Osteoarthritis year 2010 in review: pathomechanisms

Alendronate treatment rescues the effects of compressive loading of TMJ in osteogenesis imperfecta mice

BACKGROUND

Osteogenesis imperfecta (OI) is a genetic disorder of connective tissue caused by mutations associated with type I collagen, which results in defective extracellular matrix in temporomandibular joint (TMJ) cartilage and subchondral bone. TMJ is a fibrocartilaginous joint expressing type I collagen both in the cartilage and the subchondral bone. In the present study the effects of alendronate and altered loading of the TMJ was analyzed both in male and female OI mice.

MATERIALS AND METHODS

Forty-eight, 10-weeks-old male and female OI mice were divided into 3 groups: (1) Control group: unloaded group, (2) Saline + Loaded: Saline was injected for 2 weeks and then TMJ of mice was loaded for 5 days, (3) alendronate + loaded: alendronate was injected for 2 weeks and then TMJ of mice was loaded for 5 days. Mice in all the groups were euthanized 24-h after the final loading.

RESULTS

Alendronate pretreatment led to significant increase in bone volume and tissue density. Histomorphometrically, alendronate treatment led to increase in mineralization, cartilage thickness and proteoglycan distribution. Increased mineralization paralleled decreased osteoclastic activity. Our immunohistochemistry revealed decreased expression of matrix metallopeptidase 13 and ADAM metallopeptidase with thrombospondin type 1 motif 5.

CONCLUSION

The findings of this research support that alendronate prevented the detrimental effects of loading on the extracellular matrix of the TMJ cartilage and subchondral bone.

Glycosaminoglycan-Mediated Interactions in Articular, Auricular, Meniscal, and Nasal Cartilage

Glycosaminoglycans (GAGs) are ubiquitous components in the cartilage extracellular matrix (ECM). Ultrastructural arrangement of ECM and GAG-mediated interactions with collagen are known to govern the mechanics in articular cartilage, but these interactions are less clear in other cartilage types. Therefore, this article reviews the current literature on ultrastructure of articular, auricular, meniscal, and nasal septal cartilage, seeking insight into GAG-mediated interactions influencing mechanics. Ultrastructural features of these cartilages are discussed to highlight differences between them. GAG-mediated interactions are reviewed under two categories: interactions with chondrocytes and interactions with other fibrillar macromolecules of the ECM. Moreover, efforts to replicate GAG-mediated interactions to improve mechanical integrity of tissue-engineered cartilage constructs are discussed. In conclusion, studies exploring cartilage specific GAGs are poorly represented in the literature, and the ultrastructure of nasal septal and auricular cartilage is less studied compared with articular and meniscal cartilages. Understanding the contribution of GAGs in cartilage mechanics at the ultrastructural level and translating that knowledge to engineered cartilage will facilitate improvement of cartilage tissue engineering approaches.

Baicalin inhibits apoptosis and enhances chondrocyte proliferation in thiram-induced tibial dyschondroplasia in chickens by regulating Bcl-2/Caspase-9 and Sox-9/Collagen-II expressions

Avian tibial dyschondroplasia (TD) is a skeletal disease affecting fast growing chickens, resulting in non-mineralized avascular cartilage. This metabolic disorder is characterized by lameness and reduced growth performance causing economic losses. The aim of this study was to investigate the protective effects of baicalin against TD caused by thiram exposure. A total of two hundred and forty (n = 240) one day-old broiler chickens were uniformly and randomly allocated into three different groups (n = 80) viz. control, TD, and baicalin groups. All chickens received standard feed, however, to induce TD, the TD and baicalin groups received thiram (tetramethylthiuram disulfide) at a rate of 50 mg/kg feed from days 4-7. The thiram induction in TD and baicalin groups resulted in lameness, high mortality, and enlarged growth-plate, poor production performance, reduction in ALP, GSH-Px, SOD, and T-AOC levels, and increased AST and ALT, and MDA levels. Furthermore, histopathological results showed less vascularization, and mRNA and protein expression levels of Sox-9, Col-II, and Bcl-2 showed significant downward trend, while caspase-9 displayed significant up-regulation in TD-affected chickens. After the TD induction, the baicalin group was orally administered with baicalin at a rate of 200 mg/kg from days 8-18. Baicalin administration increased the vascularization, and chondrocytes with intact nuclei, alleviated lameness, decreased GP size, increased productive capacity, and restored the liver antioxidant enzymes and serum biochemical levels. Furthermore, baicalin significantly up-regulated the gene and protein expressions of Sox-9, Col-II, and Bcl-2, and significantly down-regulated the expression of caspase-9 (p < 0.05). Therefore, the obtained results suggest that baicalin could be a possible choice in thiram toxicity alleviation by regulating apoptosis and chondrocyte proliferation in thiram-induced tibial dyschondroplasia.

PPARγ activation suppresses chondrocyte ferroptosis through mitophagy in osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a prevalent disease plaguing the elderly. Recently, chondrocyte ferroptosis has been demonstrated to promote the progression of OA. Peroxisome proliferator-activated receptor-γ (PPARγ) is an important factor in maintaining cartilage health. However, the relationship between PPARγ and chondrocyte ferroptosis in OA and its mechanism is completely unclear.

METHODS

We established a surgically induced knee OA rat model to investigate PPARγ and chondrocyte ferroptosis in OA. Rat knee specimens were collected for Safranin O/Fast Green staining and immunohistochemical staining after administered orally placebo or pioglitazone (PPARγ agonist) for 4 weeks. We used RSL3 to establish a chondrocyte ferroptosis model cultured in vitro to study the role of PPARγ activation toward ferroptosis, mitochondrial function, and PTEN-induced putative kinase 1 (Pink1)/Parkin-dependent mitophagy. GW9662 (PPARγ antagonist), Mdivi-1 (mitophagy inhibitor), and chloroquine (mitophagy inhibitor) were employed to investigate the mechanism of PPARγ-Pink1/Parkin-dependent mitophagy in the inhibition of ferroptosis.

RESULTS

We found that PPARγ activation by pioglitazone attenuated not only OA but also inhibited the expression of the ferroptosis marker acyl-CoA synthetase long-chain family member 4 (ACSL4) at the same time in rats. Furthermore, in vivo and in vitro data indicated that PPARγ activation restored Pink1/Parkin-dependent mitophagy, improved mitochondrial function, inhibited chondrocyte ferroptosis, and delayed the progression of OA.

CONCLUSIONS

The present study demonstrated that PPARγ activation attenuates OA by inhibiting chondrocyte ferroptosis, and this chondroprotective effect was achieved by promoting the Pink1/Parkin-dependent mitophagy pathway.

Apoptosis Regulation in Osteoarthritis and the Influence of Lipid Interactions

Osteoarthritis (OA) is one of the most common chronic diseases in human and animal joints. The joints undergo several morphological and histological changes during the development of radiographically visible osteoarthritis. The most discussed changes include synovial inflammation, the massive destruction of articular cartilage and ongoing joint destruction accompanied by massive joint pain in the later stadium. Either the increased apoptosis of chondrocytes or the insufficient apoptosis of inflammatory macrophages and synovial fibroblasts are likely to underly this process. In this review, we discuss the current state of research on the pathogenesis of OA with special regard to the involvement of apoptosis.

Effects of a Single Intra-Articular Injection of 2% Lidocaine or 0.5% Bupivacaine on Synovial Fluid Acute Phase Protein Concentrations in Healthy Horses

The purpose of this study was to compare the extent of inflammation response in the middle carpal joints of healthy horses following intra-articular injection of 2% lidocaine, 0.5% bupivacaine, or 0.9% saline solution. The right middle carpal joint of 20 horses was injected with 5 mL of 0.5% bupivacaine (GB, n = 10) or 5 mL of 2% lidocaine (GL, n = 10). The left middle carpal joint of horses was used as a control (5 mL 0.9% saline). Serum and synovial fluid (SF) were aseptically collected before and at predetermined times after each injection. Serum and synovial fluid protein, albumin, transferrin, haptoglobin, ceruloplasmin, α1-antitripsin, and α1-acid glycoprotein concentrations were measured by sodium dodecyl sulfate polyacrylamide gel electrophoresis and compared among treatments. The results were submitted to analysis of variance using the SAS statistical program, and means were compared by the Student-Newman-Keuls test (P < .05). Both lidocaine and bupivacaine induced serum and SF changes indicative of inflammation, but the magnitude of those changes was more pronounced for lidocaine. Administration of 0.9% saline also induced an inflammatory reaction, but the magnitude of these changes was less pronounced than those caused by GB and GL. The results suggested that bupivacaine is safer than lidocaine for intra-articular injection in horses. Saline solution should not be used as an adjunct to intra-articular injections in horses.

Accelerated aging in articular cartilage by ZMPSTE24 deficiency leads to osteoarthritis with impaired metabolic signaling and epigenetic regulation

Osteoarthritis (OA) is an age-related degenerative disease without disease-modifying therapy. The lack of aging-induced osteoarthritis models makes the discovery of therapeutic drugs more challenging. The deficiency of ZMPSTE24 could induce Hutchinson-Gilford progeria syndrome (HGPS), a genetic disorder of rapid aging. However, the relationship between HGPS and OA remains unclear. Our results found that the expression of Zmpste24 was decreased in the articular cartilage during the aging process. Zmpste24 knockout mice, Prx1-Cre; Zmpste24^fl/fl mice and Col2-CreERT2; Zmpste24^fl/fl mice displayed OA phenotype. Loss of Zmpste24 in articular cartilage could exacerbate the occurrence and development of osteoarthritis. Transcriptome sequencing revealed that deletion of Zmpste24 or accumulation of progerin affects chondrocyte metabolism, inhibits cell proliferation and promotes cell senescence. Using this animal model, we elucidate the upregulation of H3K27me3 during chondrocyte senescence and discover the molecular mechanism by which lamin A mutant stabilizes EZH2 expression. The construction of aging-induced osteoarthritis models and the elucidation of the signaling pathways and molecular mechanisms of articular chondrocyte senescence would benefit the discovery and development of new drugs for OA.

The long non-coding RNA SNHG1 attenuates chondrocyte apoptosis and inflammation via the miR-195/IKK-α axis

Multiple studies have suggested that long non-coding RNAs (lncRNAs) are involved in the development and progression of osteoarthritis (OA). However, how lncRNA SNHG1 regulates OA remains unknown. This study aimed to explore how SNHG1 regulates chondrocyte apoptosis and inflammation. Our data showed that H₂O₂-treated chondrocytes exhibited lower expression of SNHG1 and secreted higher levels of IL-6, IL-8, and TNF-α than untreated cells. Further, overexpressing SNHG1 reduced chondrocyte apoptosis and production of inflammatory factors. Additionally, SNHG1 targets miR-195 directly, and IKK-α has direct biding sites for miR-195. Of note, IKK-α acts as an inhibitor of the NF-κB signaling pathway. These findings suggest that SNHG1 can upregulate IKK-α by inhibiting miR-195 and thus, inhibit NF-κB activity. Our in vivo experiments validate our in vitro findings. Thus, under oxidative stress, SNHG1 inhibits the activation of NF-κB to attenuate chondrocyte apoptosis and inflammation via the miR-195/IKK-α axis. Targeting SNHG1 may serve as a potential novel therapeutic approach for OA.

Natural Compounds: Potential Therapeutics for the Inhibition of Cartilage Matrix Degradation in Osteoarthritis

Osteoarthritis (OA) is the most common degenerative joint disease characterized by enzymatic degradation of the cartilage extracellular matrix (ECM) causing joint pain and disability. There is no disease-modifying drug available for the treatment of OA. An ideal drug is expected to stop cartilage ECM degradation and restore the degenerated ECM. The ECM primarily contains type II collagen and aggrecan but also has minor quantities of other collagen fibers and proteoglycans. In OA joints, the components of the cartilage ECM are degraded by matrix-degrading proteases and hydrolases which are produced by chondrocytes and synoviocytes. Matrix metalloproteinase-13 (MMP-13) and a disintegrin and metalloproteinase with thrombospondin motifs 4 and 5 (ADAMTS5) are the major collagenase and aggrecanase, respectively, which are highly expressed in OA cartilage and promote cartilage ECM degradation. Current studies using various in vitro and in vivo approaches show that natural compounds inhibit the expression and activity of MMP-13, ADAMTS4, and ADAMTS5 and increase the expression of ECM components. In this review, we have summarized recent advancements in OA research with a focus on natural compounds as potential therapeutics for the treatment of OA with emphasis on the prevention of cartilage ECM degradation and improvement of joint health.

Ghrelin level as a biomarker for knee osteoarthritis severity and appearance in HIV + patients

BACKGROUND

Knee Osteoarthritis (KOA) is a multifactorial disease with several mechanisms to promote articular cartilage damage. New molecules, such as ghrelin, have been recently reported to participate in the pathogenesis and progression of KOA. In HIV + patients, arthralgias are the most frequent musculoskeletal manifestations, mainly affecting joints such as the knee. Also, it has been reported that HIV + patients have a reduction of ghrelin even with treatment compared to HIV- patients. However, there is no report in the literature evaluating ghrelin and KOA in the HIV + population. We aimed to evaluate whether serum ghrelin levels can function as a biomarker for OA in HIV + patients.

METHODS

We recruited 40 patients, 20 HIV+, and 20 HIV- controls, and grouped as follows: HIV+/KOA+; HIV+/KOA-; HIV-/KOA+; HIV-/KOA-. Clinical features were obtained during clinical visits. Peripheral blood samples were acquired to measure serum ghrelin levels.

RESULTS

The HIV+/KOA + group significantly reduced serum ghrelin levels when compared with the other groups. Comparing the ghrelin levels with the patients' nadir of CD4⁺ T-cells count, we identified a statistically significant negative correlation in the KOA- group (r = -0.80, P < 0.007). An ROC curve analysis, for the accuracy of ghrelin levels to identified HIV+/KOA + from HIV+/KOA- patients, found an area under the curve of 0.83 (95 % CI 0.65-0.10; P = 0.017), with a cut-off < 4026 pg/mL serum ghrelin levels, with a sensitivity of 0.62 (95 % CI 0.32-0.86), and a specificity of 0.10 (95 % CI 0.59-0.10).

CONCLUSION

This study shows the potential use of ghrelin levels as a biomarker for KOA in the high-risk HIV population that should be further analyzed.

Anabolic Response of Intermittent Parathyroid Hormone and Alendronate on the Osteochondral Tissue of TMJ

OBJECTIVE

To characterize the effects of parathyroid hormone (PTH) and alendronate (Alend) on the osteochondral tissue of temporomandibular joint (TMJ).

MATERIALS AND METHODS

Ninety-six male and female transgenic reporter mice, 4 to 5 weeks old were divided into 6 groups: (1) Control group: Saline was injected daily for 14 days; (2) PTH: PTH was injected daily for 14 days; (3) Alend: Alend was injected every alternate days for 14 days; (4) Combined PTH and Alend: PTH was injected daily and Alend injected every alternate days for 14 days; (5) PTH then Alend: PTH was injected daily for 14 days followed by Alend injections in alternate days for 14 days; and (6) PTH wait Alend: PTH was injected daily for 14 days. There was a waiting period of 1 week before administration of Alend in alternate days for 14 days. Mice were injected with 5-ethnyl-2'-deoxyuridine (EdU), 48 and 24 hours prior to euthanization.

RESULTS

There was significant increase in bone volume and decrease in osteoclastic activity in groups in which Alend was administered after PTH in both gender. There was significant increase in cartilage thickness with PTH or Alend alone in females, whereas in males, PTH alone led to increase in cartilage thickness. Chondrocyte apoptosis was significantly decreased with PTH or Alend alone in both male and female. Matrix metallopeptidase 13, and aggreganase-2 (ADAMTS5) expression were significantly decreased with PTH and Alend alone in both gender.

CONCLUSION

PTH and Alend administration causes anabolic effects in the osteochondral tissue of TMJ.

The Role of Autophagy in Osteoarthritic Cartilage

Osteoarthritis (OA) is one of the most common diseases leading to physical disability, with age being the main risk factor, and degeneration of articular cartilage is the main focus for the pathogenesis of OA. Autophagy is a crucial intracellular homeostasis system recycling flawed macromolecules and cellular organelles to sustain the metabolism of cells. Growing evidences have revealed that autophagy is chondroprotective by regulating apoptosis and repairing the function of damaged chondrocytes. Then, OA is related to autophagy depending on different stages and models. In this review, we discuss the character of autophagy in OA and the process of the autophagy pathway, which can be modulated by some drugs, key molecules and non-coding RNAs (microRNAs, long non-coding RNAs and circular RNAs). More in-depth investigations of autophagy are needed to find therapeutic targets or diagnostic biomarkers through in vitro and in vivo situations, making autophagy a more effective way for OA treatment in the future. The aim of this review is to introduce the concept of autophagy and make readers realize its impact on OA. The database we searched in is PubMed and we used the keywords listed below to find appropriate article resources.

Identification of SCRG1 as a Potential Therapeutic Target for Human Synovial Inflammation

Synovial inflammation of joint tissue is the most important cause of tissue damage, joint destruction, and disability and is associated with higher morbidity or mortality. Therefore, this study aims to identify key genes in osteoarthritis synovitis tissue to increase our understanding of the underlying mechanisms of osteoarthritis and identify new therapeutic targets. Five GEO datasets with a total of 41 normal synovial membrane tissues and 45 osteoarthritis synovial membrane samples were used for analysis, and seven common differential genes were identified. The classification model constructed by LASSO analysis showed that six genes including CDKN1A, FOSB, STMN2, SLC2A3, TAC, and SCRG1 can be used as biomarkers of osteoarthritis, and the SCRG1 gene shows importance in osteoarthritis. Furthermore, drug database enrichment found that these six DEGs may be the drug targets of synovitis in osteoarthritis, and Valproic Acid CTD 00006977 may be a potential targeted therapeutic drug of SCRG1. Spearman correlation analysis was performed on the SCRG1 gene, and 27 genes with consistent expression were obtained. Functional analysis showed that 27 genes were mainly involved in metabolism, complement, antigen presentation, apoptosis, and regulation of immune pathways. The co-regulatory network of TFs-miRNA suggested that the SCRG1 gene may be regulated by hsa-miR-363-3p miRNA. In conclusion, SCRG1, as a diagnostic marker of osteoarthritis, co-regulates immune-related pathways through the interaction of related proteins, playing an important role in the occurrence and development of osteoarthritis, which may be a novel drug target.

The collagenases: are they tractable targets for preventing cartilage destruction in osteoarthritis?

INTRODUCTION

The etiology and pathogenesis of osteoarthritis (OA) have been intensely investigated; however, the disease course and progression are not completely understood. A prominent role for interstitial collagenases is recognized in this degenerative process, hence strategies to target them are of major interest.

AREAS COVERED

The pathogenesis of OA, the role of interstitial collagenases (MMP-1, -8 and -13) and collagenase modifying drugs are examined and discussed. We reviewed relevant papers from PubMed and Google Scholar.

EXPERT OPINION

There is strong evidence for the therapeutic potential of MMP inhibitors in OA; however, they are not expected to impact the inflammatory process. Therefore, there is a need for a relative inhibitor of MMP-13 collagenase which possesses anti-inflammatory properties. The identification of novel broad-spectrum relative multiple peptidase inhibitors could provide desirable tools for the prophylaxis, cure, or treatment of diseases involving articular cartilage (AC) degradation, in particular OA.

Sprifermin: Effects on Cartilage Homeostasis and Therapeutic Prospects in Cartilage-Related Diseases

When suffering from osteoarthritis (OA), articular cartilage homeostasis is out of balance and the living quality declines. The treatment of knee OA has always been an unsolved problem in the world. At present, symptomatic treatment is mainly adopted for OA. Drug therapy is mainly used to relieve pain symptoms, but often accompanied with adverse reactions; surgical treatment involves the problem of poor integration between the repaired or transplanted tissues and the natural cartilage, leading to the failure of repair. Biotherapy which aims to promote cartilage in situ regeneration and to restore endochondral homeostasis is expected to be an effective method for the prevention and treatment of OA. Disease-modifying osteoarthritis drugs (DMOADs) are intended for targeted treatment of OA. The DMOADs prevent excessive destruction of articular cartilage through anti-catabolism and stimulate tissue regeneration via excitoanabolic effects. Sprifermin (recombinant human FGF18, rhFGF18) is an effective DMOAD, which can not only promote the proliferation of articular chondrocyte and the synthesis of extracellular matrix, increase the thickness of cartilage in a dose-dependent manner, but also inhibit the activity of proteolytic enzymes and remarkedly slow down the degeneration of cartilage. This paper reviews the unique advantages of Sprifermin in repairing cartilage injury and improving cartilage homeostasis, aiming to provide an important strategy for the effective prevention and treatment of cartilage injury-related diseases.

Validation of the Diagnostic and Prognostic Values of ADAMTS5 and FSTL1 in Osteoarthritis Rat Model

OBJECTIVE

Osteoarthritis (OA) is a global public health problem and a leading cause of morbidity and disability. Due to lack of sensitive and specific tools for early OA diagnosis and predicting prognosis, the availability of new reliable and sensitive biomarkers is a widely appreciated need to identify patients at risk for incident disease or disease progression. Accordingly, our study was conducted to validate the usefulness of disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5) and follistatin-like protein 1 (FSTL1) to achieve this goal.

DESIGN

Fifty-four male Wistar rats were randomized into 3 groups; 24 rats were subjected to medial meniscal tear (MMT) surgery on the right knee joint (OA group), 24 rats were subjected to sham surgery (sham group), and 6 healthy rats (negative control group). Six animals from each group were sacrificed every 2 weeks. At each time point, the right knee joint of each animal was visualized radiologically, a blood sample was collected, and cartilage tissues were isolated for histopathological and western blot analysis.

RESULTS

We found that the expression levels of ADAMTS5 and FSTL1 significantly increased with OA progression, especially at weeks 4, 6, and 8 after surgery. Notably, the serum levels of ADAMTS5 and FSTL1 showed significant positive correlations with each other and with the studied inflammatory markers.

CONCLUSIONS

Our findings suggest that ADAMTS5 and FSTL1 can serve as important and informative serological markers of disease activity in OA. However, further research is needed to validate their use for improving the diagnosis and prognosis of OA in humans.

Vitamin K-Dependent Proteins in Skeletal Development and Disease

Vitamin K and Vitamin K-dependent proteins (VKDPs) are best known for their pivotal role in blood coagulation. Of the 14 VKPDs identified in humans to date, 6 play also important roles in skeletal biology and disease. Thus, osteocalcin, also termed bone Gla-protein, is the most abundant non-collagenous protein in bone. Matrix Gla protein and Ucma/GRP on the other hand are highly abundant in cartilage. Furthermore, periostin, protein S, and growth arrest specific 6 protein (GAS 6) are expressed in skeletal tissues. The roles for these VKDPs are diverse but include the control of calcification and turnover of bone and cartilage. Vitamin K plays an important role in osteoporosis and serum osteocalcin levels are recognized as a promising marker for osteoporosis. On the other hand, matrix Gla protein and Ucma/GRP are associated with osteoarthritis. This review focuses on the roles of these three VKDPs, osteocalcin, matrix Gla protein and Ucma/GRP, in skeletal development and disease but will also summarize the roles the other skeletal VKDPs (periostin, protein S and GAS6) in skeletal biology.

4-Methylumbelliferone suppresses catabolic activation in anterior cruciate ligament-derived cells via a mechanism independent of hyaluronan inhibition

BACKGROUND

The anterior cruciate ligament (ACL) has a key role as a dynamic stabilizer of the knee joints, and ACL dysfunction caused by traumatic or degenerative rupture accelerates osteoarthritis progression. Thus, it is important to prevent the degenerative rupture of the ACL. 4-Methylumbelliferone (4-MU), a pre-approved drug, exerts anti-inflammatory effects in osteoarthritis chondrocytes. It was originally used as an inhibitor of hyaluronan synthesis in chondrocytes.

METHODS

In this study, we investigated whether 4-MU affects the expression of catabolic factors, such as matrix metalloproteinase (MMP)-1, MMP-3, and interleukin (IL)-6, in ACL-derived cells and ACL explant cultures using immunohistochemistry, real-time RT-qPCR, and capillary western immunoassay. Furthermore, the hyaluronan concentration was evaluated using a colorimetric assay. Statistical analyses were conducted using analysis of variance for multi-group comparisons, followed by Tukey or Tukey-Kramer post hoc test.

RESULTS

Our results revealed, for the first time, that 4-MU suppressed the IL-β-induced upregulation of pro-catabolic factors, such as MMP-1, MMP-3, and IL-6, in ACL-derived cells. This suppressive effect was also observed in the cultured ligament tissues in ex vivo experiments. 4-MU also reversed an enhanced dependence on glycolysis in IL-1β-activated ACL-derived cells. Furthermore, we found that the suppressive effects of 4-MU were exerted directly and not through the inhibition of hyaluronan synthesis.

CONCLUSIONS

We conclude that 4-MU could be an effective and useful treatment for knee osteoarthritis, owing to its anti-inflammatory effect on, not only chondrocytes but also on ligament cells.

Stimuli-Sensitive Nanotherapies for the Treatment of Osteoarthritis

Osteoarthritis (OA) is a common chronic inflammatory disease in the joints. It is one of the leading causes of disability with increasing morbidity, which has become one of the serious clinical issues. Current treatments would only provide temporary relief due to the lack of early diagnosis and effective therapy, and thus the replacement of joints may be needed when the OA deteriorates. Although the intra-articular injection and oral administration of drugs are helpful for OA treatment, they are suffering from systemic toxicity, short retention time in joint, and insufficient bioavailability. Nanomedicine is potential to improve the drug delivery efficiency and targeting ability. In this focused progress review, the particle-based drug loading systems that can achieve targeted and triggered release are summarized. Stimuli-responsive nanocarriers that are sensitive to endogenous microenvironmental signals such as reactive oxygen species, enzymes, pH, and temperature, as well as external stimuli such as light for OA therapy are introduced in this review. Furthermore, the nanocarriers associated with targeted therapy and imaging for OA treatment are summarized. The potential applications of nanotherapies for OA treatment are finally discussed.

Inhibition of syndecan-4 reduces cartilage degradation in murine models of osteoarthritis through the downregulation of HIF-2α by miR-96-5p

The membranous receptor syndecan-4 (SDC-4) and the nuclear transcription factor hypoxia-induced factor-2α (HIF-2α) play critical roles in the pathogenesis of osteoarthritis (OA). The aim of this study was to determine whether SDC-4 inhibition downregulates HIF-2a expression by microRNA-96-5p (miR-96-5p) in murine chondrocyte and cartilage tissue. The OA model was induced surgically in mice, and SDC-4 polyclonal antibody, HIF-2α small interfering RNA (siRNA) and its control, miR-96-5p mimics and its scrambled controls or anti-miR-96-5p and its control were then injected into the knee joints. At 2 and 4 weeks after surgery, OA progression was evaluated microscopically, histologically, radiographically and immunohistochemically in these mice. Real-time polymerase chain reaction (RT-PCR) and western blotting were performed after treating with antibody and transfecting with miRNA mimic or siRNA to determine their effects on OA-related mediators. The potential miRNAs related to OA development were identified by using miRNA microarray analysis. Whether miRNAs play a pivotal role in OA development in vivo or in vitro was also investigated. MiR-96-5p expression was upregulated by SDC-4-specific antibodies in chondrocytes and cartilage tissue, and miR-96-5p directly targeted the 3'-UTR of HIF-2α to inhibit HIF-2α signaling in murine chondrocytes. Moreover, we demonstrated that anti-SDC-4-attenuated IL-1β-induced chondrocyte hypertrophy and cartilage degradation by inhibiting HIF-2α signaling by a miR-96-5p-dependent mechanism. Our study revealed that the inhibition of SDC-4 exerts its effects on both cartilage homeostasis and the chondrocyte hypertrophy phenotype by inducing miR-96-5p expression, which results in targeting HIF-2α 3'-UTR sequences and inhibiting HIF-2α in murine cartilage tissue and chondrocytes.

Niacinamide and undenatured type II collagen modulates the inflammatory response in rats with monoiodoacetate-induced osteoarthritis

The current work aimed to examine the properties of oral supplementation of niacinamide and undenatured type II collagen (UCII) on the inflammation and joint pain behavior of rats with osteoarthritis (OA). Forty-nine Wistar rats were allocated into seven groups; control (no MIA), MIA as a non-supplemental group with monosodium iodoacetate (MIA)-induced knee osteoarthritis, MIA + undenatured type II collagen (UCII) at 4 mg/kg BW, MIA + Niacinamide at 40 mg/kg BW (NA40), MIA + Niacinamide at 200 mg/kg BW (NA200), MIA + UCII + NA40 and MIA + UCII + NA200. Serum IL-1β, IL-6, TNF-α, COMP, and CRP increased in rats with OA and decreased in UCII and NA groups (p < 0.05). Rats with osteoarthritis had greater serum MDA and knee joint MMP-3, NF-κB, and TGβ protein levels and decreased in treated groups with UCII and NA (p < 0.05). The rats with OA also bore elevated joint diameters with joint pain behavior measured as decreased the stride lengths, the paw areas, and the paw widths, and increased the Kellgren-Lawrence and the Mankin scores (p < 0.05) and decreased in UCII treated groups. These results suggest the combinations with the UCII + NA supplementation as being most effective and reduce the inflammation responses for most OA symptoms in rats.

Text Mining-Based Drug Discovery in Osteoarthritis

Background

Osteoarthritis (OA) is a chronic and degenerative joint disease, which causes stiffness, pain, and decreased function. At the early stage of OA, nonsteroidal anti-inflammatory drugs (NSAIDs) are considered the first-line treatment. However, the efficacy and utility of available drug therapies are limited. We aim to use bioinformatics to identify potential genes and drugs associated with OA.

Methods

The genes related to OA and NSAIDs therapy were determined by text mining. Then, the common genes were performed for GO, KEGG pathway analysis, and protein-protein interaction (PPI) network analysis. Using the MCODE plugin-obtained hub genes, the expression levels of hub genes were verified using quantitative real-time polymerase chain reaction (qRT-PCR). The confirmed genes were queried in the Drug Gene Interaction Database to determine potential genes and drugs.

Results

The qRT-PCR result showed that the expression level of 15 genes was significantly increased in OA samples. Finally, eight potential genes were targetable to a total of 53 drugs, twenty-one of which have been employed to treat OA and 32 drugs have not yet been used in OA.

Conclusions

The 15 genes (including PTGS2, NLRP3, MMP9, IL1RN, CCL2, TNF, IL10, CD40, IL6, NGF, TP53, RELA, BCL2L1, VEGFA, and NOTCH1) and 32 drugs, which have not been used in OA but approved by the FDA for other diseases, could be potential genes and drugs, respectively, to improve OA treatment. Additionally, those methods provided tremendous opportunities to facilitate drug repositioning efforts and study novel target pharmacology in the pharmaceutical industry.

The Role of Autophagy in Osteoarthritis

Chondrocytes are the only cell type in normal cartilage. The pathological changes of osteoarthritis (OA) mostly revolve around the apoptosis and dysfunction of chondrocytes. Autophagy, as an intracellular degradation system that maintains the steady state of energy metabolism in cells, has been shown to restore the function of damaged chondrocytes, alleviating the occurrence and progression of OA. In this review, we explored the relationship between autophagy and OA and the key molecules of autophagy pathway that regulate the progression of OA, providing new ideas for OA treatment by targeting autophagy.

Parathyroid hormone (1-34) ameliorates cartilage degeneration and subchondral bone deterioration in collagenase-induced osteoarthritis model in mice

Aims

Parathyroid hormone (PTH) (1-34) exhibits potential in preventing degeneration in both cartilage and subchondral bone in osteoarthritis (OA) development. We assessed the effects of PTH (1-34) at different concentrations on bone and cartilage metabolism in a collagenase-induced mouse model of OA and examined whether PTH (1-34) affects the JAK2/STAT3 signalling pathway in this process.

Methods

Collagenase-induced OA was established in C57Bl/6 mice. Therapy with PTH (1-34) (10 μg/kg/day or 40 μg/kg/day) was initiated immediately after surgery and continued for six weeks. Cartilage pathology was evaluated by gross visual, histology, and immunohistochemical assessments. Cell apoptosis was analyzed by TUNEL staining. Microcomputed tomography (micro-CT) was used to evaluate the bone mass and the microarchitecture in subchondral bone.

Results

Enhanced matrix catabolism, increased apoptosis of chondrocytes in cartilage, and overexpressed JAK2/STAT3 and p-JAK2/p-STAT3 were observed in cartilage in this model. All of these changes were prevented by PTH (1-34) treatment, with no significant difference between the low-dose and high-dose groups. Micro-CT analysis indicated that bone mineral density (BMD), bone volume/trabecular volume (BV/TV), and trabecular thickness (Tb.Th) levels were significantly lower in the OA group than those in the Sham, PTH 10 μg, and PTH 40 μg groups, but these parameters were significantly higher in the PTH 40 μg group than in the PTH 10 μg group.

Conclusion

Intermittent administration of PTH (1-34) exhibits protective effects on both cartilage and subchondral bone in a dose-dependent manner on the latter in a collagenase-induced OA mouse model, which may be involved in regulating the JAK2/STAT3 signalling pathway.

Cite this article: Bone Joint Res 2020;9(10):675–688.

GEL-MAN Hydrogel Loaded With Triamcinolone Acetonide for the Treatment of Osteoarthritis

One of the major challenges for the treatment of osteoarthritis (OA) with therapeutic drugs is the short half-life of drugs in the joint cavity. The severity of OA often fluctuates with time and inflammatory factors. Here, we describe the use of a hydrogel material, named Gel-Man, to solve the problem of rapid release of drugs. Gel-Man could encapsulate a series of therapeutic drugs and be degraded by hydrogen peroxide. It could be decomposed, and release drugs controlled by the concentration of hydrogen peroxide in the arthritic joint cavity. This hydrogel loaded with triamcinolone acetonide (TA) could slowly release the drug upon exposure to hydrogen peroxide in the joint cavity in patients suffering from osteoarthritis. The combination of TA and GEL-MAN hydrogels can slowdown the progression of degenerative change of osteoarthritis by maximizing the therapeutic efficacy and prolong the duration of drug treatment.

Osteoclast-associated receptor blockade prevents articular cartilage destruction via chondrocyte apoptosis regulation

Osteoarthritis (OA), primarily characterized by articular cartilage destruction, is the most common form of age-related degenerative whole-joint disease. No disease-modifying treatments for OA are currently available. Although OA is primarily characterized by cartilage destruction, our understanding of the processes controlling OA progression is poor. Here, we report the association of OA with increased levels of osteoclast-associated receptor (OSCAR), an immunoglobulin-like collagen-recognition receptor. In mice, OSCAR deletion abrogates OA manifestations, such as articular cartilage destruction, subchondral bone sclerosis, and hyaline cartilage loss. These effects are a result of decreased chondrocyte apoptosis, which is caused by the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) in induced OA. Treatments with human OSCAR-Fc fusion protein attenuates OA pathogenesis caused by experimental OA. Thus, this work highlights the function of OSCAR as a catabolic regulator of OA pathogenesis, indicating that OSCAR blockade is a potential therapy for OA.

Osteoarthritis (OA) is associated with cartilage disruption, but the underlying mechanisms remain unclear. Here, the authors show that expression of osteoclast-associated receptor (OSCAR) is associated with OA, that its genetic ablation or targeting with OSCAR-Fc fusion protein ameliorates OA in mice by decreasing chondrocyte apoptosis.

BNIP3 decreases the LPS-induced inflammation and apoptosis of chondrocytes by promoting the development of autophagy

Background

Inflammation and apoptosis of chondrocytes are the pathological bases of osteoarthritis. Autophagy could alleviate the symptoms of inflammation and apoptosis. Previous study has shown that BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3) can induce the occurrence and development of autophagy. However, it is unknown whether autophagy induced by BNIP3 can alleviate the inflammation and apoptosis of chondrocytes.

Methods

We used the lentivirus to construct the overexpression BNIP3 chondrocytes. Next, the lipopolysaccharide (LPS) was used to stimulate these cells to simulate the physiological environment of osteoarthritis. After that, the enzyme-linked immunosorbent assays (ELISA) were performed to determine the levels of tumor necrosis factor-α (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6) and the flow cytometry was performed to detect the apoptosis rates of chondrocytes. At last, the expression of autophagy-related proteins was detected with the western blotting.

Results

The expression of BNIP3 was suppressed after treatment with LPS. However, overexpression of BNIP3 inhibited the secretion of proinflammatory factors (TNF-α, IL-1β, and IL-6) and decreased the apoptosis of chondrocytes. Furthermore, overexpression of BNIP3 led to the upregulation of autophagy-related protein expression including little computer 3 (LC3), autophagy-related protein 7 (ATG7), and Beclin-1. Application of autophagy inhibitor recovered the expression of proinflammatory factors and apoptosis rates of chondrocytes.

Conclusions

BNIP3 decreased the LPS-induced inflammation and apoptosis of chondrocytes by activating the autophagy.

Effects of intra-articular administration of lidocaine, mepivacaine, and the preservative methyl parahydroxybenzoate on synovial fluid biomarkers of horses

OBJECTIVE

To compare the extent of inflammation and catabolic collagen response in the middle carpal joints (MCJs) of healthy horses following intra-articular injection of 2% lidocaine, 2% mepivacaine, lactated Ringer solution (LRS), or 0.1% methyl parahydroxybenzoate.

ANIMALS

17 adult horses.

PROCEDURES

In the first of 2 experiments, the left middle carpal joint (MCJ) of each of 12 horses was injected with 10 mL of 2% lidocaine (n = 3), 2% mepivacaine (3), or LRS (control; 6). After a 4-week washout period, the right MCJ of the horses that received lidocaine or mepivacaine was injected with 10 mL of LRS, and the right MCJ of horses that received LRS was injected with 10 mL of 2% lidocaine (n = 3) or 2% mepivacaine (3). In experiment 2, the left MCJ of each of 5 horses was injected with 10 mL of 0.1% methyl parahydroxybenzoate. After a 48-hour washout period, the right MCJ of each horse was injected with 10 mL of LRS. Synovial fluid (SF) samples were aseptically collected before and at predetermined times after each injection. Synovial fluid WBC count, neutrophil percentage, and total protein, neutrophil myeloperoxidase, neutrophil elastase, and Coll2-1 concentrations were compared among treatments.

RESULTS

Both lidocaine and mepivacaine induced SF changes indicative of inflammation and a catabolic collagen response, but the magnitude of those changes was more pronounced for lidocaine. Methyl parahydroxybenzoate did not cause any SF changes indicative of inflammation.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggested that mepivacaine was safer than lidocaine for intra-articular injection in horses.

Release kinetic of pro- and anti-inflammatory biomolecules from platelet-rich plasma and functional study on osteoarthritis synovial fibroblasts

BACKGROUND AIMS

This study evaluated the release kinetics of numerous representative and less studied platelet-rich plasma (PRP) cytokines/chemokines with regard to the effects of various cellular compositions and incubation times. In addition, the biological effects of different PRPs on osteoarthritis synovial fibroblasts in vitro were tested.

METHODS

Peripheral whole blood was collected from healthy donors, and pure platelet-rich plasma (P-PRP), leukocyte-rich platelet-rich plasma (L-PRP) and platelet-poor plasma (PPP) were prepared for the analysis of the following biomolecules: IL-1β, IL-4, IL-6, IL-10, IL-17a, IL-22, MIP-1α/CCL-3, RANTES/CCL-5, MCP-3/CCL-7, Gro-α/CXCL-1, PF-4/CXCL-4, ENA-78/CXCL-5, NAP-2/CXCL-7, IL-8/CXCL-8, Fractalkine/CX3CL-1, s-CD40L P-PRP, L-PRP and PPP. Their effect on osteoarthritis synovial fibroblasts in vitro was tested by analyzing changes induced in both gene expression on a panel of representative molecules involved in physiopathology of joint environment and synthesis of IL-1β, IL-8 and hyaluronic acid.

RESULTS

This study demonstrated that among the 16 analyzed biomolecules, four were undetectable, whereas most of the detected biomolecules were more concentrated in L-PRP even when concentrations were normalized to platelet number. Despite the pro-inflammatory boost, the various PRP preparations did not alter synovial fibroblast gene expression of specific factors that play a pivotal role in joint tissue homeostasis and are able to induce anti-inflammatory (TIMP-1) biomolecules.

DISCUSSION

This study provides a set of reference data on the concentration and release kinetics of some less explored biomolecules that could represent potential specific effectors in the modulation of inflammatory processes and in tissue repair after treatment with PRP.

Site-Dependent Lineage Preference of Adipose Stem Cells

Adult stem cells have unique properties in both proliferation and differentiation preference. In this study, we hypothesized that adipose stem cells have a depot-dependent lineage preference. Four rabbits were used to provide donor-matched adipose stem cells from either subcutaneous adipose tissue (ScAT) or infrapatellar fat pad (IPFP). Proliferation and multi-lineage differentiation were evaluated in adipose stem cells from donor-matched ScAT and IPFP. RNA sequencing (RNA-seq) and proteomics were conducted to uncover potential molecular discrepancy in adipose stem cells and their corresponding matrix microenvironments. We found that stem cells from ScAT exhibited significantly higher proliferation and adipogenic capacity compared to those from donor-matched IPFP while stem cells from IPFP displayed significantly higher chondrogenic potential compared to those from donor-matched ScAT. Our findings are strongly endorsed by supportive data from transcriptome and proteomics analyses, indicating a site-dependent lineage preference of adipose stem cells.

Osteoarthritis is Prevented in Rats by Verbascoside via Nuclear Factor kappa B (NF-κB) Pathway Downregulation

Background

Cartilage degeneration during osteoarthritis (OA) most adversely affects the quality of life by hindering the movement. The present study investigated the role of verbascoside in the protection of cartilage degeneration induced by osteoarthritis.

Material/Methods

The enzyme-linked immunosorbent (ELISA) and western blot assays were used for determination of inflammatory cytokine secretion in serum and cartilage tissues, respectively.

Results

Treatment of the OA rats with verbascoside inhibited overproduction of interleukin (IL)-6, tumor necrosis factor (TNF)-α, and IL-1β in serum as well as cartilage tissues. The expression of P2X7R and matrix metalloproteinase (MMP)-13 was much higher in the rats induced with OA. However, administration of verbascoside reversed the OA-induced upregulation of P2X7R and MMP-13 expression in the cartilage tissues. The OA-mediated increase in substance P (SP) and prostaglandin E2 (PGE2) expression was also reduced in the cartilage tissues by the verbascoside treatment. Western blot assay revealed that verbascoside treatment markedly decreased the activation of IκBα and NF-κB p65 in the OA rats.

Conclusions

Thus, verbascoside inhibited inflammatory cytokine secretion in the OA rats by targeting P2X7R expression, production of matrix metalloproteinase, PGE2 and downregulation of NF-κB signaling pathway. Therefore, verbascoside may be used as potent agent for osteoarthritis treatment.

LINC00623/miR-101/HRAS axis modulates IL-1β-mediated ECM degradation, apoptosis and senescence of osteoarthritis chondrocytes

Chondrocyte apoptosis and extracellular matrix (ECM) degeneration have been implicated in the pathogenesis of osteoarthritis (OA). Based on previously reported microarray analysis, HRAS (Harvey rat sarcoma viral oncogene homolog), a member of the RAS protein family, was chosen as a potential regulator of OA chondrocyte apoptosis and ECM degradation. HRAS expression was downregulated in OA tissues, particularly in mild-OA tissues. HRAS overexpression partially attenuated IL-1β-induced OA chondrocyte apoptosis and ECM degradation. Similar to HRAS, the long non-coding RNA LINC00623 was downregulated in OA tissues. LINC00623 knockdown enhanced IL-1β-induced OA chondrocyte apoptosis and ECM degradation, which could be partially reversed by HRAS overexpression. It has been reported that lncRNAs act as ceRNAs of miRNAs to exert their function. Herein, miR-101 was predicted to bind to both LINC00623 and HRAS, which was further confirmed by luciferase reporter and RIP assays. LINC00623 competed with HRAS for miR-101 binding, therefore reducing the inhibitory effect of miR-101 on HRAS expression. More importantly, the effect of LINC00623 was partially eliminated by miR-101 inhibition. Overall, the LINC00623/miR-101/HRAS axis modulates OA chondrocyte apoptosis, senescence and ECM degradation through MAPK signaling, which might play a critical role in OA development.

Overexpression of Pitx1 attenuates the senescence of chondrocytes from osteoarthritis degeneration cartilage-A self-controlled model for studying the etiology and treatment of osteoarthritis

To explore the role of low expression of Pitx1 in degenerative cartilage tissue. A cartilage injury model was established by using the cartilage scratch method. The newly generated tissue by BrdU labeled in injured cartilage region expressed SOX-9 and Col2A1 in 5-week-old rats. Compared with that, the number of BrdU-positive cells was lower in 4-month-old cartilage injury model rats. Compared with that in lateral cartilage, the expression of Pitx1 was lower in medial cartilage. Compared with chondrocytes derived from the lateral cartilage, chondrocytes derived from the medial cartilage exhibited significantly increased cell aging, as determined by SA-β-GAL staining; downregulated Pitx1 expression; reduced autophagy levels; and decreased Col2A1 expression in a chondrogenic differentiation assay. Inhibition of Pitx1 expression in chondrocytes from the lateral cartilage significantly increased the ratio of cell senescence. Overexpression of Pitx1 in chondrocytes derived from the medial cartilage decreased the cell senescence ratio. In a luciferase assay, Pitx1 was found to promote Sirt1 gene transcription. Decreased Pitx1 expression is an essential cause of cartilage degeneration in the medial tibial plateau. The described self-controlled model is an excellent way to study OA etiology and screen therapeutic drugs for OA.

Nesfatin-1 suppresses interleukin-1β-induced inflammation, apoptosis, and cartilage matrix destruction in chondrocytes and ameliorates osteoarthritis in rats

Osteoarthritis (OA) is a chronic degenerative joint disease, related to the overexpression of matrix metalloproteinases (MMPs), a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS), inflammation, and chondrocyte apoptosis. Nesfatin-1 is an adipokine, which plays an important role in the development of OA, especially in obese people. In the present study, cartilage degradation and apoptosis observed in OA patients was evaluated. Furthermore, the anti-inflammatory and anti-apoptotic effects of nesfatin-1, and its underlying in vitro and in vivo mechanisms were investigated. The results showed that nesfatin-1 increased significantly the expression of collagen type II alpha 1 chain (Col2a1), and reduced the expression of MMPs, ADAMTS5, cyclooxygenase (COX)-2, caspase-3, nitric oxide (NO), inducible nitric oxide synthase (iNOS), prostaglandin E2 (PGE2), interleukin (IL)-6, and chondrocyte apoptosis rate, which may be induced by IL-1β in rat chondrocytes. Furthermore, nesfatin-1 treatment prevented cartilage degeneration in the rat OA model. It was found that nesfatin-1 suppressed the IL-1β-induced activation of NF-κB, the mitogen-activated protein kinase (MAPK), and the Bax/Bcl-2 signal pathway in chondrocytes. These results suggest that in vivo nesfatin-1 could play a protective role in the development of OA and can be potentially used for its treatment.

Runx2 plays a central role in Osteoarthritis development

Osteoarthritis (OA) is the most common form of arthritis, is the leading cause of impaired mobility in the elderly, and accounts for more than a third of chronic moderate to severe pain. As a degenerative joint disorder, OA affects the whole joint and results in synovial hyperplasia, degradation of articular cartilage, subchondral sclerosis, osteophyte formation, and chronic pain. Currently, there is no effective drug to decelerate OA progression and molecular targets for drug development have been insufficiently investigated. Anti-OA drug development can benefit from more and precise knowledge of molecular targets for drug development. Runt-related transcription factor 2 (Runx2) is a key transcription factor controlling osteoblast and chondrocyte differentiation and is among the most promising potential therapeutic targets. Notably, Runx2 expression is upregulated in several murine OA models, suggesting a role in disease pathogenesis. In this review article, we summarized recent findings on Runx2 related to OA development and evaluated its potential as a therapeutic target.

The translational potential of this article

A better understanding of the role of Runx2 in osteoarthritis pathogenesis will contribute to the development of novel intervention of osteoarthritis disease.

Importance of Rehabilitation in Primary Knee Osteoarthritis

In our observational study, we aim to highlight the role of rehabilitation program in the control and maintaining of the clinical and functional status of people with primary knee osteoarthritis and co-morbidities. We established that the complete rehabilitation program (diet, symptomatic medication and herbal products, electrotherapy measures and kinetic exercises) will give the optimal healthcare for this type of patients.

Activation of the leptin pathway by high expression of the long form of the leptin receptor (Ob-Rb) accelerates chondrocyte senescence in osteoarthritis

Objectives

Activation of the leptin pathway is closely correlated with human knee cartilage degeneration. However, the role of the long form of the leptin receptor (Ob-Rb) in cartilage degeneration needs further study. The aim of this study was to determine the effect of increasing the expression of Ob-Rb on chondrocytes using a lentiviral vector containing Ob-Rb.

Methods

The medial and lateral cartilage samples of the tibial plateau from 12 osteoarthritis (OA) patients were collected. Ob-Rb messenger RNA (mRNA) was detected in these samples. The Ob-Rb-overexpressing chondrocytes and controls were treated with different doses of leptin for two days. The activation of the p53/p21 pathway and the number of senescence-associated β-galactosidase (SA-β-gal)-positive cells were evaluated. The mammalian target of rapamycin (mTOR) signalling pathway and autophagy were detected after the chondrocytes were treated with a high dose of leptin.

Results

In total, 12 cases were found to have severe medial cartilage wear compared with the lateral cartilage. Immunofluorescence showed that the expression of Ob-Rb in the medial cartilage of the tibial plateau was high. High levels of leptin led to cell cycle arrest and inhibited autophagy. After overexpression of Ob-Rb, the physiological dose of leptin induced cell senescence in the chondrocytes. High doses of leptin inhibited autophagy by activating the mTOR signalling pathway. Blockade of the mTOR signalling pathway could restore autophagy and partially reverse senescence induced by leptin in chondrocytes.

Conclusion

In summary, the present study demonstrated that high doses of leptin induce cell senescence by activating the mTOR pathway in chondrocytes from OA cartilage. Highly expressed Ob-Rb accelerates chondrocyte senescence by activating the leptin pathway in OA.

Cite this article: X. Zhao, P. Huang, G. Li, L. Zhendong, G. Hu, Q. Xu. Activation of the leptin pathway by high expression of the long form of the leptin receptor (Ob-Rb) accelerates chondrocyte senescence in osteoarthritis. Bone Joint Res 2019;8:425–436. DOI: 10.1302/2046-3758.89.BJR-2018-0325.R2.

Anti-inflammatory and anti-osteoarthritis effects of Cm-02 and Ck-02

Osteoarthritis (OA) is a common degenerative joint disease characterized by progressive deterioration of articular cartilage. There have been reports that small molecule inhibitors have anti-osteoarthritis effects; however, the effects of 3-(4-chloro-2-fluorophenyl)-6-(2,4-difluorophenyl)-2H-benzo[e] [1,3]oxazine-2,4(3H)-dione (Cm-02) and 6-(2,4-difluorophenyl)-3-(3,4-difluorophenyl)-2H-benzo[e] [1,3]oxazine-2,4(3H)-dione (Ck-02), small molecule inhibitors which share many structural similarities with quercetin (a potent anti-inflammatory flavonoid), remain unclear. In this study, TNF-α-stimulated porcine and human chondrocyte models were used to investigate the inhibitory effects of Cm-02 and Ck-02 on the molecular mechanisms underlying the anti-OA effects. TNF-α was used to stimulate porcine and human chondrocytes to mimic immunomodulatory potency in-vitro. Anti-osteoarthritic effects were characterized in terms of protein and mRNA levels associated with the pathogenesis of OA. We also examined (1) the inducible nitric oxide synthase (iNOS)-nitric oxide (NO) system in cultured chondrocytes, (2) matrix metalloproteinases (MMPs) in cultured chondrocytes, and (3) aggrecan degradation in cartilage explants. Finally, we tested the activation of nuclear factor-kappaB (NF-κB), interferon regulatory factor-1 (IRF-1), and activate the protein-1 (AP-1), and we tested the signal transduction and activation of transcription-3 (STAT-3). Our results indicate that, in chondrocytes, Cm-02 and Ck-02 inhibit TNF-α induced NO production, iNOS, MMP, the expression of disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS), and the enzyme activity of MMP-13. Furthermore, both Cm-02 and Ck-02 were found to stimulate TNF-α, which has been shown to suppress the activation of several transcription factors, including NF-κB, STAT-3, and IRF-1 in porcine and human chondrocytes. Cm-02 and Ck-02 were also found to help prevent the release of proteoglycans from cartilage explants. Our findings demonstrate that both Cm-02 and Ck-02 have potent anti-inflammatory activities and the ability to protect cartilage in an OA cell model. These findings indicate that Cm-02 and Ck-02 have the potential to be further developed for the therapeutic treatment of OA.

Elevated expression of hypoxia-inducible factor-2alpha regulated catabolic factors during intervertebral disc degeneration

HEADINGS AIMS

The present study determined whether nucleus pulposus (NP) cells express hypoxia-inducible factor-2alpha (HIF-2α) and assessed its role in regulating the expression of catabolic factors during intervertebral disc degeneration.

MATERIALS AND METHODS

Human degenerated NP tissues were acquired to examine the HIF-2α expression levels using immunohistochemistry, western blotting, and Real-time PCR. Human NP cells were cultivated under normoxic or hypoxic conditions, and the HIF-2α expression was determined. Then, human NP cells were treated with HIF-2α plasmids, HIF-2α siRNA, and tumor necrosis factor-alpha (TNF-α) to evaluate the role of HIF-2α in regulating matrix metalloproteinase (MMP) and aggrecanase expression. An in vivo rabbit disc degeneration model was established to demonstrate that HIF-2α plays a critical role in disc degeneration.

KEY FINDINGS

We found that HIF-2α had a markedly elevated expression in human degenerated discs in the Grade III stage. HIF-2α protein and gene transcript levels in vitro were relatively higher under hypoxic conditions. The expression of MMP-13, ADAMTS-4 was decreased significantly in HIF-2α silencing condition, while the over-expression resulted in significantly increased levels of MMP-13 and ADAMTS-4. When cytokine TNF-α was added, HIF-2α was induced by nuclear factor-κB (NF-κB). The in vivo experiments showed that the HIF-2α controlled the catabolic factors MMP-13 and ADAMTS-4 that regulated the collagen II and aggrecan metabolism in disc degeneration.

SIGNIFICANCE

HIF-2α is a catabolic regulator in disc degeneration and directly controls the catabolic genes. The suppression of HIF-2α expression leads to decelerates extracellular matrix degradation that might represent a therapeutic target for the degenerative disc.

Peimine suppresses interleukin‑1β‑induced inflammation via MAPK downregulation in chondrocytes

Osteoarthritis (OA) is the most common type of degenerative joint disease and secreted inflammatory molecules serve a pivotal role in it. Peimine has been reported to have anti‑inflammatory activity. In order to investigate the potential therapeutic role of Peimine in OA, mouse articular chondrocytes were treated with IL‑1β and different doses of Peimine in vitro. The data revealed that Peimine not only suppressed IL‑1β‑induced production of nitric oxide (NO) and prostaglandin E2, but also reduced the protein levels of inducible NO synthase (iNOS) and cyclooxygenase‑2 (COX‑2). In addition, Peimine inhibited the IL‑1β‑induced mRNA expression of matrix metalloproteinase (MMP)‑1, MMP‑3, MMP‑9, MMP‑13, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)‑4 and ADAMTS‑5. Furthermore, Peimine inhibited IL‑1β‑induced activation of the mitogen‑activated protein kinase (MAPK) pathway. The protective effect of Peimine on IL‑1β‑treated chondrocytes was attenuated following activation of the MAPK pathway, as demonstrated by the increased expression levels of MMP‑3, MMP‑13, ADAMTS‑5, iNOS and COX‑2 compared with the Peimine group. The in vivo data suggested that Peimine limited the development of OA in the mouse model. In general, the data indicate that Peimine suppresses IL‑1β‑induced inflammation in mouse chondrocytes by inhibiting the MAPK pathway, suggesting a promising therapeutic role for Peimine in the treatment of OA.

Collagen type II suppresses articular chondrocyte hypertrophy and osteoarthritis progression by promoting integrin β1-SMAD1 interaction

Hypertrophic differentiation is not only the terminal process of endochondral ossification in the growth plate but is also an important pathological change in osteoarthritic cartilage. Collagen type II (COL2A1) was previously considered to be only a structural component of the cartilage matrix, but recently, it has been revealed to be an extracellular signaling molecule that can significantly suppress chondrocyte hypertrophy. However, the mechanisms by which COL2A1 regulates hypertrophic differentiation remain unclear. In our study, a Col2a1 p.Gly1170Ser mutant mouse model was constructed, and Col2a1 loss was demonstrated in homozygotes. Loss of Col2a1 was found to accelerate chondrocyte hypertrophy through the bone morphogenetic protein (BMP)-SMAD1 pathway. Upon interacting with COL2A1, integrin β1 (ITGB1), the major receptor for COL2A1, competed with BMP receptors for binding to SMAD1 and then inhibited SMAD1 activation and nuclear import. COL2A1 could also activate ITGB1-induced ERK1/2 phosphorylation and, through ERK1/2-SMAD1 interaction, it further repressed SMAD1 activation, thus inhibiting BMP-SMAD1-mediated chondrocyte hypertrophy. Moreover, COL2A1 expression was downregulated, while chondrocyte hypertrophic markers and BMP-SMAD1 signaling activity were upregulated in degenerative human articular cartilage. Our study reveals novel mechanisms for the inhibition of chondrocyte hypertrophy by COL2A1 and suggests that the degradation and decrease in COL2A1 might initiate and promote osteoarthritis progression.

A signaling feedback loop that contributes to cartilage degeneration may offer a fruitful target for the treatment of osteoarthritis. During the early stages of this disorder, cartilage-forming chondrocytes undergo a process of expansion known as hypertrophy, after which they die and are replaced by calcium. Researchers led by Peiqiang Su and Dongsheng Huang of Sun Yat-sen University have demonstrated that COL2A1, an important structural protein, represents an important safeguard against hypertrophy. COL2A1 helps maintain chondrocytes in their normal, healthy state, but Su and Huang showed that signaling factors produced during cartilage repair can reduce COL2A1 levels. This in turn accelerates hypertrophy, promoting further depletion of COL2A1 and ultimately leading to full-blown osteoarthritis. Drugs that break this cycle and preserve COL2A1 could thus help protect endangered joints before the damage becomes severe.

The role of ADAMTS genes in the end stage of hip osteoarthritis

PURPOSE

The aim of this study is to investigate which ADAMTS genes play a major role in the development of primary hip osteoarthritis, by comparing the tissue and blood samples in patients with hip osteoarthritis and a control group.

MATERIAL AND METHODS

Human articular cartilage was obtained from femoral heads of 15 patients with end stage osteoarthritis undergoing total hip replacement. As the control group, the cartilages was obtained from femoral heads of 15 patients, who did not have osteoarthritis or degenerative changes in hip joint, undergoing hip replacement following the fracture of the femoral neck. After the cartilage samples were taken from the resection materials, the DNA polymorphisms in the patients' cartilage samples were tested by Polymerase Chain Reaction (PCR), the serum levels of aggrecanase genes were analyzed with Enzyme-Linked ImmunoSorbent Assay (ELISA).

RESULTS

The level of ADAMTS5 and ADAMTS9 genes were found significantly lower as a result of ELISA analysis degenerative arthritis group than the control group (p < 0,05). ADAMTS 1, 4, 8, 15 were similar between the two groups in ELISA analysis (p > 0,05). As a result of quantitative real time RT-PCR analysis, the level of ADAMTS8 mRNA increased 3.5 fold in hip degenerative arthritis group when compared with femoral neck fractures group. ADAMTS1, ADAMTS4 and ADAMTS5 expression levels in hip degenerative arthritis group were decreased 2.5, 2 and 2.5 fold, respectively. ADAMTS9, 15 were found to be similar between two groups.

CONCLUSON

As a result of this study on hip osteoarthritis, the ADAMTS8 levels was found to be significantly higher in the end stage of hip osteoarthritis. Unlike similar studies on knee osteoarthritis, ADAMTS1,4,5 levels were found to be lower.

Adipose derived mesenchymal stem cells alleviated osteoarthritis and chondrocyte apoptosis through autophagy inducing

OBJECTIVE

We aim to explore the effect of adipose derived mesenchymal stem cells (ADMSCs) on a knee osteoarthritis rat model and analyze how ADMSCs affect chondrocyte apoptosis.

MATERIALS AND METHODS

A surgically induced rat knee osteoarthritis (OA) model was constructed. ADMSCs were engrafted into the right knee cavity. Hematoxylin and eosin (H&E), Masson, and Safranin O were used to compare the histopathology of synovial membrane and cartilage. Immunohistochemical (IHC) was used to measure MMP-13, Collagen 2 (Col-2), Caspase-3 (Cas-3), PARP, p62, LC3b, DDR-2, FGFR-1, Wnt, P-AKT/AKT, p-CAMKII/CAMKII, and p-Smad1/Smad1 expression in the articular cartilage. qPCR and Western blot analysis were used to detect mRNA and protein levels of markers in chondrocytes. TUNEL and Annexin-V were used to assess apoptosis.

RESULTS

Histological analysis showed that ADMSCs alleviated the deterioration of cartilage and osteoarthritis. ADMSCs coculture increase the expression of Col2 and Sox-9, while down regulated MMP-13 in IL-1β stimulated chondrocytes. ADMSCs decreased proinflammatory cytokines IL-1β, IL-6, and TNF-α. ADMSCs enhanced the viability of IL-1β stimulated chondrocytes. ADMSC attenuated chondrocyte apoptosis. The pretreatment of 3-methyladenine (3-MA) reversed the reduction of Caspase-3 caused by ADMSCs, showing that the antiapoptotic effect was associated with autophagy inducing. ADMSCs significantly reduced the expression of FGFR-1, DDR-2, and Wnt in IL-1β stimulated chondrocytes. ADMSCs reduced the ratio of p-Smad1/Smad1 and p-CAMK II/CAMKII, and increased the ratio of p-AKT/AKT.

CONCLUSIONS

ADMSCs treatment alleviate osteoarthritis in rat OA models. AMDSCs reduced the secretion of proinflammatory cytokines and protected against apoptosis through autophagy inducing. ADMSCs' function could be related to multiple signaling pathway.

The morphology and histology study on rabbit degenerated medial meniscus after posterior cruciate ligament rupture

The morphology and histology changes in the medial meniscus after posterior cruciate ligament (PCL) rupture are poorly understood. Forty-eight rabbits were divided into matched mode pairs; each rabbit had an experimental side, in which the PCL was transacted, and a control side. At the 4, 8, 16 and 24 weeks after the PCL transection, each of the 12 rabbits was killed. Histology was performed to detect the expression of the tissue inhibitors of metalloproteinases-1 (TIMP-1), matrix metalloproteinase (MMP)-1 and MMP-13 in the medial meniscus. We found that medial meniscus displayed significant degenerative characteristics in morphology. The histological evaluation of the degeneration found that the expression levels of TIMP-1, MMP-1 and MMP-13 in the medial meniscus were higher in the experiment side than those in the control side (P<0.05). The expression of both TIMP-1 and MMP-13 was initially elevated and then decreased. The MMP-1 expression reached its peak swiftly and then maintained a relatively high level. There were clear time-dependent degenerative changes in the histology of the medial meniscus after PCL rupture. The high expression of TIMP-1, MMP-1 and MMP-13 in the cartilage may be responsible for the degeneration, and PCL rupture may trigger meniscus degradation and ultimately osteoarthritis.

Vitamin D in the Prevention and Treatment of Osteoarthritis: From Clinical Interventions to Cellular Evidence

Older adults are recommended vitamin D to prevent fractures. Though this population is also at risk of osteoarthritis (OA), the effect of vitamin D on OA is unclear and may differ by disease state. The relationship between vitamin D and OA during OA initiation and progression were considered in this narrative review of in vivo and in vitro studies. Regarding OA initiation in humans, the small number of published observational studies suggest a lack of association between induction of OA and vitamin D status. Most randomized controlled trials were performed in White OA patients with relatively high vitamin D status (>50 nmol/L). These studies found no benefit of vitamin D supplementation on OA progression. However, subset analyses and one randomized controlled pilot trial indicated that vitamin D supplementation may alleviate joint pain in OA patients with low vitamin D status (<50 nmol/L). As the etiology of OA is recently being more fully uncovered, better animal and cell models are needed. According to currently available clinical results, evidence is lacking to set a vitamin D level to prevent OA, and increasing vitamin D status above 50 nmol/L does not seem to benefit OA patients.

Role of Forkhead Box O Transcription Factors in Oxidative Stress-Induced Chondrocyte Dysfunction: Possible Therapeutic Target for Osteoarthritis?

Chondrocyte dysfunction occurs during the development of osteoarthritis (OA), typically resulting from a deleterious increase in oxidative stress. Accordingly, strategies for arresting oxidative stress-induced chondrocyte dysfunction may lead to new potential therapeutic targets for OA treatment. Forkhead box O (FoxO) transcription factors have recently been shown to play a protective role in chondrocyte dysfunction through the regulation of inflammation, autophagy, aging, and oxidative stress. They also regulate growth, maturation, and matrix synthesis in chondrocytes. In this review, we discuss the recent progress made in the field of oxidative stress-induced chondrocyte dysfunction. We also discuss the protective role of FoxO transcription factors as potential molecular targets for the treatment of OA. Understanding the function of FoxO transcription factors in the OA pathology may provide new insights that will facilitate the development of next-generation therapies to prevent OA development and to slow OA progression.

Role of Forkhead Box O Transcription Factors in Oxidative Stress-Induced Chondrocyte Dysfunction: Possible Therapeutic Target for Osteoarthritis?

Chondrocyte dysfunction occurs during the development of osteoarthritis (OA), typically resulting from a deleterious increase in oxidative stress. Accordingly, strategies for arresting oxidative stress-induced chondrocyte dysfunction may lead to new potential therapeutic targets for OA treatment. Forkhead box O (FoxO) transcription factors have recently been shown to play a protective role in chondrocyte dysfunction through the regulation of inflammation, autophagy, aging, and oxidative stress. They also regulate growth, maturation, and matrix synthesis in chondrocytes. In this review, we discuss the recent progress made in the field of oxidative stress-induced chondrocyte dysfunction. We also discuss the protective role of FoxO transcription factors as potential molecular targets for the treatment of OA. Understanding the function of FoxO transcription factors in the OA pathology may provide new insights that will facilitate the development of next-generation therapies to prevent OA development and to slow OA progression.

Inhibition of Osteoarthritis-Related Molecules by Isomucronulatol 7-O-β-d-glucoside and Ecliptasaponin A in IL-1β-Stimulated Chondrosarcoma Cell Model

Osteoarthritis (OA) is the common form of arthritis and is characterized by disability and cartilage degradation. Although natural product extracts have been reported to have anti-osteoarthritic effects, the potential bioactivity of Ryupunghwan (RPH), a traditional Korean medicinal botanical formula that contains Astragalus membranaceus, Turnera diffusa, Achyranthes bidentata, Angelica gigas, Eclipta prostrata, Eucommia ulmoides, and Ilex paraguariensis, is not known well. Therefore, the inhibitory effects of single compounds isolated from RPH on the OA-related molecules were investigated using IL-1β-stimulated chondrosarcoma SW1353 (SW1353) cell model. Two bioactive compounds, isomucronulatol 7-O-β-d-glucoside (IMG) and ecliptasaponin A (ES) were isolated and purified from RPH using column chromatography, and then the structures were analyzed using ESI-MS, ¹H-NMR, and ¹³C-NMR spectrum. The expression or amount of matrix metalloproteinase 13 (MMP13), COX1/2, TNF-α, IL-1β or p65 was determined by RT-PCR, Western blot, and enzyme-linked immunosorbent assay (ELISA). RPH pretreatment reduced the expression and amounts of MMP13, and the expression of collagen II, COX1/2, TNF-α, IL-1β or p65, which were increased in IL-1β-stimulated SW1353 cells. IMG reduced the expression of all OA-related molecules, but the observed inhibitory effect was less than that of RPH extract. The other single compound ES showed the reduced expression of all OA-related molecules, and the effect was stronger than that in IMG (approximately 100 fold). Combination pretreatment of both single components remarkably reduced the expression of MMP13, compared to each single component. These synergic effects may provide potential molecular modes of action for the anti-osteoarthritic effects of RPH observed in clinical and animal studies.