 promoter regions.