Significant synovial pathology in a meniscectomy model of osteoarthritis: modification by intra-articular hyaluronan therapy

Alleviating osteoarthritis-induced damage through extracellular vesicles derived from inflammatory chondrocytes

The role of extracellular vesicles (EVs) derived from inflammatory chondrocytes in EV-based therapy for osteoarthritis (OA) has received little attention. We examined the effects of EVs derived from both normal rat chondrocytes (nEVs) and IL-1β-treated rat chondrocytes (iEVs) on IL-1β-treated rat chondrocytes, macrophages, and osteoblasts, alongside mRNA-seq and miRNA-seq analyses of both them. Additionally, nEVs and iEVs were administered intra-articularly in the joints of rat models subjected to anterior cruciate ligament transection (ACLT), and the morphological alterations across the joints were assessed. These findings indicated that iEVs, compared with nEVs, significantly enhanced collagen II synthesis in IL-1β-treated chondrocytes, accompanied by marked increases in ER stress and autophagy. In comparison to nEVs, iEVs exhibited a greater effect on facilitating M2-type macrophage polarization while simultaneously diminishing M1-type polarization, a process likely mediated by the downregulation of chemotactic cytokines such as Cxcl10, Ccl5, Cxcl9, Cxcl1, and Cxcl11. iEVs exerted a more pronounced influence on the phenotypic characteristics of IL-1β-treated osteoblasts than nEVs. In the ACLT-rat model, iEVs, akin to nEVs, effectively mitigated articular cartilage degradation. However, there was no significant difference in OARSI Scores between the two groups, despite iEVs exerting a greater effect on increasing hyaline cartilage thickness and proteoglycan content. iEVs were superior to nEVs in attenuating synovium inflammation and promoting trabecula formation in the femur subchondral bone. Consequently, iEVs, akin to nEVs, significantly alleviated OA-induced damage. Moreover, iEVs outperformed nEVs in certain aspects, notably in augmenting hyaline cartilage, reducing synovium inflammation, and promoting trabecular formation in the subchondral bone during the early stage of OA.

Alpha-2-Macroglobulin Attenuates Posttraumatic Osteoarthritis Cartilage Damage by Inhibiting Inflammatory Pathways With Modified Intra-articular Drilling in a Yucatan Minipig Model

BACKGROUND

Posttraumatic osteoarthritis (PTOA) arises secondarily to joint trauma and is driven by catabolic inflammatory pathways. Alpha-2-macroglobulin (α2M) is a naturally occurring proteinase inhibitor found in human serum and synovial fluid that binds proteases as well as proinflammatory cytokines involved in the pathogenesis of PTOA.

PURPOSE

(1) To investigate the therapeutic potential of intra-articular α2M injections during the acute stages of PTOA by inhibiting inflammatory pathways driven by the cytokines expressed by the synovium in a large preclinical Yucatan minipig model and (2) to determine if 3 intra-articular α2M injections have greater chondroprotective effects compared with 1 intra-articular injection.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 48 Yucatan minipigs were randomized into 4 groups (n = 12 each): (1) modified intra-articular drilling (mIAD) and saline (mIAD + saline), (2) mIAD and 1 intra-articular α2M injection (mIAD +α2M-1), (3) mIAD and 3 α2M injections (mIAD +α2M-3), and (4) sham control. Surgical hindlimbs were harvested at 15 weeks after surgery. Cartilage degeneration, synovial changes, inflammatory gene expression, and matrix metalloproteinase levels were evaluated. Gait asymmetry was measured before and after surgery using a pressure-sensing walkway system.

RESULTS

Macroscopic lesion areas and microscopic cartilage degeneration scores were lower in the mIAD +α2M-1 and mIAD +α2M-3 groups compared with the mIAD + saline group (P < .05) and similar to those in the sham group (P > .05). Synovial membrane scores of the mIAD +α2M-1 and mIAD +α2M-3 groups were lower than that of the mIAD + saline group (P < .05) and higher than that of the sham group (P < .05). Interleukin-1 beta, nuclear factor kappa B, and tumor necrosis factor alpha mRNA expression in the synovium and matrix metalloproteinase-1 levels in synovial fluid were significantly lower in the mIAD +α2M-1 and mIAD +α2M-3 groups compared with the mIAD + saline group (P < .05). No significant differences were observed between the mIAD +α2M-1 and mIAD +α2M-3 groups for all measured outcomes. There were early changes in gait (P < .05) between preoperative and postoperative time points for the mIAD + saline, mIAD +α2M-1, and mIAD +α2M-3 groups that normalized by 15 weeks.

CONCLUSION

Animals receiving early α2M treatment exhibited less cartilage damage, milder synovitis, and lower inflammation compared with animals with no α2M treatment. These results exemplify the early anti-inflammatory effects of α2M and provide evidence that intra-articular α2M injections may slow the progression of PTOA.

CLINICAL RELEVANCE

In patients presenting with an acute joint injury, an early intervention with α2M may have the potential to reduce cartilage degeneration from catabolic pathways and delay the development of PTOA.

Efficacy and safety of ultrasound-guided percutaneous radiofrequency ablation for synovial hyperplasia

PURPOSE

This study aimed to investigate the efficacy and safety of ultrasound-guided percutaneous radiofrequency ablation (RFA) for the treatment of synovial hyperplasia in the knee joints of antigen-induced arthritis (AIA) model rabbits.

METHODS

Forty Japanese large-eared white rabbits were divided into AIA and control groups. After successful induction of the AIA model, the knee joints were randomly assigned to RFA and non-RFA groups. The RFA group underwent ultrasound-guided RFA to treat synovial hyperplasia in the knee joint. Dynamic observation of various detection indices was conducted to evaluate the safety and effectiveness of the RFA procedure.

RESULTS

Successful synovial ablation was achieved in the RFA group, with no intraoperative or perioperative mortality. Postoperative the circumference of the knee joint reached a peak before decreasing in the third week after surgery. The incidence and diameter of postoperative skin ulcers were not significantly different compared to the non-RFA group (p > .05). Anatomical examination revealed an intact intermuscular fascia around the ablated area in the RFA group. The ablated synovial tissue initially presented as a white mass, which subsequently liquefied into a milky white viscous fluid. Gross articular cartilage was observed, along with liquefied necrosis of the synovium on pathological histology and infiltration of inflammatory cells in the surrounding soft tissue.

CONCLUSION

The experimental results demonstrated that ultrasound-guided RFA of the knee in the treatment of synovial hyperplasia in AIA model animals was both effective and safe.

HYBID in osteoarthritis: Potential target for disease progression

HYBID is a new hyaluronan-degrading enzyme and exists in various cells of the human body. Recently, HYBID was found to over-express in the osteoarthritic chondrocytes and fibroblast-like synoviocytes. According to these researches, high level of HYBID is significantly correlated with cartilage degeneration in joints and hyaluronic acid degradation in synovial fluid. In addition, HYBID can affect inflammatory cytokine secretion, cartilage and synovium fibrosis, synovial hyperplasia via multiple signaling pathways, thereby exacerbating osteoarthritis. Based on the existing research of HYBID in osteoarthritis, HYBID can break the metabolic balance of HA in joints through the degradation ability independent of HYALs/CD44 system and furthermore affect cartilage structure and mechanotransduction of chondrocytes. In particular, in addition to HYBID itself being able to trigger some signaling pathways, we believe that low-molecular-weight hyaluronan produced by excess degradation can also stimulate some disease-promoting signaling pathways by replacing high-molecular-weight hyaluronan in joints. The specific role of HYBID in osteoarthritis is gradually revealed, and the discovery of HYBID raises the new way to treat osteoarthritis. In this review, the expression and basic functions of HYBID in joints were summarized, and reveal potential role of HYBID as a key target in treatment for osteoarthritis.

Different molecular weights of hyaluronan research in knee osteoarthritis: A state-of-the-art review

Osteoarthritis (OA), the most common form of arthritis, is characterized by progressive cartilage destruction, concomitant adaptive osteogenesis, and loss of joint function. The progression of OA with aging is associated with a decrease in native hyaluronan (HA, hyaluronate or hyaluronic acid) with a high molecular weight (HMW) in synovial fluid and a subsequent increase in lower MW HA and fragments. As HMW HA possesses numerous biochemical and biological properties, we review new molecular insights into the potential of HA to modify OA processes. Different MWs in the formulation of products appear to have varying effects on knee OA (KOA) pain relief, improved function, and postponing surgery. In addition to the safety profile, more evidence indicates that intraarticular (IA) HA administration may be an effective option to treat KOA, with a particular emphasis on the use of HA with fewer injections of higher MW, including potential applications of HA of very HMW. We also analyzed published systemic reviews and meta-analyses of IA HA in treating KOA in order to discuss their conclusions and consensus statements. According to its MW, HA may offer a simple way to refine therapeutic information in selective KOA.

Construction and evaluation of a clinically relevant model of septic arthritis

Despite the creation of several experimental animal models for the study of septic arthritis, a protocol detailing the development of a reliable and easily reproducible animal model has not yet been reported. The experimental protocol described herein for the development of a clinically relevant mouse model of septic arthritis includes two main study stages: the first stage consisting of the preparation of the mice and of the methicillin-resistant Staphylococcus aureus (MRSA) cultures, followed by direct inoculation of MRSA into the knee joints of C57BL/6J mice (25-40 min); and a second study stage consisting of multiple sample collection and data analysis (1-3 days). This protocol may be carried out by researchers skilled in mouse care and trained to work with biosafety-level-2 agents such as MRSA. The model of septic arthritis described here has demonstrated clinical relevance in developing intra-articular inflammation and cartilage destruction akin to that of human patients. Moreover, we describe methods for serum, synovial fluid and knee joint tissue analysis that were used to confirm the development of septic arthritis in this model, and to test potential treatments. This protocol confers the advantages of enabling granular evaluation of the pathophysiology of MRSA infection and of the efficacy of therapeutic medications; it may also be employed to study a range of native joint diseases beyond inflammatory pathologies alone.

Mitochondrial Dysfunction Affects the Synovium of Patients with Rheumatoid Arthritis and Osteoarthritis Differently

There is growing evidence regarding the role of mitochondrial dysfunction in osteoarthritis (OA) and rheumatoid arthritis (RA). However, quantitative comparison of synovial mitochondrial derangements in these main arthritis forms is missing. A prospective clinical study was conducted on adult patients undergoing knee surgery. Patients were allocated into RA and OA groups based on disease-specific clinical scores, while patients without arthritis served as controls. Synovial samples were subjected to high-resolution respirometry to analyze mitochondrial functions. From the total of 814 patients, 109 cases were enrolled into the study (24 RA, 47 OA, and 38 control patients) between 1 September 2019 and 31 December 2021. The decrease in complex I-linked respiration and dyscoupling of mitochondria were characteristics of RA patients, while both arthritis groups displayed reduced OxPhos activity compared to the control group. However, no significant difference was found in complex II-related activity between the OA and RA groups. The cytochrome C release and H₂O₂ formation were increased in both arthritis groups. Mitochondrial dysfunction was present in both arthritis groups; however, to a different extent. Consequently, mitochondrial protective agents may have major benefits for arthritis patients. Based on our current study, we recommend focusing on respiratory complex I in rheumatoid arthritis research.

Pharmacological Management of Osteoarthritis With a Focus on Symptomatic Slow-Acting Drugs: Recommendations From Leading Russian Experts

BACKGROUND

This article describes an updated stepwise algorithm for the pharmacological management of osteoarthritis (OA) to establish a treatment method for patients with OA.

SUMMARY

In step 1, background maintenance therapy includes symptomatic slow-acting drugs for OA, especially prescription crystalline glucosamine sulfate product, for which the high-quality evidence base of efficacy is unequivocal, or prescription chondroitin sulfate. Oral nonsteroidal anti-inflammatory drugs (NSAIDs) or paracetamol only as rescue analgesia is given on top of the background therapy. Step 2: For patients with persistent OA symptoms, the use of oral NSAIDs is mandatory for maintaining supportive therapy with symptomatic slow-acting drugs for OA. It is recommended to properly stratify patients and carefully select oral NSAID therapy to maximize the benefit-to-risk ratio. Intra-articular hyaluronic acid and intra-articular corticosteroids are recommended as well in step 2 of the algorithm, especially for patients who do not respond to the previous therapies. Step 3: Duloxetine is considered along with the previous procedures, especially in patients with pain from central sensitization. Step 4: Total joint replacement is recommended for patients with severe symptoms and poor quality of life.

MAJOR CONCLUSIONS

The current guidelines and literature review provide evidence-based recommendations supported by clinical experience on how to organize the treatment process in patients with knee OA applicable in the Russian clinical practice.

FUTURE RESEARCH DIRECTIONS

International evidence-based guidelines lack consensus on different treatments, including the use of prescription crystalline glucosamine sulfate, NSAIDs, and intra-articular hyaluronic acid. The content of this article needs a further discussion about the clinical evidence and harmonization of recommendations for knee OA management.

Evaluation of the effectiveness of intra-articular administration of highly purified hyaluronic acid in knee osteoarthritis in real clinical practice

Knee osteoarthritis (kOA) is a common cause of turning for medical advice, associated with chronic pain and disability. One of the methods of OA treatment is the local administration of hyaluronic acid (HA) drugs.Objective: to evaluate the effectiveness of intra-articular (IA) administration of highly purified HA (Armaviskon Plus) in kOA.Patients and methods. The study group consisted of 58 patients (74.1% women and 25.9% men, aged 59.5±11.8 years) with kOA, experiencing moderate/severe pain (≥40 mm on a visual analogue scale, VAS). All patients received IA injection of HA Armaviskon Plus (2 ml of a 1.5% solution), 2 injections with an interval of 7 days. The effectiveness criterion was the dynamics of pain at rest and during movement (VAS 0-100 mm) and the function of the knee joint according to a numerical rating scale (NRS 0-100 points) 2 weeks, 1 and 3 months after administration of therapy.Results and discussion. During the treatment, there was a significant improvement in all indicators. The average severity of pain during movement at baseline, after 2 weeks, 1 and 3 months was 50 [40; 60], 30 [20; 40], 15 [0; 30], 20 [0; 30] mm (p<0.001), at rest 20 [10; 40], 5 [0; 20], 0 [0; 20], 10 [0; 20] mm (p<0.05) by VAS. The average values of functional indicators were 40 [10; 60], 10 [0; 40], 20 [0; 40], 10 [10; 30] scores according to the NRS. A decrease in non-steroidal anti-inflammatory drugs demand was recorded: 67.1% of patients were initially taking them, after 3 months – 36.1% (p<0.001). No serious adverse reactions were noted.Conclusion. IA administration of HA is an effective and safe method for the treatment of kOA. Armaviskon Plus, a highly purified high-molecular- weight HA drug, has shown good results in pain reduction and improvement of function in knee OA as well as a favorable safety profile, which makes it possible to recommend its use in real clinical practice.

Immunomodulatory biomaterials and their application in therapies for chronic inflammation-related diseases

The degree of tissue injuries such as the level of scarring or organ dysfunction, and the immune response against them primarily determine the outcome and speed of healing process. The successful regeneration of functional tissues requires proper modulation of inflammation-producing immune cells and bioactive factors existing in the damaged microenvironment. In the tissue repair and regeneration processes, different types of biomaterials are implanted either alone or by combined with other bioactive factors, which will interact with the immune systems including immune cells, cytokines and chemokines etc. to achieve different results highly depending on this interplay. In this review article, the influences of different types of biomaterials such as nanoparticles, hydrogels and scaffolds on the immune cells and the modification of immune-responsive factors such as reactive oxygen species (ROS), cytokines, chemokines, enzymes, and metalloproteinases in tissue microenvironment are summarized. In addition, the recent advances of immune-responsive biomaterials in therapy of inflammation-associated diseases such as myocardial infarction, spinal cord injury, osteoarthritis, inflammatory bowel disease and diabetic ulcer are discussed.

The efficacy of intra-articular HYADD4-G injection in the treatment of femoroacetabular impingement: results at one year follow up

Objective

Femoroacetabular impingement (FAI) is a condition that has been increasingly recognized as a source of hip pain and a possible risk factor to early development of hip osteoarthritis (OA). To our knowledge, the use of HA in the treatment of femoroacetabular FAI has been investigated only by two studies, both using a high molecular weight HA. The aim of this study was to evaluate the efficacy of two weekly injections of an hexadecylamide derivative of HA (HYADD4-G, HYMOVIS, Fidia Farmaceutici) in FAI.

Methods

All patients received two weekly intra-articular injections of Hymovis at baseline and after 7 days. Clinical and functional assessments were performed at baseline and was repeated after 1, 3, 6 and 12 months. Functional measures included visual analogue scale (VAS) for pain, Harris Hip score (HHS), Lequesne Index (LI), Tegner activity level scale (TALS) and monthly consumption of nonsteroidal anti-inflammatory drugs (NSAIDs).

Results

Twenty-one hips (19 patients, 2 bilateral cases) were treated. The variables VAS, HHS as well as Lequesne improved significantly from T0 to T4 (at 12 months) with the best improvement between T0 and T1. At the same time, a reduction in NSAIDs monthly intake was registered. On the other hand, a significant improvement in Tegner scale was not observed. No adverse events were registered.

Conclusion

This study states that one cycle of HYADD4-G could be a safe and effective treatment in patients with FAI, showing significative results in term of pain control as well as hip functionality and quality of life up to 1 year.

Comparing the efficacy of hyaluronic acid products with various molecular weights as mono and combined with chondroitin sulfate regimens in treatment of patients with stage I–III knee osteoarthritis

Aim: to evaluate the effectiveness of hyaluronic acid (HA) preparations with different molecular weights and in combination with chondroitin sulfate (HS) for intra-articular (IA) injections in the treatment of patients with stage I–III knee OA.

Subjects and methods. IA HA injections were performed 160 patients with primary and post-traumatic knee OA of the I–III stages at the department of traumatology-orthopedics, V.A. Nasonova Research Institute of Rheumatology for the period from September 2017 to June 2019. Patients were divided into 4 groups. Group 1 consisted of 80 patients treated with low molecular weight (LMW) HA, group 2–20 patients treated with medium molecular weight (MMW) HA, group 3–30 patients treated with high molecular weight (HMW) HA, and group 4–30 patients who were intraarticular introduced HA with HS. The course of IA injections was 2 for LMW, HMW, and HA with HS, and 3 for MMW HA. Injections were performed with an interval of 1 week. To evaluate the results of treatment, we studied the intensity of pain according to VAS and the total score of KOOS before treatment and on follow-up examinations 1, 3 and 6 months after the course of IA HA injections.

Results. The maximum reduction in pain with IA HA injections at stage I of knee OA occurred by 3 months after the course of treatment. Moreover, improvement was detected by 1 month in 84.3% of cases, and remained until the end of the study in 71.1% of patients. All HA preparations used in stage I of knee OA were effective. At stage II of the knee OA after 3 months after the course of IA HA, different efficiencies of HA preparations were revealed. So, in the groups of LMW, MMW and HA with HS, the improvement persisted up to 3 months, and in the group of HMW HA – up to 1 month. After 3 months, the best results were shown by HA with HS, by 6 months the results were comparable. IA HA injections at the II stage of knee OA led to good and excellent results 1 month after the course of treatment in 53.9% of cases, but by the end of the study, improvement remained in only 30.8% of patients. In the case of the use of HA in stage III of the knee OA, the effectiveness of the studied drugs was comparable, and the maximum improvement was achieved by 1 month. The positive effect of IA HA injections in patients with stage III of the knee OA one month after the course of treatment was obtained in 40.6% of cases, by 3 months it decreased to 18.8%, and by 6 months – to 15.7% of patients.

Conclusions. IA injections of HA at stage I of the knee OA is a highly effective method of conservative treatment, which allows to relieve pain and improve the condition of the knee joint for a period of 6 months or more. The use of HA preparations at stage II of the knee OA allows reducing pain up to 3 months with IA injections of LMW and MMW HA, as well as HA with HS. HMW HA helps reduce pain intensity for a period of 1 month. The use of HA preparations in stage III of the knee OA leads to a short-term relief of symptoms of OA.

Peripheral mechanisms of arthritic pain: A proposal to leverage large animals for in vitro studies

Pain arising from musculoskeletal disorders such as arthritis is one of the leading causes of disability. Whereas the past 20-years has seen an increase in targeted therapies for rheumatoid arthritis (RA), other arthritis conditions, especially osteoarthritis, remain poorly treated. Although modulation of central pain pathways occurs in chronic arthritis, multiple lines of evidence indicate that peripherally driven pain is important in arthritic pain. To understand the peripheral mechanisms of arthritic pain, various in vitro and in vivo models have been developed, largely in rodents. Although rodent models provide numerous advantages for studying arthritis pathogenesis and treatment, the anatomy and biomechanics of rodent joints differ considerably to those of humans. By contrast, the anatomy and biomechanics of joints in larger animals, such as dogs, show greater similarity to human joints and thus studying them can provide novel insight for arthritis research. The purpose of this article is firstly to review models of arthritis and behavioral outcomes commonly used in large animals. Secondly, we review the existing in vitro models and assays used to study arthritic pain, primarily in rodents, and discuss the potential for adopting these strategies, as well as likely limitations, in large animals. We believe that exploring peripheral mechanisms of arthritic pain in vitro in large animals has the potential to reduce the veterinary burden of arthritis in commonly afflicted species like dogs, as well as to improve translatability of pain research into the clinic.

The relationship between synovial inflammation, structural pathology, and pain in post-traumatic osteoarthritis: differential effect of stem cell and hyaluronan treatment

Background

Synovitis is implicated in the severity and progression of pain and structural pathology of osteoarthritis (OA). Increases in inflammatory or immune cell subpopulations including macrophages and lymphocytes have been reported in OA synovium, but how the particular subpopulations influence symptomatic or structural OA disease progression is unclear. Two therapies, hyaluronan (HA) and mesenchymal stem cells (MSCs), have demonstrated efficacy in some clinical settings: HA acting as device to improve joint function and provide pain relief, while MSCs may have immunomodulatory and disease-modifying effects. We used these agents to investigate whether changes in pain sensitization or structural damage were linked to modulation of the synovial inflammatory response in post-traumatic OA.

Methods

Skeletally mature C57BL6 male mice underwent medial-meniscal destabilisation (DMM) surgery followed by intra-articular injection of saline, a hyaluronan hexadecylamide derivative (Hymovis), bone marrow-derived stem cells (MSCs), or MSC + Hymovis. We quantified the progression of OA-related cartilage, subchondral bone and synovial histopathology, and associated pain sensitization (tactile allodynia). Synovial lymphocytes, monocyte/macrophages and their subpopulations were quantified by fluorescent-activated cell sorting (FACS), and the expression of key inflammatory mediators and catabolic enzyme genes quantified by real-time polymerase chain reaction (PCR).

Results

MSC but not Hymovis significantly reduced late-stage (12-week post-DMM) cartilage proteoglycan loss and structural damage. Allodynia was initially reduced by both treatments but significantly better at 8 and 12 weeks by Hymovis. Chondroprotection by MSCs was not associated with specific changes in synovial inflammatory cell populations but rather regulation of post-injury synovial Adamts4, Adamts5, Mmp3, and Mmp9 expression. Reduced acute post-injury allodynia with all treatments coincided with decreased synovial macrophage and T cell numbers, while longer-term effect on pain sensitization with Hymovis was associated with increased M2c macrophages.

Conclusions

This therapeutic study in mice demonstrated a poor correlation between cartilage, bone or synovium (histo)pathology, and pain sensitization. Changes in the specific synovial inflammatory cell subpopulations may be associated with chronic OA pain sensitization, and a novel target for symptomatic treatment.

Hyaluronan Injections Show No Histologic Evidence of Adverse Tissue Effects

Background:

The safety of hyaluronan intra-articular injections is mostly based on animal studies and clinical evidence rather than histologic studies from human administration.

Objective:

This study analyzed the histologic effects of viscosupplementation with sodium hyaluronate on the synovium and articular cartilage of human knee specimen status post total knee arthroplasty within 3 years of viscosupplementation.

Methods:

Twenty-four specimens from total knee arthroplasties from April 2012 to August 2016 at NYU Winthrop Hospital were selected for microscopic analysis. All cases had a diagnosis of end-stage osteoarthritis at the time of surgery. Thirteen of the cases had 3 viscosupplementation injections of the knee with Euflexxa, a hyaluronate-based viscosupplementation agent, within 3 years preceding a total knee replacement. The remaining 11 did not receive viscosupplementation and were incorporated as controls. Upon histologic review, synovium was categorized by degree of hyperplasia and inflammation and the presence or absence of foreign material and giant cell reactions. Residual articular cartilage was categorized by staining intensity, and the presence or absence of crystals, foreign material, and giant cell reactions.

Results:

No significant difference was found between these groups for degree of synovial hyperplasia (P = .33) or for cartilage staining density (P = .42). None of the samples displayed evidence of foreign material, crystals, or giant cell reactions.

Conclusion:

In this cohort of patients, we demonstrated that Euflexxa was administered without any discernible microscopic adverse tissue effects.

Hyaluronic Acid: Molecular Mechanisms and Therapeutic Trajectory

Hyaluronic acid (also known as hyaluronan or hyaluronate) is naturally found in many tissues and fluids, but more abundantly in articular cartilage and synovial fluid (SF). Hyaluronic acid (HA) content varies widely in different joints and species. HA is a non-sulfated, naturally occurring non-protein glycosaminoglycan (GAG), with distinct physico-chemical properties, produced by synoviocytes, fibroblasts, and chondrocytes. HA has an important role in the biomechanics of normal SF, where it is partially responsible for lubrication and viscoelasticity of the SF. The concentration of HA and its molecular weight (MW) decline as osteoarthritis (OA) progresses with aging. For that reason, HA has been used for more than four decades in the treatment of OA in dogs, horses and humans. HA produces anti-arthritic effects via multiple mechanisms involving receptors, enzymes and other metabolic pathways. HA is also used in the treatment of ophthalmic, dermal, burns, wound repair, and other health conditions. The MW of HA appears to play a critical role in the formulation of the products used in the treatment of diseases. This review provides a mechanism-based rationale for the use of HA in some disease conditions with special reference to OA.

Efficacy of local injection therapy with hyaluronic acid of different molecular weight in patients with knee osteoarthritis

Intra-articular administration of hyaluronic acid (HA) is one of the methods of conservative treatment of knee osteoarthritis (OA). However, the data of its efficacy in the modern literature are contradictory.

Objective: to assess the efficacy of intra-articular administration of HA preparations with different molecular weight in the treatment of patients with knee OA and to study the factors that can influence the effectiveness of such therapy.

Subjects and methods. HA preparations were administered to 60 patients with idiopathic and posttraumatic knee OA. The ratio of women to men was 3:1. The average age was 59.5±13.7 years and body mass index – 30.3±5.8 kg/m2. The presence of enthesitis was evaluated prior to treatment by the characteristic clinical picture. The x-ray stage of OA was determined in accordance with the classification of Kellgren–Lawrence. Distribution of of knee joint lesions, relationship of femur and tibia anatomical axes, presence of varus and valgus deformities were also evaluated. The patients were divided into three groups: 18 patients received low-molecular (LM), 19 – medium-molecular (MM) and 23 – high-molecular (HM) HA. To assess the efficacy of the treatment the severity of pain on a visual analog scale (VAS) and the total score of the Knee injury and Osteoarthritis Outcome Score (KOOS) questionnaire before, 1, 3 and 6 months after treatment were evaluated.

Results and discussion. Enthesitis was detected in 17 (28,3%) patients. Stage I of knee OA was diagnosed in 10 (16.6%), II – in 36 (60%) and III – in 14 (23.3%) patients. Varus deformity was detected in 43 (71.7%) patients, neutral axis of the lower limb - in 14 (23.3%), valgus deformity – in 3 (5%). The most significant decrease in the severity of pain was noted in patients with stage I of knee OA: from 54±17.1 to 10.0±10.0 mm. At stage II, the pain decreased from 59.4±12.6 to 45.5±20.3 mm, and at stage III – from 66.4±13.5 to 60.7±23.3 mm. By the 6th month, the severity of pain in patients with enthesitis was higher, and the values of KOOS total score were worse than in patients without it. At stages II and III of knee OA, the ratio of positive to unsatisfactory results for MM, LM and HM HA was as follows: 2:1, 3:1 and 3.6:1. In the group of patients with excellent results, the value of varus deformation averaged 8.5±1.5°, in patients with a good result – 9.8±2.8°, with a satisfactory result – 11.3±4.5°, and with an unsatisfactory – 11.5±3.2°.

Conclusion. Intra-articular injection of HA is very effective at stage I of knee OA. The expression and duration of this effect are reducedwith decrease of cartilage thickness and increase of knee joint varus deformation (i.e., at the II and III stages of knee OA). The presence of varus deformation does not affect HA efficacy. Three factors are important: the appearance of varus deformation of the lower limb with initially neutral axis; the increase of varus deformation; the value of varus deformation >10°.

The Importance of the Knee Joint Meniscal Fibrocartilages as Stabilizing Weight Bearing Structures Providing Global Protection to Human Knee-Joint Tissues

The aim of this study was to review aspects of the pathobiology of the meniscus in health and disease and show how degeneration of the meniscus can contribute to deleterious changes in other knee joint components. The menisci, distinctive semilunar weight bearing fibrocartilages, provide knee joint stability, co-ordinating functional contributions from articular cartilage, ligaments/tendons, synovium, subchondral bone and infra-patellar fat pad during knee joint articulation. The meniscus contains metabolically active cell populations responsive to growth factors, chemokines and inflammatory cytokines such as interleukin-1 and tumour necrosis factor-alpha, resulting in the synthesis of matrix metalloproteases and A Disintegrin and Metalloprotease with ThromboSpondin type 1 repeats (ADAMTS)-4 and 5 which can degrade structural glycoproteins and proteoglycans leading to function-limiting changes in meniscal and other knee joint tissues. Such degradative changes are hall-marks of osteoarthritis (OA). No drugs are currently approved that change the natural course of OA and translate to long-term, clinically relevant benefits. For any pharmaceutical therapeutic intervention in OA to be effective, disease modifying drugs will have to be developed which actively modulate the many different cell types present in the knee to provide a global therapeutic. Many individual and combinatorial approaches are being developed to treat or replace degenerate menisci using 3D printing, bioscaffolds and hydrogel delivery systems for therapeutic drugs, growth factors and replacement progenitor cell populations recognising the central role the menisci play in knee joint health.

Early Intervention with Therapeutic Low-Intensity Pulsed Ultrasound in Halting the Progression of Post-traumatic Osteoarthritis in a Rat Model

Anterior cruciate ligament (ACL) and meniscus injuries are highly correlated with post-traumatic knee osteoarthritis (PTOA). The aim of this study was to examine whether early intervention with low-intensity pulsed ultrasound (LIPUS) at an intensity of 0.1 W/cm² helps delay PTOA progression. A PTOA model was established by ACL transection and meniscectomy in male Sprague-Dawley rats. LIPUS intervention (1.0 MHz, 0.1 W/cm²) started on the third day after surgery and continued for 4 consecutive wk. Histopathological analyses and immunoassays of collagen type II and matrix metallopeptidase 13 in joints were conducted. Results indicated that compared with the sham treatment, LIPUS significantly reduced Mankin scores, inflammatory cells and matrix metallopeptidase 13 expression and increased collagen type II expression in rats with PTOA (p < 0.05). Early intervention with LIPUS has beneficial effects on delaying cartilage degradation by reducing synovial inflammation and matrix metallopeptidase 13 expression, as well as enhancing collagen type II expression in cartilage.

An Effective Translation: The Development of Hyaluronan-Based Medical Products From the Physicochemical, and Preclinical Aspects

This review shows the steps toward material selection focalized on the design and development of medical devices based on hyaluronan (HA). The selection is based on chemical and mechanical properties, biocompatibility, sterilization, safety, and scale-up costs. These facts play a vital role in the industrialization process. Approved medical devices containing-HA are illustrated to identify key parameters. The first part of this work involves the steps toward a complete characterization of chemical and mechanical aspects, reproducibility of the processes and scale up. In a second stage, we aimed to describe the preclinical in vitro and in vivo assays and selected examples of clinical trials. Furthermore, it is important to keep in mind the regulatory affairs during the research and development (R&D) using standardization (ISO standards) to achieve the main goal, which is the functionality and safety of the final device. To keep reproducible experimental data to prepare an efficient master file for the device, based on quality and recorded manufacturing data, and a rigorous R&D process may help toward clinical translation. A strong debate is still going on because the denominated basic research in HA field does not pay attention to the purity and quality of the raw materials used during the development. So that, to achieve the next generation of devices is needed to overcome the limitations of state of art in terms of efficacy, biodegradability, and non-toxicity.

Hyaluronan in experimental injured/inflamed cartilage: In vivo studies

Joint disease is characterized by an imbalance between the synthesis and degradation of articular cartilage and subchondral bone accompanied by capsular fibrosis, osteophyte formation and varying degrees of inflammation of the synovial membrane. Many animal models have been developed to study arthritis and osteoarthritis that enable experimental conditions, diet and environmental risk factors to be carefully controlled. Animal-based studies have demonstrated the positive effects of exogenous HA on the preservation of joint cartilage in different models of arthritis and osteoarthritis. Although many promising effects of exogenous HA have been reported, there remains uncertainty as to its effectiveness in reversing cartilage injury and other manifestations of joint diseases because of difficulties in interpreting and unifying the results of these studies. A review of the literature of the last decade was conducted to report the results and to determine what we have learned from animal models in relation to joint inflammation induced by experimental models and HA treatment.

Autologous Bone Marrow Concentrate in a Sheep Model of Osteoarthritis: New Perspectives for Cartilage and Meniscus Repair

INTRODUCTION

Cell-based therapies are becoming a valuable tool to treat osteoarthritis (OA). This study investigated and compared the regenerative potential of bone marrow concentrate (BMC) and mesenchymal stem cells (MSC), both engineered with Hyaff(®)-11 (HA) for OA treatment in a sheep model.

METHODS

OA was induced via unilateral medial meniscectomy. Bone marrow was aspirated from the iliac crest, followed by concentration processes or cell isolation and expansion to obtain BMC and MSC, respectively. Treatments consisted of autologous BMC and MSC seeded onto HA. The regenerative potential of bone, cartilage, menisci, and synovia was monitored using macroscopy, histology, immunohistochemistry, and micro-computed tomography at 12 weeks post-op. Data were analyzed using the general linear model with adjusted Sidak's multiple comparison and Spearman's tests.

RESULTS

BMC-HA treatment showed a greater repair ability in inhibiting OA progression compared to MSC-HA, leading to a reduction of inflammation in cartilage, meniscus, and synovium. Indeed, the decrease of inflammation positively contributed to counteract the progression of fibrotic and hypertrophic processes, known to be involved in tissue failure. Moreover, the treatment with BMC-HA showed the best results in allowing meniscus regeneration. Minor healing effects were noticed at bone level for both cell strategies; however, a downregulation of subchondral bone thickness (Cs.Th) was found in both cell treatments compared to the OA group in the femur.

CONCLUSION

The transplantation of BMC-HA provided the best effects in supporting regenerative processes in cartilage, meniscus, and synovium and at less extent in bone. On the whole, both MSC and BMC combined with HA reduced inflammation and contributed to switch off fibrotic and hypertrophic processes. The observed regenerative potential by BMC-HA on meniscus could open new perspectives, suggesting its use not only for OA care but also for the treatment of meniscal lesions, even if further analyses are necessary to confirm its healing potential at long-term follow-up.

Early Efficacy of Intra-Articular HYADD® 4 (Hymovis®) Injections for Symptomatic Knee Osteoarthritis

Purpose  The aim of the study was to evaluate the clinical effects of HYADD® 4, an hydrogel based on a hyaluronic acid derivative, in patients with symptomatic knee osteoarthritis, on symptoms, and joint function. Methods  This retrospective study of patients with Kellgren-Lawrence grade II to IV knee osteoarthritis (American College of Rheumatology criteria) enrolled patients who had received two infiltrations of HYADD® 4, (24 mg/3 mL) 1 week apart, and evaluated: pain at rest, pain with movement, change in Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score; change in nonsteroidal anti-inflammatory drugs (NSAIDs)/acetaminophen use; satisfaction with therapy; tolerability. Study duration was 6 months for all predefined endpoints, with a 6-month extension for pain symptoms only. Results  After 6 months, all predefined endpoints were evaluable in 698 of 937 enrolled patients (74.5%). Mean WOMAC scores were reduced by 56.3% from baseline ( p  < 0.05). NSAIDs/acetaminophen use ≥2 times/week (48.8% of patients at baseline) was substantially reduced after 1 month and was 19.6% after 6 months. After 6 months, 85.6% of patients were satisfied about efficacy. There were no significant adverse effects. The effect on resting pain was rapid, strong, and lasting: reduction from baseline was 45.1% at 1 month ( p  < 0.05), 56.8% at 6 months ( p  < 0.05), and 53.6% at 12 months ( p  < 0.05). Pain on moving was reduced by 47.4% after 6 months ( p  < 0.05) and 46.0% after 12 months ( p  < 0.05), results at 6 and 12 months were similar. Conclusion  HYADD® 4 is a new-generation hyaluronic acid with distinctive viscoelastic and rheological properties. In patients with mild-to-severe knee OA (Kellgren-Lawrence grades II-IV), two consecutive infiltrations 1 week apart reduced WOMAC scores and NSAIDs/acetaminophen consumption for at least 6 months. In a subpopulation ( n  = 106), efficacy on pain lasted approximately 12 months. Adverse events were reported in 11.2% of patients; the most frequent were arthralgias. No cases of allergic reactions or systemic effects were recorded. Level of Evidence  Level IV, retrospective case series.

Immunoselected STRO-3+ mesenchymal precursor cells reduce inflammation and improve clinical outcomes in a large animal model of monoarthritis

BACKGROUND

The purpose of this study was to investigate the therapeutic efficacy of intravenously administered immunoselected STRO-3 + mesenchymal precursor cells (MPCs) on clinical scores, joint pathology and cytokine production in an ovine model of monoarthritis.

METHODS

Monoarthritis was established in 16 adult merino sheep by administration of bovine type II collagen into the left hock joint following initial sensitization to this antigen. After 24 h, sheep were administered either 150 million allogeneic ovine MPCs (n = 8) or saline (n = 8) intravenously (IV). Lameness, joint swelling and pain were monitored and blood samples for leukocytes and cytokine levels were collected at intervals following arthritis induction. Animals were necropsied 14 days after arthritis induction and gross and histopathological evaluations were undertaken on tissues from the arthritic (left) and contralateral (right) joints.

RESULTS

MPC-treated sheep demonstrated significantly reduced clinical signs of lameness, joint pain and swelling compared with saline controls. They also showed decreased cartilage erosions, synovial stromal cell activation and angiogenesis. This was accompanied by decreased infiltration of the synovial tissues by CD4+ lymphocytes and CD14+ monocytes/macrophages. Over the 3 days following joint arthropathy induction, the numbers of neutrophils circulating in the blood and plasma concentrations of activin A were significantly reduced in animals administered MPCs.

CONCLUSIONS

The results of this study have demonstrated the capacity of IV-administered MPCs to mitigate the clinical signs and some of the inflammatory mediators responsible for joint tissue destruction in a large animal model of monoarthritis.

Hyaluronic acid in the management of osteoarthritis: injection therapies innovations

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by pain and progressive functional limitation. Viscosupplementation with intra-articular (IA) hyaluronic acid (HA) could be a treatment option in OA, however recommendations made in different international guidelines for the non-surgical management of OA are not always concordant with regard to the role of IA injection therapies. Results from a recent Italian Consensus Conference underline how IA-HA to treat OA represents a widely used therapy in Italy. Specifically high molecular weight HA, cross-linked HA, and mobile reticulum HA are considered very useful to treat the OA joints from a great number of expert in Italy. These kinds of HA could reduce the NSAIDs intake, furthermore high-molecular weight and mobile reticulum HA are considered to be able to delay or avoid a joint prosthetic implant. This mini review highlights the results obtained from the Italian Consensus Conference "Appropriateness of clinical and organizational criteria for intra-articular injection therapies in osteoarthritis" and give further indication about innovation in IA-HA therapies.

Chitosan oligosaccharide suppresses synovial inflammation via AMPK activation: An in vitro and in vivo study

Synovial inflammation plays an important role in the early pathogenesis of osteoarthritis (OA). Chitosan oligosaccharide (COS) has been shown to activate AMPK and suppress inflammatory responses in intestinal epithelial cells. This study aimed to investigate the effect of COS on AMPK activation and synovial inflammation using both primary cultures of synoviocytes and a rabbit model of anterior cruciate ligament (ACL) transection-induced OA. COS induced AMPK activation in both rabbit and human synoviocytes. The mechanism of COS-induced AMPK activation involves an increase in the ADP/ATP ratio but not calcium/calmodulin-dependent protein kinase kinase beta (CaMKKβ). Interestingly, COS suppressed the TNFα-induced iNOS and COX-2 expression via an AMPK-dependent mechanism in both rabbit and human synoviocytes. Importantly, oral administration of COS (10mg/kg/day) induced AMPK activation and alleviated signs of inflammation including COX-2 expression in the synovium of a rabbit ACL transection model. Taken together, our results indicate that COS suppresses synovial inflammation in vitro and in vivo via AMPK activation. COS may be useful in the prevention of OA.

Differences among Branded Hyaluronic Acids in Italy, Part 1: Data from In Vitro and Animal Studies and Instructions for Use

BACKGROUND

The use of hyaluronic acid (HA) for intra-articular (IA) injection is widespread around the world for patients affected by osteoarthritis.

AIM

The aim of this study is to identify scientific evidence from in vitro and in vivo studies supporting the use of IA HAs marketed in Italy. We also evaluated the accuracy of indications and contraindications reported in the leaflets of such HAs compared with the available scientific evidence.

MATERIALS AND METHODS

An extensive literature search was performed to identify all in vitro and in vivo model studies reporting on the effects of various HAs marketed in Italy for IA use. Data reported in the leaflets of different HA-based products for IA use were extracted and analyzed alongside evidence from in vitro and in vivo model studies.

RESULTS

Nine in vitro studies and 11 studies on animal models were examined. Comparing results with what is reported in the leaflets of HAs marketed in Italy, it was observed that many branded formulations are introduced in the market without any reporting of basic scientific evidence. Only 12.82% and 17.95% of branded products had been shown to be effective with scientific evidence from in vitro and in vivo studies, respectively. The rationale of use of these products is based on their nature, as if a class effect existed such that all HAs would yield similar effects.

CONCLUSIONS

Data on HAs deriving from in vitro and in vivo studies are scarce and relate to only a small percentage of products marketed in Italy. Many indications and contraindications are arbitrarily reported in Italian HA leaflets without the support of scientific evidence. Larger and brand-specific studies are necessary and should be reported in the leaflets to guide clinicians in making an appropriate choice regarding HA-based IA therapy.

Weekly injections of Hylan G-F 20 delay cartilage degeneration in partial meniscectomized rat knees

Background

Cross-linked hyaluronan—also called Hylan G-F 20—is a medical device developed to treat osteoarthritis of the knee. However, it is still controversial whether Hylan G-F 20 has a cartilage protective effect in trauma-induced osteoarthritis. We investigated whether Hylan G-F 20 delayed osteoarthritis progression in a partial meniscectomized rat model.

Methods

Lewis rats were used for the experiments. The anterior medial meniscus was resected at the level of the medial collateral ligament in both knees. From 1 week after the surgery, 50 μl of Hylan G-F 20 was injected weekly into the left knee and phosphate buffered saline was injected into the right knee. Cartilage was evaluated for macroscopic findings, histology with safranin-o, and expression of type II collagen at 2, 4, and 8 weeks. Synovitis was also evaluated, and immunohistochemical analysis was performed for ED1.

Results

Macroscopic findings demonstrated that India ink positive area, representing fibrillated cartilage, was significantly smaller in the Hylan G-F 20 group than in the control group at 2, 4, and 8 weeks (n = 5). There were no significant differences in osteophyte score between the Hylan G-F 20 group and the control group at 2, 4, and 8 weeks.

Histologically, the cartilage in the medial tibial plateau was destroyed at 8 weeks in the control group, while type II collagen expression was still observed at 8 weeks in the Hylan G-F 20 group. OARSI score for cartilage histology was significantly lower in the Hylan G-F 20 group than in the control group at 4 and 8 weeks (n = 5). There were no significant differences in synovial cell number or modified synovitis score between the Hylan G-F 20 group and the control group at 2, 4, and 8 weeks (n = 5). In the Hylan G-F 20 group, foreign bodies surrounded by ED1 positive macrophages were observed in the synovium.

Conclusion

Weekly injections of Hylan G-F 20 starting 1 week after surgery delayed cartilage degeneration after meniscectomy in a rat model. Synovitis induced by meniscectomy was not alleviated by Hylan G-F 20. Insoluble gels were observed in the synovium after the Hylan G-F 20 injection.

Single intra-articular dexamethasone injection immediately post-surgery in a rabbit model mitigates early inflammatory responses and post-traumatic osteoarthritis-like alterations

Despite surgical reconstruction of the anterior cruciate ligament, a significant number of patients will still develop post-traumatic osteoarthritis (PTOA). Our objective was to determine if mitigating aspects of the acute phase of inflammation following a defined knee surgery with a single administration of a glucocorticoid could prevent the development of PTOA-like changes within an established rabbit model of surgically induced PTOA. An early and late post-surgical time-point was investigated in this study (48 h and 9 weeks post-surgery) in which the following groups were repeated (each n=6, for a total of 24 rabbits per time-point, and 48 rabbits used in the study): control (age/sex matched), sham (arthrotomy), drill injury (arthrotomy+two drill holes to a non-cartilaginous area of the femoral notch), and drill injury+single intra-articular (IA) injection of dexamethasone (DEX). At 48 h post-surgery, DEX treatment significantly lowered the mRNA levels for a subset of pro-inflammatory mediators, and significantly lowered the histological grade. Nine weeks post surgery, DEX treatment significantly lowered the histological scores (presented as effect size) for synovium (3.8), lateral femoral condyle (3.9), and lateral tibial cartilage (5.1) samples. Thus, DEX likely acts to prevent injury induced inflammation that could contribute to subsequent joint damage.

Investigating triazine-based modification of hyaluronan using statistical designs

Hyaluronan (HA) and its derivatives have been extensively researched for many biomedical applications. To precisely tailor the property of HA by derivatizing it to a pre-determined extent is challenging, yet critical. In this paper, we used 2-chloro-4,6-dimethoxy-1,3,5-triazine (CDMT) and N-methylmorpholine (NMM) to derivatize HA via a triazine-based coupling reaction. Using a fractional factorial (FF) design, we observed that water content in the solvent, and molar ratios of CDMT and NaHCO3 to the carboxylate were the significant factors controlling the derivatization. We investigated how the effect of each factor changes as reaction conditions change. Moreover, by altering the amount of CDMT and NaHCO3, we developed a cubic regression model for precise control of the extent of derivatization using a response surface methodology (RSM) with a D-optimal design. No spurious peaks were detected by (1)H NMR spectrum and only 10% decrease of molecular weight of the derivatized HA was determined by GPC. The HA with 6% modification was relatively biocompatible up to 15 mg/mL.

Longitudinal Evaluation of Effects of Intra-Articular Mesenchymal Stromal Cell Administration for the Treatment of Osteoarthritis in an Ovine Model

In this study, the therapeutic effect of intra-articularly injected autologous mesenchymal stromal cells (MSCs) was evaluated in an ovine osteoarthritis (OA) model using consecutive magnetic resonance imaging (MRI), radiography, and macroscopic and histologic postmortem examination. In 12 sheep, OA was induced by bilateral, lateral meniscectomy. After 6 weeks, 20 × 106 bone marrow-derived MSCs (50% MSCs were superparamagnetic iron oxide particle labeled) were injected intra-articularly into one knee joint. The contralateral knee served as negative control. MR images were acquired before OA induction, immediately before and after MSC injection, and 1, 4, 8, and 12 weeks thereafter using a 0.5T unit and a T2* gradient echo sequence. Radiographs were obtained before OA induction, at MSC injection, and 12 weeks thereafter. The MRI scoring system included articular cartilage, bone, joint capsule, and synovial fluid evaluation. The radiographic scoring system included the joint space and bone. Postmortem evaluation entailed macroscopic and histologic assessment. Longitudinal MRI revealed a significant deceleration of OA progression in MSC-treated joints. However, at the conclusion of the study, there was no significant difference in the degree of OA detected by MRI, radiography, and postmortem evaluation between the treatment and control group. The degree of OA on MRI varied among the 12 animals at the time of injection, but there was no difference between the left and right limb. In conclusion, intra-articular MSCs decreased OA progression. However, no significant treatment effects were seen at the conclusion of the study at 12 weeks. This somewhat contradicts previously published results. Nevertheless, the choice of OA model, outcome measures, or lack of additional medication might explain the differences. Our results indicate that OA might benefit from intra-articular MSC injection, but further studies are needed to refine patient selection and injection parameters for a more substantially improved outcome.

Age-independent effects of hyaluronan amide derivative and growth hormone on human osteoarthritic chondrocytes

AIM

Increased age is the most prominent risk factor for the initiation and progression of osteoarthritis (OA). The effects of human growth hormone (hGH) combined or not with hyaluronan amide derivative (HAD) were evaluated on human OA chondrocytes, to define their biological action and potentiality in OA treatment.

MATERIAL AND METHODS

Cell viability, metabolic activity, gene expression and factors released were tested at different time points on chondrocytes treated with different concentrations of hGH (0.01-10 μg/ml) alone or in combination with HAD (1 mg/ml).

RESULTS

We found that OA chondrocytes express GH receptor and that the different doses of hGH tested did not affect cell viability, metabolic activity or the expression of collagen type 2, 1, or 10 nor did it induce the release of IGF-1 or FGF-2. Conversely, hGH treatment increased the expression of hyaluronan receptor CD44. HAD combined with hGH reduced metabolic activity, IL6 release and gene expression, but not the suppressor of cytokine signaling 2 (SOCS2), which was significantly induced and translocated into the nucleus. The parameters analyzed, independently of the treatments used proportionally decreased with increasing age of the patients.

CONCLUSIONS

hGH only induced CD44 receptor on OA chondrocytes but did not affect other parameters, such as chondrocytic gene markers or IGF-1 or FGF-2 release. HAD reduced all the effects induced by hGH partially through a significant induction of SOCS2. These data show that GH or HAD treatment does not influence the response of the OA chondrocytes, thus the modulation of cellular response is age-independent.

Inflammation in joint injury and post-traumatic osteoarthritis

Inflammation is a variable feature of osteoarthritis (OA), associated with joint symptoms and progression of disease. Signs of inflammation can be observed in joint fluids and tissues from patients with joint injuries at risk for development of post-traumatic osteoarthritis (PTOA). Furthermore, inflammatory mechanisms are hypothesized to contribute to the risk of OA development and progression after injury. Animal models of PTOA have been instrumental in understanding factors and mechanisms involved in chronic progressive cartilage degradation observed after a predisposing injury. Specific aspects of inflammation observed in humans, including cytokine and chemokine production, synovial reaction, cellular infiltration and inflammatory pathway activation, are also observed in models of PTOA. Many of these models are now being utilized to understand the impact of post-injury inflammatory response on PTOA development and progression, including risk of progressive cartilage degeneration and development of chronic symptoms post-injury. As evidenced from these models, a vigorous inflammatory response occurs very early after joint injury but is then sustained at a lower level at the later phases. This early inflammatory response contributes to the development of PTOA features including cartilage erosion and is potentially modifiable, but specific mediators may also play a role in tissue repair. Although the optimal approach and timing of anti-inflammatory interventions after joint injury are yet to be determined, this body of work should provide hope for the future of disease modification tin PTOA.

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.

Unravelling osteoarthritis-related synovial fibrosis: a step closer to solving joint stiffness

Synovial fibrosis is often found in OA, contributing heavily to joint pain and joint stiffness, the main symptoms of OA. At this moment the underlying mechanism of OA-related synovial fibrosis is not known and there is no cure available. In this review we discuss factors that have been reported to be involved in synovial fibrosis. The aim of the study was to gain insight into how these factors contribute to the fibrotic process and to determine the best targets for therapy in synovial fibrosis. In this regard, the following factors are discussed: TGF-β, connective tissue growth factor, procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2, tissue inhibitor of metalloproteinase 1, A disintegrin and metalloproteinase domain 12, urotensin-II, prostaglandin F2α and hyaluronan.

The nonlinear viscoelasticity of hyaluronic acid and its role in joint lubrication

Hyaluronic acid solutions have been widely studied due to their relevance to the rheological behavior of synovial fluid and joint lubrication. Ambulatory joint motion is typically large oscillatory deflections; therefore, large amplitude oscillatory shear strain experiments are used to examine the relevant non-linear viscoelastic properties of these solutions. Using the sequence of physical processes method to analyze data provides time dependent viscoelastic moduli, which exhibit a clear physiologically relevant behavior to hyaluronic acids non-linear viscoelasticity. In particular, it is seen that during peak strain/acceleration, the time dependent elastic modulus peaks and the loss modulus is at a minimum. The hyaluronic acid can provide an immediate elastic response to sudden forces, acting like a shock absorber during sudden changes in direction of motion or maximum deflection. However, during peak rate, the elastic modulus is at a minimum and the loss modulus is at a maximum, which provides greater efficacy to hydrodynamic shear lubrication.

IL-1ß and IL-8 are scavenged by the hexadecylamide derivative of hyaluronic acid: a new mechanism

This study aimed to investigate, using an in vitro model, the mechanisms involved in the effects linked to a novel hexadecylamide derivative of hyaluronic acid (HA), HYADD®4 (HS), on some inflammatory aspects related to the osteoarthritis process. The human leukemic monocytic cell line THP-1 was stimulated with calcium pyrophosphate (CPP) crystals or lipopolysaccaride (LPS) and cultured in the presence of HS or two unmodified HAs (500-730 kDa and >1500 kDa, respectively). The effects of the three HA derivatives were compared by examining the inhibition of IL-1ß and IL-8 release, the phagocytic capacity of THP-1, and HA's physical interference with the cytokines and their biological activity. Adding HS simultaneously with the stimuli led to a marked (nearly 100%) decrease in cytokine release and biological activity with respect to the two unmodified HAs. The effect was not altered when a CD44 function-blocking monoclonal antibody was used. Incubation of the three derivatives with IL-1ß and IL-8 led to a reduced bioavailability of the cytokines in the medium in the presence of HS but not of unmodified HA. This study examines a novel mechanism inhibiting cytokine bioactivity. The HA hexadecylamide derivative was found to suppress, in vitro, the inflammatory response induced by CPP crystals and LPS by reducing the bioavailability of the two cytokines that were analyzed.

Induction of an inflammatory and prodegradative phenotype in autologous fibroblast-like synoviocytes by the infrapatellar fat pad from patients with knee osteoarthritis

OBJECTIVE

The infrapatellar fat pad (IFP) of the knee joint has an inflammatory phenotype in osteoarthritis (OA). Its close proximity to the synovial membrane suggests that the IFP could be involved in the induction of OA synovitis. This study was undertaken to investigate the response of fibroblast-like synoviocytes (FLS) to autologous IFP and subcutaneous adipose tissue (SCAT) from patients with severe knee OA.

METHODS

Samples of IFP, SCAT, and autologous synovial membrane tissue close to the IFP were harvested during surgery from 28 patients with end-stage knee OA. FLS from 14 patients were stimulated with autologous IFP- or SCAT-conditioned medium, and levels of messenger RNA (mRNA) expression and protein release of interleukin-6 (IL-6), IL-8, secretory phospholipase A2 (sPLA2 ), cytosolic PLA2 , cyclooxygenase 2 (COX-2), microsomal prostaglandin E synthase, prostaglandin E2 (PGE2 ), and matrix metalloproteinases (MMPs) 1, 3, 9, and 13 were evaluated. Both IFP- and SCAT-conditioned medium were evaluated by enzyme-linked immunosorbent assay for secretion of IL-6, soluble IL-6 receptor (sIL-6R), IL-8, tumor necrosis factor α (TNFα), PGE2 , IL-1β, and interferon-γ. In addition, OA FLS were treated with PGE2 receptor antagonists to evaluate the contribution of IFP-derived PGE2 to the inflammatory response of FLS to the IFP.

RESULTS

Stimulation of OA FLS with IFP-conditioned medium induced the mRNA expression and protein release of IL-6, IL-8, sPLA2 , COX-2, PGE2 , and MMPs 1, 3, 9, and 13. The extent of stimulation was consistently stronger with IFP-conditioned medium than with SCAT-conditioned medium. Moreover, secretion of IL-6, sIL-6R, IL-8, TNFα, and PGE2 was greater in IFP-conditioned medium than in SCAT-conditioned medium, especially PGE2 , whose secretion was 75-fold stronger in IFP-conditioned medium (P < 0.0001). PGE2 receptor antagonists dose-dependently inhibited the release of IL-6, IL-8, and PGE2 by IFP-stimulated FLS.

CONCLUSION

This study showed that the IFP has a potential role in the induction of synovial inflammation in patients with severe knee OA. Furthermore, secretion of PGE2 by the IFP may be involved in the OA inflammatory process.

The role of protein content on the steady and oscillatory shear rheology of model synovial fluids

Recent studies have debated the role of protein content on the bulk rheology of synovial fluid; in particular, it has been questioned if proteins aggregate or interact with hyaluronic acid in synovial fluid to enhance bulk rheology, or if observed effects were due to systematic measurement error caused by interfacial rheology, stemming from protein adsorption to the interface. Utilizing several techniques to ensure results reflect only bulk rheology, an examination of the role of bovine serum albumin and γ-globulin on model synovial fluid rheology has been undertaken. When interfacial rheology caused by protein adsorption to the interface is abrogated, the bulk rheology of a model synovial fluid composed of bovine serum albumin, γ-globulin, and hyaluronic acid is found to be dominated solely by the hyaluronic acid over a wide range of shear rates, strains and frequencies. These results show that the previously reported enhanced rheological properties of model synovial fluids are solely due to interfacial rheology and not from any type of protein aggregation/interaction in bulk solution.

Changes of early post-traumatic osteoarthritis in an ovine model of simulated ACL reconstruction are associated with transient acute post-injury synovial inflammation and tissue catabolism

The study described here tested the hypothesis that early intra-articular inflammation is associated with the development of post-traumatic osteoarthritis (PTOA) in a sheep model. We extended previously published work in which we investigated joint gross morphology and synovial mRNA expression of inflammatory and catabolic molecules 2 weeks after anatomic Anterior cruciate ligament (ACL) autograft reconstructive surgery (ACL-R). The same variables have been analyzed at 20 weeks post surgery together with new experimental variables at both time points. Animals were sacrificed at 20 weeks post ACL-R surgery and their joints graded for signs of PTOA. Synovial samples were harvested for histological grading plus mRNA and protein analysis for a panel of inflammatory and catabolic molecules. The mRNA expression levels for this panel plus connective tissue matrix turnover molecules were also investigated in cartilage samples. Results of gross morphological assessments at 20 weeks post surgery showed some changes consistent with early OA, but indicated little progression of damage from the 2 week time point. While significant alterations in mRNA levels for synovial inflammatory and catabolic molecules were detected at 2 weeks, values had normalized by 20 weeks. Similarly, all mRNA expression levels for inflammatory and catabolic molecules in articular cartilage had returned to normal levels by 20 weeks post ACL-R surgery. We conclude that synovial inflammatory processes are initiated very early after ACL-R surgery and may instigate events that lead to the gross cartilage and joint abnormalities observed as early as 2 weeks. However, the absence of sustained inflammation and joint instability may prevent OA progression.

Importance of synovitis in osteoarthritis: evidence for the use of glycosaminoglycans against synovial inflammation

OBJECTIVES

After detailing the different aspects of synovial inflammation (i.e., cellular, biochemical, and vascular) and based on the current knowledge, the aim of this review was to collect the available in vitro and in vivo data regarding the potency of some glycosaminoglycan (GAG) compounds to target synovial inflammation, an important aspect of osteoarthritis.

METHODS

The first part of the review corresponds to a qualitative review of the inflammatory status of OA synovial membrane. The second part corresponds to a systematic review of the literature regarding the potential effects of some GAGs on the previously described phenomenon.

RESULTS

The synovial aspect of the inflammatory status of OA has been detailed. Chondroitin sulfate has demonstrated to control the three aspects of synovial membrane inflammation: cell infiltration and activity, biochemical mediators release, and angiogenesis. Glucosamine is also active on both cellular and molecular aspects of the inflammatory reaction. Hyaluronic acid seems to be anti-inflammatory in its native form, while products of degradation are reported to be pro-angiogenic.

CONCLUSION

Much evidence suggests that some of the studied GAG compounds could target different aspects of synovitis. Some of them could be considered in combination therapy since they exhibit complementary properties. Most of the studies have concentrated on articular cartilage and chondrocytes. In order to achieve a structure modification, one may now consider all joint tissues and investigate the drug potency on all of them. Potent treatment should trigger the most important features of OA: cartilage degradation, subchondral bone sclerosis, and all aspects of synovial inflammation.

Prevalence of naturally occurring cartilage defects in the ovine knee

OBJECTIVE

To determine the prevalence, anatomical location and severity of cartilage defects in the stifle (knee) within a population of adult ewes (N = 65).

MATERIALS AND METHODS

Articular cartilage (AC) of the distal femur, proximal tibia and patella was assessed using Osteoarthritis Research Society International (OARSI) recommendations for macroscopic and microscopic scoring of ovine cartilage. Synovial fluid analysis and histology of the synovial membrane were performed. All limbs were examined by computed tomography.

RESULTS

Twenty-eight sheep (n = 28; 43%) presented at least one score 2 or score 3 lesion. Twenty-two (n = 22; 34%) sheep were macroscopically normal. Most frequent localizations of lesions were: axial aspect of the central third of the medial tibial condyle (32.7% of the lesions), middle third of the medial femoral condyle (29.4%), middle third of the articular surface of the patella (9.8%), and axial aspect of the central third of the lateral tibial condyle (9.8%). Grade of macroscopic lesions was significantly (H (3) = 29.31, P 0.000) affected by age. Macroscopic score correlated well with histological changes that can be found in osteoarthritis (OA) (r 0.83; P 0.000). Neither clinical signs of OA, nor cytological and histological signs of inflammation were identified, while imaging abnormalities were very rare.

CONCLUSIONS

Our data seem to indicate that naturally occurring OA exists in ageing sheep, at least subclinically. It might be useful to take into account prevalent cartilage defects at baseline in studies using ovine models.

A hexadecylamide derivative of hyaluronan (HYMOVIS®) has superior beneficial effects on human osteoarthritic chondrocytes and synoviocytes than unmodified hyaluronan

Background

Intra-articular hyaluronan (HA) injection provides symptomatic benefit in the treatment of osteoarthritis (OA). Previously we found superior beneficial effects in a large animal OA model of a hexadecylamide derivative compared with unmodified HA of the same initial molecular weight. The current study sought to define possible molecular mechanisms whereby this enhanced relief of symptoms was occurring.

Methods

Chondrocytes and synovial fibroblasts were isolated from tissues of patients undergoing arthroplasty for knee OA. Monolayer cultures of cells were treated with 0, 0.5, 1.0 or 1.5 mg/mL of unmodified HA (500–730 kDa) or a hexadecylamide derivative of HA of the same initial molecular weight (HYADD4®-G; HYMOVIS®) simultaneously or 1 hour before incubation with interleukin (IL)-1beta (2 ng/mL). Cultures were terminated 15 or 30 minutes later (chondrocytes and synovial fibroblasts, respectively) for quantitation of phosphorylated-(p)-JNK, p-NFkappaB, p-p38, or at 24 hours for quantitation of gene expression (MMP1 &13, ADAMTS4 &5, TIMP1 &3, CD44, COL1A1 &2A1, ACAN, PTGS2, IL6, TNF) and matrix metalloproteinase (MMP)-13 activity.

Results

The hexadecylamide derivative of HA had significantly better amelioration of IL-1beta-induced gene expression of key matrix degrading enzymes (MMP1, MMP13, ADAMTS5), and inflammatory mediators (IL6, PTGS2) by human OA chondrocytes and synovial fibroblasts. Pre-incubation of cells with the derivatized HA for 1 hour prior to IL-1beta exposure significantly augmented the inhibition of MMP1, MMP13, ADAMTS4 and IL6 expression by chondrocytes. The reduction in MMP13 mRNA by the amide derivative of HA was mirrored in reduced MMP-13 protein and enzyme activity in IL-1beta-stimulated chondrocytes. This was associated in part with a greater inhibition of phosphorylation of the cell signalling molecules JNK, p38 and NF-kappaB.

Conclusions

The present studies have demonstrated several potential key mechanisms whereby the intra-articular injection of a hexadecylamide derivative of HA may be acting in joints with OA.

Non-terminal animal model of post-traumatic osteoarthritis induced by acute joint injury

OBJECTIVE

Develop a non-terminal animal model of acute joint injury that demonstrates clinical and morphological evidence of early post-traumatic osteoarthritis (PTOA).

METHODS

An osteochondral (OC) fragment was created arthroscopically in one metacarpophalangeal (MCP) joint of 11 horses and the contralateral joint was sham operated. Eleven additional horses served as unoperated controls. Every 2 weeks, force plate analysis, flexion response, joint circumference, and synovial effusion scores were recorded. At weeks 0 and 16, radiographs (all horses) and arthroscopic videos (OC injured and sham joints) were graded. At week 16, synovium and cartilage biopsies were taken arthroscopically from OC injured and sham joints for histologic evaluation and the OC fragment was removed.

RESULTS

OC fragments were successfully created and horses were free of clinical lameness after fragment removal. Forelimb gait asymmetry was observed at week 2 (P = 0.0012), while joint circumference (P < 0.0001) and effusion scores (P < 0.0001) were increased in injured limbs compared to baseline from weeks 2 to 16. Positive flexion response of injured limbs was noted at multiple time points. Capsular enthesophytes were seen radiographically in injured limbs. Articular cartilage damage was demonstrated arthroscopically as mild wear-lines and histologically as superficial zone chondrocyte death accompanied by mild proliferation. Synovial hyperemia and fibrosis were present at the site of OC injury.

CONCLUSION

Acute OC injury to the MCP joint resulted in clinical, imaging, and histologic changes in cartilage and synovium characteristic of early PTOA. This model will be useful for defining biomarkers of early osteoarthritis and for monitoring response to therapy and surgery.