Protective effects of emodin on subchondral bone and articular cartilage in osteoporotic osteoarthritis rats: A preclinical study.

BACKGROUND: Osteoporotic osteoarthritis (OP-OA) is a severe pathological form of OA, urgently requiring precise management strategies and more efficient interventions. Emodin (Emo), an effective ingredient found in the traditional Chinese medicine rhubarb, has been dEmonstrated to promote osteogenesis and inhibit extracellular matrix degradation. In this study, we aimed to investigate the interventional effects of Emo on the subchondral bone and cartilage of the knee joints in OP-OA model rats. METHODS: Thirty-two SD rats were randomly and equally divided into sham, OP-OA, Emo low-dose, and Emo high-dose groups. Micro-CT scanning was conducted to examine the bone microstructure of the rat knee joints. H&E and Safranin O and Fast Green staining (SO&FG) were performed for the pathomorphological evaluation of the rat cartilage tissues. ELISA was used to estimate the rat serum expression levels of inflammatory factors, including interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α). Additionally, the CCK-8 assay was utilized for determining the viability of Emo-treated BMSCs. Western blot and real-time PCR analyses were also employed to measure the bone formation indexes and cartilage synthesis and decomposition indexes. Lastly, the osteogenic and chondrogenic differentiation efficiency of the BMSCs was investigated via Alizarin Red and Alcian Blue staining. RESULTS: Emo intervention alleviated the bone microstructural disruption of the subchondral bone and articular cartilage in the OP-OA rats and up-regulated the expression of bone and cartilage anabolic metabolism indicators, decreased the expression of cartilage catabolism indicators, and diminished the expression of inflammatory factors in the rat serum (P<0.05). Furthermore, Emo reversed the decline in the osteogenic and chondrogenic differentiation ability of the BMSCs (P<0.05). CONCLUSION: Emo intervention mitigates bone loss and cartilage damage in OP-OA rats and promotes the osteogenic and chondrogenic differentiation of BMSCs.

Total glucosides of white paeony capsule alleviate articular cartilage degeneration and aberrant subchondral bone remodeling in knee osteoarthritis.

Knee osteoarthritis (KOA) is a prevalent degenerative joint disease that is primarily managed by improving the destroyed cartilage and reversing subchondral bone remodeling. Total glucosides of white paeony (TGP) capsule primarily contains extracts from the white peony root and has been shown to have various pharmacological effects, but its role in KOA still requires comprehensive evaluation. In this study, we aimed to investigate the protective effect of TGP on knee cartilage and subchondral bone, as well as elucidate the underlying molecular mechanisms. The effect of TGP on KOA progression was evaluated in the destabilization of the medial meniscus (DMM)-induced KOA model of mouse and interleukin (IL)-1ß-induced KOA model of primary mouse chondrocytes. In vivo and in vitro experiments demonstrated that TGP had a protective effect on the cartilage. Treatment with TGP could induce the synthesis of critical elements in the cartilage extracellular matrix and downregulate the synthesis of degrading enzymes in the extracellular matrix. Regarding the underlying mechanisms, TGP inhibited the phosphorylation and nuclear translocation of p65 by regulating the nuclear factor-kappa B (NF-κB) signaling pathway. In addition, TGP could reduce the secretion of IL-1ß, IL-6, and tumor necrosis factor-α (TNF-α). Moreover, it has a sustained effect on coupled subchondral bone remodeling through regulation of the OPG/RANKL/RANK pathway. In conclusion, TGP may protect articular cartilage by downregulating the NF-κB signaling pathway and may support coupled subchondral bone remodeling by regulating OPG/RANKL/RANK signaling pathway in the DMM-induced KOA model of mouse, suggesting a new therapeutic potential for KOA treatment.

Casticin ameliorates osteoarthritic cartilage damage in rats through PI3K/AKT/HIF-1α signaling.

Knee osteoarthritis (KOA) is a chronic, disabling knee joint lesion in which degeneration and defects in articular cartilage are the most important features. Casticin (CAS) is a flavonoid extracted from the Chinese herb Vitex species that has anti-inflammatory and antitumor effects. The aim of this study was to investigate the therapeutic and mechanistic effects of CAS on cartilage damage in KOA. A KOA rat model was established by anterior cruciate ligament transection (ACLT), and cartilage morphological changes were assessed by histological analysis and micro-CT scans. Subsequently, chondrocytes were treated with 10 ng/mL IL-1ß to establish an OA model. CCK-8 assays and EdU assays were performed to assess the viability of CAS-treated chondrocytes. Western blotting, flow cytometry and Hoechst 33342/PI Double Stain were used to detect chondrocyte apoptosis. Western blotting, qRT‒PCR and ELISA were used to detect changes in inflammatory mediators. In addition, cartilage matrix-related indices were detected by Western blotting, qRT‒PCR and immunofluorescence (IF) analysis. Immunohistochemistry (IHC) and Western blotting were performed to detect the expression of p-PI3K, p-AKT and HIF-1α in vivo and in vitro. Micro-CT, pathological sections and related scores showed that CAS improved the alterations in bony structures and reduced cartilage damage and osteophyte formation in the ACLT model. In vivo, CAS attenuated IL-1ß-induced cartilage matrix degradation, apoptosis and the inflammatory response. In addition, CAS inhibited the expression of the PI3K/AKT/HIF-1α signaling pathway in the ACLT animal model and IL-1ß cell model. CAS may ameliorate cartilage damage in OA by inhibiting the PI3K/AKT/HIF-1α signaling pathway, suggesting that CAS is a potential strategy for the treatment of OA.

NGF Signaling Exacerbates KOA Peripheral Hyperalgesia via the Increased TRPV1-Labeled Synovial Sensory Innervation in KOA Rats.

Objectives: Knee osteoarthritis (KOA) pain is caused by nociceptors, which are actually sensory nerve fiber endings that can detect stimuli to produce and transmit pain signals, and high levels of NGF in synovial tissue led to peripheral hyperalgesia in KOA. The purpose of this study is to investigate how sensory nerve fibers respond to the NGF/TrKA signal pathway and mediate the peripheral hyperalgesia in KOA rats. Methods: Forty SD male rats were randomly divided into 4 groups: normal, KOA, KOA + NGF, and KOA + siRNA TrKA. KOA model rats were induced by anterior cruciate ligament transection (ACLT). Mechanical and cold withdrawal thresholds (MWT and CWT) were measured 4 times in each group. The synovial tissues were harvested on day 28, and the expressions of NGF, TrKA, TRPV1, IL-1ß, and PGP9.5 were determined using western blot, qPCR, and immunofluorescence staining. The primary rat fibroblast-like synoviocytes (FLSs) and DRG cells were divided into 4 groups as in vivo. The expressions of NGF, TrKA, TRPV1, and CGRP in vitro were determined using western blot and qPCR. Results: KOA and intra-articular injection with NGF protein increased both mRNA and protein levels, not only TRPV1, PGP 9.5, and IL-1ß in the synovial tissue, but also TRPV1, PGP 9.5, and S100 in the DRG tissue, while above changes were partly reversed after siRNA TrKA intervention. Besides, siRNA TrKA could improve peripheral hyperalgesia and decreased the TRPV1 positive nerve fiber innervation in synovial tissue. The results in vitro were consistent with those in vivo. Conclusion: This study showed the activation of the NGF/TrKA signaling pathway in KOA promoted the release of pain mediators, increased the innervation of sensory nerve fibers in the synovium, and worsened peripheral hyperalgesia. It also showed increased TRPV1 positive sensory innervation in KOA was mediated by NGF/TrKA signaling and exacerbated peripheral hyperalgesia.

Activation of vascular endothelial cells by synovial fibrosis promotes Netrin-1-induced sensory nerve sprouting and exacerbates pain sensitivity.

Synovial fibrosis is one of the most dominant histopathological changes in osteoarthritis of the knee (KOA), and activation of vascular endothelial cells in synovial fibrosis is both an important factor in mediating pain in KOA and a major contributor to the generation of pain signals. At the same time, angiogenesis and nerve fibres are more likely to underlie the pathology of pain induced by synovial fibrosis. In the present study, we established a co-culture model of human umbilical vein endothelial cells (HUVECs) with dorsal root ganglion (DRG) and detected tissue and cellular Netrin-1, vascular cell adhesion molecule-1 (VCAM-1), intercellular cell adhesion molecule-1 (ICAM-1), growth-associated protein-43 (GAP43), colorectal cancer deleted (DCC), uncoordinated 5 (UNC5), and the related expression of calcitonin gene-related peptide (CGRP), substance P (SP) and nerve growth factor (NGF) in supernatant by ELISA to investigate the intervention of vascular endothelial cell activation on sensory nerve sprouting exacerbating peripheral pain sensitivity and to investigate the effect of Netrin-1 from the perspective of Netrin-1 secretion to illustrate its effector mechanism.

L-carnitine alleviates synovitis in knee osteoarthritis by regulating lipid accumulation and mitochondrial function through the AMPK-ACC-CPT1 signaling pathway.

BACKGROUND: Knee osteoarthritis (KOA) is a disability-associated condition that is rapidly growing with the increase in obesity rates worldwide. There is a pressing need for precise management and timely intervention in the development of KOA. L-carnitine has been frequently recommended as a supplement to increase physical activity in obese individuals due to its role in fatty acid metabolism, immune disorders, and in maintaining the mitochondrial acetyl-CoA/CoA ratio. In this study, we aimed to investigate the anti-inflammatory effects of L-carnitine on KOA and delineate a potential molecular mechanism. METHODS: Lipopolysaccharide-stimulated primary rat fibroblast-like synoviocytes (FLS) were treated with an AMP-activated protein kinase (AMPK) inhibitor or siRNA and carnitine palmitoyltransferase 1 (CPT1) siRNA to examine the synovial protective effects of L-carnitine. An anterior cruciate ligament transection model of rats was treated with an AMPK agonist (metformin) and CPT1 inhibitor (etomoxir) to define the therapeutic effects of L-carnitine. RESULTS: L-carnitine displayed a protective effect against synovitis of KOA in vitro and in vivo experiments. Specifically, L-carnitine treatment can reduce synovitis by inhibiting AMPK-ACC-CPT1 pathway activation and showed an increase in fatty acid ß-oxidation, a lower lipid accumulation, and a noticeable improvement in mitochondrial function. CONCLUSIONS: Our data suggested that L-carnitine can mitigate synovitis in FLS and synovial tissue, and the underlying mechanism may be related to improving mitochondrial function and reducing lipid accumulation via the AMPK-ACC-CPT1 signaling pathway. Therefore, L-carnitine may be a potential treatment strategy for KOA.

Macrophage pyroptosis promotes synovial fibrosis through the HMGB1/TGF- ß1 axis: an in vivo and in vitro study.

Macrophages and fibroblasts are the main effector cells in synovial tissue in the knee joint. Our previous studies showed that there was synovial macrophage pyroptosis in knee osteoarthritis (KOA) and that inhibiting this pyroptosis could alleviate synovial fibrosis. In the present study, we aimed to elucidate the mechanism by which macrophage pyroptosis affects synovial fibrosis. We established an LPS/ATP-induced model in macrophages that mimicked the inflammatory environment of KOA and induced macrophage pyroptosis. The TGF-ß1, SMAD3, and P-SMAD3, and the synovial fibrosis markers (Collagen I, TIMP1, Vimentin, and TGF-ß1) were significantly decreased after fibroblasts were cultured with RAGE inhibitors and SMAD3 inhibitors. Moreover, ELISA and immunofluorescence analysis showed that macrophage pyroptosis induced the release of IL-1ß, IL-18, and HMGB1 and caused the translocation of HMGB1 from the fibroblast nucleus to the cell membrane, where it could bind with RAGE. Subsequently, in the synovial tissue of KOA model rats, we observed that inhibiting HMGB1, RAGE, and SMAD3 could alleviate the expression of synovial fibrosis markers (Collagen I, TIMP1, Vimentin, and TGF-ß1) at both the mRNA and protein levels. Besides, HE and Sirius Red staining were used to observe the transverse diameter of the right knee. In conclusion, macrophage pyroptosis induced IL-1ß, IL-18, and HMGB1, which could be caused HMGB1 to translocate from the fibroblast nucleus and bind with RAGE, activating the TGF-ß1/SMAD3 signaling pathway and affecting synovial fibrosis.

Chrysin ameliorates synovitis and fibrosis of osteoarthritic fibroblast-like synoviocytes in rats through PERK/TXNIP/NLRP3 signaling.

Objective: Synovitis and fibrosis are common pathological features of knee osteoarthritis (KOA). The interaction of synovitis and fibrosis can promote KOA progression. Chrysin (CHR), a natural flavonoid, may treat inflammation and prevent fibrosis. However, the effect and mechanism of CHR in KOA synovitis and fibrosis remains unclear. Methods: The KOA model was established in male SD rats by anterior cruciate ligament transection (ACLT), and histological analysis was used to evaluate synovitis and fibrosis. IL-6, IL-1ß and TNF-α mRNA expression in synovial tissue was measured by qRT‒PCR. Immunohistochemistry (IHC) was performed to detect GRP78, ATF-6 and TXNIP expression in vivo. Synovial fibroblasts (SFs) were treated with TGF-ß1 to stimulate the inflammatory response and fibrosis. CCK-8 assays were used to detect the viability of CHR-treated SFs. The IL-1ß level was detected by immunofluorescence analysis. Coimmunoprecipitation (Co-IP) and double immunofluorescence colocalization were used to detect the physiological interaction between TXNIP and NLRP3. The expression of fibrosis-related mediators and PERK/TXNIP/NLRP3 signaling molecules was detected by western blotting and qRT-PCR. Results: Four weeks after CHR treatment, pathological sections and associated scores showed that CHR improved synovitis and fibrosis in the ACLT model. In vitro, CHR attenuated the TGF-ß1-induced inflammatory response and fibrosis in SFs. Moreover, CHR suppressed the expression of synovial fibrosis markers and PERK/TXNIP/NLRP3 signaling molecules in the synovial tissue of rats with ACLT and cultured SFs. More importantly, we found that CHR inhibited TXNIP-NLRP3 interactions in TGF-ß-induced SFs. Conclusion: Our findings indicate that CHR can ameliorate synovitis and fibrosis in KOA. The underlying mechanism may be related to the PERK/TXNIP/NLRP3 signaling pathway.

GCTOF-MS Combined LC-QTRAP-MS/MS Reveals Metabolic Difference Between Osteoarthritis and Osteoporotic Osteoarthritis and the Intervention Effect of Erxian Decoction.

Purpose: OP and OA are chronic bone diseases with high incidence in the middle-aged and elderly populations. The latest research shows that the pathological environment of OP may be involved in the aggravation of the pathological process of OA, and the pathological state of OP plays an important role in the aggravation of OA pathology. EXD is a traditional Chinese medicine decoction that has been used to treat osteoporosis. Therefore, we further study whether OA will be aggravated in the OP environment and whether EXD can alleviate OA by intervening in the OP environment. The purpose of this study was to analyze the effect of OP on OA metabolites by using metabolomic methods and to explore the intervention mechanism of EXD on osteoporotic OA. Method: Thirty-two SD rats were randomly divided into normal group, OA group, OP-OA group, and EXD group. EXD was administered by gavage. Histopathological evaluation of cartilage tissue was performed using Saffron fast green and HE staining. Western blot and qRT-PCR were used to detect the expression levels of chondrogenesis genes SOX9, COL2A1, and COMP in cartilage tissue. GC-TOFMS and LC-QTRAP-MS/MS metabolomics methods were used to analyze the changes of metabolites in serum samples of rats in each group. Result: The slice results showed that the cartilage damage in the OP-OA group was more serious than that in the OA group, which was significantly relieved after EXD intervention, indicating that the cartilage damage in the OP-OA group was more severe than that in the OA group and further reduced the protein and gene expressions of cartilage markers SOX9, COL2A1, and COMP. Thirty-seven substances were identified, and gentiopicroside, emodin, quercetin, and diosmetin were analyzed as possible active components of EXD. EXD treatment significantly reduced cartilage damage and reversed the expression of these markers. Metabolomics showed that EXD attenuated cartilage destruction by modulating the expression of cystine, chenodeoxycholate, and D-Turanose, involving glycolysis/gluconeogenesis, pantothenate, and CoA biosynthesis metabolic pathways. Conclusion: The OP environment may promote the progression of OA through metabolic factors. The benign intervention of EXD in osteoporotic OA involves cystine, chenodeoxycholate, and D-Turanose, and their associated glycolysis/gluconeogenesis, pantothenate, and CoA biosynthesis metabolic pathways. Therefore, we have a deep understanding of the metabolic-related intervention of EXD in osteoporotic OA and are eager to better understand the mechanism of multi-targeted intervention of EXD in bone metabolic lesions.

Characteristics of sensory innervation in synovium of rats within different knee osteoarthritis models and the correlation between synovial fibrosis and hyperalgesia.

Introduction: Knee osteoarthritis (KOA) showed synovial fibrosis and hyperalgesia, although the correlation between the two is unclear. Besides, the specific changes of sensory innervation in animal models are still controversial, which makes it difficult to choose the modeling methods for KOA pain research. Objectives: Study the characteristics of sensory innervation within three commonly used KOA rat models and the correlation between synovial fibrosis and hyperalgesia. Methods: KOA models were induced by destabilization of medial meniscus (DMM), anterior cruciate ligament transection (ACLT), and monoiodoacetate (MIA), respectively. Mechanical, cold and thermal withdrawal threshold (MWT, CWT and TWT) were measured. The harvested tissues were used for pathological sections, immunofluorescence and quantitative analysis. Results: KOA synovium showed more type I collagen deposition, increased expression of CD31, VEGF and TGF-ß. These changes were most pronounced in surgical models, with DMM presenting the most prominent at Day 14 and ACLT at Day 28. Day 14, changes in mechanical hyperalgesia and cold hyperalgesia were most typical in DMM model and statistically different from MIA. There was a negative correlation between the percentage of type I collagen and MWT value (r = -0.88), as well as CWT value (r = -0.95). DMM synovium showed more axonal staining, upregulated CGRP, TRPV1, NGF and Netrin1 compared with MIA. Above changes were also observed at Day 28, but ACLT replaced DMM as the most typical. In DRG, only the levels of CGRP and NGF were different among KOA models at Day 14, and the highest in DMM, which was statistically different compared with MIA. Conclusions: This study described the details of sensory innervation in different KOA model of rats, and the degree of synovial fibrosis was positively correlated with the pain sensitivity of KOA model rats. Additionally, surgical modeling especially ACLT method is more recommended for KOA pain research.

Should synovectomy be performed during total knee arthroplasty for knee osteoarthritis: A protocol for systematic review and meta-analysis.

BACKGROUND: To evaluate the effect of synovectomy performed during primary total knee arthroplasty for knee osteoarthritis on patients' postoperative pain and knee function. METHODS: We will search the following electronic databases from inception to June 2021, including PubMed, EMBASE, Web of Science, the Cochrane Library, the China National Knowledge Infrastructure, the Chinese Scientific Journals Database, the Wanfang database, and the Chinese Biomedicine Database. Eligible references will be all randomized controlled trials of initial total knee arthroplasty for primary knee osteoarthritis with or without synovectomy. Two reviewers will independently extract the data. Reviewer Manager 5.3 software will be used for statistical analysis. RESULT: It will provide results on the short- and long-term efficacy and safety of synovectomy in total knee arthroplasty by various comprehensive assessments. CONCLUSION: This study will provide solid evidence on whether and when synovectomy treatment should be performed during total knee arthroplasty.

Interventional Efects of the Topical of "Sanse Powder" Essential Oils Nanoemulsion on Knee Osteoarthritis in Rats by Targeting the ERS/TXNIP/NLRP3 Signaling Axis.

Purpose: Our recent research is dedicated to finding effective drugs for the treatment of knee osteoarthritis (KOA) from traditional Chinese medicine and trying to make full use of modern science and technology to uncover the mechanisms and targets behind them. Synovial inflammation is one of the key pathological features of KOA, and a growing number of researchers realize that early intervention of synovial inflammation may be able to reverse disease progression. The close association of traditional natural products with modern nanotechnology may be important for improving the anti-synovitis efficacy. The purpose of our research was to explore the anti-synovitis mechanism of NEs-SP-EO that might be associated with the ERS/TXNIP/NLRP3 signalling axis. Methods: Chemical composition of "Sanse Powder" essential oil (SP-EO) and NEs-SP-EO were analyzed by GC-MS. NEs-SP-EO were prepared and characterized by nanoparticle tracking analysis, polydispersity index (PDI), zeta potential (ZP), ultraviolet-visible spectroscopy, and transmission electronic microscopy. The CCK8 assay for cell viability of NEs-SP-EO was performed on fibroblast-like synovial cells (FLSs) and the inflammatory environment was stimulated by LPS to explore the therapeutic mechanisms in vitro. Experiments of NEs-SP-EO in vivo were performed in male SD rats. Results: The GC-MS results showed that 30 compounds were present in SP-EO and 11 components of NEs-SP-EO were identified. The results also showed that the formulation of NEs-SP-EO exhibited suitable particle size, negative charge, and stable system. In vitro and vivo testing, NEs-SP-EO produced anti-synovitis efficacy by reduced the induction of the ERS/TXNIP/NLRP3 signaling axis as well as regulating the overproduction of IL-1ß, IL-18. Conclusion: We have developed a new type of essential oil nanoemulsion from "Sanse Powder" and demonstrated that it can managing synovitis of KOA. Besides, we have initially explored the anti-inflammatory mechanism that may be related to the ERS/TXNIP/NLRP3 signaling axis.

MicroRNA-10a-3p Improves Cartilage Degeneration by Regulating CH25H-CYP7B1-RORα Mediated Cholesterol Metabolism in Knee Osteoarthritis Rats.

Osteoarthritis (OA) is a worldwide degenerative joint disease that seriously impaired the quality of life of patients. OA has been established as a disease with metabolic disorder. Cholesterol 25-hydroxylase (CH25H) was proved to play a key role in cartilage cholesterol metabolism. However, the biological function and mechanism of CH25H in OA remains further investigation. Growing researches have proved the vital roles of miRNAs in OA progression. In this study, we screened out miR-10a-3p through high-throughput miRNA sequencing which may bind to CH25H. Molecular mechanism investigation indicated that miR-10a-3p is an upstream target of CH25H. Functional exploration revealed miR-10a-3p suppressed the inflammatory responses, cholesterol metabolism and extracellular matrix (ECM) degradation in primary chondrocytes. Moreover, rescue assays implied that miR-10a-3p reversed CH25H plasmids induced inflammatory cytokine production and ECM degradation. Furthermore, the OA rat model was established to explore the function of miR-10a-3p in vivo. The results showed that miR-10a-3p can recover the OA features through targeting CH25H/CYP7B1/RORα axis. In conclusion, these findings implied a crucial role of miR-10a-3p/CH25H/CYP7B1/RORα axis in OA, which may provide a promising therapeutic strategy for OA.

Chrysin Attenuates the NLRP3 Inflammasome Cascade to Reduce Synovitis and Pain in KOA Rats.

PURPOSE: Our recent reports have revealed that inhibiting NLRP3 activation reduces synovial inflammation and fibrosis in knee osteoarthritis (KOA). Synovial inflammation is involved the entire process of KOA and promotes the progression of KOA. Natural flavonoid Chrysin from Scutellariae Radix, a traditional Chinese medicine, exhibits multifarious biological activities and potentially has protective activity against osteoarthritis. However, the mechanism of Chrysin in the treatment of synovial inflammation remains elusive. The purpose of our research was to explore the anti-inflammatory effects of Chrysin on KOA, which was induced by monoiodoacetic acid (MIA) in rats by targeting the NLRP3 inflammasome in the hopes of identifying an effective drug to treat KOA. METHODS: The MIA-induced KOA model was used to evaluate the cold pain threshold and paw withdrawal threshold (PWT) of joints after MIA (40 mg/mL) injection into the knee joints. Microscopically, we used LPS (5 ug/mL) and ATP (4 mmol/L) to stimulate fibroblast-like synovial cells (FLSs) to explore the underlying mechanisms and effects of Chrysin. Two staining methods, H&E and Sirius Red, were applied to assess histopathological changes in synovial membranes. Cellular signal transduction was determined by qRT-PCR and WB. Cytokine expression (inflammatory cytokines and pain-related cytokines) was detected by ELISA. The degree of chronic inflammatory pain was evaluated by c-Fos immunofluorescence. RESULTS: The results showed that Chrysin not only attenuated synovial inflammation but also reduced the secretion of pain-related factors and increased the PWT and cold pain threshold in rats. Chrysin also inhibited NLRP3 inflammasome activation and increased IL-1ß levels to alleviate the synovitis. CONCLUSION: Chrysin can relieve knee synovial inflammation and improve pain behavior in KOA rats, which may be related to the ability of Chrysin to inhibit NLRP3 inflammasome activation. Therefore, Chrysin may be developed as a new drug for the treatment of KOA.

Casticin suppresses monoiodoacetic acid-induced knee osteoarthritis through inhibiting HIF-1α/NLRP3 inflammasome signaling.

Knee osteoarthritis (KOA) is a disabling chronic inflammatory disease that is closely associated with synovium tissue hypoxia and synovial fibrosis. Casticin, a compound purified from the Chinese herb Viticis Fructus, has been proved effective in preventing inflammation and fibrosis in previous studies. However, the effect of casticin on synovial fibrosis in KOA is not clear. In present study, we aimed to investigate how did casticin affect synovial fibrosis on monoiodoacetic acid (MIA)-induced KOA in rats. The MIA-induced knee osteoarthritis model and lipopolysaccharide (LPS) stimulated primary synovial fibroblasts inflammation model were established. Pathological and morphological changes in synovial tissue were observed by H&E and sirius red staining. The hypoxia of synovium was detected by pimonidazole staining and immunohistochemistry of hypoxia-inducible factors 1α (HIF-1α). The levels of nucleotide oligomerization domain-like receptor protein 3 (NLRP3) inflammasome components, fibrogenic markers (TGF-ß, COL1A1 and TIMP1) and inflammatory cytokines were examined by western blotting, qRT-PCR or ELISA in both KOA rat models and primary synovial fibroblasts. Our data suggested that casticin improved hypoxia and inflammation in synovium tissue, as well the synovial fibrosis in rats. Besides, casticin inhibited the activation of NLRP3 inflammasome in MIA-induced KOA rats and synovial fibroblasts. In conclusion, our findings demonstrated that casticin alleviated MIA-induced KOA by inhibiting of HIF-1α/NLRP3 inflammasome activation. Therefore, casticin could be a potential treatment strategy for KOA.

Vanillic Acid Reduces Pain-Related Behavior in Knee Osteoarthritis Rats Through the Inhibition of NLRP3 Inflammasome-Related Synovitis.

Objectives: Synovitis plays an important role in knee osteoarthritis (KOA) pain. The activation of the NOD-like receptor protein 3 (NLRP3) inflammasome in fibroblast-like synoviocytes (FLSs) promotes KOA development. In this study, we aimed to investigate whether vanillic acid (VA), a monomer derived from Chinese herbal medicines, could target NLRP3 inflammasome-related synovitis to reduce pain. Methods: Rats in the KOA and KOA + VA groups were injected with monosodium iodoacetate (MIA) in the knee to induce KOA. From day 14, the KOA + VA group was given VA at 30 mg/kg every day via gastric intubation. FLSs were collected from the synovial tissues. We examined both the protein and gene expression of caspase-1, apoptosis-associated speck-like protein with a caspase recruitment domain (ASC), NLRP3, components of the NLRP3 inflammasome, and interleukin-1ß (IL-1ß) and IL-18 in vivo and in vitro. Results: The upregulation of caspase-1, ASC, and NLRP3 in the KOA model were reduced by VA. VA also lowered the level of IL-1ß and IL-18 in the KOA model. In addition, VA relieved pain-related behavior of KOA model rats and downregulated the pain mediators CGRP, NGF, and TrkA in FLSs. Interestingly, we also observed reduced synovial fibrosis in the animal experiments. Conclusion: Our research showed that VA reduces synovitis and pain-related behaviors in a rat model of KOA, which provides the basis for further investigations into the potential therapeutic impact of VA in KOA.