Intraarticular injection of liposomal adenosine reduces cartilage damage in established murine and rat models of osteoarthritis

Therapeutic Controlled Release Strategies for Human Osteoarthritis

Osteoarthritis is a progressive, irreversible debilitating whole joint disease that affects millions of people worldwide. Despite the availability of various options (non-pharmacological and pharmacological treatments and therapy, orthobiologics, and surgical interventions), none of them can definitively cure osteoarthritis in patients. Strategies based on the controlled release of therapeutic compounds via biocompatible materials may provide powerful tools to enhance the spatiotemporal delivery, expression, and activities of the candidate agents as a means to durably manage the pathological progression of osteoarthritis in the affected joints upon convenient intra-articular (injectable) delivery while reducing their clearance, dissemination, or side effects. The goal of this review is to describe the current knowledge and advancements of controlled release to treat osteoarthritis, from basic principles to applications in vivo using therapeutic recombinant molecules and drugs and more innovatively gene sequences, providing a degree of confidence to manage the disease in patients in a close future.

Electroacupuncture Inhibits Cartilage Degeneration in a Rat Knee Osteoarthritis (KOA) Model by Suppressing ADAMTS5 Expression

Background Knee osteoarthritis (KOA) is characterized by cartilage degradation, osteophyte formation, and synovitis. Cartilage degradation in KOA begins with the loss of aggrecan, primarily due to A Disintegrin and Metalloproteinase with Thrombospondin Motif 5 (ADAMTS5), which is produced by chondrocytes and synovial cells and a key target for therapeutic intervention. Current treatments for KOA primarily focus on pain relief, as disease-modifying osteoarthritis drugs (DMOADs) remain unavailable. Electroacupuncture (EA), applying electrical stimulation to acupoints, has been investigated for its potential to alleviate KOA symptoms; however, the specific effects of different acupoint combinations remain unclear. This study investigates the effect of EA on pain and cartilage degeneration in a KOA rat model by examining ADAMTS5 expression in synovial tissue. Materials and methods Male Wistar rats were divided into five groups: control, sham-operated, KOA model, KOA treated with EA at ST36 (Zusanli)-LR8 (Ququan) (KOA+LR8), and KOA treated at ST36-Ex-LE2 (Heding) (KOA+Ex-LE2). The DMM (destabilization of the medial meniscus) procedure induced KOA, and EA was applied thrice weekly for four weeks. The rotarod test was used to assess motor coordination, and samples were collected for immunofluorescence, Western blot, and histological analysis. Pain was assessed via c-fos expression in the spinal cord, while Safranin O-Fast Green staining was used to evaluate cartilage degeneration via the Osteoarthritis Research Society International (OARSI) scoring system. Results The KOA group post-surgery showed reduced motor coordination, while EA at both ST36-LR8 and ST36-Ex-LE2 enhanced performance (day 28: control: 28.8 ± 0.6, sham: 28.4 ± 3.7, KOA: 19.7 ± 0.9, KOA+LR8: 24.8 ± 1.5, KOA+Ex-LE2: 26.9 ± 1.2). Expression of c-fos, elevated in the KOA group, was significantly suppressed by EA (control: 7.6 ± 0.9, sham: 13.6 ± 2.8, KOA: 24.5 ± 2.1, KOA+LR8: 12.8 ± 0.9, KOA+Ex-LE2: 17.0 ± 1.2). Histologically, KOA rats showed severe cartilage degradation and osteophyte formation, while EA at ST36-Ex-LE2 significantly reduced these changes (control: 0.2 ± 0.1, sham: 0.4 ± 0.2, KOA: 1.8 ± 0.4, KOA+LR8: 1.0 ± 0.2, KOA+Ex-LE2: 0.5 ± 0.2). The ST36-LR8 group also showed improvements, although less pronounced than the ST36-Ex-LE2 group. Western blotting revealed that DMM-induced ADAMTS5 expression was significantly inhibited by EA at ST36-Ex-LE2 but not at ST36-LR8 (control: 1.0 ± 0, sham: 1.2 ± 0.4, KOA: 3.0 ± 0.3, KOA+LR8: 2.1 ± 0.3, KOA+Ex-LE2: 1.4 ± 0.4). Conclusion EA at ST36-Ex-LE2 showed a remarkable protective effect on articular cartilage by inhibiting ADAMTS5 expression from synovium, suggesting that it can break the vicious cycle of synovitis and cartilage destruction. In contrast, EA at ST36-LR8 had a moderate effect on cartilage degeneration and ADAMTS5 expression. The difference in efficacy may be due to the anatomical differences between acupoints. ST36-Ex-LE2 coincides with an area rich in synovial fibroblasts and mast cells involved in inflammation and pain. This highlights the importance of acupoint selection to maximize the therapeutic effect of EA. The specificity of this acupoint combination provides a potential strategy for managing KOA and slowing the progression of the disease. Further studies are needed to elucidate the detailed mechanisms behind the effects of EA and explore its potential as an alternative or complementary treatment for KOA.

CD73 alleviates osteoarthritis by maintaining anabolism and suppressing catabolism of chondrocytes extracellular matrix

Background

Osteoarthritis (OA) is the most common degenerative joint disease, with articular cartilage degeneration as primary manifestation. Intra-articular injection of exogenous liposomal adenosine in mice knee has been shown to alleviate OA progression. However, the role of CD73, the rate-limiting enzyme of extracellular adenosine synthesis, in OA is still unknown.

Methods

In this work, we explored the expression changes of adenosine-related molecules via bioinformatic analysis. In addition, the expression level of these molecules was detected in OA cartilage. We also conducted a case-control study to investigate the genetic variants of selected SNPs on genes encoded adenosine-related molecules. To further explore the function of CD73 in chondrocytes, we knocked down the expression of CD73 with small interfering RNA and overexpressed CD73 with the use of lentivirus, and detected the expression of markers for anabolism and catabolism in mouse primary chondrocytes with or without IL-1β treatment. We also conducted in vivo experiments to explore the role of CD73 in OA.

Results

We found that the expression of CD73 was upregulated in OA, and the variants of SNP rs2229523 (base A to G) on NT5E (the encoding gene of CD73) were significantly higher in OA population, which might cause the amino acid encoded by this SNP change from threonine to alanine. The original helix structure in the adjacent region of amino acid encoded by SNP rs2229523 would be deconstructed after its mutation. Furthermore, we found that CD73 promoting the expression of Col2a1 but suppressing the expression of Mmp13 expression in mouse primary chondrocytes under inflammatory environment. The overexpression of CD73 attenuated bone remodeling and alleviated cartilage degeneration in DMM mice. Moreover, the physical activities were also improved in DMM mice overexpressed CD73 with the use of adeno-associated virus.

Conclusions

The variants of SNP rs2229523 (base A to G) on NT5E were significantly higher in OA population, and CD73 could alleviate OA by maintaining anabolism and suppressing catabolism of chondrocytes extracellular matrix.

The Translational Potential of this Article

This work showed that CD73 might be one of the biological therapeutic targets of OA, which would provide a reference for future novel treatment strategy of OA.

Lubricant Strategies in Osteoarthritis Treatment: Transitioning from Natural Lubricants to Drug Delivery Particles with Lubricant Properties

Osteoarthritis (OA) is a debilitating joint disease characterized by cartilage degradation, leading to pain and functional impairment. A key contributor to OA progression is the decline in cartilage lubrication. In physiological conditions, synovial fluid (SF) macromolecules like hyaluronic acid (HA), phospholipids, and lubricin play a crucial role in the boundary lubrication of articular cartilage. In early OA, cartilage damage triggers inflammation, altering SF composition and compromising the lubrication layer. This increases friction between mating interfaces, worsening cartilage degradation and local inflammation. Therefore, early-stage restoration of lubrication (by injecting in the joint different classes of compounds and formulations) could alleviate, and potentially reverse, OA progression. In the light of this, a broad variety of lubricants have been investigated for their ability to reduce friction in OA joints and promote cartilage repair in clinical and preclinical studies. This review examines recent advancements in lubricant-based therapy for OA, focusing on natural, bioinspired, and alternative products. Starting from the currently applied therapy, mainly based on natural lubricants as HA, we will present their modified versions, either in hydrogel form or with specific biomimetic moieties with the aim of reducing their clearance from the joint and of enhancing their lubricating properties. Finally, the most advanced and recent formulation, represented by alternative strategies, will be proposed. Particular emphasis will be placed on those ones involving new types of hydrogels, microparticles, nanoparticles, and liposomes, which are currently under investigation in preclinical studies. The potential application of particles and liposomes could foster the transition from natural lubricants to Drug Delivery Systems (DDSs) with lubricant features; transition which could provide more complete OA treatments, by simultaneously providing lubrication replacement and sustained release of different payloads and active agents directly at the joint level. Within each category, we will examine relevant preclinical studies, highlighting challenges and future prospects.

Advanced nanoparticles in osteoarthritis treatment

Osteoarthritis (OA) is the most prevalent degenerative joint disorder, affecting hundreds of millions of people globally. Current clinical approaches are confined to providing only symptomatic relief. Research over the past two decades has established that OA is not merely a process of wear and tear of the articular cartilage but involves abnormal remodelling of all joint tissues. Although many new mechanisms of disease have been identified in the past several decades, the efficient and sustainable delivery of drugs targeting these mechanisms in joint tissues remains a major challenge. Nanoparticles recently emerged as favoured delivery vehicles in OA treatment, offering extended drug retention, enhanced drug targeting, and improved drug stability and solubility. In this review, we consider OA as a disease affecting the entire joint and initially explore the pathophysiology of OA across multiple joint tissues, including the articular cartilage, synovium, fat pad, bone, and meniscus. We then classify nanoparticles based on their composition and structure, such as lipids, polymers, inorganic materials, peptides/proteins, and extracellular vesicles. We summarise the recent advances in their use for treatment and diagnosis of OA. Finally, we discuss the current challenges and future directions in this field. In conclusion, nanoparticle-based nanosystems are promising carriers that advance OA treatment and diagnosis.

Translational Experimental Basis of Indirect Adenosine Receptor Agonist Stimulation for Bone Regeneration: A Review

Bone regeneration remains a significant clinical challenge, often necessitating surgical approaches when healing bone defects and fracture nonunions. Within this context, the modulation of adenosine signaling pathways has emerged as a promising therapeutic option, encouraging osteoblast activation and tempering osteoclast differentiation. A literature review of the PubMed database with relevant keywords was conducted. The search criteria involved in vitro or in vivo models, with clear methodological descriptions. Only studies that included the use of indirect adenosine agonists, looking at the effects of bone regeneration, were considered relevant according to the eligibility criteria. A total of 29 articles were identified which met the inclusion and exclusion criteria, and they were reviewed to highlight the preclinical translation of adenosine agonists. While preclinical studies demonstrate the therapeutic potential of adenosine signaling in bone regeneration, its clinical application remains unrealized, underscoring the need for further clinical trials. To date, only large, preclinical animal models using indirect adenosine agonists have been successful in stimulating bone regeneration. The adenosine receptors (A1, A2A, A2B, and A3) stimulate various pathways, inducing different cellular responses. Specifically, indirect adenosine agonists act to increase the extracellular concentration of adenosine, subsequently agonizing the respective adenosine receptors. The agonism of each receptor is dependent on its expression on the cell surface, the extracellular concentration of adenosine, and its affinity for adenosine. This comprehensive review analyzed the multitude of indirect agonists currently being studied preclinically for bone regeneration, discussing the mechanisms of each agonist, their cellular responses in vitro, and their effects on bone formation in vivo.

Purines and Adenosine Receptors in Osteoarthritis

OA is a common and debilitating condition that restricts mobility and diminishes the quality of life. Recent work indicates that the generation of adenosine at the cell surface is an important mediator of chondrocyte homeostasis, and topical application of adenosine in a slow-release form (liposomes) can halt the progression of OA and diminish the pain associated with OA. Here, we review the evidence indicating that adenosine, acting at A2A receptors, plays a critical role in endogenous and exogenous treatment and reversal of OA.

Targeting WNT signalling pathways as new therapeutic strategies for osteoarthritis

Osteoarthritis (OA) is a highly prevalent chronic joint disease and the leading cause of disability. Currently, no drugs are available to control joint damage or ease the associated pain. The wingless-type (WNT) signalling pathway is vital in OA progression. Excessive activation of the WNT signalling pathway is pertinent to OA progression and severity. Therefore, agonists and antagonists of the WNT pathway are considered potential drug candidates for OA treatment. For example, SM04690, a novel small molecule inhibitor of WNT signalling, has demonstrated its potential in a recent phase III clinical trial as a disease-modifying osteoarthritis drug (DMOAD). Therefore, targeting the WNT signalling pathway may be a distinctive approach to developing particular agents helpful in treating OA. This review aims to update the most recent progress in OA drug development by targeting the WNT pathway. In this, we introduce WNT pathways and their crosstalk with other signalling pathways in OA development and highlight the role of the WNT signalling pathway as a key regulator in OA development. Several articles have reviewed the Wnt pathway from different aspects. This candid review provides an introduction to WNT pathways and their crosstalk with other signalling pathways in OA development, highlighting the role of the WNT signalling pathway as a key regulator in OA development with the latest research. Particularly, we emphasise the state-of-the-art in targeting the WNT pathway as a promising therapeutic approach for OA and challenges in their development and the nanocarrier-based delivery of WNT modulators for treating OA.

Extracellular adenosine signaling in bone health and disease

Purinergic signaling is a key molecular pathway in the maintenance of bone health and regeneration. P1 receptor signaling, which is activated by extracellular adenosine, has emerged as a key metabolic pathway that regulates bone tissue formation, function, and homeostasis. Extracellular adenosine is mainly produced by ectonucleotidases, and alterations in the function of these enzymes or compromised adenosine generation can result in bone disorders, such as osteoporosis and impaired fracture healing. This mini review discusses the key role played by adenosine in bone health and how its alterations contribute to bone diseases, as well as potential therapeutic applications of exogenous adenosine to combat bone diseases like osteoporosis and injury.

Adenosine A2A receptor activation reduces chondrocyte senescence

Osteoarthritis (OA) pathogenesis is associated with reduced chondrocyte homeostasis and increased levels of cartilage cellular senescence. Chondrosenescence is the development of cartilage senescence that increases with aging joints and disrupts chondrocyte homeostasis and is associated with OA. Adenosine A2A receptor (A2AR) activation in cartilage via intra-articular injection of liposomal A2AR agonist, liposomal-CGS21680, leads to cartilage regeneration in vivo and chondrocyte homeostasis. A2AR knockout mice develop early OA isolated chondrocytes demonstrate upregulated expression of cellular senescence and aging-associated genes. Based on these observations, we hypothesized that A2AR activation would ameliorate cartilage senescence. We found that A2AR stimulation of chondrocytes reduced beta-galactosidase staining and regulated levels and cell localization of common senescence mediators p21 and p16 in vitro in the human TC28a2 chondrocyte cell line. In vivo analysis similarly showed A2AR activation reduced nuclear p21 and p16 in obesity-induced OA mice injected with liposomal-CGS21680 and increased nuclear p21 and p16 in A2AR knockout mouse chondrocytes compared to wild-type mice. A2AR agonism also increased activity of the chondrocyte Sirt1/AMPK energy-sensing pathway by enhancing nuclear Sirt1 localization and upregulating T172-phosphorylated (active) AMPK protein levels. Lastly, A2AR activation in TC28a2 and primary human chondrocytes reduced wild-type p53 and concomitantly increased p53 alternative splicing leading to increase in an anti-senescent p53 variant, Δ133p53α. The results reported here indicate that A2AR signaling promotes chondrocyte homeostasis in vitro and reduces OA cartilage development in vivo by reducing chondrocyte senescence.

Osteoarthritis: a narrative review of molecular approaches to disease management

Osteoarthritis (OA) is a chronic, progressive degenerative whole joint disease that affects the articular cartilage, subchondral bone, ligaments, capsule, and synovium. While it is still believed to be a mechanically driven disease, the role of underlying co-existing inflammatory processes and mediators in the onset of OA and its progression is now more appreciated. Post-traumatic osteoarthritis (PTOA) is a subtype of OA that occurs secondary to traumatic joint insults and is widely used in pre-clinical models to help understand OA in general. There is an urgent need to develop new treatments as the global burden is considerable and expanding. In this review, we focus on the recent pharmacological advances in the treatment of OA and summarize the most significant promising agents based on their molecular effects. Those are classified here into broad categories: anti-inflammatory, modulation of the activity of matrix metalloproteases, anabolic, and unconventional pleiotropic agents. We provide a comprehensive analysis of the pharmacological advances in each of these areas and highlight future insights and directions in the OA field.

An update on the effect of intra-articular intervention strategies using nanomaterials in osteoarthritis: Possible clinical application

Osteoarthritis (OA) is the most common progressive condition affecting joints. It mainly affects the knees and hips as predominant weight-bearing joints. Knee osteoarthritis (KOA) accounts for a large proportion of osteoarthritis and presents numerous symptoms that impair quality of life, such as stiffness, pain, dysfunction, and even deformity. For more than two decades, intra-articular (IA) treatment options for managing knee osteoarthritis have included analgesics, hyaluronic acid (HA), corticosteroids, and some unproven alternative therapies. Before effective disease-modifying treatments for knee osteoarthritis, treatments are primarily symptomatic, mainly including intra-articular corticosteroids and hyaluronic acid, so these agents represent the most frequently used class of drugs for managing knee osteoarthritis. But research suggests other factors, such as the placebo effect, have an essential role in the effectiveness of these drugs. Several novel intra-articular therapies are currently in the clinical trial processes, such as biological therapies, gene and cell therapies. Besides, it has been shown that the development of novel drug nanocarriers and delivery systems could improve the effectiveness of therapeutic agents in osteoarthritis. This review discusses the various treatment methods and delivery systems for knee osteoarthritis and the new agents that have been introduced or are in development.

Injectable Drug Delivery Systems for Osteoarthritis and Rheumatoid Arthritis

Joint diseases are one of the most common causes of morbidity and disability worldwide. The main diseases that affect joint cartilage are osteoarthritis and rheumatoid arthritis, which require chronic treatment focused on symptomatic relief. Conventional drugs administered through systemic or intra-articular routes have low accumulation and/or retention in articular cartilage, causing dose-limiting toxicities and reduced efficacy. Therefore, there is an urgent need to develop improved strategies for drug delivery, in particular, the use of micro- and nanotechnology-based methods. Encapsulation of therapeutic agents in delivery systems reduces drug efflux from the joint and protects against rapid cellular and enzymatic clearance following intra-articular injection. Consequently, the use of drug delivery systems decreases side effects and increases therapeutic efficacy due to enhanced drug retention in the intra-articular space. Additionally, the frequency of intra-articular administration is reduced, as delivery systems enable sustained drug release. This review summarizes various advanced drug delivery systems, such as nano- and microcarriers, developed for articular cartilage diseases.

Polymeric Nanoparticles for Drug Delivery in Osteoarthritis

Osteoarthritis (OA) is a degenerative musculoskeletal disorder affecting the whole synovial joint and globally impacts more than one in five individuals aged 40 and over, representing a huge socioeconomic burden. Drug penetration into and retention within the joints are major challenges in the development of regenerative therapies for OA. During the recent years, polymeric nanoparticles (PNPs) have emerged as promising drug carrier candidates due to their biodegradable properties, nanoscale structure, functional versatility, and reproducible manufacturing, which makes them particularly attractive for cartilage penetration and joint retention. In this review, we discuss the current development state of natural and synthetic PNPs for drug delivery and OA treatment. Evidence from in vitro and pre-clinical in vivo studies is used to show how disease pathology and key cellular pathways of joint inflammation are modulated by these nanoparticle-based therapies. Furthermore, we compare the biodegradability and surface modification of these nanocarriers in relation to the drug release profile and tissue targeting. Finally, the main challenges for nanoparticle delivery to the cartilage are discussed, as a function of disease state and physicochemical properties of PNPs such as size and surface charge.

Clinical Effect of Application of Interventional Treatment Models for Improvement of Quality of Postoperative Recovery in Elderly Patients with Total Hip Arthroplasty

OBJECTIVE

To investigate the application value of the interventional treatment model for improving the recovery of elderly patients after total hip arthroplasty (THA).

METHODS

A total of 50 patients who received THA were randomly divided into the control group (25 cases) undergoing traditional treatment and the experimental group (25 cases) undergoing intervention of cognition, emotion, environment, education, nutrition, and sleep. The mini-mental state examination (MMSE) score, the incidence and duration of postoperative cognitive dysfunction (POCD), the out-of-bed activity time, hospital stays, and the satisfaction degree of patients were compared between the two groups.

RESULTS

There was no statistically significant difference in basic information between the two groups. On days 7 and 14 after surgery, the MMSE score of the control group was significantly lower than that of the experimental group (P <0.05). The incidence of POCD in the experimental group was lower and its duration was shorter than in the control group but without statistical significance. Besides, the significantly decreased out-of-bed activity time, the reduced length of hospital stay, and the higher satisfaction degree were observed in the experimental group (P <0.05).

CONCLUSION

Interventional treatment model could significantly increase the MMSE score, accelerate the recovery of elderly patients after THA, and increase their satisfaction degree.

Therapeutic potential of nanotechnology-based approaches in osteoarthritis

Osteoarthritis (OA) is a multifactorial disease that affects the entire joint, often resulting in severe pain, disability, psychological distress, and a lower quality of life. Patient self-management is emphasized in OA clinical recommendations. Currently, the clinical treatment of OA mainly focuses on pain relief and the improvement of joint function, with few options for regenerating degenerative cartilage or slowing the progression of OA. Therefore, we first reviewed the current treatment of OA, and then summarized the research advances of nanotechnology in OA treatment, including nano drug delivery systems for small molecule drugs, nucleic acids and proteins, nano-scaffolds for cartilage regeneration, and nanoparticle lubricants. Finally, we discussed the opportunities and potential challenges of nanotechnology in OA treatment.

Nanomedicine and regenerative medicine approaches in osteoarthritis therapy

Osteoarthritis (OA), the most common chronic joint disease, is a degenerative disease that affects 7% of the worldwide population, more than 500 million people all over the world. OA is the main factor of disability in elderly people which decreases the quality of life of patients. It is characterized by joint pain, low bone density, and deterioration of the joint structure. Despite ongoing novel advances in drug discovery and drug delivery, OA therapy is still a big challenge since there is no available effective treatment and the existing therapies mainly focus on pain and symptomatic management rather than improving and/or suppressing its progression. This review aims to summarize the currently available and novel emerging therapies for OA including regenerative medicine and nanotechnology-based materials and formulations at the clinical and experimental levels. Applications of regenerative medicine and novel technologies such as nanotechnology in OA treatments have opened a new window to support OA patients by offering treatments that could halt or delay OA progression satisfactorily or provide an effective cure in near future. Nanomedicine and regenerative medicine suggest novel alternatives in the regeneration of cartilage, repair of bone damage, and control of chronic pain in OA therapy.

Knee Osteoarthritis Therapy: Recent Advances in Intra-Articular Drug Delivery Systems

Drug delivery for osteoarthritis (OA) treatment is a continuous challenge because of their poor bioavailability and rapid clearance in joints. Intra-articular (IA) drug delivery is a common strategy and its therapeutic effects depend mainly on the efficacy of the drug-delivery system used for OA therapy. Different types of IA drug-delivery systems, such as microspheres, nanoparticles, and hydrogels, have been rapidly developed over the past decade to improve their therapeutic effects. With the continuous advancement in OA mechanism research, new drugs targeting specific cell/signaling pathways in OA are rapidly evolving and effective drug delivery is critical for treating OA. In this review, recent advances in various IA drug-delivery systems for OA treatment, OA targeted strategies, and related signaling pathways in OA treatment are summarized and analyzed based on current publications.

miR-125a-5p-abundant exosomes derived from mesenchymal stem cells suppress chondrocyte degeneration via targeting E2F2 in traumatic osteoarthritis

miRNAs are broad participants in vertebrate biological processes, and they are also the major players in pathological processes. miR-125a-5p was recently found a modulator in the progression of osteoarthritis (OA). Our study was aimed to explore the role and underlying mechanisms of miR-125a-5p-abundant exosomes derived from mesenchymal stem cells (MSC) on OA progression. We separated bone marrow mesenchymal stem cells (BMSCs) as well as the exosomes from traumatic OA patients. The immunofluorescence and cartilage staining were implemented for the observation and the assessment on endocytosis of chondrocytes and exosomal miR-125a-5p efficacy to cartilage degradation. Dual luciferase reporter assay was performed to verified the relationship between miR-125a-5p and E2F2. Then, the function of exosomal miR-125a-5p were examined on chondrocyte degeneration in vitro and in vivo. Our findings indicated that E2F2 expression was elevated while the miR-125a-5p was down in traumatic OA cartilage tissue, showing a negative correlation of the former and the latter. miR-125a-5p targets E2F2 in traumatic OA cartilage tissue and leads to the down-expression of E2F2. The E2F2 expression in chondrocytes was decreased after internalization of exosomes. We additionally found that BMSCs-derived exosomes were rich in miR-125a-5p content and chondrocytes can have it internalized. miR-125a-5p is endowed with a trait of accelerating chondrocytes migration, which is going along with the up-expressions of Collagen II, aggrecan and SOX9 and the down-expression of MMP-13 in vitro. Besides that, the mice model with post-traumatic OA turned out that exosomal miR-125a-5p might beget an alleviation in chondrocyte extracellular matrix degradation. All these outcomes revealed that BMSCs-derived exosomal miR-125a-5p is a positive regulator for chondrocyte migration and inhibit cartilage degeneration We thus were reasonable to believe that transferring of exosomal miR-125a-5p is a prospective strategy for OA treatment.

Hyaluronic Acid-Binding, Anionic, Nanoparticles Inhibit ECM Degradation and Restore Compressive Stiffness in Aggrecan-Depleted Articular Cartilage Explants

Joint trauma results in the production of inflammatory cytokines that stimulate the secretion of catabolic enzymes, which degrade articular cartilage. Molecular fragments of the degraded articular cartilage further stimulate inflammatory cytokine production, with this process eventually resulting in post-traumatic osteoarthritis (PTOA). The loss of matrix component aggrecan occurs early in the progression of PTOA and results in the loss of compressive stiffness in articular cartilage. Aggrecan is highly sulfated, associates with hyaluronic acid (HA), and supports the compressive stiffness in cartilage. Presented here, we conjugated the HA-binding peptide GAHWQFNALTVRGSG (GAH) to anionic nanoparticles (hNPs). Nanoparticles conjugated with roughly 19 GAH peptides, termed 19 GAH-hNP, bound to HA in solution and increased the dynamic viscosity by 94.1% compared to an HA solution treated with unconjugated hNPs. Moreover, treating aggrecan-depleted (AD) cartilage explants with 0.10 mg of 19 GAH-hNP restored the cartilage compressive stiffness to healthy levels six days after a single nanoparticle treatment. Treatment of AD cartilage with 0.10 mg of 19 GAH-hNP inhibited the degradation of articular cartilage. Treated AD cartilage had 409% more collagen type II and 598% more GAG content than untreated-AD explants. The 19 GAH-hNP therapeutic slowed ECM degradation in AD cartilage explants, restored the compressive stiffness of damaged cartilage, and showed promise as a localized treatment for PTOA.

Adenosine A2A receptor null chondrocyte transcriptome resembles that of human osteoarthritic chondrocytes

Adenosine signaling plays a critical role in the maintenance of articular cartilage and may serve as a novel therapeutic for osteoarthritis (OA), a highly prevalent and morbid disease without effective therapeutics in the current market. Mice lacking adenosine A2A receptors (A2AR) develop spontaneous OA by 16 weeks of age, a finding relevant to human OA since loss of adenosine signaling due to diminished adenosine production (NT5E deficiency) also leads to development of OA in mice and humans. To better understand the mechanism by which A2AR and adenosine generation protect from OA development, we examined differential gene expression in neonatal chondrocytes from WT and A2AR null mice. Analysis of differentially expressed genes was analyzed by KEGG pathway analysis, and oPOSSUM and the flatiron database were used to identify transcription factor binding enrichment, and tissue-specific network analyses and patterns were compared to gene expression patterns in chondrocytes from patients with OA. There was a differential expression of 2211 genes (padj<0.05). Pathway enrichment analysis revealed that pro-inflammatory changes, increased metalloprotease, reduced matrix organization, and homeostasis are upregulated in A2AR null chondrocytes. Moreover, stress responses, including autophagy and HIF-1 signaling, seem to be important drivers of OA and bear marked resemblance to the human OA transcriptome. Although A2AR null mice are born with grossly intact articular cartilage, we identify here the molecular foundations for early-onset OA in these mice, further establishing their role as models for human disease and the potential use of adenosine as a treatment for human disease.

Adenosine A2A receptor signaling promotes FoxO associated autophagy in chondrocytes

Autophagy, a homeostatic pathway upregulated during cellular stress, is decreased in osteoarthritic chondrocytes and this reduction in autophagy is thought to contribute to the development and progression of osteoarthritis (OA). The adenosine A2A receptor (A2AR) is a potent anti-inflammatory receptor and deficiency of this receptor leads to the development of OA in mice. Moreover, treatment using liposomally conjugated adenosine or a specific A2AR agonist improved joint scores significantly in both rats with post-traumatic OA (PTOA) and mice subjected to a high fat diet obesity induced OA. Importantly, A2AR ligation is beneficial for mitochondrial health and metabolism in vitro in primary and the TC28a2 human cell line. An additional set of metabolic, stress-responsive, and homeostatic mediators include the Forkhead box O transcription factors (FoxOs). Data has shown that mouse FoxO knockouts develop early OA with reduced cartilage autophagy, indicating that FoxO-induced homeostasis is important for articular cartilage. Given the apparent similarities between A2AR and FoxO signaling, we tested the hypothesis that A2AR stimulation improves cartilage function through activation of the FoxO proteins leading to increased autophagy in chondrocytes. We analyzed the signaling pathway in the human TC28a2 cell line and corroborated these findings in vivo in a metabolically relevant obesity-induced OA mouse model. We found that A2AR stimulation increases activation and nuclear localization of FoxO1 and FoxO3, promotes an increase in autophagic flux, improves metabolic function in chondrocytes, and reduces markers of apoptosis in vitro and reduced apoptosis by TUNEL assay in vivo. A2AR ligation additionally enhances in vivo activation of FoxO1 and FoxO3 with evidence of enhanced autophagic flux upon injection of the liposome-associated A2AR agonist in a mouse obesity-induced OA model. These findings offer further evidence that A2AR may be an excellent target for promoting chondrocyte and cartilage homeostasis.

Current Nanoparticle-Based Technologies for Osteoarthritis Therapy

Osteoarthritis (OA) is a common chronic joint disease that is characterized by joint pain and stiffness, and limitation of motion and the major cause of disability, which reduces life quality of patients and brings a large economic burden to the family and society. Current clinical treatment is mostly limited to symptomatic treatment aimed at pain alleviation and functional improvement, rather than suppressing the progression of OA. Nanotechnology is a promising strategy for the treatment of OA. In this review, we summarize the current experimental progress that focuses on technologies such as liposomes, micelles, dendrimers, polymeric nanoparticles (PNPs), exosomes, and inorganic nanoparticles (NPs) for their potential treatment of OA.