Early Changes of Articular Cartilage and Subchondral Bone in The DMM Mouse Model of Osteoarthritis

Nordihydroguaiaretic acid microparticles are effective in the treatment of osteoarthritis

Several disease-modifying osteoarthritis (OA) drugs have emerged, but none have been approved for clinical use due to their systemic side effects, short half-life, and rapid clearance from the joints. Nordihydroguaiaretic acid (NDGA), a reactive oxygen species (ROS) scavenger and autophagy inducer, could be a potential treatment for OA. In this report, we show for the first time that sustained delivery of NDGA through polymeric microparticles maintains therapeutic concentrations of drug in the joint and ameliorates post-traumatic OA (PTOA) in a mouse model. In vitro treatment of oxidatively stressed primary chondrocytes from OA patients using NDGA-loaded poly(lactic-co-glycolic acid) (PLGA) microparticles (NDGA-MP) inhibited 15-lipoxygenase, induced autophagy, prevented chondrosenescence, and sustained matrix production. In vivo intra-articular delivery of NDGA-MP was non-toxic and had prolonged retention time (up to 35 days) in murine knee joints. Intra-articular therapy using NDGA-MP effectively reduced cartilage damage and reduced pain in the surgery-induced PTOA mouse model. Our studies open new avenues to modulate the immune environment and treat post-traumatic OA using ROS quenchers and autophagy inducers.

Temporal progression of subchondral bone alterations in OA models involving induction of compromised meniscus integrity in mice and rats: A scoping review

OBJECTIVE

To categorize the temporal progression of subchondral bone alterations induced by compromising meniscus integrity in mouse and rat models of knee osteoarthritis (OA).

METHOD

Scoping review of investigations reporting subchondral bone changes with appropriate negative controls in the different mouse and rat models of OA induced by compromising meniscus integrity.

RESULTS

The available literature provides appropriate temporal detail on subchondral changes in these models, covering the entire spectrum of OA with an emphasis on early and mid-term time points. Microstructural changes of the subarticular spongiosa are comprehensively described; those of the subchondral bone plate are not. In mouse models, global subchondral bone alterations are unidirectional, involving an advancing sclerosis of the trabecular structure over time. In rats, biphasic subchondral bone alterations begin with an osteopenic degeneration and loss of subchondral trabeculae, progressing to a late sclerosis of the entire subchondral bone. Rat models, independently from the applied technique, relatively faithfully mirror the early bone loss detected in larger animals, and the late subchondral bone sclerosis observed in human advanced OA.

CONCLUSION

Mice and rats allow us to study the microstructural consequences of compromising meniscus integrity at high temporal detail. Thickening of the subchondral bone plate, an early loss of thinner subarticular trabecular elements, followed by a subsequent sclerosis of the entire subchondral bone are all important and reliable hallmarks that occur in parallel with the advancing articular cartilage degeneration. Thoughtful decisions on the study design, laterality, selection of controls and volumes of interest are crucial to obtain meaningful data.

Disuse atrophy of articular cartilage can be restored by mechanical reloading in mice

BACKGROUND

Moderate mechanical stress generated by normal joint loading and movements helps maintain the health of articular cartilage. Despite growing interest in the pathogenesis of cartilage degeneration caused by reduced mechanical stress, its reversibility by mechanical reloading is less understood. This study aimed to investigate the response of articular cartilage exposed to mechanical reloading after unloading in vivo and in vitro.

METHODS AND RESULTS

Disuse atrophy was induced in the knee joint cartilage of adult mice through hindlimb unloading by tail suspension. For in vivo experiments, mice were subjected to reloading with or without daily exercise intervention or surgical destabilization of the knee joint. Microcomputed tomography and histomorphometric analyses were performed on the harvested knee joints. Matrix loss and thinning of articular cartilage due to unloading were fully or partially restored by reloading, and exercise intervention enhanced the restoration. Subchondral bone density decreased by unloading and increased to above-normal levels by reloading. The severity of cartilage damage caused by joint instability was not different even with prior non-weight bearing. For in vitro experiments, articular chondrocytes isolated from the healthy or unloaded joints of the mice were embedded in agarose gel. After dynamic compression loading, the expression levels of anabolic (Sox9, Col2a1, and Acan) and catabolic (Mmp13 and Adamts5) factors of cartilage were analyzed. In chondrocytes isolated from the unloaded joints, similar to those from healthy joints, dynamic compression increased the expression of anabolic factors but suppressed the expression of catabolic factors.

CONCLUSION

The results of this study indicate that the morphological changes in articular cartilage exposed to mechanical unloading may be restored in response to mechanical reloading by shifting extracellular matrix metabolism in chondrocytes to anabolism.

Injectable Regenerated Silk Fibroin Micro/Nanosphere with Enhanced Permeability and Stability for Osteoarthritis Therapy

In the therapy of early-stage osteoarthritis, to accomplish full infiltration of subchondral bone and cartilage, and to target osteoclast and chondrocyte simultaneously remain challenges in biomaterials design. Herein, a novel hierarchical drug delivery system is introduced, with micrometer-scale outer layer spheres composed of regenerated silk fibroin, characterized by connected porous structure through the n-butanol and regenerated silk fibroin combined emulsion route and freezing method. The design effectively resists clearance from the joint cavity, ensuring stable delivery and prolonged residence time within the joint space. Additionally, the system incorporates phenylboronic acid-enriched silk fibroin nanoparticles, stabilized through chemical cross-linking, which encapsulate isoliquiritin derived from Glycyrrhiza uralensis. These nanoparticles facilitate complete penetration of the cartilage extracellular matrix, exhibit pH-responsive behavior, neutralize reactive oxygen species, and enable controlled drug release, thereby enhancing therapeutic efficacy. The in vitro and in vivo experiments both demonstrate that the composite micro/nanospheres not only inhibit osteoclastogenesis with bone loss in subchondral bone and osteophyte formation, but also mitigate chondrocytes apoptosis, reduce oxidative stress associated with cartilage degeneration, and ameliorate neuropathic hyperalgesia, with the underlying mechanisms being elucidated. The study indicates that such an injectable strategy combining organic biomaterials with Chinese medicine holds substantial promise for the treatment of early osteoarthritis.

Gubi decoction mitigates knee osteoarthritis via promoting chondrocyte autophagy through METTL3-mediated ATG7 m6A methylation

Knee osteoarthritis (KOA) is a chronic joint disease that significantly affects the health of the elderly. As an herbal remedy, Gubi decoction (GBD) has been traditionally used for the treatment of osteoarthritis-related syndromes. However, the anti-KOA efficacy and mechanism of GBD remain unclear. This study aimed to experimentally investigate the anti-KOA efficacy and the underlying mechanism of GBD. The medial meniscus (DMM) mice model and IL-1β-stimulated chondrocytes were, respectively, constructed as in vivo and in vitro models of KOA to evaluate the osteoprotective effect and molecular mechanism of GBD. The UPLC-MS/MS analysis showed that GBD mainly contained pinoresinol diglucoside, rehmannioside D, hesperidin, liquiritin, baohuoside I, glycyrrhizic acid, kaempferol and tangeretin. Animal experiment showed that GBD could alleviate articular cartilage destruction and recover histopathological alterations in DMM mice. In addition, GBD inhibited chondrocyte apoptosis and restored DMM-induced dysregulated autophagy evidenced by the upregulation of ATG7 and LC3 II/LC3 I but decreased P62 level. Mechanistically, METTL3-mediated m6A modification decreased the expression of ATG7 in DMM mice, as it could be significantly attenuated by GBD. METTL3 overexpression significantly counteracted the protective effect of GBD on chondrocyte autophagy. Further research showed that GBD promoted proteasome-mediated ubiquitination degradation of METLL3. Our findings suggest that GBD could act as a protective agent against KOA. The protective effect of GBD may result from its promotion on chondrocyte autophagy by suppressing METTL3-dependent ATG7 m6A methylation.

Pannexin 3 deletion in mice results in knee osteoarthritis and intervertebral disc degeneration after forced treadmill running

Pannexin 3 (Panx3) is a glycoprotein that forms mechanosensitive channels expressed in chondrocytes and annulus fibrosus cells of the intervertebral disc (IVD). Evidence suggests Panx3 plays contrasting roles in traumatic versus aging osteoarthritis (OA) and intervertebral disc degeneration (IDD). However, whether its deletion influences the response of joint tissue to forced use is unknown. The purpose of this study was to determine if Panx3 deletion in mice causes increased knee joint OA and IDD after forced treadmill running. Male and female wildtype (WT) and Panx3 knockout (KO) mice were randomized to either a no-exercise group (sedentary; SED) or daily forced treadmill running (forced exercise; FEX) from 24 to 30 weeks of age. Knee cartilage and IVD histopathology were evaluated by histology, while tibial secondary ossification centers were analyzed using microcomputed tomography (µCT). Both male and female Panx3 KO mice developed larger superficial defects of the tibial cartilage after forced treadmill running compared with SED WT mice. Additionally, Panx3 KO mice developed reduced bone volume, and female PANX3 KO mice had lengthening of the lateral tubercle at the intercondylar eminence. In the lower lumbar spine, both male and female Panx3 KO mice developed histopathological features of IDD after running compared to SED WT mice. These findings suggest that the combination of deleting Panx3 and forced treadmill running induces OA and causes histopathological changes associated with the degeneration of the IVDs in mice.

Identification of osteoblastic autophagy-related genes for predicting diagnostic markers in osteoarthritis

The development of osteoarthritis (OA) involves subchondral bone lesions, but the role of osteoblastic autophagy-related genes (ARGs) in osteoarthritis is unclear. Through integrated analysis of single-cell dataset, Bulk RNA dataset, and 367 ARGs extracted from GeneCards, 40 ARGs were found. By employing multiple machine learning algorithms and PPI networks, three key genes (DDIT3, JUN, and VEGFA) were identified. Then the RF model constructed from these genes indicated great potential as a diagnostic tool. Furthermore, the model's effectiveness in predicting OA has been confirmed through external validation datasets. Moreover, the expression of ARGs was examined in osteoblasts subject to excessive mechanical stress, human and mouse tissues. Finally, the role of ARGs in OA was confirmed through co-culturing explants and osteoblasts. Thus, osteoblastic ARGs could be crucial in OA development, providing potential diagnostic and treatment strategies.

Engineered Self-Regulating Macrophages for Targeted Anti-inflammatory Drug Delivery

Background

Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by increased levels of inflammation that primarily manifests in the joints. Macrophages act as key drivers for the progression of RA, contributing to the perpetuation of chronic inflammation and dysregulation of pro-inflammatory cytokines such as interleukin 1 (IL-1). The goal of this study was to develop a macrophage-based cell therapy for biologic drug delivery in an autoregulated manner.

Methods

For proof-of-concept, we developed "smart" macrophages to mitigate the effects of IL-1 by delivering its inhibitor, IL-1 receptor antagonist (IL-1Ra). Bone marrow-derived macrophages were lentivirally transduced with a synthetic gene circuit that uses an NF-κB inducible promoter upstream of either the Il1rn or firefly luciferase transgenes. Two types of joint like cells were utilized to examine therapeutic protection in vitro, miPSCs derived cartilage and isolated primary mouse synovial fibroblasts while the K/BxN mouse model of RA was utilized to examine in vivo therapeutic protection.

Results

These engineered macrophages were able to repeatably produce therapeutic levels of IL-1Ra that could successfully mitigate inflammatory activation in co-culture with both tissue engineered cartilage constructs and synovial fibroblasts. Following injection in vivo, macrophages homed to sites of inflammation and mitigated disease severity in the K/BxN mouse model of RA.

Conclusion

These findings demonstrate the successful development of engineered macrophages that possess the ability for controlled, autoregulated production of IL-1 based on inflammatory signaling such as the NF-κB pathway to mitigate the effects of this cytokine for applications in RA or other inflammatory diseases. This system provides proof of concept for applications in other immune cell types as self-regulating delivery systems for therapeutic applications in a range of diseases.

A Mechanically Resilient Soft Hydrogel Improves Drug Delivery for Treating Post-Traumatic Osteoarthritis in Physically Active Joints

Intra-articular delivery of disease-modifying osteoarthritis drugs (DMOADs) is likely to be most effective in early post-traumatic osteoarthritis (PTOA) when symptoms are minimal and patients are physically active. DMOAD delivery systems therefore must withstand repeated mechanical loading without affecting the drug release kinetics. Although soft materials are preferred for DMOAD delivery, mechanical loading can compromise their structural integrity and disrupt drug release. Here, we report a mechanically resilient soft hydrogel that rapidly self-heals under conditions resembling human running while maintaining sustained release of the cathepsin-K inhibitor L-006235 used as a proof-of-concept DMOAD. Notably, this hydrogel outperformed a previously reported hydrogel designed for intra-articular drug delivery, used as a control in our study, which neither recovered nor maintained drug release under mechanical loading. Upon injection into mouse knee joints, the hydrogel showed consistent release kinetics of the encapsulated agent in both treadmill-running and non-running mice. In a mouse model of aggressive PTOA exacerbated by treadmill running, L-006235 hydrogel markedly reduced cartilage degeneration. To our knowledge, this is the first hydrogel proven to withstand human running conditions and enable sustained DMOAD delivery in physically active joints, and the first study demonstrating reduced disease progression in a severe PTOA model under rigorous physical activity, highlighting the hydrogel's potential for PTOA treatment in active patients.

Osteoarthritis: Insights into Diagnosis, Pathophysiology, Therapeutic Avenues, and the Potential of Natural Extracts

Osteoarthritis (OA) stands as a prevalent and progressively debilitating clinical condition globally, impacting joint structures and leading to their gradual deterioration through inflammatory mechanisms. While both non-modifiable and modifiable factors contribute to its onset, numerous aspects of OA pathophysiology remain elusive despite considerable research strides. Presently, diagnosis heavily relies on clinician expertise and meticulous differential diagnosis to exclude other joint-affecting conditions. Therapeutic approaches for OA predominantly focus on patient education for self-management alongside tailored exercise regimens, often complemented by various pharmacological interventions primarily targeting pain alleviation. However, pharmacological treatments typically exhibit short-term efficacy and local and/or systemic side effects, with prosthetic surgery being the ultimate resolution in severe cases. Thus, exploring the potential integration or substitution of conventional drug therapies with natural compounds and extracts emerges as a promising frontier in enhancing OA management. These alternatives offer improved safety profiles and possess the potential to target specific dysregulated pathways implicated in OA pathogenesis, thereby presenting a holistic approach to address the condition's complexities.

Collagen type X expression and chondrocyte hypertrophic differentiation during OA and OS development

Chondrocyte hypertrophy and the expression of its specific marker, the collagen type X gene (COL10A1), constitute key terminal differentiation stages during endochondral ossification in long bone development. Mutations in the COL10A1 gene are known to cause schmid type metaphyseal chondrodysplasia (SMCD) and spondyloepiphyseal dyschondrodysplasia (SMD). Moreover, abnormal COL10A1 expression and aberrant chondrocyte hypertrophy are strongly correlated with skeletal diseases, notably osteoarthritis (OA) and osteosarcoma (OS). Throughout the progression of OA, articular chondrocytes undergo substantial changes in gene expression and phenotype, including a transition to a hypertrophic-like state characterized by the expression of collagen type X, matrix metalloproteinase-13, and alkaline phosphatase. This state is similar to the process of endochondral ossification during cartilage development. OS, the most common pediatric bone cancer, exhibits characteristics of abnormal bone formation alongside the presence of tumor tissue containing cartilaginous components. This observation suggests a potential role for chondrogenesis in the development of OS. A deeper understanding of the shifts in collagen X expression and chondrocyte hypertrophy phenotypes in OA or OS may offer novel insights into their pathogenesis, thereby paving the way for potential therapeutic interventions. This review systematically summarizes the findings from multiple OA models (e.g., transgenic, surgically-induced, mechanically-loaded, and chemically-induced OA models), with a particular focus on their chondrogenic and/or hypertrophic phenotypes and possible signaling pathways. The OS phenotypes and pathogenesis in relation to chondrogenesis, collagen X expression, chondrocyte (hypertrophic) differentiation, and their regulatory mechanisms were also discussed. Together, this review provides novel insights into OA and OS therapeutics, possibly by intervening the process of abnormal endochondral-like pathway with altered collagen type X expression.

Suppressive Activity of Boiogito, a Japanese Traditional Kampo Medicine, on Periostin Secretion in Human Fibroblast-Like Synoviocytes In Vitro

Background Knee osteoarthritis (KOA) is a prevalent degenerative disease that affects the knee joints, particularly among individuals aged over 40 years. It leads to pain, stiffness, and reduced quality of life; affects approximately 300 million individuals worldwide; and is increasing, particularly in developed nations. Although treatments for KOA range from conservative measures to surgical interventions, such as total knee arthroplasty (TKA), the financial burden of TKA in many countries underscores the urgent need for effective conservative therapies. The pathophysiology of KOA involves articular cartilage degeneration, increased subchondral bone turnover, synovitis, and periarticular soft tissue contracture. Abnormal bone turnover, intensified by factors, such as weight gain and knee injury, precedes cartilage degeneration. Synovitis, characterized by inflammation in the synovial tissue, plays a crucial role in perpetuating the disease by triggering a cascade of catabolic and proinflammatory mediators, including cytokines, such as interleukin (IL)-1 beta, tumor necrosis factor-alpha, and IL-13. Periostin, an extracellular matrix protein, is implicated in KOA progression, with its levels increasing with disease severity. Materials & methods In this study, the preventive effect of boiogito (BOT), a traditional herbal medicine, on periostin secretion in human fibroblast-like synoviocytes (hFLS) stimulated by IL-13 was investigated. Synoviocyte Growth Medium and recombinant human IL-13 were used for cell culture and stimulation. BOT was dissolved in phosphate-buffered saline and applied to cell cultures. Periostin secretion and mRNA expression were measured using enzyme-linked immunosorbent assay and quantitative reverse transcription polymerase chain reaction, respectively. Cell viability was assessed using an MTT assay, and signal transducer and activator of transcription factor 6 (STAT6) phosphorylation was examined using Western blotting. Results IL-13 stimulation of hFLS significantly increased periostin secretion, with levels rising above 20 ng/mL after 72 h of stimulation. Pretreatment with BOT dose-dependently suppressed periostin secretion, with doses of 1,000 μg/mL significantly reducing periostin levels. Furthermore, BOT inhibited periostin mRNA expression and STAT6 phosphorylation in IL-13-stimulated hFLS, suggesting its potential in modulating IL-13-mediated inflammatory pathways in KOA. Conclusion This study demonstrated the preventive effect of BOT on periostin secretion in IL-13-stimulated hFLS, highlighting its potential as a therapeutic agent for KOA. By inhibiting periostin production and downstream signaling pathways, BOT may offer a promising conservative treatment option for KOA, addressing the inflammatory cascade implicated in disease progression. Further research is warranted to elucidate the specific herbal components responsible for the therapeutic effects of BOT and to validate its efficacy in clinical settings.

Sugar-coated bullets: Unveiling the enigmatic mystery 'sweet arsenal' in osteoarthritis

Glycosylation is a crucial post-translational modification process where sugar molecules (glycans) are covalently linked to proteins, lipids, or other biomolecules. In this highly regulated and complex process, a series of enzymes are involved in adding, modifying, or removing sugar residues. This process plays a pivotal role in various biological functions, influencing the structure, stability, and functionality of the modified molecules. Glycosylation is essential in numerous biological processes, including cell adhesion, signal transduction, immune response, and biomolecular recognition. Dysregulation of glycosylation is associated with various diseases. Glycation, a post-translational modification characterized by the non-enzymatic attachment of sugar molecules to proteins, has also emerged as a crucial factor in various diseases. This review comprehensively explores the multifaceted role of glycation in disease pathogenesis, with a specific focus on its implications in osteoarthritis (OA). Glycosylation and glycation alterations wield a profound influence on OA pathogenesis, intertwining with disease onset and progression. Diverse studies underscore the multifaceted role of aberrant glycosylation in OA, particularly emphasizing its intricate relationship with joint tissue degradation and inflammatory cascades. Distinct glycosylation patterns, including N-glycans and O-glycans, showcase correlations with inflammatory cytokines, matrix metalloproteinases, and cellular senescence pathways, amplifying the degenerative processes within cartilage. Furthermore, the impact of advanced glycation end-products (AGEs) formation in OA pathophysiology unveils critical insights into glycosylation-driven chondrocyte behavior and extracellular matrix remodeling. These findings illuminate potential therapeutic targets and diagnostic markers, signaling a promising avenue for targeted interventions in OA management. In this comprehensive review, we aim to thoroughly examine the significant impact of glycosylation or AGEs in OA and explore its varied effects on other related conditions, such as liver-related diseases, immune system disorders, and cancers, among others. By emphasizing glycosylation's role beyond OA and its implications in other diseases, we uncover insights that extend beyond the immediate focus on OA, potentially revealing novel perspectives for diagnosing and treating OA.

Evaluation of rabbit adipose derived stem cells fate in perfused multilayered silk fibroin composite scaffold for Osteochondral repair

Development of osteochondral tissue engineering approaches using scaffolds seeded with stem cells in association with mechanical stimulations has been recently considered as a promising technique for the repair of this tissue. In this study, an integrated and biomimetic trilayered silk fibroin (SF) scaffold containing SF nanofibers in each layer was fabricated. The osteogenesis and chondrogenesis of stem cells seeded on the fabricated scaffolds were investigated under a perfusion flow. 3-Dimethylthiazol-2,5-diphenyltetrazolium bromide assay showed that the perfusion flow significantly enhanced cell viability and proliferation. Analysis of gene expression by stem cells revealed that perfusion flow had significantly upregulated the expression of osteogenic and chondrogenic genes in the bone and cartilage layers and downregulated the hypertrophic gene expression in the intermediate layer of the scaffold. In conclusion, applying flow perfusion on the prepared integrated trilayered SF-based scaffold can support osteogenic and chondrogenic differentiation for repairing osteochondral defects.

An alkaloid from Menispermum dauricum, dauricine mediates Ca2+ influx and inhibits NF-κB pathway to protect chondrocytes from IL-1β-induced inflammation and catabolism

ETHNOPHARMACOLOGICAL RELEVANCE

Dauricine (DA) is a natural plant-derived alkaloid extracted from Menispermum dauricum. Menispermum dauricum has been used in traditional Chinese medicine as a classic remedy for rheumatoid arthropathy and is believed to be effective in alleviating swelling and pain in the limbs.

AIM OF THE STUDY

Osteoarthritis (OA) is a classic degenerative disease involving chondrocyte death, and there is still a lack of effective therapeutic agents that can reverse the progression of the disease. Here we explored the therapeutic effects of DA against OA and further explored the mechanism.

MATERIALS AND METHODS

The effect of DA on cell viability was assessed by CCK-8. IL-1β-treated mouse chondrocytes were used as an in vitro model of OA, and apoptosis was detected by flow cytometry. QRT-PCR, western blotting, cell staining, and immunofluorescence were used to detect relevant inflammatory factors and cartilage-specific expression. RNA sequencing was used to identify pertinent signaling pathways. The therapeutic effect of DA was verified by micro-CT, histological analysis and immunohistochemical analysis in a mouse OA model.

RESULTS

DA demonstrated a high safety profile on chondrocytes, significantly reversing the inflammatory response induced by IL-1β, and promoting factors associated with cartilage regeneration. Moreover, DA exhibited a significant protective effect on the knee joints of mice undergoing ACLT-DMM, effectively preventing cartilage degeneration and subchondral bone tissue destruction. These positive therapeutic effects were achieved through the modulation of the NF-κB pathway and the Ca2+ signaling pathway by DA.

CONCLUSION

Being derived from a traditional herb, DA exhibits remarkable therapeutic potential and safety in OA treatment, presenting a promising option for patients dealing with osteoarthritis.

TMT quantitative proteomics reveals key proteins relevant to microRNA-1-mediated regulation in osteoarthritis

Osteoarthritis (OA) is the second-commonest arthritis, but pathogenic and regulatory mechanisms underlying OA remain incompletely understood. Here, we aimed to identify the mechanisms associated with microRNA-1 (miR-1) treatment of OA in rodent OA models using a proteomic approach. First, N = 18 Sprague Dawley (SD) rats underwent sham surgery (n = 6) or ACL transection (n = 12), followed at an interval of one week by randomization of the ACL transection group to intra-articular administration of either 50 µL placebo (control group) or miR-1 agomir, a mimic of endogenous miR-1 (experimental group). After allowing for eight weeks of remodeling, articular cartilage tissue was harvested and immunohistochemically stained for the presence of MMP-13. Second, N = 30 Col2a1-cre-ERT2 /GFPf1/fl -RFP-miR-1 transgenic mice were randomized to intra-articular administration of either placebo (control group, N = 15) or tamoxifen, an inducer of miR-1 expression (experimental group, N = 15), before undergoing surgical disruption of the medial meniscus (DMM) after an interval of five days. After allowing for eight weeks of remodeling, articular cartilage tissue was harvested and underwent differential proteomic analysis. Specifically, tandem mass tagging (TMT) quantitative proteomic analysis was employed to identify inter-group differentially-expressed proteins (DEP), and selected DEPs were validated using real-time quantitative polymerase chain reaction (RT-qPCR) technology. Immunohistochemically-detected MMP-13 expression was significantly lower in the experimental rat group, and proteomic analyses of mouse tissue homogenate demonstrated that of 3526 identified proteins, 345 were differentially expressed (relative up- and down-regulation) in the experimental group. Proteins Fn1, P4ha1, P4ha2, Acan, F2, Col3a1, Fga, Rps29, Rpl34, and Fgg were the *top ten most-connected proteins, implying that miR-1 may regulate an expression network involving these proteins. Of these ten proteins, three were selected for further validation by RT-qPCR: the transcript of Fn1, known to be associated with OA, exhibited relative upregulation in the experimental group, whereas the transcripts of P4ha1 and Acan exhibited relative downregulation. These proteins may thus represent key miR-1 targets during OA-regulatory mechanisms, and may provide additional insights regarding therapeutic mechanisms of miR-1 in context of OA.

Buds of new bone formation within the Femoral Head of Hip Fracture Patients Coincide with Zones of Low Osteocyte Sclerostin

Romosozumab treatment reduces the rate of hip fractures and increases hip bone density, increasing bone formation by inhibiting sclerostin protein. We studied the normal pattern of bone formation and osteocyte expression in the human proximal femur because it is relevant to both antisclerostin treatment effects and fracture. Having visualized and quantified buds of new bone formation in trabeculae, we hypothesized that they would coincide with areas of (a) higher mechanical stress and (b) low sclerostin expression by osteocytes. In patients with hip fracture, we visualized each bud of active modeling-based formation (forming minimodeling structure [FMiS]) in trabecular cores taken from different parts of the femoral head. Trabecular bone structure was also measured with high-resolution imaging. More buds of new bone formation (by volume) were present in the higher stress superomedial zone (FMiS density, N.FMiS/T.Ar) than lower stress superolateral (p < 0.05), and inferomedial (p < 0.001) regions. There were fewer sclerostin expressing osteocytes close to or within FMiS. FMiS density correlated with greater amount, thickness, number, and connectivity of trabeculae (bone volume BV/TV, r = 0.65, p < 0.0001; bone surface BS/TV, r = 0.47, p < 0.01; trabecular thickness Tb.Th, r = 0.55, p < 0.001; trabecular number Tb.N, r = 0.47, p < 0.01; and connectivity density Conn.D, r = 0.40, p < 0.05) and lower trabecular separation (Tb.Sp, r = -0.56, p < 0.001). These results demonstrate modeling-based bone formation in femoral trabeculae from patients with hip fracture as a potential therapeutic target to enhance bone structure. © 2023 American Society for Bone and Mineral Research (ASBMR).

The Preventive Effects of Platelet-Rich Plasma Against Knee Osteoarthritis Progression in Rats

BACKGROUND

In recent years, the intra-articular administration of platelet-rich plasma (PRP), a novel therapeutic strategy for knee osteoarthritis (KOA), has gained attention. However, the efficacy of PRP in inhibiting degenerative joint changes remains unclear. The current study aimed to evaluate the therapeutic effect of the intra-articular administration of PRP in rats with induced KOA.

MATERIALS AND METHODS

PRP was prepared from the whole blood of nine-week-old male Wistar rats via centrifugation at 25°C, 200 × g, for seven minutes. KOA was induced in the right knees of the rats via destabilization of the medial meniscus (DMM) surgery. The animals were divided into the control, sham, DMM, and DMM + PRP groups (n = 5 each). The rats in the DMM + PRP group received 50 μL of intra-articular PRP in the right knee joint four weeks after surgery. The rotarod test was conducted to assess locomotive function. Eight weeks after DMM surgery, the degree of medial meniscus extrusion was measured via computed tomography (CT) images on the right knee. Then, a histological analysis of the harvested knees was conducted. KOA progression was assessed using the Osteoarthritis Research Society International (OARSI) score. The number of multinucleated tartrate-resistant acid phosphatase (TRAP)-positive osteoclasts in the subchondral bone was counted via histological analysis.

RESULTS

The degree of medial meniscus extrusion did not significantly differ between the DMM and DMM + PRP groups. Similarly, there were no significant differences in the walking time based on the rotarod test between the DMM and DMM + PRP groups. However, the DMM group had a significantly higher OARSI score than the DMM + PRP group. The number of TRAP-positive osteoclasts in the subchondral bone of the DMM group increased over time, peaking four weeks after surgery. The DMM + PRP group had a higher number of TRAP-positive osteoclasts in the subchondral bone than the control group. However, there was no significant difference between the number of TRAP-positive osteoclasts between the DMM group and the control and sham groups.

CONCLUSION

The intra-articular administration of PRP may inhibit KOA progression in a rat model, especially in the articular cartilage degradation and osteophyte formation. The results can provide further evidence about the efficacy of PRP against KOA progression and can contribute to the current practice of healthcare professionals based on accurate knowledge.

Development of Anti-OSCAR Antibodies for the Treatment of Osteoarthritis

Osteoarthritis (OA) is the most common joint disease that causes local inflammation and pain, significantly reducing the quality of life and normal social activities of patients. Currently, there are no disease-modifying OA drugs (DMOADs) available, and treatment relies on pain relief agents or arthroplasty. To address this significant unmet medical need, we aimed to develop monoclonal antibodies that can block the osteoclast-associated receptor (OSCAR). Our recent study has revealed the importance of OSCAR in OA pathogenesis as a novel catabolic regulator that induces chondrocyte apoptosis and accelerates articular cartilage destruction. It was also shown that blocking OSCAR with a soluble OSCAR decoy receptor ameliorated OA in animal models. In this study, OSCAR-neutralizing monoclonal antibodies were isolated and optimized by phage display. These antibodies bind to and directly neutralize OSCAR, unlike the decoy receptor, which binds to the ubiquitously expressed collagen and may result in reduced efficacy or deleterious off-target effects. The DMOAD potential of the anti-OSCAR antibodies was assessed with in vitro cell-based assays and an in vivo OA model. The results demonstrated that the anti-OSCAR antibodies significantly reduced cartilage destruction and other OA signs, such as subchondral bone plate sclerosis and loss of hyaline cartilage. Hence, blocking OSCAR with a monoclonal antibody could be a promising treatment strategy for OA.

Pioglitazone-Loaded Cartilage-Targeted Nanomicelles (Pio@C-HA-DOs) for Osteoarthritis Treatment

Background

Hyaluronic acid (HA) is a popular biological material for osteoarthritis (OA) treatment. Pioglitazone, a PPAR-γ agonist, has been found to inhibit OA, but its use is limited because achieving the desired local drug concentration after administration is challenging.

Purpose

Herein, we constructed HA-based cartilage-targeted nanomicelles (C-HA-DOs) to deliver pioglitazone in a sustained manner and evaluated their efficacy in vitro and in vivo.

Methods

C-HA-DOs were chemically synthesized with HA and the WYRGRL peptide and dodecylamine. The products were characterized by FT-IR, 1H NMR, zeta potential and TEM. The drug loading rate and cumulative, sustained drug release from Pio@C-HA-DOs were determined, and their biocompatibility and effect on oxidative stress in chondrocytes were evaluated. The uptake of C-HA-DOs by chondrocytes and their effect on OA-related genes were examined in vitro. The nanomicelle distribution in the joint cavity was observed by in vivo small animal fluorescence imaging (IVIS). The therapeutic effects of C-HA-DOs and Pio@C-HA-DOs in OA rats were analysed histologically.

Results

The C-HA-DOs had a particle size of 198.4±2.431 nm, a surface charge of -8.290±0.308 mV, and a critical micelle concentration of 25.66 mg/Land were stable in solution. The cumulative drug release from the Pio@C-HA-DOs was approximately 40% at pH 7.4 over 24 hours and approximately 50% at pH 6.4 over 4 hours. Chondrocytes rapidly take up C-HA-DOs, and the uptake efficiency is higher under oxidative stress. In chondrocytes, C-HA-DOs, and Pio@C-HA-DOs inhibited H2O2-induced death, reduced intracellular ROS levels, and restored the mitochondrial membrane potential. The IVIS images confirmed that the micelles target cartilage. Pio@C-HA-DOs reduced the degradation of collagen II and proteoglycans by inhibiting the expression of MMP and ADAMTS, ultimately delaying OA progression in vitro and in vivo.

Conclusion

Herein, C-HA-DOs provided targeted drug delivery to articular cartilage and improved the role of pioglitazone in the treatment of OA.

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

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

SNIP1 reduces extracellular matrix degradation and inflammation via inhibiting the NF-κB signaling pathway in osteoarthritis

Osteoarthritis (OA), the most common joint disease, is characterized by inflammation and cartilage degradation. Previous studies illustrated that Smad nuclear-interacting protein 1 (SNIP1) is an inhibitor of the TGF-β signal transduction pathway and SNIP1 has been reported as an anti-inflammatory factor. This study aimed to explore the role of SNIP1 in OA progression. In this study, the SNIP1 expression was evaluated in OA human and OA mice tissue and interleukin-1 beta (IL-1β)-induced chondrocytes. The Safranin-O (SO) staining and osteoarthritis research society international (OARSI) scoring system was used to evaluate cartilage injury. The gain- and loss-of-function studies for SNIP1 were performed in chondrocytes. The SNIP1 overexpression adenovirus was injected into mice by intra-articular injection. The SNIP1 expression was decreased in OA patients, OA mice, and IL-1β-stimulated chondrocytes. The cartilage injury of medial meniscus-induced OA (DMM-OA) mice at 8 weeks showed more severe than that at 4 weeks. The expression of SNIP1 was lower at 8 weeks than that at 4 weeks. In IL-1β-stimulated chondrocytes, SNIP1 overexpression reduced the expression of TNF-α and IL-6, alleviated ECM degradation, reduced the phosphorylation levels of p65 and IκBα, and decreased the p65 level in nuclear. Moreover, overexpression of SNIP1 alleviated cartilage injury in DMM-OA mice. In brief, our study suggested that SNIP1 alleviated OA and repressed inflammation by inhibiting the activation of NF-κB. This study might provide a new insight into OA treatment.

An in vitro and in vivo study: Valencene protects cartilage and alleviates the progression of osteoarthritis by anti-oxidative stress and anti-inflammatory effects

BACKGROUND

Osteoarthritis (OA) is a heterogeneous disease involving the whole joint. The pathogenesis involves oxidative stress levels and chronic inflammation, and Valencene (VA) has excellent anti-inflammatory and antioxidant stress abilities.

PURPOSE

The objective was to study the effects of VA therapy on combating oxidative stress and to evaluate the protective effect of chondrocytes to alleviate the progression of OA.

METHODS

C57BL6J mouse chondrocytes were used as the primary cells in this study. Mouse chondrocytes were stimulated with IL-1β, and VA was administered in different concentrations. Reactive oxygen species (ROS) assay kits, western blotting, cellular immunofluorescence, and scanning microscopy were used to evaluate VA's antioxidant stress mechanism, anti-inflammatory effect, and cartilage protective ability. The mouse arthritis model constructed by destabilization of medial meniscus (DMM) was observed by micro-CT scan and histology after different treatments.

RESULTS

We found that VA can reverse the rise of ROS under IL-1β, the degeneration of the cartilage extracellular matrix, and the production of inflammatory mediators. In terms of mechanism, VA activated NRF2/HO-1/NQO1 pathway, thus enhancing ROS clearance. The phosphorylation of IκBα is inhibited, which further reduces the downstream phosphorylation of P65 in nuclear factor-κB (NF-κB) signaling. In addition, VA inhibited mitogen-activated protein kinase (MAPK) signaling molecules P-JNK, P-ERK, and P-P38, inhibiting the production of inflammatory mediators and thus inhibiting Aggrecan and Collagen Type II （COL2）degeneration. In vivo, VA reduced DMM-induced osteophytes and spurs, suppressed subchondral bone destruction, and reduced articular cartilage erosion.

CONCLUSION

Our study demonstrated that VA is an effective candidate for OA treatment.

Analgesic efficacy of collagen peptide in knee osteoarthritis: a meta-analysis of randomized controlled trials

BACKGROUND

The management of knee osteoarthritis involves various treatment strategies. It is important to explore alternative therapies that are both safe and effective. Collagen peptides have emerged as a potential intervention for knee osteoarthritis. This study aims to evaluate the analgesic effects and safety of collagen peptide in patients diagnosed with knee osteoarthritis.

METHODS

We conducted a systematic literature search following the guidelines of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. Multiple databases including PubMed, Scopus, EMBASE, Web of Science, Cochrane, and ClinicalTrials.gov were searched for randomized controlled trials (RCTs) published up to 27 May 2023 that focused on the analgesic outcomes and adverse events associated with collagen peptides or hydrolyzed collagen in patients with osteoarthritis. We assessed the quality of the included studies and the strength of evidence using the Cochrane ROB 2.0 tool and Grading of Recommendations, Assessment, Development, and Evaluations.

RESULTS

Four trials involving 507 patients with knee osteoarthritis were included and analyzed using the random-effects model. All these trials were considered to have a high risk of bias. Our results revealed a significant difference in pain relief between the collagen peptide group and the placebo group in patients with knee osteoarthritis (standardized mean difference: - 0.58; 95% CI - 0.98, - 0.18, p = 0.004; I2: 68%; quality of evidence: moderate). However, there was no significant difference in the risk of adverse events between collagen peptide and placebo (odds ratio: 1.66; 95% CI 0.99, 2.78, p = 0.05; I2: 0%; quality of evidence: very low).

CONCLUSIONS

Our findings demonstrate significant pain relief in patients with knee osteoarthritis who received collagen peptides compared to those who received placebo. In addition, the risk of adverse events did not differ significantly between the collagen peptide group and the placebo group. However, due to potential biases and limitations, well-designed randomized controlled trials are needed to validate and confirm these findings.

Age and oxidative stress regulate Nrf2 homeostasis in human articular chondrocytes

OBJECTIVE

The purpose of this study was to investigate the effect of age and oxidative stress on regulation of nuclear factor erythroid-2-related factor 2 (Nrf2) in young, old, and osteoarthritic (OA) human articular chondrocytes.

DESIGN

Levels of Nrf2 in primary human chondrocytes isolated from young, old, and OA donors were measured by immunoblotting, qPCR, and immunohistochemistry. Effects on levels of Nrf2, antioxidant proteins regulated by Nrf2, as well as p65, and the anabolic response to insulin-like growth factor-1 (IGF-1) were evaluated after induction of oxidative stress with menadione, Nrf2 knockdown with siRNA, and/or Nrf2 activation with RTA-408.

RESULTS

Nrf2 protein levels were significantly lower in older adult chondrocytes (∼0.59 fold; p = 0.034) and OA chondrocytes (∼0.50 fold; p = 0.016) compared to younger cells. Menadione significantly increased Nrf2 protein levels in young chondrocytes by just under four-fold without changes in old chondrocytes. Nrf2 knockdown and activation differentially regulated levels of anti-oxidant proteins including sulfiredoxin and NAD(P)H quinone dehydrogenase 1. Nrf2 activation with RTA-408 also decreased basal p65 phosphorylation, increased aggrecan and type II collagen gene expression, and increased production of proteoglycans in OA chondrocytes treated with IGF-1.

CONCLUSIONS

Targeted therapeutic strategies aimed at maintaining Nrf2 activity could be useful in maintaining chondrocyte homeostasis through maintenance of intracellular antioxidant function and redox balance.

Platelet-Derived Exosomes Alleviate Knee Osteoarthritis by Attenuating Cartilage Degeneration and Subchondral Bone Loss

BACKGROUND

Osteoarthritis (OA) is the most prevalent chronic degenerative joint disease among the aged population. However, current treatments for OA are limited to alleviating symptoms, with no therapies that prevent and regenerate cartilage deterioration.

PURPOSE

To assess the effects of platelet-derived exosomes (Plt-exos) on OA and then to explore the potential molecular mechanism.

STUDY DESIGN

Controlled laboratory study.

METHODS

Exosomes derived from human apheresis platelets were isolated and identified. The effects of Plt-exos in protecting chondrocytes under interleukin 1β stimulation were evaluated by analyzing the proliferation and migration in human primary chondrocytes. RNA sequencing was later performed in vitro for primary chondrocytes to reveal the underlying mechanisms of Plt-exo treatment. Anterior cruciate ligament transection was used to construct an OA mice model, and intra-articular injection of Plt-exos was given once a week for 6 weeks. Mice were sacrificed 4 weeks after the last injection. Histologic and immunohistochemistry staining and micro-computed tomography analysis were performed to assess alterations of articular cartilage and subchondral bone.

RESULTS

Plt-exos significantly promoted proliferation and migration of chondrocytes within a dose-dependent manner, as well as dramatically promoted cartilage regeneration and attenuated abnormal tibial subchondral bone remodeling, thus slowing the progression of OA. After being treated with Plt-exos, 1797 genes were differentially expressed in chondrocytes (923 upregulated and 874 downregulated genes). Functional enrichment results and hub genes were mainly involved in anti-inflammatory effects, mediating cell adhesion, stimulating cartilage repair, promoting anabolism, and inhibiting catabolism.

CONCLUSION

Our results demonstrated that Plt-exos promoted chondrocyte proliferation and migration in vitro, as well as attenuated cartilage degeneration, improved the microarchitecture of subchondral bone, and retarded OA progression in vivo.

CLINICAL RELEVANCE

Our study illustrated that the administered Plt-exos could alleviate knee OA by attenuating cartilage degeneration and subchondral bone loss, possibly serving as a novel promising treatment for OA in the future.

Formononetin improves the inflammatory response and bone destruction in knee joint lesions by regulating the NF-kB and MAPK signaling pathways

Formononetin (FMN) is a phytoestrogen that belongs to the isoflavone family. It has antioxidant and anti-inflammatory effects, as well as, many other biological activities. Existing evidence has aroused interest in its ability to protect against osteoarthritis (OA) and promote bone remodeling. To date, research on this topic has not been thorough and many issues remain controversial. Therefore, the purpose of our study was to explore the protective effect of FMN against knee injury and clarify the possible molecular mechanisms. We found that FMN inhibited osteoclast formation induced by receptor activator of NF-κB ligand (RANKL). Inhibition of the phosphorylation and nuclear translocation of p65 in the NF-κB signaling pathway plays a role in this effect. Similarly, during the inflammatory response of primary knee cartilage cells activated by IL-1β, FMN inhibited the NF-κB signaling pathway and the phosphorylation of the ERK and JNK proteins in the MAPK signaling pathway to suppress the inflammatory response. In addition, in vivo experiments showed that both low- and high-dose FMN had a clear protective effect against knee injury in the DMM (destabilization of the medial meniscus) model, and the therapeutic effect of high-dose FMN was stronger. In conclusion, these studies provide evidence of the protective effect of FMN against knee injury.

STING signaling in inflammaging: a new target against musculoskeletal diseases

Stimulator of Interferon Gene (STING) is a critical signaling linker protein that plays a crucial role in the intrinsic immune response, particularly in the cytoplasmic DNA-mediated immune response in both pathogens and hosts. It is also involved in various signaling processes in vivo. The musculoskeletal system provides humans with morphology, support, stability, and movement. However, its aging can result in various diseases and negatively impact people's lives. While many studies have reported that cellular aging is a leading cause of musculoskeletal disorders, it also offers insight into potential treatments. Under pathological conditions, senescent osteoblasts, chondrocytes, myeloid cells, and muscle fibers exhibit persistent senescence-associated secretory phenotype (SASP), metabolic disturbances, and cell cycle arrest, which are closely linked to abnormal STING activation. The accumulation of cytoplasmic DNA due to chromatin escape from the nucleus following DNA damage or telomere shortening activates the cGAS-STING signaling pathway. Moreover, STING activation is also linked to mitochondrial dysfunction, epigenetic modifications, and impaired cytoplasmic DNA degradation. STING activation upregulates SASP and autophagy directly and indirectly promotes cell cycle arrest. Thus, STING may be involved in the onset and development of various age-related musculoskeletal disorders and represents a potential therapeutic target. In recent years, many STING modulators have been developed and used in the study of musculoskeletal disorders. Therefore, this paper summarizes the effects of STING signaling on the musculoskeletal system at the molecular level and current understanding of the mechanisms of endogenous active ligand production and accumulation. We also discuss the relationship between some age-related musculoskeletal disorders and STING, as well as the current status of STING modulator development.

"Bone-SASP" in Skeletal Aging

Senescence is a complex cell state characterized by stable cell cycle arrest and a unique secretory pattern known as the senescence-associated secretory phenotype (SASP). The SASP factors, which are heterogeneous and tissue specific, normally include chemokines, cytokines, growth factors, adhesion molecules, and lipid components that can lead to multiple age-associated disorders by eliciting local and systemic consequences. The skeleton is a highly dynamic organ that changes constantly in shape and composition. Senescent cells in bone and bone marrow produce diverse SASP factors that induce alterations of the skeleton through paracrine effects. Herein, we refer to bone cell-associated SASP as "bone-SASP." In this review, we describe current knowledge of cellular senescence and SASP, focusing on the role of senescent cells in mediating bone pathologies during natural aging and premature aging syndromes. We also summarize the role of cellular senescence and the bone-SASP in glucocorticoids-induced bone damage. In addition, we discuss the role of bone-SASP in the development of osteoarthritis, highlighting the mechanisms by which bone-SASP drives subchondral bone changes in metabolic syndrome-associated osteoarthritis.

Characterization of aberrant glycosylation associated with osteoarthritis based on integrated glycomics methods

BACKGROUND

Osteoarthritis (OA) is the most common form of arthritis, affecting millions of aging people. Investigation of abnormal glycosylation is essential for the understanding of pathological mechanisms of OA.

METHODS

The total protein was isolated from OA (n = 13) and control (n = 11) cartilages. Subsequently, glycosylation alterations of glycoproteins in OA cartilage were investigated by lectin microarrays and intact glycopeptides analysis. Finally, the expression of glycosyltransferases involved in the synthesis of altered glycosylation was assessed by qPCR and GEO database.

RESULTS

Our findings revealed that several glycopatterns, such as α-1,3/6 fucosylation and high-mannose type of N-glycans were altered in OA cartilages. Notably, over 27% of identified glycopeptides (109 glycopeptides derived from 47 glycoproteins mainly located in the extracellular region) disappeared or decreased in OA cartilages, which is related to the cartilage matrix degradation. Interestingly, the microheterogeneity of N-glycans on fibronectin and aggrecan core protein was observed in OA cartilage. Our results combined with GEO data indicated that the pro-inflammatory cytokines altered the expression of glycosyltransferases (ALG3, ALG5, MGAT4C, and MGAT5) which may contribute to the alterations in glycosylation.

CONCLUSION

Our study revealed the abnormal glycopatterns and heterogeneities of site-specific glycosylation associated with OA. To our knowledge, it is the first time that the heterogeneity of site-specific N-glycans was reported in OA cartilage. The results of gene expression analysis suggested that the expression of glycosyltransferases was impacted by pro-inflammatory cytokines, which may facilitate the degradation of protein and accelerate the process of OA. Our findings provide valuable information for the understanding of molecular mechanisms in the pathogenesis of OA.

CC-Chemokine Receptor-2 Expression in Osteoblasts Contributes to Cartilage and Bone Damage during Post-Traumatic Osteoarthritis

In osteoarthritis (OA), bone changes are radiological hallmarks and are considered important for disease progression. The C-C chemokine receptor-2 (CCR2) has been shown to play an important role in bone physiology. In this study, we investigated whether Ccr2 osteoblast-specific inactivation at different times during post-traumatic OA (PTOA) progression improves joint structures, bone parameters, and pain. We used a tamoxifen-inducible Ccr2 inactivation in Collagen1α-expressing cells to obtain osteoblasts lacking Ccr2 (CCR2-Col1αKO). We stimulated PTOA changes in CCR2-Col1αKO and CCR2+/+ mice using the destabilization of the meniscus model (DMM), inducing recombination before or after DMM (early- vs. late-inactivation). Joint damage was evaluated at two, four, eight, and twelve weeks post-DMM using multiple scores: articular-cartilage structure (ACS), Safranin-O, histomorphometry, osteophyte size/maturity, subchondral bone thickness and synovial hyperplasia. Spontaneous and evoked pain were assessed for up to 20 weeks. We found that early osteoblast-Ccr2 inactivation delayed articular cartilage damage and matrix degeneration compared to CCR2+/+, as well as DMM-induced bone thickness. Osteophyte formation and maturation were only minimally affected. Late Collagen1α-Ccr2 deletion led to less evident improvements. Osteoblast-Ccr2 deletion also improved static measures of pain, while evoked pain did not change. Our study demonstrates that Ccr2 expression in osteoblasts contributes to PTOA disease progression and pain by affecting both cartilage and bone tissues.

Exercise improves subchondral bone microenvironment through regulating bone-cartilage crosstalk

Articular cartilage degeneration has been proved to cause a variety of joint diseases, among which osteoarthritis is the most typical. Osteoarthritis is characterized by articular cartilage degeneration and persistent pain, which affects the quality of life of patients as well as brings a heavy burden to society. The occurrence and development of osteoarthritis is related to the disorder of the subchondral bone microenvironment. Appropriate exercise can improve the subchondral bone microenvironment, thus playing an essential role in preventing and treating osteoarthritis. However, the exact mechanism whereby exercise improves the subchondral bone microenvironment remains unclear. There is biomechanical interaction as well as biochemical crosstalk between bone and cartilage. And the crosstalk between bone and cartilage is the key to bone-cartilage homeostasis maintenance. From the perspective of biomechanical and biochemical crosstalk between bone and cartilage, this paper reviews the effects of exercise-mediated bone-cartilage crosstalk on the subchondral bone microenvironment, aiming to provide a theoretical basis for the prevention and treatment of degenerative bone diseases.

Stevioside protects primary articular chondrocytes against IL-1β-induced inflammation and catabolism by targeting integrin

Osteoarthritis (OA) is a common, progressive, and chronic disorder of the joints that is characterized by the inflammation and degradation of articular cartilage and is known to significantly impair quality of daily life. Stevioside (SVS) is a natural diterpenoid glycoside that has anti-inflammatory benefits. Hence, in the current research, it was hypothesized that SVS might exert anti-inflammatory effects on articular chondrocytes and alleviate cartilage degradation in mice with OA. The expression of inflammatory cytokines, like inducible nitric oxide synthase (iNOS), NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3), and cyclooxygenase-2 (COX-2) in chondrocytes after interleukin-1β (IL-1β) exposure, was inhibited by the pretreatment of SVS. As well, SVS inhibited the reduction of collagen II and sry-box transcription factor 9 (SOX9) in chondrocytes stimulated by IL-1β and suppressed the expression of MMP3 and MMP13. Further, after treatment with SVS, cell cytometry, autophagy flux, and related protein expression showed diminished cell apoptosis and reduced autophagy impairment. Moreover, SVS blocked the activation of phosphoinositide-3-kinase/Akt/nuclear factor-kappa beta (PI3K/Akt/NF-κB) and mitogen-activated protein kinase (MAPK) signaling pathways stimulated by IL-1β. This resulted in decreased cellular inflammation. In vivo experiments with intra-articular injections of SVS in mice with the DMM mouse model demonstrated a decrease in cartilage degradation and an improvement in subchondral bone remodeling. After the integrin αVβ3-related knockdown using siRNA, a reversed effect was observed on the anti-inflammatory, anabolic promoting, catabolic blocking, and NF-κB and MAPK signaling pathway inhibition of SVS on chondrocytes treated with IL-1β. The above findings highlighted that SVS blocked IL-1β, triggered an inflammatory response in mice chondrocytes, and prevented cartilage degradation in vivo through integrin αVβ3. This suggested that SVS might serve as a novel therapeutic option for OA.

MegaPro, a clinically translatable nanoparticle for in vivo tracking of stem cell implants in pig cartilage defects

Rationale: Efficient labeling methods for mesenchymal stem cells (MSCs) are crucial for tracking and understanding their behavior in regenerative medicine applications, particularly in cartilage defects. MegaPro nanoparticles have emerged as a potential alternative to ferumoxytol nanoparticles for this purpose. Methods: In this study, we employed mechanoporation to develop an efficient labeling method for MSCs using MegaPro nanoparticles and compared their effectiveness with ferumoxytol nanoparticles in tracking MSCs and chondrogenic pellets. Pig MSCs were labeled with both nanoparticles using a custom-made microfluidic device, and their characteristics were analyzed using various imaging and spectroscopy techniques. The viability and differentiation capacity of labeled MSCs were also assessed. Labeled MSCs and chondrogenic pellets were implanted into pig knee joints and monitored using MRI and histological analysis. Results: MegaPro-labeled MSCs demonstrated shorter T2 relaxation times, higher iron content, and greater nanoparticle uptake compared to ferumoxytol-labeled MSCs, without significantly affecting their viability and differentiation capacity. Post-implantation, MegaPro-labeled MSCs and chondrogenic pellets displayed a strong hypointense signal on MRI with considerably shorter T2* relaxation times compared to adjacent cartilage. The hypointense signal of both MegaPro- and ferumoxytol-labeled chondrogenic pellets decreased over time. Histological evaluations showed regenerated defect areas and proteoglycan formation with no significant differences between the labeled groups. Conclusion: Our study demonstrates that mechanoporation with MegaPro nanoparticles enables efficient MSC labeling without affecting viability or differentiation. MegaPro-labeled cells show enhanced MRI tracking compared to ferumoxytol-labeled cells, emphasizing their potential in clinical stem cell therapies for cartilage defects.

Maintaining hypoxia environment of subchondral bone alleviates osteoarthritis progression

Abnormal subchondral bone remodeling featured by overactivated osteoclastogenesis leads to articular cartilage degeneration and osteoarthritis (OA) progression, but the mechanism is unclear. We used lymphocyte cytosolic protein 1 (Lcp1) knockout mice to suppress subchondral osteoclasts in a mice OA model with anterior cruciate ligament transection (ACLT), and Lcp1^-/- mice showed decreased bone remodeling in subchondral bone and retarded cartilage degeneration. For mechanisms, the activated osteoclasts in subchondral bone induced type-H vessels and elevated oxygen concentration, which ubiquitylated hypoxia-inducible factor 1 alpha subunit (HIF-1α) in chondrocytes and led to cartilage degeneration. Lcp1 knockout impeded angiogenesis, which maintained hypoxia environment in joints and delayed the OA progression. Stabilization of HIF-1α delayed cartilage degeneration, and knockdown of Hif1a abolished the protective effects of Lcp1 knockout. Last, we showed that Oroxylin A, an Lcp1-encoded protein l-plastin (LPL) inhibitor, could alleviate OA progression. In conclusion, maintaining hypoxic environment is an attractive strategy for OA treatment.

Radical-Scavenging and Subchondral Bone-Regenerating Nanomedicine for Osteoarthritis Treatment

Osteoarthritis (OA) is characterized by cartilage degradation and subchondral bone remodeling. However, most available studies focus on either cartilage degradation or subchondral bone lesion, alone, and rarely pay attention to the synergy of these two pathological changes. Herein, a dual-functional medication is developed to simultaneously protect cartilage and achieve subchondral bone repair. Black phosphorus nanosheets (BPNSs), with a strong reactive oxygen species (ROS)-scavenging capability and high biocompatibility, also present a notable promoting effect in osteogenesis. BPNSs efficiently eliminate the intracellular ROS and, thus, protect the inherent homeostasis between cartilage matrix anabolism and catabolism. RNA sequencing results of BPNSs-treated OA chondrocytes further reveal the restoration of chondrocyte function, activation of antioxidant enzymes, and regulation of inflammation. Additional in vivo assessments solidly confirm that BPNSs inhibit cartilage degradation and prevent OA progression. Meanwhile, histological evaluation and microcomputed tomography (micro-CT) scanning analysis verify the satisfying disease-modifying effects of BPNSs on OA. Additionally, the excellent biocompatibility of BPNSs enables them as a competitive candidate for OA treatment. This distinct disease-modifying treatment of OA on the basis of BPNSs provides an insight and paradigm on the dual-functional treatment strategy focusing on both cartilage degradation and subchondral bone lesion in OA and explores a broader biomedical application of BPNS nanomedicine in orthopedics.

African Spiny Mice (Acomys) Exhibit Mild Osteoarthritis Following Meniscal Injury

OBJECTIVE

Hyaline cartilage has limited innate healing abilities and hyaline cartilage loss is a hallmark of osteoarthritis (OA). Animal models can provide important insights into cartilage regeneration potential. One such animal model, the African spiny mouse (Acomys), is capable of regenerating skin, skeletal muscle, and elastic cartilage. This study aims to evaluate whether these regenerative abilities protect Acomys with meniscal injury from OA-related joint damage and behaviors indicative of joint pain and dysfunction.

DESIGN

Acomys received destabilization of the medial meniscus (DMM) surgery (n = 11) or a skin incision (n = 10). Gait testing occurred at 4, 6, 8, 10, and 12 weeks after surgery. At endpoint, joints were processed for histology to assess cartilage damage.

RESULTS

Following joint injury, Acomys with DMM surgery altered their walking patterns by increasing the percent stance time on the contralateral limb relative to the operated limb, thereby reducing the amount of time the injured limb must bear weight on its own throughout the gait cycle. Histological grading indicated evidence of OA-related joint damage in Acomys with DMM surgery; these changes were primarily driven by loss of structural integrity in the hyaline cartilage.

CONCLUSIONS

Acomys developed gait compensations, and the hyaline cartilage in Acomys is not fully protected from OA-related joint damage following meniscal injury, although this damage was less severe than that historically found in C57BL/6 mice with an identical injury. Thus, Acomys do not appear to be completely protected from OA-related changes, despite the ability to regenerate other wounded tissues.

Effects of dexamethasone and dynamic loading on cartilage of human osteochondral explants challenged with inflammatory cytokines

Post-traumatic osteoarthritis (PTOA), characterized by articular cartilage degradation initiated in an inflammatory environment after traumatic joint injury, can lead to alterations in cartilage biomechanical properties. Low dose dexamethasone (Dex) shows chondroprotection in cartilage challenged with inflammatory cytokines, but little is known about the structural biomechanical response of human cartilage to Dex in such a diseased state. This study examined changes in the biomechanical properties and biochemical composition of the cartilage within human osteochondral explants in response to treatment with exogenous cytokines, Dex, and a regimen of cyclic loading at the start and end of culture. Osteochondral explants were harvested from five pairs of human ankle talocrural joints (Collins grade 0-1) and cultured for 10 days with/without exogenous cytokines (100 ng/mL TNFα, 50 ng/mL IL-6, 250 ng/mL sIL-6R) ± Dex (100 nM). Biomechanical testing on day-0 and day-10 enabled estimation of the unconfined compression equilibrium modulus (E_y), dynamic stiffness (E_d) and hydraulic permeability (k_p) of cartilage excised from bone, accompanied by biochemical assessment of media and cartilage tissue. Dex preserved chondrocyte cell viability and decreased sulfated glycosaminoglycan (sGAG) loss and nitric oxide release, but did not alter E_y, E_d and k_p (before or after loading) on day-10. In the cytokine/cytokine+Dex treated groups, sGAG content exhibited a weaker correlation with E_y and E_d than at baseline, suggesting an important role for structural rather than biochemical changes in producing biomechanical alterations in response to cytokines and Dex. These findings aid in forming a more complete profile of potential clinical effects of Dex for use in OA/PTOA treatment regimens.

Treatment with Mesenchymal Stem Cell-Derived Nanovesicle-Containing Gelatin Methacryloyl Hydrogels Alleviates Osteoarthritis by Modulating Chondrogenesis and Macrophage Polarization

Osteoarthritis is a degenerative disorder that can severely affect joints, and new treatment strategies are urgently needed. Administration of mesenchymal stem cell (MSC)-derived exosomes is a promising therapeutic strategy in osteoarthritis treatment. However, the poor yield of exosomes is an obstacle to the use of this modality in the clinic. Herein, a promising strategy is developed to fabricate high-yield exosome-mimicking MSC-derived nanovesicles (MSC-NVs) with enhanced regenerative and anti-inflammatory capabilities. MSC-NVs are prepared using an extrusion approach and are found to increase chondrocyte and human bone marrow MSC differentiation, proliferation, and migration, in addition to inducing M2 macrophage polarization. Furthermore, gelatin methacryloyl (GelMA) hydrogels loaded with MSC-NVs (GelMA-NVs) are formulated, which exhibit sustained release of MSC-NVs and are shown to be biocompatible with excellent mechanical properties. In a mouse osteoarthritis model constructed by surgical destabilization of the medial meniscus (DMM), GelMA-NVs effectively ameliorate osteoarthritis severity, reduce the secretion of catabolic factors, and enhance matrix synthesis. Furthermore, GelMA-NVs induce M2 macrophage polarization and inflammatory response inhibition in vivo. The findings demonstrate that GelMA-NVs hold promise for osteoarthritis treatment through modulation of chondrogenesis and macrophage polarization.

Icariin-conditioned serum combined with chitosan attenuates cartilage injury in rabbit knees with osteochondral defect

BACKGROUND

Knee osteoarthritis (KOA) is one of the most common degenerative diseases. Its development is closely related to cartilage injury and subchondral bone remodeling homeostasis. In the present study, we combined icariin-conditioned serum (ICS) with thiolated chitosan (CSSH), a material widely used in tissue engineering for cartilage repair, to demonstrate its effect on the repair of cartilage damage and abnormal subchondral remodeling.

METHODS

New Zealand rabbits were undergoing surgery for cartilage defect, and joint cavity injection was performed in each group with 0.5 mL normal saline (NS), ICS, CSSH and ICS-CSSH in the right joint every week for five times. Positioning performance was observed using VICON motion capture system. Glycosaminoglycans (GAG) secretion of articular fluid was assessed. Osteoarthritis Research Society International (OARSI) score and immunohistochemical (IHC) analysis including H&E, Safranin O and collagen II staining were employed to evaluate the morphologic repair of cartilage and subchondral bone. mRNA expression of COL2A1, MMP13 and ADAMTS5 was detected in chondrocytes from injury area.

RESULTS

ICS combined with CSSH attenuated cartilage injury and abnormal subchondral remodeling in rabbits with KOA. ICS and CSSH groups showed slight improvement in positioning performance, while ICS-CSSH group exhibited better positioning performance. ICS-CSSH group showed increased GAG secretion of articular fluid and expression of COL2A1 in articular chondrocytes. Furthermore, both macroscopic observation and IHC analysis showed femoral condyle in ICS-CSSH rabbits were repaired with more native cartilage and subchondral bone regeneration.

CONCLUSIONS

ICS combined with CSSH could promote the repair of osteochondral defect and stabilize subchondral bone remodeling in rabbit knees.

Autophagy attenuates osteoarthritis in mice by inhibiting chondrocyte pyroptosis and improving subchondral bone remodeling

Osteoarthritis (OA) is an age-related degenerative disease characterized by cartilage degeneration and abnormal bone remodeling in the subchondral bone. Autophagy maintains cellular homeostasis by self-phagocytosis. However, the underlying mechanisms of autophagy on the pathological progression of OA are still unknown. This study assessed the effects of autophagy on cartilage and subchondral bone in a mouse OA model. A mouse OA model was induced using destabilization of the medial meniscus (DMM) surgery. Assessment was performed by histomorphology, microcomputed tomography (micro-CT), immunohistochemical, immunofluorescent, and tartrate-resistant acid phosphatase (TRAP) staining. Our data revealed that autophagy can significantly delay the pathological progression of OA by increasing the thickness of hyaline cartilage and decreasing the thickness of calcified cartilage, increasing the subchondral bone volume fraction and bone mineralization density, and decreasing trabecular separation in the early stages of OA (2 weeks), whereas the opposite is true in the late stages of OA (8 weeks). Mechanistically, activation of autophagy in cartilage increased the expression of type II collagen (Col II), decreased the expression of matrix metalloproteinase 13 (MMP 13) and decreased the pyroptosis mediated by NOD-like receptor protein 3 (NLRP3) inflammasome by decreasing the expression of NLRP3, caspase-1, gasdermin D (GSDMD), and IL-1β. In the subchondral bone, activation of autophagy decreased the generation of mature osteoclasts at the early stages of OA (2 weeks) mainly by reducing the receptor activator for nuclear factor-κB ligand (RANKL)/osteoprotegerin (OPG) ratio, while it decreased osteoblastogenesis by reducing Runt-related transcription factor 2 (Runx2) expression significantly in the late stages of OA (8 weeks). In conclusion, autophagy may delay the pathological progression of OA in mice by inhibiting chondrocyte pyroptosis and improving subchondral bone remodeling.

Patellar development after patella instability and early reduction in growing rabbits

BACKGROUND

Patella-shaped disorder has been considered as a predisposing factor for patella instability. But the influence of early patella reduction for patellar development remains unclear. This study aimed to evaluate whether early operation in patella instability could improve patella morphology in growing rabbits.

METHODS

Fifty rabbits (1-month-old) were included in the study. The control group underwent no surgical procedures. The two experimental groups (reduction group and non-reduced group), underwent medial soft tissue restraint release surgery. The reduction group, rabbits underwent the medial soft tissue sutura surgery in order to stabilize the patella 2 months after release surgery. The non-reduced group, rabbits did not undergo suture surgery. Computed Tomography (CT) scans analysis in two experimental endpoints (2, 5 months after release surgery) were selected to evaluate the transverse diameter, thickness, Wiberg index and Wiberg angle. Gross observation was conducted to assess morphological changes of the patella.

RESULTS

CT scans showed significant difference in the mean transverse diameter, Wiberg angle between the two experimental groups and the control group 2 months after release surgery. 5 months after release surgery, the indices of patella were found no statistically difference in the reduction group versus the control group. However, the transverse diameter, Wiberg angle in the non-reduced group were significantly differences than that in the reduction group (P < 0.05). Gross observation showed a flattened articular surface of the patella in the non-reduced group.

CONCLUSIONS

The results indicated that patella instability may lead to patella-shaped disorder, showing a flattened morphology. Early patella reduction can improve the patella morphology in growing rabbits.

Morphological and mechanical alterations in articular cartilage and subchondral bone during spontaneous hip osteoarthritis in guinea pigs

Objectives: This study aimed to investigate the morphological and mechanical changes in articular cartilage and subchondral bone during spontaneous hip osteoarthritis in guinea pigs. Materials and methods: Hip joints of guinea pigs were investigated at 1, 3, 6, and 9 months of age (hereafter denoted as 1 M, 3 M, 6 M, and 9 M, respectively; n = 7 in each group). Morphological and mechanical alterations during spontaneous hip osteoarthritis in guinea pigs were investigated. The alterations included the micromechanical properties of articular cartilage (stiffness and creep deformation), microstructure of the subchondral bone (bone mineral density, bone volume fraction, trabecular thickness, trabecular number, and trabecular separation), micromorphology of the articular cartilage, and surface nanostructure (grain size and roughness) of the articular cartilage and subchondral bone. Results: Micromechanical properties of articular cartilage in 1 M showed the lowest stiffness and highest creep deformation with no significant differences in stiffness or creep deformation amongst 3 M, 6 M, and 9 M. Articular cartilage thickness decreased with age. The earliest degeneration of articular cartilage occurred at 6 months of age, characterised by surface unevenness and evident chondrocytes reduction in micromorphology, as well as increased grain size and decreased roughness in nanostructure. No degeneration at micro- or nanostructure of subchondral bone was observed before 9 months. Conclusion: Morphological degeneration of cartilage occurred before degeneration of mechanical properties. Meanwhile, degeneration of cartilage occurred before degeneration of subchondral bone during hip osteoarthritis. The current study provided novel insights into the structural and micromechanical interaction of hip osteoarthritis, which can serve as a theoretical basis for understanding the formation and progression of osteoarthritis.

Intra-articular injection of rapamycin microparticles prevent senescence and effectively treat osteoarthritis

Trauma to the knee joint is associated with significant cartilage degeneration and erosion of subchondral bone, which eventually leads to osteoarthritis (OA), resulting in substantial morbidity and healthcare burden. With no disease-modifying drugs in clinics, the current standard of care focuses on symptomatic relief and viscosupplementation. Modulation of autophagy and targeting senescence pathways are emerging as potential treatment strategies. Rapamycin has shown promise in OA disease amelioration by autophagy upregulation, yet its clinical use is hindered by difficulties in achieving therapeutic concentrations, necessitating multiple weekly injections. Rapamycin-loaded in poly(lactic-co-glycolic acid) microparticles (RMPs) induced autophagy, prevented senescence, and sustained sulphated glycosaminoglycans production in primary human articular chondrocytes from OA patients. RMPs were potent, nontoxic, and exhibited high retention time (up to 35 days) in mice joints. Intra-articular delivery of RMPs effectively mitigated cartilage damage and inflammation in surgery-induced OA when administered as a prophylactic or therapeutic regimen. Together, the study demonstrates the feasibility of using RMPs as a potential clinically translatable therapy to prevent the progression of post-traumatic OA.

Contrast-enhanced micro-computed tomography of compartment and time-dependent changes in femoral cartilage and subchondral plate in a murine model of osteoarthritis

A lack of understanding of the mechanisms underlying osteoarthritis (OA) progression limits the development of effective long-term treatments. Quantitatively tracking spatiotemporal patterns of cartilage and bone degeneration is critical for assessment of more appropriately targeted OA therapies. In this study, we use contrast-enhanced micro-computed tomography (μCT) to establish a timeline of subchondral plate (SCP) and cartilage changes in the murine femur after destabilization of the medial meniscus (DMM). We performed DMM or sham surgery in 10-12-week-old male C57Bl/6J mice. Femora were imaged using μCT after 0, 2, 4, or 8 weeks. Cartilage-optimized scans were performed after immersion in contrast agent CA4+. Bone mineral density distribution (BMDD), cartilage attenuation, SCP, and cartilage thickness and volume were measured, including lateral and medial femoral condyle and patellar groove compartments. As early as 2 weeks post-DMM, cartilage thickness significantly increased and cartilage attenuation, SCP volume, and BMDD mean significantly decreased. Trends in cartilage and SCP metrics within each joint compartment reflected those seen in global measurements, and both BMDD and SCP thickness were consistently greater in the lateral and medial condyles than the patellar groove. Sham surgery also resulted in significant changes to SCP and cartilage metrics, highlighting a potential limitation of using surgical models to study tissue morphology or composition changes during OA progression. Contrast-enhanced μCT analysis is an effective tool to monitor changes in morphology and composition of cartilage, and when combined with bone-optimized μCT, can be used to assess the progression of degenerative changes after joint injury.

Calycosin mitigates chondrocyte inflammation and apoptosis by inhibiting the PI3K/AKT and NF-κB pathways

ETHNOPHARMACOLOGICAL RELEVANCE

Shaoyao Gancao Decoction (SG-Tang), originated from the Treatise on Febrile Diseases, is often used to treat OA pain symptoms. Whereas its efficacy has been verified by several clinical studies, the underlying mechanism remained unclear. Network pharmacology and UPLC-QTOF-MS analysis found that calycosin could be regarded as the active components of SG-Tang in treating OA. However, the effect of calycosin on cartilage destruction and the pathogenesis of OA are not known. Therefore, we evaluated the benefits of calycosin for OA and revealed the underlying mechanisms.

AIM OF STUDY

Using network pharmacology, UPLC-QTOF-MS analysis and experiments, the active components of SG-Tang were analyzed to explore their potential therapeutic mechanism in OA.

MATERIALS AND METHODS

The components of SG-Tang were detected by UPLC-QTOF-MS, and the possible active components and mechanism of SG-Tang in the treatment of OA were screened by network pharmacology. The OA mouse model was constructed by DMM. In total, 30 mice were randomly divided into three groups: Sham, DMM, and DMM + Calycosin. H&E, safranin O/fast green staining and the OARSI scores were used to evaluate joint injury in mice. In addition, OA models were established using chondrocytes treated with 10 ng/mL IL-1β. Treatment groups were treated with 100, 200 or 400 μM calycosin. CCK-8 assay was used for assessing the cytotoxic effects of calycosin. TUNEL staining and Western blotting were used to detect chondrocyte apoptosis. In addition, PI3K/Akt and NF-κB signaling pathway-related markers and cartilage matrix-related indicators were also detected.

RESULTS

In vivo studies showed that calycosin inhibited IL-1β-induced IL-6 and TNF-α production, as well as iNOS and COX-2 expression. Meanwhile, calycosin could inhibit IL-1β-induced degradation of cartilage matrix, including downregulation of MMP3, MMP-13, collagen II and aggrecan. NF-κB and PI3K/AKT were also inhibited by calycosin in OA chondrocytes. Furthermore, calycosin inhibited IL-1β-induced apoptosis in mouse chondrocytes. In a mouse model of OA, our results suggest that calycosin has a chondroprotective effect.

CONCLUSIONS

According to this study, calycosin may act as a protective agent against OA by inhibiting the PI3K/AKT and NF-κB pathways. Furthermore, this study suggested that calycosin is a potential candidate for the treatment of OA.

Novel Therapeutic Mechanism of Adipose-Derived Mesenchymal Stem Cells in Osteoarthritis via Upregulation of BTG2

BACKGROUND

Osteoarthritis (OA) is a debilitating and degenerative joint disease, which is characterized by progressive destruction of articular cartilage. Mesenchymal stem cells (MSCs) have been implicated in the treatment of OA. However, the function of adipose-derived MSCs (AD-MSCs) in OA and its underlying mechanism remain obscure.

AIM

We aimed to explore the function of AD-MSCs in OA and investigate its potential regulatory mechanism.

METHODS

A guinea pig model of OA was constructed. AD-MSCs injected into the articular cavity of OA guinea pigs were viewed by in vivo bioluminescence imaging. The effect of AD-MSCs on the gonarthritis of OA guinea pigs was evaluated through both macroscopic and microscopic detections. The detailed molecular mechanism was predicted by GEO databases and bioinformatics tools and then verified via mechanism experiments, including ChIP assay, DNA pulldown assay, and luciferase reporter assay.

RESULTS

AD-MSCs had a significant positive therapeutic effect on the gonarthritis of the OA model, and the overall effects of it was better than that of sodium hyaluronate (SH). B-cell translocation gene 2 (BTG2) was significantly downregulated in the articular cartilage of the OA guinea pigs. Furthermore, BTG2 was positively regulated by Krüppel-like factor 4 (KLF4) in AD-MSCs at the transcriptional level. AD-MSCs performed an effect on KLF4 expression at the transcriptional levels.

CONCLUSION

AD-MSCs suppresses OA progression through KLF4-induced transcriptional activation of BTG2. Our findings revealed an AD-MSCs-dominated therapeutic method for OA.

Transient neonatal shoulder paralysis causes early osteoarthritis in a mouse model

Neonatal brachial plexus palsy (NBPP) occurs in approximately 1.5 of every 1,000 live births. The majority of children with NBPP recover function of the shoulder. However, the long-term risk of osteoarthritis (OA) in this population is unknown. The purpose of this study was to investigate the development of OA in a mouse model of transient neonatal shoulder paralysis. Neonatal mice were injected twice per week for 4 weeks with saline in the right supraspinatus muscle (Saline, control) and botulinum toxin A (BtxA, transient paralysis) in the left supraspinatus muscle, and then allowed to recover for 20 or 36 weeks. Control mice received no injections, and all mice were sacrificed at 24 or 40 weeks. BtxA mice exhibited abnormalities in gait compared to controls through 10 weeks of age, but these differences did not persist into adulthood. BtxA shoulders had decreased bone volume (-9%) and abnormal trabecular microstructure compared to controls. Histomorphometry analysis demonstrated that BtxA shoulders had higher murine shoulder arthritis scale scores (+30%), and therefore more shoulder OA compared to controls. Articular cartilage of BtxA shoulders demonstrated stiffening of the tissue. Compared with controls, articular cartilage from BtxA shoulders had 2-fold and 10-fold decreases in Dkk1 and BMP2 expression, respectively, and 3-fold and 14-fold increases in Col10A1 and BGLAP expression, respectively, consistent with established models of OA. In summary, a brief period of paralysis of the neonatal mouse shoulder was sufficient to generate early signs of OA in adult cartilage and bone.

Estrogen alleviates post-traumatic osteoarthritis progression and decreases p-EGFR levels in female mouse cartilage

Objective

To investigate the effect of estrogen on the progression of post-traumatic osteoarthritis (PTOA) in mice and its possible mechanism.

Methods

Twelve-week-old ICR mice were divided into Group A (female control group), group B (ovariectomized(OVX) group), group C (OVX group supplemented with estrogen), and group D (male group) by destabilization of the medial meniscus (DMM)or sham operation. Safranin O staining was performed at 8 weeks and 12 weeks after operation, and the degree of articular cartilage lesion was evaluated using Mankin score. Twelve weeks after the operation, tissue sections were stained to analyze the matrix metalloproteinase 13(MMP13), phosphorylated epidermal growth factor receptor (p-EGFR) expression and apoptosis of chondrocytes.

Results

Decreased estrogen can significantly increase the weight of mice in female mice. The degree of cartilage damage in the knee joint on the DMM side of female mice was significantly severer than that on the Sham side. The DMM side also showed higher MMP13 expression and increased apoptotic chondrocytes. The degree of cartilage damage in the knee joint on the DMM side of female mice was significantly reduced after estrogen supplementation, and cartilage damage in the knee joint on the DMM side of female mice was less serious than that of male mice. As estrogen levels decreased, the severity of cartilage erosion in the knee joint on the DMM side was aggravated, and p-EGFR expression in the cartilage surface was also higher in female mice contrast to that in male mice. However, minimal changes in p-EGFR expression in the cartilage surface of bilateral knee joints of male mice were observe.

Conclusion

Estrogen has a regulatory effect on PTOA and its inhibits the expression of p-EGFR in cartilage on the knee joint surface and has a protective effect on articular cartilage in female mice.