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Oral squamous cell carcinoma (OSCC) is an aggressive tumor that usually invades the maxilla or mandible. The extent and pattern of mandibular bone invasion caused by OSCC are the most important factors determining the treatment plan and patients' prognosis. Yet, the process of mandibular invasion is not fully understood. The following study explores the molecular mechanism that regulates the mandibular invasion of OSCC by focusing on bone morphogenetic protein receptor 1α (BMPR1α) and Sonic hedgehog (SHH) signals. We found that BMPR1α was positively correlated to bone defect of OSCC patients. Mechanistically, BMPR1α signaling regulated the differentiation and resorption activity of osteoclasts through the interaction of OSCC cells and osteoclast progenitors, and this process was mediated by SHH secreted by tumor cells. The inhibition of SHH protected bone from tumor‐induced osteolytic activity. These results provide a potential new treatment strategy for controlling OSCC from invading the jawbones. In oral squamous cell carcinoma (OSCC) tissues, overexpression of bone morphogenetic protein receptor 1α activates the downstream signaling and induces the expression of Sonic hedgehog (SHH) regulated by transcript factor Smad4. SHH enhances osteoclasts' differentiation and resorption activity in a paracrine way, promoting the bond defect induced by OSCC.

Research on postmenopausal osteoporosis (PMOP), a common bone metabolic disease, has traditionally focused on bone loss and imbalance in bone remodeling. However, with the development of bone immunology, the complex interactions between immune cells and bone cells in the bone marrow microenvironment have gradually been revealed, and “immune reprogramming” is considered a key factor driving the persistent bone loss in PMOP. Current evidence indicates that the postmenopausal bone marrow microenvironment undergoes significant structural and functional changes. These changes are characterized by a myeloid bias in hematopoietic stem/progenitor cells, aging of bone marrow mesenchymal stem cells (BMSCs) with a tendency toward differentiation into the adipocyte lineage, an imbalance of key immune cell subpopulations such as M1 and M2 macrophages and Th17 and regulatory T cells (Treg), as well as remodeling of cytokine and chemokine axis networks. Signaling pathways such as RANK/RANKL/OPG, Wnt/β-catenin, CXCL12–CXCR4, and S1P — along with systemic factors like estrogen deficiency, inflammatory aging, and the gut-bone-immune axis-collectively shape the characteristic bone immune microenvironment of PMOP. Based on this, this article systematically reviews the changes in cell lineage and molecular mechanisms underlying PMOP bone marrow immune reprogramming. It focuses on the key signaling networks in the bone immune microenvironment and their relationship with the mechanisms of existing anti-osteoporosis drugs. Furthermore, it proposes an immunotherapy approach represented by a three-tiered framework: traditional bone-targeted drugs, immune-guided therapy, and comprehensive intervention of the bone marrow microenvironment. Finally, in conjunction with emerging technologies such as multi-omics, single-cell, and spatial omics, this article discusses future directions for constructing a PMOP bone immune map and achieving precise stratification and individualized intervention, aiming to provide a theoretical basis and methodological reference for mechanistic research and bone immune-targeted therapy of PMOP.

The bone microenvironment is an ideal fertile soil for both primary and secondary tumors to seed. The occurrence and development of osteosarcoma, as a primary bone tumor, is closely related to the bone microenvironment. Especially, the metastasis of osteosarcoma is the remaining challenge of therapy and poor prognosis. Increasing evidence focuses on the relationship between the bone microenvironment and osteosarcoma metastasis. Many elements exist in the bone microenvironment, such as acids, hypoxia, and chemokines, which have been verified to affect the progression and malignance of osteosarcoma through various signaling pathways. We thoroughly summarized all these regulators in the bone microenvironment and the transmission cascades, accordingly, attempting to furnish hints for inhibiting osteosarcoma metastasis via the amelioration of the bone microenvironment. In addition, analysis of the cross-talk between the bone microenvironment and osteosarcoma will help us to deeply understand the development of osteosarcoma. The cellular and molecular protagonists presented in the bone microenvironment promoting osteosarcoma metastasis will accelerate the exploration of novel therapeutic strategies towards osteosarcoma.

Malignant bone tumors, which are difficult to treat with current clinical strategies, originate from bone tissues and can be classified into primary and secondary types. Due to the specificity of the bone microenvironment, the results of traditional means of treating bone tumors are often unsatisfactory, so there is an urgent need to develop new treatments for malignant bone tumors. Recently, nanoparticle-based approaches have shown great potential in diagnosis and treatment. Nanoparticles (NPs) have gained significant attention due to their versatility, making them highly suitable for applications in bone tissue engineering, advanced imaging techniques, and targeted drug delivery. For diagnosis, NPs enhance imaging contrast and sensitivity by integrating targeting ligands, which significantly improve the specific recognition and localization of tumor cells for early detection. For treatment, NPs enable targeted drug delivery, increasing drug accumulation at tumor sites while reducing systemic toxicity. In conclusion, understanding bone microenvironment and using the unique properties of NPs holds great promise in improving disease management, enhancing treatment outcomes, and ultimately improving the quality of life for patients with malignant bone tumors. Further research and development will undoubtedly contribute to the advancement of personalized medicine in the field of bone oncology.

Bone metastatic lesions are classified as osteoblastic or osteolytic lesions. Prostate and breast cancer patients frequently exhibit osteoblastic-type and osteolytic-type bone metastasis, respectively. In metastatic lesions, tumor cells interact with many different cell types, including osteoblasts, osteoclasts, and mesenchymal stem cells, resulting in an osteoblastic or osteolytic phenotype. However, the mechanisms responsible for the modification of bone remodeling have not been fully elucidated. MicroRNAs (miRNAs) are transferred between cells via exosomes and serve as intercellular communication tools, and numerous studies have demonstrated that cancer-secreted miRNAs are capable of modifying the tumor microenvironment. Thus, cancer-secreted miRNAs can induce an osteoblastic or osteolytic phenotype in the bone metastatic microenvironment. In this study, we performed a comprehensive expression analysis of exosomal miRNAs secreted by several human cancer cell lines and identified eight types of human miRNAs that were highly expressed in exosomes from osteoblastic phenotype-inducing prostate cancer cell lines. One of these miRNAs, hsa-miR-940, significantly promoted the osteogenic differentiation of human mesenchymal stem cells in vitro by targeting ARHGAP1 and FAM134A. Interestingly, although MDA-MB-231 breast cancer cells are commonly known as an osteolytic phenotype-inducing cancer cell line, the implantation of miR-940–overexpressing MDA-MB-231 cells induced extensive osteoblastic lesions in the resulting tumors by facilitating the osteogenic differentiation of host mesenchymal cells. Our results suggest that the phenotypes of bone metastases can be induced by miRNAs secreted by cancer cells in the bone microenvironment.

Myelodysplastic syndrome (MDS) are clonal haematopoietic stem cell (HSC) disorders driven by a complex combination(s) of changes within the genome that result in heterogeneity in both clinical phenotype and disease outcomes. MDS is among the most common of the haematological cancers and its incidence markedly increases with age. Currently available treatments have limited success, with <5% of patients undergoing allogeneic HSC transplantation, a procedure that offers the only possible cure. Critical contributions of the bone marrow microenvironment to the MDS have recently been investigated. Although the better understanding of the underlying biology, particularly genetics of haematopoietic stem cells, has led to better disease and risk classification; however, the role that the bone marrow microenvironment plays in the development of MDS remains largely unclear. This review provides a comprehensive overview of the latest developments in understanding the aetiology of MDS, particularly focussing on understanding how HSCs and the surrounding immune/non-immune bone marrow niche interacts together.

Osteoporotic bone defect and fracture healing remain significant challenges in clinical practice. While traditional therapeutic approaches provide some regulation of bone homeostasis, they often present limitations and adverse effects. In orthopedic procedures, bone cement serves as a crucial material for stabilizing osteoporotic bone and securing implants. However, with the exception of magnesium phosphate cement, most cement variants lack substantial bone regenerative properties. Recent developments in biomaterial science have opened new avenues for enhancing bone cement functionality through innovative modifications. These advanced materials demonstrate promising capabilities in modulating the bone microenvironment through their distinct physicochemical properties. This review provides a systematic analysis of contemporary biomaterial-based modifications of bone cement, focusing on their influence on the bone healing microenvironment. The discussion begins with an examination of bone microenvironment pathology, followed by an evaluation of various biomaterial modifications and their effects on cement properties. The review then explores regulatory strategies targeting specific microenvironmental elements, including inflammatory response, oxidative stress, osteoblast-osteoclast homeostasis, vascular network formation, and osteocyte-mediated processes. The concluding section addresses current technical challenges and emerging research directions, providing insights for the development of next-generation biomaterials with enhanced functionality and therapeutic potential. Graphical Abstract

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells (IMCs) with immunosuppressive functions, whereas IMCs originally differentiate into granulocytes, macrophages, and dendritic cells (DCs) to participate in innate immunity under steady-state conditions. At present, difficulties remain in identifying MDSCs due to lacking of specific biomarkers. To make identification of MDSCs accurately, it also needs to be determined whether having immunosuppressive functions. MDSCs play crucial roles in anti-tumor, angiogenesis, and metastasis. Meanwhile, MDSCs could make close interaction with osteoclasts, osteoblasts, chondrocytes, and other stromal cells within microenvironment of bone and joint, and thereby contributing to poor prognosis of bone-related diseases such as cancer-related bone metastasis, osteosarcoma (OS), rheumatoid arthritis (RA), osteoarthritis (OA), and orthopedic trauma. In addition, MDSCs have been shown to participate in the procedure of bone repair. In this review, we have summarized the function of MDSCs in cancer-related bone metastasis, the interaction with stromal cells within the bone microenvironment as well as joint microenvironment, and the critical role of MDSCs in bone repair. Besides, the promising value of MDSCs in the treatment for bone-related diseases is also well discussed.

The complex bone repair microenvironment remains a significant challenge in orthopedics. As pivotal regulators, bioactive metal ions can promote osseointegration by coordinating the bone immune microenvironment. To address this, we engineered Zn2+/Ce3+ double-doped whitlockite nanoparticles (Zn2+/Ce3+-WH) via a biomimetic GelMA template (GM&Zn2+/Ce3+-WH). These biomimetic GM&Zn2+/Ce3+-WH hydrogel scaffolds exhibit excellent antioxidant, significantly activated anti-inflammatory macrophage phenotypes and inhibited osteoclastogenesis. The resulting immune microenvironment favorably promoted osteogenic differentiation in vitro and facilitated implant-to-bone osteointegration in vivo. Additionally, the scaffolds demonstrated potential for post-operative anti-infection activity. Notably, GM&Zn2+/Ce3+-WH exhibited excellent overall performance. In summary, the natural bone-like Zn2+/Ce3+ co-doping strategy endows GM&Zn2+/Ce3+-WH with immunomodulatory, bacteriostatic, and osseointegrative properties, offering a distinctive and promising approach to re-establishing an immunoregulated osteogenic microenvironment for bone regeneration.