Aging and osteoarthritis: Central role of the extracellular matrix

Synovial mesenchymal stem cell-derived exosomal microRNA-320c facilitates cartilage damage repair by targeting ADAM19-dependent Wnt signalling in osteoarthritis rats

OBJECTIVE

Our previous study revealed that synovial mesenchymal stem cell (SMSC)-derived exosomal microRNA-302c enhanced chondrogenesis by targeting a disintegrin and metalloproteinase 19 (ADAM19) in vitro. This study aimed to validate the potential of SMSC-derived exosomal microRNA-302c for the treatment of osteoarthritis in vivo.

METHODS

After 4 weeks of destabilization of the medial meniscus surgery (DMM) to establish an osteoarthritis model, the rats received weekly articular cavity injection of SMSCs with or without GW4869 treatment (exosome inhibitor) or exosomes from SMSCs with or without microRNA-320c overexpression for another 4 weeks.

RESULTS

SMSCs and SMSC-derived exosomes reduced the Osteoarthritis Research Society International (OARSI) score, improved cartilage damage repair, suppressed cartilage inflammation, suppressed extracellular matrix (ECM) degradation, and inhibited chondrocyte apoptosis in DMM rats. However, these effects were largely hampered in rats that were injected with GW4869-treated SMSCs. Moreover, exosomes from microRNA-320c-overexpressing SMSCs exerted a better effect than exosomes from negative control SMSCs on decreasing the OARSI score, enhancing cartilage damage repair, suppressing cartilage inflammation, and inhibiting ECM degradation and chondrocyte apoptosis. Mechanistically, exosomes from microRNA-320c-overexpressing SMSCs reduced the levels of ADAM19, as well as β-catenin and MYC, which are two critical proteins in Wnt signalling.

CONCLUSION

SMSC-derived exosomal microRNA-320c suppresses ECM degradation and chondrocyte apoptosis to facilitate cartilage damage repair in osteoarthritis rats by targeting ADAM19-dependent Wnt signalling.

Small non-coding RNAome changes during human chondrocyte senescence as potential epigenetic targets in age-related osteoarthritis

Chondrocyte senescence is a decisive component of age-related osteoarthritis, however, the function of small noncoding RNAs (sncRNAs) in chondrocyte senescence remains underexplored. Human hip joint cartilage chondrocytes were cultivated up to passage 4 to induce senescence. RNA samples were extracted and then analyzed using small RNA sequencing and qPCR. β-galactosidase staining was used to detect the effect of sncRNA on chondrocyte aging. Results of small RNA sequencing showed that 279 miRNAs, 136 snoRNAs, 30 snRNAs, 102 piRNAs, and 5 rasiRNAs were differentially expressed in senescent chondrocytes. The differential expression of 150 sncRNAs was further validated by qPCR. Transfection of sncRNAs and β-galactosidase staining were also performed to further revealed that hsa-miR-135b-5p, SNORA80B-201, and RNU5E-1-201 have the function to restrain chondrocyte senescence, while has-piR-019102 has the function to promote chondrocyte senescence. Our data suggest that sncRNAs have therapeutic potential as novel epigenetic targets in age-related osteoarthritis.

Loss of RAP2A Aggravates Cartilage Degradation in TMJOA via YAP Signaling

Abnormal stress loading has been considered a major contributor to the initiation of temporomandibular joint osteoarthritis (TMJOA), but studies to date have not identified a functional molecule that transforms physical stress into biological or biochemical signaling in chondrocytes in response to excessive mechanical stress. Ras-related protein Rap-2a (RAP2A) is reportedly a molecular switch that relays extracellular matrix rigidity signals via the Hippo/Yes-associated protein (YAP) pathway. In the present study, RAP2A diminished with cartilage degradation in unilateral anterior crossbite-induced TMJOA mice, as well as severe cartilage matrix degeneration and TMJOA formation in Cre-loxP-mediated conditional RAP2A knockout mice. RAP2A in chondrocytes regulated the Hippo/YAP pathway directly in response to matrix stiffness, and RAP2A/Hippo/YAP was critical for a chondrocyte phenotype switch and matrix synthesis function. Loss of RAP2A impaired cartilage homeostasis and altered chondrocyte phenotype via Hippo/YAP/SRY-box transcription factor 9 signaling. It may be possible to generate therapeutic strategies using RAP2A or YAP to attenuate the TMJOA pathological process at an early stage. This is the first study to reveal the molecular function of RAP2A in TMJOA progression as a mechanotransduction molecule in condylar chondrocytes.

Unraveling the role of natural functional oils in modulating osteoarthritis related complications

Osteoarthritis (OA) is a common joint disease and has been studied extensively in recent years as no promising therapy available so far for its treatment and remains a great challenge for health care specialists. Although the identification of some major mechanisms that contribute to this disease suggests a plethora of bioactive agents in tackling the associated complications yet OA's pathophysiology is still poorly understood owing to complex mechanistic changes observed. Experimental research is now exploring a wide range of therapeutically effective agents in an effort to find a way to repair OA-related joint degeneration and halt it from getting worse. Data was acquired and reviewed from most relevant and recent studies. This review summarizes the studies that are currently available and focuses on how various unconventional functional oils affect osteoarthritis and the affected joint tissues. An analysis of the recent scientific literature allowed us to highlight the potential anti-arthritic properties of edible oils and their main constituents, which seems to suggest an interesting new potential therapeutic application. Due to eccentric nature of OA, it is necessary to concentrate initially on the management of symptoms. The evidence supporting functional oils chondroprotective potential is still accumulating, underpinning a global need for more sustainable natural sources of treatment. More clinical research that focuses on the consequences of long-term treatment, possible negative effects, and epigenetic implications is necessary to get optimistic results. However, different animal or clinical studies suggest that linolenic and linoleic fatty acids decreased chondrocyte oxidative stress, cartilage breakdown, and expression of inflammatory markers. Distinct fatty acids along with minor components of oils also reduced the generation of prostaglandins and decreased oxidative stress. Furthermore, the potential roles of the main components of edible oils and possible negative results (if any) are also reported. While no severe side effects have been reported for any edible oils. Overall, these studies identify and support the use of functional oils as an adjuvant therapy for the management of OA and as a means of symptomatic alleviation for OA patients. However, to prove the effectiveness or to draw precise conclusions, high-quality clinical trials are required.

Immunogenicity of decellularized extracellular matrix scaffolds: a bottleneck in tissue engineering and regenerative medicine

Tissue-engineered decellularized extracellular matrix (ECM) scaffolds hold great potential to address the donor shortage as well as immunologic rejection attributed to cells in conventional tissue/organ transplantation. Decellularization, as the key process in manufacturing ECM scaffolds, removes immunogen cell materials and significantly alleviates the immunogenicity and biocompatibility of derived scaffolds. However, the application of these bioscaffolds still confronts major immunologic challenges. This review discusses the interplay between damage-associated molecular patterns (DAMPs) and antigens as the main inducers of innate and adaptive immunity to aid in manufacturing biocompatible grafts with desirable immunogenicity. It also appraises the impact of various decellularization methodologies (i.e., apoptosis-assisted techniques) on provoking immune responses that participate in rejecting allogenic and xenogeneic decellularized scaffolds. In addition, the key research findings regarding the contribution of ECM alterations, cytotoxicity issues, graft sourcing, and implantation site to the immunogenicity of decellularized tissues/organs are comprehensively considered. Finally, it discusses practical solutions to overcome immunogenicity, including antigen masking by crosslinking, sterilization optimization, and antigen removal techniques such as selective antigen removal and sequential antigen solubilization.

Connection between Osteoarthritis and Nitric Oxide: From Pathophysiology to Therapeutic Target

Osteoarthritis (OA), a disabling joint inflammatory disease, is characterized by the progressive destruction of cartilage, subchondral bone remodeling, and chronic synovitis. Due to the prolongation of the human lifespan, OA has become a serious public health problem that deserves wide attention. The development of OA is related to numerous factors. Among the factors, nitric oxide (NO) plays a key role in mediating this process. NO is a small gaseous molecule that is widely distributed in the human body, and its synthesis is dependent on NO synthase (NOS). NO plays an important role in various physiological processes such as the regulation of blood volume and nerve conduction. Notably, NO acts as a double-edged sword in inflammatory diseases. Recent studies have shown that NO and its redox derivatives might be closely related to both normal and pathophysiological joint conditions. They can play vital roles as normal bone cell-conditioning agents for osteoclasts, osteoblasts, and chondrocytes. Moreover, they can also induce cartilage catabolism and cell apoptosis. Based on different conditions, the NO/NOS system can act as an anti-inflammatory or pro-inflammatory agent for OA. This review summarizes the studies related to the effects of NO on all normal and OA joints as well as the possible new treatment strategies targeting the NO/NOS system.

Plantamajoside suppresses the activation of NF-κB and MAPK and ameliorates the development of osteoarthritis

Osteoarthritis (OA) is a common degenerative bone and joint disorder characterized by progressive cartilage degeneration and secondary synovial inflammation. It is a common chronic joint disorder that affects people of all ages (especially the old). Plantamajoside is a phenylpropanoside derived from plantain. It has a variety of biological properties, including antioxidant, anti-malignant cell proliferation, and anti-inflammatory properties. In this study, the latent mechanism of plantamajoside was explored by slowing the in-vivo and in-vitro progression of osteoarthritis. The results revealed that plantamajoside pre-conditioning inhibited IL-1β induced pro-inflammatory factors like COX-2, iNOS, IL-6, and TNF-α. Moreover, plantamajoside also reversed the IL-1 β mediated type II collagen and aggrecan degradation within the extracellular matrix (ECM). The protective effects of plantamajoside have been attributed to the inhibition of both MAPK and NF-κB pathways. Furthermore, our in-vivo research found that plantamajoside could slow the progression of OA in mice. Finally, all findings point to plantamajoside as a potential anti-OA therapeutic candidate.

Exosomes treating osteoarthritis: hope with challenge

Osteoarthritis (OA) has been proven as the second primary cause of pain and disability in the elderly population, impact patients both physically and mentally, as well as imposing a heavy burden on the global healthcare system. Current treatment methods, whether conservative or surgical, that aim at relieving symptoms can not delay or reverse the degenerative process in the structure. Scientists and clinicians are facing a revolution in OA treatment strategies. The emergence of exosomes brings hope for OA treatment based on pathology, which is attributed to its full potential in protecting chondrocytes from excessive death, alleviating inflammation, maintaining cartilage matrix metabolism, and regulating angiogenesis and subchondral bone remodeling. Therefore, we summarized the recent studies of exosomes in OA, aiming to comprehensively understand the functions and mechanisms of exosomes in OA treatment, which may provide direction and theoretical support for formulating therapeutic strategies in the future.

Gardenoside ameliorates inflammation and inhibits ECM degradation in IL-1β-treated rat chondrocytes via suppressing NF-κB signaling pathways

Osteoarthritis (OA) places a significant burden on society and finance, and there is presently no effective treatment beside late replacement surgery and symptomatic relief. The therapy of OA requires additional research. Gardenoside is a naturally compound extracted from Gardenia jasminoides Ellis, which has a variety of anti-inflammatory effects. However, few studies have been conducted to determine the role of gardenoside in OA. This study aimed to explore whether gardenoside has effect in OA treatment. Rat primary chondrocytes were treated with IL-1β to simulate inflammatory environmental conditions and OA in vitro. We examined the effects of gardenoside at concentrations ranging from 0 to 200 μM on the viability of rat chondrocytes and selected 10 μM for further study. Via in vitro experiments, our study found that gardenoside lowers the gene expression of COX-2, iNOS, IL-6, and reduced the ROS production of chondrocytes induced by IL-1β. Moreover, it effectively alleviates ECM degradation caused by IL-1β and promotes the ECM synthesis in chondrocytes by upregulating collagen-II and the ACAN expression, downregulating the expression of MMP-3, MMP-13, and ADAMTS-5 expression. Further, our study showed that gardenoside inhibits NF-κB signaling pathway activated by IL-1β in chondrocytes. We established an OA rat model by anterior cruciate ligament transection (ACLT). The animals were then periodically injected with gardenoside into the knee articular cavity. In vivo study suggested that gardenoside attenuates OA progression in rats. As a whole, in vitro and in vivo results highlight gardenoside is a promising OA treatment agent.

The Regional Burden and Disability-Adjusted Life Years of Knee Osteoarthritis in Kazakhstan 2014-2020

A Global Burden of Disease (GBD) study reported that 9.6 million years lived with disability (YLDs) were lost due to hip and knee osteoarthritis (KOA) in 2017. Although the GBD study presents the disease burden at the global level, there is no information on any Central Asian country. This study aims to investigate the epidemiology of knee osteoarthritis in Kazakhstan. The data of 56,895 people with KOA between 2014-2020 was derived from the Unified National Electronic Health System of Kazakhstan and retrospectively analyzed. The majority of the cohort (76%) were women, of Kazakh ethnicity (66%), and older than 50 years of age (87%). The risk of gonarthrosis escalated for women after 50 years and peaked at 75 years with a rate of 3062 females admitted to hospital per 100,000 women in the population. This observation is approximately three times higher than for men of the same age group. A geographical analysis showed that the Jambyl oblast, West Kazakhstan, North Kazakhstan, and the Akmola oblast have the highest burden of disease. During the observation period, 127,077 age-adjusted YLDs were lost due to knee osteoarthritis. This is the first study in Kazakhstan to investigate the burden of knee osteoarthritis. This research recognizes age and sex-based differences, and regional disparities in the incidence of knee osteoarthritis. This knowledge can lead to the development of more specific diagnostic approaches and gender-personalized therapy protocols for patients.

Sustained intra-articular reactive oxygen species scavenging and alleviation of osteoarthritis by biocompatible amino-modified tantalum nanoparticles

Recent studies highlight the vital role of oxidative stress and reactive oxygen species (ROS) during progression of osteoarthritis (OA). Attenuating oxidative stress and reducing reactive oxygen species generation in joints represent reasonable strategies for the treatment of osteoarthritis. To address the potential question for clinical translation, and improve the biocompatibility and long-term performance of current antioxidants, the present study provided high biocompatible small positively charged tantalum nanoparticles (Ta-NH₂ NPs) with sustained intra-articular catalase activity and first applied to osteoarthritis intervention. Our in vitro results showed that Ta-NH₂ NPs were stable with good biocompatibility, and protected viability and hyaline-like phenotype in H₂O₂-challenged chondrocytes. In addition, the in vivo biodistribution data demonstrated a sustained retention of Ta-NH₂ NPs in the joint cavity, particularly in articular cartilage without organ toxicity and abnormality in hemogram or blood biochemistry indexes. Finally, compared with catalase (CAT), Ta-NH₂ NPs exhibited long-term therapeutic effect in monosodium iodoacetate (MIA) induced osteoarthritis model. This study preliminarily explored the potential of simply modified metal nanoparticles as effective reactive oxygen species scavenging agent for osteoarthritis intervention, and offered a novel strategy to achieve sustained reactive oxygen species suppression using biocompatible Ta-based nano-medicine in oxidative stress related diseases.

Identification of the osteoarthritis signature gene PDK1 by machine learning and its regulatory mechanisms on chondrocyte autophagy and apoptosis

Background

Osteoarthritis (OA) is a degenerative joint disease frequently diagnosed in the elderly and middle-aged population. However, its specific pathogenesis has not been clarified. This study aimed to identify biomarkers for OA diagnosis and elucidate their potential mechanisms for restoring OA-dysregulated autophagy and inhibiting chondrocyte apoptosis in vitro.

Material and methods

Two publicly available transcriptomic mRNA OA-related datasets (GSE10575 and GSE51588) were explored for biomarker identification by least absolute shrinkage and selection operator (LASSO) regression, weighted gene co-expression network analysis (WGCNA), and support vector machine recursive feature elimination (SVM-RFE). We applied the GSE32317 and GSE55457 cohorts to validate the markers' efficacy for diagnosis. The connections of markers to chondrocyte autophagy and apoptosis in OA were also comprehensively explored in vitro using molecular biology approaches, including qRT-PCR and Western blot.

Results

We identified 286 differentially expressed genes (DEGs). These DEGs were enriched in the ECM-receptor interaction and PI3K/AKT signaling pathway. After external cohort validation and protein-protein interaction (PPI) network construction, PDK1 was finally identified as a diagnostic marker for OA. The pharmacological properties of BX795-downregulated PDK1 expression inhibited LPS-induced chondrocyte inflammation and apoptosis and rescued OA-dysregulated autophagy. Additionally, the phosphorylation of the mediators associated with the MAPK and PI3K/AKT pathways was significantly downregulated, indicating the regulatory function of PDK1 in apoptosis and autophagy via MAPK and PI3K/AKT-associated signaling pathways in chondrocytes. A significantly positive association between the PDK1 expression and Neutrophils, Eosinophils, Plasma cells, and activated CD4 memory T cells, as well as an evident negative correlation between T cells follicular helper and CD4 naive T cells, were detected in the immune cell infiltration analysis.

Conclusions

PDK1 can be used as a diagnostic marker for OA. Inhibition of its expression can rescue OA-dysregulated autophagy and inhibit apoptosis by reducing the phosphorylation of PI3K/AKT and MAPK signaling pathways.

Biochanin A protects against iron overload associated knee osteoarthritis via regulating iron levels and NRF2/System xc-/GPX4 axis

BACKGROUND

Iron homeostasis plays a positive role in articular cartilage health. Excessive iron or iron overload can induce oxidative stress damage in chondrocytes and ferroptosis cell death, advancing knee osteoarthritis (KOA). However, up to date, few effective agents treat iron overload-induced KOA (IOKOA). Chinese herbal medicine (CHM) provides abundant resources for drug selection to manage bone metabolic conditions, including osteoporosis. Biochanin A (BCA) is a novel bioactive multifunctional natural compound isolated from Huangqi, which has protective effects on bone loss. Nevertheless, the function and mechanism of BCA in treating IOKOA are still elusive.

PURPOSE

This study seeks to uncover the potential therapeutic targets and mechanisms of BCA in the management of KOA with iron accumulation.

METHODS

Iron dextrin (500 mg/kg) was intraperitoneally injected into mice to establish the iron overloaded mice model. OA was induced through surgery, and the progression was evaluated eight weeks following surgery. OA severity was evaluated with micro-CT and Safranin-O/Fast green staining in vivo. Iron deposition in the knee joint and synovium was assessed using Perl's Prussian blue staining. Ferric ammonium citrate (FAC) was then administered to primary chondrocytes to evaluate iron regulators mediated iron homeostasis. Toluidine blue staining was utilized to identify chondrocytes in vitro. The vitality of the cells was assessed using the CCK-8 test. The apoptosis rate of cells was measured using Annexin V-FITC/PI assay. The intracellular iron level was detected utilizing the calcein-AM test. Reactive oxygen species (ROS), lipid-ROS, and mitochondrial membrane potentiality were reflected via fluorescence density. Utilizing RT-qPCR and western blotting, the expression level was determined.

RESULTS

Micro-CT and histological staining of knee joints showed greater cartilage degradation and higher iron buildup detected in iron-overloaded mice. BCA can reduce iron deposition and the severity of KOA. Toluidine blue staining and the CCK-8 assay indicated that BCA could rescue chondrocytes killed by iron. Cell apoptosis rates were increased due to iron overload but improved by BCA. Further, the intracellular content of iron, ROS, and lipid-ROS was increased with ferric ammonium citrate (FAC) treatment but restored after treatment with different concentrations of BCA. JC-1 staining revealed that BCA could reduce mitochondrial damage induced by iron overload.

CONCLUSION

Iron overload was shown to promote chondrocyte ferroptosis in vivo and in vitro. Moreover, iron overload suppressed the expression of collagen II and induced MMP expression by catalyzing ROS generation with mitochondrial dysfunction. Our results showed that BCA could directly reduce intracellular iron concentration by inhibiting TfR1 and promoting FPN but also target the Nrf2/system xc-/GPX4 signaling pathway to scavenge free radicals and prevent lipid peroxidation. The results of this research indicate that BCA regulates iron homeostasis during the progression of osteoarthritis, which can open a new field of treatment for KOA.

Sirtuins in osteoarthritis: current understanding

Osteoarthritis (OA) is a common disease characterized by severe chronic joint pain, that imposes a large burden on elderly people. OA is a highly heterogeneous disease, and multiple etiologies contribute to its progression. Sirtuins (SIRTs) are Class III histone deacetylases (HDACs) that regulate a comprehensive range of biological processes such as gene expression, cell differentiation, and organism development, and lifespan. Over the past three decades, increasing evidence has revealed that SIRTs are not only important energy sensors but also protectors against metabolic stresses and aging, and an increasing number of studies have focused on the functions of SIRTs in OA pathogenesis. In this review, we illustrate the biological functions of SIRTs in OA pathogenesis from the perspectives of energy metabolism, inflammation, autophagy and cellular senescence. Moreover, we offer insights into the role played by SIRTs in regulating circadian rhythm, which has recently been recognized to be crucial in OA development. Here, we provide the current understanding of SIRTs in OA to guide a new direction for OA treatment exploration.

Molecular crosstalk between articular cartilage, meniscus, synovium, and subchondral bone in osteoarthritis

AIMS

Osteoarthritis (OA) is a common degenerative joint disease worldwide, which is characterized by articular cartilage lesions. With more understanding of the disease, OA is considered to be a disorder of the whole joint. However, molecular communication within and between tissues during the disease process is still unclear. In this study, we used transcriptome data to reveal crosstalk between different tissues in OA.

METHODS

We used four groups of transcription profiles acquired from the Gene Expression Omnibus database, including articular cartilage, meniscus, synovium, and subchondral bone, to screen differentially expressed genes during OA. Potential crosstalk between tissues was depicted by ligand-receptor pairs.

RESULTS

During OA, there were 626, 97, 1,060, and 2,330 differentially expressed genes in articular cartilage, meniscus, synovium, and subchondral bone, respectively. Gene Ontology enrichment revealed that these genes were enriched in extracellular matrix and structure organization, ossification, neutrophil degranulation, and activation at different degrees. Through ligand-receptor pairing and proteome of OA synovial fluid, we predicted ligand-receptor interactions and constructed a crosstalk atlas of the whole joint. Several interactions were reproduced by transwell experiment in chondrocytes and synovial cells, including TNC-NT5E, TNC-SDC4, FN1-ITGA5, and FN1-NT5E. After lipopolysaccharide (LPS) or interleukin (IL)-1β stimulation, the ligand expression of chondrocytes and synovial cells was upregulated, and corresponding receptors of co-culture cells were also upregulated.

CONCLUSION

Each tissue displayed a different expression pattern in transcriptome, demonstrating their specific roles in OA. We highlighted tissue molecular crosstalk through ligand-receptor pairs in OA pathophysiology, and generated a crosstalk atlas. Strategies to interfere with these candidate ligands and receptors may help to discover molecular targets for future OA therapy.Cite this article: Bone Joint Res 2022;11(12):862-872.

Targeted inhibition of TXNRD1 prevents cartilage extracellular matrix degeneration by activating Nrf2 pathway in osteoarthritis

Osteoarthritis, a prevalent orthopedic disease, can affect the elderly and causes impairment. The degradation and aberrant homeostasis of cartilage extracellular matrix figure pivotally in the progression of osteoarthritis. Thioredoxin systems plays a role in a wide range of biological processes, including cell proliferation, apoptosis, and oxidative stress. The present study aimed to investigate the unique function and underlying pathophysiological mechanism of TXNRD1 in chondrocytes. An upregulated expression of TXNRD1 was observed in the articular cartilage of osteoarthritis patients compared with normal articular cartilage. Furthermore, in vitro experiments showed that the expression of TXNRD1 was also abnormally increased in IL-1β-induced primary mouse chondrocytes. Silencing TXNRD1 using siRNA in chondrocytes could effectively inhibit the expression of ADAMTS5 and MMP13, and enhance the expression of COL2A1 and SOX9. The same was true for auranofin, an inhibitor of TXNRD1. This phenomenon indicated that inhibition of TXNRD1 attenuated il-1β-induced metabolic imbalance of extracellular matrix (ECM) and the progression of chondrocyte osteoarthritis. Further mechanism analysis revealed that the activation of Nrf2 signaling pathway and the expression of heme oxygenase-1 (HO-1) were increased upon TXNRD1 inhibition. Furthermore, auranofin was found to attenuate DMM-induced osteoarthritis progression in vivo. Therefore, the pharmacological downregulation of TXNRD1 may provide an effective novel therapy for OA.

Osthole Suppresses Knee Osteoarthritis Development by Enhancing Autophagy Activated via the AMPK/ULK1 Pathway

Knee osteoarthritis (KOA) is an increasingly prevalent heterogeneous disease characterized by cartilage erosion and inflammation. As the main chemical constituent of Angelicae Pubescentis Radix (APR), an anti-inflammatory herbal medicine, the potential biological effects and underlying mechanism of osthole on chondrocytes and KOA progression remain elusive. In this study, the potential effect and mechanism of osthole on KOA were investigated in vitro and in vivo. We found that osthole inhibited IL-1β-induced apoptosis and cartilage matrix degeneration by activating autophagy in rat chondrocytes. In addition, osthole could activate autophagy through phosphorylation of AMPK/ULK1, and AMPK serves as a positive upstream regulator of ULK1. Furthermore, KOA rats treated with osthole showed phosphorylation of the AMPK/ULK1 pathway and autophagy activation, as well as cartilage protection. Collectively, the AMPK/ULK1 signaling pathway can be activated by osthole to enhance autophagy, thereby suppressing KOA development. Osthole may be a novel and effective therapeutic agent for the clinical treatment of KOA.

New insights into the interplay between autophagy and cartilage degeneration in osteoarthritis

Autophagy is an intracellular degradation system that maintains the stable state of cell energy metabolism. Some recent findings have indicated that autophagy dysfunction is an important driving factor for the occurrence and development of osteoarthritis (OA). The decrease of autophagy leads to the accumulation of damaged organelles and macromolecules in chondrocytes, which affects the survival of chondrocytes and ultimately leads to OA. An appropriate level of autophagic activation may be a new method to prevent articular cartilage degeneration in OA. This minireview discussed the mechanism of autophagy and OA, key autophagy targets regulating OA progression, and evaluated therapeutic applications of drugs targeting autophagy in preclinical and clinical research. Some critical issues worth paying attention to were also raised to guide future research efforts.

Long non-coding RNA PMS2L2 is down-regulated in osteoarthritis and inhibits chondrocyte proliferation by up-regulating miR-34a

Long non-coding RNA (lncRNA) PMS2L2 has been reported to participate in endotoxin-induced inflammatory responses. As these types of responses can promote osteoarthritis (OA), it was of interest to ascertain if PMS2L2 may be involved in OA. To explore any potential participation of PMS2L2 in OA, synovial fluid was extracted from both OA patients and healthy controls (n = 62 each) and PMS2L2 expression of each sample determined by RT-qPCR. In addition, as miR-34a has a potential binding site on PMS2L2, hypothetical interactions between PMS2L2 and miR-34a in chondrocytes were analyzed by performing over-expression experiments. Furthermore, the role of PMS2L2 and miR-34a in the regulation of chondrocyte proliferation was analyzed using CCK-8 and BrdU assays. The results showed that PMS2L2 expression in OA patient synovial fluid was lower compared to that in control group fluid, and the extent of this reduction was related to disease stage. In in vitro studies, it was seen that endotoxin treatment of chondrocytes led to decreased PMS2L2 expression. It was found that PMS2L2 over-expression caused increased miR-34a expression in OA patient chondrocytes but not in cells from healthy controls. In contrast, miR-34a over-expression in either cell population did not affect PMS2L2 expression. Lastly, over-expression of both PMS2L2 and miR-34a led to inhibited chondrocyte proliferation. Of note, a combined over-expression of PMS2L2 and miR-34a resulted in stronger effects on proliferation compared to that from either single over-expression. Based on the findings that PMS2L2 is down-regulated during ongoing states of OA, and that changes in PMS2L2 expression can lead to increases in chondrocyte expression of miR-34a - resulting in inhibition of chondrocyte proliferation in OA. From these findings, one may conclude that finding means to regulate PMS2L2 could be a promising new target in the development of regimens for the treatment of OA.

Senkyunolide A inhibits the progression of osteoarthritis by inhibiting the NLRP3 signalling pathway

CONTEXT

Osteoarthritis (OA) is a degenerative disease. Senkyunolide A (SenA) is an important phthalide from Ligusticum chuanxiong Hort (Umbelliferae) with anti-spasmodic and neuroprotective effects.

OBJECTIVE

We explored the effect of SenA on IL-1β-stimulated chondrocytes and OA mice.

MATERIALS AND METHODS

Chondrocytes were stimulated by IL-1β (10 ng/mL) to establish an OA model in vitro. Cells were treated with SenA (20, 40, 80 and 160 μg/mL) for 48 h. The in vivo OA model was established by cutting off the medial meniscus tibial ligament (MMTL) at right knee incision of male C57BL/6 mice. One week after surgery, mice were injected with SenA (intraperitoneally one week) and divided into four groups (n = 6 per group): Sham, OA, OA + SenA 20 mg/kg and OA + SenA 40 mg/kg. The OA progression was examined by haematoxylin and eosin (H&E) staining.

RESULTS

SenA treatment increased cell viability (33%), proliferation (71%), inhibited apoptosis (21%), decreased levels of catabolic marker proteins (MMP13, 23%; ADAMTS4, 31%; ADAMTS5, 19%), increased levels of anabolic marker proteins (IGF-1, 57%; aggrecan, 75%; Col2a1, 48%), reduced levels of inflammation cytokines (TNF-α, 31%; IL-6, 19%; IL-18, 20%) and decreased levels of NLRP3 (21%), ASC (20%) and caspase-1 (29%) of chondrocytes. However, NLRP3 agonist nigericin increased levels of MMP13 (55%), ADAMTS4 (70%), ADAMTS5 (53%), decreased levels of IGF-1 (36%), aggrecan (26%), Col2a1 (25%), inhibited proliferation (61%) and promoted apoptosis (76%).

DISCUSSION AND CONCLUSIONS

SenA alleviates OA progression by inhibiting NLRP3 signalling pathways. These findings provide an experimental basis for the clinical application of drugs in the treatment of OA.

Evaluation of post-COVID health status using the EuroQol-5D-5L scale

SARS-CoV-2 has had a lasting effect on the overall health of recovered patients, called 'long COVID'. Currently, there is a lack of a validated standard questionnaire to assess post-COVID health status. A retrospective observational study involving the recovered COVID patients admitted to a secondary care hospital in India between June to December 2020 (n = 123), was conducted using the EuroQol-5D-5L scale at discharge, 4 weeks and 8 weeks post-discharge. A significant difference in anxiety/depression scores was found (χ2 = 65.6, p < 0.000) among the 3 categories of time (discharge, 4 weeks and 8 weeks). The anxiety/depression dimension scores showed a significant change (p < 0.0001) between discharge and 8 weeks, using paired t-test. Age had a significant relationship with the anxiety/depression dimension at 4 weeks (OR = 5.617, 95% CI = 1.0320-30.5746, p < 0.05). A significant difference was found using Kruskal-Wallis rank-sum test on mean index scores (χ2 = 60.0, p < 0.000) among the three categories of time (discharge, 4 weeks and 8 weeks). There was a statistically significant difference of time on EQ Index scores as determined by one-way repeated measures ANOVA (F(2,375) = 18.941, p = <0.00001). Our study found time to have a statistically significant impact on the mean index scores, level sum scores and dimension scores. Smoking was found to be significantly associated with usual activity scores at 4 weeks. The most remarkable changes occurred in the anxiety/depression dimension. Overall, there was a general trend of health improvement.

High spatial resolution analysis using automated indentation mapping differentiates biomechanical properties of normal vs. degenerated articular cartilage in mice

Characterizing the biomechanical properties of articular cartilage is crucial to understanding processes of tissue homeostasis vs. degeneration. In mouse models, however, limitations are imposed by their small joint size and thin cartilage surfaces. Here we present a three-dimensional (3D) automated surface mapping system and methodology that allows for mechanical characterization of mouse cartilage with high spatial resolution. We performed repeated indentation mappings, followed by cartilage thickness measurement via needle probing, at 31 predefined positions distributed over the medial and lateral femoral condyles of healthy mice. High-resolution 3D x-ray microscopy (XRM) imaging was used to validate tissue thickness measurements. The automated indentation mapping was reproducible, and needle probing yielded cartilage thicknesses comparable to XRM imaging. When comparing healthy vs. degenerated cartilage, topographical variations in biomechanics were identified, with altered thickness and stiffness (instantaneous modulus) across condyles and within anteroposterior sub-regions. This quantitative technique comprehensively characterized cartilage function in mice femoral condyle cartilage. Hence, it has the potential to improve our understanding of tissue structure-function interplay in mouse models of repair and disease.

Emerging pharmaceutical therapeutics and delivery technologies for osteoarthritis therapy

Osteoarthritis (OA) is one of the most common joint degenerative diseases in the world. At present, the management of OA depends on the lifestyle modification and joint replacement surgery, with the lifespan of prosthesis quite limited yet. Effective drug treatment of OA is essential. However, the current drugs, such as the non-steroidal anti-inflammatory drugs and acetaminophen, as well as glucosamine, chondroitin sulfate, hyaluronic acid, are accompanied by obvious side effects, with the therapeutic efficacy to be enhanced. Recently, novel reagents such as IL-1 antagonists and nerve growth factor inhibitors have entered clinical trials. Moreover, increasing evidence demonstrated that active ingredients of natural plants have great potential for treating OA. Meanwhile, the use of novel drug delivery strategies may overcome the shortcomings of conventional preparations and enhance the bioavailability of drugs, as well as decrease the side effects significantly. This review therefore summarizes the pathological mechanisms, management strategies, and research progress in the drug molecules including the newly identified active ingredient derived from medicinal plants for OA therapy, with the drug delivery technologies also summarized, with the expectation to provide the summary and outlook for developing the next generation of drugs and preparations for OA therapy.

CircFOXO3 protects against osteoarthritis by targeting its parental gene FOXO3 and activating PI3K/AKT-mediated autophagy

Osteoarthritis (OA) is a degenerative joint disorder causing pain and functional disability. Emerging evidence reveals that circular RNAs (circRNAs) play essential roles in OA progression and development. This study aimed to investigate the role of a novel circRNA factor, circFOXO3, in the progression of OA and elucidate its underlying molecular mechanism. The function of circFOXO3 in OA and interaction between circFOXO3 and its downstream mRNA target, forkhead box O3 (FOXO3), were evaluated by western blot (WB), immunofluorescence (IF), RNA immunoprecipitation, reverse transcription-quantitative PCR (RT-qPCR), and fluorescence in situ hybridization (FISH). Upregulation of circFOXO3 and autophagic flux were detected both in vivo and in vitro by WB, transmission electron microscopy (TEM), IF, and immunohistochemistry (IHC). A mouse model of OA was also used to confirm the role of circFOXO3 in OA pathogenesis in vivo. Decreased expression of circFOXO3 in OA cartilage tissues was directly associated with excessive apoptosis and imbalance between anabolic and catabolic factors of the extracellular matrix (ECM). Mechanistically, circFOXO3 functioned in cartilage by targeting its parental gene FOXO3 and activating autophagy. Intra-articular injection of lentivirus-circFOXO3 alleviated OA in the mouse model. In conclusion, our results reveal the key role played by circFOXO3 in OA progression; circFOXO3 overexpression may alleviate apoptosis of chondrocytes and promote anabolism of the ECM via activation of FOXO3 and autophagy, providing a potentially effective novel therapeutic strategy for OA.

Carbon dots derived from folic acid attenuates osteoarthritis by protecting chondrocytes through NF-κB/MAPK pathway and reprogramming macrophages

Background

Osteoarthritis (OA) is a common joint disorder worldwide which causes great health and economic burden. However, there remains an unmet goal to develop an effective therapeutic method to prevent or delay OA. Chondrocytes, as the major cells involved in OA progression, may serve as a promising therapeutic target.

Results

A kind of carbon dots (CDs) with excellent biocompatibility was fabricated from folic acid via hydrothermal method and could effectively attenuate osteoarthritis. It was demonstrated that CDs treatment could rescue IL1β-induced proinflammatory responses, oxidative stress, cartilage degeneration and extracellular matrix degradation. Moreover, CDs reprogrammed lipopolysaccharide (LPS)-induced macrophage inflammation and polarization. Conditioned medium (CM) from CDs-treated macrophages could attenuate IL1β-induced chondrocyte injury. Also, CM from CDs-treated chondrocytes had immunoregulatory functions on macrophages. Mechanistically, CDs inhibited the activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinases (MAPK) signaling pathways in IL1β-stimulated chondrocytes. In vivo, anterior cruciate ligament transection (ACLT) mice model was adopted and it was indicated that intra-articular injection of CDs effectively delays OA pathogenesis.

Conclusions

Taken together, these findings indicated CDs could mediate OA via promoting cartilage repair and immunomodulating macrophages within local microenvironment, which may provide evidences for utilizing CDs as a novel nanomaterial for OA treatment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12951-022-01681-6.

Prestressed Composite Polymer Gels as a Model of the Extracellular-Matrix of Cartilage

Articular cartilage is a composite hydrogel found in animal and human joints, which exhibits unique load-bearing properties that have been challenging to reproduce in synthetic materials and model in molecular dynamics (MD) simulations. We computationally investigate a composite hydrogel that mimics key functional properties of articular cartilage as a potential biomimetic model to investigate its unique load-bearing properties. Specifically, we find that the emergence of prestress in composite gels derives primarily from the stiffness of the polymer matrix and the asymmetry in the enthalpic interactions of the embedded particles and polymer matrix. Our MD simulations of the development of prestress agree qualitatively with osmotic pressure measurements observed in our model composite hydrogel material.

Assessment of functional roles and therapeutic potential of integrin receptors in osteoarthritis: A systematic review and meta-analysis of preclinical studies

BACKGROUND

Integrins are heterodimeric transmembrane receptors that mediate a variety of biological function and plays a critical role in osteoarthritis (OA) pathogenesis, which may provide new targets for the development of OA therapies. However, the roles of integrins in different stages of OA remain elusive.

OBJECTIVES

This study aimed to synthesize all published preclinical evidence on the roles of integrin receptors in different stages of OA to identify the potential target for drug development in alleviating OA pathogenesis.

METHODS

Major electronic databases were used to identify related original articles. The methodological quality of all included studies was appraised using the SYRCLE risk of bias tool. We used the generic inverse variance with random effects model to calculate standardized mean differences (SMDs) and 95% confidence interval (CI).

RESULTS

Seventeen studies were included in this systematic review. Integrin α5β1 activation increases the histopathological score both in early [SMD, 6.39; 95%CI (2.90, 9.87); p = 0.0003] and late [SMD, 3.41; 95%CI (2.44, 4.38); p < 0.00001] stage of OA. Integrin α5β1 also increased the core catabolic factors like MMP-3, IL-1β, and TNF-α. Interestingly, the inactivation of α5β1 integrin did not change the histopathological score (p = 0.84). Similarly, β1 integrin notably increased histopathological score at both stages of OA [early; SMD, 7.13; 95%CI (2.01, 12.24); p = 0.006]; [late; SMD, 10.25; 95%CI (5.11, 15.39); p < 0.0001], and increased the MMP-13 levels. However, integrin β1 was upregulated at the early stage and downregulated at the late stage of OA. Furthermore, α2β1 integrin significantly increased histopathological score [SMD, 3.14; 95%CI (2.18, 4.10); p < 0.00001] and MMP-13 [SMD, 2.24; 95%CI (0.07, 4.41); p = 0.04]. Deactivating integrin α1β1 increased histopathological score in late [SMD, 1.53; 95%CI (0.80, 2.26); p < 0.0001], but not in early [SMD, 0.90; 95%CI (-1.65, 3.45); p = 0.49] stage of OA.

CONCLUSION

This study provides evidence that α5β1, α2β1, and α1β1 integrin might be the potential target for future drug development in alleviating OA pathogenesis. Further work is required to establish our findings through activating/deactivating these receptors in different stages of OA.

Cryotherapy in Anterior Cruciate Ligamentoplasty Pain: A Scoping Review

Cryotherapy is used in individuals in the postoperative period (PO) of anterior cruciate ligament (ACL) repair, owing to its effects such as increased pain threshold, decreased cellular activity, and vasoconstriction. The aim of this study was to analyze the effect of cryotherapy on pain intensity in the immediate PO of ACL reconstruction. A scoping review was performed in the databases: Cochrane, Embase, Lilacs, LIVIVO, PEDro, PubMed, Scopus, and Web of Science; and gray literature: Google Scholar, CAPES Thesis Database, and Open Grey. PRISMA recommendation was followed. Two blinded reviewers performed the selection of studies: Phase 1-reading of titles and abstracts and Phase 2-Reading of the full texts and disagreements resolved in consensus. The references of 701 studies were identified, 603 from the main databases and 98 from the gray literature. After removal of duplicates, 387 studies were left for Phase 1-reading of titles and abstracts according to eligibility criteria and for Phase 2-28 studies for reading of full texts. Two studies were excluded: one randomized clinical trial and another sandwich study. Finally, 15 studies were included in this review. Cryotherapy is effective in reducing pain intensity because there were reductions in the scores of subjective pain scales in the immediate PO of ACL reconstruction. Cryocompression was shown to be superior to conventional cryotherapy.

Therapeutic applications of adipose-derived stromal vascular fractions in osteoarthritis

Osteoarthritis (OA) is considered to be a highly heterogeneous disease with progressive cartilage loss, subchondral bone remodeling, and low-grade inflammation. It is one of the world's leading causes of disability. Most conventional clinical treatments for OA are palliative drugs, which cannot fundamentally cure this disease. The stromal vascular fraction (SVF) from adipose tissues is a heterogeneous cell population. According to previous studies, it contains a large number of mesenchymal stem cells, which have been used to treat OA with good therapeutic results. This safe, simple, and effective therapy is expected to be applied and promoted in the future. In this paper, the detailed pathogenesis, diagnosis, and current clinical treatments for OA are introduced. Then, clinical studies and the therapeutic mechanism of SVF for the treatment of OA are summarized.

The role of extracellular vesicles in osteoarthritis treatment via microenvironment regulation

Osteoarthritis (OA) is a degenerative joint disease that is common among the middle-aged and older populations, causes patients to experience recurrent pain in their joints and negatively affects their quality of life. Currently, therapeutic options for patients with OA consist of medications to alleviate pain and treat the symptoms; however, due to typically poor outcomes, patients with advanced OA are unlikely to avoid joint replacement. In recent years, several studies have linked disrupted homeostasis of the joint cavity microenvironment to the development of OA. Recently, extracellular vesicles (EVs) have received increasing attention in the field of OA. EVs are natural nano-microcarrier materials with unique biological activity that are produced by cells through paracrine action. They are composed of lipid bilayers that contain physiologically active molecules, such as nucleic acids and proteins. Moreover, EVs may participate in local and distal intercellular and intracellular communication. EVs have also recently been shown to influence OA development by regulating biochemical factors in the OA microenvironmental. In this article, we first describe the microenvironment of OA. Then, we provide an overview of EVs, summarize the main types used for the treatment of OA, and describe their mechanisms. Next, we review clinical studies using EVs for OA treatment. Finally, the specific mechanism underlying the application of miRNA-enriched EVs in OA therapy is described.

Genetically predicted tea intake increases the risk of osteoarthritis: A Mendelian randomization study

Background: This study aimed to clarify the relationship between tea consumption and osteoarthritis (OA).

Methods: Common single-nucleotide polymorphisms (SNPs) from the Open Genome-wide Association Studies database were obtained. Summary statistics on OA were retrieved from the second dataset that enrolled 50,508 participants (10,083 OA cases) of European ancestry. The causal association between tea intake and OA was tested using two-sample Mendelian randomization (MR) analysis.

Results: Tea consumption has adverse effects on OA. (inverse-variance weighted method: OR = 1.19, 95% CI = 1.08–1.30; weighted median method: OR = 1.22, 95% CI = 1.07–1.40). The MR–Egger regression intercept (MR intercept = −0.002; p = 0.73) showed no evidence of directional pleiotropy. Moreover, no evidence of underlying heterogeneity in MR analysis was found according to Cochran’s Q test and funnel and forest analyses.

Conclusion: A genetically predicted high daily tea intake can increase the risk of OA.

Multiple platelet-rich plasma injections are superior to single PRP injections or saline in osteoarthritis of the knee: the 2-year results of a randomized, double-blind, placebo-controlled clinical trial

INTRODUCTION

The primary purposes of this study were to prove the efficacy of PRP injection therapy on knee pain and functions by comparing patients with mild to moderate OA with a placebo control group, and also to understand the effectiveness of multiple doses compared to a single dose. It was hypothesized that PRP would lead to more favorable results than the placebo at 1, 3, 6, 12 and 24 months after treatment.

MATERIALS AND METHODS

237 patients diagnosed with OA were randomly separated into 4 groups, who were administered the following: single dose of PRP (n: 62), single dose of sodium saline (NS) (n: 59), three doses of PRP (n: 63), and three doses of NS (n: 53). Clinical evaluations were made pre-treatment and at 1, 3, 6, 12 and 24 months post-treatment, using the Knee Injury and Osteoarthritis Result Score (KOOS), Kujala Patellofemoral Score, knee joint range of motion (ROM), measurements of knee circumference (KC), and mechanical axis angle (MAA) and a Visual Analog Scale (VAS) for the evaluation of pain.

RESULTS

The better score values in the groups were recorded at 3 and 6 months. Patients treated with PRP maintained better scores at 3, 6 and 12 months compared to the NS groups (p < 0.05). Multiple doses of PRP were seen to be more effective than single-dose PRP at 6 and 12 months (p < 0.05). At the end of 24 months, there was no significant score difference across all the groups. The most positive change in scores was found in stage 2 OA, and the most positive change in ROM was in stage 3 OA patients. In the PRP groups, KC decreased more at 1 and 6 months (p < 0.05). Compared to other age groups, patients aged 51-65 years scored better at 6 months (p < 0.05). A negative correlation was determined with MAA scores (r = - 0.508, p < 0.001).

CONCLUSION

In comparison to the placebo (NS), leukocyte-rich PRP treatment was determined to be effective in the treatment of OA. Multiple doses of PRP increase the treatment efficacy and duration. Of all the patients treated with PRP, the best results were obtained by patients aged 51-65 years, with lower MAA, and by K/L stage 2 OA patients.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 1.

REGISTRATION

NCT04454164 (ClinicalTrials.gov identifier).

The Role of Autophagy in Osteoarthritic Cartilage

Osteoarthritis (OA) is one of the most common diseases leading to physical disability, with age being the main risk factor, and degeneration of articular cartilage is the main focus for the pathogenesis of OA. Autophagy is a crucial intracellular homeostasis system recycling flawed macromolecules and cellular organelles to sustain the metabolism of cells. Growing evidences have revealed that autophagy is chondroprotective by regulating apoptosis and repairing the function of damaged chondrocytes. Then, OA is related to autophagy depending on different stages and models. In this review, we discuss the character of autophagy in OA and the process of the autophagy pathway, which can be modulated by some drugs, key molecules and non-coding RNAs (microRNAs, long non-coding RNAs and circular RNAs). More in-depth investigations of autophagy are needed to find therapeutic targets or diagnostic biomarkers through in vitro and in vivo situations, making autophagy a more effective way for OA treatment in the future. The aim of this review is to introduce the concept of autophagy and make readers realize its impact on OA. The database we searched in is PubMed and we used the keywords listed below to find appropriate article resources.

Identification of the OA-related metabolism-related genes, corresponding transcription factors, relevant pathways, and specific bioactive small molecules

Metabolic alteration of articular cartilage is associated with the pathogenesis of Osteoarthritis (OA). This study aims to identify the metabolism-related genes, corresponding transcription factors (TFs), and relevant pathways. Overall, RNA sequencing profiles of articular cartilage were collected from the GEO database. Metabolism-related genes and OA-related hallmarks were collected from the MSigDB v7.1. Differential expression analysis, Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, and Gene Set Variation Analysis (GSVA) were conducted to identify pathways or hallmarks that were related to the pathogenesis of OA. The Pearson correlation analysis was used to establish the regulatory network among transcription factors, metabolism-related genes, and hallmarks. To further confirm the regulation of the identified transcription factors, Chromatin Immunoprecipitation-sequencing (ChIP-seq) was conducted, and single-cell sequencing was used to locate the cell clusters. Connectivity Map (CM) analysis were also conducted to identify the potential specific bioactive small molecules targeting the metabolic alteration of osteoarthritis. scTPA database was used to detect activated signaling pathways. Collectively, a total of 74 and 38 differentially expressed metabolism-related genes and TFs were retrieved. Skeletal system development, extracellular matrix, and cell adhesion molecule binding were important pathways in GO analysis. Human papillomavirus infection, PI3K-Akt signaling pathway, and Human T-cell leukemia virus 1 infection were the top 3 pathways in KEGG. 7 and 12 hallmarks were down- and up-regulated in GSVA, respectively. Ten bioactive small molecules may be potential treatments of OA by regulating the metabolism of articular cartilage. ChIP-seq analysis showed high relativity between transcription factors and their target genes. Furthermore, single-cell sequencing confirms the high expression of identified transcription factors in chondrocytes. To conclude, we established a comprehensive network integrated with transcription factors, metabolism-related genes, and hallmarks.

The role of oxidative stress in the development of knee osteoarthritis: A comprehensive research review

Knee osteoarthritis (KOA) is one of the most common degenerative diseases, and its core feature is the degeneration and damage of articular cartilage. The cartilage degeneration of KOA is due to the destruction of dynamic balance caused by the activation of chondrocytes by various factors, with oxidative stress playing an important role in the pathogenesis of KOA. The overproduction of reactive oxygen species (ROS) is a result of oxidative stress, which is caused by a redox process that goes awry in the inherent antioxidant defence system of the human body. Superoxide dismutase (SOD) inside and outside chondrocytes plays a key role in regulating ROS in cartilage. Additionally, synovitis is a key factor in the development of KOA. In an inflammatory environment, hypoxia in synovial cells leads to mitochondrial damage, which leads to an increase in ROS levels, which further aggravates synovitis. In addition, oxidative stress significantly accelerates the telomere shortening and ageing of chondrocytes, while ageing promotes the development of KOA, damages the regulation of redox of mitochondria in cartilage, and stimulates ROS production to further aggravate KOA. At present, there are many drugs to regulate the level of ROS, but these drugs still need to be developed and verified in animal models of KOA. We discuss mainly how oxidative stress plays a part in the development of KOA. Although the current research has achieved some results, more research is needed.

Role of adiponectin in osteoarthritis

Osteoarthritis (OA) is a widespread and most common joint disease which leads to social cost increasing accompany with aging population. Surgery is often the final treatment option. The major progression of OA includes cartilage degradation caused by chondrocytes metabolism imbalance. So, the molecular mechanisms of action in chondrocytes may provide insights into treatment methods for OA. Adiponectin is an adipokine with many biological functions in the cell metabolism. Numerous studies have illustrated that adiponectin has diverse biological effects, such as inhibition of cell apoptosis. It regulates various functions in different organs, including muscle, adipose tissue, brain, and bone, and regulates skeletal homeostasis. However, the relationship between adiponectin and cell death in the progression of OA needs further investigation. We elaborate the structure and function and the effect of adiponectin and state the correlation and intersection between adiponectin, autophagy, inflammation, and OA. From the perspective of oxidative stress, apoptosis, pyroptosis, and autophagy, we discuss the possible association between adiponectin, chondrocyte metabolism, and inflammatory factor efforts in OA. What’s more, we summarize the possible treatment methods, including the use of adiponectin as a drug target, and highlight the potential future mechanistic research. In this review, we summarize the molecular pathways and mechanisms of action of adiponectin in chondrocyte inflammation and death and the pathogenesis of OA. We also review the research on adiponectin as a target for treating OA. These studies provide a novel perspective to explore more effective treatment options considering the complex interrelationship between inflammation and metabolism in OA.

CircPRKCH modulates extracellular matrix formation and metabolism by regulating the miR-145/HGF axis in osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a chronic degenerative joint disease. Extracellular matrix (ECM) degradation is essential for OA progression. Previous studies have shown that circular RNAs (circRNAs) are involved in the pathological process of OA. CircPRKCH has been shown to be upregulated in OA chondrocytes. The present study was aimed to explore the roles of circPRKCH in vivo and in vitro models of OA and its underlying molecular mechanisms.

METHODS

IL-1β-induced chondrocytes and mice injected with monosodium iodoacetate were used as OA models in vitro and in vivo, respectively. RT-qPCR was performed to measure the expression of circPRKCH, miR-145, and HGF in cartilage tissues and chondrocytes. The interaction between miR-145 and circPRKCH or HGF was verified by a dual-luciferase reporter assay. Chondrocyte apoptosis, viability, and ECM-related proteins were examined by flow cytometry, MTT assay, and Western blotting, respectively. Histopathological changes were detected by HE and Safranin O-fast green staining.

RESULTS

The expression of circPRKCH and HGF was increased in OA cartilage tissues and IL-1β-treated chondrocytes, while miR-145 expression was decreased. IL-1β induced chondrocyte apoptosis and ECM degradation in chondrocytes. Moreover, circPRKCH promoted HGF expression and activated HGF/c-MET by directly binding to miR-145. miR-145 knockdown or HGF overexpression significantly reversed circPRKCH knockdown-mediated inhibition of apoptosis and ECM degradation in IL-1β-induced chondrocytes. Besides, miR-145 overexpression alleviated IL-1β-induced chondrocyte apoptosis and ECM degradation by inhibiting HGF/c-MET. Finally, circPRKCH knockdown reduced ECM degradation by regulating the miR-145/HGF axis in an experimental OA model in mice.

CONCLUSION

Our study demonstrated that circPRKCH promoted chondrocyte apoptosis and ECM degradation via the miR-145/HGF axis in OA, which may provide a novel target for OA treatment.

Synovial membrane-derived mesenchymal progenitor cells from osteoarthritic joints in dogs possess lower chondrogenic-, and higher osteogenic capacity compared to normal joints

Background

Synovial membrane-derived mesenchymal progenitor cells (SM-MPCs) are a promising candidate for the cell-based treatment of osteoarthritis (OA) considering their in vitro and in vivo capacity for cartilage repair. However, the OA environment may adversely impact their regenerative capacity. There are no studies for canine (c)SM-MPCs that compare normal to OA SM-MPCs, even though dogs are considered a relevant animal model for OA. Therefore, this study compared cSM-MPCs from normal and OA synovial membrane tissue to elucidate the effect of the OA environment on MPC numbers, indicated by CD marker profile and colony-forming unit (CFU) capacity, and the impact of the OA niche on tri-lineage differentiation.

Methods

Normal and OA synovial membrane were collected from the knee joints of healthy dogs and dogs with rupture of the cruciate ligaments. The synovium was assessed by histopathological OARSI scoring and by RT-qPCR for inflammation/synovitis-related markers. The presence of cSM-MPCs in the native tissue was further characterized with flow cytometry, RT-qPCR, and immunohistochemistry, using the MPC markers; CD90, CD73, CD44, CD271, and CD34. Furthermore, cells isolated upon enzymatic digestion were characterized by CFU capacity, and a population doublings assay. cSM-MPCs were selected based on plastic adherence, expanded to passage 2, and evaluated for the expression of MPC-related surface markers and tri-lineage differentiation capacity.

Results

Synovial tissue collected from the OA joints had a significantly higher OARSI score compared to normal joints, and significantly upregulated inflammation/synovitis markers S100A8/9, IL6, IL8, and CCL2. Both normal and OA synovial membrane contained cells displaying MPC properties, including a fibroblast-like morphology, CFU capacity, and maintained MPC marker expression over time during expansion. However, OA cSM-MPCs were unable to differentiate towards the chondrogenic lineage and had low adipogenic capacity in contrast to normal cSM-MPCs, whereas they possessed a higher osteogenic capacity. Furthermore, the OA synovial membrane contained significantly lower percentages of CD90+, CD44+, CD34+, and CD271+ cells.

Conclusions

The OA environment had adverse effects on the regenerative potential of cSM-MPCs, corroborated by decreased CFU, population doubling, and chondrogenic capacity compared to normal cSM-MPCs. OA cSM-MPCs may be a less optimal candidate for the cell-based treatment of OA than normal cSM-MPCs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13287-022-03144-z.

Silencing of Angiopoietin-Like Protein 4 (Angptl4) Decreases Inflammation, Extracellular Matrix Degradation, and Apoptosis in Osteoarthritis via the Sirtuin 1/NF-κB Pathway

Osteoarthritis (OA) is a frequently observed condition in aged people. OA cartilage is characterized by chondrocyte apoptosis, chondrocyte inflammation, and hyperactive catabolism of extracellular matrix. However, the specific molecular mechanisms remain unclear. Recent data has shown that Angptl4, a multifunctional cytokine, is involved in the regulation of inflammatory and apoptosis responses in different tissues. This study is aimed at defining the role of Angptl4 in the development of OA. We employed X-ray analysis, safranin O-fast green (S-O) staining, and hematoxylin staining to evaluate histomorphological characteristics in the knee joint of mice. Real-time quantitative polymerase chain reaction, Western blot assays, immunofluorescence staining, and enzyme-linked immunosorbent assays (ELISA) were performed to analyze the changes in gene and protein expression. Mechanically, our data demonstrated that Angptl4 knockdown improved the degradation of extracellular matrix and reduced TNF-α-mediated chondrocyte inflammation and apoptosis by suppressing sirtuin 1/NF-κB signaling pathway. In addition, animal studies showed that the suppression of Angptl4 expression might alleviate OA development. In conclusion, our findings revealed the underlying mechanisms of Angptl4 regulation in chondrocytes and its potential value in the treatment of OA.

Changes in Small Noncoding RNA Expression during Chondrocyte Senescence

OBJECTIVE

Osteoarthritis (OA) is characterized by the chronic and progressive deterioration of articular cartilage. Chondrocyte senescence could lead to a shift in the balance between extracellular matrix (ECM) component synthesis and degradation. Small noncoding RNAs (sncRNAs), including microRNAs (miRNAs), P-element-induced wimpy testis-(PIWI-) interacting RNAs (piRNAs), small nucleolar RNAs (snoRNAs), small nuclear RNAs (snRNAs), and repeat-associated siRNAs (rasiRNAs), are a class of important epigenetic molecules. We aimed to gain insights into the changes and roles of sncRNA in chondrocyte senescence.

DESIGN

Healthy mouse postnatal chondrocytes were isolated, and a replicative aging model was constructed. We used small RNA sequencing (small RNA-seq) to generate extensive small RNA data. We identified differentially expressed sncRNAs and performed tissue-specific analysis using real-time quantitative polymerase chain reaction (qRT-PCR). β-galactosidase staining was used to detect chondrocyte senescence. The results showed that the expression profiles of sncRNA in passage 5 chondrocytes were significantly different from those in passage 0 chondrocytes. The expression of sncRNA was tissue specific. We found that 40 miRNAs were upregulated and 70 miRNAs were downregulated during chondrocyte senescence, and that miR-132-5p expression inhibition prevented chondrocyte senescence. We found that 8 piRNAs were upregulated and 17 piRNAs were downregulated during chondrocyte senescence, and that piRNA piR_025576 overexpression delayed chondrocyte senescence. We found that 24 snoRNAs were upregulated and 28 snoRNAs were downregulated during chondrocyte senescence, and that snoRNA ENSMUSG00000087935 overexpression delayed chondrocyte senescence. We found that 5 snRNAs were upregulated and 6 snRNAs were downregulated during chondrocyte senescence, and that snRNA ENSMUSG00000064682 overexpression delayed chondrocyte senescence. We found that 1 rasiRNA was upregulated and 4 rasiRNAs were downregulated during chondrocyte senescence.

CONCLUSIONS

These findings might provide novel insights into OA pathogenesis and contribute to the development of candidates for targeted therapeutics in OA.

Exercise-induced modulation of myokine irisin in bone and cartilage tissue—Positive effects on osteoarthritis: A narrative review

Osteoarthritis is a chronic degenerative musculoskeletal disease characterized by pathological changes in joint structures along with the incidence of which increases with age. Exercise is recommended for all clinical treatment guidelines of osteoarthritis, but the exact molecular mechanisms are still unknown. Irisin is a newly discovered myokine released mainly by skeletal muscle in recent years—a biologically active protein capable of being released into the bloodstream as an endocrine factor, the synthesis and secretion of which is specifically induced by exercise-induced muscle contraction. Although the discovery of irisin is relatively recent, its role in affecting bone density and cartilage homeostasis has been reported. Here, we review the production and structural characteristics of irisin and discuss the effects of the different types of exercise involved in the current study on irisin and the role of irisin in anti-aging. In addition, the role of irisin in the regulation of bone mineral density, bone metabolism, and its role in chondrocyte homeostasis and metabolism is reviewed. A series of studies on irisin have provided new insights into the mechanisms of exercise training in improving bone density, resisting cartilage degeneration, and maintaining the overall environmental homeostasis of the joint. These studies further contribute to the understanding of the role of exercise in the fight against osteoarthritis and will provide an important reference and aid in the development of the field of osteoarthritis prevention and treatment.

Corosolic Acid Protects Rat Chondrocytes Against IL-1β-Induced ECM Degradation by Activating Autophagy via PI3K/AKT/mTOR Pathway and Ameliorates Rat Osteoarthritis

Purpose

Osteoarthritis (OA) is an age-related degenerative disease associated with enhanced degradation of extracellular matrix (ECM) and decreased autophagy. Our study is aimed to explore how corosolic acid (CRA) affect cartilage ECM metabolism and the potential mechanism.

Methods

Rat chondrocytes were pretreated with different concentrations of CRA (0, 2.5, 5, and 10 μM), and were stimulated with IL-1β (10ng/mL) for 24 h, subsequently. RT-qPCR, Western blot, and immunofluorescence were used to detect the expression of genes related to ECM metabolism and explore the potential molecular mechanism. The effect of CRA on articular cartilage was observed in the surgically induced OA rat model with the method of Safranin O/Fast green and immunohistochemical staining.

Results

Results showed that CRA reversed the IL-1β-induced degradation of aggrecan and type II collagen and the high expression of MMP13 and ADAMTS5. Mechanistically, CRA enhanced autophagy through inhibiting the classical PI3K/AKT/mTOR signaling pathway. Furthermore, inhibition of autophagy partly abolished the protective effects of CRA on ECM synthesis in IL-1β-treated chondrocytes. Correspondingly, the protective effect of CRA was also confirmed in a rat OA model.

Conclusion

Herein, we demonstrate that CRA can enhance autophagy by inhibiting PI3K/AKT/mTOR signaling pathway, prevent IL-1β-induced cartilage ECM degradation, and may be a potentially applicable candidate for the treatment of OA.

Nitidine Chloride Alleviates Inflammation and Cellular Senescence in Murine Osteoarthritis Through Scavenging ROS

Osteoarthritis (OA) is one of the most common chronic musculoskeletal disorder worldwide, representing a major source of disability, pain and socioeconomic burden. Yet the effective pharmaceutical treatments applied in the clinical works are merely symptomatic management with uncertainty around their long-term safety and efficacy, namely no drugs currently are capable of modulating the biological progression of OA. Here, we identified the potent anti-inflammatory as well as anti-oxidative properties of Nitidine Chloride (NitC), a bioactive phytochemical alkaloid extracted from natural herbs, in IL-1β-treated rat articular chondrocytes (RACs), LPS-stimulated RAW 264.7 and rat osteoarthritic models in vivo. We demonstrated NitC remarkably inhibited the production of inflammatory mediators including COX2 and iNOS, suppressed the activation of MAPK and NF-κB cell signaling pathway and reduced the expression of extracellular matrix (ECM) degrading enzymes including MMP3, MMP9 and MMP13 in IL-1β-treated RACs. Several emerging bioinformatics tools were performed to predict the underlying mechanism, the result of which indicated the potential reactive oxygen species (ROS) clearance potential of NitC. Further, NitC exhibited its anti-oxidative potential through ameliorating cellular senescence in IL-1β-treated RACs and decreasing NLRP3 inflammasomes activation in LPS-stimulated RAW 264.7 via scavenging ROS. Additionally, X-ray, micro-CT and other experiments in vivo demonstrated that intra-articular injection of NitC significantly alleviated the cartilage erosion, ECM degradation and subchondral alterations in OA progression. In conclusion, the present study reported the potent anti-inflammatory and anti-oxidative potential of NitC in OA biological process, providing a promising therapeutic agent for OA management.

Longevity-Promoting Pathways and Transcription Factors Respond to and Control Extracellular Matrix Dynamics During Aging and Disease

Aging is one of the largest risk factors for cancer, type 2 diabetes, osteoarthritis, cardiovascular diseases, and other age-related pathologies. Here, we give a detailed description of the interplay of chronic age-related pathologies with the remodeling of the extracellular matrix during disease development and progression. Longevity-promoting signaling pathways slow or prevent age-related diseases. In particular, we focus on the mTOR signaling pathway, sirtuins, and canonical longevity-promoting transcription factors, such as FOXO, NF-κB, and Nrf2. We extend our analysis using chromatin immunoprecipitation (ChIP) sequencing and transcriptomic data and report that many established and emerging longevity-promoting transcription factors, such as CREB1, FOXO1,3, GATA1,2,3,4, HIF1A, JUN, KLF4, MYC, NFE2L2/Nrf2, RELA/NF-κB, REST, STAT3,5A, and TP53/p53, directly regulate many extracellular matrix genes and remodelers. We propose that modulation of these pathways increases lifespan and protects from age-related diseases in part due to their effects on extracellular matrix remodeling. Therefore, to successfully treat age-related diseases, it is necessary to better understand the connection between extracellular matrix components and longevity pathways.

Asiaticoside ameliorates osteoarthritis progression through activation of Nrf2/HO-1 and inhibition of the NF-κB pathway

Osteoarthritis has become the fourth cause of disability in the world and its occurrence and development are caused by apoptosis and extracellular matrix (ECM) degradation of chondrocytes. Asiaticoside (ASI) is a triterpene saponin compound obtained from Centella Asiatica and has anti-inflammatory and anti-apoptotic effects in various diseases. However, its effects on OA are not clear. In this study, we reported that ASI has a protective effect on the occurrence and progression of OA in vivo and in vitro, and demonstrated its potential molecular mechanism. In vitro, ASI treatment inhibited the release of pro-apoptotic factors induced by TBHP and promoted the release of the anti-apoptotic proteins. In addition, ASI promotes the expression of Aggrecan and Collagen II, while inhibiting the expression of thrombospondin motifs 5 (ADAMTS5) and matrix metalloproteinase-13 (MMP-13), which causes extracellular matrix (ECM) degradation. Mechanistically, ASI exerts its anti-apoptotic effect by activating the Nrf2/HO-1 pathway and preventing p65 from binding to DNA. Similarly, in vivo, ASI has been shown to have a protective effect in a mouse OA model. The conclusion is that our research shows that ASI can be used as a potential drug for the treatment of OA.