The role of IL-1β in the bone loss during rheumatic diseases

Exploring the pharmacokinetic, toxicity and anti-arthritic activity of bioactive polyphenols to mitigate the HIF-regulated angiogenic-pannus growth in rheumatoid arthritis

Current therapies for rheumatoid arthritis, including anti-inflammatory agents and immunomodulators, primarily target common inflammatory mechanisms. However, the efficacy of most bioactive compounds claimed to possess anti-arthritic properties remains mechanistically unproven, particularly against progressive conditions like pannus development. This study investigates the pharmacokinetics, toxicity, and impact of reported anti-arthritic polyphenols on HIF-regulated pannus development in rheumatoid arthritis through in silico and in vitro approaches. Eighty bioactive compounds with documented anti-arthritic properties were selected from the literature and subjected to sequential evaluation of pharmacodynamic and pharmacokinetic activity. The study identified five promising candidates qualified to perform in vivo toxicity and in vitro biochemical assays. Toxicity testing using Galleria mellonella larvae indicated dose-dependent effects on the midgut, with no mortality observed at doses up to 2000 mg/kg body weight. In vitro assays, including antioxidant and anti-inflammatory evaluations, further validated the therapeutic potential of these compounds. Compounds that satisfied all predictive criteria were subjected to molecular interaction analysis against hub-gene targets implicated in HIF-regulated angiogenesis in rheumatoid arthritis. RA-associated proteins were identified from NCBI-GEO and DisGeNET (GWAS) databases. Functional annotation and protein-protein interaction analysis identified IL-6, IL-1β, HIF-1α, PPARG, and TIMP1 as key hub targets. Molecular docking using PyRx revealed the binding affinities of the selected bioactive compounds against these targets. These findings suggest that the screened bioactive polyphenols exhibit low toxicity and hold potential as regulators of HIF-mediated angiogenesis in rheumatoid arthritis, offering a novel therapeutic approach for progressive disease management.

The entrenchment of NLRP3 inflammasomes in autoimmune disease-related inflammation

Autoinflammation and autoimmunity are almost "opposite" phenomena characterized by chronic activation of the immune system, 'innate' in the first and 'adaptive' in the second, leading to inflammation of several tissues with specific protean effectors of tissue damage. The mechanism of involvement of multiprotein complexes called 'inflammasomes' within autoimmune pictures, differently from autoinflammatory conditions, is yet undeciphered. In this review we provide a comprehensive overview on NLRP3 inflammasome contribution into the pathogenesis of some autoimmune diseases. In response to autoantibodies against nucleic acids or tissue-specific antigens the NLRP3 inflammasome is activated within dendritic cells and macrophages of patients with systemic lupus erythematosus. Crucial is NLRP3 inflammasome to amplify tissue inflammation with interleukin-1 overexpression and matrix metalloproteinase production at the joint level in rheumatoid arthritis. A deregulated NLRP3 inflammasome activation occurs in the serous acini of salivary and lacrimal glands prone to Sjogren's syndrome, but also in the inflammatory process involving endothelial cells, leucocyte recruitment, and platelet plugging of vasculitides. Furthermore, organ-specific autoimmune diseases such as thyroiditis and hepatitis may display hyperactive NLRP3 inflammasomes at the level of resident immune cells within thyroid or liver, respectively. Therefore, it is not unexpected that preclinical studies have shown how specific inflammasome inhibitors may significantly overthrow the severity of different autoimmune diseases and slow down their trend towards an ominous progression. Specific markers of inflammasome activation could also reveal subclinical inflammatory components escaping conventional diagnostic approaches or improve monitoring of autoimmune diseases and personalizing their treatment.

Signaling pathways of pro-IL-1β production induced by mechanical stress in gingival epithelial cells

OBJECTIVES

Mechanical stress on the teeth and alveolar bone caused by bruxism, orthodontics, and implants affects the periodontal tissues, causing gingival recession and alveolar bone resorption, and entire body, including the heart and vascular system. Although the same forces exerted on the alveolar bone and teeth are exerted on gingival epithelial cells, little is known about the effects of mechanical stress on these cells. This study investigated the effects of mechanical stress on gingival epithelial cells.

METHODS

Ca9-22 cells (human gingival epithelial cells) were used. They were seeded onto the silicone and stretched cyclically. Mechanical stress-stimulated Ca9-22 cells were evaluated for pro-inflammatory interleukin (pro-IL)-1β production using Western blotting and analyzed to assess the phosphorylation level of intracellular signaling molecules.

RESULTS

Mechanical stress induced pro-IL-1β upregulation in Ca9-22 cells, which was significantly inhibited by ruthenium red. Ruthenium red significantly inhibited mechanical stress-induced phosphorylation of focal adhesion kinase (FAK), P130cas, and extracellular signal-regulated kinase 1 and 2 (ERK1/2) induced by mechanical stress. Additionally, Y15 significantly inhibited the upregulation of pro-IL-1β expression and phosphorylation of FAK, P130cas, and ERK1/2 stimulated by mechanical stress.

CONCLUSIONS

In Ca9-22 cells, mechanical stress may increase pro-IL-1β production via mechanosensitive ion channels and FAK. These findings revealed the mechanisms of inflammation in mechanically-stressed Ca9-22 cells and may aid in the development of therapeutic approaches to prevent bone resorption.

Carboxyaminotriazole: A bone savior in collagen-induced arthritis-Halting osteoclastogenesis via interleukin-1β downregulation

AIMS

Rheumatoid arthritis (RA), a prevalent autoimmune disease, features inflammation and bone erosion, correlating with osteoclast hyperactivation and enhanced responsiveness to inflammatory factors. Reducing osteoclast formation and inflammatory mediator expression might avert bone erosion in RA. Carboxyaminotriazole (CAI) holds potential for treating autoinflammatory disorders and impeding cancer-related bone metastases. Yet, its bone-protective role and mechanism remain elusive. This study targets to explore the impacts and underlying mechanisms of CAI in preventing bone erosion in RA.

MATERIALS AND METHODS

A collagen-induced arthritis (CIA) rat model was utilized to evaluate the anti-RA potential of CAI. CCK-8, TRAP staining, TRAP activity assay, pit formation assay, RT-qPCR, Western blotting, immunofluorescence, and ELISA, were conducted to assess the effects and potential mechanisms of CAI in the management of RA.

KEY FINDINGS

CAI not only reduces inflammatory symptoms, but it also offers superior bone protection compared to methotrexate (MTX) and works synergistically with MTX, the preferred anchoring agent for the treatment of RA. In vitro studies show that CAI inhibits osteoclast differentiation and function, as well as the expression of specific genes, by inhibiting NF-κB/MAPK pathways and reducing IL-1β levels. The deletion of Il-1 and the application of IL-1β inhibitors suggest that CAI retards osteoclastogenesis through the downregulation of IL-1β.

SIGNIFICANCE

CAI may have therapeutic value in treating RA-related bone erosion, likely due to its inhibition of overactive osteoclasts by suppressing the NF-κB/MAPK pathways and the subsequent expression of IL-1β.

Natural and synthetic potential drug leads for rheumatoid arthritis probing innovative target: mitochondrial dysfunction and NLRP3 inflammasome activation

Rheumatoid arthritis (RA) is an autoimmune, chronic, inflammatory disease characterized by synovial hyperplasia, bone erosion, progressive joint deterioration, and excruciating joint pain. Worldwide RA prevalence is approximately 0.1-2%, affecting women and elderly population. Limited knowledge of disease pathogenesis causes hindrance in diagnosis and treatment of RA. Deep investigation of RA pathogenesis is deemed, for the development of novel therapies. Among diverse targets for RA, proper functioning of mitochondria is essential for endurance of synovial cells and chondrocytes. Once mitochondria are damaged, these affect immune and non-immune cells in terms of their activation, survival, and differentiation prima to occurrence of RA. An innate immune complex, NLRP3 (NOD-like receptor family pyrin domain-containing 3) inflammasome plays pivotal role in RA pathogenesis through its control on the synthesis of pro-inflammatory cytokines (IL-1β & IL-18) and induction of pyroptotic cell death. Mitochondrial dysfunction is the possible primary cause of NLRP3 inflammasome activation, leading to inflammation and joint destruction in RA. This review emphasizes that how mitochondrial dysregulation affect NLRP3 inflammasome activation and contribute to RA's inflammatory cascade. It also investigates synthetic and natural substances including Berberine, Ebselen, and Resveratrol that have emerged as promising drug leads for RA by modulating mitochondrial dysfunction and inhibiting NLRP3 inflammasome activation. Furthermore, it concise the evidences from RA-associated animal models explaining beneficial impact of various therapeutic agents in attenuation of inflammation and deterioration of bone and cartilage. Hence, the current review stresses molecular pathways in mitochondrial dynamics and NLRP3 inflammasome activation, as an approach to hone RA treatment goals.

IL-1 Receptor Antagonist Anakinra Inhibits the Effect of IL-1β- Mediated Osteoclast Formation by Periodontal Ligament Fibroblasts

Rheumatoid arthritis and periodontitis are comorbidities that share mutual pathways. IL-1β is a pro-inflammatory cytokine that plays a crucial role in both diseases. One of the treatment options for rheumatoid arthritis is the use of an IL-1 receptor antagonist (IL-1RA) such as anakinra. Anakinra tempers the disease by decreasing bone resorption and it could possibly stimulate bone formation. Here, we investigate the effect of anakinra in a periodontal disease setting on osteoclastogenesis by co-culturing periodontal ligament fibroblasts (PDLFs) and peripheral blood mononuclear cells (PBMCs) that contain monocytes, a source of osteoclast precursors, as well as by culturing PBMCs alone. The effect of anakinra on PDLF-mediated osteogenesis was studied under mineralization conditions. To mimic a chronic infection such as that prevalent in periodontitis, 10 ng/mL of IL-1β was added either alone or with 10 µg/mL of anakinra. Osteoclastogenesis experiments were performed using co-cultures of PDLF and PBMCs and PBMCs only. Osteoclastogenesis was determined through the formation of multinucleated cells in co-cultures of PDLF and PBMCs, as well as PBMCs alone, at day 21, and gene expression through qPCR at day 14. Osteogenesis was determined by measuring alkaline phosphatase activity (ALP) per cell at day 14. Anakinra is effective in downregulating IL-1β mediated leukocyte clustering and osteoclastogenesis in the co-cultures of both PDLF and PMBCs and PBMCs alone. Gene expression analysis shows that IL-1β increases the expression of the osteoclastogenic marker RANKL and its own expression. This higher expression of IL-1β at the RNA level is reduced by anakinra. Moreover, IL-1β downregulates OPG expression, which is upregulated by anakinra. No effects of anakinra on osteogenesis were seen. Clinically, these findings suggest that anakinra could have a beneficial systemic effect on periodontal breakdown in rheumatoid arthritis patients taking anakinra.

Time-restricted feeding alleviates arthritis symptoms augmented by high-fat diet

Rheumatoid arthritis (RA) affects approximately 1% of the global population. Its hallmark symptoms include severe pain and joint stiffness, which significantly diminish life quality. RA's development is influenced by multiple factors including unhealthy lifestyle habits. Calorie-rich diets, particularly those high in fat and resulting in obesity, are associated with RA and exacerbate its symptoms. Consequently, dietary modifications are recommended as a complementary treatment. However, adherence is often low due to the restrictive changes required in nutrient composition or caloric intake. Our previous findings indicate that time-restricted feeding (TRF) benefits leukocyte rhythm and mitigates autoimmune responses. In this study we explored the impact of TRF on the severity of K/BxN serum-transfer arthritis (STA) in mice subjected to high-fat diet. Three feeding schedules were implemented: a control (Ctrl) with constant access to standard chow, a high-fat diet group (HF) with ad libitum food access, and a high-fat TRF group (HF-TRF) with a 10-hour feeding window during the active phase. After four weeks of conditioning, STA was induced. Although macroscopic markers of inflammation did not differ between the Ctrl and HF groups, histological analysis revealed increased inflammation in HF mice, including expanded edema, pannus formation, bone erosion, elevated synovial neutrophil infiltration and serum leptin levels. Importantly, all these inflammatory markers were significantly reduced in the HF-TRF group, along with synovial IL-1β and monocyte/macrophage counts. Our results indicate that TRF can diminish the impact of a high-fat diet on STA severity, potentially serving as a preventive method and a sustainable therapeutic support for RA management.

Tideglusib enhances ALP activity and upregulates RANKL expression in Osteoblast-macrophage Co-cultures within a 3D collagen scaffold

OBJECTIVES

Tideglusib (Tx) is known for its osteogenic potential, yet its effects on the interplay between osteoblasts and M1 macrophages remain underexplored. This in vitro study aimed to isolate and evaluate both the individual and combined roles of M1 macrophages and osteoblasts in macrophage differentiation and osteoblast function, specifically focusing on how these interactions influence protein expression of osteogenesis and osteoclastogenesis in the presence or absence of Tx.

METHODS

Osteoblast and macrophage cells were co-cultured in direct contact for 24 and 48 h, with or without the presence of Tx. ALP activity, the expression of inflammatory-related genes using RT-qPCR, and histological analyses were performed.

RESULTS

Co-culturing osteoblasts and M1 macrophages with Tx increased alkaline phosphatase production, indicative of enhanced osteoblast activity. Histological assessments revealed that Tx treatment contributed to the stability and maintenance of cell morphology within the scaffold, suggesting a supportive environment for cell viability and function. Tx significantly reduced the expression of pro-inflammatory markers, such as TNF-α and IL-1β, in the co-culture at both 24 and 48 h Tx also effectively inhibited osteoclastogenic differentiation in macrophages, thereby diminishing their pro-inflammatory phenotype.

CONCLUSIONS

Tx increased ALP activity and produced a significant up-regulation of RANKL expression, indicating enhanced osteoblast differentiation and osteoclast activation. Tx mitigates macrophage-driven inflammation.

CLINICAL SIGNIFICANCE

Tx may enhance bone regeneration by modulating inflammatory responses and preserving cell integrity.

Exploring the Potential of Moringa oleifera in Managing Bone Loss: Insights from Preclinical Studies

Moringa oleifera (MO) is renowned for its remarkable medicinal uses, supported by claims across various cultures and growing scientific evidence. Preclinical experimental evidence indicated that MO may effectively reduce bone loss and promote bone remodelling through its effects on osteoclasts and osteoblasts. In vivo studies demonstrated that MO enhances critical aspects of bone health, such as bone volume, trabecular thickness and overall bone density. Furthermore, MO positively influenced bone biomarkers including alkaline phosphatase and procollagen type 1 N-terminal propeptide, reflecting improved bone formation. Additionally, in vitro and ex vivo studies revealed that MO boosted bone regeneration, stimulated osteoblast activity and reduced inflammation. In terms of mechanisms, MO may modulate signalling pathways related to bone metabolism, such as BMP2, PI3K/Akt/FOXO1, p38α/MAPK14 and RANKL/RANK//OPG pathways. This evidence provides a strong foundation for future clinical research and potential therapeutic applications in managing and preventing bone loss conditions.

Helicobacter pylori-Related Chronic Gastritis as a Risk Factor for Lower Bone Mineral Density

We evaluated the role of Helicobacter pylori (H. pylori)-related chronic gastritis in the development of osteoporosis in a population-based study. A total of 1690 subjects in the cohort of the Research on Osteoarthritis/ osteoporosis Against Disability (ROAD) were investigated, and the association between gastritis and osteoporosis was evaluated by the presence of serologically assessed H. pylori-related chronic gastritis and its stage, based on H. pylori antibody titer and pepsinogen. The presence of the gastritis was associated with significantly lower bone mineral density (BMD) assessed by dual-energy x-ray absorptiometry and a significant risk of lower BMD was observed in femoral neck (adjusted odds ratio [OR]: 0.78, 95% confidence interval [CI]: 061-0.99). The progression of the gastritis appeared to further increase the risk. In the stage of non-atrophic gastritis, the risk of lower BMD was significantly high, especially in a subgroup with higher gastritis activity in the femoral neck (adjusted OR: 0.61, 95% CI: 0.42-0.89). Meanwhile, in the stage of atrophic gastritis, the highest and significant risk of lower BMD was observed in a subgroup with the most extensive and severe atrophy in femoral neck (adjusted OR: 0.62, 95% CI: 0.42-0.91). These results suggest that H. pylori-related chronic gastritis is involved in the risk of osteoporosis, with higher activity of gastritis and more extensive atrophy leading to further increased risk. The serologically assessed stage of the gastritis could be used to identify a high-risk group for osteoporosis in H. pylori-infected subjects from general population.

Drug Delivery Approaches for Rheumatoid Arthritis: Recent Advances and Clinical Translation Aspects

Rheumatoid arthritis (RA) is a multifactorial autoimmune disease characterized with symmetrical progression of joint deformity that is often diagnosed at a chronic condition with other associated pathological conditions such as pericarditis, keratitis, pulmonary granuloma. Despite the understanding of RA pathophysiology in disease progression, current clinical treatment options such as disease-modifying anti-rheumatic drugs (DMARDs), biologics, steroids, and non-steroidal anti-inflammatory drugs (NSAIDs) provide only palliative therapy while causing adverse side effects such as off-target multi-organ toxicity and risk of infections. Further, available drug delivery strategies to treat RA pathogenicity does not successfully reach the site of action due to various barriers such as phagocytosis and first pass effect in addition to the disease complexity and unknown etiology, thereby leading to the development of irreversible joint dysfunction. Therefore, novel and effective strategies remain an unmet need to control the disease progression and to maintain the balance between pro- and anti-inflammatory cytokines. This review provides a comprehensive outlook on the RA pathophysiology and its corresponding disease progression. Contributions of synoviocytes such as macrophages, fibroblast-like cells in increasing invasiveness to exacerbate joint damage is also outlined in this review, which could be a potential future therapeutic target to complement the existing treatment regimens in controlling RA pathogenesis. Further, various smart drug delivery approaches under research to achieve maximum therapeutic efficacy with minimal adverse side effects have been discussed, which in turn emphasize the unmet challenges and future perspectives in addressing RA complications.

Role of periodontal ligament fibroblasts in periodontitis: pathological mechanisms and therapeutic potential

Periodontal ligament fibroblasts (PDLFs) play a crucial role in the etiology of periodontitis and periodontal tissue regeneration. In healthy periodontal tissues, PDLFs maintain the homeostasis of periodontal soft and hard tissues as well as the local immune microenvironment. PDLFs also have the potential for multidirectional transdifferentiation and are involved in periodontal tissue regeneration. On the other hand, PDLFs can become dysfunctional and acquire an inflammatory phenotype to secret various inflammatory cytokines when affected by pathological factors. These cytokines further trigger immune and inflammatory events, and lead to destruction of periodontal soft and hard tissues as well as damage to the regenerative potential of PDLFs. This review summarizes the physiological functions of PDLFs. Meanwhile, this review also highlights recent insights into the pathological mechanisms driving the development of periodontitis through dysfunctional PDLFs and the negative impact on periodontal tissue regeneration. Additionally, this paper summarizes strategies for targeting PDLFs to treat periodontitis, involving blocking multiple stages of the inflammatory response induced by PDLFs and promoting the multidirectional transdifferentiation of PDLFs. Future research directions are proposed to address important questions that have not yet been answered in this field. This article provides a reference for understanding the important role of PDLFs in the pathological mechanisms of periodontitis and for developing new strategies for targeting PDLFs in periodontitis treatment.

Chlorogenic acid attenuates idiopathic pulmonary fibrosis: An integrated analysis of network pharmacology, molecular docking, and experimental validation

AIMS

Idiopathic pulmonary fibrosis (IPF) is a chronic and progressive lung condition, the cause of which remains unknown and for which no effective therapeutic treatment is currently available. Chlorogenic acid (CGA), a natural polyphenolic compound found in different plants and foods, has emerged as a promising agent due to its anti-inflammatory, antioxidant, and antifibrotic properties. However, the molecular mechanisms underlying the therapeutic effect of CGA in IPF remain unclear. The purpose of this study was to analyze the pharmacological impact and underlying mechanisms of CGA in IPF.

MAIN METHODS

Using network pharmacology analysis, genes associated with IPF and potential molecular targets of CGA were identified through specialized databases, and a protein-protein interaction (PPI) network was constructed. Molecular docking was performed to accurately select potential therapeutic targets. To investigate the effects of CGA on lung histology and key gene expression, a murine model of bleomycin-induced lung fibrosis was used.

KEY FINDINGS

Network pharmacology analysis identified 384 were overlapped between CGA and IPF. Key targets including AKT1, TP53, JUN, CASP3, BCL2, MMP9, NFKB1, EGFR, HIF1A, and IL1B were identified. Pathway analysis suggested the involvement of cancer, atherosclerosis, and inflammatory processes. Molecular docking confirmed the stable binding between CGA and targets. CGA regulated the expression mRNA of EGFR, MMP9, AKT1, BCL2 and IL1B and attenuated pulmonary fibrosis in the mouse model.

SIGNIFICANCE

CGA is a promising multi-target therapeutic agent for IPF, which is supported by its efficacy in reducing fibrosis through the modulation of key pathways. This evidence provides a basis to further investigate CGA as an IPF potential treatment.

Blackcurrants shape gut microbiota profile and reduce risk of postmenopausal osteoporosis via the gut-bone axis: Evidence from a pilot randomized controlled trial

This study aimed to investigate the effects of blackcurrant (BC) on gut microbiota abundance and composition, inflammatory and immune responses, and their relationship with bone mass changes. The effects of BC on bone mineral density (BMD), gut microbiota, and blood inflammatory and immune biomarkers were evaluated using DXA, stool and fasting blood collected from a pilot three-arm, randomized, double-blind, placebo-controlled clinical trial. Fifty-one peri- and early postmenopausal women aged 45-60 years were randomly assigned into one of three treatment groups for 6 months: control, low BC (392 mg/day) and high BC (784 mg/day); and 40 women completed the trial. BC supplementation for 6 months effectively mitigated the loss of whole-body BMD (P<.05). Six-month changes (%) in peripheral IL-1β (P=.056) and RANKL (P=.052) for the high BC group were marginally significantly lower than the control group. Six-month changes in whole-body BMD were inversely correlated with changes in RANKL (P<.01). In proteome analysis, four plasma proteins showed increased expression in the high BC group: IGFBP4, tetranectin, fetuin-B, and vitamin K-dependent protein S. BC dose-dependently increased the relative abundance of Ruminococcus 2 (P<.05), one of six bacteria correlated with BMD changes in the high BC group (P<.05), suggesting it might be the key bacteria that drove bone protective effects. Daily BC consumption for 6 months mitigated bone loss in this population potentially through modulating the gut microbiota composition and suppressing osteoclastogenic cytokines. Larger-scale clinical trials on the potential benefits of BC and connection of Ruminococcus 2 with BMD maintenance in postmenopausal women are warranted. Trial Registration: NCT04431960, https://classic.clinicaltrials.gov/ct2/show/NCT04431960.

A prospective study of vitamin D, proinflammatory cytokines, and risk of fragility fractures in women on aromatase inhibitors for breast cancer

BACKGROUND

Vitamin D is critical to bone health by regulating intestinal absorption of calcium, whereas proinflammatory cytokines, including IL-1, IL-6, IL-12, and TNF-α, are known to increase bone resorption. We hypothesized that vitamin D and these cytokines at the time of breast cancer diagnosis were predictive for fragility fractures in women receiving aromatase inhibitors (AIs).

METHODS

In a prospective cohort of 1,709 breast cancer patients treated with AIs, we measured the levels of 25-hydroxyvitamin D (25OHD), IL-1β, IL-6, IL-12, and TNF-α from baseline blood samples. The associations of these biomarkers were analyzed with bone turnover markers (BALP and TRACP), bone regulatory markers (OPG and RANKL), bone mineral density (BMD) close to cancer diagnosis, and risk of fragility fractures during a median of 7.5 years of follow up.

RESULTS

Compared to patients with vitamin D deficiency, patients with sufficient levels had higher bone turnover, lower BMD, and higher fracture risk; the latter became non-significant after controlling for covariates including BMD and no longer existed when patients taking vitamin D supplement or bisphosphonates or with history of fracture or osteoporosis were excluded. There was a non-significant trend of higher levels of IL-1β and TNF-α associated with higher risk of fracture (highest vs. lowest tertile, IL-1β: adjusted HR=1.37, 95% CI=0.94-1.99; TNF-α: adjusted HR=1.38, 95% CI=0.96-1.98).

CONCLUSIONS

Our results do not support proinflammatory cytokines or vitamin D levels as predictors for risk of fragility fractures in women receiving AIs for breast cancer.

An improved understanding of pediatric chronic nonbacterial osteomyelitis pathophysiology informs current and future treatment

Chronic nonbacterial osteomyelitis (CNO) is an autoinflammatory bone disease that primarily affects children and young people. It can cause significant pain, reduced function, bone swelling, and even (vertebral body) fractures. Because of a limited understanding of its pathophysiology, the treatment of CNO remains empiric and is based on relatively small case series, expert opinion, and personal experience. Several studies have linked pathological NOD-kike receptor (NLR) family pyrin domain containing 3 (NLRP3) inflammasome activation and the resulting imbalance between pro- and anti-inflammatory cytokine expression with CNO. This agrees with elevated pro-inflammatory (mostly) monocyte-derived protein signatures in the blood of CNO patients that may be used as future diagnostic and/or prognostic biomarkers. Recently, rare variants in the P2RX7 gene, encoding for an ATP-dependent transmembrane channel, were linked with increased NLRP3 inflammasome assembly and prolonged monocyte/macrophage survival in CNO. Although the exact molecular mechanisms remain unclear, this will inform future target-directed and individualized treatment. This manuscript reviews most recent developments and their impact on diagnostic and therapeutic strategies in CNO.

Cytoplasmic DNA and AIM2 inflammasome in RA: where they come from and where they go?

Rheumatoid arthritis is a chronic autoimmune disease of undetermined etiology characterized by symmetric synovitis with predominantly destructive and multiple joint inflammation. Cytoplasmic DNA sensors that recognize protein molecules that are not themselves or abnormal dsDNA fragments play an integral role in the generation and perpetuation of autoimmune diseases by activating different signaling pathways and triggering innate immune signaling pathways and host defenses. Among them, melanoma deficiency factor 2 (AIM2) recognizes damaged DNA and double-stranded DNA and binds to them to further assemble inflammasome, initiating the innate immune response and participating in the pathophysiological process of rheumatoid arthritis. In this article, we review the research progress on the source of cytoplasmic DNA, the mechanism of assembly and activation of AIM2 inflammasome, and the related roles of other cytoplasmic DNA sensors in rheumatoid arthritis.

Trehalose Rescues Postmenopausal Osteoporosis Induced by Ovariectomy through Alleviating Osteoblast Pyroptosis via Promoting Autophagy

BACKGROUND

Osteoporosis, a prevalent bone metabolic disease, often requires long-term drug treatments that may lead to serious side effects. Trehalose, a natural disaccharide found in various organisms, has been shown to have a promoting effect on autophagy. However, whether trehalose can improve bone mass recovery in ovariectomized rats and its underlying mechanisms remains unclear. In this study, trehalose was administered to ovariectomized rats to evaluate its therapeutic potential for osteoporosis following ovariectomy.

METHODS

Micro-computed tomography (Micro-CT), hematoxylin and eosin (HE) and immunohistochemical staining techniques were utilized to evaluate the impact of trehalose on osteoporosis induced by ovariectomy (OVX) in mice, both in imaging and histological dimensions. Furthermore, the influence of trehalose on osteoblastogenesis and functional activity was quantified through Alizarin Red S (ARS) staining and immunoblotting assays.

RESULTS

Trehalose effectively mitigated bone loss, elevated autophagy and suppressed pyroptosis in ovariectomized rats. Furthermore, 3-methyladenine diminished the protective effects of trehalose, particularly in promoting autophagy and inhibiting pyroptosis.

CONCLUSIONS

Trehalose demonstrates significant potential in treating osteoporosis by suppressing NLRP3 inflammasome-driven pyroptosis, primarily through autophagy promotion. This suggests that trehalose could be a promising, safer alternative treatment for osteoporosis.

Inflammatory response toward a Mg-based metallic biomaterial implanted in a rat femur fracture model

The immune system plays an important role in fracture healing, by modulating the pro-inflammatory and anti-inflammatory responses occurring instantly upon injury. An imbalance in these responses can lead to adverse outcomes, such as non-union of fractures. Implants are used to support and stabilize complex fractures. Biodegradable metallic implants offer the potential to avoid a second surgery for implant removal, unlike non-degradable implants. However, considering our dynamic immune system it is important to conduct in-depth studies on the immune response to these implants in living systems. In this study, we investigated the immune response to Mg and Mg-10Gd in vivo in a rat femur fracture model with external fixation. In vivo imaging using liposomal formulations was used to monitor the fluorescence-related inflammation over time. We combine ex vivo methods with our in vivo study to evaluate and understand the systemic and local effects of the implants on the immune response. We observed no significant local or systemic effects in the Mg-10Gd implanted group compared to the SHAM and Mg implanted groups over time. Our findings suggest that Mg-10Gd is a more compatible implant material than Mg, with no adverse effects observed in the early phase of fracture healing during our 4-week study. STATEMENT OF SIGNIFICANCE: Degradable metallic implants in form of Mg and Mg-10Gd intramedullary pins were assessed in a rat femur fracture model, alongside a non-implanted SHAM group with special respect to the potential to induce an inflammatory response. This pre-clinical study combines innovative non-invasive in vivo imaging techniques associated with multimodal, ex vivo cellular and molecular analytics. The study contributes to the development and evaluation of degradable biometals and their clinical application potential. The study results indicate that Mg-10Gd did not exhibit any significant harmful effects compared to the SHAM and Mg groups.

METTL14-mediated HOXA5 m6A modification alleviates osteoporosis via promoting WNK1 transcription to suppress NLRP3-dependent macrophage pyroptosis

Background

Osteoporosis is a commonly diagnosed metabolic bone disease. NLRP3 inflammasome activation and pyroptosis are observed during osteoporosis. However, the mechanism by which NLRP3-mediated pyroptosis contributes to osteoporosis remains largely undefined.

Methods

Ovariectomized (OVX) mice were employed as an in vivo model of osteoclastogenesis. H&E staining and micro-CT detected the histological changes and bone parameters in the femur tissues. RANKL-treated macrophages were used as the in vitro model of osteoclastogenesis, and LPS/ATP treatment was used as the macrophage pyroptosis model. The cytotoxicity, cytokine secretion and caspase-1 activity were assessed by LDH release assay, ELISA and flow cytometry, respectively. The osteoclast formation ability was detected by TRAP staining. qRT-PCR, IHC and Western blotting detected the expression and localization of METTL14, pyroptosis-related or osteoclast-specific molecules in femur tissues or macrophages. Mechanistically, MeRIP assessed the m6A modification of HOXA5. Luciferase and ChIP assays were employed to detect the direct association between HOXA5 and WNK1 promoter in macrophages.

Results

METTL14, HOXA5 and WNK1 were decreased in OVX mice, which was associated with pyroptosis. METTL14 or HOXA5 overexpression suppressed macrophage-osteoclast differentiation and pyroptosis, along with the upregulation of WNK1. METTL14-mediated m6A modification stabilized HOXA5 mRNA and increased its expression, and HOXA5 regulated WNK1 expression via direct binding to its promoter. Functional studies showed that WNK1 knockdown counteracted METTL14- or HOXA5-suppressed pyroptosis and macrophage-osteoclast differentiation. In OVX mice, overexpression of METTL14 or HOXA5 alleviated osteoporosis via suppressing WNK1-dependent NLRP3 signaling.

Conclusion

METTL14-mediated HOXA5 m6A modification increased its expression, thereby inducing WNK1 expression and suppressing NLRP3-dependent pyroptosis to alleviate osteoporosis. The combination of METTL14 or HOXA5 agonist with pyroptosis targeted therapy may be a promising therapeutic approach for osteoporosis.

The Translational Potential of this Article·

•METTL14 or HOXA5 overexpression suppressed macrophage-osteoclast differentiation and pyroptosis in macrophages.·•METTL14-mediated m6A modification stabilized HOXA5 mRNA and increased its expression.•HOXA5 regulated WNK1 expression via direct binding to its promoter.•Silencing of WNK1 reversed METTL14- or HOXA5-suppressed pyroptosis and macrophageosteoclast differentiation.·•METTL14 or HOXA5 overexpression alleviated osteoporosis via suppressing WNK1-dependent NLRP3 signaling in OVX mice.

Reduction of osteoclast formation and survival following suppression of cytokines by diacerein in periodontitis

Periodontitis causes an increase in several bioactive agents such as interleukins (IL), tumor necrosis factor (TNF)-α and receptor activator of NF-kB ligand (RANKL), which induce the osteoclast formation and activity. Since diacerein exerts anti-TNF-α and anti-IL-1 effects, alleviating bone destruction in osteoarthritis, we investigated whether this drug inhibits the formation and survival of osteoclast in the periodontitis. Rats were distributed into 3 groups: 1) group with periodontitis treated with 100 mg/kg diacerein (PDG), 2) group with periodontitis treated with saline (PSG) and group control (CG) without any treatment. After 7, 15 and 30 days, the maxillae were collected for light and transmission electron microscopy analyses. Gingiva samples were collected to evaluate the mRNA levels for Tnf, Il1b, Tnfsf11 and Tnfrsf11b by RT-qPCR. In PDG, the expression of Tnf and Il1b genes reduced significantly compared to PSG, except for Tnf expression at 7 days. The number of osteoclasts reduced significantly in the PDG in comparison with PSG at 7 and 15 days. In all periods, the IL-6 immunoexpression, RANKL/OPG immunoexpression and mRNA levels of Tnfsf11/Tnfrsf11b ratio were significantly lower in PDG than in PSG. PDG exhibited significantly higher frequency of TUNEL-positive osteoclasts than in PSG and CG at all time points. Osteoclasts with caspase-3-immunolabelled cytoplasm and nuclei with masses of condensed chromatin were observed in PDG, confirming osteoclast apoptosis. Diacerein inhibits osteoclastogenesis by decreasing Tnf and Il1b mRNA levels, resulting in decreased RANKL/OPG ratio, and induces apoptosis in osteoclasts of alveolar process of rat molars with periodontitis.

Potential Targeting Mechanisms for Bone-Directed Therapies

Bone development is characterized by complex regulation mechanisms, including signal transduction and transcription factor-related pathways, glycobiological processes, cellular interactions, transportation mechanisms, and, importantly, chemical formation resulting from hydroxyapatite. Any abnormal regulation in the bone development processes causes skeletal system-related problems. To some extent, the avascularity of cartilage and bone makes drug delivery more challenging than that of soft tissues. Recent studies have implemented many novel bone-targeting approaches to overcome drawbacks. However, none of these strategies fully corrects skeletal dysfunction, particularly in growth plate-related ones. Although direct recombinant enzymes (e.g., Vimizim for Morquio, Cerezyme for Gaucher, Elaprase for Hunter, Mepsevii for Sly diseases) or hormone infusions (estrogen for osteoporosis and osteoarthritis), traditional gene delivery (e.g., direct infusion of viral or non-viral vectors with no modifications on capsid, envelope, or nanoparticles), and cell therapy strategies (healthy bone marrow or hematopoietic stem cell transplantation) partially improve bone lesions, novel delivery methods must be addressed regarding target specificity, less immunogenicity, and duration in circulation. In addition to improvements in bone delivery, potential regulation of bone development mechanisms involving receptor-regulated pathways has also been utilized. Targeted drug delivery using organic and inorganic compounds is a promising approach in mostly preclinical settings and future clinical translation. This review comprehensively summarizes the current bone-targeting strategies based on bone structure and remodeling concepts while emphasizing potential approaches for future bone-targeting systems.

Differential but complementary roles of HIF-1α and HIF-2α in the regulation of bone homeostasis

Bone is a highly dynamic tissue undergoing continuous formation and resorption. Here, we investigated differential but complementary roles of hypoxia-inducible factor (HIF)-1α and HIF-2α in regulating bone remodeling. Using RNA-seq analysis, we identified that specific genes involved in regulating osteoblast differentiation were similarly but slightly differently governed by HIF-1α and HIF-2α. We found that increased HIF-1α expression inhibited osteoblast differentiation via inhibiting RUNX2 function by upregulation of Twist2, confirmed using Hif1a conditional knockout (KO) mouse. Ectopic expression of HIF-1α via adenovirus transduction resulted in the increased expression and activity of RANKL, while knockdown of Hif1a expression via siRNA or osteoblast-specific depletion of Hif1a in conditional KO mice had no discernible effect on osteoblast-mediated osteoclast activation. The unexpected outcome was elucidated by the upregulation of HIF-2α upon Hif1a overexpression, providing evidence that Hif2a is a transcriptional target of HIF-1α in regulating RANKL expression, verified through an experiment of HIF-2α knockdown after HIF-1α overexpression. The above results were validated in an ovariectomized- and aging-induced osteoporosis model using Hif1a conditional KO mice. Our findings conclude that HIF-1α plays an important role in regulating bone homeostasis by controlling osteoblast differentiation, and in influencing osteoclast formation through the regulation of RANKL secretion via HIF-2α modulation.

Pyroptosis mediates osteoporosis via the inflammation immune microenvironment

Osteoporosis represents a systemic imbalance in bone metabolism, augmenting the susceptibility to fractures among patients and emerging as a notable mortality determinant in the elderly population. It has evolved into a worldwide concern impacting the physical well-being of the elderly, imposing a substantial burden on both human society and the economy. Presently, the precise pathogenesis of osteoporosis remains inadequately characterized and necessitates further exploration. The advancement of osteoporosis is typically linked to the initiation of an inflammatory response. Cells in an inflammatory environment can cause inflammatory death including pyroptosis. Pyroptosis is a recently identified form of programmed cell death with inflammatory properties, mediated by the caspase and gasdermin families. It is regarded as the most inflammatory form of cell death in contemporary medical research. Under the influence of diverse cytokines, macrophages, and other immune cells may undergo pyroptosis, releasing inflammatory factors, such as IL-1β and IL-18. Numerous lines of evidence highlight the pivotal role of pyroptosis in the pathogenesis of inflammatory diseases, including cancer, intestinal disorders, hepatic conditions, and cutaneous ailments. Osteoporosis progression is frequently associated with inflammation; hence, pyroptosis may also play a role in the pathogenesis of osteoporosis to a certain extent, making it a potential target for treatment. This paper has provided a comprehensive summary of pertinent research concerning pyroptosis and its impact on osteoporosis. The notion proposing that pyroptosis mediates osteoporosis via the inflammatory immune microenvironment is advanced, and we subsequently investigate potential targets for treating osteoporosis through the modulation of pyroptosis.

The role of IL-1B in breast cancer bone metastasis

Interleukin-1B (IL-1B) is a potent pro-inflammatory cytokine that plays multiple, pivotal roles, in the complex interplay between breast cancer cells and the bone microenvironment. IL-1B is involved in the growth of the primary tumours, regulation of inflammation within the tumour microenvironment, promotion of epithelial to mesenchymal transition (EMT), migration and invasion. Moreover, when breast cancer cells arrive in the bone microenvironment there is an upregulation of IL-1B which promotes the creation of a conducive niche for metastatic breast cancer cells as well as stimulating initiation of the vicious cycle of bone metastasis. Pre-clinical studies have demonstrated that inhibition of IL-1 signalling reduces bone metastasis from oestrogen receptor positive/triple-negative breast cancers in various mouse models. However, effects on primary tumours and soft tissue metastasis remain controversial with some studies showing increased tumour growth in these sites, whilst others show no effects. Notably, combining anti-IL-1 therapy with standard-of-care treatments, such as chemotherapy and immunotherapy, has been demonstrated to reduce the growth of primary tumours, bone metastasis, as well as metastatic outgrowth in other organs. This review focuses on the mechanisms by which IL-1B promotes breast cancer bone metastasis.

Quercetin in Osteoporosis Treatment: A Comprehensive Review of Its Mechanisms and Therapeutic Potential

PURPOSE OF REVIEW

This review aims to provide a theoretical basis and insights for quercetin's clinical application in the prevention and treatment of osteoporosis (OP), analyzing its roles in bone formation promotion, bone resorption inhibition, anti-inflammation, antioxidant effects, and potential mechanisms.

RECENT FINDINGS

OP, a prevalent bone disorder, is marked by reduced bone mineral density and impaired bone architecture, elevating the risk of fractures in patients. The primary approach to OP management is pharmacotherapy, with quercetin, a phytochemical compound, emerging as a focus of recent interest. This natural flavonoid exerts regulatory effects on bone marrow mesenchymal stem cells, osteoblasts, and osteoclasts and promotes bone health and metabolic equilibrium via anti-inflammatory and antioxidative pathways. Although quercetin has demonstrated significant potential in regulating bone metabolism, there is a need for further high-quality clinical studies focused on medicinal quercetin.

Role of Myostatin in Rheumatoid Arthritis: A Review of the Clinical Impact

Rheumatoid arthritis (RA) is a chronic inflammatory disease that affects synovial joints and that frequently involves extra-articular organs. A multiplicity of interleukins (IL) participates in the pathogenesis of RA, including IL-6, IL-1β, transforming growth factor-beta (TGF-β), and tumor necrosis factor (TNF)-α; immune cells such as monocytes, T and B lymphocytes, and macrophages; and auto-antibodies, mainly rheumatoid factor and anti-citrullinated protein antibodies (ACPAs). Skeletal muscle is also involved in RA, with many patients developing muscle wasting and sarcopenia. Several mechanisms are involved in the myopenia observed in RA, and one of them includes the effects of some interleukins and myokines on myocytes. Myostatin is a myokine member of the TGF-β superfamily; the overproduction of myostatin acts as a negative regulator of growth and differentiates the muscle fibers, limiting their number and size. Recent studies have identified abnormalities in the serum myostatin levels of RA patients, and these have been found to be associated with muscle wasting and other manifestations of severe RA. This review analyzes recent information regarding the relationship between myostatin levels and clinical manifestations of RA and the relevance of myostatin as a therapeutic target for future research.

Exercise and osteoimmunology in bone remodeling

Bones can form the scaffolding of the body, support the organism, coordinate somatic movements, and control mineral homeostasis and hematopoiesis. The immune system plays immune supervisory, defensive, and regulatory roles in the organism, which mainly consists of immune organs (spleen, bone marrow, tonsils, lymph nodes, etc.), immune cells (granulocytes, platelets, lymphocytes, etc.), and immune molecules (immune factors, interferons, interleukins, tumor necrosis factors, etc.). Bone and the immune system have long been considered two distinct fields of study, and the bone marrow, as a shared microenvironment between the bone and the immune system, closely links the two. Osteoimmunology organically combines bone and the immune system, elucidates the role of the immune system in bone, and creatively emphasizes its interdisciplinary characteristics and the function of immune cells and factors in maintaining bone homeostasis, providing new perspectives for skeletal-related field research. In recent years, bone immunology has gradually become a hot spot in the study of bone-related diseases. As a new branch of immunology, bone immunology emphasizes that the immune system can directly or indirectly affect bones through the RANKL/RANK/OPG signaling pathway, IL family, TNF-α, TGF-β, and IFN-γ. These effects are of great significance for understanding inflammatory bone loss caused by various autoimmune or infectious diseases. In addition, as an external environment that plays an important role in immunity and bone, this study pays attention to the role of exercise-mediated bone immunity in bone reconstruction.

Neutrophils in Inflammatory Bone Diseases

PURPOSE OF REVIEW

In this review, we summarize the current evidence that suggests that neutrophils play a key role in facilitating damage to local bone structures.

RECENT FINDINGS

Neutrophil infiltration is a hallmark of inflammatory bone diseases such as rheumatoid arthritis (RA) and periodontitis disease (PD). Both of these human diseases are marked by an imbalance in bone homeostasis, favoring the degradation of local bone which ultimately leads to erosions. Osteoclasts, a multinucleated resident bone cell, are responsible for facilitating the turnover of bone and the bone damage observed in these diseases. The involvement of neutrophils and neutrophil extracellular trap formation have recently been implicated in exacerbating osteoclast function through direct and indirect mechanisms. We highlight a recent finding that NET proteins such as histones and elastase can generate non-canonical, inflammatory osteoclasts, and this process is mediated by post-translational modifications such as citrullination and carbamylation, both of which act as autoantigens in RA. It appears that NETs, autoantibodies, modified proteins, cytokines, and osteoclasts all ultimately contribute to local and permanent bone damage in RA and PD. However, more studies are needed to fully understand the role of neutrophils in inflammatory bone diseases.

The prevention effect of pulsed electromagnetic fields treatment on senile osteoporosis in vivo via improving the inflammatory bone microenvironment

This study aimed to assess PEMF in a rat model of senile osteoporosis and its relationship with NLRP3-mediated low-grade inflammation in the bone marrow microenvironment. A total of 24 Sprague Dawley (SD) rats were included in this study. Sixteen of them were 24-month natural-aged male SD rats, which were randomly distributed into the Aged group and the PEMF group (n = 8 per group). The remaining 8 3-month -old rats were used as the Young positive control group (n = 8). Rats in the PEMF group received 12 weeks of PEMF with 40 min/day, five days per week, while the other rats received placebo PEMF intervention. Bone mineral density/microarchitecture, serum levels of CTX-1 and P1CP, and NLRP3-related signaling genes and proteins in rat bone marrow were then analyzed. The 12-week of PEMF showed significant mitigation of aging-induced bone loss and bone microarchitecture deterioration, i.e. PEMF increased the bone mineral density of the proximal femur and L5 vertebral body and improved parameters of the proximal tibia and L4 vertebral body. Further analysis showed that PEMF reversed aging-induced bone turnover, specifically, decreased serum CTX-1 and elevated serum P1CP. Furthermore, PEMF also dramatically inhibited NLRP3-mediated low-grade inflammation in the bone marrow, i.e. PEMF inhibited the levels of NLRP3, proCaspase1, cleaved Caspase1, IL-1β, and GSDMD-N. The study demonstrated that PEMF could mitigate the aging-induced bone loss and reverses the deterioration of bone microarchitecture probably through inhibiting NLRP3-mediated low-grade chronic inflammation to improve the inflammatory bone microenvironment in aged rats.

Polymorphism of salivary proteins and risk of periodontal diseases: A systematic review and meta-analysis of clinical studies

OBJECTIVES

The present systematic review and meta-analysis aimed to assess the association between salivary protein polymorphisms and the risk of periodontal diseases (PD).

DATA

The review incorporated cross-sectional, case-control, retrospective/prospective cohort, and randomized controlled trials assessing the influence of salivary protein polymorphisms on the risk of PD development were included in this review.

SOURCES

A thorough literature search was conducted across electronic databases, namely PubMed, Scopus, Embase, and Web of Science, without any restrictions on publication language and year.

STUDY SELECTION

A total of 168 studies were identified, of which 19 were eligible for inclusion. The risk of bias (RoB) assessment of the included studies was conducted at the methodological level.

RESULTS

A total of 16 studies were included. Polymorphism in the gene encoding TNF-α was found to be protective against gingivitis, while those encoding IL-1α and IL-1β were associated with developing gingivitis. Of the 42 proteins investigated, various gene polymorphisms were identified as protective or risk factors for periodontitis. Protective genes include CFH, DNMT1, OPRM1, and TLR9. Conversely, certain salivary protein genes (e.g., CRP, ERN1, FAM5C, IDH2, LTA, TET2, MPA, NLRP3, TLR4) were associated with periodontitis risk. Notably, IL6, MMP9, and MUC7 genes showed no association with PD, while MMP13 was linked to early implant loss. Overall, the meta-analysis found a statistically significant association between salivary proteins' polymorphisms and risk of PD.

CONCLUSIONS

Salivary protein polymorphisms significantly influence PD, revealing protective and risk-associated genotypes. Despite limitations, findings suggest therapeutic targets, emphasizing the complex genetics-periodontal health interplay.

CLINICAL SIGNIFICANCE

This study unveils salivary protein polymorphisms as pivotal factors in PD. Protective genes including CFH and TLR9, and risk-associated genes including CRP and TLR4, indicate a genetic basis for PD susceptibility.

Danggui Buxue Decoction exerts its therapeutic effect on rheumatoid arthritis through the inhibition of Wnt/β-catenin signaling pathway

BACKGROUND

Danggui Buxue Decoction (DBD) is a traditional Chinese medicine prescription, which has the functions of benefiting Qi, generating blood and regulating the immune system. At present, various clinical reports suggest that DBD has some efficacy in Rheumatoid arthritis (RA), but its mechanism of action is still unclear. Thus, the present study explored mechanism of this preparation on RA.

METHODS

The effect of DBD was evaluated by tumor necrosis factor (TNF)-α-induced Human fibroblast-like synoviocyte of rheumatoid arthritis (HFLS-RA) cell model and collagen-induced arthritis (CIA) rat model, respectively. Inflammatory factors including TNF-ɑ, IL-1β, IL-6 and IL-10 in the culture supernatants or rat serum were measured using ELISA. The related indexes including fur luster, mental state and activity of rat and the symptoms including swelling and deformation of toes and ankles were also measured.

RESULTS

In vitro results showed that DBD cannot only inhibit the proliferation of HFLS-RA cells but also reduce the levels of pro-inflammatory factors while increasing the level of anti-inflammatory factors. Similar results were obtained from in vivo experiments. Rats receiving DBD showed a decrease in the severity of rheumatoid arthritis in rat models. Moreover, the protein levels of c-myc and β-catenin decreased significantly, while the protein level of SFRP4 increased, which indicated that DBD might inhibit the inflammatory reaction by regulating Wnt/β-catenin signaling pathway, thus alleviating the symptoms of RA.

CONCLUSION

Our findings not only provide insights for understanding the molecular mechanism of DBD in treating RA, but also provide the theoretical basis for further clinical prevention and treatment.

Differential expression of circular RNAs in interleukin 6-promoted osteogenic differentiation of human stem cells from apical papilla

INTRODUCTION

Studies have shown that interleukin 6 (IL-6) can regulate stem cell osteogenic differentiation; however, the exact mechanism is not clear. Circular RNAs (circRNAs) are closed circular non-coding RNAs that are involved in the process of stem cell osteogenic differentiation. Therefore, the purpose of this present study was to investigate the effect of IL-6 treatment on osteogenic differentiation of human apical tooth papillae stem cells (hSCAPs), and to detect the difference in circRNA expression using gene microarray technology.

METHODS

After extraction and identification of hSCAPs, alkaline phosphatase (ALP) activity, alizarin red staining, and calcium ion quantitative assay were used to determine the changes of ALP enzyme, mineralized nodules, and matrix calcium levels before and after IL-6 treatment of hSCAPs gene microarray technology was used to analyze the changes in circRNA expression levels before and after IL-6 induction of mineralization. The four selected circRNAs were validated by qRT-PCR. Moreover, gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to predict the potential functions and biological signaling pathways of circRNAs. Finally, these data are integrated and analyzed to construct circRNA-microRNA-mRNA networks.

RESULTS

Alp and Alizarin red staining confirmed that IL-6 promoted the osteogenic differentiation of hSCAPs. The gene microarray results identified 132 differentially expressed circRNAs, of which 117 were upregulated and 15 were downregulated. Bioinformatic analysis predicted that the circRNA-406620/miR-103a-3p/FAT atypical cadherin 4 (FAT4) pathway might be involved in regulating IL-6 to promote osteogenic differentiation of hSCAPs.

CONCLUSION

Differentially expressed circRNAs might be closely involved in regulating IL-6 to promote osteogenic differentiation of hSCAPs.

Alloferon-1 ameliorates estrogen deficiency-induced osteoporosis through dampening the NLRP3/caspase-1/IL-1β/IL-18 signaling pathway

Alloferon-1 is an insect polypeptide that has anti-inflammatory, antitumor and antiviral activity. This study aimed to determine the effects of alloferon-1 on estrogen deficiency-induced osteoporosis and explore the associated mechanism using a murine model of ovariectomy (OVX)-induced osteoporosis. Results showed that alloferon-1 prevented ovariectomy‑induced body weight gain, bone loss and bone mineral content reduction, affected biochemical markers of bone turnover, and restored the microstructure of bone trabeculae. Moreover, alloferon-1 suppressed the expression of the ovariectomy‑mediated inflammatory cytokines in the vertebrae bone tissues, including nucleotide-binding oligomerization domain-like-receptor family pyrin domain-containing 3 (NLRP3), cysteinyl aspartate specific proteinase-1 (Caspase-1), interleukin 1β (IL-1β) and interleukin 18 (IL-18) which were determined by immunofluorescence staining and western blot. Overall, the present study provides evidence for the effectiveness of alloferon-1 against estrogen deficiency-induced osteoporosis, suggesting an alternative drug or an auxiliary modulator for the treatment of postmenopausal osteoporosis (PMOP).

Amelioration of Rheumatoid Arthritis by Fragaria nubicola (Wild Strawberry) via Attenuation of Inflammatory Mediators in Sprague Dawley Rats

Background and Objectives: Fragaria nubicola has never been evaluated scientifically for its anti-arthritic potential despite its use in folkloric systems of medicine. The research was conducted to assess the potential of F. nubicola against rheumatoid arthritis. Materials and Methods: The current study provided scientific evidence by evaluating the effects of plants using an in vivo CFA-induced model of arthritic rats and subsequent microscopic histopathological evaluation of ankle joints along with the determination of paw edema using a digital water displacement plethysmometer. The study also gave insight by determining levels of pro-inflammatory cytokines, matrix metalloproteinase enzymes (MMPs), prostaglandin E2 (PGE2), nuclear factor kappa B (NF-κB), vascular endothelial growth factor (VEGF), and biochemical and hematological parameters. GCMS analysis was also conducted for the identification of possible anti-inflammatory plant constituents. Results: The data showed that F. nubicola-treated groups attenuated the progression of arthritis and paw edema. Microscopic histopathological evaluation validated the anti-arthritic potential by showing amelioration of bone erosion, infiltration of inflammatory cells, and pannus formation. RT-PCR analysis displayed that treatment with F. nubicola down-regulated IL1β, IL6, TNFα, NF-κB, VEGF, MMP2, MMP3, and MMP9 levels. Moreover, ELISA exhibited a reduction in levels of PGE2 levels in treatment groups. The levels of RBCs, platelets, WBCs, and Hb content were found to be nearly similar to negative control in the treated group. Statistically, a non-significant difference was found when all groups were compared for urea, creatinine, ALT, and AST analysis, indicating the safety of plant extract and fractions at test doses. GCMS analysis of extract and fractions showed the existence of many anti-inflammatory and antioxidant phytochemicals. Conclusion: In conclusion, F. nubicola possessed anti-arthritic properties that might be attributed to the amelioration of MMPs and pro-inflammatory cytokines.

Mechanism of Liuwei Dihuang Pills in treating osteoporosis based on network pharmacology

Osteoporosis is a prevalent age-related disease that poses a significant public health concern as the population continues to age. While current treatments have shown some therapeutic benefits, their long-term clinical efficacy is limited by a lack of stable curative effects and significant adverse effects. Traditional Chinese Medicine has gained attention due to its positive curative effects and fewer side effects. Liuwei Dihuang Pill has been found to enhance bone mineral density in patients with osteoporosis and rats, but the underlying mechanism is not yet clear. To shed more light on this problem, this study aims to explore the pharmacological mechanism of Liuwei Dihuang Pill in treating osteoporosis using network pharmacology and molecular docking. The findings indicate that Liuwei Dihuang Pills treat osteoporosis through various targets and channels. Specifically, it mainly involves TNF, IL17, and HIF-1 signaling pathways and helps regulate biological processes such as angiogenesis, apoptosis, hypoxia, and gene expression. Furthermore, molecular docking demonstrates excellent binding properties between the drug components and key targets. Therefore, this study offers a theoretical foundation for understanding the pharmacological mechanism and clinical application of Liuwei Dihuang Pills in treating osteoporosis more comprehensively.

Cholesterol sulfate inhibits osteoclast differentiation and survival by regulating the AMPK-Sirt1-NF-κB pathway

Cholesterol sulfate (CS) is an activator of retinoic acid-related orphan receptor α (RORα). CS treatment or RORα overexpression attenuates osteoclastogenesis in a collagen-induced arthritis mouse model. However, the mechanism by which CS and RORα regulate osteoclast differentiation remains largely unknown. Thus, we aimed to investigate the role of CS and RORα in osteoclastogenesis and their underlying mechanism. CS inhibited osteoclast differentiation, but RORα deficiency did not affect osteoclast differentiation and CS-mediated inhibition of osteoclastogenesis. CS enhanced adenosine monophosphate-activated protein kinase (AMPK) phosphorylation and sirtuin1 (Sirt1) activity, leading to nuclear factor-κB (NF-κB) inhibition by decreasing acetylation at Lys310 of p65. The NF-κB inhibition was restored by AMPK inhibitor, but the effects of CS on AMPK and NF-κB were not altered by RORα deficiency. CS also induced osteoclast apoptosis, which may be due to sustained AMPK activation and consequent NF-κB inhibition, and the effects of CS were significantly reversed by interleukin-1β treatment. Collectively, these results indicate that CS inhibits osteoclast differentiation and survival by suppressing NF-κB via the AMPK-Sirt1 axis in a RORα-independent manner. Furthermore, CS protects against bone destruction in lipopolysaccharide- and ovariectomy-mediated bone loss mouse models, suggesting that CS is a useful therapeutic candidate for treating inflammation-induced bone diseases and postmenopausal osteoporosis.

Are medication-induced salivary changes the culprit of osteonecrosis of the jaw? A systematic review

Purpose

This systematic review was performed to assess the potential influence of medication-induced salivary changes on the development of medication-related osteonecrosis of the jaw (MRONJ).

Methods

An electronic search was conducted using PubMed, Web of Science, Cochrane, and Embase databases for articles published up to June 2023. A risk of bias assessment was performed according to the modified Newcastle-Ottawa Scale (NOS). Due to the heterogeneity of the selected studies in relation to the type of medications and outcomes evaluated, a meta-analysis could not be performed.

Results

The initial search revealed 765 studies. Only 10 articles were found to be eligible based on the inclusion criteria that reported on the impact of salivary changes on MRONJ following the administration of different medications. A total of 272 cases of MRONJ (35% women, 32% men, and 32% with no gender reported) with a mean age of 66 years at the time of diagnosis were included. Patients administered with bisphosphonates, steroids, chemotherapy, thalidomide, interferon, and hormone therapy had a significantly higher association between decreased salivary flow and MRONJ occurrence. In addition, bisphosphonates, denosumab, and other bone-modifying agents showed a significantly higher risk of developing MRONJ owing to the changes in salivary microbiome profiles, cytokine profiles, interleukins, hypotaurine, and binding proteins.

Conclusion

The reduction in salivary flow and changes in the concentration of salivary proteins were associated with the development of MRONJ. However, due to the availability of limited evidence, the findings of the review should be interpreted with caution.

Prospero review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier: CRD42022327645.

Anti-Arthritic and Immunomodulatory Potential of Methanolic, n-Hexane, and Ethyl Acetate Fractions of Bark of Acacia modesta on Complete Freund's Adjuvant-Induced Arthritis in Rats

Rheumatoid arthritis is an autoimmune disorder and topic of interest for researchers due to its increasing frequency and limited treatment. Acacia modesta Wall is known to treat rheumatic disorders in the traditional system of medicinal plants. Traditional medicines are still required for the treatment of this disease due to the large number of side-effects caused by commercial medicines. In the current study, the antiarthritic potential of methanolic extract (AM-metha), n-hexane (AM-hexa) fraction, and ethyl acetate (AM-etha) fraction of the bark of A. modesta against a complete Freund's adjuvant rat model was evaluated. Evaluation using a digital plethysmometer, macroscopic evaluation, and histopathological evaluation were conducted to determine the paw volume and arthritic scoring. ELISA was performed to assess the PGE2 levels. RT-PCR was used to evaluate the expression levels of MMP2, MMP3, MMP9, NF-κB, IL6, IL1β, TNFα, and VEGF. Biochemical and hematological analyses were also conducted. GC/MS was also carried out to analyze the presence of medicinal compounds. The data revealed a marked reduction in the paw volume, arthritic scoring, and histopathological parameters, indicating the anti-arthritic potential of the plant. Treatment with plant extracts and fractions markedly down-regulated MMP2, MMP3, MMP9, NF-κB, IL6, IL1β, TNFα, and VEGF levels. Similarly, PGE2 levels were also found to be ameliorated in the treatment groups, indicating the immunomodulatory property of plant bark. Plant treatment nearly normalized hematological parameters such as counts of WBCs, RBCs, and platelets, along with Hb content, thereby validating the anti-arthritic activity. GC/MS analysis disclosed the presence of strong anti-inflammatory compounds such as lupeol, oleic acid, and squalene. The study showed that A. modesta possesses anti-arthritic and immunomodulatory potential linked to significant down-regulation of pro-inflammatory and inflammatory biomarkers.

Identification of Immune Infiltration in Odontogenic Keratocyst by Integrated Bioinformatics Analysis

BACKGROUND

Odontogenic keratocyst (OKC) is a relatively common odontogenic lesion characterized by local invasion in the maxillary and mandibular bones. In the pathological tissue slices of OKC, immune cell infiltrations are frequently observed. However, the immune cell profile and the molecular mechanism for immune cell infiltration of OKC are still unclear. We aimed to explore the immune cell profile of OKC and to explore the potential pathogenesis for immune cell infiltration in OKC.

METHODS

The microarray dataset GSE38494 including OKC and oral mucosa (OM) samples were obtained from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) in OKC were analyzed by R software. The hub genes of OKC were performed by protein-protein interaction (PPI) network. The differential immune cell infiltration and the potential relationship between immune cell infiltration and the hub genes were performed by single-sample gene set enrichment analysis (ssGSEA). The expression of COL1A1 and COL1A3 were confirmed by immunofluorescence and immunohistochemistry in 17 OKC and 8 OM samples.

RESULTS

We detected a total of 402 differentially expressed genes (DEGs), of which 247 were upregulated and 155 were downregulated. DEGs were mainly involved in collagen-containing extracellular matrix pathways, external encapsulating structure organization, and extracellular structure organization. We identified ten hub genes, namely FN1, COL1A1, COL3A1, COL1A2, BGN, POSTN, SPARC, FBN1, COL5A1, and COL5A2. A significant difference was observed in the abundances of eight types of infiltrating immune cells between the OM and OKC groups. Both COL1A1 and COL3A1 exhibited a significant positive correlation with natural killer T cells and memory B cells. Simultaneously, they demonstrated a significant negative correlation with CD56dim natural killer cells, neutrophils, immature dendritic cells, and activated dendritic cells. Immunohistochemistry analysis showed that COL1A1 (P = 0.0131) and COL1A3 (P < 0.001) were significantly elevated in OKC compared with OM.

CONCLUSIONS

Our findings provide insights into the pathogenesis of OKC and illuminate the immune microenvironment within these lesions. The key genes, including COL1A1 and COL1A3, may significantly impact the biological processes associated with OKC.

"Bone-SASP" in Skeletal Aging

Senescence is a complex cell state characterized by stable cell cycle arrest and a unique secretory pattern known as the senescence-associated secretory phenotype (SASP). The SASP factors, which are heterogeneous and tissue specific, normally include chemokines, cytokines, growth factors, adhesion molecules, and lipid components that can lead to multiple age-associated disorders by eliciting local and systemic consequences. The skeleton is a highly dynamic organ that changes constantly in shape and composition. Senescent cells in bone and bone marrow produce diverse SASP factors that induce alterations of the skeleton through paracrine effects. Herein, we refer to bone cell-associated SASP as "bone-SASP." In this review, we describe current knowledge of cellular senescence and SASP, focusing on the role of senescent cells in mediating bone pathologies during natural aging and premature aging syndromes. We also summarize the role of cellular senescence and the bone-SASP in glucocorticoids-induced bone damage. In addition, we discuss the role of bone-SASP in the development of osteoarthritis, highlighting the mechanisms by which bone-SASP drives subchondral bone changes in metabolic syndrome-associated osteoarthritis.

Identification of key immune genes of osteoporosis based on bioinformatics and machine learning

Introduction

Immunity is involved in a variety of bone metabolic processes, especially osteoporosis. The aim of this study is to explore new bone immune-related markers by bioinformatics method and evaluate their ability to predict osteoporosis.

Methods

The mRNA expression profiles were obtained from GSE7158 in Gene expression Omnibus (GEO), and immune-related genes were obtained from ImmPort database (https://www.immport.org/shared/). immune genes related to bone mineral density(BMD) were screened out for differential analysis. protein-protein interaction (PPIs) networks were used to analyze the interrelationships between different immune-related genes (DIRGs). Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses of DIRGs function were performed. A least absolute shrinkage and selection operation (LASSO) regression model and multiple Support Vector Machine-Recursive Feature Elimination (mSVM-RFE) model were constructed to identify the candidate genes for osteoporosis prediction The receiver operator characteristic (ROC) curves were used to validate the performances of predictive models and candidate genes in GEO database (GSE7158,GSE13850).Through the RT - qPCR verify the key genes differentially expressed in peripheral blood mononuclear cells Finally, we constructed a nomogram model for predicting osteoporosis based on five immune-related genes. CIBERSORT algorithm was used to calculate the relative proportion of 22 immune cells.

Results

A total of 1158 DEGs and 66 DIRGs were identified between high-BMD and low-BMD women. These DIRGs were mainly enriched in cytokine-mediated signaling pathway, positive regulation of response to external stimulus and the cellular components of genes are mostly localized to external side of plasma membrane. And the KEGG enrichment analysis were mainly involved in Cytokine-cytokine receptor interaction, PI3K-Akt signaling pathway, Neuroactive ligand-receptor interaction,Natural killer cell mediated cytotoxicity. Then five key genes (CCR5, IAPP, IFNA4, IGHV3-73 and PTGER1) were identified and used as features to construct a predictive prognostic model for osteoporosis using the GSE7158 dataset.

Conclusion

Immunity plays an important role in the development of osteoporosis.CCR5, IAPP, IFNA4, IGHV3-73 and PTGER1were play an important role in the occurrences and diagnosis of OP.

Fine-tuning osteoclastogenesis: An insight into the cellular and molecular regulation of osteoclastogenesis

Osteoclasts, the bone-resorbing cells, are essential for the bone remodeling process and are involved in the pathophysiology of several bone-related diseases. The extensive corpus of in vitro research and crucial mouse model studies in the 1990s demonstrated the key roles of monocyte/macrophage colony-stimulating factor, receptor activator of nuclear factor kappa B ligand (RANKL) and integrin αvβ3 in osteoclast biology. Our knowledge of the molecular mechanisms by which these variables control osteoclast differentiation and function has significantly advanced in the first decade of this century. Recent developments have revealed a number of novel insights into the fundamental mechanisms governing the differentiation and functional activity of osteoclasts; however, these mechanisms have not yet been adequately documented. Thus, in the present review, we discuss various regulatory factors including local and hormonal factors, innate as well as adaptive immune cells, noncoding RNAs (ncRNAs), etc., in the molecular regulation of the intricate and tightly regulated process of osteoclastogenesis. ncRNAs have a critical role as epigenetic controllers of osteoclast physiologic activities, including differentiation and bone resorption. The primary ncRNAs, which include micro-RNAs, circular RNAs, and long noncoding RNAs, form a complex network that affects gene transcription activities associated with osteoclast biological activity. Greater knowledge of the involvement of ncRNAs in osteoclast biological activities will contribute to the treatment and management of several skeletal diseases such as osteoporosis, osteoarthritis, rheumatoid arthritis, etc. Moreover, we further outline potential therapies targeting these regulatory pathways of osteoclastogenesis in distinct bone pathologies.

Multifunctional Janus Nanoplatform for Efficiently Synergistic Theranostics of Rheumatoid Arthritis

Progress has been made in the application of nanomedicine in rheumatoid arthritis (RA) treatment. However, the whole process of monitoring and treatment of RA remains a formidable challenge due to the complexity of the chronic autoimmune disease. In this study, we develop a Janus nanoplatform (denoted as Janus-CPS) composed of CeO₂-Pt nanozyme subunit on one side and periodic mesoporous organosilica (PMO) subunit on another side for simultaneous early diagnosis and synergistic therapy of RA. The Janus nanostructure, which enables more active sites to be exposed, enhances the reactive oxygen species scavenging capability of CeO₂-Pt nanozyme subunit as compared to their core-shell counterpart. Furthermore, micheliolide (MCL), an extracted compound from natural plants with anti-osteoclastogenesis effects, is loaded into the mesopores of PMO subunit to synergize with the anti-inflammation effect of nanozymes for efficient RA treatment, which has been demonstrated by in vitro cellular experiments and in vivo collagen-induced arthritis (CIA) model. In addition, by taking advantage of the second near-infrared window (NIR-II) fluorescent imaging, indocyanine green (ICG)-loaded Janus-CPS exhibits desirable effectiveness in detecting RA lesions at a very early stage. It is anticipated that such a Janus nanoplatform may offer an alternative strategy of functional integration for versatile theranostics.

Entamoeba gingivalis and Trichomonas tenax: Protozoa parasites living in the mouth

OBJECTIVE

This review article aims to summarize the existing data on the history, biology and potential pathogenicity of Entamoeba gingivalis and Trichomonas tenax in periodontal disease, as well as the available techniques for laboratory diagnosis.

DESIGN

A detailed review of scientific literature available up to October 1, 2022 in three databases (PubMed, Scopus and Web of Science) was performed relevant to biology, biochemistry, epidemiology, and experimental studies on infection by E. gingivalis and T. tenax, as well as laboratory techniques for the diagnosis of both protozoa in periodontal diseases.

RESULTS

Accumulated evidence over the decades indicates that the protozoa E. gingivalis and T. tenax are able to interact with host cells and induce inflammation in the periodontal tissue by promoting the expression of pro-inflammatory molecules and the recruitment of neutrophils, contributing to the periodontal disease process. Among the available techniques for the laboratory diagnosis, culture and molecular assays seems to be the best tools for detection of both protozoan parasites.

CONCLUSIONS

E. gingivalis and T. tenax are potentially pathogens that colonize the oral cavity of humans and may cause periodontal disease.

Oxidative Stress and Inflammation in Osteoporosis: Molecular Mechanisms Involved and the Relationship with microRNAs

Osteoporosis is characterized by the alteration of bone homeostasis due to an imbalance between osteoclastic bone resorption and osteoblastic bone formation. Estrogen deficiency causes bone loss and postmenopausal osteoporosis, the pathogenesis of which also involves oxidative stress, inflammatory processes, and the dysregulation of the expression of microRNAs (miRNAs) that control gene expression at post-transcriptional levels. Oxidative stress, due to an increase in reactive oxygen species (ROS), proinflammatory mediators and altered levels of miRNAs enhance osteoclastogenesis and reduce osteoblastogenesis through mechanisms involving the activation of MAPK and transcription factors. The present review summarizes the principal molecular mechanisms involved in the role of ROS and proinflammatory cytokines on osteoporosis. Moreover, it highlights the interplay among altered miRNA levels, oxidative stress, and an inflammatory state. In fact, ROS, by activating the transcriptional factors, can affect miRNA expression, and miRNAs can regulate ROS production and inflammatory processes. Therefore, the present review should help in identifying targets for the development of new therapeutic approaches to osteoporotic treatment and improve the quality of life of patients.

Inflammation produced by senescent osteocytes mediates age-related bone loss

Purpose

The molecular mechanisms of age-related bone loss are unclear and without valid drugs yet. The aims of this study were to explore the molecular changes that occur in bone tissue during age-related bone loss, to further clarify the changes in function, and to predict potential therapeutic drugs.

Methods

We collected bone tissues from children, middle-aged individuals, and elderly people for protein sequencing and compared the three groups of proteins pairwise, and the differentially expressed proteins (DEPs) in each group were analyzed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG). K-means cluster analysis was then used to screen out proteins that continuously increased/decreased with age. Canonical signaling pathways that were activated or inhibited in bone tissue along with increasing age were identified by Ingenuity Pathway Analysis (IPA). Prediction of potential drugs was performed using the Connectivity Map (CMap). Finally, DEPs from sequencing were verified by Western blot, and the drug treatment effect was verified by quantitative real-time PCR.

Results

The GO and KEGG analyses show that the DEPs were associated with inflammation and bone formation with aging, and the IPA analysis shows that pathways such as IL-8 signaling and acute-phase response signaling were activated, while glycolysis I and EIF2 signaling were inhibited. A total of nine potential drugs were predicted, with rapamycin ranking the highest. In cellular experiments, rapamycin reduced the senescence phenotype produced by the H₂O₂-stimulated osteocyte-like cell MLO-Y4.

Conclusion

With age, inflammatory pathways are activated in bone tissue, and signals that promote bone formation are inhibited. This study contributes to the understanding of the molecular changes that occur in bone tissue during age-related bone loss and provides evidence that rapamycin is a drug of potential clinical value for this disease. The therapeutic effects of the drug are to be further studied in animals.

Pyroptosis in bone loss

Pyroptosis could be responsible for the bone loss from bone metabolic diseases, leading to the negative impact on people's health and life. It has been shown that osteoclasts, osteoblasts, macrophages, chondrocytes, periodontal and gingival cells may be involved in bone loss linked with pyroptosis. So far, the involved mechanisms have not been fully elucidated. In this review, we introduced the related cells involved in the pyroptosis associated with bone loss and summarized the role of these cells in the bone metabolism during the process of pyroptosis. We also discuss the clinical potential of targeting mechanisms in the osteoclasts, osteoblasts, macrophages, chondrocytes, periodontal and gingival cells touched upon pyroptosis to treat bone loss from bone metabolic diseases as well as the challenges of avoiding potential side effects and producing efficient treatment methods.

Positive Effects of Biologics on Osteoporosis in Rheumatoid Arthritis

Osteoporosis is a systemic skeletal disorder that causes vulnerability of bones to fracture owing to reduction in bone density and deterioration of the bone tissue microstructure. The prevalence of osteoporosis is higher in patients with autoimmune inflammatory rheumatic diseases, including rheumatoid arthritis (RA), than in those of the general population. In this autoimmune inflammatory rheumatic disease, in addition to known risk factors for osteoporosis, various factors such as chronic inflammation, autoantibodies, metabolic disorders, drugs, and decreased physical activity contribute to additional risk. In RA, disease-related inflammation plays an important role in local or systemic bone loss, and active treatment for inflammation can help prevent osteoporosis. In addition to conventional synthetic disease-modifying anti-rheumatic drugs that have been traditionally used for treatment of RA, biologic DMARDs and targeted synthetic DMARDs have been widely used. These agents can be employed more selectively and precisely based on disease pathogenesis. It has been reported that these drugs can inhibit bone loss by not only reducing inflammation in RA, but also by inhibiting bone resorption and promoting bone formation. In this review, the pathogenesis and research results of the increase in osteoporosis in RA are reviewed, and the effects of biological agents on osteoporosis are discussed.

Pathogenesis of Collagen-Induced Arthritis: Role of Immune Cells with Associated Cytokines and Antibodies, Comparison with Rheumatoid Arthritis

Collagen-induced arthritis is the most com-mon in vivo model of rheumatoid arthritis used for investigation of new potential therapies in preclinical research. Rheumatoid arthritis is a systemic inflammatory and autoimmune disease affecting joints, accompanied by significant extra-articular symptoms. The pathogenesis of rheumatoid arthritis and collagen-induced arthritis involves a so far properly unexplored network of immune cells, cytokines, antibodies and other factors. These agents trigger the autoimmune response leading to polyarthritis with cell infiltration, bone and cartilage degeneration and synovial cell proliferation. Our review covers the knowledge about cytokines present in the rat collagen-induced arthritis model and the factors affecting them. In addition, we provide a comparison with rheumatoid arthritis and a description of their important effects on the development of both diseases. We discuss the crucial roles of various immune cells (subtypes of T and B lymphocytes, dendritic cells, monocytes, macrophages), fibroblast-like synoviocy-tes, and their related cytokines (TNF-α, IL-1β, IL-2, IL-4, IL-6, IL-8, IL-10, IL-12, IL-17, IL-23, GM-CSF, TGF-β). Finally, we also focus on key antibodies (rheu-matoid factor, anti-citrullinated protein antibodies, anti-collagen II antibodies) and tissue-degrading enzymes (matrix metalloproteinases).