Heterogeneous DNA hydrogel loaded with Apt02 modified tetrahedral framework nucleic acid accelerated critical-size bone defect repair.

Segmental bone defects, stemming from trauma, infection, and tumors, pose formidable clinical challenges. Traditional bone repair materials, such as autologous and allogeneic bone grafts, grapple with limitations including source scarcity and immune rejection risks. The advent of nucleic acid nanotechnology, particularly the use of DNA hydrogels in tissue engineering, presents a promising solution, attributed to their biocompatibility, biodegradability, and programmability. However, these hydrogels, typically hindered by high gelation temperatures (∼46 °C) and high construction costs, limit cell encapsulation and broader application. Our research introduces a novel polymer-modified DNA hydrogel, developed using nucleic acid nanotechnology, which gels at a more biocompatible temperature of 37 °C and is cost-effective. This hydrogel then incorporates tetrahedral Framework Nucleic Acid (tFNA) to enhance osteogenic mineralization. Furthermore, considering the modifiability of tFNA, we modified its chains with Aptamer02 (Apt02), an aptamer known to foster angiogenesis. This dual approach significantly accelerates osteogenic differentiation in bone marrow stromal cells (BMSCs) and angiogenesis in human umbilical vein endothelial cells (HUVECs), with cell sequencing confirming their targeting efficacy, respectively. In vivo experiments in rats with critical-size cranial bone defects demonstrate their effectiveness in enhancing new bone formation. This innovation not only offers a viable solution for repairing segmental bone defects but also opens avenues for future advancements in bone organoids construction, marking a significant advancement in tissue engineering and regenerative medicine.

Dual-network DNA-silk fibroin hydrogels with controllable surface rigidity for regulating chondrogenic differentiation.

Osteoarthritis (OA) is a common joint disease known for cartilage degeneration, leading to a substantial burden on individuals and society due to its high disability rate. However, current clinical treatments for cartilage defects remain unsatisfactory due to the unclear mechanisms underlying cartilage regeneration. Tissue engineering hydrogels have emerged as an attractive approach in cartilage repair. Recent research studies have indicated that stem cells can sense the mechanical strength of hydrogels, thereby regulating their differentiation fate. In this study, we present the groundbreaking construction of dual-network DNA-silk fibroin (SF) hydrogels with controllable surface rigidity. The supramolecular networks, formed through DNA base-pairing, induce the development of ß-sheet structures by constraining and aggregating SF molecules. Subsequently, SF was cross-linked via horseradish peroxidase (HRP)-mediated enzyme reactions to form the second network. Experimental results demonstrated a positive correlation between the surface rigidity of dual-network DNA-SF hydrogels and the DNA content. Interestingly, it was observed that dual-network DNA-SF hydrogels with moderate surface rigidity exhibited the highest effectiveness in facilitating the migration of bone marrow mesenchymal stem cells (BMSCs) and their chondrogenic differentiation. Transcriptome sequencing further confirmed that dual-network DNA-SF hydrogels primarily enhanced chondrogenic differentiation of BMSCs by upregulating the Wnt and TGF-ß signaling pathways while accelerating collagen II synthesis. Furthermore, in vivo studies revealed that dual-network DNA-SF hydrogels with moderate surface rigidity significantly accelerated cartilage regeneration. In summary, the dual-network DNA-SF hydrogels represent a promising and novel therapeutic strategy for cartilage regeneration.

Icaritin ameliorates RANKL-mediated osteoclastogenesis and ovariectomy-induced osteoporosis.

A rapidly aging society and longer life expectancy are causing osteoporosis to become a global epidemic. Over the last five decades, a number of drugs aimed at reducing bone resorption or restoring bone mass have been developed, but their efficacy and safety are limited. Icaritin (ICT) is a natural compound extracted from anti-osteoporosis herb Epimedium spp. and has been shown to inhibit osteoclast differentiation. However, the molecular mechanism by which ICT weaken RANKL-induced osteoclast differentiation has not been completely investigated. Here, we evaluated the anti-osteoclastogenic effect of ICT in vitro and the potential drug candidate for treating osteoporosis in vivo. In vitro study, ICT was found to inhibit osteoclast formation and bone resorption function via downregulating transcription factors activated T cell cytoplasm 1 (NFATc1) and c-fos, which further downregulate osteoclastogenesis-specific gene. In addition, the enhanced mitochondrial mass and function required for osteoclast differentiation was mitigated by ICT. The histomorphological results from an in vivo study showed that ICT attenuated the bone loss associated with ovariectomy (OVX). Based on these results, we propose ICT as a promising new drug strategy for osteoporosis that inhibits osteoclast differentiation.

Locking plate fixation versus intramedullary nail fixation for the treatment of multifragmentary proximal humerus fractures (OTA/AO type 11C): a preliminary comparison of clinical efficacy.

BACKGROUND: This study aimed to compare the clinical efficacy of locking plate and intramedullary nail fixations in the treatment of patients with OTA/AO type 11C proximal humerus fractures. METHODS: We retrospectively analyzed the data of patients with OTA/AO type 11C1.1 and 11C3.1 proximal humerus fractures who underwent surgery at our institution from June 2012 to June 2017. Perioperative indicators, postoperative morphological parameters of the proximal humerus, and Constant-Murley scores were evaluated and compared. RESULTS: Sixty-eight patients with OTA/AO type 11C1.1 and 11C3.1 proximal humerus fractures were enrolled in this study. Overall, 35 patients underwent open reduction and plate screw internal fixation, and 33 patients underwent limited open reduction and locking of the proximal humerus with intramedullary nail internal fixation. The total cohort had a mean follow-up duration of 17.8 months. The mean operation time of the locking plate group was significantly longer than that of the intramedullary nail group (P < 0.05), while the mean bleeding volume was significantly higher in the locking plate group than that in the intramedullary nail group (P < 0.05). The initial neck-shaft angles, final neck-shaft angles, forward flexion ranges, or Constant-Murley scores did not show significant differences between the two groups (P > 0.05). Complications, including screw penetrations, acromion impingement syndrome, infection, and aseptic necrosis of the humeral head, occurred in 8 patients (8/35, 22.8%) in the locking plate group and 5 patients in the intramedullary nail group (5/33, 15.1%; including malunion and acromion impingement syndrome), with no significant difference between the groups (P > 0.05). CONCLUSIONS: Similar satisfactory functional results can be achieved with locking plates and intramedullary nailing for OTA/AO type 11C1.1 and 11C3.1 proximal humerus fractures, with no significant difference in the number of complications between these two techniques. However, intramedullary nailing has advantages over locking plates for OTA/AO type 11C1.1 and 11C3.1 proximal humerus fractures in terms of operation time and bleeding volume.

Ultrasound-triggered in situ gelation with ROS-controlled drug release for cartilage repair.

Cartilage defects are usually caused by acute trauma and chronic degeneration. However, it is still a great challenge to improve the repair of articular cartilage defects due to the limited self-regeneration capacity of such defects. Herein, a novel ROS-responsive in situ nanocomposite hydrogel loaded with kartogenin (KGN) and bone marrow-derived stem cells (BMSCs) was designed and constructed via the enzymatic reaction of fibrinogen and thrombin. Meanwhile, a ROS-responsive thioketal (TK)-based liposome was synthesized to load the chondrogenesis-inducing factor KGN, the bioenzyme thrombin and an ultrasound-sensitive agent PpIX. Under ultrasound stimulation, the TK-based liposome was destroyed, followed by in situ gelation of fibrinogen and thrombin. Moreover, sustained release of KGN was realized by regulating the ultrasound conditions. Importantly, ROS generation and KGN release within the microenvironment of the in situ fibrin hydrogel significantly promoted chondrogenic differentiation of BMSCs via the Smad5/mTOR signalling pathway and effectively improved cartilage regeneration in a rat articular cartilage defect model. Overall, the novel in situ nanocomposite hydrogel with ROS-controlled drug release has great potential for efficient cartilage repair.

Second near-infrared photoactivatable nanomedicines for enhanced photothermal-chemodynamic therapy of cancer.

Nanomedicines have been widely used for cancer therapy, while controlling their activity for effective and safe treatment remains a big challenge. Herein, we report the development of a second near-infrared (NIR-II) photoactivatable enzyme-loaded nanomedicine for enhanced cancer therapy. Such a hybrid nanomedicine contains a thermoresponsive liposome shell loaded with copper sulfide nanoparticles (CuS NPs) and glucose oxidase (GOx). The CuS nanoparticles mediate the generation of local heat under 1064 nm laser irradiation, which not only can be used for NIR-II photothermal therapy (PTT), but also leads to the destruction of the thermal-responsive liposome shell to achieve the on-demand release of CuS nanoparticles and GOx. In a tumor microenvironment, GOx oxidizes glucose to produce hydrogen peroxide (H2O2) that acts as a medium to promote the efficacy of chemodynamic therapy (CDT) by CuS nanoparticles. This hybrid nanomedicine enables the synergetic action of NIR-II PTT and CDT to obviously improve efficacy without remarkable side effects via NIR-II photoactivatable release of therapeutic agents. Such a hybrid nanomedicine-mediated treatment can achieve complete ablation of tumors in mouse models. This study provides a promising nanomedicine with photoactivatable activity for effective and safe cancer therapy.

Intramedullary Nail Fixation by Suprapatellar and Infrapatellar Approaches for Treatment of Distal Tibial Fractures.

OBJECTIVE: To compare the functional and alignment outcomes of intramedullary nail fixation using suprapatellar and infrapatellar approaches in treating distal tibial fractures. METHODS: In this retrospective study, 132 patients with distal tibial fractures (87 men, 45 women) ranging in age from 20 to 66 years were treated with intramedullary nails using the suprapatellar (69 patients) or infrapatellar (63 patients) approach. The radiographic alignment outcomes and ankle function were compared between the two groups. Multivariate logistic regression analyses were performed to determine which variety influenced ankle functional scores and whether the suprapatellar approach intervention demonstrated a protective effect. RESULTS: The mean follow-up time was 14.22 ± 2.31 months. The mean sagittal section angle of the fracture in the suprapatellar and infrapatellar approach groups was 3.20° ± 1.20° and 5.31° ± 1.23°, respectively (P < 0.001). The mean coronal section angle was 3.51° ± 0.89° and 5.42° ± 1.05°, respectively (P < 0.001). Three patients (4.3%) in the suprapatellar approach group and 15 patients (23.8%) in the infrapatellar approach group had poor fracture reduction (P < 0.001). The mean hind foot functional score and ankle pain score were 95.91 ± 4.70 and 35.91 ± 4.70 points, respectively, in the suprapatellar approach group and 85.20 ± 5.61 and 25.20 ± 5.61 points, respectively, in the infrapatellar approach group (P < 0.001 for both). In the comparison of ankle function, the multivariate logistic regression analyses demonstrated that the odds ratio in the suprapatellar approach group was about 7 times that in the infrapatellar approach group (odds ratio, 7.574; 95% confidence interval, 2.148-28.740; P = 0.002). Of the variants measured, the statistically significant risk factors for poor ankle function were AO type A3 (P = 0.016) and diabetes mellitus (P = 0.006). Sex and the operation interval were not statistically significant risk factors for poor ankle function. CONCLUSION: Intramedullary nailing using the suprapatellar approach facilitates simple fracture reduction, excellent postoperative fracture alignment, and few complications, giving it obvious advantages over the conventional infrapatellar approach. Additionally, the suprapatellar approach is a prognostic factor associated with postoperative ankle joint function.

Ancillary ligand effects on α-olefin polymerization catalyzed by zirconium metallocene: a computational study.

The polymerization of α-olefins catalyzed by zirconium metallocene catalyst was systematically studied through experiments and density functional theory (DFT) calculations. Having achieved an agreement between theory and experiment, it was found that the effect of the catalyst ligand on the C[double bond, length as m-dash]C insertion reaction was significantly greater than that on the ß-H elimination reaction. Therefore, the molecular weight of polymers can be increased by improving the activity of the C[double bond, length as m-dash]C insertion. In addition, in comparison with propylene, the chain length of α-olefins can directly affect the stereotacticity of polymerization products, owing to steric hindrance between the polymer chain and monomer.

Open Reduction and Internal Fixation by Volar Locking Plates and the "Poking Reduction" Technique in Distal Radius Fractures with Displaced Dorsal Ulnar Fragments: A Retrospective Study.

OBJECTIVE: To investigate the clinical and radiological outcomes of distal radius fractures (DRFs) with displaced dorsal ulnar fragments treated with volar locking plate (VLP) and the "poking reduction" technique. METHODS: Between January 2014 and January 2019, 78 unilateral DRFs with displaced dorsal ulnar fragment (AO type C3) treated with VLP were conducted. According to the reduction technique of the dorsal ulnar fragment, the patients were divided into the conventional reduction (CRG) group (33 patients, 14 males and 19 females, mean age 57.2 ± 12.1 years old) and the "poking reduction" (PRG) group (45 patients, 11 males and 34 females, mean age 60.1 ± 12.4 years old). According to the AO classification, there were 21 cases of C3.1 and 12 of C3.2 in the CPG group, 27 cases of C3.1 and 18 of C3.2 in the PRG group. Clinical and radiographic data were extracted from the electronic medical record system. These data were reviewed for clinical outcomes (range of motion, grip strength), radiological outcomes (volar tilt, radial inclination, radial height, step of articular surface), and postoperative complications. The final functional recovery was evaluated by the disabilities of the arm, shoulder, and hand (DASH) score. RESULTS: The mean duration of follow-up was 27 months (range from 12 to 56). The average operation time and intraoperative blood loss did not significantly differ between groups (p > 0.05). Postoperative CT examination showed that the step of articular surface in CPG group (0.8 ± 0.3 mm) was larger than that in PRG group (0.5 ± 0.2 mm) (p < 0.001). The DASH score did not significantly differ between groups (26.1 ± 4.6 in CRG and 24.7 ± 4.0 in PRG, p > 0.05) at 3 months postoperatively. At 6 months and 12 months postoperatively, the DASH score was better in PRG group (11.8 ± 2.5 and 10.4 ± 2.0) than in CRG group (13.6 ± 2.7 and 12.2 ± 2.5) (p = 0.004, p = 0.001, respectively). At 12 months postoperatively, wrist range of motion did not significantly differ between groups (p > 0.05). There was no significant difference in radiological parameters between the two groups (p > 0.05). The incidence of complications was higher in the CRG group (7/33) than in the PRG group (2/45) (p = 0.009). CONCLUSION: The "poking reduction" technique is a wise option for reduction of dorsal ulnar fragment in DRFs. This innovative technique could restore smoothness of the radiocarpal joint effectively, and the dorsal ulnar fragment could be fixed effectively combined with the volar plate.

Protective Role of ß-Sitosterol in Glucocorticoid-Induced Osteoporosis in Rats Via the RANKL/OPG Pathway.

Introduction: Osteoporosis affects approximately 10% of the population worldwide. ß-sitosterol (BSS), a major phytosterol in plants, has been claimed for centuries to have numerous medical benefits, including bone strengthening. This study aimed to find the benefit of BSS in treating osteoporosis according to traditional methods and to investigate the protective effect of BSS on glucocorticoid-induced osteoporosis in rats. Design: Wistar rats were randomly assigned to one of four groups: the control group, the dexamethasone (DEX) group and one of two BSS-treated osteoporosis groups (100 and 200 mg/kg). Blood samples and femur bones were collected for histopathology, immunohistochemistry, biochemical and mRNA expression analysis. Results: The results indicated that BSS (100 and 200 mg/kg) increased bone length, bone weight and bone mineral density (BMD) and suppressed DEX-induced reduction in body weight, dose-dependently. Mechanistically, BSS (100 and 200 mg/kg) treatment alleviated the increase of bone resorption markers and the decline of osteogenic markers, which might be partially mediated by regulation of nuclear factor kappa-ß ligand/osteoprotegerin (RANKL/OPG) and RunX2 pathways. The immunohistochemical inducible nitric oxide synthase (iNOS) results of the rats' distal femur were negative in all groups. However, except in the DEX group, the endothelial nitric oxide synthase (eNOS) color reaction in osteoblasts was strongly positive in the other 3 groups. These results suggest that BSS showed promising effects in protection against glucocorticoid-induced osteoporosis by protecting osteoblasts and suppressing osteoclastogenesis.

Research Progress of Exosomes in Bone Diseases: Mechanism, Diagnosis and Therapy.

With the global escalation of the aging process, the number of patients with bone diseases is increasing year by year. Currently, there are limited effective treatments for bone diseases. Exosome, as a vital medium in cell-cell communication, can mediate tissue metabolism through the paracrine transmission of various cargos (proteins, nucleic acids, lipids, etc.) carried by itself. Recently, an increasing number of researchers have proven that exosomes play essential roles in the formation, metabolism, and pathological changes of bone and cartilage. Because exosomes have the advantages of small size, rich sources, and low immunogenicity, they can be used not only as substitutes for the traditional treatment of bone diseases, but also as biomarkers for the diagnosis of bone diseases. This paper reviews the research progress of several kinds of cells derived-exosomes in bone diseases and provides a theoretical basis for further research and clinical application of exosomes in bone diseases in the future.

Carnosol inhibits osteoclastogenesis in vivo and in vitro by blocking the RANKL­induced NF­κB signaling pathway.

Bone homeostasis is maintained by osteoclast-mediated bone resorption and osteoblast­mediated bone formation. Disruption of bone homeostasis due to excessive osteoclastogenesis or reduced osteogenesis results in various disorders, such as postmenopausal osteoporosis. Receptor activator of NF­κB ligand (RANKL) stimulation of the NF­κB signaling pathway is essential in osteoclastogenesis. The aim of the present study was to investigate the novel effects of carnosol, an active compound found in Rosmarinus officinalis, on RANKL­induced osteoclastogenesis both in vitro and in vivo. TRAP staining showed that carnosol significantly inhibited osteoclasts differentiation of bone marrow monocytes and RAW264.7 cells. Western blot results showed that the protein expression levels of osteoclastogenesis­associated genes, including cathepsin K, tartrate­resistant acid phosphatase and MMP­9, were markedly inhibited by carnosol, which may have suppressed osteoclast function. Furthermore, western blot and immunofluorescent staining results revealed that carnosol markedly suppressed the phosphorylation of p65 induced by RANKL and blocked its nuclear translocation, indicating the suppression of NF­κB signaling pathway. H&E staining and micro­CT results showed that in vivo treatment with carnosol significantly attenuated ovariectomy­induced bone loss in mice. In conclusion, the present study indicated that carnosol may suppress osteoclastogenesis both in vivo and in vitro by inhibiting the activation of the NF­κB signaling pathway. Carnosol may therefore be a potential novel therapeutic candidate for the clinical treatment of osteoclast­related disorders.

Exosome-Laden Hydrogels: A Novel Cell-free Strategy for In-situ Bone Tissue Regeneration.

In-situ bone tissue regeneration, which harnesses cell external microenvironment and their regenerative potential to induce cell functions and bone reconstruction through some special properties of biomaterials, has been deeply developed. In which, hydrogel was widely applied due to its 3D network structure with high water absorption and mimicking native extracellular matrix (ECM). Additionally, exosomes can participate in a variety of physiological processes such as cell differentiation, angiogenesis and tissue repair. Therefore, a novel cell-free tissue engineering (TE) using exosome-laden hydrogels has been explored and developed for bone regeneration in recent years. However, related reviews in this field are limited. Therefore, we elaborated on the shortcomings of traditional bone tissue engineering, the challenges of exosome delivery and emphasized the advantages of exosome-laden hydrogels for in-situ bone tissue regeneration. The encapsulation strategies of hydrogel and exosomes are listed, and the research progress and prospects of bioactive hydrogel composite system for continuous delivery of exosomes for in-situ bone repair are also discussed in this review.

Antibody-conjugated gold nanoparticles as nanotransducers for second near-infrared photo-stimulation of neurons in rats.

Infrared neural stimulation with the assistance of photothermal transducers holds great promise as a mini-invasive neural modulation modality. Optical nanoparticles with the absorption in the near-infrared (NIR) window have emerged as excellent photothermal transducers due to their good biocompatibility, surface modifiability, and tunable optical absorption. However, poor activation efficiency and limited stimulation depth are main predicaments encountered in the neural stimulation mediated by these nanoparticles. In this study, we prepared a targeted polydopamine (PDA)-coated gold (Au) nanoparticles with specific binding to thermo-sensitive ion channel as nanotransducers for second near-infrared (NIR-II) photo-stimulation of neurons in rats. The targeted Au nanoparticles were constructed via conjugation of anti-TRPV1 antibody with PEGylated PDA-coated Au nanoparticles and thus exhibited potent photothermal performance property in the second NIR (NIR-II) window and converted NIR-II light to heat to rapidly activate Ca2+ influx of neurons in vitro. Furthermore, wireless photothermal stimulation of neurons in living rat successfully evoke excitation in neurons in the targeted brain region as deep as 5 mm beneath cortex. This study thus demonstrates a remote-controlled strategy for neuromodulation using photothermal nanotransducers.

Synergistic Effect of Micro-Nano-Hybrid Surfaces and Sr Doping on the Osteogenic and Angiogenic Capacity of Hydroxyapatite Bioceramics Scaffolds.

BACKGROUND: The synergistic effect of chemical element doping and surface modification is considered a novel way to regulate cell biological responses and improve the osteoinductive ability of biomaterials. METHODS: Hydroxyapatite (HAp) bioceramics with micro-nano-hybrid (a mixture of microrods and nanorods) surfaces and different strontium (Sr) doping contents of 2.5, 5, 10, and 20% (Srx-mnHAp, x: 2.5, 5, 10 and 20%) were prepared via a hydrothermal transformation method. The effect of Srx-mnHAp on osteogenesis and angiogenesis of bone marrow stromal cells (BMSCs) was evaluated in vitro, and the bioceramics scaffolds were further implanted into rat calvarial defects for the observation of bone regeneration in vivo. RESULTS: HAp bioceramics with micro-nano-hybrid surfaces (mnHAp) could facilitate cell spreading, proliferation ability, ALP activity, and gene expression of osteogenic and angiogenic factors, including COL1, BSP, BMP-2, OPN, VEGF, and ANG-1. More importantly, Srx-mnHAp (x: 2.5, 5, 10 and 20%) further promoted cellular osteogenic activity, and Sr10-mnHAp possessed the best stimulatory effect. The results of calvarial defects revealed that Sr10-mnHAp could promote more bone and blood vessel regeneration, with mnHAp and HAp bioceramics (dense and flat surfaces) as compared. CONCLUSION: The present study suggests that HAp bioceramics with micro-nano-hybrid surface and Sr doping had synergistic promotion effects on bone regeneration, which can be a promising material for bone defect repair.

Knockdown of lncRNA LINC00662 suppresses malignant behaviour of osteosarcoma cells via competition with miR-30b-3p to regulate ELK1 expression.

PURPOSE: Osteosarcoma is a type of bone malignancy that mainly occurred in teenagers. This investigation is aimed to clarify the effect of long non-coding RNA (lncRNA) LINC00662 on the proliferation, migration, and invasion in osteosarcoma and explore the underlying action mechanisms. METHODS: The mRNA expression of LINC00662 was determined by real-time quantitative polymerase chain reaction. Cell proliferation, migration, and invasion were evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, wound healing, and transwell assays, respectively. A dual-luciferase reporter assay was used to validate the target relationships Between microRNA (miR)-30b-3p and LINC00662/ ETS domain-containing protein 1 (ELK1). Western blotting was performed to determine the protein expression of ELK1. Xenograft model was established to evaluate the effects of LINC00662 silencing on tumor growth in vivo. RESULTS: LncRNA LINC00662 and ELK1 were significantly increased, while miR-30b-3p was reduced in osteosarcoma tissues. The results of functional experiments indicated that transfection of small hairpin (sh)-LINC00662 and miR-30b-3p mimics repressed the migration, invasion, and proliferation of osteosarcoma cells. LncRNA LINC00662 also appeared to sponge miR-30b-3p in order to affect the expression of ELK1. Simultaneously, there were weak negative correlations between the expression of miR-30b-3p and LINC00662/ELK1 in osteosarcoma tissues. Rescue experiments suggested that ELK1 overexpression and downregulation of miR-30b-3p reversed the suppressive effects of sh-LINC00662 on the cell migration, invasion, and proliferation in osteosarcoma. CONCLUSIONS: The current study indicated that knockdown of LINC00662 repressed cell migration, invasion, and proliferation through sponging miR-30b-3p to regulate the expression of ELK1 in osteosarcoma. These results may uncover a promising target for the treatment of osteosarcoma.

Effects of urolithin A on osteoclast differentiation induced by receptor activator of nuclear factor-κB ligand via bone morphogenic protein 2.

Urolithin A (UA) is an intestinal microbial metabolite derived from ellagitannins and a promising agent for treating osteoarthritis. However, its effects on osteoporosis are unclear. This study explored the effects of urolithin A (UA) on receptor activator of nuclear factor-κB ligand (RANKL)-induced osteoclasts and its underlying molecular mechanisms. RANKL treatment significantly increased tartrate-resistant acid phosphatase (TRACP) or osteoclast marker levels (P < 0.05), while adding UA decreased the RANKL-induced levels (P < 0.05) in RAW264.7 cells. Total RNA isolated from RANKL- or RANKL + UA-treated cells was sequenced, and the obtained transcriptome dataset revealed 2,399 differentially expressed genes. They were enriched in multiple pathways involved in rheumatoid arthritis, ERK1 and ERK2 cascade, regulation of inflammatory response, ECM-receptor interactions, and TNF signaling. Scanning electron microscopy showed that RANKL promoted bone resorption pits in bone biopsy specimens, whereas UA inhibited their formation. When bone morphogenic protein 2 (BMP2) was shRNA-silenced, the bone resorption pits were restored. Moreover, while RANKL significantly enhanced the levels of p-ERK2/ERK2, p-p38/p38, p-Akt1/Akt1, p-ERK1/ERK1, and osteoclast-related proteins (P < 0.05), UA reduced them. BMP2 silencing also reversed the UA inhibitory effect. Thus, UA represses the RANKL-induced osteoclast differentiation of RAW264.7 cells by regulating Akt1, p38, and ERK1/2 signaling, and BMP2 likely reverses the UA inhibitory effect via these pathways. We propose BMP2 as a potential drug target for treating bone metabolic diseases, such as osteoporosis.