Delay Osteoarthritis Progression Research Articles

Combined exosome of adipose-derived mesenchymal stem cell and hyaluronic acid delays early osteoarthritis progression of ovine sheep model: Clinical, radiographic and macroscopic evaluation

Background Current treatment of osteoarthritis (OA) mainly focused on treating symptoms. Exosome from Adipose-derived Mesenchymal Stem Cell (Ad-MSC) have been shown to delay degenerative process. This study aimed to investigate the clinical, radiological and histological impact of combined intra-articular (IA) hyaluronic acid (HA) and exosome Ad-MSCs in-vivo using a larger animal model with low-grade OA. Methods Eighteen male Ovies aries sheep underwent total lateral meniscectomy and conventional radiography was performed to confirm low-grade OA after 6 weeks. The sheep were divided into three groups, Group 1 (G1; n=6) received thrice exosome injections, G2 (n=6) received twice HA injection, and G3 (n=6) received both treatments with a 1-week interval after 10 days of meniscectomy. Clinical evaluations were conducted using the Clinical Lameness Score (CLS), radiographic with X-ray using OA score by Innes et al, while macroscopic evaluation by Osteoarthritis Research Society International (OARSI) scores. Results Lameness parameter scored lowest in G3 significantly (2.0±0.0 VS 2.7±0.52 VS 2.7±0.52; p=0.024) at the second month although the overall CLS score did not significantly differ at the 3rd month. The best improvement of conventional total OA radiographic score at the 3rd month compared to all groups (5.2±1.17 vs 6.3±0.82 vs 6.7±1.03; p=0.053). Macroscopic OARSI evaluation showed no difference (p=0.711). Conclusions Combined repeated exosome Ad-MSC and HA IA injection proven to delay OA progression, however longer duration of follow up is required to evaluate its long-term effect.

Isoorientin inhibits NLRP3 inflammasome activation by activating Nrf2 signaling to delay the progression of osteoarthritis

Osteoarthritis (OA) is a common condition worldwide and one of the leading causes of disability. At present, there is no clear pathological mechanism or treatment to slow disease progression. ISO (Isoorientin) is a dietary flavonoid that has anti-inflammatory properties, it can also be present in edible plants and beverages. However, its effects on OA chondrocytes are not fully articulated. This study aims to investigate how ISO delays OA progression and its specific mechanism. The salvaging effects of ISO on extracellular matrix degradation and its protective effects against pyroptosis were studied. It was discovered that these effects might be mediated through the Nrf2/HO-1 and NQO1/NF-κB pathways. Nrf2-siRNA was then used for validation. Subsequently, the effects and mechanisms of ISO were evaluated in a mouse model of OA induced by surgery, and a certain degree of improvement in OA conditions due to ISO was observed.In conclusion, ISO may be a promising candidate drug for alleviating OA.

Human Infrapatellar Fat Pad Mesenchymal Stem Cell-derived Extracellular Vesicles Purified by Anion Exchange Chromatography Suppress Osteoarthritis Progression in a Mouse Model.

Human Infrapatellar Fat Pad Mesenchymal Stem Cell-derived Extracellular Vesicles Purified by Anion Exchange Chromatography Suppress Osteoarthritis Progression in a Mouse Model.

Activatable theranostic nanoprobes for Fluorescence/MR imaging and microenvironment remodeling of early cartilage degeneration

Osteoarthritis (OA) is a degenerative joint disease of the knee joint, suffering from the limited therapeutic effect and serious side effects. Unfortunately, there are currently rarely available materials to fundamentally delay and monitor OA progression. The OA microenvironment, including excessive inflammation, matrix metalloproteinases (MMPs), oxidative stress, and reactive oxygen species (ROS), play a crucial role in the pathogenesis of OA. Utilizing and remodeling OA microenvironment may be an effective strategy for the diagnosis and treatment of OA. This work developed an intelligent responsive nanoprobe, Gd-HMPB@SMT@MMP (GHPSM) by encapsulating S-methylisothiourea (SMT) loaded mesoporous Prussian Blue (Gd-HMPB) with Tetramethyl Rhodamine (TAMRA) labeled MMP-13 peptide (MMP-13-TAMRA) for this aim. GHPSM displayed enhanced accumulation in OA cartilage site due to the decrease in the content of negatively charged aminoglycans (GAGs) in early degenerative articular cartilage and activated fluorescence signal as well as SMT controlled release due to the cleavage of MMP-13-TAMRA from GHPSM by overexpressed MMP-13 matrix protease in OA microenvironment. Furthermore, integrating the function of SMT and PB nanozyme, GHPSM reshaped the OA microenvironment by reducing the release of ROS and inflammatory factors (TNF-α, IL-6, iNOS), increasing the expression of intermediate structural proteins (COL2 and Aggrescan), thereby reducing cartilage degradation and chondrocyte apoptosis, ultimately delaying the development of OA. The progressions of early OA disease after different treatments were successfully tracked based on fluorescence/MR imaging with X-ray imaging of knee joint for comparation. These findings highlight the potentials of GHPSM in monitoring the status of cartilage in real-time and delay OA progression by reshaping the OA microenvironment, providing novel ideas for future research in OA diagnosis and treatment.

Enhancing Endogenous Hyaluronic Acid in Osteoarthritic Joints with an Anti-Inflammatory Supramolecular Nanofiber Hydrogel Delivering HAS2 Lentivirus.

Osteoarthritis (OA) management remains challenging because of its intricate pathogenesis. Intra-articular injections of drugs, such as glucocorticoids and hyaluronic acid (HA), have certain limitations, including the risk of joint infection, pain, and swelling. Hydrogel-based therapeutic strategies have attracted considerable attention because of their enormous therapeutic potential. Herein, a supramolecular nanofiber hydrogel is developed using dexamethasone sodium phosphate (DexP) as a vector to deliver lentivirus-encoding hyaluronan synthase 2 (HAS2) (HAS2@DexP-Gel). During hydrogel degradation, HAS2 lentivirus and DexP molecules are slowly released. Intra-articular injection of HAS2@DexP-Gel promotes endogenous HA production and suppresses synovial inflammation. Additionally, HAS2@DexP-Gel reduces subchondral bone resorption in the anterior cruciate ligament transection-induced OA mice, attenuates cartilage degeneration, and delays OA progression. HAS2@DexP-Gel exhibited good biocompatibility both in vitro and in vivo. The therapeutic mechanisms of the HAS2@DexP-Gel are investigated using single-cell RNA sequencing. HAS2@DexP-Gel optimizes the microenvironment of the synovial tissue by modulating the proportion of synovial cell subpopulations and regulating the interactions between synovial fibroblasts and macrophages. The innovative nanofiber hydrogel, HAS2@DexP-Gel, effectively enhances endogenous HA production while reducing synovial inflammation. This comprehensive approach holds promise for improving joint function, alleviating pain, and slowing OA progression, thereby providing significant benefits to patients.

Bilirubin ameliorates osteoarthritis via activating Nrf2/HO-1 pathway and suppressing NF-κB signalling.

Osteoarthritis (OA) is a chronic degenerative joint disease that affects worldwide. Oxidative stress plays a critical role in the chronic inflammation and OA progression. Scavenging overproduced reactive oxygen species (ROS) could be rational strategy for OA treatment. Bilirubin (BR) is a potent endogenous antioxidant that can scavenge various ROS and also exhibit anti-inflammatory effects. However, whether BR could exert protection on chondrocytes for OA treatment has not yet been elucidated. Here, chondrocytes were exposed to hydrogen peroxide with or without BR treatment. The cell viability was assessed, and the intracellular ROS, inflammation cytokines were monitored to indicate the state of chondrocytes. In addition, BR was also tested on LPS-treated Raw264.7 cells to test the anti-inflammation property. An invitro bimimic OA microenvironment was constructed by LPS-treated Raw264.7 and chondrocytes, and BR also exert certain protection for chondrocytes by activating Nrf2/HO-1 pathway and suppressing NF-κB signalling. An ACLT-induced OA model was constructed to test the invivo therapeutic efficacy of BR. Compared to the clinical used HA, BR significantly reduced cartilage degeneration and delayed OA progression. Overall, our data shows that BR has a protective effect on chondrocytes and can delay OA progression caused by oxidative stress.

Bifunctional TRPV1 Targeted Magnetothermal Switch to Attenuate Osteoarthritis Progression

Transient receptor potential vanilloid family member 1 (TRPV1) has been revealed as a therapeutic target of osteoarthritis (OA), the most common deteriorating whole joint disease, by impeding macrophagic inflammation and chondrocytes ferroptosis. However, the clinical application for capsaicin as the TRPV1 agonist is largely limited by its chronic toxicity. To address this issue, we developed a bifunctional controllable magnetothermal switch targeting TRPV1 for the alleviation of OA progression by coupling of magnetic nanoparticles (MNPs) to TRPV1 monoclonal antibodies (MNPs-TRPV1). Under the alternating magnetic field (AMF) stimulation, MNPs-TRPV1 locally dissipated heat, which was sufficient to trigger the opening and activation of TRPV1, and effectively impeded macrophagic inflammation and chondrocyte ferroptosis. This magnetothermal modulation of TRPV1 simultaneously attenuated synovitis and cartilage degeneration in mice incurred by destabilization of medial meniscus surgery, indicating the delayed OA progression. Furthermore, MNPs-TRPV1 with AMF exposure remarkably reduced knee pain sensitivity, alleviated the crippled gait, and improved spontaneous ambulatory activity performance in the mice OA model. Overall, this work provides a potential pathogenesis-based precise OA therapy with temporally and spatially magnetothermal modulation of TRPV1 in a controllable manner.

Therapeutic effects of different intervention forms of human umbilical cord mesenchymal stem cells in the treatment of osteoarthritis.

Osteoarthritis (OA) is a common and disabling disease. For advanced OA, surgical treatment is still the main treatment. Human umbilical cord mesenchymal stem cells (hUC-MSCs) are self-regenerative pluripotent cells, that coordinate cartilage regeneration by secreting various trophic factors, which adjust the injured tissue environment. hUC-MSCs secret extracellular vesicles and participates in OA treatment by transmitting bioactive molecules related to migration, proliferation, apoptosis, inflammatory reaction, extracellular matrix synthesis and cartilage repair. In addition, the combination of multiple substances represented by cartilage matrix and hUC-MSCs also have a significant synergistic effect on OA treatment. Because hUC-MSCs have shown considerable promise in cartilage repair, some scholars have proposed transplanting mesenchymal stem cells into damaged cartilage to delay OA progression. This article reviews the application of hUC-MSCs as a treatment for OA. With the continuous development of routine clinical applications, more reliable intervention modalities for hUC-MSCs in OA treatment will be discovered for the time to come.

Cartilage-targeting and inflammatory-responsive nanocarriers for effective osteoarthritis treatment via reactive oxygen species scavenging and anti-angiogenesis

Osteoarthritis (OA), a common disabling joint disease, is highly associated with microenvironmental changes in the cartilage and subchondral bone. Elevated reactive oxygen species (ROS) in the cartilage and subchondral bone angiogenesis accelerate articular cartilage erosion. New cartilage-targeting drug delivery systems that are aimed at preventing ROS production and angiogenesis may be of clinical significance for OA treatment. Herein, an ROS scavenger and an inflammatory-responsive nanocarrier are designed by immobilizing the natural polyphenol (curcumin) in chitosan-catechol nanoformulations (Cur-CS-C NPs) via boronate ester. The robust cartilage-targeting effects and ROS scavenging capacities of Cur-CS-C NPs were respectively determined in cartilage explants and chondrocytes. Intra-articular injection of Cur-CS-C NPs in OA rat models efficiently suppressed angiogenesis and cartilage degradation partially via the ROS-mediated NF-κB/PI3K-Akt signaling pathway. The developed curcumin-functionalized nanocarriers can significantly delay OA progression and provide a promising therapeutic strategy for other inflammatory diseases that are characterized by oxidative stress and angiogenesis.

NADPH oxidase 4 deficiency attenuates experimental osteoarthritis in mice

ObjectiveLow-grade inflammation plays a pivotal role in osteoarthritis (OA) through exposure to reactive oxygen species (ROS). In chondrocytes, NADPH oxidase 4 (NOX4) is one of the major ROS producers. In...

Blocking TRPV4 Ameliorates Osteoarthritis by Inhibiting M1 Macrophage Polarization via the ROS/NLRP3 Signaling Pathway.

Osteoarthritis (OA) is a low-level inflammatory disease in which synovial macrophage M1 polarization exacerbates the progression of synovitis and OA. Notedly, the ROS (reactive oxygen species) level in macrophages is intimately implicated in macrophage M1 polarization. TRPV4 (transient receptor potential channel subfamily V member 4), as an ion channel, plays a pivotal role in oxidative stress and inflammation. In this study, we investigated the role of TRPV4 in OA progression and M1 macrophage polarization. Male adult Sprague-Dawley (SD) rats underwent a medial meniscus radial transection operation to create an OA model in vivo and RAW 264.7 cells were intervened with 100 ng/mL LPS (lipopolysaccharide) to induce M1-polarized macrophages in vitro. We demonstrated that the infiltration of M1 synovial macrophages and the expression of TRPV4 were increased significantly in OA synovium. In addition, intra-articular injection of HC067074 (a specific inhibitor of TRPV4) alleviated the progression of rat OA and significantly decreased synovial macrophage M1 polarization. Further mechanisms suggested that ROS production by M1 macrophages was decreased after TRPV4 inhibition. In addition, NLRP3 (pyrin domain containing protein 3) as a downstream effector of ROS in M1-polarized macrophage, was significantly suppressed following TRPV4 inhibition. In conclusion, this study discovered that inhibition of TRPV4 delays OA progression by inhibiting M1 synovial macrophage polarization through the ROS/NLRP3 pathway.

3,3'-diindolylmethane inhibits LPS-induced human chondrocytes apoptosis and extracellular matrix degradation by activating PI3K-Akt-mTOR-mediated autophagy.

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by articular cartilage destruction. The pathological mechanisms are complex; in particular, inflammation, autophagy, and apoptosis are often involved. 3,3-Diindolylmethane (DIM), a phytoconstituent extracted from cruciferous vegetables, has various effects such as anti-inflammatory, antioxidant and anti-apoptotic. However, the effects of DIM on osteoarthritic chondrocytes remain undetermined. In this study, we simulated a lipopolysaccharide (LPS)-induced osteoarthritis model in human primary chondrocytes. We found that LPS stimulation significantly inhibited autophagy, induced chondrocyte apoptosis and extracellular matrix (ECM) degradation, which could be ameliorated by DIM. DIM inhibited the expression of a disintegrin and metalloproteinase with thrombospondin motif 5 (ADAMTS-5), matrix metalloproteinase 13 (MMP13), cleaved caspase-3, Bax, and p62, and increased the expression level of collagen II, aggrecan, Bcl-2, light chain 3 Ⅱ (LC3 Ⅱ), and beclin-1. Mechanistic studies showed that DIM increased chondrocyte autophagy levels by inhibiting the activation of PI3K/AKT/mTOR pathway. In mice destabilization of the medial meniscus (DMM) model, immunohistochemical analysis showed that DIM inhibited the expression of p-PI3K and cleaved caspase-3, increased the expression of LC3 Ⅱ. Furthermore, DIM relieved joint cartilage degeneration. In conclusion, our findings demonstrate for the first time that DIM inhibits LPS-induced chondrocyte apoptosis and ECM degradation by regulating the PI3K/AKT/mTOR-autophagy axis and delays OA progression in vivo.

Galangin ameliorates osteoarthritis progression by attenuating extracellular matrix degradation in chondrocytes via the activation of PRELP expression

Osteoarthritis (OA) is primarily characterized by progressive degeneration and destruction of articular cartilage. Currently, there is no effective method to treat OA. The metabolic disturbance of cartilage extracellular matrix (ECM) and oxidative stress are critical to promote OA progression. Galangin (Gal) is a small molecule compound that pertains to flavonoids. To determine the protective effect and mechanism of Gal against OA progression, various experiments were performed in vitro and in vivo. In vitro, Gal promoted ECM production and attenuated ECM degradation in human OA chondrocytes. The expression of ECM components from human OA cartilage explants was also stimulated by Gal treatment. As demonstrated from the in vivo study, the intra-articular injection of Gal delayed OA progression in rat models. Moreover, RNA sequencing analysis showed that proline/arginine-rich end leucine repeat protein (PRELP) was a molecular target of Gal activity. Gal inhibited oxidative stress and attenuated ECM degradation by activating PRELP expression. The study demonstrated that Gal could attenuate ECM degradation and ameliorate OA progression, and PRELP may be a potential candidate drug of Gal for treating OA.

Intra-bone marrow injection of magnesium isoglyrrhizinate inhibits inflammation and delays osteoarthritis progression through the NF-κB pathway

ObjectiveOsteoarthritis (OA) presents cartilage damage in addition to chronic inflammation. However, self-recovery of damaged cartilage in an inflammatory environment is not possible. Mesenchymal stem cells (MSCs) in the bone marrow are a source of regenerative repair of damaged cartilage. To date, whether intra-luminal administration of the bone marrow can delay the progression of OA is still unknown. This study, therefore, aimed to explore the role of intra-bone marrow injection of Magnesium isoglycyrrhizinate (MgIG) in delaying the OA progression and to investigate the underlying mechanism.MethodsRabbit OA models were established using the anterior cruciate ligament transection method while a catheter was implanted into the bone marrow cavity. 1 week after surgery, MgIG treatment was started once a week for 4 weeks. The cartilage degradation was analyzed using hematoxylin–eosin staining, Masson’s trichrome staining and Alcian blue staining. Additionally, the pro-inflammatory factors and cartilage regeneration genes involved in the cartilage degeneration and the underlying mechanisms in OA were detected using enzyme-linked immunosorbent assay, quantitative real-time PCR (qRT-PCR) and Western blotting.ResultsThe results of histological staining revealed that intra-bone marrow injection of MgIG reduced degeneration and erosion of articular cartilage, substantially reducing the Osteoarthritis Research Society International scores. Furthermore, the productions of inflammatory cytokines in the bone marrow cavity and articular cavity such as interleukin-1β(IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) were inhibited upon the treatment of MgIG. At the same time, the expression of alkaline phosphate, tartrate-resistant acid phosphatase-5b (TRAP-5b) and C-telopeptides of type II collagen (CTX-II) in the blood also decreased and was positively correlated. On the contrary, cartilage-related genes in the bone marrow cavity such as type II collagen (Col II), Aggrecan (AGN), and SRY-box 9 (SOX9) were up-regulated, while matrix metalloproteinase-3 (MMP-3) was down-regulated. Mechanistically, MgIG was found to exert an anti-inflammatory effect and impart protection to the cartilage by inhibiting the NF-κB pathway.ConclusionIntra-bone marrow injection of MgIG might inhibit the activation of the NF-κB pathway in the progression of OA to exert an anti-inflammatory effect in the bone marrow cavity and articular cavity, thereby promoting cartilage regeneration of MSCs in the bone marrow, making it a potential new therapeutic intervention for the treatment of OA.

AZ-628 delays osteoarthritis progression via inhibiting the TNF-α-induced chondrocyte necroptosis and regulating osteoclast formation

As a degenerative disease, the pathogenesis and treatment of osteoarthritis (OA) are still being studied. The prevailing view is that articular cartilage dysfunction plays an essential role in the development of osteoarthritis. Similarly, dynamic bone remodeling dramatically influences the development of osteoarthritis. The inflammatory response is caused by the overexpression of inflammatory factors, among which tumor necrosis factor-α is one of the main causes of OA, and its sources include the secretion of chondrocytes themselves and osteoclast secretion of subchondral bone. Moreover, TNF-α-induced activation of RIP1, RIP3, and MLKL has been shown to play an important role in cell necroptosis and inflammatory responses. In vitro, AZ-628 alleviates chondrocyte inflammation and necroptosis by inhibiting the NF-κB signaling pathway and RIP3 activation instead of RIP1 activation. AZ-628 also reduces osteoclast activity, proliferation and differentiation, and release of inflammatory substances by inhibiting autophagy, MAPK, and NF-κB pathways. Similarly, the in vivo study demonstrated that AZ-628 could inhibit chondrocyte breakdown and lower osteoclast formation and bone resorption, thereby slowing down subchondral bone changes induced by dynamic bone remodeling and reversing the progression of osteoarthritis in mice. The results of this study indicate that AZ-628 could be used to treat OA byinhibiting chondrocyte necroptosis and regulating osteoclast formation.

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.

Osteoarthritis disease progression through the lower extremity: A review

It has long been felt that osteoarthritis is the result of wear and tear. Many physicians are not aware that biological science has now validated that this increased “wear and tear” on the joint is the result of loading-induced stresses that undermine cell function and aging. The loading creates shear forces on the cartilage that leads to increased oxidants. These oxidants then cause chondrocyte premature aging, leading to the development of what we know as osteoarthritis.
 Studies have also found a significant association between foot pain and knee and hip pain. Likewise, many physicians are not aware of the relationship between the hip, knee and foot are a result of the kinetic chain. The kinetic chain being the dynamic transfer of forces during ambulation of the foot, ankle, knee, and hip. The kinetic chain explains how the body’s joints and segments affect one another during movement, and so play a role in pain. The pain results from transferred mechanical stress from one joint to another. The same stress and shear forces that leads to osteoarthritis.
 This article involves a literature of the connection of osteoarthritis and the kinetic chain in the lower limb and highlights the need to consider related joints in the kinetic chain when addressing and injury in one joint to address and perhaps delay progression of osteoarthritis in related joints.

Silencing BLNK protects against interleukin-1β-induced chondrocyte injury through the NF-κB signaling pathway.

Osteoarthritis (OA) is the most common joint disease in the elderly and is characterized by the progressive degeneration of articular cartilage. It is necessary to study the molecular pathology of OA. This study aimed to explore the role and mechanism of BLNK in regulating interleukin-1β (IL-1β)-induced chondrocyte injury and OA progression. GSE1919 (5 normal samples and 5 OA samples) was downloaded from the Gene Expression Omnibus (GEO) database. The limma package in R software was used to identify differentially expressed genes (DEGs) between control and OA-affected cartilage. Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses of the differentially expressed genes were also performed. Apoptosis was assessed by flow cytometry. An OA rat model was established, and the relative expression of BLNK was assessed by real time quantitative PCR (qRT-PCR) and immunohistochemical staining. The expression of collagen II, MMP9, p65 and p-p65 was measured by Western blot analysis. Moreover, inflammatory factors (TNF-α and IL-18) were assessed by ELISA. The NF-κB inhibitor JSH-23 was used to assess the impact of BLNK on the NF-κB signaling pathway. In total, 1318 DEGs were identified between normal and OA-affected cartilage according to the criteria (P-value <0.05 and |logFC>1|). These DEGs were mainly enriched in the NF-κB pathway. BLNK was highly expressed in OA cartilage tissue and injured chondrocytes. Silencing BLNK significantly downregulated the IL-1β-induced apoptosis of chondrocytes. Silencing BLNK partially increased collagen II expression and downregulated MMP13 expression. Moreover, silencing BLNK partially decreased TNF-α and IL-18 expression. BLNK silencing inhibited the activation of NF-κB in OA. Silencing BLNK delayed OA progression through the NF-κB signaling pathway. Silencing BLNK delayed OA progression and IL-1β-induced chondrocyte injury by regulating the NF-κB pathway.

Dihydroartemisinin attenuates osteoclast formation and bone resorption via inhibiting the NF‑κB, MAPK and NFATc1 signaling pathways and alleviates osteoarthritis.

Osteoarthritis (OA) is a chronic, progressive and degenerative disease, and its incidence is increasing on a yearly basis. However, the pathological mechanism of OA at each stage is still unclear. The present study aimed to explore the underlying mechanism of dihydroartemisinin (DHA) in terms of its ability to inhibit osteoclast activation, and to determine its effects on OA in rats. Bone marrow-derived macrophages were isolated as osteoclast precursors. In the presence or absence of DHA, osteoclast formation was assessed by tartrate-resistant acid phosphatase (TRAP) staining, cell viability was assessed by Cell Counting Kit-8 assay, the presence of F-actin rings was assessed by immunofluorescence, bone resorption was determined by bone slices, luciferase activities of NF-κB and nuclear factor of activated T cell cytoplasmic 1 (NFATc1) were determined using luciferase assay kits, the protein levels of biomolecules associated with the NF-κB, MAPK and NFATc1 signaling pathways were determined using western blotting, and the expression of genes involved in osteoclastogenesis were measured using reverse transcription-quantitative PCR. A knee OA rat model was designed by destabilizing the medial meniscus (DMM). A total of 36 rats were assigned to three groups, namely the sham-operated, DMM + vehicle and DMM + DHA groups, and the rats were administered DHA or DMSO. At 4 and 8 weeks postoperatively, the micro-architecture of the subchondral bone was analyzed using micro-CT, the thickness of the cartilage layers was calculated using H&E staining, the extent of cartilage degeneration was scored using Safranin O-Fast Green staining, TRAP-stained osteoclasts were counted, and the levels of receptor activator of NF-κB ligand (RANKL), C-X-C-motif chemokine ligand 12 (CXCL12) and NFATc1 were measured using immunohistochemistry. DHA was found to inhibit osteoclast formation without cytotoxicity, and furthermore, it did not affect bone formation. In addition, DHA suppressed the expression levels of NF-κB, MAPK, NFATc1 and genes involved in osteoclastogenesis. Progressive cartilage loss was observed at 8 weeks postoperatively. Subchondral bone remodeling was found to be dominated by bone resorption accompanied by increases in the levels of RANKL, CXCL12 and NFATc1 during the first 4 weeks. DHA was found to delay OA progression by inhibiting osteoclast formation and bone resorption during the early phase of OA. Taken together, the results of the present study demonstrated that the mechanism through which DHA could inhibit osteoclast activation may be associated with the NF-κB, MAPK and NFATc1 signaling pathways, thereby indicating a potential novel strategy for OA treatment.

Reduction of knee joint load suppresses cartilage degeneration, osteophyte formation, and synovitis in early-stage osteoarthritis using a post-traumatic rat model.

The purpose of this study was to clarify the histological effect of reducing the loading to knee on cartilage degeneration, osteophyte formation, and synovitis in early-stage osteoarthritis (OA) using a post-traumatic rat model. Ten male rats were randomly allocated into two experimental groups: OA induction by surgical destabilization of medial meniscus (DMM, OA group) and hindlimb suspension after OA induction by DMM (OAHS group). The articular cartilage, osteophyte formation, and synovial membrane in the medial tibiofemoral joint were analyzed histologically and histomorphometrically at 2 and 4 weeks after surgery. The histological scores and changes in articular cartilage and osteophyte formation were significantly milder and slower in the OAHS group than in the OA group. At 2 and 4 weeks, there were no significant differences in cartilage thickness and matrix staining intensity between both the groups, but chondrocytes density was significantly lower in the OA group. Synovitis was milder in OAHS group than in OA group at 2 weeks. Reducing knee joint loading inhibited histological OA changes in articular cartilage, osteophyte formation, and synovial inflammation. This result supports the latest clinical guidelines for OA treatment. Further studies using biochemical and mechanical analyses are necessary to elucidate the mechanism underlying delayed OA progression caused by joint-load reduction.