Update on novel pharmacological therapies for osteoarthritis

2023 EULAR classification criteria for hand osteoarthritis

OBJECTIVES

The objective of this study is to develop classification criteria for overall hand osteoarthritis (OA), interphalangeal OA and thumb base OA based on self-reported data and radiographic features.

METHODS

The classification criteria sets were developed in three phases. In phase 1, we identified criteria that discriminated hand OA from controls. In phase 2, we used a consensus-based decision analysis approach to derive a clinician-based evaluation of the relative importance of the criteria. In phase 3, we refined the scoring system, determined the cut-offs for disease classification and compared the sensitivity and specificity of the European Alliance of Associations for Rheumatology (EULAR) criteria with the 1990 American College of Rheumatology (ACR) criteria.

RESULTS

In persons with hand symptoms and no other disease (including psoriasis) or acute injury that can explain the hand symptoms (mandatory criteria), hand OA can be classified based on age, duration of morning stiffness, number of joints with osteophytes and joint space narrowing, and concordance between symptoms and radiographic findings. Using a sum of scores based on each diagnostic element, overall hand OA can be classified if a person achieves 9 or more points on a 0-15 scale. The cut-off for interphalangeal OA and thumb base OA is 8 points. While the EULAR criteria demonstrated better sensitivity than the ACR criteria in the phase 1 data set, the performance of the two criteria sets was similar in two external cohorts.

CONCLUSIONS

International experts developed the EULAR criteria to classify overall hand OA, interphalangeal OA and thumb base OA in clinical studies using a rigorous methodology.

Pathogenic Mechanisms and Therapeutic Approaches in Obesity-Related Knee Osteoarthritis

The knee is the joint most frequently involved in osteoarthritis, a common joint disorder in the adult population that is associated with significant chronic joint pain, reduced mobility and quality of life. Recent studies have established an association between obesity and the development of knee osteoarthritis that goes beyond the increased mechanical load on the knees as weight-bearing joints. This link is based on the maintenance of a chronic low-grade inflammation, altered secretion of adipokines by the adipose tissue and development of sarcopenia. Major adipokines involved in the pathogenesis of obesity-related knee osteoarthritis include adiponectin, which appears to have a protective effect, as well as leptin, resistin and visfatin, which are associated with higher pain scores and more severe structural damage. Joint pain in knee osteoarthritis may be both nociceptive and neuropathic and is the result of complex mechanisms driven by nerve growth factor, calcitonin gene-related peptide and pro-inflammatory cytokines. The role of endogenous cannabinoids and gut microbiota in common mechanisms between obesity and knee pain has recently been studied. The aim of the present review is to highlight major pathogenic mechanisms in obesity-related knee osteoarthritis with special attention on pain and to comment on possible therapeutic approaches.

Angelica sinensis polysaccharide improves mitochondrial metabolism of osteoarthritis chondrocytes through PPARγ/SOD2/ROS pathways

Osteoarthritis (OA) is a common degenerative joint disease, which is characterized by wear of articular cartilage and narrow joint space, resulting in joint movement disorder. At present, accurate molecular mechanisms and effective interventions are still being explored. Here, we propose that angelica sinensis polysaccharide (ASP) alleviates OA progression by activating peroxisome proliferator-activated receptor gamma (PPARγ). Therapeutic effect of ASP improving mitochondrial metabolism of OA chondrocytes was evaluated in vitro and in vivo, respectively. During cell experiments, the concentration and time response of tert butyl hydroperoxide (TBHP) and ASP were determined by cell viability. Apoptosis was detected by flow cytometry. Mitochondrial metabolism was detected by reactive oxygen species (ROS), mitochondrial membrane potential (MMP), release of cytochrome C, adenosine triphosphate (ATP) production, and superoxide dismutase 2 (SOD2) activity. Expressions of Aggrecan, collagen type II (Col2a1), PPARγ, and SOD2 were detected by qRT-PCR and western blot. In animal experiments, we detected cell apoptosis and target protein expression separately through terminal deoxynucleotidyl transferase dUTP nick end-labeling (TUNEL) staining and immunohistochemistry. Pretreatment of ASP significantly activated PPARγ and SOD2 in rat chondrocytes incubated with TBHP, cleared ROS, improved mitochondrial metabolism, increased chondrocytes viability, and alleviated chondrocytes apoptosis. In vivo, the administration of ASP could effectively ameliorate cartilage degeneration in OA rats, promote extracellular matrix synthesis, and decelerate the progress of OA. Our research identifies the role of ASP in mitochondrial metabolism of OA chondrocytes through PPARγ/SOD2/ROS pathways, which provides a new idea for the treatment of OA.

Mapping the neuroethological signatures of pain, analgesia, and recovery in mice

Ongoing pain is driven by the activation and modulation of pain-sensing neurons, affecting physiology, motor function, and motivation to engage in certain behaviors. The complexity of the pain state has evaded a comprehensive definition, especially in non-verbal animals. Here, in mice, we used site-specific electrophysiology to define key time points corresponding to peripheral sensitivity in acute paw inflammation and chronic knee pain models. Using supervised and unsupervised machine learning tools, we uncovered sensory-evoked coping postures unique to each model. Through 3D pose analytics, we identified movement sequences that robustly represent different pain states and found that commonly used analgesics do not return an animal's behavior to a pre-injury state. Instead, these analgesics induce a novel set of spontaneous behaviors that are maintained even after resolution of evoked pain behaviors. Together, these findings reveal previously unidentified neuroethological signatures of pain and analgesia at heightened pain states and during recovery.

New Formulation of Platelet-Rich Plasma Enriched in Platelet and Extraplatelet Biomolecules Using Hydrogels

Platelet-rich plasma (PRP) is an autologous biologic product used in several fields of medicine for tissue repair due to the regenerative capacity of the biomolecules of its formulation. PRP consists of a plasma with a platelet concentration higher than basal levels but with basal levels of any biomolecules present out of the platelets. Plasma contains extraplatelet biomolecules known to enhance its regenerative properties. Therefore, a PRP containing not only a higher concentration of platelets but also a higher concentration of extraplatelet biomolecules that could have a stronger regenerative performance than a standard PRP. Considering this, the aim of this work is to develop a new method to obtain PRP enriched in both platelet and extraplatelet molecules. The method is based on the absorption of the water of the plasma using hydroxyethyl acrylamide (HEAA)-based hydrogels. A plasma fraction obtained from blood, containing the basal levels of platelets and proteins, was placed in contact with the HEAA hydrogel powder to absorb half the volume of the water. The resulting plasma was characterized, and its bioactivity was analyzed in vitro. The novel PRP (nPRP) showed a platelet concentration and platelet derived growth factor (PDGF) levels similar to the standard PRP (sPRP), but the concentration of the extraplatelet growth factors IGF-1 (p < 0.0001) and HGF (p < 0.001) were significantly increased. Additionally, the cells exposed to the nPRP showed increased cell viability than those exposed to a sPRP in human dermal fibroblasts (p < 0.001) and primary chondrocytes (p < 0.01). In conclusion, this novel absorption-based method produces a PRP with novel characteristics compared to the standard PRPs, with promising in vitro results that could potentially trigger improved tissue regeneration capacity.

Intra-articular delivery of micronized dehydrated human amnion/chorion membrane reduces degenerative changes after onset of post-traumatic osteoarthritis

Background: Micronized dehydrated human amnion/chorion membrane (mdHACM) has reduced short term post-traumatic osteoarthritis (PTOA) progression in rats when delivered 24 h after medial meniscal transection (MMT) and is being investigated for clinical use as a disease modifying therapy. Much remains to be assessed, including its potential for longer-term therapeutic benefit and treatment effects after onset of joint degeneration. Objectives: Characterize longer-term effects of acute treatment with mdHACM and determine whether treatment administered to joints with established PTOA could slow or reverse degeneration. Hypotheses: Acute treatment effects will be sustained for 6 weeks, and delivery of mdHACM after onset of joint degeneration will attenuate structural osteoarthritic changes. Methods: Rats underwent MMT or sham surgery (left leg). mdHACM was delivered intra-articularly 24 h or 3 weeks post-surgery (n = 5-7 per group). Six weeks post-surgery, animals were euthanized and left tibiae scanned using equilibrium partitioning of an ionic contrast agent microcomputed tomography (EPIC-µCT) to structurally quantify joint degeneration. Histology was performed to examine tibial plateau cartilage. Results: Quantitative 3D µCT showed that cartilage structural metrics (thickness, X-ray attenuation, surface roughness, exposed bone area) for delayed mdHACM treatment limbs were significantly improved over saline treatment and not significantly different from shams. Subchondral bone mineral density and thickness for the delayed treatment group were significantly improved over acute treated, and subchondral bone thickness was not significantly different from sham. Marginal osteophyte degenerative changes were decreased with delayed mdHACM treatment compared to saline. Acute treatment (24 h post-surgery) did not reduce longer-term joint tissue degeneration compared to saline. Histology supported µCT findings and further revealed that while delayed treatment reduced cartilage damage, chondrocytes displayed qualitatively different morphologies and density compared to sham. Conclusion: This study provides insight into effects of intra-articular delivery timing relative to PTOA progression and the duration of therapeutic benefit of mdHACM. Results suggest that mdHACM injection into already osteoarthritic joints can improve joint health, but a single, acute mdHACM injection post-injury does not prevent long term osteoarthritis associated with meniscal instability. Further work is needed to fully characterize the durability of therapeutic benefit in stable osteoarthritic joints and the effects of repeated injections.

Effectiveness and Safety of Glucosamine in Osteoarthritis: A Systematic Review

Knee osteoarthritis is the most popular type of osteoarthritis that causes extreme pain in the elderly. Currently, there is no cure for osteoarthritis. To lessen clinical symptoms, glucosamine was suggested. The primary goal of our systematic review study is to evaluate the effectiveness and safety of glucosamine based on recent studies. Electronic databases such as PubMed, Scopus, and Cochrane were used to assess the randomized controlled trial (RCT). From the beginning through March 2023, the papers were checked, and if they fulfilled the inclusion criteria, they were then examined. The Western Ontario and McMaster Universities Osteoarthritis (WOMAC) and Visual Analog Scale (VAS) scales were considered the main outcome measures. A total of 15 studies were selected. Global pain was significantly decreased in comparison to placebo, as measured by the VAS index, with an overall effect size of standardized mean difference (SMD) of -7.41 ([95% CI] 14.31, 0.51). The WOMAC scale confirmed that pain, stiffness, and physical function had improved, however the effects were insufficient. A statistical update also revealed that there were no reports of serious medication interactions or significant adverse events. To summarize, glucosamine is more effective than a placebo at reducing pain in knee osteoarthritis patients. In long-term treatment, oral glucosamine sulfate 1500 mg/day is believed to be well tolerated.

Tetrandrine Represses Inflammation and Attenuates Osteoarthritis by Selective Inhibition of COX-2

OBJECTIVE

There is a lack of effective and long-term safe drugs for the treatment of osteoarthritis (OA). Tetrandrine (Tet) has been approved and used to treat rheumatoid arthritis for several decades, but its effect on OA has not been investigated. Herein, we explored the effect of Tet on OA and its underlying mechanism.

METHODS

OA was induced using destabilization of the medial meniscus (DMM) in C57BL/6J mice. The animals were randomly divided into sham, DMM, Tet, celecoxib (CXB), and indomethacin (INDO) groups. Each group was given solvent or corresponding drugs by gavage for 7 weeks after convalescence. Pathological staining, OARSI scores, micro-computed tomography and behavior tests were performed to evaluate the effects of Tet.

RESULTS

Tet remarkably alleviated cartilage injury in the knee joint, limited bone remodeling in the subchondral bone, and delayed progression of OA. Tet also significantly relieved joint pain and maintained function. Further mechanistic studies revealed that Tet lowered inflammatory cytokine levels and selectively suppressed gene and protein expression of cyclooxygenase (COX)-2 but not COX-1 (P<0.01). Tet also reduced the production of prostaglandin E2 without damaging the gastric mucosa.

CONCLUSION

We found that Tet could selectively inhibit COX-2 gene expression and decrease cytokine levels in mice, thus reducing inflammation and improving OA without obvious gastric adverse events. These results provide a scientific basis for the clinical application of Tet in the treatment of OA.

The Effect of CaV1.2 Inhibitor Nifedipine on Chondrogenic Differentiation of Human Bone Marrow or Menstrual Blood-Derived Mesenchymal Stem Cells and Chondrocytes

Cartilage is an avascular tissue and sensitive to mechanical trauma and/or age-related degenerative processes leading to the development of osteoarthritis (OA). Therefore, it is important to investigate the mesenchymal cell-based chondrogenic regenerating mechanisms and possible their regulation. The aim of this study was to investigate the role of intracellular calcium (iCa2+) and its regulation through voltage-operated calcium channels (VOCC) on chondrogenic differentiation of mesenchymal stem/stromal cells derived from human bone marrow (BMMSCs) and menstrual blood (MenSCs) in comparison to OA chondrocytes. The level of iCa2+ was highest in chondrocytes, whereas iCa2+ store capacity was biggest in MenSCs and they proliferated better as compared to other cells. The level of CaV1.2 channels was also highest in OA chondrocytes than in other cells. CaV1.2 antagonist nifedipine slightly suppressed iCa2+, Cav1.2 and the proliferation of all cells and affected iCa2+ stores, particularly in BMMSCs. The expression of the CaV1.2 gene during 21 days of chondrogenic differentiation was highest in MenSCs, showing the weakest chondrogenic differentiation, which was stimulated by the nifedipine. The best chondrogenic differentiation potential showed BMMSCs (SOX9 and COL2A1 expression); however, purposeful iCa2+ and VOCC regulation by blockers can stimulate a chondrogenic response at least in MenSCs.

Regulation and therapy, the role of JAK2/STAT3 signaling pathway in OA: a systematic review

Osteoarthritis (OA) is a multifactorial chronic disease primarily characterized by the degeneration of articular cartilage. Currently, there is a lack of effective treatments for OA other than surgery. The exploration of the mechanisms of occurrence is important in exploring other new and effective treatments for OA. The current evidence shows that the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway plays a vital role in cytogenesis and is involved in OA progression. The terms "JAK2", "STAT3", and "Osteoarthritis"were used in a comprehensive literature search in PubMed to further investigate the relationship between the JAK2/STAT3 signaling pathway and OA. This review focuses on the role and mechanism of JAK2/STAT3 signaling in cartilage degradation, subchondral bone dysfunction, and synovial inflammation. In addition, this review summarizes recent evidence of therapeutic approaches to treat OA by targeting the JAK2/STAT3 pathway to accelerate the translation of evidence into the progression of strategies for OA treatment. Video abstract.

Human Cartilage Biomechanics: Experimental and Theoretical Approaches towards the Identification of Mechanical Properties in Healthy and Osteoarthritic Conditions

Articular cartilage is a complex connective tissue with the fundamental functions of load bearing, shock absorption and lubrication in joints. However, traumatic events, aging and degenerative pathologies may affect its structural integrity and function, causing pain and long-term disability. Osteoarthritis represents a health issue, which concerns an increasing number of people worldwide. Moreover, it has been observed that this pathology also affects the mechanical behavior of the articular cartilage. To better understand this correlation, the here proposed review analyzes the physiological aspects that influence cartilage microstructure and biomechanics, with a special focus on the pathological changes caused by osteoarthritis. Particularly, the experimental data on human articular cartilage are presented with reference to different techniques adopted for mechanical testing and the related theoretical mechanical models usually applied to articular cartilage are briefly discussed.

Proximal Interphalangeal Arthrodesis in Horses: A Meta-Analysis of Retrospective Studies

The aim of this study was to determine the clinical outcomes reported in retrospective studies of proximal interphalangeal arthrodesis (PIA) in horses through a meta-analysis of retrospective studies. CAB Abstracts, PubMed, ScienceDirect, Web of Science, and Scopus were searched. The primary outcomes included survival and surgical site infection (SSI) rates, return to activities, and time of hospital stay and casting. Subgroups were formed for fractures and other conditions. Meta-analyses were performed with fixed and random effects models to estimate proportions, mean values, and effect size by odds ratio (OR) with 95% confidence intervals (CI). Twenty-one full articles were included, totaling 458 horses. The survival rate was 90% (95% CI [86%-93%]), return to activities was 65% (95% CI [61%-70%]), and SSI was 12% (95% CI [8%-16%]). The mean hospitalization was 25 days (95% CI [18-35 days]) and time of casting was 29 days (95% CI [21-42 days]). The OR of survival (P = .769), return to activities (P = .576), and SSI (P = .467) were similar between cases of fractures and other conditions. PIA is an efficient and safe method to treat injuries in the pastern region, with a high survival rate and low SSI. However, the rate of return to soundness for intended use was modest, being potentially lower for fracture cases. Thus, investigations of more efficient interventions are needed to improve this outcome.

MMP-2 Silencing through siRNA Loaded Positively-Charged Nanoparticles (AcPEI-NPs) Counteracts Chondrocyte De-Differentiation

The abnormal matrix remodeling process, as well as inflammation, angiogenesis, and tumor metastasis, are related to an increase in the synthesis and secretion of matrix metalloproteinases (MMPs), the zinc-dependent proteolytic endopeptidases. Recent studies have evidenced MMPs' role in osteoarthritis (OA) development, during which chondrocytes undergo hypertrophic differentiation and exhibit enhanced catabolism. The trait of OA is extracellular matrix (ECM) progressive degradation regulated by many factors, in which MMPs play an important role, which indicates them as potential therapeutic targets. Herein, a small interfering RNA (siRNA) delivery system able to suppress MMPs' activity was synthetized. Results demonstrated that positively charged nanoparticles (AcPEI-NPs) complexed with MMP-2 siRNA are efficiently internalized by cells with endosomal escape. Moreover, avoiding lysosome degradation, MMP2/AcPEI nanocomplex increases nucleic acid delivery efficiency. Gel zymography, RT-PCR, and ELISA analyses confirmed MMP2/AcPEI nanocomplex activity even when embedded within collagen matrix resembling the natural extracellular matrix. Further, the inhibition of in vitro collagen degradation exerts a protective effect on chondrocyte dedifferentiation. The suppression of MMP-2 activity, preventing matrix degradation, protects chondrocytes against degeneration and supporting ECM homeostasis in articular cartilage. These encouraging results promote further investigation to validate the utilization of MMP-2 siRNA as ''molecular switch'' able to counteract osteoarthritis.

Quercetin prevents osteoarthritis progression possibly via regulation of local and systemic inflammatory cascades

Due to the lack of effective treatments, osteoarthritis (OA) remains a challenge for clinicians. Quercetin, a bioflavonoid, has shown potent anti-inflammatory effects. However, its effect on preventing OA progression and the underlying mechanisms are still unclear. In this study, Sprague-Dawley male rats were divided into five groups: control group, OA group (monosodium iodoacetate intra-articular injection), and three quercetin-treated groups. Quercetin-treated groups were treated with intragastric quercetin once a day for 28 days. Gross observation and histopathological analysis showed cartilage degradation and matrix loss in the OA group. High-dose quercetin-group joints showed failure in OA progression. High-dose quercetin inhibited the OA-induced expression of MMP-3, MMP-13, ADAMTS4, and ADAMTS5 and promoted the OA-reduced expression of aggrecan and collagen II. Levels of most inflammatory cytokines and growth factors tested in synovial fluid and serum were upregulated in the OA group and these increases were reversed by high-dose quercetin. Similarly, subchondral trabecular bone was degraded in the OA group and this effect was reversed in the high-dose quercetin group. Our findings indicate that quercetin has a protective effect against OA development and progression possibly via maintaining the inflammatory cascade homeostasis. Therefore, quercetin could be a potential therapeutic agent to prevent OA progression in risk groups.

Long-term results of synovectomy in total knee arthroplasty: a prospective, randomized controlled trial

BACKGROUND

Synovectomy has been introduced into total knee arthroplasty (TKA) with the aim of relieving pain and inflammation of the synovium. However, there are no long-term, comparative data to evaluate the effect of synovectomy in TKA. This study was aimed at assessing pain, function, and complications in patients undergoing synovectomy during TKA for osteoarthritis (OA) at long-term follow-up.

METHODS

This was a prospective randomized controlled trial of 42 consecutive patients who underwent staged bilateral TKA. Patients undergoing the first-side TKA were allocated to receive TKA with or without synovectomy followed by a 3-month washout period and crossover to the other strategy for the opposite-side TKA. The overall efficacy of both strategies was evaluated by determination of blood loss, the Knee Society score (KSS), and knee inflammation conditions during a 3-month postoperative period. The postoperative pain, range of motion (ROM), and complications were sequentially evaluated to compare the two groups until 10 years after surgery.

RESULTS

At the 10-year follow-up, both groups had a similarly significantly improved ROM (114.88 ± 9.84° vs. 114.02 ± 9.43°, t  = 0.221, P  = 0.815) and pain relief with no differences between the two groups (1.0 [1.0] vs. 1.0 [1.5], U  = 789.500, P  = 0.613). Similar changes in total blood loss, KSS, and knee inflammation were found in both groups during 3 months postoperatively ( P  > 0.05). Additionally, there was no significant difference regarding complications and satisfaction between the two groups ( P  > 0.05).

CONCLUSIONS

Synovectomy in conjunction with TKA for primary OA does not seem to provide any benefit regarding postoperative pain, ROM, and satisfaction during a 10-year follow-up. In addition, it may not result in more blood loss and increased incidence of long-term complications. Based on our long-term findings, it should not be performed routinely.

TRIAL REGISTRATION

Chinese Clinical Trial Registry, ChiCTR-INR-16008245; https://www.chictr.org.cn/showproj.aspx?proj=13334 .

MIA/CD-RAP Regulates MMP13 and Is a Potential New Disease-Modifying Target for Osteoarthritis Therapy

Melanoma inhibitory activity/cartilage-derived retinoicacid-sensitive protein (MIA/CD-RAP) is a protein expressed and secreted by chondrocytes and cartilaginous tissues. MIA/CD-RAP-deficient mice develop milder osteoarthritis than wildtype mice. In this study, we investigated MIA/CD-RAP downstream targets to explain this reduced disease development. As a possible mediator, we could detect matrix metalloproteinase 13 (MMP13), and the influence of MIA/CD-RAP on MMP13 regulation was analyzed in vitro using SW1353 chondrosarcoma cells and primary chondrocytes. The femoral head cartilage of WT and MIA/CD-RAP -/- mice were cultured ex vivo to further investigate MMP13 activity. Finally, osteoarthritis was surgically induced via DMM in C57BL/6 mice, and the animals were treated with an MIA/CD-RAP inhibitory peptide by subcutaneously implanted pellets. MMP13 was regulated by MIA/CD-RAP in SW1353 cells, and MIA/CD-RAP -/- murine chondrocytes showed less expression of MMP13. Further, IL-1β-treated MIA/CD-RAP -/- chondrocytes displayed less MMP13 expression and activity. Additionally, MIA/CD-RAP-deficient ex vivo cultured cartilage explants showed less MMP13 activity as well as reduced cartilage degradation. The mice treated with the MIA/CD-RAP inhibitory peptide showed less osteoarthritis development. Our findings revealed MIA/CD-RAP as a new regulator of MMP13 and highlighted its role as a potential new target for osteoarthritis therapy.

An update on the use of conventional and biological disease-modifying anti-rheumatic drugs in hand osteoarthritis

Osteoarthritis (OA) is a highly prevalent condition worldwide associated with pain, progressive disability, reduced participation in social activities, and impaired quality of life. Despite its growing burden, the therapeutic options are still limited and almost exclusively addressed to symptoms' management, while no disease-modifying OA drugs able to prevent or retard disease progression are actually available. For these reasons, in the last decades, relevant efforts to find new potential therapeutic targets in OA have been made and a number of existing conventional and biological disease-modifying anti-rheumatic drugs (DMARDs), including hydroxychloroquine (HCQ), methotrexate (MTX), tumor necrosis factor (TNF)-α, interleukin (IL)-1, and IL-6 inhibitors, commonly used to treat inflammatory rheumatic diseases, have been repurposed for the treatment of OA and explored also in hand osteoarthritis (HOA). The current narrative review was aimed to provide a comprehensive and updated understanding of the possibilities and the criticisms related to the treatment of HOA with conventional and biological DMARDs. Unfortunately, therapy with conventional and biologic drugs in HOA has not achieved the expected success, despite a rationale for their use exists. Thus, our findings outline the urgent need to enhance the exploration of HOA basic molecular mechanisms to find new potential therapeutic targets, personalized for each patient, and appropriate for the different subsets of HOA and for the different phases of disease.

Chondroitin sulfate modified chitosan nanoparticles as an efficient and targeted gene delivery vehicle to chondrocytes

Conventional treatments for osteoarthritis (OA), including drug delivery and tissue engineering approaches, could not offer a high yield of cartilage repair due to the compact and exclusive structure of cartilage. Targeted and high-efficiency delivery of gene sequences is necessary to rebalance the lost homeostatic properties of the cartilage in OA. Herein, we synthesized chitosan (CH)-chondroitin sulfate (CS) nanoparticles (NPs) as a platform for delivering gene sequences. These new nanoparticles benefit from two natural polymers that minimize the toxicity, and the presence of CS can be in favor of targeted delivery. The CAG-GFP plasmid was used as a gene sequence model, and the nanoparticles could successfully encapsulate approximately all of them in their structure. Loaded nanoparticles were characterized in terms of morphology, size, zeta potential, the efficiency of encapsulation and, DNA release pattern. Cell viability and uptake of new nanoparticles were compared to the chitosan nanoparticles and Lipofectamine. After substituting TPP with CS, NPs exhibited a significant decrease in size. In addition, there was little difference in zeta potential between nanoparticles. Furthermore, a tremendous increase in plasmid uptake and cell viability was observed by CH-CS NPs compared to CH-TPP NPs and Lipofectamine. In the final stage, the knockdown level of MMP13 was evaluated with real-time RT-PCR for confirming the potential uptake of CH-CS NPs. The results revealed cellular uptake of siRNA loaded NPs and effective knockdown of MMP13 in chondrocytes. In conclusion, CH-CS nanoparticles can be considered as a candidate for gene therapy purposes in cartilage diseases.

Progress in Composite Hydrogels and Scaffolds Enriched with Icariin for Osteochondral Defect Healing

Osteochondral structure reconstruction by tissue engineering, a challenge in regenerative medicine, requires a scaffold that ensures both articular cartilage and subchondral bone remodeling. Functional hydrogels and scaffolds present a strategy for the controlled delivery of signaling molecules (growth factors and therapeutic drugs) and are considered a promising therapeutic approach. Icariin is a pharmacologically-active small molecule of prenylated flavonol glycoside and the main bioactive flavonoid isolated from Epimedium spp. The in vitro and in vivo testing of icariin showed chondrogenic and ostseoinductive effects, comparable to bone morphogenetic proteins, and suggested its use as an alternative to growth factors, representing a low-cost, promising approach for osteochondral regeneration. This paper reviews the complex structure of the osteochondral tissue, underlining the main aspects of osteochondral defects and those specifically occurring in osteoarthritis. The significance of icariin’s structure and the extraction methods were emphasized. Studies revealing the valuable chondrogenic and osteogenic effects of icariin for osteochondral restoration were also reviewed. The review highlighted th recent state-of-the-art related to hydrogels and scaffolds enriched with icariin developed as biocompatible materials for osteochondral regeneration strategies.

A review of osteoarthritis signaling intervention using small-molecule inhibitors

Numerous small-molecule inhibitors (SMIs) have been approved as adjuvant or first-line therapies for malignancies. Based on cancer treatment using SMIs, next-generation SMIs that can be used to optimize the therapeutic index, overcome drug resistance, and establish combination therapies are in development. Osteoarthritis (OA) is the most common chronic joint disease with senescence, and there are various approaches to OA treatment; however, the gold standard treatment is controversial. Therefore, in this manuscript, we demonstrated the potential of using SMIs in OA treatment and described the general strategies for using SMIs in OA treatment.

Theaflavin-3,3 ′ -Digallate Protects Cartilage from Degradation by Modulating Inflammation and Antioxidant Pathways

Background

Osteoarthritis (OA) is a common degenerative joint disease that may be closely linked to inflammation and oxidative stress destroying the balance of cartilage matrix. Theaflavin-3,3′-digallate (TFDG), a natural substance derived from black tea, has been reported to restrict the activity of inflammatory cytokines and effectively eliminate reactive oxygen species (ROS) in various diseases. However, it is not clear whether TFDG can improve OA.

Methods

Chondrocytes were treated with or without IL-1β and 20 μM and 40 μM TFDG. The effect of TFDG on the proliferation of chondrocytes was detected by CCK8. RT-qPCR was used to detect the gene expression of inflammatory factors, extracellular matrix synthesis, and degradation genes. Western blot and immunofluorescence assays were used to detect the protein expression. The fluorescence intensity of reactive oxygen species labeled by DCFH-DA was detected by flow cytometry. We established an OA rat model by performing destabilized medial meniscus (DMM) surgery to observe whether TFDG can protect chondrocytes under arthritis in vivo.

Results

TFDG was found to inhibit proinflammatory factors (IL-6, TNF-α, iNOS, and PGE) and matrix-degrading enzymes (MMP13, MMP3, and ADAMTS5) expression and protected extracellular matrix components of chondrocytes (ACAN, COL2, and SOX9). TFDG accelerated the scavenging of ROS caused by IL-1β according to the Nrf2 signaling pathway activation. At the same time, TFDG suppressed the PI3K/AKT/NF-κB and MAPK signaling pathways to delay the inflammatory process. The cartilage of DMM rats receiving TFDG showed lower Osteoarthritis Research Society International (OARSI) scores and expressed higher levels of COL2 and Nrf2 compared with those of rats in the DMM group.

Conclusion

TFDG could protect cartilage from degradation and alleviate osteoarthritis in rats, which suggests that TFDG has potential as a drug candidate for OA therapy.

High-Efficiency Treatment for Osteoarthritis via Self-Assembled Dual-Functionalized Nanobiologics

Osteoarthritis (OA) is a progressive joint disease that has a complex pathogenesis and lacks effective drugs. OA develops with cartilage degeneration and inflammation, thus synthesizing a drug with both anti-inflammatory properties and cartilage-repair capacity provides a promising treatment strategy. Therefore, in this study, we report self-assembled nanobiologics composed of an engineered recombinant IL-1 receptor antagonist (IL-1Ra) chimeric protein with chondroitin sulfate (CS). The nanobiologics, termed ICN, exhibit extraordinary biocompatibility, low immunogenicity, and good bioefficacy. Furthermore, our study revealed that ICN significantly reduced cartilage degradation, inhibited synovial inflammation, and suppressed osteophyte formation in OA rat models. The excellent therapeutic effects on OA can be attributed to the synergistic anti-inflammatory and cartilage-repair properties of ICN's constituents. Thus, our novel strategy offers insights into the development of drugs for OA treatment and research on nanobiomedicine, which can also be adapted for other diseases with similar pathologies.

Tissue catabolism and donor-specific dexamethasone response in a human osteochondral model of post-traumatic osteoarthritis

Background

Post-traumatic osteoarthritis (PTOA) does not currently have clinical prognostic biomarkers or disease-modifying drugs, though promising candidates such as dexamethasone (Dex) exist. Many challenges in studying and treating this disease stem from tissue interactions that complicate understanding of drug effects. We present an ex vivo human osteochondral model of PTOA to investigate disease effects on cartilage and bone homeostasis and discover biomarkers for disease progression and drug efficacy.

Methods

Human osteochondral explants were harvested from normal (Collins grade 0–1) ankle talocrural joints of human donors (2 female, 5 male, ages 23–70). After pre-equilibration, osteochondral explants were treated with a single-impact mechanical injury and TNF-α, IL-6, and sIL-6R ± 100 nM Dex for 21 days and media collected every 2–3 days. Chondrocyte viability, tissue DNA content, and glycosaminoglycan (sGAG) percent loss to the media were assayed and compared to untreated controls using a linear mixed effects model. Mass spectrometry analysis was performed for both cartilage tissue and pooled culture medium, and the statistical significance of protein abundance changes was determined with the R package limma and empirical Bayes statistics. Partial least squares regression analyses of sGAG loss and Dex attenuation of sGAG loss against proteomic data were performed.

Results

Injury and cytokine treatment caused an increase in the release of matrix components, proteases, pro-inflammatory factors, and intracellular proteins, while tissue lost intracellular metabolic proteins, which was mitigated with the addition of Dex. Dex maintained chondrocyte viability and reduced sGAG loss caused by injury and cytokine treatment by 2/3 overall, with donor-specific differences in the sGAG attenuation effect. Biomarkers of bone metabolism had mixed effects, and collagen II synthesis was suppressed with both disease and Dex treatment by 2- to 5-fold. Semitryptic peptides associated with increased sGAG loss were identified. Pro-inflammatory humoral proteins and apolipoproteins were associated with lower Dex responses.

Conclusions

Catabolic effects on cartilage tissue caused by injury and cytokine treatment were reduced with the addition of Dex in this osteochondral PTOA model. This study presents potential peptide biomarkers of early PTOA progression and Dex efficacy that can help identify and treat patients at risk of PTOA.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13075-022-02828-4.

Miya Improves Osteoarthritis Characteristics via the Gut-Muscle-Joint Axis According to Multi-Omics Analyses

Background: The gut microbiota is associated with osteoarthritis (OA) progression. Miya (MY) is a product made from Clostridium butyricum, a member of gut microbiota. This study was conducted to investigate the effects of MY on OA and its underlying mechanisms.

Methods: An OA rat model was established, and MY was used to treat the rats for 4 weeks. Knee joint samples from the rats were stained with hematoxylin-eosin, and fecal samples from the OA and OA+MY groups were subjected to 16S rDNA sequencing and metabolomic analysis. The contents of succinate dehydrogenase and muscle glycogen in the tibia muscle were determined, and related genes and proteins were detected using quantitative reverse transcription polymerase chain reaction and western blotting.

Results: Hematoxylin and eosin staining showed that treatment with MY alleviated the symptoms of OA. According to the sequencing results, MY significantly increased the Chao1, Shannon, and Pielou evenness values compared to those in the untreated group. At the genus level, the abundances of Prevotella, Ruminococcus, Desulfovibrio, Shigella, Helicobacter, and Streptococcus were higher in the OA group, whereas Lactobacillus, Oscillospira, Clostridium, and Coprococcus were enriched after MY treatment. Metabolomic analysis revealed 395 differentially expressed metabolites. Additionally, MY treatment significantly increased the succinate dehydrogenase and muscle glycogen contents in the muscle caused by OA (p > 0.05). Finally, AMPK, Tfam, Myod, Ldh, Chrna1, Chrnd, Rapsyn, and Agrin were significantly downregulated in the muscles of OA mice, whereas Lcad, Mcad, and IL-1β were upregulated; MY significantly reversed these trends induced by OA.

Conclusions: MY may promote the repair of joint damage and protect against OA via the gut-muscle-joint axis.

Glucosamine as a Treatment for Osteoarthritis: What If It's True?

No disease-modifying treatments are currently available for osteoarthritis (OA). While many therapeutic approaches are now being investigated it is ethical to resort to alternative solutions as that we already possess. There are many reasons for thinking that, at sufficiently high doses, glucosamine (GlcN) sulphate possesses a clinically relevant effect on OA pain. Wide inter-individual variations in the symptomatic effects of GlcN are explained by the extreme variability of its bioavailability. In studies evaluating its structure-modifying effect, GlcN was more effective than placebo in reducing the rate of joint space narrowing in patients with knee OA. More recent data suggest that GlcN may be effective in the primary prevention of OA in sportsmen. There is no controversy concerning the safety of GlcN which does not differ to that of placebo. Several studies have recently revealed an unexpected effect of GlcN on cardiovascular mortality. After adjusting for confounding factors, the regular consumption of GlcN correlated with a 27% reduction in mortality and a 58% reduction in deaths from cardiovascular causes. These data confirm animal studies demonstrating a protective effect of GlcN against cancer and cardiovascular diseases due to modulation of the O-GlcNAcylation pathway. Disorders in O-GlcNAcylation are involved in diabetes, obesity and cancers, which all feature chronic low-grade inflammation (CLGI). By regulating CLGI, GlcN may be beneficial to the symptoms of OA, its outcome and to that of the concomitant chronic pathologies, making GlcN as a valuable candidate for the treatment of OA in patients with metabolic syndrome, diabetes or cardiovascular diseases.

Association Between Gut Microbiota and Osteoarthritis: A Review of Evidence for Potential Mechanisms and Therapeutics

Osteoarthritis (OA) is a multifactorial joint disease characterized by degeneration of articular cartilage, which leads to joints pain, disability and reduced quality of life in patients with OA. Interpreting the potential mechanisms underlying OA pathogenesis is crucial to the development of new disease modifying treatments. Although multiple factors contribute to the initiation and progression of OA, gut microbiota has gradually been regarded as an important pathogenic factor in the development of OA. Gut microbiota can be regarded as a multifunctional “organ”, closely related to a series of immune, metabolic and neurological functions. This review summarized research evidences supporting the correlation between gut microbiota and OA, and interpreted the potential mechanisms underlying the correlation from four aspects: immune system, metabolism, gut-brain axis and gut microbiota modulation. Future research should focus on whether there are specific gut microbiota composition or even specific pathogens and the corresponding signaling pathways that contribute to the initiation and progression of OA, and validate the potential of targeting gut microbiota for the treatment of patients with OA.

Synovial single-cell heterogeneity, zonation and interactions: a patchwork of effectors in arthritis

Despite extensive research, there is still no treatment that would lead to remission in all patients with rheumatoid arthritis as our understanding of the affected site, the synovium, is still incomplete. Recently, single-cell technologies helped to decipher the cellular heterogeneity of the synovium; however, certain synovial cell populations, such as endothelial cells or peripheral neurons, remain to be profiled on a single-cell level. Furthermore, associations between certain cellular states and inflammation were found; whether these cells cause the inflammation remains to be answered. Similarly, cellular zonation and interactions between individual effectors in the synovium are yet to be fully determined. A deeper understanding of cell signalling and interactions in the synovium is crucial for a better design of therapeutics with the goal of complete remission in all patients.

AI MSK clinical applications: cartilage and osteoarthritis

The advancements of artificial intelligence (AI) for osteoarthritis (OA) applications have been rapid in recent years, particularly innovations of deep learning for image classification, lesion detection, cartilage segmentation, and prediction modeling of future knee OA development. This review article focuses on AI applications in OA research, first describing machine learning (ML) techniques and workflow, followed by how these algorithms are used for OA classification tasks through imaging and non-imaging-based ML models. Deep learning applications for OA research, including analysis of both radiographs for automatic detection of OA severity, and MR images for detection of cartilage/meniscus lesions and cartilage segmentation for automatic T₂ quantification will be described. In addition, information on ML models that identify individuals at high risk of OA development will be provided. The future vision of machine learning applications in imaging of OA and cartilage hinges on implementation of AI for optimizing imaging protocols, quantitative assessment of cartilage, and automated analysis of disease burden yielding a faster and more efficient workflow for a radiologist with a higher level of reproducibility and precision. It may also provide risk assessment tools for individual patients, which is an integral part of precision medicine.

Liraglutide, a glucagon-like peptide 1 receptor agonist, exerts analgesic, anti-inflammatory and anti-degradative actions in osteoarthritis

Osteoarthritis (OA) is a common disabling disease worldwide, with no effective and safe disease-modifying drugs (DMOAD) in the market. However, studies suggest that drugs, such as liraglutide, which possess strong potential in decreasing low-grade systemic inflammation may be effective in treating OA. Therefore, the aim of this study was to examine the anti-inflammatory, analgesic, and anti-degradative effects in OA using in vitro and in vivo experiments. The results showed that intra-articular injection of liraglutide alleviated pain-related behavior in in vivo sodium monoiodoacetate OA mouse model, which was probably driven by the GLP-1R-mediated anti-inflammatory activity of liraglutide. Moreover, liraglutide treatment significantly decreased IL-6, PGE₂ and nitric oxide secretion, and the expression of inflammatory genes in vitro in chondrocytes and macrophages in a dose-dependent manner. Additionally, liraglutide shifted polarized macrophage phenotype in vitro from the pro-inflammatory M1 phenotype to the M2 anti-inflammatory phenotype. Furthermore, liraglutide exerted anti-catabolic activity by significantly decreasing the activities of metalloproteinases and aggrecanases, a family of catabolic enzymes involved in cartilage breakdown in vitro. Overall, the findings of this study showed that liraglutide ameliorated OA-associated pain, possess anti-inflammatory and analgesic properties, and could constitute a novel therapeutic candidate for OA treatment.

Bioengineering human cartilage-bone tissues for modeling of osteoarthritis

Osteoarthritis (OA) is the most common joint disease worldwide, yet we continue to lack an understanding of disease etiology and pathology, and effective treatment options. Essential to tissue homeostasis, disease pathogenesis, and therapeutic responses are the stratified organization of cartilage and the crosstalk at the osteochondral junction. Animal models may capture some of these features, but to establish clinically consistent therapeutics, there remains a need for high-fidelity models of OA that meet all the above requirements in a human, patient-specific manner. In vitro bioengineered cartilage-bone tissue models could be developed to recapitulate physiological interactions with human cells and disease initiating factors. Here we highlight human induced pluripotent stem cells (hiPSCs) as the advantageous cell source for these models and review approaches for chondrogenic fate specification from hiPSCs. To achieve native-like stratified cartilage organization with cartilage-bone interactions, spatiotemporal cues mimicking development can be delivered to engineered tissues by patterning of the cells, scaffold, and the environment. Once healthy and native-like cartilage-bone tissues are established, an OA-like state can be induced via cytokine challenge or injurious loading. Bioengineered cartilage-bone tissues fall short of recapitulating the full complexity of native tissues, but have demonstrated utility in elucidating some mechanisms of OA progression and enabled screening of candidate therapeutics in patient-specific models. With rapid progress in stem cells, tissue engineering, imaging, and high throughput -omics research in recent years, we propose that advanced human tissue models will soon offer valuable contributions to our understanding and treatment of OA.

Ononin ameliorates inflammation and cartilage degradation in rat chondrocytes with IL-1β-induced osteoarthritis by downregulating the MAPK and NF-κB pathways

BACKGROUND

Osteoarthritis (OA) treatment aims to improve inflammation and delay cartilage degeneration. However, there is no effective strategy presently available. Ononin, a representative isoflavone glycoside component extracted from natural Chinese herbs, exerts anti-inflammatory and proliferative effects. However, the therapeutic effect of ononin on chondrocyte inflammation remains unclear.

METHODS

In this study, we explored the therapeutic effect and potential mechanism of ononin in OA by establishing an interleukin-1 beta (IL-1β)-induced chondrocyte inflammation model.

RESULTS

Our results verified that ononin alleviated the IL-1β-induced decrease in chondrocyte viability, attenuated the overexpression of the inflammatory factors tumour necrosis factor α (TNF-α) and interleukin 6 (IL-6), and simultaneously inhibited the expression of cartilage extracellular matrix (ECM)-degrading enzymes such as matrix metalloproteinase-13 (MMP-13). Furthermore, the decomposition of Collagen II protein could be alleviated in the OA model by ononin. Finally, ononin improved chondrocyte inflammation by downregulating the mitogen-activated protein kinase (MAPK) and nuclear factor kappa-B (NF-κB) signalling pathways.

CONCLUSION

Our findings suggested that ononin could inhibit the IL-1β-induced proinflammatory response and ECM degradation in chondrocytes by interfering with the abnormal activation of the MAPK and NF-κB pathways, indicating its protective effect against OA.

Emodin Attenuates the ECM Degradation and Oxidative Stress of Chondrocytes through the Nrf2/NQO1/HO-1 Pathway to Ameliorate Rat Osteoarthritis

Osteoarthritis (OA) substantially reduces the quality of life of the elderly. OA therapy remains a challenge since no treatment options for its causes are so far available. Over recent years, researchers have speculated that emodin may represent a potential treatment strategy for OA. However, it remains unclear whether the mechanism of action of emodin is associated with the inhibition of OA-induced oxidative stress. In the present study, the potential antioxidant mechanism of action of emodin and its protective properties against the development of OA were investigated both in vitro and in vivo. In vitro, emodin inhibited the production of reactive oxygen species (ROS) in chondrocytes induced by hydrogen peroxide (H2O2) and reduced the expression of matrix metalloproteinase (MMP)3 and MMP13 in a concentration-dependent manner. It was found that emodin upregulated the Nrf2/NQO1/HO-1 pathway, thereby attenuating the effects of oxidative stress caused by OA. In a rat model of posttraumatic OA induced by anterior cruciate ligament transection (ACLT), emodin reduced the extent of joint swelling. Emodin attenuated oxidative damage in the cartilage by upregulating superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) activity, reducing malondialdehyde (MDA) concentration and inhibiting the expression of the extracellular matrix (ECM) degradation biomarkers cartilage oligomeric matrix protein (COMP), and C-terminal telopeptide of type I collagen (CTX-I) and type II collagen (CTX-II), thereby reducing cartilage damage. In summary, the present study indicates that emodin reduces ECM degradation and oxidative stress in chondrocytes via the Nrf2/NQO1/HO-1 pathway, thereby ameliorating OA in rats.

Efficacy and safety of hydroxychloroquine in osteoarthritis: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND/AIMS

Conventional disease-modifying anti-rheumatic drugs have been trialed in osteoarthritis (OA). Hydroxychloroquine (HCQ), which has shown its effectiveness in rheumatoid arthritis, has been trialed for the treatment of OA; however, its efficacy and safety remain unclear. This systematic review and meta-analysis evaluate efficacy and safety of HCQ for the treatment of OA.

METHODS

MEDLINE, EMBASE, and Cochrane Central were searched from inception through June 2020. Two reviewers independently screened for randomized controlled trials (RCTs) comparing HCQ with placebo or other active-comparators for the treatment of knee, hand, or hip OA, extracted data, and performed Cochrane risk of bias assessments.

RESULTS

Six RCTs, four in hand OA, two in knee OA, consisting of 842 patients (436 in HCQ arm, 406 in control arm) were included. RCTs were conducted between 2012 and 2020, one each at UK, Netherlands, Germany, Italy, Iran, and Egypt; follow-up period ranged 24 to 52 weeks. High-quality evidence showed no clinically important pain reduction with HCQ compared to placebo/active-control in hand OA (standardized mean difference [SMD], 0.14; 95% confidence interval [CI], -0.20 to 0.48). Effect on pain reduction in knee and hand OA was small and non-significant (SMD, -0.09; 95% CI, -0.44 to 0.25). High-quality evidence showed no improvement in dysfunction with HCQ compared to placebo in hand OA patients (SMD, 0.08; 95% CI, -0.23 to 0.40). Effect on dysfunction improvement in knee and hand OA was modest and statistically non-significant (SMD, -0.20; 95% CI,-0.57 to 0.18). No improvement in quality of life was observed in hand OA.

CONCLUSION

HCQ has no benefit in reducing pain and improving physical function in hand or knee OA patients.

Osteoarthritis: Advances and Emerging Treatments

Osteoarthritis (OA) is the most common joint condition globally, affecting 10% of men and 18% of women over the age of 60. Its pathogenesis is multifactorial, which has made identifying modifiable factors to slow the progression or prevent the development of OA challenging. Current treatment focuses largely on lifestyle modification, analgesia and ultimately joint replacement, with no specific therapies currently available. However, research is on-going to provide a disease-modifying drug akin to those available for rheumatoid arthritis. The heterogeneity of OA has allowed a variety of pharmaceutical agents to be considered, each aiming to modify different components of the arthritic joint. Only a limited number of targeted treatments have been found to be efficacious, and those that have been identified have been associated with adverse events, preventing their progression to clinical practice. This article reviews the current management of OA, including tissue-specific approaches and treatments and summarizes the on-going research that aims to identify further therapeutic targets and develop disease-modifying OA drugs.

Exploring the translational potential of clusterin as a biomarker of early osteoarthritis

BACKGROUND

Clusterin (CLU; also known as apolipoprotein J) is an ATP-independent holdase chaperone that prevents proteotoxicity as a consequence of protein aggregation. It is a ∼60 kDa disulfide-linked heterodimeric protein involved in the clearance of cellular debris and the regulation of apoptosis. CLU has been proposed to protect cells from cytolysis by complement components and has been implicated in Alzheimer's disease due to its ability to bind amyloid-β peptides and prevent aggregate formation in the brain. Recent studies suggest that CLU performs moonlighting functions. CLU exists in two major forms: an intracellular form and a secreted extracellular form. The intracellular form of CLU may suppress stress-induced apoptosis by forming complexes with misfolded proteins and facilitates their degradation. The secreted form of CLU functions as an extracellular chaperone that prevents protein aggregation.

METHODS

In this review, we discuss the published literature on the biology of CLU in cartilage, chondrocytes, and other synovial joint tissues. We also review clinical studies that have examined the potential for using this protein as a biomarker in synovial and systemic fluids of patients with rheumatoid arthritis (RA) or osteoarthritis (OA).

RESULTS

Since CLU functions as an extracellular chaperone, we propose that it may be involved in cytoprotective functions in osteoarticular tissues. The secreted form of CLU can be measured in synovial and systemic fluids and may have translational potential as a biomarker of early repair responses in OA.

CONCLUSION

There is significant potential for investigating synovial and systemic CLU as biomarkers of OA. Future translational and clinical orthopaedic studies should carefully consider the diverse roles of this protein and its involvement in other comorbidities. Therefore, future biomarker studies should not correlate circulating CLU levels exclusively to the process of OA pathogenesis and progression. Special attention should be paid to CLU levels in synovial fluid.

THE TRANSLATIONAL POTENTIAL OF THIS ARTICLE

There is significant potential for investigating synovial and systemic CLU as a predictive biomarker of osteoarthritis (OA) progression and response to novel treatments and interventions. Given that CLU plays diverse roles in other comorbidities such as rheumatoid arthritis (RA) and obesity, future translational and clinical orthopaedic biomarker studies should not directly correlate circulating CLU levels to the process of OA pathogenesis and progression. However, special attention should be paid to CLU levels in synovial fluid. The cytoprotective properties of CLU may support the implementation of regenerative strategies and new approaches for developing targeted therapeutics for OA.

An up to date on clinical prospects and management of osteoarthritis

The rising prevalence of osteoarthritis (OA) in the general population has necessitated the development of novel treatment options. It is critical to recognize the joint as a separate entity participating in degenerative processes, as well as the multifaceted nature of OA. OA is incurable because there is currently no medication that can stop or reverse cartilage or bone loss. As this point of view has attracted attention, more research is being directed toward determining how the various joint components are impacted and how they contribute to OA pathogenesis. Over the next few years, several prospective therapies focusing on inflammation, cartilage metabolism, subchondral bone remodelling, cellular senescence, and the peripheral nociceptive pathway are predicted to transform the OA therapy landscape. Stem cell therapies and the use of various biomaterials to target articular cartilage (AC) and osteochondral tissues are now being investigated in considerable detail. Currently, laboratory-made cartilage tissues are on the verge of being used in clinical settings. This review focuses on the update of clinical prospects and management of osteoarthritis, as well as future possibilities for the treatment of OA.

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Osteoarthritis (OA) is a general term that incorporates several different joint diseases.

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The exact pathophysiology of OA remains unclear.

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OA is incurable because there is currently no medication that can stop or reverse cartilage or bone loss.

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Nonsteroidal anti-inflammatory drugs are the most frequently prescribed medications to alleviate arthritic discomfort.

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Stem cell therapies to target articular cartilage and osteochondral tissues are now under investigation.

Cannabinoid receptor type 2 is upregulated in synovium following joint injury and mediates anti-inflammatory effects in synovial fibroblasts and macrophages

OBJECTIVE

Joint injury-induced perturbations to the endocannabinoid system (ECS), a regulator of both inflammation and nociception, remain largely uncharacterized. We employed a mouse model of ACL rupture to assess alterations to nociception, inflammation, and the ECS while using in vitro models to determine whether CB2 agonism can mitigate inflammatory signaling in macrophages and fibroblast-like synoviocytes (FLS).

DESIGN

Mice underwent noninvasive ACL rupture (ACLR) via tibial compression-based loading. Nociception was measured longitudinally using mechanical allodynia and knee hyperalgesia testing. Synovitis was assessed using histological scoring and histomorphometry. Gene and protein markers of inflammation were characterized in whole joints and synovium. Immunohistochemistry assessed injury-induced alterations to CB1+, CB2+, and F4/80+ cells in synovium. To assess whether CB2 agonism can inhibit pro-inflammatory macrophage polarization, murine bone marrow-derived macrophages (mBMDM) were stimulated with IL-1β or conditioned medium from IL-1β-treated FLS and treated with vehicle (DMSO), the CB2 agonist HU308, or cannabidiol (CBD). Macrophage polarization was assessed as the ratio of M1-associated (IL1b, MMP1b, and IL6) to M2-associated (IL10, IL4, and CD206) gene expression. Human FLS (hFLS) isolated from synovial tissue of OA patients were treated with vehicle (DMSO) or HU308 following TNF-α or IL-1β stimulation to assess inhibition of catabolic/inflammatory gene expression.

RESULTS

ACLR induces synovitis, progressively-worsening PTOA severity, and an immediate and sustained increase in both mechanical allodynia and knee hyperalgesia, which persist beyond the resolution of molecular inflammation. Enrichment of CB2, but not CB1, was observed in ACLR synovium at 3d, 14d, and 28d, and CB2 was found to be associated with F4/80 (+) cells, which are increased in number in ACLR synovium at all time points. The CB2 agonist HU308 strongly inhibited mBMDM M1-type polarization following stimulation with either IL-1β or conditioned medium from IL-1β-treated mFLS, which was characterized by reductions in Il1b, Mmp1b, and Il6 and increases in Cd206 gene expression. Cannabidiol similarly inhibited IL-1β-induced mBMDM M1 polarization via a reduction in Il1b and an increase in Cd206 and Il4 gene expression. Lastly, in OA hFLS, HU308 treatment inhibited IL-1β-induced CCL2, MMP1, MMP3, and IL6 expression and further inhibited TNF-α-induced CCL2, MMP1, and GMCSF expression, demonstrating human OA-relevant anti-inflammatory effects by targeting CB2.

CONCLUSIONS

Joint injury perturbs the intra-articular ECS, characterized by an increase in synovial F4/80(+) cells, which express CB2, but not CB1. Targeting CB2 in murine macrophages and human FLS induced potent anti-inflammatory and anti-catabolic effects, which indicates that the CB2 receptor plays a key role in regulating inflammatory signaling in the two primary effector cells in the synovium. The intraarticular ECS is therefore a potential therapeutic target for blocking pathological inflammation in future disease-modifying PTOA treatments.

Monocytes, Macrophages, and Their Potential Niches in Synovial Joints - Therapeutic Targets in Post-Traumatic Osteoarthritis?

Synovial joints are complex structures that enable normal locomotion. Following injury, they undergo a series of changes, including a prevalent inflammatory response. This increases the risk for development of osteoarthritis (OA), the most common joint disorder. In healthy joints, macrophages are the predominant immune cells. They regulate bone turnover, constantly scavenge debris from the joint cavity and, together with synovial fibroblasts, form a protective barrier. Macrophages thus work in concert with the non-hematopoietic stroma. In turn, the stroma provides a scaffold as well as molecular signals for macrophage survival and functional imprinting: “a macrophage niche”. These intricate cellular interactions are susceptible to perturbations like those induced by joint injury. With this review, we explore how the concepts of local tissue niches apply to synovial joints. We introduce the joint micro-anatomy and cellular players, and discuss their potential interactions in healthy joints, with an emphasis on molecular cues underlying their crosstalk and relevance to joint functionality. We then consider how these interactions are perturbed by joint injury and how they may contribute to OA pathogenesis. We conclude by discussing how understanding these changes might help identify novel therapeutic avenues with the potential of restoring joint function and reducing post-traumatic OA risk.

Burden, Treatment Patterns and Unmet Needs of Osteoarthritis in Dubai: a Retrospective Analysis of the Dubai Real-World Claims Database

Introduction

Osteoarthritis (OA) is a degenerative joint disease that impacts 3.3–3.6% of population globally with significant health and societal impact. The current study assessed the disease burden, treatment patterns, and healthcare resource utilisation (HCRU) and costs in patients with OA and subgroups of hip and/or knee OA, in Dubai, United Arab Emirates (UAE).

Methodology

This retrospective longitudinal case–control study collected OA-related data from January 1, 2014 to May 31, 2020 from the Dubai Real-World Claims Database (DRWD). Adults aged at least 18 years old with OA diagnosis and at least two claims and continuous enrolment during the study period were included in the study. The patients with OA were 1:1 matched with individuals without OA. The patients with OA were divided into four cohorts on the basis of an a priori algorithm: OA of the hip and/or knee (cohort 1) and (difficult-to-treat) subsets of patients with moderate-to-severe OA of the hip and/or knee (cohort 2), inadequate response or inability to tolerate at least three pain-related medications (cohort 3), and contraindications to nonsteroidal anti-inflammatory drugs (NSAIDs) (cohort 4).

Results

Disease burden of OA in Dubai and HCRU and treatment costs in patients with OA were evaluated from January 1, 2014 to May 31, 2021. Patients were compared with matched controls in 1:1 ratio. The overall cohort comprised 11,651 patients with a median age of 48 years and predominantly male population (61.6%). HCRU was calculated for each cohort and it was highest (United States dollar [USD] 11,354.39) in cohort 4 (patients with contraindication to NSAIDS); in cohort 3 (inability to respond to at least three pain-related medications), USD 495.30 and USD 765.14 were spent on medication and procedures, respectively. Highest cost burden was seen in cohort 4, USD 3120.49 on consumables and USD 228.18 on services.

Conclusion

Osteoarthritis imposes a substantial healthcare and economic burden in the UAE. The study findings elucidate the unmet need among patients with difficult-to-treat OA and inform development of new therapeutics to alleviate their burden.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40744-021-00391-z.

Therapeutic nanocarriers comprising extracellular matrix-inspired peptides and polysaccharides

INTRODUCTION

The extracellular matrix (ECM) is vital for cell and tissue development. Given its importance, extensive work has been conducted to develop biomaterials and drug delivery vehicles that capture features of ECM structure and function.

AREAS COVERED

This review highlights recent developments of ECM-inspired nanocarriers and their exploration for drug and gene delivery applications. Nanocarriers that are inspired by or created from primary components of the ECM (e.g. elastin, collagen, hyaluronic acid (HA), or combinations of these) are explicitly covered. An update on current clinical trials employing elastin-like proteins is also included.

EXPERT OPINION

Novel ECM-inspired nanoscale structures and conjugates continue to be of great interest in the materials science and bioengineering communities. Hyaluronic acid nanocarrier systems in particular are widely employed due to the functional activity of HA in mediating a large number of disease states. In contrast, collagen-like peptide nanocarriers are an emerging drug delivery platform with potential relevance to a myriad of ECM-related diseases, making their continued study most pertinent. Elastin-like peptide nanocarriers have a well-established tolerability and efficacy track record in preclinical analyses that has motivated their recent advancement into the clinical arena.

Treatment of knee osteoarthritis with intra-articular injection of allogeneic adipose-derived stem cells (ADSCs) ELIXCYTE®: a phase I/II, randomized, active-control, single-blind, multiple-center clinical trial

Objective

To evaluate the safety and efficacy of intra-articular (IA) injection of allogeneic adipose-derived stem cells (ADSCs) ELIXCYTE® for knee osteoarthritis.

Methods

This was a patient-blind, randomized, active-control trial consisted of 4 arms including hyaluronic acid (HA) control and 3 ELIXCYTE® doses. A total of 64 subjects were screened, and 57 subjects were randomized. The primary endpoints included the changes from baseline to post-treatment visit of Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score at Week 24 and the incidence of adverse events (AEs) and serious adverse events (SAEs).

Results

No ELIXCYTE®-related serious adverse events were reported during 96 weeks of follow-up and no suspected unexpected serious adverse reaction (SUSAR) or death was reported. The changes of the primary endpoint, WOMAC pain score at Week 24, showed significant differences in all ELIXCYTE® groups, as well as in HA groups between post-treatment visit and baseline. The ELIXCYTE® groups revealed significant decreases at Week 4 compared to HA group in WOMAC total scores, stiffness scores, functional limitation scores suggested the potential of ELIXCYTE® in earlier onset compared to those from HA. The significant differences of visual analog scale (VAS) pain score and Knee Society Clinical Rating System (KSCRS) functional activities score at Week 48 after ELIXCYTE® administration suggested the potential of ELIXCYTE® in the longer duration of the effectiveness compared to HA group.

Conclusions

ELIXCYTE® for knee osteoarthritis treatment was effective, safe, and well-tolerated. The efficacy results were showed that ELIXCYTE® conferred the earlier onset of reductions in pain scores and improvements in functional scores than HA group.

Trial registration: ClinicalTrials.gov Identifier: NCT02784964. Registered 16 May, 2016—Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT02784964

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-021-02631-z.

Update on Novel Non-Operative Treatment for Osteoarthritis: Current Status and Future Trends

Osteoarthritis (OA) is a leading cause of pain and disability which results in a reduced quality of life. Due to the avascular nature of cartilage, damaged cartilage has a finite capacity for healing or regeneration. To date, conservative management, including physical measures and pharmacological therapy are still the principal choices offered for OA patients. Joint arthroplasties or total replacement surgeries are served as the ultimate therapeutic option to rehabilitate the joint function of patients who withstand severe OA. However, these approaches are mainly to relieve the symptoms of OA, instead of decelerating or reversing the progress of cartilage damage. Disease-modifying osteoarthritis drugs (DMOADs) aiming to modify key structures within the OA joints are in development. Tissue engineering is a promising strategy for repairing cartilage, in which cells, genes, and biomaterials are encompassed. Here, we review the current status of preclinical investigations and clinical translations of tissue engineering in the non-operative treatment of OA. Furthermore, this review provides our perspective on the challenges and future directions of tissue engineering in cartilage regeneration.

Role of the osteochondral unit in the pathogenesis of osteoarthritis: focus on the potential use of clodronate

Osteoarthritis (OA) is a chronic disease characterized by inflammation and progressive deterioration of the joint. The etiology of OA includes genetic, phlogistic, dismetabolic and mechanical factors. Historically, cartilage was considered the target of the disease and therapy was aimed at protecting and lubricating the articular cartilage. The osteochondral unit is composed of articular cartilage, calcified cartilage, and subchondral and trabecular bone, which work synergistically to support the functional loading of the joint. Numerous studies today show that OA involves the osteochondral unit, with the participation therefore of the bone in the starting and progression of the disease, which is associated with chondropathy. Cytokines involved in the process leading to cartilage damage are also mediators of subchondral bone edema. Therefore, OA therapy must be based on the use of painkillers and bisphosphonates for both the control of osteometabolic damage and its analgesic activity. Monitoring of the disease of the osteochondral unit must be extensive, since bone marrow edema can be considered as a marker of the evolution of OA. In the present review we discuss some of the pathogenetic mechanisms associated with osteoarthritis, with particular focus on the osteochondral unit and the use of clodronate.

PTX-3 Secreted by Intra-Articular-Injected SMUP-Cells Reduces Pain in an Osteoarthritis Rat Model

Mesenchymal stem cells (MSCs) are accessible, abundantly available, and capable of regenerating; they have the potential to be developed as therapeutic agents for diseases. However, concerns remain in their further application. In this study, we developed a SMall cell+Ultra Potent+Scale UP cell (SMUP-Cell) platform to improve whole-cell processing, including manufacturing bioreactors and xeno-free solutions for commercialization. To confirm the superiority of SMUP-Cell improvements, we demonstrated that a molecule secreted by SMUP-Cells is capable of polarizing inflammatory macrophages (M1) into their anti-inflammatory phenotype (M2) at the site of injury in a pain-associated osteoarthritis (OA) model. Lipopolysaccharide-stimulated macrophages co-cultured with SMUP-Cells expressed low levels of M1-phenotype markers (CD11b, tumor necrosis factor-α, interleukin-1α, and interleukin-6), but high levels of M2 markers (CD163 and arginase-1). To identify the paracrine action underlying the anti-inflammatory effect of SMUP-Cells, we employed a cytokine array and detected increased levels of pentraxin-related protein-3 (PTX-3). Additionally, PTX-3 mRNA silencing was applied to confirm PTX-3 function. PTX-3 silencing in SMUP-Cells significantly decreased their therapeutic effects against monosodium iodoacetate (MIA)-induced OA. Thus, PTX-3 expression in injected SMUP-Cells, applied as a therapeutic strategy, reduced pain in an OA model.

Quercetin modulates the gut microbiota as well as the metabolome in a rat model of osteoarthritis

Although the mechanism of osteoarthritis (OA) has been widely studied and the use of quercetin for OA therapy is well documented, the relevant characteristics of the microbiome and metabolism remain unclear. This study reports changes in the gut microbiota and metabolism during quercetin therapy for OA in a rat model and provides an integrative analysis of the biomechanism. In this study, the rats were categorized into 3 different groups: the OA model, quercetin treatment, and control groups. The OA rats was conducted using a monoiodoacetate (MIA) injection protocol. The rats in the quercetin group received daily intragastric administration of quercetin from day 1 to day 28. Stool samples were collected, and DNA was extracted. We used an integrated approach that combined the sequencing of whole 16S rRNA, short-chain fatty acid (SCFA) measurements and metabolomics analysis by mass spectrometry (MS) to characterize the functional impact of quercetin on the gut microbiota and metabolism in a rat model of OA. The use of quercetin partially abrogated intestinal flora disorder and reversed fecal metabolite abnormalities. Compared with the control rats, the OA rats showed differences at both the class level (Clostridia, Bacteroidia, and Bacilli) and the genus level (Lactobacillus and unidentified Ruminococcaceae). Acetic acid, propionic acid and 24 metabolites were significantly altered among the three groups. However, the changes were significantly abrogated in quercetin-treated OA rats. Consequently, this study provided important evidence regarding perturbations of the gut microbiome and the function of these changes in a potential new mechanism of quercetin treatment.

Cellular senescence in knee osteoarthritis: molecular mechanisms and therapeutic implications

Cellular senescence is the inability of cells to proliferate, which has both beneficial and detrimental effects on tissue development and homeostasis. Chronic accumulation of senescent cells is associated with age-related disease, including osteoarthritis, a common joint disease responsible for joint pain and disability in older adults. The pathology of this disease includes loss of cartilage, synovium inflammation, and subchondral bone remodeling. Senescent cells are present in the cartilage of people with advanced osteoarthritis, but the link between cellular senescence and this disease is unclear. In this review, we summarize current evidence for the role of cellular senescence of different cell types in the onset and progression of osteoarthritis. We focus on the underlying mechanisms of senescence in chondrocytes, which maintain the cartilage in joints, and review the role of the Forkhead family of transcription factors, which are involved in cartilage maintenance and osteoarthritis. Finally, we discuss the potential therapeutic value and implications of targeting senescent cells using senolytic agents or immune therapies, targeting the senescence-associated secretory phenotype of these cells using senomorphic agents, and renewing the plasticity of stem cells and chondrocytes. Our review highlights current gaps in understanding of the mechanism of senescence that may, when addressed, provided new options for modifying and treating disease in osteoarthritis.

Long-term structural and symptomatic effects of intra-articular sprifermin in patients with knee osteoarthritis: 5-year results from the FORWARD study

OBJECTIVE

The FORWARD (FGF-18 Osteoarthritis Randomized Trial with Administration of Repeated Doses) trial assessed efficacy and safety of the potential disease-modifying osteoarthritis drug (DMOAD) sprifermin in patients with knee osteoarthritis. Here, we report 5-year efficacy and safety results.

METHODS

Patients were randomised to intra-articular sprifermin 100 µg or 30 µg every 6 months (q6mo) or 12 months, or placebo, for 18 months. The primary analysis was at year 2, with follow-up at years 3, 4 and 5. Additional post hoc exploratory analyses were conducted in patients with baseline minimum radiographic joint space width 1.5-3.5 mm and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain 40-90, a subgroup at risk (SAR) of progression.

RESULTS

378 (69%) patients completed the 5-year follow-up. A significant dose-response in total femorotibial joint cartilage thickness with sprifermin (trend test, p<0.001) and a 0.05 mm mean difference with sprifermin 100 µg q6mo versus placebo (95% CI 0.00 to 0.10; p=0.015) were sustained to year 5. WOMAC pain scores improved ~50% from baseline in all groups. No patient in the 100 µg q6mo group had replacement of the treated knee. 96%-98% of patients receiving sprifermin and 98% placebo reported adverse events, most were mild or moderate and deemed unrelated to treatment. Adverse event-related study withdrawals were <10%. Differentiation in WOMAC pain between sprifermin 100 µg q6mo and placebo in the SAR (n=161) at year 3 was maintained to year 5 (-10.08; 95% CI -25.68 to 5.53).

CONCLUSION

In the longest DMOAD trial reported to date, sprifermin maintained long-term structural modification of articular cartilage over 3.5 years post-treatment. Potential translation to clinical benefit was observed in the SAR.

TRIAL REGISTRATION NUMBER

NCT01919164.