Ipriflavone attenuates the degeneration of cartilage by blocking the Indian hedgehog pathway

CRISPR/CasRx-mediated RNA knockdown targeting β-catenin and Ihh signaling alleviates osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disease. Currently, OA is incurable. Abnormal activation of canonical Wnt/β-catenin or Indian hedgehog (Ihh) signaling could lead to OA development and progression. This study aimed to determine if targeting β-catenin and Ihh signaling could yield an effective therapeutic intervention for OA disease. CRISPR/CasRx is a new RNA interference tool that can precisely and efficiently cleave single-strand RNAs. In this study, we screened CRISPR-derived RNA (crRNA) targeting Ctnnb1 and Smo in vitro and selected two optimal crRNAs for each gene. CasRx-mediated Ctnnb1 and Smo knockdown showed high efficiency and specificity with no obvious off-target effects in vitro. We then performed intra-articular injection of selected crRNAs driven by the adeno-associated virus into an OA mouse model. Micro-CT, histological, and histomorphometric analyses were conducted to evaluate the efficacy of CasRx approach on OA treatment. We found that the knockdown of Ctnnb1 and Smo decelerated pathological damage in the keen joint of the experimental OA mouse model. Our findings suggest that CasRx-mediated Ctnnb1 and Smo knockdown could be a potential strategy for OA treatment.

Targeting Chondrocyte Hypertrophy as Strategies for the Treatment of Osteoarthritis

Osteoarthritis (OA) is a common joint disease characterized by pain and functional impairment, which severely impacts the quality of life of middle-aged and elderly individuals. During normal bone development, chondrocyte hypertrophy is a natural physiological process. However, in the progression of OA, chondrocyte hypertrophy becomes one of its key pathological features. Although there is no definitive evidence to date confirming that chondrocyte hypertrophy is the direct cause of OA, substantial experimental data indicate that it plays an important role in the disease's pathogenesis. In this review, we first explore the mechanisms underlying chondrocyte hypertrophy in OA and offer new insights. We then propose strategies for inhibiting chondrocyte hypertrophy from the perspectives of targeting signaling pathways and tissue engineering, ultimately envisioning the future prospects of OA treatment.

IHH-GLI-1-HIF-2α signalling influences hypertrophic chondrocytes to exacerbate osteoarthritis progression

Background

Chondrocyte hypertrophy is a potential target for osteoarthritis (OA) treatment, with Indian hedgehog (IHH), glioma-associated oncogene homolog (GLI), and hypoxia-inducible factor-2α (HIF-2α) being closely associated with chondrocyte hypertrophy during OA progression. Whereas IHH can modulate chondrocyte hypertrophy, interference with IHH signalling has not achieved the anticipated therapeutic effects and poses safety concerns, necessitating further clarification of the specific mechanisms by which IHH affects articular cartilage degeneration. Inhibition of the HIF-2α overexpression in cartilage slows the progression of early OA, but the mechanisms underlying HIF-2α accumulation in OA cartilage remain unclear. The aim of this study was to determine the function of Ihh, as well as its downstream factors, in chondrocytes, based on an early osteoarthritis (OA) mouse model and in vitro chondrocyte model.

Methods

Investigated the expression levels and locations of IHH-GLI-1 pathway in normal and early degenerated human cartilage, comparing them with HIF-2α and its downstream factors. RT-qPCR, Western blotting, Crystal violet staining, and EdU assays were used to evaluate the pecific regulatory mechanisms of the IHH-GLI-1-HIF-2α signalling axis in normal chondrocytes and in chondrocytes under inflammatory conditions. Validated the impact of IHH on early cartilage degeneration and the relationship between the IHH-GLI-1 pathway and the expression levels and expression locations of HIF-2α and its downstream factors in Col2a1-CreERT2;Ihhfl/fl mice.

Results

In early-stage degenerative joint cartilage, the GLI-1 pathway in hypertrophic chondrocytes exhibited similar changes in location and levels to HIF-2α and its downstream factor vascular endothelial growth factor (VEGF). In vitro, IHH-GLI-1-HIF-2α signalling activation in chondrocytes under physiological hypoxic conditions inhibited chondrocyte proliferation. In chondrocytes stimulated by inflammatory environments, IHH inhibited the degradation of HIF-2α via the GLI-1 pathway, thereby promoting HIF-2α protein expression. Elevated HIF-2α expression further enhanced intracellular IHH-GLI-1 levels, generating a positive feedback loop to collectively regulate the expression of downstream hypertrophic factors and matrix-degradation factors. In vivo, conditional Ihh knockout in mouse chondrocytes downregulated Hif-2α protein expression in early degenerative cartilage tissue and affected the expression of downstream Vegf and hypertrophic factors.

Conclusions

During OA progression, the IHH-GLI-1-HIF-2α axis mainly operates within hypertrophic chondrocytes, exacerbating cartilage degeneration by regulating hypertrophic chondrocyte functions, cartilage matrix degradation, and microvascular invasion.

The translational potential of this article

This study identifies the IHH-GLI-1-HIF-2α signalling axis and reveals its potential as a therapeutic target for OA.

Development of Therapeutic Agent for Osteoarthritis via Inhibition of KIAA1199 Activity: Effect of Ipriflavone In Vivo

This study aimed to clarify the effects of ipriflavone, which effectively reduces KIAA1199 activity, on osteoarthritis (OA) development and progression in an in vivo OA mouse model. The OA model mice were divided into the ipriflavone (200 mg/kg/day) group and the control group. OA onset and progression were evaluated with the Mankin score, and KIAA1199 expression and hyaluronan (HA) accumulation were analyzed by immunostaining. The molecular weight of HA in the cartilage tissue and serum HA concentration were analyzed by chromatography and competitive HA enzyme-linked immunoassay. The effects of ipriflavone on the bovine cartilage explant culture under the influence of IL-1β were also investigated. In the ipriflavone group, Safranin-O stainability was well-preserved, resulting in significant reduction of the Mankin score (p = 0.027). KIAA1199 staining positivity decreased and HA stainability was preserved in the ipriflavone group. The serum HA concentration decreased, and the molecular weight of HA in the cartilage tissue increased in the ipriflavone group. The results of the cartilage explant culture indicated that ipriflavone could reduce GAG losses and increase the molecular weight of HA. Thus, ipriflavone may have an inhibitory effect on OA development/progression. Ipriflavone could be a therapeutic drug for OA by targeting KIAA1199 activity.

Upregulated ribosome pathway plays a key role in HDAC4, improving the survival rate and biofunction of chondrocytes

Aims

To explore the novel molecular mechanisms of histone deacetylase 4 (HDAC4) in chondrocytes via RNA sequencing (RNA-seq) analysis.

Methods

Empty adenovirus (EP) and a HDAC4 overexpression adenovirus were transfected into cultured human chondrocytes. The cell survival rate was examined by real-time cell analysis (RTCA) and EdU and flow cytometry assays. Cell biofunction was detected by Western blotting. The expression profiles of messenger RNAs (mRNAs) in the EP and HDAC4 transfection groups were assessed using whole-transcriptome sequencing (RNA-seq). Volcano plot, Gene Ontology, and pathway analyses were performed to identify differentially expressed genes (DEGs). For verification of the results, the A289E/S246/467/632 A sites of HDAC4 were mutated to enhance the function of HDAC4 by increasing HDAC4 expression in the nucleus. RNA-seq was performed to identify the molecular mechanism of HDAC4 in chondrocytes. Finally, the top ten DEGs associated with ribosomes were verified by quantitative polymerase chain reaction (QPCR) in chondrocytes, and the top gene was verified both in vitro and in vivo.

Results

HDAC4 markedly improved the survival rate and biofunction of chondrocytes. RNA-seq analysis of the EP and HDAC4 groups showed that HDAC4 induced 2,668 significant gene expression changes in chondrocytes (1,483 genes upregulated and 1,185 genes downregulated, p < 0.05), and ribosomes exhibited especially large increases. The results were confirmed by RNA-seq of the EP versus mutated HDAC4 groups and the validations in vitro and in vivo.

Conclusion

The enhanced ribosome pathway plays a key role in the mechanism by which HDAC4 improves the survival rate and biofunction of chondrocytes.

Multiple roles of ALK3 in osteoarthritis

Osteoarthritis (OA) is a chronic degenerative joint disease characterized by progressive cartilage degradation, synovial membrane inflammation, osteophyte formation, and subchondral bone sclerosis. Pathological changes in cartilage and subchondral bone are the main processes in OA. In recent decades, many studies have demonstrated that activin-like kinase 3 (ALK3), a bone morphogenetic protein receptor, is essential for cartilage formation, osteogenesis, and postnatal skeletal development. Although the role of bone morphogenetic protein (BMP) signalling in articular cartilage and bone has been extensively studied, many new discoveries have been made in recent years around ALK3 targets in articular cartilage, subchondral bone, and the interaction between the two, broadening the original knowledge of the relationship between ALK3 and OA. In this review, we focus on the roles of ALK3 in OA, including cartilage and subchondral bone and related cells. It may be helpful to seek more efficient drugs or treatments for OA based on ALK3 signalling in future.

Swimming prevents cell death of chondrocytes via PI3K/AKT pathway in an experimental model

BACKGROUND

Knee Osteoarthritis (KOA) is one of the main causes of disability in the elderly and with limited treatment options. Swimming was considered as an ideal form of non-surgical management of KOA. Nevertheless, the mechanism of swimming intervene OA remains unclear. ACLT induced OA model was often used to study the pathogenesis and treatment of OA. Thus, we evaluated the protective effect of swimming on KOA mouse and tried to explore the underlying mechanism.

METHODS

Forty C57BL/6 mice were randomly divided into five groups: Blank group, ACLT group, ACLT + Swim group, Sham group and Sham + Swim group (n = 8). OA model was established by Anterior Cruciate Ligament Transection surgery (ACLT). After modeling, mice in ACLT + Swim and Sham + Swim groups were trained with a moderate swimming program, 5 d/week, for 6 weeks. HE and Safranin-O/fast staining, Immunohistochemistry, TUNEL assay and Western blot were used to detect the effect of swimming on pathological changes, cell death and the mechanism in KOA mouse.

RESULTS

Swimming significantly enhanced CoII expression and suppressed ADAMTS5 expression in cartilage of KOA mouse, thus ameliorated KOA development. Apoptotic and autophagic processes were enhanced in OA cartilage, which might be caused by down-regulation of PI3K/AKT pathway; swimming could activate PI3K/AKT pathway and thus regulate apoptosis and autophagy processes of chondrocytes.

CONCLUSION

Swimming could prevent cell death of chondrocytes via PI3K/AKT pathways, thus delayed the progression of KOA in an experimental model.

Optimizing Delivery of Therapeutic Growth Factors for Bone and Cartilage Regeneration

Bone- and cartilage-related diseases, such as osteoporosis and osteoarthritis, affect millions of people worldwide, impairing their quality of life and increasing mortality. Osteoporosis significantly increases the bone fracture risk of the spine, hip, and wrist. For successful fracture treatment and to facilitate proper healing in the most complicated cases, one of the most promising methods is to deliver a therapeutic protein to accelerate bone regeneration. Similarly, in the setting of osteoarthritis, where degraded cartilage does not regenerate, therapeutic proteins hold great promise to promote new cartilage formation. For both osteoporosis and osteoarthritis treatments, targeted delivery of therapeutic growth factors, with the aid of hydrogels, to bone and cartilage is a key to advance the field of regenerative medicine. In this review article, we propose five important aspects of therapeutic growth factor delivery for bone and cartilage regeneration: (1) protection of protein growth factors from physical and enzymatic degradation, (2) targeted growth factor delivery, (3) controlling GF release kinetics, (4) long-term stability of regenerated tissues, and (5) osteoimmunomodulatory effects of therapeutic growth factors and carriers/scaffolds.

MicroRNA Signatures in Cartilage Ageing and Osteoarthritis

Osteoarthritis is the most common degenerative joint disorder. MicroRNAs are gene expression regulators that act post-transcriptionally to control tissue homeostasis. Microarray analysis was undertaken in osteoarthritic intact, lesioned and young intact cartilage. Principal component analysis showed that young intact cartilage samples were clustered together; osteoarthritic samples had a wider distribution; and osteoarthritic intact samples were separated into two subgroups, osteoarthritic-Intact-1 and osteoarthritic-Intact-2. We identified 318 differentially expressed microRNAs between young intact and osteoarthritic lesioned cartilage, 477 between young intact and osteoarthritic-Intact-1 cartilage and 332 between young intact and osteoarthritic-Intact-2 cartilage samples. For a selected list of differentially expressed microRNAs, results were verified in additional cartilage samples using qPCR. Of the validated DE microRNAs, four-miR-107, miR-143-3p, miR-361-5p and miR-379-5p-were selected for further experiments in human primary chondrocytes treated with IL-1β. Expression of these microRNAs decreased in human primary chondrocytes treated with IL-1β. For miR-107 and miR-143-3p, gain- and loss-of-function approaches were undertaken and associated target genes and molecular pathways were investigated using qPCR and mass spectrometry proteomics. Analyses showed that WNT4 and IHH, predicted targets of miR-107, had increased expression in osteoarthritic cartilage compared to young intact cartilage and in primary chondrocytes treated with miR-107 inhibitor, and decreased expression in primary chondrocytes treated with miR-107 mimic, suggesting a role of miR-107 in chondrocyte survival and proliferation. In addition, we identified an association between miR-143-3p and EIF2 signalling and cell survival. Our work supports the role of miR-107 and miR-143-3p in important chondrocyte mechanisms regulating proliferation, hypertrophy and protein translation.

Small molecule inhibitors of osteoarthritis: Current development and future perspective

Osteoarthritis (OA) is one of the common degenerative joint diseases in clinic. It mainly damages articular cartilage, causing pain, swelling and stiffness around joints, and is the main cause of disability of the elderly. Due to the unclear pathogenesis of osteoarthritis and the poor self-healing ability of articular cartilage, the treatment options for this disease are limited. At present, NSAIDs, Glucocorticoid and Duloxetine are the most commonly used treatment choice for osteoarthritis. Although it is somewhat effective, the adverse reactions are frequent and serious. The development of safer and more effective anti-osteoarthritis drugs is essential and urgent. This review summarizes recent advances in the pharmacological treatment of OA, focusing on small molecule inhibitors targeting cartilage remodeling in osteoarthritis as well as the research idea of reducing adverse effects by optimizing the dosage form of traditional drugs for the treatment of osteoarthritis. It should provide a reference for exploration of new potential treatment options.

Osteoarthritis: a narrative review of molecular approaches to disease management

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

Primary Cilia: A Cellular Regulator of Articular Cartilage Degeneration

Osteoarthritis (OA) is the most common joint disease that can cause pain and disability in adults. The main pathological characteristic of OA is cartilage degeneration, which is caused by chondrocyte apoptosis, cartilage matrix degradation, and inflammatory factor destruction. The current treatment for patients with OA focuses on delaying its progression, such as oral anti-inflammatory analgesics or injection of sodium gluconate into the joint cavity. Primary cilia are an important structure involved in cellular signal transduction. Thus, they are very sensitive to mechanical and physicochemical stimuli. It is reported that the primary cilia may play an important role in the development of OA. Here, we review the correlation between the morphology (location, length, incidence, and orientation) of chondrocyte primary cilia and OA and summarize the relevant signaling pathways in chondrocytes that could regulate the OA process through primary cilia, including Hedgehog, Wnt, and inflammation-related signaling pathways. These data provide new ideas for OA treatment.

α2-macroglobulin-rich serum as a master inhibitor of inflammatory factors attenuates cartilage degeneration in a mini pig model of osteoarthritis induced by “idealized” anterior cruciate ligament reconstruction

Post-traumatic osteoarthritis is a special type of osteoarthritis and a common disease, with few effective treatments available. α2-Macroglobulin (α2M) is important to chondral protection in post-traumatic osteoarthritis. However, its injection into xenogeneic joint cavities involves safety hazards, limiting clinical applications. Exploring serum α2M-enriching strategies and the therapeutic effect and mechanism of α2M-rich serum (α2MRS) autologous joint injection to treat post-traumatic osteoarthritis has significant value. In the present study, a unique filtration process was used to obtain α2MRS from human and mini pig serum. We evaluated the potential of α2MRS in protecting against post-surgery cartilage degeneration. We identify the potential of α2MRS in reducing the expression of inflammatory cytokines and factors that hasten cartilage degeneration in post-operative conditions leading to post-traumatic osteoarthritis. The potential of α2MRS was analyzed in interleukin-1β induced human chondrocytes and mini pig models. In the chondrocyte model, α2MRS significantly promoted human chondrocyte proliferation and reduced apoptosis and chondrocyte catabolic cytokine gene transcription and secretion. The anterior cruciate ligament autograft reconstruction model of mini pigs was randomized into groups, operated on, and injected with α2MRS or saline. The results showed that α2MRS injection significantly suppressed the levels of inflammatory factors, improved gait, and showed significantly lower cartilage degeneration than the groups that did not receive α2MRS injections. This study highlights the chondroprotective effects of α2MRS, elucidated its potential applications against cartilage degeneration, and could provide a basis for the clinical translation of α2MRS.

miR-3960 from Mesenchymal Stem Cell-Derived Extracellular Vesicles Inactivates SDC1/Wnt/β-Catenin Axis to Relieve Chondrocyte Injury in Osteoarthritis by Targeting PHLDA2

Osteoarthritis (OA) is a serious disease of the articular cartilage characterized by excessive inflammation. Lately, mesenchymal stem cell- (MSC-) derived extracellular vesicles (EVs) have been proposed as a novel strategy for the treatment of OA. We aimed to investigate the effects of EV-encapsulated miR-3960 derived from MSCs on chondrocyte injury in OA. The cartilage tissues from OA patients were collected to experimentally determine expression patterns of miR-3960, PHLDA2, SDC1, and β-catenin. Next, luciferase assay was implemented to testify the binding affinity among miR-3960 and PHLDA2. EVs were isolated from MSCs and cocultured with IL-1β-induced OA chondrocytes. Afterwards, cellular biological behaviors and levels of extracellular matrix- (ECM-) related protein anabolic markers (collagen II and aggrecan), catabolic markers (MMP13 and ADAMTS5), and inflammatory factors (IL-6 and TNF-α) in chondrocytes were assayed upon miR-3960 and/or PHLDA2 gain- or loss-of-function. Finally, the effects of miR-3960 contained in MSC-derived EVs in OA mouse models were also explored. MSCs-EVs could reduce IL-1β-induced inflammatory response and extracellular matrix (ECM) degradation in chondrocytes. miR-3960 expression was downregulated in cartilage tissues of OA patients but enriched in MSC-derived EVs. miR-3960 could target and inhibit PHLDA2, which was positively correlated with SDC1 and Wnt/β-catenin pathway activation. miR-3960 shuttled by MSC-derived EVs protected against apoptosis and ECM degradation in chondrocytes. In vivo experiment also confirmed that miR-3960 alleviated chondrocyte injury in OA. Collectively, MSC-derived EV-loaded miR-3960 downregulated PHLDA2 to inhibit chondrocyte injury via SDC1/Wnt/β-catenin.

Possible Repositioning of an Oral Anti-Osteoporotic Drug, Ipriflavone, for Treatment of Inflammatory Arthritis via Inhibitory Activity of KIAA1199, a Novel Potent Hyaluronidase

KIAA1199 has a strong hyaluronidase activity in inflammatory arthritis. This study aimed to identify a drug that could reduce KIAA1199 activity and clarify its effects on inflammatory arthritis. Rat chondrosarcoma (RCS) cells were strongly stained with Alcian blue (AB). Its stainability was reduced in RCS cells, which were over-expressed with the KIAA1199 gene (RCS-KIAA). We screened the drugs that restore the AB stainability in RCS-KIAA. The effects of the drug were evaluated by particle exclusion assay, HA ELISA, RT-PCR, and Western blotting. We further evaluated the HA accumulation and the MMP1 and three expressions in fibroblast-like synoviocytes (FLS). In vivo, the effects of the drug on symptoms and serum concentration of HA in a collagen-induced arthritis mouse were evaluated. Ipriflavone was identified to restore AB stainability at 23%. Extracellular matrix formation was significantly increased in a dose-dependent manner (p = 0.006). Ipriflavone increased the HA accumulation and suppressed the MMP1 and MMP3 expression on TNF-α stimulated FLS. In vivo, Ipriflavone significantly improved the symptoms and reduced the serum concentrations of HA. Conclusions: We identified Ipriflavone, which has inhibitory effects on KIAA1199 activity. Ipriflavone may be a therapeutic candidate based on its reduction of KIAA1199 activity in inflammatory arthritis.

Exogenous growth hormone functionally alleviates glucocorticoid-induced longitudinal bone growth retardation in male rats by activating the Ihh/PTHrP signaling pathway

Glucocorticoid (GC)-induced longitudinal bone growth retardation is a common and severe adverse effect in pediatric patients receiving GC immunosuppressive therapy. Molecular mechanisms underlying GC-induced growth inhibition are unclear. GC withdrawal following short-term high-dose use is common, including in the immediate post-transplant period. However, whether skeleton growth recovery is sufficient or whether growth-promoting therapy is required following GC withdrawal is unknown. The aim of this study was to investigate the effect of exogenous growth hormone (GH) on growth plate impairment in GC-induced longitudinal bone growth retardation. Here, apoptotic chondrocytes in the hypertrophic layer of growth plates increased whereas Indian Hedgehog (Ihh) and Parathyroid Hormone Related Peptide (PTHrP) protein levels in the growth plate decreased following GC exposure. The hypertrophic zone of the growth plate expanded following GC withdrawal. Subcutaneously injected GH penetrated the growth plate and modified its organization in rats following GC withdrawal. Ihh and PTHrP expression in GC-induced apoptotic chondrocytes decreased in vitro. GH promoted chondrocyte proliferation by activating Ihh/PTHrP signaling. Downregulating Ihh using specific siRNAs increased chondrocyte apoptosis and inhibited PTHrP, Sox9, and type II collagen (Col2a1) protein expression. GH inhibited apoptosis of Ihh-deficient growth plate chondrocytes by upregulating PTHrP, Sox9, and Col2a1 expression. Thus, reversal of the effect of GC on growth plate impairment following its withdrawal is insufficient, and exogenous GH provides growth plate chondral protection and improved longitudinal growth following GC withdrawal by acting on the Ihh/PTHrP pathway.

Hedgehog signalling in bone and osteoarthritis: the role of Smoothened and cholesterol

Hedgehog signalling is essential for development, crucial for normal anatomical arrangement and activated during tissue damage repair. Dysregulation of hedgehog signalling is associated with cancer, developmental disorders and other diseases including osteoarthritis (OA). The hedgehog gene was first discovered in Drosophila melanogaster, and the pathway is evolutionarily conserved in most animals. Although there are several hedgehog ligands with different protein expression patterns, they share a common plasma membrane receptor, Patched1 and hedgehog signalling pathway activation is transduced through the G-protein-coupled receptor-like protein Smoothened (SMO) and downstream effectors. Functional assays revealed that activation of SMO is dependent on sterol binding, and cholesterol was observed bound to SMO in crystallography experiments. In vertebrates, hedgehog signalling coordinates endochondral ossification and balances osteoblast and osteoclast activation to maintain homeostasis. A recently discovered mutation of SMO in humans (SMO^R173C ) is predicted to alter cholesterol binding and is associated with a higher risk of hip OA. Functional studies in mice and human tissue analysis provide evidence that hedgehog signalling is pathologically activated in chondrocytes of osteoarthritic cartilage.

Intra-articular injection of loaded sPL sustained-release microspheres inhibits osteoarthritis and promotes cartilaginous repairs

BACKGROUND

Osteoarthritis is a chronic inflammatory disease of the joints associated with significant morbidity and lower quality of life. Current treatment strategies focus on reducing cartilage degeneration but fail to restore their proliferative ability. Super-activated platelet lysate (sPL) is an enhanced form of platelet-rich plasma that can be easily inactivated. The purpose of this study is to evaluate whether sPL-loaded PLGA/chitosan/gelatin microspheres can prevent and treat osteoarthritis.

METHODS

Features of biological microspheres were detected by SEM and ELISA. Osteoarthritis chondrocytes were co-cultured with hydrogel loaded with sPL. The effect of biological microspheres on chondrocyte proliferation was evaluated using a CCK-8 cell proliferation test. Cell morphology and cell necrosis were measured with a microscope. The gene expression levels of cartilage-related markers type 2 collagen, aggrecan (ACAN), and SRY type high mobility group box-9 (SOX9) were determined by real-time quantitative polymerase chain reaction (Rt-PCR). A rat osteoarthritis model was established. Micro-CT was used to characterize cartilaginous changes after the injection of biological microspheres. Histopathological HE staining, Safranin-O Fast Green staining and staining scores, type II collagen staining, and proteoglycan staining were used to evaluate the degree of cartilaginous repair.

RESULTS

Biological microspheres were able to continuously release biological factors. Exposure to loading sPL microspheres significantly increased chondrocyte proliferation, reduced cell necrosis, and increased the expression of cartilage markers type 2 collagen, ACAN, and SOX9 in osteoarthritic chondrocytes. In vivo experiments found that biological microspheres also smoothen cartilage surfaces, promote the expression of proteoglycan and type 2 collagen while also increasing cartilaginous integrity as evaluated using Safranin-O Fast Green staining.

CONCLUSIONS

PLGA/chitosan/gelatin hydrogel loaded with sPL is a promising tool for effective and non-invasive articular cartilage repair in osteoarthritis. Biological microspheres loaded with sPL release various biological factors to promote chondrocyte proliferation and upregulate chondrocyte functionalization genes (SOX9, CoX II, ACAN), leading to an overall enhanced cartilaginous matrix.

Wogonin inhibits the growth of HT144 melanoma via regulating hedgehog signaling-mediated inflammation and glycolysis

Hedgehog (Hh) signaling has been proved to be closely associated with the occurrence of melanoma. Wogonin is one of the active components of flavonoids that extracts from Scutellariae radix. Previous studies showed that wogonin could inhibit the invasion and migration of B16F10 cells, and suppress the synthesis of melanin in A375 melanoma cells. However, the regulatory effects of Hh signaling in wogonin against melanoma and its potential mechanisms remain largely unknown. The present study aimed to investigate the effect of wogonin on the growth of HT144 melanoma, and to elucidate the role of Hh signaling in wogonin-induced antitumor effects by focusing on inflammation and glycolysis regulation. Wogonin inhibited the proliferation, colony formation and tumor growth of HT144 melanoma cells. Wogonin showed strong anti-inflammatory effect in HT144 melanoma, as shown by the decreased levels of pro-inflammatory factors, the increased level of anti-inflammatory factor and the decreased expression of inflammatory cytokines. Wogonin decreased the glucose consumption and the production of lactic acid and ATP, and decreased the activities of hexokinase (HK), phosphofructokinase(PFK) and pyruvate kinase (PK), and further inhibited the expression of monocarboxylate transporter 1 (MCT-1), MCT-4 and glucosecotransporter-1 (GLUT1), showing potent anti-glycolysis effect against HT144 melanoma. Wogonin inhibited the patched and Smo expression while increased Hhip expression in HT144 cells, suggesting that wogonin blocked the Hh signaling in HT144 cells. The Hh signaling inhibitor cyclopamine, like wogonin, inhibited the colony formation of HT144 cells, however, the inhibitory effect of wogonin on colony formation of HT144 cells was abrogated by the Hh signaling agonist SAG. In addition, SAG abrogated the inhibitory effect of wogonin on the secretion of inflammatory factors and the expression of inflammatory cytokines. Furthermore, SAG abrogated the inhibitory effect of wogonin on several key molecules controlling glycolysis. Overall, these findings suggested that the anti-tumor effect of wogonin can be attributed to the inhibition of Hh signaling-mediated regulation of inflammation and glycolysis in HT144 melanoma.

Expression of VEGF-A Signaling Pathway in Cartilage of ACLT-induced Osteoarthritis Mouse Model

BACKGROUND

Anterior cruciate ligament transection surgery (ACLT)-induced OA model was often used to investigate the molecular mechanism of knee osteoarthritis (KOA). Researches have shown that vascular endothelial growth factor (VEGF) played an important role in OA. The present study aimed to investigate the pathological changes after ACLT surgery and reveal the expression characteristics of the VEGF-A/VEGFR2 signaling pathway in this model.

METHODS

Moderate KOA model was established by ACLT, and 1, 2, 4, 8, and 12 weeks after surgery, hematoxylin-eosin (HE) and Safranin-O(S-O) staining were used to detect the pathological changes in mouse knee cartilage, and the matrix biomarkers A Disintegrin and Metalloproteinase with Thrombospondin Motifs 5(ADAMTS5), Collagen II (COL-II) were detected using immunohistochemistry (IHC), CD31 was detected by immunofluorescence (IF) to show the vascular invasion in cartilage, and proteins expression of VEGF-A pathway were detected by Western blot (WB). Meanwhile, the inflammatory biomarkers cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) in cartilage were detected by WB.

RESULTS

ACLT surgery can lead to degeneration of cartilage in mice, and the characteristics of the lesion were time-dependent. The ADAMTS5-positive cells increased while COL-II decreased in OA cartilage with time, and new blood vessels labeled by CD31 can be seen from 1 week in OA cartilage, and increased in 8 and 12 weeks. The expression of VEGF-A, VEGFR2, COX-2, and iNOS were higher than control groups, which were basically consistent with the degree of osteoarthritis.

CONCLUSIONS

The degenerative degree of articular cartilage was time-dependent; angiogenesis and inflammation were important pathological changes of cartilage in KOA. The expression of the VEGF-A/VEGFR2 signaling pathway was basically correlated with the degree of KOA.

Glycitin Suppresses Cartilage Destruction of Osteoarthritis in Mice

Osteoarthritis (OA), a chronic joint disease, is characterized by cartilage surface erosion, subchondral bone rebuilding, and formation of osteophytes. To date, the nosogenesis and underlying mechanisms of OA have not yet been elucidated. However, it is widely accepted that TNF-α is a crucial cytokine in the development of OA. Glycitin, a natural isoflavone extracted from legumes, affects physiological reactions and pathological responses. Recently, the anti-inflammatory effect of glycitin has been reported. However, the function of glycitin in cartilage degeneration in OA remains to be investigated. In the current study, primary murine chondrocytes were isolated and stimulated by TNF-α to evaluate the anti-inflammatory effects and protective function of glycitin in chondrocytes. In vivo, the ACLT mouse model, a frequently-used OA model, was used to further examine the therapeutic role of glycitin in cartilage degeneration and inflammation in OA. Consequently, glycitin functions were examined both in vivo and in vitro. Moreover, the underlying mechanism of action of glycitin was investigated and was found to involve the NF-κB signaling pathway. Collectively, this study suggests that glycitin can be potentially used for the treatment of joint degenerative diseases, including OA.

MicroRNA‑1 regulates the development of osteoarthritis in a Col2a1‑Cre‑ERT2/GFPfl/fl‑RFP‑miR‑1 mouse model of osteoarthritis through the downregulation of Indian hedgehog expression

The present study assessed the effects of microRNA‑1 (miR‑1) on the development of osteoarthritis using human tissues and a Col2a1‑Cre‑ERT2/GFPfl/fl‑RFP‑miR‑1 mouse model of osteoarthritis. Human cartilage tissues (n=20) were collected for reverse transcription‑quantitative polymerase chain reaction (RT‑qPCR), histological analysis and immunohistochemistry experiments. A transgenic mouse model of osteoarthritis was established by subjecting Col2a1‑Cre‑ERT2/GFPfl/fl‑RFP‑miR‑1 transgenic mice to anterior cruciate ligament transection (ACLT). Mice were subjected to radiography and in vivo fluorescence molecular tomography (FMT), while mouse tissues were collected for histological analysis, RT‑qPCR and Safranin O staining. It was found that the miR‑1 level was downregulated, whereas the levels of Indian hedgehog (Ihh), as well as those of its downstream genes were upregulated in human osteoarthritic cartilage. In the transgenic mice, treatment with tamoxifen induced miR‑1, as well as collagen, type II (Col2a1) and Aggrecan (Acan) expression; however, it decreased Ihh, glioma‑associated oncogene homolog (Gli)1, Gli2, Gli3, smoothened homolog (Smo), matrix metalloproteinase (MMP)‑13 and collagen type X (Col10) expression. Safranin O staining revealed cartilage surface damage in the non‑tamoxifen + ACLT group, compared with that in the tamoxifen + ACLT group. Histologically, an intact cartilage surface and less fibrosis were observed in the tamoxifen + ACLT group. Immunohistochemistry revealed that the protein expression of Ihh, Col10, and MMP‑13 was significantly higher in the joint tissues of the non‑tamoxifen + ACLT group than in those of the tamoxifen + ACLT group. However, Col2a1 expression was lower in the joint tissues of the non‑tamoxifen + ACLT group than in those of the tamoxifen + ACLT group. The results of RT‑qPCR and FMT further confirmed these findings. On the whole, the findings of the present study demonstrate that miR‑1 expression protects against osteoarthritis‑induced cartilage damage and gene expression by inhibiting Ihh signaling.

Functional role of hedgehog pathway in osteoarthritis

The hedgehog signalling pathway is one of the key regulators of metazoan development, and it plays an important role in the regulation of a variety of developmental and physiological processes. But it is aberrantly activated in many human diseases, including osteoarthritis (OA). In this study, we have reviewed the association of hedgehog signalling pathway in the development and progression of OA and evaluated the efforts to target this pathway for the prevention of OA. Usually in OA, activation of hedgehog induces up-regulation of the expression of hypertrophic markers, including type X collagen, increases production of nitric oxide and prostaglandin E2, several matrix-degrading enzymes including matrix metalloproteinase and a disintegrin and metalloproteinase with thrombospondin motifs in human knee joint cartilage leading to cartilage degeneration, and thus contributes in OA. Targeting hedgehog signalling might be a viable strategy to prevent or treat OA. Chemical inhibitors of hedgehog signalling is promising, but they cause severe side effects. Knockdown of HH gene is not an option for OA treatment in humans because it is not possible to delete HH in larger animals. Efficient knockdown of HH achieved by local delivery of small interfering RNA in future studies utilizing large animal OA models might be a more efficient approach for the prevention of OA. However, it remains a major problem to develop one single scaffold due to the different physiological functions of cartilage and subchondral bones possess. More studies are necessary to identify selective inhibitors for efficiently targeting the hedgehog pathway in clinical conditions.

Scutellarin suppresses cartilage destruction in osteoarthritis mouse model by inhibiting the NF-κB and PI3K/AKT signaling pathways

Osteoarthritis (OA), a common and severe disease, is predominantly characterized by cartilage destruction, which results in the degeneration of joint surfaces. Nowadays, it is accepted that TNFα plays a critical role in OA. Scutellarin, the main bioactive flavonoid glycoside extracted form Erigeron breviscapus, has been reported to exert positive effects on anti-inflammatory reactions. However, the effect of scutellarin in OA is still unknown. In this study, we isolated and cultured primary murine chondrocytes, stimulating TNF-α, in the presence or absence of scutellarin treatment. We found that the inflammatory response stimulated by TNF-α was significantly inhibited by the addition of scutellarin. Moreover, we established OA mouse models induced by surgery. In this mouse model, both inflammatory reaction and cartilage degeneration were markedly inhibited by oral administration of scutellarin. Furthermore, the cellular mechanism underlying the protective effect of scutellarin in OA was clearly associated with the NF-κB and PI3K/AKT signaling pathways. Collectively, this study proposes scutellarin as a potential therapeutic to treat joint degenerative diseases, including OA.