Intra-articular Hyaluronan Therapy for Symptomatic Knee Osteoarthritis

Comparison of Different Molecular Weights of Intra-Articular Hyaluronic Acid Injections for Knee Osteoarthritis: A Level I Bayesian Network Meta-Analysis

Background: The present Bayesian network meta-analysis compared the efficacy of intra-articular injections of different molecular weights of hyaluronic acid (HA) in patients with knee osteoarthritis. Methods: In November 2024, the following databases were accessed: PubMed, Web of Science, Google Scholar, and Embase. All randomised controlled trials investigating the efficacy of intra-articular HA injections for knee osteoarthritis were accessed. The outcome of interest was to evaluate pain according to the visual analogue scale (VAS). The groups included for comparison were the ultra-high molecular weight (UHMW), high molecular weight (HMW), medium molecular weight (MMW), and low molecular weight (LMW). Results: Data from 9822 patients were collected. The mean age of the patients was 62.1 ± 5.0 years with given comparability at baseline. Different follow-up periods were compared. The longest control period ranged from four to six months, and the UHMW and HMW injections were the interventions associated with the greatest reduction in the VAS. LMW HA was the intervention associated with the lowest decrease in VAS, falling short of the control group. Conclusions: The main findings of the present Bayesian network meta-analysis, with a current level I of evidence, suggests that the UHMW and HMW HA has a beneficial effect on pain at 6 months post intervention in patients with knee osteoarthritis.

Intra-articular interventions in osteoarthritis: Navigating the landscape of hyaluronic acid, mesenchymal stem cells, and platelet-rich plasma

Osteoarthritis (OA) poses a substantial burden on patients, leading to pain, functional decline, and reduced quality of life. While conventional treatments focus on symptom management, disease-modifying interventions are yet to be established. This review explores the efficacy of intra-articular interventions, particularly hyaluronic acid (HA), mesenchymal stem cells (MSCs), and platelet-rich plasma (PRP), in the context of OA management. HA injections, with diverse formulations like Hylan G-F20, sodium hyaluronate, and hyaluronan, present varying outcomes, necessitating a nuanced understanding of their effectiveness and timing. MSC therapy, derived from adipose tissue, umbilical cord, or bone marrow, shows promising results in clinical improvement, with adipose-derived MSCs demonstrating efficacy in maintaining benefits over 6 mo. Conversely, bone-marrow-derived MSCs show limited effectiveness, highlighting the need for source-specific considerations. PRP has emerged as a superior option for long-term pain reduction and quality of life improvement, with leukocyte-poor formulations and a critical platelet count of 10 billion demonstrating optimal results. This comprehensive analysis underscores the potential of intra-articular interventions in OA management, emphasizing the need for personalized and evidence-based approaches to enhance treatment efficacy and patient outcomes.

Mechanobiology of Hyaluronan: Connecting Biomechanics and Bioactivity in Musculoskeletal Tissues

Hyaluronan (HA) plays well-recognized mechanical and biological roles in articular cartilage and synovial fluid, where it contributes to tissue structure and lubrication. An understanding of how HA contributes to the structure of other musculoskeletal tissues, including muscle, bone, tendon, and intervertebral discs, is growing. In addition, the use of HA-based therapies to restore damaged tissue is becoming more prevalent. Nevertheless, the relationship between biomechanical stimuli and HA synthesis, degradation, and signaling in musculoskeletal tissues remains understudied, limiting the utility of HA in regenerative medicine. In this review, we discuss the various roles and significance of endogenous HA in musculoskeletal tissues. We use what is known and unknown to motivate new lines of inquiry into HA biology within musculoskeletal tissues and in the mechanobiology governing HA metabolism by suggesting questions that remain regarding the relationship and interaction between biological and mechanical roles of HA in musculoskeletal health and disease.

Predictors of Placebo Response to Local (Intra-Articular) Therapy In Osteoarthritis: An Individual Participant Data Meta-Analysis

OBJECTIVE

We undertook this study to evaluate potential predictors of placebo response with intra-articular (IA) injections for knee/hip osteoarthritis (OA) using individual participant data (IPD) from existing trials.

METHODS

Randomized placebo-controlled trials evaluating IA glucocorticoid or hyaluronic acid published to September 2018 were selected. IPD for disease characteristics and outcome measures were acquired. Potential predictors of placebo response included participant characteristics, pain severity, intervention, and trial design. Placebo response was defined as at least a 20% reduction in baseline pain. Logistic regression models and odds ratios were computed as effect measures to evaluate patient and pain mechanisms and then pooled using a random effects model. Generalized mixed-effect models were applied to intervention and trial characteristics.

RESULTS

Of 56 eligible trials, 6 shared data, and these were combined with the existing 4 OA Trial Bank studies, yielding 10 studies with IPD of 621 placebo participants for analysis. In the total placebo population, at short-term follow-up, the use of local anesthetic and ultrasound guidance were associated with reduced odds of placebo response. At midterm follow-up, mid- to long-term trial duration was associated with increased odds of placebo response, and worse baseline function scores were associated with reduced odds of a placebo response.

CONCLUSION

The administration of local anesthetics or ultrasound guidance may reduce IA placebo response at short-term follow-up. At midterm follow-up, participants with worse baseline function scores may be less likely to respond to IA placebo, and mid- to long-term trial duration may enhance the placebo response. Further studies are required to corroborate these potential predictors of IA placebo response.

Ex Vivo Functional Benchmarking of Hyaluronan-Based Osteoarthritis Viscosupplement Products: Comprehensive Assessment of Rheological, Lubricative, Adhesive, and Stability Attributes

While many injectable viscosupplementation products are available for osteoarthritis (OA) management, multiple hydrogel functional attributes may be further optimized for efficacy enhancement. The objective of this study was to functionally benchmark four commercially available hyaluronan-based viscosupplements (Ostenil, Ostenil Plus, Synvisc, and Innoryos), focusing on critical (rheological, lubricative, adhesive, and stability) attributes. Therefore, in vitro and ex vivo quantitative characterization panels (oscillatory rheology, rotational tribology, and texture analysis with bovine cartilage) were used for hydrogel product functional benchmarking, using equine synovial fluid as a biological control. Specifically, the retained experimental methodology enabled the authors to robustly assess and discuss various functional enhancement options for hyaluronan-based hydrogels (chemical cross-linking and addition of antioxidant stabilizing agents). The results showed that the Innoryos product, a niacinamide-augmented linear hyaluronan-based hydrogel, presented the best overall functional behavior in the retained experimental settings (high adhesivity and lubricity and substantial resistance to oxidative degradation). The Ostenil product was conversely shown to present less desirable functional properties for viscosupplementation compared to the other investigated products. Generally, this study confirmed the high importance of formulation development and control methodology optimization, aiming for the enhancement of novel OA-targeting product critical functional attributes and the probability of their clinical success. Overall, this work confirmed the tangible need for a comprehensive approach to hyaluronan-based viscosupplementation product functional benchmarking (product development and product selection by orthopedists) to maximize the chances of effective clinical OA management.

Hyaluronic Acid in Rheumatology

Hyaluronic acid (HA), also known as hyaluronan, is an anionic glycosaminoglycan widely distributed throughout various tissues of the human body. It stands out from other glycosaminoglycans as it lacks sulfation and can attain considerable size: the average human synovial HA molecule weighs about 7 million Dalton (Da), equivalent to roughly 20,000 disaccharide monomers; although some sources report a lower range of 3-4 million Da. In recent years, HA has garnered significant attention in the field of rheumatology due to its involvement in joint lubrication, cartilage maintenance, and modulation of inflammatory and/or immune responses. This review aims to provide a comprehensive overview of HA's involvement in rheumatology, covering its physiology, pharmacology, therapeutic applications, and potential future directions for enhancing patient outcomes. Nevertheless, the use of HA therapy in rheumatology remains controversial with conflicting evidence regarding its efficacy and safety. In conclusion, HA represents a promising therapeutic option to improve joint function and alleviate inflammation and pain.

Efficacy of Intramuscular Injection of Calcitonin on Pain Functional Status of Patients with Knee Osteoarthritis

Background

Recently, increased attention has been paid to calcitonin for the management of osteoarthritis (OA) regarding its metabolic properties for bone turnover and cartilage.

Objectives

This study was designed to assess the efficacy of intramuscular calcitonin injection in the functional status of individuals suffering from knee OA.

Methods

A total of 40 eligible cases with OA were randomly assigned into intervention and control groups. At baseline, pain intensity and functional ability were evaluated based on the Numeric Rating scale (NRS) and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaires. Both groups were prescribed with AcetaGel (500 mg) and piroxicam (0.5% topical gel) every 8 hours as needed, and the patients were instructed about conservative treatments and lifestyle modifications. In the case group, the patients received calcitonin (50 IU/mL solution for injection; Aburaihan Pharmaceutical Co., Iran) intramuscularly (gluteal muscle) once a week for 4 consecutive weeks. One month after the last dose, the patients were evaluated based on NRS and WOMAC questionnaires.

Results

Demographic data did not show any statistically significant difference. A total of 40 cases (male and female) with mean age values of 53.10 ± 5.28 and 54.55 ± 5.26 years were included in the case and control groups, respectively. The mean body mass index values of the case and control groups were 27.45 ± 1.57 and 27.15 ± 1.53 kg/m2, respectively. After 1 month of treatment with calcitonin, significant improvements were observed in NRS outcomes (P < 0.001). The total WOMAC score was also statistically improved (P < 0.001).

Conclusions

The findings of the present study revealed that the weekly administration of 50 IU calcitonin for 28 days could significantly improve physical ability and pain intensity in OA patients.

Aggrecan and Hyaluronan: The Infamous Cartilage Polyelectrolytes - Then and Now

Cartilages are unique in the family of connective tissues in that they contain a high concentration of the glycosaminoglycans, chondroitin sulfate and keratan sulfate attached to the core protein of the proteoglycan, aggrecan. Multiple aggrecan molecules are organized in the extracellular matrix via a domain-specific molecular interaction with hyaluronan and a link protein, and these high molecular weight aggregates are immobilized within the collagen and glycoprotein network. The high negative charge density of glycosaminoglycans provides hydrophilicity, high osmotic swelling pressure and conformational flexibility, which together function to absorb fluctuations in biomechanical stresses on cartilage during movement of an articular joint. We have summarized information on the history and current knowledge obtained by biochemical and genetic approaches, on cell-mediated regulation of aggrecan metabolism and its role in skeletal development, growth as well as during the development of joint disease. In addition, we describe the pathways for hyaluronan metabolism, with particular focus on the role as a "metabolic rheostat" during chondrocyte responses in cartilage remodeling in growth and disease.Future advances in effective therapeutic targeting of cartilage loss during osteoarthritic diseases of the joint as an organ as well as in cartilage tissue engineering would benefit from 'big data' approaches and bioinformatics, to uncover novel feed-forward and feed-back mechanisms for regulating transcription and translation of genes and their integration into cell-specific pathways.

Absorption, metabolism, and functions of hyaluronic acid and its therapeutic prospects in combination with microorganisms: A review

Hyaluronic acid (HA) is key to the stability of the internal environment of tissues. HA content in tissues gradually decreases with age, causing age-related health problems. Exogenous HA supplements are used to prevent or treat these problems including skin dryness and wrinkles, intestinal imbalance, xerophthalmia, and arthritis after absorption. Moreover, some probiotics are able to promote endogenous HA synthesis and alleviate symptoms caused by HA loss, thus introducing potential preventative or therapeutic applications of HA and probiotics. Here, we review the oral absorption, metabolism, and biological function of HA as well as the potential role of probiotics and HA in increasing the efficacy of HA supplements.

The Effect of Intra-articular Hyaluronic Acid Injections and Payer Coverage on Total Knee Arthroplasty Procedures: Evidence From Large US Claims Database

Background

There is debate regarding the efficacy of intra-articular (IA) hyaluronic acid (HA) injections for the management of knee osteoarthritis (OA). This study aimed to determine if IA HA utilization and payer coverage of viscosupplementation affected the prevalence of total knee arthroplasty (TKA) procedures and the age of TKA patients.

Methods

We performed a retrospective analysis from 2014 to 2020 using a large national commercial claims data set. We analyzed the number of TKA procedures and the age of the patients in states that covered IA HA vs those with limited coverage. Mixed random effects and slopes models were used to identify the impact of the IA HA injections.

Results

Of 7,335,301 patients with knee OA, 440,606 (6.0%) received a TKA procedure at an average age of 59 years. The rate of TKA procedures increased by 0.56% per year (95% confidence interval [CI] 0.46-0.66; P < .001). Payer coverage of IA HA injections had no effect on TKA prevalence (P = .926). The age of surgical patients increased yearly by 0.15 years (95% CI 0.12-0.18; P < .001), regardless of IA HA injections (P = .990). After controlling for demographics and comorbidities, patients that received an IA HA injection had a higher probability of receiving a subsequent TKA (odds ratio = 2.83; 95% CI 2.80-2.87; P < .001); this finding was conditional of patients' age at the first diagnosis of knee OA.

Conclusions

Additional clinical trials should be employed to identify the role of HA injections in the treatment armamentarium for knee OA.

Endogenous production of hyaluronan, PRG4, and cytokines is sensitive to cyclic loading in synoviocytes

Synovial fluid is composed of hyaluronan and proteoglycan-4 (PRG4 or lubricin), which work synergistically to maintain joint lubrication. In diseases like osteoarthritis, hyaluronan and PRG4 concentrations can be altered, resulting in lowered synovial fluid viscosity, and pro-inflammatory cytokine concentrations within the synovial fluid increase. Synovial fibroblasts within the synovium are responsible for contributing to synovial fluid and can be targeted to improve endogenous production of hyaluronan and PRG4 and to alter the cytokine profile. We cyclically loaded SW982 synoviocytes to 0%, 5%, 10%, or 20% strain for three hours at 1 Hz. To assess the impact of substrate stiffness, we compared the 0% strain group to cells grown on tissue culture plastic. We measured the expression of hyaluronan turnover genes, hyaluronan localization within the cell layer, hyaluronan concentration, PRG4 concentration, and the cytokine profile within the media. Our results show that the addition of cyclic loading increased HAS3 expression, but not in a magnitude-dependent response. Hyaluronidase expression was impacted by strain magnitude, which is exemplified by the decrease in hyaluronan concentration due to cyclic loading. We also show that PRG4 concentration is increased at 5% strain, while higher strain magnitude decreases overall PRG4 concentration. Finally, 10% and 20% strain show a distinct, more pro-inflammatory cytokine profile when compared to the unloaded group. Multivariate analysis showed distinct separation between certain strain groups in being able to predict strain group, hyaluronan concentration, and PRG4 concentration from gene expression or cytokine concentration data, highlighting the complexity of the system. Overall, this study shows that cyclic loading can be used tool to modulate the endogenous production of hyaluronan, PRG4, and cytokines from synovial fibroblasts.

Hyaluronic acid in the treatment of osteoarthritis of various localization: A review

The article discusses the treatment of osteoarthritis (OA), the prevalence of which is high, and according to some forecasts it will increase by 50% in the next 20 years. The authors emphasize the high comorbidity among patients suffering from OA and high cardiovascular and gastrointestinal risks with frequent use of NSAIDs, the volume of consumption of which is constantly increasing. Discussing recommendations for the treatment of patients with OA, the article focuses on the use of hyaluronic acid (HA) preparations in the treatment of OA. The mechanisms of anti-inflammatory and chondroprotective actions of HA in the joint, its effect on cartilage and synovial membrane are discussed. Attention is drawn to the fact that, despite more than 30 years of experience in the effective use of HA preparations in the treatment of OA, this procedure is still a subject of controversy among international professional communities. The article presents data from meta-analyses and systematic reviews confirming the effectiveness of the use of intra-articular management of HA preparations in OA of various localization (knee joints, hip joints, hand joints). In conclusion, the recommendations of the technical expert group established at the International Symposium on Intra-Articular Treatment are given to determine the criteria for the successful administration of HA in OA of various localizations, as well as predictors of success and non-success of therapy with HA drugs. The experts identified indications, contraindications for intra-articular administration of HA preparations, as well as conditions associated with an increased risk of therapy failure. In conclusion, the authors draw conclusions about the importance of using HA preparations for intra-articular administration for the treatment of OA, starting from the early stages, following the recommendations of experts.

Lung Hyaluronasome: Involvement of Low Molecular Weight Ha (Lmw-Ha) in Innate Immunity

Hyaluronic acid (HA) is a major component of the extracellular matrix. It is synthesized by hyaluronan synthases (HAS) into high-molecular-weight chains (HMW-HA) that exhibit anti-inflammatory and immunomodulatory functions. In damaged, infected, and/or inflamed tissues, HMW-HA are degraded by hyaluronidases (HYAL) or reactive oxygen species (ROS) to give rise to low-molecular-weight HAs (LMW-HAs) that are potent pro-inflammatory molecules. Therefore, the size of HA regulates the balance of anti- or pro-inflammatory functions. The activities of HA depend also on its interactions with hyaladherins. HA synthesis, degradation, and activities through HA/receptors interactions define the hyaluronasome. In this review, a short overview of the role of high and low-molecular-weight HA polymers in the lungs is provided. The involvement of LMW-HA in pulmonary innate immunity via the activation of neutrophils, macrophages, dendritic cells, and epithelial cells is described to highlight LMW-HA as a therapeutic target in inflammatory respiratory diseases. Finally, the possibilities to counter LMW-HA’s deleterious effects in the lungs are discussed.

Management of Knee Osteoarthritis: What Internists Need to Know

Knee osteoarthritis (OA) is a common and morbid condition. No disease-modifying therapies exist; hence the goals of current treatment are to palliate pain and to retain function. OA pain is significantly influenced by the placebo effect. Nonpharmacologic interventions are essential and have been shown to improve outcomes. Canes, unloading braces, and therapeutic heating/cooling may be valuable. Pharmacotherapy options include topical and oral nonsteroidal anti-inflammatory drugs, duloxetine, and periodic intra-articular glucocorticoids and hyaluronans. Opioids, intra-articular stem cells, and platelet-rich plasma are not recommended. Novel targets such as nerve growth factor are under investigation and may be approved soon for OA pain.

Intra-articular placebo effect in the treatment of knee osteoarthritis: a survey of the current clinical evidence

Knee osteoarthritis (KOA) is a debilitating disease characterized by chronic pain, stiffness, and decreased mobility. Intra-articular injectable therapies show good clinical efficacy in improving symptoms; however, these therapies and their comparators (intra-articular saline) have been associated with a large underlying placebo effect. We aimed to describe the existing evidence on the challenges, hypotheses, and potential solutions to mitigate the intra-articular placebo effect in clinical trials in KOA. A targeted literature review was conducted by searching Embase, MEDLINE®, and CENTRAL using predefined study selection criteria. All eligible studies identified were extracted for relevant data, and results were narratively summarized. Forty-three studies were included following screening. Challenges associated with the intra-articular placebo effect included its ability to mask the comparative efficacy of active treatments in trials (n = 7 studies), long-lasting effects (up to 6 months; n = 3), and substantial variation of placebo effect sizes across populations (n = 3). Hypotheses for the mechanism of the placebo effect included aspiration of synovial fluid during administration (n = 6) and dilution of inflammatory mediators (n = 2). Factors affecting the placebo effect size were more invasive routes of administration (e.g., injection versus oral; n = 4) and patient expectations (n = 2). Proposed solutions included the suggestion for readers to weigh the relevance of clinical trial evidence against the presence of large underlying placebo effects (n = 9), discontinuation of intra-articular saline as an appropriate placebo (n = 5), and inclusion of 'no treatment' or sham injection as a control (n = 4). The intra-articular placebo effect is a well-documented occurrence in KOA clinical trials, and it is suggested that it be accounted for when designing randomized controlled trials. Awareness and understanding of the intra-articular placebo effect in KOA are required for fair interpretation of clinical trial evidence.

A Comprehensive Review of Viscosupplementation in Osteoarthritis of the Knee

PURPOSE OF REVIEW

The purpose of this systematic review is to discuss emerging evidence in the field of viscosupplementation for chronic knee pain secondary to Osteoarthritis (OA). This review focuses on types of viscosupplementation that are clinically available currently, evidence to support their use, contraindications, and adverse events.

RECENT FINDINGS

OA, also known as degenerative joint disease, is the most common form of arthritis in the United States, affecting 54.4 million, or 22.7% of the adult population. The knee is the most common joint affected in OA, with up to 41% involvement, 30% in the hands, and 19% in the hips. The pathophysiology of OA is complex, with contributing factors including mechanical stress to the joint, as well as many person-specific factors such as genetic susceptibility, ethnicity, nutrition, and sex. Treatment modalities include weight control, exercise, non-steroidal and steroidal anti-inflammatory drugs, opioids, intra-articular platelet-rich plasma, placebo, corticosteroid injection, intra-articular viscosupplementation, and surgery. Viscosupplementation consists of injection of hyaluronic acid (HA) into affected joints, intending to restore the physiologic viscoelasticity in the synovial fluid (SF) in the absence of inflammation. HA has also been shown to downregulate pro-inflammatory factors, such as PGE2 and NFkB, and proteases and proteinases known to break down the joint matrix.The contraindications for HA injection are similar to any other injection therapy, and adverse events are usually mild, local, and transient. Viscosupplementation (VS) is effective over placebo and more effective than NSAIDs and corticosteroids in pain reduction and improved functionality; however, guidelines recommend neither for nor against its use, demonstrating variability in the existing evidence base.Current VS options divide primarily into native vs. cross-linked and low-molecular-weight vs. high-molecular-weight. Current treatment options include Hylan g-f-20, Sodium Hyaluronate preparations (Suparts Fx, Euflexxa, Gelsyn-3, Durolane, Hyalgen), single-use agents (Gel-One, Synvisc-One, Monovisc), and Hyaluronan (Orthovisc, Monovisc, Hymovic). They share a common safety profile, and all have evidence supporting their efficacy. Their specific details are reviewed here.

SUMMARY

OA is the most common form of arthritis. It is a chronic, debilitating illness with a high impact on the functionality and quality of life of a significant part of the population in the western world. Treatments include medical management, physical therapy, activity modification, injection, and surgery. VS effectively reduces pain, increases functionality, and delays surgery in the knee to treat osteoarthritis. While previous studies have demonstrated variable results, more evidence is becoming available generally supportive of the benefit of VS in the treatment of knee OA.

Management of Knee Osteoarthritis: What Internists Need to Know

Knee osteoarthritis (OA) is a common and morbid condition. No disease-modifying therapies exist; hence the goals of current treatment are to palliate pain and to retain function. OA is significantly influenced by the placebo effect. Nonpharmacologic interventions are essential and have been shown to improve outcomes. Canes, unloading braces, and therapeutic heating/cooling may be valuable. Pharmacotherapy options include topical and oral nonsteroidal anti-inflammatory drugs, duloxetine, and periodic intra-articular glucocorticoids and hyaluronans. Opioids, intra-articular stem cells, and platelet-rich plasma are not recommended. Novel targets such as nerve growth factor are under investigation and may be approved soon for OA pain.

Addition of High Molecular Weight Hyaluronic Acid to Fibroblast-Like Stromal Cells Modulates Endogenous Hyaluronic Acid Metabolism and Enhances Proteolytic Processing and Secretion of Versican

We have examined the effect of exogenous linear chain high molecular weight hyaluronic acid (HMW HA) on endogenously synthesized hyaluronic acid (HA) and associated binding proteins in primary cultures of fibroblast-like stromal cells that were obtained by collagenase digestion of the murine peripatellar fat pad. The cultures were expanded in DMEM that was supplemented with fetal bovine serum and basic fibroblast growth factor (bFGF) then exposed to macrophage-colony-stimulating factor (MCSF) to induce macrophage properties, before activation of inflammatory pathways using E. coli lipopolysaccharide (LPS). Under all culture conditions, a significant amount of endogenously synthesized HA localized in LAMP1-positive lysosomal vesicles. However, this intracellular pool was depleted after the addition of exogenous HMW HA and was accompanied by enhanced proteolytic processing and secretion of de novo synthesized versican, much of which was associated with endosomal compartments. No changes were detected in synthesis, secretion, or proteolytic processing of aggrecan or lubricin (PRG4). The addition of HMW HA also modulated a range of LPS-affected genes in the TLR signaling and phagocytosis pathways, as well as endogenous HA metabolism genes, such as Has1, Hyal1, Hyal2, and Tmem2. However, there was no evidence for association of endogenous or exogenous HMW HA with cell surface CD44, TLR2 or TLR4 protein, suggesting that its physiochemical effects on pericelluar pH and/or ionic strength might be the primary modulators of signal transduction and vesicular trafficking by this cell type. We discuss the implications of these findings in terms of a potential in vivo effect of therapeutically applied HMW HA on the modification of osteoarthritis-related joint pathologies, such as pro-inflammatory and degradative responses of multipotent mesenchymal cells residing in the synovial membrane, the underlying adipose tissue, and the articular cartilage surface.

FSTL1 promotes nitric oxide-induced chondrocyte apoptosis via activating the SAPK/JNK/caspase3 signaling pathway

OBJECTIVE

Previous studies have shown that follistatin-like protein 1 (FSTL1) is elevated in the synovial fluid of osteoarthritis and is associated with disease activity. The experiment was performed to stuy the effect and mechanism of FSTL1 on chondrocyte apoptosis in osteoarthritis.

DESIGN

After the isolation of human normal and osteoarthritis (OA) chondrocytes, the expression of FSTL1 was detected by Q-PCR and western blot analyses. Chondrocytes were pre-transfected with FSTL1 overexpression plasmids then treated with SNP, and chondrocyte viability and apoptosis levels were detected by MTS and flow cytometry, respectively. Cartilage matrix gene expression was measured by Q-PCR and signal pathway-related proteins were assessed by western blot.

RESULTS

The expression of FSTL1 in OA chondrocytes was markedly up-regulated compared with normal human chondrocytes (P < 0.05). The apoptosis rate of chondrocytes in the FSTL1 overexpression groups was highly elevated in the comparison with the negative control groups (P < 0.05). Additionally, FSTL1 potentiated protein abundances of MMP1, MMP3, MMP-9, and Bax as well as reduced Coll2a1 and Aggrecan and Bcl-2 expression. Furthermore, western blot results showed that the SAPK/JNK/Caspase3 signal pathway was significantly activated and the Ac-DEVD-FMK impaired FSTL1 induced chondrocyte apoptosis.

CONCLUSION

FSTL1 promoted SNP-induced chondrocytes apoptosis by activating the SAPK/JNK/Caspase3 signal pathway.