Tripartite motif-containing (TRIM) family proteins are crucial E3 ubiquitin ligases that have garnered significant attention for their regulatory roles in bone metabolism in recent years. This article reviews the function and regulatory mechanisms of TRIM family proteins in bone metabolism, focusing on their dual roles in bone formation and resorption. It also provides a detailed analysis of signaling pathways and molecular mechanisms by which TRIM family members regulate the activities of osteoblasts and osteoclasts. Research findings suggest that modulating the expression or activity of TRIM family proteins could be beneficial for treating bone diseases such as osteoporosis. This review highlights the molecular mechanisms of TRIM family members in bone physiology and pathology, aiming to provide theoretical basis and scientific guidance for developing novel therapeutic strategies for bone diseases.
Humans ; Ubiquitin-Protein Ligases/physiology* ; Bone and Bones/metabolism* ; Animals ; Tripartite Motif Proteins/physiology* ; Osteoclasts/metabolism* ; Osteoblasts/metabolism* ; Signal Transduction/physiology* ; Osteogenesis/physiology*

Bone is a highly calcified and vascularized tissue. The vascular system plays a vital role in supporting bone growth and repair, such as the provision of nutrients, growth factors, and metabolic waste transfer. Moreover, the additional functions of the bone vasculature, such as the secretion of various factors and the regulation of bone-related signaling pathways, are essential for maintaining bone health. In the bone microenvironment, bone tissue cells play a critical role in regulating angiogenesis, including osteoblasts, bone marrow mesenchymal stem cells (BMSCs), and osteoclasts. Osteogenesis and bone angiogenesis are closely linked. The decrease in osteogenesis and bone angiogenesis caused by aging leads to osteoporosis. Long noncoding RNAs (lncRNAs) are involved in various physiological processes, including osteogenesis and angiogenesis. Recent studies have shown that lncRNAs could mediate the crosstalk between angiogenesis and osteogenesis. However, the mechanism by which lncRNAs regulate angiogenesis‒osteogenesis crosstalk remains unclear. In this review, we describe in detail the ways in which lncRNAs regulate the crosstalk between osteogenesis and angiogenesis to promote bone health, aiming to provide new directions for the study of the mechanism by which lncRNAs regulate bone metabolism.
RNA, Long Noncoding/physiology* ; Osteogenesis/physiology* ; Humans ; Neovascularization, Physiologic/genetics* ; Bone and Bones/metabolism* ; Animals ; Mesenchymal Stem Cells ; Signal Transduction ; Osteoblasts ; Osteoclasts ; Angiogenesis

OBJECTIVES: To investigate the effect of Qianggu Kangshu Formula (QGKSF) for alleviating osteoclast differentiation in rheumatoid arthritis and the underlying mechanism. METHODS: RAW264.7 cells cultured under hypoxic conditions were treated with RANKL to induce osteoclast differentiation and incubated with normal rat serum or sera from rats medicated with methotrexate (MTX) or QGKSF at low and high doses. Cell viability, TRAP-positive multinucleated cells and F-actin ring formation in the treated cells were assessed with CCK-8 assay, TRAP staining and Phalloidin staining, respectively. Autophagy and autophagosomes in the cells were observed with MDC staining and transmission electron microscopy. ELISA was used to measure IL-6 and TNF-α levels in the culture supernatant, and the expressions of HIF-1α, BNIP3, Bcl-2, Beclin1, LC3-I, LC3-II, P62 and TRAP mRNAs and proteins were analyzed using RT-qPCR and Western blotting. RESULTS: In hypoxia- and RANKL-induced RAW264.7 cells treated with normal rat serum, significant increments of TRAP-positive cells and F-actin ring formation were observed with an enhanced autophagic fluorescence intensity and increased autophagosomes. Treatment of the induced cells with rat sera medicated with MTX and low- and high-dose QGKSF obviously reduced the TRAP-positive cells, F-actin rings and autophagosomes as well as the autophagic fluorescence intensity. RANKL treatment significantly increased IL-6 and TNF-α levels in RAW264.7 cells, which were obviously decreased by treatment with MTX- and QGKSF-medicated sera. RANKL also significantly increased the mRNA and protein expression levels of HIF-1α, BNIP3, Bcl-2, Beclin1, LC3 and TRAP and lowered P62 expressions, and these changes were effectively reversed by treatment with MTX- and QGKSF-medicated sera. CONCLUSIONS QGKSF attenuates RANKL-induced osteoclast differentiation in hypoxic RAW264.7 cells by inhibiting the HIF-1α/BNIP3 autophagy signaling pathway, suggesting its potential for treatment of bone destruction in rheumatoid arthritis.
Animals ; Drugs, Chinese Herbal/pharmacology* ; Osteoclasts/drug effects* ; Autophagy/drug effects* ; Mice ; Signal Transduction/drug effects* ; Rats ; Cell Differentiation/drug effects* ; Arthritis, Rheumatoid/pathology* ; Hypoxia-Inducible Factor 1, alpha Subunit/metabolism* ; RAW 264.7 Cells ; Membrane Proteins/metabolism* ; Mitochondrial Proteins

Complement C3 plays a critical role in periodontitis. However, its source, role and underlying mechanisms remain unclear. In our study, by analyzing single-cell sequencing data from mouse model of periodontitis, we identified that C3 is primarily derived from periodontal fibroblasts. Subsequently, we demonstrated that C3a has a detrimental effect in ligature-induced periodontitis. C3ar^-/- mice exhibited significantly less destruction of periodontal support tissues compared to wild-type mice, characterized by mild gingival tissue damage and reduced alveolar bone loss. This reduction was associated with decreased production of pro-inflammatory mediators and reduced osteoclast infiltration in the periodontal tissues. Mechanistic studies suggested that C3a could promote macrophage polarization and osteoclast differentiation. Finally, by analyzing single-cell sequencing data from the periodontal tissues of patients with periodontitis, we found that the results observed in mice were consistent with human data. Therefore, our findings clearly demonstrate the destructive role of fibroblast-derived C3 in ligature-induced periodontitis, driven by macrophage M1 polarization and osteoclast differentiation. These data strongly support the feasibility of C3a-targeted interventions for the treatment of human periodontitis.
Animals ; Osteoclasts/cytology* ; Periodontitis/metabolism* ; Cell Differentiation ; Mice ; Fibroblasts/metabolism* ; Macrophages ; Disease Models, Animal ; Complement C3/metabolism* ; Humans ; Disease Progression ; Mice, Inbred C57BL ; Male ; Mice, Knockout

Osteoporosis is a prevalent skeletal condition characterized by reduced bone mass and strength, leading to increased fragility. Buqi-Tongluo (BQTL) decoction, a traditional Chinese medicine (TCM) prescription, has yet to be fully evaluated for its potential in treating bone diseases such as osteoporosis. To investigate the mechanism by which BQTL decoction inhibits osteoclast differentiation in vitro and validate these findings through in vivo experiments. We employed MTS assays to assess the potential proliferative or toxic effects of BQTL on bone marrow macrophages (BMMs) at various concentrations. TRAcP experiments were conducted to examine BQTL's impact on osteoclast differentiation. RT-PCR and Western blot analyses were utilized to evaluate the relative expression levels of osteoclast-specific genes and proteins under BQTL stimulation. Finally, in vivo experiments were performed using an osteoporosis model to further validate the in vitro findings. This study revealed that BQTL suppressed receptor activator of NF-κB ligand (RANKL)-induced osteoclastogenesis and osteoclast resorption activity in vitro in a dose-dependent manner without observable cytotoxicity. The inhibitory effects of BQTL on osteoclast formation and function were attributed to the downregulation of NFATc1 and c-fos activity, primarily through attenuation of the MAPK, NF-κB, and Calcineurin signaling pathways. BQTL's inhibitory capacity was further examined in vivo using an ovariectomized (OVX) rat model, demonstrating a strong protective effect against bone loss. BQTL may serve as an effective therapeutic TCM for the treatment of postmenopausal osteoporosis and the alleviation of bone loss induced by estrogen deficiency and related conditions.
Animals ; NFATC Transcription Factors/genetics* ; Drugs, Chinese Herbal/pharmacology* ; Ovariectomy ; Osteoclasts/metabolism* ; Female ; Osteogenesis/drug effects* ; Rats, Sprague-Dawley ; Rats ; NF-kappa B/genetics* ; Osteoporosis/genetics* ; Signal Transduction/drug effects* ; Bone Resorption/genetics* ; Cell Differentiation/drug effects* ; Humans ; RANK Ligand/metabolism* ; Mitogen-Activated Protein Kinases/genetics* ; Transcription Factors

This study investigated the regulatory potential of salidroside (SAL), a primary active compound in Rhodiola rosea L., on osteoclast differentiation by modulating the hypoxia-inducible factor 1-alpha (HIF-1a) pathway in osteoblasts. Luciferase reporter assay and chromatin immunoprecipitation (ChIP) assay were employed to validate whether the receptor activator of nuclear factor-?B ligand (RANKL) is the downstream target gene of HIF-1a in osteoblasts. The study also utilized lipopolysaccharide (LPS)-induced mouse osteolysis to examine the impact of SAL on osteolysis in vivo. Furthermore, conditioned medium (CM) from SAL-pretreated osteoblasts was used to investigate the paracrine effects on osteoclastogenesis through the HIF-1a pathway. Hypoxic condition-induced overexpression of HIF-1a upregulated RANKL levels by binding to the RANKL promoter and enhancing transcription in osteoblastic cells. In vivo, SAL significantly alleviated bone tissue hypoxia and decreased the expression of HIF-1a by downregulating the expression of RANKL, vascular endothelial growth factor (VEGF), interleukin 6 (IL-6), and angiopoietin-like 4 (ANGPTL4). In the paracrine experiment, conditioned media from SAL-pretreated osteoblasts inhibited differentiation through the HIF-1a/RANKL, VEGF, IL-6, and ANGPTL4 pathways. RANKL emerges as the downstream target gene regulated by HIF-1a in osteoblasts. SAL significantly alleviates bone tissue hypoxia and bone loss in LPS-induced osteolysis through the HIF-1a/RANKL, VEGF, IL-6, and ANGPTL4 pathways. SAL inhibits osteoclast differentiation by regulating osteoblast paracrine secretion.
Animals ; Osteoblasts/cytology* ; Hypoxia-Inducible Factor 1, alpha Subunit/genetics* ; Glucosides/administration & dosage* ; Cell Differentiation/drug effects* ; Phenols/administration & dosage* ; Mice ; Osteoclasts/metabolism* ; RANK Ligand/genetics* ; Rhodiola/chemistry* ; Osteogenesis/drug effects* ; Signal Transduction/drug effects* ; Interleukin-6/genetics* ; Male ; RAW 264.7 Cells ; Osteolysis/genetics* ; Humans ; Mice, Inbred C57BL

This study identified six novel azaphilones, isochromophilones G-L (1-6), and three novel biosynthetically related congeners (7-9) from Diaporthe sp. SCSIO 41011. The structures and absolute configurations were elucidated through comprehensive spectroscopic analyses combined with experimental and calculated electronic circular dichroism (ECD) spectra. Significantly, three highly oxygenated azaphilones contain an acetyl group at the terminal chain (4) or linear conjugated polyenoid moieties (5 and 6), which occur infrequently in the azaphilone family. Additionally, several compounds demonstrated inhibition of lipopolysaccharide (LPS)-induced nuclear factor kappa-B (NF-κB) activation in RAW 264.7 macrophages at 20 μmol·L^-1. The novel compound (1) effectively inhibited receptor activator of NF-κB ligand (RANKL)-induced osteoclast differentiation without exhibiting cytotoxicity in bone marrow and RAW 264.7 macrophages, indicating its potential as a promising lead compound for osteolytic disease treatment. This research presents the first documented evidence of azaphilone derivatives as inhibitors of RANKL-induced osteoclastogenesis.
Animals ; Mice ; RANK Ligand/genetics* ; RAW 264.7 Cells ; Osteoclasts/metabolism* ; Benzopyrans/isolation & purification* ; Osteogenesis/drug effects* ; Macrophages/metabolism* ; Molecular Structure ; Pigments, Biological/isolation & purification* ; Ascomycota/chemistry* ; NF-kappa B/genetics* ; Cell Differentiation/drug effects*

OBJECTIVES: This study aimed to explore the therapeutic effect and mechanism of ginsenoside Rb3 on experimental periodontitis and bone resorption in rats. METHODS: Male SD rats were randomly divided into a control group, a ligation group, an Rb3 group, and a doxycycline (Dox) group for in vivo experiments. A periodontitis model was established by ligating the maxillary second molar, and samples were collected after 3 weeks of drug treatment. Micro-CT assessment of alveolar bone resorption was performed, and hematoxylin-eosin (HE) staining was used to observe pathological changes in periodontal and visceral tissues. Tartrate resistant acid phosphatase (TRAP) staining was applied to detect the formation of osteoclasts in periodontal tissues, and enzyme-linked immunosorbent assay (ELISA) was adopted to detect the serum levels of interleukin (IL)-6, IL-8, immunoglobulin (Ig)M, and IgG. Quantitative polymerase chain reaction (qPCR) was employed to detect the expression of factors related to gingival inflammation and osteoclast formation. Immunofluorescence staining was used to detect phospho-extracellular signal-regulated kinase (p-ERK) expression. In vitro experiments were conducted by pretreating RAW264.7 cells with drugs and adding lipopolysaccharides (LPS) stimulation from Porphyromonas gingivalis (P. gingivalis). IL-1β and IL-6 mRNA expression was detected by qPCR, and Western blot was used to detect the effect of Rb3 on the mitogen-activated protein kinases (MAPKs) signaling pathway. RESULTS: Compared with the control group, the ligation group showed significant periodontitis and bone resorption. Compared with the ligation group, the Rb3 group showed a decrease in alveolar bone resorption and osteoclast formation; p-ERK/ERK ratio, IL-1β, IL-6, and nuclear factor of activated T cells (NFATc1) mRNA levels and downstream gene expression in periodontal tissues; serum IL-6, IL-8, IgG, and IgM levels. Rb3 reduced IL-8 and IL-1β mRNA expression levels and p-ERK/ERK and p-p38 MAPK/p38 MAPK ratios in RAW264.7 cells induced by P. gingivalis LPS stimulation. CONCLUSIONS Rb3 inhibits inflammation and bone resorption in experimental periodontitis in rats. Compared with Dox, Rb3 has better effects in inhibiting pro-inflammatory factors and osteoclast gene expression and may exert anti-inflammatory effects by activating the MAPK signaling pathway.
Animals ; Ginsenosides/therapeutic use* ; Rats, Sprague-Dawley ; Male ; Periodontitis/pathology* ; Rats ; Osteoclasts/drug effects* ; Interleukin-1beta/metabolism* ; Interleukin-6/blood* ; Mice ; Alveolar Bone Loss ; Interleukin-8/blood* ; Immunoglobulin G/blood* ; RAW 264.7 Cells ; Transcription Factors

This study aimed to investigate the potential role of Colquhounia Root Tablets against bone destruction in rheumatoid arthritis(RA) and its molecular mechanism. The study used ultra-performance liquid chromatography-mass spectrometry to analyze the major components of Colquhounia Root Tablets and predicted its candidate target gene set based on the major components. The key targets of RA bone destruction were obtained through GeneCards and the Database of Genetics and Medical Literature(OMIM), protein-protein interaction(PPI) network was constructed, and the key targets were identified by topological analysis. The molecular mechanism of Colquhounia Root Tablets against RA bone destruction was further revealed using Gene Ontology(GO) and Kyoto Encyclopedia of Genes and Genomes(KEGG) enrichment analysis. The effects of Colquhounia Root Tablets on macrophage viability was assessed by MTS assay and screened for non-toxic concentrations. A model of receptor activator of nuclear factor-κB(RANKL) induced osteoclast differentiation in vitro was constructed. Colquhounia Root Tablets were used to observe the formation and differentiation of osteoclasts by tartrate-resistant acid phosphatase(TRAP) staining and fibrous actin(F-actin) staining, and the effects of Colquhounia Root Tablets on the changes of core target proteins in the osteoclast differentiation system were detected by immunofluorescence and Western blot. The results showed that the main components of Colquhounia Root Tablets included 14 compounds such as triptolide, celastrol, and triptophenolide. Further network analysis revealed that heat-shock protein 90(HSP90) was the key target gene of Colquhounia Root Tablets for anti-RA bone destruction. TRAP staining and F-actin staining showed that the number and area of TRAP-positive polymorphonuclear cells, as well as actin rings, were reduced in a dose-dependent manner after the intervention of Colquhounia Root Tablets(P<0.01). Western blot results showed that the expression of HSP90 protein was significantly reduced after intervention with Colquhounia Root Tablets at 20 and 40 μg·mL~(-1)(P<0.01); Colquhounia Root Tablets at 10 μg·mL~(-1) could significantly decrease the expression of necrosis factor receptor associated molecule 6(TRAF6) and nuclear factor of activated T cells 1(NFATc1) proteins(P<0.01); moreover, all doses of Colquhounia Root Tablets significantly reduced the expression of osteoclast differentiation marker proteins matrix metalloproteinase 9(MMP9) and cathepsin K(CTSK)(P<0.01).Immunofluorescence results further confirmed that Colquhounia Root Tablets significantly inhibited HSP90 and CTSK levels, as well as NFATc1 activation in osteoblasts. In conclusion, the present study confirmed that Colquhounia Root Tablets may inhibit RANKL-induced osteoclast differentiation by regulating the key target of HSP90, thus exerting an anti-RA bone destruction effect, which will provide a new idea for Colquhounia Root Tablets to prevent and treat bone destruction in rheumatoid arthritis.
Osteoclasts/metabolism* ; Mice ; Animals ; Cell Differentiation/drug effects* ; HSP90 Heat-Shock Proteins/genetics* ; Drugs, Chinese Herbal/chemistry* ; Plant Roots/chemistry* ; Humans ; Arthritis, Rheumatoid/physiopathology* ; Protein Interaction Maps/drug effects*

Cellular immune responses as well as generalized and periarticular bone loss are the key pathogenic features of rheumatoid arthritis (RA). Under the pathological conditions of RA, dysregulated inflammation and immune processes tightly interact with skeletal system, resulting in pathological bone damage via inhibition of bone formation or induction of bone resorption. Single-cell omics technologies are revolutionary tools in the field of modern biological research.They enable the display of the state and function of cells in various environments from a single-cell resolution, thus making it conducive to identify the dysregulated molecular mechanisms of bone destruction in RA as well as the discovery of potential therapeutic targets and biomarkers. Here, we summarize the latest findings of single-cell omics technologies in osteoimmunology research in RA. These results suggest that single-cell omics have made significant contributions to transcriptomics and dynamics of specific cells involved in bone remodeling, providing a new direction for our understanding of cellular heterogeneity in the study of osteoimmunology in RA.
Humans ; Osteoclasts/physiology* ; Arthritis, Rheumatoid/pathology* ; Inflammation/pathology* ; Bone and Bones/pathology* ; Bone Resorption/pathology*