Bone remodelling in osteoarthritis

Atractylenolide-III attenuates osteoarthritis by repolarizing macrophages through inactivating TLR4/NF-κB signaling

BACKGROUND

As a common chronic musculoskeletal condition, osteoarthritis (OA) presently lacks particular treatment strategies. The aim of this study was to examine how AT-III therapies affected macrophage repolarity in order to slow down the advancement of OA.

METHODS

RAW264.7 macrophages were polarized to M1 subtypes then administered with different concentrations of AT-III. Immunofluorescence, qRT-PCR and flow cytometry were used to assess the polarization of the macrophages. The mechanism of AT-III repolarize macrophages was evaluated by western blot. Furthermore, the effects of macrophage conditioned media (CM) on the migration, proliferation, and chondrogenic differentiation of bone marrow mesenchymal stem cells (BMSCs) were investigated using CCK-8 assays, the scratch test, and alcian blue staining. The effects of macrophage CM on chondrocyte proliferation and degeneration were investigated using CCK-8 and qRT-PCR. In vivo micro-CT and histological observations were performed on rats with anterior cruciate ligament transection and partial medial meniscectomy, either with or without AT-III treatment.

RESULTS

AT-III repolarized M1 macrophages to M2 phenotype. Mechanistically, AT-III reduced the expression of Toll-like receptor(TLR) 4 induced by lipopolysaccharide in RAW264.7 and lowered nuclear factor-κB (NF-κB) signaling molecules p-p65 and p-IκBα. The TLR4 agonist RS09 reversed the effects of AT-III on macrophage repolarization. AT-III-induced macrophages CM stimulated BMSCs migration, proliferation and chondrogenic differentiation. AT-III-treated macrophage CM promoted chondrocyte proliferation while inhibiting chondrocyte degeneration. In vivo, AT-III treatment alleviated the degree of synovitis, inhibited subchondral bone remodeling and reduced cartilage destruction in the rat OA model.

CONCLUSIONS

AT-III attenuates OA by repolarizing macrophages through inactivating TLR4/NF-κB signaling. These data suggest that AT-III may be an effective therapeutic candidate for OA treatment.

Engineered MgO nanoparticles for cartilage-bone synergistic therapy

The emerging therapeutic strategies for osteoarthritis (OA) are shifting toward comprehensive approaches that target periarticular tissues, involving both cartilage and subchondral bone. This shift drives the development of single-component therapeutics capable of acting on multiple tissues and cells. Magnesium, an element essential for maintaining skeletal health, shows promise in treating OA. However, the precise effects of magnesium on cartilage and subchondral bone are not yet clear. Here, we investigated the therapeutic effect of Mg2+ on OA, unveiling its protective effects on both cartilage and bone at the cellular and animal levels. The beneficial effect on the cartilage-bone interaction is primarily mediated by the PI3K/AKT pathway. In addition, we developed poly(lactic-co-glycolic acid) (PLGA) microspheres loaded with nano-magnesium oxide modified with stearic acid (SA), MgO&SA@PLGA, for intra-articular injection. These microspheres demonstrated remarkable efficacy in alleviating OA in rat models, highlighting their translational potential in clinical applications.

Knee Measurement System with Osteoarthritis Levels Using Artificial Cartilage and Skeletons

Knee osteoarthritis (OA), also known as degenerative arthritis, is a disease characterized by irreversible changes in the cartilage and bones comprising the joints, resulting in pain, impaired function, and deformity. Furthermore, independent of natural aging, the rate of change in joint cartilage has increased in recent years, which is mainly attributed to environmental factors. The rising incidence of knee-related disorders emphasizes the importance of analyzing the morphology and kinematics of knee structure. This study introduces a knee measurement system designed to replicate the motions of knee using 3D-printing technology, providing insights into knee mechanics with OA level. The research explores the stages of OA using the Kellgren-Lawrence (KL) grade scale, highlighting the variations in the force applied to the knee bone according to movement. The developed knee-simulation system, utilizing the four-bar-link theory, presents a novel approach to studying OA levels 0 to 4. As OA progresses, the cartilage deteriorates, affecting the movement of OA. The OA-based knee measurement system that incorporates soft tissues and skeletons can assist in developing a personalized diagnostic approach for knee disease. This will also help to enhance surgical effectiveness by facilitating the creation of personalized prosthetic joints for individual patients and offering a customized surgical simulation.

Identification of key miRNAs in unilateral mastication-induced disruption of cartilage homeostasis

OBJECTIVE

The present study identified potentially pivotal miRNAs contributing to chondrogenic differentiation in temporomandibular joint suffering abnormal stress.

MATERIALS AND METHODS

Sprague-Dawley rats were randomly divided into control and experimental unilateral mastication (EUM) group. Bone micro-structure parameters was detected by micro-CT, and FGF-1 and MMP-1 expression was examined by immunohistochemistry. Differentially expressed miRNAs of bilateral condyle cartilage were screened via miRNA microarray at 4- and 8-week EUM, then further verified using quantitative reverse-transcription PCR. Over-expression of five differentially expressed miRNAs in chondrocytes was triggered by transfecting miRNA mimics. The expression of MMP-13, Col-II, OPN, and Runx2 was verified by western blotting.

RESULTS

Expressions of FGF-1 and MMP-1 in right condyles gradually increased from 2 to 6 weeks after EUM. A total of 20 differentially expressed miRNAs were regulated by EUM, which related to cell proliferation, invasion, and osteoblast differentiation pathways. The over-expression of miR-148a-3p and miR-1-3p led to down-regulation of Col-II, while MMP-13 and Runx2 were up-regulated by induction of hypotrophic differentiation or IL-1β stimulation. These findings suggested that miR-148a-3p and miR-1-3p promote chondrogenic differentiation.

CONCLUSIONS

Several pivotal miRNAs were found to be related to chondrogenic differentiation, which provides novel insight into pathogenic mechanisms of cartilage homeostasis.

Tranexamic Acid Attenuates the Progression of Posttraumatic Osteoarthritis in Mice

BACKGROUND

Posttraumatic osteoarthritis (OA) is a common disorder associated with a high socioeconomic burden, particularly in young, physically active, and working patients. Tranexamic acid (TXA) is commonly used in orthopaedic trauma surgery as an antifibrinolytic agent to control excessive bleeding. Previous studies have reported that TXA modulates inflammation and bone cell function, both of which are dysregulated during posttraumatic OA disease progression.

PURPOSE

To evaluate the therapeutic effects of systemic and topical TXA treatment on the progression of posttraumatic OA in the knee of mice.

STUDY DESIGN

Controlled laboratory study.

METHODS

OA was induced via anterior cruciate ligament (ACL) transection on the right knee of female mice. Mice were treated with TXA or vehicle intraperitoneally daily or intra-articularly weekly for 4 weeks, starting on the day of surgery. Articular cartilage degeneration, synovitis, bone erosion, and osteophyte formation were scored histologically. Micro-computed tomography evaluation was conducted to measure the subchondral bone microstructure and osteophyte volume. Cartilage thickness and bone remodeling were assessed histomorphometrically.

RESULTS

Both systemic and topical TXA treatment significantly reduced cartilage degeneration, synovitis, and bone erosion scores and increased the ratio of hyaline to calcified cartilage thickness in posttraumatic OA. Systemic TXA reversed ACL transection-induced subchondral bone loss and osteophyte formation, whereas topical treatment had no effect. Systemic TXA decreased the number and surface area of osteoclasts, whereas those of osteoblasts were not affected. No effect of topical TXA on osteoblast or osteoclast parameters was observed.

CONCLUSION

Both systemic and topical TXA exerted protective effects on the progression of posttraumatic OA. Drug repurposing of TXA may, therefore, be useful for the prevention or treatment of posttraumatic OA, particularly after ACL surgery.

CLINICAL RELEVANCE

TXA might be beneficial in patients with posttraumatic OA of the knee.

LncRNA-mediated cartilage homeostasis in osteoarthritis: a narrative review

Osteoarthritis (OA) is a degenerative disease of cartilage that affects the quality of life and has increased in morbidity and mortality in recent years. Cartilage homeostasis and dysregulation are thought to be important mechanisms involved in the development of OA. Many studies suggest that lncRNAs are involved in cartilage homeostasis in OA and that lncRNAs can be used to diagnose or treat OA. Among the existing therapeutic regimens, lncRNAs are involved in drug-and nondrug-mediated therapeutic mechanisms and are expected to improve the mechanism of adverse effects or drug resistance. Moreover, targeted lncRNA therapy may also prevent or treat OA. The purpose of this review is to summarize the links between lncRNAs and cartilage homeostasis in OA. In addition, we review the potential applications of lncRNAs at multiple levels of adjuvant and targeted therapies. This review highlights that targeting lncRNAs may be a novel therapeutic strategy for improving and modulating cartilage homeostasis in OA patients.

The Hippo-YAP Signaling Pathway in Osteoarthritis and Rheumatoid Arthritis

Arthritis is the most prevalent joint disease and is characterized by articular cartilage degradation, synovial inflammation, and changes in periarticular and subchondral bone. Recent studies have reported that Yes-associated protein (YAP) and the transcriptional coactivator with PDZ-binding motif (TAZ) have significant effects on the proliferation, migration, and survival of chondrocytes and fibroblast-like synovial cells (FLSs). YAP/TAZ signaling pathway, as well as the related Hippo-YAP signaling pathway, are responsible for the condition of cells and articular cartilage in joints. They are tightly regulated to maintain metabolism in chondrocytes and FLSs because abnormal expression may result in cartilage damage. However, the roles and mechanisms of the Hippo-YAP pathway in arthritis remain largely unknown. This review summarizes the roles and key functions of YAP/TAZ and the Hippo-YAP signaling pathway in FLSs and chondrocytes for the induction of proliferation, migration, survival, and differentiation in rheumatoid arthritis (RA) and osteoarthritis (OA) research. We also discuss the therapeutic strategies involving YAP/TAZ and the related Hippo-YAP signaling pathway involved in OA.

Nitisinone attenuates cartilage degeneration and subchondral osteoclastogenesis in osteoarthritis and concomitantly inhibits the cGAS/STING/NF-κB pathway

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by cartilage degeneration and subchondral bone remodelling. Currently, conservative treatment strategies cannot effectively alleviate the progression of OA. In this study, we used computer network analysis to show that Nitisinone (NTBC) is closely related to extracellular matrix degradation in OA and mainly interferes with the TNF-α signaling pathway. NTBC is an orphan drug used to treat hereditary type I tyrosinemia by altering phenylalanine/tyrosine metabolic flow. In this study, we found that NTBC effectively reduced chondrocyte inflammation and extracellular matrix degradation induced by TNF-α. Mechanistically, NTBC inhibited the cGAS/STING signaling pathway and reduced activation of the STING-dependent NF-κB pathway to alleviate inflammation. In addition, NTBC inhibited osteoclastogenesis and delayed the occurrence of subchondral bone remodelling. In mice with ACLT-induced osteoarthritis, intra-articular injection of NTBC significantly reduced cartilage degradation and subchondral bone remodelling. NTBC showed impressive therapeutic efficacy as a potential pharmaceutical intervention for the treatment of OA.

Biomimetic injectable and bilayered hydrogel scaffold based on collagen and chondroitin sulfate for the repair of osteochondral defects

The simultaneous regeneration of articular cartilage and subchondral bone is a major challenge. Bioinspired scaffolds with distinct regions resembling stratified anatomical architecture provide a potential strategy for osteochondral defect repair. Here, we report the development of an injectable and bilayered hydrogel scaffold with a strong interface binding force. In this bilayer hydrogel, composed of carbonyl hydrazide grafted collagen (COL-CDH) and oxidized chondroitin sulfate (OCS), which are derivatives of osteochondral tissue components, in combination with poly (ethylene glycol) diacrylate (PEGDA), functions as a cartilage layer; while zinc-doped hydroxyapatite acts as a subchondral bone layer that is based on the cartilage layer. The strong interface between the two layers involves dynamic amide bonds formed between COL-CDH and OCS, and permanent CC bonds formed by PEGDA radical reactions. This bilayer hydrogel can be used to inoculate adipose mesenchymal stem cells which can then differentiate into chondrocytes and osteoblasts, secreting glycosaminoglycan, and promoting calcium deposition. This accelerates the regeneration of cartilage and subchondral bone. Micro-CT and tissue staining revealed an increase in the amount of bone present in new subchondral bone, and new tissues with a structure similar to normal cartilage. This study therefore demonstrates that injectable bilayer hydrogels are a promising scaffold for repairing osteochondral defects.

Regulating Chondro-Bone Metabolism for Treatment of Osteoarthritis via High-Permeability Micro/Nano Hydrogel Microspheres

Destruction of cartilage due to the abnormal remodeling of subchondral bone (SB) leads to osteoarthritis (OA), and restoring chondro-bone metabolic homeostasis is the key to the treatment of OA. However, traditional intra-articular injections for the treatment of OA cannot directly break through the cartilage barrier to reach SB. In this study, the hydrothermal method is used to synthesize ultra-small size (≈5 nm) selenium-doped carbon quantum dots (Se-CQDs, SC), which conjugated with triphenylphosphine (TPP) to create TPP-Se-CQDs (SCT). Further, SCT is dynamically complexed with hyaluronic acid modified with aldehyde and methacrylic anhydride (AHAMA) to construct highly permeable micro/nano hydrogel microspheres (SCT@AHAMA) for restoring chondro-bone metabolic homeostasis. In vitro experiments confirmed that the selenium atoms scavenged reactive oxygen species (ROS) from the mitochondria of mononuclear macrophages, inhibited osteoclast differentiation and function, and suppressed early chondrocyte apoptosis to maintain a balance between cartilage matrix synthesis and catabolism. In vivo experiments further demonstrated that the delivery system inhibited osteoclastogenesis and H-vessel invasion, thereby regulating the initiation and process of abnormal bone remodeling and inhibiting cartilage degeneration in SB. In conclusion, the micro/nano hydrogel microspheres based on ultra-small quantum dots facilitate the efficient penetration of articular SB and regulate chondro-bone metabolism for OA treatment.

Harpagide inhibits the TNF-α-induced inflammatory response in rat articular chondrocytes by the glycolytic pathways for alleviating osteoarthritis

Osteoarthritis (OA) causes severe and functional dysfunction due to abnormal inflammation. The objective of this study was to evaluate the effect of Harpagide (HPG) on TNF-α-induced inflammation in vitro and in vivo. The effect of HPG on the proliferation of rat chondrocytes was studied. The anti-inflammatory effect of HPG and its molecular mechanisms were elucidated by qPCR, Western blotting, flow cytometry, metabolome analysis in vitro. In addition, the OA rat model was established, and the effect of HPG on OA was verified in vivo. We revealed 10 μM HPG demonstrated biocompatibility. The results demonstrated that HPG restored the upregulation of MMP-13, COX2, IL-1β and IL-6 induced by TNF-α. Moreover, HPG reversed TNF-α induced degradation of the extracellular matrix of chondrocytes. TNF-α treatment induced down-regulation of the mRNA/protein levels of proliferative markers Bcl2, CDK1 and Cyclin D1 were also recovered. HPG can inhibit TNF-α-induced inflammatory response through glycolytic metabolic pathways. HPG can restore TNF-α-induced upregulation of GRP78/IRE1α, and downregulation of AMPK proteins. In vivo experiments demonstrated that after HPG treatment, the appearance and physiological structure of articular cartilage were more integrated with highly organized chondrocytes and rich cartilage matrix compared with OA group. Finally, the molecular docking of HPG and selected key factors in glycolysis results showed that HPG had good binding potential with PFKM, PFKP, PFKFB3, PKM, HK2, and PFKL. In conclusion, the results shown HPG protects and activates chondrocytes, inhibits TNF-α-induced inflammatory response by glycolysis pathway in rat articular chondrocytes, and plays a role in the treatment of OA.

Carveol alleviates osteoarthritis progression by acting on synovial macrophage polarization transformation: An in vitro and in vivo study

Osteoarthritis (OA) is a heterogeneous disease that affects the entire joint. Its pathogenesis involves hypertrophy and hyperplasia of synovial cells and polarization infiltration of macrophages, in which macrophages, as a potential target, can delay the progression of the disease by improving the immune microenvironment in OA. To investigate the role and regulatory mechanism of Carveol in cartilage and synovial macrophage reprogramming and crosstalk during the development of OA. RAW264.7 mouse macrophage cell line was mainly used to stimulate macrophages to polarization towards M1 and M2 by LPS, IL4+IL13, respectively. Different concentrations of Carveol were given to intervene, and macrophage culture medium was collected to intervene mouse C57BL6J chondrocytes. ROS assay kit, western blotting, cellular immunofluorescence, scanning microscope and section histology were used to evaluate the effect of Carveol on anti-M1-polarization, M2-polarization promotion and cartilage protection. The mouse destabilization of medial meniscus (DMM) model was observed by micro-CT scan and histology. We found that CA could inhibit the increase of macrophage inflammation level under the intervention of LPS and promote the production of M2 anti-inflammatory substances under the intervention of IL-4+IL13. In addition, Carveol activated NRF2/HO-1/NQO1 pathway and enhanced ROS clearance in chondrocytes under the intervention of macrophage culture medium. The phosphorylation of I-κBα is inhibited, which further reduces the phosphorylation of P65 downstream of nuclear factor-κB (NF-κB) signaling pathway. In addition, Carveol inhibits mitogen activated protein kinase (MAPK) signaling molecules P-JNK, P-ERK and P-P38, and inhibits the production of inflammatory mediators. In vivo, Carveol can reduce osteophytes and bone spurs induced by DMM, reduce hypertrophy of synovial cells, reduce infiltration of macrophages, inhibit subchondral bone destruction, and reduce articular cartilage erosion. Our study suggests that synovial macrophages are potential targets for OA treatment, and Carveol is an effective candidate for OA treatment.

A Systemic Review on Nutraceutical Supplements used in the Management of Osteoarthritis

Osteoarthritis (OA) is a progressive degenerative joint disease. It basically impairs the structural integrity of articulate cartilage and imbalances the catabolic and anabolic signals in the joint. A degenerative disease is characterized by swelling, pain, and joint stiffness. The treatment and management of osteoarthritis are based on analgesic and anti-inflammatory agents, whereas the exact cause of OA is not known yet. The negative effects of synthetic medications have led to a daily rise in the usage of nutraceuticals and dietary supplements. Clinicians are aware of these treatments, and they also recommend nutraceuticals in addition to the currently preferred therapy. Many in-vitro and in-vivo experiments have been performed in past years to evaluate the function of these on osteoarthritis. The collection of articles was published on search engines like PubMed, Scopus, Google Scholar, ResearchGate, and ScienceDirect. The evaluation covers every potential nutraceutical utilized in osteoarthritis, together with its supporting data and mode of action. The present review discusses nutraceuticals, including devil's claw, vitamin D, boswellic acid, capsaicin, ginger, curcumin, krill oil, ginger, and avocado/soybean unsaponifiable.

Exploration and breakthrough in the mode of chondrocyte death - A potential new mechanism for osteoarthritis

Osteoarthritis (OA) is a frequent chronic joint disease in orthopedics that effects individuals and society significantly. Obesity, aging, genetic susceptibility, and joint misalignment are all known risk factors for OA, but its pathomechanism is still poorly understood. Researches have revealed that OA is a much complex process related to inflammation, metabolic and chondrocyte death. It can affect all parts of the joint and is characterized by causing chondrocyte death and extracellular matrix descent. Previously, OA was thought to develop from excessive mechanical loading leading to the destruction of articular cartilage. Since some programmed cell deaths and OA share a pattern of chondrocyte destruction, it is likely that OA also involves programmed cell death. Even though chondrocyte apoptosis and pyroptosis have been investigated in OA, clarifing solely conventional cell death pathways is still insufficient to understand the pathophysiology of osteoarthritis. With more researches, it has been discovered that osteoarthritis and other new cell death processes, including PANoptosis, ferroptosis, and cell senescence, are strongly associated. Among these, PANoptosis combines the key traits of pyroptosis, cell apoptosis, and necrotic apoptosis into a highly coordinated and dynamically balanced programmed inflammatory cell death mechanism. Furthermore, we think that PANopotosis might obstruct necroptosis and cell senescence. Therefore, in order to offer direction for therapeutic treatment, we evaluate the development of research on multiple cell death of chondrocytes in OA.

Nerve Growth Factor Receptor Limits Inflammation to Promote Remodeling and Repair of Osteoarthritic Joints

Osteoarthritis (OA) is a painful, incurable disease affecting over 500 million people. The need for relieving OA pain is paramount but inadequately addressed, partly due to limited understandings of how pain signaling regulates non-neural tissues. Here we report that nerve growth factor receptor (NGFR) is upregulated in skeletal cells during OA and plays an essential role in the remodeling and repair of osteoarthritic joints. Specifically, NGFR is expressed in osteochondral cells but not in skeletal progenitor cells and induced by TNFα to attenuate NF-κB activation, maintaining proper BMP-SMAD1 signaling and suppressing RANKL expression. NGFR deficiency hyper-activates NF-κB in murine osteoarthritic joints, which impairs bone formation and enhances bone resorption as exemplified by a reduction in subchondral bone and osteophytes. In human OA cartilage, NGFR is also negatively associated with NF-κB activation. Together, this study uncovers a role of NGFR in limiting inflammation for repair of diseased skeletal tissues.

The dual pro-inflammatory and bone-protective role of calcitonin gene-related peptide alpha in age-related osteoarthritis

BACKGROUND

The vasoactive neuropeptide calcitonin gene-related peptide alpha (αCGRP) enhances nociception in primary knee osteoarthritis (OA) and has been shown to disrupt cartilage and joint integrity in experimental rheumatoid arthritis (RA). Little is known about how αCGRP may alter articular structures in primary OA. We investigated whether αCGRP modulates local inflammation and concomitant cartilage and bone changes in a murine model of age-dependent OA.

METHODS

Sixteen- to 18-month-old αCGRP-deficient mice (αCGRP-/-aged) were compared to, first, age-matched wild type (WTaged) and, second, young 4- to 5-month-old non-OA αCGRP-deficient (αCGRP-/-CTRL) and non-OA WT animals (WTCTRL). αCGRP levels were measured in serum. Knee and hip joint inflammation, cartilage degradation, and bone alterations were assessed by histology (OARSI histopathological grading score), gene expression analysis, and µ-computed tomography.

RESULTS

WTaged mice exhibited elevated αCGRP serum levels compared to young WTCTRL animals. Marked signs of OA-induced cartilage destruction were seen in WTaged animals, while αCGRP-/-aged mice were mostly protected from this effect. Age-dependent OA was accompanied by an increased gene expression of pro-inflammatory Tnfa, Il1b, and Il6 and catabolic Mmp13, Adamts5, Ctsk, Tnfs11 (Rankl), and Cxcl12/Cxcr4 in WTaged but not in αCGRP-/-aged mice. αCGRP-deficiency however further aggravated subchondral bone sclerosis of the medial tibial plateau and accelerated bone loss in the epi- and metaphyseal trabecular tibial bone in age-dependent OA.

CONCLUSIONS

Similar to its function in experimental RA, αCGRP exerts a dual pro-inflammatory and bone-protective function in murine primary OA. Although anti-CGRP treatment was previously not successful in reducing pain in OA clinically, these data underline a crucial pathophysiological role of αCGRP in age-related OA.

What Role Does PET/MRI Play in Musculoskeletal Disorders?

Musculoskeletal disorders of nononcological origin are one of the most frequent reasons for consultation. Patients suffering from musculoskeletal disorders also consult more than once for the same reason. This results in multiple clinical follow-ups after several radiological and serum examinations, the main ones including X-rays targeting the painful anatomical region and inflammatory serum parameters. As part of their work up, patients suffering from musculoskeletal disorders often require multisequence, multi-parameter MRI. PET/MRI is a promising imaging modality for their diagnosis, with the added advantage of being able to be performed in a single visit. PET/MRI is particularly useful for diagnosing osteomyelitis, spondylodiscitis, arthritis, many pediatric pathologies, and a wide range of other musculoskeletal pathologies. PET/MRI is already used to diagnose malignant bone tumors such as osteosarcoma. However, current knowledge of the indications for PET/MRI in nononcological musculoskeletal disorders is based on studies involving only a few patients. This review focuses on the usefulness of PET/MRI for diagnosing nononcological musculoskeletal disorders.

A robust NIR fluorescence-activated probe for peroxynitrite imaging in cells and mice osteoarthritis models

Osteoarthritis (OA) is the most common type of joint disease, which is difficult to treat, but early standardized diagnosis and treatment can effectively alleviate the pain and symptoms of patients. Therefore, it is important to construct an effective tool to assist in the early diagnosis and evaluation of the therapeutic effect of OA. In this work, a near-infrared (NIR) fluorescence-activated fluorescent probe, YB-1, was constructed for the evaluation of the diagnostic and therapeutic efficacy of OA via detection and imaging of the biomarker of ONOO- in inflammatory cells and mice osteoarthritis models. YB-1 exhibited high selectivity, high sensitivity, and a high ratio yield (I668/I0) fluorescence increasing (∼30 folds). Besides, YB-1 can be used effectively to image endogenous and exogenous ONOO- in living human chondrocytes cells (TC28a2), as well as to evaluate the effect of drug (Chrysosplenol D, CD) treatment in IL-1β-induced inflammatory cells model. Interestingly, YB-1 was available for OONO- imaging analysis in the collagenase-induced mice OA models and assessment of the effect of CD treatment in mice OA models, with good results. Thus, the newly constructed YB-1 is a powerful molecular tool for the diagnosis and treatment of OA-related diseases.

Subchondral bone remodeling patterns in larger animal models of meniscal injuries inducing knee osteoarthritis - a systematic review

PURPOSE

Elucidating subchondral bone remodeling in preclinical models of traumatic meniscus injury may address clinically relevant questions about determinants of knee osteoarthritis (OA).

METHODS

Studies on subchondral bone remodeling in larger animal models applying meniscal injuries as standardizing entity were systematically analyzed. Of the identified 5367 papers reporting total or partial meniscectomy, meniscal transection or destabilization, 0.4% (in guinea pigs, rabbits, dogs, minipigs, sheep) remained eligible.

RESULTS

Only early or mid-term time points were available. Larger joint sizes allow reporting higher topographical details. The most frequently reported parameters were BV/TV (61%), BMD (41%), osteophytes (41%) and subchondral bone plate thickness (39%). Subchondral bone plate microstructure is not comprehensively, subarticular spongiosa microstructure is well characterized. The subarticular spongiosa is altered shortly before the subchondral bone plate. These early changes involve degradation of subarticular trabecular elements, reduction of their number, loss of bone volume and reduced mineralization. Soon thereafter, the previously normal subchondral bone plate becomes thicker. Its porosity first increases, then decreases.

CONCLUSION

The specific human topographical pattern of a thinner subchondral bone plate in the region below both menisci is present solely in the larger species (partly in rabbits), but absent in rodents, an important fact to consider when designing animal studies examining subchondral consequences of meniscus damage. Large animal models are capable of providing high topographical detail, suggesting that they may represent suitable study systems reflecting the clinical complexities. For advanced OA, significant gaps of knowledge exist. Future investigations assessing the subchondral bone in a standardized fashion are warranted.

Endothelial Stat3 activation promotes osteoarthritis development

The mechanism of the balance between subchondral angiogenesis and articular damage within osteoarthritis (OA) progression remains a mystery. However, the lack of specific drugs leads to limited clinical treatment options for OA, frequently failing to prevent eventual joint destruction in patients. Increasing evidence suggests that subchondral bone angiogenesis precedes cartilage injury, while proliferating endothelial cells (ECs) induce abnormal bone formation. Signal transducer and activator of transcription 3 (Stat3) is triggered by multiple cytokines in the OA microenvironment. Here, we observed elevated Stat3 activation in subchondral bone H-type vessels. Endothelial Stat3 activation will lead to stronger cell proliferation, migration and angiogenesis by simulating ECs in OA. In contrast, either Stat3 activation inhibition or knockdown of Stat3 expression could relieve such alterations. More interestingly, blocking Stat3 in ECs alleviated angiogenesis-mediated osteogenic differentiation and chondrocyte lesions. Stat3 inhibitor reversed surgically induced subchondral bone H-type vessel hyperplasia in vivo, significantly downregulating vessel volume and vessel number. Due to the reduced angiogenesis, subchondral bone deterioration and cartilage loss were alleviated. Overall, our data suggest that endothelial Stat3 activation is an essential trigger for OA development. Therefore, targeted Stat3 blockade is a novel promising therapeutic regimen for OA.

Controlled-Release Hydrogel Microspheres to Deliver Multipotent Stem Cells for Treatment of Knee Osteoarthritis

Osteoarthritis (OA) is the most common form of joint disease affecting articular cartilage and peri-articular tissues. Traditional treatments are insufficient, as they are aimed at mitigating symptoms. Multipotent Stromal Cell (MSC) therapy has been proposed as a treatment capable of both preventing cartilage destruction and treating symptoms. While many studies have investigated MSCs for treating OA, therapeutic success is often inconsistent due to low MSC viability and retention in the joint. To address this, biomaterial-assisted delivery is of interest, particularly hydrogel microspheres, which can be easily injected into the joint. Microspheres composed of hyaluronic acid (HA) were created as MSC delivery vehicles. Microrheology measurements indicated that the microspheres had structural integrity alongside sufficient permeability. Additionally, encapsulated MSC viability was found to be above 70% over one week in culture. Gene expression analysis of MSC-identifying markers showed no change in CD29 levels, increased expression of CD44, and decreased expression of CD90 after one week of encapsulation. Analysis of chondrogenic markers showed increased expressions of aggrecan (ACAN) and SRY-box transcription factor 9 (SOX9), and decreased expression of osteogenic markers, runt-related transcription factor 2 (RUNX2), and alkaline phosphatase (ALPL). In vivo analysis revealed that HA microspheres remained in the joint for up to 6 weeks. Rats that had undergone destabilization of the medial meniscus and had overt OA were treated with empty HA microspheres, MSC-laden microspheres, MSCs alone, or a control vehicle. Pain measurements taken before and after the treatment illustrated temporarily decreased pain in groups treated with encapsulated cells. Finally, the histopathological scoring of each group illustrated significantly less OA damage in those treated with encapsulated cells compared to controls. Overall, these studies demonstrate the potential of using HA-based hydrogel microspheres to enhance the therapeutic efficacy of MSCs in treating OA.

Insights into the underlying pathogenesis and therapeutic potential of endoplasmic reticulum stress in degenerative musculoskeletal diseases

Degenerative musculoskeletal diseases are structural and functional failures of the musculoskeletal system, including osteoarthritis, osteoporosis, intervertebral disc degeneration (IVDD), and sarcopenia. As the global population ages, degenerative musculoskeletal diseases are becoming more prevalent. However, the pathogenesis of degenerative musculoskeletal diseases is not fully understood. Previous studies have revealed that endoplasmic reticulum (ER) stress is a stress response that occurs when impairment of the protein folding capacity of the ER leads to the accumulation of misfolded or unfolded proteins in the ER, contributing to degenerative musculoskeletal diseases. By affecting cartilage degeneration, synovitis, meniscal lesion, subchondral bone remodeling of osteoarthritis, bone remodeling and angiogenesis of osteoporosis, nucleus pulposus degeneration, annulus fibrosus rupture, cartilaginous endplate degeneration of IVDD, and sarcopenia, ER stress is involved in the pathogenesis of degenerative musculoskeletal diseases. Preclinical studies have found that regulation of ER stress can delay the progression of multiple degenerative musculoskeletal diseases. These pilot studies provide foundations for further evaluation of the feasibility, efficacy, and safety of ER stress modulators in the treatment of musculoskeletal degenerative diseases in clinical trials. In this review, we have integrated up-to-date research findings of ER stress into the pathogenesis of degenerative musculoskeletal diseases. In a future perspective, we have also discussed possible directions of ER stress in the investigation of degenerative musculoskeletal disease, potential therapeutic strategies for degenerative musculoskeletal diseases using ER stress modulators, as well as underlying challenges and obstacles in bench-to-beside research.

Subchondral bone in knee osteoarthritis: bystander or treatment target?

The subchondral bone is an important structural component of the knee joint relevant for osteoarthritis (OA) incidence and progression once disease is established. Experimental studies have demonstrated that subchondral bone changes are not simply the result of altered biomechanics, i.e., pathologic loading. In fact, subchondral bone alterations have an impact on joint homeostasis leading to articular cartilage loss already early in the disease process. This narrative review aims to summarize the available and emerging imaging techniques used to evaluate knee OA-related subchondral bone changes and their potential role in clinical trials of disease-modifying OA drugs (DMOADs). Radiographic fractal signature analysis has been used to quantify OA-associated changes in subchondral texture and integrity. Cross-sectional modalities such as cone-beam computed tomography (CT), contrast-enhanced cone beam CT, and micro-CT can also provide high-resolution imaging of the subchondral trabecular morphometry. Magnetic resonance imaging (MRI) has been the most commonly used advanced imaging modality to evaluate OA-related subchondral bone changes such as bone marrow lesions and altered trabecular bone texture. Dual-energy X-ray absorptiometry can provide insight into OA-related changes in periarticular subchondral bone mineral density. Positron emission tomography, using physiological biomarkers of subchondral bone regeneration, has provided additional insight into OA pathogenesis. Finally, artificial intelligence algorithms have been developed to automate some of the above subchondral bone measurements. This paper will particularly focus on semiquantitative methods for assessing bone marrow lesions and their utility in identifying subjects at risk of symptomatic and structural OA progression, and evaluating treatment responses in DMOAD clinical trials.

MRI texture analysis of acetabular cancellous bone can discriminate between normal, cam positive, and cam-FAI hips

OBJECTIVES

To compare the MRI texture profile of acetabular subchondral bone in normal, asymptomatic cam positive, and symptomatic cam-FAI hips and determine the accuracy of a machine learning model for discriminating between the three hip classes.

METHODS

A case-control, retrospective study was performed including 68 subjects (19 normal, 26 asymptomatic cam, 23 symptomatic cam-FAI). Acetabular subchondral bone of unilateral hip was contoured on 1.5 T MR images. Nine first-order 3D histogram and 16 s-order texture features were evaluated using specialized texture analysis software. Between-group differences were assessed using Kruskal-Wallis and Mann-Whitney U tests, and differences in proportions compared using chi-square and Fisher's exact tests. Gradient-boosted ensemble methods of decision trees were created and trained to discriminate between the three groups of hips, with percent accuracy calculated.

RESULTS

Sixty-eight subjects (median age 32 (28-40), 60 male) were evaluated. Significant differences among all three groups were identified with first-order (4 features, all p ≤ 0.002) and second-order (11 features, all p ≤ 0.002) texture analyses. First-order texture analysis could differentiate between control and cam positive hip groups (4 features, all p ≤ 0.002). Second-order texture analysis could additionally differentiate between asymptomatic cam and symptomatic cam-FAI groups (10 features, all p ≤ 0.02). Machine learning models demonstrated high classification accuracy of 79% (SD 16) for discriminating among all three groups.

CONCLUSION

Normal, asymptomatic cam positive, and cam-FAI hips can be discriminated based on their MRI texture profile of subchondral bone using descriptive statistics and machine learning algorithms.

CLINICAL RELEVANCE STATEMENT

Texture analysis can be performed on routine MR images of the hip and used to identify early changes in bone architecture, differentiating morphologically abnormal from normal hips, prior to onset of symptoms.

KEY POINTS

• MRI texture analysis is a technique for extracting quantitative data from routine MRI images. • MRI texture analysis demonstrates that there are different bone profiles between normal hips and those with femoroacetabular impingement. • Machine learning models can be used in conjunction with MRI texture analysis to accurately differentiate between normal hips and those with femoroacetabular impingement.

Polymeric biomaterials: Advanced drug delivery systems in osteoarthritis treatment

Polymeric biomaterials have emerged as a highly promising candidate for drug delivery systems (DDS), exhibiting significant potential to enhance the therapeutic landscape of osteoarthritis (OA) therapy. Their remarkable capacity to manifest desirable physicochemical attributes, coupled with their excellent biocompatibility and biodegradability, has greatly expanded their utility in pharmacotherapeutic applications. Nevertheless, an urgent necessity exists for a comprehensive synthesis of the most recent advances in polymeric DDS, providing valuable guidance for their implementation in the context of OA therapy. This review is dedicated to summarizing and examining recent developments in the utilization of polymeric DDS for OA therapy. Initially, we present an overview of the intricate pathophysiology characterizing OA and underscore the prevailing limitations inherent to current treatment modalities. Subsequently, we introduce diverse categories of polymeric DDS, including hydrogels, nanofibers, and microspheres, elucidating their inherent advantages and limitations. Moreover, we discuss and summarize the delivery of bioactive agents through polymeric biomaterials for OA therapy, emphasizing key findings and emerging trends. Finally, we highlight prospective directions for advancing polymeric DDS, offering a promising approach to enhance their translational potential for OA therapy.

Temporomandibular joint osteoarthritis: A review of animal models induced by surgical interventions

OBJECTIVES

The pathological mechanism of temporomandibular joint osteoarthritis (TMJOA) is still unclear. Animal models induced by surgical interventions are one of the most ideal tools to imitate human pathological conditions. This review aims to define the similarities and differences of different surgical animal models.

METHODS

Articles of TMJOA surgical animal models were collected including anterior disc displacement, disc perforation, and discectomy. We analyzed their experiments strategies based on comparing preoperative selection, intraoperative methodology, and postoperative manifestations.

RESULTS

No matter which surgical intervention is selected, abnormal stress forces the whole joint to remodel its structure so that it could adapt to functional requirements, resulting in TMJOA eventually. However, anterior disc displacement needs more than 16 weeks to obtain typical manifestations, where the methodology is complicated. The course of perforation and discectomy is around 12-16 weeks, but they could cause excessive damage to the TMJ structure.

CONCLUSIONS

All surgical interventions can cause TMJOA, but the extent of pathology varies from each other. This review will assist future experiments to better understand the pathogenesis of TMJOA and choose the most appropriate model.

Atractylenolide-III alleviates osteoarthritis and chondrocyte senescence by targeting NF-κB signaling

Atractylenolide-III (AT-III) is well known as its role in antioxidant and anti-inflammatory. Present study was aimed to figure out its effects on osteoarthritis and potential mechanisms. Rat model, human osteoarthritis cartilage explants as well as rat/human chondrocyte cultures were prepared to test AT-III's effects on osteoarthritis progression and chondrocyte senescence. Potential targeted molecules of AT-III were predicted using network pharmacology and molecular docking, assessed by Western blotting and then verified with rescue experiments. AT-III treatment alleviated osteoarthritis severity (shown by OARSI grading score and micro-CT) and chondrocyte senescence (indexed by levels of SA-β-gal, P16, P53, MMP13, ROS and ratio of healthy/collapsed mitochondrial membrane potentials). Network pharmacology and molecular docking suggested that AT-III might play role through NF-κB pathway. Further experiments revealed that AT-III reduced phosphorylation of IKKα/β, IκBα and P65 in NF-κB pathway. As well as nuclear translocation of p65. Both in vivo and in vitro experiments indicated that AT-III's effects on osteoarthritis and anti-senescence were reversed by an NF-κB agonist. AT-III could alleviate osteoarthritis by inhibiting chondrocyte senescence through NF-κB pathway, which indicated that AT-III is a prospective drug for osteoarthritis treatment.

Betulinic Acid Attenuates Osteoarthritis via Limiting NLRP3 Inflammasome Activation to Decrease Interleukin-1β Maturation and Secretion

Introduction

Osteoarthritis (OA) is the most common degenerative joint disorder. Prior studies revealed that activation of NLRP3 inflammasome could promote the activation and secretion of interleukin-1β (IL-1β), which has an adverse effect on the progression of OA. Betulinic acid (BA) is a compound extract of birch, whether it can protect against OA and the mechanisms involved are still unknown.

Materials and Methods

In vivo experiments, using gait analysis, ELISA, micro-CT, and scanning electron microscopy (SEM), histological staining, immunohistological (IHC) and immunofluorescence (IF) staining, and atomic force microscopy (AFM) to assess OA progression after intraperitoneal injection of 5 and 15 mg/kg BA in an OA mouse model. In vitro experiments, caspase-1, IL-1β, and the N-terminal fragment of gasdermin D (GSDMD-NT) were measured in bone marrow-derived macrophages (BMDMs) by using ELISA, western blot, and immunofluorescence staining.

Results

We demonstrated that OA progression can be postponed with intraperitoneal injection of 5 and 15 mg/kg BA in an OA mouse model. Specifically, BA postponed DMM-induced cartilage deterioration, alleviated subchondral bone sclerosis, and relieved synovial inflammation. In vitro studies, the activated NLRP3 inflammasome produces mature IL-1β by facilitating the cleavage of pro-IL-1β, and BA could inhibit the activation of NLRP3 inflammasome in BMDMs.

Conclusions

Taken together, our analyses revealed that BA attenuates OA via limiting NLRP3 inflammasome activation to decrease the IL-1β maturation and secretion.

Bone Remodeling in Osteoarthritis-Biological and Radiological Aspects

Among available papers published on the given subject over the last century, various terms have been used as synonyms for one, now generally accepted-osteoarthritis, in some countries called "wear and tear" or "overload arthritis". The opsolent terms-hypertrophic arthritis, degenerative arthritis, arthritis deformans and osteoarthrosis-sought to highlight the dominant clinical signs of this ubiquitous, polymorph disease of the whole osteochondral unit, which by incidence and prevalence represents one of the leading chronic conditions that cause long-term pain and incapacity for work. Numerous in vitro and in vivo research resulted in broadened acknowledgments about osteoarthritis pathophysiology and pathology on both histological and cellular levels. However, the cause of osteoarthritis is still unknown and is currently the subject of a hypothesis. In this paper, we provide a review of recent findings on biological phenomena taking place in bone tissue during osteoarthritis to the extent useful for clinical practice. Choosing a proper radiological approach is a conditio sine qua non to the early diagnosis of this entity.

Hypoxia-treated adipose mesenchymal stem cell-derived exosomes attenuate lumbar facet joint osteoarthritis

BACKGROUND

Lumbar facet joint osteoarthritis (LFJ OA) is a common disease, and there is still a lack of effective disease-modifying therapies. Our aim was to determine the therapeutic effect of hypoxia-treated adipose mesenchymal stem cell (ADSC)-derived exosomes (Hypo-ADSC-Exos) on the protective effect against LFJ OA.

METHODS

The protective effect of Hypo-ADSC-Exos against LFJ OA was examined in lumbar spinal instability (LSI)-induced LFJ OA models. Spinal pain behavioural assessments and CGRP (Calcitonin Gene-Related Peptide positive) immunofluorescence were evaluated. Cartilage degradation and subchondral bone remodelling were assessed by histological methods, immunohistochemistry, synchrotron radiation-Fourier transform infrared spectroscopy (SR-FTIR), and 3D X-ray microscope scanning.

RESULTS

Hypoxia enhanced the protective effect of ADSC-Exos on LFJ OA. Specifically, tail vein injection of Hypo-ADSC-Exos protected articular cartilage from degradation, as demonstrated by lower FJ OA scores of articular cartilage and less proteoglycan loss in lumbar facet joint (LFJ) cartilage than in the ADSC-Exo group, and these parameters were significantly improved compared to those in the PBS group. In addition, the levels and distribution of collagen and proteoglycan in LFJ cartilage were increased in the Hypo-ADSC-Exo group compared to the ADSC-Exo or PBS group by SR-FTIR. Furthermore, Hypo-ADSC-Exos normalized uncoupled bone remodelling and aberrant H-type vessel formation in subchondral bone and effectively reduced symptomatic spinal pain caused by LFJ OA in mice compared with those in the ADSC-Exo or PBS group.

CONCLUSIONS

Our results show that hypoxia is an effective method to improve the therapeutic effect of ADSC-Exos on ameliorating spinal pain and LFJ OA progression.

Novel insights of EZH2-mediated epigenetic modifications in degenerative musculoskeletal diseases

Degenerative musculoskeletal diseases (Osteoporosis, Osteoarthritis, Degenerative Spinal Disease and Sarcopenia) are pathological conditions that affect the function and pain of tissues such as bone, cartilage, and muscles, and are closely associated with ageing and long-term degeneration. Enhancer of zeste homolog 2 (EZH2), an important epigenetic regulator, regulates gene expression mainly through the PRC2-dependent trimethylation of histone H3 at lysine 27 (H3K27me3). Increasing evidence suggests that EZH2 is involved in several biological processes closely related to degenerative musculoskeletal diseases, such as osteogenic-adipogenic differentiation of bone marrow mesenchymal stem cells, osteoclast activation, chondrocyte functional status, and satellite cell proliferation and differentiation, mainly through epigenetic regulation (H3K27me3). Therefore, the synthesis and elucidation of the role of EZH2 in degenerative musculoskeletal diseases have attracted increasing attention. In addition, although EZH2 inhibitors have been approved for clinical use, whether they can be repurposed for the treatment of degenerative musculoskeletal diseases needs to be considered. Here, we reviewed the role of EZH2 in the development of degenerative musculoskeletal diseases and brought forward prospects of its pharmacological inhibitors in the improvement of the treatment of the diseases.

Microstructural and cellular characterisation of the subchondral trabecular bone in human knee and hip osteoarthritis using synchrotron tomography

OBJECTIVE

It is unclear if different factors influence osteoarthritis (OA) progression and degenerative changes characterising OA disease in hip and knee. We investigated the difference between hip OA and knee OA at the subchondral bone (SCB) tissue and cellular level, relative to the degree of cartilage degeneration.

DESIGN

Bone samples were collected from 11 patients (aged 70.4 ± 10.7years) undergoing knee arthroplasty and 8 patients (aged 62.3 ± 13.4years) undergoing hip arthroplasty surgery. Trabecular bone microstructure, osteocyte-lacunar network, and bone matrix vascularity were evaluated using synchrotron micro-CT imaging. Additionally, osteocyte density, viability, and connectivity were determined histologically.

RESULTS

The associations between severe cartilage degeneration and increase of bone volume fraction (%) [- 8.7, 95% CI (-14.1, -3.4)], trabecular number (#/mm) [- 1.5, 95% CI (-0.8, -2.3)], osteocyte lacunar density (#/mm3) [4714.9; 95% CI (2079.1, 7350.6)] and decrease of trabecular separation (mm) [- 0.07, 95% CI (0.02, 0.1)] were found in both knee and hip OA. When compared to knee OA, hip OA was characterised by larger (µm3) but less spheric osteocyte lacunae [47.3; 95% CI (11.2, 83.4), - 0.04; 95% CI (-0.06, -0.02), respectively], lower vascular canal density (#/mm3) [- 22.8; 95% CI (-35.4, -10.3)], lower osteocyte cell density (#/mm2) [- 84.2; 95% CI (-102.5, -67.4)], and less senescent (#/mm2) but more apoptotic osteocytes (%) [- 2.4; 95% CI (-3.6, -1.2), 24.9; 95% CI (17.7, 32.1)], respectively.

CONCLUSION

SCB from hip OA and knee OA exhibits different characteristics at the tissue and cellular levels, suggesting different mechanisms of OA progression in different joints.

Hysterectomy and risk of osteoarthritis in women: a nationwide nested case-control study

OBJECTIVE

Hysterectomy is the most common gynaecological surgery, performed mainly for benign uterine pathologies in women. Studies have suggested that hysterectomy is associated with osteoarthritis (OA); however, the association remains controversial. This study aimed to investigate the association between hysterectomy and the risk of OA.

METHOD

We performed a population-based nested case-control study using the National Health Insurance programme database from 2000 to 2016 in Taiwan. All medical conditions for each case and control were categorized using the International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) and ICD-10. A multiple conditional logistic regression model was applied to analyse the adjusted odds ratio (aOR) and 95% confidence interval (CI) for the association between hysterectomy and OA.

RESULTS

Our analyses included 16 592 patients with OA and 66 368 matched controls. After adjustment for possible confounders, hysterectomy had a significant association with OA (aOR = 1.19, 95% CI = 1.09-1.30), especially knee OA (aOR = 1.25, 95% CI = 1.13-1.38). Furthermore, women who received oestrogen therapy (ET) alone and patients who underwent hysterectomy without ET showed a greater risk of OA development compared to women who did not receive ET (aOR = 1.14, 95% CI = 1.07-1.23, and aOR = 1.19, 95% CI = 1.08-1.31, respectively).

CONCLUSION

Our findings indicate that hysterectomy is associated with OA, especially knee OA. We also found that women who received ET alone and patients who underwent hysterectomy without ET had an increased risk of OA.

Early Degenerative Changes in a Spontaneous Osteoarthritis Model Assessed by Nanoindentation

Understanding early mechanical changes in articular cartilage (AC) and subchondral bone (SB) is crucial for improved treatment of osteoarthritis (OA). The aim of this study was to develop a method for nanoindentation of fresh, unfixed osteochondral tissue to assess the early changes in the mechanical properties of AC and SB. Nanoindentation was performed throughout the depth of AC and SB in the proximal tibia of Dunkin Hartley guinea pigs at 2 months, 3 months, and 2 years of age. The contralateral tibias were either histologically graded for OA or analyzed using immunohistochemistry. The results showed an increase in the reduced modulus (Er) in the deep zone of AC during early-stage OA (6.0 ± 1.75 MPa) compared to values at 2 months (4.04 ± 1.25 MPa) (*** p < 0.001). In severe OA (2-year) specimens, there was a significant reduction in Er throughout the superficial and middle AC zones, which correlated to increased ADAMTS 4 and 5 staining, and proteoglycan loss in these regions. In the subchondral bone, a 35.0% reduction in stiffness was observed between 2-month and 3-month specimens (*** p < 0.001). The severe OA age group had significantly increased SB stiffness of 36.2% and 109.6% compared to 2-month and 3-month-old specimens respectively (*** p < 0.001). In conclusion, this study provides useful information about the changes in the mechanical properties of both AC and SB during both early- and late-stage OA and indicates that an initial reduction in stiffness of the SB and an increase in stiffness in the deep zone of AC may precede early-stage cartilage degeneration.

Low-frequency whole-body vibration can enhance cartilage degradation with slight changes in subchondral bone in mice with knee osteoarthritis and does not have any morphologic effect on normal joints

PURPOSES

To evaluate the effects of low frequency whole-body vibration (WBV) on degeneration of articular cartilage and subchondral bone in mice with destabilization of the medial meniscus (DMM)induced osteoarthritis(OA) and mice with normal knee.

METHODS

Ten-week-old C57BL/6J male mice received DMM on right knees, while the left knees performed sham operation. There were six groups: DMM, SHAM DMM, DMM+WBV,SHAM DMM+WBV, DMM+ NON-WBV and SHAM DMM+NON-WBV. After four weeks, the knees were harvested from the DMM and SHAM DMM group. The remaining groups were treated with WBV (10 Hz) or NON-WBV. Four weeks later, the knees were harvested. Genes, containing Aggrecan(Acan) and CollagenⅡ(Col2a1), Matrix Metalloproteinases 3 and 13(MMP3,13), TNFα and IL6, were measured and staining was also performed. OA was graded with OARSI scores, and tibial plateaubone volume to tissue volume ratio(BV/TV), bone surface area to bone volume ratio (BS/BV), trabecular number(Tb.N) and trabecular thickness separation(TS) between groups were analyzed.

RESULTS

Increased OARSI scores and cartilage degradation were observed after WBV. BV/TV, Tb.N and TS were not significant between the groups. Significant reductions were observed in MMP3, MMP13, Col2a1, Acan, TNFα and IL6 in the DMM+WBV compared to SHAM DMM+WBV group. BV/TV, BS/BV, Tb.N, TS and OARSI scores were not significantly changed in the left knees. IL6 expression in the SHAM DMM+WBV group was significantly increased compared with the SHAM DMM+ NON-WBV group, while Col2a1, Acan and MMP13 expression decreased.

CONCLUSION

WBV accelerated cartilage degeneration and caused slight changes in subchondral bone in a DMM-induced OA model. WBV had no morphologic effect on normal joints.

Multifunctional hydrogels: advanced therapeutic tools for osteochondral regeneration

Various joint pathologies such as osteochondritis dissecans, osteonecrosis, rheumatic disease, and trauma, may result in severe damage of articular cartilage and other joint structures, ranging from focal defects to osteoarthritis (OA). The osteochondral unit is one of the critical actors in this pathophysiological process. New approaches and applications in tissue engineering and regenerative medicine continue to drive the development of OA treatment. Hydrogel scaffolds, a component of tissue engineering, play an indispensable role in osteochondral regeneration. In this review, tissue engineering strategies regarding osteochondral regeneration were highlighted and summarized. The application of hydrogels for osteochondral regeneration within the last five years was evaluated with an emphasis on functionalized physical and chemical properties of hydrogel scaffolds, functionalized delivery hydrogel scaffolds as well as functionalized intelligent response hydrogel scaffolds. Lastly, to serve as guidance for future efforts in the creation of bioinspired hydrogel scaffolds, a succinct summary and new views for specific mechanisms, applications, and existing limitations of the newly designed functionalized hydrogel scaffolds were offered.

Low back pain and osteoarthritis pain: a perspective of estrogen

Low back pain (LBP) is the world's leading cause of disability and is increasing in prevalence more rapidly than any other pain condition. Intervertebral disc (IVD) degeneration and facet joint osteoarthritis (FJOA) are two common causes of LBP, and both occur more frequently in elderly women than in other populations. Moreover, osteoarthritis (OA) and OA pain, regardless of the joint, are experienced by up to twice as many women as men, and this difference is amplified during menopause. Changes in estrogen may be an important contributor to these pain states. Receptors for estrogen have been found within IVD tissue and nearby joints, highlighting the potential roles of estrogen within and surrounding the IVDs and joints. In addition, estrogen supplementation has been shown to be effective at ameliorating IVD degeneration and OA progression, indicating its potential use as a therapeutic agent for people with LBP and OA pain. This review comprehensively examines the relationship between estrogen and these pain conditions by summarizing recent preclinical and clinical findings. The potential molecular mechanisms by which estrogen may relieve LBP associated with IVD degeneration and FJOA and OA pain are discussed.

Development of a method to investigate strain distribution across the cartilage-bone interface in guinea pig model of spontaneous osteoarthritis using lab-based contrast enhanced X-ray-computed tomography and digital volume correlation

OBJECTIVE

Strain changes at the cartilage-bone interface play a crucial role in osteoarthritis (OA) development. Contrast-Enhanced X-ray Computed Tomography (CECT) and Digital Volume Correlation (DVC) can measure 3D strain changes at the osteochondral interface. Using lab-based CT systems it is often difficult to visualise soft tissues such as articular cartilage without staining to enhance contrast. Contrast-Enhancing Staining Agents (CESAs), such as Phosphotungstic Acid (PTA) in 70% ethanol, can cause tissue shrinkage and alter tissue mechanics. The aims of this study were, firstly, to assess changes to the mechanical properties of osteochondral tissue after staining with a PTA/PBS solution, and secondly, to visualise articular cartilage during loading and with CECT imaging in order to compare strain across the interface in both healthy and OA joints using DVC.

DESIGN

Nanoindentation was used to assess changes to mechanical properties in articular cartilage and subchondral bone before and after staining. Hindlimbs from Dunkin-Hartley guinea pigs were stained with 1% PTA/PBS at room temperature for 6 days. Two consecutive CECT datasets were acquired for DVC error analysis. In-situ compression with a load corresponding to 2x body weight was applied, the specimen was re-imaged, and DVC was performed between the pre- and post-load tomograms.

RESULTS

Nanoindentation before and after PTA/PBS staining showed similar cartilage stiffness (p < 0.05), however, staining significantly decreased the stiffness of subchondral bone (∼9-fold; p = 0.0012). In severe OA specimens, third principal/compressive (εp3) strain was 141.7% higher and shear strain (γ) was 98.2% higher in tibial articular cartilage compared to non-OA (2 - month) specimens. A 23.1% increase in third principal stain strain and a 54.5% significant increase in the shear (γ) strain (p = 0.0027) was transferred into the mineralised regions of calcified cartilage and subchondral bone in severe OA specimens.

CONCLUSIONS

These results indicate the suitability of PTA in PBS as a contrast agent for the visualisation of cartilage during CECT imaging and allowed DVC computation of strain across the cartilage-bone interface. However, further research is needed to address the reduction in stiffness of subchondral bone after incubation in PBS.

Disease-modifying interactions between chronic kidney disease and osteoarthritis: a new comorbid mouse model

OBJECTIVE

The prevalence of comorbid chronic kidney disease (CKD) and osteoarthritis (OA) is increasing globally. While sharing common risk factors, the mechanism and consequences of concurrent CKD-OA are unclear. The aims of the study were to develop a preclinical comorbid model, and to investigate the disease-modifying interactions.

METHODS

Seventy (70) male 8-10 week-old C57BL/6 mice were subjected to 5/6 nephrectomy (5/6Nx)±destabilisation of medial meniscus (DMM) or sham surgery. OA pathology and CKD were assessed 12 weeks postinduction by blinded histology scoring, micro-CT, immunohistochemistry for osteoclast and matrix metalloproteinase (MMP)-13 activity, and serum analysis of bone metabolic markers.

RESULTS

The 5/6Nx model recapitulated characteristic features of CKD, with renal fibrosis and deranged serum alkaline phosphatase, calcium and phosphate. There was no histological evidence of cartilage pathology induced by 5/6Nx alone, however, synovial MMP-13 expression and subchondral bone osteoclastic activity were increased (p<0.05), with accompanying reductions (p<0.05) in subchondral trabecular bone, bone volume and mineral density. DMM significantly (p<0.05) increased tibiofemoral cartilage damage, subchondral bone sclerosis, marginal osteophytes and synovitis, in association with increased cartilage and synovial MMP-13. DMM alone induced (p<0.05) renal fibrosis, proteinuria and increased (p<0.05) 5/6Nx-induced serum urea. However, DMM in 5/6Nx-mice resulted in significantly reduced (p<0.05) cartilage pathology and marginal osteophyte development, in association with reduced subchondral bone volume and density, and inhibition of 5/6Nx-induced subchondral bone osteoclast activation.

CONCLUSION

This study assessed a world-first preclinical comorbid CKD-OA model. Our findings demonstrate significant bidirectional disease-modifying interaction between CKD and OA.

Effect of lorecivivint on osteoarthritis: A systematic review and meta-analysis

Objective

To comprehensively evaluate the effectiveness and safety of lorecivivint inhibitors in the treatment of osteoarthritis through meta-analysis.

Methods

A comprehensive literature search on lorecivivint inhibitors in osteoarthritis was performed using electronic databases such as PubMed, Embase, Web of Science, and CochraneLibrary up to July 30, 2022. Two reviewers independently screened, evaluated, and reviewed the eligible studies. Data analysis and processing were carried out using RevMan 5.4 software.

Results

A total of six studies involving 3056 participants were included. Meta-analysis showed that compared with the control group, lorecivivint significantly increased WOMAC discomfort (0.03 mg Week 12) (MD = -0.21, 95% CI [-1.94 - 1.53]; P = 0.81), WOMAC function (0.07 mg Week 24) (MD = -1.81, 95% CI [-4.74 - 1.12]; P = 0.23) and Joint space width (0.23 mg Week 24) (MD = -1.16, 95% CI [-3.69 - 1.38]; P = 0.37).

Conclusion

A new treatment method combining Wnt pathway modulators with intra-articular CLK2/DYRK1A inhibitors could be a promising therapy for treating osteoarthritis. Lorecivivint was found to significantly improve WOMAC discomfort, WOMAC function, and joint space width in osteoarthritis patients. It is anticipated to be a reliable, safe, and effective treatment option for osteoarthritis with significant therapeutic utility and potential applications.

Layered Double Hydroxides: A Novel Promising 2D Nanomaterial for Bone Diseases Treatment

Bone diseases including bone defects, bone infections, osteoarthritis, and bone tumors seriously affect life quality of the patient and bring serious economic burdens to social health management, for which the current clinical treatments bear dissatisfactory therapeutic effects. Biomaterial-based strategies have been widely applied in the treatment of orthopedic diseases but are still plagued by deficient bioreactivity. With the development of nanotechnology, layered double hydroxides (LDHs) with adjustable metal ion composition and alterable interlayer structure possessing charming physicochemical characteristics, versatile bioactive properties, and excellent drug loading and delivery capabilities arise widespread attention and have achieved considerable achievements for bone disease treatment in the last decade. However, to the authors' best knowledge, no review has comprehensively summarized the advances of LDHs in treating bone disease so far. Herein, the advantages of LDHs for orthopedic disorders treatment are outlined and the corresponding state-of-the-art achievements are summarized for the first time. The potential of LDHs-based nanocomposites for extended therapeutics for bone diseases is highlighted and perspectives for LDHs-based scaffold design are proposed for facilitated clinical translation.

Using Radiomics to Detect Subtle Architecture Changes of Cartilage and Subchondral Bone in Chronic Lateral Ankle Instability Patients Based on MRI PD-FS Images

RATIONALE AND OBJECTIVES

To use radiomics to detect the subtle changes of cartilage and subchondral bone in chronic lateral ankle instability (CLAI) patients based on MRI PD-FS images.

MATERIALS AND METHODS

A total of 215 CLAI patients and 186 healthy controls were included and randomly split into a training set (n=281, patients/controls=151/130) and an independent test set (n=120, patients/controls=64/56). They underwent ankle MRI examinations. On sagittal PD-FS images, eight cartilage regions and their corresponding subchondral bone regions were drawn. Radiomics models of cartilage, subchondral bone and combined cartilage and subchondral bone were built to differentiate CLAI patients from controls. A receiver operating characteristic curve (ROC) was used to assess the model's performance.

RESULTS

In the test dataset, the cartilage model yielded an area under the curve (AUC) of 0.0.912 (95% confidence interval (CI): 0.858-0.965, p<0.001), a sensitivity of 0.859, a specificity of 0.893, a negative predictive value (NPV) of 0.848, and a positive predictive value (PPV) of 0.902. The subchondral bone model yielded an AUC of 0.837 (95% CI: 0.766-0.907, p<0.001), a sensitivity of 0.875, a specificity of 0.714, an NPV of 0.833, and a PPV of 0.778. For the combined model, the AUC was 0.921 (95% CI: 0.863-0.972, p<0.001), sensitivity was 0.844, specificity was 0.911, NPV was 0.836, and PPV was 0.915, whose AUC was higher than those of both the cartilage model and the subchondral bone model.

CONCLUSION

The combined radiomics model achieved satisfying performance in detecting potential early architectural changes in cartilage and subchondral bone for CLAI patients.

Megakaryocyte Secreted Factors Regulate Bone Marrow Niche Cells During Skeletal Homeostasis, Aging, and Disease

The bone marrow microenvironment contains a diverse array of cell types under extensive regulatory control and provides for a novel and complex mechanism for bone regulation. Megakaryocytes (MKs) are one such cell type that potentially acts as a master regulator of the bone marrow microenvironment due to its effects on hematopoiesis, osteoblastogenesis, and osteoclastogenesis. While several of these processes are induced/inhibited through MK secreted factors, others are primarily regulated by direct cell-cell contact. Notably, the regulatory effects that MKs exert on these different cell populations has been found to change with aging and disease states. Overall, MKs are a critical component of the bone marrow that should be considered when examining regulation of the skeletal microenvironment. An increased understanding of the role of MKs in these physiological processes may provide insight into novel therapies that can be used to target specific pathways important in hematopoietic and skeletal disorders.

Chondrocyte Homeostasis and Differentiation: Transcriptional Control and Signaling in Healthy and Osteoarthritic Conditions

Chondrocytes are the main cell type in articular cartilage. They are embedded in an avascular, abundant, and specialized extracellular matrix (ECM). Chondrocytes are responsible for the synthesis and turnover of the ECM, in which the major macromolecular components are collagen, proteoglycans, and non-collagen proteins. The crosstalk between chondrocytes and the ECM plays several relevant roles in the regulation of cell phenotype. Chondrocytes live in an avascular environment in healthy cartilage with a low oxygen supply. Although chondrocytes are adapted to anaerobic conditions, many of their metabolic functions are oxygen-dependent, and most cartilage oxygen is supplied by the synovial fluid. This review focuses on the transcription control and signaling responsible for chondrocyte differentiation, homeostasis, senescence, and cell death and the changes that occur in osteoarthritis. The effects of chondroitin sulfate and other molecules as anti-inflammatory agents are also approached and analyzed.

Anti-NGF treatment worsens subchondral bone and cartilage measures while improving symptoms in floor-housed rabbits with osteoarthritis

Objective: Osteoarthritis (OA) is a common joint disorder often affecting the knee. It is characterized by alterations of various joint tissues including subchondral bone and by chronic pain. Anti-nerve growth factor (NGF) antibodies have demonstrated improvement in pain associated with OA in phase 3 clinical trials but have not been approved due to an increased risk of developing rapidly progressive OA. The aim of this study was to investigate effects of systemic anti-NGF-treatment on structure and symptoms in rabbits with surgically induced joint instability. Methods: This was elicited by anterior cruciate ligament transection and partial resection of the medial meniscus in right knee of 63 female rabbits, housed altogether in a 56 m² floor husbandry. Rabbits received either 0.1, 1 or 3 mg/kg anti-NGF antibody intra-venously at weeks 1, 5 and 14 after surgery or vehicle. During in-life phase, static incapacitance tests were performed and joint diameter was measured. Following necropsy, gross morphological scoring and micro-computed tomography analysis of subchondral bone and cartilage were performed. Results: After surgery, rabbits unloaded operated joints, which was improved with 0.3 and 3 mg/kg anti-NGF compared to vehicle injection during the first half of the study. The diameter of operated knee joints increased over contralateral measures. This increase was bigger in anti-NGF treated rabbits beginning 2 weeks after the first IV injection and became dose-dependent and more pronounced with time. In the 3 mg/kg anti-NGF group, the bone volume fraction and trabecular thickness increased in the medio-femoral region of operated joints compared to contralateral and to vehicle-treated animals, while cartilage volume and to a lesser extent thickness decreased. Enlarged bony areas were found in right medio-femoral cartilage surfaces of animals receiving 1 and 3 mg/kg anti-NGF. Alterations of all structural parameters were particularly distinct in a subgroup of three rabbits, which also exhibited more prominent symptomatic improvement. Conclusion: This study showed that anti-NGF administration exerted negative impact on structure in destabilized joints of rabbits, while pain-induced unloading of joints was improved. Our findings open up the possibility to better understand the effects of systemic anti-NGF, particularly on subchondral bone, and thus the occurrence of rapidly progressive OA in patients.

Mesenchymal Stromal Cells-Derived Extracellular Vesicles as Potential Treatments for Osteoarthritis

Osteoarthritis (OA) is a degenerative disease of the joints characterized by cartilage damage and severe pain. Despite various pharmacological and surgical interventions, current therapies fail to halt OA progression, leading to high morbidity and an economic burden. Thus, there is an urgent need for alternative therapeutic approaches that can effectively address the underlying pathophysiology of OA. Extracellular Vesicles (EVs) derived from mesenchymal stromal cells (MSCs) represent a new paradigm in OA treatment. MSC-EVs are small membranous particles released by MSCs during culture, both in vitro and in vivo. They possess regenerative properties and can attenuate inflammation, thereby promoting cartilage healing. Importantly, MSC-EVs have several advantages over MSCs as cell-based therapies, including lower risks of immune reactions and ethical issues. Researchers have recently explored different strategies, such as modifying EVs to enhance their delivery, targeting efficiency, and security, with promising results. This article reviews how MSC-EVs can help treat OA and how they might work. It also briefly discusses the benefits and challenges of using MSC-EVs and talks about the possibility of allogeneic and autologous MSC-EVs for medical use.

Could hypoxia rehabilitate the osteochondral diseased interface? Lessons from the interplay of hypoxia and purinergic signals elsewhere

The osteochondral unit comprises the articular cartilage (90%), subchondral bone (5%) and calcified cartilage (5%). All cells present at the osteochondral unit that is ultimately responsible for matrix production and osteochondral homeostasis, such as chondrocytes, osteoblasts, osteoclasts and osteocytes, can release adenine and/or uracil nucleotides to the local microenvironment. Nucleotides are released by these cells either constitutively or upon plasma membrane damage, mechanical stress or hypoxia conditions. Once in the extracellular space, endogenously released nucleotides can activate membrane-bound purinoceptors. Activation of these receptors is fine-tuning regulated by nucleotides' breakdown by enzymes of the ecto-nucleotidase cascade. Depending on the pathophysiological conditions, both the avascular cartilage and the subchondral bone subsist to significant changes in oxygen tension, which has a tremendous impact on tissue homeostasis. Cell stress due to hypoxic conditions directly influences the expression and activity of several purinergic signalling players, namely nucleotide release channels (e.g. Cx43), NTPDase enzymes and purinoceptors. This review gathers experimental evidence concerning the interplay between hypoxia and the purinergic signalling cascade contributing to osteochondral unit homeostasis. Reporting deviations to this relationship resulting from pathological alterations of articular joints may ultimately unravel novel therapeutic targets for osteochondral rehabilitation. At this point, one can only hypothesize how hypoxia mimetic conditions can be beneficial to the ex vivo expansion and differentiation of osteo- and chondro-progenitors for auto-transplantation and tissue regenerative purposes.

Failure of cartilage regeneration: emerging hypotheses and related therapeutic strategies

Osteoarthritis (OA) is a disabling condition that affects billions of people worldwide and places a considerable burden on patients and on society owing to its prevalence and economic cost. As cartilage injuries are generally associated with the progressive onset of OA, robustly effective approaches for cartilage regeneration are necessary. Despite extensive research, technical development and clinical experimentation, no current surgery-based, material-based, cell-based or drug-based treatment can reliably restore the structure and function of hyaline cartilage. This paucity of effective treatment is partly caused by a lack of fundamental understanding of why articular cartilage fails to spontaneously regenerate. Thus, research studies that investigate the mechanisms behind the cartilage regeneration processes and the failure of these processes are critical to instruct decisions about patient treatment or to support the development of next-generation therapies for cartilage repair and OA prevention. This Review provides a synoptic and structured analysis of the current hypotheses about failure in cartilage regeneration, and the accompanying therapeutic strategies to overcome these hurdles, including some current or potential approaches to OA therapy.

Progress in the application of 3D-printed sodium alginate-based hydrogel scaffolds in bone tissue repair

In recent years, hydrogels have been widely used in the biomedical field as materials with excellent bionic structures and biological properties. Among them, the excellent comprehensive properties of natural polymer hydrogels represented by sodium alginate have attracted the great attention of researchers. At the same time, by physically blending sodium alginate with other materials, the problems of poor cell adhesion and mechanical properties of sodium alginate hydrogels were directly improved without chemical modification of sodium alginate. The composite blending of multiple materials can also improve the functionality of sodium alginate hydrogels, and the prepared composite hydrogel also has a larger application field. In addition, based on the adjustable viscosity of sodium alginate-based hydrogels, sodium alginate-based hydrogels can be loaded with cells to prepare biological ink, and the scaffold can be printed out by 3D printing technology for the repair of bone defects. This paper first summarizes the improvement of the properties of sodium alginate and other materials after physical blending. Then, it summarizes the application progress of sodium alginate-based hydrogel scaffolds for bone tissue repair based on 3D printing technology in recent years. Moreover, we provide relevant opinions and comments to provide a theoretical basis for follow-up research.

Bone-cartilage crosstalk informed by aging mouse bone transcriptomics and human osteoarthritis genome-wide association studies

Subchondral bone participates in crosstalk with articular cartilage to maintain joint homeostasis, and disruption of either tissue results in overall joint degeneration. Among the subchondral bone changes observed in osteoarthritis (OA), subchondral bone plate (SBP) thickening has a time-dependent relationship with cartilage degeneration and has recently been shown to be regulated by osteocytes. Here, we evaluate the effect of age on SBP thickness and cartilage degeneration in aging mice. We find that SBP thickness significantly increases by 18-months of age, corresponding temporally with increased cartilage degeneration. To identify factors in subchondral bone that may participate in bone cartilage crosstalk or OA, we leveraged mouse transcriptomic data from one joint tissue compartment - osteocyte-enriched bone - to search for enrichment with human OA in UK Biobank and Arthritis Research UK Osteoarthritis Genetics (arcOGEN) GWAS using the mouse2human (M2H, www.mouse2human.org) strategy. Genes differentially expressed in aging mouse bone are significantly enriched for human OA, showing joint site-specific (knee vs. hip) relationships, exhibit temporal associations with age, and unique gene clusters are implicated in each type of OA. Application of M2H identifies genes with known and unknown functions in osteocytes and OA development that are clinically associated with human OA. Altogether, this work prioritizes genes with a potential role in bone/cartilage crosstalk for further mechanistic study based on their association with human OA in GWAS.