The contribution of the synovium, synovial derived inflammatory cytokines and neuropeptides to the pathogenesis of osteoarthritis

A phenotypic screening platform for chronic pain therapeutics using all-optical electrophysiology

ABSTRACT

Chronic pain associated with osteoarthritis (OA) remains an intractable problem with few effective treatment options. New approaches are needed to model the disease biology and to drive discovery of therapeutics. We present an in vitro model of OA pain, where dorsal root ganglion (DRG) sensory neurons were sensitized by a defined mixture of disease-relevant inflammatory mediators, here called Sensitizing PAin Reagent Composition or SPARC. Osteoarthritis-SPARC components showed synergistic or additive effects when applied in combination and induced pain phenotypes in vivo. To measure the effect of OA-SPARC on neural firing in a scalable format, we used a custom system for high throughput all-optical electrophysiology. This system enabled light-based membrane voltage recordings from hundreds of neurons in parallel with single cell and single action potential resolution and a throughput of up to 500,000 neurons per day. A computational framework was developed to construct a multiparameter OA-SPARC neuronal phenotype and to quantitatively assess phenotype reversal by candidate pharmacology. We screened ∼3000 approved drugs and mechanistically focused compounds, yielding data from over 1.2 million individual neurons with detailed assessment of functional OA-SPARC phenotype rescue and orthogonal "off-target" effects. Analysis of confirmed hits revealed diverse potential analgesic mechanisms including ion channel modulators and other mechanisms including MEK inhibitors and tyrosine kinase modulators. Our results suggest that the Raf-MEK-ERK axis in DRG neurons may integrate the inputs from multiple upstream inflammatory mediators found in osteoarthritis patient joints, and MAPK pathway activation in DRG neurons may contribute to chronic pain in patients with osteoarthritis.

Association of endometriosis with Sjögren's syndrome: Genetic insights (Review)

Patients with a history of endometriosis have an increased risk of developing various autoimmune diseases such as rheumatoid arthritis, ankylosing spondylitis, systemic lupus erythematosus, multiple sclerosis and celiac disease. There is a potential association between endometriosis and an increased susceptibility for Sjögren's syndrome (SS). SS is a common chronic, inflammatory, systemic, autoimmune, multifactorial disease of complex pathology, with genetic, epigenetic and environmental factors contributing to the development of this condition. It occurs in 0.5‑1% of the population, is characterized by the presence of ocular dryness, lymphocytic infiltrations and contributes to neurological, gastrointestinal, vascular and dermatological manifestations. Endometriosis is an inflammatory, estrogen‑dependent, multifactorial, heterogeneous gynecological disease, affecting ≤10% of reproductive‑age women. It is characterized by the occurrence of endometrial tissue outside the uterine cavity, mainly in the pelvic cavity, and is associated with pelvic pain, dysmenorrhea, deep dyspareunia and either subfertility or infertility. It is still unclear whether SS appears as a secondary response to endometriosis, or it is developed due to any potential shared mechanisms of these conditions. The aim of the present review was to explore further the biological basis only of the co‑occurrence of these disorders but not their association at clinical basis, focusing on the analysis of the partially shared genetic background between endometriosis and SS, and the clarification of the possible similarities in the underlying pathogenetic mechanisms and the relevant molecular pathways.

Use of Autologous Conditioned Serum (ACS) for Osteoarthritis Treatment in Horses: A Systematic Review of Clinical Data

The utilization of Autologous Conditioned Serum (ACS) for treating osteoarthritis (OA) in horses has seen a notable increase in recent years. In vitro studies have consistently identified ACS as a promising therapy for OA joints, contributing to its growing popularity in OA treatment. Despite this, there is a noticeable absence of systematic reviews focused solely on the clinical data of OA patients treated with ACS, excluding the in vitro perspective. This study aims to address this gap by systematically reviewing the latest literature, concentrating solely on clinical data in in vivo studies to evaluate the efficacy of ACS in OA lesions. All clinical studies involving ACS treatments for horses with OA were included in the assessment. Surprisingly, only six trials met the inclusion criteria for this systematic review. The results indicate that the majority of the considered articles support the use of ACS as a treatment for horses, albeit with a control group provided in only one study. However, the absence of a control group and the exclusion of histological evaluation diminish the validity of the majority of clinical research. While several studies suggest a beneficial effect of ACS on OA horses without significant adverse effects, this systematic review affirms that there is no definitive evidence for its effectiveness. Therefore, further investigation of the efficacy of ACS products as a treatment for OA is warranted, emphasizing the need for more controlled trials. Poorly designed and biased studies, lacking blinding or control and adopting inadequate outcome measures, may favor positive results and, thus, necessitate a more rigorous approach to validate the efficacy of ACS in OA treatment.

A pilot study to determine the optimal dose of scAAVIL-1ra in a large animal model of post-traumatic osteoarthritis

Gene therapy approaches using adeno-associated viral vectors have been successfully tested in the equine post-traumatic osteoarthritis (PTOA) model. Owing to differences in the levels of transgene expression and adverse tissue reactions observed in published studies, we sought to identify a safe therapeutic dose of scAAVIL-1ra in an inflamed and injured joint that would result in improved functional outcomes without any adverse events. scAAVIL-1ra was delivered intra-articularly over a 100-fold range, and horses were evaluated throughout and at the end of the 10-week study. A dose-related increase in IL-1ra levels with a decrease in PGE2 levels was observed, with the peak IL-1ra concentration being observed 7 days post-treatment in all groups. Perivascular infiltration with mononuclear cells was observed within the synovial membrane of the joint treated with the highest viral dose of 5 × 1012 vg, but this was absent in the lower-dosed joints. The second-highest dose of scAAVeqIL-1ra 5 × 1011 vg demonstrated elevated IL-1ra levels without any cellular response in the synovium. Taken together, the data suggest that the 10-fold lower dose of 5 × 1011vg scAAVIL-1ra would be a safe therapeutic dose in an equine model of PTOA.

Fundamentals of osteoarthritis: Inflammatory mediators in osteoarthritis

OBJECTIVES

As more has become known of the pathophysiology of osteoarthritis (OA), evidence that inflammation plays a critical role in its development and progression has accumulated. Here, we aim to review current knowledge of the complex inflammatory network in the OA joint.

DESIGN

This narrative review is presented in three main sections: local inflammation, systemic inflammation, and therapeutic implications. We focused on inflammatory mediators and their link to OA structural changes in the joint.

RESULTS

OA is characterized by chronic and low-grade inflammation mediated mostly by the innate immune system, which results in cartilage degradation, bone remodeling and synovial changes. Synovitis is regarded as an OA characteristic and associated with increased severity of symptoms and joint dysfunction. However, the articular cartilage and the subchondral bone also produce several pro-inflammatory mediators thus establishing a complex interplay between the different tissues of the joint. In addition, systemic low-grade inflammation induced by aging, obesity and metabolic syndrome can contribute to OA development and progression. The main inflammatory mediators associated with OA include cytokines, chemokines, growth factors, adipokines, and neuropeptides.

CONCLUSIONS

Future research is needed to deeper understand the molecular pathways mediating the inflammation in OA to provide new therapeutics that target these pathways, or to repurpose existing drugs.

Prokineticin System Is a Pharmacological Target to Counteract Pain and Its Comorbid Mood Alterations in an Osteoarthritis Murine Model

Osteoarthritis (OA) is the most prevalent joint disease associated with chronic pain. OA pain is often accompanied by mood disorders. We addressed the role of the Prokineticin (PK) system in pain and mood alterations in a mice OA model induced with monosodium iodoacetate (MIA). The effect of a PK antagonist (PC1) was compared to that of diclofenac. C57BL/6J male mice injected with MIA in the knee joint were characterized by allodynia, motor deficits, and fatigue. Twenty-eight days after MIA, in the knee joint, we measured high mRNA of PK2 and its receptor PKR1, pro-inflammatory cytokines, and MMP13. At the same time, in the sciatic nerve and spinal cord, we found increased levels of PK2, PKR1, IL-1β, and IL-6. These changes were in the presence of high GFAP and CD11b mRNA in the sciatic nerve and GFAP in the spinal cord. OA mice were also characterized by anxiety, depression, and neuroinflammation in the prefrontal cortex and hippocampus. In both stations, we found increased pro-inflammatory cytokines. In addition, PK upregulation and reactive astrogliosis in the hippocampus and microglia reactivity in the prefrontal cortex were detected. PC1 reduced joint inflammation and neuroinflammation in PNS and CNS and counteracted OA pain and emotional disturbances.

Culture Media Supplemented With 10% Equine Serum Provided Chondroprotection in an In Vitro Co-Culture of Cartilage and Synovial Membrane

No studies have evaluated the effect of culture in serum-free media (SF) vs. media supplemented with equine serum (ES) on co-culture of synovial membrane and cartilage tissue explants. The study objective was to evaluate the effects of equine serum supplementation on induced production of inflammatory and catabolic mediators from articular cartilage and synovial explants while in co-culture. Articular cartilage and synovial membrane explants were harvested from femoropatellar joints of five adult horses. Cartilage and synovial explants were harvested from the stifle of five horses, placed in co-culture, stimulated with IL-1β (10 ng/ml) and maintained in culture for 3, 6 and 9 days in 10% ES or SF. At each time point, media was harvested for analysis of cellular viability (Lactate dehydrogenase) and elution of glycosaminoglycans (Dimethylene Blue Binding Assay). Tissue explants were harvested for histopathologic and gene expression analyses. No differences in cell viability were observed between SF and ES groups. SF culture produced an upregulation of TNF-α in synovial membrane and ADAMTS-4 and five in articular cartilage at 9 days of culture. ES produced an upregulation of aggrecan expression in cartilage at 9 days of culture. No differences in tissue viability were found between culture media, but SF media produced a higher glycosaminoglycan concentration in media at 3 days of culture. The addition of 10% ES produced a slight chondroprotective effect in an inflamed co-culture system. This effect should be considered when designing studies evaluating treatment of serum or plasma-based orthobiologic studies in vitro.

Plantar osteochondral fragments in young Standardbreds are associated with minimal joint inflammation at the time of surgical removal

BACKGROUND

Plantar osteochondral fragments (POF) are common but their effect on joint health of young Standardbreds in race training is largely unknown.

OBJECTIVES

Evaluate the inflammatory effects of POF in metatarsophalangeal joints of young Standardbreds as a step towards developing evidence-based recommendations for surgical removal.

STUDY DESIGN

Cohort study.

METHODS

Forty-nine Standardbred horses (age 11-33 months) presented for surgical removal of POF from 56 metatarsophalangeal joints. Synovial tissue collected at arthroscopy was subjected to histopathology. IL-1β, TNF-α, and PGE-2 were measured in synovial fluid using ELISA. Digital arthroscopy images were scored for inflammation. Racing performance data were retrieved from a public database.

RESULTS

Median time in race training prior to surgery was 8 weeks (IQR 4-12; range 0-40). There was minimal evidence of synovial inflammation as assessed by histopathology (median total score 2/20, IQR 0-2, range 0-5) or arthroscopy (median average total score 2.67/15, IQR 1.79-4, range 0-8.83). IL-1β was not detected in any sample. TNF-α (median 0 pg/mL, IQR 0-0) and PGE-2 (median 56.6 pg/mL, IRQ 40.5-99.8) were measured at low levels. Weeks in training prior to surgery was associated with the number of starts in the season after surgery (incidence rate ratio 1.02, 95% CI 1.00, 1.04, P = .03).

MAIN LIMITATIONS

Small sample size from a single breed with a relatively short training time prior to surgery.

CONCLUSIONS

There was minimal evidence of synovial inflammation in the metatarsophalangeal joints in this population of young Standardbred horses with POF. It is possible that POF may result in a different inflammatory response than other fragments because they are generally well-embedded in situ. These findings suggest that, in Standardbreds, race training can commence several weeks prior to surgical removal of POF with minimal detrimental effects on joint health, although further investigation of long-term effects of POF on joint health is warranted.

Osteoarthritis models: From animals to tissue engineering

Osteoarthritis (OA) is a chronic degenerative osteoarthropathy. Although it has been revealed that a variety of factors can cause or aggravate the symptoms of OA, the pathogenic mechanisms of OA remain unknown. Reliable OA models that accurately reflect human OA disease are crucial for studies on the pathogenic mechanism of OA and therapeutic drug evaluation. This review first demonstrated the importance of OA models by briefly introducing the OA pathological features and the current limitations in the pathogenesis and treatment of OA. Then, it mainly discusses the development of different OA models, including animal and engineered models, highlighting their advantages and disadvantages from the perspective of pathogenesis and pathology analysis. In particular, the state-of-the-art engineered models and their potential were emphasized, as they may represent the future direction in the development of OA models. Finally, the challenges in obtaining reliable OA models are also discussed, and possible future directions are outlined to shed some light on this area.

Potential metabolites of Arecaceae family for the natural anti-osteoarthritis medicine: A review

Osteoarthritis (OA) is a chronic inflammatory disorder of the joints caused by fluid and cartilage matrix component reduction. This disease results in symptoms of pain, deformity, and limitation of movement. In general, OA is treated with anti-inflammatory drugs and chondroprotection compounds, includes natural nutraceutical ingredients, which are expected to be effective and have minimal side effects. Arecaceae plants are widely spread worldwide, especially in tropical areas. The objective of this review is to collect information about the Arecaceae family as anti-OA agents, with the main study focusing on the primary and secondary metabolites of plants of the Arecaceae family, i.e., sugar palm (Arenga pinnata), nipa palm (Nypa fruticans), palmyra palm (Borassus flabellifer), date palm (Phoenix dactylifera), and betel nut (Areca catechu) have potential as anti-OA agents. The Arecaceae's metabolites that show anti-inflammatory and chondroprotective effects are galactomannan, fatty acids (linoleic and linolenic acids), flavonoids (quercetin, luteolin, isorhamnetin), phenolics (coumaric acid, ferulic acid), polyphenols (epicatechin), and steroids (stigmasterol, campesterol, spirostane). Based on the reports, the Arecaceae family plants become worthy of being explored and developed into natural anti-OA products, such as supplements or nutraceuticals.

Bioimpedance Measurement of Knee Injuries Using Bipolar Electrode Configuration

Currently, there is no suitable solution for the point-of-care diagnosis of knee injuries. A potential portable and low-cost technique for accessing and monitoring knee injuries is bioimpedance measurement. This study validated the feasibility of the bipolar electrode configuration for knee bioimpedance measurement with two electrodes placed on a fixed pair of knee acupuncture locations called Xiyan. Then, the study collected 76 valid samples to investigate the relationship between bioimpedance and knee injuries, among whom 39 patients have unilateral knee injuries, and 37 individuals have healthy knees. The self-contrast results indicated that knee injuries caused a reduction of bioimpedance of the knee by about 5% on average, which was detectable at around 100 kHz (p ≈ 0.001). Furthermore, the results analyzed by principal component analysis and support vector machines show that the detection sensitivity can reach 87.18% using the leave-one-out cross-validation. We also proposed a low-cost and portable bioimpedance measurement device that meets the needs for measuring knee joint bioimpedance.

Effect of Leukoreduced Platelet Rich Plasma on Intra-Articular Pro-Inflammatory Cytokines in a Canine Pilot Study

Simple Summary

This study provides initial information on the effect of platelet rich plasma in some of the most important pro-inflammatory cytokines identified in osteoarthritic stifle joint in dogs. The use of platelet rich plasma is getting more popular in the veterinary field but its effect in those cytokines is not known.

Abstract

Evaluation of effect of Leukoreduced Platelet Rich Plasma (LrPRP) on TNF-α and IL-6 (pro-inflammatory cytokines) in joint fluid in dogs with cranial cruciate ligament rupture (CCLR). Eight client-owned dogs with CCLR were assigned to treatment (2 mL LrPRP) or control (2 mL saline) injection groups. Day of evaluation (day 0) and day of surgery (day 10–14), joint fluid was collected and joint injected. Joint fluid was also collected on day of suture removal (day 20–28). TNF-α and IL-6 concentrations of joint fluid were measured using a bead-based antibody assay. Concentrations at the later time points were expressed as a ratio to the initial level within each stifle. LrPRP had a mean concentration of platelets 1.7 times higher that of whole blood on day of evaluation and 1.4 times higher on day of the surgery. Leukocytes were reduced by 99.7%. On day of surgery, TNF-α ratios in the joint fluid from dogs injected with LrPRP were significantly different that TNF-α ratios of control group. On the day of suture removal ratios of IL-6 and TNF-α were lower in LrPRP treatment group compared with control group; however, differences were not significant. LrPRP modulate ratios of pro-inflammatory cytokine TNF-α in dogs with CCLR.

Role of Innate Immunity in Initiation and Progression of Osteoarthritis, with Emphasis on Horses

Osteoarthritis (OA) is a common condition with diverse etiologies, affecting horses, humans, and companion animals. Importantly, OA is not a single disease, but rather a disease process initiated by different events, including acute trauma, irregular or repetitive overload of articular structures, and spontaneous development with aging. Our understanding of the pathogenesis of OA is still evolving, and OA is increasingly considered a multifactorial disease in which the innate immune system plays a key role in regulating and perpetuating low-grade inflammation, resulting in sustained cartilage injury and destruction. Macrophages within the synovium and synovial fluid are considered the key regulators of immune processes in OA and are capable of both stimulating and suppressing joint inflammation, by responding to local and systemic cues. The purpose of this review is to examine the role of the innate immune system in the overall pathogenesis of OA, drawing on insights from studies in humans, animal models of OA, and from clinical and research studies in horses. This review also discusses the various therapeutic immune modulatory options currently available for managing OA and their mechanisms of action.

Hyperglycemia-induced accumulation of advanced glycosylation end products in fibroblast-like synoviocytes promotes knee osteoarthritis

Osteoarthritis (OA) is significantly associated with diabetes, but how hyperglycemia induces or aggravates OA has not been shown. The synovium plays a critical role in cartilage metabolism and substance exchange. Herein, we intended to investigate whether and how hyperglycemia affects the occurrence and progression of OA by influencing the synovium. In patients with knee OA and diabetes (DM OA), we found a more severe inflammatory response, higher endoplasmic reticulum stress (ERS) levels, and more advanced glycosylation end products (AGEs) accumulation in the synovium than in patients without diabetes. Subsequently, we found similar results in the DM OA group in a rat model. In the in vitro cocultivation system, high glucose-stimulated AGEs accumulation, ERS, and inflammation in rat fibroblast-like synoviocytes (FLSs), which resulted in chondrocyte degeneration due to inflammatory factors from FLSs. Furthermore, in the synovium of the DM OA group and FLSs treated with high glucose, the expression of glucose transporter 1 (GLUT1) and its regulatory factor hypoxia-inducible factor (HIF)-1α was increased significantly. Inhibitors of HIF-1α, GLUT1 or AGEs receptors attenuated the effect of high glucose on chondrocyte degradation in the FLS-chondrocyte coculture system. In summary, we demonstrated that hyperglycemia caused AGEs accumulation in FLSs via the HIF-1α-GLUT1 pathway, which increases the release of inflammatory factors from FLSs, subsequently inducing chondrocyte degradation and promoting OA progression.

Autologous protein solution: a promising solution for osteoarthritis?

Osteoarthritis (OA) is a global health issue with myriad pathophysiological factors and is one of the most common causes of chronic disability in adults due to pain and altered joint function.

The end stage of OA develops from a destructive inflammatory cycle, driven by the pro-inflammatory cytokines interleukin-1β (IL-1β) and tumour necrosis factor alpha (TNFα).

Owing to the less predictable results of total knee arthroplasty (TKA) in younger patients presenting with knee OA, there has been a surge in research evaluating less invasive biological treatment options, one of which is autologous protein solution (APS).

APS is an autologous blood derivative obtained by using a proprietary device, made of APS separator, which isolates white blood cells (WBCs) and platelets in a small volume of plasma, and APS concentrator, which further concentrates platelets, WBCs and plasma proteins, resulting in a concentrated solution with high levels of growth factors including the anti-inflammatory mediators against IL-1β and TNFα.

A single intraarticular injection of APS appears to be a promising solution for treatment of early-stage OA from current evidence, the majority of which comes from preclinical studies.

More clinical studies are needed before APS can be widely accepted as a treatment modality for OA.

Cite this article: EFORT Open Rev 2021;6:716-726. DOI: 10.1302/2058-5241.6.200040

Arthroscopic evaluation of the synovial membrane and its relationship with histological changes and biomarkers in equine joint disease

The synovial membrane (SM) presents itself with distinctive characteristics during arthroscopic procedures in cases of osteoarthritis (OA) as well as osteochondritis dissecans (OCD) in horses. Most of the arthroscopic findings of the SM are limited to a description of a nonspecific inflammation state. In the present study, the macroscopic and histological aspects of the SM in OA and OCD horses were compared to those of healthy horses. The expression of interleukin (IL) in SM was also investigated. Besides, the concentrations of ILs and keratan sulfate (KS) in the synovial fluid (SF), and the molecular weights of the SF hyaluronic acid (HA) were also determined and correlated to the macroscopic and histological aspects of SM. This study included 10 healthy horses (control group), 12 horses with OA, and 12 with OCD. Macroscopic scores of the SM were higher in the OA group in comparison to the control and OCD groups. However, histological scores between OA and OCD were not different, and both were higher than the control group. Only in the OA group, there was a correlation between macroscopic and histological aspects of the SM, especially between volume and quantity of villi with perivascular inflammatory cells and synovial proliferation. The OA group has shown decreased expression of IL-10 in the SM, lower IL-10 and KS, and higher IL-1β and IL-6 in the SF in comparison to the control and OCD groups. There was a significant negative correlation between the macroscopic aspect of the SM and the molecular weights AH in the OA group. There was no correlation between the macroscopic aspect of the SM and all dosages in the OA and OCD group. In the OA joints, the evaluation of the shape of the SM during arthroscopy promotes a better indicator for joint inflammatory or tissue repair processes, while in the osteochondritic joints, investigation of the histological aspects are recommended to rule out an incipient OA development process. Both are helpful and should be considered to guide the postoperative treatment.

MicroRNA-34a-5p Promotes Joint Destruction During Osteoarthritis

Objective

MicroRNA‐34a‐5p (miR‐34a‐5p) expression is elevated in the synovial fluid of patients with late‐stage knee osteoarthritis (OA); however, its exact role and therapeutic potential in OA remain to be fully elucidated. This study was undertaken to examine the role of miR‐34a‐5p in OA pathogenesis.

Methods

Expression of miR‐34a‐5p was determined in joint tissues and human plasma (n = 71). Experiments using miR‐34a‐5p mimic or antisense oligonucleotide (ASO) treatment were performed in human OA chondrocytes, fibroblast‐like synoviocytes (FLS) (n = 7–9), and mouse OA models, including destabilization of the medial meniscus (DMM; n = 22) and the accelerated, more severe model of mice fed a high‐fat diet and subjected to DMM (n = 11). Wild‐type (WT) mice (n = 9) and miR‐34a–knockout (KO) mice (n = 11) were subjected to DMM. Results were expressed as the mean ± SEM and analyzed by t‐test or analysis of variance, with appropriate post hoc tests. P values less than 0.05 were considered significant. RNA sequencing was performed on WT and KO mouse chondrocytes.

Results

Expression of miR‐34a‐5p was significantly increased in the plasma, cartilage, and synovium of patients with late‐stage OA and in the cartilage and synovium of mice subjected to DMM. Plasma miR‐34a‐5p expression was significantly increased in obese patients with late‐stage OA, and in the plasma and knee joints of mice fed a high‐fat diet. In human OA chondrocytes and FLS, miR‐34a‐5p mimic increased key OA pathology markers, while miR‐34a‐5p ASO improved cellular gene expression. Intraarticular miR‐34a‐5p mimic injection induced an OA‐like phenotype. Conversely, miR‐34a‐5p ASO injection imparted cartilage‐protective effects in the DMM and high‐fat diet/DMM models. The miR‐34a–KO mice exhibited protection against DMM‐induced cartilage damage. RNA sequencing of WT and KO chondrocytes revealed a putative miR‐34a‐5p signaling network.

Conclusion

Our findings provide comprehensive evidence of the role and therapeutic potential of miR‐34a‐5p in OA.

Neuroscience and Neuroimmunology Solutions for Osteoarthritis Pain: Biological Drugs, Growth Factors, Peptides and Monoclonal Antibodies Targeting Peripheral Nerves

Neuroscience is a vast discipline that deals with the anatomy, biochemistry, molecular biology, physiology and pathophysiology of central and peripheral nerves. Advances made through basic, translational, and clinical research in the field of neuroscience have great potential for long-lasting and beneficial impacts on human and animal health. The emerging field of biological therapy is intersecting with the disciplines of neuroscience, orthopaedics and rheumatology, creating new horizons for interdisciplinary and applied research. Biological drugs, growth factors, therapeutic peptides and monoclonal antibodies are being developed and tested for the treatment of painful arthritic and rheumatic diseases. This concise communication focuses on the solutions provided by the fields of neuroscience and neuroimmunology for real-world clinical problems in the field of orthopaedics and rheumatology, focusing on synovial joint pain and the emerging biological treatments that specifically target pathways implicated in osteoarthritis pain in peripheral nerves.

Amentadione from the Alga Cystoseira usneoides as a Novel Osteoarthritis Protective Agent in an Ex Vivo Co-Culture OA Model

Osteoarthritis (OA) remains a prevalent chronic disease without effective prevention and treatment. Amentadione (YP), a meroditerpenoid purified from the alga Cystoseira usneoides, has demonstrated anti-inflammatory activity. Here, we investigated the YP anti-osteoarthritic potential, by using a novel OA preclinical drug development pipeline designed to evaluate the anti-inflammatory and anti-mineralizing activities of potential OA-protective compounds. The workflow was based on in vitro primary cell cultures followed by human cartilage explants assays and a new OA co-culture model, combining cartilage explants with synoviocytes under interleukin-1β (IL-1β) or hydroxyapatite (HAP) stimulation. A combination of gene expression analysis and measurement of inflammatory mediators showed that the proposed model mimicked early disease stages, while YP counteracted inflammatory responses by downregulation of COX-2 and IL-6, improved cartilage homeostasis by downregulation of MMP3 and the chondrocytes hypertrophic differentiation factors Col10 and Runx2. Importantly, YP downregulated NF-κB gene expression and decreased phosphorylated IkBα/total IkBα ratio in chondrocytes. These results indicate the co-culture as a relevant pre-clinical OA model, and strongly suggest YP as a cartilage protective factor by inhibiting inflammatory, mineralizing, catabolic and differentiation processes during OA development, through inhibition of NF-κB signaling pathways, with high therapeutic potential.

Differential gene expression analysis reveals pathways important in early post-traumatic osteoarthritis in an equine model

Background

Post-traumatic osteoarthritis (PTOA) is a common and significant problem in equine athletes. It is a disease of the entire joint, with the synovium thought to be a key player in disease onset and progression due to its role in inflammation. The development of effective tools for early diagnosis and treatment of PTOA remains an elusive goal. Altered gene expression represents the earliest discernable disease-related change, and can provide valuable information about disease pathogenesis and identify potential therapeutic targets. However, there is limited work examining global gene expression changes in early disease. In this study, we quantified gene expression changes in the synovium of osteoarthritis-affected joints using an equine metacarpophalangeal joint (MCPJ) chip model of early PTOA. Synovial samples were collected arthroscopically from the MCPJ of 11 adult horses before (preOA) and after (OA) surgical induction of osteoarthritis and from sham-operated joints. After sequencing synovial RNA, Salmon was used to quasi-map reads and quantify transcript abundances. Differential expression analysis with the limma-trend method used a fold-change cutoff of log2(1.1). Functional annotation was performed with PANTHER at FDR < 0.05. Pathway and network analyses were performed in Reactome and STRING, respectively.

Results

RNA was sequenced from 28 samples (6 preOA, 11 OA, 11 sham). “Sham” and “preOA” were not different and were grouped. Three hundred ninety-seven genes were upregulated and 365 downregulated in OA synovium compared to unaffected. Gene ontology (GO) terms related to extracellular matrix (ECM) organization, angiogenesis, and cell signaling were overrepresented. There were 17 enriched pathways, involved in ECM turnover, protein metabolism, and growth factor signaling. Network analysis revealed clusters of differentially expressed genes involved in ECM organization, endothelial regulation, and cellular metabolism.

Conclusions

Enriched pathways and overrepresented GO terms reflected a state of high metabolic activity and tissue turnover in OA-affected tissue, suggesting that the synovium may retain the capacity to support healing and homeostasis in early disease. Limitations of this study include small sample size and capture of one point post-injury. Differentially expressed genes within key pathways may represent potential diagnostic markers or therapeutic targets for PTOA. Mechanistic validation of these findings is an important next step.

Physiological Effects of the Electrogenic Current Generated by the Na+/K+ Pump in Mammalian Articular Chondrocytes

Background: Although the chondrocyte is a nonexcitable cell, there is strong interest in gaining detailed knowledge of its ion pumps, channels, exchangers, and transporters. In combination, these transport mechanisms set the resting potential, regulate cell volume, and strongly modulate responses of the chondrocyte to endocrine agents and physicochemical alterations in the surrounding extracellular microenvironment. Materials and Methods: Mathematical modeling was used to assess the functional roles of energy-requiring active transport, the Na⁺/K⁺ pump, in chondrocytes. Results: Our findings illustrate plausible physiological roles for the Na⁺/K⁺ pump in regulating the resting membrane potential and suggest ways in which specific molecular components of pump can respond to the unique electrochemical environment of the chondrocyte. Conclusion: This analysis provides a basis for linking chondrocyte electrophysiology to metabolism and yields insights into novel ways of manipulating or regulating responsiveness to external stimuli both under baseline conditions and in chronic diseases such as osteoarthritis.

Caudal cruciate ligament disease in three Basset Hounds

CASE DESCRIPTION

3 adult Basset Hounds were referred for evaluation of chronic, unilateral, pelvic limb lameness with no history of trauma.

CLINICAL FINDINGS

On examination, all dogs had mild lameness of the affected limb; signs of pain were evident during manipulation of the stifle joint in the affected limb, along with effusion of that joint. No stifle joint instability was palpable. Radiographs were available for review for 2 of the 3 dogs. Effusion was confirmed radiographically, but severity of degenerative joint disease varied. Central intercondylar notch width ratios for the 2 dogs were 0.16 and 0.17, and tibial plateau angles were -10° and 15°; relative tibial tuberosity width was 1.1 for both dogs. Exploratory arthroscopy revealed moderate degeneration of the caudal cruciate ligament in all 3 dogs; the cranial cruciate ligaments were grossly normal.

TREATMENT AND OUTCOME

Corrective osteotomy to increase the tibial plateau angle was performed in 1 dog, and the lameness resolved by 2 months after surgery. The 2 other dogs were managed without additional surgery. One dog was persistently lame. The other dog reportedly had normal limb function 2.5 years after undergoing exploratory arthroscopy.

CLINICAL RELEVANCE

Morphological characteristics of the tibia in Basset Hounds may predispose to abnormal stresses on the caudal cruciate ligament. Isolated degeneration of the caudal cruciate ligament should be considered as a differential diagnosis for Basset Hounds with lameness originating from the stifle joint. Without direct inspection of the joint, caudal cruciate ligament disease could be confused for cranial cruciate ligament injury.

Inflammatory Cytokine-Producing Cells and Inflammation Markers in the Synovium of Osteoarthritis Patients Evidenced in Human Herpesvirus 7 Infection

A direct association between joint inflammation and the progression of osteoarthritis (OA) has been proposed, and synovitis is considered a powerful driver of the disease. Among infections implicated in the development of joint disease, human herpesvirus 7 (HHV-7) infection remains poorly characterized. Therefore, we assessed synovitis in OA patients; determined the occurrence and distribution of the HHV-7 antigen within the synovial membrane of OA-affected subjects; and correlated plasma levels of the pro-inflammatory cytokines tumor necrosis factor (TNF), interleukin-6 (IL-6), and TNF expressed locally within lesioned synovial tissues with HHV-7 observations, suggesting differences in persistent latent and active infection. Synovial HHV-7, CD4, CD68, and TNF antigens were detected immunohistochemically. The plasma levels of TNF and IL-6 were measured by an enzyme-linked immunosorbent assay. Our findings confirm the presence of persistent HHV-7 infection in 81.5% and reactivation in 20.5% of patients. In 35.2% of patients, virus-specific DNA was extracted from synovial membrane tissue samples. We evidenced the absence of histopathologically detectable synovitis and low-grade changes in the majority of OA patients enrolled in the study, in both HHV-7 PCR+ and HHV-7 PCR‒ groups. The number of synovial CD4-positive cells in the HHV-7 polymerase chain reaction (PCR)+ group was significantly higher than that in the HHV-7 PCR‒ group. CD4- and CD68-positive cells were differently distributed in both HHV-7 PCR+ and HHV-7 PCR‒ groups, as well as in latent and active HHV-7 infection. The number of TNF+ and HHV-7+ lymphocytes, as well as HHV-7+ vascular endothelial cells, was strongly correlated. Vascular endothelial cells, especially in the case of infection reactivation, appeared vulnerable. The balance between virus latency and reactivation is a long-term relationship between the host and infectious agent, and the immune system appears to be involved in displaying overreaction when a shift in the established equilibrium develops.

Degenerative osteoarthritis a reversible chronic disease

Osteoarthritis (OA) is the most common chronic musculoskeletal disorder. It can affect any joint and is the most frequent single cause of disability in older adults.

OA is a progressive degenerative disease involving the entire joint structure in a vicious circle that includes the capsule-bursa tissue inflammation, synovial fluid modifications, cartilage breakdown and erosions, osteochondral inflammatory damage leading to bone erosion and distortion.

Research has identified the initial inflammatory-immunologic process that starts this vicious cycle leading to so-called early OA. Research has also identified the role played in the disease advancement by synoviocytes type A and B, chondrocytes, extracellular matrix, local immune-inflammatory mediators and proteases.

This article investigates the joint-resident MSCs that play an essential local homeostatic role and regulate cell turn over and tissue repair. Resident MSCs establish and maintain a local regenerative microenvironment.

The understanding of OA physiopathology clarifies the core mechanisms by which minimally invasive interventions might be able to halt and reverse the course of early stage OA. Interventions employing PRP, MSCs and exosomes are considered in this article.

Andrographis paniculata Extract Relieves Pain and Inflammation in Monosodium Iodoacetate-Induced Osteoarthritis and Acetic Acid-Induced Writhing in Animal Models

Osteoarthritis (OA), being the most prominent degenerative joint disease is affecting millions of elderly people worldwide. Although Andrographis paniculata is an ethnic medicine with a long history of being used as analgesic agent, no study using a monosodium iodoacetate (MIA) model has investigated its potential activities against OA. In this study, experimental OA was induced in rats with a knee injection of MIA, which represents the pathological characteristics of OA in humans. A. paniculata extract (APE) substantially reversed the loss of hind limb weight-bearing and the cartilage damage resulted from the OA induction in rats. Additionally, the levels of serum pro-inflammatory cytokines, such as IL-1β, IL-6, and TNF-α as well as the concentration of matrix metalloproteinases, including MMP-1, MMP-3, MMP-8, and MMP-13 were decreased by APE administration. Acetic acid-induced writhing responses in mice which quantitatively measure pain were significantly reduced by APE. In vitro, APE inhibited the generation of NO and downregulated the expression of IL-1β, IL-6, COX-2, and iNOS in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. The above results suggest the potential use APE as a therapeutic agent against OA.

Herbal Remedies as Potential in Cartilage Tissue Engineering: An Overview of New Therapeutic Approaches and Strategies

It is estimated that by 2023, approximately 20% of the population of Western Europe and North America will suffer from a degenerative joint disease commonly known as osteoarthritis (OA). During the development of OA, pro-inflammatory cytokines are one of the major causes that drive the production of inflammatory mediators and thus of matrix-degrading enzymes. OA is a challenging disease for doctors due to the limitation of the joint cartilage's capacity to repair itself. Though new treatment approaches, in particular with mesenchymal stem cells (MSCs) that integrate the tissue engineering (TE) of cartilage tissue, are promising, they are not only expensive but more often do not lead to the regeneration of joint cartilage. Therefore, there is an increasing need for novel, safe, and more effective alternatives to promote cartilage joint regeneration and TE. Indeed, naturally occurring phytochemical compounds (herbal remedies) have a great anti-inflammatory, anti-oxidant, and anabolic potential, and they have received much attention for the development of new therapeutic strategies for the treatment of inflammatory diseases, including the prevention of age-related OA and cartilage TE. This paper summarizes recent research on herbal remedies and their chondroinductive and chondroprotective effects on cartilage and progenitor cells, and it also emphasizes the possibilities that exist in this research area, especially with regard to the nutritional support of cartilage regeneration and TE, which may not benefit from non-steroidal anti-inflammatory drugs (NSAIDs).

Pathophysiological landscape of osteoarthritis

A sharp rise in osteoarthritis (OA) incidence is expected as over 25% of world population ages in the coming decade. Although OA is considered a degenerative disease, mounting evidence suggests a strong connection with chronic metabolic conditions and low-grade inflammation. OA pathology is increasingly understood as a complex interplay of multiple pathological events including oxidative stress, synovitis and immune responses revealing its intricate nature. Cellular, biochemical and molecular aspects of these pathological events along with major outcomes of the relevant research studies in this area are discussed in the present review. With reference to their published and unpublished work, the authors strongly propose synovitis as a central OA pathology and the key OA pathological events are described in connection with it. Recent research outcomes also have succeeded to establish a linkage between metabolic syndrome and OA, which has been precisely included in the present review. Impact of aging process cannot be neglected in OA. Cell senescence is an important mechanism of aging through which it facilitates development of OA like other degenerative disorders, also discussed within a frame of OA. Conclusively, the reviewers urge low-grade inflammation linked to aging and derailed immune function as a pathological platform for OA development and progression. Thus, interventions targeted to prevent inflammaging hold a promising potential in effective OA management and efforts should be invested in this direction.

Increased Substance P Immunoreactivity in Ipsilateral Knee Cartilage of Rats Exposed to Lumbar Spine Injury

OBJECTIVE

The present study aimed to investigate whether experimentally induced lumbar facet-joint OA lead to degenerative changes and enhanced SP expression within the ipsilateral neurosegmentally linked tibiofemoral cartilage.

METHODS

Adult male Sprague-Dawley rats were assigned to left side L5-L6 facet mechanical compression injury (surgery) (n = 6), L5-L6 facet exposure with no compression (sham) (n = 5), or naïve (no surgery) (n = 4) groups. The morphology of the tibiofemoral articular cartilage was assessed using a modified Mankin scoring system. Immunohistochemistry was used to examine the density of chondrocytes stained positive for SP (cells/cm²) in the ipsilateral tibiofemoral cartilage at 28 days postintervention.

RESULTS

Tibiofemoral cartilage in the surgery group showed consistent loss of superficial zone chondrocytes, mild roughening of the articular surface and occasional chondrocyte clusters as well as a greater density of SP mainly in the superficial cartilage zone compared with sham and naïve groups, although they also had a basic SP-expression.

CONCLUSION

Our results support the hypothesis that neurogenic mechanisms may mediate the spread of SP to neurosegmentally linked heterologous joints affecting the distal cartilage homeostasis. These findings contribute additional insight into the potential role of neurogenic inflammation with implications in the pathophysiology of chronic inflammatory joint disease and OA.

Pro-inflammatory Cytokines Drive Deregulation of Potassium Channel Expression in Primary Synovial Fibroblasts

The synovium secretes synovial fluid, but is also richly innervated with nociceptors and acts as a gateway between avascular joint tissues and the circulatory system. Resident fibroblast-like synoviocytes' (FLS) calcium-activated potassium channels (K _Ca) change in activity in arthritis models and this correlates with FLS activation.

Objective

To investigate this activation in an in vitro model of inflammatory arthritis; 72 h treatment with cytokines TNFα and IL1β.

Methods

FLS cells were isolated from rat synovial membranes. We analyzed global changes in FLS mRNA by RNA-sequencing, then focused on FLS ion channel genes and the corresponding FLS electrophysiological phenotype and finally modeling data with ingenuity pathway analysis (IPA) and MATLAB.

Results

IPA showed significant activation of inflammatory, osteoarthritic and calcium signaling canonical pathways by cytokines, and we identified ∼200 channel gene transcripts. The large K _Ca (BK) channel consists of the pore forming Kcnma1 together with β-subunits. Following cytokine treatment, a significant increase in Kcnma1 RNA abundance was detected by qPCR and changes in several ion channels were detected by RNA-sequencing, including a loss of BK channel β-subunit expression Kcnmb1/2 and an increase in Kcnmb3. In electrophysiological experiments, there was a decrease in over-all current density at 20 mV without change in chord conductance at this potential.

Conclusion

TNFα and IL1β treatment of FLS in vitro recapitulated several common features of inflammatory arthritis at the transcriptomic level, including increase in Kcnma1 and Kcnmb3 gene expression.

Exosomes from adipose‑derived stem cells promote chondrogenesis and suppress inflammation by upregulating miR‑145 and miR‑221

Osteoarthritis (OA) is one of the most prevalent joint disorders globally. Patients suffering from OA are often obese and adiposity is linked to chronic inflammation. In the present study, the potential of using exosomes isolated from adipose‑derived stem cells (ADSCs) as a therapeutic tool for reducing chronic inflammation and promoting chondrogenesis was investigated using patient‑derived primary cells. First, it was tested whether patient‑derived ADSCs could differentiate into chondrogenic and osteogenic lineages. The ADSCs were then used as a source of exosomes. It was found that exosomes isolated from ADSCs, when co‑cultured with activated synovial fibroblasts, downregulated the expression of pro‑inflammatory markers interleukin (IL)‑6, NF‑κB and tumor necrosis factor‑α, while they upregulated the expression of the anti‑inflammatory cytokine IL‑10; without exosomes, the opposite observations were made. In addition, inflammation‑inflicted oxidative stress was induced in vitro by stimulating chondrocytes with H2O2. Treatment with exosomes protected articular chondrocytes from H2O2‑induced apoptosis. Furthermore, exosome treatment promoted chondrogenesis in periosteal cells and increased chondrogenic markers, including Collagen type II and β‑catenin; inhibition of Wnt/β‑catenin, using the antagonist ICG‑001, prevented exosome‑induced chondrogenesis. Periosteal cells treated with exosomes exhibited higher levels of microRNA (miR)‑145 and miR‑221. The upregulation of miR‑145 and miR‑221 was associated with the enhanced proliferation of periosteal cells and chondrogenic potential, respectively. The present study provided evidence in support for the use of patient‑derived exosomes, produced from ADSCs, for potential chondrogenic regeneration and subsequent amelioration of osteoarthritis.

Molecular taxonomy of osteoarthritis for patient stratification, disease management and drug development: biochemical markers associated with emerging clinical phenotypes and molecular endotypes

PURPOSE OF REVIEW

This review focuses on the molecular taxonomy of osteoarthritis from the perspective of molecular biomarkers. We discuss how wet biochemical markers may be used to understand disease pathogenesis and progression and define molecular endotypes of osteoarthritis and how these correspond to clinical phenotypes.

RECENT FINDINGS

Emerging evidence suggests that osteoarthritis is a heterogeneous and multifaceted disease with multiple causes, molecular endotypes and corresponding clinical phenotypes. Biomarkers may be employed as tools for patient stratification in clinical trials, enhanced disease management in the primary care centres of the future and for directing more rational and targeted osteoarthritis drug development. Proximal molecular biomarkers (e.g synovial fluid) are more likely to distinguish between molecular endotypes because there is less interference from systemic sources of biomarker noise, including comorbidities.

SUMMARY

In this review, we have focused on the molecular biomarkers of four distinct osteoarthritis subtypes including inflammatory, subchondral bone remodelling, metabolic syndrome and senescent age-related endotypes, which have corresponding phenotypes. Progress in the field of osteoarthritis endotype and phenotype research requires a better understanding of molecular biomarkers that may be used in conjunction with imaging, pain and functional assessments for the design of more effective, stratified and individualized osteoarthritis treatments.

A Clinical Approach for the Use of VIP Axis in Inflammatory and Autoimmune Diseases

The neuroendocrine and immune systems are coordinated to maintain the homeostasis of the organism, generating bidirectional communication through shared mediators and receptors. Vasoactive intestinal peptide (VIP) is the paradigm of an endogenous neuropeptide produced by neurons and endocrine and immune cells, involved in the control of both innate and adaptive immune responses. Exogenous administration of VIP exerts therapeutic effects in models of autoimmune/inflammatory diseases mediated by G-protein-coupled receptors (VPAC1 and VPAC2). Currently, there are no curative therapies for inflammatory and autoimmune diseases, and patients present complex diagnostic, therapeutic, and prognostic problems in daily clinical practice due to their heterogeneous nature. This review focuses on the biology of VIP and VIP receptor signaling, as well as its protective effects as an immunomodulatory factor. Recent progress in improving the stability, selectivity, and effectiveness of VIP/receptors analogues and new routes of administration are highlighted, as well as important advances in their use as biomarkers, contributing to their potential application in precision medicine. On the 50th anniversary of VIP's discovery, this review presents a spectrum of potential clinical benefits applied to inflammatory and autoimmune diseases.

Sigma-1 receptor modulates neuroinflammation associated with mechanical hypersensitivity and opioid tolerance in a mouse model of osteoarthritis pain

BACKGROUND AND PURPOSE

Osteoarthritic pain is a chronic disabling condition lacking effective treatment. Continuous use of opioid drugs during osteoarthritic pain induces tolerance and may result in dose escalation and abuse. Sigma-1 (σ1) receptors, a chaperone expressed in key areas for pain control, modulates μ-opioid receptor activity and represents a promising target to tackle these problems. The present study investigates the efficacy of the σ1 receptor antagonist E-52862 to inhibit pain sensitization, morphine tolerance, and associated electrophysiological and molecular changes in a murine model of osteoarthritic pain.

EXPERIMENTAL APPROACH

Mice received an intra-knee injection of monoiodoacetate followed by 14-day treatment with E-52862, morphine, or vehicle, and mechanical sensitivity was assessed before and after the daily doses.

KEY RESULTS

Monoiodoacetate-injected mice developed persistent mechanical hypersensitivity, which was dose-dependently inhibited by E-52862. Mechanical thresholds assessed before the daily E-52862 dose showed gradual recovery, reaching complete restoration by the end of the treatment. When repeated treatment started 15 days after knee injury, E-52862 produced enhanced short-term analgesia, but recovery to baseline threshold was slower. Both a σ1 receptor agonist and a μ receptor antagonist blocked the analgesic effects of E-52862. An acute, sub-effective dose of E-52862 restored morphine analgesia in opioid-tolerant mice. Moreover, E-52862 abolished spinal sensitization in osteoarthritic mice and inhibited pain-related molecular changes.

CONCLUSION AND IMPLICATIONS

These findings show dual effects of σ1 receptor antagonism alleviating both short- and long-lasting antinociception during chronic osteoarthritis pain. They identify E-52862 as a promising pharmacological agent to treat chronic pain and avoid opioid tolerance.

Synovial fluid levels of TWEAK and matrix metalloproteinase 1 in patients with osteoarthritis, and associations with disease severity

PURPOSE

This study assessed the levels of soluble tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and matrix metalloproteinase 1 (MMP-1) in the synovial fluid from osteoarthritic knees to determine their role as well as the relationship between these levels and the severity of osteoarthritis (OA).

METHODS

Synovial fluid was obtained from 44 knees of 40 patients. The Kellgren-Lawrence (KL) grade was measured using radiograph. The concentration of TWEAK and MMP-1 in the synovial fluid was assessed by enzyme-linked immunosorbent assay. The underlying inflammatory factors (erythrocyte sedimentation rate and C-reactive protein) were also measured. We analyzed the correlation between the factors measured. In addition, the samples were subdivided into three groups according to OA severity using the KL grade, and the differences in TWEAK and MMP-1 levels between groups were analyzed.

RESULTS

The TWEAK and MMP-1 levels in the synovial fluid showed a positive correlation with each other. The TWEAK and MMP-1 levels were compared between the three groups according to the KL grade, and the levels showed a significant difference. A post hoc test demonstrated that the group with advanced OA showed a lower concentration of both factors when compared to groups with early OA.

CONCLUSION

The concentration of TWEAK and MMP-1 in the synovial fluid were relatively high in the early stage of OA, and the levels decreased as the OA progressed.

[Inflammation and osteoarthritis-related pain]

Osteoarthritis (OA) is one of the major causes of chronic pain. Although OA has long been considered a non-inflammatory "wear and tear" disease leading to loss of articular cartilage, recent findings provide convincing evidence that inflammatory mechanisms play a pivotal role in the pathophysiology of OA. In OA mononuclear cells (e. g. T‑cells and macrophages) infiltrate the synovial membrane and the levels of pro-inflammatory cytokines in peripheral blood and synovial fluid samples are elevated. Increased release of inflammatory mediators including interleukin (IL) IL-1β, IL-6, IL-8, IL-15 und tumor necrosis factor alpha (TNF‑α) induces the expression of proteolytic enzymes such as matrix metalloproteinases resulting in cartilage breakdown. Molecular and cellular interactions between the immune and nervous system are also involved in the development of OA-related pain. Inflammatory mediators including IL-6 und TNF‑α lead to peripheral sensitization of joint nociceptors and growth factors (e. g. NGF) trigger the expression of TRPV1 channels in primary afferents. Moreover, neuropeptides reduce the threshold of nociceptors of OA joints. The current review highlights the role of inflammatory mechanisms in OA-induced joint pain considering clinical signs of inflammation and major inflammatory pathways.

The pathogenic role of connective tissue growth factor in osteoarthritis

Osteoarthritis (OA) is the most common form of arthritis, and connective tissue growth factor (CTGF) is found to be up-regulated in adjacent areas of cartilage surface damage. CTGF is present in osteophytes of late stage OA. In the present study, we have reviewed association of CTGF in the development and progression of OA and the potential effects of CTGF as a therapeutic agent for the treatment of OA. We have reviewed the recent articles on CTGF and OA in databases like PubMed, google scholar, and SCOPUS and collected the information for the articles. CTGF is usually up-regulated in synovial fluid of OA that stimulates the production of inflammatory cytokines. CTGF also activates nuclear factor-κB, increases the production of chemokines and cytokines, and up-regulates matrix metalloproteinases-3 (MMP-3) that in turn leads to the reduction in proteoglycan contents in joint cartilage. Consequently, cartilage homeostasis is imbalanced that might contribute to the pathogenesis of OA by developing synovial inflammation and cartilage degradation. CTGF might serve as a useful biomarker for the prognosis and treatment of OA, and recent studies have taken attempt to use CTGF as therapeutic target of OA. However, more investigations with clinical trials are necessary to validate the possibility of use of CTGF as a biomarker in OA diagnosis and therapeutic target for OA treatment.

Clinical findings, synovial fluid cytology and growth factor concentrations after intra-articular use of a platelet-rich product in horses with osteoarthritis

Osteoarthritis is a common cause of lameness in horses, resulting in poor performance. Intra-articular platelet-rich plasma can deliver a collection of bioactive molecules, such as autologous growth factors and proteins involved in the quality of tissue repair. Horses (n=5) with osteoarthritis affecting antebrachiocarpal, middle carpal or metacarpophalangeal joints, and horses (n=5) without osteoarthritis of the corresponding joints (radiographically free of osteoarthritis), were used for the production of platelet-rich plasma which was subsequently injected into selected joints. Clinical and synovial fluid changes after intra-articular injection of platelet-rich plasma as well as synovial platelet-derived growth factor-BB and transforming growth factor-beta 1 concentration changes were evaluated in these joints and compared between normal joints and joints with osteoarthritis. A gravity filtration system produced a moderately concentrated platelet-rich plasma, representing a 4.7-fold increase in baseline platelet concentration. The synovial effusion score was significantly different between the control joints and joints with osteoarthritis on Day 0 with a higher score in the group with osteoarthritis. Within the control group, the synovial effusion score was significantly higher on Days 1 and 2 compared to Day 0. For both groups, the synovial fluid nucleated cell count, predominantly intact neutrophils, was significantly increased on Days 1 and 2, with no significant difference between groups. The mean synovial platelet-derived growth factor-BB and transforming growth factor-beta 1 concentrations were increased for both groups but significantly lowered in the group with osteoarthritis on Day 1 compared to normal joints. Concentrations for platelet-derived growth factor-BB remained unchanged on Day 5, compared to Day 1, with no significant difference between groups. In conclusion, intra-articular treatment with platelet-rich plasma resulted in increased synovial growth factor concentrations in joints but with lower concentrations in joints with osteoarthritis. A transient inflammatory reaction was seen both clinically as an increase in synovial effusion and cytologically in both normal joints and joints with osteoarthritis.

Blockade of the Sigma-1 Receptor Relieves Cognitive and Emotional Impairments Associated to Chronic Osteoarthritis Pain

Osteoarthritis is the most common musculoskeletal disease worldwide, often characterized by degradation of the articular cartilage, chronic joint pain and disability. Cognitive dysfunction, anxiety and depression are common comorbidities that impact the quality of life of these patients. In this study, we evaluated the involvement of sigma-1 receptor (σ1R) on the nociceptive, cognitive and emotional alterations associated with chronic osteoarthritis pain. Monosodium iodoacetate (MIA) was injected into the knee of Swiss-albino CD1 mice to induce osteoarthritis pain, which then received a repeated treatment with the σ1R antagonist E-52862 or its vehicle. Nociceptive responses and motor performance were assessed with the von Frey and the Catwalk gait tests. Cognitive alterations were evaluated using the novel object recognition task, anxiety-like behavior with the elevated plus maze and the zero-maze tests, whereas depressive-like responses were determined using the forced swimming test. We also studied the local effect of the σ1R antagonist on cartilage degradation, and its central effects on microglial reactivity in the medial prefrontal cortex. MIA induced mechanical allodynia and gait abnormalities that were prevented by the chronic treatment with the σ1R antagonist. E-52862 also reduced the memory impairment and the depressive-like behavior associated to osteoarthritis pain. Interestingly, the effect of E-52862 on depressive-like behavior was not accompanied by a modification of anxiety-like behavior. The pain-relieving effects of the σ1R antagonist were not due to a local effect on the articular cartilage, since E-52862 treatment did not modify the histological alterations of the knee joints. However, E-52862 induced central effects revealed by a reduction of the cortical microgliosis observed in mice with osteoarthritis pain. These findings show that σ1R antagonism inhibits mechanical hypersensitivity, cognitive deficits and depressive-like states associated with osteoarthritis pain in mice. These effects are associated with central modulation of glial activity but are unrelated to changes in cartilage degradation. Therefore, targeting the σ1R with E-52862 represents a promising pharmacological approach with effects on multiple aspects of chronic osteoarthritis pain that may go beyond the strict inhibition of nociception.

A Functional Tissue-Engineered Synovium Model to Study Osteoarthritis Progression and Treatment

IMPACT STATEMENT

The synovium envelops the diarthrodial joint and plays a key regulatory role in defining the composition of the synovial fluid through filtration and biosynthesis of critical boundary lubricants. Synovium changes often precede cartilage damage in osteoarthritis. We describe a novel in vitro tissue engineered model, validated against native synovium explants, to investigate the structure-function of synovium through quantitative solute transport measures. Synovium was evaluated in the presence of a proinflammatory cytokine, interleukin-1, or the clinically relevant corticosteroid, dexamethasone. We anticipate that a better understanding of synovium transport would support efforts to develop more effective strategies aimed at restoring joint health.

Equine Allogeneic Chondrogenic Induced Mesenchymal Stem Cells Are an Effective Treatment for Degenerative Joint Disease in Horses

Degenerative joint disease is one of the main causes of equine early retirement from pleasure riding or a performance career. The disease is initially triggered by an abnormal loading of normal cartilage or a normal loading of abnormal cartilage. This primary insult is accompanied with joint inflammation, which leads to further progressive degeneration of the articular cartilage and changes in the surrounding tissues. Therefore, in search for an effective treatment, 75 adult horses with early signs of degenerative fetlock joint disease were enrolled in a randomized, multicenter, double-blinded, and placebo-controlled study. Fifty animals were injected intra-articularly with the investigational veterinary product (IVP) consisting of allogeneic chondrogenic induced mesenchymal stem cells (ciMSCs) with equine allogeneic plasma, and 25 horses were injected with 0.9% NaCl (saline) control product. From week 3 to 18 after treatment, lameness scores (P < 0.001), flexion test responses (P < 0.034), and joint effusion scores (P < 0.001) were remarkably superior in IVP-treated horses. Besides nasal discharge in both treatment groups, no adverse events were observed during the entire study period. On long-term follow-up (1 year), significantly more investigational product-treated horses were working at training level or were returned to their previous level of work (P < 0.001).

Future Cell and Gene Therapy for Osteoarthritis (OA): Potential for Using Mammalian Protein Production Platforms, Irradiated and Transfected Protein Packaging Cell Lines for Over-Production of Therapeutic Proteins and Growth Factors

In this paper I provide a personal perspective on future prospects for cell and gene therapy for osteoarthritis (OA) and how mammalian protein production platforms, virally transfected and irradiated protein packaging cell lines may be used as "cellular factories" for over-production of therapeutic proteins and growth factors, particularly in the context of intra-articular regenerative therapies. I will also speculate on future opportunities and challenges in this area of research and how new innovations in biotechnology will impact on the field of cell and gene therapy for OA, related osteoarticular disorders and the broader discipline of regenerative medicine for musculoskeletal disorders. Mammalian protein production platforms are likely to have a significant impact on synovial joint diseases that are amenable to cell and gene therapy using therapeutic proteins and growth factors. Future cell and gene therapy for OA will need to re-consider the current strategies that employ primary, aged and senescent cells with feeble regenerative properties and seriously consider the use of mammalian protein production platforms.