Osteoarthritis pain

Macrophage and chondrocyte phenotypes in inflammation

Inflammation is a complex biological process protecting the body from diverse external threats. Effectively performing this task requires an intricate, well-regulated interplay of different cells and tissues. Furthermore, several cells participating in inflammation can assume diverse phenotypes. A classic and relatively well-studied example of phenotypic diversity in inflammation is macrophage polarization. Based on the TH1/TH2 phenotypes of T helper cells, this scheme has proinflammatory "classical/M1" activation contrasted with the anti-inflammatory and healing-promoting "alternative/M2" phenotype. Some authors have extended the concept into an M17 phenotype induced by the classic TH17 cytokine IL-17. Phenotypic changes in chondrocytes have also been studied especially in the context of osteoarthritis (OA), and there are indications that these cells can also assume polarized phenotypes at least partly analogous to those of TH cells and macrophages. The therapeutic success of biological agents targeting TH1/TH2/TH17 inductor and/or effector cytokines displays the utility of the concept of polarization. The aim of this focused review is to survey the internal and external factors affecting macrophage and chondrocyte phenotypes (such as inflammatory cytokines, widely used medications and natural products) and to explore the possibility of ameliorating pathological states by modulating these phenotypes.

Unveiling the Role of Sik1 in Osteoblast Differentiation: Implications for Osteoarthritis

Osteoarthritis (OA) is a chronic degenerative disease characterized by subchondral osteosclerosis, mainly due to osteoblast activity. This research investigates the function of Sik1, a member of the AMP-activated protein kinase family, in OA. Proteomic analysis was conducted on clinical samples from 30 OA patients, revealing a negative correlation between Sik1 expression and OA. In vitro experiments utilized BMSCs to examine the effect of Sik1 on osteogenic differentiation. BMSCs were cultured and induced toward osteogenesis with specific media. Sik1 overexpression was achieved through lentiviral transfection, followed by analysis of osteogenesis-associated proteins using Western blotting, RT-qPCR, and alkaline phosphate staining. In vivo experiments involved destabilizing the medial meniscus in mice to establish an OA model, assessing the therapeutic potential of Sik1. The CT scans and histological staining were used to analyze subchondral bone alterations and cartilage damage. The findings show that Sik1 downregulation correlates with advanced OA and heightened osteogenic differentiation in BMSCs. Sik1 overexpression inhibits osteogenesis-related markers in vitro and reduces cartilage damage and subchondral osteosclerosis in vivo. Mechanistically, Sik1 modulates osteogenesis and subchondral bone changes through Runx2 activity regulation. The research emphasizes Sik1 as a promising target for treating OA, suggesting its involvement in controlling bone formation and changes in the subchondral osteosclerosis.

Harmonizing hope: navigating the osteoarthritis melody through the CCL2/CCR2 axis for innovative therapeutic avenues

Osteoarthritis (OA) is characterized by a complex interplay of molecular signals orchestrated by the CCL2/CCR2 axis. The pathogenesis of OA has been revealed to be influenced by a multifaceted effect of CCL2/CCR2 signaling on inflammation, cartilage degradation, and joint homeostasis. The CCL2/CCR2 axis promotes immune cell recruitment and tips the balance toward degeneration by influencing chondrocyte behavior. Insights into these intricate pathways will offer novel therapeutic approaches, paving the way for targeted interventions that may redefine OA management in the future. This review article explores the molecular symphony through the lens of the CCL2/CCR2 axis, providing a harmonious blend of current knowledge and future directions on OA treatment. Furthermore, in this study, through a meticulous review of recent research, the key players and molecular mechanisms that amplify the catabolic cascade within the joint microenvironment are identified, and therapeutic approaches to targeting the CCL2/CCR axis are discussed.

Lipoxin A4 ameliorates knee osteoarthritis progression in rats by antagonizing ferroptosis through activation of the ESR2/LPAR3/Nrf2 axis in synovial fibroblast-like synoviocytes

BACKGROUND

Our previous studies have shown that lipoxin A4 (LXA4) can serve as a potential biomarker for assessing the efficacy of exercise therapy in knee osteoarthritis (KOA), and fibroblast-like synoviocytes (FLSs) may play a crucial role in KOA pain as well as in the progression of the pathology.

OBJECTIVE

By analyzing the GSE29746 dataset and collecting synovial samples from patients with different Kellgren-Lawrence (KL) grades for validation, we focused on exploring the potential effect of LXA4 on ferroptosis in FLSs through the ESR2/LPAR3/Nrf2 axis to alleviate pain and pathological advancement in KOA.

METHODS

The association between FLSs ferroptosis and chondrocyte matrix degradation was explored by cell co-culture. We overexpressed and knocked down LPAR3 in vitro to explore its potential mechanism in FLSs. A rat model of monosodium iodoacetate (MIA)-induced KOA was constructed and intervened with moderate-intensity treadmill exercise and intraperitoneal injection of PHTPP to investigate the effects of the LXA4 intracellular receptor ESR2 on exercise therapy.

RESULTS

ESR2, LPAR3, and GPX4 levels in the synovium decreased with increasing KL grade. After LXA4 intervention in the co-culture system, GPX4, LPAR3, and ESR2 were upregulated in FLSs, collagen II was upregulated in chondrocytes, and MMP3 and ADAM9 were downregulated. LPAR3 overexpression upregulated the expression of GPX4, Nrf2, and SOD1 in FLSs, while downregulating the expression of MMP13 and MMP3; LPAR3 knockdown reversed these changes. Moderate-intensity platform training improved the behavioral manifestations of pain in KOA rats, whereas PHTPP treatment partially reversed the improvement in synovial and cartilage pathologies induced by platform training.

CONCLUSION

LXA4 inhibited FLSs ferroptosis by activating the ESR2/LPAR3/Nrf2 axis, thereby alleviating the pain and pathological progression of KOA. This study brings a new target for the treatment of KOA and also leads to a deeper understanding of the potential mechanisms of exercise therapy for KOA.

Pharmacotherapy for osteoarthritis-related pain: current and emerging therapies

INTRODUCTION

Osteoarthritis (OA) related pain has affected millions of people worldwide. However, the current pharmacological options for managing OA-related pain have not achieved a satisfactory effect.

AREAS COVERED

This narrative review provides an overview of the current and emerging drugs for OA-related pain. It covers the drugs' mechanism of action, safety, efficacy, and limitations. The National Library of Medicine (PubMed) database was primarily searched from 2000 to 2024.

EXPERT OPINION

Current treatment options are limited and suboptimal for OA pain management. Topical nonsteroidal anti-inflammatory drugs (NSAIDs) are the recognized and first-line treatment in the management of OA-related pain, and other drugs are inconsistent recommendations by guidelines. Emerging treatment options are promising for OA-related pain, including nerve growth factor (NGF) inhibitors, ion channel inhibitors, and calcitonin gene-related peptide (CGRP) antagonists. Besides, drugs repurposing from antidepressants and antiepileptic analgesics are shedding light on the management of OA-related pain. The management of OA-related pain is challenging as pain is heterogeneous and subjective. A more comprehensive strategy combined with non-pharmacological therapy needs to be considered, and tailored management options to individualized patients.

Knee osteoarthritis pendulum therapy: In vivo evaluation and a randomised, single-blind feasibility clinical trial

Background

Exercise is recommended as the first-line management for knee osteoarthritis (KOA); however, it is difficult to determine which specific exercises are more effective. This study aimed to explore the potential mechanism and effectiveness of a leg-swinging exercise practiced in China, called 'KOA pendulum therapy' (KOAPT). Intraarticular hydrostatic and dynamic pressure (IHDP) are suggested to partially explain the signs and symptoms of KOA. As such this paper set out to explore this mechanism in vivo in minipigs and in human volunteers alongside a feasibility clinical trial. The objective of this study is 1) to analyze the effect of KOAPT on local mechanical and circulation environment of the knee in experimental animals and healthy volunteers; and 2) to test if it is feasible to run a large sample, randomized/single blind clinical trial.

Methods

IHDP of the knee was measured in ten minipigs and ten volunteers (five healthy and five KOA patients). The effect of leg swinging on synovial blood flow and synovial fluid content depletion in minipigs were also measured. Fifty KOA patients were randomly divided into two groups for a feasibility clinical trial. One group performed KOAPT (targeting 1000 swings/leg/day), and the other performed walking exercise (targeting 4000 steps/day) for 12 weeks with 12 weeks of follow-up.

Results

The results showed dynamic intra-articular pressure changes in the knee joint, increases in local blood flow, and depletion of synovial fluid contents during pendulum leg swinging in minipigs. The intra-articular pressure in healthy human knee joints was -11.32 ± 0.21 (cmH2O), whereas in KOA patients, it was -3.52 ± 0.34 (cmH2O). Measures were completed by 100% of participants in all groups with 95-98% adherence to training in both groups in the feasibility clinical trial. There were significant decreases in the Oxford knee score in both KOAPT and walking groups after intervention (p < 0.01), but no significant differences between the two groups.

Conclusion

We conclude that KOAPT exhibited potential as an intervention to improve symptoms of KOA possibly through a mechanism of normalising mechanical pressure in the knee; however, optimisation of the method, longer-term intervention and a large sample randomized-single blind clinical trial with a minimal 524 cases are needed to demonstrate whether there is any superior benefit over other exercises.

The translational potential of this article

The research aimed to investigate the effect of an ancient leg-swinging exercise on knee osteoarthritis. A minipig animal model was used to establish the potential mechanism underlying the exercise of knee osteoarthritis pendulum therapy, followed by a randomised, single-blind feasibility clinical trial in comparison with a commonly-practised walking exercise regimen. Based on the results of the feasibility trial, a large sample clinical trial is proposed for future research, in order to develop an effective exercise therapy for KOA.

Model-Based Assessment of the Liver Safety Profile of Acetaminophen to Support its Combination Use with Topical Diclofenac in Mild-to-Moderate Osteoarthritis Pain

INTRODUCTION

The use of combination therapy of oral acetaminophen and topical diclofenac, having complementary mechanisms of action, is an attractive strategy to enhance the analgesic response in osteoarthritis (OA) pain. While topical diclofenac is considered as well tolerated due to its low systemic exposure, concerns of liver toxicity with acetaminophen at standard analgesic doses remain. Thus, this study aimed to assess the liver safety profile of acetaminophen, particularly in OA management, using a model-based meta-analysis (MBMA).

METHODS

A literature review was conducted using the MEDLINE database to identify randomized clinical trials (RCTs) reporting liver toxicity on acetaminophen use. An MBMA was implemented to assess the deviation from the upper limit of normal (ULN) of alanine aminotransferase or aspartate aminotransferase, namely > 0-1 × ULN, > 1.5-2 × ULN, and > 3 × ULN representing mild, moderate, and severe risk of liver abnormality, respectively.

RESULTS

A total of 15 RCTs were included in the MBMA, encompassing over 4800 subjects and exposure to acetaminophen ranging from 2 to 26 weeks. Of the 15 included studies, eight involved patients with OA pain, four involved healthy subjects and three were in patients with conditions such as asthma, glaucoma, chronic pain, and cardiovascular disease. Acetaminophen 1500-4000 mg/day was found to exhibit 23% (95% confidence interval (CI): 17.74-29.20), 1.35% (95% CI: 0.17-2.51) and 0.01% (95% CI: 0.00-0.32) increased risk for mild, moderate, and severe liver injury, respectively, versus placebo. Moreover, at therapeutic doses, no correlation was identified between acetaminophen intake and liver abnormality risk.

CONCLUSIONS

Overall, our analysis shows that short-term (~ 8-16 weeks) acetaminophen use at therapeutically recommended doses is associated with a low risk of clinically relevant changes in liver enzymes. Given the good tolerability of topical diclofenac, the findings support the safety of the combination of acetaminophen and topical diclofenac, at least over the short term, as treatment for mild-to-moderate OA pain.

Model-Based Meta-Analysis Supporting the Combination of Acetaminophen and Topical Diclofenac in Acute Pain: A Therapy for Mild-to-Moderate Osteoarthritis Pain?

INTRODUCTION

Acetaminophen and topical diclofenac (AtopD) have complementary mechanisms of action and are therefore candidates for combination use in osteoarthritis (OA) pain. However, an evidence gap exists on their combination use in OA pain. This study aimed to assess the effects of this combination and compare its performance relative to monotherapies on pain score reduction and opioid-sparing effect by leveraging evidence from acute pain setting using a model-based meta-analysis (MBMA).

METHODS

A literature search was conducted using the MEDLINE database to identify randomized controlled trials (RCTs) studying the combination for acute pain. Subsequently, an MBMA of RCTs was implemented in conjunction with extrapolation principles to infer efficacy in the population of interest. Pain score reduction and opioid-sparing effect (OSE) were selected as the measures of efficacy.

RESULTS

A total of 11 RCTs encompassing 1396 patients were included. Exploratory evaluation revealed AtopD combination to show greater pain score reduction versus acetaminophen monotherapy. However, pain score reduction was more susceptible to confounding by opioid patient-controlled analgesia (PCA) than OSE. Therefore, a parsimonious MBMA evaluating OSE was developed from 5 of the 11 RCTs (n = 353 patients). The analysis revealed a statistically significant interaction coefficient, suggesting a reduction of 32% in opioid use with the combination versus acetaminophen monotherapy. Differences in the effect size of the combination were less conclusive versus diclofenac monotherapy.

CONCLUSION

Our results indicate greater pain reduction and opioid-sparing efficacy for the AtopD combination versus acetaminophen monotherapy. Given the similar pain pathways and mechanisms of action of the two drugs in acute and mild-to-moderate OA pain, comparable beneficial effects from the combination therapy may be anticipated following extrapolation to chronic OA pain. Prospective RCTs and real-world studies in OA pain are needed to confirm the differences in the efficacy of the combination treatment observed in our study.

Central Sensitization and Neuropathic Pain Cumulatively Affect Patients Reporting Inferior Outcomes Following Total Knee Arthroplasty

UPDATE

This article was updated on November 17, 2023, because of previous errors, which were discovered after the preliminary version of the article was posted online. On page 102, the text that had read "In a post hoc analysis of the preoperative results, Group 1 showed significantly inferior WOMAC pain, function, and total scores compared with Group 4 (p < 0.05 for all). Groups 2 and 3 showed worse preoperative WOMAC pain, function, and total subscores compared with Group 4 (p < 0.05 for all). These results remained the same at 2 years after surgery." now reads "In a post hoc analysis of the preoperative results, Groups 1, 2, and 3 showed significantly inferior WOMAC pain, function, and total scores compared with Group 4 (p < 0.05 for all). At 2 years postoperatively, Group 1 showed inferior WOMAC pain, function, and total scores compared with the other groups (p < 0.05 for all). Also, Groups 2 and 3 had worse WOMAC pain, function and total scores compared with Group 4 (p < 0.05 for all)." Also, on page 106, the title of Table IV, which had previously read "Inter-Group Comparison of Preoperative Scores (Post Hoc Analysis)" now reads "Inter-Group Comparison of Postoperative Scores (Post Hoc Analysis)."

Cross-perspectives on care pathways for painful osteoarthritis: A qualitative analysis in patients and healthcare professionals

PURPOSE

To analyse and compare patients' and healthcare professionals' (HPs) perspectives concerning patient care pathways for painful osteoarthritis (OA).

PATIENTS AND METHODS

We performed a qualitative study of two focus groups corresponding to eight patients with painful OA and eight HPs involved in OA management.

RESULTS

Six key themes emerged from the interviews: (1) representations of OA, (2) OA pain, (3) quality of life, (4) care pathways, (5) actors involved in the care pathway, and (6) treatments. Both groups considered general practitioners, pharmacists and physiotherapists to be first-line HPs, and no well-defined OA specialist was identified. Patients and HPs reported similar difficulties concerning the adaptation of management to individual cases, late diagnosis and treatment, whereas only patients mentioned financial issues. Communication difficulties were identified as a major problem both between patients and HPs, and between HPs. Patients reported a lack of knowledge concerning pain and OA. The coordination between the various HPs is required, with education on both pain and OA. Several possible solutions were put forward by both patients and HPs.

CONCLUSION

The care pathways of patients with painful OA are complex, with an unclear definition of the roles of the various HPs and suboptimal coordination. The role of HPs should be defined and collaboration between HPs developed.

Nrf2: A promising therapeutic target in bone-related diseases

Nuclear factor erythroid-2-related factor 2 (Nrf2) plays an important role in maintaining cellular homeostasis, as it suppresses cell damage caused by external stimuli by regulating the transcription of intracellular defense-related genes. Accumulating evidence has highlighted the crucial role of reduction-oxidation (REDOX) imbalance in the development of bone-related diseases. Nrf2, a transcription factor linked to nuclear factor-erythrocyte 2, plays a pivotal role in the regulation of oxidative stress and induction of antioxidant defenses. Therefore, further investigation of the mechanism and function of Nrf2 in bone-related diseases is essential. Considerable evidence suggests that increased nuclear transcription of Nrf2 in response to external stimuli promotes the expression of intracellular antioxidant-related genes, which in turn leads to the inhibition of bone remodeling imbalance, improved fracture recovery, reduced occurrence of osteoarthritis, and greater tumor resistance. Certain natural extracts can selectively target Nrf2, potentially offering therapeutic benefits for osteogenic arthropathy. In this article, the biological characteristics of Nrf2 are reviewed, the intricate interplay between Nrf2-regulated REDOX imbalance and bone-related diseases is explored, and the potential preventive and protective effects of natural products targeting Nrf2 in these diseases are elucidated. A comprehensive understanding of the role of Nrf2 in the development of bone-related diseases provides valuable insights into clinical interventions and can facilitate the discovery of novel Nrf2-targeting drugs.

The role of exosomes and their enhancement strategies in the treatment of osteoarthritis

With the increasingly prominent problem of population aging, osteoarthritis (OA), which is closely related to aging, has become a serious illness affecting the lives and health of elderly individuals. However, effective treatments are still lacking. OA is typically considered a low-grade inflammatory state. The inflammatory infiltration of macrophages, neutrophils, T cells, and other cells is common in diseased joints. These cells create the inflammatory environment of OA and are involved in the onset and progression of the disease. Exosomes, a type of complex vesicle containing abundant RNA molecules and proteins, play a crucial role in the physiological and pathological processes of an organism. In comparison to other therapeutic methods such as stem cells, exosomes have distinct advantages of precise targeting and low immunogenicity. Moreover, research and techniques related to exosomes are more mature, indicating a promising future in disease treatment. Many studies have shown that the impact of exosomes on the inflammatory microenvironment directly or indirectly leads to the occurrence of various diseases. Furthermore, exosomes can be helpful in the management of illnesses. This article provides a comprehensive review and update on the research of exosomes, a type of extracellular vesicle, in the treatment of OA by modulating the inflammatory microenvironment. It also combines innovative studies on the modification of exosomes. In general, the application of exosomes in the treatment of OA has been validated, and the introduction of modified exosome technology holds potential for enhancing its therapeutic efficacy.

Translational evaluation of gait behavior in rodent models of arthritic disorders with the CatWalk device - a narrative review

Arthritic disorders have become one of the main contributors to the global burden of disease. Today, they are one of the leading causes of chronic pain and disability worldwide. Current therapies are incapable of treating pain sufficiently and preventing disease progression. The lack of understanding basic mechanisms underlying the initiation, maintenance and progression of arthritic disorders and related symptoms represent the major obstacle in the search for adequate treatments. For a long time, histological evaluation of joint pathology was the predominant outcome parameter in preclinical arthritis models. Nevertheless, quantification of pain and functional limitations analogs to arthritis related symptoms in humans is essential to enable bench to bedside translation and to evaluate the effectiveness of new treatment strategies. As the experience of pain and functional deficits are often associated with altered gait behavior, in the last decades, automated gait analysis has become a well-established tool for the quantitative evaluation of the sequalae of arthritic disorders in animal models. The purpose of this review is to provide a detailed overview on the current literature on the use of the CatWalk gait analysis system in rodent models of arthritic disorders, e.g., Osteoarthritis, Monoarthritis and Rheumatoid Arthritis. Special focus is put on the assessment and monitoring of pain-related behavior during the course of the disease. The capability of evaluating the effect of distinct treatment strategies and the future potential for the application of the CatWalk in rodent models of arthritic disorders is also addressed in this review. Finally, we discuss important consideration and provide recommendations on the use of the CatWalk in preclinical models of arthritic diseases.

Pain chronification impacts whole-brain functional connectivity in women with hip osteoarthritis during pain stimulation

OBJECTIVE

Previous neuroimaging studies have shown that patients with chronic pain display altered functional connectivity across distributed brain areas involved in the processing of nociceptive stimuli. The aim of the present study was to investigate how pain chronification modulates whole-brain functional connectivity during evoked clinical and tonic pain.

METHODS

Patients with osteoarthritis of the hip (n = 87) were classified into 3 stages of pain chronification (Grades I-III, Mainz Pain Staging System). Electroencephalograms were recorded during 3 conditions: baseline, evoked clinical hip pain, and tonic cold pain (cold pressor test). The effects of both factors (recording condition and pain chronification stage) on the phase-lag index, as a measure of neuronal connectivity, were examined for different frequency bands.

RESULTS

In women, we found increasing functional connectivity in the low-frequency range (delta, 0.5-4 Hz) across pain chronification stages during evoked clinical hip pain and tonic cold pain stimulation. In men, elevated functional connectivity in the delta frequency range was observed in only the tonic cold pain condition.

CONCLUSIONS

Across pain chronification stages, we found that widespread cortical networks increase their synchronization of delta oscillations in response to clinical and experimental nociceptive stimuli. In view of previous studies relating delta oscillations to salience detection and other basic motivational processes, our results hint at these mechanisms playing an important role in pain chronification, mainly in women.

Relationship between Motor Corticospinal System, Endogenous Pain Modulation Mechanisms and Clinical Symptoms in Patients with Knee Osteoarthritis: New Perspectives on an Old Disease

Knee osteoarthritis (OA) is a painful condition characterized by joint and bone changes. A growing number of studies suggest that these changes only partially explain the pain experienced by individuals with OA. The purpose of the current study was to evaluate if corticospinal and bulbospinal projection measurements were interrelated in patients with knee OA, and to explore the relationship between these neurophysiological measures and temporal summation (excitatory mechanisms of pain) on one hand, and clinical symptoms on the other. Twenty-eight (28) patients with knee OA were recruited. Corticospinal projections were measured using transcranial magnetic stimulation, while bulbospinal projections were evaluated with a conditioned pain modulation (CPM) protocol using a counter-irritation paradigm. Validated questionnaires were used to document clinical and psychological manifestations. All participants suffered from moderate to severe pain. There was a positive association between corticospinal excitability and the effectiveness of the CPM (rs = 0.67, p = 0.01, n = 13). There was also a positive relationship between pain intensity and corticospinal excitability (rs = 0.45, p = 0.03, n = 23), and between pain intensity and temporal summation (rs = 0.58, p = 0.01, n = 18). The results of this study highlight some of the central nervous system changes that could be involved in knee OA and underline the importance of interindividual variability to better understand and explain the semiology and pathophysiology of knee OA.

Assessment of Pain in Osteoarthritis of the Knee

Knee osteoarthritis (KOA) pain is a subjective and personal experience, making it challenging to characterise patients' experiences and assess their pain. In addition, there is no global standard for the assessment of pain in KOA. Therefore, this article examines the possible methods of assessing and characterising pain in patients with KOA using clinical symptoms, pain assessment tools, and imaging. We examine the current methods of assessment of pain in KOA and their application in clinical practice and clinical trials. Furthermore, we explore the possibility of creating individualised pain management plans to focus on different pain characteristics. With better evaluation and standardisation of pain assessment in these patients, it is hoped that patients would benefit from improved quality of life. At the same time, improvement in pain assessment would enable better data collection regarding symptom response in clinical trials for the treatment of osteoarthritis.

Three dimensions of pain in osteoarthritis: development and validation of the Osteoarthritis Symptom Inventory Scale

ABSTRACT

We describe here the development and validation of the Osteoarthritis Symptom Inventory Scale (OASIS), a new self-administered questionnaire specifically designed to evaluate the various osteoarthritis (OA) pain symptoms with different dimensions related to OA pain mechanisms. The initial development phase and qualitative study generated a list of 17 descriptors reflecting OA pain and other associated symptoms, leading to the first version of the questionnaire (OASIS17). Each item was quantified on a 0 to 10 Numerical Scale. Validation was performed using 123 consecutive patients with OA pain recruited at 28 centers in France, mainly general practitioner offices. Validation involved (1) determining the questionnaire's factorial structure through exploratory and confirmatory analyses, (2) analyzing convergent and divergent validities (ie, construct validity), (3) assessing each item's test-retest reliability, and (4) evaluating OASIS ability to detect treatment effects (ie, sensitivity to change). The final OASIS version includes 9 items discriminating and quantifying 3 distinct, clinically relevant OA pain dimensions sensitive to treatment. OASIS9 psychometric properties suggest that it could improve the characterization of OA pain profiles for 3 clinically relevant domains: localized, neuropathic-like, and deep pain. The OASIS9 questionnaire could be used to phenotype OA pain patients and identify responders to various therapeutic interventions as a function of OA pain dimensions.

Randomized, double-blind, placebo-controlled study to evaluate the effect of treatment with an SPMs-enriched oil on chronic pain and inflammation, functionality, and quality of life in patients with symptomatic knee osteoarthritis: GAUDI study

BACKGROUND

Specialized pro-resolving mediators (SPMs), including 18-HEPE, 17-HDHA, and 14-HDHA are recognized as potentially therapeutic in inflammatory diseases because SPMs regulate the inflammation process, which leads to, for example; swelling and the sensation of pain. In osteoarthritis (OA), chronic pain is described as the symptom that reduces patients´ quality of life (QoL). The GAUDI study evaluated the efficacy of SPMs supplementation in reducing pain in the symptomatic knee of OA patients.

METHODS

This randomized, multicenter, double-blind, and placebo-controlled parallel-group pilot study was performed in Spain and conducted on adults 18-68 years old diagnosed with symptomatic knee OA. Patients were enrolled in the study for up to 24 weeks, which included a 12-week intervention period and a follow-up visit on week 24. The primary endpoint was pain change measured through a Visual Analog Scale (VAS). Secondary endpoints included: Pain change evaluation, stiffness, and function according to the WOMAC index; assessment of constant, intermittent, and total pain according to the OMERACT-OARSI score; evaluation of changes in health-related QoL parameters; the use or not of concomitant, rescue, and anti-inflammatory medication; and safety and tolerability assessments.

RESULTS

Patients were enrolled in the study from May 2018 to September 2021. VAS pain score was evaluated in the per protocol population (n = 51 patients), in which we observed a statistically significant reduction after 8 weeks (p = 0.039) and 12 weeks (p = 0.031) of treatment in patients consuming SPMs (n = 23 subjects) vs. placebo (n = 28 subjects). In line with the OMERACT-OARSI score, intermittent pain was reduced after 12 weeks with statistical significance (p = 0.019) in patients treated with SPMs (n = 23 subjects) vs. placebo (n = 28 subjects). Functional status as WOMAC score did not significantly change after SPMs or placebo consumption. Notably, patients consuming SPMs showed improvements in all five aspects of the EUROQoL-5, including a significant improvement in the usual-activities dimension. None of the patients required rescue medication, nor were any adverse events reported.

CONCLUSIONS

These findings suggest that sustained SPMs consumption reduces pain in OA patients while also improving their Quality of Life. These results also support the safety profile of SPMs supplementation. Trial registration NCT05633849. Registered 1 December 1 2022. Retrospectively registered, https://clinicaltrials.gov/ct2/show/study/NCT05633849.

Pain in osteoarthritis from a symptom to a disease

Pain is the most frequent symptom of osteoarthritis (OA), occurring much more commonly than stiffness or disability. Classically, OA-related pain has been considered to be a nociceptive pain condition and an alarm signal correlated to the intensity of joint degradation. However, OA-related pain is a specific disease, with a complex pathophysiology, including neuropathic peripheral and central abnormalities, together with local inflammation involving all joint structures. Clinical findings emphasize that it is not a stable and linear condition, that pain experience is poorly correlated to structural modifications, and that the quality of pain in OA is important to consider, aside from its intensity. OA-related pain is modulated by many factors, including the individual patient's psychological and genetic factors, as well as the theoretical role of meteorological influences. Recent findings have improved our knowledge about the central mechanisms of OA pain, especially in persistent cases. A specific questionnaire on OA pain is currently being developed to assess more precisely the patient's experience and target specific pain mechanisms. In conclusion, OA-related pain should be analyzed specifically aside from OA, taking into account the complexity of OA pain as a disease, distinguishing different OA pain phenotypes, to guide more precisely analgesic treatment and OA global management.

Baseline Knee Pain Predicts Long-Term Response of Intra-Articular Steroid Injection in Symptomatic Knee Osteoarthritis: Data from OAI

OBJECTIVE

The current study aims to investigate the factors that could predict response to intra-articular corticosteroid injection (IACI) in patients with knee osteoarthritis (KOA).

METHODS

Data of participants were retrieved from the Osteoarthritis Initiative database. Participants with at least one IACI treatment on single or bilateral knees within the first 5 years of follow-up were retrospectively included. Demographic data, clinical and radiographic variables were collected at both baseline and the first follow-up after IACI treatment. Positive response to IACI treatment was defined as >20% reduction of Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score from V0 to V1. All the variables with P < 0.2 after the comparison between the response and non-response groups were included in a multivariable logistic regression model to identify independent response predictive patient-specific valuables. Receiver operating characteristic curves were performed to establish the cutoff values of independent predictors.

RESULTS

The current study included a total of 385 participants (473 knees), with 155 and 318 knees classified into the response group and non-response group, respectively. Those with satisfied responses to IACI treatment had significantly higher WOMAC pain score (P < 0.001), disability score (P = 0.002), and stiffness score (P = 0.015) at the baseline. Baseline WOMAC pain score showed significant association with positive response to IACI treatment in multivariate logistic analysis and the best cutoff value was 5 points. The rate of analgesics utilization was lower (P = 0.014) in the response group than the non-response group after the IACI treatment.

CONCLUSION

KOA patients with a baseline WOMAC pain score ≥5 are more likely to benefit from IACI treatment.

Circ_0002715 promotes the development of osteoarthritis through regulating LXN by sponging miR-127-5p

BACKGROUND

Our study aims to investigate the role and mechanism of circular RNA_0002715 (circ_0002715) in osteoarthritis (OA) progression.

METHODS

IL-1β-induced CHON-001 cells were used to mimic OA cell model. Circ_0002715, microRNA (miR)-127-5p and Latexin (LXN) expression was detected by quantitative real-time PCR. Cell functions were determined by MTT assay, flow cytometry and ELISA assay. Protein expression was examined by western blot.

RESULTS

Circ_0002715 was highly expressed in OA cartilage tissues. Circ_0002715 silencing inhibited inflammation, apoptosis, and ECM degradation in IL-1β-interfered CHON-001 cells. Circ_0002715 could sponge miR-127-5p, and miR-127-5p could target LXN. The effect of circ_0002715 down-regulation on chondrocyte injury was partially restored by miR-127-5p inhibitor. MiR-127-5p could suppress chondrocyte injury by inhibiting LXN expression.

CONCLUSION

Circ_0002715 might be a new therapeutic target for OA, which regulated miR-127-5p/LXN axis to promote IL-1β-induced chondrocyte injury.

Expression of CILP-2 and DDR2 and ultrastructural changes in the articular cartilage of patients with knee osteoarthritis undergoing total knee arthroplasty: a pilot morphological study

The aim of the study was to correlate the immunohistochemical expression of cartilage intermediate layer protein 2 (CILP-2) and discoidin domain receptor 2 (DDR2), and the ultrastructural changes in the cartilage with the degree of articular cartilage damage in osteoarthritis (OA) patients. Cartilage samples were obtained from twenty patients aged from 46 to 68 years undergoing total knee arthroplasty. In each patient, medial and lateral tibial plateau samples were analysed applying OARSI histopathology grading. Positive correlation was noted between the extent of CILP-2 staining intensity and OARSI grades. Abundant staining for CILP-2 was found in the superficial and middle layers and in the pericellular matrix (PCM) of the deep zone. Transmission electron microscopy studies demonstrated strong damage of chondrocytes, the organelles were often diminished or focally aggregated. As a characteristic finding, PCM was frequently expanded, which may reflect a pathogenic step in OA progression. In conclusion, CILP-2 may potentially be a relevant marker of OA progression as its expression correlated better with cartilage damage than the known marker of articular cartilage damage, DDR2.

Silencing of circ-NT5C2 retards the progression of IL-1β-induced osteoarthritis in an in vitro cell model by targeting the miR-142-5p/NAMPT axis

Osteoarthritis (OA) is a degenerative disease that occurs mostly in the elderly, and its specific pathogenesis is still unknown, but recent studies have found that circular RNA generally display aberrant expression in OA. Our study explored the expression characteristics and mechanism of action of circ-NT5C2 in OA. Circ-NT5C2, microRNA-142-5p (miR-142-5p), and nicotinamide phosphoribosyltransferase (NAMPT) mRNA levels were measured using RT-qPCR. Western blot was employed to assess the protein level of NAMPT and extracellular matrix (ECM) production-related markers. The viability, proliferation, apoptosis and inflammation were examined using 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay, 5-ethynyl-2'-deoxyuridine (EdU) assay, flow cytometry, and enzyme-linked immunosorbent assay, respectively. Relationship between miR-142-5p and circ-NT5C2 or NAMPT was demonstrated by dual-luciferase reporter system and RNA immunoprecipitation assay. We reported that circ-NT5C2 and NAMPT were greatly upregulated, and miR-142-5p level was constrained in OA tissues and in a cell model. Circ-NT5C2 silencing alleviated IL-1β-induced inhibitory effects on chondrocyte proliferation and ECM generation, meanwhile the promotional role of IL-1β on chondrocyte apoptosis and inflammation was also weakened. The targeting relationship of miR-142-5p with either circ-NT5C2 or NAMPT was confirmed. Knockdown of miR-142-5p reversed the suppressive effects of circ-NT5C2 silencing on the OA progression in vitro, and NAMPT overexpression also attenuated the effects of miR-142-5p upregulation in an OA cell model. Collectively, circ-NT5C2 accelerated the OA process by targeting the miR-142-5p/NAMPT axis. This study provides valuable information to find a better treatment for OA.

IRF1 promotes the chondrogenesis of human adipose-derived stem cells through regulating HILPDA

BACKGROUND

Osteoarthritis is a main cause of deformity in aging people. The chondrogenesis of human adipose-derived stem cells (hADSCs) has a positive effect on the cure of osteoarthritis. However, the regulatory mechanism of hADSC chondrogenesis still needs further exploration. This research investigates the role of interferon regulatory factor 1 (IRF1) in the chondrogenesis of hADSCs.

METHODS

hADSCs were purchased and cultured. The interaction between IRF1 and hypoxia inducible lipid droplet associated (HILPDA) was predicted by bioinformatics analysis, and verified through dual-luciferase reporter and chromatin immunoprecipitation assays. The expressions of IRF1 and HILPDA in osteoarthritis cartilage samples were measured through qRT-PCR. After hADSCs were transfected or further induced for chondrogenesis, the chondrogenesis was visualized by Alcian blue staining, and the expressions of IRF1, HILPDA and chondrogenesis-related factors (SOX9, Aggrecan, COL2A1, MMP13, MMP3) were determined through qRT-PCR or Western blot.

RESULTS

HILPDA bound to IRF1 in hADSCs. IRF1 and HILPDA levels were up-regulated during the chondrogenesis of hADSCs. Overexpressions of IRF1 and HILPDA promoted the chondrogenesis of hADSCs with the up-regulation of SOX9, Aggrecan and COL2A1 and the down-regulation of MMP13 and MMP3; however, IRF1 silencing generated the opposite effects. Besides, HILPDA overexpression reversed the effects of IRF1 silencing on inhibiting chondrogenesis of hADSCs and regulating the expressions of chondrogenesis-related factors.

CONCLUSION

IRF1 promotes the chondrogenesis of hADSCs through up-regulating HILPDA level, providing novel biomarkers for treating osteoarthritis.

Autologous conditioned serum for chronic pain in patients with osteoarthritis: A feasibility observational study

Background

Autologous conditioned serum is a product of blood origin, with fragmented evidence of therapeutic properties in osteoarthritis chronic pain. This pilot observational prospective study aimed to evaluate the feasibility of a treatment with conditional autologous serum (ACS) in patients with severe chronic pain and grade I-III osteoarthritis and to describe its cytokine content.

Methods

We prospectively collected data on consecutive patients affected by osteoarthritis grade I to III and treated with four weekly injections of ACS at our outpatient pain service. The primary outcome was pain intensity, measured with the visual analogic scale (VAS). Additional outcomes were symptoms evaluated using joint district-specific scales. The study also evaluated concentrations of 48 cytokines and chemokines involved in the balance pro-inflammation/anti-inflammation and tissue repair in the ACS.

Results

We included 26 patients, mostly female (65.4%), with a median age of 63.5 years [IQR 58.25-73]. A median reduction of VAS of -3 cm [-5; -1.25] was observed 6 months after the first injection of ACS. The analysis showed a statistically significant difference between the values of VAS (p < .01; X2 = 69.6; df = 6, N = 26) at the different time points. No adverse events were observed or reported by patients during the entire study period.

Conclusions

Conditional autologous serum may be a feasible option for patients with chronic pain due to grade I-III osteoarthritis refractory to other treatments. These preliminary findings should be confirmed in studies with adequate design.

Non-invasive brain stimulation for osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease, the prevalence of OA is increasing, and the elderly are the most common in patients with OA. OA has a severe impact on the daily life of patients, this increases the demand for treatment of OA. In recent years, the application of non-invasive brain stimulation (NIBS) has attracted extensive attention. It has been confirmed that NIBS plays an important role in regulating cortical excitability and oscillatory rhythm in specific brain regions. In this review, we summarized the therapeutic effects and mechanisms of different NIBS techniques in OA, clarified the potential of NIBS as a treatment choice for OA, and provided prospects for further research in the future.

CircTMOD3 promotes lipopolysaccharide-induced chondrocyte apoptosis in osteoarthritis by sponging miR-27a

INTRODUCTION

The progression of osteoarthritis (OA) requires the involvement of lipopolysaccharide (LPS)-induced inflammation, in which circTMOD3 plays an important role. We predicted that circTMOD3 could interact with miR-27a to inhibit LPS-induced chondrocyte apoptosis and explored the interaction between circTMOD3 and miR-27a in OA.

MATERIALS AND METHODS

Total RNAs were isolated from cartilage tissue samples from both OA patients (n = 62) and controls (n = 62) and subjected to RT-qPCRs to determine circTMOD3 and miR-27a (mature and premature) expression. Subcellular location of circTMOD3 and its interaction with premature miR-27a were analyzed using subcellular fractionation assay and RNA-RNA pulldown assay, respectively. CircTMOD3 was overexpressed in chondrocytes to study its role in miR-27a maturation. The roles of circTMOD3 and miR-27a in LPS-induced chondrocyte apoptosis were analyzed using cell apoptosis assay.

RESULTS

CircTMOD3 and premature miR-27a levels were increased while mature miR-27a level was decreased in OA. CircTMOD3 was located in both nuclear and cytoplasm fractions of chondrocytes. CircTMOD3 directly interacted with premature miR-27a and promoted LPS-induced chondrocyte apoptosis, while miR-27a inhibited LPS-induced chondrocyte apoptosis. Moreover, circTMOD3 overexpression suppressed miR-27a maturation and reduced the inhibitory effects of miR-27a on LPS-induced chondrocyte apoptosis.

CONCLUSION

CircTMOD3 suppresses miR-27a maturation in OA to promote chondrocyte apoptosis induced by LPS.

microRNA-4701-5p protects against interleukin-1β induced human chondrocyte CHON-001 cells injury via modulating HMGA1

Background

miRNA-4701-5p has been reported to be a vital regulator in many diseases, including rheumatoid arthritis, and miRNA-4701-5p is evidenced to be participated in synovial invasion and joint destruction. In our report, we investigated the roles of miRNA-4701-5p in osteoarthritis (OA) and analyzed the molecular mechanism.

Methods

Interleukin-1β (IL-1β) was applied for stimulating human chondrocyte CHON-001 cells to establish an OA injury model. mRNA levels and protein expression were measured using qRT-PCR and western blot assay, respectively. The proliferation ability and cytotoxicity of CHON-001 cells were checked using MTT assay and lactate dehydrogenase activity. The inflammation of chondrocytes was accessed by the secretion levels of interleukin-6 (IL-6), interleukin-8 (IL-8) and tumor necrosis factor (TNF)-α. The apoptosis of chondrocytes was determined by flow cytometry assay. Bioinformatics software Starbase v2.0 analyzed the functional binding sites between miRNA-4701-5p and HMGA1 and the interaction was further confirmed using dual luciferase reporter analysis. Results: miRNA-4701-5p was down-regulated in the IL-1β-stimulated chondrocytes and HMGA1 directly targeted miRNA-4701-5p. Up-regulation of miRNA-4701-5p could alleviate IL-1β-treated CHON-001 cells inflammation and apoptosis, and reversed the cell proliferation decrease and cytotoxicity increase after IL-1β treatment. Nevertheless, all the roles of miRNA-4701-5p overexpression in CHON-001 cells could be reversed by HMGA1 up-regulation.

Conclusions

miRNA-4701-5p could alleviate the inflammatory injury of IL-1β-treated CHON-001 cells via down-regulating HMGA1, indicating that miRNA-4701-5p/HMGA1 is a promising therapeutic target for OA.

Mid-term improvement of cognitive performance after total hip arthroplasty in patients with osteoarthritis of the hip : a prospective cohort study

Aims

The aim of this study was to determine whether total hip arthroplasty (THA) for chronic hip pain due to unilateral primary osteoarthritis (OA) has a beneficial effect on cognitive performance.

Methods

A prospective cohort study was conducted with 101 patients with end-stage hip OA scheduled for THA (mean age 67.4 years (SD 9.5), 51.5% female (n = 52)). Patients were assessed at baseline as well as after three and months. Primary outcome was cognitive performance measured by d2 Test of Attention at six months, Trail Making Test (TMT), FAS-test, Rivermead Behavioural Memory Test (RBMT; story recall subtest), and Rey-Osterrieth Complex Figure Test (ROCF). The improvement of cognitive performance was analyzed using repeated measures analysis of variance.

Results

At six months, there was significant improvement in attention, working speed and concentration (d2-test; p < 0.001), visual construction and visual memory (ROCF; p < 0.001), semantic memory (FAS-test; p = 0.009), verbal episodic memory (RBMT; immediate recall p = 0.023, delayed recall p = 0.026), as well as pain (p < 0.001) with small to large effect sizes. Attention, concentration, and visual as well as verbal episodic memory improved significantly with medium effect sizes over η²_partial = 0.06. In these cognitive domains the within-group difference exceeded the minimum clinically important difference.

Conclusion

THA is associated with clinically relevant postoperative improvement in the cognitive functions of attention, concentration, and memory. These data support the concept of a broad interaction of arthroplasty with central nervous system function.

Cite this article: Bone Joint J 2022;104-B(3):331–340.

Benefits and Mechanisms of Exercise Training for Knee Osteoarthritis

Knee osteoarthritis is a chronic degenerative disease. Cartilage and subchondral bone degeneration, as well as synovitis, are the main pathological changes associated with knee osteoarthritis. Mechanical overload, inflammation, metabolic factors, hormonal changes, and aging play a vital role in aggravating the progression of knee osteoarthritis. The main treatments for knee osteoarthritis include pharmacotherapy, physiotherapy, and surgery. However, pharmacotherapy has many side effects, and surgery is only suitable for patients with end-stage knee osteoarthritis. Exercise training, as a complementary and adjunctive physiotherapy, can prevent cartilage degeneration, inhibit inflammation, and prevent loss of the subchondral bone and metaphyseal bone trabeculae. Increasing evidence indicates that exercise training can improve pain, stiffness, joint dysfunction, and muscle weakness in patients with knee osteoarthritis. There are several exercise trainings options for the treatment of knee osteoarthritis, including aerobic exercise, strength training, neuromuscular exercise, balance training, proprioception training, aquatic exercise, and traditional exercise. For Knee osteoarthritis (KOA) experimental animals, those exercise trainings can reduce inflammation, delay cartilage and bone degeneration, change tendon, and muscle structure. In this review, we summarize the main symptoms of knee osteoarthritis, the mechanisms of exercise training, and the therapeutic effects of different exercise training methods on patients with knee osteoarthritis. We hope this review will allow patients in different situations to receive appropriate exercise therapy for knee osteoarthritis, and provide a reference for further research and clinical application of exercise training for knee osteoarthritis.

Beneficial Effects and Potential Mechanisms of Tai Chi on Lower Limb Osteoarthritis: A Biopsychosocial Perspective

Lower limb osteoarthritis (OA) is a chronic, multifactorial disease characterized by impaired physical function, chronic pain, compromised psychological health and decreased social functioning. Chronic inflammation plays a critical role in the pathophysiology of OA. Tai Chi is a type of classical mind-body exercise derived from ancient Chinese martial arts. Evidence supports that Tai Chi has significant benefits for relieving lower limb OA symptoms. Using a biopsychosocial framework, this review aims to elucidate the beneficial effects of Tai Chi in lower limb OA and disentangle its potential mechanisms from the perspective of biology, psychology, and social factors. Complex biomechanical, biochemical, neurological, psychological, and social mechanisms, including strengthening of muscles, proprioception improvement, joint mechanical stress reduction, change of brain activation and sensitization, attenuation of inflammation, emotion modulation and social support, are discussed.

Anxiety enhances pain in a model of osteoarthritis and is associated with altered endogenous opioid function and reduced opioid analgesia

Introduction

Negative affect, including anxiety and depression, is prevalent in chronic pain states such as osteoarthritis (OA) and associated with greater use of opioid analgesics, potentially contributing to present and future opioid crises.

Objectives

We tested the hypothesis that the interaction between anxiety, chronic pain, and opioid use results from altered endogenous opioid function.

Methods

A genetic model of negative affect, the Wistar-Kyoto (WKY) rat, was combined with intra-articular injection of monosodium iodoacetate (MIA; 1 mg) to mimic clinical presentation. Effects of systemic morphine (0.5-3.5 mg·kg^-1) on pain behaviour and spinal nociceptive neuronal activity were compared in WKY and normo-anxiety Wistar rats 3 weeks after MIA injection. Endogenous opioid function was probed by the blockade of opioid receptors (0.1-1 mg·kg^-1 systemic naloxone), quantification of plasma β-endorphin, and expression and phosphorylation of spinal mu-opioid receptor (MOR).

Results

Monosodium iodoacetate-treated WKY rats had enhanced OA-like pain, blunted morphine-induced analgesia, and greater mechanical hypersensitivity following systemic naloxone, compared with Wistar rats, and elevated plasma β-endorphin levels compared with saline-treated WKY controls. Increased MOR phosphorylation at the master site (serine residue 375) in the spinal cord dorsal horn of WKY rats with OA-like pain (P = 0.0312) indicated greater MOR desensitization.

Conclusions

Reduced clinical analgesic efficacy of morphine was recapitulated in a model of high anxiety and OA-like pain, in which endogenous opioid tone was altered, and MOR function attenuated, in the absence of previous exogenous opioid ligand exposure. These findings shed new light on the mechanisms underlying the increased opioid analgesic use in high anxiety patients with chronic pain.

Relationship between Oxytocin and Osteoarthritis: Hope or Despair?

Oxytocin (OT) is involved in breastfeeding and childbirth and appears to play a role in regulating the bone matrix. OT is synthesized in the supraoptic and paraventricular nuclei of the hypothalamus and is released in response to numerous stimuli. It also appears to be produced by osteoblasts in the bone marrow, acting as a paracrine–autocrine regulator of bone formation. Osteoarthritis (OA) is a disease of the whole joint. Different tissues involved in OA express OT receptors (OTRs), such as chondrocytes and osteoblasts. This hormone, which levels are reduced in patients with OA, appears to have a stimulatory effect on chondrogenesis. OT involvement in bone biology could occur at both the osteoblast and chondrocyte levels. The relationships between metabolic syndrome, body weight, and OA are well documented, and the possible effects of OT on different parameters of metabolic syndrome, such as diabetes and body weight, are important. In addition, the effects of OT on adipokines and inflammation are also discussed, especially since recent data have shown that low-grade inflammation is also associated with OA. Furthermore, OT also appears to mediate endogenous analgesia in animal and human studies. These observations provide support for the possible interest of OT in OA and its potential therapeutic treatment.

Effects of photobiomodulation therapy in chondrocyte response by in vitro experiments and experimental model of osteoarthritis in the knee of rats

The purpose of this study is to evaluate the effects of photobiomodulation (PBM) therapy in chondrocyte response by in vitro experiments and cartilage repair using an experimental model of osteoarthritis (OA) in the knee of rats. The in vitro experiment was performed with chondrocyte cells, and they were divided into two groups: non-irradiated and irradiated with PBM (808 nm; 0.8 J or 1.4 J). Then, cell proliferation was evaluated after 1, 3, and 5 days. The experimental model of osteoarthritis (OA) was performed in the knee of 64 Wistar rats, and they were assorted into control group (CG), PBM (808 nm; 1.4 J). The results of in vitro showed that PBM 1.4 J increased cell proliferation, on days 1 and 5. However, after 3 days was demonstrated a significant increase in cell proliferation in PBM 0.8 J. The in vivo experiment results demonstrated, on histological analysis, that PBM presented less intense signs of tissue degradation with an initial surface discontinuity at the superficial zone and disorganization of the chondrocytes in the cartilage region when compared to CG, after 4 and 8 weeks. These findings were confirmed by immunohistochemistry and qRT-PCR analysis which showed that PBM increased IL-4, IL-10, COL-2, Aggrecan, and TGF-β which are anabolic factors and acts on extracellular matrix. Also, PBM reduces the IL1-β, an inflammatory marker that operates as a catabolic factor on articular cartilage. In conclusion, these results suggest that PBM may have led to a return to tissue homeostasis, promoting chondroprotective effects and stimulating the components of the articular tissue.

Dexamethasone-loaded thermo-sensitive hydrogel attenuates osteoarthritis by protecting cartilage and providing effective pain relief

Background

We utilized the destabilization of medial meniscus (DMM)-induced mice to illustrate the osteoarthritis (OA) suppressing and pain-relieving effects of a novel prolonged-release intra-articular (IA)-dexamethasone-loaded thermo-sensitive hydrogel (DLTH).

Methods

The effects of temperature and pH on DLTH formation and in vitro DLTH release profile were assessed. C57BL/6J mice were randomly divided into three groups: Ctrl group, Model group and DLTH group. The DLTH group received joint injections of 10 µL DLTH (1 mg/kg) into the right knee once a week from week 2 to week 11. We performed micro-computed tomography (Micro-CT) and histological analyses of safranin O-fast green, hematoxylin and eosin, and tartrate-resistant acid phosphatase in knee joints. We also carried out immunohistochemical (IHC) staining for matrix metalloproteinase-9 (MMP-9), MMP-13, and a disintegrin and metalloproteinase with thrombospondin motifs-5 (ADAMTS-5) in cartilage and Ki-67 in synovia. Pain behavioral testing was carried out in all mice. The serum content of prostaglandin E2 (PGE2) and real-time polymerase chain reaction (PCR) of inflammatory cytokines and pain-related factors in dorsal root ganglia (DRGs) were evaluated.

Results

It took 20 minutes to form DLTH at pH 7.0 and 37 °C. The cumulative release profiles of dexamethasone (Dex) from DLTH at 37 °C revealed a rapid release in the first 24 h and a sustained slow release for 7 days. In vivo study illustrated that DLTH attenuated OA bone destruction and ameliorated synovitis and progression of OA in DMM-induced mice. The chondroprotective effects of DLTH were mediated by decreased expressions of MMP-9, MMP-13, and ADAMTS-5. The results showed that IA-DLTH exerted pain-relieving effects in OA mice. Upregulation of nociceptive response time (NRT) and downregulations of serum PGE2, inflammatory factors, and pain-related mediators in DRGs of mice in the DLTH group were recorded.

Conclusions

Data presented in this study elucidated that DLTH exhibited a long and lasting Dex release and it is a potential sustainable drug delivery system (DDS) to treat OA locally. IA-DLTH injection exerted chondroprotective and pain-relieving effects in DMM-induced arthritis. The involvement of MMP-9, MMP-13, ADAMTS-5, and inflammatory and pain-related factors, may account for the suppression of OA progression and pain.

MicroRNA-183 attenuates osteoarthritic pain by inhibiting the TGFα-mediated CCL2/CCR2 signalling axis

AIMS

MicroRNA-183 (miR-183) is known to play important roles in osteoarthritis (OA) pain. The aims of this study were to explore the specific functions of miR-183 in OA pain and to investigate the underlying mechanisms.

METHODS

Clinical samples were collected from patients with OA, and a mouse model of OA pain was constructed by surgically induced destabilization of the medial meniscus (DMM). Reverse transcription quantitative polymerase chain reaction was employed to measure the expression of miR-183, transforming growth factor α (TGFα), C-C motif chemokine ligand 2 (CCL2), proinflammatory cytokines (interleukin (IL)-6, IL-1β, and tumour necrosis factor-α (TNF-α)), and pain-related factors (transient receptor potential vanilloid subtype-1 (TRPV1), voltage-gated sodium 1.3, 1.7, and 1.8 (Nav1.3, Nav1.7, and Nav1.8)). Expression of miR-183 in the dorsal root ganglia (DRG) of mice was evaluated by in situ hybridization. TGFα, CCL2, and C-C chemokine receptor type 2 (CCR2) levels were examined by immunoblot analysis and interaction between miR-183 and TGFα, determined by luciferase reporter assay. The extent of pain in mice was measured using a behavioural assay, and OA severity assessed by Safranin O and Fast Green staining. Immunofluorescent staining was conducted to examine the infiltration of macrophages in mouse DRG.

RESULTS

miR-183 was downregulated in tissue samples from patients and mice with OA. In DMM mice, overexpression of miR-183 inhibited the expression of proinflammatory cytokines (IL-6, IL-1β, TNF-α) and pain-related factors (TRPV1, Nav1.3, Nav1.7, Nav1.8) in DRG. OA pain was relieved by miR-183-mediated inhibition of macrophage infiltration, and dual luciferase reporter assay demonstrated that miR-183 directly targeted TGFα.

CONCLUSION

Our data demonstrate that miR-183 can ameliorate OA pain by inhibiting the TGFα-CCL2/CCR2 signalling axis, providing an excellent therapeutic target for OA treatment. Cite this article: Bone Joint Res 2021;10(8):548-557.

LncRNA GAS5 upregulates Smad4 to suppress the apoptosis of chondrocytes induced by lipopolysaccharide

BACKGROUND

Osteoarthritis (OA) is closely correlated with inflammation. It has been reported that lncRNA GAS5 plays an important role in inflammation, indicating the potential involvement of GAS5 in OA. This study was carried out to investigate the function of GAS5 in OA.

METHODS

Expression levels of GAS5 in synovial fluid from 45 OA patients and 45 healthy controls were measured by RT-qPCR. Cell transfections were performed to explore the potential interactions among GAS5, miR-146a, and Smad4 in chondrocytes. Lipopolysaccharide (LPS)-induced cell apoptosis after overexpression of GAS5, miR-146a, and Smad4 was analyzed by cell apoptosis assay.

RESULTS

GAS5 was downregulated in OA. Moreover, LPS treatment downregulated GAS5 in chondrocytes. Interaction between GAS5 could with miR-146a was predicted by bioinformatics analysis and further confirmed by RNA-RNA pulldown assay. However, overexpression of GAS5 and miR-146a did not affect the expression of each other. GAS5 overexpression increased Smad4 expression in chondrocytes. In contrast, miR-146a overexpression downregulated Smad4 in chondrocytes. Moreover, GAS5 and Smad4 overexpression inhibited LPS- induced chondrocytes apoptosis, while miR-146a overexpression played an opposite role and attenuated the effects of GAS5 and Smad4 overexpression on cell apoptosis.

CONCLUSION

GAS5 might sponge miR-146a to upregulate Smad4, thereby suppressing LPS- induced chondrocytes apoptosis.

Microenvironment in subchondral bone: predominant regulator for the treatment of osteoarthritis

Osteoarthritis (OA) is a degenerative joint disease in the elderly. Although OA has been considered as primarily a disease of the articular cartilage, the participation of subchondral bone in the pathogenesis of OA has attracted increasing attention. This review summarises the microstructural and histopathological changes in subchondral bone during OA progression that are due, at the cellular level, to changes in the interactions among osteocytes, osteoblasts, osteoclasts (OCs), endothelial cells and sensory neurons. Therefore, we focus on how pathological cellular interactions in the subchondral bone microenvironment promote subchondral bone destruction at different stages of OA progression. In addition, the limited amount of research on the communication between OCs in subchondral bone and chondrocytes (CCs) in articular cartilage during OA progression is reviewed. We propose the concept of 'OC-CC crosstalk' and describe the various pathways by which the two cell types might interact. Based on the 'OC-CC crosstalk', we elaborate potential therapeutic strategies for the treatment of OA, including restoring abnormal subchondral bone remodelling and blocking the bridge-subchondral type H vessels. Finally, the review summarises the current understanding of how the subchondral bone microenvironment is related to OA pain and describes potential interventions to reduce OA pain by targeting the subchondral bone microenvironment.

CircRNA circ-IQGAP1 Knockdown Alleviates Interleukin-1β-Induced Osteoarthritis Progression via Targeting miR-671-5p/TCF4

Objective

To explore the function of circular RNA IQ motif‐containing GTPase‐activating protein 1 (circ‐IQGAP1) in interleukin (IL)‐1β‐induced osteoarthritis (OA) model and to explore whether circ‐IQGAP1 can modulate microRNA‐671‐5p (miR‐671‐5p) and transcription factor 4 (TCF4) to regulate chondrocyte apoptosis, inflammatory injury, and extracellular matrix degradation.

Methods

The cartilage tissues were collected from 32 OA patients or normal subjects. Human chondrocyte CHON‐001 cells were challenged via different doses of IL‐1β for 24 hours. CHON‐001 cells were transfected with circ‐IQGAP1 overexpression vector, TCF4 overexpression vector, small interfering RNA (siRNA) for circ‐IQGAP1, miR‐671‐5p mimic, miR‐671‐5p inhibitor or corresponding negative controls. Circ‐IQGAP1, miR‐671‐5p and TCF4 abundances in cartilage tissues or CHON‐001 cells were examined via quantitative reverse transcription polymerase chain reaction (qRT‐PCR) or western blot. Cell viability was investigated by 3‐(4, 5‐dimethylthiazol‐2‐yl)‐2, 5‐diphenyltetrazolium bromide (MTT). Cell apoptosis was measured by flow cytometry. The inflammatory injury was analyzed by the secretion levels of inflammatory cytokines (IL‐6, IL‐8 and tumor necrosis factor‐α [TNF‐α]) by enzyme‐linked immunosorbent assay (ELISA). The extracellular matrix degradation was evaluated by expression of aggrecan and matrix metalloproteinase 13 (MMP13) via western blot. The target relationship of miR‐671‐5p and circ‐IQGAP1 or TCF4 was analyzed via dual‐luciferase reporter and RNA immunoprecipitation (RIP) analyses.

Results

Circ‐IQGAP1 abundance was enhanced in the cartilage tissues from OA patients compared with normal subjects (n = 32), and its expression was increased in CHON‐001 cells after treatment of IL‐1β in a dose‐dependent pattern. MiR‐671‐5p expression was decreased in the cartilage tissues from OA patients (n = 32) and IL‐1β‐challenged CHON‐001 cells. MiR‐671‐5p expression was negatively associated with circ‐IQGAP1 level in OA patients. Circ‐IQGAP1 silence mitigated IL‐1β‐caused chondrocyte viability reduction, apoptosis promotion, secretion of inflammatory cytokine (IL‐6, IL‐8 and TNF‐α), and extracellular matrix degradation (reduction of aggrecan and increase of MMP13). MiR‐671‐5p was targeted and inhibited via circ‐IQGAP1. MiR‐671‐5p knockdown attenuated the influence of circ‐IQGAP1 interference on IL‐1β‐caused chondrocyte apoptosis, inflammatory injury, and extracellular matrix degradation. TCF4 was targeted via miR‐671‐5p, and TCF4 expression was increased in the cartilage tissues from OA patients (n = 32) and IL‐1β‐challenged CHON‐001 cells. TCF4 abundance in OA patients was negatively correlated with miR‐671‐5p expression. MiR‐671‐5p overexpression alleviated IL‐1β‐mediated chondrocyte apoptosis, inflammatory injury, and extracellular matrix degradation via decreasing TCF4 expression. Circ‐IQGAP1 silence reduced TCF4 expression via regulating miR‐671‐5p in IL‐1β‐challenged CHON‐001 cells.

Conclusion

Circ‐IQGAP1 knockdown attenuated IL‐1β‐caused chondrocyte apoptosis, inflammatory injury, and extracellular matrix degradation. Circ‐IQGAP1 could regulate miR‐671‐5p/TCF4 axis to modulate IL‐1β‐caused chondrocyte damage. Circ‐IQGAP1 might act as a new target for the treatment of OA.

Local Administration of Low-Dose Nerve Growth Factor Antibody Reduced Pain in a Rat Osteoarthritis Model

Systemic injection of a nerve growth factor (NGF) antibody has been proven to have a significant relevance in relieving osteoarthritis (OA) pain, while its adverse effects remain a safety concern for patients. A local low-dose injection is thought to minimize adverse effects. In this study, OA was induced in an 8-week-old male Sprague–Dawley (SD) rat joint by monoiodoacetate (MIA) injection for 2 weeks, and the effect of weekly injections of low-dose (1, 10, and 100 µg) NGF antibody or saline (control) was evaluated. Behavioral tests were performed, and at the end of week 6, all rats were sacrificed and their knee joints were collected for macroscopic and histological evaluations. Results showed that 100 µg NGF antibody injection relieved pain in OA rats, as evidenced from improved weight-bearing performance but not allodynia. In contrast, no significant differences were observed in macroscopic and histological scores between rats from different groups, demonstrating that intra-articular treatment does not worsen OA progression. These results suggest that local administration yielded a low effective NGF antibody dose that may serve as an alternative approach to systemic injection for the treatment of patients with OA.

Pathophysiology of musculoskeletal pain: a narrative review

Musculoskeletal pain (excluding bone cancer pain) affects more than 30% of the global population and imposes an enormous burden on patients, families, and caregivers related to functional limitation, emotional distress, effects on mood, loss of independence, and reduced quality of life. The pathogenic mechanisms of musculoskeletal pain relate to the differential sensory innervation of bones, joints, and muscles as opposed to skin and involve a number of peripheral and central nervous system cells and mediators. The interplay of neurons and non-neural cells (e.g. glial, mesenchymal, and immune cells) amplifies and sensitizes pain signals in a manner that leads to cortical remodeling. Moreover, sex, age, mood, and social factors, together with beliefs, thoughts, and pain behaviors influence the way in which musculoskeletal pain manifests and is understood and assessed. The aim of this narrative review is to summarize the different pathogenic mechanisms underlying musculoskeletal pain and how these mechanisms interact to promote the transition from acute to chronic pain.

Biomechanical analysis during single-leg squat in individuals with knee osteoarthritis

Backgroud: The single-leg squat (SLS) is a functional task to evaluate the abnormal movement patterns and potential neuromuscular deficits in the lower limbs. Still, it is unknown if SLS could provide information to older adults with knee osteoarthritis (KOA). The study's objective was to analyze the EMG pattern, kinematics, and postural control in individuals with and without KOA during SLS.

METHODS

Participated in this study, 60 volunteers of both sexes, 30 had KOA (allocated into the KOA group - KOAG), and 30 were healthy (allocated into the Healthy Group - HG) performing the single-leg squat. Surface electromyography (EMG) was assessed for the gastrocnemius medialis (GM), biceps femoris (BF), gluteus medius (GLM), rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), and tibialis anterior (TA) in two phases (downward - P1 and upward - P2). The kinematic data was evaluated using an electrogoniometer. The center of pressure (CoP) was obtained using data collected from a force plate.

RESULTS

EMG activity was increased for GM and TA muscles during the P1 of the movement and the GM and GLM muscles during P2 of the movement. The angular displacement of the KOAG was lower when compared with the HG. There was no statistical difference for the co-contraction and postural control data.

CONCLUSIONS

The SLS analysis showed that EMG activity of the muscles TA, GM, and GLM was increased in the KOAG, but this pattern could be affected by fear of movement leading to reduced knee angular displacement.

Widespread regulation of gene expression by glucocorticoids in chondrocytes from patients with osteoarthritis as determined by RNA-Seq

Background

Intra-articular glucocorticoid (GC) injections are widely used as a symptomatic treatment for osteoarthritis (OA). However, there are also concerns about their potentially harmful effects, and their detailed effects on chondrocyte phenotype remain poorly understood.

Methods

We studied the effects of dexamethasone on gene expression in OA chondrocytes with RNA-Seq. Chondrocytes were isolated from the cartilage from OA patients undergoing knee replacement surgery and cultured with or without dexamethasone for 24 h. Total RNA was isolated and sequenced, and functional analysis was performed against the Gene Ontology (GO) database. Results for selected genes were confirmed with RT-PCR. We also investigated genes linked to OA in recent genome-wide expression analysis (GWEA) studies.

Results

Dexamethasone increased the expression of 480 and reduced that of 755 genes with a fold change (FC) 2.0 or greater. Several genes associated with inflammation and cartilage anabolism/catabolism as well as lipid and carbohydrate metabolism were among the most strongly affected genes. In the GO analysis, genes involved in the extracellular matrix organization, cell proliferation and adhesion, inflammation, and collagen synthesis were enriched among the significantly affected genes. In network analysis, NGF, PI3KR1, and VCAM1 were identified as central genes among those most strongly affected by dexamethasone.

Conclusions

This is the first study investigating the genome-wide effects of GCs on the gene expression in OA chondrocytes. In addition to clear anti-inflammatory and anticatabolic effects, GCs affect lipid and glucose metabolism in chondrocytes, an observation that might be particularly important in the metabolic phenotype of OA.

Natural Antioxidant Control of Neuropathic Pain-Exploring the Role of Mitochondrial SIRT3 Pathway

Neuropathic pain is a chronic painful disease. Data have shown that reactive oxygen species (ROS) are implicated in chronic pain. Particularly, the enhanced ROS production alters the mitochondrial genome and proteome through the accumulation of lipid peroxidation products, such as 4-hydroxynonenal (4-HNE) and malondialdehyde (MDA). Sirtuin 3 (SIRT3) is a mitochondrial protein and its activity can reduce ROS levels by modulating key antioxidant enzymes, such as manganese superoxide dismutase (MnSOD). Here, we evaluated the role of SIRT3 in the maintenance of basal levels of ROS in a model of chronic constriction injury (CCI) of the sciatic nerve and the protective effects of a natural antioxidant, the bergamot polyphenolic fraction (BPF). Rats were exposed to CCI of the sciatic nerve in the presence or absence of BPF (25–75 mg/kg). Level of acetylation, post-translational modulation on cysteine residues of proteins by HNE and SIRT3 activation, were detected in the spinal cord through western blotting, WES methodology and enzymatic assays. Our results reported that SIRT3 carbonylation and therefore its inactivation contributes to mitochondrial MnSOD hyperacetylation during CCI induced neuropathic pain in rats. In particular, we have demonstrated a close relation between oxidative stress, hyperalgesia, allodynia and sirtuins inactivation reverted by BPF administration.

Pain pharmacogenetics

Pain is a significant problem in medicine. The use of PGx markers to personalize postoperative analgesia can increase its effectiveness and avoid undesirable reactions. This article describes the mechanisms of nociception and antinociception and shows the pathophysiological mechanisms of pain in the human body. The main subject of this article is pharmacogenetic approach to the selection of anesthetics. Current review presents data for local and general anesthetics, opioids, and non-steroidal anti-inflammatory drugs. None of the anesthetics currently has clinical guidelines for pharmacogenetic testing. This literature review summarizes the results of original research available, to date, and draws attention to this area.

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.

Association of weather factors with the risk of pain exacerbations in people with hip osteoarthritis

Objectives: Our objective was to evaluate the association of weather factors with the risk of pain exacerbations in people with symptomatic hip osteoarthritis (OA). Method: Eligible participants with symptomatic hip OA were instructed to log on to the study website and complete questionnaires every 10 days and additionally whenever they considered they were experiencing a pain exacerbation (case period) during the 90 day follow-up. Pain exacerbation was defined as an increase of two points in pain intensity on an 11-point numeric rating scale (0-10) during the follow-up compared with baseline. Each case period was anchored to four control periods within a 35 day interval using a time-stratified approach. Weather data were obtained for both periods from the publicly available meteorological database of the Australian Bureau of Meteorology. We examined the association of weather factors across 72 h before the index date with the risk of pain exacerbation, using conditional logistic regression. Results: Among 252 participants recruited, 129 participants had at least one episode of pain exacerbation and were included in the analysis. A significant dose-response relationship was found between average daily temperature variation in the prior 72 h and risk of pain exacerbations (p = 0.04 for linear trend). There was no significant association between maximum daily temperature, minimum daily temperature, relative humidity, precipitation, or barometric pressure and hip pain exacerbations. Conclusion: The overall results suggest that only daily temperature variation among different weather factors was associated with hip pain exacerbations in people with symptomatic hip OA.

The impact of a significant weight loss on inflammation assessed on DCE-MRI and static MRI in knee osteoarthritis: a prospective cohort study

OBJECTIVE

To study the impact of weight loss on inflammation in individuals with overweight and knee osteoarthritis (OA) using both static- and dynamic contrast-enhanced (DCE)-MRI and assess the association of these changes to pain.

DESIGN

Individuals with overweight (BMI > 27) and knee OA were examined before and after a >5% weight loss over 8 weeks (ClinicalTrials.gov NCT02905864). Using 3-T MRI, inflammation was quantified from non-contrast enhanced static-MRI according to MOAKS and contrast enhanced static MRI according to BLOKS and 11-point whole-knee synovitis score. DCE-MRI was used to assess the inflammation in the infra patellar fat pad (IPFP). Pain was assessed using KOOS.

RESULTS

Complete data were available in 117 participants with a mean age of 60 years, BMI of 35 kg/m² and KOOS pain score of 64. Mean weight loss was 12 kg and KOOS pain was improved by 13 points at follow-up. Change in inflammation was not associated with weight loss in static MRI. None of the MRI variables correlated with the change in KOOS pain.

CONCLUSION

Weight loss did not induce a significant change in inflammation in individuals with overweight and OA. The significant clinical beneficial effect of weight loss on knee pain in individuals with overweight and knee OA seems uncoupled to changes in imaging markers of synovitis.

Osteoarthritis and inflammation: a serious disease with overlapping phenotypic patterns

Globally, osteoarthritis (OA) is the most prevalent arthritic condition in those aged over 60 years. OA has a high impact on patient disability and is associated with a significant economic burden. Pain is the most common first sign of disease and the leading cause of disability. Data demonstrating the increasing global prevalence of OA, together with a greater understanding of the burden of the disease, have led to a reassessment of the seriousness of OA and calls for the designation of OA as a serious disease in line with the diseases impact on comorbidity, disability, and mortality. While OA was traditionally seen as a prototypical 'wear and tear' disease, it is now more accurately thought of as a disease of the whole joint involving cartilage together with subchondral bone and synovium. As more has become known of the pathophysiology of OA, it has become increasingly common for it to be described using a number of overlapping phenotypes. Patients with OA will likely experience multiple phenotypes during their disease. This review focuses on what we feel are three key phenotypes: post-trauma, metabolic, and aging. A greater understanding of OA phenotypes, particularly at the early stages of disease, may be necessary to improve treatment outcomes. In the future, non-pharmacological and pharmacological treatments could be tailored to patients based on the key features of their phenotype and disease pathway.