Potential role of hyaluronic acid on bone in osteoarthritis: matrix metalloproteinases, aggrecanases, and RANKL expression are partially prevented by hyaluronic acid in interleukin 1-stimulated osteoblasts

The Mechanism and Role of ADAMTS Protein Family in Osteoarthritis

Osteoarthritis (OA) is a principal cause of aches and disability worldwide. It is characterized by the inflammation of the bone leading to degeneration and loss of cartilage function. Factors, including diet, age, and obesity, impact and/or lead to osteoarthritis. In the past few years, OA has received considerable scholarly attention owing to its increasing prevalence, resulting in a cumbersome burden. At present, most of the interventions only relieve short-term symptoms, and some treatments and drugs can aggravate the disease in the long run. There is a pressing need to address the safety problems due to osteoarthritis. A disintegrin-like and metalloprotease domain with thrombospondin type 1 repeats (ADAMTS) metalloproteinase is a kind of secretory zinc endopeptidase, comprising 19 kinds of zinc endopeptidases. ADAMTS has been implicated in several human diseases, including OA. For example, aggrecanases, ADAMTS-4 and ADAMTS-5, participate in the cleavage of aggrecan in the extracellular matrix (ECM); ADAMTS-7 and ADAMTS-12 participate in the fission of Cartilage Oligomeric Matrix Protein (COMP) into COMP lyase, and ADAMTS-2, ADAMTS-3, and ADAMTS-14 promote the formation of collagen fibers. In this article, we principally review the role of ADAMTS metalloproteinases in osteoarthritis. From three different dimensions, we explain how ADAMTS participates in all the following aspects of osteoarthritis: ECM, cartilage degeneration, and synovial inflammation. Thus, ADAMTS may be a potential therapeutic target in osteoarthritis, and this article may render a theoretical basis for the study of new therapeutic methods for osteoarthritis.

Hyaluronic acid as an adjunct to microfracture in the treatment of osteochondral lesions of the talus: a systematic review of randomized controlled trials

BACKGROUND

Osteochondral lesions of the talus (OLT) are common after ankle trauma. Studies have shown that bioactive substances, such as hyaluronic acid (HA), alone, or in combination, with surgical treatment could improve cartilage regeneration and repair, but the effect of HA on patient reported outcomes is unclear.

METHODS

Literature searches were performed across four databases (PubMed, SPORTDiscus, Scopus, and The Cochrane Library) for randomized controlled trials in which at least one treatment arm involved use of HA as an adjunct to microfracture to treat patients with OLT. Primary outcomes included the American Orthopaedic Foot and Ankle Society scores (AOFAS), and the Visual Analog Scale (VAS) for pain. The level of evidence and methodological quality were evaluated using the Modified Coleman Methodology Score (MCMS).

RESULTS

Three randomized studies were eligible for review with a total of 132 patients (35, 40, 57 patients, respectively) and follow-up ranged from 10.5 to 25 months. Utilization of HA at the time of microfracture resulted in greater improvement in AOFAS scores compared to microfracture alone. The pooled effect size was moderate (Standardized Mean Difference [SMD] 0.45, 95% Confidence Interval [CI] 0.06, 0.84; P = .02) and between-study heterogeneity was low (I-squared = 0%). Utilization of HA during microfracture also led to greater improvement in VAS-pain scores compared to microfracture alone. The pooled effect size was very large (SMD -3.86, 95% CI -4.75, - 2.97; P < .001) and heterogeneity was moderate (I-squared = 69%).

CONCLUSION

Hyaluronic acid injection as an adjunct to arthroscopic MF in OLT provides clinically important improvements in function and pain at short-term follow-up compared to MF alone. Future longer-term follow-up studies are warranted to investigate the durability of MF with HA for treatment of OLT.

Role of Mitochondria in Physiology of Chondrocytes and Diseases of Osteoarthritis and Rheumatoid Arthritis

PURPOSE OF REVIEW

Mitochondria are recognized to be one of the most important organelles in chondrocytes for their role in triphosphate (ATP) generation through aerobic phosphorylation. Mitochondria also participate in many intracellular processes involving modulating reactive oxygen species (ROS), responding to instantaneous hypoxia stress, regulating cytoplasmic transport of calcium ion, and directing mitophagy to maintain the homeostasis of individual chondrocytes.

DESIGNS

To summarize the specific role of mitochondria in chondrocytes, we screened related papers in PubMed database and the search strategy is ((mitochondria) AND (chondrocyte)) AND (English [Language]). The articles published in the past 5 years were included and 130 papers were studied.

RESULTS

In recent years, the integrity of mitochondrial structure has been regarded as a prerequisite for normal chondrocyte survival and defect in mitochondrial function has been found in cartilage-related diseases, such as osteoarthritis (OA) and rheumatoid arthritis (RA). However, the understanding of mitochondria in cartilage is still largely limited. The mechanism on how the changes in mitochondrial structure and function directly lead to the occurrence and development of cartilage-related diseases remains to be elusive.

CONCLUSION

This review aims to summarize the role of mitochondria in chondrocytes under the physiological and pathological changes from ATP generation, calcium homeostasis, redox regulation, mitophagy modulation, mitochondria biogenesis to immune response activation. The enhanced understanding of molecular mechanisms in mitochondria might offer some new cues for cartilage remodeling and pathological intervention.

Characterization of hyaluronan-coated extracellular vesicles in synovial fluid of patients with osteoarthritis and rheumatoid arthritis

BACKGROUND

Hyaluronic acid (HA) is the major extracellular matrix glycosaminoglycan with a reduced synovial fluid (SF) concentration in arthropathies. Cell-derived extracellular vesicles (EV) have also been proposed to contribute to pathogenesis in joint diseases. It has recently been shown that human SF contains HA-coated EV (HA-EV), but their concentration and function in joint pathologies remain unknown.

METHODS

The aim of the present study was to develop an applicable method based on confocal laser scanning microscopy (CLSM) and image analysis for the quantification of EV, HA-particles, and HA-EV in the SF of the human knee joint. Samples were collected during total knee replacement surgery from patients with end-stage rheumatoid arthritis (RA, n = 8) and osteoarthritis (OA, n = 8), or during diagnostic/therapeutic arthroscopy unrelated to OA/RA (control, n = 7). To characterize and quantify EV, HA-particles, and HA-EV, SF was double-stained with plasma membrane and HA probes and visualized by CLSM. Comparisons between the patient groups were performed with the Kruskal-Wallis analysis of variance.

RESULTS

The size distribution of EV and HA-particles was mostly similar in the study groups. Approximately 66% of EV fluorescence was co-localized with HA verifying that a significant proportion of EV carry HA. The study groups were clearly separated by the discriminant analysis based on the CLSM data. The intensities of EV and HA-particle fluorescences were lower in the RA than in the control and OA groups.

CONCLUSIONS

CLSM analysis offers a useful tool to assess HA-EV in SF samples. The altered EV and HA intensities in the RA SF could have possible implications for diagnostics and therapy.

Regulatory Effects and Interactions of the Wnt and OPG-RANKL-RANK Signaling at the Bone-Cartilage Interface in Osteoarthritis

Cartilage and the bordering subchondral bone form a functionally active regulatory interface with a prominent role in osteoarthritis pathways. The Wnt and the OPG-RANKL-RANK signaling systems, as key mediators, interact in subchondral bone remodeling. Osteoarthritic osteoblasts polarize into two distinct phenotypes: a low secretory and an activated, pro-inflammatory and anti-resorptive subclass producing high quantities of IL-6, PGE2, and osteoprotegerin, but low levels of RANKL, thus acting as putative effectors of subchondral bone sclerosis. Wnt agonists, Wnt5a, Wisp-1 initiate excessive bone remodeling, while Wnt3a and 5a simultaneously cause loss of proteoglycans and phenotype shift in chondrocytes, with decreased expression of COL2A, aggrecan, and Sox-9. Sclerostin, a Wnt antagonist possesses a protective effect for the cartilage, while DKK-1 inhibits VEGF, suspending neoangiogenesis in the subchondral bone. Experimental conditions mimicking abnormal mechanical load, the pro-inflammatory milieu, but also a decreased OPG/RANKL ratio in the cartilage, trigger chondrocyte apoptosis and loss of the matrix via degradative matrix metalloproteinases, like MMP-13 or MMP-9. Hypoxia, an important cofactor exerts a dual role, promoting matrix synthesis via HIF-1α, a Wnt silencer, but turning on HIF-2α that enhances VEGF and MMP-13, along with aberrant collagen expression and extracellular matrix deterioration in the presence of pro-inflammatory cytokines.

Expression of the RANK/RANKL/OPG system in the human intervertebral disc: implication for the pathogenesis of intervertebral disc degeneration

BACKGROUND

The expression of the receptor activator of nuclear factor kappa B (RANK) /RANK ligand (RANKL) /osteoprotegerin (OPG) system and its association with the progression of intervertebral disc (IVD) degeneration has recently been reported in a human IVD. However, the effect of the RANK/RANKL/OPG system on the matrix metabolism of human IVD cells, especially on the expression of catabolic factors relevant to IVD degeneration, remains unknown. The purpose of this study was to examine the expression of the RANK/RANKL/OPG system, and then to evaluate the effect of this system on the expression of catabolic factors by human IVD cells.

METHODS

Annulus fibrosus (AF) and nucleus pulposus (NP) cells isolated by sequential enzyme digestion from human IVD tissues obtained during spine surgeries were monolayer cultured. The expression of the RANK/RANKL/OPG system was determined using immunohistochemical methods and real-time polymerase chain reaction (PCR). To evaluate the influence of interleukin-1 beta (IL-1β) stimulation on the mRNA expression of RANK, RANKL, and OPG, recombinant human IL-1β (rhIL-1β) was administered in the culture media of IVD cells. To examine the influence of RANKL signaling on the expression of matrix metalloprotease-3 (MMP-3), MMP-13, and IL-1β, the cells were cultured with exogenous recombinant human RANKL (rhRANKL), recombinant human OPG (rhOPG) or anti-human RANKL mouse monoclonal antibody (ahRANKL-mAB) with or without rhIL-1β.

RESULTS

Immunoreactivity to RANK/RANKL/OPG and the mRNA expression of the three genes were obviously identified in both AF and NP cells. rhIL-1β stimulation significantly upregulated the mRNA expression level of RANK/RANKL/OPG. The mRNA expression of catabolic factors was significantly upregulated by stimulation of rhRANKL in the presence of rhIL-1β. On the other hand, the administration of either rhOPG or ahRANKL-mAB significantly suppressed the mRNA expression of catabolic factors that had been upregulated by rhIL-1β stimulation. The suppressive effect of ahRANKL-mAB against rhIL-1β stimulation was also confirmed by the protein expression of MMP-3.

CONCLUSIONS

The present study showed that the RANK/RANKL/OPG system may be involved in the progression of IVD degeneration. This study also suggested the potential use of anti-RANKL monoclonal antibody and OPG as therapeutic agents to suppress the progression of IVD degeneration.

The therapeutic effect of aucubin-supplemented hyaluronic acid on interleukin-1beta-stimulated human articular chondrocytes

BACKGROUND

Injection of exogenous hyaluronic acid (HA) into the joint capsule improves symptoms of early stage osteoarthritis (OA). However, reactive oxygen species degrade HA into small oligosaccharides that can elicit pro-inflammatory responses. Likewise, disturbance of the antioxidant enzyme system and generation of oxidative stress by pro-inflammatory cytokines worsen knee OA. Accordingly, we proposed the use of aucubin, an antioxidant and anti-inflammatory compound, as a versatile adjuvant to HA for treating OA.

METHODS

Primary human chondrocytes were cultured in media supplemented with aucubin in a series of concentrations (0, 0.01, 0.1, 1, and 10 μg/ml) to study dose-dependent toxicity. We then evaluated the therapeutic effects of HA (100 μg/ml) supplemented with aucubin (10 μg/ml) on interleukin-1 beta (IL-1β, 10 ng/ml)-stimulated chondrocytes.

RESULTS

The use of aucubin did not change cell viability or alter lactate dehydrogenase release to normal chondrocytes. Although the proliferation and sulfated glycosaminoglycan production were not affected, aucubin partially restored the hypertrophic transformation of chondrocytes. Relative to treatment with HA or aucubin alone, real-time PCR revealed that aucubin-supplemented HA down-regulated the mRNA levels of tumor necrosis factor-alpha (TNF-α), corrected collagen type 1 and aggrecan, and up-regulated tissue inhibitor of metalloproteinase 1. Moreover, ELISA testing also showed a reduced TNF-α production. Although superoxide dismutases activity was still distributed, aucubin restored total antioxidant capacity of IL-1β-stimulated chondrocytes. Western blotting further showed that aucubin inhibited cyclooxygenase-2 and regulated the nuclear factor (erythroid-derived 2)-like 2 pathway.

CONCLUSION

Aucubin can enhance the anti-catabolic and anti-inflammatory effects of HA on OA chondrocytes.

Interleukin-1β signaling in osteoarthritis - chondrocytes in focus

Osteoarthritis (OA) can be regarded as a chronic, painful and degenerative disease that affects all tissues of a joint and one of the major endpoints being loss of articular cartilage. In most cases, OA is associated with a variable degree of synovial inflammation. A variety of different cell types including chondrocytes, synovial fibroblasts, adipocytes, osteoblasts and osteoclasts as well as stem and immune cells are involved in catabolic and inflammatory processes but also in attempts to counteract the cartilage loss. At the molecular level, these changes are regulated by a complex network of proteolytic enzymes, chemokines and cytokines (for review: [1]). Here, interleukin-1 signaling (IL-1) plays a central role and its effects on the different cell types involved in OA are discussed in this review with a special focus on the chondrocyte.

Hyaluronan in the experimental injury of the cartilage: biochemical action and protective effects

INTRODUCTION

Our knowledge of extracellular matrix (ECM) structure and function has increased enormously over the last decade or so. There is evidence demonstrating that ECM provides signals affecting cell adhesion, shape, migration, proliferation, survival, and differentiation. ECM presents many domains that become active after proteolytic cleavage. These active ECM fragments are called matrikines which play different roles; in particular, they may act as potent inflammatory mediators during cartilage injury.

FINDINGS

A major component of the ECM that undergoes dynamic regulation during cartilage damage and inflammation is the non-sulphated glycosaminoglycan (GAG) hyaluronan (HA). In this contest, HA is the most studied because of its different activity due to the different polymerization state. In vivo evidences have shown that low molecular weight HA exerts pro-inflammatory action, while high molecular weight HA possesses anti-inflammatory properties. Therefore, the beneficial HA effects on arthritis are not only limited to its viscosity and lubricant action on the joints, but it is especially due to a specific and effective anti-inflammatory activity. Several in vitro experimental investigations demonstrated that HA treatment may regulate different biochemical pathways involved during the cartilage damage. Emerging reports are suggesting that the ability to recognize receptors both for the HA degraded fragments, whether for the high-polymerized native HA involve interaction with integrins, toll-like receptors (TLRs), and the cluster determinant (CD44). The activation of these receptors induced by small HA fragments, via the nuclear factor kappa-light-chain enhancer of activated B cell (NF-kB) mediation, directly or other different pathways, produces the transcription of a large number of damaging intermediates that lead to cartilage erosion.

CONCLUSIONS

This review briefly summarizes a number of findings of the recent studies focused on the protective effects of HA, at the different polymerization states, on experimental arthritis in vitro both in animal and human cultured chondrocytes.

Effects of strontium ranelate treatment on osteoblasts cultivated onto scaffolds of trabeculae bovine bone

Blocks of Bovine bone have shown promising results as implantable scaffolds to promote bone regeneration. Strontium ranelate (SrR) is both an antiresorptive and an anabolic drug that has been indicated for oral administration to treat osteoporosis. Few studies, however, have investigated the local effects of SrR and its use in association with biomaterials thus far. In this work, we investigated SrR effects in cultures of primary osteoblasts (PO, from Wistar rats calvaria) and immortalized osteoblasts (IO, from MC3T3-E1 cell line) cultivated as a monolayer or in association with scaffolds of bovine bone in mineralized (MBB) and demineralized (DBB) forms. The optimum dose to induce SrR effects on cell viability was established as 0.1 mM. Our results suggested that the local administration of SrR is biocompatible and non-cytotoxic. In addition, SrR appeared to accelerate primary osteoblast cell differentiation by enhancing alkaline phosphatase activity, the expression of osteogenic differentiation markers, the synthesis of the organic matrix, and a decrease of Ca²⁺ ions in mineralized nodules. DBB was found to be a better scaffold material to promote PO and IO cell proliferation. Exposing the proteins of the demineralized bone matrix might improve scaffold osteoconductive properties. Our results indicated the importance of further investigation of the administration of SrR at sites of bone repair. The association of SrR and bone grafts suggests the possibility of using SrR as a co-adjuvant for bone tissue bioengineering and in bone regeneration therapies.

Platelets Contribute to the Accumulation of Matrix Metalloproteinase Type 2 in Synovial Fluid in Osteoarthritis

Inflammation plays a role in the initiation and progression of osteoarthritis (OA), a chronic degenerative joint disorder. Platelets are inflammatory cells, contain and release matrix metalloproteinases (MMPs) and favour the release of these enzymes, key effectors of cartilage and subchondral bone degradation, by other cells; however, their role in OA has not been investigated yet. Our aims were (1) to assess the presence of platelets and of MMP-2 in synovial fluid (SF) of OA patients; (2) to evaluate the contribution of platelets to MMP-2 release by fibroblast-like synoviocytes (FLS); and (3) to investigate if hyaluronic acid (HA) interferes with these processes. SF was collected from 27 OA patients before and after treatment with intra-articular HA (20 mg/2 mL). Moreover, FLS were co-cultured with platelets, and the release of MMP-2 in supernatants was measured. Our results show that platelets are present in OA SF and show markers of activation. OA SF also contains relevant amounts of MMP-2. Co-incubation of platelets with FLS favours the release of MMP-2 by the interaction of platelet surface P-selectin with FLS CD44 by a mechanism involving the activation of pAkt and pSrc in FLS. Administration of HA to OA patients decreased the infiltration of platelets in SF and reduced the levels of MMP-2. The addition of HA in vitro inhibited the release of MMP-2 by FLS triggered by the interaction with platelets. In conclusion, our data show that platelets may contribute to joint degeneration in OA by favouring the accumulation of MMP-2 in SF.

Multiple PRP injections are more effective than single injections and hyaluronic acid in knees with early osteoarthritis: a randomized, double-blind, placebo-controlled trial

PURPOSE

To compare the effectiveness of intraarticular (IA) multiple and single platelet-rich plasma (PRP) injections as well as hyaluronic acid (HA) injections in different stages of osteoarthritis (OA) of the knee.

METHODS

A total of 162 patients with different stages of knee OA were randomly divided into four groups receiving 3 IA doses of PRP, one dose of PRP, one dose of HA or a saline injection (control). Then, each group was subdivided into two groups: early OA (Kellgren-Lawrence grade 0 with cartilage degeneration or grade I-III) and advanced OA (Kellgren-Lawrence grade IV). The patients were evaluated before the injection and at the 6-month follow-ups using the EuroQol visual analogue scale (EQ-VAS) and International Knee Documentation Committee (IKDC) subjective scores. Adverse events and patient satisfaction were recorded.

RESULTS

There was a statistically significant improvement in the IKDC and EQ-VAS scores in all the treatment groups compared with the control group. The knee scores of patients treated with three PRP injections were significantly better than those patients of the other groups. There was no significant difference in the scores of patients injected with one dose of PRP or HA. In the early OA subgroups, significantly better clinical results were achieved in the patients treated with three PRP injections, but there was no significant difference in the clinical results of patients with advanced OA among the treatment groups.

CONCLUSION

The clinical results of this study suggest IA PRP and HA treatment for all stages of knee OA. For patients with early OA, multiple (3) PRP injections are useful in achieving better clinical results. For patients with advanced OA, multiple injections do not significantly improve the results of patients in any group.

LEVEL OF EVIDENCE

I.

The extracellular matrix in cancer progression: Role of hyalectan proteoglycans and ADAMTS enzymes

Remodelling of the extracellular matrix (ECM) has emerged as a key factor in cancer progression. Proteoglycans, including versican and other hyalectans, represent major structural elements of the ECM where they interact with other important molecules, including the glycosaminoglycan hyaluronan and the CD44 cell surface receptor. The hyalectan proteoglycans are regulated through cleavage by the proteolytic actions of A Disintegrin-like And Metalloproteinase domain with Thrombospondin-1 motif (ADAMTS) family members. Alteration in the balance between hyalectan proteoglycans and ADAMTS enzymes has been proposed to be a crucial factor in cancer progression either in a positive or negative manner depending on the context. Further complexity arises due to the formation of bioactive cleavage products, such as versikine, which may also play a role, and non-enzymatic functions for ADAMTS proteins. This research is providing fresh insights into cancer biology and opportunities for the development of new diagnostic and treatment strategies.

Evaluation of the effect of N-acetyl-glucosamine administration on biomarkers for cartilage metabolism in healthy individuals without symptoms of arthritis: A randomized double-blind placebo-controlled clinical study

The present study aimed to evaluate the effect of N-acetyl-glucosamine (GlcNAc) on the joint health of healthy individuals without arthritic symptoms. A randomized double-blind placebo-controlled clinical trial was performed to investigate the effect of oral administration of a GlcNAc-containing test supplement (low dose, 500 mg/day and high dose, 1,000 mg/day) on cartilage metabolism in healthy individuals with a mean age of 48.6±1.3 years (range, 23-64 years) by analyzing the ratio of type II collagen degradation to type II collagen synthesis using type II collagen degradation (C2C) and synthesis (PIICP) markers. The results indicated that the changes in C2C/PIICP ratios from the baseline were suppressed in the treated with low and high doses of GlcNAc, compared with the placebo group at week 16 during intervention. To further elucidate the effect of GlcNAc, subjects with impaired cartilage metabolism were evaluated. Notably, the changes in the C2C/PIICP ratios were markedly suppressed in the groups treated with low and high doses of GlcNAc at week 16. Finally, to exclude the effect of heavy body weight on joint loading, subjects weighing <70 kg with impaired cartilage metabolism were analyzed. Notably, the changes in the C2C/PIICP ratios were suppressed in the groups treated with low and high doses of GlcNAc at weeks 12 and 16. No test supplement-related adverse events were observed during or following the intervention. Together, these observations suggest that oral administration of GlcNAc at doses of 500 mg and 1,000 mg/day exhibits a chondroprotective effect on healthy individuals by reducing the C2C/PIICP ratio (relatively decreasing type II collagen degradation and increasing type II collagen synthesis) without any apparent adverse effects.

The mechanism of action for hyaluronic acid treatment in the osteoarthritic knee: a systematic review

BACKGROUND

Knee osteoarthritis (OA) is one of the leading causes of disability within the adult population. Current treatment options for OA of the knee include intra-articular (IA) hyaluronic acid (HA), a molecule found intrinsically within the knee joint that provides viscoelastic properties to the synovial fluid. A variety of mechanisms in which HA is thought to combat knee OA are reported in the current basic literature.

METHODS

We conducted a comprehensive literature search to identify currently available primary non-clinical basic science articles focussing on the mechanism of action of IA-HA treatment. Included articles were assessed and categorized based on the mechanism of action described within them. The key findings and conclusions from each included article were obtained and analyzed in aggregate with studies of the same categorical assignment.

RESULTS

Chondroprotection was the most frequent mechanism reported within the included articles, followed by proteoglycan and glycosaminoglycan synthesis, anti-inflammatory, mechanical, subchondral, and analgesic actions. HA-cluster of differentiation 44 (CD44) receptor binding was the most frequently reported biological cause of the mechanisms presented. High molecular weight HA was seen to be superior to lower molecular weight HA products. HA derived through a biological fermentation process is also described as having favorable safety outcomes over avian-derived HA products.

CONCLUSIONS

The non-clinical basic science literature provides evidence for numerous mechanisms in which HA acts on joint structures and function. These actions provide support for the purported clinical benefit of IA-HA in OA of the knee. Future research should not only focus on the pain relief provided by IA-HA treatment, but the disease modification properties that this treatment modality possesses as well.

Leptin induces oncostatin M production in osteoblasts by downregulating miR-93 through the Akt signaling pathway

Inflammatory response and articular destruction are common symptoms of osteoarthritis (OA) and rheumatoid arthritis (RA). Leptin, an adipocyte-secreted hormone that centrally regulates weight control, may exert proinflammatory effects in the joint, depending on the immune response. Yet, the mechanism of leptin interacting with the arthritic inflammatory response is unclear. This study finds that leptin increased expression of oncostatin M (OSM) in human osteoblasts in a concentration- and time-dependent manner. In addition, OBRl, but not OBRs receptor antisense oligonucleotide, abolished the leptin-mediated increase of OSM expression. On the other hand, leptin inhibited miR-93 expression; an miR-93 mimic reversed leptin-increased OSM expression. Stimulation of osteoblasts with leptin promoted Akt phosphorylation, while pretreatment of cells with Akt inhibitor or siRNA reversed leptin-inhibited miR-93 expression. Our results showed that leptin heightened OSM expression by downregulating miR-93 through the Akt signaling pathway in osteoblasts, suggesting leptin as a novel target in arthritis treatment.

CCN1 induces oncostatin M production in osteoblasts via integrin-dependent signal pathways

Inflammatory response and articular destruction are common symptoms of osteoarthritis. Cysteine-rich 61 (CCN1 or Cyr61), a secreted protein from the CCN family, is associated with the extracellular matrix involved in many cellular activities like growth and differentiation. Yet the mechanism of CCN1 interacting with arthritic inflammatory response is unclear. This study finds CCN1 increasing expression of oncostatin m (OSM) in human osteoblastic cells. Pretreatment of αvβ3 monoclonal antibody and inhibitors of focal adhesion kinase (FAK), c-Src, phosphatidylinositol 3-kinase (PI3K), and NF-κB inhibited CCN1-induced OSM expression in osteoblastic cells. Stimulation of cells with CCN1 increased phosphorylation of FAK, c-Src, PI3K, and NF-κB via αvβ3 receptor; CCN1 treatment of osteoblasts increased NF-κB-luciferase activity and p65 binding to NF-κB element on OSM promoter. Results indicate CCN1 heightening OSM expression via αvβ3 receptor, FAK, c-Src, PI3K, and NF-κB signal pathway in osteoblastic cells, suggesting CCN1 as a novel target in arthritis treatment.