Bone Microenvironment Research Articles

Intra-articular injection of MOF-based nanomaterials for the treatment of osteoarthritis by modulating the bone microenvironment

Osteoarthritis (OA) is a degenerative joint disease characterized by cartilage degradation, subchondral bone remodeling, and chronic inflammation. Current therapeutic strategies often fail to address the underlying mechanisms of OA. This study investigates the efficacy of ZIF-8 composite molybdenum (Mo) nanozymes coated by CaCO3 layer (CaCO3@ZIF@Mo-TA) as a novel therapeutic approach for OA. The nanozymes were characterized using various techniques, including transmission electron microscopy (TEM) and X-ray diffraction (XRD). In vivo studies demonstrated that administration of CaCO3@ZIF-8@Mo-TA at a dose of 100 mg/kg significantly improved joint health, reduced inflammation, and enhanced cartilage preservation in an OA rat model. Mechanistic studies revealed that the nanozymes exerted antioxidant and anti-inflammatory effects by modulating key signaling pathways, including the NLRP3 inflammasome. These findings suggest that ZIF-8@Mo-TA nanozymes represent a promising therapeutic strategy for OA management.

Piezoelectric Nanoarrays with Mechanical-Electrical Coupling Microenvironment for Innervated Bone Regeneration.

The involvement of neurons in the peripheral nervous system is crucial for bone regeneration. Mimicking extracellular matrix cues provides a more direct and effective strategy to regulate neuronal activity and enhance bone regeneration. However, the simultaneous coupling of the intrinsic mechanical-electrical microenvironment of implants to regulate innervated bone regeneration has been largely neglected. Inspired by the mechanical and bioelectric properties of the bone microenvironment, this study constructed a mechanical-electrical coupling microenvironment (M-E) model based on barium titanate piezoelectric nanoarrays, which could effectively promote innervated bone regeneration. The study found that the mechanical microenvironment provided by the nanostructure, coupled with the electrical microenvironment provided by the piezoelectric properties, created a controllable M-E. In vitro cell experiments demonstrated that this coupled microenvironment activated Piezo2 and VGCC ion channels, promoted calcium influx in DRG neurons, and activated downstream PI3K-AKT and RAS pathways. This cascade of events led to the synthesis and release of CGRP in sensory nerves, ultimately enhancing the osteogenic differentiation of BMSCs. This work not only broadens the current understanding of biomaterials that mimic the bone extracellular matrix but also provides new insights into innervated bone regeneration.

DAMPs, PAMPs, NLRs, RIGs, CLRs and TLRs - Understanding the Alphabet Soup in the Context of Bone Biology.

The purpose of this review is to summarize the current understanding of cell-autonomous innate immune pathways that contribute to bone homeostasis and disease. Germ-line encoded pattern recognition receptors (PRRs) are the first line of defense against danger and infections. In the bone microenvironment, PRRs and downstream signaling pathways, that mount immune defense, interface intimately with the core cellular processes in bone cells to alter bone formation and resorption. The role of PRR engagement on bone remodeling has been best described as a result of activated macrophages secreting effector molecules that reshape the characteristics of bone-resident cells. However, it is being increasingly recognized that local bone resident-cells like osteoclasts and osteoblasts possess an arsenal of PRRs. The engagement of these PRRs by stimuli in the bone niche can drive cell-autonomous (aka cell-intrinsic) responses that, in turn, impact bone-remodeling dramatically, irrespective of immune cell effectors. Indeed, this vital role for cell-autonomous innate immune responses is evident in how reduced PRR activity within osteoclast progenitors correlates with their reduced differentiation and abnormal bone remodeling. Further, cell-intrinsic PRR activity has now been shown to influence the behavior of osteoblasts, osteocytes and other local immune/non-immune cell populations. However, distinct PRR families have varying impact on bone homeostasis and inflammation, emphasizing the importance of investigating these different nodes of innate immune signaling in bone cells to better identify how they synergistically and/or antagonistically regulate bone remodeling in the course of an immune response. Innate immune sensing within bone resident cells is a critical determinant for bone remodeling in health and disease.

Bioelectrically Reprogramming Hydrogels Rejuvenate Vascularized Bone Regeneration in Senescence.

Senescent bone tissue displays a pathological imbalance characterized by decreased angiogenesis, disrupted bioelectric signaling, ion dysregulation, and reduced stem cell differentiation. Once bone defects occur, this pathological imbalance makes them difficult to repair. An innovative synergistic therapeutic strategy is utilized to reverse these pathological imbalances via a conductive hydrogel doped with magnesium ion (Mg2+)-modified black phosphorus (BP). The hydrogel reprograms electrical signals, restores Mg2+ homeostasis, reconstructs physiological signals, and promotes blood vessel regeneration in senile bone defects. The conductive hydrogel synergistically restores both the chemical and bioelectric signals within the bone microenvironment. This hydrogel increases the expression of vascular endothelial growth factor (VEGF) and VEGF receptor-2 (VEGFR2), activates the PI3K-AKT-eNOS pathway, and significantly increases the angiogenic ability of vascular endothelial cells in the aged state. In addition, the conductive hydrogel normalizes calcium ion (Ca2+) influx, increases the accumulation of osteogenic transcription factors in the nucleus, and promotes the osteogenic differentiation of senescent stem cells. This innovative treatment strategy restores bone-vascular coupling in areas of senile bone defects, achieves effective vascularized bone regeneration, and has good potential for the treatment of senile bone defects.

Overexpression of RGPR-p117 reveals anticancer effects by regulating multiple signaling pathways in bone metastatic human breast cancer MDA-MB-231 cells.

The role of RGPR-p117, a transcription factor, which binds to the TTGGC motif in the promoter region of the regucalcin gene, in cell regulation remains to be investigated. This study elucidated whether RGPR-p117 regulates the activity of triple-negative human breast cancer MDA-MB-231 cells in vitro. The wild-type and RGPR-p117-overexpressing cancer cells were cultured in DMEM supplemented with fetal bovine serum. RGPR-p117 overexpression suppressed colony formation and growth of cancer cells. Stimulatory effects of epidermal growth factor on cell growth were blocked by RGPR-p117 overexpression. Wild-type cell proliferation was repressed by cell cycle and intracellular signaling inhibitors. These effects were not potentiated in transfectants. Overexpressed RGPR-p117 protected cancer cells against apoptosis inducers. Mechanistic results showed that RGPR-p117 overexpression decreased the expression of Ras, PI3-kinase, Akt, mitogen-activated protein kinase, and mTOR, which are involved in cell growth, while it elevated the levels of the cancer cell suppressor p53, Rb, p21, and regucalcin. Overexpression of RGPR-p117 suppressed cancer cell migration and adhesion. Interestingly, osteoblastic MC3T3-E1 cells or macrophage RAW264.7 cells involved in the bone microenvironment were impaired by coculture with MDA-MB-231 cells. The effects of cancer cells were blocked by transfection. Coculture with conditioned medium obtained from breast cancer cells repressed proliferation and enhanced the death of osteoblastic cells and macrophages. A TNF-α signaling inhibitor blocked these effects. Thus, overexpressed RGPR-p117 was found to suppress the activity of breast cancer cells by regulating various signaling processes, providing new insight into cellular signaling regulation.

Hydrolysis of 2D Nanosheets Reverses Rheumatoid Arthritis Through Anti-Inflammation and Osteogenesis.

Rheumatoid arthritis (RA) is a kind of inflammation homeostasis disorder that dysfunctions the joints. Clinically, medications against RA focus simply on mitigating the focal inflammation, without considering pro-osteogenesis re-modeling of the bone microenvironment. In the present work, 2D layered calcium disilicide nanoparticles (CSNs) are fabricated by facile aqueous exfoliation. The hydrolysis of CSNs produces anti-oxidative H2, alkaline Ca(OH)2, and silica. These moieties play significant roles in anti-oxidation, anti-inflammation, and pro-osteogenesis resulting inconsiderably better RA therapeutic consequences than anti-inflammation alone. Hydrogen gas is validated to eliminate excessive hydroxyl radicals and regulate macrophage re-polarization; the generated Ca(OH)2 can neutralize the acidic microenvironment and inhibit the osteoclast activity; and, the dissolved Ca2+ can effectively complex with phosphates to mineralize Ca3(PO4)2, promoting the osteogenesis of the focal joint. The multifunctional performances of CSNs are further confirmed in arthritic mouse and rabbit models, providing an advanced and robust therapeutic strategy against RA with high biocompatibility and clinical transformable promises.

How the bone microenvironment shapes the pre-metastatic niche and metastasis.

The bone is a frequent metastatic site, with changes in the mineralized bone and the bone marrow milieu that can also prime other sites for metastasis by educating progenitor cells to support metastatic spread. Stromal and immune populations cooperatively maintain the organizationally complex bone niches and are dysregulated in the presence of a distant primary tumor and metastatic disease. Interrogating the bone niches that facilitate metastatic spread using innovative technologies holds the potential to aid in preventing metastasis in and mediated by the bone. Here, we review recent advances in bone niche biology and its adaptations in the context of cancer.

Application of extracellular vesicles in diabetic osteoporosis.

As the population ages, the occurrence of osteoporosis is becoming more common. Diabetes mellitus is one of the factors in the development of osteoporosis. Compared with the general population, the incidence of osteoporosis is significantly higher in diabetic patients. Diabetic osteoporosis (DOP) is a metabolic bone disease characterized by abnormal bone tissue structure due to hyperglycemia and insulin resistance, reduced bone strength and increased risk of fractures. This is a complex mechanism that occurs at the cellular level due to factors such as blood vessels, inflammation, and hyperglycemia and insulin resistance. Although the application of some drugs in clinical practice can reduce the occurrence of DOP, the incidence of fractures caused by DOP is still very high. Extracellular vesicles (EVs) are a new communication mode between cells, which can transfer miRNAs and proteins from mother cells to target cells through membrane fusion, thereby regulating the function of target cells. In recent years, the role of EVs in the pathogenesis of DOP has been widely demonstrated. In this article, we first describe the changes in the bone microenvironment of osteoporosis. Second, we describe the pathogenesis of DOP. Finally, we summarize the research progress and challenges of EVs in DOP.

USP7 Inhibition Promotes Early Osseointegration in Senile Osteoporotic Mice

Although elderly osteoporotic patients have similar implant survival rates compared with those of normal individuals, they require longer healing periods to achieve proper osseointegration. This may be related to chronic inflammatory responses and impaired stem cell repair functions in the osteoporotic bone microenvironment. Recently, the deubiquitinating enzyme, ubiquitin-specific peptidase 7 (USP7), was found to regulate the macrophage immune response and modulate stem cell osteogenic differentiation. The selective inhibitor of USP7, P5091, has also been found to promote bone repair and homeostasis in osteoporotic conditions. However, the roles of USP7 and P5091 in osteoimmunology and dental implant osseointegration under senile osteoporotic conditions remain unclear. In this study, USP7 depletion and P5091 were shown to inhibit inflammation in senescent bone marrow–derived macrophages (BMDMs) and promote osteogenic differentiation in aged bone marrow mesenchymal stromal cells (BMSCs). Furthermore, mRNA-Seq revealed that USP7 depletion could enhance efferocytosis in senescent BMDMs through the EPSIN1/low-density lipoprotein receptor-related protein 1 (LRP1) pathway and selectively induce apoptosis (senolysis) in aged BMSCs. In senile osteoporotic mice, we found that the osseointegration period was prolonged compared with young mice, and P5091 promoted the early stage of osseointegration, which may be related to macrophage efferocytosis around the implant. Collectively, this study suggests that USP7 inhibition may accelerate the osseointegration process in senile osteoporotic conditions by promoting macrophage efferocytosis and aged BMSCs apoptosis. This has implications for understanding the cellular interactions and signaling mechanisms in the peri-implant bone microenvironment under osteoporotic conditions. It may also provide clinical significance in developing new therapies to enhance osseointegration quality and shorten the edentulous period in elderly osteoporotic patients.

MOF-Based Guided Bone Regeneration Membrane for Promoting Osteogenesis by Regulating Bone Microenvironment through Cascade Effects.

Regulation of bone microenvironment (BME) including innate pH values and metal ions affects cellular functions and activities of osteoblasts and osteoclasts, thereby significantly influencing the process of bone regeneration. How to achieve multiple effective regulations of the BME through cascade effects via facile material design and fabrication to significantly facilitate osteogenesis remains a challenge. Herein, a facilely-designed resorbable guided bone regeneration membrane (PCL/DEX@Ca-Zol) based on a drug-loaded metal-organic framework is reported. Thereinto, calcium ions, zoledronic acid, and dexamethasone embedded in the membrane can be responsively released specifically inside bone defect in an acid-triggered manner to synergistically regulate BME by neutralization of pH value, enhancement of osteogenic differentiation and mineralization, and inhibition of osteoclasts in one-go. Along with polycaprolactone as a structural support in the membrane for bone regeneration with fully utilized components of the composite membrane material, enhances bone regeneration with minimized side effects is accordingly achieved with the assistance of effective modulation of BME through multiple cascade effects.

Obesity and insulinopenic type 2 diabetes differentially impact, bone phenotype, bone marrow adipose tissue, and serum levels of the cathelicidin-related antimicrobial peptide in mice.

Obesity is a risk factor of developing type 2 diabetes (T2D) and metabolic complications, through systemic inflammation and insulin resistance. It has also been associated with increased bone marrow adipocytes along with increased bone fragility and fracture risk. However, the differential effects of obesity and T2D on bone fragility remain unclear. The cathelicidin-related antimicrobial peptide (CRAMP) is a multifunctional modulator of the innate immunity that has emerged as biomarker of cardiometabolic diseases. The aims of this study were i) to assess the differential impact between hyperinsulinemic obesity versus insulinopenic T2D, on bone phenotype and bone marrow adipose tissue (BMAT), and ii) to analyse the link with CRAMP expression and its circulating levels in the context of obesity and T2D. We used C57BL/6 J male mice models of obesity induced by high-fat diet (HFD), and of insulinopenic T2D induced by streptozotocin (STZ) treatment combined with HFD, reflecting the metabolic heterogeneity of the diseases. As compared to low-fat diet (LFD) control group after 16 weeks of feeding, the HFD mice exhibit a significant weight gain, moderate hyperglycaemia, impaired glucose tolerance and insulin sensitivity, and significant increase in serum insulin levels. This hyperinsulinemic obesity led to decreased trabecular (Tb.Th) and cortical thickness (Ct.Th) in the tibia, associated with significant BMAT expansion, in addition to increased subcutaneaous (SCAT) and visceral adipose tissue (VAT). No changes were observed in the circulating levels of CRAMP peptide neither in other bone parameters. While, STZ treatment in HFD/STZ group induced a more severe hyperglycaemia, glucose intolerance and insulin resistance, and hypoinsulinemia. We also observed a negative effect on the expansion of both SCAT and VAT, as well as lower increase in BMAT as compared to HFD group. However, these mice with insulinopenic T2D exhibit early decrease in trabecular number (Tb.N) in proximal tibia, progressively from 8 to 16 weeks of protocol, and impaired femoral biomechanical stiffness. These alterations are also accompanied with decreased circulating levels of the CRAMP peptide in the HFD/STZ mice. The CRAMP mRNA levels decreased in VAT of both HFD and HFD/STZ groups. Overall, these results provide novel insights into the differential negative impact of obesity versus T2D on bone microenvironment, and suggest a link between hyperglycaemia-induced bone quality alterations during insulinopenia, and impaired regulation of the cathelicidin peptide of the innate immunity. Further investigations are needed to elucidate this relationship.

Protocol for engineering bone organoids from mesenchymal stem cells

Bone organoids are emerging as powerful tools for studying bone development and related diseases. However, the simplified design of current methods somewhat limits their application potential, as these methods produce single-tissue organoids that fail to replicate the bone microarchitecture or achieve effective mineralization. To address this issue, we propose a three-dimensional (3D) construction strategy for generating mineralized bone structures using bone marrow-derived mesenchymal stem cells (BMSCs). By mixing BMSCs with hydrogel to create a bone matrix-mimicking bioink and employing projection-based light-curing 3D printing technology, we constructed 3D-printed structures, which were then implanted subcutaneously into nude mice, away from the native bone microenvironment. Even without external stimulation, these implants spontaneously formed mineralized bone domains. With long-term culture, these structures gradually matured into fully differentiated bone tissue, completing both mineralization and vascularization. This in vivo bone organoid model offers a novel platform for studying bone development, exploring congenital diseases, testing drugs, and developing therapeutic applications.

The Role of Bone Marrow Cells and Peripheral Blood Cells in the Osteogenic Process

Abstract The osteogenic process is a complex and dynamic biological phenomenon essential for the initial formation of bones during embryonic development and the continuous remodeling and repair of bones throughout an individual’s life. It involves coordination of various cell types, signaling pathways, and environmental factors to ensure proper bone formation and maintenance. The main role in this process belongs to bone marrow cells and peripheral blood cells. This paper provides an overview of currently available literature data about different contributions of bone marrow cells and peripheral blood cells to the osteogenic process. Focusing on their differentiation, signaling pathways, and interactions within the bone microenvironment this article aims to provide a comprehensive understanding of how these cells orchestrate the osteogenic process, offering insights into their therapeutic potential. Understanding these complex cellular interactions is crucial for the development of advanced therapeutic approaches in regenerative medicine and orthopedics, which will ultimately improve outcomes in patients with bone defects and bone-related disorders.

Single-cell RNA sequencing reveals multiple immune cell subpopulations promote the formation of abnormal bone microenvironment in osteoporosis

With the aging of the population, the incidence of osteoporosis (OP) is on the rise, but the ecology of immune cell subpopulations in OP is poorly understood. Therefore, identifying cell subpopulations involved in promoting the development of OP may facilitate the development of new treatments. Based on bioinformatics analysis, we constructed a single-cell landscape of the OP microenvironment and identified immune cell subpopulations in OP to further explore the role of different subpopulations in the abnormal bone microenvironment. Among macrophages (Mac), the Mac_OLR1 subpopulation has an M1-like phenotype and significantly activates cytokine and osteoclast differentiation pathways, interacting with osteoclasts via the HBEGF-CD9 axis. In neutrophils (Neut), the Neut_RSAD2 subpopulation significantly activated cytokine and osteoclast differentiation pathways and had a high neutrophil extracellular trap (NET) score, and H1FX was identified as its potential regulator. In effector memory T (Tem) cells, the Tem_CCL4 subpopulation significantly activated osteoclast differentiation and immune inflammation-related pathways and highly expressed proinflammatory molecules such as CCL4, CCL4L2, CCL5 and IFNG. In B cells, the abundance of the B_ACSM3 subpopulation was significantly increased in the OP group and the osteoclast differentiation pathway was significantly activated, and MYB was identified as its potential regulator. In summary, we identified several immune cell subpopulations that may be involved in promoting the formation of OP, further identified the transcription factors that regulate these subpopulations, and speculated that the development of OP may be accompanied by immune inflammatory responses mediated by these subpopulations. These findings provide candidate molecules and cells for future OP research and may help facilitate the development of new therapies.

Immunotherapy in the Battle Against Bone Metastases: Mechanisms and Emerging Treatments.

Bone metastases are a prevalent complication in advanced cancers, particularly in breast, prostate, and lung cancers, and are associated with severe skeletal-related events (SREs), including fractures, spinal cord compression, and debilitating pain. Conventional bone-targeted treatments like bisphosphonates and RANKL inhibitors (denosumab) reduce osteoclast-mediated bone resorption but do not directly impact tumor progression within the bone. This review focuses on examining the growing potential of immunotherapy in targeting the unique challenges posed by bone metastases. Even though immune checkpoint inhibitors (ICIs) have significantly changed cancer treatment, their impact on bone metastases appears limited because of the bone microenvironment's immunosuppressive traits, which include high levels of transforming growth factor-beta (TGFβ) and the immune-suppressing cells, such as regulatory T cells (Tregs) and myeloid-derived suppressor cells (MDSCs). This review underscores the investigation of combined therapeutic approaches that might ease these difficulties, such as the synergy of immune checkpoint inhibitors with agents aimed at bones (denosumab, bisphosphonates), chemotherapy, and radiotherapy, as well as the combination of immune checkpoint inhibitors with different immunotherapeutic methods, including CAR T-cell therapy. This review provides a comprehensive analysis of preclinical studies and clinical trials that show the synergistic potential of these combination approaches, which aim to both enhance immune responses and mitigate bone destruction. By offering an in-depth exploration of how these strategies can be tailored to the bone microenvironment, this review underscores the need for personalized treatment approaches. The findings emphasize the urgent need for further research into overcoming immune evasion in bone metastases, with the goal of improving patient survival and quality of life.

GDF15 propeptide promotes bone metastasis of castration-resistant prostate cancer by augmenting the bone microenvironment

BackgroundBone metastasis (BM) is a common and fatal condition in patients with castration-resistant prostate cancer (CRPC). However, there are no useful blood biomarkers for CRPC with BM, and the mechanism underlying BM is unclear. In this study, we investigated precise blood biomarkers for evaluating BM that can improve the prognosis of patients with CRPC.MethodsWe comprehensively examined culture supernatants from four prostate cancer (PCa) cell lines using Orbitrap mass spectrometry to identify specific proteins secreted abundantly by PCa cells. The effects of this protein to PCa cells, osteoblasts, osteoclasts were examined, and BM mouse model. In addition, we measured the plasma concentration of this protein in CRPC patients for whom bone scan index (BSI) by bone scintigraphy was performed.ResultsA total of 2,787 proteins were identified by secretome analysis. We focused on GDF15 propeptide (GDPP), which is secreted by osteoblasts, osteoclasts, and PCa cells. GDPP promoted the proliferation, invasion, and migration of PC3 and DU145 CRPC cells, and GDPP aggravated BM in a mouse model. Importantly, GDPP accelerated bone formation and absorption in the bone microenvironment by enhancing the proliferation of osteoblasts and osteoclasts by upregulating individual transcription factors such as RUNX2, OSX, ATF4, NFATc1, and DC-STAMP. In clinical settings, including a total of 416 patients, GDPP was more diagnostic of BM than prostate-specific antigen (PSA) (AUC = 0.92 and 0.78) and the seven other blood biomarkers (alkaline phosphatase, lactate dehydrogenase, bone alkaline phosphatase, tartrate-resistant acid phosphatase 5b, osteocalcin, procollagen I N-terminal propeptide and mature GDF15) in patients with CRPC. The changes in BSI over time with systemic treatment were correlated with that of GDPP (r = 0.63) but not with that of PSA (r = -0.16).ConclusionsGDPP augments the tumor microenvironment of BM and is a novel blood biomarker of BM in CRPC, which could lead to early treatment interventions in patients with CRPC.

MicroRNAs and RNA-Binding Protein-Based Regulation of Bone Metastasis from Hepatobiliary Cancers and Potential Therapeutic Strategies.

Hepatobiliary cancers, such as hepatocellular carcinoma (HCC) and cholangiocarcinoma (CCA), are among the deadliest malignancies worldwide, leading to a significant number of cancer-related deaths. While bone metastases from these cancers are rare, they are highly aggressive and linked to poor prognosis. This review focuses on RNA-based molecular mechanisms that contribute to bone metastasis from hepatobiliary cancers. Specifically, the role of two key factors, microRNAs (miRNAs) and RNA-binding proteins (RBPs), which have not been extensively studied in the context of HCC and CCA, is discussed. These molecules often exhibit abnormal expression in hepatobiliary tumors, influencing cancer cell spread and metastasis by disrupting bone homeostasis, thereby aiding tumor cell migration and survival in the bone microenvironment. This review also discusses potential therapeutic strategies targeting these RNA-based pathways to reduce bone metastasis and improve patient outcomes. Further research is crucial for developing effective miRNA- and RBP-based diagnostic and prognostic biomarkers and treatments to prevent bone metastases in hepatobiliary cancers.

Mechanism of Bone-metastatic LUAD Cells Promoting Angiogenesis Through HGF/YAP Signaling Pathway

The early stages of tumor bone metastasis are closely associated with changes in the vascular niche of the bone microenvironment, and abnormal angiogenesis accelerates tumor metastasis and progression. However, the effects of lung adenocarcinoma (LUAD) cells reprogrammed by the bone microenvironment on the vascular niche within the bone microenvironment and the underlying mechanisms remain unclear. This study investigates the effects and mechanisms of LUAD cells reprogrammed by the bone microenvironment on endothelial cells and angiogenesis, providing insights into the influence of tumor cells on the vascular niche within the bone microenvironment. The culture media from bone-metastatic LUAD cell A549-GFP-LUC-BM3 (BM3-CM) and A549-GFP-LUC (A549-CM) were separately applied to human umbilical vein endothelial cell (HUVEC). A colony formation assay, scratch assay, and tube formation assay were conducted to evaluate the proliferation, migration, and angiogenesis of HUVEC. Gene set enrichment analysis (GSEA) was conducted to identify enriched pathways, while reverse transcription quantitative polymerase chain reaction (RT-qPCR) and enzyme linked immunosorbent assay (ELISA) were performed to quantify hepatocyte growth factor (HGF), a protein that plays a crucial role in angiogenesis. Furthermore, the pivotal function of HGF and its underlying molecular mechanisms have been substantiated through the utilisation of recombinant proteins, neutralising antibodies, pathway inhibitors, immunofluorescence staining, and Western blot. BM3-CM demonstrated a more pronounced impact on the proliferation, migration, and angiogenesis of HUVEC compared to A549-CM. Bioinformatics analysis, combined with in vitro experiment, demonstrated that the secretory protein HGF was significantly elevated in BM3 cells and BM3-CM (P<0.05). The addition of HGF neutralizing antibodies to BM3-CM inhibited the promoting effect of BM3-CM on HUVEC (P<0.05), while the addition of recombinant HGF to A549-CM reproduced that promoting effect of BM3-CM on HUVEC (P<0.05). HGF can enhance the activation of YAP (Yes-associated protein) in HUVEC, and this promotion effect may be achieved by activating Src and activating YAP into the nucleus (P<0.05), but this effect can be inhibited by HGF neutralizing antibodies (P<0.05). Furthermore, the addition of recombinant HGF to A549-CM can recapitulate the YAP activation effect of BM3-CM in HUVEC (P<0.05). Bone microenvironment reprogrammed bone-metastatic LUAD cells BM3 promote the proliferation, migration, and angiogenesis of HUVEC through the HGF/YAP axis, potentially playing a significant role in the modifications of the vascular niche.

Osteoblast-Derived ECM1 Promotes Anti-Androgen Resistance in Bone Metastatic Prostate Cancer.

Acquired resistance to hormonal therapy, particularly enzalutamide (ENZ), remains a significant obstacle in the treatment of advanced bone metastatic prostate cancer. Here, it is demonstrated that under ENZ treatment, osteoblasts in the bone microenvironment secrete increased levels of extracellular matrix protein 1 (ECM1), which affects surrounding prostate cancer cells, promoting tumor cell proliferation and anti-androgen resistance. Mechanistically, ECM1 interacts with the enolase 1 (ENO1) receptor on the prostate cancer cell membrane, leading to its phosphorylation at the Y189 site. This event further recruits adapter proteins including growth factor receptor-bound protein 2 (GRB2) and son of sevenless homolog 1 (SOS1), which activates the downstream mitogen-activated protein kinase (MAPK) signaling pathway to induce anti-androgen resistance. Furthermore, inhibiting ECM1 or utilizing the ENO1-targeting inhibitor phosphonoacetohydroxamate (PhAH) significantly restores tumor cell sensitivity to ENZ. Taken together, a potential mechanism is identified through which osteoblast-derived ECM1 drives resistance in bone metastatic prostate cancer under ENZ treatment. Additionally, the findings indicate that ECM1 and ENO1 may serve as potential targets for developing therapies for bone metastatic castration-resistant prostate cancer.

Endothelial cell-derived exosomes trigger a positive feedback loop in osteogenesis-angiogenesis coupling via up-regulating zinc finger and BTB domain containing 16 in bone marrow mesenchymal stem cell

The close spatial and temporal connection between osteogenesis and angiogenesis around type H vasculature is referred as “osteogenesis-angiogenesis coupling”, which is one of the basic mechanisms of osteogenesis. Endothelial cells (ECs), bone marrow mesenchymal stem cells (BMSCs), and their specific lineage constitute important cluster that participate in the regulation of osteogenesis and angiogenesis in bone microenvironment. However, the regulatory mechanism of osteogenesis-angiogenesis coupling under the condition of bone healing has not been unveiled. In this study, we demonstrated that the exosome derived from ECs (EC-exo) is an initiator of type H blood vessels formation, and EC-exo acts as a mediator in orchestrating osteogenesis-angiogenesis coupling by enhancing BMSC osteogenic differentiation and EC angiogenesis both in monolayer and stereoscopic co-culture system of primary human cells. The transcriptome array indicated that zinc finger and BTB domain containing 16 (ZBTB16) is a key gene in EC-exo-mediated osteogenesis, and ZBTB16 is indispensable in EC-exo-initiated osteogenesis-angiogenesis coupling. Mechanistically, EC-exo up-regulated the expression of ZBTB16 in BMSCs, thereby promoting osteoprogenitor phenotype transformation; the osteoprogenitors further promote ECs which constitute type H vessel (H-ECs) generation by activating HIF-1α pathway; and the H-ECs conversely promotes osteogenic differentiation of BMSCs. The crosstalk between BMSCs and ECs triggered by EC-exo constitutes a positive feedback loop that enhances osteogenesis-angiogenesis coupling. This study demonstrates that EC-exo can become an effective therapeutic tool to promote bone regeneration and repair.Graphical