Calcium released by osteoclastic resorption stimulates autocrine/paracrine activities in local osteogenic cells to promote coupled bone formation

Apolipoprotein E as a Potential Regulator of Osteoclast-Osteoblast Coupling in Material-Induced Bone Formation

Osteoinductive materials which induce bone formation in non-osseous sites are promising bone substitutes to repair critical-sized bone defects. It appears that innate immune response (esp. osteoclastogenesis) to materials plays an important role in material-induced bone formation. In this study, the coupling between osteoclastogenesis and subsequent osteogenesis in material-induced bone formation was investigated. Osteoclastogenesis of mouse bone marrow-derived monocytes (BMMs) on osteoinductive tricalcium phosphate (TCPs) and non-osteoinductive tricalcium phosphate (TCPb) ceramics were evaluated with high-throughput RNA sequencing (RNA-seq) and RT-qPCR regarding secretory proteins. It turned out that osteoinductive TCPs supported osteoclastogenesis and enhanced Apolipoprotein E (ApoE) production. Meanwhile, ApoE enhanced osteogenic gene expression (Alp, Runx2, Col1a1, Osterix) and ALP staining and activity of CRL-12424 cells in vitro. Additionally, western blot assay revealed that ApoE played its role in osteogenesis of CRL-12424 by activating JAK-STAT pathway instead of PI3K-AKT pathway. The overall data indicated that ApoE was a potential coupling factor between osteoclastogenesis and osteogenesis in material-induced bone formation. By secreting ApoE, osteoclasts formed on osteoinductive materials stimulated osteogenic differentiation of osteo-progenitors via JAK-STAT pathway. STATEMENT OF SIGNIFICANCE: Osteoinductive materials can repair critical-sized bone defects, while the precise mechanism osteoinductive materials driving bone formation remains unclear. Recent research has highlighted the role of osteoclastogenesis in material-induced bone formation, how osteoclastogenesis playing its role in osteogenesis was subjected to investigation in the current study. Robust ApoE gene expression shown in osteoclastogenesis with the osteoinductive material and ApoE enhancing osteogenesis of mesenchymal stromal cells (CRL-12424) indicated ApoE as a potential regulator of osteoclast-osteoblast coupling, providing thus novel insights into the complex interplay of cellular responses and contributing to the development of more effective bone substitute materials.

Microvesicles Released by Osteoclastic Cells Exhibited Chondrogenic, Osteogenic, and Anti-Inflammatory Activities: An Evaluation of the Feasibility of Their Use for Treatment of Osteoarthritis in a Mouse Model

Extracellular vesicles (EVs), particularly exosomes (EXOs) of various skeletal and stem cells, were shown to delay osteoarthritis (OA) progression, and apoptotic bodies (ABs), another EV subtype, of osteoclasts showed osteoanabolic actions and were involved in the osteoclastic-regulation of local bone formation. Moreover, this study demonstrates that microvesicles (MVs) released by osteoclasts displayed potent pro-chondrogenic, pro-osteogenic, and anti-inflammatory activities. These activities were unique to osteoclastic MVs and were not shared by osteoclastic ABs and EXOs or MVs of other cell types. Because chronic synovial inflammation, progressive articular cartilage erosion, abnormal subchondral bone remodeling, and inability to regenerate articular cartilage are key etiologies of OA, we postulate that the foregoing activities of osteoclastic MVs could simultaneously target multiple etiologies of OA and could thereby be an effective therapy for OA. Accordingly, this study sought to assess the feasibility of an osteoclastic MV-based strategy for OA with a mouse tibial plateau injury model of OA. Briefly, tibial plateau injuries were created on the right knees of adult C57BL/6J mice, MVs were intraarticularly injected into the injured joints biweekly, and the OA progression was monitored histologically at five weeks post-injury. The MV treatment reduced the OA-induced losses of articular cartilage area and thickness, decreased irregularity in the articular cartilage surface, reduced loss of gliding/intermediate zone of articular cartilage, reduced osteophyte formation, suppressed synovial inflammation, and decreased the OARSI OA score. In summary, treatment with osteoclastic MVs delayed or reversed OA progression. Thus, this study supports the feasibility of an osteoclastic MV-based therapy for OA.

Manipulation of signaling pathways in bone tissue engineering and regenerative medicine: Current knowledge, novel strategies, and future directions

During osteogenesis, a large number of bioactive molecules, macromolecules, cells, and cellular signals are activated to induce bone growth and development. The activation of molecular pathways leads to the occurrence of cellular events, ultimately resulting in observable changes. Therefore, in the studies of bone tissue engineering and regenerative medicine, it is essential to target fundamental events to exploit the mechanisms involved in osteogenesis. In this context, signaling pathways are activated during osteogenesis and trigger the activation of numerous other processes involved in osteogenesis. Direct influence of signaling pathways should allow to manipulate the signaling pathways themselves and impact osteogenesis. A combination of sequential cascades takes place to drive the progression of osteogenesis. Also, the occurrence of these processes and, more generally, cellular and molecular processes related to osteogenesis necessitate the presence of transcription factors and their activity. The present review focuses on outlining several signaling pathways and transcription factors influencing the development of osteogenesis, and describes various methods of their manipulation to induce and enhance bone formation.

3,3'-Diindolylmethane promotes bone formation - A assessment in MC3T3-E1 cells and zebrafish

Osteoporosis is a common degenerative bone disease in middle-aged and elderly people. The current drugs used to treat osteoporosis have many side effects and low patient compliance. Phytochemotherapy may be safer and more effective. 3,3'-diindolemethane (DIM) is the digestive product of indole-3-methanol in cruciferous vegetables in the stomach, which is a kind of anti-tumor and anti-oxidation phytochemical. However, the effects of DIM on osteoblasts and the mechanism by which DIM regulates bone formation are not fully understood. The aim of this study was to investigate the effects of DIM on the bone formation of mouse preosteoblasts MC3T3-E1 and zebrafish. DIM promotes proliferation and osteogenic differentiation of MC3T3-E1 cells in vitro, and also plays a bone promoting role by increasing the interaction between BRCA1-Associated Protein 1(BAP1) and Inositol 1,4,5-Trisphosphate Receptor(IP3R), up-regulating the expression of BAP1 and IP3R and downstream storage operation calcium entry (SOCE) related protein Recombinant Stromal Interaction Molecule 1(STIM1). The effect of DIM on osteoporosis was confirmed in zebrafish osteoporosis model, and its molecular mechanism may be related to BAP1/IP3R/SOCE signaling pathway. These findings highlight the potential therapeutic value of DIM in the prevention and treatment of osteoporosis.

Simulation of the bone remodelling microenvironment by calcium compound-loaded hydrogel fibrous membranes for in situ bone regeneration

The endowment of guided bone regeneration (GBR) membranes with the ability to activate the endogenous regenerative capability of bone to regenerate bone defects is of clinical significance. Herein we explored the preparation of the calcium compound (CC) (calcium sulfate (CaSL), calcium hydrophosphate (CaHP), or tricalcium phosphate (TCaP)) loaded ultrathin silk fibroin (SF)/gelatin (G) fibre membranes via electrospinning as the GBR membranes to regenerate the calvarial bone defects. The in vitro experiments demonstrated that the CaSL-loaded ultrathin fibrous membranes could simulate optimally the bone remodelling microenvironment in comparison with the CaHP- and TCaP-loaded fibrous membranes, displaying the highest activity to regulate the migration, proliferation, and differentiation of mesenchymal stem cells (MSCs). Also, the in vivo experiments demonstrated that the CaSL-loaded fibrous membranes presented the highest intrinsic osteoinduction to guide in situ regeneration of bone. Furthermore, the in vivo experiments demonstrated that the as-prepared composite fibrous membranes possessed good degradability. In summary, our results suggested that the CaSL-loaded fibrous membranes with high intrinsic osteoinduction and good degradability have potential to translate into clinical practice.

Efferocytosis and Bone Dynamics

PURPOSE OF REVIEW

This review summarizes the recently published scientific evidence regarding the role of efferocytosis in bone dynamics and skeletal health.

RECENT FINDINGS

Several types of efferocytes have been identified within the skeleton, with macrophages being the most extensively studied. Efferocytosis is not merely a 'clean-up' process vital for maintaining skeletal homeostasis; it also plays a crucial role in promoting resolution pathways and orchestrating bone dynamics, such as osteoblast-osteoclast coupling during bone remodeling. Impaired efferocytosis has been associated with aging-related bone loss and various skeletal pathologies, including osteoporosis, osteoarthritis, rheumatoid arthritis, and metastatic bone diseases. Accordingly, emerging evidence suggests that targeting efferocytic mechanisms has the potential to alleviate these conditions. While efferocytosis remains underexplored in the skeleton, recent discoveries have shed light on its pivotal role in bone dynamics, with important implications for skeletal health and pathology. However, there are several knowledge gaps and persisting technical limitations that must be addressed to fully unveil the contributions of efferocytosis in bone.

Photothermal Antibacterial and Osteoinductive Polypyrrole@Cu Implants for Biological Tissue Replacement

The treatment of bone defects caused by disease or accidents through the use of implants presents significant clinical challenges. After clinical implantation, these materials attract and accumulate bacteria and hinder the integration of the implant with bone tissue due to the lack of osteoinductive properties, both of which can cause postoperative infection and even lead to the eventual failure of the operation. This work successfully prepared a novel biomaterial coating with multiple antibacterial mechanisms for potent and durable and osteoinductive biological tissue replacement by pulsed PED (electrochemical deposition). By effectively regulating PPy (polypyrrole), the uniform composite coating achieved sound physiological stability. Furthermore, the photothermal analysis showcased exceptional potent photothermal antibacterial activity. The antibacterial assessments revealed a bacterial eradication rate of 100% for the PPy@Cu/PD composite coating following a 24 h incubation. Upon the introduction of NIR (near-infrared) irradiation, the combined effects of multiple antibacterial mechanisms led to bacterial reduction rates of 99% for E. coli and 98% for S. aureus after a 6 h incubation. Additionally, the successful promotion of osteoblast proliferation was confirmed through the application of the osteoinductive drug PD (pamidronate disodium) on the composite coating's surface. Therefore, the antimicrobial Ti-based coatings with osteoinductive properties and potent and durable antibacterial properties could serve as ideal bone implants.

Echinacoside promotes osteogenesis and angiogenesis and inhibits osteoclast formation

PURPOSE

The purpose of this research is to demonstrate echinacoside promotes osteogenesis and angiogenesis and inhibits osteoclast formation.

METHODS

We conducted a cell experiment in vitro to study how echinacoside affects angiogenesis, osteogenesis and osteoclast formation. We used polymerase chain reaction and Western blotting to detect the expression levels of proteins and genes related to angiogenesis, osteogenesis and osteoclast formation. We established a bone fracture model with rats to test angiogenesis, osteogenesis and osteoclast formation of echinacoside. We labelled osteogenic markers, blood vessels and osteoclastic markers in fracture sections of rats.

RESULTS

The in vitro cell experiments showed echinacoside improved the osteogenic activity of mouse embryo osteoblast precursor cells and promoted the migration and tube formation of human umbilical vein endothelial cells. In addition, it inhibited differentiation of mouse leukaemia cells of monocyte macrophage. Echinacoside increased the expression of related proteins and genes and improved angiogenesis and osteogenesis while inhibiting osteoclast formation by repressing the expression of related proteins and genes. From in vivo experiments, the results of IHC and HE experiments demonstrated echinacoside significantly decreased the content of MMP-9 and improved the content of VEGF and OCN. The fluorescence immunoassay showed echinacoside promoted the activities of RUNX2 and VEGF and inhibited CTSK. Echinacoside reduced the content of TNF-α, IL-1β and IL-6, thus demonstrating its anti-inflammatory activity.

CONCLUSION

Echinacoside improved angiogenesis and osteogenesis and inhibited osteoclast formation to promote fracture healing.

Metal ions: the unfading stars of bone regeneration-from bone metabolism regulation to biomaterial applications

In recent years, bone regeneration has emerged as a remarkable field that offers promising guidance for treating bone-related diseases, such as bone defects, bone infections, and osteosarcoma. Among various bone regeneration approaches, the metal ion-based strategy has surfaced as a prospective candidate approach owing to the extensive regulatory role of metal ions in bone metabolism and the diversity of corresponding delivery strategies. Various metal ions can promote bone regeneration through three primary strategies: balancing the effects of osteoblasts and osteoclasts, regulating the immune microenvironment, and promoting bone angiogenesis. In the meantime, the complex molecular mechanisms behind these strategies are being consistently explored. Moreover, the accelerated development of biomaterials broadens the prospect of metal ions applied to bone regeneration. This review highlights the potential of metal ions for bone regeneration and their underlying mechanisms. We propose that future investigations focus on refining the clinical utilization of metal ions using both mechanistic inquiry and materials engineering to bolster the clinical effectiveness of metal ion-based approaches for bone regeneration.

Kalkitoxin attenuates calcification of vascular smooth muscle cells via RUNX-2 signaling pathways

BACKGROUND

Kalkitoxin (KT) is an active lipopeptide isolated from the cyanobacterium Lyngbya majuscula found in the bed of the coral reef. Although KT suppresses cell division and inflammation, KT's mechanism of action in vascular smooth muscle cells (VSMCs) is unidentified. Therefore, our main aim was to investigate the impact of KT on vascular calcification for the treatment of cardiovascular disease.

OBJECTIVES

Using diverse calcification media, we studied the effect of KT on VSMC calcification and the underlying mechanism of this effect.

METHODS

VSMC was isolated from the 6 weeks ICR mice. Then VSMCs were treated with different concentrations of KT to check the cell viability. Alizarin red and von Kossa staining were carried out to examine the calcium deposition on VSMC. Thoracic aorta of 6 weeks mice were taken and treated with different concentrations of KT, and H and E staining was performed. Real-time polymerase chain reaction and western blot were performed to examine KT's effect on VSMC mineralization. Calcium deposition on VSMC was examined with a calcium deposition quantification kit.

RESULTS

Calcium deposition, Alizarin red, and von Kossa staining revealed that KT reduced inorganic phosphate-induced calcification phenotypes. KT also reduced Ca++-induced calcification by inhibiting genes that regulate osteoblast differentiation, such as runt-related transcription factor 2 (RUNX-2), SMAD family member 4, osterix, collagen 1α, and osteopontin. Also, KT repressed Ca2+-induced bone morphogenetic protein 2, RUNX-2, collagen 1α, osteoprotegerin, and smooth muscle actin protein expression. Likewise, Alizarin red and von Kossa staining showed that KT markedly decreased the calcification of ex vivo ring formation in the mouse thoracic aorta.

CONCLUSIONS

This experiment demonstrated that KT decreases vascular calcification and may be developed as a new therapeutic treatment for vascular calcification and arteriosclerosis.

Examining Mechanisms for Voltage-Sensitive Calcium Channel-Mediated Secretion Events in Bone Cells

In addition to their well-described functions in cell excitability, voltage-sensitive calcium channels (VSCCs) serve a critical role in calcium (Ca2+)-mediated secretion of pleiotropic paracrine and endocrine factors, including those produced in bone. Influx of Ca2+ through VSCCs activates intracellular signaling pathways to modulate a variety of cellular processes that include cell proliferation, differentiation, and bone adaptation in response to mechanical stimuli. Less well understood is the role of VSCCs in the control of bone and calcium homeostasis mediated through secreted factors. In this review, we discuss the various functions of VSCCs in skeletal cells as regulators of Ca2+ dynamics and detail how these channels might control the release of bioactive factors from bone cells. Because VSCCs are druggable, a better understanding of the multiple functions of these channels in the skeleton offers the opportunity for developing new therapies to enhance and maintain bone and to improve systemic health.

Bone mineralisation and glucose metabolism

Recent advancements in the bone biology field have identified a novel bone-metabolism axis. In this review, we highlight several novel studies that further our knowledge of new endocrine functions of bone; explore remaining unanswered questions; and discuss translational challenges in this complex era of bone biology research.

The roles of bone remodeling in normal hematopoiesis and age-related hematological malignancies

Prior research establishing that bone interacts in coordination with the bone marrow microenvironment (BMME) to regulate hematopoietic homeostasis was largely based on analyses of individual bone-associated cell populations. Recent advances in intravital imaging has suggested that the expansion of hematopoietic stem cells (HSCs) and acute myeloid leukemia cells is restricted to bone marrow microdomains during a distinct stage of bone remodeling. These findings indicate that dynamic bone remodeling likely imposes additional heterogeneity within the BMME to yield differential clonal responses. A holistic understanding of the role of bone remodeling in regulating the stem cell niche and how these interactions are altered in age-related hematological malignancies will be critical to the development of novel interventions. To advance this understanding, herein, we provide a synopsis of the cellular and molecular constituents that participate in bone turnover and their known connections to the hematopoietic compartment. Specifically, we elaborate on the coupling between bone remodeling and the BMME in homeostasis and age-related hematological malignancies and after treatment with bone-targeting approaches. We then discuss unresolved questions and ambiguities that remain in the field.

Progress of Wnt Signaling Pathway in Osteoporosis

Osteoporosis, one of the serious health diseases, involves bone mass loss, bone density diminishing, and degeneration of bone microstructure, which is accompanied by a tendency toward bone fragility and a predisposition to fracture. More than 200 million people worldwide suffer from osteoporosis, and the cost of treating osteoporotic fractures is expected to reach at least $25 billion by 2025. The generation and development of osteoporosis are regulated by genetic factors and regulatory factors such as TGF-β, BMP, and FGF through multiple pathways, including the Wnt signaling pathway, the Notch signaling pathway, and the MAPK signaling pathway. Among them, the Wnt signaling pathway is one of the most important pathways. It is not only involved in bone development and metabolism but also in the differentiation and proliferation of chondrocytes, mesenchymal stem cells, osteoclasts, and osteoblasts. Dkk-1 and SOST are Wnt inhibitory proteins that can inhibit the activation of the canonical Wnt signaling pathway and block the proliferation and differentiation of osteoblasts. Therefore, they may serve as potential targets for the treatment of osteoporosis. In this review, we analyzed the mechanisms of Wnt proteins, β-catenin, and signaling molecules in the process of signal transduction and summarized the relationship between the Wnt signaling pathway and bone-related cells. We hope to attract attention to the role of the Wnt signaling pathway in osteoporosis and offer new perspectives and approaches to making a diagnosis and giving treatment for osteoporosis.

Targeting Tumor Microenvironment by Metal Peroxide Nanoparticles in Cancer Therapy

Solid tumors have a unique tumor microenvironment (TME), which includes hypoxia, low acidity, and high hydrogen peroxide and glutathione (GSH) levels, among others. These unique factors, which offer favourable microenvironments and nourishment for tumor development and spread, also serve as a gateway for specific and successful cancer therapies. A good example is metal peroxide structures which have been synthesized and utilized to enhance oxygen supply and they have shown great promise in the alleviation of hypoxia. In a hypoxic environment, certain oxygen-dependent treatments such as photodynamic therapy and radiotherapy fail to respond and therefore modulating the hypoxic tumor microenvironment has been found to enhance the antitumor impact of certain drugs. Under acidic environments, the hydrogen peroxide produced by the reaction of metal peroxides with water not only induces oxidative stress but also produces additional oxygen. This is achieved since hydrogen peroxide acts as a reactive substrate for molecules such as catalyse enzymes, alleviating tumor hypoxia observed in the tumor microenvironment. Metal ions released in the process can also offer distinct bioactivity in their own right. Metal peroxides used in anticancer therapy are a rapidly evolving field, and there is good evidence that they are a good option for regulating the tumor microenvironment in cancer therapy. In this regard, the synthesis and mechanisms behind the successful application of metal peroxides to specifically target the tumor microenvironment are highlighted in this review. Various characteristics of TME such as angiogenesis, inflammation, hypoxia, acidity levels, and metal ion homeostasis are addressed in this regard, together with certain forms of synergistic combination treatments.