Ghrelin prevents articular cartilage matrix destruction in human chondrocytes

Bergenin protects against osteoarthritis by inhibiting STAT3, NF-κB and Jun pathways and suppressing osteoclastogenesis

Osteoarthritis (OA) is a chronic degenerative disease characterized by articular cartilage destruction and subchondral bone reconstruction in the early stages. Bergenin (Ber) is a cytoprotective polyphenol found in many medicinal plants. It has been proven to have anti-inflammatory, antioxidant, and other biological activities, which may reveal its potential role in the treatment of OA. This study aimed to determine the potential efficacy of Ber in treating OA and explore the possible underlying mechanism through network pharmacology and validation experiments. The potential co-targets and processes of Ber and OA were predicted by using network pharmacology, including a Venn diagram for intersection targets, a protein‒protein interaction (PPI) network to obtain key potential targets, and GO and KEGG pathway enrichment to reveal the probable mechanism of action of Ber on OA. Subsequently, validation experiments were carried out to investigate the effects and mechanisms of Ber in treating OA in vitro and vivo. Ber suppressed IL-1β-induced chondrocyte apoptosis and extracellular matrix catabolism by inhibiting the STAT3, NF-κB and Jun signalling pathway in vitro. Furthermore, Ber suppressed the expression of osteoclast marker genes and RANKL-induced osteoclastogenesis. Ber alleviated the progression of OA in DMM-induced OA mice model. These results demonstrated the protective efficacy and potential mechanisms of Ber against OA, which suggested that Ber could be adopted as a potential therapeutic agent for treating OA.

Excessive mechanical loading promotes osteoarthritis development by upregulating Rcn2

Exposure of articular cartilage to excessive mechanical loading is closely related to the pathogenesis of osteoarthritis (OA). However, the exact molecular mechanism by which excessive mechanical loading drives OA remains unclear. In vitro, primary chondrocytes were exposed to cyclic tensile strain at 0.5 Hz and 10 % elongation for 30 min to simulate excessive mechanical loading in OA. In vivo experiments involved mice undergoing anterior cruciate ligament transection (ACLT) to model OA, followed by interventions on Rcn2 expression through adeno-associated virus (AAV) injection and tamoxifen-induced gene deletion. 10 μL AAV2/5 containing AAV-Rcn2 or AAV-shRcn2 was administered to the mice by articular injection at 1 week post ACLT surgery, and Col2a1-creERT: Rcn2flox/flox mice were injected with tamoxifen intraperitoneally to obtain Rcn2-conditional knockout mice. Finally, we explored the mechanism of Rcn2 affecting OA. Here, we identified reticulocalbin-2 (Rcn2) as a mechanosensitive factor in chondrocytes, which was significantly elevated in chondrocytes under mechanical overloading. PIEZO type mechanosensitive ion channel component 1 (Piezo1) is a critical mechanosensitive ion channel, which mediates the effect of mechanical loading on chondrocytes, and we found that increased Rcn2 could be suppressed through knocking down Piezo1 under excessive mechanical loading. Furthermore, chondrocyte-specific deletion of Rcn2 in adult mice alleviated OA progression in the mice receiving the surgery of ACLT. On the contrary, articular injection of Rcn2-expressing adeno-associated virus (AAV) accelerated the progression of ACLT-induced OA in mice. Mechanistically, Rcn2 accelerated the progression of OA through promoting the phosphorylation and nuclear translocation of signal transducer and activator of transcription 3 (Stat3).

Platelet-rich plasma alleviates knee arthritis in rats by inhibiting p65

Knee osteoarthritis (KOA) is a chronic joint disease characterized by the degeneration of articular cartilage. In this study, we explored the potential therapeutic effects of platelet-rich plasma (PRP) and identified molecular targets for treating KOA. A rat model of KOA was established via the Hulth method and primary knee joint chondrocytes were isolated to evaluate the effects of PRP and shRNA targeting p65 (sh-p65). ELISA was used to detect inflammatory factors, including IL-6, IL-1β, and TNF-α. HE staining, Safranin O/Fast Green staining and Masson staining were performed to evaluate the morphology of articular cartilage, followed by detection of p65, COL2A1, ACAN, MMP13, and ADAMTS5 expression. The proliferation and apoptosis of primary knee chondrocytes were detected by the CCK-8 assay and TUNEL staining, respectively. Treatment with either PRP or sh-p65 decreased IL-6, IL-1β, and TNF-α levels in the peripheral blood of KOA rats and chondrocyte culture supernatants, increased COL2A1 and ACAN levels, and decreased MMP13 and ADAMTS5 expression. Furthermore, administration of PRP or sh-p65 exerted protective effects on articular cartilage, enhanced the vitality of knee joint chondrocytes, and inhibited apoptosis. Collectively, PRP inhibited inflammation, promoted chondrocyte proliferation and cartilage matrix secretion, and induced cartilage regeneration by suppressing p65 expression; these effects allow PRP to alleviate KOA progression. P65-based targeted therapy administered in combination with PRP might be a promising strategy for treating KOA.

Potential Roles of Inflammation on Post-Traumatic Osteoarthritis of the Ankle

Post-traumatic osteoarthritis of the ankle (PTOA) is frequently observed following a debilitating consequence of intra-articular ankle fractures. Numerous risk factors contribute to the pathogenesis of PTOA, including articular incongruity, joint malalignment, and concomitant soft tissue damage. Despite attempts to restore joint anatomy and manage soft tissues to avoid long-term complications after intra-articular ankle fractures, the incidence of PTOA remains markedly elevated. Inflammatory processes triggered by intra-articular ankle fractures have emerged as potential instigators that expedite the progression of PTOA. Injury to the articular cartilage and subchondral bone may lead to the release of inflammatory mediators, which can contribute to cartilage degradation and bone resorption. This study provides a narrative review on the current knowledge concerning the association between inflammation and the development of PTOA following intra-articular ankle fractures. We also discuss novel therapeutic agents that target inflammatory pathways to impede the progression of post-traumatic osteoarthritis after intra-articular ankle fractures. These medication and interventions were summarized within this review article.

IRF1 governs the expression of SMARCC1 via the GCN5-SETD2 axis and actively engages in the advancement of osteoarthritis

Background

Osteoarthritis (OA) is a degenerative joint disease characterized by the breakdown of joint cartilage and underlying bone. Macrophages are a type of white blood cell that plays a critical role in the immune system and can be found in various tissues, including joints. Research on the relationship between OA and macrophages is essential to understand the mechanisms underlying the development and progression of OA.

Objective

This study was performed to analyze the functions of the IRF1-GCN5-SETD2-SMARCC1 axis in osteoarthritis (OA) development.

Methods

A single-cell RNA sequencing (scRNA-seq) dataset, was subjected to a comprehensive analysis aiming to identify potential regulators implicated in the progression of osteoarthritis (OA). In order to investigate the role of IRF1 and SMARCC1, knockdown experiments were conducted in both OA-induced rats and interleukin (IL)-1β-stimulated chondrocytes, followed by the assessment of OA-like symptoms, secretion of inflammatory cytokines, and polarization of macrophages. Furthermore, the study delved into the identification of aberrant epigenetic modifications and functional enzymes responsible for the regulation of SMARCC1 by IRF1. To evaluate the clinical significance of the factors under scrutiny, a cohort comprising 13 patients diagnosed with OA and 7 fracture patients without OA was included in the analysis.

Results

IRF1 was found to exert regulatory control over the expression of SMARCC1, thus playing a significant role in the development of osteoarthritis (OA). The knockdown of either IRF1 or SMARCC1 disrupted the pro-inflammatory effects induced by IL-1β in chondrocytes, leading to a mitigation of OA-like symptoms, including inflammatory infiltration, cartilage degradation, and tissue injury, in rat models. Additionally, this intervention resulted in a reduction in the predominance of M1 macrophages both in vitro and in vivo. Significant epigenetic modifications, such as abundant H3K27ac and H3K4me3 marks, were observed near the SMARCC1 promoter and 10 kb upstream region. These modifications were attributed to the recruitment of GCN5 and SETD2, which are functional enzymes responsible for these modifications. Remarkably, the overexpression of either GCN5 or SETD2 restored SMARCC1 expression in rat cartilages or chondrocytes, consequently exacerbating the OA-like symptoms.

Conclusion

This research postulates that the transcriptional activity of SMARCC1 can be influenced by IRF1 through the recruitment of GCN5 and SETD2, consequently regulating the H3K27ac and H3K4me3 modifications in close proximity to the SMARCC1 promoter and 10 kb upstream region. These modifications, in turn, facilitate the M1 skewing of macrophages and contribute to the progression of osteoarthritis (OA).

The Translational Potential of this Article

The study demonstrated that the regulation of SMARCC1 by IRF1 plays a crucial role in the development of OA. Knocking down either IRF1 or SMARCC1 disrupted the pro-inflammatory effects induced by IL-1β in chondrocytes, leading to a mitigation of OA-like symptoms in rat models. These symptoms included inflammatory infiltration, cartilage degradation, and tissue injury. These findings suggest that targeting the IRF1-SMARCC1 regulatory axis, as well as the associated epigenetic modifications, could potentially be a novel approach in the development of OA therapies, offering new opportunities for disease management and improved patient outcomes.

Role and molecular mechanism of ghrelin in degenerative musculoskeletal disorders

Ghrelin is a brain-gut peptide, and the first 28-peptide that was found in the gastric mucosa. It has a growth hormone (GH)-releasing hormone-like effect and can potently promote the release of GH from pituitary GH cells; however, it is unable to stimulate GH synthesis. Therefore, ghrelin is believed to play a role in promoting bone growth and development. The correlation between ghrelin and some degenerative diseases of the musculoskeletal system has been reported recently, and ghrelin may be one of the factors influencing degenerative pathologies, such as osteoporosis, osteoarthritis, sarcopenia and intervertebral disc degeneration. With population ageing, the risk of health problems caused by degenerative diseases of the musculoskeletal system gradually increases. In this article, the roles of ghrelin in musculoskeletal disorders are summarized to reveal the potential effects of ghrelin as a key target in the treatment of related bone and muscle diseases and the need for further research.

Decreased Synovial Fluid Ghrelin Level Is Associated With Acute Cartilage Injury in Patients With Anterior Cruciate Ligament Tear

Background

Ghrelin, an amino acid hormone secreted primarily from the stomach, can regulate bone metabolism, regulate inflammation via suppressing proinflammatory cytokines, and suppress expression of matrix metalloproteinases (MMPs).

Purpose

To measure synovial fluid levels of ghrelin in young patients with anterior cruciate ligament (ACL) tear to assess the role of ghrelin as a potential biomarker for cartilage injury.

Study Design

Controlled laboratory study.

Methods

This study included 120 patients who underwent ACL reconstructionbetween January 1, 2016, and May 31, 2021. We categorized 60 patients with acute cartilage injury (International Cartilage Regeneration & Joint Preservation Society grade 2 or 3) as the acute group and 60 patients with no acute cartilage injury as the nonacute group, with the healthy contralateral knee of each patient acting as the control group (n = 120). Synovial fluid samples were collected from the knees in the operating room before ACL reconstruction. We assessed the inflammatory biomarkers interleukin (IL)-6, MMP-1, MMP-9, and MMP-13, as well as serum ghrelin level and Mankin score, and results were compared between the 3 study groups with the Mann-Whitney U test.

Results

Lower serum ghrelin levels in the synovial fluid were found in the acute group compared with the nonacute group and healthy controls (232.4 vs 434.4 vs 421.5 pg/mL, respectively; P < .001). Ghrelin level in the synovial fluid was significantly and positively correlated with IL-6 (r = 0.4223; P < .0001), MMP-13 (r = 0.3402; P < .0001), and Mankin score (r = 0.1453; P = .0244).

Conclusion

In patients with ACL injury, ghrelin synovial fluid was significantly differently expressed in patients with cartilage injury and no cartilage injury.

Clinical Relevance

Ghrelin synovial fluid has the potential to be a biomarker to predict acute cartilage injury in patients with ACL injury.

Evaluation of ghrelin as a distinguishing marker for human articular cartilage-derived chondrocytes and chondroprogenitors

Purpose of the study

Cell-based therapeutics for articular cartilage repair primarily employed bone marrow-derived mesenchymal stem cells and chondrocytes. Research to overcome their limitation of formation of a functionally poor fibro-hyaline type of repair tissue led to the discovery of chondroprogenitors (CPCs), cartilage resident stem cells. These cells isolated by adhesion assay using fibronectin (FAA-CPs) and migration of progenitors from explants (MCPs) display higher chondrogenic and lower terminal differentiation potential. During in-vitro culture, chondrocytes tend to de-differentiate and acquire characteristics similar to stem cells, thus making it challenging to distinguish them from other cell groups. Ghrelin, a cytoplasmic growth hormone secretagogue, has been proposed to play a vital role in chondrogenesis, with reports of its higher expression in chondrocytes than BM-MSCs. The aim of this study was to compare the mRNA expression of Ghrelin between BM-MSCs, chondrocytes, FAA-CPs and MCP and the possibility of it serving as a distinguishing marker.

Methods

The four populations isolated from three human osteoarthritic knee joints were characterised by CD marker expression for positive (CD 90, CD73 and CD105) and negative (HLA-DR, CD34 and CD45) MSC markers and trilineage differentiation (adipogenic, osteogenic and chondrogenic) and subjected to qRT-PCR to assess Ghrelin's gene expression.

Results

This study showed that all groups exhibited similar expression of CD markers and multilineage potential. Though chondrocytes showed greater expression of Ghrelin, it was not statistically significant to classify it as a distinguishing marker between these cell populations.

Conclusion

Ghrelin does not serve to differentiate the subpopulations in terms of their mRNA expression. Further evaluation using their associated enzymes and receptors could provide valuable information to uncover their potential as unequivocal biomarkers.

Growth hormone secretagogues modulate inflammation and fibrosis in mdx mouse model of Duchenne muscular dystrophy

Introduction

Growth hormone secretagogues (GHSs) exert multiple actions, being able to activate GHS-receptor 1a, control inflammation and metabolism, to enhance GH/insulin-like growth factor-1 (IGF-1)-mediated myogenesis, and to inhibit angiotensin-converting enzyme. These mechanisms are of interest for potentially targeting multiple steps of pathogenic cascade in Duchenne muscular dystrophy (DMD).

Methods

Here, we aimed to provide preclinical evidence for potential benefits of GHSs in DMD, via a multidisciplinary in vivo and ex vivo comparison in mdx mice, of two ad hoc synthesized compounds (EP80317 and JMV2894), with a wide but different profile. 4-week-old mdx mice were treated for 8 weeks with EP80317 or JMV2894 (320 µg/kg/d, s.c.).

Results

In vivo, both GHSs increased mice forelimb force (recovery score, RS towards WT: 20% for EP80317 and 32% for JMV2894 at week 8). In parallel, GHSs also reduced diaphragm (DIA) and gastrocnemius (GC) ultrasound echodensity, a fibrosis-related parameter (RS: ranging between 26% and 75%). Ex vivo, both drugs ameliorated DIA isometric force and calcium-related indices (e.g., RS: 40% for tetanic force). Histological analysis highlighted a relevant reduction of fibrosis in GC and DIA muscles of treated mice, paralleled by a decrease in gene expression of TGF-β1 and Col1a1. Also, decreased levels of pro-inflammatory genes (IL-6, CD68), accompanied by an increment in Sirt-1, PGC-1α and MEF2c expression, were observed in response to treatments, suggesting an overall improvement of myofiber metabolism. No detectable transcript levels of GHS receptor-1a, nor an increase of circulating IGF-1 were found, suggesting the presence of a novel receptor-independent mechanism in skeletal muscle. Preliminary docking studies revealed a potential binding capability of JMV2894 on metalloproteases involved in extracellular matrix remodeling and cytokine production, such as ADAMTS-5 and MMP-9, overactivated in DMD.

Discussion

Our results support the interest of GHSs as modulators of pathology progression in mdx mice, disclosing a direct anti-fibrotic action that may prove beneficial to contrast pathological remodeling.

Regulation and therapy, the role of JAK2/STAT3 signaling pathway in OA: a systematic review

Osteoarthritis (OA) is a multifactorial chronic disease primarily characterized by the degeneration of articular cartilage. Currently, there is a lack of effective treatments for OA other than surgery. The exploration of the mechanisms of occurrence is important in exploring other new and effective treatments for OA. The current evidence shows that the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway plays a vital role in cytogenesis and is involved in OA progression. The terms "JAK2", "STAT3", and "Osteoarthritis"were used in a comprehensive literature search in PubMed to further investigate the relationship between the JAK2/STAT3 signaling pathway and OA. This review focuses on the role and mechanism of JAK2/STAT3 signaling in cartilage degradation, subchondral bone dysfunction, and synovial inflammation. In addition, this review summarizes recent evidence of therapeutic approaches to treat OA by targeting the JAK2/STAT3 pathway to accelerate the translation of evidence into the progression of strategies for OA treatment. Video abstract.

Quercetin prevents osteoarthritis progression possibly via regulation of local and systemic inflammatory cascades

Due to the lack of effective treatments, osteoarthritis (OA) remains a challenge for clinicians. Quercetin, a bioflavonoid, has shown potent anti-inflammatory effects. However, its effect on preventing OA progression and the underlying mechanisms are still unclear. In this study, Sprague-Dawley male rats were divided into five groups: control group, OA group (monosodium iodoacetate intra-articular injection), and three quercetin-treated groups. Quercetin-treated groups were treated with intragastric quercetin once a day for 28 days. Gross observation and histopathological analysis showed cartilage degradation and matrix loss in the OA group. High-dose quercetin-group joints showed failure in OA progression. High-dose quercetin inhibited the OA-induced expression of MMP-3, MMP-13, ADAMTS4, and ADAMTS5 and promoted the OA-reduced expression of aggrecan and collagen II. Levels of most inflammatory cytokines and growth factors tested in synovial fluid and serum were upregulated in the OA group and these increases were reversed by high-dose quercetin. Similarly, subchondral trabecular bone was degraded in the OA group and this effect was reversed in the high-dose quercetin group. Our findings indicate that quercetin has a protective effect against OA development and progression possibly via maintaining the inflammatory cascade homeostasis. Therefore, quercetin could be a potential therapeutic agent to prevent OA progression in risk groups.

Ghrelin is associated with anti-mullerian hormone levels in Chinese systemic lupus erythematosus

PROBLEM

Ghrelin has been thought of as a potential link between energy homeostasis and fertility. The aim of this study was to evaluate levels of ghrelin in obese and non-obese systemic lupus erythematosus (SLE) patients, and to reveal a possible association between ghrelin and Anti-Mullerian hormone (AMH) in SLE patients.

METHOD OF STUDY

One hundred SLE patients (50 obese and 50 non-obese subjects) at childbearing age and 100 age-matched healthy controls (50 obese and 50 non-obese subjects) were included. Ghrelin and leptin were examined by enzyme-linked immunosorbent assay. AMH was tested through electrochemiluminescence. Demographics, clinical and laboratory indicators were obtained from medical records.

RESULTS

Ghrelin levels were significantly lower in obese SLE patients than non-obese SLE patients (P = .000) and obese controls (P = .002). Non-obese SLE patients and non-obese controls had similar ghrelin levels. Ghrelin levels were correlated positively with AMH (r = .2683, P = .0070) in SLE patients. And ghrelin were negatively associated with leptin (r = -.1969, P = .0496) and BMI (r = - .2401, P = .0161).

CONCLUSION

Our results provide evidence for a potential relationship between ghrelin and AMH in SLE patients, indicating that ghrelin may play a part in energy homeostasis and ovarian damage of SLE patients.

The Protective Effect of Ginsenoside Rg1 on Apoptosis in Human Ankle Joint Traumatic Arthritis Chondrocytes

The ankle biomechanics is easily changed due to the acute injury of the tissue around the ankle joint and the damage of the ankle joint structure, such as ankle instability and joint surface imbalance. When the mechanical load of the ankle changes, it can cause ankle regeneration and remodeling processes such as cartilage loss, bone remodeling, and degenerative changes. The aim of this study was to investigate the effect and mechanism of ginsenoside Rg1 against interleukin-1β (IL-1β)-induced apoptosis in human articular chondrocytes (HACs). The apoptosis model of HAC cells was established by IL-1β induction, and then the HAC cells were cultured with different concentrations of Rg1. The protective effect of Rg1 on HAC cell apoptosis was investigated by detecting the changes of apoptosis and activity of PI3K/Akt/mitochondrial signaling pathway. The results showed that a specific concentration of Rg1 could promote the proliferation of IL-1β-induced HAC cells and inhibit apoptosis. At the same time, Rg1 treatment with specific concentration can reduce the content of reactive oxygen species (ROS) and malondialdehyde (MDA) in HACs and improve the related expression of mitochondrial membrane potential (MMP). Furthermore, qRT-PCR and western blot results showed that Rg1 could improve the low expression of Bcl-2 and inhibit the high expression of Bax, caspase-3, caspase-8, caspase-9, FasL, AIF, and Cyto c in IL-1β-induced cells. In summary, Rg1 can inhibit IL-1β-induced apoptosis of HAC cells by decreasing the activity of PI3K/Akt/mitochondrial signaling pathway, and Rg1 has a protective effect on apoptosis of HAC cells.

CircPan3 Promotes the Ghrelin System and Chondrocyte Autophagy by Sponging miR-667-5p During Rat Osteoarthritis Pathogenesis

This study aimed to investigate the potential roles of circRNAs in regulating osteoarthritis (OA)-related ghrelin synthesis, autophagy induction, and the relevant molecular mechanisms. Results showed that Col2a1, Acan, ghrelin, and autophagy-related markers expression were downregulated, while matrix metalloproteinase 13 (MMP13) and a disintegrin and metalloproteinase with thrombospondin motifs 5 (ADAMTS5) expressions increased in both IL-1β-induced rat chondrocytes and cartilage tissues of OA rats. A total of 130 circRNAs and 731 mRNAs were differentially expressed in IL-1β-induced rat chondrocytes. Among them, we found that circPan3 expression was significantly decreased in both cellular and animal OA models. CircPan3 directly targeted miR-667-5p. CircPan3 overexpression promoted Col2a1, Acan, ghrelin, beclin 1, and LC3-II expression but reduced MMP13 and ADAMTS5 expression in rat chondrocytes, whereas overexpression of miR-667-5p exhibited opposite effects on the above markers. Furthermore, we found that miR-667-5p bound directly to the 3′-UTR sequence of ghrelin gene. Moreover, the circPan3-induced alterations in chondrocytes were antagonized by miR-667-5p overexpression. Taken together, our findings demonstrate that circPan3 promotes ghrelin synthesis and chondrocyte autophagy via targeting miR-667-5p, protecting against OA injury. This study provided experimental evidence that circPan3/miR-667-5p/ghrelin axis might serve as targets of drug development for the treatment of OA.

The role of tendon derived stem/progenitor cells and extracellular matrix components in the bone tendon junction repair

Fibrocartilage enthesis is the junction between bone and tendon with a typical characteristics of fibrocartilage transition zones. The regeneration of this transition zone is the bottleneck for functional restoration of bone tendon junction (BTJ). Biomimetic approaches, especially decellularized extracellular matrix (ECM) materials, are strategies which aim to mimic the components of tissues to the utmost extent, and are becoming popular in BTJ healing because of their ability not only to provide scaffolds to allow cells to attach and migrate, but also to provide a microenvironment to guide stem/progenitor cells lineage-specific differentiation. However, the cellular and molecular mechanisms of those approaches, especially the ECM proteins, remain unclear. For BTJ reconstruction, fibrocartilage regeneration is the key for good integrity of bone and tendon as well as its mechanical recovery, so the components which can guide stem cells to a chondrogenic commitment in biomimetic approaches might well be the key for fibrocartilage regeneration and eventually for the better BTJ healing. In this review, we firstly discuss the importance of cartilage-like formation in the healing process of BTJ. Next, we explore the possibility of tendon-derived stem/progenitor cells as cell sources for BTJ regeneration due to their multi-differentiation potential. Finally, we summarize the role of extracellular matrix components of BTJ in guiding stem cell fate to a chondrogenic commitment, so as to provide cues for understanding the mechanisms of lineage-specific potential of biomimetic approaches as well as to inspire researchers to incorporate unique ECM components that facilitate BTJ repair into design.

Selective STAT3 Inhibitor Alantolactone Ameliorates Osteoarthritis via Regulating Chondrocyte Autophagy and Cartilage Homeostasis

Osteoarthritis (OA), which is identified by chronic pain, impacts the quality of life. Cartilage degradation and inflammation are the most relevant aspects involved in its development. Signal transducer and activator of transcription 3(STAT3), a member of the STATs protein family, is associated with inflammation. Alantolactone (ALT), a sesquiterpene lactone compound, can selectively suppress the phosphorylation of STAT3. However, the pharmacological effect of ALT on OA is still imprecise. In this study, IL-1β (10 ng/ml) was applied to cartilage chondrocytes, which were treated with different concentrations of Alantolactone for 24 h. The expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2(COX2), matrix metalloproteinases (MMPs) and thrombospondin motifs-5 (ADAMTS5) were detected by western blot. Protein expression of Collagen Ⅱ was observed by western blot, safranin O staining and immunofluorescence. Manifestation of autophagy related proteins such as autophagy-related gene-5 (ATG5), P62, LC3Ⅱ/Ⅰ and PI3K/AKT/mTOR-related signaling molecules were measured by western blot and autophagic flux monitored by confocal microscopy. Expression of STAT3 and NF-κB-related signaling molecules were evaluated by western blot and immunofluorescence. In vivo, 2 mg/kg ALT or equal bulk of vehicle was engaged in the destabilization of medial meniscus (DMM) mouse models by intra-articular injection, the degree of cartilage destruction was classified by Safranin O/Fast green staining. Our findings reported that the enhance of inflammatory factors containing iNOS, COX2, MMPs and ADAMTS5 induced by IL-1β could be ameliorated by ALT. Additionally, the diminish of Collagen Ⅱ and autophagy which was stimulated by IL-1β could be alleviated by ALT. Mechanistically, STAT3, NF-κB and PI3K/AKT/mTOR signal pathways might be involved in the effect of ALT on IL-1β-induced mouse chondrocytes. In vivo, ALT protected cartilage in the DMM mouse model. Overall, this study illustrated that ALT attenuated IL-1β-induced inflammatory responses, relieved cartilage degeneration and promoted impaired autophagy via restraining of STAT3 and NF-κB signal pathways, implying its auspicious therapeutical effect for OA.

The Protective Effects of Parathyroid Hormone (1-34) on Cartilage and Subchondral Bone Through Down-Regulating JAK2/STAT3 and WNT5A/ROR2 in a Collagenase-Induced Osteoarthritis Mouse Model

OBJECTIVE

To assess the effects of PTH (1-34) on bone and cartilage metabolism in a collagenase-induced mouse model of osteoarthritis (OA) and examine whether PTH (1-34) affects the expression of JAK2/STAT3 and WNT5A/ROR2 in this process.

METHODS

Eighteen 12-week-old male C57Bl/6 mice were randomly assigned into three groups as follows: sham group (Group A), the collagenase + saline injection group (Group B), and the collagenase + PTH (1-34) treatment group (Group C). Collagenase was injected (intra-articular) into the knee joint of Group B and C. The PTH (1-34)-treatment was started at 6 weeks after the operation and lasted for 6 weeks. Cartilage pathology was evaluated by gross visual, histological, and immunohistochemical assessments. Subchondral bone was evaluated by microcomputed tomography (micro-CT) and immunohistochemical analyses.

RESULTS

The OARSI macroscopic and microscopic scores of Group B were higher than those of Group A (P = 0.026; P = 0.002, respectively). Group C showed statistically significant differences in macroscopic and microscopic scores from Group B (P = 0.041; P = 0.008, respectively). The results showed that the Col-II and AGG expression levels in the cartilage tissue were significantly lower in Group B than Group A (P < 0.001; P = 0.008, respectively). The Col-II and AGG expression levels were significantly higher in Group C than Group B (P = 0.009; P = 0.014, respectively). MMP-13, ADAMTS-4, Caspase-3, P53, and Bax expression levels were significantly higher in Group B than the Group A (P < 0.001; P < 0.001; P = 0.04; P < 0.001; P = 0.005, respectively); however, the cartilage tissue in Group C showed significantly less ADAMTS-4, MMP-13, Caspase-3, P53, and Bax expression than Group B (P < 0.001, P < 0.001, P = 0.044; P = 0.002; P = 0.005, respectively). Over-expressed JAK2/STAT3 and WNT5A/ROR2 were observed in both cartilage and subchondral bone in this model; however, these changes were prevented by PTH (1-34) treatment. These parameters (bone mineral density, bone volume ratio, trabecular bone pattern factor, and structure model index) of micro-CT indicated subchondral bone loss and architecture changes in Group B, but improvements in these parameters in Group C.

CONCLUSIONS

PTH (1-34) exhibits protective effects on both cartilage and subchondral bone in a collagenase-induced OA mouse model, and it may be involved in down-regulating the expression of JAK2/STAT3 and WNT5A/ROR2.

Ghrelin attenuates drowning injury via dual effects on damage protection and immune repression

Background

Seawater drowning is the major cause of accidental injury and death. The current treatment could not essentially block the source of the damage due to the complex etiology. Therefore, it is urgent to clarify the detailed mechanisms and find effective therapeutic approaches.

Methods

We performed in vitro experiments to evaluate the damage of seawater drowning to lung epithelial cells. FACS, immunofluorescent staining, and western blot were used to detect the apoptosis. CCK-8 assay, Ki67 staining, and cell cycle analysis were used to assess the proliferation. The cytokine expression was determined by qRT-PCR and ELISA. Western blot and reporter assay were used for regulation mechanism study. For neutrophils development, Transwell assay and FACS were used for further investigation. Besides, in vivo study was performed with the seawater drowning model in rats.

Results

In this study, we found that seawater drowning induced mitochondria damage, which further accelerated epithelial cell apoptosis and repressed cell proliferation. Administration of ghrelin attenuated the mitochondria damage via reducing ROS generation, decreasing the concentration of calcium ion and ceremide, and promoting ATP production. Besides, exogenous ghrelin also rescued the cell survival inhibited by seawater simulants. Mechanically, ghrelin retrieved the influence of seawater via inhibiting NF-κB signaling activation, and agonist of NF-κB could offset the function of ghrelin. Besides, ghrelin reduced the expression of inflammatory factors and chemokines responsible for neutrophils activation and recruitment, by which ghrelin suppressed the immune response. The further in vivo experiments also indicated that ghrelin treatment restored the apoptosis promotion and inflammation activation function of seawater simulants, and further alleviated the lung tissue injury.

Conclusions

Our study revealed the dual effect of ghrelin on seawater drowning induced lung injury via damage protection and immune repression, providing new insights into drowning injury pathogenesis and therapeutic strategies.

Modified Simiaowan prevents articular cartilage injury in experimental gouty arthritis by negative regulation of STAT3 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Modified Simiaowan (MSW) is a traditional Chinese medicine formula that is composed of six herbs. It has been widely used in the treatment of gouty arthritis.

AIM OF THE STUDY

This study was designed to investigate the effect of MSW on gouty arthritis and explore the possible mechanisms.

MATERIAL AND METHODS

The rat gouty arthritis model was established by intra-articular injection of Monosodium Urate (MSU) crystal, and then treated with MSW for 5 days. The perimeter of the knee joints was measured in a time-dependent manner and serum samples were collected for the detection of TNF-α, IL-1β, and IL-6 protein levels by ELISA. The protein expressions of MMP-3, TIMP-3, STAT3, and p-STAT3 in cartilage tissues and C28/I2 cells were detected by Western blot, and the levels of proteoglycan in primary chondrocytes and cartilage tissues were determined by toluidine blue staining. In addition, AG490 and IL-6 were used in vitro to explore the function of IL-6/STAT3 pathway in the protective effect of MSU.

RESULTS

MSW reduced the joint swelling rate in gouty arthritis model and inhibited MSU induced up-regulation of IL-1β, TNF-α, and IL-6 protein levels in serum and synovial fluid. IL-1β induced an increase in p-STAT3 and MMP-3 protein expression in C28/I2 cells, as well as a decrease in TIMP-3. MSW serum inhibited the protein expression changes induced by IL-1β in vitro. Furthermore, inhibition of STAT3 signaling negated the effect of MSW serum on p-STAT3, MMP-3, and TIMP-3 protein levels in C28/I2 cells. MSW also increased the content of proteoglycan significantly both in vivo and in vitro.

CONCLUSION

Our data indicated that MSW protected rats from MSU-induced experimental gouty arthritis and IL-1β/IL-6/STAT3 pathway played an essential role in the protective effect of MSU against GA.

Oxidative stress and inflammatory response of ghrelin on myocardial and aortic tissues in insulin-resistant rats

OBJECTIVES

This study was designed to clarify the effects of ghrelin on myocardial and aortic tissues in insulin-resistant rats.

METHODS

Sprague-Dawley rats were divided into the following groups: control (Group 1), insulin resistance (IR, Group 2), ghrelin (Group 3) and IR+Ghrelin (Group 4) groups. Levels of HOMA-IR, fibronectin, hydroxyproline, collagen-1, collagen-3, matrix metalloproteinase-3, and matrix metalloproteinase-9, and tissue inhibitor of metalloproteinase-1, and oxidative stress parameters as protein carbonyl (PCO), lipid hydroperoxides (LHPs), malondialdehyde, total thiol were determined in myocardial tissue. Expressions of IL-6, NF-κB and TNF-α mRNAs were detected by RT-qPCR. Aorta tissue was stained Masson trichrome.

KEY FINDINGS

The HOMA-IR level decreased in the IR+Ghrelin group compared with the IR group (P < 0.001). The PCO and LHP concentrations were higher in the IR group compared with control rats (P < 0.05). The PCO level was reduced by ghrelin in the IR+Ghrelin group compared with the IR group (P < 0.001). Ghrelin treatment reduced the mRNA expression levels of IL-6, NF-κB and TNF-α in the IR+Ghrelin group compared with the IR group (P < 0.001). There was no difference among the groups in the histology of aortic tissue.

CONCLUSIONS

Ghrelin, a regulator of appetite and energy homeostasis, may be effective in regulating oxidative stress and the inflammatory response when impaired by IR. Therefore, ghrelin may reduce the risks of myocardial dysfunction in IR.

Safflower Seed Extract Attenuates the Development of Osteoarthritis by Blocking NF-κB Signaling

Although safflower seed extract exhibits pharmacological activity against various diseases, the effects of its individual compounds on osteoarthritis (OA) have not been elucidated. Here, we evaluated the effects of these extracts and their single compounds on OA. N-(p-Coumaroyl) serotonin and N-feruloyl serotonin, main components of safflower seed extract, were isolated by high-performance liquid chromatography. Under in vitro OA mimic conditions, the expression of the matrix metalloproteinases (MMPs) MMP3/13 and a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS) ADAMTS5 were reduced in mouse chondrocytes treated with safflower seed extract. Furthermore, the oral administration of safflower seed extract attenuated cartilage destruction in a mouse OA model induced by destabilization of the medial meniscus. N-(p-Coumaroyl) serotonin and N-feruloyl serotonin, but not serotonin, reduced MMP3, MMP13, and ADAMTS5 expression in IL-1β-treated chondrocytes. Additionally, they significantly blocked the nuclear factor-κB (NF-κB) pathway by inhibiting IκB degradation and p65 phosphorylation. Our results suggest that safflower seed extract and its single compounds can attenuate cartilage destruction by suppressing MMP and ADMATS5 expression. The anti-arthritic effects are mediated by NF-κB signaling and involve the inhibition of IκB degradation and p65 phosphorylation. These results indicate that safflower seed extract may serve as a novel therapeutic agent against OA.

Quercetin suppresses apoptosis of chondrocytes induced by IL-1β via inactivation of p38 MAPK signaling pathway

The objective of the present study was to investigate the effect of quercetin and evaluate its protective effect on articular cartilage in patients with osteoarthritis (OA), by intervening the p38 pathway. The target factors of quercetin protecting articular cartilage in patients with OA were predicted scientifically and analyzed to predict the possible pathways by using network pharmacology. A pathway predicted to be closely associated with osteoarthritis was chosen for experimental verification in in vitro cells. The optimal intervention drug concentrations were selected by the of Cell Cycle Kit-8 assay, osteoarthritis and inflammatory factors relevant to osteoarthritis, interleukin-1β and tumor necrosis factor-α, were tested by of enzyme-linked immunosorbent assay, and the expression of relevant proteins and mRNA of the p38 signaling pathway was tested by reverse transcription-quantitative PCR and western blotting, following quercetin intervention. It was found that quercetin, at the concentration of 100 umol/l, can decrease inflammatory factors relevant to OA, inhibit the expression of p38, matrix metalloprotease 13 and ADAMTS in the pathway, and promote the expression of collagen Ⅱ. Therefore, it is postulated that quercetin can lower the expression of inflammatory factors in cartilage for the prevention and treatment of OA, and the expression level of relevant factors can be changed positively by blocking the p38 MAPK signaling pathway. Thus, quercetin can promote the repair of degenerative chondrocytes and protect articular chondrocytes.

Inflammation and tissue homeostasis: the NF-κB system in physiology and malignant progression

Disruption of tissue function activates cellular stress which triggers a number of mechanisms that protect the tissue from further damage. These mechanisms involve a number of homeostatic modules, which are regulated at the level of gene expression by the transactivator NF-κB. This transcription factor shifts between activation and repression of discrete, cell-dependent gene expression clusters. Some of its target genes provide feedback to NF-κB itself, thereby strengthening the inflammatory response of the tissue and later terminating inflammation to facilitate restoration of tissue homeostasis. Disruption of key feedback modules for NF-κB in certain cell types facilitates the survival of clones with genomic aberrations, and protects them from being recognized and eliminated by the immune system, to enable thereby carcinogenesis.

Sinomenine contributes to the inhibition of the inflammatory response and the improvement of osteoarthritis in mouse-cartilage cells by acting on the Nrf2/HO-1 and NF-κB signaling pathways

Pathological changes, such as articular cartilage degeneration, destruction, and hyperosteogeny, are regarded as the main features of osteoarthritis (OA). Sinomenine (SIN) is a monomeric component purified from the plant Sinomenium acutum which has been found to have anti-inflammatory effects, however, the mechanism of action of SIN on OA is not clear. In this study, we evaluated whether SIN could regulate the inflammatory response induced by interleukin (IL)-1β and improve outcomes in the instability model of OA (medial meniscus mice (DMM)) by acting on the Nrf2/HO-1 and NF-κ B signaling pathways in chondrocytes. From our experiments, which include Griess reaction, ELISA, Western blot, and immunofluorescence, we found that SIN not only down-regulated the expression of pro-inflammatory factors induced by IL-1β, including; inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), nitricoxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor alpha (TNF-α) and interleukin-6 (IL-6), but also decreased the production of IL-1β-induced cartilage matrix catabolic enzymes including; ADAMTS-5 and MMPs, in mouse chondrocytes. In addition, the degradation of aggrecan and type II collagen protein in the extracellular matrix (ECM) stimulated by IL-1β was reversed. Most importantly, we have revealed for the first time that in OA, SIN inhibited the inflammatory response and ECM degradation by activating the Nrf2/HO-1 signaling pathways and inhibiting NF-κB activity in mouse-cartilage cells. In in vivo experiments, SIN treatment helped to improve the cartilage destruction in OA model mice. In conclusion, this study has demonstrated that SIN inhibits the IL-1β-induced inflammatory response and cartilage destruction by activating the Nrf2/HO-1 signaling pathway and inhibiting the NF-κB signaling pathway in mouse chondrocytes, suggesting a new use for SIN in the treatment of OA.

Enhancement of the chondrogenic differentiation of mesenchymal stem cells and cartilage repair by ghrelin

Transforming growth factor beta (TGF-β) is commonly utilized in chondrogenic differentiation protocols, but this often results in incomplete maturation of the derived chondrocytes. Gene expression analysis, quantitation of sulfated glycosaminoglycan and collagen, and histological staining were performed to assess the effects of ghrelin. The signaling pathways involved were investigated with inhibitors or targeted by shRNAs. Joint cavity delivery of TGF-β with or without ghrelin, within a rat cartilage defect model was performed to evaluate the in vivo effects of ghrelin. Ghrelin dramatically enhanced gene expression levels of SOX9, ACAN, and COL II and resulted in increased synthesis of sulfated glycosaminoglycan (sGAG) and collagen in vitro. Combined treatment with TGF-β and ghrelin synergistically enhanced the phosphorylation of ERK1/2 and DMNT3A, which accounted for increased expression of chondrogenic genes. Delivery of ghrelin in combination with TGF-β after MSC implantation within a rat osteochondral defect model significantly enhanced de novo cartilage regeneration, as compared to delivery with TGF-β alone. In conclusion, ghrelin could significantly enhance MSC chondrogenic differentiation in vitro and can also enhance cartilage regeneration in vivo when used in combination with TGF-β. © 2019 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 37:1387-1397, 2019.

Attenuated levels of ghrelin in synovial fluid is related to the disease severity of ankle post-traumatic osteoarthritis

Post-traumatic osteoarthritis (PTOA) of ankle joints results in pain and reduced joint function. Ghrelin, a 28-amino-acid polypeptide, has been previously identified as the first cognate natural ligand that binds to the growth hormone secretagogue receptor. In the present study, ghrelin has been validated to exert cartilage-protective and anti-inflammatory effects. The current study was aimed at investigating the potential role of the levels of serum and synovial fluid (SF) ghrelin on the severity of disease in patients suffering from ankle PTOA. Ninety-seven patients with ankle osteoarthritis who received an arthroscopical examination and debridement or replacement of the ankle joint were included in the study cohort. Meanwhile, 95 healthy individuals (whose age and sex were matched) who received periodic body checkups were enrolled as healthy controls. Enzyme-linked immunosorbent assay (ELISA) was used to analyze the ghrelin levels in serum and SF. SF was also probed for cartilage degradation enzyme matrix metalloproteinases-3 (MMP-3) and tumor necrosis factor alpha (TNF-α), which is a known pro-inflammatory cytokine. The clinical evaluation was carried out using the American Orthopedic Foot and Ankle Society (AOFAS) ankle-hindfoot rating scale and visual analogue scale (VAS). The radiographic severity was evaluated using the modified Kellgren-Lawrence (K-L) grading system. We scored for the modified Mankin's score to depict histopathological changes due to cartilage lesions. The diagnostic relevance of the ghrelin concentrations in the prediction of the radiographic grading (in comparison with MMP-3 and TNF-α) was evaluated by calculating the area under the curve of the receiver operating characteristic (ROC) curve. The serum abundance of ghrelin was not significantly altered between ankle PTOA patients and healthy controls. SF ghrelin was negatively correlated with radiographic progression determined by modified ankle K-L grades. In addition SF ghrelin concentrations were negatively related to VAS scores, and positively associated with AOFAS ankle-hindfoot rating. Moreover, SF ghrelin was inversely proportional to the expressions of MMP-3 and TNF-α. ROC analysis curve demonstrated that ghrelin serves as a favorable marker for the diagnosis of radiographic severity by modified ankle K-L grade. The ghrelin concentration in SF is negatively proportional to disease progression in patients suffering from ankle PTOA. Local administration of ghrelin may function as a decent adjuvant therapy to delay the progress of ankle PTOA. © 2019 BioFactors, 45(3):463-470, 2019.

A Novel Rat Model of Patellofemoral Osteoarthritis Due to Patella Baja, or Low-Lying Patella

Background

Patella baja, or patella infera, consists of a low-lying patella that results in a limited range of motion, joint pain, and crepitations. Patellofemoral joint osteoarthritis (PFJOA) is a subtype OA of the knee. This study aimed to develop a reproducible and reliable rat model of PFJOA.

Material/Methods

Three-month-old female Sprague-Dawley rats (n=24) included a baseline group (n=8) that were euthanized at the beginning of the study. The sham group (n=8), and the patella ligament shortening (PLS) group (n=8) were euthanized and evaluated at ten weeks. The PLS model group (n=8) underwent insertion of a Kirschner wire under the patella tendon to induce patella baja. At ten weeks, the sham group and the PLS group were compared using X-ray imaging, macroscopic appearance, histology, immunohistochemistry, TUNEL staining for apoptosis, and micro-computed tomography (micro-CT). The patella height was determined using the modified Insall-Salvati (MIS) ratio.

Results

The establishment of the rat model of patella baja in the PLS group at ten weeks was confirmed by X-ray. In the PLS group, patella volume, sagittal length, and cross-sectional area were significantly increased compared with the sham group. The PFJ showed typical lesions of OA, confirmed macroscopically and histologically. Compared with the sham group, in the rat model of PFJOA, there was increased cell apoptosis, and immunohistochemistry showed increased expression of biomarkers of osteoarthritis, compared with the sham group.

Conclusions

A rat model of PFJOA was developed that was confirmed by changes in cartilage and subchondral bone.

Protective effects of calcitonin on IL-1 stimulated chondrocytes by regulating MMPs/TIMP-1 ratio via suppression of p50-NF-κB pathway

The aim of this study was to investigate the effects and underlying mechanisms of calcitonin (CT) on interleukin 1 beta (IL-1β) stimulated human chondrocytes. IL-1β (5 ng/mL) was added into chondrocytes to establish osteoarthritis (OA) model in vitro. Different concentrations of CT (0.1, 0.5, 1, 5, 10 and 50 nM) were used for treating IL-1β stimulated chondrocytes. Cell viability of chondrocytes was measured by cell counting kit-8 (CCK8) method. Western blotting was performed to evaluate the expression of matrix metalloproteinases (MMP-13), tissue inhibitor of metalloproteinases 1 (TIMP-1), p50 and p38. CT inhibited MMP-13 expression and promoted TIMP-1 expression in the IL-1β stimulated human chondrocytes. The CT-mediated alteration of MMP-13/TIMP-1 ratio was partially attributed to the inactivation of the p50- nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) pathway by suppressing p50 in IL-1β stimulated chondrocytes. CT might play a protective role in IL-1β stimulated OA model via p50-NF-κB pathway.

Abbreviations: CT: calcitonin; IL-1β: interleukin-1β; MMP-13: matrix metalloproteinases-13; TIMP-1: tissue inhibitors of metalloproteinases-1.

Erythromycin acts through the ghrelin receptor to attenuate inflammatory responses in chondrocytes and maintain joint integrity

Osteoarthritis (OA) is a prevalent disease characterized by chronic joint degeneration and low-grade localized inflammation. There is no available treatment to delay OA progression. We report that in human primary articular chondrocytes, erythromycin, a well-known macrolide antibiotic, had the ability to inhibit pro-inflammatory cytokine Interleukin 1β (IL-1β)-induced catabolic gene expression and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) activation. Furthermore, erythromycin inhibited monosodium iodoacetate (MIA)-induced joint inflammation and cartilage matrix destruction in mice, an arthritis model that reflects the inflammatory and cartilage matrix loss aspects of OA. EM900, an erythromycin-derivative lacking antibiotic function, had the same activity as erythromycin in vitro and in vivo, indicating distinct anti-inflammatory and antibiotic properties. Using an antibody against erythromycin, we found erythromycin was present on chondrocytes in a dose-dependent manner. The association of erythromycin with chondrocytes was diminished in ghrelin receptor null chondrocytes, and administration of the ghrelin ligand prevented the association of erythromycin with chondrocytes. Importantly, the anti-inflammatory activity of erythromycin was diminished in ghrelin receptor null chondrocytes. Moreover, erythromycin could not exert its chondroprotective effect in ghrelin receptor null mice, and the loss of ghrelin receptor further augmented joint damage upon MIA-injection. Therefore, our study identified a novel pharmacological mechanism for how erythromycin exerts its chondroprotective effect. This mechanism entails ghrelin receptor signaling, which is necessary for alleviating inflammation and joint destruction.