Regulation of differentiation and generation of osteoclasts in rheumatoid arthritis

A sinomenine derivative alleviates bone destruction in collagen-induced arthritis mice by suppressing mitochondrial dysfunction and oxidative stress via the NRF2/HO-1/NQO1 signaling pathway

Bone destruction in rheumatoid arthritis (RA) leads to significant disability, yet effective treatments are limited. Sinomenine (Sino) demonstrates anti-arthritic and bone-protective effects but requires high doses. In this study, we developed a Sino derivative, SINX, and evaluated its efficacy in RA. Safety assessments in mice confirmed its suitability for further study. In vitro, SINX inhibited osteoclast differentiation by reducing TRAP-positive cells, disrupting F-actin ring formation, and suppressing bone resorption pits, alongside downregulating osteoclast-specific genes. It also showed strong anti-inflammatory properties by reducing inflammatory cytokine levels. In vivo, using a collagen-induced arthritis (CIA) mouse model, SINX improved bone integrity by reducing joint inflammation, maintaining trabecular bone density, and preventing erosion. Histological and micro-CT analyses confirmed its effects, including suppressed osteoclast activity and reduced bone resorption-related gene expression. Mechanistically, SINX ameliorated mitochondrial dysfunction, decreased ROS levels, and activated the NRF2/HO-1/NQO1 pathway, enhancing antioxidant defenses. Compared to Sino, SINX achieved similar results at lower doses. These findings highlight the potential of SINX as a safe, effective treatment for RA-related bone destruction.

Advances in nanodelivery systems based on apoptosis strategies for enhanced rheumatoid arthritis therapy

Rheumatoid arthritis (RA) is a chronic systemic autoimmune disorder primarily characterized by persistent synovial inflammation and progressive bone erosion. The pathogenesis of RA involves a complex cascade of cellular and molecular events, including sustained hyperactivation of macrophages, excessive recruitment and activation of neutrophils, pathological proliferation and invasion of fibroblast-like synoviocytes (FLS), and dysregulated differentiation and function of osteoclasts (OCs). The inflammatory factors secreted by these dysregulated cells significantly disrupt the joint microenvironment through multiple pathological mechanisms, primarily by promoting synovial inflammation, cartilage matrix degradation, osteoclast-mediated bone erosion, and pathological angiogenesis. Therapeutic strategies targeting the induction of apoptosis in these malignant cells have demonstrated considerable potential in preclinical studies, offering a promising approach to enhance treatment outcomes by simultaneously reducing inflammatory cytokine production and inhibiting pathogenic cell proliferation. However, conventional therapeutic drugs are limited in clinical applications because of their high toxicity and side effects. Inflammation induces morphological and functional changes in cells within the rheumatoid arthritis microenvironment (RAM), particularly the overexpression of specific receptors on cell membranes. This phenomenon has driven the development of ligand-modified targeted nanodelivery systems (NDSs), which can specifically target and induce apoptosis in specific cell types, thereby enhancing therapeutic efficacy. This paper comprehensively reviews the research progress of targeted NDSs based on apoptosis strategies for RA therapy, with a detailed discussion of their advantages in inducing apoptosis in various disease-associated cells. Furthermore, the potential of combining apoptosis of multiple cell types for RA treatment is explored. This review is expected to improve insights into the apoptosis of malignant cells to enhance RA therapy. STATEMENT OF SIGNIFICANCE: This review highlights recent advances in nanodelivery systems (NDSs) based on apoptotic strategies for enhanced rheumatoid arthritis (RA) therapy. Unlike conventional NDSs, these optimized systems specifically induce apoptosis in malignant cells within the RA microenvironment by integrating multiple therapeutic strategies. By summarizing the latest research, our work demonstrates the potential of these NDSs to suppress inflammatory responses and prevent bone destruction through targeted elimination of malignant cells, offering a novel direction for RA treatment. This review is significant as it provides a comprehensive overview for researchers and clinicians, facilitating the development of more effective therapeutic approaches for RA and other chronic inflammatory diseases.

STAT3 Signaling Pathway in Health and Disease

Signal transducer and activator of transcription 3 (STAT3) is a critical transcription factor involved in multiple physiological and pathological processes. While STAT3 plays an essential role in homeostasis, its persistent activation has been implicated in the pathogenesis of various diseases, particularly cancer, bone-related diseases, autoimmune disorders, inflammatory diseases, cardiovascular diseases, and neurodegenerative conditions. The interleukin-6/Janus kinase (JAK)/STAT3 signaling axis is central to STAT3 activation, influencing tumor microenvironment remodeling, angiogenesis, immune evasion, and therapy resistance. Despite extensive research, the precise mechanisms underlying dysregulated STAT3 signaling in disease progression remain incompletely understood, and no United States Food and Drug Administration (USFDA)-approved direct STAT3 inhibitors currently exist. This review provides a comprehensive evaluation of STAT3's role in health and disease, emphasizing its involvement in cancer stem cell maintenance, metastasis, inflammation, and drug resistance. We systematically discuss therapeutic strategies, including JAK inhibitors (tofacitinib, ruxolitinib), Src Homology 2 domain inhibitors (S3I-201, STATTIC), antisense oligonucleotides (AZD9150), and nanomedicine-based drug delivery systems, which enhance specificity and bioavailability while reducing toxicity. By integrating molecular mechanisms, disease pathology, and emerging therapeutic interventions, this review fills a critical knowledge gap in STAT3-targeted therapy. Our insights into STAT3 signaling crosstalk, epigenetic regulation, and resistance mechanisms offer a foundation for developing next-generation STAT3 inhibitors with greater clinical efficacy and translational potential.

Tm4sf19 inhibition ameliorates inflammation and bone destruction in collagen-induced arthritis by suppressing TLR4-mediated inflammatory signaling and abnormal osteoclast activation

Rheumatoid arthritis (RA) is an autoimmune disease characterized by inflammation and abnormal osteoclast activation, leading to bone destruction. We previously demonstrated that the large extracellular loop (LEL) of Tm4sf19 is important for its function in osteoclast differentiation, and LEL-Fc, a competitive inhibitor of Tm4sf19, effectively suppresses osteoclast multinucleation and prevent bone loss associated with osteoporosis. This study aimed to investigate the role of Tm4sf19 in RA, an inflammatory and abnormal osteoclast disease, using a mouse model of collagen-induced arthritis (CIA). Tm4sf19 expression was observed in macrophages and osteoclasts within the inflamed synovium, and Tm4sf19 expression was increased together with inflammatory genes in the joint bones of CIA-induced mice compared with the sham control group. Inhibition of Tm4sf19 by LEL-Fc demonstrated both preventive and therapeutic effects in a CIA mouse model, reducing the CIA score, swelling, inflammation, cartilage damage, and bone damage. Knockout of Tm4sf19 gene or inhibition of Tm4sf19 activity by LEL-Fc suppressed LPS/IFN-γ-induced TLR4-mediated inflammatory signaling in macrophages. LEL-Fc disrupted not only the interaction between Tm4sf19 and TLR4/MD2, but also the interaction between TLR4 and MD2. μCT analysis showed that LEL-Fc treatment significantly reduced joint bone destruction and bone loss caused by hyperactivated osteoclasts in CIA mice. Taken together, these findings suggest that LEL-Fc may be a potential treatment for RA and RA-induced osteoporosis by simultaneously targeting joint inflammation and bone destruction caused by abnormal osteoclast activation.

Human nasal turbinate stem cells with specific gene signatures (HAS2, CXCL1, KRTAP1-5, GSTT2B, and C4B) attenuate rheumatoid arthritis

This study aimed to investigate the therapeutic effect of human nasal turbinate-derived stem cells (hNTSCs) on mice with rheumatoid arthritis (RA) and identify hNTSC gene signatures with therapeutic effects on RA. hNTSCs were obtained from 20 healthy controls (HCs) who had undergone nasal turbinate surgery. Collagen-induced arthritis (CIA) mice were used to investigate the therapeutic effects of hNTSCs. The engraftment and migration abilities of hNTSCs were evaluated. CD4+CD25- T cells were co-cultured with hNTSCs, and effector T cell proliferation was evaluated by flow cytometry. Osteoclast differentiation was evaluated using mouse bone marrow monocytes which were cultured with M-CSF and RANKL, then TRAP staining was performed to measure effect of hNTSCs on osteoclastogenesis. Microarray assays were performed to identify gene expression differences between hNTSCs with CIA mice therapeutic or not and were validated by RT-qPCR. hNTSCs differentiated well into osteoblasts and adipocytes and expressed high levels of CXCL1 and osteoprotegerin. Single-cell RNA sequencing showed that hNTSCs clustered into 11 cell types, and cell surface markers were compatible with mesenchymal stem cells. hNTSC-treated CIA mice showed reductions in arthritis severity scores and incidence of arthritis. In engraft measurements, hNTSCs survived for 8 to 12 weeks in mice paws. Chemokine receptors expression increased in hNTSCs by IL-1β or TNF-α stimulation. CD4+CD25- T cell proliferation was reduced by hNTSCs and reversed by adding 1-MT (indoleamine 2,3-dioxygenase inhibitor), indicating that indoleamine 2,3-dioxygenase mediated T cell suppression. Osteoclastogenesis was suppressed by hNTSCs, and this was attenuated by anti-OPG Ab. hNTSCs therapeutic in CIA mice showed specific gene signatures with up-regulated genes (KRTAP1-5, HAS2, and CXCL1) and down-regulated genes (GSTT2B and C4B) compared to hNTSCs without CIA therapeutic effects. hNTSCs exhibited therapeutic potential in RA. Therapeutic effects were mediated by effector helper T cell suppression and the inhibition of osteoclastogenesis. In addition, hNTSCs with greater therapeutic effects on RA showed significant differences in their gene signatures.

DAMPs, PAMPs, NLRs, RIGs, CLRs and TLRs - Understanding the Alphabet Soup in the Context of Bone Biology

PURPOSE OF REVIEW

The purpose of this review is to summarize the current understanding of cell-autonomous innate immune pathways that contribute to bone homeostasis and disease.

RECENT FINDINGS

Germ-line encoded pattern recognition receptors (PRRs) are the first line of defense against danger and infections. In the bone microenvironment, PRRs and downstream signaling pathways, that mount immune defense, interface intimately with the core cellular processes in bone cells to alter bone formation and resorption. The role of PRR engagement on bone remodeling has been best described as a result of activated macrophages secreting effector molecules that reshape the characteristics of bone-resident cells. However, it is being increasingly recognized that local bone resident-cells like osteoclasts and osteoblasts possess an arsenal of PRRs. The engagement of these PRRs by stimuli in the bone niche can drive cell-autonomous (aka cell-intrinsic) responses that, in turn, impact bone-remodeling dramatically, irrespective of immune cell effectors. Indeed, this vital role for cell-autonomous innate immune responses is evident in how reduced PRR activity within osteoclast progenitors correlates with their reduced differentiation and abnormal bone remodeling. Further, cell-intrinsic PRR activity has now been shown to influence the behavior of osteoblasts, osteocytes and other local immune/non-immune cell populations. However, distinct PRR families have varying impact on bone homeostasis and inflammation, emphasizing the importance of investigating these different nodes of innate immune signaling in bone cells to better identify how they synergistically and/or antagonistically regulate bone remodeling in the course of an immune response. Innate immune sensing within bone resident cells is a critical determinant for bone remodeling in health and disease.

Membrane-free stem cell components suppress osteoclast differentiation: Implications for oral regenerative treatment

Background/purpose

Membrane-free stem cell components (MFSCCs) have been developed by removing cell membranes with antigens to overcome the limitations associated with cell-based therapies and isolate effective peptides. MFSCCs have been reported to have effects on oral infection sites. Chronic inflammatory diseases cause excessive bone resorption. This study investigated the effects of MFSCCs on osteoclast differentiation in the context of the high prevalence of inflammatory bone resorption.

Materials and methods

Bone marrow macrophages (BMMs) were treated with macrophage colony-stimulating factor and receptor activator of nuclear factor kappa-B ligand. Osteoclast differentiation was assessed based on the MFSCC concentrations. Tartrate-resistant acid phosphatase (TRAP)-stained mature osteoclasts and multinucleated cells derived from BMMs were analyzed using light microscopy. The messenger RNA (mRNA) expression levels of genes related to osteoclast differentiation were measured using real-time polymerase chain reaction (RT-PCR). The relative expression levels of the key transcription factors c-fos and nuclear factor of activated T cells (NFATc1) were determined using quantitative RT-PCR and western blotting.

Results

After treatment with MFSCCs, the cell viability was similar, depending on the level of BMMs. As the MFSCC concentration increased, the number of TRAP-positive cells decreased. The mRNA and protein expression of cathepsin K, TRAP, dendritic cell-specific transmembrane protein, c-fos, and NFATc1 decreased as the MFSCC concentration increased.

Conclusion

Our findings demonstrate that MFSCCs suppress osteoclast differentiation by downregulating transcription factors, particularly, c-fos and NFATc1. Therefore, MFSCCs may serve as a conservative treatment option for chronic inflammatory bone resorption diseases of the oral cavity by suppressing excessive bone resorption.

Propionibacterium freudenreichii MJ2-derived extracellular vesicles inhibit RANKL-induced osteoclastogenesis and improve collagen-induced rheumatoid arthritis

Rheumatoid arthritis causes excessive bone loss by stimulating osteoclast differentiation. Extracellular vesicles are valuable disease markers, conveyors of distant cell-to-cell communication, and carriers for drug delivery. The aim of this study was to investigate the anti-osteoclastogenic effects of extracellular vesicles derived from dairy Propionibacterium freudenreichii MJ2 (PFEVs) and the improvement effect of PFEVs on collagen-induced arthritis (CIA) animal model. PFEVs were observed by scanning electron microscopy, transmission electron microscopy, nanoparticle tracking analysis, and LC-MS/MS. The inhibitory activity of PFEVs against receptor activator of nuclear factor kappa-B ligand (RANKL)-induced osteoclast differentiation was investigated in RAW 264.7 cells. PFEVs significantly decreased the expression levels of genes and proteins related to osteoclast differentiation. PFEVs decreased RANK-RANKL binding. In a CIA mouse model, PFEVs treatment significantly reduced arthritis scores and collagen-specific immunoglobulins. PFEVs treatment also reduced pro-inflammatory cytokines and increased anti-inflammatory cytokines. The anti-inflammatory effects were confirmed by H&E staining, and PFEVs treatment inhibited osteoclastogenesis in the CIA mouse model. In conclusion, PFEVs inhibited osteoclast differentiation by inhibiting RANK-RANKL signaling, thereby decreasing the expression of osteoclast differentiation-related genes. PFEVs also improved collagen-induced arthritis by inhibiting inflammation and osteoclastogenesis.

The effect of low-level laser therapy on osteoclast differentiation: Clinical implications for tooth movement and bone density

Background/purpose

Osteoclast differentiation is crucial for orchestrating both tooth movement and the maintenance of bone density. Therefore, the current study sought to explore the impact of low-level laser therapy (LLLT) on osteoclast differentiation, functional gene expression, molecular signaling pathways, and orthodontic tooth movement in clinical settings.

Materials and methods

The RAW 264.7 cell line served as the precursor for osteoclasts, and these cells underwent irradiation using a 808-nm LLLT. Osteoclast differentiation was assessed through tartrate-resistant acid phosphatase (TRAP) staining. Functional gene expression levels were evaluated using real-time quantitative polymerase chain reaction (RT-qPCR) while signaling molecules were examined through Western blot analysis. In the clinical study, 12 participants were enrolled. Their tooth movement was monitored using a TRIOS desktop scanner. Bone density measurements were conducted using Mimics software, which processed cone-beam computed tomography (CBCT) images exported in Digital Imaging and Communications in Medicine (DICOM) format.

Results

We found that LLLT effectively promoted receptor activator of nuclear factor-κB ligand (RANKL)-dependent osteoclast differentiation and the expression of osteoclast functional genes, including matrix metallopeptidase 9 (MMP9), nuclear factor of activated T-cells cytoplasmic 1(NFATc1), tartrate-resistant acid phosphatase (TRAP) and cathepsin K (CTSK) in RAW264.7 cells. Clinically, the cumulative tooth movement over 90 days was significantly higher in the laser group than in the control group.

Conclusion

Our research demonstrates that LLLT not only significantly promotes osteoclast differentiation but is also a valuable adjunct in orthodontic therapy.

Subchondral osteoclasts and osteoarthritis: new insights and potential therapeutic avenues

Osteoarthritis (OA) is the most common joint disease, and good therapeutic results are often difficult to obtain due to its complex pathogenesis and diverse causative factors. After decades of research and exploration of OA, it has been progressively found that subchondral bone is essential for its pathogenesis, and pathological changes in subchondral bone can be observed even before cartilage lesions develop. Osteoclasts, the main cells regulating bone resorption, play a crucial role in the pathogenesis of subchondral bone. Subchondral osteoclasts regulate the homeostasis of subchondral bone through the secretion of degradative enzymes, immunomodulation, and cell signaling pathways. In OA, osteoclasts are overactivated by autophagy, ncRNAs, and Rankl/Rank/OPG signaling pathways. Excessive bone resorption disrupts the balance of bone remodeling, leading to increased subchondral bone loss, decreased bone mineral density and consequent structural damage to articular cartilage and joint pain. With increased understanding of bone biology and targeted therapies, researchers have found that the activity and function of subchondral osteoclasts are affected by multiple pathways. In this review, we summarize the roles and mechanisms of subchondral osteoclasts in OA, enumerate the latest advances in subchondral osteoclast-targeted therapy for OA, and look forward to the future trends of subchondral osteoclast-targeted therapies in clinical applications to fill the gaps in the current knowledge of OA treatment and to develop new therapeutic strategies.

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.

Epigenetic Regulation of Autophagy in Bone Metabolism

The skeletal system is crucial for supporting bodily functions, protecting vital organs, facilitating hematopoiesis, and storing essential minerals. Skeletal homeostasis, which includes aspects such as bone density, structural integrity, and regenerative processes, is essential for normal skeletal function. Autophagy, an intricate intracellular mechanism for degrading and recycling cellular components, plays a multifaceted role in bone metabolism. It involves sequestering cellular waste, damaged proteins, and organelles within autophagosomes, which are then degraded and recycled. Autophagy's impact on bone health varies depending on factors such as regulation, cell type, environmental cues, and physiological context. Despite being traditionally considered a cytoplasmic process, autophagy is subject to transcriptional and epigenetic regulation within the nucleus. However, the precise influence of epigenetic regulation, including DNA methylation, histone modifications, and non-coding RNA expression, on cellular fate remains incompletely understood. The interplay between autophagy and epigenetic modifications adds complexity to bone cell regulation. This article provides an in-depth exploration of the intricate interplay between these two regulatory paradigms, with a focus on the epigenetic control of autophagy in bone metabolism. Such an understanding enhances our knowledge of bone metabolism-related disorders and offers insights for the development of targeted therapeutic strategies.

Exosomal Osteoclast-Derived miRNA in Rheumatoid Arthritis: From Their Pathogenesis in Bone Erosion to New Therapeutic Approaches

Rheumatoid arthritis (RA) is an autoimmune disease that causes inflammation, pain, and ultimately, bone erosion of the joints. The causes of this disease are multifactorial, including genetic factors, such as the presence of the human leukocyte antigen (HLA)-DRB1*04 variant, alterations in the microbiota, or immune factors including increased cytotoxic T lymphocytes (CTLs), neutrophils, or elevated M1 macrophages which, taken together, produce high levels of pro-inflammatory cytokines. In this review, we focused on the function exerted by osteoclasts on osteoblasts and other osteoclasts by means of the release of exosomal microRNAs (miRNAs). Based on a thorough revision, we classified these molecules into three categories according to their function: osteoclast inhibitors (miR-23a, miR-29b, and miR-214), osteoblast inhibitors (miR-22-3p, miR-26a, miR-27a, miR-29a, miR-125b, and miR-146a), and osteoblast enhancers (miR-20a, miR-34a, miR-96, miR-106a, miR-142, miR-199a, miR-324, and miR-486b). Finally, we analyzed potential therapeutic targets of these exosomal miRNAs, such as the use of antagomiRs, blockmiRs, agomiRs and competitive endogenous RNAs (ceRNAs), which are already being tested in murine and ex vivo models of RA. These strategies might have an important role in reestablishing the regulation of osteoclast and osteoblast differentiation making progress in the development of personalized medicine.

An ADAM10 Exosite Inhibitor Is Efficacious in an In Vivo Collagen-Induced Arthritis Model

Rheumatoid arthritis is a systemic autoimmune inflammatory disease that affects millions of people worldwide. There are multiple disease-modifying anti-rheumatic drugs available; however, many patients do not respond to any treatment. A disintegrin and metalloproteinase 10 has been suggested as a potential new target for RA due to its role in the release of multiple pro- and anti-inflammatory factors from cell surfaces. In the present study, we determined the pharmacokinetic parameters and in vivo efficacy of a compound CID3117694 from a novel class of non-zinc-binding inhibitors. Oral bioavailability was demonstrated in the blood and synovial fluid after a 10 mg/kg dose. To test efficacy, we established the collagen-induced arthritis model in mice. CID3117694 was administered orally at 10, 30, and 50 mg/kg/day for 28 days. CID3117694 was able to dose-dependently improve the disease score, decrease RA markers in the blood, and decrease signs of inflammation, hyperplasia, pannus formation, and cartilage erosion in the affected joints compared to the untreated control. Additionally, mice treated with CID 3117694 did not exhibit any clinical signs of distress, suggesting low toxicity. The results of this study suggest that the inhibition of ADAM10 exosite can be a viable therapeutic approach to RA.

A pH-Responsive DNA Tetrahedron/Methotrexate Drug Delivery System Used for Rheumatoid Arthritis Treatment

Rheumatoid arthritis (RA) is a chronic autoimmune disorder that leads to progressive and aggressive joint inflammation. The disease process is characterized by the activation of macrophages, which then release tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), accelerating tissue damage. Tackling tissue damage is a crucial target in the treatment of RA. In this study, a macrophage-targeted and pH-response DNA tetrahedron/methotrexate drug delivery system was constructed by loading methotrexate (MTX) onto a DNA duplex. MTX was used as a drug model, and a pH-response DNA tetrahedron (TET) was used as the drug carrier, which was modified with hyaluronic acid (HA) to target macrophages. The aim of this study was to evaluate the potential of TET as an effective drug carrier for the treatment of RA. On this basis, we successfully prepared TETs loaded with MTX, and in vitro assays showed that the MTX-TET treatment could successfully target macrophages and induce macrophages to polarize to M1 phenotype. At the same time, we also injected MTX-TET intravenously into collagen-induced arthritis (CIA) model mice, and the redness and swelling of the paws of mice were significantly alleviated, proving that the MTX-TET could successfully target inflamed joints and release MTX to treat joint swelling. In addition, the histochemical results showed that the MTX-TET could reduce synovitis and joint swelling in CIA mice, reduce the level of inflammatory factors in vivo, and improve the disease status while maintaining a good biosafety profile. This study showed that the MTX-TET treatment has beneficial therapeutic effects on RA, providing a new strategy for the clinical treatment of RA.

Rheumatoid arthritis: the old issue, the new therapeutic approach

Rheumatoid arthritis (RA) is a chronic and systemic autoimmune disease of unknown etiology. The most common form of this disease is chronic inflammatory arthritis, which begins with inflammation of the synovial membrane of the affected joints and eventually leads to disability of the affected limb. Despite significant advances in RA pharmaceutical therapies and the availability of a variety of medicines on the market, none of the available medicinal therapies has been able to completely cure the disease. In addition, a significant percentage (30-40%) of patients do not respond appropriately to any of the available medicines. Recently, mesenchymal stromal cells (MSCs) have shown promising results in controlling inflammatory and autoimmune diseases, including RA. Experimental studies and clinical trials have demonstrated the high power of MSCs in modulating the immune system. In this article, we first examine the mechanism of RA disease, the role of cytokines and existing medicinal therapies. We then discuss the immunomodulatory function of MSCs from different perspectives. Our understanding of how MSCs work in suppressing the immune system will lead to better utilization of these cells as a promising tool in the treatment of autoimmune diseases.

Fermented Rice Bran Supplementation Inhibits LPS-Induced Osteoclast Formation and Bone Resorption in Mice

Fermented rice bran (FRB) is known to have numerous beneficial bioactivities, amongst which is its anti-inflammatory properties when used as a supplement. To determine its effects, we examined osteoclastogenesis and bone resorption caused by injections of lipopolysaccharide (LPS), using mice with and without FRB supplementation. The results were favorable: those that received FRB showed reduced osteoclast numbers and bone resorption compared to those with the control diet. Notably, receptor activator of NF-κB ligand (RANKL) and tumor necrosis factor-α (TNF-α) mRNA levels were shown to be lower in the LPS-treated animals with FRB supplementation. FRB's inhibitory effect on RANKL- and TNF-α-induced osteoclastogenesis was further confirmed in vitro. In culture, macrophages exhibited decreased TNF-α mRNA levels when treated with FRB extract and LPS versus treatment with LPS alone, but there was no significant change in RANKL levels in osteoblasts. We can conclude that FRB supplementation dampens the effect of LPS-induced osteoclastogenesis and bone resorption by controlling TNF-α expression in macrophages and the direct inhibition of osteoclast formation.

Botryococcus terribilis Ethanol Extract Exerts Anti-inflammatory Effects on Murine RAW264 Cells

The present study aimed to evaluate the effects of Botryococcus terribilis ethanol extract (BTEE) on lipopolysaccharide (LPS)-induced inflammation in RAW264 cells. BTEE significantly attenuated LPS-induced nitric oxide production and inflammatory cytokines release, including Ccl2, Cox2, and Il6. On the other hand, several anti-inflammatory mediators, such as Pgc1β and Socs1, were increased in BTEE-treated cells. Further, we performed an untargeted whole-genome microarray analysis to explore the anti-inflammatory molecular mechanism of BTEE. Enrichment analysis showed BTEE significantly downregulated ‘response to stimulus’, ‘locomotion’, and ‘immune system response’ and upregulated ‘cell cycle’ gene ontologies in both 6- and 17-h post-LPS stimulation conditions. Pathway analysis revealed BTEE could downregulate the expressions of chemokines of the CC and CXC subfamily, and cytokines of the TNF family, TGFβ family, IL1-like, and class I helical. PPI analysis showed AXL receptor tyrosine kinase (Axl), a receptor tyrosine kinase from the TAM family, and its upstream transcription factors were downregulated in both conditions. Node neighborhood analysis showed several Axl coexpressed genes were also downregulated. Further, kinase enrichment and chemical perturbation analyses supported Axl inhibition in BTEE-treated conditions. Altogether, these findings suggest anti-inflammatory effects of BTEE that are mediated via the suppression of pro-inflammatory cytokines and predict its potential as an Axl inhibitor.