Therapeutic approaches in the management of knee osteoarthritis (Review)

Exosomes in Osteoarthritis: A Review on Their Isolation Techniques and Therapeutic Potential

Background

Exosomes are the smallest extracellular vesicles (30-150 nm) secreted by all cell types, including synovial fluid. However, because biological fluids are complex, heterogeneous, and contain contaminants, their isolation is difficult and time-consuming. Furthermore, the pathophysiology of osteoarthritis (OA) involves exosomes carrying complex components that cause macrophages to release chemokines and proinflammatory cytokines. This narrative review aims to provide in-depth insights into exosome biology, isolation techniques, role in OA pathophysiology, and potential role in future OA therapeutics.

Methods

A literature search was conducted using PubMed, Scopus, and Web of Science databases for studies involving exosomes in the osteoarthritis using keywords "Exosomes" and "Osteoarthritis". Relevant articles in the last 15 years involving both human and animal models were included. Studies involving exosomes in other inflammatory diseases were excluded.

Results

Despite some progress, conventional techniques for isolating exosomes remain laborious and difficult, requiring intricate and time-consuming procedures across various body fluids and sample origins. Moreover, exosomes are involved in various physiological processes associated with OA, like cartilage calcification, degradation of osteoarthritic joints, and inflammation.

Conclusion

The process of achieving standardization, integration, and high throughput of exosome isolation equipment is challenging and time-consuming. The integration of various methodologies can be employed to effectively address specific issues by leveraging their complementary benefits. Exosomes have the potential to effectively repair damaged cartilage OA, reduce inflammation, and maintain a balance between the formation and breakdown of cartilage matrix, therefore showing promise as a therapeutic option for OA.

Anxiety and depression prior to total knee arthroplasty are associated with worse pain and subjective function: A prospective comparative study

PURPOSE

The aim of this study was to investigate the influence of preoperative anxiety and depression on subjective function, pain and revision rates following total knee arthroplasty (TKA).

METHODS

A prospective comparative study was conducted, including 349 patients undergoing TKA surgery between January 2019 and April 2021. Patients completed the Hospital Anxiety and Depression Scale (HADS) questionnaire preoperatively, and a set of Patient-Reported Outcome Measures (PROMs) preoperatively and at 6, 12 and 24 months postoperatively. Patients were categorized into anxiety and depression groups based on HADS scores. PROMs included the Knee injury and Osteoarthritis Outcome Score-Physical Function Shortform (KOOS-PS), Oxford Knee Score (OKS) and NRS-Pain. Differences in PROM scores between the anxiety/depression group and, respectively, nonanxiety/nondepression group were assessed, as well as differences in minimal clinical important difference (MCID) and attainment of Patient Acceptable Symptom State (PASS). Lastly, revision rates were compared.

RESULTS

Anxiety and depression groups exhibited inferior subjective function preoperatively and postoperatively compared to nonanxiety and nondepression groups (all p < 0.05), experienced more pain preoperatively (p < 0.001) and also postoperatively for depression patients (all p < 0.05). Significantly fewer patients with anxiety and depression reached the PASS for KOOS-PS, OKS and NRS-Pain (all p < 0.05). There were no differences in the proportion of patients reaching the MCID for all PROMs (all p > 0.060), and revision rates did not differ between groups (both p > 0.96).

CONCLUSION

Preoperative anxiety and depression negatively influence subjective function and pain preoperatively and up to 2-year follow-up in patients undergoing TKA. Revision rates did not differ between groups, and there were no relevant differences in clinical improvement of subjective function and pain.

LEVEL OF EVIDENCE

Level II, prospective comparative study.

Rehabilitation Applications Based on Behavioral Therapy for People With Knee Osteoarthritis: Systematic Review

BACKGROUND

The development of digital applications based on behavioral therapies to support patients with knee osteoarthritis (KOA) has attracted increasing attention in the field of rehabilitation. This paper presents a systematic review of research on digital applications based on behavioral therapies for people with KOA.

OBJECTIVE

This review aims to describe the characteristics of relevant digital applications, with a special focus on the current state of behavioral therapies, digital interaction technologies, and user participation in design. The secondary aim is to summarize intervention outcomes and user evaluations of digital applications.

METHODS

A systematic literature search was conducted using the keywords "Knee Osteoarthritis," "Behavior Therapy," and "Digitization" in the following databases (from January 2013 to July 2023): Web of Science, Embase, Science Direct, Ovid, and PubMed. The Mixed Methods Assessment Tool (MMAT) was used to assess the quality of evidence. Two researchers independently screened and extracted the data.

RESULTS

A total of 36 studies met the inclusion criteria and were further analyzed. Behavioral change techniques (BCTs) and cognitive behavioral therapy (CBT) were frequently combined when developing digital applications. The most prevalent areas were goals and planning (n=31) and repetition and substitution (n=27), which were frequently used to develop physical activity (PA) goals and adherence. The most prevalent combination strategy was app/website plus SMS text message/telephone/email (n=12), which has tremendous potential. This area of application design offers notable advantages, primarily manifesting in pain mitigation (n=24), reduction of physical dysfunction (n=21), and augmentation of PA levels (n=12). Additionally, when formulating design strategies, it is imperative to consider the perspectives of stakeholders, especially in response to the identified shortcomings in application design elucidated within the study.

CONCLUSIONS

The results demonstrate that "goals and planning" and "repetition and substitution" are frequently used to develop PA goals and PA behavior adherence. The most prevalent combination strategy was app/website plus SMS text message/telephone/email, which has tremendous potential. Moreover, incorporating several stakeholders in the design and development stages might enhance user experience, considering the distinct variations in their requirements. To improve the efficacy and availability of digital applications, we have several proposals. First, comprehensive care for patients should be ensured by integrating multiple behavioral therapies that encompass various aspects of the rehabilitation process, such as rehabilitation exercises and status monitoring. Second, therapists could benefit from more precise recommendations by incorporating additional intelligent algorithms to analyze patient data. Third, the implementation scope should be expanded from the home environment to a broader social community rehabilitation setting.

Knowledge and attitude toward total knee arthroplasty among senior medical students in comparison to public population in Saudi Arabia: cross-sectional study

Background

Total knee arthroplasty (TKA) is currently considered one of the most common and successful orthopaedic procedures. It plays an essential role in the long-term treatment of osteoarthritis and enhances the patient's quality of life. Very little is known about public and medical students' perceptions of this procedure. The purpose of the current study was to assess the knowledge and attitudes toward TKA among medical students in comparison with the general population in Saudi Arabia.

Method

A cross-sectional study was conducted between February and March 2023. Senior-year (interns and the fifth and sixth year) medical school students (Group A) as well as the general population (Group B) were surveyed online. The distributed questionnaire was divided into three main segments: demographics, knowledge, and the prognosis of TKA. The answers were statistically compared among participants.

Results

Three hundred thirty-one participants were involved in this study, of whom 202 were from the general population and 128 were medical students. Most of the participants were males (68.3%), and the mean age was 32.95±15.22. The results were divided into three groups: demographic, knowledge, and prognosis. Medical students demonstrated a higher knowledge score (111.25±42.38) compared to the general population knowledge score (64.68±44.29), (P<0.001).

Conclusion

Senior-year medical school students and the general population showed a low level of knowledge regarding TKA. However, the students had a better awareness of the procedure. The authors recommend frequent public education programs for the benefits of TKA. In addition, medical schools are encouraged to emphasize the benefits of TKA as a treatment choice for end-stage knee arthritis in their curriculum and training.

IL24 Expression in Synovial Myofibroblasts: Implications for Female Osteoarthritis Pain through Propensity Score Matching Analysis

(1) Introduction: Despite documented clinical and pain discrepancies between male and female osteoarthritis (OA) patients, the underlying mechanisms remain unclear. Synovial myofibroblasts, implicated in synovial fibrosis and OA-related pain, offer a potential explanation for these sex differences. Additionally, interleukin-24 (IL24), known for its role in autoimmune disorders and potential myofibroblast production, adds complexity to understanding sex-specific variations in OA. We investigate its role in OA and its contribution to observed sex differences. (2) Methods: To assess gender-specific variations, we analyzed myofibroblast marker expression and IL24 levels in synovial tissue samples from propensity-matched male and female OA patients (each n = 34). Gene expression was quantified using quantitative polymerase chain reaction (qPCR). The association between IL24 expression levels and pain severity, measured by a visual analog scale (VAS), was examined to understand the link between IL24 and OA pain. Synovial fibroblast subsets, including CD45-CD31-CD39- (fibroblast) and CD45-CD31-CD39+ (myofibroblast), were magnetically isolated from female patients (n = 5), and IL24 expression was compared between these subsets. (3) Results: Females exhibited significantly higher expression of myofibroblast markers (MYH11, ET1, ENTPD2) and IL24 compared to males. IL24 expression positively correlated with pain severity in females, while no correlation was observed in males. Further exploration revealed that the myofibroblast fraction highly expressed IL24 compared to the fibroblast fraction in both male and female samples. There was no difference in the myofibroblast fraction between males and females. (4) Conclusions: Our study highlights the gender-specific role of myofibroblasts and IL24 in OA pathogenesis. Elevated IL24 levels in females, correlating with pain severity, suggest its involvement in OA pain experiences. The potential therapeutic implications of IL24, demonstrated in autoimmune disorders, open avenues for targeted interventions. Notwithstanding the limitations of the study, our findings contribute to understanding OA's multifaceted nature and advocate for future research exploring mechanistic underpinnings and clinical applications of IL24 in synovial myofibroblasts. Additionally, future research directions should focus on elucidating the precise mechanisms by which IL24 contributes to OA pathology and exploring its potential as a therapeutic target for personalized medicine approaches.

A Comprehensive Summary of the Meta-Analyses and Systematic Reviews on Platelet-Rich Plasma Therapies for Knee Osteoarthritis

INTRODUCTION

Osteoarthritis (OA), including that of the knee joint, represents a significant proportion of musculoskeletal injuries in the Canadian Armed Forces (CAF) due to the frequent, high-stress physical activity for which member participation is necessary. Platelet-rich plasma (PRP) is a conservative, autologous treatment that has the potential to relieve symptoms and improve functionality of military members to decrease the impact of the disease and ultimately strengthen the CAF.

MATERIALS AND METHODS

A search of systematic reviews and meta-analyses was conducted to determine the efficacy of PRP injections in treating knee OA. The Scopus database, PubMed database, and Omni academic search tools were scoped for relevant publications. English literature, published up to and including March 2023, that investigated only clinically randomized controlled trials (RCTs) was eligible for inclusion. The results of network meta-analyses were investigated and summarized independent of reviews and non-network meta-analyses.

RESULTS

A total of 225 unique systematic reviews and meta-analyses were initially identified, of which 39 publications, including 7 network meta-analyses, adhered to the defined inclusion and exclusion criteria. PRP was found to significantly alleviate symptoms of pain based on the visual analog scale and Western Ontario and McMaster Universities Arthritis Index pain scores within the 12-month follow-up. Function, activity, sport, quality of life, and stiffness were additionally determined to generally improve to a greater extent from PRP treatment compared to controls, while adverse effects were minor and temporary. PRP placed in the top 3 in 9 reported surface under the cumulative ranking curves, while individually reported rankings of leukocyte-poor and leukocyte-rich PRP both placed in the top 4. The clinical recommendations made were generally positive, with 17 publications acknowledging the benefits of PRP, 3 supporting possible efficacy, and an additional 8 recommending that it be an option for the conservative treatment of knee OA.

CONCLUSION

The results of this review support the efficacy of PRP for relieving symptoms of pain and improving function, stiffness, and quality of life for patients experiencing knee OA within 12 months. As a result, leukocyte-poor-PRP could be considered for members of the CAF with mild to moderate knee OA (Kellgren-Lawrence grades 1-3) to slow the progression of OA and extend the military careers of CAF members. There continues to be a need for future studies to investigate the longer-term effects of PRP to verify sustained benefits at follow-up points greater than 12 months, including findings of improvement in a delayed fashion at the 3- and 6-month timeframe compared to hyaluronic acid treatment.

Housekeeping Gene Stability in Adipose Mesenchymal Stromal Cells Cultivated in Serum/Xeno-Free Media for Osteoarthritis

Among the available therapeutics for the conservative treatment of osteoarthritis (OA), mesenchymal stromal cells (MSCs)-based products appear to be the most promising. Alongside minimally manipulated cell-based orthobiologics, where MSCs are the engine of the bioactive properties, cell expansion under good manufacturing practice (GMP) settings is actively studied to obtain clinical-grade pure populations able to concentrate the biological activity. One of the main characteristics of GMP protocols is the use of clinical-grade reagents, including the recently released serum-free/xeno-free (SFM/XFM) synthetic media, which differ significantly from the traditional reagents like those based on fetal bovine serum (FBS). As SFM/XFM are still poorly characterized, a main lack is the notion of reliable housekeeping genes (HKGs) for molecular studies, either standalone or in combination with standard conditions. Indeed, the aim of this work was to test the stability of five commonly used HKGs (ACTB, EF1A, GAPDH, RPLP0, and TBP) in adipose-derived MSCs (ASCs) cultivated in two commercially available SFM/XFM and to compare outcomes with those obtained in FBS. Four different applets widely recognized by the scientific community (NormFinder, geNorm, comparative ΔCt method, and BestKeeper) were used and data were merged to obtain a final stability order. The analysis showed that cells cultured in both synthetic media had a similar ranking for HKGs stability (GAPDH being best), albeit divergent from FBS expanded products (EF1A at top). Moreover, it was possible to identify specific HKGs for side by side studies, with EF1A/TBP being the most reliable normalizers for single SFM/XFM vs. FBS cultured cells and TBP the best one for a comprehensive analysis of all samples. In addition, stability of HKGs was donor-dependent. The normalization effect on selected genes coding for factors known to be involved in OA pathology, and whose amount should be carefully considered for the selection of the most appropriate MSC-based treatment, showed how HKGs choice might affect the perceived amount for the different media or donor. Overall, this work confirms the impact of SFM/XFM conditions on HKGs stability performance, which resulted similarly for both synthetic media analyzed in the study.

A Review of Cyclic Phosphatidic Acid and Other Potential Therapeutic Targets for Treating Osteoarthritis

Osteoarthritis (OA), a chronic degenerative joint disease, is the most common form of arthritis. OA occurs when the protective cartilage that cushions the ends of bones gradually breaks down. This leads to the rubbing of bones against each other, resulting in pain and stiffness. Cyclic phosphatidic acid (cPA) shows promise as a treatment for OA. In this article, we review the most recent findings regarding the biological functions of cPA signaling in mammalian systems, specifically in relation to OA. cPA is a naturally occurring phospholipid mediator with unique cyclic phosphate rings at the sn-2 and sn-3 positions in the glycerol backbone. cPA promotes various responses, including cell proliferation, migration, and survival. cPA possesses physiological activities that are distinct from those elicited by lysophosphatidic acid; however, its biochemical origin has rarely been studied. Although there is currently no cure for OA, advances in medical research may lead to new therapies or strategies in the future, and cPA has potential therapeutic applications.

Highlighting the Advantages and Benefits of Non-NSAID Treatment After Total Knee Arthroplasty: A Cross-sectional Study

BACKGROUND/AIM

Osteoarthritis is one of the most common degenerative conditions that causes pain, stiffness, and decreased functionality. The management of knee osteoarthritis necessitates collaboration among specialists from different disciplines, considering the primary clinical manifestations and functional level of the disease. The aim of this study was to highlight the disparities in postoperative outcomes between knee arthroplasty procedures with and without non-steroidal anti-inflammatory drugs (NSAIDs). The study specifically focuses on the immediate advantages and outcomes observed at the 6-month milestone.

PATIENTS AND METHODS

This study followed 713 patients who were randomly divided into two groups: a group that did not receive non-steroidal anti-inflammatory drugs (N-NSAIDs) consisting of 394 patients, and a group that received non-steroidal anti-inflammatory drugs (NSAIDs) comprising 319 patients. The study spanned a duration of 5 years (2018-2022), with patients being followed and evaluated for up to 6 months after the surgery.

RESULTS

It was observed that, from a therapeutic standpoint, the use of injectable treatments decreased. Significantly better differences were recorded in the N-NSAIDs group regarding return to pre-osteoarthritis activities at 6 months and reduced or absent night pain at 3 months (p<0.05).

CONCLUSION

Statistically significant improvements were observed in the N-NSAIDs group concerning the ability to resume pre-osteoarthritis activities within 6 months, as well as a reduction or absence of nighttime pain within 3 months.

Role of Syndecan-4 in the Inhibition of Articular Cartilage Degeneration in Osteoarthritis

Despite its widespread existence, there are relatively few drugs that can inhibit the progression of osteoarthritis (OA). Syndecan-4 (SDC4) is a transmembrane heparan sulfate proteoglycan that modulates cellular interactions with the extracellular matrix. Upregulated SDC4 expression in articular cartilage chondrocytes correlates with OA progression. In the present study, we treated osteoarthritic cartilage with SDC4 to elucidate its role in the disease's pathology. In this in vitro study, we used real-time polymerase chain reaction (PCR) to investigate the effects of SDC4 on anabolic and catabolic factors in cultured chondrocytes. In the in vivo study, we investigated the effect of intra-articular injection of SDC4 into the knee joints of an OA mouse model. In vitro, SDC4 upregulated the expression of tissue inhibitor of metalloproteinase (TIMP)-3 and downregulated the expression of matrix metalloproteinase (MMP)-13 and disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS)-5 in chondrocytes. Injection of SDC4 into the knee joints of OA model mice prevented articular cartilage degeneration 6 and 8 weeks postoperatively. Immunohistochemical analysis 8 weeks after SDC4 injection into the knee joint revealed decreased ADAMTS-5 expression and increased TIMP-3 expression. The results of this study suggest that the treatment of osteoarthritic articular cartilage with SDC4 inhibits cartilage degeneration.

Platelet-Rich Plasma for Knee Osteoarthritis: What Does the Evidence Say?

The utilization of platelet-rich-plasma as a therapeutic intervention for knee osteoarthritis has gained immense attention since 2008. The increase in the number of scientific publications dedicated to this area can be attributed to the majority of favorable results reported in clinical trials and basic science studies. However, despite the growing evidence, the use of platelet-rich plasma in clinical practice still poses controversial aspects. The potential mechanisms of action described for platelet-rich-plasma so far indicate that it could serve as a disease-modifying drug, acting to counteract important aspects of knee osteoarthritis pathophysiology (cartilage breakdown, inflammation, and bone remodeling). Nevertheless, its efficacy in slowing down the progression of knee osteoarthritis remains unproven. While inconsistencies have been noted, the majority of controlled clinical trials and meta-analyses advocate for the utilization of platelet-rich-plasma in treating knee osteoarthritis, as it has demonstrated greater efficacy than hyaluronic acid and placebo, with a follow-up of at least 1 year. Despite advancements made in certain areas, significant diversity persists regarding the formulations used, therapeutic regimen, extended follow-up periods, patient selection, and assessment of clinically relevant outcomes. Consequently, the leading clinical practice guidelines do not recommend its use. In light of the emerging evidence, this narrative review aims to provide an objective evaluation of the recent available scientific literature (last 5 years) focused on randomized clinical trials and meta-analyses to present a current overview of the topic.

Current Non-surgical Management of Knee Osteoarthritis

Osteoarthritis (OA) is a common chronic degenerative disease. The prevalence tends to increase with age and is influenced by underlying risk factors such as gender, obesity, joint injuries (work/sports activities), and geographic region. OA has a distinctive picture, namely, damage to the joint cartilage and the formation of new bone at the edges of the bones, also called osteophytes, due to biochemical, metabolic, physiological, and pathological changes in the joint cartilage and subchondral bone. Symptoms that can be caused include joint pain, inhibition of joint movement, crepitus, deformity, asymmetrical swelling of the joints, signs of inflammation, and changes in gait. Currently, there are various methods of managing OA in terms of reducing pain, including regeneration and non-regeneration therapy. Non-regeneration treatments include physiotherapy (exercise, biomechanical intervention, electrotherapy, diathermy), pharmacology, intra-articular injections (corticosteroids, hyaluronic acid, geniculate nerve blocks), extra-articular injections, and radiofrequency. In comparison, regeneration management includes laser and intra-articular injection (prolotherapy and PRP).

Understanding Cognitive Deficits in People with Arthritis

Cognitive deficits are commonly seen in people with arthritis. However, previous studies focused primarily on small-sized clinical samples. There is a need for cohort-based studies, which are characterized by high generalizability. In addition, these studies mainly focused on attention, memory, and executive function. However, cognition is not a single concept, but includes other cognitive domains, such as verbal fluency and arithmetic abilities. Thus, we aim to explore how arthritis can affect cognitive abilities, including episodic memory, semantic verbal fluency, fluid reasoning, and numerical ability by using a large cohort from the United Kingdom. The main findings were that people with arthritis have significantly lower immediate word recall (t(2257) = -6.40, p < 0.001, Cohen's d = -0.12, 95% C.I. = [-0.16, -0.08]), delayed word recall (t(2257) = -5.60, p < 0.001, Cohen's d = -0.11, 95% C.I. = [-0.14, -0.07]), semantic verbal fluency (t(2257) = -3.03, p < 0.01, Cohen's d = -0.06, 95% C.I. = [-0.10, -0.02]), fluid reasoning (t(2257) = -3.96, p < 0.001, Cohen's d = -0.07, 95% C.I. = [-0.11, -0.04]), and numerical ability (t(2257) = -3.85, p < 0.001, Cohen's d = -0.07, 95% C.I. = [-0.10, -0.03]) compared to what they would expect given their demographics. Interventions are needed to improve cognitive abilities in people with arthritis.

Associations between markers of inflammation and altered pain perception mechanisms in people with knee osteoarthritis: a systematic review

To provide an extensive review on the associations between knee inflammation and altered pain perception mechanisms in people with knee osteoarthritis (OA). MEDLINE, Web of Science, EMBASE and Scopus were searched up to 13 December 2022. We included articles reporting associations between knee inflammation (measured by effusion, synovitis, bone marrow lesions (BMLs) and cytokines) and signs of altered pain processing (assessed by quantitative sensory testing and/or questionnaire for neuropathic-like pain) in people with knee OA. Methodological quality was evaluated using the National Heart, Lung and Blood Institute Study Quality Assessment Tool. Level of evidence and strength of conclusion were determined using the Evidence-Based Guideline Development method. Nine studies were included, comprising of 1889 people with knee OA. Signs of greater effusion/synovitis may be positively associated with lower knee pain pressure threshold (PPT) and neuropathic-like pain. Current evidence could not establish an association between BMLs and pain sensitivity. Evidence on associations between inflammatory cytokines and pain sensitivity or neuropathic-like pain was conflicting. There are indications of a positive association between higher serum C reactive protein (CRP) levels and lower PPT and presence of temporal summation. Methodological quality varied from level C to A2. Signs of effusion/synovitis may be positively associated with neuropathic-like pain and pain sensitivity. There are indications of a possible positive association between serum CRP levels and pain sensitivity. Given the quality and the small amount of included studies, uncertainty remains. Future studies with adequate sample size and follow-up are needed to strengthen the level of evidence.PROSPERO registration number: CRD42022329245.

The Role of Ferroptosis in the Pathogenesis of Osteoarthritis

Osteoarthritis (OA) is the most common type of arthritis. Its high prevalence, especially in the elderly, and its negative impact on physical function make it a leading cause of disability in the elderly. Joint pain as well joint stiffness are the common classic signs of OA. Chondrocyte death together with loss of articular cartilage integrity are the main pathologic changes in OA. Non-steroidal anti-inflammatory drugs (NSAIDs) and glucocorticoids are commonly used for the management of OA; still, their effectiveness is limited, and no therapeutic strategy is able to fully stop OA progression. Ferroptosis is a kind of cell death, distinct from apoptosis and necroptosis, caused by iron-dependent peroxidation of membrane phospholipids that terminates cell life by disintegrating all plasma membranes. It has been suggested that ferroptosis has a critical role in decreased viability of chondrocytes in OA, and here, we review recent findings regarding the pathologic pathways that lead to chondrocyte ferroptosis, and discuss the possible therapeutic utility of ferroptosis inhibition in OA.

The Role of Tocotrienol in Arthritis Management—A Scoping Review of Literature

Arthritis is a cluster of diseases impacting joint health and causing immobility and morbidity in the elderly. Among the various forms of arthritis, osteoarthritis (OA) and rheumatoid arthritis (RA) are the most common. Currently, satisfying disease-modifying agents for arthritis are not available. Given the pro-inflammatory and oxidative stress components in the pathogenesis of arthritis, tocotrienol, a family of vitamin E with both anti-inflammatory and antioxidant properties, could be joint-protective agents. This scoping review aims to provide an overview of the effects of tocotrienol on arthritis derived from the existing scientific literature. A literature search using PubMed, Scopus and Web of Science databases was conducted to identify relevant studies. Only cell culture, animal and clinical studies with primary data that align with the objective of this review were considered. The literature search uncovered eight studies investigating the effects of tocotrienol on OA (n = 4) and RA (n = 4). Most of the studies were preclinical and revealed the positive effects of tocotrienol in preserving joint structure (cartilage and bone) in models of arthritis. In particular, tocotrienol activates the self-repair mechanism of chondrocytes exposed to assaults and attenuates osteoclastogenesis associated with RA. Tocotrienol also demonstrated strong anti-inflammatory effects in RA models. The single clinical trial available in the literature showcases that palm tocotrienol could improve joint function among patients with OA. In conclusion, tocotrienol could be a potential anti-arthritic agent pending more results from clinical studies.

The Interaction between Carbon Monoxide and Hydrogen Sulfide during Chronic Joint Pain in Young Female Mice

A relationship between carbon monoxide (CO) and hydrogen sulfide (H2S) has been described in different pathological conditions, but their interaction in modulating joint pain has not yet been investigated. In young female mice with monosodium acetate-induced joint degeneration and pain, we assessed: (1) the effects of CORM-2 (tricarbonyldichlororuthenium(II)dimer), a CO-releasing molecule, and CoPP (cobalt protoporphyrin IX), an inducer of heme oxygenase 1 (HO-1), administered alone and combined with low doses of two slow-releasing H2S donors, DADS (diallyl disulfide) and GYY4137 (morpholin-4-ium 4-methoxyphenyl(morpholino) phosphinodithioate dichloromethane complex) on the mechanical allodynia and loss of grip strength provoked by joint degeneration; (2) the role of Nrf2, NAD(P)H: quinone oxidoreductase 1 (NQO1) and HO-1 in the antinociceptive actions of H2S donors; (3) the impact of DADS and GYY4137 treatment on the expression of Nrf2 and several antioxidant proteins in dorsal root ganglia (DRG) and periaqueductal gray matter (PAG). Our data showed that treatment with H2S donors inhibited allodynia and functional deficits, while CORM-2 and CoPP only prevented allodynia. The Nrf2 pathway is implicated in the analgesic actions of DADS and GYY4137 during joint degeneration. Moreover, the co-administration of low doses of CORM-2 or CoPP with DADS or GYY4137 produced higher antiallodynic effects and greater recovery of grip strength deficits than those produced by each of these compounds alone. The activation of the antioxidant system caused by H2S donors in DRG and/or PAG might explain the enhancement of antinociceptive effects. These data reveal a positive interaction between H2S and CO in modulating joint pain in female mice.