Lithium Promotes Osteogenesis via Rab11a-Facilitated Exosomal Wnt10a Secretion and β-Catenin Signaling Activation

TiO2 Nanotube Implants Modified with Silk Fibroin and Mesoporous Silica Nanocomposite Coatings Enable Efficient Drug Release to Promote Osteogenesis

Enhanced bone healing within 1 week after post-titanium (Ti) dental implant surgery especially contributes to the subsequent long-term osseointegration, and the commonly used drug-loaded TiO2 nanotubes (TNTs) can promote osteogenesis yet still face the challenge of burst drug release that makes it difficult to maintain long-term effective drug concentrations and good osseointegration. Here, we prepared a double drug loading/release system of silk fibroin/mesoporous silica nanoparticles (SF/MSN) nanocomposite coating modified TNTs (TAMA) with AZD2858 (Wnt/β-catenin pathway agonist for promoting osteogenesis) as the therapeutic drug, realizing a long-term stable drug release and better osteogenesis. The increased β-sheet content of SF reduced the degradation rate of the SF/MSN coating, thus avoiding the AZD2858 burst release. The adsorption of MSN maintained the effective drug concentration more than 1 week that was especially critical for early bone healing. Under the protection of SF/MSN coating, the TAMA implant showed a well-organized spatial release of AZD2858, well enabling the osteogenic differentiation and mineralization at cellular level for up to 21 days. Animal experiments further demonstrated that the slow release of AZD2858 in the TAMA implant effectively activated the Wnt/β-catenin pathway, enabling rapid bone healing in the early stage of implantation and finally achieving the best osseointegration efficacy. Thus, this study proposed an efficient strategy for developing high-performance dental implants via the construction of a biodegradable SF/MSN coating.

Recent advances in osteonecrosis of the femoral head: a focus on mesenchymal stem cells and adipocytes

Osteonecrosis of the femoral head (ONFH) is a debilitating orthopedic disease characterized by femoral head collapse and destruction of bone and articular cartilage, resulting in severe joint pain and loss of hip mobility. Bone marrow mesenchymal stem cells (BMSCs) exhibit multilineage differentiation potential, including osteoblasts, adipocytes, fibroblasts, chondrocytes, and neurocytes. The imbalance between osteogenesis and adipogenesis in BMSCs plays a critical role in ONFH pathogenesis. Factors such as alcohol consumption and glucocorticoid exposure promote adipogenic differentiation while inhibiting osteogenic differentiation, leading to excessive adipocyte accumulation, reduced bone formation, and vascular impairment. We highlight the molecular mechanisms underlying ONFH with a particular focus on the role of BMSCs and further discuss the involvement of adipocytes. Moreover, we suggest that the use of adipose-derived mesenchymal stem cells (ADMSCs) is a viable approach for stem cell therapy and may have immense potential in ONFH. Several signaling pathways, including the Wnt, TGFβ/BMP, and PI3K/AKT pathways, along with various RNAs and other regulators, govern the osteogenesis and adipogenesis of BMSCs. These signaling pathways target essential transcription factors, such as Runx2 for osteogenesis and PPARγ and C/EBPs for adipogenesis. Adipocytes and their secreted adipokines, including leptin and adiponectin, strongly influence ONFH progression. Emerging therapies involving ADMSCs show potential for promoting bone regeneration and neovascularization. Our review provides a comprehensive overview of the current understanding of ONFH mechanisms by focusing on mesenchymal stem cells and adipocytes and suggests future research directions for therapeutic interventions.

Photo-curable layered double hydroxide-hyaluronic acid-composite hydrogels with multifunctional properties for growth factor-free bone regeneration

Bone regeneration is a highly complex process involving the coordinated interaction between osteogenic stem cells, the extracellular matrix (ECM), and osteoinductive signals, which are often challenged by bacterial interference. While bone prostheses incorporating growth factors such as bone morphogenetic proteins have been commercially successful, the therapeutic use of recombinant growth factors can lead to significant adverse clinical outcomes. Here, we present a photo-curable layered double hydroxide (LDH)-composite hydrogel, designed to incorporate multiple functionalities for bone regeneration without the need for exogenous growth factors. The photo-curable hyaluronic acid (HA) hydrogel features a porous microstructure, biocompatibility, precise application, and adaptability to irregular bone defects. Incorporating LDH not only enhances osteogenic signals but also provides antibacterial activity, reducing the risk of infection and promoting a more favorable environment for bone regeneration. The combination of photo-curable HA with the functional 2D-nanomaterial LDH, renowned for its ability to intercalate therapeutic molecules, results in a hydrogel scaffold that emulates the osteoconductive traits of bone ECM. Additionally, the controlled release of the osteoinductive agent simvastatin via LDH augments bone healing through stimulation of the Wnt/β-catenin pathway. This nanoengineered HA-based hydrogel demonstrates significant potential as a multifunctional bone prosthesis, offering a promising, growth factor-free solution for enhanced bone regeneration.

The multifaceted roles of extracellular vesicles in osteonecrosis of the femoral head

Osteonecrosis of the femoral head (ONFH) is a severe disease characterized by bone tissue necrosis due to vascular impairment, often leading to joint collapse and requiring surgical intervention. Extracellular vesicles (EVs) serve as crucial mediators of intercellular communication, influencing osteogenesis, angiogenesis, and immune regulation. This review summarizes the dual role of EVs in both the pathogenesis of ONFH and post-necrosis bone repair, highlighting the impact of various EV-mediated signaling pathways on bone regeneration and the potential crosstalk among these pathways. Additionally, EVs hold promise as diagnostic biomarkers or contrast agents to complement conventional imaging techniques for ONFH detection. By elucidating the role of EVs in osteonecrosis and addressing the current challenges, we aspire to establish a foundation for the timely identification and treatment of ONFH. The translational potential of this article: This review comprehensively discusses the role of EVs in ONFH, providing innovative and promising insights for its diagnosis and treatment, which also establishes a theoretical foundation for the future clinical application of EVs in ONFH.

Regulation of macrophage polarization and pyroptosis by 4-methylcatechol alleviates collagen-induced arthritis via Nrf2/HO-1 and NF-κB/NLRP3 signaling pathways

Rheumatoid arthritis (RA) is a chronic inflammatory disease that leads to joint deformity and ultimately disability. The metabolite of quercetin, 4-Methylcatechol (4-MC), has been acknowledged for its anti-inflammatory and antioxidant properties; however, the protective effects of 4-MC on RA and its underlying mechanisms remain incompletely elucidated. In a collagen-induced arthritis (CIA) model, we observed that 4-MC effectively mitigated joint inflammation and bone destruction in CIA mice. Additionally, it significantly suppressed the upregulated expression of inflammatory cytokines in synovial tissues. Mechanistically, upon lipopolysaccharide (LPS) stimulation, 4-MC inhibited M1 polarization of macrophages and induced a phenotypic switch from M1 to M2 phenotype, thereby reducing the release of pro-inflammatory cytokines by M1 macrophages while increasing the release of anti-inflammatory cytokines by M2 macrophages. Furthermore, it attenuated LPS/adenosine triphosphate (ATP)-induced pyroptosis in macrophages by downregulating NLRP3 expression levels along with cleaved caspase-1, cleaved IL-1β, and GSDMD-NT expression levels. Notably, our findings revealed that 4-MC exerted inhibitory effects on the NF-κB signaling pathway through specific modulation of the NF-κB complex as well as phosphorylation of the upstream IKK kinase complex. Collectively, these results highlight significant therapeutic potential for utilizing 4-MC in RA treatment.

Proximal Femoral Metastasis From Epidermal Growth Factor Receptor-Mutated Lung Adenocarcinoma Mimicking Osteosarcoma on Magnetic Resonance Imaging

The aggressive nature of lung cancer is frequently accompanied by a high incidence of bone metastasis; however, proximal femoral metastasis from lung cancer is comparatively uncommon when compared to other malignancies. In this report, we present the case of a 53-year-old Asian male who presented with pain in the left thigh and back. Magnetic resonance imaging revealed severe bone destruction with involvement of adjacent soft tissue mass at the left thigh, exhibiting imaging findings that mimic osteosarcoma. Subsequent bone biopsy confirmed the diagnosis of epidermal growth factor receptor (EGFR)-mutated lung adenocarcinoma with bone metastasis. The patient achieved survival following administration of osimertinib and underwent surgery for femoral metastases without palliative surgery for lung cancer. Therefore, proximal femoral metastasis from EGFR-mutated lung adenocarcinoma should be considered as a differential diagnosis in patients suspected to have osteosarcoma. The imaging findings of proximal femoral metastasis from EGFR-mutated lung adenocarcinoma were presented, and their therapeutic management was discussed.